// SPDX-License-Identifier: GPL-2.0-or-later
/* BGP open message handling
 * Copyright (C) 1998, 1999 Kunihiro Ishiguro
 */

#include <zebra.h>

#include "linklist.h"
#include "prefix.h"
#include "stream.h"
#include "frrevent.h"
#include "log.h"
#include "command.h"
#include "memory.h"
#include "queue.h"
#include "filter.h"

#include "lib/json.h"
#include "bgpd/bgpd.h"
#include "bgpd/bgp_attr.h"
#include "bgpd/bgp_debug.h"
#include "bgpd/bgp_errors.h"
#include "bgpd/bgp_fsm.h"
#include "bgpd/bgp_packet.h"
#include "bgpd/bgp_open.h"
#include "bgpd/bgp_aspath.h"
#include "bgpd/bgp_vty.h"
#include "bgpd/bgp_memory.h"

const struct message capcode_str[] = {
	{ CAPABILITY_CODE_MP, "MultiProtocol Extensions" },
	{ CAPABILITY_CODE_REFRESH, "Route Refresh" },
	{ CAPABILITY_CODE_ORF, "Cooperative Route Filtering" },
	{ CAPABILITY_CODE_RESTART, "Graceful Restart" },
	{ CAPABILITY_CODE_AS4, "4-octet AS number" },
	{ CAPABILITY_CODE_ADDPATH, "AddPath" },
	{ CAPABILITY_CODE_DYNAMIC, "Dynamic" },
	{ CAPABILITY_CODE_ENHE, "Extended Next Hop Encoding" },
	{ CAPABILITY_CODE_FQDN, "FQDN" },
	{ CAPABILITY_CODE_ENHANCED_RR, "Enhanced Route Refresh" },
	{ CAPABILITY_CODE_EXT_MESSAGE, "BGP Extended Message" },
	{ CAPABILITY_CODE_LLGR, "Long-lived BGP Graceful Restart" },
	{ CAPABILITY_CODE_ROLE, "Role" },
	{ CAPABILITY_CODE_SOFT_VERSION, "Software Version" },
	{ CAPABILITY_CODE_PATHS_LIMIT, "Paths-Limit" },
	{ CAPABILITY_CODE_LINK_LOCAL, "Link-Local Next Hop" },
	{ 0 }
};

/* Minimum sizes for length field of each cap (so not inc. the header) */
const size_t cap_minsizes[] = {
	[CAPABILITY_CODE_MP] = CAPABILITY_CODE_MP_LEN,
	[CAPABILITY_CODE_REFRESH] = CAPABILITY_CODE_REFRESH_LEN,
	[CAPABILITY_CODE_ORF] = CAPABILITY_CODE_ORF_LEN,
	[CAPABILITY_CODE_RESTART] = CAPABILITY_CODE_RESTART_LEN,
	[CAPABILITY_CODE_AS4] = CAPABILITY_CODE_AS4_LEN,
	[CAPABILITY_CODE_ADDPATH] = CAPABILITY_CODE_ADDPATH_LEN,
	[CAPABILITY_CODE_DYNAMIC] = CAPABILITY_CODE_DYNAMIC_LEN,
	[CAPABILITY_CODE_ENHE] = CAPABILITY_CODE_ENHE_LEN,
	[CAPABILITY_CODE_FQDN] = CAPABILITY_CODE_MIN_FQDN_LEN,
	[CAPABILITY_CODE_ENHANCED_RR] = CAPABILITY_CODE_ENHANCED_LEN,
	[CAPABILITY_CODE_EXT_MESSAGE] = CAPABILITY_CODE_EXT_MESSAGE_LEN,
	[CAPABILITY_CODE_LLGR] = CAPABILITY_CODE_LLGR_LEN,
	[CAPABILITY_CODE_ROLE] = CAPABILITY_CODE_ROLE_LEN,
	[CAPABILITY_CODE_SOFT_VERSION] = CAPABILITY_CODE_SOFT_VERSION_LEN,
	[CAPABILITY_CODE_PATHS_LIMIT] = CAPABILITY_CODE_PATHS_LIMIT_LEN,
	[CAPABILITY_CODE_LINK_LOCAL] = CAPABILITY_CODE_LINK_LOCAL_LEN,
};

/* value the capability must be a multiple of.
 * 0-data capabilities won't be checked against this.
 * Other capabilities whose data doesn't fall on convenient boundaries for this
 * table should be set to 1.
 */
const size_t cap_modsizes[] = {
	[CAPABILITY_CODE_MP] = 4,
	[CAPABILITY_CODE_REFRESH] = 1,
	[CAPABILITY_CODE_ORF] = 1,
	[CAPABILITY_CODE_RESTART] = 1,
	[CAPABILITY_CODE_AS4] = 4,
	[CAPABILITY_CODE_ADDPATH] = 4,
	[CAPABILITY_CODE_DYNAMIC] = 1,
	[CAPABILITY_CODE_ENHE] = 6,
	[CAPABILITY_CODE_FQDN] = 1,
	[CAPABILITY_CODE_ENHANCED_RR] = 1,
	[CAPABILITY_CODE_EXT_MESSAGE] = 1,
	[CAPABILITY_CODE_LLGR] = 1,
	[CAPABILITY_CODE_ROLE] = 1,
	[CAPABILITY_CODE_SOFT_VERSION] = 1,
	[CAPABILITY_CODE_PATHS_LIMIT] = 5,
};

/* BGP-4 Multiprotocol Extentions lead us to the complex world. We can
   negotiate remote peer supports extentions or not. But if
   remote-peer doesn't supports negotiation process itself.  We would
   like to do manual configuration.

   So there is many configurable point.  First of all we want set each
   peer whether we send capability negotiation to the peer or not.
   Next, if we send capability to the peer we want to set my capability
   inforation at each peer. */

void bgp_capability_vty_out(struct vty *vty, struct peer *peer, bool use_json,
			    json_object *json_neigh)
{
	char *pnt;
	char *end;
	struct capability_mp_data mpc;
	struct capability_header *hdr;
	json_object *json_cap = NULL;

	if (use_json)
		json_cap = json_object_new_object();

	pnt = peer->notify.data;
	end = pnt + peer->notify.length;

	while (pnt < end) {
		if (pnt + sizeof(struct capability_mp_data) + 2 > end)
			return;

		hdr = (struct capability_header *)pnt;
		if (pnt + hdr->length + 2 > end)
			return;

		memcpy(&mpc, pnt + 2, sizeof(struct capability_mp_data));

		if (hdr->code == CAPABILITY_CODE_MP) {
			afi_t afi;
			safi_t safi;

			(void)bgp_map_afi_safi_iana2int(ntohs(mpc.afi),
							mpc.safi, &afi, &safi);

			if (use_json) {
				switch (afi) {
				case AFI_IP:
					json_object_string_add(
						json_cap,
						"capabilityErrorMultiProtocolAfi",
						"IPv4");
					break;
				case AFI_IP6:
					json_object_string_add(
						json_cap,
						"capabilityErrorMultiProtocolAfi",
						"IPv6");
					break;
				case AFI_L2VPN:
					json_object_string_add(
						json_cap,
						"capabilityErrorMultiProtocolAfi",
						"L2VPN");
					break;
				case AFI_UNSPEC:
				case AFI_MAX:
					json_object_int_add(
						json_cap,
						"capabilityErrorMultiProtocolAfiUnknown",
						ntohs(mpc.afi));
					break;
				}
				switch (safi) {
				case SAFI_UNICAST:
					json_object_string_add(
						json_cap,
						"capabilityErrorMultiProtocolSafi",
						"unicast");
					break;
				case SAFI_MULTICAST:
					json_object_string_add(
						json_cap,
						"capabilityErrorMultiProtocolSafi",
						"multicast");
					break;
				case SAFI_LABELED_UNICAST:
					json_object_string_add(
						json_cap,
						"capabilityErrorMultiProtocolSafi",
						"labeled-unicast");
					break;
				case SAFI_MPLS_VPN:
					json_object_string_add(
						json_cap,
						"capabilityErrorMultiProtocolSafi",
						"MPLS-labeled VPN");
					break;
				case SAFI_ENCAP:
					json_object_string_add(
						json_cap,
						"capabilityErrorMultiProtocolSafi",
						"encap");
					break;
				case SAFI_EVPN:
					json_object_string_add(
						json_cap,
						"capabilityErrorMultiProtocolSafi",
						"EVPN");
					break;
				case SAFI_FLOWSPEC:
					json_object_string_add(
						json_cap,
						"capabilityErrorMultiProtocolSafi",
						"flowspec");
					break;
				case SAFI_UNSPEC:
				case SAFI_MAX:
					json_object_int_add(
						json_cap,
						"capabilityErrorMultiProtocolSafiUnknown",
						mpc.safi);
					break;
				}
			} else {
				vty_out(vty,
					"  Capability error for: Multi protocol ");
				switch (afi) {
				case AFI_IP:
					vty_out(vty, "AFI IPv4, ");
					break;
				case AFI_IP6:
					vty_out(vty, "AFI IPv6, ");
					break;
				case AFI_L2VPN:
					vty_out(vty, "AFI L2VPN, ");
					break;
				case AFI_UNSPEC:
				case AFI_MAX:
					vty_out(vty, "AFI Unknown %d, ",
						ntohs(mpc.afi));
					break;
				}
				switch (safi) {
				case SAFI_UNICAST:
					vty_out(vty, "SAFI Unicast");
					break;
				case SAFI_MULTICAST:
					vty_out(vty, "SAFI Multicast");
					break;
				case SAFI_LABELED_UNICAST:
					vty_out(vty, "SAFI Labeled-unicast");
					break;
				case SAFI_MPLS_VPN:
					vty_out(vty, "SAFI MPLS-labeled VPN");
					break;
				case SAFI_ENCAP:
					vty_out(vty, "SAFI ENCAP");
					break;
				case SAFI_FLOWSPEC:
					vty_out(vty, "SAFI FLOWSPEC");
					break;
				case SAFI_EVPN:
					vty_out(vty, "SAFI EVPN");
					break;
				case SAFI_UNSPEC:
				case SAFI_MAX:
					vty_out(vty, "SAFI Unknown %d ",
						mpc.safi);
					break;
				}
				vty_out(vty, "\n");
			}
		} else if (hdr->code >= 128) {
			if (use_json)
				json_object_int_add(
					json_cap,
					"capabilityErrorVendorSpecificCapabilityCode",
					hdr->code);
			else
				vty_out(vty,
					"  Capability error: vendor specific capability code %d",
					hdr->code);
		} else {
			if (use_json)
				json_object_int_add(
					json_cap,
					"capabilityErrorUnknownCapabilityCode",
					hdr->code);
			else
				vty_out(vty,
					"  Capability error: unknown capability code %d",
					hdr->code);
		}
		pnt += hdr->length + 2;
	}
	if (use_json)
		json_object_object_add(json_neigh, "capabilityErrors",
				       json_cap);
}

static void bgp_capability_mp_data(struct stream *s,
				   struct capability_mp_data *mpc)
{
	mpc->afi = stream_getw(s);
	mpc->reserved = stream_getc(s);
	mpc->safi = stream_getc(s);
}

