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

src/core/net/netif.cpp

@@ -116,14 +116,13 @@ exit:
     return rval;
 }
 
-otError Netif::SubscribeAllNodesMulticast(void)
+void Netif::SubscribeAllNodesMulticast(void)
 {
-    otError                error = OT_ERROR_NONE;
     NetifMulticastAddress *tail;
     NetifMulticastAddress &linkLocalAllNodesAddress =
         static_cast<NetifMulticastAddress &>(const_cast<otNetifMulticastAddress &>(kLinkLocalAllNodesMulticastAddress));
 
-    VerifyOrExit(!mMulticastAddresses.Contains(linkLocalAllNodesAddress), error = OT_ERROR_ALREADY);
+    VerifyOrExit(!mMulticastAddresses.Contains(linkLocalAllNodesAddress), OT_NOOP);
 
     // Append the fixed chain of three multicast addresses to the
     // tail of the list:
@@ -151,7 +150,7 @@ otError Netif::SubscribeAllNodesMulticast(void)
     }
 
 exit:
-    return error;
+    return;
 }
 
 otError Netif::UnsubscribeAllNodesMulticast(void)

src/core/net/netif.hpp

@@ -386,11 +386,8 @@ protected:
      * This method subscribes the network interface to the realm-local all MPL forwarders, link-local, and realm-local
      * all nodes address.
      *
-     * @retval OT_ERROR_NONE     Successfully subscribed to all addresses.
-     * @retval OT_ERROR_ALREADY  The multicast addresses are already subscribed.
-     *
      */
-    otError SubscribeAllNodesMulticast(void);
+    void SubscribeAllNodesMulticast(void);
 
     /**
      * This method unsubscribes the network interface from the realm-local all MPL forwarders, link-local and

src/core/thread/thread_netif.cpp

@@ -137,7 +137,7 @@ void ThreadNetif::Up(void)
 
     mIsUp = true;
 
-    IgnoreError(SubscribeAllNodesMulticast());
+    SubscribeAllNodesMulticast();
     IgnoreError(Get<Mle::MleRouter>().Enable());
     IgnoreError(Get<Coap::Coap>().Start(kCoapUdpPort));
 #if OPENTHREAD_CONFIG_DNS_CLIENT_ENABLE

tests/unit/test_netif.cpp

@@ -51,7 +51,7 @@ public:
 
     // Provide `protected` methods in `Netif` as `public` from `TestNetif`
     // so that we can verify their behavior in this test
-    otError SubscribeAllNodesMulticast(void) { return Ip6::Netif::SubscribeAllNodesMulticast(); }
+    void    SubscribeAllNodesMulticast(void) { Ip6::Netif::SubscribeAllNodesMulticast(); }
     otError UnsubscribeAllNodesMulticast(void) { return Ip6::Netif::UnsubscribeAllNodesMulticast(); }
 };
 
@@ -116,12 +116,11 @@ void TestNetifMulticastAddresses(void)
 
     VerifyMulticastAddressList(netif, addresses, 0);
 
-    SuccessOrQuit(netif.SubscribeAllNodesMulticast(), "SubscribeAllNodesMulticast() failed");
-
+    netif.SubscribeAllNodesMulticast();
     VerifyMulticastAddressList(netif, &addresses[2], 3);
 
-    VerifyOrQuit(netif.SubscribeAllNodesMulticast() == OT_ERROR_ALREADY,
-                 "SubscribeAllNodesMulticast() did not fail when already subscribed");
+    netif.SubscribeAllNodesMulticast();
+    VerifyMulticastAddressList(netif, &addresses[2], 3);
 
     SuccessOrQuit(netif.SubscribeAllRoutersMulticast(), "SubscribeAllRoutersMulticast() failed");
     VerifyMulticastAddressList(netif, &addresses[0], 5);
@@ -152,11 +151,11 @@ void TestNetifMulticastAddresses(void)
     SuccessOrQuit(netif.SubscribeExternalMulticast(address), "SubscribeExternalMulticast() failed");
     VerifyMulticastAddressList(netif, &addresses[5], 2);
 
-    SuccessOrQuit(netif.SubscribeAllNodesMulticast(), "SubscribeAllNodesMulticast() failed");
+    netif.SubscribeAllNodesMulticast();
     VerifyMulticastAddressList(netif, &addresses[2], 5);
 
-    VerifyOrQuit(netif.SubscribeExternalMulticast(address) == OT_ERROR_ALREADY,
-                 "SubscribeExternalMulticast() did not fail when address was already subscribed");
+    netif.SubscribeAllNodesMulticast();
+    VerifyMulticastAddressList(netif, &addresses[2], 5);
 
     SuccessOrQuit(netif.SubscribeAllRoutersMulticast(), "SubscribeAllRoutersMulticast() failed");
     VerifyMulticastAddressList(netif, &addresses[0], 7);