From fded01ad4faaf3a09a9d00a6f5878b2115ffc208 Mon Sep 17 00:00:00 2001
From: Tommaso Pecorella <tommaso.pecorella@unifi.it>
Date: Sun, 9 May 2021 12:09:42 +0200
Subject: [PATCH] internet: (partially fix #384) add IPv6 reachability hint
 function

---
 src/internet/model/ipv6-l3-protocol.cc | 49 ++++++++++++++++++++++++++
 src/internet/model/ipv6-l3-protocol.h  |  2 ++
 2 files changed, 51 insertions(+)

diff --git a/src/internet/model/ipv6-l3-protocol.cc b/src/internet/model/ipv6-l3-protocol.cc
index 922d01381..984552d52 100644
--- a/src/internet/model/ipv6-l3-protocol.cc
+++ b/src/internet/model/ipv6-l3-protocol.cc
@@ -1601,5 +1601,54 @@ bool Ipv6L3Protocol::IsRegisteredMulticastAddress (Ipv6Address address) const
   return true;
 }
 
+bool Ipv6L3Protocol::ReachabilityHint (uint32_t ipInterfaceIndex, Ipv6Address address)
+{
+  if (ipInterfaceIndex >= m_interfaces.size ())
+    {
+      return false;
+    }
+
+  Ptr<NdiscCache> ndiscCache = m_interfaces[ipInterfaceIndex]->GetNdiscCache ();
+  if (!ndiscCache)
+    {
+      return false;
+    }
+
+  NdiscCache::Entry* entry = ndiscCache->Lookup (address);
+  if (!entry || entry->IsIncomplete ())
+    {
+      return false;
+    }
+
+
+  if (entry->IsReachable ())
+    {
+      entry->UpdateReachableTimer ();
+    }
+  else if (entry->IsPermanent ())
+    {
+      return true;
+    }
+  else if (entry->IsProbe ())
+    {
+      // we just confirm the entry's MAC address to get the waiting packets (if any)
+      std::list<NdiscCache::Ipv6PayloadHeaderPair> waiting = entry->MarkReachable (entry->GetMacAddress ());
+      for (std::list<NdiscCache::Ipv6PayloadHeaderPair>::const_iterator it = waiting.begin (); it != waiting.end (); it++)
+        {
+          ndiscCache->GetInterface ()->Send (it->first, it->second, it->second.GetSourceAddress ());
+        }
+      entry->ClearWaitingPacket ();
+      entry->StartReachableTimer ();
+    }
+  else // STALE OR DELAY
+    {
+      entry->MarkReachable ();
+      entry->StartReachableTimer ();
+    }
+
+
+  return true;
+}
+
 } /* namespace ns3 */
 
diff --git a/src/internet/model/ipv6-l3-protocol.h b/src/internet/model/ipv6-l3-protocol.h
index da00bd7ca..815f23196 100644
--- a/src/internet/model/ipv6-l3-protocol.h
+++ b/src/internet/model/ipv6-l3-protocol.h
@@ -449,6 +449,8 @@ public:
    */
   bool IsRegisteredMulticastAddress (Ipv6Address address, uint32_t interface) const;
 
+  bool ReachabilityHint (uint32_t ipInterfaceIndex, Ipv6Address address);
+
 protected:
   /**
    * \brief Dispose object.