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

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Message-Id: <1186683234.24669.65.camel@localhost.localdomain>
Date:	Thu, 09 Aug 2007 20:13:54 +0200
From:	Unai Uribarri <unai.uribarri@...enet.com>
To:	Evgeniy Polyakov <johnpol@....mipt.ru>
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 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.



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