SUNRPC: Ensure gss-proxy connects on setup

For reasons best known to the author, gss-proxy does not implement a
NULL procedure, and returns RPC_PROC_UNAVAIL. However we still want to
ensure that we connect to the service at setup time.
So add a quirk-flag specially for this case.

Fixes: 1d658336 ("SUNRPC: Add RPC based upcall mechanism for RPCGSS auth")
Cc: stable@vger.kernel.org
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

include/linux/sunrpc/clnt.h

@@ -160,6 +160,7 @@ struct rpc_add_xprt_test {
 #define RPC_CLNT_CREATE_NO_RETRANS_TIMEOUT	(1UL << 9)
 #define RPC_CLNT_CREATE_SOFTERR		(1UL << 10)
 #define RPC_CLNT_CREATE_REUSEPORT	(1UL << 11)
+#define RPC_CLNT_CREATE_IGNORE_NULL_UNAVAIL (1UL << 12)
 
 struct rpc_clnt *rpc_create(struct rpc_create_args *args);
 struct rpc_clnt	*rpc_bind_new_program(struct rpc_clnt *,

net/sunrpc/auth_gss/gss_rpc_upcall.c

@@ -97,7 +97,7 @@ static int gssp_rpc_create(struct net *net, struct rpc_clnt **_clnt)
 		 * timeout, which would result in reconnections being
 		 * done without the correct namespace:
 		 */
-		.flags		= RPC_CLNT_CREATE_NOPING |
+		.flags		= RPC_CLNT_CREATE_IGNORE_NULL_UNAVAIL |
 				  RPC_CLNT_CREATE_NO_IDLE_TIMEOUT
 	};
 	struct rpc_clnt *clnt;

net/sunrpc/clnt.c

@@ -479,6 +479,9 @@ static struct rpc_clnt *rpc_create_xprt(struct rpc_create_args *args,
 
 	if (!(args->flags & RPC_CLNT_CREATE_NOPING)) {
 		int err = rpc_ping(clnt);
+		if ((args->flags & RPC_CLNT_CREATE_IGNORE_NULL_UNAVAIL) &&
+		    err == -EOPNOTSUPP)
+			err = 0;
 		if (err != 0) {
 			rpc_shutdown_client(clnt);
 			return ERR_PTR(err);