tcp: handle sack reneging

Type: feature

Change-Id: I201155b1b92cf7e57310af726879dab039090582
Signed-off-by: Florin Coras <fcoras@cisco.com>
(cherry picked from commit 558e3e09577a7b49e2fec58e8ac27f3f3ae0592f)

4 files changed, 203 insertions, 135 deletions

diff --git a/src/plugins/unittest/tcp_test.c b/src/plugins/unittest/tcp_test.c
index 7aa24562d7e..42fa423bfae 100644
--- a/src/plugins/unittest/tcp_test.c
+++ b/src/plugins/unittest/tcp_test.c
@@ -125,7 +125,7 @@ tcp_test_sack_rx (vlib_main_t * vm, unformat_input_t * input)
   TCP_TEST ((hole->start == 900 && hole->end == 1000),
 	    "last hole start %u end %u", hole->start, hole->end);
   TCP_TEST ((sb->sacked_bytes == 400), "sacked bytes %d", sb->sacked_bytes);
-  TCP_TEST ((sb->snd_una_adv == 0), "snd_una_adv %u", sb->snd_una_adv);
+  TCP_TEST ((!sb->is_reneging), "is not reneging");
   TCP_TEST ((sb->last_sacked_bytes == 400),
 	    "last sacked bytes %d", sb->last_sacked_bytes);
   TCP_TEST ((sb->high_sacked == 900), "high sacked %u", sb->high_sacked);
@@ -153,29 +153,36 @@ tcp_test_sack_rx (vlib_main_t * vm, unformat_input_t * input)
   TCP_TEST ((hole->start == 0 && hole->end == 100),
 	    "first hole start %u end %u", hole->start, hole->end);
   TCP_TEST ((sb->sacked_bytes == 900), "sacked bytes %d", sb->sacked_bytes);
-  TCP_TEST ((sb->snd_una_adv == 0), "snd_una_adv %u", sb->snd_una_adv);
+  TCP_TEST ((!sb->is_reneging), "is not reneging");
   TCP_TEST ((sb->high_sacked == 1000), "high sacked %u", sb->high_sacked);
   TCP_TEST ((sb->last_sacked_bytes == 500),
 	    "last sacked bytes %d", sb->last_sacked_bytes);
   TCP_TEST ((sb->lost_bytes == 100), "lost bytes %u", sb->lost_bytes);
 
   /*
-   *  Ack until byte 100, all bytes are now acked + sacked
+   *  Ack until byte 100 - this is reneging because we should ack until 1000
    */
   tcp_rcv_sacks (tc, 100);
   if (verbose)
     vlib_cli_output (vm, "\nack until byte 100:\n%U", format_tcp_scoreboard,
 		     sb, tc);
 
-  TCP_TEST ((pool_elts (sb->holes) == 0),
-	    "scoreboard has %d elements", pool_elts (sb->holes));
-  TCP_TEST ((sb->snd_una_adv == 900),
-	    "snd_una_adv after ack %u", sb->snd_una_adv);
+  TCP_TEST ((pool_elts (sb->holes) == 0), "scoreboard has %d elements",
+	    pool_elts (sb->holes));
+  TCP_TEST ((sb->is_reneging), "is reneging");
+
+  /*
+   * Sack all up to 1000
+   */
+  tc->snd_una = 100;
+  tcp_rcv_sacks (tc, 1000);
   TCP_TEST ((sb->high_sacked == 1000), "max sacked byte %u", sb->high_sacked);
   TCP_TEST ((sb->sacked_bytes == 0), "sacked bytes %d", sb->sacked_bytes);
   TCP_TEST ((sb->last_sacked_bytes == 0),
 	    "last sacked bytes %d", sb->last_sacked_bytes);
   TCP_TEST ((sb->lost_bytes == 0), "lost bytes %u", sb->lost_bytes);
+  TCP_TEST ((!sb->is_reneging), "is not reneging");
+
 
   /*
    * Add new block
@@ -196,15 +203,12 @@ tcp_test_sack_rx (vlib_main_t * vm, unformat_input_t * input)
     vlib_cli_output (vm, "\nadd [1200, 1300] snd_una_max 1500, snd_una 1000:"
 		     " \n%U", format_tcp_scoreboard, sb, tc);
 
