From 03fea775cbb957e11d04091271f0fe1a7c08fb65 Mon Sep 17 00:00:00 2001
From: Natale Patriciello <natale.patriciello@gmail.com>
Date: Tue, 14 Feb 2017 11:44:38 -0800
Subject: [PATCH] tcp:  Avoid accessing an empty packet sent list

---
 src/internet/model/tcp-tx-buffer.cc | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/internet/model/tcp-tx-buffer.cc b/src/internet/model/tcp-tx-buffer.cc
index 6ad74cc25..055dec90b 100644
--- a/src/internet/model/tcp-tx-buffer.cc
+++ b/src/internet/model/tcp-tx-buffer.cc
@@ -1022,13 +1022,13 @@ TcpTxBuffer::IsHeadRetransmitted () const
 {
   NS_LOG_FUNCTION (this);
 
-  TcpTxItem *item = m_sentList.front ();
-  if (item != 0)
+  if (m_sentSize == 0)
     {
-      return item->m_retrans;
+      return false;
     }
 
-  return false;
+  NS_ASSERT (m_sentList.size () > 0);
+  return m_sentList.front ()->m_retrans;
 }
 
 Ptr<const TcpOptionSack>