X-Git-Url: https://gerrit.fd.io/r/gitweb?a=blobdiff_plain;f=src%2Fvnet%2Ftcp%2Ftcp_output.c;h=862f4a2f3073986073ebb32e0e2a4a20e964a849;hb=2cdcd0cf4004b2c0d1d3b891e381aac5735c21f1;hp=9f38851b026e79fccbe1d78b55e076a2cf251626;hpb=d4c49be5e20406220cf89083c9df86c3c0761a81;p=vpp.git

diff --git a/src/vnet/tcp/tcp_output.c b/src/vnet/tcp/tcp_output.c
index 9f38851b026..862f4a2f307 100644
--- a/src/vnet/tcp/tcp_output.c
+++ b/src/vnet/tcp/tcp_output.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016 Cisco and/or its affiliates.
+ * Copyright (c) 2016-2019 Cisco and/or its affiliates.
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at:
@@ -16,9 +16,6 @@
 #include <vnet/tcp/tcp.h>
 #include <math.h>
 
-vlib_node_registration_t tcp4_output_node;
-vlib_node_registration_t tcp6_output_node;
-
 typedef enum _tcp_output_next
 {
   TCP_OUTPUT_NEXT_DROP,
@@ -52,9 +49,7 @@ typedef struct
   tcp_connection_t tcp_connection;
 } tcp_tx_trace_t;
 
-u16 dummy_mtu = 1460;
-
-u8 *
+static u8 *
 format_tcp_tx_trace (u8 * s, va_list * args)
 {
   CLIB_UNUSED (vlib_main_t * vm) = va_arg (*args, vlib_main_t *);
@@ -70,6 +65,7 @@ format_tcp_tx_trace (u8 * s, va_list * args)
   return s;
 }
 
+#ifndef CLIB_MARCH_VARIANT
 static u8
 tcp_window_compute_scale (u32 window)
 {
@@ -89,7 +85,7 @@ void
 tcp_update_rcv_mss (tcp_connection_t * tc)
 {
   /* TODO find our iface MTU */
-  tc->mss = dummy_mtu - sizeof (tcp_header_t);
+  tc->mss = tcp_cfg.default_mtu - sizeof (tcp_header_t);
 }
 
 /**
@@ -107,7 +103,7 @@ tcp_initial_wnd_unscaled (tcp_connection_t * tc)
      tcp_update_rcv_mss (tc);
      TCP_IW_N_SEGMENTS * tc->mss;
    */
-  return TCP_MIN_RX_FIFO_SIZE;
+  return tcp_cfg.min_rx_fifo;
 }
 
 /**
@@ -117,37 +113,28 @@ tcp_initial_wnd_unscaled (tcp_connection_t * tc)
 u32
 tcp_initial_window_to_advertise (tcp_connection_t * tc)
 {
-  tcp_main_t *tm = &tcp_main;
-  u32 max_fifo;
-
-  /* Initial wnd for SYN. Fifos are not allocated yet.
-   * Use some predefined value. For SYN-ACK we still want the
-   * scale to be computed in the same way */
-  max_fifo = tm->max_rx_fifo ? tm->max_rx_fifo : TCP_MAX_RX_FIFO_SIZE;
-
   /* Compute rcv wscale only if peer advertised support for it */
   if (tc->state != TCP_STATE_SYN_RCVD || tcp_opts_wscale (&tc->rcv_opts))
-    tc->rcv_wscale = tcp_window_compute_scale (max_fifo);
+    tc->rcv_wscale = tcp_window_compute_scale (tcp_cfg.max_rx_fifo);
 
   tc->rcv_wnd = tcp_initial_wnd_unscaled (tc);
 
   return clib_min (tc->rcv_wnd, TCP_WND_MAX);
 }
 
-static void
+static inline void
 tcp_update_rcv_wnd (tcp_connection_t * tc)
 {
+  u32 available_space, wnd;
   i32 observed_wnd;
-  u32 available_space, max_fifo, wnd;
+
+  ASSERT (tc->rcv_opts.mss < transport_rx_fifo_size (&tc->connection));
 
   /*
    * Figure out how much space we have available
    */
   available_space = transport_max_rx_enqueue (&tc->connection);
-  max_fifo = transport_rx_fifo_size (&tc->connection);
-
-  ASSERT (tc->rcv_opts.mss < max_fifo);
-  if (available_space < tc->rcv_opts.mss && available_space < max_fifo >> 3)
+  if (PREDICT_FALSE (available_space < tc->rcv_opts.mss))
     available_space = 0;
 
   /*
@@ -155,14 +142,12 @@ tcp_update_rcv_wnd (tcp_connection_t * tc)
    * to compute the new window
    */
   observed_wnd = (i32) tc->rcv_wnd - (tc->rcv_nxt - tc->rcv_las);
-  if (observed_wnd < 0)
-    observed_wnd = 0;
 
   /* Bad. Thou shalt not shrink */
-  if (available_space < observed_wnd)
+  if (PREDICT_FALSE ((i32) available_space < observed_wnd))
     {
-      wnd = observed_wnd;
-      TCP_EVT_DBG (TCP_EVT_RCV_WND_SHRUNK, tc, observed_wnd, available_space);
+      wnd = clib_max (observed_wnd, 0);
+      TCP_EVT (TCP_EVT_RCV_WND_SHRUNK, tc, observed_wnd, available_space);
     }
   else
     {
@@ -172,7 +157,7 @@ tcp_update_rcv_wnd (tcp_connection_t * tc)
   /* Make sure we have a multiple of rcv_wscale */
   if (wnd && tc->rcv_wscale)
     {
-      wnd &= ~(1 << tc->rcv_wscale);
+      wnd &= ~((1 << tc->rcv_wscale) - 1);
       if (wnd == 0)
 	wnd = 1 << tc->rcv_wscale;
     }
@@ -183,23 +168,13 @@ tcp_update_rcv_wnd (tcp_connection_t * tc)
 /**
  * Compute and return window to advertise, scaled as per RFC1323
  */
-static u32
+static inline u32
 tcp_window_to_advertise (tcp_connection_t * tc, tcp_state_t state)
 {
   if (state < TCP_STATE_ESTABLISHED)
     return tcp_initial_window_to_advertise (tc);
 
   tcp_update_rcv_wnd (tc);
-
-  if (tc->rcv_wnd == 0)
-    {
-      tc->flags |= TCP_CONN_SENT_RCV_WND0;
-    }
-  else
-    {
-      tc->flags &= ~TCP_CONN_SENT_RCV_WND0;
-    }
-
   return tc->rcv_wnd >> tc->rcv_wscale;
 }
 
@@ -253,14 +228,12 @@ tcp_options_write (u8 * data, tcp_options_t * opts)
   if (tcp_opts_sack (opts))
     {
       int i;
-      u32 n_sack_blocks = clib_min (vec_len (opts->sacks),
-				    TCP_OPTS_MAX_SACK_BLOCKS);
 
-      if (n_sack_blocks != 0)
+      if (opts->n_sack_blocks != 0)
 	{
 	  *data++ = TCP_OPTION_SACK_BLOCK;
-	  *data++ = 2 + n_sack_blocks * TCP_OPTION_LEN_SACK_BLOCK;
-	  for (i = 0; i < n_sack_blocks; i++)
+	  *data++ = 2 + opts->n_sack_blocks * TCP_OPTION_LEN_SACK_BLOCK;
+	  for (i = 0; i < opts->n_sack_blocks; i++)
 	    {
 	      buf = clib_host_to_net_u32 (opts->sacks[i].start);
 	      clib_memcpy_fast (data, &buf, seq_len);
@@ -269,7 +242,7 @@ tcp_options_write (u8 * data, tcp_options_t * opts)
 	      clib_memcpy_fast (data, &buf, seq_len);
 	      data += seq_len;
 	    }
-	  opts_len += 2 + n_sack_blocks * TCP_OPTION_LEN_SACK_BLOCK;
+	  opts_len += 2 + opts->n_sack_blocks * TCP_OPTION_LEN_SACK_BLOCK;
 	}
     }
 
