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
19 static 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
25 static 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
67 static 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
74 static 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
92 static 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
110 static 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
117 static 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
127 static 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);
170 out:
171 bh_unlock_sock(sk);
172 sock_put(sk);
173 }
174
175 /*
176 * Congestion window validation (RFC 2861).
177 */
178 static bool ccid2_do_cwv = true;
179 module_param(ccid2_do_cwv, bool, 0644);
180 MODULE_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 */
192 static 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() */
198 static 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() */
217 static 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
238 static 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, 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, 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, &hc->tx_rtotimer, 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 * @mrtt: measured RTT
357 *
358 * This code is almost identical with TCP's tcp_rtt_estimator(), since
359 * - it has a higher sampling frequency (recommended by RFC 1323),
360 * - the RTO does not collapse into RTT due to RTTVAR going towards zero,
361 * - it is simple (cf. more complex proposals such as Eifel timer or research
362 * which suggests that the gain should be set according to window size),
363 * - in tests it was found to work well with CCID2 [gerrit].
364 */
365 static void ccid2_rtt_estimator(struct sock *sk, const long mrtt)
366 {
367 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
368 long m = mrtt ? : 1;
369
370 if (hc->tx_srtt == 0) {
371 /* First measurement m */
372 hc->tx_srtt = m << 3;
373 hc->tx_mdev = m << 1;
374
375 hc->tx_mdev_max = max(hc->tx_mdev, tcp_rto_min(sk));
376 hc->tx_rttvar = hc->tx_mdev_max;
377
378 hc->tx_rtt_seq = dccp_sk(sk)->dccps_gss;
379 } else {
380 /* Update scaled SRTT as SRTT += 1/8 * (m - SRTT) */
381 m -= (hc->tx_srtt >> 3);
382 hc->tx_srtt += m;
383
384 /* Similarly, update scaled mdev with regard to |m| */
385 if (m < 0) {
386 m = -m;
387 m -= (hc->tx_mdev >> 2);
388 /*
389 * This neutralises RTO increase when RTT < SRTT - mdev
390 * (see P. Sarolahti, A. Kuznetsov,"Congestion Control
391 * in Linux TCP", USENIX 2002, pp. 49-62).
392 */
393 if (m > 0)
394 m >>= 3;
395 } else {
396 m -= (hc->tx_mdev >> 2);
397 }
398 hc->tx_mdev += m;
399
400 if (hc->tx_mdev > hc->tx_mdev_max) {
401 hc->tx_mdev_max = hc->tx_mdev;
402 if (hc->tx_mdev_max > hc->tx_rttvar)
403 hc->tx_rttvar = hc->tx_mdev_max;
404 }
405
406 /*
407 * Decay RTTVAR at most once per flight, exploiting that
408 * 1) pipe <= cwnd <= Sequence_Window = W (RFC 4340, 7.5.2)
409 * 2) AWL = GSS-W+1 <= GAR <= GSS (RFC 4340, 7.5.1)
410 * GAR is a useful bound for FlightSize = pipe.
411 * AWL is probably too low here, as it over-estimates pipe.
412 */
413 if (after48(dccp_sk(sk)->dccps_gar, hc->tx_rtt_seq)) {
414 if (hc->tx_mdev_max < hc->tx_rttvar)
415 hc->tx_rttvar -= (hc->tx_rttvar -
416 hc->tx_mdev_max) >> 2;
417 hc->tx_rtt_seq = dccp_sk(sk)->dccps_gss;
418 hc->tx_mdev_max = tcp_rto_min(sk);
419 }
420 }
421
422 /*
423 * Set RTO from SRTT and RTTVAR
424 * As in TCP, 4 * RTTVAR >= TCP_RTO_MIN, giving a minimum RTO of 200 ms.
425 * This agrees with RFC 4341, 5:
426 * "Because DCCP does not retransmit data, DCCP does not require
427 * TCP's recommended minimum timeout of one second".
