sctp: move to plugins, disabled by default

Removed sctp buffer metadata from vnet/buffer.h, added it to the
plugin. Add registration APIs for plugin-based vlib_buffer_opaque /
opaque2 decoders, used by "pcap dispatch trace ..." for display in the
wireshark dissector.

Type:refactor

Not actively maintained.

Change-Id: Ie4cb6ba66f68b3b3a7d7d2c63c917fdccf994371
Signed-off-by: Florin Coras <fcoras@cisco.com>
Signed-off-by: Dave Barach <dave@barachs.net>

1 files changed, 1568 insertions, 0 deletions

diff --git a/src/plugins/sctp/sctp_output.c b/src/plugins/sctp/sctp_output.c
new file mode 100644
index 00000000000..955010a34b3
--- /dev/null
+++ b/src/plugins/sctp/sctp_output.c
@@ -0,0 +1,1568 @@
+/*
+ * Copyright (c) 2017 SUSE LLC.
+ * 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 <sctp/sctp.h>
+#include <sctp/sctp_debug.h>
+#include <vppinfra/random.h>
+#include <openssl/hmac.h>
+
+/**
+ * Flush tx frame populated by retransmits and timer pops
+ */
+void
+sctp_flush_frame_to_output (vlib_main_t * vm, u8 thread_index, u8 is_ip4)
+{
+  if (sctp_main.tx_frames[!is_ip4][thread_index])
+    {
+      u32 next_index;
+      next_index = is_ip4 ? sctp4_output_node.index : sctp6_output_node.index;
+      vlib_put_frame_to_node (vm, next_index,
+			      sctp_main.tx_frames[!is_ip4][thread_index]);
+      sctp_main.tx_frames[!is_ip4][thread_index] = 0;
+    }
+}
+
+/**
+ * Flush ip lookup tx frames populated by timer pops
+ */
+always_inline void
+sctp_flush_frame_to_ip_lookup (vlib_main_t * vm, u8 thread_index, u8 is_ip4)
+{
+  if (sctp_main.ip_lookup_tx_frames[!is_ip4][thread_index])
+    {
+      u32 next_index;
+      next_index = is_ip4 ? ip4_lookup_node.index : ip6_lookup_node.index;
+      vlib_put_frame_to_node (vm, next_index,
+			      sctp_main.ip_lookup_tx_frames[!is_ip4]
+			      [thread_index]);
+      sctp_main.ip_lookup_tx_frames[!is_ip4][thread_index] = 0;
+    }
+}
+
+/**
+ * Flush v4 and v6 sctp and ip-lookup tx frames for thread index
+ */
+void
+sctp_flush_frames_to_output (u8 thread_index)
+{
+  vlib_main_t *vm = vlib_get_main ();
+  sctp_flush_frame_to_output (vm, thread_index, 1);
+  sctp_flush_frame_to_output (vm, thread_index, 0);
+  sctp_flush_frame_to_ip_lookup (vm, thread_index, 1);
+  sctp_flush_frame_to_ip_lookup (vm, thread_index, 0);
+}
+
+u32
+ip4_sctp_compute_checksum (vlib_main_t * vm, vlib_buffer_t * p0,
+			   ip4_header_t * ip0)
+{
+  ip_csum_t checksum;
+  u32 ip_header_length, payload_length_host_byte_order;
+  u32 n_this_buffer, n_bytes_left, n_ip_bytes_this_buffer;
+  void *data_this_buffer;
+
+  /* Initialize checksum with ip header. */
+  ip_header_length = ip4_header_bytes (ip0);
+  payload_length_host_byte_order =
+    clib_net_to_host_u16 (ip0->length) - ip_header_length;
+  checksum =
+    clib_host_to_net_u32 (payload_length_host_byte_order +
+			  (ip0->protocol << 16));
+
+  if (BITS (uword) == 32)
+    {
+      checksum =
+	ip_csum_with_carry (checksum,
+			    clib_mem_unaligned (&ip0->src_address, u32));
+      checksum =
+	ip_csum_with_carry (checksum,
+			    clib_mem_unaligned (&ip0->dst_address, u32));
+    }
+  else
+    checksum =
+      ip_csum_with_carry (checksum,
+			  clib_mem_unaligned (&ip0->src_address, u64));
+
+  n_bytes_left = n_this_buffer = payload_length_host_byte_order;
+  data_this_buffer = (void *) ip0 + ip_header_length;
+  n_ip_bytes_this_buffer =
+    p0->current_length - (((u8 *) ip0 - p0->data) - p0->current_data);
+  if (n_this_buffer + ip_header_length > n_ip_bytes_this_buffer)
+    {
+      n_this_buffer = n_ip_bytes_this_buffer > ip_header_length ?
+	n_ip_bytes_this_buffer - ip_header_length : 0;
+    }
+  while (1)
+    {
+      checksum =
+	ip_incremental_checksum (checksum, data_this_buffer, n_this_buffer);
+      n_bytes_left -= n_this_buffer;
+      if (n_bytes_left == 0)
+	break;
+
+      ASSERT (p0->flags & VLIB_BUFFER_NEXT_PRESENT);
+      p0 = vlib_get_buffer (vm, p0->next_buffer);
+      data_this_buffer = vlib_buffer_get_current (p0);
+      n_this_buffer = p0->current_length;
+    }
+
+  return checksum;
+}
+
+u32
+ip6_sctp_compute_checksum (vlib_main_t * vm, vlib_buffer_t * p0,
+			   ip6_header_t * ip0, int *bogus_lengthp)
+{
+  ip_csum_t checksum;
+  u16 payload_length_host_byte_order;
+  u32 i, n_this_buffer, n_bytes_left;
+  u32 headers_size = sizeof (ip0[0]);
+  void *data_this_buffer;
+
+  ASSERT (bogus_lengthp);
+  *bogus_lengthp = 0;
+
+  /* Initialize checksum with ip header. */
+  checksum = ip0->payload_length + clib_host_to_net_u16 (ip0->protocol);
+  payload_length_host_byte_order = clib_net_to_host_u16 (ip0->payload_length);
+  data_this_buffer = (void *) (ip0 + 1);
+
+  for (i = 0; i < ARRAY_LEN (ip0->src_address.as_uword); i++)
+    {
+      checksum = ip_csum_with_carry (checksum,
+				     clib_mem_unaligned (&ip0->
+							 src_address.as_uword
+							 [i], uword));
+      checksum =
+	ip_csum_with_carry (checksum,
+			    clib_mem_unaligned (&ip0->dst_address.as_uword[i],
+						uword));
+    }
+
+  /* some icmp packets may come with a "router alert" hop-by-hop extension header (e.g., mldv2 packets)
+   * or UDP-Ping packets */
+  if (PREDICT_FALSE (ip0->protocol == IP_PROTOCOL_IP6_HOP_BY_HOP_OPTIONS))
+    {
+      u32 skip_bytes;
+      ip6_hop_by_hop_ext_t *ext_hdr =
+	(ip6_hop_by_hop_ext_t *) data_this_buffer;
+
+      /* validate really icmp6 next */
+      ASSERT ((ext_hdr->next_hdr == IP_PROTOCOL_SCTP));
+
+      skip_bytes = 8 * (1 + ext_hdr->n_data_u64s);
+      data_this_buffer = (void *) ((u8 *) data_this_buffer + skip_bytes);
+
+      payload_length_host_byte_order -= skip_bytes;
+      headers_size += skip_bytes;
+    }
+
+  n_bytes_left = n_this_buffer = payload_length_host_byte_order;
+  if (p0 && n_this_buffer + headers_size > p0->current_length)
+    n_this_buffer =
+      p0->current_length >
+      headers_size ? p0->current_length - headers_size : 0;
+  while (1)
+    {
+      checksum =
+	ip_incremental_checksum (checksum, data_this_buffer, n_this_buffer);
+      n_bytes_left -= n_this_buffer;
+      if (n_bytes_left == 0)
+	break;
+
+      if (!(p0->flags & VLIB_BUFFER_NEXT_PRESENT))
+	{
+	  *bogus_lengthp = 1;
+	  return 0xfefe;
+	}
+      p0 = vlib_get_buffer (vm, p0->next_buffer);
+      data_this_buffer = vlib_buffer_get_current (p0);
+      n_this_buffer = p0->current_length;
+    }
+
+  return checksum;
+}
+
+void
+sctp_push_ip_hdr (sctp_main_t * tm, sctp_sub_connection_t * sctp_sub_conn,
