Re: [PATCH RFC 0/7] net: bridge: cfm: Add support for Connectivity Fault Management(CFM)

[Horatiu Vultur]

The 09/04/2020 15:44, Stephen Hemminger wrote:
> 
> On Fri, 4 Sep 2020 09:15:20 +0000
> Henrik Bjoernlund <henrik.bjoernlund@xxxxxxxxxxxxx> wrote:
> 
> > Connectivity Fault Management (CFM) is defined in 802.1Q section 12.14.
> >
> > Connectivity Fault Management (CFM) comprises capabilities for
> > detecting, verifying, and isolating connectivity failures in
> > Virtual Bridged Networks. These capabilities can be used in
> > networks operated by multiple independent organizations, each
> > with restricted management access to each other’s equipment.
> >
> > CFM functions are partitioned as follows:
> >     — Path discovery
> >     — Fault detection
> >     — Fault verification and isolation
> >     — Fault notification
> >     — Fault recovery
> >
> > The primary CFM protocol shims are called Maintenance Points (MPs).
> > A MP can be either a MEP or a MHF.
> > The MEP:
> >     -It is the Maintenance association End Point
> >      described in 802.1Q section 19.2.
> >     -It is created on a specific level (1-7) and is assuring
> >      that no CFM frames are passing through this MEP on lower levels.
> >     -It initiates and terminates/validates CFM frames on its level.
> >     -It can only exist on a port that is related to a bridge.
> > The MHF:
> >     -It is the Maintenance Domain Intermediate Point
> >      (MIP) Half Function (MHF) described in 802.1Q section 19.3.
> >     -It is created on a specific level (1-7).
> >     -It is extracting/injecting certain CFM frame on this level.
> >     -It can only exist on a port that is related to a bridge.
> >     -Currently not supported.
> >
> > There are defined the following CFM protocol functions:
> >     -Continuity Check
> >     -Loopback. Currently not supported.
> >     -Linktrace. Currently not supported.
> >
> > This CFM component supports create/delete of MEP instances and
> > configuration of the different CFM protocols. Also status information
> > can be fetched and delivered through notification due to defect status
> > change.
> >
> > The user interacts with CFM using the 'cfm' user space client program, the
> > client talks with the kernel using netlink. The kernel will try to offload
> > the requests to the HW via switchdev API (not implemented yet).
> >
> > Any notification emitted by CFM from the kernel can be monitored in user
> > space by starting 'cfm_server' program.
> >
> > Currently this 'cfm' and 'cfm_server' programs are standalone placed in a
> > cfm repository https://github.com/microchip-ung/cfm but it is considered
> > to integrate this into 'iproute2'.
> >
> > Reviewed-by: Horatiu Vultur  <horatiu.vultur@xxxxxxxxxxxxx>
> > Signed-off-by: Henrik Bjoernlund  <henrik.bjoernlund@xxxxxxxxxxxxx>

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.

-- 
/Horatiu