Process incoming IQs in the same order that they were sent.

remoting/protocol/jingle_session.cc

Index: remoting/protocol/jingle_session.cc
diff --git a/remoting/protocol/jingle_session.cc b/remoting/protocol/jingle_session.cc
index 49b1f13deeaa98a3ed24c3ae1e95c1972fdc313d..6e6457abe14fc14294f4d79c3085ea4a04b46cb9 100644
--- a/remoting/protocol/jingle_session.cc
+++ b/remoting/protocol/jingle_session.cc
@@ -10,10 +10,9 @@
 #include <utility>
 
 #include "base/bind.h"
-#include "base/rand_util.h"
 #include "base/single_thread_task_runner.h"
 #include "base/stl_util.h"
-#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_split.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/time/time.h"
 #include "remoting/base/constants.h"
@@ -25,6 +24,7 @@
 #include "remoting/protocol/transport.h"
 #include "remoting/signaling/iq_sender.h"
 #include "third_party/webrtc/libjingle/xmllite/xmlelement.h"
+#include "third_party/webrtc/libjingle/xmpp/constants.h"
 #include "third_party/webrtc/p2p/base/candidate.h"
 
 using buzz::XmlElement;
@@ -47,6 +47,13 @@ const int kSessionInitiateAndAcceptTimeout = kDefaultMessageTimeout * 3;
 // Timeout for the transport-info messages.
 const int kTransportInfoTimeout = 10 * 60;
 
+// Special value for an invalid sequential ID for an incoming IQ.
+const int kInvalid = -1;
+
+// Special value indicating that any sequential ID is valid for the next
+// incoming IQ.
+const int kAny = -1;
+
 ErrorCode AuthRejectionReasonToErrorCode(
     Authenticator::RejectionReason reason) {
   switch (reason) {
@@ -63,15 +70,107 @@ ErrorCode AuthRejectionReasonToErrorCode(
   return UNKNOWN_ERROR;
 }
 
+// Extracts a sequential id from the id attribute of the IQ stanza.
+int GetSequentialId(const std::string& id) {
+  std::vector<std::string> tokens =
+      SplitString(id, "_", base::TRIM_WHITESPACE, base::SPLIT_WANT_NONEMPTY);
+  // Legacy endpoints does not encode the IQ ordering in the ID attribute
+  if (tokens.size() != 2) {
+    return kInvalid;
+  }
+
+  int result = kInvalid;
+  if (!base::StringToInt(tokens[1].c_str(), &result)) {
+    return kInvalid;
+  }
+  return result;
+}
+
 }  // namespace
 
+// A Queue that sorts incoming messages and returns them in the ascending order
+// of sequence ids. The sequence id can be extracted from the ID attribute of
+// an IQ stanza, which have the following format <opaque_string>_<sequence_id>.
+//
+// Background:
+// The chromoting signaling channel does not guarantee that the incoming IQs are
+// delivered in the order that it is sent.
+//
+// This behavior leads to transient session setup failures.  For instance,
+// a <transport-info> that is sent after a <session-info> message is sometimes
+// delivered to the client out of order, causing the client to close the
+// session due to an unexpected request.
+class JingleSession::OrderedMessageQueue {
+ public:
+  OrderedMessageQueue() {}
+  ~OrderedMessageQueue() {}
+
+  // Returns the list of messages ordered by their sequential IDs.
+  std::vector<std::unique_ptr<PendingMessage>> OnIncomingMessage(
+      const std::string& id,
+      std::unique_ptr<PendingMessage>);
+
+ private:
+  // Implements an ordered list by using map with the |sequence_id| as the key,
+  // so that |queue_| is always sorted by |sequence_id|.
+  std::map<int, std::unique_ptr<PendingMessage>> queue_;
+
+  int next_incoming_ = kAny;
+
+  DISALLOW_COPY_AND_ASSIGN(OrderedMessageQueue);
+};
+
+std::vector<std::unique_ptr<JingleSession::PendingMessage>>
+JingleSession::OrderedMessageQueue::OnIncomingMessage(
+    const std::string& id,
+    std::unique_ptr<JingleSession::PendingMessage> message) {
+  std::vector<std::unique_ptr<JingleSession::PendingMessage>> result;
+  int current = GetSequentialId(id);
+  // If there is no sequencing order encoded in the id, just return the
+  // message.
+  if (current == kInvalid) {
+    result.push_back(std::move(message));
+    return result;
+  }
+
+  if (next_incoming_ == kAny) {
+    next_incoming_ = current;
+  }
+
+  // Ensure there are no duplicate sequence ids.
+  DCHECK_GE(current, next_incoming_);
+  DCHECK(queue_.find(current) == queue_.end());
+
+  queue_.insert(std::make_pair(current, std::move(message)));
+
+  auto it = queue_.begin();
+  while (it != queue_.end() && it->first == next_incoming_) {
+    result.push_back(std::move(it->second));
+    it = queue_.erase(it);
+    next_incoming_++;
+  }
+
+  if (current - next_incoming_ >= 3) {
+    LOG(WARNING) << "Multiple messages are missing: expected= "
+                 << next_incoming_ << " current= " << current;
+  }
+  return result;
+};
+
+JingleSession::PendingMessage::PendingMessage(
+    std::unique_ptr<JingleMessage> message,
+    const ReplyCallback& reply_callback)
+    : message(std::move(message)), reply_callback(reply_callback) {}
+
+JingleSession::PendingMessage::~PendingMessage() {}
+
 JingleSession::JingleSession(JingleSessionManager* session_manager)
     : session_manager_(session_manager),
       event_handler_(nullptr),
       state_(INITIALIZING),
       error_(OK),
-      weak_factory_(this) {
-}
+      message_queue_(new OrderedMessageQueue),
+      weak_factory_(this) {}
 
