[mirror_frr.git] / bgpd / bgp_packet.c

/* BGP packet management routine.
   Copyright (C) 1999 Kunihiro Ishiguro

This file is part of GNU Zebra.

GNU Zebra is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2, or (at your option) any
later version.

GNU Zebra is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Zebra; see the file COPYING.  If not, write to the Free
Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA.  */

#include <zebra.h>

#include "thread.h"
#include "stream.h"
#include "network.h"
#include "prefix.h"
#include "command.h"
#include "log.h"
#include "memory.h"
#include "sockunion.h"          /* for inet_ntop () */
#include "sockopt.h"
#include "linklist.h"
#include "plist.h"
#include "queue.h"
#include "filter.h"

#include "bgpd/bgpd.h"
#include "bgpd/bgp_table.h"
#include "bgpd/bgp_dump.h"
#include "bgpd/bgp_attr.h"
#include "bgpd/bgp_debug.h"
#include "bgpd/bgp_fsm.h"
#include "bgpd/bgp_route.h"
#include "bgpd/bgp_packet.h"
#include "bgpd/bgp_open.h"
#include "bgpd/bgp_aspath.h"
#include "bgpd/bgp_community.h"
#include "bgpd/bgp_ecommunity.h"
#include "bgpd/bgp_lcommunity.h"
#include "bgpd/bgp_network.h"
#include "bgpd/bgp_mplsvpn.h"
#include "bgpd/bgp_evpn.h"
#include "bgpd/bgp_encap.h"
#include "bgpd/bgp_evpn.h"
#include "bgpd/bgp_advertise.h"
#include "bgpd/bgp_vty.h"
#include "bgpd/bgp_updgrp.h"

/* Set up BGP packet marker and packet type. */
int
bgp_packet_set_marker (struct stream *s, u_char type)
{
  int i;

  /* Fill in marker. */
  for (i = 0; i < BGP_MARKER_SIZE; i++)
    stream_putc (s, 0xff);

  /* Dummy total length. This field is should be filled in later on. */
  stream_putw (s, 0);

  /* BGP packet type. */
  stream_putc (s, type);

  /* Return current stream size. */
  return stream_get_endp (s);
}

/* Set BGP packet header size entry.  If size is zero then use current
   stream size. */
int
bgp_packet_set_size (struct stream *s)
{
  int cp;

  /* Preserve current pointer. */
  cp = stream_get_endp (s);
  stream_putw_at (s, BGP_MARKER_SIZE, cp);

  return cp;
}

/* Add new packet to the peer. */
void
bgp_packet_add (struct peer *peer, struct stream *s)
{
  /* Add packet to the end of list. */
  stream_fifo_push (peer->obuf, s);
}

/* Free first packet. */
static void
bgp_packet_delete (struct peer *peer)
{
  stream_free (stream_fifo_pop (peer->obuf));
}

/* Check file descriptor whether connect is established. */
int
bgp_connect_check (struct peer *peer, int change_state)
{
  int status;
  socklen_t slen;
  int ret;

  /* Anyway I have to reset read and write thread. */
  BGP_READ_OFF (peer->t_read);
  BGP_WRITE_OFF (peer->t_write);

  /* Check file descriptor. */
  slen = sizeof (status);
  ret = getsockopt(peer->fd, SOL_SOCKET, SO_ERROR, (void *) &status, &slen);

  /* If getsockopt is fail, this is fatal error. */
  if (ret < 0)
    {
      zlog_info ("can't get sockopt for nonblocking connect");
      BGP_EVENT_ADD (peer, TCP_fatal_error);
      return -1;
    }      

  /* When status is 0 then TCP connection is established. */
  if (status == 0)
    {
      BGP_EVENT_ADD (peer, TCP_connection_open);
      return 1;
    }
  else
    {
      if (bgp_debug_neighbor_events(peer))
          zlog_debug ("%s [Event] Connect failed (%s)",
                      peer->host, safe_strerror (errno));
      if (change_state)
        BGP_EVENT_ADD (peer, TCP_connection_open_failed);
      return 0;
    }
}

static struct stream *
bgp_update_packet_eor (struct peer *peer, afi_t afi, safi_t safi)
{
  struct stream *s;
  iana_afi_t pkt_afi;
  safi_t pkt_safi;

  if (DISABLE_BGP_ANNOUNCE)
    return NULL;

  if (bgp_debug_neighbor_events(peer))
    zlog_debug ("send End-of-RIB for %s to %s", afi_safi_print (afi, safi), peer->host);

  s = stream_new (BGP_MAX_PACKET_SIZE);

  /* Make BGP update packet. */
  bgp_packet_set_marker (s, BGP_MSG_UPDATE);

  /* Unfeasible Routes Length */
  stream_putw (s, 0);

  if (afi == AFI_IP && safi == SAFI_UNICAST)
    {
      /* Total Path Attribute Length */
      stream_putw (s, 0);
    }
  else
    {
      /* Convert AFI, SAFI to values for packet. */
      bgp_map_afi_safi_int2iana (afi, safi, &pkt_afi, &pkt_safi);

      /* Total Path Attribute Length */
      stream_putw (s, 6);
      stream_putc (s, BGP_ATTR_FLAG_OPTIONAL);
      stream_putc (s, BGP_ATTR_MP_UNREACH_NLRI);
      stream_putc (s, 3);
      stream_putw (s, pkt_afi);
      stream_putc (s, pkt_safi);
    }

  bgp_packet_set_size (s);
  bgp_packet_add (peer, s);
  return s;
}

/* Get next packet to be written.  */
static struct stream *
bgp_write_packet (struct peer *peer)
{
  struct stream *s = NULL;
  struct peer_af *paf;
  struct bpacket *next_pkt;
  afi_t afi;
  safi_t safi;

  s = stream_fifo_head (peer->obuf);
  if (s)
    return s;

  /*
   * The code beyond this part deals with update packets, proceed only
   * if peer is Established and updates are not on hold (as part of
   * update-delay post processing).
   */
  if (peer->status != Established)
    return NULL;

  if (peer->bgp && peer->bgp->main_peers_update_hold)
    return NULL;

  for (afi = AFI_IP; afi < AFI_MAX; afi++)
    for (safi = SAFI_UNICAST; safi < SAFI_MAX; safi++)
      {
        paf = peer_af_find (peer, afi, safi);
        if (!paf || !PAF_SUBGRP(paf))
          continue;
        next_pkt = paf->next_pkt_to_send;

        /* Try to generate a packet for the peer if we are at the end of
         * the list. Always try to push out WITHDRAWs first. */
        if (!next_pkt || !next_pkt->buffer)
          {
            next_pkt = subgroup_withdraw_packet(PAF_SUBGRP(paf));
            if (!next_pkt || !next_pkt->buffer)
              subgroup_update_packet (PAF_SUBGRP(paf));
            next_pkt = paf->next_pkt_to_send;
          }

        /* If we still don't have a packet to send to the peer, then
         * try to find out out if we have to send eor or if not, skip to
         * the next AFI, SAFI.
         * Don't send the EOR prematurely... if the subgroup's coalesce
         * timer is running, the adjacency-out structure is not created
         * yet.
         */
        if (!next_pkt || !next_pkt->buffer)
          {
            if (CHECK_FLAG (peer->cap, PEER_CAP_RESTART_RCV))
              {
                if (!(PAF_SUBGRP(paf))->t_coalesce &&
                    peer->afc_nego[afi][safi] && peer->synctime
                    && ! CHECK_FLAG (peer->af_sflags[afi][safi],
                                     PEER_STATUS_EOR_SEND)
                    && safi != SAFI_EVPN)
                  {
                    SET_FLAG (peer->af_sflags[afi][safi],
                              PEER_STATUS_EOR_SEND);
                    return bgp_update_packet_eor (peer, afi, safi);
                  }
              }
            continue;
          }


        /*
         * Found a packet template to send, overwrite packet with appropriate
         * attributes from peer and advance peer
         */
        s = bpacket_reformat_for_peer (next_pkt, paf);
        bpacket_queue_advance_peer (paf);
        return s;
      }

  return NULL;
}

/* The next action for the peer from a write perspective */
static void
bgp_write_proceed_actions (struct peer *peer)
{
  afi_t afi;
  safi_t safi;
  struct peer_af *paf;
  struct bpacket *next_pkt;
  int fullq_found = 0;
  struct update_subgroup *subgrp;

  if (stream_fifo_head (peer->obuf))
    {
      BGP_WRITE_ON (peer->t_write, bgp_write, peer->fd);
      return;
    }

   for (afi = AFI_IP; afi < AFI_MAX; afi++)
     for (safi = SAFI_UNICAST; safi < SAFI_MAX; safi++)
      {
        paf = peer_af_find (peer, afi, safi);
        if (!paf)
          continue;
        subgrp = paf->subgroup;
        if (!subgrp)
          continue;

        next_pkt = paf->next_pkt_to_send;
        if (next_pkt && next_pkt->buffer)
          {
            BGP_WRITE_ON (peer->t_write, bgp_write, peer->fd);
            return;
          }

        /* No packets readily available for AFI/SAFI, are there subgroup packets
         * that need to be generated? */
        if (bpacket_queue_is_full(SUBGRP_INST(subgrp),
                                  SUBGRP_PKTQ(subgrp)))
          fullq_found = 1;
        else if (subgroup_packets_to_build (subgrp))
          {
            BGP_WRITE_ON (peer->t_write, bgp_write, peer->fd);
            return;
          }

        /* No packets to send, see if EOR is pending */
        if (CHECK_FLAG (peer->cap, PEER_CAP_RESTART_RCV))
          {
            if (!subgrp->t_coalesce &&
                peer->afc_nego[afi][safi] &&
                peer->synctime &&
                !CHECK_FLAG(peer->af_sflags[afi][safi],
                            PEER_STATUS_EOR_SEND) &&
                safi != SAFI_MPLS_VPN)
              {
                BGP_WRITE_ON (peer->t_write, bgp_write, peer->fd);
                return;
              }

          }
      }
  if (fullq_found)
    {
      BGP_WRITE_ON (peer->t_write, bgp_write, peer->fd);
      return;
    }
}

