[SCTP]: Tie ADD-IP and AUTH functionality as required by spec.

ADD-IP spec requires AUTH. It is, in fact, dangerous without AUTH.
So, disable ADD-IP functionality if the peer claims to support
ADD-IP, but not AUTH.
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sctp/structs.h

@@ -1543,6 +1543,7 @@ struct sctp_association {
 		__u8    asconf_capable;  /* Does peer support ADDIP? */
 		__u8    prsctp_capable;  /* Can peer do PR-SCTP? */
 		__u8	auth_capable;	 /* Is peer doing SCTP-AUTH? */
+		__u8	addip_capable;	 /* Can peer do ADD-IP */
 
 		__u32   adaptation_ind;	 /* Adaptation Code point. */
 

net/sctp/sm_make_chunk.c

@@ -1851,7 +1851,8 @@ static void sctp_process_ext_param(struct sctp_association *asoc,
 			    break;
 		    case SCTP_CID_ASCONF:
 		    case SCTP_CID_ASCONF_ACK:
-			    /* don't need to do anything for ASCONF */
+			    asoc->peer.addip_capable = 1;
+			    break;
 		    default:
 			    break;
 		}
@@ -2137,6 +2138,16 @@ int sctp_process_init(struct sctp_association *asoc, sctp_cid_t cid,
 					!asoc->peer.peer_hmacs))
 		asoc->peer.auth_capable = 0;
 
+
+	/* If the peer claims support for ADD-IP without support
+	 * for AUTH, disable support for ADD-IP.
+	 */
+	if (asoc->peer.addip_capable && !asoc->peer.auth_capable) {
+		asoc->peer.addip_disabled_mask |= (SCTP_PARAM_ADD_IP |
+						  SCTP_PARAM_DEL_IP |
+						  SCTP_PARAM_SET_PRIMARY);
+	}
+
 	/* Walk list of transports, removing transports in the UNKNOWN state. */
 	list_for_each_safe(pos, temp, &asoc->peer.transport_addr_list) {
 		transport = list_entry(pos, struct sctp_transport, transports);