#!/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

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

wlan(){
  [[ -e $SYSTEM/wlan0 ]]
}

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

state(){
  local n NEW OLD HOLD
  OLD=$(carrier $1)
  HOLD=4
  # new state should hold for at least 4 seconds
  for n in {1..4}; do
    sleep 1
    NEW=$(carrier $1)
    [[ $NEW != $OLD ]] && ((HOLD--))
  done
  [[ $HOLD -eq 0 ]] && echo $NEW || echo $OLD
}

init(){
  TASK=()
  if [[ -r $FILE ]]; then
    # initialize values from file, maintained by 'create_network_ini'
    while IFS=$'\n' read -r ROW; do
      TASK+=("$ROW")
    done <$FILE
  fi
  MD5=$(md5)
}

while :; do
  if wlan; then
    # monitor file content changes
    [[ $MD5 != $(md5) ]] && init
    LAST=
    for i in ${!TASK[@]}; do
      ADDR=(${TASK[$i]})
      PORT=${ADDR[0]}
      [[ $LAST != ${PORT%.*} ]] && STATE=$(state ${PORT%.*})
      case $STATE in
      1) # up
        case ${ADDR[1]} in
        GW4)
          # no existing default and new default is defined?
          IPV4=$(ip -4 -br addr show scope global primary dev $PORT | awk '{print $3;exit}')
          if [[ -n $IPV4 ]]; then
            ROUTE=$(ip -4 route show to default dev $PORT)
            [[ -z $ROUTE ]] && ip -4 route add dev ${TASK[$i]/GW4/}
          fi
          ;;
        GW6)
          # no existing default and new default is defined?
          IPV6=$(ip -6 -br addr show scope global primary -deprecated dev $PORT | awk '{print $3;exit}')
          if [[ -n $IPV6 ]]; then
            ROUTE=$(ip -6 route show to default dev $PORT)
            [[ -z $ROUTE ]] && ip -6 route add dev ${TASK[$i]/GW6/}
          fi
          ;;
        *)
          IPA=$(ip -br addr show to ${ADDR[1]} dev $PORT)
          if [[ -f /var/tmp/$PORT.down ]]; then
            # Special treatment for shim and vhost interfaces
            [[ -n $IPA ]] && ip addr del dev ${TASK[$i]}
          else
            # IP address not present? create it
            [[ -z $IPA ]] && ip addr add dev ${TASK[$i]}
          fi
          ;;
        esac
        ;;
      0) # down
        # IP address present, remove it
        [[ -n $(ip -br addr show to ${ADDR[1]} dev $PORT) ]] && ip addr del dev ${TASK[$i]}
        ;;
      esac
      LAST=${PORT%.*}
    done
  fi
  # check every 3 seconds
  sleep 3
done &