linux/net/dccp/ccids/ccid3.c
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   1/*
   2 *  net/dccp/ccids/ccid3.c
   3 *
   4 *  Copyright (c) 2007   The University of Aberdeen, Scotland, UK
   5 *  Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
   6 *  Copyright (c) 2005-7 Ian McDonald <ian.mcdonald@jandi.co.nz>
   7 *
   8 *  An implementation of the DCCP protocol
   9 *
  10 *  This code has been developed by the University of Waikato WAND
  11 *  research group. For further information please see http://www.wand.net.nz/
  12 *
  13 *  This code also uses code from Lulea University, rereleased as GPL by its
  14 *  authors:
  15 *  Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
  16 *
  17 *  Changes to meet Linux coding standards, to make it meet latest ccid3 draft
  18 *  and to make it work as a loadable module in the DCCP stack written by
  19 *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>.
  20 *
  21 *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
  22 *
  23 *  This program is free software; you can redistribute it and/or modify
  24 *  it under the terms of the GNU General Public License as published by
  25 *  the Free Software Foundation; either version 2 of the License, or
  26 *  (at your option) any later version.
  27 *
  28 *  This program is distributed in the hope that it will be useful,
  29 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  30 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  31 *  GNU General Public License for more details.
  32 *
  33 *  You should have received a copy of the GNU General Public License
  34 *  along with this program; if not, write to the Free Software
  35 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  36 */
  37#include "../dccp.h"
  38#include "ccid3.h"
  39
  40#include <asm/unaligned.h>
  41
  42#ifdef CONFIG_IP_DCCP_CCID3_DEBUG
  43static int ccid3_debug;
  44#define ccid3_pr_debug(format, a...)    DCCP_PR_DEBUG(ccid3_debug, format, ##a)
  45#else
  46#define ccid3_pr_debug(format, a...)
  47#endif
  48
  49/*
  50 *      Transmitter Half-Connection Routines
  51 */
  52#ifdef CONFIG_IP_DCCP_CCID3_DEBUG
  53static const char *ccid3_tx_state_name(enum ccid3_hc_tx_states state)
  54{
  55        static char *ccid3_state_names[] = {
  56        [TFRC_SSTATE_NO_SENT]  = "NO_SENT",
  57        [TFRC_SSTATE_NO_FBACK] = "NO_FBACK",
  58        [TFRC_SSTATE_FBACK]    = "FBACK",
  59        [TFRC_SSTATE_TERM]     = "TERM",
  60        };
  61
  62        return ccid3_state_names[state];
  63}
  64#endif
  65
  66static void ccid3_hc_tx_set_state(struct sock *sk,
  67                                  enum ccid3_hc_tx_states state)
  68{
  69        struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
  70        enum ccid3_hc_tx_states oldstate = hctx->ccid3hctx_state;
  71
  72        ccid3_pr_debug("%s(%p) %-8.8s -> %s\n",
  73                       dccp_role(sk), sk, ccid3_tx_state_name(oldstate),
  74                       ccid3_tx_state_name(state));
  75        WARN_ON(state == oldstate);
  76        hctx->ccid3hctx_state = state;
  77}
  78
  79/*
  80 * Compute the initial sending rate X_init in the manner of RFC 3390:
  81 *
  82 *      X_init  =  min(4 * s, max(2 * s, 4380 bytes)) / RTT
  83 *
  84 * Note that RFC 3390 uses MSS, RFC 4342 refers to RFC 3390, and rfc3448bis
  85 * (rev-02) clarifies the use of RFC 3390 with regard to the above formula.
  86 * For consistency with other parts of the code, X_init is scaled by 2^6.
  87 */
  88static inline u64 rfc3390_initial_rate(struct sock *sk)
  89{
  90        const struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
  91        const __u32 w_init = clamp_t(__u32, 4380U,
  92                        2 * hctx->ccid3hctx_s, 4 * hctx->ccid3hctx_s);
  93
  94        return scaled_div(w_init << 6, hctx->ccid3hctx_rtt);
  95}
  96
  97/*
  98 * Recalculate t_ipi and delta (should be called whenever X changes)
  99 */
 100static void ccid3_update_send_interval(struct ccid3_hc_tx_sock *hctx)
 101{
 102        /* Calculate new t_ipi = s / X_inst (X_inst is in 64 * bytes/second) */
 103        hctx->ccid3hctx_t_ipi = scaled_div32(((u64)hctx->ccid3hctx_s) << 6,
 104                                             hctx->ccid3hctx_x);
 105
 106        /* Calculate new delta by delta = min(t_ipi / 2, t_gran / 2) */
 107        hctx->ccid3hctx_delta = min_t(u32, hctx->ccid3hctx_t_ipi / 2,
 108                                           TFRC_OPSYS_HALF_TIME_GRAN);
 109
 110        ccid3_pr_debug("t_ipi=%u, delta=%u, s=%u, X=%u\n",
 111                       hctx->ccid3hctx_t_ipi, hctx->ccid3hctx_delta,
 112                       hctx->ccid3hctx_s, (unsigned)(hctx->ccid3hctx_x >> 6));
 113
 114}
 115
 116static u32 ccid3_hc_tx_idle_rtt(struct ccid3_hc_tx_sock *hctx, ktime_t now)
 117{
 118        u32 delta = ktime_us_delta(now, hctx->ccid3hctx_t_last_win_count);
 119
 120        return delta / hctx->ccid3hctx_rtt;
 121}
 122
 123/**
 124 * ccid3_hc_tx_update_x  -  Update allowed sending rate X
 125 * @stamp: most recent time if available - can be left NULL.
 126 * This function tracks draft rfc3448bis, check there for latest details.
