RE: [RFC PATCH 0/4] VRF support in FIB library

Morten Brørup
2026-03-23T09:01:50Z

> From: Stephen Hemminger [mailto:stephen@networkplumber.org]
> Sent: Sunday, 22 March 2026 17.44
>
> On Sun, 22 Mar 2026 15:42:11 +0000
> Vladimir Medvedkin <vladimir.medvedkin@intel.com> wrote:
>
> > This series adds multi-VRF support to both IPv4 and IPv6 FIB paths by
> > allowing a single FIB instance to host multiple isolated routing
> domains.
> >
> > Currently FIB instance represents one routing instance. For workloads
> that
> > need multiple VRFs, the only option is to create multiple FIB
> objects. In a
> > burst oriented datapath, packets in the same batch can belong to
> different VRFs, so
> > the application either does per-packet lookup in different FIB
> instances or
> > regroups packets by VRF before lookup. Both approaches are expensive.
> >
> > To remove that cost, this series keeps all VRFs inside one FIB
> instance and
> > extends lookup input with per-packet VRF IDs.
> >
> > The design follows the existing fast-path structure for both
> families. IPv4 and
> > IPv6 use multi-ary trees with a 2^24 associativity on a first level
> (tbl24). The
> > first-level table scales per configured VRF. This increases memory
> usage, but
> > keeps performance and lookup complexity on par with non-VRF
> implementation.
> >

I noticed the suggested API uses separate parameters for the VRF and IP.
How about using one parameter, a structure containing the {VRF, IP} tuple, instead?
I'm mainly thinking about the bulk operations, where passing one array seems more intuitive than passing two arrays.

>
>
> Not sure at all if this the right way to do VRF.
> There are multiple ways to do VRF, the Linux way, the Cisco way, ...

I think a shared table operating on the {VRF, IP} tuple makes sense.
If a table instance per VRF is preferred, that is still supported.

Can you elaborate what Linux and Cisco does differently than this?

>
>
>
> This needs way more documentation and also an example.

+1

> Like an option to l3fwd. And also an implementation in testpmd.