refactor: move mac generation logic to wire package

Author: gregnr

packages/tcpip/src/bindings/bridge-interface.ts

@@ -1,4 +1,5 @@
 import {
+  generateMacAddress,
   parseIPv4Address,
   parseMacAddress,
   serializeIPv4Cidr,
@@ -8,7 +9,7 @@ import {
   type MacAddress,
 } from '@tcpip/wire';
 import type { Pointer } from '../types.js';
-import { generateMacAddress, Hooks } from '../util.js';
+import { Hooks } from '../util.js';
 import { Bindings } from './base.js';
 import { tapInterfaceHooks, type TapInterface } from './tap-interface.js';
 

packages/tcpip/src/bindings/tap-interface.ts

@@ -1,4 +1,5 @@
 import {
+  generateMacAddress,
   parseIPv4Address,
   parseMacAddress,
   serializeIPv4Cidr,
@@ -12,7 +13,6 @@ import type { Pointer } from '../types.js';
 import {
   ExtendedReadableStream,
   fromReadable,
-  generateMacAddress,
   Hooks,
   nextMicrotask,
 } from '../util.js';

packages/tcpip/src/util.test.ts

@@ -215,23 +215,3 @@ export class ExtendedReadableStream<R> extends ReadableStream<R> {
 export async function nextMicrotask() {
   return await new Promise<void>((resolve) => queueMicrotask(resolve));
 }
-
-/**
- * Generates a random MAC address.
- *
- * The generated address is locally administered (so won't conflict
- * with real devices) and unicast (so it can be used as a source address).
- */
-export function generateMacAddress() {
-  const mac = new Uint8Array(6);
-  crypto.getRandomValues(mac);
-
-  // Control bits only apply to the first byte
-  mac[0] =
-    // Clear the 2 least significant bits
-    (mac[0]! & 0b11111100) |
-    // Set locally administered bit (bit 1) to 1 and unicast bit (bit 0) to 0
-    0b00000010;
-
-  return mac;
-}

packages/tcpip/src/util.ts

@@ -1,7 +1,11 @@
-import { describe, expect, test } from 'vitest';
-import { parseMacAddress, serializeMacAddress } from './ethernet.js';
+import { describe, expect, test, vi } from 'vitest';
+import {
+  generateMacAddress,
+  parseMacAddress,
+  serializeMacAddress,
+} from './ethernet.js';
 
-describe('parseMacAddress', () => {
+describe('serialize mac', () => {
   test('should parse a valid MAC address string into a Uint8Array', () => {
     const macString = '01:23:45:67:89:ab';
     const result = serializeMacAddress(macString);
@@ -29,7 +33,7 @@ describe('parseMacAddress', () => {
   });
 });
 
-describe('formatMacAddress', () => {
+describe('parse mac', () => {
   test('should format a valid Uint8Array into a MAC address string', () => {
     const macArray = new Uint8Array([0x01, 0x23, 0x45, 0x67, 0x89, 0xab]);
     const result = parseMacAddress(macArray);
@@ -65,3 +69,31 @@ describe('formatMacAddress', () => {
     expect(result).toBe('ff:ff:ff:ff:ff:ff');
   });
 });
+
+describe('generate mac', () => {
+  test('should generate a MAC address of length 6', () => {
+    const mac = generateMacAddress();
+    expect(mac).toHaveLength(6);
+  });
+
+  test('should set the locally administered bit and clear the unicast bit', () => {
+    const mac = generateMacAddress();
+    // Check that the locally administered bit (bit 1) is set to 1
+    expect(mac[0]! & 0b00000010).toBe(0b00000010);
+    // Check that the unicast bit (bit 0) is set to 0
+    expect(mac[0]! & 0b00000001).toBe(0b00000000);
+  });
+
+  test('should generate different MAC addresses on subsequent calls', () => {
+    const mac1 = generateMacAddress();
+    const mac2 = generateMacAddress();
+    expect(mac1).not.toEqual(mac2);
+  });
+
+  test('should use crypto.getRandomValues to generate the MAC address', () => {
+    const spy = vi.spyOn(crypto, 'getRandomValues');
+    generateMacAddress();
+    expect(spy).toHaveBeenCalled();
+    spy.mockRestore();
+  });
+});

packages/wire/src/ethernet.test.ts

@@ -125,6 +125,26 @@ export function serializeMacAddress(mac: string) {
   );
 }
 
+/**
+ * Generates a random MAC address.
+ *
+ * The generated address is locally administered (so won't conflict
+ * with real devices) and unicast (so it can be used as a source address).
+ */
+export function generateMacAddress() {
+  const mac = new Uint8Array(6);
+  crypto.getRandomValues(mac);
+
+  // Control bits only apply to the first byte
+  mac[0] =
+    // Clear the 2 least significant bits
+    (mac[0]! & 0b11111100) |
+    // Set locally administered bit (bit 1) to 1 and unicast bit (bit 0) to 0
+    0b00000010;
+
+  return mac;
+}
+
 /**
  * Parses an Ethernet type into a string.
  */