I was out of town last week and did not have a chance to respond.  Yes,
qla3xxx is (before Stephen's fix) broken on IPV6.  I will review the
changes and post a patch if necessary. 

-----Original Message-----
From: netdev-owner@vger.kernel.org 
[mailto:netdev-owner@vger.kernel.org] On Behalf Of Stephen Hemminger
Sent: Tuesday, May 29, 2007 4:46 PM
To: Michael Chan
Cc: Herbert Xu; netdev
Subject: Re: Definition and usage of NETIF_F_HW_SUM?

On Tue, 29 May 2007 17:10:52 -0700
"Michael Chan" [off-list ref] wrote:

quoted

On Wed, 2007-05-30 at 07:36 +1000, Herbert Xu wrote:

quoted

I just checked e1000 and it's correct as it does use the 

csum_offset

quoted

quoted

when doing TX offload.  However, you're definitely right that bnx2
seems to be broken.

quoted

A few devices take a offset, starting point, and 

insertion point. This looks like

quoted

quoted

quoted

the correct model. But no upper layer protocols other 

than IPV4/IPV6 can do checksum

quoted

quoted

quoted

offload at present, so it seems moot.

I could easily whip up a patch to get GRE to use it for a start :)

quoted

IMHO the correct solution would be to get rid if 

NETIF_F_HW_SUM and make a new flag

quoted

quoted

quoted

NETIF_F_IPV6_SUM. Devices that can checksum both could 

do NETIF_F_IPV4_SUM|NETI_F_IPV6_SUM.

quoted

quoted

We should definitely keep NETIF_F_HW_SUM for sane 

hardware such as the

quoted

quoted

e1000.  Unfortunately we may just have to invent IPV6_SUM 

for the broken

quoted

quoted

ones.

Ccing Michael to see if the bnx2 chip can actually do offset-based
checksum offload.

bnx2 and tg3 cannot do offset-based checksumming because 

the hardware

quoted

doesn't have room in the buffer descriptors to specify the 

offsets.  So

quoted

regrettably, the NETIF_F_HW_SUM flag has been misused in 

these drivers.

quoted

A new NETIF_F_IPV6_SUM flag will be very useful for us.

Look furthur many drivers are just plain broken and use F_HW_SUM
and can't even do IPV6 properly.  I'll fix

The worst code award goes to: qla3xxx.c
which is broken on IPV6 and goes to trouble of computing all the
offsets and they are already there in skb...



-- 
Stephen Hemminger [off-list ref]
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