udp/session: refactor to support dgram mode

- adds session layer support for datagram based protocols
- updates udp to work in pure connectionless and datagram mode. The
  existing connected mode is now 'accessible' for apps as a dummy UDPC,
  as in, connected udp, protocol.
- updates udp_echo, echo client, echo server code to work in datagram
  mode.

Change-Id: I2960c0d2d246cb166005f545794ec31fe0d546dd
Signed-off-by: Florin Coras <fcoras@cisco.com>

21 files changed, 1105 insertions, 447 deletions

diff --git a/src/svm/svm_fifo.c b/src/svm/svm_fifo.c
index b2c8e5bdb16..3552192a768 100644
--- a/src/svm/svm_fifo.c
+++ b/src/svm/svm_fifo.c
@@ -169,6 +169,9 @@ format_svm_fifo (u8 * s, va_list * args)
   svm_fifo_t *f = va_arg (*args, svm_fifo_t *);
   int verbose = va_arg (*args, int);
 
+  if (!s)
+    return s;
+
   s = format (s, "cursize %u nitems %u has_event %d\n",
 	      f->cursize, f->nitems, f->has_event);
   s = format (s, " head %d tail %d\n", f->head, f->tail);
@@ -459,7 +462,7 @@ svm_fifo_enqueue_internal (svm_fifo_t * f, u32 max_bytes,
   f->ooos_newest = OOO_SEGMENT_INVALID_INDEX;
 
   if (PREDICT_FALSE (cursize == f->nitems))
-    return -2;			/* fifo stuffed */
+    return SVM_FIFO_FULL;
 
   nitems = f->nitems;
 
@@ -615,6 +618,20 @@ svm_fifo_enqueue_with_offset (svm_fifo_t * f,
 						copy_from_here);
 }
 
+void
+svm_fifo_overwrite_head (svm_fifo_t * f, u8 * data, u32 len)
+{
+  u32 first_chunk;
+  ASSERT (len <= f->nitems);
+  if (len < f->nitems - f->head)
+    clib_memcpy (&f->data[f->head], data, len);
+  else
+    {
+      first_chunk = len - (f->nitems - f->head);
+      clib_memcpy (&f->data[f->head], data, first_chunk);
+      clib_memcpy (f->data, data + first_chunk, len - first_chunk);
+    }
+}
 
 static int
 svm_fifo_dequeue_internal (svm_fifo_t * f, u32 max_bytes, u8 * copy_here)
diff --git a/src/svm/svm_fifo.h b/src/svm/svm_fifo.h
index d06d77a42f7..39cdcc06a0c 100644
--- a/src/svm/svm_fifo.h
+++ b/src/svm/svm_fifo.h
@@ -80,6 +80,11 @@ typedef struct _svm_fifo
     CLIB_CACHE_LINE_ALIGN_MARK (data);
 } svm_fifo_t;
 
+typedef enum
+{
+  SVM_FIFO_FULL = -2,
+} svm_fifo_err_t;
+
 #if SVM_FIFO_TRACE
 #define svm_fifo_trace_add(_f, _s, _l, _t)		\
 {							\
@@ -150,6 +155,7 @@ int svm_fifo_dequeue_drop (svm_fifo_t * f, u32 max_bytes);
 u32 svm_fifo_number_ooo_segments (svm_fifo_t * f);
 ooo_segment_t *svm_fifo_first_ooo_segment (svm_fifo_t * f);
 void svm_fifo_init_pointers (svm_fifo_t * f, u32 pointer);
+void svm_fifo_overwrite_head (svm_fifo_t * f, u8 * data, u32 len);
 
 format_function_t format_svm_fifo;
 
diff --git a/src/tests/vnet/session/udp_echo.c b/src/tests/vnet/session/udp_echo.c
index d1363fc7104..fe5461d2c59 100644
--- a/src/tests/vnet/session/udp_echo.c
+++ b/src/tests/vnet/session/udp_echo.c
@@ -58,12 +58,6 @@ typedef enum
 
 typedef struct
 {
-  svm_fifo_t *server_rx_fifo;
-  svm_fifo_t *server_tx_fifo;
-} session_t;
-
-typedef struct
-{
   /* vpe input queue */
   svm_queue_t *vl_input_queue;
 
@@ -71,10 +65,13 @@ typedef struct
   u32 my_client_index;
 
   /* The URI we're playing with */
-  u8 *uri;
+  u8 *listen_uri;
+
+  /* URI for connect */
+  u8 *connect_uri;
 
   /* Session pool */
-  session_t *sessions;
+  app_session_t *sessions;
 
   /* Hash table for disconnect processing */
   uword *session_index_by_vpp_handles;
@@ -85,10 +82,9 @@ typedef struct
   /* intermediate rx buffer */
   u8 *rx_buf;
 
-  /* URI for connect */
-  u8 *connect_uri;
-
-  int i_am_master;
+  u32 fifo_size;
+  int i_am_server;
+  u8 is_connected;
 
   /* Our event queue */
   svm_queue_t *our_event_queue;
@@ -128,7 +124,8 @@ typedef struct
   u8 *connect_test_data;
 
   uword *segments_table;
-} uri_udp_test_main_t;
+  u8 do_echo;
+} udp_echo_main_t;
 
 #if CLIB_DEBUG > 0
 #define NITER 10000
@@ -136,12 +133,12 @@ typedef struct
 #define NITER 4000000
 #endif
 
-uri_udp_test_main_t uri_udp_test_main;
+udp_echo_main_t udp_echo_main;
 
 static void
 stop_signal (int signum)
 {
-  uri_udp_test_main_t *um = &uri_udp_test_main;
+  udp_echo_main_t *um = &udp_echo_main;
 
   um->time_to_stop = 1;
 }
@@ -149,7 +146,7 @@ stop_signal (int signum)
 static void
 stats_signal (int signum)
 {
-  uri_udp_test_main_t *um = &uri_udp_test_main;
+  udp_echo_main_t *um = &udp_echo_main;
 
   um->time_to_print_stats = 1;
 }
@@ -164,11 +161,146 @@ setup_signal_handlers (void)
   return 0;
 }
 
+uword
+unformat_ip4_address (unformat_input_t * input, va_list * args)
+{
+  u8 *result = va_arg (*args, u8 *);
+  unsigned a[4];
+
+  if (!unformat (input, "%d.%d.%d.%d", &a[0], &a[1], &a[2], &a[3]))
+    return 0;
+
+  if (a[0] >= 256 || a[1] >= 256 || a[2] >= 256 || a[3] >= 256)
+    return 0;
+
+  result[0] = a[0];
+  result[1] = a[1];
+  result[2] = a[2];
+  result[3] = a[3];
+
+  return 1;
+}
+
+uword
+unformat_ip6_address (unformat_input_t * input, va_list * args)
+{
+  ip6_address_t *result = va_arg (*args, ip6_address_t *);
+  u16 hex_quads[8];
+  uword hex_quad, n_hex_quads, hex_digit, n_hex_digits;
+  uword c, n_colon, double_colon_index;
+
+  n_hex_quads = hex_quad = n_hex_digits = n_colon = 0;
+  double_colon_index = ARRAY_LEN (hex_quads);
+  while ((c = unformat_get_input (input)) != UNFORMAT_END_OF_INPUT)
+    {
+      hex_digit = 16;
+      if (c >= '0' && c <= '9')
+	hex_digit = c - '0';
+      else if (c >= 'a' && c <= 'f')
+	hex_digit = c + 10 - 'a';
+      else if (c >= 'A' && c <= 'F')
+	hex_digit = c + 10 - 'A';
+      else if (c == ':' && n_colon < 2)
+	n_colon++;
+      else
+	{
+	  unformat_put_input (input);
+	  break;
+	}
+
+      /* Too many hex quads. */
+      if (n_hex_quads >= ARRAY_LEN (hex_quads))
+	return 0;
+
+      if (hex_digit < 16)
+	{
+	  hex_quad = (hex_quad << 4) | hex_digit;
+
+	  /* Hex quad must fit in 16 bits. */
+	  if (n_hex_digits >= 4)
+	    return 0;
+
+	  n_colon = 0;
+	  n_hex_digits++;
+	}
+
+      /* Save position of :: */
+      if (n_colon == 2)
+	{
+	  /* More than one :: ? */
+	  if (double_colon_index < ARRAY_LEN (hex_quads))
+	    return 0;
+	  double_colon_index = n_hex_quads;
+	}
+
+      if (n_colon > 0 && n_hex_digits > 0)
+	{
+	  hex_quads[n_hex_quads++] = hex_quad;
+	  hex_quad = 0;
+	  n_hex_digits = 0;
+	}
+    }
+
+  if (n_hex_digits > 0)
+    hex_quads[n_hex_quads++] = hex_quad;
+
+  {
+    word i;
+
+    /* Expand :: to appropriate number of zero hex quads. */
+    if (double_colon_index < ARRAY_LEN (hex_quads))
+      {
+	word n_zero = ARRAY_LEN (hex_quads) - n_hex_quads;
+
+	for (i = n_hex_quads - 1; i >= (signed) double_colon_index; i--)
+	  hex_quads[n_zero + i] = hex_quads[i];
+
+	for (i = 0; i < n_zero; i++)
+	  hex_quads[double_colon_index + i] = 0;
+
+	n_hex_quads = ARRAY_LEN (hex_quads);
+      }
+
+    /* Too few hex quads given. */
+    if (n_hex_quads < ARRAY_LEN (hex_quads))
+      return 0;
+
+    for (i = 0; i < ARRAY_LEN (hex_quads); i++)
+      result->as_u16[i] = clib_host_to_net_u16 (hex_quads[i]);
+
+    return 1;
+  }
+}
+
+uword
+unformat_uri (unformat_input_t * input, va_list * args)
+{
+  session_endpoint_extended_t *sep = va_arg (*args,
+					     session_endpoint_extended_t *);
+  u32 port;
+  char *tmp;
+
+  if (unformat (input, "%s://%U/%d", &tmp, unformat_ip4_address, &sep->ip.ip4,
+		&port))
+    {
+      sep->port = clib_host_to_net_u16 (port);
+      sep->is_ip4 = 1;
+      return 1;
+    }
+  else if (unformat (input, "%s://%U/%d", &tmp, unformat_ip6_address,
+		     &sep->ip.ip6, &port))
+    {
+      sep->port = clib_host_to_net_u16 (port);
+      sep->is_ip4 = 0;
+      return 1;
+    }
+  return 0;
+}
+
 void
-application_send_attach (uri_udp_test_main_t * utm)
+application_send_attach (udp_echo_main_t * utm)
 {
   vl_api_application_attach_t *bmp;
-  u32 fifo_size = 1 << 20;
   bmp = vl_msg_api_alloc (sizeof (*bmp));
   memset (bmp, 0, sizeof (*bmp));
 
@@ -179,8 +311,8 @@ application_send_attach (uri_udp_test_main_t * utm)
   bmp->options[APP_OPTIONS_FLAGS] |= APP_OPTIONS_FLAGS_USE_GLOBAL_SCOPE;
   bmp->options[APP_OPTIONS_FLAGS] |= APP_OPTIONS_FLAGS_USE_LOCAL_SCOPE;
   bmp->options[APP_OPTIONS_PREALLOC_FIFO_PAIRS] = 2;
-  bmp->options[APP_OPTIONS_RX_FIFO_SIZE] = fifo_size;
-  bmp->options[APP_OPTIONS_TX_FIFO_SIZE] = fifo_size;
+  bmp->options[APP_OPTIONS_RX_FIFO_SIZE] = utm->fifo_size;
+  bmp->options[APP_OPTIONS_TX_FIFO_SIZE] = utm->fifo_size;
   bmp->options[APP_OPTIONS_ADD_SEGMENT_SIZE] = 128 << 20;
   bmp->options[APP_OPTIONS_SEGMENT_SIZE] = 256 << 20;
   bmp->options[APP_OPTIONS_EVT_QUEUE_SIZE] = 16768;
@@ -188,7 +320,7 @@ application_send_attach (uri_udp_test_main_t * utm)
 }
 
 void
-application_detach (uri_udp_test_main_t * utm)
+application_detach (udp_echo_main_t * utm)
 {
   vl_api_application_detach_t *bmp;
   bmp = vl_msg_api_alloc (sizeof (*bmp));
@@ -204,7 +336,7 @@ static void
 vl_api_application_attach_reply_t_handler (vl_api_application_attach_reply_t *
 					   mp)
 {
-  uri_udp_test_main_t *utm = &uri_udp_test_main;
+  udp_echo_main_t *utm = &udp_echo_main;
   svm_fifo_segment_create_args_t _a = { 0 }, *a = &_a;
   int rv;
 
@@ -250,7 +382,7 @@ vl_api_application_detach_reply_t_handler (vl_api_application_detach_reply_t *
 u8 *
 format_api_error (u8 * s, va_list * args)
 {
-  uri_udp_test_main_t *utm = va_arg (*args, uri_udp_test_main_t *);
+  udp_echo_main_t *utm = va_arg (*args, udp_echo_main_t *);
   i32 error = va_arg (*args, u32);
   uword *p;
 
@@ -264,7 +396,7 @@ format_api_error (u8 * s, va_list * args)
 }
 
 int
-wait_for_state_change (uri_udp_test_main_t * utm, connection_state_t state)
+wait_for_state_change (udp_echo_main_t * utm, connection_state_t state)
 {
 #if CLIB_DEBUG > 0
 #define TIMEOUT 600.0
@@ -287,11 +419,11 @@ u64 server_bytes_received, server_bytes_sent;
 static void *
 cut_through_thread_fn (void *arg)
 {
-  session_t *s;
+  app_session_t *s;
   svm_fifo_t *rx_fifo;
   svm_fifo_t *tx_fifo;
   u8 *my_copy_buffer = 0;
-  uri_udp_test_main_t *utm = &uri_udp_test_main;
+  udp_echo_main_t *utm = &udp_echo_main;
   i32 actual_transfer;
   int rv;
   u32 buffer_offset;
@@ -301,8 +433,8 @@ cut_through_thread_fn (void *arg)
 
   s = pool_elt_at_index (utm->sessions, utm->cut_through_session_index);
 
-  rx_fifo = s->server_rx_fifo;
-  tx_fifo = s->server_tx_fifo;
+  rx_fifo = s->rx_fifo;
+  tx_fifo = s->tx_fifo;
 
   vec_validate (my_copy_buffer, 64 * 1024 - 1);
 
