ap-wifi-mac.cc

Go to the documentation of this file.

/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2006, 2009 INRIA
 * Copyright (c) 2009 MIRKO BANCHI
 *
 * 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: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>
 * Author: Mirko Banchi <mk.banchi@gmail.com>
 */
#include "ap-wifi-mac.h"

#include "ns3/assert.h"
#include "ns3/log.h"
#include "ns3/simulator.h"
#include "ns3/string.h"
#include "ns3/pointer.h"
#include "ns3/boolean.h"

#include "qos-tag.h"
#include "wifi-phy.h"
#include "dcf-manager.h"
#include "mac-rx-middle.h"
#include "mac-tx-middle.h"
#include "mgt-headers.h"
#include "mac-low.h"
#include "amsdu-subframe-header.h"
#include "msdu-aggregator.h"

NS_LOG_COMPONENT_DEFINE ("ApWifiMac");

namespace ns3 {

NS_OBJECT_ENSURE_REGISTERED (ApWifiMac);

TypeId
ApWifiMac::GetTypeId (void)
{
  static TypeId tid = TypeId ("ns3::ApWifiMac")
    .SetParent<RegularWifiMac> ()
    .AddConstructor<ApWifiMac> ()
    .AddAttribute ("BeaconInterval", "Delay between two beacons",
                   TimeValue (MicroSeconds (102400)),
                   MakeTimeAccessor (&ApWifiMac::GetBeaconInterval,
                                     &ApWifiMac::SetBeaconInterval),
                   MakeTimeChecker ())
    .AddAttribute ("BeaconGeneration", "Whether or not beacons are generated.",
                   BooleanValue (true),
                   MakeBooleanAccessor (&ApWifiMac::SetBeaconGeneration,
                                        &ApWifiMac::GetBeaconGeneration),
                   MakeBooleanChecker ())
  ;
  return tid;
}

ApWifiMac::ApWifiMac ()
{
  NS_LOG_FUNCTION (this);
  m_beaconDca = CreateObject<DcaTxop> ();
  m_beaconDca->SetAifsn (1);
  m_beaconDca->SetMinCw (0);
  m_beaconDca->SetMaxCw (0);
  m_beaconDca->SetLow (m_low);
  m_beaconDca->SetManager (m_dcfManager);

  // Let the lower layers know that we are acting as an AP.
  SetTypeOfStation (AP);

  m_enableBeaconGeneration = false;
}

ApWifiMac::~ApWifiMac ()
{
  NS_LOG_FUNCTION (this);
}

void
ApWifiMac::DoDispose ()
{
  NS_LOG_FUNCTION (this);
  m_beaconDca = 0;
  m_enableBeaconGeneration = false;
  m_beaconEvent.Cancel ();
  RegularWifiMac::DoDispose ();
}

void
ApWifiMac::SetAddress (Mac48Address address)
{
  // As an AP, our MAC address is also the BSSID. Hence we are
  // overriding this function and setting both in our parent class.
  RegularWifiMac::SetAddress (address);
  RegularWifiMac::SetBssid (address);
}

void
ApWifiMac::SetBeaconGeneration (bool enable)
{
  NS_LOG_FUNCTION (this << enable);
  if (!enable)
    {
      m_beaconEvent.Cancel ();
    }
  else if (enable && !m_enableBeaconGeneration)
    {
      m_beaconEvent = Simulator::ScheduleNow (&ApWifiMac::SendOneBeacon, this);
    }
  m_enableBeaconGeneration = enable;
}

bool
ApWifiMac::GetBeaconGeneration (void) const
{
  return m_enableBeaconGeneration;
}

Time
ApWifiMac::GetBeaconInterval (void) const
{
  return m_beaconInterval;
}

void
ApWifiMac::SetWifiRemoteStationManager (Ptr<WifiRemoteStationManager> stationManager)
{
  NS_LOG_FUNCTION (this << stationManager);
  m_beaconDca->SetWifiRemoteStationManager (stationManager);
  RegularWifiMac::SetWifiRemoteStationManager (stationManager);
}

void
ApWifiMac::SetLinkUpCallback (Callback<void> linkUp)
{
  NS_LOG_FUNCTION (this);
  RegularWifiMac::SetLinkUpCallback (linkUp);

