session: async rx event notifications
[vpp.git] / src / vnet / session / application_local.c
index 5a3f738..192c22b 100644 (file)
 #include <vnet/session/application_local.h>
 #include <vnet/session/session.h>
 
-static ct_connection_t *connections;
-
-static void
-ct_enable_disable_main_pre_input_node (u8 is_add)
+typedef enum ct_segment_flags_
 {
-  u32 n_conns;
+  CT_SEGMENT_F_CLIENT_DETACHED = 1 << 0,
+  CT_SEGMENT_F_SERVER_DETACHED = 1 << 1,
+} ct_segment_flags_t;
 
-  n_conns = pool_elts (connections);
-  if (n_conns > 2)
-    return;
+typedef struct ct_segment_
+{
+  u32 client_n_sessions;
+  u32 server_n_sessions;
+  u32 seg_ctx_index;
+  u32 ct_seg_index;
+  u32 segment_index;
+  ct_segment_flags_t flags;
+} ct_segment_t;
+
+typedef struct ct_segments_
+{
+  u32 sm_index;
+  u32 server_wrk;
+  u32 client_wrk;
+  u32 fifo_pair_bytes;
+  ct_segment_t *segments;
+} ct_segments_ctx_t;
+
+typedef struct ct_cleanup_req_
+{
+  u32 ct_index;
+} ct_cleanup_req_t;
 
-  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);
+typedef struct ct_worker_
+{
+  ct_connection_t *connections;              /**< Per-worker connection pools */
+  u32 *pending_connects;             /**< Fifo of pending ho indices */
+  ct_cleanup_req_t *pending_cleanups; /**< Fifo of pending indices */
+  u8 have_connects;                  /**< Set if connect rpc pending */
+  u8 have_cleanups;                  /**< Set if cleanup rpc pending */
+  clib_spinlock_t pending_connects_lock; /**< Lock for pending connects */
+  u32 *new_connects;                    /**< Burst of connects to be done */
+} ct_worker_t;
+
+typedef struct ct_main_
+{
+  ct_worker_t *wrk;                    /**< Per-worker state */
+  u32 n_workers;                       /**< Number of vpp workers */
+  u32 n_sessions;                      /**< Cumulative sessions counter */
+  u32 *ho_reusable;                    /**< Vector of reusable ho indices */
+  clib_spinlock_t ho_reuseable_lock;   /**< Lock for reusable ho indices */
+  clib_rwlock_t app_segs_lock;         /**< RW lock for seg contexts */
+  uword *app_segs_ctxs_table;          /**< App handle to segment pool map */
+  ct_segments_ctx_t *app_seg_ctxs;     /**< Pool of ct segment contexts */
+  u32 **fwrk_pending_connects;         /**< First wrk pending half-opens */
+  u32 fwrk_thread;                     /**< First worker thread */
+  u8 fwrk_have_flush;                  /**< Flag for connect flush rpc */
+} ct_main_t;
+
+static ct_main_t ct_main;
+
+static inline ct_worker_t *
+ct_worker_get (u32 thread_index)
+{
+  return &ct_main.wrk[thread_index];
 }
 
 static ct_connection_t *
-ct_connection_alloc (void)
+ct_connection_alloc (u32 thread_index)
 {
+  ct_worker_t *wrk = ct_worker_get (thread_index);
   ct_connection_t *ct;
 
-  pool_get_zero (connections, ct);
-  ct->c_c_index = ct - connections;
-  ct->c_thread_index = 0;
+  pool_get_aligned_safe (wrk->connections, ct, CLIB_CACHE_LINE_BYTES);
+  clib_memset (ct, 0, sizeof (*ct));
+  ct->c_c_index = ct - wrk->connections;
+  ct->c_thread_index = thread_index;
   ct->client_wrk = ~0;
   ct->server_wrk = ~0;
+  ct->seg_ctx_index = ~0;
+  ct->ct_seg_index = ~0;
   return ct;
 }
 
 static ct_connection_t *
-ct_connection_get (u32 ct_index)
+ct_connection_get (u32 ct_index, u32 thread_index)
 {
-  if (pool_is_free_index (connections, ct_index))
+  ct_worker_t *wrk = ct_worker_get (thread_index);
+
+  if (pool_is_free_index (wrk->connections, ct_index))
     return 0;
-  return pool_elt_at_index (connections, ct_index);
+  return pool_elt_at_index (wrk->connections, ct_index);
 }
 
 static void
 ct_connection_free (ct_connection_t * ct)
 {
+  ct_worker_t *wrk = ct_worker_get (ct->c_thread_index);
+
   if (CLIB_DEBUG)
-    memset (ct, 0xfc, sizeof (*ct));
-  pool_put (connections, ct);
+    {
+      clib_memset (ct, 0xfc, sizeof (*ct));
+      pool_put (wrk->connections, ct);
+      return;
+    }
+  pool_put (wrk->connections, ct);
+}
+
+static ct_connection_t *
+ct_half_open_alloc (void)
+{
+  ct_main_t *cm = &ct_main;
+  u32 *hip;
+
+  clib_spinlock_lock (&cm->ho_reuseable_lock);
+  vec_foreach (hip, cm->ho_reusable)
+    pool_put_index (cm->wrk[cm->fwrk_thread].connections, *hip);
+  vec_reset_length (cm->ho_reusable);
+  clib_spinlock_unlock (&cm->ho_reuseable_lock);
+
+  return ct_connection_alloc (cm->fwrk_thread);
+}
+
+static ct_connection_t *
+ct_half_open_get (u32 ho_index)
+{
+  ct_main_t *cm = &ct_main;
+  return ct_connection_get (ho_index, cm->fwrk_thread);
+}
+
+void
+ct_half_open_add_reusable (u32 ho_index)
+{
+  ct_main_t *cm = &ct_main;
+
+  clib_spinlock_lock (&cm->ho_reuseable_lock);
+  vec_add1 (cm->ho_reusable, ho_index);
+  clib_spinlock_unlock (&cm->ho_reuseable_lock);
 }
 
 session_t *
 ct_session_get_peer (session_t * s)
 {
   ct_connection_t *ct, *peer_ct;
-  ct = ct_connection_get (s->connection_index);
-  peer_ct = ct_connection_get (ct->peer_index);
-  return session_get (peer_ct->c_s_index, 0);
+  ct = ct_connection_get (s->connection_index, s->thread_index);
+  peer_ct = ct_connection_get (ct->peer_index, s->thread_index);
+  return session_get (peer_ct->c_s_index, s->thread_index);
 }
 
