Improvements to tcp rx path and debugging

- Increment rcv_nxt for fin packets
- Call tcp_segment_rcv only if buffer has data
- Parse rcv opts before deleting half-open connection
- Fix initial rcv_wnd
- Improved event logging

Change-Id: I9b83c04f432c4cec832c480b03e534deff02c3b1
Signed-off-by: Florin Coras <fcoras@cisco.com>

8 files changed, 482 insertions, 169 deletions

diff --git a/src/vnet/tcp/builtin_client.c b/src/vnet/tcp/builtin_client.c
index a92bacaa..744f50e7 100644
--- a/src/vnet/tcp/builtin_client.c
+++ b/src/vnet/tcp/builtin_client.c
@@ -410,9 +410,6 @@ builtin_session_connected_callback (u32 app_index, u32 api_context,
       return -1;
     }
 
-  /* Mark vpp session as connected */
-  s->session_state = SESSION_STATE_READY;
-
   tm->our_event_queue = session_manager_get_vpp_event_queue (s->thread_index);
   tm->vpp_event_queue = session_manager_get_vpp_event_queue (s->thread_index);
 
@@ -466,6 +463,7 @@ builtin_session_reset_callback (stream_session_t * s)
 {
   if (s->session_state == SESSION_STATE_READY)
     clib_warning ("Reset active connection %U", format_stream_session, s, 2);
+  stream_session_cleanup (s);
   return;
 }
 
@@ -478,6 +476,11 @@ builtin_session_create_callback (stream_session_t * s)
 static void
 builtin_session_disconnect_callback (stream_session_t * s)
 {
+  tclient_main_t *tm = &tclient_main;
+  vnet_disconnect_args_t _a, *a = &_a;
+  a->handle = stream_session_handle (s);
+  a->app_index = tm->app_index;
+  vnet_disconnect_session (a);
   return;
 }
 
@@ -521,7 +524,7 @@ attach_builtin_test_clients_app (void)
   options[SESSION_OPTIONS_ACCEPT_COOKIE] = 0x12345678;
   options[SESSION_OPTIONS_SEGMENT_SIZE] = (2ULL << 32);
   options[SESSION_OPTIONS_RX_FIFO_SIZE] = tm->fifo_size;
-  options[SESSION_OPTIONS_TX_FIFO_SIZE] = tm->fifo_size / 2;
+  options[SESSION_OPTIONS_TX_FIFO_SIZE] = tm->fifo_size;
   options[APP_OPTIONS_PRIVATE_SEGMENT_COUNT] = tm->private_segment_count;
   options[APP_OPTIONS_PRIVATE_SEGMENT_SIZE] = tm->private_segment_size;
   options[APP_OPTIONS_PREALLOC_FIFO_PAIRS] = prealloc_fifos;
diff --git a/src/vnet/tcp/builtin_server.c b/src/vnet/tcp/builtin_server.c
index 4ecaf56a..3416678e 100644
--- a/src/vnet/tcp/builtin_server.c
+++ b/src/vnet/tcp/builtin_server.c
@@ -213,15 +213,15 @@ builtin_server_rx_callback (stream_session_t * s)
 	  q = bsm->vpp_queue[thread_index];
 	  if (PREDICT_FALSE (q->cursize == q->maxsize))
 	    clib_warning ("out of event queue space");
-	  else if (unix_shared_memory_queue_add (q, (u8 *) & evt, 0	/* don't wait for mutex */
-		   ))
+	  else if (unix_shared_memory_queue_add (q, (u8 *) & evt, 0))
 	    clib_warning ("failed to enqueue self-tap");
 
-	  bsm->rx_retries[thread_index][s->session_index]++;
 	  if (bsm->rx_retries[thread_index][s->session_index] == 500000)
 	    {
 	      clib_warning ("session stuck: %U", format_stream_session, s, 2);
 	    }
+	  if (bsm->rx_retries[thread_index][s->session_index] < 500001)
+	    bsm->rx_retries[thread_index][s->session_index]++;
 	}
 
       return 0;
@@ -303,7 +303,7 @@ create_api_loopback (vlib_main_t * vm)
 
   /* Wait for reply */
   bsm->node_index = vlib_get_current_process (vm)->node_runtime.node_index;
-  vlib_process_wait_for_event_or_clock (vm, 1.0);
+  vlib_process_wait_for_event_or_clock (vm, 2.0);
   event_type = vlib_process_get_events (vm, &event_data);
   switch (event_type)
     {
diff --git a/src/vnet/tcp/tcp.c b/src/vnet/tcp/tcp.c
index 8ed325d2..a2214158 100644
--- a/src/vnet/tcp/tcp.c
+++ b/src/vnet/tcp/tcp.c
@@ -163,6 +163,33 @@ tcp_connection_del (tcp_connection_t * tc)
   tcp_connection_cleanup (tc);
 }
 
+/**
+ * Cleanup half-open connection
+ */
+void
+tcp_half_open_connection_del (tcp_connection_t * tc)
+{
+  tcp_main_t *tm = vnet_get_tcp_main ();
+  if (CLIB_DEBUG)
+    memset (tc, 0xFA, sizeof (*tc));
+  clib_spinlock_lock (&tm->half_open_lock);
+  pool_put (tm->half_open_connections, tc);
+  clib_spinlock_unlock (&tm->half_open_lock);
+}
+
+tcp_connection_t *
+tcp_connection_new (u8 thread_index)
+{
+  tcp_main_t *tm = vnet_get_tcp_main ();
+  tcp_connection_t *tc;
+
+  pool_get (tm->connections[thread_index], tc);
+  memset (tc, 0, sizeof (*tc));
+  tc->c_c_index = tc - tm->connections[thread_index];
+  tc->c_thread_index = thread_index;
+  return tc;
+}
+
 /** Notify session that connection has been reset.
  *
  * Switch state to closed and wait for session to call cleanup.
@@ -170,6 +197,7 @@ tcp_connection_del (tcp_connection_t * tc)
 void
 tcp_connection_reset (tcp_connection_t * tc)
 {
+  TCP_EVT_DBG (TCP_EVT_RST_RCVD, tc);
   switch (tc->state)
     {
     case TCP_STATE_SYN_RCVD:
@@ -178,12 +206,18 @@ tcp_connection_reset (tcp_connection_t * tc)
       tcp_connection_cleanup (tc);
       break;
     case TCP_STATE_SYN_SENT:
+      /* XXX remove sst from call */
+      stream_session_connect_notify (&tc->connection, tc->connection.proto,
+				     1 /* fail */ );
+      tcp_connection_cleanup (tc);
+      break;
     case TCP_STATE_ESTABLISHED:
     case TCP_STATE_CLOSE_WAIT:
     case TCP_STATE_FIN_WAIT_1:
     case TCP_STATE_FIN_WAIT_2:
     case TCP_STATE_CLOSING:
       tc->state = TCP_STATE_CLOSED;
+      TCP_EVT_DBG (TCP_EVT_STATE_CHANGE, tc);
 
       /* Make sure all timers are cleared */
       tcp_connection_timers_reset (tc);
@@ -227,6 +261,7 @@ tcp_connection_close (tcp_connection_t * tc)
     tc->state = TCP_STATE_CLOSED;
   else if (tc->state == TCP_STATE_CLOSE_WAIT)
     tc->state = TCP_STATE_LAST_ACK;
+  TCP_EVT_DBG (TCP_EVT_STATE_CHANGE, tc);
 
   /* If in CLOSED and WAITCLOSE timer is not set, delete connection now */
   if (tc->timers[TCP_TIMER_WAITCLOSE] == TCP_TIMER_HANDLE_INVALID
@@ -250,6 +285,7 @@ tcp_session_cleanup (u32 conn_index, u32 thread_index)
 
   /* Wait for the session tx events to clear */
   tc->state = TCP_STATE_CLOSED;
+  TCP_EVT_DBG (TCP_EVT_STATE_CHANGE, tc);
   tcp_timer_update (tc, TCP_TIMER_WAITCLOSE, TCP_CLEANUP_TIME);
 }
 
