Don't flood multicasts if no route found

src/internet-node/ipv4-l3-protocol.cc

@@ -284,29 +284,29 @@ Ipv4L3Protocol::Lookup (
       NS_DEBUG ("Ipv4L3Protocol::Lookup (): "
         "Multicast destination with local source");
 //
-// We have a multicast packet originating from the current node.  We didn't
-// want to force users to construct a route in order to get packets out of a
-// node, so there will have been no route found and it is left to us to send
-// the packet.  What we'll do is to send the multicast out all of the 
-// interfaces on this node.  Note that we start with interface 1 since we 
-// don't particularly want to send the packet out the loopback.
+// We have a multicast packet originating from the current node and were not
+// able to send it using the usual RequestRoute process.  Since the usual
+// process includes trying to use a default multicast route, this means that
+// there was no specific route out of the node found, and there was no default
+// multicast route set.
 //
-      NS_DEBUG ("Ipv4StaticRouting::Lookup (): "
-        "Local source. Flooding multicast packet");
+// The fallback position is to look for a default unicast route and use that
+// to get the packet off the node if we have one.
+//
+      Ipv4Route *route = m_staticRouting->GetDefaultRoute ();
 
-      for (uint32_t i = 1; i < GetNInterfaces (); ++i)
+      if (route)
         {
-          Packet p = packet;
-          Ipv4Header h = ipHeader;
-          Ipv4Route route = 
-            Ipv4Route::CreateHostRouteTo(h.GetDestination (), i);
           NS_DEBUG ("Ipv4StaticRouting::Lookup (): "
-            "Send via interface " << i);
-          routeReply (true, route, p, h);
+            "Local source. Using unicast default route for multicast packet");
+
+          routeReply (true, *route, packet, ipHeader);
+          return;
         }
-      return;
     }
-  // No route found
+//
+// No route found
+//
   routeReply (false, Ipv4Route (), packet, ipHeader);
 }
 

src/node/ipv4-route.cc

@@ -30,6 +30,7 @@ namespace ns3 {
 
 Ipv4Route::Ipv4Route ()
 {}
+
 Ipv4Route::Ipv4Route (Ipv4Route const &route)
   : m_dest (route.m_dest),
     m_destNetworkMask (route.m_destNetworkMask),
@@ -37,6 +38,13 @@ Ipv4Route::Ipv4Route (Ipv4Route const &route)
     m_interface (route.m_interface)
 {}
 
+Ipv4Route::Ipv4Route (Ipv4Route const *route)
+  : m_dest (route->m_dest),
+    m_destNetworkMask (route->m_destNetworkMask),
+    m_gateway (route->m_gateway),
+    m_interface (route->m_interface)
+{}
+
 Ipv4Route::Ipv4Route (Ipv4Address dest,
                       Ipv4Address gateway,
                       uint32_t interface)
@@ -236,6 +244,15 @@ Ipv4MulticastRoute::Ipv4MulticastRoute (Ipv4MulticastRoute const &route)
 {
 }
 
+Ipv4MulticastRoute::Ipv4MulticastRoute (Ipv4MulticastRoute const *route)
+: 
+  m_origin (route->m_origin),
+  m_group (route->m_group),
+  m_inputInterface (route->m_inputInterface),
+  m_outputInterfaces (route->m_outputInterfaces)
+{
+}
+
 Ipv4MulticastRoute::Ipv4MulticastRoute (
   Ipv4Address origin, 
   Ipv4Address group, 

src/node/ipv4-route.h

@@ -37,12 +37,19 @@ public:
    * \brief This constructor does nothing
    */
   Ipv4Route ();
+
   /**
    * \brief Copy Constructor
    * \param route The route to copy
    */
   Ipv4Route (Ipv4Route const &route);
 
+  /**
+   * \brief Copy Constructor
+   * \param route The route to copy
+   */
+  Ipv4Route (Ipv4Route const *route);
+
   bool IsHost (void) const;
   /**
    * \return The IPv4 address of the destination of this route
@@ -108,12 +115,19 @@ public:
    * \brief This constructor does nothing
    */
   Ipv4MulticastRoute ();
+
   /**
    * \brief Copy Constructor
    * \param route The route to copy
    */
   Ipv4MulticastRoute (Ipv4MulticastRoute const &route);
 
+  /**
+   * \brief Copy Constructor
+   * \param route The route to copy
+   */
+  Ipv4MulticastRoute (Ipv4MulticastRoute const *route);
+
   /**
    * \return The IPv4 address of the source of this route
    */