+		  vlib_buffer_t * b)
+{
+  sctp_header_t *th = vlib_buffer_get_current (b);
+  vlib_main_t *vm = vlib_get_main ();
+  if (sctp_sub_conn->c_is_ip4)
+    {
+      ip4_header_t *ih;
+      ih = vlib_buffer_push_ip4 (vm, b, &sctp_sub_conn->c_lcl_ip4,
+				 &sctp_sub_conn->c_rmt_ip4, IP_PROTOCOL_SCTP,
+				 1);
+      th->checksum = ip4_sctp_compute_checksum (vm, b, ih);
+    }
+  else
+    {
+      ip6_header_t *ih;
+      int bogus = ~0;
+
+      ih = vlib_buffer_push_ip6 (vm, b, &sctp_sub_conn->c_lcl_ip6,
+				 &sctp_sub_conn->c_rmt_ip6, IP_PROTOCOL_SCTP);
+      th->checksum = ip6_sctp_compute_checksum (vm, b, ih, &bogus);
+      ASSERT (!bogus);
+    }
+}
+
+always_inline void *
+sctp_reuse_buffer (vlib_main_t * vm, vlib_buffer_t * b)
+{
+  if (b->flags & VLIB_BUFFER_NEXT_PRESENT)
+    vlib_buffer_free_one (vm, b->next_buffer);
+  /* Zero all flags but free list index and trace flag */
+  b->flags &= VLIB_BUFFER_NEXT_PRESENT - 1;
+  b->current_data = 0;
+  b->current_length = 0;
+  b->total_length_not_including_first_buffer = 0;
+  sctp_buffer_opaque (b)->sctp.flags = 0;
+  sctp_buffer_opaque (b)->sctp.subconn_idx = MAX_SCTP_CONNECTIONS;
+
+  /* Leave enough space for headers */
+  return vlib_buffer_make_headroom (b, TRANSPORT_MAX_HDRS_LEN);
+}
+
+always_inline void *
+sctp_init_buffer (vlib_main_t * vm, vlib_buffer_t * b)
+{
+  ASSERT ((b->flags & VLIB_BUFFER_NEXT_PRESENT) == 0);
+  b->flags |= VNET_BUFFER_F_LOCALLY_ORIGINATED;
+  b->total_length_not_including_first_buffer = 0;
+  sctp_buffer_opaque (b)->sctp.flags = 0;
+  sctp_buffer_opaque (b)->sctp.subconn_idx = MAX_SCTP_CONNECTIONS;
+  VLIB_BUFFER_TRACE_TRAJECTORY_INIT (b);
+  /* Leave enough space for headers */
+  return vlib_buffer_make_headroom (b, TRANSPORT_MAX_HDRS_LEN);
+}
+
+always_inline int
+sctp_alloc_tx_buffers (sctp_main_t * tm, u8 thread_index, u32 n_free_buffers)
+{
+  vlib_main_t *vm = vlib_get_main ();
+  u32 current_length = vec_len (tm->tx_buffers[thread_index]);
+  u32 n_allocated;
+
+  vec_validate (tm->tx_buffers[thread_index],
+		current_length + n_free_buffers - 1);
+  n_allocated =
+    vlib_buffer_alloc (vm, &tm->tx_buffers[thread_index][current_length],
+		       n_free_buffers);
+  _vec_len (tm->tx_buffers[thread_index]) = current_length + n_allocated;
+  /* buffer shortage, report failure */
+  if (vec_len (tm->tx_buffers[thread_index]) == 0)
+    {
+      clib_warning ("out of buffers");
+      return -1;
+    }
+  return 0;
+}
+
+always_inline int
+sctp_get_free_buffer_index (sctp_main_t * tm, u32 * bidx)
+{
+  u32 *my_tx_buffers;
+  u32 thread_index = vlib_get_thread_index ();
+  if (PREDICT_FALSE (vec_len (tm->tx_buffers[thread_index]) == 0))
+    {
+      if (sctp_alloc_tx_buffers (tm, thread_index, VLIB_FRAME_SIZE))
+	return -1;
+    }
+  my_tx_buffers = tm->tx_buffers[thread_index];
+  *bidx = my_tx_buffers[vec_len (my_tx_buffers) - 1];
+  _vec_len (my_tx_buffers) -= 1;
+  return 0;
+}
+
+always_inline void
+sctp_enqueue_to_output_i (vlib_main_t * vm, vlib_buffer_t * b, u32 bi,
+			  u8 is_ip4, u8 flush)
+{
+  sctp_main_t *tm = vnet_get_sctp_main ();
+  u32 thread_index = vlib_get_thread_index ();
+  u32 *to_next, next_index;
+  vlib_frame_t *f;
+
+  b->flags |= VNET_BUFFER_F_LOCALLY_ORIGINATED;
+  b->error = 0;
+
+  /* Decide where to send the packet */
+  next_index = is_ip4 ? sctp4_output_node.index : sctp6_output_node.index;
+  sctp_trajectory_add_start (b, 2);
+
+  /* Get frame to v4/6 output node */
+  f = tm->tx_frames[!is_ip4][thread_index];
+  if (!f)
+    {
+      f = vlib_get_frame_to_node (vm, next_index);
+      ASSERT (f);
+      tm->tx_frames[!is_ip4][thread_index] = f;
+    }
+  to_next = vlib_frame_vector_args (f);
+  to_next[f->n_vectors] = bi;
+  f->n_vectors += 1;
+  if (flush || f->n_vectors == VLIB_FRAME_SIZE)
+    {
+      vlib_put_frame_to_node (vm, next_index, f);
+      tm->tx_frames[!is_ip4][thread_index] = 0;
+    }
+}
+
+always_inline void
+sctp_enqueue_to_output_now (vlib_main_t * vm, vlib_buffer_t * b, u32 bi,
+			    u8 is_ip4)
+{
+  sctp_enqueue_to_output_i (vm, b, bi, is_ip4, 1);
+}
+
+always_inline void
+sctp_enqueue_to_ip_lookup_i (vlib_main_t * vm, vlib_buffer_t * b, u32 bi,
+			     u8 is_ip4, u32 fib_index, u8 flush)
+{
+  sctp_main_t *tm = vnet_get_sctp_main ();
+  u32 thread_index = vlib_get_thread_index ();
+  u32 *to_next, next_index;
+  vlib_frame_t *f;
+
+  b->flags |= VNET_BUFFER_F_LOCALLY_ORIGINATED;
+  b->error = 0;
+
+  vnet_buffer (b)->sw_if_index[VLIB_TX] = fib_index;
+  vnet_buffer (b)->sw_if_index[VLIB_RX] = 0;
+
+  /* Send to IP lookup */
+  next_index = is_ip4 ? ip4_lookup_node.index : ip6_lookup_node.index;
+  if (VLIB_BUFFER_TRACE_TRAJECTORY > 0)
+    {
+      b->pre_data[0] = 2;
+      b->pre_data[1] = next_index;
+    }
+
+  f = tm->ip_lookup_tx_frames[!is_ip4][thread_index];
+  if (!f)
+    {
+      f = vlib_get_frame_to_node (vm, next_index);
+      ASSERT (f);
+      tm->ip_lookup_tx_frames[!is_ip4][thread_index] = f;
+    }
+
+  to_next = vlib_frame_vector_args (f);
+  to_next[f->n_vectors] = bi;
+  f->n_vectors += 1;
+  if (flush || f->n_vectors == VLIB_FRAME_SIZE)
+    {
+      vlib_put_frame_to_node (vm, next_index, f);
+      tm->ip_lookup_tx_frames[!is_ip4][thread_index] = 0;
+    }
+}
+
+always_inline void
+sctp_enqueue_to_ip_lookup (vlib_main_t * vm, vlib_buffer_t * b, u32 bi,
+			   u8 is_ip4, u32 fib_index)
+{
+  sctp_enqueue_to_ip_lookup_i (vm, b, bi, is_ip4, fib_index, 0);
+  if (vm->thread_index == 0 && vlib_num_workers ())
+    session_flush_frames_main_thread (vm);
+}
+
+/**
+ * Convert buffer to INIT
+ */
+void
+sctp_prepare_init_chunk (sctp_connection_t * sctp_conn, u8 idx,
+			 vlib_buffer_t * b)
+{
+  u32 random_seed = random_default_seed ();
+  u16 alloc_bytes = sizeof (sctp_init_chunk_t);
+  sctp_sub_connection_t *sub_conn = &sctp_conn->sub_conn[idx];
+
+  sctp_ipv4_addr_param_t *ip4_param = 0;
+  sctp_ipv6_addr_param_t *ip6_param = 0;
+
+  if (sub_conn->c_is_ip4)
+    alloc_bytes += sizeof (sctp_ipv4_addr_param_t);
+  else
+    alloc_bytes += sizeof (sctp_ipv6_addr_param_t);
+
+  /* As per RFC 4960 the chunk_length value does NOT contemplate
+   * the size of the first header (see sctp_header_t) and any padding
+   */
+  u16 chunk_len = alloc_bytes - sizeof (sctp_header_t);
+
+  alloc_bytes += vnet_sctp_calculate_padding (alloc_bytes);
+
+  sctp_init_chunk_t *init_chunk = vlib_buffer_push_uninit (b, alloc_bytes);
+
+  u16 pointer_offset = sizeof (init_chunk);
