# HG changeset patch
# User Sebastien Bindel <sebastien.bindel@uha.fr>
# Date 1478367507 -3600
# Parent  e790e7c3331c32c901c14fda801cc99cfc993e43
internet: (fixes #2483) ARP Request reception add an ARP table entry - RFC 826

diff --git a/src/internet/model/arp-l3-protocol.cc b/src/internet/model/arp-l3-protocol.cc
--- a/src/internet/model/arp-l3-protocol.cc
+++ b/src/internet/model/arp-l3-protocol.cc
@@ -175,7 +175,7 @@
   // 
   // If we're connected to a real world network, then some of the fields sizes 
   // in an ARP packet can vary in ways not seen in simulations.  We need to be
-  // able to detect ARP packets with headers we don't recongnize and not process
+  // able to detect ARP packets with headers we don't recognize and not process
   // them instead of crashing.  The ArpHeader will return 0 if it can't deal
   // with the received header.
   //
@@ -198,25 +198,49 @@
       NS_LOG_LOGIC (cache->GetInterface ()->GetAddress (i).GetLocal () << ", ");
     }
 
-  /**
-   * \internal
-   * Note: we do not update the ARP cache when we receive an ARP request
-   *  from an unknown node. See \bugid{107}
-   */
   bool found = false;
   for (uint32_t i = 0; i < cache->GetInterface ()->GetNAddresses (); i++)
     {
       if (arp.IsRequest () && arp.GetDestinationIpv4Address () == 
           cache->GetInterface ()->GetAddress (i).GetLocal ())
         {
+          ArpCache::Entry *entry = cache->Lookup (arp.GetSourceIpv4Address ());
+          if (entry!=0)
+          {
+            if (entry->IsWaitReply ())
+            {
+              NS_LOG_LOGIC ("node=" << m_node->GetId () << ", got request from " <<
+                            arp.GetSourceIpv4Address () <<
+                            " for waiting entry -- flush and later send reply");
+              entry->MarkAlive (arp.GetSourceHardwareAddress ());
+            }
+            else
+            {
+              // Ignore-- already have an entry
+              NS_LOG_LOGIC("node=" << m_node->GetId () << ", got request from " <<
+                           arp.GetSourceIpv4Address () << " for non-waiting entry");
+              entry->UpdateSeen ();
+            }
+          }
+          else
+          {
+            // No entry for this source, but add one now (RFC 826)
+            NS_LOG_LOGIC("node=" << m_node->GetId () << ", got request from " <<
+                         arp.GetSourceIpv4Address () <<
+                         " for non-existent entry -- adding ");
+            ArpCache::Entry *newEntry = cache->Add (arp.GetSourceIpv4Address ());
+            newEntry->SetMacAddresss (arp.GetSourceHardwareAddress ());
+            newEntry->UpdateSeen ();
+          }
+
           found = true;
-          NS_LOG_LOGIC ("node="<<m_node->GetId () <<", got request from " << 
+          NS_LOG_LOGIC ("node="<<m_node->GetId () <<", got request from " <<
                         arp.GetSourceIpv4Address () << " -- send reply");
           SendArpReply (cache, arp.GetDestinationIpv4Address (), arp.GetSourceIpv4Address (),
                         arp.GetSourceHardwareAddress ());
           break;
-        } 
-      else if (arp.IsReply () && 
+        }
+      else if (arp.IsReply () &&
                arp.GetDestinationIpv4Address ().IsEqual (cache->GetInterface ()->GetAddress (i).GetLocal ()) &&
                arp.GetDestinationHardwareAddress () == device->GetAddress ())
         {
@@ -228,8 +252,8 @@
               if (entry->IsWaitReply ()) 
                 {
                   NS_LOG_LOGIC ("node="<< m_node->GetId () << 
-                                ", got reply from " << arp.GetSourceIpv4Address ()
-                                       << " for waiting entry -- flush");
+                                ", got reply from " << arp.GetSourceIpv4Address () <<
+                                " for waiting entry -- flush");
                   Address from_mac = arp.GetSourceHardwareAddress ();
                   entry->MarkAlive (from_mac);
                   ArpCache::Ipv4PayloadHeaderPair pending = entry->DequeuePending ();
@@ -243,8 +267,8 @@
               else 
                 {
                   // ignore this reply which might well be an attempt 
-                  // at poisening my arp cache.
-                  NS_LOG_LOGIC ("node="<<m_node->GetId ()<<", got reply from " <<
+                  // at poisoning my arp cache.
+                  NS_LOG_LOGIC ("node=" << m_node->GetId () << ", got reply from " <<
                                 arp.GetSourceIpv4Address () <<
                                 " for non-waiting entry -- drop");
                   m_dropTrace (packet);
@@ -252,7 +276,7 @@
             } 
           else 
             {
-              NS_LOG_LOGIC ("node="<<m_node->GetId ()<<", got reply for unknown entry -- drop");
+              NS_LOG_LOGIC ("node=" << m_node->GetId () << ", got reply for unknown entry -- drop");
               m_dropTrace (packet);
             }
           break;
@@ -260,7 +284,7 @@
     }
   if (found == false)
     {
-      NS_LOG_LOGIC ("node="<<m_node->GetId ()<<", got request from " <<
+      NS_LOG_LOGIC ("node=" << m_node->GetId () << ", got request from " <<
                     arp.GetSourceIpv4Address () << " for unknown address " <<
                     arp.GetDestinationIpv4Address () << " -- drop");
     }