iptunnel: Allow GRE_KEY for vti interface

The vti interface will use GRE_KEY to match the right policy in kernel. So we
can not return fail when the tunnel is vti.
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>

ip/iptunnel.c

@@ -240,8 +240,9 @@ static int parse_args(int argc, char **argv, int cmd, struct ip_tunnel_parm *p)
 		}
 	}
 
-	if (p->iph.protocol == IPPROTO_IPIP || p->iph.protocol == IPPROTO_IPV6) {
-		if ((p->i_flags & GRE_KEY) || (p->o_flags & GRE_KEY)) {
+	if ((p->i_flags & GRE_KEY) || (p->o_flags & GRE_KEY)) {
+		if (!(p->i_flags & VTI_ISVTI) &&
+		    (p->iph.protocol != IPPROTO_GRE)) {
 			fprintf(stderr, "Keys are not allowed with ipip and sit tunnels\n");
 			return -1;
 		}