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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 ccid2_hc_tx_rto_expire(unsigned long data)
130{
131 struct sock *sk = (struct sock *)data;
132 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
133 const bool sender_was_blocked = ccid2_cwnd_network_limited(hc);
134
135 bh_lock_sock(sk);
136 if (sock_owned_by_user(sk)) {
137 sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + HZ / 5);
138 goto out;
139 }
140
141 ccid2_pr_debug("RTO_EXPIRE\n");
142
143 /* back-off timer */
144 hc->tx_rto <<= 1;
145 if (hc->tx_rto > DCCP_RTO_MAX)
146 hc->tx_rto = DCCP_RTO_MAX;
147
148 /* adjust pipe, cwnd etc */
149 hc->tx_ssthresh = hc->tx_cwnd / 2;
150 if (hc->tx_ssthresh < 2)
151 hc->tx_ssthresh = 2;
152 hc->tx_cwnd = 1;
153 hc->tx_pipe = 0;
154
155 /* clear state about stuff we sent */
156 hc->tx_seqt = hc->tx_seqh;
157 hc->tx_packets_acked = 0;
158
159 /* clear ack ratio state. */
160 hc->tx_rpseq = 0;
161 hc->tx_rpdupack = -1;
162 ccid2_change_l_ack_ratio(sk, 1);
163
164 /* if we were blocked before, we may now send cwnd=1 packet */
165 if (sender_was_blocked)
166 tasklet_schedule(&dccp_sk(sk)->dccps_xmitlet);
167 /* restart backed-off timer */
168 sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
169out:
170 bh_unlock_sock(sk);
171 sock_put(sk);
172}
173
174/*
175 * Congestion window validation (RFC 2861).
176 */
177static bool ccid2_do_cwv = true;
178module_param(ccid2_do_cwv, bool, 0644);
179MODULE_PARM_DESC(ccid2_do_cwv, "Perform RFC2861 Congestion Window Validation");
180
181/**
182 * ccid2_update_used_window - Track how much of cwnd is actually used
183 * This is done in addition to CWV. The sender needs to have an idea of how many
184 * packets may be in flight, to set the local Sequence Window value accordingly
185 * (RFC 4340, 7.5.2). The CWV mechanism is exploited to keep track of the
186 * maximum-used window. We use an EWMA low-pass filter to filter out noise.
187 */
188static void ccid2_update_used_window(struct ccid2_hc_tx_sock *hc, u32 new_wnd)
189{
190 hc->tx_expected_wnd = (3 * hc->tx_expected_wnd + new_wnd) / 4;
191}
192
193/* This borrows the code of tcp_cwnd_application_limited() */
194static void ccid2_cwnd_application_limited(struct sock *sk, const u32 now)
195{
196 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
197 /* don't reduce cwnd below the initial window (IW) */
198 u32 init_win = rfc3390_bytes_to_packets(dccp_sk(sk)->dccps_mss_cache),
199 win_used = max(hc->tx_cwnd_used, init_win);
200
201 if (win_used < hc->tx_cwnd) {
202 hc->tx_ssthresh = max(hc->tx_ssthresh,
203 (hc->tx_cwnd >> 1) + (hc->tx_cwnd >> 2));
204 hc->tx_cwnd = (hc->tx_cwnd + win_used) >> 1;
205 }
206 hc->tx_cwnd_used = 0;
207 hc->tx_cwnd_stamp = now;
208
209 ccid2_check_l_ack_ratio(sk);
210}
211
212/* This borrows the code of tcp_cwnd_restart() */
213static void ccid2_cwnd_restart(struct sock *sk, const u32 now)
214{
215 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
216 u32 cwnd = hc->tx_cwnd, restart_cwnd,
