netdev - Checking for closed TCP connection in kernel space

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Message-ID: <4D2339DB.2090603@250bpm.com>
Date:	Tue, 04 Jan 2011 16:16:43 +0100
From:	Martin Sustrik <sustrik@...bpm.com>
To:	netdev@...r.kernel.org
Subject: Checking for closed TCP connection in kernel space

Hi all,

I open a TCP socket in the kernel space (sock_create_kern). I connect or 
bind it, I send and receive data. Everything works as expected.

The problem is how to find out that the peer have closed the connection.

In user space you get 0 when calling recv() is such case. However, in 
kernel space kernel_recvmsg seems to return 0 anytime when there are no 
more data available. It doesn't return an error either.

Should I monitor the socket state using sk_state_change callback? But 
the callback seems to work in async manner, i.e. I can accidentally use 
closed socket before I get notified about the state change.

Any ideas?
Martin
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