Subject: Re: [PATCH net 3/5] fm10k: Implement ndo_gso_check()

From: Joe Stringer <[email-masked]>
Date: Thu, 6 Nov 2014 10:41:15 -0800

On Wed, Nov 05, 2014 at 06:54:00PM -0800, Alexander Duyck wrote:
> On 11/04/2014 01:56 PM, Joe Stringer wrote:
> > ndo_gso_check() was recently introduced to allow NICs to report the
> > offloading support that they have on a per-skb basis. Add an
> > implementation for this driver which checks for something that looks
> > like VXLAN.
> >
> > Implementation shamelessly stolen from Tom Herbert:
> > http://thread.gmane.org/gmane.linux.network/332428/focus=333111
> >
> > Signed-off-by: Joe Stringer <[email-masked]>
> > ---
> > Should this driver report support for GSO on packets with tunnel headers
> > up to 64B like the i40e driver does?
> > ---
> >  drivers/net/ethernet/intel/fm10k/fm10k_netdev.c |   12 ++++++++++++
> >  1 file changed, 12 insertions(+)
> >
> > diff --git a/drivers/net/ethernet/intel/fm10k/fm10k_netdev.c b/drivers/net/ethernet/intel/fm10k/fm10k_netdev.c
> > index 8811364..b9ef622 100644
> > --- a/drivers/net/ethernet/intel/fm10k/fm10k_netdev.c
> > +++ b/drivers/net/ethernet/intel/fm10k/fm10k_netdev.c
> > @@ -1350,6 +1350,17 @@ static void fm10k_dfwd_del_station(struct net_device *dev, void *priv)
> >  	}
> >  }
> >  
> > +static bool fm10k_gso_check(struct sk_buff *skb, struct net_device *dev)
> > +{
> > +	if ((skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL) &&
> > +	    (skb->inner_protocol_type != ENCAP_TYPE_ETHER ||
> > +	     skb->inner_protocol != htons(ETH_P_TEB) ||
> > +	     skb_inner_mac_header(skb) - skb_transport_header(skb) != 16))
> > +		return false;
> > +
> > +	return true;
> > +}
> > +
> >  static const struct net_device_ops fm10k_netdev_ops = {
> >  	.ndo_open		= fm10k_open,
> >  	.ndo_stop		= fm10k_close,
> > @@ -1372,6 +1383,7 @@ static const struct net_device_ops fm10k_netdev_ops = {
> >  	.ndo_do_ioctl		= fm10k_ioctl,
> >  	.ndo_dfwd_add_station	= fm10k_dfwd_add_station,
> >  	.ndo_dfwd_del_station	= fm10k_dfwd_del_station,
> > +	.ndo_gso_check		= fm10k_gso_check,
> >  };
> >  
> >  #define DEFAULT_DEBUG_LEVEL_SHIFT 3
> 
> I'm thinking this check is far too simplistic.  If you look the fm10k
> driver already has fm10k_tx_encap_offload() in the TSO function for
> verifying if it can support offloading tunnels or not.  I would
> recommend starting there or possibly even just adapting that function to
> suit your purpose.
> 
> Thanks,
> 
> Alex

Would it be enough to just call fm10k_tx_encap_offload() in a way that echoes fm10k_tso()?

+static bool fm10k_gso_check(struct sk_buff *skb, struct net_device *dev)
+{
+       if (skb->encapsulation && !fm10k_tx_encap_offload(skb))
+               return false;
+
+       return true;
+}

Thanks,
Joe