@@ -295,7 +268,7 @@ tcp_make_syn_options (tcp_options_t * opts, u8 wnd_scale)
   u8 len = 0;
 
   opts->flags |= TCP_OPTS_FLAG_MSS;
-  opts->mss = dummy_mtu;	/*XXX discover that */
+  opts->mss = tcp_cfg.default_mtu;	/*XXX discover that */
   len += TCP_OPTION_LEN_MSS;
 
   opts->flags |= TCP_OPTS_FLAG_WSCALE;
@@ -363,7 +336,7 @@ tcp_make_established_options (tcp_connection_t * tc, tcp_options_t * opts)
   if (tcp_opts_tstamp (&tc->rcv_opts))
     {
       opts->flags |= TCP_OPTS_FLAG_TSTAMP;
-      opts->tsval = tcp_time_now_w_thread (tc->c_thread_index);
+      opts->tsval = tcp_tstamp (tc);
       opts->tsecr = tc->tsval_recent;
       len += TCP_OPTION_LEN_TIMESTAMP;
     }
@@ -372,9 +345,13 @@ tcp_make_established_options (tcp_connection_t * tc, tcp_options_t * opts)
       if (vec_len (tc->snd_sacks))
 	{
 	  opts->flags |= TCP_OPTS_FLAG_SACK;
-	  opts->sacks = tc->snd_sacks;
-	  opts->n_sack_blocks = clib_min (vec_len (tc->snd_sacks),
+	  if (tc->snd_sack_pos >= vec_len (tc->snd_sacks))
+	    tc->snd_sack_pos = 0;
+	  opts->sacks = &tc->snd_sacks[tc->snd_sack_pos];
+	  opts->n_sack_blocks = vec_len (tc->snd_sacks) - tc->snd_sack_pos;
+	  opts->n_sack_blocks = clib_min (opts->n_sack_blocks,
 					  TCP_OPTS_MAX_SACK_BLOCKS);
+	  tc->snd_sack_pos += opts->n_sack_blocks;
 	  len += 2 + TCP_OPTION_LEN_SACK_BLOCK * opts->n_sack_blocks;
 	}
     }
@@ -437,6 +414,12 @@ tcp_update_burst_snd_vars (tcp_connection_t * tc)
 		     &tc->snd_opts);
 
   tcp_update_rcv_wnd (tc);
+
+  if (tc->flags & TCP_CONN_RATE_SAMPLE)
+    tc->flags |= TCP_CONN_TRACK_BURST;
+
+  if (tc->snd_una == tc->snd_nxt)
+    tcp_cc_event (tc, TCP_CC_EVT_START_TX);
 }
 
 void
@@ -462,6 +445,7 @@ tcp_init_mss (tcp_connection_t * tc)
   if (tcp_opts_tstamp (&tc->rcv_opts))
     tc->snd_mss -= TCP_OPTION_LEN_TIMESTAMP;
 }
+#endif /* CLIB_MARCH_VARIANT */
 
 static void *
 tcp_reuse_buffer (vlib_main_t * vm, vlib_buffer_t * b)
@@ -479,6 +463,7 @@ tcp_reuse_buffer (vlib_main_t * vm, vlib_buffer_t * b)
   return vlib_buffer_make_headroom (b, TRANSPORT_MAX_HDRS_LEN);
 }
 
+#ifndef CLIB_MARCH_VARIANT
 static void *
 tcp_init_buffer (vlib_main_t * vm, vlib_buffer_t * b)
 {
@@ -515,6 +500,11 @@ tcp_make_ack_i (tcp_connection_t * tc, vlib_buffer_t * b, tcp_state_t state,
 
   tcp_options_write ((u8 *) (th + 1), snd_opts);
   vnet_buffer (b)->tcp.connection_index = tc->c_c_index;
+
+  if (wnd == 0)
+    tcp_zero_rwnd_sent_on (tc);
+  else
+    tcp_zero_rwnd_sent_off (tc);
 }
 
 /**
@@ -524,7 +514,7 @@ static inline void
 tcp_make_ack (tcp_connection_t * tc, vlib_buffer_t * b)
 {
   tcp_make_ack_i (tc, b, TCP_STATE_ESTABLISHED, TCP_FLAG_ACK);
-  TCP_EVT_DBG (TCP_EVT_ACK_SENT, tc);
+  TCP_EVT (TCP_EVT_ACK_SENT, tc);
   tc->rcv_las = tc->rcv_nxt;
 }
 
@@ -535,9 +525,6 @@ void
 tcp_make_fin (tcp_connection_t * tc, vlib_buffer_t * b)
 {
   tcp_make_ack_i (tc, b, TCP_STATE_ESTABLISHED, TCP_FLAG_FIN | TCP_FLAG_ACK);
-
-  /* Reset flags, make sure ack is sent */
-  vnet_buffer (b)->tcp.flags &= ~TCP_BUF_FLAG_DUPACK;
 }
 
 /**
@@ -587,11 +574,6 @@ tcp_make_synack (tcp_connection_t * tc, vlib_buffer_t * b)
   tcp_options_write ((u8 *) (th + 1), snd_opts);
 
   vnet_buffer (b)->tcp.connection_index = tc->c_c_index;
-
-  /* Init retransmit timer. Use update instead of set because of
-   * retransmissions */
-  tcp_retransmit_timer_force_update (tc);
-  TCP_EVT_DBG (TCP_EVT_SYNACK_SENT, tc);
 }
 
 always_inline void
@@ -691,6 +673,7 @@ tcp_enqueue_to_output_now (tcp_worker_ctx_t * wrk, vlib_buffer_t * b, u32 bi,
 {
   tcp_enqueue_to_output_i (wrk, b, bi, is_ip4, 1);
 }
+#endif /* CLIB_MARCH_VARIANT */
 
 static int
 tcp_make_reset_in_place (vlib_main_t * vm, vlib_buffer_t * b0,
@@ -771,6 +754,7 @@ tcp_make_reset_in_place (vlib_main_t * vm, vlib_buffer_t * b0,
   return 0;
 }
 
+#ifndef CLIB_MARCH_VARIANT
 /**
  *  Send reset without reusing existing buffer
  *
@@ -850,7 +834,9 @@ tcp_send_reset_w_pkt (tcp_connection_t * tc, vlib_buffer_t * pkt,
     }
 
   tcp_enqueue_to_ip_lookup_now (wrk, b, bi, is_ip4, fib_index);
-  TCP_EVT_DBG (TCP_EVT_RST_SENT, tc);
+  TCP_EVT (TCP_EVT_RST_SENT, tc);
+  vlib_node_increment_counter (vm, tcp_node_index (output, tc->c_is_ip4),
+			       TCP_ERROR_RST_SENT, 1);
 }
 
 /**
@@ -882,24 +868,10 @@ tcp_send_reset (tcp_connection_t * tc)
   opts_write_len = tcp_options_write ((u8 *) (th + 1), &tc->snd_opts);
   ASSERT (opts_write_len == tc->snd_opts_len);
   vnet_buffer (b)->tcp.connection_index = tc->c_c_index;
-  if (tc->c_is_ip4)
-    {
-      ip4_header_t *ih4;
-      ih4 = vlib_buffer_push_ip4 (vm, b, &tc->c_lcl_ip.ip4,
-				  &tc->c_rmt_ip.ip4, IP_PROTOCOL_TCP, 0);
-      th->checksum = ip4_tcp_udp_compute_checksum (vm, b, ih4);
-    }
-  else
-    {
-      int bogus = ~0;
-      ip6_header_t *ih6;
-      ih6 = vlib_buffer_push_ip6 (vm, b, &tc->c_lcl_ip.ip6,
-				  &tc->c_rmt_ip.ip6, IP_PROTOCOL_TCP);
-      th->checksum = ip6_tcp_udp_icmp_compute_checksum (vm, b, ih6, &bogus);
-      ASSERT (!bogus);
-    }
-  tcp_enqueue_to_ip_lookup_now (wrk, b, bi, tc->c_is_ip4, tc->c_fib_index);
-  TCP_EVT_DBG (TCP_EVT_RST_SENT, tc);
+  tcp_enqueue_to_output (wrk, b, bi, tc->c_is_ip4);
+  TCP_EVT (TCP_EVT_RST_SENT, tc);
+  vlib_node_increment_counter (vm, tcp_node_index (output, tc->c_is_ip4),
+			       TCP_ERROR_RST_SENT, 1);
 }
 
 static void
@@ -946,12 +918,14 @@ tcp_send_syn (tcp_connection_t * tc)
    * Setup retransmit and establish timers before requesting buffer
    * such that we can return if we've ran out.
    */
-  tcp_timer_set (tc, TCP_TIMER_ESTABLISH_AO, TCP_ESTABLISH_TIME);
   tcp_timer_update (tc, TCP_TIMER_RETRANSMIT_SYN,
 		    tc->rto * TCP_TO_TIMER_TICK);
 
   if (PREDICT_FALSE (!vlib_buffer_alloc (vm, &bi, 1)))
-    return;
+    {
+      tcp_timer_update (tc, TCP_TIMER_RETRANSMIT_SYN, 1);
+      return;
+    }
 
   b = vlib_get_buffer (vm, bi);
   tcp_init_buffer (vm, b);
@@ -964,7 +938,7 @@ tcp_send_syn (tcp_connection_t * tc)
 
   tcp_push_ip_hdr (wrk, tc, b);
   tcp_enqueue_to_ip_lookup (wrk, b, bi, tc->c_is_ip4, tc->c_fib_index);
-  TCP_EVT_DBG (TCP_EVT_SYN_SENT, tc);
+  TCP_EVT (TCP_EVT_SYN_SENT, tc);
 }
 
 void
@@ -975,14 +949,20 @@ tcp_send_synack (tcp_connection_t * tc)
   vlib_buffer_t *b;
   u32 bi;
 
+  tcp_retransmit_timer_force_update (tc);
+
   if (PREDICT_FALSE (!vlib_buffer_alloc (vm, &bi, 1)))
-    return;
+    {
+      tcp_timer_update (tc, TCP_TIMER_RETRANSMIT, 1);
+      return;
+    }
 
   tc->rtt_ts = tcp_time_now_us (tc->c_thread_index);
   b = vlib_get_buffer (vm, bi);
   tcp_init_buffer (vm, b);
   tcp_make_synack (tc, b);
   tcp_enqueue_to_output (wrk, b, bi, tc->c_is_ip4);
+  TCP_EVT (TCP_EVT_SYNACK_SENT, tc);
 }
 
