.. highlight:: none .. _Configuration Reference: *********************** Configuration Reference *********************** .. _Description: Description =========== Configuration files for Knot DNS use simplified YAML format. Simplified means that not all of the features are supported. For the description of configuration items, we have to declare a meaning of the following symbols: - *INT* – Integer - *STR* – Textual string - *HEXSTR* – Hexadecimal string (with ``0x`` prefix) - *BOOL* – Boolean value (``on``/``off`` or ``true``/``false``) - *TIME* – Number of seconds, an integer with possible time multiplier suffix (``s`` ~ 1, ``m`` ~ 60, ``h`` ~ 3600 or ``d`` ~ 24 * 3600) - *SIZE* – Number of bytes, an integer with possible size multiplier suffix (``B`` ~ 1, ``K`` ~ 1024, ``M`` ~ 1024^2 or ``G`` ~ 1024^3) - *BASE64* – Base64 encoded string - *ADDR* – IPv4 or IPv6 address - *DNAME* – Domain name - ... – Multi-valued item, order of the values is preserved - [ ] – Optional value - \| – Choice There are 11 main sections (``server``, ``control``, ``log``, ``statistics``, ``keystore``, ``policy``, ``key``, ``acl``, ``remote``, ``template``, and ``zone``) and module sections with the ``mod-`` prefix. Most of the sections (excluding ``server``, ``control``, and ``statistics``) are sequences of settings blocks. Each settings block begins with a unique identifier, which can be used as a reference from other sections (such identifier must be defined in advance). A multi-valued item can be specified either as a YAML sequence:: address: [10.0.0.1, 10.0.0.2] or as more single-valued items each on an extra line:: address: 10.0.0.1 address: 10.0.0.2 If an item value contains spaces or other special characters, it is necessary to enclose such value within double quotes ``"`` ``"``. .. _Comments: Comments ======== A comment begins with a ``#`` character and is ignored during processing. Also each configuration section or sequence block allows a permanent comment using the ``comment`` item which is stored in the server beside the configuration. .. _Includes: Includes ======== Another configuration file or files, matching a pattern, can be included at the top level in the current file. If the path is not absolute, then it is considered to be relative to the current file. The pattern can be an arbitrary string meeting POSIX *glob* requirements, e.g. dir/\*.conf. Matching files are processed in sorted order. :: include: STR .. _Server section: Server section ============== General options related to the server. :: server: identity: [STR] version: [STR] nsid: [STR|HEXSTR] rundir: STR user: STR[:STR] pidfile: STR udp-workers: INT tcp-workers: INT background-workers: INT async-start: BOOL tcp-handshake-timeout: TIME tcp-idle-timeout: TIME tcp-reply-timeout: TIME max-tcp-clients: INT max-udp-payload: SIZE max-ipv4-udp-payload: SIZE max-ipv6-udp-payload: SIZE listen: ADDR[@INT] ... .. _server_identity: identity -------- An identity of the server returned in the response to the query for TXT record ``id.server.`` or ``hostname.bind.`` in the CHAOS class (see RFC 4892). Set empty value to disable. *Default:* FQDN hostname .. _server_version: version ------- A version of the server software returned in the response to the query for TXT record ``version.server.`` or ``version.bind.`` in the CHAOS class (see RFC 4892). Set empty value to disable. *Default:* server version .. _server_nsid: nsid ---- A DNS name server identifier (see RFC 5001). Set empty value to disable. *Default:* FQDN hostname .. _server_rundir: rundir ------ A path for storing run-time data (PID file, unix sockets, etc.). *Default:* ``${localstatedir}/run/knot`` (configured with ``--with-rundir=path``) .. _server_user: user ---- A system user with an optional system group (``user:group``) under which the server is run after starting and binding to interfaces. Linux capabilities are employed if supported. *Default:* root:root .. _server_pidfile: pidfile ------- A PID file location. *Default:* :ref:`rundir`/knot.pid .. _server_udp-workers: udp-workers ----------- A number of UDP workers (threads) used to process incoming queries over UDP. *Default:* auto-estimated optimal value based on the number of online CPUs .. _server_tcp-workers: tcp-workers ----------- A number of TCP workers (threads) used to process incoming queries over TCP. *Default:* auto-estimated optimal value based on the number of online CPUs .. _server_background-workers: background-workers ------------------ A number of workers (threads) used to