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, 60 insertions, 43 deletions

diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
index 7cb285f96b99..3d59c9bf8feb 100644
--- a/net/8021q/vlan_dev.c
+++ b/net/8021q/vlan_dev.c
@@ -142,6 +142,7 @@ int vlan_skb_recv(struct sk_buff *skb, struct net_device *dev,
 {
         struct vlan_hdr *vhdr;
         struct vlan_rx_stats *rx_stats;
+        struct net_device *vlan_dev;
         u16 vlan_id;
         u16 vlan_tci;
 
@@ -157,55 +158,71 @@ int vlan_skb_recv(struct sk_buff *skb, struct net_device *dev,
         vlan_id = vlan_tci & VLAN_VID_MASK;
 
         rcu_read_lock();
-        skb->dev = __find_vlan_dev(dev, vlan_id);
-        if (!skb->dev) {
-                pr_debug("%s: ERROR: No net_device for VID: %u on dev: %s\n",
-                         __func__, vlan_id, dev->name);
-                goto err_unlock;
-        }
-
-        rx_stats = per_cpu_ptr(vlan_dev_info(skb->dev)->vlan_rx_stats,
-                               smp_processor_id());
-        u64_stats_update_begin(&rx_stats->syncp);
-        rx_stats->rx_packets++;
-        rx_stats->rx_bytes += skb->len;
-
-        skb_pull_rcsum(skb, VLAN_HLEN);
-
-        skb->priority = vlan_get_ingress_priority(skb->dev, vlan_tci);
+        vlan_dev = __find_vlan_dev(dev, vlan_id);
 
-        pr_debug("%s: priority: %u for TCI: %hu\n",
-                 __func__, skb->priority, vlan_tci);
-
-        switch (skb->pkt_type) {
-        case PACKET_BROADCAST: /* Yeah, stats collect these together.. */
-                /* stats->broadcast ++; // no such counter :-( */
-                break;
-
-        case PACKET_MULTICAST:
-                rx_stats->rx_multicast++;
-                break;
+        /* If the VLAN device is defined, we use it.
+         * If not, and the VID is 0, it is a 802.1p packet (not
+         * really a VLAN), so we will just netif_rx it later to the
+         * original interface, but with the skb->proto set to the
+         * wrapped proto: we do nothing here.
+         */
 
-        case PACKET_OTHERHOST:
-                /* Our lower layer thinks this is not local, let's make sure.
-                 * This allows the VLAN to have a different MAC than the
-                 * underlying device, and still route correctly.
-                 */
-                if (!compare_ether_addr(eth_hdr(skb)->h_dest,
-                                        skb->dev->dev_addr))
-                        skb->pkt_type = PACKET_HOST;
-                break;
-        default:
-                break;
+        if (!vlan_dev) {
+                if (vlan_id) {
+                        pr_debug("%s: ERROR: No net_device for VID: %u on dev: %s\n",
+                                 __func__, vlan_id, dev->name);
+                        goto err_unlock;
+                }
+                rx_stats = NULL;
+        } else {
+                skb->dev = vlan_dev;
+
+                rx_stats = per_cpu_ptr(vlan_dev_info(skb->dev)->vlan_rx_stats,
+                                        smp_processor_id());
+                u64_stats_update_begin(&rx_stats->syncp);
+                rx_stats->rx_packets++;
+                rx_stats->rx_bytes += skb->len;
+
+                skb->priority = vlan_get_ingress_priority(skb->dev, vlan_tci);
+
+                pr_debug("%s: priority: %u for TCI: %hu\n",
+                         __func__, skb->priority, vlan_tci);
+
+                switch (skb->pkt_type) {
+                case PACKET_BROADCAST:
+                        /* Yeah, stats collect these together.. */
+                        /* stats->broadcast ++; // no such counter :-( */
+                        break;
+
+                case PACKET_MULTICAST:
+                        rx_stats->rx_multicast++;
+                        break;
+
+                case PACKET_OTHERHOST:
+                        /* Our lower layer thinks this is not local, let's make
+                         * sure.
+                         * This allows the VLAN to have a different MAC than the
+                         * underlying device, and still route correctly.
+                         */
+                        if (!compare_ether_addr(eth_hdr(skb)->h_dest,
+                                                skb->dev->dev_addr))
+                                skb->pkt_type = PACKET_HOST;
+                        break;
+                default:
+                        break;
+                }
+                u64_stats_update_end(&rx_stats->syncp);
         }
-        u64_stats_update_end(&rx_stats->syncp);
 
+        skb_pull_rcsum(skb, VLAN_HLEN);
         vlan_set_encap_proto(skb, vhdr);
 
-        skb = vlan_check_reorder_header(skb);
-        if (!skb) {
-                rx_stats->rx_errors++;
-                goto err_unlock;
+        if (vlan_dev) {
+                skb = vlan_check_reorder_header(skb);
+                if (!skb) {
+                        rx_stats->rx_errors++;
+                        goto err_unlock;
+                }
         }
 
         netif_rx(skb);