srtp: basic implementation based on libsrtp2

Type: feature

Signed-off-by: Florin Coras <fcoras@cisco.com>
Change-Id: Ic5e99938a5f130e83de6d590d2f89252d055bceb

13 files changed, 1537 insertions, 4 deletions

diff --git a/src/plugins/hs_apps/sapi/vpp_echo_common.c b/src/plugins/hs_apps/sapi/vpp_echo_common.c
index 02ce1686ea2..5ce04d1b75b 100644
--- a/src/plugins/hs_apps/sapi/vpp_echo_common.c
+++ b/src/plugins/hs_apps/sapi/vpp_echo_common.c
@@ -342,6 +342,9 @@ format_transport_proto (u8 * s, va_list * args)
     case TRANSPORT_PROTO_DTLS:
       s = format (s, "DTLS");
       break;
+    case TRANSPORT_PROTO_SRTP:
+      s = format (s, "SRTP");
+      break;
     default:
       s = format (s, "UNKNOWN");
       break;
diff --git a/src/plugins/hs_apps/vcl/vcl_test.h b/src/plugins/hs_apps/vcl/vcl_test.h
index c22eccc629b..4f67e03f72b 100644
--- a/src/plugins/hs_apps/vcl/vcl_test.h
+++ b/src/plugins/hs_apps/vcl/vcl_test.h
@@ -141,6 +141,7 @@ typedef struct vcl_test_session
   vppcom_endpt_t endpt;
   uint8_t ip[16];
   vppcom_data_segment_t ds[2];
+  void *opaque;
 } vcl_test_session_t;
 
 static __thread int __wrk_index = 0;
@@ -169,7 +170,7 @@ typedef struct
 
 typedef struct
 {
-  const vcl_test_proto_vft_t *protos[VPPCOM_PROTO_DTLS + 1];
+  const vcl_test_proto_vft_t *protos[VPPCOM_PROTO_SRTP + 1];
   uint32_t ckpair_index;
   vcl_test_cfg_t cfg;
   vcl_test_wrk_t *wrk;
diff --git a/src/plugins/hs_apps/vcl/vcl_test_protos.c b/src/plugins/hs_apps/vcl/vcl_test_protos.c
index 3c44093156a..60ee09265c9 100644
--- a/src/plugins/hs_apps/vcl/vcl_test_protos.c
+++ b/src/plugins/hs_apps/vcl/vcl_test_protos.c
@@ -677,6 +677,290 @@ static const vcl_test_proto_vft_t vcl_test_quic = {
 
 VCL_TEST_REGISTER_PROTO (VPPCOM_PROTO_QUIC, vcl_test_quic);
 
+static unsigned char test_key[46] = {
+  0xe1, 0xf9, 0x7a, 0x0d, 0x3e, 0x01, 0x8b, 0xe0, 0xd6, 0x4f, 0xa3, 0x2c,
+  0x06, 0xde, 0x41, 0x39, 0x0e, 0xc6, 0x75, 0xad, 0x49, 0x8a, 0xfe, 0xeb,
+  0xb6, 0x96, 0x0b, 0x3a, 0xab, 0xe6, 0xc1, 0x73, 0xc3, 0x17, 0xf2, 0xda,
+  0xbe, 0x35, 0x77, 0x93, 0xb6, 0x96, 0x0b, 0x3a, 0xab, 0xe6
+};
+
+typedef struct
+{
+  unsigned char cc : 4;
+  unsigned char x : 1;
+  unsigned char p : 1;
+  unsigned char version : 2;
+  unsigned char pt : 7;
+  unsigned char m : 1;
+  uint16_t seq;
+  uint32_t ts;
+  uint32_t ssrc;
+} rtp_hdr_t;
+
+typedef struct
+{
+  rtp_hdr_t tx_hdr;
+  rtp_hdr_t rx_hdr;
+} rtp_headers_t;
+
+typedef struct transport_endpt_cfg_srtp_policy
+{
+  uint32_t ssrc_type;
+  uint32_t ssrc_value;
+  uint32_t window_size;
+  uint8_t allow_repeat_tx;
+  uint8_t key_len;
+  uint8_t key[46];
+} transport_endpt_cfg_srtp_policy_t;
+
+typedef struct transport_endpt_cfg_srtp
+{
+  transport_endpt_cfg_srtp_policy_t policy[2];
+} transport_endpt_cfg_srtp_t;
+
+static void
+vt_session_add_srtp_policy (vcl_test_session_t *ts, int is_connect)
+{
+  transport_endpt_cfg_srtp_t *srtp_cfg;
+  transport_endpt_cfg_srtp_policy_t *test_policy;
+  uint32_t rx_ssrc, tx_ssrc;
+  uint32_t cfg_size;
+
+  rx_ssrc = is_connect ? 0xcafebeef : 0xbeefcafe;
+  tx_ssrc = is_connect ? 0xbeefcafe : 0xcafebeef;
+
+  cfg_size = sizeof (transport_endpt_cfg_srtp_t);
+  srtp_cfg = malloc (cfg_size);
+  memset (srtp_cfg, 0, cfg_size);
+
+  test_policy = &srtp_cfg->policy[0];
+  test_policy->ssrc_type = 1 /* ssrc_specific */;
+  test_policy->ssrc_value = rx_ssrc;
+  memcpy (test_policy->key, test_key, sizeof (test_key));
+  test_policy->key_len = sizeof (test_key);
+  test_policy->window_size = 128;
+  test_policy->allow_repeat_tx = 1;
+
+  test_policy = &srtp_cfg->policy[1];
+  test_policy->ssrc_type = 1 /* ssrc_specific */;
+  test_policy->ssrc_value = tx_ssrc;
+  memcpy (test_policy->key, test_key, sizeof (test_key));
+  test_policy->key_len = sizeof (test_key);
+  test_policy->window_size = 128;
+  test_policy->allow_repeat_tx = 1;
+
+  vppcom_session_attr (ts->fd, VPPCOM_ATTR_SET_ENDPT_EXT_CFG, srtp_cfg,
+		       &cfg_size);
+  free (srtp_cfg);
+}
+
+static void
+vt_srtp_session_init (vcl_test_session_t *ts, int is_connect)
+{
+  uint32_t rx_ssrc, tx_ssrc;
+  rtp_headers_t *rtp_hdrs;
+  rtp_hdr_t *hdr;
+
+  rx_ssrc = is_connect ? 0xcafebeef : 0xbeefcafe;
+  tx_ssrc = is_connect ? 0xbeefcafe : 0xcafebeef;
+
+  rtp_hdrs = malloc (sizeof (rtp_headers_t));
+  memset (rtp_hdrs, 0, sizeof (*rtp_hdrs));
+  ts->opaque = rtp_hdrs;
+
+  hdr = &rtp_hdrs->rx_hdr;
+  hdr->version = 2;
+  hdr->p = 0;
+  hdr->x = 0;
+  hdr->cc = 0;
+  hdr->m = 0;
+  hdr->pt = 0x1;
+  hdr->seq = 0;
+  hdr->ts = 0;
+  hdr->ssrc = htonl (rx_ssrc);
+
+  hdr = &rtp_hdrs->tx_hdr;
+  hdr->version = 2;
+  hdr->p = 0;
+  hdr->x = 0;
+  hdr->cc = 0;
+  hdr->m = 0;
+  hdr->pt = 0x1;
+  hdr->seq = 0;
+  hdr->ts = 0;
+  hdr->ssrc = htonl (tx_ssrc);
+}
+
+static int
+vt_srtp_write (vcl_test_session_t *ts, void *buf, uint32_t nbytes)
+{
+  int tx_bytes = 0, nbytes_left = nbytes, rv;
+  vcl_test_stats_t *stats = &ts->stats;
+  rtp_hdr_t *hdr;
+
+  hdr = &((rtp_headers_t *) ts->opaque)->tx_hdr;
+  hdr->seq = htons (ntohs (hdr->seq) + 1);
+  hdr->ts = htonl (ntohl (hdr->ts) + 1);
+
+  memcpy (buf, hdr, sizeof (*hdr));
+
+  do
+    {
+      stats->tx_xacts++;
+      rv = vppcom_session_write (ts->fd, buf, nbytes_left);
+      if (rv < 0)
+	{
+	  if ((rv == VPPCOM_EAGAIN || rv == VPPCOM_EWOULDBLOCK))
+	    stats->tx_eagain++;
+	  break;
+	}
+      tx_bytes += rv;
+      nbytes_left = nbytes_left - rv;
+      buf += rv;
+      stats->tx_incomp++;
+    }
+  while (tx_bytes != nbytes);
+
+  if (tx_bytes < 0)
+    return 0;
+
+  stats->tx_bytes += tx_bytes;
+
+  return (tx_bytes);
+}
