480 lines
14 KiB
HTML
480 lines
14 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
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<HTML>
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<HEAD>
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<META NAME="GENERATOR" CONTENT="SGML-Tools 1.0.9">
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<TITLE>call-back mini HOWTO: Procedure</TITLE>
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<LINK HREF="Call-back-1.html" REL=previous>
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<LINK HREF="Call-back.html#toc2" REL=contents>
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</HEAD>
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<BODY>
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Next
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<A HREF="Call-back-1.html">Previous</A>
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<A HREF="Call-back.html#toc2">Contents</A>
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<HR>
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<H2><A NAME="s2">2. Procedure</A></H2>
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<H2><A NAME="ss2.1">2.1 PART I: Net at home ?</A>
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</H2>
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<P>Most of us use the Internet in a place of work. However we offen need
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the net at home or outside the place of work. It may be possible that
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the work from home is cheaper then from a company building. I think
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that the best solution is to install call-back software on the Linux
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server. Call-back makes it possible to re-call index number at the
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cost of the company. I'll try to present how it works. An entitled
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person who calls the modem is varied for the first time in Linux server.
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Then on the user's side the "hang up modem" is switched on. At the same
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time Linux calls the user. User is verified again. We have connection
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and the server is charged. The user pays only for the initiation of the
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connection. The double verification and extra options in the call-back
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program unable the unsuitable persons to charge our bill. We can
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restrict the access to the connection only to corporation network or the
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Internet. Call-back is very flexible. Below, I'll try to present the
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configuration of a call-back server on Linux system and I'll show you
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how to set up your computer for re-calling the connection. I don't
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describe configuration of ISDN call-back because I don't use ISDN in
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my connection to the Internet. If you set call-back on ISDN send me
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your configuration.
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I had some problem when I changed my kernel from 2.2.x to 2.4.x. I will
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describe new option for a new kernel. Remember that if you change your
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kernel for high version you will have to change pppd, too.
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I don't create a new section for description of new possibility in kernels
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2.4.x but I write a new configurations in old section.
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I would like to apologise to people who asked me about options for new
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kernels.
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I didn't have time to write a new version of HOW-TO. I have changed my
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job and place of liveing. Sorry.
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<P>
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<H2><A NAME="ss2.2">2.2 PART II: The first steps with modem.</A>
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</H2>
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<P>The administrators prefer different modem but while buying a modem
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we should remember certain guidelines:
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<P>
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<UL>
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<LI>If you have USR WinModems see Linmodem-HOWTO.
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</LI>
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<LI>The externale modem is moust flexible you have more place inste your computer.
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</LI>
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<LI>The internal modem with ISA slot is better then the are with PCI
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slot (you can use your PCI slot for something different )
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</LI>
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<LI>Don't use Plug modem see Plag-and-Play-HOWTO.
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</LI>
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</UL>
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<P>
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<P>When we have the suitable modem we have to set it up in our system.
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We have to check on which com our modem is. Then we have to make a
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symbolic link to this hardware and /dev/modem. For example, if we have
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the modem for the 2nd com we write:
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<PRE>
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ln -s /dev/cua1 /dev/modem
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</PRE>
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<P>We check it
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<P>
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<PRE>
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lrwxrwxrwx 1 root uucp 9 Sep 19 19:10 /dev/modem -> /dev/cua1
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</PRE>
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<P>If we have the modem on different com we have to remember that
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<P>
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<PRE>
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/dev/cua0 is com1
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/dev/cua1 is com2
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/dev/cua2 is com3
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/dev/cua3 is com4
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</PRE>
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<P>For new kernels:
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<P>
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<PRE>
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/dev/ttyS0 is com1
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/dev/ttyS1 is com2
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/dev/ttyS2 is com3
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/dev/ttyS3 is com4
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</PRE>
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<P>Now, we check our configuration using the program minicom.
