From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Tom Spink" Subject: Re: AF_UNIX MSG_PEEK bug? Date: Tue, 8 Jan 2008 23:46:15 +0000 Message-ID: <7b9198260801081546u50f11e9ck32ec6f071efa300d@mail.gmail.com> References: <4783FBD6.1000004@hp.com> <7b9198260801081453s198af7efycc7c35668c65eaf1@mail.gmail.com> <7b9198260801081539x7aee72fbm53b5f298c5faf56@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: "Rick Jones" , netdev@vger.kernel.org, "David Miller" , linux-kernel@vger.kernel.org To: "Brent Casavant" Return-path: Received: from py-out-1112.google.com ([64.233.166.182]:10491 "EHLO py-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752755AbYAHXqQ (ORCPT ); Tue, 8 Jan 2008 18:46:16 -0500 Received: by py-out-1112.google.com with SMTP id u52so28885pyb.10 for ; Tue, 08 Jan 2008 15:46:16 -0800 (PST) In-Reply-To: <7b9198260801081539x7aee72fbm53b5f298c5faf56@mail.gmail.com> Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: On 08/01/2008, Tom Spink wrote: > On 08/01/2008, Brent Casavant wrote: > > 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@sgi.com never heard a horse sing a song. > > Silicon Graphics, Inc. -- Louis Armstrong > > > > Hi, > > But you're not consuming the size_t on the other end. You're only > peeking it, i.e. you're doing the recv to peek at the message, but > never calling recv to remove that data from the queue... or am I > missing something? > > -- > Regards, > Tom Spink > University of Edinburgh > Ach. I *am* missing something... and what I'm missing is my understanding of the sendmsg and recvmsg calls. A quick Google has sorted me out. -- Regards, Tom Spink University of Edinburgh