+
+static inline int
+vt_srtp_read (vcl_test_session_t *ts, void *buf, uint32_t nbytes)
+{
+  vcl_test_stats_t *stats = &ts->stats;
+  rtp_hdr_t *hdr;
+  int rx_bytes;
+
+  stats->rx_xacts++;
+  rx_bytes = vppcom_session_read (ts->fd, buf, nbytes);
+
+  if (rx_bytes <= 0)
+    {
+      if (rx_bytes == VPPCOM_EAGAIN || rx_bytes == VPPCOM_EWOULDBLOCK)
+	stats->rx_eagain++;
+      else
+	return -1;
+    }
+
+  if (rx_bytes < nbytes)
+    stats->rx_incomp++;
+
+  stats->rx_bytes += rx_bytes;
+
+  hdr = &((rtp_headers_t *) ts->opaque)->rx_hdr;
+  if (((rtp_hdr_t *) buf)->ssrc != hdr->ssrc)
+    hdr->ssrc = ((rtp_hdr_t *) buf)->ssrc;
+  return (rx_bytes);
+}
+
+static int
+vt_srtp_connect (vcl_test_session_t *ts, vppcom_endpt_t *endpt)
+{
+  uint32_t flags, flen;
+  int rv;
+
+  ts->fd = vppcom_session_create (VPPCOM_PROTO_SRTP, 0 /* is_nonblocking */);
+  if (ts->fd < 0)
+    {
+      vterr ("vppcom_session_create()", ts->fd);
+      return ts->fd;
+    }
+
+  vt_session_add_srtp_policy (ts, 1 /* is connect */);
+
+  /* Connect is blocking */
+  rv = vppcom_session_connect (ts->fd, endpt);
+  if (rv < 0)
+    {
+      vterr ("vppcom_session_connect()", rv);
+      return rv;
+    }
+
+  ts->read = vt_srtp_read;
+  ts->write = vt_srtp_write;
+  flags = O_NONBLOCK;
+  flen = sizeof (flags);
+  vppcom_session_attr (ts->fd, VPPCOM_ATTR_SET_FLAGS, &flags, &flen);
+  vtinf ("Test session %d (fd %d) connected.", ts->session_index, ts->fd);
+
+  vt_srtp_session_init (ts, 1 /* is connect */);
+
+  return 0;
+}
+
+static int
+vt_srtp_listen (vcl_test_session_t *ts, vppcom_endpt_t *endpt)
+{
+  int rv;
+
+  ts->fd = vppcom_session_create (VPPCOM_PROTO_SRTP, 1 /* is_nonblocking */);
+  if (ts->fd < 0)
+    {
+      vterr ("vppcom_session_create()", ts->fd);
+      return ts->fd;
+    }
+
+  vt_session_add_srtp_policy (ts, 0 /* is connect */);
+
+  rv = vppcom_session_bind (ts->fd, endpt);
+  if (rv < 0)
+    {
+      vterr ("vppcom_session_bind()", rv);
+      return rv;
+    }
+
+  rv = vppcom_session_listen (ts->fd, 10);
+  if (rv < 0)
+    {
+      vterr ("vppcom_session_listen()", rv);
+      return rv;
+    }
+
+  return 0;
+}
+
+static int
+vt_srtp_accept (int listen_fd, vcl_test_session_t *ts)
+{
+  int client_fd;
+
+  client_fd = vppcom_session_accept (listen_fd, &ts->endpt, 0);
+  if (client_fd < 0)
+    {
+      vterr ("vppcom_session_accept()", client_fd);
+      return client_fd;
+    }
+  ts->fd = client_fd;
+  ts->is_open = 1;
+  ts->read = vt_srtp_read;
+  ts->write = vt_srtp_write;
+
+  vt_srtp_session_init (ts, 0 /* is connect */);
+
+  return 0;
+}
+
+static int
+vt_srtp_close (vcl_test_session_t *ts)
+{
+  free (ts->opaque);
+  return 0;
+}
+
+static const vcl_test_proto_vft_t vcl_test_srtp = {
+  .open = vt_srtp_connect,
+  .listen = vt_srtp_listen,
+  .accept = vt_srtp_accept,
+  .close = vt_srtp_close,
+};
+
+VCL_TEST_REGISTER_PROTO (VPPCOM_PROTO_SRTP, vcl_test_srtp);
+
 /*
  * fd.io coding-style-patch-verification: ON
  *
diff --git a/src/plugins/srtp/CMakeLists.txt b/src/plugins/srtp/CMakeLists.txt
new file mode 100644
index 00000000000..acbdf3177d8
--- /dev/null
+++ b/src/plugins/srtp/CMakeLists.txt
@@ -0,0 +1,41 @@
+# Copyright (c) 2021 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 (CheckFunctionExists)
+
+vpp_plugin_find_library(srtp SRTP_LIB libsrtp2.a)
+
+if (NOT SRTP_LIB)
+  message(WARNING "srtp plugin - srtp2 lib not found - plugin disabled")
+  return()
+endif()
+
+vpp_find_path(SRTP_INCLUDE_DIR NAMES srtp2/srtp.h)
+
+if (NOT SRTP_INCLUDE_DIR)
+  message(WARNING "srtp plugin - srtp.h not found - plugin disabled")
+  return()
+endif()
+
+include_directories (${SRTP_INCLUDE_DIR})
+
+set(CMAKE_REQUIRED_FLAGS "-fPIC -shared -pthread -Wno-unused-command-line-argument ${SRTP_LIB}")
+set(CMAKE_REQUIRED_INCLUDES "${SRTP_INCLUDE_DIR}")
+
+add_vpp_plugin(srtp
+  SOURCES
+  srtp.c
+
+  LINK_LIBRARIES
+  ${SRTP_LIB}
+)
diff --git a/src/plugins/srtp/FEATURE.yaml b/src/plugins/srtp/FEATURE.yaml
new file mode 100644
index 00000000000..dbbe7121962
--- /dev/null
+++ b/src/plugins/srtp/FEATURE.yaml
@@ -0,0 +1,8 @@
+---
+name: SRTP (Secure Real-time Transport Protocol)
+maintainer: Florin Coras <fcoras@cisco.com>
+features:
+  - SRTP transport protocol implementation
+description: "SRTP transport protocol implementation based on libsrtp2"
+state: experimental
+properties: [MULTITHREAD]
diff --git a/src/plugins/srtp/srtp.c b/src/plugins/srtp/srtp.c
new file mode 100644
index 00000000000..98bf9085da3
--- /dev/null
+++ b/src/plugins/srtp/srtp.c
@@ -0,0 +1,994 @@
+/*
+ * Copyright (c) 2021 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 <srtp/srtp.h>
+#include <vnet/session/application_interface.h>
+#include <vnet/session/session.h>
+
+static srtp_main_t srtp_main;
+
+static void srtp_disconnect (u32 ctx_handle, u32 thread_index);
+static void srtp_disconnect_transport (srtp_tc_t *ctx);
+
+static inline u32
+srtp_ctx_alloc_w_thread (u32 thread_index)
+{
+  srtp_tc_t *ctx;
+  pool_get_zero (srtp_main.ctx_pool[thread_index], ctx);
+  ctx->c_thread_index = thread_index;
+  ctx->srtp_ctx_handle = ctx - srtp_main.ctx_pool[thread_index];
+  ctx->app_session_handle = SESSION_INVALID_HANDLE;
+  return ctx->srtp_ctx_handle;
+}
+
+static inline srtp_tc_t *
+srtp_ctx_get_w_thread (u32 ctx_index, u32 thread_index)
+{
+  return pool_elt_at_index (srtp_main.ctx_pool[thread_index], ctx_index);
+}
+
+static void
+srtp_init_policy (srtp_tc_t *ctx, transport_endpt_cfg_srtp_t *cfg)
+{
+  transport_endpt_cfg_srtp_policy_t *sp_cfg;
+  srtp_policy_t *sp;
+  int i;
+
+  for (i = 0; i < 2; i++)
