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1/*
2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
5 *
6 * Implementation of the Transmission Control Protocol(TCP).
7 *
8 * Authors: Ross Biro
9 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
10 * Mark Evans, <evansmp@uhura.aston.ac.uk>
11 * Corey Minyard <wf-rch!minyard@relay.EU.net>
12 * Florian La Roche, <flla@stud.uni-sb.de>
13 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
14 * Linus Torvalds, <torvalds@cs.helsinki.fi>
15 * Alan Cox, <gw4pts@gw4pts.ampr.org>
16 * Matthew Dillon, <dillon@apollo.west.oic.com>
17 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
18 * Jorge Cwik, <jorge@laser.satlink.net>
19 */
20
21/*
22 * Changes: Pedro Roque : Retransmit queue handled by TCP.
23 * : Fragmentation on mtu decrease
24 * : Segment collapse on retransmit
25 * : AF independence
26 *
27 * Linus Torvalds : send_delayed_ack
28 * David S. Miller : Charge memory using the right skb
29 * during syn/ack processing.
30 * David S. Miller : Output engine completely rewritten.
31 * Andrea Arcangeli: SYNACK carry ts_recent in tsecr.
32 * Cacophonix Gaul : draft-minshall-nagle-01
33 * J Hadi Salim : ECN support
34 *
35 */
36
37#define pr_fmt(fmt) "TCP: " fmt
38
39#include <net/tcp.h>
40
41#include <linux/compiler.h>
42#include <linux/gfp.h>
43#include <linux/module.h>
44
45/* People can turn this off for buggy TCP's found in printers etc. */
46int sysctl_tcp_retrans_collapse __read_mostly = 1;
47
48/* People can turn this on to work with those rare, broken TCPs that
49 * interpret the window field as a signed quantity.
50 */
51int sysctl_tcp_workaround_signed_windows __read_mostly = 0;
52
53/* Default TSQ limit of four TSO segments */
54int sysctl_tcp_limit_output_bytes __read_mostly = 262144;
55
56/* This limits the percentage of the congestion window which we
57 * will allow a single TSO frame to consume. Building TSO frames
58 * which are too large can cause TCP streams to be bursty.
59 */
60int sysctl_tcp_tso_win_divisor __read_mostly = 3;
61
62/* By default, RFC2861 behavior. */
63int sysctl_tcp_slow_start_after_idle __read_mostly = 1;
64
65static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
66 int push_one, gfp_t gfp);
67
68/* Account for new data that has been sent to the network. */
69static void tcp_event_new_data_sent(struct sock *sk, const struct sk_buff *skb)
70{
71 struct inet_connection_sock *icsk = inet_csk(sk);
72 struct tcp_sock *tp = tcp_sk(sk);
73 unsigned int prior_packets = tp->packets_out;
74
75 tcp_advance_send_head(sk, skb);
76 tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;
77
78 tp->packets_out += tcp_skb_pcount(skb);
79 if (!prior_packets || icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS ||
80 icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
81 tcp_rearm_rto(sk);
82 }
83
84 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT,
85 tcp_skb_pcount(skb));
86}
87
88/* SND.NXT, if window was not shrunk.
89 * If window has been shrunk, what should we make? It is not clear at all.
90 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
91 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
92 * invalid. OK, let's make this for now:
93 */
94static inline __u32 tcp_acceptable_seq(const struct sock *sk)
95{
96 const struct tcp_sock *tp = tcp_sk(sk);
97
98 if (!before(tcp_wnd_end(tp), tp->snd_nxt))
99 return tp->snd_nxt;
100 else
101 return tcp_wnd_end(tp);
102}
103
104/* Calculate mss to advertise in SYN segment.
105 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
106 *
107 * 1. It is independent of path mtu.
108 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
109 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
110 * attached devices, because some buggy hosts are confused by
111 * large MSS.
112 * 4. We do not make 3, we advertise MSS, calculated from first
113 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
114 * This may be overridden via information stored in routing table.
115 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
116 * probably even Jumbo".
117 */
118static __u16 tcp_advertise_mss(struct sock *sk)
119{
120 struct tcp_sock *tp = tcp_sk(sk);
121 const struct dst_entry *dst = __sk_dst_get(sk);
122 int mss = tp->advmss;
123
124 if (dst) {
125 unsigned int metric = dst_metric_advmss(dst);
126
127 if (metric < mss) {
128 mss = metric;
129 tp->advmss = mss;
130 }
131 }
132
133 return (__u16)mss;
134}
135
136/* RFC2861. Reset CWND after idle period longer RTO to "restart window".
137 * This is the first part of cwnd validation mechanism.
138 */
139void tcp_cwnd_restart(struct sock *sk, s32 delta)
140{
141 struct tcp_sock *tp = tcp_sk(sk);
142 u32 restart_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk));
143 u32 cwnd = tp->snd_cwnd;
144
145 tcp_ca_event(sk, CA_EVENT_CWND_RESTART);
146
147 tp->snd_ssthresh = tcp_current_ssthresh(sk);
148 restart_cwnd = min(restart_cwnd, cwnd);
149
150 while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd)
151 cwnd >>= 1;
152 tp->snd_cwnd = max(cwnd, restart_cwnd);
153 tp->snd_cwnd_stamp = tcp_time_stamp;
154 tp->snd_cwnd_used = 0;
155}
156
157/* Congestion state accounting after a packet has been sent. */
158static void tcp_event_data_sent(struct tcp_sock *tp,
159 struct sock *sk)
160{
161 struct inet_connection_sock *icsk = inet_csk(sk);
162 const u32 now = tcp_time_stamp;
163
164 if (tcp_packets_in_flight(tp) == 0)
165 tcp_ca_event(sk, CA_EVENT_TX_START);
166
167 tp->lsndtime = now;
168
169 /* If it is a reply for ato after last received
170 * packet, enter pingpong mode.
171 */
172 if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato)
173 icsk->icsk_ack.pingpong = 1;
174}
175
176/* Account for an ACK we sent. */
177static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts)
178{
179 tcp_dec_quickack_mode(sk, pkts);
180 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
181}
182
183
184u32 tcp_default_init_rwnd(u32 mss)
185{
186 /* Initial receive window should be twice of TCP_INIT_CWND to
187 * enable proper sending of new unsent data during fast recovery
188 * (RFC 3517, Section 4, NextSeg() rule (2)). Further place a
189 * limit when mss is larger than 1460.
190 */
191 u32 init_rwnd = TCP_INIT_CWND * 2;
192
193 if (mss > 1460)
194 init_rwnd = max((1460 * init_rwnd) / mss, 2U);
195 return init_rwnd;
196}
197
198/* Determine a window scaling and initial window to offer.
199 * Based on the assumption that the given amount of space
200 * will be offered. Store the results in the tp structure.
201 * NOTE: for smooth operation initial space offering should
202 * be a multiple of mss if possible. We assume here that mss >= 1.
203 * This MUST be enforced by all callers.
204 */
205void tcp_select_initial_window(int __space, __u32 mss,
206 __u32 *rcv_wnd, __u32 *window_clamp,
207 int wscale_ok, __u8 *rcv_wscale,
208 __u32 init_rcv_wnd)
209{
210 unsigned int space = (__space < 0 ? 0 : __space);
211
212 /* If no clamp set the clamp to the max possible scaled window */
213 if (*window_clamp == 0)
214 (*window_clamp) = (65535 << 14);
215 space = min(*window_clamp, space);
216
217 /* Quantize space offering to a multiple of mss if possible. */
218 if (space > mss)
219 space = (space / mss) * mss;
220
221 /* NOTE: offering an initial window larger than 32767
222 * will break some buggy TCP stacks. If the admin tells us
223 * it is likely we could be speaking with such a buggy stack
224 * we will truncate our initial window offering to 32K-1
225 * unless the remote has sent us a window scaling option,
226 * which we interpret as a sign the remote TCP is not
227 * misinterpreting the window field as a signed quantity.
228 */
229 if (sysctl_tcp_workaround_signed_windows)
230 (*rcv_wnd) = min(space, MAX_TCP_WINDOW);
231 else
232 (*rcv_wnd) = space;
233
234 (*rcv_wscale) = 0;
235 if (wscale_ok) {
236 /* Set window scaling on max possible window
237 * See RFC1323 for an explanation of the limit to 14
238 */
239 space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max);
240 space = min_t(u32, space, *window_clamp);
241 while (space > 65535 && (*rcv_wscale) < 14) {
242 space >>= 1;
243 (*rcv_wscale)++;
244 }
245 }
246
247 if (mss > (1 << *rcv_wscale)) {
248 if (!init_rcv_wnd) /* Use default unless specified otherwise */
249 init_rcv_wnd = tcp_default_init_rwnd(mss);
250 *rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss);
251 }
252
253 /* Set the clamp no higher than max representable value */
254 (*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp);
255}
256EXPORT_SYMBOL(tcp_select_initial_window);
257
258/* Chose a new window to advertise, update state in tcp_sock for the
259 * socket, and return result with RFC1323 scaling applied. The return
260 * value can be stuffed directly into th->window for an outgoing
261 * frame.
262 */
263static u16 tcp_select_window(struct sock *sk)
264{
265 struct tcp_sock *tp = tcp_sk(sk);
266 u32 old_win = tp->rcv_wnd;
267 u32 cur_win = tcp_receive_window(tp);
268 u32 new_win = __tcp_select_window(sk);
269
270 /* Never shrink the offered window */
271 if (new_win < cur_win) {
272 /* Danger Will Robinson!
273 * Don't update rcv_wup/rcv_wnd here or else
274 * we will not be able to advertise a zero
275 * window in time. --DaveM
276 *
277 * Relax Will Robinson.
278 */
279 if (new_win == 0)
280 NET_INC_STATS(sock_net(sk),
281 LINUX_MIB_TCPWANTZEROWINDOWADV);
282 new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale);
283 }
284 tp->rcv_wnd = new_win;
285 tp->rcv_wup = tp->rcv_nxt;
286
287 /* Make sure we do not exceed the maximum possible
288 * scaled window.
289 */
290 if (!tp->rx_opt.rcv_wscale && sysctl_tcp_workaround_signed_windows)
291 new_win = min(new_win, MAX_TCP_WINDOW);
292 else
293 new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
294
295 /* RFC1323 scaling applied */
296 new_win >>= tp->rx_opt.rcv_wscale;
297
298 /* If we advertise zero window, disable fast path. */
299 if (new_win == 0) {
300 tp->pred_flags = 0;
301 if (old_win)
302 NET_INC_STATS(sock_net(sk),
303 LINUX_MIB_TCPTOZEROWINDOWADV);
304 } else if (old_win == 0) {
305 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFROMZEROWINDOWADV);
306 }
307
308 return new_win;
309}
310
311/* Packet ECN state for a SYN-ACK */
312static void tcp_ecn_send_synack(struct sock *sk, struct sk_buff *skb)
313{
314 const struct tcp_sock *tp = tcp_sk(sk);
315
316 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR;
317 if (!(tp->ecn_flags & TCP_ECN_OK))
318 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE;
319 else if (tcp_ca_needs_ecn(sk))
320 INET_ECN_xmit(sk);
321}
322
323/* Packet ECN state for a SYN. */
324static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb)
325{
326 struct tcp_sock *tp = tcp_sk(sk);
327 bool use_ecn = sock_net(sk)->ipv4.sysctl_tcp_ecn == 1 ||
328 tcp_ca_needs_ecn(sk);
329
330 if (!use_ecn) {
331 const struct dst_entry *dst = __sk_dst_get(sk);
332
333 if (dst && dst_feature(dst, RTAX_FEATURE_ECN))
334 use_ecn = true;
335 }
336
337 tp->ecn_flags = 0;
338
339 if (use_ecn) {
340 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
341 tp->ecn_flags = TCP_ECN_OK;
342 if (tcp_ca_needs_ecn(sk))
343 INET_ECN_xmit(sk);
344 }
345}
346
347static void tcp_ecn_clear_syn(struct sock *sk, struct sk_buff *skb)
348{
349 if (sock_net(sk)->ipv4.sysctl_tcp_ecn_fallback)
350 /* tp->ecn_flags are cleared at a later point in time when
351 * SYN ACK is ultimatively being received.
352 */
353 TCP_SKB_CB(skb)->tcp_flags &= ~(TCPHDR_ECE | TCPHDR_CWR);
354}
355
356static void
357tcp_ecn_make_synack(const struct request_sock *req, struct tcphdr *th)
358{
359 if (inet_rsk(req)->ecn_ok)
360 th->ece = 1;
361}
362
363/* Set up ECN state for a packet on a ESTABLISHED socket that is about to
364 * be sent.
365 */
366static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb,
367 int tcp_header_len)
368{
369 struct tcp_sock *tp = tcp_sk(sk);
370
371 if (tp->ecn_flags & TCP_ECN_OK) {
372 /* Not-retransmitted data segment: set ECT and inject CWR. */
373 if (skb->len != tcp_header_len &&
374 !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) {
375 INET_ECN_xmit(sk);
376 if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) {
377 tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR;
378 tcp_hdr(skb)->cwr = 1;
379 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
380 }
381 } else if (!tcp_ca_needs_ecn(sk)) {
382 /* ACK or retransmitted segment: clear ECT|CE */
383 INET_ECN_dontxmit(sk);
384 }
385 if (tp->ecn_flags & TCP_ECN_DEMAND_CWR)
386 tcp_hdr(skb)->ece = 1;
387 }
388}
389
390/* Constructs common control bits of non-data skb. If SYN/FIN is present,
391 * auto increment end seqno.
392 */
393static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
394{
395 skb->ip_summed = CHECKSUM_PARTIAL;
396 skb->csum = 0;
397
398 TCP_SKB_CB(skb)->tcp_flags = flags;
399 TCP_SKB_CB(skb)->sacked = 0;
400
401 tcp_skb_pcount_set(skb, 1);
402
403 TCP_SKB_CB(skb)->seq = seq;
404 if (flags & (TCPHDR_SYN | TCPHDR_FIN))
405 seq++;
406 TCP_SKB_CB(skb)->end_seq = seq;
407}
408
409static inline bool tcp_urg_mode(const struct tcp_sock *tp)
410{
411 return tp->snd_una != tp->snd_up;
412}
413
414#define OPTION_SACK_ADVERTISE (1 << 0)
415#define OPTION_TS (1 << 1)
416#define OPTION_MD5 (1 << 2)
417#define OPTION_WSCALE (1 << 3)
418#define OPTION_FAST_OPEN_COOKIE (1 << 8)
419
420struct tcp_out_options {
421 u16 options; /* bit field of OPTION_* */
422 u16 mss; /* 0 to disable */
423 u8 ws; /* window scale, 0 to disable */
424 u8 num_sack_blocks; /* number of SACK blocks to include */
425 u8 hash_size; /* bytes in hash_location */
426 __u8 *hash_location; /* temporary pointer, overloaded */
427 __u32 tsval, tsecr; /* need to include OPTION_TS */
428 struct tcp_fastopen_cookie *fastopen_cookie; /* Fast open cookie */
429};
430
431/* Write previously computed TCP options to the packet.
432 *
433 * Beware: Something in the Internet is very sensitive to the ordering of
434 * TCP options, we learned this through the hard way, so be careful here.
435 * Luckily we can at least blame others for their non-compliance but from
436 * inter-operability perspective it seems that we're somewhat stuck with
437 * the ordering which we have been using if we want to keep working with
438 * those broken things (not that it currently hurts anybody as there isn't
439 * particular reason why the ordering would need to be changed).
440 *
441 * At least SACK_PERM as the first option is known to lead to a disaster
442 * (but it may well be that other scenarios fail similarly).
443 */
444static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
445 struct tcp_out_options *opts)
446{
447 u16 options = opts->options; /* mungable copy */
448
449 if (unlikely(OPTION_MD5 & options)) {
450 *ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
451 (TCPOPT_MD5SIG << 8) | TCPOLEN_MD5SIG);
452 /* overload cookie hash location */
453 opts->hash_location = (__u8 *)ptr;
454 ptr += 4;
455 }
456
457 if (unlikely(opts->mss)) {
458 *ptr++ = htonl((TCPOPT_MSS << 24) |
459 (TCPOLEN_MSS << 16) |
460 opts->mss);
461 }
462
463 if (likely(OPTION_TS & options)) {
464 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
465 *ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
466 (TCPOLEN_SACK_PERM << 16) |
467 (TCPOPT_TIMESTAMP << 8) |
468 TCPOLEN_TIMESTAMP);
469 options &= ~OPTION_SACK_ADVERTISE;
470 } else {
471 *ptr++ = htonl((TCPOPT_NOP << 24) |
472 (TCPOPT_NOP << 16) |
473 (TCPOPT_TIMESTAMP << 8) |
474 TCPOLEN_TIMESTAMP);
475 }
476 *ptr++ = htonl(opts->tsval);
477 *ptr++ = htonl(opts->tsecr);
478 }
479
480 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
481 *ptr++ = htonl((TCPOPT_NOP << 24) |
482 (TCPOPT_NOP << 16) |
483 (TCPOPT_SACK_PERM << 8) |
484 TCPOLEN_SACK_PERM);
485 }
486
487 if (unlikely(OPTION_WSCALE & options)) {
488 *ptr++ = htonl((TCPOPT_NOP << 24) |
489 (TCPOPT_WINDOW << 16) |
490 (TCPOLEN_WINDOW << 8) |
491 opts->ws);
492 }
493
494 if (unlikely(opts->num_sack_blocks)) {
495 struct tcp_sack_block *sp = tp->rx_opt.dsack ?
496 tp->duplicate_sack : tp->selective_acks;
497 int this_sack;
498
499 *ptr++ = htonl((TCPOPT_NOP << 24) |
500 (TCPOPT_NOP << 16) |
501 (TCPOPT_SACK << 8) |
502 (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
503 TCPOLEN_SACK_PERBLOCK)));
504
505 for (this_sack = 0; this_sack < opts->num_sack_blocks;
506 ++this_sack) {
507 *ptr++ = htonl(sp[this_sack].start_seq);
508 *ptr++ = htonl(sp[this_sack].end_seq);
509 }
510
511 tp->rx_opt.dsack = 0;
512 }
513
514 if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
515 struct tcp_fastopen_cookie *foc = opts->fastopen_cookie;
516 u8 *p = (u8 *)ptr;
517 u32 len; /* Fast Open option length */
518
519 if (foc->exp) {
520 len = TCPOLEN_EXP_FASTOPEN_BASE + foc->len;
521 *ptr = htonl((TCPOPT_EXP << 24) | (len << 16) |
522 TCPOPT_FASTOPEN_MAGIC);
523 p += TCPOLEN_EXP_FASTOPEN_BASE;
524 } else {
525 len = TCPOLEN_FASTOPEN_BASE + foc->len;
526 *p++ = TCPOPT_FASTOPEN;
527 *p++ = len;
528 }
529
530 memcpy(p, foc->val, foc->len);
531 if ((len & 3) == 2) {
532 p[foc->len] = TCPOPT_NOP;
533 p[foc->len + 1] = TCPOPT_NOP;
534 }
535 ptr += (len + 3) >> 2;
536 }
537}
538
539/* Compute TCP options for SYN packets. This is not the final
540 * network wire format yet.
541 */
542static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
543 struct tcp_out_options *opts,
544 struct tcp_md5sig_key **md5)
545{
546 struct tcp_sock *tp = tcp_sk(sk);
547 unsigned int remaining = MAX_TCP_OPTION_SPACE;
548 struct tcp_fastopen_request *fastopen = tp->fastopen_req;
549
550#ifdef CONFIG_TCP_MD5SIG
551 *md5 = tp->af_specific->md5_lookup(sk, sk);
552 if (*md5) {
553 opts->options |= OPTION_MD5;
554 remaining -= TCPOLEN_MD5SIG_ALIGNED;
555 }
556#else
557 *md5 = NULL;
558#endif
559
560 /* We always get an MSS option. The option bytes which will be seen in
561 * normal data packets should timestamps be used, must be in the MSS
562 * advertised. But we subtract them from tp->mss_cache so that
563 * calculations in tcp_sendmsg are simpler etc. So account for this
564 * fact here if necessary. If we don't do this correctly, as a
565 * receiver we won't recognize data packets as being full sized when we
566 * should, and thus we won't abide by the delayed ACK rules correctly.
567 * SACKs don't matter, we never delay an ACK when we have any of those
568 * going out. */
569 opts->mss = tcp_advertise_mss(sk);
570 remaining -= TCPOLEN_MSS_ALIGNED;
571
572 if (likely(sysctl_tcp_timestamps && !*md5)) {
573 opts->options |= OPTION_TS;
574 opts->tsval = tcp_skb_timestamp(skb) + tp->tsoffset;
575 opts->tsecr = tp->rx_opt.ts_recent;
576 remaining -= TCPOLEN_TSTAMP_ALIGNED;
577 }
578 if (likely(sysctl_tcp_window_scaling)) {
579 opts->ws = tp->rx_opt.rcv_wscale;
580 opts->options |= OPTION_WSCALE;
581 remaining -= TCPOLEN_WSCALE_ALIGNED;
582 }
583 if (likely(sysctl_tcp_sack)) {
584 opts->options |= OPTION_SACK_ADVERTISE;
585 if (unlikely(!(OPTION_TS & opts->options)))
586 remaining -= TCPOLEN_SACKPERM_ALIGNED;
587 }
588
589 if (fastopen && fastopen->cookie.len >= 0) {
590 u32 need = fastopen->cookie.len;
591
592 need += fastopen->cookie.exp ? TCPOLEN_EXP_FASTOPEN_BASE :
593 TCPOLEN_FASTOPEN_BASE;
594 need = (need + 3) & ~3U; /* Align to 32 bits */
595 if (remaining >= need) {
596 opts->options |= OPTION_FAST_OPEN_COOKIE;
597 opts->fastopen_cookie = &fastopen->cookie;
598 remaining -= need;
599 tp->syn_fastopen = 1;
600 tp->syn_fastopen_exp = fastopen->cookie.exp ? 1 : 0;
601 }
602 }
603
604 return MAX_TCP_OPTION_SPACE - remaining;
605}
606
607/* Set up TCP options for SYN-ACKs. */
608static unsigned int tcp_synack_options(struct request_sock *req,
609 unsigned int mss, struct sk_buff *skb,
610 struct tcp_out_options *opts,
611 const struct tcp_md5sig_key *md5,
612 struct tcp_fastopen_cookie *foc)
613{
614 struct inet_request_sock *ireq = inet_rsk(req);
615 unsigned int remaining = MAX_TCP_OPTION_SPACE;
616
617#ifdef CONFIG_TCP_MD5SIG
618 if (md5) {
619 opts->options |= OPTION_MD5;
620 remaining -= TCPOLEN_MD5SIG_ALIGNED;
621
622 /* We can't fit any SACK blocks in a packet with MD5 + TS
623 * options. There was discussion about disabling SACK
624 * rather than TS in order to fit in better with old,
625 * buggy kernels, but that was deemed to be unnecessary.
626 */
627 ireq->tstamp_ok &= !ireq->sack_ok;
628 }
629#endif
630
631 /* We always send an MSS option. */
632 opts->mss = mss;
633 remaining -= TCPOLEN_MSS_ALIGNED;
634
635 if (likely(ireq->wscale_ok)) {
636 opts->ws = ireq->rcv_wscale;
637 opts->options |= OPTION_WSCALE;
638 remaining -= TCPOLEN_WSCALE_ALIGNED;
639 }
640 if (likely(ireq->tstamp_ok)) {
641 opts->options |= OPTION_TS;
642 opts->tsval = tcp_skb_timestamp(skb);
643 opts->tsecr = req->ts_recent;
644 remaining -= TCPOLEN_TSTAMP_ALIGNED;
645 }
646 if (likely(ireq->sack_ok)) {
647 opts->options |= OPTION_SACK_ADVERTISE;
648 if (unlikely(!ireq->tstamp_ok))
649 remaining -= TCPOLEN_SACKPERM_ALIGNED;
650 }
651 if (foc != NULL && foc->len >= 0) {
652 u32 need = foc->len;
653
654 need += foc->exp ? TCPOLEN_EXP_FASTOPEN_BASE :
655 TCPOLEN_FASTOPEN_BASE;
656 need = (need + 3) & ~3U; /* Align to 32 bits */
657 if (remaining >= need) {
658 opts->options |= OPTION_FAST_OPEN_COOKIE;
659 opts->fastopen_cookie = foc;
660 remaining -= need;
661 }
662 }
663
664 return MAX_TCP_OPTION_SPACE - remaining;
665}
666
667/* Compute TCP options for ESTABLISHED sockets. This is not the
668 * final wire format yet.
669 */
670static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb,
671 struct tcp_out_options *opts,
672 struct tcp_md5sig_key **md5)
673{
674 struct tcp_sock *tp = tcp_sk(sk);
675 unsigned int size = 0;
676 unsigned int eff_sacks;
677
678 opts->options = 0;
679
680#ifdef CONFIG_TCP_MD5SIG
681 *md5 = tp->af_specific->md5_lookup(sk, sk);
682 if (unlikely(*md5)) {
683 opts->options |= OPTION_MD5;
684 size += TCPOLEN_MD5SIG_ALIGNED;
685 }
686#else
687 *md5 = NULL;
688#endif
689
690 if (likely(tp->rx_opt.tstamp_ok)) {
691 opts->options |= OPTION_TS;
692 opts->tsval = skb ? tcp_skb_timestamp(skb) + tp->tsoffset : 0;
693 opts->tsecr = tp->rx_opt.ts_recent;
694 size += TCPOLEN_TSTAMP_ALIGNED;
695 }
696
697 eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
698 if (unlikely(eff_sacks)) {
699 const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
700 opts->num_sack_blocks =
701 min_t(unsigned int, eff_sacks,
702 (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
703 TCPOLEN_SACK_PERBLOCK);
704 size += TCPOLEN_SACK_BASE_ALIGNED +
705 opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
706 }
707
708 return size;
709}
710
711
712/* TCP SMALL QUEUES (TSQ)
713 *
714 * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
715 * to reduce RTT and bufferbloat.
716 * We do this using a special skb destructor (tcp_wfree).
717 *
718 * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
719 * needs to be reallocated in a driver.
720 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
721 *
722 * Since transmit from skb destructor is forbidden, we use a tasklet
723 * to process all sockets that eventually need to send more skbs.
724 * We use one tasklet per cpu, with its own queue of sockets.
725 */
726struct tsq_tasklet {
727 struct tasklet_struct tasklet;
728 struct list_head head; /* queue of tcp sockets */
729};
730static DEFINE_PER_CPU(struct tsq_tasklet, tsq_tasklet);
731
732static void tcp_tsq_handler(struct sock *sk)
733{
734 if ((1 << sk->sk_state) &
735 (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING |
736 TCPF_CLOSE_WAIT | TCPF_LAST_ACK))
737 tcp_write_xmit(sk, tcp_current_mss(sk), tcp_sk(sk)->nonagle,
738 0, GFP_ATOMIC);
739}
740/*
741 * One tasklet per cpu tries to send more skbs.
742 * We run in tasklet context but need to disable irqs when
743 * transferring tsq->head because tcp_wfree() might
744 * interrupt us (non NAPI drivers)
745 */
746static void tcp_tasklet_func(unsigned long data)
747{
748 struct tsq_tasklet *tsq = (struct tsq_tasklet *)data;
749 LIST_HEAD(list);
750 unsigned long flags;
751 struct list_head *q, *n;
752 struct tcp_sock *tp;
753 struct sock *sk;
754
755 local_irq_save(flags);
756 list_splice_init(&tsq->head, &list);
757 local_irq_restore(flags);
758
759 list_for_each_safe(q, n, &list) {
760 tp = list_entry(q, struct tcp_sock, tsq_node);
761 list_del(&tp->tsq_node);
762
763 sk = (struct sock *)tp;
764 bh_lock_sock(sk);
765
766 if (!sock_owned_by_user(sk)) {
767 tcp_tsq_handler(sk);
768 } else {
769 /* defer the work to tcp_release_cb() */
770 set_bit(TCP_TSQ_DEFERRED, &tp->tsq_flags);
771 }
772 bh_unlock_sock(sk);
773
774 clear_bit(TSQ_QUEUED, &tp->tsq_flags);
775 sk_free(sk);
776 }
777}
778
779#define TCP_DEFERRED_ALL ((1UL << TCP_TSQ_DEFERRED) | \
780 (1UL << TCP_WRITE_TIMER_DEFERRED) | \
781 (1UL << TCP_DELACK_TIMER_DEFERRED) | \
782 (1UL << TCP_MTU_REDUCED_DEFERRED))
783/**
784 * tcp_release_cb - tcp release_sock() callback
785 * @sk: socket
786 *
787 * called from release_sock() to perform protocol dependent
788 * actions before socket release.
789 */
790void tcp_release_cb(struct sock *sk)
791{
792 struct tcp_sock *tp = tcp_sk(sk);
793 unsigned long flags, nflags;
794
795 /* perform an atomic operation only if at least one flag is set */
796 do {
797 flags = tp->tsq_flags;
798 if (!(flags & TCP_DEFERRED_ALL))
799 return;
800 nflags = flags & ~TCP_DEFERRED_ALL;
801 } while (cmpxchg(&tp->tsq_flags, flags, nflags) != flags);
802
803 if (flags & (1UL << TCP_TSQ_DEFERRED))
804 tcp_tsq_handler(sk);
805
806 /* Here begins the tricky part :
807 * We are called from release_sock() with :
808 * 1) BH disabled
809 * 2) sk_lock.slock spinlock held
810 * 3) socket owned by us (sk->sk_lock.owned == 1)
811 *
812 * But following code is meant to be called from BH handlers,
813 * so we should keep BH disabled, but early release socket ownership
814 */
815 sock_release_ownership(sk);
816
817 if (flags & (1UL << TCP_WRITE_TIMER_DEFERRED)) {
818 tcp_write_timer_handler(sk);
819 __sock_put(sk);
820 }
821 if (flags & (1UL << TCP_DELACK_TIMER_DEFERRED)) {
822 tcp_delack_timer_handler(sk);
823 __sock_put(sk);
824 }
825 if (flags & (1UL << TCP_MTU_REDUCED_DEFERRED)) {
826 inet_csk(sk)->icsk_af_ops->mtu_reduced(sk);
827 __sock_put(sk);
828 }
829}
830EXPORT_SYMBOL(tcp_release_cb);
831
832void __init tcp_tasklet_init(void)
833{
834 int i;
835
836 for_each_possible_cpu(i) {
837 struct tsq_tasklet *tsq = &per_cpu(tsq_tasklet, i);
838
839 INIT_LIST_HEAD(&tsq->head);
840 tasklet_init(&tsq->tasklet,
841 tcp_tasklet_func,
842 (unsigned long)tsq);
843 }
844}
845
846/*
847 * Write buffer destructor automatically called from kfree_skb.
