- char buf[sizeof(struct rt_msghdr) + (sizeof(struct sockaddr_in))];
- int status;
- int s, n;
- struct rt_msghdr *rtm;
- struct sockaddr_in *sin;
- int msglen = sizeof(*rtm) + (sizeof(*sin));
- char *cp;
- char msg[2048];
-
- rtm = (struct rt_msghdr *)buf;
- memset(rtm, 0, msglen);
- rtm->rtm_msglen = msglen;
- rtm->rtm_version = RTM_VERSION;
- rtm->rtm_type = RTM_GET;
- rtm->rtm_addrs = RTA_DST;
- /* rtm->rtm_addrs, rtm_flags should be set on output */
-
- sin = (struct sockaddr_in *)((u_char *)rtm + sizeof(*rtm));
- sin->sin_len = sizeof(*sin);
- sin->sin_family = AF_INET;
- sin->sin_addr.s_addr = addr;
-
- status = 0;
-
- if ((s = socket(PF_ROUTE, SOCK_RAW, 0)) < 0)
- return -1;
- if (write(s, (char *)rtm, msglen) != msglen) {
- close(s);
- return status == ESRCH? 0: -1;
- }
-
- n = read(s, msg, 2048);
- close(s);
- if (n <= 0)
- return -1;
-
- rtm = (struct rt_msghdr *) msg;
- if (rtm->rtm_version != RTM_VERSION)
- return -1;
-
- /* here we try to work out if the route is through our own interface */
- cp = (char *)(rtm + 1);
- if (rtm->rtm_addrs & RTA_DST) {
- struct sockaddr *sa = (struct sockaddr *) cp;
- cp = (char *)(((unsigned long)cp + sa->sa_len
- + sizeof(long) - 1) & ~(sizeof(long) - 1));
- }
- if (rtm->rtm_addrs & RTA_GATEWAY) {
- sin = (struct sockaddr_in *) cp;
- if (sin->sin_addr.s_addr == ifaddrs[0]
- || sin->sin_addr.s_addr == ifaddrs[1])
- return 0; /* route is through our interface */
- }
-
- return 1;