Function ifconf

freebsd/net/if.c:3199–3298

* Return interface configuration * of system. List may be used * in later ioctl's (above) to get * other information. */ ARGSUSED*/

 */
/*ARGSUSED*/
static int
ifconf(u_long cmd, caddr_t data)
{
	struct ifconf *ifc = (struct ifconf *)data;
	struct ifnet *ifp;
	struct ifaddr *ifa;
	struct ifreq ifr;
	struct sbuf *sb;
	int error, full = 0, valid_len, max_len;

	/* Limit initial buffer size to maxphys to avoid DoS from userspace. */
	max_len = maxphys - 1;

	/* Prevent hostile input from being able to crash the system */
	if (ifc->ifc_len <= 0)
		return (EINVAL);

again:
	if (ifc->ifc_len <= max_len) {
		max_len = ifc->ifc_len;
		full = 1;
	}
	sb = sbuf_new(NULL, NULL, max_len + 1, SBUF_FIXEDLEN);
	max_len = 0;
	valid_len = 0;

	IFNET_RLOCK();
	CK_STAILQ_FOREACH(ifp, &V_ifnet, if_link) {
		struct epoch_tracker et;
		int addrs;

		/*
		 * Zero the ifr to make sure we don't disclose the contents
		 * of the stack.
		 */
		memset(&ifr, 0, sizeof(ifr));

		if (strlcpy(ifr.ifr_name, ifp->if_xname, sizeof(ifr.ifr_name))
		    >= sizeof(ifr.ifr_name)) {
			sbuf_delete(sb);
			IFNET_RUNLOCK();
			return (ENAMETOOLONG);
		}

		addrs = 0;
		NET_EPOCH_ENTER(et);
		CK_STAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
			struct sockaddr *sa = ifa->ifa_addr;

			if (prison_if(curthread->td_ucred, sa) != 0)
				continue;
			addrs++;
			if (sa->sa_len <= sizeof(*sa)) {
				if (sa->sa_len < sizeof(*sa)) {
					memset(&ifr.ifr_ifru.ifru_addr, 0,
					    sizeof(ifr.ifr_ifru.ifru_addr));
					memcpy(&ifr.ifr_ifru.ifru_addr, sa,
					    sa->sa_len);