#!/usr/bin/perl
#H# This program parses the output of ifconfig and determines all of the interfaces
#H# and IP addresses currently configured on the system.  It then generates
#H# /etc/ip.[interface] files that contain the IP address of that interface.
#H# 
#H# These files are usefull in that they allow you to specify `cat /etc/ip.interface`
#H# in your services when you want to listen only on a specific interface.  That way
#H# if the IP of that interface changes all services will be updated when this command
#H# is run.
#H# 
#H# There are no parameters to this program.
#H# 
#H# This was inspired by Sun's /etc/hostname.[interface] which stores a hostname that
#H# maps to /etc/hosts instead of an IP.

# figure out what OS we are on and setup some initial vars.
$OS=`uname -s`;
chomp $OS;
%Interfaces=();
$IFFound="n";
$IPFount="n";

if ($OS eq "Linux") {
  $IFFound="n";
  $IPFound="n";
  open (IFCONFIG, "/bin/ip addr ls |");
  while (<IFCONFIG>) {
    $Line=$_;
    chomp $Line;
    if ($Line =~ /^\d:/) {
      ($junk,$InterfaceName,$junk)=split (/ /,$Line,3);
      $InterfaceName=~ s/://g;
      $IFFound="y";
      $IPFound="n";
    } elsif ($Line =~ /inet / && $IPFound eq "n") {
      $Line=~ s/^ +//g;
      ($junk,$IP,$junk) = split (/ /,$Line,3);
      $IP=~ s/\/.*//g;
      $IPFound="y";
    }
    # When we find both parts stuff it into the hash.
    if ($IFFound eq "y") {
      if ($IPFound eq "y") {
        $Interfaces{$InterfaceName}=$IP;
	$IFFound="n";
	$IPFound="n";
      }
    }
  }
} elsif ($OS eq "OpenBSD") {
  open (IFCONFIG, "ifconfig -A |");
  while (<IFCONFIG>) {
    $Line=$_;
    chomp $Line;
    if ($Line =~ /RUNNING/) {
      $InterfaceName=$Line;
      $InterfaceName =~ s/:.*//;
      $IFFound="y";
    } elsif ($Line =~ /inet /) {
      $IP=$Line;
      $IP =~ s/.*inet //;
      $IP =~ s/ .*//;
      $IPFound="y";
    }
    # When we find both parts stuff it into the hash.
    if ($IFFound eq "y") {
      if ($IPFound eq "y") {
        $Interfaces{$InterfaceName}=$IP;
	$IFFound="n";
	$IPFound="n";
      }
    }
  }
} else { die "Unsupported OS: $OS\n"; }

# write out the files in /etc
foreach $Interface (sort (keys (%Interfaces))) {
  print ("$Interface is $Interfaces{$Interface}.\n");
  open (IFFile, "> /etc/ip.$Interface");
  print (IFFile "$Interfaces{$Interface}\n");
  close (IFFile);
}