+    {
+      sp = &ctx->srtp_policy[i];
+      sp_cfg = &cfg->policies[i];
+
+      srtp_crypto_policy_set_rtp_default (&sp->rtp);
+      srtp_crypto_policy_set_rtcp_default (&sp->rtcp);
+      sp->ssrc.type = sp_cfg->ssrc_type;
+      sp->ssrc.value = sp_cfg->ssrc_value;
+      sp->key = clib_mem_alloc (sp_cfg->key_len);
+      clib_memcpy (sp->key, sp_cfg->key, sp_cfg->key_len);
+      sp->ekt = 0;
+      sp->next = i < 1 ? &ctx->srtp_policy[i + 1] : 0;
+      sp->window_size = sp_cfg->window_size;
+      sp->allow_repeat_tx = sp_cfg->allow_repeat_tx;
+    }
+}
+
+static void
+srtp_ctx_free_policy (srtp_tc_t *ctx)
+{
+  clib_mem_free (ctx->srtp_policy[0].key);
+  clib_mem_free (ctx->srtp_policy[1].key);
+}
+
+void
+srtp_ctx_free (srtp_tc_t *ctx)
+{
+  if (!ctx->is_migrated)
+    srtp_ctx_free_policy (ctx);
+  pool_put (srtp_main.ctx_pool[ctx->c_thread_index], ctx);
+}
+
+static inline u32
+srtp_ctx_attach (u32 thread_index, void *ctx_ptr)
+{
+  srtp_tc_t *ctx;
+
+  pool_get (srtp_main.ctx_pool[thread_index], ctx);
+  clib_memcpy (ctx, ctx_ptr, sizeof (*ctx));
+
+  ctx->c_thread_index = thread_index;
+  ctx->srtp_ctx_handle = ctx - srtp_main.ctx_pool[thread_index];
+  return 0;
+}
+
+static inline void *
+srtp_ctx_detach (srtp_tc_t *ctx)
+{
+  srtp_tc_t *sc;
+
+  sc = clib_mem_alloc (sizeof (*sc));
+  clib_memcpy (sc, ctx, sizeof (*sc));
+
+  return sc;
+}
+
+u32
+srtp_listener_ctx_alloc (void)
+{
+  srtp_main_t *sm = &srtp_main;
+  srtp_tc_t *ctx;
+
+  pool_get_zero (sm->listener_ctx_pool, ctx);
+  return ctx - sm->listener_ctx_pool;
+}
+
+void
+srtp_listener_ctx_free (srtp_tc_t *ctx)
+{
+  srtp_ctx_free_policy (ctx);
+  if (CLIB_DEBUG)
+    clib_memset (ctx, 0xfb, sizeof (*ctx));
+  pool_put (srtp_main.listener_ctx_pool, ctx);
+}
+
+srtp_tc_t *
+srtp_listener_ctx_get (u32 ctx_index)
+{
+  return pool_elt_at_index (srtp_main.listener_ctx_pool, ctx_index);
+}
+
+u32
+srtp_listener_ctx_index (srtp_tc_t *ctx)
+{
+  return (ctx - srtp_main.listener_ctx_pool);
+}
+
+static int
+srtp_ctx_init_client (srtp_tc_t *ctx)
+{
+  session_t *app_session;
+  app_worker_t *app_wrk;
+  session_error_t err;
+
+  if (srtp_create (&ctx->srtp_ctx, &ctx->srtp_policy[0]) != srtp_err_status_ok)
+    {
+      SRTP_DBG (0, "failed to init srtp ctx");
+      return -1;
+    }
+
+  app_wrk = app_worker_get (ctx->parent_app_wrk_index);
+  app_session = session_get (ctx->c_s_index, ctx->c_thread_index);
+  app_session->app_wrk_index = ctx->parent_app_wrk_index;
+  app_session->connection_index = ctx->srtp_ctx_handle;
+  app_session->session_type =
+    session_type_from_proto_and_ip (TRANSPORT_PROTO_SRTP, ctx->udp_is_ip4);
+
+  if ((err = app_worker_init_connected (app_wrk, app_session)))
+    goto failed;
+
+  app_session->session_state = SESSION_STATE_READY;
+  if (app_worker_connect_notify (app_wrk, app_session, SESSION_E_NONE,
+				 ctx->parent_app_api_context))
+    {
+      SRTP_DBG (0, "failed to notify app");
+      app_session->session_state = SESSION_STATE_CONNECTING;
+      srtp_disconnect (ctx->srtp_ctx_handle, vlib_get_thread_index ());
+      return -1;
+    }
+
+  ctx->app_session_handle = session_handle (app_session);
+
+  return 0;
+
+failed:
+  /* Free app session pre-allocated when transport was established */
+  session_free (session_get (ctx->c_s_index, ctx->c_thread_index));
+  ctx->no_app_session = 1;
+  srtp_disconnect (ctx->srtp_ctx_handle, vlib_get_thread_index ());
+  return app_worker_connect_notify (app_wrk, 0, err,
+				    ctx->parent_app_api_context);
+}
+
+static int
+srtp_ctx_init_server (srtp_tc_t *ctx)
+{
+  session_t *app_listener, *app_session;
+  app_worker_t *app_wrk;
+  srtp_tc_t *lctx;
+  int rv;
+
+  if (srtp_create (&ctx->srtp_ctx, ctx->srtp_policy) != srtp_err_status_ok)
+    return -1;
+
+  lctx = srtp_listener_ctx_get (ctx->listener_ctx_index);
+  app_listener = listen_session_get_from_handle (lctx->app_session_handle);
+
+  app_session = session_get (ctx->c_s_index, ctx->c_thread_index);
+  app_session->app_wrk_index = ctx->parent_app_wrk_index;
+  app_session->connection_index = ctx->srtp_ctx_handle;
+  app_session->session_type = app_listener->session_type;
+  app_session->listener_handle = listen_session_get_handle (app_listener);
+  app_session->session_state = SESSION_STATE_ACCEPTING;
+
+  if ((rv = app_worker_init_accepted (app_session)))
+    {
+      SRTP_DBG (1, "failed to allocate fifos");
+      session_free (app_session);
+      return rv;
+    }
+  ctx->app_session_handle = session_handle (app_session);
+  ctx->parent_app_wrk_index = app_session->app_wrk_index;
+  app_wrk = app_worker_get (app_session->app_wrk_index);
+  return app_worker_accept_notify (app_wrk, app_session);
+}
+
+static int
+srtp_ctx_deinit (srtp_tc_t *ctx)
+{
+  if (srtp_dealloc (ctx->srtp_ctx))
+    SRTP_DBG (0, "%u failed to cleanup srtp state", ctx->c_c_index);
+  return 0;
+}
+
+static inline int
+srtp_ctx_write (srtp_tc_t *ctx, session_t *app_session,
+		transport_send_params_t *sp)
+{
+  u32 n_wrote = 0, to_deq, dgram_sz;
+  session_dgram_pre_hdr_t hdr;
+  app_session_transport_t at;
+  svm_msg_q_t *mq;
+  session_t *us;
+  u8 buf[2000];
+  int rv, len;
+
+  sp->max_burst_size = sp->max_burst_size * TRANSPORT_PACER_MIN_MSS;
+
+  us = session_get_from_handle (ctx->srtp_session_handle);
+  to_deq = svm_fifo_max_dequeue_cons (app_session->tx_fifo);
+  mq = session_main_get_vpp_event_queue (us->thread_index);
+
+  while (to_deq > 0)
+    {
+      /* Peeking only pre-header dgram because the session is connected */
+      rv = svm_fifo_peek (app_session->tx_fifo, 0, sizeof (hdr), (u8 *) &hdr);
