Blame Manuals/Tcpi-ug/Connectivity/Dialup/server.docbook

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<sect1 id="connectivity-dialup-server">
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    <title>The Server Computer</title>
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    <para>
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        When you are configuring the server computer, you need to
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        install and configure both <application>mgetty</application>
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        and <application>pppd</application> programs.  The
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        <application>mgetty</application> program lets you attend
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        incoming calls and must be configured to run through
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        <systemitem class="daemon">init</systemitem> daemon in order
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        to take control over the Modem device. By default, inside
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        &TC;; (release 5.5), <application>mgetty</application> isn't
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        configured to start with 
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        class="daemon">init</systemitem> daemon so you need to do it
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        yourself (see 
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        linkend="connectivity-dialup-server-mgetty-inittab" />).
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        Later, for attending connection requests, you need to
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        configure <application>mgetty</application> to use the
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        <application>pppd</application> program, so the Point-to-Point
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        Protocol (PPP) can be talked and IP packages can be
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        interchanged between the client computer and the server
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        computer. Later, you need to configure
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        <application>pppd</application> to adjust it to your needs
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        (see 
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        />)Once you've configured both
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        <application>mgetty</application> and
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        <application>pppd</application> programs, the server computer
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        should be ready to attend incoming calls.
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    </para>
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    <sect2 id="connectivity-dialup-server-mgetty">
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    <title><package>mgetty</package></title>
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    <para>
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        Taken from <command>mgetty</command> man page: — Mgetty
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        is a <quote>smart</quote> getty replacement, designed to be
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        used with hayes compatible data and data/fax modems. Mgetty
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        knows about modem initialization, manual modem answering (so
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        your modem doesn’t answer if the machine isn’t ready), UUCP
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        locking (so you can use the same device for dial-in and
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        dial-out).  Mgetty provides very extensive logging facilities
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        —.
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    </para>
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    <para>
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        Before using the configuration provided here, it would be
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        useful for you to read the documentation provided by
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        <package>mgetty</package> and <package>SysVinit</package>
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        packages.  This will let you to understand what you are
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        configuring.
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    </para>
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    <sect3 id="connectivity-dialup-server-mgetty-inittab">
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    <title><filename>/etc/inittab</filename></title>
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<screen>
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# Run mgetty to control a Multi-Tech (MT5634ZBA-USB) modem attached to
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# `/dev/ttyAMC0' device. Incoming calls will be attended without fax
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# initalization.
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ACM0:2345:respawn:/sbin/mgetty -D ttyACM0
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</screen>
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    </sect3>
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    <sect3 id="connectivity-dialup-server-mgetty-login">
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    <title><filename>/etc/mgetty+sendfax/login.config</filename></title>
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<screen>
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# Automatic PPP startup on receipt of LCP configure request (AutoPPP).
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# mgetty has to be compiled with "-DAUTO_PPP" for this to work.
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# Warning: Case is significant, AUTOPPP or autoppp won't work!
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# Consult the "pppd" man page to find pppd options that work for you.
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#
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#  NOTE: for *some* users, the "-detach" option has been necessary,
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#  for others, not at all. If your pppd doesn't die after hangup, try
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#  it.
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#
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#  NOTE2: "debug" creates lots of debugging info.  LOOK AT IT if
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#  things do not work out of the box, most likely it's a ppp problem!
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#
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#  NOTE3: "man pppd" is your friend!
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#
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#  NOTE4: max. 9 arguments allowed.
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#
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#/AutoPPP/ -    a_ppp   /usr/sbin/pppd auth -chap +pap login debug
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/AutoPPP/ -     a_ppp   /usr/sbin/pppd 192.168.0.2:192.168.0.3
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</screen>
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    <para>
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        Notice that both local and remote IP address are set here. All
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        other options are taken from the <filename>options</filename>
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        file (see 
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        linkend="connectivity-dialup-server-pppd-options" />). If we
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        don't specify both local and remote IP addresses when pppd is
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        initialized, pppd will try to take such information from the
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        first Modem device you configured (e.g., ppp0) and will expect
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        the remote peer to provide its IP address. This situation can
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        introduce some contraditions (e.g., the local and remote
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        address may be on a different network.) that would make the
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        connection to fail.
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    </para>
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    <para>
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        Another issue we might face out would be the netmask
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        specification of the poin-to-point network established between
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        the two computers. Inside the pppd-2.4.4 man page there is no
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        reference to the <option>netmask</option> option, however,
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        there is a mention to it on the sample files installed with it
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        which is quiet confussing. It seems to be required that one of
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        the two computers establishing connection defines the netmask
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        information of the network they are creating. So, to do it on
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        the server computer (the one receiving calls), it is needed to
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        set the netmask definition in the Modem device configuration
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        file of it (
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        />) along with the local IP address. Otherwise, even local and
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        remote IP addresses be specified through the pppd, the
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        connection will end up having the 255.255.255.255 netmask
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        which would let you ping the computer on the other end but
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        that will not last too long before it fails and iptables seems
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        to get very confused about it.
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    </para>
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    <para>
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        Since we are already using 
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        class="daemon">pppd</systemitem> to attend login requests,
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        there is no need to invoke the
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        <application>login</application> program. So, comment the
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        related line as described below.
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    </para>
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<screen>
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#*      -       -       /bin/login @
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</screen>
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    </sect3>
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    <sect3 id="connectivity-dialup-server-mgetty-dialin">
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    <title><filename>/etc/mgetty+sendfax/dialin.config</filename></title>
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    <para>
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        I didn't touch this file, but you might need to.