/* Set negotiated capability value. */
static int bgp_capability_mp(struct peer *peer, struct capability_header *hdr)
{
	struct capability_mp_data mpc;
	struct stream *s = BGP_INPUT(peer);
	afi_t afi;
	safi_t safi;

	/* Verify length is 4 */
	if (hdr->length != 4) {
		flog_warn(
			EC_BGP_CAPABILITY_INVALID_LENGTH,
			"MP Cap: Received invalid length %d, non-multiple of 4",
			hdr->length);
		return -1;
	}

	bgp_capability_mp_data(s, &mpc);

	if (bgp_debug_neighbor_events(peer))
		zlog_debug("%s OPEN has %s capability for afi/safi: %s/%s",
			   peer->host, lookup_msg(capcode_str, hdr->code, NULL),
			   iana_afi2str(mpc.afi), iana_safi2str(mpc.safi));

	/* Convert AFI, SAFI to internal values, check. */
	if (bgp_map_afi_safi_iana2int(mpc.afi, mpc.safi, &afi, &safi))
		return -1;

	/* Now safi remapped, and afi/safi are valid array indices */
	peer->afc_recv[afi][safi] = 1;

	if (peer->afc[afi][safi])
		peer->afc_nego[afi][safi] = 1;
	else
		return -1;

	return 0;
}

static void bgp_capability_orf_not_support(struct peer *peer, iana_afi_t afi,
					   iana_safi_t safi, uint8_t type,
					   uint8_t mode)
{
	if (bgp_debug_neighbor_events(peer))
		zlog_debug(
			"%s Addr-family %d/%d has ORF type/mode %d/%d not supported",
			peer->host, afi, safi, type, mode);
}

const struct message orf_type_str[] = { { ORF_TYPE_RESERVED, "Reserved" },
					{ ORF_TYPE_PREFIX, "Prefixlist" },
					{ 0 } };

const struct message orf_mode_str[] = { { ORF_MODE_RECEIVE, "Receive" },
					{ ORF_MODE_SEND, "Send" },
					{ ORF_MODE_BOTH, "Both" },
					{ 0 } };

static int bgp_capability_orf_entry(struct peer *peer,
				    struct capability_header *hdr)
{
	struct stream *s = BGP_INPUT(peer);
	struct capability_mp_data mpc;
	uint8_t num;
	iana_afi_t pkt_afi;
	afi_t afi;
	iana_safi_t pkt_safi;
	safi_t safi;
	uint8_t type;
	uint8_t mode;
	uint16_t sm_cap = 0; /* capability send-mode receive */
	uint16_t rm_cap = 0; /* capability receive-mode receive */
	int i;

	/* ORF Entry header */
	bgp_capability_mp_data(s, &mpc);
	num = stream_getc(s);
	pkt_afi = mpc.afi;
	pkt_safi = mpc.safi;

	if (bgp_debug_neighbor_events(peer))
		zlog_debug("%s ORF Cap entry for afi/safi: %s/%s", peer->host,
			   iana_afi2str(mpc.afi), iana_safi2str(mpc.safi));

	/* Convert AFI, SAFI to internal values, check. */
	if (bgp_map_afi_safi_iana2int(pkt_afi, pkt_safi, &afi, &safi)) {
		zlog_info(
			"%s Addr-family %d/%d not supported. Ignoring the ORF capability",
			peer->host, pkt_afi, pkt_safi);
		return 0;
	}

	mpc.afi = pkt_afi;
	mpc.safi = safi;

	/* validate number field */
	if (CAPABILITY_CODE_ORF_LEN + (num * 2) > hdr->length) {
		zlog_info(
			"%s ORF Capability entry length error, Cap length %u, num %u",
			peer->host, hdr->length, num);
		bgp_notify_send(peer->connection, BGP_NOTIFY_OPEN_ERR,
				BGP_NOTIFY_OPEN_MALFORMED_ATTR);
		return -1;
	}

	for (i = 0; i < num; i++) {
		type = stream_getc(s);
		mode = stream_getc(s);

		/* ORF Mode error check */
		switch (mode) {
		case ORF_MODE_BOTH:
		case ORF_MODE_SEND:
		case ORF_MODE_RECEIVE:
			break;
		default:
			bgp_capability_orf_not_support(peer, pkt_afi, pkt_safi,
						       type, mode);
			continue;
		}
		/* ORF Type and afi/safi error checks */
		/* capcode versus type */
		switch (hdr->code) {
		case CAPABILITY_CODE_ORF:
			switch (type) {
			case ORF_TYPE_RESERVED:
				if (bgp_debug_neighbor_events(peer))
					zlog_debug(
						"%s Addr-family %d/%d has reserved ORF type, ignoring",
						peer->host, afi, safi);
				break;
			case ORF_TYPE_PREFIX:
				break;
			default:
				bgp_capability_orf_not_support(
					peer, pkt_afi, pkt_safi, type, mode);
				continue;
			}
			break;
		default:
			bgp_capability_orf_not_support(peer, pkt_afi, pkt_safi,
						       type, mode);
			continue;
		}

		/* AFI vs SAFI */
		if (!((afi == AFI_IP && safi == SAFI_UNICAST)
		      || (afi == AFI_IP && safi == SAFI_MULTICAST)
		      || (afi == AFI_IP6 && safi == SAFI_UNICAST))) {
			bgp_capability_orf_not_support(peer, pkt_afi, pkt_safi,
						       type, mode);
			continue;
		}

		if (bgp_debug_neighbor_events(peer))
			zlog_debug(
				"%s OPEN has %s ORF capability as %s for afi/safi: %s/%s",
				peer->host,
				lookup_msg(orf_type_str, type, NULL),
				lookup_msg(orf_mode_str, mode, NULL),
				iana_afi2str(pkt_afi), iana_safi2str(pkt_safi));

		if (hdr->code == CAPABILITY_CODE_ORF) {
			sm_cap = PEER_CAP_ORF_PREFIX_SM_RCV;
			rm_cap = PEER_CAP_ORF_PREFIX_RM_RCV;
		} else {
			bgp_capability_orf_not_support(peer, pkt_afi, pkt_safi,
						       type, mode);
			continue;
		}

		switch (mode) {
		case ORF_MODE_BOTH:
			SET_FLAG(peer->af_cap[afi][safi], sm_cap);
			SET_FLAG(peer->af_cap[afi][safi], rm_cap);
			break;
		case ORF_MODE_SEND:
			SET_FLAG(peer->af_cap[afi][safi], sm_cap);
			break;
		case ORF_MODE_RECEIVE:
			SET_FLAG(peer->af_cap[afi][safi], rm_cap);
			break;
		}
	}
	return 0;
}

static int bgp_capability_restart(struct peer *peer,
				  struct capability_header *caphdr)
{
	struct stream *s = BGP_INPUT(peer);
	uint16_t restart_flag_time;
	size_t end = stream_get_getp(s) + caphdr->length;

	/* Verify length is a multiple of 4 */
	if ((caphdr->length - 2) % 4) {
		flog_warn(
			EC_BGP_CAPABILITY_INVALID_LENGTH,
			"Restart Cap: Received invalid length %d, non-multiple of 4",
			caphdr->length);
		return -1;
	}

	SET_FLAG(peer->cap, PEER_CAP_RESTART_RCV);
	restart_flag_time = stream_getw(s);

	/* The most significant bit is defined in [RFC4724] as
	 * the Restart State ("R") bit.
	 */
	if (CHECK_FLAG(restart_flag_time, GRACEFUL_RESTART_R_BIT))
		SET_FLAG(peer->cap, PEER_CAP_GRACEFUL_RESTART_R_BIT_RCV);
	else
		UNSET_FLAG(peer->cap, PEER_CAP_GRACEFUL_RESTART_R_BIT_RCV);

	/* The second most significant bit is defined in this
	 * document as the Graceful Notification ("N") bit.
	 */
	if (CHECK_FLAG(restart_flag_time, GRACEFUL_RESTART_N_BIT))
		SET_FLAG(peer->cap, PEER_CAP_GRACEFUL_RESTART_N_BIT_RCV);
	else
		UNSET_FLAG(peer->cap, PEER_CAP_GRACEFUL_RESTART_N_BIT_RCV);

	UNSET_FLAG(restart_flag_time, 0xF000);
	peer->v_gr_restart = restart_flag_time;

	if (bgp_debug_neighbor_events(peer))
		zlog_debug("%pBP OPEN has GR capability, Restart time %d R-bit %s N-bit %s",
			   peer, peer->v_gr_restart,
			   CHECK_FLAG(peer->cap,
				      PEER_CAP_GRACEFUL_RESTART_R_BIT_RCV)
				   ? "SET"
				   : "NOT-SET",
			   CHECK_FLAG(peer->cap,
				      PEER_CAP_GRACEFUL_RESTART_N_BIT_RCV)
				   ? "SET"
				   : "NOT-SET");

	while (stream_get_getp(s) + 4 <= end) {
		afi_t afi;
		safi_t safi;
		iana_afi_t pkt_afi = stream_getw(s);
		iana_safi_t pkt_safi = stream_getc(s);
		uint8_t flag = stream_getc(s);

