NFS: Make clientaddr= optional

For NFSv4 mounts, the clientaddr= mount option has always been
required.  Now we have rpc_localaddr() in the kernel, which was
modeled after the same logic in the mount.nfs command that constructs
the clientaddr= mount option.  If user space doesn't provide a
clientaddr= mount option, the kernel can now construct its own.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/client.c

@@ -1346,6 +1346,7 @@ int nfs4_init_client(struct nfs_client *clp,
 		     rpc_authflavor_t authflavour,
 		     int noresvport)
 {
+	char buf[INET6_ADDRSTRLEN + 1];
 	int error;
 
 	if (clp->cl_cons_state == NFS_CS_READY) {
@@ -1361,6 +1362,20 @@ int nfs4_init_client(struct nfs_client *clp,
 				      1, noresvport);
 	if (error < 0)
 		goto error;
+
+	/* If no clientaddr= option was specified, find a usable cb address */
+	if (ip_addr == NULL) {
+		struct sockaddr_storage cb_addr;
+		struct sockaddr *sap = (struct sockaddr *)&cb_addr;
+
+		error = rpc_localaddr(clp->cl_rpcclient, sap, sizeof(cb_addr));
+		if (error < 0)
+			goto error;
+		error = rpc_ntop(sap, buf, sizeof(buf));
+		if (error < 0)
+			goto error;
+		ip_addr = (const char *)buf;
+	}
 	strlcpy(clp->cl_ipaddr, ip_addr, sizeof(clp->cl_ipaddr));
 
 	error = nfs_idmap_new(clp);

fs/nfs/super.c

@@ -2557,12 +2557,6 @@ static int nfs4_validate_text_mount_data(void *options,
 		return -EINVAL;
 	}
 
-	if (args->client_address == NULL) {
-		dfprintk(MOUNT,
-			 "NFS4: mount program didn't pass callback address\n");
-		return -EINVAL;
-	}
-
 	return nfs_parse_devname(dev_name,
 				   &args->nfs_server.hostname,
 				   NFS4_MAXNAMLEN,