Mojo EDK: Avoid redundant queueing when sending to unknown peers

mojo/edk/system/node_controller.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "mojo/edk/system/node_controller.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "base/bind.h"
@@ skipping 676 matching lines @@
       return;
     }
   }
 #endif  // defined(OS_WIN)
 
   if (peer) {
     peer->PortsMessage(std::move(channel_message));
     return;
   }
 
-  // If we don't know who the peer is, queue the message for delivery. If this
-  // is the first message queued for the peer, we also ask the broker to
-  // introduce us to them.
+  // If we don't know who the peer is and we are the broker, we can only assume
+  // the peer is invalid, i.e., it's either a junk name or has already been
+  // disconnected.
+  scoped_refptr<NodeChannel> broker = GetBrokerChannel();
+  if (!broker) {
+    DVLOG(1) << "Dropping message for unknown peer: " << name;
+    return;
+  }
 
+  // If we aren't the broker, assume we just need to be introduced and queue
+  // until that can be either confirmed or denied by the broker.
   bool needs_introduction = false;
   {
     base::AutoLock lock(peers_lock_);
     auto& queue = pending_peer_messages_[name];
     needs_introduction = queue.empty();
     queue.emplace(std::move(channel_message));
   }
-
-  if (needs_introduction) {
-    scoped_refptr<NodeChannel> broker = GetBrokerChannel();
-    if (!broker) {
-      DVLOG(1) << "Dropping message for unknown peer: " << name;
-
-      base::AutoLock lock(peers_lock_);
-      pending_peer_messages_.erase(name);
-      return;
-    }
+  if (needs_introduction)
     broker->RequestIntroduction(name);
-  }
 }
 
 void NodeController::AcceptIncomingMessages() {
   // This is an impactically large value which should never be reached in
   // practice. See the CHECK below for usage.
   constexpr size_t kMaxAcceptedMessages = 1000000;
 
   size_t num_messages_accepted = 0;
   while (incoming_messages_flag_) {
     // TODO: We may need to be more careful to avoid starving the rest of the
@@ skipping 734 matching lines @@
 NodeController::PeerConnection::~PeerConnection() = default;
 
 NodeController::PeerConnection& NodeController::PeerConnection::
 operator=(const PeerConnection& other) = default;
 
 NodeController::PeerConnection& NodeController::PeerConnection::
 operator=(PeerConnection&& other) = default;
 
 }  // namespace edk
 }  // namespace mojo