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feat(core): SYN+ACK and FIN go once, as in Java, measured with Java FILIUS

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TcpRun loses exactly one frame (loseFirst: the card's output buffer drops
it; the sender's packet log still shows it, as with setDrop) in three new
stories: lostSynAck, lostFin, lostLastFin.

Measured: Java never repeats a SYN+ACK or a FIN. The server gives a
handshake up after one timeout (3 RTT) and closes with a FIN from SYN_RCVD
(its boundary check sometimes lets it wait twice; it means once). After its
FIN a socket waits at most five times, each wait ended by a segment or the
timeout; then it is gone. The core does the same (TCP_CLOSING_WAITS, with
TIME_WAIT in the loop) and shows CLOSED where Java leaves the state
standing (a named Java bug).

One departure: a repeated SYN in SYN_RCVD gets the SYN+ACK once more and
the wait starts anew; Java closes there, but its client never repeats the
SYN. lostSynAck is compared up to the second SYN (JAVA_UNTIL); the rest is
an engine test.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This commit is contained in:
julian.kiedaisch
2026-09-30 18:08:18 +00:00
co-authored by Claude Opus 5.5
parent a88fa1512c
commit 7e0348636c
11 changed files with 1056 additions and 40 deletions
Download Patch File Download Diff File Expand all files Collapse all files
packages/core/test/engine.test.ts
+53 -1
View File
@@ -44,7 +44,7 @@ import {
type RuntimeOutput,
type ScheduledEventKind,
} from '../src/index.js';
import { device, letFramesArrive, link, pc, startedEngine, uuid } from './fixtures.js';
import { device, letFramesArrive, link, loseFirst, pc, startedEngine, uuid } from './fixtures.js';
const marker = (label: string): ScheduledEventKind => ({ kind: 'parityMarker', label });
@@ -995,6 +995,58 @@ describe('TCP sockets', () => {
expect(engine.state.packetTraces.filter((trace) => trace.detail?.includes('TCP SYN retransmission') === true)).toHaveLength(2);
});
it('answers a repeated SYN with its SYN+ACK once more: a lost SYN+ACK costs one attempt (Java would close)', () => {
const { engine, clientId, serverId } = pair(0x17f1, 0x17f2, '10.26.0');
loseFirst(engine, serverId, (segment) => segment.flags === (TCP_FLAG.synchronize | TCP_FLAG.acknowledgement));
const listenerId = engine.openTcpServerSocket(serverId, 80)!;
const clientSocketId = engine.openTcpClientSocket(clientId, '10.26.0.2', 80)!;
expect(engine.connectTcpWithResult(clientSocketId)).toBe('connected');
// The second SYN leaves a timeout after the first was handed down, its SYN+ACK comes a cable later each way.
expect(engine.state.currentTimeMilliseconds).toBe(3 * 2_750 + 2 * 55);
letFramesArrive(engine);
const acceptedSocketId = engine.state.tcpAcceptedSocketIdsByListenerId.get(listenerId)![0]!;
expect(engine.state.socketsById.get(acceptedSocketId)?.tcpState).toBe('ESTABLISHED');
expect(engine.state.packetTraces.filter((trace) => trace.detail?.startsWith('TCP SYN+ACK') === true).map((trace) => trace.detail)).toEqual([
'TCP SYN+ACK',
'TCP SYN+ACK retransmission attempt 2',
]);
});
it("gives a handshake up after one timeout and closes with a FIN, sent once, then five waits", () => {
const { engine, clientId, serverId } = pair(0x17f5, 0x17f6, '10.27.0');
const listenerId = engine.openTcpServerSocket(serverId, 80)!;
// A SYN from the client's address, but no socket there: the SYN+ACK finds no one.
