Provided by: gdnsd_1.11.1-1_amd64 
NAME
gdnsd.config - gdnsd configuration file
SYNOPSIS
options => {
log_stats => 86400
tcp_timeout => 15 ; zonefile-style comment
include_optional_ns => true
listen => [ 127.0.0.1, 192.0.2.1 ]
}
# shell-style comment
service_types => {
foosvc => { vhost => www.example.com, url_path => "/checkme" }
barsvc => $include{bar-svc.cfg}
$include{other-services.cfg}
}
plugins => {
null => {}
}
DESCRIPTION
This man page describes the syntax of the primary gdnsd configuration file.
The lower-level syntax and structure of the configuration language is described in detail at the end of
this document, but it should be fairly intuitive from the example above. It is effectively a generic
data structure language allowing arbitrarily-nested ordered hashes, ordered arrays, and scalar values.
Double-quotes are used to quote scalars containing whitespace or various ambiguous metacharacters.
The top-level implicit hash of a gdnsd configuration file allows only 3 legal keys: options,
service_types, and plugins.
Any of them which are present must have a Hash as their value.
All of them are optional, as is the configuration file itself. if you're happy with an all-default
configuration, you can simply not have a config file at all.
OPTIONS HASH
These options control the overall behavior of gdnsd(8).
username
String, defaults to "gdnsd". This is the username the daemon drops privileges to the uid/gid of on
startup if started as root.
zones_default_ttl
Integer seconds, default 86400. This is the global default time-to-live for any record in any
zonefile. It can be overridden with a more specific default within zone files themselves via the
$TTL directive (see gdnsd.zonefile(5)).
dns_port
Integer port, 1-65535, default 53. This is the global default port number for DNS listener addresses
which do not specify port numbers themselves.
http_port
Integer port, 1-65535, default 3506. This is the default HTTP port number for stats listener
addresses which do not specify port numbers themselves.
listen
The listen option specifies the socket addresses the server listens on for DNS requests.
A listen-address specification is an IP (v4 or v6) address specified as a numeric string with
standard formatting (anything numeric that "getaddrinfo()" supports on your platform), optionally
followed by a colon and a port number. If no port number is specified, it defaults to the value from
"dns_port", which defaults to 53.
Due to various parsing ambiguities, if you wish to specify a non-default port number for an IPv6
listen address, you will have to enclose the address part in square brackets, and then enclose the
entire string in double-quotes.
The structure of the listen option as a whole can take one of three basic forms. In its simplest
form, it is just a single listen-address specification as a string, such as:
options => { listen = 192.0.2.1 }
It can also take the form of an array of such addresses, as in:
options => {
listen = [
192.0.2.1,
192.0.2.2,
2001:DB8::1,
"[2001:DB8::1234]:5353",
]
}
Finally, it can also be a hash where the keys are listen addresses, and the values are per-address
options, as in:
options => {
listen => {
192.0.2.1 => {
tcp_timeout = 7
},
192.0.2.2:5353 => {
udp_threads = 5
},
}
}
The per-address options (which are identical to, and locally override, the global option of the same
name) are "tcp_threads", "tcp_timeout", "tcp_clients_per_thread", "udp_threads", "udp_recv_width",
"udp_rcvbuf", and "udp_sndbuf".
There are also two special singalur string values: "any" and "scan".
If set to "any", the daemon will listen on the "dns_port" port (default 53) on 0.0.0.0 and "::" (if
IPv6 support is detected).
options => { listen => any }
If set to "scan", scan all available IP (v4 and v6) network interfaces via "getifaddrs()" and set up
a separate listener on the "dns_port" port (again, default 53) for each address found.
options => { listen => scan }
If the listen option isn't specified at all, for historical compatibility reasons the current default
is "scan". However, this default is expected to change to "any" in a future version, so you should
specify "scan" explicitly if you require this behavior.
http_listen
Basically like listen above, but used for the HTTP listener (serving stats information), and
defaulting to port 3506. The hash form isn't supported as there are no per-address options. Also,
the default addresses are the IPv4 and IPv6 (if supported) any-addresses (0.0.0.0 and "::"), rather
than the iterated per-interface addresses that the DNS listener uses.
It makes common sense to restrict access to this service via firewall rules, as the data served leaks
information about the rate and nature of your DNS traffic. This is mostly intended for your own
internal monitoring purposes.
tcp_threads
Integer, default 1, min 0, max 1024. This is the number of separate TCP listening sockets and
corresponding listener threads that will be created for each DNS listener address. On a multi-core
host, increasing this parameter (up to at most a small multiple of the CPU core count) may increase
overall performance. Note that on hosts without SO_REUSEPORT support (notably Linux < 3.9, Solaris),
any setting greater than 1 will be forced to 1 with a warning, as support multiple sockets/threads
per-address are not supported without SO_REUSEPORT.
udp_threads
Exactly like "tcp_threads", but for UDP sockets per DNS listening address.
tcp_clients_per_thread
Integer, default 128, min 1, max 65535. This is maximum number of tcp DNS connections gdnsd will
allow to occur in parallel per listening tcp socket. Once this limit is reached by a given socket,
no new connections will be allowed to that socket until one of the existing ones closes or times out.
Note that sockets map 1:1 to threads, and thus the total client limit for connecting to a given
address would be "tcp_clients_per_thread * tcp_threads" for a given address.
tcp_timeout
Integer seconds, default 5, min 3, max 60. TCP DNS connections will be forcibly shut down if they go
idle without receiving and responding to a valid query for this many seconds. gdnsd(8) allows
multiple requests per connection, and this idle timeout applies to the time between requests as well.
udp_recv_width
Integer, default 8, min 1, max 64. On supported Linux kernels this setting tunes the use of more
efficient interfaces to receive and send multiple packets with a single syscall. Higher values
reduce syscall overhead and generally give the server higher throughput and better efficiency under
high loads.
I believe that this is basically always a win under load when supported, but values much larger than
necessary do have a chance to increase average response latency very slightly. The optimal setting
is highly dependent on local hardware, software configuration, and network load conditions.
Setting this to a value of 1 will completely disable this code, as if we were running on a platform
that didn't support it. On platforms that don't support it, this option has no effect and is
ignored. On Linux if we don't detect a 3.0 or higher kernel at runtime, we fall back to the same
code as other platforms that don't support it.
udp_rcvbuf
Integer, min 4096, max 1048576. If set, this value will be used to set the "SO_RCVBUF" socket option
on the UDP listening socket(s). Most users do not need to tune this value. If left unset, the code
only takes a somewhat heuristic approach, trying to raise the value only if the OS-supplied default
seems too low, and multiplying it a bit in the case of "udp_recv_width" > 1.
udp_sndbuf
Integer, min 4096, max 1048576. If set, this value will be used to set the "SO_SNDBUF" socket option
on the UDP listening socket(s). Tuning advice mirrors the above.
max_http_clients
Integer, default 128, min 1, max 65535. Maximum number of HTTP connections to allow in parallel at
any given time. Once this number is reached, no more new connections will be answered until an
existing connection closes or times out.
http_timeout
Integer seconds, default 5, min 3, max 60. HTTP connections will be forcibly shut down if they go
idle for more than this many seconds.
zones_strict_data
Boolean, default "false"
If false (the default), reporting of many less-serious errors in zone data are emitted as mere logged
warnings, and the zone data is still loaded and served.
If this is set to true, such warnings will be upgraded and treated the same as the more-serious class
of zone data errors which prevent successful loading of zone data. The consequences of this are
variable: on initial startup or checkconf, this results in a fatal error (failure to start, or non-
zero exit code, respectively). During a runtime zone data reload, any existing good copy of the zone
would continue to be served until the error is corrected in the source.
zones_strict_startup
Boolean, default "true"
If true (the default), on daemon startup (via "start" or "restart") if any zone fails to load
correctly, the daemon will abort. If false, the daemon will simply ignore the failed zone and
continue operations.
Runtime reloads via SIGHUP and/or periodic/inotify scanning always treat bad zone data non-fatally
(leaving any existing good copy intact in memory for lookups).
This also affects the "checkconf" action. It will only fail in terms of exit value on bad zonefiles
if this is true (although it will note any failures to stderr regardless).
zones_rfc1035_auto
Boolean, default "true".
If auto is enabled (the default), the daemon will detect changes to zone data automatically at
runtime and apply them as they appear. In the general case this is done via periodically scanning
"lstat()" data on the contents of the zones directory and looking for metadata changes since last
check.
On recent Linux systems, the daemon may also use "inotify()" to detect filesystem modifications in
realtime and not need to run the periodic full directory scan, making the average delay much smaller
(subject to compile- and run- time compatibility). You will need a runtime Linux kernel version of
2.6.36 or higher to enable this feature.
