Date: Wed, 12 Aug 1998 20:18:33 +0000 From: Kees Jan Koster <dutchman@tccn.cs.kun.nl> To: FreeBSD Questions List <freebsd-questions@FreeBSD.ORG> Cc: Kees Jan Koster <dutchman@tccn.cs.kun.nl> Subject: Userland TCP/IP <--> MASC gateway... Message-ID: <35D1F891.41C67EA6@tccn.cs.kun.nl>
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Dear Questions@FreeBSD.org
For my work I have to implement a protocol gateway that will gate the
way between TCP/IP and MASC. Since I have no experience building
gateways I was wondering if anyone does have experience with this kind
of work, or if anyone would care to answer a few questions for me.
For portability, I would like to write a userland daemon that will do
the work. My initial doodles are small daemons that listen to predefined
ports on Localhost, so that certain applications can use those ports to
talk TCP/IP over my gateway application. Thus:
:
Client PC : Host PC
:
Client App : Host App
| : |
--+------+-- (TCP/IP lo0) : --+------+-- (TCP/IP)
| : |
Client Gateway App : Central Gateway App
| : |
+----<> MASC over radio modem <>----+
:
This approach works fine for my application. The client PC will always
use a single client application, and that application always connects to
the same host and port.
A major drawback of this approach is that ping does not work, and that a
traceroute from the host only shows the path to the central gateway
application. Making a connection back to the client PC is virtually
impossible to implement cleanly. I'm sure there are other drawback I
haven't bashed my head into.
So, now I want to be able to offer end-to-end TCP/IP over MASC, but I do
not want to write my own kernel device driver. I figure that
applications like ppp, and ipfw must have a way of getting the raw IP
packets from the kernel, so I can do that too.
Now, the sources of ppp are just over 600kb. I don't know about you, but
I'd rather avoid reading 600kb of C source, however well-written. Could
someone please help me by telling me how ppp gets the IP packets from
the system? Is there any documentation about this subject?
Just as I'm sitting here a thought hit me. We are using Ericsson Mobidem
radio modems. Could I talk ppp or slip over such a modem? I don't think
they are HAYES compatible. I'd have to look up if there is documentation
about that, though.
Thanks for your time,
Kees Jan
----------------------------------------------------------------------
Kees Jan Koster Hatertseweg 468 6533 GV Nijmegen the Netherlands
tel. +31-24-3555870 e-mail: dutchman@tccn.cs.kun.nl
----------------------------------------------------------------------
The reason computer chips are so small is computers don't eat much.
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