Merge pull request #12390 from sigeryang/vrrp-interop

[mirror_frr.git] / bgpd / bgp_packet.c

/* BGP packet management routine.
 * Contains utility functions for constructing and consuming BGP messages.
 * Copyright (C) 2017 Cumulus Networks
 * 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 this program; see the file COPYING; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <zebra.h>
#include <sys/time.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 "lib_errors.h"

#include "bgpd/bgpd.h"
#include "bgpd/bgp_table.h"
#include "bgpd/bgp_dump.h"
#include "bgpd/bgp_bmp.h"
#include "bgpd/bgp_attr.h"
#include "bgpd/bgp_debug.h"
#include "bgpd/bgp_errors.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_advertise.h"
#include "bgpd/bgp_vty.h"
#include "bgpd/bgp_updgrp.h"
#include "bgpd/bgp_label.h"
#include "bgpd/bgp_io.h"
#include "bgpd/bgp_keepalives.h"
#include "bgpd/bgp_flowspec.h"
#include "bgpd/bgp_trace.h"

DEFINE_HOOK(bgp_packet_dump,
                (struct peer *peer, uint8_t type, bgp_size_t size,
                        struct stream *s),
                (peer, type, size, s));

DEFINE_HOOK(bgp_packet_send,
                (struct peer *peer, uint8_t type, bgp_size_t size,
                        struct stream *s),
                (peer, type, size, s));

/**
 * Sets marker and type fields for a BGP message.
 *
 * @param s the stream containing the packet
 * @param type the packet type
 * @return the size of the stream
 */
int bgp_packet_set_marker(struct stream *s, uint8_t 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);
}

/**
 * Sets size field for a BGP message.
 *
 * Size field is set to the size of the stream passed.
 *
 * @param s the stream containing the packet
 */
void 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);
}

/*
 * Push a packet onto the beginning of the peer's output queue.
 * This function acquires the peer's write mutex before proceeding.
 */
static void bgp_packet_add(struct peer *peer, struct stream *s)
{
        intmax_t delta;
        uint32_t holdtime;
        intmax_t sendholdtime;

        frr_with_mutex (&peer->io_mtx) {
                /* if the queue is empty, reset the "last OK" timestamp to
                 * now, otherwise if we write another packet immediately
                 * after it'll get confused
                 */
                if (!stream_fifo_count_safe(peer->obuf))
                        peer->last_sendq_ok = monotime(NULL);

                stream_fifo_push(peer->obuf, s);

                delta = monotime(NULL) - peer->last_sendq_ok;

                if (CHECK_FLAG(peer->flags, PEER_FLAG_TIMER))
                        holdtime = atomic_load_explicit(&peer->holdtime,
                                                        memory_order_relaxed);
                else
                        holdtime = peer->bgp->default_holdtime;

                sendholdtime = holdtime * 2;

                /* Note that when we're here, we're adding some packet to the
                 * OutQ.  That includes keepalives when there is nothing to
                 * do, so there's a guarantee we pass by here once in a while.
                 *
                 * That implies there is no need to go set up another separate
                 * timer that ticks down SendHoldTime, as we'll be here sooner
                 * or later anyway and will see the checks below failing.
                 */
                if (!holdtime) {
                        /* no holdtime, do nothing. */
                } else if (delta > sendholdtime) {
                        flog_err(
                                EC_BGP_SENDQ_STUCK_PROPER,
                                "%pBP has not made any SendQ progress for 2 holdtimes (%jds), terminating session",
                                peer, sendholdtime);
                        BGP_EVENT_ADD(peer, TCP_fatal_error);
                } else if (delta > (intmax_t)holdtime &&
                           monotime(NULL) - peer->last_sendq_warn > 5) {
                        flog_warn(
                                EC_BGP_SENDQ_STUCK_WARN,
                                "%pBP has not made any SendQ progress for 1 holdtime (%us), peer overloaded?",
                                peer, holdtime);
                        peer->last_sendq_warn = monotime(NULL);
                }
        }
}

static struct stream *bgp_update_packet_eor(struct peer *peer, afi_t afi,
                                            safi_t safi)
{
        struct stream *s;
        iana_afi_t pkt_afi = IANA_AFI_IPV4;
        iana_safi_t pkt_safi = IANA_SAFI_UNICAST;

        if (DISABLE_BGP_ANNOUNCE)
                return NULL;

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

        s = stream_new(peer->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);
        return s;
}

/* 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)
                                    && !CHECK_FLAG(peer->bgp->flags,
                                                   BGP_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_established(peer)) {
                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_established(peer)) {
                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);

        FOREACH_AFI_SAFI (afi, 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 didn't 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_LABELED_UNICAST:
                return bgp_nlri_parse_label(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);
        case SAFI_FLOWSPEC:
                return bgp_nlri_parse_flowspec(peer, attr, packet, mp_withdraw);
        }
        return BGP_NLRI_PARSE_ERROR;
}


/*
 * Check if route-refresh request from peer is pending (received before EoR),
 * and process it now.
 */
static void bgp_process_pending_refresh(struct peer *peer, afi_t afi,
                                        safi_t safi)
{
        if (CHECK_FLAG(peer->af_sflags[afi][safi],
                       PEER_STATUS_REFRESH_PENDING)) {
                UNSET_FLAG(peer->af_sflags[afi][safi],
                           PEER_STATUS_REFRESH_PENDING);
                bgp_route_refresh_send(peer, afi, safi, 0, 0, 0,
                                       BGP_ROUTE_REFRESH_BORR);
                if (bgp_debug_neighbor_events(peer))
                        zlog_debug(
                                "%pBP sending route-refresh (BoRR) for %s/%s (for pending REQUEST)",
                                peer, afi2str(afi), safi2str(safi));

                SET_FLAG(peer->af_sflags[afi][safi], PEER_STATUS_BORR_SEND);
                UNSET_FLAG(peer->af_sflags[afi][safi], PEER_STATUS_EORR_SEND);
                bgp_announce_route(peer, afi, safi, true);
        }
}

/*
 * Checks a variety of conditions to determine whether the peer needs to be
 * rescheduled for packet generation again, and does so if necessary.
 *
 * @param peer to check for rescheduling
 */
static void bgp_write_proceed_actions(struct peer *peer)
{
        afi_t afi;
        safi_t safi;
        struct peer_af *paf;
        struct bpacket *next_pkt;
        struct update_subgroup *subgrp;
        enum bgp_af_index index;

        for (index = BGP_AF_START; index < BGP_AF_MAX; index++) {
                paf = peer->peer_af_array[index];
                if (!paf)
                        continue;

                subgrp = paf->subgroup;
                if (!subgrp)
                        continue;

                next_pkt = paf->next_pkt_to_send;
                if (next_pkt && next_pkt->buffer) {
                        BGP_TIMER_ON(peer->t_generate_updgrp_packets,
                                     bgp_generate_updgrp_packets, 0);
                        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))
                    || subgroup_packets_to_build(subgrp)) {
                        BGP_TIMER_ON(peer->t_generate_updgrp_packets,
                                     bgp_generate_updgrp_packets, 0);
                        return;
                }

                afi = paf->afi;
                safi = paf->safi;

                /* 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_TIMER_ON(peer->t_generate_updgrp_packets,
                                             bgp_generate_updgrp_packets, 0);
                                return;
                        }
                }
        }
}

/*
 * Generate advertisement information (withdraws, updates, EOR) from each
 * update group a peer belongs to, encode this information into packets, and
 * enqueue the packets onto the peer's output buffer.
 */
void bgp_generate_updgrp_packets(struct thread *thread)
{
        struct peer *peer = THREAD_ARG(thread);

        struct stream *s;
        struct peer_af *paf;
        struct bpacket *next_pkt;
        uint32_t wpq;
        uint32_t generated = 0;
        afi_t afi;
        safi_t safi;

        wpq = atomic_load_explicit(&peer->bgp->wpkt_quanta,
                                   memory_order_relaxed);

        /*
         * 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 processing).
         */
        if (!peer_established(peer))
                return;

        if ((peer->bgp->main_peers_update_hold)
            || bgp_update_delay_active(peer->bgp))
                return;

        if (peer->t_routeadv)
                return;

        do {
                enum bgp_af_index index;

                s = NULL;
                for (index = BGP_AF_START; index < BGP_AF_MAX; index++) {
                        paf = peer->peer_af_array[index];
                        if (!paf || !PAF_SUBGRP(paf))
                                continue;

                        afi = paf->afi;
                        safi = paf->safi;
                        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 (!paf->t_announce_route) {
                                        /* Make sure we supress BGP UPDATES
                                         * for normal processing later again.
                                         */
                                        UNSET_FLAG(paf->subgroup->sflags,
                                                   SUBGRP_STATUS_FORCE_UPDATES);

                                        /* If route-refresh BoRR message was
                                         * already sent and we are done with
                                         * re-announcing tables for a decent
                                         * afi/safi, we ready to send
                                         * EoRR request.
                                         */
                                        if (CHECK_FLAG(
                                                    peer->af_sflags[afi][safi],
                                                    PEER_STATUS_BORR_SEND)) {
                                                bgp_route_refresh_send(
                                                        peer, afi, safi, 0, 0,
                                                        0,
                                                        BGP_ROUTE_REFRESH_EORR);

