offer-answer-sniff.js

// ==UserScript==
// @name         Offer Answer Sniffer
// @namespace    http://tampermonkey.net/
// @version      0.1.0
// @description  Sniff sLD/sRD
// @author       You
// @match        *://*/*
// @grant        none
// ==/UserScript==

(function () {
    'use strict';

    const orgSLD = RTCPeerConnection.prototype.setLocalDescription;
    const orgSRD = RTCPeerConnection.prototype.setRemoteDescription;

    RTCPeerConnection.prototype.setLocalDescription = function (sdp) {
        console.log('sLD:', sdp.sdp);
        return orgSLD.apply(this, [sdp]);
    };
    RTCPeerConnection.prototype.setRemoteDescription = function (sdp) {
        console.log('sRD:', sdp.sdp);
        return orgSRD.apply(this, [sdp]);
    };
})();