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Aug 12, 2025
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bgpd: Implement BGPID next-hop characteristic #19349

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b8157bb
bgpd: Implement BGPID next-hop characteristic
ton31337 Aug 6, 2025
5fc9907
tests: Check if BGPID characteristic is attached to the routes
ton31337 Aug 6, 2025
1601ac5
tests: Set router-id manually for all nodes in bgp_nhc topotest
ton31337 Aug 8, 2025
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99 changes: 62 additions & 37 deletions bgpd/bgp_attr.c
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Original file line number Diff line number Diff line change
Expand Up @@ -700,14 +700,19 @@ static uint32_t bgp_nhc_hash_key_make(const void *p)
{
const struct bgp_nhc *nhc = p;
uint32_t key = 0;
struct bgp_nhc_tlv *tlv;

key = jhash_3words(nhc->afi, nhc->safi, nhc->nh_length, key);
key = jhash_1word(nhc->tlvs_length, key);
key = jhash(&nhc->nh_ipv4, IPV4_MAX_BYTELEN, key);
key = jhash(&nhc->nh_ipv6, IPV6_MAX_BYTELEN, key);

if (nhc->tlvs)
key = jhash(nhc->tlvs, nhc->tlvs_length, key);
if (nhc->tlvs) {
for (tlv = nhc->tlvs; tlv; tlv = tlv->next) {
key = jhash_2words(tlv->code, tlv->length, key);
key = jhash(tlv->value, tlv->length, key);
}
}

return key;
}
Expand Down Expand Up @@ -3640,16 +3645,18 @@ static int bgp_attr_nhc(struct bgp_attr_parser_args *args)
iana_safi_t pkt_safi;
safi_t safi;
struct stream *s = BGP_INPUT(peer);
struct bgp_nhc *nhc;
struct bgp_nhc *nhc = bgp_attr_get_nhc(attr);
uint16_t tlv_code;
uint16_t tlv_length;
struct bgp_nhc_tlv *tlv;
uint8_t nh_length;

if (peer->discard_attrs[args->type] || peer->withdraw_attrs[args->type])
goto nhc_ignore;

if (length < BGP_NHC_MIN_LEN) {
zlog_err("%pBP rcvd BGP NHC attribute length is too short: %d", peer, length);
zlog_err("%pBP rcvd BGP NHC attribute length is too short: %d, expected minimum %d",
peer, length, BGP_NHC_MIN_LEN);
return bgp_attr_malformed(args, BGP_NOTIFY_UPDATE_OPT_ATTR_ERR, args->total);
}

Expand All @@ -3667,34 +3674,38 @@ static int bgp_attr_nhc(struct bgp_attr_parser_args *args)
zlog_debug("%pBP rcvd BGP NHC attribute with length %d for afi %s, safi %s", peer,
length, iana_afi2str(pkt_afi), iana_safi2str(pkt_safi));

nhc = XCALLOC(MTYPE_BGP_NHC, sizeof(struct bgp_nhc));
nhc->afi = afi;
nhc->safi = safi;
nhc->nh_length = stream_getc(s);
nh_length = stream_getc(s);

/* If Next-hop is IPv6, we should check if we are not out of bound too */
if (nhc->nh_length == BGP_ATTR_NHLEN_IPV6_GLOBAL) {
if (nh_length == BGP_ATTR_NHLEN_IPV6_GLOBAL) {
if (length < BGP_NHC_MIN_IPV6_LEN) {
zlog_err("%pBP rcvd BGP NHC attribute length is too short: %d", peer,
length);
zlog_err("%pBP rcvd BGP NHC attribute length is too short: %d, expected minimum %d",
peer, length, BGP_NHC_MIN_IPV6_LEN);
bgp_nhc_free(nhc);
return bgp_attr_malformed(args, BGP_NOTIFY_UPDATE_OPT_ATTR_ERR, args->total);
}
}

