From: Evgeniy Polyakov Subject: Re: [PATCH 1/1] af_packet: don't enable timestamps in mmap'ed sockets Date: Thu, 9 Aug 2007 22:18:23 +0400 Message-ID: <20070809181823.GA32449@2ka.mipt.ru> References: <1186669314.24669.56.camel@localhost.localdomain> <20070809143322.GA5345@2ka.mipt.ru> <1186683234.24669.65.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: Unai Uribarri Return-path: Received: from relay.2ka.mipt.ru ([194.85.82.65]:50757 "EHLO 2ka.mipt.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754274AbXHISSa (ORCPT ); Thu, 9 Aug 2007 14:18:30 -0400 Content-Disposition: inline In-Reply-To: <1186683234.24669.65.camel@localhost.localdomain> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Thu, Aug 09, 2007 at 08:13:54PM +0200, Unai Uribarri (unai.uribarri@optenet.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@optenet.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