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ccid3.c

/*
 *  net/dccp/ccids/ccid3.c
 *
 *  Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
 *  Copyright (c) 2005-7 Ian McDonald <ian.mcdonald@jandi.co.nz>
 *
 *  An implementation of the DCCP protocol
 *
 *  This code has been developed by the University of Waikato WAND
 *  research group. For further information please see http://www.wand.net.nz/
 *
 *  This code also uses code from Lulea University, rereleased as GPL by its
 *  authors:
 *  Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
 *
 *  Changes to meet Linux coding standards, to make it meet latest ccid3 draft
 *  and to make it work as a loadable module in the DCCP stack written by
 *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>.
 *
 *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
#include "../ccid.h"
#include "../dccp.h"
#include "lib/packet_history.h"
#include "lib/loss_interval.h"
#include "lib/tfrc.h"
#include "ccid3.h"

#include <asm/unaligned.h>

#ifdef CONFIG_IP_DCCP_CCID3_DEBUG
static int ccid3_debug;
#define ccid3_pr_debug(format, a...)      DCCP_PR_DEBUG(ccid3_debug, format, ##a)
#else
#define ccid3_pr_debug(format, a...)
#endif

static struct dccp_tx_hist *ccid3_tx_hist;
static struct dccp_rx_hist *ccid3_rx_hist;

/*
 *    Transmitter Half-Connection Routines
 */
#ifdef CONFIG_IP_DCCP_CCID3_DEBUG
static const char *ccid3_tx_state_name(enum ccid3_hc_tx_states state)
{
      static char *ccid3_state_names[] = {
      [TFRC_SSTATE_NO_SENT]  = "NO_SENT",
      [TFRC_SSTATE_NO_FBACK] = "NO_FBACK",
      [TFRC_SSTATE_FBACK]    = "FBACK",
      [TFRC_SSTATE_TERM]     = "TERM",
      };

      return ccid3_state_names[state];
}
#endif

static void ccid3_hc_tx_set_state(struct sock *sk,
                          enum ccid3_hc_tx_states state)
{
      struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
      enum ccid3_hc_tx_states oldstate = hctx->ccid3hctx_state;

      ccid3_pr_debug("%s(%p) %-8.8s -> %s\n",
                   dccp_role(sk), sk, ccid3_tx_state_name(oldstate),
                   ccid3_tx_state_name(state));
      WARN_ON(state == oldstate);
      hctx->ccid3hctx_state = state;
}

/*
 * Compute the initial sending rate X_init according to RFC 3390:
 *    w_init   =    min(4 * MSS, max(2 * MSS, 4380 bytes))
 *    X_init   =    w_init / RTT
 * For consistency with other parts of the code, X_init is scaled by 2^6.
 */
static inline u64 rfc3390_initial_rate(struct sock *sk)
{
      const struct dccp_sock *dp = dccp_sk(sk);
      const __u32 w_init = min(4 * dp->dccps_mss_cache,
                         max(2 * dp->dccps_mss_cache, 4380U));

      return scaled_div(w_init << 6, ccid3_hc_tx_sk(sk)->ccid3hctx_rtt);
}

/*
 * Recalculate t_ipi and delta (should be called whenever X changes)
 */
static inline void ccid3_update_send_interval(struct ccid3_hc_tx_sock *hctx)
{
      /* Calculate new t_ipi = s / X_inst (X_inst is in 64 * bytes/second) */
      hctx->ccid3hctx_t_ipi = scaled_div32(((u64)hctx->ccid3hctx_s) << 6,
                                   hctx->ccid3hctx_x);

      /* Calculate new delta by delta = min(t_ipi / 2, t_gran / 2) */
      hctx->ccid3hctx_delta = min_t(u32, hctx->ccid3hctx_t_ipi / 2,
                                 TFRC_OPSYS_HALF_TIME_GRAN);

      ccid3_pr_debug("t_ipi=%u, delta=%u, s=%u, X=%u\n",
                   hctx->ccid3hctx_t_ipi, hctx->ccid3hctx_delta,
                   hctx->ccid3hctx_s, (unsigned)(hctx->ccid3hctx_x >> 6));

}

/**
 * ccid3_hc_tx_update_x  -  Update allowed sending rate X
 * @stamp: most recent time if available - can be left NULL.
 * This function tracks draft rfc3448bis, check there for latest details.
 *
 * Note: X and X_recv are both stored in units of 64 * bytes/second, to support
 *       fine-grained resolution of sending rates. This requires scaling by 2^6
 *       throughout the code. Only X_calc is unscaled (in bytes/second).
 *
 */
static void ccid3_hc_tx_update_x(struct sock *sk, ktime_t *stamp)

{
      struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
      __u64 min_rate = 2 * hctx->ccid3hctx_x_recv;
      const  __u64 old_x = hctx->ccid3hctx_x;
      ktime_t now = stamp? *stamp : ktime_get_real();

      /*
       * Handle IDLE periods: do not reduce below RFC3390 initial sending rate
       * when idling [RFC 4342, 5.1]. See also draft-ietf-dccp-rfc3448bis.
       * For consistency with X and X_recv, min_rate is also scaled by 2^6.
       */
      if (unlikely(hctx->ccid3hctx_idle)) {
            min_rate = rfc3390_initial_rate(sk);
            min_rate = max(min_rate, 2 * hctx->ccid3hctx_x_recv);
      }

      if (hctx->ccid3hctx_p > 0) {

            hctx->ccid3hctx_x = min(((__u64)hctx->ccid3hctx_x_calc) << 6,
                              min_rate);
            hctx->ccid3hctx_x = max(hctx->ccid3hctx_x,
                              (((__u64)hctx->ccid3hctx_s) << 6) /
                                                TFRC_T_MBI);

