Add FEC producer fuzzing and a unittest for one of the issues found.

webrtc/test/fuzzers/producer_fec_fuzzer.cc

+/*
+ *  Copyright (c) 2015 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.
+ */
+#include "webrtc/base/checks.h"
+#include "webrtc/base/scoped_ptr.h"
+#include "webrtc/modules/rtp_rtcp/source/byte_io.h"
+#include "webrtc/modules/rtp_rtcp/source/producer_fec.h"
+
+namespace webrtc {
+
+void FuzzOneInput(const uint8_t* data, size_t size) {
+  ForwardErrorCorrection fec;
+  ProducerFec producer(&fec);
+  size_t i = 0;
+  if (size < 4)
+    return;
+  FecProtectionParams params = {data[i++] % 128, data[i++] % 1,
+                                static_cast<int>(data[i++] % 10),
+                                kFecMaskBursty};
+  producer.SetFecParameters(&params, 0);
+  uint16_t seq_num = data[i++];
+
+  while (i + 3 < size) {
+    size_t rtp_header_length = data[i++] % 10 + 12;
+    size_t payload_size = data[i++] % 10;
+    if (i + payload_size + rtp_header_length + 2 > size)
+      break;
+    rtc::scoped_ptr<uint8_t[]> packet(
+        new uint8_t[payload_size + rtp_header_length]);
+    memcpy(packet.get(), &data[i], payload_size + rtp_header_length);
+    ByteWriter<uint16_t>::WriteBigEndian(&packet[2], seq_num++);
+    i += payload_size + rtp_header_length;
+    // Make sure sequence numbers are increasing.
+    const int kRedPayloadType = 98;
+    rtc::scoped_ptr<RedPacket> red_packet(producer.BuildRedPacket(
+        packet.get(), payload_size, rtp_header_length, kRedPayloadType));
+    bool protect = static_cast<bool>(data[i++] % 2);
+    if (protect) {
+      producer.AddRtpPacketAndGenerateFec(packet.get(), payload_size,
+                                          rtp_header_length);
+    }
+    uint16_t num_fec_packets = producer.NumAvailableFecPackets();
+    std::vector<RedPacket*> fec_packets;
+    if (num_fec_packets > 0) {
+      fec_packets =
+          producer.GetFecPackets(kRedPayloadType, 99, 100, rtp_header_length);
+      RTC_CHECK_EQ(num_fec_packets, fec_packets.size());
+    }
+    for (RedPacket* fec_packet : fec_packets) {
+      delete fec_packet;
+    }
+  }
+}
+}  // namespace webrtc