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outqueue.c

/* SCTP kernel reference Implementation
 * (C) Copyright IBM Corp. 2001, 2004
 * Copyright (c) 1999-2000 Cisco, Inc.
 * Copyright (c) 1999-2001 Motorola, Inc.
 * Copyright (c) 2001-2003 Intel Corp.
 *
 * This file is part of the SCTP kernel reference Implementation
 *
 * These functions implement the sctp_outq class.   The outqueue handles
 * bundling and queueing of outgoing SCTP chunks.
 *
 * The SCTP reference implementation 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, or (at your option)
 * any later version.
 *
 * The SCTP reference implementation 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 GNU CC; see the file COPYING.  If not, write to
 * the Free Software Foundation, 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * Please send any bug reports or fixes you make to the
 * email address(es):
 *    lksctp developers <lksctp-developers@lists.sourceforge.net>
 *
 * Or submit a bug report through the following website:
 *    http://www.sf.net/projects/lksctp
 *
 * Written or modified by:
 *    La Monte H.P. Yarroll <piggy@acm.org>
 *    Karl Knutson          <karl@athena.chicago.il.us>
 *    Perry Melange         <pmelange@null.cc.uic.edu>
 *    Xingang Guo           <xingang.guo@intel.com>
 *    Hui Huang       <hui.huang@nokia.com>
 *    Sridhar Samudrala     <sri@us.ibm.com>
 *    Jon Grimm             <jgrimm@us.ibm.com>
 *
 * Any bugs reported given to us we will try to fix... any fixes shared will
 * be incorporated into the next SCTP release.
 */

#include <linux/types.h>
#include <linux/list.h>   /* For struct list_head */
#include <linux/socket.h>
#include <linux/ip.h>
#include <net/sock.h>     /* For skb_set_owner_w */

#include <net/sctp/sctp.h>
#include <net/sctp/sm.h>

/* Declare internal functions here.  */
static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn);
static void sctp_check_transmitted(struct sctp_outq *q,
                           struct list_head *transmitted_queue,
                           struct sctp_transport *transport,
                           struct sctp_sackhdr *sack,
                           __u32 highest_new_tsn);

static void sctp_mark_missing(struct sctp_outq *q,
                        struct list_head *transmitted_queue,
                        struct sctp_transport *transport,
                        __u32 highest_new_tsn,
                        int count_of_newacks);

static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 sack_ctsn);

/* Add data to the front of the queue. */
static inline void sctp_outq_head_data(struct sctp_outq *q,
                              struct sctp_chunk *ch)
{
      list_add(&ch->list, &q->out_chunk_list);
      q->out_qlen += ch->skb->len;
      return;
}

/* Take data from the front of the queue. */
static inline struct sctp_chunk *sctp_outq_dequeue_data(struct sctp_outq *q)
{
      struct sctp_chunk *ch = NULL;

      if (!list_empty(&q->out_chunk_list)) {
            struct list_head *entry = q->out_chunk_list.next;

            ch = list_entry(entry, struct sctp_chunk, list);
            list_del_init(entry);
            q->out_qlen -= ch->skb->len;
      }
      return ch;
}
/* Add data chunk to the end of the queue. */
static inline void sctp_outq_tail_data(struct sctp_outq *q,
                               struct sctp_chunk *ch)
{
      list_add_tail(&ch->list, &q->out_chunk_list);
      q->out_qlen += ch->skb->len;
      return;
}

/*
 * SFR-CACC algorithm:
 * D) If count_of_newacks is greater than or equal to 2
 * and t was not sent to the current primary then the
 * sender MUST NOT increment missing report count for t.
 */
static inline int sctp_cacc_skip_3_1_d(struct sctp_transport *primary,
                               struct sctp_transport *transport,
                               int count_of_newacks)
{
      if (count_of_newacks >=2 && transport != primary)
            return 1;
      return 0;
}

/*
 * SFR-CACC algorithm:
 * F) If count_of_newacks is less than 2, let d be the
 * destination to which t was sent. If cacc_saw_newack
 * is 0 for destination d, then the sender MUST NOT
 * increment missing report count for t.
 */
static inline int sctp_cacc_skip_3_1_f(struct sctp_transport *transport,
                               int count_of_newacks)
{
      if (count_of_newacks < 2 && !transport->cacc.cacc_saw_newack)
            return 1;
      return 0;
}

/*
 * SFR-CACC algorithm:
 * 3.1) If CYCLING_CHANGEOVER is 0, the sender SHOULD
 * execute steps C, D, F.
 *
 * C has been implemented in sctp_outq_sack
 */
static inline int sctp_cacc_skip_3_1(struct sctp_transport *primary,
                             struct sctp_transport *transport,
                             int count_of_newacks)
{
      if (!primary->cacc.cycling_changeover) {
            if (sctp_cacc_skip_3_1_d(primary, transport, count_of_newacks))
                  return 1;
            if (sctp_cacc_skip_3_1_f(transport, count_of_newacks))
                  return 1;
            return 0;
      }
      return 0;
}

/*
 * SFR-CACC algorithm:
 * 3.2) Else if CYCLING_CHANGEOVER is 1, and t is less
 * than next_tsn_at_change of the current primary, then
 * the sender MUST NOT increment missing report count
 * for t.
 */
static inline int sctp_cacc_skip_3_2(struct sctp_transport *primary, __u32 tsn)
{
      if (primary->cacc.cycling_changeover &&
          TSN_lt(tsn, primary->cacc.next_tsn_at_change))
            return 1;
      return 0;
}

/*
 * SFR-CACC algorithm:
 * 3) If the missing report count for TSN t is to be
 * incremented according to [RFC2960] and
 * [SCTP_STEWART-2002], and CHANGEOVER_ACTIVE is set,
 * then the sender MUST futher execute steps 3.1 and
 * 3.2 to determine if the missing report count for
 * TSN t SHOULD NOT be incremented.
 *
 * 3.3) If 3.1 and 3.2 do not dictate that the missing
 * report count for t should not be incremented, then
 * the sender SOULD increment missing report count for
 * t (according to [RFC2960] and [SCTP_STEWART_2002]).
 */
static inline int sctp_cacc_skip(struct sctp_transport *primary,
                         struct sctp_transport *transport,
                         int count_of_newacks,
                         __u32 tsn)
{
      if (primary->cacc.changeover_active &&
          (sctp_cacc_skip_3_1(primary, transport, count_of_newacks)
           || sctp_cacc_skip_3_2(primary, tsn)))
            return 1;
      return 0;
}

/* Initialize an existing sctp_outq.  This does the boring stuff.
 * You still need to define handlers if you really want to DO
 * something with this structure...
 */
void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q)
{
      q->asoc = asoc;
      INIT_LIST_HEAD(&q->out_chunk_list);
      INIT_LIST_HEAD(&q->control_chunk_list);
      INIT_LIST_HEAD(&q->retransmit);
      INIT_LIST_HEAD(&q->sacked);
      INIT_LIST_HEAD(&q->abandoned);

      q->outstanding_bytes = 0;
      q->empty = 1;
      q->cork  = 0;

      q->malloced = 0;
      q->out_qlen = 0;
}

/* Free the outqueue structure and any related pending chunks.
 */
void sctp_outq_teardown(struct sctp_outq *q)
{
      struct sctp_transport *transport;
      struct list_head *lchunk, *pos, *temp;
      struct sctp_chunk *chunk, *tmp;

      /* Throw away unacknowledged chunks. */
      list_for_each(pos, &q->asoc->peer.transport_addr_list) {
            transport = list_entry(pos, struct sctp_transport, transports);
            while ((lchunk = sctp_list_dequeue(&transport->transmitted)) != NULL) {
                  chunk = list_entry(lchunk, struct sctp_chunk,
                                 transmitted_list);
                  /* Mark as part of a failed message. */
                  sctp_chunk_fail(chunk, q->error);
                  sctp_chunk_free(chunk);
            }
      }