/* Write packet to the peer. */
int
bgp_write (struct thread *thread)
{
  struct peer *peer;
  u_char type;
  struct stream *s;
  int num;
  int update_last_write = 0;
  unsigned int count = 0;
  unsigned int oc = 0;

  /* Yes first of all get peer pointer. */
  peer = THREAD_ARG (thread);
  peer->t_write = NULL;

  /* For non-blocking IO check. */
  if (peer->status == Connect)
    {
      bgp_connect_check (peer, 1);
      return 0;
    }

  s = bgp_write_packet (peer);
  if (!s)
    {
      bgp_write_proceed_actions (peer);
      return 0;
    }

  sockopt_cork (peer->fd, 1);

  oc = peer->update_out;

  /* Nonblocking write until TCP output buffer is full.  */
  do
    {
      int writenum;

      /* Number of bytes to be sent.  */
      writenum = stream_get_endp (s) - stream_get_getp (s);

      /* Call write() system call.  */
      num = write (peer->fd, STREAM_PNT (s), writenum);
      if (num < 0)
        {
          /* write failed either retry needed or error */
          if (ERRNO_IO_RETRY(errno))
                break;

          BGP_EVENT_ADD (peer, TCP_fatal_error);
          return 0;
        }

      if (num != writenum)
        {
          /* Partial write */
          stream_forward_getp (s, num);
          break;
        }

      /* Retrieve BGP packet type. */
      stream_set_getp (s, BGP_MARKER_SIZE + 2);
      type = stream_getc (s);

      switch (type)
        {
        case BGP_MSG_OPEN:
          peer->open_out++;
          break;
        case BGP_MSG_UPDATE:
          peer->update_out++;
          break;
        case BGP_MSG_NOTIFY:
          peer->notify_out++;
          /* Double start timer. */
          peer->v_start *= 2;

          /* Overflow check. */
          if (peer->v_start >= (60 * 2))
            peer->v_start = (60 * 2);

          /* Flush any existing events */
          BGP_EVENT_ADD (peer, BGP_Stop);
          goto done;

        case BGP_MSG_KEEPALIVE:
          peer->keepalive_out++;
          break;
        case BGP_MSG_ROUTE_REFRESH_NEW:
        case BGP_MSG_ROUTE_REFRESH_OLD:
          peer->refresh_out++;
          break;
        case BGP_MSG_CAPABILITY:
          peer->dynamic_cap_out++;
          break;
        }

      /* OK we send packet so delete it. */
      bgp_packet_delete (peer);
      update_last_write = 1;
    }
  while (++count < peer->bgp->wpkt_quanta &&
         (s = bgp_write_packet (peer)) != NULL);

  bgp_write_proceed_actions (peer);

 done:
  /* Update last_update if UPDATEs were written. */
  if (peer->update_out > oc)
    peer->last_update = bgp_clock ();

  /* If we TXed any flavor of packet update last_write */
  if (update_last_write)
    peer->last_write = bgp_clock ();

  sockopt_cork (peer->fd, 0);
  return 0;
}

/* This is only for sending NOTIFICATION message to neighbor. */
static int
bgp_write_notify (struct peer *peer)
{
  int ret, val;
  u_char type;
  struct stream *s;

  /* There should be at least one packet. */
  s = stream_fifo_head (peer->obuf);
  if (!s)
    return 0;
  assert (stream_get_endp (s) >= BGP_HEADER_SIZE);

  /* Stop collecting data within the socket */
  sockopt_cork (peer->fd, 0);

  /* socket is in nonblocking mode, if we can't deliver the NOTIFY, well,
   * we only care about getting a clean shutdown at this point. */
  ret = write (peer->fd, STREAM_DATA (s), stream_get_endp (s));

  /* only connection reset/close gets counted as TCP_fatal_error, failure
   * to write the entire NOTIFY doesn't get different FSM treatment */
  if (ret <= 0)
    {
      BGP_EVENT_ADD (peer, TCP_fatal_error);
      return 0;
    }

  /* Disable Nagle, make NOTIFY packet go out right away */
  val = 1;
  (void) setsockopt (peer->fd, IPPROTO_TCP, TCP_NODELAY,
                            (char *) &val, sizeof (val));

  /* Retrieve BGP packet type. */
  stream_set_getp (s, BGP_MARKER_SIZE + 2);
  type = stream_getc (s);

  assert (type == BGP_MSG_NOTIFY);

  /* Type should be notify. */
  peer->notify_out++;

  /* Double start timer. */
  peer->v_start *= 2;

  /* Overflow check. */
  if (peer->v_start >= (60 * 2))
    peer->v_start = (60 * 2);

  /* Handle Graceful Restart case where the state changes to
     Connect instead of Idle */
  BGP_EVENT_ADD (peer, BGP_Stop);

  return 0;
}

/* Make keepalive packet and send it to the peer. */
void
bgp_keepalive_send (struct peer *peer)
{
  struct stream *s;

  s = stream_new (BGP_MAX_PACKET_SIZE);

  /* Make keepalive packet. */
  bgp_packet_set_marker (s, BGP_MSG_KEEPALIVE);

  /* Set packet size. */
  (void)bgp_packet_set_size (s);

  /* Dump packet if debug option is set. */
  /* bgp_packet_dump (s); */
 
  if (bgp_debug_keepalive(peer))
    zlog_debug ("%s sending KEEPALIVE", peer->host); 

  /* Add packet to the peer. */
  bgp_packet_add (peer, s);

  BGP_WRITE_ON (peer->t_write, bgp_write, peer->fd);
}

/* Make open packet and send it to the peer. */
void
bgp_open_send (struct peer *peer)
{
  struct stream *s;
  u_int16_t send_holdtime;
  as_t local_as;

  if (CHECK_FLAG (peer->config, PEER_CONFIG_TIMER))
    send_holdtime = peer->holdtime;
  else
    send_holdtime = peer->bgp->default_holdtime;

  /* local-as Change */
  if (peer->change_local_as)
    local_as = peer->change_local_as; 
  else
    local_as = peer->local_as; 

  s = stream_new (BGP_MAX_PACKET_SIZE);

  /* Make open packet. */
  bgp_packet_set_marker (s, BGP_MSG_OPEN);

  /* Set open packet values. */
  stream_putc (s, BGP_VERSION_4);        /* BGP version */
  stream_putw (s, (local_as <= BGP_AS_MAX) ? (u_int16_t) local_as 
                                           : BGP_AS_TRANS);
  stream_putw (s, send_holdtime);        /* Hold Time */
  stream_put_in_addr (s, &peer->local_id); /* BGP Identifier */

  /* Set capability code. */
  bgp_open_capability (s, peer);

  /* Set BGP packet length. */
  (void)bgp_packet_set_size (s);

  if (bgp_debug_neighbor_events(peer))
    zlog_debug ("%s sending OPEN, version %d, my as %u, holdtime %d, id %s", 
               peer->host, BGP_VERSION_4, local_as,
               send_holdtime, inet_ntoa (peer->local_id));

  /* Dump packet if debug option is set. */
  /* bgp_packet_dump (s); */

  /* Add packet to the peer. */
  bgp_packet_add (peer, s);

  BGP_WRITE_ON (peer->t_write, bgp_write, peer->fd);
}

/* Send BGP notify packet with data potion. */
void
bgp_notify_send_with_data (struct peer *peer, u_char code, u_char sub_code,
                           u_char *data, size_t datalen)
{
  struct stream *s;
  int length;

  /* Allocate new stream. */
  s = stream_new (BGP_MAX_PACKET_SIZE);

  /* Make nitify packet. */
  bgp_packet_set_marker (s, BGP_MSG_NOTIFY);

  /* Set notify packet values. */
  stream_putc (s, code);        /* BGP notify code */
  stream_putc (s, sub_code);    /* BGP notify sub_code */

  /* If notify data is present. */
  if (data)
    stream_write (s, data, datalen);
  
  /* Set BGP packet length. */
  length = bgp_packet_set_size (s);
  
  /* Add packet to the peer. */
  stream_fifo_clean (peer->obuf);
  bgp_packet_add (peer, s);

  /* For debug */
  {
    struct bgp_notify bgp_notify;
    int first = 0;
    int i;
    char c[4];

    bgp_notify.code = code;
    bgp_notify.subcode = sub_code;
    bgp_notify.data = NULL;
    bgp_notify.length = length - BGP_MSG_NOTIFY_MIN_SIZE;
    bgp_notify.raw_data = data;

    peer->notify.code = bgp_notify.code;
    peer->notify.subcode = bgp_notify.subcode;
    
    if (bgp_notify.length)
      {
        bgp_notify.data = XMALLOC (MTYPE_TMP, bgp_notify.length * 3);
        for (i = 0; i < bgp_notify.length; i++)
          if (first)
            {
              sprintf (c, " %02x", data[i]);
              strcat (bgp_notify.data, c);
            }
          else
            {
              first = 1;
              sprintf (c, "%02x", data[i]);
              strcpy (bgp_notify.data, c);
            }
      }
    bgp_notify_print (peer, &bgp_notify, "sending");

    if (bgp_notify.data)
      {
        XFREE (MTYPE_TMP, bgp_notify.data);
        bgp_notify.data = NULL;
        bgp_notify.length = 0;
      }
  }

  /* peer reset cause */
  if (code == BGP_NOTIFY_CEASE)
    {
      if (sub_code == BGP_NOTIFY_CEASE_ADMIN_RESET)
        peer->last_reset = PEER_DOWN_USER_RESET;
      else if (sub_code == BGP_NOTIFY_CEASE_ADMIN_SHUTDOWN)
        peer->last_reset = PEER_DOWN_USER_SHUTDOWN;
      else
        peer->last_reset = PEER_DOWN_NOTIFY_SEND;
    }
  else
    peer->last_reset = PEER_DOWN_NOTIFY_SEND;

  /* Call immediately. */
  BGP_WRITE_OFF (peer->t_write);

  bgp_write_notify (peer);
}

/* Send BGP notify packet. */
void
bgp_notify_send (struct peer *peer, u_char code, u_char sub_code)
{
  bgp_notify_send_with_data (peer, code, sub_code, NULL, 0);
}

