[tor-dev] How to test Linux capabilities & pluggable transports

[George Kadianakis]

Hello David,

the other day you asked for a quick way to test Linux capabilities and
pluggable transports (to combine #7875 and #8195).

What you probably want to do, is write a small script that prints the
active Linux capabilities, spawn it as a pluggable transport, and
check its output to see if the capabilities we wanted it to inherit
are active.

Here is an example of how to do this. I'm using a python script here,
but you can do whatever you want.

Use this torrc (only the final line really matters):
"""
SocksPort 0
ORPort 6666
BridgeRelay 1
PublishServerDescriptor 0

ServerTransportPlugin cap exec /usr/bin/python /home/user/cap.py
"""

where cap.py can be:
"""
#!/usr/bin/python
print "test test"
"""

If you start up tor with that torrc ($ ./src/or/tor -f my_torrc),
you will get:
"""
Mar 02 12:54:43.000 [notice] Unknown line received by managed proxy (test test).
"""
in your Tor output. You can use these lines to debug your
capabilities. Otherwise, you can log to a file and read that file
instead.

Of course in cap.py, you will probably want to print your
capabilities, or bind to a port < 1024, or something like that.

Feel free to ask any questions you have.