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Date:	Fri, 08 May 2015 17:08:59 -0500
From: (Eric W. Biederman)
To:	Cong Wang <>
Cc:	Herbert Xu <>,
	Ying Xue <>,
	netdev <>,
	Pavel Emelyanov <>,
	David Miller <>,
	Eric Dumazet <>,,
	Stephen Hemminger <>,
	Thomas Graf <>,
	Nicolas Dichtel <>,
	Tom Herbert <>,
	James Chapman <>,
	Erik Hugne <>,,
	Simon Horman <>
Subject: Re: [RFC PATCH net-next 00/11] netns: don't switch namespace while creating kernel sockets

Cong Wang <> writes:

> On Fri, May 8, 2015 at 1:27 PM, Cong Wang <> wrote:
>> On Fri, May 8, 2015 at 10:36 AM, Eric W. Biederman
>> <> wrote:
>>> It really is invalid for a network namespace init routine to grab the
>>> reference count of it's network namespace (thus making the network
>>> namespace unfreeable).  So I am wondering if perhaps all we need to do
>>> is find a clean refactoring of the socket code so this case does not
>>> come up at all.
>> Good point!
>> I _guess_ the reason is these kernel sockets have to exist longer than
>> netns' life-time, it could be due to on-flying skb's?
>> On the other hand, we do create some fb_tunnel netdevice in netns init
>> too, but we don't take a refcnt there, probably because we wait
>> for netdevice refcnt goes to zero when unregistering.
> Answer myself, it looks like we don't need to hold the refcnt at all,
> since we create the socket at init and release it at uninit, so they
> should have the same life-time?
> The reason why user-space sockets need this refcnt is they
> could have longer life-time than the netns?

User space sockets by design keep the network namespace alive.

> This seems the right direction to solve this problem for me,
> I am going to try this way to see how far I can go. ;)

I will be interested to see what you come up with.


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