 /**
@@ -1042,14 +1022,17 @@ tcp_send_fin (tcp_connection_t * tc)
 
   fin_snt = tc->flags & TCP_CONN_FINSNT;
   if (fin_snt)
-    tc->snd_nxt = tc->snd_una;
+    tc->snd_nxt -= 1;
 
   if (PREDICT_FALSE (!vlib_buffer_alloc (vm, &bi, 1)))
     {
       /* Out of buffers so program fin retransmit ASAP */
       tcp_timer_update (tc, TCP_TIMER_RETRANSMIT, 1);
       if (fin_snt)
-	tc->snd_nxt = tc->snd_una_max;
+	tc->snd_nxt += 1;
+      else
+	/* Make sure retransmit retries a fin not data */
+	tc->flags |= TCP_CONN_FINSNT;
       return;
     }
 
@@ -1058,58 +1041,27 @@ tcp_send_fin (tcp_connection_t * tc)
   tcp_init_buffer (vm, b);
   tcp_make_fin (tc, b);
   tcp_enqueue_to_output_now (wrk, b, bi, tc->c_is_ip4);
-  TCP_EVT_DBG (TCP_EVT_FIN_SENT, tc);
-
+  TCP_EVT (TCP_EVT_FIN_SENT, tc);
+  /* Account for the FIN */
+  tc->snd_nxt += 1;
   if (!fin_snt)
     {
       tc->flags |= TCP_CONN_FINSNT;
       tc->flags &= ~TCP_CONN_FINPNDG;
-      /* Account for the FIN */
-      tc->snd_una_max += 1;
-      tc->snd_nxt = tc->snd_una_max;
-    }
-  else
-    {
-      tc->snd_nxt = tc->snd_una_max;
+      tc->snd_una_max = seq_max (tc->snd_una_max, tc->snd_nxt);
     }
 }
 
-always_inline u8
-tcp_make_state_flags (tcp_connection_t * tc, tcp_state_t next_state)
-{
-  switch (next_state)
-    {
-    case TCP_STATE_ESTABLISHED:
-    case TCP_STATE_CLOSE_WAIT:
-    case TCP_STATE_TIME_WAIT:
-    case TCP_STATE_FIN_WAIT_2:
-      return TCP_FLAG_ACK;
-    case TCP_STATE_SYN_RCVD:
-      return TCP_FLAG_SYN | TCP_FLAG_ACK;
-    case TCP_STATE_SYN_SENT:
-      return TCP_FLAG_SYN;
-    case TCP_STATE_LAST_ACK:
-    case TCP_STATE_FIN_WAIT_1:
-    case TCP_STATE_CLOSING:
-      if (tc->snd_nxt + 1 < tc->snd_una_max)
-	return TCP_FLAG_ACK;
-      else
-	return TCP_FLAG_FIN;
-    default:
-      clib_warning ("Shouldn't be here!");
-    }
-  return 0;
-}
-
 /**
- * Push TCP header and update connection variables
+ * Push TCP header and update connection variables. Should only be called
+ * for segments with data, not for 'control' packets.
  */
 always_inline void
-tcp_push_hdr_i (tcp_connection_t * tc, vlib_buffer_t * b,
-		tcp_state_t next_state, u8 compute_opts, u8 maybe_burst)
+tcp_push_hdr_i (tcp_connection_t * tc, vlib_buffer_t * b, u32 snd_nxt,
+		u8 compute_opts, u8 maybe_burst, u8 update_snd_nxt)
 {
+  u8 tcp_hdr_opts_len, flags = TCP_FLAG_ACK;
   u32 advertise_wnd, data_len;
-  u8 tcp_hdr_opts_len, flags;
   tcp_main_t *tm = &tcp_main;
   tcp_header_t *th;
 
@@ -1128,16 +1080,15 @@ tcp_push_hdr_i (tcp_connection_t * tc, vlib_buffer_t * b,
   if (maybe_burst)
     advertise_wnd = tc->rcv_wnd >> tc->rcv_wscale;
   else
-    advertise_wnd = tcp_window_to_advertise (tc, next_state);
+    advertise_wnd = tcp_window_to_advertise (tc, TCP_STATE_ESTABLISHED);
 
-  flags = tcp_make_state_flags (tc, next_state);
   if (PREDICT_FALSE (tc->flags & TCP_CONN_PSH_PENDING))
     {
-      if (seq_geq (tc->psh_seq, tc->snd_nxt)
-	  && seq_lt (tc->psh_seq, tc->snd_nxt + data_len))
+      if (seq_geq (tc->psh_seq, snd_nxt)
+	  && seq_lt (tc->psh_seq, snd_nxt + data_len))
 	flags |= TCP_FLAG_PSH;
     }
-  th = vlib_buffer_push_tcp (b, tc->c_lcl_port, tc->c_rmt_port, tc->snd_nxt,
+  th = vlib_buffer_push_tcp (b, tc->c_lcl_port, tc->c_rmt_port, snd_nxt,
 			     tc->rcv_nxt, tcp_hdr_opts_len, flags,
 			     advertise_wnd);
 
@@ -1157,19 +1108,32 @@ tcp_push_hdr_i (tcp_connection_t * tc, vlib_buffer_t * b,
    * Update connection variables
    */
 
-  tc->snd_nxt += data_len;
+  if (update_snd_nxt)
+    tc->snd_nxt += data_len;
   tc->rcv_las = tc->rcv_nxt;
 
-  TCP_EVT_DBG (TCP_EVT_PKTIZE, tc);
+  tc->bytes_out += data_len;
+  tc->data_segs_out += 1;
+
+  TCP_EVT (TCP_EVT_PKTIZE, tc);
 }
 
 u32
-tcp_push_header (tcp_connection_t * tc, vlib_buffer_t * b)
+tcp_session_push_header (transport_connection_t * tconn, vlib_buffer_t * b)
 {
-  tcp_push_hdr_i (tc, b, TCP_STATE_ESTABLISHED, /* compute opts */ 0,
-		  /* burst */ 1);
-  tc->snd_una_max = tc->snd_nxt;
-  ASSERT (seq_leq (tc->snd_una_max, tc->snd_una + tc->snd_wnd));
+  tcp_connection_t *tc = (tcp_connection_t *) tconn;
+
+  if (tc->flags & TCP_CONN_TRACK_BURST)
+    {
+      tcp_bt_check_app_limited (tc);
+      tcp_bt_track_tx (tc);
+      tc->flags &= ~TCP_CONN_TRACK_BURST;
+    }
+
+  tcp_push_hdr_i (tc, b, tc->snd_nxt, /* compute opts */ 0, /* burst */ 1,
+		  /* update_snd_nxt */ 1);
+
+  tc->snd_una_max = seq_max (tc->snd_nxt, tc->snd_una_max);
   tcp_validate_txf_size (tc, tc->snd_una_max - tc->snd_una);
   /* If not tracking an ACK, start tracking */
   if (tc->rtt_ts == 0 && !tcp_in_cong_recovery (tc))
@@ -1195,7 +1159,10 @@ tcp_send_ack (tcp_connection_t * tc)
   u32 bi;
 
   if (PREDICT_FALSE (!vlib_buffer_alloc (vm, &bi, 1)))
-    return;
+    {
+      tcp_update_rcv_wnd (tc);
+      return;
+    }
   b = vlib_get_buffer (vm, bi);
   tcp_init_buffer (vm, b);
   tcp_make_ack (tc, b);
@@ -1203,21 +1170,21 @@ tcp_send_ack (tcp_connection_t * tc)
 }
 
 void
-tcp_program_ack (tcp_worker_ctx_t * wrk, tcp_connection_t * tc)
+tcp_program_ack (tcp_connection_t * tc)
 {
   if (!(tc->flags & TCP_CONN_SNDACK))
     {
-      vec_add1 (wrk->pending_acks, tc->c_c_index);
+      session_add_self_custom_tx_evt (&tc->connection, 1);
       tc->flags |= TCP_CONN_SNDACK;
     }
 }
 
 void
-tcp_program_dupack (tcp_worker_ctx_t * wrk, tcp_connection_t * tc)
+tcp_program_dupack (tcp_connection_t * tc)
 {
   if (!(tc->flags & TCP_CONN_SNDACK))
     {
-      vec_add1 (wrk->pending_acks, tc->c_c_index);
+      session_add_self_custom_tx_evt (&tc->connection, 1);
       tc->flags |= TCP_CONN_SNDACK;
     }
   if (tc->pending_dupacks < 255)
@@ -1225,31 +1192,13 @@ tcp_program_dupack (tcp_worker_ctx_t * wrk, tcp_connection_t * tc)
 }
 
 void
-tcp_send_acks (tcp_worker_ctx_t * wrk)
+tcp_program_fastretransmit (tcp_connection_t * tc)
 {
-  u32 thread_index, *pending_acks;
-  tcp_connection_t *tc;
-  int i, j, n_acks;
-
-  if (!vec_len (wrk->pending_acks))
-    return;
-
-  thread_index = wrk->vm->thread_index;
-  pending_acks = wrk->pending_acks;
-  for (i = 0; i < vec_len (pending_acks); i++)
-    {
-      tc = tcp_connection_get (pending_acks[i], thread_index);
-      tc->flags &= ~TCP_CONN_SNDACK;
-      n_acks = clib_max (1, tc->pending_dupacks);
-      /* If we're supposed to send dupacks but have no ooo data
-       * send only one ack */
-      if (tc->pending_dupacks && !vec_len (tc->snd_sacks))
-	n_acks = 1;
-      for (j = 0; j < n_acks; j++)
-	tcp_send_ack (tc);
-      tc->pending_dupacks = 0;
+  if (!(tc->flags & TCP_CONN_FRXT_PENDING))
+    {
+      session_add_self_custom_tx_evt (&tc->connection, 0);
+      tc->flags |= TCP_CONN_FRXT_PENDING;
     }
-  _vec_len (wrk->pending_acks) = 0;
 }
 
