Add an active ICE controller interface (#2/n)

This interface will be implemented by "new" ICE controllers that actively manage the connection used by the transport.

Bug: webrtc:14367, webrtc:14131
Change-Id: I0858884b0decd2a17ae9ca8617a043a085c61d54
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/271291
Commit-Queue: Sameer Vijaykar <samvi@google.com>
Reviewed-by: Jonas Oreland <jonaso@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#38066}

p2p/BUILD.gn

@@ -18,6 +18,7 @@ group("p2p") {
 rtc_library("rtc_p2p") {
   visibility = [ "*" ]
   sources = [
+    "base/active_ice_controller_interface.h",
     "base/async_stun_tcp_socket.cc",
     "base/async_stun_tcp_socket.h",
     "base/basic_async_resolver_factory.cc",

p2p/base/active_ice_controller_interface.h

@@ -0,0 +1,84 @@
+/*
+ *  Copyright 2022 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.
+ */
+
+#ifndef P2P_BASE_ACTIVE_ICE_CONTROLLER_INTERFACE_H_
+#define P2P_BASE_ACTIVE_ICE_CONTROLLER_INTERFACE_H_
+
+#include "absl/types/optional.h"
+#include "api/array_view.h"
+#include "p2p/base/connection.h"
+#include "p2p/base/ice_switch_reason.h"
+#include "p2p/base/ice_transport_internal.h"
+#include "p2p/base/transport_description.h"
+
+namespace cricket {
+
+// ActiveIceControllerInterface defines the methods for a module that actively
+// manages the connection used by an ICE transport.
+//
+// An active ICE controller receives updates from the ICE transport when
+//   - the connections state is mutated
+//   - a new connection should be selected as a result of an external event (eg.
+//     a different connection nominated by the remote peer)
+//
+// The active ICE controller takes the appropriate decisions and requests the
+// ICE agent to perform the necessary actions through the IceAgentInterface.
+class ActiveIceControllerInterface {
+ public:
+  virtual ~ActiveIceControllerInterface() = default;
+
+  // Sets the current ICE configuration.
+  virtual void SetIceConfig(const IceConfig& config) = 0;
+
+  // Called when a new connection is added to the ICE transport.
+  virtual void OnConnectionAdded(const Connection* connection) = 0;
+
+  // Called when the transport switches that connection in active use.
+  virtual void OnConnectionSwitched(const Connection* connection) = 0;
+
+  // Called when a connection is destroyed.
+  virtual void OnConnectionDestroyed(const Connection* connection) = 0;
+
+  // Called when a STUN ping has been sent on a connection. This does not
+  // indicate that a STUN response has been received.
+  virtual void OnConnectionPinged(const Connection* connection) = 0;
+
+  // Called when one of the following changes for a connection.
+  // - rtt estimate
+  // - write state
+  // - receiving
+  // - connected
+  // - nominated
+  virtual void OnConnectionUpdated(const Connection* connection) = 0;
+
+  // Compute "STUN_ATTR_USE_CANDIDATE" for a STUN ping on the given connection.
+  virtual bool GetUseCandidateAttribute(const Connection* connection,
+                                        NominationMode mode,
+                                        IceMode remote_ice_mode) const = 0;
+
+  // Called to enque a request to pick and switch to the best available
+  // connection.
+  virtual void OnSortAndSwitchRequest(IceSwitchReason reason) = 0;
+
+  // Called to pick and switch to the best available connection immediately.
+  virtual void OnImmediateSortAndSwitchRequest(IceSwitchReason reason) = 0;
+
+  // Called to switch to the given connection immediately without checking for
+  // the best available connection.
+  virtual bool OnImmediateSwitchRequest(IceSwitchReason reason,
+                                        const Connection* selected) = 0;
+
+  // Only for unit tests
+  virtual const Connection* FindNextPingableConnection() = 0;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_ACTIVE_ICE_CONTROLLER_INTERFACE_H_