Merge pull request #1 from earthstar-project/get-own-address

Make it possible to determine own external local address

examples/advertise_http.ts

@@ -1,21 +1,20 @@
 import { advertise } from "../src/dns_sd/advertise.ts";
+
 import { MulticastInterface } from "../src/mdns/multicast_interface.ts";
 
-const host = Deno.networkInterfaces().find((netInterface) => {
-  return netInterface.family === "IPv4" &&
-    netInterface.netmask === "255.255.255.0";
-})?.address || "127.0.0.1";
+const multicastInterface = new MulticastInterface();
 
-console.log(`Advertising "My Web Server" on ${host}:8080`);
+console.log(
+  `Advertising "My Web Server" on ${multicastInterface.hostname}:8080`,
+);
 
 await advertise({
   service: {
-    host: host,
     name: "My Web Server",
     port: 8080,
     protocol: "tcp",
     type: "http",
     txt: {},
   },
-  multicastInterface: new MulticastInterface(),
+  multicastInterface,
 });

src/dns_sd/advertise.ts

@@ -7,16 +7,21 @@ import {
   ResourceRecordTXT,
   ResourceType,
 } from "../decode/types.ts";
+import { getOwnAddress } from "../mdns/get_own_address.ts";
 import { MulticastInterface } from "../mdns/multicast_interface.ts";
 import { respond } from "../mdns/responder.ts";
 
 export type AdvertiseOpts = {
   service: {
+    /** Unique name, e.g. "My Computer" */
     name: string;
+    /** The type of the service, e.g. http. */
     type: string;
+    /** A list of identifiers further identifying the kind of service provided, e.g. ["printer"]. */
     subtypes?: string[];
     protocol: "tcp" | "udp";
-    host: string;
+    /** The address to advertise on. Automatically determined if omitted. */
+    host?: string;
     port: number;
     txt: Record<string, true | Uint8Array | null>;
   };
@@ -35,6 +40,9 @@ export async function advertise(opts: AdvertiseOpts) {
   let attemptsInLastTenSeconds = 0;
   const removalTimers: number[] = [];
 
+  const hostToUse = opts.service.host ||
+    await getOwnAddress(opts.multicastInterface);
+
   let renameAttempts = 1;
 
   if (opts.signal) {
@@ -114,8 +122,8 @@ export async function advertise(opts: AdvertiseOpts) {
       TTL: 120,
       isUnique: true,
       RDATA: opts.multicastInterface.family === "IPv4"
-        ? opts.service.host.split(".").map((strNum) => parseInt(strNum))
-        : opts.service.host,
+        ? hostToUse.split(".").map((strNum) => parseInt(strNum))
+        : hostToUse,
       RDLENGTH: 1,
     } as (ResourceRecordA | ResourceRecordAAAA);
 

src/mdns/default_driver.node.ts

@@ -6,7 +6,10 @@ import {
   RemoteInfo,
   Socket,
 } from "https://deno.land/[email protected]/node/dgram.ts";
-import { networkInterfaces } from "https://deno.land/[email protected]/node/os.ts";
+import {
+  hostname,
+  networkInterfaces,
+} from "https://deno.land/[email protected]/node/os.ts";
 import { Buffer } from "https://deno.land/[email protected]/node/buffer.ts";
 import { FastFIFO } from "../fast_fifo.ts";
 import { deferred } from "https://deno.land/[email protected]/async/deferred.ts";
@@ -19,6 +22,7 @@ export class DefaultDriver implements MulticastDriver {
 
   family: "IPv4" | "IPv6";
   address: string;
+  hostname = hostname();
 
   constructor(family: "IPv4" | "IPv6") {
     this.family = family;

src/mdns/default_driver.ts

@@ -9,6 +9,7 @@ export class DefaultDriver implements MulticastDriver {
 
   family: "IPv4" | "IPv6";
   address: string;
+  hostname = Deno.hostname();
 
   constructor(family: "IPv4" | "IPv6") {
     this.address = family === "IPv4" ? "0.0.0.0" : "::";

src/mdns/get_own_address.ts

@@ -0,0 +1,46 @@
+import { deferred } from "https://deno.land/[email protected]/async/deferred.ts";
+import { MulticastInterface } from "./multicast_interface.ts";
+
+export async function getOwnAddress(
+  multicastInterface: MulticastInterface,
+): Promise<string> {
+  const ownAddressPromise = deferred<string>();
+
+  multicastInterface.setLoopback(true);
+
+  // Listen to multicast messages
+  (async () => {
+    for await (const [_msg, addr] of multicastInterface.messages()) {
+      if (multicastInterface.isOwnAddress(addr.hostname)) {
+        ownAddressPromise.resolve(addr.hostname);
+      }
+    }
+  })();
+
+  // Send a message
+  await multicastInterface.send({
+    header: {
+      ID: 0,
+      QR: 0,
+      OPCODE: 0,
+      AA: 0,
+      TC: 0,
+      RD: 0,
+      RA: 0,
+      Z: 0,
+      AD: 0,
+      CD: 0,
+      RCODE: 0,
+      QDCOUNT: 0,
+      ANCOUNT: 0,
+      NSCOUNT: 0,
+      ARCOUNT: 0,
+    },
+    question: [],
+    answer: [],
+    authority: [],
+    additional: [],
+  });
+
+  return ownAddressPromise;
+}

src/mdns/multicast_interface.ts

@@ -6,10 +6,10 @@ import { DefaultDriver } from "./default_driver.ts";
 
 /** A driver which supplies the underlying methods a `MulticastInterface` uses to send and receive multicast messages. */
 export interface MulticastDriver {
-  address: string;
-
   family: "IPv4" | "IPv6";
 
+  hostname: string;
+
   send(message: Uint8Array): Promise<void>;
 
   setTTL(ttl: number): Promise<void>;
@@ -44,13 +44,17 @@ export class MulticastInterface {
       while (true) {
         const [received, origin] = await driverToUse.receive();
 
-        const event = [decodeMessage(received), origin] as [
-          DnsMessage,
-          { hostname: string; port: number },
-        ];
-
-        for (const subscriber of subscribers) {
-          subscriber.push(event);
+        try {
+          const event = [decodeMessage(received), origin] as [
+            DnsMessage,
+            { hostname: string; port: number },
+          ];
+
+          for (const subscriber of subscribers) {
+            subscriber.push(event);
+          }
+        } catch {
+          console.warn("Could not decode a message from", origin.hostname);
         }
       }
     })();
@@ -86,8 +90,8 @@ export class MulticastInterface {
     return this.driver.isOwnAddress(address);
   }
 
-  get address() {
-    return this.driver.address;
+  get hostname() {
+    return this.driver.hostname;
   }
 
   get family() {

src/mdns/query.ts

@@ -68,6 +68,10 @@ export class Query {
           break;
         }
 
+        if (multicastInterface.isOwnAddress(host.hostname)) {
+          continue;
+        }
+
         if (message.header.QR === 0) {
           this.handleQuery(message, host);
         } else {
@@ -142,7 +146,7 @@ export class Query {
     // It's a query.
 
     // Is this something we sent ourselves?
-    if (host.hostname === this.minterface.address) {
+    if (this.minterface.isOwnAddress(host.hostname)) {
       return;
     }