linux/net/dccp/ccids/ccid3.c
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   1/*
   2 *  Copyright (c) 2007   The University of Aberdeen, Scotland, UK
   3 *  Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
   4 *  Copyright (c) 2005-7 Ian McDonald <ian.mcdonald@jandi.co.nz>
   5 *
   6 *  An implementation of the DCCP protocol
   7 *
   8 *  This code has been developed by the University of Waikato WAND
   9 *  research group. For further information please see http://www.wand.net.nz/
  10 *
  11 *  This code also uses code from Lulea University, rereleased as GPL by its
  12 *  authors:
  13 *  Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
  14 *
  15 *  Changes to meet Linux coding standards, to make it meet latest ccid3 draft
  16 *  and to make it work as a loadable module in the DCCP stack written by
  17 *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>.
  18 *
  19 *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
  20 *
  21 *  This program is free software; you can redistribute it and/or modify
  22 *  it under the terms of the GNU General Public License as published by
  23 *  the Free Software Foundation; either version 2 of the License, or
  24 *  (at your option) any later version.
  25 *
  26 *  This program is distributed in the hope that it will be useful,
  27 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  28 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  29 *  GNU General Public License for more details.
  30 *
  31 *  You should have received a copy of the GNU General Public License
  32 *  along with this program; if not, write to the Free Software
  33 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  34 */
  35#include "../dccp.h"
  36#include "ccid3.h"
  37
  38#include <asm/unaligned.h>
  39
  40#ifdef CONFIG_IP_DCCP_CCID3_DEBUG
  41static bool ccid3_debug;
  42#define ccid3_pr_debug(format, a...)    DCCP_PR_DEBUG(ccid3_debug, format, ##a)
  43#else
  44#define ccid3_pr_debug(format, a...)
  45#endif
  46
  47/*
  48 *      Transmitter Half-Connection Routines
  49 */
  50#ifdef CONFIG_IP_DCCP_CCID3_DEBUG
  51static const char *ccid3_tx_state_name(enum ccid3_hc_tx_states state)
  52{
  53        static const char *const ccid3_state_names[] = {
  54        [TFRC_SSTATE_NO_SENT]  = "NO_SENT",
  55        [TFRC_SSTATE_NO_FBACK] = "NO_FBACK",
  56        [TFRC_SSTATE_FBACK]    = "FBACK",
  57        };
  58
  59        return ccid3_state_names[state];
  60}
  61#endif
  62
  63static void ccid3_hc_tx_set_state(struct sock *sk,
  64                                  enum ccid3_hc_tx_states state)
  65{
  66        struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
  67        enum ccid3_hc_tx_states oldstate = hc->tx_state;
  68
  69        ccid3_pr_debug("%s(%p) %-8.8s -> %s\n",
  70                       dccp_role(sk), sk, ccid3_tx_state_name(oldstate),
  71                       ccid3_tx_state_name(state));
  72        WARN_ON(state == oldstate);
  73        hc->tx_state = state;
  74}
  75
  76/*
  77 * Compute the initial sending rate X_init in the manner of RFC 3390:
  78 *
  79 *      X_init  =  min(4 * s, max(2 * s, 4380 bytes)) / RTT
  80 *
  81 * Note that RFC 3390 uses MSS, RFC 4342 refers to RFC 3390, and rfc3448bis
  82 * (rev-02) clarifies the use of RFC 3390 with regard to the above formula.
  83 * For consistency with other parts of the code, X_init is scaled by 2^6.
  84 */
  85static inline u64 rfc3390_initial_rate(struct sock *sk)
  86{
  87        const struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
  88        const __u32 w_init = clamp_t(__u32, 4380U, 2 * hc->tx_s, 4 * hc->tx_s);
  89
  90        return scaled_div(w_init << 6, hc->tx_rtt);
  91}
  92
  93/**
  94 * ccid3_update_send_interval  -  Calculate new t_ipi = s / X_inst
  95 * This respects the granularity of X_inst (64 * bytes/second).
  96 */
  97static void ccid3_update_send_interval(struct ccid3_hc_tx_sock *hc)
  98{
  99        hc->tx_t_ipi = scaled_div32(((u64)hc->tx_s) << 6, hc->tx_x);
 100
 101        DCCP_BUG_ON(hc->tx_t_ipi == 0);
 102        ccid3_pr_debug("t_ipi=%u, s=%u, X=%u\n", hc->tx_t_ipi,
 103                       hc->tx_s, (unsigned int)(hc->tx_x >> 6));
 104}
 105
 106static u32 ccid3_hc_tx_idle_rtt(struct ccid3_hc_tx_sock *hc, ktime_t now)
 107{
 108        u32 delta = ktime_us_delta(now, hc->tx_t_last_win_count);
 109
 110        return delta / hc->tx_rtt;
 111}
 112
 113/**
 114 * ccid3_hc_tx_update_x  -  Update allowed sending rate X
 115 * @stamp: most recent time if available - can be left NULL.
