nfsd: add support for NFSv4 callbacks over IPv6

The framework to add this is all in place. Now, add the code to allow
support for establishing a callback channel on an IPv6 socket.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Acked-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

fs/nfsd/nfs4state.c

@@ -901,17 +901,24 @@ static void
 gen_callback(struct nfs4_client *clp, struct nfsd4_setclientid *se)
 {
 	struct nfs4_cb_conn *cb = &clp->cl_cb_conn;
-
-	/* Currently, we only support tcp for the callback channel */
-	if ((se->se_callback_netid_len != 3) || memcmp((char *)se->se_callback_netid_val, "tcp", 3))
+	unsigned short expected_family;
+
+	/* Currently, we only support tcp and tcp6 for the callback channel */
+	if (se->se_callback_netid_len == 3 &&
+	    !memcmp(se->se_callback_netid_val, "tcp", 3))
+		expected_family = AF_INET;
+	else if (se->se_callback_netid_len == 4 &&
+		 !memcmp(se->se_callback_netid_val, "tcp6", 4))
+		expected_family = AF_INET6;
+	else
 		goto out_err;
 
 	cb->cb_addrlen = rpc_uaddr2sockaddr(se->se_callback_addr_val,
 					    se->se_callback_addr_len,
 					    (struct sockaddr *) &cb->cb_addr,
 					    sizeof(cb->cb_addr));
 
-	if (!cb->cb_addrlen || cb->cb_addr.ss_family != AF_INET)
+	if (!cb->cb_addrlen || cb->cb_addr.ss_family != expected_family)
 		goto out_err;
 
 	cb->cb_minorversion = 0;