Regardless of whether this setting is true or false, you can always manually trigger a rescan of the
zones directory for new data by sending the daemon a "SIGHUP" (or executing the "reload" command /
initscript action, which sends SIGHUP for you).
zones_rfc1035_auto_interval
Integer seconds, default 31, min 10, max 600. Only applies when "zones_rfc1035_auto" is "true".
Sets the time interval for periodically checking the zonefile directory for changes. On systems
which support "inotify()", however, the automatic mode will almost always use that mechanism instead
for even faster detection with less overhead. In the "inotify()" case, the interval is used only
occasionally when recovering from temporary "inotify()" failures.
zones_rfc1035_min_quiesce
Floating-point seconds, default 0.0, min 0.0, max 5.0
This short-duration quiescence timeout applies to certain internal cases when validating zonefile
update activity. (Specifically: delays after "inotify()" events for atomic move/delete and delayed
initial zonefile loading on daemon startup).
At daemon start, a heuristic test of the mtime resolution on the zones filesystem will determine
whether we can use a faster 0.01s or the default 1.02s as a basic sane minimum, and this config
setting will be adjusted upwards to the detected minimum as necessary.
Most users should not need to mess with this setting! The only reason to do so would be if you
suspected operating system or filesystem bugs related to high-res mtimes (or bugs so severe that even
~1-second mtime resolution isn't reliable, in which case you might want to try values in the 3-5s
range, or just find a new FS and/or OS...).
zones_rfc1035_quiesce
Floating-point seconds, default 5.0, min 0.0, max 60.0
This timer is related to the above, but is used in cases where we're not only worried about
filesystem-level timestamp accuracy, but also waiting for additional intentional actions by scripts,
programs, or users which might be actively modifying a zonefile. It applies to all changes detected
via SIGHUP or periodic automatic scanning, and to "inotify()" events which do not indicate atomic
operations (e.g. create/write/close, rather than move/delete. In other words, someone/something is
actually overwriting the data in-place or using an editor on the file in-place).
It is recommended that whatever tools or scripts you use to manage zonefile updates use atomic
operations to replace them. First write the new data to a dotfile, e.g. .example.com.tmp1234, in the
same zones directory (gdnsd ignores all filenames with a leading dot), and then mv(1) / rename(2) the
file to its final destination filename example.com.
If the value specified is less than the final runtime value of "zones_rfc1035_min_quiesce" above, it
will be adjusted upwards to that minimum value for correct operation.
lock_mem
Boolean, default false. Causes the daemon to do "mlockall(MCL_CURRENT|MCL_FUTURE)", which
effectively locks all daemon memory into RAM, unable to be swapped. Possibly helpful in some
production cases to ensure swap-in doesn't affect DNS latency.
When started as root with lock_mem set to true, the daemon will remove any ulimits on locked memory
before dropping privileges. When started as a regular user it may not be able to do so, and those
limits could cause the server to abort execution at any time if they are set too low.
priority
Signed integer, range -20 to +20, lower values are higher priority. If explicitly set, gdnsd will
attempt "setpriority()" to this value on startup. If left unset and gdnsd is started as a normal
user, no "setpriority()" call will be made. If left unset and gdnsd is started as root, it will
default to calling "setpriority()" with the value "-11".
disable_text_autosplit
Boolean, default false. On the wire, "TXT" (and "SPF", which are identical in wire-format other than
the RR-type) records are encoded as discrete chunks of up to 255 characters per chunk. The relevant
RFCs state that multiple chunks should be treated by clients as if they are concatenated. That is to
say, it should make no difference to a client whether the "TXT" data is sent as two 16-byte chunks or
one 32-byte chunk.
Ordinarily, you may specify chunk(s) of a "TXT" record in gdnsd zonefiles as a string of any size up
to the legal length (just short of 64K in practice), and gdnsd will auto-split the data into 255-byte
chunks for transmission over the DNS protocol correctly. If you choose to manually break up your TXT
record into multiple strings in the zonefile, gdnsd also honors these boundaries and will not attempt
to merge them into larger chunks where possible.
