Revert of TransportController refactoring.

webrtc/p2p/base/transport.cc

Index: webrtc/p2p/base/transport.cc
diff --git a/webrtc/p2p/base/transport.cc b/webrtc/p2p/base/transport.cc
index b7aba7540a5699e165994a143bbae9c5852ec5a8..d626ad3d65acf284a6022428cbfb43615a6d07e3 100644
--- a/webrtc/p2p/base/transport.cc
+++ b/webrtc/p2p/base/transport.cc
@@ -8,8 +8,6 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#include <utility>  // for std::pair
-
 #include "webrtc/p2p/base/transport.h"
 
 #include "webrtc/p2p/base/candidate.h"
@@ -23,6 +21,39 @@
 namespace cricket {
 
 using rtc::Bind;
+
+enum {
+  MSG_ONSIGNALINGREADY = 1,
+  MSG_ONREMOTECANDIDATE,
+  MSG_WRITESTATE,
+  MSG_REQUESTSIGNALING,
+  MSG_CANDIDATEREADY,
+  MSG_ROUTECHANGE,
+  MSG_CONNECTING,
+  MSG_CANDIDATEALLOCATIONCOMPLETE,
+  MSG_ROLECONFLICT,
+  MSG_COMPLETED,
+  MSG_FAILED,
+  MSG_RECEIVINGSTATE,
+};
+
+struct ChannelParams : public rtc::MessageData {
+  ChannelParams() : channel(NULL), candidate(NULL) {}
+  explicit ChannelParams(int component)
+      : component(component), channel(NULL), candidate(NULL) {}
+  explicit ChannelParams(Candidate* candidate)
+      : channel(NULL), candidate(candidate) {
+  }
+
+  ~ChannelParams() {
+    delete candidate;
+  }
+
+  std::string name;
+  int component;
+  TransportChannelImpl* channel;
+  Candidate* candidate;
+};
 
 static bool VerifyIceParams(const TransportDescription& desc) {
   // For legacy protocols.
@@ -65,59 +96,58 @@
                                new_desc.ice_ufrag, new_desc.ice_pwd);
 }
 
-Transport::Transport(const std::string& name, PortAllocator* allocator)
-    : name_(name), allocator_(allocator) {}
+Transport::Transport(rtc::Thread* signaling_thread,
+                     rtc::Thread* worker_thread,
+                     const std::string& content_name,
+                     PortAllocator* allocator)
+    : signaling_thread_(signaling_thread),
+      worker_thread_(worker_thread),
+      content_name_(content_name),
+      allocator_(allocator),
+      destroyed_(false),
+      readable_(TRANSPORT_STATE_NONE),
+      writable_(TRANSPORT_STATE_NONE),
+      receiving_(TRANSPORT_STATE_NONE),
+      was_writable_(false),
+      connect_requested_(false),
+      ice_role_(ICEROLE_UNKNOWN),
+      tiebreaker_(0),
+      remote_ice_mode_(ICEMODE_FULL),
+      channel_receiving_timeout_(-1) {
+}
 
 Transport::~Transport() {
-  ASSERT(channels_destroyed_);
-}
-
-bool Transport::AllChannelsCompleted() const {
-  // We aren't completed until at least one channel is complete, so if there
-  // are no channels, we aren't complete yet.
-  if (channels_.empty()) {
-    LOG(LS_INFO) << name() << " transport is not complete"
-                 << " because it has no TransportChannels";
-    return false;
-  }
-
-  // A Transport's ICE process is completed if all of its channels are writable,
-  // have finished allocating candidates, and have pruned all but one of their
-  // connections.
-  for (const auto& iter : channels_) {
-    const TransportChannelImpl* channel = iter.second.get();
-    bool complete =
-        channel->writable() &&
-        channel->GetState() == TransportChannelState::STATE_COMPLETED &&
-        channel->GetIceRole() == ICEROLE_CONTROLLING &&
-        channel->gathering_state() == kIceGatheringComplete;
-    if (!complete) {
-      LOG(LS_INFO) << name() << " transport is not complete"
-                   << " because a channel is still incomplete.";
-      return false;
-    }
-  }
-
-  return true;
-}
-
-bool Transport::AnyChannelFailed() const {
-  for (const auto& iter : channels_) {
-    if (iter.second->GetState() == TransportChannelState::STATE_FAILED) {
-      return true;
-    }
-  }
-  return false;
+  ASSERT(signaling_thread_->IsCurrent());
+  ASSERT(destroyed_);
 }
 
 void Transport::SetIceRole(IceRole role) {
-  ice_role_ = role;
-  for (auto& iter : channels_) {
-    iter.second->SetIceRole(ice_role_);
-  }
+  worker_thread_->Invoke<void>(Bind(&Transport::SetIceRole_w, this, role));
+}
+
+void Transport::SetCertificate(
+    const rtc::scoped_refptr<rtc::RTCCertificate>& certificate) {
+  worker_thread_->Invoke<void>(Bind(&Transport::SetCertificate_w, this,
+                                    certificate));
+}
+
+bool Transport::GetCertificate(
+    rtc::scoped_refptr<rtc::RTCCertificate>* certificate) {
+  // The identity is set on the worker thread, so for safety it must also be
+  // acquired on the worker thread.
+  return worker_thread_->Invoke<bool>(
+      Bind(&Transport::GetCertificate_w, this, certificate));
 }
 
