rtm_msg2
int rtm_msg2(int, int, struct rt_addrinfo *, caddr_t,
size = rtm_msg2(RTM_GET, RTM_VERSION, &info, NULL, w);
len = rtm_msg2(RTM_IFINFO, RTM_VERSION, &info, 0, w);
len = rtm_msg2(RTM_NEWADDR, RTM_VERSION, &info, 0, w);
len = rtm_msg2(type, RTM_VERSION, &info, NULL, NULL);
rtm_msg2(type, RTM_VERSION, &info, (caddr_t)rtm, NULL);