Date: Mon, 15 Feb 1999 23:41:50 +0100 (CET) From: Rene de Vries <rene@canyon.demon.nl> To: freebsd-isdn@FreeBSD.ORG Subject: Re: -current, dial-on-demand, hang up the phone? Message-ID: <199902152241.XAA00703@canyon.demon.nl> In-Reply-To: <m10COGf-0000CQC@hcswork.hcs.de> from Hellmuth Michaelis at "Feb 15, 1999 2:40:56 pm"
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Hi,
Currently I use ipfw (IP_FIREWALL) to prevent sendmail from initiating a isdn
connection (I also compiled sendmail without dns and I am using a smart smtp
host from my ISP). When the connection comes up for some other reason the
firewall rule is simply deleted in some "/etc/isdn/isdn-up" script. This
simple system proved out te be very effective!
The biggest problem that a filter will have is dns lookups, if you block them,
you effectively block auto dialing for anything (most connections start by
looking up a host and then connecting...).
The only strange effect that I observed is that if you change "deny" (in the
ipfw rule) to "unreach host", the connection will still be initiated. I
presume that the ICMP package that is send will go via the interface and cause
this "wake-up".
Rene
BTW: here are the important parts from my setup.
/etc/rc.firewall:
/sbin/ipfw -q add 300 deny tcp from any to any 25 out via ${oif}
/etc/isdn/isdnd.rc:
regexpr = "ISP outgoing call active"
regprog = isdn-up
regexpr = "ISP outgoing call disconnected"
regprog = isdn-down
/etc/isdn/isdn-up:
#! /bin/sh
/sbin/ipfw -q delete 300
/bin/sleep 10
/usr/sbin/sendmail -q
/etc/isdn/isdn-down:
#! /bin/sh
if ! /sbin/ipfw show 300 2>/dev/null >/dev/null ; then
/sbin/ipfw -q add 300 deny tcp from any to any 25 out via isp0
fi
> >From the keyboard of Kai.Grossjohann@CS.Uni-Dortmund.DE:
>
> > I start Emacs at work and let it (X11) display on my home machine.
> > I have a dynamic ip address. Thus, when the ISDN thingy hangs up on
> > me, the Emacs session is disrupted rather rudely.
> >
> > Thus, I want the connection to stay open (even if it costs money)
> > while I stare at a program started interactively, but I also want the
> > ability to hang up the phone when I feel like it.
>
> What you need are two things:
>
> 1) a commandline utility, where you can say "hang up the line now"
>
> 2) a dial filter, which prevents further dial tries.
>
> Then what you do with it is write two scripts, lets name them "on" and
> "off" where on contains something like:
>
> isdnconnectcontrol hangup
> isdndialfilter -installfilter telnet
>
> to close the connection and prevent further dial retries and where on
> contains something like:
>
> isdndialfilter -deinstallfilter telnet
>
> Neither isdnconnectcontrol nor isdndialfilter are existent, but a similar
> effect should be gained by issuing "ifconfig ispX down" and "ifconfig ispX up".
>
> hellmuth
--
Rene de Vries http://www.tcja.nl/~rene; mailto:rene@tcja.nl
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