From b52be989ed82ce1c3c4e90be6f0748460f0c18a0 Mon Sep 17 00:00:00 2001
From: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>
Date: Thu, 15 Nov 2007 13:37:51 +0100
Subject: [PATCH] start a backoff only if no backoff is started

---
 src/devices/wifi/dcf-manager.cc | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/devices/wifi/dcf-manager.cc b/src/devices/wifi/dcf-manager.cc
index 7b93da140..65b1c78be 100644
--- a/src/devices/wifi/dcf-manager.cc
+++ b/src/devices/wifi/dcf-manager.cc
@@ -65,6 +65,7 @@ void
 DcfState::StartBackoffNow (uint32_t nSlots)
 {
   NS_ASSERT (m_backoffSlots == 0);
+  MY_DEBUG ("start backoff="<<nSlots<<" slots");
   m_backoffSlots = nSlots;
   m_backoffStart = Simulator::Now ();
 }
@@ -196,7 +197,7 @@ DcfManager::RequestAccess (DcfState *state)
    * backoff running for this DcfState, start a new backoff
    * if needed.
    */ 
-  if (GetBackoffEndFor (state) <= Simulator::Now () && 
+  if (state->GetBackoffSlots () == 0 && 
       IsBusy ())
     {
       MY_DEBUG ("medium is busy: collision");