unbound.conf(5)                 unbound 1.13.1                 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. Level 3 gives query level information,
              output per query.  Level 4 gives  algorithm  level  information.
              Level 5 logs client identification for cache misses.  Default is
              level 1.  The verbosity can also be increased from the  command-
              line, 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).

       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[@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[@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.

       outgoing-interface: <ip address or ip6 netblock>
              Interface  to  use  to connect to the network. This interface is
              used to send queries to authoritative servers and receive  their
              replies.  Can  be given multiple times to work on several inter-
              faces. If none are given the default  (all)  is  used.  You  can
              specify  the  same  interfaces in interface: and outgoing-inter-
              face: lines, the interfaces are then  used  for  both  purposes.
              Outgoing  queries  are  sent  via a random outgoing interface to
              counter spoofing.

              If an IPv6 netblock is specified instead of an  individual  IPv6
              address,  outgoing  UDP queries will use a randomised source ad-
              dress taken from the netblock to counter spoofing. Requires  the
              IPv6  netblock to be routed to the host running unbound, and re-
              quires OS support for unprivileged  non-local  binds  (currently
              only  supported  on  Linux).  Several netblocks may be specified
              with multiple outgoing-interface: options, but  do  not  specify
              both  an  individual  IPv6  address and an IPv6 netblock, or the
              randomisation will be compromised.  Consider combining with pre-
              fer-ip6:  yes to increase the likelihood of IPv6 nameservers be-
              ing selected for queries.  On Linux you need these two  commands
              to  be able to use the freebind socket option to receive traffic
              for the ip6 netblock: ip -6 addr add mynetblock/64 dev lo &&  ip
              -6 route add local mynetblock/64 dev lo

       outgoing-range: <number>
              Number  of ports to open. This number of file descriptors can be
              opened per thread. Must be at least 1. Default depends  on  com-
              pile options. Larger numbers need extra resources from the oper-
              ating system.  For performance a very large value is  best,  use
              libevent to make this possible.

       outgoing-port-permit: <port number or range>
              Permit  unbound  to  open this port or range of ports for use to
              send queries.  A larger number of permitted outgoing  ports  in-
              creases  resilience  against  spoofing attempts. Make sure these
              ports are not needed by other daemons.  By  default  only  ports
              above 1024 that have not been assigned by IANA are used.  Give a
              port number or a range of the form "low-high", without spaces.

              The outgoing-port-permit and outgoing-port-avoid statements  are
              processed  in the line order of the config file, adding the per-
              mitted ports and subtracting the avoided ports from the  set  of
              allowed  ports.   The  processing starts with the non IANA allo-
              cated ports above 1024 in the set of allowed ports.

       outgoing-port-avoid: <port number or range>
              Do not permit unbound to open this port or range  of  ports  for
              use to send queries. Use this to make sure unbound does not grab
              a port that another daemon needs. The port  is  avoided  on  all
              outgoing  interfaces,  both  IP4 and IP6.  By default only ports
              above 1024 that have not been assigned by IANA are used.  Give a
              port number or a range of the form "low-high", without spaces.

       outgoing-num-tcp: <number>
              Number  of  outgoing TCP buffers to allocate per thread. Default
              is 10. If set to 0, or if do-tcp is "no", no TCP queries to  au-
              thoritative servers are done.  For larger installations increas-
              ing this value is a good idea.

       incoming-num-tcp: <number>
              Number of incoming TCP buffers to allocate per  thread.  Default
              is  10.  If  set to 0, or if do-tcp is "no", no TCP queries from
              clients are accepted. For larger installations  increasing  this
              value is a good idea.

       edns-buffer-size: <number>
              Number  of bytes size to advertise as the EDNS reassembly buffer
              size.  This is the value put into  datagrams  over  UDP  towards
              peers.   The actual buffer size is determined by msg-buffer-size
              (both for TCP and UDP).  Do not set higher than that value.  De-
              fault  is  1232  which  is the DNS Flag Day 2020 recommendation.
              Setting to 512 bypasses even the most stringent path  MTU  prob-
              lems,  but  is seen as extreme, since the amount of TCP fallback
              generated is excessive (probably also for  this  resolver,  con-
              sider tuning the outgoing tcp number).

       max-udp-size: <number>
              Maximum  UDP response size (not applied to TCP response).  65536
              disables the udp response size maximum, and uses the choice from
              the  client,  always.  Suggested values are 512 to 4096. Default
              is 4096.

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

       msg-buffer-size: <number>
              Number of bytes size of the message buffers.  Default  is  65552
              bytes,  enough  for 64 Kb packets, the maximum DNS message size.
              No message larger than this can be sent or received. Can be  re-
              duced  to  use less memory, but some requests for DNS data, such
              as for huge resource records, will result in a SERVFAIL reply to
              the client.

       msg-cache-size: <number>
              Number  of  bytes  size  of  the  message  cache.  Default  is 4
              megabytes.  A plain number is in bytes, append 'k', 'm'  or  'g'
              for  kilobytes,  megabytes  or  gigabytes  (1024*1024 bytes in a
              megabyte).

       msg-cache-slabs: <number>
              Number of slabs in the message cache.  Slabs  reduce  lock  con-
              tention  by  threads.   Must  be  set  to  a power of 2. Setting
              (close) to the number of cpus is a reasonable guess.

       num-queries-per-thread: <number>
              The number of queries that every thread will service  simultane-
              ously.   If  more  queries  arrive  that  need servicing, and no
              queries can  be  jostled  out  (see  jostle-timeout),  then  the
              queries  are  dropped.  This forces the client to resend after a
              timeout; allowing the  server  time  to  work  on  the  existing
              queries. Default depends on compile options, 512 or 1024.

       jostle-timeout: <msec>
              Timeout  used when the server is very busy.  Set to a value that
              usually results in one roundtrip to the authority  servers.   If
              too  many queries arrive, then 50% of the queries are allowed to
              run to completion, and the other 50% are replaced with  the  new
              incoming  query  if  they have already spent more than their al-
              lowed time.  This protects against denial  of  service  by  slow
              queries or high query rates.  Default 200 milliseconds.  The ef-
              fect is that the qps for long-lasting  queries  is  about  (num-
              queriesperthread  /  2)  /  (average time for such long queries)
              qps.  The qps  for  short  queries  can  be  about  (numqueries-
              perthread  /  2)  /  (jostletimeout  in  whole  seconds) qps per
              thread, about (1024/2)*5 = 2560 qps by default.

       delay-close: <msec>
              Extra delay for timeouted UDP ports before they are  closed,  in
              msec.   Default  is 0, and that disables it.  This prevents very
              delayed answer packets from  the  upstream  (recursive)  servers
              from  bouncing  against closed ports and setting off all sort of
              close-port counters, with eg. 1500 msec.  When  timeouts  happen
              you  need extra sockets, it checks the ID and remote IP of pack-
              ets, and unwanted packets  are  added  to  the  unwanted  packet
              counter.

       udp-connect: <yes or no>
              Perform connect for UDP sockets that mitigates ICMP side channel
              leakage.  Default is yes.