If you set this option to true, the auto-splitting behavior is disabled, and any single character
string specified in a zonefile as part of a "TXT" or "SPF" record which is larger than 255 bytes will
be considered a syntax error.
include_optional_ns
Boolean, default false. Causes the daemon to include the optional NS records in the Authority
section of simple authoritative responses containing actual response data. Leaving this option in
its default state results in smaller response packets and faster response packet generation in many
common cases. This is similar in nature to (but not exactly like) BIND's "minimal-responses" option,
except that we default to the minimal mode.
Regardless of this setting, all *necessary* Authority-section records are always included, such as
when they are necessary for delegation responses, NXDOMAIN responses, and NOERROR responses
containing no RRsets in the answer section.
plugin_search_path
A single string or an array of strings, default empty. Normally the daemon searches for plugins in
the fixed path "$PREFIX/lib/gdnsd", using filenames of the form "plugin_${name}.so". If you define
this parameter, all paths in this list will be searched in the given order for plugins *before*
trying the default, fixed search path.
realtime_stats
Boolean, default false. Normally the daemon self-imposes a limit of not recalculating the daemon-
wide statistics more often than once per second. This improves efficiency in the case that the
polling traffic on our HTTP interface gets high.
For most uses the default should be fine. If you set this option to true, the stats will be
recalculated on the spot for every stats request. The test suite uses this so that it can double-
check statistics counters between every request it sends. I don't imagine anyone else will need to
use this option, and it could even be determinental to performance on SMP machines.
max_response
Integer, default 16384, min 4096, max 62464. This number is used to size the per-I/O-thread buffers
that we construct response packets in. For any sane, normal use of the DNS, the default value is far
more than enough. For embedded or other low memory hosts, you might even consider setting this
smaller than default to save a bunch of per-socket-context buffer space.
However, if you have strange DNS data that's very large (giant RRsets, giant blobs of data in TXT
records) which might generate response packets greater than the 16K default max here, you *must* set
this parameter large enough to accommodate them or random very bad things will happen. It should be
noted that the odds are high whatever you're trying to do is misguided in the first place. You can
size this by setting it to the max and running some test queries via "dig" (or a similar tool) to
find your limit.
This number does not need to take into account UDP, IP, or any lower-level headers. Typically when
probing your data for the largest response sizes you should do "ANY" queries and/or specific RR-type
queries against the first CNAME in any CNAME chains leading to large RR-sets. Keep in mind that the
"include_optional_ns" option will affect the sizing as well. Also keep in mind that wildcards and
delegations can match any child name, including ones of maximal overall length.
max_addtl_rrsets
Integer, default 64, min 16, max 256. This is the maximum number of RR sets that will ever be added
to the Additional section of a response packet. This sets a hard limit on the number of delegation
glue NS records a subzone can have (which is checked at startup), and a runtime soft limit on other
Additional section RR sets. When the limit is reached at runtime, the remaining potential additional
RR sets are simply not added to the packet. Most users won't need to raise this value, and users on
low-memory/embedded hosts might want to lower it to save more memory.
max_cname_depth
Integer, default 16, min 4, max 24. How deep CNAME -> CNAME chains are allowed to recurse within
local data in a single zonefile. If a chain longer than this is detected between normal static CNAME
entries in the authoritative data of a single zonefile, an error will be thrown when loading the
zonefile.
If the limit is exceeded at runtime (due to "DYNC" dynamic CNAME responses) the code will halt
further recursive lookups for this request and return an empty NXDOMAIN response, and log a loud
message to syslog on every single request for this broken domainname.
Note that this is the only thing preventing infinite CNAME loops caused by bad DYNC plugin
configurations. Also note that even in the "DYNC" case, all of this applies only within a single
zone. The gdnsd code never crosses the boundary between two distinct local zonefiles when processing
queries.
debug
Boolean, default false. If (and only if) gdnsd was built in debug mode (--enable-developer, which
slows things down with a ton of assertion checks among other things), setting this option to "true"
will cause additional debugging output to syslog/stderr.
edns_client_subnet
Boolean, default true. Enables support for the edns-client-subnet option. gdnsd only includes this
EDNS option in responses to queries which also contained the option. In the case of normal responses
from static zone data, the scope mask will be set to zero. Dynamic response plugins have access to
the query's EDNS client-subnet data, and have full control over the response scope mask.
If the option is set to false, gdnsd will ignore the option in queries, never set it in its
responses, and plugins will not have access to any data provided by any ignored edns-client-subnet
option in queries.
Of the included standard plugins only "reflect" and "geoip" make use of edns-client-subnet
information. The rest will leave the scope mask at zero as normal for client-location-agnostic
static data.
