LUA rules run within the same environment as described in DNS Modes of Operation.
The Lua snippets can query the following variables:
dhDNSHeader of the received query.dnssecOKednsPKTSizeqnameDNSName.zoneDNSName.zoneidtcpecswhoNetmask.bestwhoComboAddress.whoComboAddress.localwhoifportup(portnum, addresses[, options])¶Simplistic test to see if an IP address listens on a certain port. This will
attempt a TCP connection on port portnum and consider it available if the
connection establishes. No data will be sent or read on that connection. Note
that both IPv4 and IPv6 addresses can be tested, but that it is an error to
list IPv4 addresses on an AAAA record, or IPv6 addresses on an A record.
Will return a single address from the set of available addresses. If no address is available, will return a random element of the set of addresses supplied for testing.
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Various options can be set in the options parameter:
selector: used to pick the address(es) from the list of available addresses. Choices include ‘pickclosest’, ‘random’, ‘hashed’, ‘all’ (default ‘random’).backupSelector: used to pick the address(es) from all addresses if all addresses are down. Choices include ‘pickclosest’, ‘random’, ‘hashed’, ‘all’ (default ‘random’).source: Source address to check fromtimeout: Maximum time in seconds that you allow the check to take (default 2)ifurlup(url, addresses[, options])¶More sophisticated test that attempts an actual http(s) connection to
url. In addition, a list of sets of IP addresses can be supplied. The
first set with at least one available address is selected. The selector then
selects from the subset of available addresses of the selected set.
An URL is considered available if the HTTP response code is 200 and optionally if
the content matches the stringmatch option.
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Various options can be set in the options parameter:
selector: used to pick the address(es) from the subset of available addresses of the selected set. Choices include ‘pickclosest’, ‘random’, ‘hashed’, ‘all’ (default ‘random’).backupSelector: used to pick the address from all addresses if all addresses are down. Choices include ‘pickclosest’, ‘random’, ‘hashed’, ‘all’ (default ‘random’).source: Source address to check fromtimeout: Maximum time in seconds that you allow the check to take (default 2)stringmatch: check url for this string, only declare ‘up’ if founduseragent: Set the HTTP “User-Agent” header in the requests. By default it is set to “PowerDNS Authoritative Server”byteslimit: Limit the maximum download size to byteslimit bytes (default 0 meaning no limit).An example of a list of address sets:
ifurlup("https://example.com/", { {"192.0.2.20", "203.0.113.4"}, {"203.0.113.2"} })
ifurlextup(groups-of-address-url-pairs[, options])¶Very similar to ifurlup, but the returned IPs are decoupled from their external health check URLs.
This is useful when health checking already happens elsewhere, and that state is exposed over HTTP(S).
Health checks are considered positive if the HTTP response code is 200 and optionally if the content matches the stringmatch option.
Options are identical to those for ifurlup.
Example:
ifurlextup({{['192.168.0.1']='https://example.com/',['192.168.0.2']='https://example.com/404'}})
Example with two groups:
ifurlextup({{['192.168.0.1']='https://example.net/404',['192.168.0.2']='https://example.com/404'}, {['192.168.0.3']='https://example.net/'}})"
The health checker will look up the first two URLs (using normal DNS resolution to find them - whenever possible, use URLs with IPs in them).
The 404s will cause the first group of IPs to get marked as down, after which the URL in the second group is tested.
The third IP will get marked up assuming https://example.net/ responds with HTTP response code 200.
pickrandom(values)¶Returns a random value from the list supplied.
| Parameters: | values – A list of strings such as IPv4 or IPv6 address. |
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This function also works for CNAME or TXT records.
pickrandomsample(number, values)¶Returns N random values from the list supplied.