                                                SET_FLAG(peer->af_sflags[afi]
                                                                        [safi],
                                                         PEER_STATUS_EORR_SEND);
                                                UNSET_FLAG(
                                                        peer->af_sflags[afi]
                                                                       [safi],
                                                        PEER_STATUS_BORR_SEND);

                                                if (bgp_debug_neighbor_events(
                                                            peer))
                                                        zlog_debug(
                                                                "%pBP sending route-refresh (EoRR) for %s/%s",
                                                                peer,
                                                                afi2str(afi),
                                                                safi2str(safi));
                                        }
                                }

                                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)) {
                                                /* If EOR is disabled,
                                                 * the message is  not sent
                                                 */
                                                if (BGP_SEND_EOR(peer->bgp, afi,
                                                                 safi)) {
                                                        SET_FLAG(
                                                                peer->af_sflags
                                                                        [afi]
                                                                        [safi],
                                                                PEER_STATUS_EOR_SEND);

                                                        /* Update EOR
                                                         * send time
                                                         */
                                                        peer->eor_stime[afi]
                                                                       [safi] =
                                                                monotime(NULL);

                                                        BGP_UPDATE_EOR_PKT(
                                                                peer, afi, safi,
                                                                s);
                                                        bgp_process_pending_refresh(
                                                                peer, afi,
                                                                safi);
                                                }
                                        }
                                }
                                continue;
                        }

                        /* Update packet send time */
                        peer->pkt_stime[afi][safi] = monotime(NULL);

                        /* Found a packet template to send, overwrite
                         * packet with appropriate attributes from peer
                         * and advance peer */
                        s = bpacket_reformat_for_peer(next_pkt, paf);
                        bgp_packet_add(peer, s);
                        bpacket_queue_advance_peer(paf);
                }
        } while (s && (++generated < wpq));

        if (generated)
                bgp_writes_on(peer);

        bgp_write_proceed_actions(peer);
}

/*
 * Creates a BGP Keepalive packet and appends it to the peer's output queue.
 */
void bgp_keepalive_send(struct peer *peer)
{
        struct stream *s;

        s = stream_new(BGP_STANDARD_MESSAGE_MAX_PACKET_SIZE);

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

        /* Set packet size. */
        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_writes_on(peer);
}

/*
 * Creates a BGP Open packet and appends it to the peer's output queue.
 * Sets capabilities as necessary.
 */
void bgp_open_send(struct peer *peer)
{
        struct stream *s;
        uint16_t send_holdtime;
        as_t local_as;

        if (CHECK_FLAG(peer->flags, PEER_FLAG_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_STANDARD_MESSAGE_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) ? (uint16_t)local_as
                                                : BGP_AS_TRANS);
        stream_putw(s, send_holdtime);          /* Hold Time */
        stream_put_in_addr(s, &peer->local_id); /* BGP Identifier */

        /* Set capabilities */
        if (CHECK_FLAG(peer->flags, PEER_FLAG_EXTENDED_OPT_PARAMS)) {
                (void)bgp_open_capability(s, peer, true);
        } else {
                struct stream *tmp = stream_new(STREAM_SIZE(s));

                stream_copy(tmp, s);
                if (bgp_open_capability(tmp, peer, false)
                    > BGP_OPEN_NON_EXT_OPT_LEN) {
                        stream_free(tmp);
                        (void)bgp_open_capability(s, peer, true);
                } else {
                        stream_copy(s, tmp);
                        stream_free(tmp);
                }
        }

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

        if (bgp_debug_neighbor_events(peer))
                zlog_debug(
                        "%s sending OPEN, version %d, my as %u, holdtime %d, id %pI4",
                        peer->host, BGP_VERSION_4, local_as, send_holdtime,
                        &peer->local_id);

        /* Dump packet if debug option is set. */
        /* bgp_packet_dump (s); */
        hook_call(bgp_packet_send, peer, BGP_MSG_OPEN, stream_get_endp(s), s);

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

        bgp_writes_on(peer);
}

/*
 * Writes NOTIFICATION message directly to a peer socket without waiting for
 * the I/O thread.
 *
 * There must be exactly one stream on the peer->obuf FIFO, and the data within
 * this stream must match the format of a BGP NOTIFICATION message.
 * Transmission is best-effort.
 *
 * @requires peer->io_mtx
 * @param peer
 * @return 0
 */
static void bgp_write_notify(struct peer *peer)
{
        int ret, val;
        uint8_t type;
        struct stream *s;

        /* There should be at least one packet. */
        s = stream_fifo_pop(peer->obuf);

        if (!s)
                return;

        assert(stream_get_endp(s) >= BGP_HEADER_SIZE);

        /*
         * 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) {
                stream_free(s);
                BGP_EVENT_ADD(peer, TCP_fatal_error);
                return;
        }

        /* 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. */
        atomic_fetch_add_explicit(&peer->notify_out, 1, memory_order_relaxed);

        /* 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);

        stream_free(s);
}

/*
 * Encapsulate an original BGP CEASE Notification into Hard Reset
 */
static uint8_t *bgp_notify_encapsulate_hard_reset(uint8_t code, uint8_t subcode,
                                                  uint8_t *data, size_t datalen)
{
        uint8_t *message = XCALLOC(MTYPE_BGP_NOTIFICATION, datalen + 2);

        /* ErrCode */
        message[0] = code;
        /* Subcode */
        message[1] = subcode;
        /* Data */
        if (datalen)
                memcpy(message + 2, data, datalen);

        return message;
}

/*
 * Decapsulate an original BGP CEASE Notification from Hard Reset
 */
struct bgp_notify bgp_notify_decapsulate_hard_reset(struct bgp_notify *notify)
{
        struct bgp_notify bn = {};

        bn.code = notify->raw_data[0];
        bn.subcode = notify->raw_data[1];
        bn.length = notify->length - 2;

        bn.raw_data = XMALLOC(MTYPE_BGP_NOTIFICATION, bn.length);
        memcpy(bn.raw_data, notify->raw_data + 2, bn.length);

        return bn;
}

/* Check if Graceful-Restart N-bit is exchanged */
bool bgp_has_graceful_restart_notification(struct peer *peer)
{
        return CHECK_FLAG(peer->cap, PEER_CAP_GRACEFUL_RESTART_N_BIT_RCV) &&
               CHECK_FLAG(peer->cap, PEER_CAP_GRACEFUL_RESTART_N_BIT_ADV);
}

/*
 * Check if to send BGP CEASE Notification/Hard Reset?
 */
bool bgp_notify_send_hard_reset(struct peer *peer, uint8_t code,
                                uint8_t subcode)
{
        /* When the "N" bit has been exchanged, a Hard Reset message is used to
         * indicate to the peer that the session is to be fully terminated.
         */
        if (!bgp_has_graceful_restart_notification(peer))
                return false;

        /*
         * https://datatracker.ietf.org/doc/html/rfc8538#section-5.1
         */
        if (code == BGP_NOTIFY_CEASE) {
                switch (subcode) {
                case BGP_NOTIFY_CEASE_MAX_PREFIX:
                case BGP_NOTIFY_CEASE_ADMIN_SHUTDOWN:
                case BGP_NOTIFY_CEASE_PEER_UNCONFIG:
                case BGP_NOTIFY_CEASE_HARD_RESET:
                case BGP_NOTIFY_CEASE_BFD_DOWN:
                        return true;
                case BGP_NOTIFY_CEASE_ADMIN_RESET:
                        /* Provide user control:
                         * `bgp hard-adminstrative-reset`
                         */
                        if (CHECK_FLAG(peer->bgp->flags,
                                       BGP_FLAG_HARD_ADMIN_RESET))
                                return true;
                        else
                                return false;
                default:
                        break;
                }
        }

        return false;
}

/*
 * Check if received BGP CEASE Notification/Hard Reset?
 */
bool bgp_notify_received_hard_reset(struct peer *peer, uint8_t code,
                                    uint8_t subcode)
{
        /* When the "N" bit has been exchanged, a Hard Reset message is used to
         * indicate to the peer that the session is to be fully terminated.
         */
        if (!bgp_has_graceful_restart_notification(peer))
                return false;

        if (code == BGP_NOTIFY_CEASE && subcode == BGP_NOTIFY_CEASE_HARD_RESET)
                return true;

        return false;
}

/*
 * Creates a BGP Notify and appends it to the peer's output queue.
 *
 * This function attempts to write the packet from the thread it is called
 * from, to ensure the packet gets out ASAP.
 *
 * This function may be called from multiple threads. Since the function
 * modifies I/O buffer(s) in the peer, these are locked for the duration of the
 * call to prevent tampering from other threads.
 *
 * Delivery of the NOTIFICATION is attempted once and is best-effort. After
 * return, the peer structure *must* be reset; no assumptions about session
 * state are valid.
 *
 * @param peer
 * @param code      BGP error code
 * @param sub_code  BGP error subcode
 * @param data      Data portion
 * @param datalen   length of data portion
 */
static void bgp_notify_send_internal(struct peer *peer, uint8_t code,
                                     uint8_t sub_code, uint8_t *data,
                                     size_t datalen, bool use_curr)
{
        struct stream *s;
        bool hard_reset = bgp_notify_send_hard_reset(peer, code, sub_code);

