[Swan] ?==?utf-8?q? No ipsec0 device with XFRMi

Wolfgang Nothdurft wolfgang at linogate.de
Wed Jul 29 09:32:58 UTC 2020

Am Dienstag, 28. Juli 2020 20:25 CEST, schrieb Antony Antony <antony at phenome.org>: 
> ipsec-interface=0 would translate to 
> ip link add ipsec0 type xfrm dev enp0s5 if_id 0
> when I started adding xfrmi I wasn't sure xfrm if_id 0 would work properly.
> if_id is a lookup key to find policy and state. I wonder if 0 would mean 
> also a policy with no xfrmi if_id.
> xfrm if_id 0 was confusing to me. I decided ipsec1 to start with. May be 
> time to review it while xfrmi is still expirimental.
> and also to avoid confusion from klips.

 I think the problem with if_id 0 could be the fwmark that is used to route the encrypted packets on the base interface.
 100:    from all to fwmark 0x1 lookup 50 

With fwmark 0x0 all unmarked traffic to the destination would go through the base interface instead of the ipsec interface.

But ipsec-interface=0 for ipsec0 would be very useful. All our customers use ipsec0 for the first ipsec device, so the change from klips to xfrmi would either confusing for them or a technical problem that we have to solve.

At the moment I test patching libreswan to map if_id to device name if_id-1, which works properly.

But the next problem is that we use the lower 24 bit fwmarks for our firewall rule set. The upper 8 bit was reserved for ipsec (saref) long time ago. So the next problem is that actual the fwmark is not configurable and I have also to patch either libreswan or overwork our complete rule set to reserve the lower bits for ipsec devices. 
Maybe a configurable minimal fwmark could be a nice feature.


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