dhcpd.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

		/* check for hard assignment */
		if(rp->staticbinding){
			if(memcmp(rp->ip, rp->ii.ipaddr, IPaddrlen) != 0){
				warning(0, "!Request(%s via %I): %I not valid for %E",
					rp->id, rp->gii.ipaddr, rp->ip, rp->bp->chaddr);
				sendnak(rp, "not valid");
			}
			sendack(rp, rp->ii.ipaddr, (StaticLease > minlease ? StaticLease : minlease), 1);
			return;
		}

		/* make sure the network makes sense */
		if(!samenet(rp->ip, &rp->gii)){
			warning(0, "!Request(%s via %I): bad forward of %I",
				rp->id, rp->gii.ipaddr, rp->ip);
			sendnak(rp, "wrong network");
			return;
		}
		b = iptobinding(rp->ip, 0);
		if(b == nil){
			warning(0, "!Request(%s via %I): no binding for %I for",
				rp->id, rp->gii.ipaddr, rp->ip);
			return;
		}
		if(memcmp(rp->ip, b->ip, IPaddrlen) != 0 || now > b->lease){
			warning(0, "!Request(%s via %I): %I not valid",
				rp->id, rp->gii.ipaddr, rp->ip);
			sendnak(rp, "not valid");
			return;
		}
		b->offer = b->lease - now;
		sendack(rp, b->ip, b->offer, 1);
	} else if(validip(rp->ciaddr)){
		/*
		 *  checking address - RENEWING or REBINDING
		 *
		 *  these states are indistinguishable in our action.  The only
		 *  difference is how close to lease expiration the client is.
		 *  If it is really close, it broadcasts the request hoping that
		 *  some server will answer.
		 */

		/* check for hard assignment */
		if(rp->staticbinding){
			if(ipcmp(rp->ciaddr, rp->ii.ipaddr) != 0){
				warning(0, "!Request(%s via %I): %I not valid",
					rp->id, rp->gii.ipaddr, rp->ciaddr);
				sendnak(rp, "not valid");
			}
			sendack(rp, rp->ii.ipaddr, (StaticLease > minlease ? StaticLease : minlease), 1);
			return;
		}

		/* make sure the network makes sense */
		if(!samenet(rp->ciaddr, &rp->gii)){
			warning(0, "!Request(%s via %I): bad forward of %I",
				rp->id, rp->gii.ipaddr, rp->ip);
			sendnak(rp, "wrong network");
			return;
		}
		b = iptobinding(rp->ciaddr, 0);
		if(b == nil){
			warning(0, "!Request(%s via %I): no binding for %I",
				rp->id, rp->gii.ipaddr, rp->ciaddr);
			return;
		}
		if(ipcmp(rp->ciaddr, b->ip) != 0){
			warning(0, "!Request(%I via %s): %I not valid",
				rp->id, rp->gii.ipaddr, rp->ciaddr);
			sendnak(rp, "invalid ip address");
			return;
		}
		mkoffer(b, rp->id, rp->leasetime);
		if(commitbinding(b) < 0){
			warning(0, "!Request(%s via %I): can't commit %I",
				rp->id, rp->gii.ipaddr, b->ip);
			sendnak(rp, "can't commit binding");
			return;
		}
		sendack(rp, b->ip, b->offer, 1);
	}
}

void
rcvdecline(Req *rp)
{
	Binding *b;
	char buf[64];

	if(rp->staticbinding)
		return;

	b = idtooffer(rp->id, &rp->gii);
	if(b == nil){
		warning(0, "!Decline(%s via %I): no binding",
			rp->id, rp->gii.ipaddr);
		return;
	}