848 * We can't xmit new skbs from this context, as we might already
849 * hold qdisc lock.
850 */
851void tcp_wfree(struct sk_buff *skb)
852{
853 struct sock *sk = skb->sk;
854 struct tcp_sock *tp = tcp_sk(sk);
855 int wmem;
856
857 /* Keep one reference on sk_wmem_alloc.
858 * Will be released by sk_free() from here or tcp_tasklet_func()
859 */
860 wmem = atomic_sub_return(skb->truesize - 1, &sk->sk_wmem_alloc);
861
862 /* If this softirq is serviced by ksoftirqd, we are likely under stress.
863 * Wait until our queues (qdisc + devices) are drained.
864 * This gives :
865 * - less callbacks to tcp_write_xmit(), reducing stress (batches)
866 * - chance for incoming ACK (processed by another cpu maybe)
867 * to migrate this flow (skb->ooo_okay will be eventually set)
868 */
869 if (wmem >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current)
870 goto out;
871
872 if (test_and_clear_bit(TSQ_THROTTLED, &tp->tsq_flags) &&
873 !test_and_set_bit(TSQ_QUEUED, &tp->tsq_flags)) {
874 unsigned long flags;
875 struct tsq_tasklet *tsq;
876
877 /* queue this socket to tasklet queue */
878 local_irq_save(flags);
879 tsq = this_cpu_ptr(&tsq_tasklet);
880 list_add(&tp->tsq_node, &tsq->head);
881 tasklet_schedule(&tsq->tasklet);
882 local_irq_restore(flags);
883 return;
884 }
885out:
886 sk_free(sk);
887}
888
889/* This routine actually transmits TCP packets queued in by
890 * tcp_do_sendmsg(). This is used by both the initial
891 * transmission and possible later retransmissions.
892 * All SKB's seen here are completely headerless. It is our
893 * job to build the TCP header, and pass the packet down to
894 * IP so it can do the same plus pass the packet off to the
895 * device.
896 *
897 * We are working here with either a clone of the original
898 * SKB, or a fresh unique copy made by the retransmit engine.
899 */
900static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
901 gfp_t gfp_mask)
902{
903 const struct inet_connection_sock *icsk = inet_csk(sk);
904 struct inet_sock *inet;
905 struct tcp_sock *tp;
906 struct tcp_skb_cb *tcb;
907 struct tcp_out_options opts;
908 unsigned int tcp_options_size, tcp_header_size;
909 struct tcp_md5sig_key *md5;
910 struct tcphdr *th;
911 int err;
912
913 BUG_ON(!skb || !tcp_skb_pcount(skb));
914
915 if (clone_it) {
916 skb_mstamp_get(&skb->skb_mstamp);
917
918 if (unlikely(skb_cloned(skb)))
919 skb = pskb_copy(skb, gfp_mask);
920 else
921 skb = skb_clone(skb, gfp_mask);
922 if (unlikely(!skb))
923 return -ENOBUFS;
924 }
925
926 inet = inet_sk(sk);
927 tp = tcp_sk(sk);
928 tcb = TCP_SKB_CB(skb);
929 memset(&opts, 0, sizeof(opts));
930
931 if (unlikely(tcb->tcp_flags & TCPHDR_SYN))
932 tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5);
933 else
934 tcp_options_size = tcp_established_options(sk, skb, &opts,
935 &md5);
936 tcp_header_size = tcp_options_size + sizeof(struct tcphdr);
937
938 /* if no packet is in qdisc/device queue, then allow XPS to select
939 * another queue. We can be called from tcp_tsq_handler()
940 * which holds one reference to sk_wmem_alloc.
941 *
942 * TODO: Ideally, in-flight pure ACK packets should not matter here.
943 * One way to get this would be to set skb->truesize = 2 on them.
944 */
945 skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1);
946
947 skb_push(skb, tcp_header_size);
948 skb_reset_transport_header(skb);
949
950 skb_orphan(skb);
951 skb->sk = sk;
952 skb->destructor = skb_is_tcp_pure_ack(skb) ? sock_wfree : tcp_wfree;
953 skb_set_hash_from_sk(skb, sk);
954 atomic_add(skb->truesize, &sk->sk_wmem_alloc);
955
956 /* Build TCP header and checksum it. */
957 th = tcp_hdr(skb);
958 th->source = inet->inet_sport;
959 th->dest = inet->inet_dport;
960 th->seq = htonl(tcb->seq);
961 th->ack_seq = htonl(tp->rcv_nxt);
962 *(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) |
963 tcb->tcp_flags);
964
965 if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) {
966 /* RFC1323: The window in SYN & SYN/ACK segments
967 * is never scaled.
968 */
969 th->window = htons(min(tp->rcv_wnd, 65535U));
970 } else {
971 th->window = htons(tcp_select_window(sk));
972 }
973 th->check = 0;
974 th->urg_ptr = 0;
975
976 /* The urg_mode check is necessary during a below snd_una win probe */
977 if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) {
978 if (before(tp->snd_up, tcb->seq + 0x10000)) {
979 th->urg_ptr = htons(tp->snd_up - tcb->seq);
980 th->urg = 1;
981 } else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
982 th->urg_ptr = htons(0xFFFF);
983 th->urg = 1;
984 }
985 }
986
987 tcp_options_write((__be32 *)(th + 1), tp, &opts);
988 skb_shinfo(skb)->gso_type = sk->sk_gso_type;
989 if (likely((tcb->tcp_flags & TCPHDR_SYN) == 0))
990 tcp_ecn_send(sk, skb, tcp_header_size);
991
992#ifdef CONFIG_TCP_MD5SIG
993 /* Calculate the MD5 hash, as we have all we need now */
994 if (md5) {
995 sk_nocaps_add(sk, NETIF_F_GSO_MASK);
996 tp->af_specific->calc_md5_hash(opts.hash_location,
997 md5, sk, skb);
998 }
999#endif
1000
1001 icsk->icsk_af_ops->send_check(sk, skb);
1002
1003 if (likely(tcb->tcp_flags & TCPHDR_ACK))
1004 tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
1005
1006 if (skb->len != tcp_header_size) {
1007 tcp_event_data_sent(tp, sk);
1008 tp->data_segs_out += tcp_skb_pcount(skb);
1009 }
1010
1011 if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
1012 TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
1013 tcp_skb_pcount(skb));
1014
1015 tp->segs_out += tcp_skb_pcount(skb);
1016 /* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
1017 skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb);
1018 skb_shinfo(skb)->gso_size = tcp_skb_mss(skb);
1019
1020 /* Our usage of tstamp should remain private */
1021 skb->tstamp.tv64 = 0;
1022
1023 /* Cleanup our debris for IP stacks */
1024 memset(skb->cb, 0, max(sizeof(struct inet_skb_parm),
1025 sizeof(struct inet6_skb_parm)));
1026
1027 err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
1028
1029 if (likely(err <= 0))
1030 return err;
1031
1032 tcp_enter_cwr(sk);
1033
1034 return net_xmit_eval(err);
1035}
1036
1037/* This routine just queues the buffer for sending.
1038 *
1039 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
1040 * otherwise socket can stall.
1041 */
1042static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
1043{
1044 struct tcp_sock *tp = tcp_sk(sk);
1045
1046 /* Advance write_seq and place onto the write_queue. */
1047 tp->write_seq = TCP_SKB_CB(skb)->end_seq;
1048 __skb_header_release(skb);
1049 tcp_add_write_queue_tail(sk, skb);
1050 sk->sk_wmem_queued += skb->truesize;
1051 sk_mem_charge(sk, skb->truesize);
1052}
1053
1054/* Initialize TSO segments for a packet. */
1055static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1056{
1057 if (skb->len <= mss_now || skb->ip_summed == CHECKSUM_NONE) {
1058 /* Avoid the costly divide in the normal
1059 * non-TSO case.
1060 */
1061 tcp_skb_pcount_set(skb, 1);
1062 TCP_SKB_CB(skb)->tcp_gso_size = 0;
1063 } else {
1064 tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now));
1065 TCP_SKB_CB(skb)->tcp_gso_size = mss_now;
1066 }
1067}
1068
1069/* When a modification to fackets out becomes necessary, we need to check
1070 * skb is counted to fackets_out or not.
1071 */
1072static void tcp_adjust_fackets_out(struct sock *sk, const struct sk_buff *skb,
1073 int decr)
1074{
1075 struct tcp_sock *tp = tcp_sk(sk);
1076
1077 if (!tp->sacked_out || tcp_is_reno(tp))
1078 return;
1079
1080 if (after(tcp_highest_sack_seq(tp), TCP_SKB_CB(skb)->seq))
1081 tp->fackets_out -= decr;
1082}
1083
1084/* Pcount in the middle of the write queue got changed, we need to do various
1085 * tweaks to fix counters
1086 */
1087static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
1088{
1089 struct tcp_sock *tp = tcp_sk(sk);
1090
1091 tp->packets_out -= decr;
1092
1093 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
1094 tp->sacked_out -= decr;
1095 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
1096 tp->retrans_out -= decr;
1097 if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)
1098 tp->lost_out -= decr;
1099
1100 /* Reno case is special. Sigh... */
1101 if (tcp_is_reno(tp) && decr > 0)
1102 tp->sacked_out -= min_t(u32, tp->sacked_out, decr);
1103
1104 tcp_adjust_fackets_out(sk, skb, decr);
1105
1106 if (tp->lost_skb_hint &&
1107 before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) &&
1108 (tcp_is_fack(tp) || (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)))
1109 tp->lost_cnt_hint -= decr;
1110
1111 tcp_verify_left_out(tp);
1112}
1113
1114static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2)
1115{
1116 struct skb_shared_info *shinfo = skb_shinfo(skb);
1117
1118 if (unlikely(shinfo->tx_flags & SKBTX_ANY_TSTAMP) &&
1119 !before(shinfo->tskey, TCP_SKB_CB(skb2)->seq)) {
1120 struct skb_shared_info *shinfo2 = skb_shinfo(skb2);
1121 u8 tsflags = shinfo->tx_flags & SKBTX_ANY_TSTAMP;
1122
1123 shinfo->tx_flags &= ~tsflags;
1124 shinfo2->tx_flags |= tsflags;
1125 swap(shinfo->tskey, shinfo2->tskey);
1126 }
1127}
1128
1129/* Function to create two new TCP segments. Shrinks the given segment
1130 * to the specified size and appends a new segment with the rest of the
1131 * packet to the list. This won't be called frequently, I hope.
1132 * Remember, these are still headerless SKBs at this point.
1133 */
1134int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
1135 unsigned int mss_now, gfp_t gfp)
1136{
1137 struct tcp_sock *tp = tcp_sk(sk);
1138 struct sk_buff *buff;
1139 int nsize, old_factor;
1140 int nlen;
1141 u8 flags;
1142
1143 if (WARN_ON(len > skb->len))
1144 return -EINVAL;
1145
1146 nsize = skb_headlen(skb) - len;
1147 if (nsize < 0)
1148 nsize = 0;
1149
1150 if (skb_unclone(skb, gfp))
1151 return -ENOMEM;
1152
1153 /* Get a new skb... force flag on. */
1154 buff = sk_stream_alloc_skb(sk, nsize, gfp, true);
1155 if (!buff)
1156 return -ENOMEM; /* We'll just try again later. */
1157
1158 sk->sk_wmem_queued += buff->truesize;
1159 sk_mem_charge(sk, buff->truesize);
1160 nlen = skb->len - len - nsize;
1161 buff->truesize += nlen;
1162 skb->truesize -= nlen;
1163
1164 /* Correct the sequence numbers. */
1165 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1166 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1167 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1168
1169 /* PSH and FIN should only be set in the second packet. */
1170 flags = TCP_SKB_CB(skb)->tcp_flags;
1171 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
1172 TCP_SKB_CB(buff)->tcp_flags = flags;
1173 TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
1174
1175 if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) {
1176 /* Copy and checksum data tail into the new buffer. */
1177 buff->csum = csum_partial_copy_nocheck(skb->data + len,
1178 skb_put(buff, nsize),
1179 nsize, 0);
1180
1181 skb_trim(skb, len);
1182
1183 skb->csum = csum_block_sub(skb->csum, buff->csum, len);
1184 } else {
1185 skb->ip_summed = CHECKSUM_PARTIAL;
1186 skb_split(skb, buff, len);
1187 }
1188
1189 buff->ip_summed = skb->ip_summed;
1190
1191 buff->tstamp = skb->tstamp;
1192 tcp_fragment_tstamp(skb, buff);
1193
1194 old_factor = tcp_skb_pcount(skb);
1195
1196 /* Fix up tso_factor for both original and new SKB. */
1197 tcp_set_skb_tso_segs(skb, mss_now);
1198 tcp_set_skb_tso_segs(buff, mss_now);
1199
1200 /* If this packet has been sent out already, we must
1201 * adjust the various packet counters.
1202 */
1203 if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1204 int diff = old_factor - tcp_skb_pcount(skb) -
1205 tcp_skb_pcount(buff);
1206
1207 if (diff)
1208 tcp_adjust_pcount(sk, skb, diff);
1209 }
1210
1211 /* Link BUFF into the send queue. */
1212 __skb_header_release(buff);
1213 tcp_insert_write_queue_after(skb, buff, sk);
1214
1215 return 0;
1216}
1217
1218/* This is similar to __pskb_pull_head() (it will go to core/skbuff.c
1219 * eventually). The difference is that pulled data not copied, but
1220 * immediately discarded.
1221 */
1222static void __pskb_trim_head(struct sk_buff *skb, int len)
1223{
1224 struct skb_shared_info *shinfo;
1225 int i, k, eat;
1226
1227 eat = min_t(int, len, skb_headlen(skb));
1228 if (eat) {
1229 __skb_pull(skb, eat);
1230 len -= eat;
1231 if (!len)
1232 return;
1233 }
1234 eat = len;
1235 k = 0;
1236 shinfo = skb_shinfo(skb);
1237 for (i = 0; i < shinfo->nr_frags; i++) {
1238 int size = skb_frag_size(&shinfo->frags[i]);
1239
1240 if (size <= eat) {
1241 skb_frag_unref(skb, i);
1242 eat -= size;
1243 } else {
1244 shinfo->frags[k] = shinfo->frags[i];
1245 if (eat) {
1246 shinfo->frags[k].page_offset += eat;
1247 skb_frag_size_sub(&shinfo->frags[k], eat);
1248 eat = 0;
1249 }
1250 k++;
1251 }
1252 }
1253 shinfo->nr_frags = k;
1254
1255 skb_reset_tail_pointer(skb);
1256 skb->data_len -= len;
1257 skb->len = skb->data_len;
1258}
1259
1260/* Remove acked data from a packet in the transmit queue. */
1261int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
1262{
1263 if (skb_unclone(skb, GFP_ATOMIC))
1264 return -ENOMEM;
1265
1266 __pskb_trim_head(skb, len);
1267
1268 TCP_SKB_CB(skb)->seq += len;
1269 skb->ip_summed = CHECKSUM_PARTIAL;
1270
1271 skb->truesize -= len;
1272 sk->sk_wmem_queued -= len;
1273 sk_mem_uncharge(sk, len);
1274 sock_set_flag(sk, SOCK_QUEUE_SHRUNK);
1275
1276 /* Any change of skb->len requires recalculation of tso factor. */
1277 if (tcp_skb_pcount(skb) > 1)
1278 tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb));
1279
1280 return 0;
1281}
1282
1283/* Calculate MSS not accounting any TCP options. */
1284static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu)
1285{
1286 const struct tcp_sock *tp = tcp_sk(sk);
1287 const struct inet_connection_sock *icsk = inet_csk(sk);
1288 int mss_now;
1289
1290 /* Calculate base mss without TCP options:
1291 It is MMS_S - sizeof(tcphdr) of rfc1122
1292 */
1293 mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr);
1294
1295 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1296 if (icsk->icsk_af_ops->net_frag_header_len) {
1297 const struct dst_entry *dst = __sk_dst_get(sk);
1298
1299 if (dst && dst_allfrag(dst))
1300 mss_now -= icsk->icsk_af_ops->net_frag_header_len;
1301 }
1302
1303 /* Clamp it (mss_clamp does not include tcp options) */
1304 if (mss_now > tp->rx_opt.mss_clamp)
1305 mss_now = tp->rx_opt.mss_clamp;
1306
1307 /* Now subtract optional transport overhead */
1308 mss_now -= icsk->icsk_ext_hdr_len;
1309
1310 /* Then reserve room for full set of TCP options and 8 bytes of data */
1311 if (mss_now < 48)
1312 mss_now = 48;
1313 return mss_now;
1314}
1315
1316/* Calculate MSS. Not accounting for SACKs here. */
1317int tcp_mtu_to_mss(struct sock *sk, int pmtu)
1318{
1319 /* Subtract TCP options size, not including SACKs */
1320 return __tcp_mtu_to_mss(sk, pmtu) -
1321 (tcp_sk(sk)->tcp_header_len - sizeof(struct tcphdr));
1322}
1323
1324/* Inverse of above */
1325int tcp_mss_to_mtu(struct sock *sk, int mss)
1326{
1327 const struct tcp_sock *tp = tcp_sk(sk);
1328 const struct inet_connection_sock *icsk = inet_csk(sk);
1329 int mtu;
1330
1331 mtu = mss +
1332 tp->tcp_header_len +
1333 icsk->icsk_ext_hdr_len +
1334 icsk->icsk_af_ops->net_header_len;
1335
1336 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1337 if (icsk->icsk_af_ops->net_frag_header_len) {
1338 const struct dst_entry *dst = __sk_dst_get(sk);
1339
1340 if (dst && dst_allfrag(dst))
1341 mtu += icsk->icsk_af_ops->net_frag_header_len;
1342 }
1343 return mtu;
1344}
1345
1346/* MTU probing init per socket */
1347void tcp_mtup_init(struct sock *sk)
1348{
1349 struct tcp_sock *tp = tcp_sk(sk);
1350 struct inet_connection_sock *icsk = inet_csk(sk);
1351 struct net *net = sock_net(sk);
1352
1353 icsk->icsk_mtup.enabled = net->ipv4.sysctl_tcp_mtu_probing > 1;
1354 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1355 icsk->icsk_af_ops->net_header_len;
1356 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss);
1357 icsk->icsk_mtup.probe_size = 0;
1358 if (icsk->icsk_mtup.enabled)
1359 icsk->icsk_mtup.probe_timestamp = tcp_time_stamp;
1360}
1361EXPORT_SYMBOL(tcp_mtup_init);
1362
1363/* This function synchronize snd mss to current pmtu/exthdr set.
1364
1365 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
1366 for TCP options, but includes only bare TCP header.
1367
1368 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1369 It is minimum of user_mss and mss received with SYN.
1370 It also does not include TCP options.
1371
1372 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
1373
1374 tp->mss_cache is current effective sending mss, including
1375 all tcp options except for SACKs. It is evaluated,
1376 taking into account current pmtu, but never exceeds
1377 tp->rx_opt.mss_clamp.
1378
1379 NOTE1. rfc1122 clearly states that advertised MSS
1380 DOES NOT include either tcp or ip options.
1381
1382 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1383 are READ ONLY outside this function. --ANK (980731)
1384 */
1385unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
1386{
1387 struct tcp_sock *tp = tcp_sk(sk);
1388 struct inet_connection_sock *icsk = inet_csk(sk);
1389 int mss_now;
1390
1391 if (icsk->icsk_mtup.search_high > pmtu)
1392 icsk->icsk_mtup.search_high = pmtu;
1393
1394 mss_now = tcp_mtu_to_mss(sk, pmtu);
1395 mss_now = tcp_bound_to_half_wnd(tp, mss_now);
1396
1397 /* And store cached results */
1398 icsk->icsk_pmtu_cookie = pmtu;
1399 if (icsk->icsk_mtup.enabled)
1400 mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1401 tp->mss_cache = mss_now;
1402
1403 return mss_now;
1404}
1405EXPORT_SYMBOL(tcp_sync_mss);
1406
1407/* Compute the current effective MSS, taking SACKs and IP options,
1408 * and even PMTU discovery events into account.
1409 */
1410unsigned int tcp_current_mss(struct sock *sk)
1411{
1412 const struct tcp_sock *tp = tcp_sk(sk);
1413 const struct dst_entry *dst = __sk_dst_get(sk);
1414 u32 mss_now;
1415 unsigned int header_len;
1416 struct tcp_out_options opts;
1417 struct tcp_md5sig_key *md5;
1418
1419 mss_now = tp->mss_cache;
1420
1421 if (dst) {
1422 u32 mtu = dst_mtu(dst);
1423 if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
1424 mss_now = tcp_sync_mss(sk, mtu);
1425 }
1426
1427 header_len = tcp_established_options(sk, NULL, &opts, &md5) +
1428 sizeof(struct tcphdr);
1429 /* The mss_cache is sized based on tp->tcp_header_len, which assumes
1430 * some common options. If this is an odd packet (because we have SACK
1431 * blocks etc) then our calculated header_len will be different, and
1432 * we have to adjust mss_now correspondingly */
1433 if (header_len != tp->tcp_header_len) {
1434 int delta = (int) header_len - tp->tcp_header_len;
1435 mss_now -= delta;
1436 }
1437
1438 return mss_now;
1439}
1440
1441/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
1442 * As additional protections, we do not touch cwnd in retransmission phases,
1443 * and if application hit its sndbuf limit recently.
1444 */
1445static void tcp_cwnd_application_limited(struct sock *sk)
1446{
1447 struct tcp_sock *tp = tcp_sk(sk);
1448
1449 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
1450 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
1451 /* Limited by application or receiver window. */
1452 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk));
1453 u32 win_used = max(tp->snd_cwnd_used, init_win);
1454 if (win_used < tp->snd_cwnd) {
1455 tp->snd_ssthresh = tcp_current_ssthresh(sk);
1456 tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
1457 }
1458 tp->snd_cwnd_used = 0;
1459 }
1460 tp->snd_cwnd_stamp = tcp_time_stamp;
1461}
1462
1463static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
1464{
1465 struct tcp_sock *tp = tcp_sk(sk);
1466
1467 /* Track the maximum number of outstanding packets in each
1468 * window, and remember whether we were cwnd-limited then.
1469 */
1470 if (!before(tp->snd_una, tp->max_packets_seq) ||
1471 tp->packets_out > tp->max_packets_out) {
1472 tp->max_packets_out = tp->packets_out;
1473 tp->max_packets_seq = tp->snd_nxt;
1474 tp->is_cwnd_limited = is_cwnd_limited;
1475 }
1476
1477 if (tcp_is_cwnd_limited(sk)) {
1478 /* Network is feed fully. */
1479 tp->snd_cwnd_used = 0;
1480 tp->snd_cwnd_stamp = tcp_time_stamp;
1481 } else {
1482 /* Network starves. */
1483 if (tp->packets_out > tp->snd_cwnd_used)
1484 tp->snd_cwnd_used = tp->packets_out;
1485
1486 if (sysctl_tcp_slow_start_after_idle &&
1487 (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto)
1488 tcp_cwnd_application_limited(sk);
1489 }
1490}
1491
1492/* Minshall's variant of the Nagle send check. */
1493static bool tcp_minshall_check(const struct tcp_sock *tp)
1494{
1495 return after(tp->snd_sml, tp->snd_una) &&
1496 !after(tp->snd_sml, tp->snd_nxt);
1497}
1498
1499/* Update snd_sml if this skb is under mss
1500 * Note that a TSO packet might end with a sub-mss segment
1501 * The test is really :
1502 * if ((skb->len % mss) != 0)
1503 * tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1504 * But we can avoid doing the divide again given we already have
1505 * skb_pcount = skb->len / mss_now
1506 */
1507static void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss_now,
1508 const struct sk_buff *skb)
1509{
1510 if (skb->len < tcp_skb_pcount(skb) * mss_now)
1511 tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1512}
1513
1514/* Return false, if packet can be sent now without violation Nagle's rules:
1515 * 1. It is full sized. (provided by caller in %partial bool)
1516 * 2. Or it contains FIN. (already checked by caller)
1517 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
1518 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1519 * With Minshall's modification: all sent small packets are ACKed.
1520 */
1521static bool tcp_nagle_check(bool partial, const struct tcp_sock *tp,
1522 int nonagle)
1523{
1524 return partial &&
1525 ((nonagle & TCP_NAGLE_CORK) ||
1526 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
1527}
1528
1529/* Return how many segs we'd like on a TSO packet,
1530 * to send one TSO packet per ms
1531 */
1532static u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now)
1533{
1534 u32 bytes, segs;
1535
1536 bytes = min(sk->sk_pacing_rate >> 10,
1537 sk->sk_gso_max_size - 1 - MAX_TCP_HEADER);
1538
1539 /* Goal is to send at least one packet per ms,
1540 * not one big TSO packet every 100 ms.
1541 * This preserves ACK clocking and is consistent
1542 * with tcp_tso_should_defer() heuristic.
1543 */
1544 segs = max_t(u32, bytes / mss_now, sysctl_tcp_min_tso_segs);
1545
1546 return min_t(u32, segs, sk->sk_gso_max_segs);
1547}
1548
1549/* Returns the portion of skb which can be sent right away */
1550static unsigned int tcp_mss_split_point(const struct sock *sk,
1551 const struct sk_buff *skb,
1552 unsigned int mss_now,
1553 unsigned int max_segs,
1554 int nonagle)
1555{
1556 const struct tcp_sock *tp = tcp_sk(sk);
1557 u32 partial, needed, window, max_len;
1558
1559 window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1560 max_len = mss_now * max_segs;
1561
1562 if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
1563 return max_len;
1564
1565 needed = min(skb->len, window);
1566
1567 if (max_len <= needed)
1568 return max_len;
1569
1570 partial = needed % mss_now;
1571 /* If last segment is not a full MSS, check if Nagle rules allow us
1572 * to include this last segment in this skb.
1573 * Otherwise, we'll split the skb at last MSS boundary
1574 */
1575 if (tcp_nagle_check(partial != 0, tp, nonagle))
1576 return needed - partial;
1577
1578 return needed;
1579}
1580
1581/* Can at least one segment of SKB be sent right now, according to the
1582 * congestion window rules? If so, return how many segments are allowed.
1583 */
1584static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
1585 const struct sk_buff *skb)
1586{
1587 u32 in_flight, cwnd, halfcwnd;
1588
1589 /* Don't be strict about the congestion window for the final FIN. */
1590 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
1591 tcp_skb_pcount(skb) == 1)
1592 return 1;
1593
1594 in_flight = tcp_packets_in_flight(tp);
1595 cwnd = tp->snd_cwnd;
1596 if (in_flight >= cwnd)
1597 return 0;
1598
1599 /* For better scheduling, ensure we have at least
1600 * 2 GSO packets in flight.
1601 */
1602 halfcwnd = max(cwnd >> 1, 1U);
1603 return min(halfcwnd, cwnd - in_flight);
1604}
1605
1606/* Initialize TSO state of a skb.
1607 * This must be invoked the first time we consider transmitting
1608 * SKB onto the wire.
1609 */
1610static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now)
1611{
1612 int tso_segs = tcp_skb_pcount(skb);
1613
1614 if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
1615 tcp_set_skb_tso_segs(skb, mss_now);
1616 tso_segs = tcp_skb_pcount(skb);
1617 }
1618 return tso_segs;
1619}
1620
1621
1622/* Return true if the Nagle test allows this packet to be
1623 * sent now.
1624 */
1625static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
1626 unsigned int cur_mss, int nonagle)
1627{
1628 /* Nagle rule does not apply to frames, which sit in the middle of the
1629 * write_queue (they have no chances to get new data).
1630 *
1631 * This is implemented in the callers, where they modify the 'nonagle'
1632 * argument based upon the location of SKB in the send queue.
1633 */
1634 if (nonagle & TCP_NAGLE_PUSH)
1635 return true;
1636
1637 /* Don't use the nagle rule for urgent data (or for the final FIN). */
1638 if (tcp_urg_mode(tp) || (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
1639 return true;
1640
1641 if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle))
1642 return true;
1643
1644 return false;
1645}
1646
1647/* Does at least the first segment of SKB fit into the send window? */
1648static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
1649 const struct sk_buff *skb,
1650 unsigned int cur_mss)
1651{
1652 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
1653
1654 if (skb->len > cur_mss)
1655 end_seq = TCP_SKB_CB(skb)->seq + cur_mss;
1656
1657 return !after(end_seq, tcp_wnd_end(tp));
1658}
1659
1660/* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1661 * should be put on the wire right now. If so, it returns the number of
1662 * packets allowed by the congestion window.
1663 */
1664static unsigned int tcp_snd_test(const struct sock *sk, struct sk_buff *skb,
1665 unsigned int cur_mss, int nonagle)
1666{
1667 const struct tcp_sock *tp = tcp_sk(sk);
1668 unsigned int cwnd_quota;
1669
1670 tcp_init_tso_segs(skb, cur_mss);
1671
1672 if (!tcp_nagle_test(tp, skb, cur_mss, nonagle))
1673 return 0;
1674
1675 cwnd_quota = tcp_cwnd_test(tp, skb);
1676 if (cwnd_quota && !tcp_snd_wnd_test(tp, skb, cur_mss))
1677 cwnd_quota = 0;
1678
1679 return cwnd_quota;
1680}
1681
1682/* Test if sending is allowed right now. */
1683bool tcp_may_send_now(struct sock *sk)
1684{
1685 const struct tcp_sock *tp = tcp_sk(sk);
1686 struct sk_buff *skb = tcp_send_head(sk);
1687
1688 return skb &&
1689 tcp_snd_test(sk, skb, tcp_current_mss(sk),
1690 (tcp_skb_is_last(sk, skb) ?
1691 tp->nonagle : TCP_NAGLE_PUSH));
1692}
1693
1694/* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
1695 * which is put after SKB on the list. It is very much like
1696 * tcp_fragment() except that it may make several kinds of assumptions
1697 * in order to speed up the splitting operation. In particular, we
1698 * know that all the data is in scatter-gather pages, and that the
1699 * packet has never been sent out before (and thus is not cloned).