      /* Throw away chunks that have been gap ACKed.  */
      list_for_each_safe(lchunk, temp, &q->sacked) {
            list_del_init(lchunk);
            chunk = list_entry(lchunk, struct sctp_chunk,
                           transmitted_list);
            sctp_chunk_fail(chunk, q->error);
            sctp_chunk_free(chunk);
      }

      /* Throw away any chunks in the retransmit queue. */
      list_for_each_safe(lchunk, temp, &q->retransmit) {
            list_del_init(lchunk);
            chunk = list_entry(lchunk, struct sctp_chunk,
                           transmitted_list);
            sctp_chunk_fail(chunk, q->error);
            sctp_chunk_free(chunk);
      }

      /* Throw away any chunks that are in the abandoned queue. */
      list_for_each_safe(lchunk, temp, &q->abandoned) {
            list_del_init(lchunk);
            chunk = list_entry(lchunk, struct sctp_chunk,
                           transmitted_list);
            sctp_chunk_fail(chunk, q->error);
            sctp_chunk_free(chunk);
      }

      /* Throw away any leftover data chunks. */
      while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {

            /* Mark as send failure. */
            sctp_chunk_fail(chunk, q->error);
            sctp_chunk_free(chunk);
      }

      q->error = 0;

      /* Throw away any leftover control chunks. */
      list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
            list_del_init(&chunk->list);
            sctp_chunk_free(chunk);
      }
}

/* Free the outqueue structure and any related pending chunks.  */
void sctp_outq_free(struct sctp_outq *q)
{
      /* Throw away leftover chunks. */
      sctp_outq_teardown(q);

      /* If we were kmalloc()'d, free the memory.  */
      if (q->malloced)
            kfree(q);
}

/* Put a new chunk in an sctp_outq.  */
int sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk)
{
      int error = 0;

      SCTP_DEBUG_PRINTK("sctp_outq_tail(%p, %p[%s])\n",
                    q, chunk, chunk && chunk->chunk_hdr ?
                    sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type))
                    : "Illegal Chunk");

      /* If it is data, queue it up, otherwise, send it
       * immediately.
       */
      if (SCTP_CID_DATA == chunk->chunk_hdr->type) {
            /* Is it OK to queue data chunks?  */
            /* From 9. Termination of Association
             *
             * When either endpoint performs a shutdown, the
             * association on each peer will stop accepting new
             * data from its user and only deliver data in queue
             * at the time of sending or receiving the SHUTDOWN
             * chunk.
             */
            switch (q->asoc->state) {
            case SCTP_STATE_EMPTY:
            case SCTP_STATE_CLOSED:
            case SCTP_STATE_SHUTDOWN_PENDING:
            case SCTP_STATE_SHUTDOWN_SENT:
            case SCTP_STATE_SHUTDOWN_RECEIVED:
            case SCTP_STATE_SHUTDOWN_ACK_SENT:
                  /* Cannot send after transport endpoint shutdown */
                  error = -ESHUTDOWN;
                  break;

            default:
                  SCTP_DEBUG_PRINTK("outqueueing (%p, %p[%s])\n",
                    q, chunk, chunk && chunk->chunk_hdr ?
                    sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type))
                    : "Illegal Chunk");

                  sctp_outq_tail_data(q, chunk);
                  if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
                        SCTP_INC_STATS(SCTP_MIB_OUTUNORDERCHUNKS);
                  else
                        SCTP_INC_STATS(SCTP_MIB_OUTORDERCHUNKS);
                  q->empty = 0;
                  break;
            }
      } else {
            list_add_tail(&chunk->list, &q->control_chunk_list);
            SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
      }

      if (error < 0)
            return error;

      if (!q->cork)
            error = sctp_outq_flush(q, 0);

      return error;
}

/* Insert a chunk into the sorted list based on the TSNs.  The retransmit list
 * and the abandoned list are in ascending order.
 */
static void sctp_insert_list(struct list_head *head, struct list_head *new)
{
      struct list_head *pos;
      struct sctp_chunk *nchunk, *lchunk;
      __u32 ntsn, ltsn;
      int done = 0;

      nchunk = list_entry(new, struct sctp_chunk, transmitted_list);
      ntsn = ntohl(nchunk->subh.data_hdr->tsn);

      list_for_each(pos, head) {
            lchunk = list_entry(pos, struct sctp_chunk, transmitted_list);
            ltsn = ntohl(lchunk->subh.data_hdr->tsn);
            if (TSN_lt(ntsn, ltsn)) {
                  list_add(new, pos->prev);
                  done = 1;
                  break;
            }
      }
      if (!done)
            list_add_tail(new, head);
}

/* Mark all the eligible packets on a transport for retransmission.  */
void sctp_retransmit_mark(struct sctp_outq *q,
                    struct sctp_transport *transport,
                    __u8 reason)
{
      struct list_head *lchunk, *ltemp;
      struct sctp_chunk *chunk;

      /* Walk through the specified transmitted queue.  */
      list_for_each_safe(lchunk, ltemp, &transport->transmitted) {
            chunk = list_entry(lchunk, struct sctp_chunk,
                           transmitted_list);

            /* If the chunk is abandoned, move it to abandoned list. */
            if (sctp_chunk_abandoned(chunk)) {
                  list_del_init(lchunk);
                  sctp_insert_list(&q->abandoned, lchunk);

                  /* If this chunk has not been previousely acked,
                   * stop considering it 'outstanding'.  Our peer
                   * will most likely never see it since it will
                   * not be retransmitted
                   */
                  if (!chunk->tsn_gap_acked) {
                        chunk->transport->flight_size -=
                                    sctp_data_size(chunk);
                        q->outstanding_bytes -= sctp_data_size(chunk);
                        q->asoc->peer.rwnd += (sctp_data_size(chunk) +
                                          sizeof(struct sk_buff));
                  }
                  continue;
            }

            /* If we are doing  retransmission due to a timeout or pmtu
             * discovery, only the  chunks that are not yet acked should
             * be added to the retransmit queue.
             */
            if ((reason == SCTP_RTXR_FAST_RTX  &&
                      (chunk->fast_retransmit > 0)) ||
                (reason != SCTP_RTXR_FAST_RTX  && !chunk->tsn_gap_acked)) {
                  /* If this chunk was sent less then 1 rto ago, do not
                   * retransmit this chunk, but give the peer time
                   * to acknowlege it.  Do this only when
                   * retransmitting due to T3 timeout.
                   */
                  if (reason == SCTP_RTXR_T3_RTX &&
                      (jiffies - chunk->sent_at) < transport->last_rto)
                        continue;

                  /* RFC 2960 6.2.1 Processing a Received SACK
                   *
                   * C) Any time a DATA chunk is marked for
                   * retransmission (via either T3-rtx timer expiration
                   * (Section 6.3.3) or via fast retransmit
                   * (Section 7.2.4)), add the data size of those
                   * chunks to the rwnd.
                   */
                  q->asoc->peer.rwnd += (sctp_data_size(chunk) +
                                    sizeof(struct sk_buff));
                  q->outstanding_bytes -= sctp_data_size(chunk);
                  transport->flight_size -= sctp_data_size(chunk);

                  /* sctpimpguide-05 Section 2.8.2
                   * M5) If a T3-rtx timer expires, the
                   * 'TSN.Missing.Report' of all affected TSNs is set
                   * to 0.
                   */
                  chunk->tsn_missing_report = 0;

