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

From: Stephen Hemminger <[email-masked]>
Date: Fri, 4 Sep 2020 15:44:06 -0700

On Fri, 4 Sep 2020 09:15:20 +0000
Henrik Bjoernlund <[email-masked]> 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  <[email-masked]>
> Signed-off-by: Henrik Bjoernlund  <[email-masked]>

Could this be done in userspace? It is a control plane protocol.
Could it be done by using eBPF?

Adding more code in bridge impacts a large number of users of Linux distros.
It creates bloat and potential security vulnerabilities.