unbound.conf(5)                 unbound 1.17.1                 unbound.conf(5)



NAME
       unbound.conf - Unbound configuration file.

SYNOPSIS
       unbound.conf

DESCRIPTION
       unbound.conf  is used to configure unbound(8).  The file format has at-
       tributes and values. Some attributes have attributes inside them.   The
       notation is: attribute: value.

       Comments  start with # and last to the end of line. Empty lines are ig-
       nored as is whitespace at the beginning of a line.

       The utility unbound-checkconf(8) can  be  used  to  check  unbound.conf
       prior to usage.

EXAMPLE
       An  example  config  file is shown below. Copy this to /etc/unbound/un-
       bound.conf and start the server with:

            $ unbound -c /etc/unbound/unbound.conf

       Most settings are the defaults. Stop the server with:

            $ kill `cat /etc/unbound/unbound.pid`

       Below is a minimal config file. The source distribution contains an ex-
       tensive example.conf file with all the options.

       # unbound.conf(5) config file for unbound(8).
       server:
            directory: "/etc/unbound"
            username: unbound
            # make sure unbound can access entropy from inside the chroot.
            # e.g. on linux the use these commands (on BSD, devfs(8) is used):
            #      mount --bind -n /dev/urandom /etc/unbound/dev/urandom
            # and  mount --bind -n /dev/log /etc/unbound/dev/log
            chroot: "/etc/unbound"
            # logfile: "/etc/unbound/unbound.log"  #uncomment to use logfile.
            pidfile: "/etc/unbound/unbound.pid"
            # verbosity: 1      # uncomment and increase to get more logging.
            # listen on all interfaces, answer queries from the local subnet.
            interface: 0.0.0.0
            interface: ::0
            access-control: 10.0.0.0/8 allow
            access-control: 2001:DB8::/64 allow

FILE FORMAT
       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 any-
       where, 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 in-
       cluded  files  works, relative pathnames for the included names work if
       the directory where the daemon is started equals its chroot/working di-
       rectory  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.

   Server Options
       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 iden-
              tification 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 sta-
              tistics. Default is no.

       extended-statistics: <yes or no>
              If enabled, extended statistics are  printed  from  unbound-con-
              trol(8).   Default is off, because keeping track of more statis-
              tics 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 local-
              host.  If an interface name is used instead of  an  ip  address,
              the list of ip addresses on that interface are used.  The inter-
              faces 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  se-
              lect  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  inter-
              faces.  If  none  are  given  the default (all) is used. You can
              specify the same interfaces in  interface:  and  outgoing-inter-
              face:  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  ad-
              dress  taken from the netblock to counter spoofing. Requires the
              IPv6 netblock to be routed to the host running Unbound, and  re-
              quires  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 pre-
              fer-ip6: yes to increase the likelihood of IPv6 nameservers  be-
              ing  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 com-
              pile options. Larger numbers need extra resources from the oper-
              ating  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 in-
              creases 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  per-
              mitted  ports  and subtracting the avoided ports from the set of
              allowed ports.  The processing starts with the  non  IANA  allo-
              cated 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 au-
              thoritative servers are done.  For larger installations increas-
              ing 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.  De-
              fault is 1232 which is the DNS  Flag  Day  2020  recommendation.
              Setting  to  512 bypasses even the most stringent path MTU prob-
              lems, but is seen as extreme, since the amount of  TCP  fallback
              generated  is  excessive  (probably also for this resolver, con-
              sider 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 4096.

       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 re-
              duced 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 con-
              tention 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 simultane-
              ously.  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  al-
              lowed  time.   This  protects  against denial of service by slow
              queries or high query rates.  Default 200 milliseconds.  The ef-
              fect  is  that  the  qps for long-lasting queries is about (num-
              queriesperthread / 2) / (average time  for  such  long  queries)
              qps.   The  qps  for  short  queries  can  be about (numqueries-
              perthread / 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  pack-
              ets,  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 re-
              ply.  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  buf-
              fer 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 buf-
              fer space on UDP port 53 outgoing queries.  This for  very  busy
              servers  handles  spikes in answer traffic, otherwise 'send: re-
              source temporarily unavailable' can get logged, the buffer over-
              run  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 avail-
              able  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-exis-
              tent  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 permis-
              sions 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 Un-
              bound 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 avail-
              able.