 void
@@ -83,188 +170,536 @@ ct_session_endpoint (session_t * ll, session_endpoint_t * sep)
   sep->transport_proto = ct->actual_tp;
   sep->port = ct->c_lcl_port;
   sep->is_ip4 = ct->c_is_ip4;
+  ip_copy (&sep->ip, &ct->c_lcl_ip, ct->c_is_ip4);
+}
+
+static void
+ct_set_invalid_app_wrk (ct_connection_t *ct, u8 is_client)
+{
+  ct_connection_t *peer_ct;
+
+  peer_ct = ct_connection_get (ct->peer_index, ct->c_thread_index);
+
+  if (is_client)
+    {
+      ct->client_wrk = APP_INVALID_INDEX;
+      if (peer_ct)
+       ct->client_wrk = APP_INVALID_INDEX;
+    }
+  else
+    {
+      ct->server_wrk = APP_INVALID_INDEX;
+      if (peer_ct)
+       ct->server_wrk = APP_INVALID_INDEX;
+    }
+}
+
+static void
+ct_session_dealloc_fifos (ct_connection_t *ct, svm_fifo_t *rx_fifo,
+                         svm_fifo_t *tx_fifo)
+{
+  ct_segments_ctx_t *seg_ctx;
+  ct_main_t *cm = &ct_main;
+  segment_manager_t *sm;
+  app_worker_t *app_wrk;
+  ct_segment_t *ct_seg;
+  fifo_segment_t *fs;
+  u32 seg_index;
+  session_t *s;
+  int cnt;
+
+  /*
+   * Cleanup fifos
+   */
+
+  sm = segment_manager_get (rx_fifo->segment_manager);
+  seg_index = rx_fifo->segment_index;
+
+  fs = segment_manager_get_segment_w_lock (sm, seg_index);
+  fifo_segment_free_fifo (fs, rx_fifo);
+  fifo_segment_free_fifo (fs, tx_fifo);
+  segment_manager_segment_reader_unlock (sm);
+
+  /*
+   * Atomically update segment context with readers lock
+   */
+
+  clib_rwlock_reader_lock (&cm->app_segs_lock);
+
+  seg_ctx = pool_elt_at_index (cm->app_seg_ctxs, ct->seg_ctx_index);
+  ct_seg = pool_elt_at_index (seg_ctx->segments, ct->ct_seg_index);
+
+  if (ct->flags & CT_CONN_F_CLIENT)
+    {
+      cnt =
+       __atomic_sub_fetch (&ct_seg->client_n_sessions, 1, __ATOMIC_RELAXED);
+    }
+  else
+    {
+      cnt =
+       __atomic_sub_fetch (&ct_seg->server_n_sessions, 1, __ATOMIC_RELAXED);
+    }
+
+  clib_rwlock_reader_unlock (&cm->app_segs_lock);
+
+  /*
+   * No need to do any app updates, return
+   */
+  ASSERT (cnt >= 0);
+  if (cnt)
+    return;
+
+  /*
+   * Grab exclusive lock and update flags unless some other thread
+   * added more sessions
+   */
+  clib_rwlock_writer_lock (&cm->app_segs_lock);
+
+  seg_ctx = pool_elt_at_index (cm->app_seg_ctxs, ct->seg_ctx_index);
+  ct_seg = pool_elt_at_index (seg_ctx->segments, ct->ct_seg_index);
+  if (ct->flags & CT_CONN_F_CLIENT)
+    {
+      cnt = ct_seg->client_n_sessions;
+      if (cnt)
+       goto done;
+      ct_seg->flags |= CT_SEGMENT_F_CLIENT_DETACHED;
+      s = session_get (ct->c_s_index, ct->c_thread_index);
+      if (s->app_wrk_index == APP_INVALID_INDEX)
+       ct_set_invalid_app_wrk (ct, 1 /* is_client */);
+    }
+  else
+    {
+      cnt = ct_seg->server_n_sessions;
+      if (cnt)
+       goto done;
+      ct_seg->flags |= CT_SEGMENT_F_SERVER_DETACHED;
+      s = session_get (ct->c_s_index, ct->c_thread_index);
+      if (s->app_wrk_index == APP_INVALID_INDEX)
+       ct_set_invalid_app_wrk (ct, 0 /* is_client */);
+    }
+
+  if (!(ct_seg->flags & CT_SEGMENT_F_CLIENT_DETACHED) ||
+      !(ct_seg->flags & CT_SEGMENT_F_SERVER_DETACHED))
+    goto done;
+
+  /*
+   * Remove segment context because both client and server detached
+   */
+
+  pool_put_index (seg_ctx->segments, ct->ct_seg_index);
+
+  /*
+   * No more segment indices left, remove the segments context
+   */
+  if (!pool_elts (seg_ctx->segments))
+    {
+      u64 table_handle = seg_ctx->client_wrk << 16 | seg_ctx->server_wrk;
+      table_handle = (u64) seg_ctx->sm_index << 32 | table_handle;
+      hash_unset (cm->app_segs_ctxs_table, table_handle);
+      pool_free (seg_ctx->segments);
+      pool_put_index (cm->app_seg_ctxs, ct->seg_ctx_index);
+    }
+
+  /*
+   * Segment to be removed so notify both apps
+   */
+
+  app_wrk = app_worker_get_if_valid (ct->client_wrk);
+  /* Determine if client app still needs notification, i.e., if it is
+   * still attached. If client detached and this is the last ct session
+   * on this segment, then its connects segment manager should also be
+   * detached, so do not send notification */
+  if (app_wrk)
+    {
+      segment_manager_t *csm;
+      csm = app_worker_get_connect_segment_manager (app_wrk);
+      if (!segment_manager_app_detached (csm))
+       app_worker_del_segment_notify (app_wrk, ct->segment_handle);
+    }
+
+  /* Notify server app and free segment */
+  segment_manager_lock_and_del_segment (sm, seg_index);
+
+  /* Cleanup segment manager if needed. If server detaches there's a chance
+   * the client's sessions will hold up segment removal */
+  if (segment_manager_app_detached (sm) && !segment_manager_has_fifos (sm))
+    segment_manager_free_safe (sm);
+
+done:
+
+  clib_rwlock_writer_unlock (&cm->app_segs_lock);
+}
+
+static void
+ct_session_force_disconnect_server (ct_connection_t *sct)
+{
+  sct->peer_index = ~0;
+  session_transport_closing_notify (&sct->connection);
 }
 
 int
-ct_session_connect_notify (session_t * ss)
+ct_session_connect_notify (session_t *ss, session_error_t err)
 {
-  svm_fifo_segment_private_t *seg;
+  u32 ss_index, opaque, thread_index;
   ct_connection_t *sct, *cct;
   app_worker_t *client_wrk;
-  segment_manager_t *sm;
-  u64 segment_handle;
-  int is_fail = 0;
   session_t *cs;
-  u32 ss_index;
 
   ss_index = ss->session_index;
+  thread_index = ss->thread_index;
   sct = (ct_connection_t *) session_get_transport (ss);
   client_wrk = app_worker_get (sct->client_wrk);
+  opaque = sct->client_opaque;
 
-  sm = segment_manager_get (ss->rx_fifo->segment_manager);
-  seg = segment_manager_get_segment_w_lock (sm, ss->rx_fifo->segment_index);
-  segment_handle = segment_manager_segment_handle (sm, seg);
+  cct = ct_connection_get (sct->peer_index, thread_index);
 
-  if (app_worker_add_segment_notify (client_wrk, segment_handle))
+  /* Client closed while waiting for reply from server */
+  if (PREDICT_FALSE (!cct))
     {
-      clib_warning ("failed to notify client %u of new segment",
-                   sct->client_wrk);
-      segment_manager_segment_reader_unlock (sm);
-      session_close (ss);
-      is_fail = 1;
-    }
-  else
-    {
-      segment_manager_segment_reader_unlock (sm);
+      ct_session_force_disconnect_server (sct);
+      return 0;
     }
 
