netdev - Re: Toggling link state breaks network connectivity

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Message-ID: <4b6d6e75-2054-d996-c0ec-fedc6fe3b57b@free.fr>
Date:   Tue, 13 Jun 2017 17:32:14 +0200
From:   Mason <slash.tmp@...e.fr>
To:     Florian Fainelli <f.fainelli@...il.com>,
        netdev <netdev@...r.kernel.org>
Cc:     Andrew Lunn <andrew@...n.ch>, Mans Rullgard <mans@...sr.com>,
        Thibaud Cornic <thibaud_cornic@...madesigns.com>,
        Matthias May <matthias.may@...atec.com>,
        Zefir Kurtisi <zefir.kurtisi@...atec.com>
Subject: Re: Toggling link state breaks network connectivity

On 13/06/2017 17:07, Mason wrote:

> I did note something that seems important.
> 
> If I toggle the link state in software, then connectivity breaks.
> 
> If I unplug the ethernet cable, and replug, connectivity remains.
> 
> The difference is that plugging/unplugging doesn't call the
> .ndo_stop callback. But 'ip link set eth0 down' does call it.
> 
> Should the .ndo_stop callback be symmetric to the .ndo_open callback?
> In other words, should .ndo_open(); .ndo_stop(); be a NOP?

I changed the ndo_open callback to a wrapper that calls:

	nb8800_open(dev);
	nb8800_stop(dev);
	nb8800_open(dev);

With this change, connectivity is broken from the start.
Valid ARP requests are correctly *sent* but the corresponding
ARP replies are not received.

I'm hoping this limits the scope of what needs to be investigated.

Regards.