netdev - Re: [PATCH net v4] rtnl/bond: don't send rtnl msg for unregistered iface

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Date:	Thu, 16 Jul 2015 11:06:42 +0200
From:	Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:	Kristian Evensen <kristian.evensen@...il.com>
CC:	jiri@...nulli.us, David Miller <davem@...emloft.net>,
	Network Development <netdev@...r.kernel.org>,
	j.vosburgh@...il.com, vfalico@...il.com, gospo@...ulusnetworks.com
Subject: Re: [PATCH net v4] rtnl/bond: don't send rtnl msg for unregistered
 iface

Le 13/07/2015 16:11, Kristian Evensen a écrit :
> Hello,
>
> I have a quick question about this patch.
>
> On Wed, May 13, 2015 at 2:19 PM, Nicolas Dichtel
> <nicolas.dichtel@...nd.com> wrote:
>> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
>> index 837d30b5ffed..7b25f1ef3d75 100644
>> --- a/net/core/rtnetlink.c
>> +++ b/net/core/rtnetlink.c
>> @@ -2415,6 +2415,9 @@ void rtmsg_ifinfo(int type, struct net_device *dev, unsigned int change,
>>   {
>>          struct sk_buff *skb;
>>
>> +       if (dev->reg_state != NETREG_REGISTERED)
>> +               return;
>> +
>
> Is this check correct, or placed at the correct location? The reason I
> am asking is as follows. In rollback_registered_many(), dev->reg_state
> is set to NETREG_UNREGISTERING for devices that will be unregistered.
> When rtmsg_ifinfo_build_skb(RTM_DELLINK, ...) is called in the
> following loop in rollback_registered_many, this comparison will
> always be true and no DELLINK event generated.


>
> This change led to some applications I have not behaving as expected
> due to missing DELLINK when network devices are removed. I also see no
> DELLINK with ip mon link. Removing the check restores the old behavior
> (DELLINK events are generated). My machine is running 3.18.18, which
> includes this fix.
Ok, I see the problem. My patch depends on commit
395eea6ccf2b ("rtnetlink: delay RTM_DELLINK notification until after ndo_uninit()")
which has been introduced in 3.19 (this patch is not backported in 3.18).

After 3.19, rtmsg_ifinfo_build_skb() just builds a message (an skb), it never
calls rtmsg_ifinfo(). After this call, rollback_registered_many() calls
rtmsg_ifinfo_send() (which also never calls rtmsg_ifinfo()).

I will submit a patch for the 3.18.


Regards,
Nicolas
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