 127 *
 128 * Note: X and X_recv are both stored in units of 64 * bytes/second, to support
 129 *       fine-grained resolution of sending rates. This requires scaling by 2^6
 130 *       throughout the code. Only X_calc is unscaled (in bytes/second).
 131 *
 132 */
 133static void ccid3_hc_tx_update_x(struct sock *sk, ktime_t *stamp)
 134{
 135        struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
 136        __u64 min_rate = 2 * hctx->ccid3hctx_x_recv;
 137        const  __u64 old_x = hctx->ccid3hctx_x;
 138        ktime_t now = stamp ? *stamp : ktime_get_real();
 139
 140        /*
 141         * Handle IDLE periods: do not reduce below RFC3390 initial sending rate
 142         * when idling [RFC 4342, 5.1]. Definition of idling is from rfc3448bis:
 143         * a sender is idle if it has not sent anything over a 2-RTT-period.
 144         * For consistency with X and X_recv, min_rate is also scaled by 2^6.
 145         */
 146        if (ccid3_hc_tx_idle_rtt(hctx, now) >= 2) {
 147                min_rate = rfc3390_initial_rate(sk);
 148                min_rate = max(min_rate, 2 * hctx->ccid3hctx_x_recv);
 149        }
 150
 151        if (hctx->ccid3hctx_p > 0) {
 152
 153                hctx->ccid3hctx_x = min(((__u64)hctx->ccid3hctx_x_calc) << 6,
 154                                        min_rate);
 155                hctx->ccid3hctx_x = max(hctx->ccid3hctx_x,
 156                                        (((__u64)hctx->ccid3hctx_s) << 6) /
 157                                                                TFRC_T_MBI);
 158
 159        } else if (ktime_us_delta(now, hctx->ccid3hctx_t_ld)
 160                                - (s64)hctx->ccid3hctx_rtt >= 0) {
 161
 162                hctx->ccid3hctx_x = min(2 * hctx->ccid3hctx_x, min_rate);
 163                hctx->ccid3hctx_x = max(hctx->ccid3hctx_x,
 164                            scaled_div(((__u64)hctx->ccid3hctx_s) << 6,
 165                                       hctx->ccid3hctx_rtt));
 166                hctx->ccid3hctx_t_ld = now;
 167        }
 168
 169        if (hctx->ccid3hctx_x != old_x) {
 170                ccid3_pr_debug("X_prev=%u, X_now=%u, X_calc=%u, "
 171                               "X_recv=%u\n", (unsigned)(old_x >> 6),
 172                               (unsigned)(hctx->ccid3hctx_x >> 6),
 173                               hctx->ccid3hctx_x_calc,
 174                               (unsigned)(hctx->ccid3hctx_x_recv >> 6));
 175
 176                ccid3_update_send_interval(hctx);
 177        }
 178}
 179
 180/*
 181 *      Track the mean packet size `s' (cf. RFC 4342, 5.3 and  RFC 3448, 4.1)
 182 *      @len: DCCP packet payload size in bytes
 183 */
 184static inline void ccid3_hc_tx_update_s(struct ccid3_hc_tx_sock *hctx, int len)
 185{
 186        const u16 old_s = hctx->ccid3hctx_s;
 187
 188        hctx->ccid3hctx_s = tfrc_ewma(hctx->ccid3hctx_s, len, 9);
 189
 190        if (hctx->ccid3hctx_s != old_s)
 191                ccid3_update_send_interval(hctx);
 192}
 193
 194/*
 195 *      Update Window Counter using the algorithm from [RFC 4342, 8.1].
 196 *      As elsewhere, RTT > 0 is assumed by using dccp_sample_rtt().
 197 */
 198static inline void ccid3_hc_tx_update_win_count(struct ccid3_hc_tx_sock *hctx,
 199                                                ktime_t now)
 200{
 201        u32 delta = ktime_us_delta(now, hctx->ccid3hctx_t_last_win_count),
 202            quarter_rtts = (4 * delta) / hctx->ccid3hctx_rtt;
 203
 204        if (quarter_rtts > 0) {
 205                hctx->ccid3hctx_t_last_win_count = now;
 206                hctx->ccid3hctx_last_win_count  += min(quarter_rtts, 5U);
 207                hctx->ccid3hctx_last_win_count  &= 0xF;         /* mod 16 */
 208        }
 209}
 210
 211static void ccid3_hc_tx_no_feedback_timer(unsigned long data)
 212{
 213        struct sock *sk = (struct sock *)data;
 214        struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
 215        unsigned long t_nfb = USEC_PER_SEC / 5;
 216
 217        bh_lock_sock(sk);
 218        if (sock_owned_by_user(sk)) {
 219                /* Try again later. */
 220                /* XXX: set some sensible MIB */
 221                goto restart_timer;
 222        }
 223
 224        ccid3_pr_debug("%s(%p, state=%s) - entry \n", dccp_role(sk), sk,
 225                       ccid3_tx_state_name(hctx->ccid3hctx_state));
 226
 227        if (hctx->ccid3hctx_state == TFRC_SSTATE_FBACK)
 228                ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);
 229        else if (hctx->ccid3hctx_state != TFRC_SSTATE_NO_FBACK)
 230                goto out;
 231
 232        /*
 233         * Determine new allowed sending rate X as per draft rfc3448bis-00, 4.4
 234         */
 235        if (hctx->ccid3hctx_t_rto == 0 ||       /* no feedback received yet */
 236            hctx->ccid3hctx_p == 0) {
 237
 238                /* halve send rate directly */
 239                hctx->ccid3hctx_x = max(hctx->ccid3hctx_x / 2,
 240                                        (((__u64)hctx->ccid3hctx_s) << 6) /
 241                                                                    TFRC_T_MBI);
 242                ccid3_update_send_interval(hctx);
 243        } else {
 244                /*
 245                 *  Modify the cached value of X_recv
 246                 *
 247                 *  If (X_calc > 2 * X_recv)
 248                 *    X_recv = max(X_recv / 2, s / (2 * t_mbi));
 249                 *  Else
 250                 *    X_recv = X_calc / 4;
 251                 *
 252                 *  Note that X_recv is scaled by 2^6 while X_calc is not
 253                 */
 254                BUG_ON(hctx->ccid3hctx_p && !hctx->ccid3hctx_x_calc);
 255
 256                if (hctx->ccid3hctx_x_calc > (hctx->ccid3hctx_x_recv >> 5))
 257                        hctx->ccid3hctx_x_recv =
 258                                max(hctx->ccid3hctx_x_recv / 2,
 259                                    (((__u64)hctx->ccid3hctx_s) << 6) /
 260                                                              (2 * TFRC_T_MBI));
 261                else {
 262                        hctx->ccid3hctx_x_recv = hctx->ccid3hctx_x_calc;
 263                        hctx->ccid3hctx_x_recv <<= 4;
 264                }
 265                ccid3_hc_tx_update_x(sk, NULL);
 266        }
 267        ccid3_pr_debug("Reduced X to %llu/64 bytes/sec\n",
 268                        (unsigned long long)hctx->ccid3hctx_x);
 269
 270        /*
 271         * Set new timeout for the nofeedback timer.
