There must be whitespace between keywords. Attribute keywords end with a colon
  ':'. An attribute is followed by a value, or its containing attributes in
  which case it is referred to as a clause. Clauses can be repeated throughout
  the file (or included files) to group attributes under the same clause.
Files can be included using the include: directive. It can
    appear anywhere, it accepts a single file name as argument. Processing
    continues as if the text from the included file was copied into the config
    file at that point. If also using chroot, using full path names for the
    included files works, relative pathnames for the included names work if the
    directory where the daemon is started equals its chroot/working directory or
    is specified before the include statement with directory: dir. Wildcards can
    be used to include multiple files, see glob(7).
For a more structural include option, the include-toplevel:
    directive can be used. This closes whatever clause is currently active (if
    any) and forces the use of clauses in the included files and right after
    this directive.
These options are part of the server: clause.
  - verbosity: <number>
- The verbosity number, level 0 means no verbosity, only errors. Level 1
      gives operational information. Level 2 gives detailed operational
      information including short information per query. Level 3 gives query
      level information, output per query. Level 4 gives algorithm level
      information. Level 5 logs client identification for cache misses. Default
      is level 1. The verbosity can also be increased from the commandline, see
      unbound(8).
- statistics-interval: <seconds>
- The number of seconds between printing statistics to the log for every
      thread. Disable with value 0 or "". Default is disabled. The
      histogram statistics are only printed if replies were sent during the
      statistics interval, requestlist statistics are printed for every interval
      (but can be 0). This is because the median calculation requires data to be
      present.
- statistics-cumulative: <yes or no>
- If enabled, statistics are cumulative since starting Unbound, without
      clearing the statistics counters after logging the statistics. Default is
      no.
- extended-statistics: <yes or no>
- If enabled, extended statistics are printed from
      unbound-control(8). Default is off, because keeping track of more
      statistics takes time. The counters are listed in
      unbound-control(8).
- statistics-inhibit-zero: <yes or no>
- If enabled, selected extended statistics with a value of 0 are inhibited
      from printing with unbound-control(8). These are query types, query
      classes, query opcodes, answer rcodes (except NOERROR, FORMERR, SERVFAIL,
      NXDOMAIN, NOTIMPL, REFUSED) and RPZ actions. Default is on.
- num-threads: <number>
- The number of threads to create to serve clients. Use 1 for no
    threading.
- port: <port number>
- The port number, default 53, on which the server responds to queries.
- interface: <ip address or interface name [@port]>
- Interface to use to connect to the network. This interface is listened to
      for queries from clients, and answers to clients are given from it. Can be
      given multiple times to work on several interfaces. If none are given the
      default is to listen to localhost. If an interface name is used instead of
      an ip address, the list of ip addresses on that interface are used. The
      interfaces are not changed on a reload (kill -HUP) but only on restart. A
      port number can be specified with @port (without spaces between interface
      and port number), if not specified the default port (from port) is
      used.
- ip-address: <ip address or interface name
    [@port]>
- Same as interface: (for ease of compatibility with nsd.conf).
- interface-automatic: <yes or no>
- Listen on all addresses on all (current and future) interfaces, detect the
      source interface on UDP queries and copy them to replies. This is a lot
      like ip-transparent, but this option services all interfaces whilst with
      ip-transparent you can select which (future) interfaces Unbound provides
      service on. This feature is experimental, and needs support in your OS for
      particular socket options. Default value is no.
- interface-automatic-ports: <string>
- List the port numbers that interface-automatic listens on. If empty, the
      default port is listened on. The port numbers are separated by spaces in
      the string. Default is "".
  
  - This can be used to have interface automatic to deal with the interface,
      and listen on the normal port number, by including it in the list, and
      also https or dns over tls port numbers by putting them in the list as
      well.
  - outgoing-interface: <ip address or ip6 netblock>
- Interface to use to connect to the network. This interface is used to send
      queries to authoritative servers and receive their replies. Can be given
      multiple times to work on several interfaces. If none are given the
      default (all) is used. You can specify the same interfaces in
      interface: and outgoing-interface: lines, the interfaces are
      then used for both purposes. Outgoing queries are sent via a random
      outgoing interface to counter spoofing.
  
  - If an IPv6 netblock is specified instead of an individual IPv6 address,
      outgoing UDP queries will use a randomised source address taken from the
      netblock to counter spoofing. Requires the IPv6 netblock to be routed to
      the host running Unbound, and requires OS support for unprivileged
      non-local binds (currently only supported on Linux). Several netblocks may
      be specified with multiple outgoing-interface: options, but do not
      specify both an individual IPv6 address and an IPv6 netblock, or the
      randomisation will be compromised. Consider combining with prefer-ip6:
      yes to increase the likelihood of IPv6 nameservers being selected for
      queries. On Linux you need these two commands to be able to use the
      freebind socket option to receive traffic for the ip6 netblock: ip -6 addr
      add mynetblock/64 dev lo && ip -6 route add local mynetblock/64
      dev lo
  - outgoing-range: <number>
- Number of ports to open. This number of file descriptors can be opened per
      thread. Must be at least 1. Default depends on compile options. Larger
      numbers need extra resources from the operating system. For performance a
      very large value is best, use libevent to make this possible.
- outgoing-port-permit: <port number or range>
- Permit Unbound to open this port or range of ports for use to send
      queries. A larger number of permitted outgoing ports increases resilience
      against spoofing attempts. Make sure these ports are not needed by other
      daemons. By default only ports above 1024 that have not been assigned by
      IANA are used. Give a port number or a range of the form
      "low-high", without spaces.
  