-  /* Alloc client session */
-  cct = ct_connection_get (sct->peer_index);
+  session_half_open_delete_notify (&cct->connection);
+  cct->flags &= ~CT_CONN_F_HALF_OPEN;
 
-  cs = session_alloc (0);
-  ss = session_get (ss_index, 0);
+  if (PREDICT_FALSE (err))
+    goto connect_error;
+
+  /*
+   * Alloc client session, server session assumed to be established
+   */
+
+  ASSERT (ss->session_state >= SESSION_STATE_READY);
+
+  cs = session_alloc (thread_index);
+  ss = session_get (ss_index, thread_index);
   cs->session_type = ss->session_type;
-  cs->connection_index = sct->c_c_index;
-  cs->listener_index = SESSION_INVALID_INDEX;
-  cs->session_state = SESSION_STATE_CONNECTING;
+  cs->listener_handle = SESSION_INVALID_HANDLE;
+  session_set_state (cs, 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
    * the segment manager/worker is freed */
-  if (app_worker_init_connected (client_wrk, cs))
+  if ((err = app_worker_init_connected (client_wrk, cs)))
     {
-      session_close (ss);
-      return -1;
+      session_free (cs);
+      ct_session_force_disconnect_server (sct);
+      err = SESSION_E_ALLOC;
+      goto connect_error;
     }
 
-  if (app_worker_connect_notify (client_wrk, is_fail ? 0 : cs,
-                                sct->client_opaque))
+  session_set_state (cs, SESSION_STATE_CONNECTING);
+
+  if (app_worker_connect_notify (client_wrk, cs, 0, opaque))
     {
-      session_close (ss);
-      return -1;
+      segment_manager_dealloc_fifos (cs->rx_fifo, cs->tx_fifo);
+      session_free (cs);
+      ct_session_force_disconnect_server (sct);
+      goto cleanup_client;
     }
 
-  cs = session_get (cct->c_s_index, 0);
-  cs->session_state = SESSION_STATE_READY;
+  cs = session_get (cct->c_s_index, cct->c_thread_index);
+  session_set_state (cs, SESSION_STATE_READY);
 
   return 0;
+
+connect_error:
+
+  app_worker_connect_notify (client_wrk, 0, err, cct->client_opaque);
+
+cleanup_client:
+
+  if (cct->client_rx_fifo)
+    ct_session_dealloc_fifos (cct, cct->client_rx_fifo, cct->client_tx_fifo);
+  ct_connection_free (cct);
+  return -1;
 }
 
-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)
+static inline ct_segment_t *
+ct_lookup_free_segment (ct_main_t *cm, segment_manager_t *sm,
+                       u32 seg_ctx_index)
+{
+  uword free_bytes, max_free_bytes;
+  ct_segment_t *ct_seg, *res = 0;
+  ct_segments_ctx_t *seg_ctx;
+  fifo_segment_t *fs;
+  u32 max_fifos;
+
+  seg_ctx = pool_elt_at_index (cm->app_seg_ctxs, seg_ctx_index);
+  max_free_bytes = seg_ctx->fifo_pair_bytes;
+
+  pool_foreach (ct_seg, seg_ctx->segments)
+    {
+      /* Client or server has detached so segment cannot be used */
+      fs = segment_manager_get_segment (sm, ct_seg->segment_index);
+      free_bytes = fifo_segment_available_bytes (fs);
+      max_fifos = fifo_segment_size (fs) / seg_ctx->fifo_pair_bytes;
+      if (free_bytes > max_free_bytes &&
+         fifo_segment_num_fifos (fs) / 2 < max_fifos)
+       {
+         max_free_bytes = free_bytes;
+         res = ct_seg;
+       }
+    }
+
+  return res;
+}
+
+static ct_segment_t *
+ct_alloc_segment (ct_main_t *cm, app_worker_t *server_wrk, u64 table_handle,
+                 segment_manager_t *sm, u32 client_wrk_index)
 {
-  u32 round_rx_fifo_sz, round_tx_fifo_sz, sm_index, seg_size;
-  segment_manager_properties_t *props;
-  svm_fifo_segment_private_t *seg;
+  u32 seg_ctx_index = ~0, sm_index, pair_bytes;
+  segment_manager_props_t *props;
+  const u32 margin = 16 << 10;
+  ct_segments_ctx_t *seg_ctx;
+  app_worker_t *client_wrk;
+  u64 seg_size, seg_handle;
   application_t *server;
-  segment_manager_t *sm;
-  u32 margin = 16 << 10;
-  u64 segment_handle;
-  int seg_index, rv;
+  ct_segment_t *ct_seg;
+  uword *spp;
+  int fs_index;
 
   server = application_get (server_wrk->app_index);
-
   props = application_segment_manager_properties (server);
-  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 + margin;
+  sm_index = segment_manager_index (sm);
+  pair_bytes = props->rx_fifo_size + props->tx_fifo_size + margin;
 
-  sm = app_worker_get_listen_segment_manager (server_wrk, ll);
-  seg_index = segment_manager_add_segment (sm, seg_size);
-  if (seg_index < 0)
+  /*
+   * Make sure another thread did not alloc a segment while acquiring the lock
+   */
+
+  spp = hash_get (cm->app_segs_ctxs_table, table_handle);
+  if (spp)
     {
-      clib_warning ("failed to add new cut-through segment");
-      return seg_index;
+      seg_ctx_index = *spp;
+      ct_seg = ct_lookup_free_segment (cm, sm, seg_ctx_index);
+      if (ct_seg)
+       return ct_seg;
     }
-  seg = segment_manager_get_segment_w_lock (sm, seg_index);
 
-  rv = segment_manager_try_alloc_fifos (seg, props->rx_fifo_size,
-                                       props->tx_fifo_size, &ls->rx_fifo,
-                                       &ls->tx_fifo);
-  if (rv)
+  /*
+   * No segment, try to alloc one and notify the server and the client.
+   * Make sure the segment is not used for other fifos
+   */
+  seg_size = clib_max (props->segment_size, 128 << 20);
+  fs_index =
+    segment_manager_add_segment2 (sm, seg_size, FIFO_SEGMENT_F_CUSTOM_USE);
+  if (fs_index < 0)
+    return 0;
+
+  if (seg_ctx_index == ~0)
     {
-      clib_warning ("failed to add fifos in cut-through segment");
-      segment_manager_segment_reader_unlock (sm);
-      goto failed;
+      pool_get_zero (cm->app_seg_ctxs, seg_ctx);
+      seg_ctx_index = seg_ctx - cm->app_seg_ctxs;
+      hash_set (cm->app_segs_ctxs_table, table_handle, seg_ctx_index);
+      seg_ctx->server_wrk = server_wrk->wrk_index;
+      seg_ctx->client_wrk = client_wrk_index;
+      seg_ctx->sm_index = sm_index;
+      seg_ctx->fifo_pair_bytes = pair_bytes;
     }
+  else
+    {
+      seg_ctx = pool_elt_at_index (cm->app_seg_ctxs, seg_ctx_index);
+    }
+
+  pool_get_zero (seg_ctx->segments, ct_seg);
+  ct_seg->segment_index = fs_index;
+  ct_seg->server_n_sessions = 0;
+  ct_seg->client_n_sessions = 0;
+  ct_seg->ct_seg_index = ct_seg - seg_ctx->segments;
+  ct_seg->seg_ctx_index = seg_ctx_index;
+
+  /* New segment, notify the server and client */
+  seg_handle = segment_manager_make_segment_handle (sm_index, fs_index);
+  if (app_worker_add_segment_notify (server_wrk, seg_handle))
+    goto error;
 