@@ -340,7 +472,7 @@ cut_through_thread_fn (void *arg)
 }
 
 static void
-udp_client_connect (uri_udp_test_main_t * utm)
+udp_client_connect (udp_echo_main_t * utm)
 {
   vl_api_connect_uri_t *cmp;
   cmp = vl_msg_api_alloc (sizeof (*cmp));
@@ -354,7 +486,7 @@ udp_client_connect (uri_udp_test_main_t * utm)
 }
 
 static void
-client_send_cut_through (uri_udp_test_main_t * utm, session_t * session)
+client_send_cut_through (udp_echo_main_t * utm, app_session_t * session)
 {
   int i;
   u8 *test_data = 0;
@@ -372,8 +504,8 @@ client_send_cut_through (uri_udp_test_main_t * utm, session_t * session)
   for (i = 0; i < vec_len (test_data); i++)
     test_data[i] = i & 0xff;
 
-  rx_fifo = session->server_rx_fifo;
-  tx_fifo = session->server_tx_fifo;
+  rx_fifo = session->rx_fifo;
+  tx_fifo = session->tx_fifo;
 
   before = clib_time_now (&utm->clib_time);
 
@@ -456,15 +588,12 @@ client_send_cut_through (uri_udp_test_main_t * utm, session_t * session)
 }
 
 static void
-send_test_chunk (uri_udp_test_main_t * utm, svm_fifo_t * tx_fifo, int mypid,
-		 u32 bytes)
+send_test_chunk (udp_echo_main_t * utm, app_session_t * s, u32 bytes)
 {
   u8 *test_data = utm->connect_test_data;
-  u64 bytes_sent = 0;
   int test_buf_offset = 0;
+  u64 bytes_sent = 0;
   u32 bytes_to_snd;
-  u32 queue_max_chunk = 128 << 10, actual_write;
-  session_fifo_event_t evt;
   int rv;
 
   bytes_to_snd = (bytes == 0) ? vec_len (test_data) : bytes;
@@ -473,62 +602,27 @@ send_test_chunk (uri_udp_test_main_t * utm, svm_fifo_t * tx_fifo, int mypid,
 
   while (bytes_to_snd > 0 && !utm->time_to_stop)
     {
-      actual_write = (bytes_to_snd > queue_max_chunk) ?
-	queue_max_chunk : bytes_to_snd;
-      rv = svm_fifo_enqueue_nowait (tx_fifo, actual_write,
-				    test_data + test_buf_offset);
-
+      rv = app_send (s, test_data + test_buf_offset, bytes_to_snd, 0);
       if (rv > 0)
 	{
 	  bytes_to_snd -= rv;
 	  test_buf_offset += rv;
 	  bytes_sent += rv;
-
-	  if (svm_fifo_set_event (tx_fifo))
-	    {
-	      /* Fabricate TX event, send to vpp */
-	      evt.fifo = tx_fifo;
-	      evt.event_type = FIFO_EVENT_APP_TX;
-
-	      svm_queue_add (utm->vpp_event_queue,
-			     (u8 *) & evt, 0 /* do wait for mutex */ );
-	    }
 	}
     }
 }
 
 static void
-recv_test_chunk (uri_udp_test_main_t * utm, session_t * session)
+recv_test_chunk (udp_echo_main_t * utm, app_session_t * s)
 {
-  svm_fifo_t *rx_fifo;
-  int buffer_offset, bytes_to_read = 0, rv;
-
-  rx_fifo = session->server_rx_fifo;
-  bytes_to_read = svm_fifo_max_dequeue (rx_fifo);
-  bytes_to_read =
-    vec_len (utm->rx_buf) > bytes_to_read ?
-    bytes_to_read : vec_len (utm->rx_buf);
-
-  buffer_offset = 0;
-  while (bytes_to_read > 0)
-    {
-      rv = svm_fifo_dequeue_nowait (rx_fifo, bytes_to_read,
-				    utm->rx_buf + buffer_offset);
-      if (rv > 0)
-	{
-	  bytes_to_read -= rv;
-	  buffer_offset += rv;
-	}
-    }
+  app_recv (s, utm->rx_buf, vec_len (utm->rx_buf));
 }
 
 void
-client_send_data (uri_udp_test_main_t * utm)
+client_send_data (udp_echo_main_t * utm)
 {
   u8 *test_data;
-  int mypid = getpid ();
-  session_t *session;
-  svm_fifo_t *tx_fifo;
+  app_session_t *session;
   u32 n_iterations;
   int i;
 
@@ -538,8 +632,6 @@ client_send_data (uri_udp_test_main_t * utm)
 
   test_data = utm->connect_test_data;
   session = pool_elt_at_index (utm->sessions, utm->connected_session);
-  tx_fifo = session->server_tx_fifo;
-
   ASSERT (vec_len (test_data) > 0);
 
   vec_validate (utm->rx_buf, vec_len (test_data) - 1);
@@ -547,7 +639,7 @@ client_send_data (uri_udp_test_main_t * utm)
 
   for (i = 0; i < n_iterations; i++)
     {
-      send_test_chunk (utm, tx_fifo, mypid, 0);
+      send_test_chunk (utm, session, 0);
       recv_test_chunk (utm, session);
       if (utm->time_to_stop)
 	break;
@@ -562,9 +654,9 @@ client_send_data (uri_udp_test_main_t * utm)
 }
 
 static void
-client_test (uri_udp_test_main_t * utm)
+client_test (udp_echo_main_t * utm)
 {
-  session_t *session;
+  app_session_t *session;
 
   application_send_attach (utm);
   udp_client_connect (utm);
@@ -593,7 +685,10 @@ client_test (uri_udp_test_main_t * utm)
 static void
 vl_api_bind_uri_reply_t_handler (vl_api_bind_uri_reply_t * mp)
 {
-  uri_udp_test_main_t *utm = &uri_udp_test_main;
+  udp_echo_main_t *utm = &udp_echo_main;
+  svm_fifo_t *rx_fifo, *tx_fifo;
+  app_session_t *session;
+  u32 session_index;
 
   if (mp->retval)
     {
@@ -602,13 +697,30 @@ vl_api_bind_uri_reply_t_handler (vl_api_bind_uri_reply_t * mp)
       return;
     }
 
-  utm->state = STATE_BOUND;
+  rx_fifo = uword_to_pointer (mp->rx_fifo, svm_fifo_t *);
+  tx_fifo = uword_to_pointer (mp->tx_fifo, svm_fifo_t *);
+
+  pool_get (utm->sessions, session);
+  memset (session, 0, sizeof (*session));
+  session_index = session - utm->sessions;
+
+  rx_fifo->client_session_index = session_index;
+  tx_fifo->client_session_index = session_index;
+  session->rx_fifo = rx_fifo;
+  session->tx_fifo = tx_fifo;
+  clib_memcpy (&session->transport.lcl_ip, mp->lcl_ip,
+	       sizeof (ip46_address_t));
+  session->transport.is_ip4 = mp->lcl_is_ip4;
+  session->transport.lcl_port = mp->lcl_port;
+  session->vpp_evt_q = uword_to_pointer (mp->vpp_evt_q, svm_queue_t *);
+
+  utm->state = utm->is_connected ? STATE_BOUND : STATE_READY;
 }
 
 static void
 vl_api_map_another_segment_t_handler (vl_api_map_another_segment_t * mp)
 {
-  uri_udp_test_main_t *utm = &uri_udp_test_main;
+  udp_echo_main_t *utm = &udp_echo_main;
   svm_fifo_segment_create_args_t _a, *a = &_a;
   svm_fifo_segment_private_t *seg;
   u8 *seg_name;
@@ -636,7 +748,7 @@ vl_api_map_another_segment_t_handler (vl_api_map_another_segment_t * mp)
 static void
 vl_api_unmap_segment_t_handler (vl_api_unmap_segment_t * mp)
 {
-  uri_udp_test_main_t *utm = &uri_udp_test_main;
+  udp_echo_main_t *utm = &udp_echo_main;
   svm_fifo_segment_private_t *seg;
   u64 *seg_indexp;
   u8 *seg_name;
@@ -663,13 +775,13 @@ static void
 vl_api_connect_uri_t_handler (vl_api_connect_uri_t * mp)
 {
   u32 segment_index;
-  uri_udp_test_main_t *utm = &uri_udp_test_main;
+  udp_echo_main_t *utm = &udp_echo_main;
   svm_fifo_segment_main_t *sm = &svm_fifo_segment_main;
   svm_fifo_segment_create_args_t _a, *a = &_a;
   svm_fifo_segment_private_t *seg;
   svm_queue_t *client_q;
   vl_api_connect_session_reply_t *rmp;
-  session_t *session = 0;
+  app_session_t *session = 0;
   int rv = 0;
 
   /* Create the segment */
@@ -692,16 +804,16 @@ vl_api_connect_uri_t_handler (vl_api_connect_uri_t * mp)
 
   pool_get (utm->sessions, session);
 
-  session->server_rx_fifo = svm_fifo_segment_alloc_fifo
+  session->rx_fifo = svm_fifo_segment_alloc_fifo
     (utm->seg, 128 * 1024, FIFO_SEGMENT_RX_FREELIST);
-  ASSERT (session->server_rx_fifo);
+  ASSERT (session->rx_fifo);
 
-  session->server_tx_fifo = svm_fifo_segment_alloc_fifo
+  session->tx_fifo = svm_fifo_segment_alloc_fifo
     (utm->seg, 128 * 1024, FIFO_SEGMENT_TX_FREELIST);
-  ASSERT (session->server_tx_fifo);
+  ASSERT (session->tx_fifo);
 
-  session->server_rx_fifo->master_session_index = session - utm->sessions;
-  session->server_tx_fifo->master_session_index = session - utm->sessions;
+  session->rx_fifo->master_session_index = session - utm->sessions;
+  session->tx_fifo->master_session_index = session - utm->sessions;
   utm->cut_through_session_index = session - utm->sessions;
 
   rv = pthread_create (&utm->cut_through_thread_handle,
@@ -722,8 +834,8 @@ send_reply:
   rmp->segment_name_length = vec_len (a->segment_name);
   if (session)
     {
-      rmp->server_rx_fifo = pointer_to_uword (session->server_rx_fifo);
-      rmp->server_tx_fifo = pointer_to_uword (session->server_tx_fifo);
+      rmp->server_rx_fifo = pointer_to_uword (session->rx_fifo);
+      rmp->server_tx_fifo = pointer_to_uword (session->tx_fifo);
     }
 
   memcpy (rmp->segment_name, a->segment_name, vec_len (a->segment_name));
@@ -737,7 +849,7 @@ send_reply:
 static void
 vl_api_unbind_uri_reply_t_handler (vl_api_unbind_uri_reply_t * mp)
 {
-  uri_udp_test_main_t *utm = &uri_udp_test_main;
+  udp_echo_main_t *utm = &udp_echo_main;
 
   if (mp->retval != 0)
     clib_warning ("returned %d", ntohl (mp->retval));
@@ -748,10 +860,10 @@ vl_api_unbind_uri_reply_t_handler (vl_api_unbind_uri_reply_t * mp)
 static void
 vl_api_accept_session_t_handler (vl_api_accept_session_t * mp)
 {
-  uri_udp_test_main_t *utm = &uri_udp_test_main;
+  udp_echo_main_t *utm = &udp_echo_main;
   vl_api_accept_session_reply_t *rmp;
   svm_fifo_t *rx_fifo, *tx_fifo;
-  session_t *session;
+  app_session_t *session;
   static f64 start_time;
   u32 session_index;
   int rv = 0;
@@ -759,9 +871,8 @@ vl_api_accept_session_t_handler (vl_api_accept_session_t * mp)
   if (start_time == 0.0)
     start_time = clib_time_now (&utm->clib_time);
 
-  utm->vpp_event_queue =
-    uword_to_pointer (mp->vpp_event_queue_address, svm_queue_t *);
-
+  utm->vpp_event_queue = uword_to_pointer (mp->vpp_event_queue_address,
+					   svm_queue_t *);
   rx_fifo = uword_to_pointer (mp->server_rx_fifo, svm_fifo_t *);
   tx_fifo = uword_to_pointer (mp->server_tx_fifo, svm_fifo_t *);
 
@@ -778,8 +889,8 @@ vl_api_accept_session_t_handler (vl_api_accept_session_t * mp)
       rx_fifo->master_session_index = session_index;
       tx_fifo->master_session_index = session_index;
       utm->cut_through_session_index = session_index;
-      session->server_rx_fifo = rx_fifo;
-      session->server_tx_fifo = tx_fifo;
+      session->rx_fifo = rx_fifo;
+      session->tx_fifo = tx_fifo;
 
       rv = pthread_create (&utm->cut_through_thread_handle,
 			   NULL /*attr */ , cut_through_thread_fn, 0);
@@ -788,13 +899,18 @@ vl_api_accept_session_t_handler (vl_api_accept_session_t * mp)
 	  clib_warning ("pthread_create returned %d", rv);
 	  rv = VNET_API_ERROR_SYSCALL_ERROR_1;
 	}
+      utm->do_echo = 1;
     }
   else
     {
       rx_fifo->client_session_index = session_index;
       tx_fifo->client_session_index = session_index;
-      session->server_rx_fifo = rx_fifo;
-      session->server_tx_fifo = tx_fifo;
+      session->rx_fifo = rx_fifo;
+      session->tx_fifo = tx_fifo;
+      clib_memcpy (&session->transport.rmt_ip, mp->ip,
+		   sizeof (ip46_address_t));
+      session->transport.is_ip4 = mp->is_ip4;
+      session->transport.rmt_port = mp->port;
     }
 
   hash_set (utm->session_index_by_vpp_handles, mp->handle, session_index);
@@ -821,8 +937,8 @@ vl_api_accept_session_t_handler (vl_api_accept_session_t * mp)
 static void
 vl_api_disconnect_session_t_handler (vl_api_disconnect_session_t * mp)
 {
-  uri_udp_test_main_t *utm = &uri_udp_test_main;
-  session_t *session;
+  udp_echo_main_t *utm = &udp_echo_main;
+  app_session_t *session;
   vl_api_disconnect_session_reply_t *rmp;
   uword *p;
   int rv = 0;
@@ -853,10 +969,12 @@ vl_api_disconnect_session_t_handler (vl_api_disconnect_session_t * mp)
 static void
 vl_api_connect_session_reply_t_handler (vl_api_connect_session_reply_t * mp)
 {
-  uri_udp_test_main_t *utm = &uri_udp_test_main;
-  session_t *session;
+  udp_echo_main_t *utm = &udp_echo_main;
+  unformat_input_t _input, *input = &_input;
+  session_endpoint_extended_t _sep, *sep = &_sep;
+  app_session_t *session;
 