  - The outgoing-port-permit and outgoing-port-avoid statements
      are processed in the line order of the config file, adding the permitted
      ports and subtracting the avoided ports from the set of allowed ports. The
      processing starts with the non IANA allocated ports above 1024 in the set
      of allowed ports.
  - outgoing-port-avoid: <port number or range>
- Do not permit Unbound to open this port or range of ports for use to send
      queries. Use this to make sure Unbound does not grab a port that another
      daemon needs. The port is avoided on all outgoing interfaces, both IP4 and
      IP6. By default only ports above 1024 that have not been assigned by IANA
      are used. Give a port number or a range of the form "low-high",
      without spaces.
- outgoing-num-tcp: <number>
- Number of outgoing TCP buffers to allocate per thread. Default is 10. If
      set to 0, or if do-tcp is "no", no TCP queries to authoritative
      servers are done. For larger installations increasing this value is a good
      idea.
- incoming-num-tcp: <number>
- Number of incoming TCP buffers to allocate per thread. Default is 10. If
      set to 0, or if do-tcp is "no", no TCP queries from clients are
      accepted. For larger installations increasing this value is a good
    idea.
- edns-buffer-size: <number>
- Number of bytes size to advertise as the EDNS reassembly buffer size. This
      is the value put into datagrams over UDP towards peers. The actual buffer
      size is determined by msg-buffer-size (both for TCP and UDP). Do not set
      higher than that value. Default is 1232 which is the DNS Flag Day 2020
      recommendation. Setting to 512 bypasses even the most stringent path MTU
      problems, but is seen as extreme, since the amount of TCP fallback
      generated is excessive (probably also for this resolver, consider tuning
      the outgoing tcp number).
- max-udp-size: <number>
- Maximum UDP response size (not applied to TCP response). 65536 disables
      the udp response size maximum, and uses the choice from the client,
      always. Suggested values are 512 to 4096. Default is 1232. The default
      value is the same as the default for edns-buffer-size.
- stream-wait-size: <number>
- Number of bytes size maximum to use for waiting stream buffers. Default is
      4 megabytes. A plain number is in bytes, append 'k', 'm' or 'g' for
      kilobytes, megabytes or gigabytes (1024*1024 bytes in a megabyte). As TCP
      and TLS streams queue up multiple results, the amount of memory used for
      these buffers does not exceed this number, otherwise the responses are
      dropped. This manages the total memory usage of the server (under heavy
      use), the number of requests that can be queued up per connection is also
      limited, with further requests waiting in TCP buffers.
- msg-buffer-size: <number>
- Number of bytes size of the message buffers. Default is 65552 bytes,
      enough for 64 Kb packets, the maximum DNS message size. No message larger
      than this can be sent or received. Can be reduced to use less memory, but
      some requests for DNS data, such as for huge resource records, will result
      in a SERVFAIL reply to the client.
- msg-cache-size: <number>
- Number of bytes size of the message cache. Default is 4 megabytes. A plain
      number is in bytes, append 'k', 'm' or 'g' for kilobytes, megabytes or
      gigabytes (1024*1024 bytes in a megabyte).
- msg-cache-slabs: <number>
- Number of slabs in the message cache. Slabs reduce lock contention by
      threads. Must be set to a power of 2. Setting (close) to the number of
      cpus is a reasonable guess.
- num-queries-per-thread: <number>
- The number of queries that every thread will service simultaneously. If
      more queries arrive that need servicing, and no queries can be jostled out
      (see jostle-timeout), then the queries are dropped. This forces the
      client to resend after a timeout; allowing the server time to work on the
      existing queries. Default depends on compile options, 512 or 1024.
- jostle-timeout: <msec>
- Timeout used when the server is very busy. Set to a value that usually
      results in one roundtrip to the authority servers. If too many queries
      arrive, then 50% of the queries are allowed to run to completion, and the
      other 50% are replaced with the new incoming query if they have already
      spent more than their allowed time. This protects against denial of
      service by slow queries or high query rates. Default 200 milliseconds. The
      effect is that the qps for long-lasting queries is about
      (numqueriesperthread / 2) / (average time for such long queries) qps. The
      qps for short queries can be about (numqueriesperthread / 2) /
      (jostletimeout in whole seconds) qps per thread, about (1024/2)*5 = 2560
      qps by default.
- delay-close: <msec>
- Extra delay for timeouted UDP ports before they are closed, in msec.
      Default is 0, and that disables it. This prevents very delayed answer
      packets from the upstream (recursive) servers from bouncing against closed
      ports and setting off all sort of close-port counters, with eg. 1500 msec.
      When timeouts happen you need extra sockets, it checks the ID and remote
      IP of packets, and unwanted packets are added to the unwanted packet
      counter.
- udp-connect: <yes or no>
- Perform connect for UDP sockets that mitigates ICMP side channel leakage.
      Default is yes.
- unknown-server-time-limit: <msec>
- The wait time in msec for waiting for an unknown server to reply. Increase
      this if you are behind a slow satellite link, to eg. 1128. That would then
      avoid re-querying every initial query because it times out. Default is 376
      msec.
- so-rcvbuf: <number>
- If not 0, then set the SO_RCVBUF socket option to get more buffer space on
      UDP port 53 incoming queries. So that short spikes on busy servers do not
      drop packets (see counter in netstat -su). Default is 0 (use system
      value). Otherwise, the number of bytes to ask for, try "4m" on a
      busy server. The OS caps it at a maximum, on linux Unbound needs root
      permission to bypass the limit, or the admin can use sysctl
      net.core.rmem_max. On BSD change kern.ipc.maxsockbuf in /etc/sysctl.conf.
      On OpenBSD change header and recompile kernel. On Solaris ndd -set
      /dev/udp udp_max_buf 8388608.
- so-sndbuf: <number>
- If not 0, then set the SO_SNDBUF socket option to get more buffer space on
      UDP port 53 outgoing queries. This for very busy servers handles spikes in
      answer traffic, otherwise 'send: resource temporarily unavailable' can get
      logged, the buffer overrun is also visible by netstat -su. Default is 0
      (use system value). Specify the number of bytes to ask for, try
      "4m" on a very busy server. The OS caps it at a maximum, on
      linux Unbound needs root permission to bypass the limit, or the admin can
      use sysctl net.core.wmem_max. On BSD, Solaris changes are similar to
      so-rcvbuf.
- so-reuseport: <yes or no>
- If yes, then open dedicated listening sockets for incoming queries for
      each thread and try to set the SO_REUSEPORT socket option on each socket.
      May distribute incoming queries to threads more evenly. Default is yes. On
      Linux it is supported in kernels >= 3.9. On other systems, FreeBSD, OSX
      it may also work. You can enable it (on any platform and kernel), it then
      attempts to open the port and passes the option if it was available at
      compile time, if that works it is used, if it fails, it continues silently
      (unless verbosity 3) without the option. At extreme load it could be
      better to turn it off to distribute the queries evenly, reported for Linux
      systems (4.4.x).
- ip-transparent: <yes or no>
- If yes, then use IP_TRANSPARENT socket option on sockets where Unbound is
      listening for incoming traffic. Default no. Allows you to bind to
      non-local interfaces. For example for non-existent IP addresses that are
      going to exist later on, with host failover configuration. This is a lot
      like interface-automatic, but that one services all interfaces and with
      this option you can select which (future) interfaces Unbound provides
      service on. This option needs Unbound to be started with root permissions
      on some systems. The option uses IP_BINDANY on FreeBSD systems and
      SO_BINDANY on OpenBSD systems.
- ip-freebind: <yes or no>
- If yes, then use IP_FREEBIND socket option on sockets where Unbound is
      listening to incoming traffic. Default no. Allows you to bind to IP
      addresses that are nonlocal or do not exist, like when the network
      interface or IP address is down. Exists only on Linux, where the similar
      ip-transparent option is also available.
- ip-dscp: <number>
- The value of the Differentiated Services Codepoint (DSCP) in the
      differentiated services field (DS) of the outgoing IP packet headers. The
      field replaces the outdated IPv4 Type-Of-Service field and the IPv6
      traffic class field.
- rrset-cache-size: <number>
- Number of bytes size of the RRset cache. Default is 4 megabytes. A plain
      number is in bytes, append 'k', 'm' or 'g' for kilobytes, megabytes or
      gigabytes (1024*1024 bytes in a megabyte).
- rrset-cache-slabs: <number>
- Number of slabs in the RRset cache. Slabs reduce lock contention by
      threads. Must be set to a power of 2.
- cache-max-ttl: <seconds>
- Time to live maximum for RRsets and messages in the cache. Default is
      86400 seconds (1 day). When the TTL expires, the cache item has expired.
      Can be set lower to force the resolver to query for data often, and not
      trust (very large) TTL values. Downstream clients also see the lower
    TTL.
- cache-min-ttl: <seconds>
- Time to live minimum for RRsets and messages in the cache. Default is 0.
      If the minimum kicks in, the data is cached for longer than the domain
      owner intended, and thus less queries are made to look up the data. Zero
      makes sure the data in the cache is as the domain owner intended, higher
      values, especially more than an hour or so, can lead to trouble as the
      data in the cache does not match up with the actual data any more.
- cache-max-negative-ttl: <seconds>
- Time to live maximum for negative responses, these have a SOA in the
      authority section that is limited in time. Default is 3600. This applies
      to nxdomain and nodata answers.
- infra-host-ttl: <seconds>
- Time to live for entries in the host cache. The host cache contains
      roundtrip timing, lameness and EDNS support information. Default is
    900.
- infra-cache-slabs: <number>
- Number of slabs in the infrastructure cache. Slabs reduce lock contention
      by threads. Must be set to a power of 2.
- infra-cache-numhosts: <number>
- Number of hosts for which information is cached. Default is 10000.
- infra-cache-min-rtt: <msec>
- Lower limit for dynamic retransmit timeout calculation in infrastructure
      cache. Default is 50 milliseconds. Increase this value if using forwarders
      needing more time to do recursive name resolution.
- infra-cache-max-rtt: <msec>
- Upper limit for dynamic retransmit timeout calculation in infrastructure
      cache. Default is 2 minutes.
- infra-keep-probing: <yes or no>
- If enabled the server keeps probing hosts that are down, in the one probe
      at a time regime. Default is no. Hosts that are down, eg. they did not
      respond during the one probe at a time period, are marked as down and it
      may take infra-host-ttl time to get probed again.
- define-tag: <"list of tags">
- Define the tags that can be used with local-zone and access-control.
      Enclose the list between quotes ("") and put spaces between
      tags.
- do-ip4: <yes or no>
- Enable or disable whether ip4 queries are answered or issued. Default is
      yes.
- do-ip6: <yes or no>
- Enable or disable whether ip6 queries are answered or issued. Default is
      yes. If disabled, queries are not answered on IPv6, and queries are not
      sent on IPv6 to the internet nameservers. With this option you can disable
      the IPv6 transport for sending DNS traffic, it does not impact the
      contents of the DNS traffic, which may have ip4 and ip6 addresses in
    it.
- prefer-ip4: <yes or no>
- If enabled, prefer IPv4 transport for sending DNS queries to internet
      nameservers. Default is no. Useful if the IPv6 netblock the server has,
      the entire /64 of that is not owned by one operator and the reputation of
      the netblock /64 is an issue, using IPv4 then uses the IPv4 filters that
      the upstream servers have.
- prefer-ip6: <yes or no>
- If enabled, prefer IPv6 transport for sending DNS queries to internet
      nameservers. Default is no.
- do-udp: <yes or no>
- Enable or disable whether UDP queries are answered or issued. Default is
      yes.
- do-tcp: <yes or no>
- Enable or disable whether TCP queries are answered or issued. Default is
      yes.
- tcp-mss: <number>
- Maximum segment size (MSS) of TCP socket on which the server responds to
      queries. Value lower than common MSS on Ethernet (1220 for example) will
      address path MTU problem. Note that not all platform supports socket
      option to set MSS (TCP_MAXSEG). Default is system default MSS determined
      by interface MTU and negotiation between server and client.
- outgoing-tcp-mss: <number>
- Maximum segment size (MSS) of TCP socket for outgoing queries (from
      Unbound to other servers). Value lower than common MSS on Ethernet (1220
      for example) will address path MTU problem. Note that not all platform
      supports socket option to set MSS (TCP_MAXSEG). Default is system default
      MSS determined by interface MTU and negotiation between Unbound and other
      servers.
- tcp-idle-timeout: <msec>
- The period Unbound will wait for a query on a TCP connection. If this
      timeout expires Unbound closes the connection. This option defaults to
      30000 milliseconds. When the number of free incoming TCP buffers falls
      below 50% of the total number configured, the option value used is
      progressively reduced, first to 1% of the configured value, then to 0.2%
      of the configured value if the number of free buffers falls below 35% of
      the total number configured, and finally to 0 if the number of free
      buffers falls below 20% of the total number configured. A minimum timeout
      of 200 milliseconds is observed regardless of the option value used.
- tcp-reuse-timeout: <msec>
- The period Unbound will keep TCP persistent connections open to authority
      servers. This option defaults to 60000 milliseconds.
- max-reuse-tcp-queries: <number>
- The maximum number of queries that can be sent on a persistent TCP
      connection. This option defaults to 200 queries.
- tcp-auth-query-timeout: <number>
- Timeout in milliseconds for TCP queries to auth servers. This option
      defaults to 3000 milliseconds.
- edns-tcp-keepalive: <yes or no>
- Enable or disable EDNS TCP Keepalive. Default is no.
- edns-tcp-keepalive-timeout: <msec>
- The period Unbound will wait for a query on a TCP connection when EDNS TCP
      Keepalive is active. If this timeout expires Unbound closes the
      connection. If the client supports the EDNS TCP Keepalive option, Unbound
      sends the timeout value to the client to encourage it to close the
      connection before the server times out. This option defaults to 120000
      milliseconds. When the number of free incoming TCP buffers falls below 50%
      of the total number configured, the advertised timeout is progressively
      reduced to 1% of the configured value, then to 0.2% of the configured
      value if the number of free buffers falls below 35% of the total number
      configured, and finally to 0 if the number of free buffers falls below 20%
      of the total number configured. A minimum actual timeout of 200
      milliseconds is observed regardless of the advertised timeout.
- sock-queue-timeout: <sec>
- UDP queries that have waited in the socket buffer for a long time can be
      dropped. Default is 0, disabled. The time is set in seconds, 3 could be a
      good value to ignore old queries that likely the client does not need a
      reply for any more. This could happen if the host has not been able to
      service the queries for a while, i.e. Unbound is not running, and then is
      enabled again. It uses timestamp socket options.
- tcp-upstream: <yes or no>
- Enable or disable whether the upstream queries use TCP only for transport.
      Default is no. Useful in tunneling scenarios. If set to no you can specify
      TCP transport only for selected forward or stub zones using
      forward-tcp-upstream or stub-tcp-upstream respectively.
- udp-upstream-without-downstream: <yes or no>
- Enable udp upstream even if do-udp is no. Default is no, and this does not
      change anything. Useful for TLS service providers, that want no udp
      downstream but use udp to fetch data upstream.
- tls-upstream: <yes or no>
- Enabled or disable whether the upstream queries use TLS only for
      transport. Default is no. Useful in tunneling scenarios. The TLS contains
      plain DNS in TCP wireformat. The other server must support this (see
      tls-service-key). If you enable this, also configure a
      tls-cert-bundle or use tls-win-cert or tls-system-cert to load CA certs,
      otherwise the connections cannot be authenticated. This option enables TLS
      for all of them, but if you do not set this you can configure TLS
      specifically for some forward zones with forward-tls-upstream. And also
      with stub-tls-upstream.
- ssl-upstream: <yes or no>
- Alternate syntax for tls-upstream. If both are present in the
      config file the last is used.
- tls-service-key: <file>
- If enabled, the server provides DNS-over-TLS or DNS-over-HTTPS service on
      the TCP ports marked implicitly or explicitly for these services with
      tls-port or https-port. The file must contain the private key for the TLS
      session, the public certificate is in the tls-service-pem file and it must
      also be specified if tls-service-key is specified. The default is
      "", turned off. Enabling or disabling this service requires a
      restart (a reload is not enough), because the key is read while root
      permissions are held and before chroot (if any). The ports enabled
      implicitly or explicitly via tls-port: and https-port: do
      not provide normal DNS TCP service. Unbound needs to be compiled with
      libnghttp2 in order to provide DNS-over-HTTPS.
- ssl-service-key: <file>
- Alternate syntax for tls-service-key.
- tls-service-pem: <file>
- The public key certificate pem file for the tls service. Default is
      "", turned off.
- ssl-service-pem: <file>
- Alternate syntax for tls-service-pem.
- tls-port: <number>
- The port number on which to provide TCP TLS service, default 853, only
      interfaces configured with that port number as @number get the TLS
      service.
- ssl-port: <number>
- Alternate syntax for tls-port.
- tls-cert-bundle: <file>
- If null or "", no file is used. Set it to the certificate bundle
      file, for example "/etc/pki/tls/certs/ca-bundle.crt". These
      certificates are used for authenticating connections made to outside
      peers. For example auth-zone urls, and also DNS over TLS connections. It
      is read at start up before permission drop and chroot.
- ssl-cert-bundle: <file>
- Alternate syntax for tls-cert-bundle.
- tls-win-cert: <yes or no>
- Add the system certificates to the cert bundle certificates for
      authentication. If no cert bundle, it uses only these certificates.
      Default is no. On windows this option uses the certificates from the cert
      store. Use the tls-cert-bundle option on other systems. On other systems,
      this option enables the system certificates.
- tls-system-cert: <yes or no>
- This the same setting as the tls-win-cert setting, under a different name.
      Because it is not windows specific.
- tls-additional-port: <portnr>
- List portnumbers as tls-additional-port, and when interfaces are defined,
      eg. with the @port suffix, as this port number, they provide dns over TLS
      service. Can list multiple, each on a new statement.
- tls-session-ticket-keys: <file>
- If not "", lists files with 80 bytes of random contents that are
      used to perform TLS session resumption for clients using the Unbound
      server. These files contain the secret key for the TLS session tickets.
      First key use to encrypt and decrypt TLS session tickets. Other keys use
      to decrypt only. With this you can roll over to new keys, by generating a
      new first file and allowing decrypt of the old file by listing it after
      the first file for some time, after the wait clients are not using the old
      key any more and the old key can be removed. One way to create the file is
      dd if=/dev/random bs=1 count=80 of=ticket.dat The first 16 bytes should be
      different from the old one if you create a second key, that is the name
      used to identify the key. Then there is 32 bytes random data for an AES
      key and then 32 bytes random data for the HMAC key.
- tls-ciphers: <string with cipher list>
- Set the list of ciphers to allow when serving TLS. Use "" for
      defaults, and that is the default.
- tls-ciphersuites: <string with ciphersuites list>
- Set the list of ciphersuites to allow when serving TLS. This is for newer
      TLS 1.3 connections. Use "" for defaults, and that is the
      default.
- pad-responses: <yes or no>
- If enabled, TLS serviced queries that contained an EDNS Padding option
      will cause responses padded to the closest multiple of the size specified
      in pad-responses-block-size. Default is yes.
- pad-responses-block-size: <number>
- The block size with which to pad responses serviced over TLS. Only
      responses to padded queries will be padded. Default is 468.
- pad-queries: <yes or no>
- If enabled, all queries sent over TLS upstreams will be padded to the
      closest multiple of the size specified in pad-queries-block-size.
      Default is yes.
- pad-queries-block-size: <number>
- The block size with which to pad queries sent over TLS upstreams. Default
      is 128.
- tls-use-sni: <yes or no>
- Enable or disable sending the SNI extension on TLS connections. Default is
      yes. Changing the value requires a reload.
- https-port: <number>
- The port number on which to provide DNS-over-HTTPS service, default 443,
      only interfaces configured with that port number as @number get the HTTPS
      service.
- http-endpoint: <endpoint string>
- The HTTP endpoint to provide DNS-over-HTTPS service on. Default
      "/dns-query".
- http-max-streams: <number of streams>
- Number used in the SETTINGS_MAX_CONCURRENT_STREAMS parameter in the HTTP/2
      SETTINGS frame for DNS-over-HTTPS connections. Default 100.
- http-query-buffer-size: <size in bytes>
- Maximum number of bytes used for all HTTP/2 query buffers combined. These
      buffers contain (partial) DNS queries waiting for request stream
      completion. An RST_STREAM frame will be send to streams exceeding this
      limit. Default is 4 megabytes. A plain number is in bytes, append 'k', 'm'
      or 'g' for kilobytes, megabytes or gigabytes (1024*1024 bytes in a
      megabyte).
- http-response-buffer-size: <size in bytes>
- Maximum number of bytes used for all HTTP/2 response buffers combined.
      These buffers contain DNS responses waiting to be written back to the
      clients. An RST_STREAM frame will be send to streams exceeding this limit.
      Default is 4 megabytes. A plain number is in bytes, append 'k', 'm' or 'g'
      for kilobytes, megabytes or gigabytes (1024*1024 bytes in a
    megabyte).
- http-nodelay: <yes or no>
- Set TCP_NODELAY socket option on sockets used to provide DNS-over-HTTPS
      service. Ignored if the option is not available. Default is yes.
- http-notls-downstream: <yes or no>
- Disable use of TLS for the downstream DNS-over-HTTP connections. Useful
      for local back end servers. Default is no.
- proxy-protocol-port: <portnr>
- List port numbers as proxy-protocol-port, and when interfaces are defined,
      eg. with the @port suffix, as this port number, they support and expect
      PROXYv2. In this case the proxy address will only be used for the network
      communication and initial ACL (check if the proxy itself is denied/refused
      by configuration). The proxied address (if any) will then be used as the
      true client address and will be used where applicable for logging, ACL,
      DNSTAP, RPZ and IP ratelimiting. PROXYv2 is supported for UDP and TCP/TLS
      listening interfaces. There is no support for PROXYv2 on a DoH or DNSCrypt
      listening interface. Can list multiple, each on a new statement.
- use-systemd: <yes or no>
- Enable or disable systemd socket activation. Default is no.
- do-daemonize: <yes or no>
- Enable or disable whether the Unbound server forks into the background as
      a daemon. Set the value to no when Unbound runs as systemd service.
      Default is yes.
- tcp-connection-limit: <IP netblock> <limit>
- Allow up to limit simultaneous TCP connections from the given
      netblock. When at the limit, further connections are accepted but closed
      immediately. This option is experimental at this time.
- access-control: <IP netblock> <action>
- The netblock is given as an IP4 or IP6 address with /size appended for a
      classless network block. The action can be deny, refuse,
      allow, allow_setrd, allow_snoop, allow_cookie,
      deny_non_local or refuse_non_local. The most specific
      netblock match is used, if none match refuse is used. The order of
      the access-control statements therefore does not matter.
  