217 iwnd = rfc3390_bytes_to_packets(dccp_sk(sk)->dccps_mss_cache);
218
219 hc->tx_ssthresh = max(hc->tx_ssthresh, (cwnd >> 1) + (cwnd >> 2));
220
221 /* don't reduce cwnd below the initial window (IW) */
222 restart_cwnd = min(cwnd, iwnd);
223 cwnd >>= (now - hc->tx_lsndtime) / hc->tx_rto;
224 hc->tx_cwnd = max(cwnd, restart_cwnd);
225
226 hc->tx_cwnd_stamp = now;
227 hc->tx_cwnd_used = 0;
228
229 ccid2_check_l_ack_ratio(sk);
230}
231
232static void ccid2_hc_tx_packet_sent(struct sock *sk, unsigned int len)
233{
234 struct dccp_sock *dp = dccp_sk(sk);
235 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
236 const u32 now = ccid2_time_stamp;
237 struct ccid2_seq *next;
238
239 /* slow-start after idle periods (RFC 2581, RFC 2861) */
240 if (ccid2_do_cwv && !hc->tx_pipe &&
241 (s32)(now - hc->tx_lsndtime) >= hc->tx_rto)
242 ccid2_cwnd_restart(sk, now);
243
244 hc->tx_lsndtime = now;
245 hc->tx_pipe += 1;
246
247 /* see whether cwnd was fully used (RFC 2861), update expected window */
248 if (ccid2_cwnd_network_limited(hc)) {
249 ccid2_update_used_window(hc, hc->tx_cwnd);
250 hc->tx_cwnd_used = 0;
251 hc->tx_cwnd_stamp = now;
252 } else {
253 if (hc->tx_pipe > hc->tx_cwnd_used)
254 hc->tx_cwnd_used = hc->tx_pipe;
255
256 ccid2_update_used_window(hc, hc->tx_cwnd_used);
257
258 if (ccid2_do_cwv && (s32)(now - hc->tx_cwnd_stamp) >= hc->tx_rto)
259 ccid2_cwnd_application_limited(sk, now);
260 }
261
262 hc->tx_seqh->ccid2s_seq = dp->dccps_gss;
263 hc->tx_seqh->ccid2s_acked = 0;
264 hc->tx_seqh->ccid2s_sent = now;
265
266 next = hc->tx_seqh->ccid2s_next;
267 /* check if we need to alloc more space */
268 if (next == hc->tx_seqt) {
269 if (ccid2_hc_tx_alloc_seq(hc)) {
270 DCCP_CRIT("packet history - out of memory!");
271 /* FIXME: find a more graceful way to bail out */
272 return;
273 }
274 next = hc->tx_seqh->ccid2s_next;
275 BUG_ON(next == hc->tx_seqt);
276 }
277 hc->tx_seqh = next;
278
279 ccid2_pr_debug("cwnd=%d pipe=%d\n", hc->tx_cwnd, hc->tx_pipe);
280
281 /*
282 * FIXME: The code below is broken and the variables have been removed
283 * from the socket struct. The `ackloss' variable was always set to 0,
284 * and with arsent there are several problems:
285 * (i) it doesn't just count the number of Acks, but all sent packets;
286 * (ii) it is expressed in # of packets, not # of windows, so the
287 * comparison below uses the wrong formula: Appendix A of RFC 4341
288 * comes up with the number K = cwnd / (R^2 - R) of consecutive windows
289 * of data with no lost or marked Ack packets. If arsent were the # of
290 * consecutive Acks received without loss, then Ack Ratio needs to be
291 * decreased by 1 when
292 * arsent >= K * cwnd / R = cwnd^2 / (R^3 - R^2)
293 * where cwnd / R is the number of Acks received per window of data
294 * (cf. RFC 4341, App. A). The problems are that
295 * - arsent counts other packets as well;
296 * - the comparison uses a formula different from RFC 4341;
297 * - computing a cubic/quadratic equation each time is too complicated.
298 * Hence a different algorithm is needed.
