Add an ICE agent interface (#1/n)

This interface will be implemented by P2PTransportChannel in a follow-up CL. It will allow an ICE controller to request actions to manipulate the connection used by the transport.

Bug: webrtc:14367, webrtc:1413
Change-Id: I5cd171bd09c8dfc88588f8fc06e87d74a90b5216
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/271290
Reviewed-by: Jonas Oreland <jonaso@webrtc.org>
Commit-Queue: Sameer Vijaykar <samvi@google.com>
Cr-Commit-Position: refs/heads/main@{#38062}

p2p/BUILD.gn

@@ -38,6 +38,7 @@ rtc_library("rtc_p2p") {
     "base/dtls_transport_factory.h",
     "base/dtls_transport_internal.cc",
     "base/dtls_transport_internal.h",
+    "base/ice_agent_interface.h",
     "base/ice_controller_factory_interface.h",
     "base/ice_controller_interface.cc",
     "base/ice_controller_interface.h",

p2p/base/ice_agent_interface.h

@@ -0,0 +1,80 @@
+/*
+ *  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_ICE_AGENT_INTERFACE_H_
+#define P2P_BASE_ICE_AGENT_INTERFACE_H_
+
+#include <vector>
+
+#include "p2p/base/connection.h"
+#include "p2p/base/ice_switch_reason.h"
+
+namespace cricket {
+
+// IceAgentInterface provides methods that allow an ICE controller to manipulate
+// the connections available to a transport, and used by the transport to
+// transfer data.
+class IceAgentInterface {
+ public:
+  virtual ~IceAgentInterface() = default;
+
+  // Get the time when the last ping was sent.
+  // This is only needed in some scenarios if the agent decides to ping on its
+  // own, eg. in some switchover scenarios. Otherwise the ICE controller could
+  // keep this state on its own.
+  // TODO(bugs.webrtc.org/14367): route extra pings through the ICE controller.
+  virtual int64_t GetLastPingSentMs() const = 0;
+
+  // Get the ICE role of this ICE agent.
+  virtual IceRole GetIceRole() const = 0;
+
+  // Called when a pingable connection first becomes available.
+  virtual void OnStartedPinging() = 0;
+
+  // Update the state of all available connections.
+  virtual void UpdateConnectionStates() = 0;
+
+  // Update the internal state of the ICE agent. An ICE controller should call
+  // this at the end of a sequence of actions to combine several mutations into
+  // a single state refresh.
+  // TODO(bugs.webrtc.org/14431): ICE agent state updates should be internal to
+  // the agent. If batching is necessary, use a more appropriate interface.
+  virtual void UpdateState() = 0;
+
+  // Reset the given connections to a state of newly connected connections.
+  // - STATE_WRITE_INIT
+  // - receving = false
+  // - throw away all pending request
+  // - reset RttEstimate
+  //
+  // Keep the following unchanged:
+  // - connected
+  // - remote_candidate
+  // - statistics
+  //
+  // SignalStateChange will not be triggered.
+  virtual void ForgetLearnedStateForConnections(
+      std::vector<const Connection*> connections) = 0;
+
+  // Send a STUN ping request for the given connection.
+  virtual void SendPingRequest(const Connection* connection) = 0;
+
+  // Switch the transport to use the given connection.
+  virtual void SwitchSelectedConnection(const Connection* new_connection,
+                                        IceSwitchReason reason) = 0;
+
+  // Prune away the given connections. Returns true if pruning is permitted and
+  // successfully performed.
+  virtual bool PruneConnections(std::vector<const Connection*> connections) = 0;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_BASE_ICE_AGENT_INTERFACE_H_