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

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Message-Id: <20121207.145239.1408511750725975741.davem@davemloft.net>
Date:	Fri, 07 Dec 2012 14:52:39 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	joseph.gasparakis@...el.com
Cc:	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

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.
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