From be9281b92bf4d10b995b9e0a6d8ef843aac90689 Mon Sep 17 00:00:00 2001
From: Victor Boivie <boivie@webrtc.org>
Date: Wed, 11 Aug 2021 23:30:00 +0200
Subject: [PATCH] dcsctp: Increase cwnd by serialized chunk size

For symmetry, as the outstanding_bytes is increased/decreased by
the serialized chunk size (not just the payload) - which is compared
to the congestion window, the congestion window should be increased
by the serialized size of chunks acked - not just their payload.

Bug: webrtc:12943
Change-Id: I0a06033e8ca0d58433138df6442ca80494918cf2
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/228525
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Reviewed-by: Florent Castelli <orphis@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34775}
---
 net/dcsctp/tx/retransmission_queue.cc      |  5 +++--
 net/dcsctp/tx/retransmission_queue_test.cc | 26 +++++++++++++++++++++-
 2 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/net/dcsctp/tx/retransmission_queue.cc b/net/dcsctp/tx/retransmission_queue.cc
index c3d567d42e..763a82d026 100644
--- a/net/dcsctp/tx/retransmission_queue.cc
+++ b/net/dcsctp/tx/retransmission_queue.cc
@@ -144,10 +144,11 @@ void RetransmissionQueue::AckChunk(
     AckInfo& ack_info,
     std::map<UnwrappedTSN, TxData>::iterator iter) {
   if (!iter->second.is_acked()) {
-    ack_info.bytes_acked += iter->second.data().size();
+    size_t serialized_size = GetSerializedChunkSize(iter->second.data());
+    ack_info.bytes_acked += serialized_size;
     ack_info.acked_tsns.push_back(iter->first.Wrap());
     if (iter->second.is_outstanding()) {
-      outstanding_bytes_ -= GetSerializedChunkSize(iter->second.data());
+      outstanding_bytes_ -= serialized_size;
       --outstanding_items_;
     }
     if (iter->second.should_be_retransmitted()) {
diff --git a/net/dcsctp/tx/retransmission_queue_test.cc b/net/dcsctp/tx/retransmission_queue_test.cc
index a2ec3da4c2..5974e052a5 100644
--- a/net/dcsctp/tx/retransmission_queue_test.cc
+++ b/net/dcsctp/tx/retransmission_queue_test.cc
@@ -1185,7 +1185,31 @@ TEST_F(RetransmissionQueueTest, AbandonsRtxLimit2WhenNackedNineTimes) {
                           Pair(TSN(19), State::kAcked)));
 
   EXPECT_TRUE(queue.ShouldSendForwardTsn(now_));
-}  // namespace
+}
+
+TEST_F(RetransmissionQueueTest, CwndRecoversWhenAcking) {
+  RetransmissionQueue queue = CreateQueue();
+  static constexpr size_t kCwnd = 1200;
+  queue.set_cwnd(kCwnd);
+  EXPECT_EQ(queue.cwnd(), kCwnd);
+
+  std::vector<uint8_t> payload(1000);
+  EXPECT_CALL(producer_, Produce)
+      .WillOnce([this, payload](TimeMs, size_t) {
+        return SendQueue::DataToSend(gen_.Ordered(payload, "BE"));
+      })
+      .WillRepeatedly([](TimeMs, size_t) { return absl::nullopt; });
+
+  std::vector<std::pair<TSN, Data>> chunks_to_send =
+      queue.GetChunksToSend(now_, 1500);
+  EXPECT_THAT(chunks_to_send, ElementsAre(Pair(TSN(10), _)));
+  size_t serialized_size = payload.size() + DataChunk::kHeaderSize;
+  EXPECT_EQ(queue.outstanding_bytes(), serialized_size);
+
+  queue.HandleSack(now_, SackChunk(TSN(10), kArwnd, {}, {}));
+
+  EXPECT_EQ(queue.cwnd(), kCwnd + serialized_size);
+}
 
 }  // namespace
 }  // namespace dcsctp