Warn the user about possible transparent proxying failure
The transparent proxying feature is very likely to fail for a number of reasons, the most common is lack of a firmware supporting the needed iptables magic, or bugs like #3595.
Currently orbot doesn't warn the user when this occurs, leading to a false sense of security.
- It only mentions "(Requires root)" in the settings menu: true, but not enough: a special firmware is required too. It should be mentioned (possibly with a link to https://www.torproject.org/docs/android.html.en )
- At orbot startup, a system notification message is issued, saying that transparent proxying has been correctly enabled, even when this is not the case!
Orbot should check more toroughly if transparent proxying is really working, and issue a BIG WARNING in the user interface if this is not the case (or if this can not be detected).
Also the web page at https://www.torproject.org/docs/android.html.en could be improved, though it mentions the requirement for a suitable firmware, the warning could be made more evident (now you have to read the fine print to find out about this limitation).
We could also suggest the user to always check if a particular app is behaving as expected, for example checking the current network connections using a netstat-like tool like Os monitor (see: http://f-droid.org/repository/browse/?fdfilter=os%20monitor&fdid=com.eolwral.osmonitor )