Re: Matching DNAT'd packets

[Pascal Hambourg]

Hello,

Philip Prindeville a écrit :
> 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.

May I ask why ?

> Is there a test to available in INPUT (and FORWARD) see if the packet
> had been rewritten in the PREROUTING chain?

You might try the '-m conntrack' match and its '--ctstate DNAT' option. 
Not sure it works when only remapping the port, though. Otherwise you 
can MARK packets in mangle/PREROUTING before they are remapped and 
accept or drop them after.
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