netdev - Re: [RFC PATCH net-next 00/11] netns: don't switch namespace while creating kernel sockets

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Message-ID: <87lhh0b1j1.fsf@x220.int.ebiederm.org>
Date:	Thu, 07 May 2015 15:01:06 -0500
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Cong Wang <cwang@...pensource.com>
Cc:	Ying Xue <ying.xue@...driver.com>, netdev <netdev@...r.kernel.org>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Pavel Emelyanov <xemul@...nvz.org>,
	David Miller <davem@...emloft.net>,
	Eric Dumazet <eric.dumazet@...il.com>, maxk@....qualcomm.com,
	Stephen Hemminger <stephen@...workplumber.org>,
	Thomas Graf <tgraf@...g.ch>,
	Nicolas Dichtel <nicolas.dichtel@...nd.com>,
	Tom Herbert <tom@...bertland.com>,
	James Chapman <jchapman@...alix.com>,
	Erik Hugne <erik.hugne@...csson.com>, jon.maloy@...csson.com,
	Simon Horman <horms@...ge.net.au>
Subject: Re: [RFC PATCH net-next 00/11] netns: don't switch namespace while creating kernel sockets

Cong Wang <cwang@...pensource.com> writes:

> On Thu, May 7, 2015 at 11:58 AM, Eric W. Biederman
> <ebiederm@...ssion.com> wrote:
>> Cong Wang <cwang@...pensource.com> writes:
>>
>>> On Thu, May 7, 2015 at 11:26 AM, Eric W. Biederman
>>> <ebiederm@...ssion.com> wrote:
>>>> Cong Wang <cwang@...pensource.com> writes:
>>>>
>>>>>
>>>>> Why does this have to be so complicated? We can simply avoid
>>>>> calling ops_init() by skipping those in cleanup_list, no?
>>>>
>>>> The problem is that there is a single list of methods to call and if you
>>>> simply skip calling the initialization methods for a struct net and add
>>>> yourself to the list cleanup_net will then call the cleanup methods
>>>> without calling the cleanup methods.
>>>
>>> If you mean pernet_list, ops->list has been already added before
>>> for_each_net().
>>>
>>>>
>>>> Simply limiting new network namespace registrations to a point when
>>>> network namespaces are not being registered or unregisted seems like
>>>> the simplest way to achieve this effect.
>>>>
>>>
>>> Literally, any point before ops_init().
>>
>> Think about what that what it means to add a set of operations to the
>> pernet_list and then to skip a network namespace with a count of 0 and
>> then to have that network namespace exit with those methods on
>> pernet_list.
>>
>
> That is easy to solve, isn't it?

Nope.  That doesn't work.

Eric
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