VPP-598: tcp stack initial commit

Change-Id: I49e5ce0aae6e4ff634024387ceaf7dbc432a0351
Signed-off-by: Dave Barach <dave@barachs.net>
Signed-off-by: Florin Coras <fcoras@cisco.com>

1 files changed, 2316 insertions, 0 deletions

diff --git a/src/vnet/tcp/tcp_input.c b/src/vnet/tcp/tcp_input.c
new file mode 100644
index 00000000000..daa0683b48e
--- /dev/null
+++ b/src/vnet/tcp/tcp_input.c
@@ -0,0 +1,2316 @@
+/*
+ * Copyright (c) 2016 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:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <vppinfra/sparse_vec.h>
+#include <vnet/tcp/tcp_packet.h>
+#include <vnet/tcp/tcp.h>
+#include <vnet/session/session.h>
+#include <math.h>
+
+static char *tcp_error_strings[] = {
+#define tcp_error(n,s) s,
+#include <vnet/tcp/tcp_error.def>
+#undef tcp_error
+};
+
+/* All TCP nodes have the same outgoing arcs */
+#define foreach_tcp_state_next                  \
+  _ (DROP, "error-drop")                        \
+  _ (TCP4_OUTPUT, "tcp4-output")                \
+  _ (TCP6_OUTPUT, "tcp6-output")
+
+typedef enum _tcp_established_next
+{
+#define _(s,n) TCP_ESTABLISHED_NEXT_##s,
+  foreach_tcp_state_next
+#undef _
+    TCP_ESTABLISHED_N_NEXT,
+} tcp_established_next_t;
+
+typedef enum _tcp_rcv_process_next
+{
+#define _(s,n) TCP_RCV_PROCESS_NEXT_##s,
+  foreach_tcp_state_next
+#undef _
+    TCP_RCV_PROCESS_N_NEXT,
+} tcp_rcv_process_next_t;
+
+typedef enum _tcp_syn_sent_next
+{
+#define _(s,n) TCP_SYN_SENT_NEXT_##s,
+  foreach_tcp_state_next
+#undef _
+    TCP_SYN_SENT_N_NEXT,
+} tcp_syn_sent_next_t;
+
+typedef enum _tcp_listen_next
+{
+#define _(s,n) TCP_LISTEN_NEXT_##s,
+  foreach_tcp_state_next
+#undef _
+    TCP_LISTEN_N_NEXT,
+} tcp_listen_next_t;
+
+/* Generic, state independent indices */
+typedef enum _tcp_state_next
+{
+#define _(s,n) TCP_NEXT_##s,
+  foreach_tcp_state_next
+#undef _
+    TCP_STATE_N_NEXT,
+} tcp_state_next_t;
+
+#define tcp_next_output(is_ip4) (is_ip4 ? TCP_NEXT_TCP4_OUTPUT          \
+                                        : TCP_NEXT_TCP6_OUTPUT)
+
+vlib_node_registration_t tcp4_established_node;
+vlib_node_registration_t tcp6_established_node;
+
+/**
+ * Validate segment sequence number. As per RFC793:
+ *
+ * Segment Receive Test
+ *      Length  Window
+ *      ------- -------  -------------------------------------------
+ *      0       0       SEG.SEQ = RCV.NXT
+ *      0       >0      RCV.NXT =< SEG.SEQ < RCV.NXT+RCV.WND
+ *      >0      0       not acceptable
+ *      >0      >0      RCV.NXT =< SEG.SEQ < RCV.NXT+RCV.WND
+ *                      or RCV.NXT =< SEG.SEQ+SEG.LEN-1 < RCV.NXT+RCV.WND
+ *
+ * This ultimately consists in checking if segment falls within the window.
+ * The one important difference compared to RFC793 is that we use rcv_las,
+ * or the rcv_nxt at last ack sent instead of rcv_nxt since that's the
+ * peer's reference when computing our receive window.
+ *
+ * This accepts only segments within the window.
+ */
+always_inline u8
+tcp_segment_in_rcv_wnd (tcp_connection_t * tc, u32 seq, u32 end_seq)
+{
+  return seq_leq (end_seq, tc->rcv_las + tc->rcv_wnd)
+    && seq_geq (seq, tc->rcv_nxt);
+}
+
+void
+tcp_options_parse (tcp_header_t * th, tcp_options_t * to)
+{
+  const u8 *data;
+  u8 opt_len, opts_len, kind;
+  int j;
+  sack_block_t b;
+
+  opts_len = (tcp_doff (th) << 2) - sizeof (tcp_header_t);
+  data = (const u8 *) (th + 1);
+
+  /* Zero out all flags but those set in SYN */
+  to->flags &= (TCP_OPTS_FLAG_SACK_PERMITTED | TCP_OPTS_FLAG_WSCALE);
+
+  for (; opts_len > 0; opts_len -= opt_len, data += opt_len)
+    {
+      kind = data[0];
+
+      /* Get options length */
+      if (kind == TCP_OPTION_EOL)
+	break;
+      else if (kind == TCP_OPTION_NOOP)
+	opt_len = 1;
+      else
+	{
+	  /* broken options */
+	  if (opts_len < 2)
+	    break;
+	  opt_len = data[1];
+
+	  /* weird option length */
+	  if (opt_len < 2 || opt_len > opts_len)
+	    break;
+	}
+
+      /* Parse options */
+      switch (kind)
+	{
+	case TCP_OPTION_MSS:
+	  if ((opt_len == TCP_OPTION_LEN_MSS) && tcp_syn (th))
+	    {
+	      to->flags |= TCP_OPTS_FLAG_MSS;
+	      to->mss = clib_net_to_host_u16 (*(u16 *) (data + 2));
+	    }
+	  break;
+	case TCP_OPTION_WINDOW_SCALE:
+	  if ((opt_len == TCP_OPTION_LEN_WINDOW_SCALE) && tcp_syn (th))
+	    {
+	      to->flags |= TCP_OPTS_FLAG_WSCALE;
+	      to->wscale = data[2];
+	      if (to->wscale > TCP_MAX_WND_SCALE)
+		{
+		  clib_warning ("Illegal window scaling value: %d",
+				to->wscale);
+		  to->wscale = TCP_MAX_WND_SCALE;
+		}
+	    }
+	  break;
+	case TCP_OPTION_TIMESTAMP:
+	  if (opt_len == TCP_OPTION_LEN_TIMESTAMP)
+	    {
+	      to->flags |= TCP_OPTS_FLAG_TSTAMP;
+	      to->tsval = clib_net_to_host_u32 (*(u32 *) (data + 2));
+	      to->tsecr = clib_net_to_host_u32 (*(u32 *) (data + 6));
+	    }
+	  break;
+	case TCP_OPTION_SACK_PERMITTED:
+	  if (opt_len == TCP_OPTION_LEN_SACK_PERMITTED && tcp_syn (th))
+	    to->flags |= TCP_OPTS_FLAG_SACK_PERMITTED;
+	  break;
+	case TCP_OPTION_SACK_BLOCK:
+	  /* If SACK permitted was not advertised or a SYN, break */
+	  if ((to->flags & TCP_OPTS_FLAG_SACK_PERMITTED) == 0 || tcp_syn (th))
+	    break;
+
+	  /* If too short or not correctly formatted, break */
+	  if (opt_len < 10 || ((opt_len - 2) % TCP_OPTION_LEN_SACK_BLOCK))
+	    break;
+
+	  to->flags |= TCP_OPTS_FLAG_SACK;
+	  to->n_sack_blocks = (opt_len - 2) / TCP_OPTION_LEN_SACK_BLOCK;
+	  vec_reset_length (to->sacks);
+	  for (j = 0; j < to->n_sack_blocks; j++)
+	    {
+	      b.start = clib_net_to_host_u32 (*(u32 *) (data + 2 + 4 * j));
+	      b.end = clib_net_to_host_u32 (*(u32 *) (data + 6 + 4 * j));
+	      vec_add1 (to->sacks, b);
+	    }
+	  break;
+	default:
+	  /* Nothing to see here */
+	  continue;
+	}
+    }
+}
+
+always_inline int
+tcp_segment_check_paws (tcp_connection_t * tc)
+{
+  /* XXX normally test for timestamp should be lt instead of leq, but for
+   * local testing this is not enough */
+  return tcp_opts_tstamp (&tc->opt) && tc->tsval_recent
+    && timestamp_lt (tc->opt.tsval, tc->tsval_recent);
+}
+
+/**
+ * Validate incoming segment as per RFC793 p. 69 and RFC1323 p. 19
+ *
+ * It first verifies if segment has a wrapped sequence number (PAWS) and then
+ * does the processing associated to the first four steps (ignoring security
+ * and precedence): sequence number, rst bit and syn bit checks.
+ *
+ * @return 0 if segments passes validation.
+ */
+static int
+tcp_segment_validate (vlib_main_t * vm, tcp_connection_t * tc0,
+		      vlib_buffer_t * b0, tcp_header_t * th0, u32 * next0)
+{
+  u8 paws_failed;
+
+  if (PREDICT_FALSE (!tcp_ack (th0) && !tcp_rst (th0) && !tcp_syn (th0)))
+    return -1;
+
+  tcp_options_parse (th0, &tc0->opt);
+
+  /* RFC1323: Check against wrapped sequence numbers (PAWS). If we have
+   * timestamp to echo and it's less than tsval_recent, drop segment
+   * but still send an ACK in order to retain TCP's mechanism for detecting
+   * and recovering from half-open connections */
+  paws_failed = tcp_segment_check_paws (tc0);
+  if (paws_failed)
+    {
+      clib_warning ("paws failed");
+
+      /* If it just so happens that a segment updates tsval_recent for a
+       * segment over 24 days old, invalidate tsval_recent. */
+      if (timestamp_lt (tc0->tsval_recent_age + TCP_PAWS_IDLE,
+			tcp_time_now ()))
+	{
+	  /* Age isn't reset until we get a valid tsval (bsd inspired) */
+	  tc0->tsval_recent = 0;
+	}
+      else
+	{
+	  /* Drop after ack if not rst */
+	  if (!tcp_rst (th0))
+	    {
+	      tcp_make_ack (tc0, b0);
+	      *next0 = tcp_next_output (tc0->c_is_ip4);
+	      return -1;
+	    }
+	}
+    }
+
+  /* 1st: check sequence number */
+  if (!tcp_segment_in_rcv_wnd (tc0, vnet_buffer (b0)->tcp.seq_number,
+			       vnet_buffer (b0)->tcp.seq_end))
+    {
+      if (!tcp_rst (th0))
+	{
+	  /* Send dup ack */
+	  tcp_make_ack (tc0, b0);
+	  *next0 = tcp_next_output (tc0->c_is_ip4);
+	}
+      return -1;
+    }
+
+  /* 2nd: check the RST bit */
+  if (tcp_rst (th0))
+    {
+      /* Notify session that connection has been reset. Switch
+       * state to closed and await for session to do the cleanup. */
+      stream_session_reset_notify (&tc0->connection);
+      tc0->state = TCP_STATE_CLOSED;
+      return -1;
+    }
+
+  /* 3rd: check security and precedence (skip) */
+
+  /* 4th: check the SYN bit */
+  if (tcp_syn (th0))
+    {
+      tcp_send_reset (b0, tc0->c_is_ip4);
+      return -1;
+    }
+
+  /* If PAWS passed and segment in window, save timestamp */
+  if (!paws_failed)
+    {
+      tc0->tsval_recent = tc0->opt.tsval;
+      tc0->tsval_recent_age = tcp_time_now ();
+    }
+
+  return 0;
+}
+
+always_inline int
+tcp_rcv_ack_is_acceptable (tcp_connection_t * tc0, vlib_buffer_t * tb0)
+{
+  /* SND.UNA =< SEG.ACK =< SND.NXT */
+  return (seq_leq (tc0->snd_una, vnet_buffer (tb0)->tcp.ack_number)
+	  && seq_leq (vnet_buffer (tb0)->tcp.ack_number, tc0->snd_nxt));
+}
+
+/**
+ * Compute smoothed RTT as per VJ's '88 SIGCOMM and RFC6298
+ *
+ * Note that although the original article, srtt and rttvar are scaled
+ * to minimize round-off errors, here we don't. Instead, we rely on
+ * better precision time measurements.