299 */
300#if 0
301 /* Ack Ratio. Need to maintain a concept of how many windows we sent */
302 hc->tx_arsent++;
303 /* We had an ack loss in this window... */
304 if (hc->tx_ackloss) {
305 if (hc->tx_arsent >= hc->tx_cwnd) {
306 hc->tx_arsent = 0;
307 hc->tx_ackloss = 0;
308 }
309 } else {
310 /* No acks lost up to now... */
311 /* decrease ack ratio if enough packets were sent */
312 if (dp->dccps_l_ack_ratio > 1) {
313 /* XXX don't calculate denominator each time */
314 int denom = dp->dccps_l_ack_ratio * dp->dccps_l_ack_ratio -
315 dp->dccps_l_ack_ratio;
316
317 denom = hc->tx_cwnd * hc->tx_cwnd / denom;
318
319 if (hc->tx_arsent >= denom) {
320 ccid2_change_l_ack_ratio(sk, dp->dccps_l_ack_ratio - 1);
321 hc->tx_arsent = 0;
322 }
323 } else {
324 /* we can't increase ack ratio further [1] */
325 hc->tx_arsent = 0; /* or maybe set it to cwnd*/
326 }
327 }
328#endif
329
330 sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
331
332#ifdef CONFIG_IP_DCCP_CCID2_DEBUG
333 do {
334 struct ccid2_seq *seqp = hc->tx_seqt;
335
336 while (seqp != hc->tx_seqh) {
337 ccid2_pr_debug("out seq=%llu acked=%d time=%u\n",
338 (unsigned long long)seqp->ccid2s_seq,
339 seqp->ccid2s_acked, seqp->ccid2s_sent);
340 seqp = seqp->ccid2s_next;
341 }
342 } while (0);
343 ccid2_pr_debug("=========\n");
344#endif
345}
346
347/**
348 * ccid2_rtt_estimator - Sample RTT and compute RTO using RFC2988 algorithm
349 * This code is almost identical with TCP's tcp_rtt_estimator(), since
350 * - it has a higher sampling frequency (recommended by RFC 1323),
351 * - the RTO does not collapse into RTT due to RTTVAR going towards zero,
352 * - it is simple (cf. more complex proposals such as Eifel timer or research
353 * which suggests that the gain should be set according to window size),
354 * - in tests it was found to work well with CCID2 [gerrit].
355 */
356static void ccid2_rtt_estimator(struct sock *sk, const long mrtt)
357{
358 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
359 long m = mrtt ? : 1;
360
361 if (hc->tx_srtt == 0) {
362 /* First measurement m */
363 hc->tx_srtt = m << 3;
364 hc->tx_mdev = m << 1;
365
366 hc->tx_mdev_max = max(hc->tx_mdev, tcp_rto_min(sk));
367 hc->tx_rttvar = hc->tx_mdev_max;
368
369 hc->tx_rtt_seq = dccp_sk(sk)->dccps_gss;
370 } else {
371 /* Update scaled SRTT as SRTT += 1/8 * (m - SRTT) */
372 m -= (hc->tx_srtt >> 3);
373 hc->tx_srtt += m;
374
375 /* Similarly, update scaled mdev with regard to |m| */
376 if (m < 0) {
377 m = -m;
378 m -= (hc->tx_mdev >> 2);
379 /*
380 * This neutralises RTO increase when RTT < SRTT - mdev
381 * (see P. Sarolahti, A. Kuznetsov,"Congestion Control
382 * in Linux TCP", USENIX 2002, pp. 49-62).
383 */
384 if (m > 0)
385 m >>= 3;
386 } else {
387 m -= (hc->tx_mdev >> 2);
388 }
389 hc->tx_mdev += m;
390
391 if (hc->tx_mdev > hc->tx_mdev_max) {
392 hc->tx_mdev_max = hc->tx_mdev;
393 if (hc->tx_mdev_max > hc->tx_rttvar)
394 hc->tx_rttvar = hc->tx_mdev_max;
395 }
396
397 /*
398 * Decay RTTVAR at most once per flight, exploiting that
399 * 1) pipe <= cwnd <= Sequence_Window = W (RFC 4340, 7.5.2)
400 * 2) AWL = GSS-W+1 <= GAR <= GSS (RFC 4340, 7.5.1)
401 * GAR is a useful bound for FlightSize = pipe.
