session: use vpp to switch io events for ct sessions

Instead of allocating pairs of message queues per cut-thru session and
having the applications map them, this uses vpp as an io event message
switch.

Change-Id: I51db1c7564df479a7d1a3288342394251fd188bb
Signed-off-by: Florin Coras <fcoras@cisco.com>

10 files changed, 154 insertions, 158 deletions

diff --git a/src/vnet/session/application_interface.h b/src/vnet/session/application_interface.h
index 935a352a436..d4dfeec54dc 100644
--- a/src/vnet/session/application_interface.h
+++ b/src/vnet/session/application_interface.h
@@ -283,8 +283,6 @@ typedef struct session_accepted_msg_
   uword server_tx_fifo;
   u64 segment_handle;
   uword vpp_event_queue_address;
-  uword server_event_queue_address;
-  uword client_event_queue_address;
   u16 port;
   u8 is_ip4;
   u8 ip[16];
@@ -309,9 +307,10 @@ typedef struct session_connected_msg_
   uword server_rx_fifo;
   uword server_tx_fifo;
   u64 segment_handle;
+  uword ct_rx_fifo;
+  uword ct_tx_fifo;
+  u64 ct_segment_handle;
   uword vpp_event_queue_address;
-  uword client_event_queue_address;
-  uword server_event_queue_address;
   u32 segment_size;
   u8 segment_name_length;
   u8 segment_name[64];
@@ -454,7 +453,7 @@ app_send_io_evt_to_vpp (svm_msg_q_t * mq, svm_fifo_t * f, u8 evt_type,
 always_inline int
 app_send_dgram_raw (svm_fifo_t * f, app_session_transport_t * at,
 		    svm_msg_q_t * vpp_evt_q, u8 * data, u32 len, u8 evt_type,
-		    u8 noblock)
+		    u8 do_evt, u8 noblock)
 {
   u32 max_enqueue, actual_write;
   session_dgram_hdr_t hdr;
@@ -478,7 +477,7 @@ app_send_dgram_raw (svm_fifo_t * f, app_session_transport_t * at,
 
   if ((rv = svm_fifo_enqueue_nowait (f, actual_write, data)) > 0)
     {
-      if (svm_fifo_set_event (f))
+      if (do_evt && svm_fifo_set_event (f))
 	app_send_io_evt_to_vpp (vpp_evt_q, f, evt_type, noblock);
     }
   ASSERT (rv);
@@ -489,18 +488,19 @@ always_inline int
 app_send_dgram (app_session_t * s, u8 * data, u32 len, u8 noblock)
 {
   return app_send_dgram_raw (s->tx_fifo, &s->transport, s->vpp_evt_q, data,
-			     len, SESSION_IO_EVT_TX, noblock);
+			     len, SESSION_IO_EVT_TX, 1 /* do_evt */ ,
+			     noblock);
 }
 
 always_inline int
 app_send_stream_raw (svm_fifo_t * f, svm_msg_q_t * vpp_evt_q, u8 * data,
-		     u32 len, u8 evt_type, u8 noblock)
+		     u32 len, u8 evt_type, u8 do_evt, u8 noblock)
 {
   int rv;
 
   if ((rv = svm_fifo_enqueue_nowait (f, len, data)) > 0)
     {
-      if (svm_fifo_set_event (f))
+      if (do_evt && svm_fifo_set_event (f))
 	app_send_io_evt_to_vpp (vpp_evt_q, f, evt_type, noblock);
     }
   return rv;
@@ -510,7 +510,7 @@ always_inline int
 app_send_stream (app_session_t * s, u8 * data, u32 len, u8 noblock)
 {
   return app_send_stream_raw (s->tx_fifo, s->vpp_evt_q, data, len,
-			      SESSION_IO_EVT_TX, noblock);
+			      SESSION_IO_EVT_TX, 1 /* do_evt */ , noblock);
 }
 
 always_inline int
diff --git a/src/vnet/session/application_local.c b/src/vnet/session/application_local.c
index 9378e5e6380..745b202f580 100644
--- a/src/vnet/session/application_local.c
+++ b/src/vnet/session/application_local.c
@@ -16,9 +16,28 @@
 #include <vnet/session/application_local.h>
 #include <vnet/session/session.h>
 
