How ACS behaves?

Sam Jaeschke sam.jaeschke at
Wed Apr 26 06:31:15 PDT 2017


I'm attempting to get ACS working to see how it behaves. Unfortunately
I can't get it working.

Release version:

Only differences in hostapd.conf:

Only differences in defconfig:
CONFIG_IEEE80211AC=y (should have turned that off - unused)

Using ath9k driver, with message on bootup:
[    1.891393] ath9k 0000:01:00.0: enabling device (0140 -> 0142)
[    2.018054] ieee80211 phy0: Atheros AR9300 Rev:3 mem=0xf0980000, irq=171

I turned on ACS, expecting it to automatically select the best of the
1-11 channels on 2.4GHz in 802.11n mode.

Starting up hostapd with -dd:

Starting HOSTAP Daemon: 1493191720.536396: random: Trying to read
entropy from /dev/random
1493191720.536549: Configuration file: /etc/hostapd.conf
1493191720.538374: ctrl_interface_group=0
1493191720.540665: rfkill: initial event: idx=0 type=1 op=0 soft=0 hard=0
1493191720.54115[    4.420957] IPv6: ADDRCONF(NETDEV_UP): wlan0: link
is not ready
3: nl80211: TDLS supported
1493191720.541183: nl80211: TDLS external setup
1493191720.541209: nl80211: Supported cipher 00-0f-ac:1
1493191720.541230: nl80211: Supported cipher 00-0f-ac:5
1493191720.541248: nl80211: Supported cipher 00-0f-ac:2
1493191720.541264: nl80211: Supported cipher 00-0f-ac:4
1493191720.541280: nl80211: Supported cipher 00-0f-ac:10
1493191720.541296: nl80211: Supported cipher 00-0f-ac:8
1493191720.541311: nl80211: Supported cipher 00-0f-ac:9
1493191720.541326: nl80211: Supported cipher 00-0f-ac:6
1493191720.541342: nl80211: Supported cipher 00-0f-ac:13
1493191720.541357: nl80211: Supported cipher 00-0f-ac:11
1493191720.541373: nl80211: Supported cipher 00-0f-ac:12
1493191720.541550: nl80211: Using driver-based off-channel TX
1493191720.541619: nl80211: Use separate P2P group interface (driver
advertised support)
1493191720.541639: nl80211: interface wlan0 in phy phy0
1493191720.541718: nl80211: Set mode ifindex 3 iftype 3 (AP)
1493191720.541788: nl80211: Setup AP(wlan0) - device_ap_sme=0 use_monitor=0
1493191720.541908: nl80211: Subscribe to mgmt frames with AP handle 0xad850
1493191720.541935: nl80211: Register frame type=0xb0
(WLAN_FC_STYPE_AUTH) nl_handle=0xad850 match=
1493191720.542004: nl80211: Register frame type=0x0
(WLAN_FC_STYPE_ASSOC_REQ) nl_handle=0xad850 match=
1493191720.542067: nl80211: Register frame type=0x20
(WLAN_FC_STYPE_REASSOC_REQ) nl_handle=0xad850 match=
1493191720.542129: nl80211: Register frame type=0xa0
(WLAN_FC_STYPE_DISASSOC) nl_handle=0xad850 match=
1493191720.542189: nl80211: Register frame type=0xc0
(WLAN_FC_STYPE_DEAUTH) nl_handle=0xad850 match=
1493191720.542248: nl80211: Register frame type=0xd0
(WLAN_FC_STYPE_ACTION) nl_handle=0xad850 match=
1493191720.542309: nl80211: Register frame type=0x40
(WLAN_FC_STYPE_PROBE_REQ) nl_handle=0xad850 match=
1493191720.565668: nl80211: Add own interface ifindex 3
1493191720.565707: nl80211: if_indices[16]: 3
1493191720.565754: phy: phy0
1493191720.565776: BSS count 1, BSSID mask 00:00:00:00:00:00 (0 bits)
1493191720.566559: nl80211: Regulatory information - country=00
1493191720.566591: nl80211: 2402-2472 @ 40 MHz 20 mBm
1493191720.566616: nl80211: 2457-2482 @ 40 MHz 20 mBm (no IR)
1493191720.566639: nl80211: 2474-2494 @ 20 MHz 20 mBm (no OFDM) (no IR)
1493191720.566661: nl80211: 5170-5250 @ 160 MHz 20 mBm (no IR)
1493191720.566682: nl80211: 5250-5330 @ 160 MHz 20 mBm (DFS) (no IR)
1493191720.566704: nl80211: 5490-5730 @ 160 MHz 20 mBm (DFS) (no IR)
1493191720.566726: nl80211: 5735-5835 @ 80 MHz 20 mBm (no IR)
1493191720.566747: nl80211: 57240-63720 @ 2160 MHz 0 mBm
1493191720.566819: nl80211: Added 802.11b mode based on 802.11g information
