bgpd: fix match expanded community with any community

A list of communities from an incoming BGP update is never matched
against an expanded bgp community-list configured for matching
only one of the communities. The below configuration can help:

> bgp community-list expanded com1 seq 5 permit ^44
> router bgp 65001
> [..]
> route-map r2 permit 10
>  match community com1
>  set as-path replace 65003
> exit

The received '172.16.255.32/32' prefix has a community with
'^44', but does not match the route-map rule. Observed dump:

> r1# show bgp ipv4 172.16.255.32/32
> BGP routing table entry for 172.16.255.32/32, version 4
> Paths: (1 available, best #1, table default)
>   Advertised to non peer-group peers:
>   192.168.1.2
>   65003 65002
>     192.168.1.2 from 192.168.1.2 (192.0.2.2)
>       Origin incomplete, valid, external, best (First path received)
>       Community: 11:11 22:22 33:33 44:44 44:77 44:453 55:55 66:66
>       Last update: Tue Jun 20 15:05:27 2023

The route-map rule does not make any differences with and without
the 'exact-match' keyword, and does not filter the prefix.
Change the behaviour of the route-map rule without exact-match, by
applying the regexp to each community of the received community-list.

Observed behaviour:

> r1# r1# show bgp ipv4 172.16.255.32/32
> BGP routing table entry for 172.16.255.32/32, version 5
> Paths: (1 available, best #1, table default)
>   Advertised to non peer-group peers:
>   192.168.1.2
>   65001 65002
>     192.168.1.2 from 192.168.1.2 (192.0.2.2)
>       Origin incomplete, valid, external, best (First path received)
>       Community: 11:11 22:22 33:33 44:44 44:77 44:453 55:55 66:66
>       Last update: Tue Jun 20 15:09:55 2023

Signed-off-by: Philippe Guibert <[email protected]>

bgpd/bgp_clist.c

@@ -657,6 +657,7 @@ static bool ecommunity_regexp_match(struct ecommunity *ecom, regex_t *reg)
 bool community_list_match(struct community *com, struct community_list *list)
 {
 	struct community_entry *entry;
+	int i;
 
 	for (entry = list->head; entry; entry = entry->next) {
 		if (entry->style == COMMUNITY_LIST_STANDARD) {
@@ -666,8 +667,10 @@ bool community_list_match(struct community *com, struct community_list *list)
 			if (community_match(com, entry->u.com))
 				return entry->direct == COMMUNITY_PERMIT;
 		} else if (entry->style == COMMUNITY_LIST_EXPANDED) {
-			if (community_regexp_match(com, entry->reg))
-				return entry->direct == COMMUNITY_PERMIT;
+			for (i = 0; i < com->size; i++) {
+				if (community_regexp_include(entry->reg, com, i))
+					return entry->direct == COMMUNITY_PERMIT;
+			}
 		}
 	}
 	return false;