engine.sendIPv4Packet(clientId, {
identity: engine.allocatePacketIdentity(),
senderIPAddress: '10.27.0.1',
receiverIPAddress: '10.27.0.2',
timeToLive: 64,
protocol: 'tcp',
payload: {
kind: 'tcp',
segment: { sourcePort: 5000, destinationPort: 80, sequenceNumber: 1, acknowledgementNumber: 0, flags: TCP_FLAG.synchronize, payload: new Uint8Array() },
},
});
engine.handle({ type: 'advance', toMilliseconds: 60_000 });
const acceptedSocketId = engine.state.tcpAcceptedSocketIdsByListenerId.get(listenerId)![0]!;
const states = engine.state.packetTraces
.filter((trace) => trace.nodeId === serverId && trace.detail?.includes(' -> ') === true && !trace.detail.includes('LISTEN -> CLOSED') && !trace.detail.includes('CLOSED -> LISTEN'))
.map((trace) => [trace.timeMilliseconds, trace.detail]);
// The SYN arrives after ARP there and back: 165 ms.
expect(states).toEqual([
[165, 'TCP LISTEN -> SYN_RCVD'],
[165 + 3 * 2_750, 'TCP SYN_RCVD -> FIN_WAIT_1'],
[165 + 3 * 2_750 + 5 * 3 * 2_750, 'TCP FIN_WAIT_1 -> CLOSED'],
]);
expect(engine.state.socketsById.get(acceptedSocketId)?.tcpState).toBe('CLOSED');
expect(engine.state.packetTraces.filter((trace) => trace.nodeId === serverId && trace.layer === 'transport' && trace.detail?.startsWith('TCP ') === true && trace.operation !== 'accepted' && trace.operation !== 'dropped').map((trace) => trace.detail)).toEqual([
'TCP SYN+ACK',
'TCP FIN',
]);
});
it('drops a SYN+ACK at a listening port with no connection of its own', () => {
const { engine, clientId, serverId } = pair(0x1781, 0x1782, '10.21.0');
const listenerId = engine.openTcpServerSocket(serverId, 7000)!;
packages/core/test/fixtures.ts
+22
View File
@@ -3,6 +3,8 @@
import {
deviceConfiguration,
type EthernetFrame,
type TcpSegment,
NetworkRuntimeEngine,
portSnapshot,
topologySnapshot,
@@ -62,3 +64,23 @@ export function letFramesArrive(engine: NetworkRuntimeEngine): void {
engine.handle({ type: 'advance', toMilliseconds: Math.min(...deadlines) });
}
}
/**
* The first frame the node sends whose TCP segment matches is lost, as with
* TcpRun's loseFirst: it leaves (the sender's card shows it) and never arrives.
*/
export function loseFirst(engine: NetworkRuntimeEngine, nodeId: Id, which: (segment: TcpSegment) => boolean): void {
type Depart = (fromNodeId: Id, portId: Id, endpoint: unknown, frame: EthernetFrame) => void;
const target = engine as unknown as { departEthernetFrame: Depart };
const depart = target.departEthernetFrame.bind(engine);
let lost = false;
target.departEthernetFrame = (fromNodeId, portId, endpoint, frame) => {
depart(fromNodeId, portId, endpoint, frame);
const payload = frame.payload.kind === 'ipv4' ? frame.payload.packet.payload : undefined;
if (lost || fromNodeId !== nodeId || payload?.kind !== 'tcp' || !which(payload.segment)) return;
lost = true;
engine.state.pendingEvents = engine.state.pendingEvents.filter(
(event) => !(event.kind.kind === 'ethernetLinkDelivery' && event.kind.frame.identity === frame.identity),
);
};
}
packages/core/test/scenarios/tcp-java-lostFin.java.json
+204
View File
@@ -0,0 +1,204 @@
{
"frames": {
"00000000-0000-0000-0000-000000000101": [
{
"time": 850,
"source": "02:00:00:00:01:12",
"destination": "FF:FF:FF:FF:FF:FF",
"arp": 1,
"senderIp": "192.168.0.20",
"targetIp": "192.168.0.10"
},
{
"time": 852,
"source": "02:00:00:00:01:11",
"destination": "02:00:00:00:01:12",
"arp": 2,
"senderIp": "192.168.0.10",
"targetIp": "192.168.0.20"
},
{
"time": 1079,
"source": "02:00:00:00:01:12",
"destination": "02:00:00:00:01:11",
"sourceIp": "192.168.0.20",
"destinationIp": "192.168.0.10",
"protocol": 6,
"sourcePort": 61346,
"destinationPort": 80,
"payload": null,
"tcpFlags": "S",
"sequence": 2000000,
"acknowledgement": 0
},
{
"time": 1081,
"source": "02:00:00:00:01:11",
"destination": "02:00:00:00:01:12",
"sourceIp": "192.168.0.10",
"destinationIp": "192.168.0.20",
"protocol": 6,
"sourcePort": 80,
"destinationPort": 61346,
"payload": null,
"tcpFlags": "SA",
"sequence": 1000000,
"acknowledgement": 2000001
},
{
"time": 1305,
"source": "02:00:00:00:01:12",
"destination": "02:00:00:00:01:11",
"sourceIp": "192.168.0.20",
"destinationIp": "192.168.0.10",
"protocol": 6,
"sourcePort": 61346,
"destinationPort": 80,
"payload": null,
"tcpFlags": "A",
"sequence": 2000001,
"acknowledgement": 1000001
}
],
"00000000-0000-0000-0000-000000000102": [
{
"time": 729,
"source": "02:00:00:00:01:12",
"destination": "FF:FF:FF:FF:FF:FF",
"arp": 1,
"senderIp": "192.168.0.20",
"targetIp": "192.168.0.10"
},
{
"time": 963,
"source": "02:00:00:00:01:11",
"destination": "02:00:00:00:01:12",
"arp": 2,
"senderIp": "192.168.0.10",
"targetIp": "192.168.0.20"
},
{
"time": 966,
"source": "02:00:00:00:01:12",
"destination": "02:00:00:00:01:11",
"sourceIp": "192.168.0.20",
"destinationIp": "192.168.0.10",
"protocol": 6,
"sourcePort": 61346,
"destinationPort": 80,
"payload": null,
"tcpFlags": "S",
"sequence": 2000000,
"acknowledgement": 0
},
{
"time": 1193,
"source": "02:00:00:00:01:11",
"destination": "02:00:00:00:01:12",
"sourceIp": "192.168.0.10",
"destinationIp": "192.168.0.20",
"protocol": 6,
"sourcePort": 80,
"destinationPort": 61346,
"payload": null,
"tcpFlags": "SA",
"sequence": 1000000,
"acknowledgement": 2000001
},
{
"time": 1193,
"source": "02:00:00:00:01:12",
"destination": "02:00:00:00:01:11",
"sourceIp": "192.168.0.20",
"destinationIp": "192.168.0.10",
"protocol": 6,
"sourcePort": 61346,
"destinationPort": 80,
"payload": null,
"tcpFlags": "A",
"sequence": 2000001,
"acknowledgement": 1000001
},
{
"time": 1716,
"source": "02:00:00:00:01:12",
"destination": "02:00:00:00:01:11",
"sourceIp": "192.168.0.20",
"destinationIp": "192.168.0.10",
"protocol": 6,
"sourcePort": 61346,
"destinationPort": 80,
"payload": null,
"tcpFlags": "F",
"sequence": 2000001,
"acknowledgement": 0
}
],
"00000000-0000-0000-0000-000000000103": [
{
"time": 850,
"source": "02:00:00:00:01:12",
"destination": "FF:FF:FF:FF:FF:FF",
"arp": 1,
"senderIp": "192.168.0.20",
"targetIp": "192.168.0.10"
}
]
},
"events": [
[
214,
"server oeffnen called"
],
[
715,
"client verbinden called"
],
[
1216,
"client verbinden returned"
],
[
1317,
"server oeffnen returned"
],
[
1716,
"client schliessen called"
],
[
1716,
"client schliessen returned"
],
[
1716,
"lost FIN"
]
],
"states": {
"client": [
[
715,
"CLOSED"
],
[
725,
"SYN_SENT"
],
[
1195,
"ESTABLISHED"
],
[
1717,
"FIN_WAIT_1"
]
],
"server": [
[
1317,
"ESTABLISHED"
]
]
}
}
packages/core/test/scenarios/tcp-java-lostLastFin.java.json
+268
View File
@@ -0,0 +1,268 @@
{
"frames": {
"00000000-0000-0000-0000-000000000101": [
{
"time": 856,
"source": "02:00:00:00:01:12",
"destination": "FF:FF:FF:FF:FF:FF",
"arp": 1,
"senderIp": "192.168.0.20",
"targetIp": "192.168.0.10"
},
{
"time": 858,
"source": "02:00:00:00:01:11",
"destination": "02:00:00:00:01:12",
"arp": 2,
"senderIp": "192.168.0.10",
"targetIp": "192.168.0.20"
},
{
"time": 1086,
"source": "02:00:00:00:01:12",
"destination": "02:00:00:00:01:11",
"sourceIp": "192.168.0.20",
"destinationIp": "192.168.0.10",
"protocol": 6,
"sourcePort": 54938,
"destinationPort": 80,
"payload": null,
"tcpFlags": "S",
"sequence": 2000000,
"acknowledgement": 0
},
{
"time": 1088,
"source": "02:00:00:00:01:11",
"destination": "02:00:00:00:01:12",
"sourceIp": "192.168.0.10",
"destinationIp": "192.168.0.20",
"protocol": 6,
"sourcePort": 80,
"destinationPort": 54938,
"payload": null,
"tcpFlags": "SA",
"sequence": 1000000,
"acknowledgement": 2000001
},
{
"time": 1311,
"source": "02:00:00:00:01:12",
"destination": "02:00:00:00:01:11",
"sourceIp": "192.168.0.20",
"destinationIp": "192.168.0.10",
"protocol": 6,
"sourcePort": 54938,
"destinationPort": 80,
"payload": null,
"tcpFlags": "A",
"sequence": 2000001,
"acknowledgement": 1000001
},
{
"time": 1834,
"source": "02:00:00:00:01:12",
"destination": "02:00:00:00:01:11",
"sourceIp": "192.168.0.20",
"destinationIp": "192.168.0.10",
"protocol": 6,
"sourcePort": 54938,
"destinationPort": 80,
"payload": null,
"tcpFlags": "F",
"sequence": 2000001,
"acknowledgement": 0
},
{
"time": 1834,
"source": "02:00:00:00:01:11",
"destination": "02:00:00:00:01:12",
"sourceIp": "192.168.0.10",
"destinationIp": "192.168.0.20",
"protocol": 6,
"sourcePort": 80,
"destinationPort": 54938,
"payload": null,
"tcpFlags": "A",
"sequence": 1000001,
"acknowledgement": 2000002
},
{
"time": 1890,
"source": "02:00:00:00:01:11",
"destination": "02:00:00:00:01:12",
"sourceIp": "192.168.0.10",
"destinationIp": "192.168.0.20",
"protocol": 6,
"sourcePort": 80,
"destinationPort": 54938,
"payload": null,
"tcpFlags": "F",
"sequence": 1000001,
"acknowledgement": 0
}
],
"00000000-0000-0000-0000-000000000102": [
{
"time": 734,
"source": "02:00:00:00:01:12",
"destination": "FF:FF:FF:FF:FF:FF",
"arp": 1,
"senderIp": "192.168.0.20",
"targetIp": "192.168.0.10"
},
{
"time": 970,
"source": "02:00:00:00:01:11",
"destination": "02:00:00:00:01:12",
"arp": 2,
"senderIp": "192.168.0.10",
"targetIp": "192.168.0.20"
},
{
"time": 972,
"source": "02:00:00:00:01:12",
"destination": "02:00:00:00:01:11",
"sourceIp": "192.168.0.20",
"destinationIp": "192.168.0.10",
"protocol": 6,
"sourcePort": 54938,
"destinationPort": 80,
"payload": null,
"tcpFlags": "S",
"sequence": 2000000,
"acknowledgement": 0
},
{
"time": 1199,
"source": "02:00:00:00:01:11",
"destination": "02:00:00:00:01:12",
"sourceIp": "192.168.0.10",
"destinationIp": "192.168.0.20",
"protocol": 6,
"sourcePort": 80,
"destinationPort": 54938,
"payload": null,
"tcpFlags": "SA",
"sequence": 1000000,
"acknowledgement": 2000001
},
{
"time": 1200,
"source": "02:00:00:00:01:12",
"destination": "02:00:00:00:01:11",
"sourceIp": "192.168.0.20",
"destinationIp": "192.168.0.10",
"protocol": 6,
"sourcePort": 54938,
"destinationPort": 80,
"payload": null,
"tcpFlags": "A",
"sequence": 2000001,
"acknowledgement": 1000001
},
{
"time": 1722,
"source": "02:00:00:00:01:12",
"destination": "02:00:00:00:01:11",
"sourceIp": "192.168.0.20",
"destinationIp": "192.168.0.10",
"protocol": 6,
"sourcePort": 54938,
"destinationPort": 80,
"payload": null,
"tcpFlags": "F",
"sequence": 2000001,
"acknowledgement": 0
},
{
"time": 1946,
"source": "02:00:00:00:01:11",
"destination": "02:00:00:00:01:12",
"sourceIp": "192.168.0.10",
"destinationIp": "192.168.0.20",
"protocol": 6,
"sourcePort": 80,
"destinationPort": 54938,
"payload": null,
"tcpFlags": "A",
"sequence": 1000001,
"acknowledgement": 2000002
}
],
"00000000-0000-0000-0000-000000000103": [
{
"time": 856,
"source": "02:00:00:00:01:12",
"destination": "FF:FF:FF:FF:FF:FF",
"arp": 1,
"senderIp": "192.168.0.20",
"targetIp": "192.168.0.10"
}
]
},
"events": [
[
219,
"server oeffnen called"
],
[
720,
"client verbinden called"
],
[
1221,
"client verbinden returned"
],
[
1321,
"server oeffnen returned"
],
[
1721,
"client schliessen called"
],
[
1721,
"client schliessen returned"
],
[
1890,
"lost FIN"
]
],
"states": {
"client": [
[
720,
"CLOSED"
],
[
731,
"SYN_SENT"
],
[
1201,
"ESTABLISHED"
],
[
1724,
"FIN_WAIT_1"
],
[
1947,
"FIN_WAIT_2"
]
],
"server": [
[
1322,
"ESTABLISHED"
],
[
1835,
"LAST_ACK"
]
]
}
}
packages/core/test/scenarios/tcp-java-lostSynAck.java.json
+172
View File
@@ -0,0 +1,172 @@
{
"frames": {
"00000000-0000-0000-0000-000000000101": [
{
"time": 855,
"source": "02:00:00:00:01:12",
"destination": "FF:FF:FF:FF:FF:FF",
"arp": 1,
"senderIp": "192.168.0.20",
"targetIp": "192.168.0.10"
},
{
"time": 856,
"source": "02:00:00:00:01:11",
"destination": "02:00:00:00:01:12",
"arp": 2,
"senderIp": "192.168.0.10",
"targetIp": "192.168.0.20"
},
{
"time": 1083,
"source": "02:00:00:00:01:12",
"destination": "02:00:00:00:01:11",
"sourceIp": "192.168.0.20",
"destinationIp": "192.168.0.10",
"protocol": 6,
"sourcePort": 52633,
"destinationPort": 80,
"payload": null,
"tcpFlags": "S",
"sequence": 2000000,
"acknowledgement": 0
},
{
"time": 1085,
"source": "02:00:00:00:01:11",
"destination": "02:00:00:00:01:12",
"sourceIp": "192.168.0.10",
"destinationIp": "192.168.0.20",
"protocol": 6,
"sourcePort": 80,
"destinationPort": 52633,
"payload": null,
"tcpFlags": "SA",
"sequence": 1000000,
"acknowledgement": 2000001
},
{
"time": 17585,
"source": "02:00:00:00:01:11",
"destination": "02:00:00:00:01:12",
"sourceIp": "192.168.0.10",
"destinationIp": "192.168.0.20",
"protocol": 6,
"sourcePort": 80,
"destinationPort": 52633,
"payload": null,
"tcpFlags": "F",
"sequence": 1000001,
"acknowledgement": 0
}
],
"00000000-0000-0000-0000-000000000102": [
{
"time": 733,
"source": "02:00:00:00:01:12",
"destination": "FF:FF:FF:FF:FF:FF",
"arp": 1,
"senderIp": "192.168.0.20",
"targetIp": "192.168.0.10"
},
{
"time": 968,
"source": "02:00:00:00:01:11",
"destination": "02:00:00:00:01:12",
"arp": 2,
"senderIp": "192.168.0.10",
"targetIp": "192.168.0.20"
},
{
"time": 970,
"source": "02:00:00:00:01:12",
"destination": "02:00:00:00:01:11",
"sourceIp": "192.168.0.20",
"destinationIp": "192.168.0.10",
"protocol": 6,
"sourcePort": 52633,
"destinationPort": 80,
"payload": null,
"tcpFlags": "S",
"sequence": 2000000,
"acknowledgement": 0
},
{
"time": 17697,
"source": "02:00:00:00:01:11",
"destination": "02:00:00:00:01:12",
"sourceIp": "192.168.0.10",
"destinationIp": "192.168.0.20",
"protocol": 6,
"sourcePort": 80,
"destinationPort": 52633,
"payload": null,
"tcpFlags": "F",
"sequence": 1000001,
"acknowledgement": 0
}
],
"00000000-0000-0000-0000-000000000103": [
{
"time": 855,
"source": "02:00:00:00:01:12",
"destination": "FF:FF:FF:FF:FF:FF",
"arp": 1,
"senderIp": "192.168.0.20",
"targetIp": "192.168.0.10"
}
]
},
"events": [
[
218,
"server oeffnen called"
],
[
719,
"client verbinden called"
],
[
1085,
"lost SYN+ACK"
],
[
9025,
"client verbinden failed TimeOutException"
],
[
17632,
"server oeffnen returned"
]
],
"states": {
"server": [
[
221,
"LISTEN"
],
[
1085,
"SYN_RCVD"
],
[
17585,
"FIN_WAIT_1"
]
],
"client": [
[
719,
"CLOSED"
],
[
731,
"SYN_SENT"
],
[
8980,
"CLOSED"
]
]
}
}
packages/core/test/tcpJava.test.ts
+105 -8
View File
@@ -11,12 +11,15 @@
// client draws differs (Java's random, the engine's seed); it is compared as
// "client". Times count from the client's SYN.
//
// The lost* stories lose one frame on its sender's card, as TcpRun's
// loseFirst does in Java: the card shows it, no one receives it.
import { readFileSync } from 'node:fs';
import { dirname, join } from 'node:path';
import { fileURLToPath } from 'node:url';
import { describe, expect, it } from 'vitest';
import type { Id, NetworkRuntimeEngine } from '../src/index.js';
import { TCP_FLAG, type Id, type NetworkRuntimeEngine, type TcpSegment } from '../src/index.js';
import { loseFirst } from './fixtures.js';
import { GAP_TOLERANCE_MILLISECONDS, gaps, javaFrames, watchedEngine, type JavaFrame, type SeenFrame } from './javaRun.js';
import type { Scenario } from './scenario.js';
@@ -39,12 +42,30 @@ interface JavaRun {
const text = (value: string) => new TextEncoder().encode(value);
/** The story as the engine plays it; the nodes whose socket stands for Java's "client" and "server". */
/**
* The story as the engine plays it; the node whose socket stands for Java's
* "client". Java watched the server's socket from ESTABLISHED on, or, with
* `serverListening`, from the start (LISTEN).
*/
interface Story {
readonly client: Id;
readonly serverListening?: boolean;
readonly play: (engine: NetworkRuntimeEngine, advanceTo: (milliseconds: number) => void) => void;
}
const isSynAck = (segment: TcpSegment) => (segment.flags & TCP_FLAG.synchronize) !== 0 && (segment.flags & TCP_FLAG.acknowledgement) !== 0;
const isFin = (segment: TcpSegment) => (segment.flags & TCP_FLAG.finish) !== 0;
/** Connected, then the client closes half a second later; the server closes by itself. */
function connectAndClose(engine: NetworkRuntimeEngine, advanceTo: (milliseconds: number) => void): void {
engine.openTcpServerSocket(SERVER, 80);
advanceTo(500);
const client = engine.openTcpClientSocket(CLIENT, '192.168.0.10', 80)!;
engine.connectTcpWithResult(client);
advanceTo(engine.state.currentTimeMilliseconds + 500);
engine.closeTcpSocket(client);
}
const STORIES: Record<string, Story> = {
exchange: {
client: CLIENT,
@@ -88,6 +109,30 @@ const STORIES: Record<string, Story> = {
engine.setGlobalPacketLossEnabled(false);
},
},
lostSynAck: {
client: CLIENT,
serverListening: true,
play: (engine, advanceTo) => {
loseFirst(engine, SERVER, isSynAck);
engine.openTcpServerSocket(SERVER, 80);
advanceTo(500);
engine.connectTcpWithResult(engine.openTcpClientSocket(CLIENT, '192.168.0.10', 80)!);
},
},
lostFin: {
client: CLIENT,
play: (engine, advanceTo) => {
loseFirst(engine, CLIENT, isFin);
connectAndClose(engine, advanceTo);
},
},
lostLastFin: {
client: CLIENT,
play: (engine, advanceTo) => {
loseFirst(engine, SERVER, isFin);
connectAndClose(engine, advanceTo);
},
},
};
/** The states of the node's connection socket, from the engine's traces: when each was entered. */
@@ -138,8 +183,21 @@ function normalized(frames: readonly SeenFrame[]): SeenFrame[] {
* second and third), but its timeout branch sets closeSocket, and the loop
* ends after the first: one SYN, and verbinden fails after one wait. The
* engine sends the SYN three times, a wait of three round trips each.
*
* lostFin, lostLastFin: close waits at most five times (TCP_CLOSING_WAITS),
* each ended by a segment or after the timeout, and then the socket is gone —
* but its state stays FIN_WAIT_1, FIN_WAIT_2 or LAST_ACK. The engine shows
* CLOSED after the last wait.
*/
const JAVA_TIMEOUT_MILLISECONDS = 3 * 2_750;
const JAVA_CLOSING_WAITS = 5;
/** The socket's states, with CLOSED after Java's close loop: from `state`, `waits` more waits of the timeout. */
function closedAfterWaits(states: [number, string][], state: string, waits: number): [number, string][] {
const from = states.find(([, each]) => each === state)![0];
return [...states, [from + waits * JAVA_TIMEOUT_MILLISECONDS, 'CLOSED']];
}
const JAVA_BUGS: Record<string, (java: JavaRun) => JavaRun> = {
closedPort: (java) => {
const client = OTHER_CLIENT;
@@ -157,6 +215,30 @@ const JAVA_BUGS: Record<string, (java: JavaRun) => JavaRun> = {
},
};
},
// The client's FIN is lost: its five waits pass without a segment.
lostFin: (java) => ({ ...java, states: { ...java.states, client: closedAfterWaits(java.states.client!, 'FIN_WAIT_1', JAVA_CLOSING_WAITS) } }),
// The server's FIN is lost: the client's first wait ended with the ACK, the server's five pass.
lostLastFin: (java) => ({
...java,
states: {
...java.states,
client: closedAfterWaits(java.states.client!, 'FIN_WAIT_2', JAVA_CLOSING_WAITS - 1),
server: closedAfterWaits(java.states.server!, 'LAST_ACK', JAVA_CLOSING_WAITS),
},
}),
};
/**
* Where a story is compared only up to a time (Java's, from its start):
* after it, Java follows its own error and the engine does not.
*
* lostSynAck: Java's client sends one SYN (closedPort above) and gives up a
* timeout later; the engine's client sends it again then, the server answers
* it with its SYN+ACK once more, and they connect (engine.test.ts). Compared
* up to just before the second SYN.
*/
const JAVA_UNTIL: Record<string, (java: JavaRun) => number> = {
lostSynAck: (java) => java.states.client!.find(([, state]) => state === 'SYN_SENT')![0] + JAVA_TIMEOUT_MILLISECONDS - GAP_TOLERANCE_MILLISECONDS,
};
describe('TCP as Java FILIUS runs it', () => {
@@ -167,6 +249,15 @@ describe('TCP as Java FILIUS runs it', () => {
}
});
it('cuts only where Java goes on with its error', () => {
for (const [name, until] of Object.entries(JAVA_UNTIL)) {
const java = JSON.parse(readFileSync(join(scenarioDirectory, `tcp-java-${name}.java.json`), 'utf8')) as JavaRun;
const cut = until(java);
const later = [...Object.values(java.frames).flat().map((frame) => frame.time), ...Object.values(java.states).flat().map(([time]) => time)];
expect(later.some((time) => time >= cut), name).toBe(true);
}
});
const scenario = JSON.parse(readFileSync(join(scenarioDirectory, 'tcp-lan.scenario.json'), 'utf8')) as Scenario;
for (const [name, story] of Object.entries(STORIES)) {
@@ -180,8 +271,14 @@ describe('TCP as Java FILIUS runs it', () => {
story.play(engine, advanceTo);
advanceTo(Math.max(...java.events.map(([time]) => time), ...Object.values(java.states).flatMap((each) => each.map(([time]) => time))) + 5_000);
const expected = normalized(javaFrames(java.frames));
const actual = normalized(frames());
// Times from the SYN; with JAVA_UNTIL, only what comes before the cut.
const javaSyn = java.frames[story.client]!.find((frame) => frame.tcpFlags === 'S')!.time;
const engineSyn = frames().find((frame) => / TCP .* S seq=/.test(frame.text))!.time;
const until = (JAVA_UNTIL[name]?.(measured) ?? Number.POSITIVE_INFINITY) - javaSyn;
const before = <T extends { time: number } | [number, string]>(items: T[]): T[] =>
items.filter((item) => (Array.isArray(item) ? item[0] : item.time) < until);
const expected = before(normalized(javaFrames(java.frames)));
const actual = before(normalized(frames()));
const expectedSteps = gaps(expected);
const actualSteps = gaps(actual);
for (let index = 0; index < Math.max(expectedSteps.length, actualSteps.length); index += 1) {
@@ -191,14 +288,14 @@ describe('TCP as Java FILIUS runs it', () => {
);
}
const javaSyn = java.frames[story.client]!.find((frame) => frame.tcpFlags === 'S')!.time;
const engineSyn = frames().find((frame) => / TCP .* S seq=/.test(frame.text))!.time;
const shift = (states: [number, string][], syn: number): [number, string][] => states.map(([time, state]) => [time - syn, state]);
const shift = (states: [number, string][], syn: number): [number, string][] => before(states.map(([time, state]) => [time - syn, state]));
// From SYN_SENT: Java's first CLOSED is when the socket was made.
const javaClient = java.states.client!.filter(([, state], index) => !(index === 0 && state === 'CLOSED'));
expectSameStates('client', shift(engineStates(engine, story.client, false), engineSyn), shift(javaClient, javaSyn));
if (java.states.server !== undefined) {
expectSameStates('server', shift(engineStates(engine, SERVER, true), engineSyn), shift(java.states.server, javaSyn));
// A listening server from its first change: Java's first LISTEN is when it began to listen.
const javaServer = story.serverListening === true ? java.states.server.slice(1) : java.states.server;
expectSameStates('server', shift(engineStates(engine, SERVER, story.serverListening !== true), engineSyn), shift(javaServer, javaSyn));
}
});
}