Provided by: gdnsd_3.8.0-1_amd64 
NAME
gdnsd.zonefile - gdnsd zonefile syntax
SYNOPSIS
example.com:
$TTL 86400
@ SOA ns1 dns-admin (
1 ; serial
7200 ; refresh
30M ; retry
3D ; expire
900 ; ncache
)
@ NS ns1.example.com.
@ NS ns2
@ NS ns.example.net.
ns1 A 192.0.2.1 ; a comment
ns2.example.com. A 192.0.2.2
@ 7200 MX 10 mail-a
@ 7200 MX 100 mail-b
$ttl 86400
; a comment
mail-a A 192.0.2.3
mail-b A 192.0.2.4
subz NS ns1.subz
subz NS ns2.subz
ns1.subz A 192.0.2.5
ns2.subz A 192.0.2.6
www 600/10 DYNA some_plugin!resource_name
alias CNAME www
_http._tcp 1800 SRV 5 500 80 www
foo TXT "blah blah" "blah"
_spf TXT "v=spf1 ..."
DESCRIPTION
This is the primary zonefile syntax for gdnsd(8). The syntax is designed to be as close
as possible to the standard zonefile syntax from RFC 1035 (which is the "standard" format
one typically sees with traditional BIND servers). This document will just cover a few
important highlights and/or deviations from the norm.
DIRECTIVES
The standard $TTL, $ORIGIN, and $INCLUDE directives are supported with their normal syntax
and semantics:
$TTL changes the default TTL of any records coming after it, and can occur multiple times.
Note that in the absence of a zonefile-level $TTL setting, the default TTL comes from the
global config option "zones_default_ttl", which in turn defaults to 86400 (1 day).
$ORIGIN changes what is appended to unqualified hostnames (those lacking a final ".") seen
in the zone file from that point forward, as well as any "@" entries (which is an alias
for the current origin). $ORIGIN itself may also be an unqualified name, in which case
the previous origin is appended to it. Any fully-qualified $ORIGIN must be within the
zone described by this zonefile. The default origin is the zone name itself.
$INCLUDE includes another file as if its contents existed at the point of the $INCLUDE
directive. Include directives may specify an optional origin, which has the same effect
as $ORIGIN at the top of the included file. Changes to the origin (and default ttl)
within included files have no effect on the outer file.
BIND's $GENERATE extension is not supported at this time, but there's no fundamental
reason it couldn't be added at a later date.
SPECIAL NAMES AND ORIGINS
The standard "@", as a whole name, is supported as an alias for the current origin. In
addition to this, gdnsd implements two special extensions @Z and @F. These denote the
current zone name, and the original origin (before any internal $ORIGIN declarations) of
the file currently being parsed. Unlike "@", they can also be used as the final label of
an unqualified name. @Z and @F will always be equivalent to each other in the main
zonefile for a zone, but may differ when parsing included files from "$INCLUDE". As an
example:
* zones/example.org has the line "$INCLUDE includes/foo foo"
* zones/includes/foo has these lines:
$ORIGIN bar
asdf A 192.0.2.1
$ORIGIN baz.@F
asdf A 192.0.2.2
$ORIGIN quux.@Z
asdf A 192.0.2.3
* This results in creating all of these:
asdf.bar.foo.example.org A 192.0.2.1
asdf.baz.foo.example.org A 192.0.2.2
asdf.quux.example.org A 192.0.2.3
Note that the origin changes accomplished with @F and @Z backtrack towards the root of the
name hierarchy, and thus wouldn't normally be possible without explicitly using the zone
name itself. The main benefit of these directives is they allow this kind of origin-
switching behavior while keeping all zone data relative to the zone name rather than
absolute. When combined with the fact that the zones scanner will load symlinks, this
means the above zones/example.org could also be symlinked as zones/example.com, loading
all the same files and providing an identical tree of data under the other zone name
without conflict.
SUPPORTED RESOURCE RECORD TYPES
All RRs must be of class "IN", which is the implicit default.
gdnsd(8) supports the following standard RR types with their standard RDATA formats:
traditional: SOA, A, AAAA, NS, PTR, CNAME, MX, SRV, TXT, NAPTR non-traditional: CAA
explicitly unsupported: HINFO
It also supports the generic format for unknown RR types documented in RFC 3597, which has
syntax like:
foo TYPE31337 \# 10 0123456789 ABCDEF0123
... which indicates an RR of numeric type 31337 containing 10 bytes of RDATA, specified as
the final part of the RR as a pair of 5-byte hex strings. See RFC 3597 itself for full
details.
gdnsd does not allow using the RFC3597 format to specify any of the supported traditional
standard RR types, but it can be used to encode data for the non-traditional types. It's
also not allowed to use RFC3597 to specify HINFO RRs, as these are now reserved in gdnsd
for use in handling "ANY" queries, using the RFC 8482 HINFO option.