       unknown-server-time-limit: <msec>
              The wait time in msec for waiting for an unknown server  to  re-
              ply.   Increase this if you are behind a slow satellite link, to
              eg. 1128.  That would then avoid re-querying every initial query
              because it times out.  Default is 376 msec.

       so-rcvbuf: <number>
              If  not 0, then set the SO_RCVBUF socket option to get more buf-
              fer space on UDP port 53 incoming queries.  So that short spikes
              on  busy  servers  do  not  drop packets (see counter in netstat
              -su).  Default is 0 (use system value).  Otherwise,  the  number
              of  bytes to ask for, try "4m" on a busy server.  The OS caps it
              at a maximum, on linux unbound needs root permission  to  bypass
              the  limit,  or  the admin can use sysctl net.core.rmem_max.  On
              BSD change kern.ipc.maxsockbuf in /etc/sysctl.conf.  On  OpenBSD
              change header and recompile kernel. On Solaris ndd -set /dev/udp
              udp_max_buf 8388608.

       so-sndbuf: <number>
              If not 0, then set the SO_SNDBUF socket option to get more  buf-
              fer  space  on UDP port 53 outgoing queries.  This for very busy
              servers handles spikes in answer traffic, otherwise  'send:  re-
              source temporarily unavailable' can get logged, the buffer over-
              run is also visible by netstat -su.  Default is  0  (use  system
              value).   Specify  the number of bytes to ask for, try "4m" on a
              very busy server.  The OS caps it at a maximum, on linux unbound
              needs  root permission to bypass the limit, or the admin can use
              sysctl net.core.wmem_max.  On BSD, Solaris changes  are  similar
              to so-rcvbuf.

       so-reuseport: <yes or no>
              If  yes,  then  open  dedicated  listening  sockets for incoming
              queries for each thread and try to set the  SO_REUSEPORT  socket
              option  on  each  socket.   May  distribute  incoming queries to
              threads more evenly.  Default is yes.  On Linux it is  supported
              in  kernels  >= 3.9.  On other systems, FreeBSD, OSX it may also
              work.  You can enable it (on any platform and kernel),  it  then
              attempts to open the port and passes the option if it was avail-
              able at compile time, if that works it is used, if it fails,  it
              continues  silently (unless verbosity 3) without the option.  At
              extreme load it could be better to turn it off to distribute the
              queries evenly, reported for Linux systems (4.4.x).

       ip-transparent: <yes or no>
              If  yes,  then use IP_TRANSPARENT socket option on sockets where
              unbound is listening for incoming traffic.  Default no.   Allows
              you  to bind to non-local interfaces.  For example for non-exis-
              tent IP addresses that are going to exist later  on,  with  host
              failover configuration.  This is a lot like interface-automatic,
              but that one services all interfaces and with  this  option  you
              can  select  which  (future) interfaces unbound provides service
              on.  This option needs unbound to be started with  root  permis-
              sions  on  some  systems.  The option uses IP_BINDANY on FreeBSD
              systems and SO_BINDANY on OpenBSD systems.

       ip-freebind: <yes or no>
              If yes, then use IP_FREEBIND socket option on sockets where  un-
              bound is listening to incoming traffic.  Default no.  Allows you
              to bind to IP addresses that are nonlocal or do not exist,  like
              when  the  network interface or IP address is down.  Exists only
              on Linux, where the similar ip-transparent option is also avail-
              able.

       ip-dscp: <number>
              The value of the Differentiated Services Codepoint (DSCP) in the
              differentiated services field (DS) of  the  outgoing  IP  packet
              headers.   The  field replaces the outdated IPv4 Type-Of-Service
              field and the IPV6 traffic class field.

       rrset-cache-size: <number>
              Number of bytes size of the RRset cache. Default is 4 megabytes.
              A  plain  number  is  in bytes, append 'k', 'm' or 'g' for kilo-
              bytes, megabytes or gigabytes (1024*1024 bytes in a megabyte).

       rrset-cache-slabs: <number>
              Number of slabs in the RRset cache. Slabs reduce lock contention
              by threads.  Must be set to a power of 2.

       cache-max-ttl: <seconds>
              Time  to  live maximum for RRsets and messages in the cache. De-
              fault is 86400 seconds (1 day).  When the TTL expires, the cache
              item  has  expired.   Can  be set lower to force the resolver to
              query for data often, and not trust  (very  large)  TTL  values.
              Downstream clients also see the lower TTL.

       cache-min-ttl: <seconds>
              Time  to  live minimum for RRsets and messages in the cache. De-
              fault is 0.  If the minimum kicks in, the  data  is  cached  for
              longer than the domain owner intended, and thus less queries are
              made to look up the data.  Zero makes sure the data in the cache
              is  as the domain owner intended, higher values, especially more
              than an hour or so, can lead to trouble as the data in the cache
              does not match up with the actual data any more.

       cache-max-negative-ttl: <seconds>
              Time to live maximum for negative responses, these have a SOA in
              the authority section that is limited in time.  Default is 3600.
              This applies to nxdomain and nodata answers.

       infra-host-ttl: <seconds>
              Time  to live for entries in the host cache. The host cache con-
              tains roundtrip timing, lameness and EDNS  support  information.
              Default is 900.

       infra-cache-slabs: <number>
              Number  of  slabs in the infrastructure cache. Slabs reduce lock
              contention by threads. Must be set to a power of 2.

       infra-cache-numhosts: <number>
              Number of hosts for which  information  is  cached.  Default  is
              10000.

       infra-cache-min-rtt: <msec>
              Lower limit for dynamic retransmit timeout calculation in infra-
              structure cache. Default is 50 milliseconds. Increase this value
              if using forwarders needing more time to do recursive name reso-
              lution.

       infra-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.

       edns-tcp-keepalive: <yes or no>
              Enable or disable EDNS TCP Keepalive. Default is no.

       edns-tcp-keepalive-timeout: <msec>
              The  period  Unbound  will  wait for a query on a TCP connection
              when EDNS TCP Keepalive is active. If this timeout  expires  Un-
              bound closes the connection. If the client supports the EDNS TCP
              Keepalive option, Unbound sends the timeout value to the  client
              to  encourage it to close the connection before the server times
              out.  This option defaults to  120000  milliseconds.   When  the
              number of free incoming TCP buffers falls below 50% of the total
              number configured, the advertised timeout is  progressively  re-
              duced to 1% of the configured value, then to 0.2% of the config-
              ured value if the number of free buffers falls below 35% of  the
              total  number configured, and finally to 0 if the number of free
              buffers falls below 20% of the total number configured.  A mini-
              mum actual timeout of 200 milliseconds is observed regardless of
              the advertised timeout.

       tcp-upstream: <yes or no>
              Enable or disable whether the upstream queries use TCP only  for
              transport.  Default is no.  Useful in tunneling scenarios.

       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  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.