-  ASSERT (utm->i_am_master == 0);
+  ASSERT (utm->i_am_server == 0);
 
   if (mp->retval)
     {
@@ -864,14 +982,13 @@ vl_api_connect_session_reply_t_handler (vl_api_connect_session_reply_t * mp)
       return;
     }
 
-  pool_get (utm->sessions, session);
-  session->server_rx_fifo = uword_to_pointer (mp->server_rx_fifo,
-					      svm_fifo_t *);
-  ASSERT (session->server_rx_fifo);
-  session->server_tx_fifo = uword_to_pointer (mp->server_tx_fifo,
-					      svm_fifo_t *);
-  ASSERT (session->server_tx_fifo);
+  ASSERT (mp->server_rx_fifo && mp->server_tx_fifo);
 
+  pool_get (utm->sessions, session);
+  session->rx_fifo = uword_to_pointer (mp->server_rx_fifo, svm_fifo_t *);
+  session->tx_fifo = uword_to_pointer (mp->server_tx_fifo, svm_fifo_t *);
+  session->vpp_evt_q = uword_to_pointer (mp->vpp_event_queue_address,
+					 svm_queue_t *);
   /* Cut-through case */
   if (mp->client_event_queue_address)
     {
@@ -881,12 +998,32 @@ vl_api_connect_session_reply_t_handler (vl_api_connect_session_reply_t * mp)
 					       svm_queue_t *);
       utm->our_event_queue = uword_to_pointer (mp->client_event_queue_address,
 					       svm_queue_t *);
+      utm->do_echo = 1;
     }
   else
     {
       utm->connected_session = session - utm->sessions;
       utm->vpp_event_queue = uword_to_pointer (mp->vpp_event_queue_address,
 					       svm_queue_t *);
+
+      clib_memcpy (&session->transport.lcl_ip, mp->lcl_ip,
+		   sizeof (ip46_address_t));
+      session->transport.is_ip4 = mp->is_ip4;
+      session->transport.lcl_port = mp->lcl_port;
+
+      unformat_init_vector (input, utm->connect_uri);
+      if (!unformat (input, "%U", unformat_uri, sep))
+	{
+	  clib_warning ("can't figure out remote ip and port");
+	  utm->state = STATE_FAILED;
+	  unformat_free (input);
+	  return;
+	}
+      unformat_free (input);
+      clib_memcpy (&session->transport.rmt_ip, &sep->ip,
+		   sizeof (ip46_address_t));
+      session->transport.rmt_port = sep->port;
+      session->is_dgram = !utm->is_connected;
     }
   utm->state = STATE_READY;
 }
@@ -904,7 +1041,7 @@ _(APPLICATION_ATTACH_REPLY, application_attach_reply)	\
 _(APPLICATION_DETACH_REPLY, application_detach_reply)	\
 
 void
-tcp_echo_api_hookup (uri_udp_test_main_t * utm)
+tcp_echo_api_hookup (udp_echo_main_t * utm)
 {
 #define _(N,n)                                                  \
     vl_msg_api_set_handlers(VL_API_##N, #n,                     \
@@ -921,7 +1058,7 @@ tcp_echo_api_hookup (uri_udp_test_main_t * utm)
 int
 connect_to_vpp (char *name)
 {
-  uri_udp_test_main_t *utm = &uri_udp_test_main;
+  udp_echo_main_t *utm = &udp_echo_main;
   api_main_t *am = &api_main;
 
   if (vl_client_connect_to_vlib ("/vpe-api", name, 32) < 0)
@@ -940,7 +1077,7 @@ vlib_cli_output (struct vlib_main_t *vm, char *fmt, ...)
 }
 
 static void
-init_error_string_table (uri_udp_test_main_t * utm)
+init_error_string_table (udp_echo_main_t * utm)
 {
   utm->error_string_by_error_number = hash_create (0, sizeof (uword));
 
@@ -952,43 +1089,26 @@ init_error_string_table (uri_udp_test_main_t * utm)
 }
 
 void
-server_handle_fifo_event_rx (uri_udp_test_main_t * utm,
-			     session_fifo_event_t * e)
+server_handle_fifo_event_rx (udp_echo_main_t * utm, session_fifo_event_t * e)
 {
-  svm_fifo_t *rx_fifo, *tx_fifo;
-  int nbytes;
-  session_fifo_event_t evt;
-  svm_queue_t *q;
+  app_session_t *s;
   int rv;
 
-  rx_fifo = e->fifo;
-  tx_fifo = utm->sessions[rx_fifo->client_session_index].server_tx_fifo;
-  svm_fifo_unset_event (rx_fifo);
-
-  do
-    {
-      nbytes = svm_fifo_dequeue_nowait (rx_fifo, vec_len (utm->rx_buf),
-					utm->rx_buf);
-    }
-  while (nbytes <= 0);
-  do
-    {
-      rv = svm_fifo_enqueue_nowait (tx_fifo, nbytes, utm->rx_buf);
-    }
-  while (rv == -2);
+  s = pool_elt_at_index (utm->sessions, e->fifo->client_session_index);
+  app_recv (s, utm->rx_buf, vec_len (utm->rx_buf));
 
-  if (svm_fifo_set_event (tx_fifo))
+  if (utm->do_echo)
     {
-      /* Fabricate TX event, send to vpp */
-      evt.fifo = tx_fifo;
-      evt.event_type = FIFO_EVENT_APP_TX;
-      q = utm->vpp_event_queue;
-      svm_queue_add (q, (u8 *) & evt, 0 /* do wait for mutex */ );
+      do
+	{
+	  rv = app_send_stream (s, utm->rx_buf, vec_len (utm->rx_buf), 0);
+	}
+      while (rv == SVM_FIFO_FULL);
     }
 }
 
 void
-server_handle_event_queue (uri_udp_test_main_t * utm)
+server_handle_event_queue (udp_echo_main_t * utm)
 {
   session_fifo_event_t _e, *e = &_e;
 
@@ -1022,7 +1142,7 @@ server_handle_event_queue (uri_udp_test_main_t * utm)
 }
 
 static void
-server_unbind (uri_udp_test_main_t * utm)
+server_unbind (udp_echo_main_t * utm)
 {
   vl_api_unbind_uri_t *ump;
 
@@ -1031,12 +1151,12 @@ server_unbind (uri_udp_test_main_t * utm)
 
   ump->_vl_msg_id = ntohs (VL_API_UNBIND_URI);
   ump->client_index = utm->my_client_index;
-  memcpy (ump->uri, utm->uri, vec_len (utm->uri));
+  memcpy (ump->uri, utm->listen_uri, vec_len (utm->listen_uri));
   vl_msg_api_send_shmem (utm->vl_input_queue, (u8 *) & ump);
 }
 
 static void
-server_bind (uri_udp_test_main_t * utm)
+server_bind (udp_echo_main_t * utm)
 {
   vl_api_bind_uri_t *bmp;
 
@@ -1046,22 +1166,22 @@ server_bind (uri_udp_test_main_t * utm)
   bmp->_vl_msg_id = ntohs (VL_API_BIND_URI);
   bmp->client_index = utm->my_client_index;
   bmp->context = ntohl (0xfeedface);
-  memcpy (bmp->uri, utm->uri, vec_len (utm->uri));
+  memcpy (bmp->uri, utm->listen_uri, vec_len (utm->listen_uri));
   vl_msg_api_send_shmem (utm->vl_input_queue, (u8 *) & bmp);
 }
 
 void
-udp_server_test (uri_udp_test_main_t * utm)
+udp_server_test (udp_echo_main_t * utm)
 {
-
+  u8 wait_for_state = utm->is_connected ? STATE_BOUND : STATE_READY;
   application_send_attach (utm);
 
   /* Bind to uri */
   server_bind (utm);
 
-  if (wait_for_state_change (utm, STATE_BOUND))
+  if (wait_for_state_change (utm, wait_for_state))
     {
-      clib_warning ("timeout waiting for STATE_BOUND");
+      clib_warning ("timeout waiting for state change");
       return;
     }
 
@@ -1084,11 +1204,11 @@ udp_server_test (uri_udp_test_main_t * utm)
 int
 main (int argc, char **argv)
 {
-  uri_udp_test_main_t *utm = &uri_udp_test_main;
-  u8 *bind_name = (u8 *) "udp://0.0.0.0/1234";
+  udp_echo_main_t *utm = &udp_echo_main;
+  u8 *uri = (u8 *) "udp://0.0.0.0/1234";
   unformat_input_t _argv, *a = &_argv;
-  int i_am_master = 1;
-  session_t *session;
+  int i_am_server = 1;
+  app_session_t *session;
   u8 *chroot_prefix;
   char *app_name;
   mheap_t *h;
@@ -1116,39 +1236,50 @@ main (int argc, char **argv)
   svm_fifo_segment_main_init (0x200000000ULL, 20);
   unformat_init_command_line (a, argv);
 
+  utm->fifo_size = 128 << 10;
+
   while (unformat_check_input (a) != UNFORMAT_END_OF_INPUT)
     {
       if (unformat (a, "chroot prefix %s", &chroot_prefix))
 	{
 	  vl_set_memory_root_path ((char *) chroot_prefix);
 	}
-      else if (unformat (a, "uri %s", &bind_name))
+      else if (unformat (a, "uri %s", &uri))
 	;
       else if (unformat (a, "segment-size %dM", &tmp))
 	utm->configured_segment_size = tmp << 20;
       else if (unformat (a, "segment-size %dG", &tmp))
 	utm->configured_segment_size = tmp << 30;
-      else if (unformat (a, "master"))
-	i_am_master = 1;
-      else if (unformat (a, "slave"))
-	i_am_master = 0;
+      else if (unformat (a, "server"))
+	i_am_server = 1;
+      else if (unformat (a, "client"))
+	i_am_server = 0;
       else
 	{
-	  fformat (stderr, "%s: usage [master|slave]\n");
+	  fformat (stderr, "%s: usage [server|client]\n");
 	  exit (1);
 	}
     }
 
   utm->cut_through_session_index = ~0;
-  utm->uri = format (0, "%s%c", bind_name, 0);
-  utm->i_am_master = i_am_master;
+  utm->i_am_server = i_am_server;
   utm->segment_main = &svm_fifo_segment_main;
-  utm->connect_uri = format (0, "udp://6.0.1.2/1234%c", 0);
 
   setup_signal_handlers ();
   tcp_echo_api_hookup (utm);
 
-  app_name = i_am_master ? "udp_echo_master" : "udp_echo_slave";
+  if (i_am_server)
+    {
+      utm->listen_uri = format (0, "%s%c", uri, 0);
+      utm->is_connected = (utm->listen_uri[4] == 'c');
+      app_name = "udp_echo_server";
+    }
+  else
+    {
+      app_name = "udp_echo_client";
+      utm->connect_uri = format (0, "%s%c", uri, 0);
+      utm->is_connected = (utm->connect_uri[4] == 'c');
+    }
   if (connect_to_vpp (app_name) < 0)
     {
       svm_region_exit ();
@@ -1156,7 +1287,7 @@ main (int argc, char **argv)
       exit (1);
     }
 
-  if (i_am_master == 0)
+  if (i_am_server == 0)
     {
       client_test (utm);
       exit (0);
diff --git a/src/vnet/session-apps/echo_client.c b/src/vnet/session-apps/echo_client.c
index 2cfb471413c..11528ef1899 100644
--- a/src/vnet/session-apps/echo_client.c
+++ b/src/vnet/session-apps/echo_client.c
@@ -46,23 +46,21 @@ static void
 send_data_chunk (echo_client_main_t * ecm, session_t * s)
 {
   u8 *test_data = ecm->connect_test_data;
-  int test_buf_offset;
+  int test_buf_len, test_buf_offset, rv;
   u32 bytes_this_chunk;
-  session_fifo_event_t evt;
-  svm_fifo_t *txf;
-  int rv;
 
   ASSERT (vec_len (test_data) > 0);
-
-  test_buf_offset = s->bytes_sent % vec_len (test_data);
-  bytes_this_chunk = vec_len (test_data) - test_buf_offset;
-
-  bytes_this_chunk = bytes_this_chunk < s->bytes_to_send
-    ? bytes_this_chunk : s->bytes_to_send;
-
-  txf = s->server_tx_fifo;
-  rv = svm_fifo_enqueue_nowait (txf, bytes_this_chunk,
-				test_data + test_buf_offset);
+  test_buf_len = vec_len (test_data);
+  test_buf_offset = s->bytes_sent % test_buf_len;
+  bytes_this_chunk = clib_min (test_buf_len - test_buf_offset,
+			       s->bytes_to_send);
+
+  if (!ecm->is_dgram)
+    rv = app_send_stream (&s->data, test_data + test_buf_offset,
+			  bytes_this_chunk, 0);
+  else
+    rv = app_send_dgram (&s->data, test_data + test_buf_offset,
+			 bytes_this_chunk, 0);
 
