ar71xx iw reports adhoc rx rate 1Mbps (throughput is higher)

[Musti <musti@…>]

Tested on wr741nd v4.3 r30919, iw dev wlan0-1 station dump, iw does not report the correct rx bitrate, it is always 1Mbps, although I have performed throughput tests with iperf that go up to 17Mbps in both directions.

Please note that this was tested in a multi SSID setup ap+ad-hoc, the issue was on ad-hoc interface, ap interface reports the correct bitrate only after significant traffic has been passed through.

Providing: wireless config file, iwconfgi output, station dump outputs for both wireless interfaces.

root@wr741nd-test:/# cat /etc/config/wireless 
config wifi-device  radio0
	option type     mac80211
	option channel 	8
	option macaddr	f8:d1:11:37:b8:0c
	option hwmode	11ng
	option htmode	HT20
	list ht_capab	SHORT-GI-20
	list ht_capab	SHORT-GI-40
	list ht_capab	RX-STBC1
	list ht_capab	DSSS_CCK-40

config wifi-iface
	option device   radio0
	option network  mesh
	option mode     ap
	option ssid     open
	option encryption none

config wifi-iface
	option device   radio0
	option network  mesh
	option mode     adhoc
	option ssid     mesh
	option bssid    02:CA:FF:EE:BA:BE
	option encryption none

root@wr741nd-test:/# iwconfig
lo        no wireless extensions.

edge0     no wireless extensions.

eth1      no wireless extensions.

wlan0-1   IEEE 802.11bgn  ESSID:"mesh"  
          Mode:Ad-Hoc  Frequency:2.447 GHz  Cell: 02:CA:FF:EE:BA:BE   
          Tx-Power=18 dBm   
          RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:on
          
wlan0     IEEE 802.11bgn  Mode:Master  Frequency:2.447 GHz  Tx-Power=18 dBm   
          RTS thr:off   Fragment thr:off
          Power Management:on
          
eth0      no wireless extensions.

mon.wlan0  IEEE 802.11bgn  Mode:Monitor  Frequency:2.447 GHz  Tx-Power=18 dBm   
          RTS thr:off   Fragment thr:off
          Power Management:on

root@wr741nd-test:/# iw dev wlan0 station dump
Station b8:8d:12:23:23:ba (on wlan0)
	inactive time:	20 ms
	rx bytes:	90488265
	rx packets:	69139
	tx bytes:	56742973
	tx packets:	65074
	tx retries:	442587
	tx failed:	0
	signal:  	-52 [-52] dBm
	signal avg:	-49 [-50] dBm
	tx bitrate:	72.2 MBit/s MCS 7 short GI
	rx bitrate:	72.2 MBit/s MCS 7 short GI
	authorized:	yes
	authenticated:	yes
	preamble:	short
	WMM/WME:	yes
	MFP:		no
	TDLS peer:	no

root@wr741nd-test:/# iw dev wlan0-1 station dump
Station b6:48:7a:a1:ac:14 (on wlan0-1)
	inactive time:	90 ms
	rx bytes:	25218263
	rx packets:	36782
	tx bytes:	46461786
	tx packets:	37776
	tx retries:	2301
	tx failed:	0
	signal:  	-49 [-49] dBm
	signal avg:	-47 [-47] dBm
	tx bitrate:	54.0 MBit/s
	rx bitrate:	1.0 MBit/s
	authorized:	yes
	authenticated:	yes
	preamble:	long
	WMM/WME:	yes
	MFP:		no
	TDLS peer:	no

[jow]

Milestone Attitude Adjustment 12.09 deleted

[thx1111]

This report has been open since 2012-04-01. It is ongoing still in 2016, with iw version 4.3 in openwrt, and iw version 4.7 in Arch. It is not just a problem with openwrt per se.

The problem is not always with the "receive" bitrate, but may instead be with the "transmit" bitrate. Also, the misreported rate is complementary between the access point and the station, where, for instance, iw at the station may report "rx bitrate: 1.0 MBit/s" while the access point reports "tx bitrate: 1.0 MBit/s", even though the actual access point to station channel rate is some much higher value.

I suspect that the cause may be some kind of failed interaction between iw and various wireless drivers. I have seen iw report the "correct" transmit and receive bitrates on some station hardware while the access point is still reporting "1.0 MBit/s" as the "tx bitrate".

In addition to the problem with the transmit and receive bitrate reports, I also see iw misreport the signal levels on occasion, such as "196 dBm". That suggests some kind of overflow in the conversion software.

I suppose that this bug should be treated as "Upstream".