Provided by: gdnsd_3.8.2-1build2_amd64 
NAME
gdnsd-plugin-geoip - gdnsd meta-plugin for GSLB + failover via MaxMind's GeoIP2 databases
SYNOPSIS
Minimal example gdnsd config file using this plugin:
plugins => { geoip => {
maps => {
my_prod_map => {
geoip2_db => GeoIP2-City.mmdb,
datacenters => [dc-03, dc-02, dc-01, dc-fail],
map => {
EU => {
DE => [dc-03, dc-01, dc-fail],
CH => [dc-01, dc-03, dc-fail]
},
NA => { MX => [dc-02, dc-fail] }
}
},
my_auto_map => {
geoip2_db => GeoIP2-Country.mmdb,
datacenters => [dc1, dc2],
auto_dc_coords => {
dc1 => [ 38.9, -77 ],
dc2 => [ 50.1, 8.7 ],
}
}
},
resources => {
prod_www => {
map => my_prod_map
service_types => up
dcmap => {
dc-01 => 192.0.2.1,
dc-02 => { lb01 => 192.0.2.2, lb02 => 192.0.2.3 },
dc-03 => [ 192.0.2.4, 192.0.2.5, 192.0.2.6 ],
dc-fail => last.resort.cname.example.net.
}
}
corp_www => {
map => my_auto_map
dcmap => {
dc1 => 192.0.2.100,
dc2 => 192.0.2.101
}
}
}
}}
Example zonefile RRs in zone example.com:
www 600 DYNA geoip!prod_www
www-dc01 600 DYNA geoip!prod_www/dc-01
www.corp 600 DYNA geoip!corp_www
DESCRIPTION
gdnsd-plugin-geoip uses MaxMind's GeoIP2 binary databases to map address and CNAME results based on
geography and monitored service availability. It fully supports both IPv6 and the emerging edns-client-
subnet standard. If a request contains the edns-client-subnet option with a source netmask greater than
zero, the edns-client-subnet information will be used instead of the source IP of the request (the IP of
the querying cache).
It supports the GeoIP2 format databases, which typically end in .mmdb. It does not supports the legacy
GeoIP1 format databases (which typically end in .dat).
It can also be used with no GeoIP database at all, in which case the only network-mapping input comes
from the "nets" config data or an external "nets" file, which explicitly map subnets to datacenter lists.
This plugin can operate in an automatic distance-based mode (using a City-level database's coordinate
information) It can also operate coordinate-free and rely on the user to configure a hierarchical map of
cascading default user-location-to-datacenter mappings, starting at the continent level.
The two modes can also be effectively mixed at geographic boundaries.
For each "map" you define (which maps geographic location codes to preference-ordered lists of your
datacenter locations), this plugin merges all of the raw GeoIP subnets into the largest possible
supernets which contain identical responses in your configuration. These in turn are used to set larger
edns-client-subnet scope masks than you'd see simply returning raw GeoIP results.
PLUGIN_METAFO
The documentation for gdnsd-plugin-metafo(8) is required reading for understanding the geoip plugin
documentation here. The geoip plugin is an exact superset of the metafo plugin, and re-uses almost all
of the metafo plugin's source code. Metafo does failover along a single, global, ordered list of
datacenters. What plugin_geoip adds on top of the functionality of metafo is the ability to have the
order of the datacenter failover list become dynamic per-request based on geographic hints derived from
the client's network address.
FILE LOCATIONS
The configuration of this plugin can reference several external configuration and/or data files. By
default, all files referenced in this plugin's configuration are loaded from the geoip subdirectory of
the daemon's configuration directory (default /etc/gdnsd). You can load from other locations by
specifying absolute file paths.
CONFIGURATION - TOP-LEVEL
The top level of the geoip plugin's configuration (i.e. "plugins => { geoip => { ... } }") supports only
three explicit keys. One is the optional setting "undefined_datacenters_ok".
The other two are required and expanded upon in detail in the next two sections: "maps", and "resources".
The "maps" section defines one or more named mappings of location information from GeoIP binary databases
to ordered subsets of datacenter names. The "resources" section defines one or more named resources,
each of which references one of the named maps and resolves datacenter names to specific sets of
addresses or CNAMEs.
Any other keys present at this level will be inherited down inside of each per-resource hash inside the
"resources" stanza, acting as per-resource defaults for anything not defined explicitly there.
