SCTP: Allow ADD_IP to work with AUTH for backward compatibility.

This patch adds a tunable that will allow ADD_IP to work without
AUTH for backward compatibility.  The default value is off since
the default value for ADD_IP is off as well.  People who need
to use ADD-IP with older implementations take risks of connection
hijacking and should consider upgrading or turning this tunable on.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
diff --git a/net/sctp/associola.c b/net/sctp/associola.c
index eaad5c5..013e3d3 100644
--- a/net/sctp/associola.c
+++ b/net/sctp/associola.c
@@ -262,10 +262,14 @@
 	 */
 	asoc->peer.sack_needed = 1;
 
-	/* Assume that the peer recongizes ASCONF until reported otherwise
-	 * via an ERROR chunk.
+	/* Assume that the peer will tell us if he recognizes ASCONF
+	 * as part of INIT exchange.
+	 * The sctp_addip_noauth option is there for backward compatibilty
+	 * and will revert old behavior.
 	 */
 	asoc->peer.asconf_capable = 0;
+	if (sctp_addip_noauth)
+		asoc->peer.asconf_capable = 1;
 
 	/* Create an input queue.  */
 	sctp_inq_init(&asoc->base.inqueue);