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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright (c) 2005, 2006 Andrea Bittau <a.bittau@cs.ucl.ac.uk>
4 *
5 * Changes to meet Linux coding standards, and DCCP infrastructure fixes.
6 *
7 * Copyright (c) 2006 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
8 */
9
10/*
11 * This implementation should follow RFC 4341
12 */
13#include <linux/slab.h>
14#include "../feat.h"
15#include "ccid2.h"
16
17
18#ifdef CONFIG_IP_DCCP_CCID2_DEBUG
19static bool ccid2_debug;
20#define ccid2_pr_debug(format, a...) DCCP_PR_DEBUG(ccid2_debug, format, ##a)
21#else
22#define ccid2_pr_debug(format, a...)
23#endif
24
25static int ccid2_hc_tx_alloc_seq(struct ccid2_hc_tx_sock *hc)
26{
27 struct ccid2_seq *seqp;
28 int i;
29
30 /* check if we have space to preserve the pointer to the buffer */
31 if (hc->tx_seqbufc >= (sizeof(hc->tx_seqbuf) /
32 sizeof(struct ccid2_seq *)))
33 return -ENOMEM;
34
35 /* allocate buffer and initialize linked list */
36 seqp = kmalloc_array(CCID2_SEQBUF_LEN, sizeof(struct ccid2_seq),
37 gfp_any());
38 if (seqp == NULL)
39 return -ENOMEM;
40
41 for (i = 0; i < (CCID2_SEQBUF_LEN - 1); i++) {
42 seqp[i].ccid2s_next = &seqp[i + 1];
43 seqp[i + 1].ccid2s_prev = &seqp[i];
44 }
45 seqp[CCID2_SEQBUF_LEN - 1].ccid2s_next = seqp;
46 seqp->ccid2s_prev = &seqp[CCID2_SEQBUF_LEN - 1];
47
48 /* This is the first allocation. Initiate the head and tail. */
49 if (hc->tx_seqbufc == 0)
50 hc->tx_seqh = hc->tx_seqt = seqp;
51 else {
52 /* link the existing list with the one we just created */
53 hc->tx_seqh->ccid2s_next = seqp;
54 seqp->ccid2s_prev = hc->tx_seqh;
55
56 hc->tx_seqt->ccid2s_prev = &seqp[CCID2_SEQBUF_LEN - 1];
57 seqp[CCID2_SEQBUF_LEN - 1].ccid2s_next = hc->tx_seqt;
58 }
59
60 /* store the original pointer to the buffer so we can free it */
61 hc->tx_seqbuf[hc->tx_seqbufc] = seqp;
62 hc->tx_seqbufc++;
63
64 return 0;
65}
66
67static int ccid2_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
68{
69 if (ccid2_cwnd_network_limited(ccid2_hc_tx_sk(sk)))
70 return CCID_PACKET_WILL_DEQUEUE_LATER;
71 return CCID_PACKET_SEND_AT_ONCE;
72}
73
74static void ccid2_change_l_ack_ratio(struct sock *sk, u32 val)
75{
76 u32 max_ratio = DIV_ROUND_UP(ccid2_hc_tx_sk(sk)->tx_cwnd, 2);
77
78 /*
79 * Ensure that Ack Ratio does not exceed ceil(cwnd/2), which is (2) from
80 * RFC 4341, 6.1.2. We ignore the statement that Ack Ratio 2 is always
81 * acceptable since this causes starvation/deadlock whenever cwnd < 2.
82 * The same problem arises when Ack Ratio is 0 (ie. Ack Ratio disabled).
83 */
84 if (val == 0 || val > max_ratio) {
85 DCCP_WARN("Limiting Ack Ratio (%u) to %u\n", val, max_ratio);
86 val = max_ratio;
87 }
88 dccp_feat_signal_nn_change(sk, DCCPF_ACK_RATIO,
89 min_t(u32, val, DCCPF_ACK_RATIO_MAX));
90}
91
92static void ccid2_check_l_ack_ratio(struct sock *sk)
93{
94 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
95
96 /*
97 * After a loss, idle period, application limited period, or RTO we
98 * need to check that the ack ratio is still less than the congestion
99 * window. Otherwise, we will send an entire congestion window of
100 * packets and got no response because we haven't sent ack ratio
101 * packets yet.
102 * If the ack ratio does need to be reduced, we reduce it to half of
103 * the congestion window (or 1 if that's zero) instead of to the
104 * congestion window. This prevents problems if one ack is lost.
105 */
106 if (dccp_feat_nn_get(sk, DCCPF_ACK_RATIO) > hc->tx_cwnd)
107 ccid2_change_l_ack_ratio(sk, hc->tx_cwnd/2 ? : 1U);
108}
109
110static void ccid2_change_l_seq_window(struct sock *sk, u64 val)
111{
112 dccp_feat_signal_nn_change(sk, DCCPF_SEQUENCE_WINDOW,
113 clamp_val(val, DCCPF_SEQ_WMIN,
114 DCCPF_SEQ_WMAX));
115}
116
117static void dccp_tasklet_schedule(struct sock *sk)
118{
119 struct tasklet_struct *t = &dccp_sk(sk)->dccps_xmitlet;
120
121 if (!test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) {
122 sock_hold(sk);
123 __tasklet_schedule(t);
124 }
125}
126
127static void ccid2_hc_tx_rto_expire(struct timer_list *t)
128{
129 struct ccid2_hc_tx_sock *hc = from_timer(hc, t, tx_rtotimer);
130 struct sock *sk = hc->sk;
131 const bool sender_was_blocked = ccid2_cwnd_network_limited(hc);
132
133 bh_lock_sock(sk);
134 if (sock_owned_by_user(sk)) {
135 sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + HZ / 5);
136 goto out;
137 }
138
139 ccid2_pr_debug("RTO_EXPIRE\n");
140
141 if (sk->sk_state == DCCP_CLOSED)
142 goto out;
143
144 /* back-off timer */
145 hc->tx_rto <<= 1;
146 if (hc->tx_rto > DCCP_RTO_MAX)
147 hc->tx_rto = DCCP_RTO_MAX;
148
149 /* adjust pipe, cwnd etc */
150 hc->tx_ssthresh = hc->tx_cwnd / 2;
151 if (hc->tx_ssthresh < 2)
152 hc->tx_ssthresh = 2;
153 hc->tx_cwnd = 1;
154 hc->tx_pipe = 0;
155
156 /* clear state about stuff we sent */
157 hc->tx_seqt = hc->tx_seqh;
158 hc->tx_packets_acked = 0;
159
160 /* clear ack ratio state. */
161 hc->tx_rpseq = 0;
162 hc->tx_rpdupack = -1;
163 ccid2_change_l_ack_ratio(sk, 1);
164
165 /* if we were blocked before, we may now send cwnd=1 packet */
166 if (sender_was_blocked)
167 dccp_tasklet_schedule(sk);
168 /* restart backed-off timer */
169 sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
170out:
171 bh_unlock_sock(sk);
172 sock_put(sk);
173}
174
175/*
176 * Congestion window validation (RFC 2861).
177 */
178static bool ccid2_do_cwv = true;
179module_param(ccid2_do_cwv, bool, 0644);
180MODULE_PARM_DESC(ccid2_do_cwv, "Perform RFC2861 Congestion Window Validation");
181
182/**
183 * ccid2_update_used_window - Track how much of cwnd is actually used
184 * This is done in addition to CWV. The sender needs to have an idea of how many
185 * packets may be in flight, to set the local Sequence Window value accordingly
186 * (RFC 4340, 7.5.2). The CWV mechanism is exploited to keep track of the
187 * maximum-used window. We use an EWMA low-pass filter to filter out noise.
