dnstt balancer

dnstt_balancer.sh

#!/usr/bin/env bash

IPS=(
  "217.144.106.205"
  "94.184.10.82"
  "5.190.1.83"
)

DOMAIN="t.<YOUR_DOMAIN>"
EXPECTED_NS="tns.<YOUR_DOMAIN>."
CHECK_INTERVAL=30
DIG_TIMEOUT=3

DNSTT_CMD="./dnstt"
DNSTT_ARGS="-udp %IP%:53 -pubkey-file server.pub $DOMAIN 127.0.0.1:9091"

PID_FILE="/tmp/dnstt.pid"
BEST_IP_FILE="/tmp/dnstt.best_ip"

get_best_ip() {
  local best_ip=""
  local best_time=999999

  for ip in "${IPS[@]}"; do
    start=$(date +%s%3N)

    result=$(dig +time=$DIG_TIMEOUT +tries=1 +short NS "$DOMAIN" @"$ip" 2>/dev/null)

    end=$(date +%s%3N)
    elapsed=$((end - start))

    if [[ "$result" == "$EXPECTED_NS" ]]; then
      if (( elapsed < best_time )); then
        best_time=$elapsed
        best_ip=$ip
      fi
    fi
  done

  echo "$best_ip"
}

kill_dnstt() {
  if [[ -f "$PID_FILE" ]]; then
    pid=$(cat "$PID_FILE")
    if kill -0 "$pid" 2>/dev/null; then
      kill "$pid"
      sleep 1
    fi
    rm -f "$PID_FILE"
  else
    pkill -f "$DNSTT_CMD" 2>/dev/null
  fi
}

start_dnstt() {
  local ip="$1"
  cmd=${DNSTT_ARGS//%IP%/$ip}

  nohup $DNSTT_CMD $cmd >/dev/null 2>&1 &
  echo $! > "$PID_FILE"
}

while true; do
  best_ip=$(get_best_ip)

  if [[ -z "$best_ip" ]]; then
    sleep "$CHECK_INTERVAL"
    continue
  fi

  last_ip=""
  [[ -f "$BEST_IP_FILE" ]] && last_ip=$(cat "$BEST_IP_FILE")

  if [[ "$best_ip" != "$last_ip" ]]; then
    kill_dnstt
    start_dnstt "$best_ip"
    echo "$best_ip" > "$BEST_IP_FILE"
  fi

  sleep "$CHECK_INTERVAL"
done