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freebsd-skq/contrib/isc-dhcp/common/dns.c
murray a916d35e05 Import ISC DHCP 3.0.1 RC8 client.
2002-04-01 07:54:44 +00:00

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/* dns.c
Domain Name Service subroutines. */
/*
* Copyright (c) 2001 Internet Software Consortium.
* 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. Neither the name of The Internet Software Consortium nor the names
* of its contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM 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 INTERNET SOFTWARE CONSORTIUM 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.
*
* This software has been written for the Internet Software Consortium
* by Ted Lemon in cooperation with Nominum, Inc.
* To learn more about the Internet Software Consortium, see
* ``http://www.isc.org/''. To learn more about Nominum, Inc., see
* ``http://www.nominum.com''.
*/
#ifndef lint
static char copyright[] =
"$Id: dns.c,v 1.35.2.12 2002/02/20 22:28:17 mellon Exp $ Copyright (c) 2001 The Internet Software Consortium. All rights reserved.\n";
#endif /* not lint */
#include "dhcpd.h"
#include "arpa/nameser.h"
#include "dst/md5.h"
/* This file is kind of a crutch for the BIND 8 nsupdate code, which has
* itself been cruelly hacked from its original state. What this code
* does is twofold: first, it maintains a database of zone cuts that can
* be used to figure out which server should be contacted to update any
* given domain name. Secondly, it maintains a set of named TSIG keys,
* and associates those keys with zones. When an update is requested for
* a particular zone, the key associated with that zone is used for the
* update.
*
* The way this works is that you define the domain name to which an
* SOA corresponds, and the addresses of some primaries for that domain name:
*
* zone FOO.COM {
* primary 10.0.17.1;
* secondary 10.0.22.1, 10.0.23.1;
* key "FOO.COM Key";
* }
*
* If an update is requested for GAZANGA.TOPANGA.FOO.COM, then the name
* server looks in its database for a zone record for "GAZANGA.TOPANGA.FOO.COM",
* doesn't find it, looks for one for "TOPANGA.FOO.COM", doesn't find *that*,
* looks for "FOO.COM", finds it. So it
* attempts the update to the primary for FOO.COM. If that times out, it
* tries the secondaries. You can list multiple primaries if you have some
* kind of magic name server that supports that. You shouldn't list
* secondaries that don't know how to forward updates (e.g., BIND 8 doesn't
* support update forwarding, AFAIK). If no TSIG key is listed, the update
* is attempted without TSIG.
*
* The DHCP server tries to find an existing zone for any given name by
* trying to look up a local zone structure for each domain containing
* that name, all the way up to '.'. If it finds one cached, it tries
* to use that one to do the update. That's why it tries to update
* "FOO.COM" above, even though theoretically it should try GAZANGA...
* and TOPANGA... first.
*
* If the update fails with a predefined or cached zone (we'll get to
* those in a second), then it tries to find a more specific zone. This
* is done by looking first for an SOA for GAZANGA.TOPANGA.FOO.COM. Then
* an SOA for TOPANGA.FOO.COM is sought. If during this search a predefined
* or cached zone is found, the update fails - there's something wrong
* somewhere.
*
* If a more specific zone _is_ found, that zone is cached for the length of
* its TTL in the same database as that described above. TSIG updates are
* never done for cached zones - if you want TSIG updates you _must_
* write a zone definition linking the key to the zone. In cases where you
* know for sure what the key is but do not want to hardcode the IP addresses
* of the primary or secondaries, a zone declaration can be made that doesn't
* include any primary or secondary declarations. When the DHCP server
* encounters this while hunting up a matching zone for a name, it looks up
* the SOA, fills in the IP addresses, and uses that record for the update.
* If the SOA lookup returns NXRRSET, a warning is printed and the zone is
* discarded, TSIG key and all. The search for the zone then continues as if
* the zone record hadn't been found. Zones without IP addresses don't
* match when initially hunting for a predefined or cached zone to update.
*
* When an update is attempted and no predefined or cached zone is found
* that matches any enclosing domain of the domain being updated, the DHCP
* server goes through the same process that is done when the update to a
* predefined or cached zone fails - starting with the most specific domain
* name (GAZANGA.TOPANGA.FOO.COM) and moving to the least specific (the root),
* it tries to look up an SOA record. When it finds one, it creates a cached
* zone and attempts an update, and gives up if the update fails.
*
* TSIG keys are defined like this:
*
* key "FOO.COM Key" {
* algorithm HMAC-MD5.SIG-ALG.REG.INT;
* secret <Base64>;
* }
*
* <Base64> is a number expressed in base64 that represents the key.
* It's also permissible to use a quoted string here - this will be
* translated as the ASCII bytes making up the string, and will not
* include any NUL termination. The key name can be any text string,
* and the key type must be one of the key types defined in the draft
* or by the IANA. Currently only the HMAC-MD5... key type is
* supported.
*/
dns_zone_hash_t *dns_zone_hash;
#if defined (NSUPDATE)
isc_result_t find_tsig_key (ns_tsig_key **key, const char *zname,
struct dns_zone *zone)
{
isc_result_t status;
ns_tsig_key *tkey;
if (!zone)
return ISC_R_NOTFOUND;
if (!zone -> key) {
return ISC_R_KEY_UNKNOWN;
}
if ((!zone -> key -> name ||
strlen (zone -> key -> name) > NS_MAXDNAME) ||
(!zone -> key -> algorithm ||
strlen (zone -> key -> algorithm) > NS_MAXDNAME) ||
(!zone -> key) ||
(!zone -> key -> key) ||
(zone -> key -> key -> len == 0)) {
return ISC_R_INVALIDKEY;
}
tkey = dmalloc (sizeof *tkey, MDL);
if (!tkey) {
nomem:
return ISC_R_NOMEMORY;
}
memset (tkey, 0, sizeof *tkey);
tkey -> data = dmalloc (zone -> key -> key -> len, MDL);
if (!tkey -> data) {
dfree (tkey, MDL);
goto nomem;
}
strcpy (tkey -> name, zone -> key -> name);
strcpy (tkey -> alg, zone -> key -> algorithm);
memcpy (tkey -> data,
zone -> key -> key -> value, zone -> key -> key -> len);
tkey -> len = zone -> key -> key -> len;
*key = tkey;
return ISC_R_SUCCESS;
}
void tkey_free (ns_tsig_key **key)
{
if ((*key) -> data)
dfree ((*key) -> data, MDL);
dfree ((*key), MDL);
*key = (ns_tsig_key *)0;
}
#endif
isc_result_t enter_dns_zone (struct dns_zone *zone)
{
struct dns_zone *tz = (struct dns_zone *)0;
if (dns_zone_hash) {
dns_zone_hash_lookup (&tz,
dns_zone_hash, zone -> name, 0, MDL);
if (tz == zone) {
dns_zone_dereference (&tz, MDL);
return ISC_R_SUCCESS;
}
if (tz) {
dns_zone_hash_delete (dns_zone_hash,
zone -> name, 0, MDL);
dns_zone_dereference (&tz, MDL);
}
} else {
if (!dns_zone_new_hash (&dns_zone_hash, 1, MDL))
return ISC_R_NOMEMORY;
}
dns_zone_hash_add (dns_zone_hash, zone -> name, 0, zone, MDL);
return ISC_R_SUCCESS;
}
isc_result_t dns_zone_lookup (struct dns_zone **zone, const char *name)
{
struct dns_zone *tz = (struct dns_zone *)0;
int len;
char *tname = (char *)0;
isc_result_t status;
if (!dns_zone_hash)
return ISC_R_NOTFOUND;
len = strlen (name);
if (name [len - 1] != '.') {
tname = dmalloc ((unsigned)len + 2, MDL);
if (!tname)
return ISC_R_NOMEMORY;;
strcpy (tname, name);
tname [len] = '.';
tname [len + 1] = 0;
name = tname;
}
if (!dns_zone_hash_lookup (zone, dns_zone_hash, name, 0, MDL))
status = ISC_R_NOTFOUND;
else
status = ISC_R_SUCCESS;
if (tname)
