root/net/dccp/ccids/ccid2.c

DEFINITIONS

1. ccid2_hc_tx_alloc_seq
2. ccid2_hc_tx_send_packet
3. ccid2_change_l_ack_ratio
4. ccid2_check_l_ack_ratio
5. ccid2_change_l_seq_window
6. dccp_tasklet_schedule
7. ccid2_hc_tx_rto_expire
8. ccid2_update_used_window
9. ccid2_cwnd_application_limited
10. ccid2_cwnd_restart
11. ccid2_hc_tx_packet_sent
12. ccid2_rtt_estimator
13. ccid2_new_ack
14. ccid2_congestion_event
15. ccid2_hc_tx_parse_options
16. ccid2_hc_tx_packet_recv
17. ccid2_hc_tx_init
18. ccid2_hc_tx_exit
19. ccid2_hc_rx_packet_recv

   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  * 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  */
 189 static 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() */
 195 static 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() */
 214 static 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 
 235 static 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  */
 359 static 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 
 429 static 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 
 475 static 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 
 492 static 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 
 506 static 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);
 706 done:
 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 
 713 static 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 
 745 static 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 
 758 static 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 
 771 struct 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
 786 module_param(ccid2_debug, bool, 0644);
 787 MODULE_PARM_DESC(ccid2_debug, "Enable CCID-2 debug messages");
 788 #endif