Packet Policies

dnsdist works in essence like any other loadbalancer:

It receives packets on one or several addresses it listens on, and determines whether it will process this packet based on the Access Control. Should the packet be processed, dnsdist attempts to match any of the configured rules in order and when one matches, the associated action is performed.

These rule and action combinations are considered policies.

Packet Actions

Each packet can be:

  • Dropped
  • Turned into an answer directly
  • Forwarded to a downstream server
  • Modified and forwarded to a downstream and be modified back
  • Be delayed

This decision can be taken at different times during the forwarding process.

Examples

Rules for traffic exceeding QPS limits

Traffic that exceeds a QPS limit, in total or per IP (subnet) can be matched by a rule.

For example:

addAction(MaxQPSIPRule(5, 32, 48), DelayAction(100))

This measures traffic per IPv4 address and per /48 of IPv6, and if traffic for such an address (range) exceeds 5 qps, it gets delayed by 100ms. (Please note: DelayAction() can only delay UDP traffic).

As another example:

addAction(MaxQPSIPRule(5), NoRecurseAction())

This strips the Recursion Desired (RD) bit from any traffic per IPv4 or IPv6 /64 that exceeds 5 qps. This means any those traffic bins is allowed to make a recursor do ‘work’ for only 5 qps.

If this is not enough, try:

addAction(MaxQPSIPRule(5), DropAction())

or:

addAction(MaxQPSIPRule(5), TCAction())

This will respectively drop traffic exceeding that 5 QPS limit per IP or range, or return it with TC=1, forcing clients to fall back to TCP.

To turn this per IP or range limit into a global limit, use NotRule(MaxQPSRule(5000)) instead of MaxQPSIPRule().

Regular Expressions

RegexRule() matches a regular expression on the query name, and it works like this:

addAction(RegexRule("[0-9]{5,}"), DelayAction(750)) -- milliseconds
addAction(RegexRule("[0-9]{4,}\\.example$"), DropAction())

This delays any query for a domain name with 5 or more consecutive digits in it. The second rule drops anything with more than 4 consecutive digits within a .example domain.

Note that the query name is presented without a trailing dot to the regex. The regex is applied case insensitively.

Alternatively, if compiled in, RE2Rule() provides similar functionality, but against libre2.

Rule Generators

dnsdist contains several functions that make it easier to add actions and rules.

addAnyTCRule()

Deprecated since version 1.2.0.

Set the TC-bit (truncate) on ANY queries received over UDP, forcing a retry over TCP. This function is deprecated as of 1.2.0 and will be removed in 1.3.0. This is equivalent to doing:

addAction(AndRule({QTypeRule(DNSQType.ANY), TCPRule(false)}), TCAction())

Changed in version 1.4.0: Before 1.4.0, the QTypes were in the dnsdist namespace. Use dnsdist.ANY in these versions.

addDelay(DNSrule, delay)

Deprecated since version 1.2.0.

Delay the query for delay milliseconds before sending to a backend. This function is deprecated as of 1.2.0 and will be removed in 1.3.0, please use instead:

addAction(DNSRule, DelayAction(delay))
Parameters:
  • DNSRule – The DNSRule to match traffic
  • delay (int) – The delay time in milliseconds.
addDisableValidationRule(DNSrule)

Deprecated since version 1.2.0.

Set the CD (Checking Disabled) flag to 1 for all queries matching the DNSRule. This function is deprecated as of 1.2.0 and will be removed in 1.3.0. Please use the DisableValidationAction() action instead.

addDomainBlock(domain)

Deprecated since version 1.2.0.

Drop all queries for domain and all names below it. Deprecated as of 1.2.0 and will be removed in 1.3.0, please use instead:

addAction(domain, DropAction())
Parameters:domain (string) – The domain name to block
addDomainSpoof(domain, IPv4[, IPv6])
addDomainSpoof(domain, {IP[,...]})

Deprecated since version 1.2.0.

Generate answers for A/AAAA/ANY queries. This function is deprecated as of 1.2.0 and will be removed in 1.3.0, please use:

addAction(domain, SpoofAction({IP[,…]}))

or:

addAction(domain, SpoofAction(IPv4[, IPv6]))
Parameters:
  • domain (string) – Domain name to spoof for
  • IPv4 (string) – IPv4 address to spoof in the reply
  • IPv6 (string) – IPv6 address to spoof in the reply
  • IP (string) – IP address to spoof in the reply
addDomainCNAMESpoof(domain, cname)

Deprecated since version 1.2.0.

Generate CNAME answers for queries. This function is deprecated as of 1.2.0 and will be removed in 1.3.0, in favor of using:

addAction(domain, SpoofCNAMEAction(cname))
Parameters:
  • domain (string) – Domain name to spoof for
  • cname (string) – Domain name to add CNAME to
addLuaAction(DNSrule, function[, options])

Changed in version 1.3.0: Added the optional parameter options.

Changed in version 1.3.0: The second argument returned by the function can be omitted. For earlier releases, simply return an empty string.

Deprecated since version 1.4.0: Removed in 1.4.0, use LuaAction() with addAction() instead.

