From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 31900 invoked by alias); 19 Oct 2005 20:57:18 -0000 Mailing-List: contact ecos-discuss-help@ecos.sourceware.org; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: ecos-discuss-owner@ecos.sourceware.org Received: (qmail 31798 invoked by uid 22791); 19 Oct 2005 20:57:14 -0000 Received: from londo.lunn.ch (HELO londo.lunn.ch) (80.238.139.98) by sourceware.org (qpsmtpd/0.30-dev) with ESMTP; Wed, 19 Oct 2005 20:57:14 +0000 Received: from lunn by londo.lunn.ch with local (Exim 3.36 #1 (Debian)) id 1ESKzk-0001o7-00; Wed, 19 Oct 2005 22:57:08 +0200 Date: Wed, 19 Oct 2005 20:57:00 -0000 To: Grant Edwards Cc: ecos-discuss@ecos.sourceware.org Message-ID: <20051019205708.GL7087@lunn.ch> Mail-Followup-To: Grant Edwards , ecos-discuss@ecos.sourceware.org References: <43561EFF.8030200@lmco.com> <20051019182149.575E03DAE2@rivatek.dnsalias.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20051019182149.575E03DAE2@rivatek.dnsalias.net> User-Agent: Mutt/1.5.11 From: Andrew Lunn Subject: Re: [ECOS] Re: [Fwd: FreeBSD network stack question] X-SW-Source: 2005-10/txt/msg00144.txt.bz2 On Wed, Oct 19, 2005 at 01:21:49PM -0500, Grant Edwards wrote: > In gmane.os.ecos.general, you wrote: > > > If we collect a packet trace with tcpdump, we see an ARP request and ARP > > reply, then we see the 2nd segment of the first message - the first > > segment of the first message is never transmitted. > > Now you understand why there's a "U" in "UDP". ;) Unreliable Datagram Protocol? Well its actually User Datagram Protocl. > > 1. udp_output calls ip_output > > [...] > > 8. ip_output believes that all is well with the first segment and > > proceeds to send the second. By now, the ARP resolution process has > > completed, and the second segment is transmitted normally. > > > > Is this normal? > > I think so. UDP packets are allowed to vanish pretty much > anywhere along the way. Looking at the code it seems like it will hold onto one packet until the ARP responce is received. If there are more than one request to send a packet while the ARP process is still going on, only the last packet is kept. All others are thrown away. Andrew -- Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss