feat: drop connection after too many packets

Drop the connection after sending `2^31` packets over a single connection.

Fixes #21.

src/connection.ts

@@ -918,7 +918,7 @@ export class Connection extends EventEmitter {
     let amountToSend = Long.UZERO
 
     // Set packet number to correlate response with request
-    const requestPacket = new Packet(this.nextPacketSequence++, IlpPacketType.Prepare)
+    const requestPacket = new Packet(this.getNextPacketSequence(), IlpPacketType.Prepare)
 
     // TODO make sure these aren't too big
     requestPacket.frames = this.queuedFrames
@@ -1107,6 +1107,7 @@ export class Connection extends EventEmitter {
       }
     }
   }
+
   /**
    * (Internal) Send volly of test packests to find the exchange rate, its precision, and potential other amounts to try.
    * @private
@@ -1229,7 +1230,7 @@ export class Connection extends EventEmitter {
    */
   protected async sendTestPacket (amount: Long, timeout = DEFAULT_PACKET_TIMEOUT): Promise<Packet | IlpPacket.IlpReject | null> {
     // Set packet number to correlate response with request
-    const requestPacket = new Packet(this.nextPacketSequence++, IlpPacketType.Prepare)
+    const requestPacket = new Packet(this.getNextPacketSequence(), IlpPacketType.Prepare)
 
     this.log.trace('sending test packet %s for amount: %s. timeout: %d', requestPacket.sequence, amount, timeout)
 
@@ -1314,7 +1315,7 @@ export class Connection extends EventEmitter {
       errorMessage = ''
     }
 
-    const packet = new Packet(this.nextPacketSequence, IlpPacketType.Prepare, 0, [
+    const packet = new Packet(this.nextPacketSequence++, IlpPacketType.Prepare, 0, [
       new ConnectionCloseFrame(errorCode, errorMessage)
     ])
 
@@ -1622,6 +1623,17 @@ export class Connection extends EventEmitter {
       this._totalDelivered = result.sum
     }
   }
+
+  private getNextPacketSequence (): number {
+    const sequence = this.nextPacketSequence++
+    if (sequence >= 2 ** 31) {
+      // Destroy the connection when too many packets are sent (see https://github.com/interledger/rfcs/blob/master/0029-stream/0029-stream.md#513-maximum-number-of-packets-per-connection).
+      //
+      // Throwing here will abort the current send and `destroy()` the connection.
+      throw new ConnectionError('Connection exceeded maximum number of packets', ErrorCode.InternalError)
+    }
+    return sequence
+  }
 }
 
 function isFulfill (packet: IlpPacket.IlpFulfill | IlpPacket.IlpReject): packet is IlpPacket.IlpFulfill {

test/connection.test.ts

@@ -1631,4 +1631,23 @@ describe('Connection', function () {
       assert.isFalse(this.serverConn['streams'].has(1))
     })
   })
+
+  describe('Maximum packet count handling', function () {
+    it('destroys the connection when 2^31 packets are sent', async function () {
+      const clientStream = this.clientConn.createStream()
+      const clientSpy = sinon.spy()
+      const serverSpy = sinon.spy()
+      this.clientConn.on('error', clientSpy)
+      this.serverConn.on('error', serverSpy)
+
+      this.clientConn['nextPacketSequence'] = 2 ** 31
+      clientStream.write('hello')
+      await new Promise(setImmediate)
+
+      assert.calledOnce(clientSpy)
+      assert.calledOnce(serverSpy)
+      assert.equal(clientSpy.args[0][0].message, 'Connection exceeded maximum number of packets')
+      assert.equal(serverSpy.args[0][0].message, 'Remote connection error. Code: InternalError, message: Connection exceeded maximum number of packets')
+    })
+  })
 })