domotz-remote-pawn/src/discovery/dhcp/dhcp_discovery.js

Domotz Agent

/** This file is part of Domotz Agent.
 * Copyright (C) 2016  Domotz UK LLP
 *
 * Domotz Agent is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Domotz Agent is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Domotz Agent.  If not, see <http://www.gnu.org/licenses/>.
 *
 * Listens for broadcast DHCP lease packets and sends the data to the backend
 *
 * Created by Iacopo Papalini <iacopo@domotz.com>
 *
 * 40 seconds: the assumption is that in the meantime the fast discovery
 * has produced the creation if the missing device
 */
const RETRY_INTERVAL = 35000;
const LOG_PREFIX = 'DHCP_LISTEN ';

function isWellFormed(message) {
    if (message.op.value !== 1) {
        // not a BOOTPREQUEST
        throw new Error(LOG_PREFIX + "- Not a BOOTREQUEST. Value: " + message.op.value);
    }
    if (!message.options) {
        // not a DHCP request
        throw new Error(LOG_PREFIX + "- Not a DHCP request");
    }

    var hwaddr = message.options.clientIdentifier || message.options.chaddr;

    if (!hwaddr || !hwaddr.type || hwaddr.type.value !== 1) {
        throw new Error(LOG_PREFIX + "- Not an ethernet device");
    }

    return hwaddr.address.toUpperCase();
}


var dhcpDiscoveryFactory = function (dhcpjs, random, discoveryUtils, engineRequest) {
    "use strict";

    var sentFingerprints = {}; // Filter for known devices
    var unknownDevices = {};   // Filter for unknown devices

    function signalToEngine(mac, dhcpData) {

        if (unknownDevices[mac]) { // Put filter as early as possible
            console.verbose(LOG_PREFIX + " not sending unknown devices with mac %s", mac);
            return;
        }

        var hash = random.md5(JSON.stringify(dhcpData));

        if (sentFingerprints[mac] === hash) {
            console.debug(LOG_PREFIX + " not sending to engine matching md5 (%s) for mac %s", hash, mac);
            return;
        }

        var deviceId = discoveryUtils.getDeviceIdFromMac(mac);

        if (!deviceId) {
            unknownDevices[mac] = true;
            console.warn(LOG_PREFIX + " Unknown device for mac %s, retrying " +
                "in %s ms. Fingerprint: %s", mac, RETRY_INTERVAL, JSON.stringify(dhcpData));
            setTimeout(function () {
                unknownDevices[mac] = false;
                signalToEngine(mac, dhcpData);
            }, RETRY_INTERVAL);
            return;
        }

        console.info(LOG_PREFIX + "Sending DHCP fingerprint for device %s (mac: %s) ", deviceId, mac);

        engineRequest.sendWithPromise('/device/' + deviceId + '/inspection-data/dhcp', 'PUT', dhcpData)
            .then(function () {
                sentFingerprints[mac] = hash;
            }
        );
    }

    function handleMessage(message) {
        try {
            var mac = isWellFormed(message);
            console.verbose(LOG_PREFIX + "DHCP Packet arrived: mac=%s", mac);
            signalToEngine(mac, message.options);
        } catch (err) {
            console.warn('%s %s. Ignoring unexpected packet', LOG_PREFIX, err.message);
            console.debug(LOG_PREFIX + JSON.stringify(message));
            return err.message; // For testing purpose
        }
    }

    function onListening(address) {
        console.info(LOG_PREFIX + '- listening for DHCP packets on ' + address);
    }

    function listenForLeasePackets() {
        var server = dhcpjs.createServer();

        server.on('listening', onListening);
        server.on('message', handleMessage);
        server.bind();
    }

    return {
        // ----- TEST -----
        _handleMessage: handleMessage,
        // ----- TEST -----
        listenForLeasePackets: listenForLeasePackets
    };
};

module.exports.factory = dhcpDiscoveryFactory;