       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.

       use-systemd: <yes or no>
              Enable or disable systemd socket activation.  Default is no.

       do-daemonize: <yes or no>
              Enable or disable whether the  unbound  server  forks  into  the
              background  as  a daemon.  Set the value to no when unbound runs
              as systemd service.  Default is yes.

       tcp-connection-limit: <IP netblock> <limit>
              Allow up to limit simultaneous TCP connections  from  the  given
              netblock.   When  at the limit, further connections are accepted
              but closed immediately.  This option  is  experimental  at  this
              time.

       access-control: <IP netblock> <action>
              The  netblock  is  given as an IP4 or IP6 address with /size ap-
              pended for a classless network block. The action  can  be  deny,
              refuse,   allow,  allow_setrd,  allow_snoop,  deny_non_local  or
              refuse_non_local.  The most specific netblock match is used,  if
              none match deny is used.  The order of the access-control state-
              ments therefore does not matter.

              The action deny stops queries from hosts from that netblock.

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

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

              The  allow  action does allow nonrecursive queries to access the
              local-data that is configured.  The reason is that this does not
              involve  the  unbound  server  recursive  lookup  algorithm, and
              static data is served in the reply.  This supports normal opera-
              tions  where nonrecursive queries are made for the authoritative
              data.  For nonrecursive queries any  replies  from  the  dynamic
              cache are refused.

              The  allow_setrd  action  ignores the recursion desired (RD) bit
              and treats all requests as if the recursion desired bit is  set.
              Note  that  this  behavior violates RFC 1034 which states that a
              name server should never perform recursive service unless  asked
              via  the  RD  bit since this interferes with trouble shooting of
              name servers and their databases. This prohibited  behavior  may
              be  useful  if another DNS server must forward requests for spe-
              cific zones to a resolver DNS server, but only supports stub do-
              mains  and  sends queries to the resolver DNS server with the RD
              bit cleared.

              The action allow_snoop gives nonrecursive access too.  This give
              both  recursive  and non recursive access.  The name allow_snoop
              refers to  cache  snooping,  a  technique  to  use  nonrecursive
              queries  to  examine  the  cache  contents (for malicious acts).
              However, nonrecursive queries can also be a  valuable  debugging
              tool (when you want to examine the cache contents). In that case
              use allow_snoop for your administration host.

              By default only localhost is allowed, the rest is refused.   The
              default  is  refused, because that is protocol-friendly. The DNS
              protocol is not designed to handle dropped packets due  to  pol-
              icy,  and  dropping  may  result in (possibly excessive) retried
              queries.

              The deny_non_local and refuse_non_local settings are  for  hosts
              that are only allowed to query for the authoritative local-data,
              they are not allowed full recursion but only  the  static  data.
              With  deny_non_local,  messages that are disallowed are dropped,
              with refuse_non_local they receive error code REFUSED.

       access-control-tag: <IP netblock> <"list of tags">
              Assign tags to access-control elements. Clients using  this  ac-
              cess  control element use localzones that are tagged with one of
              these tags. Tags must be defined in define-tags.   Enclose  list
              of  tags  in  quotes  ("")  and  put spaces between tags. If ac-
              cess-control-tag is configured for a netblock that does not have
              an  access-control,  an access-control element with action allow
              is configured for this netblock.

       access-control-tag-action: <IP netblock> <tag> <action>
              Set action for particular tag for given access control  element.
              If  you have multiple tag values, the tag used to lookup the ac-
              tion is the first tag match between access-control-tag  and  lo-
              cal-zone-tag  where  "first" comes from the order of the define-
              tag values.

       access-control-tag-data: <IP netblock> <tag> <"resource record string">
              Set redirect data for particular tag for  given  access  control
              element.

       access-control-view: <IP netblock> <view name>
              Set view for given access control element.

       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.

       nsid: <string>
              Add the specified nsid to the EDNS section of  the  answer  when
              queried  with an NSID EDNS enabled packet.  As a sequence of hex
              characters or with ascii_ prefix and then an ascii string.

       hide-trustanchor: <yes or no>
              If enabled trustanchor.unbound queries are refused.

       target-fetch-policy: <"list of numbers">
              Set the target fetch policy used by unbound to determine  if  it
              should  fetch nameserver target addresses opportunistically. The
              policy is described per dependency depth.

              The number of values determines  the  maximum  dependency  depth
              that  unbound  will  pursue in answering a query.  A value of -1
              means to fetch all targets opportunistically for that dependency
              depth.  A  value  of 0 means to fetch on demand only. A positive
              value fetches that many targets opportunistically.

              Enclose the list between quotes ("") and put spaces between num-
              bers.   The default is "3 2 1 0 0". Setting all zeroes, "0 0 0 0
              0" gives behaviour closer to that of BIND 9, while  setting  "-1
              -1  -1  -1  -1" gives behaviour rumoured to be closer to that of
              BIND 8.

       harden-short-bufsize: <yes or no>
              Very small EDNS buffer sizes from queries are  ignored.  Default
              is on, as described in the standard.

       harden-large-queries: <yes or no>
              Very  large queries are ignored. Default is off, since it is le-
              gal protocol wise to send these, and could be necessary for  op-
              eration if TSIG or EDNS payload is very large.

       harden-glue: <yes or no>
              Will  trust glue only if it is within the servers authority. De-
              fault is yes.

       harden-dnssec-stripped: <yes or no>
              Require DNSSEC data for trust-anchored zones, if  such  data  is
              absent,  the  zone  becomes  bogus. If turned off, and no DNSSEC
              data is received (or the DNSKEY data fails  to  validate),  then
              the  zone  is made insecure, this behaves like there is no trust
              anchor. You could turn this off if you are sometimes  behind  an
              intrusive  firewall (of some sort) that removes DNSSEC data from
              packets, or a zone changes from  signed  to  unsigned  to  badly
              signed  often. If turned off you run the risk of a downgrade at-
              tack that disables security for a zone. Default is yes.

       harden-below-nxdomain: <yes or no>
              From RFC 8020 (with title "NXDOMAIN: There Really Is Nothing Un-
              derneath"), returns nxdomain to queries for a name below another
              name that is already known to be nxdomain.  DNSSEC mandates  no-
              error  for empty nonterminals, hence this is possible.  Very old
              software might return nxdomain for empty nonterminals (that usu-
              ally happen for reverse IP address lookups), and thus may be in-
              compatible with this.  To try to avoid this  only  DNSSEC-secure
              nxdomains  are  used,  because  the  old  software does not have
              DNSSEC.  Default is yes.  The  nxdomain  must  be  secure,  this
              means nsec3 with optout is insufficient.

       harden-referral-path: <yes or no>
              Harden  the  referral  path by performing additional queries for
              infrastructure data.  Validates the replies if trust anchors are
              configured and the zones are signed.  This enforces DNSSEC vali-
              dation on nameserver NS sets and the nameserver  addresses  that
              are encountered on the referral path to the answer.  Default no,
              because it burdens the authority servers,  and  it  is  not  RFC
              standard,  and could lead to performance problems because of the
              extra query load that is generated.   Experimental  option.   If
              you  enable  it  consider  adding  more  numbers  after the tar-
              get-fetch-policy to increase the max depth that is checked to.