@@ -287,7 +323,7 @@ ip_interface_get_first_ip (u32 sw_if_index, u8 is_ip4)
  * Allocate local port and add if successful add entry to local endpoint
  * table to mark the pair as used.
  */
-u16
+int
 tcp_allocate_local_port (tcp_main_t * tm, ip46_address_t * ip)
 {
   transport_endpoint_t *tep;
@@ -484,7 +520,7 @@ tcp_connection_open (ip46_address_t * rmt_addr, u16 rmt_port, u8 is_ip4)
   fib_node_index_t fei;
   u32 sw_if_index;
   ip46_address_t lcl_addr;
-  u16 lcl_port;
+  int lcl_port;
 
   /*
    * Find the local address and allocate port
@@ -500,12 +536,19 @@ tcp_connection_open (ip46_address_t * rmt_addr, u16 rmt_port, u8 is_ip4)
 
   /* Couldn't find route to destination. Bail out. */
   if (fei == FIB_NODE_INDEX_INVALID)
-    return -1;
+    {
+      clib_warning ("no route to destination");
+      return -1;
+    }
 
   sw_if_index = fib_entry_get_resolving_interface (fei);
 
   if (sw_if_index == (u32) ~ 0)
-    return -1;
+    {
+      clib_warning ("no resolving interface for %U", format_ip46_address,
+		    rmt_addr, IP46_TYPE_IP4);
+      return -1;
+    }
 
   if (is_ip4)
     {
@@ -570,11 +613,9 @@ tcp_connection_open (ip46_address_t * rmt_addr, u16 rmt_port, u8 is_ip4)
   /* The other connection vars will be initialized after SYN ACK */
   tcp_connection_timers_init (tc);
 
-  tcp_send_syn (tc);
-
-  tc->state = TCP_STATE_SYN_SENT;
-
   TCP_EVT_DBG (TCP_EVT_OPEN, tc);
+  tc->state = TCP_STATE_SYN_SENT;
+  tcp_send_syn (tc);
 
   return tc->c_c_index;
 }
@@ -1206,7 +1247,7 @@ tcp_main_enable (vlib_main_t * vm)
   clib_bihash_init_24_8 (&tm->local_endpoints_table, "local endpoint table",
 			 200000 /* $$$$ config parameter nbuckets */ ,
 			 (64 << 20) /*$$$ config parameter table size */ );
-
+  clib_spinlock_init (&tm->half_open_lock);
   return error;
 }
 
diff --git a/src/vnet/tcp/tcp.h b/src/vnet/tcp/tcp.h
index fd0d02b9..89c30616 100644
--- a/src/vnet/tcp/tcp.h
+++ b/src/vnet/tcp/tcp.h
@@ -33,6 +33,7 @@
 
 #define TCP_DUPACK_THRESHOLD 	3
 #define TCP_MAX_RX_FIFO_SIZE 	4 << 20
+#define TCP_MIN_RX_FIFO_SIZE	4 << 10
 #define TCP_IW_N_SEGMENTS 	10
 #define TCP_ALWAYS_ACK		1	/**< On/off delayed acks */
 #define TCP_USE_SACKS		1	/**< Disable only for testing */
@@ -371,11 +372,9 @@ typedef struct _tcp_main
   /* Per worker-thread timer wheel for connections timers */
   tw_timer_wheel_16t_2w_512sl_t *timer_wheels;
 
-//  /* Convenience per worker-thread vector of connections to DELACK */
-//  u32 **delack_connections;
-
   /* Pool of half-open connections on which we've sent a SYN */
   tcp_connection_t *half_open_connections;
+  clib_spinlock_t half_open_lock;
 
   /* Pool of local TCP endpoints */
   transport_endpoint_t *local_endpoints;
@@ -455,6 +454,8 @@ tcp_get_connection_from_transport (transport_connection_t * tconn)
 void tcp_connection_close (tcp_connection_t * tc);
 void tcp_connection_cleanup (tcp_connection_t * tc);
 void tcp_connection_del (tcp_connection_t * tc);
+void tcp_half_open_connection_del (tcp_connection_t * tc);
+tcp_connection_t *tcp_connection_new (u8 thread_index);
 void tcp_connection_reset (tcp_connection_t * tc);
 
 u8 *format_tcp_connection_id (u8 * s, va_list * args);
@@ -472,13 +473,15 @@ tcp_listener_get (u32 tli)
 always_inline tcp_connection_t *
 tcp_half_open_connection_get (u32 conn_index)
 {
+  if (pool_is_free_index (tcp_main.half_open_connections, conn_index))
+    return 0;
   return pool_elt_at_index (tcp_main.half_open_connections, conn_index);
 }
 
 void tcp_make_ack (tcp_connection_t * ts, vlib_buffer_t * b);
 void tcp_make_fin (tcp_connection_t * tc, vlib_buffer_t * b);
 void tcp_make_synack (tcp_connection_t * ts, vlib_buffer_t * b);
-void tcp_send_reset (vlib_buffer_t * pkt, u8 is_ip4);
+void tcp_send_reset (tcp_connection_t * tc, vlib_buffer_t * pkt, u8 is_ip4);
 void tcp_send_syn (tcp_connection_t * tc);
 void tcp_send_fin (tcp_connection_t * tc);
 void tcp_init_mss (tcp_connection_t * tc);
@@ -658,7 +661,6 @@ tcp_timer_update (tcp_connection_t * tc, u8 timer_id, u32 interval)
 				 tc->c_c_index, timer_id, interval);
 }
 
-/* XXX Switch retransmit to faster TW */
 always_inline void
 tcp_retransmit_timer_set (tcp_connection_t * tc)
 {
diff --git a/src/vnet/tcp/tcp_debug.h b/src/vnet/tcp/tcp_debug.h
index be51bca2..e3da56f4 100755
--- a/src/vnet/tcp/tcp_debug.h
+++ b/src/vnet/tcp/tcp_debug.h
@@ -19,10 +19,9 @@
 #include <vlib/vlib.h>
 
 #define TCP_DEBUG (1)
-#define TCP_DEBUG_SM (0)
-#define TCP_DEBUG_CC (1)
-#define TCP_DEBUG_CC_STAT (1)
-#define TCP_DEBUG_SM_VERBOSE (0)
+#define TCP_DEBUG_SM (2)
+#define TCP_DEBUG_CC (0)
+#define TCP_DEBUG_CC_STAT (0)
 
 #define foreach_tcp_dbg_evt		\
   _(INIT, "")				\
@@ -33,7 +32,9 @@
   _(UNBIND, "unbind")			\
   _(DELETE, "delete")			\
   _(SYN_SENT, "SYN sent")		\
-  _(SYN_RTX, "SYN retransmit")		\
+  _(SYNACK_SENT, "SYNACK sent")		\
+  _(SYNACK_RCVD, "SYNACK rcvd")		\
+  _(SYN_RXT, "SYN retransmit")		\
   _(FIN_SENT, "FIN sent")		\
   _(ACK_SENT, "ACK sent")		\
   _(DUPACK_SENT, "DUPACK sent")		\
@@ -43,6 +44,7 @@
   _(DUPACK_RCVD, "DUPACK rcvd")		\
   _(FIN_RCVD, "FIN rcvd")		\
   _(RST_RCVD, "RST rcvd")		\
+  _(STATE_CHANGE, "state change")	\
   _(PKTIZE, "packetize")		\
   _(INPUT, "in")			\
   _(SND_WND, "snd_wnd update")		\
@@ -96,11 +98,64 @@ typedef enum _tcp_dbg_evt
   ed = ELOG_TRACK_DATA (&vlib_global_main.elog_main,			\
 			_e, _tc->c_elog_track)
 
