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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-or-later
 /* SCTP kernel 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 implementation
  *
  * These functions implement the sctp_outq class.   The outqueue handles
  * bundling and queueing of outgoing SCTP chunks.
  *
  * Please send any bug reports or fixes you make to the
  * email address(es):
  *    lksctp developers <linux-sctp@vger.kernel.org>
  *
  * 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>
  */
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
 #include <linux/types.h>
 #include <linux/list.h>   /* For struct list_head */
 #include <linux/socket.h>
 #include <linux/ip.h>
 #include <linux/slab.h>
 #include <net/sock.h>     /* For skb_set_owner_w */
 
 #include <net/sctp/sctp.h>
 #include <net/sctp/sm.h>
 #include <net/sctp/stream_sched.h>
 #include <trace/events/sctp.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,
                    union sctp_addr *saddr,
                    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_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp);
 
 /* Add data to the front of the queue. */
 static inline void sctp_outq_head_data(struct sctp_outq *q,
                        struct sctp_chunk *ch)
 {
     struct sctp_stream_out_ext *oute;
     __u16 stream;
 
     list_add(&ch->list, &q->out_chunk_list);
     q->out_qlen += ch->skb->len;
 
     stream = sctp_chunk_stream_no(ch);
     oute = SCTP_SO(&q->asoc->stream, stream)->ext;
     list_add(&ch->stream_list, &oute->outq);
 }
 
 /* Take data from the front of the queue. */
 static inline struct sctp_chunk *sctp_outq_dequeue_data(struct sctp_outq *q)
 {
     return q->sched->dequeue(q);
 }
 
 /* Add data chunk to the end of the queue. */
 static inline void sctp_outq_tail_data(struct sctp_outq *q,
                        struct sctp_chunk *ch)
 {
     struct sctp_stream_out_ext *oute;
     __u16 stream;
 
     list_add_tail(&ch->list, &q->out_chunk_list);
     q->out_qlen += ch->skb->len;
 
     stream = sctp_chunk_stream_no(ch);
     oute = SCTP_SO(&q->asoc->stream, stream)->ext;
     list_add_tail(&ch->stream_list, &oute->outq);
 }
 
 /*
  * 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 && !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 further 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 SHOULD 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)
 {
     memset(q, 0, sizeof(struct sctp_outq));
 
     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);
     sctp_sched_set_sched(asoc, sctp_sk(asoc->base.sk)->default_ss);
 }
 
 /* Free the outqueue structure and any related pending chunks.
  */
 static void __sctp_outq_teardown(struct sctp_outq *q)
 {
     struct sctp_transport *transport;
     struct list_head *lchunk, *temp;
     struct sctp_chunk *chunk, *tmp;
 
     /* Throw away unacknowledged chunks. */
     list_for_each_entry(transport, &q->asoc->peer.transport_addr_list,
             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) {
         sctp_sched_dequeue_done(q, chunk);
 
         /* Mark as send failure. */
         sctp_chunk_fail(chunk, q->error);
         sctp_chunk_free(chunk);
     }
 
     /* 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);
     }
 }
 
 void sctp_outq_teardown(struct sctp_outq *q)
 {
     __sctp_outq_teardown(q);
     sctp_outq_init(q->asoc, q);
 }
 
 /* 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);
 }
 
 /* Put a new chunk in an sctp_outq.  */
 void sctp_outq_tail(struct sctp_outq *q, struct sctp_chunk *chunk, gfp_t gfp)
 {
     struct net *net = q->asoc->base.net;
 
     pr_debug("%s: outq:%p, chunk:%p[%s]\n", __func__, 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_chunk_is_data(chunk)) {
         pr_debug("%s: outqueueing: outq:%p, chunk:%p[%s])\n",
              __func__, 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->asoc->peer.prsctp_capable &&
             SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
             chunk->asoc->sent_cnt_removable++;
         if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
             SCTP_INC_STATS(net, SCTP_MIB_OUTUNORDERCHUNKS);
         else
             SCTP_INC_STATS(net, SCTP_MIB_OUTORDERCHUNKS);
     } else {
         list_add_tail(&chunk->list, &q->control_chunk_list);
         SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);
     }
 
     if (!q->cork)
         sctp_outq_flush(q, 0, gfp);
 }
 
 /* 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);
 }
 
 static int sctp_prsctp_prune_sent(struct sctp_association *asoc,
                   struct sctp_sndrcvinfo *sinfo,
                   struct list_head *queue, int msg_len)
 {
     struct sctp_chunk *chk, *temp;
 
     list_for_each_entry_safe(chk, temp, queue, transmitted_list) {
         struct sctp_stream_out *streamout;
 
         if (!chk->msg->abandoned &&
             (!SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
              chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive))
             continue;
 
         chk->msg->abandoned = 1;
         list_del_init(&chk->transmitted_list);
         sctp_insert_list(&asoc->outqueue.abandoned,
                  &chk->transmitted_list);
 