/* Send route refresh message to the peer. */
void
bgp_route_refresh_send (struct peer *peer, afi_t afi, safi_t safi,
                        u_char orf_type, u_char when_to_refresh, int remove)
{
  struct stream *s;
  struct bgp_filter *filter;
  int orf_refresh = 0;
  iana_afi_t pkt_afi;
  safi_t pkt_safi;

  if (DISABLE_BGP_ANNOUNCE)
    return;

  filter = &peer->filter[afi][safi];

  /* Convert AFI, SAFI to values for packet. */
  bgp_map_afi_safi_int2iana (afi, safi, &pkt_afi, &pkt_safi);
  
  s = stream_new (BGP_MAX_PACKET_SIZE);

  /* Make BGP update packet. */
  if (CHECK_FLAG (peer->cap, PEER_CAP_REFRESH_NEW_RCV))
    bgp_packet_set_marker (s, BGP_MSG_ROUTE_REFRESH_NEW);
  else
    bgp_packet_set_marker (s, BGP_MSG_ROUTE_REFRESH_OLD);

  /* Encode Route Refresh message. */
  stream_putw (s, pkt_afi);
  stream_putc (s, 0);
  stream_putc (s, pkt_safi);
 
  if (orf_type == ORF_TYPE_PREFIX
      || orf_type == ORF_TYPE_PREFIX_OLD)
    if (remove || filter->plist[FILTER_IN].plist)
      {
        u_int16_t orf_len;
        unsigned long orfp;

        orf_refresh = 1; 
        stream_putc (s, when_to_refresh);
        stream_putc (s, orf_type);
        orfp = stream_get_endp (s);
        stream_putw (s, 0);

        if (remove)
          {
            UNSET_FLAG (peer->af_sflags[afi][safi], PEER_STATUS_ORF_PREFIX_SEND);
            stream_putc (s, ORF_COMMON_PART_REMOVE_ALL);
            if (bgp_debug_neighbor_events(peer))
              zlog_debug ("%s sending REFRESH_REQ to remove ORF(%d) (%s) for afi/safi: %d/%d", 
                         peer->host, orf_type,
                         (when_to_refresh == REFRESH_DEFER ? "defer" : "immediate"),
                         pkt_afi, pkt_safi);
          }
        else
          {
            SET_FLAG (peer->af_sflags[afi][safi], PEER_STATUS_ORF_PREFIX_SEND);
            prefix_bgp_orf_entry (s, filter->plist[FILTER_IN].plist,
                                  ORF_COMMON_PART_ADD, ORF_COMMON_PART_PERMIT,
                                  ORF_COMMON_PART_DENY);
            if (bgp_debug_neighbor_events(peer))
              zlog_debug ("%s sending REFRESH_REQ with pfxlist ORF(%d) (%s) for afi/safi: %d/%d", 
                         peer->host, orf_type,
                         (when_to_refresh == REFRESH_DEFER ? "defer" : "immediate"),
                         pkt_afi, pkt_safi);
          }

        /* Total ORF Entry Len. */
        orf_len = stream_get_endp (s) - orfp - 2;
        stream_putw_at (s, orfp, orf_len);
      }

  /* Set packet size. */
  (void)bgp_packet_set_size (s);

  if (bgp_debug_neighbor_events(peer))
    {
      if (! orf_refresh)
        zlog_debug ("%s sending REFRESH_REQ for afi/safi: %d/%d", 
                   peer->host, pkt_afi, pkt_safi);
    }

  /* Add packet to the peer. */
  bgp_packet_add (peer, s);

  BGP_WRITE_ON (peer->t_write, bgp_write, peer->fd);
}

/* Send capability message to the peer. */
void
bgp_capability_send (struct peer *peer, afi_t afi, safi_t safi,
                     int capability_code, int action)
{
  struct stream *s;
  iana_afi_t pkt_afi;
  safi_t pkt_safi;

  /* Convert AFI, SAFI to values for packet. */
  bgp_map_afi_safi_int2iana (afi, safi, &pkt_afi, &pkt_safi);

  s = stream_new (BGP_MAX_PACKET_SIZE);

  /* Make BGP update packet. */
  bgp_packet_set_marker (s, BGP_MSG_CAPABILITY);

  /* Encode MP_EXT capability. */
  if (capability_code == CAPABILITY_CODE_MP)
    {
      stream_putc (s, action);
      stream_putc (s, CAPABILITY_CODE_MP);
      stream_putc (s, CAPABILITY_CODE_MP_LEN);
      stream_putw (s, pkt_afi);
      stream_putc (s, 0);
      stream_putc (s, pkt_safi);

      if (bgp_debug_neighbor_events(peer))
        zlog_debug ("%s sending CAPABILITY has %s MP_EXT CAP for afi/safi: %d/%d",
                   peer->host, action == CAPABILITY_ACTION_SET ?
                   "Advertising" : "Removing", pkt_afi, pkt_safi);
    }

  /* Set packet size. */
  (void)bgp_packet_set_size (s);

  /* Add packet to the peer. */
  bgp_packet_add (peer, s);

  BGP_WRITE_ON (peer->t_write, bgp_write, peer->fd);
}

/* RFC1771 6.8 Connection collision detection. */
static int
bgp_collision_detect (struct peer *new, struct in_addr remote_id)
{
  struct peer *peer;

  /* Upon receipt of an OPEN message, the local system must examine
     all of its connections that are in the OpenConfirm state.  A BGP
     speaker may also examine connections in an OpenSent state if it
     knows the BGP Identifier of the peer by means outside of the
     protocol.  If among these connections there is a connection to a
     remote BGP speaker whose BGP Identifier equals the one in the
     OPEN message, then the local system performs the following
     collision resolution procedure: */

  if ((peer = new->doppelganger) != NULL)
    {
      /* Do not accept the new connection in Established or Clearing states.
       * Note that a peer GR is handled by closing the existing connection
       * upon receipt of new one.
       */
      if (peer->status == Established || peer->status == Clearing)
        {
          bgp_notify_send (new, BGP_NOTIFY_CEASE,
                           BGP_NOTIFY_CEASE_COLLISION_RESOLUTION);
          return (-1);
        }
      else if ((peer->status == OpenConfirm) || (peer->status == OpenSent))
        {
          /* 1. The BGP Identifier of the local system is compared to
             the BGP Identifier of the remote system (as specified in
             the OPEN message). */

          if (ntohl (peer->local_id.s_addr) < ntohl (remote_id.s_addr))
            if (!CHECK_FLAG(peer->sflags, PEER_STATUS_ACCEPT_PEER))
              {
                /* 2. If the value of the local BGP Identifier is less
                   than the remote one, the local system closes BGP
                   connection that already exists (the one that is
                   already in the OpenConfirm state), and accepts BGP
                   connection initiated by the remote system. */
                bgp_notify_send (peer, BGP_NOTIFY_CEASE,
                                 BGP_NOTIFY_CEASE_COLLISION_RESOLUTION);
                return 1;
              }
            else
              {
                bgp_notify_send (new, BGP_NOTIFY_CEASE,
                                 BGP_NOTIFY_CEASE_COLLISION_RESOLUTION);
                return -1;
              }
          else
            {
              /* 3. Otherwise, the local system closes newly created
                 BGP connection (the one associated with the newly
                 received OPEN message), and continues to use the
                 existing one (the one that is already in the
                 OpenConfirm state). */
              if (CHECK_FLAG(peer->sflags, PEER_STATUS_ACCEPT_PEER))
                {
                  bgp_notify_send (peer, BGP_NOTIFY_CEASE,
                                   BGP_NOTIFY_CEASE_COLLISION_RESOLUTION);
                  return 1;
                }
              else
                {
                  bgp_notify_send (new, BGP_NOTIFY_CEASE,
                                   BGP_NOTIFY_CEASE_COLLISION_RESOLUTION);
                  return -1;
                }
            }
        }
    }
  return 0;
}

static int
bgp_open_receive (struct peer *peer, bgp_size_t size)
{
  int ret;
  u_char version;
  u_char optlen;
  u_int16_t holdtime;
  u_int16_t send_holdtime;
  as_t remote_as;
  as_t as4 = 0;
  struct in_addr remote_id;
  int mp_capability;
  u_int8_t notify_data_remote_as[2];
  u_int8_t notify_data_remote_as4[4];
  u_int8_t notify_data_remote_id[4];
  u_int16_t *holdtime_ptr;

  /* Parse open packet. */
  version = stream_getc (peer->ibuf);
  memcpy (notify_data_remote_as, stream_pnt (peer->ibuf), 2);
  remote_as  = stream_getw (peer->ibuf);
  holdtime_ptr = (u_int16_t *)stream_pnt (peer->ibuf);
  holdtime = stream_getw (peer->ibuf);
  memcpy (notify_data_remote_id, stream_pnt (peer->ibuf), 4);
  remote_id.s_addr = stream_get_ipv4 (peer->ibuf);

  /* Receive OPEN message log  */
  if (bgp_debug_neighbor_events(peer))
    zlog_debug ("%s rcv OPEN, version %d, remote-as (in open) %u,"
                " holdtime %d, id %s",
                peer->host, version, remote_as, holdtime,
                inet_ntoa (remote_id));
  
  /* BEGIN to read the capability here, but dont do it yet */
  mp_capability = 0;
  optlen = stream_getc (peer->ibuf);
  
  if (optlen != 0)
    {
      /* If not enough bytes, it is an error. */
      if (STREAM_READABLE(peer->ibuf) < optlen)
        {
          bgp_notify_send (peer, BGP_NOTIFY_OPEN_ERR,
                           BGP_NOTIFY_OPEN_MALFORMED_ATTR);
          return -1;
        }

      /* We need the as4 capability value *right now* because
       * if it is there, we have not got the remote_as yet, and without
       * that we do not know which peer is connecting to us now.
       */ 
      as4 = peek_for_as4_capability (peer, optlen);
      memcpy (notify_data_remote_as4, &as4, 4);
    }
  
