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 d626ad3d65acf284a6022428cbfb43615a6d07e3..c96ddc724532eb90cadff2990f9423f6c5846ced 100644
--- a/webrtc/p2p/base/transport.cc
+++ b/webrtc/p2p/base/transport.cc
@@ -8,6 +8,8 @@
  *  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"
@@ -22,39 +24,6 @@ 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.
   if (desc.ice_ufrag.empty() && desc.ice_pwd.empty())
@@ -96,58 +65,59 @@ static bool IceCredentialsChanged(const TransportDescription& old_desc,
                                new_desc.ice_ufrag, new_desc.ice_pwd);
 }
 
-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(const std::string& name, PortAllocator* allocator)
+    : name_(name), allocator_(allocator) {}
 
 Transport::~Transport() {
-  ASSERT(signaling_thread_->IsCurrent());
-  ASSERT(destroyed_);
+  ASSERT(channels_destroyed_);
 }
 
-void Transport::SetIceRole(IceRole role) {
-  worker_thread_->Invoke<void>(Bind(&Transport::SetIceRole_w, this, role));
-}
+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;
+  }
 
-void Transport::SetCertificate(
-    const rtc::scoped_refptr<rtc::RTCCertificate>& certificate) {
-  worker_thread_->Invoke<void>(Bind(&Transport::SetCertificate_w, this,
-                                    certificate));
+  // 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::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::AnyChannelFailed() const {
+  for (const auto& iter : channels_) {
+    if (iter.second->GetState() == TransportChannelState::STATE_FAILED) {
+      return true;
+    }
+  }
+  return false;
 }
 
-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));
+void Transport::SetIceRole(IceRole role) {
+  ice_role_ = role;
+  for (auto& iter : channels_) {
+    iter.second->SetIceRole(ice_role_);
+  }
 }
 
-bool Transport::GetRemoteSSLCertificate_w(rtc::SSLCertificate** cert) {
-  ASSERT(worker_thread()->IsCurrent());
+bool Transport::GetRemoteSSLCertificate(rtc::SSLCertificate** cert) {
   if (channels_.empty())
     return false;
 
@@ -156,12 +126,6 @@ bool Transport::GetRemoteSSLCertificate_w(rtc::SSLCertificate** cert) {
 }
 
 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);
@@ -172,35 +136,74 @@ bool Transport::SetLocalTransportDescription(
     const TransportDescription& description,
     ContentAction action,
     std::string* error_desc) {
-  return worker_thread_->Invoke<bool>(Bind(
-      &Transport::SetLocalTransportDescription_w, this,
-      description, action, 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;
+    // This kicks off candidate gathering.
+    ConnectChannels();
+  }
+
+  return ret;
 }
 
 bool Transport::SetRemoteTransportDescription(
     const TransportDescription& description,
     ContentAction action,
     std::string* error_desc) {
-  return worker_thread_->Invoke<bool>(Bind(
-      &Transport::SetRemoteTransportDescription_w, this,
-      description, action, error_desc));
-}
+  bool ret = true;
 
-TransportChannelImpl* Transport::CreateChannel(int component) {
-  return worker_thread_->Invoke<TransportChannelImpl*>(Bind(
-      &Transport::CreateChannel_w, this, component));
+  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;
 }
 
-TransportChannelImpl* Transport::CreateChannel_w(int component) {
-  ASSERT(worker_thread()->IsCurrent());
+TransportChannelImpl* Transport::CreateChannel(int component) {
   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;
@@ -216,7 +219,7 @@ TransportChannelImpl* Transport::CreateChannel_w(int component) {
 
   // Increase the ref count.
   iterator->second.AddRef();
-  destroyed_ = false;
+  channels_destroyed_ = false;
 
   if (impl_exists) {
     // If this is an existing channel, we should just return it without
@@ -228,23 +231,21 @@ TransportChannelImpl* Transport::CreateChannel_w(int component) {
   impl->SetIceRole(ice_role_);
   impl->SetIceTiebreaker(tiebreaker_);
   impl->SetReceivingTimeout(channel_receiving_timeout_);
-  // TODO(ronghuawu): Change CreateChannel_w to be able to return error since
-  // below Apply**Description_w calls can fail.
+  // TODO(ronghuawu): Change CreateChannel to be able to return error since
+  // below Apply**Description calls can fail.
   if (local_description_)
-    ApplyLocalTransportDescription_w(impl, NULL);
+    ApplyLocalTransportDescription(impl, NULL);
   if (remote_description_)
-    ApplyRemoteTransportDescription_w(impl, NULL);
+    ApplyRemoteTransportDescription(impl, NULL);
   if (local_description_ && remote_description_)
-    ApplyNegotiatedTransportDescription_w(impl, NULL);
+    ApplyNegotiatedTransportDescription(impl, NULL);
 
