Downtown Doug Brown

Edit: With the latest kernel updates, this hack should no longer be necessary in Ubuntu 12.04 or 12.10. I’m leaving this post in place for future reference if people run into the same issue with newer iPhone revisions as they come out.

Here’s the scenario: you’re using an Ubuntu distribution (perhaps 11.10 or 12.04 or 12.10, but I’ve only tested this on 12.10) and you’ve followed the various instructions around the internet for tethering your iPhone using a USB connection in Linux, but it just doesn’t work on your iPhone 5 no matter what you try, despite it working on an older iPhone model just fine.

What gives?

The problem is that iPhone 5 support was added to the ipheth driver in the Linux kernel in October, and that particular patch hasn’t been added to the kernel Ubuntu is using yet.

Look at the patch. All they did was add an extra item to the end of a static array. It looks exactly the same as all the rest of the entries, with the exception of a different USB device ID. If you don’t want to backport the patch and recompile the kernel module and all that, we could just modify the binary ipheth driver so one of the existing iPhone device ID entries matches the iPhone 5 instead of its original device ID. It’s a little more tricky to append to the array by just modifying the binary, so changing an existing entry in the array is an easier alternative. Let’s do it!

Make a copy of /lib/modules/<your kernel version>/kernel/drivers/net/usb/ipheth.ko and put it somewhere. We’ll mess with the copy, so leave your existing driver alone just to be safe.

Decide on an iPhone model you don’t need support for. In my case, I just picked the iPhone 3GS. In the code of the ipheth driver, find its corresponding USB device ID. For the iPhone 3GS, it’s 0x1294. Now, using your favorite hex editor (I personally like running HxD in Wine), search for that string, but reverse the bytes (unless you happen to be on a big-endian system like PowerPC). So in my case, I would search for the hex string 0x9412. Once you find it, confirm that it has 0xAC05 directly before it. This just confirms it’s part of the device ID table and not just a random chunk of code or data that happens to be the same. OK, so you’ve found it. Replace the old hex string (0x9412) with the iPhone 5’s USB device ID (it’s 0x12a8, so you will use 0xa812).

Save the file.  Manually unload the old driver if it was already loaded by typing:

sudo rmmod ipheth

Now, load the new one:

sudo insmod /path/to/new/ipheth.ko

Try plugging the iPhone 5 in now. It should be recognized as a network interface!

You’ll have to manually load this kernel module with the insmod command every time you reboot your system, and every time you install a kernel update, you should probably redo the patch on the latest version of the ipheth module, but it works! If you’re feeling extra clever, I think you could actually leave the modified version of the driver in place where the regular driver goes and add a line to modules.usbmap so it will automatically load the new ipheth module when the iPhone is plugged in, but I’m not going to get into that.

So there you have it: a quick and dirty way to make your iPhone 5 USB tethering work until Ubuntu either starts using a newer kernel or backports iPhone 5 support.