        /* Lock I/O mutex to prevent other threads from pushing packets */
        frr_mutex_lock_autounlock(&peer->io_mtx);
        /* ============================================== */

        /* Allocate new stream. */
        s = stream_new(peer->max_packet_size);

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

        /* Check if we should send Hard Reset Notification or not */
        if (hard_reset) {
                uint8_t *hard_reset_message = bgp_notify_encapsulate_hard_reset(
                        code, sub_code, data, datalen);

                /* Hard Reset encapsulates another NOTIFICATION message
                 * in its data portion.
                 */
                stream_putc(s, BGP_NOTIFY_CEASE);
                stream_putc(s, BGP_NOTIFY_CEASE_HARD_RESET);
                stream_write(s, hard_reset_message, datalen + 2);

                XFREE(MTYPE_BGP_NOTIFICATION, hard_reset_message);
        } else {
                stream_putc(s, code);
                stream_putc(s, sub_code);
                if (data)
                        stream_write(s, data, datalen);
        }

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

        /* wipe output buffer */
        stream_fifo_clean(peer->obuf);

        /*
         * If possible, store last packet for debugging purposes. This check is
         * in place because we are sometimes called with a doppelganger peer,
         * who tends to have a plethora of fields nulled out.
         *
         * Some callers should not attempt this - the io pthread for example
         * should not touch internals of the peer struct.
         */
        if (use_curr && peer->curr) {
                size_t packetsize = stream_get_endp(peer->curr);
                assert(packetsize <= peer->max_packet_size);
                memcpy(peer->last_reset_cause, peer->curr->data, packetsize);
                peer->last_reset_cause_size = packetsize;
        }

        /* 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 = datalen;
                bgp_notify.raw_data = data;

                peer->notify.code = bgp_notify.code;
                peer->notify.subcode = bgp_notify.subcode;
                peer->notify.length = bgp_notify.length;

                if (bgp_notify.length && data) {
                        bgp_notify.data = XMALLOC(MTYPE_BGP_NOTIFICATION,
                                                  bgp_notify.length * 3);
                        for (i = 0; i < bgp_notify.length; i++)
                                if (first) {
                                        snprintf(c, sizeof(c), " %02x",
                                                 data[i]);

                                        strlcat(bgp_notify.data, c,
                                                bgp_notify.length);

                                } else {
                                        first = 1;
                                        snprintf(c, sizeof(c), "%02x", data[i]);

                                        strlcpy(bgp_notify.data, c,
                                                bgp_notify.length);
                                }
                }
                bgp_notify_print(peer, &bgp_notify, "sending", hard_reset);

                if (bgp_notify.data) {
                        if (data) {
                                XFREE(MTYPE_BGP_NOTIFICATION,
                                      peer->notify.data);
                                peer->notify.data = XCALLOC(
                                        MTYPE_BGP_NOTIFICATION, datalen);
                                memcpy(peer->notify.data, data, datalen);
                        }

                        XFREE(MTYPE_BGP_NOTIFICATION, bgp_notify.data);
                        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) {
                        if (CHECK_FLAG(peer->sflags, PEER_STATUS_RTT_SHUTDOWN))
                                peer->last_reset = PEER_DOWN_RTT_SHUTDOWN;
                        else
                                peer->last_reset = PEER_DOWN_USER_SHUTDOWN;
                } else
                        peer->last_reset = PEER_DOWN_NOTIFY_SEND;
        } else
                peer->last_reset = PEER_DOWN_NOTIFY_SEND;

        /* Add packet to peer's output queue */
        stream_fifo_push(peer->obuf, s);

        bgp_peer_gr_flags_update(peer);
        BGP_GR_ROUTER_DETECT_AND_SEND_CAPABILITY_TO_ZEBRA(peer->bgp,
                                                          peer->bgp->peer);

        bgp_write_notify(peer);
}

/*
 * Creates a BGP Notify and appends it to the peer's output queue.
 *
 * This function attempts to write the packet from the thread it is called
 * from, to ensure the packet gets out ASAP.
 *
 * @param peer
 * @param code      BGP error code
 * @param sub_code  BGP error subcode
 */
void bgp_notify_send(struct peer *peer, uint8_t code, uint8_t sub_code)
{
        bgp_notify_send_internal(peer, code, sub_code, NULL, 0, true);
}

/*
 * Enqueue notification; called from the main pthread, peer object access is ok.
 */
void bgp_notify_send_with_data(struct peer *peer, uint8_t code,
                               uint8_t sub_code, uint8_t *data, size_t datalen)
{
        bgp_notify_send_internal(peer, code, sub_code, data, datalen, true);
}

/*
 * For use by the io pthread, queueing a notification but avoiding access to
 * the peer object.
 */
void bgp_notify_io_invalid(struct peer *peer, uint8_t code, uint8_t sub_code,
                           uint8_t *data, size_t datalen)
{
        /* Avoid touching the peer object */
        bgp_notify_send_internal(peer, code, sub_code, data, datalen, false);
}

/*
 * Creates BGP Route Refresh packet and appends it to the peer's output queue.
 *
 * @param peer
 * @param afi               Address Family Identifier
 * @param safi              Subsequent Address Family Identifier
 * @param orf_type          Outbound Route Filtering type
 * @param when_to_refresh   Whether to refresh immediately or defer
 * @param remove            Whether to remove ORF for specified AFI/SAFI
 */
void bgp_route_refresh_send(struct peer *peer, afi_t afi, safi_t safi,
                            uint8_t orf_type, uint8_t when_to_refresh,
                            int remove, uint8_t subtype)
{
        struct stream *s;
        struct bgp_filter *filter;
        int orf_refresh = 0;
        iana_afi_t pkt_afi = IANA_AFI_IPV4;
        iana_safi_t pkt_safi = IANA_SAFI_UNICAST;

        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(peer->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);
        if (subtype)
                stream_putc(s, subtype);
        else
                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) {
                        uint16_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(
                                                "%pBP sending REFRESH_REQ to remove ORF(%d) (%s) for afi/safi: %s/%s",
                                                peer, orf_type,
                                                (when_to_refresh ==
                                                                 REFRESH_DEFER
                                                         ? "defer"
                                                         : "immediate"),
                                                iana_afi2str(pkt_afi),
                                                iana_safi2str(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(
                                                "%pBP sending REFRESH_REQ with pfxlist ORF(%d) (%s) for afi/safi: %s/%s",
                                                peer, orf_type,
                                                (when_to_refresh ==
                                                                 REFRESH_DEFER
                                                         ? "defer"
                                                         : "immediate"),
                                                iana_afi2str(pkt_afi),
                                                iana_safi2str(pkt_safi));
                        }

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

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

        if (bgp_debug_neighbor_events(peer)) {
                if (!orf_refresh)
                        zlog_debug(
                                "%pBP sending REFRESH_REQ for afi/safi: %s/%s",
                                peer, iana_afi2str(pkt_afi),
                                iana_safi2str(pkt_safi));
        }

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

        bgp_writes_on(peer);
}

/*
 * Create a BGP Capability packet and append it to the peer's output queue.
 *
 * @param peer
 * @param afi              Address Family Identifier
 * @param safi             Subsequent Address Family Identifier
 * @param capability_code  BGP Capability Code
 * @param action           Set or Remove capability
 */
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 = IANA_AFI_IPV4;
        iana_safi_t pkt_safi = IANA_SAFI_UNICAST;

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

        s = stream_new(peer->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(
                                "%pBP sending CAPABILITY has %s MP_EXT CAP for afi/safi: %s/%s",
                                peer,
                                action == CAPABILITY_ACTION_SET ? "Advertising"
                                                                : "Removing",
                                iana_afi2str(pkt_afi), iana_safi2str(pkt_safi));
        }

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

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

        bgp_writes_on(peer);
}

/* 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:
         */
        peer = new->doppelganger;
        if (peer == NULL)
                return 0;

        /*
         * 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_established(peer) || peer->status == Clearing) {
                bgp_notify_send(new, BGP_NOTIFY_CEASE,
                                BGP_NOTIFY_CEASE_COLLISION_RESOLUTION);
                return -1;
        }

        if ((peer->status != OpenConfirm) && (peer->status != OpenSent))
                return 0;

        /*
         * 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 the BGP Identifiers of the peers
         * involved in the connection collision
         * are identical, then the connection
         * initiated by the BGP speaker with the
         * larger AS number is preserved.
         */
        if (ntohl(peer->local_id.s_addr) < ntohl(remote_id.s_addr)
            || (ntohl(peer->local_id.s_addr) == ntohl(remote_id.s_addr)
                && peer->local_as < peer->as))
                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 {
                if (ntohl(peer->local_id.s_addr) == ntohl(remote_id.s_addr)
                    && peer->local_as == peer->as)
                        flog_err(EC_BGP_ROUTER_ID_SAME,
                                 "Peer's router-id %pI4 is the same as ours",
                                 &remote_id);

