Phone tethering over USB (extras/phone-tethering.sh)

SYNOPSIS

wrenctl install phone-tethering                     install it
wrenctl remove phone-tethering                      remove it
wrenctl manual phone-tethering                      print the manual steps below

Android: plug it in, then Settings > Network > Hotspot & tethering > USB tethering
iPhone:  plug it in, tap Trust, then Settings > Personal Hotspot
         (if the computer doesn't see it: idevicepair pair)
tether                 find the phone, ask, and connect (a window asks by itself, while offline)
tether --list          only show what it finds
wrenctl --wifi off     use only the phone's data

This uses a phone's mobile data on this computer through the USB cable. An Android phone needs nothing extra: the tether command is in the base install (parts/tether.sh), with or without NetworkManager. An iPhone also needs usbmuxd and the pairing tools this installs from Debian. While you are offline in sway, a phone appearing opens a window that asks whether to connect; it connects only if you say so. Otherwise, type tether. It uses NetworkManager if that is running, else dhcpcd, dhclient or busybox, whichever is there, with your sudo password. It sends no name for this computer, and leaves secure DNS alone. A phone's Wi-Fi hotspot is just a Wi-Fi network, with nothing to install.

LIMITS

• Your mobile provider sees where your traffic goes, as a home provider would; use a VPN or Tor on top for that.
• The phone sees all your traffic: it's a computer you have to trust.
• Tapping Trust lets this computer talk to the iPhone: don't tether through a port or charger you don't trust.
• tether can't tell a phone from another USB device with the same driver, and USB network adapters use some of them too. It shows what it found: if you didn't just plug in a phone, say no. Whoever runs that network sees where your traffic goes, and can choose your route.
• NetworkManager still connects a new USB device by itself if its driver isn't one phones use (parts/tether.sh names rndis_host, cdc_ether, cdc_ncm and ipheth). So a USB device that pretends to be some other network card still gets a connection: don't plug in USB devices you don't trust.
• tether's connection steps were tried with real DHCP clients and a real NetworkManager on stand-in network devices, and its window in a headless sway. It hasn't been tried with a real phone by these tests.

MANUAL INSTALL

# usbmuxd and the pairing tools, for an iPhone (Android needs nothing)
sudo apt install --no-install-recommends usbmuxd libimobiledevice-utils
# Then the tether command connects it (parts/tether.sh, in the base install)
tether

To undo:

# The iPhone tools (usbmuxd marked "automatic" instead of purged: other
# programs can need it, and autoremove takes it out only if nothing does)
sudo apt purge libimobiledevice-utils
sudo apt-mark auto usbmuxd
sudo apt autoremove --purge