l2tp_proxy_auth_id_print(netdissect_options *ndo, const u_char *dat)
{
	const uint16_t *ptr = (const uint16_t *)dat;

	ND_PRINT((ndo, "%u", EXTRACT_16BITS(ptr) & L2TP_PROXY_AUTH_ID_MASK));
}
The software reads data past the end, or before the beginning, of the intended buffer.