		/* Convert AFI, SAFI to internal values, check. */
		if (bgp_map_afi_safi_iana2int(pkt_afi, pkt_safi, &afi, &safi)) {
			if (bgp_debug_neighbor_events(peer))
				zlog_debug(
					"%s Addr-family %s/%s(afi/safi) not supported. Ignore the Graceful Restart capability for this AFI/SAFI",
					peer->host, iana_afi2str(pkt_afi),
					iana_safi2str(pkt_safi));
		} else if (!peer->afc[afi][safi]) {
			if (bgp_debug_neighbor_events(peer))
				zlog_debug(
					"%s Addr-family %s/%s(afi/safi) not enabled. Ignore the Graceful Restart capability",
					peer->host, iana_afi2str(pkt_afi),
					iana_safi2str(pkt_safi));
		} else {
			if (bgp_debug_neighbor_events(peer))
				zlog_debug("%pBP F-bit %s for %s", peer,
					   CHECK_FLAG(peer->af_cap[afi][safi],
						      PEER_CAP_RESTART_AF_PRESERVE_RCV)
						   ? "SET"
						   : "NOT-SET",
					   get_afi_safi_str(afi, safi, false));

			SET_FLAG(peer->af_cap[afi][safi],
				 PEER_CAP_RESTART_AF_RCV);
			if (CHECK_FLAG(flag, GRACEFUL_RESTART_F_BIT))
				SET_FLAG(peer->af_cap[afi][safi],
					 PEER_CAP_RESTART_AF_PRESERVE_RCV);
		}
	}
	return 0;
}

static int bgp_capability_llgr(struct peer *peer,
			       struct capability_header *caphdr)
{
	struct stream *s = BGP_INPUT(peer);
	size_t end = stream_get_getp(s) + caphdr->length;

	SET_FLAG(peer->cap, PEER_CAP_LLGR_RCV);

	while (stream_get_getp(s) + BGP_CAP_LLGR_MIN_PACKET_LEN <= end) {
		afi_t afi;
		safi_t safi;
		iana_afi_t pkt_afi = stream_getw(s);
		iana_safi_t pkt_safi = stream_getc(s);
		uint8_t flags = stream_getc(s);
		uint32_t stale_time = stream_get3(s);

		if (bgp_map_afi_safi_iana2int(pkt_afi, pkt_safi, &afi, &safi)) {
			if (bgp_debug_neighbor_events(peer))
				zlog_debug(
					"%s Addr-family %s/%s(afi/safi) not supported. Ignore the Long-lived Graceful Restart capability for this AFI/SAFI",
					peer->host, iana_afi2str(pkt_afi),
					iana_safi2str(pkt_safi));
		} else if (!peer->afc[afi][safi]
			   || !CHECK_FLAG(peer->af_cap[afi][safi],
					  PEER_CAP_RESTART_AF_RCV)) {
			if (bgp_debug_neighbor_events(peer))
				zlog_debug(
					"%s Addr-family %s/%s(afi/safi) not enabled. Ignore the Long-lived Graceful Restart capability",
					peer->host, iana_afi2str(pkt_afi),
					iana_safi2str(pkt_safi));
		} else {
			if (bgp_debug_neighbor_events(peer))
				zlog_debug(
					"%s Addr-family %s/%s(afi/safi) Long-lived Graceful Restart capability stale time %u sec",
					peer->host, iana_afi2str(pkt_afi),
					iana_safi2str(pkt_safi), stale_time);

			peer->llgr[afi][safi].flags = flags;
			peer->llgr[afi][safi].stale_time =
				MIN(stale_time, peer->bgp->llgr_stale_time);
			SET_FLAG(peer->af_cap[afi][safi], PEER_CAP_LLGR_AF_RCV);
		}
	}

	return 0;
}

/* Unlike other capability parsing routines, this one returns 0 on error */
static as_t bgp_capability_as4(struct peer *peer, struct capability_header *hdr)
{
	if (hdr->length != CAPABILITY_CODE_AS4_LEN) {
		flog_err(EC_BGP_PKT_OPEN,
			 "%s AS4 capability has incorrect data length %d",
			 peer->host, hdr->length);
		return -1;
	}

	as_t as4 = stream_getl(BGP_INPUT(peer));

	SET_FLAG(peer->cap, PEER_CAP_AS4_RCV);

	if (BGP_DEBUG(as4, AS4))
		zlog_debug(
			"%s [AS4] about to set cap PEER_CAP_AS4_RCV, got as4 %u",
			peer->host, as4);
	return as4;
}

static int bgp_capability_ext_message(struct peer *peer,
				      struct capability_header *hdr)
{
	if (hdr->length != CAPABILITY_CODE_EXT_MESSAGE_LEN) {
		flog_err(
			EC_BGP_PKT_OPEN,
			"%s: BGP Extended Message capability has incorrect data length %d",
			peer->host, hdr->length);
		return -1;
	}

	SET_FLAG(peer->cap, PEER_CAP_EXTENDED_MESSAGE_RCV);

	return 0;
}

static int bgp_capability_addpath(struct peer *peer,
				  struct capability_header *hdr)
{
	struct stream *s = BGP_INPUT(peer);
	size_t end = stream_get_getp(s) + hdr->length;

	/* Verify length is a multiple of 4 */
	if (hdr->length % CAPABILITY_CODE_ADDPATH_LEN) {
		flog_warn(
			EC_BGP_CAPABILITY_INVALID_LENGTH,
			"Add Path: Received invalid length %d, non-multiple of 4",
			hdr->length);
		return -1;
	}

	SET_FLAG(peer->cap, PEER_CAP_ADDPATH_RCV);

	while (stream_get_getp(s) + CAPABILITY_CODE_ADDPATH_LEN <= end) {
		afi_t afi;
		safi_t safi;
		iana_afi_t pkt_afi = stream_getw(s);
		iana_safi_t pkt_safi = stream_getc(s);
		uint8_t send_receive = stream_getc(s);

		/* If any other value (other than 1-3) is received, then
		 * the capability SHOULD be treated as not understood
		 * and ignored.
		 */
		if (!send_receive || send_receive > 3) {
			flog_warn(EC_BGP_CAPABILITY_INVALID_DATA,
				  "Add Path: Received invalid send/receive value %u in Add Path capability",
				  send_receive);
			continue;
		}

		if (bgp_debug_neighbor_events(peer))
			zlog_debug("%s OPEN has %s capability for afi/safi: %s/%s%s%s",
				   peer->host,
				   lookup_msg(capcode_str, hdr->code, NULL),
				   iana_afi2str(pkt_afi),
				   iana_safi2str(pkt_safi),
				   CHECK_FLAG(send_receive, BGP_ADDPATH_RX)
					   ? ", receive"
					   : "",
				   CHECK_FLAG(send_receive, BGP_ADDPATH_TX)
					   ? ", transmit"
					   : "");

		/* Convert AFI, SAFI to internal values, check. */
		if (bgp_map_afi_safi_iana2int(pkt_afi, pkt_safi, &afi, &safi)) {
			if (bgp_debug_neighbor_events(peer))
				zlog_debug(
					"%s Addr-family %s/%s(afi/safi) not supported. Ignore the Addpath Attribute for this AFI/SAFI",
					peer->host, iana_afi2str(pkt_afi),
					iana_safi2str(pkt_safi));
			continue;
		} else if (!peer->afc[afi][safi]) {
			if (bgp_debug_neighbor_events(peer))
				zlog_debug(
					"%s Addr-family %s/%s(afi/safi) not enabled. Ignore the AddPath capability for this AFI/SAFI",
					peer->host, iana_afi2str(pkt_afi),
					iana_safi2str(pkt_safi));
			continue;
		}

		if (CHECK_FLAG(send_receive, BGP_ADDPATH_RX))
			SET_FLAG(peer->af_cap[afi][safi],
				 PEER_CAP_ADDPATH_AF_RX_RCV);
		else
			UNSET_FLAG(peer->af_cap[afi][safi],
				   PEER_CAP_ADDPATH_AF_RX_RCV);

		if (CHECK_FLAG(send_receive, BGP_ADDPATH_TX))
			SET_FLAG(peer->af_cap[afi][safi],
				 PEER_CAP_ADDPATH_AF_TX_RCV);
		else
			UNSET_FLAG(peer->af_cap[afi][safi],
				   PEER_CAP_ADDPATH_AF_TX_RCV);
	}

	return 0;
}

static int bgp_capability_paths_limit(struct peer *peer,
				      struct capability_header *hdr)
{
	struct stream *s = BGP_INPUT(peer);
	size_t end = stream_get_getp(s) + hdr->length;

	if (hdr->length % CAPABILITY_CODE_PATHS_LIMIT_LEN) {
		flog_warn(EC_BGP_CAPABILITY_INVALID_LENGTH,
			  "Paths-Limit: Received invalid length %d, non-multiple of %d",
			  hdr->length, CAPABILITY_CODE_PATHS_LIMIT_LEN);
		return -1;
	}

	if (!CHECK_FLAG(peer->cap, PEER_CAP_ADDPATH_RCV)) {
		flog_warn(EC_BGP_CAPABILITY_INVALID_DATA,
			  "Paths-Limit: Received Paths-Limit capability without Add-Path capability");
		return -1;
	}

	SET_FLAG(peer->cap, PEER_CAP_PATHS_LIMIT_RCV);

	while (stream_get_getp(s) + CAPABILITY_CODE_PATHS_LIMIT_LEN <= end) {
		afi_t afi;
		safi_t safi;
		iana_afi_t pkt_afi = stream_getw(s);
		iana_safi_t pkt_safi = stream_getc(s);
		uint16_t paths_limit = stream_getw(s);

		if (bgp_debug_neighbor_events(peer))
			zlog_debug("%s OPEN has %s capability for afi/safi: %s/%s limit: %u",
				   peer->host,
				   lookup_msg(capcode_str, hdr->code, NULL),
				   iana_afi2str(pkt_afi),
				   iana_safi2str(pkt_safi), paths_limit);

		if (bgp_map_afi_safi_iana2int(pkt_afi, pkt_safi, &afi, &safi)) {
			if (bgp_debug_neighbor_events(peer))
				zlog_debug("%s Addr-family %s/%s(afi/safi) not supported. Ignore the Paths-Limit capability for this AFI/SAFI",
					   peer->host, iana_afi2str(pkt_afi),
					   iana_safi2str(pkt_safi));
			continue;
		} else if (!peer->afc[afi][safi]) {
			if (bgp_debug_neighbor_events(peer))
				zlog_debug("%s Addr-family %s/%s(afi/safi) not enabled. Ignore the Paths-Limit capability for this AFI/SAFI",
					   peer->host, iana_afi2str(pkt_afi),
					   iana_safi2str(pkt_safi));
			continue;
		}

