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

			rp->id = toid( o, n);
			break;
		case ODparams:
			if(n > sizeof(rp->requested))
				n = sizeof(rp->requested);
			memmove(rp->requested, o, n);
			break;
		case ODvendorclass:
			if(n >= sizeof(rp->vendorclass))
				n = sizeof(rp->vendorclass)-1;
			memmove(rp->vendorclass, o, n);
			rp->vendorclass[n] = 0;
			if(strncmp((char*)rp->vendorclass, "p9-", 3) == 0)
				strcpy(rp->cputype, (char*)rp->vendorclass+3);
			break;
		case OBend:
			return;
		}
	}
}

void
remrequested(Req *rp, int opt)
{
	uchar *p;

	p = memchr(rp->requested, opt, sizeof(rp->requested));
	if(p != nil)
		*p = OBpad;
}

void
miscoptions(Req *rp, uchar *ip)
{
	char *p;
	int i, j;
	uchar *addrs[2];
	uchar x[2*IPaddrlen];
	uchar vopts[64];
	uchar *op, *omax;
	char *attr[100], **a;
	int na;
	Ndbtuple *t;

	addrs[0] = x;
	addrs[1] = x+IPaddrlen;

	/* always supply these */
	maskopt(rp, OBmask, rp->gii.ipmask);
	if(validip(rp->gii.gwip)){
		remrequested(rp, OBrouter);
		addropt(rp, OBrouter, rp->gii.gwip);
	} else if(validip(rp->giaddr)){
		remrequested(rp, OBrouter);
		addropt(rp, OBrouter, rp->giaddr);
	}

	// OBhostname for the HP4000M switches
	// (this causes NT to log infinite errors - tough shit )
	if(*rp->ii.domain){
		remrequested(rp, OBhostname);
		stringopt(rp, OBhostname, rp->ii.domain);
	}
	if(*rp->ii.rootpath)
		stringopt(rp, OBrootpath, rp->ii.rootpath);

	/* figure out what we need to lookup */
	na = 0;
	a = attr;
	if(*rp->ii.domain == 0)
		a[na++] = "dom";
	for(i = 0; i < sizeof(rp->requested); i++)
		switch(rp->requested[i]){
		case OBrouter:
			a[na++] = "@ipgw";
			break;
		case OBdnserver:
			a[na++] = "@dns";
			break;
		case OBnetbiosns:
			a[na++] = "@wins";
			break;
		case OBsmtpserver:
			a[na++] = "@smtp";
			break;
		case OBpop3server:
			a[na++] = "@pop3";
			break;
		case OBwwwserver:
			a[na++] = "@www";
			break;
		case OBntpserver:
			a[na++] = "@ntp";
			break;
		case OBtimeserver:
			a[na++] = "@time";
			break;
		}
	if(strncmp((char*)rp->vendorclass, "plan9_", 6) == 0
	|| strncmp((char*)rp->vendorclass, "p9-", 3) == 0){
		a[na++] = "@fs";
		a[na++] = "@auth";
	}
	t = lookupinfo(ip, a, na);

	/* lookup anything we might be missing */
	if(*rp->ii.domain == 0)
		lookupname(rp->ii.domain, t);

	/* add any requested ones that we know about */
	for(i = 0; i < sizeof(rp->requested); i++)
		switch(rp->requested[i]){
		case OBrouter:
			j = lookupserver("ipgw", addrs, t);
			addrsopt(rp, OBrouter, addrs, j);
			break;
		case OBdnserver:
			j = lookupserver("dns", addrs, t);
			addrsopt(rp, OBdnserver, addrs, j);
			break;
		case OBhostname:
			if(*rp->ii.domain)
				stringopt(rp, OBhostname, rp->ii.domain);
			break;
		case OBdomainname:
			p = strchr(rp->ii.domain, '.');
			if(p)
				stringopt(rp, OBdomainname, p+1);
			break;
		case OBnetbiosns:
			j = lookupserver("wins", addrs, t);
			addrsopt(rp, OBnetbiosns, addrs, j);
			break;
		case OBnetbiostype:
			/* p-node: peer to peer WINS queries */
			byteopt(rp, OBnetbiostype, 0x2);
			break;
		case OBsmtpserver:
			j = lookupserver("smtp", addrs, t);
			addrsopt(rp, OBsmtpserver, addrs, j);
			break;
		case OBpop3server:
			j = lookupserver("pop3", addrs, t);
			addrsopt(rp, OBpop3server, addrs, j);
			break;
		case OBwwwserver:
			j = lookupserver("www", addrs, t);
			addrsopt(rp, OBwwwserver, addrs, j);
			break;
		case OBntpserver:
			j = lookupserver("ntp", addrs, t);
			addrsopt(rp, OBntpserver, addrs, j);
			break;
		case OBtimeserver:
			j = lookupserver("time", addrs, t);
			addrsopt(rp, OBtimeserver, addrs, j);
			break;
		case OBttl:
			byteopt(rp, OBttl, 255);
			break;
		}

