res_findzonecut.c

DHCP服务器源码

#if !defined(lint) && !defined(SABER)
static const char rcsid[] = "$Id: res_findzonecut.c,v 1.14.2.4 2004/06/10 17:59:43 dhankins Exp $";
#endif /* not lint */

/*
 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
 * Copyright (c) 1999-2003 by Internet Software Consortium
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 *   Internet Systems Consortium, Inc.
 *   950 Charter Street
 *   Redwood City, CA 94063
 *   <[e-mail]>
 *   http://www.isc.org/
 */

/* Import. */

#include <sys/param.h>
#include <sys/socket.h>
#include <sys/time.h>

#include <netinet/in.h>
#include <arpa/inet.h>

#include <errno.h>
#include <limits.h>
#include <netdb.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <isc-dhcp/list.h>

#include "minires/minires.h"
#include "arpa/nameser.h"

/* Data structures. */

typedef struct rr_a {
	ISC_LINK(struct rr_a)	link;
	struct in_addr		addr;
} rr_a;
typedef ISC_LIST(rr_a) rrset_a;

typedef struct rr_ns {
	ISC_LINK(struct rr_ns) link;
	char *name;
	rrset_a addrs;
} rr_ns;
typedef ISC_LIST(rr_ns) rrset_ns;

/* Forward. */

static int	satisfy(res_state,
			const char *, rrset_ns *, struct in_addr *, int);
static int	add_addrs(res_state, rr_ns *, struct in_addr *, int);
static ns_rcode	get_soa(res_state, const char *, ns_class,
			char *, size_t, char *, size_t,
			rrset_ns *);
static isc_result_t get_ns(res_state, const char *, ns_class, rrset_ns *);
static isc_result_t get_glue(res_state, ns_class, rrset_ns *);
static isc_result_t save_ns(res_state, ns_msg *, ns_sect,
			    const char *, ns_class, rrset_ns *);
static isc_result_t save_a(res_state, ns_msg *, ns_sect,
			   const char *, ns_class, rrset_a *);
static void	free_nsrrset(rrset_ns *);
static void	free_nsrr(rrset_ns *, rr_ns *);
static rr_ns *	find_ns(rrset_ns *, const char *);
static isc_result_t do_query(res_state, const char *, ns_class, ns_type,
			     double *, ns_msg *, int *);

/* Public. */

/*
 * int
 * res_findzonecut(res, dname, class, zname, zsize, addrs, naddrs)
 *	find enclosing zone for a <dname,class>, and some server addresses
 * parameters:
 *	res - resolver context to work within (is modified)
 *	dname - domain name whose enclosing zone is desired
 *	class - class of dname (and its enclosing zone)
 *	zname - found zone name
 *	zsize - allocated size of zname
 *	addrs - found server addresses
 *	naddrs - max number of addrs
 * return values:
 *	< 0 - an error occurred (check errno)
 *	= 0 - zname is now valid, but addrs[] wasn't changed
 *	> 0 - zname is now valid, and return value is number of addrs[] found
 * notes:
 *	this function calls res_nsend() which means it depends on correctly
 *	functioning recursive nameservers (usually defined in /etc/resolv.conf
 *	or its local equivilent).
 *
 *	we start by asking for an SOA<dname,class>.  if we get one as an
 *	answer, that just means <dname,class> is a zone top, which is fine.
 *	more than likely we'll be told to go pound sand, in the form of a
 *	negative answer.
 *
 *	note that we are not prepared to deal with referrals since that would
 *	only come from authority servers and our correctly functioning local
 *	recursive server would have followed the referral and got us something
 *	more definite.
 *
 *	if the authority section contains an SOA, this SOA should also be the
 *	closest enclosing zone, since any intermediary zone cuts would've been
 *	returned as referrals and dealt with by our correctly functioning local
 *	recursive name server.  but an SOA in the authority section should NOT
 *	match our dname (since that would have been returned in the answer
 *	section).  an authority section SOA has to be "above" our dname.
 *
 *	we cannot fail to find an SOA in this way.  ultimately we'll return
 *	a zname indicating the root zone if that's the closest enclosing zone.
 *	however, since authority section SOA's were once optional, it's
 *	possible that we'll have to go hunting for the enclosing SOA by
 *	ripping labels off the front of our dname -- this is known as "doing
 *	it the hard way."
 *
 *	ultimately we want some server addresses, which are ideally the ones
 *	pertaining to the SOA.MNAME, but only if there is a matching NS RR.
 *	so the second phase (after we find an SOA) is to go looking for the
 *	NS RRset for that SOA's zone.
 *
 *	no answer section processed by this code is allowed to contain CNAME
 *	or DNAME RR's.  for the SOA query this means we strip a label and
 *	keep going.  for the NS and A queries this means we just give up.
 */

isc_result_t
res_findzonecut(res_state statp, const char *dname, ns_class class, int opts,
		char *zname, size_t zsize, struct in_addr *addrs, int naddrs,
		int *count, void *zcookie)
{
	char mname[NS_MAXDNAME];
	u_long save_pfcode;
	rrset_ns nsrrs;
	int n = 0;
	isc_result_t rcode;

	DPRINTF(("START dname='%s' class=%s, zsize=%ld, naddrs=%d",
		 dname, p_class(class), (long)zsize, naddrs));
	save_pfcode = statp->pfcode;
	statp->pfcode |= RES_PRF_HEAD2 | RES_PRF_HEAD1 | RES_PRF_HEADX |
			 RES_PRF_QUES | RES_PRF_ANS |
			 RES_PRF_AUTH | RES_PRF_ADD;
	ISC_LIST_INIT(nsrrs);

