/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2007 Emmanuelle Laprise
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation;
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Author: Emmanuelle Laprise <emmanuelle.laprise@bluekazoo.ca
 */

#ifndef CSMA_NET_DEVICE_H
#define CSMA_NET_DEVICE_H

#include <string.h>
#include "ns3/node.h"
#include "ns3/backoff.h"
#include "ns3/address.h"
#include "ns3/net-device.h"
#include "ns3/callback.h"
#include "ns3/packet.h"
#include "ns3/traced-callback.h"
#include "ns3/nstime.h"
#include "ns3/data-rate.h"
#include "ns3/ptr.h"
#include "ns3/random-variable.h"
#include "ns3/mac48-address.h"

namespace ns3 {

class Queue;
class CsmaChannel;
class ErrorModel;

/**
 * \class CsmaNetDevice
 * \brief A Device for a Csma Network Link.
 *
 * The Csma net device class is analogous to layer 1 and 2 of the
 * TCP stack. The NetDevice takes a raw packet of bytes and creates a
 * protocol specific packet from them. 
 *
 * Each Csma net device will receive all packets written to the Csma link. 
 * The ProcessHeader function can be used to filter out the packets such that
 * higher level layers only receive packets that are addressed to their
 * associated net devices
 */
class CsmaNetDevice : public NetDevice 
{
public:
  static TypeId GetTypeId (void);

  /**
   * Enumeration of the types of packets supported in the class.
   *
   */
  enum EncapsulationMode {
    ILLEGAL,     /**< Encapsulation mode not set */
    DIX,         /**< DIX II / Ethernet II packet */
    LLC,         /**< 802.2 LLC/SNAP Packet*/  
  };

  /**
   * Construct a CsmaNetDevice
   *
   * This is the default constructor for a CsmaNetDevice.
   */
  CsmaNetDevice ();

  /**
   * Destroy a CsmaNetDevice
   *
   * This is the destructor for a CsmaNetDevice.
   */
  virtual ~CsmaNetDevice ();

  /**
   * Set the inteframe gap used to separate packets.  The interframe gap
   * defines the minimum space required between packets sent by this device.
   * As in Ethernet, it defaults to 96 bit times.
   *
   * \param t the interframe gap time
   */
  void SetInterframeGap (Time t);

  /**
   * Set the backoff parameters used to determine the wait to retry
   * transmitting a packet when the channel is busy.
   *
   * \see Attach ()
   * \param slotTime Length of a packet slot (or average packet time)
   * \param minSlots Minimum number of slots to wait
   * \param maxSlots Maximum number of slots to wait
   * \param maxRetries Maximum number of retries before packet is discard
   * \param ceiling Cap on the exponential function when calculating max slots
   */
  void SetBackoffParams (Time slotTime, uint32_t minSlots, uint32_t maxSlots, 
    uint32_t maxRetries, uint32_t ceiling);

  /**
   * Attach the device to a channel.
   *
   * The function Attach is used to add a CsmaNetDevice to a CsmaChannel.
   *
   * \see SetDataRate ()
   * \see SetInterframeGap ()
   * \param ch a pointer to the channel to which this object is being attached.
   */
  bool Attach (Ptr<CsmaChannel> ch);

  /**
   * Attach a queue to the CsmaNetDevice.
   *
   * The CsmaNetDevice "owns" a queue.  This queue may be set by higher
   * level topology objects to implement a particular queueing method such as
   * DropTail or RED.  
   *
   * \see Queue
   * \see DropTailQueue
   * \param queue a Ptr to the queue for being assigned to the device.
   */
  void SetQueue (Ptr<Queue> queue);

  /**
   * Attach a receive ErrorModel to the CsmaNetDevice.
   *
   * The CsmaNetDevice may optionally include an ErrorModel in
   * the packet receive chain to simulate data errors in during transmission.
   *
   * \see ErrorModel
   * \param em a pointer to the ErrorModel 
   */
  void SetReceiveErrorModel (Ptr<ErrorModel> em);