 116 *
 117 * This function tracks draft rfc3448bis, check there for latest details.
 118 *
 119 * Note: X and X_recv are both stored in units of 64 * bytes/second, to support
 120 *       fine-grained resolution of sending rates. This requires scaling by 2^6
 121 *       throughout the code. Only X_calc is unscaled (in bytes/second).
 122 *
 123 */
 124static void ccid3_hc_tx_update_x(struct sock *sk, ktime_t *stamp)
 125{
 126        struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
 127        __u64 min_rate = 2 * hc->tx_x_recv;
 128        const __u64 old_x = hc->tx_x;
 129        ktime_t now = stamp ? *stamp : ktime_get_real();
 130
 131        /*
 132         * Handle IDLE periods: do not reduce below RFC3390 initial sending rate
 133         * when idling [RFC 4342, 5.1]. Definition of idling is from rfc3448bis:
 134         * a sender is idle if it has not sent anything over a 2-RTT-period.
 135         * For consistency with X and X_recv, min_rate is also scaled by 2^6.
 136         */
 137        if (ccid3_hc_tx_idle_rtt(hc, now) >= 2) {
 138                min_rate = rfc3390_initial_rate(sk);
 139                min_rate = max(min_rate, 2 * hc->tx_x_recv);
 140        }
 141
 142        if (hc->tx_p > 0) {
 143
 144                hc->tx_x = min(((__u64)hc->tx_x_calc) << 6, min_rate);
 145                hc->tx_x = max(hc->tx_x, (((__u64)hc->tx_s) << 6) / TFRC_T_MBI);
 146
 147        } else if (ktime_us_delta(now, hc->tx_t_ld) - (s64)hc->tx_rtt >= 0) {
 148
 149                hc->tx_x = min(2 * hc->tx_x, min_rate);
 150                hc->tx_x = max(hc->tx_x,
 151                               scaled_div(((__u64)hc->tx_s) << 6, hc->tx_rtt));
 152                hc->tx_t_ld = now;
 153        }
 154
 155        if (hc->tx_x != old_x) {
 156                ccid3_pr_debug("X_prev=%u, X_now=%u, X_calc=%u, "
 157                               "X_recv=%u\n", (unsigned int)(old_x >> 6),
 158                               (unsigned int)(hc->tx_x >> 6), hc->tx_x_calc,
 159                               (unsigned int)(hc->tx_x_recv >> 6));
 160
 161                ccid3_update_send_interval(hc);
 162        }
 163}
 164
 165/**
 166 *      ccid3_hc_tx_update_s - Track the mean packet size `s'
 167 *      @len: DCCP packet payload size in bytes
 168 *
 169 *      cf. RFC 4342, 5.3 and  RFC 3448, 4.1
 170 */
 171static inline void ccid3_hc_tx_update_s(struct ccid3_hc_tx_sock *hc, int len)
 172{
 173        const u16 old_s = hc->tx_s;
 174
 175        hc->tx_s = tfrc_ewma(hc->tx_s, len, 9);
 176
 177        if (hc->tx_s != old_s)
 178                ccid3_update_send_interval(hc);
 179}
 180
 181/*
 182 *      Update Window Counter using the algorithm from [RFC 4342, 8.1].
 183 *      As elsewhere, RTT > 0 is assumed by using dccp_sample_rtt().
 184 */
 185static inline void ccid3_hc_tx_update_win_count(struct ccid3_hc_tx_sock *hc,
 186                                                ktime_t now)
 187{
 188        u32 delta = ktime_us_delta(now, hc->tx_t_last_win_count),
 189            quarter_rtts = (4 * delta) / hc->tx_rtt;
 190
 191        if (quarter_rtts > 0) {
 192                hc->tx_t_last_win_count = now;
 193                hc->tx_last_win_count  += min(quarter_rtts, 5U);
 194                hc->tx_last_win_count  &= 0xF;          /* mod 16 */
 195        }
 196}
 197
 198static void ccid3_hc_tx_no_feedback_timer(struct timer_list *t)
 199{
 200        struct ccid3_hc_tx_sock *hc = from_timer(hc, t, tx_no_feedback_timer);
 201        struct sock *sk = hc->sk;
 202        unsigned long t_nfb = USEC_PER_SEC / 5;
 203
 204        bh_lock_sock(sk);
 205        if (sock_owned_by_user(sk)) {
 206                /* Try again later. */
 207                /* XXX: set some sensible MIB */
 208                goto restart_timer;
 209        }
 210
 211        ccid3_pr_debug("%s(%p, state=%s) - entry\n", dccp_role(sk), sk,
 212                       ccid3_tx_state_name(hc->tx_state));
 213
 214        /* Ignore and do not restart after leaving the established state */
 215        if ((1 << sk->sk_state) & ~(DCCPF_OPEN | DCCPF_PARTOPEN))
 216                goto out;
 217
 218        /* Reset feedback state to "no feedback received" */
 219        if (hc->tx_state == TFRC_SSTATE_FBACK)
 220                ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);
 221
 222        /*
 223         * Determine new allowed sending rate X as per draft rfc3448bis-00, 4.4
 224         * RTO is 0 if and only if no feedback has been received yet.