  /* Just in case we have a silly peer who sends AS4 capability set to 0 */
  if (CHECK_FLAG (peer->cap, PEER_CAP_AS4_RCV) && !as4)
    {
      zlog_err ("%s bad OPEN, got AS4 capability, but AS4 set to 0",
                peer->host);
      bgp_notify_send_with_data (peer,
                                 BGP_NOTIFY_OPEN_ERR,
                                 BGP_NOTIFY_OPEN_BAD_PEER_AS,
                                 notify_data_remote_as4, 4);
      return -1;
    }
  
  if (remote_as == BGP_AS_TRANS)
    {
          /* Take the AS4 from the capability.  We must have received the
           * capability now!  Otherwise we have a asn16 peer who uses
           * BGP_AS_TRANS, for some unknown reason.
           */
      if (as4 == BGP_AS_TRANS)
        {
          zlog_err ("%s [AS4] NEW speaker using AS_TRANS for AS4, not allowed",
                    peer->host);
          bgp_notify_send_with_data (peer,
                                     BGP_NOTIFY_OPEN_ERR,
                                     BGP_NOTIFY_OPEN_BAD_PEER_AS,
                                     notify_data_remote_as4, 4);
          return -1;
        }
      
      if (!as4 && BGP_DEBUG (as4, AS4))
        zlog_debug ("%s [AS4] OPEN remote_as is AS_TRANS, but no AS4."
                    " Odd, but proceeding.", peer->host);
      else if (as4 < BGP_AS_MAX && BGP_DEBUG (as4, AS4))
        zlog_debug ("%s [AS4] OPEN remote_as is AS_TRANS, but AS4 (%u) fits "
                    "in 2-bytes, very odd peer.", peer->host, as4);
      if (as4)
        remote_as = as4;
    } 
  else 
    {
      /* We may have a partner with AS4 who has an asno < BGP_AS_MAX */
      /* If we have got the capability, peer->as4cap must match remote_as */
      if (CHECK_FLAG (peer->cap, PEER_CAP_AS4_RCV)
          && as4 != remote_as)
        {
          /* raise error, log this, close session */
          zlog_err ("%s bad OPEN, got AS4 capability, but remote_as %u"
                    " mismatch with 16bit 'myasn' %u in open",
                    peer->host, as4, remote_as);
          bgp_notify_send_with_data (peer,
                                     BGP_NOTIFY_OPEN_ERR,
                                     BGP_NOTIFY_OPEN_BAD_PEER_AS,
                                     notify_data_remote_as4, 4);
          return -1;
        }
    }

  /* remote router-id check. */
  if (remote_id.s_addr == 0
      || IPV4_CLASS_DE (ntohl (remote_id.s_addr))
      || ntohl (peer->local_id.s_addr) == ntohl (remote_id.s_addr))
    {
      if (bgp_debug_neighbor_events(peer))
        zlog_debug ("%s bad OPEN, wrong router identifier %s",
                   peer->host, inet_ntoa (remote_id));
      bgp_notify_send_with_data (peer, 
                                 BGP_NOTIFY_OPEN_ERR, 
                                 BGP_NOTIFY_OPEN_BAD_BGP_IDENT,
                                 notify_data_remote_id, 4);
      return -1;
    }

  /* Set remote router-id */
  peer->remote_id = remote_id;

  /* Peer BGP version check. */
  if (version != BGP_VERSION_4)
    {
      u_int16_t maxver = htons(BGP_VERSION_4);
      /* XXX this reply may not be correct if version < 4  XXX */
      if (bgp_debug_neighbor_events(peer))
        zlog_debug ("%s bad protocol version, remote requested %d, local request %d",
                   peer->host, version, BGP_VERSION_4);
      /* Data must be in network byte order here */
      bgp_notify_send_with_data (peer, 
                                 BGP_NOTIFY_OPEN_ERR, 
                                 BGP_NOTIFY_OPEN_UNSUP_VERSION,
                                 (u_int8_t *) &maxver, 2);
      return -1;
    }

  /* Check neighbor as number. */
  if (peer->as_type == AS_UNSPECIFIED)
    {
      if (bgp_debug_neighbor_events(peer))
        zlog_debug("%s bad OPEN, remote AS is unspecified currently", peer->host);
      bgp_notify_send_with_data(peer,
                                BGP_NOTIFY_OPEN_ERR,
                                BGP_NOTIFY_OPEN_BAD_PEER_AS,
                                notify_data_remote_as, 2);
      return -1;
    }
  else if (peer->as_type == AS_INTERNAL)
    {
      if (remote_as != peer->bgp->as)
        {
          if (bgp_debug_neighbor_events(peer))
            zlog_debug ("%s bad OPEN, remote AS is %u, internal specified",
                        peer->host, remote_as);
          bgp_notify_send_with_data (peer,
                                     BGP_NOTIFY_OPEN_ERR,
                                     BGP_NOTIFY_OPEN_BAD_PEER_AS,
                                     notify_data_remote_as, 2);
          return -1;
        }
      peer->as = peer->local_as;
    }
  else if (peer->as_type == AS_EXTERNAL)
    {
      if (remote_as == peer->bgp->as)
        {
          if (bgp_debug_neighbor_events(peer))
            zlog_debug ("%s bad OPEN, remote AS is %u, external specified",
                        peer->host, remote_as);
          bgp_notify_send_with_data (peer,
                                     BGP_NOTIFY_OPEN_ERR,
                                     BGP_NOTIFY_OPEN_BAD_PEER_AS,
                                     notify_data_remote_as, 2);
          return -1;
        }
      peer->as = remote_as;
    }
  else if ((peer->as_type == AS_SPECIFIED) && (remote_as != peer->as))
    {
      if (bgp_debug_neighbor_events(peer))
        zlog_debug ("%s bad OPEN, remote AS is %u, expected %u",
                    peer->host, remote_as, peer->as);
      bgp_notify_send_with_data (peer,
                                 BGP_NOTIFY_OPEN_ERR,
                                 BGP_NOTIFY_OPEN_BAD_PEER_AS,
                                 notify_data_remote_as, 2);
      return -1;
    }

  /* From the rfc: Upon receipt of an OPEN message, a BGP speaker MUST
     calculate the value of the Hold Timer by using the smaller of its
     configured Hold Time and the Hold Time received in the OPEN message.
     The Hold Time MUST be either zero or at least three seconds.  An
     implementation may reject connections on the basis of the Hold Time. */

  if (holdtime < 3 && holdtime != 0)
    {
      bgp_notify_send_with_data (peer,
                                 BGP_NOTIFY_OPEN_ERR,
                                 BGP_NOTIFY_OPEN_UNACEP_HOLDTIME,
                                 (u_char *)holdtime_ptr, 2);
      return -1;
    }
    
  /* From the rfc: A reasonable maximum time between KEEPALIVE messages
     would be one third of the Hold Time interval.  KEEPALIVE messages
     MUST NOT be sent more frequently than one per second.  An
     implementation MAY adjust the rate at which it sends KEEPALIVE
     messages as a function of the Hold Time interval. */

  if (CHECK_FLAG (peer->config, PEER_CONFIG_TIMER))
    send_holdtime = peer->holdtime;
  else
    send_holdtime = peer->bgp->default_holdtime;

  if (holdtime < send_holdtime)
    peer->v_holdtime = holdtime;
  else
    peer->v_holdtime = send_holdtime;

  if (CHECK_FLAG (peer->config, PEER_CONFIG_TIMER))
    peer->v_keepalive = peer->keepalive;
  else
    peer->v_keepalive = peer->v_holdtime / 3;

  /* Open option part parse. */
  if (optlen != 0) 
    {
      if ((ret = bgp_open_option_parse (peer, optlen, &mp_capability)) < 0)
        return ret;
    }
  else
    {
      if (bgp_debug_neighbor_events(peer))
        zlog_debug ("%s rcvd OPEN w/ OPTION parameter len: 0",
                   peer->host);
    }

  /* 
   * Assume that the peer supports the locally configured set of
   * AFI/SAFIs if the peer did not send us any Mulitiprotocol
   * capabilities, or if 'override-capability' is configured.
   */
  if (! mp_capability ||
      CHECK_FLAG (peer->flags, PEER_FLAG_OVERRIDE_CAPABILITY))
    {
      peer->afc_nego[AFI_IP][SAFI_UNICAST] = peer->afc[AFI_IP][SAFI_UNICAST];
      peer->afc_nego[AFI_IP][SAFI_MULTICAST] = peer->afc[AFI_IP][SAFI_MULTICAST];
      peer->afc_nego[AFI_IP6][SAFI_UNICAST] = peer->afc[AFI_IP6][SAFI_UNICAST];
      peer->afc_nego[AFI_IP6][SAFI_MULTICAST] = peer->afc[AFI_IP6][SAFI_MULTICAST];
    }

  /* When collision is detected and this peer is closed.  Retrun
     immidiately. */
  ret = bgp_collision_detect (peer, remote_id);
  if (ret < 0)
    return ret;

  /* Get sockname. */
  if ((ret = bgp_getsockname (peer)) < 0)
    {
      zlog_err("%s: bgp_getsockname() failed for peer: %s", __FUNCTION__,
               peer->host);
      return (ret);
    }