execute background operations (zone loading, zone updates, etc.). *Default:* auto-estimated optimal value based on the number of online CPUs .. _server_async-start: async-start ----------- If enabled, server doesn't wait for the zones to be loaded and starts responding immediately with SERVFAIL answers until the zone loads. *Default:* off .. _server_tcp-handshake-timeout: tcp-handshake-timeout --------------------- Maximum time between newly accepted TCP connection and the first query. This is useful to disconnect inactive connections faster than connections that already made at least 1 meaningful query. *Default:* 5 .. _server_tcp-idle-timeout: tcp-idle-timeout ---------------- Maximum idle time between requests on a TCP connection. This also limits receiving of a single query, each query must be received in this time limit. *Default:* 20 .. _server_tcp-reply-timeout: tcp-reply-timeout ----------------- Maximum time to wait for an outgoing connection or for a reply to an issued request (SOA, NOTIFY, AXFR...). *Default:* 10 .. _server_max-tcp-clients: max-tcp-clients --------------- A maximum number of TCP clients connected in parallel, set this below the file descriptor limit to avoid resource exhaustion. *Default:* 100 .. _server_max-udp-payload: max-udp-payload --------------- Maximum EDNS0 UDP payload size default for both IPv4 and IPv6. *Default:* 4096 .. _server_max-ipv4-udp-payload: max-ipv4-udp-payload -------------------- Maximum EDNS0 UDP payload size for IPv4. *Default:* 4096 .. _server_max-ipv6-udp-payload: max-ipv6-udp-payload -------------------- Maximum EDNS0 UDP payload size for IPv6. *Default:* 4096 .. _server_listen: listen ------ One or more IP addresses where the server listens for incoming queries. Optional port specification (default is 53) can be appended to each address using ``@`` separator. Use ``0.0.0.0`` for all configured IPv4 addresses or ``::`` for all configured IPv6 addresses. *Default:* not set .. _Key section: Key section =========== Shared TSIG keys used to authenticate communication with the server. :: key: - id: DNAME algorithm: hmac-md5 | hmac-sha1 | hmac-sha224 | hmac-sha256 | hmac-sha384 | hmac-sha512 secret: BASE64 .. _key_id: id -- A key name identifier. .. _key_algorithm: algorithm --------- A key algorithm. *Default:* not set .. _key_secret: secret ------ Shared key secret. *Default:* not set .. _ACL section: ACL section =========== Access control list rule definitions. The ACLs are used to match incoming connections to allow or deny requested operation (zone transfer request, DDNS update, etc.). :: acl: - id: STR address: ADDR[/INT] | ADDR-ADDR ... key: key_id ... action: notify | transfer | update ... deny: BOOL .. _acl_id: id -- An ACL rule identifier. .. _acl_address: address ------- An ordered list of IP addresses, network subnets, or network ranges. The query must match one of them. Empty value means that address match is not required. *Default:* not set .. _acl_key: key --- An ordered list of :ref:`reference`\ s to TSIG keys. The query must match one of them. Empty value means that TSIG key is not required. *Default:* not set .. _acl_action: action ------ An ordered list of allowed (or denied) actions. Possible values: - ``transfer`` – Allow zone transfer - ``notify`` – Allow incoming notify - ``update`` – Allow zone updates *Default:* not set .. _acl_deny: deny ---- If enabled, instead of allowing, deny the specified :ref:`action`, :ref:`address`, :ref:`key`, or combination if these items. If no action is specified, deny all actions. *Default:* off .. _Control section: Control section =============== Configuration of the server control interface. :: control: listen: STR timeout: TIME .. _control_listen: listen ------ A UNIX socket path where the server listens for control commands. *Default:* :ref:`rundir`/knot.sock .. _control_timeout: timeout ------- Maximum time the control socket operations can take. Set 0 for infinity. *Default:* 5 .. _statistics_section: Statistics section ================== Periodic server statistics dumping. :: statistics: timer: TIME file: STR append: BOOL .. _statistics_timer: timer ----- A period after which all available statistics metrics will by written to the :ref:`file`. *Default:* not set .. _statistics_file: file ---- A file path of statistics output in the YAML format. *Default:* :ref:`rundir`/stats.yaml .. _statistics_append: append ------ If enabled, the output will be appended to the :ref:`file` instead of file replacement. *Default:* off .. _Keystore section: Keystore