vlan: Enable software emulation for vlan accleration.

Currently users of hardware vlan accleration need to know whether
the device supports it before generating packets.  However, vlan
acceleration will soon be available in a more flexible manner so
knowing ahead of time becomes much more difficult.  This adds
a software fallback path for vlan packets on devices without the
necessary offloading support, similar to other types of hardware
accleration.
Signed-off-by: Jesse Gross <jesse@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -2248,9 +2248,17 @@ static inline int skb_gso_ok(struct sk_buff *skb, int features)
 
 static inline int netif_needs_gso(struct net_device *dev, struct sk_buff *skb)
 {
-	return skb_is_gso(skb) &&
-	       (!skb_gso_ok(skb, dev->features) ||
+	if (skb_is_gso(skb)) {
+		int features = dev->features;
+
+		if (skb->protocol == htons(ETH_P_8021Q) || skb->vlan_tci)
+			features &= dev->vlan_features;
+
+		return (!skb_gso_ok(skb, features) ||
 			unlikely(skb->ip_summed != CHECKSUM_PARTIAL));
+	}
+
+	return 0;
 }
 
 static inline void netif_set_gso_max_size(struct net_device *dev,

net/core/dev.c

@@ -1694,7 +1694,12 @@ static bool can_checksum_protocol(unsigned long features, __be16 protocol)
 
 static bool dev_can_checksum(struct net_device *dev, struct sk_buff *skb)
 {
-	if (can_checksum_protocol(dev->features, skb->protocol))
+	int features = dev->features;
+
+	if (vlan_tx_tag_present(skb))
+		features &= dev->vlan_features;
+
+	if (can_checksum_protocol(features, skb->protocol))
 		return true;
 
 	if (skb->protocol == htons(ETH_P_8021Q)) {
@@ -1793,6 +1798,16 @@ struct sk_buff *skb_gso_segment(struct sk_buff *skb, int features)
 	__be16 type = skb->protocol;
 	int err;
 
+	if (type == htons(ETH_P_8021Q)) {
+		struct vlan_ethhdr *veh;
+
+		if (unlikely(!pskb_may_pull(skb, VLAN_ETH_HLEN)))
+			return ERR_PTR(-EINVAL);
+
+		veh = (struct vlan_ethhdr *)skb->data;
+		type = veh->h_vlan_encapsulated_proto;
+	}
+
 	skb_reset_mac_header(skb);
 	skb->mac_len = skb->network_header - skb->mac_header;
 	__skb_pull(skb, skb->mac_len);
@@ -1964,9 +1979,14 @@ 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->protocol == htons(ETH_P_8021Q) || vlan_tx_tag_present(skb))
+		features &= dev->vlan_features;
+
 	return skb_is_nonlinear(skb) &&
-	       ((skb_has_frag_list(skb) && !(dev->features & NETIF_F_FRAGLIST)) ||
-	        (skb_shinfo(skb)->nr_frags && (!(dev->features & NETIF_F_SG) ||
+	       ((skb_has_frag_list(skb) && !(features & NETIF_F_FRAGLIST)) ||
+		(skb_shinfo(skb)->nr_frags && (!(features & NETIF_F_SG) ||
 					      illegal_highdma(dev, skb))));
 }
 
@@ -1989,6 +2009,15 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
 
 		skb_orphan_try(skb);
 
+		if (vlan_tx_tag_present(skb) &&
+		    !(dev->features & NETIF_F_HW_VLAN_TX)) {
+			skb = __vlan_put_tag(skb, vlan_tx_tag_get(skb));
+			if (unlikely(!skb))
+				goto out;
+
+			skb->vlan_tci = 0;
+		}
+
 		if (netif_needs_gso(dev, skb)) {
 			if (unlikely(dev_gso_segment(skb)))
 				goto out_kfree_skb;
@@ -2050,6 +2079,7 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
 		skb->destructor = DEV_GSO_CB(skb)->destructor;
 out_kfree_skb:
 	kfree_skb(skb);
+out:
 	return rc;
 }