#!/bin/bash
#
# script: monitor_interface
#
# Monitors a given list of interfaces and add or remove static IP addresses to these interfaces.
# The list of interfaces is provided in the file '/var/local/emhttp/statics.ini'
# This file is maintained by the script 'create_network_ini' which keep track of all IP assignments.
#
# By removing static IP addresses from inactive interfaces, these interfaces do not longer interfere with wireless.
# In other words the wired connection can be pulled without consequences.
#
# Bergware - modified for Unraid OS, May 2025

FILE=/var/local/emhttp/statics.ini
SYSTEM=/sys/class/net

state(){
  cat $SYSTEM/$1/operstate 2>/dev/null
}

md5(){
  [[ -r $FILE ]] && md5sum $FILE | awk '{print $1;exit}'
}

switch(){
  local n
  [[ -z $1 ]] && return 1
  # state change should stay stable for at least 5 seconds
  for n in {1..5}; do
    [[ $(state $1) == $2 ]] && return 1 || sleep 1
  done
  return 0
}

init(){
  PORT=(); IPV4=(); METRIC4=(); IPV6=(); METRIC6=(); STATE=();
  if [[ -r $FILE ]]; then
    # initialize values from file, maintained by 'create_network_ini'
    while IFS=$'\n' read -r ROW; do
      ROW=($ROW)
      PORT+=(${ROW[0]})
      IPV4+=(${ROW[1]:--})
      METRIC4+=(${ROW[2]:--})
      IPV6+=(${ROW[3]:--})
      METRIC6+=(${ROW[4]:--})
      STATE+=($(state ${ROW[0]}))
    done <$FILE
  fi
  MD5=$(md5)
}

while :; do
  # monitor file content changes
  [[ $MD5 != $(md5) ]] && init
  for i in ${!PORT[@]}; do
    # did interface state change?
    if switch ${PORT[$i]} ${STATE[$i]}; then
      STATE[$i]=$(state ${PORT[$i]})
      if [[ ${STATE[$i]} == up ]]; then
        [[ ${IPV4[$i]} != '-' ]] && ip addr add ${IPV4[$i]} metric ${METRIC4[$i]} dev ${PORT[$i]}
        [[ ${IPV6[$i]} != '-' ]] && ip addr add ${IPV6[$i]} metric ${METRIC6[$i]} dev ${PORT[$i]}
      elif [[ ${STATE[$i]} == down ]]; then
        ip addr flush scope global dev ${PORT[$i]}
      fi
    fi
  done
  # check every 3 seconds
  sleep 3
done &