  // The approach taken here is that, from the point of view of an AP,
  // the link is always up, so we immediately invoke the callback if
  // one is set
  linkUp ();
}

void
ApWifiMac::SetBeaconInterval (Time interval)
{
  NS_LOG_FUNCTION (this << interval);
  if ((interval.GetMicroSeconds () % 1024) != 0)
    {
      NS_LOG_WARN ("beacon interval should be multiple of 1024us, see IEEE Std. 802.11-2007, section 11.1.1.1");
    }
  m_beaconInterval = interval;
}

void
ApWifiMac::StartBeaconing (void)
{
  NS_LOG_FUNCTION (this);
  SendOneBeacon ();
}

void
ApWifiMac::ForwardDown (Ptr<const Packet> packet, Mac48Address from,
                        Mac48Address to)
{
  // If we are not a QoS AP then we definitely want to use AC_BE to
  // transmit the packet. A TID of zero will map to AC_BE (through \c
  // QosUtilsMapTidToAc()), so we use that as our default here.
  uint8_t tid = 0;

  // If we are a QoS AP then we attempt to get a TID for this packet
  if (m_qosSupported)
    {
      tid = QosUtilsGetTidForPacket (packet);
      // Any value greater than 7 is invalid and likely indicates that
      // the packet had no QoS tag, so we revert to zero, which'll
      // mean that AC_BE is used.
      if (tid >= 7)
        {
          tid = 0;
        }
    }

  ForwardDown (packet, from, to, tid);
}

void
ApWifiMac::ForwardDown (Ptr<const Packet> packet, Mac48Address from,
                        Mac48Address to, uint8_t tid)
{
  NS_LOG_FUNCTION (this << packet << from << to);
  WifiMacHeader hdr;

  // For now, an AP that supports QoS does not support non-QoS
  // associations, and vice versa. In future the AP model should
  // support simultaneously associated QoS and non-QoS STAs, at which
  // point there will need to be per-association QoS state maintained
  // by the association state machine, and consulted here.
  if (m_qosSupported)
    {
      hdr.SetType (WIFI_MAC_QOSDATA);
      hdr.SetQosAckPolicy (WifiMacHeader::NORMAL_ACK);
      hdr.SetQosNoEosp ();
      hdr.SetQosNoAmsdu ();
      // Transmission of multiple frames in the same TXOP is not
      // supported for now
      hdr.SetQosTxopLimit (0);
      // Fill in the QoS control field in the MAC header
      hdr.SetQosTid (tid);
    }
  else
    {
      hdr.SetTypeData ();
    }

  hdr.SetAddr1 (to);
  hdr.SetAddr2 (GetAddress ());
  hdr.SetAddr3 (from);
  hdr.SetDsFrom ();
  hdr.SetDsNotTo ();

  if (m_qosSupported)
    {
      // Sanity check that the TID is valid
      NS_ASSERT (tid < 8);
      m_edca[QosUtilsMapTidToAc (tid)]->Queue (packet, hdr);
    }
  else
    {
      m_dca->Queue (packet, hdr);
    }
}

void
ApWifiMac::Enqueue (Ptr<const Packet> packet, Mac48Address to, Mac48Address from)
{
  NS_LOG_FUNCTION (this << packet << to << from);
  if (to.IsBroadcast () || m_stationManager->IsAssociated (to))
    {
      ForwardDown (packet, from, to);
    }
}

void
ApWifiMac::Enqueue (Ptr<const Packet> packet, Mac48Address to)
{
  // We're sending this packet with a from address that is our own. We
  // get that address from the lower MAC and make use of the
  // from-spoofing Enqueue() method to avoid duplicated code.
  Enqueue (packet, to, m_low->GetAddress ());
}

bool
ApWifiMac::SupportsSendFrom (void) const
{
  return true;
}

SupportedRates
ApWifiMac::GetSupportedRates (void) const
{
  // send the set of supported rates and make sure that we indicate
  // the Basic Rate set in this set of supported rates.
  SupportedRates rates;
  for (uint32_t i = 0; i < m_phy->GetNModes (); i++)
    {
      WifiMode mode = m_phy->GetMode (i);
      rates.AddSupportedRate (mode.GetDataRate ());
    }
  // set the basic rates
  for (uint32_t j = 0; j < m_stationManager->GetNBasicModes (); j++)
    {
      WifiMode mode = m_stationManager->GetBasicMode (j);
      rates.SetBasicRate (mode.GetDataRate ());
    }
  return rates;
}

void
ApWifiMac::SendProbeResp (Mac48Address to)
{
  NS_LOG_FUNCTION (this << to);
  WifiMacHeader hdr;
  hdr.SetProbeResp ();
  hdr.SetAddr1 (to);
  hdr.SetAddr2 (GetAddress ());
  hdr.SetAddr3 (GetAddress ());
  hdr.SetDsNotFrom ();
  hdr.SetDsNotTo ();
  Ptr<Packet> packet = Create<Packet> ();
  MgtProbeResponseHeader probe;
  probe.SetSsid (GetSsid ());
  probe.SetSupportedRates (GetSupportedRates ());
  probe.SetBeaconIntervalUs (m_beaconInterval.GetMicroSeconds ());
  packet->AddHeader (probe);

  // The standard is not clear on the correct queue for management
  // frames if we are a QoS AP. The approach taken here is to always
  // use the DCF for these regardless of whether we have a QoS
  // association or not.
  m_dca->Queue (packet, hdr);
}

void
ApWifiMac::SendAssocResp (Mac48Address to, bool success)
{
  NS_LOG_FUNCTION (this << to << success);
  WifiMacHeader hdr;
  hdr.SetAssocResp ();
  hdr.SetAddr1 (to);
  hdr.SetAddr2 (GetAddress ());
  hdr.SetAddr3 (GetAddress ());
  hdr.SetDsNotFrom ();
  hdr.SetDsNotTo ();
  Ptr<Packet> packet = Create<Packet> ();
  MgtAssocResponseHeader assoc;
  StatusCode code;
  if (success)
    {
      code.SetSuccess ();
    }
  else
    {
      code.SetFailure ();
    }
  assoc.SetSupportedRates (GetSupportedRates ());
  assoc.SetStatusCode (code);
  packet->AddHeader (assoc);

  // The standard is not clear on the correct queue for management
  // frames if we are a QoS AP. The approach taken here is to always
  // use the DCF for these regardless of whether we have a QoS
  // association or not.
  m_dca->Queue (packet, hdr);
}

void
ApWifiMac::SendOneBeacon (void)
{
  NS_LOG_FUNCTION (this);
  WifiMacHeader hdr;
  hdr.SetBeacon ();
  hdr.SetAddr1 (Mac48Address::GetBroadcast ());
  hdr.SetAddr2 (GetAddress ());
  hdr.SetAddr3 (GetAddress ());
  hdr.SetDsNotFrom ();
  hdr.SetDsNotTo ();
  Ptr<Packet> packet = Create<Packet> ();
  MgtBeaconHeader beacon;
  beacon.SetSsid (GetSsid ());
  beacon.SetSupportedRates (GetSupportedRates ());
  beacon.SetBeaconIntervalUs (m_beaconInterval.GetMicroSeconds ());

  packet->AddHeader (beacon);

  // The beacon has it's own special queue, so we load it in there
  m_beaconDca->Queue (packet, hdr);
  m_beaconEvent = Simulator::Schedule (m_beaconInterval, &ApWifiMac::SendOneBeacon, this);
}

void
ApWifiMac::TxOk (const WifiMacHeader &hdr)
{
  NS_LOG_FUNCTION (this);
  RegularWifiMac::TxOk (hdr);

  if (hdr.IsAssocResp ()
      && m_stationManager->IsWaitAssocTxOk (hdr.GetAddr1 ()))
    {
      NS_LOG_DEBUG ("associated with sta=" << hdr.GetAddr1 ());
      m_stationManager->RecordGotAssocTxOk (hdr.GetAddr1 ());
    }
}

void
ApWifiMac::TxFailed (const WifiMacHeader &hdr)
{
  NS_LOG_FUNCTION (this);
  RegularWifiMac::TxFailed (hdr);

  if (hdr.IsAssocResp ()
      && m_stationManager->IsWaitAssocTxOk (hdr.GetAddr1 ()))
    {
      NS_LOG_DEBUG ("assoc failed with sta=" << hdr.GetAddr1 ());
      m_stationManager->RecordGotAssocTxFailed (hdr.GetAddr1 ());
    }
}

void
ApWifiMac::Receive (Ptr<Packet> packet, const WifiMacHeader *hdr)
{
  NS_LOG_FUNCTION (this << packet << hdr);

  Mac48Address from = hdr->GetAddr2 ();

  if (hdr->IsData ())
    {
      Mac48Address bssid = hdr->GetAddr1 ();
      if (!hdr->IsFromDs ()
          && hdr->IsToDs ()
          && bssid == GetAddress ()
          && m_stationManager->IsAssociated (from))
        {
          Mac48Address to = hdr->GetAddr3 ();
          if (to == GetAddress ())
            {
              NS_LOG_DEBUG ("frame for me from=" << from);
              if (hdr->IsQosData ())
                {
                  if (hdr->IsQosAmsdu ())
                    {
                      NS_LOG_DEBUG ("Received A-MSDU from=" << from << ", size=" << packet->GetSize ());
                      DeaggregateAmsduAndForward (packet, hdr);
                      packet = 0;
                    }
                  else
                    {
                      ForwardUp (packet, from, bssid);
                    }
                }
              else
                {
                  ForwardUp (packet, from, bssid);
                }
            }
          else if (to.IsGroup ()
                   || m_stationManager->IsAssociated (to))
            {
              NS_LOG_DEBUG ("forwarding frame from=" << from << ", to=" << to);
              Ptr<Packet> copy = packet->Copy ();