  /* Verify valid local address present based on negotiated address-families. */
  if (peer->afc_nego[AFI_IP][SAFI_UNICAST] ||
      peer->afc_nego[AFI_IP][SAFI_MULTICAST] ||
      peer->afc_nego[AFI_IP][SAFI_MPLS_VPN] ||
      peer->afc_nego[AFI_IP][SAFI_ENCAP])
    {
      if (!peer->nexthop.v4.s_addr)
        {
#if defined (HAVE_CUMULUS)
          zlog_err ("%s: No local IPv4 addr resetting connection, fd %d",
                    peer->host, peer->fd);
          bgp_notify_send (peer, BGP_NOTIFY_CEASE, BGP_NOTIFY_SUBCODE_UNSPECIFIC);
          return -1;
#endif
        }
    }
  if (peer->afc_nego[AFI_IP6][SAFI_UNICAST] ||
      peer->afc_nego[AFI_IP6][SAFI_MULTICAST] ||
      peer->afc_nego[AFI_IP6][SAFI_MPLS_VPN] ||
      peer->afc_nego[AFI_IP6][SAFI_ENCAP])
    {
      if (IN6_IS_ADDR_UNSPECIFIED (&peer->nexthop.v6_global))
        {
#if defined (HAVE_CUMULUS)
          zlog_err ("%s: No local IPv6 addr resetting connection, fd %d",
                    peer->host, peer->fd);
          bgp_notify_send (peer, BGP_NOTIFY_CEASE, BGP_NOTIFY_SUBCODE_UNSPECIFIC);
          return -1;
#endif
        }
    }
  peer->rtt = sockopt_tcp_rtt (peer->fd);

  if ((ret = bgp_event_update(peer, Receive_OPEN_message)) < 0)
    {
      zlog_err("%s: BGP event update failed for peer: %s", __FUNCTION__,
               peer->host);
      /* DD: bgp send notify and reset state */
      return (ret);
    }

  peer->packet_size = 0;
  if (peer->ibuf)
    stream_reset (peer->ibuf);

  return 0;
}

/* Called when there is a change in the EOR(implicit or explicit) status of a peer.
   Ends the update-delay if all expected peers are done with EORs. */
void
bgp_check_update_delay(struct bgp *bgp)
{
  struct listnode *node, *nnode;
  struct peer *peer = NULL;

  if (bgp_debug_neighbor_events(peer))
    zlog_debug ("Checking update delay, T: %d R: %d I:%d E: %d", bgp->established,
                bgp->restarted_peers, bgp->implicit_eors, bgp->explicit_eors);

  if (bgp->established <=
      bgp->restarted_peers + bgp->implicit_eors + bgp->explicit_eors)
    {
      /* This is an extra sanity check to make sure we wait for all the
         eligible configured peers. This check is performed if establish wait
         timer is on, or establish wait option is not given with the
         update-delay command */
      if (bgp->t_establish_wait ||
          (bgp->v_establish_wait == bgp->v_update_delay))
        for (ALL_LIST_ELEMENTS (bgp->peer, node, nnode, peer))
          {
            if (CHECK_FLAG(peer->flags, PEER_FLAG_CONFIG_NODE)
                && !CHECK_FLAG (peer->flags, PEER_FLAG_SHUTDOWN)
                && !peer->update_delay_over)
              {
                if (bgp_debug_neighbor_events(peer))
                  zlog_debug (" Peer %s pending, continuing read-only mode",
                              peer->host);
                return;
              }
          }

      zlog_info ("Update delay ended, restarted: %d, EORs implicit: %d, explicit: %d",
                 bgp->restarted_peers, bgp->implicit_eors, bgp->explicit_eors);
      bgp_update_delay_end(bgp);
    }
}

/* Called if peer is known to have restarted. The restart-state bit in
   Graceful-Restart capability is used for that */
void
bgp_update_restarted_peers (struct peer *peer)
{
  if (!bgp_update_delay_active(peer->bgp)) return; /* BGP update delay has ended */
  if (peer->update_delay_over) return; /* This peer has already been considered */

  if (bgp_debug_neighbor_events(peer))
    zlog_debug ("Peer %s: Checking restarted", peer->host);

  if (peer->status == Established)
    {
      peer->update_delay_over = 1;
      peer->bgp->restarted_peers++;
      bgp_check_update_delay(peer->bgp);
    }
}

/* Called as peer receives a keep-alive. Determines if this occurence can be
   taken as an implicit EOR for this peer.
   NOTE: The very first keep-alive after the Established state of a peer is
         considered implicit EOR for the update-delay purposes */
void
bgp_update_implicit_eors (struct peer *peer)
{
  if (!bgp_update_delay_active(peer->bgp)) return; /* BGP update delay has ended */
  if (peer->update_delay_over) return; /* This peer has already been considered */

  if (bgp_debug_neighbor_events(peer))
    zlog_debug ("Peer %s: Checking implicit EORs", peer->host);

  if (peer->status == Established)
    {
      peer->update_delay_over = 1;
      peer->bgp->implicit_eors++;
      bgp_check_update_delay(peer->bgp);
    }
}

/* Should be called only when there is a change in the EOR_RECEIVED status
   for any afi/safi on a peer */
static void
bgp_update_explicit_eors (struct peer *peer)
{
  afi_t afi;
  safi_t safi;

  if (!bgp_update_delay_active(peer->bgp)) return; /* BGP update delay has ended */
  if (peer->update_delay_over) return; /* This peer has already been considered */

  if (bgp_debug_neighbor_events(peer))
    zlog_debug ("Peer %s: Checking explicit EORs", peer->host);

  for (afi = AFI_IP; afi < AFI_MAX; afi++)
    for (safi = SAFI_UNICAST; safi < SAFI_MAX; safi++)
      {
        if (peer->afc_nego[afi][safi] &&
            !CHECK_FLAG(peer->af_sflags[afi][safi], PEER_STATUS_EOR_RECEIVED))
          {
            if (bgp_debug_neighbor_events(peer))
              zlog_debug ("   afi %d safi %d didnt receive EOR", afi, safi);
            return;
          }
      }

  peer->update_delay_over = 1;
  peer->bgp->explicit_eors++;
  bgp_check_update_delay(peer->bgp);
}

/* Frontend for NLRI parsing, to fan-out to AFI/SAFI specific parsers 
 * mp_withdraw, if set, is used to nullify attr structure on most of the calling safi function
 * and for evpn, passed as parameter
 */
int
bgp_nlri_parse (struct peer *peer, struct attr *attr, struct bgp_nlri *packet, int mp_withdraw)
{
  switch (packet->safi)
    {
      case SAFI_UNICAST:
      case SAFI_MULTICAST:
        return bgp_nlri_parse_ip (peer, mp_withdraw?NULL:attr, packet);
      case SAFI_MPLS_VPN:
        return bgp_nlri_parse_vpn (peer, mp_withdraw?NULL:attr, packet);
      case SAFI_EVPN:
        return bgp_nlri_parse_evpn (peer, attr, packet, mp_withdraw);
    }
  return -1;
}

/* Parse BGP Update packet and make attribute object. */
static int
bgp_update_receive (struct peer *peer, bgp_size_t size)
{
  int ret, nlri_ret;
  u_char *end;
  struct stream *s;
  struct attr attr;
  struct attr_extra extra;
  bgp_size_t attribute_len;
  bgp_size_t update_len;
  bgp_size_t withdraw_len;

  enum NLRI_TYPES {
    NLRI_UPDATE,
    NLRI_WITHDRAW,
    NLRI_MP_UPDATE,
    NLRI_MP_WITHDRAW,
    NLRI_TYPE_MAX
  };
  struct bgp_nlri nlris[NLRI_TYPE_MAX];

  /* Status must be Established. */
  if (peer->status != Established) 
    {
      zlog_err ("%s [FSM] Update packet received under status %s",
                peer->host, LOOKUP (bgp_status_msg, peer->status));
      bgp_notify_send (peer, BGP_NOTIFY_FSM_ERR, 0);
      return -1;
    }

  /* Set initial values. */
  memset (&attr, 0, sizeof (struct attr));
  memset (&extra, 0, sizeof (struct attr_extra));
  memset (&nlris, 0, sizeof (nlris));
  attr.extra = &extra;
  memset (peer->rcvd_attr_str, 0, BUFSIZ);
  peer->rcvd_attr_printed = 0;

  s = peer->ibuf;
  end = stream_pnt (s) + size;

  /* RFC1771 6.3 If the Unfeasible Routes Length or Total Attribute
     Length is too large (i.e., if Unfeasible Routes Length + Total
     Attribute Length + 23 exceeds the message Length), then the Error
     Subcode is set to Malformed Attribute List.  */
  if (stream_pnt (s) + 2 > end)
    {
      zlog_err ("%s [Error] Update packet error"
                " (packet length is short for unfeasible length)",
                peer->host);
      bgp_notify_send (peer, BGP_NOTIFY_UPDATE_ERR, 
                       BGP_NOTIFY_UPDATE_MAL_ATTR);
      return -1;
    }

  /* Unfeasible Route Length. */
  withdraw_len = stream_getw (s);

  /* Unfeasible Route Length check. */
  if (stream_pnt (s) + withdraw_len > end)
    {
      zlog_err ("%s [Error] Update packet error"
                " (packet unfeasible length overflow %d)",
                peer->host, withdraw_len);
      bgp_notify_send (peer, BGP_NOTIFY_UPDATE_ERR, 
                       BGP_NOTIFY_UPDATE_MAL_ATTR);
      return -1;
    }

  /* Unfeasible Route packet format check. */
  if (withdraw_len > 0)
    {
      nlris[NLRI_WITHDRAW].afi = AFI_IP;
      nlris[NLRI_WITHDRAW].safi = SAFI_UNICAST;
      nlris[NLRI_WITHDRAW].nlri = stream_pnt (s);
      nlris[NLRI_WITHDRAW].length = withdraw_len;
      stream_forward_getp (s, withdraw_len);
    }
  
  /* Attribute total length check. */
  if (stream_pnt (s) + 2 > end)
    {
      zlog_warn ("%s [Error] Packet Error"
                 " (update packet is short for attribute length)",
                 peer->host);
      bgp_notify_send (peer, BGP_NOTIFY_UPDATE_ERR, 
                       BGP_NOTIFY_UPDATE_MAL_ATTR);
      return -1;
    }

  /* Fetch attribute total length. */
  attribute_len = stream_getw (s);

  /* Attribute length check. */
  if (stream_pnt (s) + attribute_len > end)
    {
      zlog_warn ("%s [Error] Packet Error"
                 " (update packet attribute length overflow %d)",
                 peer->host, attribute_len);
      bgp_notify_send (peer, BGP_NOTIFY_UPDATE_ERR, 
                       BGP_NOTIFY_UPDATE_MAL_ATTR);
      return -1;
    }
  
  /* Certain attribute parsing errors should not be considered bad enough
   * to reset the session for, most particularly any partial/optional
   * attributes that have 'tunneled' over speakers that don't understand
   * them. Instead we withdraw only the prefix concerned.
   * 
   * Complicates the flow a little though..
   */
  bgp_attr_parse_ret_t attr_parse_ret = BGP_ATTR_PARSE_PROCEED;
  /* This define morphs the update case into a withdraw when lower levels
   * have signalled an error condition where this is best.
   */
#define NLRI_ATTR_ARG (attr_parse_ret != BGP_ATTR_PARSE_WITHDRAW ? &attr : NULL)