-#define TCP_EVT_INIT_HANDLER(_tc, _fmt, ...)				\
+#define TCP_DBG_IP_TAG_LCL(_tc)						\
 {									\
-  _tc->c_elog_track.name = 						\
-	(char *) format (0, _fmt, _tc->c_c_index, 0);			\
+  if (_tc->c_is_ip4)							\
+    {									\
+      ELOG_TYPE_DECLARE (_e) =						\
+      {									\
+        .format = "lcl: %d.%d.%d.%d:%d",				\
+        .format_args = "i4i4i4i4i4",					\
+      };								\
+      DECLARE_ETD(_tc, _e, 5);						\
+      ed->data[0] = _tc->c_lcl_ip.ip4.as_u8[0];				\
+      ed->data[1] = _tc->c_lcl_ip.ip4.as_u8[1];				\
+      ed->data[2] = _tc->c_lcl_ip.ip4.as_u8[2];				\
+      ed->data[3] = _tc->c_lcl_ip.ip4.as_u8[3];				\
+      ed->data[4] = clib_net_to_host_u16(_tc->c_lcl_port);		\
+    }									\
+}
+
+#define TCP_DBG_IP_TAG_RMT(_tc)						\
+{									\
+  if (_tc->c_is_ip4)							\
+    {									\
+      ELOG_TYPE_DECLARE (_e) =						\
+      {									\
+        .format = "rmt: %d.%d.%d.%d:%d",				\
+        .format_args = "i4i4i4i4i4",					\
+      };								\
+      DECLARE_ETD(_tc, _e, 5);						\
+      ed->data[0] = _tc->c_rmt_ip.ip4.as_u8[0];				\
+      ed->data[1] = _tc->c_rmt_ip.ip4.as_u8[1];				\
+      ed->data[2] = _tc->c_rmt_ip.ip4.as_u8[2];				\
+      ed->data[3] = _tc->c_rmt_ip.ip4.as_u8[3];				\
+      ed->data[4] = clib_net_to_host_u16(_tc->c_rmt_port);		\
+    }									\
+}
+
+#define TCP_EVT_INIT_HANDLER(_tc, _is_l, ...)				\
+{									\
+  char *_fmt = _is_l ? "l[%d].%d:%d%c" : "[%d].%d:%d->.%d:%d%c";	\
+  if (_tc->c_is_ip4)							\
+    {									\
+      _tc->c_elog_track.name =						\
+  	(char *) format (0, _fmt, _tc->c_thread_index, 			\
+			 _tc->c_lcl_ip.ip4.as_u8[3],			\
+			 clib_net_to_host_u16(_tc->c_lcl_port),		\
+			 _tc->c_rmt_ip.ip4.as_u8[3], 			\
+			 clib_net_to_host_u16(_tc->c_rmt_port), 0);	\
+    }									\
+  else									\
+      _tc->c_elog_track.name =						\
+	(char *) format (0, _fmt, _tc->c_thread_index, 			\
+			 _tc->c_lcl_ip.ip6.as_u8[15],			\
+			 clib_net_to_host_u16(_tc->c_lcl_port),		\
+			 _tc->c_rmt_ip.ip6.as_u8[15], 			\
+			 clib_net_to_host_u16(_tc->c_rmt_port), 0);	\
   elog_track_register (&vlib_global_main.elog_main, &_tc->c_elog_track);\
+  TCP_DBG_IP_TAG_LCL(_tc);						\
+  TCP_DBG_IP_TAG_RMT(_tc);						\
 }
 
 #define TCP_EVT_DEALLOC_HANDLER(_tc, ...)				\
@@ -110,7 +165,7 @@ typedef enum _tcp_dbg_evt
 
 #define TCP_EVT_OPEN_HANDLER(_tc, ...)					\
 {									\
-  TCP_EVT_INIT_HANDLER(_tc, "s%d%c");					\
+  TCP_EVT_INIT_HANDLER(_tc, 0);						\
   ELOG_TYPE_DECLARE (_e) =						\
   {									\
     .format = "open: index %d",						\
@@ -133,7 +188,7 @@ typedef enum _tcp_dbg_evt
 
 #define TCP_EVT_BIND_HANDLER(_tc, ...)					\
 {									\
-  TCP_EVT_INIT_HANDLER(_tc, "l%d%c");					\
+  TCP_EVT_INIT_HANDLER(_tc, 1);						\
   ELOG_TYPE_DECLARE (_e) =						\
   {									\
     .format = "bind: listener %d",					\
@@ -166,18 +221,6 @@ typedef enum _tcp_dbg_evt
   TCP_EVT_DEALLOC_HANDLER(_tc);						\
 }
 
-#define TCP_EVT_SYN_RCVD_HANDLER(_tc, ...)				\
-{									\
-  TCP_EVT_INIT_HANDLER(_tc, "s%d%c");					\
-  ELOG_TYPE_DECLARE (_e) =						\
-  {									\
-    .format = "SYNrx: irs %u",						\
-    .format_args = "i4",						\
-  };									\
-  DECLARE_ETD(_tc, _e, 1);						\
-  ed->data[0] = _tc->irs;						\
-}
-
 #define CONCAT_HELPER(_a, _b) _a##_b
 #define CC(_a, _b) CONCAT_HELPER(_a, _b)
 #define TCP_EVT_DBG(_evt, _args...) CC(_evt, _HANDLER)(_args)
@@ -190,63 +233,86 @@ typedef enum _tcp_dbg_evt
  */
 #if TCP_DEBUG_SM
 
-#define TCP_EVT_ACK_SENT_HANDLER(_tc, ...)				\
+#define TCP_EVT_STATE_CHANGE_HANDLER(_tc, ...)				\
 {									\
   ELOG_TYPE_DECLARE (_e) =						\
   {									\
-    .format = "ack_tx: acked %u rcv_nxt %u rcv_wnd %u snd_nxt %u snd_wnd %u",\
-    .format_args = "i4i4i4i4i4",					\
+    .format = "state: %s",						\
+    .format_args = "t4",						\
+    .n_enum_strings = 11,						\
+    .enum_strings = {                                           	\
+      "closed",	                                             		\
+      "listen",                                                 	\
+      "syn-sent",                                                 	\
+      "syn-rcvd",							\
+      "established",							\
+      "close_wait",							\
+      "fin-wait-1",							\
+      "last-ack",							\
+      "closing",							\
+      "fin-wait-2",							\
+      "time-wait",							\
+    },  								\
   };									\
-  DECLARE_ETD(_tc, _e, 5);						\
-  ed->data[0] = _tc->rcv_nxt - _tc->rcv_las;				\
-  ed->data[1] = _tc->rcv_nxt - _tc->irs;				\
-  ed->data[2] = _tc->rcv_wnd;						\
-  ed->data[3] = _tc->snd_nxt - _tc->iss;				\
-  ed->data[4] = _tc->snd_wnd;						\
+  DECLARE_ETD(_tc, _e, 1);						\
+  ed->data[0] = _tc->state;						\
 }
 
-#define TCP_EVT_DUPACK_SENT_HANDLER(_tc, ...)				\
+#define TCP_EVT_SYN_RCVD_HANDLER(_tc, ...)				\
 {									\
+  TCP_EVT_INIT_HANDLER(_tc, 0);						\
   ELOG_TYPE_DECLARE (_e) =						\
   {									\
-    .format = "dack_tx: rcv_nxt %u rcv_wnd %u snd_nxt %u av_wnd %u snd_wnd %u",\
-    .format_args = "i4i4i4i4i4",					\
+    .format = "syn-rx: irs %u",						\
+    .format_args = "i4",						\
   };									\
-  DECLARE_ETD(_tc, _e, 5);						\
-  ed->data[0] = _tc->rcv_nxt - _tc->irs;				\
-  ed->data[1] = _tc->rcv_wnd;						\
-  ed->data[2] = _tc->snd_nxt - _tc->iss;				\
-  ed->data[3] = tcp_available_wnd(_tc);					\
-  ed->data[4] = _tc->snd_wnd;						\
+  DECLARE_ETD(_tc, _e, 1);						\
+  ed->data[0] = _tc->irs;						\
+  TCP_EVT_STATE_CHANGE_HANDLER(_tc);					\
 }
 