Invoke a Lua function that accepts a DNSQuestion. This function works similar to using LuaAction(). The function should return both a DNSAction and its argument rule. The rule is used as an argument of the following DNSAction: DNSAction.Spoof, DNSAction.Pool and DNSAction.Delay. If the Lua code fails, ServFail is returned.

Parameters:
  • DNSRule – match queries based on this rule
  • function (string) – the name of a Lua function
  • options (table) – A table with key: value pairs with options.

Options:

  • uuid: string - UUID to assign to the new rule. By default a random UUID is generated for each rule.
function luarule(dq)
  if(dq.qtype==dnsdist.NAPTR)
  then
    return DNSAction.Pool, "abuse" -- send to abuse pool
  else
    return DNSAction.None, ""      -- no action
    -- return DNSAction.None       -- as of dnsdist version 1.3.0
  end
end

addLuaAction(AllRule(), luarule)
addLuaResponseAction(DNSrule, function[, options])

Changed in version 1.3.0: Added the optional parameter options.

Changed in version 1.3.0: The second argument returned by the function can be omitted. For earlier releases, simply return an empty string.

Deprecated since version 1.4.0: Removed in 1.4.0, use LuaResponseAction() with addResponseAction() instead.

Invoke a Lua function that accepts a DNSResponse. This function works similar to using LuaResponseAction(). The function should return both a DNSResponseAction and its argument rule. The rule is used as an argument of the DNSResponseAction.Delay. If the Lua code fails, ServFail is returned.

Parameters:
  • DNSRule – match queries based on this rule
  • function (string) – the name of a Lua function
  • options (table) – A table with key: value pairs with options.

Options:

  • uuid: string - UUID to assign to the new rule. By default a random UUID is generated for each rule.
addNoRecurseRule(DNSrule)

Deprecated since version 1.2.0.

Clear the RD flag for all queries matching the rule. This function is deprecated as of 1.2.0 and will be removed in 1.3.0, please use:

addAction(DNSRule, NoRecurseAction())
Parameters:DNSRule – match queries based on this rule
addPoolRule(DNSRule, pool)

Deprecated since version 1.2.0.

Send queries matching the first argument to the pool pool. e.g.:

addPoolRule("example.com", "myPool")

This function is deprecated as of 1.2.0 and will be removed in 1.3.0, this is equivalent to:

addAction("example.com", PoolAction("myPool"))
Parameters:
  • DNSRule – match queries based on this rule
  • pool (string) – The name of the pool to send the queries to
addQPSLimit(DNSrule, limit)

Deprecated since version 1.2.0.

Limit queries matching the DNSRule to limit queries per second. All queries over the limit are dropped. This function is deprecated as of 1.2.0 and will be removed in 1.3.0, please use:

addAction(DNSRule, QPSAction(limit))
Parameters:
  • DNSRule – match queries based on this rule
  • limit (int) – QPS limit for this rule
addQPSPoolRule(DNSRule, limit, pool)

Deprecated since version 1.2.0.

Send at most limit queries/s for this pool, letting the subsequent rules apply otherwise. This function is deprecated as of 1.2.0 and will be removed in 1.3.0, as it is only a convience function for the following syntax:

addAction("192.0.2.0/24", QPSPoolAction(15, "myPool")
Parameters:
  • DNSRule – match queries based on this rule
  • limit (int) – QPS limit for this rule
  • pool (string) – The name of the pool to send the queries to

Managing Rules

Active Rules can be shown with showRules() and removed with rmRule():

> addAction("h4xorbooter.xyz.", QPSAction(10))
> addAction({"130.161.0.0/16", "145.14.0.0/16"} , QPSAction(20))
> addAction({"nl.", "be."}, QPSAction(1))
> showRules()
#     Matches Rule                                               Action
0           0 h4xorbooter.xyz.                                   qps limit to 10
1           0 130.161.0.0/16, 145.14.0.0/16                      qps limit to 20
2           0 nl., be.                                           qps limit to 1

For Rules related to the incoming query:

addAction(DNSrule, action[, options])

Changed in version 1.3.0: Added the optional parameter options.

Add a Rule and Action to the existing rules.

Parameters:
  • rule (DNSrule) – A DNSRule, e.g. an AllRule() or a compounded bunch of rules using e.g. AndRule()
  • action – The action to take
  • options (table) – A table with key: value pairs with options.

Options:

  • uuid: string - UUID to assign to the new rule. By default a random UUID is generated for each rule.
clearRules()

Remove all current rules.

getAction(n) → Action

Returns the Action associated with rule n.

Parameters:n (int) – The rule number
mvRule(from, to)

Move rule from to a position where it is in front of to. to can be one larger than the largest rule, in which case the rule will be moved to the last position.

Parameters:
  • from (int) – Rule number to move
  • to (int) – Location to more the Rule to
newRuleAction(rule, action[, options])

Changed in version 1.3.0: Added the optional parameter options.

Return a pair of DNS Rule and DNS Action, to be used with setRules().

Parameters:
  • rule (Rule) – A Rule
  • action (Action) – The Action to apply to the matched traffic
  • options (table) – A table with key: value pairs with options.

