How to change network interface used by Android?

Question

When I boot up my Android Device and go to WiFi settings, the status of WiFi remains "Turning Wi-Fi on" forever. I looked it up in logcat logs, and below is the error that I see.

E/wpa_supplicant( 1713): nl80211: Could not set interface 'wlan0' UP
E/wpa_supplicant( 1713): wlan0: Failed to initialize driver interface
E/wpa_supplicant( 1713): Could not read interface wlan0 flags: No such device

Below is some useful information.

root@android:/ # netcfg
netcfg    
lo       UP     127.0.0.1/8   0x00000049 00:00:00:00:00:00
gannet0  DOWN     0.0.0.0/0   0x00001082 1e:e9:6e:bf:45:f7
dummy0   DOWN     0.0.0.0/0   0x00000082 ba:ad:f6:ae:6a:09
rmnet0   DOWN     0.0.0.0/0   0x00000000 00:00:00:00:00:00
rmnet1   DOWN     0.0.0.0/0   0x00000000 00:00:00:00:00:00
rmnet2   DOWN     0.0.0.0/0   0x00000000 00:00:00:00:00:00
rmnet3   DOWN     0.0.0.0/0   0x00000000 00:00:00:00:00:00
rmnet4   DOWN     0.0.0.0/0   0x00000000 00:00:00:00:00:00
rmnet5   DOWN     0.0.0.0/0   0x00000000 00:00:00:00:00:00
rmnet6   DOWN     0.0.0.0/0   0x00000000 00:00:00:00:00:00
rmnet7   DOWN     0.0.0.0/0   0x00000001 00:00:00:00:00:00
sit0     DOWN     0.0.0.0/0   0x00000080 00:00:00:00:00:00
ip6tnl0  DOWN     0.0.0.0/0   0x00000080 00:00:00:00:00:00

Contents of /system/etc/wifi/wpa_supplicant.conf:

update_config=1
ctrl_interface=wlan0
eapol_version=1
ap_scan=1
fast_reauth=1

Question: How can I enable Android to use some other interface other than wlan0?

Things tried:

1. I tried to edit ctrl_interface parameter in /system/etc/wifi/wpa_supplicant.conf using adb pull and adb push to other interfaces shown by netcfg, but Android still tries to use wlan0.

2. I also tried to start wpa_supplicant daemon using the below command.

   /system/bin/wpa_supplicant -Dnl80211 -idummy0 -c/system/etc/wifi/wpa_supplicant.conf
   

   but this gives an error.

   E/wpa_supplicant( 5390): dummy0: Failed to initialize driver interface
   

Answer 1

Are you sure dummy is a WiFi interface? The typical WiFi interface's name is wlan0.

If you're 100% sure it is the right WiFi interface, you might also need to change the wlan0 inside the wpa_supplicant.conf file.

If that still fails, run the wpa_supplicant command under strace and try to get more info from there.

Answer 2

Run in an ADB shell:

wpa_cli

It will open a new type of shell in which:

• Command help will give you all possible commands.

• Command interface will show you all your activated interfaces.

• Command interface_add will add a new interface to use, with following parameters

  interface_add <ifname> <confname> <driver> <ctrl_interface> <driver_param> <bridge_name>
  

  ifname being the single optional parameter.