linux-kernel - Re: UNIX domain socket problem

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Date:	Tue, 07 Nov 2006 11:23:08 +0100
From:	Bernd Petrovitsch <bernd@...mix.at>
To:	Bin Chen <binary.chen@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: UNIX domain socket problem

On Tue, 2006-11-07 at 09:47 +0800, Bin Chen wrote:
> Sorry for cross post, it has been posted on
> comp.os.linux.development.apps.
> 
> I wrote a domain socket sever, which is a STREAM type, let it listen a
> sun_path, and in a while loop it accept new connections. I analyze it
> using netstat.
> 
> Abstractly, the communication need two end. Even the listen socket is
> only one, each time the accept returns, there should be two end
> produced: one by connect() issued by client, one by accept() issued by
> server. These two should have different inode number.

Why should they?
The filename (actually and more to the point: the i-node) in the
filesystem is just an "anchor" so that the clients can find the server
(if you have several servers on your system, they *must* have different
filenames to bind(2) to).

> What is strange is that I sometimes find the RefCnt of some unix domain
> socket have values 2,3,4,5,6,7 or even 258, if each connection in
> stream should be in pair, why this problem occurs?

Probably (because I didn't look at source code) because every connect(2)
and/or accept(2) sys-call increments it.
And BTW I assume that you meand the in memory ref count, not the one in
the inode on the disk (which is incremented with hardlinks).

	Bernd
-- 
Firmix Software GmbH                   http://www.firmix.at/
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