From 6e57c4ef299761a8b3b9584221f6b64425ed1e03 Mon Sep 17 00:00:00 2001
From: Nivi Sarkar <55898241+nivi-apple@users.noreply.github.com>
Date: Thu, 30 Jan 2025 10:11:45 -0800
Subject: [PATCH] Handle output event of type
 TransferSession::OutputEventType::kInternalError in the ProcessOutputEvents
 API.

- If the state machine generates this event, indicating that the session is in a bad state and cannot continue,
  terminate the BDX session.
---
 .../bdx/AsyncTransferFacilitator.cpp          | 22 +++++++++++--------
 src/protocols/bdx/AsyncTransferFacilitator.h  |  6 ++++-
 2 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/src/protocols/bdx/AsyncTransferFacilitator.cpp b/src/protocols/bdx/AsyncTransferFacilitator.cpp
index 2730e17481caa6..7d9166c7b283ce 100644
--- a/src/protocols/bdx/AsyncTransferFacilitator.cpp
+++ b/src/protocols/bdx/AsyncTransferFacilitator.cpp
@@ -45,6 +45,7 @@ CHIP_ERROR AsyncTransferFacilitator::Init(System::Layer * layer, Messaging::Exch
  */
 void AsyncTransferFacilitator::ProcessOutputEvents()
 {
+
     if (mProcessingOutputEvents)
     {
         ChipLogDetail(BDX,
@@ -63,6 +64,16 @@ void AsyncTransferFacilitator::ProcessOutputEvents()
     mTransfer.GetNextAction(outEvent);
     while (outEvent.EventType != TransferSession::OutputEventType::kNone)
     {
+
+        // If the transfer session state machine generates an event of type TransferSession::OutputEventType::kInternalError,
+        // indicating that the session is in a bad state, we do not want to process any more events and terminate the session.
+        // In that case, set mDestroySelfAfterProcessingEvents to true and break from the loop so we can call DestroySelf() to clean up.
+        if (outEvent.EventType == TransferSession::OutputEventType::kInternalError)
+        {
+            mDestroySelfAfterProcessingEvents = true;
+            break;
+        }
+
         if (outEvent.EventType == TransferSession::OutputEventType::kMsgToSend)
         {
             CHIP_ERROR err = SendMessage(outEvent.msgTypeData, outEvent.MsgData);
@@ -170,27 +181,20 @@ void AsyncResponder::NotifyEventHandled(const TransferSession::OutputEventType e
     ChipLogDetail(BDX, "NotifyEventHandled : Event %s Error %" CHIP_ERROR_FORMAT,
                   TransferSession::OutputEvent::TypeToString(eventType), status.Format());
 
-    // If we are handling a status report, we should destroy ourselves and hence, terminate the transfer.
-    if (eventType == TransferSession::OutputEventType::kStatusReceived)
-    {
-        DestroySelf();
-        return;
-    }
-
     // If this is the end of the transfer (whether a clean end, or some sort of error condition), ensure that
     // we destroy ourselves after processing any output events that might have been generated by
     // the transfer session to handle end-of-transfer (e.g. in some error conditions it might want to send
     // out a status report).
     if (eventType == TransferSession::OutputEventType::kAckEOFReceived ||
+        eventType == TransferSession::OutputEventType::kStatusReceived ||
         eventType == TransferSession::OutputEventType::kInternalError ||
         eventType == TransferSession::OutputEventType::kTransferTimeout)
     {
         mDestroySelfAfterProcessingEvents = true;
     }
-
     // If there was an error handling the output event, this should notify the transfer object to abort transfer so it can send a
     // status report across the exchange when we call ProcessOutputEvents below.
-    if (status != CHIP_NO_ERROR)
+    else if (status != CHIP_NO_ERROR)
     {
         mTransfer.AbortTransfer(GetBdxStatusCodeFromChipError(status));
     }
diff --git a/src/protocols/bdx/AsyncTransferFacilitator.h b/src/protocols/bdx/AsyncTransferFacilitator.h
index 1ad95d39e98d2d..e8928664a56743 100644
--- a/src/protocols/bdx/AsyncTransferFacilitator.h
+++ b/src/protocols/bdx/AsyncTransferFacilitator.h
@@ -72,7 +72,11 @@ class AsyncTransferFacilitator : public Messaging::ExchangeDelegate
      */
     virtual void DestroySelf() = 0;
 
-    // Calling ProcessOutputEvents can destroy this object before the call returns.
+    /**
+     * Calling ProcessOutputEvents can destroy this object before the call returns for certain cases
+     * where the state machine either receives a message indicating termination of the transfer session (StatusReport
+     * or BlockAckEOF) or generates an InternalError for various error scenarios including timeout.
+     */
     void ProcessOutputEvents();
 
     // The transfer session corresponding to this AsyncTransferFacilitator object.