/* Next-hop length should be either 4 or 16 */
if (nhc->nh_length != BGP_ATTR_NHLEN_IPV4 && nhc->nh_length != BGP_ATTR_NHLEN_IPV6_GLOBAL) {
zlog_err("%pBP rcvd wrong next-hop length, %d, in NHC", peer, nhc->nh_length);
if (nh_length != BGP_ATTR_NHLEN_IPV4 && nh_length != BGP_ATTR_NHLEN_IPV6_GLOBAL) {
zlog_err("%pBP rcvd wrong next-hop length, %d, in NHC", peer, nh_length);
bgp_nhc_free(nhc);
return bgp_attr_malformed(args, BGP_NOTIFY_UPDATE_OPT_ATTR_ERR, args->total);
}

if (!nhc)
nhc = XCALLOC(MTYPE_BGP_NHC, sizeof(struct bgp_nhc));

nhc->afi = afi;
nhc->safi = safi;
nhc->nh_length = nh_length;

length -= 4; /* AFI(2) + SAFI(1) + Next-hop length(1) */

if (nhc->nh_length == BGP_ATTR_NHLEN_IPV4) {
if (nh_length == BGP_ATTR_NHLEN_IPV4) {
stream_get(&nhc->nh_ipv4, s, IPV4_MAX_BYTELEN);
length -= IPV4_MAX_BYTELEN;
} else if (nhc->nh_length == BGP_ATTR_NHLEN_IPV6_GLOBAL) {
} else if (nh_length == BGP_ATTR_NHLEN_IPV6_GLOBAL) {
stream_get(&nhc->nh_ipv6, s, IPV6_MAX_BYTELEN);
length -= IPV6_MAX_BYTELEN;
if (IN6_IS_ADDR_LINKLOCAL(&nhc->nh_ipv6)) {
Expand Down Expand Up @@ -3750,9 +3761,7 @@ static int bgp_attr_nhc(struct bgp_attr_parser_args *args)

/* draft-wang-idr-next-next-hop-nodes */
if (tlv->code == BGP_ATTR_NHC_TLV_NNHN) {
uint16_t len = tlv->length;

if (len % IPV4_MAX_BYTELEN != 0) {
if (tlv->length % IPV4_MAX_BYTELEN != 0) {
zlog_err("%pBP rcvd BGP NHC (NNHN TLV) length %d not a multiple of %d",
peer, tlv->length, IPV4_MAX_BYTELEN);
bgp_nhc_free(nhc);
Expand All @@ -3762,12 +3771,8 @@ static int bgp_attr_nhc(struct bgp_attr_parser_args *args)
}

found = bgp_nhc_tlv_find(nhc, tlv_code);
if (found) {
nhc->tlvs_length -= found->length + BGP_NHC_TLV_MIN_LEN;
bgp_nhc_tlv_free(found);
}

bgp_nhc_tlv_add(nhc, tlv);
if (!found)
bgp_nhc_tlv_add(nhc, tlv);

length -= tlv_length + BGP_NHC_TLV_MIN_LEN;
}
Expand Down Expand Up @@ -4617,19 +4622,19 @@ static void bgp_packet_nhc(struct stream *s, struct peer *peer, afi_t afi, safi_
afi_t nh_afi;
struct bgp_path_info *exists;
uint16_t total;
struct bgp_nhc *nhc = bgp_attr_get_nhc(attr);
const struct prefix *prefix = NULL;

if (!bpi)
return;

total = bgp_path_info_mpath_count(bpi) * IPV4_MAX_BYTELEN;

/* NHC now supports only draft-wang-idr-next-next-hop-nodes, thus
* do not sent NHC attribute if the path is not multipath or self
* originated.
*/
if (bpi->peer == bpi->peer->bgp->peer_self || bgp_path_info_mpath_count(bpi) < 2)
if (bgp_path_info_mpath_count(bpi) < 2 && !nhc)
return;

prefix = bgp_dest_get_prefix(bpi->net);

total = bgp_path_info_mpath_count(bpi) * IPV4_MAX_BYTELEN;

stream_putc(s, BGP_ATTR_FLAG_OPTIONAL | BGP_ATTR_FLAG_TRANS);
stream_putc(s, BGP_ATTR_NHC);
sizep = stream_get_endp(s);
Expand Down Expand Up @@ -4660,15 +4665,35 @@ static void bgp_packet_nhc(struct stream *s, struct peer *peer, afi_t afi, safi_
/* Put TLVs */

