Re: [PATCH nf-next] netfilter: nf_ct_sctp: minimal multihoming support

On Tue, Jul 14, 2015 at 03:42:03PM +0200, Florian Westphal wrote:

Michal Kubecek [off-list ref] wrote:

quoted

+	case SCTP_CID_HEARTBEAT:
+		pr_debug("SCTP_CID_HEARTBEAT");
+		i = 9;
+		break;
+	case SCTP_CID_HEARTBEAT_ACK:
+		pr_debug("SCTP_CID_HEARTBEAT_ACK");
+		i = 10;
+		break;
 	default:
 		/* Other chunks like DATA, SACK, HEARTBEAT and
 		its ACK do not cause a change in state */

@@ -329,6 +351,8 @@ static int sctp_packet(struct nf_conn *ct,
 	    !test_bit(SCTP_CID_COOKIE_ECHO, map) &&
 	    !test_bit(SCTP_CID_ABORT, map) &&
 	    !test_bit(SCTP_CID_SHUTDOWN_ACK, map) &&
+	    !test_bit(SCTP_CID_HEARTBEAT, map) &&
+	    !test_bit(SCTP_CID_HEARTBEAT_ACK, map) &&
 	    sh->vtag != ct->proto.sctp.vtag[dir]) {
 		pr_debug("Verification tag check failed\n");
 		goto out;

@@ -357,6 +381,16 @@ static int sctp_packet(struct nf_conn *ct,
 			/* Sec 8.5.1 (D) */
 			if (sh->vtag != ct->proto.sctp.vtag[dir])
 				goto out_unlock;
+		} else if (sch->type == SCTP_CID_HEARTBEAT ||
+			   sch->type == SCTP_CID_HEARTBEAT_ACK) {
+			if (ct->proto.sctp.vtag[dir] == 0) {
+				pr_debug("Setting vtag %x for dir %d\n",
+					 sh->vtag, dir);
+				ct->proto.sctp.vtag[dir] = sh->vtag;

Could you please elaborate on the [dir] == 0 test?

I see this might happen for SCTP_CID_HEARTBEAT_ACK, but why is this
needed for SCTP_CID_HEARTBEAT ?

We found a conntrack entry so shouldn't the vtag[dir] already be > 0?

Yes, you are right. This was originally intended to handle the case when
a HEARTBEAT in the reply direction is seen before the HEARTBEAT-ACK but
such HEARTBEAT would be dropped anyway in current version.

On the other hand, an alternative would be

		} else if (sch->type == SCTP_CID_HEARTBEAT_ACK &&
			   ct->proto.sctp.vtag[dir] == 0) {
			pr_debug("Setting vtag %x for dir %d\n",
				 sh->vtag, dir);
			ct->proto.sctp.vtag[dir] = sh->vtag;
		} else if ((sch->type == SCTP_CID_HEARTBEAT ||
			    sch->type == SCTP_CID_HEARTBEAT_ACK) &&
			   sh->vtag != ct->proto.sctp.vtag[dir]) {
			pr_debug("Verification tag check failed\n");
			goto out_unlock;
		}

I'm not sure it looks better.

Michal Kubecek