Options:

  • uuid: string - UUID to assign to the new rule. By default a random UUID is generated for each rule.
setRules(rules)

Replace the current rules with the supplied list of pairs of DNS Rules and DNS Actions (see newRuleAction())

Parameters:rules ([RuleAction]) – A list of RuleActions
showRules([options])

Changed in version 1.3.0: options optional parameter added

Show all defined rules for queries, optionally displaying their UUIDs.

Parameters:options (table) – A table with key: value pairs with display options.

Options:

  • showUUIDs=false: bool - Whether to display the UUIDs, defaults to false.
  • truncateRuleWidth=-1: int - Truncate rules output to truncateRuleWidth size. Defaults to -1 to display the full rule.
topRule()

Move the last rule to the first position.

rmRule(id)

Changed in version 1.3.0: id can now be an UUID.

Remove rule id.

Parameters:id (int) – The UUID of the rule to remove if id is an UUID, its position otherwise

For Rules related to responses:

addResponseAction(DNSRule, action[, options])

Changed in version 1.3.0: Added the optional parameter options.

Add a Rule and Action for responses to the existing rules.

Parameters:
  • DNSRule – A DNSRule, e.g. an AllRule() or a compounded bunch of rules using e.g. AndRule()
  • action – The action to take
  • options (table) – A table with key: value pairs with options.

Options:

  • uuid: string - UUID to assign to the new rule. By default a random UUID is generated for each rule.
mvResponseRule(from, to)

Move response rule from to a position where it is in front of to. to can be one larger than the largest rule, in which case the rule will be moved to the last position.

Parameters:
  • from (int) – Rule number to move
  • to (int) – Location to more the Rule to
rmResponseRule(id)

Changed in version 1.3.0: id can now be an UUID.

Remove response rule id.

Parameters:id (int) – The UUID of the rule to remove if id is an UUID, its position otherwise
showResponseRules([options])

Changed in version 1.3.0: options optional parameter added

Show all defined response rules, optionally displaying their UUIDs.

Parameters:options (table) – A table with key: value pairs with display options.

Options:

  • showUUIDs=false: bool - Whether to display the UUIDs, defaults to false.
  • truncateRuleWidth=-1: int - Truncate rules output to truncateRuleWidth size. Defaults to -1 to display the full rule.
topResponseRule()

Move the last response rule to the first position.

Functions for manipulating Cache Hit Respone Rules:

addCacheHitResponseAction(DNSRule, action[, options])

New in version 1.2.0.

Changed in version 1.3.0: Added the optional parameter options.

Add a Rule and ResponseAction for Cache Hits to the existing rules.

Parameters:
  • DNSRule – A DNSRule, e.g. an AllRule() or a compounded bunch of rules using e.g. AndRule()
  • action – The action to take
  • options (table) – A table with key: value pairs with options.

Options:

  • uuid: string - UUID to assign to the new rule. By default a random UUID is generated for each rule.
mvCacheHitResponseRule(from, to)

New in version 1.2.0.

Move cache hit response rule from to a position where it is in front of to. to can be one larger than the largest rule, in which case the rule will be moved to the last position.

Parameters:
  • from (int) – Rule number to move
  • to (int) – Location to more the Rule to
rmCacheHitResponseRule(id)

New in version 1.2.0.

Changed in version 1.3.0: id can now be an UUID.

Parameters:id (int) – The UUID of the rule to remove if id is an UUID, its position otherwise
showCacheHitResponseRules([options])

New in version 1.2.0.

Changed in version 1.3.0: options optional parameter added

Show all defined cache hit response rules, optionally displaying their UUIDs.

Parameters:options (table) – A table with key: value pairs with display options.

Options:

  • showUUIDs=false: bool - Whether to display the UUIDs, defaults to false.
  • truncateRuleWidth=-1: int - Truncate rules output to truncateRuleWidth size. Defaults to -1 to display the full rule.
topCacheHitResponseRule()

New in version 1.2.0.

Move the last cache hit response rule to the first position.

Functions for manipulating Self-Answered Response Rules:

addSelfAnsweredResponseAction(DNSRule, action[, options])

New in version 1.3.0.

Add a Rule and Action for Self-Answered queries to the existing rules.

Parameters:
  • DNSRule – A DNSRule, e.g. an AllRule() or a compounded bunch of rules using e.g. AndRule()
  • action – The action to take
mvSelfAnsweredResponseRule(from, to)

New in version 1.3.0.

Move self answered response rule from to a position where it is in front of to. to can be one larger than the largest rule, in which case the rule will be moved to the last position.

Parameters:
  • from (int) – Rule number to move
  • to (int) – Location to more the Rule to
rmSelfAnsweredResponseRule(id)

New in version 1.3.0.

Remove self answered response rule id.

Parameters:id (int) – The UUID of the rule to remove if id is an UUID, its position otherwise
showSelfAnsweredResponseRules([options])

New in version 1.3.0.

Show all defined self answered response rules, optionally displaying their UUIDs.

Parameters:options (table) – A table with key: value pairs with display options.

Options:

  • showUUIDs=false: bool - Whether to display the UUIDs, defaults to false.
  • truncateRuleWidth=-1: int - Truncate rules output to truncateRuleWidth size. Defaults to -1 to display the full rule.
topSelfAnsweredResponseRule()

New in version 1.3.0.

Move the last self answered response rule to the first position.

