mac-802_11.cc

802.11的.cc文件

		pktTx_ = 0;

		/*
		 * Backoff at end of TX.
		 */
		rst_cw();
		mhBackoff_.start(cw_, is_idle());

		return;
	}

	macmib_.ACKFailureCount++;

	if((u_int32_t) ch->size() <= macmib_.getRTSThreshold()) {
                rcount = &ssrc_;
               thresh = macmib_.getShortRetryLimit();
        } else {
                rcount = &slrc_;
               thresh = macmib_.getLongRetryLimit();
        }

	(*rcount)++;

	if(*rcount >= thresh) {
		/* IEEE Spec section 9.2.3.5 says this should be greater than
		   or equal */
		macmib_.FailedCount++;
		/* tell the callback the send operation failed 
		   before discarding the packet */
		hdr_cmn *ch = HDR_CMN(pktTx_);
		if (ch->xmit_failure_) {
                        ch->size() -= phymib_.getHdrLen11();
			ch->xmit_reason_ = XMIT_REASON_ACK;
                        ch->xmit_failure_(pktTx_->copy(),
                                          ch->xmit_failure_data_);
                }

		discard(pktTx_, DROP_MAC_RETRY_COUNT_EXCEEDED); 
		pktTx_ = 0;
		*rcount = 0;
		rst_cw();
	}
	else {
		struct hdr_mac802_11 *dh;
		dh = HDR_MAC802_11(pktTx_);
		dh->dh_fc.fc_retry = 1;


		sendRTS(ETHER_ADDR(mh->dh_ra));
		inc_cw();
		mhBackoff_.start(cw_, is_idle());
	}
}

/* ======================================================================
   Incoming Packet Routines
   ====================================================================== */
void
Mac802_11::send(Packet *p, Handler *h)
{
	double rTime;
	struct hdr_mac802_11* dh = HDR_MAC802_11(p);

	EnergyModel *em = netif_->node()->energy_model();
	if (em && em->sleep()) {
		em->set_node_sleep(0);
		em->set_node_state(EnergyModel::INROUTE);
	}
	
	callback_ = h;
	sendDATA(p);
	sendRTS(ETHER_ADDR(dh->dh_ra));

	/*
	 * Assign the data packet a sequence number.
	 */
	dh->dh_scontrol = sta_seqno_++;

	/*
	 *  If the medium is IDLE, we must wait for a DIFS
	 *  Space before transmitting.
	 */
	if(mhBackoff_.busy() == 0) {
		if(is_idle()) {
			if (mhDefer_.busy() == 0) {
				/*
				 * If we are already deferring, there is no
				 * need to reset the Defer timer.
				 */
				if (bugFix_timer_) {
					 mhBackoff_.start(cw_, is_idle(), 
							  phymib_.getDIFS());
				}
				else {
					rTime = (Random::random() % cw_)
						* (phymib_.getSlotTime());
					mhDefer_.start(phymib_.getDIFS() + 
						       rTime);
				}
			}
		} else {
			/*
			 * If the medium is NOT IDLE, then we start
			 * the backoff timer.
			 */
			mhBackoff_.start(cw_, is_idle());
		}
	}
}

void
Mac802_11::recv(Packet *p, Handler *h)
{
	struct hdr_cmn *hdr = HDR_CMN(p);
	/*
	 * Sanity Check
	 */
	assert(initialized());

	/*
	 *  Handle outgoing packets.
	 */
	if(hdr->direction() == hdr_cmn::DOWN) {
                send(p, h);
                return;
        }
	/*
	 *  Handle incoming packets.
	 *
	 *  We just received the 1st bit of a packet on the network
	 *  interface.
	 *
	 */

	/*
	 *  If the interface is currently in transmit mode, then
	 *  it probably won't even see this packet.  However, the
	 *  "air" around me is BUSY so I need to let the packet
	 *  proceed.  Just set the error flag in the common header
	 *  to that the packet gets thrown away.
	 */
	if(tx_active_ && hdr->error() == 0) {
		hdr->error() = 1;
	}

	if(rx_state_ == MAC_IDLE) {
		setRxState(MAC_RECV);
		pktRx_ = p;
		/*
		 * Schedule the reception of this packet, in
		 * txtime seconds.
		 */
		mhRecv_.start(txtime(p));
	} else {
		/*
		 *  If the power of the incoming packet is smaller than the
		 *  power of the packet currently being received by at least
                 *  the capture threshold, then we ignore the new packet.
		 */
		if(pktRx_->txinfo_.RxPr / p->txinfo_.RxPr >= p->txinfo_.CPThresh) {
			capture(p);
		} else {
			collision(p);
		}
	}
}

void
Mac802_11::recv_timer()
{
	u_int32_t src; 
	hdr_cmn *ch = HDR_CMN(pktRx_);
	hdr_mac802_11 *mh = HDR_MAC802_11(pktRx_);
	u_int32_t dst = ETHER_ADDR(mh->dh_ra);
	
	u_int8_t  type = mh->dh_fc.fc_type;
	u_int8_t  subtype = mh->dh_fc.fc_subtype;

	assert(pktRx_);
	assert(rx_state_ == MAC_RECV || rx_state_ == MAC_COLL);
	
        /*
         *  If the interface is in TRANSMIT mode when this packet
         *  "arrives", then I would never have seen it and should
         *  do a silent discard without adjusting the NAV.
         */
        if(tx_active_) {
                Packet::free(pktRx_);
                goto done;
        }

	/*
	 * Handle collisions.
	 */
	if(rx_state_ == MAC_COLL) {
		discard(pktRx_, DROP_MAC_COLLISION);		
		set_nav(usec(phymib_.getEIFS()));
		goto done;
	}

	/*
	 * Check to see if this packet was received with enough
	 * bit errors that the current level of FEC still could not
	 * fix all of the problems - ie; after FEC, the checksum still
	 * failed.
	 */
	if( ch->error() ) {
		Packet::free(pktRx_);
		set_nav(usec(phymib_.getEIFS()));
		goto done;
	}

	/*
	 * IEEE 802.11 specs, section 9.2.5.6
	 *	- update the NAV (Network Allocation Vector)
	 */
	if(dst != (u_int32_t)index_) {
		set_nav(mh->dh_duration);
	}

        /* tap out - */
        if (tap_ && type == MAC_Type_Data &&
            MAC_Subtype_Data == subtype ) 
		tap_->tap(pktRx_);
	/*
	 * Adaptive Fidelity Algorithm Support - neighborhood infomation 
	 * collection
	 *
	 * Hacking: Before filter the packet, log the neighbor node
	 * I can hear the packet, the src is my neighbor
	 */
	if (netif_->node()->energy_model() && 
	    netif_->node()->energy_model()->adaptivefidelity()) {
		src = ETHER_ADDR(mh->dh_ta);
		netif_->node()->energy_model()->add_neighbor(src);
	}
	/*
	 * Address Filtering
	 */
	if(dst != (u_int32_t)index_ && dst != MAC_BROADCAST) {
		/*
		 *  We don't want to log this event, so we just free
		 *  the packet instead of calling the drop routine.
		 */
		discard(pktRx_, "---");
		goto done;
	}

	switch(type) {

	case MAC_Type_Management:
		discard(pktRx_, DROP_MAC_PACKET_ERROR);
		goto done;
	case MAC_Type_Control:
		switch(subtype) {
		case MAC_Subtype_RTS:
			recvRTS(pktRx_);
			break;
		case MAC_Subtype_CTS:
			recvCTS(pktRx_);
			break;
		case MAC_Subtype_ACK:
			recvACK(pktRx_);
			break;
		default:
			fprintf(stderr,"recvTimer1:Invalid MAC Control Subtype %x\n",
				subtype);
			exit(1);
		}
		break;
	case MAC_Type_Data:
		switch(subtype) {
		case MAC_Subtype_Data:
			recvDATA(pktRx_);
			break;
		default:
			fprintf(stderr, "recv_timer2:Invalid MAC Data Subtype %x\n",
				subtype);
			exit(1);
		}
		break;
	default:
		fprintf(stderr, "recv_timer3:Invalid MAC Type %x\n", subtype);
		exit(1);
	}
 done:
	pktRx_ = 0;
	rx_resume();
}