 /**
@@ -1268,6 +1217,27 @@ tcp_timer_delack_handler (u32 index)
   tcp_send_ack (tc);
 }
 
+/**
+ * Send Window Update ACK,
+ * ensuring that it will be sent once, if RWND became non-zero,
+ * after zero RWND has been advertised in ACK before
+ */
+void
+tcp_send_window_update_ack (tcp_connection_t * tc)
+{
+  u32 win;
+
+  if (tcp_zero_rwnd_sent (tc))
+    {
+      win = tcp_window_to_advertise (tc, tc->state);
+      if (win > 0)
+	{
+	  tcp_zero_rwnd_sent_off (tc);
+	  tcp_program_ack (tc);
+	}
+    }
+}
+
 /**
  * Allocate a new buffer and build a new tcp segment
  *
@@ -1308,13 +1278,12 @@ tcp_prepare_segment (tcp_worker_ctx_t * wrk, tcp_connection_t * tc,
 	return 0;
       *b = vlib_get_buffer (vm, bi);
       data = tcp_init_buffer (vm, *b);
-      n_bytes = stream_session_peek_bytes (&tc->connection, data, offset,
-					   max_deq_bytes);
+      n_bytes = session_tx_fifo_peek_bytes (&tc->connection, data, offset,
+					    max_deq_bytes);
       ASSERT (n_bytes == max_deq_bytes);
       b[0]->current_length = n_bytes;
-      tcp_push_hdr_i (tc, *b, tc->state, /* compute opts */ 0, /* burst */ 0);
-      if (seq_gt (tc->snd_nxt, tc->snd_una_max))
-	tc->snd_una_max = tc->snd_nxt;
+      tcp_push_hdr_i (tc, *b, tc->snd_una + offset, /* compute opts */ 0,
+		      /* burst */ 0, /* update_snd_nxt */ 0);
     }
   /* Split mss into multiple buffers */
   else
@@ -1338,9 +1307,9 @@ tcp_prepare_segment (tcp_worker_ctx_t * wrk, tcp_connection_t * tc,
 
       *b = vlib_get_buffer (vm, wrk->tx_buffers[--n_bufs]);
       data = tcp_init_buffer (vm, *b);
-      n_bytes = stream_session_peek_bytes (&tc->connection, data, offset,
-					   bytes_per_buffer -
-					   TRANSPORT_MAX_HDRS_LEN);
+      n_bytes = session_tx_fifo_peek_bytes (&tc->connection, data, offset,
+					    bytes_per_buffer -
+					    TRANSPORT_MAX_HDRS_LEN);
       b[0]->current_length = n_bytes;
       b[0]->flags |= VLIB_BUFFER_TOTAL_LENGTH_VALID;
       b[0]->total_length_not_including_first_buffer = 0;
@@ -1355,8 +1324,9 @@ tcp_prepare_segment (tcp_worker_ctx_t * wrk, tcp_connection_t * tc,
 	  chain_b = vlib_get_buffer (vm, chain_bi);
 	  chain_b->current_data = 0;
 	  data = vlib_buffer_get_current (chain_b);
-	  n_peeked = stream_session_peek_bytes (&tc->connection, data,
-						offset + n_bytes, len_to_deq);
+	  n_peeked = session_tx_fifo_peek_bytes (&tc->connection, data,
+						 offset + n_bytes,
+						 len_to_deq);
 	  ASSERT (n_peeked == len_to_deq);
 	  n_bytes += n_peeked;
 	  chain_b->current_length = n_peeked;
@@ -1370,9 +1340,8 @@ tcp_prepare_segment (tcp_worker_ctx_t * wrk, tcp_connection_t * tc,
 	  b[0]->total_length_not_including_first_buffer += n_peeked;
 	}
 
-      tcp_push_hdr_i (tc, *b, tc->state, /* compute opts */ 0, /* burst */ 0);
-      if (seq_gt (tc->snd_nxt, tc->snd_una_max))
-	tc->snd_una_max = tc->snd_nxt;
+      tcp_push_hdr_i (tc, *b, tc->snd_una + offset, /* compute opts */ 0,
+		      /* burst */ 0, /* update_snd_nxt */ 0);
 
       if (PREDICT_FALSE (n_bufs))
 	{
@@ -1407,7 +1376,7 @@ tcp_prepare_retransmit_segment (tcp_worker_ctx_t * wrk,
   /*
    * Make sure we can retransmit something
    */
-  available_bytes = session_tx_fifo_max_dequeue (&tc->connection);
+  available_bytes = transport_max_tx_dequeue (&tc->connection);
   ASSERT (available_bytes >= offset);
   available_bytes -= offset;
   if (!available_bytes)
@@ -1419,14 +1388,14 @@ tcp_prepare_retransmit_segment (tcp_worker_ctx_t * wrk,
   /* Start is beyond snd_congestion */
   start = tc->snd_una + offset;
   if (seq_geq (start, tc->snd_congestion))
-    goto done;
+    return 0;
 
   /* Don't overshoot snd_congestion */
   if (seq_gt (start + max_deq_bytes, tc->snd_congestion))
     {
       max_deq_bytes = tc->snd_congestion - start;
       if (max_deq_bytes == 0)
-	goto done;
+	return 0;
     }
 
   n_bytes = tcp_prepare_segment (wrk, tc, offset, max_deq_bytes, b);
@@ -1434,10 +1403,15 @@ tcp_prepare_retransmit_segment (tcp_worker_ctx_t * wrk,
     return 0;
 
   if (tcp_in_fastrecovery (tc))
-    tc->snd_rxt_bytes += n_bytes;
+    {
+      tc->snd_rxt_bytes += n_bytes;
+      if (tc->flags & TCP_CONN_RATE_SAMPLE)
+	tcp_bt_track_rxt (tc, start, start + n_bytes);
+    }
 
-done:
-  TCP_EVT_DBG (TCP_EVT_CC_RTX, tc, offset, n_bytes);
+  tc->bytes_retrans += n_bytes;
+  tc->segs_retrans += 1;
+  TCP_EVT (TCP_EVT_CC_RTX, tc, offset, n_bytes);
   return n_bytes;
 }
 
@@ -1445,32 +1419,31 @@ done:
  * Reset congestion control, switch cwnd to loss window and try again.
  */
 static void
-tcp_rxt_timeout_cc (tcp_connection_t * tc)
+tcp_cc_init_rxt_timeout (tcp_connection_t * tc)
 {
-  TCP_EVT_DBG (TCP_EVT_CC_EVT, tc, 6);
+  TCP_EVT (TCP_EVT_CC_EVT, tc, 6);
   tc->prev_ssthresh = tc->ssthresh;
   tc->prev_cwnd = tc->cwnd;
 
-  /* Cleanly recover cc (also clears up fast retransmit) */
+  /* Clear fast recovery state if needed */
   if (tcp_in_fastrecovery (tc))
-    {
-      /* TODO be less aggressive about this */
-      scoreboard_clear (&tc->sack_sb);
-      tcp_cc_fastrecovery_exit (tc);
-    }
+    tcp_cc_fastrecovery_clear (tc);
+
+  /* Let cc algo decide loss cwnd and ssthresh */
+  tcp_cc_loss (tc);
 
   /* Start again from the beginning */
-  tc->cc_algo->congestion (tc);
-  tc->cwnd = tcp_loss_wnd (tc);
-  tc->snd_congestion = tc->snd_una_max;
+  tc->snd_congestion = tc->snd_nxt;
+  tc->rcv_dupacks = 0;
   tc->rtt_ts = 0;
   tc->cwnd_acc_bytes = 0;
+  tc->tr_occurences += 1;
   tcp_connection_tx_pacer_reset (tc, tc->cwnd, 2 * tc->snd_mss);
   tcp_recovery_on (tc);
 }
 
-static inline void
-tcp_timer_retransmit_handler_i (u32 index, u8 is_syn)
+void
+tcp_timer_retransmit_handler (u32 tc_index)
 {
   u32 thread_index = vlib_get_thread_index ();
   tcp_worker_ctx_t *wrk = tcp_get_worker (thread_index);
@@ -1479,32 +1452,24 @@ tcp_timer_retransmit_handler_i (u32 index, u8 is_syn)
   vlib_buffer_t *b = 0;
   u32 bi, n_bytes;
 