	/* mark ip address as in use */
	snprint(buf, sizeof(buf), "declined by %s", rp->id);
	mkoffer(b, buf, 0x7fffffff);
	commitbinding(b);
}

void
rcvrelease(Req *rp)
{
	Binding *b;

	if(rp->staticbinding)
		return;

	b = idtobinding(rp->id, &rp->gii, 0);
	if(b == nil){
		warning(0, "!Release(%s via %I): no binding",
			rp->id, rp->gii.ipaddr);
		return;
	}
	if(strcmp(rp->id, b->boundto) != 0){
		warning(0, "!Release(%s via %I): invalid release of %I",
			rp->id, rp->gii.ipaddr, rp->ip);
		return;
	}
	warning(0, "Release(%s via %I): releasing %I", b->boundto, rp->gii.ipaddr, b->ip);
	if(releasebinding(b, rp->id) < 0)
		warning(0, "release: couldn't release");
}

void
rcvinform(Req *rp)
{
	Binding *b;

	if(rp->staticbinding){
		sendack(rp, rp->ii.ipaddr, 0, 0);
		return;
	}

	b = iptobinding(rp->ciaddr, 0);
	if(b == nil){
		warning(0, "!Inform(%s via %I): no binding for %I",
			rp->id, rp->gii.ipaddr, rp->ip);
		return;
	}
	sendack(rp, b->ip, 0, 0);
}

int
setsiaddr(uchar *siaddr, uchar *saddr, uchar *laddr)
{
	if(ipcmp(saddr, IPnoaddr) != 0){
		v6tov4(siaddr, saddr);
		return 0;
	} else {
		v6tov4(siaddr, laddr);
		return 1;
	}
}

int
ismuted(Req *rp)
{
	return mute || (mutestat && rp->staticbinding);
}

void
sendoffer(Req *rp, uchar *ip, int offer)
{
	int n;
	ushort flags;
	Bootp *bp;
	OUdphdr *up;

	bp = rp->bp;
	up = rp->up;

	/*
	 *  set destination
	 */
	flags = nhgets(bp->flags);
	if(validip(rp->giaddr)){
		ipmove(up->raddr, rp->giaddr);
		hnputs(up->rport, 67);
	} else if(flags & Fbroadcast){
		ipmove(up->raddr, IPv4bcast);
		hnputs(up->rport, 68);
	} else {
		ipmove(up->raddr, ip);
		if(bp->htype == 1)
			arpenter(up->raddr, bp->chaddr);
		hnputs(up->rport, 68);
	}

	/*
	 *  fill in standard bootp part
	 */
	bp->op = Bootreply;
	bp->hops = 0;
	hnputs(bp->secs, 0);
	memset(bp->ciaddr, 0, sizeof(bp->ciaddr));
	v6tov4(bp->giaddr, rp->giaddr);
	v6tov4(bp->yiaddr, ip);
	setsiaddr(bp->siaddr, rp->ii.tftp, up->laddr);
	strncpy(bp->sname, mysysname, sizeof(bp->sname));
	strncpy(bp->file, rp->ii.bootf, sizeof(bp->file));

	/*
	 *  set options
	 */
	byteopt(rp, ODtype, Offer);
	longopt(rp, ODlease, offer);
	addropt(rp, ODserverid, up->laddr);
	miscoptions(rp, ip);
	termopt(rp);

	logdhcpout(rp, "Offer");

	/*
	 *  send
	 */
	n = rp->p - rp->buf;
	if(!ismuted(rp) && write(rp->fd, rp->buf, n) != n)
		warning(0, "offer: write failed: %r");
}

void
sendack(Req *rp, uchar *ip, int offer, int sendlease)
{
	int n;
	ushort flags;
	Bootp *bp;
	OUdphdr *up;

	bp = rp->bp;
	up = rp->up;

	/*
	 *  set destination
	 */
	flags = nhgets(bp->flags);
	if(validip(rp->giaddr)){
		ipmove(up->raddr, rp->giaddr);
		hnputs(up->rport, 67);
	} else if(flags & Fbroadcast){
		ipmove(up->raddr, IPv4bcast);
		hnputs(up->rport, 68);
	} else {
		ipmove(up->raddr, ip);
		if(bp->htype == 1)
			arpenter(up->raddr, bp->chaddr);
		hnputs(up->rport, 68);
	}

	/*
	 *  fill in standard bootp part
	 */
	bp->op = Bootreply;
	bp->hops = 0;
	hnputs(bp->secs, 0);
	v6tov4(bp->giaddr, rp->giaddr);
	v6tov4(bp->yiaddr, ip);
	setsiaddr(bp->siaddr, rp->ii.tftp, up->laddr);
	strncpy(bp->sname, mysysname, sizeof(bp->sname));
	strncpy(bp->file, rp->ii.bootf, sizeof(bp->file));