       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  kilo-
              bytes, 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.  De-
              fault 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.  De-
              fault  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  con-
              tains  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 infra-
              structure cache. Default is 50 milliseconds. Increase this value
              if using forwarders needing more time to do recursive name reso-
              lution.

       infra-cache-max-rtt: <msec>
              Upper limit for dynamic retransmit timeout calculation in infra-
              structure 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-con-
              trol.   Enclose  the list between quotes ("") and put spaces be-
              tween 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 in-
              ternet  nameservers. Default is no.  Useful if the IPv6 netblock
              the server has, the entire /64 of that is not owned by one oper-
              ator  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 in-
              ternet 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 re-
              sponds 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).   De-
              fault  is system default MSS determined by interface MTU and ne-
              gotiation 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  in-
              terface 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 op-
              tion  defaults  to  30000 milliseconds.  When the number of free
              incoming TCP buffers falls below 50% of the total number config-
              ured,  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 num-
              ber configured, and finally to 0 if the number of  free  buffers
              falls  below 20% of the total number configured. A minimum time-
              out 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 Un-
              bound 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 re-
              duced to 1% of the configured value, then to 0.2% of the config-
              ured  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 mini-
              mum actual timeout of 200 milliseconds is observed regardless of
              the advertised timeout.

       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 for-
              ward or stub zones using  forward-tcp-upstream  or  stub-tcp-up-
              stream 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-sys-
              tem-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  con-
              tain 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  implic-
              itly  or explicitly via tls-port: and https-port: do not provide
              normal DNS TCP service. Unbound needs to be compiled  with  lib-
              nghttp2 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.  De-
              fault 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  bun-
              dle 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  certifi-
              cates.  Default is no.  On windows this option uses the certifi-
              cates 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  dif-
              ferent 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 Un-
              bound server.  These files contain the secret key  for  the  TLS
              session  tickets.  First key use to encrypt and decrypt TLS ses-
              sion 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  cre-
              ate  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  up-
              streams.  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,  de-
              fault  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.  De-
              fault 100.

       http-query-buffer-size: <size in bytes>
              Maximum  number  of bytes used for all HTTP/2 query buffers com-
              bined. 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. De-
              fault 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 mul-
              tiple, 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 ap-
              pended for a classless network block. The action  can  be  deny,
              refuse,   allow,  allow_setrd,  allow_snoop,  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 action deny stops queries from hosts from that netblock.

              The action refuse stops queries too, but sends a DNS  rcode  RE-
              FUSED error message back.

              The action allow 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 opera-
              tions  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 spe-
              cific zones to a resolver DNS server, but only supports stub do-
              mains  and  sends queries to the resolver DNS server with the RD
              bit cleared.

              The action allow_snoop 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.

              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  pol-
              icy,  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  ac-
              cess  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 ac-
              cess-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 ac-
              tion is the first tag match between access-control-tag  and  lo-
              cal-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-con-
              trol:.  Interfaces are refused by default.  By default only  lo-
              calhost (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  in-
              terface: and that any access-control*: setting overrides all in-
              terface-*: 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  in-
              terface: and that any access-control*: setting overrides all in-
              terface-*: settings for targeted clients.

       interface-tag-action: <ip address or interface name [@port]> <tag> <ac-
       tion>
              Similar to access-control-tag-action: but for interfaces.

              Note  that  the interface needs to be already specified with in-
              terface: and that any access-control*: setting overrides all in-
              terface-*: settings for targeted clients.

       interface-tag-data:  <ip address or interface name [@port]> <tag> <"re-
       source record string">
              Similar to access-control-tag-data: but for interfaces.

              Note that the interface needs to be already specified  with  in-
              terface: and that any access-control*: setting overrides all in-
              terface-*: 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  in-
              terface: and that any access-control*: setting overrides all in-
              terface-*: 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  di-
              rectory,  or  as an absolute path relative to the original root.
              In the last case the path is adjusted to remove the unused  por-
              tion.

