一、WPA_SUPPLICANT簡介

1. 什麼是wpa_supplicant

wpa_supplicant is a WPA Supplicant for Linux, BSD, Mac OS X, and Windows with support for WPA and WPA2 (IEEE 802.11i / RSN). It is suitable for both desktop/laptop computers and embedded systems. Supplicant is the IEEE 802.1X/WPA component that is used in the client stations. It implements key negotiation with a WPA Authenticator and it controls the roaming and IEEE 802.11 authentication/association of the wlan driver.

wpa_supplicant is designed to be a "daemon" program that runs in the background and acts as the backend component controlling the wireless connection. wpa_supplicant supports separate frontend programs and a text-based frontend (wpa_cli) and a GUI (wpa_gui) are included with wpa_supplicant.

wpa_supplicant uses a flexible build configuration that can be used to select which features are included. This allows minimal code size (from ca. 50 kB binary for WPA/WPA2-Personal and 130 kB binary for WPA/WPA2-Enterprise without debugging code to 450 kB with most features and full debugging support; these example sizes are from a build for x86 target).

2. 支援的WPA/IEEE 802.11i feature

4. WPA如何和AP建立聯絡

二、移植wpa_supplicant和wifi驅動的步驟

1.  將廠商提供的HAL程式碼複製到hardware目錄下，並修改Makefile

例如：realteck、broadcom、ti、qcomm等。

2.  修改ANDROID_SDK /device/<soc_vendor_name>/<board_name>/目錄下的BoardConfig.mk

例如：

BOARD_WIFI_VENDOR := realtek
ifeq ($(BOARD_WIFI_VENDOR), realtek)
WPA_SUPPLICANT_VERSION := VER_0_8_X
BOARD_WPA_SUPPLICANT_DRIVER := NL80211
CONFIG_DRIVER_WEXT :=y
BOARD_WPA_SUPPLICANT_PRIVATE_LIB := lib_driver_cmd_rtl
BOARD_HOSTAPD_DRIVER := NL80211
BOARD_HOSTAPD_PRIVATE_LIB := lib_driver_cmd_rtl
BOARD_WLAN_DEVICE := rtl8192cu
#BOARD_WLAN_DEVICE := rtl8192du
#BOARD_WLAN_DEVICE := rtl8192ce
#BOARD_WLAN_DEVICE := rtl8192de
#BOARD_WLAN_DEVICE := rtl8723as
#BOARD_WLAN_DEVICE := rtl8723au
#BOARD_WLAN_DEVICE := rtl8189es
#BOARD_WLAN_DEVICE := rtl8723bs
#BOARD_WLAN_DEVICE := rtl8723bu
WIFI_DRIVER_MODULE_NAME := "wlan"
WIFI_DRIVER_MODULE_PATH  := "/system/lib/modules/wlan.ko"
WIFI_DRIVER_MODULE_ARG := "ifname=wlan0 if2name=p2p0"
endif

3. 修改ANDROID_SDK/device/<soc_vendor_name>/<board_name>/目錄下的init.xxx.rc

例如：

service rtw_suppl_con /system/bin/wpa_supplicant \
-ip2p0 -Dnl80211 -c/data/misc/wifi/p2p_supplicant.conf \
-e/data/misc/wifi/entropy.bin -N \
-iwlan0 -Dnl80211 -c/data/misc/wifi/wpa_supplicant.conf \
-O/data/misc/wifi/sockets \
[email protected]:wpa_wlan0
class main
socket wpa_wlan0 dgram 660 wifi wifi
disabled
oneshot

service rtw_suppl /system/bin/wpa_supplicant \
-iwlan0 -Dnl80211 -c/data/misc/wifi/wpa_supplicant.conf \
-O/data/misc/wifi/sockets \
-e/data/misc/wifi/entropy.bin
[email protected]:wpa_wlan0
class main
socket wpa_wlan0 dgram 660 wifi wifi
disabled

