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

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Date:	Fri, 7 Dec 2012 10:07:27 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Joseph Gasparakis <joseph.gasparakis@...el.com>
CC:	<davem@...emloft.net>, <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 <peter.p.waskiewicz.jr@...el.com>,
	Alexander Duyck <alexander.h.duyck@...el.com>
Subject: Re: [PATCH v3 1/4] net: Add support for hardware-offloaded
 encapsulation

On Thu, 2012-12-06 at 17:56 -0800, Joseph Gasparakis wrote:
> This patch adds support in the kernel for offloading in the NIC Tx and Rx
> checksumming for encapsulated packets (such as VXLAN and IP GRE).
[...]
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -1063,6 +1063,8 @@ struct net_device {
>  	netdev_features_t	wanted_features;
>  	/* mask of features inheritable by VLAN devices */
>  	netdev_features_t	vlan_features;
> +	/* mask of features inherited by encapsulating devices */
> +	netdev_features_t	hw_enc_features;
[...]

How will the networking core know *which* encapsulations this applies
to?  I notice that your implementation in ixgbe does not set
NETIF_F_HW_CSUM here, so presumably the hardware will parse headers to
find which ranges should be checksummed and it won't cover the next
encapsulation protocol that comes along.

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.

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