session: improve cli

Type: feature

Allow session cli filtering based on thread index, transport protocol,
session state and range of session pool indices. For instance

show session thread 1 proto tcp state ready range 0 20 verbose

Shows the session ids for the first 20 tcp sessions in thread 1 that are
in ready state.

To avoid excessive output that could reasult in the worker barrier being
held by the main thread for long periods of time, the session cli will
only output:
- session ids (verbose == 1) for a maximum of 50 sessions / worker
- verbose > 1 details for a maximum of 10 sessions

Change-Id: I2cfb351b548e2e0a1d5b4345810be613e2917d17
Signed-off-by: Florin Coras <fcoras@cisco.com>

7 files changed, 348 insertions, 148 deletions

diff --git a/src/plugins/hs_apps/sapi/vpp_echo_proto_quic.c b/src/plugins/hs_apps/sapi/vpp_echo_proto_quic.c
index 28c89a65fbf..41f9cd9e09c 100644
--- a/src/plugins/hs_apps/sapi/vpp_echo_proto_quic.c
+++ b/src/plugins/hs_apps/sapi/vpp_echo_proto_quic.c
@@ -54,7 +54,7 @@ quic_echo_on_connected_connect (session_connected_msg_t * mp,
 {
   echo_main_t *em = &echo_main;
   quic_echo_proto_main_t *eqm = &quic_echo_proto_main;
-  u8 *uri = format (0, "QUIC://session/%lu", mp->handle);
+  u8 *uri = format (0, "quic://session/%lu", mp->handle);
   u64 i;
 
   echo_notify_event (em, ECHO_EVT_FIRST_SCONNECT);
@@ -107,7 +107,7 @@ quic_echo_on_accept_connect (session_accepted_msg_t * mp, u32 session_index)
   echo_main_t *em = &echo_main;
   quic_echo_proto_main_t *eqm = &quic_echo_proto_main;
   ECHO_LOG (1, "Accept on QSession 0x%lx %u", mp->handle);
-  u8 *uri = format (0, "QUIC://session/%lu", mp->handle);
+  u8 *uri = format (0, "quic://session/%lu", mp->handle);
   u32 i;
 
   echo_notify_event (em, ECHO_EVT_FIRST_SCONNECT);
@@ -303,7 +303,7 @@ quic_echo_retry_connect (u32 session_index)
   else
     {
       session = pool_elt_at_index (em->sessions, session_index);
-      uri = format (0, "QUIC://session/%lu", session->vpp_session_handle);
+      uri = format (0, "quic://session/%lu", session->vpp_session_handle);
       ECHO_LOG (1, "Retrying connect %s", uri);
       echo_send_rpc (em, echo_send_connect, (void *) uri, session_index);
     }
diff --git a/src/vnet/session/session.h b/src/vnet/session/session.h
index 04fdebed791..cb0cac7cda6 100644
--- a/src/vnet/session/session.h
+++ b/src/vnet/session/session.h
@@ -584,6 +584,14 @@ session_main_get_worker (u32 thread_index)
   return &session_main.wrk[thread_index];
 }
 
+static inline session_worker_t *
+session_main_get_worker_if_valid (u32 thread_index)
+{
+  if (pool_is_free_index (session_main.wrk, thread_index))
+    return 0;
+  return &session_main.wrk[thread_index];
+}
+
 always_inline svm_msg_q_t *
 session_main_get_vpp_event_queue (u32 thread_index)
 {
@@ -598,8 +606,8 @@ session_main_is_enabled ()
 
 #define session_cli_return_if_not_enabled()				\
 do {									\
-    if (!session_main.is_enabled)				\
-      return clib_error_return(0, "session layer is not enabled");	\
+    if (!session_main.is_enabled)					\
+      return clib_error_return (0, "session layer is not enabled");	\
 } while (0)
 
 int session_main_flush_enqueue_events (u8 proto, u32 thread_index);
diff --git a/src/vnet/session/session_cli.c b/src/vnet/session/session_cli.c
index fd598f45d3e..d8aedd64e23 100755
--- a/src/vnet/session/session_cli.c
+++ b/src/vnet/session/session_cli.c
@@ -162,6 +162,27 @@ unformat_stream_session_id (unformat_input_t * input, va_list * args)
 }
 
