tlug: Linux as proxy server

[Jim Tittsler <jwt@example.com>]

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tlug note from Jim Tittsler <jwt@example.com>
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On Wed, May 28, 1997 at 02:29:02PM +0900, LNJPTYO1.MDARCY01@example.com wrote:
> The LAN would be using TCP/IP with a bogus IP network address. When one of the
> clients trys to connect to a
> valid internet address (i.e. www.sun.com) the LINUX server dials-out and acts
> like a proxy. When there is no activity for a specified
> time it drops the connection.

IP Masquerading works great for this application.  Build a kernel that
includes the Network firewalls, IP forwarding/gatewaying, IP firewalls, and
IPmasquerading features.  It is transparent to the other clients on the LAN.
(You may want to install some of the modules for FTP, Real Audio, IRC, if
you want LAN access for these... but this can be sorted out later.) The
'ipfwadm' utility is used to control what types of packets get masqueraded.
At the most basic level, you can set it up with a shell script like:
  #!/bin/sh
  /sbin/ipfwadm -F -a m -S 172.16.1.0/24 -D 0.0.0.0/0
  /sbin/ipfwadm -F -p deny
I actually have a few more deny clauses to keep some Win95 nmb stuff from
leaking out.

diald is a great daemon for doing demand dialing to automatically establish
a PPP connection (with or without IP masq).  It can be tuned to prohibit
calls during certain times of day, control how long the link stays up after
activity based on billing increment and/or type of connection, and can force
a connection during certain hours (and will automatically redial if the line
falls). Available from sunsite or RedHat.  More info:
http://www.dna.lth.se/~erics/diald.html

The IP address translation and automating a dial-up IP connection are not
directly related, so you can work on getting them going independently.

-- 
Jim Tittsler, Tokyo  7j1ajh@example.com  http://shrine.cyber.ad.jp/~jwt/

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