+  client_wrk = app_worker_get (client_wrk_index);
+  if (app_worker_add_segment_notify (client_wrk, seg_handle))
+    {
+      app_worker_del_segment_notify (server_wrk, seg_handle);
+      goto error;
+    }
+
+  return ct_seg;
+
+error:
+
+  segment_manager_lock_and_del_segment (sm, fs_index);
+  pool_put_index (seg_ctx->segments, ct_seg->seg_ctx_index);
+  return 0;
+}
+
+static int
+ct_init_accepted_session (app_worker_t *server_wrk, ct_connection_t *ct,
+                         session_t *ls, session_t *ll)
+{
+  segment_manager_props_t *props;
+  u64 seg_handle, table_handle;
+  u32 sm_index, fs_index = ~0;
+  ct_segments_ctx_t *seg_ctx;
+  ct_main_t *cm = &ct_main;
+  application_t *server;
+  segment_manager_t *sm;
+  ct_segment_t *ct_seg;
+  fifo_segment_t *fs;
+  uword *spp;
+  int rv;
+
+  sm = app_worker_get_listen_segment_manager (server_wrk, ll);
   sm_index = segment_manager_index (sm);
-  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;
-  ls->tx_fifo->segment_index = seg_index;
+  server = application_get (server_wrk->app_index);
+  props = application_segment_manager_properties (server);
+
+  table_handle = ct->client_wrk << 16 | server_wrk->wrk_index;
+  table_handle = (u64) sm_index << 32 | table_handle;
 
-  segment_handle = segment_manager_segment_handle (sm, seg);
-  if ((rv = app_worker_add_segment_notify (server_wrk, segment_handle)))
+  /*
+   * Check if we already have a segment that can hold the fifos
+   */
+
+  clib_rwlock_reader_lock (&cm->app_segs_lock);
+
+  spp = hash_get (cm->app_segs_ctxs_table, table_handle);
+  if (spp)
+    {
+      ct_seg = ct_lookup_free_segment (cm, sm, *spp);
+      if (ct_seg)
+       {
+         ct->seg_ctx_index = ct_seg->seg_ctx_index;
+         ct->ct_seg_index = ct_seg->ct_seg_index;
+         fs_index = ct_seg->segment_index;
+         ct_seg->flags &=
+           ~(CT_SEGMENT_F_SERVER_DETACHED | CT_SEGMENT_F_CLIENT_DETACHED);
+         __atomic_add_fetch (&ct_seg->server_n_sessions, 1, __ATOMIC_RELAXED);
+         __atomic_add_fetch (&ct_seg->client_n_sessions, 1, __ATOMIC_RELAXED);
+       }
+    }
+
+  clib_rwlock_reader_unlock (&cm->app_segs_lock);
+
+  /*
+   * If not, grab exclusive lock and allocate segment
+   */
+  if (fs_index == ~0)
+    {
+      clib_rwlock_writer_lock (&cm->app_segs_lock);
+
+      ct_seg =
+       ct_alloc_segment (cm, server_wrk, table_handle, sm, ct->client_wrk);
+      if (!ct_seg)
+       {
+         clib_rwlock_writer_unlock (&cm->app_segs_lock);
+         return -1;
+       }
+
+      ct->seg_ctx_index = ct_seg->seg_ctx_index;
+      ct->ct_seg_index = ct_seg->ct_seg_index;
+      ct_seg->server_n_sessions += 1;
+      ct_seg->client_n_sessions += 1;
+      fs_index = ct_seg->segment_index;
+
+      clib_rwlock_writer_unlock (&cm->app_segs_lock);
+    }
+
+  /*
+   * Allocate and initialize the fifos
+   */
+  fs = segment_manager_get_segment_w_lock (sm, fs_index);
+  rv = segment_manager_try_alloc_fifos (
+    fs, ls->thread_index, props->rx_fifo_size, props->tx_fifo_size,
+    &ls->rx_fifo, &ls->tx_fifo);
+  if (rv)
     {
-      clib_warning ("failed to notify server of new segment");
       segment_manager_segment_reader_unlock (sm);
-      goto failed;
+
+      clib_rwlock_reader_lock (&cm->app_segs_lock);
+
+      seg_ctx = pool_elt_at_index (cm->app_seg_ctxs, ct->seg_ctx_index);
+      ct_seg = pool_elt_at_index (seg_ctx->segments, ct->ct_seg_index);
+      __atomic_sub_fetch (&ct_seg->server_n_sessions, 1, __ATOMIC_RELAXED);
+      __atomic_sub_fetch (&ct_seg->client_n_sessions, 1, __ATOMIC_RELAXED);
+
+      clib_rwlock_reader_unlock (&cm->app_segs_lock);
+
+      return rv;
     }
+
+  ls->rx_fifo->shr->master_session_index = ls->session_index;
+  ls->tx_fifo->shr->master_session_index = ls->session_index;
+  ls->rx_fifo->master_thread_index = ls->thread_index;
+  ls->tx_fifo->master_thread_index = ls->thread_index;
+
+  seg_handle = segment_manager_segment_handle (sm, fs);
   segment_manager_segment_reader_unlock (sm);
-  ct->segment_handle = segment_handle;
 
-  return 0;
+  ct->segment_handle = seg_handle;
 
-failed:
-  segment_manager_del_segment (sm, seg);
-  return rv;
+  return 0;
 }
 
-static int
-ct_connect (app_worker_t * client_wrk, session_t * ll,
-           session_endpoint_cfg_t * sep)
+static void
+ct_accept_one (u32 thread_index, u32 ho_index)
 {
-  u32 cct_index, ll_index, ll_ct_index;
-  ct_connection_t *sct, *cct, *ll_ct;
+  ct_connection_t *sct, *cct, *ho;
+  transport_connection_t *ll_ct;
   app_worker_t *server_wrk;
-  session_t *ss;
-
-  ll_index = ll->session_index;
-  ll_ct_index = ll->connection_index;
+  u32 cct_index, ll_index;
+  session_t *ss, *ll;
 
-  cct = ct_connection_alloc ();
+  /*
+   * Alloc client ct and initialize from ho
+   */
+  cct = ct_connection_alloc (thread_index);
   cct_index = cct->c_c_index;
-  sct = ct_connection_alloc ();
-  ll_ct = ct_connection_get (ll_ct_index);
 
-  /*
-   * Alloc and init client transport
+  ho = ct_half_open_get (ho_index);
+
+  /* Unlikely but half-open session and transport could have been freed */
+  if (PREDICT_FALSE (!ho))
+    {
+      ct_connection_free (cct);
+      return;
+    }
+
+  clib_memcpy (cct, ho, sizeof (*ho));
+  cct->c_c_index = cct_index;
+  cct->c_thread_index = thread_index;
+  cct->flags |= CT_CONN_F_HALF_OPEN;
+
+  /* Notify session layer that half-open is on a different thread
+   * and mark ho connection index reusable. Avoids another rpc
    */
-  cct = ct_connection_get (cct_index);
-  cct->c_thread_index = 0;
-  cct->c_rmt_port = sep->port;
-  cct->c_lcl_port = 0;
-  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;
+  session_half_open_migrate_notify (&cct->connection);
+  session_half_open_migrated_notify (&cct->connection);
+  ct_half_open_add_reusable (ho_index);
 
   /*
-   * Init server transport
+   * Alloc and init server transport
    */
-  sct->c_thread_index = 0;
+
+  ll_index = cct->peer_index;
+  ll = listen_session_get (ll_index);
+  sct = ct_connection_alloc (thread_index);
+  /* Transport not necessarily ct but it might, so grab after sct alloc */
+  ll_ct = listen_session_get_transport (ll);
+
+  /* Make sure cct is valid after sct alloc */
+  cct = ct_connection_get (cct_index, thread_index);
+
   sct->c_rmt_port = 0;
-  sct->c_lcl_port = ll_ct->c_lcl_port;
-  sct->c_is_ip4 = sep->is_ip4;
-  clib_memcpy (&sct->c_lcl_ip, &ll_ct->c_lcl_ip, sizeof (ll_ct->c_lcl_ip));
-  sct->client_wrk = client_wrk->wrk_index;
+  sct->c_lcl_port = ll_ct->lcl_port;
+  sct->c_is_ip4 = cct->c_is_ip4;
+  clib_memcpy (&sct->c_lcl_ip, &cct->c_rmt_ip, sizeof (cct->c_rmt_ip));
+  sct->client_wrk = cct->client_wrk;
   sct->c_proto = TRANSPORT_PROTO_NONE;
-  sct->client_opaque = sep->opaque;
-  sct->actual_tp = ll_ct->actual_tp;
+  sct->client_opaque = cct->client_opaque;
+  sct->actual_tp = cct->actual_tp;
 
   sct->peer_index = cct->c_c_index;
   cct->peer_index = sct->c_c_index;
@@ -273,56 +708,203 @@ ct_connect (app_worker_t * client_wrk, session_t * ll,
    * Accept server session. Client session is created only after
    * server confirms accept.
    */
-  ss = session_alloc (0);
+  ss = session_alloc (thread_index);
   ll = listen_session_get (ll_index);
-  ss->session_type = ll->session_type;
+  ss->session_type = session_type_from_proto_and_ip (TRANSPORT_PROTO_NONE,
+                                                    sct->c_is_ip4);
   ss->connection_index = sct->c_c_index;
-  ss->listener_index = ll->session_index;
-  ss->session_state = SESSION_STATE_CREATED;
+  ss->listener_handle = listen_session_get_handle (ll);
+  session_set_state (ss, SESSION_STATE_CREATED);
 
   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;
 
-  if (ct_init_local_session (client_wrk, server_wrk, sct, ss, ll))
+  if (ct_init_accepted_session (server_wrk, sct, ss, ll))
     {
-      clib_warning ("failed");
+      ct_session_connect_notify (ss, SESSION_E_ALLOC);
       ct_connection_free (sct);
       session_free (ss);
-      return -1;
+      return;
     }
 
-  ss->session_state = SESSION_STATE_ACCEPTING;
+  cct->server_wrk = sct->server_wrk;
+  cct->seg_ctx_index = sct->seg_ctx_index;
+  cct->ct_seg_index = sct->ct_seg_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++;
+  cct->segment_handle = sct->segment_handle;
+
+  session_set_state (ss, SESSION_STATE_ACCEPTING);
   if (app_worker_accept_notify (server_wrk, ss))
     {
-      clib_warning ("failed");
+      ct_session_connect_notify (ss, SESSION_E_REFUSED);
+      ct_session_dealloc_fifos (sct, ss->rx_fifo, ss->tx_fifo);
       ct_connection_free (sct);
-      session_free_w_fifos (ss);
-      return -1;
+      session_free (ss);
     }
+}
 
