unbound.conf(5)                 unbound 1.19.1                 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  1232.  The  default  value  is  the  same as the default for
              edns-buffer-size.

       stream-wait-size: <number>
              Number of bytes size maximum to use for waiting stream  buffers.
              Default is 4 megabytes.  A plain number is in bytes, append 'k',
              'm' or 'g' for  kilobytes,  megabytes  or  gigabytes  (1024*1024
              bytes  in a megabyte).  As TCP and TLS streams queue up multiple
              results, the amount of memory used for these  buffers  does  not
              exceed  this  number, otherwise the responses are dropped.  This
              manages the total memory usage of the server (under heavy  use),
              the  number  of requests that can be queued up per connection is
              also limited, with further requests waiting in TCP buffers.

       msg-buffer-size: <number>
              Number of bytes size of the message buffers.  Default  is  65552
              bytes,  enough  for 64 Kb packets, the maximum DNS message size.
              No message larger than this can be sent or received. Can be  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.

       sock-queue-timeout: <sec>
              UDP queries that have waited in the socket  buffer  for  a  long
              time  can be dropped. Default is 0, disabled. The time is set in
              seconds, 3 could be a good value  to  ignore  old  queries  that
              likely the client does not need a reply for any more. This could
              happen if the host has not been able to service the queries  for
              a while, i.e. Unbound is not running, and then is enabled again.
              It uses timestamp socket options.

       tcp-upstream: <yes or no>
              Enable or disable whether the upstream queries use TCP only  for
              transport.   Default  is  no.  Useful in tunneling scenarios. If
              set to no you can specify TCP transport only for  selected  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,    allow_cookie,
              deny_non_local  or refuse_non_local.  The most specific netblock
              match is used, if none match refuse is used.  The order  of  the
              access-control statements therefore does not matter.

              The deny action stops queries from hosts from that netblock.

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

              The allow action gives access to clients from that netblock.  It
              gives  only  access  for recursion clients (which is what almost
              all clients need).  Nonrecursive queries are refused.

              The allow action does allow nonrecursive queries to  access  the
              local-data that is configured.  The reason is that this does not
              involve the  Unbound  server  recursive  lookup  algorithm,  and
              static data is served in the reply.  This supports normal 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 allow_snoop action gives nonrecursive access too.  This give
              both recursive and non recursive access.  The  name  allow_snoop
              refers  to  cache  snooping,  a  technique  to  use nonrecursive
              queries to examine the  cache  contents  (for  malicious  acts).
              However,  nonrecursive  queries can also be a valuable debugging
              tool (when you want to examine the cache contents). In that case
              use allow_snoop for your administration host.

              The  allow_cookie  action allows access to UDP queries that con-
              tain a valid DNS Cookie as specified in RFC 7873 and  RFC  9018,
              when  the answer-cookie option is enabled.  UDP queries contain-
              ing only a DNS Client Cookie and no Server Cookie, or an invalid
              DNS  Cookie, will receive a BADCOOKIE response including a newly
              generated DNS Cookie, allowing clients to retry  with  that  DNS
              Cookie.   The allow_cookie action will also accept requests over
              stateful transports, regardless of the presence of an DNS Cookie
              and regardless of the answer-cookie setting.  If ip-ratelimit is
              used, clients with a valid DNS Cookie will bypass the ratelimit.
              If  a  ratelimit  for  such  clients  is  still needed, ip-rate-
              limit-cookie can be used instead.

