From b0d4b415cc59916a300ceb478b29759bcb94cf8f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Niels=20M=C3=B6ller?= <nisse@webrtc.org>
Date: Tue, 28 Aug 2018 13:58:15 +0200
Subject: [PATCH] Use a lock to protect members accessed by
 RtpVideoStreamReceiver::GetSyncInfo()
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Proper synchronization was overlooked in
https://webrtc-review.googlesource.com/93261

Bug: chromium:878319, webrtc:7135
Change-Id: Ifc850c4d67a4e9dd2660dab9b6da67258338553e
Reviewed-on: https://webrtc-review.googlesource.com/96461
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24495}
---
 video/rtp_video_stream_receiver.cc | 22 ++++++++++++++--------
 video/rtp_video_stream_receiver.h  |  6 ++++--
 2 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/video/rtp_video_stream_receiver.cc b/video/rtp_video_stream_receiver.cc
index 46563477e2..e2139b8e8b 100644
--- a/video/rtp_video_stream_receiver.cc
+++ b/video/rtp_video_stream_receiver.cc
@@ -176,17 +176,20 @@ void RtpVideoStreamReceiver::AddReceiveCodec(
 }
 
 absl::optional<Syncable::Info> RtpVideoStreamReceiver::GetSyncInfo() const {
-  if (!last_received_rtp_timestamp_ || !last_received_rtp_system_time_ms_) {
-    return absl::nullopt;
-  }
   Syncable::Info info;
   if (rtp_rtcp_->RemoteNTP(&info.capture_time_ntp_secs,
                            &info.capture_time_ntp_frac, nullptr, nullptr,
                            &info.capture_time_source_clock) != 0) {
     return absl::nullopt;
   }
-  info.latest_received_capture_timestamp = *last_received_rtp_timestamp_;
-  info.latest_receive_time_ms = *last_received_rtp_system_time_ms_;
+  {
+    rtc::CritScope lock(&last_seq_num_cs_);
+    if (!last_received_rtp_timestamp_ || !last_received_rtp_system_time_ms_) {
+      return absl::nullopt;
+    }
+    info.latest_received_capture_timestamp = *last_received_rtp_timestamp_;
+    info.latest_receive_time_ms = *last_received_rtp_system_time_ms_;
+  }
 
   // Leaves info.current_delay_ms uninitialized.
   return info;
@@ -279,10 +282,13 @@ void RtpVideoStreamReceiver::OnRtpPacket(const RtpPacketReceived& packet) {
 
   if (!packet.recovered()) {
     int64_t now_ms = clock_->TimeInMilliseconds();
-    // TODO(nisse): Exclude out-of-order packets?
-    last_received_rtp_timestamp_ = packet.Timestamp();
-    last_received_rtp_system_time_ms_ = now_ms;
+    {
+      rtc::CritScope lock(&last_seq_num_cs_);
 
+      // TODO(nisse): Exclude out-of-order packets?
+      last_received_rtp_timestamp_ = packet.Timestamp();
+      last_received_rtp_system_time_ms_ = now_ms;
+    }
     // Periodically log the RTP header of incoming packets.
     if (now_ms - last_packet_log_ms_ > kPacketLogIntervalMs) {
       std::stringstream ss;
diff --git a/video/rtp_video_stream_receiver.h b/video/rtp_video_stream_receiver.h
index a351c92eaf..e67d66389e 100644
--- a/video/rtp_video_stream_receiver.h
+++ b/video/rtp_video_stream_receiver.h
@@ -177,8 +177,10 @@ class RtpVideoStreamReceiver : public RtpData,
       RTC_GUARDED_BY(last_seq_num_cs_);
   video_coding::H264SpsPpsTracker tracker_;
 
-  absl::optional<uint32_t> last_received_rtp_timestamp_;
-  absl::optional<int64_t> last_received_rtp_system_time_ms_;
+  absl::optional<uint32_t> last_received_rtp_timestamp_
+      RTC_GUARDED_BY(last_seq_num_cs_);
+  absl::optional<int64_t> last_received_rtp_system_time_ms_
+      RTC_GUARDED_BY(last_seq_num_cs_);
   std::map<uint8_t, VideoCodecType> pt_codec_type_;
   // TODO(johan): Remove pt_codec_params_ once
   // https://bugs.chromium.org/p/webrtc/issues/detail?id=6883 is resolved.