dfree (tname, MDL);
return status;
}
int dns_zone_dereference (ptr, file, line)
struct dns_zone **ptr;
const char *file;
int line;
{
int i;
struct dns_zone *dns_zone;
if (!ptr || !*ptr) {
log_error ("%s(%d): null pointer", file, line);
#if defined (POINTER_DEBUG)
abort ();
#else
return 0;
#endif
}
dns_zone = *ptr;
*ptr = (struct dns_zone *)0;
--dns_zone -> refcnt;
rc_register (file, line, ptr, dns_zone, dns_zone -> refcnt, 1, RC_MISC);
if (dns_zone -> refcnt > 0)
return 1;
if (dns_zone -> refcnt < 0) {
log_error ("%s(%d): negative refcnt!", file, line);
#if defined (DEBUG_RC_HISTORY)
dump_rc_history (dns_zone);
#endif
#if defined (POINTER_DEBUG)
abort ();
#else
return 0;
#endif
}
if (dns_zone -> name)
dfree (dns_zone -> name, file, line);
if (dns_zone -> key)
omapi_auth_key_dereference (&dns_zone -> key, file, line);
if (dns_zone -> primary)
option_cache_dereference (&dns_zone -> primary, file, line);
if (dns_zone -> secondary)
option_cache_dereference (&dns_zone -> secondary, file, line);
dfree (dns_zone, file, line);
return 1;
}
#if defined (NSUPDATE)
isc_result_t find_cached_zone (const char *dname, ns_class class,
char *zname, size_t zsize,
struct in_addr *addrs,
int naddrs, int *naddrout,
struct dns_zone **zcookie)
{
isc_result_t status = ISC_R_NOTFOUND;
const char *np;
struct dns_zone *zone = (struct dns_zone *)0;
struct data_string nsaddrs;
int ix;
/* The absence of the zcookie pointer indicates that we
succeeded previously, but the update itself failed, meaning
that we shouldn't use the cached zone. */
if (!zcookie)
return ISC_R_NOTFOUND;
/* We can't look up a null zone. */
if (!dname || !*dname)
return ISC_R_INVALIDARG;
/* For each subzone, try to find a cached zone. */
for (np = dname; np; np = strchr (np, '.')) {
np++;
status = dns_zone_lookup (&zone, np);
if (status == ISC_R_SUCCESS)
break;
}
if (status != ISC_R_SUCCESS)
return status;
/* Make sure the zone is valid. */
if (zone -> timeout && zone -> timeout < cur_time) {
dns_zone_dereference (&zone, MDL);
return ISC_R_CANCELED;
}
/* Make sure the zone name will fit. */
if (strlen (zone -> name) > zsize) {
dns_zone_dereference (&zone, MDL);
return ISC_R_NOSPACE;
}
strcpy (zname, zone -> name);
memset (&nsaddrs, 0, sizeof nsaddrs);
ix = 0;
if (zone -> primary) {
if (evaluate_option_cache (&nsaddrs, (struct packet *)0,
(struct lease *)0,
(struct client_state *)0,
(struct option_state *)0,
(struct option_state *)0,
&global_scope,
zone -> primary, MDL)) {
int ip = 0;
while (ix < naddrs) {
if (ip + 4 > nsaddrs.len)
break;
memcpy (&addrs [ix], &nsaddrs.data [ip], 4);
ip += 4;
ix++;
}
data_string_forget (&nsaddrs, MDL);
}
}
if (zone -> secondary) {
if (evaluate_option_cache (&nsaddrs, (struct packet *)0,
(struct lease *)0,
(struct client_state *)0,
(struct option_state *)0,
(struct option_state *)0,
&global_scope,
zone -> secondary, MDL)) {
int ip = 0;
while (ix < naddrs) {
if (ip + 4 > nsaddrs.len)
break;
memcpy (&addrs [ix], &nsaddrs.data [ip], 4);
ip += 4;
ix++;
}
data_string_forget (&nsaddrs, MDL);
}
}
/* It's not an error for zcookie to have a value here - actually,
it's quite likely, because res_nupdate cycles through all the
names in the update looking for their zones. */
if (!*zcookie)
dns_zone_reference (zcookie, zone, MDL);
dns_zone_dereference (&zone, MDL);
if (naddrout)
*naddrout = ix;
return ISC_R_SUCCESS;
}
void forget_zone (struct dns_zone **zone)
{
dns_zone_dereference (zone, MDL);
}
void repudiate_zone (struct dns_zone **zone)
{
/* XXX Currently we're not differentiating between a cached
XXX zone and a zone that's been repudiated, which means
XXX that if we reap cached zones, we blow away repudiated
XXX zones. This isn't a big problem since we're not yet
XXX caching zones... :'} */
(*zone) -> timeout = cur_time - 1;
dns_zone_dereference (zone, MDL);
}
void cache_found_zone (ns_class class,
char *zname, struct in_addr *addrs, int naddrs)
{
isc_result_t status = ISC_R_NOTFOUND;
struct dns_zone *zone = (struct dns_zone *)0;
struct data_string nsaddrs;
int ix = strlen (zname);
if (zname [ix - 1] == '.')
ix = 0;
/* See if there's already such a zone. */
if (dns_zone_lookup (&zone, zname) == ISC_R_SUCCESS) {
/* If it's not a dynamic zone, leave it alone. */
if (!zone -> timeout)
return;
/* Address may have changed, so just blow it away. */
if (zone -> primary)
option_cache_dereference (&zone -> primary, MDL);
if (zone -> secondary)
option_cache_dereference (&zone -> secondary, MDL);
} else if (!dns_zone_allocate (&zone, MDL))
return;
if (!zone -> name) {
zone -> name =
dmalloc (strlen (zname) + 1 + (ix != 0), MDL);
if (!zone -> name) {
dns_zone_dereference (&zone, MDL);
return;
}
strcpy (zone -> name, zname);
/* Add a trailing '.' if it was missing. */
if (ix) {
zone -> name [ix] = '.';
zone -> name [ix + 1] = 0;
}
}
/* XXX Need to get the lower-level code to push the actual zone
XXX TTL up to us. */
zone -> timeout = cur_time + 1800;
if (!option_cache_allocate (&zone -> primary, MDL)) {
dns_zone_dereference (&zone, MDL);
return;
}
if (!buffer_allocate (&zone -> primary -> data.buffer,
naddrs * sizeof (struct in_addr), MDL)) {
dns_zone_dereference (&zone, MDL);
return;
}
memcpy (zone -> primary -> data.buffer -> data,
addrs, naddrs * sizeof *addrs);
zone -> primary -> data.data =
&zone -> primary -> data.buffer -> data [0];
zone -> primary -> data.len = naddrs * sizeof *addrs;
enter_dns_zone (zone);
}
/* Have to use TXT records for now. */
#define T_DHCID T_TXT
int get_dhcid (struct data_string *id,
int type, const u_int8_t *data, unsigned len)
{
unsigned char buf[MD5_DIGEST_LENGTH];
MD5_CTX md5;
int i;
/* Types can only be 0..(2^16)-1. */
if (type < 0 || type > 65535)
return 0;
/* Hexadecimal MD5 digest plus two byte type and NUL. */
if (!buffer_allocate (&id -> buffer,
(MD5_DIGEST_LENGTH * 2) + 3, MDL))
return 0;
id -> data = id -> buffer -> data;
/*
* DHCP clients and servers should use the following forms of client
* identification, starting with the most preferable, and finishing
* with the least preferable. If the client does not send any of these
* forms of identification, the DHCP/DDNS interaction is not defined by
* this specification. The most preferable form of identification is
* the Globally Unique Identifier Option [TBD]. Next is the DHCP
* Client Identifier option. Last is the client's link-layer address,
* as conveyed in its DHCPREQUEST message. Implementors should note
* that the link-layer address cannot be used if there are no
* significant bytes in the chaddr field of the DHCP client's request,
* because this does not constitute a unique identifier.
