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

[ 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@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

3 files changed, 28 insertions, 2 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 96e4c21e15e0..abf7756eaf9e 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1772,6 +1772,15 @@ 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 1cd3d2a406f5..4af64afc7022 100644
--- a/net/8021q/vlan_dev.c
+++ b/net/8021q/vlan_dev.c
@@ -549,6 +549,23 @@ 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 struct device_type vlan_type = {
         .name   = "vlan",
 };
@@ -592,7 +609,7 @@ static int vlan_dev_init(struct net_device *dev)
 
         dev->needed_headroom = real_dev->needed_headroom;
         if (real_dev->features & NETIF_F_HW_VLAN_CTAG_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;
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 0034b611fa5e..49aeab86f317 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1274,7 +1274,7 @@ int neigh_compat_output(struct neighbour *neigh, struct sk_buff *skb)
 
         if (dev_hard_header(skb, dev, ntohs(skb->protocol), NULL, NULL,
                             skb->len) < 0 &&
-            dev->header_ops->rebuild(skb))
+            dev_rebuild_header(skb))
                 return 0;
 
         return dev_queue_xmit(skb);