VPP-659 TCP improvements

- builtin test echo server
- fix SYN-ACK retransmit canceling
- avoid sending spurious ACK if in LAST_ACK
- improved client dummy test app
- renamed tx fifo dequeuing and sending functions to avoid confusion
- improved RST handling

Change-Id: Ia14aad3df319540dcf6e6a4e18a9f8d423a4b83b
Signed-off-by: Florin Coras <fcoras@cisco.com>
Signed-off-by: Dave Barach <dave@barachs.net>

1 files changed, 44 insertions, 19 deletions

diff --git a/src/vnet/tcp/tcp_input.c b/src/vnet/tcp/tcp_input.c
index 0a907d0a..f19fbf87 100644
--- a/src/vnet/tcp/tcp_input.c
+++ b/src/vnet/tcp/tcp_input.c
@@ -274,10 +274,7 @@ tcp_segment_validate (vlib_main_t * vm, tcp_connection_t * tc0,
   /* 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;
+      tcp_connection_reset (tc0);
       return -1;
     }
 
@@ -1023,6 +1020,12 @@ tcp46_established_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	  tc0 = tcp_connection_get (vnet_buffer (b0)->tcp.connection_index,
 				    my_thread_index);
 
+	  if (PREDICT_FALSE (tc0 == 0))
+	    {
+	      error0 = TCP_ERROR_INVALID_CONNECTION;
+	      goto drop;
+	    }
+
 	  /* Checksum computed by ipx_local no need to compute again */
 
 	  if (is_ip4)
@@ -1072,12 +1075,12 @@ tcp46_established_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	  /* 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);
+	      /* 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;
 	      stream_session_disconnect_notify (&tc0->connection);
+	      tcp_timer_set (tc0, TCP_TIMER_WAITCLOSE, TCP_CLOSEWAIT_TIME);
 	    }
 
 	drop:
@@ -1468,7 +1471,7 @@ VLIB_REGISTER_NODE (tcp6_syn_sent_node) =
 
 VLIB_NODE_FUNCTION_MULTIARCH (tcp6_syn_sent_node, tcp6_syn_sent_rcv);
 /**
- * Handles reception for all states except LISTEN, SYN-SEND and ESTABLISHED
+ * Handles reception for all states except LISTEN, SYN-SENT and ESTABLISHED
  * as per RFC793 p. 64
  */
 always_inline uword
@@ -1511,6 +1514,11 @@ tcp46_rcv_process_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	  b0 = vlib_get_buffer (vm, bi0);
 	  tc0 = tcp_connection_get (vnet_buffer (b0)->tcp.connection_index,
 				    my_thread_index);
+	  if (PREDICT_FALSE (tc0 == 0))
+	    {
+	      error0 = TCP_ERROR_INVALID_CONNECTION;
+	      goto drop;
+	    }
 
 	  /* Checksum computed by ipx_local no need to compute again */
 
@@ -1587,7 +1595,8 @@ tcp46_rcv_process_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	      /* Shoulder tap the server */
 	      stream_session_accept_notify (&tc0->connection);
 
-	      tcp_timer_reset (tc0, TCP_TIMER_RETRANSMIT_SYN);
+	      /* Reset SYN-ACK retransmit timer */
+	      tcp_timer_reset (tc0, TCP_TIMER_RETRANSMIT);
 	      break;
 	    case TCP_STATE_ESTABLISHED:
 	      /* We can get packets in established state here because they
@@ -1602,9 +1611,14 @@ tcp46_rcv_process_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	       * 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);
+
+	      /* If FIN is ACKed */
+	      if (tc0->snd_una == tc0->snd_una_max)
+		{
+		  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
@@ -1639,7 +1653,17 @@ tcp46_rcv_process_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	      if (!tcp_rcv_ack_is_acceptable (tc0, b0))
 		goto drop;
 
-	      tcp_connection_del (tc0);
+	      tc0->state = TCP_STATE_CLOSED;
+
+	      /* Don't delete the connection/session yet. Instead, wait a
+	       * reasonable amount of time until the pipes are cleared. In
+	       * particular, this makes sure that we won't have dead sessions
+	       * when processing events on the tx path */
+	      tcp_timer_update (tc0, TCP_TIMER_WAITCLOSE, TCP_CLEANUP_TIME);
+
+	      /* Stop retransmit */
+	      tcp_timer_reset (tc0, TCP_TIMER_RETRANSMIT);
+
 	      goto drop;
 
 	      break;
@@ -1684,7 +1708,7 @@ tcp46_rcv_process_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	    case TCP_STATE_SYN_RCVD:
 	      /* Send FIN-ACK notify app and enter CLOSE-WAIT */
 	      tcp_connection_timers_reset (tc0);
-	      tcp_make_finack (tc0, b0);
+	      tcp_make_fin (tc0, b0);
 	      next0 = tcp_next_output (tc0->c_is_ip4);
 	      stream_session_disconnect_notify (&tc0->connection);
 	      tc0->state = TCP_STATE_CLOSE_WAIT;
@@ -1697,12 +1721,12 @@ tcp46_rcv_process_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	    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);
+	      tcp_timer_set (tc0, TCP_TIMER_WAITCLOSE, 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_timer_set (tc0, TCP_TIMER_WAITCLOSE, TCP_2MSL_TIME);
 	      tcp_make_ack (tc0, b0);
 	      next0 = tcp_next_output (is_ip4);
 	      break;
@@ -1710,7 +1734,7 @@ tcp46_rcv_process_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	      /* Remain in the TIME-WAIT state. Restart the 2 MSL time-wait
 	       * timeout.
 	       */
-	      tcp_timer_update (tc0, TCP_TIMER_2MSL, TCP_2MSL_TIME);
+	      tcp_timer_update (tc0, TCP_TIMER_WAITCLOSE, TCP_2MSL_TIME);
 	      break;
 	    }
 
@@ -2113,6 +2137,7 @@ tcp46_input_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	  n_left_to_next -= 1;
 
 	  b0 = vlib_get_buffer (vm, bi0);
+	  vnet_buffer (b0)->tcp.flags = 0;
 
 	  if (is_ip4)
 	    {
@@ -2168,7 +2193,6 @@ tcp46_input_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	      /* 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;
@@ -2288,6 +2312,7 @@ do {                                                       	\
   _(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);
+  _(ESTABLISHED, TCP_FLAG_RST, 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,