Session layer improvements

Among others:
- Moved app event queue to shared memory segment
- Use private memory segment for builtin apps
- Remove pid from svm fifo
- Protect session fifo (de)allocation
- Use fifo event for session disconnects
- Have session queue node poll in all wk threads

Change-Id: I89dbf7fdfebef12f5ef2b34ba3ef3c2c07f49ff2
Signed-off-by: Florin Coras <fcoras@cisco.com>

10 files changed, 330 insertions, 218 deletions

diff --git a/src/vnet/session/application.c b/src/vnet/session/application.c
index 5a45537b798..ccf9837f4cc 100644
--- a/src/vnet/session/application.c
+++ b/src/vnet/session/application.c
@@ -87,8 +87,6 @@ application_new ()
 void
 application_del (application_t * app)
 {
-  api_main_t *am = &api_main;
-  void *oldheap;
   segment_manager_t *sm;
   u64 handle;
   u32 index, *handles = 0;
@@ -96,6 +94,11 @@ application_del (application_t * app)
   vnet_unbind_args_t _a, *a = &_a;
 
   /*
+   * The app event queue allocated in first segment is cleared with
+   * the segment manager. No need to explicitly free it.
+   */
+
+  /*
    * Cleanup segment managers
    */
   if (app->connects_seg_manager != (u32) ~ 0)
@@ -120,14 +123,6 @@ application_del (application_t * app)
       vnet_unbind (a);
     }
 
-  /*
-   * Free the event fifo in the /vpe-api shared-memory segment
-   */
-  oldheap = svm_push_data_heap (am->vlib_rp);
-  if (app->event_queue)
-    unix_shared_memory_queue_free (app->event_queue);
-  svm_pop_heap (oldheap);
-
   application_table_del (app);
   pool_put (app_pool, app);
 }
@@ -149,30 +144,14 @@ int
 application_init (application_t * app, u32 api_client_index, u64 * options,
 		  session_cb_vft_t * cb_fns)
 {
-  api_main_t *am = &api_main;
   segment_manager_t *sm;
   segment_manager_properties_t *props;
-  void *oldheap;
-  u32 app_evt_queue_size;
+  u32 app_evt_queue_size, first_seg_size;
   int rv;
 
   app_evt_queue_size = options[APP_EVT_QUEUE_SIZE] > 0 ?
     options[APP_EVT_QUEUE_SIZE] : default_app_evt_queue_size;
 
-  /* Allocate event fifo in the /vpe-api shared-memory segment */
-  oldheap = svm_push_data_heap (am->vlib_rp);
-
-  /* Allocate server event queue */
-  app->event_queue =
-    unix_shared_memory_queue_init (app_evt_queue_size,
-				   sizeof (session_fifo_event_t),
-				   0 /* consumer pid */ ,
-				   0
-				   /* (do not) signal when queue non-empty */
-    );
-
-  svm_pop_heap (oldheap);
-
   /* Setup segment manager */
   sm = segment_manager_new ();
   sm->app_index = app->index;
@@ -181,16 +160,21 @@ application_init (application_t * app, u32 api_client_index, u64 * options,
   props->rx_fifo_size = options[SESSION_OPTIONS_RX_FIFO_SIZE];
   props->tx_fifo_size = options[SESSION_OPTIONS_TX_FIFO_SIZE];
   props->add_segment = props->add_segment_size != 0;
+  props->use_private_segment = options[APP_OPTIONS_FLAGS]
+    & APP_OPTIONS_FLAGS_BUILTIN_APP;
 
-  if ((rv = segment_manager_init (sm, props,
-				  options[SESSION_OPTIONS_SEGMENT_SIZE])))
+  first_seg_size = options[SESSION_OPTIONS_SEGMENT_SIZE];
+  if ((rv = segment_manager_init (sm, props, first_seg_size)))
     return rv;
 
   app->first_segment_manager = segment_manager_index (sm);
   app->api_client_index = api_client_index;
-  app->flags = options[SESSION_OPTIONS_FLAGS];
+  app->flags = options[APP_OPTIONS_FLAGS];
   app->cb_fns = *cb_fns;
 
+  /* Allocate app event queue in the first shared-memory segment */
+  app->event_queue = segment_manager_alloc_queue (sm, app_evt_queue_size);
+
   /* Check that the obvious things are properly set up */
   application_verify_cb_fns (cb_fns);
 
@@ -451,8 +435,8 @@ application_format_connects (application_t * app, int verbose)
 	    continue;
 
 	  fifo = fifos[i];
-	  session_index = fifo->server_session_index;
-	  thread_index = fifo->server_thread_index;
+	  session_index = fifo->master_session_index;
+	  thread_index = fifo->master_thread_index;
 
 	  session = stream_session_get (session_index, thread_index);
 	  str = format (0, "%U", format_stream_session, session, verbose);
diff --git a/src/vnet/session/application.h b/src/vnet/session/application.h
index 6bcee9d312e..35caae85dbb 100644
--- a/src/vnet/session/application.h
+++ b/src/vnet/session/application.h
@@ -61,18 +61,6 @@ typedef struct _application
   /** Flags */
   u32 flags;
 
-  /* Stream server mode: accept or connect
-   * TODO REMOVE*/
-  u8 mode;
-
-  /** Index of the listen session or connect session
-   * TODO REMOVE*/
-  u32 session_index;
-
-  /** Session thread index for client connect sessions
-   * TODO REMOVE */
-  u32 thread_index;
-
   /*
    * Binary API interface to external app
    */
diff --git a/src/vnet/session/application_interface.c b/src/vnet/session/application_interface.c
index 96d2c62132a..ad44baa15c3 100644
--- a/src/vnet/session/application_interface.c
+++ b/src/vnet/session/application_interface.c
@@ -142,7 +142,7 @@ vnet_connect_i (u32 app_index, u32 api_context, session_type_t sst,
        * Server is willing to have a direct fifo connection created
        * instead of going through the state machine, etc.
        */
-      if (server->flags & SESSION_OPTIONS_FLAGS_USE_FIFO)
+      if (server->flags & APP_OPTIONS_FLAGS_USE_FIFO)
 	return server->cb_fns.
 	  redirect_connect_callback (server->api_client_index, mp);
     }
@@ -363,7 +363,11 @@ vnet_disconnect_session (vnet_disconnect_args_t * a)
   if (!s || s->app_index != a->app_index)
     return VNET_API_ERROR_INVALID_VALUE;
 
-  stream_session_disconnect (s);
+  /* We're peeking into another's thread pool. Make sure */
+  ASSERT (s->session_index == index);
+
+  session_send_session_evt_to_thread (a->handle, FIFO_EVENT_DISCONNECT,
+				      thread_index);
   return 0;
 }
 
@@ -395,24 +399,6 @@ vnet_connect (vnet_connect_args_t * a)
   return vnet_connect_i (a->app_index, a->api_context, sst, &a->tep, a->mp);
 }
 
-int
-vnet_disconnect (vnet_disconnect_args_t * a)
-{
-  stream_session_t *session;
-  u32 session_index, thread_index;
-
-  if (api_parse_session_handle (a->handle, &session_index, &thread_index))
-    {
-      clib_warning ("Invalid handle");
-      return -1;
-    }
-
-  session = stream_session_get (session_index, thread_index);
-  stream_session_disconnect (session);
-
-  return 0;
-}
-
 /*
  * fd.io coding-style-patch-verification: ON
  *
diff --git a/src/vnet/session/application_interface.h b/src/vnet/session/application_interface.h
index 2c497531533..7d924c146a4 100644
--- a/src/vnet/session/application_interface.h
+++ b/src/vnet/session/application_interface.h
@@ -30,10 +30,18 @@ typedef enum _session_api_proto
 
 typedef struct _vnet_app_attach_args_t
 {
+  /** Binary API client index */
   u32 api_client_index;
+
+  /** Application and segment manager options */
   u64 *options;
+
+  /** Session to application callback functions */
   session_cb_vft_t *session_cb_vft;
 
+  /** Flag that indicates if app is builtin */
+  u8 builtin;
+
   /*
    * Results
    */
@@ -110,7 +118,7 @@ typedef struct _vnet_disconnect_args_t
 typedef enum
 {
   APP_EVT_QUEUE_SIZE,
-  SESSION_OPTIONS_FLAGS,
+  APP_OPTIONS_FLAGS,
   SESSION_OPTIONS_SEGMENT_SIZE,
   SESSION_OPTIONS_ADD_SEGMENT_SIZE,
   SESSION_OPTIONS_RX_FIFO_SIZE,
@@ -119,11 +127,30 @@ typedef enum
   SESSION_OPTIONS_N_OPTIONS
 } app_attach_options_index_t;
 
-/** Server can handle delegated connect requests from local clients */
-#define SESSION_OPTIONS_FLAGS_USE_FIFO	(1<<0)
+#define foreach_app_options_flags				\
+  _(USE_FIFO, "Use FIFO with redirects")			\
+  _(ADD_SEGMENT, "Add segment and signal app if needed")	\
+  _(BUILTIN_APP, "Application is builtin")			\
+
+typedef enum _app_options
+{
+#define _(sym, str) APP_OPTIONS_##sym,
+  foreach_app_options_flags
+#undef _
+} app_options_t;
+
+typedef enum _app_options_flags
+{
+#define _(sym, str) APP_OPTIONS_FLAGS_##sym = 1 << APP_OPTIONS_##sym,
+  foreach_app_options_flags
+#undef _
+} app_options_flags_t;
 
-/** Server wants vpp to add segments when out of memory for fifos */
-#define SESSION_OPTIONS_FLAGS_ADD_SEGMENT   (1<<1)
+///** Server can handle delegated connect requests from local clients */
+//#define APP_OPTIONS_FLAGS_USE_FIFO    (1<<0)
+//
+///** Server wants vpp to add segments when out of memory for fifos */
+//#define APP_OPTIONS_FLAGS_ADD_SEGMENT   (1<<1)
 
 #define VNET_CONNECT_REDIRECTED	123
 
@@ -138,7 +165,6 @@ int vnet_disconnect_session (vnet_disconnect_args_t * a);
 int vnet_bind (vnet_bind_args_t * a);
 int vnet_connect (vnet_connect_args_t * a);
 int vnet_unbind (vnet_unbind_args_t * a);
-int vnet_disconnect (vnet_disconnect_args_t * a);
 
 int
 api_parse_session_handle (u64 handle, u32 * session_index,
diff --git a/src/vnet/session/node.c b/src/vnet/session/node.c
index dd211c51a59..210754fa723 100644
--- a/src/vnet/session/node.c
+++ b/src/vnet/session/node.c
@@ -218,8 +218,8 @@ session_tx_fifo_read_and_snd_i (vlib_main_t * vm, vlib_node_runtime_t * node,
 	   *      2) buffer chains */
 	  if (peek_data)
 	    {
-	      n_bytes_read = svm_fifo_peek (s0->server_tx_fifo, s0->pid,
-					    rx_offset, len_to_deq0, data0);
+	      n_bytes_read = svm_fifo_peek (s0->server_tx_fifo, rx_offset,
+					    len_to_deq0, data0);
 	      if (n_bytes_read <= 0)
 		goto dequeue_fail;
 
@@ -230,8 +230,7 @@ session_tx_fifo_read_and_snd_i (vlib_main_t * vm, vlib_node_runtime_t * node,
 	  else
 	    {
 	      n_bytes_read = svm_fifo_dequeue_nowait (s0->server_tx_fifo,
-						      s0->pid, len_to_deq0,
-						      data0);
+						      len_to_deq0, data0);
 	      if (n_bytes_read <= 0)
 		goto dequeue_fail;
 	    }
@@ -301,6 +300,26 @@ session_tx_fifo_dequeue_and_snd (vlib_main_t * vm, vlib_node_runtime_t * node,
 					 n_tx_pkts, 0);
 }
 
+stream_session_t *
+session_event_get_session (session_fifo_event_t * e0, u8 thread_index)
+{
+  svm_fifo_t *f0;
+  stream_session_t *s0;
+  u32 session_index0;
+
+  f0 = e0->fifo;
+  session_index0 = f0->master_session_index;
+
+  /* $$$ add multiple event queues, per vpp worker thread */
+  ASSERT (f0->master_thread_index == thread_index);
+
+  s0 = stream_session_get_if_valid (session_index0, thread_index);
+
+  ASSERT (s0->thread_index == thread_index);
+
+  return s0;
+}
+
 static uword
 session_queue_node_fn (vlib_main_t * vm, vlib_node_runtime_t * node,
 		       vlib_frame_t * frame)
@@ -370,34 +389,24 @@ skip_dequeue:
   n_events = vec_len (my_fifo_events);
   for (i = 0; i < n_events; i++)
     {
-      svm_fifo_t *f0;		/* $$$ prefetch 1 ahead maybe */
-      stream_session_t *s0;
-      u32 session_index0;
+      stream_session_t *s0;	/* $$$ prefetch 1 ahead maybe */
       session_fifo_event_t *e0;
 
       e0 = &my_fifo_events[i];
-      f0 = e0->fifo;
-      session_index0 = f0->server_session_index;
-
-      /* $$$ add multiple event queues, per vpp worker thread */
-      ASSERT (f0->server_thread_index == my_thread_index);
 
-      s0 = stream_session_get_if_valid (session_index0, my_thread_index);
-
-      if (CLIB_DEBUG && !s0)
+      switch (e0->event_type)
 	{
-	  clib_warning ("It's dead, Jim!");
-	  continue;
-	}
-
-      if (PREDICT_FALSE (s0->session_state == SESSION_STATE_CLOSED))
-	continue;
+	case FIFO_EVENT_APP_TX:
+	  s0 = session_event_get_session (e0, my_thread_index);
 
-      ASSERT (s0->thread_index == my_thread_index);
+	  if (CLIB_DEBUG && !s0)
+	    {
+	      clib_warning ("It's dead, Jim!");
+	      continue;
+	    }
 
-      switch (e0->event_type)
-	{
-	case FIFO_EVENT_SERVER_TX:
+	  if (PREDICT_FALSE (s0->session_state == SESSION_STATE_CLOSED))
+	    continue;
 	  /* Spray packets in per session type frames, since they go to
 	   * different nodes */
 	  rv = (smm->session_tx_fns[s0->session_type]) (vm, node, smm, e0, s0,
@@ -408,10 +417,12 @@ skip_dequeue:
 	    goto done;
 
 	  break;
-	case FIFO_EVENT_SERVER_EXIT:
+	case FIFO_EVENT_DISCONNECT:
+	  s0 = stream_session_get_from_handle (e0->session_handle);
 	  stream_session_disconnect (s0);
 	  break;
 	case FIFO_EVENT_BUILTIN_RX:
+	  s0 = session_event_get_session (e0, my_thread_index);
 	  svm_fifo_unset_event (s0->server_rx_fifo);
 	  /* Get session's server */
 	  app = application_get (s0->app_index);
diff --git a/src/vnet/session/segment_manager.c b/src/vnet/session/segment_manager.c
index 16e5bc56736..e053232001d 100644
--- a/src/vnet/session/segment_manager.c
+++ b/src/vnet/session/segment_manager.c
@@ -28,6 +28,11 @@ u32 segment_name_counter = 0;
 segment_manager_t *segment_managers = 0;
 
 /**
+ * Process private segment index
+ */
+u32 private_segment_index = ~0;
+
+/**
  * Default fifo and segment size. TODO config.
  */
 u32 default_fifo_size = 1 << 16;
@@ -100,6 +105,26 @@ session_manager_add_first_segment (segment_manager_t * sm, u32 segment_size)
   return rv;
 }
 
+static void
+segment_manager_alloc_process_private_segment ()
+{
+  svm_fifo_segment_create_args_t _a, *a = &_a;
+
+  if (private_segment_index != ~0)
+    return;
+
+  memset (a, 0, sizeof (*a));
+  a->segment_name = "process-private-segment";
+  a->segment_size = ~0;
+  a->new_segment_index = ~0;
+
+  if (svm_fifo_segment_create_process_private (a))
+    clib_warning ("Failed to create process private segment");
+
+  private_segment_index = a->new_segment_index;
+  ASSERT (private_segment_index != ~0);
+}
+
 /**
  * Initializes segment manager based on options provided.
  * Returns error if svm segment allocation fails.
@@ -114,7 +139,9 @@ segment_manager_init (segment_manager_t * sm,
   /* app allocates these */
   sm->properties = properties;
 
-  if (first_seg_size > 0)
+  first_seg_size = first_seg_size > 0 ? first_seg_size : default_segment_size;
+
+  if (sm->properties->use_private_segment == 0)
     {
       rv = session_manager_add_first_segment (sm, first_seg_size);
       if (rv)
@@ -123,7 +150,15 @@ segment_manager_init (segment_manager_t * sm,
 	  return rv;
 	}
     }
+  else
+    {
+      if (private_segment_index == ~0)
+	segment_manager_alloc_process_private_segment ();
+      ASSERT (private_segment_index != ~0);
+      vec_add1 (sm->segment_indices, private_segment_index);
+    }
 
+  clib_spinlock_init (&sm->lockp);
   return 0;
 }
 
@@ -162,8 +197,8 @@ segment_manager_del (segment_manager_t * sm)
 	  stream_session_t *session;
 
 	  fifo = fifos[i];
-	  session_index = fifo->server_session_index;
-	  thread_index = fifo->server_thread_index;
+	  session_index = fifo->master_session_index;
+	  thread_index = fifo->master_thread_index;
 
 	  session = stream_session_get (session_index, thread_index);
 
@@ -183,7 +218,9 @@ segment_manager_del (segment_manager_t * sm)
 					deleted_thread_indices[i]);
 
 	  /* Instead of directly removing the session call disconnect */
-	  stream_session_disconnect (session);
+	  session_send_session_evt_to_thread (stream_session_handle (session),
+					      FIFO_EVENT_DISCONNECT,
+					      deleted_thread_indices[i]);
 
 	  /*
 	     stream_session_table_del (smm, session);
@@ -200,6 +237,7 @@ segment_manager_del (segment_manager_t * sm)
       /* svm_fifo_segment_delete (fifo_segment); */
     }
 
+  clib_spinlock_free (&sm->lockp);
   vec_free (deleted_sessions);
   vec_free (deleted_thread_indices);
   pool_put (segment_managers, sm);
@@ -232,9 +270,13 @@ segment_manager_alloc_session_fifos (segment_manager_t * sm,
   u8 added_a_segment = 0;
   int i;
 
-  /* Allocate svm fifos */
   ASSERT (vec_len (sm->segment_indices));
 
+  /* Make sure we don't have multiple threads trying to allocate segments
+   * at the same time. */
+  clib_spinlock_lock (&sm->lockp);
+
+  /* Allocate svm fifos */
 again:
   for (i = 0; i < vec_len (sm->segment_indices); i++)
     {
@@ -283,7 +325,9 @@ again:
 	    }
 
 	  if (session_manager_add_segment (sm))
-	    return VNET_API_ERROR_URI_FIFO_CREATE_FAILED;
+	    {
+	      return VNET_API_ERROR_URI_FIFO_CREATE_FAILED;
+	    }
 
 	  added_a_segment = 1;
 	  goto again;
@@ -295,14 +339,16 @@ again:
 	}
     }
 
-  if (added_a_segment)
-    return segment_manager_notify_app_seg_add (sm, *fifo_segment_index);
-
   /* Backpointers to segment manager */
   sm_index = segment_manager_index (sm);
   (*server_tx_fifo)->segment_manager = sm_index;
   (*server_rx_fifo)->segment_manager = sm_index;
 
+  clib_spinlock_unlock (&sm->lockp);
+
+  if (added_a_segment)
+    return segment_manager_notify_app_seg_add (sm, *fifo_segment_index);
+
   return 0;
 }
 
@@ -313,26 +359,72 @@ segment_manager_dealloc_fifos (u32 svm_segment_index, svm_fifo_t * rx_fifo,
   segment_manager_t *sm;
   svm_fifo_segment_private_t *fifo_segment;
 
+  sm = segment_manager_get_if_valid (rx_fifo->segment_manager);
+
+  /* It's possible to have no segment manager if the session was removed
+   * as result of a detach */
+  if (!sm)
+    return;
+
   fifo_segment = svm_fifo_get_segment (svm_segment_index);
   svm_fifo_segment_free_fifo (fifo_segment, rx_fifo);
   svm_fifo_segment_free_fifo (fifo_segment, tx_fifo);
 
-  /* If we have segment manager, try doing some cleanup.
-   * It's possible to have no segment manager if the session was removed
-   * as result of a detach */
-  sm = segment_manager_get_if_valid (rx_fifo->segment_manager);
-  if (sm)
+  /* Remove segment only if it holds no fifos and not the first */
+  if (sm->segment_indices[0] != svm_segment_index
+      && !svm_fifo_segment_has_fifos (fifo_segment))
     {
-      /* Remove segment only if it holds no fifos and not the first */
-      if (sm->segment_indices[0] != svm_segment_index
-	  && !svm_fifo_segment_has_fifos (fifo_segment))
-	{
-	  svm_fifo_segment_delete (fifo_segment);
-	  vec_del1 (sm->segment_indices, svm_segment_index);
-	}
+      svm_fifo_segment_delete (fifo_segment);
+      vec_del1 (sm->segment_indices, svm_segment_index);
     }
 }
 
+/**
+ * Allocates shm queue in the first segment
+ */
+unix_shared_memory_queue_t *
+segment_manager_alloc_queue (segment_manager_t * sm, u32 queue_size)
+{
+  ssvm_shared_header_t *sh;
+  svm_fifo_segment_private_t *segment;
+  unix_shared_memory_queue_t *q;
+  void *oldheap;
+
+  ASSERT (sm->segment_indices != 0);
+
+  segment = svm_fifo_get_segment (sm->segment_indices[0]);
+  sh = segment->ssvm.sh;
+
+  oldheap = ssvm_push_heap (sh);
+  q =
+    unix_shared_memory_queue_init (queue_size, sizeof (session_fifo_event_t),
+				   0 /* consumer pid */ , 0
+				   /* signal when queue non-empty */ );
+  ssvm_pop_heap (oldheap);
+  return q;
+}
+
+/**
+ * Frees shm queue allocated in the first segment
+ */
+void
+segment_manager_dealloc_queue (segment_manager_t * sm,
+			       unix_shared_memory_queue_t * q)
+{
+  ssvm_shared_header_t *sh;
+  svm_fifo_segment_private_t *segment;
+  void *oldheap;
+
+  ASSERT (sm->segment_indices != 0);
+
+  segment = svm_fifo_get_segment (sm->segment_indices[0]);
+  sh = segment->ssvm.sh;
+
+  oldheap = ssvm_push_heap (sh);
+  unix_shared_memory_queue_free (q);
+  ssvm_pop_heap (oldheap);
+}
+
 /*
  * fd.io coding-style-patch-verification: ON
  *
diff --git a/src/vnet/session/segment_manager.h b/src/vnet/session/segment_manager.h
index 778d6040e94..2710bb544d7 100644
--- a/src/vnet/session/segment_manager.h
+++ b/src/vnet/session/segment_manager.h
@@ -18,6 +18,10 @@
 #include <vnet/vnet.h>
 #include <svm/svm_fifo_segment.h>
 
+#include <vlibmemory/unix_shared_memory_queue.h>
+#include <vlibmemory/api.h>
+#include <vppinfra/lock.h>
+
 typedef struct _segment_manager_properties
 {
   /** Session fifo sizes.  */
@@ -30,10 +34,14 @@ typedef struct _segment_manager_properties
   /** Flag that indicates if additional segments should be created */
   u8 add_segment;
 
+  /** Use private memory segment instead of shared memory */
+  u8 use_private_segment;
 } segment_manager_properties_t;
 
 typedef struct _segment_manager
 {
+  clib_spinlock_t lockp;
+
   /** segments mapped by this manager */
   u32 *segment_indices;
 
@@ -95,6 +103,10 @@ segment_manager_alloc_session_fifos (segment_manager_t * sm,
 void
 segment_manager_dealloc_fifos (u32 svm_segment_index, svm_fifo_t * rx_fifo,
 			       svm_fifo_t * tx_fifo);
+unix_shared_memory_queue_t *segment_manager_alloc_queue (segment_manager_t *
+							 sm, u32 queue_size);
+void segment_manager_dealloc_queue (segment_manager_t * sm,
+				    unix_shared_memory_queue_t * q);
 
 #endif /* SRC_VNET_SESSION_SEGMENT_MANAGER_H_ */
 /*
diff --git a/src/vnet/session/session.c b/src/vnet/session/session.c
index e6cfe7dab3d..d17c93f8f69 100644
--- a/src/vnet/session/session.c
+++ b/src/vnet/session/session.c
@@ -377,33 +377,6 @@ stream_session_lookup_transport6 (ip6_address_t * lcl, ip6_address_t * rmt,
   return 0;
 }
 
-/**
- * Allocate vpp event queue (once) per worker thread
- */
-void
-session_vpp_event_queue_allocate (session_manager_main_t * smm,
-				  u32 thread_index)
-{
-  api_main_t *am = &api_main;
-  void *oldheap;
-
-  if (smm->vpp_event_queues[thread_index] == 0)
-    {
-      /* Allocate event fifo in the /vpe-api shared-memory segment */
-      oldheap = svm_push_data_heap (am->vlib_rp);
-
-      smm->vpp_event_queues[thread_index] =
-	unix_shared_memory_queue_init (2048 /* nels $$$$ config */ ,
-				       sizeof (session_fifo_event_t),
-				       0 /* consumer pid */ ,
-				       0
-				       /* (do not) send signal when queue non-empty */
-	);
-
-      svm_pop_heap (oldheap);
-    }
-}
-
 int
 stream_session_create_i (segment_manager_t * sm, transport_connection_t * tc,
 			 stream_session_t ** ret_s)
@@ -428,11 +401,11 @@ stream_session_create_i (segment_manager_t * sm, transport_connection_t * tc,
 
   /* Initialize backpointers */
   pool_index = s - smm->sessions[thread_index];
-  server_rx_fifo->server_session_index = pool_index;
-  server_rx_fifo->server_thread_index = thread_index;
+  server_rx_fifo->master_session_index = pool_index;
+  server_rx_fifo->master_thread_index = thread_index;
 
-  server_tx_fifo->server_session_index = pool_index;
-  server_tx_fifo->server_thread_index = thread_index;
+  server_tx_fifo->master_session_index = pool_index;
+  server_tx_fifo->master_thread_index = thread_index;
 
   s->server_rx_fifo = server_rx_fifo;
   s->server_tx_fifo = server_tx_fifo;
@@ -485,7 +458,7 @@ stream_session_enqueue_data (transport_connection_t * tc, u8 * data, u16 len,
   if (PREDICT_FALSE (len > svm_fifo_max_enqueue (s->server_rx_fifo)))
     return -1;
 
-  enqueued = svm_fifo_enqueue_nowait (s->server_rx_fifo, s->pid, len, data);
+  enqueued = svm_fifo_enqueue_nowait (s->server_rx_fifo, len, data);
 
   if (queue_event)
     {
@@ -527,14 +500,14 @@ stream_session_peek_bytes (transport_connection_t * tc, u8 * buffer,
 			   u32 offset, u32 max_bytes)
 {
   stream_session_t *s = stream_session_get (tc->s_index, tc->thread_index);
-  return svm_fifo_peek (s->server_tx_fifo, s->pid, offset, max_bytes, buffer);
+  return svm_fifo_peek (s->server_tx_fifo, offset, max_bytes, buffer);
 }
 
 u32
 stream_session_dequeue_drop (transport_connection_t * tc, u32 max_bytes)
 {
   stream_session_t *s = stream_session_get (tc->s_index, tc->thread_index);
-  return svm_fifo_dequeue_drop (s->server_tx_fifo, s->pid, max_bytes);
+  return svm_fifo_dequeue_drop (s->server_tx_fifo, max_bytes);
 }
 
 /**
@@ -568,7 +541,7 @@ stream_session_enqueue_notify (stream_session_t * s, u8 block)
     {
       /* Fabricate event */
       evt.fifo = s->server_rx_fifo;
-      evt.event_type = FIFO_EVENT_SERVER_RX;
+      evt.event_type = FIFO_EVENT_APP_RX;
       evt.event_id = serial_number++;
 
       /* Add event to server's event queue */
@@ -899,37 +872,45 @@ stream_session_stop_listen (stream_session_t * s)
   return 0;
 }
 
+void
+session_send_session_evt_to_thread (u64 session_handle,
+				    fifo_event_type_t evt_type,
+				    u32 thread_index)
+{
+  static u16 serial_number = 0;
+  session_fifo_event_t evt;
+  unix_shared_memory_queue_t *q;
+
+  /* Fabricate event */
+  evt.session_handle = session_handle;
+  evt.event_type = evt_type;
+  evt.event_id = serial_number++;
+
+  q = session_manager_get_vpp_event_queue (thread_index);
+
+  /* Based on request block (or not) for lack of space */
+  if (PREDICT_TRUE (q->cursize < q->maxsize))
+    unix_shared_memory_queue_add (q, (u8 *) & evt,
+				  0 /* do wait for mutex */ );
+  else
+    {
+      clib_warning ("queue full");
+      return;
+    }
+}
+
 /**
  * Disconnect session and propagate to transport. This should eventually
  * result in a delete notification that allows us to cleanup session state.
  * Called for both active/passive disconnects.
+ *
+ * Should be called from the session's thread.
  */
 void
 stream_session_disconnect (stream_session_t * s)
 {
-//  session_fifo_event_t evt;
-
   s->session_state = SESSION_STATE_CLOSED;
-  /* RPC to vpp evt queue in the right thread */
-
   tp_vfts[s->session_type].close (s->connection_index, s->thread_index);
-
-//  {
-//  /* Fabricate event */
-//  evt.fifo = s->server_rx_fifo;
-//  evt.event_type = FIFO_EVENT_SERVER_RX;
-//  evt.event_id = serial_number++;
-//
-//  /* Based on request block (or not) for lack of space */
-//  if (PREDICT_TRUE(q->cursize < q->maxsize))
-//    unix_shared_memory_queue_add (app->event_queue, (u8 *) &evt,
-//                                0 /* do wait for mutex */);
-//  else
-//    {
-//      clib_warning("fifo full");
-//      return -1;
-//    }
-//  }
 }
 
 /**
@@ -976,6 +957,33 @@ session_get_transport_vft (u8 type)
   return &tp_vfts[type];
 }
 
+/**
+ * Allocate vpp event queue (once) per worker thread
+ */
+void
+session_vpp_event_queue_allocate (session_manager_main_t * smm,
+				  u32 thread_index)
+{
+  api_main_t *am = &api_main;
+  void *oldheap;
+
+  if (smm->vpp_event_queues[thread_index] == 0)
+    {
+      /* Allocate event fifo in the /vpe-api shared-memory segment */
+      oldheap = svm_push_data_heap (am->vlib_rp);
+
+      smm->vpp_event_queues[thread_index] =
+	unix_shared_memory_queue_init (2048 /* nels $$$$ config */ ,
+				       sizeof (session_fifo_event_t),
+				       0 /* consumer pid */ ,
+				       0
+				       /* (do not) send signal when queue non-empty */
+	);
+
+      svm_pop_heap (oldheap);
+    }
+}
+
 static clib_error_t *
 session_manager_main_enable (vlib_main_t * vm)
 {
@@ -1043,6 +1051,18 @@ session_manager_main_enable (vlib_main_t * vm)
   return 0;
 }
 
+void
+session_node_enable_disable (u8 is_en)
+{
+  u8 state = is_en ? VLIB_NODE_STATE_POLLING : VLIB_NODE_STATE_DISABLED;
+  /* *INDENT-OFF* */
+  foreach_vlib_main (({
+    vlib_node_set_state (this_vlib_main, session_queue_node.index,
+                         state);
+  }));
+  /* *INDENT-ON* */
+}
+
 clib_error_t *
 vnet_session_enable_disable (vlib_main_t * vm, u8 is_en)
 {
@@ -1051,16 +1071,14 @@ vnet_session_enable_disable (vlib_main_t * vm, u8 is_en)
       if (session_manager_main.is_enabled)
 	return 0;
 
-      vlib_node_set_state (vm, session_queue_node.index,
-			   VLIB_NODE_STATE_POLLING);
+      session_node_enable_disable (is_en);
 
       return session_manager_main_enable (vm);
     }
   else
     {
       session_manager_main.is_enabled = 0;
-      vlib_node_set_state (vm, session_queue_node.index,
-			   VLIB_NODE_STATE_DISABLED);
+      session_node_enable_disable (is_en);
     }
 
   return 0;
diff --git a/src/vnet/session/session.h b/src/vnet/session/session.h
index 6e4ea96dd5c..8cd72f3577a 100644
--- a/src/vnet/session/session.h
+++ b/src/vnet/session/session.h
@@ -17,9 +17,6 @@
 
 #include <vnet/session/transport.h>
 #include <vlibmemory/unix_shared_memory_queue.h>
-#include <vlibmemory/api.h>
-#include <vppinfra/sparse_vec.h>
-#include <svm/svm_fifo_segment.h>
 #include <vnet/session/session_debug.h>
 #include <vnet/session/segment_manager.h>
 
@@ -31,10 +28,10 @@
 
 typedef enum
 {
-  FIFO_EVENT_SERVER_RX,
-  FIFO_EVENT_SERVER_TX,
+  FIFO_EVENT_APP_RX,
+  FIFO_EVENT_APP_TX,
   FIFO_EVENT_TIMEOUT,
-  FIFO_EVENT_SERVER_EXIT,
+  FIFO_EVENT_DISCONNECT,
   FIFO_EVENT_BUILTIN_RX
 } fifo_event_type_t;
 
@@ -96,7 +93,11 @@ typedef enum
 
 /* *INDENT-OFF* */
 typedef CLIB_PACKED (struct {
-  svm_fifo_t * fifo;
+  union
+    {
+      svm_fifo_t * fifo;
+      u64 session_handle;
+    };
   u8 event_type;
   u16 event_id;
 }) session_fifo_event_t;
@@ -370,7 +371,9 @@ int stream_session_listen (stream_session_t * s, transport_endpoint_t * tep);
 int stream_session_stop_listen (stream_session_t * s);
 void stream_session_disconnect (stream_session_t * s);
 void stream_session_cleanup (stream_session_t * s);
-
+void session_send_session_evt_to_thread (u64 session_handle,
+					 fifo_event_type_t evt_type,
+					 u32 thread_index);
 u8 *format_stream_session (u8 * s, va_list * args);
 
 void session_register_transport (u8 type, const transport_proto_vft_t * vft);
diff --git a/src/vnet/session/session_api.c b/src/vnet/session/session_api.c
index 8116b673a32..79d67a2fece 100755
--- a/src/vnet/session/session_api.c
+++ b/src/vnet/session/session_api.c
@@ -96,7 +96,7 @@ send_session_accept_callback (stream_session_t * s)
   memset (mp, 0, sizeof (*mp));
 
   mp->_vl_msg_id = clib_host_to_net_u16 (VL_API_ACCEPT_SESSION);
-
+  mp->context = server->index;
   listener = listen_session_get (s->session_type, s->listener_index);
   tp_vft = session_get_transport_vft (s->session_type);
   tc = tp_vft->get_connection (s->connection_index, s->thread_index);
@@ -270,23 +270,6 @@ static session_cb_vft_t uri_session_cb_vft = {
   .redirect_connect_callback = redirect_connect_callback
 };
 
-static int
-api_session_not_valid (u32 session_index, u32 thread_index)
-{
-  session_manager_main_t *smm = vnet_get_session_manager_main ();
-  stream_session_t *pool;
-
-  if (thread_index >= vec_len (smm->sessions))
-    return VNET_API_ERROR_INVALID_VALUE;
-
-  pool = smm->sessions[thread_index];
-
-  if (pool_is_free_index (pool, session_index))
-    return VNET_API_ERROR_INVALID_VALUE_2;
-
-  return 0;
-}
-
 static void
 vl_api_session_enable_disable_t_handler (vl_api_session_enable_disable_t * mp)
 {
@@ -324,9 +307,9 @@ vl_api_application_attach_t_handler (vl_api_application_attach_t * mp)
   rv = vnet_application_attach (a);
 
 done:
+
   /* *INDENT-OFF* */
   REPLY_MACRO2 (VL_API_APPLICATION_ATTACH_REPLY, ({
-    rmp->retval = rv;
     if (!rv)
       {
 	rmp->segment_name_length = 0;
@@ -558,24 +541,33 @@ static void
 vl_api_accept_session_reply_t_handler (vl_api_accept_session_reply_t * mp)
 {
   stream_session_t *s;
-  int rv;
   u32 session_index, thread_index;
-  session_index = stream_session_index_from_handle (mp->handle);
-  thread_index = stream_session_thread_from_handle (mp->handle);
-  if (api_session_not_valid (session_index, thread_index))
-    return;
-
-  s = stream_session_get (session_index, thread_index);
-  rv = mp->retval;
+  vnet_disconnect_args_t _a, *a = &_a;
 
-  if (rv)
+  /* Server isn't interested, kill the session */
+  if (mp->retval)
     {
-      /* Server isn't interested, kill the session */
-      stream_session_disconnect (s);
-      return;
+      a->app_index = mp->context;
+      a->handle = mp->handle;
+      vnet_disconnect_session (a);
+    }
+  else
+    {
+      stream_session_parse_handle (mp->handle, &session_index, &thread_index);
+      s = stream_session_get_if_valid (session_index, thread_index);
+      if (!s)
+	{
+	  clib_warning ("session doesn't exist");
+	  return;
+	}
+      if (s->app_index != mp->context)
+	{
+	  clib_warning ("app doesn't own session");
+	  return;
+	}
+      /* XXX volatile? */
+      s->session_state = SESSION_STATE_READY;
     }
-
-  s->session_state = SESSION_STATE_READY;
 }
 
 static void