[PATCH net-next v5 1/5] xen-netback: add support for IPv6 checksum offload to guest

[Paul Durrant <paul.durrant@citrix.com>]

Check xenstore flag feature-ipv6-csum-offload to determine if a
guest is happy to accept IPv6 packets with only partial checksum.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
---
 drivers/net/xen-netback/common.h    |    3 ++-
 drivers/net/xen-netback/interface.c |   10 +++++++---
 drivers/net/xen-netback/xenbus.c    |    7 ++++++-
 include/xen/interface/io/netif.h    |    7 +++++++
 4 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index 5715318..b4a9a3c 100644
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -153,7 +153,8 @@ struct xenvif {
 	u8 can_sg:1;
 	u8 gso:1;
 	u8 gso_prefix:1;
-	u8 csum:1;
+	u8 ip_csum:1;
+	u8 ipv6_csum:1;
 
 	/* Internal feature information. */
 	u8 can_queue:1;	    /* can queue packets for receiver? */
diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index 01bb854..8e92783 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -216,8 +216,10 @@ static netdev_features_t xenvif_fix_features(struct net_device *dev,
 		features &= ~NETIF_F_SG;
 	if (!vif->gso && !vif->gso_prefix)
 		features &= ~NETIF_F_TSO;
-	if (!vif->csum)
+	if (!vif->ip_csum)
 		features &= ~NETIF_F_IP_CSUM;
+	if (!vif->ipv6_csum)
+		features &= ~NETIF_F_IPV6_CSUM;
 
 	return features;
 }
@@ -306,7 +308,7 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t domid,
 	vif->domid  = domid;
 	vif->handle = handle;
 	vif->can_sg = 1;
-	vif->csum = 1;
+	vif->ip_csum = 1;
 	vif->dev = dev;
 
 	vif->credit_bytes = vif->remaining_credit = ~0UL;
@@ -316,7 +318,9 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t domid,
 	vif->credit_timeout.expires = jiffies;
 
 	dev->netdev_ops	= &xenvif_netdev_ops;
-	dev->hw_features = NETIF_F_SG | NETIF_F_IP_CSUM | NETIF_F_TSO;
+	dev->hw_features = NETIF_F_SG |
+		NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM |
+		NETIF_F_TSO;
 	dev->features = dev->hw_features;
 	SET_ETHTOOL_OPS(dev, &xenvif_ethtool_ops);
 
diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
index 1b08d87..ad27b15 100644
--- a/drivers/net/xen-netback/xenbus.c
+++ b/drivers/net/xen-netback/xenbus.c
@@ -574,7 +574,12 @@ static int connect_rings(struct backend_info *be)
 	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-no-csum-offload",
 			 "%d", &val) < 0)
 		val = 0;
-	vif->csum = !val;
+	vif->ip_csum = !val;
+
+	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-ipv6-csum-offload",
+			 "%d", &val) < 0)
+		val = 0;
+	vif->ipv6_csum = !!val;
 
 	/* Map the shared frame, irq etc. */
 	err = xenvif_connect(vif, tx_ring_ref, rx_ring_ref,
diff --git a/include/xen/interface/io/netif.h b/include/xen/interface/io/netif.h
index eb262e3..c9e8184 100644
--- a/include/xen/interface/io/netif.h
+++ b/include/xen/interface/io/netif.h
@@ -51,6 +51,13 @@
  */
 
 /*
+ * "feature-no-csum-offload" should be used to turn IPv4 TCP/UDP checksum
+ * offload off or on. If it is missing then the feature is assumed to be on.
+ * "feature-ipv6-csum-offload" should be used to turn IPv6 TCP/UDP checksum
+ * offload on or off. If it is missing then the feature is assumed to be off.
+ */
+
+/*
  * This is the 'wire' format for packets:
  *  Request 1: xen_netif_tx_request  -- XEN_NETTXF_* (any flags)
  * [Request 2: xen_netif_extra_info]    (only if request 1 has XEN_NETTXF_extra_info)
-- 
1.7.10.4