                  /* If a chunk that is being used for RTT measurement
                   * has to be retransmitted, we cannot use this chunk
                   * anymore for RTT measurements. Reset rto_pending so
                   * that a new RTT measurement is started when a new
                   * data chunk is sent.
                   */
                  if (chunk->rtt_in_progress) {
                        chunk->rtt_in_progress = 0;
                        transport->rto_pending = 0;
                  }

                  /* Move the chunk to the retransmit queue. The chunks
                   * on the retransmit queue are always kept in order.
                   */
                  list_del_init(lchunk);
                  sctp_insert_list(&q->retransmit, lchunk);
            }
      }

      SCTP_DEBUG_PRINTK("%s: transport: %p, reason: %d, "
                    "cwnd: %d, ssthresh: %d, flight_size: %d, "
                    "pba: %d\n", __FUNCTION__,
                    transport, reason,
                    transport->cwnd, transport->ssthresh,
                    transport->flight_size,
                    transport->partial_bytes_acked);

}

/* Mark all the eligible packets on a transport for retransmission and force
 * one packet out.
 */
void sctp_retransmit(struct sctp_outq *q, struct sctp_transport *transport,
                 sctp_retransmit_reason_t reason)
{
      int error = 0;

      switch(reason) {
      case SCTP_RTXR_T3_RTX:
            SCTP_INC_STATS(SCTP_MIB_T3_RETRANSMITS);
            sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_T3_RTX);
            /* Update the retran path if the T3-rtx timer has expired for
             * the current retran path.
             */
            if (transport == transport->asoc->peer.retran_path)
                  sctp_assoc_update_retran_path(transport->asoc);
            break;
      case SCTP_RTXR_FAST_RTX:
            SCTP_INC_STATS(SCTP_MIB_FAST_RETRANSMITS);
            sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
            break;
      case SCTP_RTXR_PMTUD:
            SCTP_INC_STATS(SCTP_MIB_PMTUD_RETRANSMITS);
            break;
      case SCTP_RTXR_T1_RTX:
            SCTP_INC_STATS(SCTP_MIB_T1_RETRANSMITS);
            break;
      default:
            BUG();
      }

      sctp_retransmit_mark(q, transport, reason);

      /* PR-SCTP A5) Any time the T3-rtx timer expires, on any destination,
       * the sender SHOULD try to advance the "Advanced.Peer.Ack.Point" by
       * following the procedures outlined in C1 - C5.
       */
      sctp_generate_fwdtsn(q, q->asoc->ctsn_ack_point);

      error = sctp_outq_flush(q, /* rtx_timeout */ 1);

      if (error)
            q->asoc->base.sk->sk_err = -error;
}

/*
 * Transmit DATA chunks on the retransmit queue.  Upon return from
 * sctp_outq_flush_rtx() the packet 'pkt' may contain chunks which
 * need to be transmitted by the caller.
 * We assume that pkt->transport has already been set.
 *
 * The return value is a normal kernel error return value.
 */
static int sctp_outq_flush_rtx(struct sctp_outq *q, struct sctp_packet *pkt,
                         int rtx_timeout, int *start_timer)
{
      struct list_head *lqueue;
      struct list_head *lchunk, *lchunk1;
      struct sctp_transport *transport = pkt->transport;
      sctp_xmit_t status;
      struct sctp_chunk *chunk, *chunk1;
      struct sctp_association *asoc;
      int error = 0;

      asoc = q->asoc;
      lqueue = &q->retransmit;

      /* RFC 2960 6.3.3 Handle T3-rtx Expiration
       *
       * E3) Determine how many of the earliest (i.e., lowest TSN)
       * outstanding DATA chunks for the address for which the
       * T3-rtx has expired will fit into a single packet, subject
       * to the MTU constraint for the path corresponding to the
       * destination transport address to which the retransmission
       * is being sent (this may be different from the address for
       * which the timer expires [see Section 6.4]). Call this value
       * K. Bundle and retransmit those K DATA chunks in a single
       * packet to the destination endpoint.
       *
       * [Just to be painfully clear, if we are retransmitting
       * because a timeout just happened, we should send only ONE
       * packet of retransmitted data.]
       */
      lchunk = sctp_list_dequeue(lqueue);

      while (lchunk) {
            chunk = list_entry(lchunk, struct sctp_chunk,
                           transmitted_list);

            /* Make sure that Gap Acked TSNs are not retransmitted.  A
             * simple approach is just to move such TSNs out of the
             * way and into a 'transmitted' queue and skip to the
             * next chunk.
             */
            if (chunk->tsn_gap_acked) {
                  list_add_tail(lchunk, &transport->transmitted);
                  lchunk = sctp_list_dequeue(lqueue);
                  continue;
            }

            /* Attempt to append this chunk to the packet. */
            status = sctp_packet_append_chunk(pkt, chunk);

            switch (status) {
            case SCTP_XMIT_PMTU_FULL:
                  /* Send this packet.  */
                  if ((error = sctp_packet_transmit(pkt)) == 0)
                        *start_timer = 1;

                  /* If we are retransmitting, we should only
                   * send a single packet.
                   */
                  if (rtx_timeout) {
                        list_add(lchunk, lqueue);
                        lchunk = NULL;
                  }

                  /* Bundle lchunk in the next round.  */
                  break;

            case SCTP_XMIT_RWND_FULL:
                  /* Send this packet. */
                  if ((error = sctp_packet_transmit(pkt)) == 0)
                        *start_timer = 1;

                  /* Stop sending DATA as there is no more room
                   * at the receiver.
                   */
                  list_add(lchunk, lqueue);
                  lchunk = NULL;
                  break;

            case SCTP_XMIT_NAGLE_DELAY:
                  /* Send this packet. */
                  if ((error = sctp_packet_transmit(pkt)) == 0)
                        *start_timer = 1;

                  /* Stop sending DATA because of nagle delay. */
                  list_add(lchunk, lqueue);
                  lchunk = NULL;
                  break;

            default:
                  /* The append was successful, so add this chunk to
                   * the transmitted list.
                   */
                  list_add_tail(lchunk, &transport->transmitted);

                  /* Mark the chunk as ineligible for fast retransmit
                   * after it is retransmitted.
                   */
                  if (chunk->fast_retransmit > 0)
                        chunk->fast_retransmit = -1;

                  *start_timer = 1;
                  q->empty = 0;

                  /* Retrieve a new chunk to bundle. */
                  lchunk = sctp_list_dequeue(lqueue);
                  break;
            }

            /* If we are here due to a retransmit timeout or a fast
             * retransmit and if there are any chunks left in the retransmit
             * queue that could not fit in the PMTU sized packet, they need
             * to be marked as ineligible for a subsequent fast retransmit.
             */
            if (rtx_timeout && !lchunk) {
                  list_for_each(lchunk1, lqueue) {
                        chunk1 = list_entry(lchunk1, struct sctp_chunk,
                                        transmitted_list);
                        if (chunk1->fast_retransmit > 0)
                              chunk1->fast_retransmit = -1;
                  }
            }
      }

      return error;
}

/* Cork the outqueue so queued chunks are really queued. */
int sctp_outq_uncork(struct sctp_outq *q)
{
      int error = 0;
      if (q->cork)
            q->cork = 0;
      error = sctp_outq_flush(q, 0);
      return error;
}

/*
 * Try to flush an outqueue.
 *
 * Description: Send everything in q which we legally can, subject to
 * congestion limitations.
 * * Note: This function can be called from multiple contexts so appropriate
 * locking concerns must be made.  Today we use the sock lock to protect
 * this function.
 */
int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
{
      struct sctp_packet *packet;
      struct sctp_packet singleton;
      struct sctp_association *asoc = q->asoc;
      __u16 sport = asoc->base.bind_addr.port;
      __u16 dport = asoc->peer.port;
      __u32 vtag = asoc->peer.i.init_tag;
      struct sctp_transport *transport = NULL;
      struct sctp_transport *new_transport;
      struct sctp_chunk *chunk, *tmp;
      sctp_xmit_t status;
      int error = 0;
      int start_timer = 0;

