Re: [BUG?] bonding, slave selection, carrier loss, etc.

On Fri, 2012-02-10 at 17:53 -0800, Jay Vosburgh wrote:

Chris Friesen [off-list ref] wrote:

quoted

I'm resurrecting an ancient discussion I had with Jay, because I think
the issue described below is still present and the code he talked about
submitting to close it doesn't appear to have ever gone in.

	Yah, I never got it to work quite right; I don't remember
exactly why.

quoted

Basically in active/backup mode with mii monitoring there is a window
between the active slave device losing carrier and calling
netif_carrier_off() and the miimon code actually detecting the loss of
the carrier and selecting a new active slave.

The best solution would be for bonding to just register for notification
of the link going down.  Presumably most drivers should be doing that
properly by now, and for devices that get interrupt-driven notification
of link status changes this would allow the bonding code to react much
quicker.

	A quick look at some drivers shows that at least acenic still
doesn't do netif_carrier_off, so converting entirely to a notifier-based
failover mechanism would break drivers that work today.

[...]

It might be worth having some sort of feature flag (in priv_flags) that
indicates whether the driver updates the link state.  Alternately,
disable polling of a device once you see a notification.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.