service dhcpcd_wlan0 /system/bin/dhcpcd -aABDKL
class main
disabled
oneshot

service dhcpcd_p2p /system/bin/dhcpcd -aABKL
class main
disabled
oneshot

service iprenew_wlan0 /system/bin/dhcpcd -n
class main
disabled
oneshot

service iprenew_p2p /system/bin/dhcpcd -n
class main
disabled
oneshot

4. 修改ANDROID_SDK/device/<soc_vendor_name>/<board_name>/目錄下的device.mk

例如：

PRODUCT_COPY_FILES += \
frameworks/native/data/etc/android.hardware.wifi.xml:system/etc/permissions/android.hardware.
wifi.xml
PRODUCT_COPY_FILES += \
frameworks/native/data/etc/android.hardware.wifi.direct.xml:system/etc/permissions/android.hard
ware.wifi.direct.xml
PRODUCT_PROPERTY_OVERRIDES += \
wifi.interface=wlan0

5. 修改ANDROID_SDK/frameworks/base/core/res/res/values/config.xml，配置wifi網路屬性

<string-array translatable="false" name="networkAttributes">
<item>"wifi,1,1,1,-1,true"</item>
<item>"bluetooth,7,7,0,-1,true"</item>
<item>"ethernet,9,9,2,-1,true"</item>
</string-array>

<string-array translatable="false" name="radioAttributes">
<item>"1,1"</item>
<item>"7,1"</item>
<item>"9,1"</item>
</string-array>

<string-array translatable="false" name="config_tether_wifi_regexs">
<item>"wlan0"</item>
</string-array>

<integer-array translatable="false" name="config_tether_upstream_types">
<item>1</item>
<item>9</item>
</integer-array>

6. 將廠商提供的WPA_SUPPLICANT替換到ANDROID_SDK/external/wpa_suppliant_8目錄下

7. 編譯wifi驅動，將驅動配置成模組載入的方式，將生成的ko檔案存放到BoardConfig.mk裡面設定的ko檔案路徑下，並確認驅動模組名稱一致

三、常用除錯命令和技巧

1. 除錯命令

     通過wpa_cli命令可以檢測wpa_supplicant的執行狀態

• PING：心跳檢測命令。客戶端用它判斷WPAS是否工作正常。WPAS收到”PING”命令後需要回復“PONG”。
• MIB：客戶端用該命令獲取裝置的MIB資訊。
• STATUS：客戶端用該命令來獲取WPAS的工作狀態。
• ADD_NETWORK：為WPAS新增一個新的無線網路。它將返回此新無線網路的id（從0開始）。注意：此network id非常重要，客戶端後續將通過它來指明自己想操作的無線網路。
• SET_NETWORK <network id> <variable> <value>：network id是無線網路的id。此命令用於設定指定無線網路的資訊。其中variable為引數名，value為引數的值。
• ENABLE_NETWORK <network id>：使能某個無線網路。此命令最終將促使WPAS發起一系列操作以加入該無線網路。

2. 除錯技巧

    可以在wpa_supplicant裡面增加一些log來跟蹤指令的下發流程。

    通過在命令列終端輸入getprop init.svc.wpa_servername 來檢查wpa_supplicant程序是否在執行。

    wpa_supplicant起來後，可以通過檢視wpa_cli ping或者wpa_cli status來檢測wpa_suppliant通道是否正常。

    檢查/system/etc/wifi/wpa_supplicant.conf和/data/misc/wifi/wpa_supplicant.conf中ctrl_interface是否正確。

    檢查/dev/socket/wpa_wlan0、/data/misc/wifi/sockets/wlan0、/data/misc/wifi/sockets/p2p、wpa_ctrl_*等節點是否成功建立。

    通過lsmod檢查驅動模組是否成功載入。

    通過檢視/sys/class/rfkill/目錄下是否生成rfkill*節點判斷驅動載入過程是否OK。