              By default only localhost is allowed, the rest is refused.   The
              default  is  refused, because that is protocol-friendly. The DNS
              protocol is not designed to handle dropped packets due  to  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.

       harden-unknown-additional: <yes or no>
              Harden  against unknown records in the authority section and ad-
              ditional section. Default is no. If no, such records are  copied
              from  the upstream and presented to the client together with the
              answer. If yes, it could  hamper  future  protocol  developments
              that want to add records.

       use-caps-for-id: <yes or no>
              Use  0x20-encoded  random  bits  in  the query to foil spoof 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".

       disable-edns-do: <yes or no>
              Disable the EDNS DO flag in upstream requests.  It breaks DNSSEC
              validation  for Unbound's clients.  This results in the upstream
              name servers to not include DNSSEC records in their replies  and
              could  be helpful for devices that cannot handle DNSSEC informa-
              tion.  When the option is enabled, clients that set the DO  flag
              receive  no  EDNS record in the response to indicate the lack of
              support to them.  If this option is enabled but Unbound  is  al-
              ready configured for DNSSEC validation (i.e., the validator mod-
              ule is enabled; default) this option is  implicitly  turned  off
              with  a  warning  as  to not break DNSSEC validation in Unbound.
              Default is no.

       serve-expired: <yes or no>
              If enabled, Unbound attempts to serve old responses  from  cache
              with  a  TTL  of serve-expired-reply-ttl in the response without
              waiting for the actual resolution to finish.  The actual 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,
              block_a, always_refuse,  always_nxdomain,  always_null,  noview,
              and  are  explained  below.  After that the default settings are
              listed. Use local-data: to enter data into the local  zone.  An-
              swers  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.

            block_a
                 Like transparent, but ignores local data  and  resolves  nor-
                 mally  all query types excluding A. For A queries it uncondi-
                 tionally returns NODATA.  Useful in cases  when  there  is  a
                 need  to  explicitly  force all apps to use IPv6 protocol and
                 avoid any queries to IPv4.

            always_refuse
                 Like refuse, but ignores local data and refuses the query.

            always_nxdomain
                 Like static, but ignores local data and returns nxdomain  for
                 the query.

            always_nodata
                 Like  static,  but  ignores local data and returns nodata for
                 the query.

            always_deny
                 Like deny, but ignores local data and drops the query.

            always_null
                 Always returns 0.0.0.0 or ::0 for every  name  in  the  zone.
                 Like  redirect  with zero data for A and AAAA.  Ignores local
                 data in the zone.  Used for some block lists.

            noview
                 Breaks out of that view and moves towards  the  global  local
                 zones  for  answer  to  the  query.  If the view first is no,
                 it'll resolve normally.  If  view  first  is  enabled,  it'll
                 break  perform  that  step and check the global answers.  For
                 when the view has view specific overrides but some  zone  has
                 to be answered from global local zone contents.

            nodefault
                 Used  to turn off default contents for AS112 zones. The other
                 types also turn off default contents for the zone. The '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.
            This  option  is  experimental  at this time.  The ratelimit is in
            queries per second that are allowed.  More queries are  completely
            dropped  and  will not receive a reply, SERVFAIL or otherwise.  IP
            ratelimiting happens before looking in the cache. This may be use-
            ful  for  mitigating  amplification  attacks.   Default is 0 (dis-
            abled).

       ip-ratelimit-cookie: <number or 0>
            Enable global ratelimiting of queries accepted per IP address with
            a  valid  DNS  Cookie.   This option is experimental at this time.
            The ratelimit is in queries per second  that  are  allowed.   More
            queries are completely dropped and will not receive a reply, SERV-
            FAIL or otherwise.  IP ratelimiting happens before looking in  the
            cache.   This  option  could  be  useful  in  combination with al-
            low_cookie in an attempt to mitigate other  amplification  attacks
            than  UDP  reflections  (e.g.,  attacks  targeting Unbound itself)
            which are already handled with DNS Cookies.  If used, the value is
            suggested  to  be higher than ip-ratelimit e.g., tenfold.  Default
            is 0 (disabled).

       ip-ratelimit-size: <memory size>
            Give the size of the data structure in which the  current  ongoing
            rates  are  kept  track in.  Default 4m.  In bytes or use m(mega),
            k(kilo), g(giga).  The ip ratelimit structure is  small,  so  this
            data structure likely does not need to be large.

       ip-ratelimit-slabs: <number>
            Give  power of 2 number of slabs, this is used to reduce lock 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.