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This function also works for CNAME or TXT records.
pickhashed(values)¶Based on the hash of bestwho, returns a random value from the list supplied.
| Parameters: | values – A list of strings such as IPv4 or IPv6 address. |
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This function also works for CNAME or TXT records.
pickclosest(addresses)¶Returns IP address deemed closest to the bestwho IP address.
| Parameters: | addresses – A list of strings with the possible IP addresses. |
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latlon()¶Returns text listing fractional latitude/longitude associated with the bestwho IP address.
latlonloc()¶Returns text in LOC record format listing latitude/longitude associated with the bestwho IP address.
closestMagic()¶Suitable for use as a wildcard LUA A record. Will parse the query name which should be in format:
192-0-2-1.192-0-2-2.198-51-100-1.magic.v4.powerdns.org
It will then resolve to an A record with the IP address closest to bestwho from the list
of supplied addresses.
In the magic.v4.powerdns.org this looks like:
*.magic.v4.powerdns.org IN LUA A "closestMagic()"
In another zone, a record is then present like this:
www-balanced.powerdns.org IN CNAME 192-0-2-1.192-0-2-2.198-51-100-1.magic.v4.powerdns.org
This effectively opens up your server to being a ‘geographical load balancer as a service’.
Performs no uptime checking.
all(values)¶Returns all values.
| Parameters: | values – A list of strings such as IPv4 or IPv6 address. |
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This function also works for CNAME or TXT records.
view(pairs)¶Shorthand function to implement ‘views’ for all record types.
| Parameters: | pairs – A list of netmask/result pairs. |
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An example:
view.v4.powerdns.org IN LUA A ("view({ "
"{ {'192.168.0.0/16'}, {'192.168.1.54'}},"
"{ {'0.0.0.0/0'}, {'192.0.2.1'}} "
" }) " )
This will return IP address 192.168.1.54 for queries coming from 192.168.0.0/16, and 192.0.2.1 for all other queries.
This function also works for CNAME or TXT records.
pickchashed(values)¶Based on the hash of bestwho, returns a string from the list
supplied, as weighted by the various weight parameters and distributed consistently.
Performs no uptime checking.
| Parameters: | values – table of weight, string (such as IPv4 or IPv6 address). |
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This function works almost like pickwhashed() while bringing the following properties:
- reordering the list of entries won’t affect the distribution
- updating the weight of an entry will only affect a part of the distribution
- because of the previous properties, the CPU and memory cost is a bit higher than pickwhashed()
Hashes will be pre computed the first time such a record is hit and refreshed if needed. If updating the list is done often, the cash may grow. A cleanup routine is performed every lua-consistent-hashes-cleanup-interval seconds (default 1h) and cleans cached entries for records that haven’t been used for lua-consistent-hashes-expire-delay seconds (default 24h)
An example:
mydomain.example.com IN LUA A ("pickchashed({ "
" {15, "192.0.2.1"}, "
" {100, "198.51.100.5"} "
"}) ")
pickwhashed(values)¶Based on the hash of bestwho, returns a string from the list
supplied, as weighted by the various weight parameters.
Performs no uptime checking.
| Parameters: | values – table of weight, string (such as IPv4 or IPv6 address). |
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Because of the hash, the same client keeps getting the same answer, but given sufficient clients, the load is still spread according to the weight factors.
This function also works for CNAME or TXT records.
An example:
mydomain.example.com IN LUA A ("pickwhashed({ "
" {15, "192.0.2.1"}, "
" {100, "198.51.100.5"} "
"}) ")
picknamehashed(values)¶Based on the hash of the DNS record name, returns a string from the list supplied, as weighted by the various weight parameters.
Performs no uptime checking.
| Parameters: | values – table of weight, string (such as IPv4 or IPv6 address). |
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This allows basic persistent load balancing across a number of backends.
It means that test.mydomain.example.com will always resolve to the same IP, but test2.mydomain.example.com may go elsewhere.
This function is only useful for wildcard records.
This works similar to round-robin load balancing, but has the advantage of making traffic for the same domain always end up on the same server which can help cache hit rates.
This function also works for CNAME or TXT records.