      /* These transports have chunks to send. */
      struct list_head transport_list;
      struct list_head *ltransport;

      INIT_LIST_HEAD(&transport_list);
      packet = NULL;

      /*
       * 6.10 Bundling
       *   ...
       *   When bundling control chunks with DATA chunks, an
       *   endpoint MUST place control chunks first in the outbound
       *   SCTP packet.  The transmitter MUST transmit DATA chunks
       *   within a SCTP packet in increasing order of TSN.
       *   ...
       */

      list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
            list_del_init(&chunk->list);

            /* Pick the right transport to use. */
            new_transport = chunk->transport;

            if (!new_transport) {
                  new_transport = asoc->peer.active_path;
            } else if ((new_transport->state == SCTP_INACTIVE) ||
                     (new_transport->state == SCTP_UNCONFIRMED)) {
                  /* If the chunk is Heartbeat or Heartbeat Ack,
                   * send it to chunk->transport, even if it's
                   * inactive.
                   *
                   * 3.3.6 Heartbeat Acknowledgement:
                   * ...
                   * A HEARTBEAT ACK is always sent to the source IP
                   * address of the IP datagram containing the
                   * HEARTBEAT chunk to which this ack is responding.
                   * ...
                   */
                  if (chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT &&
                      chunk->chunk_hdr->type != SCTP_CID_HEARTBEAT_ACK)
                        new_transport = asoc->peer.active_path;
            }

            /* Are we switching transports?
             * Take care of transport locks.
             */
            if (new_transport != transport) {
                  transport = new_transport;
                  if (list_empty(&transport->send_ready)) {
                        list_add_tail(&transport->send_ready,
                                    &transport_list);
                  }
                  packet = &transport->packet;
                  sctp_packet_config(packet, vtag,
                                 asoc->peer.ecn_capable);
            }

            switch (chunk->chunk_hdr->type) {
            /*
             * 6.10 Bundling
             *   ...
             *   An endpoint MUST NOT bundle INIT, INIT ACK or SHUTDOWN
             *   COMPLETE with any other chunks.  [Send them immediately.]
             */
            case SCTP_CID_INIT:
            case SCTP_CID_INIT_ACK:
            case SCTP_CID_SHUTDOWN_COMPLETE:
                  sctp_packet_init(&singleton, transport, sport, dport);
                  sctp_packet_config(&singleton, vtag, 0);
                  sctp_packet_append_chunk(&singleton, chunk);
                  error = sctp_packet_transmit(&singleton);
                  if (error < 0)
                        return error;
                  break;

            case SCTP_CID_ABORT:
            case SCTP_CID_SACK:
            case SCTP_CID_HEARTBEAT:
            case SCTP_CID_HEARTBEAT_ACK:
            case SCTP_CID_SHUTDOWN:
            case SCTP_CID_SHUTDOWN_ACK:
            case SCTP_CID_ERROR:
            case SCTP_CID_COOKIE_ECHO:
            case SCTP_CID_COOKIE_ACK:
            case SCTP_CID_ECN_ECNE:
            case SCTP_CID_ECN_CWR:
            case SCTP_CID_ASCONF:
            case SCTP_CID_ASCONF_ACK:
            case SCTP_CID_FWD_TSN:
                  sctp_packet_transmit_chunk(packet, chunk);
                  break;

            default:
                  /* We built a chunk with an illegal type! */
                  BUG();
            }
      }

      /* Is it OK to send data chunks?  */
      switch (asoc->state) {
      case SCTP_STATE_COOKIE_ECHOED:
            /* Only allow bundling when this packet has a COOKIE-ECHO
             * chunk.
             */
            if (!packet || !packet->has_cookie_echo)
                  break;

            /* fallthru */
      case SCTP_STATE_ESTABLISHED:
      case SCTP_STATE_SHUTDOWN_PENDING:
      case SCTP_STATE_SHUTDOWN_RECEIVED:
            /*
             * RFC 2960 6.1  Transmission of DATA Chunks
             *
             * C) When the time comes for the sender to transmit,
             * before sending new DATA chunks, the sender MUST
             * first transmit any outstanding DATA chunks which
             * are marked for retransmission (limited by the
             * current cwnd).
             */
            if (!list_empty(&q->retransmit)) {
                  if (transport == asoc->peer.retran_path)
                        goto retran;

                  /* Switch transports & prepare the packet.  */

                  transport = asoc->peer.retran_path;

                  if (list_empty(&transport->send_ready)) {
                        list_add_tail(&transport->send_ready,
                                    &transport_list);
                  }

                  packet = &transport->packet;
                  sctp_packet_config(packet, vtag,
                                 asoc->peer.ecn_capable);
            retran:
                  error = sctp_outq_flush_rtx(q, packet,
                                        rtx_timeout, &start_timer);

                  if (start_timer)
                        sctp_transport_reset_timers(transport);

                  /* This can happen on COOKIE-ECHO resend.  Only
                   * one chunk can get bundled with a COOKIE-ECHO.
                   */
                  if (packet->has_cookie_echo)
                        goto sctp_flush_out;

                  /* Don't send new data if there is still data
                   * waiting to retransmit.
                   */
                  if (!list_empty(&q->retransmit))
                        goto sctp_flush_out;
            }

            /* Finally, transmit new packets.  */
            start_timer = 0;
            while ((chunk = sctp_outq_dequeue_data(q)) != NULL) {
                  /* RFC 2960 6.5 Every DATA chunk MUST carry a valid
                   * stream identifier.
                   */
                  if (chunk->sinfo.sinfo_stream >=
                      asoc->c.sinit_num_ostreams) {

                        /* Mark as failed send. */
                        sctp_chunk_fail(chunk, SCTP_ERROR_INV_STRM);
                        sctp_chunk_free(chunk);
                        continue;
                  }

                  /* Has this chunk expired? */
                  if (sctp_chunk_abandoned(chunk)) {
                        sctp_chunk_fail(chunk, 0);
                        sctp_chunk_free(chunk);
                        continue;
                  }

                  /* If there is a specified transport, use it.
                   * Otherwise, we want to use the active path.
                   */
                  new_transport = chunk->transport;
                  if (!new_transport ||
                      ((new_transport->state == SCTP_INACTIVE) ||
                       (new_transport->state == SCTP_UNCONFIRMED)))
                        new_transport = asoc->peer.active_path;

                  /* Change packets if necessary.  */
                  if (new_transport != transport) {
                        transport = new_transport;

                        /* Schedule to have this transport's
                         * packet flushed.
                         */
                        if (list_empty(&transport->send_ready)) {
                              list_add_tail(&transport->send_ready,
                                          &transport_list);
                        }

                        packet = &transport->packet;
                        sctp_packet_config(packet, vtag,
                                       asoc->peer.ecn_capable);
                  }

                  SCTP_DEBUG_PRINTK("sctp_outq_flush(%p, %p[%s]), ",
                                q, chunk,
                                chunk && chunk->chunk_hdr ?
                                sctp_cname(SCTP_ST_CHUNK(
                                      chunk->chunk_hdr->type))
                                : "Illegal Chunk");

                  SCTP_DEBUG_PRINTK("TX TSN 0x%x skb->head "
                              "%p skb->users %d.\n",
                              ntohl(chunk->subh.data_hdr->tsn),
                              chunk->skb ?chunk->skb->head : NULL,
                              chunk->skb ?
                              atomic_read(&chunk->skb->users) : -1);

