When stack receives pkt: [802.1P vlan 0][802.1AD vlan 100][IPv4],
vlan_do_receive() returns false if it does not find vlan_dev. Later
__netif_receive_skb_core() fails to find packet type handler for
skb->protocol 801.1AD and drops the packet.

801.1P header with vlan id 0 should be handled as untagged packets.
This patch fixes it by checking if vlan_id is 0 and processes next vlan
header.

Signed-off-by: Govindarajulu Varadarajan <gvara...@cisco.com>
---
 net/8021q/vlan_core.c | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/net/8021q/vlan_core.c b/net/8021q/vlan_core.c
index a313165e7a67..0cde54c02c3f 100644
--- a/net/8021q/vlan_core.c
+++ b/net/8021q/vlan_core.c
@@ -9,14 +9,32 @@
 bool vlan_do_receive(struct sk_buff **skbp)
 {
        struct sk_buff *skb = *skbp;
-       __be16 vlan_proto = skb->vlan_proto;
-       u16 vlan_id = skb_vlan_tag_get_id(skb);
+       __be16 vlan_proto;
+       u16 vlan_id;
        struct net_device *vlan_dev;
        struct vlan_pcpu_stats *rx_stats;
 
+again:
+       vlan_proto = skb->vlan_proto;
+       vlan_id = skb_vlan_tag_get_id(skb);
        vlan_dev = vlan_find_dev(skb->dev, vlan_proto, vlan_id);
-       if (!vlan_dev)
+       if (!vlan_dev) {
+               /* Incase of 802.1P header with vlan id 0, continue if
+                * vlan_dev is not found.
+                */
+               if (unlikely(!vlan_id)) {
+                       __vlan_hwaccel_clear_tag(skb);
+                       if (skb->protocol == cpu_to_be16(ETH_P_8021Q) ||
+                           skb->protocol == cpu_to_be16(ETH_P_8021AD)) {
+                               skb = skb_vlan_untag(skb);
+                               *skbp = skb;
+                               if (unlikely(!skb))
+                                       return false;
+                               goto again;
+                       }
+               }
                return false;
+       }
 
        skb = *skbp = skb_share_check(skb, GFP_ATOMIC);
        if (unlikely(!skb))
-- 
2.22.0

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