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

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Message-Id: <20160304.175032.1728003538386465719.davem@davemloft.net>
Date:	Fri, 04 Mar 2016 17:50:32 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	gorcunov@...il.com
Cc:	netdev@...r.kernel.org, solar@...nwall.com, vvs@...tuozzo.com,
	avagin@...tuozzo.com, xemul@...tuozzo.com, vdavydov@...tuozzo.com,
	khorenko@...tuozzo.com, eric.dumazet@...il.com
Subject: Re: [RFC] net: ipv4 -- Introduce ifa limit per net

From: Cyrill Gorcunov <gorcunov@...il.com>
Date: Sat, 5 Mar 2016 00:39:20 +0300

> Currenlty all the kernels (including vanilla) free ifa
> list under rtln_lock() taken which takes a huge time
> to release all entries when we stop the container.
> Moreover it's allowed to create unlimited number
> of addresses from inside of net-namespace if
> CAP-NET_ADMIN granted (which is common for containers).
> 
> Lets introduce per-net limit (4096 by default)
> of addresses, which can be tuned up via sysfs
> entry /proc/sys/net/ipv4/ifa_limit.
> 
> Reported-by: Solar Designer <solar@...nwall.com>
> Signed-off-by: Cyrill Gorcunov <gorcunov@...tuozzo.com>

Arbitrary limits are... arbitrary.

If the freeing loop is the issue, splice the list at teardown and
process that list asynchronously via a workqueue or similar.

Thanks.