Subject: Re: [PATCH net v2] ipv6: Handle race in addrconf_dad_work

From: Eric Dumazet <[email-masked]>
Date: Wed, 2 Oct 2019 15:36:47 -0700

On 10/2/19 3:33 PM, David Ahern wrote:
> On 10/2/19 4:21 PM, Eric Dumazet wrote:
>> o syzbot this time, but complete lack of connectivity on some of my test hosts.
>>
>> Incoming IPv6 packets go to ip6_forward() (!!!) and are dropped there.
> 
> what does 'ip -6 addr sh' show when it is in this state? Any idea of the
> order of events?

This might be related to a use of a bonding device, with a mlx4 slave.

"ip -6 addr sh" shows the same output before/after the patch.

lpaa23:~# ip -6 addr sh dev eth0
2: eth0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 5102 state UP 
    inet6 2607:f8b0:8099:e17::/128 scope global nodad 
       valid_lft forever preferred_lft forever
    inet6 fe80::21a:11ff:fec3:d7f/64 scope link 
       valid_lft forever preferred_lft forever

> 
> I flipped to IF_READY based on addrconf_ifdown and idev checks seeming
> more appropriate.
>