feat(core): DHCP client after Java, measured with Java FILIUS
The client follows Java's DHCPClient instead of Swift: one DISCOVER or REQUEST per attempt, an answer that does not fit is read and dropped, the ARP check waits a round trip (an answer for the address ends it at once, then DECLINE), a timeout repeats the state's message, and the fifth turns to a link-local address 169.254.1.x/16 (ARP probe, ARP reply to all); no old address is given back. DHCP round trip times follow the speed as in Java (50 cables, 2750 ms at 90 %; Swift: fixed 2500 ms). Not taken from Java: the client gives up after five occupied link-local addresses (Java searches on without end), and an ARP packet for another address does not end the check. dhcpJava.test.ts compares the four DHCP scenarios with DhcpRun's Java runs; the Swift comparison only checks that they differ. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This commit is contained in:
Claude Opus 5.5
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// DHCP as Java FILIUS runs it. tools/java-oracle's DhcpRun built each
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// scenario's network in Java FILIUS, ran it and wrote what every network card
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// saw (<name>.java.json, FILIUS' own packet log). The engine runs the same
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// network. For each DHCP client, the frames that concern it must come in the
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// same order, with the same content, at about the same distance from each
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// other, and every host must end with the same addresses.
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//
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// A frame counts when it first shows on any card (sent, or received), in
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// Java and in the engine alike. Not only on the client's own card: there,
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// FILIUS' log misses the DISCOVER of the client that sends second when two
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// start together (measured in four of four runs of dhcp-lan; the server
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// receives it) — a fault of the log, not of the network. Java logs no frame
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// identity; the same text within DUPLICATE_WINDOW_MILLISECONDS is one frame
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// (measured: a frame reaches the last card within some 130 ms; the closest
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// two distinct frames of the same text are the DISCOVERs around a DECLINE,
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// some 520 ms apart).
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//
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// Java runs on threads in real time, at the default speed of 90 % (55 ms a
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// cable, a round trip time of 2750 ms). Its gaps match the engine's within a
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// few milliseconds, except where a card sends two frames at once: Java's
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// cable carries one frame at a time (SimplexVerbindung sleeps the delay with
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// the port's buffer locked, and the sender waits), the engine's cable all of
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// them together — up to three cables' delay, measured. A gap may differ by
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// GAP_TOLERANCE_MILLISECONDS; a wrong round trip time (250 ms) may not. Java draws the link-local
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// address with Math.random; it is compared as 169.254.1.x. Where several
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// clients start together, which one is first varies in Java (the first
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// thread pays for loading the classes); a client is therefore compared
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// without the other clients' frames and the answers to them.
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import { readdirSync, readFileSync } from 'node:fs';
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import { dirname, join } from 'node:path';
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import { fileURLToPath } from 'node:url';
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import { describe, expect, it } from 'vitest';
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import { NetworkRuntimeEngine, stableMacAddress, type EthernetFrame } from '../src/index.js';
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import { snapshotOf, type Scenario } from './scenario.js';
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const scenarioDirectory = join(dirname(fileURLToPath(import.meta.url)), 'scenarios');
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const GAP_TOLERANCE_MILLISECONDS = 200;
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const DUPLICATE_WINDOW_MILLISECONDS = 300;
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interface JavaFrame {
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time: number;
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source: string;
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destination: string;
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arp?: number;
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senderIp?: string;
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targetIp?: string;
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sourceIp?: string;
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destinationIp?: string;
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protocol?: number;
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sourcePort?: number;
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destinationPort?: number;
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payload?: string;
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icmp?: number;
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}
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interface JavaRun {
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frames: Record<string, JavaFrame[]>;
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devices: Record<string, [string, string, string, string]>;
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}
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interface SeenFrame {
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readonly time: number;
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readonly text: string;
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}
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const LINK_LOCAL = /169\.254\.1\.\d+/g;
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function javaText(frame: JavaFrame): string {
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const macs = `${frame.source} > ${frame.destination}`.toUpperCase();
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if (frame.arp !== undefined) return `${macs} ARP ${frame.arp === 1 ? 'request' : 'reply'} ${frame.senderIp} > ${frame.targetIp}`;
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if (frame.icmp !== undefined) return `${macs} ICMP ${frame.icmp}`;
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return `${macs} UDP ${frame.sourceIp}:${frame.sourcePort} > ${frame.destinationIp}:${frame.destinationPort} ${frame.payload}`;
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}
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function engineText(frame: EthernetFrame): string {
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const macs = `${frame.sourceMacAddress} > ${frame.destinationMacAddress}`.toUpperCase();
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if (frame.payload.kind === 'arp') {
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const arp = frame.payload.packet;
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return `${macs} ARP ${arp.operation} ${arp.senderIPAddress} > ${arp.targetIPAddress}`;
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}
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const packet = frame.payload.packet;
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if (packet.payload.kind !== 'udp') return `${macs} ${packet.payload.kind.toUpperCase()}`;
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const datagram = packet.payload.datagram;
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return `${macs} UDP ${packet.senderIPAddress}:${datagram.sourcePort} > ${packet.receiverIPAddress}:${datagram.destinationPort} ${new TextDecoder().decode(datagram.payload)}`;
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}
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/** The engine's run of the scenario's network, without its steps, for `milliseconds`. */
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function runEngine(scenario: Scenario, milliseconds: number) {
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const engine = new NetworkRuntimeEngine(scenario.seed);
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const framesByIdentity = new Map<number, EthernetFrame>();
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const send = engine.sendEthernetFrame.bind(engine);
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engine.sendEthernetFrame = (fromNodeId, outgoingPortId, frame) => {
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framesByIdentity.set(frame.identity, frame);
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send(fromNodeId, outgoingPortId, frame);
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};
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engine.handle({ type: 'start', snapshot: snapshotOf(scenario), seed: scenario.seed, initialTimeMilliseconds: 0 });
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engine.handle({ type: 'advance', toMilliseconds: milliseconds });
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// Every frame when it first shows on a host's card (as FILIUS logs it: sent, or received).
