[PATCH] net: update the usage of CHECKSUM_UNNECESSARY

[PATCH] net: update the usage of CHECKSUM_UNNECESSARY

[Yi Zou]

As suggested by Ben, this adds the clarification on the usage of
CHECKSUM_UNNECESSARY on the outgoing patch. Also add the usage
description of NETIF_F_FCOE_CRC and CHECKSUM_UNNECESSARY
for the kernel FCoE protocol driver.

This is a follow-up to the following:
http://patchwork.ozlabs.org/patch/147315/

Signed-off-by: Yi Zou <yi.zou@intel.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>
Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Cc: www.Open-FCoE.org <devel@open-fcoe.org>
---

 include/linux/skbuff.h |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 8dc8257..a2b9953 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -94,6 +94,13 @@
  *			  about CHECKSUM_UNNECESSARY. 8)
  *	NETIF_F_IPV6_CSUM about as dumb as the last one but does IPv6 instead.
  *
+ *	UNNECESSARY: device will do per protocol specific csum. Protocol drivers
+ *	that do not want net to perform the checksum calculation should use
+ *	this flag in their outgoing skbs.
+ *	NETIF_F_FCOE_CRC  this indicates the device can do FCoE FC CRC
+ *			  offload. Correspondingly, the FCoE protocol driver
+ *			  stack should use CHECKSUM_UNNECESSARY.
+ *
  *	Any questions? No questions, good. 		--ANK
  */
 

Re: [PATCH] net: update the usage of CHECKSUM_UNNECESSARY

[David Miller]

From: Yi Zou <yi.zou@intel.com>
Date: Mon, 19 Mar 2012 14:12:41 -0700

> As suggested by Ben, this adds the clarification on the usage of
> CHECKSUM_UNNECESSARY on the outgoing patch. Also add the usage
> description of NETIF_F_FCOE_CRC and CHECKSUM_UNNECESSARY
> for the kernel FCoE protocol driver.
> 
> This is a follow-up to the following:
> http://patchwork.ozlabs.org/patch/147315/
> 
> Signed-off-by: Yi Zou <yi.zou@intel.com>
> Cc: Ben Hutchings <bhutchings@solarflare.com>
> Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
> Cc: www.Open-FCoE.org <devel@open-fcoe.org>

Applied.

Re: [PATCH] net: update the usage of CHECKSUM_UNNECESSARY

[Michael S. Tsirkin]

On Mon, Mar 19, 2012 at 02:12:41PM -0700, Yi Zou wrote:
> As suggested by Ben, this adds the clarification on the usage of
> CHECKSUM_UNNECESSARY on the outgoing patch. Also add the usage
> description of NETIF_F_FCOE_CRC and CHECKSUM_UNNECESSARY
> for the kernel FCoE protocol driver.
> 
> This is a follow-up to the following:
> http://patchwork.ozlabs.org/patch/147315/
> 
> Signed-off-by: Yi Zou <yi.zou@intel.com>
> Cc: Ben Hutchings <bhutchings@solarflare.com>
> Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
> Cc: www.Open-FCoE.org <devel@open-fcoe.org>
> ---
> 
>  include/linux/skbuff.h |    7 +++++++
>  1 files changed, 7 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 8dc8257..a2b9953 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -94,6 +94,13 @@
>   *			  about CHECKSUM_UNNECESSARY. 8)
>   *	NETIF_F_IPV6_CSUM about as dumb as the last one but does IPv6 instead.
>   *
> + *	UNNECESSARY: device will do per protocol specific csum. Protocol drivers
> + *	that do not want net to perform the checksum calculation should use
> + *	this flag in their outgoing skbs.
> + *	NETIF_F_FCOE_CRC  this indicates the device can do FCoE FC CRC
> + *			  offload. Correspondingly, the FCoE protocol driver
> + *			  stack should use CHECKSUM_UNNECESSARY.
> + *
>   *	Any questions? No questions, good. 		--ANK
>   */
>  

So just to make sure I understand, you never get
UNNECESSARY packets on tx unless you declared NETIF_F_FCOE_CRC?

Maybe the comment says this somehow but could not figure it out.