                  /* Add the chunk to the packet.  */
                  status = sctp_packet_transmit_chunk(packet, chunk);

                  switch (status) {
                  case SCTP_XMIT_PMTU_FULL:
                  case SCTP_XMIT_RWND_FULL:
                  case SCTP_XMIT_NAGLE_DELAY:
                        /* We could not append this chunk, so put
                         * the chunk back on the output queue.
                         */
                        SCTP_DEBUG_PRINTK("sctp_outq_flush: could "
                              "not transmit TSN: 0x%x, status: %d\n",
                              ntohl(chunk->subh.data_hdr->tsn),
                              status);
                        sctp_outq_head_data(q, chunk);
                        goto sctp_flush_out;
                        break;

                  case SCTP_XMIT_OK:
                        break;

                  default:
                        BUG();
                  }

                  /* BUG: We assume that the sctp_packet_transmit()
                   * call below will succeed all the time and add the
                   * chunk to the transmitted list and restart the
                   * timers.
                   * It is possible that the call can fail under OOM
                   * conditions.
                   *
                   * Is this really a problem?  Won't this behave
                   * like a lost TSN?
                   */
                  list_add_tail(&chunk->transmitted_list,
                              &transport->transmitted);

                  sctp_transport_reset_timers(transport);

                  q->empty = 0;

                  /* Only let one DATA chunk get bundled with a
                   * COOKIE-ECHO chunk.
                   */
                  if (packet->has_cookie_echo)
                        goto sctp_flush_out;
            }
            break;

      default:
            /* Do nothing.  */
            break;
      }

sctp_flush_out:

      /* Before returning, examine all the transports touched in
       * this call.  Right now, we bluntly force clear all the
       * transports.  Things might change after we implement Nagle.
       * But such an examination is still required.
       *
       * --xguo
       */
      while ((ltransport = sctp_list_dequeue(&transport_list)) != NULL ) {
            struct sctp_transport *t = list_entry(ltransport,
                                          struct sctp_transport,
                                          send_ready);
            packet = &t->packet;
            if (!sctp_packet_empty(packet))
                  error = sctp_packet_transmit(packet);
      }

      return error;
}

/* Update unack_data based on the incoming SACK chunk */
static void sctp_sack_update_unack_data(struct sctp_association *assoc,
                              struct sctp_sackhdr *sack)
{
      sctp_sack_variable_t *frags;
      __u16 unack_data;
      int i;

      unack_data = assoc->next_tsn - assoc->ctsn_ack_point - 1;

      frags = sack->variable;
      for (i = 0; i < ntohs(sack->num_gap_ack_blocks); i++) {
            unack_data -= ((ntohs(frags[i].gab.end) -
                        ntohs(frags[i].gab.start) + 1));
      }

      assoc->unack_data = unack_data;
}

/* Return the highest new tsn that is acknowledged by the given SACK chunk. */
static __u32 sctp_highest_new_tsn(struct sctp_sackhdr *sack,
                          struct sctp_association *asoc)
{
      struct list_head *ltransport, *lchunk;
      struct sctp_transport *transport;
      struct sctp_chunk *chunk;
      __u32 highest_new_tsn, tsn;
      struct list_head *transport_list = &asoc->peer.transport_addr_list;

      highest_new_tsn = ntohl(sack->cum_tsn_ack);

      list_for_each(ltransport, transport_list) {
            transport = list_entry(ltransport, struct sctp_transport,
                               transports);
            list_for_each(lchunk, &transport->transmitted) {
                  chunk = list_entry(lchunk, struct sctp_chunk,
                                 transmitted_list);
                  tsn = ntohl(chunk->subh.data_hdr->tsn);

                  if (!chunk->tsn_gap_acked &&
                      TSN_lt(highest_new_tsn, tsn) &&
                      sctp_acked(sack, tsn))
                        highest_new_tsn = tsn;
            }
      }

      return highest_new_tsn;
}

/* This is where we REALLY process a SACK.
 *
 * Process the SACK against the outqueue.  Mostly, this just frees
 * things off the transmitted queue.
 */
int sctp_outq_sack(struct sctp_outq *q, struct sctp_sackhdr *sack)
{
      struct sctp_association *asoc = q->asoc;
      struct sctp_transport *transport;
      struct sctp_chunk *tchunk = NULL;
      struct list_head *lchunk, *transport_list, *pos, *temp;
      sctp_sack_variable_t *frags = sack->variable;
      __u32 sack_ctsn, ctsn, tsn;
      __u32 highest_tsn, highest_new_tsn;
      __u32 sack_a_rwnd;
      unsigned outstanding;
      struct sctp_transport *primary = asoc->peer.primary_path;
      int count_of_newacks = 0;

      /* Grab the association's destination address list. */
      transport_list = &asoc->peer.transport_addr_list;

      sack_ctsn = ntohl(sack->cum_tsn_ack);

      /*
       * SFR-CACC algorithm:
       * On receipt of a SACK the sender SHOULD execute the
       * following statements.
       *
       * 1) If the cumulative ack in the SACK passes next tsn_at_change
       * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
       * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
       * all destinations.
       */
      if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
            primary->cacc.changeover_active = 0;
            list_for_each(pos, transport_list) {
                  transport = list_entry(pos, struct sctp_transport,
                              transports);
                  transport->cacc.cycling_changeover = 0;
            }
      }

      /*
       * SFR-CACC algorithm:
       * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
       * is set the receiver of the SACK MUST take the following actions:
       *
       * A) Initialize the cacc_saw_newack to 0 for all destination
       * addresses.
       */
      if (sack->num_gap_ack_blocks &&
          primary->cacc.changeover_active) {
            list_for_each(pos, transport_list) {
                  transport = list_entry(pos, struct sctp_transport,
                              transports);
                  transport->cacc.cacc_saw_newack = 0;
            }
      }

      /* Get the highest TSN in the sack. */
      highest_tsn = sack_ctsn;
      if (sack->num_gap_ack_blocks)
            highest_tsn +=
                ntohs(frags[ntohs(sack->num_gap_ack_blocks) - 1].gab.end);

      if (TSN_lt(asoc->highest_sacked, highest_tsn)) {
            highest_new_tsn = highest_tsn;
            asoc->highest_sacked = highest_tsn;
      } else {
            highest_new_tsn = sctp_highest_new_tsn(sack, asoc);
      }

      /* Run through the retransmit queue.  Credit bytes received
       * and free those chunks that we can.
       */
      sctp_check_transmitted(q, &q->retransmit, NULL, sack, highest_new_tsn);
      sctp_mark_missing(q, &q->retransmit, NULL, highest_new_tsn, 0);

      /* Run through the transmitted queue.
       * Credit bytes received and free those chunks which we can.
       *
       * This is a MASSIVE candidate for optimization.
       */
      list_for_each(pos, transport_list) {
            transport  = list_entry(pos, struct sctp_transport,
                              transports);
            sctp_check_transmitted(q, &transport->transmitted,
                               transport, sack, highest_new_tsn);
            /*
             * SFR-CACC algorithm:
             * C) Let count_of_newacks be the number of
             * destinations for which cacc_saw_newack is set.
             */
            if (transport->cacc.cacc_saw_newack)
                  count_of_newacks ++;
      }

      list_for_each(pos, transport_list) {
            transport  = list_entry(pos, struct sctp_transport,
                              transports);
            sctp_mark_missing(q, &transport->transmitted, transport,
                          highest_new_tsn, count_of_newacks);
      }

      /* Move the Cumulative TSN Ack Point if appropriate.  */
      if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn))
            asoc->ctsn_ack_point = sack_ctsn;