   /* If we managed to enqueue data... */
   if (rv > 0)
@@ -89,35 +87,24 @@ send_data_chunk (echo_client_main_t * ecm, session_t * s)
 	  ed->data[1] = s->bytes_sent;
 	  ed->data[2] = s->bytes_to_send;
 	}
-
-      /* Poke the session layer */
-      if (svm_fifo_set_event (txf))
-	{
-	  /* Fabricate TX event, send to vpp */
-	  evt.fifo = txf;
-	  evt.event_type = FIFO_EVENT_APP_TX;
-
-	  if (svm_queue_add
-	      (ecm->vpp_event_queue[txf->master_thread_index], (u8 *) & evt,
-	       0 /* do wait for mutex */ ))
-	    clib_warning ("could not enqueue event");
-	}
     }
 }
 
 static void
 receive_data_chunk (echo_client_main_t * ecm, session_t * s)
 {
-  svm_fifo_t *rx_fifo = s->server_rx_fifo;
-  u32 my_thread_index = vlib_get_thread_index ();
+  svm_fifo_t *rx_fifo = s->data.rx_fifo;
+  u32 thread_index = vlib_get_thread_index ();
   int n_read, i;
 
   if (ecm->test_bytes)
     {
-      n_read = svm_fifo_dequeue_nowait (rx_fifo,
-					vec_len (ecm->rx_buf
-						 [my_thread_index]),
-					ecm->rx_buf[my_thread_index]);
+      if (!ecm->is_dgram)
+	n_read = app_recv_stream (&s->data, ecm->rx_buf[thread_index],
+				  vec_len (ecm->rx_buf[thread_index]));
+      else
+	n_read = app_recv_dgram (&s->data, ecm->rx_buf[thread_index],
+				 vec_len (ecm->rx_buf[thread_index]));
     }
   else
     {
@@ -148,17 +135,18 @@ receive_data_chunk (echo_client_main_t * ecm, session_t * s)
 	{
 	  for (i = 0; i < n_read; i++)
 	    {
-	      if (ecm->rx_buf[my_thread_index][i]
+	      if (ecm->rx_buf[thread_index][i]
 		  != ((s->bytes_received + i) & 0xff))
 		{
 		  clib_warning ("read %d error at byte %lld, 0x%x not 0x%x",
 				n_read, s->bytes_received + i,
-				ecm->rx_buf[my_thread_index][i],
+				ecm->rx_buf[thread_index][i],
 				((s->bytes_received + i) & 0xff));
 		  ecm->test_failed = 1;
 		}
 	    }
 	}
+      ASSERT (n_read <= s->bytes_to_receive);
       s->bytes_to_receive -= n_read;
       s->bytes_received += n_read;
     }
@@ -230,20 +218,15 @@ echo_client_node_fn (vlib_main_t * vm, vlib_node_runtime_t * node,
 	}
       if (sp->bytes_to_receive > 0)
 	{
-	  receive_data_chunk (ecm, sp);
 	  delete_session = 0;
 	}
       if (PREDICT_FALSE (delete_session == 1))
 	{
-	  u32 index, thread_index;
 	  stream_session_t *s;
 
 	  __sync_fetch_and_add (&ecm->tx_total, sp->bytes_sent);
 	  __sync_fetch_and_add (&ecm->rx_total, sp->bytes_received);
-
-	  session_parse_handle (sp->vpp_session_handle,
-				&index, &thread_index);
-	  s = session_get_if_valid (index, thread_index);
+	  s = session_get_from_handle_if_valid (sp->vpp_session_handle);
 
 	  if (s)
 	    {
@@ -312,8 +295,8 @@ echo_clients_init (vlib_main_t * vm)
 
   num_threads = 1 /* main thread */  + vtm->n_threads;
 
-  /* Init test data. Bigecmuffer */
-  vec_validate (ecm->connect_test_data, 1024 * 1024 - 1);
+  /* Init test data. Big buffer */
+  vec_validate (ecm->connect_test_data, 4 * 1024 * 1024 - 1);
   for (i = 0; i < vec_len (ecm->connect_test_data); i++)
     ecm->connect_test_data[i] = i & 0xff;
 
@@ -363,12 +346,22 @@ echo_clients_session_connected_callback (u32 app_index, u32 api_context,
   session_index = session - ecm->sessions;
   session->bytes_to_send = ecm->bytes_to_send;
   session->bytes_to_receive = ecm->no_return ? 0ULL : ecm->bytes_to_send;
-  session->server_rx_fifo = s->server_rx_fifo;
-  session->server_rx_fifo->client_session_index = session_index;
-  session->server_tx_fifo = s->server_tx_fifo;
-  session->server_tx_fifo->client_session_index = session_index;
+  session->data.rx_fifo = s->server_rx_fifo;
+  session->data.rx_fifo->client_session_index = session_index;
+  session->data.tx_fifo = s->server_tx_fifo;
+  session->data.tx_fifo->client_session_index = session_index;
+  session->data.vpp_evt_q = ecm->vpp_event_queue[thread_index];
   session->vpp_session_handle = session_handle (s);
 
+  if (ecm->is_dgram)
+    {
+      transport_connection_t *tc;
+      tc = session_get_transport (s);
+      clib_memcpy (&session->data.transport, tc,
+		   sizeof (session->data.transport));
+      session->data.is_dgram = 1;
+    }
+
   vec_add1 (ecm->connection_index_by_thread[thread_index], session_index);
   __sync_fetch_and_add (&ecm->ready_connections, 1);
   if (ecm->ready_connections == ecm->expected_connections)
@@ -410,6 +403,28 @@ echo_clients_session_disconnect_callback (stream_session_t * s)
 static int
 echo_clients_rx_callback (stream_session_t * s)
 {
+  echo_client_main_t *ecm = &echo_client_main;
+  session_t *sp;
+
+  sp = pool_elt_at_index (ecm->sessions,
+			  s->server_rx_fifo->client_session_index);
+  receive_data_chunk (ecm, sp);
+
+  if (svm_fifo_max_dequeue (s->server_rx_fifo))
+    {
+      session_fifo_event_t evt;
+      svm_queue_t *q;
+      if (svm_fifo_set_event (s->server_rx_fifo))
+	{
+	  evt.fifo = s->server_rx_fifo;
+	  evt.event_type = FIFO_EVENT_BUILTIN_RX;
+	  q = session_manager_get_vpp_event_queue (s->thread_index);
+	  if (PREDICT_FALSE (q->cursize == q->maxsize))
+	    clib_warning ("out of event queue space");
+	  else if (svm_queue_add (q, (u8 *) & evt, 0))
+	    clib_warning ("failed to enqueue self-tap");
+	}
+    }
   return 0;
 }
 
@@ -544,7 +559,7 @@ echo_clients_connect (vlib_main_t * vm, u32 n_clients)
 }
 
 #define ec_cli_output(_fmt, _args...) 			\
-  if (!ecm->no_output)  					\
+  if (!ecm->no_output)  				\
     vlib_cli_output(vm, _fmt, ##_args)
 
 static clib_error_t *
@@ -663,6 +678,9 @@ echo_clients_command_fn (vlib_main_t * vm,
       ecm->connect_uri = format (0, "%s%c", default_uri, 0);
     }
 
+  if (ecm->connect_uri[0] == 'u' && ecm->connect_uri[3] != 'c')
+    ecm->is_dgram = 1;
+
 #if ECHO_CLIENT_PTHREAD
   echo_clients_start_tx_pthread ();
 #endif
diff --git a/src/vnet/session-apps/echo_client.h b/src/vnet/session-apps/echo_client.h
index 5712da5b8c8..344e43865b5 100644
--- a/src/vnet/session-apps/echo_client.h
+++ b/src/vnet/session-apps/echo_client.h
@@ -30,15 +30,13 @@
 
 typedef struct
 {
+  app_session_t data;
   u64 bytes_to_send;
   u64 bytes_sent;
   u64 bytes_to_receive;
   u64 bytes_received;
-
-  svm_fifo_t *server_rx_fifo;
-  svm_fifo_t *server_tx_fifo;
-
   u64 vpp_session_handle;
+  u8 thread_index;
 } session_t;
 
 typedef struct
@@ -46,7 +44,7 @@ typedef struct
   /*
    * Application setup parameters
    */
-  svm_queue_t *vl_input_queue;	/**< vpe input queue */
+  svm_queue_t *vl_input_queue;		/**< vpe input queue */
   svm_queue_t **vpp_event_queue;
 
   u32 cli_node_index;			/**< cli process node index */
@@ -65,6 +63,7 @@ typedef struct
   u32 private_segment_count;		/**< Number of private fifo segs */
   u32 private_segment_size;		/**< size of private fifo segs */
   u32 tls_engine;			/**< TLS engine mbedtls/openssl */
+  u8 is_dgram;
   /*
    * Test state variables
    */
diff --git a/src/vnet/session-apps/echo_server.c b/src/vnet/session-apps/echo_server.c
index 0bde2e4995f..85e6c299919 100644
--- a/src/vnet/session-apps/echo_server.c
+++ b/src/vnet/session-apps/echo_server.c
@@ -34,13 +34,14 @@ typedef struct
    * Config params
    */
   u8 no_echo;			/**< Don't echo traffic */
-  u32 fifo_size;			/**< Fifo size */
+  u32 fifo_size;		/**< Fifo size */
   u32 rcv_buffer_size;		/**< Rcv buffer size */
   u32 prealloc_fifos;		/**< Preallocate fifos */
   u32 private_segment_count;	/**< Number of private segments  */
   u32 private_segment_size;	/**< Size of private segments  */
   char *server_uri;		/**< Server URI */
   u32 tls_engine;		/**< TLS engine: mbedtls/openssl */
+  u8 is_dgram;			/**< set if transport is dgram */
   /*
    * Test state
    */
@@ -126,25 +127,13 @@ test_bytes (echo_server_main_t * esm, int actual_transfer)
 }
 
 /*
- * If no-echo, just read the data and be done with it
+ * If no-echo, just drop the data and be done with it.
  */
 int
 echo_server_builtin_server_rx_callback_no_echo (stream_session_t * s)
 {
-  echo_server_main_t *esm = &echo_server_main;
-  u32 my_thread_id = vlib_get_thread_index ();
-  int actual_transfer;
-  svm_fifo_t *rx_fifo;
-
-  rx_fifo = s->server_rx_fifo;
-
-  do
-    {
-      actual_transfer =
-	svm_fifo_dequeue_nowait (rx_fifo, esm->rcv_buffer_size,
-				 esm->rx_buf[my_thread_id]);
-    }
-  while (actual_transfer > 0);
+  svm_fifo_t *rx_fifo = s->server_rx_fifo;
+  svm_fifo_dequeue_drop (rx_fifo, svm_fifo_max_dequeue (rx_fifo));
   return 0;
 }
 
@@ -157,6 +146,8 @@ echo_server_rx_callback (stream_session_t * s)
   echo_server_main_t *esm = &echo_server_main;
   session_fifo_event_t evt;
   u32 thread_index = vlib_get_thread_index ();
+  app_session_transport_t at;
+  svm_queue_t *q;
 
   ASSERT (s->thread_index == thread_index);
 
@@ -166,14 +157,29 @@ echo_server_rx_callback (stream_session_t * s)
   ASSERT (rx_fifo->master_thread_index == thread_index);
   ASSERT (tx_fifo->master_thread_index == thread_index);
 
-  max_dequeue = svm_fifo_max_dequeue (s->server_rx_fifo);
-  max_enqueue = svm_fifo_max_enqueue (s->server_tx_fifo);
+  max_enqueue = svm_fifo_max_enqueue (tx_fifo);
+  if (!esm->is_dgram)
+    {
+      max_dequeue = svm_fifo_max_dequeue (rx_fifo);
+    }
+  else
+    {
+      session_dgram_pre_hdr_t ph;
+      svm_fifo_peek (rx_fifo, 0, sizeof (ph), (u8 *) & ph);
+      max_dequeue = ph.data_length - ph.data_offset;
+      if (!esm->vpp_queue[s->thread_index])
+	{
+	  q = session_manager_get_vpp_event_queue (s->thread_index);
+	  esm->vpp_queue[s->thread_index] = q;
+	}
+      max_enqueue -= sizeof (session_dgram_hdr_t);
+    }
 
   if (PREDICT_FALSE (max_dequeue == 0))
     return 0;
 
   /* Number of bytes we're going to copy */
-  max_transfer = (max_dequeue < max_enqueue) ? max_dequeue : max_enqueue;
+  max_transfer = clib_min (max_dequeue, max_enqueue);
 
   /* No space in tx fifo */
   if (PREDICT_FALSE (max_transfer == 0))
@@ -184,16 +190,16 @@ echo_server_rx_callback (stream_session_t * s)
       /* Program self-tap to retry */
       if (svm_fifo_set_event (rx_fifo))
 	{
-	  svm_queue_t *q;
 	  evt.fifo = rx_fifo;
 	  evt.event_type = FIFO_EVENT_BUILTIN_RX;
 
-	  q = esm->vpp_queue[thread_index];
+	  q = esm->vpp_queue[s->thread_index];
 	  if (PREDICT_FALSE (q->cursize == q->maxsize))
 	    clib_warning ("out of event queue space");
 	  else if (svm_queue_add (q, (u8 *) & evt, 0))
 	    clib_warning ("failed to enqueue self-tap");
 
+	  vec_validate (esm->rx_retries[s->thread_index], s->session_index);
 	  if (esm->rx_retries[thread_index][s->session_index] == 500000)
 	    {
 	      clib_warning ("session stuck: %U", format_stream_session, s, 2);
@@ -205,36 +211,47 @@ echo_server_rx_callback (stream_session_t * s)
       return 0;
     }
 
-  _vec_len (esm->rx_buf[thread_index]) = max_transfer;
-
-  actual_transfer = svm_fifo_dequeue_nowait (rx_fifo, max_transfer,
-					     esm->rx_buf[thread_index]);
+  vec_validate (esm->rx_buf[thread_index], max_transfer);
+  if (!esm->is_dgram)
+    {
+      actual_transfer = app_recv_stream_raw (rx_fifo,
+					     esm->rx_buf[thread_index],
+					     max_transfer,
+					     0 /* don't clear event */ );
+    }
+  else
+    {
+      actual_transfer = app_recv_dgram_raw (rx_fifo,
+					    esm->rx_buf[thread_index],
+					    max_transfer, &at,
+					    0 /* don't clear event */ );
+    }
   ASSERT (actual_transfer == max_transfer);
-
-//  test_bytes (esm, actual_transfer);
+  /* test_bytes (esm, actual_transfer); */
 
   /*
    * Echo back
    */
 
-  n_written = svm_fifo_enqueue_nowait (tx_fifo, actual_transfer,
-				       esm->rx_buf[thread_index]);
-
-  if (n_written != max_transfer)
-    clib_warning ("short trout!");
-
-  if (svm_fifo_set_event (tx_fifo))
+  if (!esm->is_dgram)
     {
-      /* Fabricate TX event, send to vpp */
-      evt.fifo = tx_fifo;
-      evt.event_type = FIFO_EVENT_APP_TX;
-
-      if (svm_queue_add (esm->vpp_queue[s->thread_index],
-			 (u8 *) & evt, 0 /* do wait for mutex */ ))
-	clib_warning ("failed to enqueue tx evt");
+      n_written = app_send_stream_raw (tx_fifo,
+				       esm->vpp_queue[thread_index],
+				       esm->rx_buf[thread_index],
+				       actual_transfer, 0);
     }
+  else
+    {
+      n_written = app_send_dgram_raw (tx_fifo, &at,
+				      esm->vpp_queue[s->thread_index],
+				      esm->rx_buf[thread_index],
+				      actual_transfer, 0);
+    }
+
+  if (n_written != max_transfer)
+    clib_warning ("short trout! written %u read %u", n_written, max_transfer);
 
