Start ICE connectivity checks as soon as the first pair is pingable.

webrtc/p2p/base/p2ptransportchannel.cc

 /*
  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #include "webrtc/p2p/base/p2ptransportchannel.h"
 
 #include <algorithm>
 #include <set>
 
 #include "webrtc/base/common.h"
 #include "webrtc/base/crc32.h"
 #include "webrtc/base/logging.h"
 #include "webrtc/base/stringencode.h"
 #include "webrtc/p2p/base/candidate.h"
 #include "webrtc/p2p/base/candidatepairinterface.h"
 #include "webrtc/p2p/base/common.h"
 #include "webrtc/p2p/base/relayport.h"  // For RELAY_PORT_TYPE.
 #include "webrtc/p2p/base/stunport.h"   // For STUN_PORT_TYPE.
 #include "webrtc/system_wrappers/include/field_trial.h"
 
 namespace {
 
 // messages for queuing up work for ourselves
-enum { MSG_SORT = 1, MSG_CHECK_AND_PING };
+enum { MSG_SORT_AND_UPDATE_STATE = 1, MSG_CHECK_AND_PING };
 
 // The minimum improvement in RTT that justifies a switch.
 static const double kMinImprovement = 10;
 
 bool IsRelayRelay(const cricket::Connection* conn) {
   return conn->local_candidate().type() == cricket::RELAY_PORT_TYPE &&
          conn->remote_candidate().type() == cricket::RELAY_PORT_TYPE;
 }
 
 bool IsUdp(cricket::Connection* conn) {
@@ skipping 239 matching lines @@
     }
   }
   // We need to update the credentials and generation for any peer reflexive
   // candidates.
   for (Connection* conn : connections_) {
     conn->MaybeSetRemoteIceCredentialsAndGeneration(
         ice_ufrag, ice_pwd,
         static_cast<int>(remote_ice_parameters_.size() - 1));
   }
   // Updating the remote ICE candidate generation could change the sort order.
-  RequestSort();
+  RequestSortAndStateUpdate();
 }
 
 void P2PTransportChannel::SetRemoteIceMode(IceMode mode) {
   remote_ice_mode_ = mode;
 }
 
 void P2PTransportChannel::SetIceConfig(const IceConfig& config) {
   config_.gather_continually = config.gather_continually;
   LOG(LS_INFO) << "Set gather_continually to " << config_.gather_continually;
 
@@ skipping 44 matching lines @@
       LOG(LS_INFO) << "Set presume writable when fully relayed to "
                    << config_.presume_writable_when_fully_relayed;
     }
   }
 }
 
 const IceConfig& P2PTransportChannel::config() const {
   return config_;
 }
 
-// Go into the state of processing candidates, and running in general
-void P2PTransportChannel::Connect() {
-  ASSERT(worker_thread_ == rtc::Thread::Current());
+void P2PTransportChannel::MaybeStartGathering() {
   if (ice_ufrag_.empty() || ice_pwd_.empty()) {
-    ASSERT(false);
-    LOG(LS_ERROR) << "P2PTransportChannel::Connect: The ice_ufrag_ and the "
-                  << "ice_pwd_ are not set.";
     return;
   }
-
-  // Start checking and pinging as the ports come in.
-  thread()->Post(RTC_FROM_HERE, this, MSG_CHECK_AND_PING);
-}
-
-void P2PTransportChannel::MaybeStartGathering() {
   // Start gathering if we never started before, or if an ICE restart occurred.
   if (allocator_sessions_.empty() ||
       IceCredentialsChanged(allocator_sessions_.back()->ice_ufrag(),
                             allocator_sessions_.back()->ice_pwd(), ice_ufrag_,
                             ice_pwd_)) {
     if (gathering_state_ != kIceGatheringGathering) {
       gathering_state_ = kIceGatheringGathering;
       SignalGatheringState(this);
     }
     // Time for a new allocator.
@@ skipping 56 matching lines @@
 
   // Attempt to create a connection from this new port to all of the remote
   // candidates that we were given so far.
 