188 */
189static void ccid2_update_used_window(struct ccid2_hc_tx_sock *hc, u32 new_wnd)
190{
191 hc->tx_expected_wnd = (3 * hc->tx_expected_wnd + new_wnd) / 4;
192}
193
194/* This borrows the code of tcp_cwnd_application_limited() */
195static void ccid2_cwnd_application_limited(struct sock *sk, const u32 now)
196{
197 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
198 /* don't reduce cwnd below the initial window (IW) */
199 u32 init_win = rfc3390_bytes_to_packets(dccp_sk(sk)->dccps_mss_cache),
200 win_used = max(hc->tx_cwnd_used, init_win);
201
202 if (win_used < hc->tx_cwnd) {
203 hc->tx_ssthresh = max(hc->tx_ssthresh,
204 (hc->tx_cwnd >> 1) + (hc->tx_cwnd >> 2));
205 hc->tx_cwnd = (hc->tx_cwnd + win_used) >> 1;
206 }
207 hc->tx_cwnd_used = 0;
208 hc->tx_cwnd_stamp = now;
209
210 ccid2_check_l_ack_ratio(sk);
211}
212
213/* This borrows the code of tcp_cwnd_restart() */
214static void ccid2_cwnd_restart(struct sock *sk, const u32 now)
215{
216 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
217 u32 cwnd = hc->tx_cwnd, restart_cwnd,
218 iwnd = rfc3390_bytes_to_packets(dccp_sk(sk)->dccps_mss_cache);
219 s32 delta = now - hc->tx_lsndtime;
220
221 hc->tx_ssthresh = max(hc->tx_ssthresh, (cwnd >> 1) + (cwnd >> 2));
222
223 /* don't reduce cwnd below the initial window (IW) */
224 restart_cwnd = min(cwnd, iwnd);
225
226 while ((delta -= hc->tx_rto) >= 0 && cwnd > restart_cwnd)
227 cwnd >>= 1;
228 hc->tx_cwnd = max(cwnd, restart_cwnd);
229 hc->tx_cwnd_stamp = now;
230 hc->tx_cwnd_used = 0;
231
232 ccid2_check_l_ack_ratio(sk);
233}
234
235static void ccid2_hc_tx_packet_sent(struct sock *sk, unsigned int len)
236{
237 struct dccp_sock *dp = dccp_sk(sk);
238 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
239 const u32 now = ccid2_jiffies32;
240 struct ccid2_seq *next;
241
242 /* slow-start after idle periods (RFC 2581, RFC 2861) */
243 if (ccid2_do_cwv && !hc->tx_pipe &&
244 (s32)(now - hc->tx_lsndtime) >= hc->tx_rto)
245 ccid2_cwnd_restart(sk, now);
246
247 hc->tx_lsndtime = now;
248 hc->tx_pipe += 1;
249
250 /* see whether cwnd was fully used (RFC 2861), update expected window */
251 if (ccid2_cwnd_network_limited(hc)) {
252 ccid2_update_used_window(hc, hc->tx_cwnd);
253 hc->tx_cwnd_used = 0;
254 hc->tx_cwnd_stamp = now;
255 } else {
256 if (hc->tx_pipe > hc->tx_cwnd_used)
257 hc->tx_cwnd_used = hc->tx_pipe;
258
259 ccid2_update_used_window(hc, hc->tx_cwnd_used);
260
261 if (ccid2_do_cwv && (s32)(now - hc->tx_cwnd_stamp) >= hc->tx_rto)
262 ccid2_cwnd_application_limited(sk, now);
263 }
264
265 hc->tx_seqh->ccid2s_seq = dp->dccps_gss;
266 hc->tx_seqh->ccid2s_acked = 0;
267 hc->tx_seqh->ccid2s_sent = now;
268
269 next = hc->tx_seqh->ccid2s_next;
270 /* check if we need to alloc more space */
271 if (next == hc->tx_seqt) {
272 if (ccid2_hc_tx_alloc_seq(hc)) {
273 DCCP_CRIT("packet history - out of memory!");
274 /* FIXME: find a more graceful way to bail out */
275 return;
276 }
277 next = hc->tx_seqh->ccid2s_next;
278 BUG_ON(next == hc->tx_seqt);
279 }
280 hc->tx_seqh = next;
281
282 ccid2_pr_debug("cwnd=%d pipe=%d\n", hc->tx_cwnd, hc->tx_pipe);
283
284 /*
285 * FIXME: The code below is broken and the variables have been removed
286 * from the socket struct. The `ackloss' variable was always set to 0,
287 * and with arsent there are several problems:
288 * (i) it doesn't just count the number of Acks, but all sent packets;
289 * (ii) it is expressed in # of packets, not # of windows, so the
290 * comparison below uses the wrong formula: Appendix A of RFC 4341
291 * comes up with the number K = cwnd / (R^2 - R) of consecutive windows
292 * of data with no lost or marked Ack packets. If arsent were the # of
293 * consecutive Acks received without loss, then Ack Ratio needs to be
294 * decreased by 1 when
295 * arsent >= K * cwnd / R = cwnd^2 / (R^3 - R^2)
296 * where cwnd / R is the number of Acks received per window of data
297 * (cf. RFC 4341, App. A). The problems are that
298 * - arsent counts other packets as well;
299 * - the comparison uses a formula different from RFC 4341;
300 * - computing a cubic/quadratic equation each time is too complicated.
301 * Hence a different algorithm is needed.
302 */
303#if 0
304 /* Ack Ratio. Need to maintain a concept of how many windows we sent */
305 hc->tx_arsent++;
306 /* We had an ack loss in this window... */
307 if (hc->tx_ackloss) {
308 if (hc->tx_arsent >= hc->tx_cwnd) {
309 hc->tx_arsent = 0;
310 hc->tx_ackloss = 0;
311 }
312 } else {
313 /* No acks lost up to now... */
314 /* decrease ack ratio if enough packets were sent */
315 if (dp->dccps_l_ack_ratio > 1) {
316 /* XXX don't calculate denominator each time */
317 int denom = dp->dccps_l_ack_ratio * dp->dccps_l_ack_ratio -
318 dp->dccps_l_ack_ratio;
319
320 denom = hc->tx_cwnd * hc->tx_cwnd / denom;
321
322 if (hc->tx_arsent >= denom) {
323 ccid2_change_l_ack_ratio(sk, dp->dccps_l_ack_ratio - 1);
324 hc->tx_arsent = 0;
325 }
326 } else {
327 /* we can't increase ack ratio further [1] */
328 hc->tx_arsent = 0; /* or maybe set it to cwnd*/
329 }
330 }
331#endif
332
333 sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
334
335#ifdef CONFIG_IP_DCCP_CCID2_DEBUG
336 do {
337 struct ccid2_seq *seqp = hc->tx_seqt;
338
339 while (seqp != hc->tx_seqh) {
340 ccid2_pr_debug("out seq=%llu acked=%d time=%u\n",
341 (unsigned long long)seqp->ccid2s_seq,
342 seqp->ccid2s_acked, seqp->ccid2s_sent);
343 seqp = seqp->ccid2s_next;
344 }
345 } while (0);
346 ccid2_pr_debug("=========\n");
347#endif
348}
349
350/**
351 * ccid2_rtt_estimator - Sample RTT and compute RTO using RFC2988 algorithm
352 * This code is almost identical with TCP's tcp_rtt_estimator(), since
353 * - it has a higher sampling frequency (recommended by RFC 1323),
354 * - the RTO does not collapse into RTT due to RTTVAR going towards zero,
355 * - it is simple (cf. more complex proposals such as Eifel timer or research
356 * which suggests that the gain should be set according to window size),
357 * - in tests it was found to work well with CCID2 [gerrit].
358 */
359static void ccid2_rtt_estimator(struct sock *sk, const long mrtt)
360{
361 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
362 long m = mrtt ? : 1;
363
364 if (hc->tx_srtt == 0) {
365 /* First measurement m */
366 hc->tx_srtt = m << 3;
367 hc->tx_mdev = m << 1;
368
369 hc->tx_mdev_max = max(hc->tx_mdev, tcp_rto_min(sk));
370 hc->tx_rttvar = hc->tx_mdev_max;
371
372 hc->tx_rtt_seq = dccp_sk(sk)->dccps_gss;
373 } else {
374 /* Update scaled SRTT as SRTT += 1/8 * (m - SRTT) */
375 m -= (hc->tx_srtt >> 3);
376 hc->tx_srtt += m;
377
378 /* Similarly, update scaled mdev with regard to |m| */
379 if (m < 0) {
380 m = -m;
381 m -= (hc->tx_mdev >> 2);
382 /*
383 * This neutralises RTO increase when RTT < SRTT - mdev
384 * (see P. Sarolahti, A. Kuznetsov,"Congestion Control
385 * in Linux TCP", USENIX 2002, pp. 49-62).