* -- "Interaction between DHCP and DNS"
* <draft-ietf-dhc-dhcp-dns-12.txt>
* M. Stapp, Y. Rekhter
*/
/* Put the type in the first two bytes. */
id -> buffer -> data [0] = "0123456789abcdef" [type >> 4];
id -> buffer -> data [1] = "0123456789abcdef" [type % 15];
/* Mash together an MD5 hash of the identifier. */
MD5_Init (&md5);
MD5_Update (&md5, data, len);
MD5_Final (buf, &md5);
/* Convert into ASCII. */
for (i = 0; i < MD5_DIGEST_LENGTH; i++) {
id -> buffer -> data [i * 2 + 2] =
"0123456789abcdef" [(buf [i] >> 4) & 0xf];
id -> buffer -> data [i * 2 + 3] =
"0123456789abcdef" [buf [i] & 0xf];
}
id -> len = MD5_DIGEST_LENGTH * 2 + 2;
id -> buffer -> data [id -> len] = 0;
id -> terminated = 1;
return 1;
}
/* Now for the DDNS update code that is shared between client and
server... */
isc_result_t ddns_update_a (struct data_string *ddns_fwd_name,
struct iaddr ddns_addr,
struct data_string *ddns_dhcid,
unsigned long ttl, int rrsetp)
{
ns_updque updqueue;
ns_updrec *updrec;
isc_result_t result;
char ddns_address [16];
if (ddns_addr.len != 4)
return ISC_R_INVALIDARG;
#ifndef NO_SNPRINTF
snprintf (ddns_address, 16, "%d.%d.%d.%d",
ddns_addr.iabuf[0], ddns_addr.iabuf[1],
ddns_addr.iabuf[2], ddns_addr.iabuf[3]);
#else
sprintf (ddns_address, "%d.%d.%d.%d",
ddns_addr.iabuf[0], ddns_addr.iabuf[1],
ddns_addr.iabuf[2], ddns_addr.iabuf[3]);
#endif
/*
* When a DHCP client or server intends to update an A RR, it first
* prepares a DNS UPDATE query which includes as a prerequisite the
* assertion that the name does not exist. The update section of the
* query attempts to add the new name and its IP address mapping (an A
* RR), and the DHCID RR with its unique client-identity.
* -- "Interaction between DHCP and DNS"
*/
ISC_LIST_INIT (updqueue);
/*
* A RR does not exist.
*/
updrec = minires_mkupdrec (S_PREREQ,
(const char *)ddns_fwd_name -> data,
C_IN, T_A, 0);
if (!updrec) {
result = ISC_R_NOMEMORY;
goto error;
}
updrec -> r_data = (unsigned char *)0;
updrec -> r_size = 0;
updrec -> r_opcode = rrsetp ? NXRRSET : NXDOMAIN;
ISC_LIST_APPEND (updqueue, updrec, r_link);
/*
* Add A RR.
*/
updrec = minires_mkupdrec (S_UPDATE,
(const char *)ddns_fwd_name -> data,
C_IN, T_A, ttl);
if (!updrec) {
result = ISC_R_NOMEMORY;
goto error;
}
updrec -> r_data = (unsigned char *)ddns_address;
updrec -> r_size = strlen (ddns_address);
updrec -> r_opcode = ADD;
ISC_LIST_APPEND (updqueue, updrec, r_link);
/*
* Add DHCID RR.
