From owner-freebsd-net@FreeBSD.ORG Sun Sep 17 19:21:11 2006 Return-Path: X-Original-To: freebsd-net@freebsd.org Delivered-To: freebsd-net@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 72FB316A40F for ; Sun, 17 Sep 2006 19:21:11 +0000 (UTC) (envelope-from lists@wm-access.no) Received: from lakepoint.domeneshop.no (lakepoint.domeneshop.no [194.63.248.54]) by mx1.FreeBSD.org (Postfix) with ESMTP id CDC8443D5E for ; Sun, 17 Sep 2006 19:21:09 +0000 (GMT) (envelope-from lists@wm-access.no) Received: from [192.168.4.8] (nets.arcticwireless.no [194.19.37.80]) (authenticated bits=0) by lakepoint.domeneshop.no (8.13.8/8.13.8) with ESMTP id k8HJKedt001344 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NOT); Sun, 17 Sep 2006 21:20:41 +0200 Message-ID: <450D9FE2.5030902@wm-access.no> Date: Sun, 17 Sep 2006 21:20:02 +0200 From: =?ISO-8859-1?Q?Sten_Daniel_S=F8rsdal?= User-Agent: Thunderbird 1.5.0.7 (Windows/20060909) MIME-Version: 1.0 To: Sam Leffler References: <44F4CF17.8060203@xs4all.nl> <44F70983.40705@errno.com> <44F71402.1060405@xs4all.nl> <44F7558A.4030907@errno.com> <450B48C2.7030501@xs4all.nl> <450C21B4.5030703@errno.com> In-Reply-To: <450C21B4.5030703@errno.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: freebsd-net@freebsd.org, Hans Nieser Subject: Re: iwi discarding oversized packets while mtu=1500 for src/dst X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 17 Sep 2006 19:21:11 -0000 Sam Leffler wrote: > Hans Nieser wrote: >> Sam Leffler wrote: >>> Hans Nieser wrote: >>> >>>> root@aphax-laptop:~# uname -a >>>> FreeBSD aphax-laptop.lan 6.1-RELEASE FreeBSD 6.1-RELEASE #0: Thu May= 11 >>>> 07:17:09 CEST 2006 >>>> root@aphax-laptop.nieser.local:/usr/obj/usr/src/sys/APHAX-LAPTOP i3= 86 >>> Are you running the iwi driver that came with 6.1-release? If so it = has >>> numerous problems that have been fixed in 6-STABLE and HEAD. I'm not= >>> sure how best to update your system except by going to 6-STABLE via a= >>> src upgrade. >> Today I have upgraded my laptop to 6-STABLE, but unfortunately the >> problems remain. I don't even know wether iwi is to blame, because I c= an't >> figure out wether perhaps xl on my server really is sending out too la= rge >> packets. >> >> That is, so far I've been assuming that an mtu of 1500 may not mean th= at >> there's exactly 1500 bytes going over the wire (overhead of protocols = to >> which the mtu doesn't apply or something, I dunno, I'm no networking >> expert obviously :), because xl is definitely sending out packets of 1= 518 >> bytes. Which iwi on my laptop doesn't like, but the NIC in my desktop >> machine (which runs Linux) has no problem with. Maybe someone can tell= me >> which of the machines is in error here, at least I'd know what to blam= e :( >> >> The fact that my Linux box doesn't discard these packages coming from = my >> server made me suspicious of iwi initially, but maybe iwi is doing not= hing >> wrong and my Linux box is simply willing to accept these oversized pac= kets. >> >=20 > I can't speak to linux but an mtu of 1500 will cause a 1518 byte packet= > to be discarded. I don't recall what your problem was but if the iwi > driver is receiving the frame and passing it up only to be discarded by= > the 802.3 layer then you've received a frame that's too large and you > should look at the sender side for why it's being generated. If you > don't want to do that you can probably just up the mtu on iwi and let > the frame through. >=20 This does sound awfully lot like the driver doesn't strip the 4 byte checksum of a basic 802.[23] ethernet frame. My initial thought was that it was a vlan frame but the frame protocol indicates it's an IP packet. Perhaps it's a frame that slips through the AP's checks on it's way out to the wireless? --=20 Sten Daniel S=F8rsdal