iPhone tethering does not work after the default mode change from 1 to 3

[httpstorm]

[1] changes to mode 3 CDC NCM by default. In this mode the iPhone exposes an Ethernet interface, handled by kmod-usb-net-cdc-ncm. This mode is intended for reverse tethering, where the computer shares its Internet connection with an iPhone. The iPhone is a DHCP client.

Since most people expect to use tethering, where the iPhone shares its Internet connection with a computer, it would be more appropriate to revert default mode back to 1 [2]. With mode 1, the kmod-usb-net-ipheth driver is used, where support for CDC NCM is available since Linux kernel 6.6, and iPhones are automatically configured in this mode.

[1] https://github.com/libimobiledevice/usbmuxd/commit/c7a0dd9b82633ea347497626282e3051a469ef50 [2] Revert default mode back to 1 (PR): https://github.com/libimobiledevice/usbmuxd/pull/242 [3] Description of different modes https://www.synacktiv.com/en/publications/ios-a-journey-in-the-usb-networking-stack

Any comments? @nikias @marcan @qmfrederik @FunkyM @BalkanMadman @Blefish @Forst @mbilker

[Forst]

Mode 3 indeed does not support internet sharing from phone to computer, as in this mode "AppleUSBEthernet" interfaces are not exposed in any available configuration. Mode 3 only has reverse tethering available. This Synacktiv article has a good overview.

For compatibility with older iOS versions, I recommend sticking to mode 1.

Newer iOS versions have mode 4, which supports both regular and reverse tethering simultaneously. However this mode is not yet supported by the ipheth kernel module in Linux.

The past couple of weeks I've been working on updating the ipheth module to support mode 4, usbmuxd minimal support for modes 4 and 5, and documenting the different available modes, configurations and interfaces. I can post WIPs if there is interest, but I'd rather clean them up a bit first 🙂