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const hosts = new Set(scenario.nodes.filter((node) => node.kind !== 'networkSwitch').map((node) => node.id));
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const firstSeen = new Map<number, SeenFrame>();
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for (const event of engine.state.packetTraces) {
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if (event.layer !== 'physical' || !hosts.has(event.nodeId) || event.frameIdentity === undefined) continue;
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if (!((event.direction === 'outbound' && event.operation === 'sent') || (event.direction === 'inbound' && event.operation === 'received'))) continue;
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if (firstSeen.has(event.frameIdentity)) continue;
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firstSeen.set(event.frameIdentity, { time: event.timeMilliseconds, text: engineText(framesByIdentity.get(event.frameIdentity)!) });
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}
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const devices = Object.fromEntries(
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[...engine.state.topologySnapshot.deviceConfigurations].map(([node, device]) => [
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node,
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[device.ipAddress, device.subnetMask, device.defaultGateway, device.dnsServer],
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]),
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);
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return { frames: [...firstSeen.values()], devices };
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}
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/** Java's frames of all cards, each once: the same text within the window is the same frame. */
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function javaFrames(java: JavaRun): SeenFrame[] {
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const all = Object.values(java.frames)
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.flat()
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.map((frame) => ({ time: frame.time, text: javaText(frame) }))
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.sort((lhs, rhs) => lhs.time - rhs.time);
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const frames: SeenFrame[] = [];
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for (const frame of all) {
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if (frames.some((each) => each.text === frame.text && frame.time - each.time <= DUPLICATE_WINDOW_MILLISECONDS)) continue;
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frames.push(frame);
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}
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return frames;
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}
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/** Consecutive frames without the other clients' own: the text, and the time since the one before. */
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function steps(frames: readonly SeenFrame[], otherClientMacs: readonly string[]) {
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const theirs = (frame: SeenFrame) =>
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otherClientMacs.some((mac) => frame.text.startsWith(`${mac} >`) || frame.text.includes(`chaddr=${mac}`));
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const own = frames.filter((frame) => !theirs(frame));
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return own.map((frame, index) => ({
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text: frame.text.replace(LINK_LOCAL, '169.254.1.x'),
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gap: index === 0 ? 0 : frame.time - own[index - 1]!.time,
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}));
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}
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function clientMac(scenario: Scenario, nodeId: string): string {
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const port = scenario.nodes.find((node) => node.id === nodeId)!.ports[0]!;
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return (port.mac ?? stableMacAddress(port.id)).toUpperCase();
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}
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const runs = readdirSync(scenarioDirectory)
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.filter((name) => name.endsWith('.java.json'))
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.map((name) => name.replace('.java.json', ''))
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.sort();
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describe('DHCP as Java FILIUS runs it', () => {
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it('has Java runs', () => {
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expect(runs.length).toBeGreaterThan(0);
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});
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for (const name of runs) {
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it(name, () => {
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const scenario = JSON.parse(readFileSync(join(scenarioDirectory, `${name}.scenario.json`), 'utf8')) as Scenario;
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const java = JSON.parse(readFileSync(join(scenarioDirectory, `${name}.java.json`), 'utf8')) as JavaRun;
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const lastJavaFrame = Math.max(...Object.values(java.frames).flatMap((frames) => frames.map((frame) => frame.time)));
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const engine = runEngine(scenario, lastJavaFrame + 10_000);
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const clients = scenario.dhcpClients ?? [];
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for (const client of clients) {
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const others = clients.filter((each) => each !== client).map((each) => clientMac(scenario, each));
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const expected = steps(javaFrames(java), others);
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const actual = steps(engine.frames, others);
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for (let index = 0; index < Math.max(expected.length, actual.length); index += 1) {
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expect(actual[index]?.text, `${client} frame #${index + 1}`).toBe(expected[index]?.text);
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expect(Math.abs(actual[index]!.gap - expected[index]!.gap), `${client} gap before frame #${index + 1}`).toBeLessThanOrEqual(
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GAP_TOLERANCE_MILLISECONDS,
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);
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}
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}
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const linkLocal = (devices: Record<string, string[]>) =>
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Object.fromEntries(Object.entries(devices).map(([node, device]) => [node, device.map((value) => value.replace(LINK_LOCAL, '169.254.1.x'))]));
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expect(linkLocal(engine.devices)).toEqual(linkLocal(java.devices));
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});
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}
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it('builds the MACs as DhcpRun does', () => {
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expect(stableMacAddress('00000000-0000-0000-0000-000000000112')).toBe('02:00:00:00:01:12');
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});
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});
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