NFS: Enable NFSv4 callback server to listen on AF_INET6 sockets

Allow the NFS callback server to listen for requests via an AF_INET6 or
AF_INET socket when IPv6 support is present in the kernel.

Signed-off-by: Chuck Lever <[e-mail]>
Signed-off-by: Trond Myklebust <[e-mail]>

fs/nfs/callback.c

···
 static const int nfs_set_port_min = 0;
 static const int nfs_set_port_max = 65535;
 
+/*
+ * If the kernel has IPv6 support available, always listen for
+ * both AF_INET and AF_INET6 requests.
+ */
+#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
+static const sa_family_t	nfs_callback_family = AF_INET6;
+#else
+static const sa_family_t	nfs_callback_family = AF_INET;
+#endif
+
 static int param_set_port(const char *val, struct kernel_param *kp)
 {
 	char *endp;
···
 	if (nfs_callback_info.users++ || nfs_callback_info.task != NULL)
 		goto out;
 	serv = svc_create(&nfs4_callback_program, NFS4_CALLBACK_BUFSIZE,
-				AF_INET, NULL);
+				nfs_callback_family, NULL);
 	ret = -ENOMEM;
 	if (!serv)
 		goto out_err;
···
 	if (ret <= 0)
 		goto out_err;
 	nfs_callback_tcpport = ret;
-	dprintk("Callback port = 0x%x\n", nfs_callback_tcpport);
+	dprintk("NFS: Callback listener port = %u (af %u)\n",
+			nfs_callback_tcpport, nfs_callback_family);
 
 	nfs_callback_info.rqst = svc_prepare_thread(serv, &serv->sv_pools[0]);
 	if (IS_ERR(nfs_callback_info.rqst)) {
···
 	mutex_unlock(&nfs_callback_mutex);
 	return ret;
 out_err:
-	dprintk("Couldn't create callback socket or server thread; err = %d\n",
-		ret);
+	dprintk("NFS: Couldn't create callback socket or server thread; "
+		"err = %d\n", ret);
 	nfs_callback_info.users--;
 	goto out;
 }