-  TCP_TEST ((sb->snd_una_adv == 0),
-	    "snd_una_adv after ack %u", sb->snd_una_adv);
+  TCP_TEST ((!sb->is_reneging), "is not reneging");
   TCP_TEST ((pool_elts (sb->holes) == 2),
 	    "scoreboard has %d holes", pool_elts (sb->holes));
   hole = scoreboard_first_hole (sb);
   TCP_TEST ((hole->start == 1000 && hole->end == 1200),
 	    "first hole start %u end %u", hole->start, hole->end);
-  TCP_TEST ((sb->snd_una_adv == 0),
-	    "snd_una_adv after ack %u", sb->snd_una_adv);
   TCP_TEST ((sb->high_sacked == 1300), "max sacked byte %u", sb->high_sacked);
   hole = scoreboard_last_hole (sb);
   TCP_TEST ((hole->start == 1300 && hole->end == 1500),
@@ -217,28 +221,28 @@ tcp_test_sack_rx (vlib_main_t * vm, unformat_input_t * input)
    */
 
   vec_reset_length (tc->rcv_opts.sacks);
-  tcp_rcv_sacks (tc, 1200);
+  /* Ack up to 1300 to avoid reneging */
+  tcp_rcv_sacks (tc, 1300);
 
   if (verbose)
-    vlib_cli_output (vm, "\nsb ack up to byte 1200:\n%U",
+    vlib_cli_output (vm, "\nsb ack up to byte 1300:\n%U",
 		     format_tcp_scoreboard, sb, tc);
 
-  TCP_TEST ((sb->snd_una_adv == 100),
-	    "snd_una_adv after ack %u", sb->snd_una_adv);
   TCP_TEST ((sb->sacked_bytes == 0), "sacked bytes %d", sb->sacked_bytes);
-  TCP_TEST ((pool_elts (sb->holes) == 0),
+  TCP_TEST ((pool_elts (sb->holes) == 1),
 	    "scoreboard has %d elements", pool_elts (sb->holes));
   TCP_TEST ((sb->last_bytes_delivered == 100), "last bytes delivered %d",
 	    sb->last_bytes_delivered);
   TCP_TEST ((sb->lost_bytes == 0), "lost bytes %u", sb->lost_bytes);
-  TCP_TEST ((sb->head == TCP_INVALID_SACK_HOLE_INDEX), "head %u", sb->head);
-  TCP_TEST ((sb->tail == TCP_INVALID_SACK_HOLE_INDEX), "tail %u", sb->tail);
+  TCP_TEST ((sb->head != TCP_INVALID_SACK_HOLE_INDEX), "head %u", sb->head);
+  TCP_TEST ((sb->tail != TCP_INVALID_SACK_HOLE_INDEX), "tail %u", sb->tail);
+  TCP_TEST ((!sb->is_reneging), "is not reneging");
 
   /*
    * Add some more blocks and then remove all
    */
   vec_reset_length (tc->rcv_opts.sacks);
-  tc->snd_una += sb->snd_una_adv;
+  tc->snd_una = 1300;
   tc->snd_nxt = tc->snd_una_max = 1900;
   for (i = 0; i < 5; i++)
     {
@@ -265,6 +269,7 @@ tcp_test_sack_rx (vlib_main_t * vm, unformat_input_t * input)
   tc->snd_una = 0;
   tc->snd_una_max = 1000;
   tc->snd_nxt = 1000;
+  vec_reset_length (tc->rcv_opts.sacks);
   for (i = 0; i < 5; i++)
     {
       vec_add1 (tc->rcv_opts.sacks, sacks[i * 2 + 1]);
@@ -272,25 +277,34 @@ tcp_test_sack_rx (vlib_main_t * vm, unformat_input_t * input)
   tc->rcv_opts.n_sack_blocks = vec_len (tc->rcv_opts.sacks);
   tcp_rcv_sacks (tc, 0);
   if (verbose)
-    vlib_cli_output (vm, "\nsb added odd blocks snd_una 0 snd_una_max 1500:"
+    vlib_cli_output (vm, "\nsb added odd blocks snd_una 0 snd_una_max 1000:"
 		     "\n%U", format_tcp_scoreboard, sb, tc);
   TCP_TEST ((pool_elts (sb->holes) == 5),
 	    "scoreboard has %d elements", pool_elts (sb->holes));
   TCP_TEST ((sb->lost_bytes == 300), "lost bytes %u", sb->lost_bytes);
+  hole = scoreboard_last_hole (sb);
+  TCP_TEST ((hole->end == 900), "last hole end %u", hole->end);
+  TCP_TEST ((sb->high_sacked == 1000), "high sacked %u", sb->high_sacked);
 
+  /*
+   * Renege bytes from 950 to 1000
+   */
   tcp_rcv_sacks (tc, 950);
 
   if (verbose)
     vlib_cli_output (vm, "\nack [0, 950]:\n%U", format_tcp_scoreboard, sb,
 		     tc);
 