                /*
                 * 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;
                }
        }
}

/* Packet processing routines ---------------------------------------------- */
/*
 * This is a family of functions designed to be called from
 * bgp_process_packet(). These functions all share similar behavior and should
 * adhere to the following invariants and restrictions:
 *
 * Return codes
 * ------------
 * The return code of any one of those functions should be one of the FSM event
 * codes specified in bgpd.h. If a NOTIFY was sent, this event code MUST be
 * BGP_Stop. Otherwise, the code SHOULD correspond to the function's expected
 * packet type. For example, bgp_open_receive() should return BGP_Stop upon
 * error and Receive_OPEN_message otherwise.
 *
 * If no action is necessary, the correct return code is BGP_PACKET_NOOP as
 * defined below.
 *
 * Side effects
 * ------------
 * - May send NOTIFY messages
 * - May not modify peer->status
 * - May not call bgp_event_update()
 */

#define BGP_PACKET_NOOP 0

/**
 * Process BGP OPEN message for peer.
 *
 * If any errors are encountered in the OPEN message, immediately sends NOTIFY
 * and returns BGP_Stop.
 *
 * @param peer
 * @param size size of the packet
 * @return as in summary
 */
static int bgp_open_receive(struct peer *peer, bgp_size_t size)
{
        int ret;
        uint8_t version;
        uint16_t optlen;
        uint16_t holdtime;
        uint16_t send_holdtime;
        as_t remote_as;
        as_t as4 = 0, as4_be;
        struct in_addr remote_id;
        int mp_capability;
        uint8_t notify_data_remote_as[2];
        uint8_t notify_data_remote_as4[4];
        uint8_t notify_data_remote_id[4];
        uint16_t *holdtime_ptr;

        /* Parse open packet. */
        version = stream_getc(peer->curr);
        memcpy(notify_data_remote_as, stream_pnt(peer->curr), 2);
        remote_as = stream_getw(peer->curr);
        holdtime_ptr = (uint16_t *)stream_pnt(peer->curr);
        holdtime = stream_getw(peer->curr);
        memcpy(notify_data_remote_id, stream_pnt(peer->curr), 4);
        remote_id.s_addr = stream_get_ipv4(peer->curr);

        /* BEGIN to read the capability here, but dont do it yet */
        mp_capability = 0;
        optlen = stream_getc(peer->curr);

        /* Extended Optional Parameters Length for BGP OPEN Message */
        if (optlen == BGP_OPEN_NON_EXT_OPT_LEN
            || CHECK_FLAG(peer->flags, PEER_FLAG_EXTENDED_OPT_PARAMS)) {
                uint8_t opttype;

                if (STREAM_READABLE(peer->curr) < 1) {
                        flog_err(
                                EC_BGP_PKT_OPEN,
                                "%s: stream does not have enough bytes for extended optional parameters",
                                peer->host);
                        bgp_notify_send(peer, BGP_NOTIFY_OPEN_ERR,
                                        BGP_NOTIFY_OPEN_MALFORMED_ATTR);
                        return BGP_Stop;
                }

                opttype = stream_getc(peer->curr);
                if (opttype == BGP_OPEN_NON_EXT_OPT_TYPE_EXTENDED_LENGTH) {
                        if (STREAM_READABLE(peer->curr) < 2) {
                                flog_err(
                                        EC_BGP_PKT_OPEN,
                                        "%s: stream does not have enough bytes to read the extended optional parameters optlen",
                                        peer->host);
                                bgp_notify_send(peer, BGP_NOTIFY_OPEN_ERR,
                                                BGP_NOTIFY_OPEN_MALFORMED_ATTR);
                                return BGP_Stop;
                        }
                        optlen = stream_getw(peer->curr);
                        SET_FLAG(peer->sflags,
                                 PEER_STATUS_EXT_OPT_PARAMS_LENGTH);
                }
        }

        /* Receive OPEN message log  */
        if (bgp_debug_neighbor_events(peer))
                zlog_debug(
                        "%s rcv OPEN%s, version %d, remote-as (in open) %u, holdtime %d, id %pI4",
                        peer->host,
                        CHECK_FLAG(peer->sflags,
                                   PEER_STATUS_EXT_OPT_PARAMS_LENGTH)
                                ? " (Extended)"
                                : "",
                        version, remote_as, holdtime, &remote_id);

        if (optlen != 0) {
                /* If not enough bytes, it is an error. */
                if (STREAM_READABLE(peer->curr) < optlen) {
                        flog_err(EC_BGP_PKT_OPEN,
                                 "%s: stream has not enough bytes (%u)",
                                 peer->host, optlen);
                        bgp_notify_send(peer, BGP_NOTIFY_OPEN_ERR,
                                        BGP_NOTIFY_OPEN_MALFORMED_ATTR);
                        return BGP_Stop;
                }

                /* 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);
        }

        as4_be = htonl(as4);
        memcpy(notify_data_remote_as4, &as4_be, 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) {
                flog_err(EC_BGP_PKT_OPEN,
                         "%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 BGP_Stop;
        }

        /* Codification of AS 0 Processing */
        if (remote_as == BGP_AS_ZERO) {
                flog_err(EC_BGP_PKT_OPEN, "%s bad OPEN, got AS set to 0",
                         peer->host);
                bgp_notify_send(peer, BGP_NOTIFY_OPEN_ERR,
                                BGP_NOTIFY_OPEN_BAD_PEER_AS);
                return BGP_Stop;
        }

        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) {
                        flog_err(
                                EC_BGP_PKT_OPEN,
                                "%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 BGP_Stop;
                }

                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 */
                        flog_err(
                                EC_BGP_PKT_OPEN,
                                "%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 BGP_Stop;
                }
        }

        /* rfc6286:
         * If the BGP Identifier field of the OPEN message
         * is zero, or if it is the same as the BGP Identifier
         * of the local BGP speaker and the message is from an
         * internal peer, then the Error Subcode is set to
         * "Bad BGP Identifier".
         */
        if (remote_id.s_addr == INADDR_ANY
            || (peer->sort == BGP_PEER_IBGP
                && 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 %pI4",
                                   peer->host, &remote_id);
                bgp_notify_send_with_data(peer, BGP_NOTIFY_OPEN_ERR,
                                          BGP_NOTIFY_OPEN_BAD_BGP_IDENT,
                                          notify_data_remote_id, 4);
                return BGP_Stop;
        }

        /* Peer BGP version check. */
        if (version != BGP_VERSION_4) {
                uint16_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,
                                          (uint8_t *)&maxver, 2);
                return BGP_Stop;
        }

        /* 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 BGP_Stop;
        } 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 BGP_Stop;
                }
                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 BGP_Stop;
                }
                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 BGP_Stop;
        }

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

        /* Get sockname. */
        if (bgp_getsockname(peer) < 0) {
                flog_err_sys(EC_LIB_SOCKET,
                             "%s: bgp_getsockname() failed for peer: %s",
                             __func__, peer->host);
                return BGP_Stop;
        }

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

        /* 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,
                                          (uint8_t *)holdtime_ptr, 2);
                return BGP_Stop;
        }

        /* Send notification message when Hold Time received in the OPEN message
         * is smaller than configured minimum Hold Time. */
        if (holdtime < peer->bgp->default_min_holdtime
            && peer->bgp->default_min_holdtime != 0) {
                bgp_notify_send_with_data(peer, BGP_NOTIFY_OPEN_ERR,
                                          BGP_NOTIFY_OPEN_UNACEP_HOLDTIME,
                                          (uint8_t *)holdtime_ptr, 2);
                return BGP_Stop;
        }

        /* 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->flags, PEER_FLAG_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;

        /* Set effective keepalive to 1/3 the effective holdtime.
         * Use configured keeplive when < effective keepalive.
         */
        peer->v_keepalive = peer->v_holdtime / 3;
        if (CHECK_FLAG(peer->flags, PEER_FLAG_TIMER)) {
                if (peer->keepalive && peer->keepalive < peer->v_keepalive)
                        peer->v_keepalive = peer->keepalive;
        } else {
                if (peer->bgp->default_keepalive
                    && peer->bgp->default_keepalive < peer->v_keepalive)
                        peer->v_keepalive = peer->bgp->default_keepalive;
        }

        /* Open option part parse. */
        if (optlen != 0) {
                if (bgp_open_option_parse(peer, optlen, &mp_capability) < 0)
                        return BGP_Stop;
        } 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_IP][SAFI_LABELED_UNICAST] =
                        peer->afc[AFI_IP][SAFI_LABELED_UNICAST];
                peer->afc_nego[AFI_IP][SAFI_FLOWSPEC] =
                        peer->afc[AFI_IP][SAFI_FLOWSPEC];
                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];
                peer->afc_nego[AFI_IP6][SAFI_LABELED_UNICAST] =
                        peer->afc[AFI_IP6][SAFI_LABELED_UNICAST];
                peer->afc_nego[AFI_L2VPN][SAFI_EVPN] =
                        peer->afc[AFI_L2VPN][SAFI_EVPN];
                peer->afc_nego[AFI_IP6][SAFI_FLOWSPEC] =
                        peer->afc[AFI_IP6][SAFI_FLOWSPEC];
        }

