Tinc1.1 generates Port automatically when port is occupied

[Guus Sliepen]

On Mon, Feb 02, 2015 at 07:46:11PM +0100, Eric Feliksik wrote:

> I like the config generator of tinc 1.1! An issue to consider on the
> default behavior:
> 
> It turns out 'tinc -n mynet init mynodename' makes up a default Port=...
> when the standard port is taken:
> "Warning: could not bind to port 655. Tinc will instead listen on port
> 22911".

The goal is to create a working setup as easily as possible. 

> - if people are able to read it, you can just as well leave it to a warning
> and suggest running again with a --autoport flag to enable automatic port
> generation

I'm sure I will get some emails from people complaining that if tinc
complains that you should rerun it with --autoport, why doesn't it do it
itself the first time?

> - if you cannot read it (e.g. you use configuration management tools to
> setup tinc and distribute keys), you're in trouble. it will silently do
> things different from what you want.

That's true. I could make it skip the automatic port selection step if
it's not running in an interactive TTY.

> - it is too clever to be expected. You might not have tested this scenario,
> especially since it will work as expected if you run the configuration an
> even number of times (!)

I don't understand this? Either port 655 is available or not. There is
one issue though, and that is when you run tinc init for multiple
netnames consecutively, without starting them. If port 655 is available,
then they will all try to use port 655. I could also have it check
existing configuration files instead for Port statements.

> You can prevent this by  calling "tinc -n mynet set Port 655" explicitly of
> course. But then you must first run into this issue to note it.

Can you tell me more about how you are generating tinc configuration?
Because normally I would expect that if port 655 is taken when you run
"tinc init", you really don't want the new tinc network to try to run on
port 655 as well. So I assume it is an issue if you are on one computer,
and trying to generate a configuration for another computer, instead of
running "tinc init" directly on that other computer. It would of course
be nice if tinc could deduce the intended behavior automatically.

-- 
Met vriendelijke groet / with kind regards,
     Guus Sliepen <guus at tinc-vpn.org>
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