opn-arp.sh

opn-arp.sh

#!/usr/local/bin/bash

# This file is located under /usr/local/bin/opn-arp.sh

# Source configuration file
. /usr/local/etc/opn-arp.conf # This file defines:
                              # - interfaces to be used
                              # - dhcpv6_range_start
                              # - dhcpv6_range_stop

# Define file paths for IPv4 and IPv6 ARP/NDP tables
CURRENT4="/tmp/current_arp_table4.txt"
STATIC4="/tmp/static_arp_table4.txt"
OUT4="/tmp/result_arp_table4.txt"

CURRENT6="/tmp/current_arp_table6.txt"
STATIC6="/tmp/static_arp_table6.txt"
OUT6="/tmp/result_arp_table6.txt"

# Ensure all necessary files exist
touch $CURRENT4 $STATIC4 $OUT4 $CURRENT6 $STATIC6 $OUT6

# Function to normalize IPv6 address
normalize_ipv6() {
    local ip=$1
    # Remove interface name if present
    ip=${ip%\%*}
    # Expand :: to appropriate number of :0:
    if [[ $ip == *::* ]]; then
        local colons=${ip//[^:]};
        local missing=$((8 - ${#colons}))
        local replacement=$(printf ':0%.0s' $(seq 1 $missing))
        ip=${ip/::/$replacement:}
    fi
    # Add leading zeros to each group
    ip=$(echo $ip | awk -F: '{for(i=1;i<=NF;i++) printf "%04x:", substr("0000" $i, length($i)+1)}' | sed 's/:$//')
    echo $ip
}

# Function to compare two IPv6 addresses
compare_ipv6() {
    local a=$(normalize_ipv6 $1)
    local b=$(normalize_ipv6 $2)
    if [[ $a < $b ]]; then
        echo -1
    elif [[ $a > $b ]]; then
        echo 1
    else
        echo 0
    fi
}

# Function to check if an IPv6 address is in the specified range
is_ipv6_in_range() {
    local ip=$1
    local start=$2
    local stop=$3
    
    # Check if it's a link-local address (starts with fe80)
    if [[ $ip == fe80::* ]]; then
        return 0  # Always include link-local addresses
    fi

    # Check if it's a ULA address (starts with fd)
    if [[ $ip == fd* ]]; then
        return 0  # Always include ULA addresses
    fi

    local cmp_start=$(compare_ipv6 "$ip" "$start")
    local cmp_stop=$(compare_ipv6 "$ip" "$stop")
    
    [ $cmp_start -ge 0 ] && [ $cmp_stop -le 0 ]
}

# Main loop
while true
do
  # Clear previous content
  > "$CURRENT4"
  > "$CURRENT6"

  if [ -z "$interfaces" ]
  then
    # If no specific interfaces are defined, check all
    arp -an | grep -v 'incomplete' | grep -v 'permanent' | awk '{print $2 " | " $4}' > "$CURRENT4"
    ndp -an | grep -v 'incomplete' | grep -v 'permanent' | grep -v 'Neighbor' | awk '{print $1 " | " $2}' | while read -r line; do
      ip=$(echo "$line" | cut -d '|' -f1 | tr -d ' ')
      if [ -z "$dhcpv6_range_start" ] || [ -z "$dhcpv6_range_stop" ] || is_ipv6_in_range "$ip" "$dhcpv6_range_start" "$dhcpv6_range_stop"; then
          echo "$line" >> "$CURRENT6"
      fi
    done
    echo "Processed all interfaces"
  else
    # If specific interfaces are defined, check only those
    for a in $interfaces
    do
      echo "Processing interface: $a"
      arp -an | grep -v 'incomplete' | grep -v 'permanent' | grep "$a" | awk '{print $2 " | " $4}' >> "$CURRENT4"
      ndp -an | grep -v 'incomplete' | grep -v 'permanent' | grep -v 'Neighbor' | grep "$a" | awk '{print $1 " | " $2}' | while read -r line; do
        ip=$(echo "$line" | cut -d '|' -f1 | tr -d ' ')
        if [ -z "$dhcpv6_range_start" ] || [ -z "$dhcpv6_range_stop" ] || is_ipv6_in_range "$ip" "$dhcpv6_range_start" "$dhcpv6_range_stop"; then
            echo "$line" >> "$CURRENT6"
        fi
      done
    done
  fi

  # Compare current and static tables, output new entries
  comm -2 -3 <(sort -u "$CURRENT4") <(sort -u "$STATIC4") > "$OUT4"
  comm -2 -3 <(sort -u "$CURRENT6") <(sort -u "$STATIC6") > "$OUT6"
  
  # Log and add new IPv4 entries
  while read -r line; do
    logger -p daemon.notice "New IPv4/MAC pair seen: $line"
    echo "$line" >> "$STATIC4"
  done < "$OUT4"
  
  # Log and add new IPv6 entries
  while read -r line; do
    logger -p daemon.notice "New IPv6/MAC pair seen: $line"
    echo "$line" >> "$STATIC6"
  done < "$OUT6"

  # Sort and remove duplicates from static tables
  sort -u -o "$STATIC4" "$STATIC4"
  sort -u -o "$STATIC6" "$STATIC6"

  # Wait before next iteration
  sleep 5
done