> 
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Re: [PATCH] net: update the usage of CHECKSUM_UNNECESSARY

[Ben Hutchings]

On Tue, 2012-05-08 at 20:48 +0300, Michael S. Tsirkin wrote:
> On Mon, Mar 19, 2012 at 02:12:41PM -0700, Yi Zou wrote:
> > As suggested by Ben, this adds the clarification on the usage of
> > CHECKSUM_UNNECESSARY on the outgoing patch. Also add the usage
> > description of NETIF_F_FCOE_CRC and CHECKSUM_UNNECESSARY
> > for the kernel FCoE protocol driver.
> > 
> > This is a follow-up to the following:
> > http://patchwork.ozlabs.org/patch/147315/
> > 
> > Signed-off-by: Yi Zou <yi.zou-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> > Cc: Ben Hutchings <bhutchings-s/n/eUQHGBpZroRs9YW3xA@public.gmane.org>
> > Cc: Jeff Kirsher <jeffrey.t.kirsher-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> > Cc: www.Open-FCoE.org <devel-s9riP+hp16TNLxjTenLetw@public.gmane.org>
> > ---
> > 
> >  include/linux/skbuff.h |    7 +++++++
> >  1 files changed, 7 insertions(+), 0 deletions(-)
> > 
> > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> > index 8dc8257..a2b9953 100644
> > --- a/include/linux/skbuff.h
> > +++ b/include/linux/skbuff.h
> > @@ -94,6 +94,13 @@
> >   *			  about CHECKSUM_UNNECESSARY. 8)
> >   *	NETIF_F_IPV6_CSUM about as dumb as the last one but does IPv6 instead.
> >   *
> > + *	UNNECESSARY: device will do per protocol specific csum. Protocol drivers
> > + *	that do not want net to perform the checksum calculation should use
> > + *	this flag in their outgoing skbs.
> > + *	NETIF_F_FCOE_CRC  this indicates the device can do FCoE FC CRC
> > + *			  offload. Correspondingly, the FCoE protocol driver
> > + *			  stack should use CHECKSUM_UNNECESSARY.
> > + *
> >   *	Any questions? No questions, good. 		--ANK
> >   */
> >  
> 
> So just to make sure I understand, you never get
> UNNECESSARY packets on tx unless you declared NETIF_F_FCOE_CRC?
> 
> Maybe the comment says this somehow but could not figure it out.

That's what should happen now.  In future CHECKSUM_UNNECESSARY could be
used on output by other protocols which don't use TCP/IP-style
checksums, but always dependent on the output device supporting the
relevant offload feature.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

Re: [PATCH] net: update the usage of CHECKSUM_UNNECESSARY

[Michael S. Tsirkin]

On Tue, May 08, 2012 at 07:20:58PM +0100, Ben Hutchings wrote:
> On Tue, 2012-05-08 at 20:48 +0300, Michael S. Tsirkin wrote:
> > On Mon, Mar 19, 2012 at 02:12:41PM -0700, Yi Zou wrote:
> > > As suggested by Ben, this adds the clarification on the usage of
> > > CHECKSUM_UNNECESSARY on the outgoing patch. Also add the usage
> > > description of NETIF_F_FCOE_CRC and CHECKSUM_UNNECESSARY
> > > for the kernel FCoE protocol driver.
> > > 
> > > This is a follow-up to the following:
> > > http://patchwork.ozlabs.org/patch/147315/
> > > 
> > > Signed-off-by: Yi Zou <yi.zou@intel.com>
> > > Cc: Ben Hutchings <bhutchings@solarflare.com>
> > > Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
> > > Cc: www.Open-FCoE.org <devel@open-fcoe.org>
> > > ---
> > > 
> > >  include/linux/skbuff.h |    7 +++++++
> > >  1 files changed, 7 insertions(+), 0 deletions(-)
> > > 
> > > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> > > index 8dc8257..a2b9953 100644
> > > --- a/include/linux/skbuff.h
> > > +++ b/include/linux/skbuff.h
> > > @@ -94,6 +94,13 @@
> > >   *			  about CHECKSUM_UNNECESSARY. 8)
> > >   *	NETIF_F_IPV6_CSUM about as dumb as the last one but does IPv6 instead.
> > >   *
> > > + *	UNNECESSARY: device will do per protocol specific csum. Protocol drivers
> > > + *	that do not want net to perform the checksum calculation should use
> > > + *	this flag in their outgoing skbs.
> > > + *	NETIF_F_FCOE_CRC  this indicates the device can do FCoE FC CRC
> > > + *			  offload. Correspondingly, the FCoE protocol driver
> > > + *			  stack should use CHECKSUM_UNNECESSARY.
> > > + *
> > >   *	Any questions? No questions, good. 		--ANK
> > >   */
> > >  
> > 
> > So just to make sure I understand, you never get
> > UNNECESSARY packets on tx unless you declared NETIF_F_FCOE_CRC?
> > 
> > Maybe the comment says this somehow but could not figure it out.
> 
> That's what should happen now.  In future CHECKSUM_UNNECESSARY could be
> used on output by other protocols which don't use TCP/IP-style
> checksums, but always dependent on the output device supporting the
> relevant offload feature.
> 
> Ben.