+      ASSERT (rv == sizeof (hdr) && hdr.data_length < vec_len (buf));
+      ASSERT (to_deq >= hdr.data_length + SESSION_CONN_HDR_LEN);
+
+      dgram_sz = hdr.data_length + SESSION_CONN_HDR_LEN;
+      if (svm_fifo_max_enqueue_prod (us->tx_fifo) < dgram_sz + 1000)
+	{
+	  svm_fifo_add_want_deq_ntf (us->tx_fifo, SVM_FIFO_WANT_DEQ_NOTIF);
+	  transport_connection_deschedule (&ctx->connection);
+	  sp->flags |= TRANSPORT_SND_F_DESCHED;
+	  goto done;
+	}
+
+      rv = svm_fifo_peek (app_session->tx_fifo, SESSION_CONN_HDR_LEN,
+			  hdr.data_length, buf);
+      ASSERT (rv == hdr.data_length);
+      svm_fifo_dequeue_drop (app_session->tx_fifo, dgram_sz);
+
+      len = rv;
+
+      rv = srtp_protect (ctx->srtp_ctx, buf, &len);
+      if (rv != srtp_err_status_ok)
+	{
+	  SRTP_DBG (0, "failed to protect %u", rv);
+	  return 0;
+	}
+
+      rv = app_send_dgram_raw (us->tx_fifo, &at, mq, (u8 *) buf, len,
+			       SESSION_IO_EVT_TX, 1 /* do_evt */,
+			       0 /* noblock */);
+      ASSERT (rv == len);
+
+      n_wrote += rv;
+      to_deq -= dgram_sz;
+    }
+
+done:
+
+  if (svm_fifo_needs_deq_ntf (app_session->tx_fifo, n_wrote))
+    session_dequeue_notify (app_session);
+
+  if (n_wrote)
+    {
+      if (svm_fifo_set_event (us->tx_fifo))
+	session_send_io_evt_to_thread (us->tx_fifo, SESSION_IO_EVT_TX);
+    }
+
+  if (PREDICT_FALSE (ctx->app_closed &&
+		     !svm_fifo_max_enqueue_prod (us->rx_fifo)))
+    {
+      srtp_disconnect_transport (ctx);
+      session_transport_closed_notify (&ctx->connection);
+    }
+
+  return n_wrote > 0 ? clib_max (n_wrote / TRANSPORT_PACER_MIN_MSS, 1) : 0;
+}
+
+int
+srtp_add_vpp_q_builtin_rx_evt (session_t *s)
+{
+  if (svm_fifo_set_event (s->rx_fifo))
+    session_send_io_evt_to_thread (s->rx_fifo, SESSION_IO_EVT_BUILTIN_RX);
+  return 0;
+}
+
+void
+srtp_notify_app_enqueue (srtp_tc_t *ctx, session_t *app_session)
+{
+  app_worker_t *app_wrk;
+  app_wrk = app_worker_get_if_valid (app_session->app_wrk_index);
+  if (PREDICT_TRUE (app_wrk != 0))
+    app_worker_lock_and_send_event (app_wrk, app_session, SESSION_IO_EVT_RX);
+}
+
+static inline int
+srtp_ctx_read (srtp_tc_t *ctx, session_t *us)
+{
+  app_session_transport_t at;
+  session_dgram_hdr_t hdr;
+  session_t *app_session;
+  u32 n_read = 0;
+  u8 buf[2000];
+  int rv, len;
+
+  app_session = session_get_from_handle (ctx->app_session_handle);
+  svm_fifo_fill_chunk_list (app_session->rx_fifo);
+
+  while (svm_fifo_max_dequeue_cons (us->rx_fifo) > 0)
+    {
+      if (svm_fifo_max_enqueue_prod (app_session->rx_fifo) < 2000)
+	{
+	  srtp_add_vpp_q_builtin_rx_evt (us);
+	  goto done;
+	}
+
+      rv = app_recv_dgram_raw (us->rx_fifo, (u8 *) buf, 2000, &at,
+			       0 /* clear evt */, 0 /* peek */);
+      ASSERT (rv > 0);
+      len = rv;
+
+      rv = srtp_unprotect (ctx->srtp_ctx, buf, &len);
+
+      if (rv != srtp_err_status_ok)
+	{
+	  SRTP_DBG (0, "failed to unprotect %d", rv);
+	  return 0;
+	}
+      n_read += len;
+
+      hdr.data_length = len;
+      hdr.data_offset = 0;
+
+      svm_fifo_seg_t segs[2] = { { (u8 *) &hdr, sizeof (hdr) }, { buf, len } };
+
+      rv = svm_fifo_enqueue_segments (app_session->rx_fifo, segs, 2,
+				      0 /* allow partial */);
+      ASSERT (rv > 0);
+    }
+
+done:
+
+  srtp_notify_app_enqueue (ctx, app_session);
+
+  return n_read;
+}
+
+int
+srtp_add_segment_callback (u32 client_index, u64 segment_handle)
+{
+  /* No-op for builtin */
+  return 0;
+}
+
+int
+srtp_del_segment_callback (u32 client_index, u64 segment_handle)
+{
+  return 0;
+}
+
+void
+srtp_session_disconnect_callback (session_t *us)
+{
+  clib_warning ("udp %u disconnected?", us->session_index);
+}
+
+void
+srtp_session_reset_callback (session_t *us)
+{
+  clib_warning ("udp %u reset?", us->session_index);
+}
+
+static int
+srtp_session_connected_callback (u32 srtp_app_index, u32 ctx_handle,
+				 session_t *us, session_error_t err)
+{
+  session_t *app_session;
+  session_type_t st;
+  srtp_tc_t *ctx;
+
+  ctx = srtp_ctx_get_w_thread (ctx_handle, 1 /* udp allocs on thread 1 */);
+
+  ctx->srtp_session_handle = session_handle (us);
+  ctx->c_flags |= TRANSPORT_CONNECTION_F_NO_LOOKUP;
+  us->opaque = ctx_handle;
+
+  /* Preallocate app session. Avoids allocating a session on srtp_session rx
+   * and potentially invalidating the session pool */
+  app_session = session_alloc (ctx->c_thread_index);
+  app_session->session_state = SESSION_STATE_CREATED;
+  ctx->c_s_index = app_session->session_index;
+
+  st = session_type_from_proto_and_ip (TRANSPORT_PROTO_SRTP, ctx->udp_is_ip4);
+  app_session->session_type = st;
+  app_session->connection_index = ctx->srtp_ctx_handle;
+
+  return srtp_ctx_init_client (ctx);
+}
+
+int
+srtp_session_accept_callback (session_t *us)
+{
+  session_t *srtp_listener, *app_session;
+  srtp_tc_t *lctx, *ctx;
+  u32 ctx_handle;
+
+  srtp_listener = listen_session_get_from_handle (us->listener_handle);
+  lctx = srtp_listener_ctx_get (srtp_listener->opaque);
+
+  ctx_handle = srtp_ctx_alloc_w_thread (us->thread_index);
+  ctx = srtp_ctx_get_w_thread (ctx_handle, us->thread_index);
+  clib_memcpy_fast (ctx, lctx, sizeof (*lctx));
+  ctx->c_thread_index = vlib_get_thread_index ();
+  ctx->srtp_ctx_handle = ctx_handle;
+  us->session_state = SESSION_STATE_READY;
+  us->opaque = ctx_handle;
+  ctx->srtp_session_handle = session_handle (us);
+  ctx->listener_ctx_index = srtp_listener->opaque;
+  ctx->c_flags |= TRANSPORT_CONNECTION_F_NO_LOOKUP;
+
+  ctx->srtp_policy[0].key = clib_mem_alloc (SRTP_MAX_KEYLEN);