  /**
   * Receive a packet from a connected CsmaChannel.
   *
   * The CsmaNetDevice receives packets from its connected channel
   * and forwards them up the protocol stack.  This is the public method
   * used by the channel to indicate that the last bit of a packet has 
   * arrived at the device.
   *
   * \see CsmaChannel
   * \param p a reference to the received packet
   * \param sender the CsmaNetDevice that transmitted the packet in the first place
   */
  void Receive (Ptr<Packet> p, Ptr<CsmaNetDevice> sender);

  /**
   * Is the send side of the network device enabled?
   *
   * \returns True if the send side is enabled, otherwise false.
   */
  bool IsSendEnabled (void);

  /**
   * Enable or disable the send side of the network device.
   *
   * \param enable Enable the send side if true, otherwise disable.
   */
  void SetSendEnable (bool enable);

  /**
   * Is the receive side of the network device enabled?
   *
   * \returns True if the receiver side is enabled, otherwise false.
   */
  bool IsReceiveEnabled (void);

  /**
   * Enable or disable the receive side of the network device.
   *
   * \param enable Enable the receive side if true, otherwise disable.
   */
  void SetReceiveEnable (bool enable);

  /**
   * Set the MAC address of the the network device.
   *
   * \param addr The Mac48Address to use as the address of the device.
   */
  void SetAddress (Mac48Address addr);