386 */
387 if (m > 0)
388 m >>= 3;
389 } else {
390 m -= (hc->tx_mdev >> 2);
391 }
392 hc->tx_mdev += m;
393
394 if (hc->tx_mdev > hc->tx_mdev_max) {
395 hc->tx_mdev_max = hc->tx_mdev;
396 if (hc->tx_mdev_max > hc->tx_rttvar)
397 hc->tx_rttvar = hc->tx_mdev_max;
398 }
399
400 /*
401 * Decay RTTVAR at most once per flight, exploiting that
402 * 1) pipe <= cwnd <= Sequence_Window = W (RFC 4340, 7.5.2)
403 * 2) AWL = GSS-W+1 <= GAR <= GSS (RFC 4340, 7.5.1)
404 * GAR is a useful bound for FlightSize = pipe.
405 * AWL is probably too low here, as it over-estimates pipe.
406 */
407 if (after48(dccp_sk(sk)->dccps_gar, hc->tx_rtt_seq)) {
408 if (hc->tx_mdev_max < hc->tx_rttvar)
409 hc->tx_rttvar -= (hc->tx_rttvar -
410 hc->tx_mdev_max) >> 2;
411 hc->tx_rtt_seq = dccp_sk(sk)->dccps_gss;
412 hc->tx_mdev_max = tcp_rto_min(sk);
413 }
414 }
415
416 /*
417 * Set RTO from SRTT and RTTVAR
418 * As in TCP, 4 * RTTVAR >= TCP_RTO_MIN, giving a minimum RTO of 200 ms.
419 * This agrees with RFC 4341, 5:
420 * "Because DCCP does not retransmit data, DCCP does not require
421 * TCP's recommended minimum timeout of one second".
422 */
423 hc->tx_rto = (hc->tx_srtt >> 3) + hc->tx_rttvar;
424
425 if (hc->tx_rto > DCCP_RTO_MAX)
426 hc->tx_rto = DCCP_RTO_MAX;
427}
428
429static void ccid2_new_ack(struct sock *sk, struct ccid2_seq *seqp,
430 unsigned int *maxincr)
431{
432 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
433 struct dccp_sock *dp = dccp_sk(sk);
434 int r_seq_used = hc->tx_cwnd / dp->dccps_l_ack_ratio;
435
436 if (hc->tx_cwnd < dp->dccps_l_seq_win &&
437 r_seq_used < dp->dccps_r_seq_win) {
438 if (hc->tx_cwnd < hc->tx_ssthresh) {
439 if (*maxincr > 0 && ++hc->tx_packets_acked >= 2) {
440 hc->tx_cwnd += 1;
441 *maxincr -= 1;
442 hc->tx_packets_acked = 0;
443 }
444 } else if (++hc->tx_packets_acked >= hc->tx_cwnd) {
445 hc->tx_cwnd += 1;
446 hc->tx_packets_acked = 0;
447 }
448 }
449
450 /*
451 * Adjust the local sequence window and the ack ratio to allow about
452 * 5 times the number of packets in the network (RFC 4340 7.5.2)
453 */
454 if (r_seq_used * CCID2_WIN_CHANGE_FACTOR >= dp->dccps_r_seq_win)
455 ccid2_change_l_ack_ratio(sk, dp->dccps_l_ack_ratio * 2);
456 else if (r_seq_used * CCID2_WIN_CHANGE_FACTOR < dp->dccps_r_seq_win/2)
457 ccid2_change_l_ack_ratio(sk, dp->dccps_l_ack_ratio / 2 ? : 1U);
458
459 if (hc->tx_cwnd * CCID2_WIN_CHANGE_FACTOR >= dp->dccps_l_seq_win)
460 ccid2_change_l_seq_window(sk, dp->dccps_l_seq_win * 2);
461 else if (hc->tx_cwnd * CCID2_WIN_CHANGE_FACTOR < dp->dccps_l_seq_win/2)
462 ccid2_change_l_seq_window(sk, dp->dccps_l_seq_win / 2);
463
464 /*
465 * FIXME: RTT is sampled several times per acknowledgment (for each
466 * entry in the Ack Vector), instead of once per Ack (as in TCP SACK).
467 * This causes the RTT to be over-estimated, since the older entries
468 * in the Ack Vector have earlier sending times.
469 * The cleanest solution is to not use the ccid2s_sent field at all
470 * and instead use DCCP timestamps: requires changes in other places.
471 */
472 ccid2_rtt_estimator(sk, ccid2_jiffies32 - seqp->ccid2s_sent);
473}
474
475static void ccid2_congestion_event(struct sock *sk, struct ccid2_seq *seqp)
476{
477 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
478
479 if ((s32)(seqp->ccid2s_sent - hc->tx_last_cong) < 0) {
480 ccid2_pr_debug("Multiple losses in an RTT---treating as one\n");
481 return;
482 }
483
484 hc->tx_last_cong = ccid2_jiffies32;
485
486 hc->tx_cwnd = hc->tx_cwnd / 2 ? : 1U;
487 hc->tx_ssthresh = max(hc->tx_cwnd, 2U);
488
489 ccid2_check_l_ack_ratio(sk);
490}
491
492static int ccid2_hc_tx_parse_options(struct sock *sk, u8 packet_type,
493 u8 option, u8 *optval, u8 optlen)
494{
495 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
496
497 switch (option) {
498 case DCCPO_ACK_VECTOR_0:
499 case DCCPO_ACK_VECTOR_1:
500 return dccp_ackvec_parsed_add(&hc->tx_av_chunks, optval, optlen,
501 option - DCCPO_ACK_VECTOR_0);
502 }
503 return 0;
504}
505
506static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
507{
508 struct dccp_sock *dp = dccp_sk(sk);
509 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
510 const bool sender_was_blocked = ccid2_cwnd_network_limited(hc);
511 struct dccp_ackvec_parsed *avp;
512 u64 ackno, seqno;
513 struct ccid2_seq *seqp;
514 int done = 0;
515 unsigned int maxincr = 0;
516
517 /* check reverse path congestion */
518 seqno = DCCP_SKB_CB(skb)->dccpd_seq;
519
520 /* XXX this whole "algorithm" is broken. Need to fix it to keep track
521 * of the seqnos of the dupacks so that rpseq and rpdupack are correct
522 * -sorbo.
523 */
524 /* need to bootstrap */
525 if (hc->tx_rpdupack == -1) {
526 hc->tx_rpdupack = 0;
527 hc->tx_rpseq = seqno;
528 } else {
529 /* check if packet is consecutive */
530 if (dccp_delta_seqno(hc->tx_rpseq, seqno) == 1)
531 hc->tx_rpseq = seqno;
532 /* it's a later packet */
533 else if (after48(seqno, hc->tx_rpseq)) {
534 hc->tx_rpdupack++;
535
536 /* check if we got enough dupacks */
537 if (hc->tx_rpdupack >= NUMDUPACK) {
538 hc->tx_rpdupack = -1; /* XXX lame */
539 hc->tx_rpseq = 0;
540#ifdef __CCID2_COPES_GRACEFULLY_WITH_ACK_CONGESTION_CONTROL__
541 /*
542 * FIXME: Ack Congestion Control is broken; in
543 * the current state instabilities occurred with
544 * Ack Ratios greater than 1; causing hang-ups
545 * and long RTO timeouts. This needs to be fixed
546 * before opening up dynamic changes. -- gerrit
547 */
548 ccid2_change_l_ack_ratio(sk, 2 * dp->dccps_l_ack_ratio);
549#endif
550 }
551 }
552 }
553
554 /* check forward path congestion */
555 if (dccp_packet_without_ack(skb))
556 return;
557
558 /* still didn't send out new data packets */
559 if (hc->tx_seqh == hc->tx_seqt)
560 goto done;
561
562 ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
563 if (after48(ackno, hc->tx_high_ack))
564 hc->tx_high_ack = ackno;
565
566 seqp = hc->tx_seqt;
567 while (before48(seqp->ccid2s_seq, ackno)) {
568 seqp = seqp->ccid2s_next;
569 if (seqp == hc->tx_seqh) {
570 seqp = hc->tx_seqh->ccid2s_prev;
571 break;
572 }
573 }
574
575 /*
576 * In slow-start, cwnd can increase up to a maximum of Ack Ratio/2
577 * packets per acknowledgement. Rounding up avoids that cwnd is not
578 * advanced when Ack Ratio is 1 and gives a slight edge otherwise.
