Handle the CLUSTER_LIST attribute as described in RFC7606

Just drop the attribute if received from an external peer.
Treat as withdraw if the len is 0 or not % 4.
OK tb@

diff --git a/usr.sbin/bgpd/rde.c b/usr.sbin/bgpd/rde.c
index a855f27..fb58c5e 100644 (file)
--- a/usr.sbin/bgpd/rde.c
+++ b/usr.sbin/bgpd/rde.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: rde.c,v 1.631 2024/09/09 14:58:47 claudio Exp $ */
+/*     $OpenBSD: rde.c,v 1.632 2024/09/09 15:00:45 claudio Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -2192,8 +2192,22 @@ rde_attr_parse(struct ibuf *buf, struct rde_peer *peer,
        case ATTR_CLUSTER_LIST:
                if (!CHECK_FLAGS(flags, ATTR_OPTIONAL, 0))
                        goto bad_flags;
-               if (ibuf_size(&attrbuf) % 4 != 0)
-                       goto bad_len;
+               if (peer->conf.ebgp) {
+                       /* As per RFC7606 use "attribute discard" here. */
+                       log_peer_warnx(&peer->conf, "bad CLUSTER_LIST, "
+                           "received from external peer, attribute discarded");
+                       break;
+               }
+               if (ibuf_size(&attrbuf) % 4 != 0 || ibuf_size(&attrbuf) == 0) {
+                       /*
+                        * mark update as bad and withdraw all routes as per
+                        * RFC 7606
+                        */
+                       a->flags |= F_ATTR_PARSE_ERR;
+                       log_peer_warnx(&peer->conf, "bad CLUSTER_LIST, "
+                           "path invalidated and prefix withdrawn");
+                       break;
+               }
                goto optattr;
        case ATTR_MP_REACH_NLRI:
                if (!CHECK_FLAGS(flags, ATTR_OPTIONAL, 0))