 272         * See comments in packet_recv() regarding the value of t_RTO.
 273         */
 274        if (unlikely(hctx->ccid3hctx_t_rto == 0))       /* no feedback yet */
 275                t_nfb = TFRC_INITIAL_TIMEOUT;
 276        else
 277                t_nfb = max(hctx->ccid3hctx_t_rto, 2 * hctx->ccid3hctx_t_ipi);
 278
 279restart_timer:
 280        sk_reset_timer(sk, &hctx->ccid3hctx_no_feedback_timer,
 281                           jiffies + usecs_to_jiffies(t_nfb));
 282out:
 283        bh_unlock_sock(sk);
 284        sock_put(sk);
 285}
 286
 287/*
 288 * returns
 289 *   > 0: delay (in msecs) that should pass before actually sending
 290 *   = 0: can send immediately
 291 *   < 0: error condition; do not send packet
 292 */
 293static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
 294{
 295        struct dccp_sock *dp = dccp_sk(sk);
 296        struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
 297        ktime_t now = ktime_get_real();
 298        s64 delay;
 299
 300        /*
 301         * This function is called only for Data and DataAck packets. Sending
 302         * zero-sized Data(Ack)s is theoretically possible, but for congestion
 303         * control this case is pathological - ignore it.
 304         */
 305        if (unlikely(skb->len == 0))
 306                return -EBADMSG;
 307
 308        switch (hctx->ccid3hctx_state) {
 309        case TFRC_SSTATE_NO_SENT:
 310                sk_reset_timer(sk, &hctx->ccid3hctx_no_feedback_timer,
 311                               (jiffies +
 312                                usecs_to_jiffies(TFRC_INITIAL_TIMEOUT)));
 313                hctx->ccid3hctx_last_win_count   = 0;
 314                hctx->ccid3hctx_t_last_win_count = now;
 315
 316                /* Set t_0 for initial packet */
 317                hctx->ccid3hctx_t_nom = now;
 318
 319                hctx->ccid3hctx_s = skb->len;
 320
 321                /*
 322                 * Use initial RTT sample when available: recommended by erratum
 323                 * to RFC 4342. This implements the initialisation procedure of
 324                 * draft rfc3448bis, section 4.2. Remember, X is scaled by 2^6.
 325                 */
 326                if (dp->dccps_syn_rtt) {
 327                        ccid3_pr_debug("SYN RTT = %uus\n", dp->dccps_syn_rtt);
 328                        hctx->ccid3hctx_rtt  = dp->dccps_syn_rtt;
 329                        hctx->ccid3hctx_x    = rfc3390_initial_rate(sk);
 330                        hctx->ccid3hctx_t_ld = now;
 331                } else {
 332                        /*
 333                         * Sender does not have RTT sample:
 334                         * - set fallback RTT (RFC 4340, 3.4) since a RTT value
 335                         *   is needed in several parts (e.g.  window counter);
 336                         * - set sending rate X_pps = 1pps as per RFC 3448, 4.2.
 337                         */
 338                        hctx->ccid3hctx_rtt = DCCP_FALLBACK_RTT;
 339                        hctx->ccid3hctx_x   = hctx->ccid3hctx_s;
 340                        hctx->ccid3hctx_x <<= 6;
 341                }
 342                ccid3_update_send_interval(hctx);
 343
 344                ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);
 345                break;
 346        case TFRC_SSTATE_NO_FBACK:
 347        case TFRC_SSTATE_FBACK:
 348                delay = ktime_us_delta(hctx->ccid3hctx_t_nom, now);
 349                ccid3_pr_debug("delay=%ld\n", (long)delay);
 350                /*
 351                 *      Scheduling of packet transmissions [RFC 3448, 4.6]
 352                 *
 353                 * if (t_now > t_nom - delta)
 354                 *       // send the packet now
 355                 * else
 356                 *       // send the packet in (t_nom - t_now) milliseconds.