	// add plan9 specific options
	if(strncmp((char*)rp->vendorclass, "plan9_", 6) == 0
	|| strncmp((char*)rp->vendorclass, "p9-", 3) == 0){
		// point to temporary area
		op = rp->p;
		omax = rp->max;
		rp->p = vopts;
		rp->max = vopts + sizeof(vopts) - 1;

		j = lookupserver("fs", addrs, t);
		addrsopt(rp, OP9fs, addrs, j);
		j = lookupserver("auth", addrs, t);
		addrsopt(rp, OP9auth, addrs, j);

		// point back
		j = rp->p - vopts;
		rp->p = op;
		rp->max = omax;
		vectoropt(rp, OBvendorinfo, vopts, j);
	}

	ndbfree(t);
}

int
openlisten(char *net)
{
	int fd, cfd;
	char data[128];
	char devdir[40];

	sprint(data, "%s/udp!*!bootp", net);
	cfd = announce(data, devdir);
	if(cfd < 0)
		fatal(1, "can't announce");
	if(fprint(cfd, "headers") < 0)
		fatal(1, "can't set header mode");
	fprint(cfd, "oldheaders");

	sprint(data, "%s/data", devdir);

	fd = open(data, ORDWR);
	if(fd < 0)
		fatal(1, "open udp data");
	return fd;
}

void
fatal(int syserr, char *fmt, ...)
{
	char buf[ERRMAX];
	va_list arg;

	va_start(arg, fmt);
	vseprint(buf, buf+sizeof(buf), fmt, arg);
	va_end(arg);
	if(syserr)
		syslog(1, blog, "%s: %r", buf);
	else
		syslog(1, blog, "%s", buf);
	exits(buf);
}

extern void
warning(int syserr, char *fmt, ...)
{
	char buf[256];
	va_list arg;

	va_start(arg, fmt);
	vseprint(buf, buf+sizeof(buf), fmt, arg);
	va_end(arg);
	if(syserr){
		syslog(0, blog, "%s: %r", buf);
		if(debug)
			fprint(2, "%s: %r\n", buf);
	} else {
		syslog(0, blog, "%s", buf);
		if(debug)
			fprint(2, "%s\n", buf);
	}
}

char*
readsysname(void)
{
	static char name[128];
	char *p;
	int n, fd;

	fd = open("/dev/sysname", OREAD);
	if(fd >= 0){
		n = read(fd, name, sizeof(name)-1);
		close(fd);
		if(n > 0){
			name[n] = 0;
			return name;
		}
	}
	p = getenv("sysname");
	if(p == nil || *p == 0)
		return "unknown";
	return p;
}

extern int
validip(uchar *ip)
{
	if(ipcmp(ip, IPnoaddr) == 0)
		return 0;
	if(ipcmp(ip, v4prefix) == 0)
		return 0;
	return 1;
}

void
longopt(Req *rp, int t, long v)
{
	if(rp->p + 6 > rp->max)
		return;
	*rp->p++ = t;
	*rp->p++ = 4;
	hnputl(rp->p, v);
	rp->p += 4;

	op = seprint(op, oe, "%s(%ld)", optname[t], v);
}

void
addropt(Req *rp, int t, uchar *ip)
{
	if(rp->p + 6 > rp->max)
		return;
	*rp->p++ = t;
	*rp->p++ = 4;
	memmove(rp->p, ip+IPv4off, 4);
	rp->p += 4;

	op = seprint(op, oe, "%s(%I)", optname[t], ip);
}

void
maskopt(Req *rp, int t, uchar *ip)
{
	if(rp->p + 6 > rp->max)
		return;
	*rp->p++ = t;
	*rp->p++ = 4;
	memmove(rp->p, ip+IPv4off, 4);
	rp->p += 4;

	op = seprint(op, oe, "%s(%M)", optname[t], ip);
}

void
addrsopt(Req *rp, int t, uchar **ip, int i)
{
	if(i <= 0)
		return;
	if(rp->p + 2 + 4*i > rp->max)
		return;
	*rp->p++ = t;
	*rp->p++ = 4*i;
	op = seprint(op, oe, "%s(", optname[t]);
	while(i-- > 0){
		v6tov4(rp->p, *ip);
		rp->p += 4;
		op = seprint(op, oe, "%I", *ip);
		ip++;
		if(i > 0)
			op = seprint(op, oe, " ");
	}
	op = seprint(op, oe, ")");
}

void
byteopt(Req *rp, int t, uchar v)
{
	if(rp->p + 3 > rp->max)
		return;
	*rp->p++ = t;
	*rp->p++ = 1;
	*rp->p++ = v;

	op = seprint(op, oe, "%s(%d)", optname[t], v);
}

void
termopt(Req *rp)
{
	if(rp->p + 1 > rp->max)
		return;
	*rp->p++ = OBend;
}

void
stringopt(Req *rp, int t, char *str)
{
	int n;

