Subject: Re: [RFC PATCH net-next 00/15] Simplify IPv4 route offload API

From: Ido Schimmel <[email-masked]>
Date: Thu, 3 Oct 2019 08:18:32 +0300

On Wed, Oct 02, 2019 at 08:17:59PM +0200, Jiri Pirko wrote:
> Wed, Oct 02, 2019 at 10:40:48AM CEST, [email-masked] wrote:
> >From: Ido Schimmel <[email-masked]>
> >
> >Today, whenever an IPv4 route is added or deleted a notification is sent
> >in the FIB notification chain and it is up to offload drivers to decide
> >if the route should be programmed to the hardware or not. This is not an
> >easy task as in hardware routes are keyed by {prefix, prefix length,
> >table id}, whereas the kernel can store multiple such routes that only
> >differ in metric / TOS / nexthop info.
> >
> >This series makes sure that only routes that are actually used in the
> >data path are notified to offload drivers. This greatly simplifies the
> >work these drivers need to do, as they are now only concerned with
> >programming the hardware and do not need to replicate the IPv4 route
> >insertion logic and store multiple identical routes.
> >
> >The route that is notified is the first FIB alias in the FIB node with
> >the given {prefix, prefix length, table ID}. In case the route is
> >deleted and there is another route with the same key, a replace
> >notification is emitted. Otherwise, a delete notification is emitted.
> >
> >The above means that in the case of multiple routes with the same key,
> >but different TOS, only the route with the highest TOS is notified.
> >While the kernel can route a packet based on its TOS, this is not
> >supported by any hardware devices I'm familiar with. Moreover, this is
> >not supported by IPv6 nor by BIRD/FRR from what I could see. Offload
> >drivers should therefore use the presence of a non-zero TOS as an
> >indication to trap packets matching the route and let the kernel route
> >them instead. mlxsw has been doing it for the past two years.
> >
> >The series also adds an "in hardware" indication to routes, in addition
> 
> I think this might be a separate patchset. I mean patch "ipv4: Replace
> route in list before notifying" and above.

OK. I mainly wanted to have it together in order to submit the tests
with the patchset itself. I can split it into two.