src/vnet/session/node.c - fdio/vpp - Gitiles

 /*
  * Copyright (c) 2017 Cisco and/or its affiliates.
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at:
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #include <math.h>
 #include <vlib/vlib.h>
 #include <vnet/vnet.h>
 #include <vnet/tcp/tcp.h>
 #include <vppinfra/elog.h>
 #include <vnet/session/application.h>
 #include <vnet/session/session_debug.h>
 #include <vlibmemory/unix_shared_memory_queue.h>

 vlib_node_registration_t session_queue_node;

 typedef struct
 {
   u32 session_index;
   u32 server_thread_index;
 } session_queue_trace_t;

 /* packet trace format function */
 static u8 *
 format_session_queue_trace (u8 * s, va_list * args)
 {
   CLIB_UNUSED (vlib_main_t * vm) = va_arg (*args, vlib_main_t *);
   CLIB_UNUSED (vlib_node_t * node) = va_arg (*args, vlib_node_t *);
   session_queue_trace_t *t = va_arg (*args, session_queue_trace_t *);

   s = format (s, "SESSION_QUEUE: session index %d, server thread index %d",
 	      t->session_index, t->server_thread_index);
   return s;
 }

 vlib_node_registration_t session_queue_node;

 #define foreach_session_queue_error		\
 _(TX, "Packets transmitted")                  	\
 _(TIMER, "Timer events")

 typedef enum
 {
 #define _(sym,str) SESSION_QUEUE_ERROR_##sym,
   foreach_session_queue_error
 #undef _
     SESSION_QUEUE_N_ERROR,
 } session_queue_error_t;

 static char *session_queue_error_strings[] = {
 #define _(sym,string) string,
   foreach_session_queue_error
 #undef _
 };

 static u32 session_type_to_next[] = {
   SESSION_QUEUE_NEXT_TCP_IP4_OUTPUT,
   SESSION_QUEUE_NEXT_IP4_LOOKUP,
   SESSION_QUEUE_NEXT_TCP_IP6_OUTPUT,
   SESSION_QUEUE_NEXT_IP6_LOOKUP,
 };

 always_inline int
 session_tx_fifo_read_and_snd_i (vlib_main_t * vm, vlib_node_runtime_t * node,
 				session_manager_main_t * smm,
 				session_fifo_event_t * e0,
 				stream_session_t * s0, u32 thread_index,
 				int *n_tx_packets, u8 peek_data)
 {
   u32 n_trace = vlib_get_trace_count (vm, node);
   u32 left_to_snd0, max_len_to_snd0, len_to_deq0, n_bufs, snd_space0;
   u32 n_frame_bytes, n_frames_per_evt;
   transport_connection_t *tc0;
   transport_proto_vft_t *transport_vft;
   u32 next_index, next0, *to_next, n_left_to_next, bi0;
   vlib_buffer_t *b0;
   u32 rx_offset = 0, max_dequeue0;
   u16 snd_mss0;
   u8 *data0;
   int i, n_bytes_read;

   next_index = next0 = session_type_to_next[s0->session_type];

   transport_vft = session_get_transport_vft (s0->session_type);
   tc0 = transport_vft->get_connection (s0->connection_index, thread_index);

   /* Make sure we have space to send and there's something to dequeue */
   snd_space0 = transport_vft->send_space (tc0);
   snd_mss0 = transport_vft->send_mss (tc0);

   /* Can't make any progress */
   if (snd_space0 == 0 || snd_mss0 == 0)
     {
       vec_add1 (smm->evts_partially_read[thread_index], *e0);
       return 0;
     }

   if (peek_data)
     {
       /* Offset in rx fifo from where to peek data  */
       rx_offset = transport_vft->tx_fifo_offset (tc0);
     }

   /* Check how much we can pull. If buffering, subtract the offset */
   max_dequeue0 = svm_fifo_max_dequeue (s0->server_tx_fifo) - rx_offset;

   /* Allow enqueuing of a new event */
   svm_fifo_unset_event (s0->server_tx_fifo);

   /* Nothing to read return */
   if (max_dequeue0 == 0)
     return 0;