        /* Verify valid local address present based on negotiated
         * address-families. */
        if (peer->afc_nego[AFI_IP][SAFI_UNICAST]
            || peer->afc_nego[AFI_IP][SAFI_LABELED_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 == INADDR_ANY) {
#if defined(HAVE_CUMULUS)
                        zlog_warn("%s: No local IPv4 addr, BGP routing may not work",
                                  peer->host);
#endif
                }
        }
        if (peer->afc_nego[AFI_IP6][SAFI_UNICAST]
            || peer->afc_nego[AFI_IP6][SAFI_LABELED_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_warn("%s: No local IPv6 address, BGP routing may not work",
                                  peer->host);
#endif
                }
        }
        peer->rtt = sockopt_tcp_rtt(peer->fd);

        return Receive_OPEN_message;
}

/**
 * Process BGP KEEPALIVE message for peer.
 *
 * @param peer
 * @param size size of the packet
 * @return as in summary
 */
static int bgp_keepalive_receive(struct peer *peer, bgp_size_t size)
{
        if (bgp_debug_keepalive(peer))
                zlog_debug("%s KEEPALIVE rcvd", peer->host);

        bgp_update_implicit_eors(peer);

        peer->rtt = sockopt_tcp_rtt(peer->fd);

        /* If the peer's RTT is higher than expected, shutdown
         * the peer automatically.
         */
        if (!CHECK_FLAG(peer->flags, PEER_FLAG_RTT_SHUTDOWN))
                return Receive_KEEPALIVE_message;

        if (peer->rtt > peer->rtt_expected) {
                peer->rtt_keepalive_rcv++;

                if (peer->rtt_keepalive_rcv > peer->rtt_keepalive_conf) {
                        char rtt_shutdown_reason[BUFSIZ] = {};

                        snprintfrr(
                                rtt_shutdown_reason,
                                sizeof(rtt_shutdown_reason),
                                "shutdown due to high round-trip-time (%dms > %dms, hit %u times)",
                                peer->rtt, peer->rtt_expected,
                                peer->rtt_keepalive_rcv);
                        zlog_warn("%s %s", peer->host, rtt_shutdown_reason);
                        SET_FLAG(peer->sflags, PEER_STATUS_RTT_SHUTDOWN);
                        peer_tx_shutdown_message_set(peer, rtt_shutdown_reason);
                        peer_flag_set(peer, PEER_FLAG_SHUTDOWN);
                }
        } else {
                if (peer->rtt_keepalive_rcv)
                        peer->rtt_keepalive_rcv--;
        }

        return Receive_KEEPALIVE_message;
}

static void bgp_refresh_stalepath_timer_expire(struct thread *thread)
{
        struct peer_af *paf;

        paf = THREAD_ARG(thread);

        afi_t afi = paf->afi;
        safi_t safi = paf->safi;
        struct peer *peer = paf->peer;

        peer->t_refresh_stalepath = NULL;

        if (peer->nsf[afi][safi])
                bgp_clear_stale_route(peer, afi, safi);

        if (bgp_debug_neighbor_events(peer))
                zlog_debug(
                        "%pBP route-refresh (BoRR) timer expired for afi/safi: %d/%d",
                        peer, afi, safi);

        bgp_timer_set(peer);
}

/**
 * Process BGP UPDATE message for peer.
 *
 * Parses UPDATE and creates attribute object.
 *
 * @param peer
 * @param size size of the packet
 * @return as in summary
 */
static int bgp_update_receive(struct peer *peer, bgp_size_t size)
{
        int ret, nlri_ret;
        uint8_t *end;
        struct stream *s;
        struct attr attr;
        bgp_size_t attribute_len;
        bgp_size_t update_len;
        bgp_size_t withdraw_len;
        bool restart = false;

        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_established(peer)) {
                flog_err(EC_BGP_INVALID_STATUS,
                         "%s [FSM] Update packet received under status %s",
                         peer->host,
                         lookup_msg(bgp_status_msg, peer->status, NULL));
                bgp_notify_send(peer, BGP_NOTIFY_FSM_ERR,
                                bgp_fsm_error_subcode(peer->status));
                return BGP_Stop;
        }

        /* Set initial values. */
        memset(&attr, 0, sizeof(attr));
        attr.label_index = BGP_INVALID_LABEL_INDEX;
        attr.label = MPLS_INVALID_LABEL;
        memset(&nlris, 0, sizeof(nlris));
        memset(peer->rcvd_attr_str, 0, BUFSIZ);
        peer->rcvd_attr_printed = 0;

        s = peer->curr;
        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) {
                flog_err(EC_BGP_UPDATE_RCV,
                         "%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 BGP_Stop;
        }

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

        /* Unfeasible Route Length check. */
        if (stream_pnt(s) + withdraw_len > end) {
                flog_err(EC_BGP_UPDATE_RCV,
                         "%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 BGP_Stop;
        }

        /* 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) {
                flog_warn(
                        EC_BGP_UPDATE_PACKET_SHORT,
                        "%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 BGP_Stop;
        }

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

        /* Attribute length check. */
        if (stream_pnt(s) + attribute_len > end) {
                flog_warn(
                        EC_BGP_UPDATE_PACKET_LONG,
                        "%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 BGP_Stop;
        }

        /* 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..
         */
        enum bgp_attr_parse_ret 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 BGP_Stop;
                }
        }

        /* 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(&attr, peer->rcvd_attr_str,
                                    sizeof(peer->rcvd_attr_str));

                peer->stat_upd_7606++;

                if (attr_parse_ret == BGP_ATTR_PARSE_WITHDRAW)
                        flog_err(
                                EC_BGP_UPDATE_RCV,
                                "%pBP rcvd UPDATE with errors in attr(s)!! Withdrawing route.",
                                peer);

                if (ret && bgp_debug_update(peer, NULL, NULL, 1)) {
                        zlog_debug("%pBP rcvd UPDATE w/ attr: %s", peer,
                                   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 (CHECK_FLAG(attr.flag, ATTR_FLAG_BIT(BGP_ATTR_MP_REACH_NLRI))) {
                        /*
                         * We skipped nexthop attribute validation earlier so
                         * validate the nexthop now.
                         */
                        if (bgp_attr_nexthop_valid(peer, &attr) < 0) {
                                bgp_attr_unintern_sub(&attr);
                                return BGP_Stop;
                        }
                }
        }

        if (BGP_DEBUG(update, UPDATE_IN))
                zlog_debug("%pBP rcvd UPDATE wlen %d attrlen %d alen %d", peer,
                           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 = BGP_NLRI_PARSE_ERROR;
                }

                if (nlri_ret < BGP_NLRI_PARSE_OK
                    && nlri_ret != BGP_NLRI_PARSE_ERROR_PREFIX_OVERFLOW) {
                        flog_err(EC_BGP_UPDATE_RCV,
                                 "%s [Error] Error parsing NLRI", peer->host);
                        if (peer_established(peer))
                                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 BGP_Stop;
                }
        }

        /* 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)
            || (attr_parse_ret == BGP_ATTR_PARSE_EOR)) {
                afi_t afi = 0;
                safi_t safi;
                struct graceful_restart_info *gr_info;

                /* Restarting router */
                if (BGP_PEER_GRACEFUL_RESTART_CAPABLE(peer)
                    && BGP_PEER_RESTARTING_MODE(peer))
                        restart = true;

                /* 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;
                } else if (attr_parse_ret == BGP_ATTR_PARSE_EOR) {
                        afi = nlris[NLRI_MP_UPDATE].afi;
                        safi = nlris[NLRI_MP_UPDATE].safi;
                }

                if (afi && peer->afc[afi][safi]) {
                        struct vrf *vrf = vrf_lookup_by_id(peer->bgp->vrf_id);

                        /* 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);
                                /* Update graceful restart information */
                                gr_info = &(peer->bgp->gr_info[afi][safi]);
                                if (restart)
                                        gr_info->eor_received++;
                                /* If EOR received from all peers and selection
                                 * deferral timer is running, cancel the timer
                                 * and invoke the best path calculation
                                 */
                                if (gr_info->eor_required
                                    == gr_info->eor_received) {
                                        if (bgp_debug_neighbor_events(peer))
                                                zlog_debug(
                                                        "%s %d, %s %d",
                                                        "EOR REQ",
                                                        gr_info->eor_required,
                                                        "EOR RCV",
                                                        gr_info->eor_received);
                                        if (gr_info->t_select_deferral) {
                                                void *info = THREAD_ARG(
                                                        gr_info->t_select_deferral);
                                                XFREE(MTYPE_TMP, info);
                                        }
                                        THREAD_OFF(gr_info->t_select_deferral);
                                        gr_info->eor_required = 0;
                                        gr_info->eor_received = 0;
                                        /* Best path selection */
                                        bgp_best_path_select_defer(peer->bgp,
                                                                   afi, safi);
                                }
                        }