-  TCP_TEST ((pool_elts (sb->holes) == 0),
-	    "scoreboard has %d elements", pool_elts (sb->holes));
-  TCP_TEST ((sb->snd_una_adv == 50), "snd_una_adv %u", sb->snd_una_adv);
-  TCP_TEST ((sb->sacked_bytes == 0), "sacked bytes %d", sb->sacked_bytes);
-  TCP_TEST ((sb->last_sacked_bytes == 0),
-	    "last sacked bytes %d", sb->last_sacked_bytes);
+  TCP_TEST ((pool_elts (sb->holes) == 0), "scoreboard has %d elements",
+	    pool_elts (sb->holes));
+  TCP_TEST ((sb->is_reneging), "is reneging");
+  TCP_TEST ((sb->sacked_bytes == 50), "sacked bytes %d", sb->sacked_bytes);
+  TCP_TEST ((sb->last_sacked_bytes == 0), "last sacked bytes %d",
+	    sb->last_sacked_bytes);
   TCP_TEST ((sb->lost_bytes == 0), "lost bytes %u", sb->lost_bytes);
+  TCP_TEST ((sb->high_sacked == 1000), "high sacked %u", sb->high_sacked);
+
+  scoreboard_clear (sb);
 
   /*
    * Inject one block, ack it and overlap hole
@@ -317,17 +331,17 @@ tcp_test_sack_rx (vlib_main_t * vm, unformat_input_t * input)
     vlib_cli_output (vm, "\nsb ack [0, 800]:\n%U", format_tcp_scoreboard, sb,
 		     tc);
 
-  TCP_TEST ((pool_elts (sb->holes) == 0),
+  TCP_TEST ((pool_elts (sb->holes) == 1),
 	    "scoreboard has %d elements", pool_elts (sb->holes));
-  TCP_TEST ((sb->snd_una_adv == 0), "snd_una_adv %u", sb->snd_una_adv);
+  TCP_TEST ((!sb->is_reneging), "is not reneging");
   TCP_TEST ((sb->sacked_bytes == 0), "sacked bytes %d", sb->sacked_bytes);
   TCP_TEST ((sb->last_sacked_bytes == 0), "last sacked bytes %d",
 	    sb->last_sacked_bytes);
   TCP_TEST ((sb->last_bytes_delivered == 400),
 	    "last bytes delivered %d", sb->last_bytes_delivered);
   TCP_TEST ((sb->lost_bytes == 0), "lost bytes %u", sb->lost_bytes);
-  TCP_TEST ((sb->head == TCP_INVALID_SACK_HOLE_INDEX), "head %u", sb->head);
-  TCP_TEST ((sb->tail == TCP_INVALID_SACK_HOLE_INDEX), "tail %u", sb->tail);
+  TCP_TEST ((sb->head != TCP_INVALID_SACK_HOLE_INDEX), "head %u", sb->head);
+  TCP_TEST ((sb->tail != TCP_INVALID_SACK_HOLE_INDEX), "tail %u", sb->tail);
 
   /*
    * One hole close to head, patch head, split in two and start acking
@@ -370,46 +384,66 @@ tcp_test_sack_rx (vlib_main_t * vm, unformat_input_t * input)
 	    sb->last_bytes_delivered);
   TCP_TEST ((sb->lost_bytes == 300), "lost bytes %u", sb->lost_bytes);
 
+  /*
+   * Ack [100 300] in two steps
+   *
+   * Step 1. Ack [100 200] which delivers 100 of the bytes lost
+   */
   tc->snd_una = 100;
   tcp_rcv_sacks (tc, 200);
+  TCP_TEST ((sb->sacked_bytes == 600), "sacked bytes %d", sb->sacked_bytes);
+  TCP_TEST ((sb->last_bytes_delivered == 0), "last bytes delivered %d",
+	    sb->last_bytes_delivered);
+  TCP_TEST ((sb->lost_bytes == 200), "lost bytes %u", sb->lost_bytes);
+
+  /*
+   * Step 2. Ack up to 300, although 300 400 is sacked, so this is interpreted
+   * as reneging.
+   */
   tc->snd_una = 200;
   tcp_rcv_sacks (tc, 300);
   if (verbose)
-    vlib_cli_output (vm, "\nacked [0, 300] in two steps:\n%U",
+    vlib_cli_output (vm, "\nacked [100, 300] in two steps:\n%U",
 		     format_tcp_scoreboard, sb, tc);
-  TCP_TEST ((sb->sacked_bytes == 500), "sacked bytes %d", sb->sacked_bytes);
+  TCP_TEST ((sb->sacked_bytes == 600), "sacked bytes %d", sb->sacked_bytes);
   TCP_TEST ((sb->lost_bytes == 100), "lost bytes %u", sb->lost_bytes);
-  TCP_TEST ((sb->last_bytes_delivered == 100), "last bytes delivered %d",
+  TCP_TEST ((sb->last_bytes_delivered == 0), "last bytes delivered %d",
 	    sb->last_bytes_delivered);
+  TCP_TEST ((sb->is_reneging), "is reneging");
 
