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

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Message-ID: <43e2c04f-a601-3363-1f98-26fd007be960@gmail.com>
Date:   Thu, 3 Oct 2019 09:32:34 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Ahern <dsahern@...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 10/3/19 8:50 AM, David Ahern wrote:
> On 10/2/19 3:23 PM, Eric Dumazet wrote:

>>
>> It seems we need to allow the code to do some changes if IF_READY is not set.
>>
> 
> That statement was correct. Prior to the patch in question ifp->state is
> bumped to INET6_IFADDR_STATE_DAD in addrconf_dad_work. When
> NETDEV_CHANGE event happens, addrconf_notify calls addrconf_dad_run
> which calls addrconf_dad_kick to restart dad after the dad process
> (applies even if nodad is set -- yes, odd).
> 
> With the patch, IF_READY is not set when the bond device is created and
> dad_work skips bumping the state. When the CHANGE event comes through
> the state is not INET6_IFADDR_STATE_DAD (and the restart argument is not
> set), so addrconf_dad_run does not call addrconf_dad_kick.
> 
> Bottom line, regardless of IF_READY we need the state change to happen
> in dad_work, we just need to skip the call to addconf_dad_begin.
> 
> Can you test the change below on your boxes? It applies on current net.
> 
> Rajendra: can you test as well and make sure your problem is still
> resolved?
> 
> Thanks,
> 
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index dd3be06d5a06..fce0d0dca7bb 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -4032,12 +4032,6 @@ static void addrconf_dad_work(struct work_struct *w)
> 
>         rtnl_lock();
> 
> -       /* check if device was taken down before this delayed work
> -        * function could be canceled
> -        */
> -       if (idev->dead || !(idev->if_flags & IF_READY))
> -               goto out;
> -
>         spin_lock_bh(&ifp->lock);
>         if (ifp->state == INET6_IFADDR_STATE_PREDAD) {
>                 action = DAD_BEGIN;
> @@ -4068,6 +4062,12 @@ static void addrconf_dad_work(struct work_struct *w)
>         }
>         spin_unlock_bh(&ifp->lock);
> 
> +       /* check if device was taken down before this delayed work
> +        * function could be canceled
> +        */
> +       if (idev->dead || !(idev->if_flags & IF_READY))
> +               goto out;
> +
>         if (action == DAD_BEGIN) {
>                 addrconf_dad_begin(ifp);
>                 goto out;
> 

Still no luck for me :/