+  if (sub_conn->c_is_ip4)
+    {
+      ip4_param = (sctp_ipv4_addr_param_t *) init_chunk + pointer_offset;
+      ip4_param->address.as_u32 = sub_conn->c_lcl_ip.ip4.as_u32;
+
+      pointer_offset += sizeof (sctp_ipv4_addr_param_t);
+    }
+  else
+    {
+      ip6_param = (sctp_ipv6_addr_param_t *) init_chunk + pointer_offset;
+      ip6_param->address.as_u64[0] = sub_conn->c_lcl_ip.ip6.as_u64[0];
+      ip6_param->address.as_u64[1] = sub_conn->c_lcl_ip.ip6.as_u64[1];
+
+      pointer_offset += sizeof (sctp_ipv6_addr_param_t);
+    }
+
+  init_chunk->sctp_hdr.src_port = sub_conn->c_lcl_port;	/* No need of host_to_net conversion, already in net-byte order */
+  init_chunk->sctp_hdr.dst_port = sub_conn->c_rmt_port;	/* No need of host_to_net conversion, already in net-byte order */
+  init_chunk->sctp_hdr.checksum = 0;
+  /* The sender of an INIT must set the VERIFICATION_TAG to 0 as per RFC 4960 Section 8.5.1 */
+  init_chunk->sctp_hdr.verification_tag = 0x0;
+
+  vnet_sctp_set_chunk_type (&init_chunk->chunk_hdr, INIT);
+  vnet_sctp_set_chunk_length (&init_chunk->chunk_hdr, chunk_len);
+  vnet_sctp_common_hdr_params_host_to_net (&init_chunk->chunk_hdr);
+
+  sctp_init_cwnd (sctp_conn);
+
+  init_chunk->a_rwnd = clib_host_to_net_u32 (sctp_conn->sub_conn[idx].cwnd);
+  init_chunk->initiate_tag = clib_host_to_net_u32 (random_u32 (&random_seed));
+  init_chunk->inboud_streams_count =
+    clib_host_to_net_u16 (INBOUND_STREAMS_COUNT);
+  init_chunk->outbound_streams_count =
+    clib_host_to_net_u16 (OUTBOUND_STREAMS_COUNT);
+
+  init_chunk->initial_tsn =
+    clib_host_to_net_u32 (sctp_conn->local_initial_tsn);
+  SCTP_CONN_TRACKING_DBG ("sctp_conn->local_initial_tsn = %u",
+			  sctp_conn->local_initial_tsn);
+
+  sctp_conn->local_tag = init_chunk->initiate_tag;
+
+  sctp_buffer_opaque (b)->sctp.connection_index = sub_conn->c_c_index;
+  sctp_buffer_opaque (b)->sctp.subconn_idx = idx;
+
+  SCTP_DBG_STATE_MACHINE ("CONN_INDEX = %u, CURR_CONN_STATE = %u (%s), "
+			  "CHUNK_TYPE = %s, "
+			  "SRC_PORT = %u, DST_PORT = %u",
+			  sub_conn->connection.c_index,
+			  sctp_conn->state,
+			  sctp_state_to_string (sctp_conn->state),
+			  sctp_chunk_to_string (INIT),
+			  init_chunk->sctp_hdr.src_port,
+			  init_chunk->sctp_hdr.dst_port);
+}
+
+void
+sctp_compute_mac (sctp_connection_t * sctp_conn,
+		  sctp_state_cookie_param_t * state_cookie)
+{
+#if OPENSSL_VERSION_NUMBER >= 0x10100000L
+  HMAC_CTX *ctx;
+#else
+  HMAC_CTX ctx;
+#endif
+  unsigned int len = 0;
+  const EVP_MD *md = EVP_sha1 ();
+#if OPENSSL_VERSION_NUMBER >= 0x10100000L
+  ctx = HMAC_CTX_new ();
+  HMAC_Init_ex (ctx, &state_cookie->creation_time,
+		sizeof (state_cookie->creation_time), md, NULL);
+  HMAC_Update (ctx, (const unsigned char *) &sctp_conn, sizeof (sctp_conn));
+  HMAC_Final (ctx, state_cookie->mac, &len);
+#else
+  HMAC_CTX_init (&ctx);
+  HMAC_Init_ex (&ctx, &state_cookie->creation_time,
+		sizeof (state_cookie->creation_time), md, NULL);
+  HMAC_Update (&ctx, (const unsigned char *) &sctp_conn, sizeof (sctp_conn));
+  HMAC_Final (&ctx, state_cookie->mac, &len);
+  HMAC_CTX_cleanup (&ctx);
+#endif
+
+  ENDIANESS_SWAP (state_cookie->mac);
+}
+
+void
+sctp_prepare_cookie_ack_chunk (sctp_connection_t * sctp_conn, u8 idx,
+			       vlib_buffer_t * b)
+{
+  vlib_main_t *vm = vlib_get_main ();
+
+  sctp_reuse_buffer (vm, b);
+
+  u16 alloc_bytes = sizeof (sctp_cookie_ack_chunk_t);
+
+  /* As per RFC 4960 the chunk_length value does NOT contemplate
+   * the size of the first header (see sctp_header_t) and any padding
+   */
+  u16 chunk_len = alloc_bytes - sizeof (sctp_header_t);
+
+  alloc_bytes += vnet_sctp_calculate_padding (alloc_bytes);
+
+  sctp_cookie_ack_chunk_t *cookie_ack_chunk =
+    vlib_buffer_push_uninit (b, alloc_bytes);
+
+  cookie_ack_chunk->sctp_hdr.checksum = 0;
+  cookie_ack_chunk->sctp_hdr.src_port =
+    sctp_conn->sub_conn[idx].connection.lcl_port;
+  cookie_ack_chunk->sctp_hdr.dst_port =
+    sctp_conn->sub_conn[idx].connection.rmt_port;
+  cookie_ack_chunk->sctp_hdr.verification_tag = sctp_conn->remote_tag;
+  vnet_sctp_set_chunk_type (&cookie_ack_chunk->chunk_hdr, COOKIE_ACK);
+  vnet_sctp_set_chunk_length (&cookie_ack_chunk->chunk_hdr, chunk_len);
+
+  sctp_buffer_opaque (b)->sctp.connection_index =
+    sctp_conn->sub_conn[idx].connection.c_index;
+  sctp_buffer_opaque (b)->sctp.subconn_idx = idx;
+}
+
+void
+sctp_prepare_cookie_echo_chunk (sctp_connection_t * sctp_conn, u8 idx,
+				vlib_buffer_t * b, u8 reuse_buffer)
+{
+  vlib_main_t *vm = vlib_get_main ();
+
+  if (reuse_buffer)
+    sctp_reuse_buffer (vm, b);
+
+  /* The minimum size of the message is given by the sctp_init_ack_chunk_t */
+  u16 alloc_bytes = sizeof (sctp_cookie_echo_chunk_t);
+  /* As per RFC 4960 the chunk_length value does NOT contemplate
+   * the size of the first header (see sctp_header_t) and any padding
+   */
+  u16 chunk_len = alloc_bytes - sizeof (sctp_header_t);
+  alloc_bytes += vnet_sctp_calculate_padding (alloc_bytes);
+  sctp_cookie_echo_chunk_t *cookie_echo_chunk =
+    vlib_buffer_push_uninit (b, alloc_bytes);
+  cookie_echo_chunk->sctp_hdr.checksum = 0;
+  cookie_echo_chunk->sctp_hdr.src_port =
+    sctp_conn->sub_conn[idx].connection.lcl_port;
+  cookie_echo_chunk->sctp_hdr.dst_port =
+    sctp_conn->sub_conn[idx].connection.rmt_port;
+  cookie_echo_chunk->sctp_hdr.verification_tag = sctp_conn->remote_tag;
+  vnet_sctp_set_chunk_type (&cookie_echo_chunk->chunk_hdr, COOKIE_ECHO);
+  vnet_sctp_set_chunk_length (&cookie_echo_chunk->chunk_hdr, chunk_len);
+  clib_memcpy_fast (&(cookie_echo_chunk->cookie), &sctp_conn->cookie_param,
+		    sizeof (sctp_state_cookie_param_t));
+
+  sctp_buffer_opaque (b)->sctp.connection_index =
+    sctp_conn->sub_conn[idx].connection.c_index;
+  sctp_buffer_opaque (b)->sctp.subconn_idx = idx;
+}
+
+
+/*
+ *  Send COOKIE_ECHO
+ */
+void
+sctp_send_cookie_echo (sctp_connection_t * sctp_conn)
+{
+  vlib_buffer_t *b;
+  u32 bi;
+  sctp_main_t *tm = vnet_get_sctp_main ();
+  vlib_main_t *vm = vlib_get_main ();
+
+  if (PREDICT_FALSE (sctp_conn->init_retransmit_err > SCTP_MAX_INIT_RETRANS))
+    {
+      clib_warning ("Reached MAX_INIT_RETRANS times. Aborting connection.");
+
+      session_stream_connect_notify (&sctp_conn->sub_conn
+				     [SCTP_PRIMARY_PATH_IDX].connection, 1);
+
+      sctp_connection_timers_reset (sctp_conn);
+
+      sctp_connection_cleanup (sctp_conn);
+    }
+