 bool Transport::GetRemoteSSLCertificate(rtc::SSLCertificate** cert) {
+  // Channels can be deleted on the worker thread, so for safety the remote
+  // certificate is acquired on the worker thread.
+  return worker_thread_->Invoke<bool>(
+      Bind(&Transport::GetRemoteSSLCertificate_w, this, cert));
+}
+
+bool Transport::GetRemoteSSLCertificate_w(rtc::SSLCertificate** cert) {
+  ASSERT(worker_thread()->IsCurrent());
   if (channels_.empty())
     return false;
 
@@ -126,6 +156,12 @@
 }
 
 void Transport::SetChannelReceivingTimeout(int timeout_ms) {
+  worker_thread_->Invoke<void>(
+      Bind(&Transport::SetChannelReceivingTimeout_w, this, timeout_ms));
+}
+
+void Transport::SetChannelReceivingTimeout_w(int timeout_ms) {
+  ASSERT(worker_thread()->IsCurrent());
   channel_receiving_timeout_ = timeout_ms;
   for (const auto& kv : channels_) {
     kv.second->SetReceivingTimeout(timeout_ms);
@@ -136,73 +172,35 @@
     const TransportDescription& description,
     ContentAction action,
     std::string* error_desc) {
-  bool ret = true;
-
-  if (!VerifyIceParams(description)) {
-    return BadTransportDescription("Invalid ice-ufrag or ice-pwd length",
-                                   error_desc);
-  }
-
-  if (local_description_ &&
-      IceCredentialsChanged(*local_description_, description)) {
-    IceRole new_ice_role =
-        (action == CA_OFFER) ? ICEROLE_CONTROLLING : ICEROLE_CONTROLLED;
-
-    // It must be called before ApplyLocalTransportDescription, which may
-    // trigger an ICE restart and depends on the new ICE role.
-    SetIceRole(new_ice_role);
-  }
-
-  local_description_.reset(new TransportDescription(description));
-
-  for (auto& iter : channels_) {
-    ret &= ApplyLocalTransportDescription(iter.second.get(), error_desc);
-  }
-  if (!ret) {
-    return false;
-  }
-
-  // If PRANSWER/ANSWER is set, we should decide transport protocol type.
-  if (action == CA_PRANSWER || action == CA_ANSWER) {
-    ret &= NegotiateTransportDescription(action, error_desc);
-  }
-  if (ret) {
-    local_description_set_ = true;
-    ConnectChannels();
-  }
-
-  return ret;
+  return worker_thread_->Invoke<bool>(Bind(
+      &Transport::SetLocalTransportDescription_w, this,
+      description, action, error_desc));
 }
 
 bool Transport::SetRemoteTransportDescription(
     const TransportDescription& description,
     ContentAction action,
     std::string* error_desc) {
-  bool ret = true;
-
-  if (!VerifyIceParams(description)) {
-    return BadTransportDescription("Invalid ice-ufrag or ice-pwd length",
-                                   error_desc);
-  }
-
-  remote_description_.reset(new TransportDescription(description));
-  for (auto& iter : channels_) {
-    ret &= ApplyRemoteTransportDescription(iter.second.get(), error_desc);
-  }
-
-  // If PRANSWER/ANSWER is set, we should decide transport protocol type.
-  if (action == CA_PRANSWER || action == CA_ANSWER) {
-    ret = NegotiateTransportDescription(CA_OFFER, error_desc);
-  }
-  if (ret) {
-    remote_description_set_ = true;
-  }
-
-  return ret;
+  return worker_thread_->Invoke<bool>(Bind(
+      &Transport::SetRemoteTransportDescription_w, this,
+      description, action, error_desc));
 }
 
 TransportChannelImpl* Transport::CreateChannel(int component) {
+  return worker_thread_->Invoke<TransportChannelImpl*>(Bind(
+      &Transport::CreateChannel_w, this, component));
+}
+
+TransportChannelImpl* Transport::CreateChannel_w(int component) {
+  ASSERT(worker_thread()->IsCurrent());
   TransportChannelImpl* impl;
+  // TODO(tommi): We don't really need to grab the lock until the actual call
+  // to insert() below and presumably hold it throughout initialization of
+  // |impl| after the impl_exists check.  Maybe we can factor that out to
+  // a separate function and not grab the lock in this function.
+  // Actually, we probably don't need to hold the lock while initializing
+  // |impl| since we can just do the insert when that's done.
+  rtc::CritScope cs(&crit_);
 
   // Create the entry if it does not exist.
   bool impl_exists = false;
@@ -218,7 +216,7 @@
 
