From c9191ae79d70f30e446b6460de3e9544a7b9884b Mon Sep 17 00:00:00 2001
From: Jonathan Hui <jonhui@nestlabs.com>
Date: Sun, 12 Mar 2017 10:10:47 -0700
Subject: [PATCH] Add retransmission logic to MLE Child Update exchanges from
 child. (#1457)

---
 src/core/thread/mle.cpp           | 47 +++++++++++++++----------------
 src/core/thread/mle.hpp           |  2 +-
 src/core/thread/mle_constants.hpp |  1 +
 3 files changed, 25 insertions(+), 25 deletions(-)

diff --git a/src/core/thread/mle.cpp b/src/core/thread/mle.cpp
index 0dd9c723d..b83bca352 100644
--- a/src/core/thread/mle.cpp
+++ b/src/core/thread/mle.cpp
@@ -236,9 +236,9 @@ ThreadError Mle::Start(bool aEnableReattach)
     }
     else
     {
-        SendChildUpdateRequest();
         mParentRequestState = kParentSynchronize;
-        mParentRequestTimer.Start(kParentRequestRouterTimeout);
+        mChildUpdateAttempts = 0;
+        SendChildUpdateRequest();
     }
 
 exit:
@@ -546,10 +546,10 @@ ThreadError Mle::SetStateChild(uint16_t aRloc16)
     SetRloc16(aRloc16);
     mDeviceState = kDeviceStateChild;
     mParentRequestState = kParentIdle;
+    mChildUpdateAttempts = 0;
 
     if ((mDeviceMode & ModeTlv::kModeRxOnWhenIdle) != 0)
     {
-        mKeepAliveAttemptsSent = 0;
         mParentRequestTimer.Start(Timer::SecToMsec(mTimeout / kMaxChildKeepAliveAttempts));
     }
 
@@ -579,6 +579,8 @@ uint32_t Mle::GetTimeout(void) const
 
 ThreadError Mle::SetTimeout(uint32_t aTimeout)
 {
+    VerifyOrExit(mTimeout != aTimeout, ;);
+
     if (aTimeout < 4)
     {
         aTimeout = 4;
@@ -589,13 +591,9 @@ ThreadError Mle::SetTimeout(uint32_t aTimeout)
     if (mDeviceState == kDeviceStateChild)
     {
         SendChildUpdateRequest();
-
-        if ((mDeviceMode & ModeTlv::kModeRxOnWhenIdle) != 0)
-        {
-            mParentRequestTimer.Start(Timer::SecToMsec(mTimeout / kMaxChildKeepAliveAttempts));
-        }
     }
 
+exit:
     return kThreadError_None;
 }
 
@@ -611,6 +609,7 @@ ThreadError Mle::SetDeviceMode(uint8_t aDeviceMode)
 
     VerifyOrExit((aDeviceMode & ModeTlv::kModeFFD) == 0 || (aDeviceMode & ModeTlv::kModeRxOnWhenIdle) != 0,
                  error = kThreadError_InvalidArgs);
+    VerifyOrExit(mDeviceMode != aDeviceMode, ;);
 
     mDeviceMode = aDeviceMode;
 
@@ -1265,20 +1264,7 @@ void Mle::HandleParentRequestTimer(void)
     case kParentIdle:
         if (mParent.mState == Neighbor::kStateValid)
         {
-            if (mDeviceMode & ModeTlv::kModeRxOnWhenIdle)
-            {
-                if (mKeepAliveAttemptsSent >= kMaxChildKeepAliveAttempts)
-                {
-                    // Reattach when no Child Update Response received for more than kMaxChildKeepAliveAttempts
-                    BecomeDetached();
-                }
-                else
-                {
-                    SendChildUpdateRequest();
-                    mKeepAliveAttemptsSent++;
-                    mParentRequestTimer.Start(Timer::SecToMsec(mTimeout / kMaxChildKeepAliveAttempts));
-                }
-            }
+            SendChildUpdateRequest();
         }
         else
         {
@@ -1651,7 +1637,17 @@ ThreadError Mle::SendChildUpdateRequest(void)
 {
     ThreadError error = kThreadError_None;
     Ip6::Address destination;
-    Message *message;
+    Message *message = NULL;
+
+    if (mChildUpdateAttempts >= kMaxChildKeepAliveAttempts)
+    {
+        mChildUpdateAttempts = 0;
+        BecomeDetached();
+        ExitNow();
+    }
+
+    mParentRequestTimer.Start(kUnicastRetransmissionDelay);
+    mChildUpdateAttempts++;
 
     VerifyOrExit((message = NewMleMessage()) != NULL, ;);
     SuccessOrExit(error = AppendHeader(*message, Header::kCommandChildUpdateRequest));
@@ -2942,13 +2938,16 @@ ThreadError Mle::HandleChildUpdateResponse(const Message &aMessage, const Ip6::M
         {
             mNetif.GetMeshForwarder().SetPollPeriod(Timer::SecToMsec(mTimeout / kMaxChildKeepAliveAttempts));
             mNetif.GetMeshForwarder().SetRxOnWhenIdle(false);
+            mParentRequestTimer.Stop();
         }
         else
         {
-            mKeepAliveAttemptsSent = 0;
+            mParentRequestTimer.Start(Timer::SecToMsec(mTimeout / kMaxChildKeepAliveAttempts));
             mNetif.GetMeshForwarder().SetRxOnWhenIdle(true);
         }
 
+        mChildUpdateAttempts = 0;
+
         break;
 
     default:
diff --git a/src/core/thread/mle.hpp b/src/core/thread/mle.hpp
index c2d425c1b..3d61f9f3b 100644
--- a/src/core/thread/mle.hpp
+++ b/src/core/thread/mle.hpp
@@ -1429,7 +1429,7 @@ private:
     uint8_t mParentLinkQuality3;
     uint8_t mParentLinkQuality2;
     uint8_t mParentLinkQuality1;
-    uint8_t mKeepAliveAttemptsSent;
+    uint8_t mChildUpdateAttempts;
     LeaderDataTlv mParentLeaderData;
     bool mParentIsSingleton;
 
diff --git a/src/core/thread/mle_constants.hpp b/src/core/thread/mle_constants.hpp
index 39fa9a395..663094a56 100644
--- a/src/core/thread/mle_constants.hpp
+++ b/src/core/thread/mle_constants.hpp
@@ -61,6 +61,7 @@ enum
     kParentRequestChildTimeout     = 1250,  ///< End Device Request timeout
     kParentResponseMaxDelayRouters = 500,   ///< Maximum delay for response for Parent Request sent to routers only
     kParentResponseMaxDelayAll     = 1000,  ///< Maximum delay for response for Parent Request sent to all devices
+    kUnicastRetransmissionDelay    = 1000,  ///< Base delay before retransmitting an MLE unicast.
     kMaxResponseDelay              = 1000,  ///< Maximum delay before responding to a multicast request
     kMaxChildIdRequestTimeout      = 5000,  ///< Maximum delay for receiving a Child ID Request
     kChildUpdateRequestPeriod      = 100,   ///< The period for sending Child Update Request