datapath: Move segmentation compatibility code into a compatibility function

Move segmentation compatibility code out of netdev_send and into
rpl_dev_queue_xmit(), a compatibility function used in place
of dev_queue_xmit() as necessary.

As suggested by Jesse Gross.

Some minor though verbose implementation notes:

* This rpl_dev_queue_xmit() endeavours to return a valid error code or
  zero on success as per dev_queue_xmit(). The exception is that when
  dev_queue_xmit() is called in a loop only the status of the last call is
  taken into account, thus ignoring any errors returned by previous calls.
  This is derived from the previous calls to dev_queue_xmit() in a loop
  where netdev_send() ignores the return value of dev_queue_xmit()
  entirely.

* netdev_send() continues to ignore the value of dev_queue_xmit().
  So the discussion of the return value of rpl_dev_queue_xmit()
  above is has no bearing on run-time behaviour.

* The return value of netdev_send() may differ from the previous
  implementation in the case where segmentation is performed before
  calling the real dev_queue_xmit(). This is because previously in
  this case netdev_send() would return the combined length of the
  skbs resulting from segmentation. Whereas the current code
  always returns the length of the original skb.

Signed-off-by: Simon Horman <horms@verge.net.au>
[jesse: adjust error path in netdev_send() to match upstream]
Signed-off-by: Jesse Gross <jesse@nicira.com>

1 files changed, 80 insertions, 0 deletions

diff --git a/datapath/linux/compat/gso.c b/datapath/linux/compat/gso.c
index 30332a2dc..32f906c82 100644
--- a/datapath/linux/compat/gso.c
+++ b/datapath/linux/compat/gso.c
@@ -36,6 +36,86 @@
 
 #include "gso.h"
 
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,37) && \
+	!defined(HAVE_VLAN_BUG_WORKAROUND)
+#include <linux/module.h>
+
+static int vlan_tso __read_mostly;
+module_param(vlan_tso, int, 0644);
+MODULE_PARM_DESC(vlan_tso, "Enable TSO for VLAN packets");
+#else
+#define vlan_tso true
+#endif
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,37)
+static bool dev_supports_vlan_tx(struct net_device *dev)
+{
+#if defined(HAVE_VLAN_BUG_WORKAROUND)
+	return dev->features & NETIF_F_HW_VLAN_TX;
+#else
+	/* Assume that the driver is buggy. */
+	return false;
+#endif
+}
+
+int rpl_dev_queue_xmit(struct sk_buff *skb)
+{
+#undef dev_queue_xmit
+	int err = -ENOMEM;
+
+	if (vlan_tx_tag_present(skb) && !dev_supports_vlan_tx(skb->dev)) {
+		int features;
+
+		features = netif_skb_features(skb);
+
+		if (!vlan_tso)
+			features &= ~(NETIF_F_TSO | NETIF_F_TSO6 |
+				      NETIF_F_UFO | NETIF_F_FSO);
+
+		skb = __vlan_put_tag(skb, skb->vlan_proto, vlan_tx_tag_get(skb));
+		if (unlikely(!skb))
+			return err;
+		vlan_set_tci(skb, 0);
+
+		if (netif_needs_gso(skb, features)) {
+			struct sk_buff *nskb;
+
+			nskb = skb_gso_segment(skb, features);
+			if (!nskb) {
+				if (unlikely(skb_cloned(skb) &&
+				    pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
+					goto drop;
+
+				skb_shinfo(skb)->gso_type &= ~SKB_GSO_DODGY;
+				goto xmit;
+			}
+
+			if (IS_ERR(nskb)) {
+				err = PTR_ERR(nskb);
+				goto drop;
+			}
+			consume_skb(skb);
+			skb = nskb;
+
+			do {
+				nskb = skb->next;
+				skb->next = NULL;
+				err = dev_queue_xmit(skb);
+				skb = nskb;
+			} while (skb);
+
+			return err;
+		}
+	}
+xmit:
+	return dev_queue_xmit(skb);
+
+drop:
+	kfree_skb(skb);
+	return err;
+}
+#endif /* kernel version < 2.6.37 */
+
 static __be16 __skb_network_protocol(struct sk_buff *skb)
 {
 	__be16 type = skb->protocol;