         streamout = SCTP_SO(&asoc->stream, chk->sinfo.sinfo_stream);
         asoc->sent_cnt_removable--;
         asoc->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
         streamout->ext->abandoned_sent[SCTP_PR_INDEX(PRIO)]++;
 
         if (queue != &asoc->outqueue.retransmit &&
             !chk->tsn_gap_acked) {
             if (chk->transport)
                 chk->transport->flight_size -=
                         sctp_data_size(chk);
             asoc->outqueue.outstanding_bytes -= sctp_data_size(chk);
         }
 
         msg_len -= chk->skb->truesize + sizeof(struct sctp_chunk);
         if (msg_len <= 0)
             break;
     }
 
     return msg_len;
 }
 
 static int sctp_prsctp_prune_unsent(struct sctp_association *asoc,
                     struct sctp_sndrcvinfo *sinfo, int msg_len)
 {
     struct sctp_outq *q = &asoc->outqueue;
     struct sctp_chunk *chk, *temp;
 
     q->sched->unsched_all(&asoc->stream);
 
     list_for_each_entry_safe(chk, temp, &q->out_chunk_list, list) {
         if (!chk->msg->abandoned &&
             (!(chk->chunk_hdr->flags & SCTP_DATA_FIRST_FRAG) ||
              !SCTP_PR_PRIO_ENABLED(chk->sinfo.sinfo_flags) ||
              chk->sinfo.sinfo_timetolive <= sinfo->sinfo_timetolive))
             continue;
 
         chk->msg->abandoned = 1;
         sctp_sched_dequeue_common(q, chk);
         asoc->sent_cnt_removable--;
         asoc->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
         if (chk->sinfo.sinfo_stream < asoc->stream.outcnt) {
             struct sctp_stream_out *streamout =
                 SCTP_SO(&asoc->stream, chk->sinfo.sinfo_stream);
 
             streamout->ext->abandoned_unsent[SCTP_PR_INDEX(PRIO)]++;
         }
 
         msg_len -= chk->skb->truesize + sizeof(struct sctp_chunk);
         sctp_chunk_free(chk);
         if (msg_len <= 0)
             break;
     }
 
     q->sched->sched_all(&asoc->stream);
 
     return msg_len;
 }
 
 /* Abandon the chunks according their priorities */
 void sctp_prsctp_prune(struct sctp_association *asoc,
                struct sctp_sndrcvinfo *sinfo, int msg_len)
 {
     struct sctp_transport *transport;
 
     if (!asoc->peer.prsctp_capable || !asoc->sent_cnt_removable)
         return;
 
     msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
                      &asoc->outqueue.retransmit,
                      msg_len);
     if (msg_len <= 0)
         return;
 
     list_for_each_entry(transport, &asoc->peer.transport_addr_list,
                 transports) {
         msg_len = sctp_prsctp_prune_sent(asoc, sinfo,
                          &transport->transmitted,
                          msg_len);
         if (msg_len <= 0)
             return;
     }
 
     sctp_prsctp_prune_unsent(asoc, sinfo, msg_len);
 }
 
 /* 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) {
                 if (chunk->transport)
                     chunk->transport->flight_size -=
                             sctp_data_size(chunk);
                 q->outstanding_bytes -= sctp_data_size(chunk);
                 q->asoc->peer.rwnd += sctp_data_size(chunk);
             }
             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 == SCTP_NEED_FRTX)) ||
             (reason != SCTP_RTXR_FAST_RTX  && !chunk->tsn_gap_acked)) {
             /* 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);
             q->outstanding_bytes -= sctp_data_size(chunk);
             if (chunk->transport)
                 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);
         }
     }
 
     pr_debug("%s: transport:%p, reason:%d, cwnd:%d, ssthresh:%d, "
          "flight_size:%d, pba:%d\n", __func__, 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,
              enum sctp_retransmit_reason reason)
 {
     struct net *net = q->asoc->base.net;
 
     switch (reason) {
     case SCTP_RTXR_T3_RTX:
         SCTP_INC_STATS(net, 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);
         transport->asoc->rtx_data_chunks +=
             transport->asoc->unack_data;
         if (transport->pl.state == SCTP_PL_COMPLETE &&
             transport->asoc->unack_data)
             sctp_transport_reset_probe_timer(transport);
         break;
     case SCTP_RTXR_FAST_RTX:
         SCTP_INC_STATS(net, SCTP_MIB_FAST_RETRANSMITS);
         sctp_transport_lower_cwnd(transport, SCTP_LOWER_CWND_FAST_RTX);
         q->fast_rtx = 1;
         break;
     case SCTP_RTXR_PMTUD:
         SCTP_INC_STATS(net, SCTP_MIB_PMTUD_RETRANSMITS);
         break;
     case SCTP_RTXR_T1_RTX:
         SCTP_INC_STATS(net, SCTP_MIB_T1_RETRANSMITS);
         transport->asoc->init_retries++;
         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.
      */
     if (reason == SCTP_RTXR_T3_RTX)
         q->asoc->stream.si->generate_ftsn(q, q->asoc->ctsn_ack_point);
 
