Add ::Connect method to the media transport interface

In order to enable ::Connect method, we also need to split the factory and create a method that creates media transport, but doesn't connect it.

So far media transport was connecting right away after creation. We would however want to expose some of the settings in SDP. SDP is created before connection is connected (and before ICE transport is created), and so we would like to be able to get the settings from the caller to the callee.

Bug: webrtc:9719
Change-Id: I1dc2f30c9a2dae8b3db04f14c8b334cd1b3ab5ab
Reviewed-on: https://webrtc-review.googlesource.com/c/124517
Reviewed-by: Bjorn Mellem <mellem@webrtc.org>
Commit-Queue: Peter Slatala <psla@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26863}

api/media_transport_interface.cc

@@ -41,9 +41,28 @@ MediaTransportFactory::CreateMediaTransport(
   return std::unique_ptr<MediaTransportInterface>(nullptr);
 }
 
+RTCErrorOr<std::unique_ptr<MediaTransportInterface>>
+MediaTransportFactory::CreateMediaTransport(
+    rtc::Thread* network_thread,
+    const MediaTransportSettings& settings) {
+  return std::unique_ptr<MediaTransportInterface>(nullptr);
+}
+
+std::string MediaTransportFactory::GetTransportName() const {
+  return "";
+}
+
 MediaTransportInterface::MediaTransportInterface() = default;
 MediaTransportInterface::~MediaTransportInterface() = default;
 
+absl::optional<std::string>
+MediaTransportInterface::GetTransportParametersOffer() const {
+  return absl::nullopt;
+}
+
+void MediaTransportInterface::Connect(
+    rtc::PacketTransportInternal* packet_transport) {}
+
 void MediaTransportInterface::SetKeyFrameRequestCallback(
     MediaTransportKeyFrameRequestCallback* callback) {}
 

api/media_transport_interface.h

@@ -71,6 +71,10 @@ struct MediaTransportSettings final {
   // future.
   absl::optional<std::string> pre_shared_key;
 
+  // If present, this is a config passed from the caller to the answerer in the
+  // offer. Each media transport knows how to understand its own parameters.
+  absl::optional<std::string> remote_transport_parameters;
+
   // If present, provides the event log that media transport should use.
   // Media transport does not own it. The lifetime of |event_log| will exceed
   // the lifetime of the instance of MediaTransportInterface instance.
@@ -187,6 +191,27 @@ class MediaTransportInterface {
   MediaTransportInterface();
   virtual ~MediaTransportInterface();
 
+  // Retrieves callers config (i.e. media transport offer) that should be passed
+  // to the callee, before the call is connected. Such config is opaque to SDP
+  // (sdp just passes it through). The config is a binary blob, so SDP may
+  // choose to use base64 to serialize it (or any other approach that guarantees
+  // that the binary blob goes through). This should only be called for the
+  // caller's perspective.
+  //
+  // This may return an unset optional, which means that the given media
+  // transport is not supported / disabled and shouldn't be reported in SDP.
+  //
+  // It may also return an empty string, in which case the media transport is
+  // supported, but without any extra settings.
+  // TODO(psla): Make abstract.
+  virtual absl::optional<std::string> GetTransportParametersOffer() const;
+
+  // Connect the media transport to the ICE transport.
+  // The implementation must be able to ignore incoming packets that don't
+  // belong to it.
+  // TODO(psla): Make abstract.
+  virtual void Connect(rtc::PacketTransportInternal* packet_transport);
+
   // Start asynchronous send of audio frame. The status returned by this method
   // only pertains to the synchronous operations (e.g.
   // serialization/packetization), not to the asynchronous operation.
@@ -322,6 +347,24 @@ class MediaTransportFactory {
   CreateMediaTransport(rtc::PacketTransportInternal* packet_transport,
                        rtc::Thread* network_thread,
                        const MediaTransportSettings& settings);
+
+  // Creates a new Media Transport in a disconnected state. If the media
+  // transport for the caller is created, one can then call
+  // MediaTransportInterface::GetTransportParametersOffer on that new instance.
+  // TODO(psla): Make abstract.
+  virtual RTCErrorOr<std::unique_ptr<webrtc::MediaTransportInterface>>
+  CreateMediaTransport(rtc::Thread* network_thread,
+                       const MediaTransportSettings& settings);
+
+  // Gets a transport name which is supported by the implementation.
+  // Different factories should return different transport names, and at runtime
+  // it will be checked that different names were used.
+  // For example, "rtp" or "generic" may be returned by two different
+  // implementations.
+  // The value returned by this method must never change in the lifetime of the
+  // factory.
+  // TODO(psla): Make abstract.
+  virtual std::string GetTransportName() const;
 };
 
 }  // namespace webrtc