*/
updrec = minires_mkupdrec (S_UPDATE,
(const char *)ddns_fwd_name -> data,
C_IN, T_DHCID, ttl);
if (!updrec) {
result = ISC_R_NOMEMORY;
goto error;
}
updrec -> r_data = ddns_dhcid -> data;
updrec -> r_size = ddns_dhcid -> len;
updrec -> r_opcode = ADD;
ISC_LIST_APPEND (updqueue, updrec, r_link);
/*
* Attempt to perform the update.
*/
result = minires_nupdate (&resolver_state, ISC_LIST_HEAD (updqueue));
#ifdef DEBUG_DNS_UPDATES
print_dns_status ((int)result, &updqueue);
#endif
/*
* If this update operation succeeds, the updater can conclude that it
* has added a new name whose only RRs are the A and DHCID RR records.
* The A RR update is now complete (and a client updater is finished,
* while a server might proceed to perform a PTR RR update).
* -- "Interaction between DHCP and DNS"
*/
if (result == ISC_R_SUCCESS) {
log_info ("Added new forward map from %.*s to %s",
(int)ddns_fwd_name -> len,
(const char *)ddns_fwd_name -> data, ddns_address);
goto error;
}
/*
* If the first update operation fails with YXDOMAIN, the updater can
* conclude that the intended name is in use. The updater then
* attempts to confirm that the DNS name is not being used by some
* other host. The updater prepares a second UPDATE query in which the
* prerequisite is that the desired name has attached to it a DHCID RR
* whose contents match the client identity. The update section of
* this query deletes the existing A records on the name, and adds the
* A record that matches the DHCP binding and the DHCID RR with the
* client identity.
* -- "Interaction between DHCP and DNS"
*/
if (result != (rrsetp ? ISC_R_YXRRSET : ISC_R_YXDOMAIN)) {
log_error ("Unable to add forward map from %.*s to %s: %s",
(int)ddns_fwd_name -> len,
(const char *)ddns_fwd_name -> data, ddns_address,
isc_result_totext (result));
goto error;
}
while (!ISC_LIST_EMPTY (updqueue)) {
updrec = ISC_LIST_HEAD (updqueue);
ISC_LIST_UNLINK (updqueue, updrec, r_link);
minires_freeupdrec (updrec);
}
/*
* DHCID RR exists, and matches client identity.
*/
updrec = minires_mkupdrec (S_PREREQ,
(const char *)ddns_fwd_name -> data,
C_IN, T_DHCID, 0);
if (!updrec) {
result = ISC_R_NOMEMORY;
goto error;
}
updrec -> r_data = ddns_dhcid -> data;
updrec -> r_size = ddns_dhcid -> len;
updrec -> r_opcode = YXRRSET;
ISC_LIST_APPEND (updqueue, updrec, r_link);
/*
* Delete A RRset.
*/
updrec = minires_mkupdrec (S_UPDATE,
(const char *)ddns_fwd_name -> data,
C_IN, T_A, 0);
if (!updrec) {
result = ISC_R_NOMEMORY;
goto error;
}
updrec -> r_data = (unsigned char *)0;
updrec -> r_size = 0;
updrec -> r_opcode = DELETE;
ISC_LIST_APPEND (updqueue, updrec, r_link);
/*
* Add A RR.
*/
updrec = minires_mkupdrec (S_UPDATE,
(const char *)ddns_fwd_name -> data,
C_IN, T_A, ttl);
if (!updrec) {
result = ISC_R_NOMEMORY;
goto error;
}
updrec -> r_data = (unsigned char *)ddns_address;
updrec -> r_size = strlen (ddns_address);
updrec -> r_opcode = ADD;
ISC_LIST_APPEND (updqueue, updrec, r_link);
/*
* Attempt to perform the update.