+  if (PREDICT_FALSE (sctp_get_free_buffer_index (tm, &bi)))
+    return;
+
+  b = vlib_get_buffer (vm, bi);
+  u8 idx = SCTP_PRIMARY_PATH_IDX;
+
+  sctp_init_buffer (vm, b);
+  sctp_prepare_cookie_echo_chunk (sctp_conn, idx, b, 0);
+  sctp_enqueue_to_output_now (vm, b, bi, sctp_conn->sub_conn[idx].c_is_ip4);
+
+  /* Start the T1_INIT timer */
+  sctp_timer_set (sctp_conn, idx, SCTP_TIMER_T1_INIT,
+		  sctp_conn->sub_conn[idx].RTO);
+
+  /* Change state to COOKIE_WAIT */
+  sctp_conn->state = SCTP_STATE_COOKIE_WAIT;
+
+  /* Measure RTT with this */
+  sctp_conn->sub_conn[idx].rtt_ts = sctp_time_now ();
+}
+
+
+/**
+ * Convert buffer to ERROR
+ */
+void
+sctp_prepare_operation_error (sctp_connection_t * sctp_conn, u8 idx,
+			      vlib_buffer_t * b, u8 err_cause)
+{
+  vlib_main_t *vm = vlib_get_main ();
+
+  sctp_reuse_buffer (vm, b);
+
+  /* The minimum size of the message is given by the sctp_operation_error_t */
+  u16 alloc_bytes =
+    sizeof (sctp_operation_error_t) + sizeof (sctp_err_cause_param_t);
+
+  /* As per RFC 4960 the chunk_length value does NOT contemplate
+   * the size of the first header (see sctp_header_t) and any padding
+   */
+  u16 chunk_len = alloc_bytes - sizeof (sctp_header_t);
+
+  alloc_bytes += vnet_sctp_calculate_padding (alloc_bytes);
+
+  sctp_operation_error_t *err_chunk =
+    vlib_buffer_push_uninit (b, alloc_bytes);
+
+  /* src_port & dst_port are already in network byte-order */
+  err_chunk->sctp_hdr.checksum = 0;
+  err_chunk->sctp_hdr.src_port = sctp_conn->sub_conn[idx].connection.lcl_port;
+  err_chunk->sctp_hdr.dst_port = sctp_conn->sub_conn[idx].connection.rmt_port;
+  /* As per RFC4960 Section 5.2.2: copy the INITIATE_TAG into the VERIFICATION_TAG of the ABORT chunk */
+  err_chunk->sctp_hdr.verification_tag = sctp_conn->local_tag;
+
+  err_chunk->err_causes[0].param_hdr.length =
+    clib_host_to_net_u16 (sizeof (err_chunk->err_causes[0].param_hdr.type) +
+			  sizeof (err_chunk->err_causes[0].param_hdr.length));
+  err_chunk->err_causes[0].param_hdr.type = clib_host_to_net_u16 (err_cause);
+
+  vnet_sctp_set_chunk_type (&err_chunk->chunk_hdr, OPERATION_ERROR);
+  vnet_sctp_set_chunk_length (&err_chunk->chunk_hdr, chunk_len);
+
+  sctp_buffer_opaque (b)->sctp.connection_index =
+    sctp_conn->sub_conn[idx].connection.c_index;
+  sctp_buffer_opaque (b)->sctp.subconn_idx = idx;
+}
+
+/**
+ * Convert buffer to ABORT
+ */
+void
+sctp_prepare_abort_for_collision (sctp_connection_t * sctp_conn, u8 idx,
+				  vlib_buffer_t * b, ip4_address_t * ip4_addr,
+				  ip6_address_t * ip6_addr)
+{
+  vlib_main_t *vm = vlib_get_main ();
+
+  sctp_reuse_buffer (vm, b);
+
+  /* The minimum size of the message is given by the sctp_abort_chunk_t */
+  u16 alloc_bytes = sizeof (sctp_abort_chunk_t);
+
+  /* As per RFC 4960 the chunk_length value does NOT contemplate
+   * the size of the first header (see sctp_header_t) and any padding
+   */
+  u16 chunk_len = alloc_bytes - sizeof (sctp_header_t);
+
+  alloc_bytes += vnet_sctp_calculate_padding (alloc_bytes);
+
+  sctp_abort_chunk_t *abort_chunk = vlib_buffer_push_uninit (b, alloc_bytes);
+
+  /* src_port & dst_port are already in network byte-order */
+  abort_chunk->sctp_hdr.checksum = 0;
+  abort_chunk->sctp_hdr.src_port =
+    sctp_conn->sub_conn[idx].connection.lcl_port;
+  abort_chunk->sctp_hdr.dst_port =
+    sctp_conn->sub_conn[idx].connection.rmt_port;
+  /* As per RFC4960 Section 5.2.2: copy the INITIATE_TAG into the VERIFICATION_TAG of the ABORT chunk */
+  abort_chunk->sctp_hdr.verification_tag = sctp_conn->local_tag;
+
+  vnet_sctp_set_chunk_type (&abort_chunk->chunk_hdr, ABORT);
+  vnet_sctp_set_chunk_length (&abort_chunk->chunk_hdr, chunk_len);
+
+  sctp_buffer_opaque (b)->sctp.connection_index =
+    sctp_conn->sub_conn[idx].connection.c_index;
+  sctp_buffer_opaque (b)->sctp.subconn_idx = idx;
+}
+
+/**
+ * Convert buffer to INIT-ACK
+ */
+void
+sctp_prepare_initack_chunk_for_collision (sctp_connection_t * sctp_conn,
+					  u8 idx, vlib_buffer_t * b,
+					  ip4_address_t * ip4_addr,
+					  ip6_address_t * ip6_addr)
+{
+  vlib_main_t *vm = vlib_get_main ();
+  sctp_ipv4_addr_param_t *ip4_param = 0;
+  sctp_ipv6_addr_param_t *ip6_param = 0;
+
+  sctp_reuse_buffer (vm, b);
+
+  /* The minimum size of the message is given by the sctp_init_ack_chunk_t */
+  u16 alloc_bytes =
+    sizeof (sctp_init_ack_chunk_t) + sizeof (sctp_state_cookie_param_t);
+
+  if (PREDICT_TRUE (ip4_addr != NULL))
+    {
+      /* Create room for variable-length fields in the INIT_ACK chunk */
+      alloc_bytes += SCTP_IPV4_ADDRESS_TYPE_LENGTH;
+    }
+  if (PREDICT_TRUE (ip6_addr != NULL))
+    {
+      /* Create room for variable-length fields in the INIT_ACK chunk */
+      alloc_bytes += SCTP_IPV6_ADDRESS_TYPE_LENGTH;
+    }
+
+  if (sctp_conn->sub_conn[idx].connection.is_ip4)
+    alloc_bytes += sizeof (sctp_ipv4_addr_param_t);
+  else
+    alloc_bytes += sizeof (sctp_ipv6_addr_param_t);
+
+  /* As per RFC 4960 the chunk_length value does NOT contemplate
+   * the size of the first header (see sctp_header_t) and any padding
+   */
+  u16 chunk_len = alloc_bytes - sizeof (sctp_header_t);
+
+  alloc_bytes += vnet_sctp_calculate_padding (alloc_bytes);
+
+  sctp_init_ack_chunk_t *init_ack_chunk =
+    vlib_buffer_push_uninit (b, alloc_bytes);
+
+  u16 pointer_offset = sizeof (sctp_init_ack_chunk_t);
+
+  /* Create State Cookie parameter */
+  sctp_state_cookie_param_t *state_cookie_param =
+    (sctp_state_cookie_param_t *) ((char *) init_ack_chunk + pointer_offset);
+
+  state_cookie_param->param_hdr.type =
+    clib_host_to_net_u16 (SCTP_STATE_COOKIE_TYPE);
+  state_cookie_param->param_hdr.length =
+    clib_host_to_net_u16 (sizeof (sctp_state_cookie_param_t));
+  state_cookie_param->creation_time = clib_host_to_net_u64 (sctp_time_now ());
+  state_cookie_param->cookie_lifespan =
+    clib_host_to_net_u32 (SCTP_VALID_COOKIE_LIFE);
+
+  sctp_compute_mac (sctp_conn, state_cookie_param);
+
+  pointer_offset += sizeof (sctp_state_cookie_param_t);
+
+  if (PREDICT_TRUE (ip4_addr != NULL))
+    {
+      sctp_ipv4_addr_param_t *ipv4_addr =
+	(sctp_ipv4_addr_param_t *) init_ack_chunk + pointer_offset;
+
+      ipv4_addr->param_hdr.type =
+	clib_host_to_net_u16 (SCTP_IPV4_ADDRESS_TYPE);
+      ipv4_addr->param_hdr.length =
+	clib_host_to_net_u16 (SCTP_IPV4_ADDRESS_TYPE_LENGTH);
+      ipv4_addr->address.as_u32 = ip4_addr->as_u32;
+
+      pointer_offset += SCTP_IPV4_ADDRESS_TYPE_LENGTH;
+    }