1700 */
1701static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
1702 unsigned int mss_now, gfp_t gfp)
1703{
1704 struct sk_buff *buff;
1705 int nlen = skb->len - len;
1706 u8 flags;
1707
1708 /* All of a TSO frame must be composed of paged data. */
1709 if (skb->len != skb->data_len)
1710 return tcp_fragment(sk, skb, len, mss_now, gfp);
1711
1712 buff = sk_stream_alloc_skb(sk, 0, gfp, true);
1713 if (unlikely(!buff))
1714 return -ENOMEM;
1715
1716 sk->sk_wmem_queued += buff->truesize;
1717 sk_mem_charge(sk, buff->truesize);
1718 buff->truesize += nlen;
1719 skb->truesize -= nlen;
1720
1721 /* Correct the sequence numbers. */
1722 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1723 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1724 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1725
1726 /* PSH and FIN should only be set in the second packet. */
1727 flags = TCP_SKB_CB(skb)->tcp_flags;
1728 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
1729 TCP_SKB_CB(buff)->tcp_flags = flags;
1730
1731 /* This packet was never sent out yet, so no SACK bits. */
1732 TCP_SKB_CB(buff)->sacked = 0;
1733
1734 buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL;
1735 skb_split(skb, buff, len);
1736 tcp_fragment_tstamp(skb, buff);
1737
1738 /* Fix up tso_factor for both original and new SKB. */
1739 tcp_set_skb_tso_segs(skb, mss_now);
1740 tcp_set_skb_tso_segs(buff, mss_now);
1741
1742 /* Link BUFF into the send queue. */
1743 __skb_header_release(buff);
1744 tcp_insert_write_queue_after(skb, buff, sk);
1745
1746 return 0;
1747}
1748
1749/* Try to defer sending, if possible, in order to minimize the amount
1750 * of TSO splitting we do. View it as a kind of TSO Nagle test.
1751 *
1752 * This algorithm is from John Heffner.
1753 */
1754static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
1755 bool *is_cwnd_limited, u32 max_segs)
1756{
1757 const struct inet_connection_sock *icsk = inet_csk(sk);
1758 u32 age, send_win, cong_win, limit, in_flight;
1759 struct tcp_sock *tp = tcp_sk(sk);
1760 struct skb_mstamp now;
1761 struct sk_buff *head;
1762 int win_divisor;
1763
1764 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
1765 goto send_now;
1766
1767 if (icsk->icsk_ca_state >= TCP_CA_Recovery)
1768 goto send_now;
1769
1770 /* Avoid bursty behavior by allowing defer
1771 * only if the last write was recent.
1772 */
1773 if ((s32)(tcp_time_stamp - tp->lsndtime) > 0)
1774 goto send_now;
1775
1776 in_flight = tcp_packets_in_flight(tp);
1777
1778 BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight));
1779
1780 send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1781
1782 /* From in_flight test above, we know that cwnd > in_flight. */
1783 cong_win = (tp->snd_cwnd - in_flight) * tp->mss_cache;
1784
1785 limit = min(send_win, cong_win);
1786
1787 /* If a full-sized TSO skb can be sent, do it. */
1788 if (limit >= max_segs * tp->mss_cache)
1789 goto send_now;
1790
1791 /* Middle in queue won't get any more data, full sendable already? */
1792 if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len))
1793 goto send_now;
1794
1795 win_divisor = ACCESS_ONCE(sysctl_tcp_tso_win_divisor);
1796 if (win_divisor) {
1797 u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache);
1798
1799 /* If at least some fraction of a window is available,
1800 * just use it.
1801 */
1802 chunk /= win_divisor;
1803 if (limit >= chunk)
1804 goto send_now;
1805 } else {
1806 /* Different approach, try not to defer past a single
1807 * ACK. Receiver should ACK every other full sized
1808 * frame, so if we have space for more than 3 frames
1809 * then send now.
1810 */
1811 if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
1812 goto send_now;
1813 }
1814
1815 head = tcp_write_queue_head(sk);
1816 skb_mstamp_get(&now);
1817 age = skb_mstamp_us_delta(&now, &head->skb_mstamp);
1818 /* If next ACK is likely to come too late (half srtt), do not defer */
1819 if (age < (tp->srtt_us >> 4))
1820 goto send_now;
1821
1822 /* Ok, it looks like it is advisable to defer. */
1823
1824 if (cong_win < send_win && cong_win <= skb->len)
1825 *is_cwnd_limited = true;
1826
1827 return true;
1828
1829send_now:
1830 return false;
1831}
1832
1833static inline void tcp_mtu_check_reprobe(struct sock *sk)
1834{
1835 struct inet_connection_sock *icsk = inet_csk(sk);
1836 struct tcp_sock *tp = tcp_sk(sk);
1837 struct net *net = sock_net(sk);
1838 u32 interval;
1839 s32 delta;
1840
1841 interval = net->ipv4.sysctl_tcp_probe_interval;
1842 delta = tcp_time_stamp - icsk->icsk_mtup.probe_timestamp;
1843 if (unlikely(delta >= interval * HZ)) {
1844 int mss = tcp_current_mss(sk);
1845
1846 /* Update current search range */
1847 icsk->icsk_mtup.probe_size = 0;
1848 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp +
1849 sizeof(struct tcphdr) +
1850 icsk->icsk_af_ops->net_header_len;
1851 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
1852
1853 /* Update probe time stamp */
1854 icsk->icsk_mtup.probe_timestamp = tcp_time_stamp;
1855 }
1856}
1857
1858/* Create a new MTU probe if we are ready.
1859 * MTU probe is regularly attempting to increase the path MTU by
1860 * deliberately sending larger packets. This discovers routing
1861 * changes resulting in larger path MTUs.
1862 *
1863 * Returns 0 if we should wait to probe (no cwnd available),
1864 * 1 if a probe was sent,
1865 * -1 otherwise
1866 */
1867static int tcp_mtu_probe(struct sock *sk)
1868{
1869 struct tcp_sock *tp = tcp_sk(sk);
1870 struct inet_connection_sock *icsk = inet_csk(sk);
1871 struct sk_buff *skb, *nskb, *next;
1872 struct net *net = sock_net(sk);
1873 int len;
1874 int probe_size;
1875 int size_needed;
1876 int copy;
1877 int mss_now;
1878 int interval;
1879
1880 /* Not currently probing/verifying,
1881 * not in recovery,
1882 * have enough cwnd, and
1883 * not SACKing (the variable headers throw things off) */
1884 if (!icsk->icsk_mtup.enabled ||
1885 icsk->icsk_mtup.probe_size ||
1886 inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
1887 tp->snd_cwnd < 11 ||
1888 tp->rx_opt.num_sacks || tp->rx_opt.dsack)
1889 return -1;
1890
1891 /* Use binary search for probe_size between tcp_mss_base,
1892 * and current mss_clamp. if (search_high - search_low)
1893 * smaller than a threshold, backoff from probing.
1894 */
1895 mss_now = tcp_current_mss(sk);
1896 probe_size = tcp_mtu_to_mss(sk, (icsk->icsk_mtup.search_high +
1897 icsk->icsk_mtup.search_low) >> 1);
1898 size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
1899 interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low;
1900 /* When misfortune happens, we are reprobing actively,
1901 * and then reprobe timer has expired. We stick with current
1902 * probing process by not resetting search range to its orignal.
1903 */
1904 if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) ||
1905 interval < net->ipv4.sysctl_tcp_probe_threshold) {
1906 /* Check whether enough time has elaplased for
1907 * another round of probing.
1908 */
1909 tcp_mtu_check_reprobe(sk);
1910 return -1;
1911 }
1912
1913 /* Have enough data in the send queue to probe? */
1914 if (tp->write_seq - tp->snd_nxt < size_needed)
1915 return -1;
1916
1917 if (tp->snd_wnd < size_needed)
1918 return -1;
1919 if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
1920 return 0;
1921
1922 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
1923 if (tcp_packets_in_flight(tp) + 2 > tp->snd_cwnd) {
1924 if (!tcp_packets_in_flight(tp))
1925 return -1;
1926 else
1927 return 0;
1928 }
1929
1930 /* We're allowed to probe. Build it now. */
1931 nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC, false);
1932 if (!nskb)
1933 return -1;
1934 sk->sk_wmem_queued += nskb->truesize;
1935 sk_mem_charge(sk, nskb->truesize);
1936
1937 skb = tcp_send_head(sk);
1938
1939 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq;
1940 TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size;
1941 TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
1942 TCP_SKB_CB(nskb)->sacked = 0;
1943 nskb->csum = 0;
1944 nskb->ip_summed = skb->ip_summed;
1945
1946 tcp_insert_write_queue_before(nskb, skb, sk);
1947
1948 len = 0;
1949 tcp_for_write_queue_from_safe(skb, next, sk) {
1950 copy = min_t(int, skb->len, probe_size - len);
1951 if (nskb->ip_summed)
1952 skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
1953 else
1954 nskb->csum = skb_copy_and_csum_bits(skb, 0,
1955 skb_put(nskb, copy),
1956 copy, nskb->csum);
1957
1958 if (skb->len <= copy) {
1959 /* We've eaten all the data from this skb.
1960 * Throw it away. */
1961 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
1962 tcp_unlink_write_queue(skb, sk);
1963 sk_wmem_free_skb(sk, skb);
1964 } else {
1965 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
1966 ~(TCPHDR_FIN|TCPHDR_PSH);
1967 if (!skb_shinfo(skb)->nr_frags) {
1968 skb_pull(skb, copy);
1969 if (skb->ip_summed != CHECKSUM_PARTIAL)
1970 skb->csum = csum_partial(skb->data,
1971 skb->len, 0);
1972 } else {
1973 __pskb_trim_head(skb, copy);
1974 tcp_set_skb_tso_segs(skb, mss_now);
1975 }
1976 TCP_SKB_CB(skb)->seq += copy;
1977 }
1978
1979 len += copy;
1980
1981 if (len >= probe_size)
1982 break;
1983 }
1984 tcp_init_tso_segs(nskb, nskb->len);
1985
1986 /* We're ready to send. If this fails, the probe will
1987 * be resegmented into mss-sized pieces by tcp_write_xmit().
1988 */
1989 if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
1990 /* Decrement cwnd here because we are sending
1991 * effectively two packets. */
1992 tp->snd_cwnd--;
1993 tcp_event_new_data_sent(sk, nskb);
1994
1995 icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
1996 tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq;
1997 tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq;
1998
1999 return 1;
2000 }
2001
2002 return -1;
2003}
2004
2005/* This routine writes packets to the network. It advances the
2006 * send_head. This happens as incoming acks open up the remote
2007 * window for us.
2008 *
2009 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
2010 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
2011 * account rare use of URG, this is not a big flaw.
2012 *
2013 * Send at most one packet when push_one > 0. Temporarily ignore
2014 * cwnd limit to force at most one packet out when push_one == 2.
2015
2016 * Returns true, if no segments are in flight and we have queued segments,
2017 * but cannot send anything now because of SWS or another problem.
2018 */
2019static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
2020 int push_one, gfp_t gfp)
2021{
2022 struct tcp_sock *tp = tcp_sk(sk);
2023 struct sk_buff *skb;
2024 unsigned int tso_segs, sent_pkts;
2025 int cwnd_quota;
2026 int result;
2027 bool is_cwnd_limited = false;
2028 u32 max_segs;
2029
2030 sent_pkts = 0;
2031
2032 if (!push_one) {
2033 /* Do MTU probing. */
2034 result = tcp_mtu_probe(sk);
2035 if (!result) {
2036 return false;
2037 } else if (result > 0) {
2038 sent_pkts = 1;
2039 }
2040 }
2041
2042 max_segs = tcp_tso_autosize(sk, mss_now);
2043 while ((skb = tcp_send_head(sk))) {
2044 unsigned int limit;
2045
2046 tso_segs = tcp_init_tso_segs(skb, mss_now);
2047 BUG_ON(!tso_segs);
2048
2049 if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
2050 /* "skb_mstamp" is used as a start point for the retransmit timer */
2051 skb_mstamp_get(&skb->skb_mstamp);
2052 goto repair; /* Skip network transmission */
2053 }
2054
2055 cwnd_quota = tcp_cwnd_test(tp, skb);
2056 if (!cwnd_quota) {
2057 if (push_one == 2)
2058 /* Force out a loss probe pkt. */
2059 cwnd_quota = 1;
2060 else
2061 break;
2062 }
2063
2064 if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now)))
2065 break;
2066
2067 if (tso_segs == 1) {
2068 if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
2069 (tcp_skb_is_last(sk, skb) ?
2070 nonagle : TCP_NAGLE_PUSH))))
2071 break;
2072 } else {
2073 if (!push_one &&
2074 tcp_tso_should_defer(sk, skb, &is_cwnd_limited,
2075 max_segs))
2076 break;
2077 }
2078
2079 limit = mss_now;
2080 if (tso_segs > 1 && !tcp_urg_mode(tp))
2081 limit = tcp_mss_split_point(sk, skb, mss_now,
2082 min_t(unsigned int,
2083 cwnd_quota,
2084 max_segs),
2085 nonagle);
2086
2087 if (skb->len > limit &&
2088 unlikely(tso_fragment(sk, skb, limit, mss_now, gfp)))
2089 break;
2090
2091 /* TCP Small Queues :
2092 * Control number of packets in qdisc/devices to two packets / or ~1 ms.
2093 * This allows for :
2094 * - better RTT estimation and ACK scheduling
2095 * - faster recovery
2096 * - high rates
2097 * Alas, some drivers / subsystems require a fair amount
2098 * of queued bytes to ensure line rate.
2099 * One example is wifi aggregation (802.11 AMPDU)
2100 */
2101 limit = max(2 * skb->truesize, sk->sk_pacing_rate >> 10);
2102 limit = min_t(u32, limit, sysctl_tcp_limit_output_bytes);
2103
2104 if (atomic_read(&sk->sk_wmem_alloc) > limit) {
2105 set_bit(TSQ_THROTTLED, &tp->tsq_flags);
2106 /* It is possible TX completion already happened
2107 * before we set TSQ_THROTTLED, so we must
2108 * test again the condition.
2109 */
2110 smp_mb__after_atomic();
2111 if (atomic_read(&sk->sk_wmem_alloc) > limit)
2112 break;
2113 }
2114
2115 if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
2116 break;
2117
2118repair:
2119 /* Advance the send_head. This one is sent out.
2120 * This call will increment packets_out.
2121 */
2122 tcp_event_new_data_sent(sk, skb);
2123
2124 tcp_minshall_update(tp, mss_now, skb);
2125 sent_pkts += tcp_skb_pcount(skb);
2126
2127 if (push_one)
2128 break;
2129 }
2130
2131 if (likely(sent_pkts)) {
2132 if (tcp_in_cwnd_reduction(sk))
2133 tp->prr_out += sent_pkts;
2134
2135 /* Send one loss probe per tail loss episode. */
2136 if (push_one != 2)
2137 tcp_schedule_loss_probe(sk);
2138 is_cwnd_limited |= (tcp_packets_in_flight(tp) >= tp->snd_cwnd);
2139 tcp_cwnd_validate(sk, is_cwnd_limited);
2140 return false;
2141 }
2142 return !tp->packets_out && tcp_send_head(sk);
2143}
2144
2145bool tcp_schedule_loss_probe(struct sock *sk)
2146{
2147 struct inet_connection_sock *icsk = inet_csk(sk);
2148 struct tcp_sock *tp = tcp_sk(sk);
2149 u32 timeout, tlp_time_stamp, rto_time_stamp;
2150 u32 rtt = usecs_to_jiffies(tp->srtt_us >> 3);
2151
2152 if (WARN_ON(icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS))
2153 return false;
2154 /* No consecutive loss probes. */
2155 if (WARN_ON(icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)) {
2156 tcp_rearm_rto(sk);
2157 return false;
2158 }
2159 /* Don't do any loss probe on a Fast Open connection before 3WHS
2160 * finishes.
2161 */
2162 if (tp->fastopen_rsk)
2163 return false;
2164
2165 /* TLP is only scheduled when next timer event is RTO. */
2166 if (icsk->icsk_pending != ICSK_TIME_RETRANS)
2167 return false;
2168
2169 /* Schedule a loss probe in 2*RTT for SACK capable connections
2170 * in Open state, that are either limited by cwnd or application.
2171 */
2172 if (sysctl_tcp_early_retrans < 3 || !tp->packets_out ||
2173 !tcp_is_sack(tp) || inet_csk(sk)->icsk_ca_state != TCP_CA_Open)
2174 return false;
2175
2176 if ((tp->snd_cwnd > tcp_packets_in_flight(tp)) &&
2177 tcp_send_head(sk))
2178 return false;
2179
2180 /* Probe timeout is at least 1.5*rtt + TCP_DELACK_MAX to account
2181 * for delayed ack when there's one outstanding packet. If no RTT
2182 * sample is available then probe after TCP_TIMEOUT_INIT.
2183 */
2184 timeout = rtt << 1 ? : TCP_TIMEOUT_INIT;
2185 if (tp->packets_out == 1)
2186 timeout = max_t(u32, timeout,
2187 (rtt + (rtt >> 1) + TCP_DELACK_MAX));
2188 timeout = max_t(u32, timeout, msecs_to_jiffies(10));
2189
2190 /* If RTO is shorter, just schedule TLP in its place. */
2191 tlp_time_stamp = tcp_time_stamp + timeout;
2192 rto_time_stamp = (u32)inet_csk(sk)->icsk_timeout;
2193 if ((s32)(tlp_time_stamp - rto_time_stamp) > 0) {
2194 s32 delta = rto_time_stamp - tcp_time_stamp;
2195 if (delta > 0)
2196 timeout = delta;
2197 }
2198
2199 inet_csk_reset_xmit_timer(sk, ICSK_TIME_LOSS_PROBE, timeout,
2200 TCP_RTO_MAX);
2201 return true;
2202}
2203
2204/* Thanks to skb fast clones, we can detect if a prior transmit of
2205 * a packet is still in a qdisc or driver queue.
2206 * In this case, there is very little point doing a retransmit !
2207 * Note: This is called from BH context only.
2208 */
2209static bool skb_still_in_host_queue(const struct sock *sk,
2210 const struct sk_buff *skb)
2211{
2212 if (unlikely(skb_fclone_busy(sk, skb))) {
2213 NET_INC_STATS_BH(sock_net(sk),
2214 LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
2215 return true;
2216 }
2217 return false;
2218}
2219
2220/* When probe timeout (PTO) fires, try send a new segment if possible, else
2221 * retransmit the last segment.
2222 */
2223void tcp_send_loss_probe(struct sock *sk)
2224{
2225 struct tcp_sock *tp = tcp_sk(sk);
2226 struct sk_buff *skb;
2227 int pcount;
2228 int mss = tcp_current_mss(sk);
2229
2230 skb = tcp_send_head(sk);
2231 if (skb) {
2232 if (tcp_snd_wnd_test(tp, skb, mss)) {
2233 pcount = tp->packets_out;
2234 tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC);
2235 if (tp->packets_out > pcount)
2236 goto probe_sent;
2237 goto rearm_timer;
2238 }
2239 skb = tcp_write_queue_prev(sk, skb);
2240 } else {
2241 skb = tcp_write_queue_tail(sk);
2242 }
2243
2244 /* At most one outstanding TLP retransmission. */
2245 if (tp->tlp_high_seq)
2246 goto rearm_timer;
2247
2248 /* Retransmit last segment. */
2249 if (WARN_ON(!skb))
2250 goto rearm_timer;
2251
2252 if (skb_still_in_host_queue(sk, skb))
2253 goto rearm_timer;
2254
2255 pcount = tcp_skb_pcount(skb);
2256 if (WARN_ON(!pcount))
2257 goto rearm_timer;
2258
2259 if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
2260 if (unlikely(tcp_fragment(sk, skb, (pcount - 1) * mss, mss,
2261 GFP_ATOMIC)))
2262 goto rearm_timer;
2263 skb = tcp_write_queue_next(sk, skb);
2264 }
2265
2266 if (WARN_ON(!skb || !tcp_skb_pcount(skb)))
2267 goto rearm_timer;
2268
2269 if (__tcp_retransmit_skb(sk, skb))
2270 goto rearm_timer;
2271
2272 /* Record snd_nxt for loss detection. */
2273 tp->tlp_high_seq = tp->snd_nxt;
2274
2275probe_sent:
2276 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSSPROBES);
2277 /* Reset s.t. tcp_rearm_rto will restart timer from now */
2278 inet_csk(sk)->icsk_pending = 0;
2279rearm_timer:
2280 tcp_rearm_rto(sk);
2281}
2282
2283/* Push out any pending frames which were held back due to
2284 * TCP_CORK or attempt at coalescing tiny packets.
2285 * The socket must be locked by the caller.
2286 */
2287void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
2288 int nonagle)
2289{
2290 /* If we are closed, the bytes will have to remain here.
2291 * In time closedown will finish, we empty the write queue and
2292 * all will be happy.
2293 */
2294 if (unlikely(sk->sk_state == TCP_CLOSE))
2295 return;
2296
2297 if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
2298 sk_gfp_mask(sk, GFP_ATOMIC)))
2299 tcp_check_probe_timer(sk);
2300}
2301
2302/* Send _single_ skb sitting at the send head. This function requires
2303 * true push pending frames to setup probe timer etc.
2304 */
2305void tcp_push_one(struct sock *sk, unsigned int mss_now)
2306{
2307 struct sk_buff *skb = tcp_send_head(sk);
2308
2309 BUG_ON(!skb || skb->len < mss_now);
2310
2311 tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
2312}
2313
2314/* This function returns the amount that we can raise the
2315 * usable window based on the following constraints
2316 *
2317 * 1. The window can never be shrunk once it is offered (RFC 793)
2318 * 2. We limit memory per socket
2319 *
2320 * RFC 1122:
2321 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
2322 * RECV.NEXT + RCV.WIN fixed until:
2323 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
2324 *
2325 * i.e. don't raise the right edge of the window until you can raise
2326 * it at least MSS bytes.
2327 *
2328 * Unfortunately, the recommended algorithm breaks header prediction,
2329 * since header prediction assumes th->window stays fixed.
2330 *
2331 * Strictly speaking, keeping th->window fixed violates the receiver
2332 * side SWS prevention criteria. The problem is that under this rule
2333 * a stream of single byte packets will cause the right side of the
2334 * window to always advance by a single byte.
2335 *
2336 * Of course, if the sender implements sender side SWS prevention
2337 * then this will not be a problem.
2338 *
2339 * BSD seems to make the following compromise:
2340 *
2341 * If the free space is less than the 1/4 of the maximum
2342 * space available and the free space is less than 1/2 mss,
2343 * then set the window to 0.
2344 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
2345 * Otherwise, just prevent the window from shrinking
2346 * and from being larger than the largest representable value.
2347 *
2348 * This prevents incremental opening of the window in the regime
2349 * where TCP is limited by the speed of the reader side taking
2350 * data out of the TCP receive queue. It does nothing about
2351 * those cases where the window is constrained on the sender side
2352 * because the pipeline is full.
2353 *
2354 * BSD also seems to "accidentally" limit itself to windows that are a
2355 * multiple of MSS, at least until the free space gets quite small.
2356 * This would appear to be a side effect of the mbuf implementation.
2357 * Combining these two algorithms results in the observed behavior
2358 * of having a fixed window size at almost all times.
2359 *
2360 * Below we obtain similar behavior by forcing the offered window to
2361 * a multiple of the mss when it is feasible to do so.
2362 *
2363 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
2364 * Regular options like TIMESTAMP are taken into account.
2365 */
2366u32 __tcp_select_window(struct sock *sk)
2367{
2368 struct inet_connection_sock *icsk = inet_csk(sk);
2369 struct tcp_sock *tp = tcp_sk(sk);
2370 /* MSS for the peer's data. Previous versions used mss_clamp
2371 * here. I don't know if the value based on our guesses
2372 * of peer's MSS is better for the performance. It's more correct
2373 * but may be worse for the performance because of rcv_mss
2374 * fluctuations. --SAW 1998/11/1
2375 */
2376 int mss = icsk->icsk_ack.rcv_mss;
2377 int free_space = tcp_space(sk);
2378 int allowed_space = tcp_full_space(sk);
2379 int full_space = min_t(int, tp->window_clamp, allowed_space);
2380 int window;
2381
2382 if (mss > full_space)
2383 mss = full_space;
2384
2385 if (free_space < (full_space >> 1)) {
2386 icsk->icsk_ack.quick = 0;
2387
2388 if (tcp_under_memory_pressure(sk))
2389 tp->rcv_ssthresh = min(tp->rcv_ssthresh,
2390 4U * tp->advmss);
2391
2392 /* free_space might become our new window, make sure we don't
2393 * increase it due to wscale.
2394 */
2395 free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale);
2396
2397 /* if free space is less than mss estimate, or is below 1/16th
2398 * of the maximum allowed, try to move to zero-window, else
2399 * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and
2400 * new incoming data is dropped due to memory limits.
2401 * With large window, mss test triggers way too late in order
2402 * to announce zero window in time before rmem limit kicks in.
2403 */
2404 if (free_space < (allowed_space >> 4) || free_space < mss)
2405 return 0;
2406 }
2407
2408 if (free_space > tp->rcv_ssthresh)
2409 free_space = tp->rcv_ssthresh;
2410
2411 /* Don't do rounding if we are using window scaling, since the
2412 * scaled window will not line up with the MSS boundary anyway.
2413 */
2414 window = tp->rcv_wnd;
2415 if (tp->rx_opt.rcv_wscale) {
2416 window = free_space;
2417
2418 /* Advertise enough space so that it won't get scaled away.
2419 * Import case: prevent zero window announcement if
2420 * 1<<rcv_wscale > mss.
2421 */
2422 if (((window >> tp->rx_opt.rcv_wscale) << tp->rx_opt.rcv_wscale) != window)
2423 window = (((window >> tp->rx_opt.rcv_wscale) + 1)
2424 << tp->rx_opt.rcv_wscale);
2425 } else {
2426 /* Get the largest window that is a nice multiple of mss.
2427 * Window clamp already applied above.
2428 * If our current window offering is within 1 mss of the
2429 * free space we just keep it. This prevents the divide
2430 * and multiply from happening most of the time.
2431 * We also don't do any window rounding when the free space
2432 * is too small.
2433 */
2434 if (window <= free_space - mss || window > free_space)
2435 window = (free_space / mss) * mss;
2436 else if (mss == full_space &&
2437 free_space > window + (full_space >> 1))
2438 window = free_space;
2439 }
2440
2441 return window;
2442}
2443
2444void tcp_skb_collapse_tstamp(struct sk_buff *skb,
2445 const struct sk_buff *next_skb)
2446{
2447 const struct skb_shared_info *next_shinfo = skb_shinfo(next_skb);
2448 u8 tsflags = next_shinfo->tx_flags & SKBTX_ANY_TSTAMP;
2449
2450 if (unlikely(tsflags)) {
2451 struct skb_shared_info *shinfo = skb_shinfo(skb);
2452
2453 shinfo->tx_flags |= tsflags;
2454 shinfo->tskey = next_shinfo->tskey;
2455 }
2456}
2457
2458/* Collapses two adjacent SKB's during retransmission. */
2459static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
2460{
2461 struct tcp_sock *tp = tcp_sk(sk);
2462 struct sk_buff *next_skb = tcp_write_queue_next(sk, skb);
2463 int skb_size, next_skb_size;
2464
2465 skb_size = skb->len;
2466 next_skb_size = next_skb->len;
2467
2468 BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
2469
2470 tcp_highest_sack_combine(sk, next_skb, skb);
2471
2472 tcp_unlink_write_queue(next_skb, sk);
2473
2474 skb_copy_from_linear_data(next_skb, skb_put(skb, next_skb_size),
2475 next_skb_size);
2476
2477 if (next_skb->ip_summed == CHECKSUM_PARTIAL)
2478 skb->ip_summed = CHECKSUM_PARTIAL;
2479
2480 if (skb->ip_summed != CHECKSUM_PARTIAL)
2481 skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size);
2482
2483 /* Update sequence range on original skb. */
2484 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
2485
2486 /* Merge over control information. This moves PSH/FIN etc. over */
2487 TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
2488
2489 /* All done, get rid of second SKB and account for it so
2490 * packet counting does not break.
2491 */
2492 TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS;
2493
2494 /* changed transmit queue under us so clear hints */
2495 tcp_clear_retrans_hints_partial(tp);
2496 if (next_skb == tp->retransmit_skb_hint)
2497 tp->retransmit_skb_hint = skb;
2498
2499 tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));
2500
2501 tcp_skb_collapse_tstamp(skb, next_skb);
2502
2503 sk_wmem_free_skb(sk, next_skb);
2504}
2505
2506/* Check if coalescing SKBs is legal. */
2507static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
2508{
2509 if (tcp_skb_pcount(skb) > 1)
2510 return false;
2511 /* TODO: SACK collapsing could be used to remove this condition */
2512 if (skb_shinfo(skb)->nr_frags != 0)
2513 return false;
2514 if (skb_cloned(skb))
2515 return false;
2516 if (skb == tcp_send_head(sk))
2517 return false;
2518 /* Some heurestics for collapsing over SACK'd could be invented */
2519 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
2520 return false;
2521
2522 return true;
2523}
2524
2525/* Collapse packets in the retransmit queue to make to create
2526 * less packets on the wire. This is only done on retransmission.
2527 */
2528static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
2529 int space)
2530{
2531 struct tcp_sock *tp = tcp_sk(sk);
2532 struct sk_buff *skb = to, *tmp;
2533 bool first = true;
2534
2535 if (!sysctl_tcp_retrans_collapse)
2536 return;
2537 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2538 return;
2539
2540 tcp_for_write_queue_from_safe(skb, tmp, sk) {
2541 if (!tcp_can_collapse(sk, skb))
2542 break;
2543
2544 space -= skb->len;
2545
2546 if (first) {
2547 first = false;
2548 continue;
2549 }
2550
2551 if (space < 0)
2552 break;
2553 /* Punt if not enough space exists in the first SKB for
2554 * the data in the second
2555 */
2556 if (skb->len > skb_availroom(to))
2557 break;
2558
2559 if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp)))
2560 break;
2561
2562 tcp_collapse_retrans(sk, to);
2563 }
2564}
2565
2566/* This retransmits one SKB. Policy decisions and retransmit queue
2567 * state updates are done by the caller. Returns non-zero if an
2568 * error occurred which prevented the send.