 225         */
 226        if (hc->tx_t_rto == 0 || hc->tx_p == 0) {
 227
 228                /* halve send rate directly */
 229                hc->tx_x = max(hc->tx_x / 2,
 230                               (((__u64)hc->tx_s) << 6) / TFRC_T_MBI);
 231                ccid3_update_send_interval(hc);
 232        } else {
 233                /*
 234                 *  Modify the cached value of X_recv
 235                 *
 236                 *  If (X_calc > 2 * X_recv)
 237                 *    X_recv = max(X_recv / 2, s / (2 * t_mbi));
 238                 *  Else
 239                 *    X_recv = X_calc / 4;
 240                 *
 241                 *  Note that X_recv is scaled by 2^6 while X_calc is not
 242                 */
 243                if (hc->tx_x_calc > (hc->tx_x_recv >> 5))
 244                        hc->tx_x_recv =
 245                                max(hc->tx_x_recv / 2,
 246                                    (((__u64)hc->tx_s) << 6) / (2*TFRC_T_MBI));
 247                else {
 248                        hc->tx_x_recv = hc->tx_x_calc;
 249                        hc->tx_x_recv <<= 4;
 250                }
 251                ccid3_hc_tx_update_x(sk, NULL);
 252        }
 253        ccid3_pr_debug("Reduced X to %llu/64 bytes/sec\n",
 254                        (unsigned long long)hc->tx_x);
 255
 256        /*
 257         * Set new timeout for the nofeedback timer.
 258         * See comments in packet_recv() regarding the value of t_RTO.
 259         */
 260        if (unlikely(hc->tx_t_rto == 0))        /* no feedback received yet */
 261                t_nfb = TFRC_INITIAL_TIMEOUT;
 262        else
 263                t_nfb = max(hc->tx_t_rto, 2 * hc->tx_t_ipi);
 264
 265restart_timer:
 266        sk_reset_timer(sk, &hc->tx_no_feedback_timer,
 267                           jiffies + usecs_to_jiffies(t_nfb));
 268out:
 269        bh_unlock_sock(sk);
 270        sock_put(sk);
 271}
 272
 273/**
 274 * ccid3_hc_tx_send_packet  -  Delay-based dequeueing of TX packets
 275 * @skb: next packet candidate to send on @sk
 276 *
 277 * This function uses the convention of ccid_packet_dequeue_eval() and
 278 * returns a millisecond-delay value between 0 and t_mbi = 64000 msec.
 279 */
 280static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
 281{
 282        struct dccp_sock *dp = dccp_sk(sk);
 283        struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
 284        ktime_t now = ktime_get_real();
 285        s64 delay;
 286
 287        /*
 288         * This function is called only for Data and DataAck packets. Sending
 289         * zero-sized Data(Ack)s is theoretically possible, but for congestion
 290         * control this case is pathological - ignore it.
 291         */
 292        if (unlikely(skb->len == 0))
 293                return -EBADMSG;
 294
 295        if (hc->tx_state == TFRC_SSTATE_NO_SENT) {
 296                sk_reset_timer(sk, &hc->tx_no_feedback_timer, (jiffies +
 297                               usecs_to_jiffies(TFRC_INITIAL_TIMEOUT)));
 298                hc->tx_last_win_count   = 0;
 299                hc->tx_t_last_win_count = now;
 300
 301                /* Set t_0 for initial packet */
 302                hc->tx_t_nom = now;
 303
 304                hc->tx_s = skb->len;
 305
 306                /*
 307                 * Use initial RTT sample when available: recommended by erratum
 308                 * to RFC 4342. This implements the initialisation procedure of
 309                 * draft rfc3448bis, section 4.2. Remember, X is scaled by 2^6.
 310                 */
 311                if (dp->dccps_syn_rtt) {
 312                        ccid3_pr_debug("SYN RTT = %uus\n", dp->dccps_syn_rtt);
 313                        hc->tx_rtt  = dp->dccps_syn_rtt;
 314                        hc->tx_x    = rfc3390_initial_rate(sk);
 315                        hc->tx_t_ld = now;
 316                } else {
 317                        /*
 318                         * Sender does not have RTT sample:
 319                         * - set fallback RTT (RFC 4340, 3.4) since a RTT value
 320                         *   is needed in several parts (e.g.  window counter);
 321                         * - set sending rate X_pps = 1pps as per RFC 3448, 4.2.