579 */
580 if (hc->tx_cwnd < hc->tx_ssthresh)
581 maxincr = DIV_ROUND_UP(dp->dccps_l_ack_ratio, 2);
582
583 /* go through all ack vectors */
584 list_for_each_entry(avp, &hc->tx_av_chunks, node) {
585 /* go through this ack vector */
586 for (; avp->len--; avp->vec++) {
587 u64 ackno_end_rl = SUB48(ackno,
588 dccp_ackvec_runlen(avp->vec));
589
590 ccid2_pr_debug("ackvec %llu |%u,%u|\n",
591 (unsigned long long)ackno,
592 dccp_ackvec_state(avp->vec) >> 6,
593 dccp_ackvec_runlen(avp->vec));
594 /* if the seqno we are analyzing is larger than the
595 * current ackno, then move towards the tail of our
596 * seqnos.
597 */
598 while (after48(seqp->ccid2s_seq, ackno)) {
599 if (seqp == hc->tx_seqt) {
600 done = 1;
601 break;
602 }
603 seqp = seqp->ccid2s_prev;
604 }
605 if (done)
606 break;
607
608 /* check all seqnos in the range of the vector
609 * run length
610 */
611 while (between48(seqp->ccid2s_seq,ackno_end_rl,ackno)) {
612 const u8 state = dccp_ackvec_state(avp->vec);
613
614 /* new packet received or marked */
615 if (state != DCCPAV_NOT_RECEIVED &&
616 !seqp->ccid2s_acked) {
617 if (state == DCCPAV_ECN_MARKED)
618 ccid2_congestion_event(sk,
619 seqp);
620 else
621 ccid2_new_ack(sk, seqp,
622 &maxincr);
623
624 seqp->ccid2s_acked = 1;
625 ccid2_pr_debug("Got ack for %llu\n",
626 (unsigned long long)seqp->ccid2s_seq);
627 hc->tx_pipe--;
628 }
629 if (seqp == hc->tx_seqt) {
630 done = 1;
631 break;
632 }
633 seqp = seqp->ccid2s_prev;
634 }
635 if (done)
636 break;
637
638 ackno = SUB48(ackno_end_rl, 1);
639 }
640 if (done)
641 break;
642 }
643
644 /* The state about what is acked should be correct now
645 * Check for NUMDUPACK
646 */
647 seqp = hc->tx_seqt;
648 while (before48(seqp->ccid2s_seq, hc->tx_high_ack)) {
649 seqp = seqp->ccid2s_next;
650 if (seqp == hc->tx_seqh) {
651 seqp = hc->tx_seqh->ccid2s_prev;
652 break;
653 }
654 }
655 done = 0;
656 while (1) {
657 if (seqp->ccid2s_acked) {
658 done++;
659 if (done == NUMDUPACK)
660 break;
661 }
662 if (seqp == hc->tx_seqt)
663 break;
664 seqp = seqp->ccid2s_prev;
665 }
666
667 /* If there are at least 3 acknowledgements, anything unacknowledged
668 * below the last sequence number is considered lost
669 */
670 if (done == NUMDUPACK) {
671 struct ccid2_seq *last_acked = seqp;
672
673 /* check for lost packets */
674 while (1) {
675 if (!seqp->ccid2s_acked) {
676 ccid2_pr_debug("Packet lost: %llu\n",
677 (unsigned long long)seqp->ccid2s_seq);
678 /* XXX need to traverse from tail -> head in
679 * order to detect multiple congestion events in
680 * one ack vector.
681 */
682 ccid2_congestion_event(sk, seqp);
683 hc->tx_pipe--;
684 }
685 if (seqp == hc->tx_seqt)
686 break;
687 seqp = seqp->ccid2s_prev;
688 }
689
690 hc->tx_seqt = last_acked;
691 }
692
693 /* trim acked packets in tail */
694 while (hc->tx_seqt != hc->tx_seqh) {
695 if (!hc->tx_seqt->ccid2s_acked)
696 break;
697
698 hc->tx_seqt = hc->tx_seqt->ccid2s_next;
699 }
700
701 /* restart RTO timer if not all outstanding data has been acked */
702 if (hc->tx_pipe == 0)
703 sk_stop_timer(sk, &hc->tx_rtotimer);
704 else
705 sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
706done:
707 /* check if incoming Acks allow pending packets to be sent */
708 if (sender_was_blocked && !ccid2_cwnd_network_limited(hc))
709 dccp_tasklet_schedule(sk);
710 dccp_ackvec_parsed_cleanup(&hc->tx_av_chunks);
711}
712
713static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
714{
715 struct ccid2_hc_tx_sock *hc = ccid_priv(ccid);
716 struct dccp_sock *dp = dccp_sk(sk);
717 u32 max_ratio;
718
719 /* RFC 4341, 5: initialise ssthresh to arbitrarily high (max) value */
720 hc->tx_ssthresh = ~0U;
721
722 /* Use larger initial windows (RFC 4341, section 5). */
723 hc->tx_cwnd = rfc3390_bytes_to_packets(dp->dccps_mss_cache);
724 hc->tx_expected_wnd = hc->tx_cwnd;
725
726 /* Make sure that Ack Ratio is enabled and within bounds. */
727 max_ratio = DIV_ROUND_UP(hc->tx_cwnd, 2);
728 if (dp->dccps_l_ack_ratio == 0 || dp->dccps_l_ack_ratio > max_ratio)
729 dp->dccps_l_ack_ratio = max_ratio;
730
731 /* XXX init ~ to window size... */
732 if (ccid2_hc_tx_alloc_seq(hc))
733 return -ENOMEM;
734
735 hc->tx_rto = DCCP_TIMEOUT_INIT;
736 hc->tx_rpdupack = -1;
737 hc->tx_last_cong = hc->tx_lsndtime = hc->tx_cwnd_stamp = ccid2_jiffies32;
738 hc->tx_cwnd_used = 0;
739 hc->sk = sk;
740 timer_setup(&hc->tx_rtotimer, ccid2_hc_tx_rto_expire, 0);
741 INIT_LIST_HEAD(&hc->tx_av_chunks);
742 return 0;
743}
744
745static void ccid2_hc_tx_exit(struct sock *sk)
746{
747 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
748 int i;
749
750 sk_stop_timer(sk, &hc->tx_rtotimer);
751
752 for (i = 0; i < hc->tx_seqbufc; i++)
753 kfree(hc->tx_seqbuf[i]);
754 hc->tx_seqbufc = 0;
755 dccp_ackvec_parsed_cleanup(&hc->tx_av_chunks);
756}
757
758static void ccid2_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
759{
760 struct ccid2_hc_rx_sock *hc = ccid2_hc_rx_sk(sk);
761
762 if (!dccp_data_packet(skb))
763 return;
764
765 if (++hc->rx_num_data_pkts >= dccp_sk(sk)->dccps_r_ack_ratio) {
766 dccp_send_ack(sk);
767 hc->rx_num_data_pkts = 0;
768 }
769}
770
771struct ccid_operations ccid2_ops = {
772 .ccid_id = DCCPC_CCID2,
773 .ccid_name = "TCP-like",
774 .ccid_hc_tx_obj_size = sizeof(struct ccid2_hc_tx_sock),
775 .ccid_hc_tx_init = ccid2_hc_tx_init,
776 .ccid_hc_tx_exit = ccid2_hc_tx_exit,
777 .ccid_hc_tx_send_packet = ccid2_hc_tx_send_packet,
778 .ccid_hc_tx_packet_sent = ccid2_hc_tx_packet_sent,
779 .ccid_hc_tx_parse_options = ccid2_hc_tx_parse_options,
780 .ccid_hc_tx_packet_recv = ccid2_hc_tx_packet_recv,
781 .ccid_hc_rx_obj_size = sizeof(struct ccid2_hc_rx_sock),
782 .ccid_hc_rx_packet_recv = ccid2_hc_rx_packet_recv,
783};
784
785#ifdef CONFIG_IP_DCCP_CCID2_DEBUG
786module_param(ccid2_debug, bool, 0644);
787MODULE_PARM_DESC(ccid2_debug, "Enable CCID-2 debug messages");
788#endif
1/*
2 * Copyright (c) 2005, 2006 Andrea Bittau <a.bittau@cs.ucl.ac.uk>
3 *
4 * Changes to meet Linux coding standards, and DCCP infrastructure fixes.
