WMM doesn't work for VLAN frame

[Cedric VONCKEN <cedric.voncken@acksys.fr>]

	Hi all,

	I have an issue with vlan frames and WMM management.
	I use an AP and a STA. The AP have a basic setings (wifi is bridged with lan interface).
	On the sta, I add a 802.1q device on wlan interface (vconfig add wlan0 7) and this interface is routed with the LAN. The settings works correctly I can ping the computer connected to the AP from a computer connect to the sta.

	On the computer connected to the sta I launch iperf with the parameter -S0xc0, with wireshark I checked the frame on the air, and the WMM priority is set to Best effort.
	I added some printk in my kernel, and the call order is
	[   64.134443] __dev_queue_xmit called
	[   64.137935] validate_xmit_vlan called
	[   64.144290] ieee80211_subif_start_xmit: called 
	[   64.151343] cfg80211_classify8021d: called 

	Explantation of the issue
		1. The validate_xmit_vlan function add the the vlan tag in the skb frame, set skb->protocol to VLAN protocol (0x8100) and set skb->vlan_tci to 0.
		2. The cfg80211_classify8021d use these fields to determine the frame priority, but the skb->protocol value (0x8100) is not handled byt this function and this function return a default value 0.

	I found this issue with the backport 5.4-rc8-1 from openwrt and the kernel 4.9

	With an older backport (2017-11-01) and the same kernel version the call order is differant
		[  536.195431] __dev_queue_xmit called
		[  536.198922] cfg80211_classify8021d called
		[  536.205799] validate_xmit_vlan called

	With this order the cfg80211_classify8021d work correctly and my traffic use the correct WMM class.

	Do you have any idea to fix this issue?
Regards

Cedric Voncken