     /* Flush the queues only on timeout, since fast_rtx is only
      * triggered during sack processing and the queue
      * will be flushed at the end.
      */
     if (reason != SCTP_RTXR_FAST_RTX)
         sctp_outq_flush(q, /* rtx_timeout */ 1, GFP_ATOMIC);
 }
 
 /*
  * 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, gfp_t gfp)
 {
     struct sctp_transport *transport = pkt->transport;
     struct sctp_chunk *chunk, *chunk1;
     struct list_head *lqueue;
     enum sctp_xmit status;
     int error = 0;
     int timer = 0;
     int done = 0;
     int fast_rtx;
 
     lqueue = &q->retransmit;
     fast_rtx = q->fast_rtx;
 
     /* This loop handles time-out retransmissions, fast retransmissions,
      * and retransmissions due to opening of whindow.
      *
      * 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.]
      *
      * For fast retransmissions we also send only ONE packet.  However,
      * if we are just flushing the queue due to open window, we'll
      * try to send as much as possible.
      */
     list_for_each_entry_safe(chunk, chunk1, lqueue, transmitted_list) {
         /* If the chunk is abandoned, move it to abandoned list. */
         if (sctp_chunk_abandoned(chunk)) {
             list_del_init(&chunk->transmitted_list);
             sctp_insert_list(&q->abandoned,
                      &chunk->transmitted_list);
             continue;
         }
 
         /* 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_move_tail(&chunk->transmitted_list,
                        &transport->transmitted);
             continue;
         }
 
         /* If we are doing fast retransmit, ignore non-fast_rtransmit
          * chunks
          */
         if (fast_rtx && !chunk->fast_retransmit)
             continue;
 
 redo:
         /* Attempt to append this chunk to the packet. */
         status = sctp_packet_append_chunk(pkt, chunk);
 
         switch (status) {
         case SCTP_XMIT_PMTU_FULL:
             if (!pkt->has_data && !pkt->has_cookie_echo) {
                 /* If this packet did not contain DATA then
                  * retransmission did not happen, so do it
                  * again.  We'll ignore the error here since
                  * control chunks are already freed so there
                  * is nothing we can do.
                  */
                 sctp_packet_transmit(pkt, gfp);
                 goto redo;
             }
 
             /* Send this packet.  */
             error = sctp_packet_transmit(pkt, gfp);
 
             /* If we are retransmitting, we should only
              * send a single packet.
              * Otherwise, try appending this chunk again.
              */
             if (rtx_timeout || fast_rtx)
                 done = 1;
             else
                 goto redo;
 
             /* Bundle next chunk in the next round.  */
             break;
 
         case SCTP_XMIT_RWND_FULL:
             /* Send this packet. */
             error = sctp_packet_transmit(pkt, gfp);
 
             /* Stop sending DATA as there is no more room
              * at the receiver.
              */
             done = 1;
             break;
 
         case SCTP_XMIT_DELAY:
             /* Send this packet. */
             error = sctp_packet_transmit(pkt, gfp);
 
             /* Stop sending DATA because of nagle delay. */
             done = 1;
             break;
 
         default:
             /* The append was successful, so add this chunk to
              * the transmitted list.
              */
             list_move_tail(&chunk->transmitted_list,
                        &transport->transmitted);
 
             /* Mark the chunk as ineligible for fast retransmit
              * after it is retransmitted.
              */
             if (chunk->fast_retransmit == SCTP_NEED_FRTX)
                 chunk->fast_retransmit = SCTP_DONT_FRTX;
 
             q->asoc->stats.rtxchunks++;
             break;
         }
 
         /* Set the timer if there were no errors */
         if (!error && !timer)
             timer = 1;
 
         if (done)
             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 || fast_rtx) {
         list_for_each_entry(chunk1, lqueue, transmitted_list) {
             if (chunk1->fast_retransmit == SCTP_NEED_FRTX)
                 chunk1->fast_retransmit = SCTP_DONT_FRTX;
         }
     }
 
     *start_timer = timer;
 
     /* Clear fast retransmit hint */
     if (fast_rtx)
         q->fast_rtx = 0;
 
     return error;
 }
 
 /* Cork the outqueue so queued chunks are really queued. */
 void sctp_outq_uncork(struct sctp_outq *q, gfp_t gfp)
 {
     if (q->cork)
         q->cork = 0;
 
     sctp_outq_flush(q, 0, gfp);
 }
 
 static int sctp_packet_singleton(struct sctp_transport *transport,
                  struct sctp_chunk *chunk, gfp_t gfp)
 {
     const struct sctp_association *asoc = transport->asoc;
     const __u16 sport = asoc->base.bind_addr.port;
     const __u16 dport = asoc->peer.port;
     const __u32 vtag = asoc->peer.i.init_tag;
     struct sctp_packet singleton;
 
     sctp_packet_init(&singleton, transport, sport, dport);
     sctp_packet_config(&singleton, vtag, 0);
     if (sctp_packet_append_chunk(&singleton, chunk) != SCTP_XMIT_OK) {
         list_del_init(&chunk->list);
         sctp_chunk_free(chunk);
         return -ENOMEM;
     }
     return sctp_packet_transmit(&singleton, gfp);
 }
 
 /* Struct to hold the context during sctp outq flush */
 struct sctp_flush_ctx {
     struct sctp_outq *q;
     /* Current transport being used. It's NOT the same as curr active one */
     struct sctp_transport *transport;
     /* These transports have chunks to send. */
     struct list_head transport_list;
     struct sctp_association *asoc;
     /* Packet on the current transport above */
     struct sctp_packet *packet;
     gfp_t gfp;
 };
 
 /* transport: current transport */
 static void sctp_outq_select_transport(struct sctp_flush_ctx *ctx,
                        struct sctp_chunk *chunk)
 {
     struct sctp_transport *new_transport = chunk->transport;
 
     if (!new_transport) {
         if (!sctp_chunk_is_data(chunk)) {
             /* If we have a prior transport pointer, see if
              * the destination address of the chunk
              * matches the destination address of the
              * current transport.  If not a match, then
              * try to look up the transport with a given
              * destination address.  We do this because
              * after processing ASCONFs, we may have new
              * transports created.
              */
             if (ctx->transport && sctp_cmp_addr_exact(&chunk->dest,
                             &ctx->transport->ipaddr))
                 new_transport = ctx->transport;
             else
                 new_transport = sctp_assoc_lookup_paddr(ctx->asoc,
                                   &chunk->dest);
         }
 
         /* if we still don't have a new transport, then
          * use the current active path.
          */
         if (!new_transport)
             new_transport = ctx->asoc->peer.active_path;
     } else {
         __u8 type;
 
         switch (new_transport->state) {
         case SCTP_INACTIVE:
         case SCTP_UNCONFIRMED:
         case SCTP_PF:
             /* 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.
              * ...
              *
              * ASCONF_ACKs also must be sent to the source.
              */
             type = chunk->chunk_hdr->type;
             if (type != SCTP_CID_HEARTBEAT &&
                 type != SCTP_CID_HEARTBEAT_ACK &&
                 type != SCTP_CID_ASCONF_ACK)
                 new_transport = ctx->asoc->peer.active_path;
             break;
         default:
             break;
         }
     }
 
     /* Are we switching transports? Take care of transport locks. */
     if (new_transport != ctx->transport) {
         ctx->transport = new_transport;
         ctx->packet = &ctx->transport->packet;
 
         if (list_empty(&ctx->transport->send_ready))
             list_add_tail(&ctx->transport->send_ready,
                       &ctx->transport_list);
 
         sctp_packet_config(ctx->packet,
                    ctx->asoc->peer.i.init_tag,
                    ctx->asoc->peer.ecn_capable);
         /* We've switched transports, so apply the
          * Burst limit to the new transport.
          */
         sctp_transport_burst_limited(ctx->transport);
     }
 }
 
 static void sctp_outq_flush_ctrl(struct sctp_flush_ctx *ctx)
 {
     struct sctp_chunk *chunk, *tmp;
     enum sctp_xmit status;
     int one_packet, error;
 
     list_for_each_entry_safe(chunk, tmp, &ctx->q->control_chunk_list, list) {
         one_packet = 0;
 
         /* RFC 5061, 5.3
          * F1) This means that until such time as the ASCONF
          * containing the add is acknowledged, the sender MUST
          * NOT use the new IP address as a source for ANY SCTP
          * packet except on carrying an ASCONF Chunk.
          */
         if (ctx->asoc->src_out_of_asoc_ok &&
             chunk->chunk_hdr->type != SCTP_CID_ASCONF)
             continue;
 
         list_del_init(&chunk->list);
 
         /* Pick the right transport to use. Should always be true for
          * the first chunk as we don't have a transport by then.
          */
         sctp_outq_select_transport(ctx, chunk);
 
         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:
             error = sctp_packet_singleton(ctx->transport, chunk,
                               ctx->gfp);
             if (error < 0) {
                 ctx->asoc->base.sk->sk_err = -error;
                 return;
             }
             ctx->asoc->stats.octrlchunks++;
             break;
 
         case SCTP_CID_ABORT:
             if (sctp_test_T_bit(chunk))
                 ctx->packet->vtag = ctx->asoc->c.my_vtag;
             fallthrough;
 
