REEDs or rx-on-when-idle End Devices should attempt to maintain one-way synchronization with neighboring routers (#222)

from which incoming MLE advertisments are from

src/core/thread/mle.cpp

@@ -1437,7 +1437,7 @@ ThreadError Mle::HandleAdvertisement(const Message &aMessage, const Ip6::Message
 
     otLogInfoMle("Received advertisement from %04x\n", sourceAddress.GetRloc16());
 
-    if ((mDeviceState != kDeviceStateDetached) && (mDeviceMode & ModeTlv::kModeFFD))
+    if (mDeviceState != kDeviceStateDetached)
     {
         SuccessOrExit(error = mMleRouter.HandleAdvertisement(aMessage, aMessageInfo));
     }
@@ -1458,19 +1458,12 @@ ThreadError Mle::HandleAdvertisement(const Message &aMessage, const Ip6::Message
             break;
         }
 
-        if (mParent.mValid.mRloc16 != sourceAddress.GetRloc16())
+        if ((mParent.mValid.mRloc16 == sourceAddress.GetRloc16()) &&
+            (leaderData.GetPartitionId() != mLeaderData.GetPartitionId() ||
+             leaderData.GetLeaderRouterId() != GetLeaderId()))
         {
-            SetStateDetached();
+            SetLeaderData(leaderData.GetPartitionId(), leaderData.GetWeighting(), leaderData.GetLeaderRouterId());
-            ExitNow(error = kThreadError_NoRoute);
+            mRetrieveNewNetworkData = true;
-        }
-        else
-        {
-            if (leaderData.GetPartitionId() != mLeaderData.GetPartitionId() ||
-                leaderData.GetLeaderRouterId() != GetLeaderId())
-            {
-                SetLeaderData(leaderData.GetPartitionId(), leaderData.GetWeighting(), leaderData.GetLeaderRouterId());
-                mRetrieveNewNetworkData = true;
-            }
         }
 
         isNeighbor = true;

src/core/thread/mle_router.cpp

@@ -1125,6 +1125,11 @@ ThreadError MleRouter::HandleAdvertisement(const Message &aMessage, const Ip6::M
                      leaderData.GetWeighting(), peerParitionId,
                      mLeaderData.GetWeighting(), mLeaderData.GetPartitionId());
 
+        if ((GetDeviceState() == kDeviceStateChild) && (memcmp(&mParent.mMacAddr, &macAddr, sizeof(mParent.mMacAddr)) == 0))
+        {
+            ExitNow();
+        }
+
         if ((leaderData.GetWeighting() > mLeaderData.GetWeighting()) ||
             (leaderData.GetWeighting() == mLeaderData.GetWeighting() &&
              peerParitionId > mLeaderData.GetPartitionId()))
@@ -1137,8 +1142,13 @@ ThreadError MleRouter::HandleAdvertisement(const Message &aMessage, const Ip6::M
     }
     else if (leaderData.GetLeaderRouterId() != GetLeaderId())
     {
-        BecomeDetached();
+        if (GetDeviceState() != kDeviceStateChild)
-        ExitNow(error = kThreadError_Drop);
+        {
+            BecomeDetached();
+            error = kThreadError_Drop;
+        }
+
+        ExitNow();
     }
 
     VerifyOrExit(GetChildId(sourceAddress.GetRloc16()) == 0, ;);
@@ -1147,7 +1157,10 @@ ThreadError MleRouter::HandleAdvertisement(const Message &aMessage, const Ip6::M
     SuccessOrExit(error = Tlv::GetTlv(aMessage, Tlv::kRoute, sizeof(route), route));
     VerifyOrExit(route.IsValid(), error = kThreadError_Parse);
 
-    SuccessOrExit(error = ProcessRouteTlv(route));
+    if (mDeviceMode & ModeTlv::kModeFFD)
+    {
+        SuccessOrExit(error = ProcessRouteTlv(route));
+    }
 
     VerifyOrExit((routerId = GetRouterId(sourceAddress.GetRloc16())) < kMaxRouterId, error = kThreadError_Parse);
 
@@ -1170,7 +1183,7 @@ ThreadError MleRouter::HandleAdvertisement(const Message &aMessage, const Ip6::M
             }
         }
 
-        if (routerCount < mRouterUpgradeThreshold)
+        if ((mDeviceMode & ModeTlv::kModeFFD) && (routerCount < mRouterUpgradeThreshold))
         {
             BecomeRouter();
             ExitNow();