feat: Update connectionManager to allow configuration of incoming and outgoing connection limits

doc/CONFIGURATION.md

@@ -556,7 +556,8 @@ const node = await createLibp2p({
   streamMuxers: [mplex()],
   connectionEncryption: [noise()],
   connectionManager: {
-    maxConnections: Infinity,
+    maxIncomingConnections: Infinity,
+    maxOutgoingConnections: Infinity,
     minConnections: 0,
     pollInterval: 2000,
     // The below values will only be taken into account when Metrics are enabled

doc/LIMITS.md

@@ -23,8 +23,6 @@ This is important for [DoS](https://en.wikipedia.org/wiki/Denial-of-service_atta
 
 It's possible to limit the total amount of connections a node is able to make (combining incoming and outgoing). When this limit is reached and an attempt to open a new connection is made, existing connections may be closed to make room for the new connection (see [Closing connections][#closing-connections]).
 
-* Note: there currently isn't a way to specify different limits for incoming vs. outgoing. Connection limits are applied across both incoming and outgoing connections combined. There is a backlog item for this [here](https://github.com/libp2p/js-libp2p/issues/1508).
-
 We can also limit the number of connections in a "pending" state. These connections have been opened by a remote peer but peer IDs have yet to be exchanged and/or connection encryption and multiplexing negotiated. Once this limit is hit further connections will be closed unless the remote peer has an address in the [allow list](#allowdeny-lists).
 
 All fields are optional. The default values are defined in [src/connection-manager/index.ts](https://github.com/libp2p/js-libp2p/blob/master/src/connection-manager/index.ts) - please see that file for the current values.
@@ -33,9 +31,14 @@ All fields are optional. The default values are defined in [src/connection-manag
 const node = await createLibp2pNode({
   connectionManager: {
     /**
-     * The total number of connections allowed to be open at one time
+     * The total number of incoming connections allowed to be open at one time
      */
-    maxConnections: number
+    maxIncomingConnections: number
+
+    /**
+     * The total number of outgoing connections allowed to be open at one time
+    */
+    maxOutgoingConnections: number
 
