net: Add ndo_gso_check

Add ndo_gso_check which a device can define to indicate whether is
is capable of doing GSO on a packet. This funciton would be called from
the stack to determine whether software GSO is needed to be done. A
driver should populate this function if it advertises GSO types for
which there are combinations that it wouldn't be able to handle. For
instance a device that performs UDP tunneling might only implement
support for transparent Ethernet bridging type of inner packets
or might have limitations on lengths of inner headers.

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 1 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 838407aea705..74fd5d37f15a 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -998,6 +998,12 @@ typedef u16 (*select_queue_fallback_t)(struct net_device *dev,
  *      Callback to use for xmit over the accelerated station. This
  *      is used in place of ndo_start_xmit on accelerated net
  *      devices.
+ * bool (*ndo_gso_check) (struct sk_buff *skb,
+ *                        struct net_device *dev);
+ *      Called by core transmit path to determine if device is capable of
+ *      performing GSO on a packet. The device returns true if it is
+ *      able to GSO the packet, false otherwise. If the return value is
+ *      false the stack will do software GSO.
  */
 struct net_device_ops {
         int                     (*ndo_init)(struct net_device *dev);
@@ -1147,6 +1153,8 @@ struct net_device_ops {
                                                         struct net_device *dev,
                                                         void *priv);
         int                     (*ndo_get_lock_subclass)(struct net_device *dev);
+        bool                    (*ndo_gso_check) (struct sk_buff *skb,
+                                                  struct net_device *dev);
 };
 
 /**
@@ -3572,10 +3580,12 @@ static inline bool skb_gso_ok(struct sk_buff *skb, netdev_features_t features)
                (!skb_has_frag_list(skb) || (features & NETIF_F_FRAGLIST));
 }
 
-static inline bool netif_needs_gso(struct sk_buff *skb,
+static inline bool netif_needs_gso(struct net_device *dev, struct sk_buff *skb,
                                    netdev_features_t features)
 {
         return skb_is_gso(skb) && (!skb_gso_ok(skb, features) ||
+                (dev->netdev_ops->ndo_gso_check &&
+                 !dev->netdev_ops->ndo_gso_check(skb, dev)) ||
                 unlikely((skb->ip_summed != CHECKSUM_PARTIAL) &&
                          (skb->ip_summed != CHECKSUM_UNNECESSARY)));
 }