       harden-algo-downgrade: <yes or no>
              Harden against algorithm downgrade when multiple algorithms  are
              advertised  in  the  DS record.  If no, allows the weakest algo-
              rithm to validate the zone.  Default is no.  Zone  signers  must
              produce  zones  that  allow  this feature to work, but sometimes
              they do not, and turning this option off avoids that  validation
              failure.

       use-caps-for-id: <yes or no>
              Use  0x20-encoded  random  bits  in  the query to foil spoof at-
              tempts.  This perturbs the  lowercase  and  uppercase  of  query
              names  sent  to  authority servers and checks if the reply still
              has the correct casing.  Disabled by default.  This  feature  is
              an experimental implementation of draft dns-0x20.

       caps-exempt: <domain>
              Exempt  the  domain so that it does not receive caps-for-id per-
              turbed queries.  For domains that do not support 0x20  and  also
              fail  with fallback because they keep sending different answers,
              like some load balancers.  Can be given multiple times, for dif-
              ferent domains.

       caps-whitelist: <yes or no>
              Alternate syntax for caps-exempt.

       qname-minimisation: <yes or no>
              Send  minimum  amount  of information to upstream servers to en-
              hance privacy.  Only send minimum required labels of  the  QNAME
              and  set  QTYPE  to  A when possible. Best effort approach; full
              QNAME and original QTYPE will be sent when upstream replies with
              a  RCODE other than NOERROR, except when receiving NXDOMAIN from
              a DNSSEC signed zone. Default is yes.

       qname-minimisation-strict: <yes or no>
              QNAME minimisation in strict mode. Do not fall-back  to  sending
              full  QNAME  to potentially broken nameservers. A lot of domains
              will not be resolvable when this option in enabled. Only use  if
              you  know  what you are doing.  This option only has effect when
              qname-minimisation is enabled. Default is no.

       aggressive-nsec: <yes or no>
              Aggressive NSEC uses the DNSSEC NSEC chain to  synthesize  NXDO-
              MAIN  and  other  denials, using information from previous NXDO-
              MAINs answers.  Default is no.  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  doesn't  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
              validator,  iterator.  Setting this to "iterator" will result in
              a non-validating server.  Setting this to  "validator  iterator"
              will  turn on DNSSEC validation.  The ordering of the modules is
              important.  You must also set trust-anchors for validation to be
              useful.   The  default is "validator iterator".  When the server
              is built with EDNS client subnet support the default is "subnet-
              cache  validator iterator".  Most modules that need to be listed
              here have to be listed  at  the  beginning  of  the  line.   The
              cachedb  module  has to be listed just before the iterator.  The
              python module can be listed in different places,  it  then  pro-
              cesses  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-bogus-ttl: <number>
              The  time  to  live for bogus data. This is data that has failed
              validation; due to invalid signatures or other checks.  The  TTL
              from  that  data  cannot  be trusted, and this value is used in-
              stead. The value is in seconds, default 60.  The  time  interval
              prevents repeated revalidation of bogus data.

       val-clean-additional: <yes or no>
              Instruct  the  validator to remove data from the additional sec-
              tion of secure messages that are not signed  properly.  Messages
              that are insecure, bogus, indeterminate or unchecked are not af-
              fected. Default is yes. Use this setting to  protect  the  users
              that  rely on this validator for authentication from potentially
              bad data in the additional section.

       val-log-level: <number>
              Have the validator print validation failures to  the  log.   Re-
              gardless  of  the  verbosity setting.  Default is 0, off.  At 1,
              for every user query that fails a line is printed to  the  logs.
              This  way  you  can monitor what happens with validation.  Use a
              diagnosis tool, such as dig or drill, to find out why validation
              is  failing  for  these  queries.  At 2, not only the query that
              failed is printed but also the reason why unbound thought it was
              wrong and which server sent the faulty data.

       val-permissive-mode: <yes or no>
              Instruct  the validator to mark bogus messages as indeterminate.
              The security checks are performed, but if the  result  is  bogus
              (failed  security),  the  reply  is not withheld from the client
              with SERVFAIL as usual. The client receives the bogus data.  For
              messages  that  are  found  to  be  secure  the AD bit is set in
              replies. Also logging is performed as for full validation.   The
              default value is "no".

       ignore-cd-flag: <yes or no>
              Instruct  unbound  to ignore the CD flag from clients and refuse
              to return bogus answers to them.  Thus, the  CD  (Checking  Dis-
              abled)  flag does not disable checking any more.  This is useful
              if legacy (w2008) servers that set the CD flag but cannot  vali-
              date  DNSSEC  themselves  are the clients, and then unbound pro-
              vides them with DNSSEC protection.  The default value is "no".

       serve-expired: <yes or no>
              If enabled, unbound attempts to serve old responses  from  cache
              with  a  TTL  of serve-expired-reply-ttl in the response without
              waiting for the actual resolution to finish.  The actual resolu-
              tion answer ends up in the cache later on.  Default is "no".

       serve-expired-ttl: <seconds>
              Limit  serving  of expired responses to configured seconds after
              expiration. 0 disables the limit.  This option only applies when
              serve-expired is enabled.  A suggested value per RFC 8767 is be-
              tween 86400 (1 day) and 259200 (3 days).  The default is 0.

       serve-expired-ttl-reset: <yes or no>
              Set the TTL of expired records to  the  serve-expired-ttl  value
              after  a  failed  attempt  to retrieve the record from upstream.
              This makes sure that the expired records will be served as  long
              as there are queries for it.  Default is "no".

       serve-expired-reply-ttl: <seconds>
              TTL  value to use when replying with expired data.  If serve-ex-
              pired-client-timeout is also used then it is RECOMMENDED to  use
              30 as the value (RFC 8767).  The default is 30.

       serve-expired-client-timeout: <msec>
              Time  in milliseconds before replying to the client with expired
              data.  This essentially  enables  the  serve-stale  behavior  as
              specified in RFC 8767 that first tries to resolve before immedi-
              ately responding with expired data.  A recommended value per RFC
              8767  is  1800.   Setting  this to 0 will disable this behavior.
              Default is 0.

       serve-original-ttl: <yes or no>
              If enabled, unbound will always return the original TTL  as  re-
              ceived  from the upstream name server rather than the decrement-
              ing TTL as stored in the cache.  This feature may be  useful  if
              unbound  serves  as  a  front-end to a hidden authoritative name
              server. Enabling this feature does not impact cache  expiry,  it
              only  changes  the  TTL  unbound embeds in responses to queries.
              Note that enabling this feature implicitly disables  enforcement
              of  the  configured  minimum  and  maximum TTL, as it is assumed
              users who enable this feature do not want unbound to change  the
              TTL  obtained from an upstream server.  Thus, the values set us-
              ing cache-min-ttl and cache-max-ttl  are  ignored.   Default  is
              "no".

       val-nsec3-keysize-iterations: <"list of values">
              List of keysize and iteration count values, separated by spaces,
              surrounded by quotes. Default is "1024 150 2048 500 4096  2500".
              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.

       add-holddown: <seconds>
              Instruct the auto-trust-anchor-file probe mechanism for  RFC5011
              autotrust  updates to add new trust anchors only after they have
              been visible for this time.  Default is 30 days as per the RFC.

