[network-data] introduce 5s delay between SRV_DATA.ntf when deregister for child (#4485)

src/core/thread/network_data.cpp

@@ -977,8 +977,16 @@ otError NetworkData::SendServerDataNotification(uint16_t aRloc16)
     Coap::Message *  message = NULL;
     Ip6::MessageInfo messageInfo;
 
-    VerifyOrExit(mLastAttempt.GetValue() == 0 || ((TimerMilli::GetNow() - mLastAttempt) > kDataResubmitDelay),
+    if (mLastAttempt.GetValue() != 0)
-                 error = OT_ERROR_ALREADY);
+    {
+        uint32_t diff = TimerMilli::GetNow() - mLastAttempt;
+
+        if (((mType == kTypeLocal) && (diff > kDataResubmitDelay)) ||
+            ((mType == kTypeLeader) && (diff > kProxyResubmitDelay)))
+        {
+            ExitNow(error = OT_ERROR_ALREADY);
+        }
+    }
 
     VerifyOrExit((message = Get<Coap::Coap>().NewMessage()) != NULL, error = OT_ERROR_NO_BUFS);
 
@@ -1007,16 +1015,13 @@ otError NetworkData::SendServerDataNotification(uint16_t aRloc16)
     messageInfo.SetPeerPort(kCoapUdpPort);
     SuccessOrExit(error = Get<Coap::Coap>().SendMessage(*message, messageInfo));
 
-    if (mType == kTypeLocal)
+    mLastAttempt = TimerMilli::GetNow();
-    {
-        mLastAttempt = TimerMilli::GetNow();
 
-        // `0` is a special value to indicate no delay limitation on sending SRV_DATA.ntf.
+    // `0` is a special value to indicate no delay limitation on sending SRV_DATA.ntf.
-        // Here avoids possible impact in rate limitation of SRV_DATA.ntf in case of wrap.
+    // Here avoids possible impact in rate limitation of SRV_DATA.ntf in case of wrap.
-        if (mLastAttempt.GetValue() == 0)
+    if (mLastAttempt.GetValue() == 0)
-        {
+    {
-            mLastAttempt.SetValue(1);
+        mLastAttempt.SetValue(1);
-        }
     }
 
     otLogInfoNetData("Sent server data notification");

src/core/thread/network_data.hpp

@@ -496,7 +496,9 @@ protected:
 private:
     enum
     {
-        kDataResubmitDelay = 300000, ///< DATA_RESUBMIT_DELAY (milliseconds)
+        kDataResubmitDelay  = 300000, ///< DATA_RESUBMIT_DELAY (milliseconds) if the device itself is the server.
+        kProxyResubmitDelay = 5000,   ///< Resubmit delay (milliseconds) if deregister as the child server proxy.
+
     };
 
     class NetworkDataIterator