  - The deny action stops queries from hosts from that netblock.
- The refuse action stops queries too, but sends a DNS rcode REFUSED
      error message back.
- The allow action gives access to clients from that netblock. It
      gives only access for recursion clients (which is what almost all clients
      need). Nonrecursive queries are refused.
- The allow action does allow nonrecursive queries to access the
      local-data that is configured. The reason is that this does not involve
      the Unbound server recursive lookup algorithm, and static data is served
      in the reply. This supports normal operations where nonrecursive queries
      are made for the authoritative data. For nonrecursive queries any replies
      from the dynamic cache are refused.
- The allow_setrd action ignores the recursion desired (RD) bit and
      treats all requests as if the recursion desired bit is set. Note that this
      behavior violates RFC 1034 which states that a name server should never
      perform recursive service unless asked via the RD bit since this
      interferes with trouble shooting of name servers and their databases. This
      prohibited behavior may be useful if another DNS server must forward
      requests for specific zones to a resolver DNS server, but only supports
      stub domains and sends queries to the resolver DNS server with the RD bit
      cleared.
- The allow_snoop action gives nonrecursive access too. This give
      both recursive and non recursive access. The name allow_snoop
      refers to cache snooping, a technique to use nonrecursive queries to
      examine the cache contents (for malicious acts). However, nonrecursive
      queries can also be a valuable debugging tool (when you want to examine
      the cache contents). In that case use allow_snoop for your
      administration host.
- The allow_cookie action allows access to UDP queries that contain a
      valid DNS Cookie as specified in RFC 7873 and RFC 9018, when the
      answer-cookie option is enabled. UDP queries containing only a DNS
      Client Cookie and no Server Cookie, or an invalid DNS Cookie, will receive
      a BADCOOKIE response including a newly generated DNS Cookie, allowing
      clients to retry with that DNS Cookie. The allow_cookie action will
      also accept requests over stateful transports, regardless of the presence
      of an DNS Cookie and regardless of the answer-cookie setting. If
      ip-ratelimit is used, clients with a valid DNS Cookie will bypass
      the ratelimit. If a ratelimit for such clients is still needed,
      ip-ratelimit-cookie can be used instead.
- By default only localhost is allowed, the rest is refused.
      The default is refused, because that is protocol-friendly. The DNS
      protocol is not designed to handle dropped packets due to policy, and
      dropping may result in (possibly excessive) retried queries.
- The deny_non_local and refuse_non_local settings are for hosts that are
      only allowed to query for the authoritative local-data, they are not
      allowed full recursion but only the static data. With deny_non_local,
      messages that are disallowed are dropped, with refuse_non_local they
      receive error code REFUSED.
  - access-control-tag: <IP netblock> <"list of
    tags">
- Assign tags to access-control elements. Clients using this access control
      element use localzones that are tagged with one of these tags. Tags must
      be defined in define-tags. Enclose list of tags in quotes
      ("") and put spaces between tags. If access-control-tag is
      configured for a netblock that does not have an access-control, an
      access-control element with action allow is configured for this
      netblock.
- access-control-tag-action: <IP netblock> <tag>
    <action>
- Set action for particular tag for given access control element. If you
      have multiple tag values, the tag used to lookup the action is the first
      tag match between access-control-tag and local-zone-tag where
      "first" comes from the order of the define-tag values.
- access-control-tag-data: <IP netblock> <tag>
    <"resource record string">
- Set redirect data for particular tag for given access control
    element.
- access-control-view: <IP netblock> <view
    name>
- Set view for given access control element.
- interface-action: <ip address or interface name [@port]>
    <action>
- Similar to access-control: but for interfaces.
  
  - The action is the same as the ones defined under access-control:.
      Interfaces are refused by default. By default only localhost (the
      IP netblock, not the loopback interface) is allowed through the
      default access-control: behavior.
- Note that the interface needs to be already specified with
      interface: and that any access-control*: setting overrides
      all interface-*: settings for targeted clients.
  - interface-tag: <ip address or interface name [@port]>
    <"list of tags">
- Similar to access-control-tag: but for interfaces.
  
  - Note that the interface needs to be already specified with
      interface: and that any access-control*: setting overrides
      all interface-*: settings for targeted clients.
  - interface-tag-action: <ip address or interface name [@port]>
    <tag> <action>
- Similar to access-control-tag-action: but for interfaces.
  
  - Note that the interface needs to be already specified with
      interface: and that any access-control*: setting overrides
      all interface-*: settings for targeted clients.
  - interface-tag-data: <ip address or interface name [@port]>
    <tag> <"resource record string">
- Similar to access-control-tag-data: but for interfaces.
  
  - Note that the interface needs to be already specified with
      interface: and that any access-control*: setting overrides
      all interface-*: settings for targeted clients.
  - interface-view: <ip address or interface name [@port]>
    <view name>
- Similar to access-control-view: but for interfaces.
  
  - Note that the interface needs to be already specified with
      interface: and that any access-control*: setting overrides
      all interface-*: settings for targeted clients.
  - chroot: <directory>
- If chroot is enabled, you should pass the configfile (from the
      commandline) as a full path from the original root. After the chroot has
      been performed the now defunct portion of the config file path is removed
      to be able to reread the config after a reload.
  
  - All other file paths (working dir, logfile, roothints, and key files) can
      be specified in several ways: as an absolute path relative to the new
      root, as a relative path to the working directory, or as an absolute path
      relative to the original root. In the last case the path is adjusted to
      remove the unused portion.
- The pidfile can be either a relative path to the working directory, or an
      absolute path relative to the original root. It is written just prior to
      chroot and dropping permissions. This allows the pidfile to be
      /var/run/unbound.pid and the chroot to be /var/unbound, for example. Note
      that Unbound is not able to remove the pidfile after termination when it
      is located outside of the chroot directory.
- Additionally, Unbound may need to access /dev/urandom (for entropy) from
      inside the chroot.
- If given a chroot is done to the given directory. By default chroot is
      enabled and the default is "/var/chroot/unbound". If you give
      "" no chroot is performed.
  - username: <name>
- If given, after binding the port the user privileges are dropped. Default
      is "_unbound". If you give username: "" no user change
      is performed.
  
  - If this user is not capable of binding the port, reloads (by signal HUP)
      will still retain the opened ports. If you change the port number in the
      config file, and that new port number requires privileges, then a reload
      will fail; a restart is needed.
  - directory: <directory>
- Sets the working directory for the program. Default is
      "/var/chroot/unbound/etc/unbound". On Windows the string
      "%EXECUTABLE%" tries to change to the directory that unbound.exe
      resides in. If you give a server: directory: dir before include: file
      statements then those includes can be relative to the working
    directory.
- logfile: <filename>
- If "" is given, logging goes to stderr, or nowhere once
      daemonized. The logfile is appended to, in the following format:
    
[seconds since 1970] unbound[pid:tid]: type: message.
    If this option is given, the use-syslog is option is set to "no".
      The logfile is reopened (for append) when the config file is reread, on
      SIGHUP.
- use-syslog: <yes or no>
- Sets Unbound to send log messages to the syslogd, using syslog(3).
      The log facility LOG_DAEMON is used, with identity "unbound".
      The logfile setting is overridden when use-syslog is turned on. The
      default is to log to syslog.
- log-identity: <string>
- If "" is given (default), then the name of the executable,
      usually "unbound" is used to report to the log. Enter a string
      to override it with that, which is useful on systems that run more than
      one instance of Unbound, with different configurations, so that the logs
      can be easily distinguished against.
- log-time-ascii: <yes or no>
- Sets logfile lines to use a timestamp in UTC ascii. Default is no, which
      prints the seconds since 1970 in brackets. No effect if using syslog, in
      that case syslog formats the timestamp printed into the log files.
- log-queries: <yes or no>
- Prints one line per query to the log, with the log timestamp and IP
      address, name, type and class. Default is no. Note that it takes time to
      print these lines which makes the server (significantly) slower. Odd
      (nonprintable) characters in names are printed as '?'.
- log-replies: <yes or no>
- Prints one line per reply to the log, with the log timestamp and IP
      address, name, type, class, return code, time to resolve, from cache and
      response size. Default is no. Note that it takes time to print these lines
      which makes the server (significantly) slower. Odd (nonprintable)
      characters in names are printed as '?'.
- log-tag-queryreply: <yes or no>
- Prints the word 'query' and 'reply' with log-queries and log-replies. This
      makes filtering logs easier. The default is off (for backwards
      compatibility).
- log-local-actions: <yes or no>
- Print log lines to inform about local zone actions. These lines are like
      the local-zone type inform prints out, but they are also printed for the
      other types of local zones.
- log-servfail: <yes or no>
- Print log lines that say why queries return SERVFAIL to clients. This is
      separate from the verbosity debug logs, much smaller, and printed at the
      error level, not the info level of debug info from verbosity.
- pidfile: <filename>
- The process id is written to the file. Default is
      "/var/run/unbound.pid". So,
    
kill -HUP `cat /var/run/unbound.pid`
    triggers a reload,
kill -TERM `cat /var/run/unbound.pid`
    gracefully terminates.
- root-hints: <filename>
- Read the root hints from this file. Default is nothing, using builtin
      hints for the IN class. The file has the format of zone files, with root
      nameserver names and addresses only. The default may become outdated, when
      servers change, therefore it is good practice to use a root-hints
    file.
- hide-identity: <yes or no>
- If enabled id.server and hostname.bind queries are refused.
- identity: <string>
- Set the identity to report. If set to "", the default, then the
      hostname of the server is returned.
- hide-version: <yes or no>
- If enabled version.server and version.bind queries are refused.
- version: <string>
- Set the version to report. If set to "", the default, then the
      package version is returned.
- hide-http-user-agent: <yes or no>
- If enabled the HTTP header User-Agent is not set. Use with caution as some
      webserver configurations may reject HTTP requests lacking this header. If
      needed, it is better to explicitly set the http-user-agent
    below.
- http-user-agent: <string>
- Set the HTTP User-Agent header for outgoing HTTP requests. If set to
      "", the default, then the package name and version are
    used.
- nsid: <string>
- Add the specified nsid to the EDNS section of the answer when queried with
      an NSID EDNS enabled packet. As a sequence of hex characters or with
      ascii_ prefix and then an ascii string.
- hide-trustanchor: <yes or no>
- If enabled trustanchor.unbound queries are refused.
- target-fetch-policy: <"list of
    numbers">
- Set the target fetch policy used by Unbound to determine if it should
      fetch nameserver target addresses opportunistically. The policy is
      described per dependency depth.
  
  - The number of values determines the maximum dependency depth that Unbound
      will pursue in answering a query. A value of -1 means to fetch all targets
      opportunistically for that dependency depth. A value of 0 means to fetch
      on demand only. A positive value fetches that many targets
      opportunistically.
- Enclose the list between quotes ("") and put spaces between
      numbers. The default is "3 2 1 0 0". Setting all zeroes, "0
      0 0 0 0" gives behaviour closer to that of BIND 9, while setting
      "-1 -1 -1 -1 -1" gives behaviour rumoured to be closer to that
      of BIND 8.
  - harden-short-bufsize: <yes or no>
- Very small EDNS buffer sizes from queries are ignored. Default is on, as
      described in the standard.
- harden-large-queries: <yes or no>
- Very large queries are ignored. Default is off, since it is legal protocol
      wise to send these, and could be necessary for operation if TSIG or EDNS
      payload is very large.
- harden-glue: <yes or no>
- Will trust glue only if it is within the servers authority. Default is
      yes.
- harden-dnssec-stripped: <yes or no>
- Require DNSSEC data for trust-anchored zones, if such data is absent, the
      zone becomes bogus. If turned off, and no DNSSEC data is received (or the
      DNSKEY data fails to validate), then the zone is made insecure, this
      behaves like there is no trust anchor. You could turn this off if you are
      sometimes behind an intrusive firewall (of some sort) that removes DNSSEC
      data from packets, or a zone changes from signed to unsigned to badly
      signed often. If turned off you run the risk of a downgrade attack that
      disables security for a zone. Default is yes.
- harden-below-nxdomain: <yes or no>
- From RFC 8020 (with title "NXDOMAIN: There Really Is Nothing
      Underneath"), returns nxdomain to queries for a name below another
      name that is already known to be nxdomain. DNSSEC mandates noerror for
      empty nonterminals, hence this is possible. Very old software might return
      nxdomain for empty nonterminals (that usually happen for reverse IP
      address lookups), and thus may be incompatible with this. To try to avoid
      this only DNSSEC-secure nxdomains are used, because the old software does
      not have DNSSEC. Default is yes. The nxdomain must be secure, this means
      nsec3 with optout is insufficient.
- harden-referral-path: <yes or no>
- Harden the referral path by performing additional queries for
      infrastructure data. Validates the replies if trust anchors are configured
      and the zones are signed. This enforces DNSSEC validation on nameserver NS
      sets and the nameserver addresses that are encountered on the referral
      path to the answer. Default no, because it burdens the authority servers,
      and it is not RFC standard, and could lead to performance problems because
      of the extra query load that is generated. Experimental option. If you
      enable it consider adding more numbers after the target-fetch-policy to
      increase the max depth that is checked to.
- harden-algo-downgrade: <yes or no>
- Harden against algorithm downgrade when multiple algorithms are advertised
      in the DS record. If no, allows the weakest algorithm to validate the
      zone. Default is no. Zone signers must produce zones that allow this
      feature to work, but sometimes they do not, and turning this option off
      avoids that validation failure.
- harden-unknown-additional: <yes or no>
- Harden against unknown records in the authority section and additional
      section. Default is no. If no, such records are copied from the upstream
      and presented to the client together with the answer. If yes, it could
      hamper future protocol developments that want to add records.
- use-caps-for-id: <yes or no>
- Use 0x20-encoded random bits in the query to foil spoof attempts. This
      perturbs the lowercase and uppercase of query names sent to authority
      servers and checks if the reply still has the correct casing. Disabled by
      default. This feature is an experimental implementation of draft
    dns-0x20.
- caps-exempt: <domain>
- Exempt the domain so that it does not receive caps-for-id perturbed
      queries. For domains that do not support 0x20 and also fail with fallback
      because they keep sending different answers, like some load balancers. Can
      be given multiple times, for different domains.
- caps-whitelist: <yes or no>
- Alternate syntax for caps-exempt.
- qname-minimisation: <yes or no>
- Send minimum amount of information to upstream servers to enhance privacy.
      Only send minimum required labels of the QNAME and set QTYPE to A when
      possible. Best effort approach; full QNAME and original QTYPE will be sent
      when upstream replies with a RCODE other than NOERROR, except when
      receiving NXDOMAIN from a DNSSEC signed zone. Default is yes.
- qname-minimisation-strict: <yes or no>
- QNAME minimisation in strict mode. Do not fall-back to sending full QNAME
      to potentially broken nameservers. A lot of domains will not be resolvable
      when this option in enabled. Only use if you know what you are doing. This
      option only has effect when qname-minimisation is enabled. Default is
    no.
- aggressive-nsec: <yes or no>
- Aggressive NSEC uses the DNSSEC NSEC chain to synthesize NXDOMAIN and
      other denials, using information from previous NXDOMAINs answers. Default
      is yes. It helps to reduce the query rate towards targets that get a very
      high nonexistent name lookup rate.
- private-address: <IP address or subnet>
- Give IPv4 of IPv6 addresses or classless subnets. These are addresses on
      your private network, and are not allowed to be returned for public
      internet names. Any occurrence of such addresses are removed from DNS
      answers. Additionally, the DNSSEC validator may mark the answers bogus.
      This protects against so-called DNS Rebinding, where a user browser is
      turned into a network proxy, allowing remote access through the browser to
      other parts of your private network. Some names can be allowed to contain
      your private addresses, by default all the local-data that you
      configured is allowed to, and you can specify additional names using
      private-domain. No private addresses are enabled by default. We
      consider to enable this for the RFC1918 private IP address space by
      default in later releases. That would enable private addresses for
      10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 169.254.0.0/16 fd00::/8 and
      fe80::/10, since the RFC standards say these addresses should not be
      visible on the public internet. Turning on 127.0.0.0/8 would hinder many
      spamblocklists as they use that. Adding ::ffff:0:0/96 stops IPv4-mapped
      IPv6 addresses from bypassing the filter.
- private-domain: <domain name>
- Allow this domain, and all its subdomains to contain private addresses.
      Give multiple times to allow multiple domain names to contain private
      addresses. Default is none.
- unwanted-reply-threshold: <number>
- If set, a total number of unwanted replies is kept track of in every
      thread. When it reaches the threshold, a defensive action is taken and a
      warning is printed to the log. The defensive action is to clear the rrset
      and message caches, hopefully flushing away any poison. A value of 10
      million is suggested. Default is 0 (turned off).
- do-not-query-address: <IP address>
- Do not query the given IP address. Can be IP4 or IP6. Append /num to
      indicate a classless delegation netblock, for example like 10.2.3.4/24 or
      2001::11/64.
- do-not-query-localhost: <yes or no>
- If yes, localhost is added to the do-not-query-address entries, both IP6
      ::1 and IP4 127.0.0.1/8. If no, then localhost can be used to send queries
      to. Default is yes.
- prefetch: <yes or no>
- If yes, message cache elements are prefetched before they expire to keep
      the cache up to date. Default is no. Turning it on gives about 10 percent
      more traffic and load on the machine, but popular items do not expire from
      the cache.
- prefetch-key: <yes or no>
- If yes, fetch the DNSKEYs earlier in the validation process, when a DS
      record is encountered. This lowers the latency of requests. It does use a
      little more CPU. Also if the cache is set to 0, it is no use. Default is
      no.
- deny-any: <yes or no>
- If yes, deny queries of type ANY with an empty response. Default is no. If
      disabled, Unbound responds with a short list of resource records if some
      can be found in the cache and makes the upstream type ANY query if there
      are none.
- rrset-roundrobin: <yes or no>
- If yes, Unbound rotates RRSet order in response (the random number is
      taken from the query ID, for speed and thread safety). Default is
    yes.
- minimal-responses: <yes or no>
- If yes, Unbound does not insert authority/additional sections into
      response messages when those sections are not required. This reduces
      response size significantly, and may avoid TCP fallback for some
      responses. This may cause a slight speedup. The default is yes, even
      though the DNS protocol RFCs mandate these sections, and the additional
      content could be of use and save roundtrips for clients. Because they are
      not used, and the saved roundtrips are easier saved with prefetch, whilst
      this is faster.
- disable-dnssec-lame-check: <yes or no>
- If true, disables the DNSSEC lameness check in the iterator. This check
      sees if RRSIGs are present in the answer, when dnssec is expected, and
      retries another authority if RRSIGs are unexpectedly missing. The
      validator will insist in RRSIGs for DNSSEC signed domains regardless of
      this setting, if a trust anchor is loaded.
- module-config: <"module names">
- Module configuration, a list of module names separated by spaces, surround
      the string with quotes (""). The modules can be respip,
      validator, or iterator (and possibly more, see below).
      Setting this to just "iterator" will result in a
      non-validating server. Setting this to "validator
      iterator" will turn on DNSSEC validation. The ordering of the
      modules is significant, the order decides the order of processing. You
      must also set trust-anchors for validation to be useful. Adding
      respip to the front will cause RPZ processing to be done on all
      queries. The default is "validator iterator".
  