  /**
   * Set The max frame size of packets sent over this device.
   *
   * Okay, that was easy to say, but the details are a bit thorny.  We have a MAC-level MTU that is the payload that higher 
   * level protocols see.  We have a PHY-level MTU which is the maximum number of bytes we can send over the link 
   * (cf. 1500 bytes for Ethernet).  We also have a frame size which is some total number of bytes in a packet which could
   * or could not include any framing and overhead.  There can be a lot of inconsistency in definitions of these terms.  For
   * example, RFC 1042 asserts that the terms maximum transmission unit and maximum packet size are equivalent.  RFC 791, 
   * however, defines MTU as the maximum sized IP datagram that can be sent.  Packet size and frame size are sometimes
   * used interchangeably.
   *
   * So, some careful definitions are in order to avoid confusion:
   *
   * In real Ethernet, a packet on the wire starts with a preamble of seven bytes of alternating ones and zeroes followed by
   * a Start-of-Frame-Delimeter (10101011).  This is followed by what is usually called the packet: a MAC destination and 
   * source, a type field, payload, a possible padding field and a CRC.  To be strictly and pedantically correct the frame 
   * size is necessarily larger than the packet size on a real Ethernet.  But, this isn't a real Ethernet, it's a simulation
   * of a device similar to Ethernet, and we have no good reason to add framing bits.  So, in the case of the CSMA device, 
   * the frame size is equal to the packet size.  Since these two values are equal, there is no danger in assuming they are 
   * identical.  We do not implement any padding out to a minimum frame size, so padding is a non-issue.  We define packet 
   * size to be equal to frame size and this excludes the preamble and SFD bytes of a real Ethernet frame.  We define a 
   * single (MAC-level) MTU that coresponds to the payload size of the packet, which is the IP-centric view of the term as
   * seen in RFC 791.
   *
   * To make this concrete, consider DIX II (Digital Equipment, Intel, Xerox type II) framing, which is used in most TCP/IP 
   * stacks.  NetWare and Wireshark call this framing Ethernet II, by the way.  In this framing scheme, a real packet on the 
   * wire starts with the preamble and Start-of-Frame-Delimeter (10101011).  We ignore these bits on this device since it they 
   * are not  needed.  In DIX II, the SFD is followed by the MAC (48) destination address (6 bytes), source address (6 bytes), 
   * the EtherType field (2 bytes), payload (0-1500 bytes) and a CRC (4 bytes) -- this corresponds to our entire frame.  The
   * payload of the packet/frame in DIX can be from 0 to 1500 bytes.  It is the maxmimum value of this payload that we call
   * the MTU.  Typically, one sees the MTU set to 1500 bytes and the maximum frame size set to 1518 bytes in Ethernet-based
   * networks.
   *
   * Different framing schemes can make for different MTU and frame size relationships.  For example, we support LLC/SNAP
   * encapsulation which adds eight bytes of header overhead to the usual DIX framing.  In this case, if the maximum frame
   * size is left at 1518 bytes, we need to export an MTU that reflects the loss of eight bytes for a total of 1492.
   * 
   * Another complication is that IEEE 802.1Q adds four bytes to the maximum frame size for VLAN tagging.  In order to 
   * provide an MTU of 1500 bytes, the frame size would need to increased to 1522 bytes to absorb the additional overhead.
   *
   * So, there are really three variables that are not entirely free at work here.  There is the maximum frame size, the
   * MTU and the framing scheme which we call the encapsulation mode.
   *
   * So, what do we do since there are be three values which must always be consistent in the driver?  Which values to we
   * allow to be changed and how do we ensure the other two are consistent?  We want to actually allow a user to change 
   * these three variables in flexible ways, but we want the results (even at intermediate stages of her ultimate change) to 
   * be consistent.  We certainly don't want to require that users must understand the various requirements of an enapsulation
   * mode in order to set these variables.
   *
   * Consider the following situation:  A user wants to set the maximum frame size to 1418 bytes instead of 1518.  This
   * user shouldn't have to concern herself that the current encapuslation mode is LLC/SNAP and this will consume eight bytes.
   * She should not have to also figure out that the MTU needs to be set to 1392 bytes, and she should certainly not have to 
   * do this in some special order to keep intermediate steps consistent.
   *
   * Similarly, a user who is interested in setting the MTU to 1400 bytes should not be forced to understand that 
   * (based on encapsulation mode) the frame size may need to be set to eighteen + eight bytes more than what he wants 
   * in certain cases (802,3 + LLC/SNAP), twenty-two + zero bytes in others (802.1Q) and other inscrutable combinations
   *
   * Now, consider a user who is only interested in changing the encapsulation mode from LLC/SNAP to DIX.  This 
   * is going to change the relationship between the MTU and the frame size.  We've may have to come up with a new value 
   * for at least one of the these?  Which one?  There are too many free variables.
   *
   * We could play games trying to figure out what the user wants to do, but that is typically a bad plan and programmers
   * have a long and distinguished history of guessing wrong.  We'll avoid all of that and just define a flexible behavior
   * that can be worked to get what you want.  Here it is:
   *
   * - If the user is changing the encapsulation mode, the PHY MTU will remain fixed and the MAC MTU will change, if required,
   * to make the three values consistent;
   *
   * - If the user is changing the MTU, she is interested in getting that part of the system set, so the frame size
   * will be changed to make the three values consistent;
   *
   * - If the user is changing the frame size, he is interested in getting that part of the system set, so the MTU
   * will be changed to make the three values consistent;
   *
   * - You cannot define the MTU and frame size separately -- they are always tied together by the emulation mode.  This
   * is not a restriction.  Consider what this means.  Perhaps you want to set the frame size to some large number and the
   * MTU to some small number.  The largest packet you can send is going to be limited by the MTU, so it is not possible to
   * send a frame larger than the MTU plus overhead.  The larger frame size is not useful.
   * 
   * So, if a user calls SetFrameSize, we assume that the maximum frame size is the interesting thing for that user and
   * we just adjust the MTU to a new "correct value" based on the current encapsulation mode.  If a user calls SetMtu, we 
   * assume that the MTU is the interesting property for that user, and we adjust the frame size to a new "correct value" 
   * for the current encapsulation mode.  If a user calls SetEncapsulationMode, then we take the MTU as the free variable 
   * and set its value to match the current frame size.
   *
   * \param frameSize The max frame size of packets sent over this device.
   */
  void SetFrameSize (uint16_t frameSize);

  /**
   * Get The max frame size of packets sent over this device.
   *
   * \returns The max frame size of packets sent over this device.
   */
  uint16_t GetFrameSize (void) const;

  /**
   * Set the encapsulation mode of this device.
   *
   * \param mode The encapsulation mode of this device.
   *
   * \see SetFrameSize
   */
  void SetEncapsulationMode (CsmaNetDevice::EncapsulationMode mode);

  /**
   * Get the encapsulation mode of this device.
   *
   * \returns The encapsulation mode of this device.
   */
  CsmaNetDevice::EncapsulationMode  GetEncapsulationMode (void);