 357                 */
 358                if (delay - (s64)hctx->ccid3hctx_delta >= 1000)
 359                        return (u32)delay / 1000L;
 360
 361                ccid3_hc_tx_update_win_count(hctx, now);
 362                break;
 363        case TFRC_SSTATE_TERM:
 364                DCCP_BUG("%s(%p) - Illegal state TERM", dccp_role(sk), sk);
 365                return -EINVAL;
 366        }
 367
 368        /* prepare to send now (add options etc.) */
 369        dp->dccps_hc_tx_insert_options = 1;
 370        DCCP_SKB_CB(skb)->dccpd_ccval = hctx->ccid3hctx_last_win_count;
 371
 372        /* set the nominal send time for the next following packet */
 373        hctx->ccid3hctx_t_nom = ktime_add_us(hctx->ccid3hctx_t_nom,
 374                                             hctx->ccid3hctx_t_ipi);
 375        return 0;
 376}
 377
 378static void ccid3_hc_tx_packet_sent(struct sock *sk, int more,
 379                                    unsigned int len)
 380{
 381        struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
 382
 383        ccid3_hc_tx_update_s(hctx, len);
 384
 385        if (tfrc_tx_hist_add(&hctx->ccid3hctx_hist, dccp_sk(sk)->dccps_gss))
 386                DCCP_CRIT("packet history - out of memory!");
 387}
 388
 389static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
 390{
 391        struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
 392        struct ccid3_options_received *opt_recv;
 393        ktime_t now;
 394        unsigned long t_nfb;
 395        u32 pinv, r_sample;
 396
 397        /* we are only interested in ACKs */
 398        if (!(DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_ACK ||
 399              DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_DATAACK))
 400                return;
 401        /* ... and only in the established state */
 402        if (hctx->ccid3hctx_state != TFRC_SSTATE_FBACK &&
 403            hctx->ccid3hctx_state != TFRC_SSTATE_NO_FBACK)
 404                return;
 405
 406        opt_recv = &hctx->ccid3hctx_options_received;
 407        now = ktime_get_real();
 408
 409        /* Estimate RTT from history if ACK number is valid */
 410        r_sample = tfrc_tx_hist_rtt(hctx->ccid3hctx_hist,
 411                                    DCCP_SKB_CB(skb)->dccpd_ack_seq, now);
 412        if (r_sample == 0) {
 413                DCCP_WARN("%s(%p): %s with bogus ACK-%llu\n", dccp_role(sk), sk,
 414                          dccp_packet_name(DCCP_SKB_CB(skb)->dccpd_type),
 415                          (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq);
 416                return;
 417        }
 418
 419        /* Update receive rate in units of 64 * bytes/second */
 420        hctx->ccid3hctx_x_recv = opt_recv->ccid3or_receive_rate;
 421        hctx->ccid3hctx_x_recv <<= 6;
 422
 423        /* Update loss event rate (which is scaled by 1e6) */
 424        pinv = opt_recv->ccid3or_loss_event_rate;
 425        if (pinv == ~0U || pinv == 0)          /* see RFC 4342, 8.5   */
 426                hctx->ccid3hctx_p = 0;
 427        else                                   /* can not exceed 100% */
 428                hctx->ccid3hctx_p = scaled_div(1, pinv);
 429        /*
 430         * Validate new RTT sample and update moving average
 431         */
 432        r_sample = dccp_sample_rtt(sk, r_sample);
 433        hctx->ccid3hctx_rtt = tfrc_ewma(hctx->ccid3hctx_rtt, r_sample, 9);
 434        /*
 435         * Update allowed sending rate X as per draft rfc3448bis-00, 4.2/3
 436         */
 437        if (hctx->ccid3hctx_state == TFRC_SSTATE_NO_FBACK) {
 438                ccid3_hc_tx_set_state(sk, TFRC_SSTATE_FBACK);
 439
 440                if (hctx->ccid3hctx_t_rto == 0) {
 441                        /*
 442                         * Initial feedback packet: Larger Initial Windows (4.2)
 443                         */
 444                        hctx->ccid3hctx_x    = rfc3390_initial_rate(sk);
 445                        hctx->ccid3hctx_t_ld = now;
 446
 447                        ccid3_update_send_interval(hctx);
 448
 449                        goto done_computing_x;
 450                } else if (hctx->ccid3hctx_p == 0) {
 451                        /*
 452                         * First feedback after nofeedback timer expiry (4.3)
 453                         */
 454                        goto done_computing_x;
 455                }
 456        }
 457
 458        /* Update sending rate (step 4 of [RFC 3448, 4.3]) */
 459        if (hctx->ccid3hctx_p > 0)
 460                hctx->ccid3hctx_x_calc =
 461                                tfrc_calc_x(hctx->ccid3hctx_s,
 462                                            hctx->ccid3hctx_rtt,
 463                                            hctx->ccid3hctx_p);
 464        ccid3_hc_tx_update_x(sk, &now);
 465
 466done_computing_x:
 467        ccid3_pr_debug("%s(%p), RTT=%uus (sample=%uus), s=%u, "
 468                               "p=%u, X_calc=%u, X_recv=%u, X=%u\n",
 469                               dccp_role(sk),
 470                               sk, hctx->ccid3hctx_rtt, r_sample,
 471                               hctx->ccid3hctx_s, hctx->ccid3hctx_p,
 472                               hctx->ccid3hctx_x_calc,
 473                               (unsigned)(hctx->ccid3hctx_x_recv >> 6),
 474                               (unsigned)(hctx->ccid3hctx_x >> 6));
 475
 476        /* unschedule no feedback timer */
 477        sk_stop_timer(sk, &hctx->ccid3hctx_no_feedback_timer);
 478
 479        /*
 480         * As we have calculated new ipi, delta, t_nom it is possible
 481         * that we now can send a packet, so wake up dccp_wait_for_ccid
 482         */
 483        sk->sk_write_space(sk);
 484
 485        /*
 486         * Update timeout interval for the nofeedback timer.
