Openswan, iptables (fiaif) and 2.6.16 kernel

Openswan, iptables (fiaif) and 2.6.16 kernel

[Laurent CARON]

Hi,

I'm running an openswan gateway for quite a long time now.

I have used 2.4.X and 2.6.X kernels without any problem until i decided 
to upgrade to 2.6.16 kernel.

Summary of problem:

Under 2.6.15 everything is fine

Under 2.6.16 my tunnels establish well, but i can't even ping a single 
computer located on the other end of the tunnel when the firewall is up.
Disabling the firewall solves the problem (but is not an option for me).

$ cat ip_conntrack | grep 192.168.10
icmp     1 8 src=192.168.0.192 dst=192.168.10.1 type=8 code=0 id=793 
packets=4 bytes=116 [UNREPLIED] src=192.168.10.1 dst=XXX.XXX.XXX.XXX 
type=0 code=0 id=793 packets=0 bytes=0 mark=0 use=1

192.168.0.0/24 is my lan subnet (natted so that lan computers can access 
the internet through the public ip address)
192.168.0.192 is a workstation on my lan
192.168.10.0/24 is the other subnet
XXX.XXX.XXX.XXX is my public ip address


If i disable the nat of 192.168.0.0/24, i can ping the other end.

Re-enabling the nat however disables the ability to ping the other end.

Seems iptables is trying to nat packets the wrong way :$, or that I 
missed a major change in 2.6.16.

Do anyone have any clue about this weiredness?

Thanks

Laurent
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Re: Openswan, iptables (fiaif) and 2.6.16 kernel

[Patrick McHardy]

Laurent CARON wrote:
> Hi,
> 
> I'm running an openswan gateway for quite a long time now.
> 
> I have used 2.4.X and 2.6.X kernels without any problem until i decided
> to upgrade to 2.6.16 kernel.
> 
> Summary of problem:
> 
> Under 2.6.15 everything is fine
> 
> Under 2.6.16 my tunnels establish well, but i can't even ping a single
> computer located on the other end of the tunnel when the firewall is up.
> Disabling the firewall solves the problem (but is not an option for me).
> 
> $ cat ip_conntrack | grep 192.168.10
> icmp     1 8 src=192.168.0.192 dst=192.168.10.1 type=8 code=0 id=793
> packets=4 bytes=116 [UNREPLIED] src=192.168.10.1 dst=XXX.XXX.XXX.XXX
> type=0 code=0 id=793 packets=0 bytes=0 mark=0 use=1
> 
> 192.168.0.0/24 is my lan subnet (natted so that lan computers can access
> the internet through the public ip address)
> 192.168.0.192 is a workstation on my lan
> 192.168.10.0/24 is the other subnet
> XXX.XXX.XXX.XXX is my public ip address
> 
> 
> If i disable the nat of 192.168.0.0/24, i can ping the other end.
> 
> Re-enabling the nat however disables the ability to ping the other end.
> 
> Seems iptables is trying to nat packets the wrong way :$, or that I
> missed a major change in 2.6.16.

2.6.16 does a second policy lookup after SNAT, you probably SNAT
the packets to an address that doesn't match the policy anymore.

Re: Openswan, iptables (fiaif) and 2.6.16 kernel

[Andrey Borzenkov]

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> 2.6.16 does a second policy lookup after SNAT, you probably SNAT
> the packets to an address that doesn't match the policy anymore.

Could you please give pointers where is it documented? All documents I have 
suggest that SNAT is done as the last step, so any rule should use real and 
not SNAT'ed address.

Thank you

Andrey
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