__ip_tun_set_dst
tun_dst = __ip_tun_set_dst(key.enc_ipv4.src, key.enc_ipv4.dst,
tun_dst = __ip_tun_set_dst(iph->saddr, iph->daddr, iph->tos, iph->ttl,
tunnel_dst = __ip_tun_set_dst(0, 0, 0, 0, 0, flags,
metadata = __ip_tun_set_dst(0, 0, 0, 0, 0, flags, key, 0);
metadata = __ip_tun_set_dst(saddr, daddr, tos, ttl,