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, size: sizeof(struct ccid2_seq),
37 flags: 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(hc: 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, feat: 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, feat: DCCPF_ACK_RATIO) > hc->tx_cwnd)
107 ccid2_change_l_ack_ratio(sk, val: 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, feat: 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(nr: TASKLET_STATE_SCHED, addr: &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, timer: &hc->tx_rtotimer, expires: 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, val: 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, timer: &hc->tx_rtotimer, expires: 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 * @hc: socket to update window
185 * @new_wnd: new window values to add into the filter
186 *
187 * This is done in addition to CWV. The sender needs to have an idea of how many
188 * packets may be in flight, to set the local Sequence Window value accordingly
189 * (RFC 4340, 7.5.2). The CWV mechanism is exploited to keep track of the
190 * maximum-used window. We use an EWMA low-pass filter to filter out noise.
191 */
192static void ccid2_update_used_window(struct ccid2_hc_tx_sock *hc, u32 new_wnd)
193{
194 hc->tx_expected_wnd = (3 * hc->tx_expected_wnd + new_wnd) / 4;
195}
196
197/* This borrows the code of tcp_cwnd_application_limited() */
198static void ccid2_cwnd_application_limited(struct sock *sk, const u32 now)
199{
200 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
201 /* don't reduce cwnd below the initial window (IW) */
202 u32 init_win = rfc3390_bytes_to_packets(dccp_sk(sk)->dccps_mss_cache),
203 win_used = max(hc->tx_cwnd_used, init_win);
204
205 if (win_used < hc->tx_cwnd) {
206 hc->tx_ssthresh = max(hc->tx_ssthresh,
207 (hc->tx_cwnd >> 1) + (hc->tx_cwnd >> 2));
208 hc->tx_cwnd = (hc->tx_cwnd + win_used) >> 1;
209 }
210 hc->tx_cwnd_used = 0;
211 hc->tx_cwnd_stamp = now;
212
213 ccid2_check_l_ack_ratio(sk);
214}
215
216/* This borrows the code of tcp_cwnd_restart() */
217static void ccid2_cwnd_restart(struct sock *sk, const u32 now)
218{
219 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
220 u32 cwnd = hc->tx_cwnd, restart_cwnd,
221 iwnd = rfc3390_bytes_to_packets(dccp_sk(sk)->dccps_mss_cache);
222 s32 delta = now - hc->tx_lsndtime;
223
224 hc->tx_ssthresh = max(hc->tx_ssthresh, (cwnd >> 1) + (cwnd >> 2));
225
226 /* don't reduce cwnd below the initial window (IW) */
227 restart_cwnd = min(cwnd, iwnd);
228
229 while ((delta -= hc->tx_rto) >= 0 && cwnd > restart_cwnd)
230 cwnd >>= 1;
231 hc->tx_cwnd = max(cwnd, restart_cwnd);
232 hc->tx_cwnd_stamp = now;
233 hc->tx_cwnd_used = 0;
234
235 ccid2_check_l_ack_ratio(sk);
236}
237
238static void ccid2_hc_tx_packet_sent(struct sock *sk, unsigned int len)
239{
240 struct dccp_sock *dp = dccp_sk(sk);
241 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
242 const u32 now = ccid2_jiffies32;
243 struct ccid2_seq *next;
244
245 /* slow-start after idle periods (RFC 2581, RFC 2861) */
246 if (ccid2_do_cwv && !hc->tx_pipe &&
247 (s32)(now - hc->tx_lsndtime) >= hc->tx_rto)
248 ccid2_cwnd_restart(sk, now);
249
250 hc->tx_lsndtime = now;
251 hc->tx_pipe += 1;
252
253 /* see whether cwnd was fully used (RFC 2861), update expected window */
254 if (ccid2_cwnd_network_limited(hc)) {
255 ccid2_update_used_window(hc, new_wnd: hc->tx_cwnd);
256 hc->tx_cwnd_used = 0;
257 hc->tx_cwnd_stamp = now;
258 } else {
259 if (hc->tx_pipe > hc->tx_cwnd_used)
260 hc->tx_cwnd_used = hc->tx_pipe;
261
262 ccid2_update_used_window(hc, new_wnd: hc->tx_cwnd_used);
263
