Re: SNAT before IPSec

[Jorge Davila <davila@nicaraguaopensource.com>]

I'm guessing that you can use the "normal" approach and apply the SNAT rules 
to the outgoing traffic flowing in the ipsec interfaces.

The ipsec encryption algorithm is a kernel space tool and iptables is a user 
space tool to the netfilter kernel module.

All traffic that pass the POSTROUTING chain in the NAT table is leaving the 
firewall box (through a physical interface e.g.:eth0 or through a virtual 
interface e.g.:ipsec0).

Jorge Davila..

On Tue, 5 Jun 2007 15:29:47 +0300
  "noa levy" <noalevy@gmail.com> wrote:
> Hi All,
> 
> I have a setup where I need to SNAT traffic that will be going out via
> an IPSec tunnel. The NAT must take place before the IPSec
> encryption+encapsulation, so I need the packet to first go through
> SNAT and then match an IPSec policy. After being IPSec-ified, I need
> the packets to go through routing again.
> My question:
> SNAT takes place in POST_ROUTING. Can IPSec be applied after that? I
> have read that after IPSec the packet gets injected to LOCAL_OUT
> again, but when does the actual IPSec policy decision take place?
> Won't it happen *before* SNAT? Can I control it?
> 
> Thanks,
> Noa
> 
> 

Jorge Isaac Davila Lopez
Nicaragua Open Source
+505 430 5462
davila@nicaraguaopensource.com