bug 702: make global routing robust to link/device events

src/routing/global-routing/global-routing.h

@@ -33,22 +33,28 @@
  * The model assumes that all nodes on an ns-3 channel are reachable to
  * one another, regardless of whether the nodes can use the channel
  * successfully (in the case of wireless).  Therefore, this model
- * should typically be used only on wired topologies.  API does not
- * yet exist to control the subset of a topology to which this global
- * static routing is applied.
+ * should typically be used only on wired topologies.  Layer-2 bridge
+ * devices are supported.  API does not yet exist to control the subset 
+ * of a topology to which this global static routing is applied.
  * 
- * This model also does not yet deal with the possible presence of
- * layer-2 relays such as switches, bridges, and hubs, although ns-3 does
- * not have such devices yet.
+ * If the topology changes during the simulation, by default, routing
+ * will not adjust.  There are two ways to make it adjust.
+ * - Set the attribute Ipv4GlobalRouting::RespondToInterfaceEvents to true 
+ * - Manually call the sequence of GlobalRouteManager methods to delte global
+ *   routes, build global routing database, and initialize routes.
+ *   There is a helper method that encapsulates this 
+ *   (Ipv4GlobalRoutingHelper::RecomputeRoutingTables())
  * 
  * \section api API and Usage
  * 
  * Users must include ns3/global-route-manager.h header file.  After the
  * IPv4 topology has been built and addresses assigned, users call
  * ns3::GlobalRouteManager::PopulateRoutingTables (), prior to the 
- * ns3::Simulator::Run() call.  There are no other attributes or
- * public methods that are typically called, or ways to parameterize
- * the behavior.
+ * ns3::Simulator::Run() call.  
+ *
+ * There are two attributes of Ipv4GlobalRouting that govern behavior.
+ * - Ipv4GlobalRouting::RandomEcmpRouting
+ * - Ipv4GlobalRouting::RespondToInterfaceEvents  
  *
  * \section impl Implementation
  *

src/routing/global-routing/ipv4-global-routing.cc

@@ -17,6 +17,7 @@
 //
 
 #include "ns3/log.h"
+#include "ns3/simulator.h"
 #include "ns3/object.h"
 #include "ns3/packet.h"
 #include "ns3/net-device.h"
@@ -24,6 +25,7 @@
 #include "ns3/ipv4-routing-table-entry.h"
 #include "ns3/boolean.h"
 #include "ipv4-global-routing.h"
+#include "global-route-manager.h"
 #include <vector>
 
 NS_LOG_COMPONENT_DEFINE ("Ipv4GlobalRouting");
@@ -42,12 +44,18 @@ Ipv4GlobalRouting::GetTypeId (void)
                    BooleanValue(false),
                    MakeBooleanAccessor (&Ipv4GlobalRouting::m_randomEcmpRouting),
                    MakeBooleanChecker ())
+    .AddAttribute ("RespondToInterfaceEvents",
+                   "Set to true if you want to dynamically recompute the global routes upon Interface notification events (up/down, or add/remove address)",
+                   BooleanValue(false),
+                   MakeBooleanAccessor (&Ipv4GlobalRouting::m_respondToInterfaceEvents),
+                   MakeBooleanChecker ())
     ;
   return tid;
 }
 
 Ipv4GlobalRouting::Ipv4GlobalRouting () 
-: m_randomEcmpRouting (false) 
+: m_randomEcmpRouting (false),
+  m_respondToInterfaceEvents (false) 
 {
   NS_LOG_FUNCTION_NOARGS ();
 }
@@ -485,16 +493,52 @@ Ipv4GlobalRouting::RouteInput  (Ptr<const Packet> p, const Ipv4Header &header, P
 }
 void 
 Ipv4GlobalRouting::NotifyInterfaceUp (uint32_t i)
-{}
+{
+  NS_LOG_FUNCTION (this << i);
+  if (m_respondToInterfaceEvents && Simulator::Now ().GetSeconds () > 0)  // avoid startup events
+    {
+      GlobalRouteManager::DeleteGlobalRoutes ();
+      GlobalRouteManager::BuildGlobalRoutingDatabase ();
+      GlobalRouteManager::InitializeRoutes ();
+    }
+}
+
 void 
 Ipv4GlobalRouting::NotifyInterfaceDown (uint32_t i)
-{}
+{
+  NS_LOG_FUNCTION (this << i);
+  if (m_respondToInterfaceEvents && Simulator::Now ().GetSeconds () > 0)  // avoid startup events
+    {
+      GlobalRouteManager::DeleteGlobalRoutes ();
+      GlobalRouteManager::BuildGlobalRoutingDatabase ();
+      GlobalRouteManager::InitializeRoutes ();
+    }
+}
+
 void 
 Ipv4GlobalRouting::NotifyAddAddress (uint32_t interface, Ipv4InterfaceAddress address)
-{}
+{
+  NS_LOG_FUNCTION (this << interface << address);
+  if (m_respondToInterfaceEvents && Simulator::Now ().GetSeconds () > 0)  // avoid startup events
+    {
+      GlobalRouteManager::DeleteGlobalRoutes ();
+      GlobalRouteManager::BuildGlobalRoutingDatabase ();
+      GlobalRouteManager::InitializeRoutes ();
+    }
+}
+
 void 
 Ipv4GlobalRouting::NotifyRemoveAddress (uint32_t interface, Ipv4InterfaceAddress address)
-{}
+{
+  NS_LOG_FUNCTION (this << interface << address);
+  if (m_respondToInterfaceEvents && Simulator::Now ().GetSeconds () > 0)  // avoid startup events
+    {
+      GlobalRouteManager::DeleteGlobalRoutes ();
+      GlobalRouteManager::BuildGlobalRoutingDatabase ();
+      GlobalRouteManager::InitializeRoutes ();
+    }
+}
+
 void 
 Ipv4GlobalRouting::SetIpv4 (Ptr<Ipv4> ipv4)
 {

src/routing/global-routing/ipv4-global-routing.h

@@ -81,6 +81,7 @@ public:
   Ipv4GlobalRouting ();
   virtual ~Ipv4GlobalRouting ();
 
+  // These methods inherited from base class
   virtual Ptr<Ipv4Route> RouteOutput (Ptr<Packet> p, const Ipv4Header &header, Ptr<NetDevice> oif, Socket::SocketErrno &sockerr);
 
   virtual bool RouteInput  (Ptr<const Packet> p, const Ipv4Header &header, Ptr<const NetDevice> idev,
@@ -215,6 +216,8 @@ protected:
 private:
   /// Set to true if packets are randomly routed among ECMP; set to false for using only one route consistently
   bool m_randomEcmpRouting;
+  /// Set to true if this interface should respond to interface events by globallly recomputing routes 
+  bool m_respondToInterfaceEvents;
   /// A uniform random number generator for randomly routing packets among ECMP 
   UniformVariable m_rand;