Healthcheck an anycast DNS

dns-healthcheck.sh

#!/bin/bash

function healthcheck() {
  local domain=$1
  local total_tests=$2

  local total_failed_count=0
  local ip_list=()

  for ((i = 0; i < total_tests; i++)); do
    # DNS may returns multiple records, skip CNAMEs, take only the first one. 
    local test_ip
    test_ip=$(dig +short "$domain" | grep -E '^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$' | head -n 1)

    echo "Testing $test_ip"
    ip_list+=("$test_ip")

    if ! ping -c 1 -W 2 "$test_ip" &> /dev/null; then
      echo "Failed to connect: $test_ip"
      total_failed_count=$((total_failed_count + 1))
    fi
  done

  echo
  echo "Total Tests: $total_tests"
  echo "Total Failed Tests: $total_failed_count"

  local failure_ratio
  failure_ratio=$(echo "scale=3; $total_failed_count / $total_tests * 100" | bc)
  printf "Failure Ratio: %.2f%%\n" "$failure_ratio"
  echo

  local unique_ip_list
  unique_ip_list=($(printf "%s\n" "${ip_list[@]}" | sort -u))
  echo "Tested IPs:"
  for ip in "${unique_ip_list[@]}"; do
    echo "- $ip"
  done
}

healthcheck "vercel.com" 1000

scan.sh

#!/bin/bash

ip_to_int() {
  local ip="$1"
  local a b c d
  IFS='.' read -r a b c d <<< "$ip"
  echo "$((a * 256 ** 3 + b * 256 ** 2 + c * 256 + d))"
}

int_to_ip() {
  local int="$1"
  echo "$((int >> 24 & 255)).$((int >> 16 & 255)).$((int >> 8 & 255)).$((int & 255))"
}

start_int=$(ip_to_int "76.76.21.1")
end_int=$(ip_to_int "76.76.21.254")

for ((ip_int = start_int; ip_int <= end_int; ip_int++)); do
  current_ip=$(int_to_ip "$ip_int")
  if ! ping -c 1 -W 2 "$current_ip" &> /dev/null; then
    echo "Failed: $current_ip"
  fi
done