+  clib_memcpy (ctx->srtp_policy[0].key, lctx->srtp_policy[0].key,
+	       SRTP_MAX_KEYLEN);
+  ctx->srtp_policy[1].key = clib_mem_alloc (SRTP_MAX_KEYLEN);
+  clib_memcpy (ctx->srtp_policy[1].key, lctx->srtp_policy[1].key,
+	       SRTP_MAX_KEYLEN);
+
+  app_session = session_alloc (ctx->c_thread_index);
+  app_session->session_state = SESSION_STATE_CREATED;
+  ctx->c_s_index = app_session->session_index;
+
+  SRTP_DBG (1, "Accept on listener %u new connection [%u]%x",
+	    srtp_listener->opaque, vlib_get_thread_index (), ctx_handle);
+
+  return srtp_ctx_init_server (ctx);
+}
+
+int
+srtp_app_rx_callback (session_t *us)
+{
+  srtp_tc_t *ctx;
+
+  ctx = srtp_ctx_get_w_thread (us->opaque, us->thread_index);
+  srtp_ctx_read (ctx, us);
+  return 0;
+}
+
+int
+srtp_app_tx_callback (session_t *us)
+{
+  srtp_tc_t *ctx;
+
+  ctx = srtp_ctx_get_w_thread (us->opaque, us->thread_index);
+  transport_connection_reschedule (&ctx->connection);
+
+  return 0;
+}
+
+static void
+srtp_app_session_cleanup (session_t *s, session_cleanup_ntf_t ntf)
+{
+  srtp_tc_t *ctx;
+
+  if (ntf == SESSION_CLEANUP_TRANSPORT)
+    {
+      /* Allow cleanup of tcp session */
+      if (s->session_state == SESSION_STATE_TRANSPORT_DELETED)
+	session_close (s);
+      return;
+    }
+
+  ctx = srtp_ctx_get_w_thread (s->opaque, s->thread_index);
+  if (!ctx->no_app_session)
+    session_transport_delete_notify (&ctx->connection);
+  srtp_ctx_deinit (ctx);
+  srtp_ctx_free (ctx);
+}
+
+static void
+srtp_migrate_ctx_reply (void *arg)
+{
+  u32 ctx_index = pointer_to_uword (arg);
+  srtp_tc_t *ctx;
+
+  ctx = srtp_ctx_get_w_thread (ctx_index, vlib_get_thread_index ());
+  srtp_ctx_free (ctx);
+}
+
+static void
+srtp_migrate_ctx (void *arg)
+{
+  u32 ctx_handle, thread_index, old_thread_index, old_ctx_index;
+  srtp_tc_t *ctx = (srtp_tc_t *) arg;
+  session_t *us, *new_app_session;
+  void *rargs;
+
+  old_thread_index = ctx->c_thread_index;
+  old_ctx_index = ctx->c_c_index;
+  thread_index = session_thread_from_handle (ctx->srtp_session_handle);
+  ASSERT (thread_index == vlib_get_thread_index ());
+
+  ctx_handle = srtp_ctx_attach (thread_index, ctx);
+  ctx = srtp_ctx_get_w_thread (ctx_handle, thread_index);
+  ctx->srtp_ctx_handle = ctx_handle;
+  SRTP_DBG (1, "migrated ctx handle %u", ctx_handle);
+
+  us = session_get_from_handle (ctx->srtp_session_handle);
+  us->opaque = ctx_handle;
+  us->flags &= ~SESSION_F_IS_MIGRATING;
+  if (svm_fifo_max_dequeue (us->tx_fifo))
+    session_send_io_evt_to_thread (us->tx_fifo, SESSION_IO_EVT_TX);
+
+  /* Migrate app session as well */
+  session_dgram_connect_notify (&ctx->connection, old_thread_index,
+				&new_app_session);
+
+  /* Call back original thread and ask for cleanup */
+  rargs = uword_to_pointer ((uword) old_ctx_index, void *);
+  session_send_rpc_evt_to_thread (old_thread_index, srtp_migrate_ctx_reply,
+				  rargs);
+}
+
+static void
+srtp_session_migrate_callback (session_t *us, session_handle_t new_sh)
+{
+  u32 new_thread = session_thread_from_handle (new_sh);
+  srtp_tc_t *ctx, *cloned_ctx;
+
+  ctx = srtp_ctx_get_w_thread (us->opaque, us->thread_index);
+  ctx->srtp_session_handle = new_sh;
+  cloned_ctx = srtp_ctx_detach (ctx);
+  SRTP_DBG (1, "ctx %u attached to udp %x session migrating",
+	    cloned_ctx->c_c_index, new_sh);
+
+  session_send_rpc_evt_to_thread (new_thread, srtp_migrate_ctx,
+				  (void *) cloned_ctx);
+
+  /* Can't free ctx now because app might be sending as srtp is not
+   * connection oriented, so it won't wait for a handshake */
+  ctx->is_migrated = 1;
+}
+
+static session_cb_vft_t srtp_app_cb_vft = {
+  .session_accept_callback = srtp_session_accept_callback,
+  .session_disconnect_callback = srtp_session_disconnect_callback,
+  .session_connected_callback = srtp_session_connected_callback,
+  .session_reset_callback = srtp_session_reset_callback,
+  .add_segment_callback = srtp_add_segment_callback,
+  .del_segment_callback = srtp_del_segment_callback,
+  .builtin_app_rx_callback = srtp_app_rx_callback,
+  .builtin_app_tx_callback = srtp_app_tx_callback,
+  .session_migrate_callback = srtp_session_migrate_callback,
+  .session_cleanup_callback = srtp_app_session_cleanup,
+};
+
+static clib_error_t *
+srtp_enable (vlib_main_t *vm, u8 is_en)
+{
+  u32 add_segment_size = 256 << 20, first_seg_size = 32 << 20;
+  vnet_app_detach_args_t _da, *da = &_da;
+  vnet_app_attach_args_t _a, *a = &_a;
+  u64 options[APP_OPTIONS_N_OPTIONS];
+  srtp_main_t *sm = &srtp_main;
+  u32 fifo_size = 128 << 12;
+
+  if (!is_en)
+    {
+      da->app_index = sm->app_index;
+      da->api_client_index = APP_INVALID_INDEX;
+      vnet_application_detach (da);
+      return 0;
+    }
+
+  srtp_init ();
+  vec_validate (sm->ctx_pool, vlib_num_workers ());
+
+  first_seg_size = sm->first_seg_size ? sm->first_seg_size : first_seg_size;
+  fifo_size = sm->fifo_size ? sm->fifo_size : fifo_size;
+
+  clib_memset (a, 0, sizeof (*a));
+  clib_memset (options, 0, sizeof (options));
+
+  a->session_cb_vft = &srtp_app_cb_vft;
+  a->api_client_index = APP_INVALID_INDEX;
+  a->options = options;
+  a->name = format (0, "srtp");
+  a->options[APP_OPTIONS_SEGMENT_SIZE] = first_seg_size;
+  a->options[APP_OPTIONS_ADD_SEGMENT_SIZE] = add_segment_size;
+  a->options[APP_OPTIONS_RX_FIFO_SIZE] = fifo_size;
+  a->options[APP_OPTIONS_TX_FIFO_SIZE] = fifo_size;
+  a->options[APP_OPTIONS_FLAGS] = APP_OPTIONS_FLAGS_IS_BUILTIN;
+  a->options[APP_OPTIONS_FLAGS] |= APP_OPTIONS_FLAGS_USE_GLOBAL_SCOPE;
+  a->options[APP_OPTIONS_FLAGS] |= APP_OPTIONS_FLAGS_IS_TRANSPORT_APP;
+