  //
  // The following methods are inherited from NetDevice base class.
  //
  virtual void SetName (const std::string name);
  virtual std::string GetName (void) const;
  virtual void SetIfIndex (const uint32_t index);
  virtual uint32_t GetIfIndex (void) const;
  virtual Ptr<Channel> GetChannel (void) const;
  virtual bool SetMtu (const uint16_t mtu);
  virtual uint16_t GetMtu (void) const;
  virtual Address GetAddress (void) const;
  virtual bool IsLinkUp (void) const;
  virtual void SetLinkChangeCallback (Callback<void> callback);
  virtual bool IsBroadcast (void) const;
  virtual Address GetBroadcast (void) const;
  virtual bool IsMulticast (void) const;

  /**
   * \brief Make and return a MAC multicast address using the provided
   *        multicast group
   *
   * RFC 1112 says that an Ipv4 host group address is mapped to an Ethernet 
   * multicast address by placing the low-order 23-bits of the IP address into 
   * the low-order 23 bits of the Ethernet multicast address 
   * 01-00-5E-00-00-00 (hex).
   *
   * This method performs the multicast address creation function appropriate
   * to an EUI-48-based CSMA device.  This MAC address is encapsulated in an
   *  abstract Address to avoid dependencies on the exact address format.
   *
   * \param multicastGroup The IP address for the multicast group destination
   * of the packet.
   * \return The MAC multicast Address used to send packets to the provided
   * multicast group.
   *
   * \see Ipv4Address
   * \see Mac48Address
   * \see Address
   */
  virtual Address GetMulticast (Ipv4Address multicastGroup) const;

  /**
   * Is this a point to point link?
   * \returns false.
   */
  virtual bool IsPointToPoint (void) const;

  /**
   * Is this a bridge?
   * \returns false.
   */
  virtual bool IsBridge (void) const;

  /**
   * Start sending a packet down the channel.
   */
  virtual bool Send (Ptr<Packet> packet, const Address& dest, 
    uint16_t protocolNumber);

  /**
   * Start sending a packet down the channel, with MAC spoofing
   */
  virtual bool SendFrom (Ptr<Packet> packet, const Address& source, const Address& dest, 
                         uint16_t protocolNumber);

  /**
   * Get the node to which this device is attached.
   *
   * \returns Ptr to the Node to which the device is attached.
   */
  virtual Ptr<Node> GetNode (void) const;

  /**
   * Set the node to which this device is being attached.
   *
   * \param node Ptr to the Node to which the device is being attached.
   */
  virtual void SetNode (Ptr<Node> node);

  /**
   * Does this device need to use the address resolution protocol?
   *
   * \returns True if the encapsulation mode is set to a value that requires
   * ARP (IP_ARP or LLC).
   */
  virtual bool NeedsArp (void) const;

  /**
   * Set the callback to be used to notify higher layers when a packet has been
   * received.
   *
   * \param cb The callback.
   */
  virtual void SetReceiveCallback (NetDevice::ReceiveCallback cb);

  /**
   * \brief Get the MAC multicast address corresponding
   * to the IPv6 address provided.
   * \param addr IPv6 address
   * \return the MAC multicast address
   * \warning Calling this method is invalid if IsMulticast returns not true.
   */
  virtual Address GetMulticast (Ipv6Address addr) const;


  virtual void SetPromiscReceiveCallback (PromiscReceiveCallback cb);
  virtual bool SupportsSendFrom (void) const;

protected:
  /**
   * Perform any object release functionality required to break reference 
   * cycles in reference counted objects held by the device.
   */
  virtual void DoDispose (void);

  /**
   * Get a copy of the attached Queue.
   *
   * This method is provided for any derived class that may need to get
   * direct access to the underlying queue.
   *
   * \return a pointer to the queue.
   */
  Ptr<Queue> GetQueue (void) const; 

  /**
   * Adds the necessary headers and trailers to a packet of data in order to
   * respect the packet type
   *
   * \param p Packet to which header should be added
   * \param source MAC source address from which packet should be sent
   * \param dest MAC destination address to which packet should be sent
   * \param protocolNumber In some protocols, identifies the type of
   * payload contained in this packet.
   */
  void AddHeader (Ptr<Packet> p, Mac48Address source, Mac48Address dest, uint16_t protocolNumber);

  /**
   * Removes, from a packet of data, all headers and trailers that
   * relate to the packet type
   *
   * \param p Packet whose headers need to be processed
   * \param param An integer parameter that can be set by the function
   * to return information gathered in the header
   * \return Returns true if the packet should be forwarded up the
   * protocol stack.
   */
  bool ProcessHeader (Ptr<Packet> p, uint16_t & param);

private:

  /**
   * Operator = is declared but not implemented.  This disables the assigment
   * operator for CsmaNetDevice objects.

   */
  CsmaNetDevice &operator = (const CsmaNetDevice &o);

  /**
   * Copy constructor is declared but not implemented.  This disables the
   * copy constructor for CsmaNetDevice objects.
   */
  CsmaNetDevice (const CsmaNetDevice &o);

  /**
   * Initialization function used during object construction.
   */
  void Init (bool sendEnable, bool receiveEnable);

  /**
   * Calculate the value for the MTU that would result from 
   * setting the frame size to the given value.
   */
  uint32_t MtuFromFrameSize (uint32_t frameSize);

  /**
   * Calculate the value for the frame size that would be required
   * to be able to set the MTU to the given value.
   */
  uint32_t FrameSizeFromMtu (uint32_t mtu);

  /**
   * Start Sending a Packet Down the Wire.
   *
   * The TransmitStart method is the method that is used internally in
   * the CsmaNetDevice to begin the process of sending a packet
   * out on the channel.  A corresponding method is called on the
   * channel to let it know that the physical device this class
   * represents has actually started sending signals, this causes the
   * channel to enter the BUSY state.  An event is scheduled for the time at
   * which the bits have been completely transmitted. 
   *
   * If the channel is found to be BUSY, this method reschedules itself for
   * execution at a later time (within the backoff period).
   *
   * \see CsmaChannel::TransmitStart ()
   * \see TransmitCompleteEvent ()
   */
  void TransmitStart ();

  /**
   * Stop Sending a Packet Down the Wire and Begin the Interframe Gap.
   *
   * The TransmitCompleteEvent method is used internally to finish the process
   * of sending a packet out on the channel.  During execution of this method
   * the TransmitEnd method is called on the channel to let it know that the
   * physical device this class represents has finished sending simulated
   * signals.  The channel uses this event to begin its speed of light delay
   * timer after which it notifies the Net Device(s) at the other end of the 
   * link that new bits have arrived (it delivers the Packet).  During this 
   * method, the net device also schedules the TransmitReadyEvent at which
   * time the transmitter becomes ready to send the next packet.
   *
   * \see CsmaChannel::TransmitEnd ()
   * \see TransmitReadyEvent ()
   */
  void TransmitCompleteEvent (void);

  /**
   * Cause the Transmitter to Become Ready to Send Another Packet.
   *
   * The TransmitReadyEvent method is used internally to re-enable the 
   * transmit machine of the net device.  It is scheduled after a suitable
   * interframe gap after the completion of the previous transmission.
   * The queue is checked at this time, and if there is a packet waiting on
   * the queue, the transmission process is begun.
   *
   * If a packet is in the queue, it is extracted for the queue as the
   * next packet to be transmitted by the net device.
   *
   * \see TransmitStart ()
   */
  void TransmitReadyEvent (void);

  /**
   * Aborts the transmission of the current packet
   *
   * If the net device has tried to transmit a packet for more times
   * than the maximum allowed number of retries (channel always busy)
   * then the packet is dropped.
   */
  void TransmitAbort (void);

  /**
   * Notify any interested parties that the link has come up.
   */
  void NotifyLinkUp (void);

  /** 
   * Device ID returned by the attached functions. It is used by the
   * mp-channel to identify each net device to make sure that only
   * active net devices are writing to the channel
   */
  uint32_t m_deviceId; 

  /**
   * Enable net device to send packets. True by default
   */
  bool m_sendEnable;

