net: Fix stacked vlan offload features computation

[ Upstream commit 796f2da81bead71ffc91ef70912cd8d1827bf756 ]

When vlan tags are stacked, it is very likely that the outer tag is stored
in skb->vlan_tci and skb->protocol shows the inner tag's vlan_proto.
Currently netif_skb_features() first looks at skb->protocol even if there
is the outer tag in vlan_tci, thus it incorrectly retrieves the protocol
encapsulated by the inner vlan instead of the inner vlan protocol.
This allows GSO packets to be passed to HW and they end up being
corrupted.

Fixes: 58e998c6d239 ("offloading: Force software GSO for multiple vlan tags.")
Signed-off-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

diff --git a/net/core/dev.c b/net/core/dev.c
index 70876db1ade2b3633ed7cb560b0c365d1d1dd885..5f26b64da9ac6b261a7028be11e913e7b1c8dc56 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2504,11 +2504,14 @@ netdev_features_t netif_skb_dev_features(struct sk_buff *skb,
        if (skb_shinfo(skb)->gso_segs > dev->gso_max_segs)
                features &= ~NETIF_F_GSO_MASK;
 
-       if (protocol == htons(ETH_P_8021Q) || protocol == htons(ETH_P_8021AD)) {
-               struct vlan_ethhdr *veh = (struct vlan_ethhdr *)skb->data;
-               protocol = veh->h_vlan_encapsulated_proto;
-       } else if (!vlan_tx_tag_present(skb)) {
-               return harmonize_features(skb, dev, features);
+       if (!vlan_tx_tag_present(skb)) {
+               if (unlikely(protocol == htons(ETH_P_8021Q) ||
+                            protocol == htons(ETH_P_8021AD))) {
+                       struct vlan_ethhdr *veh = (struct vlan_ethhdr *)skb->data;
+                       protocol = veh->h_vlan_encapsulated_proto;
+               } else {
+                       return harmonize_features(skb, dev, features);
+               }
        }
 
        features = netdev_intersect_features(features,