+  if (vnet_application_attach (a))
+    return clib_error_return (0, "failed to attach srtp app");
+
+  sm->app_index = a->app_index;
+  vec_free (a->name);
+
+  return 0;
+}
+
+int
+srtp_connect (transport_endpoint_cfg_t *tep)
+{
+  vnet_connect_args_t _cargs = { {}, }, *cargs = &_cargs;
+  session_endpoint_cfg_t *sep;
+  srtp_main_t *sm = &srtp_main;
+  app_worker_t *app_wrk;
+  application_t *app;
+  srtp_tc_t *ctx;
+  u32 ctx_index;
+  int rv;
+
+  sep = (session_endpoint_cfg_t *) tep;
+  if (!sep->ext_cfg)
+    return SESSION_E_NOEXTCFG;
+
+  app_wrk = app_worker_get (sep->app_wrk_index);
+  app = application_get (app_wrk->app_index);
+
+  ctx_index = srtp_ctx_alloc_w_thread (1 /* because of udp */);
+  ctx = srtp_ctx_get_w_thread (ctx_index, 1);
+  ctx->parent_app_wrk_index = sep->app_wrk_index;
+  ctx->parent_app_api_context = sep->opaque;
+  ctx->udp_is_ip4 = sep->is_ip4;
+  ctx->srtp_ctx_handle = ctx_index;
+
+  srtp_init_policy (ctx, (transport_endpt_cfg_srtp_t *) sep->ext_cfg->data);
+
+  clib_memcpy_fast (&cargs->sep, sep, sizeof (session_endpoint_t));
+  cargs->sep.transport_proto = TRANSPORT_PROTO_UDP;
+  cargs->sep_ext.transport_flags = TRANSPORT_CFG_F_CONNECTED;
+  cargs->app_index = sm->app_index;
+  cargs->api_context = ctx_index;
+  cargs->sep_ext.ns_index = app->ns_index;
+  if ((rv = vnet_connect (cargs)))
+    return rv;
+
+  SRTP_DBG (1, "New connect request %u", ctx_index);
+  return 0;
+}
+
+static void
+srtp_disconnect_transport (srtp_tc_t *ctx)
+{
+  vnet_disconnect_args_t a = {
+    .handle = ctx->srtp_session_handle,
+    .app_index = srtp_main.app_index,
+  };
+
+  if (vnet_disconnect_session (&a))
+    SRTP_DBG (0, "disconnect returned");
+}
+
+static void
+srtp_disconnect (u32 ctx_handle, u32 thread_index)
+{
+  session_t *app_session;
+  srtp_tc_t *ctx;
+
+  SRTP_DBG (1, "App disconnecting %x", ctx_handle);
+
+  ctx = srtp_ctx_get_w_thread (ctx_handle, thread_index);
+
+  app_session = session_get_from_handle (ctx->app_session_handle);
+  if (!svm_fifo_max_dequeue_cons (app_session->tx_fifo))
+    {
+      /* Confirm close */
+      srtp_disconnect_transport (ctx);
+      session_transport_closed_notify (&ctx->connection);
+    }
+  else
+    {
+      /* Wait for all data to be written to udp */
+      ctx->app_closed = 1;
+    }
+}
+
+static u32
+srtp_start_listen (u32 app_listener_index, transport_endpoint_t *tep)
+{
+  vnet_listen_args_t _bargs, *args = &_bargs;
+  session_handle_t udp_al_handle;
+  srtp_main_t *sm = &srtp_main;
+  session_endpoint_cfg_t *sep;
+  session_t *srtp_listener;
+  session_t *app_listener;
+  app_worker_t *app_wrk;
+  application_t *app;
+  app_listener_t *al;
+  srtp_tc_t *lctx;
+  u32 lctx_index;
+
+  sep = (session_endpoint_cfg_t *) tep;
+  if (!sep->ext_cfg)
+    return SESSION_E_NOEXTCFG;
+
+  app_wrk = app_worker_get (sep->app_wrk_index);
+  app = application_get (app_wrk->app_index);
+
+  clib_memset (args, 0, sizeof (*args));
+  args->app_index = sm->app_index;
+  args->sep_ext = *sep;
+  args->sep_ext.ns_index = app->ns_index;
+  args->sep_ext.transport_proto = TRANSPORT_PROTO_UDP;
+  args->sep_ext.transport_flags = TRANSPORT_CFG_F_CONNECTED;
+  if (vnet_listen (args))
+    return -1;
+
+  lctx_index = srtp_listener_ctx_alloc ();
+  udp_al_handle = args->handle;
+  al = app_listener_get_w_handle (udp_al_handle);
+  srtp_listener = app_listener_get_session (al);
+  srtp_listener->opaque = lctx_index;
+
+  app_listener = listen_session_get (app_listener_index);
+
+  lctx = srtp_listener_ctx_get (lctx_index);
+  lctx->parent_app_wrk_index = sep->app_wrk_index;
+  lctx->srtp_session_handle = udp_al_handle;
+  lctx->app_session_handle = listen_session_get_handle (app_listener);
+  lctx->udp_is_ip4 = sep->is_ip4;
+
+  srtp_init_policy (lctx, (transport_endpt_cfg_srtp_t *) sep->ext_cfg->data);
+
+  SRTP_DBG (1, "Started listening %d", lctx_index);
+  return lctx_index;
+}
+
+u32
+srtp_stop_listen (u32 lctx_index)
+{
+  session_endpoint_t sep = SESSION_ENDPOINT_NULL;
+  transport_connection_t *lc;
+  srtp_tc_t *lctx;
+  session_t *ls;
+  int rv;
+
+  lctx = srtp_listener_ctx_get (lctx_index);
+
+  /* Cleanup listener from session lookup table */
+  ls = session_get_from_handle (lctx->srtp_session_handle);
+  lc = session_get_transport (ls);
+
+  sep.fib_index = lc->fib_index;
+  sep.port = lc->lcl_port;
+  sep.is_ip4 = lc->is_ip4;
+  sep.transport_proto = TRANSPORT_PROTO_SRTP;
+  clib_memcpy (&sep.ip, &lc->lcl_ip, sizeof (lc->lcl_ip));
+  session_lookup_del_session_endpoint2 (&sep);
+
+  vnet_unlisten_args_t a = {
+    .handle = lctx->srtp_session_handle,
+    .app_index = srtp_main.app_index,
+    .wrk_map_index = 0 /* default wrk */
+  };
+  if ((rv = vnet_unlisten (&a)))
+    SRTP_DBG (0, "unlisten returned %d", rv);
+
+  srtp_listener_ctx_free (lctx);
+  return 0;
+}
+
+transport_connection_t *
+srtp_connection_get (u32 ctx_index, u32 thread_index)
+{
+  srtp_tc_t *ctx;
+  ctx = srtp_ctx_get_w_thread (ctx_index, thread_index);
+  return &ctx->connection;
+}
+
+transport_connection_t *
+srtp_listener_get (u32 listener_index)
+{
+  srtp_tc_t *ctx;
+  ctx = srtp_listener_ctx_get (listener_index);
+  return &ctx->connection;
+}
+
+int
+srtp_custom_tx_callback (void *session, transport_send_params_t *sp)
+{
+  session_t *app_session = (session_t *) session;
+  srtp_tc_t *ctx;
+
+  if (PREDICT_FALSE (app_session->session_state >=
+		     SESSION_STATE_TRANSPORT_CLOSED))
+    return 0;
+
+  sp->flags = 0;
+  ctx = srtp_ctx_get_w_thread (app_session->connection_index,
+			       app_session->thread_index);
