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*** Warnings ***
linux as host os is required, windows might be possible but is untested
You can easily destroy your emulator. Backup your emulator
Root access required
Preface
${android_sdk} refers to your android sdk root folder
Your emulator consists of three images:
- ${android_sdk}/tools/lib/images/ramdisk.img (cpio[cnew] archive, gzip compressed)
- ${android_sdk}/tools/lib/images/system.img (yaffs2 formated)
- ${android_sdk}/tools/lib/images/userdata.img (yaffs2 formated)
Step 0 - backup
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cp ${android_sdk}/tools/lib/images/ramdisk.img ${android_sdk}/tools/lib/images/ramdisk.img.old
Step 1 - extracting the ramdisk
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mkdir ramdisk
cd ramdisk
cat ${android_sdk}/tools/lib/images/ramdisk.img | gunzip | sudo cpio -i
This will populate "ramdisk" with the ramdisks content.
Step 2 - looking at a simple boot skript
Android requires some special code to boot in the emulator, the code can be found in etc/qemu-init.sh
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sudo vim etc/qemu-init.sh
Here is the original content:
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#!/system/bin/sh
# Some special case stuff for running under emulation
qemu=`getprop ro.kernel.qemu`
case "$qemu" in
"1" )
ifconfig eth0 10.0.2.15 netmask 255.255.255.0 up
route add default gw 10.0.2.2 dev eth0
radio_ril=`getprop ro.kernel.android.ril`
case "$radio_ril" in
ttyS*) # a modem is emulated as a serial device
;;
*) # no need for the radio interface daemon
# telephony is entirely emulated in Java
setprop ro.radio.noril yes
stop ril-daemon
;;
esac
setprop net.eth0.dns1 10.0.2.3
setprop net.gprs.local-ip 10.0.2.15
setprop ro.radio.use-ppp no
setprop ro.config.nocheckin yes
setprop status.battery.state Slow
setprop status.battery.level 5
setprop status.battery.level_raw 50
setprop status.battery.level_scale 9
stop dund
stop usbd
;;
esac
Step 3 - the target networking environment
Android is hardcoded to use 10.0.2.3 and 10.0.2.2 for comunication - especially with adb. You can not use anything except this userspace emulation for eth0.
Android
- device: eth0, ip: 10.0.2.15, net: 10.0.2.0/255.255.255.0 - this will keep adb happy
- device: eth1, ip: 192.168.1.2, net: 192.168.1.0/255.255.255.0 - this will be used for real communication
- default gateway: 192.168.1.1 - or whatever suits your network
- DNS: 10.0.2.3 - we simply keep this, no disadvantages except harder debugging
- net_android, virtual android network device
- br0, network bridge linking eth0 and net_android
Step 4 - altering the android network
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#!/system/bin/sh
# Some special case stuff for running under emulation
qemu=`getprop ro.kernel.qemu`
case "$qemu" in
"1" )
if ifconfig eth1 up; then
ifconfig eth1 down
# Should we really check for eth1 that way?
# DHCP - broken?
# netcfg eth1 dhcp
ifconfig eth1 192.168.1.2 netmask 255.255.255.0 up
route add default gw 192.168.1.1 dev eth1
ifconfig eth0 10.0.2.15 netmask 255.255.255.0 up
setprop net.eth0.dns1 10.0.2.3
setprop net.eth1.dns1 10.0.2.3
setprop net.gprs.local-ip 192.168.1.2
else
ifconfig eth0 10.0.2.15 netmask 255.255.255.0 up
route add default gw 10.0.2.2 dev eth0
setprop net.eth0.dns1 10.0.2.3
setprop net.gprs.local-ip 10.0.2.15
fi
# Proxy support - broken too?
# setprop net.gprs.http-proxy http://proxy:8080/
# No longer needed
# ifconfig eth0 10.0.2.15 netmask 255.255.255.0 up
# route add default gw 10.0.2.2 dev eth0
radio_ril=`getprop ro.kernel.android.ril`
case "$radio_ril" in
ttyS*) # a modem is emulated as a serial device
;;
*) # no need for the radio interface daemon
# telephony is entirely emulated in Java
setprop ro.radio.noril yes
stop ril-daemon
;;
esac
# no longer needed
# setprop net.eth0.dns1 10.0.2.3
# setprop net.gprs.local-ip 10.0.2.15
setprop ro.radio.use-ppp no
setprop ro.config.nocheckin yes
setprop status.battery.state Slow
# Interresting - is this the way to check battery status?
setprop status.battery.level 5
setprop status.battery.level_raw 50
setprop status.battery.level_scale 9
stop dund
stop usbd
;;
esac
This will keep your classic config if eth1 doesn't exist and if it exists adb will still work.
Step 5 - packing your new ramdisk
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sudo find | sudo cpio -o -H newc | gzip -9 > ${android_sdk}/tools/lib/images/ramdisk.img
Step 6 - Host configuration
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sudo brctl addbr br0
sudo tunctl -u $USER -t net_android
sudo ifconfig eth0 0.0.0.0 promisc up
sudo ifconfig net_android 0.0.0.0 promisc up
sudo brctl addif br0 eth0
sudo brctl addif br0 net_android
sudo dhclient3 br0
Depending on you sodu configuration you might need to substitute $USER with your username. Depending on your local network you might need to substitute sudo dhclient3 br0 with your normal network initialization.
Step 7 - boot and test
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${android_sdk}/tools/emulator -debug-kernel -qemu -net nic -net user -net nic -net tap,ifname=net_android
Now on your host system do
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ping 192.168.2.2
adb shell
If everything went well both commands will work.
Enjoy!
TODO1: Tutorial how to use the new network link from within dalvik.
TODO2: Find a windows user who will try the ramdisk with windows and openvpn/tun/tap driver