-  cct->segment_handle = sct->segment_handle;
-  ct_enable_disable_main_pre_input_node (1 /* is_add */ );
-  return 0;
+static void
+ct_accept_rpc_wrk_handler (void *rpc_args)
+{
+  u32 thread_index, n_connects, i, n_pending;
+  const u32 max_connects = 32;
+  ct_worker_t *wrk;
+  u8 need_rpc = 0;
+
+  thread_index = pointer_to_uword (rpc_args);
+  wrk = ct_worker_get (thread_index);
+
+  /* Connects could be handled without worker barrier so grab lock */
+  clib_spinlock_lock (&wrk->pending_connects_lock);
+
+  n_pending = clib_fifo_elts (wrk->pending_connects);
+  n_connects = clib_min (n_pending, max_connects);
+  vec_validate (wrk->new_connects, n_connects);
+
+  for (i = 0; i < n_connects; i++)
+    clib_fifo_sub1 (wrk->pending_connects, wrk->new_connects[i]);
+
+  if (n_pending == n_connects)
+    wrk->have_connects = 0;
+  else
+    need_rpc = 1;
+
+  clib_spinlock_unlock (&wrk->pending_connects_lock);
+
+  for (i = 0; i < n_connects; i++)
+    ct_accept_one (thread_index, wrk->new_connects[i]);
+
+  if (need_rpc)
+    session_send_rpc_evt_to_thread_force (
+      thread_index, ct_accept_rpc_wrk_handler,
+      uword_to_pointer (thread_index, void *));
+}
+
+static void
+ct_fwrk_flush_connects (void *rpc_args)
+{
+  u32 thread_index, fwrk_index, n_workers;
+  ct_main_t *cm = &ct_main;
+  ct_worker_t *wrk;
+  u8 need_rpc;
+
+  fwrk_index = cm->fwrk_thread;
+  n_workers = vec_len (cm->fwrk_pending_connects);
+
+  for (thread_index = fwrk_index; thread_index < n_workers; thread_index++)
+    {
+      if (!vec_len (cm->fwrk_pending_connects[thread_index]))
+       continue;
+
+      wrk = ct_worker_get (thread_index);
+
+      /* Connects can be done without worker barrier, grab dst worker lock */
+      if (thread_index != fwrk_index)
+       clib_spinlock_lock (&wrk->pending_connects_lock);
+
+      clib_fifo_add (wrk->pending_connects,
+                    cm->fwrk_pending_connects[thread_index],
+                    vec_len (cm->fwrk_pending_connects[thread_index]));
+      if (!wrk->have_connects)
+       {
+         wrk->have_connects = 1;
+         need_rpc = 1;
+       }
+
+      if (thread_index != fwrk_index)
+       clib_spinlock_unlock (&wrk->pending_connects_lock);
+
+      vec_reset_length (cm->fwrk_pending_connects[thread_index]);
+
+      if (need_rpc)
+       session_send_rpc_evt_to_thread_force (
+         thread_index, ct_accept_rpc_wrk_handler,
+         uword_to_pointer (thread_index, void *));
+    }
+
+  cm->fwrk_have_flush = 0;
+}
+
+static void
+ct_program_connect_to_wrk (u32 ho_index)
+{
+  ct_main_t *cm = &ct_main;
+  u32 thread_index;
+
+  /* Simple round-robin policy for spreading sessions over workers. We skip
+   * thread index 0, i.e., offset the index by 1, when we have workers as it
+   * is the one dedicated to main thread. Note that n_workers does not include
+   * main thread */
+  cm->n_sessions += 1;
+  thread_index = cm->n_workers ? (cm->n_sessions % cm->n_workers) + 1 : 0;
+
+  /* Pospone flushing of connect request to dst worker until after session
+   * layer fully initializes the half-open session. */
+  vec_add1 (cm->fwrk_pending_connects[thread_index], ho_index);
+  if (!cm->fwrk_have_flush)
+    {
+      session_send_rpc_evt_to_thread_force (
+       cm->fwrk_thread, ct_fwrk_flush_connects,
+       uword_to_pointer (thread_index, void *));
+      cm->fwrk_have_flush = 1;
+    }
+}
+
+static int
+ct_connect (app_worker_t *client_wrk, session_t *ll,
+           session_endpoint_cfg_t *sep)
+{
+  ct_connection_t *ho;
+  u32 ho_index;
+
+  /*
+   * Alloc and init client half-open transport
+   */
+
+  ho = ct_half_open_alloc ();
+  ho_index = ho->c_c_index;
+  ho->c_rmt_port = sep->port;
+  ho->c_lcl_port = 0;
+  ho->c_is_ip4 = sep->is_ip4;
+  ho->client_opaque = sep->opaque;
+  ho->client_wrk = client_wrk->wrk_index;
+  ho->peer_index = ll->session_index;
+  ho->c_proto = TRANSPORT_PROTO_NONE;
+  ho->c_flags |= TRANSPORT_CONNECTION_F_NO_LOOKUP;
+  clib_memcpy (&ho->c_rmt_ip, &sep->ip, sizeof (sep->ip));
+  ho->flags |= CT_CONN_F_CLIENT;
+  ho->c_s_index = ~0;
+  ho->actual_tp = sep->original_tp;
+
+  /*
+   * Program connect on a worker, connected reply comes
+   * after server accepts the connection.
+   */
+  ct_program_connect_to_wrk (ho_index);
+
+  return ho_index;
 }
 
 static u32
-ct_start_listen (u32 app_listener_index, transport_endpoint_t * tep)
+ct_start_listen (u32 app_listener_index, transport_endpoint_cfg_t *tep)
 {
   session_endpoint_cfg_t *sep;
   ct_connection_t *ct;
 
   sep = (session_endpoint_cfg_t *) tep;
-  ct = ct_connection_alloc ();
+  ct = ct_connection_alloc (0);
   ct->server_wrk = sep->app_wrk_index;
   ct->c_is_ip4 = sep->is_ip4;
   clib_memcpy (&ct->c_lcl_ip, &sep->ip, sizeof (sep->ip));
   ct->c_lcl_port = sep->port;
+  ct->c_s_index = app_listener_index;
   ct->actual_tp = sep->transport_proto;
-  ct_enable_disable_main_pre_input_node (1 /* is_add */ );
   return ct->c_c_index;
 }
 
@@ -330,23 +912,53 @@ static u32
 ct_stop_listen (u32 ct_index)
 {
   ct_connection_t *ct;
-  ct = ct_connection_get (ct_index);
+  ct = ct_connection_get (ct_index, 0);
   ct_connection_free (ct);
-  ct_enable_disable_main_pre_input_node (0 /* is_add */ );
   return 0;
 }
 
 static transport_connection_t *
 ct_listener_get (u32 ct_index)
 {
-  return (transport_connection_t *) ct_connection_get (ct_index);
+  return (transport_connection_t *) ct_connection_get (ct_index, 0);
+}
+
+static transport_connection_t *
+ct_session_half_open_get (u32 ct_index)
+{
+  return (transport_connection_t *) ct_half_open_get (ct_index);
+}
+
+static void
+ct_session_cleanup (u32 conn_index, u32 thread_index)
+{
+  ct_connection_t *ct, *peer_ct;
+
+  ct = ct_connection_get (conn_index, thread_index);
+  if (!ct)
+    return;
+
+  peer_ct = ct_connection_get (ct->peer_index, thread_index);
+  if (peer_ct)
+    peer_ct->peer_index = ~0;
+
+  ct_connection_free (ct);
+}
+
+static void
+ct_cleanup_ho (u32 ho_index)
+{
+  ct_connection_t *ho;
+
+  ho = ct_half_open_get (ho_index);
+  ct_connection_free (ho);
 }
 
 static int
 ct_session_connect (transport_endpoint_cfg_t * tep)
 {
   session_endpoint_cfg_t *sep_ext;
-  session_endpoint_t *sep;
+  session_endpoint_t _sep, *sep = &_sep;
   app_worker_t *app_wrk;
   session_handle_t lh;
   application_t *app;
@@ -356,7 +968,7 @@ ct_session_connect (transport_endpoint_cfg_t * tep)
   u8 fib_proto;
 
   sep_ext = (session_endpoint_cfg_t *) tep;
-  sep = (session_endpoint_t *) tep;
+  _sep = *(session_endpoint_t *) tep;
   app_wrk = app_worker_get (sep_ext->app_wrk_index);
   app = application_get (app_wrk->app_index);
 
@@ -364,7 +976,7 @@ ct_session_connect (transport_endpoint_cfg_t * tep)
   table_index = application_local_session_table (app);
   lh = session_lookup_local_endpoint (table_index, sep);
   if (lh == SESSION_DROP_HANDLE)
-    return VNET_API_ERROR_APP_CONNECT_FILTERED;
+    return SESSION_E_FILTERED;
 
   if (lh == SESSION_INVALID_HANDLE)
     goto global_scope;
@@ -389,53 +1001,191 @@ ct_session_connect (transport_endpoint_cfg_t * tep)
 
 global_scope:
   if (session_endpoint_is_local (sep))
-    return VNET_API_ERROR_SESSION_CONNECT;
+    return SESSION_E_NOROUTE;
 
   if (!application_has_global_scope (app))
-    return VNET_API_ERROR_APP_CONNECT_SCOPE;
+    return SESSION_E_SCOPE;
 
   fib_proto = session_endpoint_fib_proto (sep);
-  table_index = application_session_table (app, fib_proto);
-  ll = session_lookup_listener (table_index, sep);
+  table_index = session_lookup_get_index_for_fib (fib_proto, sep->fib_index);
+  ll = session_lookup_listener_wildcard (table_index, sep);
 
