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

From: Cyrill Gorcunov <[email-masked]>
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?

	Cyrill