+ *
+ * TODO support us rtt resolution
+ */
+static void
+tcp_estimate_rtt (tcp_connection_t * tc, u32 mrtt)
+{
+  int err;
+
+  if (tc->srtt != 0)
+    {
+      err = mrtt - tc->srtt;
+      tc->srtt += err >> 3;
+
+      /* XXX Drop in RTT results in RTTVAR increase and bigger RTO.
+       * The increase should be bound */
+      tc->rttvar += (clib_abs (err) - tc->rttvar) >> 2;
+    }
+  else
+    {
+      /* First measurement. */
+      tc->srtt = mrtt;
+      tc->rttvar = mrtt << 1;
+    }
+}
+
+/** Update RTT estimate and RTO timer
+ *
+ * Measure RTT: We have two sources of RTT measurements: TSOPT and ACK
+ * timing. Middle boxes are known to fiddle with TCP options so we
+ * should give higher priority to ACK timing.
+ *
+ * return 1 if valid rtt 0 otherwise
+ */
+static int
+tcp_update_rtt (tcp_connection_t * tc, u32 ack)
+{
+  u32 mrtt = 0;
+
+  /* Karn's rule, part 1. Don't use retransmitted segments to estimate
+   * RTT because they're ambiguous. */
+  if (tc->rtt_seq && seq_gt (ack, tc->rtt_seq) && !tc->rto_boff)
+    {
+      mrtt = tcp_time_now () - tc->rtt_ts;
+      tc->rtt_seq = 0;
+    }
+
+  /* As per RFC7323 TSecr can be used for RTTM only if the segment advances
+   * snd_una, i.e., the left side of the send window:
+   * seq_lt (tc->snd_una, ack). Note: last condition could be dropped, we don't
+   * try to update rtt for dupacks */
+  else if (tcp_opts_tstamp (&tc->opt) && tc->opt.tsecr && tc->bytes_acked)
+    {
+      mrtt = tcp_time_now () - tc->opt.tsecr;
+    }
+
+  /* Ignore dubious measurements */
+  if (mrtt == 0 || mrtt > TCP_RTT_MAX)
+    return 0;
+
+  tcp_estimate_rtt (tc, mrtt);
+
+  tc->rto = clib_min (tc->srtt + (tc->rttvar << 2), TCP_RTO_MAX);
+
+  return 1;
+}
+
+/**
+ * Dequeue bytes that have been acked and while at it update RTT estimates.
+ */
+static void
+tcp_dequeue_acked (tcp_connection_t * tc, u32 ack)
+{
+  /* Dequeue the newly ACKed bytes */
+  stream_session_dequeue_drop (&tc->connection, tc->bytes_acked);
+
+  /* Update rtt and rto */
+  if (tcp_update_rtt (tc, ack))
+    {
+      /* Good ACK received and valid RTT, make sure retransmit backoff is 0 */
+      tc->rto_boff = 0;
+    }
+}
+
+/** Check if dupack as per RFC5681 Sec. 2 */
+always_inline u8
+tcp_ack_is_dupack (tcp_connection_t * tc, vlib_buffer_t * b, u32 new_snd_wnd)
+{
+  return ((vnet_buffer (b)->tcp.ack_number == tc->snd_una)
+	  && seq_gt (tc->snd_una_max, tc->snd_una)
+	  && (vnet_buffer (b)->tcp.seq_end == vnet_buffer (b)->tcp.seq_number)
+	  && (new_snd_wnd == tc->snd_wnd));
+}
+
+void
+scoreboard_remove_hole (sack_scoreboard_t * sb, sack_scoreboard_hole_t * hole)
+{
+  sack_scoreboard_hole_t *next, *prev;
+
+  if (hole->next != TCP_INVALID_SACK_HOLE_INDEX)
+    {
+      next = pool_elt_at_index (sb->holes, hole->next);
+      next->prev = hole->prev;
+    }
+
+  if (hole->prev != TCP_INVALID_SACK_HOLE_INDEX)
+    {
+      prev = pool_elt_at_index (sb->holes, hole->prev);
+      prev->next = hole->next;
+    }
+  else
+    {
+      sb->head = hole->next;
+    }
+
+  pool_put (sb->holes, hole);
+}
+
+sack_scoreboard_hole_t *
+scoreboard_insert_hole (sack_scoreboard_t * sb, sack_scoreboard_hole_t * prev,
+			u32 start, u32 end)
+{
+  sack_scoreboard_hole_t *hole, *next;
+  u32 hole_index;
+
+  pool_get (sb->holes, hole);
+  memset (hole, 0, sizeof (*hole));
+
+  hole->start = start;
+  hole->end = end;
+  hole_index = hole - sb->holes;
+
+  if (prev)
+    {
+      hole->prev = prev - sb->holes;
+      hole->next = prev->next;
+
+      if ((next = scoreboard_next_hole (sb, hole)))
+	next->prev = hole_index;
+
+      prev->next = hole_index;
+    }
+  else
+    {
+      sb->head = hole_index;
+      hole->prev = TCP_INVALID_SACK_HOLE_INDEX;
+      hole->next = TCP_INVALID_SACK_HOLE_INDEX;
+    }
+
+  return hole;
+}
+
+static void
+tcp_rcv_sacks (tcp_connection_t * tc, u32 ack)
+{
+  sack_scoreboard_t *sb = &tc->sack_sb;
+  sack_block_t *blk, tmp;
+  sack_scoreboard_hole_t *hole, *next_hole;
+  u32 blk_index = 0;
+  int i, j;
+
+  if (!tcp_opts_sack (tc) && sb->head == TCP_INVALID_SACK_HOLE_INDEX)
+    return;
+
+  /* Remove invalid blocks */
+  vec_foreach (blk, tc->opt.sacks)
+  {
+    if (seq_lt (blk->start, blk->end)
+	&& seq_gt (blk->start, tc->snd_una)
+	&& seq_gt (blk->start, ack) && seq_lt (blk->end, tc->snd_nxt))
+      continue;
+
+    vec_del1 (tc->opt.sacks, blk - tc->opt.sacks);
+  }
+
+  /* Add block for cumulative ack */
+  if (seq_gt (ack, tc->snd_una))
+    {
+      tmp.start = tc->snd_una;
+      tmp.end = ack;
+      vec_add1 (tc->opt.sacks, tmp);
+    }
+
+  if (vec_len (tc->opt.sacks) == 0)
+    return;
+
+  /* Make sure blocks are ordered */
+  for (i = 0; i < vec_len (tc->opt.sacks); i++)
+    for (j = i; j < vec_len (tc->opt.sacks); j++)
+      if (seq_lt (tc->opt.sacks[j].start, tc->opt.sacks[i].start))
+	{
+	  tmp = tc->opt.sacks[i];
+	  tc->opt.sacks[i] = tc->opt.sacks[j];
+	  tc->opt.sacks[j] = tmp;
+	}
+
+  /* If no holes, insert the first that covers all outstanding bytes */
+  if (sb->head == TCP_INVALID_SACK_HOLE_INDEX)
+    {
+      scoreboard_insert_hole (sb, 0, tc->snd_una, tc->snd_una_max);
+    }
+
+  /* Walk the holes with the SACK blocks */
+  hole = pool_elt_at_index (sb->holes, sb->head);
+  while (hole && blk_index < vec_len (tc->opt.sacks))
+    {
+      blk = &tc->opt.sacks[blk_index];
+
+      if (seq_leq (blk->start, hole->start))
+	{
+	  /* Block covers hole. Remove hole */
+	  if (seq_geq (blk->end, hole->end))
+	    {
+	      next_hole = scoreboard_next_hole (sb, hole);
+
+	      /* Byte accounting */
+	      if (seq_lt (hole->end, ack))
+		{
+		  /* Bytes lost because snd wnd left edge advances */
+		  if (seq_lt (next_hole->start, ack))
+		    sb->sacked_bytes -= next_hole->start - hole->end;
+		  else
+		    sb->sacked_bytes -= ack - hole->end;
+		}
+	      else
+		{
+		  sb->sacked_bytes += scoreboard_hole_bytes (hole);
+		}
+
+	      scoreboard_remove_hole (sb, hole);
+	      hole = next_hole;
+	    }
+	  /* Partial overlap */
+	  else
+	    {
+	      sb->sacked_bytes += blk->end - hole->start;
+	      hole->start = blk->end;
+	      blk_index++;
+	    }
+	}
+      else
+	{
+	  /* Hole must be split */
+	  if (seq_leq (blk->end, hole->end))
+	    {
+	      sb->sacked_bytes += blk->end - blk->start;
+	      scoreboard_insert_hole (sb, hole, blk->end, hole->end);
+	      hole->end = blk->start - 1;
+	      blk_index++;
+	    }
+	  else
+	    {
+	      sb->sacked_bytes += hole->end - blk->start + 1;
+	      hole->end = blk->start - 1;
+	      hole = scoreboard_next_hole (sb, hole);
+	    }
+	}
+    }
+}
+
+/** Update snd_wnd
+ *
+ * If (SND.WL1 < SEG.SEQ or (SND.WL1 = SEG.SEQ and SND.WL2 =< SEG.ACK)), set
+ * SND.WND <- SEG.WND, set SND.WL1 <- SEG.SEQ, and set SND.WL2 <- SEG.ACK */
+static void
+tcp_update_snd_wnd (tcp_connection_t * tc, u32 seq, u32 ack, u32 snd_wnd)
+{
+  if (tc->snd_wl1 < seq || (tc->snd_wl1 == seq && tc->snd_wl2 <= ack))
+    {
+      tc->snd_wnd = snd_wnd;
+      tc->snd_wl1 = seq;
+      tc->snd_wl2 = ack;
+    }
+}
+
+static void
+tcp_cc_congestion (tcp_connection_t * tc)
+{
+  tc->cc_algo->congestion (tc);
+}
+
+static void
+tcp_cc_recover (tcp_connection_t * tc)
+{
+  if (tcp_in_fastrecovery (tc))
+    {
+      tc->cc_algo->recovered (tc);
+      tcp_recovery_off (tc);
+    }
+  else if (tcp_in_recovery (tc))
+    {
+      tcp_recovery_off (tc);
+      tc->cwnd = tcp_loss_wnd (tc);
+    }
+}
+
+static void