   // Increase the ref count.
   iterator->second.AddRef();
-  channels_destroyed_ = false;
+  destroyed_ = false;
 
   if (impl_exists) {
     // If this is an existing channel, we should just return it without
@@ -230,21 +228,23 @@
   impl->SetIceRole(ice_role_);
   impl->SetIceTiebreaker(tiebreaker_);
   impl->SetReceivingTimeout(channel_receiving_timeout_);
-  // TODO(ronghuawu): Change CreateChannel to be able to return error since
-  // below Apply**Description calls can fail.
+  // TODO(ronghuawu): Change CreateChannel_w to be able to return error since
+  // below Apply**Description_w calls can fail.
   if (local_description_)
-    ApplyLocalTransportDescription(impl, NULL);
+    ApplyLocalTransportDescription_w(impl, NULL);
   if (remote_description_)
-    ApplyRemoteTransportDescription(impl, NULL);
+    ApplyRemoteTransportDescription_w(impl, NULL);
   if (local_description_ && remote_description_)
-    ApplyNegotiatedTransportDescription(impl, NULL);
+    ApplyNegotiatedTransportDescription_w(impl, NULL);
 
   impl->SignalWritableState.connect(this, &Transport::OnChannelWritableState);
   impl->SignalReceivingState.connect(this, &Transport::OnChannelReceivingState);
-  impl->SignalGatheringState.connect(this, &Transport::OnChannelGatheringState);
-  impl->SignalCandidateGathered.connect(this,
-                                        &Transport::OnChannelCandidateGathered);
+  impl->SignalRequestSignaling.connect(
+      this, &Transport::OnChannelRequestSignaling);
+  impl->SignalCandidateReady.connect(this, &Transport::OnChannelCandidateReady);
   impl->SignalRouteChange.connect(this, &Transport::OnChannelRouteChange);
+  impl->SignalCandidatesAllocationDone.connect(
+      this, &Transport::OnChannelCandidatesAllocationDone);
   impl->SignalRoleConflict.connect(this, &Transport::OnRoleConflict);
   impl->SignalConnectionRemoved.connect(
       this, &Transport::OnChannelConnectionRemoved);
@@ -254,22 +254,36 @@
     if (channels_.size() == 1) {
       // If this is the first channel, then indicate that we have started
       // connecting.
-      SignalConnecting(this);
+      signaling_thread()->Post(this, MSG_CONNECTING, NULL);
     }
   }
   return impl;
 }
 
 TransportChannelImpl* Transport::GetChannel(int component) {
+  // TODO(tommi,pthatcher): Since we're returning a pointer from the channels_
+  // map, shouldn't we assume that we're on the worker thread? (The pointer
+  // will be used outside of the lock).
+  // And if we're on the worker thread, which is the only thread that modifies
+  // channels_, can we skip grabbing the lock?
+  rtc::CritScope cs(&crit_);
   ChannelMap::iterator iter = channels_.find(component);
   return (iter != channels_.end()) ? iter->second.get() : NULL;
 }
 
 bool Transport::HasChannels() {
+  rtc::CritScope cs(&crit_);
   return !channels_.empty();
 }
 
 void Transport::DestroyChannel(int component) {
+  worker_thread_->Invoke<void>(Bind(
+      &Transport::DestroyChannel_w, this, component));
+}
+
+void Transport::DestroyChannel_w(int component) {
+  ASSERT(worker_thread()->IsCurrent());
+
   ChannelMap::iterator iter = channels_.find(component);
   if (iter == channels_.end())
     return;
@@ -279,30 +293,34 @@
   iter->second.DecRef();
   if (!iter->second.ref()) {
     impl = iter->second.get();
+    rtc::CritScope cs(&crit_);
     channels_.erase(iter);
   }
 
   if (connect_requested_ && channels_.empty()) {
     // We're no longer attempting to connect.
-    SignalConnecting(this);
+    signaling_thread()->Post(this, MSG_CONNECTING, NULL);
   }
 
   if (impl) {
+    // Check in case the deleted channel was the only non-writable channel.
+    OnChannelWritableState(impl);
     DestroyTransportChannel(impl);
-    // Need to update aggregate state after destroying a channel,
-    // for example if it was the only one that wasn't yet writable.
-    UpdateWritableState();
-    UpdateReceivingState();
-    UpdateGatheringState();
-    MaybeSignalCompleted();
   }
 }
 
 void Transport::ConnectChannels() {
+  ASSERT(signaling_thread()->IsCurrent());
+  worker_thread_->Invoke<void>(Bind(&Transport::ConnectChannels_w, this));
+}
+
+void Transport::ConnectChannels_w() {
+  ASSERT(worker_thread()->IsCurrent());
   if (connect_requested_ || channels_.empty())
     return;
 
   connect_requested_ = true;
+  signaling_thread()->Post(this, MSG_CANDIDATEREADY, NULL);
 