-  tc->snd_una = 400;
+  /*
+   * Ack [300 500]. Delivers reneged segment [300 400] and reneges bytes
+   * above 500
+   */
+  tc->snd_una = 300;
   tcp_rcv_sacks (tc, 500);
   if (verbose)
     vlib_cli_output (vm, "\nacked [400, 500]:\n%U", format_tcp_scoreboard, sb,
 		     tc);
   TCP_TEST ((pool_elts (sb->holes) == 0),
 	    "scoreboard has %d elements", pool_elts (sb->holes));
-  TCP_TEST ((sb->sacked_bytes == 0), "sacked bytes %d", sb->sacked_bytes);
+  TCP_TEST ((sb->sacked_bytes == 500), "sacked bytes %d", sb->sacked_bytes);
   TCP_TEST ((sb->last_sacked_bytes == 0), "last sacked bytes %d",
 	    sb->last_sacked_bytes);
-  TCP_TEST ((sb->last_bytes_delivered == 500), "last bytes delivered %d",
+  TCP_TEST ((sb->last_bytes_delivered == 100), "last bytes delivered %d",
 	    sb->last_bytes_delivered);
-  TCP_TEST ((sb->lost_bytes == 0), "lost bytes %u", sb->lost_bytes);
-  TCP_TEST ((sb->snd_una_adv == 500), "snd_una_adv %u", sb->snd_una_adv);
+  TCP_TEST ((sb->is_reneging), "is reneging");
   TCP_TEST ((sb->head == TCP_INVALID_SACK_HOLE_INDEX), "head %u", sb->head);
   TCP_TEST ((sb->tail == TCP_INVALID_SACK_HOLE_INDEX), "tail %u", sb->tail);
 
   /*
-   * Re-ack high sacked, to make sure last_bytes_delivered and
-   * snd_una_adv are 0-ed
+   * Ack up to 1000 to deliver all bytes
    */
+  tc->snd_una = 500;
   tcp_rcv_sacks (tc, 1000);
   if (verbose)
     vlib_cli_output (vm, "\nAck high sacked:\n%U", format_tcp_scoreboard, sb,
 		     tc);
-  TCP_TEST ((sb->last_bytes_delivered == 0), "last bytes delivered %d",
+  TCP_TEST ((sb->last_sacked_bytes == 0), "last sacked bytes %d",
+	    sb->last_sacked_bytes);
+  TCP_TEST ((sb->last_bytes_delivered == 500), "last bytes delivered %d",
 	    sb->last_bytes_delivered);
-  TCP_TEST ((sb->snd_una_adv == 0), "snd_una_adv %u", sb->snd_una_adv);
+  TCP_TEST ((!sb->is_reneging), "is not reneging");
 
   /*
    * Add [1200, 1500] and test that [1000, 1200] is lost (bytes condition)
@@ -434,7 +468,7 @@ tcp_test_sack_rx (vlib_main_t * vm, unformat_input_t * input)
   TCP_TEST ((sb->last_bytes_delivered == 0), "last bytes delivered %d",
 	    sb->last_bytes_delivered);
   TCP_TEST ((sb->lost_bytes == 200), "lost bytes %u", sb->lost_bytes);
-  TCP_TEST ((sb->snd_una_adv == 0), "snd_una_adv %u", sb->snd_una_adv);
+  TCP_TEST ((!sb->is_reneging), "is not reneging");
 
   return 0;
 }
diff --git a/src/vnet/tcp/tcp.c b/src/vnet/tcp/tcp.c
index cbb95777820..b898dd5902d 100644
--- a/src/vnet/tcp/tcp.c
+++ b/src/vnet/tcp/tcp.c
@@ -268,6 +268,8 @@ tcp_connection_cleanup (tcp_connection_t * tc)
       tcp_cc_cleanup (tc);
       vec_free (tc->snd_sacks);
       vec_free (tc->snd_sacks_fl);
+      vec_free (tc->rcv_opts.sacks);
+      pool_free (tc->sack_sb.holes);
 
       if (tc->flags & TCP_CONN_RATE_SAMPLE)
 	tcp_bt_cleanup (tc);
@@ -1139,9 +1141,9 @@ format_tcp_scoreboard (u8 * s, va_list * args)
 
   s = format (s, "sacked_bytes %u last_sacked_bytes %u lost_bytes %u\n",
 	      sb->sacked_bytes, sb->last_sacked_bytes, sb->lost_bytes);
-  s = format (s, "%Ulast_bytes_delivered %u high_sacked %u snd_una_adv %u\n",
+  s = format (s, "%Ulast_bytes_delivered %u high_sacked %u is_reneging %u\n",
 	      format_white_space, indent, sb->last_bytes_delivered,
-	      sb->high_sacked - tc->iss, sb->snd_una_adv);
+	      sb->high_sacked - tc->iss, sb->is_reneging);
   s = format (s, "%Ucur_rxt_hole %u high_rxt %u rescue_rxt %u",
 	      format_white_space, indent, sb->cur_rxt_hole,
 	      sb->high_rxt - tc->iss, sb->rescue_rxt - tc->iss);
@@ -2141,7 +2143,7 @@ tcp_scoreboard_replay (u8 * s, tcp_connection_t * tc, u8 verbose)
       /* Push segments */
       tcp_rcv_sacks (dummy_tc, next_ack);
       if (has_new_ack)
-	dummy_tc->snd_una = next_ack + dummy_tc->sack_sb.snd_una_adv;
+	dummy_tc->snd_una = next_ack;
 