  - When the server is built with EDNS client subnet support the default is
      "subnetcache validator iterator". Most modules
      that need to be listed here have to be listed at the beginning of the
      line. The subnetcachedb module has to be listed just before the iterator.
      The python module can be listed in different places, it then processes the
      output of the module it is just before. The dynlib module can be listed
      pretty much anywhere, it is only a very thin wrapper that allows dynamic
      libraries to run in its place.
  - trust-anchor-file: <filename>
- File with trusted keys for validation. Both DS and DNSKEY entries can
      appear in the file. The format of the file is the standard DNS Zone file
      format. Default is "", or no trust anchor file.
- auto-trust-anchor-file: <filename>
- File with trust anchor for one zone, which is tracked with RFC5011 probes.
      The probes are run several times per month, thus the machine must be
      online frequently. The initial file can be one with contents as described
      in trust-anchor-file. The file is written to when the anchor is
      updated, so the Unbound user must have write permission. Write permission
      to the file, but also to the directory it is in (to create a temporary
      file, which is necessary to deal with filesystem full events), it must
      also be inside the chroot (if that is used).
- trust-anchor: <"Resource Record">
- A DS or DNSKEY RR for a key to use for validation. Multiple entries can be
      given to specify multiple trusted keys, in addition to the
      trust-anchor-files. The resource record is entered in the same format as
      'dig' or 'drill' prints them, the same format as in the zone file. Has to
      be on a single line, with "" around it. A TTL can be specified
      for ease of cut and paste, but is ignored. A class can be specified, but
      class IN is default.
- trusted-keys-file: <filename>
- File with trusted keys for validation. Specify more than one file with
      several entries, one file per entry. Like trust-anchor-file but has
      a different file format. Format is BIND-9 style format, the trusted-keys {
      name flag proto algo "key"; }; clauses are read. It is possible
      to use wildcards with this statement, the wildcard is expanded on start
      and on reload.
- trust-anchor-signaling: <yes or no>
- Send RFC8145 key tag query after trust anchor priming. Default is
    yes.
- root-key-sentinel: <yes or no>
- Root key trust anchor sentinel. Default is yes.
- domain-insecure: <domain name>
- Sets domain name to be insecure, DNSSEC chain of trust is ignored towards
      the domain name. So a trust anchor above the domain name can not make the
      domain secure with a DS record, such a DS record is then ignored. Can be
      given multiple times to specify multiple domains that are treated as if
      unsigned. If you set trust anchors for the domain they override this
      setting (and the domain is secured).
  
  - This can be useful if you want to make sure a trust anchor for external
      lookups does not affect an (unsigned) internal domain. A DS record
      externally can create validation failures for that internal domain.
  - val-override-date: <rrsig-style date spec>
- Default is "" or "0", which disables this debugging
      feature. If enabled by giving a RRSIG style date, that date is used for
      verifying RRSIG inception and expiration dates, instead of the current
      date. Do not set this unless you are debugging signature inception and
      expiration. The value -1 ignores the date altogether, useful for some
      special applications.
- val-sig-skew-min: <seconds>
- Minimum number of seconds of clock skew to apply to validated signatures.
      A value of 10% of the signature lifetime (expiration - inception) is used,
      capped by this setting. Default is 3600 (1 hour) which allows for daylight
      savings differences. Lower this value for more strict checking of short
      lived signatures.
- val-sig-skew-max: <seconds>
- Maximum number of seconds of clock skew to apply to validated signatures.
      A value of 10% of the signature lifetime (expiration - inception) is used,
      capped by this setting. Default is 86400 (24 hours) which allows for
      timezone setting problems in stable domains. Setting both min and max very
      low disables the clock skew allowances. Setting both min and max very high
      makes the validator check the signature timestamps less strictly.
- val-max-restart: <number>
- The maximum number the validator should restart validation with another
      authority in case of failed validation. Default is 5.
- val-bogus-ttl: <number>
- The time to live for bogus data. This is data that has failed validation;
      due to invalid signatures or other checks. The TTL from that data cannot
      be trusted, and this value is used instead. The value is in seconds,
      default 60. The time interval prevents repeated revalidation of bogus
      data.
- val-clean-additional: <yes or no>
- Instruct the validator to remove data from the additional section of
      secure messages that are not signed properly. Messages that are insecure,
      bogus, indeterminate or unchecked are not affected. Default is yes. Use
      this setting to protect the users that rely on this validator for
      authentication from potentially bad data in the additional section.
- val-log-level: <number>
- Have the validator print validation failures to the log. Regardless of the
      verbosity setting. Default is 0, off. At 1, for every user query that
      fails a line is printed to the logs. This way you can monitor what happens
      with validation. Use a diagnosis tool, such as dig or drill, to find out
      why validation is failing for these queries. At 2, not only the query that
      failed is printed but also the reason why Unbound thought it was wrong and
      which server sent the faulty data.
- val-permissive-mode: <yes or no>
- Instruct the validator to mark bogus messages as indeterminate. The
      security checks are performed, but if the result is bogus (failed
      security), the reply is not withheld from the client with SERVFAIL as
      usual. The client receives the bogus data. For messages that are found to
      be secure the AD bit is set in replies. Also logging is performed as for
      full validation. The default value is "no".
- ignore-cd-flag: <yes or no>
- Instruct Unbound to ignore the CD flag from clients and refuse to return
      bogus answers to them. Thus, the CD (Checking Disabled) flag does not
      disable checking any more. This is useful if legacy (w2008) servers that
      set the CD flag but cannot validate DNSSEC themselves are the clients, and
      then Unbound provides them with DNSSEC protection. The default value is
      "no".
- disable-edns-do: <yes or no>
- Disable the EDNS DO flag in upstream requests. It breaks DNSSEC validation
      for Unbound's clients. This results in the upstream name servers to not
      include DNSSEC records in their replies and could be helpful for devices
      that cannot handle DNSSEC information. When the option is enabled, clients
      that set the DO flag receive no EDNS record in the response to indicate
      the lack of support to them. If this option is enabled but Unbound is
      already configured for DNSSEC validation (i.e., the validator module is
      enabled; default) this option is implicitly turned off with a warning as
      to not break DNSSEC validation in Unbound. Default is no.
- serve-expired: <yes or no>
- If enabled, Unbound attempts to serve old responses from cache with a TTL
      of serve-expired-reply-ttl in the response without waiting for the
      actual resolution to finish. The actual resolution answer ends up in the
      cache later on. Default is "no".
- serve-expired-ttl: <seconds>
- Limit serving of expired responses to configured seconds after expiration.
      0 disables the limit. This option only applies when serve-expired
      is enabled. A suggested value per RFC 8767 is between 86400 (1 day) and
      259200 (3 days). The default is 0.
- serve-expired-ttl-reset: <yes or no>
- Set the TTL of expired records to the serve-expired-ttl value after
      a failed attempt to retrieve the record from upstream. This makes sure
      that the expired records will be served as long as there are queries for
      it. Default is "no".
- serve-expired-reply-ttl: <seconds>
- TTL value to use when replying with expired data. If
      serve-expired-client-timeout is also used then it is RECOMMENDED to
      use 30 as the value (RFC 8767). The default is 30.
- serve-expired-client-timeout: <msec>
- Time in milliseconds before replying to the client with expired data. This
      essentially enables the serve-stale behavior as specified in RFC 8767 that
      first tries to resolve before immediately responding with expired data. A
      recommended value per RFC 8767 is 1800. Setting this to 0 will disable
      this behavior. Default is 0.
- serve-original-ttl: <yes or no>
- If enabled, Unbound will always return the original TTL as received from
      the upstream name server rather than the decrementing TTL as stored in the
      cache. This feature may be useful if Unbound serves as a front-end to a
      hidden authoritative name server. Enabling this feature does not impact
      cache expiry, it only changes the TTL Unbound embeds in responses to
      queries. Note that enabling this feature implicitly disables enforcement
      of the configured minimum and maximum TTL, as it is assumed users who
      enable this feature do not want Unbound to change the TTL obtained from an
      upstream server. Thus, the values set using cache-min-ttl and
      cache-max-ttl are ignored. Default is "no".
- val-nsec3-keysize-iterations: <"list of
    values">
- List of keysize and iteration count values, separated by spaces,
      surrounded by quotes. Default is "1024 150 2048 150 4096 150".
      This determines the maximum allowed NSEC3 iteration count before a message
      is simply marked insecure instead of performing the many hashing
      iterations. The list must be in ascending order and have at least one
      entry. If you set it to "1024 65535" there is no restriction to
      NSEC3 iteration values. This table must be kept short; a very long list
      could cause slower operation.
- zonemd-permissive-mode: <yes or no>
- If enabled the ZONEMD verification failures are only logged and do not
      cause the zone to be blocked and only return servfail. Useful for testing
      out if it works, or if the operator only wants to be notified of a problem
      without disrupting service. Default is no.
- add-holddown: <seconds>
- Instruct the auto-trust-anchor-file probe mechanism for RFC5011
      autotrust updates to add new trust anchors only after they have been
      visible for this time. Default is 30 days as per the RFC.
- del-holddown: <seconds>
- Instruct the auto-trust-anchor-file probe mechanism for RFC5011
      autotrust updates to remove revoked trust anchors after they have been
      kept in the revoked list for this long. Default is 30 days as per the
    RFC.
- keep-missing: <seconds>
- Instruct the auto-trust-anchor-file probe mechanism for RFC5011
      autotrust updates to remove missing trust anchors after they have been
      unseen for this long. This cleans up the state file if the target zone
      does not perform trust anchor revocation, so this makes the auto probe
      mechanism work with zones that perform regular (non-5011) rollovers. The
      default is 366 days. The value 0 does not remove missing anchors, as per
      the RFC.
- permit-small-holddown: <yes or no>
- Debug option that allows the autotrust 5011 rollover timers to assume very
      small values. Default is no.
- key-cache-size: <number>
- Number of bytes size of the key cache. Default is 4 megabytes. A plain
      number is in bytes, append 'k', 'm' or 'g' for kilobytes, megabytes or
      gigabytes (1024*1024 bytes in a megabyte).
- key-cache-slabs: <number>
- Number of slabs in the key cache. Slabs reduce lock contention by threads.
      Must be set to a power of 2. Setting (close) to the number of cpus is a
      reasonable guess.
- neg-cache-size: <number>
- Number of bytes size of the aggressive negative cache. Default is 1
      megabyte. A plain number is in bytes, append 'k', 'm' or 'g' for
      kilobytes, megabytes or gigabytes (1024*1024 bytes in a megabyte).
- unblock-lan-zones: <yes or no>
- Default is disabled. If enabled, then for private address space, the
      reverse lookups are no longer filtered. This allows Unbound when running
      as dns service on a host where it provides service for that host, to put
      out all of the queries for the 'lan' upstream. When enabled, only
      localhost, 127.0.0.1 reverse and ::1 reverse zones are configured with
      default local zones. Disable the option when Unbound is running as a
      (DHCP-) DNS network resolver for a group of machines, where such lookups
      should be filtered (RFC compliance), this also stops potential data
      leakage about the local network to the upstream DNS servers.
- insecure-lan-zones: <yes or no>
- Default is disabled. If enabled, then reverse lookups in private address
      space are not validated. This is usually required whenever
      unblock-lan-zones is used.
- local-zone: <zone> <type>
- Configure a local zone. The type determines the answer to give if there is
      no match from local-data. The types are deny, refuse, static, transparent,
      redirect, nodefault, typetransparent, inform, inform_deny,
      inform_redirect, always_transparent, block_a, always_refuse,
      always_nxdomain, always_null, noview, and are explained below. After that
      the default settings are listed. Use local-data: to enter data into the
      local zone. Answers for local zones are authoritative DNS answers. By
      default the zones are class IN.
  
