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>

net/sctp/protocol.c

@@ -1179,6 +1179,7 @@ SCTP_STATIC __init int sctp_init(void)
 
 	/* Disable ADDIP by default. */
 	sctp_addip_enable = 0;
+	sctp_addip_noauth = 0;
 
 	/* Enable PR-SCTP by default. */
 	sctp_prsctp_enable = 1;