"undefined_datacenters_ok = false"
Boolean, default false. If set to true, geoip resources are allowed to leave some of the datacenters
specified in their "map" undefined in their resource-level "dcmap". For example, a map M might define 3
datacenters named A, B, and C, but a resource using map M might only define result addresses for
datacenters B and C in its "dcmap". This would otherwise be a hard configuration error.
!!! DANGER !!! - Setting this value to true is a good way to shoot yourself in the foot if you're not
very careful about how your maps and resources are configured with respect to each other, especially in
"City Auto Mode". Maps are calculated without any knowledge of the resources that use them. If a
specific network or location maps to a list of datacenters which contains none of the defined datacenters
for a given resource, the results of runtime queries for that resource from that location or network will
be the empty set (no answer records at all). This is virtually guaranteed to happen in "City Auto Mode"
if the number of undefined datacenters in a resource is greater than or equal to the map's
"auto_dc_limit".
CONFIGURATION - MAPS
All "maps"-level configuration keys are the names of the maps you choose to define. A map, conceptually,
is a mapping between geography and/or network topology to varying ordered datacenter sub-sets. The value
of each named map must be a hash, and the following configuration keys apply within:
"geoip2_db = GeoIP2-City.mmdb"
String, filename, optional. This is the filename of a MaxMind GeoIP2 format database. It should contain
either the City or Country data model. There is no distinction made here for the IP version, and it is
normal for these databases to contain both IPv4 and IPv6 data together. If one or the other is missing,
clients using that address family will be defaulted.
"datacenters = [ one, two, three, ... ]"
Array of strings, required. This is the total set of datacenter names used by this map. You must define
at least one datacenter name (although 2 or more would be infinitely more useful). At this time, there
is a maximum limit of 254 datacenter names per map, although this could be raised if anyone requires it.
The order specified here is the fallback default result ordering in various default cases (e.g. if no
explicit top-level map default list is given).
"ignore_ecs = true"
Boolean, default false. If this is set to "true", all resources using this map will ignore EDNS Client
Subnet (ECS) information when performing lookups against the map, relying solely on the DNS source IP for
the lookup. If the client provided ECS in such a query, the response will also contain the ECS option to
signal that we're ECS aware in general, but the response scope mask will be set to zero to signal the
cache that the ECS data wasn't used and the result is globally cacheable.
This is useful for situations in which the map is intentionally meant to operate solely on recursor IPs
rather than ECS IPs, but other maps serviced by the same authserver do make use of ECS data, and thus the
global edns_client_subnet config option can't be used to disable handling the option completely for the
whole server.
"nets = { ... }"
Key-value hash, optional (see below for alternate form). If specified, the contents should be key-value
pairs of "network/netmask" mapped to a datacenter name (or an array of datacenter names). Any network-
to-datacenter mappings specified here will override mappings determined via GeoIP. Note that it is
illegal to specify networks in the IPv4-like subspaces of IPv6 other than v4compat, but it is legal to
specify actual IPv4 networks (which are treated identically to v4compat). See the section on IPv4
Compatible Addresses later in this document for more details. The order of the networks is unimportant;
they will always be sorted and inserted such that an entry which is a subnet of another entry is not
obliterated by the parent supernet.
nets => {
10.0.0.0/8 => [ dc1, dc2 ],
192.0.2.128/25 => dc3
2001:DB8::/32 => [ dc4, dc5, dc6 ],
}
In the case that one entry is a subnet of another with a different result dclist, the entries are merged
correctly such that the supernet surrounds the subnet. In the case of an exact duplicate entry (or an
effective one, after merging smaller subnets) with a different dclist, it is arbitrary which one "wins"
and the condition is warned about. If you care about this case, you should sanitize your nets data
beforehand with an external tool and/or parse for the warning message in log outputs.
"nets = nets_file_name"
String pathname, optional. A variant of the above, but the contents of the key-value hash are loaded
from the named external file. This makes life easier for external tools and scripts generating large
sets of nets entries (e.g. from BGP data). The file will be monitored for changes and reloaded at
runtime much like the GeoIP databases.
"map = { ... }"
Key-value hash, optional. This is the heart of a named map which uses GeoIP: the map itself, which maps
places to ordered lists of datacenters. It requires "geoip2_db" is also specified, and makes no sense
without it.
This is a nested key-value hash. At each level, the keys are location codes (continent, country,
region/subdivision, or city information depending on depth), and the values are either an ordered
datacenter array (e.g. "[ dc03, dc01, dc04 ]"), or a sub-hash containing a deeper level of distinction.
At each layer, a special key named "default" is available, which sets the default for everything within
the current scope. The top-level default itself defaults to the ordered list from "datacenters" in the
normal case. If the entire "map" stanza is missing or empty, you just get the default behavior of
"default". A datacenter array can also be empty, which implies that this location is mapped to receive
no response data (the server will still respond to the query, and will not issue an NXDOMAIN. It will
simply be a NODATA/NOERROR response like you'd get if there were no records of this type, but could be
records of other types for the same name).
GeoIP2 Location Data Hierarchy
The top level of the map hierarchy is comprised of MaxMind's seven continent codes: "AF" for Africa, "AS"
for Asia, "NA" for North America, "SA" for South America, "EU" for Europe, "OC" for Oceania, and "AN" for
Antarctica. The next level is the ISO 3166-1 2-letter country code.
From here there are a number of Subdivision levels, the count of which varies for different network
database entries. In the US, for example, there is only one level of subdivision data for the US States.
In the Czech Republic there are two levels of subdivision: first into 14 regions, and then further into
91 districts. Subdivisions are all specified using their ISO 3166-2 codes directly.
After all subdivision levels, the final level is the City level. The City names are all in the UTF-8
character set. Currently this plugin only uses the English city names from the database, even though
other languages may be available depending on the database.
As a pragmatic answer to the issues that can arise with multiple subdivision layers, the map
automatically searches deeper in the database data when no map match is found at a given level of the map
hierarchy beneath the Country level. This means you can skip over any levels of Subdivision detail in
your map that are irrelevant to you.
For example, this targets the New Zealand regional council subdivision of Otago without explicitly
specifying the enclosing subdivision for the South Island:
{ OC => { NZ => { OTA => [...] } } }
As another example, this works correctly for targeting the city of Paris without caring about what layers
of subdivisions lie between it and FR:
{ EU => { FR => { Paris => [...] } } }
CONFIGURATION - MAPS - CITY AUTO MODE
"City-auto-mode" is a special mode of operation that automatically maps out the world to your datacenters
based on coordinate math, so that you don't have to manually construct a complex hierarchical "map". It
can still be mixed with "map" of course, allowing you to use auto-mode for only select geographic areas
if you wish (or disabling it for select areas by specifying manual lists). The key parameter is
"auto_dc_coords", which enables city-auto-mode. This requires a City-level GeoIP2 database; the Country
ones don't contain coordinate information.
"auto_dc_coords = { ... }"
Key-value hash, optional. If this option is specified, the whole map's basic mode of operation
changes to "city-auto-mode". The contents of the hash are a key for each datacenter named in
"datacenters", with their values set to an array of "[lat, lon]" in decimal degree units. When city-
auto-mode is enabled by this, the following configuration-validation changes occur from the default,
static-mapping mode: the loaded GeoIP2 database(s) are required be City-level databases, and the
special keyword "auto" becomes a legal "datacenter list" in the "map" stanza.
With city-auto-mode enabled, the top-level map "default" defaults to "auto", but can be overridden
with a manual list. For any location that maps to "auto", the coordinates specified here in
"auto_dc_coords" will be compared with the coordinates from the City-level database(s) to determine
an automatic distance-sorted datacenter list.
If you omit one or more defined datacenters from the coordinate list in "auto_dc_coords", those
datacenters will not be used in automatic results, but will still be available for manual use via
"map" and/or "nets" entries.
"auto_dc_limit = N"
Unsigned integer, optional, default 3. When city-auto-mode is in effect, this is the upper length
limit for auto-generated lists. 3 is a reasonable default even if you have a considerably longer set
of datacenters, as this provides a primary as well as two fallbacks. Raising this to a large number
in the presence of a long datacenter list will cause the set of unique result datacenter lists to
increase rapidly, and thus reduce the optimization of the final result database for edns-client-
subnet purposes. It's really not worth raising this value in almost any case, unless you really need
to handle more than 3 random datacenters going offline at the same time and still have clients fail
elsewhere. The value zero is treated as unlimited (highly un-recommended).
Under city-auto-mode, when the top-level default is (explicitly or implicitly) "auto", there is still a
fallback static ordering which is the whole ordered "datacenters" list, which is the normal static
default "default" when not in city-auto-mode. This fallback is used when no location information is
available at all (e.g. IPv6 client vs IPv4 GeoIP DB, Anonymous Proxies, etc).
