feat: switch to server mode automatically when addresses change (#473)

If the node is in client mode, and the `self:peer:update` event is
emitted, and the event detail contains publicly routable addresses,
switch to server mode.

If the event is emitted and we are in server mode and the event detail
contains only private addresses, switch back to client mode.

src/dual-kad-dht.ts

@@ -6,11 +6,13 @@ import { EventEmitter, CustomEvent } from '@libp2p/interfaces/events'
 import { logger } from '@libp2p/logger'
 import drain from 'it-drain'
 import merge from 'it-merge'
+import isPrivate from 'private-ip'
 import { DefaultKadDHT } from './kad-dht.js'
 import { queryErrorEvent } from './query/events.js'
 import type { DualKadDHT, KadDHT, KadDHTComponents, KadDHTInit, QueryEvent, QueryOptions } from './index.js'
 import type { PeerId } from '@libp2p/interface-peer-id'
 import type { PeerInfo } from '@libp2p/interface-peer-info'
+import type { Multiaddr } from '@multiformats/multiaddr'
 import type { CID } from 'multiformats/cid'
 
 const log = logger('libp2p:kad-dht')
@@ -81,6 +83,44 @@ class DHTPeerRouting implements PeerRouting {
   }
 }
 
+// see https://github.com/multiformats/multiaddr/blob/master/protocols.csv
+const P2P_CIRCUIT_CODE = 290
+const DNS4_CODE = 54
+const DNS6_CODE = 55
+const DNSADDR_CODE = 56
+const IP4_CODE = 4
+const IP6_CODE = 41
+
+function multiaddrIsPublic (multiaddr: Multiaddr): boolean {
+  const tuples = multiaddr.stringTuples()
+
+  // p2p-circuit should not enable server mode
+  for (const tuple of tuples) {
+    if (tuple[0] === P2P_CIRCUIT_CODE) {
+      return false
+    }
+  }
+
+  // dns4 or dns6 or dnsaddr
+  if (tuples[0][0] === DNS4_CODE || tuples[0][0] === DNS6_CODE || tuples[0][0] === DNSADDR_CODE) {
+    log('%m is public %s', multiaddr, true)
+
+    return true
+  }
+
+  // ip4 or ip6
+  if (tuples[0][0] === IP4_CODE || tuples[0][0] === IP6_CODE) {
+    const result = isPrivate(`${tuples[0][1]}`)
+    const isPublic = result == null || !result
+
+    log('%m is public %s', multiaddr, isPublic)
+
+    return isPublic
+  }
+
+  return false
+}
+
 /**
  * A DHT implementation modelled after Kademlia with S/Kademlia modifications.
  * Original implementation in go: https://github.com/libp2p/go-libp2p-kad-dht.
@@ -123,6 +163,30 @@ export class DefaultDualKadDHT extends EventEmitter<PeerDiscoveryEvents> impleme
         detail: evt.detail
       }))
     })
+
+    components.events.addEventListener('self:peer:update', (evt) => {
+      log('received update of self-peer info')
+      const hasPublicAddress = evt.detail.peer.addresses
+        .some(({ multiaddr }) => {
+          const isPublic = multiaddrIsPublic(multiaddr)
+
+          log('%m is public %s', multiaddr, isPublic)
+
+          return isPublic
+        })
+
+      this.getMode()
+        .then(async mode => {
+          if (hasPublicAddress && mode === 'client') {
+            await this.setMode('server')
+          } else if (mode === 'server' && !hasPublicAddress) {
+            await this.setMode('client')
+          }
+        })
+        .catch(err => {
+          log.error('error setting dht server mode', err)
+        })
+    })
   }
 
   readonly [Symbol.toStringTag] = '@libp2p/dual-kad-dht'

src/index.ts

@@ -2,12 +2,14 @@ import { DefaultDualKadDHT } from './dual-kad-dht.js'
 import type { ProvidersInit } from './providers.js'
 import type { AddressManager } from '@libp2p/interface-address-manager'
 import type { ConnectionManager } from '@libp2p/interface-connection-manager'
+import type { Libp2pEvents } from '@libp2p/interface-libp2p'
 import type { Metrics } from '@libp2p/interface-metrics'
 import type { PeerId } from '@libp2p/interface-peer-id'
 import type { PeerInfo } from '@libp2p/interface-peer-info'
 import type { PeerStore } from '@libp2p/interface-peer-store'
 import type { Registrar } from '@libp2p/interface-registrar'
 import type { AbortOptions } from '@libp2p/interfaces'
+import type { EventEmitter } from '@libp2p/interfaces/events'
 import type { Datastore } from 'interface-datastore'
 import type { CID } from 'multiformats/cid'
 import type { ProgressOptions, ProgressEvent } from 'progress-events'
@@ -311,6 +313,7 @@ export interface KadDHTComponents {
   metrics?: Metrics
   connectionManager: ConnectionManager
   datastore: Datastore
+  events: EventEmitter<Libp2pEvents>
 }
 