   if (!local_description_) {
     // TOOD(mallinath) : TransportDescription(TD) shouldn't be generated here.
@@ -311,28 +329,38 @@
     // Session.
     // Session must generate local TD before remote candidates pushed when
     // initiate request initiated by the remote.
-    LOG(LS_INFO) << "Transport::ConnectChannels: No local description has "
+    LOG(LS_INFO) << "Transport::ConnectChannels_w: No local description has "
                  << "been set. Will generate one.";
-    TransportDescription desc(
-        std::vector<std::string>(), rtc::CreateRandomString(ICE_UFRAG_LENGTH),
-        rtc::CreateRandomString(ICE_PWD_LENGTH), ICEMODE_FULL,
-        CONNECTIONROLE_NONE, NULL, Candidates());
-    SetLocalTransportDescription(desc, CA_OFFER, NULL);
-  }
-
-  CallChannels(&TransportChannelImpl::Connect);
-  if (HasChannels()) {
-    SignalConnecting(this);
-  }
-}
-
-void Transport::MaybeStartGathering() {
-  if (connect_requested_) {
-    CallChannels(&TransportChannelImpl::MaybeStartGathering);
-  }
+    TransportDescription desc(std::vector<std::string>(),
+                              rtc::CreateRandomString(ICE_UFRAG_LENGTH),
+                              rtc::CreateRandomString(ICE_PWD_LENGTH),
+                              ICEMODE_FULL, CONNECTIONROLE_NONE, NULL,
+                              Candidates());
+    SetLocalTransportDescription_w(desc, CA_OFFER, NULL);
+  }
+
+  CallChannels_w(&TransportChannelImpl::Connect);
+  if (!channels_.empty()) {
+    signaling_thread()->Post(this, MSG_CONNECTING, NULL);
+  }
+}
+
+void Transport::OnConnecting_s() {
+  ASSERT(signaling_thread()->IsCurrent());
+  SignalConnecting(this);
 }
 
 void Transport::DestroyAllChannels() {
+  ASSERT(signaling_thread()->IsCurrent());
+  worker_thread_->Invoke<void>(Bind(&Transport::DestroyAllChannels_w, this));
+  worker_thread()->Clear(this);
+  signaling_thread()->Clear(this);
+  destroyed_ = true;
+}
+
+void Transport::DestroyAllChannels_w() {
+  ASSERT(worker_thread()->IsCurrent());
+
   std::vector<TransportChannelImpl*> impls;
   for (auto& iter : channels_) {
     iter.second.DecRef();
@@ -340,15 +368,27 @@
       impls.push_back(iter.second.get());
   }
 
-  channels_.clear();
-
-  for (TransportChannelImpl* impl : impls) {
-    DestroyTransportChannel(impl);
-  }
-  channels_destroyed_ = true;
-}
-
-void Transport::CallChannels(TransportChannelFunc func) {
+  {
+    rtc::CritScope cs(&crit_);
+    channels_.clear();
+  }
+
+  for (size_t i = 0; i < impls.size(); ++i)
+    DestroyTransportChannel(impls[i]);
+}
+
+void Transport::OnSignalingReady() {
+  ASSERT(signaling_thread()->IsCurrent());
+  if (destroyed_) return;
+
+  worker_thread()->Post(this, MSG_ONSIGNALINGREADY, NULL);
+
+  // Notify the subclass.
+  OnTransportSignalingReady();
+}
+
+void Transport::CallChannels_w(TransportChannelFunc func) {
+  ASSERT(worker_thread()->IsCurrent());
   for (const auto& iter : channels_) {
     ((iter.second.get())->*func)();
   }
@@ -387,7 +427,14 @@
 
 
 bool Transport::GetStats(TransportStats* stats) {
-  stats->transport_name = name();
+  ASSERT(signaling_thread()->IsCurrent());
+  return worker_thread_->Invoke<bool>(Bind(
+      &Transport::GetStats_w, this, stats));
+}
+
+bool Transport::GetStats_w(TransportStats* stats) {
+  ASSERT(worker_thread()->IsCurrent());
+  stats->content_name = content_name();
   stats->channel_stats.clear();
   for (auto iter : channels_) {
     ChannelMapEntry& entry = iter.second;
@@ -403,45 +450,82 @@
   return true;
 }
 
