From 80fba25fc394f6a603ef452f6fb0768326079ce8 Mon Sep 17 00:00:00 2001
From: stefan <stefan@webrtc.org>
Date: Tue, 18 Apr 2017 06:45:12 -0700
Subject: [PATCH] Fix crash when all acks in a feedback message arrive too
 late.

BUG=b/37279144

Review-Url: https://codereview.webrtc.org/2820353002
Cr-Commit-Position: refs/heads/master@{#17739}
---
 .../congestion_controller/delay_based_bwe.cc       |  8 +++++++-
 .../delay_based_bwe_unittest.cc                    | 14 ++++++++++++++
 .../send_side_congestion_controller.cc             |  2 --
 3 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/webrtc/modules/congestion_controller/delay_based_bwe.cc b/webrtc/modules/congestion_controller/delay_based_bwe.cc
index 453b03e347..7b19685d99 100644
--- a/webrtc/modules/congestion_controller/delay_based_bwe.cc
+++ b/webrtc/modules/congestion_controller/delay_based_bwe.cc
@@ -172,11 +172,17 @@ DelayBasedBwe::DelayBasedBwe(RtcEventLog* event_log, const Clock* clock)
 DelayBasedBwe::Result DelayBasedBwe::IncomingPacketFeedbackVector(
     const std::vector<PacketFeedback>& packet_feedback_vector) {
   RTC_DCHECK(network_thread_.CalledOnValidThread());
-  RTC_DCHECK(!packet_feedback_vector.empty());
 
   std::vector<PacketFeedback> sorted_packet_feedback_vector;
   SortPacketFeedbackVector(packet_feedback_vector,
                            &sorted_packet_feedback_vector);
+  // TOOD(holmer): An empty feedback vector here likely means that
+  // all acks were too late and that the send time history had
+  // timed out. We should reduce the rate when this occurs.
+  if (sorted_packet_feedback_vector.empty()) {
+    LOG(LS_WARNING) << "Very late feedback received.";
+    return DelayBasedBwe::Result();
+  }
 
   if (!uma_recorded_) {
     RTC_HISTOGRAM_ENUMERATION(kBweTypeHistogram,
diff --git a/webrtc/modules/congestion_controller/delay_based_bwe_unittest.cc b/webrtc/modules/congestion_controller/delay_based_bwe_unittest.cc
index 44407b37e9..b72d00604f 100644
--- a/webrtc/modules/congestion_controller/delay_based_bwe_unittest.cc
+++ b/webrtc/modules/congestion_controller/delay_based_bwe_unittest.cc
@@ -25,6 +25,20 @@ const PacedPacketInfo kPacingInfo0(0, kNumProbesCluster0, 2000);
 const PacedPacketInfo kPacingInfo1(1, kNumProbesCluster1, 4000);
 }  // namespace
 
+TEST_F(DelayBasedBweTest, NoCrashEmptyFeedback) {
+  std::vector<PacketFeedback> packet_feedback_vector;
+  bitrate_estimator_->IncomingPacketFeedbackVector(packet_feedback_vector);
+}
+
+TEST_F(DelayBasedBweTest, NoCrashOnlyLostFeedback) {
+  std::vector<PacketFeedback> packet_feedback_vector;
+  packet_feedback_vector.push_back(
+      PacketFeedback(-1, -1, 0, 1500, PacedPacketInfo()));
+  packet_feedback_vector.push_back(
+      PacketFeedback(-1, -1, 1, 1500, PacedPacketInfo()));
+  bitrate_estimator_->IncomingPacketFeedbackVector(packet_feedback_vector);
+}
+
 TEST_F(DelayBasedBweTest, ProbeDetection) {
   int64_t now_ms = clock_.TimeInMilliseconds();
   uint16_t seq_num = 0;
diff --git a/webrtc/modules/congestion_controller/send_side_congestion_controller.cc b/webrtc/modules/congestion_controller/send_side_congestion_controller.cc
index e3f84d0e53..78b7f32ad8 100644
--- a/webrtc/modules/congestion_controller/send_side_congestion_controller.cc
+++ b/webrtc/modules/congestion_controller/send_side_congestion_controller.cc
@@ -240,8 +240,6 @@ void SendSideCongestionController::OnTransportFeedback(
   transport_feedback_adapter_.OnTransportFeedback(feedback);
   std::vector<PacketFeedback> feedback_vector =
       transport_feedback_adapter_.GetTransportFeedbackVector();
-  if (feedback_vector.empty())
-    return;
   DelayBasedBwe::Result result;
   {
     rtc::CritScope cs(&bwe_lock_);