An example:
*.mydomain.example.com IN LUA A ("picknamehashed({ "
" {15, "192.0.2.1"}, "
" {100, "198.51.100.5"} "
"}) ")
pickwrandom(values)¶Returns a random string from the list supplied, as weighted by the
various weight parameters. Performs no uptime checking.
| Parameters: | values – table of weight, string (such as IPv4 or IPv6 address). |
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See pickwhashed() for an example.
This function also works for CNAME or TXT records.
Warning
For createForward() and createForward6(), we recommend filtering with filterForward(), to prevent PowerDNS from generating A/AAAA responses to addresses outside of your network.
Not limiting responses like this may, in some situations, help attackers with impersonation and attacks like such as cookie stealing.
createReverse(format[, exceptions])¶Used for generating default hostnames from IPv4 wildcard reverse DNS records, e.g. *.0.0.127.in-addr.arpa
See createReverse6() for IPv6 records (ip6.arpa)
See createForward() for creating the A records on a wildcard record such as *.static.example.com
Returns a formatted hostname based on the format string passed.
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Formatting options:
%1% to %4% are individual octets1.0.0.127.in-addr.arpa%1% = 127%2% = 0%3% = 0%4% = 1%5% joins the four decimal octets together with dashes%5%.static.example.com is equivalent to %1%-%2%-%3%-%4%.static.example.com%6% converts each octet from decimal to hexadecimal and joins them together15.0.0.127.in-addr.arpa%6 would be 7f00000f (127 is 7f, and 15 is 0f in hexadecimal)Example records:
*.0.0.127.in-addr.arpa IN LUA PTR "createReverse('%1%.%2%.%3%.%4%.static.example.com')"
*.1.0.127.in-addr.arpa IN LUA PTR "createReverse('%5%.static.example.com')"
*.2.0.127.in-addr.arpa IN LUA PTR "createReverse('%6%.static.example.com')"
When queried:
# -x is syntactic sugar to request the PTR record for an IPv4/v6 address such as 127.0.0.5
# Equivalent to dig PTR 5.0.0.127.in-addr.arpa
$ dig +short -x 127.0.0.5 @ns1.example.com
127.0.0.5.static.example.com.
$ dig +short -x 127.0.1.5 @ns1.example.com
127-0-0-5.static.example.com.
$ dig +short -x 127.0.2.5 @ns1.example.com
7f000205.static.example.com.
createForward()¶Used to generate the reverse DNS domains made from createReverse()
Generates an A record for a dotted or hexadecimal IPv4 domain (e.g. 127.0.0.1.static.example.com)
It does not take any parameters, it simply interprets the zone record to find the IP address.
An example record for zone static.example.com:
*.static.example.com IN LUA A "createForward()"
This function supports the forward dotted format (127.0.0.1.static.example.com), and the hex format, when prefixed by two ignored characters (ip40414243.static.example.com)
When queried:
$ dig +short A 127.0.0.5.static.example.com @ns1.example.com
127.0.0.5
Since 4.8.0: the hex format can be prefixed by any number of characters (within DNS label length limits), including zero characters (so no prefix).
createReverse6(format[, exceptions])¶Used for generating default hostnames from IPv6 wildcard reverse DNS records, e.g. *.1.0.0.2.ip6.arpa
For simplicity purposes, only small sections of IPv6 rDNS domains are used in most parts of this guide, as a full ip6.arpa record is around 80 characters long
See createReverse() for IPv4 records (in-addr.arpa)
See createForward6() for creating the AAAA records on a wildcard record such as *.static.example.com
Returns a formatted hostname based on the format string passed.