-bool Transport::AddRemoteCandidates(const std::vector<Candidate>& candidates,
-                                    std::string* error) {
-  ASSERT(!channels_destroyed_);
-  // Verify each candidate before passing down to transport layer.
-  for (const Candidate& cand : candidates) {
-    if (!VerifyCandidate(cand, error)) {
-      return false;
-    }
-    if (!HasChannel(cand.component())) {
-      *error = "Candidate has unknown component: " + cand.ToString() +
-               " for content: " + name();
-      return false;
-    }
-  }
-
+bool Transport::GetSslRole(rtc::SSLRole* ssl_role) const {
+  return worker_thread_->Invoke<bool>(Bind(
+      &Transport::GetSslRole_w, this, ssl_role));
+}
+
+bool Transport::SetSslMaxProtocolVersion(rtc::SSLProtocolVersion version) {
+  return worker_thread_->Invoke<bool>(Bind(
+      &Transport::SetSslMaxProtocolVersion_w, this, version));
+}
+
+void Transport::OnRemoteCandidates(const std::vector<Candidate>& candidates) {
   for (std::vector<Candidate>::const_iterator iter = candidates.begin();
        iter != candidates.end();
        ++iter) {
-    TransportChannelImpl* channel = GetChannel(iter->component());
-    if (channel != NULL) {
-      channel->AddRemoteCandidate(*iter);
-    }
-  }
-  return true;
+    OnRemoteCandidate(*iter);
+  }
+}
+
+void Transport::OnRemoteCandidate(const Candidate& candidate) {
+  ASSERT(signaling_thread()->IsCurrent());
+  if (destroyed_) return;
+
+  if (!HasChannel(candidate.component())) {
+    LOG(LS_WARNING) << "Ignoring candidate for unknown component "
+                    << candidate.component();
+    return;
+  }
+
+  ChannelParams* params = new ChannelParams(new Candidate(candidate));
+  worker_thread()->Post(this, MSG_ONREMOTECANDIDATE, params);
+}
+
+void Transport::OnRemoteCandidate_w(const Candidate& candidate) {
+  ASSERT(worker_thread()->IsCurrent());
+  ChannelMap::iterator iter = channels_.find(candidate.component());
+  // It's ok for a channel to go away while this message is in transit.
+  if (iter != channels_.end()) {
+    iter->second->OnCandidate(candidate);
+  }
 }
 
 void Transport::OnChannelWritableState(TransportChannel* channel) {
-  LOG(LS_INFO) << name() << " TransportChannel " << channel->component()
-               << " writability changed to " << channel->writable()
-               << ". Check if transport is complete.";
-  UpdateWritableState();
-  MaybeSignalCompleted();
+  ASSERT(worker_thread()->IsCurrent());
+  signaling_thread()->Post(this, MSG_WRITESTATE, NULL);
+
+  MaybeCompleted_w();
+}
+
+void Transport::OnChannelWritableState_s() {
+  ASSERT(signaling_thread()->IsCurrent());
+  TransportState writable = GetTransportState_s(TRANSPORT_WRITABLE_STATE);
+  if (writable_ != writable) {
+    was_writable_ = (writable_ == TRANSPORT_STATE_ALL);
+    writable_ = writable;
+    SignalWritableState(this);
+  }
 }
 
 void Transport::OnChannelReceivingState(TransportChannel* channel) {
-  UpdateReceivingState();
-}
-
-TransportState Transport::GetTransportState(TransportStateType state_type) {
+  ASSERT(worker_thread()->IsCurrent());
+  signaling_thread()->Post(this, MSG_RECEIVINGSTATE);
+}
+
+void Transport::OnChannelReceivingState_s() {
+  ASSERT(signaling_thread()->IsCurrent());
+  TransportState receiving = GetTransportState_s(TRANSPORT_RECEIVING_STATE);
+  if (receiving_ != receiving) {
+    receiving_ = receiving;
+    SignalReceivingState(this);
+  }
+}
+
+TransportState Transport::GetTransportState_s(TransportStateType state_type) {
+  ASSERT(signaling_thread()->IsCurrent());
+
+  rtc::CritScope cs(&crit_);
   bool any = false;
   bool all = !channels_.empty();
   for (const auto iter : channels_) {
@@ -469,44 +553,106 @@
   return TRANSPORT_STATE_NONE;
 }
 
-void Transport::OnChannelGatheringState(TransportChannelImpl* channel) {
-  ASSERT(channels_.find(channel->component()) != channels_.end());
-  UpdateGatheringState();
-  if (gathering_state_ == kIceGatheringComplete) {
-    // If UpdateGatheringState brought us to kIceGatheringComplete, check if
-    // our connection state is also "Completed". Otherwise, there's no point in
-    // checking (since it would only produce log messages).
-    MaybeSignalCompleted();
-  }
-}
-
-void Transport::OnChannelCandidateGathered(TransportChannelImpl* channel,
-                                           const Candidate& candidate) {
+void Transport::OnChannelRequestSignaling(TransportChannelImpl* channel) {
+  ASSERT(worker_thread()->IsCurrent());
+  // Resetting ICE state for the channel.
+  ChannelMap::iterator iter = channels_.find(channel->component());
+  if (iter != channels_.end())
+    iter->second.set_candidates_allocated(false);
+  signaling_thread()->Post(this, MSG_REQUESTSIGNALING, nullptr);
+}
+
+void Transport::OnChannelRequestSignaling_s() {
+  ASSERT(signaling_thread()->IsCurrent());
+  LOG(LS_INFO) << "Transport: " << content_name_ << ", allocating candidates";
+  SignalRequestSignaling(this);
+}
+
+void Transport::OnChannelCandidateReady(TransportChannelImpl* channel,
+                                        const Candidate& candidate) {
   // We should never signal peer-reflexive candidates.
   if (candidate.type() == PRFLX_PORT_TYPE) {
     ASSERT(false);
     return;
   }
 
