netdev - Re: [PATCH v3 1/4] net: Add support for hardware-offloaded encapsulation

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Date:	Fri, 7 Dec 2012 12:18:03 -0800 (PST)
From:	Joseph Gasparakis <joseph.gasparakis@...el.com>
To:	David Miller <davem@...emloft.net>
cc:	joseph.gasparakis@...el.com, bhutchings@...arflare.com,
	alexander.h.duyck@...el.com, shemminger@...tta.com,
	chrisw@...s-sol.org, gospo@...hat.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, dmitry@...adcom.com,
	saeed.bishara@...il.com, peter.p.waskiewicz.jr@...el.com
Subject: Re: [PATCH v3 1/4] net: Add support for hardware-offloaded
 encapsulation



On Fri, 7 Dec 2012, David Miller wrote:

> From: Joseph Gasparakis <joseph.gasparakis@...el.com>
> Date: Fri, 7 Dec 2012 11:52:43 -0800 (PST)
> 
> > 
> > 
> > On Fri, 7 Dec 2012, David Miller wrote:
> > 
> >> From: Joseph Gasparakis <joseph.gasparakis@...el.com>
> >> Date: Fri, 7 Dec 2012 11:41:46 -0800 (PST)
> >> 
> >> > 
> >> > 
> >> > On Fri, 7 Dec 2012, David Miller wrote:
> >> > 
> >> >> From: Joseph Gasparakis <joseph.gasparakis@...el.com>
> >> >> Date: Fri, 7 Dec 2012 10:24:17 -0800 (PST)
> >> >> 
> >> >> > So the idea here is that the driver will use the headers for checksumming 
> >> >> > if the skb->encapsulation bit is on. The bit should be set in the protocol 
> >> >> > driver.
> >> >> > 
> >> >> > To answer the second comment, the flags that we use in this series of 
> >> >> > patches is NETIF_F_IP_CSUM, NETIF_F_IPV6_CSUM and NETIF_F_SG. These are 
> >> >> > the bits that we propose will be used for checksumming of encapsulation. 
> >> >> > As per a previous comment in v2, the hw_enc_features field should be used 
> >> >> > also in the future when NICs have more encap offloads, so one could
> >> >> > indicate these features there from the driver.
> >> >> > 
> >> >> > Furthermore, I submitted a patch for Rx checksumming, where NETIF_F_RXCSUM 
> >> >> > is used, again in conjunction with skb->encapsulation flag. As I mention 
> >> >> > in my logs, the driver is expected to set the ip_summed to UNNECESSARY and 
> >> >> > turn the skb->encapsulation on, to indicate that the inner headers are 
> >> >> > already HW checksummed.
> >> >> > 
> >> >> 
> >> >> This is the kind of language that belongs in the commit message and
> >> >> code comments.
> >> >> 
> >> > Sure. I'll wait to gather some more feedback if there is any and I will 
> >> > re-spin this off adding more code comments and clarify this in the logs.
> >> 
> >> Great.
> >> 
> >> Please note that this request applies to your receive side change too.
> >> 
> > I believe the logs are sufficient in the rx patch:
> > 
> > This patch adds capability in vxlan to identify received
> > checksummed inner packets and signal them to the upper layers of
> > the stack. The driver needs to set the skb->encapsulation bit
> > and also set the skb->ip_summed to CHECKSUM_UNNECESSARY.
> > 
> > ...but I can add more comments to the code if this is what you are 
> > referring to.
> 
> Yes, please do.
> 
I will! Thanks.
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