Isn't there another case: a device passes UNNECESSARY in on rx,
and the skb is forwarded to another device?
For example it is handled this way by tun, giving a nice
performance boost for VMs, see 10a8d94a95742bb15b4e617ee9884bb4381362be

> -- 
> Ben Hutchings, Staff Engineer, Solarflare
> Not speaking for my employer; that's the marketing department's job.
> They asked us to note that Solarflare product names are trademarked.

Re: [PATCH] net: update the usage of CHECKSUM_UNNECESSARY

[Ben Hutchings]

On Wed, 2012-05-09 at 09:03 +0300, Michael S. Tsirkin wrote:
> On Tue, May 08, 2012 at 07:20:58PM +0100, Ben Hutchings wrote:
> > On Tue, 2012-05-08 at 20:48 +0300, Michael S. Tsirkin wrote:
> > > On Mon, Mar 19, 2012 at 02:12:41PM -0700, Yi Zou wrote:
> > > > As suggested by Ben, this adds the clarification on the usage of
> > > > CHECKSUM_UNNECESSARY on the outgoing patch. Also add the usage
> > > > description of NETIF_F_FCOE_CRC and CHECKSUM_UNNECESSARY
> > > > for the kernel FCoE protocol driver.
> > > > 
> > > > This is a follow-up to the following:
> > > > http://patchwork.ozlabs.org/patch/147315/
> > > > 
> > > > Signed-off-by: Yi Zou <yi.zou@intel.com>
> > > > Cc: Ben Hutchings <bhutchings@solarflare.com>
> > > > Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
> > > > Cc: www.Open-FCoE.org <devel@open-fcoe.org>
> > > > ---
> > > > 
> > > >  include/linux/skbuff.h |    7 +++++++
> > > >  1 files changed, 7 insertions(+), 0 deletions(-)
> > > > 
> > > > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> > > > index 8dc8257..a2b9953 100644
> > > > --- a/include/linux/skbuff.h
> > > > +++ b/include/linux/skbuff.h
> > > > @@ -94,6 +94,13 @@
> > > >   *			  about CHECKSUM_UNNECESSARY. 8)
> > > >   *	NETIF_F_IPV6_CSUM about as dumb as the last one but does IPv6 instead.
> > > >   *
> > > > + *	UNNECESSARY: device will do per protocol specific csum. Protocol drivers
> > > > + *	that do not want net to perform the checksum calculation should use
> > > > + *	this flag in their outgoing skbs.
> > > > + *	NETIF_F_FCOE_CRC  this indicates the device can do FCoE FC CRC
> > > > + *			  offload. Correspondingly, the FCoE protocol driver
> > > > + *			  stack should use CHECKSUM_UNNECESSARY.
> > > > + *
> > > >   *	Any questions? No questions, good. 		--ANK
> > > >   */
> > > >  
> > > 
> > > So just to make sure I understand, you never get
> > > UNNECESSARY packets on tx unless you declared NETIF_F_FCOE_CRC?
> > > 
> > > Maybe the comment says this somehow but could not figure it out.
> > 
> > That's what should happen now.  In future CHECKSUM_UNNECESSARY could be
> > used on output by other protocols which don't use TCP/IP-style
> > checksums, but always dependent on the output device supporting the
> > relevant offload feature.
> > 
> > Ben.
> 
> Isn't there another case: a device passes UNNECESSARY in on rx,
> and the skb is forwarded to another device?
> For example it is handled this way by tun, giving a nice
> performance boost for VMs, see 10a8d94a95742bb15b4e617ee9884bb4381362be

