https://bugs.gentoo.org/471142

snipped from fedora

# dhclient -6: bind socket to interface (#1001742)
# (Submitted to dhcp-bugs@isc.org - [ISC-Bugs #34784])

--- a/common/socket.c
+++ b/common/socket.c
@@ -266,7 +266,7 @@
 
 #if defined(SO_BINDTODEVICE)
 	/* Bind this socket to this interface. */
-	if ((local_family != AF_INET6) && (info->ifp != NULL) &&
+	if (((do_multicast == 0)||(*do_multicast == 0)) && (info->ifp != NULL) &&
 	    setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE,
 		       (char *)(info -> ifp), sizeof(*(info -> ifp))) < 0) {
 		log_fatal("Can't set SO_BINDTODEVICE on dhcp socket for"