		SET_FLAG(peer->af_cap[afi][safi], PEER_CAP_PATHS_LIMIT_AF_RCV);
		peer->addpath_paths_limit[afi][safi].receive = paths_limit;
	}

	return 0;
}

static int bgp_capability_enhe(struct peer *peer, struct capability_header *hdr)
{
	struct stream *s = BGP_INPUT(peer);
	size_t end = stream_get_getp(s) + hdr->length;

	/* Verify length is a multiple of 4 */
	if (hdr->length % 6) {
		flog_warn(
			EC_BGP_CAPABILITY_INVALID_LENGTH,
			"Extended NH: Received invalid length %d, non-multiple of 6",
			hdr->length);
		return -1;
	}

	while (stream_get_getp(s) + 6 <= end) {
		iana_afi_t pkt_afi = stream_getw(s);
		afi_t afi;
		iana_safi_t pkt_safi = stream_getw(s);
		safi_t safi;
		iana_afi_t pkt_nh_afi = stream_getw(s);
		afi_t nh_afi;

		if (bgp_debug_neighbor_events(peer))
			zlog_debug(
				"%s Received with afi/safi/next-hop afi: %s/%s/%u",
				peer->host, iana_afi2str(pkt_afi),
				iana_safi2str(pkt_safi), pkt_nh_afi);

		/* Convert AFI, SAFI to internal values, check. */
		if (bgp_map_afi_safi_iana2int(pkt_afi, pkt_safi, &afi, &safi)) {
			if (bgp_debug_neighbor_events(peer))
				zlog_debug(
					"%s Addr-family %s/%s(afi/safi) not supported. Ignore the ENHE Attribute for this AFI/SAFI",
					peer->host, iana_afi2str(pkt_afi),
					iana_safi2str(pkt_safi));
			continue;
		}

		/* RFC 5549 specifies use of this capability only for IPv4 AFI,
		 * with
		 * the Nexthop AFI being IPv6. A future spec may introduce other
		 * possibilities, so we ignore other values with a log. Also,
		 * only
		 * SAFI_UNICAST and SAFI_LABELED_UNICAST are currently supported
		 * (and expected).
		 */
		nh_afi = afi_iana2int(pkt_nh_afi);

		if (afi != AFI_IP || nh_afi != AFI_IP6
		    || !(safi == SAFI_UNICAST || safi == SAFI_MPLS_VPN
			 || safi == SAFI_LABELED_UNICAST)) {
			flog_warn(
				EC_BGP_CAPABILITY_INVALID_DATA,
				"%s Unexpected afi/safi/next-hop afi: %s/%s/%u in Extended Next-hop capability, ignoring",
				peer->host, iana_afi2str(pkt_afi),
				iana_safi2str(pkt_safi), pkt_nh_afi);
			continue;
		}

		SET_FLAG(peer->af_cap[afi][safi], PEER_CAP_ENHE_AF_RCV);

		if (CHECK_FLAG(peer->af_cap[afi][safi], PEER_CAP_ENHE_AF_ADV))
			SET_FLAG(peer->af_cap[afi][safi],
				 PEER_CAP_ENHE_AF_NEGO);
	}

	SET_FLAG(peer->cap, PEER_CAP_ENHE_RCV);

	return 0;
}

static int bgp_capability_hostname(struct peer *peer,
				   struct capability_header *hdr)
{
	struct stream *s = BGP_INPUT(peer);
	char str[BGP_MAX_HOSTNAME + 1];
	size_t end = stream_get_getp(s) + hdr->length;
	uint8_t len;

	len = stream_getc(s);
	if (stream_get_getp(s) + len > end) {
		flog_warn(
			EC_BGP_CAPABILITY_INVALID_DATA,
			"%s: Received malformed hostname capability from peer %s",
			__func__, peer->host);
		return -1;
	}

	if (len > BGP_MAX_HOSTNAME) {
		stream_get(str, s, BGP_MAX_HOSTNAME);
		stream_forward_getp(s, len - BGP_MAX_HOSTNAME);
		len = BGP_MAX_HOSTNAME; /* to set the '\0' below */
	} else if (len)
		stream_get(str, s, len);

	if (len) {
		str[len] = '\0';

		XFREE(MTYPE_BGP_PEER_HOST, peer->hostname);
		XFREE(MTYPE_BGP_PEER_HOST, peer->domainname);

		peer->hostname = XSTRDUP(MTYPE_BGP_PEER_HOST, str);
	}

	if (stream_get_getp(s) + 1 > end) {
		flog_warn(
			EC_BGP_CAPABILITY_INVALID_DATA,
			"%s: Received invalid domain name len (hostname capability) from peer %s",
			__func__, peer->host);
		return -1;
	}

	len = stream_getc(s);
	if (stream_get_getp(s) + len > end) {
		flog_warn(
			EC_BGP_CAPABILITY_INVALID_DATA,
			"%s: Received runt domain name (hostname capability) from peer %s",
			__func__, peer->host);
		return -1;
	}

	if (len > BGP_MAX_HOSTNAME) {
		stream_get(str, s, BGP_MAX_HOSTNAME);
		stream_forward_getp(s, len - BGP_MAX_HOSTNAME);
		len = BGP_MAX_HOSTNAME; /* to set the '\0' below */
	} else if (len)
		stream_get(str, s, len);

	if (len) {
		str[len] = '\0';

		XFREE(MTYPE_BGP_PEER_HOST, peer->domainname);

		peer->domainname = XSTRDUP(MTYPE_BGP_PEER_HOST, str);
	}

	SET_FLAG(peer->cap, PEER_CAP_HOSTNAME_RCV);

	if (bgp_debug_neighbor_events(peer)) {
		zlog_debug("%s received hostname %s, domainname %s", peer->host,
			   peer->hostname, peer->domainname);
	}

	return 0;
}

static int bgp_capability_role(struct peer *peer, struct capability_header *hdr)
{
	if (hdr->length != CAPABILITY_CODE_ROLE_LEN) {
		flog_warn(EC_BGP_CAPABILITY_INVALID_LENGTH,
			  "Role: Received invalid length %d", hdr->length);
		return -1;
	}

	uint8_t role = stream_getc(BGP_INPUT(peer));

	SET_FLAG(peer->cap, PEER_CAP_ROLE_RCV);

	peer->remote_role = role;
	return 0;
}

static int bgp_capability_software_version(struct peer *peer,
					   struct capability_header *hdr)
{
	struct stream *s = BGP_INPUT(peer);
	char str[BGP_MAX_SOFT_VERSION + 1];
	size_t end = stream_get_getp(s) + hdr->length;
	uint8_t len;

	len = stream_getc(s);
	if (stream_get_getp(s) + len > end) {
		flog_warn(
			EC_BGP_CAPABILITY_INVALID_DATA,
			"%s: Received malformed Software Version capability from peer %s",
			__func__, peer->host);
		return -1;
	}

	SET_FLAG(peer->cap, PEER_CAP_SOFT_VERSION_RCV);

	if (len > BGP_MAX_SOFT_VERSION) {
		flog_warn(EC_BGP_CAPABILITY_INVALID_LENGTH,
			  "%s: Received Software Version, but the length is too big, truncating, from peer %s",
			  __func__, peer->host);
		stream_get(str, s, BGP_MAX_SOFT_VERSION);
		stream_forward_getp(s, len - BGP_MAX_SOFT_VERSION);
		len = BGP_MAX_SOFT_VERSION;
	} else if (len) {
		stream_get(str, s, len);
	}

	if (len) {
		str[len] = '\0';

		XFREE(MTYPE_BGP_SOFT_VERSION, peer->soft_version);

		peer->soft_version = XSTRDUP(MTYPE_BGP_SOFT_VERSION, str);

		if (bgp_debug_neighbor_events(peer))
			zlog_debug("%s received Software Version: %s",
				   peer->host, peer->soft_version);
	}

	return 0;
}

/**
 * Parse given capability.
 * XXX: This is reading into a stream, but not using stream API
 *
 * @param[out] mp_capability Set to 1 on return iff one or more Multiprotocol
 *                           capabilities were encountered.
 */
static int bgp_capability_parse(struct peer *peer, size_t length,
				int *mp_capability, uint8_t **error)
{
	int ret;
	struct stream *s = BGP_INPUT(peer);
	size_t end = stream_get_getp(s) + length;
	uint16_t restart_flag_time = 0;

	assert(STREAM_READABLE(s) >= length);

	while (stream_get_getp(s) < end) {
		size_t start;
		uint8_t *sp = stream_pnt(s);
		struct capability_header caphdr;

		ret = 0;
		/* We need at least capability code and capability length. */
		if (stream_get_getp(s) + 2 > end) {
			zlog_info("%s Capability length error (< header)",
				  peer->host);
			bgp_notify_send(peer->connection, BGP_NOTIFY_OPEN_ERR,
					BGP_NOTIFY_OPEN_MALFORMED_ATTR);
			return -1;
		}

		caphdr.code = stream_getc(s);
		caphdr.length = stream_getc(s);
		start = stream_get_getp(s);

		/* Capability length check sanity check. */
		if (start + caphdr.length > end) {
			zlog_info("%s Capability length error (< length)",
				  peer->host);
			bgp_notify_send(peer->connection, BGP_NOTIFY_OPEN_ERR,
					BGP_NOTIFY_OPEN_MALFORMED_ATTR);
			return -1;
		}

		if (bgp_debug_neighbor_events(peer))
			zlog_debug("%s OPEN has %s capability (%u), length %u",
				   peer->host,
				   lookup_msg(capcode_str, caphdr.code, NULL),
				   caphdr.code, caphdr.length);