       answer-cookie: <yes or no>
            If enabled, Unbound will answer to requests containing DNS Cookies
            as specified in RFC 7873 and RFC 9018.  Default is no.

       cookie-secret: <128 bit hex string>
            Server's  secret  for DNS Cookie generation.  Useful to explicitly
            set for servers in an anycast deployment that need  to  share  the
            secret in order to verify each other's Server Cookies.  An example
            hex string would be  "000102030405060708090a0b0c0d0e0f".   Default
            is a 128 bits random secret generated at startup time.

       edns-client-string: <IP netblock> <string>
            Include  an  EDNS0  option  containing  configured ascii string in
            queries with destination address matching the configured  IP  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 can be processed on two distinct, non-ex-
       clusive, configurable stages.

       With for-downstream: yes (default), authority zones are processed after
       local-zones  and  before  cache.  When used in this manner, Unbound re-
       sponds like an authority server with no further processing  other  than
       returning an answer from the zone contents.  A notable example, in this
       case, is CNAME  records  which  are  returned  verbatim  to  downstream
       clients without further resolution.

       With  for-upstream:  yes (default), authority zones are processed after
       the cache lookup, just before going to the network to fetch information
       for  recursion.   When used in this manner they provide a local copy of
       an authority server that speeds up lookups for that data during resolv-
       ing.

       If  both options are enabled (default), client queries for an authority
       zone are answered authoritatively from Unbound, while internal  queries
       that  require  data from the authority zone consult the local zone data
       instead of going to the network.

       An interesting configuration is for-downstream: no,  for-upstream:  yes
       that  allows  for  hyperlocal  behavior  where both client and internal
       queries consult the local zone data while resolving.  In this case, the
       aforementioned  CNAME  example will result in a thoroughly resolved an-
       swer.

       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.

   NAT64 Operation
       NAT64 operation allows using a NAT64 prefix for  outbound  requests  to
       IPv4-only servers.  It is controlled by two options in the server: sec-
       tion:

       do-nat64: <yes or no>
              Use NAT64 to reach IPv4-only servers.   Consider  also  enabling
              prefer-ip6  to  prefer  native  IPv6 connections to nameservers.
              Default no.

       nat64-prefix: <IPv6 prefix>
              Use a specific NAT64 prefix to  reach  IPv4-only  servers.   De-
              faults  to using the prefix configured in dns64-prefix, which in
              turn defaults to 64:ff9b::/96.  The prefix length must be one of
              /32, /40, /48, /56, /64 or /96.

   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".

       cachedb-no-store: <yes or no>
              If  the  backend  should  be read from, but not written to. This
              makes this instance not store dns messages in the  backend.  But
              if data is available it is retrieved. The default is no.

       The following cachedb options are specific to the redis backend.

       redis-server-host: <server address or name>
              The  IP  (either  v6  or v4) address or domain name of the Redis
              server.  In general an IP address should be specified as  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-server-path: <unix socket path>
              The unix socket path to connect to the redis server. Off by  de-
              fault,  and  it  can be set to "" to turn this off. Unix sockets
              may have better throughput than the IP address option.

       redis-server-password: "<password>"
              The Redis AUTH password to use for the redis server.  Only rele-
              vant  if  Redis is configured for client password authorisation.
              Off by default, and it can be set to "" to turn this off.

       redis-timeout: <msec>
              The period until when Unbound waits for a response from the  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.

       redis-logical-db: <logical database index>
              The  logical  database  in Redis to use.  These are databases in
              the same Redis instance sharing the same configuration and  per-
              sisted in the same RDB/AOF file.  If unsure about using this op-
              tion,  Redis  documentation  (https://redis.io/commands/select/)
              suggests  not  to use a single Redis instance for multiple unre-
              lated applications.  The default database in Redis  is  0  while
              other  logical  databases  need  to be explicitly SELECT'ed upon
              connecting.  This option defaults to 0.

   DNSTAP 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                       Feb 13, 2024                  unbound.conf(5)