Matching Packets (Selectors)

Packets can be matched by selectors, called a DNSRule. These DNSRules be one of the following items:

  • A string that is either a domain name or netmask
  • A list of strings that are either domain names or netmasks
  • A DNSName
  • A list of DNSNames
  • A (compounded) Rule

New in version 1.2.0: A DNSRule can also be a DNSName or a list of these

AllRule()

Matches all traffic

DNSSECRule()

Matches queries with the DO flag set

DSTPortRule(port)

Matches questions received to the destination port.

Parameters:port (int) – Match destination port.
EDNSOptionRule(optcode)

New in version 1.4.0.

Matches queries or responses with the specified EDNS option present. optcode is specified as an integer, or a constant such as EDNSOptionCode.ECS.

EDNSVersionRule(version)

New in version 1.4.0.

Matches queries or responses with an OPT record whose EDNS version is greater than the specified EDNS version.

Parameters:version (int) – The EDNS version to match on
ERCodeRule(rcode)

Matches queries or responses with the specified rcode. rcode can be specified as an integer or as one of the built-in RCode. The full 16bit RCode will be matched. If no EDNS OPT RR is present, the upper 12 bits are treated as 0.

Parameters:rcode (int) – The RCODE to match on
HTTPHeaderRule(name, regex)

New in version 1.4.0.

Matches DNS over HTTPS queries with a HTTP header name whose content matches the regular expression regex.

Parameters:
  • name (str) – The case-insensitive name of the HTTP header to match on
  • regex (str) – A regular expression to match the content of the specified header
HTTPPathRegexRule(regex)

New in version 1.4.0.

Matches DNS over HTTPS queries with a HTTP path matching the regular expression supplied in regex. For example, if the query has been sent to the https://192.0.2.1:443/PowerDNS?dns=… URL, the path would be ‘/PowerDNS’. Only valid DNS over HTTPS queries are matched. If you want to match all HTTP queries, see DOHFrontend.setResponsesMap() instead.

Parameters:regex (str) – The regex to match on
HTTPPathRule(path)

New in version 1.4.0.

Matches DNS over HTTPS queries with a HTTP path of path. For example, if the query has been sent to the https://192.0.2.1:443/PowerDNS?dns=… URL, the path would be ‘/PowerDNS’. Only valid DNS over HTTPS queries are matched. If you want to match all HTTP queries, see DOHFrontend.setResponsesMap() instead.

Parameters:path (str) – The exact HTTP path to match on
KeyValueStoreLookupRule(kvs, lookupKey)

New in version 1.4.0.

As of 1.4.0, this code is considered experimental.

Return true if the key returned by ‘lookupKey’ exists in the key value store referenced by ‘kvs’. The store can be a CDB (newCDBKVStore()) or a LMDB database (newLMDBKVStore()). The key can be based on the qname (KeyValueLookupKeyQName() and KeyValueLookupKeySuffix()), source IP (KeyValueLookupKeySourceIP()) or the value of an existing tag (KeyValueLookupKeyTag()).

Parameters:
  • kvs (KeyValueStore) – The key value store to query
  • lookupKey (KeyValueLookupKey) – The key to use for the lookup
MaxQPSIPRule(qps[, v4Mask[, v6Mask[, burst[, expiration[, cleanupDelay[, scanFraction]]]]]])

Changed in version 1.3.1: Added the optional parameters expiration, cleanupDelay and scanFraction.

Matches traffic for a subnet specified by v4Mask or v6Mask exceeding qps queries per second up to burst allowed. This rule keeps track of QPS by netmask or source IP. This state is cleaned up regularly if cleanupDelay is greater than zero, removing existing netmasks or IP addresses that have not been seen in the last expiration seconds.

Parameters:
  • qps (int) – The number of queries per second allowed, above this number traffic is matched
  • v4Mask (int) – The IPv4 netmask to match on. Default is 32 (the whole address)
  • v6Mask (int) – The IPv6 netmask to match on. Default is 64
  • burst (int) – The number of burstable queries per second allowed. Default is same as qps
  • expiration (int) – How long to keep netmask or IP addresses after they have last been seen, in seconds. Default is 300
  • cleanupDelay (int) – The number of seconds between two cleanups. Default is 60
  • scanFraction (int) – The maximum fraction of the store to scan for expired entries, for example 5 would scan at most 20% of it. Default is 10 so 10%
MaxQPSRule(qps)

Matches traffic not exceeding this qps limit. If e.g. this is set to 50, starting at the 51st query of the current second traffic stops being matched. This can be used to enforce a global QPS limit.

Parameters:qps (int) – The number of queries per second allowed, above this number the traffic is not matched anymore
NetmaskGroupRule(nmg[, src[, quiet]])

Changed in version 1.4.0: quiet parameter added

Matches traffic from/to the network range specified in nmg.

Set the src parameter to false to match nmg against destination address instead of source address. This can be used to differentiate between clients

Parameters:
  • nmg (NetMaskGroup) – The NetMaskGroup to match on
  • src (bool) – Whether to match source or destination address of the packet. Defaults to true (matches source)
  • quiet (bool) – Do not display the list of matched netmasks in Rules. Default is false.
OpcodeRule(code)

Matches queries with opcode code. code can be directly specified as an integer, or one of the built-in DNSOpcodes.

