bgpd: Fallback to destination peer when using match src-peer ...

If using at incoming direction, e.g.:

route-map test permit 10
 match src-peer 10.0.0.1
!
router bgp 65000
 neighbor 10.0.0.1 route-map test in
!

Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>

bgpd/bgp_routemap.c

@@ -362,6 +362,15 @@ static enum route_map_cmd_result_t route_match_src_peer(void *rule, const struct
 	bpi = object;
 	peer = bpi->from;
 
+	/* Fallback to destination (current) peer. This is mostly
+	 * happens if `match src-peer ...` is used at incoming direction.
+	 */
+	if (!peer)
+		peer = bpi->peer;
+
+	if (!peer)
+		return RMAP_NOMATCH;
+
 	if (pc->interface) {
 		if (!peer->conf_if && !peer->group)
 			return RMAP_NOMATCH;