 JingleSession::~JingleSession() {
   session_manager_->SessionDestroyed(this);
@@ -220,9 +319,12 @@ void JingleSession::SendTransportInfo(
       peer_address_, JingleMessage::TRANSPORT_INFO, session_id_));
   message->transport_info = std::move(transport_info);
 
+  std::unique_ptr<buzz::XmlElement> stanza = message->ToXml();
+  stanza->AddAttr(buzz::QN_ID, GetNextOutgoingId());
+
   auto request = session_manager_->iq_sender()->SendIq(
-      message->ToXml(), base::Bind(&JingleSession::OnTransportInfoResponse,
-                                   base::Unretained(this)));
+      std::move(stanza), base::Bind(&JingleSession::OnTransportInfoResponse,
+                                    base::Unretained(this)));
   if (request) {
     request->SetTimeout(base::TimeDelta::FromSeconds(kTransportInfoTimeout));
     transport_info_requests_.push_back(std::move(request));
@@ -283,9 +385,12 @@ void JingleSession::Close(protocol::ErrorCode error) {
 void JingleSession::SendMessage(std::unique_ptr<JingleMessage> message) {
   DCHECK(thread_checker_.CalledOnValidThread());
 
+  std::unique_ptr<buzz::XmlElement> stanza = message->ToXml();
+  stanza->AddAttr(buzz::QN_ID, GetNextOutgoingId());
+
   auto request = session_manager_->iq_sender()->SendIq(
-      message->ToXml(), base::Bind(&JingleSession::OnMessageResponse,
-                                   base::Unretained(this), message->action));
+      std::move(stanza), base::Bind(&JingleSession::OnMessageResponse,
+                                    base::Unretained(this), message->action));
 
   int timeout = kDefaultMessageTimeout;
   if (message->action == JingleMessage::SESSION_INITIATE ||
@@ -369,8 +474,22 @@ void JingleSession::OnTransportInfoResponse(IqRequest* request,
   }
 }
 
-void JingleSession::OnIncomingMessage(std::unique_ptr<JingleMessage> message,
+void JingleSession::OnIncomingMessage(const std::string& id,
+                                      std::unique_ptr<JingleMessage> message,
                                       const ReplyCallback& reply_callback) {
+  std::unique_ptr<PendingMessage> item(
+      new PendingMessage(std::move(message), reply_callback));
+  std::vector<std::unique_ptr<PendingMessage>> ordered =
+      message_queue_->OnIncomingMessage(id, std::move(item));
+  for (auto& message : ordered) {
+    ProcessIncomingMessage(std::move(message->message),
+                           message->reply_callback);
+  }
+}
+
+void JingleSession::ProcessIncomingMessage(
+    std::unique_ptr<JingleMessage> message,
+    const ReplyCallback& reply_callback) {
   DCHECK(thread_checker_.CalledOnValidThread());
 
   if (peer_address_ != message->from) {
@@ -396,8 +515,7 @@ void JingleSession::OnIncomingMessage(std::unique_ptr<JingleMessage> message,
       }
 
       if (!message->transport_info ||
-          !transport_->ProcessTransportInfo(
-              message->transport_info.get())) {
+          !transport_->ProcessTransportInfo(message->transport_info.get())) {
         reply_callback.Run(JingleMessageReply::BAD_REQUEST);
         return;
       }
@@ -609,5 +727,9 @@ bool JingleSession::is_session_active() {
         state_ == AUTHENTICATING || state_ == AUTHENTICATED;
 }
 
+std::string JingleSession::GetNextOutgoingId() {
+  return outgoing_id_prefix_ + "_" + base::IntToString(++next_outgoing_id_);
+}
+
 }  // namespace protocol
 }  // namespace remoting