From mboxrd@z Thu Jan  1 00:00:00 1970
From: ebiederm@xmission.com (Eric W. Biederman)
Subject: Re: [RFC PATCH net-next 00/11] netns: don't switch namespace while creating kernel sockets
Date: Thu, 07 May 2015 13:58:29 -0500
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Cc: Ying Xue <ying.xue@windriver.com>, netdev <netdev@vger.kernel.org>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	Pavel Emelyanov <xemul@openvz.org>,
	David Miller <davem@davemloft.net>,
	Eric Dumazet <eric.dumazet@gmail.com>, maxk@qti.qualcomm.com,
	Stephen Hemminger <stephen@networkplumber.org>,
	Thomas Graf <tgraf@suug.ch>,
	Nicolas Dichtel <nicolas.dichtel@6wind.com>,
	Tom Herbert <tom@herbertland.com>,
	James Chapman <jchapman@katalix.com>,
	Erik Hugne <erik.hugne@ericsson.com>, jon.maloy@ericsson.com,
	Simon Horman <horms@verge.net.au>
To: Cong Wang <cwang@twopensource.com>
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	(Cong Wang's message of "Thu, 7 May 2015 11:53:32 -0700")
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Cong Wang <cwang@twopensource.com> writes:

> On Thu, May 7, 2015 at 11:26 AM, Eric W. Biederman
> <ebiederm@xmission.com> wrote:
>> Cong Wang <cwang@twopensource.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.

Eric