Error for wireless request "Set Mode"
Issue: When doing iwconfig wlan0 mode master I get the following error:
root@OpenWrt:~# iwconfig wlan0 mode master
Error for wireless request "Set Mode" (8B06) :
SET failed on device wlan0 ; Invalid argument.
Root cause + solution:
The mac80211 subsystem moves all aspects of master mode (a.k.a. AP mode) into user space, thus it depends on hostapd (also read Hostapd) to
- handle authenticating clients,
- set encryption keys,
- establishing key rotation policy,
- handle other aspects of the wireless infrastructure.
Due to this, the old method of issuing iwconfig <wireless interface> mode master no longer works. Userspace programs like hostapd now use netlink (the nl80211 driver) to create a master mode interface for your traffic and a monitor mode interface for receiving and transmitting management frames.