402 * AWL is probably too low here, as it over-estimates pipe.
403 */
404 if (after48(dccp_sk(sk)->dccps_gar, hc->tx_rtt_seq)) {
405 if (hc->tx_mdev_max < hc->tx_rttvar)
406 hc->tx_rttvar -= (hc->tx_rttvar -
407 hc->tx_mdev_max) >> 2;
408 hc->tx_rtt_seq = dccp_sk(sk)->dccps_gss;
409 hc->tx_mdev_max = tcp_rto_min(sk);
410 }
411 }
412
413 /*
414 * Set RTO from SRTT and RTTVAR
415 * As in TCP, 4 * RTTVAR >= TCP_RTO_MIN, giving a minimum RTO of 200 ms.
416 * This agrees with RFC 4341, 5:
417 * "Because DCCP does not retransmit data, DCCP does not require
418 * TCP's recommended minimum timeout of one second".
419 */
420 hc->tx_rto = (hc->tx_srtt >> 3) + hc->tx_rttvar;
421
422 if (hc->tx_rto > DCCP_RTO_MAX)
423 hc->tx_rto = DCCP_RTO_MAX;
424}
425
426static void ccid2_new_ack(struct sock *sk, struct ccid2_seq *seqp,
427 unsigned int *maxincr)
428{
429 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
430 struct dccp_sock *dp = dccp_sk(sk);
431 int r_seq_used = hc->tx_cwnd / dp->dccps_l_ack_ratio;
432
433 if (hc->tx_cwnd < dp->dccps_l_seq_win &&
434 r_seq_used < dp->dccps_r_seq_win) {
435 if (hc->tx_cwnd < hc->tx_ssthresh) {
436 if (*maxincr > 0 && ++hc->tx_packets_acked >= 2) {
437 hc->tx_cwnd += 1;
438 *maxincr -= 1;
439 hc->tx_packets_acked = 0;
440 }
441 } else if (++hc->tx_packets_acked >= hc->tx_cwnd) {
442 hc->tx_cwnd += 1;
443 hc->tx_packets_acked = 0;
444 }
445 }
446
447 /*
448 * Adjust the local sequence window and the ack ratio to allow about
449 * 5 times the number of packets in the network (RFC 4340 7.5.2)
450 */
451 if (r_seq_used * CCID2_WIN_CHANGE_FACTOR >= dp->dccps_r_seq_win)
452 ccid2_change_l_ack_ratio(sk, dp->dccps_l_ack_ratio * 2);
453 else if (r_seq_used * CCID2_WIN_CHANGE_FACTOR < dp->dccps_r_seq_win/2)
454 ccid2_change_l_ack_ratio(sk, dp->dccps_l_ack_ratio / 2 ? : 1U);
455
456 if (hc->tx_cwnd * CCID2_WIN_CHANGE_FACTOR >= dp->dccps_l_seq_win)
457 ccid2_change_l_seq_window(sk, dp->dccps_l_seq_win * 2);
458 else if (hc->tx_cwnd * CCID2_WIN_CHANGE_FACTOR < dp->dccps_l_seq_win/2)
459 ccid2_change_l_seq_window(sk, dp->dccps_l_seq_win / 2);
460
461 /*
462 * FIXME: RTT is sampled several times per acknowledgment (for each
463 * entry in the Ack Vector), instead of once per Ack (as in TCP SACK).
464 * This causes the RTT to be over-estimated, since the older entries
465 * in the Ack Vector have earlier sending times.
466 * The cleanest solution is to not use the ccid2s_sent field at all
467 * and instead use DCCP timestamps: requires changes in other places.
468 */
469 ccid2_rtt_estimator(sk, ccid2_time_stamp - seqp->ccid2s_sent);
470}
471
472static void ccid2_congestion_event(struct sock *sk, struct ccid2_seq *seqp)
473{
474 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
475
476 if ((s32)(seqp->ccid2s_sent - hc->tx_last_cong) < 0) {
477 ccid2_pr_debug("Multiple losses in an RTT---treating as one\n");
478 return;
479 }
480
481 hc->tx_last_cong = ccid2_time_stamp;
482
483 hc->tx_cwnd = hc->tx_cwnd / 2 ? : 1U;
484 hc->tx_ssthresh = max(hc->tx_cwnd, 2U);
485
486 ccid2_check_l_ack_ratio(sk);
487}
488
489static int ccid2_hc_tx_parse_options(struct sock *sk, u8 packet_type,
490 u8 option, u8 *optval, u8 optlen)
491{
492 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
493
494 switch (option) {
495 case DCCPO_ACK_VECTOR_0:
496 case DCCPO_ACK_VECTOR_1:
497 return dccp_ackvec_parsed_add(&hc->tx_av_chunks, optval, optlen,
498 option - DCCPO_ACK_VECTOR_0);
499 }
500 return 0;
501}
502
503static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
504{
505 struct dccp_sock *dp = dccp_sk(sk);
506 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
507 const bool sender_was_blocked = ccid2_cwnd_network_limited(hc);
508 struct dccp_ackvec_parsed *avp;
509 u64 ackno, seqno;
510 struct ccid2_seq *seqp;
511 int done = 0;
512 unsigned int maxincr = 0;
513
514 /* check reverse path congestion */
515 seqno = DCCP_SKB_CB(skb)->dccpd_seq;
516
517 /* XXX this whole "algorithm" is broken. Need to fix it to keep track
518 * of the seqnos of the dupacks so that rpseq and rpdupack are correct
519 * -sorbo.
520 */
521 /* need to bootstrap */
522 if (hc->tx_rpdupack == -1) {
523 hc->tx_rpdupack = 0;
524 hc->tx_rpseq = seqno;
525 } else {
526 /* check if packet is consecutive */
527 if (dccp_delta_seqno(hc->tx_rpseq, seqno) == 1)
528 hc->tx_rpseq = seqno;
529 /* it's a later packet */
530 else if (after48(seqno, hc->tx_rpseq)) {
531 hc->tx_rpdupack++;
532
533 /* check if we got enough dupacks */
534 if (hc->tx_rpdupack >= NUMDUPACK) {
535 hc->tx_rpdupack = -1; /* XXX lame */
536 hc->tx_rpseq = 0;
537#ifdef __CCID2_COPES_GRACEFULLY_WITH_ACK_CONGESTION_CONTROL__
538 /*
539 * FIXME: Ack Congestion Control is broken; in
540 * the current state instabilities occurred with
541 * Ack Ratios greater than 1; causing hang-ups
542 * and long RTO timeouts. This needs to be fixed
543 * before opening up dynamic changes. -- gerrit
544 */
545 ccid2_change_l_ack_ratio(sk, 2 * dp->dccps_l_ack_ratio);
546#endif
547 }
548 }
549 }
550
551 /* check forward path congestion */
552 if (dccp_packet_without_ack(skb))
553 return;
554
555 /* still didn't send out new data packets */
556 if (hc->tx_seqh == hc->tx_seqt)
557 goto done;
558
559 ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
560 if (after48(ackno, hc->tx_high_ack))
561 hc->tx_high_ack = ackno;
562
563 seqp = hc->tx_seqt;
564 while (before48(seqp->ccid2s_seq, ackno)) {
565 seqp = seqp->ccid2s_next;
566 if (seqp == hc->tx_seqh) {
567 seqp = hc->tx_seqh->ccid2s_prev;
568 break;
569 }
570 }
571
572 /*
573 * In slow-start, cwnd can increase up to a maximum of Ack Ratio/2
574 * packets per acknowledgement. Rounding up avoids that cwnd is not
575 * advanced when Ack Ratio is 1 and gives a slight edge otherwise.
576 */
577 if (hc->tx_cwnd < hc->tx_ssthresh)
578 maxincr = DIV_ROUND_UP(dp->dccps_l_ack_ratio, 2);
579
580 /* go through all ack vectors */
581 list_for_each_entry(avp, &hc->tx_av_chunks, node) {
582 /* go through this ack vector */
583 for (; avp->len--; avp->vec++) {
584 u64 ackno_end_rl = SUB48(ackno,
585 dccp_ackvec_runlen(avp->vec));
586
587 ccid2_pr_debug("ackvec %llu |%u,%u|\n",
588 (unsigned long long)ackno,
589 dccp_ackvec_state(avp->vec) >> 6,
590 dccp_ackvec_runlen(avp->vec));
591 /* if the seqno we are analyzing is larger than the
592 * current ackno, then move towards the tail of our
593 * seqnos.
594 */
595 while (after48(seqp->ccid2s_seq, ackno)) {
596 if (seqp == hc->tx_seqt) {
597 done = 1;
598 break;
599 }
600 seqp = seqp->ccid2s_prev;
601 }
602 if (done)
603 break;
604
605 /* check all seqnos in the range of the vector
606 * run length
607 */
608 while (between48(seqp->ccid2s_seq,ackno_end_rl,ackno)) {
609 const u8 state = dccp_ackvec_state(avp->vec);
610
611 /* new packet received or marked */
612 if (state != DCCPAV_NOT_RECEIVED &&
613 !seqp->ccid2s_acked) {
614 if (state == DCCPAV_ECN_MARKED)
615 ccid2_congestion_event(sk,
616 seqp);
617 else
618 ccid2_new_ack(sk, seqp,
619 &maxincr);
620
621 seqp->ccid2s_acked = 1;
622 ccid2_pr_debug("Got ack for %llu\n",
623 (unsigned long long)seqp->ccid2s_seq);
624 hc->tx_pipe--;
625 }
626 if (seqp == hc->tx_seqt) {
627 done = 1;
628 break;
629 }
630 seqp = seqp->ccid2s_prev;
631 }
632 if (done)
633 break;
634
635 ackno = SUB48(ackno_end_rl, 1);
636 }
637 if (done)
638 break;
639 }
640
641 /* The state about what is acked should be correct now
642 * Check for NUMDUPACK
643 */
644 seqp = hc->tx_seqt;
645 while (before48(seqp->ccid2s_seq, hc->tx_high_ack)) {
646 seqp = seqp->ccid2s_next;
647 if (seqp == hc->tx_seqh) {
648 seqp = hc->tx_seqh->ccid2s_prev;
649 break;
650 }
651 }
652 done = 0;
653 while (1) {
654 if (seqp->ccid2s_acked) {
655 done++;
656 if (done == NUMDUPACK)
657 break;
658 }
659 if (seqp == hc->tx_seqt)
660 break;
661 seqp = seqp->ccid2s_prev;
662 }
663
664 /* If there are at least 3 acknowledgements, anything unacknowledged
665 * below the last sequence number is considered lost
666 */
667 if (done == NUMDUPACK) {
668 struct ccid2_seq *last_acked = seqp;
669
670 /* check for lost packets */
671 while (1) {
672 if (!seqp->ccid2s_acked) {
673 ccid2_pr_debug("Packet lost: %llu\n",
674 (unsigned long long)seqp->ccid2s_seq);
675 /* XXX need to traverse from tail -> head in
676 * order to detect multiple congestion events in
677 * one ack vector.
678 */
679 ccid2_congestion_event(sk, seqp);
680 hc->tx_pipe--;
681 }
682 if (seqp == hc->tx_seqt)
683 break;
684 seqp = seqp->ccid2s_prev;
685 }
686
687 hc->tx_seqt = last_acked;
688 }
689
690 /* trim acked packets in tail */
691 while (hc->tx_seqt != hc->tx_seqh) {
692 if (!hc->tx_seqt->ccid2s_acked)
693 break;
694
695 hc->tx_seqt = hc->tx_seqt->ccid2s_next;
696 }
697
698 /* restart RTO timer if not all outstanding data has been acked */
699 if (hc->tx_pipe == 0)
700 sk_stop_timer(sk, &hc->tx_rtotimer);
701 else
702 sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
703done:
704 /* check if incoming Acks allow pending packets to be sent */
705 if (sender_was_blocked && !ccid2_cwnd_network_limited(hc))
706 tasklet_schedule(&dccp_sk(sk)->dccps_xmitlet);
707 dccp_ackvec_parsed_cleanup(&hc->tx_av_chunks);
708}
709
710static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
711{
712 struct ccid2_hc_tx_sock *hc = ccid_priv(ccid);
713 struct dccp_sock *dp = dccp_sk(sk);
714 u32 max_ratio;
715
716 /* RFC 4341, 5: initialise ssthresh to arbitrarily high (max) value */
717 hc->tx_ssthresh = ~0U;
718
719 /* Use larger initial windows (RFC 4341, section 5). */
720 hc->tx_cwnd = rfc3390_bytes_to_packets(dp->dccps_mss_cache);
721 hc->tx_expected_wnd = hc->tx_cwnd;
722
723 /* Make sure that Ack Ratio is enabled and within bounds. */
724 max_ratio = DIV_ROUND_UP(hc->tx_cwnd, 2);
725 if (dp->dccps_l_ack_ratio == 0 || dp->dccps_l_ack_ratio > max_ratio)
726 dp->dccps_l_ack_ratio = max_ratio;
727
728 /* XXX init ~ to window size... */
729 if (ccid2_hc_tx_alloc_seq(hc))
730 return -ENOMEM;
731
732 hc->tx_rto = DCCP_TIMEOUT_INIT;
733 hc->tx_rpdupack = -1;
734 hc->tx_last_cong = hc->tx_lsndtime = hc->tx_cwnd_stamp = ccid2_time_stamp;
735 hc->tx_cwnd_used = 0;
736 setup_timer(&hc->tx_rtotimer, ccid2_hc_tx_rto_expire,
737 (unsigned long)sk);
738 INIT_LIST_HEAD(&hc->tx_av_chunks);
739 return 0;
740}
741
742static void ccid2_hc_tx_exit(struct sock *sk)
743{
744 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
745 int i;
746
747 sk_stop_timer(sk, &hc->tx_rtotimer);
748
749 for (i = 0; i < hc->tx_seqbufc; i++)
750 kfree(hc->tx_seqbuf[i]);
751 hc->tx_seqbufc = 0;
752}
753
754static void ccid2_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
755{
756 struct ccid2_hc_rx_sock *hc = ccid2_hc_rx_sk(sk);
757
758 if (!dccp_data_packet(skb))
759 return;
760
761 if (++hc->rx_num_data_pkts >= dccp_sk(sk)->dccps_r_ack_ratio) {
762 dccp_send_ack(sk);
763 hc->rx_num_data_pkts = 0;
764 }
765}
766
767struct ccid_operations ccid2_ops = {
768 .ccid_id = DCCPC_CCID2,
769 .ccid_name = "TCP-like",
770 .ccid_hc_tx_obj_size = sizeof(struct ccid2_hc_tx_sock),
771 .ccid_hc_tx_init = ccid2_hc_tx_init,
772 .ccid_hc_tx_exit = ccid2_hc_tx_exit,
773 .ccid_hc_tx_send_packet = ccid2_hc_tx_send_packet,
774 .ccid_hc_tx_packet_sent = ccid2_hc_tx_packet_sent,
775 .ccid_hc_tx_parse_options = ccid2_hc_tx_parse_options,
776 .ccid_hc_tx_packet_recv = ccid2_hc_tx_packet_recv,
777 .ccid_hc_rx_obj_size = sizeof(struct ccid2_hc_rx_sock),
778 .ccid_hc_rx_packet_recv = ccid2_hc_rx_packet_recv,
779};
780
781#ifdef CONFIG_IP_DCCP_CCID2_DEBUG
782module_param(ccid2_debug, bool, 0644);
783MODULE_PARM_DESC(ccid2_debug, "Enable CCID-2 debug messages");
784#endif