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Re: [GNUnet-developers] On applications using GNUnet

From: Alessio Vanni
Subject: Re: [GNUnet-developers] On applications using GNUnet
Date: Tue, 06 Aug 2019 17:18:20 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/26.2 (gnu/linux)

> I don't know which documentation sentence in what manual you are
> referencing here, but I think that documentation is simply wrong. CADET
> is port-scan resistant, in that the peer will simply not send anything
> back if the port is not open. In fact, CADET will accept your incoming
> request into an internal table in anticipation that maybe in the future
> a local application will open that port, and then establish the
> connection (as the client might have just been a bit faster than the
> service opening the port). So as a client connecting to a closed port
> will just seem to take "a long time" (= forever), until and unless some
> application opens the port, at which point the session is acknowledged
> and properly opened. But by design you cannot distinguish between a
> closed port and CADET actually failing to reach the target peer -- or
> things just being slow.

In gnunet_cadet_service.h, the documentation comment for
GNUNET_CADET_channel_create says:

 * Create a new channel towards a remote peer.
 * If the destination port is not open by any peer or the destination peer
 * does not accept the channel, @a disconnects will be called
 * for this channel.

According to this comment, if the destination peer does not have the
specified port opened, then at some point in time I should be notified
about it by the `disconnects' callback.  However, if CADET works like
you says, then this comment is wrong (or outdated.)

> Yes, generally it is expected that the application protocol will use the
> session once it is up and exchange messages ;-).

I understand, thanks.

> In addition to Martin's answer, I would add that if you replace ".fun"
> with say ".pin" (our FCFS TLD), it will work. Or if you use ".fr" and
> are using GNS to resolve things in the French .fr TLD.  Or see Martin's
> suggestions. Many choices, some will work, some won't. In particular,
> putting "party.alessio" is unlikely to work, unless most operating
> system distributions ship with your zone in their root zone file ;-).

Yes, thanks to Martin now I figured how it works.  I need to experiment,
but I should have the basics down.

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