From 8c5638012955a198b5e79a455c57bc31cfb8a846 Mon Sep 17 00:00:00 2001
From: Per Kjellander <perkj@webrtc.org>
Date: Tue, 6 Sep 2022 17:12:18 +0200
Subject: [PATCH] Dont probe further if BWE is loss limited.

Bug: webrtc:14392
Change-Id: I2fc9b804943305bef6675fc024591548a30be3e8
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/274261
Reviewed-by: Diep Bui <diepbp@webrtc.org>
Commit-Queue: Per Kjellander <perkj@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#38029}
---
 .../goog_cc/probe_controller.cc               |  4 ++
 .../goog_cc/probe_controller_unittest.cc      | 61 +++++++++++++++++++
 2 files changed, 65 insertions(+)

diff --git a/modules/congestion_controller/goog_cc/probe_controller.cc b/modules/congestion_controller/goog_cc/probe_controller.cc
index b9e6151877..00875d878c 100644
--- a/modules/congestion_controller/goog_cc/probe_controller.cc
+++ b/modules/congestion_controller/goog_cc/probe_controller.cc
@@ -268,6 +268,10 @@ std::vector<ProbeClusterConfig> ProbeController::SetEstimatedBitrate(
     DataRate bitrate,
     bool bwe_limited_due_to_packet_loss,
     Timestamp at_time) {
+  if (bwe_limited_due_to_packet_loss != bwe_limited_due_to_packet_loss_ &&
+      config_.limit_probe_target_rate_to_loss_bwe) {
+    state_ = State::kProbingComplete;
+  }
   bwe_limited_due_to_packet_loss_ = bwe_limited_due_to_packet_loss;
   if (bitrate < kBitrateDropThreshold * estimated_bitrate_) {
     time_of_last_large_drop_ = at_time;
diff --git a/modules/congestion_controller/goog_cc/probe_controller_unittest.cc b/modules/congestion_controller/goog_cc/probe_controller_unittest.cc
index 290760607d..63a377624a 100644
--- a/modules/congestion_controller/goog_cc/probe_controller_unittest.cc
+++ b/modules/congestion_controller/goog_cc/probe_controller_unittest.cc
@@ -770,5 +770,66 @@ TEST(ProbeControllerTest, ProbeAfterLargeNetworkStateDropLossLimited) {
   EXPECT_EQ(probes[0].target_data_rate, kStartBitrate / 3);
 }
 
+TEST(ProbeControllerTest, DontProbeFurtherWhenLossLimited) {
+  ProbeControllerFixture fixture(
+      "WebRTC-Bwe-ProbingConfiguration/"
+      "network_state_interval:5s,limit_probe_target_rate_to_loss_bwe:true/");
+  std::unique_ptr<ProbeController> probe_controller =
+      fixture.CreateController();
+
+  auto probes = probe_controller->SetBitrates(
+      kMinBitrate, kStartBitrate, kMaxBitrate, fixture.CurrentTime());
+  ASSERT_FALSE(probes.empty());
+
+  // Need to wait at least one second before process can trigger a new probe.
+  fixture.AdvanceTime(TimeDelta::Millis(1100));
+  probes = probe_controller->Process(fixture.CurrentTime());
+  EXPECT_TRUE(probes.empty());
+
+  NetworkStateEstimate state_estimate;
+  state_estimate.link_capacity_upper = 3 * kStartBitrate;
+  probe_controller->SetNetworkStateEstimate(state_estimate);
+  fixture.AdvanceTime(TimeDelta::Seconds(5));
+  probes = probe_controller->Process(fixture.CurrentTime());
+  EXPECT_FALSE(probes.empty());
+  EXPECT_LT(probes[0].target_data_rate, state_estimate.link_capacity_upper);
+  // Expect that no more probes are sent immediately if BWE is loss limited.
+  probes = probe_controller->SetEstimatedBitrate(
+      probes[0].target_data_rate, /*bwe_limited_due_to_packet_loss=*/true,
+      fixture.CurrentTime());
+  EXPECT_TRUE(probes.empty());
+}
+
+TEST(ProbeControllerTest, ProbeFurtherWhenDelayBasedLimited) {
+  ProbeControllerFixture fixture(
+      "WebRTC-Bwe-ProbingConfiguration/"
+      "network_state_interval:5s,limit_probe_target_rate_to_loss_bwe:true/");
+  std::unique_ptr<ProbeController> probe_controller =
+      fixture.CreateController();
+
+  auto probes = probe_controller->SetBitrates(
+      kMinBitrate, kStartBitrate, kMaxBitrate, fixture.CurrentTime());
+  ASSERT_FALSE(probes.empty());
+
+  // Need to wait at least one second before process can trigger a new probe.
+  fixture.AdvanceTime(TimeDelta::Millis(1100));
+  probes = probe_controller->Process(fixture.CurrentTime());
+  EXPECT_TRUE(probes.empty());
+
+  NetworkStateEstimate state_estimate;
+  state_estimate.link_capacity_upper = 3 * kStartBitrate;
+  probe_controller->SetNetworkStateEstimate(state_estimate);
+  fixture.AdvanceTime(TimeDelta::Seconds(5));
+  probes = probe_controller->Process(fixture.CurrentTime());
+  EXPECT_FALSE(probes.empty());
+  EXPECT_LT(probes[0].target_data_rate, state_estimate.link_capacity_upper);
+  // Since the probe was successfull, expect to continue probing.
+  probes = probe_controller->SetEstimatedBitrate(
+      probes[0].target_data_rate, /*bwe_limited_due_to_packet_loss=*/false,
+      fixture.CurrentTime());
+  EXPECT_FALSE(probes.empty());
+  EXPECT_EQ(probes[0].target_data_rate, state_estimate.link_capacity_upper);
+}
+
 }  // namespace test
 }  // namespace webrtc