+  if (PREDICT_FALSE (ctx->is_migrated))
+    return 0;
+
+  return srtp_ctx_write (ctx, app_session, sp);
+}
+
+u8 *
+format_srtp_ctx (u8 *s, va_list *args)
+{
+  srtp_tc_t *ctx = va_arg (*args, srtp_tc_t *);
+  u32 udp_si, udp_ti;
+
+  session_parse_handle (ctx->srtp_session_handle, &udp_si, &udp_ti);
+  s = format (s, "[%d:%d][SRTP] app_wrk %u index %u udp %d:%d",
+	      ctx->c_thread_index, ctx->c_s_index, ctx->parent_app_wrk_index,
+	      ctx->srtp_ctx_handle, udp_ti, udp_si);
+
+  return s;
+}
+
+static u8 *
+format_srtp_listener_ctx (u8 *s, va_list *args)
+{
+  session_t *udp_listener;
+  app_listener_t *al;
+  srtp_tc_t *ctx;
+
+  ctx = va_arg (*args, srtp_tc_t *);
+
+  al = app_listener_get_w_handle (ctx->srtp_session_handle);
+  udp_listener = app_listener_get_session (al);
+  s = format (s, "[%d:%d][SRTP] app_wrk %u udp %d:%d", ctx->c_thread_index,
+	      ctx->c_s_index, ctx->parent_app_wrk_index,
+	      udp_listener->thread_index, udp_listener->session_index);
+
+  return s;
+}
+
+static u8 *
+format_srtp_ctx_state (u8 *s, va_list *args)
+{
+  srtp_tc_t *ctx;
+  session_t *us;
+
+  ctx = va_arg (*args, srtp_tc_t *);
+  us = session_get (ctx->c_s_index, ctx->c_thread_index);
+  if (us->session_state == SESSION_STATE_LISTENING)
+    s = format (s, "%s", "LISTEN");
+  else
+    {
+      if (us->session_state >= SESSION_STATE_TRANSPORT_CLOSED)
+	s = format (s, "%s", "CLOSED");
+      else if (us->session_state == SESSION_STATE_APP_CLOSED)
+	s = format (s, "%s", "APP-CLOSED");
+      else if (us->session_state >= SESSION_STATE_TRANSPORT_CLOSING)
+	s = format (s, "%s", "CLOSING");
+      else
+	s = format (s, "%s", "ESTABLISHED");
+    }
+
+  return s;
+}
+
+u8 *
+format_srtp_connection (u8 *s, va_list *args)
+{
+  u32 ctx_index = va_arg (*args, u32);
+  u32 thread_index = va_arg (*args, u32);
+  u32 verbose = va_arg (*args, u32);
+  srtp_tc_t *ctx;
+
+  ctx = srtp_ctx_get_w_thread (ctx_index, thread_index);
+  if (!ctx)
+    return s;
+
+  s = format (s, "%-" SESSION_CLI_ID_LEN "U", format_srtp_ctx, ctx);
+  if (verbose)
+    {
+      s =
+	format (s, "%-" SESSION_CLI_STATE_LEN "U", format_srtp_ctx_state, ctx);
+      if (verbose > 1)
+	s = format (s, "\n");
+    }
+  return s;
+}
+
+u8 *
+format_srtp_listener (u8 *s, va_list *args)
+{
+  u32 tc_index = va_arg (*args, u32);
+  u32 __clib_unused thread_index = va_arg (*args, u32);
+  u32 verbose = va_arg (*args, u32);
+  srtp_tc_t *ctx = srtp_listener_ctx_get (tc_index);
+
+  s = format (s, "%-" SESSION_CLI_ID_LEN "U", format_srtp_listener_ctx, ctx);
+  if (verbose)
+    s = format (s, "%-" SESSION_CLI_STATE_LEN "U", format_srtp_ctx_state, ctx);
+  return s;
+}
+
+u8 *
+format_srtp_half_open (u8 *s, va_list *args)
+{
+  return 0;
+}
+
+static void
+srtp_transport_endpoint_get (u32 ctx_handle, u32 thread_index,
+			     transport_endpoint_t *tep, u8 is_lcl)
+{
+  srtp_tc_t *ctx = srtp_ctx_get_w_thread (ctx_handle, thread_index);
+  session_t *udp_session;
+
+  udp_session = session_get_from_handle (ctx->srtp_session_handle);
+  session_get_endpoint (udp_session, tep, is_lcl);
+}
+
+static void
+srtp_transport_listener_endpoint_get (u32 ctx_handle,
+				      transport_endpoint_t *tep, u8 is_lcl)
+{
+  session_t *srtp_listener;
+  app_listener_t *al;
+  srtp_tc_t *ctx = srtp_listener_ctx_get (ctx_handle);
+
+  al = app_listener_get_w_handle (ctx->srtp_session_handle);
+  srtp_listener = app_listener_get_session (al);
+  session_get_endpoint (srtp_listener, tep, is_lcl);
+}
+
+static const transport_proto_vft_t srtp_proto = {
+  .enable = srtp_enable,
+  .connect = srtp_connect,
+  .close = srtp_disconnect,
+  .start_listen = srtp_start_listen,
+  .stop_listen = srtp_stop_listen,
+  .get_connection = srtp_connection_get,
+  .get_listener = srtp_listener_get,
+  .custom_tx = srtp_custom_tx_callback,
+  .format_connection = format_srtp_connection,
+  .format_half_open = format_srtp_half_open,
+  .format_listener = format_srtp_listener,
+  .get_transport_endpoint = srtp_transport_endpoint_get,
+  .get_transport_listener_endpoint = srtp_transport_listener_endpoint_get,
+  .transport_options = {
+    .name = "srtp",
+    .short_name = "R",
+    .tx_type = TRANSPORT_TX_INTERNAL,
+    .service_type = TRANSPORT_SERVICE_APP,
+  },
+};
+
+static clib_error_t *
+srtp_transport_init (vlib_main_t *vm)
+{
+  transport_register_protocol (TRANSPORT_PROTO_SRTP, &srtp_proto,
+			       FIB_PROTOCOL_IP4, ~0);
+  transport_register_protocol (TRANSPORT_PROTO_SRTP, &srtp_proto,
+			       FIB_PROTOCOL_IP6, ~0);
+  return 0;
+}
+
+VLIB_INIT_FUNCTION (srtp_transport_init);
+
+VLIB_PLUGIN_REGISTER () = {
+  .version = VPP_BUILD_VER,
+  .description = "Secure Real-time Transport Protocol (SRTP)",
+  /* .default_disabled = 1, */
+};
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */
diff --git a/src/plugins/srtp/srtp.h b/src/plugins/srtp/srtp.h
new file mode 100644
index 00000000000..16475b0bd2f
--- /dev/null
+++ b/src/plugins/srtp/srtp.h
@@ -0,0 +1,120 @@
+/*
+ * Copyright (c) 2021 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 <vnet/plugin/plugin.h>
+#include <vpp/app/version.h>
+
+#include <vnet/session/application_interface.h>
+#include <vnet/session/application.h>
+
+#include <srtp2/srtp.h>
+
+#ifndef SRC_PLUGINS_SRTP_SRTP_H_
+#define SRC_PLUGINS_SRTP_SRTP_H_
+
+#define SRTP_DEBUG 0
+
+#if SRTP_DEBUG
+#define SRTP_DBG(_lvl, _fmt, _args...)                                        \
+  if (_lvl <= SRTP_DEBUG)                                                     \
+  clib_warning (_fmt, ##_args)
+#else
+#define SRTP_DBG(_lvl, _fmt, _args...)