   std::vector<RemoteCandidate>::iterator iter;
   for (iter = remote_candidates_.begin(); iter != remote_candidates_.end();
        ++iter) {
     CreateConnection(port, *iter, iter->origin_port());
   }
 
-  SortConnections();
+  SortConnectionsAndUpdateState();
 }
 
 // A new candidate is available, let listeners know
 void P2PTransportChannel::OnCandidatesReady(
     PortAllocatorSession* session,
     const std::vector<Candidate>& candidates) {
   ASSERT(worker_thread_ == rtc::Thread::Current());
   for (size_t i = 0; i < candidates.size(); ++i) {
     SignalCandidateGathered(this, candidates[i]);
   }
@@ skipping 121 matching lines @@
 
   LOG(LS_INFO) << "Adding connection from "
                << (remote_candidate_is_new ? "peer reflexive" : "resurrected")
                << " candidate: " << remote_candidate.ToString();
   AddConnection(connection);
   connection->HandleBindingRequest(stun_msg);
 
   // Update the list of connections since we just added another.  We do this
   // after sending the response since it could (in principle) delete the
   // connection in question.
-  SortConnections();
+  SortConnectionsAndUpdateState();
 }
 
 void P2PTransportChannel::OnRoleConflict(PortInterface* port) {
   SignalRoleConflict(this);  // STUN ping will be sent when SetRole is called
                              // from Transport.
 }
 
 const IceParameters* P2PTransportChannel::FindRemoteIceFromUfrag(
     const std::string& ufrag,
     uint32_t* generation) {
@@ skipping 23 matching lines @@
         << conn->ToString();
     return;
   }
 
   LOG(LS_INFO)
       << "Switching selected connection on controlled side due to nomination: "
       << conn->ToString();
   SwitchSelectedConnection(conn);
   // Now that we have selected a connection, it is time to prune other
   // connections and update the read/write state of the channel.
-  RequestSort();
+  RequestSortAndStateUpdate();
 }
 
 void P2PTransportChannel::AddRemoteCandidate(const Candidate& candidate) {
   ASSERT(worker_thread_ == rtc::Thread::Current());
 
   uint32_t generation = GetRemoteCandidateGeneration(candidate);
   // If a remote candidate with a previous generation arrives, drop it.
   if (generation < remote_ice_generation()) {
     LOG(LS_WARNING) << "Dropping a remote candidate because its ufrag "
                     << candidate.username()
@@ skipping 26 matching lines @@
   // If this candidate matches what was thought to be a peer reflexive
   // candidate, we need to update the candidate priority/etc.
   for (Connection* conn : connections_) {
     conn->MaybeUpdatePeerReflexiveCandidate(new_remote_candidate);
   }
 
   // Create connections to this remote candidate.
   CreateConnections(new_remote_candidate, NULL);
 
   // Resort the connections list, which may have new elements.
-  SortConnections();
+  SortConnectionsAndUpdateState();
 }
 
 void P2PTransportChannel::RemoveRemoteCandidate(
     const Candidate& cand_to_remove) {
   auto iter =
       std::remove_if(remote_candidates_.begin(), remote_candidates_.end(),
                      [cand_to_remove](const Candidate& candidate) {
                        return cand_to_remove.MatchesForRemoval(candidate);
                      });
   if (iter != remote_candidates_.end()) {
@@ skipping 248 matching lines @@
 void P2PTransportChannel::UpdateConnectionStates() {
   int64_t now = rtc::TimeMillis();
 
   // We need to copy the list of connections since some may delete themselves
   // when we call UpdateState.
   for (size_t i = 0; i < connections_.size(); ++i)
     connections_[i]->UpdateState(now);
 }
 
 // Prepare for best candidate sorting.
-void P2PTransportChannel::RequestSort() {
+void P2PTransportChannel::RequestSortAndStateUpdate() {
   if (!sort_dirty_) {
-    worker_thread_->Post(RTC_FROM_HERE, this, MSG_SORT);
+    worker_thread_->Post(RTC_FROM_HERE, this, MSG_SORT_AND_UPDATE_STATE);
     sort_dirty_ = true;
   }
 }
 
