mirror of
https://github.com/mailscope/kumomta.git
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Wez Furlong
142 lines
3.2 KiB
Markdown
142 lines
3.2 KiB
Markdown
# define_resolver
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```lua
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kumo.dns.define_resolver(NAME, CONFIG)
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```
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{{since('2025.12.02-67ee9e96')}}
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This function defines an alternative resolver from the default configured via
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[configure_resolver](configure_resolver.md), and gives it a name.
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The alternate resolver name can then be optionally passed as a parameter to a
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number of other `kumo.dns` functions.
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The intended use case is to define an alternate resolver that points to an
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[rbldnsd](https://www.corpit.ru/mjt/rbldnsd.html) or similar specialized
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resolver that provides access to a
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[DNSBL](https://en.wikipedia.org/wiki/Domain_Name_System_blocklist).
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The `NAME` parameter is a string that defines the name of the alternate resolver.
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The `CONFIG` parameter defines the parameters for the resolver. It can have
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one of the following shapes:
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!!! note
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This function should be called only from inside your
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[init](../events/init.md) event handler.
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## Hickory with an explicit upstream
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If you have `rbldnsd` or similar available on `10.0.0.1:53`, then you might use this:
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```lua
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kumo.dns.define_resolver('rbl', {
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Hickory = {
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name_servers = {
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'10.0.0.1:53',
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},
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},
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})
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```
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You can then query it:
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```lua
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local answer, reason = kumo.dns.rbl_lookup(IP, 'rbl.domain', 'rbl')
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```
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## Test or static DNS
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If you have fixed and locally available zone data, then you can query
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that explicitly:
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```lua
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kumo.dns.define_resolver('rbl', {
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Test = {
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zones = {
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[[
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$ORIGIN rbl.domain.
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1.0.0.10 30 IN A 127.0.0.2
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1.0.0.10 300 TXT "Blocked for a very good reason!"
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]],
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},
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},
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})
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```
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You can then query it:
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```lua
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local answer, reason = kumo.dns.rbl_lookup('10.0.0.1', 'rbl.domain', 'rbl')
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```
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This mode of operation was originally intended for testing, but may prove
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useful in other situations.
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## System Default
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```lua
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kumo.dns.define_resolver('myresolver', 'HickorySystemConfig')
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```
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Parses the system resolver configuration and applies that to a separate
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instance of the hickory DNS resolver client. This is equivalent to the default
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resolver settings in kumomta.
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## Unbound with an explicit upstream
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!!! note
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We generally recommend sticking with Hickory unless you have a very good
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reason.
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If you have `rbldnsd` or similar available on `10.0.0.1:53`, then you might use this:
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```lua
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kumo.dns.define_resolver('rbl', {
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Unbound = {
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name_servers = {
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'10.0.0.1:53',
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},
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},
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})
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```
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You can then query it:
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```lua
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local answer, reason = kumo.dns.rbl_lookup(IP, 'rbl.domain', 'rbl')
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```
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## Aggregating Different Resolvers
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If you have a mixture of local zone files and a remote DNS, then you can
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mix them together; have the local zones queried before falling back to
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a remote host.
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In the example below, the local zone is used first before falling back
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to querying the upstream specified by the system.
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```lua
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kumo.dns.define_resolve('aggregate', {
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Aggregate = {
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-- The value of `Aggregate` here is an array style table
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-- listing out one of the CONFIG options shown in the
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-- examples above.
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-- First we have a Test setup
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Test = {
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zones = {
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[[
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$ORIGIN 0.0.127.in-addr.arpa.
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1 30 IN PTR localhost.
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]],
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},
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},
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-- Then we have a system default setup
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'HickorySystemConfig',
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},
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})
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```
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