MAP TESTING
A binary program "gdnsd_geoip_test" is included. This can be used directly from the commandline, parses
the relevant bits of your gdnsd config file for geoip map info, and then provides datacenter list results
for IP address + map combinations supplied by the user. Useful for debugging your maps and testing the
mapping of client IPs. It has a separate manpage gdnsd_geoip_test(1).
CONFIGURATION - RESOURCES
Resource-level configuration within the "resources" stanza is nearly identical to the resources
configuration of the metafo plugin, with all of the same basic behaviors about synthesizing or directly
referencing the configuration of other plugins per-datacenter.
One difference is that metafo's per-resource "datacenters" array is replaced with "map => mapname", which
references one of the maps defined in the "maps" stanza, described in detail earlier. The set of defined
datacenters in the "dcmap" stanza must match the total set of datacenters defined by the referenced map,
unless "undefined_datacenters_ok" is set to "true" (see warnings and documentation above).
The "skip_first" flag can also be set per resource, and is much more useful with the geoip plugin than it
is with the basic metafo plugin. If this flag is set, the first datacenter in the failover list for a
given lookup will be skipped, allowing the definition of a "second choice" resource using the same basic
map definition as the first choice. In this case the original first choice is *never* a possible answer,
and the rest of the logic (e.g. skipping datacenters marked as down) proceeds as normal with the
remaining list. If the map entry and/or the resource definition have already reduced the effective
datacenter count to one, the flag has no effect.
META-PLUGIN INTERACTION
Both of the meta-plugins ("metafo" and "geoip") can reference their own as well as each others' resources
by direct reference within a "dcmap", so long as a resource does not directly refer to itself. This
allows plugin-layering configurations such as geoip -> metafo -> weighted, or metafo -> geoip -> multifo,
or even metafo -> metafo -> simplefo, etc.
Bear in mind that once you begin using inter-meta-plugin references, you could create a reference loop.
gdnsd does not currently detect or prevent such loops, and they will cause complete runtime failure when
queried, probably by running out of stack space during recursion.
Additionally, "geoip" can synthesize configuration for "metafo" resources, but the reverse does not hold;
"metafo" cannot synthesize configuration for "geoip" resources.
IPv4 Compatible Addresses
This plugin knows of six different relatively-trivial ways to map IPv4 addresses into the IPv6 address
space. These are shown below in as much detail matters to this plugin, with "NNNN:NNNN" in place of the
copied IPv4 address bytes:
::0000:NNNN:NNNN/96 # RFC 4291 - v4compat (deprecated)
::ffff:NNNN:NNNN/96 # RFC 4291 - v4mapped
::ffff:0000:NNNN:NNNN/96 # RFC 2765 - SIIT (obsoleted)
64:ff9b::NNNN:NNNN/96 # RFC 6052 - Well-Known Prefix
2001:0000:X:NNNN:NNNN/32 # RFC 4380 - Teredo (IPv4 bits are flipped)
2002:NNNN:NNNN::/16 # RFC 3056 - 6to4
(in the Teredo case above, "X" represents some variable non-zero bytes
that occupy the center 64 bits of the address).
All of this plugin's internal lookup databases are IPv6 databases, and any IPv4-like information is
always stored in the v4compat space within these databases. When doing runtime lookups all other v4-like
addresses (raw IPv4 addresses, v4mapped, SIIT, WKP, Teredo, and 6to4) are converted to the canonical
v4compat IPv6 representation before querying the internal databases. The other representations
(v4mapped, SIIT, WKP, Teredo, 6to4) are Undefined internally, and will never be referenced at lookup-time
due to the v4compat conversion mentioned earlier.
The "nets" stanza is not allowed to specify entries in the five undefined v4-like IPv6 spaces (those
other than v4compat). Specify those networks as normal IPv4 networks or v4compat networks instead.
Legitimate IPv6 "nets" entries which happen to be a supernet of any v4-like spaces will *not* unduly
affect v4-like lookups. There is no functional difference between v4compat and native v4 forms in
"nets", e.g. "192.0.2.0/24" and "::C000:0200/120" are completely identical.
GeoIP databases that are natively IPv4-only get all of their data loaded into the v4compat space only.
For normal IPv6 GeoIP databases, by default we load the v4compat space directly (which is where MaxMind
stores IPv4 data in their IPv6 databases), but ignore the v4mapped/SIIT/Teredo/6to4 spaces (some of which
are empty in MaxMind's databases, and some of which simply alias the v4compat space).
