sixlowpan: use RFC7973 EtherType and remove obsolete attributes

CHANGES.md

@@ -36,6 +36,7 @@ Changes from ns-3.40 to ns-3-dev
 * (spectrum) `PhasedArraySpectrumPropagationLossModel::CalcRxPowerSpectralDensity` return type is changed from `Ptr<SpectrumValue>` to `Ptr<SpectrumSignalParameters>` to support MIMO, because when multiple transmit and receive antenna ports are present, it is not enough to have a single PSD (represented by `Ptr<SpectrumValue>`) but also the 3D channel matrix is needed per receive and transmit antenna port. Notice that `CalcRxPowerSpectralDensity` is typically called from within `MultiModelSpectrumChannel`, but if some external ns-3 module is calling directly this function, it can still access to its original return value through `Ptr<SpectrumSignalParameters>` which contains `Ptr<SpectrumValue>`.
 * (wifi) The default value for `WifiRemoteStationManager::RtsCtsThreshold` has been increased from 65535 to 4692480.
 * (lr-wpan) Add the capability to see the enum values of the MAC transition states in log prints for easier debugging.
+* (sixlowpan) Remove `ForceEtherType` and `EtherType` attributes, and use RFC 7973 EtherType for interfaces supporting an EtherType.
 
 ### Changes to build system
 

src/sixlowpan/doc/sixlowpan.rst

@@ -52,8 +52,6 @@ The attributes are:
 * FragmentReassemblyListSize (integer, default 0), indicating the number of packets that can be reassembled at the same time. If the limit is reached, the oldest packet is discarded. Zero means infinite.
 * FragmentExpirationTimeout (Time, default 60 seconds), being the timeout to wait for further fragments before discarding a partial packet.
 * CompressionThreshold (unsigned 32 bits integer, default 0), minimum compressed payload size.
-* ForceEtherType (boolean, default false).
-* EtherType (unsigned 16 bits integer, default 0xFFFF), to force a particular L2 EtherType.
 * UseMeshUnder (boolean, default false), it enables mesh-under flood routing.
 * MeshUnderRadius (unsigned 8 bits integer, default 10), the maximum number of hops that a packet will be forwarded.
 * MeshCacheLength (unsigned 16 bits integer, default 10), the length of the cache for each source.
@@ -65,23 +63,8 @@ used (plus one byte for the correct dispatch header).
 This option is useful when a MAC requires a minimum frame size (e.g., ContikiMAC) and the
 compression would violate the requirement.
 
-The last two attributes are needed to use the module with a NetDevice other than 802.15.4, as
-neither IANA or IEEE did reserve an EtherType for 6LoWPAN. As a consequence there might be a
-conflict with the L2 multiplexer/demultiplexer which is based on EtherType. The default
-value is 0xFFFF, which is reserved by IEEE (see [IANA802]_ and [Ethertype]_).
-The default module behaviour is to not change the EtherType, however this would not work with
-any NetDevice actually understanding and using the EtherType.
-
-Note that the `ForceEtherType` parameter have also a direct effect on the MAC address kind the
-module is expecting to handle:
-* ForceEtherType true: Mac48Address (Ethernet, WiFi, etc.).
-* ForceEtherType false: Mac16Address or Mac64Address (IEEE 802.15.4).
-
-Note that using 6LoWPAN over any NetDevice other than 802.15.4 will produce valid .pcap files,
-but they will not be correctly dissected by Wireshark.
-The reason lies on the fact that 6LoWPAN was really meant to be used only over 802.15.4, so
-Wireshark dissectors will not even try to decode 6LoWPAN headers on top of protocols other than
-802.15.4.
+Note that 6LoWPAN will use an EtherType equal to 0xA0ED, as mandated by :rfc:`7973`.
+If the device does not support EtherTypes (e.g., 802.15.4), this value is discarded.
 
 The Trace sources are:
 

src/sixlowpan/examples/example-sixlowpan.cc

@@ -88,7 +88,6 @@ main(int argc, char** argv)
     NetDeviceContainer d1 = csma.Install(net1);
 
     SixLowPanHelper sixlowpan;
-    sixlowpan.SetDeviceAttribute("ForceEtherType", BooleanValue(true));
     NetDeviceContainer six1 = sixlowpan.Install(d1);
 
     NS_LOG_INFO("Create networks and assign IPv6 Addresses.");

src/sixlowpan/model/sixlowpan-net-device.cc

@@ -83,16 +83,6 @@ SixLowPanNetDevice::GetTypeId()
                           UintegerValue(0x0),
                           MakeUintegerAccessor(&SixLowPanNetDevice::m_compressionThreshold),
                           MakeUintegerChecker<uint32_t>())
-            .AddAttribute("ForceEtherType",
-                          "Force a specific EtherType in L2 frames.",
-                          BooleanValue(false),
-                          MakeBooleanAccessor(&SixLowPanNetDevice::m_forceEtherType),
-                          MakeBooleanChecker())
-            .AddAttribute("EtherType",
-                          "The specific EtherType to be used in L2 frames.",
-                          UintegerValue(0xFFFF),
-                          MakeUintegerAccessor(&SixLowPanNetDevice::m_etherType),
-                          MakeUintegerChecker<uint16_t>())
             .AddAttribute("UseMeshUnder",
                           "Use a mesh-under routing protocol.",
                           BooleanValue(false),
@@ -158,10 +148,13 @@ SixLowPanNetDevice::SetNetDevice(Ptr<NetDevice> device)
 
     NS_LOG_DEBUG("RegisterProtocolHandler for " << device->GetInstanceTypeId().GetName());
 
-    uint16_t protocolType = 0;
-    if (m_forceEtherType)
+    uint16_t protocolType = PROT_NUMBER;
+    if (device->GetInstanceTypeId().GetName() == "ns3::LrWpanNetDevice")
     {
-        protocolType = m_etherType;
+        // LrWpanNetDevice does not have a protocol number in the frame.
+        // Hence, we must register for any protocol, and assume that any
+        // packet is 6LoWPAN.
+        protocolType = 0;
     }
     m_node->RegisterProtocolHandler(MakeCallback(&SixLowPanNetDevice::ReceiveFromDevice, this),
                                     protocolType,
@@ -596,10 +589,7 @@ SixLowPanNetDevice::DoSend(Ptr<Packet> packet,
 
     bool useMesh = m_meshUnder;
 
-    if (m_forceEtherType)
-    {
-        protocolNumber = m_etherType;
-    }
+    protocolNumber = PROT_NUMBER;
 
     if (m_useIphc)
     {

src/sixlowpan/model/sixlowpan-net-device.h

@@ -85,6 +85,11 @@ class SixLowPanNetDevice : public NetDevice
                                              //!< context
     };
 
+    /**
+     * \brief The protocol number for 6LoWPAN (0xA0ED) - see \RFC{7973}.
+     */
+    static constexpr uint16_t PROT_NUMBER{0xA0ED};
+
     /**
      * \brief Get the type ID.
      * \return The object TypeId.
@@ -626,14 +631,6 @@ class SixLowPanNetDevice : public NetDevice
     Ptr<NetDevice> m_netDevice; //!< Smart pointer to the underlying NetDevice.
     uint32_t m_ifIndex;         //!< Interface index.
 
-    /**
-     * \brief Force the EtherType number.
-     * Also implying that the underlying NetDevice is using 48-bit Addresses, e.g., Ethernet, Wi-Fi,
-     * etc.
-     */
-    bool m_forceEtherType;
-
-    uint16_t m_etherType;   //!< EtherType number (used only if m_forceEtherType is true).
     bool m_omitUdpChecksum; //!< Omit UDP checksum in NC1 encoding.
 
     uint32_t m_compressionThreshold; //!< Minimum L2 payload size.

src/sixlowpan/test/sixlowpan-fragmentation-test.cc

@@ -289,7 +289,6 @@ SixlowpanFragmentationTest::DoRun()
         serverNode->AddDevice(serverDev);
 
         Ptr<SixLowPanNetDevice> serverSix = CreateObject<SixLowPanNetDevice>();
-        serverSix->SetAttribute("ForceEtherType", BooleanValue(true));
         serverNode->AddDevice(serverSix);
         serverSix->SetNetDevice(serverDev);
 
@@ -320,7 +319,6 @@ SixlowpanFragmentationTest::DoRun()
         clientNode->AddDevice(clientDev);
 
         Ptr<SixLowPanNetDevice> clientSix = CreateObject<SixLowPanNetDevice>();
-        clientSix->SetAttribute("ForceEtherType", BooleanValue(true));
         clientNode->AddDevice(clientSix);
         clientSix->SetNetDevice(clientDev);
 

src/sixlowpan/test/sixlowpan-hc1-test.cc

@@ -142,7 +142,6 @@ SixlowpanHc1ImplTest::DoRun()
         rxNode->AddDevice(rxDev);
 
         Ptr<SixLowPanNetDevice> rxSix = CreateObject<SixLowPanNetDevice>();
-        rxSix->SetAttribute("ForceEtherType", BooleanValue(true));
         rxSix->SetAttribute("Rfc6282", BooleanValue(false));
         rxNode->AddDevice(rxSix);
         rxSix->SetNetDevice(rxDev);
@@ -166,7 +165,6 @@ SixlowpanHc1ImplTest::DoRun()
         txNode->AddDevice(txDev);
 
         Ptr<SixLowPanNetDevice> txSix = CreateObject<SixLowPanNetDevice>();
-        txSix->SetAttribute("ForceEtherType", BooleanValue(true));
         txSix->SetAttribute("Rfc6282", BooleanValue(false));
         txNode->AddDevice(txSix);
         txSix->SetNetDevice(txDev);

src/sixlowpan/test/sixlowpan-iphc-test.cc

@@ -142,7 +142,6 @@ SixlowpanIphcImplTest::DoRun()
         rxNode->AddDevice(rxDev);
 
         Ptr<SixLowPanNetDevice> rxSix = CreateObject<SixLowPanNetDevice>();
-        rxSix->SetAttribute("ForceEtherType", BooleanValue(true));
         rxNode->AddDevice(rxSix);
         rxSix->SetNetDevice(rxDev);
 
@@ -165,7 +164,6 @@ SixlowpanIphcImplTest::DoRun()
         txNode->AddDevice(txDev);
 
         Ptr<SixLowPanNetDevice> txSix = CreateObject<SixLowPanNetDevice>();
-        txSix->SetAttribute("ForceEtherType", BooleanValue(true));
         txNode->AddDevice(txSix);
         txSix->SetNetDevice(txDev);