linux-kernel - Re: AF_UNIX MSG

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Message-ID: <alpine.BSF.1.00.0801081716010.24286@pkunk.americas.sgi.com>
Date:	Tue, 8 Jan 2008 17:18:48 -0600 (CST)
From:	Brent Casavant <bcasavan@....com>
To:	Tom Spink <tspink@...il.com>
cc:	Rick Jones <rick.jones2@...com>, netdev@...r.kernel.org,
	David Miller <davem@...emloft.net>,
	linux-kernel@...r.kernel.org
Subject: Re: AF_UNIX MSG_PEEK bug?

On Tue, 8 Jan 2008, Tom Spink wrote:

> Where in the code is the message length being sent across the socket?

In do_producer(), there are the following lines in the main loop:

	/* Send random lengths of data */
	messages[i].length = (rand() % MAXLEN) + sizeof(size_t);
	iov[i].iov_len = messages[i].length;

The entire "struct sockmsg" is sent across the socket, so the first
size_t in each message contains the length of the entire message
(including the size_t).  This size gets picked up at the
recv(...,MSG_PEEK) line in do_consumer().

Thanks,
Brent

-- 
Brent Casavant                          All music is folk music.  I ain't
bcasavan@....com                        never heard a horse sing a song.
Silicon Graphics, Inc.                    -- Louis Armstrong
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