From 0cfaa610ca17016be030709bdba17340dffa8c6a Mon Sep 17 00:00:00 2001
From: Victor Boivie <boivie@webrtc.org>
Date: Fri, 18 Mar 2022 09:16:35 +0100
Subject: [PATCH] dcsctp: Add test case for pending paused streams

This use case was missing test coverage and sufficient comments in the
code.

Bug: None
Change-Id: I95b54a64f714b68a347fdbeef79eb38e715adbc3
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/257166
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36393}
---
 net/dcsctp/tx/rr_send_queue.cc      |  4 +++-
 net/dcsctp/tx/rr_send_queue_test.cc | 30 +++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/net/dcsctp/tx/rr_send_queue.cc b/net/dcsctp/tx/rr_send_queue.cc
index f8f5ff2946..68db6f1870 100644
--- a/net/dcsctp/tx/rr_send_queue.cc
+++ b/net/dcsctp/tx/rr_send_queue.cc
@@ -44,7 +44,9 @@ bool RRSendQueue::OutgoingStream::HasDataToSend(TimeMs now) {
   while (!items_.empty()) {
     RRSendQueue::OutgoingStream::Item& item = items_.front();
     if (item.message_id.has_value()) {
-      // Already partially sent messages can always continue to be sent.
+      // Already partially sent messages can always continue to be sent. This
+      // ensures e.g. that paused streams with partially sent messages get to
+      // send the partial message in full before resetting.
       return true;
     }
 
diff --git a/net/dcsctp/tx/rr_send_queue_test.cc b/net/dcsctp/tx/rr_send_queue_test.cc
index 425027762d..78f7616766 100644
--- a/net/dcsctp/tx/rr_send_queue_test.cc
+++ b/net/dcsctp/tx/rr_send_queue_test.cc
@@ -323,6 +323,36 @@ TEST_F(RRSendQueueTest, EnqueuedItemsArePausedDuringStreamReset) {
   EXPECT_EQ(buf_.total_buffered_amount(), 0u);
 }
 
+TEST_F(RRSendQueueTest, PausedStreamsStillSendPartialMessagesUntilEnd) {
+  constexpr size_t kPayloadSize = 100;
+  constexpr size_t kFragmentSize = 50;
+  std::vector<uint8_t> payload(kPayloadSize);
+
+  buf_.Add(kNow, DcSctpMessage(kStreamID, kPPID, payload));
+  buf_.Add(kNow, DcSctpMessage(kStreamID, kPPID, payload));
+
+  absl::optional<SendQueue::DataToSend> chunk_one =
+      buf_.Produce(kNow, kFragmentSize);
+  ASSERT_TRUE(chunk_one.has_value());
+  EXPECT_EQ(chunk_one->data.stream_id, kStreamID);
+  EXPECT_EQ(buf_.total_buffered_amount(), 2 * kPayloadSize - kFragmentSize);
+
+  // This will stop the second message from being sent.
+  StreamID stream_ids[] = {StreamID(1)};
+  buf_.PrepareResetStreams(stream_ids);
+  EXPECT_EQ(buf_.total_buffered_amount(), 1 * kPayloadSize - kFragmentSize);
+
+  // Should still produce fragments until end of message.
+  absl::optional<SendQueue::DataToSend> chunk_two =
+      buf_.Produce(kNow, kFragmentSize);
+  ASSERT_TRUE(chunk_two.has_value());
+  EXPECT_EQ(chunk_two->data.stream_id, kStreamID);
+  EXPECT_EQ(buf_.total_buffered_amount(), 0ul);
+
+  // But shouldn't produce any more messages as the stream is paused.
+  EXPECT_FALSE(buf_.Produce(kNow, kFragmentSize).has_value());
+}
+
 TEST_F(RRSendQueueTest, CommittingResetsSSN) {
   std::vector<uint8_t> payload(50);