1493191720.566840: Allowed channel: mode=1 chan=1 freq=2412 MHz
max_tx_power=20 dBm
1493191720.566859: Allowed channel: mode=1 chan=2 freq=2417 MHz
max_tx_power=20 dBm
1493191720.566877: Allowed channel: mode=1 chan=3 freq=2422 MHz
max_tx_power=20 dBm
1493191720.566894: Allowed channel: mode=1 chan=4 freq=2427 MHz
max_tx_power=20 dBm
1493191720.566910: Allowed channel: mode=1 chan=5 freq=2432 MHz
max_tx_power=20 dBm
1493191720.566927: Allowed channel: mode=1 chan=6 freq=2437 MHz
max_tx_power=20 dBm
1493191720.566944: Allowed channel: mode=1 chan=7 freq=2442 MHz
max_tx_power=20 dBm
1493191720.566960: Allowed channel: mode=1 chan=8 freq=2447 MHz
max_tx_power=20 dBm
1493191720.566977: Allowed channel: mode=1 chan=9 freq=2452 MHz
max_tx_power=20 dBm
1493191720.566994: Allowed channel: mode=1 chan=10 freq=2457 MHz
max_tx_power=20 dBm
1493191720.567010: Allowed channel: mode=1 chan=11 freq=2462 MHz
max_tx_power=20 dBm
1493191720.567028: Allowed channel: mode=0 chan=1 freq=2412 MHz
max_tx_power=20 dBm
1493191720.567045: Allowed channel: mode=0 chan=2 freq=2417 MHz
max_tx_power=20 dBm
1493191720.567062: Allowed channel: mode=0 chan=3 freq=2422 MHz
max_tx_power=20 dBm
1493191720.567078: Allowed channel: mode=0 chan=4 freq=2427 MHz
max_tx_power=20 dBm
1493191720.567095: Allowed channel: mode=0 chan=5 freq=2432 MHz
max_tx_power=20 dBm
1493191720.567112: Allowed channel: mode=0 chan=6 freq=2437 MHz
max_tx_power=20 dBm
1493191720.567128: Allowed channel: mode=0 chan=7 freq=2442 MHz
max_tx_power=20 dBm
1493191720.900419: Allowed channel: mode=0 chan=8 freq=2447 MHz
max_tx_power=20 dBm
1493191720.900452: Allowed channel: mode=0 chan=9 freq=2452 MHz
max_tx_power=20 dBm
1493191720.900471: Allowed channel: mode=0 chan=10 freq=2457 MHz
max_tx_power=20 dBm
1493191720.900489: Allowed channel: mode=0 chan=11 freq=2462 MHz
max_tx_power=20 dBm
1493191720.900508: ACS: Automatic channel selection started, this may take a bit
1493191720.900527: ACS: Scanning 1 / 5
1493191720.900552: wlan0: nl80211: scan request
1493191720.900584: nl80211: Scan frequency 2412 MHz
1493191720.900601: nl80211: Scan frequency 2417 MHz
1493191720.900616: nl80211: Scan frequency 2422 MHz
1493191720.900630: nl80211: Scan frequency 2427 MHz
1493191720.900644: nl80211: Scan frequency 2432 MHz
1493191720.900659: nl80211: Scan frequency 2437 MHz
1493191720.900673: nl80211: Scan frequency 2442 MHz
1493191720.900687: nl80211: Scan frequency 2447 MHz
1493191720.900701: nl80211: Scan frequency 2452 MHz
1493191720.900714: nl80211: Scan frequency 2457 MHz
1493191720.900728: nl80211: Scan frequency 2462 MHz
1493191720.912015: Scan requested (ret=0) - scan timeout 10 seconds
1493191720.912068: wlan0: interface state UNINITIALIZED->ACS
1493191720.912107: wlan0: ACS-STARTED
1493191720.912134: Interface initialization will be completed in a
callback (ACS)
1493191720.912159: ctrl_iface not configured!
hostapd.    <--------- this indicates the end of hostapd output
[   10.971004] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready

So hostapd does work and provide an AP, but it's not on an automatic
channel, and it's seems to always pick channel 1 regardless of how
crowded it is with other devices.
My understanding is that it should output some ACS scan info at the
end, but it's not.

Any ideas why ACS would not be working?

I have been reading the ACS documentation (and the comments in the
hostapd.conf), and haven't worked out how it does behave yet. Does it
only scan once on startup? Or does it scan periodically while
operation, and jump channels when it sees fit?

Many thanks,

More information about the Hostap mailing list