      } else if (ktime_us_delta(now, hctx->ccid3hctx_t_ld)
                        - (s64)hctx->ccid3hctx_rtt >= 0) {

            hctx->ccid3hctx_x =
                  max(min(2 * hctx->ccid3hctx_x, min_rate),
                      scaled_div(((__u64)hctx->ccid3hctx_s) << 6,
                               hctx->ccid3hctx_rtt));
            hctx->ccid3hctx_t_ld = now;
      }

      if (hctx->ccid3hctx_x != old_x) {
            ccid3_pr_debug("X_prev=%u, X_now=%u, X_calc=%u, "
                         "X_recv=%u\n", (unsigned)(old_x >> 6),
                         (unsigned)(hctx->ccid3hctx_x >> 6),
                         hctx->ccid3hctx_x_calc,
                         (unsigned)(hctx->ccid3hctx_x_recv >> 6));

            ccid3_update_send_interval(hctx);
      }
}

/*
 *    Track the mean packet size `s' (cf. RFC 4342, 5.3 and  RFC 3448, 4.1)
 *    @len: DCCP packet payload size in bytes
 */
static inline void ccid3_hc_tx_update_s(struct ccid3_hc_tx_sock *hctx, int len)
{
      const u16 old_s = hctx->ccid3hctx_s;

      hctx->ccid3hctx_s = old_s == 0 ? len : (9 * old_s + len) / 10;

      if (hctx->ccid3hctx_s != old_s)
            ccid3_update_send_interval(hctx);
}

/*
 *    Update Window Counter using the algorithm from [RFC 4342, 8.1].
 *    The algorithm is not applicable if RTT < 4 microseconds.
 */
static inline void ccid3_hc_tx_update_win_count(struct ccid3_hc_tx_sock *hctx,
                                    ktime_t now)
{
      u32 quarter_rtts;

      if (unlikely(hctx->ccid3hctx_rtt < 4))    /* avoid divide-by-zero */
            return;

      quarter_rtts = ktime_us_delta(now, hctx->ccid3hctx_t_last_win_count);
      quarter_rtts /= hctx->ccid3hctx_rtt / 4;

      if (quarter_rtts > 0) {
            hctx->ccid3hctx_t_last_win_count = now;
            hctx->ccid3hctx_last_win_count      += min_t(u32, quarter_rtts, 5);
            hctx->ccid3hctx_last_win_count      &= 0xF;           /* mod 16 */
      }
}

static void ccid3_hc_tx_no_feedback_timer(unsigned long data)
{
      struct sock *sk = (struct sock *)data;
      struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
      unsigned long t_nfb = USEC_PER_SEC / 5;

      bh_lock_sock(sk);
      if (sock_owned_by_user(sk)) {
            /* Try again later. */
            /* XXX: set some sensible MIB */
            goto restart_timer;
      }

      ccid3_pr_debug("%s(%p, state=%s) - entry \n", dccp_role(sk), sk,
                   ccid3_tx_state_name(hctx->ccid3hctx_state));

      hctx->ccid3hctx_idle = 1;

      switch (hctx->ccid3hctx_state) {
      case TFRC_SSTATE_NO_FBACK:
            /* RFC 3448, 4.4: Halve send rate directly */
            hctx->ccid3hctx_x = max(hctx->ccid3hctx_x / 2,
                              (((__u64)hctx->ccid3hctx_s) << 6) /
                                                    TFRC_T_MBI);

            ccid3_pr_debug("%s(%p, state=%s), updated tx rate to %u "
                         "bytes/s\n", dccp_role(sk), sk,
                         ccid3_tx_state_name(hctx->ccid3hctx_state),
                         (unsigned)(hctx->ccid3hctx_x >> 6));
            /* The value of R is still undefined and so we can not recompute
             * the timeout value. Keep initial value as per [RFC 4342, 5]. */
            t_nfb = TFRC_INITIAL_TIMEOUT;
            ccid3_update_send_interval(hctx);
            break;
      case TFRC_SSTATE_FBACK:
            /*
             *  Modify the cached value of X_recv [RFC 3448, 4.4]
             *
             *  If (p == 0 || X_calc > 2 * X_recv)
             *    X_recv = max(X_recv / 2, s / (2 * t_mbi));
             *  Else
             *    X_recv = X_calc / 4;
             *
             *  Note that X_recv is scaled by 2^6 while X_calc is not
             */
            BUG_ON(hctx->ccid3hctx_p && !hctx->ccid3hctx_x_calc);

            if (hctx->ccid3hctx_p == 0 ||
                (hctx->ccid3hctx_x_calc > (hctx->ccid3hctx_x_recv >> 5))) {

                  hctx->ccid3hctx_x_recv =
                        max(hctx->ccid3hctx_x_recv / 2,
                            (((__u64)hctx->ccid3hctx_s) << 6) /
                                                (2 * TFRC_T_MBI));
            } else {
                  hctx->ccid3hctx_x_recv = hctx->ccid3hctx_x_calc;
                  hctx->ccid3hctx_x_recv <<= 4;
            }
            /* Now recalculate X [RFC 3448, 4.3, step (4)] */
            ccid3_hc_tx_update_x(sk, NULL);
            /*
             * Schedule no feedback timer to expire in
             * max(t_RTO, 2 * s/X)  =  max(t_RTO, 2 * t_ipi)
             * See comments in packet_recv() regarding the value of t_RTO.
             */
            t_nfb = max(hctx->ccid3hctx_t_rto, 2 * hctx->ccid3hctx_t_ipi);
            break;
      case TFRC_SSTATE_NO_SENT:
            DCCP_BUG("%s(%p) - Illegal state NO_SENT", dccp_role(sk), sk);
            /* fall through */
      case TFRC_SSTATE_TERM:
            goto out;
      }

restart_timer:
      sk_reset_timer(sk, &hctx->ccid3hctx_no_feedback_timer,
                     jiffies + usecs_to_jiffies(t_nfb));
out:
      bh_unlock_sock(sk);
      sock_put(sk);
}

