fixes '_' in interface names bug (iptables)
fixes '+' in interface names bug (iptables-save)
diff --git a/ip6tables.c b/ip6tables.c
index ad2fc80..123d6a4 100644
--- a/ip6tables.c
+++ b/ip6tables.c
@@ -745,7 +745,7 @@
 		memset(mask + vialen + 1, 0, IFNAMSIZ - vialen - 1);
 	}
 	for (i = 0; vianame[i]; i++) {
-		if (!isalnum(vianame[i])) {
+		if (!isalnum(vianame[i]) && vianame[i] != '_') {
 			printf("Warning: wierd character in interface"
 			       " `%s' (No aliases, :, ! or *).\n",
 			       vianame);