  /* Parse attribute when it exists. */
  if (attribute_len)
    {
      attr_parse_ret = bgp_attr_parse (peer, &attr, attribute_len, 
                            &nlris[NLRI_MP_UPDATE], &nlris[NLRI_MP_WITHDRAW]);
      if (attr_parse_ret == BGP_ATTR_PARSE_ERROR)
        {
          bgp_attr_unintern_sub (&attr);
          return -1;
        }
    }
  
  /* Logging the attribute. */
  if (attr_parse_ret == BGP_ATTR_PARSE_WITHDRAW ||
      BGP_DEBUG (update, UPDATE_IN) ||
      BGP_DEBUG (update, UPDATE_PREFIX))
    {
      ret = bgp_dump_attr (peer, &attr, peer->rcvd_attr_str, BUFSIZ);
      
      if (attr_parse_ret == BGP_ATTR_PARSE_WITHDRAW)
        zlog_err ("%s rcvd UPDATE with errors in attr(s)!! Withdrawing route.",
                  peer->host);

      if (ret && bgp_debug_update(peer, NULL, NULL, 1))
        {
          zlog_debug ("%s rcvd UPDATE w/ attr: %s", peer->host, peer->rcvd_attr_str);
          peer->rcvd_attr_printed = 1;
        }
    }
  
  /* Network Layer Reachability Information. */
  update_len = end - stream_pnt (s);

  if (update_len)
    {
      /* Set NLRI portion to structure. */
      nlris[NLRI_UPDATE].afi = AFI_IP;
      nlris[NLRI_UPDATE].safi = SAFI_UNICAST;
      nlris[NLRI_UPDATE].nlri = stream_pnt (s);
      nlris[NLRI_UPDATE].length = update_len;
      stream_forward_getp (s, update_len);
    }

  if (BGP_DEBUG (update, UPDATE_IN))
    zlog_debug("%s rcvd UPDATE wlen %d attrlen %d alen %d",
               peer->host, withdraw_len, attribute_len, update_len);

  /* Parse any given NLRIs */
  for (int i = NLRI_UPDATE; i < NLRI_TYPE_MAX; i++)
    {
      if (!nlris[i].nlri)
        continue;

      /* NLRI is processed iff the peer if configured for the specific afi/safi */
      if (!peer->afc[nlris[i].afi][nlris[i].safi])
        {
          zlog_info ("%s [Info] UPDATE for non-enabled AFI/SAFI %u/%u",
                     peer->host, nlris[i].afi, nlris[i].safi);
          continue;
        }

      /* EoR handled later */
      if (nlris[i].length == 0)
        continue;

      switch (i)
        {
          case NLRI_UPDATE:
          case NLRI_MP_UPDATE:
            nlri_ret = bgp_nlri_parse (peer, NLRI_ATTR_ARG, &nlris[i], 0);
            break;
          case NLRI_WITHDRAW:
          case NLRI_MP_WITHDRAW:
            nlri_ret = bgp_nlri_parse (peer, &attr, &nlris[i], 1);
            break;
          default:
            nlri_ret = -1;
        }

      if (nlri_ret < 0)
        {
          zlog_err("%s [Error] Error parsing NLRI", peer->host);
          if (peer->status == Established)
            bgp_notify_send (peer, BGP_NOTIFY_UPDATE_ERR,
                             i <= NLRI_WITHDRAW ? BGP_NOTIFY_UPDATE_INVAL_NETWORK
                                                : BGP_NOTIFY_UPDATE_OPT_ATTR_ERR);
          bgp_attr_unintern_sub (&attr);
          return -1;
        }
    }

  /* EoR checks
   *
   * Non-MP IPv4/Unicast EoR is a completely empty UPDATE
   * and MP EoR should have only an empty MP_UNREACH
   */
  if (!update_len && !withdraw_len
      && nlris[NLRI_MP_UPDATE].length == 0)
    {
      afi_t afi = 0;
      safi_t safi;

      /* Non-MP IPv4/Unicast is a completely emtpy UPDATE - already checked
       * update and withdraw NLRI lengths are 0.
       */
      if (!attribute_len)
        {
          afi = AFI_IP;
          safi = SAFI_UNICAST;
        }
      else if (attr.flag & ATTR_FLAG_BIT (BGP_ATTR_MP_UNREACH_NLRI)
               && nlris[NLRI_MP_WITHDRAW].length == 0)
        {
          afi = nlris[NLRI_MP_WITHDRAW].afi;
          safi = nlris[NLRI_MP_WITHDRAW].safi;
        }

      if (afi && peer->afc[afi][safi])
        {
          /* End-of-RIB received */
          if (!CHECK_FLAG (peer->af_sflags[afi][safi], PEER_STATUS_EOR_RECEIVED))
            {
              SET_FLAG (peer->af_sflags[afi][safi],
                        PEER_STATUS_EOR_RECEIVED);
              bgp_update_explicit_eors(peer);
            }

          /* NSF delete stale route */
          if (peer->nsf[afi][safi])
            bgp_clear_stale_route (peer, afi, safi);

          if (bgp_debug_neighbor_events(peer))
            {
              zlog_debug ("rcvd End-of-RIB for %s from %s",
                          afi_safi_print (afi, safi), peer->host);
            }
        }
    }

  /* Everything is done.  We unintern temporary structures which
     interned in bgp_attr_parse(). */
  bgp_attr_unintern_sub (&attr);

  /* If peering is stopped due to some reason, do not generate BGP
     event.  */
  if (peer->status != Established)
    return 0;

  /* Increment packet counter. */
  peer->update_in++;
  peer->update_time = bgp_clock ();

  /* Rearm holdtime timer */
  BGP_TIMER_OFF (peer->t_holdtime);
  bgp_timer_set (peer);

  return 0;
}

/* Notify message treatment function. */
static void
bgp_notify_receive (struct peer *peer, bgp_size_t size)
{
  struct bgp_notify bgp_notify;

  if (peer->notify.data)
    {
      XFREE (MTYPE_TMP, peer->notify.data);
      peer->notify.data = NULL;
      peer->notify.length = 0;
    }

  bgp_notify.code = stream_getc (peer->ibuf);
  bgp_notify.subcode = stream_getc (peer->ibuf);
  bgp_notify.length = size - 2;
  bgp_notify.data = NULL;

  /* Preserv notify code and sub code. */
  peer->notify.code = bgp_notify.code;
  peer->notify.subcode = bgp_notify.subcode;
  /* For further diagnostic record returned Data. */
  if (bgp_notify.length)
    {
      peer->notify.length = size - 2;
      peer->notify.data = XMALLOC (MTYPE_TMP, size - 2);
      memcpy (peer->notify.data, stream_pnt (peer->ibuf), size - 2);
    }

  /* For debug */
  {
    int i;
    int first = 0;
    char c[4];

    if (bgp_notify.length)
      {
        bgp_notify.data = XMALLOC (MTYPE_TMP, bgp_notify.length * 3);
        for (i = 0; i < bgp_notify.length; i++)
          if (first)
            {
              sprintf (c, " %02x", stream_getc (peer->ibuf));
              strcat (bgp_notify.data, c);
            }
          else
            {
              first = 1;
              sprintf (c, "%02x", stream_getc (peer->ibuf));
              strcpy (bgp_notify.data, c);
            }
        bgp_notify.raw_data = (u_char*)peer->notify.data;
      }

    bgp_notify_print(peer, &bgp_notify, "received");
    if (bgp_notify.data)
      {
        XFREE (MTYPE_TMP, bgp_notify.data);
        bgp_notify.data = NULL;
        bgp_notify.length = 0;
      }
  }

  /* peer count update */
  peer->notify_in++;

  peer->last_reset = PEER_DOWN_NOTIFY_RECEIVED;

  /* We have to check for Notify with Unsupported Optional Parameter.
     in that case we fallback to open without the capability option.
     But this done in bgp_stop. We just mark it here to avoid changing
     the fsm tables.  */
  if (bgp_notify.code == BGP_NOTIFY_OPEN_ERR &&
      bgp_notify.subcode == BGP_NOTIFY_OPEN_UNSUP_PARAM )
    UNSET_FLAG (peer->sflags, PEER_STATUS_CAPABILITY_OPEN);

  BGP_EVENT_ADD (peer, Receive_NOTIFICATION_message);
}

/* Keepalive treatment function -- get keepalive send keepalive */
static void
bgp_keepalive_receive (struct peer *peer, bgp_size_t size)
{
  if (bgp_debug_keepalive(peer))
    zlog_debug ("%s KEEPALIVE rcvd", peer->host); 
  
  BGP_EVENT_ADD (peer, Receive_KEEPALIVE_message);
}

/* Route refresh message is received. */
static void
bgp_route_refresh_receive (struct peer *peer, bgp_size_t size)
{
  iana_afi_t pkt_afi;
  afi_t afi;
  safi_t pkt_safi, safi;
  struct stream *s;
  struct peer_af *paf;
  struct update_group *updgrp;
  struct peer *updgrp_peer;

  /* If peer does not have the capability, send notification. */
  if (! CHECK_FLAG (peer->cap, PEER_CAP_REFRESH_ADV))
    {
      zlog_err ("%s [Error] BGP route refresh is not enabled",
                peer->host);
      bgp_notify_send (peer,
                       BGP_NOTIFY_HEADER_ERR,
                       BGP_NOTIFY_HEADER_BAD_MESTYPE);
      return;
    }

  /* Status must be Established. */
  if (peer->status != Established) 
    {
      zlog_err ("%s [Error] Route refresh packet received under status %s",
                peer->host, LOOKUP (bgp_status_msg, peer->status));
      bgp_notify_send (peer, BGP_NOTIFY_FSM_ERR, 0);
      return;
    }

  s = peer->ibuf;
  
  /* Parse packet. */
  pkt_afi = stream_getw (s);
  (void)stream_getc (s);
  pkt_safi = stream_getc (s);

  if (bgp_debug_update(peer, NULL, NULL, 0))
    zlog_debug ("%s rcvd REFRESH_REQ for afi/safi: %d/%d",
               peer->host, pkt_afi, pkt_safi);

  /* Convert AFI, SAFI to internal values and check. */
  if (bgp_map_afi_safi_iana2int (pkt_afi, pkt_safi, &afi, &safi))
    {
      zlog_info ("%s REFRESH_REQ for unrecognized afi/safi: %d/%d - ignored",
                 peer->host, pkt_afi, pkt_safi);
      return;
    }

  if (size != BGP_MSG_ROUTE_REFRESH_MIN_SIZE - BGP_HEADER_SIZE)
    {
      u_char *end;
      u_char when_to_refresh;
      u_char orf_type;
      u_int16_t orf_len;

      if (size - (BGP_MSG_ROUTE_REFRESH_MIN_SIZE - BGP_HEADER_SIZE) < 5)
        {
          zlog_info ("%s ORF route refresh length error", peer->host);
          bgp_notify_send (peer, BGP_NOTIFY_CEASE, 0);
          return;
        }

      when_to_refresh = stream_getc (s);
      end = stream_pnt (s) + (size - 5);

      while ((stream_pnt (s) + 2) < end)
        {
          orf_type = stream_getc (s); 
          orf_len = stream_getw (s);
          
          /* orf_len in bounds? */
          if ((stream_pnt (s) + orf_len) > end)
            break; /* XXX: Notify instead?? */
          if (orf_type == ORF_TYPE_PREFIX
              || orf_type == ORF_TYPE_PREFIX_OLD)
            {
              uint8_t *p_pnt = stream_pnt (s);
              uint8_t *p_end = stream_pnt (s) + orf_len;
              struct orf_prefix orfp;
              u_char common = 0;
              u_int32_t seq;
              int psize;
              char name[BUFSIZ];
              int ret = CMD_SUCCESS;

              if (bgp_debug_neighbor_events(peer))
                {
                  zlog_debug ("%s rcvd Prefixlist ORF(%d) length %d",
                             peer->host, orf_type, orf_len);
                }

              /* we're going to read at least 1 byte of common ORF header,
               * and 7 bytes of ORF Address-filter entry from the stream
               */
              if (orf_len < 7)
                break; 
                
              /* ORF prefix-list name */
              sprintf (name, "%s.%d.%d", peer->host, afi, safi);

              while (p_pnt < p_end)
                {
                  /* If the ORF entry is malformed, want to read as much of it
                   * as possible without going beyond the bounds of the entry,
                   * to maximise debug information.
                   */
                  int ok;
                  memset (&orfp, 0, sizeof (struct orf_prefix));
                  common = *p_pnt++;
                  /* after ++: p_pnt <= p_end */
                  if (common & ORF_COMMON_PART_REMOVE_ALL)
                    {
                      if (bgp_debug_neighbor_events(peer))
                        zlog_debug ("%s rcvd Remove-All pfxlist ORF request", peer->host);
                      prefix_bgp_orf_remove_all (afi, name);
                      break;
                    }
                  ok = ((u_int32_t)(p_end - p_pnt) >= sizeof(u_int32_t)) ;
                  if (ok)
                    {
                      memcpy (&seq, p_pnt, sizeof (u_int32_t));
                      p_pnt += sizeof (u_int32_t);
                      orfp.seq = ntohl (seq);
                    }
                  else
                    p_pnt = p_end ;

                  if ((ok = (p_pnt < p_end)))
                    orfp.ge = *p_pnt++ ;      /* value checked in prefix_bgp_orf_set() */
                  if ((ok = (p_pnt < p_end)))
                    orfp.le = *p_pnt++ ;      /* value checked in prefix_bgp_orf_set() */
                  if ((ok = (p_pnt < p_end)))
                    orfp.p.prefixlen = *p_pnt++ ;
                  orfp.p.family = afi2family (afi);   /* afi checked already  */

                  psize = PSIZE (orfp.p.prefixlen);   /* 0 if not ok          */
                  if (psize > prefix_blen(&orfp.p))   /* valid for family ?   */
                    {
                      ok = 0 ;
                      psize = prefix_blen(&orfp.p) ;
                    }
                  if (psize > (p_end - p_pnt))        /* valid for packet ?   */
                    {
                      ok = 0 ;
                      psize = p_end - p_pnt ;
                    }

                  if (psize > 0)
                    memcpy (&orfp.p.u.prefix, p_pnt, psize);
                  p_pnt += psize;

                  if (bgp_debug_neighbor_events(peer))
                    {
                      char buf[INET6_BUFSIZ];

                      zlog_debug ("%s rcvd %s %s seq %u %s/%d ge %d le %d%s",
                                 peer->host,
                                 (common & ORF_COMMON_PART_REMOVE ? "Remove" : "Add"),
                                 (common & ORF_COMMON_PART_DENY ? "deny" : "permit"),
                                 orfp.seq,
                                 inet_ntop (orfp.p.family, &orfp.p.u.prefix, buf, INET6_BUFSIZ),
                                 orfp.p.prefixlen, orfp.ge, orfp.le,
                                 ok ? "" : " MALFORMED");
                    }

                  if (ok)
                    ret = prefix_bgp_orf_set (name, afi, &orfp,
                                   (common & ORF_COMMON_PART_DENY ? 0 : 1 ),
                                   (common & ORF_COMMON_PART_REMOVE ? 0 : 1));

                  if (!ok || (ok && ret != CMD_SUCCESS))
                    {
                      zlog_info ("%s Received misformatted prefixlist ORF."
                                 " Remove All pfxlist", peer->host);
                      prefix_bgp_orf_remove_all (afi, name);
                      break;
                    }
                }

              peer->orf_plist[afi][safi] = prefix_bgp_orf_lookup (afi, name);
            }
          stream_forward_getp (s, orf_len);
        }
      if (bgp_debug_neighbor_events(peer))
        zlog_debug ("%s rcvd Refresh %s ORF request", peer->host,
                   when_to_refresh == REFRESH_DEFER ? "Defer" : "Immediate");
      if (when_to_refresh == REFRESH_DEFER)
        return;
    }

  /* First update is deferred until ORF or ROUTE-REFRESH is received */
  if (CHECK_FLAG (peer->af_sflags[afi][safi], PEER_STATUS_ORF_WAIT_REFRESH))
    UNSET_FLAG (peer->af_sflags[afi][safi], PEER_STATUS_ORF_WAIT_REFRESH);

  paf = peer_af_find (peer, afi, safi);
  if (paf && paf->subgroup)
    {
      if (peer->orf_plist[afi][safi])
        {
          updgrp = PAF_UPDGRP(paf);
          updgrp_peer = UPDGRP_PEER(updgrp);
          updgrp_peer->orf_plist[afi][safi] = peer->orf_plist[afi][safi];
        }

      /* If the peer is configured for default-originate clear the
       * SUBGRP_STATUS_DEFAULT_ORIGINATE flag so that we will re-advertise the
       * default
       */
      if (CHECK_FLAG (paf->subgroup->sflags, SUBGRP_STATUS_DEFAULT_ORIGINATE))
        UNSET_FLAG (paf->subgroup->sflags, SUBGRP_STATUS_DEFAULT_ORIGINATE);
    }

  /* Perform route refreshment to the peer */
  bgp_announce_route (peer, afi, safi);
}

static int
bgp_capability_msg_parse (struct peer *peer, u_char *pnt, bgp_size_t length)
{
  u_char *end;
  struct capability_mp_data mpc;
  struct capability_header *hdr;
  u_char action;
  iana_afi_t pkt_afi;
  afi_t afi;
  safi_t pkt_safi, safi;

  end = pnt + length;

  while (pnt < end)
    {      
      /* We need at least action, capability code and capability length. */
      if (pnt + 3 > end)
        {
          zlog_info ("%s Capability length error", peer->host);
          bgp_notify_send (peer, BGP_NOTIFY_CEASE, 0);
          return -1;
        }
      action = *pnt;
      hdr = (struct capability_header *)(pnt + 1);
      
      /* Action value check.  */
      if (action != CAPABILITY_ACTION_SET
          && action != CAPABILITY_ACTION_UNSET)
        {
          zlog_info ("%s Capability Action Value error %d",
                     peer->host, action);
          bgp_notify_send (peer, BGP_NOTIFY_CEASE, 0);
          return -1;
        }

      if (bgp_debug_neighbor_events(peer))
        zlog_debug ("%s CAPABILITY has action: %d, code: %u, length %u",
                   peer->host, action, hdr->code, hdr->length);

      /* Capability length check. */
      if ((pnt + hdr->length + 3) > end)
        {
          zlog_info ("%s Capability length error", peer->host);
          bgp_notify_send (peer, BGP_NOTIFY_CEASE, 0);
          return -1;
        }

      /* Fetch structure to the byte stream. */
      memcpy (&mpc, pnt + 3, sizeof (struct capability_mp_data));

      /* We know MP Capability Code. */
      if (hdr->code == CAPABILITY_CODE_MP)
        {
          pkt_afi = ntohs (mpc.afi);
          pkt_safi = mpc.safi;

          /* Ignore capability when override-capability is set. */
          if (CHECK_FLAG (peer->flags, PEER_FLAG_OVERRIDE_CAPABILITY))
            continue;
          
          /* Convert AFI, SAFI to internal values. */
          if (bgp_map_afi_safi_iana2int (pkt_afi, pkt_safi, &afi, &safi))
            {
              if (bgp_debug_neighbor_events(peer))
                zlog_debug ("%s Dynamic Capability MP_EXT afi/safi invalid "
                            "(%u/%u)", peer->host, pkt_afi, pkt_safi);
              continue;
            }
          
          /* Address family check.  */
          if (bgp_debug_neighbor_events(peer))
            zlog_debug ("%s CAPABILITY has %s MP_EXT CAP for afi/safi: %u/%u",
                       peer->host,
                       action == CAPABILITY_ACTION_SET 
                       ? "Advertising" : "Removing",
                       pkt_afi, pkt_safi);
              
          if (action == CAPABILITY_ACTION_SET)
            {
              peer->afc_recv[afi][safi] = 1;
              if (peer->afc[afi][safi])
                {
                  peer->afc_nego[afi][safi] = 1;
                  bgp_announce_route (peer, afi, safi);
                }
            }
          else
            {
              peer->afc_recv[afi][safi] = 0;
              peer->afc_nego[afi][safi] = 0;

              if (peer_active_nego (peer))
                bgp_clear_route (peer, afi, safi);
              else
                BGP_EVENT_ADD (peer, BGP_Stop);
            }
        }
      else
        {
          zlog_warn ("%s unrecognized capability code: %d - ignored",
                     peer->host, hdr->code);
        }
      pnt += hdr->length + 3;
    }
  return 0;
}

