Hi !
Background: ath5k-based card, wireless-testing
v2.6.32-rc6-41576-g4408b3b, wpa_supplicant hostap_0_6_7-581-geb999fe
I just got disconnected all the time to some AP and I wondered what
the issue was. That's the output from "iw event:"
wlan0 (phy #4): auth 00:1b:d4:44:35:90 -> 00:15:e9:84:1a:54 status: 0: Successful
wlan0 (phy #4): assoc 00:1b:d4:44:35:90 -> 00:15:e9:84:1a:54 status: 25: Association request rejected due to requesting station not supporting the short slot time option
wlan0 (phy #4): failed to connect to 00:1b:d4:44:35:90, status: 25: Association request rejected due to requesting station not supporting the short slot time option
First thing: the error message is confused. I turned off
short-slot-time on the AP, so it's the AP that does not support it.
However, the real question remains: why does the station
(ath5k+mac80211) tries to use short-slot-time in the first place? In
the probe response, the AP says clearly that he doesn't support this.
Here's the (partial) assoc request, followed by a (partial) assoc
response. And to shed evidence on the turned-off-status of the AP, at
the end is also a probe response from the AP:
IEEE 802.11
Type/Subtype: Association Request (0)
Frame Control: 0x0000 (Normal)
Version: 0
Type: Management frame (0)
Subtype: 0
Flags: 0x0
DS status: Not leaving DS or network is operating in AD-HOC mode (To DS: 0 From DS: 0) (0x00)
.... .0.. = More Fragments: This is the last fragment
.... 0... = Retry: Frame is not being retransmitted
...0 .... = PWR MGT: STA will stay up
..0. .... = More Data: No data buffered
.0.. .... = Protected flag: Data is not protected
0... .... = Order flag: Not strictly ordered
Duration: 314
Destination address: 00:1b:d4:44:35:90 (00:1b:d4:44:35:90)
Source address: 00:15:e9:84:1a:54 (00:15:e9:84:1a:54)
BSS Id: 00:1b:d4:44:35:90 (00:1b:d4:44:35:90)
Fragment number: 0
Sequence number: 15
IEEE 802.11 wireless LAN management frame
Fixed parameters (4 bytes)
Capability Information: 0x0431
.... .... .... ...1 = ESS capabilities: Transmitter is an AP
.... .... .... ..0. = IBSS status: Transmitter belongs to a BSS
.... ..0. .... 00.. = CFP participation capabilities: No point coordinator at AP (0x0000)
.... .... ...1 .... = Privacy: AP/STA can support WEP
.... .... ..1. .... = Short Preamble: Short preamble allowed
.... .... .0.. .... = PBCC: PBCC modulation not allowed
.... .... 0... .... = Channel Agility: Channel agility not in use
.... ...0 .... .... = Spectrum Management: dot11SpectrumManagementRequired FALSE
.... .1.. .... .... = Short Slot Time: Short slot time in use
.... 0... .... .... = Automatic Power Save Delivery: apsd not implemented
..0. .... .... .... = DSSS-OFDM: DSSS-OFDM modulation not allowed
.0.. .... .... .... = Delayed Block Ack: delayed block ack not implented
0... .... .... .... = Immediate Block Ack: immediate block ack not implented
Listen Interval: 0x0001
...
CONCLUSION: mac80211 tries to use short-slot time.
