netdev - Re: [PATCH net] net: handle 802.1P vlan 0 packets properly

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Date:   Mon, 10 Jun 2019 19:08:36 -0400
From:   Stephen Suryaputra <ssuryaextr@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     gvaradar@...co.com, benve@...co.com, netdev@...r.kernel.org,
        govind.varadar@...il.com
Subject: Re: [PATCH net] net: handle 802.1P vlan 0 packets properly

On Mon, Jun 10, 2019 at 02:28:10PM -0700, David Miller wrote:
> From: Govindarajulu Varadarajan <gvaradar@...co.com>
> Date: Mon, 10 Jun 2019 07:27:02 -0700
> 
> > 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 <gvaradar@...co.com>
> 
> Under Linux we absolutely do not decapsulate the VLAN protocol unless
> a VLAN device is configured on that interface.

VLAN ID 0 is treated as if the VLAN protocol isn't there. It is used so
that the 802.1 priority bits can be encoded and acted upon.