void
Mac802_11::recvRTS(Packet *p)
{
	struct rts_frame *rf = (struct rts_frame*)p->access(hdr_mac::offset_);

	if(tx_state_ != MAC_IDLE) {
		discard(p, DROP_MAC_BUSY);
		return;
	}

	/*
	 *  If I'm responding to someone else, discard this RTS.
	 */
	if(pktCTRL_) {
		discard(p, DROP_MAC_BUSY);
		return;
	}

	sendCTS(ETHER_ADDR(rf->rf_ta), rf->rf_duration);

	/*
	 *  Stop deferring - will be reset in tx_resume().
	 */
	if(mhDefer_.busy()) mhDefer_.stop();

	tx_resume();

	mac_log(p);
}

/*
 * txtime()	- pluck the precomputed tx time from the packet header
 */
double
Mac802_11::txtime(Packet *p)
{
	struct hdr_cmn *ch = HDR_CMN(p);
	double t = ch->txtime();
	if (t < 0.0) {
		drop(p, "XXX");
 		exit(1);
	}
	return t;
}

 
/*
 * txtime()	- calculate tx time for packet of size "psz" bytes 
 *		  at rate "drt" bps
 */
double
Mac802_11::txtime(double psz, double drt)
{
	double dsz = psz - phymib_.getPLCPhdrLen();
        int plcp_hdr = phymib_.getPLCPhdrLen() << 3;	
	int datalen = (int)dsz << 3;
	double t = (((double)plcp_hdr)/phymib_.getPLCPDataRate())
                                       + (((double)datalen)/drt);
	return(t);
}



void
Mac802_11::recvCTS(Packet *p)
{
	if(tx_state_ != MAC_RTS) {
		discard(p, DROP_MAC_INVALID_STATE);
		return;
	}

	assert(pktRTS_);
	Packet::free(pktRTS_); pktRTS_ = 0;

	assert(pktTx_);	
	mhSend_.stop();

	/*
	 * The successful reception of this CTS packet implies
	 * that our RTS was successful. 
	 * According to the IEEE spec 9.2.5.3, you must 
	 * reset the ssrc_, but not the congestion window.
	 */
	ssrc_ = 0;
	tx_resume();

	mac_log(p);
}

void
Mac802_11::recvDATA(Packet *p)
{
	struct hdr_mac802_11 *dh = HDR_MAC802_11(p);
	u_int32_t dst, src, size;
	struct hdr_cmn *ch = HDR_CMN(p);

	dst = ETHER_ADDR(dh->dh_ra);
	src = ETHER_ADDR(dh->dh_ta);
	size = ch->size();
	/*
	 * Adjust the MAC packet size - ie; strip
	 * off the mac header
	 */
	ch->size() -= phymib_.getHdrLen11();
	ch->num_forwards() += 1;

	/*
	 *  If we sent a CTS, clean up...
	 */
	if(dst != MAC_BROADCAST) {
		if(size >= macmib_.getRTSThreshold()) {
			if (tx_state_ == MAC_CTS) {
				assert(pktCTRL_);
				Packet::free(pktCTRL_); pktCTRL_ = 0;
				mhSend_.stop();
				/*
				 * Our CTS got through.
				 */
			} else {
				discard(p, DROP_MAC_BUSY);
				return;
			}
			sendACK(src);
			tx_resume();
		} else {
			/*
			 *  We did not send a CTS and there's no
			 *  room to buffer an ACK.
			 */
			if(pktCTRL_) {
				discard(p, DROP_MAC_BUSY);
				return;
			}
			sendACK(src);
			if(mhSend_.busy() == 0)
				tx_resume();
		}
	}
	
	/* ============================================================
	   Make/update an entry in our sequence number cache.
	   ============================================================ */

	/* Changed by Debojyoti Dutta. This upper loop of if{}else was 
	   suggested by Joerg Diederich <[e-mail]>. 
	   Changed on 19th Oct'2000 */

        if(dst != MAC_BROADCAST) {
                if (src < (u_int32_t) cache_node_count_) {
                        Host *h = &cache_[src];

                        if(h->seqno && h->seqno == dh->dh_scontrol) {
                                discard(p, DROP_MAC_DUPLICATE);
                                return;
                        }
                        h->seqno = dh->dh_scontrol;
                } else {
			static int count = 0;
			if (++count <= 10) {
				printf ("MAC_802_11: accessing MAC cache_ array out of range (src %u, dst %u, size %d)!\n", src, dst, cache_node_count_);
				if (count == 10)
					printf ("[suppressing additional MAC cache_ warnings]\n");
			};
		};
	}

	/*
	 *  Pass the packet up to the link-layer.
	 *  XXX - we could schedule an event to account
	 *  for this processing delay.
	 */
	
	/* in BSS mode, if a station receives a packet via
	 * the AP, and higher layers are interested in looking
	 * at the src address, we might need to put it at
	 * the right place - lest the higher layers end up
	 * believing the AP address to be the src addr! a quick
	 * grep didn't turn up any higher layers interested in
	 * the src addr though!
	 * anyway, here if I'm the AP and the destination
	 * address (in dh_3a) isn't me, then we have to fwd
	 * the packet; we pick the real destination and set
	 * set it up for the LL; we save the real src into
	 * the dh_3a field for the 'interested in the info'
	 * receiver; we finally push the packet towards the
	 * LL to be added back to my queue - accomplish this
	 * by reversing the direction!*/

	if ((bss_id() == addr()) && ((u_int32_t)ETHER_ADDR(dh->dh_ra)!= MAC_BROADCAST)&& ((u_int32_t)ETHER_ADDR(dh->dh_3a) != ((u_int32_t)addr()))) {
		struct hdr_cmn *ch = HDR_CMN(p);
		u_int32_t dst = ETHER_ADDR(dh->dh_3a);
		u_int32_t src = ETHER_ADDR(dh->dh_ta);
		/* if it is a broadcast pkt then send a copy up
		 * my stack also
		 */
		if (dst == MAC_BROADCAST) {
			uptarget_->recv(p->copy(), (Handler*) 0);
		}

		ch->next_hop() = dst;
		STORE4BYTE(&src, (dh->dh_3a));
		ch->addr_type() = NS_AF_ILINK;
		ch->direction() = hdr_cmn::DOWN;
	}

	uptarget_->recv(p, (Handler*) 0);
}


void
Mac802_11::recvACK(Packet *p)
{	
	if(tx_state_ != MAC_SEND) {
		discard(p, DROP_MAC_INVALID_STATE);
		return;
	}
	assert(pktTx_);

	mhSend_.stop();

	/*
	 * The successful reception of this ACK packet implies
	 * that our DATA transmission was successful.  Hence,
	 * we can reset the Short/Long Retry Count and the CW.
	 *
	 * need to check the size of the packet we sent that's being
	 * ACK'd, not the size of the ACK packet.
	 */
	if((u_int32_t) HDR_CMN(pktTx_)->size() <= macmib_.getRTSThreshold())
		ssrc_ = 0;
	else
		slrc_ = 0;
	rst_cw();
	Packet::free(pktTx_); 
	pktTx_ = 0;
	
	/*
	 * Backoff before sending again.
	 */
	assert(mhBackoff_.busy() == 0);
	mhBackoff_.start(cw_, is_idle());

	tx_resume();

	mac_log(p);
}