src/vcl/vcl_private.c - fdio/vpp - Gitiles

 /*
  * Copyright (c) 2018-2019 Cisco and/or its affiliates.
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this
  * 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 <vcl/vcl_private.h>

 static pthread_key_t vcl_worker_stop_key;

 static const char *
 vppcom_app_state_str (app_state_t state)
 {
   char *st;

   switch (state)
     {
     case STATE_APP_START:
       st = "STATE_APP_START";
       break;

     case STATE_APP_CONN_VPP:
       st = "STATE_APP_CONN_VPP";
       break;

     case STATE_APP_ENABLED:
       st = "STATE_APP_ENABLED";
       break;

     case STATE_APP_ATTACHED:
       st = "STATE_APP_ATTACHED";
       break;

     default:
       st = "UNKNOWN_APP_STATE";
       break;
     }

   return st;
 }

 int
 vcl_wait_for_app_state_change (app_state_t app_state)
 {
   vcl_worker_t *wrk = vcl_worker_get_current ();
   f64 timeout = clib_time_now (&wrk->clib_time) + vcm->cfg.app_timeout;

   while (clib_time_now (&wrk->clib_time) < timeout)
     {
       if (vcm->app_state == app_state)
 	return VPPCOM_OK;
       if (vcm->app_state == STATE_APP_FAILED)
 	return VPPCOM_ECONNABORTED;
     }
   VDBG (0, "timeout waiting for state %s (%d)",
 	vppcom_app_state_str (app_state), app_state);
   vcl_evt (VCL_EVT_SESSION_TIMEOUT, vcm, app_state);

   return VPPCOM_ETIMEDOUT;
 }

 vcl_mq_evt_conn_t *
 vcl_mq_evt_conn_alloc (vcl_worker_t * wrk)
 {
   vcl_mq_evt_conn_t *mqc;
   pool_get (wrk->mq_evt_conns, mqc);
   memset (mqc, 0, sizeof (*mqc));
   return mqc;
 }

 u32
 vcl_mq_evt_conn_index (vcl_worker_t * wrk, vcl_mq_evt_conn_t * mqc)
 {
   return (mqc - wrk->mq_evt_conns);
 }

 vcl_mq_evt_conn_t *
 vcl_mq_evt_conn_get (vcl_worker_t * wrk, u32 mq_conn_idx)
 {
   return pool_elt_at_index (wrk->mq_evt_conns, mq_conn_idx);
 }

 int
 vcl_mq_epoll_add_evfd (vcl_worker_t * wrk, svm_msg_q_t * mq)
 {
   struct epoll_event e = { 0 };
   vcl_mq_evt_conn_t *mqc;
   u32 mqc_index;
   int mq_fd;

   mq_fd = svm_msg_q_get_consumer_eventfd (mq);

   if (wrk->mqs_epfd < 0 || mq_fd == -1)
     return -1;

   mqc = vcl_mq_evt_conn_alloc (wrk);
   mqc_index = vcl_mq_evt_conn_index (wrk, mqc);
   mqc->mq_fd = mq_fd;
   mqc->mq = mq;

   e.events = EPOLLIN;
   e.data.u32 = mqc_index;
   if (epoll_ctl (wrk->mqs_epfd, EPOLL_CTL_ADD, mq_fd, &e) < 0)
     {
       VDBG (0, "failed to add mq eventfd to mq epoll fd");
       return -1;
     }

   return mqc_index;
 }

 int
 vcl_mq_epoll_del_evfd (vcl_worker_t * wrk, u32 mqc_index)
 {
   vcl_mq_evt_conn_t *mqc;

   if (wrk->mqs_epfd || mqc_index == ~0)
     return -1;

   mqc = vcl_mq_evt_conn_get (wrk, mqc_index);
   if (epoll_ctl (wrk->mqs_epfd, EPOLL_CTL_DEL, mqc->mq_fd, 0) < 0)
     {
       VDBG (0, "failed to del mq eventfd to mq epoll fd");
       return -1;
     }
   return 0;
 }

 static vcl_worker_t *
 vcl_worker_alloc (void)
 {
   vcl_worker_t *wrk;
   pool_get (vcm->workers, wrk);
   memset (wrk, 0, sizeof (*wrk));
   wrk->wrk_index = wrk - vcm->workers;
   wrk->forked_child = ~0;
   return wrk;
 }

