/src/openthread/third_party/tcplp/bsdtcp/tcp_sack.c

Source
/*-
 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
 *  The Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *  @(#)tcp_sack.c  8.12 (Berkeley) 5/24/95
 */

/*-
 *  @@(#)COPYRIGHT  1.1 (NRL) 17 January 1995
 *
 * NRL grants permission for redistribution and use in source and binary
 * forms, with or without modification, of the software and documentation
 * created at NRL provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgements:
 *  This product includes software developed by the University of
 *  California, Berkeley and its contributors.
 *  This product includes software developed at the Information
 *  Technology Division, US Naval Research Laboratory.
 * 4. Neither the name of the NRL nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THE SOFTWARE PROVIDED BY NRL IS PROVIDED BY NRL AND CONTRIBUTORS ``AS
 * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
 * PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL NRL OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * The views and conclusions contained in the software and documentation
 * are those of the authors and should not be interpreted as representing
 * official policies, either expressed or implied, of the US Naval
 * Research Laboratory (NRL).
 */

/* samkumar: Removed a bunch of #include's and VNET declarations. */

#include <strings.h>
#include "tcp.h"
#include "tcp_fsm.h"
#include "tcp_seq.h"
#include "tcp_timer.h"
#include "tcp_var.h"
#include "sys/queue.h"

enum tcp_sack_consts {
  V_tcp_sack_maxholes = MAX_SACKHOLES
};

/*
 * samkumar: Removed tcp_sack_globalmaxholes and tcp_sack_globalholes.
 * There used to be a counter, V_tcp_sack_globalholes, that kept track of the
 * total number of SACK holes allocated across all TCP connections.
 */

/*
 * samkumar: I added these three functions. The first, tcp_sack_init,
 * initializes a per-connection pool of SACK holes.
 *
 * The next two, sackhole_alloc and sackhole_free, allocate and deallocate SACK
 * holes from the pool. Previously, the FreeBSD code would allocate SACK holes
 * dynamically, for example, using the code
 * "hole = (struct sackhole *)uma_zalloc(V_sack_hole_zone, M_NOWAIT);".
 * TCPlp avoids dynamic memory allocation in the TCP implementation, so we
 * replace it with this per-connection pool.
 */

void
tcp_sack_init(struct tcpcb* tp)
{
  bmp_init(tp->sackhole_bmp, SACKHOLE_BMP_SIZE);
}

struct sackhole* sackhole_alloc(struct tcpcb* tp) {
    size_t freeindex = bmp_countset(tp->sackhole_bmp, SACKHOLE_BMP_SIZE, 0, SACKHOLE_BMP_SIZE);
    if (freeindex >= SACKHOLE_BMP_SIZE) {
      return NULL; // all sackholes are allocated already!
    }
    bmp_setrange(tp->sackhole_bmp, freeindex, 1);
    return &tp->sackhole_pool[freeindex];
}

void sackhole_free(struct tcpcb* tp, struct sackhole* tofree) {
  size_t freeindex = (size_t) (tofree - &tp->sackhole_pool[0]);
  KASSERT(tofree == &tp->sackhole_pool[freeindex], ("sackhole pool unaligned"));
  bmp_clrrange(tp->sackhole_bmp, freeindex, 1);
}

/*
 * samkumar: Throughout the remaining functions, I have replaced allocation and
 * deallocation of SACK holes, which previously used uma_zalloc and uma_zfree,
 * with calls to sackhole_alloc and sackhole_free. I've also removed code for
 * locking, global stats collection, global SACK hole limits, and debugging
 * probes.
 */


/*
 * This function is called upon receipt of new valid data (while not in
 * header prediction mode), and it updates the ordered list of sacks.
 */
void
tcp_update_sack_list(struct tcpcb *tp, tcp_seq rcv_start, tcp_seq rcv_end)
{
  /*
   * First reported block MUST be the most recent one.  Subsequent
   * blocks SHOULD be in the order in which they arrived at the
   * receiver.  These two conditions make the implementation fully
   * compliant with RFC 2018.
   */
  struct sackblk head_blk, saved_blks[MAX_SACK_BLKS];
  int num_head, num_saved, i;

  /* Check arguments. */
  KASSERT(SEQ_LT(rcv_start, rcv_end), ("rcv_start < rcv_end"));

  /* SACK block for the received segment. */
  head_blk.start = rcv_start;
  head_blk.end = rcv_end;