 uword
+unformat_session_state (unformat_input_t * input, va_list * args)
+{
+  session_state_t *state = va_arg (*args, session_state_t *);
+  u8 *state_vec = 0;
+  int rv = 0;
+
+#define _(sym, str)					\
+  if (unformat (input, str))				\
+    {							\
+      *state = SESSION_STATE_ ## sym;			\
+      rv = 1;						\
+      goto done;					\
+    }
+  foreach_session_state
+#undef _
+done:
+  vec_free (state_vec);
+  return rv;
+}
+
+uword
 unformat_session (unformat_input_t * input, va_list * args)
 {
   session_t **result = va_arg (*args, session_t **);
@@ -227,42 +248,270 @@ unformat_transport_connection (unformat_input_t * input, va_list * args)
   return 0;
 }
 
+static void
+session_cli_show_all_sessions (vlib_main_t * vm, int verbose)
+{
+  session_main_t *smm = &session_main;
+  u32 n_closed = 0, thread_index;
+  session_t *pool, *s;
+
+  for (thread_index = 0; thread_index < vec_len (smm->wrk); thread_index++)
+    {
+      pool = smm->wrk[thread_index].sessions;
+
+      if (!pool_elts (pool))
+	{
+	  vlib_cli_output (vm, "Thread %d: no sessions", thread_index);
+	  continue;
+	}
+
+      if (!verbose)
+	{
+	  vlib_cli_output (vm, "Thread %d: %d sessions", thread_index,
+			   pool_elts (pool));
+	  continue;
+	}
+
+      if (pool_elts (pool) > 50)
+	{
+	  vlib_cli_output (vm, "Thread %u: %d sessions. Verbose output "
+			   "suppressed. For more details use filters.",
+			   thread_index, pool_elts (pool));
+	  continue;
+	}
+
+      if (verbose == 1)
+	vlib_cli_output (vm, "%s%-50s%-15s%-10s%-10s",
+			 thread_index ? "\n" : "",
+			 "Connection", "State", "Rx-f", "Tx-f");
+
+      /* *INDENT-OFF* */
+      pool_foreach(s, pool, ({
+        if (s->session_state >= SESSION_STATE_TRANSPORT_DELETED)
+          {
+            n_closed += 1;
+            continue;
+          }
+        vlib_cli_output (vm, "%U", format_session, s, verbose);
+      }));
+      /* *INDENT-ON* */
+
+      if (!n_closed)
+	vlib_cli_output (vm, "Thread %d: active sessions %u", thread_index,
+			 pool_elts (pool) - n_closed);
+      else
+	vlib_cli_output (vm, "Thread %d: active sessions %u closed %u",
+			 thread_index, pool_elts (pool) - n_closed, n_closed);
+    }
+}
+
+static int
+session_cli_filter_check (session_t * s, session_state_t * states,
+			  transport_proto_t tp)
+{
+  if (states)
+    {
+      session_state_t *state;
+      vec_foreach (state, states) if (s->session_state == *state)
+	goto check_transport;
+      return 0;
+    }
+
+check_transport:
+
+  if (tp != TRANSPORT_N_PROTO && session_get_transport_proto (s) != tp)
+    return 0;
+
+  return 1;
+}
+
+static void
+session_cli_show_session_filter (vlib_main_t * vm, u32 thread_index,
+				 u32 start, u32 end, session_state_t * states,
+				 transport_proto_t tp, int verbose)
+{
+  u8 output_suppressed = 0;
+  session_worker_t *wrk;
+  session_t *pool, *s;
+  u32 count = 0, max_index;
+  int i;
+
+  wrk = session_main_get_worker_if_valid (thread_index);
+  if (!wrk)
+    {
+      vlib_cli_output (vm, "invalid thread index %u", thread_index);
+      return;
+    }
+
+  pool = wrk->sessions;
+
+  if (tp == TRANSPORT_N_PROTO && states == 0 && !verbose
+      && (start == 0 && end == ~0))
+    {
+      vlib_cli_output (vm, "Thread %d: %u sessions", thread_index,
+		       pool_elts (pool));
+      return;
+    }
+
+  max_index = pool_elts (pool) ? pool_elts (pool) - 1 : 0;
+  for (i = start; i <= clib_min (end, max_index); i++)
+    {
+      if (pool_is_free_index (pool, i))
+	continue;
+
+      s = pool_elt_at_index (pool, i);
+
+      if (session_cli_filter_check (s, states, tp))
+	{
+	  count += 1;
+	  if (verbose)
+	    {
+	      if (count > 50 || (verbose > 1 && count > 10))
+		{
+		  output_suppressed = 1;
+		  continue;
+		}
+	      if (s->session_state < SESSION_STATE_TRANSPORT_DELETED)
+		vlib_cli_output (vm, "%U", format_session, s, verbose);
+	    }
+	}
+    }
+
+  if (!output_suppressed)
+    vlib_cli_output (vm, "Thread %d: %u sessions matched filter",
+		     thread_index, count);
+  else
+    vlib_cli_output (vm, "Thread %d: %u sessions matched filter. Not all"
+		     " shown. Use finer grained filter.", thread_index,
+		     count);
+}
+
+static void
+session_cli_print_transport_protos (vlib_main_t * vm)
+{
+#define _(sym, str, sstr) vlib_cli_output (vm, str);
+  foreach_transport_proto
+#undef _
+}
+
+static void
+session_cli_print_session_states (vlib_main_t * vm)
+{
+#define _(sym, str) vlib_cli_output (vm, str);
+  foreach_session_state
+#undef _
+}
+
 static clib_error_t *
 show_session_command_fn (vlib_main_t * vm, unformat_input_t * input,
 			 vlib_cli_command_t * cmd)
 {
-  u8 one_session = 0, do_listeners = 0, sst, do_elog = 0;
+  u8 one_session = 0, do_listeners = 0, sst, do_elog = 0, do_filter = 0;
+  u32 track_index, thread_index = 0, start = 0, end = ~0, session_index;
+  unformat_input_t _line_input, *line_input = &_line_input;
+  transport_proto_t transport_proto = TRANSPORT_N_PROTO;
+  session_state_t state = SESSION_N_STATES, *states = 0;
   session_main_t *smm = &session_main;
-  u32 transport_proto = ~0, track_index;
-  session_t *pool, *s;
-  transport_connection_t *tc;
+  clib_error_t *error = 0;
   app_worker_t *app_wrk;
-  int verbose = 0, i;
+  u32 transport_index;
   const u8 *app_name;
+  int verbose = 0;
+  session_t *s;
 
-  if (!smm->is_enabled)
+  session_cli_return_if_not_enabled ();
+
+  if (!unformat_user (input, unformat_line_input, line_input))
     {
-      return clib_error_return (0, "session layer is not enabled");
+      session_cli_show_all_sessions (vm, 0);
+      return 0;
     }
 
-  while (unformat_check_input (input) != UNFORMAT_END_OF_INPUT)
+  while (unformat_check_input (line_input) != UNFORMAT_END_OF_INPUT)
     {
-      if (unformat (input, "verbose %d", &verbose))
+      if (unformat (line_input, "verbose %d", &verbose))
 	;
-      else if (unformat (input, "verbose"))
+      else if (unformat (line_input, "verbose"))
 	verbose = 1;
-      else if (unformat (input, "listeners %U", unformat_transport_proto,
+      else if (unformat (line_input, "listeners %U", unformat_transport_proto,
 			 &transport_proto))
 	do_listeners = 1;
-      else if (unformat (input, "%U", unformat_session, &s))
+      else if (unformat (line_input, "%U", unformat_session, &s))
 	{
 	  one_session = 1;
 	}
-      else if (unformat (input, "elog"))
+      else if (unformat (line_input, "thread %u index %u", &thread_index,
+			 &session_index))
+	{
+	  s = session_get_if_valid (session_index, thread_index);
+	  if (!s)
+	    {
+	      vlib_cli_output (vm, "session is not allocated");
+	      goto done;
+	    }
+	  one_session = 1;
+	}
+      else if (unformat (line_input, "thread %u", &thread_index))
+	{
+	  do_filter = 1;
+	}
+      else
+	if (unformat (line_input, "state %U", unformat_session_state, &state))
+	{
+	  vec_add1 (states, state);
+	  do_filter = 1;
+	}
+      else if (unformat (line_input, "proto %U index %u",
+			 unformat_transport_proto, &transport_proto,
+			 &transport_index))
+	{
+	  transport_connection_t *tc;
+	  tc = transport_get_connection (transport_proto, transport_index,
+					 thread_index);
+	  if (!tc)
+	    {
+	      vlib_cli_output (vm, "transport connection %u thread %u is not"
+			       " allocated", transport_index, thread_index);
+	      goto done;
+	    }
+	  s = session_get_if_valid (tc->s_index, thread_index);
+	  if (!s)
+	    {
+	      vlib_cli_output (vm, "session for transport connection %u "
+			       "thread %u does not exist", transport_index,
+			       thread_index);
+	      goto done;
+	    }
+	  one_session = 1;
+	}
+      else if (unformat (line_input, "proto %U", unformat_transport_proto,
+			 &transport_proto))
+	do_filter = 1;
+      else if (unformat (line_input, "range %u %u", &start, &end))
+	do_filter = 1;
+      else if (unformat (line_input, "range %u", &start))
+	{
+	  end = start + 50;
+	  do_filter = 1;
+	}
+      else if (unformat (line_input, "elog"))
 	do_elog = 1;
+      else if (unformat (line_input, "protos"))
+	{
+	  session_cli_print_transport_protos (vm);
+	  goto done;
+	}
+      else if (unformat (line_input, "states"))
+	{
+	  session_cli_print_session_states (vm);
+	  goto done;
+	}
       else
-	return clib_error_return (0, "unknown input `%U'",
-				  format_unformat_error, input);
+	{
+	  error = clib_error_return (0, "unknown input `%U'",
+				     format_unformat_error, line_input);
+	  goto done;
+	}
     }
 
   if (one_session)
@@ -271,6 +520,7 @@ show_session_command_fn (vlib_main_t * vm, unformat_input_t * input,
       if (do_elog && s->session_state != SESSION_STATE_LISTENING)
 	{
 	  elog_main_t *em = &vm->elog_main;
+	  transport_connection_t *tc;
 	  f64 dt;
 
 	  tc = session_get_transport (s);
@@ -283,7 +533,7 @@ show_session_command_fn (vlib_main_t * vm, unformat_input_t * input,
 	}
       vlib_cli_output (vm, "%v", str);
       vec_free (str);
-      return 0;
+      goto done;
     }
 
   if (do_listeners)
@@ -301,53 +551,28 @@ show_session_command_fn (vlib_main_t * vm, unformat_input_t * input,
 			 app_name);
       }));
       /* *INDENT-ON* */
-      return 0;
+      goto done;
     }
 
-  for (i = 0; i < vec_len (smm->wrk); i++)
+  if (do_filter)
     {
-      u32 once_per_pool = 1, n_closed = 0;
-
-      pool = smm->wrk[i].sessions;
-      if (!pool_elts (pool))
-	{
-	  vlib_cli_output (vm, "Thread %d: no sessions", i);
-	  continue;
-	}
-
-      if (!verbose)
-	{
-	  vlib_cli_output (vm, "Thread %d: %d sessions", i, pool_elts (pool));
-	  continue;
-	}
-
-      if (once_per_pool && verbose == 1)
+      if (end < start)
 	{
-	  vlib_cli_output (vm, "%s%-50s%-15s%-10s%-10s", i ? "\n" : "",
-			   "Connection", "State", "Rx-f", "Tx-f");
-	  once_per_pool = 0;
+	  error = clib_error_return (0, "invalid range start: %u end: %u",
+				     start, end);
+	  goto done;
 	}
-
-      /* *INDENT-OFF* */
-      pool_foreach (s, pool, ({
-        if (s->session_state >= SESSION_STATE_TRANSPORT_DELETED)
-          {
-            n_closed += 1;
-            continue;
-          }
-        vlib_cli_output (vm, "%U", format_session, s, verbose);
-      }));
-      /* *INDENT-ON* */
-
-      if (!n_closed)
-	vlib_cli_output (vm, "Thread %d: active sessions %u", i,
-			 pool_elts (pool) - n_closed);
-      else
-	vlib_cli_output (vm, "Thread %d: active sessions %u closed %u", i,
-			 pool_elts (pool) - n_closed, n_closed);
+      session_cli_show_session_filter (vm, thread_index, start, end, states,
+				       transport_proto, verbose);
+      goto done;
     }
 
-  return 0;
+  session_cli_show_all_sessions (vm, verbose);
+
+done:
+  unformat_free (line_input);
+  vec_free (states);
+  return error;
 }
 
 /* *INDENT-OFF* */
@@ -355,7 +580,9 @@ VLIB_CLI_COMMAND (vlib_cli_show_session_command) =
 {
   .path = "show session",
   .short_help = "show session [verbose [n]] [listeners <proto>] "
-		"[<session-id> [elog]]",
+		"[<session-id> [elog]] [thread <n> [index <n>] "
+		"[proto <proto>] [state <state>] [range <min> [<max>]] "
+		"[protos] [states] ",
   .function = show_session_command_fn,
 };
 /* *INDENT-ON* */
diff --git a/src/vnet/session/session_types.h b/src/vnet/session/session_types.h
index 52a79e3beb5..bf45855e264 100644
--- a/src/vnet/session/session_types.h
+++ b/src/vnet/session/session_types.h
@@ -121,21 +121,26 @@ typedef enum
 /*
  * Session states
  */
+#define foreach_session_state				\
+  _(CREATED, "created")					\
+  _(LISTENING, "listening")				\
+  _(CONNECTING, "connecting")				\
+  _(ACCEPTING, "accepting")				\
+  _(READY, "ready")					\
+  _(OPENED, "opened")					\
+  _(TRANSPORT_CLOSING, "transport-closing")		\
+  _(CLOSING, "closing")					\
+  _(APP_CLOSED, "app-closed")				\
+  _(TRANSPORT_CLOSED, "transport-closed")		\
+  _(TRANSPORT_DELETED, "transport-deleted")		\
+  _(CLOSED, "closed")					\
+
 typedef enum
 {
-  SESSION_STATE_CREATED,
-  SESSION_STATE_LISTENING,
-  SESSION_STATE_CONNECTING,
-  SESSION_STATE_ACCEPTING,
-  SESSION_STATE_READY,
-  SESSION_STATE_OPENED,
-  SESSION_STATE_TRANSPORT_CLOSING,
-  SESSION_STATE_CLOSING,
-  SESSION_STATE_APP_CLOSED,
-  SESSION_STATE_TRANSPORT_CLOSED,
-  SESSION_STATE_TRANSPORT_DELETED,
-  SESSION_STATE_CLOSED,
-  SESSION_STATE_N_STATES,
+#define _(sym, str) SESSION_STATE_ ## sym,
+  foreach_session_state
+#undef _
+    SESSION_N_STATES,
 } session_state_t;
 
 typedef enum session_flags_
diff --git a/src/vnet/session/transport.c b/src/vnet/session/transport.c
index aa8deac5400..c1c908eae1a 100644
--- a/src/vnet/session/transport.c
+++ b/src/vnet/session/transport.c
@@ -57,27 +57,12 @@ format_transport_proto (u8 * s, va_list * args)
   u32 transport_proto = va_arg (*args, u32);
   switch (transport_proto)
     {
-    case TRANSPORT_PROTO_TCP:
-      s = format (s, "TCP");
-      break;
-    case TRANSPORT_PROTO_UDP:
-      s = format (s, "UDP");
-      break;
-    case TRANSPORT_PROTO_SCTP:
-      s = format (s, "SCTP");
-      break;
-    case TRANSPORT_PROTO_NONE:
-      s = format (s, "NONE");
-      break;
-    case TRANSPORT_PROTO_TLS:
-      s = format (s, "TLS");
-      break;
-    case TRANSPORT_PROTO_UDPC:
-      s = format (s, "UDPC");
-      break;
-    case TRANSPORT_PROTO_QUIC:
-      s = format (s, "QUIC");
+#define _(sym, str, sstr) 			\
+    case TRANSPORT_PROTO_ ## sym:		\
+      s = format (s, str);			\
       break;
+      foreach_transport_proto
+#undef _
     default:
       s = format (s, "UNKNOWN");
       break;
@@ -91,27 +76,12 @@ format_transport_proto_short (u8 * s, va_list * args)
   u32 transport_proto = va_arg (*args, u32);
   switch (transport_proto)
     {
-    case TRANSPORT_PROTO_TCP:
-      s = format (s, "T");
-      break;
-    case TRANSPORT_PROTO_UDP:
-      s = format (s, "U");
-      break;
-    case TRANSPORT_PROTO_SCTP:
-      s = format (s, "S");
-      break;
-    case TRANSPORT_PROTO_NONE:
-      s = format (s, "N");
-      break;
-    case TRANSPORT_PROTO_TLS:
-      s = format (s, "J");
-      break;
-    case TRANSPORT_PROTO_UDPC:
-      s = format (s, "U");
-      break;
-    case TRANSPORT_PROTO_QUIC:
-      s = format (s, "Q");
+#define _(sym, str, sstr) 			\
+    case TRANSPORT_PROTO_ ## sym:		\
+      s = format (s, sstr);			\
       break;
+      foreach_transport_proto
+#undef _
     default:
       s = format (s, "?");
       break;
@@ -179,33 +149,16 @@ uword
 unformat_transport_proto (unformat_input_t * input, va_list * args)
 {
   u32 *proto = va_arg (*args, u32 *);
-  if (unformat (input, "tcp"))
-    *proto = TRANSPORT_PROTO_TCP;
-  else if (unformat (input, "TCP"))
-    *proto = TRANSPORT_PROTO_TCP;
-  else if (unformat (input, "udpc"))
-    *proto = TRANSPORT_PROTO_UDPC;
-  else if (unformat (input, "UDPC"))
-    *proto = TRANSPORT_PROTO_UDPC;
-  else if (unformat (input, "udp"))
-    *proto = TRANSPORT_PROTO_UDP;
-  else if (unformat (input, "UDP"))
-    *proto = TRANSPORT_PROTO_UDP;
-  else if (unformat (input, "sctp"))
-    *proto = TRANSPORT_PROTO_SCTP;
-  else if (unformat (input, "SCTP"))
-    *proto = TRANSPORT_PROTO_SCTP;
-  else if (unformat (input, "tls"))
-    *proto = TRANSPORT_PROTO_TLS;
-  else if (unformat (input, "TLS"))
-    *proto = TRANSPORT_PROTO_TLS;
-  else if (unformat (input, "quic"))
-    *proto = TRANSPORT_PROTO_QUIC;
-  else if (unformat (input, "QUIC"))
-    *proto = TRANSPORT_PROTO_QUIC;
-  else
+
+#define _(sym, str, sstr)						\
+  if (unformat (input, str))						\
+    {									\
+      *proto = TRANSPORT_PROTO_ ## sym;					\
+      return 1;								\
+    }
+  foreach_transport_proto
+#undef _
     return 0;
-  return 1;
 }
 
 u32
diff --git a/src/vnet/session/transport_types.h b/src/vnet/session/transport_types.h
index 41897c6d170..ac2177c77b0 100644
--- a/src/vnet/session/transport_types.h
+++ b/src/vnet/session/transport_types.h
@@ -139,15 +139,20 @@ STATIC_ASSERT (STRUCT_OFFSET_OF (transport_connection_t, s_index)
 STATIC_ASSERT (sizeof (transport_connection_t) <= 128,
 	       "moved into 3rd cache line");
 
+#define foreach_transport_proto				\
+  _(TCP, "tcp", "T")					\
+  _(UDP, "udp", "U")					\
+  _(SCTP, "sctp", "S")					\
+  _(NONE, "ct", "C")					\
+  _(TLS, "tls", "J")					\
+  _(UDPC, "udpc", "U")					\
+  _(QUIC, "quic", "Q")					\
+
 typedef enum _transport_proto
 {
-  TRANSPORT_PROTO_TCP,
-  TRANSPORT_PROTO_UDP,
-  TRANSPORT_PROTO_SCTP,
-  TRANSPORT_PROTO_NONE,
-  TRANSPORT_PROTO_TLS,
-  TRANSPORT_PROTO_UDPC,
-  TRANSPORT_PROTO_QUIC,
+#define _(sym, str, sstr) TRANSPORT_PROTO_ ## sym,
+  foreach_transport_proto
+#undef _
   TRANSPORT_N_PROTO
 } transport_proto_t;
 
diff --git a/src/vnet/tcp/tcp.c b/src/vnet/tcp/tcp.c
index d060654a037..5090b7dd2d7 100644
--- a/src/vnet/tcp/tcp.c
+++ b/src/vnet/tcp/tcp.c
@@ -1165,6 +1165,8 @@ static transport_connection_t *
 tcp_session_get_transport (u32 conn_index, u32 thread_index)
 {
   tcp_connection_t *tc = tcp_connection_get (conn_index, thread_index);
+  if (PREDICT_FALSE (!tc))
+    return 0;
   return &tc->connection;
 }