/* Begin NNHN TLV */
stream_putw(s, BGP_ATTR_NHC_TLV_NNHN);
stream_putw(s, total);
stream_put_ipv4(s, bpi->peer->remote_id.s_addr);
if (bgp_path_info_mpath_count(bpi) > 1) {
if (bgp_debug_update(peer, NULL, NULL, 1))
zlog_debug("%pBP: Sending NHC TLV (%d) for %pFX", peer,
BGP_ATTR_NHC_TLV_NNHN, prefix);
stream_putw(s, BGP_ATTR_NHC_TLV_NNHN);
stream_putw(s, total);
stream_put_ipv4(s, bpi->peer->remote_id.s_addr);

for (exists = bgp_path_info_mpath_first(bpi); exists;
exists = bgp_path_info_mpath_next(exists))
stream_put_ipv4(s, exists->peer->remote_id.s_addr);
for (exists = bgp_path_info_mpath_first(bpi); exists;
exists = bgp_path_info_mpath_next(exists))
stream_put_ipv4(s, exists->peer->remote_id.s_addr);
}
/* End NNHN TLV */

/* Other TLVs */
if (nhc) {
struct bgp_nhc_tlv *tlv = NULL;

for (tlv = nhc->tlvs; tlv; tlv = tlv->next) {
if (bgp_debug_update(peer, NULL, NULL, 1))
zlog_debug("%pBP: Sending NHC TLV (%u) for %pFX", peer, tlv->code,
prefix);
stream_putw(s, tlv->code);
stream_putw(s, tlv->length);
stream_put(s, tlv->value, tlv->length);
}
}
/* Other TLVs */

stream_putc_at(s, sizep, (stream_get_endp(s) - sizep) - 1);
}

Expand Down
16 changes: 15 additions & 1 deletion bgpd/bgp_nhc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,20 @@ void bgp_nhc_tlv_add(struct bgp_nhc *nhc, struct bgp_nhc_tlv *tlv)
nhc->tlvs_length += tlv->length + BGP_NHC_TLV_MIN_LEN;
}

struct bgp_nhc_tlv *bgp_nhc_tlv_new(uint16_t code, uint16_t length, const void *value)
{
struct bgp_nhc_tlv *tlv;

tlv = XCALLOC(MTYPE_BGP_NHC_TLV, sizeof(struct bgp_nhc_tlv) + IPV4_MAX_BYTELEN);
tlv->code = code;
tlv->length = length;
tlv->value = XCALLOC(MTYPE_BGP_NHC_TLV_VAL, length);

memcpy(tlv->value, value, length);

return tlv;
}

struct bgp_nhc_tlv *bgp_nhc_tlv_find(struct bgp_nhc *nhc, uint16_t code)
{
struct bgp_nhc_tlv *tlv = NULL;
Expand All @@ -35,7 +49,7 @@ struct bgp_nhc_tlv *bgp_nhc_tlv_find(struct bgp_nhc *nhc, uint16_t code)
return tlv;
}

return tlv;
return NULL;
}

void bgp_nhc_tlv_free(struct bgp_nhc_tlv *tlv)
Expand Down
3 changes: 3 additions & 0 deletions bgpd/bgp_nhc.h
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Original file line number Diff line number Diff line change
Expand Up @@ -47,11 +47,14 @@ struct bgp_nhc {
/* TLV values: */
/* draft-wang-idr-next-next-hop-nodes */
#define BGP_ATTR_NHC_TLV_NNHN 2
/* draft-ietf-idr-entropy-label */
#define BGP_ATTR_NHC_TLV_BGPID 3

extern void bgp_nhc_tlv_add(struct bgp_nhc *nhc, struct bgp_nhc_tlv *tlv);
extern struct bgp_nhc_tlv *bgp_nhc_tlv_find(struct bgp_nhc *nhc, uint16_t code);
extern void bgp_nhc_tlv_free(struct bgp_nhc_tlv *tlv);
extern void bgp_nhc_tlvs_free(struct bgp_nhc_tlv *tlv);
extern void bgp_nhc_free(struct bgp_nhc *bnc);
extern struct bgp_nhc_tlv *bgp_nhc_tlv_new(uint16_t code, uint16_t length, const void *value);