  - If you need more complicated authoritative data, with referrals,
      wildcards, CNAME/DNAME support, or DNSSEC authoritative service, setup a
      stub-zone for it as detailed in the stub zone section below. A stub-zone
      can be used to have unbound send queries to another server, an
      authoritative server, to fetch the information. With a forward-zone,
      unbound sends queries to a server that is a recursive server to fetch the
      information. With an auth-zone a zone can be loaded from file and used, it
      can be used like a local-zone for users downstream, or the auth-zone
      information can be used to fetch information from when resolving like it
      is an upstream server. The forward-zone and auth-zone options are
      described in their sections below. If you want to perform filtering of the
      information that the users can fetch, the local-zone and local-data
      statements allow for this, but also the rpz functionality can be used,
      described in the RPZ section.
  - deny
- Do not send an answer, drop the query. If there is a match from local
      data, the query is answered.
- refuse
- Send an error message reply, with rcode REFUSED. If there is a match from
      local data, the query is answered.
- static
- If there is a match from local data, the query is answered. Otherwise, the
      query is answered with nodata or nxdomain. For a negative answer a SOA is
      included in the answer if present as local-data for the zone apex
    domain.
- transparent
- If there is a match from local data, the query is answered. Otherwise if
      the query has a different name, the query is resolved normally. If the
      query is for a name given in localdata but no such type of data is given
      in localdata, then a noerror nodata answer is returned. If no local-zone
      is given local-data causes a transparent zone to be created by
    default.
- typetransparent
- If there is a match from local data, the query is answered. If the query
      is for a different name, or for the same name but for a different type,
      the query is resolved normally. So, similar to transparent but types that
      are not listed in local data are resolved normally, so if an A record is
      in the local data that does not cause a nodata reply for AAAA
    queries.
- redirect
- The query is answered from the local data for the zone name. There may be
      no local data beneath the zone name. This answers queries for the zone,
      and all subdomains of the zone with the local data for the zone. It can be
      used to redirect a domain to return a different address record to the end
      user, with local-zone: "example.com." redirect and local-data:
      "example.com. A 127.0.0.1" queries for www.example.com and
      www.foo.example.com are redirected, so that users with web browsers cannot
      access sites with suffix example.com.
- inform
- The query is answered normally, same as transparent. The client IP address
      (@portnumber) is printed to the logfile. The log message is: timestamp,
      unbound-pid, info: zonename inform IP@port queryname type class. This
      option can be used for normal resolution, but machines looking up infected
      names are logged, eg. to run antivirus on them.
- inform_deny
- The query is dropped, like 'deny', and logged, like 'inform'. Ie. find
      infected machines without answering the queries.
- inform_redirect
- The query is redirected, like 'redirect', and logged, like 'inform'. Ie.
      answer queries with fixed data and also log the machines that ask.
- always_transparent
- Like transparent, but ignores local data and resolves normally.
- block_a
- Like transparent, but ignores local data and resolves normally all query
      types excluding A. For A queries it unconditionally returns NODATA. Useful
      in cases when there is a need to explicitly force all apps to use IPv6
      protocol and avoid any queries to IPv4.
- always_refuse
- Like refuse, but ignores local data and refuses the query.
- always_nxdomain
- Like static, but ignores local data and returns nxdomain for the
    query.
- always_nodata
- Like static, but ignores local data and returns nodata for the query.
- always_deny
- Like deny, but ignores local data and drops the query.
- always_null
- Always returns 0.0.0.0 or ::0 for every name in the zone. Like redirect
      with zero data for A and AAAA. Ignores local data in the zone. Used for
      some block lists.
- noview
- Breaks out of that view and moves towards the global local zones for
      answer to the query. If the view first is no, it'll resolve normally. If
      view first is enabled, it'll break perform that step and check the global
      answers. For when the view has view specific overrides but some zone has
      to be answered from global local zone contents.
- nodefault
- Used to turn off default contents for AS112 zones. The other types also
      turn off default contents for the zone. The 'nodefault' option has no
      other effect than turning off default contents for the given zone. Use
      nodefault if you use exactly that zone, if you want to use a
      subzone, use transparent.
The default zones are localhost, reverse 127.0.0.1 and ::1, the
    home.arpa, the onion, test, invalid and the AS112 zones. The AS112 zones are
    reverse DNS zones for private use and reserved IP addresses for which the
    servers on the internet cannot provide correct answers. They are configured
    by default to give nxdomain (no reverse information) answers. The defaults
    can be turned off by specifying your own local-zone of that name, or using
    the 'nodefault' type. Below is a list of the default zone contents.
  - localhost
- The IP4 and IP6 localhost information is given. NS and SOA records are
      provided for completeness and to satisfy some DNS update tools. Default
      content:
    
local-zone: "localhost." redirect
local-data: "localhost. 10800 IN NS localhost."
local-data: "localhost. 10800 IN
    SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
local-data: "localhost. 10800 IN A 127.0.0.1"
local-data: "localhost. 10800 IN AAAA ::1"
    
- reverse IPv4 loopback
- Default content:
    
local-zone: "127.in-addr.arpa." static
local-data: "127.in-addr.arpa. 10800 IN NS localhost."
local-data: "127.in-addr.arpa. 10800 IN
    SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
local-data: "1.0.0.127.in-addr.arpa. 10800 IN
    PTR localhost."
    
- reverse IPv6 loopback
- Default content:
    
local-zone: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
    0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa." static
local-data: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
    0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa. 10800 IN
    NS localhost."
local-data: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
    0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa. 10800 IN
    SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
local-data: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
    0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa. 10800 IN
    PTR localhost."
    
- home.arpa (RFC 8375)
- Default content:
    
local-zone: "home.arpa." static
local-data: "home.arpa. 10800 IN NS localhost."
local-data: "home.arpa. 10800 IN
    SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
    
- onion (RFC 7686)
- Default content:
    
local-zone: "onion." static
local-data: "onion. 10800 IN NS localhost."
local-data: "onion. 10800 IN
    SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
    
- test (RFC 6761)
- Default content:
    
local-zone: "test." static
local-data: "test. 10800 IN NS localhost."
local-data: "test. 10800 IN
    SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
    
- invalid (RFC 6761)
- Default content:
    
local-zone: "invalid." static
local-data: "invalid. 10800 IN NS localhost."
local-data: "invalid. 10800 IN
    SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
    
- reverse RFC1918 local use zones
- Reverse data for zones 10.in-addr.arpa, 16.172.in-addr.arpa to
      31.172.in-addr.arpa, 168.192.in-addr.arpa. The local-zone: is set
      static and as local-data: SOA and NS records are provided.
- reverse RFC3330 IP4 this, link-local, testnet and broadcast
- Reverse data for zones 0.in-addr.arpa, 254.169.in-addr.arpa,
      2.0.192.in-addr.arpa (TEST NET 1), 100.51.198.in-addr.arpa (TEST NET 2),
      113.0.203.in-addr.arpa (TEST NET 3), 255.255.255.255.in-addr.arpa. And
      from 64.100.in-addr.arpa to 127.100.in-addr.arpa (Shared Address
    Space).
- reverse RFC4291 IP6 unspecified
- Reverse data for zone
    
0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa.
    
- reverse RFC4193 IPv6 Locally Assigned Local Addresses
- Reverse data for zone D.F.ip6.arpa.
- reverse RFC4291 IPv6 Link Local Addresses
- Reverse data for zones 8.E.F.ip6.arpa to B.E.F.ip6.arpa.
- reverse IPv6 Example Prefix
- Reverse data for zone 8.B.D.0.1.0.0.2.ip6.arpa. This zone is used for
      tutorials and examples. You can remove the block on this zone with:
    
  local-zone: 8.B.D.0.1.0.0.2.ip6.arpa. nodefault
    You can also selectively unblock a part of the zone by making that part
      transparent with a local-zone statement. This also works with the other
      default zones.
- local-data: "<resource record string>"
- Configure local data, which is served in reply to queries for it. The
      query has to match exactly unless you configure the local-zone as
      redirect. If not matched exactly, the local-zone type determines further
      processing. If local-data is configured that is not a subdomain of a
      local-zone, a transparent local-zone is configured. For record types such
      as TXT, use single quotes, as in local-data: 'example. TXT
      "text"'.
  
  - If you need more complicated authoritative data, with referrals,
      wildcards, CNAME/DNAME support, or DNSSEC authoritative service, setup a
      stub-zone for it as detailed in the stub zone section below.
  - local-data-ptr: "IPaddr name"
- Configure local data shorthand for a PTR record with the reversed IPv4 or
      IPv6 address and the host name. For example "192.0.2.4
      www.example.com". TTL can be inserted like this: "2001:DB8::4
      7200 www.example.com"
- local-zone-tag: <zone> <"list of
    tags">
- Assign tags to localzones. Tagged localzones will only be applied when the
      used access-control element has a matching tag. Tags must be defined in
      define-tags. Enclose list of tags in quotes ("") and put
      spaces between tags. When there are multiple tags it checks if the
      intersection of the list of tags for the query and local-zone-tag is
      non-empty.
- local-zone-override: <zone> <IP netblock>
    <type>
- Override the localzone type for queries from addresses matching netblock.
      Use this localzone type, regardless the type configured for the local-zone
      (both tagged and untagged) and regardless the type configured using
      access-control-tag-action.
- response-ip: <IP-netblock> <action>
- This requires use of the "respip" module.
  
  - If the IP address in an AAAA or A RR in the answer section of a response
      matches the specified IP netblock, the specified action will apply.
      <action> has generally the same semantics as that for
      access-control-tag-action, but there are some exceptions.
- Actions for response-ip are different from those for
      local-zone in that in case of the former there is no point of such
      conditions as "the query matches it but there is no local data".
      Because of this difference, the semantics of response-ip actions
      are modified or simplified as follows: The static, refuse,
      transparent, typetransparent, and nodefault actions are
      invalid for response-ip. Using any of these will cause the
      configuration to be rejected as faulty. The deny action is
      non-conditional, i.e. it always results in dropping the corresponding
      query. The resolution result before applying the deny action is still
      cached and can be used for other queries.
  - response-ip-data: <IP-netblock> <"resource record
    string">
- This requires use of the "respip" module.
  
  - This specifies the action data for response-ip with action being to
      redirect as specified by "resource record string".
      "Resource record string" is similar to that of
      access-control-tag-action, but it must be of either AAAA, A or
      CNAME types. If the IP-netblock is an IPv6/IPv4 prefix, the record must be
      AAAA/A respectively, unless it is a CNAME (which can be used for both
      versions of IP netblocks). If it is CNAME there must not be more than one
      response-ip-data for the same IP-netblock. Also, CNAME and other
      types of records must not coexist for the same IP-netblock, following the
      normal rules for CNAME records. The textual domain name for the CNAME does
      not have to be explicitly terminated with a dot ("."); the root
      name is assumed to be the origin for the name.
  - response-ip-tag: <IP-netblock> <"list of
    tags">
- This requires use of the "respip" module.
  
