bss_ragent.cc

对IEEE 802.11e里的分布式信道接入算法EDCA进行改进

/* -*-	Mode:C++; c-basic-offset:8; tab-width:8; indent-tabs-mode:t -*- */
/*
 * Copyright (c) 1997 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the Computer Systems
 *	Engineering Group at Lawrence Berkeley Laboratory.
 * 4. Neither the name of the University nor of the Laboratory may be used
 *    to endorse or promote products derived from this software without
 *    specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */


extern "C" {
#include <stdarg.h>
#include <float.h>
};

#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <cmu-trace.h>
#include <address.h>
#include <mobilenode.h>

#include "bss_ragent.h"

////////////////////////////////////////////////////////////////////////////////////

static int diff_subnet(int src, int dst) 
{
	char* srcnet = Address::instance().get_subnetaddr(src);
	char* dstnet = Address::instance().get_subnetaddr(dst);

	if (srcnet != NULL) {
		if (dstnet != NULL) {
			if (strcmp(dstnet, srcnet) != 0) {
				delete [] dstnet;
				return 1;
			}
			delete [] dstnet;
		}
		delete [] srcnet;
	}
	return 0;
}

////////////////////////////////////////////////////////////////////////////////////

static class BSS_RAgent_Class: public TclClass {
public:
	BSS_RAgent_Class(): TclClass("Agent/BSS") { }
	TclObject* create(int, const char* const*) {
		return (new BSS_RAgent());
	}
} class_bss_ragent;

////////////////////////////////////////////////////////////////////////////////////

void BSS_RAgent::trace(char* fmt, ...)
{
	va_list ap;

	if (!tracetarget)
		return;

	va_start(ap, fmt);
	vsprintf(tracetarget->buffer(), fmt, ap);
	tracetarget->dump();
	va_end(ap);
}

void BSS_RAgent::recv(Packet* p, Handler* h)
{
	hdr_cmn* cmh = HDR_CMN(p);
	hdr_ip* iph = HDR_IP(p);
	int dst = Address::instance().get_nodeaddr(iph->daddr());
	int src = Address::instance().get_nodeaddr(iph->saddr());

	assert(node_ && mac_);
	int me = node_->address();

	/* Remember that I'm a router! I work with IP addresses
	 * only; ns routing happens via (a chain) of classifiers
	 * based on the assumption that there is only one node at
	 * the end of every link, it doesn't work very well for
	 * wireless/ethernet scenarios => having a real router for
	 * them; given the way a wireless node is organized, we
	 * end up essentially being the default gateway => only
	 * one wireless NIC per node; my routing policy is rather
	 * simple for now! if I'm a station, my default gateway is
	 * the DS; if I'm an DS, hey I can talk to anyone in the
	 * BSS, and each of them could be a gateway => I need a real
	 * routing table with a real routing protocol; trying to
	 * keep this simple for now => DS won't route via the BSS
	 * and will drop such packets
	 */

	if (dst == me) {
		/* locally or remotely originated packet
		 * intended for this node; the port_demux
		 * didn't catch it => either there is no
		 * agent to sink this pkt, or its a routing
		 * update! we aren't running a real routing
		 * protocol which sends routing updates etc.
		 * here! so either way this pkt can be dropped!
		 */
		drop(p, "BSSR");
		return;
	}

	if (diff_subnet(me, dst)) {
		if (mac_->addr() == mac_->bss_id()) {
			/* see comment above - DS doesn't route here!
			 */
			drop(p, DROP_RTR_NO_ROUTE);
			return;
		}
		/* Packet I'm forwarding... check the TTL;
		 * discard if 0; xxxamanxxx: am assuming
		 * that IP header has already been added
		 * to the pkt size even if I'm the source
		 * - the original dsdv agent code didn't
		 * think so!
		 */
		if ((src != me) && (--iph->ttl_ == 0)) {
			drop(p, DROP_RTR_TTL);
			return;
		}
		/* DS is my defacto router! I don't need to
		 * know its IP address though :-)
		 */
		cmh->addr_type_ = NS_AF_ILINK;
		cmh->next_hop_ = mac_->bss_id();
	} else {
		cmh->addr_type_ = NS_AF_INET;
		cmh->next_hop_ = dst;
	}

	send(p, h);
	return;
}

int BSS_RAgent::command(int argc, const char* const* argv)
{
	if (argc == 3) {
		TclObject *obj;
		if ((obj = TclObject::lookup(argv[2])) == 0) {
			fprintf (stderr, "%s: %s lookup of %s failed\n", __FILE__, argv[1], argv[2]);
			return TCL_ERROR;
		}
		if (strcasecmp(argv[1], "tracetarget") == 0) {
			tracetarget = (Trace *)obj;
			return TCL_OK;
		} else if (strcasecmp(argv[1], "node") == 0) {
			node_ = (MobileNode*)obj;
			return TCL_OK;
		} else if (strcasecmp(argv[1], "mac") == 0) {
			mac_ = (Mac802_11*)obj;
			return TCL_OK;
		}
	}
	return (Agent::command (argc, argv));
}