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>

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 0c6adaa..65e2892 100644 (file)
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -298,7 +298,7 @@ static rx_handler_result_t macvtap_handle_frame(struct sk_buff **pskb)
         */
        if (q->flags & IFF_VNET_HDR)
                features |= vlan->tap_features;
-       if (netif_needs_gso(skb, features)) {
+       if (netif_needs_gso(dev, skb, features)) {
                struct sk_buff *segs = __skb_gso_segment(skb, features, false);
 
                if (IS_ERR(segs))

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index ca82f54..3c0b375 100644 (file)
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -638,7 +638,7 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
 
        if (unlikely(!netif_carrier_ok(dev) ||
                     (slots > 1 && !xennet_can_sg(dev)) ||
-                    netif_needs_gso(skb, netif_skb_features(skb)))) {
+                    netif_needs_gso(dev, skb, netif_skb_features(skb)))) {
                spin_unlock_irqrestore(&queue->tx_lock, flags);
                goto drop;
        }

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 838407a..74fd5d3 100644 (file)
--- 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)));
 }

diff --git a/net/core/dev.c b/net/core/dev.c
index 4699dcf..9f77a78 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2675,7 +2675,7 @@ static struct sk_buff *validate_xmit_skb(struct sk_buff *skb, struct net_device
        if (skb->encapsulation)
                features &= dev->hw_enc_features;
 
-       if (netif_needs_gso(skb, features)) {
+       if (netif_needs_gso(dev, skb, features)) {
                struct sk_buff *segs;
 
                segs = skb_gso_segment(skb, features);