Date: Thu, 27 Sep 2001 09:31:32 -0600 (MDT) From: Ronald G Minnich <rminnich@lanl.gov> To: Andrew Gallatin <gallatin@cs.duke.edu> Cc: "Louis A. Mamakos" <louie@TransSys.COM>, <hackers@FreeBSD.ORG> Subject: Re: TCP&IP cksum offload on FreeBSD 4.2 Message-ID: <Pine.LNX.4.33.0109270929410.27057-100000@snaresland.acl.lanl.gov> In-Reply-To: <15283.14648.430630.163513@grasshopper.cs.duke.edu>
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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
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