From owner-freebsd-hackers Thu Sep 27 8:31:36 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from acl.lanl.gov (acl.lanl.gov [128.165.147.1]) by hub.freebsd.org (Postfix) with SMTP id 1D95C37B41C for ; Thu, 27 Sep 2001 08:31:33 -0700 (PDT) Received: (qmail 93681 invoked from network); 27 Sep 2001 09:31:32 -0600 Received: from snaresland.acl.lanl.gov (128.165.147.113) by acl.lanl.gov with SMTP; 27 Sep 2001 09:31:32 -0600 Received: (qmail 27153 invoked by uid 3499); 27 Sep 2001 09:31:32 -0600 Received: from localhost (sendmail-bs@127.0.0.1) by localhost with SMTP; 27 Sep 2001 09:31:32 -0600 Date: Thu, 27 Sep 2001 09:31:32 -0600 (MDT) From: Ronald G Minnich X-X-Sender: To: Andrew Gallatin Cc: "Louis A. Mamakos" , Subject: Re: TCP&IP cksum offload on FreeBSD 4.2 In-Reply-To: <15283.14648.430630.163513@grasshopper.cs.duke.edu> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII 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 On Thu, 27 Sep 2001, Andrew Gallatin wrote: > No, you're missing the point almost entirely. The checksum is not > skipped. It is calculated by the DMA engine based on the data that's > transferred across the I/O bus on the receiver (and / or the sender). > If the data is incorrect as seen by the receiving nic, the checksum > will be wrong and the packet will be dropped. you still have a potential problem here with variance in chipsets, namely the case of broken ABORT or other unusual PCI cycle handling (missed word problem). I agree it's a low probability. But we've seen it, just a week or two ago on a brand new box. But then we tend to see things here nobody else sees due to our scale. ron To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message