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<H2><A NAME="ss2.3">2.3 PART III Call Linux</A>
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</H2>
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<P>The first step to make the call-back on Linux accessible is to set up
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a suitable parameters in kernel. Then we check whether our kernel
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serves the protocol ppp. If you don't have ppp in your kernel or in
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module you will have to compile your kernel and add ppp. You will find
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more information in Kernel-HOWTO.In the kernels 2.4.x series you have to
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mark follow options:
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<P>CONFIG_PPP=m
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# CONFIG_PPP_MULTILINK is not set
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CONFIG_PPP_ASYNC=m
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CONFIG_PPP_SYNC_TTY=m
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CONFIG_PPP_DEFLATE=m
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CONFIG_PPP_BSDCOMP=m
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<P>After compilation you have to add some lines for /etc/modules.conf
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<P>
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<P>alias /dev/ppp ppp_generic
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alias char-major-108 ppp_generic
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alias tty-ldisc-3 ppp_async
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alias tty-ldisc-14 ppp_synctty
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alias ppp-compress-21 bsd_comp
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alias ppp-compress-24 ppp_deflate
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alias ppp-compress-26 ppp_deflate
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<P>You can't forget that you need new pppd demon for kernels 2.4.x (for me
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it was ppp-2.4.0 this ppp has some mistake you have to get latest from ftp.samba.org in /pub/ppp
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).
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<P>
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<P>OK. We have a good kernel. Now, we have to set up the software to our system.
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The call-back program is a part of mgetty-sendfax and ppp. You will
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find it all in your distribution.
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Because the call-back system has double verification we create a
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user who will be running ppp on the side of server.
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In /etc/passwd you have new user and you have to change their shall.
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<P>
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<P>
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<PRE>
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pppuser:klkIOM89mn65H:230:PPP Dialin:/home/pppuser:/etc/ppp/ppplogin
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</PRE>
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<P>I changed the above line for kernel 2.4.x this line in /etc/passwd (I use shadow
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and you don't see password)
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<P>
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<PRE>
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pppuser:x:6778:44:PPP Dialin:/etc/ppp/:/usr/sbin/pppd
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</PRE>
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<P>I don't use a special script for the running of pppd but I run it directly
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while login pppuser.
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<P>Then change the password. We have to add information abut password in
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the file <CODE>/etc/ppp/pap-secrets</CODE> (more in man pppd)
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<P>
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<P>
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<PRE>
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pppuser * password_for_pppuser *
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</PRE>
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<P>In the 2.4.x kernels you have to write in <CODE>/etc/ppp/pap-secrets</CODE>
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<P>
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<P>
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<PRE>
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* * "" *
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</PRE>
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<P>This user doesn't have a usual shell but a file <CODE>/etc/ppp/ppplogin</CODE>.
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We have to make it ourselves. For example <CODE>vi /etc/ppp/ppplogin</CODE> and
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we type:
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<P>
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<PRE>
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#!/bin/sh
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exec /usr/sbin/pppd -detach 192.168.1.1:192.168.1.2
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</PRE>
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<P>where the address 192.168.1.1 is the address of server with modem and
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the address 192.168.1.2 is the address which we assigned to our modem.
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We set up executable options for this file. Because we will use the
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ppp demon we have to set up the options for this demon. We edit file
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<CODE>/etc/ppp/options</CODE>:
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<P>
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<PRE>
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proxyarp
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lock
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crtscts
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modem
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</PRE>
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<P>If it's 2.4.x kernel you write in <CODE>/etc/ppp/options</CODE>
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<P>
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<PRE>
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-detach
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asyncmap 0
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modem
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crtscts
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proxyarp
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lock
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require-pap
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refuse-chap
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ms-dns 192.168.1.1
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usepeerdns
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</PRE>
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<P>The last 3rd option is very important. You use only PAP authentication
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,require-pap. Don't use chap authentication, refuse-chap.
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You can use ms-dns, If you have M$ Windows system clients you can send
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them information about DNS server. If you wont to send IP of DNS server
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for Linux/UNIX machine you use usepeerdns option, more in man pppd.
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<P>
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<P>Proxyarp is the most important from the above options, because you
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can go to Internet by the modem in the server. The remaining options
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are used to control your modem. You can only work on the server if you remove proxyarp option.
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You have to see PPP-HOWTO and man pppd for more information. We will set up our modem now.
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Our server must be ready to receive a connection after start.
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We edit file <CODE>/etc/inittab</CODE>
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and we add it's to modem on the 2en com.