2569 */
2570int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
2571{
2572 struct tcp_sock *tp = tcp_sk(sk);
2573 struct inet_connection_sock *icsk = inet_csk(sk);
2574 unsigned int cur_mss;
2575 int err;
2576
2577 /* Inconslusive MTU probe */
2578 if (icsk->icsk_mtup.probe_size) {
2579 icsk->icsk_mtup.probe_size = 0;
2580 }
2581
2582 /* Do not sent more than we queued. 1/4 is reserved for possible
2583 * copying overhead: fragmentation, tunneling, mangling etc.
2584 */
2585 if (atomic_read(&sk->sk_wmem_alloc) >
2586 min(sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2), sk->sk_sndbuf))
2587 return -EAGAIN;
2588
2589 if (skb_still_in_host_queue(sk, skb))
2590 return -EBUSY;
2591
2592 if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) {
2593 if (before(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
2594 BUG();
2595 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
2596 return -ENOMEM;
2597 }
2598
2599 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
2600 return -EHOSTUNREACH; /* Routing failure or similar. */
2601
2602 cur_mss = tcp_current_mss(sk);
2603
2604 /* If receiver has shrunk his window, and skb is out of
2605 * new window, do not retransmit it. The exception is the
2606 * case, when window is shrunk to zero. In this case
2607 * our retransmit serves as a zero window probe.
2608 */
2609 if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) &&
2610 TCP_SKB_CB(skb)->seq != tp->snd_una)
2611 return -EAGAIN;
2612
2613 if (skb->len > cur_mss) {
2614 if (tcp_fragment(sk, skb, cur_mss, cur_mss, GFP_ATOMIC))
2615 return -ENOMEM; /* We'll try again later. */
2616 } else {
2617 int oldpcount = tcp_skb_pcount(skb);
2618
2619 if (unlikely(oldpcount > 1)) {
2620 if (skb_unclone(skb, GFP_ATOMIC))
2621 return -ENOMEM;
2622 tcp_init_tso_segs(skb, cur_mss);
2623 tcp_adjust_pcount(sk, skb, oldpcount - tcp_skb_pcount(skb));
2624 }
2625 }
2626
2627 /* RFC3168, section 6.1.1.1. ECN fallback */
2628 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN_ECN) == TCPHDR_SYN_ECN)
2629 tcp_ecn_clear_syn(sk, skb);
2630
2631 tcp_retrans_try_collapse(sk, skb, cur_mss);
2632
2633 /* Make a copy, if the first transmission SKB clone we made
2634 * is still in somebody's hands, else make a clone.
2635 */
2636
2637 /* make sure skb->data is aligned on arches that require it
2638 * and check if ack-trimming & collapsing extended the headroom
2639 * beyond what csum_start can cover.
2640 */
2641 if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) ||
2642 skb_headroom(skb) >= 0xFFFF)) {
2643 struct sk_buff *nskb;
2644
2645 skb_mstamp_get(&skb->skb_mstamp);
2646 nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
2647 err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
2648 -ENOBUFS;
2649 } else {
2650 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
2651 }
2652
2653 if (likely(!err)) {
2654 TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
2655 /* Update global TCP statistics. */
2656 TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
2657 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2658 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
2659 tp->total_retrans++;
2660 }
2661 return err;
2662}
2663
2664int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
2665{
2666 struct tcp_sock *tp = tcp_sk(sk);
2667 int err = __tcp_retransmit_skb(sk, skb);
2668
2669 if (err == 0) {
2670#if FASTRETRANS_DEBUG > 0
2671 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2672 net_dbg_ratelimited("retrans_out leaked\n");
2673 }
2674#endif
2675 TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
2676 tp->retrans_out += tcp_skb_pcount(skb);
2677
2678 /* Save stamp of the first retransmit. */
2679 if (!tp->retrans_stamp)
2680 tp->retrans_stamp = tcp_skb_timestamp(skb);
2681
2682 } else if (err != -EBUSY) {
2683 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL);
2684 }
2685
2686 if (tp->undo_retrans < 0)
2687 tp->undo_retrans = 0;
2688 tp->undo_retrans += tcp_skb_pcount(skb);
2689 return err;
2690}
2691
2692/* Check if we forward retransmits are possible in the current
2693 * window/congestion state.
2694 */
2695static bool tcp_can_forward_retransmit(struct sock *sk)
2696{
2697 const struct inet_connection_sock *icsk = inet_csk(sk);
2698 const struct tcp_sock *tp = tcp_sk(sk);
2699
2700 /* Forward retransmissions are possible only during Recovery. */
2701 if (icsk->icsk_ca_state != TCP_CA_Recovery)
2702 return false;
2703
2704 /* No forward retransmissions in Reno are possible. */
2705 if (tcp_is_reno(tp))
2706 return false;
2707
2708 /* Yeah, we have to make difficult choice between forward transmission
2709 * and retransmission... Both ways have their merits...
2710 *
2711 * For now we do not retransmit anything, while we have some new
2712 * segments to send. In the other cases, follow rule 3 for
2713 * NextSeg() specified in RFC3517.
2714 */
2715
2716 if (tcp_may_send_now(sk))
2717 return false;
2718
2719 return true;
2720}
2721
2722/* This gets called after a retransmit timeout, and the initially
2723 * retransmitted data is acknowledged. It tries to continue
2724 * resending the rest of the retransmit queue, until either
2725 * we've sent it all or the congestion window limit is reached.
2726 * If doing SACK, the first ACK which comes back for a timeout
2727 * based retransmit packet might feed us FACK information again.
2728 * If so, we use it to avoid unnecessarily retransmissions.
2729 */
2730void tcp_xmit_retransmit_queue(struct sock *sk)
2731{
2732 const struct inet_connection_sock *icsk = inet_csk(sk);
2733 struct tcp_sock *tp = tcp_sk(sk);
2734 struct sk_buff *skb;
2735 struct sk_buff *hole = NULL;
2736 u32 last_lost;
2737 int mib_idx;
2738 int fwd_rexmitting = 0;
2739
2740 if (!tp->packets_out)
2741 return;
2742
2743 if (!tp->lost_out)
2744 tp->retransmit_high = tp->snd_una;
2745
2746 if (tp->retransmit_skb_hint) {
2747 skb = tp->retransmit_skb_hint;
2748 last_lost = TCP_SKB_CB(skb)->end_seq;
2749 if (after(last_lost, tp->retransmit_high))
2750 last_lost = tp->retransmit_high;
2751 } else {
2752 skb = tcp_write_queue_head(sk);
2753 last_lost = tp->snd_una;
2754 }
2755
2756 tcp_for_write_queue_from(skb, sk) {
2757 __u8 sacked = TCP_SKB_CB(skb)->sacked;
2758
2759 if (skb == tcp_send_head(sk))
2760 break;
2761 /* we could do better than to assign each time */
2762 if (!hole)
2763 tp->retransmit_skb_hint = skb;
2764
2765 /* Assume this retransmit will generate
2766 * only one packet for congestion window
2767 * calculation purposes. This works because
2768 * tcp_retransmit_skb() will chop up the
2769 * packet to be MSS sized and all the
2770 * packet counting works out.
2771 */
2772 if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
2773 return;
2774
2775 if (fwd_rexmitting) {
2776begin_fwd:
2777 if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
2778 break;
2779 mib_idx = LINUX_MIB_TCPFORWARDRETRANS;
2780
2781 } else if (!before(TCP_SKB_CB(skb)->seq, tp->retransmit_high)) {
2782 tp->retransmit_high = last_lost;
2783 if (!tcp_can_forward_retransmit(sk))
2784 break;
2785 /* Backtrack if necessary to non-L'ed skb */
2786 if (hole) {
2787 skb = hole;
2788 hole = NULL;
2789 }
2790 fwd_rexmitting = 1;
2791 goto begin_fwd;
2792
2793 } else if (!(sacked & TCPCB_LOST)) {
2794 if (!hole && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
2795 hole = skb;
2796 continue;
2797
2798 } else {
2799 last_lost = TCP_SKB_CB(skb)->end_seq;
2800 if (icsk->icsk_ca_state != TCP_CA_Loss)
2801 mib_idx = LINUX_MIB_TCPFASTRETRANS;
2802 else
2803 mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS;
2804 }
2805
2806 if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
2807 continue;
2808
2809 if (tcp_retransmit_skb(sk, skb))
2810 return;
2811
2812 NET_INC_STATS_BH(sock_net(sk), mib_idx);
2813
2814 if (tcp_in_cwnd_reduction(sk))
2815 tp->prr_out += tcp_skb_pcount(skb);
2816
2817 if (skb == tcp_write_queue_head(sk))
2818 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
2819 inet_csk(sk)->icsk_rto,
2820 TCP_RTO_MAX);
2821 }
2822}
2823
2824/* We allow to exceed memory limits for FIN packets to expedite
2825 * connection tear down and (memory) recovery.
2826 * Otherwise tcp_send_fin() could be tempted to either delay FIN
2827 * or even be forced to close flow without any FIN.
2828 * In general, we want to allow one skb per socket to avoid hangs
2829 * with edge trigger epoll()
2830 */
2831void sk_forced_mem_schedule(struct sock *sk, int size)
2832{
2833 int amt;
2834
2835 if (size <= sk->sk_forward_alloc)
2836 return;
2837 amt = sk_mem_pages(size);
2838 sk->sk_forward_alloc += amt * SK_MEM_QUANTUM;
2839 sk_memory_allocated_add(sk, amt);
2840
2841 if (mem_cgroup_sockets_enabled && sk->sk_memcg)
2842 mem_cgroup_charge_skmem(sk->sk_memcg, amt);
2843}
2844
2845/* Send a FIN. The caller locks the socket for us.
2846 * We should try to send a FIN packet really hard, but eventually give up.
2847 */
2848void tcp_send_fin(struct sock *sk)
2849{
2850 struct sk_buff *skb, *tskb = tcp_write_queue_tail(sk);
2851 struct tcp_sock *tp = tcp_sk(sk);
2852
2853 /* Optimization, tack on the FIN if we have one skb in write queue and
2854 * this skb was not yet sent, or we are under memory pressure.
2855 * Note: in the latter case, FIN packet will be sent after a timeout,
2856 * as TCP stack thinks it has already been transmitted.
2857 */
2858 if (tskb && (tcp_send_head(sk) || tcp_under_memory_pressure(sk))) {
2859coalesce:
2860 TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
2861 TCP_SKB_CB(tskb)->end_seq++;
2862 tp->write_seq++;
2863 if (!tcp_send_head(sk)) {
2864 /* This means tskb was already sent.
2865 * Pretend we included the FIN on previous transmit.
2866 * We need to set tp->snd_nxt to the value it would have
2867 * if FIN had been sent. This is because retransmit path
2868 * does not change tp->snd_nxt.
2869 */
2870 tp->snd_nxt++;
2871 return;
2872 }
2873 } else {
2874 skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation);
2875 if (unlikely(!skb)) {
2876 if (tskb)
2877 goto coalesce;
2878 return;
2879 }
2880 skb_reserve(skb, MAX_TCP_HEADER);
2881 sk_forced_mem_schedule(sk, skb->truesize);
2882 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
2883 tcp_init_nondata_skb(skb, tp->write_seq,
2884 TCPHDR_ACK | TCPHDR_FIN);
2885 tcp_queue_skb(sk, skb);
2886 }
2887 __tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF);
2888}
2889
2890/* We get here when a process closes a file descriptor (either due to
2891 * an explicit close() or as a byproduct of exit()'ing) and there
2892 * was unread data in the receive queue. This behavior is recommended
2893 * by RFC 2525, section 2.17. -DaveM
2894 */
2895void tcp_send_active_reset(struct sock *sk, gfp_t priority)
2896{
2897 struct sk_buff *skb;
2898
2899 /* NOTE: No TCP options attached and we never retransmit this. */
2900 skb = alloc_skb(MAX_TCP_HEADER, priority);
2901 if (!skb) {
2902 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
2903 return;
2904 }
2905
2906 /* Reserve space for headers and prepare control bits. */
2907 skb_reserve(skb, MAX_TCP_HEADER);
2908 tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
2909 TCPHDR_ACK | TCPHDR_RST);
2910 skb_mstamp_get(&skb->skb_mstamp);
2911 /* Send it off. */
2912 if (tcp_transmit_skb(sk, skb, 0, priority))
2913 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
2914
2915 TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
2916}
2917
2918/* Send a crossed SYN-ACK during socket establishment.
2919 * WARNING: This routine must only be called when we have already sent
2920 * a SYN packet that crossed the incoming SYN that caused this routine
2921 * to get called. If this assumption fails then the initial rcv_wnd
2922 * and rcv_wscale values will not be correct.
2923 */
2924int tcp_send_synack(struct sock *sk)
2925{
2926 struct sk_buff *skb;
2927
2928 skb = tcp_write_queue_head(sk);
2929 if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
2930 pr_debug("%s: wrong queue state\n", __func__);
2931 return -EFAULT;
2932 }
2933 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
2934 if (skb_cloned(skb)) {
2935 struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
2936 if (!nskb)
2937 return -ENOMEM;
2938 tcp_unlink_write_queue(skb, sk);
2939 __skb_header_release(nskb);
2940 __tcp_add_write_queue_head(sk, nskb);
2941 sk_wmem_free_skb(sk, skb);
2942 sk->sk_wmem_queued += nskb->truesize;
2943 sk_mem_charge(sk, nskb->truesize);
2944 skb = nskb;
2945 }
2946
2947 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
2948 tcp_ecn_send_synack(sk, skb);
2949 }
2950 return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
2951}
2952
2953/**
2954 * tcp_make_synack - Prepare a SYN-ACK.
2955 * sk: listener socket
2956 * dst: dst entry attached to the SYNACK
2957 * req: request_sock pointer
2958 *
2959 * Allocate one skb and build a SYNACK packet.
2960 * @dst is consumed : Caller should not use it again.
2961 */
2962struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
2963 struct request_sock *req,
2964 struct tcp_fastopen_cookie *foc,
2965 bool attach_req)
2966{
2967 struct inet_request_sock *ireq = inet_rsk(req);
2968 const struct tcp_sock *tp = tcp_sk(sk);
2969 struct tcp_md5sig_key *md5 = NULL;
2970 struct tcp_out_options opts;
2971 struct sk_buff *skb;
2972 int tcp_header_size;
2973 struct tcphdr *th;
2974 u16 user_mss;
2975 int mss;
2976
2977 skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
2978 if (unlikely(!skb)) {
2979 dst_release(dst);
2980 return NULL;
2981 }
2982 /* Reserve space for headers. */
2983 skb_reserve(skb, MAX_TCP_HEADER);
2984
2985 if (attach_req) {
2986 skb_set_owner_w(skb, req_to_sk(req));
2987 } else {
2988 /* sk is a const pointer, because we want to express multiple
2989 * cpu might call us concurrently.
2990 * sk->sk_wmem_alloc in an atomic, we can promote to rw.
2991 */
2992 skb_set_owner_w(skb, (struct sock *)sk);
2993 }
2994 skb_dst_set(skb, dst);
2995
2996 mss = dst_metric_advmss(dst);
2997 user_mss = READ_ONCE(tp->rx_opt.user_mss);
2998 if (user_mss && user_mss < mss)
2999 mss = user_mss;
3000
3001 memset(&opts, 0, sizeof(opts));
3002#ifdef CONFIG_SYN_COOKIES
3003 if (unlikely(req->cookie_ts))
3004 skb->skb_mstamp.stamp_jiffies = cookie_init_timestamp(req);
3005 else
3006#endif
3007 skb_mstamp_get(&skb->skb_mstamp);
3008
3009#ifdef CONFIG_TCP_MD5SIG
3010 rcu_read_lock();
3011 md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));
3012#endif
3013 skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4);
3014 tcp_header_size = tcp_synack_options(req, mss, skb, &opts, md5, foc) +
3015 sizeof(*th);
3016
3017 skb_push(skb, tcp_header_size);
3018 skb_reset_transport_header(skb);
3019
3020 th = tcp_hdr(skb);
3021 memset(th, 0, sizeof(struct tcphdr));
3022 th->syn = 1;
3023 th->ack = 1;
3024 tcp_ecn_make_synack(req, th);
3025 th->source = htons(ireq->ir_num);
3026 th->dest = ireq->ir_rmt_port;
3027 /* Setting of flags are superfluous here for callers (and ECE is
3028 * not even correctly set)
3029 */
3030 tcp_init_nondata_skb(skb, tcp_rsk(req)->snt_isn,
3031 TCPHDR_SYN | TCPHDR_ACK);
3032
3033 th->seq = htonl(TCP_SKB_CB(skb)->seq);
3034 /* XXX data is queued and acked as is. No buffer/window check */
3035 th->ack_seq = htonl(tcp_rsk(req)->rcv_nxt);
3036
3037 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
3038 th->window = htons(min(req->rsk_rcv_wnd, 65535U));
3039 tcp_options_write((__be32 *)(th + 1), NULL, &opts);
3040 th->doff = (tcp_header_size >> 2);
3041 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_OUTSEGS);
3042
3043#ifdef CONFIG_TCP_MD5SIG
3044 /* Okay, we have all we need - do the md5 hash if needed */
3045 if (md5)
3046 tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
3047 md5, req_to_sk(req), skb);
3048 rcu_read_unlock();
3049#endif
3050
3051 /* Do not fool tcpdump (if any), clean our debris */
3052 skb->tstamp.tv64 = 0;
3053 return skb;
3054}
3055EXPORT_SYMBOL(tcp_make_synack);
3056
3057static void tcp_ca_dst_init(struct sock *sk, const struct dst_entry *dst)
3058{
3059 struct inet_connection_sock *icsk = inet_csk(sk);
3060 const struct tcp_congestion_ops *ca;
3061 u32 ca_key = dst_metric(dst, RTAX_CC_ALGO);
3062
3063 if (ca_key == TCP_CA_UNSPEC)
3064 return;
3065
3066 rcu_read_lock();
3067 ca = tcp_ca_find_key(ca_key);
3068 if (likely(ca && try_module_get(ca->owner))) {
3069 module_put(icsk->icsk_ca_ops->owner);
3070 icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst);
3071 icsk->icsk_ca_ops = ca;
3072 }
3073 rcu_read_unlock();
3074}
3075
3076/* Do all connect socket setups that can be done AF independent. */
3077static void tcp_connect_init(struct sock *sk)
3078{
3079 const struct dst_entry *dst = __sk_dst_get(sk);
3080 struct tcp_sock *tp = tcp_sk(sk);
3081 __u8 rcv_wscale;
3082
3083 /* We'll fix this up when we get a response from the other end.
3084 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
3085 */
3086 tp->tcp_header_len = sizeof(struct tcphdr) +
3087 (sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0);
3088
3089#ifdef CONFIG_TCP_MD5SIG
3090 if (tp->af_specific->md5_lookup(sk, sk))
3091 tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
3092#endif
3093
3094 /* If user gave his TCP_MAXSEG, record it to clamp */
3095 if (tp->rx_opt.user_mss)
3096 tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
3097 tp->max_window = 0;
3098 tcp_mtup_init(sk);
3099 tcp_sync_mss(sk, dst_mtu(dst));
3100
3101 tcp_ca_dst_init(sk, dst);
3102
3103 if (!tp->window_clamp)
3104 tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
3105 tp->advmss = dst_metric_advmss(dst);
3106 if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->advmss)
3107 tp->advmss = tp->rx_opt.user_mss;
3108
3109 tcp_initialize_rcv_mss(sk);
3110
3111 /* limit the window selection if the user enforce a smaller rx buffer */
3112 if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
3113 (tp->window_clamp > tcp_full_space(sk) || tp->window_clamp == 0))
3114 tp->window_clamp = tcp_full_space(sk);
3115
3116 tcp_select_initial_window(tcp_full_space(sk),
3117 tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),
3118 &tp->rcv_wnd,
3119 &tp->window_clamp,
3120 sysctl_tcp_window_scaling,
3121 &rcv_wscale,
3122 dst_metric(dst, RTAX_INITRWND));
3123
3124 tp->rx_opt.rcv_wscale = rcv_wscale;
3125 tp->rcv_ssthresh = tp->rcv_wnd;
3126
3127 sk->sk_err = 0;
3128 sock_reset_flag(sk, SOCK_DONE);
3129 tp->snd_wnd = 0;
3130 tcp_init_wl(tp, 0);
3131 tp->snd_una = tp->write_seq;
3132 tp->snd_sml = tp->write_seq;
3133 tp->snd_up = tp->write_seq;
3134 tp->snd_nxt = tp->write_seq;
3135
3136 if (likely(!tp->repair))
3137 tp->rcv_nxt = 0;
3138 else
3139 tp->rcv_tstamp = tcp_time_stamp;
3140 tp->rcv_wup = tp->rcv_nxt;
3141 tp->copied_seq = tp->rcv_nxt;
3142
3143 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
3144 inet_csk(sk)->icsk_retransmits = 0;
3145 tcp_clear_retrans(tp);
3146}
3147
3148static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb)
3149{
3150 struct tcp_sock *tp = tcp_sk(sk);
3151 struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
3152
3153 tcb->end_seq += skb->len;
3154 __skb_header_release(skb);
3155 __tcp_add_write_queue_tail(sk, skb);
3156 sk->sk_wmem_queued += skb->truesize;
3157 sk_mem_charge(sk, skb->truesize);
3158 tp->write_seq = tcb->end_seq;
3159 tp->packets_out += tcp_skb_pcount(skb);
3160}
3161
3162/* Build and send a SYN with data and (cached) Fast Open cookie. However,
3163 * queue a data-only packet after the regular SYN, such that regular SYNs
3164 * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges
3165 * only the SYN sequence, the data are retransmitted in the first ACK.
3166 * If cookie is not cached or other error occurs, falls back to send a
3167 * regular SYN with Fast Open cookie request option.
3168 */
3169static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
3170{
3171 struct tcp_sock *tp = tcp_sk(sk);
3172 struct tcp_fastopen_request *fo = tp->fastopen_req;
3173 int syn_loss = 0, space, err = 0;
3174 unsigned long last_syn_loss = 0;
3175 struct sk_buff *syn_data;
3176
3177 tp->rx_opt.mss_clamp = tp->advmss; /* If MSS is not cached */
3178 tcp_fastopen_cache_get(sk, &tp->rx_opt.mss_clamp, &fo->cookie,
3179 &syn_loss, &last_syn_loss);
3180 /* Recurring FO SYN losses: revert to regular handshake temporarily */
3181 if (syn_loss > 1 &&
3182 time_before(jiffies, last_syn_loss + (60*HZ << syn_loss))) {
3183 fo->cookie.len = -1;
3184 goto fallback;
3185 }
3186
3187 if (sysctl_tcp_fastopen & TFO_CLIENT_NO_COOKIE)
3188 fo->cookie.len = -1;
3189 else if (fo->cookie.len <= 0)
3190 goto fallback;
3191
3192 /* MSS for SYN-data is based on cached MSS and bounded by PMTU and
3193 * user-MSS. Reserve maximum option space for middleboxes that add
3194 * private TCP options. The cost is reduced data space in SYN :(
3195 */
3196 if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->rx_opt.mss_clamp)
3197 tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
3198 space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
3199 MAX_TCP_OPTION_SPACE;
3200
3201 space = min_t(size_t, space, fo->size);
3202
3203 /* limit to order-0 allocations */
3204 space = min_t(size_t, space, SKB_MAX_HEAD(MAX_TCP_HEADER));
3205
3206 syn_data = sk_stream_alloc_skb(sk, space, sk->sk_allocation, false);
3207 if (!syn_data)
3208 goto fallback;
3209 syn_data->ip_summed = CHECKSUM_PARTIAL;
3210 memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
3211 if (space) {
3212 int copied = copy_from_iter(skb_put(syn_data, space), space,
3213 &fo->data->msg_iter);
3214 if (unlikely(!copied)) {
3215 kfree_skb(syn_data);
3216 goto fallback;
3217 }
3218 if (copied != space) {
3219 skb_trim(syn_data, copied);
3220 space = copied;
3221 }
3222 }
3223 /* No more data pending in inet_wait_for_connect() */
3224 if (space == fo->size)
3225 fo->data = NULL;
3226 fo->copied = space;
3227
3228 tcp_connect_queue_skb(sk, syn_data);
3229
3230 err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation);
3231
3232 syn->skb_mstamp = syn_data->skb_mstamp;
3233
3234 /* Now full SYN+DATA was cloned and sent (or not),
3235 * remove the SYN from the original skb (syn_data)
3236 * we keep in write queue in case of a retransmit, as we
3237 * also have the SYN packet (with no data) in the same queue.
3238 */
3239 TCP_SKB_CB(syn_data)->seq++;
3240 TCP_SKB_CB(syn_data)->tcp_flags = TCPHDR_ACK | TCPHDR_PSH;
3241 if (!err) {
3242 tp->syn_data = (fo->copied > 0);
3243 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
3244 goto done;
3245 }
3246
3247fallback:
3248 /* Send a regular SYN with Fast Open cookie request option */
3249 if (fo->cookie.len > 0)
3250 fo->cookie.len = 0;
3251 err = tcp_transmit_skb(sk, syn, 1, sk->sk_allocation);
3252 if (err)
3253 tp->syn_fastopen = 0;
3254done:
3255 fo->cookie.len = -1; /* Exclude Fast Open option for SYN retries */
3256 return err;
3257}
3258
3259/* Build a SYN and send it off. */
3260int tcp_connect(struct sock *sk)
3261{
3262 struct tcp_sock *tp = tcp_sk(sk);
3263 struct sk_buff *buff;
3264 int err;
3265
3266 tcp_connect_init(sk);
3267
3268 if (unlikely(tp->repair)) {
3269 tcp_finish_connect(sk, NULL);
3270 return 0;
3271 }
3272
3273 buff = sk_stream_alloc_skb(sk, 0, sk->sk_allocation, true);
3274 if (unlikely(!buff))
3275 return -ENOBUFS;
3276
3277 tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
3278 tp->retrans_stamp = tcp_time_stamp;
3279 tcp_connect_queue_skb(sk, buff);
3280 tcp_ecn_send_syn(sk, buff);
3281
3282 /* Send off SYN; include data in Fast Open. */
3283 err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) :
3284 tcp_transmit_skb(sk, buff, 1, sk->sk_allocation);
3285 if (err == -ECONNREFUSED)
3286 return err;
3287
3288 /* We change tp->snd_nxt after the tcp_transmit_skb() call
3289 * in order to make this packet get counted in tcpOutSegs.
3290 */
3291 tp->snd_nxt = tp->write_seq;
3292 tp->pushed_seq = tp->write_seq;
3293 TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
3294
3295 /* Timer for repeating the SYN until an answer. */
3296 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
3297 inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
3298 return 0;
3299}
3300EXPORT_SYMBOL(tcp_connect);
3301
3302/* Send out a delayed ack, the caller does the policy checking
3303 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
3304 * for details.
3305 */
3306void tcp_send_delayed_ack(struct sock *sk)
3307{
3308 struct inet_connection_sock *icsk = inet_csk(sk);
3309 int ato = icsk->icsk_ack.ato;
3310 unsigned long timeout;
3311
3312 tcp_ca_event(sk, CA_EVENT_DELAYED_ACK);
3313
3314 if (ato > TCP_DELACK_MIN) {
3315 const struct tcp_sock *tp = tcp_sk(sk);
3316 int max_ato = HZ / 2;
3317
3318 if (icsk->icsk_ack.pingpong ||
3319 (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
3320 max_ato = TCP_DELACK_MAX;
3321
3322 /* Slow path, intersegment interval is "high". */
3323
3324 /* If some rtt estimate is known, use it to bound delayed ack.
3325 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
3326 * directly.
3327 */
3328 if (tp->srtt_us) {
3329 int rtt = max_t(int, usecs_to_jiffies(tp->srtt_us >> 3),
3330 TCP_DELACK_MIN);
3331
3332 if (rtt < max_ato)
3333 max_ato = rtt;
3334 }
3335
3336 ato = min(ato, max_ato);
3337 }
3338
3339 /* Stay within the limit we were given */
3340 timeout = jiffies + ato;
3341
3342 /* Use new timeout only if there wasn't a older one earlier. */
3343 if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
3344 /* If delack timer was blocked or is about to expire,
3345 * send ACK now.
3346 */
3347 if (icsk->icsk_ack.blocked ||
3348 time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
3349 tcp_send_ack(sk);
3350 return;
3351 }
3352
3353 if (!time_before(timeout, icsk->icsk_ack.timeout))
3354 timeout = icsk->icsk_ack.timeout;
3355 }
3356 icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
3357 icsk->icsk_ack.timeout = timeout;
3358 sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
3359}
3360
3361/* This routine sends an ack and also updates the window. */
3362void tcp_send_ack(struct sock *sk)
3363{
3364 struct sk_buff *buff;
3365
3366 /* If we have been reset, we may not send again. */
3367 if (sk->sk_state == TCP_CLOSE)
3368 return;
3369
3370 tcp_ca_event(sk, CA_EVENT_NON_DELAYED_ACK);
3371
3372 /* We are not putting this on the write queue, so
3373 * tcp_transmit_skb() will set the ownership to this
3374 * sock.
3375 */
3376 buff = alloc_skb(MAX_TCP_HEADER,
3377 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
3378 if (unlikely(!buff)) {
3379 inet_csk_schedule_ack(sk);
3380 inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
3381 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
3382 TCP_DELACK_MAX, TCP_RTO_MAX);
3383 return;
3384 }
3385
3386 /* Reserve space for headers and prepare control bits. */
3387 skb_reserve(buff, MAX_TCP_HEADER);
3388 tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
3389
3390 /* We do not want pure acks influencing TCP Small Queues or fq/pacing
3391 * too much.
3392 * SKB_TRUESIZE(max(1 .. 66, MAX_TCP_HEADER)) is unfortunately ~784
3393 * We also avoid tcp_wfree() overhead (cache line miss accessing
3394 * tp->tsq_flags) by using regular sock_wfree()
3395 */
3396 skb_set_tcp_pure_ack(buff);
3397
3398 /* Send it off, this clears delayed acks for us. */
3399 skb_mstamp_get(&buff->skb_mstamp);
3400 tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0);
3401}
3402EXPORT_SYMBOL_GPL(tcp_send_ack);
3403
3404/* This routine sends a packet with an out of date sequence
3405 * number. It assumes the other end will try to ack it.
