Activating Android USB tethering via adb

I have an oldish Android 2.3.6 phone (a Samsung Galaxy Mini). The last few months, I have been tethering it to my laptop via USB. It’s a bit tedious to manually activate tethering every time I connect the phone.

Luckily, Android contains a utility called service (which lives in /system/bin/service). This utility lets you issue calls to Android services through adb shell. You can list all available services by running service list. Apparently, services provide API endpoints identified by a numerical identifier, and every endpoint accepts some number of arguments. The service utility lets you pass strings or 32-bit integers, like this:

$ service call [service_name] [endpoint_id] s16 [string_arg] i32 [int_arg] ...

By Googling around, I found that Android phones have a connectivity service, which is probably implemented as an instance of android.net.IConnectivityManager. Unfortunately, I couldn’t find any API definition that would exactly match what my phone seemed to have. Maybe the API was updated a few times between my Android version and the current one?

By blindly probing and looking at adb logcat, I found the following interesting call IDs:

• Numbers 4 and 5 seem to describe some aspects of the available mobile networks.

  # service call connectivity 4
  Result: Parcel(
    0x00000000: 00000000 00000001 00000000 00000008 '................'
    0x00000010: 00000006 006f006d 00690062 0065006c '....m.o.b.i.l.e.'
    0x00000020: 00000000 00000005 00530048 00500044 '........H.S.D.P.'
    0x00000030: 00000041 00000009 004f0043 004e004e 'A.......C.O.N.N.'
    0x00000040: 00430045 00450054 00000044 00000009 'E.C.T.E.D.......'
    0x00000050: 004f0043 004e004e 00430045 00450054 'C.O.N.N.E.C.T.E.'
    0x00000060: 00000044 00000000 00000001 00000000 'D...............'
    0x00000070: 00000009 00690073 004c006d 0061006f '....s.i.m.L.o.a.'
    0x00000080: 00650064 00000064 00000008 006e0069 'd.e.d.......i.n.'
    0x00000090: 00650074 006e0072 00740065 00000000 't.e.r.n.e.t.....')
  # (similar for 5)
  

• 6 is apparently setWifiEnabled. Calling service call connectivity 6 i32 1 calls setWifiEnabled(true). Looks useful.
• 9 is stopUsingNetworkFeature.
• 10 is requestRouteToHost.
• 13 is getMobileDataEnabled.
• 14 is setMobileDataEnabled. Calling with i32 0 turns off mobile data, i32 1 turns mobile data on.
• 15 starts tethering on a network interface. The name of the interface is passed as the first string argument.

I aborted my search here, because I found what I came for: calling service call connectivity 15 s16 usb0 starts tethering via USB. So, to get an Android 2.3.6 phone to tether with your PC, you can call: adb shell su -c service call connectivity 15 s16 usb0. I’ll probably turn this snippet into a mini-script. Unfortunately, you need to use a rooted phone and the su part: otherwise, you’ll get back a Parcel with a permission complaint.

And, just as I finished my search, I found this interesting blog post, where the author describes a better way of getting at the service codes than wild probing: apparently if you know your Android version and the service name you want, you can find an AIDL (Android Interface Definition Language) with the service description on https://android.googlesource.com/.

YMMV. Cheers.