function getIPs()

in tools/CCPConnectivityTestTools/scripts/detectRTC.js [546:652]
53 lines of code
19 McCabe index (conditional complexity)

    function getIPs(callback, stream) {
        if (typeof document === 'undefined' || typeof document.getElementById !== 'function') {
            return;
        }

        var ipDuplicates = {};

        var RTCPeerConnection = window.RTCPeerConnection || window.mozRTCPeerConnection || window.webkitRTCPeerConnection;

        if (!RTCPeerConnection) {
            var iframe = document.getElementById('iframe');
            if (!iframe) {
                return;
            }
            var win = iframe.contentWindow;
            RTCPeerConnection = win.RTCPeerConnection || win.mozRTCPeerConnection || win.webkitRTCPeerConnection;
        }

        if (!RTCPeerConnection) {
            return;
        }

        var peerConfig = null;

        if (DetectRTC.browser === 'Chrome' && DetectRTC.browser.version < 58) {
            // todo: add support for older Opera
            peerConfig = {
                optional: [{
                    RtpDataChannels: true
                }]
            };
        }

        var servers = {
            iceServers: [{
                urls: 'stun:stun.l.google.com:19302'
            }]
        };

        var pc = new RTCPeerConnection(servers, peerConfig);

        if (stream) {
            if (pc.addStream) {
                pc.addStream(stream);
            } else if (pc.addTrack && stream.getTracks()[0]) {
                pc.addTrack(stream.getTracks()[0], stream);
            }
        }

        function handleCandidate(candidate) {
            if (!candidate) {
                callback(); // Pass nothing to tell that ICE-gathering-ended
                return;
            }

            var match = regexIpv4.exec(candidate);
            if (!match) {
                return;
            }
            var ipAddress = match[1];
            const isPublic = (candidate.match(regexIpv4Local)),
                isIpv4 = true;

            if (ipDuplicates[ipAddress] === undefined) {
                callback(ipAddress, isPublic, isIpv4);
            }

            ipDuplicates[ipAddress] = true;
        }

        // listen for candidate events
        pc.onicecandidate = function(event) {
            if (event.candidate && event.candidate.candidate) {
                handleCandidate(event.candidate.candidate);
            } else {
                handleCandidate(); // Pass nothing to tell that ICE-gathering-ended
            }
        };

        // create data channel
        if (!stream) {
            try {
                pc.createDataChannel('sctp', {});
            } catch (e) {}
        }

        // create an offer sdp
        if (DetectRTC.isPromisesSupported) {
            pc.createOffer().then(function(result) {
                pc.setLocalDescription(result).then(afterCreateOffer);
            });
        } else {
            pc.createOffer(function(result) {
                pc.setLocalDescription(result, afterCreateOffer, function() {});
            }, function() {});
        }

        function afterCreateOffer() {
            var lines = pc.localDescription.sdp.split('\n');

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