-  if (is_syn)
-    {
-      tc = tcp_half_open_connection_get (index);
-      /* Note: the connection may have transitioned to ESTABLISHED... */
-      if (PREDICT_FALSE (tc == 0 || tc->state != TCP_STATE_SYN_SENT))
-	return;
-      tc->timers[TCP_TIMER_RETRANSMIT_SYN] = TCP_TIMER_HANDLE_INVALID;
-    }
-  else
-    {
-      tc = tcp_connection_get (index, thread_index);
-      /* Note: the connection may have been closed and pool_put */
-      if (PREDICT_FALSE (tc == 0 || tc->state == TCP_STATE_SYN_SENT))
-	return;
-      tc->timers[TCP_TIMER_RETRANSMIT] = TCP_TIMER_HANDLE_INVALID;
-      /* Wait-close and retransmit could pop at the same time */
-      if (tc->state == TCP_STATE_CLOSED)
-	return;
-    }
+  tc = tcp_connection_get (tc_index, thread_index);
+
+  /* Note: the connection may have been closed and pool_put */
+  if (PREDICT_FALSE (tc == 0 || tc->state == TCP_STATE_SYN_SENT))
+    return;
+
+  tc->timers[TCP_TIMER_RETRANSMIT] = TCP_TIMER_HANDLE_INVALID;
+
+  /* Wait-close and retransmit could pop at the same time */
+  if (tc->state == TCP_STATE_CLOSED)
+    return;
 
   if (tc->state >= TCP_STATE_ESTABLISHED)
     {
-      TCP_EVT_DBG (TCP_EVT_CC_EVT, tc, 2);
+      TCP_EVT (TCP_EVT_CC_EVT, tc, 2);
 
       /* Lost FIN, retransmit and return */
-      if (tcp_is_lost_fin (tc))
+      if (tc->flags & TCP_CONN_FINSNT)
 	{
 	  tcp_send_fin (tc);
 	  tc->rto_boff += 1;
@@ -1514,7 +1479,7 @@ tcp_timer_retransmit_handler_i (u32 index, u8 is_syn)
 
       /* Shouldn't be here. This condition is tricky because it has to take
        * into account boff > 0 due to persist timeout. */
-      if ((tc->rto_boff == 0 && tc->snd_una == tc->snd_una_max)
+      if ((tc->rto_boff == 0 && tc->snd_una == tc->snd_nxt)
 	  || (tc->rto_boff > 0 && seq_geq (tc->snd_una, tc->snd_congestion)
 	      && !tcp_flight_size (tc)))
 	{
@@ -1531,99 +1496,87 @@ tcp_timer_retransmit_handler_i (u32 index, u8 is_syn)
 	  tcp_update_rto (tc);
 	}
 
+      /* Peer is dead or network connectivity is lost. Close connection.
+       * RFC 1122 section 4.2.3.5 recommends a value of at least 100s. For
+       * a min rto of 0.2s we need to retry about 8 times. */
+      if (tc->rto_boff >= TCP_RTO_BOFF_MAX)
+	{
+	  tcp_send_reset (tc);
+	  tcp_connection_set_state (tc, TCP_STATE_CLOSED);
+	  session_transport_closing_notify (&tc->connection);
+	  tcp_connection_timers_reset (tc);
+	  tcp_timer_update (tc, TCP_TIMER_WAITCLOSE, tcp_cfg.closewait_time);
+	  return;
+	}
+
       /* Increment RTO backoff (also equal to number of retries) and go back
        * to first un-acked byte  */
       tc->rto_boff += 1;
 
+      /* TODO be less aggressive about clearing scoreboard */
+      scoreboard_clear (&tc->sack_sb);
+
       /* First retransmit timeout */
       if (tc->rto_boff == 1)
-	tcp_rxt_timeout_cc (tc);
-      else
-	scoreboard_clear (&tc->sack_sb);
+	{
+	  tcp_cc_init_rxt_timeout (tc);
+	  /* Record timestamp. Eifel detection algorithm RFC3522 */
+	  tc->snd_rxt_ts = tcp_tstamp (tc);
+	}
 
-      /* If we've sent beyond snd_congestion, update it */
-      if (seq_gt (tc->snd_una_max, tc->snd_congestion))
-	tc->snd_congestion = tc->snd_una_max;
+      if (tc->flags & TCP_CONN_RATE_SAMPLE)
+	tcp_bt_flush_samples (tc);
 
-      tc->snd_una_max = tc->snd_nxt = tc->snd_una;
-      tc->rto = clib_min (tc->rto << 1, TCP_RTO_MAX);
+      /* If we've sent beyond snd_congestion, update it */
+      tc->snd_congestion = seq_max (tc->snd_nxt, tc->snd_congestion);
+      tc->snd_nxt = tc->snd_una;
 
-      /* Send one segment. Note that n_bytes may be zero due to buffer
-       * shortfall */
+      /* Send one segment. n_bytes may be zero due to buffer shortfall */
       n_bytes = tcp_prepare_retransmit_segment (wrk, tc, 0, tc->snd_mss, &b);
       if (!n_bytes)
 	{
-	  tcp_retransmit_timer_force_update (tc);
+	  tcp_timer_update (tc, TCP_TIMER_RETRANSMIT, 1);
 	  return;
 	}
 
       bi = vlib_get_buffer_index (vm, b);
-
-      /* For first retransmit, record timestamp (Eifel detection RFC3522) */
-      if (tc->rto_boff == 1)
-	tc->snd_rxt_ts = tcp_time_now_w_thread (tc->c_thread_index);
-
       tcp_enqueue_to_output (wrk, b, bi, tc->c_is_ip4);
+
+      tc->rto = clib_min (tc->rto << 1, TCP_RTO_MAX);
       tcp_retransmit_timer_force_update (tc);
     }
-  /* Retransmit for SYN */
-  else if (tc->state == TCP_STATE_SYN_SENT)
+  /* Retransmit SYN-ACK */
+  else if (tc->state == TCP_STATE_SYN_RCVD)
     {
-      /* Half-open connection actually moved to established but we were
-       * waiting for syn retransmit to pop to call cleanup from the right
-       * thread. */
-      if (tc->flags & TCP_CONN_HALF_OPEN_DONE)
+      TCP_EVT (TCP_EVT_CC_EVT, tc, 2);
+
+      tc->rtt_ts = 0;
+
+      /* Passive open establish timeout */
+      if (tc->rto > TCP_ESTABLISH_TIME >> 1)
 	{
-	  if (tcp_half_open_connection_cleanup (tc))
-	    TCP_DBG ("could not remove half-open connection");
+	  tcp_connection_set_state (tc, TCP_STATE_CLOSED);
+	  tcp_connection_timers_reset (tc);
+	  tcp_timer_update (tc, TCP_TIMER_WAITCLOSE, tcp_cfg.cleanup_time);
 	  return;
 	}
 
-      TCP_EVT_DBG (TCP_EVT_CC_EVT, tc, 2);
-
-      /* Try without increasing RTO a number of times. If this fails,
-       * start growing RTO exponentially */
-      tc->rto_boff += 1;
-      if (tc->rto_boff > TCP_RTO_SYN_RETRIES)
-	tc->rto = clib_min (tc->rto << 1, TCP_RTO_MAX);
-
-      tcp_timer_update (tc, TCP_TIMER_RETRANSMIT_SYN,
-			tc->rto * TCP_TO_TIMER_TICK);
-
       if (PREDICT_FALSE (!vlib_buffer_alloc (vm, &bi, 1)))
-	return;
-
-      b = vlib_get_buffer (vm, bi);
-      tcp_init_buffer (vm, b);
-      tcp_make_syn (tc, b);
-
-      tc->rtt_ts = 0;
-      TCP_EVT_DBG (TCP_EVT_SYN_RXT, tc, 0);
-
-      /* This goes straight to ipx_lookup. Retransmit timer set already */
-      tcp_push_ip_hdr (wrk, tc, b);
-      tcp_enqueue_to_ip_lookup (wrk, b, bi, tc->c_is_ip4, tc->c_fib_index);
-    }
-  /* Retransmit SYN-ACK */
-  else if (tc->state == TCP_STATE_SYN_RCVD)
-    {
-      TCP_EVT_DBG (TCP_EVT_CC_EVT, tc, 2);
+	{
+	  tcp_timer_update (tc, TCP_TIMER_RETRANSMIT, 1);
+	  return;
+	}
 
       tc->rto_boff += 1;
       if (tc->rto_boff > TCP_RTO_SYN_RETRIES)
 	tc->rto = clib_min (tc->rto << 1, TCP_RTO_MAX);
-      tc->rtt_ts = 0;
 
-      if (PREDICT_FALSE (!vlib_buffer_alloc (vm, &bi, 1)))
-	{
-	  tcp_retransmit_timer_force_update (tc);
-	  return;
-	}
+      tcp_retransmit_timer_force_update (tc);
 
       b = vlib_get_buffer (vm, bi);
       tcp_init_buffer (vm, b);
       tcp_make_synack (tc, b);
-      TCP_EVT_DBG (TCP_EVT_SYN_RXT, tc, 1);
+      TCP_EVT (TCP_EVT_SYN_RXT, tc, 1);
 
       /* Retransmit timer already updated, just enqueue to output */
       tcp_enqueue_to_output (wrk, b, bi, tc->c_is_ip4);
@@ -1635,16 +1588,72 @@ tcp_timer_retransmit_handler_i (u32 index, u8 is_syn)
     }
 }
 