       del-holddown: <seconds>
              Instruct the auto-trust-anchor-file probe mechanism for  RFC5011
              autotrust  updates  to  remove  revoked trust anchors after they
              have been kept in the revoked list for this long.  Default is 30
              days as per the RFC.

       keep-missing: <seconds>
              Instruct  the auto-trust-anchor-file probe mechanism for RFC5011
              autotrust updates to remove missing  trust  anchors  after  they
              have  been  unseen for this long.  This cleans up the state file
              if the target zone does not perform trust anchor revocation,  so
              this makes the auto probe mechanism work with zones that perform
              regular (non-5011) rollovers.  The default  is  366  days.   The
              value 0 does not remove missing anchors, as per the RFC.

       permit-small-holddown: <yes or no>
              Debug  option  that allows the autotrust 5011 rollover timers to
              assume very small values.  Default is no.

       key-cache-size: <number>
              Number of bytes size of the key cache. Default is  4  megabytes.
              A  plain  number  is  in bytes, append 'k', 'm' or 'g' for kilo-
              bytes, megabytes or gigabytes (1024*1024 bytes in a megabyte).

       key-cache-slabs: <number>
              Number of slabs in the key cache. Slabs reduce  lock  contention
              by threads.  Must be set to a power of 2. Setting (close) to the
              number of cpus is a reasonable guess.

       neg-cache-size: <number>
              Number of bytes size of the aggressive negative  cache.  Default
              is  1  megabyte.  A plain number is in bytes, append 'k', 'm' or
              'g' for kilobytes, megabytes or gigabytes (1024*1024 bytes in  a
              megabyte).

       unblock-lan-zones: <yes or no>
              Default  is  disabled.   If  enabled,  then  for private address
              space, the reverse lookups are no longer filtered.  This  allows
              unbound  when running as dns service on a host where it provides
              service for that host, to put out all of  the  queries  for  the
              'lan' upstream.  When enabled, only localhost, 127.0.0.1 reverse
              and ::1 reverse zones are configured with default  local  zones.
              Disable the option when unbound is running as a (DHCP-) DNS net-
              work resolver for a group of machines, where such lookups should
              be  filtered  (RFC  compliance),  this also stops potential data
              leakage about the local network to the upstream DNS servers.

       insecure-lan-zones: <yes or no>
              Default is disabled.  If enabled, then reverse lookups  in  pri-
              vate  address space are not validated.  This is usually required
              whenever unblock-lan-zones is used.

       local-zone: <zone> <type>
              Configure a local zone. The type determines the answer  to  give
              if  there  is  no  match  from  local-data.  The types are deny,
              refuse, static, transparent, redirect, nodefault,  typetranspar-
              ent,  inform,  inform_deny, inform_redirect, always_transparent,
              always_refuse, always_nxdomain, always_null, noview, and are ex-
              plained  below.  After that the default settings are listed. Use
              local-data: to enter data into the local zone. Answers for local
              zones  are  authoritative  DNS answers. By default the zones are
              class IN.

              If you need more complicated authoritative data, with referrals,
              wildcards, CNAME/DNAME support, or DNSSEC authoritative service,
              setup a stub-zone for it as detailed in the  stub  zone  section
              below.

            deny Do  not  send an answer, drop the query.  If there is a match
                 from local data, the query is answered.

            refuse
                 Send an error message reply, with rcode REFUSED.  If there is
                 a match from local data, the query is answered.

            static
                 If  there  is a match from local data, the query is answered.
                 Otherwise, the query is answered  with  nodata  or  nxdomain.
                 For  a  negative  answer  a  SOA is included in the answer if
                 present as local-data for the zone apex domain.

            transparent
                 If there is a match from local data, the query  is  answered.
                 Otherwise if the query has a different name, the query is re-
                 solved normally.  If the query is for a name given in  local-
                 data  but  no such type of data is given in localdata, then a
                 noerror nodata answer is returned.  If no local-zone is given
                 local-data  causes  a  transparent  zone to be created by de-
                 fault.

            typetransparent
                 If there is a match from local data, the query  is  answered.
                 If  the  query  is for a different name, or for the same name
                 but for a different type, the  query  is  resolved  normally.
                 So,  similar  to transparent but types that are not listed in
                 local data are resolved normally, so if an A record is in the
                 local  data  that  does  not  cause  a  nodata reply for AAAA
                 queries.

            redirect
                 The query is answered from the local data for the zone  name.
                 There  may  be no local data beneath the zone name.  This an-
                 swers queries for the zone, and all subdomains  of  the  zone
                 with the local data for the zone.  It can be used to redirect
                 a domain to return a different  address  record  to  the  end
                 user,   with  local-zone:  "example.com."  redirect  and  lo-
                 cal-data: "example.com. A 127.0.0.1"  queries  for  www.exam-
                 ple.com and www.foo.example.com are redirected, so that users
                 with web browsers  cannot  access  sites  with  suffix  exam-
                 ple.com.

            inform
                 The  query  is  answered  normally, same as transparent.  The
                 client IP address (@portnumber) is printed  to  the  logfile.
                 The  log  message  is: timestamp, unbound-pid, info: zonename
                 inform IP@port queryname type class.  This option can be used
                 for normal resolution, but machines looking up infected names
                 are logged, eg. to run antivirus on them.

            inform_deny
                 The query is dropped, like 'deny', and logged, like 'inform'.
                 Ie. find infected machines without answering the queries.

            inform_redirect
                 The  query  is  redirected, like 'redirect', and logged, like
                 'inform'.  Ie. answer queries with fixed data  and  also  log
                 the machines that ask.

            always_transparent
                 Like  transparent,  but  ignores local data and resolves nor-
                 mally.

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

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

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

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

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

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

            nodefault
                 Used  to turn off default contents for AS112 zones. The other
                 types also turn off default contents for the zone. The 'node-
                 fault'  option  has  no other effect than turning off default
                 contents for the given zone.  Use nodefault if  you  use  ex-
                 actly  that zone, if you want to use a subzone, use transpar-
                 ent.

       The default zones are localhost, reverse 127.0.0.1 and ::1, the  onion,
       test,  invalid  and  the  AS112  zones. The AS112 zones are reverse DNS
       zones for private use and reserved IP addresses for which  the  servers
       on  the internet cannot provide correct answers. They are configured by
       default to give nxdomain (no reverse information) answers. The defaults
       can  be  turned  off by specifying your own local-zone of that name, or
       using the 'nodefault' type. Below is a list of the  default  zone  con-
       tents.

            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."

            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.

       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.