  /*
   * Merge updated SACK blocks into head_blk, and save unchanged SACK
   * blocks into saved_blks[].  num_saved will have the number of the
   * saved SACK blocks.
   */
  num_saved = 0;
  for (i = 0; i < tp->rcv_numsacks; i++) {
    tcp_seq start = tp->sackblks[i].start;
    tcp_seq end = tp->sackblks[i].end;
    if (SEQ_GEQ(start, end) || SEQ_LEQ(start, tp->rcv_nxt)) {
      /*
       * Discard this SACK block.
       */
    } else if (SEQ_LEQ(head_blk.start, end) &&
         SEQ_GEQ(head_blk.end, start)) {
      /*
       * Merge this SACK block into head_blk.  This SACK
       * block itself will be discarded.
       */
      if (SEQ_GT(head_blk.start, start))
        head_blk.start = start;
      if (SEQ_LT(head_blk.end, end))
        head_blk.end = end;
    } else {
      /*
       * Save this SACK block.
       */
      saved_blks[num_saved].start = start;
      saved_blks[num_saved].end = end;
      num_saved++;
    }
  }

  /*
   * Update SACK list in tp->sackblks[].
   */
  num_head = 0;
  if (SEQ_GT(head_blk.start, tp->rcv_nxt)) {
    /*
     * The received data segment is an out-of-order segment.  Put
     * head_blk at the top of SACK list.
     */
    tp->sackblks[0] = head_blk;
    num_head = 1;
    /*
     * If the number of saved SACK blocks exceeds its limit,
     * discard the last SACK block.
     */
    if (num_saved >= MAX_SACK_BLKS)
      num_saved--;
  }
  if (num_saved > 0) {
    /*
     * Copy the saved SACK blocks back.
     */
    bcopy(saved_blks, &tp->sackblks[num_head],
          sizeof(struct sackblk) * num_saved);
  }

  /* Save the number of SACK blocks. */
  tp->rcv_numsacks = num_head + num_saved;
}

/*
 * Delete all receiver-side SACK information.
 */
void
tcp_clean_sackreport(struct tcpcb *tp)
{
  int i;

  tp->rcv_numsacks = 0;
  for (i = 0; i < MAX_SACK_BLKS; i++)
    tp->sackblks[i].start = tp->sackblks[i].end=0;
}

/*
 * Allocate struct sackhole.
 */
static struct sackhole *
tcp_sackhole_alloc(struct tcpcb *tp, tcp_seq start, tcp_seq end)
{
  struct sackhole *hole;

  /*
   * samkumar: This if block also used to also return NULL if
   * V_tcp_sack_globalholes >= V_tcp_sack_globalmaxholes
   * but I removed that check since it doesn't make sense to enforce a global
   * limit on SACK holes when we have a fixed-size pool (moreover, a separate
   * pool per connection). The per-connection limit is sufficient.
   */
  if (tp->snd_numholes >= V_tcp_sack_maxholes) {
    return NULL;
  }

  hole = sackhole_alloc(tp);
  if (hole == NULL)
    return NULL;

  hole->start = start;
  hole->end = end;
  hole->rxmit = start;

  tp->snd_numholes++;

  return hole;
}

/*
 * Free struct sackhole.
 */
static void
tcp_sackhole_free(struct tcpcb *tp, struct sackhole *hole)
{
  sackhole_free(tp, hole);

  tp->snd_numholes--;

  KASSERT(tp->snd_numholes >= 0, ("tp->snd_numholes >= 0"));
}

/*
 * Insert new SACK hole into scoreboard.
 */
static struct sackhole *
tcp_sackhole_insert(struct tcpcb *tp, tcp_seq start, tcp_seq end,
    struct sackhole *after)
{
  struct sackhole *hole;

  /* Allocate a new SACK hole. */
  hole = tcp_sackhole_alloc(tp, start, end);
  if (hole == NULL)
    return NULL;

  /* Insert the new SACK hole into scoreboard. */
  if (after != NULL)
    TAILQ_INSERT_AFTER(&tp->snd_holes, after, hole, scblink);
  else
    TAILQ_INSERT_TAIL(&tp->snd_holes, hole, scblink);

  /* Update SACK hint. */
  if (tp->sackhint.nexthole == NULL)
    tp->sackhint.nexthole = hole;

  return hole;
}

/*
 * Remove SACK hole from scoreboard.
 */
static void
tcp_sackhole_remove(struct tcpcb *tp, struct sackhole *hole)
{

  /* Update SACK hint. */
  if (tp->sackhint.nexthole == hole)
    tp->sackhint.nexthole = TAILQ_NEXT(hole, scblink);

  /* Remove this SACK hole. */
  TAILQ_REMOVE(&tp->snd_holes, hole, scblink);

