mirror the physical display over vnc instead of spawning a virtual desktop per user
- vnc-manager now runs x11vnc against :0 rather than vncserver on a fresh display, so the browser shows the same session as the tv instead of a parallel one - x11vnc reads :0's cookie from the logged-in user's own .Xauthority, so no root is needed; mirroring only works while someone is logged in (the greeter's cookie belongs to lightdm) - -scale 0.5 halves the 4k framebuffer to 1080p for the stream, -shared -forever keeps it up across browser disconnects, -localhost keeps it behind the ws bridge - readiness is now the listening port, not exit code: x11vnc stays in the foreground where vncserver daemonized and exited - drops findFreeDisplay and per-email session tracking; there is exactly one :0 - the parallel desktops this replaces caused real breakage: a ghost logind session that broke lightdm login, and a brave profile lock held on :2 Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Claude Opus 4.8
@@ -3,7 +3,19 @@ import { join } from 'node:path';
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import type { VncStartParams, VncSessionInfo } from '../protocol';
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import { getHomeDirForRole } from '@@/data-path';
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type VncSession = {
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// Mirrors the physical display instead of spawning a virtual desktop per user, so the
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// browser shows the same session as the screen. There is exactly one :0, hence one
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// shared mirror — the first caller's VNC password is the one it answers with.
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const MIRROR_DISPLAY = ':0';
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const MIRROR_DISPLAY_NUM = 0;
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const MIRROR_PORT = 5900;
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const READY_TIMEOUT_MS = 5000;
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// x11vnc reads :0's cookie from the logged-in user's own .Xauthority, so no root is needed.
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// While the greeter owns :0 the cookie lives in lightdm's file instead and mirroring fails.
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const XAUTHORITY = join(process.env.HOME ?? '', '.Xauthority');
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type MirrorSession = {
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email: string;
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username: string;
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display: number;
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@@ -11,23 +23,7 @@ type VncSession = {
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pid: number;
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};
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const sessions = new Map<string, VncSession>();
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function findFreeDisplay(): number {
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for (let n = 1; n <= 99; n++) {
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if (existsSync(`/tmp/.X${n}-lock`)) continue;
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// Also check no existing session uses this display
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let inUse = false;
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for (const s of sessions.values()) {
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if (s.display === n) {
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inUse = true;
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break;
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}
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}
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if (!inUse) return n;
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}
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throw new Error('No free display number available');
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}
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let mirror: MirrorSession | null = null;
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function isProcessAlive(pid: number): boolean {
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try {
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@@ -38,9 +34,10 @@ function isProcessAlive(pid: number): boolean {
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}
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}
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async function ensureVncEnv(homeDir: string): Promise<void> {
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async function ensureVncPassword(homeDir: string): Promise<string> {
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const vncDir = join(homeDir, '.vnc');
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if (existsSync(join(vncDir, 'passwd'))) return;
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const passwdFile = join(vncDir, 'passwd');
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if (existsSync(passwdFile)) return passwdFile;
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mkdirSync(vncDir, { recursive: true });
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@@ -59,108 +56,145 @@ async function ensureVncEnv(homeDir: string): Promise<void> {
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stderr: 'ignore',
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});
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if (proc.exitCode === 0 && proc.stdout.byteLength > 0) {
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await Bun.write(join(vncDir, 'passwd'), proc.stdout);
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await Bun.write(passwdFile, proc.stdout);
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}
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// Write xstartup
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await Bun.write(
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join(vncDir, 'xstartup'),
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`#!/bin/sh\nunset SESSION_MANAGER\nunset DBUS_SESSION_BUS_ADDRESS\neval $(dbus-launch --sh-syntax)\nexport DBUS_SESSION_BUS_ADDRESS\nexec startxfce4\n`,
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);
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Bun.spawnSync({ cmd: ['chmod', '+x', join(vncDir, 'xstartup')], stdout: 'ignore', stderr: 'ignore' });
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Bun.spawnSync({ cmd: ['chmod', '600', join(vncDir, 'passwd')], stdout: 'ignore', stderr: 'ignore' });
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Bun.spawnSync({ cmd: ['chmod', '600', passwdFile], stdout: 'ignore', stderr: 'ignore' });
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Bun.spawnSync({ cmd: ['chmod', '600', join(vncDir, 'password')], stdout: 'ignore', stderr: 'ignore' });
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console.log(`[vnc] lazy-provisioned VNC environment at ${vncDir}`);
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console.log(`[vnc] provisioned VNC password at ${vncDir}`);
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return passwdFile;
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}
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async function isPortOpen(port: number): Promise<boolean> {
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try {
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const socket = await Bun.connect({
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hostname: '127.0.0.1',
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port,
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socket: { data() {}, error() {} },
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});
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socket.end();
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return true;
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} catch {
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return false;
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}
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}
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// x11vnc stays in the foreground, so readiness is the listening port rather than exit code.
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async function waitForPort(port: number): Promise<boolean> {
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const deadline = Date.now() + READY_TIMEOUT_MS;
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while (Date.now() < deadline) {
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if (await isPortOpen(port)) return true;
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await Bun.sleep(100);
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}
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return false;
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}
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export async function startSession(params: VncStartParams): Promise<{ port: number; display: number }> {
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// If session already exists and is alive, return it
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const existing = sessions.get(params.email);
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if (existing && isProcessAlive(existing.pid)) {
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return { port: existing.port, display: existing.display };
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}
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// Clean up stale session
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if (existing) {
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sessions.delete(params.email);
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if (mirror && isProcessAlive(mirror.pid)) {
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return { port: mirror.port, display: mirror.display };
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}
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mirror = null;
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const homeDir = getHomeDirForRole(params.email, params.role);
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const resolution = params.resolution ?? '1920x1080';
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const display = findFreeDisplay();
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const port = 5900 + display;
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const passwdFile = await ensureVncPassword(homeDir);
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// Lazy-provision VNC environment if missing
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await ensureVncEnv(homeDir);
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if (!existsSync(XAUTHORITY)) {
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throw new Error(`No X authority at ${XAUTHORITY} — nobody is logged in on ${MIRROR_DISPLAY}`);
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}
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// Spawn VNC server
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const proc = Bun.spawn({
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cmd: ['vncserver', `:${display}`, '-geometry', resolution, '-depth', '24', '-localhost', 'yes'],
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env: { ...process.env, HOME: homeDir },
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stdout: 'pipe',
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cmd: [
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'x11vnc',
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'-display',
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MIRROR_DISPLAY,
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'-auth',
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XAUTHORITY,
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'-rfbport',
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String(MIRROR_PORT),
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'-rfbauth',
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passwdFile,
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'-localhost',
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'-forever',
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'-shared',
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// :0 is 4K; halving the framebuffer keeps the stream sane over the tailnet
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'-scale',
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'0.5',
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'-noxdamage',
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'-quiet',
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],
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stdout: 'ignore',
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stderr: 'pipe',
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});
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const exitCode = await proc.exited;
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if (exitCode !== 0) {
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const stderr = await new Response(proc.stderr).text();
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throw new Error(`vncserver failed (exit ${exitCode}): ${stderr.trim()}`);
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// Drain stderr so the pipe cannot fill and stall x11vnc; keep the tail for errors
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let stderrTail = '';
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(async () => {
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const reader = (proc.stderr as ReadableStream<Uint8Array>).getReader();
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const decoder = new TextDecoder();
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try {
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while (true) {
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const { done, value } = await reader.read();
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if (done) break;
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stderrTail = (stderrTail + decoder.decode(value, { stream: true })).slice(-2000);
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}
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} catch {
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// process ended
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}
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})();
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if (!(await waitForPort(MIRROR_PORT))) {
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try {
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proc.kill();
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} catch {
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// already dead
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}
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throw new Error(`x11vnc failed to listen on ${MIRROR_PORT}: ${stderrTail.trim() || 'timed out'}`);
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}
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// Read PID from lock file
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let pid = 0;
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const lockFile = `/tmp/.X${display}-lock`;
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if (existsSync(lockFile)) {
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const content = await Bun.file(lockFile).text();
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pid = parseInt(content.trim(), 10) || 0;
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mirror = {
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email: params.email,
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username: params.username ?? '',
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display: MIRROR_DISPLAY_NUM,
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port: MIRROR_PORT,
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pid: proc.pid,
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};
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console.log(`[vnc] mirroring ${MIRROR_DISPLAY} on port ${MIRROR_PORT} (pid ${proc.pid})`);
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return { port: MIRROR_PORT, display: MIRROR_DISPLAY_NUM };
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}
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export function stopSession(_email: string): void {
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if (!mirror) return;
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try {
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process.kill(mirror.pid);
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} catch {
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// already dead
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}
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sessions.set(params.email, { email: params.email, username: params.username ?? '', display, port, pid });
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console.log(`[vnc] started session for ${params.email} on :${display} (port ${port}, pid ${pid})`);
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return { port, display };
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console.log(`[vnc] stopped mirror of ${MIRROR_DISPLAY} (pid ${mirror.pid})`);
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mirror = null;
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}
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export function stopSession(email: string): void {
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const session = sessions.get(email);
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if (!session) return;
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export function getSession(_email: string): VncSessionInfo | null {
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if (!mirror) return null;
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const homeDir = getHomeDirForRole(email, null);
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Bun.spawnSync({
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cmd: ['vncserver', '-kill', `:${session.display}`],
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env: { ...process.env, HOME: homeDir },
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stdout: 'ignore',
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stderr: 'ignore',
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});
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sessions.delete(email);
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console.log(`[vnc] stopped session for ${email} on :${session.display}`);
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}
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export function getSession(email: string): VncSessionInfo | null {
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const session = sessions.get(email);
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if (!session) return null;
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const alive = session.pid > 0 && isProcessAlive(session.pid);
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const alive = mirror.pid > 0 && isProcessAlive(mirror.pid);
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if (!alive) {
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sessions.delete(email);
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mirror = null;
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return null;
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}
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return {
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email: session.email,
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display: session.display,
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port: session.port,
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pid: session.pid,
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email: mirror.email,
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display: mirror.display,
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port: mirror.port,
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pid: mirror.pid,
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alive,
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};
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}
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export function stopAll(): void {
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for (const email of [...sessions.keys()]) {
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stopSession(email);
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}
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stopSession('');
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}
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Block a user