IEEE 802.11
Type/Subtype: Association Response (1)
Frame Control: 0x0010 (Normal)
Version: 0
Type: Management frame (0)
Subtype: 1
Flags: 0x0
DS status: Not leaving DS or network is operating in AD-HOC mode (To DS: 0 From DS: 0) (0x00)
.... .0.. = More Fragments: This is the last fragment
.... 0... = Retry: Frame is not being retransmitted
...0 .... = PWR MGT: STA will stay up
..0. .... = More Data: No data buffered
.0.. .... = Protected flag: Data is not protected
0... .... = Order flag: Not strictly ordered
Duration: 314
Destination address: 00:15:e9:84:1a:54 (00:15:e9:84:1a:54)
Source address: 00:1b:d4:44:35:90 (00:1b:d4:44:35:90)
BSS Id: 00:1b:d4:44:35:90 (00:1b:d4:44:35:90)
Fragment number: 0
Sequence number: 1014
IEEE 802.11 wireless LAN management frame
Fixed parameters (6 bytes)
Capability Information: 0x0000
.... .... .... ...0 = ESS capabilities: Transmitter is a STA
.... .... .... ..0. = IBSS status: Transmitter belongs to a BSS
.... ..0. .... 00.. = CFP participation capabilities: Station is not CF-Pollable (0x0000)
.... .... ...0 .... = Privacy: AP/STA cannot support WEP
.... .... ..0. .... = Short Preamble: Short preamble not allowed
.... .... .0.. .... = PBCC: PBCC modulation not allowed
.... .... 0... .... = Channel Agility: Channel agility not in use
.... ...0 .... .... = Spectrum Management: dot11SpectrumManagementRequired FALSE
.... .0.. .... .... = Short Slot Time: Short slot time not in use
.... 0... .... .... = Automatic Power Save Delivery: apsd not implemented
..0. .... .... .... = DSSS-OFDM: DSSS-OFDM modulation not allowed
.0.. .... .... .... = Delayed Block Ack: delayed block ack not implented
0... .... .... .... = Immediate Block Ack: immediate block ack not implented
Status code: Association denied due to requesting station not supporting short slot operation (0x0019)
Association ID: 0x0000
Tagged parameters (0 bytes)
...
CONCLUSION: the AP doesn't like that. And the textual representation
from tshark for this error as also confused about the roles of AP and
station :-)
IEEE 802.11
Type/Subtype: Probe Response (5)
Frame Control: 0x0050 (Normal)
Version: 0
Type: Management frame (0)
Subtype: 5
Flags: 0x0
DS status: Not leaving DS or network is operating in AD-HOC mode (To DS: 0 From DS: 0) (0x00)
.... .0.. = More Fragments: This is the last fragment
.... 0... = Retry: Frame is not being retransmitted
...0 .... = PWR MGT: STA will stay up
..0. .... = More Data: No data buffered
.0.. .... = Protected flag: Data is not protected
0... .... = Order flag: Not strictly ordered
Duration: 314
Destination address: 00:20:a6:a0:56:1b (00:20:a6:a0:56:1b)
Source address: 00:1b:d4:44:35:90 (00:1b:d4:44:35:90)
BSS Id: 00:1b:d4:44:35:90 (00:1b:d4:44:35:90)
Fragment number: 0
Sequence number: 1845
IEEE 802.11 wireless LAN management frame
Fixed parameters (12 bytes)
Timestamp: 0x0000004DA3BDE1FA
Beacon Interval: 0.102400 [Seconds]
Capability Information: 0x0011
.... .... .... ...1 = ESS capabilities: Transmitter is an AP
.... .... .... ..0. = IBSS status: Transmitter belongs to a BSS
.... ..0. .... 00.. = CFP participation capabilities: No point coordinator at AP (0x0000)
.... .... ...1 .... = Privacy: AP/STA can support WEP
.... .... ..0. .... = Short Preamble: Short preamble not allowed
.... .... .0.. .... = PBCC: PBCC modulation not allowed
.... .... 0... .... = Channel Agility: Channel agility not in use
.... ...0 .... .... = Spectrum Management: dot11SpectrumManagementRequired FALSE
.... .0.. .... .... = Short Slot Time: Short slot time not in use
.... 0... .... .... = Automatic Power Save Delivery: apsd not implemented
..0. .... .... .... = DSSS-OFDM: DSSS-OFDM modulation not allowed
.0.. .... .... .... = Delayed Block Ack: delayed block ack not implented
0... .... .... .... = Immediate Block Ack: immediate block ack not implented
...
Who's the culprit, mac80211 or wpa_supplicant?
--
http://www.holgerschurig.de
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