Do not shut down the session upon receiving unknown messages.

RFC 5036 says the following about the receipt of unknown messages:
  "Unknown message bit.  Upon receipt of an unknown message, if U is
  clear (=0), a notification is returned to the message originator;
  if U is set (=1), the unknown message is silently ignored".

We were correctly ignoring unknown messages when the U-bit was set. But
when this bit was not set, we were shutting down the session when the
correct thing to do is to just send a non-fatal notification message.

Fix IxANVL LDP test 22.13.

1 files changed, 7 insertions, 9 deletions

diff --git a/usr.sbin/ldpd/packet.c b/usr.sbin/ldpd/packet.c
index e4b672db8f2..040b3ef31e4 100644
--- a/usr.sbin/ldpd/packet.c
+++ b/usr.sbin/ldpd/packet.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: packet.c,v 1.59 2016/06/06 15:30:59 renato Exp $ */
+/*	$OpenBSD: packet.c,v 1.60 2016/06/09 17:41:52 renato Exp $ */
 
 /*
  * Copyright (c) 2013, 2016 Renato Westphal <renato@openbsd.org>
@@ -559,15 +559,13 @@ session_read(int fd, short event, void *arg)
 				    type);
 				break;
 			default:
-				log_debug("%s: unknown LDP packet from nbr %s",
+				log_debug("%s: unknown LDP message from nbr %s",
 				    __func__, inet_ntoa(nbr->id));
-				if (!(ntohs(ldp_msg->type) & UNKNOWN_FLAG)) {
-					session_shutdown(nbr, S_UNKNOWN_MSG,
-					    ldp_msg->msgid, ldp_msg->type);
-					free(buf);
-					return;
-				}
-				/* unknown flag is set, ignore the message */
+				if (!(ntohs(ldp_msg->type) & UNKNOWN_FLAG))
+					send_notification_nbr(nbr,
+					    S_UNKNOWN_MSG, ldp_msg->msgid,
+					    ldp_msg->type);
+				/* ignore the message */
 				ret = 0;
 				break;
 			}