SCTP: Uncomfirmed transports can't become Inactive

Do not set Unconfirmed transports to Inactive state. This may
result in an inactive association being destroyed since we start
counting errors on "inactive" transports against the association.
This was found at the SCTP interop event.

Signed-off-by: Vlad Yasevich <[e-mail]>

net/sctp/associola.c

···
 		break;
 
 	case SCTP_TRANSPORT_DOWN:
-		transport->state = SCTP_INACTIVE;
+		/* if the transort was never confirmed, do not transition it
+		 * to inactive state.
+		 */
+		if (transport->state != SCTP_UNCONFIRMED)
+			transport->state = SCTP_INACTIVE;
+
 		spc_state = SCTP_ADDR_UNREACHABLE;
 		break;