+  ASSERT(worker_thread()->IsCurrent());
+  rtc::CritScope cs(&crit_);
+  ready_candidates_.push_back(candidate);
+
+  // We hold any messages until the client lets us connect.
+  if (connect_requested_) {
+    signaling_thread()->Post(
+        this, MSG_CANDIDATEREADY, NULL);
+  }
+}
+
+void Transport::OnChannelCandidateReady_s() {
+  ASSERT(signaling_thread()->IsCurrent());
   ASSERT(connect_requested_);
+
   std::vector<Candidate> candidates;
-  candidates.push_back(candidate);
-  SignalCandidatesGathered(this, candidates);
+  {
+    rtc::CritScope cs(&crit_);
+    candidates.swap(ready_candidates_);
+  }
+
+  // we do the deleting of Candidate* here to keep the new above and
+  // delete below close to each other
+  if (!candidates.empty()) {
+    SignalCandidatesReady(this, candidates);
+  }
 }
 
 void Transport::OnChannelRouteChange(TransportChannel* channel,
                                      const Candidate& remote_candidate) {
+  ASSERT(worker_thread()->IsCurrent());
+  ChannelParams* params = new ChannelParams(new Candidate(remote_candidate));
+  params->channel = static_cast<cricket::TransportChannelImpl*>(channel);
+  signaling_thread()->Post(this, MSG_ROUTECHANGE, params);
+}
+
+void Transport::OnChannelRouteChange_s(const TransportChannel* channel,
+                                       const Candidate& remote_candidate) {
+  ASSERT(signaling_thread()->IsCurrent());
   SignalRouteChange(this, remote_candidate.component(), remote_candidate);
 }
 
+void Transport::OnChannelCandidatesAllocationDone(
+    TransportChannelImpl* channel) {
+  ASSERT(worker_thread()->IsCurrent());
+  ChannelMap::iterator iter = channels_.find(channel->component());
+  ASSERT(iter != channels_.end());
+  LOG(LS_INFO) << "Transport: " << content_name_ << ", component "
+               << channel->component() << " allocation complete";
+
+  iter->second.set_candidates_allocated(true);
+
+  // If all channels belonging to this Transport got signal, then
+  // forward this signal to upper layer.
+  // Can this signal arrive before all transport channels are created?
+  for (auto& iter : channels_) {
+    if (!iter.second.candidates_allocated())
+      return;
+  }
+  signaling_thread_->Post(this, MSG_CANDIDATEALLOCATIONCOMPLETE);
+
+  MaybeCompleted_w();
+}
+
+void Transport::OnChannelCandidatesAllocationDone_s() {
+  ASSERT(signaling_thread()->IsCurrent());
+  LOG(LS_INFO) << "Transport: " << content_name_ << " allocation complete";
+  SignalCandidatesAllocationDone(this);
+}
+
 void Transport::OnRoleConflict(TransportChannelImpl* channel) {
-  SignalRoleConflict();
+  signaling_thread_->Post(this, MSG_ROLECONFLICT);
 }
 
 void Transport::OnChannelConnectionRemoved(TransportChannelImpl* channel) {
-  LOG(LS_INFO) << name() << " TransportChannel " << channel->component()
-               << " connection removed. Check if transport is complete.";
-  MaybeSignalCompleted();
+  ASSERT(worker_thread()->IsCurrent());
+  MaybeCompleted_w();
 
   // Check if the state is now Failed.
   // Failed is only available in the Controlling ICE role.
@@ -514,97 +660,158 @@
     return;
   }
 
-  // Failed can only occur after candidate gathering has stopped.
-  if (channel->gathering_state() != kIceGatheringComplete) {
+  ChannelMap::iterator iter = channels_.find(channel->component());
+  ASSERT(iter != channels_.end());
+  // Failed can only occur after candidate allocation has stopped.
+  if (!iter->second.candidates_allocated()) {
     return;
   }
 