-ct_connection_t *connections;
+static ct_connection_t *connections;
 
-ct_connection_t *
+static void
+ct_enable_disable_main_pre_input_node (u8 is_add)
+{
+  u32 n_conns;
+
+  n_conns = pool_elts (connections);
+  if (n_conns > 2)
+    return;
+
+  if (n_conns > 0 && is_add)
+    vlib_node_set_state (vlib_get_main (),
+			 session_queue_pre_input_node.index,
+			 VLIB_NODE_STATE_POLLING);
+  else if (n_conns == 0)
+    vlib_node_set_state (vlib_get_main (),
+			 session_queue_pre_input_node.index,
+			 VLIB_NODE_STATE_DISABLED);
+}
+
+static ct_connection_t *
 ct_connection_alloc (void)
 {
   ct_connection_t *ct;
@@ -31,7 +50,7 @@ ct_connection_alloc (void)
   return ct;
 }
 
-ct_connection_t *
+static ct_connection_t *
 ct_connection_get (u32 ct_index)
 {
   if (pool_is_free_index (connections, ct_index))
@@ -39,7 +58,7 @@ ct_connection_get (u32 ct_index)
   return pool_elt_at_index (connections, ct_index);
 }
 
-void
+static void
 ct_connection_free (ct_connection_t * ct)
 {
   if (CLIB_DEBUG)
@@ -110,8 +129,14 @@ ct_session_connect_notify (session_t * ss)
   cs->session_state = SESSION_STATE_CONNECTING;
   cs->app_wrk_index = client_wrk->wrk_index;
   cs->connection_index = cct->c_c_index;
+  cs->t_app_index = client_wrk->app_index;
 
   cct->c_s_index = cs->session_index;
+  cct->client_rx_fifo = ss->tx_fifo;
+  cct->client_tx_fifo = ss->rx_fifo;
+
+  cct->client_rx_fifo->refcnt++;
+  cct->client_tx_fifo->refcnt++;
 
   /* This will allocate fifos for the session. They won't be used for
    * exchanging data but they will be used to close the connection if
@@ -135,47 +160,25 @@ ct_session_connect_notify (session_t * ss)
   return 0;
 }
 
-static void
-ct_session_fix_eventds (svm_msg_q_t * sq, svm_msg_q_t * cq)
-{
-  int fd;
-
-  /*
-   * segment manager initializes only the producer eventds, since vpp is
-   * typically the producer. But for local sessions, we also pass to the
-   * apps the mqs they listen on for events from peer apps, so they are also
-   * consumer fds.
-   */
-  fd = svm_msg_q_get_producer_eventfd (sq);
-  svm_msg_q_set_consumer_eventfd (sq, fd);
-  fd = svm_msg_q_get_producer_eventfd (cq);
-  svm_msg_q_set_consumer_eventfd (cq, fd);
-}
-
-int
+static int
 ct_init_local_session (app_worker_t * client_wrk, app_worker_t * server_wrk,
 		       ct_connection_t * ct, session_t * ls, session_t * ll)
 {
-  u32 seg_size, evt_q_sz, evt_q_elts, margin = 16 << 10;
-  u32 round_rx_fifo_sz, round_tx_fifo_sz, sm_index;
-  segment_manager_properties_t *props, *cprops;
+  u32 round_rx_fifo_sz, round_tx_fifo_sz, sm_index, seg_size;
+  segment_manager_properties_t *props;
   svm_fifo_segment_private_t *seg;
-  application_t *server, *client;
+  application_t *server;
   segment_manager_t *sm;
-  svm_msg_q_t *sq, *cq;
+  u32 margin = 16 << 10;
   u64 segment_handle;
   int seg_index, rv;
 
   server = application_get (server_wrk->app_index);
-  client = application_get (client_wrk->app_index);
 
   props = application_segment_manager_properties (server);
-  cprops = application_segment_manager_properties (client);
-  evt_q_elts = props->evt_q_size + cprops->evt_q_size;
-  evt_q_sz = segment_manager_evt_q_expected_size (evt_q_elts);
   round_rx_fifo_sz = 1 << max_log2 (props->rx_fifo_size);
   round_tx_fifo_sz = 1 << max_log2 (props->tx_fifo_size);
-  seg_size = round_rx_fifo_sz + round_tx_fifo_sz + evt_q_sz + margin;
+  seg_size = round_rx_fifo_sz + round_tx_fifo_sz + margin;
 
   sm = app_worker_get_listen_segment_manager (server_wrk, ll);
   seg_index = segment_manager_add_segment (sm, seg_size);
@@ -185,14 +188,7 @@ ct_init_local_session (app_worker_t * client_wrk, app_worker_t * server_wrk,
       return seg_index;
     }
   seg = segment_manager_get_segment_w_lock (sm, seg_index);
-  sq = segment_manager_alloc_queue (seg, props);
-  cq = segment_manager_alloc_queue (seg, cprops);
-
-  if (props->use_mq_eventfd)
-    ct_session_fix_eventds (sq, cq);
 
-  ct->server_evt_q = pointer_to_uword (sq);
-  ct->client_evt_q = pointer_to_uword (cq);
   rv = segment_manager_try_alloc_fifos (seg, props->rx_fifo_size,
 					props->tx_fifo_size, &ls->rx_fifo,
 					&ls->tx_fifo);
@@ -204,8 +200,8 @@ ct_init_local_session (app_worker_t * client_wrk, app_worker_t * server_wrk,
     }
 
   sm_index = segment_manager_index (sm);
-  ls->rx_fifo->ct_session_index = ls->session_index;
-  ls->tx_fifo->ct_session_index = ls->session_index;
+  ls->rx_fifo->master_session_index = ls->session_index;
+  ls->tx_fifo->master_session_index = ls->session_index;
   ls->rx_fifo->segment_manager = sm_index;
   ls->tx_fifo->segment_manager = sm_index;
   ls->rx_fifo->segment_index = seg_index;
@@ -228,7 +224,7 @@ failed:
   return rv;
 }
 
-int
+static int
 ct_connect (app_worker_t * client_wrk, session_t * ll,
 	    session_endpoint_cfg_t * sep)
 {
@@ -255,6 +251,7 @@ ct_connect (app_worker_t * client_wrk, session_t * ll,
   cct->c_is_ip4 = sep->is_ip4;
   clib_memcpy (&cct->c_rmt_ip, &sep->ip, sizeof (sep->ip));
   cct->actual_tp = ll_ct->actual_tp;
+  cct->is_client = 1;
 
   /*
    * Init server transport
@@ -285,6 +282,7 @@ ct_connect (app_worker_t * client_wrk, session_t * ll,
 
   server_wrk = application_listener_select_worker (ll);
   ss->app_wrk_index = server_wrk->wrk_index;
+  ss->t_app_index = server_wrk->app_index;
 
   sct->c_s_index = ss->session_index;
   sct->server_wrk = ss->app_wrk_index;
@@ -306,14 +304,12 @@ ct_connect (app_worker_t * client_wrk, session_t * ll,
       return -1;
     }
 
-  cct->client_evt_q = sct->client_evt_q;
-  cct->server_evt_q = sct->server_evt_q;
   cct->segment_handle = sct->segment_handle;
-
+  ct_enable_disable_main_pre_input_node (1 /* is_add */ );
   return 0;
 }
 
-u32
+static u32
 ct_start_listen (u32 app_listener_index, transport_endpoint_t * tep)
 {
   session_endpoint_cfg_t *sep;
@@ -326,25 +322,27 @@ ct_start_listen (u32 app_listener_index, transport_endpoint_t * tep)
   clib_memcpy (&ct->c_lcl_ip, &sep->ip, sizeof (sep->ip));
   ct->c_lcl_port = sep->port;
   ct->actual_tp = sep->transport_proto;
+  ct_enable_disable_main_pre_input_node (1 /* is_add */ );
   return ct->c_c_index;
 }
 
-u32
+static u32
 ct_stop_listen (u32 ct_index)
 {
   ct_connection_t *ct;
   ct = ct_connection_get (ct_index);
   ct_connection_free (ct);
+  ct_enable_disable_main_pre_input_node (0 /* is_add */ );
   return 0;
 }
 
-transport_connection_t *
+static transport_connection_t *
 ct_listener_get (u32 ct_index)
 {
   return (transport_connection_t *) ct_connection_get (ct_index);
 }
 
-int
+static int
 ct_session_connect (transport_endpoint_cfg_t * tep)
 {
   session_endpoint_cfg_t *sep_ext;
@@ -407,10 +405,11 @@ global_scope:
   return 1;
 }
 
-void
+static void
 ct_session_close (u32 ct_index, u32 thread_index)
 {
   ct_connection_t *ct, *peer_ct;
+  app_worker_t *app_wrk;
   session_t *s;
 
   ct = ct_connection_get (ct_index);
@@ -422,13 +421,18 @@ ct_session_close (u32 ct_index, u32 thread_index)
     }
 
   s = session_get (ct->c_s_index, 0);
-  app_worker_del_segment_notify (app_worker_get (s->app_wrk_index),
-				 ct->segment_handle);
+  app_wrk = app_worker_get_if_valid (s->app_wrk_index);
+  if (app_wrk)
+    app_worker_del_segment_notify (app_wrk, ct->segment_handle);
   session_free_w_fifos (s);
+  if (ct->is_client)
+    segment_manager_dealloc_fifos (ct->client_rx_fifo, ct->client_tx_fifo);
+
   ct_connection_free (ct);
+  ct_enable_disable_main_pre_input_node (0 /* is_add */ );
 }
 
-transport_connection_t *
+static transport_connection_t *
 ct_session_get (u32 ct_index, u32 thread_index)
 {
   return (transport_connection_t *) ct_connection_get (ct_index);
@@ -460,7 +464,7 @@ format_ct_connection_id (u8 * s, va_list * args)
   return s;
 }
 
-u8 *
+static u8 *
 format_ct_listener (u8 * s, va_list * args)
 {
   u32 tc_index = va_arg (*args, u32);
@@ -472,7 +476,7 @@ format_ct_listener (u8 * s, va_list * args)
   return s;
 }
 
-u8 *
+static u8 *
 format_ct_connection (u8 * s, va_list * args)
 {
   ct_connection_t *ct = va_arg (*args, ct_connection_t *);
@@ -492,7 +496,7 @@ format_ct_connection (u8 * s, va_list * args)
   return s;
 }
 
-u8 *
+static u8 *
 format_ct_session (u8 * s, va_list * args)
 {
   u32 ct_index = va_arg (*args, u32);
@@ -526,11 +530,29 @@ const static transport_proto_vft_t cut_thru_proto = {
 };
 /* *INDENT-ON* */
 
+int
+ct_session_tx (session_t * s)
+{
+  ct_connection_t *ct, *peer_ct;
+  session_t *peer_s;
+
+  ct = (ct_connection_t *) session_get_transport (s);
+  peer_ct = ct_connection_get (ct->peer_index);
+  if (!peer_ct)
+    return -1;
+  peer_s = session_get (peer_ct->c_s_index, 0);
+  if (peer_s->session_state >= SESSION_STATE_TRANSPORT_CLOSING)
+    return 0;
+  return session_enqueue_notify (peer_s);
+}
+
 static clib_error_t *
 ct_transport_init (vlib_main_t * vm)
 {
   transport_register_protocol (TRANSPORT_PROTO_NONE, &cut_thru_proto,
 			       FIB_PROTOCOL_IP4, ~0);
+  transport_register_protocol (TRANSPORT_PROTO_NONE, &cut_thru_proto,
+			       FIB_PROTOCOL_IP6, ~0);
   return 0;
 }
 
diff --git a/src/vnet/session/application_local.h b/src/vnet/session/application_local.h
index 5d6e6c1ec7b..7b937d32f0b 100644
--- a/src/vnet/session/application_local.h
+++ b/src/vnet/session/application_local.h
@@ -27,16 +27,18 @@ typedef struct ct_connection_
   u32 server_wrk;
   u32 transport_listener_index;
   transport_proto_t actual_tp;
-  u64 server_evt_q;
-  u64 client_evt_q;
   u32 client_opaque;
   u32 peer_index;
   u64 segment_handle;
+  svm_fifo_t *client_rx_fifo;
+  svm_fifo_t *client_tx_fifo;
+  u8 is_client;
 } ct_connection_t;
 
 session_t *ct_session_get_peer (session_t * s);
 void ct_session_endpoint (session_t * ll, session_endpoint_t * sep);
 int ct_session_connect_notify (session_t * ls);
+int ct_session_tx (session_t * s);
 
 #endif /* SRC_VNET_SESSION_APPLICATION_LOCAL_H_ */
 
diff --git a/src/vnet/session/application_worker.c b/src/vnet/session/application_worker.c
index 9dfa3aa0243..7c888882093 100644
--- a/src/vnet/session/application_worker.c
+++ b/src/vnet/session/application_worker.c
@@ -543,7 +543,7 @@ app_send_io_evt_rx (app_worker_t * app_wrk, session_t * s, u8 lock)
       return app->cb_fns.builtin_app_rx_callback (s);
     }
 
-  if (svm_fifo_has_event (s->rx_fifo) || svm_fifo_is_empty (s->rx_fifo))
+  if (svm_fifo_has_event (s->rx_fifo))
     return 0;
 
   mq = app_wrk->event_queue;
@@ -608,9 +608,8 @@ app_send_io_evt_tx (app_worker_t * app_wrk, session_t * s, u8 lock)
 typedef int (app_send_evt_handler_fn) (app_worker_t *app,
 				       session_t *s,
 				       u8 lock);
-static app_send_evt_handler_fn * const app_send_evt_handler_fns[3] = {
+static app_send_evt_handler_fn * const app_send_evt_handler_fns[2] = {
     app_send_io_evt_rx,
-    0,
     app_send_io_evt_tx,
 };
 /* *INDENT-ON* */
diff --git a/src/vnet/session/segment_manager.c b/src/vnet/session/segment_manager.c
index b7467bbbd43..25b641de167 100644
--- a/src/vnet/session/segment_manager.c
+++ b/src/vnet/session/segment_manager.c
@@ -408,12 +408,10 @@ segment_manager_del_sessions (segment_manager_t * sm)
      */
     while (fifo)
       {
-	if (fifo->ct_session_index != SVM_FIFO_INVALID_SESSION_INDEX)
-	  session = session_get (fifo->ct_session_index, 0);
-	else
-	  session = session_get (fifo->master_session_index,
-	                         fifo->master_thread_index);
-	vec_add1 (handles, session_handle (session));
+	session = session_get_if_valid (fifo->master_session_index,
+	                                fifo->master_thread_index);
+	if (session)
+	  vec_add1 (handles, session_handle (session));
 	fifo = fifo->next;
       }
 
diff --git a/src/vnet/session/session.c b/src/vnet/session/session.c
index 57567926a1c..6e24d562f98 100644
--- a/src/vnet/session/session.c
+++ b/src/vnet/session/session.c
@@ -124,13 +124,6 @@ session_program_transport_close (session_t * s)
   session_worker_t *wrk;
   session_event_t *evt;
 
-  if (!session_has_transport (s))
-    {
-      /* Polling may not be enabled on main thread so close now */
-      session_transport_close (s);
-      return;
-    }
-
   /* If we are in the handler thread, or being called with the worker barrier
    * held, just append a new event to pending disconnects vector. */
   if (vlib_thread_is_main_w_barrier () || thread_index == s->thread_index)
@@ -483,7 +476,7 @@ session_notify_subscribers (u32 app_index, session_t * s,
  * @return 0 on success or negative number if failed to send notification.
  */
 static inline int
-session_enqueue_notify (session_t * s)
+session_enqueue_notify_inline (session_t * s)
 {
   app_worker_t *app_wrk;
 
@@ -513,6 +506,12 @@ session_enqueue_notify (session_t * s)
 }
 
 int
+session_enqueue_notify (session_t * s)
+{
+  return session_enqueue_notify_inline (s);
+}
+
+int
 session_dequeue_notify (session_t * s)
 {
   app_worker_t *app_wrk;
@@ -560,7 +559,11 @@ session_main_flush_enqueue_events (u8 transport_proto, u32 thread_index)
 	  errors++;
 	  continue;
 	}
-      if (PREDICT_FALSE (session_enqueue_notify (s)))
+
+      if (svm_fifo_is_empty (s->rx_fifo))
+	continue;
+
+      if (PREDICT_FALSE (session_enqueue_notify_inline (s)))
 	errors++;
     }
 
diff --git a/src/vnet/session/session.h b/src/vnet/session/session.h
index a7c91949eb3..cea1b375108 100644
--- a/src/vnet/session/session.h
+++ b/src/vnet/session/session.h
@@ -187,6 +187,7 @@ typedef struct session_main_
 extern session_main_t session_main;
 extern vlib_node_registration_t session_queue_node;
 extern vlib_node_registration_t session_queue_process_node;
+extern vlib_node_registration_t session_queue_pre_input_node;
 
 #define SESSION_Q_PROCESS_FLUSH_FRAMES	1
 #define SESSION_Q_PROCESS_STOP		2
@@ -196,6 +197,9 @@ session_is_valid (u32 si, u8 thread_index)
 {
   session_t *s;
   s = pool_elt_at_index (session_main.wrk[thread_index].sessions, si);
+  if (s->session_state == SESSION_STATE_CLOSED)
+    return 1;
+
   if (s->thread_index != thread_index || s->session_index != si)
     return 0;
   return 1;
@@ -331,6 +335,7 @@ void session_transport_close (session_t * s);
 void session_transport_cleanup (session_t * s);
 int session_send_io_evt_to_thread (svm_fifo_t * f,
 				   session_evt_type_t evt_type);
+int session_enqueue_notify (session_t * s);
 int session_dequeue_notify (session_t * s);
 int session_send_io_evt_to_thread_custom (void *data, u32 thread_index,
 					  session_evt_type_t evt_type);
diff --git a/src/vnet/session/session_api.c b/src/vnet/session/session_api.c
index 8ee25a9a2ce..525f63799be 100755
--- a/src/vnet/session/session_api.c
+++ b/src/vnet/session/session_api.c
@@ -150,54 +150,6 @@ send_del_segment_callback (u32 api_client_index, u64 segment_handle)
 }
 
 static int
-send_app_cut_through_registration_add (u32 api_client_index,
-				       u32 wrk_map_index, u64 mq_addr,
-				       u64 peer_mq_addr)
-{
-  vl_api_app_cut_through_registration_add_t *mp;
-  vl_api_registration_t *reg;
-  svm_msg_q_t *mq, *peer_mq;
-  int fds[2];
-
-  reg = vl_mem_api_client_index_to_registration (api_client_index);
-  if (!reg)
-    {
-      clib_warning ("no registration: %u", api_client_index);
-      return -1;
-    }
-
-  mp = vl_mem_api_alloc_as_if_client_w_reg (reg, sizeof (*mp));
-  clib_memset (mp, 0, sizeof (*mp));
-  mp->_vl_msg_id =
-    clib_host_to_net_u16 (VL_API_APP_CUT_THROUGH_REGISTRATION_ADD);
-
-  mp->evt_q_address = mq_addr;
-  mp->peer_evt_q_address = peer_mq_addr;
-  mp->wrk_index = wrk_map_index;
-
-  mq = uword_to_pointer (mq_addr, svm_msg_q_t *);
-  peer_mq = uword_to_pointer (peer_mq_addr, svm_msg_q_t *);
-
-  if (svm_msg_q_get_producer_eventfd (mq) != -1)
-    {
-      mp->fd_flags |= SESSION_FD_F_MQ_EVENTFD;
-      mp->n_fds = 2;
-      /* app will overwrite exactly the fds we pass here. So
-       * when we swap mq with peer_mq (accept vs connect) the
-       * fds will still be valid */
-      fds[0] = svm_msg_q_get_consumer_eventfd (mq);
-      fds[1] = svm_msg_q_get_producer_eventfd (peer_mq);
-    }
-
-  vl_msg_api_send_shmem (reg->vl_input_queue, (u8 *) & mp);
-
-  if (mp->n_fds != 0)
-    session_send_fds (reg, fds, mp->n_fds);
-
-  return 0;
-}
-
-static int
 mq_try_lock_and_alloc_msg (svm_msg_q_t * app_mq, svm_msg_q_msg_t * msg)
 {
   int rv;
@@ -268,25 +220,17 @@ mq_send_session_accepted_cb (session_t * s)
     }
   else
     {
-      u8 main_thread = vlib_num_workers ()? 1 : 0;
       ct_connection_t *ct;
 
       ct = (ct_connection_t *) session_get_transport (s);
-      send_app_cut_through_registration_add (app_wrk->api_client_index,
-					     app_wrk->wrk_map_index,
-					     ct->server_evt_q,
-					     ct->client_evt_q);
-
       listener = listen_session_get (s->listener_index);
       al = app_listener_get (app, listener->al_index);
       mp->listener_handle = app_listener_handle (al);
       mp->is_ip4 = session_type_is_ip4 (listener->session_type);
       mp->handle = session_handle (s);
       mp->port = ct->c_rmt_port;
-      vpp_queue = session_main_get_vpp_event_queue (main_thread);
+      vpp_queue = session_main_get_vpp_event_queue (0);
       mp->vpp_event_queue_address = pointer_to_uword (vpp_queue);
-      mp->client_event_queue_address = ct->client_evt_q;
-      mp->server_event_queue_address = ct->server_evt_q;
     }
   svm_msg_q_add_and_unlock (app_mq, msg);
 
@@ -415,26 +359,22 @@ mq_send_session_connected_cb (u32 app_wrk_index, u32 api_context,
     }
   else
     {
-      u8 main_thread = vlib_num_workers ()? 1 : 0;
       ct_connection_t *cct;
       session_t *ss;
 
       cct = (ct_connection_t *) session_get_transport (s);
-      send_app_cut_through_registration_add (app_wrk->api_client_index,
-					     app_wrk->wrk_map_index,
-					     cct->client_evt_q,
-					     cct->server_evt_q);
-
       mp->handle = session_handle (s);
       mp->lcl_port = cct->c_lcl_port;
-      vpp_mq = session_main_get_vpp_event_queue (main_thread);
+      mp->is_ip4 = cct->c_is_ip4;
+      vpp_mq = session_main_get_vpp_event_queue (0);
       mp->vpp_event_queue_address = pointer_to_uword (vpp_mq);
-      mp->client_event_queue_address = cct->client_evt_q;
-      mp->server_event_queue_address = cct->server_evt_q;
+      mp->server_rx_fifo = pointer_to_uword (s->rx_fifo);
+      mp->server_tx_fifo = pointer_to_uword (s->tx_fifo);
+      mp->segment_handle = session_segment_handle (s);
       ss = ct_session_get_peer (s);
-      mp->server_rx_fifo = pointer_to_uword (ss->tx_fifo);
-      mp->server_tx_fifo = pointer_to_uword (ss->rx_fifo);
-      mp->segment_handle = session_segment_handle (ss);
+      mp->ct_rx_fifo = pointer_to_uword (ss->tx_fifo);
+      mp->ct_tx_fifo = pointer_to_uword (ss->rx_fifo);
+      mp->ct_segment_handle = session_segment_handle (ss);
     }
 
 done:
@@ -505,11 +445,20 @@ done:
   return 0;
 }
 
+static int
+mq_app_tx_callback (session_t * s)
+{
+  if (session_has_transport (s))
+    return 0;
+  return ct_session_tx (s);
+}
+
 static session_cb_vft_t session_mq_cb_vft = {
   .session_accept_callback = mq_send_session_accepted_cb,
   .session_disconnect_callback = mq_send_session_disconnected_cb,
   .session_connected_callback = mq_send_session_connected_cb,
   .session_reset_callback = mq_send_session_reset_cb,
+  .builtin_app_tx_callback = mq_app_tx_callback,
   .add_segment_callback = send_add_segment_callback,
   .del_segment_callback = send_del_segment_callback,
 };
diff --git a/src/vnet/session/session_node.c b/src/vnet/session/session_node.c
index d0936c7e13d..db5123b8b2d 100644
--- a/src/vnet/session/session_node.c
+++ b/src/vnet/session/session_node.c
@@ -74,9 +74,9 @@ session_mq_accepted_reply_handler (void *data)
 
   if (!session_has_transport (s))
     {
+      s->session_state = SESSION_STATE_READY;
       if (ct_session_connect_notify (s))
 	return;
-      s->session_state = SESSION_STATE_READY;
     }
   else
     {
@@ -1234,6 +1234,26 @@ VLIB_REGISTER_NODE (session_queue_process_node) =
 };
 /* *INDENT-ON* */
 
+static_always_inline uword
+session_queue_pre_input_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
+				vlib_frame_t * frame)
+{
+  session_main_t *sm = &session_main;
+  if (!sm->wrk[0].vpp_event_queue)
+    return 0;
+  return session_queue_node_fn (vm, node, frame);
+}
+
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (session_queue_pre_input_node) =
+{
+  .function = session_queue_pre_input_inline,
+  .type = VLIB_NODE_TYPE_PRE_INPUT,
+  .name = "session-queue-main",
+  .state = VLIB_NODE_STATE_DISABLED,
+};
+/* *INDENT-ON* */
+
 /*
  * fd.io coding-style-patch-verification: ON
  *
diff --git a/src/vnet/session/session_types.h b/src/vnet/session/session_types.h
index c4240ab420a..9e51d69db42 100644
--- a/src/vnet/session/session_types.h
+++ b/src/vnet/session/session_types.h
@@ -278,9 +278,7 @@ session_parse_handle (session_handle_t handle, u32 * index,
 typedef enum
 {
   SESSION_IO_EVT_RX,
-  SESSION_IO_EVT_CT_RX,
   SESSION_IO_EVT_TX,
-  SESSION_IO_EVT_CT_TX,
   SESSION_IO_EVT_TX_FLUSH,
   SESSION_IO_EVT_BUILTIN_RX,
   SESSION_IO_EVT_BUILTIN_TX,