		/* Length sanity check, type-specific, for known capabilities */
		switch (caphdr.code) {
		case CAPABILITY_CODE_MP:
		case CAPABILITY_CODE_REFRESH:
		case CAPABILITY_CODE_ORF:
		case CAPABILITY_CODE_RESTART:
		case CAPABILITY_CODE_AS4:
		case CAPABILITY_CODE_ADDPATH:
		case CAPABILITY_CODE_DYNAMIC:
		case CAPABILITY_CODE_ENHE:
		case CAPABILITY_CODE_FQDN:
		case CAPABILITY_CODE_ENHANCED_RR:
		case CAPABILITY_CODE_EXT_MESSAGE:
		case CAPABILITY_CODE_ROLE:
		case CAPABILITY_CODE_SOFT_VERSION:
		case CAPABILITY_CODE_PATHS_LIMIT:
			/* Check length. */
			if (caphdr.length < cap_minsizes[caphdr.code]) {
				zlog_info(
					"%s %s Capability length error: got %u, expected at least %u",
					peer->host,
					lookup_msg(capcode_str, caphdr.code,
						   NULL),
					caphdr.length,
					(unsigned)cap_minsizes[caphdr.code]);
				bgp_notify_send(peer->connection,
						BGP_NOTIFY_OPEN_ERR,
						BGP_NOTIFY_OPEN_MALFORMED_ATTR);
				return -1;
			}
			if (caphdr.length
			    && caphdr.length % cap_modsizes[caphdr.code] != 0) {
				zlog_info(
					"%s %s Capability length error: got %u, expected a multiple of %u",
					peer->host,
					lookup_msg(capcode_str, caphdr.code,
						   NULL),
					caphdr.length,
					(unsigned)cap_modsizes[caphdr.code]);
				bgp_notify_send(peer->connection,
						BGP_NOTIFY_OPEN_ERR,
						BGP_NOTIFY_OPEN_MALFORMED_ATTR);
				return -1;
			}
			break;
		/* we deliberately ignore unknown codes, see below */
		default:
			break;
		}

		switch (caphdr.code) {
		case CAPABILITY_CODE_MP: {
			*mp_capability = 1;

			/* Ignore capability when override-capability is set. */
			if (!CHECK_FLAG(peer->flags,
					PEER_FLAG_OVERRIDE_CAPABILITY)) {
				/* Set negotiated value. */
				ret = bgp_capability_mp(peer, &caphdr);

				/* Unsupported Capability. */
				if (ret < 0) {
					/* Store return data. */
					memcpy(*error, sp, caphdr.length + 2);
					*error += caphdr.length + 2;
				}
				ret = 0; /* Don't return error for this */
			}
		} break;
		case CAPABILITY_CODE_ENHANCED_RR:
		case CAPABILITY_CODE_REFRESH: {
			/* BGP refresh capability */
			if (caphdr.code == CAPABILITY_CODE_ENHANCED_RR)
				SET_FLAG(peer->cap, PEER_CAP_ENHANCED_RR_RCV);
			else
				SET_FLAG(peer->cap, PEER_CAP_REFRESH_RCV);
		} break;
		case CAPABILITY_CODE_ORF:
			ret = bgp_capability_orf_entry(peer, &caphdr);
			break;
		case CAPABILITY_CODE_RESTART:
			ret = bgp_capability_restart(peer, &caphdr);
			break;
		case CAPABILITY_CODE_LLGR:
			ret = bgp_capability_llgr(peer, &caphdr);
			break;
		case CAPABILITY_CODE_DYNAMIC:
			SET_FLAG(peer->cap, PEER_CAP_DYNAMIC_RCV);
			break;
		case CAPABILITY_CODE_AS4:
			/* Already handled as a special-case parsing of the
			 * capabilities
			 * at the beginning of OPEN processing. So we care not a
			 * jot
			 * for the value really, only error case.
			 */
			if (!bgp_capability_as4(peer, &caphdr))
				ret = -1;
			break;
		case CAPABILITY_CODE_ADDPATH:
			ret = bgp_capability_addpath(peer, &caphdr);
			break;
		case CAPABILITY_CODE_ENHE:
			ret = bgp_capability_enhe(peer, &caphdr);
			break;
		case CAPABILITY_CODE_EXT_MESSAGE:
			ret = bgp_capability_ext_message(peer, &caphdr);
			break;
		case CAPABILITY_CODE_FQDN:
			ret = bgp_capability_hostname(peer, &caphdr);
			break;
		case CAPABILITY_CODE_ROLE:
			ret = bgp_capability_role(peer, &caphdr);
			break;
		case CAPABILITY_CODE_SOFT_VERSION:
			ret = bgp_capability_software_version(peer, &caphdr);
			break;
		case CAPABILITY_CODE_LINK_LOCAL:
			SET_FLAG(peer->cap, PEER_CAP_LINK_LOCAL_RCV);
			break;
		case CAPABILITY_CODE_PATHS_LIMIT:
			ret = bgp_capability_paths_limit(peer, &caphdr);
			break;
		default:
			if (caphdr.code > 128) {
				/* We don't send Notification for unknown vendor
				   specific
				   capabilities.  It seems reasonable for now...
				   */
				flog_warn(EC_BGP_CAPABILITY_VENDOR,
					  "%s Vendor specific capability %d",
					  peer->host, caphdr.code);
			} else {
				flog_warn(
					EC_BGP_CAPABILITY_UNKNOWN,
					"%s unrecognized capability code: %d - ignored",
					peer->host, caphdr.code);
				memcpy(*error, sp, caphdr.length + 2);
				*error += caphdr.length + 2;
			}
		}

		if (ret < 0) {
			bgp_notify_send(peer->connection, BGP_NOTIFY_OPEN_ERR,
					BGP_NOTIFY_OPEN_MALFORMED_ATTR);
			return -1;
		}
		if (stream_get_getp(s) != (start + caphdr.length)) {
			if (stream_get_getp(s) > (start + caphdr.length))
				flog_warn(
					EC_BGP_CAPABILITY_INVALID_LENGTH,
					"%s Cap-parser for %s read past cap-length, %u!",
					peer->host,
					lookup_msg(capcode_str, caphdr.code,
						   NULL),
					caphdr.length);
			stream_set_getp(s, start + caphdr.length);
		}

		if (!CHECK_FLAG(peer->cap, PEER_CAP_RESTART_RCV)) {
			UNSET_FLAG(restart_flag_time, 0xF000);
			peer->v_gr_restart = restart_flag_time;
		}
	}
	return 0;
}

static bool strict_capability_same(struct peer *peer)
{
	int i, j;

	for (i = AFI_IP; i < AFI_MAX; i++)
		for (j = SAFI_UNICAST; j < SAFI_MAX; j++)
			if (peer->afc[i][j] != peer->afc_nego[i][j])
				return false;
	return true;
}


static bool bgp_role_violation(struct peer *peer)
{
	uint8_t local_role = peer->local_role;
	uint8_t remote_role = peer->remote_role;

	if (local_role != ROLE_UNDEFINED && remote_role != ROLE_UNDEFINED &&
	    !((local_role == ROLE_PEER && remote_role == ROLE_PEER) ||
	      (local_role == ROLE_PROVIDER && remote_role == ROLE_CUSTOMER) ||
	      (local_role == ROLE_CUSTOMER && remote_role == ROLE_PROVIDER) ||
	      (local_role == ROLE_RS_SERVER && remote_role == ROLE_RS_CLIENT) ||
	      (local_role == ROLE_RS_CLIENT &&
	       remote_role == ROLE_RS_SERVER))) {
		bgp_notify_send(peer->connection, BGP_NOTIFY_OPEN_ERR,
				BGP_NOTIFY_OPEN_ROLE_MISMATCH);
		return true;
	}
	if (remote_role == ROLE_UNDEFINED &&
	    CHECK_FLAG(peer->flags, PEER_FLAG_ROLE_STRICT_MODE)) {
		const char *err_msg =
			"Strict mode. Please set the role on your side.";
		bgp_notify_send_with_data(peer->connection, BGP_NOTIFY_OPEN_ERR,
					  BGP_NOTIFY_OPEN_ROLE_MISMATCH,
					  (uint8_t *)err_msg, strlen(err_msg));
		return true;
	}
	return false;
}


/* peek into option, stores ASN to *as4 if the AS4 capability was found.
 * Returns  0 if no as4 found, as4cap value otherwise.
 */
as_t peek_for_as4_capability(struct peer *peer, uint16_t length)
{
	struct stream *s = BGP_INPUT(peer);
	size_t orig_getp = stream_get_getp(s);
	size_t end = orig_getp + length;
	as_t as4 = 0;

	if (BGP_DEBUG(as4, AS4))
		zlog_debug(
			"%s [AS4] rcv OPEN w/ OPTION parameter len: %u, peeking for as4",
			peer->host, length);
	/* the error cases we DONT handle, we ONLY try to read as4 out of
	 * correctly formatted options.
	 */
	while (stream_get_getp(s) < end) {
		uint8_t opt_type;
		uint16_t opt_length;

		/* Ensure we can read the option type */
		if (stream_get_getp(s) + 1 > end)
			goto end;

		/* Fetch the option type */
		opt_type = stream_getc(s);

		/*
		 * Check the length and fetch the opt_length
		 * If the peer is BGP_OPEN_EXT_OPT_PARAMS_CAPABLE(peer)
		 * then we do a getw which is 2 bytes.  So we need to
		 * ensure that we can read that as well
		 */
		if (BGP_OPEN_EXT_OPT_PARAMS_CAPABLE(peer)) {
			if (stream_get_getp(s) + 2 > end)
				goto end;

			opt_length = stream_getw(s);
		} else {
			if (stream_get_getp(s) + 1 > end)
				goto end;

			opt_length = stream_getc(s);
		}

		/* Option length check. */
		if (stream_get_getp(s) + opt_length > end)
			goto end;

		if (opt_type == BGP_OPEN_OPT_CAP) {
			unsigned long capd_start = stream_get_getp(s);
			unsigned long capd_end = capd_start + opt_length;

			assert(capd_end <= end);

			while (stream_get_getp(s) < capd_end) {
				struct capability_header hdr;

				if (stream_get_getp(s) + 2 > capd_end)
					goto end;

				hdr.code = stream_getc(s);
				hdr.length = stream_getc(s);

				if ((stream_get_getp(s) + hdr.length)
				    > capd_end)
					goto end;

				if (hdr.code == CAPABILITY_CODE_AS4) {
					if (BGP_DEBUG(as4, AS4))
						zlog_debug(
							"[AS4] found AS4 capability, about to parse");
					as4 = bgp_capability_as4(peer, &hdr);

					goto end;
				}
				stream_forward_getp(s, hdr.length);
			}
		}
	}

end:
	stream_set_getp(s, orig_getp);
	return as4;
}

/**
 * Parse open option.
 *
 * @param[out] mp_capability @see bgp_capability_parse() for semantics.
 */
int bgp_open_option_parse(struct peer *peer, uint16_t length,
			  int *mp_capability)
{
	int ret = 0;
	uint8_t *error;
	uint8_t error_data[BGP_STANDARD_MESSAGE_MAX_PACKET_SIZE];
	struct stream *s = BGP_INPUT(peer);
	size_t end = stream_get_getp(s) + length;

	error = error_data;

	if (bgp_debug_neighbor_events(peer))
		zlog_debug("%s rcv OPEN w/ OPTION parameter len: %u",
			   peer->host, length);

