netdev - Re: [RFC] net: ipv4 -- Introduce ifa limit per net

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Date:	Thu, 10 Mar 2016 15:03:11 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	gorcunov@...il.com
Cc:	xiyou.wangcong@...il.com, alexei.starovoitov@...il.com,
	eric.dumazet@...il.com, netdev@...r.kernel.org, solar@...nwall.com,
	vvs@...tuozzo.com, avagin@...tuozzo.com, xemul@...tuozzo.com,
	vdavydov@...tuozzo.com, khorenko@...tuozzo.com,
	pablo@...filter.org, netfilter-devel@...r.kernel.org
Subject: Re: [RFC] net: ipv4 -- Introduce ifa limit per net

From: Cyrill Gorcunov <gorcunov@...il.com>
Date: Thu, 10 Mar 2016 23:01:34 +0300

> On Thu, Mar 10, 2016 at 02:55:43PM -0500, David Miller wrote:
>> > 
>> > Hmm, but inetdev_destroy() is only called when NETDEV_UNREGISTER
>> > is happening and masq already registers a netdev notifier...
>> 
>> Indeed, good catch.  Therefore:
>> 
>> 1) Keep the masq netdev notifier.  That will flush the conntrack table
>>    for the inetdev_destroy event.
>> 
>> 2) Make the inetdev notifier only do something if inetdev->dead is
>>    false.  (ie. we are flushing an individual address)
>> 
>> And then we don't need the NETDEV_UNREGISTER thing at all:
>> 
>> diff --git a/net/ipv4/netfilter/nf_nat_masquerade_ipv4.c b/net/ipv4/netfilter/nf_nat_masquerade_ipv4.c
>> index c6eb421..f71841a 100644
>> --- a/net/ipv4/netfilter/nf_nat_masquerade_ipv4.c
>> +++ b/net/ipv4/netfilter/nf_nat_masquerade_ipv4.c
>> @@ -108,10 +108,20 @@ static int masq_inet_event(struct notifier_block *this,
>>  			   unsigned long event,
>>  			   void *ptr)
>>  {
>> -	struct net_device *dev = ((struct in_ifaddr *)ptr)->ifa_dev->dev;
>>  	struct netdev_notifier_info info;
>> +	struct in_ifaddr *ifa = ptr;
>> +	struct in_device *idev;
>>  
>> -	netdev_notifier_info_init(&info, dev);
>> +	/* The masq_dev_notifier will catch the case of the device going
>> +	 * down.  So if the inetdev is dead and being destroyed we have
>> +	 * no work to do.  Otherwise this is an individual address removal
>> +	 * and we have to perform the flush.
>> +	 */
>> +	idev = ifa->ifa_dev;
>> +	if (idev->dead)
>> +		return NOTIFY_DONE;
>> +
>> +	netdev_notifier_info_init(&info, idev->dev);
>>  	return masq_device_event(this, event, &info);
>>  }
> 
> Guys, I'm lost. Currently masq_device_event calls for conntrack
> cleanup with device index, so that once device is going down, the
> appropriate conntracks gonna be dropped off. Now if device is dead
> nobody will cleanup the conntracks?

Both notifiers are run in the inetdev_destroy() case.

Maybe that's what you are missing.