SUNRPC: transport switch API for setting port number

 At some point, transport endpoint addresses will no longer be IPv4.  To hide
 the structure of the rpc_xprt's address field from ULPs and port mappers,
 add an API for setting the port number during an RPC bind operation.

 Test-plan:
 Destructive testing (unplugging the network temporarily).  Connectathon
 with UDP and TCP.  NFSv2/3 and NFSv4 mounting should be carefully checked.
 Probably need to rig a server where certain services aren't running, or
 that returns an error for some typical operation.

 Signed-off-by: Chuck Lever <cel@netapp.com>
 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

include/linux/sunrpc/xprt.h

@@ -104,6 +104,7 @@ struct rpc_xprt_ops {
 	void		(*set_buffer_size)(struct rpc_xprt *xprt, size_t sndsize, size_t rcvsize);
 	int		(*reserve_xprt)(struct rpc_task *task);
 	void		(*release_xprt)(struct rpc_xprt *xprt, struct rpc_task *task);
+	void		(*set_port)(struct rpc_xprt *xprt, unsigned short port);
 	void		(*connect)(struct rpc_task *task);
 	void *		(*buf_alloc)(struct rpc_task *task, size_t size);
 	void		(*buf_free)(struct rpc_task *task);

net/sunrpc/pmap_clnt.c

@@ -131,10 +131,13 @@ static void
 pmap_getport_done(struct rpc_task *task)
 {
 	struct rpc_clnt	*clnt = task->tk_client;
+	struct rpc_xprt *xprt = task->tk_xprt;
 	struct rpc_portmap *map = clnt->cl_pmap;
 
 	dprintk("RPC: %4d pmap_getport_done(status %d, port %d)\n",
 			task->tk_pid, task->tk_status, clnt->cl_port);
+
+	xprt->ops->set_port(xprt, 0);
 	if (task->tk_status < 0) {
 		/* Make the calling task exit with an error */
 		task->tk_action = rpc_exit_task;
@@ -142,9 +145,8 @@ pmap_getport_done(struct rpc_task *task)
 		/* Program not registered */
 		rpc_exit(task, -EACCES);
 	} else {
-		/* byte-swap port number first */
+		xprt->ops->set_port(xprt, clnt->cl_port);
 		clnt->cl_port = htons(clnt->cl_port);
-		clnt->cl_xprt->addr.sin_port = clnt->cl_port;
 	}
 	spin_lock(&pmap_lock);
 	map->pm_binding = 0;
@@ -205,7 +207,7 @@ pmap_create(char *hostname, struct sockaddr_in *srvaddr, int proto, int privileg
 	xprt = xprt_create_proto(proto, srvaddr, NULL);
 	if (IS_ERR(xprt))
 		return (struct rpc_clnt *)xprt;
-	xprt->addr.sin_port = htons(RPC_PMAP_PORT);
+	xprt->ops->set_port(xprt, RPC_PMAP_PORT);
 	if (!privileged)
 		xprt->resvport = 0;
 

net/sunrpc/xprtsock.c

@@ -921,6 +921,18 @@ static void xs_udp_timer(struct rpc_task *task)
 	xprt_adjust_cwnd(task, -ETIMEDOUT);
 }
 
+/**
+ * xs_set_port - reset the port number in the remote endpoint address
+ * @xprt: generic transport
+ * @port: new port number
+ *
+ */
+static void xs_set_port(struct rpc_xprt *xprt, unsigned short port)
+{
+	dprintk("RPC:      setting port for xprt %p to %u\n", xprt, port);
+	xprt->addr.sin_port = htons(port);
+}
+
 static int xs_bindresvport(struct rpc_xprt *xprt, struct socket *sock)
 {
 	struct sockaddr_in myaddr = {
@@ -1161,6 +1173,7 @@ static struct rpc_xprt_ops xs_udp_ops = {
 	.set_buffer_size	= xs_udp_set_buffer_size,
 	.reserve_xprt		= xprt_reserve_xprt_cong,
 	.release_xprt		= xprt_release_xprt_cong,
+	.set_port		= xs_set_port,
 	.connect		= xs_connect,
 	.buf_alloc		= rpc_malloc,
 	.buf_free		= rpc_free,
@@ -1175,6 +1188,7 @@ static struct rpc_xprt_ops xs_udp_ops = {
 static struct rpc_xprt_ops xs_tcp_ops = {
 	.reserve_xprt		= xprt_reserve_xprt,
 	.release_xprt		= xprt_release_xprt,
+	.set_port		= xs_set_port,
 	.connect		= xs_connect,
 	.buf_alloc		= rpc_malloc,
 	.buf_free		= rpc_free,