+/**
+ * SYN retransmit timer handler. Active open only.
+ */
 void
-tcp_timer_retransmit_handler (u32 index)
+tcp_timer_retransmit_syn_handler (u32 tc_index)
 {
-  tcp_timer_retransmit_handler_i (index, 0);
-}
+  u32 thread_index = vlib_get_thread_index ();
+  tcp_worker_ctx_t *wrk = tcp_get_worker (thread_index);
+  vlib_main_t *vm = wrk->vm;
+  tcp_connection_t *tc;
+  vlib_buffer_t *b = 0;
+  u32 bi;
 
-void
-tcp_timer_retransmit_syn_handler (u32 index)
-{
-  tcp_timer_retransmit_handler_i (index, 1);
+  tc = tcp_half_open_connection_get (tc_index);
+
+  /* Note: the connection may have transitioned to ESTABLISHED... */
+  if (PREDICT_FALSE (tc == 0 || tc->state != TCP_STATE_SYN_SENT))
+    return;
+
+  tc->timers[TCP_TIMER_RETRANSMIT_SYN] = TCP_TIMER_HANDLE_INVALID;
+
+  /* Half-open connection actually moved to established but we were
+   * waiting for syn retransmit to pop to call cleanup from the right
+   * thread. */
+  if (tc->flags & TCP_CONN_HALF_OPEN_DONE)
+    {
+      if (tcp_half_open_connection_cleanup (tc))
+	TCP_DBG ("could not remove half-open connection");
+      return;
+    }
+
+  TCP_EVT (TCP_EVT_CC_EVT, tc, 2);
+  tc->rtt_ts = 0;
+
+  /* Active open establish timeout */
+  if (tc->rto >= TCP_ESTABLISH_TIME >> 1)
+    {
+      session_stream_connect_notify (&tc->connection, 1 /* fail */ );
+      tcp_connection_cleanup (tc);
+      return;
+    }
+
+  if (PREDICT_FALSE (!vlib_buffer_alloc (vm, &bi, 1)))
+    {
+      tcp_timer_update (tc, TCP_TIMER_RETRANSMIT_SYN, 1);
+      return;
+    }
+
+  /* Try without increasing RTO a number of times. If this fails,
+   * start growing RTO exponentially */
+  tc->rto_boff += 1;
+  if (tc->rto_boff > TCP_RTO_SYN_RETRIES)
+    tc->rto = clib_min (tc->rto << 1, TCP_RTO_MAX);
+
+  b = vlib_get_buffer (vm, bi);
+  tcp_init_buffer (vm, b);
+  tcp_make_syn (tc, b);
+
+  TCP_EVT (TCP_EVT_SYN_RXT, tc, 0);
+
+  /* This goes straight to ipx_lookup */
+  tcp_push_ip_hdr (wrk, tc, b);
+  tcp_enqueue_to_ip_lookup (wrk, b, bi, tc->c_is_ip4, tc->c_fib_index);
+
+  tcp_timer_update (tc, TCP_TIMER_RETRANSMIT_SYN,
+		    tc->rto * TCP_TO_TIMER_TICK);
 }
 
 /**
@@ -1665,7 +1674,6 @@ tcp_timer_persist_handler (u32 index)
   u8 *data;
 
   tc = tcp_connection_get_if_valid (index, thread_index);
-
   if (!tc)
     return;
 
@@ -1673,12 +1681,12 @@ tcp_timer_persist_handler (u32 index)
   tc->timers[TCP_TIMER_PERSIST] = TCP_TIMER_HANDLE_INVALID;
 
   /* Problem already solved or worse */
-  if (tc->state == TCP_STATE_CLOSED || tc->state > TCP_STATE_ESTABLISHED
-      || tc->snd_wnd > tc->snd_mss)
+  if (tc->state == TCP_STATE_CLOSED || tc->snd_wnd > tc->snd_mss
+      || (tc->flags & TCP_CONN_FINSNT))
     return;
 
-  available_bytes = session_tx_fifo_max_dequeue (&tc->connection);
-  offset = tc->snd_una_max - tc->snd_una;
+  available_bytes = transport_max_tx_dequeue (&tc->connection);
+  offset = tc->snd_nxt - tc->snd_una;
 
   /* Reprogram persist if no new bytes available to send. We may have data
    * next time */
@@ -1711,17 +1719,18 @@ tcp_timer_persist_handler (u32 index)
 
   tcp_validate_txf_size (tc, offset);
   tc->snd_opts_len = tcp_make_options (tc, &tc->snd_opts, tc->state);
-  max_snd_bytes =
-    clib_min (tc->snd_mss, tm->bytes_per_buffer - TRANSPORT_MAX_HDRS_LEN);
-  n_bytes =
-    stream_session_peek_bytes (&tc->connection, data, offset, max_snd_bytes);
+  max_snd_bytes = clib_min (tc->snd_mss,
+			    tm->bytes_per_buffer - TRANSPORT_MAX_HDRS_LEN);
+  n_bytes = session_tx_fifo_peek_bytes (&tc->connection, data, offset,
+					max_snd_bytes);
   b->current_length = n_bytes;
   ASSERT (n_bytes != 0 && (tcp_timer_is_active (tc, TCP_TIMER_RETRANSMIT)
 			   || tc->snd_nxt == tc->snd_una_max
 			   || tc->rto_boff > 1));
 
-  tcp_push_hdr_i (tc, b, tc->state, /* compute opts */ 0, /* burst */ 0);
-  tc->snd_una_max = tc->snd_nxt;
+  tcp_push_hdr_i (tc, b, tc->snd_nxt, /* compute opts */ 0,
+		  /* burst */ 0, /* update_snd_nxt */ 1);
+  tc->snd_una_max = seq_max (tc->snd_nxt, tc->snd_una_max);
   tcp_validate_txf_size (tc, tc->snd_una_max - tc->snd_una);
   tcp_enqueue_to_output (wrk, b, bi, tc->c_is_ip4);
 
@@ -1735,14 +1744,11 @@ tcp_timer_persist_handler (u32 index)
 int
 tcp_retransmit_first_unacked (tcp_worker_ctx_t * wrk, tcp_connection_t * tc)
 {
-  u32 bi, old_snd_nxt, n_bytes;
   vlib_main_t *vm = wrk->vm;
   vlib_buffer_t *b;
+  u32 bi, n_bytes;
 
-  old_snd_nxt = tc->snd_nxt;
-  tc->snd_nxt = tc->snd_una;
-
-  TCP_EVT_DBG (TCP_EVT_CC_EVT, tc, 1);
+  TCP_EVT (TCP_EVT_CC_EVT, tc, 1);
 
   n_bytes = tcp_prepare_retransmit_segment (wrk, tc, 0, tc->snd_mss, &b);
   if (!n_bytes)
@@ -1750,7 +1756,6 @@ tcp_retransmit_first_unacked (tcp_worker_ctx_t * wrk, tcp_connection_t * tc)
 
   bi = vlib_get_buffer_index (vm, b);
   tcp_enqueue_to_output (wrk, b, bi, tc->c_is_ip4);
-  tc->snd_nxt = old_snd_nxt;
 
   return 0;
 }
@@ -1759,12 +1764,14 @@ static int
 tcp_fast_retransmit_unsent (tcp_worker_ctx_t * wrk, tcp_connection_t * tc,
 			    u32 burst_size)
 {
-  u32 offset, n_segs = 0, n_written, bi;
+  u32 offset, n_segs = 0, n_written, bi, available_wnd;
   vlib_main_t *vm = wrk->vm;
   vlib_buffer_t *b = 0;
 
-  tc->snd_nxt = tc->snd_una_max;
-  offset = tc->snd_una_max - tc->snd_una;
+  offset = tc->snd_nxt - tc->snd_una;
+  available_wnd = tc->snd_wnd - offset;
+  burst_size = clib_min (burst_size, available_wnd / tc->snd_mss);
+
   while (n_segs < burst_size)
     {
       n_written = tcp_prepare_segment (wrk, tc, offset, tc->snd_mss, &b);
@@ -1775,6 +1782,9 @@ tcp_fast_retransmit_unsent (tcp_worker_ctx_t * wrk, tcp_connection_t * tc,
       tcp_enqueue_to_output (wrk, b, bi, tc->c_is_ip4);
       offset += n_written;
       n_segs += 1;
+
+      tc->snd_nxt += n_written;
+      tc->snd_una_max = seq_max (tc->snd_nxt, tc->snd_una_max);
     }
 
 done:
@@ -1797,9 +1807,8 @@ tcp_fast_retransmit_sack (tcp_worker_ctx_t * wrk, tcp_connection_t * tc,
   vlib_main_t *vm = wrk->vm;
   vlib_buffer_t *b = 0;
   sack_scoreboard_t *sb;
-  u32 bi, old_snd_nxt;
+  u32 bi, max_deq;
   int snd_space;
-  u32 max_deq;
   u8 snd_limited = 0, can_rescue = 0;
 
   ASSERT (tcp_in_fastrecovery (tc));
@@ -1807,17 +1816,16 @@ tcp_fast_retransmit_sack (tcp_worker_ctx_t * wrk, tcp_connection_t * tc,
   snd_space = tcp_available_cc_snd_space (tc);
   if (snd_space < tc->snd_mss)
     {
-      tcp_program_fastretransmit (wrk, tc);
+      tcp_program_fastretransmit (tc);
       return 0;
     }
 
-  TCP_EVT_DBG (TCP_EVT_CC_EVT, tc, 0);
-  old_snd_nxt = tc->snd_nxt;
+  TCP_EVT (TCP_EVT_CC_EVT, tc, 0);
   sb = &tc->sack_sb;
   hole = scoreboard_get_hole (sb, sb->cur_rxt_hole);
 
-  max_deq = session_tx_fifo_max_dequeue (&tc->connection);
-  max_deq -= tc->snd_una_max - tc->snd_una;
+  max_deq = transport_max_tx_dequeue (&tc->connection);
+  max_deq -= tc->snd_nxt - tc->snd_una;
 
   while (snd_space > 0 && n_segs < burst_size)
     {
@@ -1832,7 +1840,7 @@ tcp_fast_retransmit_sack (tcp_worker_ctx_t * wrk, tcp_connection_t * tc,
 				     snd_space / tc->snd_mss);
 	      n_segs_now = tcp_fast_retransmit_unsent (wrk, tc, burst_size);
 	      if (max_deq > n_segs_now * tc->snd_mss)
-		tcp_program_fastretransmit (wrk, tc);
+		tcp_program_fastretransmit (tc);
 	      n_segs += n_segs_now;
 	      goto done;
 	    }
@@ -1850,7 +1858,6 @@ tcp_fast_retransmit_sack (tcp_worker_ctx_t * wrk, tcp_connection_t * tc,
 	  max_bytes = clib_min (max_bytes, snd_space);
 	  offset = tc->snd_congestion - tc->snd_una - max_bytes;
 	  sb->rescue_rxt = tc->snd_congestion;
-	  tc->snd_nxt = tc->snd_una + offset;
 	  n_written = tcp_prepare_retransmit_segment (wrk, tc, offset,
 						      max_bytes, &b);
 	  if (!n_written)
@@ -1868,7 +1875,6 @@ tcp_fast_retransmit_sack (tcp_worker_ctx_t * wrk, tcp_connection_t * tc,
 	break;
 
       offset = sb->high_rxt - tc->snd_una;
-      tc->snd_nxt = sb->high_rxt;
       n_written = tcp_prepare_retransmit_segment (wrk, tc, offset, max_bytes,
 						  &b);
       ASSERT (n_written <= snd_space);
@@ -1886,11 +1892,9 @@ tcp_fast_retransmit_sack (tcp_worker_ctx_t * wrk, tcp_connection_t * tc,
     }
 
   if (hole)
-    tcp_program_fastretransmit (wrk, tc);
+    tcp_program_fastretransmit (tc);
 
 done:
-  /* If window allows, send 1 SMSS of new data */
-  tc->snd_nxt = old_snd_nxt;
   return n_segs;
 }
 
@@ -1901,22 +1905,21 @@ int
 tcp_fast_retransmit_no_sack (tcp_worker_ctx_t * wrk, tcp_connection_t * tc,
 			     u32 burst_size)
 {
-  u32 n_written = 0, offset = 0, bi, old_snd_nxt, max_deq, n_segs_now;
+  u32 n_written = 0, offset = 0, bi, max_deq, n_segs_now;
   vlib_main_t *vm = wrk->vm;
   int snd_space, n_segs = 0;
   vlib_buffer_t *b;
 
   ASSERT (tcp_in_fastrecovery (tc));
-  TCP_EVT_DBG (TCP_EVT_CC_EVT, tc, 0);
-  old_snd_nxt = tc->snd_nxt;
+  TCP_EVT (TCP_EVT_CC_EVT, tc, 0);
+
+  snd_space = tcp_available_cc_snd_space (tc);
 
   if (!tcp_fastrecovery_first (tc))
     goto send_unsent;
 
   /* RFC 6582: [If a partial ack], retransmit the first unacknowledged
    * segment. */
-  snd_space = tc->sack_sb.last_bytes_delivered;
-  tc->snd_nxt = tc->snd_una;
   while (snd_space > 0 && n_segs < burst_size)
     {
       n_written = tcp_prepare_retransmit_segment (wrk, tc, offset,
@@ -1939,25 +1942,21 @@ tcp_fast_retransmit_no_sack (tcp_worker_ctx_t * wrk, tcp_connection_t * tc,
 send_unsent:
 
   /* RFC 6582: Send a new segment if permitted by the new value of cwnd. */
-  snd_space = tcp_available_cc_snd_space (tc);
   if (snd_space < tc->snd_mss || tc->snd_mss == 0)
     goto done;
 
-  max_deq = session_tx_fifo_max_dequeue (&tc->connection);
-  max_deq -= tc->snd_una_max - tc->snd_una;
+  max_deq = transport_max_tx_dequeue (&tc->connection);
+  max_deq -= tc->snd_nxt - tc->snd_una;
   if (max_deq)
     {
       snd_space = clib_min (max_deq, snd_space);
       burst_size = clib_min (burst_size - n_segs, snd_space / tc->snd_mss);
       n_segs_now = tcp_fast_retransmit_unsent (wrk, tc, burst_size);
       if (max_deq > n_segs_now * tc->snd_mss)
-	tcp_program_fastretransmit (wrk, tc);
+	tcp_program_fastretransmit (tc);
       n_segs += n_segs_now;
     }
 
-  /* Restore snd_nxt */
-  tc->snd_nxt = old_snd_nxt;
-
 done:
   tcp_fastrecovery_first_off (tc);
   return n_segs;
@@ -1976,6 +1975,111 @@ tcp_fast_retransmit (tcp_worker_ctx_t * wrk, tcp_connection_t * tc,
     return tcp_fast_retransmit_no_sack (wrk, tc, burst_size);
 }
 
+static int
+tcp_send_acks (tcp_connection_t * tc, u32 max_burst_size)
+{
+  int j, n_acks;
+
+  if (!tc->pending_dupacks)
+    {
+      tcp_send_ack (tc);
+      return 1;
+    }
+
+  /* If we're supposed to send dupacks but have no ooo data
+   * send only one ack */
+  if (!vec_len (tc->snd_sacks))
+    {
+      tcp_send_ack (tc);
+      return 1;
+    }
+
+  /* Start with first sack block */
+  tc->snd_sack_pos = 0;
+
+  /* Generate enough dupacks to cover all sack blocks. Do not generate
+   * more sacks than the number of packets received. But do generate at
+   * least 3, i.e., the number needed to signal congestion, if needed. */
+  n_acks = vec_len (tc->snd_sacks) / TCP_OPTS_MAX_SACK_BLOCKS;
+  n_acks = clib_min (n_acks, tc->pending_dupacks);
+  n_acks = clib_max (n_acks, clib_min (tc->pending_dupacks, 3));
+  for (j = 0; j < clib_min (n_acks, max_burst_size); j++)
+    tcp_send_ack (tc);
+
+  if (n_acks < max_burst_size)
+    {
+      tc->pending_dupacks = 0;
+      tc->snd_sack_pos = 0;
+      tc->dupacks_out += n_acks;
+      return n_acks;
+    }
+  else
+    {
+      TCP_DBG ("constrained by burst size");
+      tc->pending_dupacks = n_acks - max_burst_size;
+      tc->dupacks_out += max_burst_size;
+      tcp_program_dupack (tc);
+      return max_burst_size;
+    }
+}
+
+static int
+tcp_do_fastretransmit (tcp_connection_t * tc, u32 max_burst_size)
+{
+  u32 n_segs = 0, burst_size, sent_bytes, burst_bytes;
+  tcp_worker_ctx_t *wrk;
+
+  wrk = tcp_get_worker (tc->c_thread_index);
+  burst_bytes = transport_connection_tx_pacer_burst (&tc->connection,
+						     wrk->vm->
+						     clib_time.last_cpu_time);
+  burst_size = clib_min (max_burst_size, burst_bytes / tc->snd_mss);
+  if (!burst_size)
+    {
+      tcp_program_fastretransmit (tc);
+      return 0;
+    }
+
+  n_segs = tcp_fast_retransmit (wrk, tc, burst_size);
+  sent_bytes = clib_min (n_segs * tc->snd_mss, burst_bytes);
+  transport_connection_tx_pacer_update_bytes (&tc->connection, sent_bytes);
+  return n_segs;
+}
+
+int
+tcp_session_custom_tx (void *conn, u32 max_burst_size)
+{
+  tcp_connection_t *tc = (tcp_connection_t *) conn;
+  u32 n_segs = 0;
+
+  if (tcp_in_fastrecovery (tc) && (tc->flags & TCP_CONN_FRXT_PENDING))
+    {
+      tc->flags &= ~TCP_CONN_FRXT_PENDING;
+      n_segs = tcp_do_fastretransmit (tc, max_burst_size);
+      max_burst_size -= n_segs;
+    }
+
+  if (!(tc->flags & TCP_CONN_SNDACK))
+    return n_segs;
+
+  tc->flags &= ~TCP_CONN_SNDACK;
+
+  /* We have retransmitted packets and no dupack */
+  if (n_segs && !tc->pending_dupacks)
+    return n_segs;
+
+  if (!max_burst_size)
+    {
+      tcp_program_ack (tc);
+      return max_burst_size;
+    }
+
+  n_segs += tcp_send_acks (tc, max_burst_size);
+
+  return n_segs;
+}
+#endif /* CLIB_MARCH_VARIANT */
+
 static void
 tcp_output_handle_link_local (tcp_connection_t * tc0, vlib_buffer_t * b0,
 			      u16 * next0, u32 * error0)
@@ -2038,7 +2142,7 @@ tcp_output_push_ip (vlib_main_t * vm, vlib_buffer_t * b0,
   tcp_header_t *th0 = 0;
 
