Topic: using ipmasqadm with a dynamic ppp0 inet address

[Yann Nottara]

I need to forward some ports from my E-smith gateway to an internal server using ipmasqasm. While searching through posts on the forum, I found this very informative link about the use of ipmasqadm with a dynamic IP:

http://www.linux.org/docs/ldp/howto/mini/IPMasquerading+Napster-5.html

As my external interface is connected to the Net via ADSL (PPPoE) with a dynamic IP address, the script I'm interested in is :

#!/bin/sh
ppp_ip="/sbin/ifconfig ppp0 | grep 'inet addr' | awk '{print $2}' | sed -e
's/.*://'"
/usr/sbin/ipmasqadm portfw -f
/usr/sbin/ipmasqadm portfw -a -P tcp -L ${ppp_ip} 20 -R 192.168.0.2 20
/usr/sbin/ipmasqadm portfw -a -P tcp -L ${ppp_ip} 21 -R 192.168.0.2 21

My question is : Is such a script directly usable in E-smith 4.1 & if yes, in which template should I put it (I'm considering /etc/e-smith/templates/etc/ppp/ip-up.local/signal-event) ?

And what would be the "cleanest" way to insert it ?

If that's not appropriate, could you suggest any other option ?

Thanks in advance for any help !

[Yann Nottara]

Answering to myself & if anyone interested, here's what I found in the E-smith Devloper mailing-list :
devinfo-subscribe@lists.e-smith.org

infos here : http://www.e-smith.org/content/developers/



Subject:
        [e-smith-devinfo] RE: Additional Webserver behind gateway
   Date:
        Wed, 28 Feb 2001 15:51:04 -0800
   From:
        Dan B
     To:
        David Boccabella
    CC:
        devinfo@lists.e-smith.org


Everytime your ip address changes, you need to run the following
script.  If you are on ppp, then put this in the bottom of your
/etc/sysconfig/network-scripts/ifup-post, if you are on some DSL/cable
DHCP, then that *might* not work for you (does anyone know of a script that
dhcpcd execs after every new ip addy?).

#this should calculate your ip address from ifconfig
#or you can use EXTIP=$IPADDR if it is in ifup-post

#EXTIP=$IPADDR
EXTIP=ifconfig ${DEVICE} | grep 'inet addr' |
             awk -F: '{ print $2 } ' | awk '{ print $1 }'
     eval /bin/ipcalc --silent --hostname ${IPADDR} && set_hostname $HOSTNAME

INTIP=10.0.0.65
ipmasqadm portfw -f
ipmasqadm portfw -a -P tcp -L $EXTIP 80 -R $INTIP 80


Maybe this will help someone else / or others on the list will have comments.

Dan Browning, Cyclone Computer Systems, danb@cyclonecomputers.com


And now the reply from Gordon Rowell

On Wed, Feb 28, 2001 at 03:51:04PM -0800, Dan B wrote:
> [...]
> Everytime your ip address changes, you need to run the following
> script.  If you are on ppp, then put this in the bottom of your
> /etc/sysconfig/network-scripts/ifup-post, if you are on some DSL/cable
> DHCP, then that *might* not work for you (does anyone know of a script that
> dhcpcd execs after every new ip addy?).

The {interface}.exe files in /etc/dhcpcd/ and e-smith then calls the
ip-change event. You don't need to touch anything in /etc/dhcpd - we've
already done that for you.

> [...]
> Maybe this will help someone else / or others on the list will have comments.

Why are you doing it the hard way?

The scripts in /etc/e-smith/events/ip-change are called when your external
IP changes. No calculation required. The new external IP can be retrieved
with

/sbin/e-smith/config get ExternalIP

in shell. There are plenty of Perl examples in that directory to show you
how to get direct access to the config database.

Gordon