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BGP: Improve 'invalid next hop' error reporting

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Distinguish multiple causes of 'invalid next hop' message and report
the relevant next hop address.

Thanks to Simon Ruderich for the original patch.
This commit is contained in:
Ondrej Zajicek (work) 2022-01-28 05:03:03 +01:00
parent 9dbb7eb6eb
commit 75d01ecc2d
1 changed files with 17 additions and 11 deletions
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28
proto/bgp/packets.c
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@ -937,6 +937,7 @@ bgp_rx_open(struct bgp_conn *conn, byte *pkt, uint len)
#define NO_NEXT_HOP "Missing NEXT_HOP attribute"
#define NO_LABEL_STACK "Missing MPLS stack"
#define MISMATCHED_AF " - mismatched address family (%I for %s)"
static void
bgp_apply_next_hop(struct bgp_parse_state *s, rta *a, ip_addr gw, ip_addr ll)
@ -949,13 +950,18 @@ bgp_apply_next_hop(struct bgp_parse_state *s, rta *a, ip_addr gw, ip_addr ll)
neighbor *nbr = NULL;
/* GW_DIRECT -> single_hop -> p->neigh != NULL */
if (ipa_nonzero(gw))
if (ipa_nonzero2(gw))
nbr = neigh_find(&p->p, gw, NULL, 0);
else if (ipa_nonzero(ll))
nbr = neigh_find(&p->p, ll, p->neigh->iface, 0);
else
WITHDRAW(BAD_NEXT_HOP " - zero address");
if (!nbr || (nbr->scope == SCOPE_HOST))
WITHDRAW(BAD_NEXT_HOP);
if (!nbr)
WITHDRAW(BAD_NEXT_HOP " - address %I not directly reachable", ipa_nonzero(gw) ? gw : ll);
if (nbr->scope == SCOPE_HOST)
WITHDRAW(BAD_NEXT_HOP " - address %I is local", nbr->addr);
a->dest = RTD_UNICAST;
a->nh.gw = nbr->addr;
@ -964,8 +970,8 @@ bgp_apply_next_hop(struct bgp_parse_state *s, rta *a, ip_addr gw, ip_addr ll)
}
else /* GW_RECURSIVE */
{
if (ipa_zero(gw))
WITHDRAW(BAD_NEXT_HOP);
if (ipa_zero2(gw))
WITHDRAW(BAD_NEXT_HOP " - zero address");
rtable *tab = ipa_is_ip4(gw) ? c->igp_table_ip4 : c->igp_table_ip6;
s->hostentry = rt_get_hostentry(tab, gw, ll, c->c.table);
@ -1127,17 +1133,17 @@ bgp_update_next_hop_ip(struct bgp_export_state *s, eattr *a, ea_list **to)
uint len = a->u.ptr->length;
/* Forbid zero next hop */
if (ipa_zero(nh[0]) && ((len != 32) || ipa_zero(nh[1])))
WITHDRAW(BAD_NEXT_HOP);
if (ipa_zero2(nh[0]) && ((len != 32) || ipa_zero(nh[1])))
WITHDRAW(BAD_NEXT_HOP " - zero address");
/* Forbid next hop equal to neighbor IP */
if (ipa_equal(peer, nh[0]) || ((len == 32) && ipa_equal(peer, nh[1])))
WITHDRAW(BAD_NEXT_HOP);
WITHDRAW(BAD_NEXT_HOP " - neighbor address %I", peer);
/* Forbid next hop with non-matching AF */
if ((ipa_is_ip4(nh[0]) != bgp_channel_is_ipv4(s->channel)) &&
!s->channel->ext_next_hop)
WITHDRAW(BAD_NEXT_HOP);
WITHDRAW(BAD_NEXT_HOP MISMATCHED_AF, nh[0], s->channel->desc->name);
/* Just check if MPLS stack */
if (s->mpls && !bgp_find_attr(*to, BA_MPLS_LABEL_STACK))
@ -1212,7 +1218,7 @@ bgp_decode_next_hop_ip(struct bgp_parse_state *s, byte *data, uint len, rta *a)
ad->length = 16;
if ((bgp_channel_is_ipv4(c) != ipa_is_ip4(nh[0])) && !c->ext_next_hop)
WITHDRAW(BAD_NEXT_HOP);
WITHDRAW(BAD_NEXT_HOP MISMATCHED_AF, nh[0], c->desc->name);
// XXXX validate next hop
@ -1293,7 +1299,7 @@ bgp_decode_next_hop_vpn(struct bgp_parse_state *s, byte *data, uint len, rta *a)
bgp_parse_error(s, 9);
if ((bgp_channel_is_ipv4(c) != ipa_is_ip4(nh[0])) && !c->ext_next_hop)
WITHDRAW(BAD_NEXT_HOP);
WITHDRAW(BAD_NEXT_HOP MISMATCHED_AF, nh[0], c->desc->name);
// XXXX validate next hop