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

                        zlog_info(
                                "%s: rcvd End-of-RIB for %s from %s in vrf %s",
                                __func__, get_afi_safi_str(afi, safi, false),
                                peer->host, vrf ? vrf->name : VRF_DEFAULT_NAME);
                }
        }

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

        peer->update_time = monotime(NULL);

        /* Notify BGP Conditional advertisement scanner process */
        peer->advmap_table_change = true;

        return Receive_UPDATE_message;
}

/**
 * Process BGP NOTIFY message for peer.
 *
 * @param peer
 * @param size size of the packet
 * @return as in summary
 */
static int bgp_notify_receive(struct peer *peer, bgp_size_t size)
{
        struct bgp_notify outer = {};
        struct bgp_notify inner = {};
        bool hard_reset = false;

        if (peer->notify.data) {
                XFREE(MTYPE_BGP_NOTIFICATION, peer->notify.data);
                peer->notify.length = 0;
                peer->notify.hard_reset = false;
        }

        outer.code = stream_getc(peer->curr);
        outer.subcode = stream_getc(peer->curr);
        outer.length = size - 2;
        outer.data = NULL;
        outer.raw_data = NULL;
        if (outer.length) {
                outer.raw_data = XMALLOC(MTYPE_BGP_NOTIFICATION, outer.length);
                memcpy(outer.raw_data, stream_pnt(peer->curr), outer.length);
        }

        hard_reset =
                bgp_notify_received_hard_reset(peer, outer.code, outer.subcode);
        if (hard_reset && outer.length) {
                inner = bgp_notify_decapsulate_hard_reset(&outer);
                peer->notify.hard_reset = true;
        } else {
                inner = outer;
        }

        /* Preserv notify code and sub code. */
        peer->notify.code = inner.code;
        peer->notify.subcode = inner.subcode;
        /* For further diagnostic record returned Data. */
        if (inner.length) {
                peer->notify.length = inner.length;
                peer->notify.data =
                        XMALLOC(MTYPE_BGP_NOTIFICATION, inner.length);
                memcpy(peer->notify.data, inner.raw_data, inner.length);
        }

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

                if (inner.length) {
                        inner.data = XMALLOC(MTYPE_BGP_NOTIFICATION,
                                             inner.length * 3);
                        for (i = 0; i < inner.length; i++)
                                if (first) {
                                        snprintf(c, sizeof(c), " %02x",
                                                stream_getc(peer->curr));

                                        strlcat(inner.data, c,
                                                inner.length * 3);

                                } else {
                                        first = 1;
                                        snprintf(c, sizeof(c), "%02x",
                                                 stream_getc(peer->curr));

                                        strlcpy(inner.data, c,
                                                inner.length * 3);
                                }
                }

                bgp_notify_print(peer, &inner, "received", hard_reset);
                if (inner.length) {
                        XFREE(MTYPE_BGP_NOTIFICATION, inner.data);
                        inner.length = 0;
                }
                if (outer.length) {
                        XFREE(MTYPE_BGP_NOTIFICATION, outer.data);
                        XFREE(MTYPE_BGP_NOTIFICATION, outer.raw_data);

                        /* If this is a Hard Reset notification, we MUST free
                         * the inner (encapsulated) notification too.
                         */
                        if (hard_reset)
                                XFREE(MTYPE_BGP_NOTIFICATION, inner.raw_data);
                        outer.length = 0;
                }
        }

        /* peer count update */
        atomic_fetch_add_explicit(&peer->notify_in, 1, memory_order_relaxed);

        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 (inner.code == BGP_NOTIFY_OPEN_ERR &&
            inner.subcode == BGP_NOTIFY_OPEN_UNSUP_PARAM)
                UNSET_FLAG(peer->sflags, PEER_STATUS_CAPABILITY_OPEN);

        /* If Graceful-Restart N-bit (Notification) is exchanged,
         * and it's not a Hard Reset, let's retain the routes.
         */
        if (bgp_has_graceful_restart_notification(peer) && !hard_reset &&
            CHECK_FLAG(peer->sflags, PEER_STATUS_NSF_MODE))
                SET_FLAG(peer->sflags, PEER_STATUS_NSF_WAIT);

        bgp_peer_gr_flags_update(peer);
        BGP_GR_ROUTER_DETECT_AND_SEND_CAPABILITY_TO_ZEBRA(peer->bgp,
                                                          peer->bgp->peer);

        return Receive_NOTIFICATION_message;
}

/**
 * Process BGP ROUTEREFRESH message for peer.
 *
 * @param peer
 * @param size size of the packet
 * @return as in summary
 */
static int bgp_route_refresh_receive(struct peer *peer, bgp_size_t size)
{
        iana_afi_t pkt_afi;
        afi_t afi;
        iana_safi_t pkt_safi;
        safi_t safi;
        struct stream *s;
        struct peer_af *paf;
        struct update_group *updgrp;
        struct peer *updgrp_peer;
        uint8_t subtype;
        bool force_update = false;
        bgp_size_t msg_length =
                size - (BGP_MSG_ROUTE_REFRESH_MIN_SIZE - BGP_HEADER_SIZE);

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

        /* Status must be Established. */
        if (!peer_established(peer)) {
                flog_err(
                        EC_BGP_INVALID_STATUS,
                        "%s [Error] Route refresh packet received under status %s",
                        peer->host,
                        lookup_msg(bgp_status_msg, peer->status, NULL));
                bgp_notify_send(peer, BGP_NOTIFY_FSM_ERR,
                                bgp_fsm_error_subcode(peer->status));
                return BGP_Stop;
        }

        s = peer->curr;

        /* Parse packet. */
        pkt_afi = stream_getw(s);
        subtype = stream_getc(s);
        pkt_safi = stream_getc(s);

        /* 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: %s/%s - ignored",
                        peer->host, iana_afi2str(pkt_afi),
                        iana_safi2str(pkt_safi));
                return BGP_PACKET_NOOP;
        }

        if (size != BGP_MSG_ROUTE_REFRESH_MIN_SIZE - BGP_HEADER_SIZE) {
                uint8_t *end;
                uint8_t when_to_refresh;
                uint8_t orf_type;
                uint16_t orf_len;

                if (subtype) {
                        /* If the length, excluding the fixed-size message
                         * header, of the received ROUTE-REFRESH message with
                         * Message Subtype 1 and 2 is not 4, then the BGP
                         * speaker MUST send a NOTIFICATION message with the
                         * Error Code of "ROUTE-REFRESH Message Error" and the
                         * subcode of "Invalid Message Length".
                         */
                        if (msg_length != 4) {
                                zlog_err(
                                        "%s Enhanced Route Refresh message length error",
                                        peer->host);
                                bgp_notify_send(
                                        peer, BGP_NOTIFY_ROUTE_REFRESH_ERR,
                                        BGP_NOTIFY_ROUTE_REFRESH_INVALID_MSG_LEN);
                        }

                        /* When the BGP speaker receives a ROUTE-REFRESH message
                         * with a "Message Subtype" field other than 0, 1, or 2,
                         * it MUST ignore the received ROUTE-REFRESH message.
                         */
                        if (subtype > 2)
                                zlog_err(
                                        "%s Enhanced Route Refresh invalid subtype",
                                        peer->host);
                }

                if (msg_length < 5) {
                        zlog_info("%s ORF route refresh length error",
                                  peer->host);
                        bgp_notify_send(peer, BGP_NOTIFY_CEASE,
                                        BGP_NOTIFY_SUBCODE_UNSPECIFIC);
                        return BGP_Stop;
                }

                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;
                                uint8_t common = 0;
                                uint32_t seq;
                                int psize;
                                char name[BUFSIZ];
                                int ret = CMD_SUCCESS;

                                if (bgp_debug_neighbor_events(peer)) {
                                        zlog_debug(
                                                "%pBP rcvd Prefixlist ORF(%d) length %d",
                                                peer, orf_type, orf_len);
                                }

                                /* ORF prefix-list name */
                                snprintf(name, sizeof(name), "%s.%d.%d",
                                         peer->host, afi, safi);

                                /* 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 (*p_pnt & ORF_COMMON_PART_REMOVE_ALL) {
                                        if (bgp_debug_neighbor_events(peer))
                                                zlog_debug(
                                                        "%pBP rcvd Remove-All pfxlist ORF request",
                                                        peer);
                                        prefix_bgp_orf_remove_all(afi, name);
                                        break;
                                }

                                if (orf_len < 7)
                                        break;

                                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(orfp));
                                        common = *p_pnt++;
                                        /* after ++: p_pnt <= p_end */
                                        ok = ((uint32_t)(p_end - p_pnt)
                                              >= sizeof(uint32_t));
                                        if (ok) {
                                                memcpy(&seq, p_pnt,
                                                       sizeof(uint32_t));
                                                p_pnt += sizeof(uint32_t);
                                                orfp.seq = ntohl(seq);
                                        } else
                                                p_pnt = p_end;