 487         * We use a configuration option to increase the lower bound.
 488         * This can help avoid triggering the nofeedback timer too
 489         * often ('spinning') on LANs with small RTTs.
 490         */
 491        hctx->ccid3hctx_t_rto = max_t(u32, 4 * hctx->ccid3hctx_rtt,
 492                                           (CONFIG_IP_DCCP_CCID3_RTO *
 493                                            (USEC_PER_SEC / 1000)));
 494        /*
 495         * Schedule no feedback timer to expire in
 496         * max(t_RTO, 2 * s/X)  =  max(t_RTO, 2 * t_ipi)
 497         */
 498        t_nfb = max(hctx->ccid3hctx_t_rto, 2 * hctx->ccid3hctx_t_ipi);
 499
 500        ccid3_pr_debug("%s(%p), Scheduled no feedback timer to "
 501                       "expire in %lu jiffies (%luus)\n",
 502                       dccp_role(sk),
 503                       sk, usecs_to_jiffies(t_nfb), t_nfb);
 504
 505        sk_reset_timer(sk, &hctx->ccid3hctx_no_feedback_timer,
 506                           jiffies + usecs_to_jiffies(t_nfb));
 507}
 508
 509static int ccid3_hc_tx_parse_options(struct sock *sk, unsigned char option,
 510                                     unsigned char len, u16 idx,
 511                                     unsigned char *value)
 512{
 513        int rc = 0;
 514        const struct dccp_sock *dp = dccp_sk(sk);
 515        struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
 516        struct ccid3_options_received *opt_recv;
 517        __be32 opt_val;
 518
 519        opt_recv = &hctx->ccid3hctx_options_received;
 520
 521        if (opt_recv->ccid3or_seqno != dp->dccps_gsr) {
 522                opt_recv->ccid3or_seqno              = dp->dccps_gsr;
 523                opt_recv->ccid3or_loss_event_rate    = ~0;
 524                opt_recv->ccid3or_loss_intervals_idx = 0;
 525                opt_recv->ccid3or_loss_intervals_len = 0;
 526                opt_recv->ccid3or_receive_rate       = 0;
 527        }
 528
 529        switch (option) {
 530        case TFRC_OPT_LOSS_EVENT_RATE:
 531                if (unlikely(len != 4)) {
 532                        DCCP_WARN("%s(%p), invalid len %d "
 533                                  "for TFRC_OPT_LOSS_EVENT_RATE\n",
 534                                  dccp_role(sk), sk, len);
 535                        rc = -EINVAL;
 536                } else {
 537                        opt_val = get_unaligned((__be32 *)value);
 538                        opt_recv->ccid3or_loss_event_rate = ntohl(opt_val);
 539                        ccid3_pr_debug("%s(%p), LOSS_EVENT_RATE=%u\n",
 540                                       dccp_role(sk), sk,
 541                                       opt_recv->ccid3or_loss_event_rate);
 542                }
 543                break;
 544        case TFRC_OPT_LOSS_INTERVALS:
 545                opt_recv->ccid3or_loss_intervals_idx = idx;
 546                opt_recv->ccid3or_loss_intervals_len = len;
 547                ccid3_pr_debug("%s(%p), LOSS_INTERVALS=(%u, %u)\n",
 548                               dccp_role(sk), sk,
 549                               opt_recv->ccid3or_loss_intervals_idx,
 550                               opt_recv->ccid3or_loss_intervals_len);
 551                break;
 552        case TFRC_OPT_RECEIVE_RATE:
 553                if (unlikely(len != 4)) {
 554                        DCCP_WARN("%s(%p), invalid len %d "
 555                                  "for TFRC_OPT_RECEIVE_RATE\n",
 556                                  dccp_role(sk), sk, len);
 557                        rc = -EINVAL;
 558                } else {
 559                        opt_val = get_unaligned((__be32 *)value);
 560                        opt_recv->ccid3or_receive_rate = ntohl(opt_val);
 561                        ccid3_pr_debug("%s(%p), RECEIVE_RATE=%u\n",
 562                                       dccp_role(sk), sk,
 563                                       opt_recv->ccid3or_receive_rate);
 564                }
 565                break;
 566        }
 567
 568        return rc;
 569}
 570
 571static int ccid3_hc_tx_init(struct ccid *ccid, struct sock *sk)
 572{
 573        struct ccid3_hc_tx_sock *hctx = ccid_priv(ccid);
 574
 575        hctx->ccid3hctx_state = TFRC_SSTATE_NO_SENT;
 576        hctx->ccid3hctx_hist = NULL;
 577        setup_timer(&hctx->ccid3hctx_no_feedback_timer,
 578                        ccid3_hc_tx_no_feedback_timer, (unsigned long)sk);
 579
 580        return 0;
 581}
 582
 583static void ccid3_hc_tx_exit(struct sock *sk)
 584{
 585        struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
 586
 587        ccid3_hc_tx_set_state(sk, TFRC_SSTATE_TERM);
 588        sk_stop_timer(sk, &hctx->ccid3hctx_no_feedback_timer);
 589
 590        tfrc_tx_hist_purge(&hctx->ccid3hctx_hist);
 591}
 592
 593static void ccid3_hc_tx_get_info(struct sock *sk, struct tcp_info *info)
 594{
 595        struct ccid3_hc_tx_sock *hctx;
 596
 597        /* Listen socks doesn't have a private CCID block */
 598        if (sk->sk_state == DCCP_LISTEN)
 599                return;
 600
 601        hctx = ccid3_hc_tx_sk(sk);
 602        info->tcpi_rto = hctx->ccid3hctx_t_rto;
 603        info->tcpi_rtt = hctx->ccid3hctx_rtt;
 604}
 605
 606static int ccid3_hc_tx_getsockopt(struct sock *sk, const int optname, int len,
 607                                  u32 __user *optval, int __user *optlen)
 608{
 609        const struct ccid3_hc_tx_sock *hctx;
 610        const void *val;