       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-for-domain: <domain> <number qps or 0>
            Override  the global ratelimit for an exact match domain name with
            the listed number.  You can give this for  any  number  of  names.
            For  example, for a top-level-domain you may want to have a higher
            limit than other names.  A value of 0  will  disable  ratelimiting
            for that domain.

       ratelimit-below-domain: <domain> <number qps or 0>
            Override  the global ratelimit for a domain name that ends in this
            name.  You can give this multiple times, it then describes differ-
            ent  settings  in  different  parts of the namespace.  The closest
            matching suffix is used to determine the qps limit.  The rate  for
            the   exact  matching  domain  name  is  not  changed,  use  rate-
            limit-for-domain to set that, you might want to use different set-
            tings  for  a  top-level-domain and subdomains.  A value of 0 will
            disable ratelimiting for domain names that end in this name.

       ip-ratelimit: <number or 0>
            Enable global ratelimiting of queries accepted per ip address.  If
            0,  the  default,  it is disabled.  This option is experimental at
            this time.  The ratelimit is in queries per second  that  are  al-
            lowed.  More queries are completely dropped and will not receive a
            reply, SERVFAIL or  otherwise.   IP  ratelimiting  happens  before
            looking in the cache. This may be useful for mitigating amplifica-
            tion attacks.

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

       ip-ratelimit-slabs: <number>
            Give  power of 2 number of slabs, this is used to reduce lock con-
            tention in the ip ratelimit tracking data structure.  Close to the
            number of cpus is a fairly good setting.

       ip-ratelimit-factor: <number>
            Set  the  amount  of  queries  to rate limit when the limit is ex-
            ceeded.  If set to 0, all queries are dropped for addresses  where
            the  limit is exceeded.  If set to another value, 1 in that number
            is allowed through to complete.   Default  is  10,  allowing  1/10
            traffic to flow normally.  This can make ordinary queries complete
            (if repeatedly queried for), and enter the cache, whilst also mit-
            igating the traffic flow by the factor given.

       fast-server-permil: <number>
            Specify how many times out of 1000 to pick from the set of fastest
            servers.  0 turns the feature off.  A value of 900 would pick from
            the fastest servers 90 percent of the time, and would perform nor-
            mal exploration of random servers for  the  remaining  time.  When
            prefetch  is  enabled  (or serve-expired), such prefetches are not
            sped up, because there is no one waiting for it, and it presents a
            good moment to perform server exploration. The fast-server-num op-
            tion can be used to specify the size of the fastest  servers  set.
            The default for fast-server-permil is 0.

       fast-server-num: <number>
            Set  the number of servers that should be used for fast server se-
            lection. Only use the fastest specified number of servers with the
            fast-server-permil  option, that turns this on or off. The default
            is to use the fastest 3 servers.

       edns-client-string: <IP netblock> <string>
            Include an EDNS0 option  containing  configured  ascii  string  in
            queries  with  destination address matching the configured IP net-
            block.  This configuration option can be used multiple times.  The
            most specific match will be used.

       edns-client-string-opcode: <opcode>
            EDNS0  option  code  for  the edns-client-string option, from 0 to
            65535.  A value from the `Reserved for  Local/Experimental`  range
            (65001-65534) should be used.  Default is 65001.

   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 path>
            Give IPv4 or IPv6 addresses or local socket path to listen on  for
            control  commands.   By  default  localhost (127.0.0.1 and ::1) is
            listened to.  Use 0.0.0.0 and ::0 to listen to all interfaces.  If
            you  change  this  and  permissions  have  been  dropped, you must
            restart the server for the change to take effect.

            If you set it to an absolute path, a local socket  is  used.   The
            local  socket  does  not  use  the certificates and keys, so those
            files need not be present.  To restrict access, unbound sets  per-
            missions on the file to the user and group that is configured, the
            access bits are set to allow the group members to access the  con-
            trol 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.

       stub-host: <domain name>
              Name of stub zone nameserver. Is itself resolved  before  it  is
              used.

       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.

       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-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.

       forward-host: <domain name>
              Name  of  server  to forward to. Is itself resolved before it is
              used.

       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.

              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-no-cache: <yes or no>
              Default  is  no.   If  enabled,  data  inside the forward is not
              cached.  This is useful when you want immediate  changes  to  be
              visible.

   Authority Zone Options
       Authority  zones are configured with auth-zone:, and each one must have
       a name:.  There can be multiple ones,  by  listing  multiple  auth-zone
       clauses,  each  with  a  different name, pertaining to that part of the
       namespace.  The authority zone with the name closest to the name looked
       up is used.  Authority zones are processed after local-zones and before
       cache (for-downstream: yes), and when used in this manner make  unbound
       respond  like  an authority server.  Authority zones are also processed
       after cache, just before going to the network to fetch information  for
       recursion  (for-upstream:  yes), and when used in this manner provide a
       local copy of an authority server that speeds up lookups of that data.

       Authority zones can be read from zonefile.  And can be kept updated via
       AXFR  and  IXFR.   After  update the zonefile is rewritten.  The update
       mechanism uses the SOA timer values and performs SOA UDP queries to de-
       tect zone changes.

       If  the  update  fetch  fails, the timers in the SOA record are used to
       time another fetch attempt.  Until the SOA  expiry  timer  is  reached.
       Then  the  zone  is expired.  When a zone is expired, queries are SERV-
       FAIL, and any new serial number is accepted from the primary  (even  if
       older),  and  if  fallback  is enabled, the fallback activates to fetch
       from the upstream instead of the SERVFAIL.

       name: <zone name>
              Name of the authority zone.

       primary: <IP address or host name>
              Where to download a copy of the zone from, with AXFR  and  IXFR.
              Multiple  primaries can be specified.  They are all tried if one
              fails.  With the "ip#name" notation a AXFR over TLS can be used.
              If  you  point it at another Unbound instance, it would not work
              because that does not support AXFR/IXFR for the zone, but if you
              used  url:  to  download the zonefile as a text file from a web-
              server that would work.  If you specify the hostname, you cannot
              use  the  domain from the zonefile, because it may not have that
              when retrieving that data, instead use a  plain  IP  address  to
              avoid a circular dependency on retrieving that IP address.

       master: <IP address or host name>
              Alternate syntax for primary.

       url: <url to zonefile>
              Where  to download a zonefile for the zone.  With http or https.
              An  example  for  the   url   is   "http://www.example.com/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: statements are al-
              lowed 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.

       zonefile: <filename>
              The filename where the zone is stored.  If  not  given  then  no
              zonefile  is  used.  If the file does not exist or is empty, un-
              bound will attempt to fetch zone  data  (eg.  from  the  primary
              servers).

   View Options
       There may be multiple view: clauses. Each with a name: and zero or more
       local-zone and local-data elements. Views can also contain  view-first,
       response-ip, response-ip-data and local-data-ptr elements.  View can be
       mapped to requests by  specifying  the  view  name  in  an  access-con-
       trol-view element. Options from matching views will override global op-
       tions. Global options will be used if no matching  view  is  found,  or
       when the matching view does not have the option specified.

       name: <view name>
              Name  of  the  view.  Must  be  unique. This name is used in ac-
              cess-control-view elements.

       local-zone: <zone> <type>
              View specific local-zone elements. Has the same types and behav-
              iour  as  the global local-zone elements. When there is at least
              one local-zone specified and view-first is no, the  default  lo-
              cal-zones  will be added to this view.  Defaults can be disabled
              using the nodefault type. When view-first is yes or when a  view
              does  not  have a local-zone, the global local-zone will be used
              including it's default zones.

       local-data: "<resource record string>"
              View specific local-data elements. Has the same behaviour as the
              global local-data elements.

       local-data-ptr: "IPaddr name"
              View specific local-data-ptr elements. Has the same behaviour as
              the global local-data-ptr elements.

       view-first: <yes or no>
              If enabled, it attempts to use the  global  local-zone  and  lo-
              cal-data if there is no match in the view specific options.  The
              default is no.