   /* Ensure we're not writing more than transport window allows */
   if (max_dequeue0 < snd_space0)
     {
       /* Constrained by tx queue. Try to send only fully formed segments */
       max_len_to_snd0 = (max_dequeue0 > snd_mss0) ?
 	max_dequeue0 - max_dequeue0 % snd_mss0 : max_dequeue0;
       /* TODO Nagle ? */
     }
   else
     {
       max_len_to_snd0 = snd_space0;
     }

   n_frame_bytes = snd_mss0 * VLIB_FRAME_SIZE;
   n_frames_per_evt = ceil ((double) max_len_to_snd0 / n_frame_bytes);

   n_bufs = vec_len (smm->tx_buffers[thread_index]);
   left_to_snd0 = max_len_to_snd0;
   for (i = 0; i < n_frames_per_evt; i++)
     {
       /* Make sure we have at least one full frame of buffers ready */
       if (PREDICT_FALSE (n_bufs < VLIB_FRAME_SIZE))
 	{
 	  vec_validate (smm->tx_buffers[thread_index],
 			n_bufs + VLIB_FRAME_SIZE - 1);
 	  n_bufs +=
 	    vlib_buffer_alloc (vm, &smm->tx_buffers[thread_index][n_bufs],
 			       VLIB_FRAME_SIZE);

 	  /* buffer shortage
 	   * XXX 0.9 because when debugging we might not get a full frame */
 	  if (PREDICT_FALSE (n_bufs < 0.9 * VLIB_FRAME_SIZE))
 	    {
 	      if (svm_fifo_set_event (s0->server_tx_fifo))
 		{
 		  vec_add1 (smm->evts_partially_read[thread_index], *e0);
 		}
 	      return -1;
 	    }

 	  _vec_len (smm->tx_buffers[thread_index]) = n_bufs;
 	}

       vlib_get_next_frame (vm, node, next_index, to_next, n_left_to_next);
       while (left_to_snd0 && n_left_to_next)
 	{
 	  /* Get free buffer */
 	  n_bufs--;
 	  bi0 = smm->tx_buffers[thread_index][n_bufs];
 	  _vec_len (smm->tx_buffers[thread_index]) = n_bufs;

 	  b0 = vlib_get_buffer (vm, bi0);
 	  b0->error = 0;
 	  b0->flags = VLIB_BUFFER_TOTAL_LENGTH_VALID
 	    | VNET_BUFFER_LOCALLY_ORIGINATED;
 	  b0->current_data = 0;

 	  /* RX on the local interface. tx in default fib */
 	  vnet_buffer (b0)->sw_if_index[VLIB_RX] = 0;
 	  vnet_buffer (b0)->sw_if_index[VLIB_TX] = (u32) ~ 0;

 	  /* usual speculation, or the enqueue_x1 macro will barf */
 	  to_next[0] = bi0;
 	  to_next += 1;
 	  n_left_to_next -= 1;

 	  VLIB_BUFFER_TRACE_TRAJECTORY_INIT (b0);
 	  if (PREDICT_FALSE (n_trace > 0))
 	    {
 	      session_queue_trace_t *t0;
 	      vlib_trace_buffer (vm, node, next_index, b0,
 				 1 /* follow_chain */ );
 	      vlib_set_trace_count (vm, node, --n_trace);
 	      t0 = vlib_add_trace (vm, node, b0, sizeof (*t0));
 	      t0->session_index = s0->session_index;
 	      t0->server_thread_index = s0->thread_index;
 	    }

 	  len_to_deq0 = (left_to_snd0 < snd_mss0) ? left_to_snd0 : snd_mss0;

 	  /* *INDENT-OFF* */
 	  SESSION_EVT_DBG(SESSION_EVT_DEQ, s0, ({
 	      ed->data[0] = e0->event_id;
 	      ed->data[1] = max_dequeue0;
 	      ed->data[2] = len_to_deq0;
 	      ed->data[3] = left_to_snd0;
 	  }));
 	  /* *INDENT-ON* */

 	  /* Make room for headers */
 	  data0 = vlib_buffer_make_headroom (b0, MAX_HDRS_LEN);

 	  /* Dequeue the data
 	   * TODO 1) peek instead of dequeue
 	   *      2) buffer chains */
 	  if (peek_data)
 	    {
 	      n_bytes_read = svm_fifo_peek (s0->server_tx_fifo, s0->pid,
 					    rx_offset, len_to_deq0, data0);
 	      if (n_bytes_read <= 0)
 		goto dequeue_fail;