     /**
      * If the number of open connections goes below this number, the node
@@ -255,9 +258,9 @@ const node = await createLibp2pNode({
       /**
        * Once this many connections are open on this listener any further connections
        * will be rejected - this will have no effect if it is larger than the value
-       * configured for the ConnectionManager maxConnections parameter
+       * configured for the ConnectionManager maxIncomingConnections parameter
        */
-      maxConnections: number
+      maxIncomingConnections: number
     })
   ]
 })
@@ -310,7 +313,7 @@ Important details for ascertaining this are:
 As a result, the max amount of memory buffered by libp2p is approximately:
 
 ```
-connectionManager.maxConnections *
+(connectionManager.maxOutgoingConnections + connectionManager.maxIncomingConnections) *
   (muxer.maxUnprocessedMessageQueueSize
    + (muxer.maxInboundStreams * muxer.maxStreamBufferSize)
    + (muxer.maxOutboundStreams * muxer.maxStreamBufferSize)

src/config.ts

@@ -20,7 +20,8 @@ const DefaultConfig: Partial<Libp2pInit> = {
     announceFilter: (multiaddrs: Multiaddr[]) => multiaddrs
   },
   connectionManager: {
-    maxConnections: 300,
+    maxIncomingConnections: 300,
+    maxOutgoingConnections: 300,
     minConnections: 50,
     autoDial: true,
     autoDialInterval: 10000,

src/connection-manager/auto-dialler.ts

@@ -20,7 +20,7 @@ export interface AutoDiallerInit {
   enabled?: boolean
 
   /**
-   * The minimum number of connections to avoid pruning
+   * The minimum number of incoming connections to avoid pruning
    */
   minConnections?: number
 
@@ -107,7 +107,7 @@ export class AutoDialler implements Startable {
       this.autoDialTimeout.clear()
     }
 
-    const minConnections = this.options.minConnections
+    const { minConnections } = this.options
 
     // Already has enough connections
     if (this.components.connectionManager.getConnections().length >= minConnections) {

src/connection-manager/index.ts

@@ -27,7 +27,12 @@ export interface ConnectionManagerConfig {
   /**
    * The maximum number of connections libp2p is willing to have before it starts disconnecting. Defaults to `Infinity`
    */
-  maxConnections: number
+  maxIncomingConnections: number
+
+  /**
+   * The maximum number of outgoing connections to keep open
+   */
+  maxOutgoingConnections: number
 
   /**
    * The minimum number of connections below which libp2p not activate preemptive disconnections. Defaults to `0`.
@@ -100,7 +105,7 @@ export interface ConnectionManagerConfig {
 
   /**
    * A list of multiaddrs that will always be allowed (except if they are in the
-   * deny list) to open connections to this node even if we've reached maxConnections
+   * deny list) to open connections to this node even if we've reached maxnOutgoingConnections
    */
   allow?: string[]
 
@@ -124,7 +129,8 @@ export interface ConnectionManagerConfig {
 }
 
 const defaultOptions: Partial<ConnectionManagerConfig> = {
-  maxConnections: Infinity,
+  maxIncomingConnections: Infinity,
+  maxOutgoingConnections: Infinity,
   minConnections: 0,
   maxEventLoopDelay: Infinity,
   pollInterval: 2000,
@@ -167,8 +173,18 @@ export class DefaultConnectionManager extends EventEmitter<ConnectionManagerEven
 
     this.opts = mergeOptions.call({ ignoreUndefined: true }, defaultOptions, init)
 
-    if (this.opts.maxConnections < this.opts.minConnections) {
-      throw errCode(new Error('Connection Manager maxConnections must be greater than minConnections'), codes.ERR_INVALID_PARAMETERS)
+    if (this.opts.maxIncomingConnections < this.opts.minConnections) {
+      throw errCode(
+        new Error('Connection Manager maxIncomingConnections must be greater than minConnections'),
+        codes.ERR_INVALID_PARAMETERS
+      )
+    }
+
+    if (this.opts.maxOutgoingConnections < this.opts.minConnections) {
+      throw errCode(
+        new Error('Connection Manager maxOutgoingConnections must be greater than minConnections'),
+        codes.ERR_INVALID_PARAMETERS
+      )
     }
 
     log('options: %o', this.opts)
@@ -427,9 +443,9 @@ export class DefaultConnectionManager extends EventEmitter<ConnectionManagerEven
     }
 
     const numConnections = this.getConnections().length
-    const toPrune = numConnections - this.opts.maxConnections
+    const toPrune = numConnections - this.opts.maxOutgoingConnections
 
-    await this._checkMaxLimit('maxConnections', numConnections, toPrune)
+    await this._checkMaxLimit('maxOutgoingConnections', numConnections, toPrune)
     this.dispatchEvent(new CustomEvent<Connection>('peer:connect', { detail: connection }))
   }
 
@@ -489,6 +505,13 @@ export class DefaultConnectionManager extends EventEmitter<ConnectionManagerEven
       }
     }
 
+    if ((this.getConnections().length + 1) > this.opts.maxOutgoingConnections) {
+      throw errCode(
+        new Error('Connection Manager maxOutgoing connections exceeded'),
+        codes.ERR_CONNECTION_DENIED
+      )
+    }
+
     let timeoutController: TimeoutController | undefined
 
     if (options?.signal == null) {
@@ -712,7 +735,7 @@ export class DefaultConnectionManager extends EventEmitter<ConnectionManagerEven
       }
     }
 
-    if (this.getConnections().length < this.opts.maxConnections) {
+    if (this.getConnections().length < this.opts.maxIncomingConnections) {
       this.incomingPendingConnections++
 
       return true

test/connection-manager/index.node.ts

@@ -57,8 +57,9 @@ describe('Connection Manager', () => {
       upgrader,
       peerStore
     }, {
-      maxConnections: 1000,
+      maxIncomingConnections: 1000,
       minConnections: 50,
+      maxOutgoingConnections: 1000,
       autoDialInterval: 1000,
       inboundUpgradeTimeout: 1000
     })
@@ -97,8 +98,9 @@ describe('Connection Manager', () => {
       upgrader,
       peerStore
     }, {
-      maxConnections: 1000,
+      maxIncomingConnections: 1000,
       minConnections: 50,
+      maxOutgoingConnections: 1000,
       autoDialInterval: 1000,
       inboundUpgradeTimeout: 1000
     })
@@ -233,7 +235,7 @@ describe('libp2p.connections', () => {
           },
           connectionManager: {
             minConnections,
-            maxConnections: 1
+            maxIncomingConnections: 1
           }
         }
       })
@@ -265,7 +267,7 @@ describe('libp2p.connections', () => {
           },
           connectionManager: {
             minConnections,
-            maxConnections: 1
+            maxIncomingConnections: 1
           }
         }
       })