	/* Unset any previously received GR capability. */
	UNSET_FLAG(peer->cap, PEER_CAP_RESTART_RCV);

	while (stream_get_getp(s) < end) {
		uint8_t opt_type;
		uint16_t opt_length;

		/*
		 * Check that we can read the opt_type and fetch it
		 */
		if (STREAM_READABLE(s) < 1) {
			zlog_err("%s Option length error", peer->host);
			bgp_notify_send(peer->connection, BGP_NOTIFY_OPEN_ERR,
					BGP_NOTIFY_OPEN_MALFORMED_ATTR);
			return -1;
		}
		opt_type = stream_getc(s);

		/*
		 * Check the length of the stream to ensure that
		 * FRR can properly read the opt_length. Then read it
		 */
		if (BGP_OPEN_EXT_OPT_PARAMS_CAPABLE(peer)) {
			if (STREAM_READABLE(s) < 2) {
				zlog_err("%s Option length error", peer->host);
				bgp_notify_send(peer->connection,
						BGP_NOTIFY_OPEN_ERR,
						BGP_NOTIFY_OPEN_MALFORMED_ATTR);
				return -1;
			}

			opt_length = stream_getw(s);
		} else {
			if (STREAM_READABLE(s) < 1) {
				zlog_err("%s Option length error", peer->host);
				bgp_notify_send(peer->connection,
						BGP_NOTIFY_OPEN_ERR,
						BGP_NOTIFY_OPEN_MALFORMED_ATTR);
				return -1;
			}

			opt_length = stream_getc(s);
		}

		/* Option length check. */
		if (STREAM_READABLE(s) < opt_length) {
			zlog_err("%s Option length error (%d)", peer->host,
				 opt_length);
			bgp_notify_send(peer->connection, BGP_NOTIFY_OPEN_ERR,
					BGP_NOTIFY_OPEN_MALFORMED_ATTR);
			return -1;
		}

		if (bgp_debug_neighbor_events(peer))
			zlog_debug(
				"%s rcvd OPEN w/ optional parameter type %u (%s) len %u",
				peer->host, opt_type,
				opt_type == BGP_OPEN_OPT_CAP ? "Capability"
							     : "Unknown",
				opt_length);

		switch (opt_type) {
		case BGP_OPEN_OPT_CAP:
			ret = bgp_capability_parse(peer, opt_length,
						   mp_capability, &error);
			break;
		default:
			bgp_notify_send(peer->connection, BGP_NOTIFY_OPEN_ERR,
					BGP_NOTIFY_OPEN_UNSUP_PARAM);
			ret = -1;
			break;
		}

		/* Parse error.  To accumulate all unsupported capability codes,
		   bgp_capability_parse does not return -1 when encounter
		   unsupported capability code.  To detect that, please check
		   error and erro_data pointer, like below.  */
		if (ret < 0)
			return -1;
	}

	/* All OPEN option is parsed.  Check capability when strict compare
	   flag is enabled.*/
	if (CHECK_FLAG(peer->flags, PEER_FLAG_STRICT_CAP_MATCH)) {
		/* If Unsupported Capability exists or local capability does
		 * not negotiated with remote peer
		 */
		if (error != error_data || !strict_capability_same(peer)) {
			bgp_notify_send_with_data(peer->connection,
						  BGP_NOTIFY_OPEN_ERR,
						  BGP_NOTIFY_OPEN_UNSUP_CAPBL,
						  error_data,
						  error - error_data);
			return -1;
		}
	}

	/* Extended Message Support */
	peer->max_packet_size =
		(CHECK_FLAG(peer->cap, PEER_CAP_EXTENDED_MESSAGE_RCV)
		 && CHECK_FLAG(peer->cap, PEER_CAP_EXTENDED_MESSAGE_ADV))
			? BGP_EXTENDED_MESSAGE_MAX_PACKET_SIZE
			: BGP_STANDARD_MESSAGE_MAX_PACKET_SIZE;

	/* Check that roles are corresponding to each other */
	if (bgp_role_violation(peer))
		return -1;

	/* Check there are no common AFI/SAFIs and send Unsupported Capability
	   error. */
	if (*mp_capability
	    && !CHECK_FLAG(peer->flags, PEER_FLAG_OVERRIDE_CAPABILITY)) {
		if (!peer->afc_nego[AFI_IP][SAFI_UNICAST]
		    && !peer->afc_nego[AFI_IP][SAFI_MULTICAST]
		    && !peer->afc_nego[AFI_IP][SAFI_LABELED_UNICAST]
		    && !peer->afc_nego[AFI_IP][SAFI_MPLS_VPN]
		    && !peer->afc_nego[AFI_IP][SAFI_ENCAP]
		    && !peer->afc_nego[AFI_IP][SAFI_FLOWSPEC]
		    && !peer->afc_nego[AFI_IP6][SAFI_UNICAST]
		    && !peer->afc_nego[AFI_IP6][SAFI_MULTICAST]
		    && !peer->afc_nego[AFI_IP6][SAFI_LABELED_UNICAST]
		    && !peer->afc_nego[AFI_IP6][SAFI_MPLS_VPN]
		    && !peer->afc_nego[AFI_IP6][SAFI_ENCAP]
		    && !peer->afc_nego[AFI_IP6][SAFI_FLOWSPEC]
		    && !peer->afc_nego[AFI_L2VPN][SAFI_EVPN]) {
			flog_err(EC_BGP_PKT_OPEN,
				 "%s [Error] Configured AFI/SAFIs do not overlap with received MP capabilities",
				 peer->host);

			bgp_notify_send_with_data(peer->connection,
						  BGP_NOTIFY_OPEN_ERR,
						  BGP_NOTIFY_OPEN_UNSUP_CAPBL,
						  error_data,
						  error - error_data);
		}
	}
	return 0;
}

static void bgp_open_capability_orf(struct stream *s, struct peer *peer,
				    afi_t afi, safi_t safi, uint8_t code,
				    bool ext_opt_params)
{
	uint16_t cap_len;
	uint8_t orf_len;
	unsigned long capp;
	unsigned long orfp;
	unsigned long numberp;
	int number_of_orfs = 0;
	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);

	stream_putc(s, BGP_OPEN_OPT_CAP);
	capp = stream_get_endp(s); /* Set Capability Len Pointer */
	ext_opt_params ? stream_putw(s, 0)
		       : stream_putc(s, 0); /* Capability Length */
	stream_putc(s, code);      /* Capability Code */
	orfp = stream_get_endp(s); /* Set ORF Len Pointer */
	stream_putc(s, 0);	 /* ORF Length */
	stream_putw(s, pkt_afi);
	stream_putc(s, 0);
	stream_putc(s, pkt_safi);
	numberp = stream_get_endp(s); /* Set Number Pointer */
	stream_putc(s, 0);	    /* Number of ORFs */

	/* Address Prefix ORF */
	if (CHECK_FLAG(peer->af_flags[afi][safi], PEER_FLAG_ORF_PREFIX_SM)
	    || CHECK_FLAG(peer->af_flags[afi][safi], PEER_FLAG_ORF_PREFIX_RM)) {
		stream_putc(s, ORF_TYPE_PREFIX);

		if (CHECK_FLAG(peer->af_flags[afi][safi],
			       PEER_FLAG_ORF_PREFIX_SM)
		    && CHECK_FLAG(peer->af_flags[afi][safi],
				  PEER_FLAG_ORF_PREFIX_RM)) {
			SET_FLAG(peer->af_cap[afi][safi],
				 PEER_CAP_ORF_PREFIX_SM_ADV);
			SET_FLAG(peer->af_cap[afi][safi],
				 PEER_CAP_ORF_PREFIX_RM_ADV);
			stream_putc(s, ORF_MODE_BOTH);
		} else if (CHECK_FLAG(peer->af_flags[afi][safi],
				      PEER_FLAG_ORF_PREFIX_SM)) {
			SET_FLAG(peer->af_cap[afi][safi],
				 PEER_CAP_ORF_PREFIX_SM_ADV);
			stream_putc(s, ORF_MODE_SEND);
		} else {
			SET_FLAG(peer->af_cap[afi][safi],
				 PEER_CAP_ORF_PREFIX_RM_ADV);
			stream_putc(s, ORF_MODE_RECEIVE);
		}
		number_of_orfs++;
	}

	/* Total Number of ORFs. */
	stream_putc_at(s, numberp, number_of_orfs);

	/* Total ORF Len. */
	orf_len = stream_get_endp(s) - orfp - 1;
	stream_putc_at(s, orfp, orf_len);

	/* Total Capability Len. */
	cap_len = stream_get_endp(s) - capp - 1;
	ext_opt_params ? stream_putw_at(s, capp, cap_len)
		       : stream_putc_at(s, capp, cap_len);
}

static void bgp_peer_send_gr_capability(struct stream *s, struct peer *peer,
					bool ext_opt_params)
{
	int len;
	iana_afi_t pkt_afi = IANA_AFI_IPV4;
	afi_t afi;
	safi_t safi;
	iana_safi_t pkt_safi = IANA_SAFI_UNICAST;
	uint32_t restart_time;
	unsigned long capp = 0;
	unsigned long rcapp = 0;
	struct bgp *bgp = peer->bgp;

	if (!CHECK_FLAG(peer->flags, PEER_FLAG_GRACEFUL_RESTART)
	    && !CHECK_FLAG(peer->flags, PEER_FLAG_GRACEFUL_RESTART_HELPER))
		return;