 	      /* Keep track of progress locally, transport is also supposed to
 	       * increment it independently when pushing the header */
 	      rx_offset += n_bytes_read;
 	    }
 	  else
 	    {
 	      n_bytes_read = svm_fifo_dequeue_nowait (s0->server_tx_fifo,
 						      s0->pid, len_to_deq0,
 						      data0);
 	      if (n_bytes_read <= 0)
 		goto dequeue_fail;
 	    }

 	  b0->current_length = n_bytes_read;

 	  /* Ask transport to push header */
 	  transport_vft->push_header (tc0, b0);

 	  left_to_snd0 -= n_bytes_read;
 	  *n_tx_packets = *n_tx_packets + 1;

 	  vlib_validate_buffer_enqueue_x1 (vm, node, next_index,
 					   to_next, n_left_to_next,
 					   bi0, next0);
 	}
       vlib_put_next_frame (vm, node, next_index, n_left_to_next);
     }

   /* If we couldn't dequeue all bytes mark as partially read */
   if (max_len_to_snd0 < max_dequeue0)
     {
       /* If we don't already have new event */
       if (svm_fifo_set_event (s0->server_tx_fifo))
 	{
 	  vec_add1 (smm->evts_partially_read[thread_index], *e0);
 	}
     }
   return 0;

 dequeue_fail:
   /*
    * Can't read from fifo. If we don't already have an event, save as partially
    * read, return buff to free list and return
    */
   clib_warning ("dequeue fail");

   if (svm_fifo_set_event (s0->server_tx_fifo))
     {
       vec_add1 (smm->evts_partially_read[thread_index], *e0);
     }
   vlib_put_next_frame (vm, node, next_index, n_left_to_next + 1);
   _vec_len (smm->tx_buffers[thread_index]) += 1;

   return 0;
 }

 int
 session_tx_fifo_peek_and_snd (vlib_main_t * vm, vlib_node_runtime_t * node,
 			      session_manager_main_t * smm,
 			      session_fifo_event_t * e0,
 			      stream_session_t * s0, u32 thread_index,
 			      int *n_tx_pkts)
 {
   return session_tx_fifo_read_and_snd_i (vm, node, smm, e0, s0, thread_index,
 					 n_tx_pkts, 1);
 }

 int
 session_tx_fifo_dequeue_and_snd (vlib_main_t * vm, vlib_node_runtime_t * node,
 				 session_manager_main_t * smm,
 				 session_fifo_event_t * e0,
 				 stream_session_t * s0, u32 thread_index,
 				 int *n_tx_pkts)
 {
   return session_tx_fifo_read_and_snd_i (vm, node, smm, e0, s0, thread_index,
 					 n_tx_pkts, 0);
 }

 static uword
 session_queue_node_fn (vlib_main_t * vm, vlib_node_runtime_t * node,
 		       vlib_frame_t * frame)
 {
   session_manager_main_t *smm = vnet_get_session_manager_main ();
   session_fifo_event_t *my_fifo_events, *e;
   u32 n_to_dequeue, n_events;
   unix_shared_memory_queue_t *q;
   application_t *app;
   int n_tx_packets = 0;
   u32 my_thread_index = vm->thread_index;
   int i, rv;
   f64 now = vlib_time_now (vm);

   SESSION_EVT_DBG (SESSION_EVT_POLL_GAP_TRACK, smm, my_thread_index);

   /*
    *  Update TCP time
    */
   tcp_update_time (now, my_thread_index);

   /*
    * Get vpp queue events
    */
   q = smm->vpp_event_queues[my_thread_index];
   if (PREDICT_FALSE (q == 0))
     return 0;

   /* min number of events we can dequeue without blocking */
   n_to_dequeue = q->cursize;
   my_fifo_events = smm->fifo_events[my_thread_index];

   if (n_to_dequeue == 0 && vec_len (my_fifo_events) == 0)
     return 0;

   SESSION_EVT_DBG (SESSION_EVT_DEQ_NODE, 0);

   /*
    * If we didn't manage to process previous events try going
    * over them again without dequeuing new ones.
    */
   /* XXX: Block senders to sessions that can't keep up */
   if (vec_len (my_fifo_events) >= 100)
     {
       clib_warning ("too many fifo events unsolved");
       goto skip_dequeue;
     }

   /* See you in the next life, don't be late */
   if (pthread_mutex_trylock (&q->mutex))
     return 0;

   for (i = 0; i < n_to_dequeue; i++)
     {
       vec_add2 (my_fifo_events, e, 1);
       unix_shared_memory_queue_sub_raw (q, (u8 *) e);
     }

   /* The other side of the connection is not polling */
   if (q->cursize < (q->maxsize / 8))
     (void) pthread_cond_broadcast (&q->condvar);
   pthread_mutex_unlock (&q->mutex);

   smm->fifo_events[my_thread_index] = my_fifo_events;

 skip_dequeue:
   n_events = vec_len (my_fifo_events);
   for (i = 0; i < n_events; i++)
     {
       svm_fifo_t *f0;		/* $$$ prefetch 1 ahead maybe */
       stream_session_t *s0;
       u32 session_index0;
       session_fifo_event_t *e0;

       e0 = &my_fifo_events[i];
       f0 = e0->fifo;
       session_index0 = f0->server_session_index;

       /* $$$ add multiple event queues, per vpp worker thread */
       ASSERT (f0->server_thread_index == my_thread_index);

       s0 = stream_session_get_if_valid (session_index0, my_thread_index);

       if (CLIB_DEBUG && !s0)
 	{
 	  clib_warning ("It's dead, Jim!");
 	  continue;
 	}

       if (PREDICT_FALSE (s0->session_state == SESSION_STATE_CLOSED))
 	continue;

       ASSERT (s0->thread_index == my_thread_index);

       switch (e0->event_type)
 	{
 	case FIFO_EVENT_SERVER_TX:
 	  /* 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,
 							my_thread_index,
 							&n_tx_packets);
 	  /* Out of buffers */
 	  if (rv < 0)
 	    goto done;

 	  break;
 	case FIFO_EVENT_SERVER_EXIT:
 	  stream_session_disconnect (s0);
 	  break;
 	case FIFO_EVENT_BUILTIN_RX:
 	  svm_fifo_unset_event (s0->server_rx_fifo);
 	  /* Get session's server */
 	  app = application_get (s0->app_index);
 	  app->cb_fns.builtin_server_rx_callback (s0);
 	  break;
 	default:
 	  clib_warning ("unhandled event type %d", e0->event_type);
 	}
     }

 done:

   /* Couldn't process all events. Probably out of buffers */
   if (PREDICT_FALSE (i < n_events))
     {
       session_fifo_event_t *partially_read =
 	smm->evts_partially_read[my_thread_index];
       vec_add (partially_read, &my_fifo_events[i], n_events - i);
       vec_free (my_fifo_events);
       smm->fifo_events[my_thread_index] = partially_read;
       smm->evts_partially_read[my_thread_index] = 0;
     }
   else
     {
       vec_free (smm->fifo_events[my_thread_index]);
       smm->fifo_events[my_thread_index] =
 	smm->evts_partially_read[my_thread_index];
       smm->evts_partially_read[my_thread_index] = 0;
     }

   vlib_node_increment_counter (vm, session_queue_node.index,
 			       SESSION_QUEUE_ERROR_TX, n_tx_packets);

   SESSION_EVT_DBG (SESSION_EVT_DEQ_NODE, 1);

   return n_tx_packets;
 }

 /* *INDENT-OFF* */
 VLIB_REGISTER_NODE (session_queue_node) =
 {
   .function = session_queue_node_fn,
   .name = "session-queue",
   .format_trace = format_session_queue_trace,
   .type = VLIB_NODE_TYPE_INPUT,
   .n_errors = ARRAY_LEN (session_queue_error_strings),
   .error_strings = session_queue_error_strings,
   .n_next_nodes = SESSION_QUEUE_N_NEXT,
   .state = VLIB_NODE_STATE_DISABLED,
   .next_nodes =
   {
       [SESSION_QUEUE_NEXT_DROP] = "error-drop",
       [SESSION_QUEUE_NEXT_IP4_LOOKUP] = "ip4-lookup",
       [SESSION_QUEUE_NEXT_IP6_LOOKUP] = "ip6-lookup",
       [SESSION_QUEUE_NEXT_TCP_IP4_OUTPUT] = "tcp4-output",
       [SESSION_QUEUE_NEXT_TCP_IP6_OUTPUT] = "tcp6-output",
   },
 };
 /* *INDENT-ON* */