+tcp_cc_rcv_ack (tcp_connection_t * tc)
+{
+  u8 partial_ack;
+
+  if (tcp_in_recovery (tc))
+    {
+      partial_ack = seq_lt (tc->snd_una, tc->snd_una_max);
+      if (!partial_ack)
+	{
+	  /* Clear retransmitted bytes. */
+	  tc->rtx_bytes = 0;
+	  tcp_cc_recover (tc);
+	}
+      else
+	{
+	  /* Clear retransmitted bytes. XXX should we clear all? */
+	  tc->rtx_bytes = 0;
+	  tc->cc_algo->rcv_cong_ack (tc, TCP_CC_PARTIALACK);
+
+	  /* Retransmit first unacked segment */
+	  tcp_retransmit_first_unacked (tc);
+	}
+    }
+  else
+    {
+      tc->cc_algo->rcv_ack (tc);
+    }
+
+  tc->rcv_dupacks = 0;
+  tc->tsecr_last_ack = tc->opt.tsecr;
+}
+
+static void
+tcp_cc_rcv_dupack (tcp_connection_t * tc, u32 ack)
+{
+  ASSERT (tc->snd_una == ack);
+
+  tc->rcv_dupacks++;
+  if (tc->rcv_dupacks == TCP_DUPACK_THRESHOLD)
+    {
+      /* RFC6582 NewReno heuristic to avoid multiple fast retransmits */
+      if (tc->opt.tsecr != tc->tsecr_last_ack)
+	{
+	  tc->rcv_dupacks = 0;
+	  return;
+	}
+
+      tcp_fastrecovery_on (tc);
+
+      /* Handle congestion and dupack */
+      tcp_cc_congestion (tc);
+      tc->cc_algo->rcv_cong_ack (tc, TCP_CC_DUPACK);
+
+      tcp_fast_retransmit (tc);
+
+      /* Post retransmit update cwnd to ssthresh and account for the
+       * three segments that have left the network and should've been
+       * buffered at the receiver */
+      tc->cwnd = tc->ssthresh + TCP_DUPACK_THRESHOLD * tc->snd_mss;
+    }
+  else if (tc->rcv_dupacks > TCP_DUPACK_THRESHOLD)
+    {
+      ASSERT (tcp_in_fastrecovery (tc));
+
+      tc->cc_algo->rcv_cong_ack (tc, TCP_CC_DUPACK);
+    }
+}
+
+void
+tcp_cc_init (tcp_connection_t * tc)
+{
+  tc->cc_algo = tcp_cc_algo_get (TCP_CC_NEWRENO);
+  tc->cc_algo->init (tc);
+}
+
+static int
+tcp_rcv_ack (tcp_connection_t * tc, vlib_buffer_t * b,
+	     tcp_header_t * th, u32 * next, u32 * error)
+{
+  u32 new_snd_wnd;
+
+  /* If the ACK acks something not yet sent (SEG.ACK > SND.NXT) then send an
+   * ACK, drop the segment, and return  */
+  if (seq_gt (vnet_buffer (b)->tcp.ack_number, tc->snd_nxt))
+    {
+      tcp_make_ack (tc, b);
+      *next = tcp_next_output (tc->c_is_ip4);
+      *error = TCP_ERROR_ACK_INVALID;
+      return -1;
+    }
+
+  /* If old ACK, discard */
+  if (seq_lt (vnet_buffer (b)->tcp.ack_number, tc->snd_una))
+    {
+      *error = TCP_ERROR_ACK_OLD;
+      return -1;
+    }
+
+  if (tcp_opts_sack_permitted (&tc->opt))
+    tcp_rcv_sacks (tc, vnet_buffer (b)->tcp.ack_number);
+
+  new_snd_wnd = clib_net_to_host_u32 (th->window) << tc->snd_wscale;
+
+  if (tcp_ack_is_dupack (tc, b, new_snd_wnd))
+    {
+      tcp_cc_rcv_dupack (tc, vnet_buffer (b)->tcp.ack_number);
+      *error = TCP_ERROR_ACK_DUP;
+      return -1;
+    }
+
+  /* Valid ACK */
+  tc->bytes_acked = vnet_buffer (b)->tcp.ack_number - tc->snd_una;
+  tc->snd_una = vnet_buffer (b)->tcp.ack_number;
+
+  /* Dequeue ACKed packet and update RTT */
+  tcp_dequeue_acked (tc, vnet_buffer (b)->tcp.ack_number);
+
+  tcp_update_snd_wnd (tc, vnet_buffer (b)->tcp.seq_number,
+		      vnet_buffer (b)->tcp.ack_number, new_snd_wnd);
+
+  /* Updates congestion control (slow start/congestion avoidance) */
+  tcp_cc_rcv_ack (tc);
+
+  /* If everything has been acked, stop retransmit timer
+   * otherwise update */
+  if (tc->snd_una == tc->snd_una_max)
+    tcp_timer_reset (tc, TCP_TIMER_RETRANSMIT);
+  else
+    tcp_timer_update (tc, TCP_TIMER_RETRANSMIT, tc->rto);
+
+  return 0;
+}
+
+/**
+ * Build SACK list as per RFC2018.
+ *
+ * Makes sure the first block contains the segment that generated the current
+ * ACK and the following ones are the ones most recently reported in SACK
+ * blocks.
+ *
+ * @param tc TCP connection for which the SACK list is updated
+ * @param start Start sequence number of the newest SACK block
+ * @param end End sequence of the newest SACK block
+ */
+static void
+tcp_update_sack_list (tcp_connection_t * tc, u32 start, u32 end)
+{
+  sack_block_t *new_list = 0, block;
+  u32 n_elts;
+  int i;
+  u8 new_head = 0;
+
+  /* If the first segment is ooo add it to the list. Last write might've moved
+   * rcv_nxt over the first segment. */
+  if (seq_lt (tc->rcv_nxt, start))
+    {
+      block.start = start;
+      block.end = end;
+      vec_add1 (new_list, block);
+      new_head = 1;
+    }
+
+  /* Find the blocks still worth keeping. */
+  for (i = 0; i < vec_len (tc->snd_sacks); i++)
+    {
+      /* Discard if:
+       * 1) rcv_nxt advanced beyond current block OR
+       * 2) Segment overlapped by the first segment, i.e., it has been merged
+       *    into it.*/
+      if (seq_leq (tc->snd_sacks[i].start, tc->rcv_nxt)
+	  || seq_leq (tc->snd_sacks[i].start, end))
+	continue;
+
+      /* Save subsequent segments to new SACK list. */
+      n_elts = clib_min (vec_len (tc->snd_sacks) - i,
+			 TCP_MAX_SACK_BLOCKS - new_head);
+      vec_insert_elts (new_list, &tc->snd_sacks[i], n_elts, new_head);
+      break;
+    }
+
+  /* Replace old vector with new one */
+  vec_free (tc->snd_sacks);
+  tc->snd_sacks = new_list;
+}
+
+/** Enqueue data for delivery to application */
+always_inline u32
+tcp_session_enqueue_data (tcp_connection_t * tc, vlib_buffer_t * b,
+			  u16 data_len)
+{
+  int written;
+
+  /* Pure ACK. Update rcv_nxt and be done. */
+  if (PREDICT_FALSE (data_len == 0))
+    {
+      tc->rcv_nxt = vnet_buffer (b)->tcp.seq_end;
+      return TCP_ERROR_PURE_ACK;
+    }
+
+  written = stream_session_enqueue_data (&tc->connection,
+					 vlib_buffer_get_current (b),
+					 data_len, 1 /* queue event */ );
+
+  /* Update rcv_nxt */
+  if (PREDICT_TRUE (written == data_len))
+    {
+      tc->rcv_nxt = vnet_buffer (b)->tcp.seq_end;
+    }
+  /* If more data written than expected, account for out-of-order bytes. */
+  else if (written > data_len)
+    {
+      tc->rcv_nxt = vnet_buffer (b)->tcp.seq_end + written - data_len;
+
+      /* Send ACK confirming the update */
+      tc->flags |= TCP_CONN_SNDACK;
+
+      /* Update SACK list if need be */
+      if (tcp_opts_sack_permitted (&tc->opt))
+	{
+	  /* Remove SACK blocks that have been delivered */
+	  tcp_update_sack_list (tc, tc->rcv_nxt, tc->rcv_nxt);
+	}
+    }
+  else
+    {
+      ASSERT (0);
+      return TCP_ERROR_FIFO_FULL;
+    }
+
+  return TCP_ERROR_ENQUEUED;
+}
+
+/** Enqueue out-of-order data */
+always_inline u32
+tcp_session_enqueue_ooo (tcp_connection_t * tc, vlib_buffer_t * b,
+			 u16 data_len)
+{
+  stream_session_t *s0;
+  u32 offset, seq;
+
+  s0 = stream_session_get (tc->c_s_index, tc->c_thread_index);
+  seq = vnet_buffer (b)->tcp.seq_number;
+  offset = seq - tc->rcv_nxt;
+
+  if (svm_fifo_enqueue_with_offset (s0->server_rx_fifo, s0->pid, offset,
+				    data_len, vlib_buffer_get_current (b)))
+    return TCP_ERROR_FIFO_FULL;
+
+  /* Update SACK list if in use */
+  if (tcp_opts_sack_permitted (&tc->opt))
+    {
+      ooo_segment_t *newest;
+      u32 start, end;
+
+      /* Get the newest segment from the fifo */
+      newest = svm_fifo_newest_ooo_segment (s0->server_rx_fifo);
+      start = tc->rcv_nxt + ooo_segment_offset (s0->server_rx_fifo, newest);
+      end = tc->rcv_nxt + ooo_segment_end_offset (s0->server_rx_fifo, newest);
+
+      tcp_update_sack_list (tc, start, end);
+    }
+
+  return TCP_ERROR_ENQUEUED;
+}
+
+/**
+ * Check if ACK could be delayed. DELACK timer is set only after frame is
+ * processed so this can return true for a full bursts of packets.