  /**
   * Enable net device to receive packets. True by default
   */
  bool m_receiveEnable;

  /**
   * Enumeration of the states of the transmit machine of the net device.
   */
  enum TxMachineState
    {
      READY, /**< The transmitter is ready to begin transmission of a packet */
      BUSY,  /**< The transmitter is busy transmitting a packet */
      GAP,    /**< The transmitter is in the interframe gap time */
      BACKOFF    /**< The transmitter is waiting for the channel to be free */
    };

  /**
   * The state of the Net Device transmit state machine.
   * \see TxMachineState
   */
  TxMachineState m_txMachineState;
  
  /**
   * The type of packet that should be created by the AddHeader
   * function and that should be processed by the ProcessHeader
   * function.
   */
  EncapsulationMode m_encapMode;

  /**
   * The data rate that the Net Device uses to simulate packet transmission
   * timing.
   * \see class DataRate
   */
  DataRate m_bps;

  /**
   * The interframe gap that the Net Device uses insert time between packet
   * transmission
   * \see class Time
   */
  Time m_tInterframeGap;

  /**
   * Holds the backoff parameters and is used to calculate the next
   * backoff time to use when the channel is busy and the net device
   * is ready to transmit
   */
  Backoff m_backoff;

  /**
   * Next packet that will be transmitted (if transmitter is not
   * currently transmitting) or packet that is currently being
   * transmitted.
   */
  Ptr<Packet> m_currentPkt;

  /**
   * The CsmaChannel to which this CsmaNetDevice has been
   * attached.
   * \see class CsmaChannel
   */
  Ptr<CsmaChannel> m_channel;

  /**
   * The Queue which this CsmaNetDevice uses as a packet source.
   * Management of this Queue has been delegated to the CsmaNetDevice
   * and it has the responsibility for deletion.
   * \see class Queue
   * \see class DropTailQueue
   */
  Ptr<Queue> m_queue;

  /**
   * Error model for receive packet events
   */
  Ptr<ErrorModel> m_receiveErrorModel;

  /**
   * The trace source for the packet reception events that the device can
   * fire.
   *
   * \see class CallBackTraceSource
   */
  TracedCallback<Ptr<const Packet> > m_rxTrace;

  /**
   * The trace source for the packet drop events that the device can
   * fire.
   *
   * \see class CallBackTraceSource
   */
  TracedCallback<Ptr<const Packet> > m_dropTrace;

  /**
   * The Node to which this device is attached.
   */
  Ptr<Node> m_node;

  /**
   * The MAC address which has been assigned to this device.
   */
  Mac48Address m_address;

  /**
   * The callback used to notify higher layers that a packet has been received.
   */
  NetDevice::ReceiveCallback m_rxCallback;
  /**
   * The callback used to notify higher layers that a packet has been received in promiscuous mode.
   */
  NetDevice::PromiscReceiveCallback m_promiscRxCallback;

  /**
   * The interface index (really net evice index) that has been assigned to 
   * this network device.
   */
  uint32_t m_ifIndex;

  /**
   * The human readable name of this device.
   */
  std::string m_name;

  /**
   * Flag indicating whether or not the link is up.  In this case,
   * whether or not the device is connected to a channel.
   */
  bool m_linkUp;

  /**
   * Callback to fire if the link changes state (up or down).
   */
  Callback<void> m_linkChangeCallback;

  static const uint16_t DEFAULT_FRAME_SIZE = 1518;
  static const uint16_t ETHERNET_OVERHEAD = 18;

  /**
   * The frame size/packet size.  This corresponds to the maximum 
   * number of bytes that can be transmitted as a packet without framing.
   * This corresponds to the 1518 byte packet size often seen on Ethernet.
   */
  uint32_t m_frameSize;

  /**
   * The Maxmimum Transmission Unit.  This corresponds to the maximum 
   * number of bytes that can be transmitted as seen from higher layers.
   * This corresponds to the 1500 byte MTU size often seen on IP over 
   * Ethernet.
   */
  uint32_t m_mtu;
};

}; // namespace ns3

#endif // CSMA_NET_DEVICE_H