       if (verbose)
 	s = format (s, "result: %U", format_tcp_scoreboard,
diff --git a/src/vnet/tcp/tcp.h b/src/vnet/tcp/tcp.h
index 99735f2af70..4c4a9a525af 100644
--- a/src/vnet/tcp/tcp.h
+++ b/src/vnet/tcp/tcp.h
@@ -166,13 +166,13 @@ typedef struct _sack_scoreboard
   u32 sacked_bytes;			/**< Number of bytes sacked in sb */
   u32 last_sacked_bytes;		/**< Number of bytes last sacked */
   u32 last_bytes_delivered;		/**< Sack bytes delivered to app */
-  u32 snd_una_adv;			/**< Bytes to add to snd_una */
   u32 high_sacked;			/**< Highest byte sacked (fack) */
   u32 high_rxt;				/**< Highest retransmitted sequence */
   u32 rescue_rxt;			/**< Rescue sequence number */
   u32 lost_bytes;			/**< Bytes lost as per RFC6675 */
   u32 last_lost_bytes;			/**< Number of bytes last lost */
   u32 cur_rxt_hole;			/**< Retransmitting from this hole */
+  u8 is_reneging;
 
 #if TCP_SCOREBOARD_TRACE
   scoreboard_trace_elt_t *trace;
diff --git a/src/vnet/tcp/tcp_input.c b/src/vnet/tcp/tcp_input.c
index 9c1f6309b96..7ab7020ee9b 100755
--- a/src/vnet/tcp/tcp_input.c
+++ b/src/vnet/tcp/tcp_input.c
@@ -622,7 +622,7 @@ tcp_program_dequeue (tcp_worker_ctx_t * wrk, tcp_connection_t * tc)
       vec_add1 (wrk->pending_deq_acked, tc->c_c_index);
       tc->flags |= TCP_CONN_DEQ_PENDING;
     }
-  tc->burst_acked += tc->bytes_acked + tc->sack_sb.snd_una_adv;
+  tc->burst_acked += tc->bytes_acked;
 }
 
 /**
@@ -781,51 +781,71 @@ scoreboard_insert_hole (sack_scoreboard_t * sb, u32 prev_index,
 #endif /* CLIB_MARCH_VARIANT */
 
 #ifndef CLIB_MARCH_VARIANT
-static void
-scoreboard_update_bytes (tcp_connection_t * tc, sack_scoreboard_t * sb)
+
+always_inline void
+scoreboard_update_bytes (sack_scoreboard_t * sb, u32 ack, u32 snd_mss)
 {
   sack_scoreboard_hole_t *left, *right;
-  u32 bytes = 0, blks = 0;
+  u32 sacked = 0, blks = 0, old_sacked;
+
+  old_sacked = sb->sacked_bytes;
 
   sb->last_lost_bytes = 0;
   sb->lost_bytes = 0;
   sb->sacked_bytes = 0;
-  left = scoreboard_last_hole (sb);
-  if (!left)
-    return;
 
-  if (seq_gt (sb->high_sacked, left->end))
+  right = scoreboard_last_hole (sb);
+  if (!right)
+    {
+      sb->sacked_bytes = sb->high_sacked - ack;
+      return;
+    }
+
+  if (seq_gt (sb->high_sacked, right->end))
     {
-      bytes = sb->high_sacked - left->end;
+      sacked = sb->high_sacked - right->end;
       blks = 1;
     }
 
-  while ((right = left)
-	 && bytes < (TCP_DUPACK_THRESHOLD - 1) * tc->snd_mss
-	 && blks < TCP_DUPACK_THRESHOLD
-	 /* left not updated if above conditions fail */
-	 && (left = scoreboard_prev_hole (sb, right)))
+  while (sacked < (TCP_DUPACK_THRESHOLD - 1) * snd_mss
+	 && blks < TCP_DUPACK_THRESHOLD)
     {
-      bytes += right->start - left->end;
+      if (right->is_lost)
+	sb->lost_bytes += scoreboard_hole_bytes (right);
+
+      left = scoreboard_prev_hole (sb, right);
+      if (!left)
+	{
+	  ASSERT (right->start == ack || sb->is_reneging);
+	  sacked += right->start - ack;
+	  right = 0;
+	  break;
+	}
+
+      sacked += right->start - left->end;
       blks++;
+      right = left;
     }
 
