model.fw: Correcting a "slightly" broken NACKs, though still not sure if everything works as it should.
diff --git a/model/fw/green-yellow-red.cc b/model/fw/green-yellow-red.cc
index 6611c13..3351cda 100644
--- a/model/fw/green-yellow-red.cc
+++ b/model/fw/green-yellow-red.cc
@@ -107,12 +107,15 @@
 void
 GreenYellowRed::DidReceiveValidNack (Ptr<Face> inFace,
                                      uint32_t nackCode,
+                                     Ptr<const InterestHeader> header,
+                                     Ptr<const Packet> origPacket,
                                      Ptr<pit::Entry> pitEntry)
 {
-  super::DidReceiveValidNack (inFace, nackCode, pitEntry);
+  super::DidReceiveValidNack (inFace, nackCode, header, origPacket, pitEntry);
 
   if (inFace != 0 &&
-      nackCode != InterestHeader::NACK_LOOP)
+      (nackCode == InterestHeader::NACK_CONGESTION ||
+       nackCode == InterestHeader::NACK_GIVEUP_PIT))
     {
       pitEntry->GetFibEntry ()->UpdateStatus (inFace, fib::FaceMetric::NDN_FIB_YELLOW);
     }