Function getifaddrs

tools/compat/getifaddrs.c:81–341

#define MAX_SYSCTL_TRY 5

int
getifaddrs(struct ifaddrs **pif)
{
	int icnt = 1;
	int dcnt = 0;
	int ncnt = 0;
	int ntry = 0;
	int mib[6];
	size_t needed;
	char *buf;
	char *next;
	struct ifaddrs *cif;
	char *p, *p0;
	struct rt_msghdr *rtm;
	struct if_msghdrl *ifm;
	struct ifa_msghdrl *ifam;
	struct sockaddr_dl *dl;
	struct sockaddr *sa;
	struct ifaddrs *ifa, *ift;
	struct if_data *if_data;
	u_short idx = 0;
	int i;
	size_t len, alen;
	char *data;
	char *names;

	mib[0] = CTL_NET;
	mib[1] = PF_ROUTE;
	mib[2] = 0;             /* protocol */
	mib[3] = 0;             /* wildcard address family */
	mib[4] = NET_RT_IFLISTL;/* extra fields for extensible msghdr structs */
	mib[5] = 0;             /* no flags */
	do {
		/*
		 * We'll try to get addresses several times in case that
		 * the number of addresses is unexpectedly increased during
		 * the two sysctl calls.  This should rarely happen, but we'll
		 * try to do our best for applications that assume success of
		 * this library (which should usually be the case).
		 * Portability note: since FreeBSD does not add margin of
		 * memory at the first sysctl, the possibility of failure on
		 * the second sysctl call is a bit higher.
		 */

		if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0)
			return (-1);
		if ((buf = malloc(needed)) == NULL)
			return (-1);
		if (sysctl(mib, 6, buf, &needed, NULL, 0) < 0) {
			if (errno != ENOMEM || ++ntry >= MAX_SYSCTL_TRY) {
				free(buf);
				return (-1);
			}
			free(buf);
			buf = NULL;
		} 
	} while (buf == NULL);