net/9p: enable 9p to work in non-default network namespace

Teach 9p filesystem to work in container with non-default network namespace.
(Note: I also patched the unix domain socket code but don't have a test case
for that.  It's the same fix, I just don't have a server for it...)

To test, run diod server (http://code.google.com/p/diod):
  diod -n -f -L stderr -l 172.23.255.1:9999 -c /dev/null -e /root
and then mount like so:
  mount -t 9p -o port=9999,aname=/root,version=9p2000.L 172.23.255.1 /mnt

A container test environment is described at http://landley.net/lxcSigned-off-by: Rob Landley <rob@landley.net>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

net/9p/trans_fd.c

@@ -916,8 +916,8 @@ p9_fd_create_tcp(struct p9_client *client, const char *addr, char *args)
 	sin_server.sin_family = AF_INET;
 	sin_server.sin_addr.s_addr = in_aton(addr);
 	sin_server.sin_port = htons(opts.port);
-	err = sock_create_kern(PF_INET, SOCK_STREAM, IPPROTO_TCP, &csocket);
-
+	err = __sock_create(read_pnet(&current->nsproxy->net_ns), PF_INET,
+			    SOCK_STREAM, IPPROTO_TCP, &csocket, 1);
 	if (err) {
 		P9_EPRINTK(KERN_ERR, "p9_trans_tcp: problem creating socket\n");
 		return err;
@@ -954,7 +954,8 @@ p9_fd_create_unix(struct p9_client *client, const char *addr, char *args)
 
 	sun_server.sun_family = PF_UNIX;
 	strcpy(sun_server.sun_path, addr);
-	err = sock_create_kern(PF_UNIX, SOCK_STREAM, 0, &csocket);
+	err = __sock_create(read_pnet(&current->nsproxy->net_ns), PF_UNIX,
+			    SOCK_STREAM, 0, &csocket, 1);
 	if (err < 0) {
 		P9_EPRINTK(KERN_ERR, "p9_trans_unix: problem creating socket\n");
 		return err;