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    </para>
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    </sect3>
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    <sect3 id="connectivity-dialup-server-mgetty-config">
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    <title><filename>/etc/mgetty+sendfax/mgetty.config</filename></title>
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    <para>
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        I didn't touch this file, but you might need to.
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    </para>
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    </sect3>
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    </sect2>
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    <sect2 id="connectivity-dialup-server-pppd">
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    <title><package>pppd</package></title>
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    <para>
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        Taken from pppd man page: — PPP is the protocol used for
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        establishing internet links over dial-up modems, DSL
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        connections, and many other types of point-to-point links.
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        The pppd daemon works together with the kernel PPP driver to
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        establish and maintain a PPP link with another system (called
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        the peer) and to negotiate Internet Protocol (IP) addresses
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        for each end of the link. Pppd can also authenticate the peer
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        and/or supply authentication information to the peer.  PPP can
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        be used with other network protocols besides IP, but such use
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        is becoming increasingly rare —.
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    </para>
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    <para>
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        Before using the configuration provided here, it would be
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        useful for you to read the documentation provided by
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        <package>ppp</package> package.  This will let you to
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        understand what you are configuring.
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    </para>
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    <sect3 id="connectivity-dialup-server-pppd-options">
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    <title><filename>/etc/pppd/options</filename></title>
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<screen>
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# Enables connection debugging facilities.  If this option is given,
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# pppd will log the contents of all control packets sent or received
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# in a readable form.  The packets are logged through syslog with
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# facility daemon and level debug.  This information can be directed
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# to a file by setting up /etc/syslog.conf appropriately (see
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# syslog.conf(5)).
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debug
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# Require the peer to authenticate itself before allowing network
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# packets to be sent or received. This option is the default if the
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# system has a default route.  If neither this option nor the noauth
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# option is specified, pppd will only allow the peer to use IP
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# addresses to which the system does not already have a route.
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auth
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# Specifies that pppd should create a UUCP-style lock file for the
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# serial device to ensure exclusive access to the device.  By default,
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# pppd will not create a lock file.
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lock
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# Specify which DNS Servers the incoming Win95 or WinNT Connection
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# should use Two Servers can be remotely configured
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ms-dns 192.168.0.1
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# If this option is given, pppd will send an LCP echo-request frame to
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# the peer every n seconds. Under Linux, the echo-request is sent when
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# no packets have been received from the peer for n seconds. Normally
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# the peer should respond to the echo-request by sending an
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# echo-reply.  This option can be used with the lcp-echo-failure
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# option to detect that the peer is no longer connected.
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lcp-echo-interval 30
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# If this option is given, pppd will presume the peer to be dead if n
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# LCP echo-requests are sent without receiving a valid LCP echo-reply.
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# If this happens, pppd will terminate the connection.  Use of this
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# option requires a non-zero value for the lcp-echo-interval
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# parameter.  This option can be used to enable pppd to terminate
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# after the physical connection has been broken (e.g., the modem has
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# hung up) in situations where no hardware modem control lines are
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# available.
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lcp-echo-failure 4
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# Specifies that pppd should disconnect if the link is idle for n
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# seconds.
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idle 60
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# Specifies that pppd should disconnect if the link have been active
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# for n seconds.
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maxconnect 900
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# Disable the IPXCP and IPX protocols.
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noipx
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</screen>
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    </sect3>
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    <sect3 id="connectivity-dialup-server-pppd-cha">
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    <title><filename>/etc/pppd/cha-secrets</filename></title>
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<screen>
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# Secrets for authentication using CHAP
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# client        server  secret                  IP addresses
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# Specify the client configuration. This is when this manchine calls
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# someone's else machine and tries to establish a point-to-point
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# connection. Most of this configuration is handled by the
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# `system-config-network' utility.
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#
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####### redhat-config-network will overwrite this part!!! (begin) ##########
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####### redhat-config-network will overwrite this part!!! (end) ############
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# Specify the server configuration. This is when someone's else
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# machine calls this machine trying to establish a point-to-point
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# connection.  This part of the configuration isn't handled by
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# `system-config-network' utility. By default, there is one line to
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# verify client's identity with authenticating it and one line to let
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# the server computer to authenticate itself with the client computer
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# in case the client computer requires so. All client computers will
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# be authenticated through the `faith' user.  However, it is possible
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# to provide anonymous authentication to client computers by using an
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# empty client identity (as explained in pppd's man page) in order to
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# restrict the IP address they can use.
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#
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"faith"         "projects"      "mail4u.2k10"   "192.168.0.3"
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#""             "projects"      ""              "192.168.0.3"
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"projects"      *               "mail4u.2k10"
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</screen>
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    <para>
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        Assuming the hostname of the server computer is
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        <quote>projects</quote>, when a client computer uses the faith
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        username to login on it, the 
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        class="ipaddress">192.168.0.3</systemitem> IP address will be
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        assigned to that client computer after a successful
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        authentication.  This configuration is just for one Modem
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        device attached to the server computer.  In case you have more
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        than one Modem device attached to the server computer, it
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        would be necessary to add one username for each Modem device
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        you have, in order to permit the client computers to connect
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        simultaneously. It is not possible to have two or more
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        computers with the same IP address in the same network.
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    </para>
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    </sect3>
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    <sect3 id="connectivity-dialup-server-pppd-pap">
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    <title><filename>/etc/pppd/pap-secrets</filename></title>
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    <para>
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        This file contains the same information of
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        <filename>pap-secrets</filename> file does. See 
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        linkend="connectivity-dialup-server-pppd-cha" />. 
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    </para>
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    </sect3>
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    </sect2>
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</sect1>