 322                         */
 323                        hc->tx_rtt = DCCP_FALLBACK_RTT;
 324                        hc->tx_x   = hc->tx_s;
 325                        hc->tx_x <<= 6;
 326                }
 327                ccid3_update_send_interval(hc);
 328
 329                ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);
 330
 331        } else {
 332                delay = ktime_us_delta(hc->tx_t_nom, now);
 333                ccid3_pr_debug("delay=%ld\n", (long)delay);
 334                /*
 335                 *      Scheduling of packet transmissions (RFC 5348, 8.3)
 336                 *
 337                 * if (t_now > t_nom - delta)
 338                 *       // send the packet now
 339                 * else
 340                 *       // send the packet in (t_nom - t_now) milliseconds.
 341                 */
 342                if (delay >= TFRC_T_DELTA)
 343                        return (u32)delay / USEC_PER_MSEC;
 344
 345                ccid3_hc_tx_update_win_count(hc, now);
 346        }
 347
 348        /* prepare to send now (add options etc.) */
 349        dp->dccps_hc_tx_insert_options = 1;
 350        DCCP_SKB_CB(skb)->dccpd_ccval  = hc->tx_last_win_count;
 351
 352        /* set the nominal send time for the next following packet */
 353        hc->tx_t_nom = ktime_add_us(hc->tx_t_nom, hc->tx_t_ipi);
 354        return CCID_PACKET_SEND_AT_ONCE;
 355}
 356
 357static void ccid3_hc_tx_packet_sent(struct sock *sk, unsigned int len)
 358{
 359        struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
 360
 361        ccid3_hc_tx_update_s(hc, len);
 362
 363        if (tfrc_tx_hist_add(&hc->tx_hist, dccp_sk(sk)->dccps_gss))
 364                DCCP_CRIT("packet history - out of memory!");
 365}
 366
 367static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
 368{
 369        struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
 370        struct tfrc_tx_hist_entry *acked;
 371        ktime_t now;
 372        unsigned long t_nfb;
 373        u32 r_sample;
 374
 375        /* we are only interested in ACKs */
 376        if (!(DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_ACK ||
 377              DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_DATAACK))
 378                return;
 379        /*
 380         * Locate the acknowledged packet in the TX history.
 381         *
 382         * Returning "entry not found" here can for instance happen when
 383         *  - the host has not sent out anything (e.g. a passive server),
 384         *  - the Ack is outdated (packet with higher Ack number was received),
 385         *  - it is a bogus Ack (for a packet not sent on this connection).
 386         */
 387        acked = tfrc_tx_hist_find_entry(hc->tx_hist, dccp_hdr_ack_seq(skb));
 388        if (acked == NULL)
 389                return;
 390        /* For the sake of RTT sampling, ignore/remove all older entries */
 391        tfrc_tx_hist_purge(&acked->next);
 392
 393        /* Update the moving average for the RTT estimate (RFC 3448, 4.3) */
 394        now       = ktime_get_real();
 395        r_sample  = dccp_sample_rtt(sk, ktime_us_delta(now, acked->stamp));
 396        hc->tx_rtt = tfrc_ewma(hc->tx_rtt, r_sample, 9);
 397
 398        /*
 399         * Update allowed sending rate X as per draft rfc3448bis-00, 4.2/3
 400         */
 401        if (hc->tx_state == TFRC_SSTATE_NO_FBACK) {
 402                ccid3_hc_tx_set_state(sk, TFRC_SSTATE_FBACK);
 403
 404                if (hc->tx_t_rto == 0) {
 405                        /*
 406                         * Initial feedback packet: Larger Initial Windows (4.2)
 407                         */
 408                        hc->tx_x    = rfc3390_initial_rate(sk);
 409                        hc->tx_t_ld = now;
 410
 411                        ccid3_update_send_interval(hc);
 412
 413                        goto done_computing_x;
 414                } else if (hc->tx_p == 0) {
 415                        /*
 416                         * First feedback after nofeedback timer expiry (4.3)
 417                         */
 418                        goto done_computing_x;
 419                }
 420        }
 421
 422        /* Update sending rate (step 4 of [RFC 3448, 4.3]) */
 423        if (hc->tx_p > 0)
 424                hc->tx_x_calc = tfrc_calc_x(hc->tx_s, hc->tx_rtt, hc->tx_p);
 425        ccid3_hc_tx_update_x(sk, &now);
 426
 427done_computing_x:
 428        ccid3_pr_debug("%s(%p), RTT=%uus (sample=%uus), s=%u, "
 429                               "p=%u, X_calc=%u, X_recv=%u, X=%u\n",
 430                               dccp_role(sk), sk, hc->tx_rtt, r_sample,
 431                               hc->tx_s, hc->tx_p, hc->tx_x_calc,
 432                               (unsigned int)(hc->tx_x_recv >> 6),
 433                               (unsigned int)(hc->tx_x >> 6));
 434
 435        /* unschedule no feedback timer */
 436        sk_stop_timer(sk, &hc->tx_no_feedback_timer);
 437
 438        /*
 439         * As we have calculated new ipi, delta, t_nom it is possible
 440         * that we now can send a packet, so wake up dccp_wait_for_ccid
 441         */
 442        sk->sk_write_space(sk);
 443
 444        /*
 445         * Update timeout interval for the nofeedback timer. In order to control
 446         * rate halving on networks with very low RTTs (<= 1 ms), use per-route
 447         * tunable RTAX_RTO_MIN value as the lower bound.
