tipc: withdraw tipc topology server name when namespace is deleted

The TIPC topology server is a per namespace service associated with the
tipc name {1, 1}. When a namespace is deleted, that name must be withdrawn
before we call sk_release_kernel because the kernel socket release is
done in init_net and trying to withdraw a TIPC name published in another
namespace will fail with an error as:

[  170.093264] Unable to remove local publication
[  170.093264] (type=1, lower=1, ref=2184244004, key=2184244005)

We fix this by breaking the association between the topology server name
and socket before calling sk_release_kernel.
Signed-off-by: Ying Xue <ying.xue@windriver.com>
Reviewed-by: Erik Hugne <erik.hugne@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/server.c

@@ -90,6 +90,7 @@ static void tipc_clean_outqueues(struct tipc_conn *con);
 static void tipc_conn_kref_release(struct kref *kref)
 {
 	struct tipc_conn *con = container_of(kref, struct tipc_conn, kref);
+	struct sockaddr_tipc *saddr = con->server->saddr;
 	struct socket *sock = con->sock;
 	struct sock *sk;
 
@@ -99,6 +100,8 @@ static void tipc_conn_kref_release(struct kref *kref)
 			__module_get(sock->ops->owner);
 			__module_get(sk->sk_prot_creator->owner);
 		}
+		saddr->scope = -TIPC_NODE_SCOPE;
+		kernel_bind(sock, (struct sockaddr *)saddr, sizeof(*saddr));
 		sk_release_kernel(sk);
 		con->sock = NULL;
 	}