Re: Matching DNAT'd packets

[Graham Murray]

Philip Prindeville <philipp_subx@xxxxxxxxxxxxxxxxxxxxx> writes:

> I've got the following scenario:
>
> iptables -t nat -A PREROUTING -i $EXTIF -p tcp --dport 8080 -j DNAT --to-destination :80
>
>
> but later in the INPUT chain, I'd like to be able to distinguish between
> a packet that came in directly to port 80 (which I'd reject) versus a
> packet that came in to a different port (like 8080 above) and was
> remapped... which I'd like to accept.
>
> Is there a test to available in INPUT (and FORWARD) see if the packet
> had been rewritten in the PREROUTING chain?

You could try using the mangle table

iptables -t mangle -A PREROUTING -p tcp --dport 8080 -j MARK --set-mark 1

iptables -A INPUT -m mark --mark 1 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP

--
To unsubscribe from this list: send the line "unsubscribe linux-net" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html