  /* Free this SACK hole. */
  tcp_sackhole_free(tp, hole);
}

/*
 * Process cumulative ACK and the TCP SACK option to update the scoreboard.
 * tp->snd_holes is an ordered list of holes (oldest to newest, in terms of
 * the sequence space).
 */
void
tcp_sack_doack(struct tcpcb *tp, struct tcpopt *to, tcp_seq th_ack)
{
  struct sackhole *cur, *temp;
  struct sackblk sack, sack_blocks[TCP_MAX_SACK + 1], *sblkp;
  int i, j, num_sack_blks;

  num_sack_blks = 0;
  /*
   * If SND.UNA will be advanced by SEG.ACK, and if SACK holes exist,
   * treat [SND.UNA, SEG.ACK) as if it is a SACK block.
   */
  if (SEQ_LT(tp->snd_una, th_ack) && !TAILQ_EMPTY(&tp->snd_holes)) {
    sack_blocks[num_sack_blks].start = tp->snd_una;
    sack_blocks[num_sack_blks++].end = th_ack;
  }
  /*
   * Append received valid SACK blocks to sack_blocks[], but only if we
   * received new blocks from the other side.
   */
  if (to->to_flags & TOF_SACK) {
    for (i = 0; i < to->to_nsacks; i++) {
      bcopy((to->to_sacks + i * TCPOLEN_SACK),
          &sack, sizeof(sack));
      sack.start = ntohl(sack.start);
      sack.end = ntohl(sack.end);
      if (SEQ_GT(sack.end, sack.start) &&
          SEQ_GT(sack.start, tp->snd_una) &&
          SEQ_GT(sack.start, th_ack) &&
          SEQ_LT(sack.start, tp->snd_max) &&
          SEQ_GT(sack.end, tp->snd_una) &&
          SEQ_LEQ(sack.end, tp->snd_max))
        sack_blocks[num_sack_blks++] = sack;
    }
  }
  /*
   * Return if SND.UNA is not advanced and no valid SACK block is
   * received.
   */
  if (num_sack_blks == 0)
    return;

