Index of /archives/net/bind/9.9.0rc1/bind-9.9.0rc1/contrib/dlz/example
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OVERVIEW:
DLZ (Dynamically Loadable Zones) is an extention to BIND 9 that
allows zone data to be retrieved directly from an external database.
There is no required format or schema. DLZ drivers exist for several
different database backends including PostgreSQL, MySQL, and LDAP and
can be written for any other.
Historically, DLZ drivers had to be statically linked with the named
binary and were turned on via a configure option at compile time (for
example, "configure --with-dlz-ldap"). Currently, the drivers provided
in the BIND 9 tarball in contrib/dlz/drivers are still linked this way.
However, as of BIND 9.8, it is also possible to link some DLZ modules
dynamically at runtime, via the DLZ "dlopen" driver, which acts as a
generic wrapper around a shared object that implements the DLZ API. The
"dlopen" driver is linked into named by default, so configure options are
no longer necessary.
When the DLZ module provides data to named, it does so in text format.
The response is converted to DNS wire format by named. This conversion,
and the lack of any internal caching, places significant limits on the
query performance of DLZ modules. Consequently, DLZ is not recommended
for use on high-volume servers. However, it can be used in a hidden
master configuration, with slaves retrieving zone updates via AXFR.
(Note, however, that DLZ has no built-in support for DNS notify; slaves
are not automatically informed of changes to the zones in the database.)
EXAMPLE DRIVER:
This directory contains an example of an externally-lodable DLZ module,
dlz_example.c, which demonstrates the features of the DLZ API. It sets up
a single zone, whose name is configured in named.conf. The zone can answer
queries and AXFR requests, and accept DDNS updates.
By default, at runtime, the zone implemented by this driver will contain
an SOA, NS, and a single A record at the apex. If configured in named.conf
to use the name "example.nil", then, the zone will look like this:
example.nil. 3600 IN SOA example.nil. hostmaster.example.nil. (
123 900 600 86400 3600
)
example.nil. 3600 IN NS example.nil.
example.nil. 1800 IN A 10.53.0.1
The driver is also capable of retrieving information about the querying
client, and altering its response on the basis of this information. To
demonstrate this feature, the example driver responds to queries for
"source-addr.<zonename>/TXT" with the source address of the query.
Note, however, that this record will *not* be included in AXFR or ANY
responses. (Normally, this feature would be used to alter responses in
some other fashion, e.g., by providing different address records for
a particular name depending on the network from which the query arrived.)
IMPLEMENTATION NOTES:
The minimal set of type definitions, prototypes, and macros needed
for implementing a DLZ driver is in dlz_minimal.h. Copy this header
file into your source tree when creating an external DLZ module.
The DLZ dlopen driver provides a set of callback functions:
- void log(int level, const char *fmt, ...);
Writes the specified string to the named log, at the specified
log level. Uses printf() format semantics.
- isc_result_t putrr(dns_sdlzlookup_t *lookup, const char *type,
dns_ttl_t ttl, const char *data);
Puts a DNS resource record into the query response, which
referenced by the opaque structure 'lookup' provided by named.
- isc_result_t putnamedrr(dns_sdlzallnotes_t *allnodes,
const char *name, const char *type,
dns_ttl_t ttl, const char *data);
Puts a DNS resource record into an AXFR response, which is
referenced by the opaque structure 'allnodes' provided by named.
- isc_result_t writable_zone(dns_view_t *view, const char *zone_name);
Allows the DLZ module to inform named that a given zone can recieve
DDNS updates.
The external DLZ module can define the following functions (some of these
are mandatory, others optional).
- int dlz_version(unsigned int *flags);
Required for alL external DLZ modules, to indicate the version number
of the DLZ dlopen driver that this module supports. It should return
the value DLZ_DLOPEN_VERSION, which is defined in dlz_minimal.h and
is currently 2. 'flags' is updated to indicate capabilities
of the module. In particular, if the module is thread-safe then it
sets 'flags' to include DNS_SDLZFLAG_THREADSAFE. (Other capability
flags may be added in the future.)
- isc_result_t dlz_create(const char *dlzname,
unsigned int argc, char *argv[],
void **dbdata, ...);
Required for all external DLZ modules; this call initializes the
module.
- void dlz_destroy(void *dbdata);
Optional. If supplied, this will be called when the driver is
unloaded.
- isc_result_t dlz_findzonedb(void *dbdata, const char *name);
Required for all external DLZ modules. This indicates whether
the DLZ module can answer for the given name. Returns ISC_R_SUCCESS
if so, and ISC_R_NOTFOUND if not. As an optimization, it can
also return ISC_R_NOMORE: this indicates that the DLZ module has
no data for the given name or for any name above it in the DNS.
This prevents named from searching for a zone cut.
- isc_result_t dlz_lookup(const char *zone, const char *name, void *dbdata,
dns_sdlzlookup_t *lookup,
dns_clientinfomethods_t *methods,
dns_clientinfo_t *clientinfo);
Required for all external DLZ modules. This carries out the database
lookup for a query.
- isc_result_t dlz_allowzonexfr(void *dbdata, const char *name,
const char *client);
Optional. Supply this if you want the module to support AXFR
for the specified zone and client. A return value of ISC_R_SUCCESS
means AXFR is allowed, any other value means it isn't.
- isc_result_t dlz_allnodes(const char *zone, void *dbdata,
dns_sdlzallnodes_t *allnodes);
Optional, but must be supplied dlz_allowzonexfr() is. This function
returns all nodes in the zone in order to perform a zone transfer.
- isc_result_t dlz_newversion(const char *zone, void *dbdata,
void **versionp);
Optional. Supply this if you want the module to support DDNS
updates. This function starts a transaction in the database.
- void dlz_closeversion(const char *zone, isc_boolean_t commit,
void *dbdata, void **versionp);
Optional, but must be supplied if dlz_newversion() is. This function
closes a transaction. 'commit' indicates whether to commit the changes
to the database, or ignore them.
- isc_result_t dlz_configure(dns_view_t *view, void *dbdata);
Optional, but must be supplied in order to support DDNS updates.
- isc_boolean_t dlz_ssumatch(const char *signer, const char *name,
const char *tcpaddr, const char *type,
const char *key, uint32_t keydatalen,
uint8_t *keydata, void *dbdata);
Optional, but must be supplied in order to support DDNS updates.
- isc_result_t dlz_addrdataset(const char *name, const char *rdatastr,
void *dbdata, void *version);
Optional, but must be supplied in order to support DDNS updates.
Adds the data in 'rdatastr' to a database node.
- isc_result_t dlz_subrdataset(const char *name, const char *rdatastr,
void *dbdata, void *version);
Optional, but must be supplied in order to support DDNS updates.
Removes the data in 'rdatastr' from a database node.
- isc_result_t dlz_delrdataset(const char *name, const char *rdatastr,
void *dbdata, void *version);
Optional, but must be supplied in order to support DDNS updates.
Deletes all data matching the type specified in 'rdatastr' from
the database.