 448         */
 449        hc->tx_t_rto = max_t(u32, 4 * hc->tx_rtt,
 450                                  USEC_PER_SEC/HZ * tcp_rto_min(sk));
 451        /*
 452         * Schedule no feedback timer to expire in
 453         * max(t_RTO, 2 * s/X)  =  max(t_RTO, 2 * t_ipi)
 454         */
 455        t_nfb = max(hc->tx_t_rto, 2 * hc->tx_t_ipi);
 456
 457        ccid3_pr_debug("%s(%p), Scheduled no feedback timer to "
 458                       "expire in %lu jiffies (%luus)\n",
 459                       dccp_role(sk), sk, usecs_to_jiffies(t_nfb), t_nfb);
 460
 461        sk_reset_timer(sk, &hc->tx_no_feedback_timer,
 462                           jiffies + usecs_to_jiffies(t_nfb));
 463}
 464
 465static int ccid3_hc_tx_parse_options(struct sock *sk, u8 packet_type,
 466                                     u8 option, u8 *optval, u8 optlen)
 467{
 468        struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
 469        __be32 opt_val;
 470
 471        switch (option) {
 472        case TFRC_OPT_RECEIVE_RATE:
 473        case TFRC_OPT_LOSS_EVENT_RATE:
 474                /* Must be ignored on Data packets, cf. RFC 4342 8.3 and 8.5 */
 475                if (packet_type == DCCP_PKT_DATA)
 476                        break;
 477                if (unlikely(optlen != 4)) {
 478                        DCCP_WARN("%s(%p), invalid len %d for %u\n",
 479                                  dccp_role(sk), sk, optlen, option);
 480                        return -EINVAL;
 481                }
 482                opt_val = ntohl(get_unaligned((__be32 *)optval));
 483
 484                if (option == TFRC_OPT_RECEIVE_RATE) {
 485                        /* Receive Rate is kept in units of 64 bytes/second */
 486                        hc->tx_x_recv = opt_val;
 487                        hc->tx_x_recv <<= 6;
 488
 489                        ccid3_pr_debug("%s(%p), RECEIVE_RATE=%u\n",
 490                                       dccp_role(sk), sk, opt_val);
 491                } else {
 492                        /* Update the fixpoint Loss Event Rate fraction */
 493                        hc->tx_p = tfrc_invert_loss_event_rate(opt_val);
 494
 495                        ccid3_pr_debug("%s(%p), LOSS_EVENT_RATE=%u\n",
 496                                       dccp_role(sk), sk, opt_val);
 497                }
 498        }
 499        return 0;
 500}
 501
 502static int ccid3_hc_tx_init(struct ccid *ccid, struct sock *sk)
 503{
 504        struct ccid3_hc_tx_sock *hc = ccid_priv(ccid);
 505
 506        hc->tx_state = TFRC_SSTATE_NO_SENT;
 507        hc->tx_hist  = NULL;
 508        hc->sk       = sk;
 509        timer_setup(&hc->tx_no_feedback_timer,
 510                    ccid3_hc_tx_no_feedback_timer, 0);
 511        return 0;
 512}
 513
 514static void ccid3_hc_tx_exit(struct sock *sk)
 515{
 516        struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
 517
 518        sk_stop_timer(sk, &hc->tx_no_feedback_timer);
 519        tfrc_tx_hist_purge(&hc->tx_hist);
 520}
 521
 522static void ccid3_hc_tx_get_info(struct sock *sk, struct tcp_info *info)
 523{
 524        info->tcpi_rto = ccid3_hc_tx_sk(sk)->tx_t_rto;
 525        info->tcpi_rtt = ccid3_hc_tx_sk(sk)->tx_rtt;
 526}
 527
 528static int ccid3_hc_tx_getsockopt(struct sock *sk, const int optname, int len,
 529                                  u32 __user *optval, int __user *optlen)
 530{
 531        const struct ccid3_hc_tx_sock *hc = ccid3_hc_tx_sk(sk);
 532        struct tfrc_tx_info tfrc;
 533        const void *val;
 534
 535        switch (optname) {
 536        case DCCP_SOCKOPT_CCID_TX_INFO:
 537                if (len < sizeof(tfrc))
 538                        return -EINVAL;
 539                memset(&tfrc, 0, sizeof(tfrc));
 540                tfrc.tfrctx_x      = hc->tx_x;
 541                tfrc.tfrctx_x_recv = hc->tx_x_recv;
 542                tfrc.tfrctx_x_calc = hc->tx_x_calc;
 543                tfrc.tfrctx_rtt    = hc->tx_rtt;
 544                tfrc.tfrctx_p      = hc->tx_p;
 545                tfrc.tfrctx_rto    = hc->tx_t_rto;
 546                tfrc.tfrctx_ipi    = hc->tx_t_ipi;
 547                len = sizeof(tfrc);
 548                val = &tfrc;
 549                break;
 550        default:
 551                return -ENOPROTOOPT;
 552        }
 553
 554        if (put_user(len, optlen) || copy_to_user(optval, val, len))