*/
result = minires_nupdate (&resolver_state, ISC_LIST_HEAD (updqueue));
if (result != ISC_R_SUCCESS) {
if (result == YXRRSET || result == YXDOMAIN ||
result == NXRRSET || result == NXDOMAIN)
log_error ("Forward map from %.*s to %s already in use",
(int)ddns_fwd_name -> len,
(const char *)ddns_fwd_name -> data,
ddns_address);
else
log_error ("Can't update forward map %.*s to %s: %s",
(int)ddns_fwd_name -> len,
(const char *)ddns_fwd_name -> data,
ddns_address, isc_result_totext (result));
} else {
log_info ("Added new forward map from %.*s to %s",
(int)ddns_fwd_name -> len,
(const char *)ddns_fwd_name -> data, ddns_address);
}
#if defined (DEBUG_DNS_UPDATES)
print_dns_status ((int)result, &updqueue);
#endif
/*
* If this query succeeds, the updater can conclude that the current
* client was the last client associated with the domain name, and that
* the name now contains the updated A RR. The A RR update is now
* complete (and a client updater is finished, while a server would
* then proceed to perform a PTR RR update).
* -- "Interaction between DHCP and DNS"
*/
/*
* If the second query fails with NXRRSET, the updater must conclude
* that the client's desired name is in use by another host. At this
* juncture, the updater can decide (based on some administrative
* configuration outside of the scope of this document) whether to let
* the existing owner of the name keep that name, and to (possibly)
* perform some name disambiguation operation on behalf of the current
* client, or to replace the RRs on the name with RRs that represent
* the current client. If the configured policy allows replacement of
* existing records, the updater submits a query that deletes the
* existing A RR and the existing DHCID RR, adding A and DHCID RRs that
* represent the IP address and client-identity of the new client.
* -- "Interaction between DHCP and DNS"
*/
error:
while (!ISC_LIST_EMPTY (updqueue)) {
updrec = ISC_LIST_HEAD (updqueue);
ISC_LIST_UNLINK (updqueue, updrec, r_link);
minires_freeupdrec (updrec);
}
return result;
}
isc_result_t ddns_remove_a (struct data_string *ddns_fwd_name,
struct iaddr ddns_addr,
struct data_string *ddns_dhcid)
{
ns_updque updqueue;
ns_updrec *updrec;
isc_result_t result = SERVFAIL;
char ddns_address [16];
if (ddns_addr.len != 4)
return ISC_R_INVALIDARG;
#ifndef NO_SNPRINTF
snprintf (ddns_address, 16, "%d.%d.%d.%d",
ddns_addr.iabuf[0], ddns_addr.iabuf[1],
ddns_addr.iabuf[2], ddns_addr.iabuf[3]);
#else
sprintf (ddns_address, "%d.%d.%d.%d",
ddns_addr.iabuf[0], ddns_addr.iabuf[1],
ddns_addr.iabuf[2], ddns_addr.iabuf[3]);
#endif
/*
* The entity chosen to handle the A record for this client (either the
* client or the server) SHOULD delete the A record that was added when
* the lease was made to the client.
*
* In order to perform this delete, the updater prepares an UPDATE
* query which contains two prerequisites. The first prerequisite
* asserts that the DHCID RR exists whose data is the client identity
* described in Section 4.3. The second prerequisite asserts that the
* data in the A RR contains the IP address of the lease that has
* expired or been released.
* -- "Interaction between DHCP and DNS"
*/
ISC_LIST_INIT (updqueue);
/*
* DHCID RR exists, and matches client identity.
*/
updrec = minires_mkupdrec (S_PREREQ,
(const char *)ddns_fwd_name -> data,
C_IN, T_DHCID,0);
if (!updrec) {
result = ISC_R_NOMEMORY;
goto error;
}
updrec -> r_data = ddns_dhcid -> data;
updrec -> r_size = ddns_dhcid -> len;
updrec -> r_opcode = YXRRSET;
ISC_LIST_APPEND (updqueue, updrec, r_link);
/*
* A RR matches the expiring lease.