Relevant links documenting edns-client-subnet:
<http://www.afasterinternet.com/>
<http://tools.ietf.org/html/draft-vandergaast-edns-client-subnet-00>
monitor_force_v6_up
Boolean, default false. Forces all monitored resources with IPv6 addresses permanently to the UP
state, and does not actually send them monitoring requests. Useful if some of your DNS servers don't
have working or reliable IPv6 routing, which would otherwise fail IPv6 polls and force the related
addresses to be marked DOWN. A better alternative would be to only host DNS for v6-capable services
on v6-capable DNS hosts, or install a Tunnelbroker/Sixxs/Teredo/Miredo/etc tunnel to get v6
routability.
"chaos_response"
String, default "gdnsd". When gdnsd receives any query with the class "CH" ("Chaos"), as opposed to
the normal "IN" ("Internet"), it will return a single response record of class "CH" and type "TXT",
which contains the string defined here. This is something like BIND's version reporting, which
responds to "version.bind" queries in the "CH" class, and is what a client will see if they use such
a query against a gdnsd server.
SERVICE_TYPES
service_types is used in conjunction with certain gdnsd plugins. If you are not using such a plugin, you
can safely ignore this section and omit it from your configuration.
The service_types hash contains generic definitions for how to monitor the given types of service. Each
service type uses a protocol-specific plugin, and the default is the included plugin "http_status", which
checks HTTP status code responses.
The other included monitoring plugins are "tcp_connect" (documented below alongside "http_status", just
checks TCP), and "extmon", which executes external monitoring commands/scripts and has its own
documentation at gdnsd-plugin-extmon(8).
There are several generic parameters related to timing and anti-flap, as well as plugin-specific
parameters that vary per plugin.
A service type does not, however, specify a name or address for a specific instance of a service. Those
would occur on a per-address basis in a resolving plugin's configuration down in the "plugins" stanza,
and the plugin's configuration would then reference a named service type to be used when monitoring said
address.
A service monitored through these mechanisms can be in one of three states at runtime: "UP", "DANGER", or
"DOWN". The UP state means that all is perfectly well. The DANGER state means that some isolated
failures have been seen in the recent past (perhaps even just one), but that gdnsd has not yet seen a
consistent enough pattern of failure to declare the service dead. The DOWN state, obviously, means that
gdnsd does consider the service dead. These states are presented to the plugin that requested the
monitoring. It is up to the plugin to determine how this affects DNS responses.
Any services monitored for plugins are also have their state reported alongside the standard gdnsd
statistics report, served by the built-in HTTP server (default port is 3506).
There are five built-in service types that can't be overridden:
One built-in service type is implicitly named "default". It uses the default "http_status" plugin and is
defined to all of the default parameters shown below.
The other four are named "none", "up", "danger", and "down".
These do no actual monitoring, and simply force the state of resources using these service_types to a
fixed state. "none" is just an alias for "up".
The following are the generic parameters for all service_types:
up_thresh
Integer, default 20, min 1, max 255. Number of monitoring requests which must succeed with no
intervening failures to transition a given IP for this resource from the DOWN state to the UP state.
ok_thresh
Integer, default 10, min 1, max 255. Number of monitoring requests which must succeed with no
intervening failures to transition a given IP for this resource from the DANGER state to the UP
state.
down_thresh
Integer, default 10, min 1, max 255. Number of monitoring requests which must fail, regardless of
any intervening successes, to transition a given IP for this resource from the DANGER state to the
DOWN state.
interval
Integer seconds, default 10, min 1, max 255. Number of seconds between successive monitoring
requests to a given IP address for this resource.
timeout
Integer seconds, default 3, min 1, max 255. Maximum time the monitoring code will wait for a
successful response before giving up and considering the request to be a failure. Must be less than
90% of interval.
plugin
String, default "http_status". This indicates which protocol-specific plugin to use to execute the
monitoring requests. Any parameters other than the generic ones listed here are consumed by the
plugin.
The "tcp_connect" plugin has just one plugin-specific parameter:
port
Integer, required. This is the port number to contact on the remote host to check this service type.
It has no default and must be specified.