/* Dynamic Capability is received. 
 *
 * This is exported for unit-test purposes
 */
int
bgp_capability_receive (struct peer *peer, bgp_size_t size)
{
  u_char *pnt;

  /* Fetch pointer. */
  pnt = stream_pnt (peer->ibuf);

  if (bgp_debug_neighbor_events(peer))
    zlog_debug ("%s rcv CAPABILITY", peer->host);

  /* If peer does not have the capability, send notification. */
  if (! CHECK_FLAG (peer->cap, PEER_CAP_DYNAMIC_ADV))
    {
      zlog_err ("%s [Error] BGP dynamic capability is not enabled",
                peer->host);
      bgp_notify_send (peer,
                       BGP_NOTIFY_HEADER_ERR,
                       BGP_NOTIFY_HEADER_BAD_MESTYPE);
      return -1;
    }

  /* Status must be Established. */
  if (peer->status != Established)
    {
      zlog_err ("%s [Error] Dynamic capability packet received under status %s",
                peer->host, LOOKUP (bgp_status_msg, peer->status));
      bgp_notify_send (peer, BGP_NOTIFY_FSM_ERR, 0);
      return -1;
    }

  /* Parse packet. */
  return bgp_capability_msg_parse (peer, pnt, size);
}

/* BGP read utility function. */
static int
bgp_read_packet (struct peer *peer)
{
  int nbytes;
  int readsize;

  readsize = peer->packet_size - stream_get_endp (peer->ibuf);

  /* If size is zero then return. */
  if (! readsize)
    return 0;

  /* Read packet from fd. */
  nbytes = stream_read_try (peer->ibuf, peer->fd, readsize);

  /* If read byte is smaller than zero then error occured. */
  if (nbytes < 0) 
    {
      /* Transient error should retry */
      if (nbytes == -2)
        return -1;

      zlog_err ("%s [Error] bgp_read_packet error: %s",
                peer->host, safe_strerror (errno));

      if (peer->status == Established) 
        {
          if (CHECK_FLAG (peer->sflags, PEER_STATUS_NSF_MODE))
            {
              peer->last_reset = PEER_DOWN_NSF_CLOSE_SESSION;
              SET_FLAG (peer->sflags, PEER_STATUS_NSF_WAIT);
            }
          else
            peer->last_reset = PEER_DOWN_CLOSE_SESSION;
        }

      BGP_EVENT_ADD (peer, TCP_fatal_error);
      return -1;
    }  

  /* When read byte is zero : clear bgp peer and return */
  if (nbytes == 0) 
    {
      if (bgp_debug_neighbor_events(peer))
        zlog_debug ("%s [Event] BGP connection closed fd %d",
                    peer->host, peer->fd);

      if (peer->status == Established) 
        {
          if (CHECK_FLAG (peer->sflags, PEER_STATUS_NSF_MODE))
            {
              peer->last_reset = PEER_DOWN_NSF_CLOSE_SESSION;
              SET_FLAG (peer->sflags, PEER_STATUS_NSF_WAIT);
            }
          else
            peer->last_reset = PEER_DOWN_CLOSE_SESSION;
        }

      BGP_EVENT_ADD (peer, TCP_connection_closed);
      return -1;
    }

  /* We read partial packet. */
  if (stream_get_endp (peer->ibuf) != peer->packet_size)
    return -1;

  return 0;
}

/* Marker check. */
static int
bgp_marker_all_one (struct stream *s, int length)
{
  int i;

  for (i = 0; i < length; i++)
    if (s->data[i] != 0xff)
      return 0;

  return 1;
}

/* Starting point of packet process function. */
int
bgp_read (struct thread *thread)
{
  int ret;
  u_char type = 0;
  struct peer *peer;
  bgp_size_t size;
  char notify_data_length[2];
  u_int32_t notify_out;

  /* Yes first of all get peer pointer. */
  peer = THREAD_ARG (thread);
  peer->t_read = NULL;

  /* Note notify_out so we can check later to see if we sent another one */
  notify_out = peer->notify_out;

  /* For non-blocking IO check. */
  if (peer->status == Connect)
    {
      bgp_connect_check (peer, 1);
      goto done;
    }
  else
    {
      if (peer->fd < 0)
        {
          zlog_err ("bgp_read peer's fd is negative value %d", peer->fd);
          return -1;
        }
      BGP_READ_ON (peer->t_read, bgp_read, peer->fd);
    }

  /* Read packet header to determine type of the packet */
  if (peer->packet_size == 0)
    peer->packet_size = BGP_HEADER_SIZE;

  if (stream_get_endp (peer->ibuf) < BGP_HEADER_SIZE)
    {
      ret = bgp_read_packet (peer);

      /* Header read error or partial read packet. */
      if (ret < 0) 
        goto done;

      /* Get size and type. */
      stream_forward_getp (peer->ibuf, BGP_MARKER_SIZE);
      memcpy (notify_data_length, stream_pnt (peer->ibuf), 2);
      size = stream_getw (peer->ibuf);
      type = stream_getc (peer->ibuf);

      /* Marker check */
      if (((type == BGP_MSG_OPEN) || (type == BGP_MSG_KEEPALIVE))
          && ! bgp_marker_all_one (peer->ibuf, BGP_MARKER_SIZE))
        {
          bgp_notify_send (peer,
                           BGP_NOTIFY_HEADER_ERR, 
                           BGP_NOTIFY_HEADER_NOT_SYNC);
          goto done;
        }

      /* BGP type check. */
      if (type != BGP_MSG_OPEN && type != BGP_MSG_UPDATE 
          && type != BGP_MSG_NOTIFY && type != BGP_MSG_KEEPALIVE 
          && type != BGP_MSG_ROUTE_REFRESH_NEW
          && type != BGP_MSG_ROUTE_REFRESH_OLD
          && type != BGP_MSG_CAPABILITY)
        {
          if (bgp_debug_neighbor_events(peer))
            zlog_debug ("%s unknown message type 0x%02x",
                        peer->host, type);
          bgp_notify_send_with_data (peer,
                                     BGP_NOTIFY_HEADER_ERR,
                                     BGP_NOTIFY_HEADER_BAD_MESTYPE,
                                     &type, 1);
          goto done;
        }
      /* Mimimum packet length check. */
      if ((size < BGP_HEADER_SIZE)
          || (size > BGP_MAX_PACKET_SIZE)
          || (type == BGP_MSG_OPEN && size < BGP_MSG_OPEN_MIN_SIZE)
          || (type == BGP_MSG_UPDATE && size < BGP_MSG_UPDATE_MIN_SIZE)
          || (type == BGP_MSG_NOTIFY && size < BGP_MSG_NOTIFY_MIN_SIZE)
          || (type == BGP_MSG_KEEPALIVE && size != BGP_MSG_KEEPALIVE_MIN_SIZE)
          || (type == BGP_MSG_ROUTE_REFRESH_NEW && size < BGP_MSG_ROUTE_REFRESH_MIN_SIZE)
          || (type == BGP_MSG_ROUTE_REFRESH_OLD && size < BGP_MSG_ROUTE_REFRESH_MIN_SIZE)
          || (type == BGP_MSG_CAPABILITY && size < BGP_MSG_CAPABILITY_MIN_SIZE))
        {
          if (bgp_debug_neighbor_events(peer))
            zlog_debug ("%s bad message length - %d for %s",
                        peer->host, size,
                        type == 128 ? "ROUTE-REFRESH" :
                        bgp_type_str[(int) type]);
          bgp_notify_send_with_data (peer,
                                     BGP_NOTIFY_HEADER_ERR,
                                     BGP_NOTIFY_HEADER_BAD_MESLEN,
                                     (u_char *) notify_data_length, 2);
          goto done;
        }

      /* Adjust size to message length. */
      peer->packet_size = size;
    }

  ret = bgp_read_packet (peer);
  if (ret < 0) 
    goto done;

  /* Get size and type again. */
  (void)stream_getw_from (peer->ibuf, BGP_MARKER_SIZE);
  type = stream_getc_from (peer->ibuf, BGP_MARKER_SIZE + 2);

  /* BGP packet dump function. */
  bgp_dump_packet (peer, type, peer->ibuf);
  
  size = (peer->packet_size - BGP_HEADER_SIZE);

  /* Read rest of the packet and call each sort of packet routine */
  switch (type) 
    {
    case BGP_MSG_OPEN:
      peer->open_in++;
      bgp_open_receive (peer, size); /* XXX return value ignored! */
      break;
    case BGP_MSG_UPDATE:
      peer->readtime = monotime (NULL);
      bgp_update_receive (peer, size);
      break;
    case BGP_MSG_NOTIFY:
      bgp_notify_receive (peer, size);
      break;
    case BGP_MSG_KEEPALIVE:
      peer->readtime = monotime (NULL);
      bgp_keepalive_receive (peer, size);
      break;
    case BGP_MSG_ROUTE_REFRESH_NEW:
    case BGP_MSG_ROUTE_REFRESH_OLD:
      peer->refresh_in++;
      bgp_route_refresh_receive (peer, size);
      break;
    case BGP_MSG_CAPABILITY:
      peer->dynamic_cap_in++;
      bgp_capability_receive (peer, size);
      break;
    }

  /* If reading this packet caused us to send a NOTIFICATION then store a copy
   * of the packet for troubleshooting purposes
   */
  if (notify_out < peer->notify_out)
    {
      memcpy(peer->last_reset_cause, peer->ibuf->data, peer->packet_size);
      peer->last_reset_cause_size = peer->packet_size;
      notify_out = peer->notify_out;
    }

  /* Clear input buffer. */
  peer->packet_size = 0;
  if (peer->ibuf)
    stream_reset (peer->ibuf);

 done:
  /* If reading this packet caused us to send a NOTIFICATION then store a copy
   * of the packet for troubleshooting purposes
   */
  if (notify_out < peer->notify_out)
    {
      memcpy(peer->last_reset_cause, peer->ibuf->data, peer->packet_size);
      peer->last_reset_cause_size = peer->packet_size;
    }

  return 0;
}