/* -*- 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. 

 */

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 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 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 void SetAddress (Address address);

  virtual Address GetAddress (void) const;

  virtual bool IsLinkUp (void) const;

  virtual void AddLinkChangeCallback (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.

   * \param packet packet to send

   * \param dest layer 2 destination address

   * \param protocolNumber protocol number

   * \return true if successfull, false otherwise (drop, ...)

   */

  virtual bool Send (Ptr<Packet> packet, const Address& dest, 

    uint16_t protocolNumber);

  /**

   * Start sending a packet down the channel, with MAC spoofing

   * \param packet packet to send

   * \param source layer 2 source address

   * \param dest layer 2 destination address

   * \param protocolNumber protocol number

   * \return true if successfull, false otherwise (drop, ...)

   */

  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);

private:

  /**

   * Operator = is declared but not implemented.  This disables the assigment

   * operator for CsmaNetDevice objects.

   * \param o object to copy

   */

  CsmaNetDevice &operator = (const CsmaNetDevice &o);

  /**

   * Copy constructor is declared but not implemented.  This disables the

   * copy constructor for CsmaNetDevice objects.

   * \param o object to copy

   */

  CsmaNetDevice (const CsmaNetDevice &o);

  /**

   * Initialization function used during object construction.

   * \param sendEnable if device will be allowed to send

   * \param receiveEnable if device will be allowed to receive

   */

  void Init (bool sendEnable, bool receiveEnable);

  /**

   * Calculate the value for the MTU that would result from 

   * setting the frame size to the given value.

   * \param frameSize size of frame

   */

  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.

   * \param mtu MTU

   */

  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 ()