Re: [RFC PATCH net-next 0/3] ethtool: Add link down reason reporting

On Wed, 21 Jun 2017 16:04:43 +0300
Gal Pressman [off-list ref] wrote:

Hi All,

Currently, drivers can only tell whether the link is up/down through
ETHTOOL_GLINK callback, but no additional information is given in case
of link down/failure.

This series provides an infrastructure to ethtool that allows 
netdevice drivers to hint the user with the reason why the link is down,
in order to ease the debug process.

In addition two more mlx5 patches to demonstrate the usage.

Reasons are separated to two types, generic and vendor specific.
Drivers can reply with a generic reason using the predefined enums 
(and the ones that will be added in the future), which will be
translated to strings by the userspace ethtool.
In case of a vendor specific reason, drivers can reply with
ETHTOOL_VENDOR_SPECIFIC reason, in this case the vendor_reason field
should be filled with a vendor specific status code which will be parsed
by the vendor specific userspace parser if one is available.

This kind of information can save system administrators precious time,
which will not be wasted trying to understand why the link won't go up.
    
For example, when the cable is unplugged:
    $ ethtool ethXX
    ...
    Link detected: no (Cable unplugged)

Thanks,
Gal.

Ethtool doesn't work well as a monitoring/event interface.
Maybe this would be better as extended information with the  netlink UP/DOW event.