	/*
	 *  set options
	 */
	byteopt(rp, ODtype, Ack);
	if(sendlease){
		longopt(rp, ODlease, offer);
	}
	addropt(rp, ODserverid, up->laddr);
	miscoptions(rp, ip);
	termopt(rp);

	logdhcpout(rp, "Ack");

	/*
	 *  send
	 */
	n = rp->p - rp->buf;
	if(!ismuted(rp) && write(rp->fd, rp->buf, n) != n)
		warning(0, "ack: write failed: %r");
}

void
sendnak(Req *rp, char *msg)
{
	int n;
	Bootp *bp;
	OUdphdr *up;

	bp = rp->bp;
	up = rp->up;

	/*
	 *  set destination (always broadcast)
	 */
	if(validip(rp->giaddr)){
		ipmove(up->raddr, rp->giaddr);
		hnputs(up->rport, 67);
	} else {
		ipmove(up->raddr, IPv4bcast);
		hnputs(up->rport, 68);
	}

	/*
	 *  fill in standard bootp part
	 */
	bp->op = Bootreply;
	bp->hops = 0;
	hnputs(bp->secs, 0);
	v6tov4(bp->giaddr, rp->giaddr);
	memset(bp->ciaddr, 0, sizeof(bp->ciaddr));
	memset(bp->yiaddr, 0, sizeof(bp->yiaddr));
	memset(bp->siaddr, 0, sizeof(bp->siaddr));

	/*
	 *  set options
	 */
	byteopt(rp, ODtype, Nak);
	addropt(rp, ODserverid, up->laddr);
	if(msg)
		stringopt(rp, ODmessage, msg);
	if(strncmp(rp->id, "id", 2) == 0)
		hexopt(rp, ODclientid, rp->id+2);
	termopt(rp);

	logdhcpout(rp, "Nak");

	/*
	 *  send nak
	 */
	n = rp->p - rp->buf;
	if(!ismuted(rp) && write(rp->fd, rp->buf, n) != n)
		warning(0, "nak: write failed: %r");
}

void
bootp(Req *rp)
{
	int n;
	Bootp *bp;
	OUdphdr *up;
	ushort flags;
	Iplifc *lifc;
	Info *iip;

	warning(0, "bootp %s %I->%I from %s via %I, file %s",
		rp->genrequest ? "generic" : (rp->p9request ? "p9" : ""),
		rp->up->raddr, rp->up->laddr,
		rp->id, rp->gii.ipaddr,
		rp->bp->file);

	if(nobootp)
		return;

	bp = rp->bp;
	up = rp->up;
	iip = &rp->ii;

	if(rp->staticbinding == 0){
		warning(0, "bootp from unknown %s via %I", rp->id, rp->gii.ipaddr);
		return;
	}

	/* ignore if not for us */
	if(*bp->sname){
		if(strcmp(bp->sname, mysysname) != 0){
			bp->sname[20] = 0;
			warning(0, "bootp for server %s", bp->sname);
			return;
		}
	} else
		slowdelay(rp);

	/* ignore if we don't know what file to load */
	if(*bp->file == 0){
		if(rp->genrequest && *iip->bootf2)	/* if not plan 9 and we have an alternate file... */
			strncpy(bp->file, iip->bootf2, sizeof(bp->file));
		else if(*iip->bootf)
			strncpy(bp->file, iip->bootf, sizeof(bp->file));
		else if(*bp->sname)		/* if we were asked, respond no matter what */
			bp->file[0] = '\0';
		else {
			warning(0, "no bootfile for %I", iip->ipaddr);
			return;
		}
	}