   if (channel->GetState() == TransportChannelState::STATE_FAILED) {
     // A Transport has failed if any of its channels have no remaining
     // connections.
-    SignalFailed(this);
-  }
-}
-
-void Transport::MaybeSignalCompleted() {
-  if (AllChannelsCompleted()) {
-    LOG(LS_INFO) << name() << " transport is complete"
-                 << " because all the channels are complete.";
-    SignalCompleted(this);
-  }
-  // TODO(deadbeef): Should we do anything if we previously were completed,
-  // but now are not (if, for example, a new remote candidate is added)?
-}
-
-void Transport::UpdateGatheringState() {
-  IceGatheringState new_state = kIceGatheringNew;
-  bool any_gathering = false;
-  bool all_complete = !channels_.empty();
-  for (const auto& kv : channels_) {
-    any_gathering =
-        any_gathering || kv.second->gathering_state() != kIceGatheringNew;
-    all_complete =
-        all_complete && kv.second->gathering_state() == kIceGatheringComplete;
-  }
-  if (all_complete) {
-    new_state = kIceGatheringComplete;
-  } else if (any_gathering) {
-    new_state = kIceGatheringGathering;
-  }
-
-  if (gathering_state_ != new_state) {
-    gathering_state_ = new_state;
-    if (gathering_state_ == kIceGatheringGathering) {
-      LOG(LS_INFO) << "Transport: " << name_ << ", gathering candidates";
-    } else if (gathering_state_ == kIceGatheringComplete) {
-      LOG(LS_INFO) << "Transport " << name() << " gathering complete.";
+    signaling_thread_->Post(this, MSG_FAILED);
+  }
+}
+
+void Transport::MaybeCompleted_w() {
+  ASSERT(worker_thread()->IsCurrent());
+
+  // When there is no channel created yet, calling this function could fire an
+  // IceConnectionCompleted event prematurely.
+  if (channels_.empty()) {
+    return;
+  }
+
+  // A Transport's ICE process is completed if all of its channels are writable,
+  // have finished allocating candidates, and have pruned all but one of their
+  // connections.
+  for (const auto& iter : channels_) {
+    const TransportChannelImpl* channel = iter.second.get();
+    if (!(channel->writable() &&
+          channel->GetState() == TransportChannelState::STATE_COMPLETED &&
+          channel->GetIceRole() == ICEROLE_CONTROLLING &&
+          iter.second.candidates_allocated())) {
+      return;
     }
-    SignalGatheringState(this);
-  }
-}
-
-void Transport::UpdateReceivingState() {
-  TransportState receiving = GetTransportState(TRANSPORT_RECEIVING_STATE);
-  if (receiving_ != receiving) {
-    receiving_ = receiving;
-    SignalReceivingState(this);
-  }
-}
-
-void Transport::UpdateWritableState() {
-  TransportState writable = GetTransportState(TRANSPORT_WRITABLE_STATE);
-  LOG(LS_INFO) << name() << " transport writable state changed? " << writable_
-               << " => " << writable;
-  if (writable_ != writable) {
-    was_writable_ = (writable_ == TRANSPORT_STATE_ALL);
-    writable_ = writable;
-    SignalWritableState(this);
-  }
-}
-
-bool Transport::ApplyLocalTransportDescription(TransportChannelImpl* ch,
-                                               std::string* error_desc) {
+  }
+
+  signaling_thread_->Post(this, MSG_COMPLETED);
+}
+
+void Transport::SetIceRole_w(IceRole role) {
+  ASSERT(worker_thread()->IsCurrent());
+  rtc::CritScope cs(&crit_);
+  ice_role_ = role;
+  for (auto& iter : channels_) {
+    iter.second->SetIceRole(ice_role_);
+  }
+}
+
+void Transport::SetRemoteIceMode_w(IceMode mode) {
+  ASSERT(worker_thread()->IsCurrent());
+  remote_ice_mode_ = mode;
+  // Shouldn't channels be created after this method executed?
+  for (auto& iter : channels_) {
+    iter.second->SetRemoteIceMode(remote_ice_mode_);
+  }
+}
+
+bool Transport::SetLocalTransportDescription_w(
+    const TransportDescription& desc,
+    ContentAction action,
+    std::string* error_desc) {
+  ASSERT(worker_thread()->IsCurrent());
+  bool ret = true;
+
+  if (!VerifyIceParams(desc)) {
+    return BadTransportDescription("Invalid ice-ufrag or ice-pwd length",
+                                   error_desc);
+  }
+
+  // TODO(tommi,pthatcher): I'm not sure why we need to grab this lock at this
+  // point. |local_description_| seems to always be modified on the worker
+  // thread, so we should be able to use it here without grabbing the lock.
+  // However, we _might_ need it before the call to reset() below?
+  // Raw access to |local_description_| is granted to derived transports outside
+  // of locking (see local_description() in the header file).
+  // The contract is that the derived implementations must be aware of when the
+  // description might change and do appropriate synchronization.
+  rtc::CritScope cs(&crit_);
+  if (local_description_ && IceCredentialsChanged(*local_description_, desc)) {
+    IceRole new_ice_role = (action == CA_OFFER) ? ICEROLE_CONTROLLING
+                                                : ICEROLE_CONTROLLED;
+
+    // It must be called before ApplyLocalTransportDescription_w, which may
+    // trigger an ICE restart and depends on the new ICE role.
+    SetIceRole_w(new_ice_role);
+  }
+
+  local_description_.reset(new TransportDescription(desc));
+
+  for (auto& iter : channels_) {
+    ret &= ApplyLocalTransportDescription_w(iter.second.get(), error_desc);
+  }
+  if (!ret)
+    return false;
+
+  // If PRANSWER/ANSWER is set, we should decide transport protocol type.
+  if (action == CA_PRANSWER || action == CA_ANSWER) {
+    ret &= NegotiateTransportDescription_w(action, error_desc);
+  }
+  return ret;
+}
+
+bool Transport::SetRemoteTransportDescription_w(
+    const TransportDescription& desc,
+    ContentAction action,
+    std::string* error_desc) {
+  bool ret = true;
+
+  if (!VerifyIceParams(desc)) {
+    return BadTransportDescription("Invalid ice-ufrag or ice-pwd length",
+                                   error_desc);
+  }
+
+  // TODO(tommi,pthatcher): See todo for local_description_ above.
+  rtc::CritScope cs(&crit_);
+  remote_description_.reset(new TransportDescription(desc));
+  for (auto& iter : channels_) {
+    ret &= ApplyRemoteTransportDescription_w(iter.second.get(), error_desc);
+  }
+
+  // If PRANSWER/ANSWER is set, we should decide transport protocol type.
+  if (action == CA_PRANSWER || action == CA_ANSWER) {
+    ret = NegotiateTransportDescription_w(CA_OFFER, error_desc);
+  }
+  return ret;
+}
+
+bool Transport::ApplyLocalTransportDescription_w(TransportChannelImpl* ch,
+                                                 std::string* error_desc) {
+  ASSERT(worker_thread()->IsCurrent());
   ch->SetIceCredentials(local_description_->ice_ufrag,
                         local_description_->ice_pwd);
   return true;
 }
 
