The Care and Feeding of ISDN4BSD
13.3 Userland PPP setup	13.3 Userland PPP setup	13.3.2 Site-B Setup

13.3.1 Site-A Setup:

If Site-A wants to establish a connection, it dials out to Site-B which rejects the call and in turn calls back Site-A to establish the connection.

• /etc/isdn/isdnd.rc:

  The isdnd.rc is straightforward, there are only two remarkable configuration items:

  1. calledbackwait is set to 30 seconds because Site-B has a strange PBX where the callback call gets out about 20 seconds after the initial setup call from Site-A
  2. regexpr and regprog are setup to execute a script called /etc/isdn/ppp_in_trigger_siteb as soon as a connection has been made successfully from Site-B to Site-A. The reason for this is explained later in detail.
  # SYSTEM section:

  system

  ratesfile = /etc/isdn/isdnd.rates

  useacctfile = yes

  acctall = on

  acctfile = /var/log/isdnd.acct

  rtprio = 25

  regexpr = "PPP2SITEB incoming call active"

  regprog = ppp_in_trigger_siteb

  # ENTRY section:

  entry

  name = PPP2SITEB

  usrdevicename = rbch

  usrdeviceunit = 0

  isdncontroller = 0

  isdnchannel = -1

  local-phone-incoming = 25

  remote-phone-incoming = 0987654321

  local-phone-dialout = 25

  remote-phone-dialout = 0987654321

  remdial-handling = first

  dialin-reaction = accept

  dialout-type = calledback

  b1protocol = hdlc

  idletime-incoming = 300

  idletime-outgoing = 30

  ratetype = 0

  unitlength = 90

  unitlengthsrc = rate

  dialretries = 3

  dialrandincr = off

  recoverytime = 5

  calledbackwait = 30

  usedown = off

  
  

• /etc/ppp/ppp.conf:

  This is the configuration file for ppp(8) running in daemon mode on Site-A. The ``set server'' line in the default configuration entry makes it possible for the pppctl(8) program to connect to the ppp daemon and control its operation. Please consult the pppctl(8) manual page for further information on this. We need this for the script called from isdnd (configured by its regprog-keyword), see further down for a complete explanation.

  We use CHAP to exchange passwords and we want to use deflate-compression for data transfer.

  default:

  # let pppctl come in

  set server 452 secret-password-3

  siteb:

  # THIS IS NEW FOR 4.0 !!!!!!!!!!

  set phone 0987654321

  # use CHAP

  enable chap

  # want to use deflate compression

  enable deflate

  accept deflate

  disable pred1

  deny pred1

  # CHAP key and password

  set authkey secret-password-5

  set authname sitea

  # wait time for carrier

  link * set cd 30

  # device to use

  set device /dev/i4brbch0

  # set no dial chat-script used

  set dial

  # set no hangup chat-script used

  set hangup

  # myaddr hisaddr netmask

  set ifaddr 192.168.192.1 192.168.168.1 255.255.255.255

  # add route to remote network

  add 192.168.168.0/24 192.168.168.1

  # set no login chat-script used

  set login

  # set dial on demand mode

  set mode auto

  # the the process title

  set proctitle ppp2siteb

  # we are a synchronous device

  set speed sync

  # idletimeout mintimeout

  set timeout 60 300

  set reconnect 5 0

  
  

• /etc/isdn/ppp_in_trigger_siteb:

  This shell script does the trick: when isdnd detects the string configured by the isdnd.rc keyword regexpr in its log output, it executes the program configured with the regexpr keyword. In our case this program is the following shell script.

  To understand why this script is needed at all, one must know that ppp(8) in auto mode only looks for packets at its network (tun) interfaces: if a packet is arriving there, ppp tries to establish a connection with the remote site. But the opposite is not true, it does not look on its associated /dev/i4brbch interface for arriving packets.

  Because of this, in case a remote site establishes a connection, the local ppp(8) daemon would never notice its existence. To make him aware of the fact that a connection is established, isdnd calls this script when the connection is ready for data transfer: the script simply say ppp that this should open the associated /dev/i4brbch interface and the the PPP protocol start its negotiation operations:

  #!/bin/sh

  /usr/sbin/pppctl -p secret-password-3 sitea:452 open

  exit 0

  
  

• /etc/ppp/ppp.secret:

  Just for the completeness, this is the content of the ppp.secret file for Site-A:

  # Authname Authkey

  siteb secret-password-4

  
  

• /usr/local/etc/rc.d/ppp2siteb.sh:

  This shell script is used to start the ppp(8) daemon at boot time in auto mode.

  #!/bin/sh

  if [ -f /etc/ppp/ppp.conf ]

  then

  echo -n ' ppp2siteb'

  /usr/sbin/ppp -auto -unit0 -quiet siteb

  fi