From owner-freebsd-sparc64@FreeBSD.ORG Wed Jun 16 05:07:16 2004 Return-Path: Delivered-To: freebsd-sparc64@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 5233916A4CF for ; Wed, 16 Jun 2004 05:07:16 +0000 (GMT) Received: from ns.kt-is.co.kr (ns.kt-is.co.kr [211.218.149.125]) by mx1.FreeBSD.org (Postfix) with ESMTP id 76C4443D46 for ; Wed, 16 Jun 2004 05:07:15 +0000 (GMT) (envelope-from yongari@kt-is.co.kr) Received: from michelle.kt-is.co.kr (ns2.kt-is.co.kr [220.76.118.193]) (authenticated bits=128) by ns.kt-is.co.kr (8.12.10/8.12.10) with ESMTP id i5G53wAh071964 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=FAIL); Wed, 16 Jun 2004 14:03:58 +0900 (KST) Received: from michelle.kt-is.co.kr (localhost.kt-is.co.kr [127.0.0.1]) by michelle.kt-is.co.kr (8.12.10/8.12.10) with ESMTP id i5G55G1r008591 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Wed, 16 Jun 2004 14:05:16 +0900 (KST) (envelope-from yongari@kt-is.co.kr) Received: (from yongari@localhost) by michelle.kt-is.co.kr (8.12.10/8.12.10/Submit) id i5G55FiI008590; Wed, 16 Jun 2004 14:05:15 +0900 (KST) (envelope-from yongari@kt-is.co.kr) Date: Wed, 16 Jun 2004 14:05:15 +0900 From: Pyun YongHyeon To: Kevin Day Message-ID: <20040616050515.GA8540@kt-is.co.kr> References: <20040616034520.GB7887@kt-is.co.kr> <264D82AE-BF4F-11D8-A89B-000A95A8A1F2@dragondata.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <264D82AE-BF4F-11D8-A89B-000A95A8A1F2@dragondata.com> User-Agent: Mutt/1.4.1i X-Filter-Version: 1.11a (ns.kt-is.co.kr) cc: freebsd-sparc64@freebsd.org Subject: Re: TCP/UDP cksum offload on hme(4) X-BeenThere: freebsd-sparc64@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list Reply-To: yongari@kt-is.co.kr List-Id: Porting FreeBSD to the Sparc List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 16 Jun 2004 05:07:16 -0000 On Tue, Jun 15, 2004 at 11:39:27PM -0500, Kevin Day wrote: > > On Jun 15, 2004, at 10:45 PM, Pyun YongHyeon wrote: > > > > 1. UDP TX cksum offload has an issue. The hardware doesn't flip the > > cksum bits when the computed cksum is 0x0000. I have no idea this > > is the reason why STP2002QFP says it supports only TCP RX/TX cksum. > > (pp. 29, pp. 40, pp. 42) > > > > > > I'm not sure if you're aware of this or not, but: > > >If the computed checksum is zero, it is transmitted as all ones > >(the > >equivalent in one's complement arithmetic). An all zero > >transmitted > >checksum value means that the transmitter generated no checksum > >(for > >debugging or for higher level protocols that don't care) > > > So, if a UDP packet has an all zero checksum, it's supposed to mean > there was no checksum performed. If you legitimately came up with > 0x0000 for a checksum, you're supposed to set the header field to > 0xffff. > The TX cksumming is performed during DMA by the hardware. So when the hardware computes the cksum I have no chance to reset to 0xffff. (i.e. The mbuf was already passed to TX FIFO.) I verified the deficiency with manually created UDP payload. Regards, Pyun YongHyeon -- Pyun YongHyeon