-  /* left is first lost */
-  if (left)
+  /* right is first lost */
+  while (right)
     {
-      do
+      sb->lost_bytes += scoreboard_hole_bytes (right);
+      sb->last_lost_bytes += right->is_lost ? 0 : right->end - right->start;
+      right->is_lost = 1;
+      left = scoreboard_prev_hole (sb, right);
+      if (!left)
 	{
-	  sb->lost_bytes += scoreboard_hole_bytes (right);
-	  sb->last_lost_bytes += left->is_lost ? 0 : left->end - left->start;
-	  left->is_lost = 1;
-	  left = scoreboard_prev_hole (sb, right);
-	  if (left)
-	    bytes += right->start - left->end;
+	  ASSERT (right->start == ack || sb->is_reneging);
+	  sacked += right->start - ack;
+	  break;
 	}
-      while ((right = left));
+      sacked += right->start - left->end;
+      right = left;
     }
 
-  sb->sacked_bytes = bytes;
+  sb->sacked_bytes = sacked;
+  sb->last_sacked_bytes = sacked - (old_sacked - sb->last_bytes_delivered);
 }
 
 /**
@@ -924,12 +944,12 @@ scoreboard_clear (sack_scoreboard_t * sb)
   sb->sacked_bytes = 0;
   sb->last_sacked_bytes = 0;
   sb->last_bytes_delivered = 0;
-  sb->snd_una_adv = 0;
   sb->high_sacked = 0;
   sb->high_rxt = 0;
   sb->lost_bytes = 0;
   sb->last_lost_bytes = 0;
   sb->cur_rxt_hole = TCP_INVALID_SACK_HOLE_INDEX;
+  sb->is_reneging = 0;
 }
 #endif /* CLIB_MARCH_VARIANT */
 
@@ -953,22 +973,18 @@ tcp_scoreboard_is_sane_post_recovery (tcp_connection_t * tc)
 void
 tcp_rcv_sacks (tcp_connection_t * tc, u32 ack)
 {
-  sack_scoreboard_hole_t *hole, *next_hole, *last_hole;
-  u32 blk_index = 0, old_sacked_bytes, hole_index;
+  sack_scoreboard_hole_t *hole, *next_hole;
   sack_scoreboard_t *sb = &tc->sack_sb;
-  sack_block_t *blk, tmp;
-  int i, j;
+  sack_block_t *blk, *rcv_sacks;
+  u32 blk_index = 0, i, j;
 
   sb->last_sacked_bytes = 0;
   sb->last_bytes_delivered = 0;
-  sb->snd_una_adv = 0;
 
   if (!tcp_opts_sack (&tc->rcv_opts)
       && sb->head == TCP_INVALID_SACK_HOLE_INDEX)
     return;
 
-  old_sacked_bytes = sb->sacked_bytes;
-
   /* Remove invalid blocks */
   blk = tc->rcv_opts.sacks;
   while (blk < vec_end (tc->rcv_opts.sacks))
@@ -988,9 +1004,9 @@ tcp_rcv_sacks (tcp_connection_t * tc, u32 ack)
   /* Add block for cumulative ack */
   if (seq_gt (ack, tc->snd_una))
     {
-      tmp.start = tc->snd_una;
-      tmp.end = ack;
-      vec_add1 (tc->rcv_opts.sacks, tmp);
+      vec_add2 (tc->rcv_opts.sacks, blk, 1);
+      blk->start = tc->snd_una;
+      blk->end = ack;
     }
 
   if (vec_len (tc->rcv_opts.sacks) == 0)
@@ -999,35 +1015,60 @@ tcp_rcv_sacks (tcp_connection_t * tc, u32 ack)
   tcp_scoreboard_trace_add (tc, ack);
 
   /* Make sure blocks are ordered */
-  for (i = 0; i < vec_len (tc->rcv_opts.sacks); i++)
-    for (j = i + 1; j < vec_len (tc->rcv_opts.sacks); j++)
-      if (seq_lt (tc->rcv_opts.sacks[j].start, tc->rcv_opts.sacks[i].start))
+  rcv_sacks = tc->rcv_opts.sacks;
+  for (i = 0; i < vec_len (rcv_sacks); i++)
+    for (j = i + 1; j < vec_len (rcv_sacks); j++)
+      if (seq_lt (rcv_sacks[j].start, rcv_sacks[i].start))
 	{
-	  tmp = tc->rcv_opts.sacks[i];
-	  tc->rcv_opts.sacks[i] = tc->rcv_opts.sacks[j];
-	  tc->rcv_opts.sacks[j] = tmp;
+	  sack_block_t tmp = rcv_sacks[i];
+	  rcv_sacks[i] = rcv_sacks[j];
+	  rcv_sacks[j] = tmp;
 	}
 
