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 * 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 */ 364 static 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 } 433 434 static 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, 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, 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, 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, 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 } 479 480 static 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 } 496 497 static 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(&hc->tx_av_chunks, optval, optlen, 506 option - DCCPO_ACK_VECTOR_0); 507 } 508 return 0; 509 } 510 511 static 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(hc->tx_rpseq, 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(seqp->ccid2s_seq, 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(seqp->ccid2s_seq,ackno_end_rl,ackno)) { 617 const u8 state = dccp_ackvec_state(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); 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(seqp->ccid2s_seq, 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, &hc->tx_rtotimer); 709 else 710 sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto); 711 done: 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(&hc->tx_av_chunks); 716 } 717 718 static 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(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(&hc->tx_av_chunks); 747 return 0; 748 } 749 750 static 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, &hc->tx_rtotimer); 756 757 for (i = 0; i < hc->tx_seqbufc; i++) 758 kfree(hc->tx_seqbuf[i]); 759 hc->tx_seqbufc = 0; 760 dccp_ackvec_parsed_cleanup(&hc->tx_av_chunks); 761 } 762 763 static 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 } 775 776 struct 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 791 module_param(ccid2_debug, bool, 0644); 792 MODULE_PARM_DESC(ccid2_debug, "Enable CCID-2 debug messages"); 793 #endif 794