GdnsdPluginGeoip

Brandon Black edited this page Feb 16, 2019 · 11 revisions

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 /usr/local/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).

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. The only real 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).

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/>.

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