 611
 612        /* Listen socks doesn't have a private CCID block */
 613        if (sk->sk_state == DCCP_LISTEN)
 614                return -EINVAL;
 615
 616        hctx = ccid3_hc_tx_sk(sk);
 617        switch (optname) {
 618        case DCCP_SOCKOPT_CCID_TX_INFO:
 619                if (len < sizeof(hctx->ccid3hctx_tfrc))
 620                        return -EINVAL;
 621                len = sizeof(hctx->ccid3hctx_tfrc);
 622                val = &hctx->ccid3hctx_tfrc;
 623                break;
 624        default:
 625                return -ENOPROTOOPT;
 626        }
 627
 628        if (put_user(len, optlen) || copy_to_user(optval, val, len))
 629                return -EFAULT;
 630
 631        return 0;
 632}
 633
 634/*
 635 *      Receiver Half-Connection Routines
 636 */
 637
 638/* CCID3 feedback types */
 639enum ccid3_fback_type {
 640        CCID3_FBACK_NONE = 0,
 641        CCID3_FBACK_INITIAL,
 642        CCID3_FBACK_PERIODIC,
 643        CCID3_FBACK_PARAM_CHANGE
 644};
 645
 646#ifdef CONFIG_IP_DCCP_CCID3_DEBUG
 647static const char *ccid3_rx_state_name(enum ccid3_hc_rx_states state)
 648{
 649        static char *ccid3_rx_state_names[] = {
 650        [TFRC_RSTATE_NO_DATA] = "NO_DATA",
 651        [TFRC_RSTATE_DATA]    = "DATA",
 652        [TFRC_RSTATE_TERM]    = "TERM",
 653        };
 654
 655        return ccid3_rx_state_names[state];
 656}
 657#endif
 658
 659static void ccid3_hc_rx_set_state(struct sock *sk,
 660                                  enum ccid3_hc_rx_states state)
 661{
 662        struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
 663        enum ccid3_hc_rx_states oldstate = hcrx->ccid3hcrx_state;
 664
 665        ccid3_pr_debug("%s(%p) %-8.8s -> %s\n",
 666                       dccp_role(sk), sk, ccid3_rx_state_name(oldstate),
 667                       ccid3_rx_state_name(state));
 668        WARN_ON(state == oldstate);
 669        hcrx->ccid3hcrx_state = state;
 670}
 671
 672static void ccid3_hc_rx_send_feedback(struct sock *sk,
 673                                      const struct sk_buff *skb,
 674                                      enum ccid3_fback_type fbtype)
 675{
 676        struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
 677        struct dccp_sock *dp = dccp_sk(sk);
 678        ktime_t now;
 679        s64 delta = 0;
 680
 681        if (unlikely(hcrx->ccid3hcrx_state == TFRC_RSTATE_TERM))
 682                return;
 683
 684        now = ktime_get_real();
 685
 686        switch (fbtype) {
 687        case CCID3_FBACK_INITIAL:
 688                hcrx->ccid3hcrx_x_recv = 0;
 689                hcrx->ccid3hcrx_pinv   = ~0U;   /* see RFC 4342, 8.5 */
 690                break;
 691        case CCID3_FBACK_PARAM_CHANGE:
 692                /*
 693                 * When parameters change (new loss or p > p_prev), we do not
 694                 * have a reliable estimate for R_m of [RFC 3448, 6.2] and so
 695                 * need to  reuse the previous value of X_recv. However, when
 696                 * X_recv was 0 (due to early loss), this would kill X down to
 697                 * s/t_mbi (i.e. one packet in 64 seconds).
 698                 * To avoid such drastic reduction, we approximate X_recv as
 699                 * the number of bytes since last feedback.
 700                 * This is a safe fallback, since X is bounded above by X_calc.
 701                 */
 702                if (hcrx->ccid3hcrx_x_recv > 0)
 703                        break;
 704                /* fall through */
 705        case CCID3_FBACK_PERIODIC:
 706                delta = ktime_us_delta(now, hcrx->ccid3hcrx_tstamp_last_feedback);
 707                if (delta <= 0)
 708                        DCCP_BUG("delta (%ld) <= 0", (long)delta);
 709                else
 710                        hcrx->ccid3hcrx_x_recv =
 711                                scaled_div32(hcrx->ccid3hcrx_bytes_recv, delta);
 712                break;
 713        default:
 714                return;
 715        }
 716
 717        ccid3_pr_debug("Interval %ldusec, X_recv=%u, 1/p=%u\n", (long)delta,
 718                       hcrx->ccid3hcrx_x_recv, hcrx->ccid3hcrx_pinv);
 719
 720        hcrx->ccid3hcrx_tstamp_last_feedback = now;
 721        hcrx->ccid3hcrx_last_counter         = dccp_hdr(skb)->dccph_ccval;
 722        hcrx->ccid3hcrx_bytes_recv           = 0;
 723
 724        dp->dccps_hc_rx_insert_options = 1;
 725        dccp_send_ack(sk);
 726}
 727
 728static int ccid3_hc_rx_insert_options(struct sock *sk, struct sk_buff *skb)
 729{
 730        const struct ccid3_hc_rx_sock *hcrx;
 731        __be32 x_recv, pinv;
 732
 733        if (!(sk->sk_state == DCCP_OPEN || sk->sk_state == DCCP_PARTOPEN))
 734                return 0;
 735
 736        hcrx = ccid3_hc_rx_sk(sk);
 737
 738        if (dccp_packet_without_ack(skb))
 739                return 0;
 740
 741        x_recv = htonl(hcrx->ccid3hcrx_x_recv);
 742        pinv   = htonl(hcrx->ccid3hcrx_pinv);
 743
 744        if (dccp_insert_option(sk, skb, TFRC_OPT_LOSS_EVENT_RATE,
 745                               &pinv, sizeof(pinv)) ||
 746            dccp_insert_option(sk, skb, TFRC_OPT_RECEIVE_RATE,
 747                               &x_recv, sizeof(x_recv)))
 748                return -1;
 749
 750        return 0;
 751}
 752
 753/** ccid3_first_li  -  Implements [RFC 3448, 6.3.1]
 754 *
 755 * Determine the length of the first loss interval via inverse lookup.
