vlan_dev: VLAN 0 should be treated as "no vlan tag" (802.1p packet)

- Without the 8021q module loaded in the kernel, all 802.1p packets 
(VLAN 0 but QoS tagging) are silently discarded (as expected, as 
the protocol is not loaded).
 
- Without this patch in 8021q module, these packets are forwarded to 
the module, but they are discarded also if VLAN 0 is not configured,
which should not be the default behaviour, as VLAN 0 is not really
a VLANed packet but a 802.1p packet. Defining VLAN 0 makes it almost
impossible to communicate with mixed 802.1p and non 802.1p devices on
the same network due to arp table issues.

- Changed logic to skip vlan specific code in vlan_skb_recv if VLAN 
is 0 and we have not defined a VLAN with ID 0, but we accept the 
packet with the encapsulated proto and pass it later to netif_rx.

- In the vlan device event handler, added some logic to add VLAN 0 
to HW filter in devices that support it (this prevented any traffic
in VLAN 0 to reach the stack in e1000e with HW filter under 2.6.35,
and probably also with other HW filtered cards, so we fix it here).

- In the vlan unregister logic, prevent the elimination of VLAN 0 
in devices with HW filter.

- The default behaviour is to ignore the VLAN 0 tagging and accept
the packet as if it was not tagged, but we can still define a 
VLAN 0 if desired (so it is backwards compatible).

Signed-off-by: Pedro Garcia <pedro.netdev@dondevamos.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 2 deletions

diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c
index 3c1c8c14e929..a2ad15250575 100644
--- a/net/8021q/vlan.c
+++ b/net/8021q/vlan.c
@@ -155,9 +155,10 @@ void unregister_vlan_dev(struct net_device *dev, struct list_head *head)
         BUG_ON(!grp);
 
         /* Take it out of our own structures, but be sure to interlock with
-         * HW accelerating devices or SW vlan input packet processing.
+         * HW accelerating devices or SW vlan input packet processing if
+         * VLAN is not 0 (leave it there for 802.1p).
          */
-        if (real_dev->features & NETIF_F_HW_VLAN_FILTER)
+        if (vlan_id && (real_dev->features & NETIF_F_HW_VLAN_FILTER))
                 ops->ndo_vlan_rx_kill_vid(real_dev, vlan_id);
 
         grp->nr_vlans--;
@@ -419,6 +420,14 @@ static int vlan_device_event(struct notifier_block *unused, unsigned long event,
         if (is_vlan_dev(dev))
                 __vlan_device_event(dev, event);
 
+        if ((event == NETDEV_UP) &&
+            (dev->features & NETIF_F_HW_VLAN_FILTER) &&
+            dev->netdev_ops->ndo_vlan_rx_add_vid) {
+                pr_info("8021q: adding VLAN 0 to HW filter on device %s\n",
+                        dev->name);
+                dev->netdev_ops->ndo_vlan_rx_add_vid(dev, 0);
+        }
+
         grp = __vlan_find_group(dev);
         if (!grp)
                 goto out;