 /*
  * fd.io coding-style-patch-verification: ON
  *
  * Local Variables:
  * eval: (c-set-style "gnu")
  * End:
  */
	/*
	* Copyright (c) 2017 Cisco and/or its affiliates.
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at:
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include <math.h>
	#include <vlib/vlib.h>
	#include <vnet/vnet.h>
	#include <vnet/tcp/tcp.h>
	#include <vppinfra/elog.h>
	#include <vnet/session/application.h>
	#include <vnet/session/session_debug.h>
	#include <vlibmemory/unix_shared_memory_queue.h>

	vlib_node_registration_t session_queue_node;

	typedef struct
	{
	u32 session_index;
	u32 server_thread_index;
	} session_queue_trace_t;

	/* packet trace format function */
	static u8 *
	format_session_queue_trace (u8 * s, va_list * args)
	{
	CLIB_UNUSED (vlib_main_t * vm) = va_arg (args, vlib_main_t );
	CLIB_UNUSED (vlib_node_t * node) = va_arg (args, vlib_node_t );
	session_queue_trace_t t = va_arg (args, session_queue_trace_t *);

	s = format (s, "SESSION_QUEUE: session index %d, server thread index %d",
	t->session_index, t->server_thread_index);
	return s;
	}

	vlib_node_registration_t session_queue_node;

	#define foreach_session_queue_error \
	_(TX, "Packets transmitted") \
	_(TIMER, "Timer events")

	typedef enum
	{
	#define _(sym,str) SESSION_QUEUE_ERROR_##sym,
	foreach_session_queue_error
	#undef _
	SESSION_QUEUE_N_ERROR,
	} session_queue_error_t;

	static char *session_queue_error_strings[] = {
	#define _(sym,string) string,
	foreach_session_queue_error
	#undef _
	};

	static u32 session_type_to_next[] = {
	SESSION_QUEUE_NEXT_TCP_IP4_OUTPUT,
	SESSION_QUEUE_NEXT_IP4_LOOKUP,
	SESSION_QUEUE_NEXT_TCP_IP6_OUTPUT,
	SESSION_QUEUE_NEXT_IP6_LOOKUP,
	};

	always_inline int
	session_tx_fifo_read_and_snd_i (vlib_main_t * vm, vlib_node_runtime_t * node,
	session_manager_main_t * smm,
	session_fifo_event_t * e0,
	stream_session_t * s0, u32 thread_index,
	int *n_tx_packets, u8 peek_data)
	{
	u32 n_trace = vlib_get_trace_count (vm, node);
	u32 left_to_snd0, max_len_to_snd0, len_to_deq0, n_bufs, snd_space0;
	u32 n_frame_bytes, n_frames_per_evt;
	transport_connection_t *tc0;
	transport_proto_vft_t *transport_vft;
	u32 next_index, next0, *to_next, n_left_to_next, bi0;
	vlib_buffer_t *b0;
	u32 rx_offset = 0, max_dequeue0;
	u16 snd_mss0;
	u8 *data0;
	int i, n_bytes_read;

	next_index = next0 = session_type_to_next[s0->session_type];

	transport_vft = session_get_transport_vft (s0->session_type);
	tc0 = transport_vft->get_connection (s0->connection_index, thread_index);

	/* Make sure we have space to send and there's something to dequeue */
	snd_space0 = transport_vft->send_space (tc0);
	snd_mss0 = transport_vft->send_mss (tc0);

	/* Can't make any progress */
	if (snd_space0 == 0 \|\| snd_mss0 == 0)
	{
	vec_add1 (smm->evts_partially_read[thread_index], *e0);
	return 0;
	}

	if (peek_data)
	{
	/* Offset in rx fifo from where to peek data */
	rx_offset = transport_vft->tx_fifo_offset (tc0);
	}

	/* Check how much we can pull. If buffering, subtract the offset */
	max_dequeue0 = svm_fifo_max_dequeue (s0->server_tx_fifo) - rx_offset;

	/* Allow enqueuing of a new event */
	svm_fifo_unset_event (s0->server_tx_fifo);