5 *
6 * Copyright (c) 2006 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
12 *
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
17 *
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
21 */
22
23/*
24 * This implementation should follow RFC 4341
25 */
26#include <linux/slab.h>
27#include "../feat.h"
28#include "ccid2.h"
29
30
31#ifdef CONFIG_IP_DCCP_CCID2_DEBUG
32static bool ccid2_debug;
33#define ccid2_pr_debug(format, a...) DCCP_PR_DEBUG(ccid2_debug, format, ##a)
34#else
35#define ccid2_pr_debug(format, a...)
36#endif
37
38static int ccid2_hc_tx_alloc_seq(struct ccid2_hc_tx_sock *hc)
39{
40 struct ccid2_seq *seqp;
41 int i;
42
43 /* check if we have space to preserve the pointer to the buffer */
44 if (hc->tx_seqbufc >= (sizeof(hc->tx_seqbuf) /
45 sizeof(struct ccid2_seq *)))
46 return -ENOMEM;
47
48 /* allocate buffer and initialize linked list */
49 seqp = kmalloc(CCID2_SEQBUF_LEN * sizeof(struct ccid2_seq), gfp_any());
50 if (seqp == NULL)
51 return -ENOMEM;
52
53 for (i = 0; i < (CCID2_SEQBUF_LEN - 1); i++) {
54 seqp[i].ccid2s_next = &seqp[i + 1];
55 seqp[i + 1].ccid2s_prev = &seqp[i];
56 }
57 seqp[CCID2_SEQBUF_LEN - 1].ccid2s_next = seqp;
58 seqp->ccid2s_prev = &seqp[CCID2_SEQBUF_LEN - 1];
59
60 /* This is the first allocation. Initiate the head and tail. */
61 if (hc->tx_seqbufc == 0)
62 hc->tx_seqh = hc->tx_seqt = seqp;
63 else {
64 /* link the existing list with the one we just created */
65 hc->tx_seqh->ccid2s_next = seqp;
66 seqp->ccid2s_prev = hc->tx_seqh;
67
68 hc->tx_seqt->ccid2s_prev = &seqp[CCID2_SEQBUF_LEN - 1];
69 seqp[CCID2_SEQBUF_LEN - 1].ccid2s_next = hc->tx_seqt;
70 }
71
72 /* store the original pointer to the buffer so we can free it */
73 hc->tx_seqbuf[hc->tx_seqbufc] = seqp;
74 hc->tx_seqbufc++;
75
76 return 0;
77}
78
79static int ccid2_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
80{
81 if (ccid2_cwnd_network_limited(ccid2_hc_tx_sk(sk)))
82 return CCID_PACKET_WILL_DEQUEUE_LATER;
83 return CCID_PACKET_SEND_AT_ONCE;
84}
85
86static void ccid2_change_l_ack_ratio(struct sock *sk, u32 val)
87{
88 u32 max_ratio = DIV_ROUND_UP(ccid2_hc_tx_sk(sk)->tx_cwnd, 2);
89
90 /*
91 * Ensure that Ack Ratio does not exceed ceil(cwnd/2), which is (2) from
92 * RFC 4341, 6.1.2. We ignore the statement that Ack Ratio 2 is always
93 * acceptable since this causes starvation/deadlock whenever cwnd < 2.
94 * The same problem arises when Ack Ratio is 0 (ie. Ack Ratio disabled).
95 */
96 if (val == 0 || val > max_ratio) {
97 DCCP_WARN("Limiting Ack Ratio (%u) to %u\n", val, max_ratio);
98 val = max_ratio;
99 }
100 dccp_feat_signal_nn_change(sk, DCCPF_ACK_RATIO,
101 min_t(u32, val, DCCPF_ACK_RATIO_MAX));
102}
103
104static void ccid2_check_l_ack_ratio(struct sock *sk)
105{
106 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
107
108 /*
109 * After a loss, idle period, application limited period, or RTO we
110 * need to check that the ack ratio is still less than the congestion
111 * window. Otherwise, we will send an entire congestion window of
112 * packets and got no response because we haven't sent ack ratio
113 * packets yet.
114 * If the ack ratio does need to be reduced, we reduce it to half of
115 * the congestion window (or 1 if that's zero) instead of to the
116 * congestion window. This prevents problems if one ack is lost.
117 */
118 if (dccp_feat_nn_get(sk, DCCPF_ACK_RATIO) > hc->tx_cwnd)
119 ccid2_change_l_ack_ratio(sk, hc->tx_cwnd/2 ? : 1U);
120}
121
122static void ccid2_change_l_seq_window(struct sock *sk, u64 val)
123{
124 dccp_feat_signal_nn_change(sk, DCCPF_SEQUENCE_WINDOW,
125 clamp_val(val, DCCPF_SEQ_WMIN,
126 DCCPF_SEQ_WMAX));
127}
128
129static void dccp_tasklet_schedule(struct sock *sk)
130{
131 struct tasklet_struct *t = &dccp_sk(sk)->dccps_xmitlet;
132
133 if (!test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) {
134 sock_hold(sk);
135 __tasklet_schedule(t);
136 }
137}
138
139static void ccid2_hc_tx_rto_expire(struct timer_list *t)
140{
141 struct ccid2_hc_tx_sock *hc = from_timer(hc, t, tx_rtotimer);
142 struct sock *sk = hc->sk;
143 const bool sender_was_blocked = ccid2_cwnd_network_limited(hc);
144
145 bh_lock_sock(sk);
146 if (sock_owned_by_user(sk)) {
147 sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + HZ / 5);
148 goto out;
149 }
150
151 ccid2_pr_debug("RTO_EXPIRE\n");
152
153 if (sk->sk_state == DCCP_CLOSED)
154 goto out;
155
156 /* back-off timer */
157 hc->tx_rto <<= 1;
158 if (hc->tx_rto > DCCP_RTO_MAX)
159 hc->tx_rto = DCCP_RTO_MAX;
160
161 /* adjust pipe, cwnd etc */
162 hc->tx_ssthresh = hc->tx_cwnd / 2;
163 if (hc->tx_ssthresh < 2)
164 hc->tx_ssthresh = 2;
165 hc->tx_cwnd = 1;
166 hc->tx_pipe = 0;
167
168 /* clear state about stuff we sent */
169 hc->tx_seqt = hc->tx_seqh;
170 hc->tx_packets_acked = 0;
171
172 /* clear ack ratio state. */
173 hc->tx_rpseq = 0;
174 hc->tx_rpdupack = -1;
175 ccid2_change_l_ack_ratio(sk, 1);
176
177 /* if we were blocked before, we may now send cwnd=1 packet */
178 if (sender_was_blocked)
179 dccp_tasklet_schedule(sk);
180 /* restart backed-off timer */
181 sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
182out:
183 bh_unlock_sock(sk);
184 sock_put(sk);
185}
186
187/*
188 * Congestion window validation (RFC 2861).
189 */
190static bool ccid2_do_cwv = true;
191module_param(ccid2_do_cwv, bool, 0644);
192MODULE_PARM_DESC(ccid2_do_cwv, "Perform RFC2861 Congestion Window Validation");
193
194/**
195 * ccid2_update_used_window - Track how much of cwnd is actually used
196 * This is done in addition to CWV. The sender needs to have an idea of how many
197 * packets may be in flight, to set the local Sequence Window value accordingly
198 * (RFC 4340, 7.5.2). The CWV mechanism is exploited to keep track of the
199 * maximum-used window. We use an EWMA low-pass filter to filter out noise.