/*
 * returns
 *   > 0: delay (in msecs) that should pass before actually sending
 *   = 0: can send immediately
 *   < 0: error condition; do not send packet
 */
static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
{
      struct dccp_sock *dp = dccp_sk(sk);
      struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
      ktime_t now = ktime_get_real();
      s64 delay;

      /*
       * This function is called only for Data and DataAck packets. Sending
       * zero-sized Data(Ack)s is theoretically possible, but for congestion
       * control this case is pathological - ignore it.
       */
      if (unlikely(skb->len == 0))
            return -EBADMSG;

      switch (hctx->ccid3hctx_state) {
      case TFRC_SSTATE_NO_SENT:
            sk_reset_timer(sk, &hctx->ccid3hctx_no_feedback_timer,
                         (jiffies +
                        usecs_to_jiffies(TFRC_INITIAL_TIMEOUT)));
            hctx->ccid3hctx_last_win_count       = 0;
            hctx->ccid3hctx_t_last_win_count = now;

            /* Set t_0 for initial packet */
            hctx->ccid3hctx_t_nom = now;

            hctx->ccid3hctx_s = skb->len;

            /*
             * Use initial RTT sample when available: recommended by erratum
             * to RFC 4342. This implements the initialisation procedure of
             * draft rfc3448bis, section 4.2. Remember, X is scaled by 2^6.
             */
            if (dp->dccps_syn_rtt) {
                  ccid3_pr_debug("SYN RTT = %uus\n", dp->dccps_syn_rtt);
                  hctx->ccid3hctx_rtt  = dp->dccps_syn_rtt;
                  hctx->ccid3hctx_x    = rfc3390_initial_rate(sk);
                  hctx->ccid3hctx_t_ld = now;
            } else {
                  /* Sender does not have RTT sample: X = MSS/second */
                  hctx->ccid3hctx_x = dp->dccps_mss_cache;
                  hctx->ccid3hctx_x <<= 6;
            }
            ccid3_update_send_interval(hctx);

            ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);
            break;
      case TFRC_SSTATE_NO_FBACK:
      case TFRC_SSTATE_FBACK:
            delay = ktime_us_delta(hctx->ccid3hctx_t_nom, now);
            ccid3_pr_debug("delay=%ld\n", (long)delay);
            /*
             *    Scheduling of packet transmissions [RFC 3448, 4.6]
             *
             * if (t_now > t_nom - delta)
             *       // send the packet now
             * else
             *       // send the packet in (t_nom - t_now) milliseconds.
             */
            if (delay - (s64)hctx->ccid3hctx_delta >= 1000)
                  return (u32)delay / 1000L;

            ccid3_hc_tx_update_win_count(hctx, now);
            break;
      case TFRC_SSTATE_TERM:
            DCCP_BUG("%s(%p) - Illegal state TERM", dccp_role(sk), sk);
            return -EINVAL;
      }

      /* prepare to send now (add options etc.) */
      dp->dccps_hc_tx_insert_options = 1;
      DCCP_SKB_CB(skb)->dccpd_ccval = hctx->ccid3hctx_last_win_count;
      hctx->ccid3hctx_idle = 0;

      /* set the nominal send time for the next following packet */
      hctx->ccid3hctx_t_nom = ktime_add_us(hctx->ccid3hctx_t_nom,
                                   hctx->ccid3hctx_t_ipi);
      return 0;
}

static void ccid3_hc_tx_packet_sent(struct sock *sk, int more,
                            unsigned int len)
{
      struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
      struct dccp_tx_hist_entry *packet;

      ccid3_hc_tx_update_s(hctx, len);

      packet = dccp_tx_hist_entry_new(ccid3_tx_hist, GFP_ATOMIC);
      if (unlikely(packet == NULL)) {
            DCCP_CRIT("packet history - out of memory!");
            return;
      }
      dccp_tx_hist_add_entry(&hctx->ccid3hctx_hist, packet);

      packet->dccphtx_tstamp = ktime_get_real();
      packet->dccphtx_seqno  = dccp_sk(sk)->dccps_gss;
      packet->dccphtx_rtt    = hctx->ccid3hctx_rtt;
      packet->dccphtx_sent   = 1;
}

static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
{
      struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
      struct ccid3_options_received *opt_recv;
      struct dccp_tx_hist_entry *packet;
      ktime_t now;
      unsigned long t_nfb;
      u32 pinv, r_sample;

      /* we are only interested in ACKs */
      if (!(DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_ACK ||
            DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_DATAACK))
            return;

      opt_recv = &hctx->ccid3hctx_options_received;

      switch (hctx->ccid3hctx_state) {
      case TFRC_SSTATE_NO_FBACK:
      case TFRC_SSTATE_FBACK:
            /* get packet from history to look up t_recvdata */
            packet = dccp_tx_hist_find_entry(&hctx->ccid3hctx_hist,
                                    DCCP_SKB_CB(skb)->dccpd_ack_seq);
            if (unlikely(packet == NULL)) {
                  DCCP_WARN("%s(%p), seqno %llu(%s) doesn't exist "
                          "in history!\n",  dccp_role(sk), sk,
                      (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq,
                        dccp_packet_name(DCCP_SKB_CB(skb)->dccpd_type));
                  return;
            }

