From mboxrd@z Thu Jan 1 00:00:00 1970 From: andrei radulescu-banu Subject: Re: Linux, tcpdump and vlan Date: Thu, 19 Jul 2007 14:38:20 -0700 (PDT) Message-ID: <930446.33248.qm@web56601.mail.re3.yahoo.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ascii Cc: Stephen Hemminger , Krzysztof Halasa , linux-kernel@vger.kernel.org, Linux Netdev List To: Patrick McHardy Return-path: Received: from web56601.mail.re3.yahoo.com ([66.196.97.45]:34223 "HELO web56601.mail.re3.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752109AbXGSViW (ORCPT ); Thu, 19 Jul 2007 17:38:22 -0400 Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org During debugging, I noticed that dev_queue_xmit() is called twice for tx vlan frames. This results in a frame being passed twice to a packet socket bound to 'any' interface. If the packet socket is bound to a specific interface, though, it will get only one copy of the tx frame, which is good. In more detail: suppose we're tx'ing a frame, and the route table lookup yields a vlan outgoing device eth0.2. dev_queue_xmit() is called, which calls dev_queue_xmit_nit() for dev = eth0.2 then dev->hard_start_xmit() for dev = eth0.2. The latter call gets into the vlan layer, which attaches the vlan id 2 (accelerated or not... in my e1000 case accelerated) then calls dev_queue_xmit() again. This time around dev_queue_xmit_nit() is called for dev = eth0, and dev->hard_start_xmit() actually calls the ethernet driver. The net result is that dev_queue_xmit_nit() is called twice, once for dev=eth0.2 then for dev=eth0. ____________________________________________________________________________________ Shape Yahoo! in your own image. Join our Network Research Panel today! http://surveylink.yahoo.com/gmrs/yahoo_panel_invite.asp?a=7