   Python Module Options
       The python: clause gives the settings for the python(1) script  module.
       This module acts like the iterator and validator modules do, on queries
       and answers.  To enable the script module it has to  be  compiled  into
       the  daemon,  and the word "python" has to be put in the module-config:
       option (usually first, or between the validator and iterator). Multiple
       instances  of  the  python  module  are  supported  by  adding the word
       "python" more than once.

       If the chroot: option is enabled, you should make sure Python's library
       directory  structure  is  bind mounted in the new root environment, see
       mount(8).  Also the python-script: path should be specified as an abso-
       lute  path relative to the new root, or as a relative path to the work-
       ing directory.

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

   Dynamic Library Module Options
       The dynlib: clause gives the settings for the dynlib module.  This mod-
       ule is only a very small wrapper that  allows  dynamic  modules  to  be
       loaded  on  runtime  instead of being compiled into the application. To
       enable the dynlib module it has to be compiled into the daemon, and the
       word  "dynlib" has to be put in the module-config: option. Multiple in-
       stances of dynamic libraries are supported by adding the word  "dynlib"
       more than once.

       The  dynlib-file: path should be specified as an absolute path relative
       to the new path set by chroot: option, or as a  relative  path  to  the
       working directory.

       dynlib-file: <dynlib file>
              The  dynamic  library file to load. Repeat this option for every
              dynlib module instance added to the module-config: option.

   DNS64 Module Options
       The dns64 module must be configured in the module-config:  "dns64  val-
       idator  iterator"  directive  and be compiled into the daemon to be en-
       abled.  These settings go in the server: section.

       dns64-prefix: <IPv6 prefix>
              This sets the DNS64 prefix to use  to  synthesize  AAAA  records
              with.   It  must  be  /96  or  shorter.   The  default prefix is
              64:ff9b::/96.

       dns64-synthall: <yes or no>
              Debug option, default  no.   If  enabled,  synthesize  all  AAAA
              records despite the presence of actual AAAA records.

       dns64-ignore-aaaa: <name>
              List  domain  for  which  the AAAA records are ignored and the A
              record is used by dns64 processing instead.  Can be entered mul-
              tiple  times,  list  a  new domain for which it applies, one per
              line.  Applies also to names underneath the name given.

   DNSCrypt Options
       The dnscrypt: clause gives the settings of the dnscrypt channel.  While
       those  options  are  available, they are only meaningful if unbound was
       compiled with --enable-dnscrypt.  Currently certificate and secret/pub-
       lic  keys cannot be generated by unbound.  You can use dnscrypt-wrapper
       to generate those:  https://github.com/cofyc/dnscrypt-wrapper/blob/mas-
       ter/README.md#usage

       dnscrypt-enable: <yes or no>
              Whether  or  not  the dnscrypt config should be enabled. You may
              define configuration but not activate it.  The default is no.

       dnscrypt-port: <port number>
              On which port should dnscrypt should be activated. Note that you
              should  have  a  matching interface option defined in the server
              section for this port.

       dnscrypt-provider: <provider name>
              The provider name to use to distribute certificates. This is  of
              the form: 2.dnscrypt-cert.example.com.. The name MUST end with a
              dot.

       dnscrypt-secret-key: <path to secret key file>
              Path to the time limited secret key file.  This  option  may  be
              specified multiple times.

       dnscrypt-provider-cert: <path to cert file>
              Path  to  the  certificate  related to the dnscrypt-secret-keys.
              This option may be specified multiple times.

       dnscrypt-provider-cert-rotated: <path to cert file>
              Path to a certificate that we should be able to  serve  existing
              connection   from   but   do   not   want   to   advertise  over
              dnscrypt-provider's TXT record certs  distribution.   A  typical
              use  case  is  when  rotating certificates, existing clients may
              still use the client magic from the old cert  in  their  queries
              until they fetch and update the new cert. Likewise, it would al-
              low one to prime the new cert/key without distributing  the  new
              cert yet, this can be useful when using a network of servers us-
              ing anycast and on which the configuration may not  get  updated
              at  the  exact  same  time. By priming the cert, the servers can
              handle both old and new certs traffic  while  distributing  only
              one.  This option may be specified multiple times.

       dnscrypt-shared-secret-cache-size: <memory size>
              Give  the  size of the data structure in which the shared secret
              keys are kept  in.   Default  4m.   In  bytes  or  use  m(mega),
              k(kilo),  g(giga).   The shared secret cache is used when a same
              client is making multiple queries using the same public key.  It
              saves a substantial amount of CPU.

       dnscrypt-shared-secret-cache-slabs: <number>
              Give  power  of  2  number of slabs, this is used to reduce lock
              contention in the dnscrypt shared secrets cache.  Close  to  the
              number of cpus is a fairly good setting.

       dnscrypt-nonce-cache-size: <memory size>
              Give  the  size of the data structure in which the client nonces
              are kept in.  Default 4m. In  bytes  or  use  m(mega),  k(kilo),
              g(giga).   The  nonce  cache is used to prevent dnscrypt message
              replaying. Client nonce should be unique for any pair of  client
              pk/server sk.

       dnscrypt-nonce-cache-slabs: <number>
              Give  power  of  2  number of slabs, this is used to reduce lock
              contention in the dnscrypt nonce cache.  Close to the number  of
              cpus is a fairly good setting.

   EDNS Client Subnet Module Options
       The  ECS  module  must be configured in the module-config: "subnetcache
       validator iterator" directive and be compiled into the daemon to be en-
       abled.  These settings go in the server: section.

       If the destination address is allowed in the configuration Unbound will
       add the EDNS0 option to the query containing the relevant part  of  the
       client's  address.  When an answer contains the ECS option the response
       and the option are placed in a specialized cache. If the authority  in-
       dicated no support, the response is stored in the regular cache.

       Additionally, when a client includes the option in its queries, Unbound
       will forward the option when sending the query to  addresses  that  are
       explicitly  allowed  in the configuration using send-client-subnet. The
       option will always be forwarded, regardless the allowed  addresses,  if
       client-subnet-always-forward  is set to yes. In this case the lookup in
       the regular cache is skipped.

       The maximum size of the ECS cache is controlled by 'msg-cache-size'  in
       the configuration file. On top of that, for each query only 100 differ-
       ent subnets are allowed to be stored for each address family. Exceeding
       that number, older entries will be purged from cache.

       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 the daemon to be en-
       abled.  These settings go in the server: section.

       When  unbound  receives  an  A/AAAA  query that is not in the cache and
       finds a valid answer, it will withhold returning the answer and instead
       will generate an IPSECKEY subquery for the same domain name.  If an an-
       swer was found, unbound will call an external hook passing the  follow-
       ing arguments:

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

            IPSECKEY TTL
                 TTL of the IPSECKEY RRset.