	n = strlen(str);
	if(n > 255)
		n = 255;
	if(rp->p+n+2 > rp->max)
		return;
	*rp->p++ = t;
	*rp->p++ = n;
	memmove(rp->p, str, n);
	rp->p += n;

	op = seprint(op, oe, "%s(%s)", optname[t], str);
}

void
vectoropt(Req *rp, int t, uchar *v, int n)
{
	int i;

	if(n > 255)
		n = 255;
	if(rp->p+n+2 > rp->max)
		return;
	*rp->p++ = t;
	*rp->p++ = n;
	memmove(rp->p, v, n);
	rp->p += n;

	op = seprint(op, oe, "%s(", optname[t]);
	if(n > 0)
		op = seprint(op, oe, "%ud", 0);
	for(i = 1; i < n; i++)
		op = seprint(op, oe, " %ud", v[i]);
}

int
fromhex(int x)
{
	if(x >= '0' && x <= '9')
		return x - '0';
	return x - 'a';
}

void
hexopt(Req *rp, int t, char *str)
{
	int n;

	n = strlen(str);
	n /= 2;
	if(n > 255)
		n = 255;
	if(rp->p+n+2 > rp->max)
		return;
	*rp->p++ = t;
	*rp->p++ = n;
	while(n-- > 0){
		*rp->p++ = (fromhex(str[0])<<4)|fromhex(str[1]);
		str += 2;
	}

	op = seprint(op, oe, "%s(%s)", optname[t], str);
}

void
arpenter(uchar *ip, uchar *ether)
{
	int f;
	char buf[256];

	/* brazil */
	sprint(buf, "%s/arp", net);
	f = open(buf, OWRITE);
	if(f < 0){
		syslog(debug, blog, "open %s: %r", buf);
		return;
	}
	fprint(f, "add ether %I %E", ip, ether);
	close(f);
}

char *dhcpmsgname[] =
{
	[Discover]	"Discover",
	[Offer]		"Offer",
	[Request]	"Request",
	[Decline]	"Decline",
	[Ack]		"Ack",
	[Nak]		"Nak",
	[Release]	"Release",
	[Inform]	"Inform",
};

void
logdhcp(Req *rp)
{
	char buf[4096];
	char *p, *e;
	int i;

	p = buf;
	e = buf + sizeof(buf);
	if(rp->dhcptype > 0 && rp->dhcptype <= Inform)
		p = seprint(p, e, "%s(", dhcpmsgname[rp->dhcptype]);
	else
		p = seprint(p, e, "%d(", rp->dhcptype);
	p = seprint(p, e, "%I->%I) xid(%ux)flag(%ux)", rp->up->raddr, rp->up->laddr,
		nhgetl(rp->bp->xid), nhgets(rp->bp->flags));
	if(rp->bp->htype == 1)
		p = seprint(p, e, "ea(%E)", rp->bp->chaddr);
	if(validip(rp->ciaddr))
		p = seprint(p, e, "ci(%I)", rp->ciaddr);
	if(validip(rp->giaddr))
		p = seprint(p, e, "gi(%I)", rp->giaddr);
	if(validip(rp->ip))
		p = seprint(p, e, "ip(%I)", rp->ip);
	if(rp->id != nil)
		p = seprint(p, e, "id(%s)", rp->id);
	if(rp->leasetime)
		p = seprint(p, e, "leas(%d)", rp->leasetime);
	if(validip(rp->server))
		p = seprint(p, e, "sid(%I)", rp->server);
	p = seprint(p, e, "need(");
	for(i = 0; i < sizeof(rp->requested); i++)
		if(rp->requested[i] != 0)
			p = seprint(p, e, "%s ", optname[rp->requested[i]]);
	p = seprint(p, e, ")");

	USED(p);
	syslog(0, blog, "%s", buf);
}

void
logdhcpout(Req *rp, char *type)
{
	syslog(0, blog, "%s(%I-%I)id(%s)ci(%V)gi(%V)yi(%V)si(%V) %s",
		type, rp->up->laddr, rp->up->raddr, rp->id,
		rp->bp->ciaddr, rp->bp->giaddr, rp->bp->yiaddr, rp->bp->siaddr, optbuf);
}

/*
 *  if we get behind, it's useless to try answering since the sender
 *  will probably have retransmitted with a differnt sequence number.
 *  So dump all the last message in the queue.
 */
void ding(void*, char *msg)
{
	if(strstr(msg, "alarm"))
		noted(NCONT);
	else
		noted(NDFLT);
}

int
readlast(int fd, uchar *buf, int len)
{
	int lastn, n;

	notify(ding);

	lastn = 0;
	for(;;){
		alarm(20);
		n = read(fd, buf, len);
		alarm(0);
		if(n < 0){
			if(lastn > 0)
				return lastn;
			break;
		}
		lastn = n;
	}
	return read(fd, buf, len);
}