Re: [Xen-devel] [PATCH net-next] xen-netfront: add support for IPv6 offloads

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 15/01/14 15:18, Paul Durrant wrote:
> This patch adds support for IPv6 checksum offload and GSO when those
> features are available in the backend.
>
> Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> Cc: David Vrabel <david.vrabel@citrix.com>
> ---
>  drivers/net/xen-netfront.c |   48 +++++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 43 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
> index c41537b..321759f 100644
> --- a/drivers/net/xen-netfront.c
> +++ b/drivers/net/xen-netfront.c
> @@ -617,7 +617,9 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
>  		tx->flags |= XEN_NETTXF_extra_info;
>  
>  		gso->u.gso.size = skb_shinfo(skb)->gso_size;
> -		gso->u.gso.type = XEN_NETIF_GSO_TYPE_TCPV4;
> +		gso->u.gso.type = (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6) ?
> +			XEN_NETIF_GSO_TYPE_TCPV6 :
> +			XEN_NETIF_GSO_TYPE_TCPV4;
>  		gso->u.gso.pad = 0;
>  		gso->u.gso.features = 0;
>  
> @@ -809,15 +811,18 @@ static int xennet_set_skb_gso(struct sk_buff *skb,
>  		return -EINVAL;
>  	}
>  
> -	/* Currently only TCPv4 S.O. is supported. */
> -	if (gso->u.gso.type != XEN_NETIF_GSO_TYPE_TCPV4) {
> +	if (gso->u.gso.type != XEN_NETIF_GSO_TYPE_TCPV4 &&
> +	    gso->u.gso.type != XEN_NETIF_GSO_TYPE_TCPV6) {
>  		if (net_ratelimit())
>  			pr_warn("Bad GSO type %d\n", gso->u.gso.type);
>  		return -EINVAL;
>  	}
>  
>  	skb_shinfo(skb)->gso_size = gso->u.gso.size;
> -	skb_shinfo(skb)->gso_type = SKB_GSO_TCPV4;
> +	skb_shinfo(skb)->gso_type =
> +		(gso->u.gso.type == XEN_NETIF_GSO_TYPE_TCPV4) ?
> +		SKB_GSO_TCPV4 :
> +		SKB_GSO_TCPV6;
>  
>  	/* Header must be checked, and gso_segs computed. */
>  	skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY;
> @@ -1191,6 +1196,15 @@ static netdev_features_t xennet_fix_features(struct net_device *dev,
>  			features &= ~NETIF_F_SG;
>  	}
>  
> +	if (features & NETIF_F_IPV6_CSUM) {
> +		if (xenbus_scanf(XBT_NIL, np->xbdev->otherend,
> +				 "feature-ipv6-csum-offload", "%d", &val) < 0)
> +			val = 0;
> +
> +		if (!val)
> +			features &= ~NETIF_F_IPV6_CSUM;
> +	}
> +
>  	if (features & NETIF_F_TSO) {
>  		if (xenbus_scanf(XBT_NIL, np->xbdev->otherend,
>  				 "feature-gso-tcpv4", "%d", &val) < 0)
> @@ -1200,6 +1214,15 @@ static netdev_features_t xennet_fix_features(struct net_device *dev,
>  			features &= ~NETIF_F_TSO;
>  	}
>  
> +	if (features & NETIF_F_TSO6) {
> +		if (xenbus_scanf(XBT_NIL, np->xbdev->otherend,
> +				 "feature-gso-tcpv6", "%d", &val) < 0)
> +			val = 0;
> +
> +		if (!val)
> +			features &= ~NETIF_F_TSO6;
> +	}
> +
>  	return features;
>  }
>  
> @@ -1338,7 +1361,9 @@ static struct net_device *xennet_create_dev(struct xenbus_device *dev)
>  	netif_napi_add(netdev, &np->napi, xennet_poll, 64);
>  	netdev->features        = NETIF_F_IP_CSUM | NETIF_F_RXCSUM |
>  				  NETIF_F_GSO_ROBUST;
> -	netdev->hw_features	= NETIF_F_IP_CSUM | NETIF_F_SG | NETIF_F_TSO;
> +	netdev->hw_features	= NETIF_F_SG |
> +				  NETIF_F_IPV6_CSUM |
> +				  NETIF_F_TSO | NETIF_F_TSO6;
>  
>  	/*
>           * Assume that all hw features are available for now. This set
> @@ -1716,6 +1741,19 @@ again:
>  		goto abort_transaction;
>  	}
>  
> +	err = xenbus_printf(xbt, dev->nodename, "feature-gso-tcpv6", "%d", 1);

"%d", 1 results in a constant string.  xenbus_write() would avoid a
transitory memory allocation.

~Andrew

> +	if (err) {
> +		message = "writing feature-gso-tcpv6";
> +		goto abort_transaction;
> +	}
> +
> +	err = xenbus_printf(xbt, dev->nodename, "feature-ipv6-csum-offload",
> +			    "%d", 1);
> +	if (err) {
> +		message = "writing feature-ipv6-csum-offload";
> +		goto abort_transaction;
> +	}
> +
>  	err = xenbus_transaction_end(xbt, 0);
>  	if (err) {
>  		if (err == -EAGAIN)