Hmm... I thought UNNECESSARY was supposed to be replaced by NONE on
output, but I don't see where that would happen.  Which would mean we
had an undocumented case here, and now we have ambiguity. :-(

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

Re: [PATCH] net: update the usage of CHECKSUM_UNNECESSARY

[Michael S. Tsirkin]

On Thu, May 10, 2012 at 01:05:01AM +0100, Ben Hutchings wrote:
> On Wed, 2012-05-09 at 09:03 +0300, Michael S. Tsirkin wrote:
> > On Tue, May 08, 2012 at 07:20:58PM +0100, Ben Hutchings wrote:
> > > On Tue, 2012-05-08 at 20:48 +0300, Michael S. Tsirkin wrote:
> > > > On Mon, Mar 19, 2012 at 02:12:41PM -0700, Yi Zou wrote:
> > > > > As suggested by Ben, this adds the clarification on the usage of
> > > > > CHECKSUM_UNNECESSARY on the outgoing patch. Also add the usage
> > > > > description of NETIF_F_FCOE_CRC and CHECKSUM_UNNECESSARY
> > > > > for the kernel FCoE protocol driver.
> > > > > 
> > > > > This is a follow-up to the following:
> > > > > http://patchwork.ozlabs.org/patch/147315/
> > > > > 
> > > > > Signed-off-by: Yi Zou <yi.zou@intel.com>
> > > > > Cc: Ben Hutchings <bhutchings@solarflare.com>
> > > > > Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
> > > > > Cc: www.Open-FCoE.org <devel@open-fcoe.org>
> > > > > ---
> > > > > 
> > > > >  include/linux/skbuff.h |    7 +++++++
> > > > >  1 files changed, 7 insertions(+), 0 deletions(-)
> > > > > 
> > > > > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> > > > > index 8dc8257..a2b9953 100644
> > > > > --- a/include/linux/skbuff.h
> > > > > +++ b/include/linux/skbuff.h
> > > > > @@ -94,6 +94,13 @@
> > > > >   *			  about CHECKSUM_UNNECESSARY. 8)
> > > > >   *	NETIF_F_IPV6_CSUM about as dumb as the last one but does IPv6 instead.
> > > > >   *
> > > > > + *	UNNECESSARY: device will do per protocol specific csum. Protocol drivers
> > > > > + *	that do not want net to perform the checksum calculation should use
> > > > > + *	this flag in their outgoing skbs.
> > > > > + *	NETIF_F_FCOE_CRC  this indicates the device can do FCoE FC CRC
> > > > > + *			  offload. Correspondingly, the FCoE protocol driver
> > > > > + *			  stack should use CHECKSUM_UNNECESSARY.
> > > > > + *
> > > > >   *	Any questions? No questions, good. 		--ANK
> > > > >   */
> > > > >  
> > > > 
> > > > So just to make sure I understand, you never get
> > > > UNNECESSARY packets on tx unless you declared NETIF_F_FCOE_CRC?
> > > > 
> > > > Maybe the comment says this somehow but could not figure it out.
> > > 
> > > That's what should happen now.  In future CHECKSUM_UNNECESSARY could be
> > > used on output by other protocols which don't use TCP/IP-style
> > > checksums, but always dependent on the output device supporting the
> > > relevant offload feature.
> > > 
> > > Ben.
> > 
> > Isn't there another case: a device passes UNNECESSARY in on rx,
> > and the skb is forwarded to another device?
> > For example it is handled this way by tun, giving a nice
> > performance boost for VMs, see 10a8d94a95742bb15b4e617ee9884bb4381362be
> 
> Hmm... I thought UNNECESSARY was supposed to be replaced by NONE on
> output, but I don't see where that would happen.  Which would mean we
> had an undocumented case here, and now we have ambiguity. :-(
> 
> Ben.

Ambiguity with FCoE? Why doesn't that use PARTIAL btw? Simply to
avoid teaching net core about that protocol and NETIF_F_FCOE_CRC?

> -- 
> Ben Hutchings, Staff Engineer, Solarflare
> Not speaking for my employer; that's the marketing department's job.
> They asked us to note that Solarflare product names are trademarked.