	/* Nothing to read return */
	if (max_dequeue0 == 0)
	return 0;

	/* Ensure we're not writing more than transport window allows */
	if (max_dequeue0 < snd_space0)
	{
	/* Constrained by tx queue. Try to send only fully formed segments */
	max_len_to_snd0 = (max_dequeue0 > snd_mss0) ?
	max_dequeue0 - max_dequeue0 % snd_mss0 : max_dequeue0;
	/* TODO Nagle ? */
	}
	else
	{
	max_len_to_snd0 = snd_space0;
	}

	n_frame_bytes = snd_mss0 * VLIB_FRAME_SIZE;
	n_frames_per_evt = ceil ((double) max_len_to_snd0 / n_frame_bytes);

	n_bufs = vec_len (smm->tx_buffers[thread_index]);
	left_to_snd0 = max_len_to_snd0;
	for (i = 0; i < n_frames_per_evt; i++)
	{
	/* Make sure we have at least one full frame of buffers ready */
	if (PREDICT_FALSE (n_bufs < VLIB_FRAME_SIZE))
	{
	vec_validate (smm->tx_buffers[thread_index],
	n_bufs + VLIB_FRAME_SIZE - 1);
	n_bufs +=
	vlib_buffer_alloc (vm, &smm->tx_buffers[thread_index][n_bufs],
	VLIB_FRAME_SIZE);

	/* buffer shortage
	* XXX 0.9 because when debugging we might not get a full frame */
	if (PREDICT_FALSE (n_bufs < 0.9 * VLIB_FRAME_SIZE))
	{
	if (svm_fifo_set_event (s0->server_tx_fifo))
	{
	vec_add1 (smm->evts_partially_read[thread_index], *e0);
	}
	return -1;
	}

	_vec_len (smm->tx_buffers[thread_index]) = n_bufs;
	}

	vlib_get_next_frame (vm, node, next_index, to_next, n_left_to_next);
	while (left_to_snd0 && n_left_to_next)
	{
	/* Get free buffer */
	n_bufs--;
	bi0 = smm->tx_buffers[thread_index][n_bufs];
	_vec_len (smm->tx_buffers[thread_index]) = n_bufs;

	b0 = vlib_get_buffer (vm, bi0);
	b0->error = 0;
	b0->flags = VLIB_BUFFER_TOTAL_LENGTH_VALID
	\| VNET_BUFFER_LOCALLY_ORIGINATED;
	b0->current_data = 0;

	/* RX on the local interface. tx in default fib */
	vnet_buffer (b0)->sw_if_index[VLIB_RX] = 0;
	vnet_buffer (b0)->sw_if_index[VLIB_TX] = (u32) ~ 0;

	/* usual speculation, or the enqueue_x1 macro will barf */
	to_next[0] = bi0;
	to_next += 1;
	n_left_to_next -= 1;

	VLIB_BUFFER_TRACE_TRAJECTORY_INIT (b0);
	if (PREDICT_FALSE (n_trace > 0))
	{
	session_queue_trace_t *t0;
	vlib_trace_buffer (vm, node, next_index, b0,
	1 /* follow_chain */ );
	vlib_set_trace_count (vm, node, --n_trace);
	t0 = vlib_add_trace (vm, node, b0, sizeof (*t0));
	t0->session_index = s0->session_index;
	t0->server_thread_index = s0->thread_index;
	}

	len_to_deq0 = (left_to_snd0 < snd_mss0) ? left_to_snd0 : snd_mss0;

	/* INDENT-OFF */
	SESSION_EVT_DBG(SESSION_EVT_DEQ, s0, ({
	ed->data[0] = e0->event_id;
	ed->data[1] = max_dequeue0;
	ed->data[2] = len_to_deq0;
	ed->data[3] = left_to_snd0;
	}));
	/* INDENT-ON */

	/* Make room for headers */
	data0 = vlib_buffer_make_headroom (b0, MAX_HDRS_LEN);

	/* Dequeue the data
	* TODO 1) peek instead of dequeue
	* 2) buffer chains */
	if (peek_data)
	{
	n_bytes_read = svm_fifo_peek (s0->server_tx_fifo, s0->pid,
	rx_offset, len_to_deq0, data0);
	if (n_bytes_read <= 0)
	goto dequeue_fail;