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<P>
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<PRE>
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s1:2345:respawn:/sbin/mgetty ttyS1 -D /dev/ttyS1 vt100
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</PRE>
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or
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<PRE>
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s1:2345:respawn:/sbin/mgetty ttyS1 -s 115200 -D /dev/ttyS1
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</PRE>
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<P>For the 1st com line looks as follows:
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<P>
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<PRE>
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s0:2345:respawn:/sbin/mgetty ttyS1 -D /dev/ttyS1 vt100
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</PRE>
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or
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<PRE>
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s0:2345:respawn:/sbin/mgetty ttyS0 -s 115200 -D /dev/ttyS0
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</PRE>
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We make <CODE>init q</CODE>. If we don't have information about any mistakes in
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logs we go to the next step. We come back to directory <CODE>/etc/ppp</CODE> and
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create <CODE>options.ttyS1</CODE> (for modem com1 <CODE>options.ttyS0</CODE>)
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<P>
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<PRE>
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IP_local: IP_remote
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</PRE>
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<P>for our net it will be
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<P>
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<PRE>
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192.168.1.1:192.168.1.2
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</PRE>
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<P>We have done a lot work so far. Now, we check the file
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<CODE>/etc/mgetty+sendfax/login.config</CODE>. The most important line is:
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<P>
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<PRE>
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/AutoPPP/ - a_ppp /usr/sbin/pppd auth -chap +pap login detach 7 debug
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</PRE>
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<P>If you have 2.4.x kernel you have write in this file:
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<PRE>
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/AutoPPP/ - a_ppp /usr/sbin/pppd file /etc/ppp/options
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</PRE>
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The remaining lines can be marked <CODE>#</CODE>.
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<P>
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<P>We have to set up suid for ppp demon, because pppuser has to run pppd
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and make interface work.
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I insert have to insert opinion of Bill Staehle
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"NOTE: Some distributions think they know better than you, and delete this
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permission when their 'admin' tool (yast in SuSE, linuxconf in many others)
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is used. Read the documentation of the "tool" to see how to stop this crap."
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<P>
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<PRE>
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chmod u+s /usr/sbin/pppd
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</PRE>
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<P>and its effect is:
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<P>
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<PRE>
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-rwsr-xr-x 1 root root 106892 Jan 11 1999 /usr/sbin/pppd
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</PRE>
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<P>I think that it is a good idea is to add it to cron becouse I had a
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problem after restart of my server pppd changed preference. It's
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normal situation in.
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I add opinion of Bill Staehle
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"COMMENT: This is what I was referring to. In Red Hat, look at
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/usr/lib/linuxconf/redhat/perm/ppp (delete or rename the file)."
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<P>Our server will work as router. We have to enable IP forwarding and
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we add this line for the file <CODE>/etc/rc.d/rc.local</CODE> :
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<P>
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<PRE>
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echo "1" > /proc/sys/net/ipv4/ip_forward
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</PRE>
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<P>If you are RedHat user you can change in <CODE>/etc/sysconfig/network</CODE> from
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<CODE>FORWARD_IPV4=false</CODE> to <CODE>FORWARD_IPV4=true</CODE>.
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<P>
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<P>For verification we call to Linux. We use scripts for it. If we do this in
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MS Windows we mark options <CODE>"call out a terminal after connection"</CODE>.
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We login as pppuser with its password. I hope that all is OK.
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<P>
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<H2><A NAME="ss2.4">2.4 PART IV Linux calls us</A>
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</H2>
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<P>We can already call our Linux. Now it's time Linux called us. It's
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not very diffucalt. We have to edit only two files. We create a file
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<CODE>/etc/mgetty+sendfax/callback.conf</CODE> and we leave it empty.
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<P>
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<P>Then we have to ask our users for their phone number. It's time to
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write the numbers we have connected earlier. In order to do it we
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edit <CODE>/etc/mgetty+sendfax/login.conf</CODE> and add line:
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<P>
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<PRE>
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call - - /usr/sbin/callback -S 123456
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</PRE>
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<P>where call is a pseudo-user needed to initiate the connection. The
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line in the <CODE>/etc/mgetty+sendfax/login.conf</CODE> puts in motion the program
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calling the given number (in this case it's 123456). The same procedures
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can be applied to other users. I'll try to explain how it works. When
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we call a server. It asks us to give verification. We login as pseudo-user,
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in this case it calls. The script in our computer hangs up the modem.
