From 7aadbb7b9a02742e370563e39bef129b1df079b5 Mon Sep 17 00:00:00 2001
From: Simon Lin <simonlin@google.com>
Date: Fri, 10 Sep 2021 12:49:07 +0800
Subject: [PATCH] [mle] send Delayed Data Request with latest Active/Pending
 Timestamp (#6995)

This commit fixes a potential bug that delayed Data Requests may use
wrong Active and Pending Timestamps because the Active & Pending
Timestamps may change while a Data Request is being delayed.
---
 src/core/thread/mle.cpp | 29 ++++++++++++++++++++++-------
 src/core/thread/mle.hpp | 17 +++++++++++------
 2 files changed, 33 insertions(+), 13 deletions(-)

diff --git a/src/core/thread/mle.cpp b/src/core/thread/mle.cpp
index 915169794..24773514f 100644
--- a/src/core/thread/mle.cpp
+++ b/src/core/thread/mle.cpp
@@ -1959,10 +1959,20 @@ void Mle::HandleDelayedResponseTimer(void)
         }
         else
         {
+            Error error = kErrorNone;
+
             mDelayedResponses.Dequeue(*message);
             metadata.RemoveFrom(*message);
 
-            if (SendMessage(*message, metadata.mDestination) == kErrorNone)
+            if (metadata.mAppendTimestamps)
+            {
+                error = AppendActiveTimestamp(*message);
+                error = (error == kErrorNone) ? AppendPendingTimestamp(*message) : error;
+            }
+
+            error = (error == kErrorNone) ? SendMessage(*message, metadata.mDestination) : error;
+
+            if (error == kErrorNone)
             {
                 Log(kMessageSend, kTypeGenericDelayed, metadata.mDestination);
 
@@ -2153,8 +2163,6 @@ Error Mle::SendDataRequest(const Ip6::Address &aDestination,
     VerifyOrExit((message = NewMleMessage()) != nullptr, error = kErrorNoBufs);
     SuccessOrExit(error = AppendHeader(*message, kCommandDataRequest));
     SuccessOrExit(error = AppendTlvRequest(*message, aTlvs, aTlvsLength));
-    SuccessOrExit(error = AppendActiveTimestamp(*message));
-    SuccessOrExit(error = AppendPendingTimestamp(*message));
 
     if (aExtraTlvs != nullptr && aExtraTlvsLength > 0)
     {
@@ -2163,11 +2171,14 @@ Error Mle::SendDataRequest(const Ip6::Address &aDestination,
 
     if (aDelay)
     {
-        SuccessOrExit(error = AddDelayedResponse(*message, aDestination, aDelay));
+        SuccessOrExit(error = AddDelayedResponse(*message, aDestination, aDelay, /* aAppendTimestamps */ true));
         Log(kMessageDelay, kTypeDataRequest, aDestination);
     }
     else
     {
+        SuccessOrExit(error = AppendActiveTimestamp(*message));
+        SuccessOrExit(error = AppendPendingTimestamp(*message));
+
         SuccessOrExit(error = SendMessage(*message, aDestination));
         Log(kMessageSend, kTypeDataRequest, aDestination);
 
@@ -2651,13 +2662,17 @@ exit:
     return error;
 }
 
-Error Mle::AddDelayedResponse(Message &aMessage, const Ip6::Address &aDestination, uint16_t aDelay)
+Error Mle::AddDelayedResponse(Message &           aMessage,
+                              const Ip6::Address &aDestination,
+                              uint16_t            aDelay,
+                              bool                aAppendTimestamps)
 {
     Error                   error = kErrorNone;
     DelayedResponseMetadata metadata;
 
-    metadata.mSendTime    = TimerMilli::GetNow() + aDelay;
-    metadata.mDestination = aDestination;
+    metadata.mSendTime         = TimerMilli::GetNow() + aDelay;
+    metadata.mDestination      = aDestination;
+    metadata.mAppendTimestamps = aAppendTimestamps;
 
     SuccessOrExit(error = metadata.AppendTo(aMessage));
     mDelayedResponses.Enqueue(aMessage);
diff --git a/src/core/thread/mle.hpp b/src/core/thread/mle.hpp
index b54bc7c97..436d42a4e 100644
--- a/src/core/thread/mle.hpp
+++ b/src/core/thread/mle.hpp
@@ -1442,15 +1442,19 @@ protected:
     /**
      * This method adds a message to the message queue. The queued message will be transmitted after given delay.
      *
-     * @param[in]  aMessage      The message to transmit after given delay.
-     * @param[in]  aDestination  The IPv6 address of the recipient of the message.
-     * @param[in]  aDelay        The delay in milliseconds before transmission of the message.
+     * @param[in]  aMessage             The message to transmit after given delay.
+     * @param[in]  aDestination         The IPv6 address of the recipient of the message.
+     * @param[in]  aDelay               The delay in milliseconds before transmission of the message.
+     * @param[in]  aAppendTimestamps    Whether or not to append Active and Pending Timestamps before sending.
      *
      * @retval kErrorNone     Successfully queued the message to transmit after the delay.
      * @retval kErrorNoBufs   Insufficient buffers to queue the message.
      *
      */
-    Error AddDelayedResponse(Message &aMessage, const Ip6::Address &aDestination, uint16_t aDelay);
+    Error AddDelayedResponse(Message &           aMessage,
+                             const Ip6::Address &aDestination,
+                             uint16_t            aDelay,
+                             bool                aAppendTimestamps = false);
 
 #if (OPENTHREAD_CONFIG_LOG_LEVEL >= OT_LOG_LEVEL_INFO) && (OPENTHREAD_CONFIG_LOG_MLE == 1)
     /**
@@ -1667,8 +1671,9 @@ private:
         void  ReadFrom(const Message &aMessage);
         void  RemoveFrom(Message &aMessage) const;
 
-        Ip6::Address mDestination; // IPv6 address of the message destination.
-        TimeMilli    mSendTime;    // Time when the message shall be sent.
+        Ip6::Address mDestination;          // IPv6 address of the message destination.
+        TimeMilli    mSendTime;             // Time when the message shall be sent.
+        bool         mAppendTimestamps : 1; // Append Active Timestamp and Pending Timestamp before sending.
     };
 
     OT_TOOL_PACKED_BEGIN