The following are the plugin-specific parameters for the default monitoring plugin "http_status":
port
Integer, default 80. This is the port number to contact on the remote host to check this service
type.
url_path
String, default "/". This is the URL that should be used when checking this service type.
vhost
Hostname, no default. If defined, the HTTP/1.0 monitoring request will include this as a "Host:"
header in the monitoring request. If not defined, no "Host:" header will be sent.
ok_codes
Array of 3-digit HTTP status codes, default "[ 200 ]". This defines the HTTP status codes in
responses that will be accepted as successful.
PLUGINS
The plugins hash is optional, and contains one key for every dynamic resolution plugin you wish to load
and use. The value must be a hash, and the contents of that hash are supplied to the plugin to use in
configuring itself. If the plugin requires no configuration, the empty hash "{}" will suffice. It is up
to the plugin to determine whether the supplied hash of configuration data is legal or not.
Monitoring-only plugins can also be given plugin-global level configuration here if the plugin author
deemed it necessary.
gdnsd ships with 3 very trivial dynamic resolution plugins named "null", "static", and "reflect".
"null" simply returns all-zeros addresses for DYNA records, and "invalid." as the RHS of DYNC records.
It does not pay attention to any plugin-specific configuration.
The "static" plugin can be configured with a map of resource names to IPv4 addresses or CNAME hostnames,
and it will do the obvious: map those resource names statically for use in either DYNA or DYNC zonefile
records.
"reflect" is primarily for real-world testing and debugging. It attempts to reflect back to the query
originator an address answer showing the server's view of where the client is located on the network.
Currently in the common case this will be the address of the intermediate cache server which communicated
directly with gdnsd. However, if the query contains the draft edns-client-subnet option, the response
can reflect that as well.
It accepts 4 fixed resource names at the zonefile level: "dns", "edns", "best", and "both". "dns" means
to ignore edns-client-subnet and always return the cache's address. "edns" means to ignore the cache's
address and always return edns-client-subnet information, (or 0.0.0.0 if not available). "best" will
return the edns-client-subnet information if available, or the cache's address if not. "both" returns
both addresses if edns-client-subnet is available, or just the cache otherwise. The default behavior is
"best".
gdnsd also includes five other plugins that are more production-useful, all of which have their own
separate manpage documentation (e.g. "man gdnsd-plugin-FOO"):
simplefo
Simple primary->secondary failover of monitored addresses
multifo
All-active failover of monitored round-robin address groups
weighted
Weighted-round-robin responses with a variety of behavioral flavors, for both monitored addresses and
CNAMEs
metafo
Static-ordered address(-group) meta-failover between 'datacenters', which are resources defined in
terms of other plugins
geoip
Combines metafo's functionality with MaxMind GeoIP databases to select different datacenter
address(-group) preference/failover orderings for different clients based on approximate geographic
location. Supports geographically-differentiated CNAME resolution as well.
A configuration example showing the trivial plugins, as well as demonstrating the service_types described
earlier:
service_types => {
corpwww_type => {
vhost => www.corp.example.com
url_path => /check_me
down_thresh => 5
interval => 5
}
}
plugins => {
null => {},
reflect => {},
static => {
foo = 192.0.2.2
bar = 192.0.2.123
somehost = somehost.example.net.
},
}
And then in your example.com zonefile, you could have (among your other RRs):
zeros 600 DYNA null
reflect 10 DYNA reflect
reflect-both 10 DYNA reflect!both
pointless 42 DYNA static!foo
acname 400 DYNC static!somehost
LOW-LEVEL SYNTAX
At the lowest level, the syntax of gdnsd config files roughly resembles an anonymous Perl data structure
(using reference syntax). There are three basic data types for values: ordered hashes (associative
arrays mapping keys to values), ordered arrays of values, and simple strings. Hashes and arrays can be
nested to arbitrary depth. Generally speaking, whitespace is optional. Single-line comments in both
shell ("#") and DNS zonefile styles (";") are allowed. They run to the end of the current line and are
considered to be whitespace by the parser.
A hash is surrounded by curly braces ("{" and "}"). Keys are separated from their values by either "=>"
or "=" (at your stylistic discretion). Hash keys follow the same rules as simple string values. Hash
values can be simple strings, arrays, or hashes. Key/value pairs can optionally have a trailing comma
for stylistic clarity and separation.
An array is surrounded by square braces ("[" and "]"). Values can be simple strings, arrays, or hashes.
Values can optionally have a trailing comma for style.