#endif /* _FRR_BGP_NHC_H */
36 changes: 33 additions & 3 deletions bgpd/bgp_route.c
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Original file line number Diff line number Diff line change
Expand Up @@ -7396,6 +7396,9 @@ void bgp_static_update(struct bgp *bgp, const struct prefix *p,
uint8_t num_labels = 0;
struct bgp *bgp_nexthop = bgp;
struct bgp_labels labels = {};
struct bgp_nhc_tlv *tlv;
struct bgp_nhc *nhc;
uint8_t nh_length = IPV6_MAX_BYTELEN;

assert(bgp_static);

Expand All @@ -7408,13 +7411,26 @@ void bgp_static_update(struct bgp *bgp, const struct prefix *p,

bgp_attr_default_set(&attr, bgp, BGP_ORIGIN_IGP);

if (afi == AFI_IP)
nh_length = IPV4_MAX_BYTELEN;

/* NHC */
nhc = XCALLOC(MTYPE_BGP_NHC, sizeof(struct bgp_nhc));
nhc->afi = afi;
nhc->safi = safi;
nhc->nh_length = nh_length;
nhc->tlvs_length = IPV4_MAX_BYTELEN;

tlv = bgp_nhc_tlv_new(BGP_ATTR_NHC_TLV_BGPID, IPV4_MAX_BYTELEN, &bgp->router_id);
bgp_nhc_tlv_add(nhc, tlv);
bgp_attr_set_nhc(&attr, nhc);
/* NHC */

attr.nexthop = bgp_static->igpnexthop;
attr.mp_nexthop_len = nh_length;

bgp_attr_set_med(&attr, bgp_static->igpmetric);

if (afi == AFI_IP)
attr.mp_nexthop_len = BGP_ATTR_NHLEN_IPV4;

if (bgp_static->atomic)
SET_FLAG(attr.flag, ATTR_FLAG_BIT(BGP_ATTR_ATOMIC_AGGREGATE));

Expand Down Expand Up @@ -12310,6 +12326,9 @@ void route_vty_out_detail(struct vty *vty, struct bgp *bgp, struct bgp_dest *bn,
struct bgp_nhc_tlv *tlv = NULL;

if (nhc) {
if (!json_paths)
vty_out(vty, " Characteristics:\n");

for (tlv = nhc->tlvs; tlv; tlv = tlv->next) {
if (tlv->code == BGP_ATTR_NHC_TLV_NNHN) {
json_object *json_nhc_nnhn = NULL;
Expand All @@ -12333,6 +12352,17 @@ void route_vty_out_detail(struct vty *vty, struct bgp *bgp, struct bgp_dest *bn,
if (json_paths)
json_object_object_add(json_path, "nextNextHopNodes",
json_nhc_nnhn);
} else if (tlv->code == BGP_ATTR_NHC_TLV_BGPID) {
struct in_addr router_id;

memcpy(&router_id.s_addr, tlv->value,
sizeof(router_id.s_addr));

if (!json_paths)
vty_out(vty, " BGPID: %pI4\n", &router_id);
else
json_object_string_addf(json_path, "bgpId", "%pI4",
&router_id);
}
}
}
Expand Down
1 change: 1 addition & 0 deletions bgpd/bgp_updgrp_adv.c
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,7 @@
#include "bgpd/bgp_updgrp.h"
#include "bgpd/bgp_advertise.h"
#include "bgpd/bgp_addpath.h"
#include "bgpd/bgp_nhc.h"