              The  pidfile can be either a relative path to the working direc-
              tory, or an absolute path relative to the original root.  It  is
              written  just prior to chroot and dropping permissions. This al-
              lows the pidfile to be /var/run/unbound.pid and the chroot to be
              /var/unbound,  for example. Note that Unbound is not able to re-
              move the pidfile after termination when it is located outside of
              the chroot directory.

              Additionally,  Unbound  may need to access /dev/urandom (for en-
              tropy) from inside the chroot.

              If given a chroot is done to the given directory. By default ch-
              root  is enabled and the default is "/usr/local/etc/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 re-
              quires privileges, then a reload will fail; a restart is needed.

       directory: <directory>
              Sets the working directory for the program. Default is "/usr/lo-
              cal/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 daemo-
              nized.  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  sys-
              log(3).  The log facility LOG_DAEMON is used, with identity "un-
              bound".  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, usu-
              ally "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 (signifi-
              cantly)  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 (signifi-
              cantly) 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  "/usr/lo-
              cal/etc/unbound/unbound.pid".  So,
              kill -HUP `cat /usr/local/etc/unbound/unbound.pid`
              triggers a reload,
              kill -TERM `cat /usr/local/etc/unbound/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 de-
              fault 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 cau-
              tion 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 num-
              bers.   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 le-
              gal protocol wise to send these, and could be necessary for  op-
              eration if TSIG or EDNS payload is very large.

       harden-glue: <yes or no>
              Will  trust glue only if it is within the servers authority. De-
              fault 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 at-
              tack 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 Un-
              derneath"), returns nxdomain to queries for a name below another
              name that is already known to be nxdomain.  DNSSEC mandates  no-
              error  for empty nonterminals, hence this is possible.  Very old
              software might return nxdomain for empty nonterminals (that usu-
              ally happen for reverse IP address lookups), and thus may be in-
              compatible 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 vali-
              dation 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 tar-
              get-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 algo-
              rithm 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.

       use-caps-for-id: <yes or no>
              Use  0x20-encoded  random  bits  in  the query to foil spoof at-
              tempts.  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 per-
              turbed 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 dif-
              ferent 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 en-
              hance 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  NXDO-
              MAIN  and  other  denials, using information from previous NXDO-
              MAINs 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  ad-
              dresses  on  your private network, and are not allowed to be re-
              turned for public internet names.  Any occurrence  of  such  ad-
              dresses  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 addi-
              tional names using private-domain.  No private addresses are en-
              abled  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 spam-
              blocklists   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 ad-
              dresses.   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 ac-
              tion  is to clear the rrset and message caches, hopefully flush-
              ing away any poison.  A value of 10 million is  suggested.   De-
              fault 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 re-
              quests.  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.  De-
              fault 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 num-
              ber  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  unex-
              pectedly  missing.   The  validator  will  insist  in RRSIGs for
              DNSSEC signed domains regardless of this setting, if a trust an-
              chor is loaded.

       module-config: <"module names">
              Module  configuration,  a list of module names separated by spa-
              ces, 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 de-
              fault  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  en-
              tries  can  appear  in  the  file. The format of the file is the
              standard DNS Zone file format.  Default is "", or no  trust  an-
              chor 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 en-
              tries 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 ig-
              nored.  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-an-
              chor-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 ig-
              nored towards the domain name.  So a trust anchor above the  do-
              main  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 ver-
              ifying RRSIG inception and expiration dates, instead of the cur-
              rent  date.  Do  not set this unless you are debugging signature
              inception and expiration. The value -1 ignores  the  date  alto-
              gether, 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  (expira-
              tion  -  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 signa-
              tures.