Parameters:code (int) – The opcode to match
ProbaRule(probability)

New in version 1.3.0.

Matches queries with a given probability. 1.0 means “always”

Parameters:probability (double) – Probability of a match
QClassRule(qclass)

Matches queries with the specified qclass. class can be specified as an integer or as one of the built-in DNSClass.

Parameters:qclass (int) – The Query Class to match on
QNameRule(qname)

New in version 1.2.0: Matches queries with the specified qname exactly.

param string qname:
 Qname to match
QNameSetRule(set)

New in version 1.4.0: Matches if the set contains exact qname.

To match subdomain names, see SuffixMatchNodeRule().

param DNSNameSet set:
 Set with qnames.
QNameLabelsCountRule(min, max)

Matches if the qname has less than min or more than max labels.

Parameters:
  • min (int) – Minimum number of labels
  • max (int) – Maximum nimber of labels
QNameWireLengthRule(min, max)

Matches if the qname’s length on the wire is less than min or more than max bytes.

Parameters:
  • min (int) – Minimum number of bytes
  • max (int) – Maximum nimber of bytes
QTypeRule(qtype)

Matches queries with the specified qtype qtype may be specified as an integer or as one of the built-in QTypes. For instance dnsdist.A, dnsdist.TXT and dnsdist.ANY.

Parameters:qtype (int) – The QType to match on
RCodeRule(rcode)

Matches queries or responses with the specified rcode. rcode can be specified as an integer or as one of the built-in RCode. Only the non-extended RCode is matched (lower 4bits).

Parameters:rcode (int) – The RCODE to match on
RDRule()

New in version 1.2.0.

Matches queries with the RD flag set.

RegexRule(regex)

Matches the query name against the regex.

addAction(RegexRule("[0-9]{5,}"), DelayAction(750)) -- milliseconds
addAction(RegexRule("[0-9]{4,}\\.example$"), DropAction())

This delays any query for a domain name with 5 or more consecutive digits in it. The second rule drops anything with more than 4 consecutive digits within a .EXAMPLE domain.

Note that the query name is presented without a trailing dot to the regex. The regex is applied case insensitively.

Parameters:regex (string) – A regular expression to match the traffic on
RecordsCountRule(section, minCount, maxCount)

Matches if there is at least minCount and at most maxCount records in the section section. section can be specified as an integer or as a DNS Packet Sections.

Parameters:
  • section (int) – The section to match on
  • minCount (int) – The minimum number of entries
  • maxCount (int) – The maximum number of entries
RecordsTypeCountRule(section, qtype, minCount, maxCount)

Matches if there is at least minCount and at most maxCount records of type type in the section section. section can be specified as an integer or as a DNS Packet Sections. qtype may be specified as an integer or as one of the built-in QTypes, for instance DNSQType.A or DNSQType.TXT.

Parameters:
  • section (int) – The section to match on
  • qtype (int) – The QTYPE to match on
  • minCount (int) – The minimum number of entries
  • maxCount (int) – The maximum number of entries
RE2Rule(regex)

Matches the query name against the supplied regex using the RE2 engine.

For an example of usage, see RegexRule().

Note:Only available when dnsdist was built with libre2 support.
Parameters:regex (str) – The regular expression to match the QNAME.
SNIRule(name)

New in version 1.4.0.

Matches against the TLS Server Name Indication value sent by the client, if any. Only makes sense for DoT or DoH, and for that last one matching on the HTTP Host header using HTTPHeaderRule() might provide more consistent results. As of the version 2.3.0-beta of h2o, it is unfortunately not possible to extract the SNI value from DoH connections, and it is therefore necessary to use the HTTP Host header until version 2.3.0 is released.

Parameters:name (str) – The exact SNI name to match.
SuffixMatchNodeRule(smn[, quiet])

Matches based on a group of domain suffixes for rapid testing of membership. Pass true as second parameter to prevent listing of all domains matched.

To match domain names exactly, see QNameSetRule().

Parameters:
  • smb (SuffixMatchNode) – The SuffixMatchNode to match on
  • quiet (bool) – Do not display the list of matched domains in Rules. Default is false.
TagRule(name[, value])

New in version 1.3.0.

Matches question or answer with a tag named name set. If value is specified, the existing tag value should match too.

Parameters:
  • name (bool) – The name of the tag that has to be set
  • value (bool) – If set, the value the tag has to be set to. Default is unset
TCPRule([tcp])

Matches question received over TCP if tcp is true, over UDP otherwise.

Parameters:tcp (bool) – Match TCP traffic. Default is true.
TrailingDataRule()

Matches if the query has trailing data.

PoolAvailableRule(poolname)

New in version 1.3.3.

Check whether a pool has any servers available to handle queries

--- Send queries to default pool when servers are available
addAction(PoolAvailableRule(""), PoolAction(""))
--- Send queries to fallback pool if not
addAction(AllRule(), PoolAction("fallback"))
Parameters:poolname (string) – Pool to check

Combining Rules

AndRule(selectors)

Matches traffic if all selectors match.

Parameters:selectors ({Rule}) – A table of Rules
NotRule(selector)

Matches the traffic if the selector rule does not match;

Parameters:selector (Rule) – A Rule
OrRule(selectors)

Matches the traffic if one or more of the the selectors Rules does match.