      /* Update unack_data field in the assoc. */
      sctp_sack_update_unack_data(asoc, sack);

      ctsn = asoc->ctsn_ack_point;

      /* Throw away stuff rotting on the sack queue.  */
      list_for_each_safe(lchunk, temp, &q->sacked) {
            tchunk = list_entry(lchunk, struct sctp_chunk,
                            transmitted_list);
            tsn = ntohl(tchunk->subh.data_hdr->tsn);
            if (TSN_lte(tsn, ctsn))
                  sctp_chunk_free(tchunk);
      }

      /* ii) Set rwnd equal to the newly received a_rwnd minus the
       *     number of bytes still outstanding after processing the
       *     Cumulative TSN Ack and the Gap Ack Blocks.
       */

      sack_a_rwnd = ntohl(sack->a_rwnd);
      outstanding = q->outstanding_bytes;

      if (outstanding < sack_a_rwnd)
            sack_a_rwnd -= outstanding;
      else
            sack_a_rwnd = 0;

      asoc->peer.rwnd = sack_a_rwnd;

      sctp_generate_fwdtsn(q, sack_ctsn);

      SCTP_DEBUG_PRINTK("%s: sack Cumulative TSN Ack is 0x%x.\n",
                    __FUNCTION__, sack_ctsn);
      SCTP_DEBUG_PRINTK("%s: Cumulative TSN Ack of association, "
                    "%p is 0x%x. Adv peer ack point: 0x%x\n",
                    __FUNCTION__, asoc, ctsn, asoc->adv_peer_ack_point);

      /* See if all chunks are acked.
       * Make sure the empty queue handler will get run later.
       */
      q->empty = (list_empty(&q->out_chunk_list) &&
                list_empty(&q->control_chunk_list) &&
                list_empty(&q->retransmit));
      if (!q->empty)
            goto finish;

      list_for_each(pos, transport_list) {
            transport  = list_entry(pos, struct sctp_transport,
                              transports);
            q->empty = q->empty && list_empty(&transport->transmitted);
            if (!q->empty)
                  goto finish;
      }

      SCTP_DEBUG_PRINTK("sack queue is empty.\n");
finish:
      return q->empty;
}

/* Is the outqueue empty?  */
int sctp_outq_is_empty(const struct sctp_outq *q)
{
      return q->empty;
}

/********************************************************************
 * 2nd Level Abstractions
 ********************************************************************/

/* Go through a transport's transmitted list or the association's retransmit
 * list and move chunks that are acked by the Cumulative TSN Ack to q->sacked.
 * The retransmit list will not have an associated transport.
 *
 * I added coherent debug information output.   --xguo
 *
 * Instead of printing 'sacked' or 'kept' for each TSN on the
 * transmitted_queue, we print a range: SACKED: TSN1-TSN2, TSN3, TSN4-TSN5.
 * KEPT TSN6-TSN7, etc.
 */
static void sctp_check_transmitted(struct sctp_outq *q,
                           struct list_head *transmitted_queue,
                           struct sctp_transport *transport,
                           struct sctp_sackhdr *sack,
                           __u32 highest_new_tsn_in_sack)
{
      struct list_head *lchunk;
      struct sctp_chunk *tchunk;
      struct list_head tlist;
      __u32 tsn;
      __u32 sack_ctsn;
      __u32 rtt;
      __u8 restart_timer = 0;
      int bytes_acked = 0;

      /* These state variables are for coherent debug output. --xguo */

#if SCTP_DEBUG
      __u32 dbg_ack_tsn = 0;  /* An ACKed TSN range starts here... */
      __u32 dbg_last_ack_tsn = 0;  /* ...and finishes here.      */
      __u32 dbg_kept_tsn = 0; /* An un-ACKed range starts here...  */
      __u32 dbg_last_kept_tsn = 0; /* ...and finishes here.      */

      /* 0 : The last TSN was ACKed.
       * 1 : The last TSN was NOT ACKed (i.e. KEPT).
       * -1: We need to initialize.
       */
      int dbg_prt_state = -1;
#endif /* SCTP_DEBUG */

      sack_ctsn = ntohl(sack->cum_tsn_ack);

      INIT_LIST_HEAD(&tlist);

      /* The while loop will skip empty transmitted queues. */
      while (NULL != (lchunk = sctp_list_dequeue(transmitted_queue))) {
            tchunk = list_entry(lchunk, struct sctp_chunk,
                            transmitted_list);

            if (sctp_chunk_abandoned(tchunk)) {
                  /* Move the chunk to abandoned list. */
                  sctp_insert_list(&q->abandoned, lchunk);

                  /* If this chunk has not been acked, stop
                   * considering it as 'outstanding'.
                   */
                  if (!tchunk->tsn_gap_acked) {
                        tchunk->transport->flight_size -=
                                    sctp_data_size(tchunk);
                        q->outstanding_bytes -= sctp_data_size(tchunk);
                  }
                  continue;
            }

            tsn = ntohl(tchunk->subh.data_hdr->tsn);
            if (sctp_acked(sack, tsn)) {
                  /* If this queue is the retransmit queue, the
                   * retransmit timer has already reclaimed
                   * the outstanding bytes for this chunk, so only
                   * count bytes associated with a transport.
                   */
                  if (transport) {
                        /* If this chunk is being used for RTT
                         * measurement, calculate the RTT and update
                         * the RTO using this value.
                         *
                         * 6.3.1 C5) Karn's algorithm: RTT measurements
                         * MUST NOT be made using packets that were
                         * retransmitted (and thus for which it is
                         * ambiguous whether the reply was for the
                         * first instance of the packet or a later
                         * instance).
                         */
                        if (!tchunk->tsn_gap_acked &&
                            !tchunk->resent &&
                            tchunk->rtt_in_progress) {
                              tchunk->rtt_in_progress = 0;
                              rtt = jiffies - tchunk->sent_at;
                              sctp_transport_update_rto(transport,
                                                  rtt);
                        }
                  }
                  if (TSN_lte(tsn, sack_ctsn)) {
                        /* RFC 2960  6.3.2 Retransmission Timer Rules
                         *
                         * R3) Whenever a SACK is received
                         * that acknowledges the DATA chunk
                         * with the earliest outstanding TSN
                         * for that address, restart T3-rtx
                         * timer for that address with its
                         * current RTO.
                         */
                        restart_timer = 1;

                        if (!tchunk->tsn_gap_acked) {
                              tchunk->tsn_gap_acked = 1;
                              bytes_acked += sctp_data_size(tchunk);
                              /*
                               * SFR-CACC algorithm:
                               * 2) If the SACK contains gap acks
                               * and the flag CHANGEOVER_ACTIVE is
                               * set the receiver of the SACK MUST
                               * take the following action:
                               *
                               * B) For each TSN t being acked that
                               * has not been acked in any SACK so
                               * far, set cacc_saw_newack to 1 for
                               * the destination that the TSN was
                               * sent to.
                               */
                              if (transport &&
                                  sack->num_gap_ack_blocks &&
                                  q->asoc->peer.primary_path->cacc.
                                  changeover_active)
                                    transport->cacc.cacc_saw_newack
                                          = 1;
                        }

                        list_add_tail(&tchunk->transmitted_list,
                                    &q->sacked);
                  } else {
                        /* RFC2960 7.2.4, sctpimpguide-05 2.8.2
                         * M2) Each time a SACK arrives reporting
                         * 'Stray DATA chunk(s)' record the highest TSN
                         * reported as newly acknowledged, call this
                         * value 'HighestTSNinSack'. A newly
                         * acknowledged DATA chunk is one not
                         * previously acknowledged in a SACK.
                         *
                         * When the SCTP sender of data receives a SACK
                         * chunk that acknowledges, for the first time,
                         * the receipt of a DATA chunk, all the still
                         * unacknowledged DATA chunks whose TSN is
                         * older than that newly acknowledged DATA
                         * chunk, are qualified as 'Stray DATA chunks'.
                         */
                        if (!tchunk->tsn_gap_acked) {
                              tchunk->tsn_gap_acked = 1;
                              bytes_acked += sctp_data_size(tchunk);
                        }
                        list_add_tail(lchunk, &tlist);
                  }

