Android wpa_supplicant with different virtual network interface for WiFi Station Mode (wlan0) and P2P (p2p0)

[Xuebing Wang]

Hi,

I am working on WiFi Direct (originally WiFi P2P) on Android 4.4.2, 
using Realtek RTL8812AU. I use "-Dnl80211" to use nl80211 driver.

1) I understand if I use "use_p2p_group_interface=1", I will get virtual 
network interface like "p2p-wlan0-0". Is there a nl80211 command (then 
cfg80211) to the kernel driver to actually create this virtual network 
interface?

Realtek driver does not support this, however it supports Concurrent 
mode, and it creates 2 network interface "wlan0" and "p2p0".


2) I build Realtek driver with CONFIG_CONCURRENT_MODE defined, and I use 
both Station Mode and P2P on wlan0, and everything is fine. init.rc is 
like below:
-------------------------------
service wpa_supplicant /system/bin/wpa_supplicant \
     -iwlan0 -Dnl80211 -c/data/misc/wifi/wpa_supplicant.conf \
     -I/system/etc/wifi/wpa_supplicant_overlay.conf \
     -O/data/misc/wifi/sockets \
     -e/data/misc/wifi/entropy.bin -g at android:wpa_wlan0
     #   we will start as root and wpa_supplicant will switch to user wifi
     #   after setting up the capabilities required for WEXT
     #   user wifi
     #   group wifi inet keystore
     class main
     socket wpa_wlan0 dgram 660 wifi wifi
     disabled
     oneshot

service p2p_supplicant /system/bin/wpa_supplicant \
     -iwlan0 -Dnl80211 -iwlan0 -c/data/misc/wifi/wpa_supplicant.conf \
     -I/system/etc/wifi/wpa_supplicant_overlay.conf \
     -O/data/misc/wifi/sockets -N \
     -ip2p0 -Dnl80211 -c /data/misc/wifi/p2p_supplicant.conf \
     -I/system/etc/wifi/p2p_supplicant_overlay.conf \
     -puse_p2p_group_interface=1 -e/data/misc/wifi/entropy.bin \
     -g at android:wpa_wlan0
#   we will start as root and wpa_supplicant will switch to user wifi
#   after setting up the capabilities required for WEXT
#   user wifi
#   group wifi inet keystore
     class main
     socket wpa_wlan0 dgram 660 wifi wifi
     disabled
     oneshot
-------------------------------

Above is actually copy/paste from AOSP source for device Asus Grouper 
(Android version 4.4.4), link is below:
https://android.googlesource.com/device/asus/grouper/+/kitkat-release/init.grouper.rc


3) I tried to use different virtual interface for Station Mode (wlan0) 
and P2P (p2p0), and change init.${ro.hardware}.rc as below:
-------------------------------
service p2p_supplicant /system/bin/wpa_supplicant \
     -ip2p0 -Dnl80211 -iwlan0 -c/data/misc/wifi/wpa_supplicant.conf \
-------------------------------

Only change from "-iwlan0" to "-ip2p0" for service p2p_supplicant.

P2P works on interface p2p0, without issues.

The problem is that interface wlan0 is inactive by run command 
"/system/xbin/ifconfig". Of course "/system/xbin/ifconfig -a" shows all 
the interfaces, including wlan0.


4) I run command "netcfg wlan0 up", there is error "IPv6: 
ADDRCONF(NETDEV_UP): wlan0: link is not ready", this error message is 
from kernel source "net/ipv6/addrconf.c".


5) I am not sure if my problem in step (3) above is because of Realtek 
driver. In order to use interface p2p0, it is simple as that to use 
-ip2p0 rather than -iwlan0 in init.${ro.hardware}.rc? Do I need to do 
more changes? Any suggestions?


Thanks.
xuebing wang