   if (sb->head == TCP_INVALID_SACK_HOLE_INDEX)
     {
-      /* If no holes, insert the first that covers all outstanding bytes */
-      last_hole = scoreboard_insert_hole (sb, TCP_INVALID_SACK_HOLE_INDEX,
-					  tc->snd_una, tc->snd_nxt);
-      sb->tail = scoreboard_hole_index (sb, last_hole);
-      tmp = tc->rcv_opts.sacks[vec_len (tc->rcv_opts.sacks) - 1];
-      sb->high_sacked = tmp.end;
+      /* Handle reneging as a special case */
+      if (PREDICT_FALSE (sb->is_reneging))
+	{
+	  /* No holes, only sacked bytes */
+	  if (seq_leq (tc->snd_nxt, sb->high_sacked))
+	    {
+	      /* No progress made so return */
+	      if (seq_leq (ack, tc->snd_una))
+		return;
+
+	      /* Update sacked bytes delivered and return */
+	      sb->last_bytes_delivered = ack - tc->snd_una;
+	      sb->sacked_bytes -= sb->last_bytes_delivered;
+	      sb->is_reneging = seq_lt (ack, sb->high_sacked);
+	      return;
+	    }
+
+	  /* New hole above high sacked. Add it and process normally */
+	  hole = scoreboard_insert_hole (sb, TCP_INVALID_SACK_HOLE_INDEX,
+					 sb->high_sacked, tc->snd_nxt);
+	  sb->tail = scoreboard_hole_index (sb, hole);
+	}
+      /* Not reneging and no holes. Insert the first that covers all
+       * outstanding bytes */
+      else
+	{
+	  hole = scoreboard_insert_hole (sb, TCP_INVALID_SACK_HOLE_INDEX,
+					 tc->snd_una, tc->snd_nxt);
+	  sb->tail = scoreboard_hole_index (sb, hole);
+	}
+      sb->high_sacked = rcv_sacks[vec_len (rcv_sacks) - 1].end;
     }
   else
     {
-      /* If we have holes but snd_una_max is beyond the last hole, update
-       * last hole end */
-      tmp = tc->rcv_opts.sacks[vec_len (tc->rcv_opts.sacks) - 1];
-      last_hole = scoreboard_last_hole (sb);
-      if (seq_gt (tc->snd_nxt, last_hole->end))
+      /* If we have holes but snd_nxt is beyond the last hole, update
+       * last hole end or add new hole after high sacked */
+      hole = scoreboard_last_hole (sb);
+      if (seq_gt (tc->snd_nxt, hole->end))
 	{
-	  if (seq_geq (last_hole->start, sb->high_sacked))
+	  if (seq_geq (hole->start, sb->high_sacked))
 	    {
-	      last_hole->end = tc->snd_nxt;
+	      hole->end = tc->snd_nxt;
 	    }
 	  /* New hole after high sacked block */
 	  else if (seq_lt (sb->high_sacked, tc->snd_nxt))
@@ -1036,17 +1077,22 @@ tcp_rcv_sacks (tcp_connection_t * tc, u32 ack)
 				      tc->snd_nxt);
 	    }
 	}
+
       /* Keep track of max byte sacked for when the last hole
        * is acked */
-      if (seq_gt (tmp.end, sb->high_sacked))
-	sb->high_sacked = tmp.end;
+      sb->high_sacked = seq_max (rcv_sacks[vec_len (rcv_sacks) - 1].end,
+				 sb->high_sacked);
     }
 
   /* Walk the holes with the SACK blocks */
   hole = pool_elt_at_index (sb->holes, sb->head);
-  while (hole && blk_index < vec_len (tc->rcv_opts.sacks))
+
+  if (PREDICT_FALSE (sb->is_reneging))
+    sb->last_bytes_delivered += hole->start - tc->snd_una;
+
+  while (hole && blk_index < vec_len (rcv_sacks))
     {
-      blk = &tc->rcv_opts.sacks[blk_index];
+      blk = &rcv_sacks[blk_index];
       if (seq_leq (blk->start, hole->start))
 	{
 	  /* Block covers hole. Remove hole */
@@ -1054,21 +1100,19 @@ tcp_rcv_sacks (tcp_connection_t * tc, u32 ack)
 	    {
 	      next_hole = scoreboard_next_hole (sb, hole);
 