-  if (PREDICT_FALSE (n_written < max_dequeue))
+  if (PREDICT_FALSE (svm_fifo_max_dequeue (rx_fifo)))
     goto rx_event;
 
   return 0;
@@ -411,6 +428,7 @@ echo_server_create_command_fn (vlib_main_t * vm, unformat_input_t * input,
   esm->private_segment_count = 0;
   esm->private_segment_size = 0;
   esm->tls_engine = TLS_ENGINE_OPENSSL;
+  esm->is_dgram = 0;
   vec_free (esm->server_uri);
 
   while (unformat_check_input (input) != UNFORMAT_END_OF_INPUT)
@@ -479,6 +497,8 @@ echo_server_create_command_fn (vlib_main_t * vm, unformat_input_t * input,
       clib_warning ("No uri provided! Using default: %s", default_uri);
       esm->server_uri = (char *) format (0, "%s%c", default_uri, 0);
     }
+  if (esm->server_uri[0] == 'u' && esm->server_uri[3] != 'c')
+    esm->is_dgram = 1;
 
   rv = echo_server_create (vm, appns_id, appns_flags, appns_secret);
   vec_free (appns_id);
diff --git a/src/vnet/session/application.c b/src/vnet/session/application.c
index 1c46e786e13..68bbd59098e 100644
--- a/src/vnet/session/application.c
+++ b/src/vnet/session/application.c
@@ -445,13 +445,9 @@ application_start_listen (application_t * srv, session_endpoint_t * sep,
   s = listen_session_new (0, sst);
   s->app_index = srv->index;
 
-  if (stream_session_listen (s, sep))
-    goto err;
-
   /* Allocate segment manager. All sessions derived out of a listen session
    * have fifos allocated by the same segment manager. */
-  sm = application_alloc_segment_manager (srv);
-  if (sm == 0)
+  if (!(sm = application_alloc_segment_manager (srv)))
     goto err;
 
   /* Add to app's listener table. Useful to find all child listeners
@@ -459,6 +455,13 @@ application_start_listen (application_t * srv, session_endpoint_t * sep,
   handle = listen_session_get_handle (s);
   hash_set (srv->listeners_table, handle, segment_manager_index (sm));
 
+  if (stream_session_listen (s, sep))
+    {
+      segment_manager_del (sm);
+      hash_unset (srv->listeners_table, handle);
+      goto err;
+    }
+
   *res = handle;
   return 0;
 
diff --git a/src/vnet/session/application_interface.h b/src/vnet/session/application_interface.h
index 5dc237f6e7b..5fd218533dc 100644
--- a/src/vnet/session/application_interface.h
+++ b/src/vnet/session/application_interface.h
@@ -173,6 +173,163 @@ extern const u32 test_srv_crt_rsa_len;
 extern const char test_srv_key_rsa[];
 extern const u32 test_srv_key_rsa_len;
 
+typedef struct app_session_transport_
+{
+  ip46_address_t rmt_ip;	/**< remote ip */
+  ip46_address_t lcl_ip;	/**< local ip */
+  u16 rmt_port;			/**< remote port */
+  u16 lcl_port;			/**< local port */
+  u8 is_ip4;			/**< set if uses ip4 networking */
+} app_session_transport_t;
+
+typedef struct app_session_
+{
+  svm_fifo_t *rx_fifo;			/**< rx fifo */
+  svm_fifo_t *tx_fifo;			/**< tx fifo */
+  session_type_t session_type;		/**< session type */
+  volatile u8 session_state;		/**< session state */
+  u32 session_index;			/**< index in owning pool */
+  app_session_transport_t transport;	/**< transport info */
+  svm_queue_t *vpp_evt_q;		/**< vpp event queue for session */
+  u8 is_dgram;				/**< set if it works in dgram mode */
+} app_session_t;
+
+always_inline int
+app_send_dgram_raw (svm_fifo_t * f, app_session_transport_t * at,
+		    svm_queue_t * vpp_evt_q, u8 * data, u32 len, u8 noblock)
+{
+  u32 max_enqueue, actual_write;
+  session_dgram_hdr_t hdr;
+  session_fifo_event_t evt;
+  int rv;
+
+  max_enqueue = svm_fifo_max_enqueue (f);
+  if (svm_fifo_max_enqueue (f) <= sizeof (session_dgram_hdr_t))
+    return 0;
+
+  max_enqueue -= sizeof (session_dgram_hdr_t);
+  actual_write = clib_min (len, max_enqueue);
+  hdr.data_length = actual_write;
+  hdr.data_offset = 0;
+  clib_memcpy (&hdr.rmt_ip, &at->rmt_ip, sizeof (ip46_address_t));
+  hdr.is_ip4 = at->is_ip4;
+  hdr.rmt_port = at->rmt_port;
+  clib_memcpy (&hdr.lcl_ip, &at->lcl_ip, sizeof (ip46_address_t));
+  hdr.lcl_port = at->lcl_port;
+  rv = svm_fifo_enqueue_nowait (f, sizeof (hdr), (u8 *) & hdr);
+  if (rv <= 0)
+    return 0;
+
+  ASSERT (rv == sizeof (hdr));
+
+  if ((rv = svm_fifo_enqueue_nowait (f, actual_write, data)) > 0)
+    {
+      if (svm_fifo_set_event (f))
+	{
+	  evt.fifo = f;
+	  evt.event_type = FIFO_EVENT_APP_TX;
+	  svm_queue_add (vpp_evt_q, (u8 *) & evt, noblock);
+	}
+    }
+  return rv;
+}
+
+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, noblock);
+}
+
+always_inline int
+app_send_stream_raw (svm_fifo_t * f, svm_queue_t * vpp_evt_q, u8 * data,
+		     u32 len, u8 noblock)
+{
+  session_fifo_event_t evt;
+  int rv;
+
+  if ((rv = svm_fifo_enqueue_nowait (f, len, data)) > 0)
+    {
+      if (svm_fifo_set_event (f))
+	{
+	  evt.fifo = f;
+	  evt.event_type = FIFO_EVENT_APP_TX;
+	  svm_queue_add (vpp_evt_q, (u8 *) & evt, noblock);
+	}
+    }
+  return rv;
+}
+
+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, noblock);
+}
+
+always_inline int
+app_send (app_session_t * s, u8 * data, u32 len, u8 noblock)
+{
+  if (s->is_dgram)
+    return app_send_dgram (s, data, len, noblock);
+  return app_send_stream (s, data, len, noblock);
+}
+
+always_inline int
+app_recv_dgram_raw (svm_fifo_t * f, u8 * buf, u32 len,
+		    app_session_transport_t * at, u8 clear_evt)
+{
+  session_dgram_pre_hdr_t ph;
+  u32 max_deq;
+  int rv;
+
+  if (clear_evt)
+    svm_fifo_unset_event (f);
+  max_deq = svm_fifo_max_dequeue (f);
+  if (max_deq < sizeof (session_dgram_hdr_t))
+    return 0;
+
+  svm_fifo_peek (f, 0, sizeof (ph), (u8 *) & ph);
+  ASSERT (ph.data_length >= ph.data_offset);
+  if (!ph.data_offset)
+    svm_fifo_peek (f, sizeof (ph), sizeof (*at), (u8 *) at);
+  len = clib_min (len, ph.data_length - ph.data_offset);
+  rv = svm_fifo_peek (f, ph.data_offset + SESSION_CONN_HDR_LEN, len, buf);
+  ph.data_offset += rv;
+  if (ph.data_offset == ph.data_length)
+    svm_fifo_dequeue_drop (f, ph.data_length + SESSION_CONN_HDR_LEN);
+  else
+    svm_fifo_overwrite_head (f, (u8 *) & ph, sizeof (ph));
+  return rv;
+}
+
+always_inline int
+app_recv_dgram (app_session_t * s, u8 * buf, u32 len)
+{
+  return app_recv_dgram_raw (s->rx_fifo, buf, len, &s->transport, 1);
+}
+
+always_inline int
+app_recv_stream_raw (svm_fifo_t * f, u8 * buf, u32 len, u8 clear_evt)
+{
+  if (clear_evt)
+    svm_fifo_unset_event (f);
+  return svm_fifo_dequeue_nowait (f, len, buf);
+}
+
+always_inline int
+app_recv_stream (app_session_t * s, u8 * buf, u32 len)
+{
+  return app_recv_stream_raw (s->rx_fifo, buf, len, 1);
+}
+
+always_inline int
+app_recv (app_session_t * s, u8 * data, u32 len)
+{
+  if (s->is_dgram)
+    return app_recv_dgram (s, data, len);
+  return app_recv_stream (s, data, len);
+}
+
 #endif /* __included_uri_h__ */
 
 /*
diff --git a/src/vnet/session/session.api b/src/vnet/session/session.api
index bf88e82f336..98748d8fbbb 100644
--- a/src/vnet/session/session.api
+++ b/src/vnet/session/session.api
@@ -13,7 +13,7 @@
  * limitations under the License.
  */
 
-option version = "1.0.2";
+option version = "1.0.3";
 
 /** \brief client->vpp, attach application to session layer
     @param client_index - opaque cookie to identify the sender
@@ -119,13 +119,25 @@ autoreply define unmap_segment {
                  "tcp://::/0/80" [ipv6] etc.
     @param options - socket options, fifo sizes, etc.
 */
-autoreply define bind_uri {
+define bind_uri {
   u32 client_index;
   u32 context;
   u32 accept_cookie;
   u8 uri[128];
 };
 
+define bind_uri_reply {
+  u32 context;
+  u64 handle;
+  i32 retval;
+  u64 rx_fifo;
+  u64 tx_fifo;
+  u8 lcl_is_ip4;
+  u8 lcl_ip[16];
+  u16 lcl_port;
+  u64 vpp_evt_q;
+};
+
 /** \brief Unbind a given URI
     @param client_index - opaque cookie to identify the sender
     @param context - sender context, to match reply w/ request
@@ -314,8 +326,12 @@ autoreply define connect_sock {
     @param context - sender context, to match reply w/ request
     @param handle - bind handle
     @param retval - return code for the request
-    @param event_queue_address - vpp event queue address or 0 if this 
-                                 connection shouldn't send events
+    @param lcl_is_ip4 - local ip address type
+    @param lcl_ip6 - local ip address
+    @param lcl_port - local port
+    @param rx_fifo - rx fifo address if allocated (connectionless)
+    @param tx_fifo - tx fifo address if allocated (connectionless) 
+    @param vpp_evt_q - vpp event queue address (connectionless)
     @param segment_name_length - length of segment name 
     @param segment_name - name of segment client needs to attach to
 */
@@ -323,10 +339,12 @@ define bind_sock_reply {
   u32 context;
   u64 handle;
   i32 retval;
-  u64 server_event_queue_address;
   u8 lcl_is_ip4;
   u8 lcl_ip[16];
   u16 lcl_port;
+  u64 rx_fifo;
+  u64 tx_fifo;
+  u64 vpp_evt_q;
   u32 segment_size;
   u8 segment_name_length;
   u8 segment_name[128];
diff --git a/src/vnet/session/session.c b/src/vnet/session/session.c
index d258b82c983..dfc967b12dc 100644
--- a/src/vnet/session/session.c
+++ b/src/vnet/session/session.c
@@ -355,14 +355,19 @@ session_enqueue_stream_connection (transport_connection_t * tc,
   return enqueued;
 }
 
+
 int
-session_enqueue_dgram_connection (stream_session_t * s, vlib_buffer_t * b,
-				  u8 proto, u8 queue_event)
+session_enqueue_dgram_connection (stream_session_t * s,
+				  session_dgram_hdr_t * hdr,
+				  vlib_buffer_t * b, u8 proto, u8 queue_event)
 {
   int enqueued = 0, rv, in_order_off;
 
-  if (svm_fifo_max_enqueue (s->server_rx_fifo) < b->current_length)
-    return -1;
+  ASSERT (svm_fifo_max_enqueue (s->server_rx_fifo)
+	  >= b->current_length + sizeof (*hdr));
+
+  svm_fifo_enqueue_nowait (s->server_rx_fifo, sizeof (session_dgram_hdr_t),
+			   (u8 *) hdr);
   enqueued = svm_fifo_enqueue_nowait (s->server_rx_fifo, b->current_length,
 				      vlib_buffer_get_current (b));
   if (PREDICT_FALSE ((b->flags & VLIB_BUFFER_NEXT_PRESENT) && enqueued >= 0))
@@ -530,6 +535,16 @@ session_manager_flush_enqueue_events (u8 transport_proto, u32 thread_index)
   return errors;
 }
 
+int
+session_manager_flush_all_enqueue_events (u8 transport_proto)
+{
+  vlib_thread_main_t *vtm = vlib_get_thread_main ();
+  int i, errors = 0;
+  for (i = 0; i < 1 + vtm->n_threads; i++)
+    errors += session_manager_flush_enqueue_events (transport_proto, i);
+  return errors;
+}
+
 /**
  * Init fifo tail and head pointers
  *
@@ -825,7 +840,7 @@ session_open_cl (u32 app_index, session_endpoint_t * rmt, u32 opaque)
   if (session_alloc_and_init (sm, tc, 1, &s))
     return -1;
   s->app_index = app->index;
-  s->session_state = SESSION_STATE_CONNECTING_READY;
+  s->session_state = SESSION_STATE_OPENED;
 
   /* Tell the app about the new event fifo for this session */
   app->cb_fns.session_connected_callback (app->index, opaque, s, 0);
@@ -841,10 +856,6 @@ session_open_vc (u32 app_index, session_endpoint_t * rmt, u32 opaque)
   u64 handle;
   int rv;
 
-  /* TODO until udp is fixed */
-  if (rmt->transport_proto == TRANSPORT_PROTO_UDP)
-    return session_open_cl (app_index, rmt, opaque);
-
   tep = session_endpoint_to_transport (rmt);
   rv = tp_vfts[rmt->transport_proto].open (tep);
   if (rv < 0)
@@ -912,14 +923,6 @@ session_open (u32 app_index, session_endpoint_t * rmt, u32 opaque)
   return session_open_srv_fns[tst] (app_index, rmt, opaque);
 }
 