section ================ DNSSEC keystore configuration. :: keystore: - id: STR backend: pem | pkcs11 config: STR .. _keystore_id: id -- A keystore identifier. .. _keystore_backend: backend ------- A key storage backend type. A directory with PEM files or a PKCS #11 storage. *Default:* pem .. _keystore_config: config ------ A backend specific configuration. A directory with PEM files (the path can be specified as a relative path to :ref:`kasp-db`) or a configuration string for PKCS #11 storage. .. NOTE:: Example configuration string for PKCS #11:: "pkcs11:token=knot;pin-value=1234 /usr/lib64/pkcs11/libsofthsm2.so" *Default:* :ref:`kasp-db`/keys .. _Policy section: Policy section ============== DNSSEC policy configuration. :: policy: - id: STR keystore: STR manual: BOOL single-type-signing: BOOL algorithm: dsa | rsasha1 | dsa-nsec3-sha1 | rsasha1-nsec3-sha1 | rsasha256 | rsasha512 | ecdsap256sha256 | ecdsap384sha384 ksk-size: SIZE zsk-size: SIZE dnskey-ttl: TIME zsk-lifetime: TIME propagation-delay: TIME rrsig-lifetime: TIME rrsig-refresh: TIME nsec3: BOOL nsec3-iterations: INT nsec3-salt-length: INT nsec3-salt-lifetime: TIME .. _policy_id: id -- A policy identifier. .. _policy_keystore: keystore -------- A :ref:`reference` to a keystore holding private key material for zones. A special *default* value can be used for the default keystore settings. *Default:* default .. _policy_manual: manual ------ If enabled, automatic key management is not used. *Default:* off .. _policy_single-type-signing: single-type-signing ------------------- If enabled, Single-Type Signing Scheme is used in the automatic key management mode. .. NOTE:: Because key rollover is not supported yet, just one combined signing key is generated if none is available. *Default:* off .. _policy_algorithm: algorithm --------- An algorithm of signing keys and issued signatures. *Default:* ecdsap256sha256 .. _policy_ksk-size: ksk-size -------- A length of newly generated :abbr:`KSK (Key Signing Key)` keys. *Default:* 1024 (dsa*), 2048 (rsa*), 256 (ecdsap256*), 384 (ecdsap384*) .. _policy_zsk-size: zsk-size -------- A length of newly generated :abbr:`ZSK (Zone Signing Key)` keys. *Default:* see default for :ref:`ksk-size` .. _policy_dnskey-ttl: dnskey-ttl ---------- A TTL value for DNSKEY records added into zone apex. *Default:* zone SOA TTL .. NOTE:: has infuence over ZSK key lifetime .. _policy_zsk-lifetime: zsk-lifetime ------------ A period between ZSK publication and the next rollover initiation. *Default:* 30 days .. NOTE:: ZSK key lifetime is also infuenced by propagation-delay and dnskey-ttl .. _policy_propagation-delay: propagation-delay ----------------- An extra delay added for each key rollover step. This value should be high enough to cover propagation of data from the master server to all slaves. *Default:* 1 day .. NOTE:: has infuence over ZSK key lifetime .. _policy_rrsig-lifetime: rrsig-lifetime -------------- A validity period of newly issued signatures. *Default:* 14 days .. _policy_rrsig-refresh: rrsig-refresh ------------- A period how long before a signature expiration the signature will be refreshed. *Default:* 7 days .. _policy_nsec: nsec3 ----- Specifies if NSEC3 will be used instead of NSEC. *Default:* off .. _policy_nsec3-iterations: nsec3-iterations ---------------- A number of additional times the hashing is performed. *Default:* 5 .. _policy_nsec3-salt-length: nsec3-salt-length ----------------- A length of a salt field in octets, which is appended to the original owner name before hashing. *Default:* 8 .. _policy_nsec3-salt-lifetime: nsec3-salt-lifetime ------------------- A validity period of newly issued salt field. *Default:* 30 days .. _Remote section: Remote section ============== Definitions of remote servers for outgoing connections (source of a zone transfer, target for a notification, etc.). :: remote: - id: STR address: ADDR[@INT] ... via: ADDR[@INT] ... key: key_id .. _remote_id: id -- A remote identifier. .. _remote_address: address ------- An ordered list of destination IP addresses which are used for communication with the remote server. The addresses are tried in sequence unless the operation is successful. Optional destination port (default is 53) can be appended to the address using ``@`` separator. *Default:* not set .. _remote_via: via --- An ordered list of source IP addresses. The first address with the same family as the destination address is used. Optional source port (default is random) can be appended to the address using ``@`` separator. *Default:* not set .. _remote_key: key --- A :ref:`reference` to the TSIG key which is used to authenticate the communication with the remote server. *Default:* not set .. _Template section: Template section ================ A template is a shareable zone setting which can be used for configuration of many zones in one place. A special default template (with the *default* identifier) can be used for global querying configuration or as an implicit configuration if a zone doesn't have another template specified. :: template: - id: STR timer-db: STR journal-db: STR journal-db-mode: robust | asynchronous max-journal-db-size: SIZE global-module: STR/STR ... # All zone options (excluding 'template' item) .. _template_id: id -- A template identifier. .. _template_timer-db: timer-db -------- Specifies a path of the persistent timer database. The path can be specified as a relative path to the *default* template :ref:`storage`. .. NOTE:: This option is only available in the *default* template. *Default:* :ref:`storage`/timers .. _template_journal-db: journal-db ---------- Specifies a path of the persistent journal database. The path can be specified as a relative path to the *default* template :ref:`storage`. .. NOTE:: This option is only available in the *default* template. *Default:* :ref:`storage`/journal .. _template_journal-db-mode: journal-db-mode --------------- Specifies journal LMDB backend configuration, which influences performance and durability. Possible values: - ``robust`` – The journal DB disk sychronization ensures DB durability but is generally slower - ``asynchronous`` – The journal DB disk synchronization is optimized for better perfomance at the expense of lower DB durability; this mode is recommended only on slave nodes with many zones .. NOTE:: This option is only available in the *default* template. *Default:* robust .. _template_max-journal-db-size: max-journal-db-size ------------------- Hard limit for the common journal DB. There is no cleanup logic in journal to recover from reaching this limit: journal simply starts refusing changes across all zones. Decreasing this value has no effect if lower than actual DB file size. It is recommended to limit :ref:`max-journal-usage` per-zone instead of max-journal-size in most cases. Please keep this value large enough. This value also influences server's usage of virtual memory. .. NOTE:: This option is only available in the *default* template. *Default:* 20 GiB .. _template_global-module: global-module ------------- An ordered list of references to query modules in the form of *module_name* or *module_name/module_id*. These modules apply to all queries. .. NOTE:: This option is only available in the *default* template. *Default:* not set .. _Zone section: Zone section ============ Definition of zones served by the server. :: zone: - domain: DNAME template: template_id storage: STR file: STR master: remote_id ... ddns-master: remote_id notify: remote_id ... acl: acl_id ... semantic-checks: BOOL disable-any: BOOL zonefile-sync: TIME ixfr-from-differences: BOOL max-journal-usage: SIZE max-journal-depth: INT max-zone-size : SIZE dnssec-signing: BOOL dnssec-policy: STR kasp-db: STR request-edns-option: INT:[HEXSTR] serial-policy: increment | unixtime module: STR/STR ... .. _zone_domain: domain ------ A zone name identifier. .. _zone_template: template -------- A :ref:`reference` to a configuration template. *Default:* not set or *default* (if the template exists) .. _zone_storage: storage ------- A data directory for storing zone files, journal files and timers database. *Default:* ``${localstatedir}/lib/knot`` (configured with ``--with-storage=path``) .. _zone_file: file ---- A path to the zone file. Non absolute path is relative to :ref:`storage`. It is also possible to use the following formatters: - ``%c[``\ *N*\ ``]`` or ``%c[``\ *N*\ ``-``\ *M*\ ``]`` – means the *N*\ th character or a sequence of characters beginning from the *N*\ th and ending with the *M*\ th character of the textual zone name (see ``%s``). The indexes are counted from 0 from the left. All dots (including the terminal one) are considered. If the character is not available, the formatter has no effect. - ``%l[``\ *N*\ ``]`` – means the *N*\ th label of the textual zone name (see ``%s``). The index is counted from 0 from the right (0 ~ TLD). If the label is not available, the formatter has no effect. - ``%s`` – means the current zone name in the textual representation (beware of special characters which are escaped or encoded in the \\DDD form where DDD is corresponding decimal ASCII code). The zone name doesn't include the terminating dot (the result for the root zone is the empty string!). - ``%%`` – means the ``%`` character *Default:* :ref:`storage`/``%s``\ .zone .. _zone_master: master ------ An ordered list of :ref:`references` to zone master servers. *Default:* not set .. _zone_ddns-master: ddns-master ----------- A :ref:`reference` to zone primary master server. If not specified, the first :ref:`master` server is used. *Default:* not set .. _zone_notify: notify ------ An ordered list of :ref:`references` to remotes to which notify message is sent if the zone changes. *Default:* not set .. _zone_acl: acl --- An ordered list of :ref:`references` to ACL rules which can allow or disallow zone transfers, updates or incoming notifies. *Default:* not set .. _zone_semantic-checks: semantic-checks --------------- If enabled, extra zone file semantic checks are turned on. Several checks are enabled by default and cannot be turned off. An error in mandatory checks causes zone not to be loaded. An error in extra checks is logged only. Mandatory checks: - An extra record together with CNAME record (except for RRSIG and DS) - SOA record missing in the zone (RFC 1034) - DNAME records having records under it (DNAME children) (RFC 2672) Extra checks: - Missing NS record at the zone apex - Missing glue A or AAAA records - Broken or non-cyclic NSEC(3) chain - Wrong NSEC(3) type bitmap - Multiple NSEC records at the same node - Missing NSEC records at authoritative nodes - NSEC3 insecure delegation that is not part of Opt-out span - Wrong original TTL value in NSEC3 records - Wrong RDATA TTL value in RRSIG record - Signer name in RRSIG RR not the same as in DNSKEY - Signed RRSIG - Wrong key flags or wrong key in RRSIG record (not the same as ZSK) *Default:* off .. _zone_disable-any: disable-any ----------- If enabled, all authoritative ANY queries sent over UDP will be answered with an empty response and with the TC bit set. Use this option to minimize the risk of DNS reflection attack. *Default:* off .. _zone_zonefile-sync: zonefile-sync ------------- The time after which the current zone in memory will be synced with a zone file on the disk (see :ref:`file`). The server will serve the latest zone even after a restart using zone journal, but the zone file on the disk will only be synced after ``zonefile-sync`` time has expired (or after manual zone flush). This is applicable when the zone is updated via IXFR, DDNS or automatic DNSSEC signing. In order to disable automatic zonefile synchronization, -1 value can be used (manual zone flush is still possible). .. NOTE:: If you are serving large zones with frequent updates where the immediate sync with a zone file is not desirable, increase the value. .. WARNING:: If the zone file is not up-to-date, the zone should be flushed before its zone file editation or the SOA record must be untouched after editation. Otherwise the journal can't be applied. *Default:* 0 (immediate) .. _zone_ixfr-from-differences: ixfr-from-differences --------------------- If enabled, the server creates zone differences from changes you made to the zone file upon server reload. This option is relevant only if the server is a master server for the zone. .. NOTE:: This option has no effect with enabled :ref:`dnssec-signing`. *Default:* off .. _zone_max-journal-usage: max-journal-usage ----------------- Policy how much space in journal DB will the zone's journal occupy. *Default:* 100 MiB .. NOTE:: Journal DB may grow far above the sum of max-journal-usage across all zones, because of DB free space fragmentation. .. _zone_max_journal_depth: max-journal-depth ----------------- Maximum history length of journal. *Default:* 2^64 .. _zone_max_zone_size: max-zone-size ---------------- Maximum size of the zone. The size is measured as size of the zone records in wire format without compression. The limit is enforced for incoming zone transfers and dynamic updates. For incremental transfers (IXFR), the effective limit for the total size of the records in the transfer is twice the configured value. However the final size of the zone must satisfy the configured value. *Default:* 2^64 .. _zone_dnssec-signing: dnssec-signing -------------- If enabled, automatic DNSSEC signing for the zone is turned on. .. NOTE:: Cannot be enabled on a slave zone. *Default:* off .. _zone_dnssec-policy: dnssec-policy ------------- A :ref:`reference` to DNSSEC signing policy. A special *default* value can be used for the default policy settings. *Required* .. _zone_kasp-db: kasp-db ------- A KASP database path. Non absolute path is relative to :ref:`storage`. *Default:* :ref:`storage`/keys .. _zone_request_edns_option: request-edns-option ------------------- An arbitrary EDNS0 option which is included into a server request (AXFR, IXFR, SOA, or NOTIFY). The value is in the option_code:option_data format. *Default:* not set .. _zone_serial-policy: serial-policy ------------- Specifies how the zone serial is updated after a dynamic update or automatic DNSSEC signing. If the serial is changed by the dynamic update, no change is made. Possible values: - ``increment`` – The serial is incremented according to serial number arithmetic - ``unixtime`` – The serial is set to the current unix time .. NOTE:: If your serial was in other than unix time format, be careful with the transition to unix time. It may happen that the new serial will be \'lower\' than the old one. If this is the case, the transition should be done by hand (see RFC 1982). *Default:* increment .. _zone_module: module ------ An ordered list of references to query modules in the form of *module_name* or *module_name/module_id*. These modules apply only to the current zone queries. *Default:* not set .. _Logging section: Logging section =============== Server can be configured to log to the standard output, standard error output, syslog (or systemd journal if systemd is enabled) or into an arbitrary file. There are 6 logging severity levels: - ``critical`` – Non-recoverable error resulting in server shutdown - ``error`` – Recoverable error, action should be taken - ``warning`` – Warning that might require user action - ``notice`` – Server notice or hint - ``info`` – Informational message - ``debug`` – Debug messages (must be turned on at compile time) In the case of missing log section, ``warning`` or more serious messages will be logged to both standard error output and syslog. The ``info`` and ``notice`` messages will be logged to standard output. :: log: - target: stdout | stderr | syslog | STR server: critical | error | warning | notice | info | debug control: critical | error | warning | notice | info | debug zone: critical | error | warning | notice | info | debug any: critical | error | warning | notice | info | debug .. _log_target: target ------ A logging output. Possible values: - ``stdout`` – Standard output - ``stderr`` – Standard error output - ``syslog`` – Syslog - *file\_name* – File .. _log_server: server ------ Minimum severity level for messages related to general operation of the server that are logged. *Default:* not set .. _log_control: control ------- Minimum severity level for messages related to server control that are logged. *Default:* not set .. _log_zone: zone ---- Minimum severity level for messages related to zones that are logged. *Default:* not set .. _log_any: any --- Minimum severity level for all message types that are logged. *Default:* not set .. _mod-rrl: Module rrl ========== A response rate limiting module. :: mod-rrl: - id: STR rate-limit: INT slip: INT table-size: INT whitelist: ADDR[/INT] | ADDR-ADDR ... .. _mod-rrl_id: id -- A module identifier. .. _mod-rrl_rate-limit: rate-limit ---------- Rate limiting is based on the token bucket scheme. A rate basically represents a number of tokens available each second. Each response is processed and classified (based on several discriminators, e.g. source netblock, query type, zone name, rcode, etc.). Classified responses are then hashed and assigned to a bucket containing number of available tokens, timestamp and metadata. When available tokens are exhausted, response is dropped or sent as truncated (see :ref:`mod-rrl_slip`). Number of available tokens is recalculated each second. *Required* .. _mod-rrl_table-size: table-size ---------- Size of the hash table in a number of buckets. The larger the hash table, the lesser the probability of a hash collision, but at the expense of additional memory costs. Each bucket is estimated roughly to 32 bytes. The size should be selected as a reasonably large prime due to better hash function distribution properties. Hash table is internally chained and works well up to a fill rate of 90 %, general rule of thumb is to select a prime near 1.2 * maximum_qps. *Default:* 393241 .. _mod-rrl_slip: slip ---- As attacks using DNS/UDP are usually based on a forged source address, an attacker could deny services to the victim's netblock if all responses would be completely blocked. The idea behind SLIP mechanism is to send each N\ :sup:`th` response as truncated, thus allowing client to reconnect via TCP for at least some degree of service. It is worth noting, that some responses can't be truncated (e.g. SERVFAIL). - Setting the value to **0** will cause that all rate-limited responses will be dropped. The outbound bandwidth and packet rate will be strictly capped by the :ref:`mod-rrl_rate-limit` option. All legitimate requestors affected by the limit will face denial of service and will observe excessive timeouts. Therefore this setting is not recommended. - Setting the value to **1** will cause that all rate-limited responses will be sent as truncated. The amplification factor of the attack will be reduced, but the outbound data bandwidth won't be lower than the incoming bandwidth. Also the outbound packet rate will be the same as without RRL. - Setting the value to **2** will cause that half of the rate-limited responses will be dropped, the other half will be sent as truncated. With this configuration, both outbound bandwidth and packet rate will be lower than the inbound. On the other hand, the dropped responses enlarge the time window for possible cache poisoning attack on the resolver. - Setting the value to anything **larger than 2** will keep on decreasing the outgoing rate-limited bandwidth, packet rate, and chances to notify legitimate requestors to reconnect using TCP. These attributes are inversely proportional to the configured value. Setting the value high is not advisable. *Default:* 1 .. _mod-rrl_whitelist: whitelist --------- A list of IP addresses, network subnets, or network ranges to exempt from rate limiting. Empty list means that no incoming connection will be white-listed. *Default:* not set .. _Module dnstap: Module dnstap ============= The module dnstap allows query and response logging. For all queries logging, use this module in the *default* template. For zone-specific logging, use this module in the proper zone configuration. :: mod-dnstap: - id: STR sink: STR identity: STR version: STR log-queries: BOOL log-responses: BOOL .. _mod-dnstap_id: id -- A module identifier. .. _mod-dnstap_sink: sink ---- A sink path, which can be either a file or a UNIX socket when prefixed with ``unix:``. *Required* .. _mod-dnstap_identity: identity -------- A DNS server identity. Set empty value to disable. *Default:* FQDN hostname .. _mod-dnstap_version: version ------- A DNS server version. Set empty value to disable. *Default:* server version .. _mod-dnstap_log-queries: log-queries ----------- If enabled, query messages will be logged. *Default:* on .. _mod-dnstap_log-responses: log-responses ------------- If enabled, response messages will be logged. *Default:* on .. _Module online-sign: Module online-sign ================== The module provides online DNSSEC signing. Instead of pre-computing the zone signatures when the zone is loaded into the server or instead of loading an externally signed zone, the signatures are computed on-the-fly during answering. :: mod-online-sign: - id: STR policy: STR .. _mod-online-sign_id: id -- A module identifier. .. _mod-online-sign_policy: policy ------ A :ref:`reference` to DNSSEC signing policy. A special *default* value can be used for the default policy settings. .. _Module synth-record: Module synth-record =================== This module is able to synthesize either forward or reverse records for the given prefix and subnet. :: mod-synth-record: - id: STR type: forward | reverse prefix: STR origin: DNAME ttl: INT network: ADDR[/INT] | ADDR-ADDR .. _mod-synth-record_id: id -- A module identifier. .. _mod-synth-record_type: type ---- The type of generated records. Possible values: - ``forward`` – Forward records - ``reverse`` – Reverse records *Required* .. _mod-synth-record_prefix: prefix ------ A record owner prefix. .. NOTE:: The value doesn’t allow dots, address parts in the synthetic names are separated with a dash. *Default:* empty .. _mod-synth-record_origin: origin ------ A zone origin (only valid for the :ref:`reverse type`). *Required* .. _mod-synth-record_ttl: ttl --- Time to live of the generated records. *Default:* 3600 .. _mod-synth-record_network: network ------- An IP address, a network subnet, or a network range the query must match. *Required* .. _Module dnsproxy: Module dnsproxy =============== The module catches all unsatisfied queries and forwards them to the indicated server for resolution. :: mod-dnsproxy: - id: STR remote: remote_id timeout: INT fallback: BOOL catch-nxdomain: BOOL .. _mod-dnsproxy_id: id -- A module identifier. .. _mod-dnsproxy_remote: remote ------ A :ref:`reference` to a remote server where the queries are forwarded to. *Required* .. _mod-dnsproxy_timeout: timeout ------- A remote response timeout in milliseconds. *Default:* 500 .. _mod-dnsproxy_fallback: fallback -------- If enabled, localy unsatisfied queries leading to REFUSED (no zone) are forwarded. If disabled, all queries are directly forwarded without any local attempts to resolve them. *Default:* on .. _mod-dnsproxy_catch-nxdomain: catch-nxdomain -------------- If enabled, localy unsatisfied queries leading to NXDOMAIN are forwarded. This option is only relevant in the fallback mode. *Default:* off .. _Module rosedb: Module rosedb ============= The module provides a mean to override responses for certain queries before the available zones are searched for the record. :: mod-rosedb: - id: STR dbdir: STR .. _mod-rosedb_id: id -- A module identifier. .. _mod-rosedb_dbdir: dbdir ----- A path to the directory where the database is stored. *Required* .. _mod-stats: Module stats ============ The module provides incoming query processing statistics. .. NOTE:: Leading 16-bit message size over TCP is not considered. :: mod-stats: - id: STR request-protocol: BOOL server-operation: BOOL request-bytes: BOOL response-bytes: BOOL edns-presence: BOOL flag-presence: BOOL response-code: BOOL reply-nodata: BOOL query-type: BOOL query-size: BOOL reply-size: BOOL .. _mod-stats_id: id -- A module identifier. .. _mod-stats_request-protocol: request-protocol ---------------- If enabled, all incoming requests are counted by the network protocol: * udp4 - UDP over IPv4 * tcp4 - TCP over IPv4 * udp6 - UDP over IPv6 * tcp6 - TCP over IPv6 *Default:* on .. _mod-stats_server-operation: server-operation ---------------- If enabled, all incoming requests are counted by the server operation. The server operation is based on message header OpCode and message query (meta) type: * query - Normal query operation * update - Dynamic update operation * notify - NOTIFY request operation * axfr - Full zone transfer operation * ixfr - Incremental zone transfer operation * invalid - Invalid server operation *Default:* on .. _mod-stats_request-bytes: request-bytes ------------- If enabled, all incoming request bytes are counted by the server operation: * query - Normal query bytes * update - Dynamic update bytes * other - Other request bytes *Default:* on .. _mod-stats_response-bytes: response-bytes -------------- If enabled, outgoing response bytes are counted by the server operation: * reply - Normal response bytes * transfer - Zone transfer bytes * other - Other response bytes .. WARNING:: Dynamic update response bytes are not counted by this module. *Default:* on .. _mod-stats_edns-presence: edns-presence ------------- If enabled, EDNS pseudo section presence is counted by the message direction: * request - EDNS present in request * response - EDNS present in response *Default:* off .. _mod-stats_flag-presence: flag-presence ------------- If enabled, some message header flags are counted: * TC - Truncated Answer in response * DO - DNSSEC OK in request *Default:* off .. _mod-stats_response-code: response-code ------------- If enabled, outgoing response code is counted: * NOERROR * ... * NOTZONE * BADVERS * ... * BADCOOKIE * other - All other codes .. NOTE:: In the case of multi-message zone transfer response, just one counter is incremented. .. WARNING:: Dynamic update response code is not counted by this module. *Default:* on .. _mod-stats_reply-nodata: reply-nodata ------------ If enabled, NODATA pseudo RCODE (see RFC 2308, Section 2.2) is counted by the query type: * A * AAAA * other - All other types *Default:* off .. _mod-stats_query-type: query-type ---------- If enabled, normal query type is counted: * A (TYPE1) * ... * TYPE65 * SPF (TYPE99) * ... * TYPE110 * ANY (TYPE255) * ... * TYPE260 * other - All other types .. NOTE:: Not all assigned meta types (IXFR, AXFR,...) have their own counters, because such types are not processed as normal query. *Default:* off .. _mod-stats_query-size: query-size ---------- If enabled, normal query message size distribution is counted by the size range in bytes: * 0-15 * 16-31 * ... * 272-287 * 288-65535 *Default:* off .. _mod-stats_reply-size: reply-size ---------- If enabled, normal reply message size distribution is counted by the size range in bytes: * 0-15 * 16-31 * ... * 4080-4095 * 4096-65535 *Default:* off