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bgpd: stop removing and replacing private asn if it matches the peer

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Problems reported that if multiple peers have "remove-private-AS
replace-AS" with each other and all are using private asns, the as-path
gets hosed and continues to grow when a prefix is removed.  This fix
disallows removing and replacing the private asn if it matches the
peer's ASN so that normal as-path loop prevention will operate correctly.

Ticket: CM-25489
Signed-off-by: Don Slice <dslice@cumulusnetworks.com>
This commit is contained in:
Don Slice 2019-07-25 11:35:06 -04:00
parent a041a8fff2
commit bf26b80eba
3 changed files with 16 additions and 18 deletions
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23
bgpd/bgp_aspath.c
View File

@ -1232,7 +1232,8 @@ struct aspath *aspath_replace_specific_asn(struct aspath *aspath,
} }
/* Replace all private ASNs with our own ASN */ /* Replace all private ASNs with our own ASN */
struct aspath *aspath_replace_private_asns(struct aspath *aspath, as_t asn) struct aspath *aspath_replace_private_asns(struct aspath *aspath, as_t asn,
as_t peer_asn)
{ {
struct aspath *new; struct aspath *new;
struct assegment *seg; struct assegment *seg;
@ -1244,7 +1245,9 @@ struct aspath *aspath_replace_private_asns(struct aspath *aspath, as_t asn)
int i; int i;
for (i = 0; i < seg->length; i++) { for (i = 0; i < seg->length; i++) {
if (BGP_AS_IS_PRIVATE(seg->as[i])) /* Don't replace if public ASN or peer's ASN */
if (BGP_AS_IS_PRIVATE(seg->as[i])
&& (seg->as[i] != peer_asn))
seg->as[i] = asn; seg->as[i] = asn;
} }
seg = seg->next; seg = seg->next;
@ -1255,7 +1258,7 @@ struct aspath *aspath_replace_private_asns(struct aspath *aspath, as_t asn)
} }
/* Remove all private ASNs */ /* Remove all private ASNs */
struct aspath *aspath_remove_private_asns(struct aspath *aspath) struct aspath *aspath_remove_private_asns(struct aspath *aspath, as_t peer_asn)
{ {
struct aspath *new; struct aspath *new;
struct assegment *seg; struct assegment *seg;
@ -1282,16 +1285,9 @@ struct aspath *aspath_remove_private_asns(struct aspath *aspath)
} }
} }
// The entire segment is private so skip it
if (!public) {
seg = seg->next;
continue;
}
// The entire segment is public so copy it // The entire segment is public so copy it
else if (public == seg->length) { if (public == seg->length)
new_seg = assegment_dup(seg); new_seg = assegment_dup(seg);
}
// The segment is a mix of public and private ASNs. Copy as many // The segment is a mix of public and private ASNs. Copy as many
// spots as // spots as
@ -1301,8 +1297,9 @@ struct aspath *aspath_remove_private_asns(struct aspath *aspath)
new_seg = assegment_new(seg->type, public); new_seg = assegment_new(seg->type, public);
j = 0; j = 0;
for (i = 0; i < seg->length; i++) { for (i = 0; i < seg->length; i++) {
// ASN is public // keep ASN if public or matches peer's ASN
if (!BGP_AS_IS_PRIVATE(seg->as[i])) { if (!BGP_AS_IS_PRIVATE(seg->as[i])
|| (seg->as[i] == peer_asn)) {
new_seg->as[j] = seg->as[i]; new_seg->as[j] = seg->as[i];
j++; j++;
} }

5
bgpd/bgp_aspath.h
View File

@ -112,8 +112,9 @@ extern struct aspath *aspath_replace_specific_asn(struct aspath *aspath,
as_t target_asn, as_t target_asn,
as_t our_asn); as_t our_asn);
extern struct aspath *aspath_replace_private_asns(struct aspath *aspath, extern struct aspath *aspath_replace_private_asns(struct aspath *aspath,
as_t asn); as_t asn, as_t peer_asn);
extern struct aspath *aspath_remove_private_asns(struct aspath *aspath); extern struct aspath *aspath_remove_private_asns(struct aspath *aspath,
as_t peer_asn);
extern int aspath_firstas_check(struct aspath *, as_t); extern int aspath_firstas_check(struct aspath *, as_t);
extern int aspath_confed_check(struct aspath *); extern int aspath_confed_check(struct aspath *);
extern int aspath_left_confed_check(struct aspath *); extern int aspath_left_confed_check(struct aspath *);

6
bgpd/bgp_route.c
View File

@ -1366,7 +1366,7 @@ static void bgp_peer_remove_private_as(struct bgp *bgp, afi_t afi, safi_t safi,
peer, afi, safi, peer, afi, safi,
PEER_FLAG_REMOVE_PRIVATE_AS_ALL_REPLACE)) PEER_FLAG_REMOVE_PRIVATE_AS_ALL_REPLACE))
attr->aspath = aspath_replace_private_asns( attr->aspath = aspath_replace_private_asns(
attr->aspath, bgp->as); attr->aspath, bgp->as, peer->as);
// The entire aspath consists of private ASNs so create // The entire aspath consists of private ASNs so create
// an empty aspath // an empty aspath
@ -1377,7 +1377,7 @@ static void bgp_peer_remove_private_as(struct bgp *bgp, afi_t afi, safi_t safi,
// the private ASNs // the private ASNs
else else
attr->aspath = aspath_remove_private_asns( attr->aspath = aspath_remove_private_asns(
attr->aspath); attr->aspath, peer->as);
} }
// 'all' was not specified so the entire aspath must be private // 'all' was not specified so the entire aspath must be private
@ -1388,7 +1388,7 @@ static void bgp_peer_remove_private_as(struct bgp *bgp, afi_t afi, safi_t safi,
peer, afi, safi, peer, afi, safi,
PEER_FLAG_REMOVE_PRIVATE_AS_REPLACE)) PEER_FLAG_REMOVE_PRIVATE_AS_REPLACE))
attr->aspath = aspath_replace_private_asns( attr->aspath = aspath_replace_private_asns(
attr->aspath, bgp->as); attr->aspath, bgp->as, peer->as);
else else
attr->aspath = aspath_empty_get(); attr->aspath = aspath_empty_get();
} }