 export function kadDHT (init?: KadDHTInit): (components: KadDHTComponents) => DualKadDHT {

test/enable-server-mode.spec.ts

@@ -0,0 +1,74 @@
+/* eslint-env mocha */
+/* eslint max-nested-callbacks: ["error", 8] */
+
+import { multiaddr } from '@multiformats/multiaddr'
+import { expect } from 'aegir/chai'
+import delay from 'delay'
+import { TestDHT } from './utils/test-dht.js'
+
+const testCases: Array<[string, string, string]> = [
+  ['should enable server mode when public IP4 addresses are found', '/ip4/139.178.91.71/udp/4001/quic', 'server'],
+  ['should enable server mode when public IP6 addresses are found', '/ip6/2604:1380:45e3:6e00::1/udp/4001/quic', 'server'],
+  ['should enable server mode when DNS4 addresses are found', '/dns4/sv15.bootstrap.libp2p.io/tcp/443/wss/p2p/QmNnooDu7bfjPFoTZYxMNLWUQJyrVwtbZg5gBMjTezGAJN', 'server'],
+  ['should enable server mode when DNS6 addresses are found', '/dns6/sv15.bootstrap.libp2p.io/tcp/443/wss/p2p/QmNnooDu7bfjPFoTZYxMNLWUQJyrVwtbZg5gBMjTezGAJN', 'server'],
+  ['should enable server mode when DNSADDR addresses are found', '/dnsaddr/sv15.bootstrap.libp2p.io/tcp/443/wss/p2p/QmNnooDu7bfjPFoTZYxMNLWUQJyrVwtbZg5gBMjTezGAJN', 'server'],
+  ['should not enable server mode when private IP4 addresses are found', '/ip4/127.0.0.1/udp/4001/quic', 'client'],
+  ['should not enable server mode when private IP6 addresses are found', '/ip6/::1/udp/4001/quic', 'client'],
+  ['should not enable server mode when otherwise public circuit relay addresses are found', '/dns4/sv15.bootstrap.libp2p.io/tcp/443/wss/p2p/QmNnooDu7bfjPFoTZYxMNLWUQJyrVwtbZg5gBMjTezGAJN/p2p-circuit', 'client']
+]
+
+describe('enable server mode', () => {
+  let tdht: TestDHT
+
+  beforeEach(() => {
+    tdht = new TestDHT()
+  })
+
+  afterEach(async () => {
+    await tdht.teardown()
+  })
+
+  testCases.forEach(([name, addr, result]) => {
+    it(name, async function () {
+      const dht = await tdht.spawn()
+
+      await expect(dht.getMode()).to.eventually.equal('client')
+
+      dht.components.events.safeDispatchEvent('self:peer:update', {
+        detail: {
+          peer: {
+            addresses: [{
+              multiaddr: multiaddr('/ip4/127.0.0.1/tcp/4001'),
+              isCertified: true
+            }, {
+              multiaddr: multiaddr('/ip6/::1/tcp/4001'),
+              isCertified: true
+            }, {
+              multiaddr: multiaddr(addr),
+              isCertified: true
+            }]
+          }
+        }
+      })
+
+      await delay(100)
+
+      await expect(dht.getMode()).to.eventually.equal(result, `did not change to "${result}" mode after updating with address ${addr}`)
+
+      dht.components.events.safeDispatchEvent('self:peer:update', {
+        detail: {
+          peer: {
+            addresses: [{
+              multiaddr: multiaddr('/ip4/127.0.0.1/tcp/4001'),
+              isCertified: true
+            }]
+          }
+        }
+      })
+
+      await delay(100)
+
+      await expect(dht.getMode()).to.eventually.equal('client', `did not reset to client mode after updating with address ${addr}`)
+    })
+  })
+})

test/utils/test-dht.ts

@@ -37,7 +37,8 @@ export class TestDHT {
       // connectionGater: mockConnectionGater(),
       addressManager: stubInterface<AddressManager>(),
       peerStore: stubInterface<PeerStore>(),
-      connectionManager: stubInterface<ConnectionManager>()
+      connectionManager: stubInterface<ConnectionManager>(),
+      events
     }
     components.connectionManager = mockConnectionManager({
       ...components,