[PATCH 3.2 12/79] vlan: Fix header ops passthru when doing TX VLAN offload.

[Ben Hutchings]

3.2.55-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: "David S. Miller" <davem@xxxxxxxxxxxxx>

[ Upstream commit 2205369a314e12fcec4781cc73ac9c08fc2b47de ]

When the vlan code detects that the real device can do TX VLAN offloads
in hardware, it tries to arrange for the real device's header_ops to
be invoked directly.

But it does so illegally, by simply hooking the real device's
header_ops up to the VLAN device.

This doesn't work because we will end up invoking a set of header_ops
routines which expect a device type which matches the real device, but
will see a VLAN device instead.

Fix this by providing a pass-thru set of header_ops which will arrange
to pass the proper real device instead.

To facilitate this add a dev_rebuild_header().  There are
implementations which provide a ->cache and ->create but not a
->rebuild (f.e. PLIP).  So we need a helper function just like
dev_hard_header() to avoid crashes.

Use this helper in the one existing place where the
header_ops->rebuild was being invoked, the neighbour code.

With lots of help from Florian Westphal.

Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 include/linux/netdevice.h |  9 +++++++++
 net/8021q/vlan_dev.c      | 18 +++++++++++++++++-
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 8c43fd1..4b04097 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1719,6 +1719,15 @@ static inline int dev_parse_header(const struct sk_buff *skb,
 	return dev->header_ops->parse(skb, haddr);
 }
 
+static inline int dev_rebuild_header(struct sk_buff *skb)
+{
+	const struct net_device *dev = skb->dev;
+
+	if (!dev->header_ops || !dev->header_ops->rebuild)
+		return 0;
+	return dev->header_ops->rebuild(skb);
+}
+
 typedef int gifconf_func_t(struct net_device * dev, char __user * bufptr, int len);
 extern int		register_gifconf(unsigned int family, gifconf_func_t * gifconf);
 static inline int unregister_gifconf(unsigned int family)
diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
index b40d3da..48a62d8 100644
--- a/net/8021q/vlan_dev.c
+++ b/net/8021q/vlan_dev.c
@@ -522,6 +522,22 @@ static const struct header_ops vlan_header_ops = {
 	.parse	 = eth_header_parse,
 };
 
+static int vlan_passthru_hard_header(struct sk_buff *skb, struct net_device *dev,
+				     unsigned short type,
+				     const void *daddr, const void *saddr,
+				     unsigned int len)
+{
+	struct net_device *real_dev = vlan_dev_info(dev)->real_dev;
+
+	return dev_hard_header(skb, real_dev, type, daddr, saddr, len);
+}
+
+static const struct header_ops vlan_passthru_header_ops = {
+	.create	 = vlan_passthru_hard_header,
+	.rebuild = dev_rebuild_header,
+	.parse	 = eth_header_parse,
+};
+
 static const struct net_device_ops vlan_netdev_ops;
 
 static int vlan_dev_init(struct net_device *dev)
@@ -561,7 +577,7 @@ static int vlan_dev_init(struct net_device *dev)
 
 	dev->needed_headroom = real_dev->needed_headroom;
 	if (real_dev->features & NETIF_F_HW_VLAN_TX) {
-		dev->header_ops      = real_dev->header_ops;
+		dev->header_ops      = &vlan_passthru_header_ops;
 		dev->hard_header_len = real_dev->hard_header_len;
 	} else {
 		dev->header_ops      = &vlan_header_ops;

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