+  if (PREDICT_TRUE (ip6_addr != NULL))
+    {
+      sctp_ipv6_addr_param_t *ipv6_addr =
+	(sctp_ipv6_addr_param_t *) init_ack_chunk + pointer_offset;
+
+      ipv6_addr->param_hdr.type =
+	clib_host_to_net_u16 (SCTP_IPV6_ADDRESS_TYPE);
+      ipv6_addr->param_hdr.length =
+	clib_host_to_net_u16 (SCTP_IPV6_ADDRESS_TYPE_LENGTH);
+      ipv6_addr->address.as_u64[0] = ip6_addr->as_u64[0];
+      ipv6_addr->address.as_u64[1] = ip6_addr->as_u64[1];
+
+      pointer_offset += SCTP_IPV6_ADDRESS_TYPE_LENGTH;
+    }
+
+  if (sctp_conn->sub_conn[idx].connection.is_ip4)
+    {
+      ip4_param = (sctp_ipv4_addr_param_t *) init_ack_chunk + pointer_offset;
+      ip4_param->address.as_u32 =
+	sctp_conn->sub_conn[idx].connection.lcl_ip.ip4.as_u32;
+
+      pointer_offset += sizeof (sctp_ipv4_addr_param_t);
+    }
+  else
+    {
+      ip6_param = (sctp_ipv6_addr_param_t *) init_ack_chunk + pointer_offset;
+      ip6_param->address.as_u64[0] =
+	sctp_conn->sub_conn[idx].connection.lcl_ip.ip6.as_u64[0];
+      ip6_param->address.as_u64[1] =
+	sctp_conn->sub_conn[idx].connection.lcl_ip.ip6.as_u64[1];
+
+      pointer_offset += sizeof (sctp_ipv6_addr_param_t);
+    }
+
+  /* src_port & dst_port are already in network byte-order */
+  init_ack_chunk->sctp_hdr.checksum = 0;
+  init_ack_chunk->sctp_hdr.src_port =
+    sctp_conn->sub_conn[idx].connection.lcl_port;
+  init_ack_chunk->sctp_hdr.dst_port =
+    sctp_conn->sub_conn[idx].connection.rmt_port;
+  /* the sctp_conn->verification_tag is already in network byte-order (being a copy of the init_tag coming with the INIT chunk) */
+  init_ack_chunk->sctp_hdr.verification_tag = sctp_conn->remote_tag;
+  init_ack_chunk->initial_tsn =
+    clib_host_to_net_u32 (sctp_conn->local_initial_tsn);
+  SCTP_CONN_TRACKING_DBG ("init_ack_chunk->initial_tsn = %u",
+			  init_ack_chunk->initial_tsn);
+
+  vnet_sctp_set_chunk_type (&init_ack_chunk->chunk_hdr, INIT_ACK);
+  vnet_sctp_set_chunk_length (&init_ack_chunk->chunk_hdr, chunk_len);
+
+  init_ack_chunk->initiate_tag = sctp_conn->local_tag;
+
+  init_ack_chunk->a_rwnd =
+    clib_host_to_net_u32 (sctp_conn->sub_conn[idx].cwnd);
+  init_ack_chunk->inboud_streams_count =
+    clib_host_to_net_u16 (INBOUND_STREAMS_COUNT);
+  init_ack_chunk->outbound_streams_count =
+    clib_host_to_net_u16 (OUTBOUND_STREAMS_COUNT);
+
+  sctp_buffer_opaque (b)->sctp.connection_index =
+    sctp_conn->sub_conn[idx].connection.c_index;
+  sctp_buffer_opaque (b)->sctp.subconn_idx = idx;
+}
+
+/**
+ * Convert buffer to INIT-ACK
+ */
+void
+sctp_prepare_initack_chunk (sctp_connection_t * sctp_conn, u8 idx,
+			    vlib_buffer_t * b, ip4_address_t * ip4_addr,
+			    u8 add_ip4, ip6_address_t * ip6_addr, u8 add_ip6)
+{
+  vlib_main_t *vm = vlib_get_main ();
+  sctp_ipv4_addr_param_t *ip4_param = 0;
+  sctp_ipv6_addr_param_t *ip6_param = 0;
+  u32 random_seed = random_default_seed ();
+
+  sctp_reuse_buffer (vm, b);
+
+  /* The minimum size of the message is given by the sctp_init_ack_chunk_t */
+  u16 alloc_bytes =
+    sizeof (sctp_init_ack_chunk_t) + sizeof (sctp_state_cookie_param_t);
+
+  if (PREDICT_FALSE (add_ip4 == 1))
+    {
+      /* Create room for variable-length fields in the INIT_ACK chunk */
+      alloc_bytes += SCTP_IPV4_ADDRESS_TYPE_LENGTH;
+    }
+  if (PREDICT_FALSE (add_ip6 == 1))
+    {
+      /* Create room for variable-length fields in the INIT_ACK chunk */
+      alloc_bytes += SCTP_IPV6_ADDRESS_TYPE_LENGTH;
+    }
+
+  if (sctp_conn->sub_conn[idx].connection.is_ip4)
+    alloc_bytes += sizeof (sctp_ipv4_addr_param_t);
+  else
+    alloc_bytes += sizeof (sctp_ipv6_addr_param_t);
+
+  /* As per RFC 4960 the chunk_length value does NOT contemplate
+   * the size of the first header (see sctp_header_t) and any padding
+   */
+  u16 chunk_len = alloc_bytes - sizeof (sctp_header_t);
+
+  alloc_bytes += vnet_sctp_calculate_padding (alloc_bytes);
+
+  sctp_init_ack_chunk_t *init_ack_chunk =
+    vlib_buffer_push_uninit (b, alloc_bytes);
+
+  u16 pointer_offset = sizeof (sctp_init_ack_chunk_t);
+
+  /* Create State Cookie parameter */
+  sctp_state_cookie_param_t *state_cookie_param =
+    (sctp_state_cookie_param_t *) ((char *) init_ack_chunk + pointer_offset);
+
+  state_cookie_param->param_hdr.type =
+    clib_host_to_net_u16 (SCTP_STATE_COOKIE_TYPE);
+  state_cookie_param->param_hdr.length =
+    clib_host_to_net_u16 (sizeof (sctp_state_cookie_param_t));
+  state_cookie_param->creation_time = clib_host_to_net_u64 (sctp_time_now ());
+  state_cookie_param->cookie_lifespan =
+    clib_host_to_net_u32 (SCTP_VALID_COOKIE_LIFE);
+
+  sctp_compute_mac (sctp_conn, state_cookie_param);
+
+  pointer_offset += sizeof (sctp_state_cookie_param_t);
+
+  if (PREDICT_TRUE (ip4_addr != NULL))
+    {
+      sctp_ipv4_addr_param_t *ipv4_addr =
+	(sctp_ipv4_addr_param_t *) init_ack_chunk + pointer_offset;
+
+      ipv4_addr->param_hdr.type =
+	clib_host_to_net_u16 (SCTP_IPV4_ADDRESS_TYPE);
+      ipv4_addr->param_hdr.length =
+	clib_host_to_net_u16 (SCTP_IPV4_ADDRESS_TYPE_LENGTH);
+      ipv4_addr->address.as_u32 = ip4_addr->as_u32;
+
+      pointer_offset += SCTP_IPV4_ADDRESS_TYPE_LENGTH;
+    }
+  if (PREDICT_TRUE (ip6_addr != NULL))
+    {
+      sctp_ipv6_addr_param_t *ipv6_addr =
+	(sctp_ipv6_addr_param_t *) init_ack_chunk + pointer_offset;
+
+      ipv6_addr->param_hdr.type =
+	clib_host_to_net_u16 (SCTP_IPV6_ADDRESS_TYPE);
+      ipv6_addr->param_hdr.length =
+	clib_host_to_net_u16 (SCTP_IPV6_ADDRESS_TYPE_LENGTH);
+      ipv6_addr->address.as_u64[0] = ip6_addr->as_u64[0];
+      ipv6_addr->address.as_u64[1] = ip6_addr->as_u64[1];
+
+      pointer_offset += SCTP_IPV6_ADDRESS_TYPE_LENGTH;
+    }
+
+  if (sctp_conn->sub_conn[idx].connection.is_ip4)
+    {
+      ip4_param = (sctp_ipv4_addr_param_t *) init_ack_chunk + pointer_offset;
+      ip4_param->address.as_u32 =
+	sctp_conn->sub_conn[idx].connection.lcl_ip.ip4.as_u32;
+
+      pointer_offset += sizeof (sctp_ipv4_addr_param_t);
+    }
+  else
+    {
+      ip6_param = (sctp_ipv6_addr_param_t *) init_ack_chunk + pointer_offset;
+      ip6_param->address.as_u64[0] =
+	sctp_conn->sub_conn[idx].connection.lcl_ip.ip6.as_u64[0];
+      ip6_param->address.as_u64[1] =
+	sctp_conn->sub_conn[idx].connection.lcl_ip.ip6.as_u64[1];
+
+      pointer_offset += sizeof (sctp_ipv6_addr_param_t);
+    }
+
+  /* src_port & dst_port are already in network byte-order */
+  init_ack_chunk->sctp_hdr.checksum = 0;
+  init_ack_chunk->sctp_hdr.src_port =