428 */
429 hc->tx_rto = (hc->tx_srtt >> 3) + hc->tx_rttvar;
430
431 if (hc->tx_rto > DCCP_RTO_MAX)
432 hc->tx_rto = DCCP_RTO_MAX;
433 }
434
435 static void ccid2_new_ack(struct sock *sk, struct ccid2_seq *seqp,
436 unsigned int *maxincr)
437 {
438 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
439 struct dccp_sock *dp = dccp_sk(sk);
440 int r_seq_used = hc->tx_cwnd / dp->dccps_l_ack_ratio;
441
442 if (hc->tx_cwnd < dp->dccps_l_seq_win &&
443 r_seq_used < dp->dccps_r_seq_win) {
444 if (hc->tx_cwnd < hc->tx_ssthresh) {
445 if (*maxincr > 0 && ++hc->tx_packets_acked >= 2) {
446 hc->tx_cwnd += 1;
447 *maxincr -= 1;
448 hc->tx_packets_acked = 0;
449 }
450 } else if (++hc->tx_packets_acked >= hc->tx_cwnd) {
451 hc->tx_cwnd += 1;
452 hc->tx_packets_acked = 0;
453 }
454 }
455
456 /*
457 * Adjust the local sequence window and the ack ratio to allow about
458 * 5 times the number of packets in the network (RFC 4340 7.5.2)
459 */
460 if (r_seq_used * CCID2_WIN_CHANGE_FACTOR >= dp->dccps_r_seq_win)
461 ccid2_change_l_ack_ratio(sk, dp->dccps_l_ack_ratio * 2);
462 else if (r_seq_used * CCID2_WIN_CHANGE_FACTOR < dp->dccps_r_seq_win/2)
463 ccid2_change_l_ack_ratio(sk, dp->dccps_l_ack_ratio / 2 ? : 1U);
464
465 if (hc->tx_cwnd * CCID2_WIN_CHANGE_FACTOR >= dp->dccps_l_seq_win)
466 ccid2_change_l_seq_window(sk, dp->dccps_l_seq_win * 2);
467 else if (hc->tx_cwnd * CCID2_WIN_CHANGE_FACTOR < dp->dccps_l_seq_win/2)
468 ccid2_change_l_seq_window(sk, dp->dccps_l_seq_win / 2);
469
470 /*
471 * FIXME: RTT is sampled several times per acknowledgment (for each
472 * entry in the Ack Vector), instead of once per Ack (as in TCP SACK).
473 * This causes the RTT to be over-estimated, since the older entries
474 * in the Ack Vector have earlier sending times.
475 * The cleanest solution is to not use the ccid2s_sent field at all
476 * and instead use DCCP timestamps: requires changes in other places.
477 */
478 ccid2_rtt_estimator(sk, ccid2_jiffies32 - seqp->ccid2s_sent);
479 }
480
481 static void ccid2_congestion_event(struct sock *sk, struct ccid2_seq *seqp)
482 {
483 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
484
485 if ((s32)(seqp->ccid2s_sent - hc->tx_last_cong) < 0) {
486 ccid2_pr_debug("Multiple losses in an RTT---treating as one\n");
487 return;
488 }
489
490 hc->tx_last_cong = ccid2_jiffies32;
491
492 hc->tx_cwnd = hc->tx_cwnd / 2 ? : 1U;
493 hc->tx_ssthresh = max(hc->tx_cwnd, 2U);
494
495 ccid2_check_l_ack_ratio(sk);
496 }
497
498 static int ccid2_hc_tx_parse_options(struct sock *sk, u8 packet_type,
499 u8 option, u8 *optval, u8 optlen)
500 {
501 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
502
503 switch (option) {
504 case DCCPO_ACK_VECTOR_0:
505 case DCCPO_ACK_VECTOR_1:
506 return dccp_ackvec_parsed_add(&hc->tx_av_chunks, optval, optlen,
507 option - DCCPO_ACK_VECTOR_0);
508 }
509 return 0;
510 }
511
512 static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
513 {
514 struct dccp_sock *dp = dccp_sk(sk);
515 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
516 const bool sender_was_blocked = ccid2_cwnd_network_limited(hc);
517 struct dccp_ackvec_parsed *avp;
518 u64 ackno, seqno;
519 struct ccid2_seq *seqp;
520 int done = 0;
521 unsigned int maxincr = 0;
522
523 /* check reverse path congestion */
524 seqno = DCCP_SKB_CB(skb)->dccpd_seq;
525
526 /* XXX this whole "algorithm" is broken. Need to fix it to keep track
527 * of the seqnos of the dupacks so that rpseq and rpdupack are correct
528 * -sorbo.