   impl->SignalWritableState.connect(this, &Transport::OnChannelWritableState);
   impl->SignalReceivingState.connect(this, &Transport::OnChannelReceivingState);
-  impl->SignalRequestSignaling.connect(
-      this, &Transport::OnChannelRequestSignaling);
-  impl->SignalCandidateReady.connect(this, &Transport::OnChannelCandidateReady);
+  impl->SignalGatheringState.connect(this, &Transport::OnChannelGatheringState);
+  impl->SignalCandidateGathered.connect(this,
+                                        &Transport::OnChannelCandidateGathered);
   impl->SignalRouteChange.connect(this, &Transport::OnChannelRouteChange);
-  impl->SignalCandidatesAllocationDone.connect(
-      this, &Transport::OnChannelCandidatesAllocationDone);
   impl->SignalRoleConflict.connect(this, &Transport::OnRoleConflict);
   impl->SignalConnectionRemoved.connect(
       this, &Transport::OnChannelConnectionRemoved);
@@ -254,36 +255,22 @@ TransportChannelImpl* Transport::CreateChannel_w(int component) {
     if (channels_.size() == 1) {
       // If this is the first channel, then indicate that we have started
       // connecting.
-      signaling_thread()->Post(this, MSG_CONNECTING, NULL);
+      SignalConnecting(this);
     }
   }
   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;
@@ -293,34 +280,35 @@ void Transport::DestroyChannel_w(int component) {
   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.
-    signaling_thread()->Post(this, MSG_CONNECTING, NULL);
+    SignalConnecting(this);
   }
 
   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 (!ready_candidates_.empty()) {
+    SignalCandidatesGathered(this, ready_candidates_);
+    ready_candidates_.clear();
+  }
 
   if (!local_description_) {
     // TOOD(mallinath) : TransportDescription(TD) shouldn't be generated here.
@@ -329,38 +317,22 @@ void Transport::ConnectChannels_w() {
     // Session.
     // Session must generate local TD before remote candidates pushed when
     // initiate request initiated by the remote.
-    LOG(LS_INFO) << "Transport::ConnectChannels_w: No local description has "
+    LOG(LS_INFO) << "Transport::ConnectChannels: 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_w(desc, CA_OFFER, NULL);
+    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_w(&TransportChannelImpl::Connect);
-  if (!channels_.empty()) {
-    signaling_thread()->Post(this, MSG_CONNECTING, NULL);
+  CallChannels(&TransportChannelImpl::Connect);
+  if (HasChannels()) {
+    SignalConnecting(this);
   }
 }
 
-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();
@@ -368,27 +340,15 @@ void Transport::DestroyAllChannels_w() {
       impls.push_back(iter.second.get());
   }
 
-  {
-    rtc::CritScope cs(&crit_);
-    channels_.clear();
-  }
-
-  for (size_t i = 0; i < impls.size(); ++i)
-    DestroyTransportChannel(impls[i]);
-}
+  channels_.clear();
 
-void Transport::OnSignalingReady() {
-  ASSERT(signaling_thread()->IsCurrent());
-  if (destroyed_) return;
-
-  worker_thread()->Post(this, MSG_ONSIGNALINGREADY, NULL);
-
-  // Notify the subclass.
-  OnTransportSignalingReady();
+  for (TransportChannelImpl* impl : impls) {
+    DestroyTransportChannel(impl);
+  }
+  channels_destroyed_ = true;
 }
 
-void Transport::CallChannels_w(TransportChannelFunc func) {
-  ASSERT(worker_thread()->IsCurrent());
+void Transport::CallChannels(TransportChannelFunc func) {
   for (const auto& iter : channels_) {
     ((iter.second.get())->*func)();
   }
@@ -427,14 +387,7 @@ bool Transport::VerifyCandidate(const Candidate& cand, std::string* error) {
 
 
 bool Transport::GetStats(TransportStats* stats) {
-  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->transport_name = name();
   stats->channel_stats.clear();
   for (auto iter : channels_) {
     ChannelMapEntry& entry = iter.second;
@@ -450,82 +403,45 @@ bool Transport::GetStats_w(TransportStats* stats) {
   return true;
 }
 
-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));
-}
+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;
+    }
+  }
 
-void Transport::OnRemoteCandidates(const std::vector<Candidate>& candidates) {
   for (std::vector<Candidate>::const_iterator iter = candidates.begin();
        iter != candidates.end();
        ++iter) {
-    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);
+    TransportChannelImpl* channel = GetChannel(iter->component());
+    if (channel != NULL) {
+      channel->AddRemoteCandidate(*iter);
+    }
   }
+  return true;
 }
 
 void Transport::OnChannelWritableState(TransportChannel* channel) {
-  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);
-  }
+  LOG(LS_INFO) << name() << " TransportChannel " << channel->component()
+               << " writability changed to " << channel->writable()
+               << ". Check if transport is complete.";
+  UpdateWritableState();
+  MaybeSignalCompleted();
 }
 
 void Transport::OnChannelReceivingState(TransportChannel* channel) {
-  ASSERT(worker_thread()->IsCurrent());
-  signaling_thread()->Post(this, MSG_RECEIVINGSTATE);
+  UpdateReceivingState();
 }
 
-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_);
+TransportState Transport::GetTransportState(TransportStateType state_type) {
   bool any = false;
   bool all = !channels_.empty();
   for (const auto iter : channels_) {
@@ -553,106 +469,48 @@ TransportState Transport::GetTransportState_s(TransportStateType state_type) {
   return TRANSPORT_STATE_NONE;
 }
 
