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SubjectRe: [PATCH RFC 0/7] net: bridge: cfm: Add support for Connectivity Fault Management(CFM)
On Sun, 2020-09-06 at 20:21 +0200, Horatiu Vultur wrote:
> The 09/04/2020 15:44, Stephen Hemminger wrote:
> > On Fri, 4 Sep 2020 09:15:20 +0000
> > Henrik Bjoernlund <> wrote:
> >
> > > Connectivity Fault Management (CFM) is defined in 802.1Q section 12.14.
> > >
> > >
> > > Currently this 'cfm' and 'cfm_server' programs are standalone placed in a
> > > cfm repository but it is considered
> > > to integrate this into 'iproute2'.
> > >
> > > Reviewed-by: Horatiu Vultur <>
> > > Signed-off-by: Henrik Bjoernlund <>
> Hi Stephen,
> > Could this be done in userspace? It is a control plane protocol.
> > Could it be done by using eBPF?
> I might be able to answer this. We have not considered this approach of
> using eBPF. Because we want actually to push this in HW extending
> switchdev API. I know that this series doesn't cover the switchdev part
> but we posted like this because we wanted to get some feedback from
> community. We had a similar approach for MRP, where we extended the
> bridge and switchdev API, so we tought that is the way to go forward.
> Regarding eBPF, I can't say that it would work or not because I lack
> knowledge in this.
> > Adding more code in bridge impacts a large number of users of Linux distros.
> > It creates bloat and potential security vulnerabilities.

I also had the same initial thought - this really doesn't seem to affect the
bridge in any way, it's only collecting and transmitting information. I get
that you'd like to use the bridge as a passthrough device to switchdev to
program your hw, could you share what would be offloaded more specifically ?

All you do - snooping and blocking these packets can easily be done from user-
space with the help of ebtables, but since we need to have a software
implementation/fallback of anything being offloaded via switchdev we might need
this after all, I'd just prefer to push as much as possible to user-space.

I plan to review the individual patches tomorrow.


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