 555                return -EFAULT;
 556
 557        return 0;
 558}
 559
 560/*
 561 *      Receiver Half-Connection Routines
 562 */
 563
 564/* CCID3 feedback types */
 565enum ccid3_fback_type {
 566        CCID3_FBACK_NONE = 0,
 567        CCID3_FBACK_INITIAL,
 568        CCID3_FBACK_PERIODIC,
 569        CCID3_FBACK_PARAM_CHANGE
 570};
 571
 572#ifdef CONFIG_IP_DCCP_CCID3_DEBUG
 573static const char *ccid3_rx_state_name(enum ccid3_hc_rx_states state)
 574{
 575        static const char *const ccid3_rx_state_names[] = {
 576        [TFRC_RSTATE_NO_DATA] = "NO_DATA",
 577        [TFRC_RSTATE_DATA]    = "DATA",
 578        };
 579
 580        return ccid3_rx_state_names[state];
 581}
 582#endif
 583
 584static void ccid3_hc_rx_set_state(struct sock *sk,
 585                                  enum ccid3_hc_rx_states state)
 586{
 587        struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
 588        enum ccid3_hc_rx_states oldstate = hc->rx_state;
 589
 590        ccid3_pr_debug("%s(%p) %-8.8s -> %s\n",
 591                       dccp_role(sk), sk, ccid3_rx_state_name(oldstate),
 592                       ccid3_rx_state_name(state));
 593        WARN_ON(state == oldstate);
 594        hc->rx_state = state;
 595}
 596
 597static void ccid3_hc_rx_send_feedback(struct sock *sk,
 598                                      const struct sk_buff *skb,
 599                                      enum ccid3_fback_type fbtype)
 600{
 601        struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
 602        struct dccp_sock *dp = dccp_sk(sk);
 603        ktime_t now = ktime_get();
 604        s64 delta = 0;
 605
 606        switch (fbtype) {
 607        case CCID3_FBACK_INITIAL:
 608                hc->rx_x_recv = 0;
 609                hc->rx_pinv   = ~0U;   /* see RFC 4342, 8.5 */
 610                break;
 611        case CCID3_FBACK_PARAM_CHANGE:
 612                /*
 613                 * When parameters change (new loss or p > p_prev), we do not
 614                 * have a reliable estimate for R_m of [RFC 3448, 6.2] and so
 615                 * need to  reuse the previous value of X_recv. However, when
 616                 * X_recv was 0 (due to early loss), this would kill X down to
 617                 * s/t_mbi (i.e. one packet in 64 seconds).
 618                 * To avoid such drastic reduction, we approximate X_recv as
 619                 * the number of bytes since last feedback.
 620                 * This is a safe fallback, since X is bounded above by X_calc.
 621                 */
 622                if (hc->rx_x_recv > 0)
 623                        break;
 624                /* fall through */
 625        case CCID3_FBACK_PERIODIC:
 626                delta = ktime_us_delta(now, hc->rx_tstamp_last_feedback);
 627                if (delta <= 0)
 628                        delta = 1;
 629                hc->rx_x_recv = scaled_div32(hc->rx_bytes_recv, delta);
 630                break;
 631        default:
 632                return;
 633        }
 634
 635        ccid3_pr_debug("Interval %lldusec, X_recv=%u, 1/p=%u\n", delta,
 636                       hc->rx_x_recv, hc->rx_pinv);
 637
 638        hc->rx_tstamp_last_feedback = now;
 639        hc->rx_last_counter         = dccp_hdr(skb)->dccph_ccval;
 640        hc->rx_bytes_recv           = 0;
 641
 642        dp->dccps_hc_rx_insert_options = 1;
 643        dccp_send_ack(sk);
 644}
 645
 646static int ccid3_hc_rx_insert_options(struct sock *sk, struct sk_buff *skb)
 647{
 648        const struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
 649        __be32 x_recv, pinv;
 650
 651        if (!(sk->sk_state == DCCP_OPEN || sk->sk_state == DCCP_PARTOPEN))
 652                return 0;
 653
 654        if (dccp_packet_without_ack(skb))
 655                return 0;
 656
 657        x_recv = htonl(hc->rx_x_recv);
 658        pinv   = htonl(hc->rx_pinv);
 659
 660        if (dccp_insert_option(skb, TFRC_OPT_LOSS_EVENT_RATE,
 661                               &pinv, sizeof(pinv)) ||
 662            dccp_insert_option(skb, TFRC_OPT_RECEIVE_RATE,
 663                               &x_recv, sizeof(x_recv)))
 664                return -1;
 665
 666        return 0;
 667}
 668
 669/**
 670 * ccid3_first_li  -  Implements [RFC 5348, 6.3.1]
 671 *
 672 * Determine the length of the first loss interval via inverse lookup.