-/**
- * Ask transport to listen on local transport endpoint.
- *
- * @param s Session for which listen will be called. Note that unlike
- * 	    established sessions, listen sessions are not associated to a
- * 	    thread.
- * @param tep Local endpoint to be listened on.
- */
 int
 session_listen_vc (stream_session_t * s, session_endpoint_t * sep)
 {
@@ -948,6 +951,40 @@ session_listen_vc (stream_session_t * s, session_endpoint_t * sep)
 }
 
 int
+session_listen_cl (stream_session_t * s, session_endpoint_t * sep)
+{
+  transport_connection_t *tc;
+  application_t *server;
+  segment_manager_t *sm;
+  u32 tci;
+
+  /* Transport bind/listen  */
+  tci = tp_vfts[sep->transport_proto].bind (s->session_index,
+					    session_endpoint_to_transport
+					    (sep));
+
+  if (tci == (u32) ~ 0)
+    return -1;
+
+  /* Attach transport to session */
+  s->connection_index = tci;
+  tc = tp_vfts[sep->transport_proto].get_listener (tci);
+
+  /* Weird but handle it ... */
+  if (tc == 0)
+    return -1;
+
+  server = application_get (s->app_index);
+  sm = application_get_listen_segment_manager (server, s);
+  if (session_alloc_fifos (sm, s))
+    return -1;
+
+  /* Add to the main lookup table */
+  session_lookup_add_connection (tc, s->session_index);
+  return 0;
+}
+
+int
 session_listen_app (stream_session_t * s, session_endpoint_t * sep)
 {
   session_endpoint_extended_t esep;
@@ -965,11 +1002,19 @@ typedef int (*session_listen_service_fn) (stream_session_t *,
 static session_listen_service_fn
 session_listen_srv_fns[TRANSPORT_N_SERVICES] = {
   session_listen_vc,
-  session_listen_vc,
+  session_listen_cl,
   session_listen_app,
 };
 /* *INDENT-ON* */
 
+/**
+ * Ask transport to listen on local transport endpoint.
+ *
+ * @param s Session for which listen will be called. Note that unlike
+ * 	    established sessions, listen sessions are not associated to a
+ * 	    thread.
+ * @param tep Local endpoint to be listened on.
+ */
 int
 stream_session_listen (stream_session_t * s, session_endpoint_t * sep)
 {
@@ -1125,7 +1170,8 @@ session_manager_get_evt_q_segment (void)
 static session_fifo_rx_fn *session_tx_fns[TRANSPORT_TX_N_FNS] = {
     session_tx_fifo_peek_and_snd,
     session_tx_fifo_dequeue_and_snd,
-    session_tx_fifo_dequeue_internal
+    session_tx_fifo_dequeue_internal,
+    session_tx_fifo_dequeue_and_snd
 };
 /* *INDENT-ON* */
 
@@ -1228,11 +1274,12 @@ session_manager_main_enable (vlib_main_t * vm)
   vec_validate (smm->peekers_rw_locks, num_threads - 1);
 
   for (i = 0; i < TRANSPORT_N_PROTO; i++)
-    for (j = 0; j < num_threads; j++)
-      {
-	vec_validate (smm->session_to_enqueue[i], num_threads - 1);
-	vec_validate (smm->current_enqueue_epoch[i], num_threads - 1);
-      }
+    {
+      vec_validate (smm->current_enqueue_epoch[i], num_threads - 1);
+      vec_validate (smm->session_to_enqueue[i], num_threads - 1);
+      for (j = 0; j < num_threads; j++)
+	smm->current_enqueue_epoch[i][j] = 1;
+    }
 
   for (i = 0; i < num_threads; i++)
     {
diff --git a/src/vnet/session/session.h b/src/vnet/session/session.h
index 0b53f61a10a..9d534aec19b 100644
--- a/src/vnet/session/session.h
+++ b/src/vnet/session/session.h
@@ -204,6 +204,31 @@ struct _session_manager_main
 
 };
 
+typedef struct session_dgram_pre_hdr_
+{
+  u32 data_length;
+  u32 data_offset;
+} session_dgram_pre_hdr_t;
+
+/* *INDENT-OFF* */
+typedef CLIB_PACKED (struct session_dgram_header_
+{
+  u32 data_length;
+  u32 data_offset;
+  ip46_address_t rmt_ip;
+  ip46_address_t lcl_ip;
+  u16 rmt_port;
+  u16 lcl_port;
+  u8 is_ip4;
+}) session_dgram_hdr_t;
+/* *INDENT-ON* */
+
+#define SESSION_CONN_ID_LEN 37
+#define SESSION_CONN_HDR_LEN 45
+
+STATIC_ASSERT (sizeof (session_dgram_hdr_t) == (SESSION_CONN_ID_LEN + 8),
+	       "session conn id wrong length");
+
 extern session_manager_main_t session_manager_main;
 extern vlib_node_registration_t session_queue_node;
 
@@ -342,6 +367,14 @@ session_has_transport (stream_session_t * s)
   return (session_get_transport_proto (s) != TRANSPORT_PROTO_NONE);
 }
 
+always_inline transport_service_type_t
+session_transport_service_type (stream_session_t * s)
+{
+  transport_proto_t tp;
+  tp = session_get_transport_proto (s);
+  return transport_protocol_service_type (tp);
+}
+
 /**
  * Acquires a lock that blocks a session pool from expanding.
  *
@@ -442,8 +475,10 @@ int
 session_enqueue_stream_connection (transport_connection_t * tc,
 				   vlib_buffer_t * b, u32 offset,
 				   u8 queue_event, u8 is_in_order);
-int session_enqueue_dgram_connection (stream_session_t * s, vlib_buffer_t * b,
-				      u8 proto, u8 queue_event);
+int session_enqueue_dgram_connection (stream_session_t * s,
+				      session_dgram_hdr_t * hdr,
+				      vlib_buffer_t * b, u8 proto,
+				      u8 queue_event);
 int stream_session_peek_bytes (transport_connection_t * tc, u8 * buffer,
 			       u32 offset, u32 max_bytes);
 u32 stream_session_dequeue_drop (transport_connection_t * tc, u32 max_bytes);
@@ -490,6 +525,7 @@ session_manager_get_vpp_event_queue (u32 thread_index)
 }
 
 int session_manager_flush_enqueue_events (u8 proto, u32 thread_index);
+int session_manager_flush_all_enqueue_events (u8 transport_proto);
 
 always_inline u64
 listen_session_get_handle (stream_session_t * s)
diff --git a/src/vnet/session/session_api.c b/src/vnet/session/session_api.c
index 2a74a196201..67c42faf692 100755
--- a/src/vnet/session/session_api.c
+++ b/src/vnet/session/session_api.c
@@ -480,9 +480,12 @@ done:
 static void
 vl_api_bind_uri_t_handler (vl_api_bind_uri_t * mp)
 {
-  vl_api_bind_uri_reply_t *rmp;
+  transport_connection_t *tc = 0;
   vnet_bind_args_t _a, *a = &_a;
-  application_t *app;
+  vl_api_bind_uri_reply_t *rmp;
+  stream_session_t *s;
+  application_t *app = 0;
+  svm_queue_t *vpp_evt_q;
   int rv;
 
   if (session_manager_is_enabled () == 0)
@@ -505,7 +508,30 @@ vl_api_bind_uri_t_handler (vl_api_bind_uri_t * mp)
     }
 
 done:
-  REPLY_MACRO (VL_API_BIND_URI_REPLY);
+
+  /* *INDENT-OFF* */
+  REPLY_MACRO2 (VL_API_BIND_URI_REPLY, ({
+    if (!rv)
+      {
+        rmp->handle = a->handle;
+	rmp->lcl_is_ip4 = tc->is_ip4;
+  	rmp->lcl_port = tc->lcl_port;
+        if (app && application_has_global_scope (app))
+            {
+              s = listen_session_get_from_handle (a->handle);
+              tc = listen_session_get_transport (s);
+              clib_memcpy (rmp->lcl_ip, &tc->lcl_ip, sizeof(tc->lcl_ip));
+              if (session_transport_service_type (s) == TRANSPORT_SERVICE_CL)
+                {
+                  rmp->rx_fifo = pointer_to_uword (s->server_rx_fifo);
+                  rmp->tx_fifo = pointer_to_uword (s->server_tx_fifo);
+                  vpp_evt_q = session_manager_get_vpp_event_queue (0);
+                  rmp->vpp_evt_q = pointer_to_uword (vpp_evt_q);
+                }
+            }
+      }
+  }));
+  /* *INDENT-ON* */
 }
 
 static void
@@ -733,6 +759,7 @@ vl_api_bind_sock_t_handler (vl_api_bind_sock_t * mp)
   stream_session_t *s;
   transport_connection_t *tc = 0;
   ip46_address_t *ip46;
+  svm_queue_t *vpp_evt_q;
 
   if (session_manager_is_enabled () == 0)
     {
@@ -775,8 +802,14 @@ done:
 	  {
 	    s = listen_session_get_from_handle (a->handle);
 	    tc = listen_session_get_transport (s);
-            rmp->lcl_is_ip4 = tc->is_ip4;
             clib_memcpy (rmp->lcl_ip, &tc->lcl_ip, sizeof (tc->lcl_ip));
+            if (session_transport_service_type (s) == TRANSPORT_SERVICE_CL)
+              {
+        	rmp->rx_fifo = pointer_to_uword (s->server_rx_fifo);
+        	rmp->tx_fifo = pointer_to_uword (s->server_tx_fifo);
+        	vpp_evt_q = session_manager_get_vpp_event_queue (0);
+        	rmp->vpp_evt_q = pointer_to_uword (vpp_evt_q);
+              }
 	  }
       }
   }));
diff --git a/src/vnet/session/session_cli.c b/src/vnet/session/session_cli.c
index 52833554a53..201f6f1d66e 100755
--- a/src/vnet/session/session_cli.c
+++ b/src/vnet/session/session_cli.c
@@ -23,6 +23,9 @@ format_stream_session_fifos (u8 * s, va_list * args)
   session_fifo_event_t _e, *e = &_e;
   u8 found;
 
+  if (!ss->server_rx_fifo || !ss->server_tx_fifo)
+    return s;
+
   s = format (s, " Rx fifo: %U", format_svm_fifo, ss->server_rx_fifo, 1);
   if (verbose > 2 && ss->server_rx_fifo->has_event)
     {
@@ -76,6 +79,8 @@ format_stream_session (u8 * s, va_list * args)
     {
       s = format (s, "%-40U%v", tp_vft->format_listener, ss->connection_index,
 		  str);
+      if (verbose > 1)
+	s = format (s, "\n%U", format_stream_session_fifos, ss, verbose);
     }
   else if (ss->session_state == SESSION_STATE_CONNECTING)
     {
diff --git a/src/vnet/session/session_node.c b/src/vnet/session/session_node.c
index b8f429eb1d7..14716965547 100644
--- a/src/vnet/session/session_node.c
+++ b/src/vnet/session/session_node.c
@@ -70,7 +70,7 @@ session_tx_fifo_chain_tail (session_manager_main_t * smm, vlib_main_t * vm,
 			    vlib_buffer_t * b0, u32 bi0, u8 n_bufs_per_seg,
 			    u32 left_from_seg, u32 * left_to_snd0,
 			    u16 * n_bufs, u32 * tx_offset, u16 deq_per_buf,
-			    u8 peek_data)
+			    u8 peek_data, transport_tx_fn_type_t tx_type)
 {
   vlib_buffer_t *chain_b0, *prev_b0;
   u32 chain_bi0, to_deq;
@@ -102,7 +102,23 @@ session_tx_fifo_chain_tail (session_manager_main_t * smm, vlib_main_t * vm,
 	}
       else
 	{
-	  n_bytes_read = svm_fifo_dequeue_nowait (fifo, len_to_deq0, data0);
+	  if (tx_type == TRANSPORT_TX_DGRAM)
+	    {
+	      session_dgram_hdr_t *hdr;
+	      u16 deq_now;
+	      hdr = (session_dgram_hdr_t *) svm_fifo_head (fifo);
+	      deq_now = clib_min (hdr->data_length - hdr->data_offset,
+				  len_to_deq0);
+	      n_bytes_read = svm_fifo_peek (fifo, hdr->data_offset, deq_now,
+					    data0);
+	      ASSERT (n_bytes_read > 0);
+
+	      hdr->data_offset += n_bytes_read;
+	      if (hdr->data_offset == hdr->data_length)
+		svm_fifo_dequeue_drop (fifo, hdr->data_length);
+	    }
+	  else
+	    n_bytes_read = svm_fifo_dequeue_nowait (fifo, len_to_deq0, data0);
 	}
       ASSERT (n_bytes_read == len_to_deq0);
       chain_b0->current_length = n_bytes_read;
@@ -145,12 +161,35 @@ session_tx_fifo_read_and_snd_i (vlib_main_t * vm, vlib_node_runtime_t * node,
   int i, n_bytes_read;
   u32 n_bytes_per_buf, deq_per_buf, deq_per_first_buf;
   u32 bufs_alloc, bufs_now;
+  session_dgram_hdr_t hdr;
 
   next_index = next0 = smm->session_type_to_next[s0->session_type];
-
   tp = session_get_transport_proto (s0);
   transport_vft = transport_protocol_get_vft (tp);
-  tc0 = transport_vft->get_connection (s0->connection_index, thread_index);
+  if (peek_data)
+    {
+      if (PREDICT_FALSE (s0->session_state < SESSION_STATE_READY))
+	{
+	  /* Can retransmit for closed sessions but can't send new data if
+	   * session is not ready or closed */
+	  vec_add1 (smm->pending_event_vector[thread_index], *e0);
+	  return 0;
+	}
+      tc0 =
+	transport_vft->get_connection (s0->connection_index, thread_index);
+    }
+  else
+    {
+      if (s0->session_state == SESSION_STATE_LISTENING)
+	tc0 = transport_vft->get_listener (s0->connection_index);
+      else
+	{
+	  if (PREDICT_FALSE (s0->session_state == SESSION_STATE_CLOSED))
+	    return 0;
+	  tc0 = transport_vft->get_connection (s0->connection_index,
+					       thread_index);
+	}
+    }
 
   /* Make sure we have space to send and there's something to dequeue */
   snd_mss0 = transport_vft->send_mss (tc0);
@@ -168,20 +207,26 @@ session_tx_fifo_read_and_snd_i (vlib_main_t * vm, vlib_node_runtime_t * node,
 
   /* Check how much we can pull. */
   max_dequeue0 = svm_fifo_max_dequeue (s0->server_tx_fifo);
-
   if (peek_data)
     {
       /* Offset in rx fifo from where to peek data */
       tx_offset = transport_vft->tx_fifo_offset (tc0);
       if (PREDICT_FALSE (tx_offset >= max_dequeue0))
-	max_dequeue0 = 0;
-      else
-	max_dequeue0 -= tx_offset;
+	return 0;
+      max_dequeue0 -= tx_offset;
     }
-
-  /* Nothing to read return */
-  if (max_dequeue0 == 0)
-    return 0;
+  else
+    {
+      if (transport_vft->tx_type == TRANSPORT_TX_DGRAM)
+	{
+	  if (max_dequeue0 < sizeof (hdr))
+	    return 0;
+	  svm_fifo_peek (s0->server_tx_fifo, 0, sizeof (hdr), (u8 *) & hdr);
+	  ASSERT (hdr.data_length > hdr.data_offset);
+	  max_dequeue0 = hdr.data_length - hdr.data_offset;
+	}
+    }
+  ASSERT (max_dequeue0 > 0);
 
