netdev - RE: [PATCH net-next 2/2] bnx2x: add RSS capability for GRE traffic

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Date:	Tue, 19 Mar 2013 12:21:47 +0000
From:	"Dmitry Kravkov" <dmitry@...adcom.com>
To:	Maciej Żenczykowski <maze@...gle.com>
cc:	"Eric Dumazet" <eric.dumazet@...il.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"Eilon Greenstein" <eilong@...adcom.com>,
	"Tom Herbert" <therbert@...gle.com>
Subject: RE: [PATCH net-next 2/2] bnx2x: add RSS capability for GRE
 traffic


> -----Original Message-----
> From: Maciej Żenczykowski [mailto:maze@...gle.com]
> Sent: Tuesday, March 19, 2013 11:18 AM
> To: Dmitry Kravkov
> Cc: Eric Dumazet; davem@...emloft.net; netdev@...r.kernel.org; Eilon Greenstein; Tom Herbert
> Subject: Re: [PATCH net-next 2/2] bnx2x: add RSS capability for GRE traffic
> 
> Can the HW calculate and return a 1s complement sum of the entire
> packet (or a large portion there-of)?
No, it can't :(

> Fixing that up to be only of the outer IPv4, inner IPv4 and inner TCP
> relevant portions should still be simpler (well faster) than
> calculating the TCP checksum.
> I'm pretty sure that some relationship between 1s complement sum of
> all bytes, outer IPv4 checksum, inner IPv4 checksum and TCP checksum
> could be pulled out of a hat with some deeper thought.  (similarly for
> IPv4/GRE/IPv6/TCP and other combinations)
> 
> What portions of the packet can the HW/FW [partially] checksum - and
> return the value to the driver for further processing?
> Can it return 1s complement sum of data portion of outer IPv4 (ie. in
> IPv4/GRE/IPv4/TCP return a 1s complement sum of GRE/IPv4/TCP bytes)
> 
> Maciej Żenczykowski, Kernel Networking Developer @ Google
> 
> On Mon, Mar 18, 2013 at 11:30 PM, Dmitry Kravkov <dmitry@...adcom.com> wrote:
> >> -----Original Message-----
> >> From: netdev-owner@...r.kernel.org [mailto:netdev-owner@...r.kernel.org] On Behalf Of Eric Dumazet
> >> Sent: Tuesday, March 19, 2013 2:08 AM
> >> To: Dmitry Kravkov
> >> Cc: davem@...emloft.net; netdev@...r.kernel.org; Eilon Greenstein; Tom Herbert; Maciej Żenczykowski
> >> Subject: Re: [PATCH net-next 2/2] bnx2x: add RSS capability for GRE traffic
> >>
> >> On Mon, 2013-03-18 at 18:51 +0200, Dmitry Kravkov wrote:
> >> > The patch drives FW to perform RSS for GRE traffic,
> >> > based on inner headers.
> >> >
> >> > Signed-off-by: Dmitry Kravkov <dmitry@...adcom.com>
> >> > Signed-off-by: Eilon Greenstein <eilong@...adcom.com>
> >> > ---
> >> >  drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.h |    3 +++
> >> >  drivers/net/ethernet/broadcom/bnx2x/bnx2x_sp.c  |   23 ++++++++++++-----------
> >> >  drivers/net/ethernet/broadcom/bnx2x/bnx2x_sp.h  |    9 +++++++++
> >> >  3 files changed, 24 insertions(+), 11 deletions(-)
> >>
> >> This works very well.
> >>
> >> Problem is we skb_set_queue_mapping(skb, 0); in __skb_tunnel_rx()
> >>
> >> (this was a patch from Tom Herbert, commit
> >> 693019e90ca45d881109d32c0c6d29adf03f6447 (net: reset skb queue mapping
> >> when rx'ing over tunnel )
> >>
> >> Meaning we hit a single cpu for the GRO stuff in ip_gre.
> >>
> >> I have to think about it.
> >>
> >>
> >> Another question is :
> >>
> >> Can bnx2x check the tcp checksum if GRE encapsulated ?
> >>
> > Current HW can't provide this. Probably, it's possible to separate CSUM from GRO/TPA then stack will have to handle CSUM
> validation for huge packets. Is it worth?
> >