通过BASH脚本实现DNS优选

0 2 * * * /root/mysqlbeifen.sh
*/10 * * * * /root/dns_update.sh






#!/bin/bash

LOG_DIR="/var/log/dns_script"
HOST_FILE="/etc/hosts_NC"
DOMAIN="sso.ccnhub.com"
DNS_SERVER="114.114.114.114"  # Replace with your DNS server IP

log() {
  local log_file="$LOG_DIR/$(date +\%Y-\%m-\%d).log"
  echo "$(date +\%Y-\%m-\%d\ \%H:\%M:\%S) - $1" >> "$log_file"
}

get_dns_ips() {
  local domain="$1"
  local dns_server="$2"
  local resolved_ips

  resolved_ips=$(nslookup "$domain" "$dns_server" | awk '/^Address: / {print $2}')

  if [ -z "$resolved_ips" ]; then
    log "域名 $domain 的DNS解析失败。请检查DNS配置或域名是否存在。检测IP后脚本停止执行"
        host_file_ips2=($(get_host_file_ips "$DOMAIN"))  #重新读取HOSTS文件
        ping_and_remove_unreachable "$HOST_FILE" "$DOMAIN" "${host_file_ips2[@]}"

    exit 1

  fi

  # Filter out IPv6 addresses
  resolved_ips=$(echo "$resolved_ips" | grep -E "([0-9]{1,3}\.){3}[0-9]{1,3}")

  echo "$resolved_ips"
}

get_host_file_ips() {
  local domain="$1"
  local host_ips

  host_ips=$(awk -v d="$domain" '$2==d {print $1}' "$HOST_FILE")

  if [ -z "$host_ips" ]; then
    log "在$HOST_FILE中未找到$domain的条目。请检查Hosts文件是否正确。"
    exit 1
  fi

  echo "$host_ips"
}

delete_host_file_entry() {
  local host_file="$1"
  local domain="$2"
  shift 2
  local ips_to_delete=("$@")

  # Check if the array is empty
  if [ "${#ips_to_delete[@]}" -eq 0 ]; then
    echo "数组为空，不执行删除操作。"
    return
  fi

  # Remove entries with the specified IP and domain
  for ip in "${ips_to_delete[@]}"; do
    sed -i -e "/^[[:space:]]*$ip[[:space:]]*$domain[[:space:]]*$/d" "$host_file"
    log "$ip $domain 为过期IP，已经从HOSTS文件删除。"
  done
}

update_host_file() {
  local host_file="$1"
  local domain="$2"
  shift 2
  local ips_to_update=("$@")

  # Check if the array is empty
  if [ "${#ips_to_update[@]}" -eq 0 ]; then
    echo "数组为空，不执行插入操作。"
    return
  fi

  # Remove existing entries with the specified domain
  #sed -i -e "/^[[:space:]]*${ips_to_update[0]}[[:space:]]*$domain[[:space:]]*$/d" "$host_file"

  # Append new IPs to the file
  for ip in "${ips_to_update[@]}"; do


   # if ping -c 1 "$ip" &> /dev/null; then
   if  nc -z -w 1 "$ip" 443 &> /dev/null; then

      echo "$ip $domain" >> "$host_file"
      log "$ip 新IP的NC端口检测成功。执行插入"

    else


      log "$ip 的Ping测试失败。不执行插入操作"
    fi



  done
}

ping_and_remove_unreachable() {
  local host_file="$1"
  local domain="$2"
  local host_ips=("${@:3}")

  for ip in "${host_ips[@]}"; do
    #if ping -c 1 "$ip" &> /dev/null; then
    if nc -z -w 1 "$ip" 443  &> /dev/null; then
      log "$ip 的Ping测试成功。"
    else

      sed -i -e "/^[[:space:]]*$ip[[:space:]]*$domain[[:space:]]*$/d" "$host_file"
      log "$ip 的Ping测试失败。已从$host_file中移除该条目。"
    fi
  done
}

initialize_log_directory() {
  if [ ! -d "$LOG_DIR" ]; then
    mkdir -p "$LOG_DIR"
  fi
}

main() {
  initialize_log_directory

  log "脚本执行开始。"

  # 通过DNS解析获取域名的IP地址
  dns_ips=($(get_dns_ips "$DOMAIN" "$DNS_SERVER"))
         # 检查 resolve_domain 的返回值
        if [ $? -ne 0 ]; then
                # resolve_domain 返回非零，说明出错，直接退出脚本
                log "DNS解析失败。退出整体脚本。"
         exit 1
        fi

  # 通过Host文件获取已有的IP地址
  host_file_ips=($(get_host_file_ips "$DOMAIN"))

  # 寻找Host文件中有而DNS解析中没有的IP
  missing_ips=($(comm -23 <(printf "%s\n" "${host_file_ips[@]}" | sort) <(printf "%s\n" "${dns_ips[@]}" | sort)))

  # 删除Host文件中多余的IP
  delete_host_file_entry "$HOST_FILE" "$DOMAIN" "${missing_ips[@]}"

  # 寻找DNS解析中有而Host文件中没有的IP
  missing_ips2=($(comm -23 <(printf "%s\n" "${dns_ips[@]}" | sort) <(printf "%s\n" "${host_file_ips[@]}" | sort)))

  # 插入更新Host文件中的IP，插入前检测
  update_host_file "$HOST_FILE" "$DOMAIN" "${missing_ips2[@]}"

  # 执行循环NC端口检测，发现不可达的IP，从Host文件中删除相应的记录
  #ping_and_remove_unreachable "$HOST_FILE" "$DOMAIN" "${host_file_ips[@]}"  #已经当作多余IP清理掉，不用重复
  host_file_ips2=($(get_host_file_ips "$DOMAIN"))  #重新读取HOSTS文件
  ping_and_remove_unreachable "$HOST_FILE" "$DOMAIN" "${host_file_ips2[@]}"

  log "脚本执行完成。"

  # 清理旧的日志文件（保留3天的日志）
  find "$LOG_DIR" -name "*.log" -mtime +3 -exec rm {} \;
}

main

cat /etc/hosts_NC



127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
61.14.138.136 sso.ccnhub.com
203.116.74.71 sso.ccnhub.com
58.185.85.222 sso.ccnhub.com
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