	SET_FLAG(peer->cap, PEER_CAP_RESTART_ADV);
	stream_putc(s, BGP_OPEN_OPT_CAP);
	capp = stream_get_endp(s); /* Set Capability Len Pointer */
	ext_opt_params ? stream_putw(s, 0)
		       : stream_putc(s, 0); /* Capability Length */
	stream_putc(s, CAPABILITY_CODE_RESTART);
	/* Set Restart Capability Len Pointer */
	rcapp = stream_get_endp(s);
	stream_putc(s, 0);
	restart_time = bgp->restart_time;
	if (peer->bgp->t_startup || bgp_in_graceful_restart()) {
		SET_FLAG(restart_time, GRACEFUL_RESTART_R_BIT);
		SET_FLAG(peer->cap, PEER_CAP_GRACEFUL_RESTART_R_BIT_ADV);
	}

	if (CHECK_FLAG(bgp->flags, BGP_FLAG_GRACEFUL_NOTIFICATION)) {
		SET_FLAG(restart_time, GRACEFUL_RESTART_N_BIT);
		SET_FLAG(peer->cap, PEER_CAP_GRACEFUL_RESTART_N_BIT_ADV);
	}

	stream_putw(s, restart_time);

	if (BGP_DEBUG(graceful_restart, GRACEFUL_RESTART))
		zlog_debug("%s: Sending GR Capability, Restart time %d R-bit %s, N-bit %s",
			   peer->host, bgp->restart_time,
			   CHECK_FLAG(peer->cap,
				      PEER_CAP_GRACEFUL_RESTART_R_BIT_ADV)
				   ? "SET"
				   : "NOT-SET",
			   CHECK_FLAG(peer->cap,
				      PEER_CAP_GRACEFUL_RESTART_N_BIT_ADV)
				   ? "SET"
				   : "NOT-SET");

	/* Send address-family specific graceful-restart capability
	 * only when GR config is present
	 */
	if (CHECK_FLAG(peer->flags, PEER_FLAG_GRACEFUL_RESTART)) {
		FOREACH_AFI_SAFI (afi, safi) {
			bool f_bit = false;

			if (!peer->afc[afi][safi])
				continue;

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

			f_bit = bgp_gr_is_forwarding_preserved(bgp);

			if (BGP_DEBUG(graceful_restart, GRACEFUL_RESTART))
				zlog_debug("... F-bit %s for %s",
					   f_bit ? "SET" : "NOT-SET",
					   get_afi_safi_str(afi, safi, false));

			stream_putc(s, f_bit ? GRACEFUL_RESTART_F_BIT : 0);
		}
	}

	/* Total Graceful restart capability Len. */
	len = stream_get_endp(s) - rcapp - 1;
	stream_putc_at(s, rcapp, len);

	/* Total Capability Len. */
	len = stream_get_endp(s) - capp - 1;
	ext_opt_params ? stream_putw_at(s, capp, len - 1)
		       : stream_putc_at(s, capp, len);
}

static void bgp_peer_send_llgr_capability(struct stream *s, struct peer *peer,
					  bool ext_opt_params)
{
	int len;
	iana_afi_t pkt_afi = IANA_AFI_IPV4;
	afi_t afi;
	safi_t safi;
	iana_safi_t pkt_safi = IANA_SAFI_UNICAST;
	unsigned long capp = 0;
	unsigned long rcapp = 0;

	if (!CHECK_FLAG(peer->cap, PEER_CAP_RESTART_ADV))
		return;

	SET_FLAG(peer->cap, PEER_CAP_LLGR_ADV);

	stream_putc(s, BGP_OPEN_OPT_CAP);
	capp = stream_get_endp(s); /* Set Capability Len Pointer */
	ext_opt_params ? stream_putw(s, 0)
		       : stream_putc(s, 0); /* Capability Length */
	stream_putc(s, CAPABILITY_CODE_LLGR);

	rcapp = stream_get_endp(s);
	stream_putc(s, 0);

	FOREACH_AFI_SAFI (afi, safi) {
		if (!peer->afc[afi][safi])
			continue;

		bgp_map_afi_safi_int2iana(afi, safi, &pkt_afi, &pkt_safi);

		stream_putw(s, pkt_afi);
		stream_putc(s, pkt_safi);
		stream_putc(s, LLGR_F_BIT);
		stream_put3(s, peer->bgp->llgr_stale_time);

		SET_FLAG(peer->af_cap[afi][safi], PEER_CAP_LLGR_AF_ADV);
	}

	/* Total Long-lived Graceful Restart capability Len. */
	len = stream_get_endp(s) - rcapp - 1;
	stream_putc_at(s, rcapp, len);

	/* Total Capability Len. */
	len = stream_get_endp(s) - capp - 1;
	ext_opt_params ? stream_putw_at(s, capp, len - 1)
		       : stream_putc_at(s, capp, len);
}

/* Fill in capability open option to the packet. */
uint16_t bgp_open_capability(struct stream *s, struct peer *peer,
			     bool ext_opt_params)
{
	uint16_t len;
	unsigned long cp, capp, rcapp, eopl = 0;
	iana_afi_t pkt_afi = IANA_AFI_IPV4;
	afi_t afi;
	safi_t safi;
	iana_safi_t pkt_safi = IANA_SAFI_UNICAST;
	as_t local_as;
	uint8_t afi_safi_count = 0;
	bool adv_addpath_tx = false;

	/* Non-Ext OP Len. */
	cp = stream_get_endp(s);
	stream_putc(s, 0);

	if (ext_opt_params) {
		/* Non-Ext OP Len. */
		stream_putc_at(s, cp, BGP_OPEN_NON_EXT_OPT_LEN);

		/* Non-Ext OP Type */
		stream_putc(s, BGP_OPEN_NON_EXT_OPT_TYPE_EXTENDED_LENGTH);

		/* Extended Opt. Parm. Length */
		eopl = stream_get_endp(s);
		stream_putw(s, 0);
	}

	/* Do not send capability. */
	if (!CHECK_FLAG(peer->sflags, PEER_STATUS_CAPABILITY_OPEN)
	    || CHECK_FLAG(peer->flags, PEER_FLAG_DONT_CAPABILITY))
		return 0;

	/* MP capability for configured AFI, SAFI */
	FOREACH_AFI_SAFI (afi, safi) {
		if (peer->afc[afi][safi]) {
			/* Convert AFI, SAFI to values for packet. */
			bgp_map_afi_safi_int2iana(afi, safi, &pkt_afi,
						  &pkt_safi);

			peer->afc_adv[afi][safi] = 1;
			stream_putc(s, BGP_OPEN_OPT_CAP);
			ext_opt_params
				? stream_putw(s, CAPABILITY_CODE_MP_LEN + 2)
				: stream_putc(s, CAPABILITY_CODE_MP_LEN + 2);
			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);

			/* Extended nexthop capability - currently
			 * supporting RFC-5549 for
			 * Link-Local peering only
			 */
			if (CHECK_FLAG(peer->flags, PEER_FLAG_CAPABILITY_ENHE) &&
			    peer->connection->su.sa.sa_family == AF_INET6 &&
			    afi == AFI_IP &&
			    (safi == SAFI_UNICAST || safi == SAFI_MPLS_VPN ||
			     safi == SAFI_LABELED_UNICAST)) {
				/* RFC 5549 Extended Next Hop Encoding
				 */
				SET_FLAG(peer->cap, PEER_CAP_ENHE_ADV);
				stream_putc(s, BGP_OPEN_OPT_CAP);
				ext_opt_params
					? stream_putw(s,
						      CAPABILITY_CODE_ENHE_LEN
							      + 2)
					: stream_putc(s,
						      CAPABILITY_CODE_ENHE_LEN
							      + 2);
				stream_putc(s, CAPABILITY_CODE_ENHE);
				stream_putc(s, CAPABILITY_CODE_ENHE_LEN);

				SET_FLAG(peer->af_cap[AFI_IP][safi],
					 PEER_CAP_ENHE_AF_ADV);
				stream_putw(s, pkt_afi);
				stream_putw(s, pkt_safi);
				stream_putw(s, afi_int2iana(AFI_IP6));

				if (CHECK_FLAG(peer->af_cap[afi][safi],
					       PEER_CAP_ENHE_AF_RCV))
					SET_FLAG(peer->af_cap[afi][safi],
						 PEER_CAP_ENHE_AF_NEGO);
			}
		}
	}

	/* Route refresh. */
	SET_FLAG(peer->cap, PEER_CAP_REFRESH_ADV);
	stream_putc(s, BGP_OPEN_OPT_CAP);
	ext_opt_params ? stream_putw(s, CAPABILITY_CODE_REFRESH_LEN + 2)
		       : stream_putc(s, CAPABILITY_CODE_REFRESH_LEN + 2);
	stream_putc(s, CAPABILITY_CODE_REFRESH);
	stream_putc(s, CAPABILITY_CODE_REFRESH_LEN);

	/* Enhanced Route Refresh. */
	SET_FLAG(peer->cap, PEER_CAP_ENHANCED_RR_ADV);
	stream_putc(s, BGP_OPEN_OPT_CAP);
	ext_opt_params ? stream_putw(s, CAPABILITY_CODE_ENHANCED_LEN + 2)
		       : stream_putc(s, CAPABILITY_CODE_ENHANCED_LEN + 2);
	stream_putc(s, CAPABILITY_CODE_ENHANCED_RR);
	stream_putc(s, CAPABILITY_CODE_ENHANCED_LEN);

	/* AS4 */
	SET_FLAG(peer->cap, PEER_CAP_AS4_ADV);
	stream_putc(s, BGP_OPEN_OPT_CAP);
	ext_opt_params ? stream_putw(s, CAPABILITY_CODE_AS4_LEN + 2)
		       : stream_putc(s, CAPABILITY_CODE_AS4_LEN + 2);
	stream_putc(s, CAPABILITY_CODE_AS4);
	stream_putc(s, CAPABILITY_CODE_AS4_LEN);
	if (peer->change_local_as)
		local_as = peer->change_local_as;
	else
		local_as = peer->local_as;
	stream_putl(s, local_as);

	/* Extended Message Support */
	SET_FLAG(peer->cap, PEER_CAP_EXTENDED_MESSAGE_ADV);
	stream_putc(s, BGP_OPEN_OPT_CAP);
	ext_opt_params ? stream_putw(s, CAPABILITY_CODE_EXT_MESSAGE_LEN + 2)
		       : stream_putc(s, CAPABILITY_CODE_EXT_MESSAGE_LEN + 2);
	stream_putc(s, CAPABILITY_CODE_EXT_MESSAGE);
	stream_putc(s, CAPABILITY_CODE_EXT_MESSAGE_LEN);