 #define TCP_EVT_SYN_SENT_HANDLER(_tc, ...)				\
 {									\
   ELOG_TYPE_DECLARE (_e) =						\
   {									\
-    .format = "SYNtx: iss %u",						\
+    .format = "syn-tx: iss %u",						\
     .format_args = "i4",						\
   };									\
   DECLARE_ETD(_tc, _e, 1);						\
   ed->data[0] = _tc->iss;						\
+  TCP_EVT_STATE_CHANGE_HANDLER(_tc);					\
 }
 
-#define TCP_EVT_SYN_RTX_HANDLER(_tc, ...)				\
+#define TCP_EVT_SYNACK_SENT_HANDLER(_tc, ...)				\
 {									\
   ELOG_TYPE_DECLARE (_e) =						\
   {									\
-    .format = "SYNrtx: iss %u",						\
-    .format_args = "i4",						\
+    .format = "synack-tx: iss %u irs %u",				\
+    .format_args = "i4i4",						\
   };									\
-  DECLARE_ETD(_tc, _e, 1);						\
+  DECLARE_ETD(_tc, _e, 2);						\
+  ed->data[0] = _tc->iss;						\
+  ed->data[1] = _tc->irs;						\
+}
+
+#define TCP_EVT_SYNACK_RCVD_HANDLER(_tc, ...)				\
+{									\
+  ELOG_TYPE_DECLARE (_e) =						\
+  {									\
+    .format = "synack-rx: iss %u irs %u",				\
+    .format_args = "i4i4",						\
+  };									\
+  DECLARE_ETD(_tc, _e, 2);						\
   ed->data[0] = _tc->iss;						\
+  ed->data[1] = _tc->irs;						\
+  TCP_EVT_STATE_CHANGE_HANDLER(_tc);					\
 }
 
 #define TCP_EVT_FIN_SENT_HANDLER(_tc, ...)				\
 {									\
   ELOG_TYPE_DECLARE (_e) =						\
   {									\
-    .format = "FINtx: snd_nxt %d rcv_nxt %d",				\
+    .format = "fin-tx: snd_nxt %d rcv_nxt %d",				\
     .format_args = "i4i4",						\
   };									\
   DECLARE_ETD(_tc, _e, 2);						\
@@ -258,19 +324,20 @@ typedef enum _tcp_dbg_evt
 {									\
   ELOG_TYPE_DECLARE (_e) =						\
   {									\
-    .format = "RSTtx: snd_nxt %d rcv_nxt %d",				\
+    .format = "rst-tx: snd_nxt %d rcv_nxt %d",				\
     .format_args = "i4i4",						\
   };									\
   DECLARE_ETD(_tc, _e, 2);						\
   ed->data[0] = _tc->snd_nxt - _tc->iss;				\
   ed->data[1] = _tc->rcv_nxt - _tc->irs;				\
+  TCP_EVT_STATE_CHANGE_HANDLER(_tc);					\
 }
 
 #define TCP_EVT_FIN_RCVD_HANDLER(_tc, ...)				\
 {									\
   ELOG_TYPE_DECLARE (_e) =						\
   {									\
-    .format = "FINrx: snd_nxt %d rcv_nxt %d",				\
+    .format = "fin-rx: snd_nxt %d rcv_nxt %d",				\
     .format_args = "i4i4",						\
   };									\
   DECLARE_ETD(_tc, _e, 2);						\
@@ -282,7 +349,7 @@ typedef enum _tcp_dbg_evt
 {									\
   ELOG_TYPE_DECLARE (_e) =						\
   {									\
-    .format = "RSTrx: snd_nxt %d rcv_nxt %d",				\
+    .format = "rst-rx: snd_nxt %d rcv_nxt %d",				\
     .format_args = "i4i4",						\
   };									\
   DECLARE_ETD(_tc, _e, 2);						\
@@ -290,6 +357,67 @@ typedef enum _tcp_dbg_evt
   ed->data[1] = _tc->rcv_nxt - _tc->irs;				\
 }
 
+#define TCP_EVT_SYN_RXT_HANDLER(_tc, _type, ...)			\
+{									\
+  ELOG_TYPE_DECLARE (_e) =						\
+  {									\
+    .format = "%s-rxt: iss %u",						\
+    .format_args = "t4i4",						\
+    .n_enum_strings = 2,						\
+    .enum_strings = {                                           	\
+	"syn",	                                             		\
+        "syn-ack",							\
+    },  								\
+  };									\
+  DECLARE_ETD(_tc, _e, 2);						\
+  ed->data[0] = _type;							\
+  ed->data[1] = _tc->iss;						\
+}
+
+#else
+#define TCP_EVT_SYN_SENT_HANDLER(_tc, ...)
+#define TCP_EVT_SYNACK_SENT_HANDLER(_tc, ...)
+#define TCP_EVT_SYNACK_RCVD_HANDLER(_tc, ...)
+#define TCP_EVT_SYN_RXT_HANDLER(_tc, ...)
+#define TCP_EVT_FIN_SENT_HANDLER(_tc, ...)
+#define TCP_EVT_RST_SENT_HANDLER(_tc, ...)
+#define TCP_EVT_FIN_RCVD_HANDLER(_tc, ...)
+#define TCP_EVT_RST_RCVD_HANDLER(_tc, ...)
+#define TCP_EVT_STATE_CHANGE_HANDLER(_tc, ...)
+#endif
+
+#if TCP_DEBUG_SM > 1
+
+#define TCP_EVT_ACK_SENT_HANDLER(_tc, ...)				\
+{									\
+  ELOG_TYPE_DECLARE (_e) =						\
+  {									\
+    .format = "ack-tx: acked %u rcv_nxt %u rcv_wnd %u snd_nxt %u snd_wnd %u",\
+    .format_args = "i4i4i4i4i4",					\
+  };									\
+  DECLARE_ETD(_tc, _e, 5);						\
+  ed->data[0] = _tc->rcv_nxt - _tc->rcv_las;				\
+  ed->data[1] = _tc->rcv_nxt - _tc->irs;				\
+  ed->data[2] = _tc->rcv_wnd;						\
+  ed->data[3] = _tc->snd_nxt - _tc->iss;				\
+  ed->data[4] = _tc->snd_wnd;						\
+}
+
+#define TCP_EVT_DUPACK_SENT_HANDLER(_tc, ...)				\
+{									\
+  ELOG_TYPE_DECLARE (_e) =						\
+  {									\
+    .format = "dack-tx: rcv_nxt %u rcv_wnd %u snd_nxt %u av_wnd %u snd_wnd %u",\
+    .format_args = "i4i4i4i4i4",					\
+  };									\
+  DECLARE_ETD(_tc, _e, 5);						\
+  ed->data[0] = _tc->rcv_nxt - _tc->irs;				\
+  ed->data[1] = _tc->rcv_wnd;						\
+  ed->data[2] = _tc->snd_nxt - _tc->iss;				\
+  ed->data[3] = tcp_available_wnd(_tc);					\
+  ed->data[4] = _tc->snd_wnd;						\
+}
+
 #define TCP_EVT_ACK_RCVD_HANDLER(_tc, ...)				\
 {									\
   ELOG_TYPE_DECLARE (_e) =						\
@@ -309,7 +437,7 @@ typedef enum _tcp_dbg_evt
 {									\
   ELOG_TYPE_DECLARE (_e) =						\
   {									\
-    .format = "dack_rx: snd_una %u cwnd %u snd_wnd %u flight %u rcv_wnd %u",\
+    .format = "dack-rx: snd_una %u cwnd %u snd_wnd %u flight %u rcv_wnd %u",\
     .format_args = "i4i4i4i4i4",					\
   };									\
   DECLARE_ETD(_tc, _e, 5);						\
@@ -370,7 +498,7 @@ typedef enum _tcp_dbg_evt
     }                                                           	\
   ELOG_TYPE_DECLARE (_e) =                                      	\
   {                                                             	\
-    .format = "TimerPop: %s (%d)",                              	\
+    .format = "timer-pop: %s (%d)",                              	\
     .format_args = "t4i4",                                      	\
     .n_enum_strings = 7,                                        	\
     .enum_strings = {                                           	\
@@ -391,7 +519,8 @@ typedef enum _tcp_dbg_evt
     }									\
   else									\
     {									\
-      clib_warning ("pop for unexisting connection %d", _tc_index);	\
+      clib_warning ("pop %d for unexisting connection %d", _timer_id,	\
+		    _tc_index);						\
     }									\
 }
 
