基于Nginx 反向代理获取真实IP的问题详解

server {
  listen  9461; # 监听端口号
  server_name localhost 192.168.88.22; # 访问地址
  location / {
   root 项目路径; # 例如：E:/Publish/xxx/;
   index index.html;
   
   # 此处用于处理 Vue、Angular、React 使用H5 的 History时 重写的问题
   if (!-e $request_filename) {
    rewrite ^(.*) /index.html last;
    break;
   }
  }
  
  # 代理服务端接口
  location /api {
   proxy_pass http://localhost:9460/api;# 代理接口地址
   # Host配置以及域名传递
   proxy_set_header Host $host;
   proxy_set_header X-Real-IP $remote_addr;
   proxy_set_header REMOTE-HOST $remote_addr;
   proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
  }
 }

#region Ip(客户端IP地址)
/// <summary>
/// 客户端IP地址
/// </summary>
public static string Ip
{
 get
 {
  var result = string.Empty;
  if (HttpContext.Current != null)
  {
   result = GetWebClientIp();
  }
  if (string.IsNullOrWhiteSpace(result))
  {
   result = GetLanIp();
  }
  return result;
 }
}
/// <summary>
/// 获取Web客户端的IP
/// </summary>
/// <returns></returns>
private static string GetWebClientIp()
{
 var ip = GetWebProxyRealIp() ?? GetWebRemoteIp();
 foreach (var hostAddress in Dns.GetHostAddresses(ip))
 {
  if (hostAddress.AddressFamily == AddressFamily.InterNetwork)
  {
   return hostAddress.ToString();
  }
 }
 return string.Empty;
}
/// <summary>
/// 获取Web远程IP
/// </summary>
/// <returns></returns>
private static string GetWebRemoteIp()
{
 try
 {
  return HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"] ??
    HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"] ?? "";
 }
 catch (Exception e)
 {
  return string.Empty;
 }
}
/// <summary>
/// 获取Web代理真实IP
/// </summary>
/// <returns></returns>
private static string GetWebProxyRealIp()
{
 var request = HttpContext.Current.Request;
 string ip = request.Headers.Get("x-forwarded-for");
 if (string.IsNullOrEmpty(ip) || string.Equals("unknown", ip, StringComparison.OrdinalIgnoreCase))
 {
  ip = request.Headers.Get("Proxy-Client-IP");
 }
 if (string.IsNullOrEmpty(ip) || string.Equals("unknown", ip, StringComparison.OrdinalIgnoreCase))
 {
  ip = request.Headers.Get("WL-Proxy-Client-IP");
 }
 if (string.IsNullOrEmpty(ip) || string.Equals("unknown", ip, StringComparison.OrdinalIgnoreCase))
 {
  ip = request.UserHostAddress;
 }
 if (string.IsNullOrEmpty(ip))
 {
  return string.Empty;
 }
 // 可能存在如下格式：X-Forwarded-For: client, proxy1, proxy2
 if (ip.Contains(", "))
 {
  // 如果存在多个反向代理，获得的IP是一个用逗号分隔的IP集合，取第一个
  // X-Forwarded-For: client 第一个
  string[] ips = ip.Split(new string[1] {", "}, StringSplitOptions.RemoveEmptyEntries);
  var i = 0;
  for (i = 0; i < ips.Length; i++)
  {
   if (ips[i] != "")
   {
    // 判断是否为内网IP
    if (false == IsInnerIp(ips[i]))
    {
     IPAddress realIp;
     if (IPAddress.TryParse(ips[i], out realIp) && ips[i].Split('.').Length == 4)
     {
      //合法IP
      return ips[i];
     }
     return "";
    }
   }
  }
  ip = ips[0];// 默认获取第一个IP地址
 }
 return ip;
}
/// <summary>
/// 判断IP地址是否为内网IP地址
/// </summary>
/// <param name="ip">IP地址</param>
/// <returns></returns>
private static bool IsInnerIp(string ip)
{
 bool isInnerIp = false;
 ulong ipNum = Ip2Ulong(ip);
 /**
  * 私有IP
  * A类：10.0.0.0-10.255.255.255
  * B类：172.16.0.0-172.31.255.255
  * C类：192.168.0.0-192.168.255.255
  * 当然，还有127这个网段是环回地址
  */
 ulong aBegin = Ip2Ulong("10.0.0.0");
 ulong aEnd = Ip2Ulong("10.255.255.255");
 ulong bBegin = Ip2Ulong("172.16.0.0");
 ulong bEnd = Ip2Ulong("10.31.255.255");
 ulong cBegin = Ip2Ulong("192.168.0.0");
 ulong cEnd = Ip2Ulong("192.168.255.255");
 isInnerIp = IsInner(ipNum, aBegin, aEnd) || IsInner(ipNum, bBegin, bEnd) || IsInner(ipNum, cBegin, cEnd) ||
    ip.Equals("127.0.0.1");
 return isInnerIp;
}
/// <summary>
/// 将IP地址转换为Long型数字
/// </summary>
/// <param name="ip">IP地址</param>
/// <returns></returns>
private static ulong Ip2Ulong(string ip)
{
 byte[] bytes = IPAddress.Parse(ip).GetAddressBytes();
 ulong ret = 0;
 foreach (var b in bytes)
 {
  ret <<= 8;
  ret |= b;
 }
 return ret;
}
/// <summary>
/// 判断用户IP地址转换为Long型后是否在内网IP地址所在范围
/// </summary>
/// <param name="userIp">用户IP</param>
/// <param name="begin">开始范围</param>
/// <param name="end">结束范围</param>
/// <returns></returns>
private static bool IsInner(ulong userIp, ulong begin, ulong end)
{
 return (userIp >= begin) && (userIp <= end);
}
/// <summary>
/// 获取局域网IP
/// </summary>
/// <returns></returns>
private static string GetLanIp()
{
 foreach (var hostAddress in Dns.GetHostAddresses(Dns.GetHostName()))
 {
  if (hostAddress.AddressFamily == AddressFamily.InterNetwork)
  {
   return hostAddress.ToString();
  }
 }
 return string.Empty;
}
#endregion