Parameters:selector ({Rule}) – A table of Rules

Convenience Functions

makeRule(rule)

Make a NetmaskGroupRule() or a SuffixMatchNodeRule(), depending on it is called. makeRule("0.0.0.0/0") will for example match all IPv4 traffic, makeRule({"be","nl","lu"}) will match all Benelux DNS traffic.

Parameters:rule (string) – A string to convert to a rule.

Actions

Matching Packets (Selectors) need to be combined with an action for them to actually do something with the matched packets. Some actions allow further processing of rules, this is noted in their description. The following actions exist.

AllowAction()

Let these packets go through.

AllowResponseAction()

Let these packets go through.

ContinueAction(action)

New in version 1.4.0.

Execute the specified action and override its return with None, making it possible to continue the processing. Subsequent rules are processed after this action.

Parameters:action (int) – Any other action
DelayAction(milliseconds)

Delay the response by the specified amount of milliseconds (UDP-only). Subsequent rules are processed after this action.

Parameters:milliseconds (int) – The amount of milliseconds to delay the response
DelayResponseAction(milliseconds)

Delay the response by the specified amount of milliseconds (UDP-only). Subsequent rules are processed after this action.

Parameters:milliseconds (int) – The amount of milliseconds to delay the response
DisableECSAction()

Disable the sending of ECS to the backend. Subsequent rules are processed after this action.

DisableValidationAction()

Set the CD bit in the query and let it go through.

DnstapLogAction(identity, logger[, alterFunction])

New in version 1.3.0.

Send the the current query to a remote logger as a dnstap message. alterFunction is a callback, receiving a DNSQuestion and a DnstapMessage, that can be used to modify the message. Subsequent rules are processed after this action.

Parameters:
  • identity (string) – Server identity to store in the dnstap message
  • logger – The FrameStreamLogger or RemoteLogger object to write to
  • alterFunction – A Lua function to alter the message before sending
DnstapLogResponseAction(identity, logger[, alterFunction])

New in version 1.3.0.

Send the the current response to a remote logger as a dnstap message. alterFunction is a callback, receiving a DNSQuestion and a DnstapMessage, that can be used to modify the message. Subsequent rules are processed after this action.

Parameters:
  • identity (string) – Server identity to store in the dnstap message
  • logger – The FrameStreamLogger or RemoteLogger object to write to
  • alterFunction – A Lua function to alter the message before sending
DropAction()

Drop the packet.

DropResponseAction()

Drop the packet.

ECSOverrideAction(override)

Whether an existing EDNS Client Subnet value should be overridden (true) or not (false). Subsequent rules are processed after this action.

Parameters:override (bool) – Whether or not to override ECS value
ECSPrefixLengthAction(v4, v6)

Set the ECS prefix length. Subsequent rules are processed after this action.

Parameters:
  • v4 (int) – The IPv4 netmask length
  • v6 (int) – The IPv6 netmask length
ERCodeAction(rcode[, options])

New in version 1.4.0.

Changed in version 1.5.0: Added the optional parameter options.

Reply immediately by turning the query into a response with the specified EDNS extended rcode. rcode can be specified as an integer or as one of the built-in RCode.

Parameters:
  • rcode (int) – The extended RCODE to respond with.
  • options (table) – A table with key: value pairs with options.

Options:

  • aa: bool - Set the AA bit to this value (true means the bit is set, false means it’s cleared). Default is to clear it.
  • ad: bool - Set the AD bit to this value (true means the bit is set, false means it’s cleared). Default is to clear it.
  • ra: bool - Set the RA bit to this value (true means the bit is set, false means it’s cleared). Default is to copy the value of the RD bit from the incoming query.
HTTPStatusAction(status, body, contentType=""[, options])

New in version 1.4.0.

Changed in version 1.5.0: Added the optional parameter options.

Return an HTTP response with a status code of ‘’status’’. For HTTP redirects, ‘’body’’ should be the redirect URL.

Parameters:
  • status (int) – The HTTP status code to return.
  • body (string) – The body of the HTTP response, or a URL if the status code is a redirect (3xx).
  • contentType (string) – The HTTP Content-Type header to return for a 200 response, ignored otherwise. Default is ‘’application/dns-message’’.
  • options (table) – A table with key: value pairs with options.

Options:

  • aa: bool - Set the AA bit to this value (true means the bit is set, false means it’s cleared). Default is to clear it.
  • ad: bool - Set the AD bit to this value (true means the bit is set, false means it’s cleared). Default is to clear it.
  • ra: bool - Set the RA bit to this value (true means the bit is set, false means it’s cleared). Default is to copy the value of the RD bit from the incoming query.
KeyValueStoreLookupAction(kvs, lookupKey, destinationTag)

New in version 1.4.0.

As of 1.4.0, this code is considered experimental.

Does a lookup into the key value store referenced by ‘kvs’ using the key returned by ‘lookupKey’, and storing the result if any into the tag named ‘destinationTag’. The store can be a CDB (newCDBKVStore()) or a LMDB database (newLMDBKVStore()). The key can be based on the qname (KeyValueLookupKeyQName() and KeyValueLookupKeySuffix()), source IP (KeyValueLookupKeySourceIP()) or the value of an existing tag (KeyValueLookupKeyTag()).

