I am using hostapd_cli(http://www.freebsd.org/cgi/man.cgi?query=hostapd_cli&sektion=8) to interact with my hostapd to change the channel. I am using "chan_switch" command to switch channels.
But this command gets failed with "CSA is not supported" as the error message. Any inputs on how I should go about solving this issue would be greatly appreciated.
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As per your question, I have tried chan_switch using hostapd_cli without killing hostapd. All you need to do is update your backports version, in my case, I am using backports-4.2.6-1. Just build it and then you can try chan_switch if channel switch is possible it should give OK message else FAIL. I have tried it with more than 10 interfaces at the same time and I was able to change the channel. Attached a screen shot for reference.
Hope this helps..!!
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CSA is Channel Switch Announcement; which goes inside the beacon to let connected station know that AP is changing the channel. For this things to work device/hw/firmware should able to configure CSA-IE.
In your case, either the device doesn't support CSA or it supports it but have not notified the same in its capabilities.
If you just want to change the channel, which will make stations connected to disconnect first and then reconnect, then you can just change the 'channel' field in hostapd.conf and just reload by 'kill -1'.