+void P2PTransportChannel::MaybeStartPinging() {
+  if (started_pinging_) {
+    return;
+  }
+  LOG(LS_INFO) << "IN maybestartpinging";
+
+  int64_t now = rtc::TimeMillis();
+  if (std::any_of(
+          connections_.begin(), connections_.end(),
+          [this, now](const Connection* c) { return IsPingable(c, now); })) {
+    LOG_J(LS_INFO, this) << "Have a pingable connection for the first time; "
+                         << "starting to ping.";
+    thread()->Post(RTC_FROM_HERE, this, MSG_CHECK_AND_PING);
+    started_pinging_ = true;
+  }
+}
+
 // Compare two connections based on their writing, receiving, and connected
 // states.
 int P2PTransportChannel::CompareConnectionStates(const Connection* a,
                                                  const Connection* b) const {
   // First, prefer a connection that's writable or presumed writable over
   // one that's not writable.
   bool a_writable = a->writable() || PresumedWritable(a);
   bool b_writable = b->writable() || PresumedWritable(b);
   if (a_writable && !b_writable) {
     return a_is_better;
@@ skipping 156 matching lines @@
   int prefs_cmp = CompareConnectionCandidates(selected, conn);
   if (prefs_cmp != 0) {
     return prefs_cmp < 0;
   }
 
   return selected->rtt() - conn->rtt() >= kMinImprovement;
 }
 
 // Sort the available connections to find the best one.  We also monitor
 // the number of available connections and the current state.
-void P2PTransportChannel::SortConnections() {
+void P2PTransportChannel::SortConnectionsAndUpdateState() {
   ASSERT(worker_thread_ == rtc::Thread::Current());
 
   // Make sure the connection states are up-to-date since this affects how they
   // will be sorted.
   UpdateConnectionStates();
 
   // Any changes after this point will require a re-sort.
   sort_dirty_ = false;
 
   // Find the best alternative connection by sorting.  It is important to note
@@ skipping 48 matching lines @@
       break;
     }
   }
 
   // Now update the writable state of the channel with the information we have
   // so far.
   if (all_connections_timedout) {
     HandleAllTimedOut();
   }
 
-  // Update the state of this channel.  This method is called whenever the
-  // state of any connection changes, so this is a good place to do this.
+  // Update the state of this channel.
   UpdateState();
+
+  // Also possibly start pinging.
+  // We could start pinging if:
+  // * The first connection was created.
+  // * ICE credentials were provided.
+  // * A TCP connection became connected.

[pthatcher1, 2016/06/29 17:45:43]

Oh, wow, good catch about TCP.  And much cleaner.

[Taylor Brandstetter, 2016/06/29 18:04:56]

It actually wasn't my catch; it was the unit tests doing their job (yay, unit
tests!)

+  MaybeStartPinging();
 }
 
 void P2PTransportChannel::PruneConnections() {
   // We can prune any connection for which there is a connected, writable
   // connection on the same network with better or equal priority.  We leave
   // those with better priority just in case they become writable later (at
   // which point, we would prune out the current selected connection).  We leave
   // connections on other networks because they may not be using the same
   // resources and they may represent very distinct paths over which we can
   // switch. If the |premier| connection is not connected, we may be
@@ skipping 50 matching lines @@
   }
   SignalSelectedCandidatePairChanged(this, selected_connection_,
                                      last_sent_packet_id_);
 }
 