ANOTHER CONFIG EXAMPLE
A relatively-maximal example config, showing the interaction of valid "maps" and "resources" sections:
service_types => {
xmpp_svc => { plugin => "tcp_connect", ... }
www_svc => { plugin => "http_status", ... }
}
plugins => {
geoip => {
maps => {
my_prod_map => {
geoip2_db => GeoIP2-City.mmdb,
datacenters => [us-01, de-01, sg-01],
map => {
# Hierarchy is Continent -> Country -> Region -> City
NA => {
US => {
Dallas => [sg-01],
}
}
SA => [us-01, sg-01, de-01],
EU => {
default => [de-01, us-01, sg-01],
CH => {
Geneve => {
Geneva => [sg-01],
}
}
}
AF => [de-01, us-01, sg-01],
AS => [sg-01, de-01, us-01],
OC => [sg-01, us-01, de-01],
}
nets => {
10.0.0.0/8 => [ de-01 ],
2001:DB8::/32 => [ us-01 ],
}
}
my_auto_map => {
geoip2_db => GeoIP2-City.mmdb,
datacenters => [us-01, de-01, sg-01],
auto_dc_coords => {
us-01 => [ 38.9, -77 ],
de-01 => [ 50.1, 8.7 ],
sg-01 => [ 1.3, 103.9 ],
}
}
}
resources => {
prod_app => {
map => my_auto_map
# these two are inherited multifo config keys
# for all of the dcmap below:
service_types => [www_svc, xmpp_svc],
up_thresh => 0.4,
dcmap => {
us-01 => {
lb01 => 192.0.2.1,
lb02 => 192.0.2.2,
lb03 => 192.0.2.3,
lb01.v6 => 2001:DB8::1,
lb02.v6 => 2001:DB8::2,
lb03.v6 => 2001:DB8::3,
},
sg-01 => {
lb01 => 192.0.2.4,
lb02 => 192.0.2.5,
lb03 => 192.0.2.6,
lb01.v6 => 2001:DB8::4,
lb02.v6 => 2001:DB8::5,
lb03.v6 => 2001:DB8::6,
},
de-01 => {
lb01 => 192.0.2.7,
lb02 => 192.0.2.8,
lb03 => 192.0.2.9,
lb01.v6 => 2001:DB8::7,
lb02.v6 => 2001:DB8::8,
lb03.v6 => 2001:DB8::9,
},
}
},
prod_cdn => {
map => my_prod_map,
dcmap => {
us-01 => us-cdn-provider.example.net.
sg-01 => asia-cdn-provider.example.net.
de-01 => europe-cdn-provider.example.net.
}
}
}
}
}
Example zonefile RRs in zone example.com:
app 600 DYNA geoip!prod_app
app.us 600 DYNA geoip!prod_app/us-01
app.sg 600 DYNA geoip!prod_app/sg-01
app.de 600 DYNA geoip!prod_app/de-01
content 600 DYNC geoip!prod_cdn
EXAMPLE OF METAFO->GEOIP CITY-AUTO-MODE w/ LAST RESORT CNAME
plugins => {
geoip => {
maps => {
auto_map => {
geoip2_db => GeoIP2-City.mmdb,
datacenters => [dc1, dc2, dc3, dc4],
auto_dc_coords => {
dc1 => [ 38.9, -77 ],
dc2 => [ 50.1, 8.7 ],
dc3 => [ 20.2, 88.9 ],
dc4 => [ 39.0, -20 ],
},
# only fail through the nearest 2 before giving up:
auto_dc_limit => 2,
}
},
resources => {
www_real => {
map => my_auto_map,
service_types => [ http, xmpp ],
dcmap => {
dc1 => 192.0.2.100,
dc2 => 192.0.2.101,
dc3 => 192.0.2.102,
dc4 => 192.0.2.103
}
}
}
},
metafo => {
resources => {
www => {
datacenters => [ real, backup ],
dcmap => {
real => %geoip!www_real,
backup => backup-host.example.net.
}
}
}
}
}
And in the example.com zonefile:
; This tries through the closest 2/4 datacenters to
; the client from the geoip map, and if both of
; those are down it returns a CNAME to backup-host.example.net.
; for a downtime message or something:
www DYNC metafo!www
SEE ALSO
gdnsd-plugin-metafo(8), gdnsd_geoip_test(1), gdnsd.config(5), gdnsd.zonefile(5), gdnsd(8)
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 3.8.2 2024-03-31 GDNSD-PLUGIN-GEOIP(8)