	/* Role*/
	if (peer->local_role != ROLE_UNDEFINED) {
		SET_FLAG(peer->cap, PEER_CAP_ROLE_ADV);
		stream_putc(s, BGP_OPEN_OPT_CAP);
		stream_putc(s, CAPABILITY_CODE_ROLE_LEN + 2);
		stream_putc(s, CAPABILITY_CODE_ROLE);
		stream_putc(s, CAPABILITY_CODE_ROLE_LEN);
		stream_putc(s, peer->local_role);
	}

	/* AddPath */
	FOREACH_AFI_SAFI (afi, safi) {
		if (peer->afc[afi][safi]) {
			afi_safi_count++;

			/* Only advertise addpath TX if a feature that
			 * will use it is
			 * configured */
			if (peer->addpath_type[afi][safi] != BGP_ADDPATH_NONE)
				adv_addpath_tx = true;

			/* If we have enabled labeled unicast, we MUST check
			 * against unicast SAFI because addpath IDs are
			 * allocated under unicast SAFI, the same as the RIB
			 * is managed in unicast SAFI.
			 */
			if (safi == SAFI_LABELED_UNICAST)
				if (peer->addpath_type[afi][SAFI_UNICAST] !=
				    BGP_ADDPATH_NONE)
					adv_addpath_tx = true;
		}
	}

	SET_FLAG(peer->cap, PEER_CAP_ADDPATH_ADV);
	stream_putc(s, BGP_OPEN_OPT_CAP);
	ext_opt_params
		? stream_putw(s, (CAPABILITY_CODE_ADDPATH_LEN * afi_safi_count)
					 + 2)
		: stream_putc(s, (CAPABILITY_CODE_ADDPATH_LEN * afi_safi_count)
					 + 2);
	stream_putc(s, CAPABILITY_CODE_ADDPATH);
	stream_putc(s, CAPABILITY_CODE_ADDPATH_LEN * afi_safi_count);

	FOREACH_AFI_SAFI (afi, safi) {
		if (peer->afc[afi][safi]) {
			bool adv_addpath_rx =
				!CHECK_FLAG(peer->af_flags[afi][safi],
					    PEER_FLAG_DISABLE_ADDPATH_RX);
			uint8_t flags = 0;

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

			stream_putw(s, pkt_afi);
			stream_putc(s, pkt_safi);

			if (adv_addpath_rx) {
				SET_FLAG(flags, BGP_ADDPATH_RX);
				SET_FLAG(peer->af_cap[afi][safi],
					 PEER_CAP_ADDPATH_AF_RX_ADV);
			} else {
				UNSET_FLAG(peer->af_cap[afi][safi],
					   PEER_CAP_ADDPATH_AF_RX_ADV);
			}

			if (adv_addpath_tx) {
				SET_FLAG(flags, BGP_ADDPATH_TX);
				SET_FLAG(peer->af_cap[afi][safi],
					 PEER_CAP_ADDPATH_AF_TX_ADV);
				if (safi == SAFI_LABELED_UNICAST)
					SET_FLAG(
						peer->af_cap[afi][SAFI_UNICAST],
						PEER_CAP_ADDPATH_AF_TX_ADV);
			} else {
				UNSET_FLAG(peer->af_cap[afi][safi],
					   PEER_CAP_ADDPATH_AF_TX_ADV);
			}

			stream_putc(s, flags);
		}
	}

	/* Paths-Limit capability */
	SET_FLAG(peer->cap, PEER_CAP_PATHS_LIMIT_ADV);
	stream_putc(s, BGP_OPEN_OPT_CAP);
	ext_opt_params ? stream_putw(s, (CAPABILITY_CODE_PATHS_LIMIT_LEN *
					 afi_safi_count) +
						2)
		       : stream_putc(s, (CAPABILITY_CODE_PATHS_LIMIT_LEN *
					 afi_safi_count) +
						2);
	stream_putc(s, CAPABILITY_CODE_PATHS_LIMIT);
	stream_putc(s, CAPABILITY_CODE_PATHS_LIMIT_LEN * afi_safi_count);

	FOREACH_AFI_SAFI (afi, safi) {
		if (!peer->afc[afi][safi])
			continue;

		bgp_map_afi_safi_int2iana(afi, safi, &pkt_afi, &pkt_safi);

		stream_putw(s, pkt_afi);
		stream_putc(s, pkt_safi);
		stream_putw(s, peer->addpath_paths_limit[afi][safi].send);

		SET_FLAG(peer->af_cap[afi][safi], PEER_CAP_PATHS_LIMIT_AF_ADV);
	}

	/* ORF capability. */
	FOREACH_AFI_SAFI (afi, safi) {
		if (CHECK_FLAG(peer->af_flags[afi][safi],
			       PEER_FLAG_ORF_PREFIX_SM)
		    || CHECK_FLAG(peer->af_flags[afi][safi],
				  PEER_FLAG_ORF_PREFIX_RM)) {
			bgp_open_capability_orf(s, peer, afi, safi,
						CAPABILITY_CODE_ORF,
						ext_opt_params);
		}
	}

	/* Dynamic capability. */
	if (peergroup_flag_check(peer, PEER_FLAG_DYNAMIC_CAPABILITY)) {
		SET_FLAG(peer->cap, PEER_CAP_DYNAMIC_ADV);
		stream_putc(s, BGP_OPEN_OPT_CAP);
		ext_opt_params
			? stream_putw(s, CAPABILITY_CODE_DYNAMIC_LEN + 2)
			: stream_putc(s, CAPABILITY_CODE_DYNAMIC_LEN + 2);
		stream_putc(s, CAPABILITY_CODE_DYNAMIC);
		stream_putc(s, CAPABILITY_CODE_DYNAMIC_LEN);
	}

	/* Link-Local Next Hop capability. */
	if (peergroup_flag_check(peer, PEER_FLAG_CAPABILITY_LINK_LOCAL)) {
		SET_FLAG(peer->cap, PEER_CAP_LINK_LOCAL_ADV);
		stream_putc(s, BGP_OPEN_OPT_CAP);
		ext_opt_params ? stream_putw(s, CAPABILITY_CODE_LINK_LOCAL_LEN + 2)
			       : stream_putc(s, CAPABILITY_CODE_LINK_LOCAL_LEN + 2);
		stream_putc(s, CAPABILITY_CODE_LINK_LOCAL);
		stream_putc(s, CAPABILITY_CODE_LINK_LOCAL_LEN);
	}

	/* FQDN capability */
	if (CHECK_FLAG(peer->flags, PEER_FLAG_CAPABILITY_FQDN)
	    && cmd_hostname_get()) {
		SET_FLAG(peer->cap, PEER_CAP_HOSTNAME_ADV);
		stream_putc(s, BGP_OPEN_OPT_CAP);
		rcapp = stream_get_endp(s); /* Ptr to length placeholder */
		ext_opt_params ? stream_putw(s, 0)
			       : stream_putc(s, 0); /* Capability Length */
		stream_putc(s, CAPABILITY_CODE_FQDN);
		capp = stream_get_endp(s);
		stream_putc(s, 0); /* dummy len for now */
		len = strlen(cmd_hostname_get());
		if (len > BGP_MAX_HOSTNAME)
			len = BGP_MAX_HOSTNAME;

		stream_putc(s, len);
		stream_put(s, cmd_hostname_get(), len);
		if (cmd_domainname_get()) {
			len = strlen(cmd_domainname_get());
			if (len > BGP_MAX_HOSTNAME)
				len = BGP_MAX_HOSTNAME;

			stream_putc(s, len);
			stream_put(s, cmd_domainname_get(), len);
		} else
			stream_putc(s, 0); /* 0 length */

		/* Set the lengths straight */
		len = stream_get_endp(s) - rcapp - 1;
		ext_opt_params ? stream_putw_at(s, rcapp, len - 1)
			       : stream_putc_at(s, rcapp, len);

		len = stream_get_endp(s) - capp - 1;
		stream_putc_at(s, capp, len);

		if (bgp_debug_neighbor_events(peer))
			zlog_debug(
				"%s Sending hostname cap with hn = %s, dn = %s",
				peer->host, cmd_hostname_get(),
				cmd_domainname_get());
	}

	bgp_peer_send_gr_capability(s, peer, ext_opt_params);
	bgp_peer_send_llgr_capability(s, peer, ext_opt_params);

	/* Software Version capability
	 * An implementation is REQUIRED Extended Optional Parameters
	 * Length for BGP OPEN Message support as defined in [RFC9072].
	 * The inclusion of the Software Version Capability is OPTIONAL.
	 * If an implementation supports the inclusion of the capability,
	 * the implementation MUST include a configuration switch to enable
	 * or disable its use, and that switch MUST be off by default.
	 */
	if (peergroup_flag_check(peer, PEER_FLAG_CAPABILITY_SOFT_VERSION) ||
	    peer->sort == BGP_PEER_IBGP || peer->sub_sort == BGP_PEER_EBGP_OAD) {
		SET_FLAG(peer->cap, PEER_CAP_SOFT_VERSION_ADV);
		stream_putc(s, BGP_OPEN_OPT_CAP);
		rcapp = stream_get_endp(s);
		ext_opt_params ? stream_putw(s, 0)
			       : stream_putc(s, 0); /* Capability Length */
		stream_putc(s, CAPABILITY_CODE_SOFT_VERSION);
		capp = stream_get_endp(s);
		stream_putc(s, 0); /* dummy placeholder len */

		/* The Capability Length SHOULD be no greater than 64.
		 * This is the limit to allow other capabilities as much
		 * space as they require.
		 */
		len = strlen(cmd_software_version_get());
		if (len > BGP_MAX_SOFT_VERSION)
			len = BGP_MAX_SOFT_VERSION;

		stream_putc(s, len);
		stream_put(s, cmd_software_version_get(), len);

		/* Software Version capability Len. */
		len = stream_get_endp(s) - rcapp - 1;
		ext_opt_params ? stream_putw_at(s, rcapp, len - 1)
			       : stream_putc_at(s, rcapp, len);

		/* Total Capability Len. */
		len = stream_get_endp(s) - capp - 1;
		stream_putc_at(s, capp, len);

		if (bgp_debug_neighbor_events(peer))
			zlog_debug("%s Sending Software Version cap, value: %s",
				   peer->host, cmd_software_version_get());
	}

	/* Total Opt Parm Len. */
	len = stream_get_endp(s) - cp - 1;

	if (ext_opt_params) {
		len = stream_get_endp(s) - eopl - 2;
		stream_putw_at(s, eopl, len);
	} else {
		stream_putc_at(s, cp, len);
	}

	return len;
}
