From owner-freebsd-hackers  Mon May 13 13:56:56 2002
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Date: Mon, 13 May 2002 13:56:36 -0700
From: Alfred Perlstein <bright@mu.org>
To: David Greenman-Lawrence <dg@root.com>
Cc: Terry Lambert <tlambert2@mindspring.com>,
	Matthew Dillon <dillon@apollo.backplane.com>,
	jamie@tridentmicrosystems.co.uk, freebsd-hackers@FreeBSD.ORG
Subject: Re: Broadcom BCM5701 Chipset problems
Message-ID: <20020513205636.GB90188@elvis.mu.org>
References: <20020513115600.A50967@mufuf.trident-uk.co.uk> <3CDFF60C.48A2EA65@mindspring.com> <20020513102526.H72322@nexus.root.com> <200205131758.g4DHwJFj068941@apollo.backplane.com> <3CE00B14.E8CA43A8@mindspring.com> <200205131901.g4DJ1U8s069604@apollo.backplane.com> <3CE01595.D045B70D@mindspring.com> <20020513124807.R72322@nexus.root.com> <3CE01A3A.AAB85F64@mindspring.com> <20020513130924.W72322@nexus.root.com>
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* David Greenman-Lawrence <dg@root.com> [020513 13:10] wrote:
> 
>    The card doesn't drop the packet if the IP/TCP checksum is wrong. In my
> tests, I did a software checksum on the supposedly bad packet, and found it
> to be good every time. So it DMA's correctly, the checksum is just calculated
> incorrectly by the hardware.

Probably pretty obvious, but adding a flag "if bad hwsum, then try softsum"
probably wouldn't be too hard.

Of course it depends on how often it mangles the checksum, if it's quite
often it's probably just a better idea to do it in software to lift some
load from the card if doing the hw checksum actually taxes the card.
(like i've heard about tigonII)

-Alfred

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