                                        /* val checked in prefix_bgp_orf_set */
                                        if (p_pnt < p_end)
                                                orfp.ge = *p_pnt++;

                                        /* val checked in prefix_bgp_orf_set */
                                        if (p_pnt < p_end)
                                                orfp.le = *p_pnt++;

                                        if ((ok = (p_pnt < p_end)))
                                                orfp.p.prefixlen = *p_pnt++;

                                        /* afi checked already */
                                        orfp.p.family = afi2family(afi);

                                        /* 0 if not ok */
                                        psize = PSIZE(orfp.p.prefixlen);
                                        /* valid for family ? */
                                        if (psize > prefix_blen(&orfp.p)) {
                                                ok = 0;
                                                psize = prefix_blen(&orfp.p);
                                        }
                                        /* valid for packet ? */
                                        if (psize > (p_end - p_pnt)) {
                                                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(
                                                        "%pBP rcvd %s %s seq %u %s/%d ge %d le %d%s",
                                                        peer,
                                                        (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(
                                                        "%pBP Received misformatted prefixlist ORF. Remove All pfxlist",
                                                        peer);
                                                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("%pBP rcvd Refresh %s ORF request", peer,
                                   when_to_refresh == REFRESH_DEFER
                                           ? "Defer"
                                           : "Immediate");
                if (when_to_refresh == REFRESH_DEFER)
                        return BGP_PACKET_NOOP;
        }

        /* 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];
                }

                /* Avoid supressing duplicate routes later
                 * when processing in subgroup_announce_table().
                 */
                force_update = true;

                /* 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);
        }

        if (subtype == BGP_ROUTE_REFRESH_BORR) {
                /* A BGP speaker that has received the Graceful Restart
                 * Capability from its neighbor MUST ignore any BoRRs for
                 * an <AFI, SAFI> from the neighbor before the speaker
                 * receives the EoR for the given <AFI, SAFI> from the
                 * neighbor.
                 */
                if (CHECK_FLAG(peer->cap, PEER_CAP_RESTART_RCV)
                    && !CHECK_FLAG(peer->af_sflags[afi][safi],
                                   PEER_STATUS_EOR_RECEIVED)) {
                        if (bgp_debug_neighbor_events(peer))
                                zlog_debug(
                                        "%pBP rcvd route-refresh (BoRR) for %s/%s before EoR",
                                        peer, afi2str(afi), safi2str(safi));
                        return BGP_PACKET_NOOP;
                }

                if (peer->t_refresh_stalepath) {
                        if (bgp_debug_neighbor_events(peer))
                                zlog_debug(
                                        "%pBP rcvd route-refresh (BoRR) for %s/%s, whereas BoRR already received",
                                        peer, afi2str(afi), safi2str(safi));
                        return BGP_PACKET_NOOP;
                }

                SET_FLAG(peer->af_sflags[afi][safi], PEER_STATUS_BORR_RECEIVED);
                UNSET_FLAG(peer->af_sflags[afi][safi],
                           PEER_STATUS_EORR_RECEIVED);

                /* When a BGP speaker receives a BoRR message from
                 * a peer, it MUST mark all the routes with the given
                 * Address Family Identifier and Subsequent Address
                 * Family Identifier, <AFI, SAFI> [RFC2918], from
                 * that peer as stale.
                 */
                if (peer_active_nego(peer)) {
                        SET_FLAG(peer->af_sflags[afi][safi],
                                 PEER_STATUS_ENHANCED_REFRESH);
                        bgp_set_stale_route(peer, afi, safi);
                }

                if (peer_established(peer))
                        thread_add_timer(bm->master,
                                         bgp_refresh_stalepath_timer_expire,
                                         paf, peer->bgp->stalepath_time,
                                         &peer->t_refresh_stalepath);

                if (bgp_debug_neighbor_events(peer))
                        zlog_debug(
                                "%pBP rcvd route-refresh (BoRR) for %s/%s, triggering timer for %u seconds",
                                peer, afi2str(afi), safi2str(safi),
                                peer->bgp->stalepath_time);
        } else if (subtype == BGP_ROUTE_REFRESH_EORR) {
                if (!peer->t_refresh_stalepath) {
                        zlog_err(
                                "%pBP rcvd route-refresh (EoRR) for %s/%s, whereas no BoRR received",
                                peer, afi2str(afi), safi2str(safi));
                        return BGP_PACKET_NOOP;
                }

                THREAD_OFF(peer->t_refresh_stalepath);

                SET_FLAG(peer->af_sflags[afi][safi], PEER_STATUS_EORR_RECEIVED);
                UNSET_FLAG(peer->af_sflags[afi][safi],
                           PEER_STATUS_BORR_RECEIVED);

                if (bgp_debug_neighbor_events(peer))
                        zlog_debug(
                                "%pBP rcvd route-refresh (EoRR) for %s/%s, stopping BoRR timer",
                                peer, afi2str(afi), safi2str(safi));

                if (peer->nsf[afi][safi])
                        bgp_clear_stale_route(peer, afi, safi);
        } else {
                if (bgp_debug_neighbor_events(peer))
                        zlog_debug(
                                "%pBP rcvd route-refresh (REQUEST) for %s/%s",
                                peer, afi2str(afi), safi2str(safi));

                /* In response to a "normal route refresh request" from the
                 * peer, the speaker MUST send a BoRR message.
                 */
                if (CHECK_FLAG(peer->cap, PEER_CAP_ENHANCED_RR_RCV)) {
                        /* For a BGP speaker that supports the BGP Graceful
                         * Restart, it MUST NOT send a BoRR for an <AFI, SAFI>
                         * to a neighbor before it sends the EoR for the
                         * <AFI, SAFI> to the neighbor.
                         */
                        if (!CHECK_FLAG(peer->af_sflags[afi][safi],
                                        PEER_STATUS_EOR_SEND)) {
                                if (bgp_debug_neighbor_events(peer))
                                        zlog_debug(
                                                "%pBP rcvd route-refresh (REQUEST) for %s/%s before EoR",
                                                peer, afi2str(afi),
                                                safi2str(safi));
                                /* Can't send BoRR now, postpone after EoR */
                                SET_FLAG(peer->af_sflags[afi][safi],
                                         PEER_STATUS_REFRESH_PENDING);
                                return BGP_PACKET_NOOP;
                        }

                        bgp_route_refresh_send(peer, afi, safi, 0, 0, 0,
                                               BGP_ROUTE_REFRESH_BORR);

                        if (bgp_debug_neighbor_events(peer))
                                zlog_debug(
                                        "%pBP sending route-refresh (BoRR) for %s/%s",
                                        peer, afi2str(afi), safi2str(safi));

                        /* Set flag Ready-To-Send to know when we can send EoRR
                         * message.
                         */
                        SET_FLAG(peer->af_sflags[afi][safi],
                                 PEER_STATUS_BORR_SEND);
                        UNSET_FLAG(peer->af_sflags[afi][safi],
                                   PEER_STATUS_EORR_SEND);
                }
        }

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

        /* No FSM action necessary */
        return BGP_PACKET_NOOP;
}

/**
 * Parse BGP CAPABILITY message for peer.
 *
 * @param peer
 * @param size size of the packet
 * @return as in summary
 */
static int bgp_capability_msg_parse(struct peer *peer, uint8_t *pnt,
                                    bgp_size_t length)
{
        uint8_t *end;
        struct capability_mp_data mpc;
        struct capability_header *hdr;
        uint8_t action;
        iana_afi_t pkt_afi;
        afi_t afi;
        iana_safi_t pkt_safi;
        safi_t 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,
                                        BGP_NOTIFY_SUBCODE_UNSPECIFIC);
                        return BGP_Stop;
                }
                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,
                                        BGP_NOTIFY_SUBCODE_UNSPECIFIC);
                        return BGP_Stop;
                }

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

                if (hdr->length < sizeof(struct capability_mp_data)) {
                        zlog_info(
                                "%pBP Capability structure is not properly filled out, expected at least %zu bytes but header length specified is %d",
                                peer, sizeof(struct capability_mp_data),
                                hdr->length);
                        return BGP_Stop;
                }

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

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

                /* 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 (%s/%s)",
                                                peer->host,
                                                iana_afi2str(pkt_afi),
                                                iana_safi2str(pkt_safi));
                                continue;
                        }

                        /* Address family check.  */
                        if (bgp_debug_neighbor_events(peer))
                                zlog_debug(
                                        "%s CAPABILITY has %s MP_EXT CAP for afi/safi: %s/%s",
                                        peer->host,
                                        action == CAPABILITY_ACTION_SET
                                                ? "Advertising"
                                                : "Removing",
                                        iana_afi2str(pkt_afi),
                                        iana_safi2str(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,
                                                           false);
                                }
                        } 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
                                        return BGP_Stop;
                        }
                } else {
                        flog_warn(
                                EC_BGP_UNRECOGNIZED_CAPABILITY,
                                "%s unrecognized capability code: %d - ignored",
                                peer->host, hdr->code);
                }
        }

