判断内网请求的时候内网的后端IP 外网请求就是外网的IP 前端代码实现

在前端实现判断内网请求和外网请求需要借助浏览器提供的 API，比如 WebRTC API。下面是一个简单的示例代码：

function getIPs(callback){
    var ip_dups = {};

    //compatibility for firefox and chrome
    var RTCPeerConnection = window.RTCPeerConnection
        || window.mozRTCPeerConnection
        || window.webkitRTCPeerConnection;
    var useWebKit = !!window.webkitRTCPeerConnection;

    //bypass naive webrtc blocking using an iframe
    if(!RTCPeerConnection){
        var iframe = document.createElement('iframe');
        iframe.style.display = 'none';
        document.body.appendChild(iframe);
        var win = iframe.contentWindow;
        window.RTCPeerConnection = win.RTCPeerConnection;
        window.mozRTCPeerConnection = win.mozRTCPeerConnection;
        window.webkitRTCPeerConnection = win.webkitRTCPeerConnection;
        RTCPeerConnection = window.RTCPeerConnection
            || window.mozRTCPeerConnection
            || window.webkitRTCPeerConnection;
        useWebKit = !!window.webkitRTCPeerConnection;
    }

    //minimal requirements for data connection
    var mediaConstraints = {
        optional: [{RtpDataChannels: true}]
    };

    var servers = {iceServers: [{urls: "stun:stun.services.mozilla.com"}]};

    //construct a new RTCPeerConnection
    var pc = new RTCPeerConnection(servers, mediaConstraints);

    function handleCandidate(candidate){
        //match just the IP address
        var ip_regex = /([0-9]{1,3}(\.[0-9]{1,3}){3})/
        var ip_addr = ip_regex.exec(candidate)[1];

        //remove duplicates
        if(ip_dups[ip_addr] === undefined)
            callback(ip_addr);

        ip_dups[ip_addr] = true;
    }

    //listen for candidate events
    pc.onicecandidate = function(ice){

        //skip non-candidate events
        if(ice.candidate){

            //match just the IP address
            var ip_regex = /([0-9]{1,3}(\.[0-9]{1,3}){3})/
            var ip_addr = ip_regex.exec(ice.candidate.candidate)[1];

            //remove duplicates
            if(ip_dups[ip_addr] === undefined)
                handleCandidate(ice.candidate.candidate);

            ip_dups[ip_addr] = true;
        }
    };

    //create a bogus data channel
    pc.createDataChannel("");

    //create an offer sdp
    pc.createOffer(function(result){

        //trigger the stun server request
        pc.setLocalDescription(result, function(){}, function(){});

    }, function(){});

    //wait for a while to let everything done
    setTimeout(function(){
        //read candidate info from local description
        var lines = pc.localDescription.sdp.split('\n');

        lines.forEach(function(line){
            if(line.indexOf('a=candidate:') === 0)
                handleCandidate(line);
        });
    }, 1000);
}

//调用 getIPs 方法获取本机IP
getIPs(function(ip){
    console.log(ip);
    // TODO: 根据IP判断是内网请求还是外网请求
});

在上述代码中，`getIPs` 方法使用 WebRTC API 获取本机的 IP 地址，然后通过判断 IP 地址的前缀来判断请求是内网请求还是外网请求。具体的实现细节需要根据实际情况进行调整。