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 10.8.2 (Mountain Lion), 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⁾

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.

• The latest version available is release 4: HoRNDIS-rel4.pkg (60519 bytes) (md5sum 8cf81024d8514d2a8654420fc7491b84). Actually fixes issue #5 and #9, adding support for Samsung Galaxy S II and HTC Desire S (thanks to Griskha). Improves compatibility with older versions of OS X (early 10.6).
• Older versions:
  • Release 3: HoRNDIS-rel3.pkg (60488 bytes) (md5sum a46960e3cdb2a046e08af00c766b6ff9). Fixes issue #3 (reenabling installation on 32-bit machines). Adds potential fix for issue #5.
  • Release 2: HoRNDIS-rel2.pkg (60843 bytes) (md5sum 8b2c371e78ccfe3b07750fbe07f55bb5). Disables installation on 32-bit machines, and includes new device support.
  • Release 1: HoRNDIS-rel1.pkg (38681 bytes) (md5sum 4169c222448e2a2caaa067caf84189d3). Fixes issue #2.
  • Release 0: HoRNDIS-rel0.pkg (36807 bytes) (md5sum be4e879198d3b6e52af993b008198e8e). Initial release.

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).

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; then, restart your Mac to be sure it is unloaded.

(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 use PackageMaker to assemble the package in the package/ 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…

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!