nfsd: unregister with rpcbind when deleting a transport

When a listener is added, a part of creation of transport also registers
program/port with rpcbind. However, when the listener is removed,
while transport goes away, rpcbind still has the entry for that
port/type.

When deleting the transport, unregister with rpcbind when appropriate.

---v2 created a new xpt_flag XPT_RPCB_UNREG to mark TCP and UDP
transport and at xprt destroy send rpcbind unregister if flag set.

Suggested-by: Chuck Lever <[e-mail]>
Fixes: d093c9089260 ("nfsd: fix management of listener transports")
Cc: [e-mail]
Signed-off-by: Olga Kornievskaia <[e-mail]>
Reviewed-by: Jeff Layton <[e-mail]>
Signed-off-by: Chuck Lever <[e-mail]>

include/linux/sunrpc/svc_xprt.h

···
 				 * it has access to.  It is NOT counted
 				 * in ->sv_tmpcnt.
 				 */
+	XPT_RPCB_UNREG,		/* transport that needs unregistering
+				 * with rpcbind (TCP, UDP) on destroy
+				 */
 };
 
 /*

net/sunrpc/svc_xprt.c

···
 	struct svc_serv	*serv = xprt->xpt_server;
 	struct svc_deferred_req *dr;
 
+	/* unregister with rpcbind for when transport type is TCP or UDP.
+	 */
+	if (test_bit(XPT_RPCB_UNREG, &xprt->xpt_flags)) {
+		struct svc_sock *svsk = container_of(xprt, struct svc_sock,
+						     sk_xprt);
+		struct socket *sock = svsk->sk_sock;
+
+		if (svc_register(serv, xprt->xpt_net, sock->sk->sk_family,
+				 sock->sk->sk_protocol, 0) < 0)
+			pr_warn("failed to unregister %s with rpcbind\n",
+				xprt->xpt_class->xcl_name);
+	}
+
 	if (test_and_set_bit(XPT_DEAD, &xprt->xpt_flags))
 		return;
 

net/sunrpc/svcsock.c

···
 	/* data might have come in before data_ready set up */
 	set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);
 	set_bit(XPT_CHNGBUF, &svsk->sk_xprt.xpt_flags);
+	set_bit(XPT_RPCB_UNREG, &svsk->sk_xprt.xpt_flags);
 
 	/* make sure we get destination address info */
 	switch (svsk->sk_sk->sk_family) {
···
 	if (sk->sk_state == TCP_LISTEN) {
 		strcpy(svsk->sk_xprt.xpt_remotebuf, "listener");
 		set_bit(XPT_LISTENER, &svsk->sk_xprt.xpt_flags);
+		set_bit(XPT_RPCB_UNREG, &svsk->sk_xprt.xpt_flags);
 		sk->sk_data_ready = svc_tcp_listen_data_ready;
 		set_bit(XPT_CONN, &svsk->sk_xprt.xpt_flags);
 	} else {