+#endif
+
+typedef struct srtp_cxt_id_
+{
+  union
+  {
+    session_handle_t app_session_handle;
+    u32 parent_app_api_ctx;
+  };
+  session_handle_t srtp_session_handle;
+  u32 parent_app_wrk_index;
+  u32 srtp_ctx;
+  u32 listener_ctx_index;
+  u8 udp_is_ip4;
+} srtp_ctx_id_t;
+
+STATIC_ASSERT (sizeof (srtp_ctx_id_t) <= TRANSPORT_CONN_ID_LEN,
+	       "ctx id must be less than TRANSPORT_CONN_ID_LEN");
+
+#define SRTP_MAX_KEYLEN 46 /**< libsrtp AES 256 key len with salt */
+
+typedef struct transport_endpt_cfg_srtp_policy
+{
+  u32 ssrc_type;
+  u32 ssrc_value;
+  u32 window_size;
+  u8 allow_repeat_tx;
+  u8 key_len;
+  u8 key[SRTP_MAX_KEYLEN];
+} transport_endpt_cfg_srtp_policy_t;
+
+typedef struct transport_endpt_cfg_srtp
+{
+  transport_endpt_cfg_srtp_policy_t policies[2];
+} transport_endpt_cfg_srtp_t;
+
+typedef struct srtp_ctx_
+{
+  union
+  {
+    transport_connection_t connection;
+    srtp_ctx_id_t c_srtp_ctx_id;
+  };
+#define parent_app_wrk_index c_srtp_ctx_id.parent_app_wrk_index
+#define app_session_handle   c_srtp_ctx_id.app_session_handle
+#define srtp_session_handle  c_srtp_ctx_id.srtp_session_handle
+#define listener_ctx_index   c_srtp_ctx_id.listener_ctx_index
+#define udp_is_ip4	     c_srtp_ctx_id.udp_is_ip4
+#define srtp_ctx_engine	     c_srtp_ctx_id.srtp_engine_id
+#define srtp_ssl_ctx	     c_srtp_ctx_id.ssl_ctx
+#define srtp_ctx_handle	     c_c_index
+  /* Temporary storage for session open opaque. Overwritten once
+   * underlying tcp connection is established */
+#define parent_app_api_context c_srtp_ctx_id.parent_app_api_ctx
+
+  u8 is_passive_close;
+  u8 resume;
+  u8 app_closed;
+  u8 no_app_session;
+  u8 is_migrated;
+  srtp_t srtp_ctx;
+  srtp_policy_t srtp_policy[2];
+} srtp_tc_t;
+
+typedef struct srtp_main_
+{
+  srtp_tc_t **ctx_pool;
+  srtp_tc_t *listener_ctx_pool;
+  u32 app_index;
+  clib_rwlock_t half_open_rwlock;
+  /*
+   * Config
+   */
+  u64 first_seg_size;
+  u32 fifo_size;
+} srtp_main_t;
+
+#endif /* SRC_PLUGINS_SRTP_SRTP_H_ */
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */
diff --git a/src/plugins/srtp/srtp_plugin.md b/src/plugins/srtp/srtp_plugin.md
new file mode 100644
index 00000000000..81185864dbe
--- /dev/null
+++ b/src/plugins/srtp/srtp_plugin.md
@@ -0,0 +1,72 @@
+# SRTP (Secure Real-time Transport Protocol) {#srtp_doc}
+
+libsrtp2 based SRTP transport protocol implementation.
+
+## Maturity level
+Experimental
+
+## Quickstart
+
+1. Install libsrtp2-dev. On debian based OS:
+
+```
+sudo apt get install libsrtp2-dev
+```
+
+2. Build vpp
+
+```
+make build
+```
+
+3. Test protocol using vcl test server and client. On server side, start vpp and server app:
+
+```
+export VT_PATH=$WS/build-root/build-vpp_debug-native/vpp/bin
+$VT_PATH/vcl_test_server 1234 -p srtp
+```
+
+On client side:
+
+```
+export VT_PATH=$WS/build-root/build-vpp_debug-native/vpp/bin
+$VT_PATH/vcl_test_client <server-ip> 1234 -U -X -S -N 10000 -T 128 -p srtp
+```
+
+## Custom libsrtp2 build
+
+1. Create `build/external/packages/srtp.mk` with following example contents:
+
+```
+srtp_version := 2.3.0
+srtp_tarball := srtp_$(srtp_version).tar.gz
+srtp_tarball_md5sum := da38ee5d9c31be212a12964c22d7f795
+srtp_tarball_strip_dirs := 1
+srtp_url := https://github.com/cisco/libsrtp/archive/v$(srtp_version).tar.gz
+
+define  srtp_build_cmds
+	@cd $(srtp_build_dir) && \
+		$(CMAKE) -DCMAKE_INSTALL_PREFIX:PATH=$(srtp_install_dir)	\
+		-DCMAKE_C_FLAGS='-fPIC -fvisibility=hidden'  $(srtp_src_dir) > $(srtp_build_log)
+	@$(MAKE) $(MAKE_ARGS) -C $(srtp_build_dir) > $(srtp_build_log)
+endef
+
+define  srtp_config_cmds
+	@true
+endef
+
+define  srtp_install_cmds
+	@$(MAKE) $(MAKE_ARGS) -C $(srtp_build_dir) install > $(srtp_install_log)
+endef
+
+
+$(eval $(call package,srtp))
+```
+
+2. Include `srtp.mk` in `build/external/Makefile` and add to install target.
+
+3. Rebuild external dependencies:
+
+```
+make install-ext-deps
+```
diff --git a/src/vcl/vcl_private.h b/src/vcl/vcl_private.h
index f68ab45171e..628b7310788 100644
--- a/src/vcl/vcl_private.h
+++ b/src/vcl/vcl_private.h
@@ -626,7 +626,8 @@ vcl_ip_copy_to_ep (ip46_address_t * ip, vppcom_endpt_t * ep, u8 is_ip4)
 static inline int
 vcl_proto_is_dgram (uint8_t proto)
 {
-  return proto == VPPCOM_PROTO_UDP || proto == VPPCOM_PROTO_DTLS;
+  return proto == VPPCOM_PROTO_UDP || proto == VPPCOM_PROTO_DTLS ||
+	 proto == VPPCOM_PROTO_SRTP;
 }
 
 static inline u8
diff --git a/src/vcl/vppcom.c b/src/vcl/vppcom.c
index 0713a7b2d33..b3efdcd9817 100644
--- a/src/vcl/vppcom.c
+++ b/src/vcl/vppcom.c
@@ -1666,6 +1666,10 @@ vppcom_unformat_proto (uint8_t * proto, char *proto_str)
     *proto = VPPCOM_PROTO_DTLS;
   else if (!strcmp (proto_str, "dtls"))
     *proto = VPPCOM_PROTO_DTLS;
+  else if (!strcmp (proto_str, "SRTP"))
+    *proto = VPPCOM_PROTO_SRTP;
+  else if (!strcmp (proto_str, "srtp"))
+    *proto = VPPCOM_PROTO_SRTP;
   else
     return 1;
   return 0;
@@ -4128,6 +4132,9 @@ vppcom_proto_str (vppcom_proto_t proto)
     case VPPCOM_PROTO_DTLS:
       proto_str = "DTLS";
       break;
+    case VPPCOM_PROTO_SRTP:
+      proto_str = "SRTP";
+      break;
     default:
       proto_str = "UNKNOWN";
       break;
diff --git a/src/vcl/vppcom.h b/src/vcl/vppcom.h
index 72e5d46bc8f..ae157ccc8b4 100644
--- a/src/vcl/vppcom.h
+++ b/src/vcl/vppcom.h
@@ -53,6 +53,7 @@ extern "C"
     VPPCOM_PROTO_TLS,
     VPPCOM_PROTO_QUIC,
     VPPCOM_PROTO_DTLS,
+    VPPCOM_PROTO_SRTP,
   } vppcom_proto_t;
 
   typedef enum
diff --git a/src/vnet/session/session.c b/src/vnet/session/session.c
index e82c1d662e2..56a1fd71f5a 100644
--- a/src/vnet/session/session.c
+++ b/src/vnet/session/session.c
@@ -1966,7 +1966,7 @@ session_main_init (vlib_main_t * vm)
   smm->evt_qs_segment_size = 1 << 20;
 #endif
 
-  smm->last_transport_proto_type = TRANSPORT_PROTO_DTLS;
+  smm->last_transport_proto_type = TRANSPORT_PROTO_SRTP;
 
   return 0;
 }
diff --git a/src/vnet/session/transport_types.h b/src/vnet/session/transport_types.h
index 75fd1b8993b..9fabac5deaa 100644
--- a/src/vnet/session/transport_types.h
+++ b/src/vnet/session/transport_types.h
@@ -163,7 +163,8 @@ STATIC_ASSERT (sizeof (transport_connection_t) <= 128,
   _ (NONE, "ct", "C")                                                         \
   _ (TLS, "tls", "J")                                                         \
   _ (QUIC, "quic", "Q")                                                       \
-  _ (DTLS, "dtls", "D")
+  _ (DTLS, "dtls", "D")                                                       \
+  _ (SRTP, "srtp", "R")
 
 typedef enum _transport_proto
 {