SUNRPC: Ensure that the gssproxy client can start in a connected state

Ensure that the gssproxy client connects to the server from the gssproxy
daemon process context so that the AF_LOCAL socket connection is done
using the correct path and namespaces.

Fixes: 1d658336b05f ("SUNRPC: Add RPC based upcall mechanism for RPCGSS auth")
Cc: [e-mail]
Signed-off-by: Trond Myklebust <[e-mail]>

include/linux/sunrpc/clnt.h

···
 #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_CONNECTED	(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

···
 		 * done without the correct namespace:
 		 */
 		.flags		= RPC_CLNT_CREATE_NOPING |
+				  RPC_CLNT_CREATE_CONNECTED |
 				  RPC_CLNT_CREATE_NO_IDLE_TIMEOUT
 	};
 	struct rpc_clnt *clnt;

net/sunrpc/clnt.c

···
 static int	rpc_decode_header(struct rpc_task *task,
 				  struct xdr_stream *xdr);
 static int	rpc_ping(struct rpc_clnt *clnt);
+static int	rpc_ping_noreply(struct rpc_clnt *clnt);
 static void	rpc_check_timeout(struct rpc_task *task);
 
 static void rpc_register_client(struct rpc_clnt *clnt)
···
 
 	if (!(args->flags & RPC_CLNT_CREATE_NOPING)) {
 		int err = rpc_ping(clnt);
+		if (err != 0) {
+			rpc_shutdown_client(clnt);
+			return ERR_PTR(err);
+		}
+	} else if (args->flags & RPC_CLNT_CREATE_CONNECTED) {
+		int err = rpc_ping_noreply(clnt);
 		if (err != 0) {
 			rpc_shutdown_client(clnt);
 			return ERR_PTR(err);
···
 	.p_decode = rpcproc_decode_null,
 };
 
+static const struct rpc_procinfo rpcproc_null_noreply = {
+	.p_encode = rpcproc_encode_null,
+};
+
 static void
 rpc_null_call_prepare(struct rpc_task *task, void *data)
 {
···
 	int status;
 
 	task = rpc_call_null_helper(clnt, NULL, NULL, 0, NULL, NULL);
+	if (IS_ERR(task))
+		return PTR_ERR(task);
+	status = task->tk_status;
+	rpc_put_task(task);
+	return status;
+}
+
+static int rpc_ping_noreply(struct rpc_clnt *clnt)
+{
+	struct rpc_message msg = {
+		.rpc_proc = &rpcproc_null_noreply,
+	};
+	struct rpc_task_setup task_setup_data = {
+		.rpc_client = clnt,
+		.rpc_message = &msg,
+		.callback_ops = &rpc_null_ops,
+		.flags = RPC_TASK_SOFT | RPC_TASK_SOFTCONN | RPC_TASK_NULLCREDS,
+	};
+	struct rpc_task	*task;
+	int status;
+
+	task = rpc_run_task(&task_setup_data);
 	if (IS_ERR(task))
 		return PTR_ERR(task);
 	status = task->tk_status;