MPLS: Use mpls_features to activate software MPLS GSO segmentation

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 software segmentation was activated by
skb_gso_ok().

This introduces the overhead of an extra call to skb_network_protocol()
in the case where where CONFIG_NET_MPLS_GSO is set and
skb->ip_summed == CHECKSUM_NONE.

Thanks to Jesse Gross for prompting me to investigate this.

Signed-off-by: Simon Horman <horms@verge.net.au>
Acked-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Acked-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 27 insertions, 1 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index a9a08e4a4857..ed8fe62d41af 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2513,13 +2513,39 @@ static int dev_gso_segment(struct sk_buff *skb, netdev_features_t features)
         return 0;
 }
 
+/* If MPLS offload request, verify we are testing hardware MPLS features
+ * instead of standard features for the netdev.
+ */
+#ifdef CONFIG_NET_MPLS_GSO
+static netdev_features_t net_mpls_features(struct sk_buff *skb,
+                                           netdev_features_t features,
+                                           __be16 type)
+{
+        if (type == htons(ETH_P_MPLS_UC) || type == htons(ETH_P_MPLS_MC))
+                features &= skb->dev->mpls_features;
+
+        return features;
+}
+#else
+static netdev_features_t net_mpls_features(struct sk_buff *skb,
+                                           netdev_features_t features,
+                                           __be16 type)
+{
+        return features;
+}
+#endif
+
 static netdev_features_t harmonize_features(struct sk_buff *skb,
         netdev_features_t features)
 {
         int tmp;
+        __be16 type;
+
+        type = skb_network_protocol(skb, &tmp);
+        features = net_mpls_features(skb, features, type);
 
         if (skb->ip_summed != CHECKSUM_NONE &&
-            !can_checksum_protocol(features, skb_network_protocol(skb, &tmp))) {
+            !can_checksum_protocol(features, type)) {
                 features &= ~NETIF_F_ALL_CSUM;
         } else if (illegal_highdma(skb->dev, skb)) {
                 features &= ~NETIF_F_SG;