feat: add isLinkLocalIp function (libp2p#2863)

To detect when an IP address is link local, add a function,

packages/utils/package.json

@@ -84,6 +84,10 @@
       "types": "./dist/src/is-promise.d.ts",
       "import": "./dist/src/is-promise.js"
     },
+    "./link-local-ip": {
+      "types": "./dist/src/link-local-ip.d.ts",
+      "import": "./dist/src/link-local-ip.js"
+    },
     "./moving-average": {
       "types": "./dist/src/moving-average.d.ts",
       "import": "./dist/src/moving-average.js"

packages/utils/src/link-local-ip.ts

@@ -0,0 +1,13 @@
+import { isIPv4, isIPv6 } from '@chainsafe/is-ip'
+
+export function isLinkLocalIp (ip: string): boolean {
+  if (isIPv4(ip)) {
+    return ip.startsWith('169.254.')
+  }
+
+  if (isIPv6(ip)) {
+    return ip.toLowerCase().startsWith('fe80')
+  }
+
+  return false
+}

packages/utils/test/link-local-ip.spec.ts

@@ -0,0 +1,58 @@
+/* eslint-env mocha */
+
+import { expect } from 'aegir/chai'
+import { isLinkLocalIp } from '../src/link-local-ip.js'
+
+describe('isLinkLocalIp', () => {
+  it('identifies link-local ip4 multiaddrs', () => {
+    [
+      '169.254.35.4',
+      '169.254.35.4',
+      '169.254.0.0',
+      '169.254.255.255'
+    ].forEach(ma => {
+      expect(isLinkLocalIp(ma)).to.be.true()
+    })
+  })
+
+  it('identifies non link-local ip4 multiaddrs', () => {
+    [
+      '101.0.26.90',
+      '10.0.0.1',
+      '192.168.0.1',
+      '172.16.0.1'
+    ].forEach(ma => {
+      expect(isLinkLocalIp(ma)).to.be.false()
+    })
+  })
+
+  it('identifies link-local ip6 multiaddrs', () => {
+    [
+      'fe80::1%lo0',
+      'fe80::1%lo0',
+      'fe80::1893:def4:af04:635a%en',
+      'fe80::1893:def4:af04:635a',
+      'fe80::1893:def4:af04:635a'
+    ].forEach(ma => {
+      expect(isLinkLocalIp(ma)).to.be.true()
+    })
+  })
+
+  it('identifies non link-local ip6 multiaddrs', () => {
+    [
+      '2001:8a0:7ac5:4201:3ac9:86ff:fe31',
+      '::'
+    ].forEach(ma => {
+      expect(isLinkLocalIp(ma)).to.be.false()
+    })
+  })
+
+  it('identifies other multiaddrs as not link-local addresses', () => {
+    [
+      'wss0.bootstrap.libp2p.io',
+      'wss0.bootstrap.libp2p.io'
+    ].forEach(ma => {
+      expect(isLinkLocalIp(ma)).to.be.false()
+    })
+  })
+})