"SOA" records' negative-caching TTL is set to the minimum of the traditional "minimum"
(last) field (which always means "negative cache TTL" as of RFC 2308), and the actual TTL
of the SOA record itself. This TTL is used as the actual TTL of the SOA record any time
it is emitted, whether for negative or positive answers.
Additionally, gdnsd supports two special-case, non-standard virtual resource record types
DYNA and DYNC:
DYNA
"DYNA" is for dynamically-determined address records (both A and AAAA) via plugin code.
The right-hand-side of a "DYNA" RR is a plugin name and a resource name separated by an
exclamation mark. The named plugin will be fed the resource name and the DNS client's IP
address and/or edns-client-subnet information, and it is up to the plugin code which
addresses of which types to return in the response.
The dynamic plugin lookup for "DYNA" will be used anywhere that regular "A" and/or "AAAA"
records would be used. "DYNA" cannot co-exist with actual static A or AAAA records at the
same name, but can co-exist with any other RR-type.
"DYNA" and "DYNAAAA" RRs cannot be used to supply the addresses of nameservers. In other
words, any name that exists in zone scope on the right-hand-side of an "NS" record cannot
have "DYNA" or "DYNAAAA" (and relatedly, must have at least one of "A" or "AAAA").
Example:
; asks plugin 'geoip' to provide address data from
; its resource named 'pubwww' for address queries.
foo DYNA geoip!pubwww
foo MX 10 mail
DYNC
"DYNC" has the same syntax as "DYNA" above, but different data rules. Plugins results
returned via "DYNC" can be either addresses or a "CNAME" record. "DYNC" cannot co-exist
with any other resource record at the same name, much like normal "CNAME" RRs. This also
implies that "DYNC" cannot be used at the zone root, as the zone root requires "NS" and
"SOA" RRs.
"DYNC"'s dynamic CNAME targets cannot be used to point at names in the same zonefile as
the "DYNC" record; they must be used to point at other zones.
Example:
; asks plugin 'geoip' to provide address data or a CNAME
; (at the plugin's discretion) for its resource named
; 'www'. No other RRs of any type for name 'foo' are
; legal alongside this record.
foo DYNC geoip!www
DYNA/DYNC TTLs
"DYNA" and "DYNC" TTL fields have a syntax extension and slightly different meanings than
the TTL field of a traditional, fixed RR. The format for DYNA/DYNC TTLs is "MAX[/MIN]",
with "MIN" defaulting to half of "MAX" if not specified explicitly.
Based on the configuration and state of the underlying monitored services, (see
"service_types" in gdnsd.config(8)), gdnsd knows the minimum time to the next possible
state-change which could affect a given "DYNA" or "DYNC" result. For example, given the
configuration and state, it may be known that in order for a currently "DOWN" address to
transition to the "UP" state (and thus change the answer to a given query) would require 7
more successful monitoring checks in a row at 8-second intervals, and therefore cannot
happen in less than 56 seconds. In this case 56 seconds would be the internally-
calculated TTL.
In cases where multiple monitored resources factor into a plugin's decision and/or
response (e.g. multifo), the calculated TTL will generally be the minimum of all involved
internal monitoring TTLs. This calculated TTL is then clamped to the "MAX" and "MIN"
limits from the zonefile.
Examples:
; Explicit range of 30 - 300:
www 300/30 DYNC weighted!foo
; Implicit range of 150 - 300:
www 300 DYNA metafo!myservice
; Avoid all TTL-mangling and use a fixed value of 10 minutes:
www 600/600 DYNA geoip!foo-dist
TXT data auto-splitting
gdnsd's "TXT" RRs support the auto-splitting of long string constants. Rather than
manually breaking the data into 255-byte chunks as required by the protocol, you can
specify a single long chunk and have the server break it at 255 byte boundaries
automatically. (this behavior can be disabled via gdnsd.config(5) as well, which will
turn oversized chunks into zonefile parsing errors).
TXT records are limited to a maximum of 16000 bytes when encoded in rdata form for wire
transmission.
SEE ALSO
gdnsd(8), gdnsd.config(5)
The gdnsd manual.
COPYRIGHT AND LICENSE
Copyright (c) 2012 Brandon L Black <blblack@gmail.com>
This file is part of gdnsd.
gdnsd is free software: you can redistribute it and/or modify it under the terms of the
GNU General Public License as published by the Free Software Foundation, either version 3
of the License, or (at your option) any later version.
gdnsd is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with gdnsd. If
not, see <http://www.gnu.org/licenses/>.