NFS: Support raw IPv6 address hostnames during NFS mount operation

Traditionally the mount command has looked for a ":" to separate the
server's hostname from the export path in the mounted on device name,
like this:

	mount server:/export /mounted/on/dir

The server's hostname is "server" and the export path is "/export".

You can also substitute a specific IPv4 network address for the server
hostname, like this:

	mount 192.168.0.55:/export /mounted/on/dir

Raw IPv6 addresses present a problem, however, because they look
something like this:

	fe80::200:5aff:fe00:30b

Note the use of colons.

To get around the presence of colons, copy the Solaris convention used for
mounting IPv6 servers by address: wrap a raw IPv6 address with square
brackets.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 82 insertions, 8 deletions

diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index c4ee8b3a27c1..ea4abd266a7a 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -1195,14 +1195,9 @@ static int nfs_try_mount(struct nfs_parsed_mount_data *args,
         return status;
 }
 
-/*
- * Split "dev_name" into "hostname:export_path".
- *
- * Note: caller frees hostname and export path, even on error.
- */
-static int nfs_parse_devname(const char *dev_name,
-                             char **hostname, size_t maxnamlen,
-                             char **export_path, size_t maxpathlen)
+static int nfs_parse_simple_hostname(const char *dev_name,
+                                     char **hostname, size_t maxnamlen,
+                                     char **export_path, size_t maxpathlen)
 {
         size_t len;
         char *colon, *comma;
@@ -1257,6 +1252,85 @@ out_path:
 }
 
 /*
+ * Hostname has square brackets around it because it contains one or
+ * more colons.  We look for the first closing square bracket, and a
+ * colon must follow it.
+ */
+static int nfs_parse_protected_hostname(const char *dev_name,
+                                        char **hostname, size_t maxnamlen,
+                                        char **export_path, size_t maxpathlen)
+{
+        size_t len;
+        char *start, *end;
+
+        start = (char *)(dev_name + 1);
+
+        end = strchr(start, ']');
+        if (end == NULL)
+                goto out_bad_devname;
+        if (*(end + 1) != ':')
+                goto out_bad_devname;
+
+        len = end - start;
+        if (len > maxnamlen)
+                goto out_hostname;
+
+        /* N.B. caller will free nfs_server.hostname in all cases */
+        *hostname = kstrndup(start, len, GFP_KERNEL);
+        if (*hostname == NULL)
+                goto out_nomem;
+
+        end += 2;
+        len = strlen(end);
+        if (len > maxpathlen)
+                goto out_path;
+        *export_path = kstrndup(end, len, GFP_KERNEL);
+        if (!*export_path)
+                goto out_nomem;
+
+        return 0;
+
+out_bad_devname:
+        dfprintk(MOUNT, "NFS: device name not in host:path format\n");
+        return -EINVAL;
+
+out_nomem:
+        dfprintk(MOUNT, "NFS: not enough memory to parse device name\n");
+        return -ENOMEM;
+
+out_hostname:
+        dfprintk(MOUNT, "NFS: server hostname too long\n");
+        return -ENAMETOOLONG;
+
+out_path:
+        dfprintk(MOUNT, "NFS: export pathname too long\n");
+        return -ENAMETOOLONG;
+}
+
+/*
+ * Split "dev_name" into "hostname:export_path".
+ *
+ * The leftmost colon demarks the split between the server's hostname
+ * and the export path.  If the hostname starts with a left square
+ * bracket, then it may contain colons.
+ *
+ * Note: caller frees hostname and export path, even on error.
+ */
+static int nfs_parse_devname(const char *dev_name,
+                             char **hostname, size_t maxnamlen,
+                             char **export_path, size_t maxpathlen)
+{
+        if (*dev_name == '[')
+                return nfs_parse_protected_hostname(dev_name,
+                                                    hostname, maxnamlen,
+                                                    export_path, maxpathlen);
+
+        return nfs_parse_simple_hostname(dev_name,
+                                         hostname, maxnamlen,
+                                         export_path, maxpathlen);
+}
+
+/*
  * Validate the NFS2/NFS3 mount data
  * - fills in the mount root filehandle
  *