+int lcc_server_set_interface (lcc_server_t *srv, char const *interface) /* {{{ */
+{
+ int if_index;
+ int status;
+
+ if ((srv == NULL) || (interface == NULL))
+ return (EINVAL);
+
+ if_index = if_nametoindex (interface);
+ if (if_index == 0)
+ return (ENOENT);
+
+ /* IPv4 multicast */
+ if (srv->sa->sa_family == AF_INET)
+ {
+ struct sockaddr_in *addr = (struct sockaddr_in *) srv->sa;
+
+ if (IN_MULTICAST (ntohl (addr->sin_addr.s_addr)))
+ {
+#if HAVE_STRUCT_IP_MREQN_IMR_IFINDEX
+ /* If possible, use the "ip_mreqn" structure which has
+ * an "interface index" member. Using the interface
+ * index is preferred here, because of its similarity
+ * to the way IPv6 handles this. Unfortunately, it
+ * appears not to be portable. */
+ struct ip_mreqn mreq;
+
+ memset (&mreq, 0, sizeof (mreq));
+ mreq.imr_multiaddr.s_addr = addr->sin_addr.s_addr;
+ mreq.imr_address.s_addr = ntohl (INADDR_ANY);
+ mreq.imr_ifindex = if_index;
+#else
+ struct ip_mreq mreq;
+
+ memset (&mreq, 0, sizeof (mreq));
+ mreq.imr_multiaddr.s_addr = addr->sin_addr.s_addr;
+ mreq.imr_interface.s_addr = ntohl (INADDR_ANY);
+#endif
+
+ status = setsockopt (srv->fd, IPPROTO_IP, IP_MULTICAST_IF,
+ &mreq, sizeof (mreq));
+ if (status != 0)
+ return (status);
+
+ return (0);
+ }
+ }
+
+ /* IPv6 multicast */
+ if (srv->sa->sa_family == AF_INET6)
+ {
+ struct sockaddr_in6 *addr = (struct sockaddr_in6 *) srv->sa;
+
+ if (IN6_IS_ADDR_MULTICAST (&addr->sin6_addr))
+ {
+ status = setsockopt (srv->fd, IPPROTO_IPV6, IPV6_MULTICAST_IF,
+ &if_index, sizeof (if_index));
+ if (status != 0)
+ return (status);
+
+ return (0);
+ }
+ }
+
+ /* else: Not a multicast interface. */
+#if defined(SO_BINDTODEVICE)
+ status = setsockopt (srv->fd, SOL_SOCKET, SO_BINDTODEVICE,
+ interface, strlen (interface) + 1);
+ if (status != 0)
+ return (-1);
+#endif
+
+ return (0);
+} /* }}} int lcc_server_set_interface */
+