Parameters:
  • kvs (KeyValueStore) – The key value store to query
  • lookupKey (KeyValueLookupKey) – The key to use for the lookup
  • destinationTag (string) – The name of the tag to store the result into
LogAction([filename[, binary[, append[, buffered[, verboseOnly[, includeTimestamp]]]]]])

Changed in version 1.4.0: Added the optional parameters verboseOnly and includeTimestamp, made filename optional.

Log a line for each query, to the specified file if any, to the console (require verbose) if the empty string is given as filename.

If an empty string is supplied in the file name, the logging is done to stdout, and only in verbose mode by default. This can be changed by setting verboseOnly to false.

When logging to a file, the binary optional parameter specifies whether we log in binary form (default) or in textual form. Before 1.4.0 the binary log format only included the qname and qtype. Since 1.4.0 it includes an optional timestamp, the query ID, qname, qtype, remote address and port.

The append optional parameter specifies whether we open the file for appending or truncate each time (default). The buffered optional parameter specifies whether writes to the file are buffered (default) or not.

Subsequent rules are processed after this action.

Parameters:
  • filename (string) – File to log to. Set to an empty string to log to the normal stdout log, this only works when -v is set on the command line.
  • binary (bool) – Do binary logging. Default true
  • append (bool) – Append to the log. Default false
  • buffered (bool) – Use buffered I/O. Default true
  • verboseOnly (bool) – Whether to log only in verbose mode when logging to stdout. Default is true
  • includeTimestamp (bool) – Whether to include a timestamp for every entry. Default is false
LogResponseAction([filename[, append[, buffered[, verboseOnly[, includeTimestamp]]]]]])

New in version 1.5.0.

Log a line for each response, to the specified file if any, to the console (require verbose) if the empty string is given as filename.

If an empty string is supplied in the file name, the logging is done to stdout, and only in verbose mode by default. This can be changed by setting verboseOnly to false.

The append optional parameter specifies whether we open the file for appending or truncate each time (default). The buffered optional parameter specifies whether writes to the file are buffered (default) or not.

Subsequent rules are processed after this action.

Parameters:
  • filename (string) – File to log to. Set to an empty string to log to the normal stdout log, this only works when -v is set on the command line.
  • append (bool) – Append to the log. Default false
  • buffered (bool) – Use buffered I/O. Default true
  • verboseOnly (bool) – Whether to log only in verbose mode when logging to stdout. Default is true
  • includeTimestamp (bool) – Whether to include a timestamp for every entry. Default is false
LuaAction(function)

Invoke a Lua function that accepts a DNSQuestion.

The function should return a DNSAction. If the Lua code fails, ServFail is returned.

Parameters:function (string) – the name of a Lua function
LuaResponseAction(function)

Invoke a Lua function that accepts a DNSResponse.

The function should return a DNSResponseAction. If the Lua code fails, ServFail is returned.

Parameters:function (string) – the name of a Lua function
MacAddrAction(option)

Add the source MAC address to the query as EDNS0 option option. This action is currently only supported on Linux. Subsequent rules are processed after this action.

Parameters:option (int) – The EDNS0 option number
NoneAction()

Does nothing. Subsequent rules are processed after this action.

NoRecurseAction()

Strip RD bit from the question, let it go through. Subsequent rules are processed after this action.

PoolAction(poolname)

Send the packet into the specified pool.

Parameters:poolname (string) – The name of the pool
QPSAction(maxqps)

Drop a packet if it does exceed the maxqps queries per second limits. Letting the subsequent rules apply otherwise.

Parameters:maxqps (int) – The QPS limit
QPSPoolAction(maxqps, poolname)

Send the packet into the specified pool only if it does not exceed the maxqps queries per second limits. Letting the subsequent rules apply otherwise.

Parameters:
  • maxqps (int) – The QPS limit for that pool
  • poolname (string) – The name of the pool
RCodeAction(rcode[, options])

Changed in version 1.5.0: Added the optional parameter options.

Reply immediately by turning the query into a response with the specified rcode. rcode can be specified as an integer or as one of the built-in RCode.

Parameters:
  • rcode (int) – The RCODE to respond with.
  • options (table) – A table with key: value pairs with options.

Options:

  • aa: bool - Set the AA bit to this value (true means the bit is set, false means it’s cleared). Default is to clear it.
  • ad: bool - Set the AD bit to this value (true means the bit is set, false means it’s cleared). Default is to clear it.
  • ra: bool - Set the RA bit to this value (true means the bit is set, false means it’s cleared). Default is to copy the value of the RD bit from the incoming query.
RemoteLogAction(remoteLogger[, alterFunction[, options]])

Changed in version 1.3.0: options optional parameter added.

Changed in version 1.4.0: ipEncryptKey optional key added to the options table.

Send the content of this query to a remote logger via Protocol Buffer. alterFunction is a callback, receiving a DNSQuestion and a DNSDistProtoBufMessage, that can be used to modify the Protocol Buffer content, for example for anonymization purposes. Subsequent rules are processed after this action.

