Hi there,

I've been playing around with various BBS software packages recently, and it
seems Mystic is by far the best comprise between features and ease of use (from
 a user's as well as a SysOp's perspective) these days.

However, I'm seeing a strange problem I have no explanation for: Incoming
telnet connections get terminated immediately after they've been established.
On a client, it looks like this:

(13:41:51) root@Roanoke:/usr/local/mystic # telnet -K BBS 2323
Trying 178.32.212.121...
Connected to BBS.NetWorkXXIII.de.
Escape character is '^]'.
Connection closed by foreign host.
(13:42:03) root@Roanoke:/usr/local/mystic #

The server itself sees the connection but drops it immediately. This is what
the log has to say about it:

(13:42:03) root@Roanoke:/usr/local/mystic # grep -i telnet logs/mis.log
+ 2019.01.06 13:41:42  TELNET Listening on IPV4 port 2323 using interface
"178.32.212.121"
+ 2019.01.06 13:42:03  TELNET > Connect on slot 1/1000 (178.32.212.121)
+ 2019.01.06 13:42:03  TELNET 1-HostName bbs.networkxxiii.de
+ 2019.01.06 13:42:03  TELNET 1-Creating terminal process
+ 2019.01.06 13:42:03  TELNET 1-Closing terminal process
+ 2019.01.06 13:42:09  MANAGER Shutdown: TELNET
(13:51:01) root@Roanoke:/usr/local/mystic #

No error messages whatsoever are being logged. Since I'm running Mystic under
GNU/Linux binary emulation on NetBSD 8.0_STABLE amd64 x86_64, I would usually
be willing to blame it on incompatibilities on some low-level device handling
stuff and just call 
it a day although establishing a telnet session through a regular TTY is not
actually a very exotic thing, and MBSE for instance seems to be doing that just
 fine (though through a standalone program being launched by inetd).

So I did a ktrace of a failed connection attempt which can be found here
https://pastebin.com/Nb5nmTVK - the telnet session begins at line 5287 - to see
 if there are any uncaught (and thus untranslated by the emulation layer)
GNU/Linux system calls, but 
the only calls that are actually not implemented are at the very bottom when I
manually shut down MIS.

However, all the other networking stuff in MIS I've tried so far seems to work,
 i. e. I can connect to the builtin FTP, NNTP, SMTP, POP3, and BINKP severs
just fine. It is really just the telnet server that gives me headaches.

Okay, that's not entirely true - SSH fails in pretty much the same manner. I
can, however, connect and enter my password (and if I enter an incorrect
password it refuses to log me on altogether):

(14:07:42) root@Roanoke:/usr/local/mystic # ssh BBS -c aes128-cbc -l thiesi
thiesi@bbs's password:
Connection to bbs closed by remote host.
Connection to bbs closed.

I'm assuming both telnet and SSH share some code as in how the session is being
 established and handled internally, although I don't understand why it would
be that much different from, say, FTP which is apparently working for me.

Long story short, I don't have any clue where else to look. I did notice MIS is
 running with "loglevel 3", but I don't know if that's hardocded or if there is
 any way for me to increase that to get maybe some more insight. 

Also, for the record: "mystic -l" works just fine (even via a telnet session if
 run by inetd) so I am quite sure it has something to do with the networking
code in MIS. Also, as you can see, I've the configured telnet server to listen
on port 2323, but 
as I'm currently running MIS as root that should not even be required (and
doesn't seem to be an issue as FTP and NNTP and POP3 and SMTP all seem to work
on their respective standard ports and the telnet behavior does not change when
 using the standard 
port of 23).

Oh, and one last remark: I also tried "downgrading" to older versions (as in I
just did a quick vanilla install and fired up MIS) but to no avail. I think I
went as far back as to 112a31.

Any help or pointers would be greatly appreciated.

--Mirko

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