+ */
+always_inline int
+tcp_can_delack (tcp_connection_t * tc)
+{
+  /* If there's no DELACK timer set and the last window sent wasn't 0 we
+   * can safely delay. */
+  if (!tcp_timer_is_active (tc, TCP_TIMER_DELACK)
+      && (tc->flags & TCP_CONN_SENT_RCV_WND0) == 0
+      && (tc->flags & TCP_CONN_SNDACK) == 0)
+    return 1;
+
+  return 0;
+}
+
+static int
+tcp_segment_rcv (tcp_main_t * tm, tcp_connection_t * tc, vlib_buffer_t * b,
+		 u16 n_data_bytes, u32 * next0)
+{
+  u32 error = 0;
+
+  /* Handle out-of-order data */
+  if (PREDICT_FALSE (vnet_buffer (b)->tcp.seq_number != tc->rcv_nxt))
+    {
+      error = tcp_session_enqueue_ooo (tc, b, n_data_bytes);
+
+      /* Don't send more than 3 dupacks per burst
+       * XXX decide if this is good */
+      if (tc->snt_dupacks < 3)
+	{
+	  /* RFC2581: Send DUPACK for fast retransmit */
+	  tcp_make_ack (tc, b);
+	  *next0 = tcp_next_output (tc->c_is_ip4);
+
+	  /* Mark as DUPACK. We may filter these in output if
+	   * the burst fills the holes. */
+	  vnet_buffer (b)->tcp.flags = TCP_BUF_FLAG_DUPACK;
+
+	  tc->snt_dupacks++;
+	}
+
+      goto done;
+    }
+
+  /* In order data, enqueue. Fifo figures out by itself if any out-of-order
+   * segments can be enqueued after fifo tail offset changes. */
+  error = tcp_session_enqueue_data (tc, b, n_data_bytes);
+
+  /* Check if ACK can be delayed */
+  if (tcp_can_delack (tc))
+    {
+      /* Nothing to do for pure ACKs */
+      if (n_data_bytes == 0)
+	goto done;
+
+      /* If connection has not been previously marked for delay ack
+       * add it to the list and flag it */
+      if (!tc->flags & TCP_CONN_DELACK)
+	{
+	  vec_add1 (tm->delack_connections[tc->c_thread_index],
+		    tc->c_c_index);
+	  tc->flags |= TCP_CONN_DELACK;
+	}
+    }
+  else
+    {
+      /* Check if a packet has already been enqueued to output for burst.
+       * If yes, then drop this one, otherwise, let it pass through to
+       * output */
+      if ((tc->flags & TCP_CONN_BURSTACK) == 0)
+	{
+	  *next0 = tcp_next_output (tc->c_is_ip4);
+	  tcp_make_ack (tc, b);
+	  error = TCP_ERROR_ENQUEUED;
+
+	  /* TODO: maybe add counter to ensure N acks will be sent/burst */
+	  tc->flags |= TCP_CONN_BURSTACK;
+	}
+    }
+
+done:
+  return error;
+}
+
+void
+delack_timers_init (tcp_main_t * tm, u32 thread_index)
+{
+  tcp_connection_t *tc;
+  u32 i, *conns;
+  tw_timer_wheel_16t_2w_512sl_t *tw;
+
+  tw = &tm->timer_wheels[thread_index];
+  conns = tm->delack_connections[thread_index];
+  for (i = 0; i < vec_len (conns); i++)
+    {
+      tc = pool_elt_at_index (tm->connections[thread_index], conns[i]);
+      ASSERT (0 != tc);
+
+      tc->timers[TCP_TIMER_DELACK]
+	= tw_timer_start_16t_2w_512sl (tw, conns[i],
+				       TCP_TIMER_DELACK, TCP_DELACK_TIME);
+    }
+  vec_reset_length (tm->delack_connections[thread_index]);
+}
+
+always_inline uword
+tcp46_established_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
+			  vlib_frame_t * from_frame, int is_ip4)
+{
+  u32 n_left_from, next_index, *from, *to_next;
+  u32 my_thread_index = vm->cpu_index, errors = 0;
+  tcp_main_t *tm = vnet_get_tcp_main ();
+
+  from = vlib_frame_vector_args (from_frame);
+  n_left_from = from_frame->n_vectors;
+
+  next_index = node->cached_next_index;
+
+  while (n_left_from > 0)
+    {
+      u32 n_left_to_next;
+
+      vlib_get_next_frame (vm, node, next_index, to_next, n_left_to_next);
+
+      while (n_left_from > 0 && n_left_to_next > 0)
+	{
+	  u32 bi0;
+	  vlib_buffer_t *b0;
+	  tcp_header_t *th0 = 0;
+	  tcp_connection_t *tc0;
+	  ip4_header_t *ip40;
+	  ip6_header_t *ip60;
+	  u32 n_advance_bytes0, n_data_bytes0;
+	  u32 next0 = TCP_ESTABLISHED_NEXT_DROP, error0 = TCP_ERROR_ENQUEUED;
+
+	  bi0 = from[0];
+	  to_next[0] = bi0;
+	  from += 1;
+	  to_next += 1;
+	  n_left_from -= 1;
+	  n_left_to_next -= 1;
+
+	  b0 = vlib_get_buffer (vm, bi0);
+	  tc0 = tcp_connection_get (vnet_buffer (b0)->tcp.connection_index,
+				    my_thread_index);
+
+	  /* Checksum computed by ipx_local no need to compute again */
+
+	  if (is_ip4)
+	    {
+	      ip40 = vlib_buffer_get_current (b0);
+	      th0 = ip4_next_header (ip40);
+	      n_advance_bytes0 = (ip4_header_bytes (ip40)
+				  + tcp_header_bytes (th0));
+	      n_data_bytes0 = clib_net_to_host_u16 (ip40->length)
+		- n_advance_bytes0;
+	    }
+	  else
+	    {
+	      ip60 = vlib_buffer_get_current (b0);
+	      th0 = ip6_next_header (ip60);
+	      n_advance_bytes0 = tcp_header_bytes (th0);
+	      n_data_bytes0 = clib_net_to_host_u16 (ip60->payload_length)
+		- n_advance_bytes0;
+	      n_advance_bytes0 += sizeof (ip60[0]);
+	    }
+
+	  /* SYNs, FINs and data consume sequence numbers */
+	  vnet_buffer (b0)->tcp.seq_end = vnet_buffer (b0)->tcp.seq_number
+	    + tcp_is_syn (th0) + tcp_is_fin (th0) + n_data_bytes0;
+
+	  /* TODO header prediction fast path */
+
+	  /* 1-4: check SEQ, RST, SYN */
+	  if (PREDICT_FALSE (tcp_segment_validate (vm, tc0, b0, th0, &next0)))
+	    {
+	      error0 = TCP_ERROR_SEGMENT_INVALID;
+	      goto drop;
+	    }
+
+	  /* 5: check the ACK field  */
+	  if (tcp_rcv_ack (tc0, b0, th0, &next0, &error0))
+	    {
+	      goto drop;
+	    }
+
+	  /* 6: check the URG bit TODO */
+
+	  /* 7: process the segment text */
+	  vlib_buffer_advance (b0, n_advance_bytes0);
+	  error0 = tcp_segment_rcv (tm, tc0, b0, n_data_bytes0, &next0);
+
+	  /* 8: check the FIN bit */
+	  if (tcp_fin (th0))
+	    {
+	      /* Send ACK and enter CLOSE-WAIT */
+	      tcp_make_ack (tc0, b0);
+	      tcp_connection_force_ack (tc0, b0);
+	      next0 = tcp_next_output (tc0->c_is_ip4);
+	      tc0->state = TCP_STATE_CLOSE_WAIT;
+	      stream_session_disconnect_notify (&tc0->connection);
+	    }
+
+	drop:
+	  b0->error = node->errors[error0];
+	  if (PREDICT_FALSE (b0->flags & VLIB_BUFFER_IS_TRACED))
+	    {
+
+	    }
+
+	  vlib_validate_buffer_enqueue_x1 (vm, node, next_index, to_next,
+					   n_left_to_next, bi0, next0);
+	}
+
+      vlib_put_next_frame (vm, node, next_index, n_left_to_next);
+    }
+
+  errors = session_manager_flush_enqueue_events (my_thread_index);
+  if (errors)
+    {
+      if (is_ip4)
+	vlib_node_increment_counter (vm, tcp4_established_node.index,
+				     TCP_ERROR_EVENT_FIFO_FULL, errors);
+      else
+	vlib_node_increment_counter (vm, tcp6_established_node.index,
+				     TCP_ERROR_EVENT_FIFO_FULL, errors);
+    }
+
+  delack_timers_init (tm, my_thread_index);
+
+  return from_frame->n_vectors;
+}
+
+static uword
+tcp4_established (vlib_main_t * vm, vlib_node_runtime_t * node,
+		  vlib_frame_t * from_frame)
+{
+  return tcp46_established_inline (vm, node, from_frame, 1 /* is_ip4 */ );
+}
+
+static uword
+tcp6_established (vlib_main_t * vm, vlib_node_runtime_t * node,
+		  vlib_frame_t * from_frame)
+{
+  return tcp46_established_inline (vm, node, from_frame, 0 /* is_ip4 */ );
+}
+
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (tcp4_established_node) =
+{
+  .function = tcp4_established,
+  .name = "tcp4-established",
+  /* Takes a vector of packets. */
+  .vector_size = sizeof (u32),
+  .n_errors = TCP_N_ERROR,.error_strings = tcp_error_strings,
+  .n_next_nodes = TCP_ESTABLISHED_N_NEXT,
+  .next_nodes =
+  {
+#define _(s,n) [TCP_ESTABLISHED_NEXT_##s] = n,
+    foreach_tcp_state_next
+#undef _
+  },
+};
+/* *INDENT-ON* */
+
+VLIB_NODE_FUNCTION_MULTIARCH (tcp4_established_node, tcp4_established);
+
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (tcp6_established_node) =
+{
+  .function = tcp6_established,
+  .name = "tcp6-established",
+  /* Takes a vector of packets. */
+  .vector_size = sizeof (u32),
+  .n_errors = TCP_N_ERROR,
+  .error_strings = tcp_error_strings,
+  .n_next_nodes = TCP_ESTABLISHED_N_NEXT,
+  .next_nodes =
+  {
+#define _(s,n) [TCP_ESTABLISHED_NEXT_##s] = n,
+    foreach_tcp_state_next
+#undef _
+  },
+};
+/* *INDENT-ON* */
+
+
+VLIB_NODE_FUNCTION_MULTIARCH (tcp6_established_node, tcp6_established);
+
+vlib_node_registration_t tcp4_syn_sent_node;
+vlib_node_registration_t tcp6_syn_sent_node;
+
+always_inline uword
+tcp46_syn_sent_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
+		       vlib_frame_t * from_frame, int is_ip4)
+{
+  tcp_main_t *tm = vnet_get_tcp_main ();
+  u32 n_left_from, next_index, *from, *to_next;
+  u32 my_thread_index = vm->cpu_index, errors = 0;
+  u8 sst = is_ip4 ? SESSION_TYPE_IP4_TCP : SESSION_TYPE_IP6_TCP;
+
+  from = vlib_frame_vector_args (from_frame);
+  n_left_from = from_frame->n_vectors;
+
+  next_index = node->cached_next_index;
+
+  while (n_left_from > 0)
+    {
+      u32 n_left_to_next;
+
+      vlib_get_next_frame (vm, node, next_index, to_next, n_left_to_next);
+
+      while (n_left_from > 0 && n_left_to_next > 0)
+	{
+	  u32 bi0, ack0, seq0;
+	  vlib_buffer_t *b0;
+	  tcp_header_t *tcp0 = 0;
+	  tcp_connection_t *tc0;
+	  ip4_header_t *ip40;
+	  ip6_header_t *ip60;
+	  u32 n_advance_bytes0, n_data_bytes0;
+	  tcp_connection_t *new_tc0;
+	  u32 next0 = TCP_SYN_SENT_NEXT_DROP, error0 = TCP_ERROR_ENQUEUED;
+
+	  bi0 = from[0];
+	  to_next[0] = bi0;
+	  from += 1;
+	  to_next += 1;
+	  n_left_from -= 1;
+	  n_left_to_next -= 1;
+
+	  b0 = vlib_get_buffer (vm, bi0);
+	  tc0 =
+	    tcp_half_open_connection_get (vnet_buffer (b0)->
+					  tcp.connection_index);
+
+	  ack0 = vnet_buffer (b0)->tcp.ack_number;
+	  seq0 = vnet_buffer (b0)->tcp.seq_number;
+
+	  /* Checksum computed by ipx_local no need to compute again */
+
+	  if (is_ip4)
+	    {
+	      ip40 = vlib_buffer_get_current (b0);
+	      tcp0 = ip4_next_header (ip40);
+	      n_advance_bytes0 = (ip4_header_bytes (ip40)
+				  + tcp_header_bytes (tcp0));
+	      n_data_bytes0 = clib_net_to_host_u16 (ip40->length)
+		- n_advance_bytes0;
+	    }
+	  else
+	    {
+	      ip60 = vlib_buffer_get_current (b0);
+	      tcp0 = ip6_next_header (ip60);
+	      n_advance_bytes0 = tcp_header_bytes (tcp0);
+	      n_data_bytes0 = clib_net_to_host_u16 (ip60->payload_length)
+		- n_advance_bytes0;
+	      n_advance_bytes0 += sizeof (ip60[0]);
+	    }
+
+	  if (PREDICT_FALSE
+	      (!tcp_ack (tcp0) && !tcp_rst (tcp0) && !tcp_syn (tcp0)))
+	    goto drop;
+
+	  /* SYNs, FINs and data consume sequence numbers */
+	  vnet_buffer (b0)->tcp.seq_end = seq0 + tcp_is_syn (tcp0)
+	    + tcp_is_fin (tcp0) + n_data_bytes0;
+
+	  /*
+	   *  1. check the ACK bit
+	   */
+
+	  /*
+	   *   If the ACK bit is set
+	   *     If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send a reset (unless
+	   *     the RST bit is set, if so drop the segment and return)
+	   *       <SEQ=SEG.ACK><CTL=RST>
+	   *     and discard the segment.  Return.