       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 (expira-
              tion - 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 in-
              stead. 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 sec-
              tion of secure messages that are not signed  properly.  Messages
              that are insecure, bogus, indeterminate or unchecked are not af-
              fected. 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.   Re-
              gardless  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  Dis-
              abled)  flag does not disable checking any more.  This is useful
              if legacy (w2008) servers that set the CD flag but cannot  vali-
              date  DNSSEC  themselves  are the clients, and then Unbound pro-
              vides them with DNSSEC protection.  The default value 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 resolu-
              tion 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 be-
              tween 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-ex-
              pired-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 immedi-
              ately 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  re-
              ceived  from the upstream name server rather than the decrement-
              ing 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 us-
              ing 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 kilo-
              bytes, 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 net-
              work 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  pri-
              vate  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,  typetranspar-
              ent,  inform,  inform_deny, inform_redirect, always_transparent,
              always_refuse, always_nxdomain, always_null, noview, and are ex-
              plained  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  informa-
              tion.  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 re-
                 solved normally.  If the query is for a name given in  local-
                 data  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 de-
                 fault.

            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 an-
                 swers 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  lo-
                 cal-data: "example.com. A 127.0.0.1"  queries  for  www.exam-
                 ple.com and www.foo.example.com are redirected, so that users
                 with web browsers  cannot  access  sites  with  suffix  exam-
                 ple.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 nor-
                 mally.

            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 'node-
                 fault'  option  has  no other effect than turning off default
                 contents for the given zone.  Use nodefault if  you  use  ex-
                 actly  that zone, if you want to use a subzone, use transpar-
                 ent.

       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  informa-
       tion)  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   lo-
                 cal-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  deter-
            mines  further processing. If local-data is configured that is not
            a subdomain of a local-zone, a transparent local-zone  is  config-
            ured.   For record types such as TXT, use single quotes, as in lo-
            cal-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  be-
            low.

       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, type-
            transparent, 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-net-
            block  is  an  IPv6/IPv4 prefix, the record must be AAAA/A respec-
            tively, 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, fol-
            lowing 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 spec-
            ified  IP-netblock,  the specified tags are assigned to the IP ad-
            dress.  Then, if an access-control-tag is defined for  the  client
            and  it  includes  one of the tags for the response IP, the corre-
            sponding access-control-tag-action will apply.  Tag matching  rule
            is  the  same as that for access-control-tag and local-zones.  Un-
            like local-zone-tag, response-ip-tag can be defined for an IP-net-
            block  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 ig-
            nored.  However, this will not be flagged as a  configuration  er-
            ror, 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 con-
            figuration, then the result will be NOERROR/NODATA.  The only case
            where  NXDOMAIN  is returned is when an always_nxdomain action ap-
            plies.

       ratelimit: <number or 0>
            Enable ratelimiting of queries sent to nameserver  for  performing
            recursion.  If 0, the default, it is disabled.  This option is ex-
            perimental 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 rate-
            limited 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  con-
            tention  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  ex-
            ceeded.   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 mit-
            igating 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, ex-
            cept for ratelimit-factor, until demand decreases below  the  con-
            figured ratelimit for a 2 second rate window.  Useful to set rate-
            limit 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 differ-
            ent  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  rate-
            limit-for-domain to set that, you might want to use different set-
            tings  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.  If
            0,  the  default,  it is disabled.  This option is experimental at
            this time.  The ratelimit is in queries per second  that  are  al-
            lowed.  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 amplifica-
            tion attacks.

       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 con-
            tention 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 ex-
            ceeded.  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 mit-
            igating 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,  ex-
            cept  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 re-
            ceived.  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  (re-
            solve) 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 nor-
            mal 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 op-
            tion 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 se-
            lection. 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.

       edns-client-string: <IP netblock> <string>
            Include an EDNS0 option  containing  configured  ascii  string  in
            queries  with  destination address matching the configured IP net-
            block.  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  re-
            sponse for various errors. Default is "no".

            When the val-log-level option is also set to 2, responses with Ex-
            tended 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".

   Remote Control Options
       In  the remote-control: clause are the declarations for the remote con-
       trol 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 un-
       bound-control(8)  utility also reads the remote-control section for op-
       tions.  To setup the  correct  self-signed  certificates  use  the  un-
       bound-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  per-
            missions  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 ef-
            fect.

       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  un-
            bound_server.pem.   This  file  is  generated  by the unbound-con-
            trol-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_con-
            trol.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_con-
            trol.pem.  This certificate has to be signed with the server  cer-
            tificate.   This  file  is  generated by the unbound-control-setup
            utility.  This file is used by unbound-control.