/********************
Expand Down
1 change: 1 addition & 0 deletions tests/topotests/bgp_nhc/r1/frr.conf
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@ int r1-eth1
ip address 10.255.16.1/24
!
router bgp 65001
bgp router-id 10.255.0.1
no bgp ebgp-requires-policy
neighbor 10.255.0.2 timers 1 3
neighbor 10.255.0.2 timers connect 1
Expand Down
5 changes: 5 additions & 0 deletions tests/topotests/bgp_nhc/r2/frr.conf
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Original file line number Diff line number Diff line change
Expand Up @@ -6,8 +6,10 @@ int r2-eth1
ip address 10.254.0.2/24
!
router bgp 65002
bgp router-id 10.255.0.2
no bgp ebgp-requires-policy
no bgp suppress-duplicates
no bgp network import-check
bgp bestpath as-path multipath-relax
neighbor 10.255.0.1 remote-as external
neighbor 10.255.0.1 timers 1 3
Expand All @@ -22,4 +24,7 @@ router bgp 65002
neighbor 10.254.0.5 remote-as external
neighbor 10.254.0.5 timers 1 3
neighbor 10.254.0.5 timers connect 1
address-family ipv4 unicast
network 10.0.0.2/32
exit-address-family
!
3 changes: 3 additions & 0 deletions tests/topotests/bgp_nhc/r3/frr.conf
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Original file line number Diff line number Diff line change
Expand Up @@ -3,12 +3,15 @@ int r3-eth0
ip address 10.254.0.3/24
!
router bgp 65003
bgp router-id 10.255.0.3
no bgp ebgp-requires-policy
no bgp network import-check
neighbor 10.254.0.2 remote-as external
neighbor 10.254.0.2 timers 1 3
neighbor 10.254.0.2 timers connect 1
neighbor 10.254.0.2 send-nexthop-characteristics
address-family ipv4 unicast
network 10.0.0.1/32
network 10.0.0.3/32
exit-address-family
!
1 change: 1 addition & 0 deletions tests/topotests/bgp_nhc/r4/frr.conf
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Expand Up @@ -3,6 +3,7 @@ int r4-eth0
ip address 10.254.0.4/24
!
router bgp 65004
bgp router-id 10.255.0.4
no bgp ebgp-requires-policy
no bgp network import-check
neighbor 10.254.0.2 remote-as external
Expand Down
1 change: 1 addition & 0 deletions tests/topotests/bgp_nhc/r5/frr.conf
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@ int r5-eth0
ip address 10.254.0.5/24
!
router bgp 65005
bgp router-id 10.255.0.5
no bgp ebgp-requires-policy
no bgp network import-check
neighbor 10.254.0.2 remote-as external
Expand Down
1 change: 1 addition & 0 deletions tests/topotests/bgp_nhc/r6/frr.conf
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Expand Up @@ -9,6 +9,7 @@ int r6-eth2
ip address 10.255.68.6/24
!
router bgp 65006
bgp router-id 10.255.0.6
no bgp ebgp-requires-policy
no bgp suppress-duplicates
bgp bestpath as-path multipath-relax
Expand Down
2 changes: 1 addition & 1 deletion tests/topotests/bgp_nhc/r7/frr.conf
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Expand Up @@ -3,7 +3,7 @@ int r7-eth0
ip address 10.255.67.7/24
!
router bgp 65007
bgp router-id 10.254.0.7
bgp router-id 10.255.0.7
no bgp ebgp-requires-policy
no bgp network import-check
neighbor 10.255.67.6 remote-as external
Expand Down
2 changes: 1 addition & 1 deletion tests/topotests/bgp_nhc/r8/frr.conf
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,7 @@ int r8-eth0
ip address 10.255.68.8/24
!
router bgp 65008
bgp router-id 10.254.0.8
bgp router-id 10.255.0.8
no bgp ebgp-requires-policy
no bgp network import-check
neighbor 10.255.68.6 remote-as external
Expand Down
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