3406 *
3407 * Question: what should we make while urgent mode?
3408 * 4.4BSD forces sending single byte of data. We cannot send
3409 * out of window data, because we have SND.NXT==SND.MAX...
3410 *
3411 * Current solution: to send TWO zero-length segments in urgent mode:
3412 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
3413 * out-of-date with SND.UNA-1 to probe window.
3414 */
3415static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib)
3416{
3417 struct tcp_sock *tp = tcp_sk(sk);
3418 struct sk_buff *skb;
3419
3420 /* We don't queue it, tcp_transmit_skb() sets ownership. */
3421 skb = alloc_skb(MAX_TCP_HEADER,
3422 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN));
3423 if (!skb)
3424 return -1;
3425
3426 /* Reserve space for headers and set control bits. */
3427 skb_reserve(skb, MAX_TCP_HEADER);
3428 /* Use a previous sequence. This should cause the other
3429 * end to send an ack. Don't queue or clone SKB, just
3430 * send it.
3431 */
3432 tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
3433 skb_mstamp_get(&skb->skb_mstamp);
3434 NET_INC_STATS(sock_net(sk), mib);
3435 return tcp_transmit_skb(sk, skb, 0, (__force gfp_t)0);
3436}
3437
3438void tcp_send_window_probe(struct sock *sk)
3439{
3440 if (sk->sk_state == TCP_ESTABLISHED) {
3441 tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1;
3442 tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE);
3443 }
3444}
3445
3446/* Initiate keepalive or window probe from timer. */
3447int tcp_write_wakeup(struct sock *sk, int mib)
3448{
3449 struct tcp_sock *tp = tcp_sk(sk);
3450 struct sk_buff *skb;
3451
3452 if (sk->sk_state == TCP_CLOSE)
3453 return -1;
3454
3455 skb = tcp_send_head(sk);
3456 if (skb && before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
3457 int err;
3458 unsigned int mss = tcp_current_mss(sk);
3459 unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
3460
3461 if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
3462 tp->pushed_seq = TCP_SKB_CB(skb)->end_seq;
3463
3464 /* We are probing the opening of a window
3465 * but the window size is != 0
3466 * must have been a result SWS avoidance ( sender )
3467 */
3468 if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq ||
3469 skb->len > mss) {
3470 seg_size = min(seg_size, mss);
3471 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3472 if (tcp_fragment(sk, skb, seg_size, mss, GFP_ATOMIC))
3473 return -1;
3474 } else if (!tcp_skb_pcount(skb))
3475 tcp_set_skb_tso_segs(skb, mss);
3476
3477 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3478 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
3479 if (!err)
3480 tcp_event_new_data_sent(sk, skb);
3481 return err;
3482 } else {
3483 if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
3484 tcp_xmit_probe_skb(sk, 1, mib);
3485 return tcp_xmit_probe_skb(sk, 0, mib);
3486 }
3487}
3488
3489/* A window probe timeout has occurred. If window is not closed send
3490 * a partial packet else a zero probe.
3491 */
3492void tcp_send_probe0(struct sock *sk)
3493{
3494 struct inet_connection_sock *icsk = inet_csk(sk);
3495 struct tcp_sock *tp = tcp_sk(sk);
3496 struct net *net = sock_net(sk);
3497 unsigned long probe_max;
3498 int err;
3499
3500 err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE);
3501
3502 if (tp->packets_out || !tcp_send_head(sk)) {
3503 /* Cancel probe timer, if it is not required. */
3504 icsk->icsk_probes_out = 0;
3505 icsk->icsk_backoff = 0;
3506 return;
3507 }
3508
3509 if (err <= 0) {
3510 if (icsk->icsk_backoff < net->ipv4.sysctl_tcp_retries2)
3511 icsk->icsk_backoff++;
3512 icsk->icsk_probes_out++;
3513 probe_max = TCP_RTO_MAX;
3514 } else {
3515 /* If packet was not sent due to local congestion,
3516 * do not backoff and do not remember icsk_probes_out.
3517 * Let local senders to fight for local resources.
3518 *
3519 * Use accumulated backoff yet.
3520 */
3521 if (!icsk->icsk_probes_out)
3522 icsk->icsk_probes_out = 1;
3523 probe_max = TCP_RESOURCE_PROBE_INTERVAL;
3524 }
3525 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3526 tcp_probe0_when(sk, probe_max),
3527 TCP_RTO_MAX);
3528}
3529
3530int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
3531{
3532 const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific;
3533 struct flowi fl;
3534 int res;
3535
3536 tcp_rsk(req)->txhash = net_tx_rndhash();
3537 res = af_ops->send_synack(sk, NULL, &fl, req, NULL, true);
3538 if (!res) {
3539 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_RETRANSSEGS);
3540 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
3541 }
3542 return res;
3543}
3544EXPORT_SYMBOL(tcp_rtx_synack);
1/*
2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
5 *
6 * Implementation of the Transmission Control Protocol(TCP).
7 *
8 * Authors: Ross Biro
9 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
10 * Mark Evans, <evansmp@uhura.aston.ac.uk>
11 * Corey Minyard <wf-rch!minyard@relay.EU.net>
12 * Florian La Roche, <flla@stud.uni-sb.de>
13 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
14 * Linus Torvalds, <torvalds@cs.helsinki.fi>
15 * Alan Cox, <gw4pts@gw4pts.ampr.org>
16 * Matthew Dillon, <dillon@apollo.west.oic.com>
17 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
18 * Jorge Cwik, <jorge@laser.satlink.net>
19 */
20
21/*
22 * Changes: Pedro Roque : Retransmit queue handled by TCP.
23 * : Fragmentation on mtu decrease
24 * : Segment collapse on retransmit
25 * : AF independence
26 *
27 * Linus Torvalds : send_delayed_ack
28 * David S. Miller : Charge memory using the right skb
29 * during syn/ack processing.
30 * David S. Miller : Output engine completely rewritten.
31 * Andrea Arcangeli: SYNACK carry ts_recent in tsecr.
32 * Cacophonix Gaul : draft-minshall-nagle-01
33 * J Hadi Salim : ECN support
34 *
35 */
36
37#define pr_fmt(fmt) "TCP: " fmt
38
39#include <net/tcp.h>
40
41#include <linux/compiler.h>
42#include <linux/gfp.h>
43#include <linux/module.h>
44
45/* People can turn this off for buggy TCP's found in printers etc. */
46int sysctl_tcp_retrans_collapse __read_mostly = 1;
47
48/* People can turn this on to work with those rare, broken TCPs that
49 * interpret the window field as a signed quantity.
50 */
51int sysctl_tcp_workaround_signed_windows __read_mostly = 0;
52
53/* Default TSQ limit of two TSO segments */
54int sysctl_tcp_limit_output_bytes __read_mostly = 131072;
55
56/* This limits the percentage of the congestion window which we
57 * will allow a single TSO frame to consume. Building TSO frames
58 * which are too large can cause TCP streams to be bursty.
59 */
60int sysctl_tcp_tso_win_divisor __read_mostly = 3;
61
62int sysctl_tcp_mtu_probing __read_mostly = 0;
63int sysctl_tcp_base_mss __read_mostly = TCP_BASE_MSS;
64
65/* By default, RFC2861 behavior. */
66int sysctl_tcp_slow_start_after_idle __read_mostly = 1;
67
68unsigned int sysctl_tcp_notsent_lowat __read_mostly = UINT_MAX;
69EXPORT_SYMBOL(sysctl_tcp_notsent_lowat);
70
71static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
72 int push_one, gfp_t gfp);
73
74/* Account for new data that has been sent to the network. */
75static void tcp_event_new_data_sent(struct sock *sk, const struct sk_buff *skb)
76{
77 struct inet_connection_sock *icsk = inet_csk(sk);
78 struct tcp_sock *tp = tcp_sk(sk);
79 unsigned int prior_packets = tp->packets_out;
80
81 tcp_advance_send_head(sk, skb);
82 tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;
83
84 tp->packets_out += tcp_skb_pcount(skb);
85 if (!prior_packets || icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS ||
86 icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
87 tcp_rearm_rto(sk);
88 }
89
90 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT,
91 tcp_skb_pcount(skb));
92}
93
94/* SND.NXT, if window was not shrunk.
95 * If window has been shrunk, what should we make? It is not clear at all.
96 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
97 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
98 * invalid. OK, let's make this for now:
99 */
100static inline __u32 tcp_acceptable_seq(const struct sock *sk)
101{
102 const struct tcp_sock *tp = tcp_sk(sk);
103
104 if (!before(tcp_wnd_end(tp), tp->snd_nxt))
105 return tp->snd_nxt;
106 else
107 return tcp_wnd_end(tp);
108}
109
110/* Calculate mss to advertise in SYN segment.
111 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
112 *
113 * 1. It is independent of path mtu.
114 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
115 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
116 * attached devices, because some buggy hosts are confused by
117 * large MSS.
118 * 4. We do not make 3, we advertise MSS, calculated from first
119 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
120 * This may be overridden via information stored in routing table.
121 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
122 * probably even Jumbo".
123 */
124static __u16 tcp_advertise_mss(struct sock *sk)
125{
126 struct tcp_sock *tp = tcp_sk(sk);
127 const struct dst_entry *dst = __sk_dst_get(sk);
128 int mss = tp->advmss;
129
130 if (dst) {
131 unsigned int metric = dst_metric_advmss(dst);
132
133 if (metric < mss) {
134 mss = metric;
135 tp->advmss = mss;
136 }
137 }
138
139 return (__u16)mss;
140}
141
142/* RFC2861. Reset CWND after idle period longer RTO to "restart window".
143 * This is the first part of cwnd validation mechanism. */
144static void tcp_cwnd_restart(struct sock *sk, const struct dst_entry *dst)
145{
146 struct tcp_sock *tp = tcp_sk(sk);
147 s32 delta = tcp_time_stamp - tp->lsndtime;
148 u32 restart_cwnd = tcp_init_cwnd(tp, dst);
149 u32 cwnd = tp->snd_cwnd;
150
151 tcp_ca_event(sk, CA_EVENT_CWND_RESTART);
152
153 tp->snd_ssthresh = tcp_current_ssthresh(sk);
154 restart_cwnd = min(restart_cwnd, cwnd);
155
156 while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd)
157 cwnd >>= 1;
158 tp->snd_cwnd = max(cwnd, restart_cwnd);
159 tp->snd_cwnd_stamp = tcp_time_stamp;
160 tp->snd_cwnd_used = 0;
161}
162
163/* Congestion state accounting after a packet has been sent. */
164static void tcp_event_data_sent(struct tcp_sock *tp,
165 struct sock *sk)
166{
167 struct inet_connection_sock *icsk = inet_csk(sk);
168 const u32 now = tcp_time_stamp;
169 const struct dst_entry *dst = __sk_dst_get(sk);
170
171 if (sysctl_tcp_slow_start_after_idle &&
172 (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto))
173 tcp_cwnd_restart(sk, __sk_dst_get(sk));
174
175 tp->lsndtime = now;
176
177 /* If it is a reply for ato after last received
178 * packet, enter pingpong mode.
179 */
180 if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato &&
181 (!dst || !dst_metric(dst, RTAX_QUICKACK)))
182 icsk->icsk_ack.pingpong = 1;
183}
184
185/* Account for an ACK we sent. */
186static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts)
187{
188 tcp_dec_quickack_mode(sk, pkts);
189 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
190}
191
192
193u32 tcp_default_init_rwnd(u32 mss)
194{
195 /* Initial receive window should be twice of TCP_INIT_CWND to
196 * enable proper sending of new unsent data during fast recovery
197 * (RFC 3517, Section 4, NextSeg() rule (2)). Further place a
198 * limit when mss is larger than 1460.
199 */
200 u32 init_rwnd = TCP_INIT_CWND * 2;
201
202 if (mss > 1460)
203 init_rwnd = max((1460 * init_rwnd) / mss, 2U);
204 return init_rwnd;
205}
206
207/* Determine a window scaling and initial window to offer.
208 * Based on the assumption that the given amount of space
209 * will be offered. Store the results in the tp structure.
210 * NOTE: for smooth operation initial space offering should
211 * be a multiple of mss if possible. We assume here that mss >= 1.
212 * This MUST be enforced by all callers.
213 */
214void tcp_select_initial_window(int __space, __u32 mss,
215 __u32 *rcv_wnd, __u32 *window_clamp,
216 int wscale_ok, __u8 *rcv_wscale,
217 __u32 init_rcv_wnd)
218{
219 unsigned int space = (__space < 0 ? 0 : __space);
220
221 /* If no clamp set the clamp to the max possible scaled window */
222 if (*window_clamp == 0)
223 (*window_clamp) = (65535 << 14);
224 space = min(*window_clamp, space);
225
226 /* Quantize space offering to a multiple of mss if possible. */
227 if (space > mss)
228 space = (space / mss) * mss;
229
230 /* NOTE: offering an initial window larger than 32767
231 * will break some buggy TCP stacks. If the admin tells us
232 * it is likely we could be speaking with such a buggy stack
233 * we will truncate our initial window offering to 32K-1
234 * unless the remote has sent us a window scaling option,
235 * which we interpret as a sign the remote TCP is not
236 * misinterpreting the window field as a signed quantity.
237 */
238 if (sysctl_tcp_workaround_signed_windows)
239 (*rcv_wnd) = min(space, MAX_TCP_WINDOW);
240 else
241 (*rcv_wnd) = space;
242
243 (*rcv_wscale) = 0;
244 if (wscale_ok) {
245 /* Set window scaling on max possible window
246 * See RFC1323 for an explanation of the limit to 14
247 */
248 space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max);
249 space = min_t(u32, space, *window_clamp);
250 while (space > 65535 && (*rcv_wscale) < 14) {
251 space >>= 1;
252 (*rcv_wscale)++;
253 }
254 }
255
256 if (mss > (1 << *rcv_wscale)) {
257 if (!init_rcv_wnd) /* Use default unless specified otherwise */
258 init_rcv_wnd = tcp_default_init_rwnd(mss);
259 *rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss);
260 }
261
262 /* Set the clamp no higher than max representable value */
263 (*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp);
264}
265EXPORT_SYMBOL(tcp_select_initial_window);
266
267/* Chose a new window to advertise, update state in tcp_sock for the
268 * socket, and return result with RFC1323 scaling applied. The return
269 * value can be stuffed directly into th->window for an outgoing
270 * frame.
271 */
272static u16 tcp_select_window(struct sock *sk)
273{
274 struct tcp_sock *tp = tcp_sk(sk);
275 u32 old_win = tp->rcv_wnd;
276 u32 cur_win = tcp_receive_window(tp);
277 u32 new_win = __tcp_select_window(sk);
278
279 /* Never shrink the offered window */
280 if (new_win < cur_win) {
281 /* Danger Will Robinson!
282 * Don't update rcv_wup/rcv_wnd here or else
283 * we will not be able to advertise a zero
284 * window in time. --DaveM
285 *
286 * Relax Will Robinson.
287 */
288 if (new_win == 0)
289 NET_INC_STATS(sock_net(sk),
290 LINUX_MIB_TCPWANTZEROWINDOWADV);
291 new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale);
292 }
293 tp->rcv_wnd = new_win;
294 tp->rcv_wup = tp->rcv_nxt;
295
296 /* Make sure we do not exceed the maximum possible
297 * scaled window.
298 */
299 if (!tp->rx_opt.rcv_wscale && sysctl_tcp_workaround_signed_windows)
300 new_win = min(new_win, MAX_TCP_WINDOW);
301 else
302 new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
303
304 /* RFC1323 scaling applied */
305 new_win >>= tp->rx_opt.rcv_wscale;
306
307 /* If we advertise zero window, disable fast path. */
308 if (new_win == 0) {
309 tp->pred_flags = 0;
310 if (old_win)
311 NET_INC_STATS(sock_net(sk),
312 LINUX_MIB_TCPTOZEROWINDOWADV);
313 } else if (old_win == 0) {
314 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFROMZEROWINDOWADV);
315 }
316
317 return new_win;
318}
319
320/* Packet ECN state for a SYN-ACK */
321static inline void TCP_ECN_send_synack(const struct tcp_sock *tp, struct sk_buff *skb)
322{
323 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR;
324 if (!(tp->ecn_flags & TCP_ECN_OK))
325 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE;
326}
327
328/* Packet ECN state for a SYN. */
329static inline void TCP_ECN_send_syn(struct sock *sk, struct sk_buff *skb)
330{
331 struct tcp_sock *tp = tcp_sk(sk);
332
333 tp->ecn_flags = 0;
334 if (sock_net(sk)->ipv4.sysctl_tcp_ecn == 1) {
335 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
336 tp->ecn_flags = TCP_ECN_OK;
337 }
338}
339
340static __inline__ void
341TCP_ECN_make_synack(const struct request_sock *req, struct tcphdr *th)
342{
343 if (inet_rsk(req)->ecn_ok)
344 th->ece = 1;
345}
346
347/* Set up ECN state for a packet on a ESTABLISHED socket that is about to
348 * be sent.
349 */
350static inline void TCP_ECN_send(struct sock *sk, struct sk_buff *skb,
351 int tcp_header_len)
352{
353 struct tcp_sock *tp = tcp_sk(sk);
354
355 if (tp->ecn_flags & TCP_ECN_OK) {
356 /* Not-retransmitted data segment: set ECT and inject CWR. */
357 if (skb->len != tcp_header_len &&
358 !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) {
359 INET_ECN_xmit(sk);
360 if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) {
361 tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR;
362 tcp_hdr(skb)->cwr = 1;
363 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
364 }
365 } else {
366 /* ACK or retransmitted segment: clear ECT|CE */
367 INET_ECN_dontxmit(sk);
368 }
369 if (tp->ecn_flags & TCP_ECN_DEMAND_CWR)
370 tcp_hdr(skb)->ece = 1;
371 }
372}
373
374/* Constructs common control bits of non-data skb. If SYN/FIN is present,
375 * auto increment end seqno.
376 */
377static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
378{
379 struct skb_shared_info *shinfo = skb_shinfo(skb);
380
381 skb->ip_summed = CHECKSUM_PARTIAL;
382 skb->csum = 0;
383
384 TCP_SKB_CB(skb)->tcp_flags = flags;
385 TCP_SKB_CB(skb)->sacked = 0;
386
387 shinfo->gso_segs = 1;
388 shinfo->gso_size = 0;
389 shinfo->gso_type = 0;
390
391 TCP_SKB_CB(skb)->seq = seq;
392 if (flags & (TCPHDR_SYN | TCPHDR_FIN))
393 seq++;
394 TCP_SKB_CB(skb)->end_seq = seq;
395}
396
397static inline bool tcp_urg_mode(const struct tcp_sock *tp)
398{
399 return tp->snd_una != tp->snd_up;
400}
401
402#define OPTION_SACK_ADVERTISE (1 << 0)
403#define OPTION_TS (1 << 1)
404#define OPTION_MD5 (1 << 2)
405#define OPTION_WSCALE (1 << 3)
406#define OPTION_FAST_OPEN_COOKIE (1 << 8)
407
408struct tcp_out_options {
409 u16 options; /* bit field of OPTION_* */
410 u16 mss; /* 0 to disable */
411 u8 ws; /* window scale, 0 to disable */
412 u8 num_sack_blocks; /* number of SACK blocks to include */
413 u8 hash_size; /* bytes in hash_location */
414 __u8 *hash_location; /* temporary pointer, overloaded */
415 __u32 tsval, tsecr; /* need to include OPTION_TS */
416 struct tcp_fastopen_cookie *fastopen_cookie; /* Fast open cookie */
417};
418
419/* Write previously computed TCP options to the packet.
420 *
421 * Beware: Something in the Internet is very sensitive to the ordering of
422 * TCP options, we learned this through the hard way, so be careful here.
423 * Luckily we can at least blame others for their non-compliance but from
424 * inter-operability perspective it seems that we're somewhat stuck with
425 * the ordering which we have been using if we want to keep working with
426 * those broken things (not that it currently hurts anybody as there isn't
427 * particular reason why the ordering would need to be changed).
428 *
429 * At least SACK_PERM as the first option is known to lead to a disaster
430 * (but it may well be that other scenarios fail similarly).
431 */
432static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
433 struct tcp_out_options *opts)
434{
435 u16 options = opts->options; /* mungable copy */
436
437 if (unlikely(OPTION_MD5 & options)) {
438 *ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
439 (TCPOPT_MD5SIG << 8) | TCPOLEN_MD5SIG);
440 /* overload cookie hash location */
441 opts->hash_location = (__u8 *)ptr;
442 ptr += 4;
443 }
444
445 if (unlikely(opts->mss)) {
446 *ptr++ = htonl((TCPOPT_MSS << 24) |
447 (TCPOLEN_MSS << 16) |
448 opts->mss);
449 }
450
451 if (likely(OPTION_TS & options)) {
452 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
453 *ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
454 (TCPOLEN_SACK_PERM << 16) |
455 (TCPOPT_TIMESTAMP << 8) |
456 TCPOLEN_TIMESTAMP);
457 options &= ~OPTION_SACK_ADVERTISE;
458 } else {
459 *ptr++ = htonl((TCPOPT_NOP << 24) |
460 (TCPOPT_NOP << 16) |
461 (TCPOPT_TIMESTAMP << 8) |
462 TCPOLEN_TIMESTAMP);
463 }
464 *ptr++ = htonl(opts->tsval);
465 *ptr++ = htonl(opts->tsecr);
466 }
467
468 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
469 *ptr++ = htonl((TCPOPT_NOP << 24) |
470 (TCPOPT_NOP << 16) |
471 (TCPOPT_SACK_PERM << 8) |
472 TCPOLEN_SACK_PERM);
473 }
474
475 if (unlikely(OPTION_WSCALE & options)) {
476 *ptr++ = htonl((TCPOPT_NOP << 24) |
477 (TCPOPT_WINDOW << 16) |
478 (TCPOLEN_WINDOW << 8) |
479 opts->ws);
480 }
481
482 if (unlikely(opts->num_sack_blocks)) {
483 struct tcp_sack_block *sp = tp->rx_opt.dsack ?
484 tp->duplicate_sack : tp->selective_acks;
485 int this_sack;
486
487 *ptr++ = htonl((TCPOPT_NOP << 24) |
488 (TCPOPT_NOP << 16) |
489 (TCPOPT_SACK << 8) |
490 (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
491 TCPOLEN_SACK_PERBLOCK)));
492
493 for (this_sack = 0; this_sack < opts->num_sack_blocks;
494 ++this_sack) {
495 *ptr++ = htonl(sp[this_sack].start_seq);
496 *ptr++ = htonl(sp[this_sack].end_seq);
497 }
498
499 tp->rx_opt.dsack = 0;
500 }
501
502 if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
503 struct tcp_fastopen_cookie *foc = opts->fastopen_cookie;
504
505 *ptr++ = htonl((TCPOPT_EXP << 24) |
506 ((TCPOLEN_EXP_FASTOPEN_BASE + foc->len) << 16) |
507 TCPOPT_FASTOPEN_MAGIC);
508
509 memcpy(ptr, foc->val, foc->len);
510 if ((foc->len & 3) == 2) {
511 u8 *align = ((u8 *)ptr) + foc->len;
512 align[0] = align[1] = TCPOPT_NOP;
513 }
514 ptr += (foc->len + 3) >> 2;
515 }
516}
517
518/* Compute TCP options for SYN packets. This is not the final
519 * network wire format yet.
520 */
521static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
522 struct tcp_out_options *opts,
523 struct tcp_md5sig_key **md5)
524{
525 struct tcp_sock *tp = tcp_sk(sk);
526 unsigned int remaining = MAX_TCP_OPTION_SPACE;
527 struct tcp_fastopen_request *fastopen = tp->fastopen_req;
528
529#ifdef CONFIG_TCP_MD5SIG
530 *md5 = tp->af_specific->md5_lookup(sk, sk);
531 if (*md5) {
532 opts->options |= OPTION_MD5;
533 remaining -= TCPOLEN_MD5SIG_ALIGNED;
534 }
535#else
536 *md5 = NULL;
537#endif
538
539 /* We always get an MSS option. The option bytes which will be seen in
540 * normal data packets should timestamps be used, must be in the MSS
541 * advertised. But we subtract them from tp->mss_cache so that
542 * calculations in tcp_sendmsg are simpler etc. So account for this
543 * fact here if necessary. If we don't do this correctly, as a
544 * receiver we won't recognize data packets as being full sized when we
545 * should, and thus we won't abide by the delayed ACK rules correctly.
546 * SACKs don't matter, we never delay an ACK when we have any of those
547 * going out. */
548 opts->mss = tcp_advertise_mss(sk);
549 remaining -= TCPOLEN_MSS_ALIGNED;
550
551 if (likely(sysctl_tcp_timestamps && *md5 == NULL)) {
552 opts->options |= OPTION_TS;
553 opts->tsval = TCP_SKB_CB(skb)->when + tp->tsoffset;
554 opts->tsecr = tp->rx_opt.ts_recent;
555 remaining -= TCPOLEN_TSTAMP_ALIGNED;
556 }
557 if (likely(sysctl_tcp_window_scaling)) {
558 opts->ws = tp->rx_opt.rcv_wscale;
559 opts->options |= OPTION_WSCALE;
560 remaining -= TCPOLEN_WSCALE_ALIGNED;
561 }
562 if (likely(sysctl_tcp_sack)) {
563 opts->options |= OPTION_SACK_ADVERTISE;
564 if (unlikely(!(OPTION_TS & opts->options)))
565 remaining -= TCPOLEN_SACKPERM_ALIGNED;
566 }
567
568 if (fastopen && fastopen->cookie.len >= 0) {
569 u32 need = TCPOLEN_EXP_FASTOPEN_BASE + fastopen->cookie.len;
570 need = (need + 3) & ~3U; /* Align to 32 bits */
571 if (remaining >= need) {
572 opts->options |= OPTION_FAST_OPEN_COOKIE;
573 opts->fastopen_cookie = &fastopen->cookie;
574 remaining -= need;
575 tp->syn_fastopen = 1;
576 }
577 }
578
579 return MAX_TCP_OPTION_SPACE - remaining;
580}
581
582/* Set up TCP options for SYN-ACKs. */
583static unsigned int tcp_synack_options(struct sock *sk,
584 struct request_sock *req,
585 unsigned int mss, struct sk_buff *skb,
586 struct tcp_out_options *opts,
587 struct tcp_md5sig_key **md5,
588 struct tcp_fastopen_cookie *foc)
589{
590 struct inet_request_sock *ireq = inet_rsk(req);
591 unsigned int remaining = MAX_TCP_OPTION_SPACE;
592
593#ifdef CONFIG_TCP_MD5SIG
594 *md5 = tcp_rsk(req)->af_specific->md5_lookup(sk, req);
595 if (*md5) {
596 opts->options |= OPTION_MD5;
597 remaining -= TCPOLEN_MD5SIG_ALIGNED;
598
599 /* We can't fit any SACK blocks in a packet with MD5 + TS
600 * options. There was discussion about disabling SACK
601 * rather than TS in order to fit in better with old,
602 * buggy kernels, but that was deemed to be unnecessary.
603 */
604 ireq->tstamp_ok &= !ireq->sack_ok;
605 }
606#else
607 *md5 = NULL;
608#endif
609
610 /* We always send an MSS option. */
611 opts->mss = mss;
612 remaining -= TCPOLEN_MSS_ALIGNED;
613
614 if (likely(ireq->wscale_ok)) {
615 opts->ws = ireq->rcv_wscale;
616 opts->options |= OPTION_WSCALE;
617 remaining -= TCPOLEN_WSCALE_ALIGNED;
618 }
619 if (likely(ireq->tstamp_ok)) {
620 opts->options |= OPTION_TS;
621 opts->tsval = TCP_SKB_CB(skb)->when;
622 opts->tsecr = req->ts_recent;
623 remaining -= TCPOLEN_TSTAMP_ALIGNED;
624 }
625 if (likely(ireq->sack_ok)) {
626 opts->options |= OPTION_SACK_ADVERTISE;
627 if (unlikely(!ireq->tstamp_ok))
628 remaining -= TCPOLEN_SACKPERM_ALIGNED;
629 }
630 if (foc != NULL) {
631 u32 need = TCPOLEN_EXP_FASTOPEN_BASE + foc->len;
632 need = (need + 3) & ~3U; /* Align to 32 bits */
633 if (remaining >= need) {
634 opts->options |= OPTION_FAST_OPEN_COOKIE;
635 opts->fastopen_cookie = foc;
636 remaining -= need;
637 }
638 }
639
640 return MAX_TCP_OPTION_SPACE - remaining;
641}
642
643/* Compute TCP options for ESTABLISHED sockets. This is not the
644 * final wire format yet.
645 */
646static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb,
647 struct tcp_out_options *opts,
648 struct tcp_md5sig_key **md5)
649{
650 struct tcp_skb_cb *tcb = skb ? TCP_SKB_CB(skb) : NULL;
651 struct tcp_sock *tp = tcp_sk(sk);
652 unsigned int size = 0;
653 unsigned int eff_sacks;
654
655 opts->options = 0;
656
657#ifdef CONFIG_TCP_MD5SIG
658 *md5 = tp->af_specific->md5_lookup(sk, sk);
659 if (unlikely(*md5)) {
660 opts->options |= OPTION_MD5;
661 size += TCPOLEN_MD5SIG_ALIGNED;
662 }
663#else
664 *md5 = NULL;
665#endif
666
667 if (likely(tp->rx_opt.tstamp_ok)) {
668 opts->options |= OPTION_TS;
669 opts->tsval = tcb ? tcb->when + tp->tsoffset : 0;
670 opts->tsecr = tp->rx_opt.ts_recent;
671 size += TCPOLEN_TSTAMP_ALIGNED;
672 }
673
674 eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
675 if (unlikely(eff_sacks)) {
676 const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
677 opts->num_sack_blocks =
678 min_t(unsigned int, eff_sacks,
679 (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
680 TCPOLEN_SACK_PERBLOCK);
681 size += TCPOLEN_SACK_BASE_ALIGNED +
682 opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
683 }
684
685 return size;
686}
687
688
689/* TCP SMALL QUEUES (TSQ)
690 *
691 * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
692 * to reduce RTT and bufferbloat.
693 * We do this using a special skb destructor (tcp_wfree).
694 *
695 * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
696 * needs to be reallocated in a driver.
697 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
698 *
699 * Since transmit from skb destructor is forbidden, we use a tasklet
700 * to process all sockets that eventually need to send more skbs.
