From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: twice past the taps, thence out to net? Date: Thu, 15 Dec 2011 19:54:37 +0100 Message-ID: <1323975277.2769.20.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC> References: <4EE8F884.1010304@hp.com> <1323970998.2769.18.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC> <4EEA3D58.5010101@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Vijay Subramanian , tcpdump-workers@lists.tcpdump.org, netdev@vger.kernel.org To: Rick Jones Return-path: Received: from mail-we0-f174.google.com ([74.125.82.174]:41646 "EHLO mail-we0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751749Ab1LOSyl (ORCPT ); Thu, 15 Dec 2011 13:54:41 -0500 Received: by werm1 with SMTP id m1so162939wer.19 for ; Thu, 15 Dec 2011 10:54:40 -0800 (PST) In-Reply-To: <4EEA3D58.5010101@hp.com> Sender: netdev-owner@vger.kernel.org List-ID: Le jeudi 15 d=C3=A9cembre 2011 =C3=A0 10:32 -0800, Rick Jones a =C3=A9c= rit : > > More exactly, we call dev_queue_xmit_nit() from dev_hard_start_xmit= () > > _before_ giving skb to device driver. > > > > If device driver returns NETDEV_TX_BUSY, and a qdisc was setup on t= he > > device, packet is requeued. > > > > Later, when queue is allowed to send again packets, packet is > > retransmitted (and traced a second time in dev_queue_xmit_nit()) >=20 > Is this then an unintended consequence bug, or a known feature? >=20 Its a well known feature, some people attempted to remove it ;) http://answers.softpicks.net/answers/topic/-PATCH-tcpdump-may-trace-som= e-outbound-packets-twice--2204640-1.htm