From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Greear Subject: Re: pktgen question Date: Sun, 23 Sep 2007 23:30:00 -0700 Message-ID: <46F75968.4010307@candelatech.com> References: <46F6905C.6030309@opengridcomputing.com> <20070923172803.GA11997@2ka.mipt.ru> <46F6A887.1030301@opengridcomputing.com> <1190571527.4256.78.camel@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Steve Wise , Evgeniy Polyakov , netdev@vger.kernel.org, Robert Olsson To: hadi@cyberus.ca Return-path: Received: from ns2.lanforge.com ([66.165.47.211]:48873 "EHLO ns2.lanforge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751487AbXIXGaV (ORCPT ); Mon, 24 Sep 2007 02:30:21 -0400 In-Reply-To: <1190571527.4256.78.camel@localhost> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org jamal wrote: > On Sun, 2007-23-09 at 12:55 -0500, Steve Wise wrote: > > >> Its a hack that breaks cxgb3 because cxgb3 uses the skb->cb area for >> each skb passed down. So cxgb3 is at fault then? IE a driver cannot >> use the skb->cb field if the users count is > 1? Or maybe a driver can >> _never_ use the cb field? >> > > any layer can use the cb structure whichever way they wish. There are > violations, e.g: > the vlan code also uses the cb field to pass vlan details for hardware > acceleration. How does pktgen affect it though, clone() will just copy > the cb field and pktgen doesnt touch it. > In retrospect, pktgen may have to use clone - ccing Robert Olsson. > Pktgen abuses the ref count, as far as I can tell. It works with most ethernet drivers, but that multi-pkt will also fail with things like vlans because the skb->dev is changed as it is transmitted (to the lower-level device). I'd say just don't use the multi-pkt with pktgen on devices that can't handle it. Thanks, Ben -- Ben Greear Candela Technologies Inc http://www.candelatech.com