Create the SrtpTransportInterface.

Create the SrtpTransportInterface, a subclass of RtpTransportInterface, which
allows the user to set the send and receive keys. The functionalities are
implemented inside the RtpTransportAdapters on top of BaseChannel.

BUG=webrtc:7013

Review-Url: https://codereview.webrtc.org/2714813004
Cr-Commit-Position: refs/heads/master@{#17023}
diff --git a/webrtc/api/ortc/ortcfactoryinterface.h b/webrtc/api/ortc/ortcfactoryinterface.h
index 855e3b0..62ed90d 100644
--- a/webrtc/api/ortc/ortcfactoryinterface.h
+++ b/webrtc/api/ortc/ortcfactoryinterface.h
@@ -23,6 +23,7 @@
 #include "webrtc/api/ortc/packettransportinterface.h"
 #include "webrtc/api/ortc/rtptransportcontrollerinterface.h"
 #include "webrtc/api/ortc/rtptransportinterface.h"
+#include "webrtc/api/ortc/srtptransportinterface.h"
 #include "webrtc/api/ortc/udptransportinterface.h"
 #include "webrtc/api/rtcerror.h"
 #include "webrtc/api/rtpparameters.h"
@@ -126,6 +127,14 @@
       PacketTransportInterface* rtcp,
       RtpTransportControllerInterface* transport_controller) = 0;
 
+  // Creates an SrtpTransport which is an RTP transport that uses SRTP.
+  virtual RTCErrorOr<std::unique_ptr<SrtpTransportInterface>>
+  CreateSrtpTransport(
+      const RtcpParameters& rtcp_parameters,
+      PacketTransportInterface* rtp,
+      PacketTransportInterface* rtcp,
+      RtpTransportControllerInterface* transport_controller) = 0;
+
   // Returns the capabilities of an RTP sender of type |kind|. These
   // capabilities can be used to determine what RtpParameters to use to create
   // an RtpSender.
diff --git a/webrtc/api/ortc/ortcrtpsenderinterface.h b/webrtc/api/ortc/ortcrtpsenderinterface.h
index e369b53..a0fc208 100644
--- a/webrtc/api/ortc/ortcrtpsenderinterface.h
+++ b/webrtc/api/ortc/ortcrtpsenderinterface.h
@@ -18,8 +18,8 @@
 #ifndef WEBRTC_API_ORTC_ORTCRTPSENDERINTERFACE_H_
 #define WEBRTC_API_ORTC_ORTCRTPSENDERINTERFACE_H_
 
-#include "webrtc/api/mediatypes.h"
 #include "webrtc/api/mediastreaminterface.h"
+#include "webrtc/api/mediatypes.h"
 #include "webrtc/api/ortc/rtptransportinterface.h"
 #include "webrtc/api/rtcerror.h"
 #include "webrtc/api/rtpparameters.h"
diff --git a/webrtc/api/ortc/srtptransportinterface.h b/webrtc/api/ortc/srtptransportinterface.h
new file mode 100644
index 0000000..f64618c
--- /dev/null
+++ b/webrtc/api/ortc/srtptransportinterface.h
@@ -0,0 +1,48 @@
+/*
+ *  Copyright 2017 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 WEBRTC_API_ORTC_SRTPTRANSPORTINTERFACE_H_
+#define WEBRTC_API_ORTC_SRTPTRANSPORTINTERFACE_H_
+
+#include "webrtc/api/ortc/rtptransportinterface.h"
+#include "webrtc/api/rtcerror.h"
+#include "webrtc/media/base/cryptoparams.h"
+
+namespace webrtc {
+
+// The subclass of the RtpTransport which uses SRTP. The keying information
+// is explicitly passed in from the application.
+//
+// If using SDP and SDES (RFC4568) for signaling, then after applying the
+// answer, the negotiated keying information from the offer and answer would be
+// set and the SRTP would be active.
+//
+// Note that Edge's implementation of ORTC provides a similar API point, called
+// RTCSrtpSdesTransport:
+// https://msdn.microsoft.com/en-us/library/mt502527(v=vs.85).aspx
+class SrtpTransportInterface : public RtpTransportInterface {
+ public:
+  virtual ~SrtpTransportInterface() {}
+
+  // There are some limitations of the current implementation:
+  //  1. Send and receive keys must use the same crypto suite.
+  //  2. The keys can't be changed after initially set.
+  //  3. The keys must be set before creating a sender/receiver using the SRTP
+  //     transport.
+  // Set the SRTP keying material for sending RTP and RTCP.
+  virtual RTCError SetSrtpSendKey(const cricket::CryptoParams& params) = 0;
+
+  // Set the SRTP keying material for receiving RTP and RTCP.
+  virtual RTCError SetSrtpReceiveKey(const cricket::CryptoParams& params) = 0;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_API_ORTC_SRTPTRANSPORTINTERFACE_H_