Copyright (C) 1999, 2000 Internet Software Consortium.

See COPYRIGHT in the source root or http://isc.org/copyright.html for terms.

Zones

$Id: zone,v 1.8 2000/08/09 04:37:29 tale Exp $

Overview

Zones are the unit of delegation in the DNS and may go from holding

RR's only at the zone top to holding the complete hierachy (private

roots zones). Zones have an associated database which is the

container for the RR sets that make up the zone.

Zone have certain properties associated with them.

* name

* class

* master / slave / stub / hint / cache / forward

* serial number

* signed / unsigned

* update periods (refresh / retry) (slave / stub)

* last update time (slave / stub)

* access restrictions

* transfer restrictions (master / slave)

* update restictions (master / slave)

* expire period (slave / stub)

* children => bottom

* glue

* rrsets / data

* transfer "in" in progress

* transfers "out" in progress

* "current" check in progress

* our masters

* primary master name (required to auto generate our masters)

* master file name

* database name

* database type

* initially only master_file (BIND 4 & 8)

* expanded axfr + ixfr

* transaction logs

* notification lists

* NS's

* static additional sites (stealth servers)

* dynamically learned sites (soa queries)

Zones have two types of versions associated with them.

Type 1.

The image of the "current" zone when a AXFR out is in progress.

There may be several of these at once but they cease to need

to exist once the AXFR's on this version has completed. These

are maintained by the various database access methods.

Type 2.

These are virtual versions of the zone and are required to

support IXFR requests. While the entire contents of the old

version does not need to be kept, a change log needs to be

kept. An index into this log would be useful in speeding

up replies. These versions have an explict expiry date.

"How long are we going to keep them operationally?"

While there are expriry dates based on last update /

change time + expire. In practice holding the deltas

for a few refresh periods should be enough. If the network

and servers are up one is enough.

"How are we going to generate them from a master file?"

UPDATE should not be the only answer to this question.

We need a tool that takes the current zone & new zone.

Verifies the new zone, generates a delta and feeds this

at named. It could well be part of ndc but does not have

to be.

Zones need to have certain operations performed on them. The need to

be:

* loaded

* unloaded

* dumped

* updated (UPDATE / IXFR)

* copied out in full (AXFR) or as partial deltas (IXFR)

* read from

* validated

* generate a delta between two given versions.

* signed / resigned

* maintenance

validate current soa

remove old deltas / consolidation

purge stale rrsets (cache)

* notification

responding to

generating

While not strictly a nameserver function, bad delegation and bad

slave setups are continual and ongoing sources of problems in the

DNS. Periodic checks to ensure parent and child servers agree on

the list of nameservers and that slaves are tracking the changes

made in the master server's zone will allow problems in

configurations to be identified earlier providing for a more stable

DNS.

Compatability:

Zones are required to be configuration file compatable with

BIND 8.x.

Types:

typedef enum {

dns_zone_none = 0,

dns_zone_master,

dns_zone_slave,

dns_zone_stub,

dns_zone_hint,

dns_zone_cache,

dns_zone_forward

} dns_zonetypes_t;

typedef struct dns_ixfr dns_ixfr_t;

struct dns_ixfr {

unsigned int magic; /* IXFR */

isc_uint32_t serial;

time_t expire;

unsigned int offset;

ISC_LINK(dns_ixfr_t) link;

};

struct dns_zone {

unsigned int magic; /* ZONE */

dns_name_t name;

dns_rdataclass_t class;

dns_zonetypes_t type;

dns_bt_t top;

isc_uint32_t version;

isc_uint32_t serial;

isc_uint32_t refresh;

isc_uint32_t retry;

isc_uint32_t serial;

char *masterfile;

dns_acl_t *access;

dns_acl_t *transfer;

struct {

dns_acl_t *acl;

dns_scl_t *scl; /* tsig based acl */

} update;

char *database;

ISC_LIST(dns_ixfr_t) ixfr;

...

};

Operations:

Loading:

Functions:

void

dns_zone_init(dns_zone_t *zone, dns_rdataclass_t class, isc_mem_t *mxtc);

void

dns_zone_invalidate(dns_zone_t *zone);

void

dns_ixfr_init(dns_ixfr_t *ixfr, unsigned long serial, time_t expire);

void

dns_ixfr_invalidate(dns_ixfr_t *ixfr);

dns_zone_axfrout(dns_zone_t *zone);

Initiate outgoing zone transfer.

dns_zone_axfrin(dns_zone_t *zone, isc_sockaddr_t *addr);

Initiate transfer of the zone from the given server or the

masters masters listed in the zone structure.

dns_zone_maintenance(dns_zone_t *zone);

Perform any maintenance operations required on the zone

* initiate up to date checks

* expire zones

* initiate ixfr version expire consolidation

dns_zone_locateprimary(dns_zone_t *zone);

Working from the root zone locate the primary master for the zone.

Used if masters are not given in named.conf.

dns_zone_locateservers(dns_zone_t *zone);

Working from the root zone locate the servers for the zone.

Primary master moved to first in list if in NS set. Remove self

from list.

Used if masters are not given in named.conf.

dns_zone_notify(dns_zone_t *);

Queue notify messages.

dns_zone_checkparents(dns_zone_t *);

check that the parent nameservers NS lists for this zone agree with

the NS list this zone, check glue A records. Warn if not identical.

This operation is performed on master zones.

dns_zone_checkchildren(dns_zone_t *);

check that the child zones NS lists agree with the NS lists in this

zone, check glue records. Warn if not identical.

dns_zone_checkservers(dns_zone_t *);

check that all the listed servers for the zone agree on NS list and

serial number. NOTE only errors which continue over several refresh

periods to be reported.

dns_zone_dump(dns_zone_t *, FILE *fp);

Write the contents of the zone to the file associated with fp.

dns_zone_validate(dns_zone_t *);

Validate the zone contents using DNSSEC.

dns_zone_tordatalist(dns_zone_t *zone, dns_rdatalist_t *list)

dns_zone_addmaster(dns_zone_t *zone, isc_sockaddr_t *addr);

Add addr to the set of masters for the zone.

dns_zone_clearmasters(dns_zone_t *zone);

Clear the master set.

dns_zone_setreadacl(dns_zone_t *, dns_acl_t *)

dns_zone_setxfracl(dns_zone_t *, dns_acl_t *)

dns_zone_addnotify(dns_zone_t *, isc_sockaddr_t *addr, isc_boolean_t perm);

dns_zone_clearnotify(dns_zone_t *)

dns_zone_load(dns_zone_t *);

dns_zone_consolidate(dns_zone_t *);

Consolidate on disk copy of zone.