-  if (ll)
+  /* Avoid connecting app to own listener */
+  if (ll && ll->app_index != app->app_index)
     return ct_connect (app_wrk, ll, sep_ext);
 
   /* Failed to connect but no error */
-  return 1;
+  return SESSION_E_LOCAL_CONNECT;
+}
+
+static inline int
+ct_close_is_reset (ct_connection_t *ct, session_t *s)
+{
+  if (ct->flags & CT_CONN_F_CLIENT)
+    return (svm_fifo_max_dequeue (ct->client_rx_fifo) > 0);
+  else
+    return (svm_fifo_max_dequeue (s->rx_fifo) > 0);
 }
 
 static void
-ct_session_close (u32 ct_index, u32 thread_index)
+ct_session_cleanup_server_session (session_t *s)
 {
-  ct_connection_t *ct, *peer_ct;
+  ct_connection_t *ct;
+
+  ct = (ct_connection_t *) session_get_transport (s);
+  ct_session_dealloc_fifos (ct, s->rx_fifo, s->tx_fifo);
+  session_free (s);
+  ct_connection_free (ct);
+}
+
+static void
+ct_session_postponed_cleanup (ct_connection_t *ct)
+{
+  ct_connection_t *peer_ct;
   app_worker_t *app_wrk;
   session_t *s;
 
-  ct = ct_connection_get (ct_index);
-  peer_ct = ct_connection_get (ct->peer_index);
+  s = session_get (ct->c_s_index, ct->c_thread_index);
+  app_wrk = app_worker_get_if_valid (s->app_wrk_index);
+
+  peer_ct = ct_connection_get (ct->peer_index, ct->c_thread_index);
   if (peer_ct)
     {
-      peer_ct->peer_index = ~0;
-      session_transport_closing_notify (&peer_ct->connection);
+      if (ct_close_is_reset (ct, s))
+       session_transport_reset_notify (&peer_ct->connection);
+      else
+       session_transport_closing_notify (&peer_ct->connection);
     }
+  session_transport_closed_notify (&ct->connection);
 
-  s = session_get (ct->c_s_index, 0);
-  app_wrk = app_worker_get_if_valid (s->app_wrk_index);
+  /* It would be cleaner to call session_transport_delete_notify
+   * but then we can't control session cleanup lower */
+  session_set_state (s, SESSION_STATE_TRANSPORT_DELETED);
   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);
+    app_worker_cleanup_notify (app_wrk, s, SESSION_CLEANUP_TRANSPORT);
 
-  ct_connection_free (ct);
-  ct_enable_disable_main_pre_input_node (0 /* is_add */ );
+  if (ct->flags & CT_CONN_F_CLIENT)
+    {
+      /* Normal free for client session as the fifos are allocated through
+       * the connects segment manager in a segment that's not shared with
+       * the server */
+      ct_session_dealloc_fifos (ct, ct->client_rx_fifo, ct->client_tx_fifo);
+      session_program_cleanup (s);
+      ct_connection_free (ct);
+    }
+  else
+    {
+      /* Manual session and fifo segment cleanup to avoid implicit
+       * segment manager cleanups and notifications */
+      if (app_wrk)
+       {
+         /* Remove custom cleanup notify infra when/if switching to normal
+          * session cleanup. Note that ct is freed in the cb function */
+         app_worker_cleanup_notify_custom (app_wrk, s,
+                                           SESSION_CLEANUP_SESSION,
+                                           ct_session_cleanup_server_session);
+       }
+      else
+       {
+         ct_connection_free (ct);
+       }
+    }
+}
+
+static void
+ct_handle_cleanups (void *args)
+{
+  uword thread_index = pointer_to_uword (args);
+  const u32 max_cleanups = 100;
+  ct_cleanup_req_t *req;
+  ct_connection_t *ct;
+  u32 n_to_handle = 0;
+  ct_worker_t *wrk;
+  session_t *s;
+
+  wrk = ct_worker_get (thread_index);
+  wrk->have_cleanups = 0;
+  n_to_handle = clib_fifo_elts (wrk->pending_cleanups);
+  n_to_handle = clib_min (n_to_handle, max_cleanups);
+
+  while (n_to_handle)
+    {
+      clib_fifo_sub2 (wrk->pending_cleanups, req);
+      ct = ct_connection_get (req->ct_index, thread_index);
+      s = session_get (ct->c_s_index, ct->c_thread_index);
+      if (!svm_fifo_has_event (s->tx_fifo))
+       ct_session_postponed_cleanup (ct);
+      else
+       clib_fifo_add1 (wrk->pending_cleanups, *req);
+      n_to_handle -= 1;
+    }
+
+  if (clib_fifo_elts (wrk->pending_cleanups))
+    {
+      wrk->have_cleanups = 1;
+      session_send_rpc_evt_to_thread_force (
+       thread_index, ct_handle_cleanups,
+       uword_to_pointer (thread_index, void *));
+    }
+}
+
+static void
+ct_program_cleanup (ct_connection_t *ct)
+{
+  ct_cleanup_req_t *req;
+  uword thread_index;
+  ct_worker_t *wrk;
+
+  thread_index = ct->c_thread_index;
+  wrk = ct_worker_get (ct->c_thread_index);
+
+  clib_fifo_add2 (wrk->pending_cleanups, req);
+  req->ct_index = ct->c_c_index;
+
+  if (wrk->have_cleanups)
+    return;
+
+  wrk->have_cleanups = 1;
+  session_send_rpc_evt_to_thread_force (
+    thread_index, ct_handle_cleanups, uword_to_pointer (thread_index, void *));
+}
+
+static void
+ct_session_close (u32 ct_index, u32 thread_index)
+{
+  ct_connection_t *ct, *peer_ct;
+  session_t *s;
+
+  ct = ct_connection_get (ct_index, thread_index);
+  s = session_get (ct->c_s_index, ct->c_thread_index);
+  peer_ct = ct_connection_get (ct->peer_index, thread_index);
+  if (peer_ct)
+    {
+      peer_ct->peer_index = ~0;
+      /* Make sure session was allocated */
+      if (peer_ct->flags & CT_CONN_F_HALF_OPEN)
+       {
+         ct_session_connect_notify (s, SESSION_E_REFUSED);
+         ct->peer_index = ~0;
+       }
+      else if (peer_ct->c_s_index == ~0)
+       {
+         /* should not happen */
+         clib_warning ("ct peer without session");
+         ct_connection_free (peer_ct);
+       }
+    }
+
+  /* Do not send closed notify to make sure pending tx events are
+   * still delivered and program cleanup */
+  ct_program_cleanup (ct);
 }
 
 static transport_connection_t *
 ct_session_get (u32 ct_index, u32 thread_index)
 {
-  return (transport_connection_t *) ct_connection_get (ct_index);
+  return (transport_connection_t *) ct_connection_get (ct_index,
+                                                      thread_index);
 }
 
 static u8 *
@@ -465,23 +1215,64 @@ format_ct_connection_id (u8 * s, va_list * args)
 }
 
