From owner-freebsd-hackers Thu Sep 27 9:55:30 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from duke.cs.duke.edu (duke.cs.duke.edu [152.3.140.1]) by hub.freebsd.org (Postfix) with ESMTP id C06F437B50E for ; Thu, 27 Sep 2001 09:55:25 -0700 (PDT) Received: from grasshopper.cs.duke.edu (grasshopper.cs.duke.edu [152.3.145.30]) by duke.cs.duke.edu (8.9.3/8.9.3) with ESMTP id MAA14922; Thu, 27 Sep 2001 12:55:21 -0400 (EDT) Received: (from gallatin@localhost) by grasshopper.cs.duke.edu (8.11.3/8.9.1) id f8RGste83955; Thu, 27 Sep 2001 12:54:55 -0400 (EDT) (envelope-from gallatin@cs.duke.edu) From: Andrew Gallatin MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <15283.23007.137091.883110@grasshopper.cs.duke.edu> Date: Thu, 27 Sep 2001 12:54:55 -0400 (EDT) To: "Louis A. Mamakos" Cc: hackers@FreeBSD.ORG Subject: Re: TCP&IP cksum offload on FreeBSD 4.2 In-Reply-To: <200109271631.f8RGVCZ65964@whizzo.transsys.com> References: <200109271416.f8REGaZ64624@whizzo.transsys.com> <15283.14648.430630.163513@grasshopper.cs.duke.edu> <200109271631.f8RGVCZ65964@whizzo.transsys.com> X-Mailer: VM 6.75 under 21.1 (patch 12) "Channel Islands" XEmacs Lucid Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG Louis A. Mamakos writes: > I was referring to the case on the transmit side where the wrong > data get's gathered up by the DMA engine because of software related > errors. You get a valid checksum, but for the wrong data. You might > have the wrong data because a drive screwed up setting the DMA descriptors, > or some other I/O transfer splatted over the buffer waiting in a > transmit queue. What happens if that same i/o transfer splatted over the buffer waiting in user space prior to the copyin, or sitting in the socket buffer prior to a software checksum being done? Software checksums are not quite the panacea you make them out to be. And they're very expensive. Geez. All I wanted to do was pat Jonathan on the back for coming up with what is apparently the most flexible and well though out mechanism out there. These issues have been argued to death; I don't feel like arguing with you. I'm satisified that I'm not going to convince you & you're not going to convince me. Drew To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message