+	   *     If SND.UNA =< SEG.ACK =< SND.NXT then the ACK is acceptable.
+	   */
+	  if (tcp_ack (tcp0))
+	    {
+	      if (ack0 <= tc0->iss || ack0 > tc0->snd_nxt)
+		{
+		  if (!tcp_rst (tcp0))
+		    tcp_send_reset (b0, is_ip4);
+
+		  goto drop;
+		}
+
+	      /* Make sure ACK is valid */
+	      if (tc0->snd_una > ack0)
+		goto drop;
+	    }
+
+	  /*
+	   * 2. check the RST bit
+	   */
+
+	  if (tcp_rst (tcp0))
+	    {
+	      /* If ACK is acceptable, signal client that peer is not
+	       * willing to accept connection and drop connection*/
+	      if (tcp_ack (tcp0))
+		{
+		  stream_session_connect_notify (&tc0->connection, sst,
+						 1 /* fail */ );
+		  tcp_connection_cleanup (tc0);
+		}
+	      goto drop;
+	    }
+
+	  /*
+	   * 3. check the security and precedence (skipped)
+	   */
+
+	  /*
+	   * 4. check the SYN bit
+	   */
+
+	  /* No SYN flag. Drop. */
+	  if (!tcp_syn (tcp0))
+	    goto drop;
+
+	  /* Stop connection establishment and retransmit timers */
+	  tcp_timer_reset (tc0, TCP_TIMER_ESTABLISH);
+	  tcp_timer_reset (tc0, TCP_TIMER_RETRANSMIT_SYN);
+
+	  /* Valid SYN or SYN-ACK. Move connection from half-open pool to
+	   * current thread pool. */
+	  pool_get (tm->connections[my_thread_index], new_tc0);
+	  clib_memcpy (new_tc0, tc0, sizeof (*new_tc0));
+
+	  new_tc0->c_thread_index = my_thread_index;
+
+	  /* Cleanup half-open connection XXX lock */
+	  pool_put (tm->half_open_connections, tc0);
+
+	  new_tc0->rcv_nxt = vnet_buffer (b0)->tcp.seq_end;
+	  new_tc0->irs = seq0;
+
+	  /* Parse options */
+	  tcp_options_parse (tcp0, &new_tc0->opt);
+	  tcp_connection_init_vars (new_tc0);
+
+	  if (tcp_opts_tstamp (&new_tc0->opt))
+	    {
+	      new_tc0->tsval_recent = new_tc0->opt.tsval;
+	      new_tc0->tsval_recent_age = tcp_time_now ();
+	    }
+
+	  if (tcp_opts_wscale (&new_tc0->opt))
+	    new_tc0->snd_wscale = new_tc0->opt.wscale;
+
+	  new_tc0->snd_wnd = clib_net_to_host_u32 (tcp0->window)
+	    << new_tc0->snd_wscale;
+	  new_tc0->snd_wl1 = seq0;
+	  new_tc0->snd_wl2 = ack0;
+
+	  /* SYN-ACK: See if we can switch to ESTABLISHED state */
+	  if (tcp_ack (tcp0))
+	    {
+	      /* Our SYN is ACKed: we have iss < ack = snd_una */
+
+	      /* TODO Dequeue acknowledged segments if we support Fast Open */
+	      new_tc0->snd_una = ack0;
+	      new_tc0->state = TCP_STATE_ESTABLISHED;
+
+	      /* Notify app that we have connection */
+	      stream_session_connect_notify (&new_tc0->connection, sst, 0);
+
+	      /* Make sure after data segment processing ACK is sent */
+	      new_tc0->flags |= TCP_CONN_SNDACK;
+	    }
+	  /* SYN: Simultaneous open. Change state to SYN-RCVD and send SYN-ACK */
+	  else
+	    {
+	      new_tc0->state = TCP_STATE_SYN_RCVD;
+
+	      /* Notify app that we have connection XXX */
+	      stream_session_connect_notify (&new_tc0->connection, sst, 0);
+
+	      tcp_make_synack (new_tc0, b0);
+	      next0 = tcp_next_output (is_ip4);
+
+	      goto drop;
+	    }
+
+	  /* Read data, if any */
+	  if (n_data_bytes0)
+	    {
+	      error0 =
+		tcp_segment_rcv (tm, new_tc0, b0, n_data_bytes0, &next0);
+	      if (error0 == TCP_ERROR_PURE_ACK)
+		error0 = TCP_ERROR_SYN_ACKS_RCVD;
+	    }
+	  else
+	    {
+	      tcp_make_ack (new_tc0, b0);
+	      next0 = tcp_next_output (new_tc0->c_is_ip4);
+	    }
+
+	drop:
+
+	  b0->error = error0 ? node->errors[error0] : 0;
+	  if (PREDICT_FALSE (b0->flags & VLIB_BUFFER_IS_TRACED))
+	    {
+
+	    }
+
+	  vlib_validate_buffer_enqueue_x1 (vm, node, next_index, to_next,
+					   n_left_to_next, bi0, next0);
+	}
+
+      vlib_put_next_frame (vm, node, next_index, n_left_to_next);
+    }
+
+  errors = session_manager_flush_enqueue_events (my_thread_index);
+  if (errors)
+    {
+      if (is_ip4)
+	vlib_node_increment_counter (vm, tcp4_established_node.index,
+				     TCP_ERROR_EVENT_FIFO_FULL, errors);
+      else
+	vlib_node_increment_counter (vm, tcp6_established_node.index,
+				     TCP_ERROR_EVENT_FIFO_FULL, errors);
+    }
+
+  return from_frame->n_vectors;
+}
+
+static uword
+tcp4_syn_sent (vlib_main_t * vm, vlib_node_runtime_t * node,
+	       vlib_frame_t * from_frame)
+{
+  return tcp46_syn_sent_inline (vm, node, from_frame, 1 /* is_ip4 */ );
+}
+
+static uword
+tcp6_syn_sent_rcv (vlib_main_t * vm, vlib_node_runtime_t * node,
+		   vlib_frame_t * from_frame)
+{
+  return tcp46_syn_sent_inline (vm, node, from_frame, 0 /* is_ip4 */ );
+}
+
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (tcp4_syn_sent_node) =
+{
+  .function = tcp4_syn_sent,
+  .name = "tcp4-syn-sent",
+  /* Takes a vector of packets. */
+  .vector_size = sizeof (u32),
+  .n_errors = TCP_N_ERROR,
+  .error_strings = tcp_error_strings,
+  .n_next_nodes = TCP_SYN_SENT_N_NEXT,
+  .next_nodes =
+  {
+#define _(s,n) [TCP_SYN_SENT_NEXT_##s] = n,
+    foreach_tcp_state_next
+#undef _
+  },
+};
+/* *INDENT-ON* */
+
+VLIB_NODE_FUNCTION_MULTIARCH (tcp4_syn_sent_node, tcp4_syn_sent);
+
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (tcp6_syn_sent_node) =
+{
+  .function = tcp6_syn_sent_rcv,
+  .name = "tcp6-syn-sent",
+  /* Takes a vector of packets. */
+  .vector_size = sizeof (u32),
+  .n_errors = TCP_N_ERROR,
+  .error_strings = tcp_error_strings,
+  .n_next_nodes = TCP_SYN_SENT_N_NEXT,
+  .next_nodes =
+  {
+#define _(s,n) [TCP_SYN_SENT_NEXT_##s] = n,
+    foreach_tcp_state_next
+#undef _
+  }
+,};
+/* *INDENT-ON* */
+
+VLIB_NODE_FUNCTION_MULTIARCH (tcp6_syn_sent_node, tcp6_syn_sent_rcv);
+/**
+ * Handles reception for all states except LISTEN, SYN-SEND and ESTABLISHED
+ * as per RFC793 p. 64
+ */
+always_inline uword
+tcp46_rcv_process_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
+			  vlib_frame_t * from_frame, int is_ip4)
+{
+  tcp_main_t *tm = vnet_get_tcp_main ();
+  u32 n_left_from, next_index, *from, *to_next;
+  u32 my_thread_index = vm->cpu_index, errors = 0;
+
+  from = vlib_frame_vector_args (from_frame);
+  n_left_from = from_frame->n_vectors;
+
+  next_index = node->cached_next_index;
+
+  while (n_left_from > 0)
+    {
+      u32 n_left_to_next;
+
+      vlib_get_next_frame (vm, node, next_index, to_next, n_left_to_next);
+
+      while (n_left_from > 0 && n_left_to_next > 0)
+	{
+	  u32 bi0;
+	  vlib_buffer_t *b0;
+	  tcp_header_t *tcp0 = 0;
+	  tcp_connection_t *tc0;
+	  ip4_header_t *ip40;
+	  ip6_header_t *ip60;
+	  u32 n_advance_bytes0, n_data_bytes0;
+	  u32 next0 = TCP_RCV_PROCESS_NEXT_DROP, error0 = TCP_ERROR_ENQUEUED;
+
+	  bi0 = from[0];
+	  to_next[0] = bi0;
+	  from += 1;
+	  to_next += 1;
+	  n_left_from -= 1;
+	  n_left_to_next -= 1;
+
+	  b0 = vlib_get_buffer (vm, bi0);
+	  tc0 = tcp_connection_get (vnet_buffer (b0)->tcp.connection_index,
+				    my_thread_index);
+
+	  /* Checksum computed by ipx_local no need to compute again */
+
+	  if (is_ip4)
+	    {
+	      ip40 = vlib_buffer_get_current (b0);
+	      tcp0 = ip4_next_header (ip40);
+	      n_advance_bytes0 = (ip4_header_bytes (ip40)
+				  + tcp_header_bytes (tcp0));
+	      n_data_bytes0 = clib_net_to_host_u16 (ip40->length)
+		- n_advance_bytes0;
+	    }
+	  else
+	    {
+	      ip60 = vlib_buffer_get_current (b0);
+	      tcp0 = ip6_next_header (ip60);
+	      n_advance_bytes0 = tcp_header_bytes (tcp0);
+	      n_data_bytes0 = clib_net_to_host_u16 (ip60->payload_length)
+		- n_advance_bytes0;
+	      n_advance_bytes0 += sizeof (ip60[0]);
+	    }
+
+	  /* SYNs, FINs and data consume sequence numbers */
+	  vnet_buffer (b0)->tcp.seq_end = vnet_buffer (b0)->tcp.seq_number
+	    + tcp_is_syn (tcp0) + tcp_is_fin (tcp0) + n_data_bytes0;
+
+	  /*
+	   * Special treatment for CLOSED
+	   */
+	  switch (tc0->state)
+	    {
+	    case TCP_STATE_CLOSED:
+	      goto drop;
+	      break;
+	    }
+
+	  /*
+	   * For all other states (except LISTEN)
+	   */
+
+	  /* 1-4: check SEQ, RST, SYN */
+	  if (PREDICT_FALSE
+	      (tcp_segment_validate (vm, tc0, b0, tcp0, &next0)))
+	    {
+	      error0 = TCP_ERROR_SEGMENT_INVALID;
+	      goto drop;
+	    }
+
+	  /* 5: check the ACK field  */
+	  switch (tc0->state)
+	    {
+	    case TCP_STATE_SYN_RCVD:
+	      /*
+	       * If the segment acknowledgment is not acceptable, form a
+	       * reset segment,
+	       *  <SEQ=SEG.ACK><CTL=RST>
+	       * and send it.