   /* Ensure we're not writing more than transport window allows */
   if (max_dequeue0 < snd_space0)
@@ -286,14 +331,42 @@ 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,
-						      len_to_deq0, data0);
-	      if (n_bytes_read <= 0)
-		goto dequeue_fail;
+	      if (transport_vft->tx_type == TRANSPORT_TX_DGRAM)
+		{
+		  svm_fifo_t *f = s0->server_tx_fifo;
+		  u16 deq_now;
+		  u32 offset;
+
+		  ASSERT (hdr.data_length > hdr.data_offset);
+		  deq_now = clib_min (hdr.data_length - hdr.data_offset,
+				      len_to_deq0);
+		  offset = hdr.data_offset + SESSION_CONN_HDR_LEN;
+		  n_bytes_read = svm_fifo_peek (f, offset, deq_now, data0);
+		  if (PREDICT_FALSE (n_bytes_read <= 0))
+		    goto dequeue_fail;
+
+		  if (s0->session_state == SESSION_STATE_LISTENING)
+		    {
+		      ip_copy (&tc0->rmt_ip, &hdr.rmt_ip, tc0->is_ip4);
+		      tc0->rmt_port = hdr.rmt_port;
+		    }
+		  hdr.data_offset += n_bytes_read;
+		  if (hdr.data_offset == hdr.data_length)
+		    {
+		      offset = hdr.data_length + SESSION_CONN_HDR_LEN;
+		      svm_fifo_dequeue_drop (f, offset);
+		    }
+		}
+	      else
+		{
+		  n_bytes_read = svm_fifo_dequeue_nowait (s0->server_tx_fifo,
+							  len_to_deq0, data0);
+		  if (n_bytes_read <= 0)
+		    goto dequeue_fail;
+		}
 	    }
 
 	  b0->current_length = n_bytes_read;
-
 	  left_to_snd0 -= n_bytes_read;
 	  *n_tx_packets = *n_tx_packets + 1;
 
@@ -307,7 +380,8 @@ session_tx_fifo_read_and_snd_i (vlib_main_t * vm, vlib_node_runtime_t * node,
 					  s0->server_tx_fifo, b0, bi0,
 					  n_bufs_per_seg, left_for_seg,
 					  &left_to_snd0, &n_bufs, &tx_offset,
-					  deq_per_buf, peek_data);
+					  deq_per_buf, peek_data,
+					  transport_vft->tx_type);
 	    }
 
 	  /* Ask transport to push header after current_length and
@@ -345,12 +419,18 @@ session_tx_fifo_read_and_snd_i (vlib_main_t * vm, vlib_node_runtime_t * node,
 
   /* If we couldn't dequeue all bytes mark as partially read */
   if (max_len_to_snd0 < max_dequeue0)
+    if (svm_fifo_set_event (s0->server_tx_fifo))
+      vec_add1 (smm->pending_event_vector[thread_index], *e0);
+
+  if (!peek_data && transport_vft->tx_type == TRANSPORT_TX_DGRAM)
     {
-      /* If we don't already have new event */
-      if (svm_fifo_set_event (s0->server_tx_fifo))
-	{
-	  vec_add1 (smm->pending_event_vector[thread_index], *e0);
-	}
+      /* Fix dgram pre header */
+      if (max_len_to_snd0 < max_dequeue0)
+	svm_fifo_overwrite_head (s0->server_tx_fifo, (u8 *) & hdr,
+				 sizeof (session_dgram_pre_hdr_t));
+      /* More data needs to be read */
+      else if (svm_fifo_max_dequeue (s0->server_tx_fifo) > 0)
+	vec_add1 (smm->pending_event_vector[thread_index], *e0);
     }
   return 0;
 
@@ -360,7 +440,6 @@ dequeue_fail:
    * read, return buff to free list and return
    */
   clib_warning ("dequeue fail");
-
   if (svm_fifo_set_event (s0->server_tx_fifo))
     {
       vec_add1 (smm->pending_event_vector[thread_index], *e0);
@@ -638,13 +717,6 @@ skip_dequeue:
 	      clib_warning ("It's dead, Jim!");
 	      continue;
 	    }
-	  /* Can retransmit for closed sessions but can't do anything if
-	   * session is not ready or closed */
-	  if (PREDICT_FALSE (s0->session_state < SESSION_STATE_READY))
-	    {
-	      vec_add1 (smm->pending_event_vector[my_thread_index], *e0);
-	      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,
diff --git a/src/vnet/session/stream_session.h b/src/vnet/session/stream_session.h
index b7a5eee4b12..9e0e4d98990 100644
--- a/src/vnet/session/stream_session.h
+++ b/src/vnet/session/stream_session.h
@@ -31,30 +31,19 @@ typedef enum
   SESSION_STATE_CONNECTING,
   SESSION_STATE_ACCEPTING,
   SESSION_STATE_READY,
-  SESSION_STATE_CONNECTING_READY,
+  SESSION_STATE_OPENED,
   SESSION_STATE_CLOSED,
   SESSION_STATE_N_STATES,
 } stream_session_state_t;
 
-/* TODO convert to macro once cleanup completed */
-typedef struct app_session_
+typedef struct generic_session_
 {
-  /** fifo pointers. Once allocated, these do not move */
-  svm_fifo_t *server_rx_fifo;
-  svm_fifo_t *server_tx_fifo;
-
-  /** Type */
-  session_type_t session_type;
-
-  /** State */
-  volatile u8 session_state;
-
-  /** Session index in owning pool */
-  u32 session_index;
-
-  /** Application index */
-  u32 app_index;
-} app_session_t;
+  svm_fifo_t *rx_fifo;		/**< rx fifo */
+  svm_fifo_t *tx_fifo;		/**< tx fifo */
+  session_type_t session_type;	/**< session type */
+  volatile u8 session_state;	/**< session state */
+  u32 session_index;		/**< index in owning pool */
+} generic_session_t;
 
 typedef struct _stream_session_t
 {
diff --git a/src/vnet/session/transport.c b/src/vnet/session/transport.c
index 797bdad1eaa..20b912929b4 100644
--- a/src/vnet/session/transport.c
+++ b/src/vnet/session/transport.c
@@ -57,6 +57,9 @@ format_transport_proto (u8 * s, va_list * args)
     case TRANSPORT_PROTO_SCTP:
       s = format (s, "SCTP");
       break;
+    case TRANSPORT_PROTO_UDPC:
+      s = format (s, "UDPC");
+      break;
     }
   return s;
 }
@@ -76,6 +79,9 @@ format_transport_proto_short (u8 * s, va_list * args)
     case TRANSPORT_PROTO_SCTP:
       s = format (s, "S");
       break;
+    case TRANSPORT_PROTO_UDPC:
+      s = format (s, "U");
+      break;
     }
   return s;
 }
@@ -100,6 +106,10 @@ unformat_transport_proto (unformat_input_t * input, va_list * args)
     *proto = TRANSPORT_PROTO_TLS;
   else if (unformat (input, "TLS"))
     *proto = TRANSPORT_PROTO_TLS;
+  else if (unformat (input, "udpc"))
+    *proto = TRANSPORT_PROTO_UDPC;
+  else if (unformat (input, "UDPC"))
+    *proto = TRANSPORT_PROTO_UDPC;
   else
     return 0;
   return 1;
@@ -185,6 +195,12 @@ transport_protocol_get_vft (transport_proto_t transport_proto)
   return &tp_vfts[transport_proto];
 }
 
+transport_service_type_t
+transport_protocol_service_type (transport_proto_t tp)
+{
+  return tp_vfts[tp].service_type;
+}
+
 #define PORT_MASK ((1 << 16)- 1)
 
 void
diff --git a/src/vnet/session/transport.h b/src/vnet/session/transport.h
index ed9eb02754e..8340fd859ac 100644
--- a/src/vnet/session/transport.h
+++ b/src/vnet/session/transport.h
@@ -35,10 +35,10 @@ typedef struct _transport_connection
     {
       ip46_address_t rmt_ip;	/**< Remote IP */
       ip46_address_t lcl_ip;	/**< Local IP */
-      u16 lcl_port;		/**< Local port */
       u16 rmt_port;		/**< Remote port */
-      u8 proto;			/**< Protocol id */
+      u16 lcl_port;		/**< Local port */
       u8 is_ip4;		/**< Flag if IP4 connection */
+      u8 proto;			/**< Protocol id */
       u32 fib_index;		/**< Network namespace */
     };
     /*
@@ -88,6 +88,7 @@ typedef enum _transport_proto
   TRANSPORT_PROTO_SCTP,
   TRANSPORT_PROTO_NONE,
   TRANSPORT_PROTO_TLS,
+  TRANSPORT_PROTO_UDPC,
   TRANSPORT_N_PROTO
 } transport_proto_t;
 
@@ -99,7 +100,7 @@ uword unformat_transport_proto (unformat_input_t * input, va_list * args);
   _(u32, sw_if_index) 	/**< interface endpoint is associated with  */	\
   _(ip46_address_t, ip) /**< ip address */				\
   _(u32, fib_index)	/**< fib table endpoint is associated with */	\
-  _(u8, is_ip4)	/**< 1 if ip4 */					\
+  _(u8, is_ip4)		/**< set if ip4 */				\
   _(u16, port)		/**< port in net order */			\
 
 typedef struct _transport_endpoint
@@ -125,18 +126,6 @@ transport_endpoint_fib_proto (transport_endpoint_t * tep)
   return tep->is_ip4 ? FIB_PROTOCOL_IP4 : FIB_PROTOCOL_IP6;
 }
 
-always_inline u8
-transport_is_stream (u8 proto)
-{
-  return ((proto == TRANSPORT_PROTO_TCP) || (proto == TRANSPORT_PROTO_SCTP));
-}
-
-always_inline u8
-transport_is_dgram (u8 proto)
-{
-  return (proto == TRANSPORT_PROTO_UDP);
-}
-
 int transport_alloc_local_port (u8 proto, ip46_address_t * ip);
 int transport_alloc_local_endpoint (u8 proto, transport_endpoint_t * rmt,
 				    ip46_address_t * lcl_addr,
diff --git a/src/vnet/session/transport_interface.h b/src/vnet/session/transport_interface.h
index 04a5ff263b1..f21e483c715 100644
--- a/src/vnet/session/transport_interface.h
+++ b/src/vnet/session/transport_interface.h
@@ -23,7 +23,8 @@ typedef enum transport_dequeue_type_
 {
   TRANSPORT_TX_PEEK,		/**< reliable transport protos */
   TRANSPORT_TX_DEQUEUE,		/**< unreliable transport protos */
-  TRANSPORT_TX_INTERNAL,		/**< apps acting as transports */
+  TRANSPORT_TX_INTERNAL,	/**< apps acting as transports */
+  TRANSPORT_TX_DGRAM,		/**< datagram mode */
   TRANSPORT_TX_N_FNS
 } transport_tx_fn_type_t;
 
@@ -31,7 +32,7 @@ typedef enum transport_service_type_
 {
   TRANSPORT_SERVICE_VC,		/**< virtual circuit service */
   TRANSPORT_SERVICE_CL,		/**< connectionless service */
-  TRANSPORT_SERVICE_APP,		/**< app transport service */
+  TRANSPORT_SERVICE_APP,	/**< app transport service */
   TRANSPORT_N_SERVICES
 } transport_service_type_t;
 
@@ -96,6 +97,7 @@ void transport_register_protocol (transport_proto_t transport_proto,
 				  const transport_proto_vft_t * vft,
 				  fib_protocol_t fib_proto, u32 output_node);
 transport_proto_vft_t *transport_protocol_get_vft (transport_proto_t tp);
+transport_service_type_t transport_protocol_service_type (transport_proto_t);
 void transport_update_time (f64 time_now, u8 thread_index);
 void transport_enable_disable (vlib_main_t * vm, u8 is_en);
 
diff --git a/src/vnet/udp/udp.c b/src/vnet/udp/udp.c
index 3b8b707abe1..947cc1e38e1 100644
--- a/src/vnet/udp/udp.c
+++ b/src/vnet/udp/udp.c
@@ -49,6 +49,7 @@ udp_connection_alloc (u32 thread_index)
   uc->c_c_index = uc - um->connections[thread_index];
   uc->c_thread_index = thread_index;
   uc->c_proto = TRANSPORT_PROTO_UDP;
+  clib_spinlock_init (&uc->rx_lock);
   return uc;
 }
 