	/* Keep track of progress locally, transport is also supposed to
	* increment it independently when pushing the header */
	rx_offset += n_bytes_read;
	}
	else
	{
	n_bytes_read = svm_fifo_dequeue_nowait (s0->server_tx_fifo,
	s0->pid, len_to_deq0,
	data0);
	if (n_bytes_read <= 0)
	goto dequeue_fail;
	}

	b0->current_length = n_bytes_read;

	/* Ask transport to push header */
	transport_vft->push_header (tc0, b0);

	left_to_snd0 -= n_bytes_read;
	n_tx_packets = n_tx_packets + 1;

	vlib_validate_buffer_enqueue_x1 (vm, node, next_index,
	to_next, n_left_to_next,
	bi0, next0);
	}
	vlib_put_next_frame (vm, node, next_index, n_left_to_next);
	}

	/* If we couldn't dequeue all bytes mark as partially read */
	if (max_len_to_snd0 < max_dequeue0)
	{
	/* If we don't already have new event */
	if (svm_fifo_set_event (s0->server_tx_fifo))
	{
	vec_add1 (smm->evts_partially_read[thread_index], *e0);
	}
	}
	return 0;

	dequeue_fail:
	/*
	* Can't read from fifo. If we don't already have an event, save as partially
	* read, return buff to free list and return
	*/
	clib_warning ("dequeue fail");

	if (svm_fifo_set_event (s0->server_tx_fifo))
	{
	vec_add1 (smm->evts_partially_read[thread_index], *e0);
	}
	vlib_put_next_frame (vm, node, next_index, n_left_to_next + 1);
	_vec_len (smm->tx_buffers[thread_index]) += 1;

	return 0;
	}

	int
	session_tx_fifo_peek_and_snd (vlib_main_t * vm, vlib_node_runtime_t * node,
	session_manager_main_t * smm,
	session_fifo_event_t * e0,
	stream_session_t * s0, u32 thread_index,
	int *n_tx_pkts)
	{
	return session_tx_fifo_read_and_snd_i (vm, node, smm, e0, s0, thread_index,
	n_tx_pkts, 1);
	}

	int
	session_tx_fifo_dequeue_and_snd (vlib_main_t * vm, vlib_node_runtime_t * node,
	session_manager_main_t * smm,
	session_fifo_event_t * e0,
	stream_session_t * s0, u32 thread_index,
	int *n_tx_pkts)
	{
	return session_tx_fifo_read_and_snd_i (vm, node, smm, e0, s0, thread_index,
	n_tx_pkts, 0);
	}

	static uword
	session_queue_node_fn (vlib_main_t * vm, vlib_node_runtime_t * node,
	vlib_frame_t * frame)
	{
	session_manager_main_t *smm = vnet_get_session_manager_main ();
	session_fifo_event_t my_fifo_events, e;
	u32 n_to_dequeue, n_events;
	unix_shared_memory_queue_t *q;
	application_t *app;
	int n_tx_packets = 0;
	u32 my_thread_index = vm->thread_index;
	int i, rv;
	f64 now = vlib_time_now (vm);

	SESSION_EVT_DBG (SESSION_EVT_POLL_GAP_TRACK, smm, my_thread_index);

	/*
	* Update TCP time
	*/
	tcp_update_time (now, my_thread_index);

	/*
	* Get vpp queue events
	*/
	q = smm->vpp_event_queues[my_thread_index];
	if (PREDICT_FALSE (q == 0))
	return 0;

	/* min number of events we can dequeue without blocking */
	n_to_dequeue = q->cursize;
	my_fifo_events = smm->fifo_events[my_thread_index];

	if (n_to_dequeue == 0 && vec_len (my_fifo_events) == 0)
	return 0;

	SESSION_EVT_DBG (SESSION_EVT_DEQ_NODE, 0);

	/*
	* If we didn't manage to process previous events try going
	* over them again without dequeuing new ones.
	*/
	/* XXX: Block senders to sessions that can't keep up */
	if (vec_len (my_fifo_events) >= 100)
	{
	clib_warning ("too many fifo events unsolved");
	goto skip_dequeue;
	}