-	      /* Byte accounting: snd_una needs to be advanced */
+	      /* If covered by ack, compute delivered bytes */
 	      if (blk->end == ack)
 		{
-		  if (next_hole)
+		  u32 sacked = next_hole ? next_hole->start : sb->high_sacked;
+		  if (PREDICT_FALSE (seq_lt (ack, sacked)))
 		    {
-		      if (seq_lt (ack, next_hole->start))
-			sb->snd_una_adv = next_hole->start - ack;
-		      sb->last_bytes_delivered +=
-			next_hole->start - hole->end;
+		      sb->last_bytes_delivered += ack - hole->end;
+		      sb->is_reneging = 1;
 		    }
 		  else
 		    {
-		      ASSERT (seq_geq (sb->high_sacked, ack));
-		      sb->snd_una_adv = sb->high_sacked - ack;
-		      sb->last_bytes_delivered += sb->high_sacked - hole->end;
+		      sb->last_bytes_delivered += sacked - hole->end;
+		      sb->is_reneging = 0;
 		    }
 		}
 	      scoreboard_remove_hole (sb, hole);
@@ -1089,10 +1133,9 @@ tcp_rcv_sacks (tcp_connection_t * tc, u32 ack)
 	  /* Hole must be split */
 	  if (seq_lt (blk->end, hole->end))
 	    {
-	      hole_index = scoreboard_hole_index (sb, hole);
+	      u32 hole_index = scoreboard_hole_index (sb, hole);
 	      next_hole = scoreboard_insert_hole (sb, hole_index, blk->end,
 						  hole->end);
-
 	      /* Pool might've moved */
 	      hole = scoreboard_get_hole (sb, hole_index);
 	      hole->end = blk->start;
@@ -1107,24 +1150,15 @@ tcp_rcv_sacks (tcp_connection_t * tc, u32 ack)
 	}
     }
 
-  if (pool_elts (sb->holes) == 1)
-    {
-      hole = scoreboard_first_hole (sb);
-      if (hole->start == ack + sb->snd_una_adv && hole->end == tc->snd_nxt)
-	scoreboard_remove_hole (sb, hole);
-    }
-
-  scoreboard_update_bytes (tc, sb);
-  sb->last_sacked_bytes = sb->sacked_bytes
-    - (old_sacked_bytes - sb->last_bytes_delivered);
+  scoreboard_update_bytes (sb, ack, tc->snd_mss);
 
   ASSERT (sb->last_sacked_bytes <= sb->sacked_bytes || tcp_in_recovery (tc));
   ASSERT (sb->sacked_bytes == 0 || tcp_in_recovery (tc)
-	  || sb->sacked_bytes < tc->snd_nxt - seq_max (tc->snd_una, ack));
+	  || sb->sacked_bytes <= tc->snd_nxt - seq_max (tc->snd_una, ack));
   ASSERT (sb->last_sacked_bytes + sb->lost_bytes <= tc->snd_nxt
 	  - seq_max (tc->snd_una, ack) || tcp_in_recovery (tc));
   ASSERT (sb->head == TCP_INVALID_SACK_HOLE_INDEX || tcp_in_recovery (tc)
-	  || sb->holes[sb->head].start == ack + sb->snd_una_adv);
+	  || sb->is_reneging || sb->holes[sb->head].start == ack);
   ASSERT (sb->last_lost_bytes <= sb->lost_bytes);
 
   TCP_EVT (TCP_EVT_CC_SCOREBOARD, tc);
@@ -1464,16 +1498,14 @@ partial_ack:
   /* Remove retransmitted bytes that have been delivered */
   if (tcp_opts_sack_permitted (&tc->rcv_opts))
     {
-      ASSERT (tc->bytes_acked + tc->sack_sb.snd_una_adv
-	      >= tc->sack_sb.last_bytes_delivered
+      ASSERT (tc->bytes_acked >= tc->sack_sb.last_bytes_delivered
 	      || (tc->flags & TCP_CONN_FINSNT));
 
       /* If we have sacks and we haven't gotten an ack beyond high_rxt,
        * remove sacked bytes delivered */
       if (seq_lt (tc->snd_una, tc->sack_sb.high_rxt))
 	{
-	  rxt_delivered = tc->bytes_acked + tc->sack_sb.snd_una_adv
-	    - tc->sack_sb.last_bytes_delivered;
+	  rxt_delivered = tc->bytes_acked - tc->sack_sb.last_bytes_delivered;
 	  ASSERT (tc->snd_rxt_bytes >= rxt_delivered);
 	  tc->snd_rxt_bytes -= rxt_delivered;
 	}
@@ -1559,7 +1591,7 @@ process_ack:
 		      vnet_buffer (b)->tcp.ack_number,
 		      clib_net_to_host_u16 (th->window) << tc->snd_wscale);
   tc->bytes_acked = vnet_buffer (b)->tcp.ack_number - tc->snd_una;
-  tc->snd_una = vnet_buffer (b)->tcp.ack_number + tc->sack_sb.snd_una_adv;
+  tc->snd_una = vnet_buffer (b)->tcp.ack_number;
   tcp_validate_txf_size (tc, tc->bytes_acked);
 
   if (tc->bytes_acked)