  - Assign tags to response IP-netblocks. If the IP address in an AAAA or A RR
      in the answer section of a response matches the specified IP-netblock, the
      specified tags are assigned to the IP address. Then, if an
      access-control-tag is defined for the client and it includes one of
      the tags for the response IP, the corresponding
      access-control-tag-action will apply. Tag matching rule is the same
      as that for access-control-tag and local-zones. Unlike
      local-zone-tag, response-ip-tag can be defined for an
      IP-netblock even if no response-ip is defined for that netblock. If
      multiple response-ip-tag options are specified for the same
      IP-netblock in different statements, all but the first will be ignored.
      However, this will not be flagged as a configuration error, but the result
      is probably not what was intended.
- Actions specified in an access-control-tag-action that has a
      matching tag with response-ip-tag can be those that are
      "invalid" for response-ip listed above, since
      access-control-tag-actions can be shared with local zones. For
      these actions, if they behave differently depending on whether local data
      exists or not in case of local zones, the behavior for
      response-ip-data will generally result in NOERROR/NODATA instead of
      NXDOMAIN, since the response-ip data are inherently type specific,
      and non-existence of data does not indicate anything about the existence
      or non-existence of the qname itself. For example, if the matching tag
      action is static but there is no data for the corresponding
      response-ip configuration, then the result will be NOERROR/NODATA.
      The only case where NXDOMAIN is returned is when an always_nxdomain
      action applies.
  - ratelimit: <number or 0>
- Enable ratelimiting of queries sent to nameserver for performing
      recursion. If 0, the default, it is disabled. This option is experimental
      at this time. The ratelimit is in queries per second that are allowed.
      More queries are turned away with an error (servfail). This stops
      recursive floods, eg. random query names, but not spoofed reflection
      floods. Cached responses are not ratelimited by this setting. The zone of
      the query is determined by examining the nameservers for it, the zone name
      is used to keep track of the rate. For example, 1000 may be a suitable
      value to stop the server from being overloaded with random names, and
      keeps Unbound from sending traffic to the nameservers for those zones.
      Configured forwarders are excluded from ratelimiting.
- ratelimit-size: <memory size>
- Give the size of the data structure in which the current ongoing rates are
      kept track in. Default 4m. In bytes or use m(mega), k(kilo), g(giga). The
      ratelimit structure is small, so this data structure likely does not need
      to be large.
- ratelimit-slabs: <number>
- Give power of 2 number of slabs, this is used to reduce lock contention in
      the ratelimit tracking data structure. Close to the number of cpus is a
      fairly good setting.
- ratelimit-factor: <number>
- Set the amount of queries to rate limit when the limit is exceeded. If set
      to 0, all queries are dropped for domains where the limit is exceeded. If
      set to another value, 1 in that number is allowed through to complete.
      Default is 10, allowing 1/10 traffic to flow normally. This can make
      ordinary queries complete (if repeatedly queried for), and enter the
      cache, whilst also mitigating the traffic flow by the factor given.
- ratelimit-backoff: <yes or no>
- If enabled, the ratelimit is treated as a hard failure instead of the
      default maximum allowed constant rate. When the limit is reached, traffic
      is ratelimited and demand continues to be kept track of for a 2 second
      rate window. No traffic is allowed, except for ratelimit-factor, until
      demand decreases below the configured ratelimit for a 2 second rate
      window. Useful to set ratelimit to a suspicious rate to aggressively limit
      unusually high traffic. Default is off.
- ratelimit-for-domain: <domain> <number qps or
    0>
- Override the global ratelimit for an exact match domain name with the
      listed number. You can give this for any number of names. For example, for
      a top-level-domain you may want to have a higher limit than other names. A
      value of 0 will disable ratelimiting for that domain.
- ratelimit-below-domain: <domain> <number qps or
    0>
- Override the global ratelimit for a domain name that ends in this name.
      You can give this multiple times, it then describes different settings in
      different parts of the namespace. The closest matching suffix is used to
      determine the qps limit. The rate for the exact matching domain name is
      not changed, use ratelimit-for-domain to set that, you might want to use
      different settings for a top-level-domain and subdomains. A value of 0
      will disable ratelimiting for domain names that end in this name.
- ip-ratelimit: <number or 0>
- Enable global ratelimiting of queries accepted per IP address. This option
      is experimental at this time. The ratelimit is in queries per second that
      are allowed. More queries are completely dropped and will not receive a
      reply, SERVFAIL or otherwise. IP ratelimiting happens before looking in
      the cache. This may be useful for mitigating amplification attacks.
      Default is 0 (disabled).
- ip-ratelimit-cookie: <number or 0>
- Enable global ratelimiting of queries accepted per IP address with a valid
      DNS Cookie. This option is experimental at this time. The ratelimit is in
      queries per second that are allowed. More queries are completely dropped
      and will not receive a reply, SERVFAIL or otherwise. IP ratelimiting
      happens before looking in the cache. This option could be useful in
      combination with allow_cookie in an attempt to mitigate other
      amplification attacks than UDP reflections (e.g., attacks targeting
      Unbound itself) which are already handled with DNS Cookies. If used, the
      value is suggested to be higher than ip-ratelimit e.g., tenfold.
      Default is 0 (disabled).
- ip-ratelimit-size: <memory size>
- Give the size of the data structure in which the current ongoing rates are
      kept track in. Default 4m. In bytes or use m(mega), k(kilo), g(giga). The
      ip ratelimit structure is small, so this data structure likely does not
      need to be large.
- ip-ratelimit-slabs: <number>
- Give power of 2 number of slabs, this is used to reduce lock contention in
      the ip ratelimit tracking data structure. Close to the number of cpus is a
      fairly good setting.
- ip-ratelimit-factor: <number>
- Set the amount of queries to rate limit when the limit is exceeded. If set
      to 0, all queries are dropped for addresses where the limit is exceeded.
      If set to another value, 1 in that number is allowed through to complete.
      Default is 10, allowing 1/10 traffic to flow normally. This can make
      ordinary queries complete (if repeatedly queried for), and enter the
      cache, whilst also mitigating the traffic flow by the factor given.
- ip-ratelimit-backoff: <yes or no>
- If enabled, the ratelimit is treated as a hard failure instead of the
      default maximum allowed constant rate. When the limit is reached, traffic
      is ratelimited and demand continues to be kept track of for a 2 second
      rate window. No traffic is allowed, except for ip-ratelimit-factor, until
      demand decreases below the configured ratelimit for a 2 second rate
      window. Useful to set ip-ratelimit to a suspicious rate to aggressively
      limit unusually high traffic. Default is off.
- outbound-msg-retry: <number>
- The number of retries, per upstream nameserver in a delegation, that
      Unbound will attempt in case a throwaway response is received. No response
      (timeout) contributes to the retry counter. If a forward/stub zone is
      used, this is the number of retries per nameserver in the zone. Default is
      5.
- max-sent-count: <number>
- Hard limit on the number of outgoing queries Unbound will make while
      resolving a name, making sure large NS sets do not loop. Results in
      SERVFAIL when reached. It resets on query restarts (e.g., CNAME) and
      referrals. Default is 32.
- max-query-restarts: <number>
- Hard limit on the number of times Unbound is allowed to restart a query
      upon encountering a CNAME record. Results in SERVFAIL when reached.
      Changing this value needs caution as it can allow long CNAME chains to be
      accepted, where Unbound needs to verify (resolve) each link individually.
      Default is 11.
- fast-server-permil: <number>
- Specify how many times out of 1000 to pick from the set of fastest
      servers. 0 turns the feature off. A value of 900 would pick from the
      fastest servers 90 percent of the time, and would perform normal
      exploration of random servers for the remaining time. When prefetch is
      enabled (or serve-expired), such prefetches are not sped up, because there
      is no one waiting for it, and it presents a good moment to perform server
      exploration. The fast-server-num option can be used to specify the
      size of the fastest servers set. The default for fast-server-permil is
    0.
- fast-server-num: <number>
- Set the number of servers that should be used for fast server selection.
      Only use the fastest specified number of servers with the
      fast-server-permil option, that turns this on or off. The default is to
      use the fastest 3 servers.
- answer-cookie: <yes or no>
- If enabled, Unbound will answer to requests containing DNS Cookies as
      specified in RFC 7873 and RFC 9018. Default is no.
- cookie-secret: <128 bit hex string>
- Server's secret for DNS Cookie generation. Useful to explicitly set for
      servers in an anycast deployment that need to share the secret in order to
      verify each other's Server Cookies. An example hex string would be
      "000102030405060708090a0b0c0d0e0f". Default is a 128 bits random
      secret generated at startup time.
- edns-client-string: <IP netblock> <string>
- Include an EDNS0 option containing configured ascii string in queries with
      destination address matching the configured IP netblock. This
      configuration option can be used multiple times. The most specific match
      will be used.
- edns-client-string-opcode: <opcode>
- EDNS0 option code for the edns-client-string option, from 0 to
      65535. A value from the `Reserved for Local/Experimental` range
      (65001-65534) should be used. Default is 65001.
- ede: <yes or no>
- If enabled, Unbound will respond with Extended DNS Error codes (RFC8914).
      These EDEs attach informative error messages to a response for various
      errors. Default is "no".
    When the val-log-level option is also set to 2,
        responses with Extended DNS Errors concerning DNSSEC failures that are
        not served from cache, will also contain a descriptive text message
        about the reason for the failure. 
- ede-serve-expired: <yes or no>
- If enabled, Unbound will attach an Extended DNS Error (RFC8914) Code 3 -
      Stale Answer as EDNS0 option to the expired response. Note that this will
      not attach the EDE code without setting the global ede option to
      "yes" as well. Default is "no".
In the remote-control: clause are the declarations for the remote control
  facility. If this is enabled, the unbound-control(8) utility can be
  used to send commands to the running Unbound server. The server uses these
  clauses to setup TLSv1 security for the connection. The
  unbound-control(8) utility also reads the remote-control section
  for options. To setup the correct self-signed certificates use the
  unbound-control-setup(8) utility.
  - control-enable: <yes or no>
- The option is used to enable remote control, default is "no". If
      turned off, the server does not listen for control commands.
- control-interface: <ip address or interface name or
    path>
- Give IPv4 or IPv6 addresses or local socket path to listen on for control
      commands. If an interface name is used instead of an ip address, the list
      of ip addresses on that interface are used. By default localhost
      (127.0.0.1 and ::1) is listened to. Use 0.0.0.0 and ::0 to listen to all
      interfaces. If you change this and permissions have been dropped, you must
      restart the server for the change to take effect.
  
  - If you set it to an absolute path, a unix domain socket is used. This
      socket does not use the certificates and keys, so those files need not be
      present. To restrict access, Unbound sets permissions on the file to the
      user and group that is configured, the access bits are set to allow the
      group members to access the control socket file. Put users that need to
      access the socket in the that group. To restrict access further, create a
      directory to put the control socket in and restrict access to that
      directory.
  - control-port: <port number>
- The port number to listen on for IPv4 or IPv6 control interfaces, default
      is 8953. If you change this and permissions have been dropped, you must
      restart the server for the change to take effect.
- control-use-cert: <yes or no>
- For localhost control-interface you can disable the use of TLS by setting
      this option to "no", default is "yes". For local
      sockets, TLS is disabled and the value of this option is ignored.
- server-key-file: <private key file>
- Path to the server private key, by default unbound_server.key. This file
      is generated by the unbound-control-setup utility. This file is
      used by the Unbound server, but not by unbound-control.
- server-cert-file: <certificate file.pem>
- Path to the server self signed certificate, by default unbound_server.pem.
      This file is generated by the unbound-control-setup utility. This
      file is used by the Unbound server, and also by
    unbound-control.
- control-key-file: <private key file>
- Path to the control client private key, by default unbound_control.key.
      This file is generated by the unbound-control-setup utility. This
      file is used by unbound-control.
- control-cert-file: <certificate file.pem>
- Path to the control client certificate, by default unbound_control.pem.
      This certificate has to be signed with the server certificate. This file
      is generated by the unbound-control-setup utility. This file is
      used by unbound-control.
There may be multiple stub-zone: clauses. Each with a name: and zero or
  more hostnames or IP addresses. For the stub zone this list of nameservers is
  used. Class IN is assumed. The servers should be authority servers, not
  recursors; Unbound performs the recursive processing itself for stub zones.The stub zone can be used to configure authoritative data to be
    used by the resolver that cannot be accessed using the public internet
    servers. This is useful for company-local data or private zones. Setup an
    authoritative server on a different host (or different port). Enter a config
    entry for Unbound with stub-addr: <ip address of host[@port]>.
    The Unbound resolver can then access the data, without referring to the
    public internet for it.
This setup allows DNSSEC signed zones to be served by that
    authoritative server, in which case a trusted key entry with the public key
    can be put in config, so that Unbound can validate the data and set the AD
    bit on replies for the private zone (authoritative servers do not set the AD
    bit). This setup makes Unbound capable of answering queries for the private
    zone, and can even set the AD bit ('authentic'), but the AA
    ('authoritative') bit is not set on these replies.
Consider adding server: statements for
    domain-insecure: and for local-zone: name nodefault for
    the zone if it is a locally served zone. The insecure clause stops DNSSEC
    from invalidating the zone. The local zone nodefault (or transparent)
    clause makes the (reverse-) zone bypass Unbound's filtering of RFC1918
    zones.
  - name: <domain name>
- Name of the stub zone. This is the full domain name of the zone.
- stub-host: <domain name>
- Name of stub zone nameserver. Is itself resolved before it is used. To use
      a nondefault port for DNS communication append '@' with the port number.
      If tls is enabled, then you can append a '#' and a name, then it'll check
      the tls authentication certificates with that name. If you combine the '@'
      and '#', the '@' comes first. If only '#' is used the default port is the
      configured tls-port.
- stub-addr: <IP address>
- IP address of stub zone nameserver. Can be IP 4 or IP 6. To use a
      nondefault port for DNS communication append '@' with the port number. If
      tls is enabled, then you can append a '#' and a name, then it'll check the
      tls authentication certificates with that name. If you combine the '@' and
      '#', the '@' comes first. If only '#' is used the default port is the
      configured tls-port.
- stub-prime: <yes or no>
- This option is by default no. If enabled it performs NS set priming, which
      is similar to root hints, where it starts using the list of nameservers
      currently published by the zone. Thus, if the hint list is slightly
      outdated, the resolver picks up a correct list online.
- stub-first: <yes or no>
- If enabled, a query is attempted without the stub clause if it fails. The
      data could not be retrieved and would have caused SERVFAIL because the
      servers are unreachable, instead it is tried without this clause. The
      default is no.
- stub-tls-upstream: <yes or no>
- Enabled or disable whether the queries to this stub use TLS for transport.
      Default is no.
- stub-ssl-upstream: <yes or no>
- Alternate syntax for stub-tls-upstream.
- stub-tcp-upstream: <yes or no>
- If it is set to "yes" then upstream queries use TCP only for
      transport regardless of global flag tcp-upstream. Default is no.
- stub-no-cache: <yes or no>
- Default is no. If enabled, data inside the stub is not cached. This is
      useful when you want immediate changes to be visible.
There may be multiple forward-zone: clauses. Each with a name: and
  zero or more hostnames or IP addresses. For the forward zone this list of
  nameservers is used to forward the queries to. The servers listed as
  forward-host: and forward-addr: have to handle further recursion
  for the query. Thus, those servers are not authority servers, but are (just
  like Unbound is) recursive servers too; Unbound does not perform recursion
  itself for the forward zone, it lets the remote server do it. Class IN is
  assumed. CNAMEs are chased by Unbound itself, asking the remote server for
  every name in the indirection chain, to protect the local cache from illegal
  indirect referenced items. A forward-zone entry with name "." and a
  forward-addr target will forward all queries to that other server (unless it
  can answer from the cache).
  - name: <domain name>
- Name of the forward zone. This is the full domain name of the zone.
- forward-host: <domain name>
- Name of server to forward to. Is itself resolved before it is used. To use
      a nondefault port for DNS communication append '@' with the port number.
      If tls is enabled, then you can append a '#' and a name, then it'll check
      the tls authentication certificates with that name. If you combine the '@'
      and '#', the '@' comes first. If only '#' is used the default port is the
      configured tls-port.
- forward-addr: <IP address>
- IP address of server to forward to. Can be IP 4 or IP 6. To use a
      nondefault port for DNS communication append '@' with the port number. If
      tls is enabled, then you can append a '#' and a name, then it'll check the
      tls authentication certificates with that name. If you combine the '@' and
      '#', the '@' comes first. If only '#' is used the default port is the
      configured tls-port.
  
  - At high verbosity it logs the TLS certificate, with TLS enabled. If you
      leave out the '#' and auth name from the forward-addr, any name is
      accepted. The cert must also match a CA from the tls-cert-bundle.
  - forward-first: <yes or no>
- If a forwarded query is met with a SERVFAIL error, and this option is
      enabled, Unbound will fall back to normal recursive resolution for this
      query as if no query forwarding had been specified. The default is
      "no".
- forward-tls-upstream: <yes or no>
- Enabled or disable whether the queries to this forwarder use TLS for
      transport. Default is no. If you enable this, also configure a
      tls-cert-bundle or use tls-win-cert to load CA certs, otherwise the
      connections cannot be authenticated.
- forward-ssl-upstream: <yes or no>
- Alternate syntax for forward-tls-upstream.
- forward-tcp-upstream: <yes or no>
- If it is set to "yes" then upstream queries use TCP only for
      transport regardless of global flag tcp-upstream. Default is no.
- forward-no-cache: <yes or no>
- Default is no. If enabled, data inside the forward is not cached. This is
      useful when you want immediate changes to be visible.
Authority zones are configured with auth-zone:, and each one must have a
  name:. There can be multiple ones, by listing multiple auth-zone
  clauses, each with a different name, pertaining to that part of the namespace.
  The authority zone with the name closest to the name looked up is used.
  Authority zones can be processed on two distinct, non-exclusive, configurable
  stages.With for-downstream: yes (default), authority zones
    are processed after local-zones and before cache. When used in this
    manner, Unbound responds like an authority server with no further processing
    other than returning an answer from the zone contents. A notable example, in
    this case, is CNAME records which are returned verbatim to downstream
    clients without further resolution.
With for-upstream: yes (default), authority zones
    are processed after the cache lookup, just before going to the network to
    fetch information for recursion. When used in this manner they provide a
    local copy of an authority server that speeds up lookups for that data
    during resolving.
If both options are enabled (default), client queries for an
    authority zone are answered authoritatively from Unbound, while internal
    queries that require data from the authority zone consult the local zone
    data instead of going to the network.
An interesting configuration is for-downstream: no,
    for-upstream: yes that allows for hyperlocal behavior where
    both client and internal queries consult the local zone data while
    resolving. In this case, the aforementioned CNAME example will result in a
    thoroughly resolved answer.
Authority zones can be read from zonefile. And can be kept updated
    via AXFR and IXFR. After update the zonefile is rewritten. The update
    mechanism uses the SOA timer values and performs SOA UDP queries to detect
    zone changes.
If the update fetch fails, the timers in the SOA record are used
    to time another fetch attempt. Until the SOA expiry timer is reached. Then
    the zone is expired. When a zone is expired, queries are SERVFAIL, and any
    new serial number is accepted from the primary (even if older), and if
    fallback is enabled, the fallback activates to fetch from the upstream
    instead of the SERVFAIL.
  - name: <zone name>
- Name of the authority zone.
- primary: <IP address or host name>
- Where to download a copy of the zone from, with AXFR and IXFR. Multiple
      primaries can be specified. They are all tried if one fails. To use a
      nondefault port for DNS communication append '@' with the port number. You
      can append a '#' and a name, then AXFR over TLS can be used and the tls
      authentication certificates will be checked with that name. If you combine
      the '@' and '#', the '@' comes first. If you point it at another Unbound
      instance, it would not work because that does not support AXFR/IXFR for
      the zone, but if you used url: to download the zonefile as a text
      file from a webserver that would work. If you specify the hostname, you
      cannot use the domain from the zonefile, because it may not have that when
      retrieving that data, instead use a plain IP address to avoid a circular
      dependency on retrieving that IP address.
- master: <IP address or host name>
- Alternate syntax for primary.
- url: <url to zonefile>
- Where to download a zonefile for the zone. With http or https. An example
      for the url is "http://www.example.com/example.org.zone".
      Multiple url statements can be given, they are tried in turn. If only urls
      are given the SOA refresh timer is used to wait for making new downloads.
      If also primaries are listed, the primaries are first probed with UDP SOA
      queries to see if the SOA serial number has changed, reducing the number
      of downloads. If none of the urls work, the primaries are tried with IXFR
      and AXFR. For https, the tls-cert-bundle and the hostname from the
      url are used to authenticate the connection. If you specify a hostname in
      the URL, you cannot use the domain from the zonefile, because it may not
      have that when retrieving that data, instead use a plain IP address to
      avoid a circular dependency on retrieving that IP address. Avoid
      dependencies on name lookups by using a notation like
      "http://192.0.2.1/unbound-primaries/example.com.zone", with an
      explicit IP address.
- allow-notify: <IP address or host name or
    netblockIP/prefix>
- With allow-notify you can specify additional sources of notifies. When
      notified, the server attempts to first probe and then zone transfer. If
      the notify is from a primary, it first attempts that primary. Otherwise
      other primaries are attempted. If there are no primaries, but only urls,
      the file is downloaded when notified. The primaries from primary: and url:
      statements are allowed notify by default.
- fallback-enabled: <yes or no>
- Default no. If enabled, Unbound falls back to querying the internet as a
      resolver for this zone when lookups fail. For example for DNSSEC
      validation failures.
- for-downstream: <yes or no>
- Default yes. If enabled, Unbound serves authority responses to downstream
      clients for this zone. This option makes Unbound behave, for the queries
      with names in this zone, like one of the authority servers for that zone.
      Turn it off if you want Unbound to provide recursion for the zone but have
      a local copy of zone data. If for-downstream is no and for-upstream is
      yes, then Unbound will DNSSEC validate the contents of the zone before
      serving the zone contents to clients and store validation results in the
      cache.
- for-upstream: <yes or no>
- Default yes. If enabled, Unbound fetches data from this data collection
      for answering recursion queries. Instead of sending queries over the
      internet to the authority servers for this zone, it'll fetch the data
      directly from the zone data. Turn it on when you want Unbound to provide
      recursion for downstream clients, and use the zone data as a local copy to
      speed up lookups.
- zonemd-check: <yes or no>
- Enable this option to check ZONEMD records in the zone. Default is
      disabled. The ZONEMD record is a checksum over the zone data. This
      includes glue in the zone and data from the zone file, and excludes
      comments from the zone file. When there is a DNSSEC chain of trust, DNSSEC
      signatures are checked too.
- zonemd-reject-absence: <yes or no>
- Enable this option to reject the absence of the ZONEMD record. Without it,
      when zonemd is not there it is not checked. It is useful to enable for a
      nonDNSSEC signed zone where the operator wants to require the verification
      of a ZONEMD, hence a missing ZONEMD is a failure. The action upon failure
      is controlled by the zonemd-permissive-mode option, for log only or
      also block the zone. The default is no.
  