@@ -414,7 +543,7 @@ typedef enum _tcp_dbg_evt
 {									\
   ELOG_TYPE_DECLARE (_e) =						\
   {									\
-    .format = "paws fail: seq %u end %u tsval %u tsval_recent %u",	\
+    .format = "paws-err: seq %u end %u tsval %u tsval_recent %u",	\
     .format_args = "i4i4i4i4",						\
   };									\
   DECLARE_ETD(_tc, _e, 4);						\
@@ -465,12 +594,6 @@ if (_av > 0) 								\
 #else
 #define TCP_EVT_ACK_SENT_HANDLER(_tc, ...)
 #define TCP_EVT_DUPACK_SENT_HANDLER(_tc, ...)
-#define TCP_EVT_SYN_SENT_HANDLER(_tc, ...)
-#define TCP_EVT_SYN_RTX_HANDLER(_tc, ...)
-#define TCP_EVT_FIN_SENT_HANDLER(_tc, ...)
-#define TCP_EVT_RST_SENT_HANDLER(_tc, ...)
-#define TCP_EVT_FIN_RCVD_HANDLER(_tc, ...)
-#define TCP_EVT_RST_RCVD_HANDLER(_tc, ...)
 #define TCP_EVT_ACK_RCVD_HANDLER(_tc, ...)
 #define TCP_EVT_DUPACK_RCVD_HANDLER(_tc, ...)
 #define TCP_EVT_PKTIZE_HANDLER(_tc, ...)
@@ -485,12 +608,12 @@ if (_av > 0) 								\
 /*
  * State machine verbose
  */
-#if TCP_DBG_SM_VERBOSE
+#if TCP_DEBUG_SM > 2
 #define TCP_EVT_SND_WND_HANDLER(_tc, ...)				\
 {									\
   ELOG_TYPE_DECLARE (_e) =						\
   {									\
-    .format = "snd_wnd update: %u ",					\
+    .format = "snd-wnd update: %u ",					\
     .format_args = "i4",						\
   };									\
   DECLARE_ETD(_tc, _e, 1);						\
@@ -617,6 +740,7 @@ if (_tc->c_cc_stat_tstamp + STATS_INTERVAL < tcp_time_now())		\
 #define TCP_EVT_CC_RTX_HANDLER(_tc, offset, n_bytes, ...)
 #define TCP_EVT_CC_EVT_HANDLER(_tc, _sub_evt, ...)
 #define TCP_EVT_CC_PACK_HANDLER(_tc, ...)
+#define TCP_EVT_CC_STAT_HANDLER(_tc, ...)
 #endif
 
 #endif /* SRC_VNET_TCP_TCP_DEBUG_H_ */
diff --git a/src/vnet/tcp/tcp_input.c b/src/vnet/tcp/tcp_input.c
index bc7d9015..cc5cecdc 100644
--- a/src/vnet/tcp/tcp_input.c
+++ b/src/vnet/tcp/tcp_input.c
@@ -349,7 +349,10 @@ tcp_segment_validate (vlib_main_t * vm, tcp_connection_t * tc0,
   /* 4th: check the SYN bit */
   if (tcp_syn (th0))
     {
-      tcp_send_reset (b0, tc0->c_is_ip4);
+      /* TODO implement RFC 5961 */
+      tcp_make_ack (tc0, b0);
+      *next0 = tcp_next_output (tc0->c_is_ip4);
+      TCP_EVT_DBG (TCP_EVT_SYN_RCVD, tc0);
       return -1;
     }
 
@@ -1246,8 +1249,6 @@ tcp_rcv_ack (tcp_connection_t * tc, vlib_buffer_t * b,
    * Looks okay, process feedback
    */
 
-  TCP_EVT_DBG (TCP_EVT_ACK_RCVD, tc);
-
   if (tcp_opts_sack_permitted (&tc->rcv_opts))
     tcp_rcv_sacks (tc, vnet_buffer (b)->tcp.ack_number);
 
@@ -1263,6 +1264,8 @@ tcp_rcv_ack (tcp_connection_t * tc, vlib_buffer_t * b,
   if (tc->bytes_acked)
     tcp_dequeue_acked (tc, vnet_buffer (b)->tcp.ack_number);
 
+  TCP_EVT_DBG (TCP_EVT_ACK_RCVD, tc);
+
   /*
    * Check if we have congestion event
    */
@@ -1496,9 +1499,13 @@ tcp_can_delack (tcp_connection_t * tc)
 
 static int
 tcp_segment_rcv (tcp_main_t * tm, tcp_connection_t * tc, vlib_buffer_t * b,
-		 u16 n_data_bytes, u32 * next0)
+		 u32 * next0)
 {
-  u32 error = 0, n_bytes_to_drop;
+  u32 error = 0, n_bytes_to_drop, n_data_bytes;
+
+  vlib_buffer_advance (b, vnet_buffer (b)->tcp.data_offset);
+  n_data_bytes = vnet_buffer (b)->tcp.data_len;
+  ASSERT (n_data_bytes);
 
   /* Handle out-of-order data */
   if (PREDICT_FALSE (vnet_buffer (b)->tcp.seq_number != tc->rcv_nxt))
@@ -1512,7 +1519,12 @@ tcp_segment_rcv (tcp_main_t * tm, tcp_connection_t * tc, vlib_buffer_t * b,
 
 	  /* Completely in the past (possible retransmit) */
 	  if (seq_leq (vnet_buffer (b)->tcp.seq_end, tc->rcv_nxt))
-	    goto done;
+	    {
+	      /* Ack retransmissions since we may not have any data to send */
+	      tcp_make_ack (tc, b);
+	      *next0 = tcp_next_output (tc->c_is_ip4);
+	      goto done;
+	    }
 
 	  /* Chop off the bytes in the past */
 	  n_bytes_to_drop = tc->rcv_nxt - vnet_buffer (b)->tcp.seq_number;
@@ -1550,12 +1562,6 @@ in_order:
    * segments can be enqueued after fifo tail offset changes. */
   error = tcp_session_enqueue_data (tc, b, n_data_bytes);
 
-  if (n_data_bytes == 0)
-    {
-      *next0 = TCP_NEXT_DROP;
-      goto done;
-    }
-
   /* Check if ACK can be delayed */
   if (tcp_can_delack (tc))
     {
@@ -1680,7 +1686,9 @@ tcp46_established_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	    }
 
 	  th0 = tcp_buffer_hdr (b0);
-	  is_fin = (th0->flags & TCP_FLAG_FIN) != 0;
+	  /* N.B. buffer is rewritten if segment is ooo. Thus, th0 becomes a
+	   * dangling reference. */
+	  is_fin = tcp_is_fin (th0);
 
 	  /* SYNs, FINs and data consume sequence numbers */
 	  vnet_buffer (b0)->tcp.seq_end = vnet_buffer (b0)->tcp.seq_number
@@ -1700,29 +1708,23 @@ tcp46_established_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 
 	  /* 5: check the ACK field  */
 	  if (tcp_rcv_ack (tc0, b0, th0, &next0, &error0))
-	    {
-	      goto done;
-	    }
+	    goto done;
 
 	  /* 6: check the URG bit TODO */
 
 	  /* 7: process the segment text */
-
-	  vlib_buffer_advance (b0, vnet_buffer (b0)->tcp.data_offset);
-	  error0 = tcp_segment_rcv (tm, tc0, b0,
-				    vnet_buffer (b0)->tcp.data_len, &next0);
-
-	  /* N.B. buffer is rewritten if segment is ooo. Thus, th0 becomes a
-	   * dangling reference. */
+	  if (vnet_buffer (b0)->tcp.data_len)
+	    error0 = tcp_segment_rcv (tm, tc0, b0, &next0);
 