   Stub Zone Options
       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 name-
       servers is used. Class IN is assumed.  The servers should be  authority
       servers,  not  recursors; Unbound performs the recursive processing it-
       self 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  au-
       thoritative  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  authorita-
       tive  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  lo-
       cal-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 certifi-
              cates with that name.  If you combine the '@' and '#',  the  '@'
              comes  first.   If only '#' is used the default port is the con-
              figured 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.

   Forward Zone Options
       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 en-
       try 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 certifi-
              cates with that name.  If you combine the '@' and '#',  the  '@'
              comes  first.   If only '#' is used the default port is the con-
              figured 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  op-
              tion is enabled, Unbound will fall back to normal recursive res-
              olution for this query as if no query forwarding had been speci-
              fied.  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 config-
              ure a tls-cert-bundle or use tls-win-cert to load CA certs, oth-
              erwise 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 Zone Options
       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 are processed after local-zones and before
       cache  (for-downstream: yes), and when used in this manner make Unbound
       respond like an authority server.  Authority zones are  also  processed
       after  cache, just before going to the network to fetch information for
       recursion (for-upstream: yes), and when used in this manner  provide  a
       local copy of an authority server that speeds up lookups of that data.

       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 de-
       tect 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  SERV-
       FAIL,  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 certifi-
              cates will be checked with that name.  If you  combine  the  '@'
              and  '#',  the  '@' comes first.  If you point it at another Un-
              bound 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 depen-
              dency 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/exam-
              ple.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 noti-
              fies.  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 in-
              ternet as a resolver for this zone when lookups fail.  For exam-
              ple 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 be-
              have,  for  the queries with names in this zone, like one of the
              authority servers for that zone.  Turn it off if  you  want  Un-
              bound 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 be-
              fore 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,  Un-
              bound  will  attempt  to  fetch  zone data (eg. from the primary
              servers).

   View Options
       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-con-
       trol-view element. Options from matching views will override global op-
       tions.  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  ac-
              cess-control-view elements.

       local-zone: <zone> <type>
              View specific local-zone elements. Has the same types and behav-
              iour as the global local-zone elements. When there is  at  least
              one  local-zone  specified and view-first is no, the default lo-
              cal-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 lo-
              cal-data if there is no match in the view specific options.  The
              default is no.

   Python Module Options
       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 abso-
       lute path relative to the new root, or as a relative path to the  work-
       ing directory.

       python-script: <python file>
              The  script  file  to  load. Repeat this option for every python
              module instance added to the module-config: option.

   Dynamic Library Module Options
       The dynlib: clause gives the settings for the dynlib module.  This mod-
       ule  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  in-
       stances  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.

   DNS64 Module Options
       The  dns64  module must be configured in the module-config: "dns64 val-
       idator iterator" directive and be compiled into the daemon  to  be  en-
       abled.  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 mul-
              tiple times, list a new domain for which  it  applies,  one  per
              line.  Applies also to names underneath the name given.

   DNSCrypt Options
       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/pub-
       lic keys cannot be generated by Unbound.  You can use  dnscrypt-wrapper
       to  generate those: https://github.com/cofyc/dnscrypt-wrapper/blob/mas-
       ter/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 al-
              low  one  to prime the new cert/key without distributing the new
              cert yet, this can be useful when using a network of servers us-
              ing  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.

   EDNS Client Subnet Module Options
       The ECS module must be configured in  the  module-config:  "subnetcache
       validator iterator" directive and be compiled into the daemon to be en-
       abled.  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 in-
       dicated 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 differ-
       ent 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: op-
       tions.

       send-client-subnet: <IP address>
              Send client source address to this authority. Append /num to in-
              dicate  a  classless  delegation  netblock,  for  example   like
              10.2.3.4/24 or 2001::11/64. Can be given multiple times. Author-
              ities not listed will not receive edns-subnet  information,  un-
              less 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  en-
              abled,  the  address check is skipped when the client query con-
              tains 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.

   Opportunistic IPsec Support Module Options
       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: sec-
       tion.