  - Without the option absence of a ZONEMD is only a failure when the zone is
      DNSSEC signed, and we have a trust anchor, and the DNSSEC verification of
      the absence of the ZONEMD fails. With the option enabled, the absence of a
      ZONEMD is always a failure, also for nonDNSSEC signed zones.
  - zonefile: <filename>
- The filename where the zone is stored. If not given then no zonefile is
      used. If the file does not exist or is empty, Unbound will attempt to
      fetch zone data (eg. from the primary servers).
There may be multiple view: clauses. Each with a name: and zero or
  more local-zone and local-data elements. Views can also contain
  view-first, response-ip, response-ip-data and local-data-ptr elements. View
  can be mapped to requests by specifying the view name in an
  access-control-view element. Options from matching views will override
  global options. Global options will be used if no matching view is found, or
  when the matching view does not have the option specified.
  - name: <view name>
- Name of the view. Must be unique. This name is used in access-control-view
      elements.
- local-zone: <zone> <type>
- View specific local-zone elements. Has the same types and behaviour as the
      global local-zone elements. When there is at least one local-zone
      specified and view-first is no, the default local-zones will be added to
      this view. Defaults can be disabled using the nodefault type. When
      view-first is yes or when a view does not have a local-zone, the global
      local-zone will be used including it's default zones.
- local-data: "<resource record string>"
- View specific local-data elements. Has the same behaviour as the global
      local-data elements.
- local-data-ptr: "IPaddr name"
- View specific local-data-ptr elements. Has the same behaviour as the
      global local-data-ptr elements.
- view-first: <yes or no>
- If enabled, it attempts to use the global local-zone and local-data if
      there is no match in the view specific options. The default is no.
The python: clause gives the settings for the python(1) script
  module. This module acts like the iterator and validator modules do, on
  queries and answers. To enable the script module it has to be compiled into
  the daemon, and the word "python" has to be put in the
  module-config: option (usually first, or between the validator and
  iterator). Multiple instances of the python module are supported by adding the
  word "python" more than once.If the chroot: option is enabled, you should make sure
    Python's library directory structure is bind mounted in the new root
    environment, see mount(8). Also the python-script: path should
    be specified as an absolute path relative to the new root, or as a relative
    path to the working directory.
  - python-script: <python file>
- The script file to load. Repeat this option for every python module
      instance added to the module-config: option.
The dynlib: clause gives the settings for the dynlib module. This
  module is only a very small wrapper that allows dynamic modules to be loaded
  on runtime instead of being compiled into the application. To enable the
  dynlib module it has to be compiled into the daemon, and the word
  "dynlib" has to be put in the module-config: option. Multiple
  instances of dynamic libraries are supported by adding the word
  "dynlib" more than once.The dynlib-file: path should be specified as an absolute
    path relative to the new path set by chroot: option, or as a relative
    path to the working directory.
  - dynlib-file: <dynlib file>
- The dynamic library file to load. Repeat this option for every dynlib
      module instance added to the module-config: option.
The dns64 module must be configured in the module-config: "dns64
  validator iterator" directive and be compiled into the daemon to be
  enabled. These settings go in the server: section.
  - dns64-prefix: <IPv6 prefix>
- This sets the DNS64 prefix to use to synthesize AAAA records with. It must
      be /96 or shorter. The default prefix is 64:ff9b::/96.
- dns64-synthall: <yes or no>
- Debug option, default no. If enabled, synthesize all AAAA records despite
      the presence of actual AAAA records.
- dns64-ignore-aaaa: <name>
- List domain for which the AAAA records are ignored and the A record is
      used by dns64 processing instead. Can be entered multiple times, list a
      new domain for which it applies, one per line. Applies also to names
      underneath the name given.
NAT64 operation allows using a NAT64 prefix for outbound requests to IPv4-only
  servers. It is controlled by two options in the server: section:
  - do-nat64: <yes or no>
- Use NAT64 to reach IPv4-only servers. Consider also enabling
      prefer-ip6 to prefer native IPv6 connections to nameservers.
      Default no.
- nat64-prefix: <IPv6 prefix>
- Use a specific NAT64 prefix to reach IPv4-only servers. Defaults to using
      the prefix configured in dns64-prefix, which in turn defaults to
      64:ff9b::/96. The prefix length must be one of /32, /40, /48, /56, /64 or
      /96.
The dnscrypt: clause gives the settings of the dnscrypt channel. While
  those options are available, they are only meaningful if Unbound was compiled
  with --enable-dnscrypt. Currently certificate and secret/public keys
  cannot be generated by Unbound. You can use dnscrypt-wrapper to generate
  those: https://github.com/cofyc/dnscrypt-wrapper/blob/master/README.md#usage
  - dnscrypt-enable: <yes or no>
- Whether or not the dnscrypt config should be enabled. You may
      define configuration but not activate it. The default is no.
- dnscrypt-port: <port number>
- On which port should dnscrypt should be activated. Note that you
      should have a matching interface option defined in the
      server section for this port.
- dnscrypt-provider: <provider name>
- The provider name to use to distribute certificates. This is of the form:
      2.dnscrypt-cert.example.com.. The name MUST end with a
    dot.
- dnscrypt-secret-key: <path to secret key file>
- Path to the time limited secret key file. This option may be specified
      multiple times.
- dnscrypt-provider-cert: <path to cert file>
- Path to the certificate related to the dnscrypt-secret-keys. This
      option may be specified multiple times.
- dnscrypt-provider-cert-rotated: <path to cert
    file>
- Path to a certificate that we should be able to serve existing connection
      from but do not want to advertise over dnscrypt-provider's TXT
      record certs distribution. A typical use case is when rotating
      certificates, existing clients may still use the client magic from the old
      cert in their queries until they fetch and update the new cert. Likewise,
      it would allow one to prime the new cert/key without distributing the new
      cert yet, this can be useful when using a network of servers using anycast
      and on which the configuration may not get updated at the exact same time.
      By priming the cert, the servers can handle both old and new certs traffic
      while distributing only one. This option may be specified multiple
    times.
- dnscrypt-shared-secret-cache-size: <memory size>
- Give the size of the data structure in which the shared secret keys are
      kept in. Default 4m. In bytes or use m(mega), k(kilo), g(giga). The shared
      secret cache is used when a same client is making multiple queries using
      the same public key. It saves a substantial amount of CPU.
- dnscrypt-shared-secret-cache-slabs: <number>
- Give power of 2 number of slabs, this is used to reduce lock contention in
      the dnscrypt shared secrets cache. Close to the number of cpus is a fairly
      good setting.
- dnscrypt-nonce-cache-size: <memory size>
- Give the size of the data structure in which the client nonces are kept
      in. Default 4m. In bytes or use m(mega), k(kilo), g(giga). The nonce cache
      is used to prevent dnscrypt message replaying. Client nonce should be
      unique for any pair of client pk/server sk.
- dnscrypt-nonce-cache-slabs: <number>
- Give power of 2 number of slabs, this is used to reduce lock contention in
      the dnscrypt nonce cache. Close to the number of cpus is a fairly good
      setting.
The ECS module must be configured in the module-config: "subnetcache
  validator iterator" directive and be compiled into the daemon to be
  enabled. These settings go in the server: section.If the destination address is allowed in the configuration Unbound
    will add the EDNS0 option to the query containing the relevant part of the
    client's address. When an answer contains the ECS option the response and
    the option are placed in a specialized cache. If the authority indicated no
    support, the response is stored in the regular cache.
Additionally, when a client includes the option in its queries,
    Unbound will forward the option when sending the query to addresses that are
    explicitly allowed in the configuration using send-client-subnet. The
    option will always be forwarded, regardless the allowed addresses, if
    client-subnet-always-forward is set to yes. In this case the lookup
    in the regular cache is skipped.
The maximum size of the ECS cache is controlled by
    'msg-cache-size' in the configuration file. On top of that, for each query
    only 100 different subnets are allowed to be stored for each address family.
    Exceeding that number, older entries will be purged from cache.
This module does not interact with the serve-expired* and
    prefetch: options.
  - send-client-subnet: <IP address>
- Send client source address to this authority. Append /num to indicate a
      classless delegation netblock, for example like 10.2.3.4/24 or
      2001::11/64. Can be given multiple times. Authorities not listed will not
      receive edns-subnet information, unless domain in query is specified in
      client-subnet-zone.
- client-subnet-zone: <domain>
- Send client source address in queries for this domain and its subdomains.
      Can be given multiple times. Zones not listed will not receive edns-subnet
      information, unless hosted by authority specified in
      send-client-subnet.
- client-subnet-always-forward: <yes or no>
- Specify whether the ECS address check (configured using
      send-client-subnet) is applied for all queries, even if the
      triggering query contains an ECS record, or only for queries for which the
      ECS record is generated using the querier address (and therefore did not
      contain ECS data in the client query). If enabled, the address check is
      skipped when the client query contains an ECS record. And the lookup in
      the regular cache is skipped. Default is no.
- max-client-subnet-ipv6: <number>
- Specifies the maximum prefix length of the client source address we are
      willing to expose to third parties for IPv6. Defaults to 56.
- max-client-subnet-ipv4: <number>
- Specifies the maximum prefix length of the client source address we are
      willing to expose to third parties for IPv4. Defaults to 24.
- min-client-subnet-ipv6: <number>
- Specifies the minimum prefix length of the IPv6 source mask we are willing
      to accept in queries. Shorter source masks result in REFUSED answers.
      Source mask of 0 is always accepted. Default is 0.
- min-client-subnet-ipv4: <number>
- Specifies the minimum prefix length of the IPv4 source mask we are willing
      to accept in queries. Shorter source masks result in REFUSED answers.
      Source mask of 0 is always accepted. Default is 0.
- max-ecs-tree-size-ipv4: <number>
- Specifies the maximum number of subnets ECS answers kept in the ECS radix
      tree. This number applies for each qname/qclass/qtype tuple. Defaults to
      100.
- max-ecs-tree-size-ipv6: <number>
- Specifies the maximum number of subnets ECS answers kept in the ECS radix
      tree. This number applies for each qname/qclass/qtype tuple. Defaults to
      100.
The IPsec module must be configured in the module-config: "ipsecmod
  validator iterator" directive and be compiled into Unbound by using
  --enable-ipsecmod to be enabled. These settings go in the
  server: section.When Unbound receives an A/AAAA query that is not in the cache and
    finds a valid answer, it will withhold returning the answer and instead will
    generate an IPSECKEY subquery for the same domain name. If an answer was
    found, Unbound will call an external hook passing the following
  arguments:
  - QNAME
- Domain name of the A/AAAA and IPSECKEY query. In string format.
- IPSECKEY TTL
- TTL of the IPSECKEY RRset.
- A/AAAA
- String of space separated IP addresses present in the A/AAAA RRset. The IP
      addresses are in string format.
- IPSECKEY
- String of space separated IPSECKEY RDATA present in the IPSECKEY RRset.
      The IPSECKEY RDATA are in DNS presentation format.
The A/AAAA answer is then cached and returned to the client. If
    the external hook was called the TTL changes to ensure it doesn't surpass
    ipsecmod-max-ttl.
The same procedure is also followed when prefetch: is used,
    but the A/AAAA answer is given to the client before the hook is called.
    ipsecmod-max-ttl ensures that the A/AAAA answer given from cache is
    still relevant for opportunistic IPsec.
  - ipsecmod-enabled: <yes or no>
- Specifies whether the IPsec module is enabled or not. The IPsec module
      still needs to be defined in the module-config: directive. This
      option facilitates turning on/off the module without restarting/reloading
      Unbound. Defaults to yes.
- ipsecmod-hook: <filename>
- Specifies the external hook that Unbound will call with system(3).
      The file can be specified as an absolute/relative path. The file needs the
      proper permissions to be able to be executed by the same user that runs
      Unbound. It must be present when the IPsec module is defined in the
      module-config: directive.
- ipsecmod-strict: <yes or no>
- If enabled Unbound requires the external hook to return a success value of
      0. Failing to do so Unbound will reply with SERVFAIL. The A/AAAA answer
      will also not be cached. Defaults to no.
- ipsecmod-max-ttl: <seconds>
- Time to live maximum for A/AAAA cached records after calling the external
      hook. Defaults to 3600.
- ipsecmod-ignore-bogus: <yes or no>
- Specifies the behaviour of Unbound when the IPSECKEY answer is bogus. If
      set to yes, the hook will be called and the A/AAAA answer will be returned
      to the client. If set to no, the hook will not be called and the answer to
      the A/AAAA query will be SERVFAIL. Mainly used for testing. Defaults to
      no.
- ipsecmod-allow: <domain>
- Allow the ipsecmod functionality for the domain so that the module logic
      will be executed. Can be given multiple times, for different domains. If
      the option is not specified, all domains are treated as being allowed
      (default).
- ipsecmod-whitelist: <yes or no>
- Alternate syntax for ipsecmod-allow.
The Cache DB module must be configured in the module-config:
  "validator cachedb iterator" directive and be compiled into the
  daemon with --enable-cachedb. If this module is enabled and configured,
  the specified backend database works as a second level cache: When Unbound
  cannot find an answer to a query in its built-in in-memory cache, it consults
  the specified backend. If it finds a valid answer in the backend, Unbound uses
  it to respond to the query without performing iterative DNS resolution. If
  Unbound cannot even find an answer in the backend, it resolves the query as
  usual, and stores the answer in the backend.This module interacts with the serve-expired-* options and
    will reply with expired data if Unbound is configured for that. Currently
    the use of serve-expired-client-timeout: and
    serve-expired-reply-ttl: is not consistent for data originating from
    the external cache as these will result in a reply with 0 TTL without trying
    to update the data first, ignoring the configured values.
If Unbound was built with --with-libhiredis on a system
    that has installed the hiredis C client library of Redis, then the
    "redis" backend can be used. This backend communicates with the
    specified Redis server over a TCP connection to store and retrieve cache
    data. It can be used as a persistent and/or shared cache backend. It should
    be noted that Unbound never removes data stored in the Redis server, even if
    some data have expired in terms of DNS TTL or the Redis server has cached
    too much data; if necessary the Redis server must be configured to limit the
    cache size, preferably with some kind of least-recently-used eviction
    policy. Additionally, the redis-expire-records option can be used in
    order to set the relative DNS TTL of the message as timeout to the Redis
    records; keep in mind that some additional memory is used per key and that
    the expire information is stored as absolute Unix timestamps in Redis
    (computer time must be stable). This backend uses synchronous communication
    with the Redis server based on the assumption that the communication is
    stable and sufficiently fast. The thread waiting for a response from the
    Redis server cannot handle other DNS queries. Although the backend has the
    ability to reconnect to the server when the connection is closed
    unexpectedly and there is a configurable timeout in case the server is
    overly slow or hangs up, these cases are assumed to be very rare. If
    connection close or timeout happens too often, Unbound will be effectively
    unusable with this backend. It's the administrator's responsibility to make
    the assumption hold.
The cachedb: clause gives custom settings of the cache DB
    module.
  - backend: <backend name>
- Specify the backend database name. The default database is the in-memory
      backend named "testframe", which, as the name suggests, is not
      of any practical use. Depending on the build-time configuration,
      "redis" backend may also be used as described above.
- secret-seed: <"secret string">
- Specify a seed to calculate a hash value from query information. This
      value will be used as the key of the corresponding answer for the backend
      database and can be customized if the hash should not be predictable
      operationally. If the backend database is shared by multiple Unbound
      instances, all instances must use the same secret seed. This option
      defaults to "default".
- cachedb-no-store: <yes or no>
- If the backend should be read from, but not written to. This makes this
      instance not store dns messages in the backend. But if data is available
      it is retrieved. The default is no.
The following cachedb options are specific to the redis
    backend.
  - redis-server-host: <server address or name>
- The IP (either v6 or v4) address or domain name of the Redis server. In
      general an IP address should be specified as otherwise Unbound will have
      to resolve the name of the server every time it establishes a connection
      to the server. This option defaults to "127.0.0.1".
- redis-server-port: <port number>
- The TCP port number of the Redis server. This option defaults to
    6379.
- redis-server-path: <unix socket path>
- The unix socket path to connect to the redis server. Off by default, and
      it can be set to "" to turn this off. Unix sockets may have
      better throughput than the IP address option.
- redis-server-password: "<password>"
- The Redis AUTH password to use for the redis server. Only relevant if
      Redis is configured for client password authorisation. Off by default, and
      it can be set to "" to turn this off.
- redis-timeout: <msec>
- The period until when Unbound waits for a response from the Redis sever.
      If this timeout expires Unbound closes the connection, treats it as if the
      Redis server does not have the requested data, and will try to
      re-establish a new connection later. This option defaults to 100
      milliseconds.
- redis-expire-records: <yes or no>
- If Redis record expiration is enabled. If yes, Unbound sets timeout for
      Redis records so that Redis can evict keys that have expired
      automatically. If Unbound is configured with serve-expired and
      serve-expired-ttl is 0, this option is internally reverted to
      "no". Redis SETEX support is required for this option (Redis
      >= 2.0.0). This option defaults to no.
- redis-logical-db: <logical database index>
- The logical database in Redis to use. These are databases in the same
      Redis instance sharing the same configuration and persisted in the same
      RDB/AOF file. If unsure about using this option, Redis documentation
      (https://redis.io/commands/select/) suggests not to use a single Redis
      instance for multiple unrelated applications. The default database in
      Redis is 0 while other logical databases need to be explicitly SELECT'ed
      upon connecting. This option defaults to 0.
DNSTAP support, when compiled in by using --enable-dnstap, is enabled in
  the dnstap: section. This starts an extra thread (when compiled with
  threading) that writes the log information to the destination. If Unbound is
  compiled without threading it does not spawn a thread, but connects
  per-process to the destination.
  - dnstap-enable: <yes or no>
- If dnstap is enabled. Default no. If yes, it connects to the dnstap server
      and if any of the dnstap-log-..-messages options is enabled it sends logs
      for those messages to the server.
- dnstap-bidirectional: <yes or no>
- Use frame streams in bidirectional mode to transfer DNSTAP messages.
      Default is yes.
- dnstap-socket-path: <file name>
- Sets the unix socket file name for connecting to the server that is
      listening on that socket. Default is
    "@DNSTAP_SOCKET_PATH@".
- dnstap-ip: <IPaddress[@port]>
- If "", the unix socket is used, if set with an IP address (IPv4
      or IPv6) that address is used to connect to the server.
- dnstap-tls: <yes or no>
- Set this to use TLS to connect to the server specified in
      dnstap-ip. The default is yes. If set to no, TCP is used to connect
      to the server.
- dnstap-tls-server-name: <name of TLS
    authentication>
- The TLS server name to authenticate the server with. Used when
      dnstap-tls is enabled. If "" it is ignored, default
      "".
- dnstap-tls-cert-bundle: <file name of cert
    bundle>
- The pem file with certs to verify the TLS server certificate. If
      "" the server default cert bundle is used, or the windows cert
      bundle on windows. Default is "".
- dnstap-tls-client-key-file: <file name>
- The client key file for TLS client authentication. If "" client
      authentication is not used. Default is "".
- dnstap-tls-client-cert-file: <file name>
- The client cert file for TLS client authentication. Default is
      "".
- dnstap-send-identity: <yes or no>
- If enabled, the server identity is included in the log messages. Default
      is no.
- dnstap-send-version: <yes or no>
- If enabled, the server version if included in the log messages. Default is
      no.
- dnstap-identity: <string>
- The identity to send with messages, if "" the hostname is used.
      Default is "".
- dnstap-version: <string>
- The version to send with messages, if "" the package version is
      used. Default is "".
- dnstap-log-resolver-query-messages: <yes or no>
- Enable to log resolver query messages. Default is no. These are messages
      from Unbound to upstream servers.
- dnstap-log-resolver-response-messages: <yes or
    no>
- Enable to log resolver response messages. Default is no. These are replies
      from upstream servers to Unbound.
- dnstap-log-client-query-messages: <yes or no>
- Enable to log client query messages. Default is no. These are client
      queries to Unbound.
- dnstap-log-client-response-messages: <yes or no>
- Enable to log client response messages. Default is no. These are responses
      from Unbound to clients.
- dnstap-log-forwarder-query-messages: <yes or no>
- Enable to log forwarder query messages. Default is no.
- dnstap-log-forwarder-response-messages: <yes or
    no>
- Enable to log forwarder response messages. Default is no.
Response Policy Zones are configured with rpz:, and each one must have a
  name:. There can be multiple ones, by listing multiple rpz clauses,
  each with a different name. RPZ clauses are applied in order of configuration.
  The respip module needs to be added to the module-config, e.g.:
  module-config: "respip validator iterator".QNAME, Response IP Address, nsdname, nsip and clientip triggers
    are supported. Supported actions are: NXDOMAIN, NODATA, PASSTHRU, DROP,
    Local Data, tcp-only and drop. RPZ QNAME triggers are applied after
    local-zones and before auth-zones.
The rpz zone is formatted with a SOA start record as usual. The
    items in the zone are entries, that specify what to act on (the trigger) and
    what to do (the action). The trigger to act on is recorded in the name, the
    action to do is recorded as the resource record. The names all end in the
    zone name, so you could type the trigger names without a trailing dot in the
    zonefile.
An example RPZ record, that answers example.com with NXDOMAIN
	example.com CNAME .
The triggers are encoded in the name on the left
	name                          query name
	netblock.rpz-client-ip        client IP address
	netblock.rpz-ip               response IP address in the answer
	name.rpz-nsdname              nameserver name
	netblock.rpz-nsip             nameserver IP address
The netblock is written as <netblocklen>.<ip address in reverse>.
  For IPv6 use 'zz' for '::'. Specify individual addresses with scope length of
  32 or 128. For example, 24.10.100.51.198.rpz-ip is 198.51.100.10/24 and
  32.10.zz.db8.2001.rpz-ip is 2001:db8:0:0:0:0:0:10/32.
The actions are specified with the record on the right
	CNAME .                      nxdomain reply
	CNAME *.                     nodata reply
	CNAME rpz-passthru.          do nothing, allow to continue
	CNAME rpz-drop.              the query is dropped
	CNAME rpz-tcp-only.          answer over TCP
	A 192.0.2.1                  answer with this IP address
Other records like AAAA, TXT and other CNAMEs (not rpz-..) can also be used to
  answer queries with that content.
The RPZ zones can be configured in the config file with these
    settings in the rpz: block.
  - name: <zone name>
- Name of the authority zone.
- primary: <IP address or host name>
- Where to download a copy of the zone from, with AXFR and IXFR. Multiple
      primaries can be specified. They are all tried if one fails. To use a
      nondefault port for DNS communication append '@' with the port number. You
      can append a '#' and a name, then AXFR over TLS can be used and the tls
      authentication certificates will be checked with that name. If you combine
      the '@' and '#', the '@' comes first. If you point it at another Unbound
      instance, it would not work because that does not support AXFR/IXFR for
      the zone, but if you used url: to download the zonefile as a text
      file from a webserver that would work. If you specify the hostname, you
      cannot use the domain from the zonefile, because it may not have that when
      retrieving that data, instead use a plain IP address to avoid a circular
      dependency on retrieving that IP address.
- master: <IP address or host name>
- Alternate syntax for primary.
- url: <url to zonefile>
- Where to download a zonefile for the zone. With http or https. An example
      for the url is "http://www.example.com/example.org.zone".
      Multiple url statements can be given, they are tried in turn. If only urls
      are given the SOA refresh timer is used to wait for making new downloads.
      If also primaries are listed, the primaries are first probed with UDP SOA
      queries to see if the SOA serial number has changed, reducing the number
      of downloads. If none of the urls work, the primaries are tried with IXFR
      and AXFR. For https, the tls-cert-bundle and the hostname from the
      url are used to authenticate the connection.
- allow-notify: <IP address or host name or
    netblockIP/prefix>
- With allow-notify you can specify additional sources of notifies. When
      notified, the server attempts to first probe and then zone transfer. If
      the notify is from a primary, it first attempts that primary. Otherwise
      other primaries are attempted. If there are no primaries, but only urls,
      the file is downloaded when notified. The primaries from primary: and url:
      statements are allowed notify by default.
- zonefile: <filename>
- The filename where the zone is stored. If not given then no zonefile is
      used. If the file does not exist or is empty, Unbound will attempt to
      fetch zone data (eg. from the primary servers).
- rpz-action-override: <action>
- Always use this RPZ action for matching triggers from this zone. Possible
      action are: nxdomain, nodata, passthru, drop, disabled and cname.
- rpz-cname-override: <domain>
- The CNAME target domain to use if the cname action is configured for
      rpz-action-override.
- rpz-log: <yes or no>
- Log all applied RPZ actions for this RPZ zone. Default is no.
- rpz-log-name: <name>
- Specify a string to be part of the log line, for easy referencing.
- rpz-signal-nxdomain-ra: <yes or no>
- Signal when a query is blocked by the RPZ with NXDOMAIN with an unset RA
      flag. This allows certain clients, like dnsmasq, to infer that the domain
      is externally blocked. Default is no.
- for-downstream: <yes or no>
- If enabled the zone is authoritatively answered for and queries for the
      RPZ zone information are answered to downstream clients. This is useful
      for monitoring scripts, that can then access the SOA information to check
      if the rpz information is up to date. Default is no.
- tags: <list of tags>
- Limit the policies from this RPZ clause to clients with a matching tag.
      Tags need to be defined in define-tag and can be assigned to client
      addresses using access-control-tag. Enclose list of tags in quotes
      ("") and put spaces between tags. If no tags are specified the
      policies from this clause will be applied for all clients.