IP_DEV_NAME
ipfd = open(IP_DEV_NAME, O_RDWR | O_NONBLOCK, 0);
error("Couldn't open IP device (%s): %m", IP_DEV_NAME);
ipfd = open(IP_DEV_NAME, O_RDWR);
msglog("open " IP_DEV_NAME ": %s", rip_strerror(errno));
myname, IP_DEV_NAME, strerror(errno));