-bool Transport::ApplyRemoteTransportDescription(TransportChannelImpl* ch,
-                                                std::string* error_desc) {
+bool Transport::ApplyRemoteTransportDescription_w(TransportChannelImpl* ch,
+                                                  std::string* error_desc) {
   ch->SetRemoteIceCredentials(remote_description_->ice_ufrag,
                               remote_description_->ice_pwd);
   return true;
 }
 
-bool Transport::ApplyNegotiatedTransportDescription(
-    TransportChannelImpl* channel,
-    std::string* error_desc) {
+bool Transport::ApplyNegotiatedTransportDescription_w(
+    TransportChannelImpl* channel, std::string* error_desc) {
+  ASSERT(worker_thread()->IsCurrent());
   channel->SetRemoteIceMode(remote_ice_mode_);
   return true;
 }
 
-bool Transport::NegotiateTransportDescription(ContentAction local_role,
-                                              std::string* error_desc) {
+bool Transport::NegotiateTransportDescription_w(ContentAction local_role,
+                                                std::string* error_desc) {
+  ASSERT(worker_thread()->IsCurrent());
   // TODO(ekr@rtfm.com): This is ICE-specific stuff. Refactor into
   // P2PTransport.
 
@@ -612,7 +819,7 @@
   // ice_lite, this local end point should take CONTROLLING role.
   if (ice_role_ == ICEROLE_CONTROLLED &&
       remote_description_->ice_mode == ICEMODE_LITE) {
-    SetIceRole(ICEROLE_CONTROLLING);
+    SetIceRole_w(ICEROLE_CONTROLLING);
   }
 
   // Update remote ice_mode to all existing channels.
@@ -624,10 +831,57 @@
   // creation, we have the negotiation state saved until a new
   // negotiation happens.
   for (auto& iter : channels_) {
-    if (!ApplyNegotiatedTransportDescription(iter.second.get(), error_desc))
+    if (!ApplyNegotiatedTransportDescription_w(iter.second.get(), error_desc))
       return false;
   }
   return true;
 }
 
+void Transport::OnMessage(rtc::Message* msg) {
+  switch (msg->message_id) {
+    case MSG_ONSIGNALINGREADY:
+      CallChannels_w(&TransportChannelImpl::OnSignalingReady);
+      break;
+    case MSG_ONREMOTECANDIDATE: {
+        ChannelParams* params = static_cast<ChannelParams*>(msg->pdata);
+        OnRemoteCandidate_w(*params->candidate);
+        delete params;
+      }
+      break;
+    case MSG_CONNECTING:
+      OnConnecting_s();
+      break;
+    case MSG_WRITESTATE:
+      OnChannelWritableState_s();
+      break;
+    case MSG_RECEIVINGSTATE:
+      OnChannelReceivingState_s();
+      break;
+    case MSG_REQUESTSIGNALING:
+      OnChannelRequestSignaling_s();
+      break;
+    case MSG_CANDIDATEREADY:
+      OnChannelCandidateReady_s();
+      break;
+    case MSG_ROUTECHANGE: {
+        ChannelParams* params = static_cast<ChannelParams*>(msg->pdata);
+        OnChannelRouteChange_s(params->channel, *params->candidate);
+        delete params;
+      }
+      break;
+    case MSG_CANDIDATEALLOCATIONCOMPLETE:
+      OnChannelCandidatesAllocationDone_s();
+      break;
+    case MSG_ROLECONFLICT:
+      SignalRoleConflict();
+      break;
+    case MSG_COMPLETED:
+      SignalCompleted(this);
+      break;
+    case MSG_FAILED:
+      SignalFailed(this);
+      break;
+  }
+}
+
 }  // namespace cricket