On Fri, 2012-12-07 at 08:45 -0800, Alexander Duyck wrote:
> On 12/07/2012 02:07 AM, Ben Hutchings wrote:
> > 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.
> >
>
> Actually the offload is generic to any encapsulation that does not
> compute a checksum on the inner headers. So as long as you can treat
> the outer headers as one giant L2 header you can pretty much ignore what
> is in there as long as the inner network and transport header values are
> set. There are a number of tunnels that fall into that category since
> most just use IP as the L2 and the L3 usually doesn't contain any checksum.
Yes, that should work, but it requires that the driver/hardware uses the
header offsets from the skb rather than parsing the packet. This is not
currently required for devices with the NETIF_F_IP_CSUM and
NETIF_F_IPV6_CSUM features.
Please do state explicitly which feature flags are valid in
hw_enc_features, any changes in semantics, and in particular in what
cases the driver/hardware is supposed to use header offsets from the skb
vs parsing the packet.
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.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