        /* No FSM action necessary */
        return BGP_PACKET_NOOP;
}

/**
 * Parse BGP CAPABILITY message for peer.
 *
 * Exported for unit testing.
 *
 * @param peer
 * @param size size of the packet
 * @return as in summary
 */
int bgp_capability_receive(struct peer *peer, bgp_size_t size)
{
        uint8_t *pnt;

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

        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)) {
                flog_err(EC_BGP_NO_CAP,
                         "%s [Error] BGP dynamic capability is not enabled",
                         peer->host);
                bgp_notify_send(peer, BGP_NOTIFY_HEADER_ERR,
                                BGP_NOTIFY_HEADER_BAD_MESTYPE);
                return BGP_Stop;
        }

        /* Status must be Established. */
        if (!peer_established(peer)) {
                flog_err(
                        EC_BGP_NO_CAP,
                        "%s [Error] Dynamic capability packet received under status %s",
                        peer->host,
                        lookup_msg(bgp_status_msg, peer->status, NULL));
                bgp_notify_send(peer, BGP_NOTIFY_FSM_ERR,
                                bgp_fsm_error_subcode(peer->status));
                return BGP_Stop;
        }

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

/**
 * Processes a peer's input buffer.
 *
 * This function sidesteps the event loop and directly calls bgp_event_update()
 * after processing each BGP message. This is necessary to ensure proper
 * ordering of FSM events and unifies the behavior that was present previously,
 * whereby some of the packet handling functions would update the FSM and some
 * would not, making event flow difficult to understand. Please think twice
 * before hacking this.
 *
 * Thread type: THREAD_EVENT
 * @param thread
 * @return 0
 */
void bgp_process_packet(struct thread *thread)
{
        /* Yes first of all get peer pointer. */
        struct peer *peer;      // peer
        uint32_t rpkt_quanta_old; // how many packets to read
        int fsm_update_result;    // return code of bgp_event_update()
        int mprc;                 // message processing return code

        peer = THREAD_ARG(thread);
        rpkt_quanta_old = atomic_load_explicit(&peer->bgp->rpkt_quanta,
                                               memory_order_relaxed);
        fsm_update_result = 0;

        /* Guard against scheduled events that occur after peer deletion. */
        if (peer->status == Deleted || peer->status == Clearing)
                return;

        unsigned int processed = 0;

        while (processed < rpkt_quanta_old) {
                uint8_t type = 0;
                bgp_size_t size;
                char notify_data_length[2];

                frr_with_mutex (&peer->io_mtx) {
                        peer->curr = stream_fifo_pop(peer->ibuf);
                }

                if (peer->curr == NULL) // no packets to process, hmm...
                        return;

                /* skip the marker and copy the packet length */
                stream_forward_getp(peer->curr, BGP_MARKER_SIZE);
                memcpy(notify_data_length, stream_pnt(peer->curr), 2);

                /* read in the packet length and type */
                size = stream_getw(peer->curr);
                type = stream_getc(peer->curr);

                hook_call(bgp_packet_dump, peer, type, size, peer->curr);

                /* adjust size to exclude the marker + length + type */
                size -= BGP_HEADER_SIZE;

                /* Read rest of the packet and call each sort of packet routine
                 */
                switch (type) {
                case BGP_MSG_OPEN:
                        frrtrace(2, frr_bgp, open_process, peer, size);
                        atomic_fetch_add_explicit(&peer->open_in, 1,
                                                  memory_order_relaxed);
                        mprc = bgp_open_receive(peer, size);
                        if (mprc == BGP_Stop)
                                flog_err(
                                        EC_BGP_PKT_OPEN,
                                        "%s: BGP OPEN receipt failed for peer: %s",
                                        __func__, peer->host);
                        break;
                case BGP_MSG_UPDATE:
                        frrtrace(2, frr_bgp, update_process, peer, size);
                        atomic_fetch_add_explicit(&peer->update_in, 1,
                                                  memory_order_relaxed);
                        peer->readtime = monotime(NULL);
                        mprc = bgp_update_receive(peer, size);
                        if (mprc == BGP_Stop)
                                flog_err(
                                        EC_BGP_UPDATE_RCV,
                                        "%s: BGP UPDATE receipt failed for peer: %s",
                                        __func__, peer->host);
                        break;
                case BGP_MSG_NOTIFY:
                        frrtrace(2, frr_bgp, notification_process, peer, size);
                        atomic_fetch_add_explicit(&peer->notify_in, 1,
                                                  memory_order_relaxed);
                        mprc = bgp_notify_receive(peer, size);
                        if (mprc == BGP_Stop)
                                flog_err(
                                        EC_BGP_NOTIFY_RCV,
                                        "%s: BGP NOTIFY receipt failed for peer: %s",
                                        __func__, peer->host);
                        break;
                case BGP_MSG_KEEPALIVE:
                        frrtrace(2, frr_bgp, keepalive_process, peer, size);
                        peer->readtime = monotime(NULL);
                        atomic_fetch_add_explicit(&peer->keepalive_in, 1,
                                                  memory_order_relaxed);
                        mprc = bgp_keepalive_receive(peer, size);
                        if (mprc == BGP_Stop)
                                flog_err(
                                        EC_BGP_KEEP_RCV,
                                        "%s: BGP KEEPALIVE receipt failed for peer: %s",
                                        __func__, peer->host);
                        break;
                case BGP_MSG_ROUTE_REFRESH_NEW:
                case BGP_MSG_ROUTE_REFRESH_OLD:
                        frrtrace(2, frr_bgp, refresh_process, peer, size);
                        atomic_fetch_add_explicit(&peer->refresh_in, 1,
                                                  memory_order_relaxed);
                        mprc = bgp_route_refresh_receive(peer, size);
                        if (mprc == BGP_Stop)
                                flog_err(
                                        EC_BGP_RFSH_RCV,
                                        "%s: BGP ROUTEREFRESH receipt failed for peer: %s",
                                        __func__, peer->host);
                        break;
                case BGP_MSG_CAPABILITY:
                        frrtrace(2, frr_bgp, capability_process, peer, size);
                        atomic_fetch_add_explicit(&peer->dynamic_cap_in, 1,
                                                  memory_order_relaxed);
                        mprc = bgp_capability_receive(peer, size);
                        if (mprc == BGP_Stop)
                                flog_err(
                                        EC_BGP_CAP_RCV,
                                        "%s: BGP CAPABILITY receipt failed for peer: %s",
                                        __func__, peer->host);
                        break;
                default:
                        /* Suppress uninitialized variable warning */
                        mprc = 0;
                        (void)mprc;
                        /*
                         * The message type should have been sanitized before
                         * we ever got here. Receipt of a message with an
                         * invalid header at this point is indicative of a
                         * security issue.
                         */
                        assert (!"Message of invalid type received during input processing");
                }

                /* delete processed packet */
                stream_free(peer->curr);
                peer->curr = NULL;
                processed++;

                /* Update FSM */
                if (mprc != BGP_PACKET_NOOP)
                        fsm_update_result = bgp_event_update(peer, mprc);
                else
                        continue;

                /*
                 * If peer was deleted, do not process any more packets. This
                 * is usually due to executing BGP_Stop or a stub deletion.
                 */
                if (fsm_update_result == FSM_PEER_TRANSFERRED
                    || fsm_update_result == FSM_PEER_STOPPED)
                        break;
        }

        if (fsm_update_result != FSM_PEER_TRANSFERRED
            && fsm_update_result != FSM_PEER_STOPPED) {
                frr_with_mutex (&peer->io_mtx) {
                        // more work to do, come back later
                        if (peer->ibuf->count > 0)
                                thread_add_event(
                                        bm->master, bgp_process_packet, peer, 0,
                                        &peer->t_process_packet);
                }
        }
}

/* Send EOR when routes are processed by selection deferral timer */
void bgp_send_delayed_eor(struct bgp *bgp)
{
        struct peer *peer;
        struct listnode *node, *nnode;

        /* EOR message sent in bgp_write_proceed_actions */
        for (ALL_LIST_ELEMENTS(bgp->peer, node, nnode, peer))
                bgp_write_proceed_actions(peer);
}

/*
 * Task callback to handle socket error encountered in the io pthread. We avoid
 * having the io pthread try to enqueue fsm events or mess with the peer
 * struct.
 */
void bgp_packet_process_error(struct thread *thread)
{
        struct peer *peer;
        int code;

        peer = THREAD_ARG(thread);
        code = THREAD_VAL(thread);

        if (bgp_debug_neighbor_events(peer))
                zlog_debug("%s [Event] BGP error %d on fd %d",
                           peer->host, code, peer->fd);

        /* Closed connection or error on the socket */
        if (peer_established(peer)) {
                if ((CHECK_FLAG(peer->flags, PEER_FLAG_GRACEFUL_RESTART)
                     || CHECK_FLAG(peer->flags,
                                   PEER_FLAG_GRACEFUL_RESTART_HELPER))
                    && 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_update(peer, code);
}