Fix potential OOB during negotiation

Reported by @Grivus with SoftEther.

Closes #143

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+
+### Fixed
+
+- Index out of range during negotiation (Grivus). [#143](https://github.com/passepartoutvpn/tunnelkit/pull/143)
+
 ## 2.2.1 (2019-12-14)
 
 ### Fixed

TunnelKit/Sources/Protocols/OpenVPN/ControlChannel.swift

@@ -199,10 +199,8 @@ extension OpenVPN {
             }
             
             // drop queued out packets if ack-ed
-            for (i, packet) in queue.outbound.enumerated() {
-                if packetIds.contains(packet.packetId) {
-                    queue.outbound.remove(at: i)
-                }
+            queue.outbound.removeAll {
+                return packetIds.contains($0.packetId)
             }
             
             // remove ack-ed packets from pending