264 if (ccid2_do_cwv && (s32)(now - hc->tx_cwnd_stamp) >= hc->tx_rto)
265 ccid2_cwnd_application_limited(sk, now);
266 }
267
268 hc->tx_seqh->ccid2s_seq = dp->dccps_gss;
269 hc->tx_seqh->ccid2s_acked = 0;
270 hc->tx_seqh->ccid2s_sent = now;
271
272 next = hc->tx_seqh->ccid2s_next;
273 /* check if we need to alloc more space */
274 if (next == hc->tx_seqt) {
275 if (ccid2_hc_tx_alloc_seq(hc)) {
276 DCCP_CRIT("packet history - out of memory!");
277 /* FIXME: find a more graceful way to bail out */
278 return;
279 }
280 next = hc->tx_seqh->ccid2s_next;
281 BUG_ON(next == hc->tx_seqt);
282 }
283 hc->tx_seqh = next;
284
285 ccid2_pr_debug("cwnd=%d pipe=%d\n", hc->tx_cwnd, hc->tx_pipe);
286
287 /*
288 * FIXME: The code below is broken and the variables have been removed
289 * from the socket struct. The `ackloss' variable was always set to 0,
290 * and with arsent there are several problems:
291 * (i) it doesn't just count the number of Acks, but all sent packets;
292 * (ii) it is expressed in # of packets, not # of windows, so the
293 * comparison below uses the wrong formula: Appendix A of RFC 4341
294 * comes up with the number K = cwnd / (R^2 - R) of consecutive windows
295 * of data with no lost or marked Ack packets. If arsent were the # of
296 * consecutive Acks received without loss, then Ack Ratio needs to be
297 * decreased by 1 when
298 * arsent >= K * cwnd / R = cwnd^2 / (R^3 - R^2)
299 * where cwnd / R is the number of Acks received per window of data
300 * (cf. RFC 4341, App. A). The problems are that
301 * - arsent counts other packets as well;
302 * - the comparison uses a formula different from RFC 4341;
303 * - computing a cubic/quadratic equation each time is too complicated.
304 * Hence a different algorithm is needed.
305 */
306#if 0
307 /* Ack Ratio. Need to maintain a concept of how many windows we sent */
308 hc->tx_arsent++;
309 /* We had an ack loss in this window... */
310 if (hc->tx_ackloss) {
311 if (hc->tx_arsent >= hc->tx_cwnd) {
312 hc->tx_arsent = 0;
313 hc->tx_ackloss = 0;
314 }
315 } else {
316 /* No acks lost up to now... */
317 /* decrease ack ratio if enough packets were sent */
318 if (dp->dccps_l_ack_ratio > 1) {
319 /* XXX don't calculate denominator each time */
320 int denom = dp->dccps_l_ack_ratio * dp->dccps_l_ack_ratio -
321 dp->dccps_l_ack_ratio;
322
323 denom = hc->tx_cwnd * hc->tx_cwnd / denom;
324
325 if (hc->tx_arsent >= denom) {
326 ccid2_change_l_ack_ratio(sk, dp->dccps_l_ack_ratio - 1);
327 hc->tx_arsent = 0;
328 }
329 } else {
330 /* we can't increase ack ratio further [1] */
331 hc->tx_arsent = 0; /* or maybe set it to cwnd*/
332 }
333 }
334#endif
335
336 sk_reset_timer(sk, timer: &hc->tx_rtotimer, expires: jiffies + hc->tx_rto);
337
338#ifdef CONFIG_IP_DCCP_CCID2_DEBUG
339 do {
340 struct ccid2_seq *seqp = hc->tx_seqt;
341
342 while (seqp != hc->tx_seqh) {
343 ccid2_pr_debug("out seq=%llu acked=%d time=%u\n",
344 (unsigned long long)seqp->ccid2s_seq,
345 seqp->ccid2s_acked, seqp->ccid2s_sent);
346 seqp = seqp->ccid2s_next;
347 }
348 } while (0);
349 ccid2_pr_debug("=========\n");
350#endif
351}
352
353/**
354 * ccid2_rtt_estimator - Sample RTT and compute RTO using RFC2988 algorithm
355 * @sk: socket to perform estimator on
356 *
357 * This code is almost identical with TCP's tcp_rtt_estimator(), since
358 * - it has a higher sampling frequency (recommended by RFC 1323),
359 * - the RTO does not collapse into RTT due to RTTVAR going towards zero,
360 * - it is simple (cf. more complex proposals such as Eifel timer or research
361 * which suggests that the gain should be set according to window size),
362 * - in tests it was found to work well with CCID2 [gerrit].