*/
updrec = minires_mkupdrec (S_PREREQ,
(const char *)ddns_fwd_name -> data,
C_IN, T_A, 0);
if (!updrec) {
result = ISC_R_NOMEMORY;
goto error;
}
updrec -> r_data = (unsigned char *)ddns_address;
updrec -> r_size = strlen (ddns_address);
updrec -> r_opcode = YXRRSET;
ISC_LIST_APPEND (updqueue, updrec, r_link);
/*
* Delete appropriate A RR.
*/
updrec = minires_mkupdrec (S_UPDATE,
(const char *)ddns_fwd_name -> data,
C_IN, T_A, 0);
if (!updrec) {
result = ISC_R_NOMEMORY;
goto error;
}
updrec -> r_data = (unsigned char *)ddns_address;
updrec -> r_size = strlen (ddns_address);
updrec -> r_opcode = DELETE;
ISC_LIST_APPEND (updqueue, updrec, r_link);
/*
* Attempt to perform the update.
*/
result = minires_nupdate (&resolver_state, ISC_LIST_HEAD (updqueue));
print_dns_status ((int)result, &updqueue);
/*
* If the query fails, the updater MUST NOT delete the DNS name. It
* may be that the host whose lease on the server has expired has moved
* to another network and obtained a lease from a different server,
* which has caused the client's A RR to be replaced. It may also be
* that some other client has been configured with a name that matches
* the name of the DHCP client, and the policy was that the last client
* to specify the name would get the name. In this case, the DHCID RR
* will no longer match the updater's notion of the client-identity of
* the host pointed to by the DNS name.
* -- "Interaction between DHCP and DNS"
*/
if (result != ISC_R_SUCCESS) {
/* If the rrset isn't there, we didn't need to do the
delete, which is success. */
if (result == ISC_R_NXRRSET || result == ISC_R_NXDOMAIN)
result = ISC_R_SUCCESS;
goto error;
}
while (!ISC_LIST_EMPTY (updqueue)) {
updrec = ISC_LIST_HEAD (updqueue);
ISC_LIST_UNLINK (updqueue, updrec, r_link);
minires_freeupdrec (updrec);
}
/* If the deletion of the A succeeded, and there are no A records
left for this domain, then we can blow away the DHCID record
as well. We can't blow away the DHCID record above because
it's possible that more than one A has been added to this
domain name. */
ISC_LIST_INIT (updqueue);
/*
* A RR does not exist.
*/
updrec = minires_mkupdrec (S_PREREQ,
(const char *)ddns_fwd_name -> data,
C_IN, T_A, 0);
if (!updrec) {
result = ISC_R_NOMEMORY;
goto error;
}
updrec -> r_data = (unsigned char *)0;
updrec -> r_size = 0;
updrec -> r_opcode = NXRRSET;
ISC_LIST_APPEND (updqueue, updrec, r_link);
/*
* Delete appropriate DHCID RR.
*/
updrec = minires_mkupdrec (S_UPDATE,
(const char *)ddns_fwd_name -> data,
C_IN, T_DHCID, 0);
if (!updrec) {
result = ISC_R_NOMEMORY;
goto error;
}
updrec -> r_data = ddns_dhcid -> data;
updrec -> r_size = ddns_dhcid -> len;
updrec -> r_opcode = DELETE;
ISC_LIST_APPEND (updqueue, updrec, r_link);
/*
* Attempt to perform the update.
*/
result = minires_nupdate (&resolver_state, ISC_LIST_HEAD (updqueue));
print_dns_status ((int)result, &updqueue);
/* Fall through. */
error:
while (!ISC_LIST_EMPTY (updqueue)) {
updrec = ISC_LIST_HEAD (updqueue);
ISC_LIST_UNLINK (updqueue, updrec, r_link);
minires_freeupdrec (updrec);
}
return result;
}
#endif /* NSUPDATE */
HASH_FUNCTIONS (dns_zone, const char *, struct dns_zone, dns_zone_hash_t,
dns_zone_reference, dns_zone_dereference)
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