	DPRINTF (("look for a predefined zone statement"));
	rcode = find_cached_zone (dname, class, zname, zsize,
				  addrs, naddrs, &n, zcookie);
	if (rcode == ISC_R_SUCCESS)
		goto done;

	DPRINTF(("get the soa, and see if it has enough glue"));
	if ((rcode = get_soa(statp, dname, class, zname, zsize,
			     mname, sizeof mname, &nsrrs)) != ISC_R_SUCCESS ||
	    ((opts & RES_EXHAUSTIVE) == 0 &&
	     (n = satisfy(statp, mname, &nsrrs, addrs, naddrs)) > 0))
		goto done;

	DPRINTF(("get the ns rrset and see if it has enough glue"));
	if ((rcode = get_ns(statp, zname, class, &nsrrs)) != ISC_R_SUCCESS ||
	    ((opts & RES_EXHAUSTIVE) == 0 &&
	     (n = satisfy(statp, mname, &nsrrs, addrs, naddrs)) > 0))
		goto done;

	DPRINTF(("get the missing glue and see if it's finally enough"));
	if ((rcode = get_glue(statp, class, &nsrrs)) == ISC_R_SUCCESS)
		n = satisfy(statp, mname, &nsrrs, addrs, naddrs);

	/* If we found the zone, cache it. */
	if (n > 0)
		cache_found_zone (class, zname, addrs, n);
 done:
	DPRINTF(("FINISH n=%d (%s)", n, (n < 0) ? strerror(errno) : "OK"));
	free_nsrrset(&nsrrs);
	statp->pfcode = save_pfcode;
	if (count)
		*count = n;
	return rcode;
}

/* Private. */

static int
satisfy(res_state statp,
	const char *mname, rrset_ns *nsrrsp, struct in_addr *addrs, int naddrs)
{
	rr_ns *nsrr;
	int n, x;

	n = 0;
	nsrr = find_ns(nsrrsp, mname);
	if (nsrr != NULL) {
		x = add_addrs(statp, nsrr, addrs, naddrs);
		addrs += x;
		naddrs -= x;
		n += x;
	}
	for (nsrr = ISC_LIST_HEAD(*nsrrsp);
	     nsrr != NULL && naddrs > 0;
	     nsrr = ISC_LIST_NEXT(nsrr, link))
		if (ns_samename(nsrr->name, mname) != 1) {
			x = add_addrs(statp, nsrr, addrs, naddrs);
			addrs += x;
			naddrs -= x;
			n += x;
		}
	DPRINTF(("satisfy(%s): %d", mname, n));
	return (n);
}

static int
add_addrs(res_state statp, rr_ns *nsrr, struct in_addr *addrs, int naddrs) {
	rr_a *arr;
	int n = 0;

	for (arr = ISC_LIST_HEAD(nsrr->addrs);
	     arr != NULL; arr = ISC_LIST_NEXT(arr, link)) {
		if (naddrs <= 0)
			return (0);
		*addrs++ = arr->addr;
		naddrs--;
		n++;
	}
	DPRINTF(("add_addrs: %d", n));
	return (n);
}

static ns_rcode
get_soa(res_state statp, const char *dname, ns_class class,
	char *zname, size_t zsize, char *mname, size_t msize,
	rrset_ns *nsrrsp)
{
	char tname[NS_MAXDNAME];
	double resp[NS_PACKETSZ / sizeof (double)];
	int n, i, ancount, nscount;
	ns_sect sect;
	ns_msg msg;
	u_int rcode;
	isc_result_t status;

	/*
	 * Find closest enclosing SOA, even if it's for the root zone.
	 */

	/* First canonicalize dname (exactly one unescaped trailing "."). */
	status = ns_makecanon(dname, tname, sizeof tname);
	if (status != ISC_R_SUCCESS)
		return status;
	dname = tname;

	/* Now grovel the subdomains, hunting for an SOA answer or auth. */
	for (;;) {
		/* Leading or inter-label '.' are skipped here. */
		while (*dname == '.')
			dname++;

		/* Is there an SOA? */
		rcode = do_query(statp, dname, class, ns_t_soa,
				 resp, &msg, &n);
		if (rcode != ISC_R_SUCCESS) {
			DPRINTF(("get_soa: do_query('%s', %s) failed (%d)",
				 dname, p_class(class), n));
			return rcode;
		}
		if (n > 0) {
			DPRINTF(("get_soa: CNAME or DNAME found"));
			sect = ns_s_max, n = 0;
		} else {
			ancount = ns_msg_count(msg, ns_s_an);
			nscount = ns_msg_count(msg, ns_s_ns);
			if (ancount > 0 && rcode == ISC_R_SUCCESS)
				sect = ns_s_an, n = ancount;
			else if (nscount > 0)
				sect = ns_s_ns, n = nscount;
			else
				sect = ns_s_max, n = 0;
		}
		for (i = 0; i < n; i++) {
			const char *t;
			const u_char *rdata;
			int rdlen;
			ns_rr rr;

			rcode = ns_parserr(&msg, sect, i, &rr) < 0;
			if (rcode != ISC_R_SUCCESS) {
				DPRINTF(("get_soa: ns_parserr(%s, %d) failed",
					 p_section(sect, ns_o_query), i));
				return rcode;
			}
			if (ns_rr_type(rr) == ns_t_cname ||
			    ns_rr_type(rr) == ns_t_dname)
				break;
			if (ns_rr_type(rr) != ns_t_soa ||