 // Warning: UpdateState should eventually be called whenever a connection
 // is added, deleted, or the write state of any connection changes so that the
 // transport controller will get the up-to-date channel state. However it
 // should not be called too often; in the case that multiple connection states
 // change, it should be called after all the connection states have changed. For
-// example, we call this at the end of SortConnections.
+// example, we call this at the end of SortConnectionsAndUpdateState.
 void P2PTransportChannel::UpdateState() {
   TransportChannelState state = ComputeState();
   if (state_ != state) {
     LOG_J(LS_INFO, this) << "Transport channel state changed from " << state_
                          << " to " << state;
     // Check that the requested transition is allowed. Note that
     // P2PTransportChannel does not (yet) implement a direct mapping of the ICE
     // states from the standard; the difference is covered by
     // TransportController and PeerConnection.
     switch (state_) {
@@ skipping 88 matching lines @@
       return connections_[i];
     }
   }
 
   return NULL;
 }
 
 // Handle any queued up requests
 void P2PTransportChannel::OnMessage(rtc::Message *pmsg) {
   switch (pmsg->message_id) {
-    case MSG_SORT:
-      OnSort();
+    case MSG_SORT_AND_UPDATE_STATE:
+      SortConnectionsAndUpdateState();
       break;
     case MSG_CHECK_AND_PING:
       OnCheckAndPing();
       break;
     default:
       ASSERT(false);
       break;
   }
 }
 
-// Handle queued up sort request
-void P2PTransportChannel::OnSort() {
-  // Resort the connections based on the new statistics.
-  SortConnections();
-}
-
 // Handle queued up check-and-ping request
 void P2PTransportChannel::OnCheckAndPing() {
   // Make sure the states of the connections are up-to-date (since this affects
   // which ones are pingable).
   UpdateConnectionStates();
   // When the selected connection is not receiving or not writable, or any
   // active connection has not been pinged enough times, use the weak ping
   // interval.
   bool need_more_pings_at_weak_interval = std::any_of(
       connections_.begin(), connections_.end(), [](Connection* conn) {
         return conn->active() &&
                conn->num_pings_sent() < MIN_PINGS_AT_WEAK_PING_INTERVAL;
       });
   int ping_interval = (weak() || need_more_pings_at_weak_interval)
                           ? weak_ping_interval_
                           : STRONG_PING_INTERVAL;
   if (rtc::TimeMillis() >= last_ping_sent_ms_ + ping_interval) {
     Connection* conn = FindNextPingableConnection();
     if (conn) {
       PingConnection(conn);
       MarkConnectionPinged(conn);
     }
   }
   int delay = std::min(ping_interval, check_receiving_interval_);
   thread()->PostDelayed(RTC_FROM_HERE, delay, this, MSG_CHECK_AND_PING);
 }
 
 // A connection is considered a backup connection if the channel state
 // is completed, the connection is not the selected connection and it is active.
-bool P2PTransportChannel::IsBackupConnection(Connection* conn) const {
+bool P2PTransportChannel::IsBackupConnection(const Connection* conn) const {
   return state_ == STATE_COMPLETED && conn != selected_connection_ &&
          conn->active();
 }
 
 // Is the connection in a state for us to even consider pinging the other side?
 // We consider a connection pingable even if it's not connected because that's
 // how a TCP connection is kicked into reconnecting on the active side.
-bool P2PTransportChannel::IsPingable(Connection* conn, int64_t now) {
+bool P2PTransportChannel::IsPingable(const Connection* conn,
+                                     int64_t now) const {
   const Candidate& remote = conn->remote_candidate();
   // We should never get this far with an empty remote ufrag.
   ASSERT(!remote.username().empty());
   if (remote.username().empty() || remote.password().empty()) {
     // If we don't have an ICE ufrag and pwd, there's no way we can ping.
     return false;
   }
 
   // A failed connection will not be pinged.
   if (conn->state() == Connection::STATE_FAILED) {
@@ skipping 37 matching lines @@
 bool P2PTransportChannel::IsSelectedConnectionPingable(int64_t now) {
   if (!selected_connection_ || !selected_connection_->connected() ||
       !selected_connection_->writable()) {
     return false;
   }
 
   int interval = CalculateActiveWritablePingInterval(selected_connection_, now);
   return selected_connection_->last_ping_sent() + interval <= now;
 }
 