            /* Update receive rate in units of 64 * bytes/second */
            hctx->ccid3hctx_x_recv = opt_recv->ccid3or_receive_rate;
            hctx->ccid3hctx_x_recv <<= 6;

            /* Update loss event rate */
            pinv = opt_recv->ccid3or_loss_event_rate;
            if (pinv == ~0U || pinv == 0)        /* see RFC 4342, 8.5   */
                  hctx->ccid3hctx_p = 0;
            else                           /* can not exceed 100% */
                  hctx->ccid3hctx_p = 1000000 / pinv;

            now = ktime_get_real();
            /*
             * Calculate new round trip sample as per [RFC 3448, 4.3] by
             *    R_sample  =  (now - t_recvdata) - t_elapsed
             */
            r_sample = dccp_sample_rtt(sk, ktime_us_delta(now, packet->dccphtx_tstamp));

            /*
             * Update RTT estimate by
             * If (No feedback recv)
             *    R = R_sample;
             * Else
             *    R = q * R + (1 - q) * R_sample;
             *
             * q is a constant, RFC 3448 recomments 0.9
             */
            if (hctx->ccid3hctx_state == TFRC_SSTATE_NO_FBACK) {
                  /*
                   * Larger Initial Windows [RFC 4342, sec. 5]
                   */
                  hctx->ccid3hctx_rtt  = r_sample;
                  hctx->ccid3hctx_x    = rfc3390_initial_rate(sk);
                  hctx->ccid3hctx_t_ld = now;

                  ccid3_update_send_interval(hctx);

                  ccid3_pr_debug("%s(%p), s=%u, MSS=%u, "
                               "R_sample=%uus, X=%u\n", dccp_role(sk),
                               sk, hctx->ccid3hctx_s,
                               dccp_sk(sk)->dccps_mss_cache, r_sample,
                               (unsigned)(hctx->ccid3hctx_x >> 6));

                  ccid3_hc_tx_set_state(sk, TFRC_SSTATE_FBACK);
            } else {
                  hctx->ccid3hctx_rtt = (9 * hctx->ccid3hctx_rtt +
                                       r_sample) / 10;

                  /* Update sending rate (step 4 of [RFC 3448, 4.3]) */
                  if (hctx->ccid3hctx_p > 0)
                        hctx->ccid3hctx_x_calc =
                              tfrc_calc_x(hctx->ccid3hctx_s,
                                        hctx->ccid3hctx_rtt,
                                        hctx->ccid3hctx_p);
                  ccid3_hc_tx_update_x(sk, &now);

                  ccid3_pr_debug("%s(%p), RTT=%uus (sample=%uus), s=%u, "
                               "p=%u, X_calc=%u, X_recv=%u, X=%u\n",
                               dccp_role(sk),
                               sk, hctx->ccid3hctx_rtt, r_sample,
                               hctx->ccid3hctx_s, hctx->ccid3hctx_p,
                               hctx->ccid3hctx_x_calc,
                               (unsigned)(hctx->ccid3hctx_x_recv >> 6),
                               (unsigned)(hctx->ccid3hctx_x >> 6));
            }

            /* unschedule no feedback timer */
            sk_stop_timer(sk, &hctx->ccid3hctx_no_feedback_timer);

            /* remove all packets older than the one acked from history */
            dccp_tx_hist_purge_older(ccid3_tx_hist,
                               &hctx->ccid3hctx_hist, packet);
            /*
             * As we have calculated new ipi, delta, t_nom it is possible
             * that we now can send a packet, so wake up dccp_wait_for_ccid
             */
            sk->sk_write_space(sk);

            /*
             * Update timeout interval for the nofeedback timer.
             * We use a configuration option to increase the lower bound.
             * This can help avoid triggering the nofeedback timer too
             * often ('spinning') on LANs with small RTTs.
             */
            hctx->ccid3hctx_t_rto = max_t(u32, 4 * hctx->ccid3hctx_rtt,
                                       CONFIG_IP_DCCP_CCID3_RTO *
                                       (USEC_PER_SEC/1000));
            /*
             * Schedule no feedback timer to expire in
             * max(t_RTO, 2 * s/X)  =  max(t_RTO, 2 * t_ipi)
             */
            t_nfb = max(hctx->ccid3hctx_t_rto, 2 * hctx->ccid3hctx_t_ipi);

            ccid3_pr_debug("%s(%p), Scheduled no feedback timer to "
                         "expire in %lu jiffies (%luus)\n",
                         dccp_role(sk),
                         sk, usecs_to_jiffies(t_nfb), t_nfb);

            sk_reset_timer(sk, &hctx->ccid3hctx_no_feedback_timer,
                           jiffies + usecs_to_jiffies(t_nfb));

            /* set idle flag */
            hctx->ccid3hctx_idle = 1;
            break;
      case TFRC_SSTATE_NO_SENT:     /* fall through */
      case TFRC_SSTATE_TERM:        /* ignore feedback when closing */
            break;
      }
}

static int ccid3_hc_tx_parse_options(struct sock *sk, unsigned char option,
                             unsigned char len, u16 idx,
                             unsigned char *value)
{
      int rc = 0;
      const struct dccp_sock *dp = dccp_sk(sk);
      struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
      struct ccid3_options_received *opt_recv;
      __be32 opt_val;

      opt_recv = &hctx->ccid3hctx_options_received;

      if (opt_recv->ccid3or_seqno != dp->dccps_gsr) {
            opt_recv->ccid3or_seqno            = dp->dccps_gsr;
            opt_recv->ccid3or_loss_event_rate    = ~0;
            opt_recv->ccid3or_loss_intervals_idx = 0;
            opt_recv->ccid3or_loss_intervals_len = 0;
            opt_recv->ccid3or_receive_rate           = 0;
      }

