netdev - Re: netns refcnt leak for kernel accept sock

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Message-ID: <CAHA+R7PzsOCR-UmJ+73jXJaacc_adz9F3-Qs4zB0cSFajpJREw@mail.gmail.com>
Date:	Mon, 27 Jul 2015 11:37:35 -0700
From:	Cong Wang <cwang@...pensource.com>
To:	Sowmini Varadhan <sowmini.varadhan@...cle.com>
Cc:	netdev <netdev@...r.kernel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	David Miller <davem@...emloft.net>
Subject: Re: netns refcnt leak for kernel accept sock

On Mon, Jul 27, 2015 at 11:19 AM, Sowmini Varadhan
<sowmini.varadhan@...cle.com> wrote:
> On (07/27/15 11:13), Cong Wang wrote:
>>
>> That refcnt should be released in sock destructor too, when the tcp
>> connection is terminated.
>
> yes, but in my case, the listen socket is opened as part of
> the ->init indirection in pernet_operations (thus it is a kernel socket)
> and the expectation is that this listen socket, and any accept sockets
> derived from it, will be closed in ->exit.
>
> But if the accept socket is treated as a uspace socket (thus holds a get_net())
> then it will block cleanup_net() and the associated ->exit cleanup operations.
>
> This is probably not a problem for other systems like vxlan/gue/geneve etc
> because they all use udp sockets, thus dont have the "accept" equivalent.
>

dlm uses a kernel TCP socket too, but it allocates a new socket and calls
->accept() by itself. ;)
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