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, 15 insertions, 4 deletions

diff --git a/net/8021q/vlan_core.c b/net/8021q/vlan_core.c
index 1b9406a31f0..01ddb0472f8 100644
--- a/net/8021q/vlan_core.c
+++ b/net/8021q/vlan_core.c
@@ -8,6 +8,9 @@
 int __vlan_hwaccel_rx(struct sk_buff *skb, struct vlan_group *grp,
 		      u16 vlan_tci, int polling)
 {
+	struct net_device *vlan_dev;
+	u16 vlan_id;
+
 	if (netpoll_rx(skb))
 		return NET_RX_DROP;
 
@@ -16,9 +19,12 @@ int __vlan_hwaccel_rx(struct sk_buff *skb, struct vlan_group *grp,
 
 	skb->skb_iif = skb->dev->ifindex;
 	__vlan_hwaccel_put_tag(skb, vlan_tci);
-	skb->dev = vlan_group_get_device(grp, vlan_tci & VLAN_VID_MASK);
+	vlan_id = vlan_tci & VLAN_VID_MASK;
+	vlan_dev = vlan_group_get_device(grp, vlan_id);
 
-	if (!skb->dev)
+	if (vlan_dev)
+		skb->dev = vlan_dev;
+	else if (vlan_id)
 		goto drop;
 
 	return (polling ? netif_receive_skb(skb) : netif_rx(skb));
@@ -83,15 +89,20 @@ vlan_gro_common(struct napi_struct *napi, struct vlan_group *grp,
 		unsigned int vlan_tci, struct sk_buff *skb)
 {
 	struct sk_buff *p;
+	struct net_device *vlan_dev;
+	u16 vlan_id;
 
 	if (skb_bond_should_drop(skb, ACCESS_ONCE(skb->dev->master)))
 		skb->deliver_no_wcard = 1;
 
 	skb->skb_iif = skb->dev->ifindex;
 	__vlan_hwaccel_put_tag(skb, vlan_tci);
-	skb->dev = vlan_group_get_device(grp, vlan_tci & VLAN_VID_MASK);
+	vlan_id = vlan_tci & VLAN_VID_MASK;
+	vlan_dev = vlan_group_get_device(grp, vlan_id);
 
-	if (!skb->dev)
+	if (vlan_dev)
+		skb->dev = vlan_dev;
+	else if (vlan_id)
 		goto drop;
 
 	for (p = napi->gro_list; p; p = p->next) {