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From: David Miller <davem@davemloft.net>
Subject: Re: [RFC] r8169 : why SG / TX checksum are default disabled
Date: Fri, 20 Jul 2012 09:17:36 -0700 (PDT)
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From: hayeswang <hayeswang@realtek.com>
Date: Fri, 20 Jul 2012 15:14:26 +0800

> I find that the total length field of IP header would be modified if the hw
> checksum is enabled. Therefore, skb_padto + hw checksum wouldn't work. The
> software checksum is necessary.

It's really strange that the hardware has any reason to update the IP
header length field when it is asked to compute the checksum.