1 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
2 /*
3  * Copyright (c) 2007 Emmanuelle Laprise
4  *
5  * This program is free software; you can redistribute it and/or modify
6  * it under the terms of the GNU General Public License version 2 as
7  * published by the Free Software Foundation;
8  *
9  * This program is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12  * GNU General Public License for more details.
13  *
14  * You should have received a copy of the GNU General Public License
15  * along with this program; if not, write to the Free Software
16  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
17  *
18  * Author: Emmanuelle Laprise <emmanuelle.laprise@bluekazoo.ca>
19  */
20 
21 #ifndef ETHERNET_TRAILER_H
22 #define ETHERNET_TRAILER_H
23 
24 #include "ns3/trailer.h"
25 #include "ns3/packet.h"
26 #include <string>
27 
28 namespace ns3 {
29 
30 
31 /**
32  * \ingroup network
33  *
34  * \brief Packet trailer for Ethernet
35  *
36  * This class can be used to add and verify the FCS at the end of an
37  * Ethernet packet.
38  */
39 class EthernetTrailer : public Trailer
40 {
41 public:
42   /**
43    * \brief Construct a null ethernet trailer
44    */
45   EthernetTrailer ();
46 
47   /**
48    * \brief Enable or disable FCS checking and calculations
49    * \param enable If true, enables FCS calculations.
50    */
51   void EnableFcs (bool enable);
52 
53   /**
54    * \brief Updates the Fcs Field to the correct FCS
55    * \param p Reference to a packet on which the FCS should be
56    * calculated. The packet should not currently contain an
57    * EthernetTrailer.
58    */
59   void CalcFcs (Ptr<const Packet> p);
60 
61   /**
62    * \brief Sets the FCS to a new value
63    * \param fcs New FCS value
64    */
65   void SetFcs (uint32_t fcs);
66 
67   /**
68    * \return the FCS contained in this trailer
69    */
70   uint32_t GetFcs () const;
71 
72   /**
73    * Calculate an FCS on the provided packet and check this value against
74    * the FCS found when the trailer was deserialized (the one in the transmitted
75    * packet).
76    *
77    * If FCS checking is disabled, this method will always
78    * return true.
79    *
80    * \param p Reference to the packet on which the FCS should be
81    * calculated. The packet should not contain an EthernetTrailer.
82    *
83    * \return Returns true if the Packet FCS matches the FCS in the trailer,
84    * false otherwise.
85    */
86   bool CheckFcs (Ptr<const Packet> p) const;
87 
88   /**
89    *\return Returns the size of the trailer
90    */
91   uint32_t GetTrailerSize () const;
92 
93   /**
94    * \brief Get the type ID.
95    * \return the object TypeId
96    */
97   static TypeId GetTypeId (void);
98   virtual TypeId GetInstanceTypeId (void) const;
99   virtual void Print (std::ostream &os) const;
100   virtual uint32_t GetSerializedSize (void) const;
101   virtual void Serialize (Buffer::Iterator end) const;
102   virtual uint32_t Deserialize (Buffer::Iterator end);
103 private:
104   /**
105    * Enabled FCS calculations. If false, m_fcs is set to 0 and CheckFcs
106    * returns true.
107    */
108   bool m_calcFcs;
109   uint32_t m_fcs; //!< Value of the fcs contained in the trailer
110 
111 };
112 
113 } // namespace ns3
114 
115 #endif /* ETHERNET_TRAILER_H */
116