sip_nat_settings

#!/bin/sh

# sip_nat_settings: generate NAT settings for sip.conf of an Asterisk system
#                   that is behind a NAT router.
#
# This is a script to generate sane defaults for externip and localnet
# of sip.conf. The output should be included in the [general] section of
# sip.conf .
#
# Multiple network interfaces: If you have multiple network interfaces,
# this script will generate a 'localnet' line for each of them that has a
# broadcast (ipv4) address, except the loopback interface (lo). You can
# later rem-out all of those you don't need.
#
# Alternatively, provide a network interface as a parameter an a localnet
# line will only be generated for its network.
#
# Copyright (C) 2005 by Tzafrir Cohen <tzafrir.cohen@xorcom.com>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

# see http://unix.stackexchange.com/q/22615
externip=`dig @resolver1.opendns.com -4 myip.opendns.com A +short`

# optional parameter: network interface to use. By default: none.
IFACE="$1"

OS=`uname -s`
case "$OS" in
Linux)
  echo "externip = $externip"
  if [ -x "${IFACE}" ]; then
	  ip --brief -family inet address show scope global up dev $IFACE | awk '{print "localnet = " $3}'
  else
	  ip --brief -family inet address show scope global up | awk '{print "localnet = " $3}'
  fi
  ;;
OpenBSD|FreeBSD)
  if [ "${OS}" = "FreeBSD" ]; then
	  VER=`uname -r | cut -d . -f 1`
	  if [ ${VER} -lt 7 ]; then
		  echo "Unsupported OS"
		  exit 1
	  fi
  fi
  echo "externip = $externip"
  ip=`/sbin/ifconfig $IFACE | awk '/\tinet .* broadcast/{print $6}'`
  x=`/sbin/ifconfig $IFACE | awk '/\tinet .* broadcast/{print $4}'`
  printf 'localnet = %s/%u.%u.%u.%u\n' $ip $(($x>>24&0xff)) $(($x>>16&0xff)) $(($x>>8&0xff)) $(($x&0xff))
  ;;
*)
  echo >&2 "$0: Unsupported OS $OS"
  exit 1
  ;;
esac