feat: add isLinkLocal function

Add function for detecting link-local multiaddrs

packages/utils/package.json

@@ -88,6 +88,10 @@
       "types": "./dist/src/moving-average.d.ts",
       "import": "./dist/src/moving-average.js"
     },
+    "./multiaddr/is-link-local": {
+      "types": "./dist/src/multiaddr/is-link-local.d.ts",
+      "import": "./dist/src/multiaddr/is-link-local.js"
+    },
     "./multiaddr/is-loopback": {
       "types": "./dist/src/multiaddr/is-loopback.d.ts",
       "import": "./dist/src/multiaddr/is-loopback.js"

packages/utils/src/multiaddr/is-link-local.ts

@@ -0,0 +1,29 @@
+import type { Multiaddr } from '@multiformats/multiaddr'
+
+const CODEC_IP4 = 0x04
+const CODEC_IP6 = 0x29
+
+/**
+ * Check if a given multiaddr is a link-local address
+ */
+export function isLinkLocal (ma: Multiaddr): boolean {
+  try {
+    const [[codec, value]] = ma.stringTuples()
+
+    if (value == null) {
+      return false
+    }
+
+    if (codec === CODEC_IP4) {
+      return value.startsWith('169.254.')
+    }
+
+    if (codec === CODEC_IP6) {
+      return value.toLowerCase().startsWith('fe80')
+    }
+  } catch {
+
+  }
+
+  return false
+}

packages/utils/test/multiaddr/is-link-local.spec.ts

@@ -0,0 +1,59 @@
+/* eslint-env mocha */
+
+import { multiaddr } from '@multiformats/multiaddr'
+import { expect } from 'aegir/chai'
+import { isLinkLocal } from '../../src/multiaddr/is-link-local.js'
+
+describe('multiaddr isLinkLocal', () => {
+  it('identifies link-local ip4 multiaddrs', () => {
+    [
+      multiaddr('/ip4/169.254.35.4'),
+      multiaddr('/ip4/169.254.35.4/tcp/1000'),
+      multiaddr('/ip4/169.254.0.0/tcp/1000'),
+      multiaddr('/ip4/169.254.255.255/tcp/1000')
+    ].forEach(ma => {
+      expect(isLinkLocal(ma)).to.be.true()
+    })
+  })
+
+  it('identifies non link-local ip4 multiaddrs', () => {
+    [
+      multiaddr('/ip4/101.0.26.90/tcp/1000'),
+      multiaddr('/ip4/10.0.0.1/tcp/1000'),
+      multiaddr('/ip4/192.168.0.1/tcp/1000'),
+      multiaddr('/ip4/172.16.0.1/tcp/1000')
+    ].forEach(ma => {
+      expect(isLinkLocal(ma)).to.be.false()
+    })
+  })
+
+  it('identifies link-local ip6 multiaddrs', () => {
+    [
+      multiaddr('/ip6/fe80::1%lo0'),
+      multiaddr('/ip6/fe80::1%lo0/tcp/1000'),
+      multiaddr('/ip6/fe80::1893:def4:af04:635a%en'),
+      multiaddr('/ip6/fe80::1893:def4:af04:635a'),
+      multiaddr('/ip6/fe80::1893:def4:af04:635a/udp/2183')
+    ].forEach(ma => {
+      expect(isLinkLocal(ma)).to.be.true()
+    })
+  })
+
+  it('identifies non link-local ip6 multiaddrs', () => {
+    [
+      multiaddr('/ip6/2001:8a0:7ac5:4201:3ac9:86ff:fe31:7095/tcp/1000'),
+      multiaddr('/ip6/::/tcp/1000')
+    ].forEach(ma => {
+      expect(isLinkLocal(ma)).to.be.false()
+    })
+  })
+
+  it('identifies other multiaddrs as not link-local addresses', () => {
+    [
+      multiaddr('/dns4/wss0.bootstrap.libp2p.io/tcp/443'),
+      multiaddr('/dns6/wss0.bootstrap.libp2p.io/tcp/443')
+    ].forEach(ma => {
+      expect(isLinkLocal(ma)).to.be.false()
+    })
+  })
+})