 	  /* 8: check the FIN bit */
-	  if (is_fin)
+	  if (PREDICT_FALSE (is_fin))
 	    {
 	      /* Enter CLOSE-WAIT and notify session. Don't send ACK, instead
 	       * wait for session to call close. To avoid lingering
 	       * in CLOSE-WAIT, set timer (reuse WAITCLOSE). */
 	      tc0->state = TCP_STATE_CLOSE_WAIT;
 	      TCP_EVT_DBG (TCP_EVT_FIN_RCVD, tc0);
+	      tc0->rcv_nxt += (vnet_buffer (b0)->tcp.data_len == 0);
 	      stream_session_disconnect_notify (&tc0->connection);
 	      tcp_timer_set (tc0, TCP_TIMER_WAITCLOSE, TCP_CLOSEWAIT_TIME);
 	    }
@@ -1856,6 +1858,21 @@ tcp46_syn_sent_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	  seq0 = vnet_buffer (b0)->tcp.seq_number;
 	  tcp0 = tcp_buffer_hdr (b0);
 
+	  if (!tc0)
+	    {
+	      ip4_header_t *ip40 = vlib_buffer_get_current (b0);
+	      tcp0 = ip4_next_header (ip40);
+	      tc0 =
+		(tcp_connection_t *)
+		stream_session_lookup_transport_wt4 (&ip40->dst_address,
+						     &ip40->src_address,
+						     tcp0->dst_port,
+						     tcp0->src_port,
+						     SESSION_TYPE_IP4_TCP,
+						     my_thread_index);
+	      ASSERT (0);
+	      goto drop;
+	    }
 	  if (PREDICT_FALSE
 	      (!tcp_ack (tcp0) && !tcp_rst (tcp0) && !tcp_syn (tcp0)))
 	    goto drop;
@@ -1881,8 +1898,7 @@ tcp46_syn_sent_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	      if (ack0 <= tc0->iss || ack0 > tc0->snd_nxt)
 		{
 		  if (!tcp_rst (tcp0))
-		    tcp_send_reset (b0, is_ip4);
-
+		    tcp_send_reset (tc0, b0, is_ip4);
 		  goto drop;
 		}
 
@@ -1900,11 +1916,7 @@ tcp46_syn_sent_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	      /* 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);
-		}
+		tcp_connection_reset (tc0);
 	      goto drop;
 	    }
 
@@ -1920,6 +1932,10 @@ tcp46_syn_sent_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	  if (!tcp_syn (tcp0))
 	    goto drop;
 
+	  /* Parse options */
+	  if (tcp_options_parse (tcp0, &tc0->rcv_opts))
+	    goto drop;
+
 	  /* Stop connection establishment and retransmit timers */
 	  tcp_timer_reset (tc0, TCP_TIMER_ESTABLISH);
 	  tcp_timer_reset (tc0, TCP_TIMER_RETRANSMIT_SYN);
@@ -1928,19 +1944,11 @@ tcp46_syn_sent_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	   * 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;
 	  new_tc0->c_c_index = new_tc0 - tm->connections[my_thread_index];
-
-	  /* Cleanup half-open connection XXX lock */
-	  pool_put (tm->half_open_connections, tc0);
-
+	  new_tc0->c_thread_index = my_thread_index;
 	  new_tc0->rcv_nxt = vnet_buffer (b0)->tcp.seq_end;
 	  new_tc0->irs = seq0;
-
-	  /* Parse options */
-	  if (tcp_options_parse (tcp0, &new_tc0->rcv_opts))
-	    goto drop;
+	  tcp_half_open_connection_del (tc0);
 
 	  if (tcp_opts_tstamp (&new_tc0->rcv_opts))
 	    {
@@ -1959,7 +1967,7 @@ tcp46_syn_sent_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	  tcp_connection_init_vars (new_tc0);
 
 	  /* SYN-ACK: See if we can switch to ESTABLISHED state */
-	  if (tcp_ack (tcp0))
+	  if (PREDICT_TRUE (tcp_ack (tcp0)))
 	    {
 	      /* Our SYN is ACKed: we have iss < ack = snd_una */
 
@@ -1976,7 +1984,7 @@ tcp46_syn_sent_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 						 0))
 		{
 		  tcp_connection_cleanup (new_tc0);
-		  tcp_send_reset (b0, is_ip4);
+		  tcp_send_reset (tc0, b0, is_ip4);
 		  goto drop;
 		}
 
@@ -1986,6 +1994,7 @@ tcp46_syn_sent_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	      /* Update rtt with the syn-ack sample */
 	      new_tc0->bytes_acked = 1;
 	      tcp_update_rtt (new_tc0, vnet_buffer (b0)->tcp.ack_number);
+	      TCP_EVT_DBG (TCP_EVT_SYNACK_RCVD, new_tc0);
 	    }
 	  /* SYN: Simultaneous open. Change state to SYN-RCVD and send SYN-ACK */
 	  else
@@ -1997,12 +2006,12 @@ tcp46_syn_sent_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 		  (&new_tc0->connection, sst, 0))
 		{
 		  tcp_connection_cleanup (new_tc0);
-		  tcp_send_reset (b0, is_ip4);
+		  tcp_send_reset (tc0, b0, is_ip4);
+		  TCP_EVT_DBG (TCP_EVT_RST_SENT, tc0);
 		  goto drop;
 		}
 
 	      tc0->rtt_ts = 0;
-
 	      tcp_make_synack (new_tc0, b0);
 	      next0 = tcp_next_output (is_ip4);
 
@@ -2010,12 +2019,10 @@ tcp46_syn_sent_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	    }
 
 	  /* Read data, if any */
-	  if (vnet_buffer (b0)->tcp.data_len)
+	  if (PREDICT_FALSE (vnet_buffer (b0)->tcp.data_len))
 	    {
-	      vlib_buffer_advance (b0, vnet_buffer (b0)->tcp.data_offset);
-	      error0 = tcp_segment_rcv (tm, new_tc0, b0,
-					vnet_buffer (b0)->tcp.data_len,
-					&next0);
+	      ASSERT (0);
+	      error0 = tcp_segment_rcv (tm, new_tc0, b0, &next0);
 	      if (error0 == TCP_ERROR_PURE_ACK)
 		error0 = TCP_ERROR_SYN_ACKS_RCVD;
 	    }
@@ -2114,6 +2121,7 @@ VLIB_REGISTER_NODE (tcp6_syn_sent_node) =
 /* *INDENT-ON* */
 
 VLIB_NODE_FUNCTION_MULTIARCH (tcp6_syn_sent_node, tcp6_syn_sent_rcv);
+
 /**
  * Handles reception for all states except LISTEN, SYN-SENT and ESTABLISHED
  * as per RFC793 p. 64
@@ -2202,7 +2210,7 @@ tcp46_rcv_process_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	       */
 	      if (!tcp_rcv_ack_is_acceptable (tc0, b0))
 		{
-		  tcp_send_reset (b0, is_ip4);
+		  tcp_send_reset (tc0, b0, is_ip4);
 		  goto drop;
 		}
 
@@ -2243,6 +2251,8 @@ tcp46_rcv_process_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 		{
 		  ASSERT (tcp_fin (tcp0));
 		  tc0->state = TCP_STATE_FIN_WAIT_2;
+		  TCP_EVT_DBG (TCP_EVT_STATE_CHANGE, tc0);
+
 		  /* Stop all timers, 2MSL will be set lower */
 		  tcp_connection_timers_reset (tc0);
 		}
@@ -2269,6 +2279,7 @@ tcp46_rcv_process_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 
 	      /* XXX test that send queue empty */
 	      tc0->state = TCP_STATE_TIME_WAIT;
+	      TCP_EVT_DBG (TCP_EVT_STATE_CHANGE, tc0);
 	      goto drop;
 
 	      break;
@@ -2289,6 +2300,7 @@ tcp46_rcv_process_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 		}
 
 	      tc0->state = TCP_STATE_CLOSED;
+	      TCP_EVT_DBG (TCP_EVT_STATE_CHANGE, tc0);
 
