Re: [PATCH ipsec-next 3/3] xfrm: lwtunnel: add lwtunnel support for xfrm interfaces in collect_md mode

Hi Nicolas,

On Wed, Aug 24, 2022 at 6:21 PM Nicolas Dichtel
[off-list ref] wrote:

Le 23/08/2022 à 17:45, Eyal Birger a écrit :

quoted

Allow specifying the xfrm interface if_id as part of a route metadata
using the lwtunnel infrastructure.

This allows for example using a single xfrm interface in collect_md
mode as the target of multiple routes each specifying a different if_id.

With the appropriate changes to iproute2, considering an xfrm device
ipsec1 in collect_md mode one can for example add a route specifying
an if_id like so:

ip route add <SUBNET> dev ipsec1 encap xfrm if_id 1

It would be nice to be able to specify the link also. It may help to combine
this with vrf. Something like
ip route add <SUBNET> dev ipsec1 encap xfrm if_id 1 dev eth0

I think I understand how this would work on xmit - if you mean adding link
to the metadata and using it to set fl.flowi_oif in xfrmi_xmit() - in which
case the link would be used in the underlying lookup such that routes in
a vrf could specify a device which is part of the vrf for egress.

On RX we could assign the link in the metadata in xfrmi_rcv_cb() to the original
skb->dev. I suspect this would be aligned with the link device, but any input
you may have on this would be useful.

Eyal.