701 * We use one tasklet per cpu, with its own queue of sockets.
702 */
703struct tsq_tasklet {
704 struct tasklet_struct tasklet;
705 struct list_head head; /* queue of tcp sockets */
706};
707static DEFINE_PER_CPU(struct tsq_tasklet, tsq_tasklet);
708
709static void tcp_tsq_handler(struct sock *sk)
710{
711 if ((1 << sk->sk_state) &
712 (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING |
713 TCPF_CLOSE_WAIT | TCPF_LAST_ACK))
714 tcp_write_xmit(sk, tcp_current_mss(sk), tcp_sk(sk)->nonagle,
715 0, GFP_ATOMIC);
716}
717/*
718 * One tasklet per cpu tries to send more skbs.
719 * We run in tasklet context but need to disable irqs when
720 * transferring tsq->head because tcp_wfree() might
721 * interrupt us (non NAPI drivers)
722 */
723static void tcp_tasklet_func(unsigned long data)
724{
725 struct tsq_tasklet *tsq = (struct tsq_tasklet *)data;
726 LIST_HEAD(list);
727 unsigned long flags;
728 struct list_head *q, *n;
729 struct tcp_sock *tp;
730 struct sock *sk;
731
732 local_irq_save(flags);
733 list_splice_init(&tsq->head, &list);
734 local_irq_restore(flags);
735
736 list_for_each_safe(q, n, &list) {
737 tp = list_entry(q, struct tcp_sock, tsq_node);
738 list_del(&tp->tsq_node);
739
740 sk = (struct sock *)tp;
741 bh_lock_sock(sk);
742
743 if (!sock_owned_by_user(sk)) {
744 tcp_tsq_handler(sk);
745 } else {
746 /* defer the work to tcp_release_cb() */
747 set_bit(TCP_TSQ_DEFERRED, &tp->tsq_flags);
748 }
749 bh_unlock_sock(sk);
750
751 clear_bit(TSQ_QUEUED, &tp->tsq_flags);
752 sk_free(sk);
753 }
754}
755
756#define TCP_DEFERRED_ALL ((1UL << TCP_TSQ_DEFERRED) | \
757 (1UL << TCP_WRITE_TIMER_DEFERRED) | \
758 (1UL << TCP_DELACK_TIMER_DEFERRED) | \
759 (1UL << TCP_MTU_REDUCED_DEFERRED))
760/**
761 * tcp_release_cb - tcp release_sock() callback
762 * @sk: socket
763 *
764 * called from release_sock() to perform protocol dependent
765 * actions before socket release.
766 */
767void tcp_release_cb(struct sock *sk)
768{
769 struct tcp_sock *tp = tcp_sk(sk);
770 unsigned long flags, nflags;
771
772 /* perform an atomic operation only if at least one flag is set */
773 do {
774 flags = tp->tsq_flags;
775 if (!(flags & TCP_DEFERRED_ALL))
776 return;
777 nflags = flags & ~TCP_DEFERRED_ALL;
778 } while (cmpxchg(&tp->tsq_flags, flags, nflags) != flags);
779
780 if (flags & (1UL << TCP_TSQ_DEFERRED))
781 tcp_tsq_handler(sk);
782
783 /* Here begins the tricky part :
784 * We are called from release_sock() with :
785 * 1) BH disabled
786 * 2) sk_lock.slock spinlock held
787 * 3) socket owned by us (sk->sk_lock.owned == 1)
788 *
789 * But following code is meant to be called from BH handlers,
790 * so we should keep BH disabled, but early release socket ownership
791 */
792 sock_release_ownership(sk);
793
794 if (flags & (1UL << TCP_WRITE_TIMER_DEFERRED)) {
795 tcp_write_timer_handler(sk);
796 __sock_put(sk);
797 }
798 if (flags & (1UL << TCP_DELACK_TIMER_DEFERRED)) {
799 tcp_delack_timer_handler(sk);
800 __sock_put(sk);
801 }
802 if (flags & (1UL << TCP_MTU_REDUCED_DEFERRED)) {
803 sk->sk_prot->mtu_reduced(sk);
804 __sock_put(sk);
805 }
806}
807EXPORT_SYMBOL(tcp_release_cb);
808
809void __init tcp_tasklet_init(void)
810{
811 int i;
812
813 for_each_possible_cpu(i) {
814 struct tsq_tasklet *tsq = &per_cpu(tsq_tasklet, i);
815
816 INIT_LIST_HEAD(&tsq->head);
817 tasklet_init(&tsq->tasklet,
818 tcp_tasklet_func,
819 (unsigned long)tsq);
820 }
821}
822
823/*
824 * Write buffer destructor automatically called from kfree_skb.
825 * We can't xmit new skbs from this context, as we might already
826 * hold qdisc lock.
827 */
828void tcp_wfree(struct sk_buff *skb)
829{
830 struct sock *sk = skb->sk;
831 struct tcp_sock *tp = tcp_sk(sk);
832
833 if (test_and_clear_bit(TSQ_THROTTLED, &tp->tsq_flags) &&
834 !test_and_set_bit(TSQ_QUEUED, &tp->tsq_flags)) {
835 unsigned long flags;
836 struct tsq_tasklet *tsq;
837
838 /* Keep a ref on socket.
839 * This last ref will be released in tcp_tasklet_func()
840 */
841 atomic_sub(skb->truesize - 1, &sk->sk_wmem_alloc);
842
843 /* queue this socket to tasklet queue */
844 local_irq_save(flags);
845 tsq = &__get_cpu_var(tsq_tasklet);
846 list_add(&tp->tsq_node, &tsq->head);
847 tasklet_schedule(&tsq->tasklet);
848 local_irq_restore(flags);
849 } else {
850 sock_wfree(skb);
851 }
852}
853
854/* This routine actually transmits TCP packets queued in by
855 * tcp_do_sendmsg(). This is used by both the initial
856 * transmission and possible later retransmissions.
857 * All SKB's seen here are completely headerless. It is our
858 * job to build the TCP header, and pass the packet down to
859 * IP so it can do the same plus pass the packet off to the
860 * device.
861 *
862 * We are working here with either a clone of the original
863 * SKB, or a fresh unique copy made by the retransmit engine.
864 */
865static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
866 gfp_t gfp_mask)
867{
868 const struct inet_connection_sock *icsk = inet_csk(sk);
869 struct inet_sock *inet;
870 struct tcp_sock *tp;
871 struct tcp_skb_cb *tcb;
872 struct tcp_out_options opts;
873 unsigned int tcp_options_size, tcp_header_size;
874 struct tcp_md5sig_key *md5;
875 struct tcphdr *th;
876 int err;
877
878 BUG_ON(!skb || !tcp_skb_pcount(skb));
879
880 if (clone_it) {
881 const struct sk_buff *fclone = skb + 1;
882
883 skb_mstamp_get(&skb->skb_mstamp);
884
885 if (unlikely(skb->fclone == SKB_FCLONE_ORIG &&
886 fclone->fclone == SKB_FCLONE_CLONE))
887 NET_INC_STATS(sock_net(sk),
888 LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
889
890 if (unlikely(skb_cloned(skb)))
891 skb = pskb_copy(skb, gfp_mask);
892 else
893 skb = skb_clone(skb, gfp_mask);
894 if (unlikely(!skb))
895 return -ENOBUFS;
896 /* Our usage of tstamp should remain private */
897 skb->tstamp.tv64 = 0;
898 }
899
900 inet = inet_sk(sk);
901 tp = tcp_sk(sk);
902 tcb = TCP_SKB_CB(skb);
903 memset(&opts, 0, sizeof(opts));
904
905 if (unlikely(tcb->tcp_flags & TCPHDR_SYN))
906 tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5);
907 else
908 tcp_options_size = tcp_established_options(sk, skb, &opts,
909 &md5);
910 tcp_header_size = tcp_options_size + sizeof(struct tcphdr);
911
912 if (tcp_packets_in_flight(tp) == 0)
913 tcp_ca_event(sk, CA_EVENT_TX_START);
914
915 /* if no packet is in qdisc/device queue, then allow XPS to select
916 * another queue.
917 */
918 skb->ooo_okay = sk_wmem_alloc_get(sk) == 0;
919
920 skb_push(skb, tcp_header_size);
921 skb_reset_transport_header(skb);
922
923 skb_orphan(skb);
924 skb->sk = sk;
925 skb->destructor = tcp_wfree;
926 atomic_add(skb->truesize, &sk->sk_wmem_alloc);
927
928 /* Build TCP header and checksum it. */
929 th = tcp_hdr(skb);
930 th->source = inet->inet_sport;
931 th->dest = inet->inet_dport;
932 th->seq = htonl(tcb->seq);
933 th->ack_seq = htonl(tp->rcv_nxt);
934 *(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) |
935 tcb->tcp_flags);
936
937 if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) {
938 /* RFC1323: The window in SYN & SYN/ACK segments
939 * is never scaled.
940 */
941 th->window = htons(min(tp->rcv_wnd, 65535U));
942 } else {
943 th->window = htons(tcp_select_window(sk));
944 }
945 th->check = 0;
946 th->urg_ptr = 0;
947
948 /* The urg_mode check is necessary during a below snd_una win probe */
949 if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) {
950 if (before(tp->snd_up, tcb->seq + 0x10000)) {
951 th->urg_ptr = htons(tp->snd_up - tcb->seq);
952 th->urg = 1;
953 } else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
954 th->urg_ptr = htons(0xFFFF);
955 th->urg = 1;
956 }
957 }
958
959 tcp_options_write((__be32 *)(th + 1), tp, &opts);
960 if (likely((tcb->tcp_flags & TCPHDR_SYN) == 0))
961 TCP_ECN_send(sk, skb, tcp_header_size);
962
963#ifdef CONFIG_TCP_MD5SIG
964 /* Calculate the MD5 hash, as we have all we need now */
965 if (md5) {
966 sk_nocaps_add(sk, NETIF_F_GSO_MASK);
967 tp->af_specific->calc_md5_hash(opts.hash_location,
968 md5, sk, NULL, skb);
969 }
970#endif
971
972 icsk->icsk_af_ops->send_check(sk, skb);
973
974 if (likely(tcb->tcp_flags & TCPHDR_ACK))
975 tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
976
977 if (skb->len != tcp_header_size)
978 tcp_event_data_sent(tp, sk);
979
980 if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
981 TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
982 tcp_skb_pcount(skb));
983
984 err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
985 if (likely(err <= 0))
986 return err;
987
988 tcp_enter_cwr(sk, 1);
989
990 return net_xmit_eval(err);
991}
992
993/* This routine just queues the buffer for sending.
994 *
995 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
996 * otherwise socket can stall.
997 */
998static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
999{
1000 struct tcp_sock *tp = tcp_sk(sk);
1001
1002 /* Advance write_seq and place onto the write_queue. */
1003 tp->write_seq = TCP_SKB_CB(skb)->end_seq;
1004 skb_header_release(skb);
1005 tcp_add_write_queue_tail(sk, skb);
1006 sk->sk_wmem_queued += skb->truesize;
1007 sk_mem_charge(sk, skb->truesize);
1008}
1009
1010/* Initialize TSO segments for a packet. */
1011static void tcp_set_skb_tso_segs(const struct sock *sk, struct sk_buff *skb,
1012 unsigned int mss_now)
1013{
1014 struct skb_shared_info *shinfo = skb_shinfo(skb);
1015
1016 /* Make sure we own this skb before messing gso_size/gso_segs */
1017 WARN_ON_ONCE(skb_cloned(skb));
1018
1019 if (skb->len <= mss_now || skb->ip_summed == CHECKSUM_NONE) {
1020 /* Avoid the costly divide in the normal
1021 * non-TSO case.
1022 */
1023 shinfo->gso_segs = 1;
1024 shinfo->gso_size = 0;
1025 shinfo->gso_type = 0;
1026 } else {
1027 shinfo->gso_segs = DIV_ROUND_UP(skb->len, mss_now);
1028 shinfo->gso_size = mss_now;
1029 shinfo->gso_type = sk->sk_gso_type;
1030 }
1031}
1032
1033/* When a modification to fackets out becomes necessary, we need to check
1034 * skb is counted to fackets_out or not.
1035 */
1036static void tcp_adjust_fackets_out(struct sock *sk, const struct sk_buff *skb,
1037 int decr)
1038{
1039 struct tcp_sock *tp = tcp_sk(sk);
1040
1041 if (!tp->sacked_out || tcp_is_reno(tp))
1042 return;
1043
1044 if (after(tcp_highest_sack_seq(tp), TCP_SKB_CB(skb)->seq))
1045 tp->fackets_out -= decr;
1046}
1047
1048/* Pcount in the middle of the write queue got changed, we need to do various
1049 * tweaks to fix counters
1050 */
1051static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr)
1052{
1053 struct tcp_sock *tp = tcp_sk(sk);
1054
1055 tp->packets_out -= decr;
1056
1057 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
1058 tp->sacked_out -= decr;
1059 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
1060 tp->retrans_out -= decr;
1061 if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)
1062 tp->lost_out -= decr;
1063
1064 /* Reno case is special. Sigh... */
1065 if (tcp_is_reno(tp) && decr > 0)
1066 tp->sacked_out -= min_t(u32, tp->sacked_out, decr);
1067
1068 tcp_adjust_fackets_out(sk, skb, decr);
1069
1070 if (tp->lost_skb_hint &&
1071 before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) &&
1072 (tcp_is_fack(tp) || (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)))
1073 tp->lost_cnt_hint -= decr;
1074
1075 tcp_verify_left_out(tp);
1076}
1077
1078/* Function to create two new TCP segments. Shrinks the given segment
1079 * to the specified size and appends a new segment with the rest of the
1080 * packet to the list. This won't be called frequently, I hope.
1081 * Remember, these are still headerless SKBs at this point.
1082 */
1083int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
1084 unsigned int mss_now)
1085{
1086 struct tcp_sock *tp = tcp_sk(sk);
1087 struct sk_buff *buff;
1088 int nsize, old_factor;
1089 int nlen;
1090 u8 flags;
1091
1092 if (WARN_ON(len > skb->len))
1093 return -EINVAL;
1094
1095 nsize = skb_headlen(skb) - len;
1096 if (nsize < 0)
1097 nsize = 0;
1098
1099 if (skb_unclone(skb, GFP_ATOMIC))
1100 return -ENOMEM;
1101
1102 /* Get a new skb... force flag on. */
1103 buff = sk_stream_alloc_skb(sk, nsize, GFP_ATOMIC);
1104 if (buff == NULL)
1105 return -ENOMEM; /* We'll just try again later. */
1106
1107 sk->sk_wmem_queued += buff->truesize;
1108 sk_mem_charge(sk, buff->truesize);
1109 nlen = skb->len - len - nsize;
1110 buff->truesize += nlen;
1111 skb->truesize -= nlen;
1112
1113 /* Correct the sequence numbers. */
1114 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1115 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1116 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1117
1118 /* PSH and FIN should only be set in the second packet. */
1119 flags = TCP_SKB_CB(skb)->tcp_flags;
1120 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
1121 TCP_SKB_CB(buff)->tcp_flags = flags;
1122 TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
1123
1124 if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) {
1125 /* Copy and checksum data tail into the new buffer. */
1126 buff->csum = csum_partial_copy_nocheck(skb->data + len,
1127 skb_put(buff, nsize),
1128 nsize, 0);
1129
1130 skb_trim(skb, len);
1131
1132 skb->csum = csum_block_sub(skb->csum, buff->csum, len);
1133 } else {
1134 skb->ip_summed = CHECKSUM_PARTIAL;
1135 skb_split(skb, buff, len);
1136 }
1137
1138 buff->ip_summed = skb->ip_summed;
1139
1140 /* Looks stupid, but our code really uses when of
1141 * skbs, which it never sent before. --ANK
1142 */
1143 TCP_SKB_CB(buff)->when = TCP_SKB_CB(skb)->when;
1144 buff->tstamp = skb->tstamp;
1145
1146 old_factor = tcp_skb_pcount(skb);
1147
1148 /* Fix up tso_factor for both original and new SKB. */
1149 tcp_set_skb_tso_segs(sk, skb, mss_now);
1150 tcp_set_skb_tso_segs(sk, buff, mss_now);
1151
1152 /* If this packet has been sent out already, we must
1153 * adjust the various packet counters.
1154 */
1155 if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1156 int diff = old_factor - tcp_skb_pcount(skb) -
1157 tcp_skb_pcount(buff);
1158
1159 if (diff)
1160 tcp_adjust_pcount(sk, skb, diff);
1161 }
1162
1163 /* Link BUFF into the send queue. */
1164 skb_header_release(buff);
1165 tcp_insert_write_queue_after(skb, buff, sk);
1166
1167 return 0;
1168}
1169
1170/* This is similar to __pskb_pull_head() (it will go to core/skbuff.c
1171 * eventually). The difference is that pulled data not copied, but
1172 * immediately discarded.
1173 */
1174static void __pskb_trim_head(struct sk_buff *skb, int len)
1175{
1176 struct skb_shared_info *shinfo;
1177 int i, k, eat;
1178
1179 eat = min_t(int, len, skb_headlen(skb));
1180 if (eat) {
1181 __skb_pull(skb, eat);
1182 len -= eat;
1183 if (!len)
1184 return;
1185 }
1186 eat = len;
1187 k = 0;
1188 shinfo = skb_shinfo(skb);
1189 for (i = 0; i < shinfo->nr_frags; i++) {
1190 int size = skb_frag_size(&shinfo->frags[i]);
1191
1192 if (size <= eat) {
1193 skb_frag_unref(skb, i);
1194 eat -= size;
1195 } else {
1196 shinfo->frags[k] = shinfo->frags[i];
1197 if (eat) {
1198 shinfo->frags[k].page_offset += eat;
1199 skb_frag_size_sub(&shinfo->frags[k], eat);
1200 eat = 0;
1201 }
1202 k++;
1203 }
1204 }
1205 shinfo->nr_frags = k;
1206
1207 skb_reset_tail_pointer(skb);
1208 skb->data_len -= len;
1209 skb->len = skb->data_len;
1210}
1211
1212/* Remove acked data from a packet in the transmit queue. */
1213int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
1214{
1215 if (skb_unclone(skb, GFP_ATOMIC))
1216 return -ENOMEM;
1217
1218 __pskb_trim_head(skb, len);
1219
1220 TCP_SKB_CB(skb)->seq += len;
1221 skb->ip_summed = CHECKSUM_PARTIAL;
1222
1223 skb->truesize -= len;
1224 sk->sk_wmem_queued -= len;
1225 sk_mem_uncharge(sk, len);
1226 sock_set_flag(sk, SOCK_QUEUE_SHRUNK);
1227
1228 /* Any change of skb->len requires recalculation of tso factor. */
1229 if (tcp_skb_pcount(skb) > 1)
1230 tcp_set_skb_tso_segs(sk, skb, tcp_skb_mss(skb));
1231
1232 return 0;
1233}
1234
1235/* Calculate MSS not accounting any TCP options. */
1236static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu)
1237{
1238 const struct tcp_sock *tp = tcp_sk(sk);
1239 const struct inet_connection_sock *icsk = inet_csk(sk);
1240 int mss_now;
1241
1242 /* Calculate base mss without TCP options:
1243 It is MMS_S - sizeof(tcphdr) of rfc1122
1244 */
1245 mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr);
1246
1247 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1248 if (icsk->icsk_af_ops->net_frag_header_len) {
1249 const struct dst_entry *dst = __sk_dst_get(sk);
1250
1251 if (dst && dst_allfrag(dst))
1252 mss_now -= icsk->icsk_af_ops->net_frag_header_len;
1253 }
1254
1255 /* Clamp it (mss_clamp does not include tcp options) */
1256 if (mss_now > tp->rx_opt.mss_clamp)
1257 mss_now = tp->rx_opt.mss_clamp;
1258
1259 /* Now subtract optional transport overhead */
1260 mss_now -= icsk->icsk_ext_hdr_len;
1261
1262 /* Then reserve room for full set of TCP options and 8 bytes of data */
1263 if (mss_now < 48)
1264 mss_now = 48;
1265 return mss_now;
1266}
1267
1268/* Calculate MSS. Not accounting for SACKs here. */
1269int tcp_mtu_to_mss(struct sock *sk, int pmtu)
1270{
1271 /* Subtract TCP options size, not including SACKs */
1272 return __tcp_mtu_to_mss(sk, pmtu) -
1273 (tcp_sk(sk)->tcp_header_len - sizeof(struct tcphdr));
1274}
1275
1276/* Inverse of above */
1277int tcp_mss_to_mtu(struct sock *sk, int mss)
1278{
1279 const struct tcp_sock *tp = tcp_sk(sk);
1280 const struct inet_connection_sock *icsk = inet_csk(sk);
1281 int mtu;
1282
1283 mtu = mss +
1284 tp->tcp_header_len +
1285 icsk->icsk_ext_hdr_len +
1286 icsk->icsk_af_ops->net_header_len;
1287
1288 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1289 if (icsk->icsk_af_ops->net_frag_header_len) {
1290 const struct dst_entry *dst = __sk_dst_get(sk);
1291
1292 if (dst && dst_allfrag(dst))
1293 mtu += icsk->icsk_af_ops->net_frag_header_len;
1294 }
1295 return mtu;
1296}
1297
1298/* MTU probing init per socket */
1299void tcp_mtup_init(struct sock *sk)
1300{
1301 struct tcp_sock *tp = tcp_sk(sk);
1302 struct inet_connection_sock *icsk = inet_csk(sk);
1303
1304 icsk->icsk_mtup.enabled = sysctl_tcp_mtu_probing > 1;
1305 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1306 icsk->icsk_af_ops->net_header_len;
1307 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, sysctl_tcp_base_mss);
1308 icsk->icsk_mtup.probe_size = 0;
1309}
1310EXPORT_SYMBOL(tcp_mtup_init);
1311
1312/* This function synchronize snd mss to current pmtu/exthdr set.
1313
1314 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
1315 for TCP options, but includes only bare TCP header.
1316
1317 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1318 It is minimum of user_mss and mss received with SYN.
1319 It also does not include TCP options.
1320
1321 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
1322
1323 tp->mss_cache is current effective sending mss, including
1324 all tcp options except for SACKs. It is evaluated,
1325 taking into account current pmtu, but never exceeds
1326 tp->rx_opt.mss_clamp.
1327
1328 NOTE1. rfc1122 clearly states that advertised MSS
1329 DOES NOT include either tcp or ip options.
1330
1331 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1332 are READ ONLY outside this function. --ANK (980731)
1333 */
1334unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
1335{
1336 struct tcp_sock *tp = tcp_sk(sk);
1337 struct inet_connection_sock *icsk = inet_csk(sk);
1338 int mss_now;
1339
1340 if (icsk->icsk_mtup.search_high > pmtu)
1341 icsk->icsk_mtup.search_high = pmtu;
1342
1343 mss_now = tcp_mtu_to_mss(sk, pmtu);
1344 mss_now = tcp_bound_to_half_wnd(tp, mss_now);
1345
1346 /* And store cached results */
1347 icsk->icsk_pmtu_cookie = pmtu;
1348 if (icsk->icsk_mtup.enabled)
1349 mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1350 tp->mss_cache = mss_now;
1351
1352 return mss_now;
1353}
1354EXPORT_SYMBOL(tcp_sync_mss);
1355
1356/* Compute the current effective MSS, taking SACKs and IP options,
1357 * and even PMTU discovery events into account.
1358 */
1359unsigned int tcp_current_mss(struct sock *sk)
1360{
1361 const struct tcp_sock *tp = tcp_sk(sk);
1362 const struct dst_entry *dst = __sk_dst_get(sk);
1363 u32 mss_now;
1364 unsigned int header_len;
1365 struct tcp_out_options opts;
1366 struct tcp_md5sig_key *md5;
1367
1368 mss_now = tp->mss_cache;
1369
1370 if (dst) {
1371 u32 mtu = dst_mtu(dst);
1372 if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
1373 mss_now = tcp_sync_mss(sk, mtu);
1374 }
1375
1376 header_len = tcp_established_options(sk, NULL, &opts, &md5) +
1377 sizeof(struct tcphdr);
1378 /* The mss_cache is sized based on tp->tcp_header_len, which assumes
1379 * some common options. If this is an odd packet (because we have SACK
1380 * blocks etc) then our calculated header_len will be different, and
1381 * we have to adjust mss_now correspondingly */
1382 if (header_len != tp->tcp_header_len) {
1383 int delta = (int) header_len - tp->tcp_header_len;
1384 mss_now -= delta;
1385 }
1386
1387 return mss_now;
1388}
1389
1390/* Congestion window validation. (RFC2861) */
1391static void tcp_cwnd_validate(struct sock *sk)
1392{
1393 struct tcp_sock *tp = tcp_sk(sk);
1394
1395 if (tp->packets_out >= tp->snd_cwnd) {
1396 /* Network is feed fully. */
1397 tp->snd_cwnd_used = 0;
1398 tp->snd_cwnd_stamp = tcp_time_stamp;
1399 } else {
1400 /* Network starves. */
1401 if (tp->packets_out > tp->snd_cwnd_used)
1402 tp->snd_cwnd_used = tp->packets_out;
1403
1404 if (sysctl_tcp_slow_start_after_idle &&
1405 (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto)
1406 tcp_cwnd_application_limited(sk);
1407 }
1408}
1409
1410/* Minshall's variant of the Nagle send check. */
1411static bool tcp_minshall_check(const struct tcp_sock *tp)
1412{
1413 return after(tp->snd_sml, tp->snd_una) &&
1414 !after(tp->snd_sml, tp->snd_nxt);
1415}
1416
1417/* Update snd_sml if this skb is under mss
1418 * Note that a TSO packet might end with a sub-mss segment
1419 * The test is really :
1420 * if ((skb->len % mss) != 0)
1421 * tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1422 * But we can avoid doing the divide again given we already have
1423 * skb_pcount = skb->len / mss_now
1424 */
1425static void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss_now,
1426 const struct sk_buff *skb)
1427{
1428 if (skb->len < tcp_skb_pcount(skb) * mss_now)
1429 tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1430}
1431
1432/* Return false, if packet can be sent now without violation Nagle's rules:
1433 * 1. It is full sized. (provided by caller in %partial bool)
1434 * 2. Or it contains FIN. (already checked by caller)
1435 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
1436 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1437 * With Minshall's modification: all sent small packets are ACKed.
1438 */
1439static bool tcp_nagle_check(bool partial, const struct tcp_sock *tp,
1440 int nonagle)
1441{
1442 return partial &&
1443 ((nonagle & TCP_NAGLE_CORK) ||
1444 (!nonagle && tp->packets_out && tcp_minshall_check(tp)));
1445}
1446/* Returns the portion of skb which can be sent right away */
1447static unsigned int tcp_mss_split_point(const struct sock *sk,
1448 const struct sk_buff *skb,
1449 unsigned int mss_now,
1450 unsigned int max_segs,
1451 int nonagle)
1452{
1453 const struct tcp_sock *tp = tcp_sk(sk);
1454 u32 partial, needed, window, max_len;
1455
1456 window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1457 max_len = mss_now * max_segs;
1458
1459 if (likely(max_len <= window && skb != tcp_write_queue_tail(sk)))
1460 return max_len;
1461
1462 needed = min(skb->len, window);
1463
1464 if (max_len <= needed)
1465 return max_len;
1466
1467 partial = needed % mss_now;
1468 /* If last segment is not a full MSS, check if Nagle rules allow us
1469 * to include this last segment in this skb.
1470 * Otherwise, we'll split the skb at last MSS boundary
1471 */
1472 if (tcp_nagle_check(partial != 0, tp, nonagle))
1473 return needed - partial;
1474
1475 return needed;
1476}
1477
1478/* Can at least one segment of SKB be sent right now, according to the
1479 * congestion window rules? If so, return how many segments are allowed.
1480 */
1481static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp,
1482 const struct sk_buff *skb)
1483{
1484 u32 in_flight, cwnd;
1485
1486 /* Don't be strict about the congestion window for the final FIN. */
1487 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) &&
1488 tcp_skb_pcount(skb) == 1)
1489 return 1;
1490
1491 in_flight = tcp_packets_in_flight(tp);
1492 cwnd = tp->snd_cwnd;
1493 if (in_flight < cwnd)
1494 return (cwnd - in_flight);
1495
1496 return 0;
1497}
1498
1499/* Initialize TSO state of a skb.
1500 * This must be invoked the first time we consider transmitting
1501 * SKB onto the wire.
1502 */
1503static int tcp_init_tso_segs(const struct sock *sk, struct sk_buff *skb,
1504 unsigned int mss_now)
1505{
1506 int tso_segs = tcp_skb_pcount(skb);
1507
1508 if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
1509 tcp_set_skb_tso_segs(sk, skb, mss_now);
1510 tso_segs = tcp_skb_pcount(skb);
1511 }
1512 return tso_segs;
1513}
1514
1515
1516/* Return true if the Nagle test allows this packet to be
1517 * sent now.
1518 */
1519static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb,
1520 unsigned int cur_mss, int nonagle)
1521{
1522 /* Nagle rule does not apply to frames, which sit in the middle of the
1523 * write_queue (they have no chances to get new data).
1524 *
1525 * This is implemented in the callers, where they modify the 'nonagle'
1526 * argument based upon the location of SKB in the send queue.
1527 */
1528 if (nonagle & TCP_NAGLE_PUSH)
1529 return true;
1530
1531 /* Don't use the nagle rule for urgent data (or for the final FIN). */
1532 if (tcp_urg_mode(tp) || (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
1533 return true;
1534
1535 if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle))
1536 return true;
1537
1538 return false;
1539}
1540
1541/* Does at least the first segment of SKB fit into the send window? */
1542static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
1543 const struct sk_buff *skb,
1544 unsigned int cur_mss)
1545{
1546 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
1547
1548 if (skb->len > cur_mss)
1549 end_seq = TCP_SKB_CB(skb)->seq + cur_mss;
1550
1551 return !after(end_seq, tcp_wnd_end(tp));
1552}
1553
1554/* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1555 * should be put on the wire right now. If so, it returns the number of
1556 * packets allowed by the congestion window.
1557 */
1558static unsigned int tcp_snd_test(const struct sock *sk, struct sk_buff *skb,
1559 unsigned int cur_mss, int nonagle)
1560{
1561 const struct tcp_sock *tp = tcp_sk(sk);
1562 unsigned int cwnd_quota;
1563
1564 tcp_init_tso_segs(sk, skb, cur_mss);
1565
1566 if (!tcp_nagle_test(tp, skb, cur_mss, nonagle))
1567 return 0;
1568
1569 cwnd_quota = tcp_cwnd_test(tp, skb);
1570 if (cwnd_quota && !tcp_snd_wnd_test(tp, skb, cur_mss))
1571 cwnd_quota = 0;
1572
1573 return cwnd_quota;
1574}
1575
1576/* Test if sending is allowed right now. */
1577bool tcp_may_send_now(struct sock *sk)
1578{
1579 const struct tcp_sock *tp = tcp_sk(sk);
1580 struct sk_buff *skb = tcp_send_head(sk);
1581
1582 return skb &&
1583 tcp_snd_test(sk, skb, tcp_current_mss(sk),
1584 (tcp_skb_is_last(sk, skb) ?
1585 tp->nonagle : TCP_NAGLE_PUSH));
1586}
1587
1588/* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
1589 * which is put after SKB on the list. It is very much like
1590 * tcp_fragment() except that it may make several kinds of assumptions
1591 * in order to speed up the splitting operation. In particular, we
1592 * know that all the data is in scatter-gather pages, and that the
1593 * packet has never been sent out before (and thus is not cloned).
1594 */
1595static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
1596 unsigned int mss_now, gfp_t gfp)
1597{
1598 struct sk_buff *buff;
1599 int nlen = skb->len - len;
1600 u8 flags;
1601
1602 /* All of a TSO frame must be composed of paged data. */
1603 if (skb->len != skb->data_len)
1604 return tcp_fragment(sk, skb, len, mss_now);
1605
1606 buff = sk_stream_alloc_skb(sk, 0, gfp);
1607 if (unlikely(buff == NULL))
1608 return -ENOMEM;
1609
1610 sk->sk_wmem_queued += buff->truesize;
1611 sk_mem_charge(sk, buff->truesize);
1612 buff->truesize += nlen;
1613 skb->truesize -= nlen;
1614
1615 /* Correct the sequence numbers. */
1616 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1617 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1618 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1619
1620 /* PSH and FIN should only be set in the second packet. */
1621 flags = TCP_SKB_CB(skb)->tcp_flags;
1622 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH);
1623 TCP_SKB_CB(buff)->tcp_flags = flags;
1624
1625 /* This packet was never sent out yet, so no SACK bits. */
1626 TCP_SKB_CB(buff)->sacked = 0;
1627
1628 buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL;
1629 skb_split(skb, buff, len);
1630
1631 /* Fix up tso_factor for both original and new SKB. */
1632 tcp_set_skb_tso_segs(sk, skb, mss_now);
1633 tcp_set_skb_tso_segs(sk, buff, mss_now);
1634
1635 /* Link BUFF into the send queue. */
1636 skb_header_release(buff);
1637 tcp_insert_write_queue_after(skb, buff, sk);
1638
1639 return 0;
1640}
1641
1642/* Try to defer sending, if possible, in order to minimize the amount
1643 * of TSO splitting we do. View it as a kind of TSO Nagle test.
1644 *
1645 * This algorithm is from John Heffner.
1646 */
1647static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb)
1648{
1649 struct tcp_sock *tp = tcp_sk(sk);
1650 const struct inet_connection_sock *icsk = inet_csk(sk);
1651 u32 send_win, cong_win, limit, in_flight;
1652 int win_divisor;
1653
1654 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
1655 goto send_now;
1656
1657 if (icsk->icsk_ca_state != TCP_CA_Open)
1658 goto send_now;
1659
1660 /* Defer for less than two clock ticks. */
1661 if (tp->tso_deferred &&
1662 (((u32)jiffies << 1) >> 1) - (tp->tso_deferred >> 1) > 1)
1663 goto send_now;
1664
1665 in_flight = tcp_packets_in_flight(tp);
1666
1667 BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight));
1668
1669 send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1670
1671 /* From in_flight test above, we know that cwnd > in_flight. */
1672 cong_win = (tp->snd_cwnd - in_flight) * tp->mss_cache;
1673
1674 limit = min(send_win, cong_win);
1675
1676 /* If a full-sized TSO skb can be sent, do it. */
1677 if (limit >= min_t(unsigned int, sk->sk_gso_max_size,
1678 tp->xmit_size_goal_segs * tp->mss_cache))
1679 goto send_now;
1680
1681 /* Middle in queue won't get any more data, full sendable already? */
1682 if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len))
1683 goto send_now;
1684
1685 win_divisor = ACCESS_ONCE(sysctl_tcp_tso_win_divisor);
1686 if (win_divisor) {
1687 u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache);
1688
1689 /* If at least some fraction of a window is available,
1690 * just use it.
1691 */
1692 chunk /= win_divisor;
1693 if (limit >= chunk)
1694 goto send_now;
1695 } else {
1696 /* Different approach, try not to defer past a single
1697 * ACK. Receiver should ACK every other full sized
1698 * frame, so if we have space for more than 3 frames
1699 * then send now.
1700 */
1701 if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache)
1702 goto send_now;
1703 }
1704
1705 /* Ok, it looks like it is advisable to defer.
1706 * Do not rearm the timer if already set to not break TCP ACK clocking.
1707 */
1708 if (!tp->tso_deferred)
1709 tp->tso_deferred = 1 | (jiffies << 1);
1710
1711 return true;
1712
1713send_now:
1714 tp->tso_deferred = 0;
1715 return false;
1716}
1717
1718/* Create a new MTU probe if we are ready.
1719 * MTU probe is regularly attempting to increase the path MTU by
1720 * deliberately sending larger packets. This discovers routing
1721 * changes resulting in larger path MTUs.
1722 *
1723 * Returns 0 if we should wait to probe (no cwnd available),
1724 * 1 if a probe was sent,
1725 * -1 otherwise
1726 */
1727static int tcp_mtu_probe(struct sock *sk)
1728{
1729 struct tcp_sock *tp = tcp_sk(sk);
1730 struct inet_connection_sock *icsk = inet_csk(sk);
1731 struct sk_buff *skb, *nskb, *next;
1732 int len;
1733 int probe_size;
1734 int size_needed;
1735 int copy;
1736 int mss_now;
1737
1738 /* Not currently probing/verifying,
1739 * not in recovery,
1740 * have enough cwnd, and
1741 * not SACKing (the variable headers throw things off) */
1742 if (!icsk->icsk_mtup.enabled ||
1743 icsk->icsk_mtup.probe_size ||
1744 inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
1745 tp->snd_cwnd < 11 ||
1746 tp->rx_opt.num_sacks || tp->rx_opt.dsack)
1747 return -1;
1748
1749 /* Very simple search strategy: just double the MSS. */
1750 mss_now = tcp_current_mss(sk);
1751 probe_size = 2 * tp->mss_cache;
1752 size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
1753 if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high)) {
1754 /* TODO: set timer for probe_converge_event */
1755 return -1;
1756 }
1757
1758 /* Have enough data in the send queue to probe? */
1759 if (tp->write_seq - tp->snd_nxt < size_needed)
1760 return -1;
1761
1762 if (tp->snd_wnd < size_needed)
1763 return -1;
1764 if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
1765 return 0;
1766
1767 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
1768 if (tcp_packets_in_flight(tp) + 2 > tp->snd_cwnd) {
1769 if (!tcp_packets_in_flight(tp))
1770 return -1;
1771 else
1772 return 0;
1773 }
1774
1775 /* We're allowed to probe. Build it now. */
1776 if ((nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC)) == NULL)
1777 return -1;
1778 sk->sk_wmem_queued += nskb->truesize;
1779 sk_mem_charge(sk, nskb->truesize);
1780
1781 skb = tcp_send_head(sk);
1782
1783 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq;
1784 TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size;
1785 TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK;
1786 TCP_SKB_CB(nskb)->sacked = 0;
1787 nskb->csum = 0;
1788 nskb->ip_summed = skb->ip_summed;
1789
1790 tcp_insert_write_queue_before(nskb, skb, sk);
1791
1792 len = 0;
1793 tcp_for_write_queue_from_safe(skb, next, sk) {
1794 copy = min_t(int, skb->len, probe_size - len);
1795 if (nskb->ip_summed)
1796 skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
1797 else
1798 nskb->csum = skb_copy_and_csum_bits(skb, 0,
1799 skb_put(nskb, copy),
1800 copy, nskb->csum);
1801
1802 if (skb->len <= copy) {
1803 /* We've eaten all the data from this skb.
1804 * Throw it away. */
1805 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
1806 tcp_unlink_write_queue(skb, sk);
1807 sk_wmem_free_skb(sk, skb);
1808 } else {
1809 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags &
1810 ~(TCPHDR_FIN|TCPHDR_PSH);
1811 if (!skb_shinfo(skb)->nr_frags) {
1812 skb_pull(skb, copy);
1813 if (skb->ip_summed != CHECKSUM_PARTIAL)
1814 skb->csum = csum_partial(skb->data,
1815 skb->len, 0);
1816 } else {
1817 __pskb_trim_head(skb, copy);
1818 tcp_set_skb_tso_segs(sk, skb, mss_now);
1819 }
1820 TCP_SKB_CB(skb)->seq += copy;
1821 }
1822
1823 len += copy;
1824
1825 if (len >= probe_size)
1826 break;
1827 }
1828 tcp_init_tso_segs(sk, nskb, nskb->len);
1829
1830 /* We're ready to send. If this fails, the probe will
1831 * be resegmented into mss-sized pieces by tcp_write_xmit(). */
1832 TCP_SKB_CB(nskb)->when = tcp_time_stamp;
1833 if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
1834 /* Decrement cwnd here because we are sending
1835 * effectively two packets. */
1836 tp->snd_cwnd--;
1837 tcp_event_new_data_sent(sk, nskb);
1838
1839 icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
1840 tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq;
1841 tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq;
1842
1843 return 1;
1844 }
1845
1846 return -1;
1847}
1848
1849/* This routine writes packets to the network. It advances the
1850 * send_head. This happens as incoming acks open up the remote
1851 * window for us.
1852 *
1853 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
1854 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
1855 * account rare use of URG, this is not a big flaw.
1856 *
1857 * Send at most one packet when push_one > 0. Temporarily ignore
1858 * cwnd limit to force at most one packet out when push_one == 2.
1859
1860 * Returns true, if no segments are in flight and we have queued segments,
1861 * but cannot send anything now because of SWS or another problem.
1862 */
1863static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
1864 int push_one, gfp_t gfp)
1865{
1866 struct tcp_sock *tp = tcp_sk(sk);
1867 struct sk_buff *skb;
1868 unsigned int tso_segs, sent_pkts;
1869 int cwnd_quota;
1870 int result;
1871
1872 sent_pkts = 0;
1873
1874 if (!push_one) {
1875 /* Do MTU probing. */
1876 result = tcp_mtu_probe(sk);
1877 if (!result) {
1878 return false;
1879 } else if (result > 0) {
1880 sent_pkts = 1;
1881 }
1882 }
1883
1884 while ((skb = tcp_send_head(sk))) {
1885 unsigned int limit;
1886
1887 tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
1888 BUG_ON(!tso_segs);
1889
1890 if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE)
1891 goto repair; /* Skip network transmission */
1892
1893 cwnd_quota = tcp_cwnd_test(tp, skb);
1894 if (!cwnd_quota) {
1895 if (push_one == 2)
1896 /* Force out a loss probe pkt. */
1897 cwnd_quota = 1;
1898 else
1899 break;
1900 }
1901
1902 if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now)))
1903 break;
1904
1905 if (tso_segs == 1) {
1906 if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
1907 (tcp_skb_is_last(sk, skb) ?
1908 nonagle : TCP_NAGLE_PUSH))))
1909 break;
1910 } else {
1911 if (!push_one && tcp_tso_should_defer(sk, skb))
1912 break;
1913 }
1914
1915 /* TCP Small Queues :
1916 * Control number of packets in qdisc/devices to two packets / or ~1 ms.
1917 * This allows for :
1918 * - better RTT estimation and ACK scheduling
1919 * - faster recovery
1920 * - high rates
1921 * Alas, some drivers / subsystems require a fair amount
1922 * of queued bytes to ensure line rate.
1923 * One example is wifi aggregation (802.11 AMPDU)
1924 */
1925 limit = max_t(unsigned int, sysctl_tcp_limit_output_bytes,
1926 sk->sk_pacing_rate >> 10);
1927
1928 if (atomic_read(&sk->sk_wmem_alloc) > limit) {
1929 set_bit(TSQ_THROTTLED, &tp->tsq_flags);
1930 /* It is possible TX completion already happened
1931 * before we set TSQ_THROTTLED, so we must
1932 * test again the condition.
1933 * We abuse smp_mb__after_clear_bit() because
1934 * there is no smp_mb__after_set_bit() yet
1935 */
1936 smp_mb__after_clear_bit();
1937 if (atomic_read(&sk->sk_wmem_alloc) > limit)
1938 break;
1939 }
1940
1941 limit = mss_now;
1942 if (tso_segs > 1 && !tcp_urg_mode(tp))
1943 limit = tcp_mss_split_point(sk, skb, mss_now,
1944 min_t(unsigned int,
1945 cwnd_quota,
1946 sk->sk_gso_max_segs),
1947 nonagle);
1948
1949 if (skb->len > limit &&
1950 unlikely(tso_fragment(sk, skb, limit, mss_now, gfp)))
1951 break;
1952
1953 TCP_SKB_CB(skb)->when = tcp_time_stamp;
1954
1955 if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
1956 break;
1957
1958repair:
1959 /* Advance the send_head. This one is sent out.
1960 * This call will increment packets_out.
1961 */
1962 tcp_event_new_data_sent(sk, skb);
1963
1964 tcp_minshall_update(tp, mss_now, skb);
1965 sent_pkts += tcp_skb_pcount(skb);
1966
1967 if (push_one)
1968 break;
1969 }
1970
1971 if (likely(sent_pkts)) {
1972 if (tcp_in_cwnd_reduction(sk))
1973 tp->prr_out += sent_pkts;
1974
1975 /* Send one loss probe per tail loss episode. */
1976 if (push_one != 2)
1977 tcp_schedule_loss_probe(sk);
1978 tcp_cwnd_validate(sk);
1979 return false;
1980 }
1981 return (push_one == 2) || (!tp->packets_out && tcp_send_head(sk));
1982}
1983
1984bool tcp_schedule_loss_probe(struct sock *sk)
1985{
1986 struct inet_connection_sock *icsk = inet_csk(sk);
1987 struct tcp_sock *tp = tcp_sk(sk);
1988 u32 timeout, tlp_time_stamp, rto_time_stamp;
1989 u32 rtt = usecs_to_jiffies(tp->srtt_us >> 3);
1990
1991 if (WARN_ON(icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS))
1992 return false;
1993 /* No consecutive loss probes. */
1994 if (WARN_ON(icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)) {
1995 tcp_rearm_rto(sk);
1996 return false;
1997 }
1998 /* Don't do any loss probe on a Fast Open connection before 3WHS
1999 * finishes.
2000 */
2001 if (sk->sk_state == TCP_SYN_RECV)
2002 return false;
2003
2004 /* TLP is only scheduled when next timer event is RTO. */
2005 if (icsk->icsk_pending != ICSK_TIME_RETRANS)
2006 return false;
2007
2008 /* Schedule a loss probe in 2*RTT for SACK capable connections
2009 * in Open state, that are either limited by cwnd or application.
2010 */
2011 if (sysctl_tcp_early_retrans < 3 || !tp->srtt_us || !tp->packets_out ||
2012 !tcp_is_sack(tp) || inet_csk(sk)->icsk_ca_state != TCP_CA_Open)
2013 return false;
2014
2015 if ((tp->snd_cwnd > tcp_packets_in_flight(tp)) &&
2016 tcp_send_head(sk))
2017 return false;
2018
2019 /* Probe timeout is at least 1.5*rtt + TCP_DELACK_MAX to account
2020 * for delayed ack when there's one outstanding packet.
2021 */
2022 timeout = rtt << 1;
2023 if (tp->packets_out == 1)
2024 timeout = max_t(u32, timeout,
2025 (rtt + (rtt >> 1) + TCP_DELACK_MAX));
2026 timeout = max_t(u32, timeout, msecs_to_jiffies(10));
2027
2028 /* If RTO is shorter, just schedule TLP in its place. */
2029 tlp_time_stamp = tcp_time_stamp + timeout;
2030 rto_time_stamp = (u32)inet_csk(sk)->icsk_timeout;
2031 if ((s32)(tlp_time_stamp - rto_time_stamp) > 0) {
2032 s32 delta = rto_time_stamp - tcp_time_stamp;
2033 if (delta > 0)
2034 timeout = delta;
2035 }
2036
2037 inet_csk_reset_xmit_timer(sk, ICSK_TIME_LOSS_PROBE, timeout,
2038 TCP_RTO_MAX);
2039 return true;
2040}
2041
2042/* When probe timeout (PTO) fires, send a new segment if one exists, else
2043 * retransmit the last segment.
2044 */
2045void tcp_send_loss_probe(struct sock *sk)
2046{
2047 struct tcp_sock *tp = tcp_sk(sk);
2048 struct sk_buff *skb;
2049 int pcount;
2050 int mss = tcp_current_mss(sk);
2051 int err = -1;
2052
2053 if (tcp_send_head(sk) != NULL) {
2054 err = tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC);
2055 goto rearm_timer;
2056 }
2057
2058 /* At most one outstanding TLP retransmission. */
2059 if (tp->tlp_high_seq)
2060 goto rearm_timer;
2061
2062 /* Retransmit last segment. */
2063 skb = tcp_write_queue_tail(sk);
2064 if (WARN_ON(!skb))
2065 goto rearm_timer;
2066
2067 pcount = tcp_skb_pcount(skb);
2068 if (WARN_ON(!pcount))
2069 goto rearm_timer;
2070
2071 if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
2072 if (unlikely(tcp_fragment(sk, skb, (pcount - 1) * mss, mss)))
2073 goto rearm_timer;
2074 skb = tcp_write_queue_tail(sk);
2075 }
2076
2077 if (WARN_ON(!skb || !tcp_skb_pcount(skb)))
2078 goto rearm_timer;
2079
2080 /* Probe with zero data doesn't trigger fast recovery. */
2081 if (skb->len > 0)
2082 err = __tcp_retransmit_skb(sk, skb);
2083
2084 /* Record snd_nxt for loss detection. */
2085 if (likely(!err))
2086 tp->tlp_high_seq = tp->snd_nxt;
2087
2088rearm_timer:
2089 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
2090 inet_csk(sk)->icsk_rto,
2091 TCP_RTO_MAX);
2092
2093 if (likely(!err))
2094 NET_INC_STATS_BH(sock_net(sk),
2095 LINUX_MIB_TCPLOSSPROBES);
2096}
2097
2098/* Push out any pending frames which were held back due to
2099 * TCP_CORK or attempt at coalescing tiny packets.
2100 * The socket must be locked by the caller.
2101 */
2102void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
2103 int nonagle)
2104{
2105 /* If we are closed, the bytes will have to remain here.
2106 * In time closedown will finish, we empty the write queue and
2107 * all will be happy.
2108 */
2109 if (unlikely(sk->sk_state == TCP_CLOSE))
2110 return;
2111
2112 if (tcp_write_xmit(sk, cur_mss, nonagle, 0,
2113 sk_gfp_atomic(sk, GFP_ATOMIC)))
2114 tcp_check_probe_timer(sk);
2115}
2116
2117/* Send _single_ skb sitting at the send head. This function requires
2118 * true push pending frames to setup probe timer etc.
2119 */
2120void tcp_push_one(struct sock *sk, unsigned int mss_now)
2121{
2122 struct sk_buff *skb = tcp_send_head(sk);
2123
2124 BUG_ON(!skb || skb->len < mss_now);
2125
2126 tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
2127}
2128
2129/* This function returns the amount that we can raise the
2130 * usable window based on the following constraints
2131 *
2132 * 1. The window can never be shrunk once it is offered (RFC 793)
2133 * 2. We limit memory per socket
2134 *
2135 * RFC 1122:
2136 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
2137 * RECV.NEXT + RCV.WIN fixed until:
2138 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
2139 *
2140 * i.e. don't raise the right edge of the window until you can raise
2141 * it at least MSS bytes.
2142 *
2143 * Unfortunately, the recommended algorithm breaks header prediction,
2144 * since header prediction assumes th->window stays fixed.
2145 *
2146 * Strictly speaking, keeping th->window fixed violates the receiver
2147 * side SWS prevention criteria. The problem is that under this rule
2148 * a stream of single byte packets will cause the right side of the
2149 * window to always advance by a single byte.
2150 *
2151 * Of course, if the sender implements sender side SWS prevention
2152 * then this will not be a problem.
2153 *
2154 * BSD seems to make the following compromise:
2155 *
2156 * If the free space is less than the 1/4 of the maximum
2157 * space available and the free space is less than 1/2 mss,
2158 * then set the window to 0.
2159 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
2160 * Otherwise, just prevent the window from shrinking
2161 * and from being larger than the largest representable value.
2162 *
2163 * This prevents incremental opening of the window in the regime
2164 * where TCP is limited by the speed of the reader side taking
2165 * data out of the TCP receive queue. It does nothing about
2166 * those cases where the window is constrained on the sender side
2167 * because the pipeline is full.
2168 *
2169 * BSD also seems to "accidentally" limit itself to windows that are a
2170 * multiple of MSS, at least until the free space gets quite small.
2171 * This would appear to be a side effect of the mbuf implementation.
2172 * Combining these two algorithms results in the observed behavior
2173 * of having a fixed window size at almost all times.
2174 *
2175 * Below we obtain similar behavior by forcing the offered window to
2176 * a multiple of the mss when it is feasible to do so.
2177 *
2178 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
2179 * Regular options like TIMESTAMP are taken into account.
2180 */
2181u32 __tcp_select_window(struct sock *sk)
2182{
2183 struct inet_connection_sock *icsk = inet_csk(sk);
2184 struct tcp_sock *tp = tcp_sk(sk);
2185 /* MSS for the peer's data. Previous versions used mss_clamp
2186 * here. I don't know if the value based on our guesses
2187 * of peer's MSS is better for the performance. It's more correct
2188 * but may be worse for the performance because of rcv_mss
2189 * fluctuations. --SAW 1998/11/1
2190 */
2191 int mss = icsk->icsk_ack.rcv_mss;
2192 int free_space = tcp_space(sk);
2193 int allowed_space = tcp_full_space(sk);
2194 int full_space = min_t(int, tp->window_clamp, allowed_space);
2195 int window;
2196
2197 if (mss > full_space)
2198 mss = full_space;
2199
2200 if (free_space < (full_space >> 1)) {
2201 icsk->icsk_ack.quick = 0;
2202
2203 if (sk_under_memory_pressure(sk))
2204 tp->rcv_ssthresh = min(tp->rcv_ssthresh,
2205 4U * tp->advmss);
2206
2207 /* free_space might become our new window, make sure we don't
2208 * increase it due to wscale.
2209 */
2210 free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale);
2211
2212 /* if free space is less than mss estimate, or is below 1/16th
2213 * of the maximum allowed, try to move to zero-window, else
2214 * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and
2215 * new incoming data is dropped due to memory limits.
2216 * With large window, mss test triggers way too late in order
2217 * to announce zero window in time before rmem limit kicks in.
2218 */
2219 if (free_space < (allowed_space >> 4) || free_space < mss)
2220 return 0;
2221 }
2222
2223 if (free_space > tp->rcv_ssthresh)
2224 free_space = tp->rcv_ssthresh;
2225
2226 /* Don't do rounding if we are using window scaling, since the
2227 * scaled window will not line up with the MSS boundary anyway.
2228 */
2229 window = tp->rcv_wnd;
2230 if (tp->rx_opt.rcv_wscale) {
2231 window = free_space;
2232
2233 /* Advertise enough space so that it won't get scaled away.
2234 * Import case: prevent zero window announcement if
2235 * 1<<rcv_wscale > mss.
2236 */
2237 if (((window >> tp->rx_opt.rcv_wscale) << tp->rx_opt.rcv_wscale) != window)
2238 window = (((window >> tp->rx_opt.rcv_wscale) + 1)
2239 << tp->rx_opt.rcv_wscale);
2240 } else {
2241 /* Get the largest window that is a nice multiple of mss.
2242 * Window clamp already applied above.
2243 * If our current window offering is within 1 mss of the
2244 * free space we just keep it. This prevents the divide
2245 * and multiply from happening most of the time.
2246 * We also don't do any window rounding when the free space
2247 * is too small.
2248 */
2249 if (window <= free_space - mss || window > free_space)
2250 window = (free_space / mss) * mss;
2251 else if (mss == full_space &&
2252 free_space > window + (full_space >> 1))
2253 window = free_space;
2254 }
2255
2256 return window;
2257}
2258
2259/* Collapses two adjacent SKB's during retransmission. */
2260static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
2261{
2262 struct tcp_sock *tp = tcp_sk(sk);
2263 struct sk_buff *next_skb = tcp_write_queue_next(sk, skb);
2264 int skb_size, next_skb_size;
2265
2266 skb_size = skb->len;
2267 next_skb_size = next_skb->len;
2268
2269 BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
2270
2271 tcp_highest_sack_combine(sk, next_skb, skb);
2272
2273 tcp_unlink_write_queue(next_skb, sk);
2274
2275 skb_copy_from_linear_data(next_skb, skb_put(skb, next_skb_size),
2276 next_skb_size);
2277
2278 if (next_skb->ip_summed == CHECKSUM_PARTIAL)
2279 skb->ip_summed = CHECKSUM_PARTIAL;
2280
2281 if (skb->ip_summed != CHECKSUM_PARTIAL)
2282 skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size);
2283
2284 /* Update sequence range on original skb. */
2285 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
2286
2287 /* Merge over control information. This moves PSH/FIN etc. over */
2288 TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags;
2289
2290 /* All done, get rid of second SKB and account for it so
2291 * packet counting does not break.
2292 */
2293 TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS;
2294
2295 /* changed transmit queue under us so clear hints */
2296 tcp_clear_retrans_hints_partial(tp);
2297 if (next_skb == tp->retransmit_skb_hint)
2298 tp->retransmit_skb_hint = skb;
2299
2300 tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));
2301
2302 sk_wmem_free_skb(sk, next_skb);
2303}
2304
2305/* Check if coalescing SKBs is legal. */
2306static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
2307{
2308 if (tcp_skb_pcount(skb) > 1)
2309 return false;
2310 /* TODO: SACK collapsing could be used to remove this condition */
2311 if (skb_shinfo(skb)->nr_frags != 0)
2312 return false;
2313 if (skb_cloned(skb))
2314 return false;
2315 if (skb == tcp_send_head(sk))
2316 return false;
2317 /* Some heurestics for collapsing over SACK'd could be invented */
2318 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
2319 return false;
2320
2321 return true;
2322}
2323
2324/* Collapse packets in the retransmit queue to make to create
2325 * less packets on the wire. This is only done on retransmission.
2326 */
2327static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
2328 int space)
2329{
2330 struct tcp_sock *tp = tcp_sk(sk);
2331 struct sk_buff *skb = to, *tmp;
2332 bool first = true;
2333
2334 if (!sysctl_tcp_retrans_collapse)
2335 return;
2336 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2337 return;
2338
2339 tcp_for_write_queue_from_safe(skb, tmp, sk) {
2340 if (!tcp_can_collapse(sk, skb))
2341 break;
2342
2343 space -= skb->len;
2344
2345 if (first) {
2346 first = false;
2347 continue;
2348 }
2349
2350 if (space < 0)
2351 break;
2352 /* Punt if not enough space exists in the first SKB for
2353 * the data in the second
2354 */
2355 if (skb->len > skb_availroom(to))
2356 break;
2357
2358 if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp)))
2359 break;
2360
2361 tcp_collapse_retrans(sk, to);
2362 }
2363}
2364
2365/* This retransmits one SKB. Policy decisions and retransmit queue
2366 * state updates are done by the caller. Returns non-zero if an
2367 * error occurred which prevented the send.
2368 */
2369int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
2370{
2371 struct tcp_sock *tp = tcp_sk(sk);
2372 struct inet_connection_sock *icsk = inet_csk(sk);
2373 unsigned int cur_mss;
2374 int err;
2375
2376 /* Inconslusive MTU probe */
2377 if (icsk->icsk_mtup.probe_size) {
2378 icsk->icsk_mtup.probe_size = 0;
2379 }
2380
2381 /* Do not sent more than we queued. 1/4 is reserved for possible
2382 * copying overhead: fragmentation, tunneling, mangling etc.
2383 */
2384 if (atomic_read(&sk->sk_wmem_alloc) >
2385 min(sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2), sk->sk_sndbuf))
2386 return -EAGAIN;
2387
2388 if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) {
2389 if (before(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
2390 BUG();
2391 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
2392 return -ENOMEM;
2393 }
2394
2395 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
2396 return -EHOSTUNREACH; /* Routing failure or similar. */
2397
2398 cur_mss = tcp_current_mss(sk);
2399
2400 /* If receiver has shrunk his window, and skb is out of
2401 * new window, do not retransmit it. The exception is the
2402 * case, when window is shrunk to zero. In this case
2403 * our retransmit serves as a zero window probe.
2404 */
2405 if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) &&
2406 TCP_SKB_CB(skb)->seq != tp->snd_una)
2407 return -EAGAIN;
2408
2409 if (skb->len > cur_mss) {
2410 if (tcp_fragment(sk, skb, cur_mss, cur_mss))
2411 return -ENOMEM; /* We'll try again later. */
2412 } else {
2413 int oldpcount = tcp_skb_pcount(skb);
2414
2415 if (unlikely(oldpcount > 1)) {
2416 if (skb_unclone(skb, GFP_ATOMIC))
2417 return -ENOMEM;
2418 tcp_init_tso_segs(sk, skb, cur_mss);
2419 tcp_adjust_pcount(sk, skb, oldpcount - tcp_skb_pcount(skb));
2420 }
2421 }
2422
2423 tcp_retrans_try_collapse(sk, skb, cur_mss);
2424
2425 /* Make a copy, if the first transmission SKB clone we made
2426 * is still in somebody's hands, else make a clone.
2427 */
2428 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2429
2430 /* make sure skb->data is aligned on arches that require it
2431 * and check if ack-trimming & collapsing extended the headroom
2432 * beyond what csum_start can cover.
