Merge branch 'master' into release to roll forward to cl/340553187.

cpp/core/internal/base_endpoint_channel.cc

@@ -259,6 +259,11 @@ void BaseEndpointChannel::EnableEncryption(
   crypto_context_ = context;
 }
 
+void BaseEndpointChannel::DisableEncryption() {
+  MutexLock crypto_lock(&crypto_mutex_);
+  crypto_context_.reset();
+}
+
 bool BaseEndpointChannel::IsPaused() const {
   MutexLock lock(&is_paused_mutex_);
   return is_paused_;

cpp/core/internal/base_endpoint_channel.h

@@ -67,6 +67,9 @@ class BaseEndpointChannel : public EndpointChannel {
   // before entering data phase, where Payloads may be exchanged.
   void EnableEncryption(std::shared_ptr<EncryptionContext> context) override;
 
+  // Disables encryption on the EndpointChannel.
+  void DisableEncryption() override;
+
   // True if the EndpointChannel is currently pausing all writes.
   bool IsPaused() const ABSL_LOCKS_EXCLUDED(is_paused_mutex_) override;
 

cpp/core/internal/bwu_manager.cc

@@ -562,8 +562,15 @@ void BwuManager::ProcessSafeToClosePriorChannelEvent(
              "trying to upgrade endpoint %s.",
              endpoint_id.c_str());
 
+  // Each encrypted message includes the key to decrypt the next message. The
+  // disconnect message is optional and may not be received under normal
+  // circumstances so it is necessary to send it unencrypted. This way the
+  // serial crypto context does not increment here.
+  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));
   previous_endpoint_channel->Close(DisconnectionReason::UPGRADED);

cpp/core/internal/encryption_runner_test.cc

@@ -55,6 +55,7 @@ class FakeEndpointChannel : public EndpointChannel {
   std::string GetName() const override { return "fake-channel"; }
   Medium GetMedium() const override { return Medium::BLE; }
   void EnableEncryption(std::shared_ptr<EncryptionContext> context) override {}
+  void DisableEncryption() override {}
   bool IsPaused() const override { return false; }
   void Pause() override {}
   void Resume() override {}

cpp/core/internal/endpoint_channel.h

@@ -59,6 +59,9 @@ class EndpointChannel {
   // Enables encryption on the EndpointChannel.
   virtual void EnableEncryption(std::shared_ptr<EncryptionContext> context) = 0;
 
+  // Disables encryption on the EndpointChannel.
+  virtual void DisableEncryption() = 0;
+
   // True if the EndpointChannel is currently pausing all writes.
   virtual bool IsPaused() const = 0;
 

cpp/core/internal/endpoint_manager_test.cc

@@ -56,6 +56,7 @@ class MockEndpointChannel : public EndpointChannel {
   MOCK_METHOD(Medium, GetMedium, (), (const override));
   MOCK_METHOD(void, EnableEncryption,
               (std::shared_ptr<EncryptionContext> context), (override));
+  MOCK_METHOD(void, DisableEncryption, (), (override));
   MOCK_METHOD(bool, IsPaused, (), (const override));
   MOCK_METHOD(void, Pause, (), (override));
   MOCK_METHOD(void, Resume, (), (override));