tipc: fix cancellation of topology subscriptions

When cancelling a subscription, we have to clear the cancel bit in the
request before iterating over any established subscriptions with memcmp.
Otherwise no subscription will ever be found, and it will not be
possible to explicitly unsubscribe individual subscriptions.

Fixes: 8985ecc7 ("tipc: simplify endianness handling in topology subscriber")
Signed-off-by: Erik Hugne <erik.hugne@gmail.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/topsrv.c

@@ -363,6 +363,7 @@ static int tipc_conn_rcv_sub(struct tipc_topsrv *srv,
 	struct tipc_subscription *sub;
 
 	if (tipc_sub_read(s, filter) & TIPC_SUB_CANCEL) {
+		s->filter &= __constant_ntohl(~TIPC_SUB_CANCEL);
 		tipc_conn_delete_sub(con, s);
 		return 0;
 	}