 	      /* Don't delete the connection/session yet. Instead, wait a
 	       * reasonable amount of time until the pipes are cleared. In
@@ -2329,10 +2341,8 @@ tcp46_rcv_process_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	    case TCP_STATE_ESTABLISHED:
 	    case TCP_STATE_FIN_WAIT_1:
 	    case TCP_STATE_FIN_WAIT_2:
-	      vlib_buffer_advance (b0, vnet_buffer (b0)->tcp.data_offset);
-	      error0 = tcp_segment_rcv (tm, tc0, b0,
-					vnet_buffer (b0)->tcp.data_len,
-					&next0);
+	      if (vnet_buffer (b0)->tcp.data_len)
+		error0 = tcp_segment_rcv (tm, tc0, b0, &next0);
 	      break;
 	    case TCP_STATE_CLOSE_WAIT:
 	    case TCP_STATE_CLOSING:
@@ -2357,6 +2367,7 @@ tcp46_rcv_process_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	      next0 = tcp_next_output (tc0->c_is_ip4);
 	      stream_session_disconnect_notify (&tc0->connection);
 	      tc0->state = TCP_STATE_CLOSE_WAIT;
+	      TCP_EVT_DBG (TCP_EVT_STATE_CHANGE, tc0);
 	      break;
 	    case TCP_STATE_CLOSE_WAIT:
 	    case TCP_STATE_CLOSING:
@@ -2367,6 +2378,7 @@ tcp46_rcv_process_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	      tc0->state = TCP_STATE_TIME_WAIT;
 	      tcp_connection_timers_reset (tc0);
 	      tcp_timer_set (tc0, TCP_TIMER_WAITCLOSE, TCP_2MSL_TIME);
+	      TCP_EVT_DBG (TCP_EVT_STATE_CHANGE, tc0);
 	      break;
 	    case TCP_STATE_FIN_WAIT_2:
 	      /* Got FIN, send ACK! */
@@ -2375,6 +2387,7 @@ tcp46_rcv_process_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	      tcp_timer_set (tc0, TCP_TIMER_WAITCLOSE, TCP_CLOSEWAIT_TIME);
 	      tcp_make_ack (tc0, b0);
 	      next0 = tcp_next_output (is_ip4);
+	      TCP_EVT_DBG (TCP_EVT_STATE_CHANGE, tc0);
 	      break;
 	    case TCP_STATE_TIME_WAIT:
 	      /* Remain in the TIME-WAIT state. Restart the 2 MSL time-wait
@@ -2486,7 +2499,6 @@ tcp46_listen_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 {
   u32 n_left_from, next_index, *from, *to_next;
   u32 my_thread_index = vm->thread_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);
@@ -2549,14 +2561,10 @@ tcp46_listen_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	  /* 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 = tcp_connection_new (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;
 	  child0->state = TCP_STATE_SYN_RCVD;
 
 	  if (is_ip4)
@@ -2605,7 +2613,6 @@ tcp46_listen_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	  child0->snd_wl2 = vnet_buffer (b0)->tcp.ack_number;
 
 	  tcp_connection_init_vars (child0);
-
 	  TCP_EVT_DBG (TCP_EVT_SYN_RCVD, child0);
 
 	  /* Reuse buffer to make syn-ack and send */
@@ -2722,6 +2729,31 @@ typedef enum _tcp_input_next
 
 #define filter_flags (TCP_FLAG_SYN|TCP_FLAG_ACK|TCP_FLAG_RST|TCP_FLAG_FIN)
 
+static u8
+tcp_lookup_is_valid (tcp_connection_t * tc, tcp_header_t * hdr)
+{
+  transport_connection_t *tmp;
+  if (!tc)
+    return 1;
+
+  u8 is_valid = (tc->c_lcl_port == hdr->dst_port
+		 && (tc->state == TCP_STATE_LISTEN
+		     || tc->c_rmt_port == hdr->src_port));
+
+  if (!is_valid)
+    {
+      if ((tmp = stream_session_lookup_half_open (&tc->connection)))
+	{
+	  if (tmp->lcl_port == hdr->dst_port
+	      && tmp->rmt_port == hdr->src_port)
+	    {
+	      clib_warning ("half-open is valid!");
+	    }
+	}
+    }
+  return is_valid;
+}
+
 always_inline uword
 tcp46_input_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 		    vlib_frame_t * from_frame, int is_ip4)
@@ -2774,7 +2806,6 @@ tcp46_input_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	      n_data_bytes0 = clib_net_to_host_u16 (ip40->length)
 		- n_advance_bytes0;
 
-	      /* lookup session */
 	      tc0 =
 		(tcp_connection_t *)
 		stream_session_lookup_transport_wt4 (&ip40->dst_address,
@@ -2783,6 +2814,7 @@ tcp46_input_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 						     tcp0->src_port,
 						     SESSION_TYPE_IP4_TCP,
 						     my_thread_index);
+	      ASSERT (tcp_lookup_is_valid (tc0, tcp0));
 	    }
 	  else
 	    {
@@ -2795,12 +2827,13 @@ tcp46_input_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 
 	      tc0 =
 		(tcp_connection_t *)
-		stream_session_lookup_transport_wt6 (&ip60->src_address,
-						     &ip60->dst_address,
-						     tcp0->src_port,
+		stream_session_lookup_transport_wt6 (&ip60->dst_address,
+						     &ip60->src_address,
 						     tcp0->dst_port,
+						     tcp0->src_port,
 						     SESSION_TYPE_IP6_TCP,
 						     my_thread_index);
+	      ASSERT (tcp_lookup_is_valid (tc0, tcp0));
 	    }
 
 	  /* Length check */
diff --git a/src/vnet/tcp/tcp_output.c b/src/vnet/tcp/tcp_output.c
index 35f3eba1..5e9ecf11 100644
--- a/src/vnet/tcp/tcp_output.c
+++ b/src/vnet/tcp/tcp_output.c
@@ -75,12 +75,34 @@ tcp_window_compute_scale (u32 available_space)
 }
 
 /**
- * TCP's IW as recommended by RFC6928
+ * Update max segment size we're able to process.
+ *
+ * The value is constrained by our interface's MTU and IP options. It is
+ * also what we advertise to our peer.
+ */
+void
+tcp_update_rcv_mss (tcp_connection_t * tc)
+{
+  /* TODO find our iface MTU */
+  tc->mss = dummy_mtu;
+}
+
+/**
+ * TCP's initial window
  */
 always_inline u32
 tcp_initial_wnd_unscaled (tcp_connection_t * tc)
 {
-  return TCP_IW_N_SEGMENTS * tc->mss;
+  /* RFC 6928 recommends the value lower. However at the time our connections
+   * are initialized, fifos may not be allocated. Therefore, advertise the
+   * smallest possible unscaled window size and update once fifos are
+   * assigned to the session.
+   */
+  /*
+     tcp_update_rcv_mss (tc);
+     TCP_IW_N_SEGMENTS * tc->mss;
+   */
+  return TCP_MIN_RX_FIFO_SIZE;
 }
 
 /**
@@ -373,19 +395,6 @@ tcp_make_options (tcp_connection_t * tc, tcp_options_t * opts,
 }
 
 /**
- * Update max segment size we're able to process.
- *
- * The value is constrained by our interface's MTU and IP options. It is
- * also what we advertise to our peer.
- */
-void
-tcp_update_rcv_mss (tcp_connection_t * tc)
-{
-  /* TODO find our iface MTU */
-  tc->mss = dummy_mtu;
-}
-
-/**
  * Update snd_mss to reflect the effective segment size that we can send
  * by taking into account all TCP options, including SACKs
  */
@@ -576,6 +585,7 @@ tcp_make_synack (tcp_connection_t * tc, vlib_buffer_t * b)
 
