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Server with DHCP (iface eth0 172.5.1.1/24) gives internet via openvpn tunnel(iface tun0 10.8.1.6) to lan clients. I need to mark tcp connections from exact lan client, for example 172.5.1.123

iptables -I FORWARD -m conntrack --ctorigsrc 172.5.1.123 --ctproto tcp -j CONNMARK --set-mark 123

While executing on server 172.5.1.1 command conntrack -L --mark 123 i can see all tcp connections from source 172.5.1.123

The question is how to catch connection markers from source ip 172.5.1.123 on vpn server's tunnel interface 10.8.1.1 ?

h3llflee7
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1 Answers1

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Use iptables mark to match it.

iptables -I FORWARD -m conntrack --ctorigsrc 172.5.1.123 --ctproto tcp -j MARK --set-mark 123

iptables -A PREROUTING -t mangle -m mark --mark 123 -j LOG