IPT_PRE="iptables  -t mangle -A PREROUTING  -m layer7 --l7proto"
IPT_POST="iptables -t mangle -A POSTROUTING -m layer7 --l7proto"
$IPT_PRE  fasttrack -j MARK --set-mark 13
$IPT_POST fasttrack -j MARK --set-mark 13
[...]
iptables -A FORWARD -m mark --mark 13 -j DROP
iptables -A INPUT   -m mark --mark 13 -j DROP