netdev - Re: [PATCH net v2] ipv6: Handle race in addrconf_dad

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Message-ID: <6b74af81-d12d-6abd-fd4f-5c1e758fdde7@gmail.com>
Date:   Wed, 2 Oct 2019 18:10:04 -0600
From:   David Ahern <dsahern@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>,
        David Ahern <dsahern@...nel.org>, davem@...emloft.net,
        jakub.kicinski@...ronome.com
Cc:     netdev@...r.kernel.org, rajendra.dendukuri@...adcom.com
Subject: Re: [PATCH net v2] ipv6: Handle race in addrconf_dad_work

On 10/2/19 4:36 PM, Eric Dumazet wrote:
> This might be related to a use of a bonding device, with a mlx4 slave.
> 

does it only happen with bonds?

bond shows IF_READY even though the underlying device is carrier down
which seems wrong; if a lower device is not carrier up then DAD does not
really happen.

A quick test with a VM (and setting carrier off on the tap) shows that
with the current patch in place the bond address stays in tentative
state. Reverting this patch and the tentative flag is removed. DAD never
happens since carrier is off on the one link in the bond, so the
tentative flag getting cleared is wrong.

I need to step out; come back to this later.