MRT_ADD_MFC
if (setsockopt(s, IPPROTO_IP, MRT_ADD_MFC, &mfc, sizeof(mfc)) == -1)
case MRT_ADD_MFC:
case MRT_ADD_MFC:
if (setsockopt(fd, IPPROTO_IP, MRT_ADD_MFC, &mc, sizeof(mc))
if (setsockopt(igmp_socket, IPPROTO_IP, MRT_ADD_MFC,