 756 * Assume that X_recv can be computed by the throughput equation
 757 *                  s
 758 *      X_recv = --------
 759 *               R * fval
 760 * Find some p such that f(p) = fval; return 1/p (scaled).
 761 */
 762static u32 ccid3_first_li(struct sock *sk)
 763{
 764        struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
 765        u32 x_recv, p, delta;
 766        u64 fval;
 767
 768        if (hcrx->ccid3hcrx_rtt == 0) {
 769                DCCP_WARN("No RTT estimate available, using fallback RTT\n");
 770                hcrx->ccid3hcrx_rtt = DCCP_FALLBACK_RTT;
 771        }
 772
 773        delta = ktime_to_us(net_timedelta(hcrx->ccid3hcrx_tstamp_last_feedback));
 774        x_recv = scaled_div32(hcrx->ccid3hcrx_bytes_recv, delta);
 775        if (x_recv == 0) {              /* would also trigger divide-by-zero */
 776                DCCP_WARN("X_recv==0\n");
 777                if ((x_recv = hcrx->ccid3hcrx_x_recv) == 0) {
 778                        DCCP_BUG("stored value of X_recv is zero");
 779                        return ~0U;
 780                }
 781        }
 782
 783        fval = scaled_div(hcrx->ccid3hcrx_s, hcrx->ccid3hcrx_rtt);
 784        fval = scaled_div32(fval, x_recv);
 785        p = tfrc_calc_x_reverse_lookup(fval);
 786
 787        ccid3_pr_debug("%s(%p), receive rate=%u bytes/s, implied "
 788                       "loss rate=%u\n", dccp_role(sk), sk, x_recv, p);
 789
 790        return p == 0 ? ~0U : scaled_div(1, p);
 791}
 792
 793static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
 794{
 795        struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
 796        enum ccid3_fback_type do_feedback = CCID3_FBACK_NONE;
 797        const u64 ndp = dccp_sk(sk)->dccps_options_received.dccpor_ndp;
 798        const bool is_data_packet = dccp_data_packet(skb);
 799
 800        if (unlikely(hcrx->ccid3hcrx_state == TFRC_RSTATE_NO_DATA)) {
 801                if (is_data_packet) {
 802                        const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4;
 803                        do_feedback = CCID3_FBACK_INITIAL;
 804                        ccid3_hc_rx_set_state(sk, TFRC_RSTATE_DATA);
 805                        hcrx->ccid3hcrx_s = payload;
 806                        /*
 807                         * Not necessary to update ccid3hcrx_bytes_recv here,
 808                         * since X_recv = 0 for the first feedback packet (cf.
 809                         * RFC 3448, 6.3) -- gerrit
 810                         */
 811                }
 812                goto update_records;
 813        }
 814
 815        if (tfrc_rx_hist_duplicate(&hcrx->ccid3hcrx_hist, skb))
 816                return; /* done receiving */
 817
 818        if (is_data_packet) {
 819                const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4;
 820                /*
 821                 * Update moving-average of s and the sum of received payload bytes
 822                 */
 823                hcrx->ccid3hcrx_s = tfrc_ewma(hcrx->ccid3hcrx_s, payload, 9);
 824                hcrx->ccid3hcrx_bytes_recv += payload;
 825        }
 826
 827        /*
 828         * Perform loss detection and handle pending losses
 829         */
 830        if (tfrc_rx_handle_loss(&hcrx->ccid3hcrx_hist, &hcrx->ccid3hcrx_li_hist,
 831                                skb, ndp, ccid3_first_li, sk)) {
 832                do_feedback = CCID3_FBACK_PARAM_CHANGE;
 833                goto done_receiving;
 834        }
 835
 836        if (tfrc_rx_hist_loss_pending(&hcrx->ccid3hcrx_hist))
 837                return; /* done receiving */
 838
 839        /*
 840         * Handle data packets: RTT sampling and monitoring p
 841         */
 842        if (unlikely(!is_data_packet))
 843                goto update_records;
 844
 845        if (!tfrc_lh_is_initialised(&hcrx->ccid3hcrx_li_hist)) {
 846                const u32 sample = tfrc_rx_hist_sample_rtt(&hcrx->ccid3hcrx_hist, skb);
 847                /*
 848                 * Empty loss history: no loss so far, hence p stays 0.
 849                 * Sample RTT values, since an RTT estimate is required for the
 850                 * computation of p when the first loss occurs; RFC 3448, 6.3.1.
 851                 */
 852                if (sample != 0)
 853                        hcrx->ccid3hcrx_rtt = tfrc_ewma(hcrx->ccid3hcrx_rtt, sample, 9);
 854
 855        } else if (tfrc_lh_update_i_mean(&hcrx->ccid3hcrx_li_hist, skb)) {
 856                /*
 857                 * Step (3) of [RFC 3448, 6.1]: Recompute I_mean and, if I_mean
 858                 * has decreased (resp. p has increased), send feedback now.
