HoRNDIS: USB tethering driver for Mac OS X

HoRNDIS: USB tethering driver for Mac OS X

HoRNDIS (pronounce: “horrendous”) is a driver for Mac OS X that allows you to use your Android phone's native USB tethering mode to get Internet access. It is known to work with Mac OS X versions 10.6.8 (Snow Leopard) through 10.10 (Yosemite – see notes below), and has been tested on a wide variety of phones. Although you should be careful with all drivers that you install on your computer, HoRNDIS has been tested at least well enough for the author (and many others) to run full time on their own personal computers.

HoRNDIS is implemented as a kext, rather than as a user-space program that opens a TAP or TUN device; this means that it does not conflict with other TAP/TUN kexts that you might have installed (like OpenVPN, Tunnelblick, or Cisco VPN). The driver implements Microsoft's proprietary RNDIS protocol, which is the only protocol supported natively by Android devices; although Linux and Windows users have enjoyed native RNDIS drivers for years, Mac OS X supports only CDC Ethernet devices out of the box.1)

The chief advantage of HoRNDIS over other tethering solutions is that it uses the a first-class supported feature in the phone's firmware. Other solutions either take over the phone's Wi-Fi stack without the Android operating system's knowledge, or create an emulation IP stack in userspace on the phone; in many cases, the built-in USB tethering support can be more stable, more reliable, and faster.2)

Downloading and installing HoRNDIS

HoRNDIS is available in source form from its project page on GitHub, and in binary form on this site. For quick start instructions:

  • Download the latest binary package, and double-click on it in your Downloads folder. Follow the instructions in the installer.
  • Assuming that the installation proceeds without errors, after it completes, connect your phone to your Mac by USB.
  • Enter the settings menu on your phone.
  • In the connections section, below Wi-Fi and Bluetooth, select “More...”.
  • Select “Tethering & portable hotspot”.
  • Check the “USB tethering” box. It should flash once, and then become solidly checked.

On some versions of OS X, a dialog box may pop up, prompting you to configure the device; follow its instructions. To verify that the device is connected, start the System Preferences program, and select “Network”; you should see your phone appear in the box at left. With any luck, you should be able to turn off Wi-Fi on your Mac, and browse the Internet through your phone's network connection.

Available versions

A special note about 32-bit machines

In previous versions, HoRNDIS required a 64-bit kernel. If you get an error message about 64-bit support on installing HoRNDIS, please try again with the version 3 package (or newer).

Notes about Mavericks and Yosemite

OS X 10.9 (Mavericks) and 10.10 (Yosemite) are supported by HoRNDIS, but there are some gotchas. If you upgraded from an earlier version of OS X, you may find that phones appear to be replicating with abandon in your network control panel. If this happens to you, one somewhat heavy-handed workaround is to clean your network configuration files – take a backup of /Library/Preferences/SystemConfiguration/NetworkInterfaces.plist and /Library/Preferences/SystemConfiguration/preferences.plist, and then either move them out of the way or delete them. (Note that this will remove any custom network configuration that you have performed!) I am still not sure what causes this problem, and so I do not yet have a workaround with finer granularity.


If, for some reason, you need to uninstall HoRNDIS, you can simply drag the extension to the trash. In the Finder, go to the “Go” menu, and select “Go to folder...”; in that, type ”/System/Library/Extensions”. Find “HoRNDIS.kext”, and drag it to the trash. When prompted, type your password. Do the same for the “HoRNDIS.kext” that lives in ”/Library/Extensions”, as well. Then, restart your Mac to be sure it is unloaded.

Getting and building the source

(Fork me on GitHub!) The source is available on GitHub; it is licensed under the GNU General Purpose License, version 3. To build the source, you'll need Xcode 4.0+ installed; to build a version that will work under Snow Leopard, you will also need the Snow Leopard SDK installed. Unfortunately, the Snow Leopard SDK is hard to come by nowadays; you'll need to find it somewhere on the web, and manually install it into your Xcode SDKs folder. (For most applications, it's OK to build against a newer SDK; for a kernel module, the magic vtable space-saving tricks require you to compile against the lowest common denominator.)

Simply running xcodebuild in the checkout directory should be sufficient to build the kext. If you wish to package it up, you can run make to assemble the package in the build/ directory (though please don't publish versions you built as if they were official!).


On the shoulders of giants, I stand. My vague thanks to Apple for having at least some IOKit sample code available (even though the last time it successfully built was 10.2.x); it was a decent start reading to understand how I might want to structure this. Substantial thanks to David Brownell, who wrote the rndis_host driver for Linux; some portions of HoRNDIS were ported over from that work. David Brownell also wrote the f_rndis driver that allows Android/Linux devices to behave like RNDIS devices; reading that source helped to understand why HoRNDIS wasn't working in the early stages. (Sadly, David Brownell passed away in April of 2011. Thanks for all of your hard work, David; may you rest in peace.)

Thanks also to those who helped test HoRNDIS before I released it, as well as all of the other folks from the days of the unrEVOked project, without whom I would likely not be involved in Android development at all...

Support and contact

Being free software, HoRNDIS comes with no warranty (not even a guarantee that it won't break your phone! But I'm pretty sure it won't.), express or implied. (For more on that, read the license.) However, I hope that it works for you; if it doesn't, and you're able to assist in debugging, I'd like to hear from you.

So, for feedback, feel free to get in touch with me; especially if it works for you, or makes your life easier, I'd like to hear about it!

1) You might ask – if CDC is the standard way to act like a network device over USB, why did Google choose the Microsoft proprietary way? Sadly, it turns out to have been something of a compromise; in Windows XP, CDC Ethernet devices were not supported, and in the choice between XP users and Mac users, we got the short end of the stick.
2) Of course, the downside to using a tethering solution with first-class support is that the phone itself must support USB tethering, and it may need to be explicitly permitted by your carrier. Consult your nearest phone hacking forum for instructions on how to bypass such limitations, as needed.