 static int
-ct_custom_tx (void *session)
+ct_custom_tx (void *session, transport_send_params_t * sp)
 {
   session_t *s = (session_t *) session;
   if (session_has_transport (s))
     return 0;
-  return ct_session_tx (s);
+  /* If event enqueued towards peer, remove from scheduler and remove
+   * session tx flag, i.e., accept new tx events. Unset fifo flag now to
+   * avoid missing events if peer did not clear fifo flag yet, which is
+   * interpreted as successful notification and session is descheduled. */
+  svm_fifo_unset_event (s->tx_fifo);
+  if (!ct_session_tx (s))
+    sp->flags = TRANSPORT_SND_F_DESCHED;
+
+  /* The scheduler uses packet count as a means of upper bounding the amount
+   * of work done per dispatch. So make it look like we have sent something */
+  return 1;
+}
+
+static int
+ct_app_rx_evt (transport_connection_t * tc)
+{
+  ct_connection_t *ct = (ct_connection_t *) tc, *peer_ct;
+  session_t *ps, *s;
+
+  s = session_get (ct->c_s_index, ct->c_thread_index);
+  if (session_has_transport (s) || s->session_state < SESSION_STATE_READY)
+    return -1;
+  peer_ct = ct_connection_get (ct->peer_index, tc->thread_index);
+  if (!peer_ct || (peer_ct->flags & CT_CONN_F_HALF_OPEN))
+    return -1;
+  ps = session_get (peer_ct->c_s_index, peer_ct->c_thread_index);
+  if (ps->session_state >= SESSION_STATE_TRANSPORT_CLOSING)
+    return -1;
+  return session_dequeue_notify (ps);
 }
 
 static u8 *
 format_ct_listener (u8 * s, va_list * args)
 {
   u32 tc_index = va_arg (*args, u32);
+  u32 __clib_unused thread_index = va_arg (*args, u32);
   u32 __clib_unused verbose = va_arg (*args, u32);
-  ct_connection_t *ct = ct_connection_get (tc_index);
-  s = format (s, "%-50U", format_ct_connection_id, ct);
+  ct_connection_t *ct = ct_connection_get (tc_index, 0);
+  s = format (s, "%-" SESSION_CLI_ID_LEN "U", format_ct_connection_id, ct);
+  if (verbose)
+    s = format (s, "%-" SESSION_CLI_STATE_LEN "s", "LISTEN");
+  return s;
+}
+
+static u8 *
+format_ct_half_open (u8 *s, va_list *args)
+{
+  u32 ho_index = va_arg (*args, u32);
+  u32 verbose = va_arg (*args, u32);
+  ct_connection_t *ct = ct_half_open_get (ho_index);
+  s = format (s, "%-" SESSION_CLI_ID_LEN "U", format_ct_connection_id, ct);
   if (verbose)
-    s = format (s, "%-15s", "LISTEN");
+    s = format (s, "%-" SESSION_CLI_STATE_LEN "s", "HALF-OPEN");
   return s;
 }
 
@@ -493,10 +1284,10 @@ format_ct_connection (u8 * s, va_list * args)
 
   if (!ct)
     return s;
-  s = format (s, "%-50U", format_ct_connection_id, ct);
+  s = format (s, "%-" SESSION_CLI_ID_LEN "U", format_ct_connection_id, ct);
   if (verbose)
     {
-      s = format (s, "%-15s", "ESTABLISHED");
+      s = format (s, "%-" SESSION_CLI_STATE_LEN "s", "ESTABLISHED");
       if (verbose > 1)
        {
          s = format (s, "\n");
@@ -509,11 +1300,11 @@ static u8 *
 format_ct_session (u8 * s, va_list * args)
 {
   u32 ct_index = va_arg (*args, u32);
-  u32 __clib_unused thread_index = va_arg (*args, u32);
+  u32 thread_index = va_arg (*args, u32);
   u32 verbose = va_arg (*args, u32);
   ct_connection_t *ct;
 
-  ct = ct_connection_get (ct_index);
+  ct = ct_connection_get (ct_index, thread_index);
   if (!ct)
     {
       s = format (s, "empty\n");
@@ -524,33 +1315,71 @@ format_ct_session (u8 * s, va_list * args)
   return s;
 }
 
+clib_error_t *
+ct_enable_disable (vlib_main_t * vm, u8 is_en)
+{
+  vlib_thread_main_t *vtm = &vlib_thread_main;
+  ct_main_t *cm = &ct_main;
+  ct_worker_t *wrk;
+
+  cm->n_workers = vlib_num_workers ();
+  cm->fwrk_thread = transport_cl_thread ();
+  vec_validate (cm->wrk, vtm->n_vlib_mains);
+  vec_foreach (wrk, cm->wrk)
+    clib_spinlock_init (&wrk->pending_connects_lock);
+  clib_spinlock_init (&cm->ho_reuseable_lock);
+  clib_rwlock_init (&cm->app_segs_lock);
+  vec_validate (cm->fwrk_pending_connects, cm->n_workers);
+  return 0;
+}
+
 /* *INDENT-OFF* */
-const static transport_proto_vft_t cut_thru_proto = {
+static const transport_proto_vft_t cut_thru_proto = {
+  .enable = ct_enable_disable,
   .start_listen = ct_start_listen,
   .stop_listen = ct_stop_listen,
+  .get_connection = ct_session_get,
   .get_listener = ct_listener_get,
+  .get_half_open = ct_session_half_open_get,
+  .cleanup = ct_session_cleanup,
+  .cleanup_ho = ct_cleanup_ho,
   .connect = ct_session_connect,
   .close = ct_session_close,
-  .get_connection = ct_session_get,
   .custom_tx = ct_custom_tx,
-  .tx_type = TRANSPORT_TX_INTERNAL,
-  .service_type = TRANSPORT_SERVICE_APP,
+  .app_rx_evt = ct_app_rx_evt,
   .format_listener = format_ct_listener,
+  .format_half_open = format_ct_half_open,
   .format_connection = format_ct_session,
+  .transport_options = {
+    .name = "ct",
+    .short_name = "C",
+    .tx_type = TRANSPORT_TX_INTERNAL,
+    .service_type = TRANSPORT_SERVICE_VC,
+  },
 };
 /* *INDENT-ON* */
 
+static inline int
+ct_session_can_tx (session_t *s)
+{
+  return (s->session_state == SESSION_STATE_READY ||
+         s->session_state == SESSION_STATE_CLOSING ||
+         s->session_state == SESSION_STATE_APP_CLOSED);
+}
+
 int
 ct_session_tx (session_t * s)
 {
   ct_connection_t *ct, *peer_ct;
   session_t *peer_s;
 
+  if (!ct_session_can_tx (s))
+    return 0;
   ct = (ct_connection_t *) session_get_transport (s);
-  peer_ct = ct_connection_get (ct->peer_index);
+  peer_ct = ct_connection_get (ct->peer_index, ct->c_thread_index);
   if (!peer_ct)
-    return -1;
-  peer_s = session_get (peer_ct->c_s_index, 0);
+    return 0;
+  peer_s = session_get (peer_ct->c_s_index, peer_ct->c_thread_index);
   if (peer_s->session_state >= SESSION_STATE_TRANSPORT_CLOSING)
     return 0;
   return session_enqueue_notify (peer_s);