#!/bin/sh

# Copyright (C) RealVNC Ltd.  All Rights Reserved.

# Get the IP address of the primary network interface

error_exit()
{
    echo $1
    exit 1
}

primary_ip_linux()
{
    # On Linux, we can get the network interface corresponding to the
    # default route from /proc/net/route, and feed it into "ifconfig"
    # to get the IP address.
    interf=`$awk '$2=="00000000" && int($4/2)%2==1 {print $1; exit}' /proc/net/route`
    [ -n "$interf" ] || error_exit "No default network interface"
    ip=`$ifconfig $interf 2>/dev/null | \
        $tr ':' ' ' | \
        $awk '$1=="inet" && $2=="addr" {print $3; exit}
              $1=="inet" {print $2; exit}'`
    [ -n "$ip" ] || ip=`$ipb -4 addr show $interf 2>/dev/null | \
        $awk '$1 == "inet" {gsub(/\/.*$/, "", $2); print $2; exit}'`
    [ -n "$ip" ] || error_exit "No IP address found"
    echo $ip
    exit 0
}

primary_ip_darwin()
{
    # On Darwin, "route get <IP-address>" tells us the network interface
    # corresponding to the default route, and "ifconfig" tells us its IP
    # address.  We use realvnc.com's current IP address as a fairly arbitrary
    # address.
    interf=$(route get 162.159.135.42 | \
                 awk '$1 == "interface:" {print$2; exit}')
    [ -n "$interf" ] || error_exit "No default network interface"
    ip=`$ifconfig $interf 2>/dev/null | \
        $awk '$1 == "inet" { print $2; exit }'`
    [ -n "$ip" ] || error_exit "No IP address found"
    echo $ip
    exit 0
}

# Default program locations
awk=/usr/bin/awk
ifconfig=/sbin/ifconfig
ipb=/sbin/ip
netstat=/bin/netstat
tr=/usr/bin/tr

# Override any locale settings that might affect the output of commands
if test "${LANG+set}" = set; then LANG=C; export LANG; fi
if test "${LC_ALL+set}" = set; then LC_ALL=C; export LC_ALL; fi
if test "${LC_MESSAGES+set}" = set; then LC_MESSAGES=C; export LC_MESSAGES; fi
if test "${LC_CTYPE+set}" = set; then LC_CTYPE=C; export LC_CTYPE; fi

# Platform-specific overrides
SYSNAME=`uname -s`
case "$SYSNAME" in
    Linux)
        primary_ip_linux
        ;;
    Darwin)
        netstat=/usr/sbin/netstat
        primary_ip_darwin
        ;;
    *)
        error_exit "Unsupported platform"
        ;;
esac