The PowerDNS Recursor uses a native format for the names it handles. This native format is exposed to Lua as well.
The PowerDNS Recursor’s Lua engine has the notion of a DNSName
, an object that represents a name in the DNS.
It is returned by several functions and has several functions to programmatically interact with it.
DNSNames
can be compared against each other using the :equal
function or the ==
operator.
As names in the DNS are case-insensitive, www.powerdns.com
is equal to Www.PowerDNS.cOM
.
Creating a DNSName
is done with newDN()
.
The PowerDNS Recursor will complain loudly if the name is invalid (e.g. too long, dot in the wrong place).
A small example of the functionality of a DNSName
is shown below:
myname = newDN("www.example.com")
print(myname:countLabels()) -- prints "3"
print(myname:wirelength()) -- prints "17"
name2 = newDN(myname)
name2:chopoff() -- returns true, as 'www' was stripped
print(name2:countLabels()) -- prints "2"
if myname:isPartOf(name2) then -- prints "it is"
print('it is')
end
newDN
(name) → DNSName¶Returns the DNSName
object of name
.
Parameters: | name (string) – The name to create a DNSName for |
---|
DNSName
¶A DNSName
object represents a name in the DNS.
:
chopOff
() → bool¶Removes the left-most label and returns true
.
false
is returned if no label was removed
:
countLabels
() → int¶Returns the number of DNSLabels in the name
:
equal
(name) → bool¶Returns true when both names are equal for the DNS, i.e case insensitive.
To compare two DNSName
objects, use ==
.
Parameters: | string (DNSName) – The name to compare against. |
---|
:
isPartOf
(name) → bool¶Returns true if the DNSName is part of the DNS tree of name
.
newDN("www.powerdns.com"):isPartOf(newDN("CoM.")) -- true
Parameters: | name (DNSName) – The name to check against |
---|
:
toString
() → str¶:
toStringNoDot
() → str¶Returns a human-readable form of the DNSName. With or without trailing dot.
:
wirelength
() → int¶Returns the length in bytes of the DNSName as it would be on the wire.
The newDS()
function creates a “Suffix Match group” that allows fast checking if a DNSName
is part of a group.
This could e.g. be used to answer questions for known malware domains.
To check e.g. the dq.qname
against a list:
m = newDS()
m:add({'example.com', 'example.net'})
m:check(dq.qname) -- Would be true is dq.qname is a name in example.com or example.net
newDS
() → DNSSuffixMatchGroup¶Creates a new DNS Suffix Match Group.
DNSSuffixMatchGroup
¶This class represents a group of DNS names that can be used to quickly compare a single DNSName
against.
:
add
(domain)¶:
add
(domains)Add one or more domains to the Suffix Match Group.
Parameters: |
|
---|
:
check
(domain) → bool¶Check domain
against the Suffix Match Group.
Returns true if it is matched, false otherwise.
Parameters: | domain (DNSName) – The domain name to check |
---|
:
toString
() → str¶Returns a string of the set of suffixes matched by the Suffix Match Group