 859                 */
 860                do_feedback = CCID3_FBACK_PARAM_CHANGE;
 861        }
 862
 863        /*
 864         * Check if the periodic once-per-RTT feedback is due; RFC 4342, 10.3
 865         */
 866        if (SUB16(dccp_hdr(skb)->dccph_ccval, hcrx->ccid3hcrx_last_counter) > 3)
 867                do_feedback = CCID3_FBACK_PERIODIC;
 868
 869update_records:
 870        tfrc_rx_hist_add_packet(&hcrx->ccid3hcrx_hist, skb, ndp);
 871
 872done_receiving:
 873        if (do_feedback)
 874                ccid3_hc_rx_send_feedback(sk, skb, do_feedback);
 875}
 876
 877static int ccid3_hc_rx_init(struct ccid *ccid, struct sock *sk)
 878{
 879        struct ccid3_hc_rx_sock *hcrx = ccid_priv(ccid);
 880
 881        hcrx->ccid3hcrx_state = TFRC_RSTATE_NO_DATA;
 882        tfrc_lh_init(&hcrx->ccid3hcrx_li_hist);
 883        return tfrc_rx_hist_alloc(&hcrx->ccid3hcrx_hist);
 884}
 885
 886static void ccid3_hc_rx_exit(struct sock *sk)
 887{
 888        struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
 889
 890        ccid3_hc_rx_set_state(sk, TFRC_RSTATE_TERM);
 891
 892        tfrc_rx_hist_purge(&hcrx->ccid3hcrx_hist);
 893        tfrc_lh_cleanup(&hcrx->ccid3hcrx_li_hist);
 894}
 895
 896static void ccid3_hc_rx_get_info(struct sock *sk, struct tcp_info *info)
 897{
 898        const struct ccid3_hc_rx_sock *hcrx;
 899
 900        /* Listen socks doesn't have a private CCID block */
 901        if (sk->sk_state == DCCP_LISTEN)
 902                return;
 903
 904        hcrx = ccid3_hc_rx_sk(sk);
 905        info->tcpi_ca_state = hcrx->ccid3hcrx_state;
 906        info->tcpi_options  |= TCPI_OPT_TIMESTAMPS;
 907        info->tcpi_rcv_rtt  = hcrx->ccid3hcrx_rtt;
 908}
 909
 910static int ccid3_hc_rx_getsockopt(struct sock *sk, const int optname, int len,
 911                                  u32 __user *optval, int __user *optlen)
 912{
 913        const struct ccid3_hc_rx_sock *hcrx;
 914        struct tfrc_rx_info rx_info;
 915        const void *val;
 916
 917        /* Listen socks doesn't have a private CCID block */
 918        if (sk->sk_state == DCCP_LISTEN)
 919                return -EINVAL;
 920
 921        hcrx = ccid3_hc_rx_sk(sk);
 922        switch (optname) {
 923        case DCCP_SOCKOPT_CCID_RX_INFO:
 924                if (len < sizeof(rx_info))
 925                        return -EINVAL;
 926                rx_info.tfrcrx_x_recv = hcrx->ccid3hcrx_x_recv;
 927                rx_info.tfrcrx_rtt    = hcrx->ccid3hcrx_rtt;
 928                rx_info.tfrcrx_p      = hcrx->ccid3hcrx_pinv == 0 ? ~0U :
 929                                           scaled_div(1, hcrx->ccid3hcrx_pinv);
 930                len = sizeof(rx_info);
 931                val = &rx_info;
 932                break;
 933        default:
 934                return -ENOPROTOOPT;
 935        }
 936
 937        if (put_user(len, optlen) || copy_to_user(optval, val, len))
 938                return -EFAULT;
 939
 940        return 0;
 941}
 942
 943struct ccid_operations ccid3_ops = {
 944        .ccid_id                   = DCCPC_CCID3,
 945        .ccid_name                 = "TCP-Friendly Rate Control",
 946        .ccid_hc_tx_obj_size       = sizeof(struct ccid3_hc_tx_sock),
 947        .ccid_hc_tx_init           = ccid3_hc_tx_init,
 948        .ccid_hc_tx_exit           = ccid3_hc_tx_exit,
 949        .ccid_hc_tx_send_packet    = ccid3_hc_tx_send_packet,
 950        .ccid_hc_tx_packet_sent    = ccid3_hc_tx_packet_sent,
 951        .ccid_hc_tx_packet_recv    = ccid3_hc_tx_packet_recv,
 952        .ccid_hc_tx_parse_options  = ccid3_hc_tx_parse_options,
 953        .ccid_hc_rx_obj_size       = sizeof(struct ccid3_hc_rx_sock),
 954        .ccid_hc_rx_init           = ccid3_hc_rx_init,
 955        .ccid_hc_rx_exit           = ccid3_hc_rx_exit,
 956        .ccid_hc_rx_insert_options = ccid3_hc_rx_insert_options,
 957        .ccid_hc_rx_packet_recv    = ccid3_hc_rx_packet_recv,
 958        .ccid_hc_rx_get_info       = ccid3_hc_rx_get_info,
 959        .ccid_hc_tx_get_info       = ccid3_hc_tx_get_info,
 960        .ccid_hc_rx_getsockopt     = ccid3_hc_rx_getsockopt,
 961        .ccid_hc_tx_getsockopt     = ccid3_hc_tx_getsockopt,
 962};
 963
 964#ifdef CONFIG_IP_DCCP_CCID3_DEBUG
 965module_param(ccid3_debug, bool, 0644);
 966MODULE_PARM_DESC(ccid3_debug, "Enable CCID-3 debug messages");
 967#endif
 968