   /* Init retransmit timer */
   tcp_retransmit_timer_set (tc);
+  TCP_EVT_DBG (TCP_EVT_SYNACK_SENT, tc);
 }
 
 always_inline void
@@ -684,7 +694,7 @@ tcp_make_reset_in_place (vlib_main_t * vm, vlib_buffer_t * b0,
  *  Send reset without reusing existing buffer
  */
 void
-tcp_send_reset (vlib_buffer_t * pkt, u8 is_ip4)
+tcp_send_reset (tcp_connection_t * tc, vlib_buffer_t * pkt, u8 is_ip4)
 {
   vlib_buffer_t *b;
   u32 bi;
@@ -720,7 +730,7 @@ tcp_send_reset (vlib_buffer_t * pkt, u8 is_ip4)
     {
       flags = TCP_FLAG_RST;
       seq = pkt_th->ack_number;
-      ack = 0;
+      ack = (tc && tc->state >= TCP_STATE_SYN_RCVD) ? tc->rcv_nxt : 0;
     }
   else
     {
@@ -754,6 +764,7 @@ tcp_send_reset (vlib_buffer_t * pkt, u8 is_ip4)
     }
 
   tcp_enqueue_to_ip_lookup (vm, b, bi, is_ip4);
+  TCP_EVT_DBG (TCP_EVT_RST_SENT, tc);
 }
 
 void
@@ -839,6 +850,7 @@ tcp_send_syn (tcp_connection_t * tc)
 
   tcp_push_ip_hdr (tm, tc, b);
   tcp_enqueue_to_ip_lookup (vm, b, bi, tc->c_is_ip4);
+  TCP_EVT_DBG (TCP_EVT_SYN_SENT, tc);
 }
 
 always_inline void
@@ -1148,12 +1160,13 @@ tcp_timer_retransmit_handler_i (u32 index, u8 is_syn)
 	tc->rto = clib_min (tc->rto << 1, TCP_RTO_MAX);
 
       vlib_buffer_make_headroom (b, MAX_HDRS_LEN);
-
       tcp_push_hdr_i (tc, b, tc->state, 1);
 
       /* Account for the SYN */
       tc->snd_nxt += 1;
       tc->rtt_ts = 0;
+      TCP_EVT_DBG (TCP_EVT_SYN_RXT, tc,
+		   (tc->state == TCP_STATE_SYN_SENT ? 0 : 1));
     }
   else
     {
@@ -1173,8 +1186,6 @@ tcp_timer_retransmit_handler_i (u32 index, u8 is_syn)
     {
       ASSERT (tc->state == TCP_STATE_SYN_SENT);
 
-      TCP_EVT_DBG (TCP_EVT_SYN_RTX, tc);
-
       /* This goes straight to ipx_lookup */
       tcp_push_ip_hdr (tm, tc, b);
       tcp_enqueue_to_ip_lookup (vm, b, bi, tc->c_is_ip4);
diff --git a/src/vnet/tcp/tcp_test.c b/src/vnet/tcp/tcp_test.c
index f37ba96d..5c40ddf9 100644
--- a/src/vnet/tcp/tcp_test.c
+++ b/src/vnet/tcp/tcp_test.c
@@ -1551,6 +1551,101 @@ tcp_test_fifo (vlib_main_t * vm, unformat_input_t * input)
 }
 
 static int
+tcp_test_lookup (vlib_main_t * vm, unformat_input_t * input)
+{
+  session_manager_main_t *smm = &session_manager_main;
+  tcp_main_t *tm = &tcp_main;
+  transport_connection_t _tc1, *tc1 = &_tc1, _tc2, *tc2 = &_tc2, *tconn;
+  tcp_connection_t *tc;
+  stream_session_t *s;
+  u8 cmp = 0;
+
+  pool_get (smm->sessions[0], s);
+  memset (s, 0, sizeof (*s));
+  s->session_index = s - smm->sessions[0];
+
+  pool_get (tm->connections[0], tc);
+  memset (tc, 0, sizeof (*tc));
+  tc->connection.c_index = tc - tm->connections[0];
+  tc->connection.s_index = s->session_index;
+  s->connection_index = tc->connection.c_index;
+
+  tc->connection.lcl_ip.ip4.as_u32 = clib_host_to_net_u32 (0x06000101);
+  tc->connection.rmt_ip.ip4.as_u32 = clib_host_to_net_u32 (0x06000103);
+  tc->connection.lcl_port = 35051;
+  tc->connection.rmt_port = 53764;
+  tc->connection.proto = 0;
+  clib_memcpy (tc1, &tc->connection, sizeof (*tc1));
+
+  pool_get (session_manager_main.sessions[0], s);
+  memset (s, 0, sizeof (*s));
+  s->session_index = s - smm->sessions[0];
+  pool_get (tm->connections[0], tc);
+  memset (tc, 0, sizeof (*tc));
+  tc->connection.c_index = tc - tm->connections[0];
+  tc->connection.s_index = s->session_index;
+  s->connection_index = tc->connection.c_index;
+
+  tc->connection.lcl_ip.ip4.as_u32 = clib_host_to_net_u32 (0x06000101);
+  tc->connection.rmt_ip.ip4.as_u32 = clib_host_to_net_u32 (0x06000102);
+  tc->connection.lcl_port = 38225;
+  tc->connection.rmt_port = 53764;
+  tc->connection.proto = 0;
+  clib_memcpy (tc2, &tc->connection, sizeof (*tc2));
+
+  /*
+   * Confirm that connection lookup works
+   */
+
+  stream_session_table_add_for_tc (tc1, tc1->s_index);
+  tconn = stream_session_lookup_transport_wt4 (&tc1->lcl_ip.ip4,
+					       &tc1->rmt_ip.ip4,
+					       tc1->lcl_port, tc1->rmt_port,
+					       tc1->proto, 0);
+  cmp = (memcmp (&tconn->rmt_ip, &tc1->rmt_ip, sizeof (tc1->rmt_ip)) == 0);
+  TCP_TEST ((cmp), "rmt ip is identical %d", cmp);
+  TCP_TEST ((tconn->lcl_port == tc1->lcl_port),
+	    "rmt port is identical %d", tconn->lcl_port == tc1->lcl_port);
+
+  /*
+   * Non-existing connection lookup should not work
+   */
+
+  tconn = stream_session_lookup_transport_wt4 (&tc2->lcl_ip.ip4,
+					       &tc2->rmt_ip.ip4,
+					       tc2->lcl_port, tc2->rmt_port,
+					       tc2->proto, 0);
+  TCP_TEST ((tconn == 0), "lookup result should be null");
+
+  /*
+   * Delete and lookup again
+   */
+  stream_session_table_del_for_tc (tc1);
+  tconn = stream_session_lookup_transport_wt4 (&tc1->lcl_ip.ip4,
+					       &tc1->rmt_ip.ip4,
+					       tc1->lcl_port, tc1->rmt_port,
+					       tc1->proto, 0);
+  TCP_TEST ((tconn == 0), "lookup result should be null");
+  tconn = stream_session_lookup_transport_wt4 (&tc2->lcl_ip.ip4,
+					       &tc2->rmt_ip.ip4,
+					       tc2->lcl_port, tc2->rmt_port,
+					       tc2->proto, 0);
+  TCP_TEST ((tconn == 0), "lookup result should be null");
+
+  /*
+   * Re-add and lookup tc2
+   */
+  stream_session_table_add_for_tc (tc1, tc1->s_index);
+  tconn = stream_session_lookup_transport_wt4 (&tc2->lcl_ip.ip4,
+					       &tc2->rmt_ip.ip4,
+					       tc2->lcl_port, tc2->rmt_port,
+					       tc2->proto, 0);
+  TCP_TEST ((tconn == 0), "lookup result should be null");
+
+  return 0;
+}
+
+static int
 tcp_test_session (vlib_main_t * vm, unformat_input_t * input)
 {
   int rv = 0;
@@ -1632,6 +1727,10 @@ tcp_test (vlib_main_t * vm,
 	{
 	  res = tcp_test_session (vm, input);
 	}
+      else if (unformat (input, "lookup"))
+	{
+	  res = tcp_test_lookup (vm, input);
+	}
       else
 	break;
     }