       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 an-
       swer  was found, Unbound will call an external hook passing the follow-
       ing arguments:

            QNAME
                 Domain name of the A/AAAA and IPSECKEY query.  In string for-
                 mat.

            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.  ipsec-
       mod-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:  direc-
              tive.  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  sys-
              tem(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  suc-
              cess value of 0.  Failing to do so Unbound will reply with SERV-
              FAIL.  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 mod-
              ule  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.

   Cache DB Module Options
       The Cache DB module must be configured in the module-config: "validator
       cachedb iterator" directive and be compiled into the daemon with  --en-
       able-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,  Un-
       bound  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  in-
       stalled 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  time-
       stamps in Redis (computer time must be stable).  This backend uses syn-
       chronous 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  con-
       figurable  timeout in case the server is overly slow or hangs up, these
       cases are assumed to be very rare.  If connection close or timeout hap-
       pens 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 sug-
              gests, 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 data-
              base is shared by multiple Unbound instances, all instances must
              use the same secret seed.  This option defaults to "default".

       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  other-
              wise  Unbound  will have to resolve the name of the server every
              time it establishes a connection to the server.  This option de-
              faults to "127.0.0.1".

       redis-server-port: <port number>
              The  TCP  port number of the Redis server.  This option defaults
              to 6379.

       redis-timeout: <msec>
              The period until when Unbound waits for a response from the  Re-
              dis  sever.   If this timeout expires Unbound closes the connec-
              tion, treats it as if the Redis server does  not  have  the  re-
              quested  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-ex-
              pired  and serve-expired-ttl is 0, this option is internally re-
              verted to "no".  Redis SETEX support is required for this option
              (Redis >= 2.0.0).  This option defaults to no.

   DNSTAP Logging Options
       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 mes-
              sages. 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-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 Zone Options
       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 config-
       uration. 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  certifi-
              cates  will  be  checked with that name.  If you combine the '@'
              and '#', the '@' comes first.  If you point it  at  another  Un-
              bound  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  depen-
              dency 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/exam-
              ple.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  noti-
              fies.   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, Un-
              bound 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  referenc-
              ing.

       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 match-
              ing tag. Tags need to be defined in define-tag and  can  be  as-
              signed  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.

MEMORY CONTROL EXAMPLE
       In the example config settings below memory usage is reduced. Some ser-
       vice  levels are lower, notable very large data and a high TCP load are
       no longer supported. Very large data and high TCP loads are exceptional
       for the DNS.  DNSSEC validation is enabled, just add trust anchors.  If
       you do not have to worry about programs using more than 3 Mb of memory,
       the below example is not for you. Use the defaults to receive full ser-
       vice, which on BSD-32bit tops out at 30-40 Mb after heavy usage.

       # example settings that reduce memory usage
       server:
            num-threads: 1
            outgoing-num-tcp: 1 # this limits TCP service, uses less buffers.
            incoming-num-tcp: 1
            outgoing-range: 60  # uses less memory, but less performance.
            msg-buffer-size: 8192   # note this limits service, 'no huge stuff'.
            msg-cache-size: 100k
            msg-cache-slabs: 1
            rrset-cache-size: 100k
            rrset-cache-slabs: 1
            infra-cache-numhosts: 200
            infra-cache-slabs: 1
            key-cache-size: 100k
            key-cache-slabs: 1
            neg-cache-size: 10k
            num-queries-per-thread: 30
            target-fetch-policy: "2 1 0 0 0 0"
            harden-large-queries: "yes"
            harden-short-bufsize: "yes"

FILES
       /usr/local/etc/unbound
              default Unbound working directory.

       /usr/local/etc/unbound
              default chroot(2) location.

       /usr/local/etc/unbound/unbound.conf
              Unbound configuration file.

       /usr/local/etc/unbound/unbound.pid
              default Unbound pidfile with process ID of the running daemon.

       unbound.log
              Unbound log file. default is to log to syslog(3).

SEE ALSO
       unbound(8), unbound-checkconf(8).

AUTHORS
       Unbound was written by NLnet Labs. Please see CREDITS file in the  dis-
       tribution for further details.



NLnet Labs                       Jan 12, 2023                  unbound.conf(5)