Parameters:
  • remoteLogger (string) – The remoteLogger object to write to
  • alterFunction (string) – Name of a function to modify the contents of the logs before sending
  • options (table) – A table with key: value pairs.

Options:

  • serverID="": str - Set the Server Identity field.
  • ipEncryptKey="": str - A key, that can be generated via the makeIPCipherKey() function, to encrypt the IP address of the requestor for anonymization purposes. The encryption is done using ipcrypt for IPv4 and a 128-bit AES ECB operation for IPv6.
RemoteLogResponseAction(remoteLogger[, alterFunction[, includeCNAME[, options]]])

Changed in version 1.3.0: options optional parameter added.

Changed in version 1.4.0: ipEncryptKey optional key added to the options table.

Send the content of this response to a remote logger via Protocol Buffer. alterFunction is the same callback that receiving a DNSQuestion and a DNSDistProtoBufMessage, that can be used to modify the Protocol Buffer content, for example for anonymization purposes. includeCNAME indicates whether CNAME records inside the response should be parsed and exported. The default is to only exports A and AAAA records. Subsequent rules are processed after this action.

Parameters:
  • remoteLogger (string) – The remoteLogger object to write to
  • alterFunction (string) – Name of a function to modify the contents of the logs before sending
  • includeCNAME (bool) – Whether or not to parse and export CNAMEs. Default false
  • options (table) – A table with key: value pairs.

Options:

  • serverID="": str - Set the Server Identity field.
  • ipEncryptKey="": str - A key, that can be generated via the makeIPCipherKey() function, to encrypt the IP address of the requestor for anonymization purposes. The encryption is done using ipcrypt for IPv4 and a 128-bit AES ECB operation for IPv6.
SetECSAction(v4[, v6])

New in version 1.3.1.

Set the ECS prefix and prefix length sent to backends to an arbitrary value. If both IPv4 and IPv6 masks are supplied the IPv4 one will be used for IPv4 clients and the IPv6 one for IPv6 clients. Otherwise the first mask is used for both, and can actually be an IPv6 mask. Subsequent rules are processed after this action.

Parameters:
  • v4 (string) – The IPv4 netmask, for example “192.0.2.1/32”
  • v6 (string) – The IPv6 netmask, if any
SkipCacheAction()

Don’t lookup the cache for this query, don’t store the answer.

SNMPTrapAction([message])

Send an SNMP trap, adding the optional message string as the query description. Subsequent rules are processed after this action.

Parameters:message (string) – The message to include
SNMPTrapResponseAction([message])

Send an SNMP trap, adding the optional message string as the query description. Subsequent rules are processed after this action.

Parameters:message (string) – The message to include
SpoofAction(ip[, options])
SpoofAction(ips[, options])

Changed in version 1.5.0: Added the optional parameter options.

Forge a response with the specified IPv4 (for an A query) or IPv6 (for an AAAA) addresses. If you specify multiple addresses, all that match the query type (A, AAAA or ANY) will get spoofed in.

Parameters:
  • ip (string) – An IPv4 and/or IPv6 address to spoof
  • ips ({string}) – A table of IPv4 and/or IPv6 addresses to spoof
  • options (table) – A table with key: value pairs with options.

Options:

  • aa: bool - Set the AA bit to this value (true means the bit is set, false means it’s cleared). Default is to clear it.
  • ad: bool - Set the AD bit to this value (true means the bit is set, false means it’s cleared). Default is to clear it.
  • ra: bool - Set the RA bit to this value (true means the bit is set, false means it’s cleared). Default is to copy the value of the RD bit from the incoming query.
SpoofCNAMEAction(cname[, options])

Changed in version 1.5.0: Added the optional parameter options.

Forge a response with the specified CNAME value.

Parameters:
  • cname (string) – The name to respond with
  • options (table) – A table with key: value pairs with options.

Options:

  • aa: bool - Set the AA bit to this value (true means the bit is set, false means it’s cleared). Default is to clear it.
  • ad: bool - Set the AD bit to this value (true means the bit is set, false means it’s cleared). Default is to clear it.
  • ra: bool - Set the RA bit to this value (true means the bit is set, false means it’s cleared). Default is to copy the value of the RD bit from the incoming query.
TagAction(name, value)

New in version 1.3.0.

Associate a tag named name with a value of value to this query, that will be passed on to the response. Subsequent rules are processed after this action.

Parameters:
  • name (string) – The name of the tag to set
  • value (string) – The value of the tag
TagResponseAction(name, value)

New in version 1.3.0.

Associate a tag named name with a value of value to this response. Subsequent rules are processed after this action.

Parameters:
  • name (string) – The name of the tag to set
  • value (string) – The value of the tag
TCAction()

Create answer to query with TC and RD bits set, to force the client to TCP.

TeeAction(remote[, addECS])

Send copy of query to remote, keep stats on responses. If addECS is set to true, EDNS Client Subnet information will be added to the query.

Parameters:
  • remote (string) – An IP:PORT conbination to send the copied queries to
  • addECS (bool) – Whether or not to add ECS information. Default false
TempFailureCacheTTLAction(ttl)

Set the cache TTL to use for ServFail and Refused replies. TTL is not applied for successful replies.

Parameters:ttl (int) – Cache TTL for temporary failure replies