+static bool can_checksum_protocol(unsigned long features, __be16 protocol)
+{
+ return ((features & NETIF_F_GEN_CSUM) ||
+ ((features & NETIF_F_V4_CSUM) &&
+ protocol == htons(ETH_P_IP)) ||
+ ((features & NETIF_F_V6_CSUM) &&
+ protocol == htons(ETH_P_IPV6)) ||
+ ((features & NETIF_F_FCOE_CRC) &&
+ protocol == htons(ETH_P_FCOE)));
+}
+
+static int harmonize_features(struct sk_buff *skb, __be16 protocol, int features)
+{
+ if (!can_checksum_protocol(protocol, features)) {
+ features &= ~NETIF_F_ALL_CSUM;
+ features &= ~NETIF_F_SG;
+ } else if (illegal_highdma(skb->dev, skb)) {
+ features &= ~NETIF_F_SG;
+ }
+
+ return features;
+}
+
+int netif_skb_features(struct sk_buff *skb)
+{
+ __be16 protocol = skb->protocol;
+ int features = skb->dev->features;
+
+ if (protocol == htons(ETH_P_8021Q)) {
+ 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, protocol, features);
+ }
+
+ features &= skb->dev->vlan_features;
+
+ if (protocol != htons(ETH_P_8021Q)) {
+ return harmonize_features(skb, protocol, features);
+ } else {
+ features &= NETIF_F_SG | NETIF_F_HIGHDMA | NETIF_F_FRAGLIST |
+ NETIF_F_GEN_CSUM;
+ return harmonize_features(skb, protocol, features);
+ }
+}
+EXPORT_SYMBOL(netif_skb_features);
+