#if SCTP_DEBUG
                  switch (dbg_prt_state) {
                  case 0:     /* last TSN was ACKed */
                        if (dbg_last_ack_tsn + 1 == tsn) {
                              /* This TSN belongs to the
                               * current ACK range.
                               */
                              break;
                        }

                        if (dbg_last_ack_tsn != dbg_ack_tsn) {
                              /* Display the end of the
                               * current range.
                               */
                              SCTP_DEBUG_PRINTK("-%08x",
                                            dbg_last_ack_tsn);
                        }

                        /* Start a new range.  */
                        SCTP_DEBUG_PRINTK(",%08x", tsn);
                        dbg_ack_tsn = tsn;
                        break;

                  case 1:     /* The last TSN was NOT ACKed. */
                        if (dbg_last_kept_tsn != dbg_kept_tsn) {
                              /* Display the end of current range. */
                              SCTP_DEBUG_PRINTK("-%08x",
                                            dbg_last_kept_tsn);
                        }

                        SCTP_DEBUG_PRINTK("\n");

                        /* FALL THROUGH... */
                  default:
                        /* This is the first-ever TSN we examined.  */
                        /* Start a new range of ACK-ed TSNs.  */
                        SCTP_DEBUG_PRINTK("ACKed: %08x", tsn);
                        dbg_prt_state = 0;
                        dbg_ack_tsn = tsn;
                  }

                  dbg_last_ack_tsn = tsn;
#endif /* SCTP_DEBUG */

            } else {
                  if (tchunk->tsn_gap_acked) {
                        SCTP_DEBUG_PRINTK("%s: Receiver reneged on "
                                      "data TSN: 0x%x\n",
                                      __FUNCTION__,
                                      tsn);
                        tchunk->tsn_gap_acked = 0;

                        bytes_acked -= sctp_data_size(tchunk);

                        /* RFC 2960 6.3.2 Retransmission Timer Rules
                         *
                         * R4) Whenever a SACK is received missing a
                         * TSN that was previously acknowledged via a
                         * Gap Ack Block, start T3-rtx for the
                         * destination address to which the DATA
                         * chunk was originally
                         * transmitted if it is not already running.
                         */
                        restart_timer = 1;
                  }

                  list_add_tail(lchunk, &tlist);

#if SCTP_DEBUG
                  /* See the above comments on ACK-ed TSNs. */
                  switch (dbg_prt_state) {
                  case 1:
                        if (dbg_last_kept_tsn + 1 == tsn)
                              break;

                        if (dbg_last_kept_tsn != dbg_kept_tsn)
                              SCTP_DEBUG_PRINTK("-%08x",
                                            dbg_last_kept_tsn);

                        SCTP_DEBUG_PRINTK(",%08x", tsn);
                        dbg_kept_tsn = tsn;
                        break;

                  case 0:
                        if (dbg_last_ack_tsn != dbg_ack_tsn)
                              SCTP_DEBUG_PRINTK("-%08x",
                                            dbg_last_ack_tsn);
                        SCTP_DEBUG_PRINTK("\n");

                        /* FALL THROUGH... */
                  default:
                        SCTP_DEBUG_PRINTK("KEPT: %08x",tsn);
                        dbg_prt_state = 1;
                        dbg_kept_tsn = tsn;
                  }

                  dbg_last_kept_tsn = tsn;
#endif /* SCTP_DEBUG */
            }
      }

#if SCTP_DEBUG
      /* Finish off the last range, displaying its ending TSN.  */
      switch (dbg_prt_state) {
      case 0:
            if (dbg_last_ack_tsn != dbg_ack_tsn) {
                  SCTP_DEBUG_PRINTK("-%08x\n", dbg_last_ack_tsn);
            } else {
                  SCTP_DEBUG_PRINTK("\n");
            }
      break;

      case 1:
            if (dbg_last_kept_tsn != dbg_kept_tsn) {
                  SCTP_DEBUG_PRINTK("-%08x\n", dbg_last_kept_tsn);
            } else {
                  SCTP_DEBUG_PRINTK("\n");
            }
      }
#endif /* SCTP_DEBUG */
      if (transport) {
            if (bytes_acked) {
                  /* 8.2. When an outstanding TSN is acknowledged,
                   * the endpoint shall clear the error counter of
                   * the destination transport address to which the
                   * DATA chunk was last sent.
                   * The association's overall error counter is
                   * also cleared.
                   */
                  transport->error_count = 0;
                  transport->asoc->overall_error_count = 0;

                  /* Mark the destination transport address as
                   * active if it is not so marked.
                   */
                  if ((transport->state == SCTP_INACTIVE) ||
                      (transport->state == SCTP_UNCONFIRMED)) {
                        sctp_assoc_control_transport(
                              transport->asoc,
                              transport,
                              SCTP_TRANSPORT_UP,
                              SCTP_RECEIVED_SACK);
                  }

                  sctp_transport_raise_cwnd(transport, sack_ctsn,
                                      bytes_acked);

                  transport->flight_size -= bytes_acked;
                  q->outstanding_bytes -= bytes_acked;
            } else {
                  /* RFC 2960 6.1, sctpimpguide-06 2.15.2
                   * When a sender is doing zero window probing, it
                   * should not timeout the association if it continues
                   * to receive new packets from the receiver. The
                   * reason is that the receiver MAY keep its window
                   * closed for an indefinite time.
                   * A sender is doing zero window probing when the
                   * receiver's advertised window is zero, and there is
                   * only one data chunk in flight to the receiver.
                   */
                  if (!q->asoc->peer.rwnd &&
                      !list_empty(&tlist) &&
                      (sack_ctsn+2 == q->asoc->next_tsn)) {
                        SCTP_DEBUG_PRINTK("%s: SACK received for zero "
                                      "window probe: %u\n",
                                      __FUNCTION__, sack_ctsn);
                        q->asoc->overall_error_count = 0;
                        transport->error_count = 0;
                  }
            }

            /* RFC 2960 6.3.2 Retransmission Timer Rules
             *
             * R2) Whenever all outstanding data sent to an address have
             * been acknowledged, turn off the T3-rtx timer of that
             * address.
             */
            if (!transport->flight_size) {
                  if (timer_pending(&transport->T3_rtx_timer) &&
                      del_timer(&transport->T3_rtx_timer)) {
                        sctp_transport_put(transport);
                  }
            } else if (restart_timer) {
                  if (!mod_timer(&transport->T3_rtx_timer,
                               jiffies + transport->rto))
                        sctp_transport_hold(transport);
            }
      }

      list_splice(&tlist, transmitted_queue);
}

/* Mark chunks as missing and consequently may get retransmitted. */
static void sctp_mark_missing(struct sctp_outq *q,
                        struct list_head *transmitted_queue,
                        struct sctp_transport *transport,
                        __u32 highest_new_tsn_in_sack,
                        int count_of_newacks)
{
      struct sctp_chunk *chunk;
      struct list_head *pos;
      __u32 tsn;
      char do_fast_retransmit = 0;
      struct sctp_transport *primary = q->asoc->peer.primary_path;

      list_for_each(pos, transmitted_queue) {

            chunk = list_entry(pos, struct sctp_chunk, transmitted_list);
            tsn = ntohl(chunk->subh.data_hdr->tsn);