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Formatting options:
%1% to %32% are individual characters (nibbles)a.0.0.0.1.0.0.2.ip6.arpa%1% = 2%2% = 0%3% = 0%4% = 1%33% converts the compressed address format into a dashed format, e.g. 2001:a::1 to 2001-a--1%34% to %41% represent the 8 uncompressed 2-byte chunks2001:a:b::123%34% - returns 2001 (chunk 1)%35% - returns 000a (chunk 2)%41% - returns 0123 (chunk 8)Example records:
*.1.0.0.2.ip6.arpa IN LUA PTR "createReverse6('%33%.static6.example.com')"
*.2.0.0.2.ip6.arpa IN LUA PTR "createReverse6('%34%.%35%.static6.example.com')"
When queried:
# -x is syntactic sugar to request the PTR record for an IPv4/v6 address such as 2001::1
# Equivalent to dig PTR 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.b.0.0.0.a.0.0.0.1.0.0.2.ip6.arpa
# readable version: 1.0.0.0 .0.0.0.0 .0.0.0.0 .0.0.0.0 .0.0.0.0 .b.0.0.0 .a.0.0.0 .1.0.0.2 .ip6.arpa
$ dig +short -x 2001:a:b::1 @ns1.example.com
2001-a-b--1.static6.example.com.
$ dig +short -x 2002:a:b::1 @ns1.example.com
2002.000a.static6.example.com
createForward6()¶Used to generate the reverse DNS domains made from createReverse6()
Generates an AAAA record for a dashed compressed IPv6 domain (e.g. 2001-a-b--1.static6.example.com)
It does not take any parameters, it simply interprets the zone record to find the IP address.
An example record for zone static.example.com:
*.static6.example.com IN LUA AAAA "createForward6()"
This function supports the dashed compressed format (i.e. 2001-a-b--1.static6.example.com), and the dot-split uncompressed format (2001.db8.6.5.4.3.2.1.static6.example.com)
When queried:
$ dig +short AAAA 2001-a-b--1.static6.example.com @ns1.example.com
2001:a:b::1
Since 4.8.0: a non-split full length format (20010002000300040005000600070db8.example.com) is also supported, optionally prefixed, in which case the last 32 characters will be considered.
filterForward(address, masks[, fallback])¶New in version 4.5.0.
Used for limiting the output of createForward() and createForward6() to a set of netmasks.
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Example:
*.static4.example.com IN LUA A "filterForward(createForward(), newNMG({'192.0.2.0/24', '10.0.0.0/8'}))"
Since 4.9.0: if the fallback parameter is an empty string, filterForward returns an empty set, yielding a NODATA answer.
You cannot combine this feature with DNSSEC.
asnum(number)¶asnum(numbers)Returns true if the bestwho IP address is determined to be from
any of the listed AS numbers.
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country(country)¶country(countries)Returns true if the bestwho IP address of the client is within the
two letter ISO country code passed, as described in GeoIP backend.
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countryCode()¶Returns two letter ISO country code based bestwho IP address, as described in GeoIP backend.
If the two letter ISO country code is unknown “–” will be returned.
region(region)¶region(regions)Returns true if the bestwho IP address of the client is within the
two letter ISO region code passed, as described in GeoIP backend.
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regionCode()¶Returns two letter ISO region code based bestwho IP address, as described in GeoIP backend.
If the two letter ISO region code is unknown “–” will be returned.
continent(continent)¶continent(continents)Returns true if the bestwho IP address of the client is within the
continent passed, as described in GeoIP backend.
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continentCode()¶Returns two letter ISO continent code based bestwho IP address, as described in GeoIP backend.
If the two letter ISO continent code is unknown “–” will be returned.
netmask(netmasks)¶Returns true if bestwho is within any of the listed subnets.
| Parameters: | netmasks ([string]) – The list of IP addresses to check against |
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dblookup(name, type)¶New in version 4.9.0.
Does a database lookup for name and type, and returns a (possibly empty) array of string results.
Please keep the following in mind:
dblookup('www.example.org', pdns.A)[1] to take the first item from the arrayifurlupExample usage:
www IN LUA A "ifurlup('https://www.example.com/', {dblookup('www1.example.com', pdns.A), dblookup('www2.example.com', pdns.A), dblookup('www3.example.com', pdns.A)})"
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