Re: [Q] Virtual hosts and routing...

["David H. Silber" <dhs@orbits.com>]

On Fri, Jun 18, 1999 at 09:17:56AM -0400, David H. Silber wrote:
> #  Set up a virtual interface.
> #
> #  Usage:
> #    virtualif <Interface> <IP number> <netmask> <broadcast> [reset]
> virtualif() {

I didn't like that my previous solution, because it only dealt reasonably
with one physical interface at a time.  By making a virtual variable to
track the virtual interface for each physical interface, the virtualif()
function no longer requires that the administrator set up all of the
virtual interfaces for a given physical interface before setting up the
next physical interface.  This allows the administrator who maintains
separate domains over the the same network to group entries in the
/etc/init.d/network file in a more logical manner.  There is also no
longer a need to reset the counter manually.

#! /bin/sh
#
#  virtualif() - Set up a virtual interface.
#
#  Usage:
#    virtualif <Interface> <IP number> <Netmask> <Broadcast>
#
#  Example:
#    virtualif eth0 192.168.246.1 255.255.255.128 192.168.246.127
#    virtualif eth0 192.168.246.2 255.255.255.128 192.168.246.127
#    virtualif eth0 192.168.246.3 255.255.255.128 192.168.246.127
#    virtualif eth1 192.168.246.129 255.255.255.128 192.168.246.255
#    virtualif eth1 192.168.246.130 255.255.255.128 192.168.246.255
#    virtualif eth0 192.168.246.4 255.255.255.128 192.168.246.127
#    virtualif eth0 192.168.246.5 255.255.255.128 192.168.246.127
#    virtualif eth0 192.168.246.6 255.255.255.128 192.168.246.127
#    virtualif eth1 192.168.246.131 255.255.255.128 192.168.246.255
#    virtualif eth2 10.10.10.1 255.255.255.0 192.168.246.255
#
#  virtualif() sets up a virtual network interface and adds a route so
#  that local references to the IP can be routed.  It keeps track of the
#  next available virtual interface for each physical interface, so that
#  you don't have to.
#
#  Installation:  Insert the virtualif() function at the top of the
#  /etc/init.d/network file.
#
#  $VCOUNTER contains the name of the counter of virtual interfaces for
#  the current physical interface.  This name is built from the string
#  ``COUNTER'', concatenated with the name of the physical interface.
#  By using eval, we can use this name as a variable.  Since applying
#  the name of a different physical interface to this scheme generates
#  a different variable name, we can keep a separate counter for each
#  physical interface.
#
#  Version 1.1
#
#  David H. Silber -- June 18, 1999
#  dhs@orbits.com -- http://www.orbits.com/~dhs
#
#  (I keep thinking that there ought to be a way to simplify this, but
#  it escapes me.  If you find a better way to do this, please send
#  email to the address above.)
virtualif() {
  INTERFACE=$1
  IP=$2
  NETMASK=$3
  BROADCAST=$4

  COUNTER='$COUNTER'

  VCOUNTER=`echo COUNTER$INTERFACE`
  if [ ! "`eval echo $\`echo $VCOUNTER\``" ]
  then
    eval "$VCOUNTER=0"
  fi

  #  Build the virtual interface name string.
  VIRTUAL=${INTERFACE}:`eval echo $\`echo $VCOUNTER\``

  #  The point of all of this is to:
  echo "Creating virtual interface $VIRTUAL and local route for $IP."
  /sbin/ifconfig ${VIRTUAL} ${IP} netmask ${NETMASK} broadcast ${BROADCAST}
  /sbin/route add -host ${IP} ${VIRTUAL}

  #  Increment the virtual interface counter.
  eval "$VCOUNTER=`/usr/bin/expr \`eval echo $\\\`echo $VCOUNTER\\\`\` + 1`"
}


-- 
David H. Silber  --   http://www.orbits.com/~dhs/   --   dhs@orbits.com

  For custom software, see:                http://www.SilberSoft.com/
  Palm OS / Linux Documentation:          http://www.orbits.com/Palm/