linux/net/dccp/ccids/ccid2.c
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   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 *  Copyright (c) 2005, 2006 Andrea Bittau <a.bittau@cs.ucl.ac.uk>
   4 *
   5 *  Changes to meet Linux coding standards, and DCCP infrastructure fixes.
   6 *
   7 *  Copyright (c) 2006 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
   8 */
   9
  10/*
  11 * This implementation should follow RFC 4341
  12 */
  13#include <linux/slab.h>
  14#include "../feat.h"
  15#include "ccid2.h"
  16
  17
  18#ifdef CONFIG_IP_DCCP_CCID2_DEBUG
  19static bool ccid2_debug;
  20#define ccid2_pr_debug(format, a...)    DCCP_PR_DEBUG(ccid2_debug, format, ##a)
  21#else
  22#define ccid2_pr_debug(format, a...)
  23#endif
  24
  25static int ccid2_hc_tx_alloc_seq(struct ccid2_hc_tx_sock *hc)
  26{
  27        struct ccid2_seq *seqp;
  28        int i;
  29
  30        /* check if we have space to preserve the pointer to the buffer */
  31        if (hc->tx_seqbufc >= (sizeof(hc->tx_seqbuf) /
  32                               sizeof(struct ccid2_seq *)))
  33                return -ENOMEM;
  34
  35        /* allocate buffer and initialize linked list */
  36        seqp = kmalloc_array(CCID2_SEQBUF_LEN, sizeof(struct ccid2_seq),
  37                             gfp_any());
  38        if (seqp == NULL)
  39                return -ENOMEM;
  40
  41        for (i = 0; i < (CCID2_SEQBUF_LEN - 1); i++) {
  42                seqp[i].ccid2s_next = &seqp[i + 1];
  43                seqp[i + 1].ccid2s_prev = &seqp[i];
  44        }
  45        seqp[CCID2_SEQBUF_LEN - 1].ccid2s_next = seqp;
  46        seqp->ccid2s_prev = &seqp[CCID2_SEQBUF_LEN - 1];
  47
  48        /* This is the first allocation.  Initiate the head and tail.  */
  49        if (hc->tx_seqbufc == 0)
  50                hc->tx_seqh = hc->tx_seqt = seqp;
  51        else {
  52                /* link the existing list with the one we just created */
  53                hc->tx_seqh->ccid2s_next = seqp;
  54                seqp->ccid2s_prev = hc->tx_seqh;
  55
  56                hc->tx_seqt->ccid2s_prev = &seqp[CCID2_SEQBUF_LEN - 1];
  57                seqp[CCID2_SEQBUF_LEN - 1].ccid2s_next = hc->tx_seqt;
  58        }
  59
  60        /* store the original pointer to the buffer so we can free it */
  61        hc->tx_seqbuf[hc->tx_seqbufc] = seqp;
  62        hc->tx_seqbufc++;
  63
  64        return 0;
  65}
  66
  67static int ccid2_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
  68{
  69        if (ccid2_cwnd_network_limited(ccid2_hc_tx_sk(sk)))
  70                return CCID_PACKET_WILL_DEQUEUE_LATER;
  71        return CCID_PACKET_SEND_AT_ONCE;
  72}
  73
  74static void ccid2_change_l_ack_ratio(struct sock *sk, u32 val)
  75{
  76        u32 max_ratio = DIV_ROUND_UP(ccid2_hc_tx_sk(sk)->tx_cwnd, 2);
  77
  78        /*
  79         * Ensure that Ack Ratio does not exceed ceil(cwnd/2), which is (2) from
  80         * RFC 4341, 6.1.2. We ignore the statement that Ack Ratio 2 is always
  81         * acceptable since this causes starvation/deadlock whenever cwnd < 2.
  82         * The same problem arises when Ack Ratio is 0 (ie. Ack Ratio disabled).
