15.2. Using User PPP

15.2.1.5.3.1. 어떤 getty를 사용할 것인가?

Configuring FreeBSD for Dial-up Services은 getty를 이용해 회선 서비스를 사용하는 것에 대해 자세히 설명하고 있습니다.

getty의 대안은 전화회선에 맞게 디자인된 더욱 깔끔한 mgetty 입니다.

mgetty를 사용하는 잇점은 모뎀과 끊임없는 통신을 한다는 점인데, 이는 /etc/ttys 에서 포트가 닫혀져 있다면 모뎀이 전화를 받지 않게 된다는 것을 의미합니다.

mgetty의 새버전(0.99beta 이후) 또한 서버에 클라이언트가 스크립트(script-less)없이 접근하는 것을 허용하면서 PPP 스트림(stream)을 자동으로 탐지하는 것을 지원합니다.

mgetty의 더 자세한 것은 Mgetty와 AutoPPP를 참조하십시오.

15.2.1.5.3.2. PPP 권한

ppp는 보통 사용자id 0으로 실행되어야 하지만, command must normally be run as user id 0. If however, you wish to allow ppp to run in server mode as a normal user by executing ppp as described below, that user must be given permission to run ppp by adding them to the network group in /etc/group.

You will also need to give them access to one or more sections of the configuration file using the allow command:

    allow users fred mary

If this command is used in the default section, it gives the specified users access to everything.

15.2.1.5.3.3. PPP Shells for Dynamic-IP Users

Create a file called /etc/ppp/ppp-shell containing the following:

    #!/bin/sh
    IDENT=`echo $0 | sed -e 's/^.*-\(.*\)$/\1/'`
    CALLEDAS="$IDENT"
    TTY=`tty`
    
    if [ x$IDENT = xdialup ]; then
            IDENT=`basename $TTY`
    fi
    
    echo "PPP for $CALLEDAS on $TTY"
    echo "Starting PPP for $IDENT"
    
    exec /usr/sbin/ppp -direct $IDENT

This script should be executable. Now make a symbolic link called ppp-dialup to this script using the following commands:

    # ln -s ppp-shell /etc/ppp/ppp-dialup

You should use this script as the shell for all of your dialup users. This is an example from /etc/password for a dialup PPP user with username pchilds (remember don't directly edit the password file, use vipw).

    pchilds:*:1011:300:Peter Childs PPP:/home/ppp:/etc/ppp/ppp-dialup

Create a /home/ppp directory that is world readable containing the following 0 byte files:

    -r--r--r--   1 root     wheel           0 May 27 02:23 .hushlogin
    -r--r--r--   1 root     wheel           0 May 27 02:22 .rhosts

which prevents /etc/motd from being displayed.

15.2.1.5.3.4. PPP shells for Static-IP Users

Create the ppp-shell file as above and for each account with statically assigned IPs create a symbolic link to ppp-shell.

For example, if you have three dialup customers fred, sam, and mary, that you route class C networks for, you would type the following:

    # ln -s /etc/ppp/ppp-shell /etc/ppp/ppp-fred
    # ln -s /etc/ppp/ppp-shell /etc/ppp/ppp-sam
    # ln -s /etc/ppp/ppp-shell /etc/ppp/ppp-mary

Each of these users dialup accounts should have their shell set to the symbolic link created above (i.e., mary's shell should be /etc/ppp/ppp-mary).

15.2.1.5.3.5. Setting up ppp.conf for dynamic-IP users

The /etc/ppp/ppp.conf file should contain something along the lines of:

    default:
      set debug phase lcp chat
      set timeout 0
    
    ttyd0:
      set ifaddr 203.14.100.1 203.14.100.20 255.255.255.255
      enable proxy
    
    ttyd1:
      set ifaddr 203.14.100.1 203.14.100.21 255.255.255.255
      enable proxy

The default: section is loaded for each session. For each dialup line enabled in /etc/ttys create an entry similar to the one for ttyd0: above. Each line should get a unique IP address from your pool of IP addresses for dynamic users.

15.2.1.5.3.6. Setting up ppp.conf for static-IP users

Along with the contents of the sample /usr/share/examples/ppp/ppp.conf above you should add a section for each of the statically assigned dialup users. We will continue with our fred, sam, and mary example.

    fred:
      set ifaddr 203.14.100.1 203.14.101.1 255.255.255.255
    
    sam:
      set ifaddr 203.14.100.1 203.14.102.1 255.255.255.255
    
    mary:
      set ifaddr 203.14.100.1 203.14.103.1 255.255.255.255

The file /etc/ppp/ppp.linkup should also contain routing information for each static IP user if required. The line below would add a route for the 203.14.101.0 class C via the client's ppp link.

    fred:
      add 203.14.101.0 netmask 255.255.255.0 HISADDR
    
    sam:
      add 203.14.102.0 netmask 255.255.255.0 HISADDR
    
    mary:
      add 203.14.103.0 netmask 255.255.255.0 HISADDR

15.2.1.5.4.1. mgetty and AutoPPP

Configuring and compiling mgetty with the AUTO_PPP option enabled allows mgetty to detect the LCP phase of PPP connections and automatically spawn off a ppp shell. However, since the default login/password sequence does not occur it is necessary to authenticate users using either PAP or CHAP.

This section assumes the user has successfully configured, compiled, and installed a version of mgetty with the AUTO_PPP option (v0.99beta or later).

Make sure your /usr/local/etc/mgetty+sendfax/login.config file has the following in it:

    /AutoPPP/ -     -                     /etc/ppp/ppp-pap-dialup

This will tell mgetty to run the ppp-pap-dialup script for detected PPP connections.

Create a file called /etc/ppp/ppp-pap-dialup containing the following (the file should be executable):

    #!/bin/sh
    exec /usr/sbin/ppp -direct pap$IDENT

For each dialup line enabled in /etc/ttys, create a corresponding entry in /etc/ppp/ppp.conf. This will happily co-exist with the definitions we created above.

    pap:
      enable pap          
      set ifaddr 203.14.100.1 203.14.100.20-203.14.100.40
      enable proxy

Each user logging in with this method will need to have a username/password in /etc/ppp/ppp.secret file, or alternatively add the following option to authenticate users via PAP from /etc/password file.

    enable passwdauth

If you wish to assign some users a static IP number, you can specify the number as the third argument in /etc/ppp/ppp.secret. See /usr/share/examples/ppp/ppp.secret.sample for examples.

15.2.1.5.4.2. MS extensions

It is possible to configure PPP to supply DNS and NetBIOS nameserver addresses on demand.

To enable these extensions with PPP version 1.x, the following lines might be added to the relevant section of /etc/ppp/ppp.conf.

    enable msext
    set ns 203.14.100.1 203.14.100.2
    set nbns 203.14.100.5

And for PPP version 2 and above:

    accept dns
    set dns 203.14.100.1 203.14.100.2
    set nbns 203.14.100.5

This will tell the clients the primary and secondary name server addresses, and a netbios nameserver host.

In version 2 and above, if the set dns line is omitted, PPP will use the values found in /etc/resolv.conf.