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bgpd: Set NO_ADVERTISE community if blackhole community received

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rfc7999:
A BGP speaker receiving an announcement tagged with the BLACKHOLE
community SHOULD add the NO_ADVERTISE or NO_EXPORT community as
defined in [RFC1997], or a similar community, to prevent propagation
of the prefix outside the local AS.  The community to prevent
propagation SHOULD be chosen according to the operator's routing
policy.

Sent:
```
router bgp 65534
 no bgp ebgp-requires-policy
 neighbor 192.168.0.2 remote-as 65030
 !
 address-family ipv4 unicast
  redistribute connected
  neighbor 192.168.0.2 route-map spine out
 exit-address-family
 !
!
ip prefix-list self seq 5 permit 192.168.100.1/32
!
route-map spine permit 10
 match ip address prefix-list self
 set community blackhole
!
```

Received:
```
spine1-debian-9# show ip bgp 192.168.100.1/32
BGP routing table entry for 192.168.100.1/32
Paths: (1 available, best #1, table default, inform peer to blackhole prefix)
  Not advertised to any peer
  65534
    192.168.0.1 from 192.168.0.1 (192.168.100.1)
      Origin incomplete, metric 0, valid, external, best (First path received)
      Community: blackhole no-advertise
      Last update: Thu Jan 21 12:56:39 2021
```

Signed-off-by: Donatas Abraitis <donatas.abraitis@gmail.com>
This commit is contained in:
Donatas Abraitis 2021-01-21 15:03:40 +02:00
parent 7dac521ffb
commit 2721dd613f
4 changed files with 49 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
bgpd/bgp_community.c
View File

@ -56,7 +56,7 @@ void community_free(struct community **com)
}
/* Add one community value to the community. */
static void community_add_val(struct community *com, uint32_t val)
void community_add_val(struct community *com, uint32_t val)
{
com->size++;
if (com->val)

1
bgpd/bgp_community.h
View File

@ -88,6 +88,7 @@ extern struct community *community_delete(struct community *,
struct community *);
extern struct community *community_dup(struct community *);
extern bool community_include(struct community *, uint32_t);
extern void community_add_val(struct community *com, uint32_t val);
extern void community_del_val(struct community *, uint32_t *);
extern unsigned long community_count(void);
extern struct hash *community_hash(void);

42
bgpd/bgp_route.c
View File

@ -3505,6 +3505,34 @@ bool bgp_update_martian_nexthop(struct bgp *bgp, afi_t afi, safi_t safi,
return ret;
}
static void bgp_attr_add_no_advertise_community(struct attr *attr)
{
struct community *old;
struct community *new;
struct community *merge;
struct community *noadv;
old = attr->community;
noadv = community_str2com("no-advertise");
if (old) {
merge = community_merge(community_dup(old), noadv);
if (!old->refcnt)
community_free(&old);
new = community_uniq_sort(merge);
community_free(&merge);
} else {
new = community_dup(noadv);
}
community_free(&noadv);
attr->community = new;
attr->flag |= ATTR_FLAG_BIT(BGP_ATTR_COMMUNITIES);
}
int bgp_update(struct peer *peer, const struct prefix *p, uint32_t addpath_id,
struct attr *attr, afi_t afi, safi_t safi, int type,
int sub_type, struct prefix_rd *prd, mpls_label_t *label,
@ -3697,6 +3725,20 @@ int bgp_update(struct peer *peer, const struct prefix *p, uint32_t addpath_id,
if (peer->sort == BGP_PEER_EBGP) {
/* rfc7999:
* A BGP speaker receiving an announcement tagged with the
* BLACKHOLE community SHOULD add the NO_ADVERTISE or
* NO_EXPORT community as defined in RFC1997, or a
* similar community, to prevent propagation of the
* prefix outside the local AS. The community to prevent
* propagation SHOULD be chosen according to the operator's
* routing policy.
*/
if (new_attr.community
&& community_include(new_attr.community,
COMMUNITY_BLACKHOLE))
bgp_attr_add_no_advertise_community(&new_attr);
/* If we receive the graceful-shutdown community from an eBGP
* peer we must lower local-preference */
if (new_attr.community

5
bgpd/bgp_routemap.c
View File

@ -4822,6 +4822,11 @@ DEFUN (set_community,
buffer_putstr(b, "no-export");
continue;
}
if (strncmp(argv[i]->arg, "blackhole", strlen(argv[i]->arg))
== 0) {
buffer_putstr(b, "blackhole");
continue;
}
if (strncmp(argv[i]->arg, "graceful-shutdown",
strlen(argv[i]->arg))
== 0) {