Symbolic names for (ethernet) interfaces

[James Long]

On Mon, Jul 07, 2003 at 10:29:58PM +0200, Dirk-Willem van Gulik wrote:
> 
> How does one specify a 'symbolic' name for an ethernet interface; i.e. be
> able to refer to rl0, vx1 or ep0 by a name like 'net0, net1' or 'net2'.
> 
> With net1 et.al. tied to a specific PCI slot or card Mac address. So that
> it becomes easier to write HW independed rc.conf or zebra.conf files.

Consider this snippet of my rc.conf, wherein I declare my outside
interface as symbolic name ${oif} and my inside interface as ${iif}.
Where I define iif or oif you might choose to define net0 or net1
instead.


oif="dc0"
oip="206.29.169.27"
omask="255.255.255.0"

iif="tl0"
iip="206.29.168.233"
imask="255.255.255.248"

eval ifconfig_${oif}="\"inet ${oip} netmask ${omask}\""
eval ifconfig_${iif}="\"inet ${iip} netmask ${imask}\""
# eval ifconfig_${iif}="\"DHCP\""


Then I can source rc.conf in my firewall script, and say stuff like
you see below, and if I ever have to change IPs (or more likely, I
clone the script to set up another machine), I just edit rc.conf.

#!/usr/local/bin/bash

# Suck in the configuration variables oif, oip, iif, iip, imask
if [ -f /etc/defaults/rc.conf ]; then
  echo Reading /etc/defaults/rc.conf
  . /etc/defaults/rc.conf
  source_rc_confs
fi

  fw="/sbin/ipfw"

# inside network
  inet="${iip}:${imask}"

...

  ${fw} add deny log all from 127.0.0.0/8 to any via ${oif}
  ${fw} add deny log all from 127.0.0.0/8 to any via ${iif}
  ${fw} add deny log all from any to 127.0.0.0/8 via ${oif}
  ${fw} add deny log all from any to 127.0.0.0/8 via ${iif}

  ${fw} add allow all from any to any via lo0

  ${fw} add deny log all from ${inet} to any recv ${oif}
  ${fw} add deny log all from not ${inet} to any recv ${iif}

...

#   Allow DHCP on internal interface
  ${fw} add allow udp from any to any 67-68 via ${iif}


###########################
#
#  NAT
#
###########################

  ${fw} add divert natd ip from any to any via ${oif}


(etc.)