Subject: Re: Question about xfrm by MARK feature

From: Patrick McHardy <[email-masked]>
Date: Wed, 23 Jun 2010 18:15:12 +0200

Gerd v. Egidy wrote:
> Hi Jamal,
>
> while looking through the 2.6.34 changelog I found the xfrm by MARK feature 
> you developed in february. I'm currently working on NAT for ipsec connections 
> and thought your feature might help me.
>
> For example I have 2 different remote networks with the same ip network each 
> and both of them have a tunnel to the same local network. I map their IPs to 
> something different so I can distinguish them in the local network. But after 
> the nat the xfrm code sees two tunnels with exactly the same values. So this 
> can't work.
>
> But if I understood your feature correctly, I can now mark the packets (e.g. 
> in iptables with ... -j MARK --set-mark 1) and have xfrm select the correct 
> ipsec tunnel via the mark. Correct?
>
> But does your feature also set the mark on packets decrypted by xfrm? I need 
> some way to find out from which tunnel the packet came to correctly treat it. 
>   

You should be able to use the policy match to distinguish the tunnels,
f.i. by matching on the tunnel endpoints.