	/* ignore if the file is unreadable */
	if((!rp->genrequest) && bp->file[0] && access(bp->file, 4) < 0){
		warning(0, "inaccessible bootfile1 %s", bp->file);
		return;
	}

	bp->op = Bootreply;
	v6tov4(bp->yiaddr, iip->ipaddr);
	if(rp->p9request){
		warning(0, "p9bootp: %I", iip->ipaddr);
		memmove(bp->optmagic, plan9opt, 4);
		if(iip->gwip == 0)
			v4tov6(iip->gwip, bp->giaddr);
		rp->p += sprint((char*)rp->p, "%V %I %I %I", iip->ipmask+IPv4off, iip->fsip,
				iip->auip, iip->gwip);
		sprint(optbuf, "%s", (char*)(bp->optmagic));
	} else if(rp->genrequest){
		warning(0, "genericbootp: %I", iip->ipaddr);
		memmove(bp->optmagic, genericopt, 4);
		miscoptions(rp, iip->ipaddr);
		termopt(rp);
	} else if(iip->vendor[0] != 0) {
		warning(0, "bootp vendor field: %s", iip->vendor);
		memset(rp->p, 0, 128-4);
		rp->p += sprint((char*)bp->optmagic, "%s", iip->vendor);
	} else {
		memset(rp->p, 0, 128-4);
		rp->p += 128-4;
	}

	/*
	 *  set destination
	 */
	flags = nhgets(bp->flags);
	if(validip(rp->giaddr)){
		ipmove(up->raddr, rp->giaddr);
		hnputs(up->rport, 67);
	} else if(flags & Fbroadcast){
		ipmove(up->raddr, IPv4bcast);
		hnputs(up->rport, 68);
	} else {
		v4tov6(up->raddr, bp->yiaddr);
		if(bp->htype == 1)
			arpenter(up->raddr, bp->chaddr);
		hnputs(up->rport, 68);
	}

	/*
	 *  select best local address if destination is directly connected
	 */
	lifc = findlifc(up->raddr);
	if(lifc)
		ipmove(up->laddr, lifc->ip);

	/*
	 *  our identity
	 */
	strncpy(bp->sname, mysysname, sizeof(bp->sname));

	/*
	 *  set tftp server
	 */
	setsiaddr(bp->siaddr, iip->tftp, up->laddr);
	if(rp->genrequest && *iip->bootf2)
		setsiaddr(bp->siaddr, iip->tftp2, up->laddr);

	/*
	 * RFC 1048 says that we must pad vendor field with
	 * zeros until we have a 64 byte field.
	 */
	n = rp->p - rp->bp->optdata;
	if(n < 64-4) {
		memset(rp->p, 0, (64-4)-n);
		rp->p += (64-4)-n;
	}

	/*
	 *  send
	 */
	n = rp->p - rp->buf;
	if(!ismuted(rp) && write(rp->fd, rp->buf, n) != n)
		warning(0, "bootp: write failed: %r");

	warning(0, "bootp via %I: file %s xid(%ux)flag(%ux)ci(%V)gi(%V)yi(%V)si(%V) %s",
			up->raddr, bp->file, nhgetl(bp->xid), nhgets(bp->flags),
			bp->ciaddr, bp->giaddr, bp->yiaddr, bp->siaddr,
			optbuf);
}

void
parseoptions(Req *rp)
{
	int n, c, code;
	uchar *o, *p;

	p = rp->p;

	while(p < rp->e){
		code = *p++;
		if(code == 255)
			break;
		if(code == 0)
			continue;

		/* ignore anything that's too long */
		n = *p++;
		o = p;
		p += n;
		if(p > rp->e)
			return;

		switch(code){
		case ODipaddr:	/* requested ip address */
			if(n == IPv4addrlen)
				v4tov6(rp->ip, o);
			break;
		case ODlease:	/* requested lease time */
			rp->leasetime = nhgetl(o);
			if(rp->leasetime > MaxLease || rp->leasetime < 0)
				rp->leasetime = MaxLease;
			break;
		case ODtype:
			c = *o;
			if(c < 10 && c > 0)
				rp->dhcptype = c;
			break;
		case ODserverid:
			if(n == IPv4addrlen)
				v4tov6(rp->server, o);
			break;
		case ODmessage:
			if(n > sizeof rp->msg-1)
				n = sizeof rp->msg-1;
			memmove(rp->msg, o, n);
			rp->msg[n] = 0;
			break;
		case ODmaxmsg:
			c = nhgets(o);
			c -= 28;
			c += OUdphdrsize;
			if(c > 0)
				rp->max = rp->buf + c;
			break;
		case ODclientid:
			if(n <= 1)
				break;