363 */
364static void ccid2_rtt_estimator(struct sock *sk, const long mrtt)
365{
366 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
367 long m = mrtt ? : 1;
368
369 if (hc->tx_srtt == 0) {
370 /* First measurement m */
371 hc->tx_srtt = m << 3;
372 hc->tx_mdev = m << 1;
373
374 hc->tx_mdev_max = max(hc->tx_mdev, tcp_rto_min(sk));
375 hc->tx_rttvar = hc->tx_mdev_max;
376
377 hc->tx_rtt_seq = dccp_sk(sk)->dccps_gss;
378 } else {
379 /* Update scaled SRTT as SRTT += 1/8 * (m - SRTT) */
380 m -= (hc->tx_srtt >> 3);
381 hc->tx_srtt += m;
382
383 /* Similarly, update scaled mdev with regard to |m| */
384 if (m < 0) {
385 m = -m;
386 m -= (hc->tx_mdev >> 2);
387 /*
388 * This neutralises RTO increase when RTT < SRTT - mdev
389 * (see P. Sarolahti, A. Kuznetsov,"Congestion Control
390 * in Linux TCP", USENIX 2002, pp. 49-62).
391 */
392 if (m > 0)
393 m >>= 3;
394 } else {
395 m -= (hc->tx_mdev >> 2);
396 }
397 hc->tx_mdev += m;
398
399 if (hc->tx_mdev > hc->tx_mdev_max) {
400 hc->tx_mdev_max = hc->tx_mdev;
401 if (hc->tx_mdev_max > hc->tx_rttvar)
402 hc->tx_rttvar = hc->tx_mdev_max;
403 }
404
405 /*
406 * Decay RTTVAR at most once per flight, exploiting that
407 * 1) pipe <= cwnd <= Sequence_Window = W (RFC 4340, 7.5.2)
408 * 2) AWL = GSS-W+1 <= GAR <= GSS (RFC 4340, 7.5.1)
409 * GAR is a useful bound for FlightSize = pipe.
410 * AWL is probably too low here, as it over-estimates pipe.
411 */
412 if (after48(dccp_sk(sk)->dccps_gar, hc->tx_rtt_seq)) {
413 if (hc->tx_mdev_max < hc->tx_rttvar)
414 hc->tx_rttvar -= (hc->tx_rttvar -
415 hc->tx_mdev_max) >> 2;
416 hc->tx_rtt_seq = dccp_sk(sk)->dccps_gss;
417 hc->tx_mdev_max = tcp_rto_min(sk);
418 }
419 }
420
421 /*
422 * Set RTO from SRTT and RTTVAR
423 * As in TCP, 4 * RTTVAR >= TCP_RTO_MIN, giving a minimum RTO of 200 ms.
424 * This agrees with RFC 4341, 5:
425 * "Because DCCP does not retransmit data, DCCP does not require
426 * TCP's recommended minimum timeout of one second".