200 */
201static void ccid2_update_used_window(struct ccid2_hc_tx_sock *hc, u32 new_wnd)
202{
203 hc->tx_expected_wnd = (3 * hc->tx_expected_wnd + new_wnd) / 4;
204}
205
206/* This borrows the code of tcp_cwnd_application_limited() */
207static void ccid2_cwnd_application_limited(struct sock *sk, const u32 now)
208{
209 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
210 /* don't reduce cwnd below the initial window (IW) */
211 u32 init_win = rfc3390_bytes_to_packets(dccp_sk(sk)->dccps_mss_cache),
212 win_used = max(hc->tx_cwnd_used, init_win);
213
214 if (win_used < hc->tx_cwnd) {
215 hc->tx_ssthresh = max(hc->tx_ssthresh,
216 (hc->tx_cwnd >> 1) + (hc->tx_cwnd >> 2));
217 hc->tx_cwnd = (hc->tx_cwnd + win_used) >> 1;
218 }
219 hc->tx_cwnd_used = 0;
220 hc->tx_cwnd_stamp = now;
221
222 ccid2_check_l_ack_ratio(sk);
223}
224
225/* This borrows the code of tcp_cwnd_restart() */
226static void ccid2_cwnd_restart(struct sock *sk, const u32 now)
227{
228 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
229 u32 cwnd = hc->tx_cwnd, restart_cwnd,
230 iwnd = rfc3390_bytes_to_packets(dccp_sk(sk)->dccps_mss_cache);
231
232 hc->tx_ssthresh = max(hc->tx_ssthresh, (cwnd >> 1) + (cwnd >> 2));
233
234 /* don't reduce cwnd below the initial window (IW) */
235 restart_cwnd = min(cwnd, iwnd);
236 cwnd >>= (now - hc->tx_lsndtime) / hc->tx_rto;
237 hc->tx_cwnd = max(cwnd, restart_cwnd);
238
239 hc->tx_cwnd_stamp = now;
240 hc->tx_cwnd_used = 0;
241
242 ccid2_check_l_ack_ratio(sk);
243}
244
245static void ccid2_hc_tx_packet_sent(struct sock *sk, unsigned int len)
246{
247 struct dccp_sock *dp = dccp_sk(sk);
248 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
249 const u32 now = ccid2_jiffies32;
250 struct ccid2_seq *next;
251
252 /* slow-start after idle periods (RFC 2581, RFC 2861) */
253 if (ccid2_do_cwv && !hc->tx_pipe &&
254 (s32)(now - hc->tx_lsndtime) >= hc->tx_rto)
255 ccid2_cwnd_restart(sk, now);
256
257 hc->tx_lsndtime = now;
258 hc->tx_pipe += 1;
259
260 /* see whether cwnd was fully used (RFC 2861), update expected window */
261 if (ccid2_cwnd_network_limited(hc)) {
262 ccid2_update_used_window(hc, hc->tx_cwnd);
263 hc->tx_cwnd_used = 0;
264 hc->tx_cwnd_stamp = now;
265 } else {
266 if (hc->tx_pipe > hc->tx_cwnd_used)
267 hc->tx_cwnd_used = hc->tx_pipe;
268
269 ccid2_update_used_window(hc, hc->tx_cwnd_used);
270
271 if (ccid2_do_cwv && (s32)(now - hc->tx_cwnd_stamp) >= hc->tx_rto)
272 ccid2_cwnd_application_limited(sk, now);
273 }
274
275 hc->tx_seqh->ccid2s_seq = dp->dccps_gss;
276 hc->tx_seqh->ccid2s_acked = 0;
277 hc->tx_seqh->ccid2s_sent = now;
278
279 next = hc->tx_seqh->ccid2s_next;
280 /* check if we need to alloc more space */
281 if (next == hc->tx_seqt) {
282 if (ccid2_hc_tx_alloc_seq(hc)) {
283 DCCP_CRIT("packet history - out of memory!");
284 /* FIXME: find a more graceful way to bail out */
285 return;
286 }
287 next = hc->tx_seqh->ccid2s_next;
288 BUG_ON(next == hc->tx_seqt);
289 }
290 hc->tx_seqh = next;
291
292 ccid2_pr_debug("cwnd=%d pipe=%d\n", hc->tx_cwnd, hc->tx_pipe);
293
294 /*
295 * FIXME: The code below is broken and the variables have been removed
296 * from the socket struct. The `ackloss' variable was always set to 0,
297 * and with arsent there are several problems:
298 * (i) it doesn't just count the number of Acks, but all sent packets;
299 * (ii) it is expressed in # of packets, not # of windows, so the
300 * comparison below uses the wrong formula: Appendix A of RFC 4341
301 * comes up with the number K = cwnd / (R^2 - R) of consecutive windows
302 * of data with no lost or marked Ack packets. If arsent were the # of
303 * consecutive Acks received without loss, then Ack Ratio needs to be
304 * decreased by 1 when
305 * arsent >= K * cwnd / R = cwnd^2 / (R^3 - R^2)
306 * where cwnd / R is the number of Acks received per window of data
307 * (cf. RFC 4341, App. A). The problems are that
308 * - arsent counts other packets as well;
309 * - the comparison uses a formula different from RFC 4341;
310 * - computing a cubic/quadratic equation each time is too complicated.
311 * Hence a different algorithm is needed.
312 */
313#if 0
314 /* Ack Ratio. Need to maintain a concept of how many windows we sent */
315 hc->tx_arsent++;
316 /* We had an ack loss in this window... */
317 if (hc->tx_ackloss) {
318 if (hc->tx_arsent >= hc->tx_cwnd) {
319 hc->tx_arsent = 0;
320 hc->tx_ackloss = 0;
321 }
322 } else {
323 /* No acks lost up to now... */
324 /* decrease ack ratio if enough packets were sent */
325 if (dp->dccps_l_ack_ratio > 1) {
326 /* XXX don't calculate denominator each time */
327 int denom = dp->dccps_l_ack_ratio * dp->dccps_l_ack_ratio -
328 dp->dccps_l_ack_ratio;
329
330 denom = hc->tx_cwnd * hc->tx_cwnd / denom;
331
332 if (hc->tx_arsent >= denom) {
333 ccid2_change_l_ack_ratio(sk, dp->dccps_l_ack_ratio - 1);
334 hc->tx_arsent = 0;
335 }
336 } else {
337 /* we can't increase ack ratio further [1] */
338 hc->tx_arsent = 0; /* or maybe set it to cwnd*/
339 }
340 }
341#endif
342
343 sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
344
345#ifdef CONFIG_IP_DCCP_CCID2_DEBUG
346 do {
347 struct ccid2_seq *seqp = hc->tx_seqt;
348
349 while (seqp != hc->tx_seqh) {
350 ccid2_pr_debug("out seq=%llu acked=%d time=%u\n",
351 (unsigned long long)seqp->ccid2s_seq,
352 seqp->ccid2s_acked, seqp->ccid2s_sent);
353 seqp = seqp->ccid2s_next;
354 }
355 } while (0);
356 ccid2_pr_debug("=========\n");
357#endif
358}
359
360/**
361 * ccid2_rtt_estimator - Sample RTT and compute RTO using RFC2988 algorithm
362 * This code is almost identical with TCP's tcp_rtt_estimator(), since
363 * - it has a higher sampling frequency (recommended by RFC 1323),
364 * - the RTO does not collapse into RTT due to RTTVAR going towards zero,
365 * - it is simple (cf. more complex proposals such as Eifel timer or research
366 * which suggests that the gain should be set according to window size),
367 * - in tests it was found to work well with CCID2 [gerrit].
368 */
369static void ccid2_rtt_estimator(struct sock *sk, const long mrtt)
370{
371 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
372 long m = mrtt ? : 1;
373
374 if (hc->tx_srtt == 0) {
375 /* First measurement m */
376 hc->tx_srtt = m << 3;
377 hc->tx_mdev = m << 1;
378
379 hc->tx_mdev_max = max(hc->tx_mdev, tcp_rto_min(sk));
380 hc->tx_rttvar = hc->tx_mdev_max;
381
382 hc->tx_rtt_seq = dccp_sk(sk)->dccps_gss;
383 } else {
384 /* Update scaled SRTT as SRTT += 1/8 * (m - SRTT) */
385 m -= (hc->tx_srtt >> 3);
386 hc->tx_srtt += m;
387
388 /* Similarly, update scaled mdev with regard to |m| */
389 if (m < 0) {
390 m = -m;
391 m -= (hc->tx_mdev >> 2);
392 /*
393 * This neutralises RTO increase when RTT < SRTT - mdev
394 * (see P. Sarolahti, A. Kuznetsov,"Congestion Control
395 * in Linux TCP", USENIX 2002, pp. 49-62).