@@ -92,6 +93,7 @@ udp_session_bind (u32 session_index, transport_endpoint_t * lcl)
   listener->c_proto = TRANSPORT_PROTO_UDP;
   listener->c_s_index = session_index;
   listener->c_fib_index = lcl->fib_index;
+  clib_spinlock_init (&listener->rx_lock);
 
   node_index = lcl->is_ip4 ? udp4_input_node.index : udp6_input_node.index;
   udp_register_dst_port (vm, clib_net_to_host_u16 (lcl->port), node_index,
@@ -140,7 +142,7 @@ udp_push_header (transport_connection_t * tc, vlib_buffer_t * b)
       vnet_buffer (b)->l3_hdr_offset = (u8 *) ih - b->data;
     }
   vnet_buffer (b)->sw_if_index[VLIB_RX] = 0;
-  vnet_buffer (b)->sw_if_index[VLIB_TX] = ~0;
+  vnet_buffer (b)->sw_if_index[VLIB_TX] = uc->c_fib_index;
   b->flags |= VNET_BUFFER_F_LOCALLY_ORIGINATED;
 
   return 0;
@@ -210,7 +212,7 @@ format_udp_connection (u8 * s, va_list * args)
   if (verbose)
     {
       if (verbose == 1)
-	s = format (s, "%-15s", "-");
+	s = format (s, "%-15s\n", "-");
       else
 	s = format (s, "\n");
     }
@@ -322,8 +324,52 @@ const static transport_proto_vft_t udp_proto = {
   .format_connection = format_udp_session,
   .format_half_open = format_udp_half_open_session,
   .format_listener = format_udp_listener_session,
+  .tx_type = TRANSPORT_TX_DGRAM,
+  .service_type = TRANSPORT_SERVICE_CL,
+};
+/* *INDENT-ON* */
+
+
+int
+udpc_connection_open (transport_endpoint_t * rmt)
+{
+  udp_connection_t *uc;
+  u32 uc_index;
+  uc_index = udp_open_connection (rmt);
+  uc = udp_connection_get (uc_index, vlib_get_thread_index ());
+  uc->is_connected = 1;
+  return uc_index;
+}
+
+u32
+udpc_connection_listen (u32 session_index, transport_endpoint_t * lcl)
+{
+  udp_connection_t *listener;
+  u32 li;
+  li = udp_session_bind (session_index, lcl);
+  listener = udp_listener_get (li);
+  listener->is_connected = 1;
+  return li;
+}
+
+/* *INDENT-OFF* */
+const static transport_proto_vft_t udpc_proto = {
+  .bind = udpc_connection_listen,
+  .open = udpc_connection_open,
+  .unbind = udp_session_unbind,
+  .push_header = udp_push_header,
+  .get_connection = udp_session_get,
+  .get_listener = udp_session_get_listener,
+  .get_half_open = udp_half_open_session_get_transport,
+  .close = udp_session_close,
+  .cleanup = udp_session_cleanup,
+  .send_mss = udp_send_mss,
+  .send_space = udp_send_space,
+  .format_connection = format_udp_session,
+  .format_half_open = format_udp_half_open_session,
+  .format_listener = format_udp_listener_session,
   .tx_type = TRANSPORT_TX_DEQUEUE,
-  .service_type = TRANSPORT_SERVICE_VC,
+  .service_type = TRANSPORT_SERVICE_CL,
 };
 /* *INDENT-ON* */
 
@@ -361,6 +407,10 @@ udp_init (vlib_main_t * vm)
 			       FIB_PROTOCOL_IP4, ip4_lookup_node.index);
   transport_register_protocol (TRANSPORT_PROTO_UDP, &udp_proto,
 			       FIB_PROTOCOL_IP6, ip6_lookup_node.index);
+  transport_register_protocol (TRANSPORT_PROTO_UDPC, &udpc_proto,
+			       FIB_PROTOCOL_IP4, ip4_lookup_node.index);
+  transport_register_protocol (TRANSPORT_PROTO_UDPC, &udpc_proto,
+			       FIB_PROTOCOL_IP6, ip6_lookup_node.index);
 
   /*
    * Initialize data structures
diff --git a/src/vnet/udp/udp.h b/src/vnet/udp/udp.h
index af6c6b82c6a..8e3ab9ec59e 100644
--- a/src/vnet/udp/udp.h
+++ b/src/vnet/udp/udp.h
@@ -36,9 +36,9 @@ typedef enum
 
 typedef struct
 {
-  transport_connection_t connection;	      /** must be first */
-  /** ersatz MTU to limit fifo pushes to test data size */
-  u32 mtu;
+  transport_connection_t connection;	/**< must be first */
+  clib_spinlock_t rx_lock;		/**< rx fifo lock */
+  u8 is_connected;			/**< connected mode */
 } udp_connection_t;
 
 #define foreach_udp4_dst_port			\
@@ -207,7 +207,7 @@ udp_pool_remove_peeker (u32 thread_index)
 }
 
 always_inline udp_connection_t *
-udp_conenction_clone_safe (u32 connection_index, u32 thread_index)
+udp_connection_clone_safe (u32 connection_index, u32 thread_index)
 {
   udp_connection_t *old_c, *new_c;
   u32 current_thread_index = vlib_get_thread_index ();
diff --git a/src/vnet/udp/udp_input.c b/src/vnet/udp/udp_input.c
index 8170cfbe49a..ad469f69667 100644
--- a/src/vnet/udp/udp_input.c
+++ b/src/vnet/udp/udp_input.c
@@ -13,20 +13,19 @@
  * limitations under the License.
  */
 
+#include <vlibmemory/api.h>
 #include <vlib/vlib.h>
-#include <vnet/vnet.h>
-#include <vnet/pg/pg.h>
-#include <vnet/ip/ip.h>
 
-#include <vnet/udp/udp.h>
 #include <vppinfra/hash.h>
 #include <vppinfra/error.h>
 #include <vppinfra/elog.h>
 
+#include <vnet/vnet.h>
+#include <vnet/pg/pg.h>
+#include <vnet/ip/ip.h>
+#include <vnet/udp/udp.h>
 #include <vnet/udp/udp_packet.h>
-
-#include <vlibmemory/api.h>
-#include "../session/application_interface.h"
+#include <vnet/session/session.h>
 
 static char *udp_error_strings[] = {
 #define udp_error(n,s) s,
@@ -106,9 +105,11 @@ udp46_input_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	  ip6_header_t *ip60;
 	  u8 *data0;
 	  stream_session_t *s0;
-	  transport_connection_t *tc0 = 0;
-	  udp_connection_t *child0, *new_uc0;
-	  int written0;
+	  udp_connection_t *uc0, *child0, *new_uc0;
+	  transport_connection_t *tc0;
+	  int wrote0;
+	  void *rmt_addr, *lcl_addr;
+	  session_dgram_hdr_t hdr0;
 
 	  /* speculatively enqueue b0 to the current next frame */
 	  bi0 = from[0];
@@ -127,11 +128,14 @@ udp46_input_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 
 	  if (is_ip4)
 	    {
-	      /* $$$$ fixme: udp_local doesn't do ip options correctly anyhow */
+	      /* TODO: must fix once udp_local does ip options correctly */
 	      ip40 = (ip4_header_t *) (((u8 *) udp0) - sizeof (*ip40));
 	      s0 = session_lookup_safe4 (fib_index0, &ip40->dst_address,
 					 &ip40->src_address, udp0->dst_port,
 					 udp0->src_port, TRANSPORT_PROTO_UDP);
+	      lcl_addr = &ip40->dst_address;
+	      rmt_addr = &ip40->src_address;
+
 	    }
 	  else
 	    {
@@ -139,67 +143,83 @@ udp46_input_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	      s0 = session_lookup_safe6 (fib_index0, &ip60->dst_address,
 					 &ip60->src_address, udp0->dst_port,
 					 udp0->src_port, TRANSPORT_PROTO_UDP);
+	      lcl_addr = &ip60->dst_address;
+	      rmt_addr = &ip60->src_address;
 	    }
 
-	  if (PREDICT_FALSE (s0 == 0))
+	  if (PREDICT_FALSE (!s0))
 	    {
 	      error0 = UDP_ERROR_NO_LISTENER;
 	      goto trace0;
 	    }
 
-	  if (PREDICT_TRUE (s0->session_state == SESSION_STATE_READY))
+	  if (s0->session_state == SESSION_STATE_OPENED)
 	    {
+	      /* TODO optimization: move cl session to right thread
+	       * However, since such a move would affect the session handle,
+	       * which we pass 'raw' to the app, we'd also have notify the
+	       * app of the change or change the way we pass handles to apps.
+	       */
 	      tc0 = session_get_transport (s0);
+	      uc0 = udp_get_connection_from_transport (tc0);
+	      if (uc0->is_connected)
+		{
+		  /*
+		   * Clone the transport. It will be cleaned up with the
+		   * session once we notify the session layer.
+		   */
+		  new_uc0 = udp_connection_clone_safe (s0->connection_index,
+						       s0->thread_index);
+		  ASSERT (s0->session_index == new_uc0->c_s_index);
+
+		  /*
+		   * Drop the 'lock' on pool resize
+		   */
+		  session_pool_remove_peeker (s0->thread_index);
+		  session_dgram_connect_notify (&new_uc0->connection,
+						s0->thread_index, &s0);
+		  tc0 = &new_uc0->connection;
+		}
 	    }
-	  else if (s0->session_state == SESSION_STATE_CONNECTING_READY)
+	  else if (s0->session_state == SESSION_STATE_READY)
 	    {
-	      /*
-	       * Clone the transport. It will be cleaned up with the
-	       * session once we notify the session layer.
-	       */
-	      new_uc0 = udp_conenction_clone_safe (s0->connection_index,
-						   s0->thread_index);
-	      ASSERT (s0->session_index == new_uc0->c_s_index);
-
-	      /*
-	       * Drop the 'lock' on pool resize
-	       */
-	      session_pool_remove_peeker (s0->thread_index);
-	      session_dgram_connect_notify (&new_uc0->connection,
-					    s0->thread_index, &s0);
-	      tc0 = &new_uc0->connection;
+	      tc0 = session_get_transport (s0);
+	      uc0 = udp_get_connection_from_transport (tc0);
 	    }
 	  else if (s0->session_state == SESSION_STATE_LISTENING)
 	    {
 	      tc0 = listen_session_get_transport (s0);
-
-	      child0 = udp_connection_alloc (my_thread_index);
-	      if (is_ip4)
-		{
-		  ip_set (&child0->c_lcl_ip, &ip40->dst_address, 1);
-		  ip_set (&child0->c_rmt_ip, &ip40->src_address, 1);
-		}
-	      else
-		{
-		  ip_set (&child0->c_lcl_ip, &ip60->dst_address, 0);
-		  ip_set (&child0->c_rmt_ip, &ip60->src_address, 0);
-		}
-	      child0->c_lcl_port = udp0->dst_port;
-	      child0->c_rmt_port = udp0->src_port;
-	      child0->c_is_ip4 = is_ip4;
-	      child0->mtu = 1460;	/* $$$$ policy */
-
-	      if (stream_session_accept
-		  (&child0->connection, tc0->s_index, 1))
+	      uc0 = udp_get_connection_from_transport (tc0);
+	      if (uc0->is_connected)
 		{
-		  error0 = UDP_ERROR_CREATE_SESSION;
-		  goto trace0;
+		  child0 = udp_connection_alloc (my_thread_index);
+		  if (is_ip4)
+		    {
+		      ip_set (&child0->c_lcl_ip, &ip40->dst_address, 1);
+		      ip_set (&child0->c_rmt_ip, &ip40->src_address, 1);
+		    }
+		  else
+		    {
+		      ip_set (&child0->c_lcl_ip, &ip60->dst_address, 0);
+		      ip_set (&child0->c_rmt_ip, &ip60->src_address, 0);
+		    }
+		  child0->c_lcl_port = udp0->dst_port;
+		  child0->c_rmt_port = udp0->src_port;
+		  child0->c_is_ip4 = is_ip4;
+
+		  if (stream_session_accept (&child0->connection,
+					     tc0->s_index, 1))
+		    {
+		      error0 = UDP_ERROR_CREATE_SESSION;
+		      goto trace0;
+		    }
+		  s0 =
+		    session_get (child0->c_s_index, child0->c_thread_index);
+		  s0->session_state = SESSION_STATE_READY;
+		  tc0 = &child0->connection;
+		  uc0 = udp_get_connection_from_transport (tc0);
+		  error0 = UDP_ERROR_LISTENER;
 		}
-	      s0 = session_get (child0->c_s_index, child0->c_thread_index);
-	      s0->session_state = SESSION_STATE_READY;
-	      tc0 = &child0->connection;
-
-	      error0 = UDP_ERROR_LISTENER;
 	    }
 	  else
 	    {
@@ -207,15 +227,48 @@ udp46_input_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	      goto trace0;
 	    }
 
-	  written0 = session_enqueue_dgram_connection (s0, b0, tc0->proto,
-						       1 /* queue evt */ );
-	  if (PREDICT_FALSE (written0 < 0))
+	  if (!uc0->is_connected)
 	    {
-	      error0 = UDP_ERROR_FIFO_FULL;
-	      goto trace0;
+	      if (svm_fifo_max_enqueue (s0->server_rx_fifo)
+		  < b0->current_length + sizeof (session_dgram_hdr_t))
+		{
+		  error0 = UDP_ERROR_FIFO_FULL;
+		  goto trace0;
+		}
+	      hdr0.data_length = b0->current_length;
+	      hdr0.data_offset = 0;
+	      ip_set (&hdr0.lcl_ip, lcl_addr, is_ip4);
+	      ip_set (&hdr0.rmt_ip, rmt_addr, is_ip4);
+	      hdr0.lcl_port = udp0->dst_port;
+	      hdr0.rmt_port = udp0->src_port;
+	      hdr0.is_ip4 = is_ip4;
+
+	      clib_spinlock_lock (&uc0->rx_lock);
+	      wrote0 = session_enqueue_dgram_connection (s0, &hdr0, b0,
+							 TRANSPORT_PROTO_UDP,
+							 1 /* queue evt */ );
+	      clib_spinlock_unlock (&uc0->rx_lock);
+	      ASSERT (wrote0 > 0);
+
+	      if (s0->session_state != SESSION_STATE_LISTENING)
+		session_pool_remove_peeker (s0->thread_index);
+	    }
+	  else
+	    {
+	      if (svm_fifo_max_enqueue (s0->server_rx_fifo)
+		  < b0->current_length)
+		{
+		  error0 = UDP_ERROR_FIFO_FULL;
+		  goto trace0;
+		}
+	      wrote0 = session_enqueue_stream_connection (tc0, b0, 0,
+							  1 /* queue evt */ ,
+							  1 /* in order */ );
+	      ASSERT (wrote0 > 0);
 	    }
 
 	trace0:
+
 	  b0->error = node->errors[error0];
 
 	  if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE)
@@ -224,7 +277,7 @@ udp46_input_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
 	      udp_input_trace_t *t = vlib_add_trace (vm, node, b0,
 						     sizeof (*t));
 
-	      t->connection = tc0 ? tc0->c_index : ~0;
+	      t->connection = s0 ? s0->connection_index : ~0;
 	      t->disposition = error0;
 	      t->thread_index = my_thread_index;
 	    }
@@ -237,14 +290,11 @@ udp46_input_inline (vlib_main_t * vm, vlib_node_runtime_t * node,
       vlib_put_next_frame (vm, node, next_index, n_left_to_next);
     }
 
-  errors = session_manager_flush_enqueue_events (TRANSPORT_PROTO_UDP,
-						 my_thread_index);
+  errors = session_manager_flush_all_enqueue_events (TRANSPORT_PROTO_UDP);
   udp_input_inc_counter (vm, is_ip4, UDP_ERROR_EVENT_FIFO_FULL, errors);
   return frame->n_vectors;
 }
 
-vlib_node_registration_t udp4_input_node;
-vlib_node_registration_t udp6_input_node;
 
 static uword
 udp4_input (vlib_main_t * vm, vlib_node_runtime_t * node,