[3.5.y.z extended stable] Patch "vlan: Fix header ops passthru when doing TX VLAN offload." has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    vlan: Fix header ops passthru when doing TX VLAN offload.

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From e6c74b3f707a05d45ffd418140814f3a4ba4ad4c Mon Sep 17 00:00:00 2001
From: "David S. Miller" <davem at davemloft.net>
Date: Tue, 31 Dec 2013 16:23:35 -0500
Subject: vlan: Fix header ops passthru when doing TX VLAN offload.

commit 2205369a314e12fcec4781cc73ac9c08fc2b47de upstream.

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 at davemloft.net>
[ luis: backported to 3.5: used davem's backport to 3.4 ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 include/linux/netdevice.h |  9 +++++++++
 net/8021q/vlan_dev.c      | 19 ++++++++++++++++++-
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 735cb59..e80df17 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1726,6 +1726,15 @@ 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 b8cf84e..ce40df8 100644
--- a/net/8021q/vlan_dev.c
+++ b/net/8021q/vlan_dev.c
@@ -525,6 +525,23 @@ 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 vlan_dev_priv *vlan = vlan_dev_priv(dev);
+	struct net_device *real_dev = vlan->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)
@@ -564,7 +581,7 @@ 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;
--
1.8.3.2