	/* See you in the next life, don't be late */
	if (pthread_mutex_trylock (&q->mutex))
	return 0;

	for (i = 0; i < n_to_dequeue; i++)
	{
	vec_add2 (my_fifo_events, e, 1);
	unix_shared_memory_queue_sub_raw (q, (u8 *) e);
	}

	/* The other side of the connection is not polling */
	if (q->cursize < (q->maxsize / 8))
	(void) pthread_cond_broadcast (&q->condvar);
	pthread_mutex_unlock (&q->mutex);

	smm->fifo_events[my_thread_index] = my_fifo_events;

	skip_dequeue:
	n_events = vec_len (my_fifo_events);
	for (i = 0; i < n_events; i++)
	{
	svm_fifo_t f0; / $$$ prefetch 1 ahead maybe */
	stream_session_t *s0;
	u32 session_index0;
	session_fifo_event_t *e0;

	e0 = &my_fifo_events[i];
	f0 = e0->fifo;
	session_index0 = f0->server_session_index;

	/* $$$ add multiple event queues, per vpp worker thread */
	ASSERT (f0->server_thread_index == my_thread_index);

	s0 = stream_session_get_if_valid (session_index0, my_thread_index);

	if (CLIB_DEBUG && !s0)
	{
	clib_warning ("It's dead, Jim!");
	continue;
	}

	if (PREDICT_FALSE (s0->session_state == SESSION_STATE_CLOSED))
	continue;

	ASSERT (s0->thread_index == my_thread_index);

	switch (e0->event_type)
	{
	case FIFO_EVENT_SERVER_TX:
	/* 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,
	my_thread_index,
	&n_tx_packets);
	/* Out of buffers */
	if (rv < 0)
	goto done;

	break;
	case FIFO_EVENT_SERVER_EXIT:
	stream_session_disconnect (s0);
	break;
	case FIFO_EVENT_BUILTIN_RX:
	svm_fifo_unset_event (s0->server_rx_fifo);
	/* Get session's server */
	app = application_get (s0->app_index);
	app->cb_fns.builtin_server_rx_callback (s0);
	break;
	default:
	clib_warning ("unhandled event type %d", e0->event_type);
	}
	}

	done:

	/* Couldn't process all events. Probably out of buffers */
	if (PREDICT_FALSE (i < n_events))
	{
	session_fifo_event_t *partially_read =
	smm->evts_partially_read[my_thread_index];
	vec_add (partially_read, &my_fifo_events[i], n_events - i);
	vec_free (my_fifo_events);
	smm->fifo_events[my_thread_index] = partially_read;
	smm->evts_partially_read[my_thread_index] = 0;
	}
	else
	{
	vec_free (smm->fifo_events[my_thread_index]);
	smm->fifo_events[my_thread_index] =
	smm->evts_partially_read[my_thread_index];
	smm->evts_partially_read[my_thread_index] = 0;
	}

	vlib_node_increment_counter (vm, session_queue_node.index,
	SESSION_QUEUE_ERROR_TX, n_tx_packets);

	SESSION_EVT_DBG (SESSION_EVT_DEQ_NODE, 1);

	return n_tx_packets;
	}

	/* INDENT-OFF */
	VLIB_REGISTER_NODE (session_queue_node) =
	{
	.function = session_queue_node_fn,
	.name = "session-queue",
	.format_trace = format_session_queue_trace,
	.type = VLIB_NODE_TYPE_INPUT,
	.n_errors = ARRAY_LEN (session_queue_error_strings),
	.error_strings = session_queue_error_strings,
	.n_next_nodes = SESSION_QUEUE_N_NEXT,
	.state = VLIB_NODE_STATE_DISABLED,
	.next_nodes =
	{
	[SESSION_QUEUE_NEXT_DROP] = "error-drop",
	[SESSION_QUEUE_NEXT_IP4_LOOKUP] = "ip4-lookup",
	[SESSION_QUEUE_NEXT_IP6_LOOKUP] = "ip6-lookup",
	[SESSION_QUEUE_NEXT_TCP_IP4_OUTPUT] = "tcp4-output",
	[SESSION_QUEUE_NEXT_TCP_IP6_OUTPUT] = "tcp6-output",
	},
	};
	/* INDENT-ON */

	/*
	* fd.io coding-style-patch-verification: ON
	*
	* Local Variables:
	* eval: (c-set-style "gnu")
	* End:
	*/