Update reverse-tethering.rst

- Add more details.
- Adjust required steps to the more recent versions of UT and Ubuntu.
- Add some known issues and another reference.
- Fix some formatting issues.

Tested with Ubuntu Touch 16.04 (OTA-24) and Ubuntu 22.04.

userguide/advanceduse/reverse-tethering.rst

@@ -1,34 +1,77 @@
 Reverse tethering
 =================
 
-This tutorial helps you to connect your Ubuntu Touch device to your computer to access the Internet on it.
-This is useful if there is no available Wi-Fi connection or you don't have a data subscription on your Ubuntu Touch device.
-
-Prerequisite: A Ubuntu Touch device with "Developer mode" on, attached via USB to the computer connected to the Internet.
+This tutorial explains how you get your Ubuntu Touch device online using a USB cable and a computer with internet access.
+This is useful if there is no available Wi-Fi connection or you don't have a data subscription on your device.
 
 Steps
 -----
 
-1. On the Ubuntu Touch device: ``android-gadget-service enable rndis``
+#. Prepare your device (Ubuntu Touch) and your computer:
 
-2. On your computer: get your RNDIS IP address e.g:``hostname -I``
+   - Turn `Developer Mode` on in Ubuntu Touch.
+   - Connect your computer to the internet.
+   - Attach your device to your computer via USB.
 
-3. On the Ubuntu Touch device: 
+#. On the *device*:
 
-      add a gateway: ``sudo route add default gw YOUR_COMPUTER_RNDIS_IP``
+   - Run: ``android-gadget-service enable rndis``
+   - Reboot the phone.
 
-      add nameservers: ``echo "nameserver 8.8.8.8" | sudo tee /etc/resolv.conf``
+#. On your *computer*: 
 
-      refresh the DNS table: ``resolvconf -u``
+   - Get your RNDIS IP address:
 
-4. On computer: 
+     - Run: ``ip a``
+     - Look for an interface named ``usb0`` in the output:
 
-      Turn on IP forwarding: ``echo 1 | sudo tee /proc/sys/net/ipv4/ip_forward``
+       ::
 
-      Apply NAT: ``sudo iptables -t nat -A POSTROUTING -s 10.0.0.0/8 -o eth0 -j MASQUERADE``
-
+         5: usb0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UNKNOWN group default qlen 1000
+            link/ether 12:34:56:ab:cd:ef brd ff:ff:ff:ff:ff:ff
+            inet 10.42.0.1/24 brd 10.42.0.255 scope global noprefixroute usb0
+              valid_lft forever preferred_lft forever
+
+       - Your IP is: ``10.42.0.1``
+
+#. On the *device*:
+
+   - Get your RNDIS interface: Run ``ip a``
+
+     ::
+
+       31: rndis0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
+           link/ether 12:34:56:ab:cd:ef brd ff:ff:ff:ff:ff:ff
+           inet 10.0.0.1/8 brd 10.255.255.255 scope global rndis0
+             valid_lft forever preferred_lft forever
+
+     - Your interface is: ``rndis0``
 
+   - Change your IP address: ``sudo ifconfig rndis0 10.42.0.2``
+   - Add your computer as default gateway: ``sudo route add default gw 10.42.0.1``
+   - Add a nameserver of your choice: ``echo "nameserver 1.1.1.1" | sudo tee -a /etc/resolv.conf``
+   - Open Morph Browser and test your internet connection!
+
+#. If it's not working yet, on your *computer*:
+
+   - Turn on IP forwarding: ``echo 1 | sudo tee /proc/sys/net/ipv4/ip_forward``
+   - Apply NAT: ``sudo iptables -t nat -A POSTROUTING -s 10.42.0.0/8 -o eth0 -j MASQUERADE``
+
+     - Make sure you replace ``eth0`` by the interface that connects your computer to the internet.
+
+   - NOTE: These steps are usually performed automatically by the NetworkManager on Ubuntu 22.04.
+
+Known Issues
+------------
+
+- The Updates page in the System Settings displays: ``Connect to the Internet to check for updates.``
+- After a while Teleports looses its internet connection and must be restarted.
+
 References
 ----------
 
-* Ask Ubuntu: https://askubuntu.com/questions/655321/ubuntu-touch-reverse-tethering-and-click-apps-updates
+- `Ask Ubuntu`_
+- RidgeRun_
+
+.. _Ask Ubuntu: https://askubuntu.com/questions/655321/ubuntu-touch-reverse-tethering-and-click-apps-updates
+.. _RidgeRun: https://developer.ridgerun.com/wiki/index.php/How_to_use_USB_device_networking