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

[Paul Wouters]

On Wed, 29 Jul 2020, Wolfgang Nothdurft wrote:

> 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.

AFAIK, if_id 0 means the same as "no if_id mark". So it cannot be used.

>> and also to avoid confusion from klips.

That was a reason too, but as Wolfgang points out, perhaps the wrong
consideration to have made.

> 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 10.0.12.2 fwmark 0x1 lookup 50
>
> With fwmark 0x0 all unmarked traffic to the destination would go through the base interface instead of the ipsec interface.

I thought fwmark and if_id were different type of marks?

> 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.

That is not a patch we could easilly carry. And as an option it is a bit
confusing. How about mapping ipsec0 to max(if_id) - 1  ?

> 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.

I don't think if_id marks are related to fwmarks ?

Paul