427 */
428 hc->tx_rto = (hc->tx_srtt >> 3) + hc->tx_rttvar;
429
430 if (hc->tx_rto > DCCP_RTO_MAX)
431 hc->tx_rto = DCCP_RTO_MAX;
432}
433
434static void ccid2_new_ack(struct sock *sk, struct ccid2_seq *seqp,
435 unsigned int *maxincr)
436{
437 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
438 struct dccp_sock *dp = dccp_sk(sk);
439 int r_seq_used = hc->tx_cwnd / dp->dccps_l_ack_ratio;
440
441 if (hc->tx_cwnd < dp->dccps_l_seq_win &&
442 r_seq_used < dp->dccps_r_seq_win) {
443 if (hc->tx_cwnd < hc->tx_ssthresh) {
444 if (*maxincr > 0 && ++hc->tx_packets_acked >= 2) {
445 hc->tx_cwnd += 1;
446 *maxincr -= 1;
447 hc->tx_packets_acked = 0;
448 }
449 } else if (++hc->tx_packets_acked >= hc->tx_cwnd) {
450 hc->tx_cwnd += 1;
451 hc->tx_packets_acked = 0;
452 }
453 }
454
455 /*
456 * Adjust the local sequence window and the ack ratio to allow about
457 * 5 times the number of packets in the network (RFC 4340 7.5.2)
458 */
459 if (r_seq_used * CCID2_WIN_CHANGE_FACTOR >= dp->dccps_r_seq_win)
460 ccid2_change_l_ack_ratio(sk, val: dp->dccps_l_ack_ratio * 2);
461 else if (r_seq_used * CCID2_WIN_CHANGE_FACTOR < dp->dccps_r_seq_win/2)
462 ccid2_change_l_ack_ratio(sk, val: dp->dccps_l_ack_ratio / 2 ? : 1U);
463
464 if (hc->tx_cwnd * CCID2_WIN_CHANGE_FACTOR >= dp->dccps_l_seq_win)
465 ccid2_change_l_seq_window(sk, val: dp->dccps_l_seq_win * 2);
466 else if (hc->tx_cwnd * CCID2_WIN_CHANGE_FACTOR < dp->dccps_l_seq_win/2)
467 ccid2_change_l_seq_window(sk, val: dp->dccps_l_seq_win / 2);
468
469 /*
470 * FIXME: RTT is sampled several times per acknowledgment (for each
471 * entry in the Ack Vector), instead of once per Ack (as in TCP SACK).
472 * This causes the RTT to be over-estimated, since the older entries
473 * in the Ack Vector have earlier sending times.
474 * The cleanest solution is to not use the ccid2s_sent field at all
475 * and instead use DCCP timestamps: requires changes in other places.
476 */
477 ccid2_rtt_estimator(sk, ccid2_jiffies32 - seqp->ccid2s_sent);
478}
479
480static void ccid2_congestion_event(struct sock *sk, struct ccid2_seq *seqp)
481{
482 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
483
484 if ((s32)(seqp->ccid2s_sent - hc->tx_last_cong) < 0) {
485 ccid2_pr_debug("Multiple losses in an RTT---treating as one\n");
486 return;
487 }
488
489 hc->tx_last_cong = ccid2_jiffies32;
490
491 hc->tx_cwnd = hc->tx_cwnd / 2 ? : 1U;
492 hc->tx_ssthresh = max(hc->tx_cwnd, 2U);
493
494 ccid2_check_l_ack_ratio(sk);
495}
496
497static int ccid2_hc_tx_parse_options(struct sock *sk, u8 packet_type,
498 u8 option, u8 *optval, u8 optlen)
499{
500 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
501
502 switch (option) {
503 case DCCPO_ACK_VECTOR_0:
504 case DCCPO_ACK_VECTOR_1:
505 return dccp_ackvec_parsed_add(head: &hc->tx_av_chunks, vec: optval, len: optlen,
506 nonce: option - DCCPO_ACK_VECTOR_0);
507 }
508 return 0;
509}
510
511static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
512{
513 struct dccp_sock *dp = dccp_sk(sk);
514 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
515 const bool sender_was_blocked = ccid2_cwnd_network_limited(hc);
516 struct dccp_ackvec_parsed *avp;
517 u64 ackno, seqno;
518 struct ccid2_seq *seqp;
519 int done = 0;
520 unsigned int maxincr = 0;
521
522 /* check reverse path congestion */
523 seqno = DCCP_SKB_CB(skb)->dccpd_seq;
524
525 /* XXX this whole "algorithm" is broken. Need to fix it to keep track
526 * of the seqnos of the dupacks so that rpseq and rpdupack are correct
527 * -sorbo.
