openwrt / openwrt/mt76

MT7615 iw scan doesn't work when on DFS channel

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Dominant language
C
Stars
888
Forks
436
PR merge metrics
No merged PRs in 30d

Description

Using the OpenWrt 22.03.0-rc5 snapshot.

Doing a scan when on DFS channels, such as 100, doesn't work:

# iw dev wlan1 scan
command failed: Resource busy (-16)

The relevant config for the 5GHz radio:

config wifi-device 'radio1'
        option type 'mac80211'
        option path '1e140000.pcie/pci0000:00/0000:00:01.0/0000:02:00.0'
        option band '5g'
        option htmode 'VHT80'
        option channel '100'
        option country 'KR'
        option cell_density '0'

config wifi-iface 'default_radio1'
        option device 'radio1'
        option network 'lan'
        option mode 'ap'
        option ssid 'OpenWrt'
        option dtim_period '3'
        option encryption 'sae-mixed'
        option key '<password>'

If I change the channel to 149 (non-DFS), and issue a wifi reload, the iw scan will succeed.

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Reproduce the failure with an MT7615 radio on DFS channel 100 using iw dev wlan1 scan, then compare it with channel 149 after wifi reload. Start by tracing the MT7615 DFS/channel handling and scan path; done means scans succeed while the radio remains configured on a DFS channel.

Written by the indexing model from the issue text.

Assessment

Tech stack
c
Domain
networking
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
25/100

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