+    sctp_conn->sub_conn[idx].connection.lcl_port;
+  init_ack_chunk->sctp_hdr.dst_port =
+    sctp_conn->sub_conn[idx].connection.rmt_port;
+  /* the sctp_conn->verification_tag is already in network byte-order (being a copy of the init_tag coming with the INIT chunk) */
+  init_ack_chunk->sctp_hdr.verification_tag = sctp_conn->remote_tag;
+  init_ack_chunk->initial_tsn =
+    clib_host_to_net_u32 (sctp_conn->local_initial_tsn);
+  SCTP_CONN_TRACKING_DBG ("init_ack_chunk->initial_tsn = %u",
+			  init_ack_chunk->initial_tsn);
+
+  vnet_sctp_set_chunk_type (&init_ack_chunk->chunk_hdr, INIT_ACK);
+  vnet_sctp_set_chunk_length (&init_ack_chunk->chunk_hdr, chunk_len);
+
+  init_ack_chunk->initiate_tag =
+    clib_host_to_net_u32 (random_u32 (&random_seed));
+
+  init_ack_chunk->a_rwnd =
+    clib_host_to_net_u32 (sctp_conn->sub_conn[idx].cwnd);
+  init_ack_chunk->inboud_streams_count =
+    clib_host_to_net_u16 (INBOUND_STREAMS_COUNT);
+  init_ack_chunk->outbound_streams_count =
+    clib_host_to_net_u16 (OUTBOUND_STREAMS_COUNT);
+
+  sctp_conn->local_tag = init_ack_chunk->initiate_tag;
+
+  sctp_buffer_opaque (b)->sctp.connection_index =
+    sctp_conn->sub_conn[idx].connection.c_index;
+  sctp_buffer_opaque (b)->sctp.subconn_idx = idx;
+}
+
+/**
+ * Convert buffer to SHUTDOWN
+ */
+void
+sctp_prepare_shutdown_chunk (sctp_connection_t * sctp_conn, u8 idx,
+			     vlib_buffer_t * b)
+{
+  u16 alloc_bytes = sizeof (sctp_shutdown_association_chunk_t);
+
+  /* As per RFC 4960 the chunk_length value does NOT contemplate
+   * the size of the first header (see sctp_header_t) and any padding
+   */
+  u16 chunk_len = alloc_bytes - sizeof (sctp_header_t);
+
+  alloc_bytes += vnet_sctp_calculate_padding (alloc_bytes);
+
+  sctp_shutdown_association_chunk_t *shutdown_chunk =
+    vlib_buffer_push_uninit (b, alloc_bytes);
+
+  shutdown_chunk->sctp_hdr.checksum = 0;
+  /* No need of host_to_net conversion, already in net-byte order */
+  shutdown_chunk->sctp_hdr.src_port =
+    sctp_conn->sub_conn[idx].connection.lcl_port;
+  shutdown_chunk->sctp_hdr.dst_port =
+    sctp_conn->sub_conn[idx].connection.rmt_port;
+  shutdown_chunk->sctp_hdr.verification_tag = sctp_conn->remote_tag;
+  vnet_sctp_set_chunk_type (&shutdown_chunk->chunk_hdr, SHUTDOWN);
+  vnet_sctp_set_chunk_length (&shutdown_chunk->chunk_hdr, chunk_len);
+
+  shutdown_chunk->cumulative_tsn_ack = sctp_conn->last_rcvd_tsn;
+
+  sctp_buffer_opaque (b)->sctp.connection_index =
+    sctp_conn->sub_conn[idx].connection.c_index;
+  sctp_buffer_opaque (b)->sctp.subconn_idx = idx;
+}
+
+/*
+ * Send SHUTDOWN
+ */
+void
+sctp_send_shutdown (sctp_connection_t * sctp_conn)
+{
+  vlib_buffer_t *b;
+  u32 bi;
+  sctp_main_t *tm = vnet_get_sctp_main ();
+  vlib_main_t *vm = vlib_get_main ();
+
+  if (sctp_check_outstanding_data_chunks (sctp_conn) > 0)
+    return;
+
+  if (PREDICT_FALSE (sctp_get_free_buffer_index (tm, &bi)))
+    return;
+
+  u8 idx = SCTP_PRIMARY_PATH_IDX;
+
+  b = vlib_get_buffer (vm, bi);
+  sctp_init_buffer (vm, b);
+  sctp_prepare_shutdown_chunk (sctp_conn, idx, b);
+
+  sctp_enqueue_to_output_now (vm, b, bi,
+			      sctp_conn->sub_conn[idx].connection.is_ip4);
+}
+
+/**
+ * Convert buffer to SHUTDOWN_ACK
+ */
+void
+sctp_prepare_shutdown_ack_chunk (sctp_connection_t * sctp_conn, u8 idx,
+				 vlib_buffer_t * b)
+{
+  u16 alloc_bytes = sizeof (sctp_shutdown_association_chunk_t);
+  alloc_bytes += vnet_sctp_calculate_padding (alloc_bytes);
+
+  u16 chunk_len = alloc_bytes - sizeof (sctp_header_t);
+
+  sctp_shutdown_ack_chunk_t *shutdown_ack_chunk =
+    vlib_buffer_push_uninit (b, alloc_bytes);
+
+  shutdown_ack_chunk->sctp_hdr.checksum = 0;
+  /* No need of host_to_net conversion, already in net-byte order */
+  shutdown_ack_chunk->sctp_hdr.src_port =
+    sctp_conn->sub_conn[idx].connection.lcl_port;
+  shutdown_ack_chunk->sctp_hdr.dst_port =
+    sctp_conn->sub_conn[idx].connection.rmt_port;
+  shutdown_ack_chunk->sctp_hdr.verification_tag = sctp_conn->remote_tag;
+
+  vnet_sctp_set_chunk_type (&shutdown_ack_chunk->chunk_hdr, SHUTDOWN_ACK);
+  vnet_sctp_set_chunk_length (&shutdown_ack_chunk->chunk_hdr, chunk_len);
+
+  sctp_buffer_opaque (b)->sctp.connection_index =
+    sctp_conn->sub_conn[idx].connection.c_index;
+  sctp_buffer_opaque (b)->sctp.subconn_idx = idx;
+}
+
+/*
+ * Send SHUTDOWN_ACK
+ */
+void
+sctp_send_shutdown_ack (sctp_connection_t * sctp_conn, u8 idx,
+			vlib_buffer_t * b)
+{
+  vlib_main_t *vm = vlib_get_main ();
+
+  if (sctp_check_outstanding_data_chunks (sctp_conn) > 0)
+    return;
+
+  sctp_reuse_buffer (vm, b);
+
+  sctp_prepare_shutdown_ack_chunk (sctp_conn, idx, b);
+}
+
+/**
+ * Convert buffer to SACK
+ */
+void
+sctp_prepare_sack_chunk (sctp_connection_t * sctp_conn, u8 idx,
+			 vlib_buffer_t * b)
+{
+  vlib_main_t *vm = vlib_get_main ();
+
+  sctp_reuse_buffer (vm, b);
+
+  u16 alloc_bytes = sizeof (sctp_selective_ack_chunk_t);
+
+  /* As per RFC 4960 the chunk_length value does NOT contemplate
+   * the size of the first header (see sctp_header_t) and any padding
+   */
+  u16 chunk_len = alloc_bytes - sizeof (sctp_header_t);
+
+  alloc_bytes += vnet_sctp_calculate_padding (alloc_bytes);
+
+  sctp_selective_ack_chunk_t *sack = vlib_buffer_push_uninit (b, alloc_bytes);
+
+  sack->sctp_hdr.checksum = 0;
+  sack->sctp_hdr.src_port = sctp_conn->sub_conn[idx].connection.lcl_port;
+  sack->sctp_hdr.dst_port = sctp_conn->sub_conn[idx].connection.rmt_port;
+  sack->sctp_hdr.verification_tag = sctp_conn->remote_tag;
+  vnet_sctp_set_chunk_type (&sack->chunk_hdr, SACK);
+  vnet_sctp_set_chunk_length (&sack->chunk_hdr, chunk_len);
+
+  sack->cumulative_tsn_ack = sctp_conn->next_tsn_expected;
+
+  sctp_conn->ack_state = 0;
+
+  sctp_buffer_opaque (b)->sctp.connection_index =
+    sctp_conn->sub_conn[idx].connection.c_index;
+  sctp_buffer_opaque (b)->sctp.subconn_idx = idx;
+}
+
+/**
+ * Convert buffer to HEARTBEAT_ACK
+ */
+void
+sctp_prepare_heartbeat_ack_chunk (sctp_connection_t * sctp_conn, u8 idx,
+				  vlib_buffer_t * b)
+{
+  vlib_main_t *vm = vlib_get_main ();
+
+  u16 alloc_bytes = sizeof (sctp_hb_ack_chunk_t);
+
+  sctp_reuse_buffer (vm, b);
+
+  /* As per RFC 4960 the chunk_length value does NOT contemplate
+   * the size of the first header (see sctp_header_t) and any padding
+   */
+  u16 chunk_len = alloc_bytes - sizeof (sctp_header_t);
+
+  alloc_bytes += vnet_sctp_calculate_padding (alloc_bytes);
+
+  sctp_hb_ack_chunk_t *hb_ack = vlib_buffer_push_uninit (b, alloc_bytes);
