netdev - Re: [PATCH net 5/6] rtnetlink: check DO_SETLINK_NOTIFY correctly in do

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Message-ID: <47e8fd3f-fa47-0e3b-1041-b931c64aa45b@6wind.com>
Date:   Thu, 26 Oct 2017 09:41:05 +0200
From:   Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:     vyasevic@...hat.com, David Ahern <dsahern@...il.com>,
        Xin Long <lucien.xin@...il.com>,
        network dev <netdev@...r.kernel.org>
Cc:     davem@...emloft.net, hannes@...essinduktion.org
Subject: Re: [PATCH net 5/6] rtnetlink: check DO_SETLINK_NOTIFY correctly in
 do_setlink

Le 26/10/2017 à 08:52, Vlad Yasevich a écrit :
> On 10/16/2017 02:20 PM, Nicolas Dichtel wrote:
>> Le 16/10/2017 à 03:17, David Ahern a écrit :
>>> [ cc'ed Nicolas ]
>>>
>>> On 10/15/17 4:13 AM, Xin Long wrote:
>>>> The check 'status & DO_SETLINK_NOTIFY' in do_setlink doesn't really
>>>> work after status & DO_SETLINK_MODIFIED, as:
>>>>
>>>>   DO_SETLINK_MODIFIED 0x1
>>>>   DO_SETLINK_NOTIFY 0x3
>>>>
>>>> Considering that notifications are suppposed to be sent only when
>>>> status have the flag DO_SETLINK_NOTIFY, the right check would be:
>>>>
>>>>   (status & DO_SETLINK_NOTIFY) == DO_SETLINK_NOTIFY
>>>>
>>>> This would avoid lots of duplicated notifications when setting some
>>>> properties of a link.
>>>>
>>>> Fixes: ba9989069f4e ("rtnl/do_setlink(): notify when a netdev is modified")
>>>> Signed-off-by: Xin Long <lucien.xin@...il.com>
>> Good catch, thank you.
>>
>> Acked-by: Nicolas Dichtel <nicolas.dichtel@...nd.com>
>>
> 
> So I found this the first timer around when looking at this code, but was told that
> notification are expected anytime we modified any setting thus the code was simply
> checking for MODIFIED bit.  Has that thinking changed?

No, you're right, thank you for pointing this out. I was focus on the duplicated
notifications and forget the initial goal.

I will ask for a revert.


Regards,
Nicolas