  83         */
  84        if (val == 0 || val > max_ratio) {
  85                DCCP_WARN("Limiting Ack Ratio (%u) to %u\n", val, max_ratio);
  86                val = max_ratio;
  87        }
  88        dccp_feat_signal_nn_change(sk, DCCPF_ACK_RATIO,
  89                                   min_t(u32, val, DCCPF_ACK_RATIO_MAX));
  90}
  91
  92static void ccid2_check_l_ack_ratio(struct sock *sk)
  93{
  94        struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
  95
  96        /*
  97         * After a loss, idle period, application limited period, or RTO we
  98         * need to check that the ack ratio is still less than the congestion
  99         * window. Otherwise, we will send an entire congestion window of
 100         * packets and got no response because we haven't sent ack ratio
 101         * packets yet.
 102         * If the ack ratio does need to be reduced, we reduce it to half of
 103         * the congestion window (or 1 if that's zero) instead of to the
 104         * congestion window. This prevents problems if one ack is lost.
 105         */
 106        if (dccp_feat_nn_get(sk, DCCPF_ACK_RATIO) > hc->tx_cwnd)
 107                ccid2_change_l_ack_ratio(sk, hc->tx_cwnd/2 ? : 1U);
 108}
 109
 110static void ccid2_change_l_seq_window(struct sock *sk, u64 val)
 111{
 112        dccp_feat_signal_nn_change(sk, DCCPF_SEQUENCE_WINDOW,
 113                                   clamp_val(val, DCCPF_SEQ_WMIN,
 114                                                  DCCPF_SEQ_WMAX));
 115}
 116
 117static void dccp_tasklet_schedule(struct sock *sk)
 118{
 119        struct tasklet_struct *t = &dccp_sk(sk)->dccps_xmitlet;
 120
 121        if (!test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) {
 122                sock_hold(sk);
 123                __tasklet_schedule(t);
 124        }
 125}
 126
 127static void ccid2_hc_tx_rto_expire(struct timer_list *t)
 128{
 129        struct ccid2_hc_tx_sock *hc = from_timer(hc, t, tx_rtotimer);
 130        struct sock *sk = hc->sk;
 131        const bool sender_was_blocked = ccid2_cwnd_network_limited(hc);
 132
 133        bh_lock_sock(sk);
 134        if (sock_owned_by_user(sk)) {
 135                sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + HZ / 5);
 136                goto out;
 137        }
 138
 139        ccid2_pr_debug("RTO_EXPIRE\n");
 140
 141        if (sk->sk_state == DCCP_CLOSED)
 142                goto out;
 143
 144        /* back-off timer */
 145        hc->tx_rto <<= 1;
 146        if (hc->tx_rto > DCCP_RTO_MAX)
 147                hc->tx_rto = DCCP_RTO_MAX;
 148
 149        /* adjust pipe, cwnd etc */
 150        hc->tx_ssthresh = hc->tx_cwnd / 2;
 151        if (hc->tx_ssthresh < 2)
 152                hc->tx_ssthresh = 2;
 153        hc->tx_cwnd     = 1;
 154        hc->tx_pipe     = 0;
 155
 156        /* clear state about stuff we sent */
 157        hc->tx_seqt = hc->tx_seqh;
 158        hc->tx_packets_acked = 0;
 159
 160        /* clear ack ratio state. */
 161        hc->tx_rpseq    = 0;
 162        hc->tx_rpdupack = -1;
 163        ccid2_change_l_ack_ratio(sk, 1);
 164
 165        /* if we were blocked before, we may now send cwnd=1 packet */
 166        if (sender_was_blocked)
 167                dccp_tasklet_schedule(sk);
 168        /* restart backed-off timer */
 169        sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
 170out:
 171        bh_unlock_sock(sk);
 172        sock_put(sk);
 173}
 174
 175/*
 176 *      Congestion window validation (RFC 2861).
 177 */
 178static bool ccid2_do_cwv = true;
 179module_param(ccid2_do_cwv, bool, 0644);
 180MODULE_PARM_DESC(ccid2_do_cwv, "Perform RFC2861 Congestion Window Validation");
 181
 182/**
 183 * ccid2_update_used_window  -  Track how much of cwnd is actually used
 184 * @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, 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 */
 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, 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
 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(&hc->tx_av_chunks, optval, optlen,
 506                                              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(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);
 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(&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(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
 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, &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
 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