Index: scan_engine.cc
===================================================================
--- scan_engine.cc	(revision 12102)
+++ scan_engine.cc	(working copy)
@@ -256,9 +256,12 @@
   const probespec *pspec() { return &mypspec; }
 
   /* Returns true if the given tryno and pingseq match those within this
-     probe. */
+     probe.  Note that since we traverse the list of probes starting at
+     the most recently sent probe, this->tryno should never be greater
+     than tryno. */
   bool check_tryno_pingseq(unsigned int tryno, unsigned int pingseq) {
-    return (pingseq == 0 && tryno >= this->tryno) || (pingseq > 0 && pingseq == this->pingseq);
+    return (pingseq == 0 && tryno == this->tryno) ||
+	   (pingseq > 0 && pingseq == this->pingseq);
   }
 
   u8 tryno; /* Try (retransmission) number of this probe */