[Xen-devel] [PATCH net-next 1/5] xen-netback: add IPv6 checksum offload to guest

[Paul Durrant <paul.durrant@xxxxxxxxxx>]

Check xenstore flag feature-ipv6-csum-offload to determine if a
guest is happy to accept IPv6 packets with only partial checksum.
Also check analogous feature-ip-csum-offload to determone if a
guest is happy to accept IPv4 packets with only partial checksum
as a replacement for a negated feature-no-csum-offload value and
add a comment to deprecate use of feature-no-csum-offload.

Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
Cc: Wei Liu <wei.liuw2@xxxxxxxxxx>
Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
 drivers/net/xen-netback/common.h    |    3 ++-
 drivers/net/xen-netback/interface.c |   10 +++++++---
 drivers/net/xen-netback/xenbus.c    |   24 +++++++++++++++++++++++-
 3 files changed, 32 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 b45bce2..5e45b00 100644
--- a/drivers/net/xen-netback/xenbus.c
+++ b/drivers/net/xen-netback/xenbus.c
@@ -567,10 +567,32 @@ static int connect_rings(struct backend_info *be)
                val = 0;
        vif->gso_prefix = !!val;
 
+       /* Before feature-ipv6-csum-offload was introduced, checksum offload
+        * was turned on by a zero value in (or lack of)
+        * feature-no-csum-offload. Therefore, for compatibility, assume
+        * that if feature-ip-csum-offload is missing that IP (v4) offload
+        * is turned on. If this is not the case then the flag will be
+        * cleared when we subsequently sample feature-no-csum-offload.
+        */
+       if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-ip-csum-offload",
+                        "%d", &val) < 0)
+               val = 1;
+       vif->ip_csum = !!val;
+
+       if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-ipv6-csum-offload",
+                        "%d", &val) < 0)
+               val = 0;
+       vif->ipv6_csum = !!val;
+
+       /* This is deprecated. Frontends should set IP v4 and v6 checksum
+        * offload using feature-ip-csum-offload and
+        * feature-ipv6-csum-offload respectively.
+        */
        if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-no-csum-offload",
                         "%d", &val) < 0)
                val = 0;
-       vif->csum = !val;
+       if (val)
+               vif->ip_csum = 0;
 
        /* Map the shared frame, irq etc. */
        err = xenvif_connect(vif, tx_ring_ref, rx_ring_ref,
-- 
1.7.10.4


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