 static void
 vcl_worker_free (vcl_worker_t * wrk)
 {
   pool_put (vcm->workers, wrk);
 }

 void
 vcl_worker_cleanup (vcl_worker_t * wrk, u8 notify_vpp)
 {
   clib_spinlock_lock (&vcm->workers_lock);
   if (notify_vpp)
     {
       if (wrk->wrk_index == vcl_get_worker_index ())
 	vcl_send_app_worker_add_del (0 /* is_add */ );
       else
 	vcl_send_child_worker_del (wrk);
     }
   if (wrk->mqs_epfd > 0)
     close (wrk->mqs_epfd);
   hash_free (wrk->session_index_by_vpp_handles);
   vec_free (wrk->mq_events);
   vec_free (wrk->mq_msg_vector);
   vcl_worker_free (wrk);
   clib_spinlock_unlock (&vcm->workers_lock);
 }

 static void
 vcl_worker_cleanup_cb (void *arg)
 {
   vcl_worker_t *wrk = vcl_worker_get_current ();
   u32 wrk_index = wrk->wrk_index;
   vcl_worker_cleanup (wrk, 1 /* notify vpp */ );
   vcl_set_worker_index (~0);
   VDBG (0, "cleaned up worker %u", wrk_index);
 }

 vcl_worker_t *
 vcl_worker_alloc_and_init ()
 {
   vcl_worker_t *wrk;

   /* This was initialized already */
   if (vcl_get_worker_index () != ~0)
     return 0;

   /* Use separate heap map entry for worker */
   clib_mem_set_thread_index ();

   if (pool_elts (vcm->workers) == vcm->cfg.max_workers)
     {
       VDBG (0, "max-workers %u limit reached", vcm->cfg.max_workers);
       return 0;
     }

   clib_spinlock_lock (&vcm->workers_lock);
   wrk = vcl_worker_alloc ();
   vcl_set_worker_index (wrk->wrk_index);
   wrk->thread_id = pthread_self ();
   wrk->current_pid = getpid ();

   wrk->mqs_epfd = -1;
   if (vcm->cfg.use_mq_eventfd)
     {
       wrk->mqs_epfd = epoll_create (1);
       if (wrk->mqs_epfd < 0)
 	{
 	  clib_unix_warning ("epoll_create() returned");
 	  goto done;
 	}
     }

   wrk->session_index_by_vpp_handles = hash_create (0, sizeof (uword));
   clib_time_init (&wrk->clib_time);
   vec_validate (wrk->mq_events, 64);
   vec_validate (wrk->mq_msg_vector, 128);
   vec_reset_length (wrk->mq_msg_vector);
   vec_validate (wrk->unhandled_evts_vector, 128);
   vec_reset_length (wrk->unhandled_evts_vector);
   clib_spinlock_unlock (&vcm->workers_lock);

 done:
   return wrk;
 }

 int
 vcl_worker_register_with_vpp (void)
 {
   vcl_worker_t *wrk = vcl_worker_get_current ();

   clib_spinlock_lock (&vcm->workers_lock);

   vcm->app_state = STATE_APP_ADDING_WORKER;
   vcl_send_app_worker_add_del (1 /* is_add */ );
   if (vcl_wait_for_app_state_change (STATE_APP_READY))
     {
       VDBG (0, "failed to add worker to vpp");
       return -1;
     }
   if (pthread_key_create (&vcl_worker_stop_key, vcl_worker_cleanup_cb))
     VDBG (0, "failed to add pthread cleanup function");
   if (pthread_setspecific (vcl_worker_stop_key, &wrk->thread_id))
     VDBG (0, "failed to setup key value");

   clib_spinlock_unlock (&vcm->workers_lock);

   VDBG (0, "added worker %u", wrk->wrk_index);
   return 0;
 }

 int
 vcl_worker_set_bapi (void)
 {
   vcl_worker_t *wrk = vcl_worker_get_current ();
   int i;

   /* Find the first worker with the same pid */
   for (i = 0; i < vec_len (vcm->workers); i++)
     {
       if (i == wrk->wrk_index)
 	continue;
       if (vcm->workers[i].current_pid == wrk->current_pid)
 	{
 	  wrk->vl_input_queue = vcm->workers[i].vl_input_queue;
 	  wrk->my_client_index = vcm->workers[i].my_client_index;
 	  return 0;
 	}
     }
   return -1;
 }

 svm_msg_q_t *
 vcl_worker_ctrl_mq (vcl_worker_t * wrk)
 {
   return wrk->ctrl_mq;
 }

 void
 vcl_segment_table_add (u64 segment_handle, u32 svm_segment_index)
 {
   clib_rwlock_writer_lock (&vcm->segment_table_lock);
   hash_set (vcm->segment_table, segment_handle, svm_segment_index);
   clib_rwlock_writer_unlock (&vcm->segment_table_lock);
 }

 u32
 vcl_segment_table_lookup (u64 segment_handle)
 {
   uword *seg_indexp;

   clib_rwlock_reader_lock (&vcm->segment_table_lock);
   seg_indexp = hash_get (vcm->segment_table, segment_handle);
   clib_rwlock_reader_unlock (&vcm->segment_table_lock);

   if (!seg_indexp)
     return VCL_INVALID_SEGMENT_INDEX;
   return ((u32) * seg_indexp);
 }

 void
 vcl_segment_table_del (u64 segment_handle)
 {
   clib_rwlock_writer_lock (&vcm->segment_table_lock);
   hash_unset (vcm->segment_table, segment_handle);
   clib_rwlock_writer_unlock (&vcm->segment_table_lock);
 }

 void
 vcl_cleanup_bapi (void)
 {
   socket_client_main_t *scm = &socket_client_main;
   api_main_t *am = vlibapi_get_main ();

   am->my_client_index = ~0;
   am->my_registration = 0;
   am->vl_input_queue = 0;
   am->msg_index_by_name_and_crc = 0;
   scm->socket_fd = 0;

   vl_client_api_unmap ();
 }

 int
 vcl_session_read_ready (vcl_session_t * session)
 {
   /* Assumes caller has acquired spinlock: vcm->sessions_lockp */
   if (PREDICT_FALSE (session->is_vep))
     {
       VDBG (0, "ERROR: session %u: cannot read from an epoll session!",
 	    session->session_index);
       return VPPCOM_EBADFD;
     }

   if (PREDICT_FALSE (!(session->session_state & (STATE_OPEN | STATE_LISTEN))))
     {
       vcl_session_state_t state = session->session_state;
       int rv;

       rv = ((state & STATE_DISCONNECT) ? VPPCOM_ECONNRESET : VPPCOM_ENOTCONN);

       VDBG (1, "session %u [0x%llx]: not open! state 0x%x (%s), ret %d (%s)",
 	    session->session_index, session->vpp_handle, state,
 	    vppcom_session_state_str (state), rv, vppcom_retval_str (rv));
       return rv;
     }

   if (session->session_state & STATE_LISTEN)
     return clib_fifo_elts (session->accept_evts_fifo);

   if (vcl_session_is_ct (session))
     return svm_fifo_max_dequeue_cons (session->ct_rx_fifo);

   return svm_fifo_max_dequeue_cons (session->rx_fifo);
 }

 int
 vcl_session_write_ready (vcl_session_t * session)
 {
   /* Assumes caller has acquired spinlock: vcm->sessions_lockp */
   if (PREDICT_FALSE (session->is_vep))
     {
       VDBG (0, "session %u [0x%llx]: cannot write to an epoll session!",
 	    session->session_index, session->vpp_handle);
       return VPPCOM_EBADFD;
     }

   if (PREDICT_FALSE (session->session_state & STATE_LISTEN))
     {
       if (session->tx_fifo)
 	return svm_fifo_max_enqueue_prod (session->tx_fifo);
       else
 	return VPPCOM_EBADFD;
     }

   if (PREDICT_FALSE (!(session->session_state & STATE_OPEN)))
     {
       vcl_session_state_t state = session->session_state;
       int rv;

       rv = ((state & STATE_DISCONNECT) ? VPPCOM_ECONNRESET : VPPCOM_ENOTCONN);
       VDBG (0, "session %u [0x%llx]: not open! state 0x%x (%s), ret %d (%s)",
 	    session->session_index, session->vpp_handle, state,
 	    vppcom_session_state_str (state), rv, vppcom_retval_str (rv));
       return rv;
     }

   if (vcl_session_is_ct (session))
     return svm_fifo_max_enqueue_prod (session->ct_tx_fifo);

   return svm_fifo_max_enqueue_prod (session->tx_fifo);
 }

 /*
  * fd.io coding-style-patch-verification: ON
  *
  * Local Variables:
  * eval: (c-set-style "gnu")
  * End:
  */
	/*
	* Copyright (c) 2018-2019 Cisco and/or its affiliates.
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this
	* 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 <vcl/vcl_private.h>

	static pthread_key_t vcl_worker_stop_key;

	static const char *
	vppcom_app_state_str (app_state_t state)
	{
	char *st;

	switch (state)
	{
	case STATE_APP_START:
	st = "STATE_APP_START";
	break;

	case STATE_APP_CONN_VPP:
	st = "STATE_APP_CONN_VPP";
	break;

	case STATE_APP_ENABLED:
	st = "STATE_APP_ENABLED";
	break;

	case STATE_APP_ATTACHED:
	st = "STATE_APP_ATTACHED";
	break;

	default:
	st = "UNKNOWN_APP_STATE";
	break;
	}

	return st;
	}

	int
	vcl_wait_for_app_state_change (app_state_t app_state)
	{
	vcl_worker_t *wrk = vcl_worker_get_current ();
	f64 timeout = clib_time_now (&wrk->clib_time) + vcm->cfg.app_timeout;

	while (clib_time_now (&wrk->clib_time) < timeout)
	{
	if (vcm->app_state == app_state)
	return VPPCOM_OK;
	if (vcm->app_state == STATE_APP_FAILED)
	return VPPCOM_ECONNABORTED;
	}
	VDBG (0, "timeout waiting for state %s (%d)",
	vppcom_app_state_str (app_state), app_state);
	vcl_evt (VCL_EVT_SESSION_TIMEOUT, vcm, app_state);

	return VPPCOM_ETIMEDOUT;
	}

	vcl_mq_evt_conn_t *
	vcl_mq_evt_conn_alloc (vcl_worker_t * wrk)
	{
	vcl_mq_evt_conn_t *mqc;
	pool_get (wrk->mq_evt_conns, mqc);
	memset (mqc, 0, sizeof (*mqc));
	return mqc;
	}

	u32
	vcl_mq_evt_conn_index (vcl_worker_t * wrk, vcl_mq_evt_conn_t * mqc)
	{
	return (mqc - wrk->mq_evt_conns);
	}

	vcl_mq_evt_conn_t *
	vcl_mq_evt_conn_get (vcl_worker_t * wrk, u32 mq_conn_idx)
	{
	return pool_elt_at_index (wrk->mq_evt_conns, mq_conn_idx);
	}

	int
	vcl_mq_epoll_add_evfd (vcl_worker_t * wrk, svm_msg_q_t * mq)
	{
	struct epoll_event e = { 0 };
	vcl_mq_evt_conn_t *mqc;
	u32 mqc_index;
	int mq_fd;

	mq_fd = svm_msg_q_get_consumer_eventfd (mq);

	if (wrk->mqs_epfd < 0 \|\| mq_fd == -1)
	return -1;

	mqc = vcl_mq_evt_conn_alloc (wrk);
	mqc_index = vcl_mq_evt_conn_index (wrk, mqc);
	mqc->mq_fd = mq_fd;
	mqc->mq = mq;

	e.events = EPOLLIN;
	e.data.u32 = mqc_index;
	if (epoll_ctl (wrk->mqs_epfd, EPOLL_CTL_ADD, mq_fd, &e) < 0)
	{
	VDBG (0, "failed to add mq eventfd to mq epoll fd");
	return -1;
	}

	return mqc_index;
	}

	int
	vcl_mq_epoll_del_evfd (vcl_worker_t * wrk, u32 mqc_index)
	{
	vcl_mq_evt_conn_t *mqc;

	if (wrk->mqs_epfd \|\| mqc_index == ~0)
	return -1;

	mqc = vcl_mq_evt_conn_get (wrk, mqc_index);
	if (epoll_ctl (wrk->mqs_epfd, EPOLL_CTL_DEL, mqc->mq_fd, 0) < 0)
	{
	VDBG (0, "failed to del mq eventfd to mq epoll fd");
	return -1;
	}
	return 0;
	}

	static vcl_worker_t *
	vcl_worker_alloc (void)
	{
	vcl_worker_t *wrk;
	pool_get (vcm->workers, wrk);
	memset (wrk, 0, sizeof (*wrk));
	wrk->wrk_index = wrk - vcm->workers;
	wrk->forked_child = ~0;
	return wrk;
	}

	static void
	vcl_worker_free (vcl_worker_t * wrk)
	{
	pool_put (vcm->workers, wrk);
	}

	void
	vcl_worker_cleanup (vcl_worker_t * wrk, u8 notify_vpp)
	{
	clib_spinlock_lock (&vcm->workers_lock);
	if (notify_vpp)
	{
	if (wrk->wrk_index == vcl_get_worker_index ())
	vcl_send_app_worker_add_del (0 /* is_add */ );
	else
	vcl_send_child_worker_del (wrk);
	}
	if (wrk->mqs_epfd > 0)
	close (wrk->mqs_epfd);
	hash_free (wrk->session_index_by_vpp_handles);
	vec_free (wrk->mq_events);
	vec_free (wrk->mq_msg_vector);
	vcl_worker_free (wrk);
	clib_spinlock_unlock (&vcm->workers_lock);
	}

	static void
	vcl_worker_cleanup_cb (void *arg)
	{
	vcl_worker_t *wrk = vcl_worker_get_current ();
	u32 wrk_index = wrk->wrk_index;
	vcl_worker_cleanup (wrk, 1 /* notify vpp */ );
	vcl_set_worker_index (~0);
	VDBG (0, "cleaned up worker %u", wrk_index);
	}

	vcl_worker_t *
	vcl_worker_alloc_and_init ()
	{
	vcl_worker_t *wrk;

	/* This was initialized already */
	if (vcl_get_worker_index () != ~0)
	return 0;

	/* Use separate heap map entry for worker */
	clib_mem_set_thread_index ();

	if (pool_elts (vcm->workers) == vcm->cfg.max_workers)
	{
	VDBG (0, "max-workers %u limit reached", vcm->cfg.max_workers);
	return 0;
	}

	clib_spinlock_lock (&vcm->workers_lock);
	wrk = vcl_worker_alloc ();
	vcl_set_worker_index (wrk->wrk_index);
	wrk->thread_id = pthread_self ();
	wrk->current_pid = getpid ();

	wrk->mqs_epfd = -1;
	if (vcm->cfg.use_mq_eventfd)
	{
	wrk->mqs_epfd = epoll_create (1);
	if (wrk->mqs_epfd < 0)
	{
	clib_unix_warning ("epoll_create() returned");
	goto done;
	}
	}

	wrk->session_index_by_vpp_handles = hash_create (0, sizeof (uword));
	clib_time_init (&wrk->clib_time);
	vec_validate (wrk->mq_events, 64);
	vec_validate (wrk->mq_msg_vector, 128);
	vec_reset_length (wrk->mq_msg_vector);
	vec_validate (wrk->unhandled_evts_vector, 128);
	vec_reset_length (wrk->unhandled_evts_vector);
	clib_spinlock_unlock (&vcm->workers_lock);

	done:
	return wrk;
	}

	int
	vcl_worker_register_with_vpp (void)
	{
	vcl_worker_t *wrk = vcl_worker_get_current ();

	clib_spinlock_lock (&vcm->workers_lock);

	vcm->app_state = STATE_APP_ADDING_WORKER;
	vcl_send_app_worker_add_del (1 /* is_add */ );
	if (vcl_wait_for_app_state_change (STATE_APP_READY))
	{
	VDBG (0, "failed to add worker to vpp");
	return -1;
	}
	if (pthread_key_create (&vcl_worker_stop_key, vcl_worker_cleanup_cb))
	VDBG (0, "failed to add pthread cleanup function");
	if (pthread_setspecific (vcl_worker_stop_key, &wrk->thread_id))
	VDBG (0, "failed to setup key value");

	clib_spinlock_unlock (&vcm->workers_lock);

	VDBG (0, "added worker %u", wrk->wrk_index);
	return 0;
	}

	int
	vcl_worker_set_bapi (void)
	{
	vcl_worker_t *wrk = vcl_worker_get_current ();
	int i;

