Internal change

PiperOrigin-RevId: 365906963

cpp/core/internal/bwu_manager.cc

@@ -717,10 +717,12 @@ void BwuManager::ProcessSafeToClosePriorChannelEvent(
   previous_endpoint_channel->DisableEncryption();
   previous_endpoint_channel->Write(parser::ForDisconnection());
 
-  // TODO(b/172380349): Match the Java implementation with no sleep call
-
-  // Wait for in-flight messages to reach their peers.
-  SystemClock::Sleep(absl::Seconds(1));
+  // Attempt to read the disconnect message from the previous channel. We don't
+  // care whether we successfully read it or whether we get an exception here.
+  // The idea is just to make sure the other side has had a chance to receive
+  // the full SAFE_TO_CLOSE_PRIOR_CHANNEL message before we actually close the
+  // channel. See b/172380349 for more context.
+  previous_endpoint_channel->Read();
   previous_endpoint_channel->Close(DisconnectionReason::UPGRADED);
 
   // Now that the old channel has been drained, we can unpause the new channel

cpp/core/internal/bwu_manager_test.cc

@@ -21,6 +21,7 @@
 #include "core/internal/endpoint_manager.h"
 #include "core/internal/mediums/mediums.h"
 #include "core/internal/mediums/utils.h"
+#include "core/internal/offline_frames.h"
 #include "platform/public/system_clock.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
@@ -57,20 +58,30 @@ TEST(BwuManagerTest, CanInitiateBwu) {
   bwu_manager.Shutdown();
 }
 
-TEST(BwuManagerTest, CanProcessPathAvailableFrame) {
+TEST(BwuManagerTest, CanProcessBandwidthUpgradeFrames) {
   ClientProxy client;
   std::string endpoint_id("EP_A");
+  LocationHint location_hint = Utils::BuildLocationHint("US");
   Mediums mediums;
   EndpointChannelManager ecm;
   EndpointManager em{&ecm};
   BwuManager bwu_manager{mediums, em, ecm, {}, {}};
 
-  LocationHint location_hint = Utils::BuildLocationHint("US");
-  ExceptionOr<OfflineFrame> wrapped_frame = parser::FromBytes(
+  ExceptionOr<OfflineFrame> path_available_frame = parser::FromBytes(
       parser::ForBwuWebrtcPathAvailable("my_id", location_hint));
+  bwu_manager.OnIncomingFrame(path_available_frame.result(), endpoint_id,
+                              &client, Medium::WEB_RTC);
 
-  bwu_manager.OnIncomingFrame(wrapped_frame.result(), endpoint_id, &client,
+  ExceptionOr<OfflineFrame> last_write_frame =
+      parser::FromBytes(parser::ForBwuLastWrite());
+  bwu_manager.OnIncomingFrame(last_write_frame.result(), endpoint_id, &client,
                               Medium::WEB_RTC);
+
+  ExceptionOr<OfflineFrame> safe_to_close_frame =
+      parser::FromBytes(parser::ForBwuSafeToClose());
+  bwu_manager.OnIncomingFrame(safe_to_close_frame.result(), endpoint_id,
+                              &client, Medium::WEB_RTC);
+
   bwu_manager.Shutdown();
 }