+	       */
+	      if (!tcp_rcv_ack_is_acceptable (tc0, b0))
+		{
+		  tcp_send_reset (b0, is_ip4);
+		  goto drop;
+		}
+	      /* Switch state to ESTABLISHED */
+	      tc0->state = TCP_STATE_ESTABLISHED;
+
+	      /* Initialize session variables */
+	      tc0->snd_una = vnet_buffer (b0)->tcp.ack_number;
+	      tc0->snd_wnd = clib_net_to_host_u32 (tcp0->window)
+		<< tc0->opt.wscale;
+	      tc0->snd_wl1 = vnet_buffer (b0)->tcp.seq_number;
+	      tc0->snd_wl2 = vnet_buffer (b0)->tcp.ack_number;
+
+	      /* Shoulder tap the server */
+	      stream_session_accept_notify (&tc0->connection);
+
+	      tcp_timer_reset (tc0, TCP_TIMER_RETRANSMIT_SYN);
+	      break;
+	    case TCP_STATE_ESTABLISHED:
+	      /* We can get packets in established state here because they
+	       * were enqueued before state change */
+	      if (tcp_rcv_ack (tc0, b0, tcp0, &next0, &error0))
+		goto drop;
+
+	      break;
+	    case TCP_STATE_FIN_WAIT_1:
+	      /* In addition to the processing for the ESTABLISHED state, if
+	       * our FIN is now acknowledged then enter FIN-WAIT-2 and
+	       * continue processing in that state. */
+	      if (tcp_rcv_ack (tc0, b0, tcp0, &next0, &error0))
+		goto drop;
+	      tc0->state = TCP_STATE_FIN_WAIT_2;
+	      /* Stop all timers, 2MSL will be set lower */
+	      tcp_connection_timers_reset (tc0);
+	      break;
+	    case TCP_STATE_FIN_WAIT_2:
+	      /* In addition to the processing for the ESTABLISHED state, if
+	       * the retransmission queue is empty, the user's CLOSE can be
+	       * acknowledged ("ok") but do not delete the TCB. */
+	      if (tcp_rcv_ack (tc0, b0, tcp0, &next0, &error0))
+		goto drop;
+	      /* check if rtx queue is empty and ack CLOSE TODO */
+	      break;
+	    case TCP_STATE_CLOSE_WAIT:
+	      /* Do the same processing as for the ESTABLISHED state. */
+	      if (tcp_rcv_ack (tc0, b0, tcp0, &next0, &error0))
+		goto drop;
+	      break;
+	    case TCP_STATE_CLOSING:
+	      /* In addition to the processing for the ESTABLISHED state, if
+	       * the ACK acknowledges our FIN then enter the TIME-WAIT state,
+	       * otherwise ignore the segment. */
+	      if (tcp_rcv_ack (tc0, b0, tcp0, &next0, &error0))
+		goto drop;
+
+	      /* XXX test that send queue empty */
+	      tc0->state = TCP_STATE_TIME_WAIT;
+	      goto drop;
+
+	      break;
+	    case TCP_STATE_LAST_ACK:
+	      /* The only thing that can arrive in this state is an
+	       * acknowledgment of our FIN. If our FIN is now acknowledged,
+	       * delete the TCB, enter the CLOSED state, and return. */
+
+	      if (!tcp_rcv_ack_is_acceptable (tc0, b0))
+		goto drop;
+
+	      tcp_connection_del (tc0);
+	      goto drop;
+
+	      break;
+	    case TCP_STATE_TIME_WAIT:
+	      /* The only thing that can arrive in this state is a
+	       * retransmission of the remote FIN. Acknowledge it, and restart
+	       * the 2 MSL timeout. */
+
+	      /* TODO */
+	      goto drop;
+	      break;
+	    default:
+	      ASSERT (0);
+	    }
+
+	  /* 6: check the URG bit TODO */
+
+	  /* 7: process the segment text */
+	  switch (tc0->state)
+	    {
+	    case TCP_STATE_ESTABLISHED:
+	    case TCP_STATE_FIN_WAIT_1:
+	    case TCP_STATE_FIN_WAIT_2:
+	      error0 = tcp_segment_rcv (tm, tc0, b0, n_data_bytes0, &next0);
+	      break;
+	    case TCP_STATE_CLOSE_WAIT:
+	    case TCP_STATE_CLOSING:
+	    case TCP_STATE_LAST_ACK:
+	    case TCP_STATE_TIME_WAIT:
+	      /* This should not occur, since a FIN has been received from the
+	       * remote side.  Ignore the segment text. */
+	      break;
+	    }
+
+	  /* 8: check the FIN bit */
+	  if (!tcp_fin (tcp0))
+	    goto drop;
+
+	  switch (tc0->state)
+	    {
+	    case TCP_STATE_ESTABLISHED:
+	    case TCP_STATE_SYN_RCVD:
+	      /* Send FIN-ACK notify app and enter CLOSE-WAIT */
+	      tcp_connection_timers_reset (tc0);
+	      tcp_make_finack (tc0, b0);
+	      next0 = tcp_next_output (tc0->c_is_ip4);
+	      stream_session_disconnect_notify (&tc0->connection);
+	      tc0->state = TCP_STATE_CLOSE_WAIT;
+	      break;
+	    case TCP_STATE_CLOSE_WAIT:
+	    case TCP_STATE_CLOSING:
+	    case TCP_STATE_LAST_ACK:
+	      /* move along .. */
+	      break;
+	    case TCP_STATE_FIN_WAIT_1:
+	      tc0->state = TCP_STATE_TIME_WAIT;
+	      tcp_connection_timers_reset (tc0);
+	      tcp_timer_set (tc0, TCP_TIMER_2MSL, TCP_2MSL_TIME);
+	      break;
+	    case TCP_STATE_FIN_WAIT_2:
+	      /* Got FIN, send ACK! */
+	      tc0->state = TCP_STATE_TIME_WAIT;
+	      tcp_timer_set (tc0, TCP_TIMER_2MSL, TCP_2MSL_TIME);
+	      tcp_make_ack (tc0, b0);
+	      next0 = tcp_next_output (is_ip4);
+	      break;
+	    case TCP_STATE_TIME_WAIT:
+	      /* Remain in the TIME-WAIT state. Restart the 2 MSL time-wait
+	       * timeout.
+	       */
+	      tcp_timer_update (tc0, TCP_TIMER_2MSL, TCP_2MSL_TIME);
+	      break;
+	    }
+
+	  b0->error = error0 ? node->errors[error0] : 0;
+
+	drop:
+	  if (PREDICT_FALSE (b0->flags & VLIB_BUFFER_IS_TRACED))
+	    {
+
+	    }
+
+	  vlib_validate_buffer_enqueue_x1 (vm, node, next_index, to_next,
+					   n_left_to_next, bi0, next0);
+	}
+
+      vlib_put_next_frame (vm, node, next_index, n_left_to_next);
+    }
+
+  errors = session_manager_flush_enqueue_events (my_thread_index);
+  if (errors)
+    {
+      if (is_ip4)
+	vlib_node_increment_counter (vm, tcp4_established_node.index,
+				     TCP_ERROR_EVENT_FIFO_FULL, errors);
+      else
+	vlib_node_increment_counter (vm, tcp6_established_node.index,
+				     TCP_ERROR_EVENT_FIFO_FULL, errors);
+    }
+
+  return from_frame->n_vectors;
+}
+
+static uword
+tcp4_rcv_process (vlib_main_t * vm, vlib_node_runtime_t * node,
+		  vlib_frame_t * from_frame)
+{
+  return tcp46_rcv_process_inline (vm, node, from_frame, 1 /* is_ip4 */ );
+}
+
+static uword
+tcp6_rcv_process (vlib_main_t * vm, vlib_node_runtime_t * node,
+		  vlib_frame_t * from_frame)
+{
+  return tcp46_rcv_process_inline (vm, node, from_frame, 0 /* is_ip4 */ );
+}
+
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (tcp4_rcv_process_node) =
+{
+  .function = tcp4_rcv_process,
+  .name = "tcp4-rcv-process",
+  /* Takes a vector of packets. */
+  .vector_size = sizeof (u32),
+  .n_errors = TCP_N_ERROR,
+  .error_strings = tcp_error_strings,
+  .n_next_nodes = TCP_RCV_PROCESS_N_NEXT,
+  .next_nodes =
+  {
+#define _(s,n) [TCP_RCV_PROCESS_NEXT_##s] = n,
+    foreach_tcp_state_next
+#undef _
+  },
+};
+/* *INDENT-ON* */
+
+VLIB_NODE_FUNCTION_MULTIARCH (tcp4_rcv_process_node, tcp4_rcv_process);
+
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (tcp6_rcv_process_node) =
+{
+  .function = tcp6_rcv_process,
+  .name = "tcp6-rcv-process",
+  /* Takes a vector of packets. */
+  .vector_size = sizeof (u32),
+  .n_errors = TCP_N_ERROR,
+  .error_strings = tcp_error_strings,
+  .n_next_nodes = TCP_RCV_PROCESS_N_NEXT,
+  .next_nodes =
+  {
+#define _(s,n) [TCP_RCV_PROCESS_NEXT_##s] = n,
+    foreach_tcp_state_next
+#undef _
+  },
+};
+/* *INDENT-ON* */
+
+VLIB_NODE_FUNCTION_MULTIARCH (tcp6_rcv_process_node, tcp6_rcv_process);
+
+vlib_node_registration_t tcp4_listen_node;
+vlib_node_registration_t tcp6_listen_node;
+
+/**
+ * LISTEN state processing as per RFC 793 p. 65
+ */
+always_inline uword
+tcp46_listen_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
+		     vlib_frame_t * from_frame, int is_ip4)
+{
+  u32 n_left_from, next_index, *from, *to_next;
+  u32 my_thread_index = vm->cpu_index;
+  tcp_main_t *tm = vnet_get_tcp_main ();
+  u8 sst = is_ip4 ? SESSION_TYPE_IP4_TCP : SESSION_TYPE_IP6_TCP;
+
+  from = vlib_frame_vector_args (from_frame);
+  n_left_from = from_frame->n_vectors;
+
+  next_index = node->cached_next_index;
+
+  while (n_left_from > 0)
+    {
+      u32 n_left_to_next;
+
+      vlib_get_next_frame (vm, node, next_index, to_next, n_left_to_next);
+
+      while (n_left_from > 0 && n_left_to_next > 0)
+	{
+	  u32 bi0;
+	  vlib_buffer_t *b0;
+	  tcp_header_t *th0 = 0;
+	  tcp_connection_t *lc0;
+	  ip4_header_t *ip40;
+	  ip6_header_t *ip60;
+	  tcp_connection_t *child0;
+	  u32 error0 = TCP_ERROR_SYNS_RCVD, next0 = TCP_LISTEN_NEXT_DROP;
+
+	  bi0 = from[0];
+	  to_next[0] = bi0;
+	  from += 1;
+	  to_next += 1;
+	  n_left_from -= 1;
+	  n_left_to_next -= 1;
+
+	  b0 = vlib_get_buffer (vm, bi0);
+	  lc0 = tcp_listener_get (vnet_buffer (b0)->tcp.connection_index);
+
+	  if (is_ip4)
+	    {
+	      ip40 = vlib_buffer_get_current (b0);
+	      th0 = ip4_next_header (ip40);
+	    }
+	  else
+	    {
+	      ip60 = vlib_buffer_get_current (b0);
+	      th0 = ip6_next_header (ip60);
+	    }
+
+	  /* Create child session. For syn-flood protection use filter */
+
+	  /* 1. first check for an RST */
+	  if (tcp_rst (th0))
+	    goto drop;
+
+	  /* 2. second check for an ACK */
+	  if (tcp_ack (th0))
+	    {
+	      tcp_send_reset (b0, is_ip4);
+	      goto drop;
+	    }
+
+	  /* 3. check for a SYN (did that already) */
+
+	  /* Create child session and send SYN-ACK */
+	  pool_get (tm->connections[my_thread_index], child0);
+	  memset (child0, 0, sizeof (*child0));
+
+	  child0->c_c_index = child0 - tm->connections[my_thread_index];
+	  child0->c_lcl_port = lc0->c_lcl_port;
+	  child0->c_rmt_port = th0->src_port;
+	  child0->c_is_ip4 = is_ip4;
+	  child0->c_thread_index = my_thread_index;
+
+	  if (is_ip4)
+	    {
+	      child0->c_lcl_ip4.as_u32 = ip40->dst_address.as_u32;
+	      child0->c_rmt_ip4.as_u32 = ip40->src_address.as_u32;
+	    }
+	  else
+	    {
+	      clib_memcpy (&child0->c_lcl_ip6, &ip60->dst_address,
+			   sizeof (ip6_address_t));
+	      clib_memcpy (&child0->c_rmt_ip6, &ip60->src_address,
+			   sizeof (ip6_address_t));
+	    }
+
+	  if (stream_session_accept (&child0->connection, lc0->c_s_index, sst,
+				     0 /* notify */ ))
+	    {
+	      error0 = TCP_ERROR_CREATE_SESSION_FAIL;
+	      goto drop;
+	    }
+
+	  tcp_options_parse (th0, &child0->opt);
+	  tcp_connection_init_vars (child0);
+
+	  child0->irs = vnet_buffer (b0)->tcp.seq_number;
+	  child0->rcv_nxt = vnet_buffer (b0)->tcp.seq_number + 1;
+	  child0->state = TCP_STATE_SYN_RCVD;
+
+	  /* RFC1323: TSval timestamps sent on {SYN} and {SYN,ACK}
+	   * segments are used to initialize PAWS. */
+	  if (tcp_opts_tstamp (&child0->opt))
+	    {
+	      child0->tsval_recent = child0->opt.tsval;
+	      child0->tsval_recent_age = tcp_time_now ();
+	    }
+
+	  /* Reuse buffer to make syn-ack and send */
+	  tcp_make_synack (child0, b0);
+	  next0 = tcp_next_output (is_ip4);
+
+	drop:
+	  if (PREDICT_FALSE (b0->flags & VLIB_BUFFER_IS_TRACED))
+	    {
+
+	    }
+
+	  b0->error = error0 ? node->errors[error0] : 0;
+
+	  vlib_validate_buffer_enqueue_x1 (vm, node, next_index, to_next,
+					   n_left_to_next, bi0, next0);
+	}
+
+      vlib_put_next_frame (vm, node, next_index, n_left_to_next);
+    }
+  return from_frame->n_vectors;
+}
+
+static uword
+tcp4_listen (vlib_main_t * vm, vlib_node_runtime_t * node,
+	     vlib_frame_t * from_frame)
+{
+  return tcp46_listen_inline (vm, node, from_frame, 1 /* is_ip4 */ );
+}
+
+static uword
+tcp6_listen (vlib_main_t * vm, vlib_node_runtime_t * node,
+	     vlib_frame_t * from_frame)
+{
+  return tcp46_listen_inline (vm, node, from_frame, 0 /* is_ip4 */ );
+}
+
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (tcp4_listen_node) =
+{
+  .function = tcp4_listen,
+  .name = "tcp4-listen",
+  /* Takes a vector of packets. */
+  .vector_size = sizeof (u32),
+  .n_errors = TCP_N_ERROR,
+  .error_strings = tcp_error_strings,
+  .n_next_nodes = TCP_LISTEN_N_NEXT,
+  .next_nodes =
+  {
+#define _(s,n) [TCP_LISTEN_NEXT_##s] = n,
+    foreach_tcp_state_next
+#undef _
+  },
+};
+/* *INDENT-ON* */
+
+VLIB_NODE_FUNCTION_MULTIARCH (tcp4_listen_node, tcp4_listen);
+
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (tcp6_listen_node) =
+{
+  .function = tcp6_listen,
+  .name = "tcp6-listen",
+  /* Takes a vector of packets. */
+  .vector_size = sizeof (u32),
+  .n_errors = TCP_N_ERROR,
+  .error_strings = tcp_error_strings,
+  .n_next_nodes = TCP_LISTEN_N_NEXT,
+  .next_nodes =
+  {
+#define _(s,n) [TCP_LISTEN_NEXT_##s] = n,
+    foreach_tcp_state_next
+#undef _
+  },
+};
+/* *INDENT-ON* */
+
+VLIB_NODE_FUNCTION_MULTIARCH (tcp6_listen_node, tcp6_listen);
+
+vlib_node_registration_t tcp4_input_node;
+vlib_node_registration_t tcp6_input_node;
+
+typedef enum _tcp_input_next
+{
+  TCP_INPUT_NEXT_DROP,
+  TCP_INPUT_NEXT_LISTEN,
+  TCP_INPUT_NEXT_RCV_PROCESS,
+  TCP_INPUT_NEXT_SYN_SENT,
+  TCP_INPUT_NEXT_ESTABLISHED,
+  TCP_INPUT_NEXT_RESET,
+  TCP_INPUT_N_NEXT
+} tcp_input_next_t;
+
+#define foreach_tcp4_input_next                 \
+  _ (DROP, "error-drop")                        \
+  _ (LISTEN, "tcp4-listen")                     \
+  _ (RCV_PROCESS, "tcp4-rcv-process")           \
+  _ (SYN_SENT, "tcp4-syn-sent")                 \
+  _ (ESTABLISHED, "tcp4-established")		\
+  _ (RESET, "tcp4-reset")
+
+#define foreach_tcp6_input_next                 \
+  _ (DROP, "error-drop")                        \
+  _ (LISTEN, "tcp6-listen")                     \
+  _ (RCV_PROCESS, "tcp6-rcv-process")           \
+  _ (SYN_SENT, "tcp6-syn-sent")                 \
+  _ (ESTABLISHED, "tcp6-established")		\