  /*
   * Sort the SACK blocks so we can update the scoreboard with just one
   * pass. The overhead of sorting upto 4+1 elements is less than
   * making upto 4+1 passes over the scoreboard.
   */
  for (i = 0; i < num_sack_blks; i++) {
    for (j = i + 1; j < num_sack_blks; j++) {
      if (SEQ_GT(sack_blocks[i].end, sack_blocks[j].end)) {
        sack = sack_blocks[i];
        sack_blocks[i] = sack_blocks[j];
        sack_blocks[j] = sack;
      }
    }
  }
  if (TAILQ_EMPTY(&tp->snd_holes))
    /*
     * Empty scoreboard. Need to initialize snd_fack (it may be
     * uninitialized or have a bogus value). Scoreboard holes
     * (from the sack blocks received) are created later below
     * (in the logic that adds holes to the tail of the
     * scoreboard).
     */
    tp->snd_fack = SEQ_MAX(tp->snd_una, th_ack);
  /*
   * In the while-loop below, incoming SACK blocks (sack_blocks[]) and
   * SACK holes (snd_holes) are traversed from their tails with just
   * one pass in order to reduce the number of compares especially when
   * the bandwidth-delay product is large.
   *
   * Note: Typically, in the first RTT of SACK recovery, the highest
   * three or four SACK blocks with the same ack number are received.
   * In the second RTT, if retransmitted data segments are not lost,
   * the highest three or four SACK blocks with ack number advancing
   * are received.
   */
  sblkp = &sack_blocks[num_sack_blks - 1];  /* Last SACK block */
  tp->sackhint.last_sack_ack = sblkp->end;
  if (SEQ_LT(tp->snd_fack, sblkp->start)) {
    /*
     * The highest SACK block is beyond fack.  Append new SACK
     * hole at the tail.  If the second or later highest SACK
     * blocks are also beyond the current fack, they will be
     * inserted by way of hole splitting in the while-loop below.
     */
    temp = tcp_sackhole_insert(tp, tp->snd_fack,sblkp->start,NULL);
    if (temp != NULL) {
      tp->snd_fack = sblkp->end;
      /* Go to the previous sack block. */
      sblkp--;
    } else {
      /*
       * We failed to add a new hole based on the current
       * sack block.  Skip over all the sack blocks that
       * fall completely to the right of snd_fack and
       * proceed to trim the scoreboard based on the
       * remaining sack blocks.  This also trims the
       * scoreboard for th_ack (which is sack_blocks[0]).
       */
      while (sblkp >= sack_blocks &&
             SEQ_LT(tp->snd_fack, sblkp->start))
        sblkp--;
      if (sblkp >= sack_blocks &&
          SEQ_LT(tp->snd_fack, sblkp->end))
        tp->snd_fack = sblkp->end;
    }
  } else if (SEQ_LT(tp->snd_fack, sblkp->end))
    /* fack is advanced. */
    tp->snd_fack = sblkp->end;
  /* We must have at least one SACK hole in scoreboard. */
  KASSERT(!TAILQ_EMPTY(&tp->snd_holes),
      ("SACK scoreboard must not be empty"));
  cur = TAILQ_LAST(&tp->snd_holes, sackhole_head); /* Last SACK hole. */
  /*
   * Since the incoming sack blocks are sorted, we can process them
   * making one sweep of the scoreboard.
   */
  while (sblkp >= sack_blocks  && cur != NULL) {
    if (SEQ_GEQ(sblkp->start, cur->end)) {
      /*
       * SACKs data beyond the current hole.  Go to the
       * previous sack block.
       */
      sblkp--;
      continue;
    }
    if (SEQ_LEQ(sblkp->end, cur->start)) {
      /*
       * SACKs data before the current hole.  Go to the
       * previous hole.
       */
      cur = TAILQ_PREV(cur, sackhole_head, scblink);
      continue;
    }
    tp->sackhint.sack_bytes_rexmit -= (cur->rxmit - cur->start);
    KASSERT(tp->sackhint.sack_bytes_rexmit >= 0,
        ("sackhint bytes rtx >= 0"));
    if (SEQ_LEQ(sblkp->start, cur->start)) {
      /* Data acks at least the beginning of hole. */
      if (SEQ_GEQ(sblkp->end, cur->end)) {
        /* Acks entire hole, so delete hole. */
        temp = cur;
        cur = TAILQ_PREV(cur, sackhole_head, scblink);
        tcp_sackhole_remove(tp, temp);
        /*
         * The sack block may ack all or part of the
         * next hole too, so continue onto the next
         * hole.
         */
        continue;
      } else {
        /* Move start of hole forward. */
        cur->start = sblkp->end;
        cur->rxmit = SEQ_MAX(cur->rxmit, cur->start);
      }
    } else {
      /* Data acks at least the end of hole. */
      if (SEQ_GEQ(sblkp->end, cur->end)) {
        /* Move end of hole backward. */
        cur->end = sblkp->start;
        cur->rxmit = SEQ_MIN(cur->rxmit, cur->end);
      } else {
        /*
         * ACKs some data in middle of a hole; need
         * to split current hole
         */
        temp = tcp_sackhole_insert(tp, sblkp->end,
            cur->end, cur);
        if (temp != NULL) {
          if (SEQ_GT(cur->rxmit, temp->rxmit)) {
            temp->rxmit = cur->rxmit;
            tp->sackhint.sack_bytes_rexmit
                += (temp->rxmit
                - temp->start);
          }
          cur->end = sblkp->start;
          cur->rxmit = SEQ_MIN(cur->rxmit,
              cur->end);
        }
      }
    }
    tp->sackhint.sack_bytes_rexmit += (cur->rxmit - cur->start);
    /*
     * Testing sblkp->start against cur->start tells us whether
     * we're done with the sack block or the sack hole.
     * Accordingly, we advance one or the other.
     */
    if (SEQ_LEQ(sblkp->start, cur->start))
      cur = TAILQ_PREV(cur, sackhole_head, scblink);
    else
      sblkp--;
  }
}

/*
 * Free all SACK holes to clear the scoreboard.
 */
void
tcp_free_sackholes(struct tcpcb *tp)
{
  struct sackhole *q;

  while ((q = TAILQ_FIRST(&tp->snd_holes)) != NULL)
    tcp_sackhole_remove(tp, q);
  tp->sackhint.sack_bytes_rexmit = 0;

  KASSERT(tp->snd_numholes == 0, ("tp->snd_numholes == 0"));
  KASSERT(tp->sackhint.nexthole == NULL,
    ("tp->sackhint.nexthole == NULL"));
}

/*
 * Partial ack handling within a sack recovery episode.  Keeping this very
 * simple for now.  When a partial ack is received, force snd_cwnd to a value
 * that will allow the sender to transmit no more than 2 segments.  If
 * necessary, a better scheme can be adopted at a later point, but for now,
 * the goal is to prevent the sender from bursting a large amount of data in
 * the midst of sack recovery.
 */
void
tcp_sack_partialack(struct tcpcb *tp, struct tcphdr *th)
{
  int num_segs = 1;

  tcp_timer_activate(tp, TT_REXMT, 0);
  tp->t_rtttime = 0;
  /* Send one or 2 segments based on how much new data was acked. */
  if ((BYTES_THIS_ACK(tp, th) / tp->t_maxseg) >= 2)
    num_segs = 2;
  tp->snd_cwnd = (tp->sackhint.sack_bytes_rexmit +
      (tp->snd_nxt - tp->sack_newdata) + num_segs * tp->t_maxseg);
  if (tp->snd_cwnd > tp->snd_ssthresh)
    tp->snd_cwnd = tp->snd_ssthresh;
  tp->t_flags |= TF_ACKNOW;
  (void) tcplp_output(tp);
}

/*
 * samkumar: Removed this function for now, but I left it in as a comment
 * (using #if 0) in case it is useful later for debugging.
 */
#if 0
/*
 * Debug version of tcp_sack_output() that walks the scoreboard.  Used for
 * now to sanity check the hint.
 */
static struct sackhole *
tcp_sack_output_debug(struct tcpcb *tp, int *sack_bytes_rexmt)
{
  struct sackhole *p;

  INP_WLOCK_ASSERT(tp->t_inpcb);
  *sack_bytes_rexmt = 0;
  TAILQ_FOREACH(p, &tp->snd_holes, scblink) {
    if (SEQ_LT(p->rxmit, p->end)) {
      if (SEQ_LT(p->rxmit, tp->snd_una)) {/* old SACK hole */
        continue;
      }
      *sack_bytes_rexmt += (p->rxmit - p->start);
      break;
    }
    *sack_bytes_rexmt += (p->rxmit - p->start);
  }
  return (p);
}
#endif

/*
 * Returns the next hole to retransmit and the number of retransmitted bytes
 * from the scoreboard.  We store both the next hole and the number of
 * retransmitted bytes as hints (and recompute these on the fly upon SACK/ACK
 * reception).  This avoids scoreboard traversals completely.
 *
 * The loop here will traverse *at most* one link.  Here's the argument.  For
 * the loop to traverse more than 1 link before finding the next hole to
 * retransmit, we would need to have at least 1 node following the current
 * hint with (rxmit == end).  But, for all holes following the current hint,
 * (start == rxmit), since we have not yet retransmitted from them.
 * Therefore, in order to traverse more 1 link in the loop below, we need to
 * have at least one node following the current hint with (start == rxmit ==
 * end).  But that can't happen, (start == end) means that all the data in
 * that hole has been sacked, in which case, the hole would have been removed
 * from the scoreboard.
 */
struct sackhole *
tcp_sack_output(struct tcpcb *tp, int *sack_bytes_rexmt)
{
  struct sackhole *hole = NULL;

  *sack_bytes_rexmt = tp->sackhint.sack_bytes_rexmit;
  hole = tp->sackhint.nexthole;
  if (hole == NULL || SEQ_LT(hole->rxmit, hole->end))
    goto out;
  while ((hole = TAILQ_NEXT(hole, scblink)) != NULL) {
    if (SEQ_LT(hole->rxmit, hole->end)) {
      tp->sackhint.nexthole = hole;
      break;
    }
  }
out:
  return (hole);
}

/*
 * After a timeout, the SACK list may be rebuilt.  This SACK information
 * should be used to avoid retransmitting SACKed data.  This function
 * traverses the SACK list to see if snd_nxt should be moved forward.
 */
void
tcp_sack_adjust(struct tcpcb *tp)
{
  struct sackhole *p, *cur = TAILQ_FIRST(&tp->snd_holes);

  if (cur == NULL)
    return; /* No holes */
  if (SEQ_GEQ(tp->snd_nxt, tp->snd_fack))
    return; /* We're already beyond any SACKed blocks */
  /*-
   * Two cases for which we want to advance snd_nxt:
   * i) snd_nxt lies between end of one hole and beginning of another
   * ii) snd_nxt lies between end of last hole and snd_fack
   */
  while ((p = TAILQ_NEXT(cur, scblink)) != NULL) {
    if (SEQ_LT(tp->snd_nxt, cur->end))
      return;
    if (SEQ_GEQ(tp->snd_nxt, p->start))
      cur = p;
    else {
      tp->snd_nxt = p->start;
      return;
    }
  }
  if (SEQ_LT(tp->snd_nxt, cur->end))
    return;
  tp->snd_nxt = tp->snd_fack;
}

Coverage Report

Created: 2025-10-10 07:08