         /* The following chunks are "response" chunks, i.e.
          * they are generated in response to something we
          * received.  If we are sending these, then we can
          * send only 1 packet containing these chunks.
          */
         case SCTP_CID_HEARTBEAT_ACK:
         case SCTP_CID_SHUTDOWN_ACK:
         case SCTP_CID_COOKIE_ACK:
         case SCTP_CID_COOKIE_ECHO:
         case SCTP_CID_ERROR:
         case SCTP_CID_ECN_CWR:
         case SCTP_CID_ASCONF_ACK:
             one_packet = 1;
             fallthrough;
 
         case SCTP_CID_HEARTBEAT:
             if (chunk->pmtu_probe) {
                 error = sctp_packet_singleton(ctx->transport,
                                   chunk, ctx->gfp);
                 if (!error)
                     ctx->asoc->stats.octrlchunks++;
                 break;
             }
             fallthrough;
         case SCTP_CID_SACK:
         case SCTP_CID_SHUTDOWN:
         case SCTP_CID_ECN_ECNE:
         case SCTP_CID_ASCONF:
         case SCTP_CID_FWD_TSN:
         case SCTP_CID_I_FWD_TSN:
         case SCTP_CID_RECONF:
             status = sctp_packet_transmit_chunk(ctx->packet, chunk,
                                 one_packet, ctx->gfp);
             if (status != SCTP_XMIT_OK) {
                 /* put the chunk back */
                 list_add(&chunk->list, &ctx->q->control_chunk_list);
                 break;
             }
 
             ctx->asoc->stats.octrlchunks++;
             /* PR-SCTP C5) If a FORWARD TSN is sent, the
              * sender MUST assure that at least one T3-rtx
              * timer is running.
              */
             if (chunk->chunk_hdr->type == SCTP_CID_FWD_TSN ||
                 chunk->chunk_hdr->type == SCTP_CID_I_FWD_TSN) {
                 sctp_transport_reset_t3_rtx(ctx->transport);
                 ctx->transport->last_time_sent = jiffies;
             }
 
             if (chunk == ctx->asoc->strreset_chunk)
                 sctp_transport_reset_reconf_timer(ctx->transport);
 
             break;
 
         default:
             /* We built a chunk with an illegal type! */
             BUG();
         }
     }
 }
 
 /* Returns false if new data shouldn't be sent */
 static bool sctp_outq_flush_rtx(struct sctp_flush_ctx *ctx,
                 int rtx_timeout)
 {
     int error, start_timer = 0;
 
     if (ctx->asoc->peer.retran_path->state == SCTP_UNCONFIRMED)
         return false;
 
     if (ctx->transport != ctx->asoc->peer.retran_path) {
         /* Switch transports & prepare the packet.  */
         ctx->transport = ctx->asoc->peer.retran_path;
         ctx->packet = &ctx->transport->packet;
 
         if (list_empty(&ctx->transport->send_ready))
             list_add_tail(&ctx->transport->send_ready,
                       &ctx->transport_list);
 
         sctp_packet_config(ctx->packet, ctx->asoc->peer.i.init_tag,
                    ctx->asoc->peer.ecn_capable);
     }
 
     error = __sctp_outq_flush_rtx(ctx->q, ctx->packet, rtx_timeout,
                       &start_timer, ctx->gfp);
     if (error < 0)
         ctx->asoc->base.sk->sk_err = -error;
 
     if (start_timer) {
         sctp_transport_reset_t3_rtx(ctx->transport);
         ctx->transport->last_time_sent = jiffies;
     }
 
     /* This can happen on COOKIE-ECHO resend.  Only
      * one chunk can get bundled with a COOKIE-ECHO.
      */
     if (ctx->packet->has_cookie_echo)
         return false;
 
     /* Don't send new data if there is still data
      * waiting to retransmit.
      */
     if (!list_empty(&ctx->q->retransmit))
         return false;
 
     return true;
 }
 
 static void sctp_outq_flush_data(struct sctp_flush_ctx *ctx,
                  int rtx_timeout)
 {
     struct sctp_chunk *chunk;
     enum sctp_xmit status;
 
     /* Is it OK to send data chunks?  */
     switch (ctx->asoc->state) {
     case SCTP_STATE_COOKIE_ECHOED:
         /* Only allow bundling when this packet has a COOKIE-ECHO
          * chunk.
          */
         if (!ctx->packet || !ctx->packet->has_cookie_echo)
             return;
 
         fallthrough;
     case SCTP_STATE_ESTABLISHED:
     case SCTP_STATE_SHUTDOWN_PENDING:
     case SCTP_STATE_SHUTDOWN_RECEIVED:
         break;
 
     default:
         /* Do nothing. */
         return;
     }
 
     /* 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(&ctx->q->retransmit) &&
         !sctp_outq_flush_rtx(ctx, rtx_timeout))
         return;
 
     /* Apply Max.Burst limitation to the current transport in
      * case it will be used for new data.  We are going to
      * rest it before we return, but we want to apply the limit
      * to the currently queued data.
      */
     if (ctx->transport)
         sctp_transport_burst_limited(ctx->transport);
 
     /* Finally, transmit new packets.  */
     while ((chunk = sctp_outq_dequeue_data(ctx->q)) != NULL) {
         __u32 sid = ntohs(chunk->subh.data_hdr->stream);
         __u8 stream_state = SCTP_SO(&ctx->asoc->stream, sid)->state;
 
         /* Has this chunk expired? */
         if (sctp_chunk_abandoned(chunk)) {
             sctp_sched_dequeue_done(ctx->q, chunk);
             sctp_chunk_fail(chunk, 0);
             sctp_chunk_free(chunk);
             continue;
         }
 
         if (stream_state == SCTP_STREAM_CLOSED) {
             sctp_outq_head_data(ctx->q, chunk);
             break;
         }
 
         sctp_outq_select_transport(ctx, chunk);
 
         pr_debug("%s: outq:%p, chunk:%p[%s], tx-tsn:0x%x skb->head:%p skb->users:%d\n",
              __func__, ctx->q, chunk, chunk && chunk->chunk_hdr ?
              sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)) :
              "illegal chunk", ntohl(chunk->subh.data_hdr->tsn),
              chunk->skb ? chunk->skb->head : NULL, chunk->skb ?
              refcount_read(&chunk->skb->users) : -1);
 
         /* Add the chunk to the packet.  */
         status = sctp_packet_transmit_chunk(ctx->packet, chunk, 0,
                             ctx->gfp);
         if (status != SCTP_XMIT_OK) {
             /* We could not append this chunk, so put
              * the chunk back on the output queue.
              */
             pr_debug("%s: could not transmit tsn:0x%x, status:%d\n",
                  __func__, ntohl(chunk->subh.data_hdr->tsn),
                  status);
 
             sctp_outq_head_data(ctx->q, chunk);
             break;
         }
 
         /* The sender is in the SHUTDOWN-PENDING state,
          * The sender MAY set the I-bit in the DATA
          * chunk header.
          */
         if (ctx->asoc->state == SCTP_STATE_SHUTDOWN_PENDING)
             chunk->chunk_hdr->flags |= SCTP_DATA_SACK_IMM;
         if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED)
             ctx->asoc->stats.ouodchunks++;
         else
             ctx->asoc->stats.oodchunks++;
 
         /* Only now it's safe to consider this
          * chunk as sent, sched-wise.
          */
         sctp_sched_dequeue_done(ctx->q, chunk);
 
         list_add_tail(&chunk->transmitted_list,
                   &ctx->transport->transmitted);
 
         sctp_transport_reset_t3_rtx(ctx->transport);
         ctx->transport->last_time_sent = jiffies;
 
         /* Only let one DATA chunk get bundled with a
          * COOKIE-ECHO chunk.
          */
         if (ctx->packet->has_cookie_echo)
             break;
     }
 }
 
 static void sctp_outq_flush_transports(struct sctp_flush_ctx *ctx)
 {
     struct sock *sk = ctx->asoc->base.sk;
     struct list_head *ltransport;
     struct sctp_packet *packet;
     struct sctp_transport *t;
     int error = 0;
 
     while ((ltransport = sctp_list_dequeue(&ctx->transport_list)) != NULL) {
         t = list_entry(ltransport, struct sctp_transport, send_ready);
         packet = &t->packet;
         if (!sctp_packet_empty(packet)) {
             rcu_read_lock();
             if (t->dst && __sk_dst_get(sk) != t->dst) {
                 dst_hold(t->dst);
                 sk_setup_caps(sk, t->dst);
             }
             rcu_read_unlock();
             error = sctp_packet_transmit(packet, ctx->gfp);
             if (error < 0)
                 ctx->q->asoc->base.sk->sk_err = -error;
         }
 
         /* Clear the burst limited state, if any */
         sctp_transport_burst_reset(t);
     }
 }
 
 /* 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.
  */
 
 static void sctp_outq_flush(struct sctp_outq *q, int rtx_timeout, gfp_t gfp)
 {
     struct sctp_flush_ctx ctx = {
         .q = q,
         .transport = NULL,
         .transport_list = LIST_HEAD_INIT(ctx.transport_list),
         .asoc = q->asoc,
         .packet = NULL,
         .gfp = gfp,
     };
 
     /* 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.
      *   ...
      */
 
     sctp_outq_flush_ctrl(&ctx);
 
     if (q->asoc->src_out_of_asoc_ok)
         goto sctp_flush_out;
 
     sctp_outq_flush_data(&ctx, rtx_timeout);
 
 sctp_flush_out:
 
     sctp_outq_flush_transports(&ctx);
 }
 
 /* Update unack_data based on the incoming SACK chunk */
 static void sctp_sack_update_unack_data(struct sctp_association *assoc,
                     struct sctp_sackhdr *sack)
 {
     union sctp_sack_variable *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;
 }
 
 /* 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_chunk *chunk)
 {
     struct sctp_association *asoc = q->asoc;
     struct sctp_sackhdr *sack = chunk->subh.sack_hdr;
     struct sctp_transport *transport;
     struct sctp_chunk *tchunk = NULL;
     struct list_head *lchunk, *transport_list, *temp;
     union sctp_sack_variable *frags = sack->variable;
     __u32 sack_ctsn, ctsn, tsn;
     __u32 highest_tsn, highest_new_tsn;
     __u32 sack_a_rwnd;
     unsigned int outstanding;
     struct sctp_transport *primary = asoc->peer.primary_path;
     int count_of_newacks = 0;
     int gap_ack_blocks;
     u8 accum_moved = 0;
 
     /* Grab the association's destination address list. */
     transport_list = &asoc->peer.transport_addr_list;
 
     /* SCTP path tracepoint for congestion control debugging. */
     if (trace_sctp_probe_path_enabled()) {
         list_for_each_entry(transport, transport_list, transports)
             trace_sctp_probe_path(transport, asoc);
     }
 
     sack_ctsn = ntohl(sack->cum_tsn_ack);
     gap_ack_blocks = ntohs(sack->num_gap_ack_blocks);
     asoc->stats.gapcnt += gap_ack_blocks;
     /*
      * 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.
      * 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.
      *
      * Only bother if changeover_active is set. Otherwise, this is
      * totally suboptimal to do on every SACK.
      */
     if (primary->cacc.changeover_active) {
         u8 clear_cycling = 0;
 
         if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
             primary->cacc.changeover_active = 0;
             clear_cycling = 1;
         }
 
         if (clear_cycling || gap_ack_blocks) {
             list_for_each_entry(transport, transport_list,
                     transports) {
                 if (clear_cycling)
                     transport->cacc.cycling_changeover = 0;
                 if (gap_ack_blocks)
                     transport->cacc.cacc_saw_newack = 0;
             }
         }
     }
 
     /* Get the highest TSN in the sack. */
     highest_tsn = sack_ctsn;
     if (gap_ack_blocks)
         highest_tsn += ntohs(frags[gap_ack_blocks - 1].gab.end);
 
     if (TSN_lt(asoc->highest_sacked, highest_tsn))
         asoc->highest_sacked = highest_tsn;
 
     highest_new_tsn = sack_ctsn;
 
     /* Run through the retransmit queue.  Credit bytes received
      * and free those chunks that we can.
      */
     sctp_check_transmitted(q, &q->retransmit, NULL, NULL, sack, &highest_new_tsn);
 
     /* 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_entry(transport, transport_list, transports) {
         sctp_check_transmitted(q, &transport->transmitted,
                        transport, &chunk->source, 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++;
     }
 
     /* Move the Cumulative TSN Ack Point if appropriate.  */
     if (TSN_lt(asoc->ctsn_ack_point, sack_ctsn)) {
         asoc->ctsn_ack_point = sack_ctsn;
         accum_moved = 1;
     }
 
     if (gap_ack_blocks) {
 
         if (asoc->fast_recovery && accum_moved)
             highest_new_tsn = highest_tsn;
 
         list_for_each_entry(transport, transport_list, transports)
             sctp_mark_missing(q, &transport->transmitted, transport,
                       highest_new_tsn, count_of_newacks);
     }
 
     /* 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)) {
             list_del_init(&tchunk->transmitted_list);
             if (asoc->peer.prsctp_capable &&
                 SCTP_PR_PRIO_ENABLED(chunk->sinfo.sinfo_flags))
                 asoc->sent_cnt_removable--;
             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);
     asoc->peer.zero_window_announced = !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;
 
     asoc->stream.si->generate_ftsn(q, sack_ctsn);
 
     pr_debug("%s: sack cumulative tsn ack:0x%x\n", __func__, sack_ctsn);
     pr_debug("%s: cumulative tsn ack of assoc:%p is 0x%x, "
          "advertised peer ack point:0x%x\n", __func__, asoc, ctsn,
          asoc->adv_peer_ack_point);
 
     return sctp_outq_is_empty(q);
 }
 
 /* Is the outqueue empty?
  * The queue is empty when we have not pending data, no in-flight data
  * and nothing pending retransmissions.
  */
 int sctp_outq_is_empty(const struct sctp_outq *q)
 {
     return q->out_qlen == 0 && q->outstanding_bytes == 0 &&
            list_empty(&q->retransmit);
 }
 
 /********************************************************************
  * 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,
                    union sctp_addr *saddr,
                    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;
     int migrate_bytes = 0;
     bool forward_progress = false;
 
     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 (transmitted_queue != &q->retransmit &&
                 !tchunk->tsn_gap_acked) {
                 if (tchunk->transport)
                     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 && !tchunk->tsn_gap_acked) {
                 /* 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 (!sctp_chunk_retransmitted(tchunk) &&
                     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)) {
                     /*
                      * 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 (sack->num_gap_ack_blocks &&
                         q->asoc->peer.primary_path->cacc.
                         changeover_active)
                         transport->cacc.cacc_saw_newack
                             = 1;
                 }
             }
 
             /* If the chunk hasn't been marked as ACKED,
              * mark it and account bytes_acked if the
              * chunk had a valid transport (it will not
              * have a transport if ASCONF had deleted it
              * while DATA was outstanding).
              */
             if (!tchunk->tsn_gap_acked) {
                 tchunk->tsn_gap_acked = 1;
                 if (TSN_lt(*highest_new_tsn_in_sack, tsn))
                     *highest_new_tsn_in_sack = tsn;
                 bytes_acked += sctp_data_size(tchunk);
                 if (!tchunk->transport)
                     migrate_bytes += sctp_data_size(tchunk);
                 forward_progress = true;
             }
 
             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;
                 forward_progress = true;
 
                 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'.
                  */
                 list_add_tail(lchunk, &tlist);
             }
         } else {
             if (tchunk->tsn_gap_acked) {
                 pr_debug("%s: receiver reneged on data TSN:0x%x\n",
                      __func__, tsn);
 
                 tchunk->tsn_gap_acked = 0;
 
                 if (tchunk->transport)
                     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 (transport) {
         if (bytes_acked) {
             struct sctp_association *asoc = transport->asoc;
 
             /* We may have counted DATA that was migrated
              * to this transport due to DEL-IP operation.
              * Subtract those bytes, since the were never
              * send on this transport and shouldn't be
              * credited to this transport.
              */
             bytes_acked -= migrate_bytes;
 
             /* 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;
             forward_progress = true;
 
             /*
              * While in SHUTDOWN PENDING, we may have started
              * the T5 shutdown guard timer after reaching the
              * retransmission limit. Stop that timer as soon
              * as the receiver acknowledged any data.
              */
             if (asoc->state == SCTP_STATE_SHUTDOWN_PENDING &&
                 del_timer(&asoc->timers
                 [SCTP_EVENT_TIMEOUT_T5_SHUTDOWN_GUARD]))
                     sctp_association_put(asoc);
 
             /* Mark the destination transport address as
              * active if it is not so marked.
              */
             if ((transport->state == SCTP_INACTIVE ||
                  transport->state == SCTP_UNCONFIRMED) &&
                 sctp_cmp_addr_exact(&transport->ipaddr, saddr)) {
                 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;
             if (transport->flight_size == 0)
                 transport->partial_bytes_acked = 0;
             q->outstanding_bytes -= bytes_acked + migrate_bytes;
         } 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.
              *
              * Allow the association to timeout while in SHUTDOWN
              * PENDING or SHUTDOWN RECEIVED in case the receiver
              * stays in zero window mode forever.
              */
             if (!q->asoc->peer.rwnd &&
                 !list_empty(&tlist) &&
                 (sack_ctsn+2 == q->asoc->next_tsn) &&
                 q->asoc->state < SCTP_STATE_SHUTDOWN_PENDING) {
                 pr_debug("%s: sack received for zero window "
                      "probe:%u\n", __func__, 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 (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);
         }
 
         if (forward_progress) {
             if (transport->dst)
                 sctp_transport_dst_confirm(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;
     __u32 tsn;
     char do_fast_retransmit = 0;
     struct sctp_association *asoc = q->asoc;
     struct sctp_transport *primary = asoc->peer.primary_path;
 
     list_for_each_entry(chunk, transmitted_queue, 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 == SCTP_CAN_FRTX &&
             !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,
                         chunk->transport,
                         count_of_newacks, tsn)) {
                 chunk->tsn_missing_report++;
 
                 pr_debug("%s: tsn:0x%x missing counter:%d\n",
                      __func__, 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 = SCTP_NEED_FRTX;
             do_fast_retransmit = 1;
         }
     }
 
     if (transport) {
         if (do_fast_retransmit)
             sctp_retransmit(q, transport, SCTP_RTXR_FAST_RTX);
 
         pr_debug("%s: transport:%p, cwnd:%d, ssthresh:%d, "
              "flight_size:%d, pba:%d\n",  __func__, 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)
 {
     __u32 ctsn = ntohl(sack->cum_tsn_ack);
     union sctp_sack_variable *frags;
     __u16 tsn_offset, blocks;
     int i;
 
     if (TSN_lte(tsn, ctsn))
         goto pass;
 
     /* 3.3.4 Selective Acknowledgment (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;
     blocks = ntohs(sack->num_gap_ack_blocks);
     tsn_offset = tsn - ctsn;
     for (i = 0; i < blocks; ++i) {
         if (tsn_offset >= ntohs(frags[i].gab.start) &&
             tsn_offset <= 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. */
 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;
 
     if (!asoc->peer.prsctp_capable)
         return;
 
     /* 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(asoc->base.net, SCTP_MIB_OUTCTRLCHUNKS);
     }
 }

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