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We wait and the connection is cut off. The program call-back starts
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working and recalls us. We verify ourselves again as pppuser with
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password. We combine the connection and interface ppp. That's all. The
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configuration of work-stations is very simple. When you have MS
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Windows, you have to install dial-up for your number. In the modem
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propriety we find " propriety--->extended---> extra options" where
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we write.
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<P>
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<PRE>
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&c0s0=1
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</PRE>
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<P>We close the window and call. We log in according to the description
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given above. If we want to use Linux, we must refer to the script.
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It's difficult to give only one good script for our Linux. A good
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configuration of ppp in the system is of primary importance. (You
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can call it as pppuser through the scripts first).The scripts below
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were whiten by A. Gozdz. I suggest putting everything to catalogue.
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It is only my suggestion & you don't have to start the scripts here.
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Detailed information cocernig writing scripts on Linux can found in
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PPP-HOWTO.
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<P>
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<P>The configuration file of daemon ppp (an example for modem on com2)
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<B>THESE SCRIPTS WORK GOOD WITH LINUX RED HAT 6.x</B>
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<P>
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<UL>
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<LI>/etc/ppp/options
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<PRE>
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lock
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defaultroute
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noipdefault
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modem
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115200
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crtscts
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debug
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passive
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asyncmap 0
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</PRE>
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</LI>
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<LI>/etc/ppp/pppcallback
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<PRE>
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TIMEOUT 5
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ABORT 'ERROR'
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ABORT 'BUSY'
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ABORT 'NO ANSWER'
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ABORT 'NO DIALTONE'
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ABORT '\nVOICE\r'
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ABORT '\nRINGING\r\n\r\nRINGING\r'
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'' AT&FH0 'OK-+++\c-OK' 'AT&C0S0=1'
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TIMEOUT 40
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OK ATDT5376443 CONNECT ''
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ogin:-ogin: ppp-pseudo-user
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'\nNO CARRIER\r' ''
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TIMEOUT 180
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'\nRING\r' AT&C1A
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CONNECT ''
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TIMEOUT 20
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ogin:-ogin: pppuser
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sword:-sword password_for_ppuser
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</PRE>
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</LI>
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<LI>/usr/bin/ppp-call
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<PRE>
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#!/bin/bash
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teksta="Connection failed"
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tekstb="Probably, You will be connect"
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# /sbin/setserial /dev/ttyS1 spd_vhi
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killall -INT pppd 2>/dev/null
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rm -f /var/lock/LCK* /var/run/ppp*.pid
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(/usr/sbin/pppd -detach call ppp_call &) || \
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(echo $teksta; ls marsss >/dev/null; exit 1)
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echo $tekstb
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exit 0
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</PRE>
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</LI>
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<LI>You can run ppp-call, now. :)
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</LI>
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</UL>
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<P>
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<P>If you have M$ Windows you can use this script for conection. I don't
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test it (I use terminal) you can ask some more Adrian Debkowski
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(
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<A HREF="mailto:adrian@cr-media.pl">adrian@cr-media.pl</A>).
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<P>
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<PRE>
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proc main
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delay 1
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waitfor "ogin:"
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transmit "call^M"
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waitfor "RING"
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transmit "ATA^M"
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waitfor "CONNECT"
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waitfor "ogin:"
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transmit "pppuser^M"
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waitfor "word:"
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transmit "ppp^M"
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endproc
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</PRE>
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<P>
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<H2><A NAME="ss2.5">2.5 PART V Summary</A>
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</H2>
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<P>The Configuration of call-back is not complicated. The most important
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thing is a proper arrangement of ppp server on Linux. I don't know a
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better way of setting up an access - server. The configuration
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presented above is a result of numerous attempts and it can be done in
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a different way. That's way I suggest reading all the documents concerning
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the issue man pppd, NET-HOWTO, PPP-HOWTO,ISP-Setup-RedHat-HOWTO,Modem-HOWTO .
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A special thanks for Bill Staehle.
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<HR>
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Next
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<A HREF="Call-back-1.html">Previous</A>
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<A HREF="Call-back.html#toc2">Contents</A>
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