+
+  hb_ack->sctp_hdr.checksum = 0;
+  /* No need of host_to_net conversion, already in net-byte order */
+  hb_ack->sctp_hdr.src_port = sctp_conn->sub_conn[idx].connection.lcl_port;
+  hb_ack->sctp_hdr.dst_port = sctp_conn->sub_conn[idx].connection.rmt_port;
+  hb_ack->sctp_hdr.verification_tag = sctp_conn->remote_tag;
+  hb_ack->hb_info.param_hdr.type = clib_host_to_net_u16 (1);
+  hb_ack->hb_info.param_hdr.length =
+    clib_host_to_net_u16 (sizeof (hb_ack->hb_info.hb_info));
+
+  vnet_sctp_set_chunk_type (&hb_ack->chunk_hdr, HEARTBEAT_ACK);
+  vnet_sctp_set_chunk_length (&hb_ack->chunk_hdr, chunk_len);
+
+  sctp_buffer_opaque (b)->sctp.connection_index =
+    sctp_conn->sub_conn[idx].connection.c_index;
+  sctp_buffer_opaque (b)->sctp.subconn_idx = idx;
+}
+
+/**
+ * Convert buffer to HEARTBEAT
+ */
+void
+sctp_prepare_heartbeat_chunk (sctp_connection_t * sctp_conn, u8 idx,
+			      vlib_buffer_t * b)
+{
+  u16 alloc_bytes = sizeof (sctp_hb_req_chunk_t);
+
+  /* As per RFC 4960 the chunk_length value does NOT contemplate
+   * the size of the first header (see sctp_header_t) and any padding
+   */
+  u16 chunk_len = alloc_bytes - sizeof (sctp_header_t);
+
+  alloc_bytes += vnet_sctp_calculate_padding (alloc_bytes);
+
+  sctp_hb_req_chunk_t *hb_req = vlib_buffer_push_uninit (b, alloc_bytes);
+
+  hb_req->sctp_hdr.checksum = 0;
+  /* No need of host_to_net conversion, already in net-byte order */
+  hb_req->sctp_hdr.src_port = sctp_conn->sub_conn[idx].connection.lcl_port;
+  hb_req->sctp_hdr.dst_port = sctp_conn->sub_conn[idx].connection.rmt_port;
+  hb_req->sctp_hdr.verification_tag = sctp_conn->remote_tag;
+  hb_req->hb_info.param_hdr.type = clib_host_to_net_u16 (1);
+  hb_req->hb_info.param_hdr.length =
+    clib_host_to_net_u16 (sizeof (hb_req->hb_info.hb_info));
+
+  vnet_sctp_set_chunk_type (&hb_req->chunk_hdr, HEARTBEAT);
+  vnet_sctp_set_chunk_length (&hb_req->chunk_hdr, chunk_len);
+
+  sctp_buffer_opaque (b)->sctp.connection_index =
+    sctp_conn->sub_conn[idx].connection.c_index;
+  sctp_buffer_opaque (b)->sctp.subconn_idx = idx;
+}
+
+void
+sctp_send_heartbeat (sctp_connection_t * sctp_conn)
+{
+  vlib_buffer_t *b;
+  u32 bi;
+  sctp_main_t *tm = vnet_get_sctp_main ();
+  vlib_main_t *vm = vlib_get_main ();
+
+  u8 i;
+  u64 now = sctp_time_now ();
+
+  for (i = 0; i < MAX_SCTP_CONNECTIONS; i++)
+    {
+      if (sctp_conn->sub_conn[i].state == SCTP_SUBCONN_STATE_DOWN)
+	continue;
+
+      if (now > (sctp_conn->sub_conn[i].last_seen + SCTP_HB_INTERVAL))
+	{
+	  if (PREDICT_FALSE (sctp_get_free_buffer_index (tm, &bi)))
+	    return;
+
+	  b = vlib_get_buffer (vm, bi);
+	  sctp_init_buffer (vm, b);
+	  sctp_prepare_heartbeat_chunk (sctp_conn, i, b);
+
+	  sctp_enqueue_to_output_now (vm, b, bi,
+				      sctp_conn->sub_conn[i].
+				      connection.is_ip4);
+
+	  sctp_conn->sub_conn[i].unacknowledged_hb += 1;
+	}
+    }
+}
+
+/**
+ * Convert buffer to SHUTDOWN_COMPLETE
+ */
+void
+sctp_prepare_shutdown_complete_chunk (sctp_connection_t * sctp_conn, u8 idx,
+				      vlib_buffer_t * b)
+{
+  u16 alloc_bytes = sizeof (sctp_shutdown_association_chunk_t);
+  alloc_bytes += vnet_sctp_calculate_padding (alloc_bytes);
+
+  u16 chunk_len = alloc_bytes - sizeof (sctp_header_t);
+
+  sctp_shutdown_complete_chunk_t *shutdown_complete =
+    vlib_buffer_push_uninit (b, alloc_bytes);
+
+  shutdown_complete->sctp_hdr.checksum = 0;
+  /* No need of host_to_net conversion, already in net-byte order */
+  shutdown_complete->sctp_hdr.src_port =
+    sctp_conn->sub_conn[idx].connection.lcl_port;
+  shutdown_complete->sctp_hdr.dst_port =
+    sctp_conn->sub_conn[idx].connection.rmt_port;
+  shutdown_complete->sctp_hdr.verification_tag = sctp_conn->remote_tag;
+
+  vnet_sctp_set_chunk_type (&shutdown_complete->chunk_hdr, SHUTDOWN_COMPLETE);
+  vnet_sctp_set_chunk_length (&shutdown_complete->chunk_hdr, chunk_len);
+
+  sctp_buffer_opaque (b)->sctp.connection_index =
+    sctp_conn->sub_conn[idx].connection.c_index;
+  sctp_buffer_opaque (b)->sctp.subconn_idx = idx;
+}
+
+void
+sctp_send_shutdown_complete (sctp_connection_t * sctp_conn, u8 idx,
+			     vlib_buffer_t * b0)
+{
+  vlib_main_t *vm = vlib_get_main ();
+
+  if (sctp_check_outstanding_data_chunks (sctp_conn) > 0)
+    return;
+
+  sctp_reuse_buffer (vm, b0);
+
+  sctp_prepare_shutdown_complete_chunk (sctp_conn, idx, b0);
+}
+
+/*
+ *  Send INIT
+ */
+void
+sctp_send_init (sctp_connection_t * sctp_conn)
+{
+  vlib_buffer_t *b;
+  u32 bi;
+  sctp_main_t *tm = vnet_get_sctp_main ();
+  vlib_main_t *vm = vlib_get_main ();
+
+  if (PREDICT_FALSE (sctp_conn->init_retransmit_err > SCTP_MAX_INIT_RETRANS))
+    {
+      clib_warning ("Reached MAX_INIT_RETRANS times. Aborting connection.");
+
+      session_stream_connect_notify (&sctp_conn->sub_conn
+				     [SCTP_PRIMARY_PATH_IDX].connection, 1);
+
+      sctp_connection_timers_reset (sctp_conn);
+
+      sctp_connection_cleanup (sctp_conn);
+
+      return;
+    }
+
+  if (PREDICT_FALSE (sctp_get_free_buffer_index (tm, &bi)))
+    return;
+
+  b = vlib_get_buffer (vm, bi);
+  u8 idx = SCTP_PRIMARY_PATH_IDX;
+
+  sctp_init_buffer (vm, b);
+  sctp_prepare_init_chunk (sctp_conn, idx, b);
+
+  sctp_push_ip_hdr (tm, &sctp_conn->sub_conn[idx], b);
+  sctp_enqueue_to_ip_lookup (vm, b, bi, sctp_conn->sub_conn[idx].c_is_ip4,
+			     sctp_conn->sub_conn[idx].c_fib_index);
+
+  /* Start the T1_INIT timer */
+  sctp_timer_set (sctp_conn, idx, SCTP_TIMER_T1_INIT,
+		  sctp_conn->sub_conn[idx].RTO);
+
+  /* Change state to COOKIE_WAIT */
+  sctp_conn->state = SCTP_STATE_COOKIE_WAIT;
+
+  /* Measure RTT with this */
+  sctp_conn->sub_conn[idx].rtt_ts = sctp_time_now ();
+}
+
+/**
+ * Push SCTP header and update connection variables
+ */
+static void
+sctp_push_hdr_i (sctp_connection_t * sctp_conn, vlib_buffer_t * b,
+		 sctp_state_t next_state)
+{
+  u16 data_len = b->current_length;
+
+  if (b->flags & VLIB_BUFFER_TOTAL_LENGTH_VALID)
+    data_len += b->total_length_not_including_first_buffer;
+
+  ASSERT (!b->total_length_not_including_first_buffer
+	  || (b->flags & VLIB_BUFFER_NEXT_PRESENT)
+	  || !(b->flags & VLIB_BUFFER_TOTAL_LENGTH_VALID));
+
+  SCTP_ADV_DBG_OUTPUT ("b->current_length = %u, "
+		       "b->current_data = %p "
+		       "data_len = %u",
+		       b->current_length, b->current_data, data_len);
+
+  u16 data_padding = vnet_sctp_calculate_padding (b->current_length);
+  if (data_padding > 0)
