Merge pull request #3 from Cascoda/elie-mpl-seed-set-no-update

[Mpl] Don't maintain a seed set if rx-off-when-idle

src/core/net/ip6_mpl.cpp

@@ -41,6 +41,8 @@
 #include "common/serial_number.hpp"
 #include "net/ip6.hpp"
 
+#include <openthread/thread.h>
+
 namespace ot {
 namespace Ip6 {
 
@@ -95,7 +97,13 @@ Error Mpl::ProcessOption(Message &aMessage, const Address &aAddress, bool aIsOut
     }
 
     // Check if the MPL Data Message is new.
-    error = UpdateSeedSet(option.GetSeedId(), option.GetSequence());
+    // NOTE: Don't maintain the seed set if the device is a rx-off-when-idle child,
+    //       because that causes the sleepy device to wake up periodically in order
+    //       to update the LifeTimes in the Seed Set.
+    if (otThreadGetLinkMode(GetInstancePtr()).mRxOnWhenIdle)
+        error = UpdateSeedSet(option.GetSeedId(), option.GetSequence());
+    else
+        error = kErrorNone;
 
     if (error == kErrorNone)
     {

src/core/net/ip6_mpl.hpp

@@ -322,6 +322,9 @@ class Mpl : public InstanceLocator, private NonCopyable
     TimerMilli   mRetransmissionTimer;
     uint8_t      mTimerExpirations;
 #endif // OPENTHREAD_FTD
+
+    otInstance *GetInstancePtr(void) { return reinterpret_cast<otInstance *>(&InstanceLocator::GetInstance()); }
+
 };
 
 /**