feat: add autonat support

Implements the [autonat](https://github.com/libp2p/specs/blob/master/autonat/README.md)
spec to give us confidence in our external addresses and to open the
door to things like switching DHT server mode on automatically, hole
punching, v2 circuit relay etc.

Depends on:

- [ ] libp2p/js-libp2p-interfaces#269

package.json

@@ -83,6 +83,7 @@
     "prepublishOnly": "node scripts/update-version.js",
     "build": "aegir build",
     "generate": "run-s generate:proto:*",
+    "generate:proto:autonat": "protons ./src/autonat/pb/index.proto",
     "generate:proto:circuit": "protons ./src/circuit/pb/index.proto",
     "generate:proto:fetch": "protons ./src/fetch/pb/proto.proto",
     "generate:proto:identify": "protons ./src/identify/pb/message.proto",

src/address-manager/index.ts

@@ -3,6 +3,7 @@ import { CustomEvent, EventEmitter } from '@libp2p/interfaces/events'
 import { Multiaddr } from '@multiformats/multiaddr'
 import { peerIdFromString } from '@libp2p/peer-id'
 import type { Components } from '@libp2p/components'
+import type { PeerId } from '@libp2p/interface-peer-id'
 
 export interface AddressManagerInit {
   announceFilter?: AddressFilter
@@ -29,11 +30,31 @@ export interface AddressFilter {
 
 const defaultAddressFilter = (addrs: Multiaddr[]): Multiaddr[] => addrs
 
+interface ObservedAddressMetadata {
+  confident: boolean
+}
+
+function stripPeerId (ma: Multiaddr, peerId: PeerId) {
+  const observedPeerId = ma.getPeerId()
+
+  // strip our peer id if it has been passed
+  if (observedPeerId != null) {
+    const peerId = peerIdFromString(observedPeerId)
+
+    // use same encoding for comparison
+    if (peerId.equals(peerId)) {
+      ma = ma.decapsulate(new Multiaddr(`/p2p/${peerId.toString()}`))
+    }
+  }
+
+  return ma
+}
+
 export class DefaultAddressManager extends EventEmitter<AddressManagerEvents> {
   private readonly components: Components
   private readonly listen: Set<string>
   private readonly announce: Set<string>
-  private readonly observed: Set<string>
+  private readonly observed: Map<string, ObservedAddressMetadata>
   private readonly announceFilter: AddressFilter
 
   /**
@@ -50,7 +71,7 @@ export class DefaultAddressManager extends EventEmitter<AddressManagerEvents> {
     this.components = components
     this.listen = new Set(listen.map(ma => ma.toString()))
     this.announce = new Set(announce.map(ma => ma.toString()))
-    this.observed = new Set()
+    this.observed = new Map()
     this.announceFilter = init.announceFilter ?? defaultAddressFilter
   }
 
@@ -72,35 +93,51 @@ export class DefaultAddressManager extends EventEmitter<AddressManagerEvents> {
    * Get observed multiaddrs
    */
   getObservedAddrs (): Multiaddr[] {
-    return Array.from(this.observed).map((a) => new Multiaddr(a))
+    return Array.from(this.observed)
+      .map(([ma]) => new Multiaddr(ma))
   }
 
   /**
    * Add peer observed addresses
    */
-  addObservedAddr (addr: string | Multiaddr): void {
-    let ma = new Multiaddr(addr)
-    const remotePeer = ma.getPeerId()
-
-    // strip our peer id if it has been passed
-    if (remotePeer != null) {
-      const remotePeerId = peerIdFromString(remotePeer)
-
-      // use same encoding for comparison
-      if (remotePeerId.equals(this.components.getPeerId())) {
-        ma = ma.decapsulate(new Multiaddr(`/p2p/${this.components.getPeerId().toString()}`))
-      }
-    }
-
-    const addrString = ma.toString()
+  addObservedAddr (addr: Multiaddr): void {
+    addr = stripPeerId(addr, this.components.getPeerId())
+    const addrString = addr.toString()
 
-    // do not trigger the change:addresses event if we already know about this address
     if (this.observed.has(addrString)) {
       return
     }
 
-    this.observed.add(addrString)
-    this.dispatchEvent(new CustomEvent('change:addresses'))
+    this.observed.set(addrString, {
+      confident: false
+    })
+  }
+
+  confirmObservedAddr (addr: Multiaddr) {
+    addr = stripPeerId(addr, this.components.getPeerId())
+    const addrString = addr.toString()
+
+    const metadata = this.observed.get(addrString) ?? {
+      confident: false
+    }
+
+    const startingConfidence = metadata.confident
+
+    this.observed.set(addrString, {
+      confident: true
+    })
+
+    // only trigger the change:addresses event if our confidence in an address has changed
+    if (startingConfidence === false) {
+      this.dispatchEvent(new CustomEvent('change:addresses'))
+    }
+  }
+
+  removeObservedAddr (addr: Multiaddr) {
+    addr = stripPeerId(addr, this.components.getPeerId())
+    const addrString = addr.toString()
+
+    this.observed.delete(addrString)
   }
 
   getAddresses (): Multiaddr[] {
@@ -111,7 +148,12 @@ export class DefaultAddressManager extends EventEmitter<AddressManagerEvents> {
       addrs = this.components.getTransportManager().getAddrs().map(ma => ma.toString())
     }
 
-    addrs = addrs.concat(this.getObservedAddrs().map(ma => ma.toString()))
+    // add observed addresses we are confident in
+    addrs = addrs.concat(
+      Array.from(this.observed)
+        .filter(([ma, metadata]) => metadata.confident)
+        .map(([ma]) => ma)
+    )
 
     // dedupe multiaddrs
     const addrSet = new Set(addrs)

src/autonat/constants.ts

@@ -0,0 +1,4 @@
+
+export const PROTOCOL = '/libp2p/autonat/1.0.0'
+export const PROTOCOL_VERSION = '1.0.0'
+export const PROTOCOL_NAME = 'autonat'