Since Android 7, AOSP dhcpcd (standard dhcp client) was replaced by dhcpcd-6.8.2 that is, reading in Android.mk, a “D-Bus enabled and compatible with Brillo daemons” dhcp client based on dhcpcd: let’s see how it should be customized for running hooks after completing some actions.
For my tests I’m using the Hikey960, even though there should not be almost anything board related in the next steps besides package availability: in fact dhcpcd does not belong to the default packages of the Hikey build, so it should be added.
Open the device makefile (device/linaro/hikey/hikey960/device-hikey960.mk) and add the following line:
PRODUCT_PACKAGES += dhcpcd-6.8.2
After a successful build the package is ready to be used (generally through the definition of a service), but, by default, it won’t run any hook.
Taking a look at the Android makefile (external/dhcpcd-6.8.2/Android.mk) we can see the interesting symbol DHCPCD_USE_SCRIPT: this should be set to ‘yes’ to enable hook execution, so add the line
DHCPCD_USE_SCRIPT := yes
after the first instance of LOCAL_PATH
Now you need two other elements:
- The bash script used for running the hooks
- The hooks to be run
The first one could be easily generated using the standard makefile: open a shell in the dhcpcd directory and type
$ make dhcpcd-run-hooks
to create a script called dhcpcd-run-hooks used for running the hooks.
However, with my setup it was not properly working as it was generated, so I had to customize the path of sh: instead of
for the Hikey960 it was
I had also to modify the hooks directory in the following block
for hook in \ /dhcpcd.enter-hook \ /dhcpcd-hooks/* \ /dhcpcd.exit-hook
e.g. in my system I placed the hooks in /system/etc/dhcpcd/dhcpcd-hooks, so the block becomes
for hook in \ /system/etc/dhcpcd/dhcpcd.enter-hook \ /system/etc/dhcpcd/dhcpcd-hooks/* \ /system/etc/dhcpcd/dhcpcd.exit-hook
Some hooks can be found in
Choose the needed ones (or create a new one): I find especially useful 50-dhcpcd-compat.
Once identified the hooks you need, the Android makefile should be changed for copying the right files in the filesystem. Android.mk has the following commented part:
# Each build target using dhcpcd-6.8.2 should define its own source # and destination for its dhcpcd.conf file. # include $(CLEAR_VARS) # LOCAL_MODULE := dhcpcd-6.8.2.conf # LOCAL_MODULE_CLASS := ETC # LOCAL_MODULE_PATH := $(TARGET_OUT)/etc/dhcpcd-6.8.2 # LOCAL_SRC_FILES := android.conf # include $(BUILD_PREBUILT)
We can use similar lines for copying the hooks running script and the needed hooks, like the following
include $(CLEAR_VARS) LOCAL_MODULE := dhcpcd-run-hooks LOCAL_MODULE_CLASS := EXECUTABLES LOCAL_MODULE_PATH := $(TARGET_OUT_ETC)/dhcpcd LOCAL_SRC_FILES := $(LOCAL_MODULE) include $(BUILD_PREBUILT) include $(CLEAR_VARS) LOCAL_MODULE := 50-dhcpcd-compat LOCAL_MODULE_CLASS := ETC LOCAL_MODULE_PATH := $(TARGET_OUT_ETC)/dhcpcd/dhcpcd-hooks LOCAL_SRC_FILES := dhcpcd/$(LOCAL_MODULE) include $(BUILD_PREBUILT)
Do not forget to set the executability bit to the various scripts, add the new created packages, rebuild and you should have your hooks properly working.