From c79a9055289af53a08f59827dda9feba766fe39a Mon Sep 17 00:00:00 2001
From: Abtin Keshavarzian <abtink@google.com>
Date: Fri, 23 Jun 2017 11:58:08 -0700
Subject: [PATCH] [mesh-forwarder] Drop a message if all tx attempts fail for
 one of its fragments (#1933)

Existing code already enables this behavior for indirect message
transmissions. This commits adds support for direct transmission and
also introduces `OPENTHREAD_CONFIG_DROP_MESSAGE_ON_FRAGMENT_TX_FAILURE`
as a new configuration option to control this feature. If enabled
OpenThread will drop a message (and not send any remaining fragments
of the message) if all transmit attempts fail for a fragment of the
message. For a direct transmission, a failure occurs after all MAC
transmission attempts for a given fragment are unsuccessful. For an
indirect transmission, a failure occurs after all data poll triggered
transmission attempts for a given fragment fail. If this feature is
disabled, OpenThread will attempt to send subsequent fragments,
whether or not all transmission attempts fail for a given fragment.
Default setting enables this behavior.
---
 src/core/openthread-core-default-config.h | 16 ++++++++++++++
 src/core/thread/mesh_forwarder.cpp        | 26 +++++++++++++++++------
 2 files changed, 35 insertions(+), 7 deletions(-)

diff --git a/src/core/openthread-core-default-config.h b/src/core/openthread-core-default-config.h
index 667279994..496e8a003 100644
--- a/src/core/openthread-core-default-config.h
+++ b/src/core/openthread-core-default-config.h
@@ -149,6 +149,22 @@
 #define OPENTHREAD_CONFIG_MAX_TX_ATTEMPTS_INDIRECT_POLLS        4
 #endif // OPENTHREAD_CONFIG_MAX_TX_ATTEMPTS_INDIRECT_POLLS
 
+/**
+ * @def OPENTHREAD_CONFIG_DROP_MESSAGE_ON_FRAGMENT_TX_FAILURE
+ *
+ * Define as 1 for OpenThread to drop a message (and not send any remaining fragments of the message) if all transmit
+ * attempts fail for a fragment of the message. For a direct transmission, a failure occurs after all MAC transmission
+ * attempts for a given fragment are unsuccessful. For an indirect transmission, a failure occurs after all data poll
+ * triggered transmission attempts for a given fragment fail.
+ *
+ * If set to zero (disabled), OpenThread will attempt to send subsequent fragments, whether or not all transmission
+ * attempts fail for a given fragment.
+ *
+ */
+#ifndef OPENTHREAD_CONFIG_DROP_MESSAGE_ON_FRAGMENT_TX_FAILURE
+#define OPENTHREAD_CONFIG_DROP_MESSAGE_ON_FRAGMENT_TX_FAILURE   1
+#endif // OPENTHREAD_CONFIG_DROP_MESSAGE_ON_FRAGMENT_TX_FAILURE
+
 /**
  * @def OPENTHREAD_CONFIG_ATTACH_DATA_POLL_PERIOD
  *
diff --git a/src/core/thread/mesh_forwarder.cpp b/src/core/thread/mesh_forwarder.cpp
index 2369f0b41..b8df4ce75 100644
--- a/src/core/thread/mesh_forwarder.cpp
+++ b/src/core/thread/mesh_forwarder.cpp
@@ -1491,13 +1491,12 @@ void MeshForwarder::HandleSentFrame(Mac::Frame &aFrame, otError aError)
 
         if (mSendMessage == child->GetIndirectMessage())
         {
-            switch (aError)
+            if (aError == OT_ERROR_NONE)
             {
-            case OT_ERROR_NONE:
                 child->ResetIndirectTxAttempts();
-                break;
-
-            default:
+            }
+            else
+            {
                 child->IncrementIndirectTxAttempts();
 
                 if (child->GetIndirectTxAttempts() < kMaxPollTriggeredTxAttempts)
@@ -1526,13 +1525,13 @@ void MeshForwarder::HandleSentFrame(Mac::Frame &aFrame, otError aError)
 
                 child->ResetIndirectTxAttempts();
 
+#if OPENTHREAD_CONFIG_DROP_MESSAGE_ON_FRAGMENT_TX_FAILURE
                 // We set the NextOffset to end of message, since there is no need to
                 // send any remaining fragments in the message to the child, if all tx
                 // attempts of current frame already failed.
 
                 mMessageNextOffset = mSendMessage->GetLength();
-
-                break;
+#endif
             }
         }
 
@@ -1581,6 +1580,19 @@ void MeshForwarder::HandleSentFrame(Mac::Frame &aFrame, otError aError)
 
     if (mSendMessage->GetDirectTransmission())
     {
+
+#if OPENTHREAD_CONFIG_DROP_MESSAGE_ON_FRAGMENT_TX_FAILURE
+
+        if (aError != OT_ERROR_NONE)
+        {
+            // We set the NextOffset to end of message to avoid sending
+            // any remaining fragments in the message.
+
+            mMessageNextOffset = mSendMessage->GetLength();
+        }
+
+#endif
+
         if (mMessageNextOffset < mSendMessage->GetLength())
         {
             mSendMessage->SetOffset(mMessageNextOffset);