528 */
529 /* need to bootstrap */
530 if (hc->tx_rpdupack == -1) {
531 hc->tx_rpdupack = 0;
532 hc->tx_rpseq = seqno;
533 } else {
534 /* check if packet is consecutive */
535 if (dccp_delta_seqno(seqno1: hc->tx_rpseq, seqno2: seqno) == 1)
536 hc->tx_rpseq = seqno;
537 /* it's a later packet */
538 else if (after48(seqno, hc->tx_rpseq)) {
539 hc->tx_rpdupack++;
540
541 /* check if we got enough dupacks */
542 if (hc->tx_rpdupack >= NUMDUPACK) {
543 hc->tx_rpdupack = -1; /* XXX lame */
544 hc->tx_rpseq = 0;
545#ifdef __CCID2_COPES_GRACEFULLY_WITH_ACK_CONGESTION_CONTROL__
546 /*
547 * FIXME: Ack Congestion Control is broken; in
548 * the current state instabilities occurred with
549 * Ack Ratios greater than 1; causing hang-ups
550 * and long RTO timeouts. This needs to be fixed
551 * before opening up dynamic changes. -- gerrit
552 */
553 ccid2_change_l_ack_ratio(sk, 2 * dp->dccps_l_ack_ratio);
554#endif
555 }
556 }
557 }
558
559 /* check forward path congestion */
560 if (dccp_packet_without_ack(skb))
561 return;
562
563 /* still didn't send out new data packets */
564 if (hc->tx_seqh == hc->tx_seqt)
565 goto done;
566
567 ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
568 if (after48(ackno, hc->tx_high_ack))
569 hc->tx_high_ack = ackno;
570
571 seqp = hc->tx_seqt;
572 while (before48(seq1: seqp->ccid2s_seq, seq2: ackno)) {
573 seqp = seqp->ccid2s_next;
574 if (seqp == hc->tx_seqh) {
575 seqp = hc->tx_seqh->ccid2s_prev;
576 break;
577 }
578 }
579
580 /*
581 * In slow-start, cwnd can increase up to a maximum of Ack Ratio/2
582 * packets per acknowledgement. Rounding up avoids that cwnd is not
583 * advanced when Ack Ratio is 1 and gives a slight edge otherwise.
584 */
585 if (hc->tx_cwnd < hc->tx_ssthresh)
586 maxincr = DIV_ROUND_UP(dp->dccps_l_ack_ratio, 2);
587
588 /* go through all ack vectors */
589 list_for_each_entry(avp, &hc->tx_av_chunks, node) {
590 /* go through this ack vector */
591 for (; avp->len--; avp->vec++) {
592 u64 ackno_end_rl = SUB48(ackno,
593 dccp_ackvec_runlen(avp->vec));
594
595 ccid2_pr_debug("ackvec %llu |%u,%u|\n",
596 (unsigned long long)ackno,
597 dccp_ackvec_state(avp->vec) >> 6,
598 dccp_ackvec_runlen(avp->vec));
599 /* if the seqno we are analyzing is larger than the
600 * current ackno, then move towards the tail of our
601 * seqnos.
602 */
603 while (after48(seqp->ccid2s_seq, ackno)) {
604 if (seqp == hc->tx_seqt) {
605 done = 1;
606 break;
607 }
608 seqp = seqp->ccid2s_prev;
609 }
610 if (done)
611 break;
612
613 /* check all seqnos in the range of the vector
614 * run length
615 */
616 while (between48(seq1: seqp->ccid2s_seq,seq2: ackno_end_rl,seq3: ackno)) {
617 const u8 state = dccp_ackvec_state(cell: avp->vec);
618
619 /* new packet received or marked */
620 if (state != DCCPAV_NOT_RECEIVED &&
621 !seqp->ccid2s_acked) {
622 if (state == DCCPAV_ECN_MARKED)
623 ccid2_congestion_event(sk,
624 seqp);
625 else
626 ccid2_new_ack(sk, seqp,
627 maxincr: &maxincr);
628
629 seqp->ccid2s_acked = 1;
630 ccid2_pr_debug("Got ack for %llu\n",
631 (unsigned long long)seqp->ccid2s_seq);
632 hc->tx_pipe--;
633 }
634 if (seqp == hc->tx_seqt) {
635 done = 1;
636 break;
637 }
638 seqp = seqp->ccid2s_prev;
639 }
640 if (done)
641 break;
642
643 ackno = SUB48(ackno_end_rl, 1);
644 }
645 if (done)
646 break;
647 }
648
649 /* The state about what is acked should be correct now
650 * Check for NUMDUPACK
651 */
652 seqp = hc->tx_seqt;
653 while (before48(seq1: seqp->ccid2s_seq, seq2: hc->tx_high_ack)) {
654 seqp = seqp->ccid2s_next;
655 if (seqp == hc->tx_seqh) {
656 seqp = hc->tx_seqh->ccid2s_prev;
657 break;
658 }
659 }
660 done = 0;
661 while (1) {
662 if (seqp->ccid2s_acked) {
663 done++;
664 if (done == NUMDUPACK)
665 break;
666 }
667 if (seqp == hc->tx_seqt)
668 break;
669 seqp = seqp->ccid2s_prev;
670 }
671
672 /* If there are at least 3 acknowledgements, anything unacknowledged
673 * below the last sequence number is considered lost
674 */
675 if (done == NUMDUPACK) {
676 struct ccid2_seq *last_acked = seqp;
677
678 /* check for lost packets */
679 while (1) {
680 if (!seqp->ccid2s_acked) {
681 ccid2_pr_debug("Packet lost: %llu\n",
682 (unsigned long long)seqp->ccid2s_seq);
683 /* XXX need to traverse from tail -> head in
684 * order to detect multiple congestion events in
685 * one ack vector.
686 */
687 ccid2_congestion_event(sk, seqp);
688 hc->tx_pipe--;
689 }
690 if (seqp == hc->tx_seqt)
691 break;
692 seqp = seqp->ccid2s_prev;
693 }
694
695 hc->tx_seqt = last_acked;
696 }
697
698 /* trim acked packets in tail */
699 while (hc->tx_seqt != hc->tx_seqh) {
700 if (!hc->tx_seqt->ccid2s_acked)
701 break;
702
703 hc->tx_seqt = hc->tx_seqt->ccid2s_next;
704 }
705
706 /* restart RTO timer if not all outstanding data has been acked */
707 if (hc->tx_pipe == 0)
708 sk_stop_timer(sk, timer: &hc->tx_rtotimer);
709 else
710 sk_reset_timer(sk, timer: &hc->tx_rtotimer, expires: jiffies + hc->tx_rto);
711done:
712 /* check if incoming Acks allow pending packets to be sent */
713 if (sender_was_blocked && !ccid2_cwnd_network_limited(hc))
714 dccp_tasklet_schedule(sk);
715 dccp_ackvec_parsed_cleanup(parsed_chunks: &hc->tx_av_chunks);
716}
717
718static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
719{
720 struct ccid2_hc_tx_sock *hc = ccid_priv(ccid);
721 struct dccp_sock *dp = dccp_sk(sk);
722 u32 max_ratio;
723
724 /* RFC 4341, 5: initialise ssthresh to arbitrarily high (max) value */
725 hc->tx_ssthresh = ~0U;
726
727 /* Use larger initial windows (RFC 4341, section 5). */
728 hc->tx_cwnd = rfc3390_bytes_to_packets(smss: dp->dccps_mss_cache);
729 hc->tx_expected_wnd = hc->tx_cwnd;
730
731 /* Make sure that Ack Ratio is enabled and within bounds. */
732 max_ratio = DIV_ROUND_UP(hc->tx_cwnd, 2);
733 if (dp->dccps_l_ack_ratio == 0 || dp->dccps_l_ack_ratio > max_ratio)
734 dp->dccps_l_ack_ratio = max_ratio;
735
736 /* XXX init ~ to window size... */
737 if (ccid2_hc_tx_alloc_seq(hc))
738 return -ENOMEM;
739
740 hc->tx_rto = DCCP_TIMEOUT_INIT;
741 hc->tx_rpdupack = -1;
742 hc->tx_last_cong = hc->tx_lsndtime = hc->tx_cwnd_stamp = ccid2_jiffies32;
743 hc->tx_cwnd_used = 0;
744 hc->sk = sk;
745 timer_setup(&hc->tx_rtotimer, ccid2_hc_tx_rto_expire, 0);
746 INIT_LIST_HEAD(list: &hc->tx_av_chunks);
747 return 0;
748}
749
750static void ccid2_hc_tx_exit(struct sock *sk)
751{
752 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
753 int i;
754
755 sk_stop_timer(sk, timer: &hc->tx_rtotimer);
756
757 for (i = 0; i < hc->tx_seqbufc; i++)
758 kfree(objp: hc->tx_seqbuf[i]);
759 hc->tx_seqbufc = 0;
760 dccp_ackvec_parsed_cleanup(parsed_chunks: &hc->tx_av_chunks);
761}
762
763static void ccid2_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
764{
765 struct ccid2_hc_rx_sock *hc = ccid2_hc_rx_sk(sk);
766
767 if (!dccp_data_packet(skb))
768 return;
769
770 if (++hc->rx_num_data_pkts >= dccp_sk(sk)->dccps_r_ack_ratio) {
771 dccp_send_ack(sk);
772 hc->rx_num_data_pkts = 0;
773 }
774}
775
776struct ccid_operations ccid2_ops = {
777 .ccid_id = DCCPC_CCID2,
778 .ccid_name = "TCP-like",
779 .ccid_hc_tx_obj_size = sizeof(struct ccid2_hc_tx_sock),
780 .ccid_hc_tx_init = ccid2_hc_tx_init,
781 .ccid_hc_tx_exit = ccid2_hc_tx_exit,
782 .ccid_hc_tx_send_packet = ccid2_hc_tx_send_packet,
783 .ccid_hc_tx_packet_sent = ccid2_hc_tx_packet_sent,
784 .ccid_hc_tx_parse_options = ccid2_hc_tx_parse_options,
785 .ccid_hc_tx_packet_recv = ccid2_hc_tx_packet_recv,
786 .ccid_hc_rx_obj_size = sizeof(struct ccid2_hc_rx_sock),
787 .ccid_hc_rx_packet_recv = ccid2_hc_rx_packet_recv,
788};
789
790#ifdef CONFIG_IP_DCCP_CCID2_DEBUG
791module_param(ccid2_debug, bool, 0644);
792MODULE_PARM_DESC(ccid2_debug, "Enable CCID-2 debug messages");
793#endif
794

source code of linux/net/dccp/ccids/ccid2.c