   th0 = vlib_buffer_get_current (b0);
-  TCP_EVT_DBG (TCP_EVT_OUTPUT, tc0, th0->flags, b0->current_length);
+  TCP_EVT (TCP_EVT_OUTPUT, tc0, th0->flags, b0->current_length);
   if (is_ip4)
     {
       vlib_buffer_push_ip4 (vm, b0, &tc0->c_lcl_ip4, &tc0->c_rmt_ip4,
@@ -2061,14 +2165,14 @@ tcp_output_push_ip (vlib_main_t * vm, vlib_buffer_t * b0,
 
 always_inline void
 tcp_output_handle_packet (tcp_connection_t * tc0, vlib_buffer_t * b0,
-			  u32 * error0, u16 * next0, u8 is_ip4)
+			  vlib_node_runtime_t * error_node, u16 * next0,
+			  u8 is_ip4)
 {
-
-  if (PREDICT_FALSE (tc0->state == TCP_STATE_CLOSED))
+  /* If next_index is not drop use it */
+  if (tc0->next_node_index)
     {
-      *error0 = TCP_ERROR_INVALID_CONNECTION;
-      *next0 = TCP_OUTPUT_NEXT_DROP;
-      return;
+      *next0 = tc0->next_node_index;
+      vnet_buffer (b0)->tcp.next_node_opaque = tc0->next_node_opaque;
     }
 
   vnet_buffer (b0)->sw_if_index[VLIB_TX] = tc0->c_fib_index;
@@ -2076,12 +2180,22 @@ tcp_output_handle_packet (tcp_connection_t * tc0, vlib_buffer_t * b0,
 
   if (!is_ip4)
     {
+      u32 error0 = 0;
+
       if (PREDICT_FALSE (ip6_address_is_link_local_unicast (&tc0->c_rmt_ip6)))
-	tcp_output_handle_link_local (tc0, b0, next0, error0);
+	tcp_output_handle_link_local (tc0, b0, next0, &error0);
+
+      if (PREDICT_FALSE (error0))
+	{
+	  b0->error = error_node->errors[error0];
+	  return;
+	}
     }
 
   if (!TCP_ALWAYS_ACK)
     tcp_timer_reset (tc0, TCP_TIMER_DELACK);
+
+  tc0->segs_out += 1;
 }
 
 always_inline uword
@@ -2091,6 +2205,9 @@ tcp46_output_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
   u32 n_left_from, *from, thread_index = vm->thread_index;
   vlib_buffer_t *bufs[VLIB_FRAME_SIZE], **b;
   u16 nexts[VLIB_FRAME_SIZE], *next;
+  vlib_node_runtime_t *error_node;
+
+  error_node = vlib_node_get_runtime (vm, tcp_node_index (output, is_ip4));
 
   from = vlib_frame_vector_args (frame);
   n_left_from = frame->n_vectors;
@@ -2105,7 +2222,6 @@ tcp46_output_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 
   while (n_left_from >= 4)
     {
-      u32 error0 = TCP_ERROR_PKTS_SENT, error1 = TCP_ERROR_PKTS_SENT;
       tcp_connection_t *tc0, *tc1;
 
       {
@@ -2126,8 +2242,8 @@ tcp46_output_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
       tcp_output_push_ip (vm, b[0], tc0, is_ip4);
       tcp_output_push_ip (vm, b[1], tc1, is_ip4);
 
-      tcp_output_handle_packet (tc0, b[0], &error0, &next[0], is_ip4);
-      tcp_output_handle_packet (tc1, b[1], &error1, &next[1], is_ip4);
+      tcp_output_handle_packet (tc0, b[0], error_node, &next[0], is_ip4);
+      tcp_output_handle_packet (tc1, b[1], error_node, &next[1], is_ip4);
 
       b += 2;
       next += 2;
@@ -2135,7 +2251,6 @@ tcp46_output_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
     }
   while (n_left_from > 0)
     {
-      u32 error0 = TCP_ERROR_PKTS_SENT;
       tcp_connection_t *tc0;
 
       if (n_left_from > 1)
@@ -2149,7 +2264,7 @@ tcp46_output_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 				thread_index);
 
       tcp_output_push_ip (vm, b[0], tc0, is_ip4);
-      tcp_output_handle_packet (tc0, b[0], &error0, &next[0], is_ip4);
+      tcp_output_handle_packet (tc0, b[0], error_node, &next[0], is_ip4);
 
       b += 1;
       next += 1;
@@ -2157,19 +2272,19 @@ tcp46_output_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
     }
 
   vlib_buffer_enqueue_to_next (vm, node, from, nexts, frame->n_vectors);
+  vlib_node_increment_counter (vm, tcp_node_index (output, is_ip4),
+			       TCP_ERROR_PKTS_SENT, frame->n_vectors);
   return frame->n_vectors;
 }
 
-static uword
-tcp4_output (vlib_main_t * vm, vlib_node_runtime_t * node,
-	     vlib_frame_t * from_frame)
+VLIB_NODE_FN (tcp4_output_node) (vlib_main_t * vm, vlib_node_runtime_t * node,
+				 vlib_frame_t * from_frame)
 {
   return tcp46_output_inline (vm, node, from_frame, 1 /* is_ip4 */ );
 }
 
-static uword
-tcp6_output (vlib_main_t * vm, vlib_node_runtime_t * node,
-	     vlib_frame_t * from_frame)
+VLIB_NODE_FN (tcp6_output_node) (vlib_main_t * vm, vlib_node_runtime_t * node,
+				 vlib_frame_t * from_frame)
 {
   return tcp46_output_inline (vm, node, from_frame, 0 /* is_ip4 */ );
 }
@@ -2177,7 +2292,6 @@ tcp6_output (vlib_main_t * vm, vlib_node_runtime_t * node,
 /* *INDENT-OFF* */
 VLIB_REGISTER_NODE (tcp4_output_node) =
 {
-  .function = tcp4_output,
   .name = "tcp4-output",
   /* Takes a vector of packets. */
   .vector_size = sizeof (u32),
@@ -2195,12 +2309,9 @@ VLIB_REGISTER_NODE (tcp4_output_node) =
 };
 /* *INDENT-ON* */
 
-VLIB_NODE_FUNCTION_MULTIARCH (tcp4_output_node, tcp4_output);
-
 /* *INDENT-OFF* */
 VLIB_REGISTER_NODE (tcp6_output_node) =
 {
-  .function = tcp6_output,
   .name = "tcp6-output",
     /* Takes a vector of packets. */
   .vector_size = sizeof (u32),
@@ -2218,8 +2329,6 @@ VLIB_REGISTER_NODE (tcp6_output_node) =
 };
 /* *INDENT-ON* */
 
-VLIB_NODE_FUNCTION_MULTIARCH (tcp6_output_node, tcp6_output);
-
 typedef enum _tcp_reset_next
 {
   TCP_RESET_NEXT_DROP,
@@ -2305,23 +2414,20 @@ tcp46_send_reset_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
   return from_frame->n_vectors;
 }
 
-static uword
-tcp4_send_reset (vlib_main_t * vm, vlib_node_runtime_t * node,
-		 vlib_frame_t * from_frame)
+VLIB_NODE_FN (tcp4_reset_node) (vlib_main_t * vm, vlib_node_runtime_t * node,
+				vlib_frame_t * from_frame)
 {
   return tcp46_send_reset_inline (vm, node, from_frame, 1);
 }
 
-static uword
-tcp6_send_reset (vlib_main_t * vm, vlib_node_runtime_t * node,
-		 vlib_frame_t * from_frame)
+VLIB_NODE_FN (tcp6_reset_node) (vlib_main_t * vm, vlib_node_runtime_t * node,
+				vlib_frame_t * from_frame)
 {
   return tcp46_send_reset_inline (vm, node, from_frame, 0);
 }
 
 /* *INDENT-OFF* */
 VLIB_REGISTER_NODE (tcp4_reset_node) = {
-  .function = tcp4_send_reset,
   .name = "tcp4-reset",
   .vector_size = sizeof (u32),
   .n_errors = TCP_N_ERROR,
@@ -2336,11 +2442,8 @@ VLIB_REGISTER_NODE (tcp4_reset_node) = {
 };
 /* *INDENT-ON* */
 
-VLIB_NODE_FUNCTION_MULTIARCH (tcp4_reset_node, tcp4_send_reset);
-
 /* *INDENT-OFF* */
 VLIB_REGISTER_NODE (tcp6_reset_node) = {
-  .function = tcp6_send_reset,
   .name = "tcp6-reset",
   .vector_size = sizeof (u32),
   .n_errors = TCP_N_ERROR,
@@ -2355,8 +2458,6 @@ VLIB_REGISTER_NODE (tcp6_reset_node) = {
 };
 /* *INDENT-ON* */
 
-VLIB_NODE_FUNCTION_MULTIARCH (tcp6_reset_node, tcp6_send_reset);
-
 /*
  * fd.io coding-style-patch-verification: ON
  *