529 */
530 /* need to bootstrap */
531 if (hc->tx_rpdupack == -1) {
532 hc->tx_rpdupack = 0;
533 hc->tx_rpseq = seqno;
534 } else {
535 /* check if packet is consecutive */
536 if (dccp_delta_seqno(hc->tx_rpseq, seqno) == 1)
537 hc->tx_rpseq = seqno;
538 /* it's a later packet */
539 else if (after48(seqno, hc->tx_rpseq)) {
540 hc->tx_rpdupack++;
541
542 /* check if we got enough dupacks */
543 if (hc->tx_rpdupack >= NUMDUPACK) {
544 hc->tx_rpdupack = -1; /* XXX lame */
545 hc->tx_rpseq = 0;
546 #ifdef __CCID2_COPES_GRACEFULLY_WITH_ACK_CONGESTION_CONTROL__
547 /*
548 * FIXME: Ack Congestion Control is broken; in
549 * the current state instabilities occurred with
550 * Ack Ratios greater than 1; causing hang-ups
551 * and long RTO timeouts. This needs to be fixed
552 * before opening up dynamic changes. -- gerrit
553 */
554 ccid2_change_l_ack_ratio(sk, 2 * dp->dccps_l_ack_ratio);
555 #endif
556 }
557 }
558 }
559
560 /* check forward path congestion */
561 if (dccp_packet_without_ack(skb))
562 return;
563
564 /* still didn't send out new data packets */
565 if (hc->tx_seqh == hc->tx_seqt)
566 goto done;
567
568 ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
569 if (after48(ackno, hc->tx_high_ack))
570 hc->tx_high_ack = ackno;
571
572 seqp = hc->tx_seqt;
573 while (before48(seqp->ccid2s_seq, ackno)) {
574 seqp = seqp->ccid2s_next;
575 if (seqp == hc->tx_seqh) {
576 seqp = hc->tx_seqh->ccid2s_prev;
577 break;
578 }
579 }
580
581 /*
582 * In slow-start, cwnd can increase up to a maximum of Ack Ratio/2
583 * packets per acknowledgement. Rounding up avoids that cwnd is not
584 * advanced when Ack Ratio is 1 and gives a slight edge otherwise.
585 */
586 if (hc->tx_cwnd < hc->tx_ssthresh)
587 maxincr = DIV_ROUND_UP(dp->dccps_l_ack_ratio, 2);
588
589 /* go through all ack vectors */
590 list_for_each_entry(avp, &hc->tx_av_chunks, node) {
591 /* go through this ack vector */
592 for (; avp->len--; avp->vec++) {
593 u64 ackno_end_rl = SUB48(ackno,
594 dccp_ackvec_runlen(avp->vec));
595
596 ccid2_pr_debug("ackvec %llu |%u,%u|\n",
597 (unsigned long long)ackno,
598 dccp_ackvec_state(avp->vec) >> 6,
599 dccp_ackvec_runlen(avp->vec));
600 /* if the seqno we are analyzing is larger than the
601 * current ackno, then move towards the tail of our
602 * seqnos.
603 */
604 while (after48(seqp->ccid2s_seq, ackno)) {
605 if (seqp == hc->tx_seqt) {
606 done = 1;
607 break;
608 }
609 seqp = seqp->ccid2s_prev;
610 }
611 if (done)
612 break;
613
614 /* check all seqnos in the range of the vector
615 * run length
616 */
617 while (between48(seqp->ccid2s_seq,ackno_end_rl,ackno)) {
618 const u8 state = dccp_ackvec_state(avp->vec);
619
620 /* new packet received or marked */
621 if (state != DCCPAV_NOT_RECEIVED &&
622 !seqp->ccid2s_acked) {
623 if (state == DCCPAV_ECN_MARKED)
624 ccid2_congestion_event(sk,
625 seqp);
626 else
627 ccid2_new_ack(sk, seqp,
628 &maxincr);
629
630 seqp->ccid2s_acked = 1;
631 ccid2_pr_debug("Got ack for %llu\n",
632 (unsigned long long)seqp->ccid2s_seq);
633 hc->tx_pipe--;
634 }
635 if (seqp == hc->tx_seqt) {
636 done = 1;
637 break;
638 }
639 seqp = seqp->ccid2s_prev;
640 }
641 if (done)
642 break;
643
644 ackno = SUB48(ackno_end_rl, 1);
645 }
646 if (done)
647 break;
648 }
649
650 /* The state about what is acked should be correct now
651 * Check for NUMDUPACK
652 */
653 seqp = hc->tx_seqt;
654 while (before48(seqp->ccid2s_seq, hc->tx_high_ack)) {
655 seqp = seqp->ccid2s_next;
656 if (seqp == hc->tx_seqh) {
657 seqp = hc->tx_seqh->ccid2s_prev;
658 break;
659 }
660 }
661 done = 0;
662 while (1) {
663 if (seqp->ccid2s_acked) {
664 done++;
665 if (done == NUMDUPACK)
666 break;
667 }
668 if (seqp == hc->tx_seqt)
669 break;
670 seqp = seqp->ccid2s_prev;
671 }
672
673 /* If there are at least 3 acknowledgements, anything unacknowledged
674 * below the last sequence number is considered lost
675 */
676 if (done == NUMDUPACK) {
677 struct ccid2_seq *last_acked = seqp;
678
679 /* check for lost packets */
680 while (1) {
681 if (!seqp->ccid2s_acked) {
682 ccid2_pr_debug("Packet lost: %llu\n",
683 (unsigned long long)seqp->ccid2s_seq);
684 /* XXX need to traverse from tail -> head in
685 * order to detect multiple congestion events in
686 * one ack vector.
687 */
688 ccid2_congestion_event(sk, seqp);
689 hc->tx_pipe--;
690 }
691 if (seqp == hc->tx_seqt)
692 break;
693 seqp = seqp->ccid2s_prev;
694 }
695
696 hc->tx_seqt = last_acked;
697 }
698
699 /* trim acked packets in tail */
700 while (hc->tx_seqt != hc->tx_seqh) {
701 if (!hc->tx_seqt->ccid2s_acked)
702 break;
703
704 hc->tx_seqt = hc->tx_seqt->ccid2s_next;
705 }
706
707 /* restart RTO timer if not all outstanding data has been acked */
708 if (hc->tx_pipe == 0)
709 sk_stop_timer(sk, &hc->tx_rtotimer);
710 else
711 sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
712 done:
713 /* check if incoming Acks allow pending packets to be sent */
714 if (sender_was_blocked && !ccid2_cwnd_network_limited(hc))
715 dccp_tasklet_schedule(sk);
716 dccp_ackvec_parsed_cleanup(&hc->tx_av_chunks);
717 }
718
719 static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
720 {
721 struct ccid2_hc_tx_sock *hc = ccid_priv(ccid);
722 struct dccp_sock *dp = dccp_sk(sk);
723 u32 max_ratio;
724
725 /* RFC 4341, 5: initialise ssthresh to arbitrarily high (max) value */
726 hc->tx_ssthresh = ~0U;
727
728 /* Use larger initial windows (RFC 4341, section 5). */
729 hc->tx_cwnd = rfc3390_bytes_to_packets(dp->dccps_mss_cache);
730 hc->tx_expected_wnd = hc->tx_cwnd;
731
732 /* Make sure that Ack Ratio is enabled and within bounds. */
733 max_ratio = DIV_ROUND_UP(hc->tx_cwnd, 2);
734 if (dp->dccps_l_ack_ratio == 0 || dp->dccps_l_ack_ratio > max_ratio)
735 dp->dccps_l_ack_ratio = max_ratio;
736
737 /* XXX init ~ to window size... */
738 if (ccid2_hc_tx_alloc_seq(hc))
739 return -ENOMEM;
740
741 hc->tx_rto = DCCP_TIMEOUT_INIT;
742 hc->tx_rpdupack = -1;
743 hc->tx_last_cong = hc->tx_lsndtime = hc->tx_cwnd_stamp = ccid2_jiffies32;
744 hc->tx_cwnd_used = 0;
745 hc->sk = sk;
746 timer_setup(&hc->tx_rtotimer, ccid2_hc_tx_rto_expire, 0);
747 INIT_LIST_HEAD(&hc->tx_av_chunks);
748 return 0;
749 }
750
751 static void ccid2_hc_tx_exit(struct sock *sk)
752 {
753 struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
754 int i;
755
756 sk_stop_timer(sk, &hc->tx_rtotimer);
757
758 for (i = 0; i < hc->tx_seqbufc; i++)
759 kfree(hc->tx_seqbuf[i]);
760 hc->tx_seqbufc = 0;
761 dccp_ackvec_parsed_cleanup(&hc->tx_av_chunks);
762 }
763
764 static void ccid2_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
765 {
766 struct ccid2_hc_rx_sock *hc = ccid2_hc_rx_sk(sk);
767
768 if (!dccp_data_packet(skb))
769 return;
770
771 if (++hc->rx_num_data_pkts >= dccp_sk(sk)->dccps_r_ack_ratio) {
772 dccp_send_ack(sk);
773 hc->rx_num_data_pkts = 0;
774 }
775 }
776
777 struct ccid_operations ccid2_ops = {
778 .ccid_id = DCCPC_CCID2,
779 .ccid_name = "TCP-like",
780 .ccid_hc_tx_obj_size = sizeof(struct ccid2_hc_tx_sock),
781 .ccid_hc_tx_init = ccid2_hc_tx_init,
782 .ccid_hc_tx_exit = ccid2_hc_tx_exit,
783 .ccid_hc_tx_send_packet = ccid2_hc_tx_send_packet,
784 .ccid_hc_tx_packet_sent = ccid2_hc_tx_packet_sent,
785 .ccid_hc_tx_parse_options = ccid2_hc_tx_parse_options,
786 .ccid_hc_tx_packet_recv = ccid2_hc_tx_packet_recv,
787 .ccid_hc_rx_obj_size = sizeof(struct ccid2_hc_rx_sock),
788 .ccid_hc_rx_packet_recv = ccid2_hc_rx_packet_recv,
789 };
790
791 #ifdef CONFIG_IP_DCCP_CCID2_DEBUG
792 module_param(ccid2_debug, bool, 0644);
793 MODULE_PARM_DESC(ccid2_debug, "Enable CCID-2 debug messages");
794 #endif
795
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