              // If the frame we are forwarding is of type QoS Data,
              // then we need to preserve the UP in the QoS control
              // header...
              if (hdr->IsQosData ())
                {
                  ForwardDown (packet, from, to, hdr->GetQosTid ());
                }
              else
                {
                  ForwardDown (packet, from, to);
                }
              ForwardUp (copy, from, to);
            }
          else
            {
              ForwardUp (packet, from, to);
            }
        }
      else if (hdr->IsFromDs ()
               && hdr->IsToDs ())
        {
          // this is an AP-to-AP frame
          // we ignore for now.
          NotifyRxDrop (packet);
        }
      else
        {
          // we can ignore these frames since
          // they are not targeted at the AP
          NotifyRxDrop (packet);
        }
      return;
    }
  else if (hdr->IsMgt ())
    {
      if (hdr->IsProbeReq ())
        {
          NS_ASSERT (hdr->GetAddr1 ().IsBroadcast ());
          SendProbeResp (from);
          return;
        }
      else if (hdr->GetAddr1 () == GetAddress ())
        {
          if (hdr->IsAssocReq ())
            {
              // first, verify that the the station's supported
              // rate set is compatible with our Basic Rate set
              MgtAssocRequestHeader assocReq;
              packet->RemoveHeader (assocReq);
              SupportedRates rates = assocReq.GetSupportedRates ();
              bool problem = false;
              for (uint32_t i = 0; i < m_stationManager->GetNBasicModes (); i++)
                {
                  WifiMode mode = m_stationManager->GetBasicMode (i);
                  if (!rates.IsSupportedRate (mode.GetDataRate ()))
                    {
                      problem = true;
                      break;
                    }
                }
              if (problem)
                {
                  // one of the Basic Rate set mode is not
                  // supported by the station. So, we return an assoc
                  // response with an error status.
                  SendAssocResp (hdr->GetAddr2 (), false);
                }
              else
                {
                  // station supports all rates in Basic Rate Set.
                  // record all its supported modes in its associated WifiRemoteStation
                  for (uint32_t j = 0; j < m_phy->GetNModes (); j++)
                    {
                      WifiMode mode = m_phy->GetMode (j);
                      if (rates.IsSupportedRate (mode.GetDataRate ()))
                        {
                          m_stationManager->AddSupportedMode (from, mode);
                        }
                    }
                  m_stationManager->RecordWaitAssocTxOk (from);
                  // send assoc response with success status.
                  SendAssocResp (hdr->GetAddr2 (), true);
                }
              return;
            }
          else if (hdr->IsDisassociation ())
            {
              m_stationManager->RecordDisassociated (from);
              return;
            }
        }
    }

  // Invoke the receive handler of our parent class to deal with any
  // other frames. Specifically, this will handle Block Ack-related
  // Management Action frames.
  RegularWifiMac::Receive (packet, hdr);
}

void
ApWifiMac::DeaggregateAmsduAndForward (Ptr<Packet> aggregatedPacket,
                                       const WifiMacHeader *hdr)
{
  MsduAggregator::DeaggregatedMsdus packets =
    MsduAggregator::Deaggregate (aggregatedPacket);

  for (MsduAggregator::DeaggregatedMsdusCI i = packets.begin ();
       i != packets.end (); ++i)
    {
      if ((*i).second.GetDestinationAddr () == GetAddress ())
        {
          ForwardUp ((*i).first, (*i).second.GetSourceAddr (),
                     (*i).second.GetDestinationAddr ());
        }
      else
        {
          Mac48Address from = (*i).second.GetSourceAddr ();
          Mac48Address to = (*i).second.GetDestinationAddr ();
          NS_LOG_DEBUG ("forwarding QoS frame from=" << from << ", to=" << to);
          ForwardDown ((*i).first, from, to, hdr->GetQosTid ());
        }
    }
}

void
ApWifiMac::DoStart (void)
{
  m_beaconDca->Start ();
  m_beaconEvent.Cancel ();
  if (m_enableBeaconGeneration)
    {
      m_beaconEvent = Simulator::ScheduleNow (&ApWifiMac::SendOneBeacon, this);
    }
  RegularWifiMac::DoStart ();
}

} // namespace ns3