+  _ (RESET, "tcp6-reset")
+
+typedef struct
+{
+  u16 src_port;
+  u16 dst_port;
+  u8 state;
+} tcp_rx_trace_t;
+
+const char *tcp_fsm_states[] = {
+#define _(sym, str) str,
+  foreach_tcp_fsm_state
+#undef _
+};
+
+u8 *
+format_tcp_state (u8 * s, va_list * args)
+{
+  tcp_state_t *state = va_arg (*args, tcp_state_t *);
+
+  if (state[0] < TCP_N_STATES)
+    s = format (s, "%s", tcp_fsm_states[state[0]]);
+  else
+    s = format (s, "UNKNOWN");
+
+  return s;
+}
+
+u8 *
+format_tcp_rx_trace (u8 * s, va_list * args)
+{
+  CLIB_UNUSED (vlib_main_t * vm) = va_arg (*args, vlib_main_t *);
+  CLIB_UNUSED (vlib_node_t * node) = va_arg (*args, vlib_node_t *);
+  tcp_rx_trace_t *t = va_arg (*args, tcp_rx_trace_t *);
+
+  s = format (s, "TCP: src-port %d dst-port %U%s\n",
+	      clib_net_to_host_u16 (t->src_port),
+	      clib_net_to_host_u16 (t->dst_port), format_tcp_state, t->state);
+
+  return s;
+}
+
+#define filter_flags (TCP_FLAG_SYN|TCP_FLAG_ACK|TCP_FLAG_RST|TCP_FLAG_FIN)
+
+always_inline uword
+tcp46_input_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
+		    vlib_frame_t * from_frame, int is_ip4)
+{
+  u32 n_left_from, next_index, *from, *to_next;
+  u32 my_thread_index = vm->cpu_index;
+  tcp_main_t *tm = vnet_get_tcp_main ();
+  session_manager_main_t *ssm = vnet_get_session_manager_main ();
+
+  from = vlib_frame_vector_args (from_frame);
+  n_left_from = from_frame->n_vectors;
+
+  next_index = node->cached_next_index;
+
+  while (n_left_from > 0)
+    {
+      u32 n_left_to_next;
+
+      vlib_get_next_frame (vm, node, next_index, to_next, n_left_to_next);
+
+      while (n_left_from > 0 && n_left_to_next > 0)
+	{
+	  u32 bi0;
+	  vlib_buffer_t *b0;
+	  tcp_header_t *tcp0 = 0;
+	  tcp_connection_t *tc0;
+	  ip4_header_t *ip40;
+	  ip6_header_t *ip60;
+	  u32 error0 = TCP_ERROR_NO_LISTENER, next0 = TCP_INPUT_NEXT_DROP;
+	  u8 flags0;
+
+	  bi0 = from[0];
+	  to_next[0] = bi0;
+	  from += 1;
+	  to_next += 1;
+	  n_left_from -= 1;
+	  n_left_to_next -= 1;
+
+	  b0 = vlib_get_buffer (vm, bi0);
+
+	  if (is_ip4)
+	    {
+	      ip40 = vlib_buffer_get_current (b0);
+	      tcp0 = ip4_next_header (ip40);
+
+	      /* lookup session */
+	      tc0 =
+		(tcp_connection_t *) stream_session_lookup_transport4 (ssm,
+								       &ip40->dst_address,
+								       &ip40->src_address,
+								       tcp0->dst_port,
+								       tcp0->src_port,
+								       SESSION_TYPE_IP4_TCP,
+								       my_thread_index);
+	    }
+	  else
+	    {
+	      ip60 = vlib_buffer_get_current (b0);
+	      tcp0 = ip6_next_header (ip60);
+	      tc0 =
+		(tcp_connection_t *) stream_session_lookup_transport6 (ssm,
+								       &ip60->src_address,
+								       &ip60->dst_address,
+								       tcp0->src_port,
+								       tcp0->dst_port,
+								       SESSION_TYPE_IP6_TCP,
+								       my_thread_index);
+	    }
+
+	  /* Session exists */
+	  if (PREDICT_TRUE (0 != tc0))
+	    {
+	      /* Save connection index */
+	      vnet_buffer (b0)->tcp.connection_index = tc0->c_c_index;
+	      vnet_buffer (b0)->tcp.seq_number =
+		clib_net_to_host_u32 (tcp0->seq_number);
+	      vnet_buffer (b0)->tcp.ack_number =
+		clib_net_to_host_u32 (tcp0->ack_number);
+
+	      flags0 = tcp0->flags & filter_flags;
+	      next0 = tm->dispatch_table[tc0->state][flags0].next;
+	      error0 = tm->dispatch_table[tc0->state][flags0].error;
+
+	      if (PREDICT_FALSE (error0 == TCP_ERROR_DISPATCH))
+		{
+		  /* Overload tcp flags to store state */
+		  vnet_buffer (b0)->tcp.flags = tc0->state;
+		}
+	    }
+	  else
+	    {
+	      /* Send reset */
+	      next0 = TCP_INPUT_NEXT_RESET;
+	      error0 = TCP_ERROR_NO_LISTENER;
+	      vnet_buffer (b0)->tcp.flags = 0;
+	    }
+
+	  b0->error = error0 ? node->errors[error0] : 0;
+
+	  if (PREDICT_FALSE (b0->flags & VLIB_BUFFER_IS_TRACED))
+	    {
+
+	    }
+
+	  vlib_validate_buffer_enqueue_x1 (vm, node, next_index, to_next,
+					   n_left_to_next, bi0, next0);
+	}
+
+      vlib_put_next_frame (vm, node, next_index, n_left_to_next);
+    }
+
+  return from_frame->n_vectors;
+}
+
+static uword
+tcp4_input (vlib_main_t * vm, vlib_node_runtime_t * node,
+	    vlib_frame_t * from_frame)
+{
+  return tcp46_input_inline (vm, node, from_frame, 1 /* is_ip4 */ );
+}
+
+static uword
+tcp6_input (vlib_main_t * vm, vlib_node_runtime_t * node,
+	    vlib_frame_t * from_frame)
+{
+  return tcp46_input_inline (vm, node, from_frame, 0 /* is_ip4 */ );
+}
+
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (tcp4_input_node) =
+{
+  .function = tcp4_input,
+  .name = "tcp4-input",
+  /* Takes a vector of packets. */
+  .vector_size = sizeof (u32),
+  .n_errors = TCP_N_ERROR,
+  .error_strings = tcp_error_strings,
+  .n_next_nodes = TCP_INPUT_N_NEXT,
+  .next_nodes =
+  {
+#define _(s,n) [TCP_INPUT_NEXT_##s] = n,
+    foreach_tcp4_input_next
+#undef _
+  },
+  .format_buffer = format_tcp_header,
+  .format_trace = format_tcp_rx_trace,
+};
+/* *INDENT-ON* */
+
+VLIB_NODE_FUNCTION_MULTIARCH (tcp4_input_node, tcp4_input);
+
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (tcp6_input_node) =
+{
+  .function = tcp6_input,
+  .name = "tcp6-input",
+  /* Takes a vector of packets. */
+  .vector_size = sizeof (u32),
+  .n_errors = TCP_N_ERROR,
+  .error_strings = tcp_error_strings,
+  .n_next_nodes = TCP_INPUT_N_NEXT,
+  .next_nodes =
+  {
+#define _(s,n) [TCP_INPUT_NEXT_##s] = n,
+    foreach_tcp6_input_next
+#undef _
+  },
+  .format_buffer = format_tcp_header,
+  .format_trace = format_tcp_rx_trace,
+};
+/* *INDENT-ON* */
+
+VLIB_NODE_FUNCTION_MULTIARCH (tcp6_input_node, tcp6_input);
+void
+tcp_update_time (f64 now, u32 thread_index)
+{
+  tcp_main_t *tm = vnet_get_tcp_main ();
+  tw_timer_expire_timers_16t_2w_512sl (&tm->timer_wheels[thread_index], now);
+}
+
+static void
+tcp_dispatch_table_init (tcp_main_t * tm)
+{
+  int i, j;
+  for (i = 0; i < ARRAY_LEN (tm->dispatch_table); i++)
+    for (j = 0; j < ARRAY_LEN (tm->dispatch_table[i]); j++)
+      {
+	tm->dispatch_table[i][j].next = TCP_INPUT_NEXT_DROP;
+	tm->dispatch_table[i][j].error = TCP_ERROR_DISPATCH;
+      }
+
+#define _(t,f,n,e)                                           	\
+do {                                                       	\
+    tm->dispatch_table[TCP_STATE_##t][f].next = (n);         	\
+    tm->dispatch_table[TCP_STATE_##t][f].error = (e);        	\
+} while (0)
+
+  /* SYNs for new connections -> tcp-listen. */
+  _(LISTEN, TCP_FLAG_SYN, TCP_INPUT_NEXT_LISTEN, TCP_ERROR_NONE);
+  /* ACK for for a SYN-ACK -> tcp-rcv-process. */
+  _(SYN_RCVD, TCP_FLAG_ACK, TCP_INPUT_NEXT_RCV_PROCESS, TCP_ERROR_NONE);
+  /* SYN-ACK for a SYN */
+  _(SYN_SENT, TCP_FLAG_SYN | TCP_FLAG_ACK, TCP_INPUT_NEXT_SYN_SENT,
+    TCP_ERROR_NONE);
+  _(SYN_SENT, TCP_FLAG_ACK, TCP_INPUT_NEXT_SYN_SENT, TCP_ERROR_NONE);
+  _(SYN_SENT, TCP_FLAG_RST, TCP_INPUT_NEXT_SYN_SENT, TCP_ERROR_NONE);
+  _(SYN_SENT, TCP_FLAG_RST | TCP_FLAG_ACK, TCP_INPUT_NEXT_SYN_SENT,
+    TCP_ERROR_NONE);
+  /* ACK for for established connection -> tcp-established. */
+  _(ESTABLISHED, TCP_FLAG_ACK, TCP_INPUT_NEXT_ESTABLISHED, TCP_ERROR_NONE);
+  /* FIN for for established connection -> tcp-established. */
+  _(ESTABLISHED, TCP_FLAG_FIN, TCP_INPUT_NEXT_ESTABLISHED, TCP_ERROR_NONE);
+  _(ESTABLISHED, TCP_FLAG_FIN | TCP_FLAG_ACK, TCP_INPUT_NEXT_ESTABLISHED,
+    TCP_ERROR_NONE);
+  /* ACK or FIN-ACK to our FIN */
+  _(FIN_WAIT_1, TCP_FLAG_ACK, TCP_INPUT_NEXT_RCV_PROCESS, TCP_ERROR_NONE);
+  _(FIN_WAIT_1, TCP_FLAG_ACK | TCP_FLAG_FIN, TCP_INPUT_NEXT_RCV_PROCESS,
+    TCP_ERROR_NONE);
+  /* FIN in reply to our FIN from the other side */
+  _(FIN_WAIT_1, TCP_FLAG_FIN, TCP_INPUT_NEXT_RCV_PROCESS, TCP_ERROR_NONE);
+  /* FIN confirming that the peer (app) has closed */
+  _(FIN_WAIT_2, TCP_FLAG_FIN, TCP_INPUT_NEXT_RCV_PROCESS, TCP_ERROR_NONE);
+  _(FIN_WAIT_2, TCP_FLAG_FIN | TCP_FLAG_ACK, TCP_INPUT_NEXT_RCV_PROCESS,
+    TCP_ERROR_NONE);
+  _(LAST_ACK, TCP_FLAG_ACK, TCP_INPUT_NEXT_RCV_PROCESS, TCP_ERROR_NONE);
+#undef _
+}
+
+clib_error_t *
+tcp_input_init (vlib_main_t * vm)
+{
+  clib_error_t *error = 0;
+  tcp_main_t *tm = vnet_get_tcp_main ();
+
+  if ((error = vlib_call_init_function (vm, tcp_init)))
+    return error;
+
+  /* Initialize dispatch table. */
+  tcp_dispatch_table_init (tm);
+
+  return error;
+}
+
+VLIB_INIT_FUNCTION (tcp_input_init);
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */