internet: Add TracedCallback to trace invalid address on DAD failure

src/internet/model/icmpv6-l4-protocol.cc

@@ -142,7 +142,11 @@ Icmpv6L4Protocol::GetTypeId()
                           "Multicast RS maximum retransmission duration (0 means unbound).",
                           TimeValue(Seconds(0)),
                           MakeTimeAccessor(&Icmpv6L4Protocol::m_rsMaxRetransmissionDuration),
-                          MakeTimeChecker());
+                          MakeTimeChecker())
+            .AddTraceSource("FailedDad",
+                            "Duplicate Address detected during DAD, the address is now INVALID",
+                            MakeTraceSourceAccessor(&Icmpv6L4Protocol::m_failedDadAddressTrace),
+                            "ns3::Ipv6Address::TracedCallback");
     return tid;
 }
 
@@ -873,6 +877,7 @@ Icmpv6L4Protocol::HandleNA(Ptr<Packet> packet,
             if (ifaddr.GetState() == Ipv6InterfaceAddress::TENTATIVE ||
                 ifaddr.GetState() == Ipv6InterfaceAddress::TENTATIVE_OPTIMISTIC)
             {
+                m_failedDadAddressTrace(ifaddr.GetAddress());
                 interface->SetState(ifaddr.GetAddress(), Ipv6InterfaceAddress::INVALID);
             }
         }

src/internet/model/icmpv6-l4-protocol.h

@@ -28,6 +28,7 @@
 
 #include "ns3/ipv6-address.h"
 #include "ns3/random-variable-stream.h"
+#include "ns3/traced-callback.h"
 
 #include <list>
 
@@ -697,6 +698,12 @@ class Icmpv6L4Protocol : public IpL4Protocol
     EventId m_handleRsTimeoutEvent;
 
     IpL4Protocol::DownTargetCallback6 m_downTarget; //!< callback to Ipv6::Send
+
+    /**
+     * The trace fired when a DAD fails, changing the address state to INVALID.
+     * Includes the address whose state has been changed.
+     */
+    ns3::TracedCallback<const Ipv6Address&> m_failedDadAddressTrace;
 };
 
 } /* namespace ns3 */