Strings (and thus keys) can be written in both quoted and unquoted forms. In the quoted form, the string
is surrounded by double-quotes ("""), and can contain any literal byte value (even binary/utf-8 stuff, or
NUL) other than """ or "\". Those two characters must be escaped by "\", i.e. "\"" and "\\".
In the unquoted form, there are no surrounding quotes, and the allowed set of unescaped characters is
further restricted. The following are not allowed: "][}{;#,"=\" (that is, square brackets, curly
brackets, semicolons, octothorpes, commas, double quotes, equal signs, and backslashes). Additionally,
the first character cannot be a "$" (dollar sign).
Both forms use the same escaping rules, which are the same RFC-standard escaping rules used in zone
files. The escapes always start with "\". "\" followed by any single byte other than a digit (0 - 9) is
interepreted as that byte. "\" followed by exactly 3 digits interprets those digits as the unsigned
decimal integer value of the desired byte (the 3 digit value cannot exceed 255).
To illustrate the escaping and quoting, the following sets of example strings show different encodings of
the same parsed value:
example
"example"
ex\097mpl\e
"ex\097mpl\e"
internal\"doublequote
"internal\"doublequote"
white\ space
"white space"
"braces{every[where]oh}my"
braces\{every\[where\]oh\}my
"\\==="
"\092==="
"\092\=\=\="
\\\=\=\=
\092\=\=\=
The top level of the config file is an implicit hash with no bracing by default, but can also be an array
bounded by square brackets. This is not legal for the primary gdnsd configuration file, but could be
useful in includefiles (see below).
As a general rule, anywhere the higher-level syntax allows an array of values, you can substitute a
single value. The code will treat it as if it were an array of length 1.
When we refer in other sections above to a value as being an "Integer" (or other specific scalar type),
we're referring to constraints on the content of the character string value. All scalar values are
character strings. "Boolean" values are characters strings which have the value "true" or "false", in
any mix of upper or lower case.
The following 3 example configuration files are identical in their parsed meanings, and should clarify
anything miscommunicated above:
Example 1 (simple and clean):
options = {
listen = [ 192.0.2.1, 192.0.2.2 ],
http_listen = 127.0.0.1,
}
Example 2 (fat arrows, no commas, some arbitrary quoting):
"options" => {
listen => [ 192.0.2.1 192.0.2.2 ]
http_listen => "127.0.0.1"
}
Example 3 (compressed and ugly):
options={listen=[192.0.2.1 192.0.2.2]http_listen=127.0.0.1}
INCLUDING OTHER FILES
vscf now has a mechanism for config includefiles. The syntax is
$include{filename}
where "filename" can use the same kinds of escaping and/or double-quoting as normal scalar string data.
Whitespace between the filename and the surrounding brackets is optional. Whitespace between $include
and the following "{" is not. If the filename is relative (does not begin with /), it is interpreted as
relative to the directory containing the parent file. Include files can nest other include files to
arbitrary depth.
Keep in mind that at the top level of any given vscf file (even include files), the file must
syntactically be either an implicit hash or an explicit, square-bracket-bounded, array.
The include statement can be used in two distinct contexts within the syntax structure of a config file:
Value Context
The include statement can replace any whole value (that is, the right hand side of a hash map entry
or a member of an array) with its own contents, which are either a hash or an array. Note that there
is no mechanism for flattening an include-file's array into the parent array (the whole included
array would be a single array item within the parent array). Examples:
main config:
options => { listen => $include{foo} }
foo:
[ 127.0.0.1, 127.0.0.2 ]
main config:
plugins => $include{ "bar" }
bar:
geoip => { ... }
extmon => { ... }
Hash-Merge Context
The include statement can also appear in a hash where a key would normally be expected. In this
case, the included file must be in hash (rather than array) form at the top level, and its contents
are merged into the parent hash. Example:
main config:
options => { ... },
plugins => {
extmon => { ... },
metafo => { ... },
$include{geoip_cfg},
simplefo => { ... }
}
geoip_cfg:
geoip => { ... },
weighted => { ... }
SEE ALSO
gdnsd(8), gdnsd.zonefile(5), gdnsd-plugin-simplefo(8), gdnsd-plugin-multifo(8), gdnsd-plugin-weighted(8),
gdnsd-plugin-metafo(8), gdnsd-plugin-geoip(8), gdnsd-plugin-extmon(8), gdnsd-plugin-api(3)
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/>.
gdnsd 1.11.1 2014-02-08 GDNSD.CONFIG(5)