-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::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::OnChannelCandidateReady(TransportChannelImpl* channel,
-                                        const Candidate& candidate) {
+void Transport::OnChannelCandidateGathered(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;
-  {
-    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);
+    std::vector<Candidate> candidates;
+    candidates.push_back(candidate);
+    SignalCandidatesGathered(this, candidates);
+  } else {
+    // We hold any candidates until the client lets us connect.
+    ready_candidates_.push_back(candidate);
   }
 }
 
 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) {
-  signaling_thread_->Post(this, MSG_ROLECONFLICT);
+  SignalRoleConflict();
 }
 
 void Transport::OnChannelConnectionRemoved(TransportChannelImpl* channel) {
-  ASSERT(worker_thread()->IsCurrent());
-  MaybeCompleted_w();
+  LOG(LS_INFO) << name() << " TransportChannel " << channel->component()
+               << " connection removed. Check if transport is complete.";
+  MaybeSignalCompleted();
 
   // Check if the state is now Failed.
   // Failed is only available in the Controlling ICE role.
@@ -660,158 +518,97 @@ void Transport::OnChannelConnectionRemoved(TransportChannelImpl* channel) {
     return;
   }
 
-  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()) {
+  // Failed can only occur after candidate gathering has stopped.
+  if (channel->gathering_state() != kIceGatheringComplete) {
     return;
   }
 
   if (channel->GetState() == TransportChannelState::STATE_FAILED) {
     // A Transport has failed if any of its channels have no remaining
     // connections.
-    signaling_thread_->Post(this, MSG_FAILED);
+    SignalFailed(this);
   }
 }
 
-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;
+void Transport::MaybeSignalCompleted() {
+  if (AllChannelsCompleted()) {
+    LOG(LS_INFO) << name() << " transport is complete"
+                 << " because all the channels are complete.";
+    SignalCompleted(this);
   }
-
-  // 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;
-    }
-  }
-
-  signaling_thread_->Post(this, MSG_COMPLETED);
+  // 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::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_);
+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.";
+    }
+    SignalGatheringState(this);
   }
 }
 
-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);
+void Transport::UpdateReceivingState() {
+  TransportState receiving = GetTransportState(TRANSPORT_RECEIVING_STATE);
+  if (receiving_ != receiving) {
+    receiving_ = receiving;
+    SignalReceivingState(this);
   }
-  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);
+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);
   }
-  return ret;
 }
 
-bool Transport::ApplyLocalTransportDescription_w(TransportChannelImpl* ch,
-                                                 std::string* error_desc) {
-  ASSERT(worker_thread()->IsCurrent());
+bool Transport::ApplyLocalTransportDescription(TransportChannelImpl* ch,
+                                               std::string* error_desc) {
   ch->SetIceCredentials(local_description_->ice_ufrag,
                         local_description_->ice_pwd);
   return true;
 }
 
-bool Transport::ApplyRemoteTransportDescription_w(TransportChannelImpl* ch,
-                                                  std::string* error_desc) {
+bool Transport::ApplyRemoteTransportDescription(TransportChannelImpl* ch,
+                                                std::string* error_desc) {
   ch->SetRemoteIceCredentials(remote_description_->ice_ufrag,
                               remote_description_->ice_pwd);
   return true;
 }
 
-bool Transport::ApplyNegotiatedTransportDescription_w(
-    TransportChannelImpl* channel, std::string* error_desc) {
-  ASSERT(worker_thread()->IsCurrent());
+bool Transport::ApplyNegotiatedTransportDescription(
+    TransportChannelImpl* channel,
+    std::string* error_desc) {
   channel->SetRemoteIceMode(remote_ice_mode_);
   return true;
 }
 
-bool Transport::NegotiateTransportDescription_w(ContentAction local_role,
-                                                std::string* error_desc) {
-  ASSERT(worker_thread()->IsCurrent());
+bool Transport::NegotiateTransportDescription(ContentAction local_role,
+                                              std::string* error_desc) {
   // TODO(ekr@rtfm.com): This is ICE-specific stuff. Refactor into
   // P2PTransport.
 
@@ -819,7 +616,7 @@ bool Transport::NegotiateTransportDescription_w(ContentAction local_role,
   // ice_lite, this local end point should take CONTROLLING role.
   if (ice_role_ == ICEROLE_CONTROLLED &&
       remote_description_->ice_mode == ICEMODE_LITE) {
-    SetIceRole_w(ICEROLE_CONTROLLING);
+    SetIceRole(ICEROLE_CONTROLLING);
   }
 
   // Update remote ice_mode to all existing channels.
@@ -831,57 +628,10 @@ bool Transport::NegotiateTransportDescription_w(ContentAction local_role,
   // creation, we have the negotiation state saved until a new
   // negotiation happens.
   for (auto& iter : channels_) {
-    if (!ApplyNegotiatedTransportDescription_w(iter.second.get(), error_desc))
+    if (!ApplyNegotiatedTransportDescription(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