[PATCH v2 04/14] vlan: Enable software emulation for vlan accleration.

[Jesse Gross <jesse@nicira.com>]

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>
---
 include/linux/netdevice.h |   14 +++++++++++---
 net/core/dev.c            |   36 +++++++++++++++++++++++++++++++++---
 2 files changed, 44 insertions(+), 6 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 880d565..2861565 100644
--- a/include/linux/netdevice.h
+++ b/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) ||
-		unlikely(skb->ip_summed != CHECKSUM_PARTIAL));
+	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,
diff --git a/net/core/dev.c b/net/core/dev.c
index 4c3ac53..1bfd96b 100644
--- a/net/core/dev.c
+++ b/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 @@ out_kfree_gso_skb:
 		skb->destructor = DEV_GSO_CB(skb)->destructor;
 out_kfree_skb:
 	kfree_skb(skb);
+out:
 	return rc;
 }
 
-- 
1.7.1