	/* Find the first worker with the same pid */
	for (i = 0; i < vec_len (vcm->workers); i++)
	{
	if (i == wrk->wrk_index)
	continue;
	if (vcm->workers[i].current_pid == wrk->current_pid)
	{
	wrk->vl_input_queue = vcm->workers[i].vl_input_queue;
	wrk->my_client_index = vcm->workers[i].my_client_index;
	return 0;
	}
	}
	return -1;
	}

	svm_msg_q_t *
	vcl_worker_ctrl_mq (vcl_worker_t * wrk)
	{
	return wrk->ctrl_mq;
	}

	void
	vcl_segment_table_add (u64 segment_handle, u32 svm_segment_index)
	{
	clib_rwlock_writer_lock (&vcm->segment_table_lock);
	hash_set (vcm->segment_table, segment_handle, svm_segment_index);
	clib_rwlock_writer_unlock (&vcm->segment_table_lock);
	}

	u32
	vcl_segment_table_lookup (u64 segment_handle)
	{
	uword *seg_indexp;

	clib_rwlock_reader_lock (&vcm->segment_table_lock);
	seg_indexp = hash_get (vcm->segment_table, segment_handle);
	clib_rwlock_reader_unlock (&vcm->segment_table_lock);

	if (!seg_indexp)
	return VCL_INVALID_SEGMENT_INDEX;
	return ((u32) * seg_indexp);
	}

	void
	vcl_segment_table_del (u64 segment_handle)
	{
	clib_rwlock_writer_lock (&vcm->segment_table_lock);
	hash_unset (vcm->segment_table, segment_handle);
	clib_rwlock_writer_unlock (&vcm->segment_table_lock);
	}

	void
	vcl_cleanup_bapi (void)
	{
	socket_client_main_t *scm = &socket_client_main;
	api_main_t *am = vlibapi_get_main ();

	am->my_client_index = ~0;
	am->my_registration = 0;
	am->vl_input_queue = 0;
	am->msg_index_by_name_and_crc = 0;
	scm->socket_fd = 0;

	vl_client_api_unmap ();
	}

	int
	vcl_session_read_ready (vcl_session_t * session)
	{
	/* Assumes caller has acquired spinlock: vcm->sessions_lockp */
	if (PREDICT_FALSE (session->is_vep))
	{
	VDBG (0, "ERROR: session %u: cannot read from an epoll session!",
	session->session_index);
	return VPPCOM_EBADFD;
	}

	if (PREDICT_FALSE (!(session->session_state & (STATE_OPEN \| STATE_LISTEN))))
	{
	vcl_session_state_t state = session->session_state;
	int rv;

	rv = ((state & STATE_DISCONNECT) ? VPPCOM_ECONNRESET : VPPCOM_ENOTCONN);

	VDBG (1, "session %u [0x%llx]: not open! state 0x%x (%s), ret %d (%s)",
	session->session_index, session->vpp_handle, state,
	vppcom_session_state_str (state), rv, vppcom_retval_str (rv));
	return rv;
	}

	if (session->session_state & STATE_LISTEN)
	return clib_fifo_elts (session->accept_evts_fifo);

	if (vcl_session_is_ct (session))
	return svm_fifo_max_dequeue_cons (session->ct_rx_fifo);

	return svm_fifo_max_dequeue_cons (session->rx_fifo);
	}

	int
	vcl_session_write_ready (vcl_session_t * session)
	{
	/* Assumes caller has acquired spinlock: vcm->sessions_lockp */
	if (PREDICT_FALSE (session->is_vep))
	{
	VDBG (0, "session %u [0x%llx]: cannot write to an epoll session!",
	session->session_index, session->vpp_handle);
	return VPPCOM_EBADFD;
	}

	if (PREDICT_FALSE (session->session_state & STATE_LISTEN))
	{
	if (session->tx_fifo)
	return svm_fifo_max_enqueue_prod (session->tx_fifo);
	else
	return VPPCOM_EBADFD;
	}

	if (PREDICT_FALSE (!(session->session_state & STATE_OPEN)))
	{
	vcl_session_state_t state = session->session_state;
	int rv;

	rv = ((state & STATE_DISCONNECT) ? VPPCOM_ECONNRESET : VPPCOM_ENOTCONN);
	VDBG (0, "session %u [0x%llx]: not open! state 0x%x (%s), ret %d (%s)",
	session->session_index, session->vpp_handle, state,
	vppcom_session_state_str (state), rv, vppcom_retval_str (rv));
	return rv;
	}

	if (vcl_session_is_ct (session))
	return svm_fifo_max_enqueue_prod (session->ct_tx_fifo);

	return svm_fifo_max_enqueue_prod (session->tx_fifo);
	}

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