/* -*- 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;

   /**

    * 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