Device Emulation (contd.): 'Resolve Neighbors' will now resend ARP/NDP requests for unresolved entries

server/abstractport.cpp

@@ -625,6 +625,19 @@ void AbstractPort::clearDeviceNeighbors()
 
 void AbstractPort::resolveDeviceNeighbors()
 {
+    // For a user triggered 'Resolve Neighbors', the behaviour we want is
+    //   IP not in cache - send ARP/NDP request
+    //   IP present in cache, but unresolved - re-send ARP/NDP request
+    //   IP present in cache and resolved - don't sent ARP/NDP
+    //
+    // Device does not resend ARP/NDP requests if the IP address is
+    // already present in the cache, irrespective of whether it is
+    // resolved or not (this is done to avoid sending duplicate requests).
+    //
+    // So, to get the behaviour we want, let's clear all unresolved neighbors
+    // before calling resolve
+    deviceManager_->clearDeviceNeighbors(Device::kUnresolvedNeighbors);
+
     // Resolve gateway for each device first ...
     deviceManager_->resolveDeviceGateways();
 

server/device.cpp

@@ -265,10 +265,33 @@ void Device::resolveGateway()
         sendNeighborSolicit(ip6Gateway_);
 }
 
-void Device::clearNeighbors()
+void Device::clearNeighbors(Device::NeighborSet set)
 {
+    QMutableHashIterator<quint32, quint64> arpIter(arpTable_);
+    QMutableHashIterator<UInt128, quint64> ndpIter(ndpTable_);
+
+    switch (set) {
+    case kAllNeighbors:
         arpTable_.clear();
         ndpTable_.clear();
+        break;
+
+    case kUnresolvedNeighbors:
+        while (arpIter.hasNext()) {
+            arpIter.next();
+            if (arpIter.value() == 0)
+                arpIter.remove();
+        }
+
+        while (ndpIter.hasNext()) {
+            ndpIter.next();
+            if (ndpIter.value() == 0)
+                ndpIter.remove();
+        }
+        break;
+    default:
+        Q_ASSERT(false); // Unreachable!
+    }
 }
 
 // Resolve the Neighbor IP address for this to-be-transmitted pktBuf
@@ -564,8 +587,12 @@ void Device::sendArpRequest(quint32 tgtIp)
     if (!tgtIp)
         return;
 
-    // Do we already have a ARP entry (resolved or unresolved)?
-    // XXX: No NDP state machine for now
+    // This function will be called once per unique stream - which
+    // may all have the same dst IP; even if dst IP are different the
+    // gateway for the different dst IP may all be same. However,
+    // we don't want to send duplicate ARP requests, so we check
+    // if the tgtIP is already in the cache (resolved or unresolved)
+    // and if so, we don't resend it
     if (arpTable_.contains(tgtIp))
         return;
 
@@ -945,7 +972,7 @@ void Device::sendNeighborSolicit(UInt128 tgtIp)
         return;
 
     // Do we already have a NDP entry (resolved or unresolved)?
-    // XXX: No ARP state machine for now
+    // If so, don't resend (see note in sendArpRequest())
     if (ndpTable_.contains(tgtIp))
         return;
 

server/device.h

@@ -39,6 +39,11 @@ class Device
 public:
     static const quint16 kVlanTpid = 0x8100;
 
+    enum NeighborSet {
+        kAllNeighbors,
+        kUnresolvedNeighbors
+    };
+
 public:
     Device(DeviceManager *deviceManager);
 
@@ -61,7 +66,7 @@ public:
 
     void resolveGateway();
 
-    void clearNeighbors();
+    void clearNeighbors(Device::NeighborSet set);
     void resolveNeighbor(PacketBuffer *pktBuf);
     void getNeighbors(OstEmul::DeviceNeighborList *neighbors);
 

server/devicemanager.cpp

@@ -258,10 +258,10 @@ void DeviceManager::resolveDeviceGateways()
     }
 }
 
-void DeviceManager::clearDeviceNeighbors()
+void DeviceManager::clearDeviceNeighbors(Device::NeighborSet set)
 {
     foreach(Device *device, deviceList_)
-        device->clearNeighbors();
+        device->clearNeighbors(set);
 }
 
 void DeviceManager::getDeviceNeighbors(

server/devicemanager.h

@@ -55,7 +55,7 @@ public:
 
     void resolveDeviceGateways();
 
-    void clearDeviceNeighbors();
+    void clearDeviceNeighbors(Device::NeighborSet set = Device::kAllNeighbors);
     void resolveDeviceNeighbor(PacketBuffer *pktBuf);
     void getDeviceNeighbors(OstProto::PortNeighborList *neighborList);