[netif] change UnsubscribeAllRoutersMulticast() to return void (#4942)

src/core/net/netif.cpp

@@ -258,9 +258,8 @@ exit:
     return;
 }
 
-otError Netif::UnsubscribeAllRoutersMulticast(void)
+void Netif::UnsubscribeAllRoutersMulticast(void)
 {
-    otError                error;
     NetifMulticastAddress *prev;
     NetifMulticastAddress &linkLocalAllRoutersAddress = static_cast<NetifMulticastAddress &>(
         const_cast<otNetifMulticastAddress &>(kLinkLocalAllRoutersMulticastAddress));
@@ -277,7 +276,7 @@ otError Netif::UnsubscribeAllRoutersMulticast(void)
     // to point to `LinkLocalAll` instead (so that tail contains the
     // three fixed addresses at end of the chain).
 
-    SuccessOrExit(error = mMulticastAddresses.Find(linkLocalAllRoutersAddress, prev));
+    SuccessOrExit(mMulticastAddresses.Find(linkLocalAllRoutersAddress, prev));
 
     if (prev == NULL)
     {
@@ -299,7 +298,7 @@ otError Netif::UnsubscribeAllRoutersMulticast(void)
     }
 
 exit:
-    return error;
+    return;
 }
 
 void Netif::SubscribeMulticast(NetifMulticastAddress &aAddress)

src/core/net/netif.hpp

@@ -287,11 +287,8 @@ public:
     /**
      * This method unsubscribes the network interface to the link-local and realm-local all routers address.
      *
-     * @retval OT_ERROR_NONE       Successfully unsubscribed from the link-local and realm-local all routers address
-     * @retval OT_ERROR_NOT_FOUND  The multicast addresses were not found.
-     *
      */
-    otError UnsubscribeAllRoutersMulticast(void);
+    void UnsubscribeAllRoutersMulticast(void);
 
     /**
      * This method returns a pointer to the list of multicast addresses.

src/core/thread/mle_router.cpp

@@ -219,7 +219,7 @@ void MleRouter::StopLeader(void)
     Get<MeshCoP::PendingDataset>().StopLeader();
     StopAdvertiseTimer();
     Get<NetworkData::Leader>().Stop();
-    IgnoreError(Get<ThreadNetif>().UnsubscribeAllRoutersMulticast());
+    Get<ThreadNetif>().UnsubscribeAllRoutersMulticast();
 }
 
 void MleRouter::HandleDetachStart(void)

src/core/thread/thread_netif.cpp

@@ -169,7 +169,7 @@ void ThreadNetif::Down(void)
     IgnoreError(Get<Mle::MleRouter>().Disable());
     RemoveAllExternalUnicastAddresses();
     UnsubscribeAllExternalMulticastAddresses();
-    IgnoreError(UnsubscribeAllRoutersMulticast());
+    UnsubscribeAllRoutersMulticast();
     UnsubscribeAllNodesMulticast();
 
     mIsUp = false;

tests/unit/test_netif.cpp

@@ -128,11 +128,11 @@ void TestNetifMulticastAddresses(void)
     netif.SubscribeAllRoutersMulticast();
     VerifyMulticastAddressList(netif, &addresses[0], 5);
 
-    SuccessOrQuit(netif.UnsubscribeAllRoutersMulticast(), "UnsubscribeAllRoutersMulticast() failed");
+    netif.UnsubscribeAllRoutersMulticast();
     VerifyMulticastAddressList(netif, &addresses[2], 3);
 
-    VerifyOrQuit(netif.UnsubscribeAllRoutersMulticast() == OT_ERROR_NOT_FOUND,
-                 "UnsubscribeAllRoutersMulticast() did not fail when not subscribed");
+    netif.UnsubscribeAllRoutersMulticast();
+    VerifyMulticastAddressList(netif, &addresses[2], 3);
 
     IgnoreError(netifAddress.GetAddress().FromString(kTestAddress1));
     netif.SubscribeMulticast(netifAddress);
@@ -175,11 +175,11 @@ void TestNetifMulticastAddresses(void)
     VerifyOrQuit(netif.UnsubscribeExternalMulticast(address) == OT_ERROR_INVALID_ARGS,
                  "UnsubscribeExternalMulticast() did not fail when address was fixed address");
 
-    SuccessOrQuit(netif.UnsubscribeAllRoutersMulticast(), "UnsubscribeAllRoutersMulticast() failed");
+    netif.UnsubscribeAllRoutersMulticast();
     VerifyMulticastAddressList(netif, &addresses[2], 6);
 
-    VerifyOrQuit(netif.UnsubscribeAllRoutersMulticast() == OT_ERROR_NOT_FOUND,
-                 "UnsubscribeAllRoutersMulticast() did not fail when not subscribed");
+    netif.UnsubscribeAllRoutersMulticast();
+    VerifyMulticastAddressList(netif, &addresses[2], 6);
 
     netif.UnsubscribeAllExternalMulticastAddresses();
     VerifyMulticastAddressList(netif, &addresses[2], 4);