netdev - Re: [PATCH 3/3] net: Fix drivers advertising HW_CSUM feature to use csum

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Date:	Wed, 15 Dec 2010 19:16:55 +0100
From:	Michał Mirosław <mirq-linux@...e.qmqm.pl>
To:	Stephen Hemminger <shemminger@...ux-foundation.org>
Cc:	netdev@...r.kernel.org, e1000-devel@...ts.sourceforge.net,
	Vasanthy Kolluri <vkolluri@...co.com>,
	Roopa Prabhu <roprabhu@...co.com>,
	David Wang <dwang2@...co.com>,
	Andrew Gallatin <gallatin@...i.com>,
	Brice Goglin <brice@...i.com>,
	Shreyas Bhatewara <sbhatewara@...are.com>,
	"VMware, Inc." <pv-drivers@...are.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Jiri Pirko <jpirko@...hat.com>,
	H Hartley Sweeten <hsweeten@...ionengravers.com>,
	Jie Yang <Jie.Yang@...eros.com>, Joe Perches <joe@...ches.com>
Subject: Re: [PATCH 3/3] net: Fix drivers advertising HW_CSUM feature to
	use csum_start

On Tue, Dec 14, 2010 at 07:07:27PM -0800, Stephen Hemminger wrote:
> On Wed, 15 Dec 2010 02:24:08 +0100 (CET)
> Michał Mirosław <mirq-linux@...e.qmqm.pl> wrote:
> > Some drivers are using skb_transport_offset(skb) instead of skb->csum_start
> > for NETIF_F_HW_CSUM offload.  This does not matter now, but if someone
> > implements checksumming of encapsulated packets then this will break silently.
> > 
> > TSO output paths are left as they are, since they are for IP+TCP only
> > (might be worth converting though).
> > 
> > Signed-off-by: Michał Mirosław <mirq-linux@...e.qmqm.pl>
> Which if any of these drivers did you test on real hardware?

I'm running it on skge, with additional patch that changes it to use
NETIF_F_HW_CSUM instead of NETIF_F_IP_CSUM. BTW, why it is not advertising
full HW checksum in vanilla kernel? Are there any known hardware bugs in there?

Best Regards,
Michał Mirosław

---
lspci:

02:05.0 Ethernet controller: 3Com Corporation 3c940 10/100/1000Base-T [Marvell] (rev 12)
        Subsystem: ASUSTeK Computer Inc. A7V600/P4P800/K8V motherboard
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV+ VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
        Status: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
        Latency: 64 (5750ns min, 7750ns max), Cache Line Size: 16 bytes
        Interrupt: pin A routed to IRQ 22
        Region 0: Memory at feafc000 (32-bit, non-prefetchable) [size=16K]
        Region 1: I/O ports at d800 [size=256]
        Capabilities: <access denied>
        Kernel driver in use: skge
        Kernel modules: skge

ethtool -k:

Offload parameters for eth3:
rx-checksumming: on
tx-checksumming: on
scatter-gather: on
tcp segmentation offload: off
udp fragmentation offload: off
generic segmentation offload: on
large receive offload: off

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