offloading: Make scatter/gather more tolerant of vlans.

When checking if it is necessary to linearize a packet, we currently
use vlan_features if the packet contains either an in-band or out-
of-band vlan tag.  However, in-band tags aren't special in any way
for scatter/gather since they are part of the packet buffer and are
simply more data to DMA.  Therefore, only use vlan_features for out-
of-band tags, which could potentially have some interaction with
scatter/gather.

Signed-off-by: Jesse Gross <jesse@nicira.com>
CC: Ben Hutchings <bhutchings@solarflare.com>
Reviewed-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/dev.c b/net/core/dev.c
index 5968c822c99993ec67e285817bf27c25716f16e3..0b403d5033111cf4a9de5e865f6949f84c4e2343 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1976,15 +1976,20 @@ static inline void skb_orphan_try(struct sk_buff *skb)
 static inline int skb_needs_linearize(struct sk_buff *skb,
                                      struct net_device *dev)
 {
-       int features = dev->features;
+       if (skb_is_nonlinear(skb)) {
+               int features = dev->features;
 
-       if (skb->protocol == htons(ETH_P_8021Q) || vlan_tx_tag_present(skb))
-               features &= dev->vlan_features;
+               if (vlan_tx_tag_present(skb))
+                       features &= dev->vlan_features;
 
-       return skb_is_nonlinear(skb) &&
-              ((skb_has_frag_list(skb) && !(features & NETIF_F_FRAGLIST)) ||
-               (skb_shinfo(skb)->nr_frags && (!(features & NETIF_F_SG) ||
-                                             illegal_highdma(dev, skb))));
+               return (skb_has_frag_list(skb) &&
+                       !(features & NETIF_F_FRAGLIST)) ||
+                       (skb_shinfo(skb)->nr_frags &&
+                       (!(features & NETIF_F_SG) ||
+                       illegal_highdma(dev, skb)));
+       }
+
+       return 0;
 }
 
 int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,