 673 * Assume that X_recv can be computed by the throughput equation
 674 *                  s
 675 *      X_recv = --------
 676 *               R * fval
 677 * Find some p such that f(p) = fval; return 1/p (scaled).
 678 */
 679static u32 ccid3_first_li(struct sock *sk)
 680{
 681        struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
 682        u32 x_recv, p;
 683        s64 delta;
 684        u64 fval;
 685
 686        if (hc->rx_rtt == 0) {
 687                DCCP_WARN("No RTT estimate available, using fallback RTT\n");
 688                hc->rx_rtt = DCCP_FALLBACK_RTT;
 689        }
 690
 691        delta = ktime_us_delta(ktime_get(), hc->rx_tstamp_last_feedback);
 692        if (delta <= 0)
 693                delta = 1;
 694        x_recv = scaled_div32(hc->rx_bytes_recv, delta);
 695        if (x_recv == 0) {              /* would also trigger divide-by-zero */
 696                DCCP_WARN("X_recv==0\n");
 697                if (hc->rx_x_recv == 0) {
 698                        DCCP_BUG("stored value of X_recv is zero");
 699                        return ~0U;
 700                }
 701                x_recv = hc->rx_x_recv;
 702        }
 703
 704        fval = scaled_div(hc->rx_s, hc->rx_rtt);
 705        fval = scaled_div32(fval, x_recv);
 706        p = tfrc_calc_x_reverse_lookup(fval);
 707
 708        ccid3_pr_debug("%s(%p), receive rate=%u bytes/s, implied "
 709                       "loss rate=%u\n", dccp_role(sk), sk, x_recv, p);
 710
 711        return p == 0 ? ~0U : scaled_div(1, p);
 712}
 713
 714static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
 715{
 716        struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
 717        enum ccid3_fback_type do_feedback = CCID3_FBACK_NONE;
 718        const u64 ndp = dccp_sk(sk)->dccps_options_received.dccpor_ndp;
 719        const bool is_data_packet = dccp_data_packet(skb);
 720
 721        if (unlikely(hc->rx_state == TFRC_RSTATE_NO_DATA)) {
 722                if (is_data_packet) {
 723                        const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4;
 724                        do_feedback = CCID3_FBACK_INITIAL;
 725                        ccid3_hc_rx_set_state(sk, TFRC_RSTATE_DATA);
 726                        hc->rx_s = payload;
 727                        /*
 728                         * Not necessary to update rx_bytes_recv here,
 729                         * since X_recv = 0 for the first feedback packet (cf.
 730                         * RFC 3448, 6.3) -- gerrit
 731                         */
 732                }
 733                goto update_records;
 734        }
 735
 736        if (tfrc_rx_hist_duplicate(&hc->rx_hist, skb))
 737                return; /* done receiving */
 738
 739        if (is_data_packet) {
 740                const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4;
 741                /*
 742                 * Update moving-average of s and the sum of received payload bytes
 743                 */
 744                hc->rx_s = tfrc_ewma(hc->rx_s, payload, 9);
 745                hc->rx_bytes_recv += payload;
 746        }
 747
 748        /*
 749         * Perform loss detection and handle pending losses
 750         */
 751        if (tfrc_rx_handle_loss(&hc->rx_hist, &hc->rx_li_hist,
 752                                skb, ndp, ccid3_first_li, sk)) {
 753                do_feedback = CCID3_FBACK_PARAM_CHANGE;
 754                goto done_receiving;
 755        }
 756
 757        if (tfrc_rx_hist_loss_pending(&hc->rx_hist))
 758                return; /* done receiving */
 759
 760        /*
 761         * Handle data packets: RTT sampling and monitoring p
 762         */
 763        if (unlikely(!is_data_packet))
 764                goto update_records;
 765
 766        if (!tfrc_lh_is_initialised(&hc->rx_li_hist)) {
 767                const u32 sample = tfrc_rx_hist_sample_rtt(&hc->rx_hist, skb);
 768                /*
 769                 * Empty loss history: no loss so far, hence p stays 0.
 770                 * Sample RTT values, since an RTT estimate is required for the
 771                 * computation of p when the first loss occurs; RFC 3448, 6.3.1.
 772                 */
 773                if (sample != 0)
 774                        hc->rx_rtt = tfrc_ewma(hc->rx_rtt, sample, 9);
 775
 776        } else if (tfrc_lh_update_i_mean(&hc->rx_li_hist, skb)) {
 777                /*
 778                 * Step (3) of [RFC 3448, 6.1]: Recompute I_mean and, if I_mean
 779                 * has decreased (resp. p has increased), send feedback now.
