Enhance mcjoin to ease integration into test automation

[nabaco]

I'd like to use mcjoin in my automated tests, and as such wanted to ask whether the following enhancements are possible?

1. Have JSON output at the end of a run (such as iperf3 has).
2. Have no-output mode (no progress bar at all).
3. Compile mcjoin as library for integration into test software (e.g. into a robot-framework test library).
4. Support explicit IGMP/MLD version . I know this can be done through sysctl, the question is can it be done through the application?

I'm opening this as one ticket as to not flood you with many new ticket suddenly :) If accepted, I can open separate tickets, and even try to contribute some of the code changes.

[troglobit]

Technically it's all possible of course, it's just software. A lot of refactoring needs to be done though to get all that in place, but it's not ideas I would oppose merging.

I considered that also for my own testing of pimd/mrouted/etc. but instead went for using a smaller more dedicated tool, mping, which loops back packets so you can get the output/status/result from a single process. It has the downside of being a duplex connection though, so not always a relevant test case for multicast.

[nabaco]

In my use-cases a duplex connection is less relevant. It also seems that mping doesn't support IPv6.
I'll start playing around with the code and see if I can raise any PRs

[troglobit]

OK, yeah I've just not gotten around to adding IPv6 to it yet, thanks for the reminder! :)

[troglobit]

mping now has IPv6 support.