Update the current RTP parser fuzzer to handle header extensions.

webrtc/test/fuzzers/rtp_packet_fuzzer.cc

Index: webrtc/test/fuzzers/rtp_packet_fuzzer.cc
diff --git a/webrtc/test/fuzzers/rtp_packet_fuzzer.cc b/webrtc/test/fuzzers/rtp_packet_fuzzer.cc
index a9efdb96ecfe4f7a77873f54edbb55108c9497f9..2a67a8bea73115fc97a97867394e4d906906d490 100644
--- a/webrtc/test/fuzzers/rtp_packet_fuzzer.cc
+++ b/webrtc/test/fuzzers/rtp_packet_fuzzer.cc
@@ -7,13 +7,41 @@
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
+
+#include "webrtc/modules/rtp_rtcp/source/rtp_header_extension.h"
+#include "webrtc/modules/rtp_rtcp/source/rtp_header_extensions.h"
 #include "webrtc/modules/rtp_rtcp/source/rtp_packet_received.h"
 
 namespace webrtc {
 
+// We decide which header extensions to register by reading one byte
+// from the beginning of |data| and interpreting it as a bitmask over
+// the RTPExtensionType enum. This assert ensures one byte is enough.
+static_assert(kRtpExtensionNumberOfExtensions <= 8,
+              "Insufficient bits read to configure all header extensions. Add "
+              "an extra byte and update the switches.");
+
 void FuzzOneInput(const uint8_t* data, size_t size) {
-  RtpPacketReceived packet;
+  if (size <= 1)
+    return;
+
+  // Don't use the configuration byte as part of the packet.
+  std::bitset<8> extensionMask(data[0]);
+  data++;
+  size--;
+
+  RtpPacketReceived::ExtensionManager extensions;
+  for (int i = 0; i < kRtpExtensionNumberOfExtensions; i++) {
+    RTPExtensionType extension_type = static_cast<RTPExtensionType>(i);
+    if (extensionMask[i] && extension_type != kRtpExtensionNone) {
+      // Extensions are registered with an ID, which you signal to the
+      // peer so they know what to expect. This code only cares about
+      // parsing so the value of the ID isn't relevant; we use i.
+      extensions.Register(extension_type, i);
+    }
+  }
 
+  RtpPacketReceived packet(&extensions);
   packet.Parse(data, size);
 
   // Call packet accessors because they have extra checks.
@@ -23,7 +51,40 @@ void FuzzOneInput(const uint8_t* data, size_t size) {
   packet.Timestamp();
   packet.Ssrc();
   packet.Csrcs();
-}
 
+  // Each extension has its own getter. It is supported behaviour to
+  // call GetExtension on an extension which was not registered, so we
+  // don't check the bitmask here.
+  for (int i = 0; i < kRtpExtensionNumberOfExtensions; i++) {
+    switch (static_cast<RTPExtensionType>(i)) {
+      case kRtpExtensionNone:
+      case kRtpExtensionNumberOfExtensions:
+        break;
+      case kRtpExtensionTransmissionTimeOffset:
+        int32_t offset;
+        packet.GetExtension<TransmissionOffset>(&offset);
+        break;
+      case kRtpExtensionAudioLevel:
+        bool voice_activity;
+        uint8_t audio_level;
+        packet.GetExtension<AudioLevel>(&voice_activity, &audio_level);
+        break;
+      case kRtpExtensionAbsoluteSendTime:
+        uint32_t sendtime;
+        packet.GetExtension<AbsoluteSendTime>(&sendtime);
+        break;
+      case kRtpExtensionVideoRotation:
+        uint8_t rotation;
+        packet.GetExtension<VideoOrientation>(&rotation);
+        break;
+      case kRtpExtensionTransportSequenceNumber:
+        uint16_t seqnum;
+        packet.GetExtension<TransportSequenceNumber>(&seqnum);
+        break;
+      case kRtpExtensionPlayoutDelay:
+        // TODO(katrielc) Add this once it's written.
+        break;
+    }
+  }
+}
 }  // namespace webrtc
-