      switch (option) {
      case TFRC_OPT_LOSS_EVENT_RATE:
            if (unlikely(len != 4)) {
                  DCCP_WARN("%s(%p), invalid len %d "
                          "for TFRC_OPT_LOSS_EVENT_RATE\n",
                          dccp_role(sk), sk, len);
                  rc = -EINVAL;
            } else {
                  opt_val = get_unaligned((__be32 *)value);
                  opt_recv->ccid3or_loss_event_rate = ntohl(opt_val);
                  ccid3_pr_debug("%s(%p), LOSS_EVENT_RATE=%u\n",
                               dccp_role(sk), sk,
                               opt_recv->ccid3or_loss_event_rate);
            }
            break;
      case TFRC_OPT_LOSS_INTERVALS:
            opt_recv->ccid3or_loss_intervals_idx = idx;
            opt_recv->ccid3or_loss_intervals_len = len;
            ccid3_pr_debug("%s(%p), LOSS_INTERVALS=(%u, %u)\n",
                         dccp_role(sk), sk,
                         opt_recv->ccid3or_loss_intervals_idx,
                         opt_recv->ccid3or_loss_intervals_len);
            break;
      case TFRC_OPT_RECEIVE_RATE:
            if (unlikely(len != 4)) {
                  DCCP_WARN("%s(%p), invalid len %d "
                          "for TFRC_OPT_RECEIVE_RATE\n",
                          dccp_role(sk), sk, len);
                  rc = -EINVAL;
            } else {
                  opt_val = get_unaligned((__be32 *)value);
                  opt_recv->ccid3or_receive_rate = ntohl(opt_val);
                  ccid3_pr_debug("%s(%p), RECEIVE_RATE=%u\n",
                               dccp_role(sk), sk,
                               opt_recv->ccid3or_receive_rate);
            }
            break;
      }

      return rc;
}

static int ccid3_hc_tx_init(struct ccid *ccid, struct sock *sk)
{
      struct ccid3_hc_tx_sock *hctx = ccid_priv(ccid);

      hctx->ccid3hctx_state = TFRC_SSTATE_NO_SENT;
      INIT_LIST_HEAD(&hctx->ccid3hctx_hist);

      hctx->ccid3hctx_no_feedback_timer.function =
                        ccid3_hc_tx_no_feedback_timer;
      hctx->ccid3hctx_no_feedback_timer.data     = (unsigned long)sk;
      init_timer(&hctx->ccid3hctx_no_feedback_timer);

      return 0;
}

static void ccid3_hc_tx_exit(struct sock *sk)
{
      struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);

      ccid3_hc_tx_set_state(sk, TFRC_SSTATE_TERM);
      sk_stop_timer(sk, &hctx->ccid3hctx_no_feedback_timer);

      /* Empty packet history */
      dccp_tx_hist_purge(ccid3_tx_hist, &hctx->ccid3hctx_hist);
}

static void ccid3_hc_tx_get_info(struct sock *sk, struct tcp_info *info)
{
      struct ccid3_hc_tx_sock *hctx;

      /* Listen socks doesn't have a private CCID block */
      if (sk->sk_state == DCCP_LISTEN)
            return;

      hctx = ccid3_hc_tx_sk(sk);
      info->tcpi_rto = hctx->ccid3hctx_t_rto;
      info->tcpi_rtt = hctx->ccid3hctx_rtt;
}

static int ccid3_hc_tx_getsockopt(struct sock *sk, const int optname, int len,
                          u32 __user *optval, int __user *optlen)
{
      const struct ccid3_hc_tx_sock *hctx;
      const void *val;

      /* Listen socks doesn't have a private CCID block */
      if (sk->sk_state == DCCP_LISTEN)
            return -EINVAL;

      hctx = ccid3_hc_tx_sk(sk);
      switch (optname) {
      case DCCP_SOCKOPT_CCID_TX_INFO:
            if (len < sizeof(hctx->ccid3hctx_tfrc))
                  return -EINVAL;
            len = sizeof(hctx->ccid3hctx_tfrc);
            val = &hctx->ccid3hctx_tfrc;
            break;
      default:
            return -ENOPROTOOPT;
      }

      if (put_user(len, optlen) || copy_to_user(optval, val, len))
            return -EFAULT;

      return 0;
}

/*
 *    Receiver Half-Connection Routines
 */
#ifdef CONFIG_IP_DCCP_CCID3_DEBUG
static const char *ccid3_rx_state_name(enum ccid3_hc_rx_states state)
{
      static char *ccid3_rx_state_names[] = {
      [TFRC_RSTATE_NO_DATA] = "NO_DATA",
      [TFRC_RSTATE_DATA]    = "DATA",
      [TFRC_RSTATE_TERM]    = "TERM",
      };

      return ccid3_rx_state_names[state];
}
#endif

static void ccid3_hc_rx_set_state(struct sock *sk,
                          enum ccid3_hc_rx_states state)
{
      struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
      enum ccid3_hc_rx_states oldstate = hcrx->ccid3hcrx_state;

      ccid3_pr_debug("%s(%p) %-8.8s -> %s\n",
                   dccp_role(sk), sk, ccid3_rx_state_name(oldstate),
                   ccid3_rx_state_name(state));
      WARN_ON(state == oldstate);
      hcrx->ccid3hcrx_state = state;
}

static inline void ccid3_hc_rx_update_s(struct ccid3_hc_rx_sock *hcrx, int len)
{
      if (unlikely(len == 0)) /* don't update on empty packets (e.g. ACKs) */
            ccid3_pr_debug("Packet payload length is 0 - not updating\n");
      else
            hcrx->ccid3hcrx_s = hcrx->ccid3hcrx_s == 0 ? len :
                            (9 * hcrx->ccid3hcrx_s + len) / 10;
}

static void ccid3_hc_rx_send_feedback(struct sock *sk)
{
      struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
      struct dccp_sock *dp = dccp_sk(sk);
      struct dccp_rx_hist_entry *packet;
      ktime_t now;
      suseconds_t delta;

      ccid3_pr_debug("%s(%p) - entry \n", dccp_role(sk), sk);

      now = ktime_get_real();

      switch (hcrx->ccid3hcrx_state) {
      case TFRC_RSTATE_NO_DATA:
            hcrx->ccid3hcrx_x_recv = 0;
            break;
      case TFRC_RSTATE_DATA:
            delta = ktime_us_delta(now,
                               hcrx->ccid3hcrx_tstamp_last_feedback);
            DCCP_BUG_ON(delta < 0);
            hcrx->ccid3hcrx_x_recv =
                  scaled_div32(hcrx->ccid3hcrx_bytes_recv, delta);
            break;
      case TFRC_RSTATE_TERM:
            DCCP_BUG("%s(%p) - Illegal state TERM", dccp_role(sk), sk);
            return;
      }

      packet = dccp_rx_hist_find_data_packet(&hcrx->ccid3hcrx_hist);
      if (unlikely(packet == NULL)) {
            DCCP_WARN("%s(%p), no data packet in history!\n",
                    dccp_role(sk), sk);
            return;
      }

      hcrx->ccid3hcrx_tstamp_last_feedback = now;
      hcrx->ccid3hcrx_ccval_last_counter   = packet->dccphrx_ccval;
      hcrx->ccid3hcrx_bytes_recv         = 0;

      /* Elapsed time information [RFC 4340, 13.2] in units of 10 * usecs */
      delta = ktime_us_delta(now, packet->dccphrx_tstamp);
      DCCP_BUG_ON(delta < 0);
      hcrx->ccid3hcrx_elapsed_time = delta / 10;

      if (hcrx->ccid3hcrx_p == 0)
            hcrx->ccid3hcrx_pinv = ~0U;   /* see RFC 4342, 8.5 */
      else if (hcrx->ccid3hcrx_p > 1000000) {
            DCCP_WARN("p (%u) > 100%%\n", hcrx->ccid3hcrx_p);
            hcrx->ccid3hcrx_pinv = 1;     /* use 100% in this case */
      } else
            hcrx->ccid3hcrx_pinv = 1000000 / hcrx->ccid3hcrx_p;

      dp->dccps_hc_rx_insert_options = 1;
      dccp_send_ack(sk);
}

static int ccid3_hc_rx_insert_options(struct sock *sk, struct sk_buff *skb)
{
      const struct ccid3_hc_rx_sock *hcrx;
      __be32 x_recv, pinv;

      if (!(sk->sk_state == DCCP_OPEN || sk->sk_state == DCCP_PARTOPEN))
            return 0;

      hcrx = ccid3_hc_rx_sk(sk);
      DCCP_SKB_CB(skb)->dccpd_ccval = hcrx->ccid3hcrx_ccval_last_counter;

      if (dccp_packet_without_ack(skb))
            return 0;

      x_recv = htonl(hcrx->ccid3hcrx_x_recv);
      pinv   = htonl(hcrx->ccid3hcrx_pinv);

      if ((hcrx->ccid3hcrx_elapsed_time != 0 &&
           dccp_insert_option_elapsed_time(sk, skb,
                                   hcrx->ccid3hcrx_elapsed_time)) ||
          dccp_insert_option_timestamp(sk, skb) ||
          dccp_insert_option(sk, skb, TFRC_OPT_LOSS_EVENT_RATE,
                         &pinv, sizeof(pinv)) ||
          dccp_insert_option(sk, skb, TFRC_OPT_RECEIVE_RATE,
                         &x_recv, sizeof(x_recv)))
            return -1;

      return 0;
}

static int ccid3_hc_rx_detect_loss(struct sock *sk,
                            struct dccp_rx_hist_entry *packet)
{
      struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
      struct dccp_rx_hist_entry *rx_hist =
                        dccp_rx_hist_head(&hcrx->ccid3hcrx_hist);
      u64 seqno = packet->dccphrx_seqno;
      u64 tmp_seqno;
      int loss = 0;
      u8 ccval;


      tmp_seqno = hcrx->ccid3hcrx_seqno_nonloss;

      if (!rx_hist ||
         follows48(packet->dccphrx_seqno, hcrx->ccid3hcrx_seqno_nonloss)) {
            hcrx->ccid3hcrx_seqno_nonloss = seqno;
            hcrx->ccid3hcrx_ccval_nonloss = packet->dccphrx_ccval;
            goto detect_out;
      }


      while (dccp_delta_seqno(hcrx->ccid3hcrx_seqno_nonloss, seqno)
         > TFRC_RECV_NUM_LATE_LOSS) {
            loss = 1;
            dccp_li_update_li(sk,
                          &hcrx->ccid3hcrx_li_hist,
                          &hcrx->ccid3hcrx_hist,
                          hcrx->ccid3hcrx_tstamp_last_feedback,
                          hcrx->ccid3hcrx_s,
                          hcrx->ccid3hcrx_bytes_recv,
                          hcrx->ccid3hcrx_x_recv,
                          hcrx->ccid3hcrx_seqno_nonloss,
                          hcrx->ccid3hcrx_ccval_nonloss);
            tmp_seqno = hcrx->ccid3hcrx_seqno_nonloss;
            dccp_inc_seqno(&tmp_seqno);
            hcrx->ccid3hcrx_seqno_nonloss = tmp_seqno;
            dccp_inc_seqno(&tmp_seqno);
            while (dccp_rx_hist_find_entry(&hcrx->ccid3hcrx_hist,
               tmp_seqno, &ccval)) {
                  hcrx->ccid3hcrx_seqno_nonloss = tmp_seqno;
                  hcrx->ccid3hcrx_ccval_nonloss = ccval;
                  dccp_inc_seqno(&tmp_seqno);
            }
      }

      /* FIXME - this code could be simplified with above while */
      /* but works at moment */
      if (follows48(packet->dccphrx_seqno, hcrx->ccid3hcrx_seqno_nonloss)) {
            hcrx->ccid3hcrx_seqno_nonloss = seqno;
            hcrx->ccid3hcrx_ccval_nonloss = packet->dccphrx_ccval;
      }

detect_out:
      dccp_rx_hist_add_packet(ccid3_rx_hist, &hcrx->ccid3hcrx_hist,
               &hcrx->ccid3hcrx_li_hist, packet,
               hcrx->ccid3hcrx_seqno_nonloss);
      return loss;
}

static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
{
      struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
      const struct dccp_options_received *opt_recv;
      struct dccp_rx_hist_entry *packet;
      u32 p_prev, r_sample, rtt_prev;
      int loss, payload_size;
      ktime_t now;

      opt_recv = &dccp_sk(sk)->dccps_options_received;

      switch (DCCP_SKB_CB(skb)->dccpd_type) {
      case DCCP_PKT_ACK:
            if (hcrx->ccid3hcrx_state == TFRC_RSTATE_NO_DATA)
                  return;
      case DCCP_PKT_DATAACK:
            if (opt_recv->dccpor_timestamp_echo == 0)
                  break;
            r_sample = dccp_timestamp() - opt_recv->dccpor_timestamp_echo;
            rtt_prev = hcrx->ccid3hcrx_rtt;
            r_sample = dccp_sample_rtt(sk, 10 * r_sample);

            if (hcrx->ccid3hcrx_state == TFRC_RSTATE_NO_DATA)
                  hcrx->ccid3hcrx_rtt = r_sample;
            else
                  hcrx->ccid3hcrx_rtt = (hcrx->ccid3hcrx_rtt * 9) / 10 +
                                    r_sample / 10;

            if (rtt_prev != hcrx->ccid3hcrx_rtt)
                  ccid3_pr_debug("%s(%p), New RTT=%uus, elapsed time=%u\n",
                               dccp_role(sk), sk, hcrx->ccid3hcrx_rtt,
                               opt_recv->dccpor_elapsed_time);
            break;
      case DCCP_PKT_DATA:
            break;
      default: /* We're not interested in other packet types, move along */
            return;
      }

      packet = dccp_rx_hist_entry_new(ccid3_rx_hist, opt_recv->dccpor_ndp,
                              skb, GFP_ATOMIC);
      if (unlikely(packet == NULL)) {
            DCCP_WARN("%s(%p), Not enough mem to add rx packet "
                    "to history, consider it lost!\n", dccp_role(sk), sk);
            return;
      }

      loss = ccid3_hc_rx_detect_loss(sk, packet);

      if (DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_ACK)
            return;

      payload_size = skb->len - dccp_hdr(skb)->dccph_doff * 4;
      ccid3_hc_rx_update_s(hcrx, payload_size);

      switch (hcrx->ccid3hcrx_state) {
      case TFRC_RSTATE_NO_DATA:
            ccid3_pr_debug("%s(%p, state=%s), skb=%p, sending initial "
                         "feedback\n", dccp_role(sk), sk,
                         dccp_state_name(sk->sk_state), skb);
            ccid3_hc_rx_send_feedback(sk);
            ccid3_hc_rx_set_state(sk, TFRC_RSTATE_DATA);
            return;
      case TFRC_RSTATE_DATA:
            hcrx->ccid3hcrx_bytes_recv += payload_size;
            if (loss)
                  break;

            now = ktime_get_real();
            if ((ktime_us_delta(now, hcrx->ccid3hcrx_tstamp_last_ack) -
                 (s64)hcrx->ccid3hcrx_rtt) >= 0) {
                  hcrx->ccid3hcrx_tstamp_last_ack = now;
                  ccid3_hc_rx_send_feedback(sk);
            }
            return;
      case TFRC_RSTATE_TERM:
            DCCP_BUG("%s(%p) - Illegal state TERM", dccp_role(sk), sk);
            return;
      }

      /* Dealing with packet loss */
      ccid3_pr_debug("%s(%p, state=%s), data loss! Reacting...\n",
                   dccp_role(sk), sk, dccp_state_name(sk->sk_state));

      p_prev = hcrx->ccid3hcrx_p;

      /* Calculate loss event rate */
      if (!list_empty(&hcrx->ccid3hcrx_li_hist)) {
            u32 i_mean = dccp_li_hist_calc_i_mean(&hcrx->ccid3hcrx_li_hist);

            /* Scaling up by 1000000 as fixed decimal */
            if (i_mean != 0)
                  hcrx->ccid3hcrx_p = 1000000 / i_mean;
      } else
            DCCP_BUG("empty loss history");

      if (hcrx->ccid3hcrx_p > p_prev) {
            ccid3_hc_rx_send_feedback(sk);
            return;
      }
}

static int ccid3_hc_rx_init(struct ccid *ccid, struct sock *sk)
{
      struct ccid3_hc_rx_sock *hcrx = ccid_priv(ccid);

      ccid3_pr_debug("entry\n");

      hcrx->ccid3hcrx_state = TFRC_RSTATE_NO_DATA;
      INIT_LIST_HEAD(&hcrx->ccid3hcrx_hist);
      INIT_LIST_HEAD(&hcrx->ccid3hcrx_li_hist);
      hcrx->ccid3hcrx_tstamp_last_feedback =
            hcrx->ccid3hcrx_tstamp_last_ack = ktime_get_real();
      return 0;
}

static void ccid3_hc_rx_exit(struct sock *sk)
{
      struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);

      ccid3_hc_rx_set_state(sk, TFRC_RSTATE_TERM);

      /* Empty packet history */
      dccp_rx_hist_purge(ccid3_rx_hist, &hcrx->ccid3hcrx_hist);

      /* Empty loss interval history */
      dccp_li_hist_purge(&hcrx->ccid3hcrx_li_hist);
}

static void ccid3_hc_rx_get_info(struct sock *sk, struct tcp_info *info)
{
      const struct ccid3_hc_rx_sock *hcrx;

      /* Listen socks doesn't have a private CCID block */
      if (sk->sk_state == DCCP_LISTEN)
            return;

      hcrx = ccid3_hc_rx_sk(sk);
      info->tcpi_ca_state = hcrx->ccid3hcrx_state;
      info->tcpi_options  |= TCPI_OPT_TIMESTAMPS;
      info->tcpi_rcv_rtt  = hcrx->ccid3hcrx_rtt;
}

static int ccid3_hc_rx_getsockopt(struct sock *sk, const int optname, int len,
                          u32 __user *optval, int __user *optlen)
{
      const struct ccid3_hc_rx_sock *hcrx;
      const void *val;

      /* Listen socks doesn't have a private CCID block */
      if (sk->sk_state == DCCP_LISTEN)
            return -EINVAL;

      hcrx = ccid3_hc_rx_sk(sk);
      switch (optname) {
      case DCCP_SOCKOPT_CCID_RX_INFO:
            if (len < sizeof(hcrx->ccid3hcrx_tfrc))
                  return -EINVAL;
            len = sizeof(hcrx->ccid3hcrx_tfrc);
            val = &hcrx->ccid3hcrx_tfrc;
            break;
      default:
            return -ENOPROTOOPT;
      }

      if (put_user(len, optlen) || copy_to_user(optval, val, len))
            return -EFAULT;

      return 0;
}

static struct ccid_operations ccid3 = {
      .ccid_id             = DCCPC_CCID3,
      .ccid_name           = "ccid3",
      .ccid_owner          = THIS_MODULE,
      .ccid_hc_tx_obj_size       = sizeof(struct ccid3_hc_tx_sock),
      .ccid_hc_tx_init     = ccid3_hc_tx_init,
      .ccid_hc_tx_exit     = ccid3_hc_tx_exit,
      .ccid_hc_tx_send_packet    = ccid3_hc_tx_send_packet,
      .ccid_hc_tx_packet_sent    = ccid3_hc_tx_packet_sent,
      .ccid_hc_tx_packet_recv    = ccid3_hc_tx_packet_recv,
      .ccid_hc_tx_parse_options  = ccid3_hc_tx_parse_options,
      .ccid_hc_rx_obj_size       = sizeof(struct ccid3_hc_rx_sock),
      .ccid_hc_rx_init     = ccid3_hc_rx_init,
      .ccid_hc_rx_exit     = ccid3_hc_rx_exit,
      .ccid_hc_rx_insert_options = ccid3_hc_rx_insert_options,
      .ccid_hc_rx_packet_recv    = ccid3_hc_rx_packet_recv,
      .ccid_hc_rx_get_info       = ccid3_hc_rx_get_info,
      .ccid_hc_tx_get_info       = ccid3_hc_tx_get_info,
      .ccid_hc_rx_getsockopt     = ccid3_hc_rx_getsockopt,
      .ccid_hc_tx_getsockopt     = ccid3_hc_tx_getsockopt,
};

#ifdef CONFIG_IP_DCCP_CCID3_DEBUG
module_param(ccid3_debug, bool, 0444);
MODULE_PARM_DESC(ccid3_debug, "Enable debug messages");
#endif

static __init int ccid3_module_init(void)
{
      int rc = -ENOBUFS;

      ccid3_rx_hist = dccp_rx_hist_new("ccid3");
      if (ccid3_rx_hist == NULL)
            goto out;

      ccid3_tx_hist = dccp_tx_hist_new("ccid3");
      if (ccid3_tx_hist == NULL)
            goto out_free_rx;

      rc = ccid_register(&ccid3);
      if (rc != 0)
            goto out_free_tx;
out:
      return rc;

out_free_tx:
      dccp_tx_hist_delete(ccid3_tx_hist);
      ccid3_tx_hist = NULL;
out_free_rx:
      dccp_rx_hist_delete(ccid3_rx_hist);
      ccid3_rx_hist = NULL;
      goto out;
}
module_init(ccid3_module_init);

static __exit void ccid3_module_exit(void)
{
      ccid_unregister(&ccid3);

      if (ccid3_tx_hist != NULL) {
            dccp_tx_hist_delete(ccid3_tx_hist);
            ccid3_tx_hist = NULL;
      }
      if (ccid3_rx_hist != NULL) {
            dccp_rx_hist_delete(ccid3_rx_hist);
            ccid3_rx_hist = NULL;
      }
}
module_exit(ccid3_module_exit);

MODULE_AUTHOR("Ian McDonald <ian.mcdonald@jandi.co.nz>, "
            "Arnaldo Carvalho de Melo <acme@ghostprotocols.net>");
MODULE_DESCRIPTION("DCCP TFRC CCID3 CCID");
MODULE_LICENSE("GPL");
MODULE_ALIAS("net-dccp-ccid-3");

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