396 */
397 if (m > 0)
398 m >>= 3;
399 } else {
400 m -= (hc->tx_mdev >> 2);
401 }
402 hc->tx_mdev += m;
403
404 if (hc->tx_mdev > hc->tx_mdev_max) {
405 hc->tx_mdev_max = hc->tx_mdev;
406 if (hc->tx_mdev_max > hc->tx_rttvar)
407 hc->tx_rttvar = hc->tx_mdev_max;
408 }
409
410 /*
411 * Decay RTTVAR at most once per flight, exploiting that
412 * 1) pipe <= cwnd <= Sequence_Window = W (RFC 4340, 7.5.2)
413 * 2) AWL = GSS-W+1 <= GAR <= GSS (RFC 4340, 7.5.1)
414 * GAR is a useful bound for FlightSize = pipe.
415 * AWL is probably too low here, as it over-estimates pipe.
416 */
417 if (after48(dccp_sk(sk)->dccps_gar, hc->tx_rtt_seq)) {
418 if (hc->tx_mdev_max < hc->tx_rttvar)
419 hc->tx_rttvar -= (hc->tx_rttvar -
420 hc->tx_mdev_max) >> 2;
421 hc->tx_rtt_seq = dccp_sk(sk)->dccps_gss;
422 hc->tx_mdev_max = tcp_rto_min(sk);
423 }
424 }
425
426 /*
427 * Set RTO from SRTT and RTTVAR
428 * As in TCP, 4 * RTTVAR >= TCP_RTO_MIN, giving a minimum RTO of 200 ms.
429 * This agrees with RFC 4341, 5:
430 * "Because DCCP does not retransmit data, DCCP does not require
431 * TCP's recommended minimum timeout of one second".
432 */
433 hc->tx_rto = (hc->tx_srtt >> 3) + hc->tx_rttvar;
434
435 if (hc->tx_rto > DCCP_RTO_MAX)
436 hc->tx_rto = DCCP_RTO_MAX;
437}
438
439static void ccid2_new_ack(struct sock *sk, struct ccid2_seq *seqp,
440 unsigned int *maxincr)
441{
442 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
443 struct dccp_sock *dp = dccp_sk(sk);
444 int r_seq_used = hc->tx_cwnd / dp->dccps_l_ack_ratio;
445
446 if (hc->tx_cwnd < dp->dccps_l_seq_win &&
447 r_seq_used < dp->dccps_r_seq_win) {
448 if (hc->tx_cwnd < hc->tx_ssthresh) {
449 if (*maxincr > 0 && ++hc->tx_packets_acked >= 2) {
450 hc->tx_cwnd += 1;
451 *maxincr -= 1;
452 hc->tx_packets_acked = 0;
453 }
454 } else if (++hc->tx_packets_acked >= hc->tx_cwnd) {
455 hc->tx_cwnd += 1;
456 hc->tx_packets_acked = 0;
457 }
458 }
459
460 /*
461 * Adjust the local sequence window and the ack ratio to allow about
462 * 5 times the number of packets in the network (RFC 4340 7.5.2)
463 */
464 if (r_seq_used * CCID2_WIN_CHANGE_FACTOR >= dp->dccps_r_seq_win)
465 ccid2_change_l_ack_ratio(sk, dp->dccps_l_ack_ratio * 2);
466 else if (r_seq_used * CCID2_WIN_CHANGE_FACTOR < dp->dccps_r_seq_win/2)
467 ccid2_change_l_ack_ratio(sk, dp->dccps_l_ack_ratio / 2 ? : 1U);
468
469 if (hc->tx_cwnd * CCID2_WIN_CHANGE_FACTOR >= dp->dccps_l_seq_win)
470 ccid2_change_l_seq_window(sk, dp->dccps_l_seq_win * 2);
471 else if (hc->tx_cwnd * CCID2_WIN_CHANGE_FACTOR < dp->dccps_l_seq_win/2)
472 ccid2_change_l_seq_window(sk, dp->dccps_l_seq_win / 2);
473
474 /*
475 * FIXME: RTT is sampled several times per acknowledgment (for each
476 * entry in the Ack Vector), instead of once per Ack (as in TCP SACK).
477 * This causes the RTT to be over-estimated, since the older entries
478 * in the Ack Vector have earlier sending times.
479 * The cleanest solution is to not use the ccid2s_sent field at all
480 * and instead use DCCP timestamps: requires changes in other places.
481 */
482 ccid2_rtt_estimator(sk, ccid2_jiffies32 - seqp->ccid2s_sent);
483}
484
485static void ccid2_congestion_event(struct sock *sk, struct ccid2_seq *seqp)
486{
487 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
488
489 if ((s32)(seqp->ccid2s_sent - hc->tx_last_cong) < 0) {
490 ccid2_pr_debug("Multiple losses in an RTT---treating as one\n");
491 return;
492 }
493
494 hc->tx_last_cong = ccid2_jiffies32;
495
496 hc->tx_cwnd = hc->tx_cwnd / 2 ? : 1U;
497 hc->tx_ssthresh = max(hc->tx_cwnd, 2U);
498
499 ccid2_check_l_ack_ratio(sk);
500}
501
502static int ccid2_hc_tx_parse_options(struct sock *sk, u8 packet_type,
503 u8 option, u8 *optval, u8 optlen)
504{
505 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
506
507 switch (option) {
508 case DCCPO_ACK_VECTOR_0:
509 case DCCPO_ACK_VECTOR_1:
510 return dccp_ackvec_parsed_add(&hc->tx_av_chunks, optval, optlen,
511 option - DCCPO_ACK_VECTOR_0);
512 }
513 return 0;
514}
515
516static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
517{
518 struct dccp_sock *dp = dccp_sk(sk);
519 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
520 const bool sender_was_blocked = ccid2_cwnd_network_limited(hc);
521 struct dccp_ackvec_parsed *avp;
522 u64 ackno, seqno;
523 struct ccid2_seq *seqp;
524 int done = 0;
525 unsigned int maxincr = 0;
526
527 /* check reverse path congestion */
528 seqno = DCCP_SKB_CB(skb)->dccpd_seq;
529
530 /* XXX this whole "algorithm" is broken. Need to fix it to keep track
531 * of the seqnos of the dupacks so that rpseq and rpdupack are correct
532 * -sorbo.
533 */
534 /* need to bootstrap */
535 if (hc->tx_rpdupack == -1) {
536 hc->tx_rpdupack = 0;
537 hc->tx_rpseq = seqno;
538 } else {
539 /* check if packet is consecutive */
540 if (dccp_delta_seqno(hc->tx_rpseq, seqno) == 1)
541 hc->tx_rpseq = seqno;
542 /* it's a later packet */
543 else if (after48(seqno, hc->tx_rpseq)) {
544 hc->tx_rpdupack++;
545
546 /* check if we got enough dupacks */
547 if (hc->tx_rpdupack >= NUMDUPACK) {
548 hc->tx_rpdupack = -1; /* XXX lame */
549 hc->tx_rpseq = 0;
550#ifdef __CCID2_COPES_GRACEFULLY_WITH_ACK_CONGESTION_CONTROL__
551 /*
552 * FIXME: Ack Congestion Control is broken; in
553 * the current state instabilities occurred with
554 * Ack Ratios greater than 1; causing hang-ups
555 * and long RTO timeouts. This needs to be fixed
556 * before opening up dynamic changes. -- gerrit
557 */
558 ccid2_change_l_ack_ratio(sk, 2 * dp->dccps_l_ack_ratio);
559#endif
560 }
561 }
562 }
563
564 /* check forward path congestion */
565 if (dccp_packet_without_ack(skb))
566 return;
567
568 /* still didn't send out new data packets */
569 if (hc->tx_seqh == hc->tx_seqt)
570 goto done;
571
572 ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
573 if (after48(ackno, hc->tx_high_ack))
574 hc->tx_high_ack = ackno;
575
576 seqp = hc->tx_seqt;
577 while (before48(seqp->ccid2s_seq, ackno)) {
578 seqp = seqp->ccid2s_next;
579 if (seqp == hc->tx_seqh) {
580 seqp = hc->tx_seqh->ccid2s_prev;
581 break;
582 }
583 }
584
585 /*
586 * In slow-start, cwnd can increase up to a maximum of Ack Ratio/2
587 * packets per acknowledgement. Rounding up avoids that cwnd is not
588 * advanced when Ack Ratio is 1 and gives a slight edge otherwise.