+    {
+      u8 *p_tail = vlib_buffer_put_uninit (b, data_padding);
+      clib_memset_u8 (p_tail, 0, data_padding);
+    }
+
+  u16 bytes_to_add = sizeof (sctp_payload_data_chunk_t);
+  u16 chunk_length = data_len + bytes_to_add - sizeof (sctp_header_t);
+
+  sctp_payload_data_chunk_t *data_chunk =
+    vlib_buffer_push_uninit (b, bytes_to_add);
+
+  u8 idx = sctp_data_subconn_select (sctp_conn);
+  SCTP_DBG_OUTPUT
+    ("SCTP_CONN = %p, IDX = %u, S_INDEX = %u, C_INDEX = %u, sctp_conn->[...].LCL_PORT = %u, sctp_conn->[...].RMT_PORT = %u",
+     sctp_conn, idx, sctp_conn->sub_conn[idx].connection.s_index,
+     sctp_conn->sub_conn[idx].connection.c_index,
+     sctp_conn->sub_conn[idx].connection.lcl_port,
+     sctp_conn->sub_conn[idx].connection.rmt_port);
+  data_chunk->sctp_hdr.checksum = 0;
+  data_chunk->sctp_hdr.src_port =
+    sctp_conn->sub_conn[idx].connection.lcl_port;
+  data_chunk->sctp_hdr.dst_port =
+    sctp_conn->sub_conn[idx].connection.rmt_port;
+  data_chunk->sctp_hdr.verification_tag = sctp_conn->remote_tag;
+
+  data_chunk->tsn = clib_host_to_net_u32 (sctp_conn->next_tsn);
+  data_chunk->stream_id = clib_host_to_net_u16 (0);
+  data_chunk->stream_seq = clib_host_to_net_u16 (0);
+
+  vnet_sctp_set_chunk_type (&data_chunk->chunk_hdr, DATA);
+  vnet_sctp_set_chunk_length (&data_chunk->chunk_hdr, chunk_length);
+
+  vnet_sctp_set_bbit (&data_chunk->chunk_hdr);
+  vnet_sctp_set_ebit (&data_chunk->chunk_hdr);
+
+  SCTP_ADV_DBG_OUTPUT ("POINTER_WITH_DATA = %p, DATA_OFFSET = %u",
+		       b->data, b->current_data);
+
+  if (sctp_conn->sub_conn[idx].state != SCTP_SUBCONN_AWAITING_SACK)
+    {
+      sctp_conn->sub_conn[idx].state = SCTP_SUBCONN_AWAITING_SACK;
+      sctp_conn->last_unacked_tsn = sctp_conn->next_tsn;
+    }
+
+  sctp_conn->next_tsn += data_len;
+
+  u32 inflight = sctp_conn->next_tsn - sctp_conn->last_unacked_tsn;
+  /* Section 7.2.2; point (3) */
+  if (sctp_conn->sub_conn[idx].partially_acked_bytes >=
+      sctp_conn->sub_conn[idx].cwnd
+      && inflight >= sctp_conn->sub_conn[idx].cwnd)
+    {
+      sctp_conn->sub_conn[idx].cwnd += sctp_conn->sub_conn[idx].PMTU;
+      sctp_conn->sub_conn[idx].partially_acked_bytes -=
+	sctp_conn->sub_conn[idx].cwnd;
+    }
+
+  sctp_conn->sub_conn[idx].last_data_ts = sctp_time_now ();
+
+  sctp_buffer_opaque (b)->sctp.connection_index =
+    sctp_conn->sub_conn[idx].connection.c_index;
+
+  sctp_buffer_opaque (b)->sctp.subconn_idx = idx;
+}
+
+u32
+sctp_push_header (transport_connection_t * trans_conn, vlib_buffer_t * b)
+{
+  sctp_connection_t *sctp_conn =
+    sctp_get_connection_from_transport (trans_conn);
+
+  SCTP_DBG_OUTPUT ("TRANS_CONN = %p, SCTP_CONN = %p, "
+		   "S_INDEX = %u, C_INDEX = %u,"
+		   "trans_conn->LCL_PORT = %u, trans_conn->RMT_PORT = %u",
+		   trans_conn,
+		   sctp_conn,
+		   trans_conn->s_index,
+		   trans_conn->c_index,
+		   trans_conn->lcl_port, trans_conn->rmt_port);
+
+  sctp_push_hdr_i (sctp_conn, b, SCTP_STATE_ESTABLISHED);
+
+  sctp_trajectory_add_start (b, 3);
+
+  return 0;
+}
+
+u32
+sctp_prepare_data_retransmit (sctp_connection_t * sctp_conn,
+			      u8 idx,
+			      u32 offset,
+			      u32 max_deq_bytes, vlib_buffer_t ** b)
+{
+  sctp_main_t *tm = vnet_get_sctp_main ();
+  vlib_main_t *vm = vlib_get_main ();
+  int n_bytes = 0;
+  u32 bi, available_bytes, seg_size;
+  u8 *data;
+
+  ASSERT (sctp_conn->state >= SCTP_STATE_ESTABLISHED);
+  ASSERT (max_deq_bytes != 0);
+
+  /*
+   * Make sure we can retransmit something
+   */
+  available_bytes =
+    transport_max_tx_dequeue (&sctp_conn->sub_conn[idx].connection);
+  ASSERT (available_bytes >= offset);
+  available_bytes -= offset;
+  if (!available_bytes)
+    return 0;
+  max_deq_bytes = clib_min (sctp_conn->sub_conn[idx].cwnd, max_deq_bytes);
+  max_deq_bytes = clib_min (available_bytes, max_deq_bytes);
+
+  seg_size = max_deq_bytes;
+
+  /*
+   * Allocate and fill in buffer(s)
+   */
+
+  if (PREDICT_FALSE (sctp_get_free_buffer_index (tm, &bi)))
+    return 0;
+  *b = vlib_get_buffer (vm, bi);
+  data = sctp_init_buffer (vm, *b);
+
+  /* Easy case, buffer size greater than mss */
+  if (PREDICT_TRUE (seg_size <= tm->bytes_per_buffer))
+    {
+      n_bytes =
+	session_tx_fifo_peek_bytes (&sctp_conn->sub_conn[idx].connection,
+				    data, offset, max_deq_bytes);
+      ASSERT (n_bytes == max_deq_bytes);
+      b[0]->current_length = n_bytes;
+      sctp_push_hdr_i (sctp_conn, *b, sctp_conn->state);
+    }
+
+  return n_bytes;
+}
+
+void
+sctp_data_retransmit (sctp_connection_t * sctp_conn)
+{
+  vlib_main_t *vm = vlib_get_main ();
+  vlib_buffer_t *b = 0;
+  u32 bi, n_bytes = 0;
+
+  u8 idx = sctp_data_subconn_select (sctp_conn);
+
+  SCTP_DBG_OUTPUT
+    ("SCTP_CONN = %p, IDX = %u, S_INDEX = %u, C_INDEX = %u, sctp_conn->[...].LCL_PORT = %u, sctp_conn->[...].RMT_PORT = %u",
+     sctp_conn, idx, sctp_conn->sub_conn[idx].connection.s_index,
+     sctp_conn->sub_conn[idx].connection.c_index,
+     sctp_conn->sub_conn[idx].connection.lcl_port,
+     sctp_conn->sub_conn[idx].connection.rmt_port);
+
+  if (sctp_conn->state >= SCTP_STATE_ESTABLISHED)
+    {
+      return;
+    }
+
+  n_bytes =
+    sctp_prepare_data_retransmit (sctp_conn, idx, 0,
+				  sctp_conn->sub_conn[idx].cwnd, &b);
+  if (n_bytes > 0)
+    SCTP_DBG_OUTPUT ("We have data (%u bytes) to retransmit", n_bytes);
+
+  bi = vlib_get_buffer_index (vm, b);
+
+  sctp_enqueue_to_output_now (vm, b, bi,
+			      sctp_conn->sub_conn[idx].connection.is_ip4);
+
+  return;
+}
+
+#if SCTP_DEBUG_STATE_MACHINE
+always_inline u8
+sctp_validate_output_state_machine (sctp_connection_t * sctp_conn,
+				    u8 chunk_type)
+{
+  u8 result = 0;
+  switch (sctp_conn->state)
+    {
+    case SCTP_STATE_CLOSED:
+      if (chunk_type != INIT && chunk_type != INIT_ACK)
+	result = 1;
+      break;
+    case SCTP_STATE_ESTABLISHED:
+      if (chunk_type != DATA && chunk_type != HEARTBEAT &&
+	  chunk_type != HEARTBEAT_ACK && chunk_type != SACK &&
+	  chunk_type != COOKIE_ACK && chunk_type != SHUTDOWN)
+	result = 1;
+      break;
+    case SCTP_STATE_COOKIE_WAIT:
+      if (chunk_type != COOKIE_ECHO)
+	result = 1;
+      break;
+    case SCTP_STATE_SHUTDOWN_SENT:
+      if (chunk_type != SHUTDOWN_COMPLETE)
+	result = 1;
+      break;
+    case SCTP_STATE_SHUTDOWN_RECEIVED:
+      if (chunk_type != SHUTDOWN_ACK)
+	result = 1;
+      break;
+    }
+  return result;
+}
+#endif
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */