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This PR implements a multicast DNS (mDNS) resolver which gives users the ability to navigate to http://simbridge.local:${PORT} on any device[^1]
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,188 @@ | ||
| import { AddressInfo, createConnection } from 'net'; | ||
| import { platform } from 'os'; | ||
| import { execSync } from 'child_process'; | ||
| import { Injectable, Logger, OnApplicationShutdown } from '@nestjs/common'; | ||
| import * as createMDNSServer from 'multicast-dns'; | ||
| import { MulticastDNS, QueryPacket } from 'multicast-dns'; | ||
| import { StringAnswer } from 'dns-packet'; | ||
| import { RemoteInfo } from 'dgram'; | ||
|
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| @Injectable() | ||
| export class NetworkService implements OnApplicationShutdown { | ||
| private readonly logger = new Logger(NetworkService.name); | ||
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| private mDNSServer: MulticastDNS | undefined; | ||
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| constructor() { | ||
| this.startMDNSServer(); | ||
| } | ||
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| async startMDNSServer() { | ||
| const localIp = await this.getLocalIp(); | ||
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| if (!localIp) { | ||
| this.logger.warn('Couldn\'t determine local IP, mDNS server won\'t be started and simbridge.local will not be available'); | ||
| return; | ||
| } | ||
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| this.logger.log(`Local IP is ${localIp}`); | ||
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| this.mDNSServer = createMDNSServer({ | ||
| interface: localIp, | ||
| multicast: true, | ||
| reuseAddr: true, | ||
| }); | ||
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| this.mDNSServer.on('error', (error) => { | ||
| this.logger.warn(`mDNS server couldn't be started. Error: ${error.message}`); | ||
| }); | ||
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| this.mDNSServer.on('warning', (error) => { | ||
| this.logger.warn(`mDNS server warning: ${error.message}`); | ||
| }); | ||
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| this.mDNSServer.on('ready', () => { | ||
| this.makeAnnouncement(localIp); | ||
| }); | ||
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| this.mDNSServer.on('query', (query, client) => { | ||
| this.onMDNSQuery(query, client); | ||
| }); | ||
| } | ||
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| makeAnnouncement(localIp: string) { | ||
| this.logger.log('mDNS server started, simbridge.local is available'); | ||
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| // First, make two announcements, one second apart (https://www.rfc-editor.org/rfc/rfc6762.html#section-8.3) | ||
| this.mDNSServer.respond([{ | ||
| name: 'simbridge.local', | ||
| type: 'A', | ||
| ttl: 1, | ||
| flush: true, | ||
| data: localIp, | ||
| }]); | ||
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| setTimeout(() => { | ||
| this.mDNSServer.respond([{ | ||
| name: 'simbridge.local', | ||
| type: 'A', | ||
| ttl: 1, | ||
| flush: true, | ||
| data: localIp, | ||
| }]); | ||
| }, 1000); | ||
| } | ||
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| async onMDNSQuery(query: QueryPacket, client: RemoteInfo) { | ||
| // TODO: Handle AAAA records (https://www.rfc-editor.org/rfc/rfc6762.html#section-6.2) or send NSEC (https://www.rfc-editor.org/rfc/rfc6762.html#section-6.1) | ||
| if (query.questions.some((q) => q.type === 'A' && q.name === 'simbridge.local')) { | ||
| // Make sure that the IP is always up-to-date despite DHCP shenanigans | ||
| const localIp = await this.getLocalIp(); | ||
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| if (!localIp) { | ||
| this.logger.warn('Couldn\'t determine the local IP address, no mDNS answer will be sent'); | ||
| return; | ||
| } | ||
|
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| // Whether this is a simple mDNS resolver or not (https://www.rfc-editor.org/rfc/rfc6762.html#section-6.7) | ||
| const isSimpleResolver = client.port !== 5353; | ||
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| const answer: StringAnswer = { | ||
| name: 'simbridge.local', | ||
| type: 'A', | ||
| ttl: isSimpleResolver ? 10 : 120, | ||
| data: localIp, | ||
| }; | ||
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| if (isSimpleResolver) { | ||
| // Simple resolvers require the ID and questions be included in the response, and the response to be sent via unicast | ||
| const response = { | ||
| id: query.id, | ||
| questions: query.questions, | ||
| answers: [answer], | ||
| }; | ||
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| this.mDNSServer.respond(response, client); | ||
| } else { | ||
| const response = { answers: [answer] }; | ||
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| this.mDNSServer.respond(response); | ||
| } | ||
| } | ||
| } | ||
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| /** | ||
| * Get the local (LAN) IP address of the computer. By default it creates a TCP connection to api.flybywire.com:443 | ||
| * but has fallbacks for Windows and Linux in case internet connection is not available. | ||
| * @param defaultToLocalhost Returns 'localhost' in case the IP address couldn't be determined, instead of undefined | ||
| * @returns the local IP address, undefined or 'localhost' | ||
| */ | ||
| async getLocalIp(defaultToLocalhost = false): Promise<string | undefined> { | ||
| return new Promise<string | undefined>((resolve) => { | ||
| const conn = createConnection({ host: 'api.flybywiresim.com', port: 443, timeout: 1000 }) | ||
| .on('connect', () => { | ||
| resolve((conn.address() as AddressInfo).address); | ||
| }) | ||
| .on('timeout', () => { | ||
| resolve(this.getLocalIpFallback(defaultToLocalhost)); | ||
| }) | ||
| .on('error', () => { | ||
| resolve(this.getLocalIpFallback(defaultToLocalhost)); | ||
| }); | ||
| }); | ||
| } | ||
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| onApplicationShutdown(_signal?: string) { | ||
| this.logger.log(`Destroying ${NetworkService.name}`); | ||
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| if (this.mDNSServer) { | ||
| this.mDNSServer.destroy(); | ||
| } | ||
| } | ||
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| private getLocalIpFallback(defaultToLocalhost = true) { | ||
| const ipv4Regex = /^(\d{1,3}\.){3}\d{1,3}$/; | ||
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| if (platform() === 'win32') { | ||
| let lines: string[]; | ||
| try { | ||
| lines = execSync('route print 0.0.0.0', { encoding: 'utf-8', stdio: 'pipe' }).split('\n'); | ||
| } catch (e) { | ||
| this.logger.warn(`Couldn't execute \`route\`. This is probably a bug. Details: ${e.stderr.trim()}`); | ||
| } | ||
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| for (const [i, line] of lines.entries()) { | ||
| if (line.startsWith('Network Destination')) { | ||
| const ip = lines[i + 1].trim().split(' ').filter((p) => p !== '')[3].trim(); | ||
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| if (ipv4Regex.test(ip)) { | ||
| return ip; | ||
| } | ||
| } | ||
| } | ||
| } else if (platform() === 'linux') { | ||
| /** Example output: | ||
| * > 1.0.0.0 via 172.20.96.1 dev eth0 src 172.20.108.184 uid 1000 | ||
| * > cache | ||
| */ | ||
| let parts: string[]; | ||
| try { | ||
| parts = execSync('ip -4 route get to 1', { encoding: 'utf-8', stdio: 'pipe' }).split('\n')[0].split(' '); | ||
| } catch (e) { | ||
| this.logger.warn(`Couldn't execute \`ip\`. Make sure the \`iproute2\` (or equivalent) package is installed. Details: '${e.stderr.trim()}'`); | ||
| } | ||
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| const ip = parts[parts.indexOf('src') + 1].trim(); | ||
|
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| if (ipv4Regex.test(ip)) { | ||
| return ip; | ||
| } | ||
| } | ||
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| if (defaultToLocalhost) { | ||
| return 'localhost'; | ||
| } | ||
|
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| return undefined; | ||
| } | ||
| } |
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