589 */
590 if (hc->tx_cwnd < hc->tx_ssthresh)
591 maxincr = DIV_ROUND_UP(dp->dccps_l_ack_ratio, 2);
592
593 /* go through all ack vectors */
594 list_for_each_entry(avp, &hc->tx_av_chunks, node) {
595 /* go through this ack vector */
596 for (; avp->len--; avp->vec++) {
597 u64 ackno_end_rl = SUB48(ackno,
598 dccp_ackvec_runlen(avp->vec));
599
600 ccid2_pr_debug("ackvec %llu |%u,%u|\n",
601 (unsigned long long)ackno,
602 dccp_ackvec_state(avp->vec) >> 6,
603 dccp_ackvec_runlen(avp->vec));
604 /* if the seqno we are analyzing is larger than the
605 * current ackno, then move towards the tail of our
606 * seqnos.
607 */
608 while (after48(seqp->ccid2s_seq, ackno)) {
609 if (seqp == hc->tx_seqt) {
610 done = 1;
611 break;
612 }
613 seqp = seqp->ccid2s_prev;
614 }
615 if (done)
616 break;
617
618 /* check all seqnos in the range of the vector
619 * run length
620 */
621 while (between48(seqp->ccid2s_seq,ackno_end_rl,ackno)) {
622 const u8 state = dccp_ackvec_state(avp->vec);
623
624 /* new packet received or marked */
625 if (state != DCCPAV_NOT_RECEIVED &&
626 !seqp->ccid2s_acked) {
627 if (state == DCCPAV_ECN_MARKED)
628 ccid2_congestion_event(sk,
629 seqp);
630 else
631 ccid2_new_ack(sk, seqp,
632 &maxincr);
633
634 seqp->ccid2s_acked = 1;
635 ccid2_pr_debug("Got ack for %llu\n",
636 (unsigned long long)seqp->ccid2s_seq);
637 hc->tx_pipe--;
638 }
639 if (seqp == hc->tx_seqt) {
640 done = 1;
641 break;
642 }
643 seqp = seqp->ccid2s_prev;
644 }
645 if (done)
646 break;
647
648 ackno = SUB48(ackno_end_rl, 1);
649 }
650 if (done)
651 break;
652 }
653
654 /* The state about what is acked should be correct now
655 * Check for NUMDUPACK
656 */
657 seqp = hc->tx_seqt;
658 while (before48(seqp->ccid2s_seq, hc->tx_high_ack)) {
659 seqp = seqp->ccid2s_next;
660 if (seqp == hc->tx_seqh) {
661 seqp = hc->tx_seqh->ccid2s_prev;
662 break;
663 }
664 }
665 done = 0;
666 while (1) {
667 if (seqp->ccid2s_acked) {
668 done++;
669 if (done == NUMDUPACK)
670 break;
671 }
672 if (seqp == hc->tx_seqt)
673 break;
674 seqp = seqp->ccid2s_prev;
675 }
676
677 /* If there are at least 3 acknowledgements, anything unacknowledged
678 * below the last sequence number is considered lost
679 */
680 if (done == NUMDUPACK) {
681 struct ccid2_seq *last_acked = seqp;
682
683 /* check for lost packets */
684 while (1) {
685 if (!seqp->ccid2s_acked) {
686 ccid2_pr_debug("Packet lost: %llu\n",
687 (unsigned long long)seqp->ccid2s_seq);
688 /* XXX need to traverse from tail -> head in
689 * order to detect multiple congestion events in
690 * one ack vector.
691 */
692 ccid2_congestion_event(sk, seqp);
693 hc->tx_pipe--;
694 }
695 if (seqp == hc->tx_seqt)
696 break;
697 seqp = seqp->ccid2s_prev;
698 }
699
700 hc->tx_seqt = last_acked;
701 }
702
703 /* trim acked packets in tail */
704 while (hc->tx_seqt != hc->tx_seqh) {
705 if (!hc->tx_seqt->ccid2s_acked)
706 break;
707
708 hc->tx_seqt = hc->tx_seqt->ccid2s_next;
709 }
710
711 /* restart RTO timer if not all outstanding data has been acked */
712 if (hc->tx_pipe == 0)
713 sk_stop_timer(sk, &hc->tx_rtotimer);
714 else
715 sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
716done:
717 /* check if incoming Acks allow pending packets to be sent */
718 if (sender_was_blocked && !ccid2_cwnd_network_limited(hc))
719 dccp_tasklet_schedule(sk);
720 dccp_ackvec_parsed_cleanup(&hc->tx_av_chunks);
721}
722
723static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
724{
725 struct ccid2_hc_tx_sock *hc = ccid_priv(ccid);
726 struct dccp_sock *dp = dccp_sk(sk);
727 u32 max_ratio;
728
729 /* RFC 4341, 5: initialise ssthresh to arbitrarily high (max) value */
730 hc->tx_ssthresh = ~0U;
731
732 /* Use larger initial windows (RFC 4341, section 5). */
733 hc->tx_cwnd = rfc3390_bytes_to_packets(dp->dccps_mss_cache);
734 hc->tx_expected_wnd = hc->tx_cwnd;
735
736 /* Make sure that Ack Ratio is enabled and within bounds. */
737 max_ratio = DIV_ROUND_UP(hc->tx_cwnd, 2);
738 if (dp->dccps_l_ack_ratio == 0 || dp->dccps_l_ack_ratio > max_ratio)
739 dp->dccps_l_ack_ratio = max_ratio;
740
741 /* XXX init ~ to window size... */
742 if (ccid2_hc_tx_alloc_seq(hc))
743 return -ENOMEM;
744
745 hc->tx_rto = DCCP_TIMEOUT_INIT;
746 hc->tx_rpdupack = -1;
747 hc->tx_last_cong = hc->tx_lsndtime = hc->tx_cwnd_stamp = ccid2_jiffies32;
748 hc->tx_cwnd_used = 0;
749 hc->sk = sk;
750 timer_setup(&hc->tx_rtotimer, ccid2_hc_tx_rto_expire, 0);
751 INIT_LIST_HEAD(&hc->tx_av_chunks);
752 return 0;
753}
754
755static void ccid2_hc_tx_exit(struct sock *sk)
756{
757 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
758 int i;
759
760 sk_stop_timer(sk, &hc->tx_rtotimer);
761
762 for (i = 0; i < hc->tx_seqbufc; i++)
763 kfree(hc->tx_seqbuf[i]);
764 hc->tx_seqbufc = 0;
765 dccp_ackvec_parsed_cleanup(&hc->tx_av_chunks);
766}
767
768static void ccid2_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
769{
770 struct ccid2_hc_rx_sock *hc = ccid2_hc_rx_sk(sk);
771
772 if (!dccp_data_packet(skb))
773 return;
774
775 if (++hc->rx_num_data_pkts >= dccp_sk(sk)->dccps_r_ack_ratio) {
776 dccp_send_ack(sk);
777 hc->rx_num_data_pkts = 0;
778 }
779}
780
781struct ccid_operations ccid2_ops = {
782 .ccid_id = DCCPC_CCID2,
783 .ccid_name = "TCP-like",
784 .ccid_hc_tx_obj_size = sizeof(struct ccid2_hc_tx_sock),
785 .ccid_hc_tx_init = ccid2_hc_tx_init,
786 .ccid_hc_tx_exit = ccid2_hc_tx_exit,
787 .ccid_hc_tx_send_packet = ccid2_hc_tx_send_packet,
788 .ccid_hc_tx_packet_sent = ccid2_hc_tx_packet_sent,
789 .ccid_hc_tx_parse_options = ccid2_hc_tx_parse_options,
790 .ccid_hc_tx_packet_recv = ccid2_hc_tx_packet_recv,
791 .ccid_hc_rx_obj_size = sizeof(struct ccid2_hc_rx_sock),
792 .ccid_hc_rx_packet_recv = ccid2_hc_rx_packet_recv,
793};
794
795#ifdef CONFIG_IP_DCCP_CCID2_DEBUG
796module_param(ccid2_debug, bool, 0644);
797MODULE_PARM_DESC(ccid2_debug, "Enable CCID-2 debug messages");
798#endif