If an MPLS packet requires segmentation then use mpls_features
to determine if the software implementation should be used.
As no driver advertises MPLS GSO segmentation this will always be
the case.
I had not noticed that this was necessary before as software MPLS GSO
segmentation was already being used in my test environment. I believe that
the reason for that is the skbs in question always had fragments and the
driver I used does not advertise NETIF_F_FRAGLIST (which seems to be the
case for most drivers). Thus Thus software segmentation was activated by
skb_gso_ok().
Thanks to Jesse Gross for prompting me to investigate this.
Cc: Jesse Gross <je...@nicira.com>
Signed-off-by: Simon Horman <ho...@verge.net.au>
---
net/core/dev.c | 36 ++++++++++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)
diff --git a/net/core/dev.c b/net/core/dev.c
index 867adb2..ade6029 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2540,6 +2540,40 @@ netdev_features_t netif_skb_features(struct sk_buff *skb)
}
EXPORT_SYMBOL(netif_skb_features);
+/* If MPLS offload request, verify we are testing hardware MPLS features
+ * instead of standard features for the netdev.
+ */
+#ifdef CONFIG_NET_MPLS_GSO
+static inline netdev_features_t net_mpls_features(struct sk_buff *skb,
+ struct net_device *dev, netdev_features_t features)
+{
+ /* There is no support for MPLS LRO. So the only way that
+ * an MPLS skb could require GSO segmentation is if it
+ * was received as a non-MPLS skb and then became an MPLS skb.
+ * This may be effected by Open vSwitch in which case the
+ * mac_len will non-zero and not equal to skb_network_offset
+ * as the former indicates the end of L2 the latter indicates
+ * the beginning of L3 and there is a gap between them occupied
+ * by the MPLS label stack.
+ *
+ * Thus it is possible to avoid traversing any VLAN tags that are
+ * present to determine if the ethtype is MPLS. Instead the
+ * inequality of mac_llen and skb_network_offset are used to
+ * determine if a packet is MPLS for the purpose of determining
+ * offload features.
+ */
+ if (skb->mac_len && skb->mac_len != skb_network_offset(skb))
+ features &= dev->mpls_features;
+ return features;
+}
+#else
+static inline netdev_features_t net_mpls_features(struct sk_buff *skb,
+ struct net_device *dev, netdev_features_t features)
+{
+ return features;
+}
+#endif
+
int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
struct netdev_queue *txq)
{
@@ -2576,6 +2610,8 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct
net_device *dev,
if (skb->encapsulation)
features &= dev->hw_enc_features;
+ features = net_mpls_features(skb, dev, features);
+
if (netif_needs_gso(skb, features)) {
if (unlikely(dev_gso_segment(skb, features)))
goto out_kfree_skb;
--
1.8.4
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