linux-kernel - Re: [PATCH 1/1] af_packet: don't enable timestamps in mmap'ed sockets

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Message-ID: <20070809181823.GA32449@2ka.mipt.ru>
Date:	Thu, 9 Aug 2007 22:18:23 +0400
From:	Evgeniy Polyakov <johnpol@....mipt.ru>
To:	Unai Uribarri <unai.uribarri@...enet.com>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] af_packet: don't enable timestamps in mmap'ed sockets

On Thu, Aug 09, 2007 at 08:13:54PM +0200, Unai Uribarri (unai.uribarri@...enet.com) wrote:
> On jue, 2007-08-09 at 18:33 +0400, Evgeniy Polyakov wrote:
> > On Thu, Aug 09, 2007 at 04:21:54PM +0200, Unai Uribarri (unai.uribarri@...enet.com) wrote:
> > > The attached patch removes the automatic timestamp activation, that
> > > only mmap'ed AF_PACKET sockets perform. I known it can break user
> > > applications, but I believe that it's the correct solution.
> > 
> > How tcpdump with mmap libpcap will work with it?
> 
> In Linux, you can enable timestamps on any socket executing:
> 
> int val = 1;
> setsockopt(sock, SOL_SOCKET, SO_TIMESTAMP, &val, sizeof(val));
> 
> PD: Current release of tcpdump doesn't mmap the reception ring and
> timestamps packets at user space with gettimeofday. It isn't the best
> performing alternative, but it's portable.
 
IIRC, there was/is a libpcap which worked with mapped sockets, mybe not 
official though. Any application which depened on having timestamps with
packets will not work now. Why not to implement an
absolutely_turn_off_timestamps option instead of breaking compatibility?

-- 
	Evgeniy Polyakov
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