2433 */
2434 if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) ||
2435 skb_headroom(skb) >= 0xFFFF)) {
2436 struct sk_buff *nskb = __pskb_copy(skb, MAX_TCP_HEADER,
2437 GFP_ATOMIC);
2438 err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
2439 -ENOBUFS;
2440 } else {
2441 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
2442 }
2443
2444 if (likely(!err)) {
2445 TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
2446 /* Update global TCP statistics. */
2447 TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
2448 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
2449 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
2450 tp->total_retrans++;
2451 }
2452 return err;
2453}
2454
2455int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
2456{
2457 struct tcp_sock *tp = tcp_sk(sk);
2458 int err = __tcp_retransmit_skb(sk, skb);
2459
2460 if (err == 0) {
2461#if FASTRETRANS_DEBUG > 0
2462 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2463 net_dbg_ratelimited("retrans_out leaked\n");
2464 }
2465#endif
2466 if (!tp->retrans_out)
2467 tp->lost_retrans_low = tp->snd_nxt;
2468 TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
2469 tp->retrans_out += tcp_skb_pcount(skb);
2470
2471 /* Save stamp of the first retransmit. */
2472 if (!tp->retrans_stamp)
2473 tp->retrans_stamp = TCP_SKB_CB(skb)->when;
2474
2475 tp->undo_retrans += tcp_skb_pcount(skb);
2476
2477 /* snd_nxt is stored to detect loss of retransmitted segment,
2478 * see tcp_input.c tcp_sacktag_write_queue().
2479 */
2480 TCP_SKB_CB(skb)->ack_seq = tp->snd_nxt;
2481 } else {
2482 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL);
2483 }
2484 return err;
2485}
2486
2487/* Check if we forward retransmits are possible in the current
2488 * window/congestion state.
2489 */
2490static bool tcp_can_forward_retransmit(struct sock *sk)
2491{
2492 const struct inet_connection_sock *icsk = inet_csk(sk);
2493 const struct tcp_sock *tp = tcp_sk(sk);
2494
2495 /* Forward retransmissions are possible only during Recovery. */
2496 if (icsk->icsk_ca_state != TCP_CA_Recovery)
2497 return false;
2498
2499 /* No forward retransmissions in Reno are possible. */
2500 if (tcp_is_reno(tp))
2501 return false;
2502
2503 /* Yeah, we have to make difficult choice between forward transmission
2504 * and retransmission... Both ways have their merits...
2505 *
2506 * For now we do not retransmit anything, while we have some new
2507 * segments to send. In the other cases, follow rule 3 for
2508 * NextSeg() specified in RFC3517.
2509 */
2510
2511 if (tcp_may_send_now(sk))
2512 return false;
2513
2514 return true;
2515}
2516
2517/* This gets called after a retransmit timeout, and the initially
2518 * retransmitted data is acknowledged. It tries to continue
2519 * resending the rest of the retransmit queue, until either
2520 * we've sent it all or the congestion window limit is reached.
2521 * If doing SACK, the first ACK which comes back for a timeout
2522 * based retransmit packet might feed us FACK information again.
2523 * If so, we use it to avoid unnecessarily retransmissions.
2524 */
2525void tcp_xmit_retransmit_queue(struct sock *sk)
2526{
2527 const struct inet_connection_sock *icsk = inet_csk(sk);
2528 struct tcp_sock *tp = tcp_sk(sk);
2529 struct sk_buff *skb;
2530 struct sk_buff *hole = NULL;
2531 u32 last_lost;
2532 int mib_idx;
2533 int fwd_rexmitting = 0;
2534
2535 if (!tp->packets_out)
2536 return;
2537
2538 if (!tp->lost_out)
2539 tp->retransmit_high = tp->snd_una;
2540
2541 if (tp->retransmit_skb_hint) {
2542 skb = tp->retransmit_skb_hint;
2543 last_lost = TCP_SKB_CB(skb)->end_seq;
2544 if (after(last_lost, tp->retransmit_high))
2545 last_lost = tp->retransmit_high;
2546 } else {
2547 skb = tcp_write_queue_head(sk);
2548 last_lost = tp->snd_una;
2549 }
2550
2551 tcp_for_write_queue_from(skb, sk) {
2552 __u8 sacked = TCP_SKB_CB(skb)->sacked;
2553
2554 if (skb == tcp_send_head(sk))
2555 break;
2556 /* we could do better than to assign each time */
2557 if (hole == NULL)
2558 tp->retransmit_skb_hint = skb;
2559
2560 /* Assume this retransmit will generate
2561 * only one packet for congestion window
2562 * calculation purposes. This works because
2563 * tcp_retransmit_skb() will chop up the
2564 * packet to be MSS sized and all the
2565 * packet counting works out.
2566 */
2567 if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
2568 return;
2569
2570 if (fwd_rexmitting) {
2571begin_fwd:
2572 if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
2573 break;
2574 mib_idx = LINUX_MIB_TCPFORWARDRETRANS;
2575
2576 } else if (!before(TCP_SKB_CB(skb)->seq, tp->retransmit_high)) {
2577 tp->retransmit_high = last_lost;
2578 if (!tcp_can_forward_retransmit(sk))
2579 break;
2580 /* Backtrack if necessary to non-L'ed skb */
2581 if (hole != NULL) {
2582 skb = hole;
2583 hole = NULL;
2584 }
2585 fwd_rexmitting = 1;
2586 goto begin_fwd;
2587
2588 } else if (!(sacked & TCPCB_LOST)) {
2589 if (hole == NULL && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
2590 hole = skb;
2591 continue;
2592
2593 } else {
2594 last_lost = TCP_SKB_CB(skb)->end_seq;
2595 if (icsk->icsk_ca_state != TCP_CA_Loss)
2596 mib_idx = LINUX_MIB_TCPFASTRETRANS;
2597 else
2598 mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS;
2599 }
2600
2601 if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
2602 continue;
2603
2604 if (tcp_retransmit_skb(sk, skb))
2605 return;
2606
2607 NET_INC_STATS_BH(sock_net(sk), mib_idx);
2608
2609 if (tcp_in_cwnd_reduction(sk))
2610 tp->prr_out += tcp_skb_pcount(skb);
2611
2612 if (skb == tcp_write_queue_head(sk))
2613 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
2614 inet_csk(sk)->icsk_rto,
2615 TCP_RTO_MAX);
2616 }
2617}
2618
2619/* Send a fin. The caller locks the socket for us. This cannot be
2620 * allowed to fail queueing a FIN frame under any circumstances.
2621 */
2622void tcp_send_fin(struct sock *sk)
2623{
2624 struct tcp_sock *tp = tcp_sk(sk);
2625 struct sk_buff *skb = tcp_write_queue_tail(sk);
2626 int mss_now;
2627
2628 /* Optimization, tack on the FIN if we have a queue of
2629 * unsent frames. But be careful about outgoing SACKS
2630 * and IP options.
2631 */
2632 mss_now = tcp_current_mss(sk);
2633
2634 if (tcp_send_head(sk) != NULL) {
2635 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_FIN;
2636 TCP_SKB_CB(skb)->end_seq++;
2637 tp->write_seq++;
2638 } else {
2639 /* Socket is locked, keep trying until memory is available. */
2640 for (;;) {
2641 skb = alloc_skb_fclone(MAX_TCP_HEADER,
2642 sk->sk_allocation);
2643 if (skb)
2644 break;
2645 yield();
2646 }
2647
2648 /* Reserve space for headers and prepare control bits. */
2649 skb_reserve(skb, MAX_TCP_HEADER);
2650 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
2651 tcp_init_nondata_skb(skb, tp->write_seq,
2652 TCPHDR_ACK | TCPHDR_FIN);
2653 tcp_queue_skb(sk, skb);
2654 }
2655 __tcp_push_pending_frames(sk, mss_now, TCP_NAGLE_OFF);
2656}
2657
2658/* We get here when a process closes a file descriptor (either due to
2659 * an explicit close() or as a byproduct of exit()'ing) and there
2660 * was unread data in the receive queue. This behavior is recommended
2661 * by RFC 2525, section 2.17. -DaveM
2662 */
2663void tcp_send_active_reset(struct sock *sk, gfp_t priority)
2664{
2665 struct sk_buff *skb;
2666
2667 /* NOTE: No TCP options attached and we never retransmit this. */
2668 skb = alloc_skb(MAX_TCP_HEADER, priority);
2669 if (!skb) {
2670 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
2671 return;
2672 }
2673
2674 /* Reserve space for headers and prepare control bits. */
2675 skb_reserve(skb, MAX_TCP_HEADER);
2676 tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
2677 TCPHDR_ACK | TCPHDR_RST);
2678 /* Send it off. */
2679 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2680 if (tcp_transmit_skb(sk, skb, 0, priority))
2681 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
2682
2683 TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
2684}
2685
2686/* Send a crossed SYN-ACK during socket establishment.
2687 * WARNING: This routine must only be called when we have already sent
2688 * a SYN packet that crossed the incoming SYN that caused this routine
2689 * to get called. If this assumption fails then the initial rcv_wnd
2690 * and rcv_wscale values will not be correct.
2691 */
2692int tcp_send_synack(struct sock *sk)
2693{
2694 struct sk_buff *skb;
2695
2696 skb = tcp_write_queue_head(sk);
2697 if (skb == NULL || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
2698 pr_debug("%s: wrong queue state\n", __func__);
2699 return -EFAULT;
2700 }
2701 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
2702 if (skb_cloned(skb)) {
2703 struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
2704 if (nskb == NULL)
2705 return -ENOMEM;
2706 tcp_unlink_write_queue(skb, sk);
2707 skb_header_release(nskb);
2708 __tcp_add_write_queue_head(sk, nskb);
2709 sk_wmem_free_skb(sk, skb);
2710 sk->sk_wmem_queued += nskb->truesize;
2711 sk_mem_charge(sk, nskb->truesize);
2712 skb = nskb;
2713 }
2714
2715 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
2716 TCP_ECN_send_synack(tcp_sk(sk), skb);
2717 }
2718 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2719 return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
2720}
2721
2722/**
2723 * tcp_make_synack - Prepare a SYN-ACK.
2724 * sk: listener socket
2725 * dst: dst entry attached to the SYNACK
2726 * req: request_sock pointer
2727 *
2728 * Allocate one skb and build a SYNACK packet.
2729 * @dst is consumed : Caller should not use it again.
2730 */
2731struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
2732 struct request_sock *req,
2733 struct tcp_fastopen_cookie *foc)
2734{
2735 struct tcp_out_options opts;
2736 struct inet_request_sock *ireq = inet_rsk(req);
2737 struct tcp_sock *tp = tcp_sk(sk);
2738 struct tcphdr *th;
2739 struct sk_buff *skb;
2740 struct tcp_md5sig_key *md5;
2741 int tcp_header_size;
2742 int mss;
2743
2744 skb = sock_wmalloc(sk, MAX_TCP_HEADER, 1, GFP_ATOMIC);
2745 if (unlikely(!skb)) {
2746 dst_release(dst);
2747 return NULL;
2748 }
2749 /* Reserve space for headers. */
2750 skb_reserve(skb, MAX_TCP_HEADER);
2751
2752 skb_dst_set(skb, dst);
2753 security_skb_owned_by(skb, sk);
2754
2755 mss = dst_metric_advmss(dst);
2756 if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < mss)
2757 mss = tp->rx_opt.user_mss;
2758
2759 if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */
2760 __u8 rcv_wscale;
2761 /* Set this up on the first call only */
2762 req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW);
2763
2764 /* limit the window selection if the user enforce a smaller rx buffer */
2765 if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
2766 (req->window_clamp > tcp_full_space(sk) || req->window_clamp == 0))
2767 req->window_clamp = tcp_full_space(sk);
2768
2769 /* tcp_full_space because it is guaranteed to be the first packet */
2770 tcp_select_initial_window(tcp_full_space(sk),
2771 mss - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
2772 &req->rcv_wnd,
2773 &req->window_clamp,
2774 ireq->wscale_ok,
2775 &rcv_wscale,
2776 dst_metric(dst, RTAX_INITRWND));
2777 ireq->rcv_wscale = rcv_wscale;
2778 }
2779
2780 memset(&opts, 0, sizeof(opts));
2781#ifdef CONFIG_SYN_COOKIES
2782 if (unlikely(req->cookie_ts))
2783 TCP_SKB_CB(skb)->when = cookie_init_timestamp(req);
2784 else
2785#endif
2786 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2787 tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, &md5,
2788 foc) + sizeof(*th);
2789
2790 skb_push(skb, tcp_header_size);
2791 skb_reset_transport_header(skb);
2792
2793 th = tcp_hdr(skb);
2794 memset(th, 0, sizeof(struct tcphdr));
2795 th->syn = 1;
2796 th->ack = 1;
2797 TCP_ECN_make_synack(req, th);
2798 th->source = htons(ireq->ir_num);
2799 th->dest = ireq->ir_rmt_port;
2800 /* Setting of flags are superfluous here for callers (and ECE is
2801 * not even correctly set)
2802 */
2803 tcp_init_nondata_skb(skb, tcp_rsk(req)->snt_isn,
2804 TCPHDR_SYN | TCPHDR_ACK);
2805
2806 th->seq = htonl(TCP_SKB_CB(skb)->seq);
2807 /* XXX data is queued and acked as is. No buffer/window check */
2808 th->ack_seq = htonl(tcp_rsk(req)->rcv_nxt);
2809
2810 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
2811 th->window = htons(min(req->rcv_wnd, 65535U));
2812 tcp_options_write((__be32 *)(th + 1), tp, &opts);
2813 th->doff = (tcp_header_size >> 2);
2814 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_OUTSEGS);
2815
2816#ifdef CONFIG_TCP_MD5SIG
2817 /* Okay, we have all we need - do the md5 hash if needed */
2818 if (md5) {
2819 tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
2820 md5, NULL, req, skb);
2821 }
2822#endif
2823
2824 return skb;
2825}
2826EXPORT_SYMBOL(tcp_make_synack);
2827
2828/* Do all connect socket setups that can be done AF independent. */
2829static void tcp_connect_init(struct sock *sk)
2830{
2831 const struct dst_entry *dst = __sk_dst_get(sk);
2832 struct tcp_sock *tp = tcp_sk(sk);
2833 __u8 rcv_wscale;
2834
2835 /* We'll fix this up when we get a response from the other end.
2836 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
2837 */
2838 tp->tcp_header_len = sizeof(struct tcphdr) +
2839 (sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0);
2840
2841#ifdef CONFIG_TCP_MD5SIG
2842 if (tp->af_specific->md5_lookup(sk, sk) != NULL)
2843 tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
2844#endif
2845
2846 /* If user gave his TCP_MAXSEG, record it to clamp */
2847 if (tp->rx_opt.user_mss)
2848 tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
2849 tp->max_window = 0;
2850 tcp_mtup_init(sk);
2851 tcp_sync_mss(sk, dst_mtu(dst));
2852
2853 if (!tp->window_clamp)
2854 tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
2855 tp->advmss = dst_metric_advmss(dst);
2856 if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->advmss)
2857 tp->advmss = tp->rx_opt.user_mss;
2858
2859 tcp_initialize_rcv_mss(sk);
2860
2861 /* limit the window selection if the user enforce a smaller rx buffer */
2862 if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
2863 (tp->window_clamp > tcp_full_space(sk) || tp->window_clamp == 0))
2864 tp->window_clamp = tcp_full_space(sk);
2865
2866 tcp_select_initial_window(tcp_full_space(sk),
2867 tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),
2868 &tp->rcv_wnd,
2869 &tp->window_clamp,
2870 sysctl_tcp_window_scaling,
2871 &rcv_wscale,
2872 dst_metric(dst, RTAX_INITRWND));
2873
2874 tp->rx_opt.rcv_wscale = rcv_wscale;
2875 tp->rcv_ssthresh = tp->rcv_wnd;
2876
2877 sk->sk_err = 0;
2878 sock_reset_flag(sk, SOCK_DONE);
2879 tp->snd_wnd = 0;
2880 tcp_init_wl(tp, 0);
2881 tp->snd_una = tp->write_seq;
2882 tp->snd_sml = tp->write_seq;
2883 tp->snd_up = tp->write_seq;
2884 tp->snd_nxt = tp->write_seq;
2885
2886 if (likely(!tp->repair))
2887 tp->rcv_nxt = 0;
2888 else
2889 tp->rcv_tstamp = tcp_time_stamp;
2890 tp->rcv_wup = tp->rcv_nxt;
2891 tp->copied_seq = tp->rcv_nxt;
2892
2893 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
2894 inet_csk(sk)->icsk_retransmits = 0;
2895 tcp_clear_retrans(tp);
2896}
2897
2898static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb)
2899{
2900 struct tcp_sock *tp = tcp_sk(sk);
2901 struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
2902
2903 tcb->end_seq += skb->len;
2904 skb_header_release(skb);
2905 __tcp_add_write_queue_tail(sk, skb);
2906 sk->sk_wmem_queued += skb->truesize;
2907 sk_mem_charge(sk, skb->truesize);
2908 tp->write_seq = tcb->end_seq;
2909 tp->packets_out += tcp_skb_pcount(skb);
2910}
2911
2912/* Build and send a SYN with data and (cached) Fast Open cookie. However,
2913 * queue a data-only packet after the regular SYN, such that regular SYNs
2914 * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges
2915 * only the SYN sequence, the data are retransmitted in the first ACK.
2916 * If cookie is not cached or other error occurs, falls back to send a
2917 * regular SYN with Fast Open cookie request option.
2918 */
2919static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
2920{
2921 struct tcp_sock *tp = tcp_sk(sk);
2922 struct tcp_fastopen_request *fo = tp->fastopen_req;
2923 int syn_loss = 0, space, i, err = 0, iovlen = fo->data->msg_iovlen;
2924 struct sk_buff *syn_data = NULL, *data;
2925 unsigned long last_syn_loss = 0;
2926
2927 tp->rx_opt.mss_clamp = tp->advmss; /* If MSS is not cached */
2928 tcp_fastopen_cache_get(sk, &tp->rx_opt.mss_clamp, &fo->cookie,
2929 &syn_loss, &last_syn_loss);
2930 /* Recurring FO SYN losses: revert to regular handshake temporarily */
2931 if (syn_loss > 1 &&
2932 time_before(jiffies, last_syn_loss + (60*HZ << syn_loss))) {
2933 fo->cookie.len = -1;
2934 goto fallback;
2935 }
2936
2937 if (sysctl_tcp_fastopen & TFO_CLIENT_NO_COOKIE)
2938 fo->cookie.len = -1;
2939 else if (fo->cookie.len <= 0)
2940 goto fallback;
2941
2942 /* MSS for SYN-data is based on cached MSS and bounded by PMTU and
2943 * user-MSS. Reserve maximum option space for middleboxes that add
2944 * private TCP options. The cost is reduced data space in SYN :(
2945 */
2946 if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->rx_opt.mss_clamp)
2947 tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
2948 space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
2949 MAX_TCP_OPTION_SPACE;
2950
2951 space = min_t(size_t, space, fo->size);
2952
2953 /* limit to order-0 allocations */
2954 space = min_t(size_t, space, SKB_MAX_HEAD(MAX_TCP_HEADER));
2955
2956 syn_data = skb_copy_expand(syn, MAX_TCP_HEADER, space,
2957 sk->sk_allocation);
2958 if (syn_data == NULL)
2959 goto fallback;
2960
2961 for (i = 0; i < iovlen && syn_data->len < space; ++i) {
2962 struct iovec *iov = &fo->data->msg_iov[i];
2963 unsigned char __user *from = iov->iov_base;
2964 int len = iov->iov_len;
2965
2966 if (syn_data->len + len > space)
2967 len = space - syn_data->len;
2968 else if (i + 1 == iovlen)
2969 /* No more data pending in inet_wait_for_connect() */
2970 fo->data = NULL;
2971
2972 if (skb_add_data(syn_data, from, len))
2973 goto fallback;
2974 }
2975
2976 /* Queue a data-only packet after the regular SYN for retransmission */
2977 data = pskb_copy(syn_data, sk->sk_allocation);
2978 if (data == NULL)
2979 goto fallback;
2980 TCP_SKB_CB(data)->seq++;
2981 TCP_SKB_CB(data)->tcp_flags &= ~TCPHDR_SYN;
2982 TCP_SKB_CB(data)->tcp_flags = (TCPHDR_ACK|TCPHDR_PSH);
2983 tcp_connect_queue_skb(sk, data);
2984 fo->copied = data->len;
2985
2986 /* syn_data is about to be sent, we need to take current time stamps
2987 * for the packets that are in write queue : SYN packet and DATA
2988 */
2989 skb_mstamp_get(&syn->skb_mstamp);
2990 data->skb_mstamp = syn->skb_mstamp;
2991
2992 if (tcp_transmit_skb(sk, syn_data, 0, sk->sk_allocation) == 0) {
2993 tp->syn_data = (fo->copied > 0);
2994 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
2995 goto done;
2996 }
2997 syn_data = NULL;
2998
2999fallback:
3000 /* Send a regular SYN with Fast Open cookie request option */
3001 if (fo->cookie.len > 0)
3002 fo->cookie.len = 0;
3003 err = tcp_transmit_skb(sk, syn, 1, sk->sk_allocation);
3004 if (err)
3005 tp->syn_fastopen = 0;
3006 kfree_skb(syn_data);
3007done:
3008 fo->cookie.len = -1; /* Exclude Fast Open option for SYN retries */
3009 return err;
3010}
3011
3012/* Build a SYN and send it off. */
3013int tcp_connect(struct sock *sk)
3014{
3015 struct tcp_sock *tp = tcp_sk(sk);
3016 struct sk_buff *buff;
3017 int err;
3018
3019 tcp_connect_init(sk);
3020
3021 if (unlikely(tp->repair)) {
3022 tcp_finish_connect(sk, NULL);
3023 return 0;
3024 }
3025
3026 buff = alloc_skb_fclone(MAX_TCP_HEADER + 15, sk->sk_allocation);
3027 if (unlikely(buff == NULL))
3028 return -ENOBUFS;
3029
3030 /* Reserve space for headers. */
3031 skb_reserve(buff, MAX_TCP_HEADER);
3032
3033 tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
3034 tp->retrans_stamp = TCP_SKB_CB(buff)->when = tcp_time_stamp;
3035 tcp_connect_queue_skb(sk, buff);
3036 TCP_ECN_send_syn(sk, buff);
3037
3038 /* Send off SYN; include data in Fast Open. */
3039 err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) :
3040 tcp_transmit_skb(sk, buff, 1, sk->sk_allocation);
3041 if (err == -ECONNREFUSED)
3042 return err;
3043
3044 /* We change tp->snd_nxt after the tcp_transmit_skb() call
3045 * in order to make this packet get counted in tcpOutSegs.
3046 */
3047 tp->snd_nxt = tp->write_seq;
3048 tp->pushed_seq = tp->write_seq;
3049 TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
3050
3051 /* Timer for repeating the SYN until an answer. */
3052 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
3053 inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
3054 return 0;
3055}
3056EXPORT_SYMBOL(tcp_connect);
3057
3058/* Send out a delayed ack, the caller does the policy checking
3059 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
3060 * for details.
3061 */
3062void tcp_send_delayed_ack(struct sock *sk)
3063{
3064 struct inet_connection_sock *icsk = inet_csk(sk);
3065 int ato = icsk->icsk_ack.ato;
3066 unsigned long timeout;
3067
3068 if (ato > TCP_DELACK_MIN) {
3069 const struct tcp_sock *tp = tcp_sk(sk);
3070 int max_ato = HZ / 2;
3071
3072 if (icsk->icsk_ack.pingpong ||
3073 (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
3074 max_ato = TCP_DELACK_MAX;
3075
3076 /* Slow path, intersegment interval is "high". */
3077
3078 /* If some rtt estimate is known, use it to bound delayed ack.
3079 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
3080 * directly.
3081 */
3082 if (tp->srtt_us) {
3083 int rtt = max_t(int, usecs_to_jiffies(tp->srtt_us >> 3),
3084 TCP_DELACK_MIN);
3085
3086 if (rtt < max_ato)
3087 max_ato = rtt;
3088 }
3089
3090 ato = min(ato, max_ato);
3091 }
3092
3093 /* Stay within the limit we were given */
3094 timeout = jiffies + ato;
3095
3096 /* Use new timeout only if there wasn't a older one earlier. */
3097 if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
3098 /* If delack timer was blocked or is about to expire,
3099 * send ACK now.
3100 */
3101 if (icsk->icsk_ack.blocked ||
3102 time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
3103 tcp_send_ack(sk);
3104 return;
3105 }
3106
3107 if (!time_before(timeout, icsk->icsk_ack.timeout))
3108 timeout = icsk->icsk_ack.timeout;
3109 }
3110 icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
3111 icsk->icsk_ack.timeout = timeout;
3112 sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
3113}
3114
3115/* This routine sends an ack and also updates the window. */
3116void tcp_send_ack(struct sock *sk)
3117{
3118 struct sk_buff *buff;
3119
3120 /* If we have been reset, we may not send again. */
3121 if (sk->sk_state == TCP_CLOSE)
3122 return;
3123
3124 /* We are not putting this on the write queue, so
3125 * tcp_transmit_skb() will set the ownership to this
3126 * sock.
3127 */
3128 buff = alloc_skb(MAX_TCP_HEADER, sk_gfp_atomic(sk, GFP_ATOMIC));
3129 if (buff == NULL) {
3130 inet_csk_schedule_ack(sk);
3131 inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
3132 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
3133 TCP_DELACK_MAX, TCP_RTO_MAX);
3134 return;
3135 }
3136
3137 /* Reserve space for headers and prepare control bits. */
3138 skb_reserve(buff, MAX_TCP_HEADER);
3139 tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
3140
3141 /* Send it off, this clears delayed acks for us. */
3142 TCP_SKB_CB(buff)->when = tcp_time_stamp;
3143 tcp_transmit_skb(sk, buff, 0, sk_gfp_atomic(sk, GFP_ATOMIC));
3144}
3145
3146/* This routine sends a packet with an out of date sequence
3147 * number. It assumes the other end will try to ack it.
3148 *
3149 * Question: what should we make while urgent mode?
3150 * 4.4BSD forces sending single byte of data. We cannot send
3151 * out of window data, because we have SND.NXT==SND.MAX...
3152 *
3153 * Current solution: to send TWO zero-length segments in urgent mode:
3154 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
3155 * out-of-date with SND.UNA-1 to probe window.
3156 */
3157static int tcp_xmit_probe_skb(struct sock *sk, int urgent)
3158{
3159 struct tcp_sock *tp = tcp_sk(sk);
3160 struct sk_buff *skb;
3161
3162 /* We don't queue it, tcp_transmit_skb() sets ownership. */
3163 skb = alloc_skb(MAX_TCP_HEADER, sk_gfp_atomic(sk, GFP_ATOMIC));
3164 if (skb == NULL)
3165 return -1;
3166
3167 /* Reserve space for headers and set control bits. */
3168 skb_reserve(skb, MAX_TCP_HEADER);
3169 /* Use a previous sequence. This should cause the other
3170 * end to send an ack. Don't queue or clone SKB, just
3171 * send it.
3172 */
3173 tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
3174 TCP_SKB_CB(skb)->when = tcp_time_stamp;
3175 return tcp_transmit_skb(sk, skb, 0, GFP_ATOMIC);
3176}
3177
3178void tcp_send_window_probe(struct sock *sk)
3179{
3180 if (sk->sk_state == TCP_ESTABLISHED) {
3181 tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1;
3182 tcp_xmit_probe_skb(sk, 0);
3183 }
3184}
3185
3186/* Initiate keepalive or window probe from timer. */
3187int tcp_write_wakeup(struct sock *sk)
3188{
3189 struct tcp_sock *tp = tcp_sk(sk);
3190 struct sk_buff *skb;
3191
3192 if (sk->sk_state == TCP_CLOSE)
3193 return -1;
3194
3195 if ((skb = tcp_send_head(sk)) != NULL &&
3196 before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
3197 int err;
3198 unsigned int mss = tcp_current_mss(sk);
3199 unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
3200
3201 if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
3202 tp->pushed_seq = TCP_SKB_CB(skb)->end_seq;
3203
3204 /* We are probing the opening of a window
3205 * but the window size is != 0
3206 * must have been a result SWS avoidance ( sender )
3207 */
3208 if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq ||
3209 skb->len > mss) {
3210 seg_size = min(seg_size, mss);
3211 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3212 if (tcp_fragment(sk, skb, seg_size, mss))
3213 return -1;
3214 } else if (!tcp_skb_pcount(skb))
3215 tcp_set_skb_tso_segs(sk, skb, mss);
3216
3217 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
3218 TCP_SKB_CB(skb)->when = tcp_time_stamp;
3219 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
3220 if (!err)
3221 tcp_event_new_data_sent(sk, skb);
3222 return err;
3223 } else {
3224 if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
3225 tcp_xmit_probe_skb(sk, 1);
3226 return tcp_xmit_probe_skb(sk, 0);
3227 }
3228}
3229
3230/* A window probe timeout has occurred. If window is not closed send
3231 * a partial packet else a zero probe.
3232 */
3233void tcp_send_probe0(struct sock *sk)
3234{
3235 struct inet_connection_sock *icsk = inet_csk(sk);
3236 struct tcp_sock *tp = tcp_sk(sk);
3237 int err;
3238
3239 err = tcp_write_wakeup(sk);
3240
3241 if (tp->packets_out || !tcp_send_head(sk)) {
3242 /* Cancel probe timer, if it is not required. */
3243 icsk->icsk_probes_out = 0;
3244 icsk->icsk_backoff = 0;
3245 return;
3246 }
3247
3248 if (err <= 0) {
3249 if (icsk->icsk_backoff < sysctl_tcp_retries2)
3250 icsk->icsk_backoff++;
3251 icsk->icsk_probes_out++;
3252 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3253 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
3254 TCP_RTO_MAX);
3255 } else {
3256 /* If packet was not sent due to local congestion,
3257 * do not backoff and do not remember icsk_probes_out.
3258 * Let local senders to fight for local resources.
3259 *
3260 * Use accumulated backoff yet.
3261 */
3262 if (!icsk->icsk_probes_out)
3263 icsk->icsk_probes_out = 1;
3264 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
3265 min(icsk->icsk_rto << icsk->icsk_backoff,
3266 TCP_RESOURCE_PROBE_INTERVAL),
3267 TCP_RTO_MAX);
3268 }
3269}