            A/AAAA
                 String of space separated IP addresses present in the  A/AAAA
                 RRset.  The IP addresses are in string format.

            IPSECKEY
                 String  of  space  separated  IPSECKEY  RDATA  present in the
                 IPSECKEY RRset.  The IPSECKEY RDATA are in  DNS  presentation
                 format.

       The  A/AAAA  answer  is then cached and returned to the client.  If the
       external hook was called the TTL changes to ensure it  doesn't  surpass
       ipsecmod-max-ttl.

       The  same  procedure  is  also followed when prefetch: is used, but the
       A/AAAA answer is given to the client before the hook is called.  ipsec-
       mod-max-ttl  ensures  that  the A/AAAA answer given from cache is still
       relevant for opportunistic IPsec.

       ipsecmod-enabled: <yes or no>
              Specifies whether the IPsec module is enabled or not.  The IPsec
              module  still  needs  to be defined in the module-config: direc-
              tive.  This option facilitates turning on/off the module without
              restarting/reloading unbound.  Defaults to yes.

       ipsecmod-hook: <filename>
              Specifies  the  external  hook  that unbound will call with sys-
              tem(3).  The file can be specified as an absolute/relative path.
              The  file needs the proper permissions to be able to be executed
              by the same user that runs unbound.  It must be present when the
              IPsec module is defined in the module-config: directive.

       ipsecmod-strict: <yes or no>
              If  enabled  unbound requires the external hook to return a suc-
              cess value of 0.  Failing to do so unbound will reply with SERV-
              FAIL.   The  A/AAAA answer will also not be cached.  Defaults to
              no.

       ipsecmod-max-ttl: <seconds>
              Time to live maximum for A/AAAA cached records after calling the
              external hook.  Defaults to 3600.

       ipsecmod-ignore-bogus: <yes or no>
              Specifies  the  behaviour of unbound when the IPSECKEY answer is
              bogus.  If set to yes, the hook will be called  and  the  A/AAAA
              answer  will  be returned to the client.  If set to no, the hook
              will not be called and the answer to the A/AAAA  query  will  be
              SERVFAIL.  Mainly used for testing.  Defaults to no.

       ipsecmod-allow: <domain>
              Allow the ipsecmod functionality for the domain so that the mod-
              ule logic will be executed.  Can be given  multiple  times,  for
              different  domains.  If the option is not specified, all domains
              are treated as being allowed (default).

       ipsecmod-whitelist: <yes or no>
              Alternate syntax for ipsecmod-allow.

   Cache DB Module Options
       The Cache DB module must be configured in the module-config: "validator
       cachedb  iterator" directive and be compiled into the daemon with --en-
       able-cachedb.  If this module is enabled and configured, the  specified
       backend  database  works  as  a second level cache: When Unbound cannot
       find an answer to a query in its built-in in-memory cache, it  consults
       the  specified backend.  If it finds a valid answer in the backend, Un-
       bound uses it to respond to the query without performing iterative  DNS
       resolution.   If  Unbound cannot even find an answer in the backend, it
       resolves the query as usual, and stores the answer in the backend.

       This module interacts with the serve-expired-* options and  will  reply
       with expired data if unbound is configured for that.  Currently the use
       of serve-expired-client-timeout: and  serve-expired-reply-ttl:  is  not
       consistent  for  data originating from the external cache as these will
       result in a reply with 0 TTL without trying to update the  data  first,
       ignoring the configured values.

       If  Unbound  was  built with --with-libhiredis on a system that has in-
       stalled the hiredis C client library of Redis, then the "redis" backend
       can be used.  This backend communicates with the specified Redis server
       over a TCP connection to store and retrieve cache data.  It can be used
       as  a  persistent and/or shared cache backend.  It should be noted that
       Unbound never removes data stored in the Redis  server,  even  if  some
       data  have  expired  in terms of DNS TTL or the Redis server has cached
       too much data; if necessary the Redis  server  must  be  configured  to
       limit  the cache size, preferably with some kind of least-recently-used
       eviction policy.  Additionally, the redis-expire-records option can  be
       used  in order to set the relative DNS TTL of the message as timeout to
       the Redis records; keep in mind that some additional memory is used per
       key  and  that  the expire information is stored as absolute Unix time-
       stamps in Redis (computer time must be stable).  This backend uses syn-
       chronous  communication  with  the Redis server based on the assumption
       that the communication is stable and  sufficiently  fast.   The  thread
       waiting  for  a  response from the Redis server cannot handle other DNS
       queries.  Although the backend has the  ability  to  reconnect  to  the
       server  when  the connection is closed unexpectedly and there is a con-
       figurable timeout in case the server is overly slow or hangs up,  these
       cases are assumed to be very rare.  If connection close or timeout hap-
       pens too often, Unbound will be effectively unusable with this backend.
       It's the administrator's responsibility to make the assumption hold.

       The cachedb: clause gives custom settings of the cache DB module.

       backend: <backend name>
              Specify  the backend database name.  The default database is the
              in-memory backend named "testframe", which,  as  the  name  sug-
              gests, is not of any practical use.  Depending on the build-time
              configuration, "redis" backend may also  be  used  as  described
              above.

       secret-seed: <"secret string">
              Specify a seed to calculate a hash value from query information.
              This value will be used as the key of the  corresponding  answer
              for  the  backend  database  and  can  be customized if the hash
              should not be predictable operationally.  If the  backend  data-
              base is shared by multiple Unbound instances, all instances must
              use the same secret seed.  This option defaults to "default".

       The following cachedb otions are specific to the redis backend.

       redis-server-host: <server address or name>
              The IP (either v6 or v4) address or domain  name  of  the  Redis
              server.   In general an IP address should be specified as other-
              wise Unbound will have to resolve the name of the  server  every
              time it establishes a connection to the server.  This option de-
              faults to "127.0.0.1".

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

       redis-timeout: <msec>
              The  period until when Unbound waits for a response from the Re-
              dis sever.  If this timeout expires Unbound closes  the  connec-
              tion,  treats  it  as  if the Redis server does not have the re-
              quested data, and will try  to  re-establish  a  new  connection
              later.  This option defaults to 100 milliseconds.

       redis-expire-records: <yes or no>
              If  Redis  record  expiration  is enabled.  If yes, unbound sets
              timeout for Redis records so that Redis can evict keys that have
              expired  automatically.  If unbound is configured with serve-ex-
              pired and serve-expired-ttl is 0, this option is internally  re-
              verted to "no".  Redis SETEX support is required for this option
              (Redis >= 2.0.0).  This option defaults to no.

   DNSTAP Logging Options
       DNSTAP support, when compiled in, 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".

       Only the QNAME and Response IP Address triggers are supported. The sup-
       ported  RPZ  actions  are:  NXDOMAIN,  NODATA, PASSTHRU, DROP and Local
       Data. RPZ QNAME triggers are applied after local-zones and before auth-
       zones.

       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.

       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: statements are al-
              lowed 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.

       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  9, 2021                  unbound.conf(5)