 780                 */
 781                do_feedback = CCID3_FBACK_PARAM_CHANGE;
 782        }
 783
 784        /*
 785         * Check if the periodic once-per-RTT feedback is due; RFC 4342, 10.3
 786         */
 787        if (SUB16(dccp_hdr(skb)->dccph_ccval, hc->rx_last_counter) > 3)
 788                do_feedback = CCID3_FBACK_PERIODIC;
 789
 790update_records:
 791        tfrc_rx_hist_add_packet(&hc->rx_hist, skb, ndp);
 792
 793done_receiving:
 794        if (do_feedback)
 795                ccid3_hc_rx_send_feedback(sk, skb, do_feedback);
 796}
 797
 798static int ccid3_hc_rx_init(struct ccid *ccid, struct sock *sk)
 799{
 800        struct ccid3_hc_rx_sock *hc = ccid_priv(ccid);
 801
 802        hc->rx_state = TFRC_RSTATE_NO_DATA;
 803        tfrc_lh_init(&hc->rx_li_hist);
 804        return tfrc_rx_hist_alloc(&hc->rx_hist);
 805}
 806
 807static void ccid3_hc_rx_exit(struct sock *sk)
 808{
 809        struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
 810
 811        tfrc_rx_hist_purge(&hc->rx_hist);
 812        tfrc_lh_cleanup(&hc->rx_li_hist);
 813}
 814
 815static void ccid3_hc_rx_get_info(struct sock *sk, struct tcp_info *info)
 816{
 817        info->tcpi_ca_state = ccid3_hc_rx_sk(sk)->rx_state;
 818        info->tcpi_options  |= TCPI_OPT_TIMESTAMPS;
 819        info->tcpi_rcv_rtt  = ccid3_hc_rx_sk(sk)->rx_rtt;
 820}
 821
 822static int ccid3_hc_rx_getsockopt(struct sock *sk, const int optname, int len,
 823                                  u32 __user *optval, int __user *optlen)
 824{
 825        const struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
 826        struct tfrc_rx_info rx_info;
 827        const void *val;
 828
 829        switch (optname) {
 830        case DCCP_SOCKOPT_CCID_RX_INFO:
 831                if (len < sizeof(rx_info))
 832                        return -EINVAL;
 833                rx_info.tfrcrx_x_recv = hc->rx_x_recv;
 834                rx_info.tfrcrx_rtt    = hc->rx_rtt;
 835                rx_info.tfrcrx_p      = tfrc_invert_loss_event_rate(hc->rx_pinv);
 836                len = sizeof(rx_info);
 837                val = &rx_info;
 838                break;
 839        default:
 840                return -ENOPROTOOPT;
 841        }
 842
 843        if (put_user(len, optlen) || copy_to_user(optval, val, len))
 844                return -EFAULT;
 845
 846        return 0;
 847}
 848
 849struct ccid_operations ccid3_ops = {
 850        .ccid_id                   = DCCPC_CCID3,
 851        .ccid_name                 = "TCP-Friendly Rate Control",
 852        .ccid_hc_tx_obj_size       = sizeof(struct ccid3_hc_tx_sock),
 853        .ccid_hc_tx_init           = ccid3_hc_tx_init,
 854        .ccid_hc_tx_exit           = ccid3_hc_tx_exit,
 855        .ccid_hc_tx_send_packet    = ccid3_hc_tx_send_packet,
 856        .ccid_hc_tx_packet_sent    = ccid3_hc_tx_packet_sent,
 857        .ccid_hc_tx_packet_recv    = ccid3_hc_tx_packet_recv,
 858        .ccid_hc_tx_parse_options  = ccid3_hc_tx_parse_options,
 859        .ccid_hc_rx_obj_size       = sizeof(struct ccid3_hc_rx_sock),
 860        .ccid_hc_rx_init           = ccid3_hc_rx_init,
 861        .ccid_hc_rx_exit           = ccid3_hc_rx_exit,
 862        .ccid_hc_rx_insert_options = ccid3_hc_rx_insert_options,
 863        .ccid_hc_rx_packet_recv    = ccid3_hc_rx_packet_recv,
 864        .ccid_hc_rx_get_info       = ccid3_hc_rx_get_info,
 865        .ccid_hc_tx_get_info       = ccid3_hc_tx_get_info,
 866        .ccid_hc_rx_getsockopt     = ccid3_hc_rx_getsockopt,
 867        .ccid_hc_tx_getsockopt     = ccid3_hc_tx_getsockopt,
 868};
 869
 870#ifdef CONFIG_IP_DCCP_CCID3_DEBUG
 871module_param(ccid3_debug, bool, 0644);
 872MODULE_PARM_DESC(ccid3_debug, "Enable CCID-3 debug messages");
 873#endif
 874