X-Forwarded-Forheaderrequestreplace

使用Node.js的Express框架，使用中间件进行替换。具体代码示例如下：

const express = require('express');
const app = express();

// 中间件函数，将X-Forwarded-For替换为真实的客户端IP
function replaceXFFHeader(req, res, next) {
  const forwardedHeader = req.headers['x-forwarded-for'];
  const clientIp = req.ip;

  if (forwardedHeader) {
    const forwardedIps = forwardedHeader.split(',');
    forwardedIps.unshift(clientIp);
    req.headers['x-forwarded-for'] = forwardedIps.join(',');
  } else {
    req.headers['x-forwarded-for'] = clientIp;
  }

  next();
}

// 使用中间件函数
app.use(replaceXFFHeader);

// 实际路由处理函数
app.get('/', (req, res) => {
  const clientIp = req.headers['x-forwarded-for'];
  res.send(`Your IP address is ${clientIp}`);
});

app.listen(3000, () => console.log('Example app listening on port 3000!'));