            /* RFC 2960 7.2.4, sctpimpguide-05 2.8.2 M3) Examine all
             * 'Unacknowledged TSN's', if the TSN number of an
             * 'Unacknowledged TSN' is smaller than the 'HighestTSNinSack'
             * value, increment the 'TSN.Missing.Report' count on that
             * chunk if it has NOT been fast retransmitted or marked for
             * fast retransmit already.
             */
            if (!chunk->fast_retransmit &&
                !chunk->tsn_gap_acked &&
                TSN_lt(tsn, highest_new_tsn_in_sack)) {

                  /* SFR-CACC may require us to skip marking
                   * this chunk as missing.
                   */
                  if (!transport || !sctp_cacc_skip(primary, transport,
                                  count_of_newacks, tsn)) {
                        chunk->tsn_missing_report++;

                        SCTP_DEBUG_PRINTK(
                              "%s: TSN 0x%x missing counter: %d\n",
                              __FUNCTION__, tsn,
                              chunk->tsn_missing_report);
                  }
            }
            /*
             * M4) If any DATA chunk is found to have a
             * 'TSN.Missing.Report'
             * value larger than or equal to 3, mark that chunk for
             * retransmission and start the fast retransmit procedure.
             */

            if (chunk->tsn_missing_report >= 3) {
                  chunk->fast_retransmit = 1;
                  do_fast_retransmit = 1;
            }
      }

      if (transport) {
            if (do_fast_retransmit)
                  sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);

            SCTP_DEBUG_PRINTK("%s: transport: %p, cwnd: %d, "
                          "ssthresh: %d, flight_size: %d, pba: %d\n",
                          __FUNCTION__, transport, transport->cwnd,
                          transport->ssthresh, transport->flight_size,
                          transport->partial_bytes_acked);
      }
}

/* Is the given TSN acked by this packet?  */
static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
{
      int i;
      sctp_sack_variable_t *frags;
      __u16 gap;
      __u32 ctsn = ntohl(sack->cum_tsn_ack);

      if (TSN_lte(tsn, ctsn))
            goto pass;

      /* 3.3.4 Selective Acknowledgement (SACK) (3):
       *
       * Gap Ack Blocks:
       *  These fields contain the Gap Ack Blocks. They are repeated
       *  for each Gap Ack Block up to the number of Gap Ack Blocks
       *  defined in the Number of Gap Ack Blocks field. All DATA
       *  chunks with TSNs greater than or equal to (Cumulative TSN
       *  Ack + Gap Ack Block Start) and less than or equal to
       *  (Cumulative TSN Ack + Gap Ack Block End) of each Gap Ack
       *  Block are assumed to have been received correctly.
       */

      frags = sack->variable;
      gap = tsn - ctsn;
      for (i = 0; i < ntohs(sack->num_gap_ack_blocks); ++i) {
            if (TSN_lte(ntohs(frags[i].gab.start), gap) &&
                TSN_lte(gap, ntohs(frags[i].gab.end)))
                  goto pass;
      }

      return 0;
pass:
      return 1;
}

static inline int sctp_get_skip_pos(struct sctp_fwdtsn_skip *skiplist,
                            int nskips, __be16 stream)
{
      int i;

      for (i = 0; i < nskips; i++) {
            if (skiplist[i].stream == stream)
                  return i;
      }
      return i;
}

/* Create and add a fwdtsn chunk to the outq's control queue if needed. */
static void sctp_generate_fwdtsn(struct sctp_outq *q, __u32 ctsn)
{
      struct sctp_association *asoc = q->asoc;
      struct sctp_chunk *ftsn_chunk = NULL;
      struct sctp_fwdtsn_skip ftsn_skip_arr[10];
      int nskips = 0;
      int skip_pos = 0;
      __u32 tsn;
      struct sctp_chunk *chunk;
      struct list_head *lchunk, *temp;

      /* PR-SCTP C1) Let SackCumAck be the Cumulative TSN ACK carried in the
       * received SACK.
       *
       * If (Advanced.Peer.Ack.Point < SackCumAck), then update
       * Advanced.Peer.Ack.Point to be equal to SackCumAck.
       */
      if (TSN_lt(asoc->adv_peer_ack_point, ctsn))
            asoc->adv_peer_ack_point = ctsn;

      /* PR-SCTP C2) Try to further advance the "Advanced.Peer.Ack.Point"
       * locally, that is, to move "Advanced.Peer.Ack.Point" up as long as
       * the chunk next in the out-queue space is marked as "abandoned" as
       * shown in the following example:
       *
       * Assuming that a SACK arrived with the Cumulative TSN ACK 102
       * and the Advanced.Peer.Ack.Point is updated to this value:
       *
       *   out-queue at the end of  ==>   out-queue after Adv.Ack.Point
       *   normal SACK processing           local advancement
       *                ...                           ...
       *   Adv.Ack.Pt-> 102 acked                     102 acked
       *                103 abandoned                 103 abandoned
       *                104 abandoned     Adv.Ack.P-> 104 abandoned
       *                105                           105
       *                106 acked                     106 acked
       *                ...                           ...
       *
       * In this example, the data sender successfully advanced the
       * "Advanced.Peer.Ack.Point" from 102 to 104 locally.
       */
      list_for_each_safe(lchunk, temp, &q->abandoned) {
            chunk = list_entry(lchunk, struct sctp_chunk,
                              transmitted_list);
            tsn = ntohl(chunk->subh.data_hdr->tsn);

            /* Remove any chunks in the abandoned queue that are acked by
             * the ctsn.
             */
            if (TSN_lte(tsn, ctsn)) {
                  list_del_init(lchunk);
                  sctp_chunk_free(chunk);
            } else {
                  if (TSN_lte(tsn, asoc->adv_peer_ack_point+1)) {
                        asoc->adv_peer_ack_point = tsn;
                        if (chunk->chunk_hdr->flags &
                               SCTP_DATA_UNORDERED)
                              continue;
                        skip_pos = sctp_get_skip_pos(&ftsn_skip_arr[0],
                                    nskips,
                                    chunk->subh.data_hdr->stream);
                        ftsn_skip_arr[skip_pos].stream =
                              chunk->subh.data_hdr->stream;
                        ftsn_skip_arr[skip_pos].ssn =
                               chunk->subh.data_hdr->ssn;
                        if (skip_pos == nskips)
                              nskips++;
                        if (nskips == 10)
                              break;
                  } else
                        break;
            }
      }

      /* PR-SCTP C3) If, after step C1 and C2, the "Advanced.Peer.Ack.Point"
       * is greater than the Cumulative TSN ACK carried in the received
       * SACK, the data sender MUST send the data receiver a FORWARD TSN
       * chunk containing the latest value of the
       * "Advanced.Peer.Ack.Point".
       *
       * C4) For each "abandoned" TSN the sender of the FORWARD TSN SHOULD
       * list each stream and sequence number in the forwarded TSN. This
       * information will enable the receiver to easily find any
       * stranded TSN's waiting on stream reorder queues. Each stream
       * SHOULD only be reported once; this means that if multiple
       * abandoned messages occur in the same stream then only the
       * highest abandoned stream sequence number is reported. If the
       * total size of the FORWARD TSN does NOT fit in a single MTU then
       * the sender of the FORWARD TSN SHOULD lower the
       * Advanced.Peer.Ack.Point to the last TSN that will fit in a
       * single MTU.
       */
      if (asoc->adv_peer_ack_point > ctsn)
            ftsn_chunk = sctp_make_fwdtsn(asoc, asoc->adv_peer_ack_point,
                                    nskips, &ftsn_skip_arr[0]);

      if (ftsn_chunk) {
            list_add_tail(&ftsn_chunk->list, &q->control_chunk_list);
            SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
      }
}

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