feat: add acceptIncomingConnection to ConnectionManager (#295)

* feat: add acceptIncomingConnection to ConnectionManager

In order to check we can accept an incoming connection before exchanging
PeerIds, add a method to the ConnectionManager interface that can
be called by the upgrader.

* chore: return boolean

packages/interface-connection-manager/src/index.ts

@@ -1,6 +1,6 @@
 import type { AbortOptions } from '@libp2p/interfaces'
 import type { EventEmitter } from '@libp2p/interfaces/events'
-import type { Connection } from '@libp2p/interface-connection'
+import type { Connection, MultiaddrConnection } from '@libp2p/interface-connection'
 import type { PeerId } from '@libp2p/interface-peer-id'
 import type { Multiaddr } from '@multiformats/multiaddr'
 
@@ -24,6 +24,14 @@ export interface ConnectionManager extends EventEmitter<ConnectionManagerEvents>
    * Close our connections to a peer
    */
   closeConnections: (peer: PeerId) => Promise<void>
+
+  /**
+   * Invoked after an incoming connection is opened but before PeerIds are
+   * exchanged, this lets the ConnectionManager check we have sufficient
+   * resources to accept the connection in which case it will return true,
+   * otherwise it will return false.
+   */
+  acceptIncomingConnection: (maConn: MultiaddrConnection) => Promise<boolean>
 }
 
 export interface Dialer {

packages/interface-mocks/src/connection-manager.ts

@@ -134,6 +134,10 @@ class MockConnectionManager extends EventEmitter<ConnectionManagerEvents> implem
 
     await componentsB.getConnectionManager().closeConnections(this.components.getPeerId())
   }
+
+  async acceptIncomingConnection (): Promise<boolean> {
+    return true
+  }
 }
 
 export function mockConnectionManager () {