-int P2PTransportChannel::CalculateActiveWritablePingInterval(Connection* conn,
-                                                             int64_t now) {
+int P2PTransportChannel::CalculateActiveWritablePingInterval(
+    const Connection* conn,
+    int64_t now) const {
   // Ping each connection at a higher rate at least
   // MIN_PINGS_AT_WEAK_PING_INTERVAL times.
   if (conn->num_pings_sent() < MIN_PINGS_AT_WEAK_PING_INTERVAL) {
     return weak_ping_interval_;
   }
 
   int stable_interval = config_.stable_writable_connection_ping_interval;
   int stablizing_interval =
       std::min(stable_interval, STABILIZING_WRITABLE_CONNECTION_PING_INTERVAL);
 
@@ skipping 64 matching lines @@
   // changing from (writable, receiving) to (writable, not receiving).
   bool strongly_connected = !connection->weak();
   bool latest_generation = connection->local_candidate().generation() >=
                            allocator_session()->generation();
   if (strongly_connected && latest_generation) {
     MaybeStopPortAllocatorSessions();
   }
 
   // We have to unroll the stack before doing this because we may be changing
   // the state of connections while sorting.
-  RequestSort();
+  RequestSortAndStateUpdate();
 }
 
 // When a connection is removed, edit it out, and then update our best
 // connection.
 void P2PTransportChannel::OnConnectionDestroyed(Connection* connection) {
   ASSERT(worker_thread_ == rtc::Thread::Current());
 
   // Note: the previous selected_connection_ may be destroyed by now, so don't
   // use it.
 
   // Remove this connection from the list.
   std::vector<Connection*>::iterator iter =
       std::find(connections_.begin(), connections_.end(), connection);
   ASSERT(iter != connections_.end());
   pinged_connections_.erase(*iter);
   unpinged_connections_.erase(*iter);
   connections_.erase(iter);
 
   LOG_J(LS_INFO, this) << "Removed connection ("
     << static_cast<int>(connections_.size()) << " remaining)";
 
   // If this is currently the selected connection, then we need to pick a new
-  // one. The call to SortConnections will pick a new one.  It looks at the
-  // current selected connection in order to avoid switching between fairly
-  // similar ones. Since this connection is no longer an option, we can just
-  // set selected to nullptr and re-choose a best assuming that there was no
-  // selected connection.
+  // one. The call to SortConnectionsAndUpdateState will pick a new one. It
+  // looks at the current selected connection in order to avoid switching
+  // between fairly similar ones. Since this connection is no longer an option,
+  // we can just set selected to nullptr and re-choose a best assuming that
+  // there was no selected connection.
   if (selected_connection_ == connection) {
     LOG(LS_INFO) << "selected connection destroyed. Will choose a new one.";
     SwitchSelectedConnection(nullptr);
-    RequestSort();
+    RequestSortAndStateUpdate();
   }

[pthatcher1, 2016/06/29 17:45:43]

Do we need to update the state even if the destroyed connection isn't the
selected connection?  Looking at ComputeState, it appears that we would miss
going to the failed/completed state when the last non-selected connection is
destroyed.

Perhaps just add "else { UpdateState(); }" ?

[Taylor Brandstetter, 2016/06/29 18:04:56]

You're right; I didn't mean to delete that. But it's probably a good idea to put
it in an "else", because that means if the selected connection is destroyed but
we have a backup, we'll seamlessly switch to the backup instead of emitting a
"disconnected" briefly before the connections are sorted.

-
-  UpdateState();
 }
 
 // When a port is destroyed remove it from our list of ports to use for
 // connection attempts.
 void P2PTransportChannel::OnPortDestroyed(PortInterface* port) {
   ASSERT(worker_thread_ == rtc::Thread::Current());
 
   // Remove this port from the lists (if we didn't drop it already).
   ports_.erase(std::remove(ports_.begin(), ports_.end(), port), ports_.end());
   removed_ports_.erase(
@@ skipping 173 matching lines @@
 
   // During the initial state when nothing has been pinged yet, return the first
   // one in the ordered |connections_|.
   return *(std::find_if(connections_.begin(), connections_.end(),
                         [conn1, conn2](Connection* conn) {
                           return conn == conn1 || conn == conn2;
                         }));
 }
 
 }  // namespace cricket