nsd.conf(5)                        nsd 4.3.1                       nsd.conf(5)



NAME
       nsd.conf - NSD configuration file

SYNOPSIS
       nsd.conf

DESCRIPTION
       Nsd.conf  is  used  to configure nsd(8). The file format has attributes
       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
       ignored as is whitespace at the beginning of  a  line.  Quotes  can  be
       used, for names with spaces, eg. "file name.zone".

       Nsd.conf  specifies  options  for the nsd server, zone files, primaries
       and secondaries.

EXAMPLE
       An example of a short nsd.conf file is below.

       # Example.com nsd.conf file
       # This is a comment.

       server:
            server-count: 1 # use this number of cpu cores
            database: ""  # or use "/var/db/nsd/nsd.db"
            zonelistfile: "/var/db/nsd/zone.list"
            username: nsd
            logfile: "/var/log/nsd.log"
            pidfile: "/var/run/nsd.pid"
            xfrdfile: "/var/db/nsd/xfrd.state"

       zone:
            name: example.com
            zonefile: /etc/nsd/example.com.zone

       zone:
            # this server is master, 192.0.2.1 is the secondary.
            name: masterzone.com
            zonefile: /etc/nsd/masterzone.com.zone
            notify: 192.0.2.1 NOKEY
            provide-xfr: 192.0.2.1 NOKEY

       zone:
            # this server is secondary, 192.0.2.2 is master.
            name: secondzone.com
            zonefile: /etc/nsd/secondzone.com.zone
            allow-notify: 192.0.2.2 NOKEY
            request-xfr: 192.0.2.2 NOKEY

       Then, use kill -HUP to reload changes from master zone files.  And  use
       kill -TERM to stop the server.

FILE FORMAT
       There  must be whitespace between keywords. Attribute keywords end with
       a colon ':'. An attribute is followed by its containing attributes,  or
       a value.

       At  the  top level only server:, key:, pattern:, zone:, and remote-con-
       trol: are allowed. These are followed by their attributes or a new top-
       level  keyword.  The  zone:  attribute is followed by zone options. The
       server: attribute is followed by global options for the NSD  server.  A
       key:  attribute is used to define keys for authentication. The pattern:
       attribute is followed by the zone options for zones that use  the  pat-
       tern.

       Files  can be included using the include: directive. It can appear any-
       where, and takes a single filename as an argument. Processing continues
       as  if  the text from the included file was copied into the config file
       at that point.  If a chroot is used  an  absolute  filename  is  needed
       (with  the  chroot prepended), so that the include can be parsed before
       and after application of the chroot (and the  knowledge  of  what  that
       chroot  is).  You can use '*' to include a wildcard match of files, eg.
       "foo/nsd.d/*.conf".  Also '?', '{}', '[]', and '~' work,  see  glob(7).
       If no files match the pattern, this is not an error.

   Server Options
       The  global  options  (if  not overridden from the NSD commandline) are
       taken from the server: clause. There may only be one server: clause.

       ip-address: <ip4 or ip6>[@port] [servers]
              NSD will bind to the listed ip-address. Can  be  given  multiple
              times  to  bind multiple ip-addresses. Optionally, a port number
              can be given.  If none are given NSD  listens  to  the  wildcard
              interface.  Same  as  commandline option -a.  To limit which NSD
              server(s) listen on the given interface,  specify  one  or  more
              servers separated by whitespace after <ip>[@port]. Ranges can be
              used as a shorthand to specify multiple consecutive servers.  By
              default every server will listen.   For servers with multiple IP
              addresses that can be used to send traffic to the internet, list
              them  one  by  one,  or  the  source address of replies could be
              wrong.  This is because if the udp socket  associates  a  source
              address  of  0.0.0.0  then  the  kernel picks an ip-address with
              which to send to the internet, and it picks the wrong one.  Typ-
              ically  needed  for anycast instances.  Use ip-transparent to be
              able to list addresses that turn on later (typical  for  certain
              load-balancing).

       interface: <ip4 or ip6>[@port] [servers] [setfib]
              Same   as   ip-address   (for   easy   of   compatibility   with
              unbound.conf).

       ip-transparent: <yes or no>
              Allows NSD to bind to non local addresses.  This  is  useful  to
              have  NSD listen to IP addresses that are not (yet) added to the
              network interface, so that it can answer  immediately  when  the
              address is added. Default is no.

       ip-freebind: <yes or no>
              Set  the  IP_FREEBIND  option  to bind to nonlocal addresses and
              interfaces that are down.  Similar to  ip-transparent.   Default
              is no.

       reuseport: <yes or no>
              Use  the SO_REUSEPORT socket option, and create file descriptors
              for every server in the server-count.  This improves performance
              of  the network stack.  Only really useful if you also configure
              a server-count higher than 1 (such as, equal to  the  number  of
              cpus).  The default is no.  It works on Linux, but does not work
              on FreeBSD, and likely does not work on other systems.

       bindtodevice: <yes or no>
              Use the SO_BINDTODEVICE socket option to bind the socket to  the
              device  to ensure responses go out the same interface the corre-
              sponding query came in on and skip interface  selection  by  the
              kernel.

       send-buffer-size: <number>
              Set  the send buffer size for query-servicing sockets.  Set to 0
              to use the default settings.

       receive-buffer-size: <number>
              Set the receive buffer size for query-servicing sockets.  Set to
              0 to use the default settings.

       debug-mode: <yes or no>
              Turns on debugging mode for nsd, does not fork a daemon process.
              Default is no. Same as commandline option -d.  If set to yes  it
              does  not fork and stays in the foreground, which can be helpful
              for commandline debugging, but is also used  by  certain  server
              supervisor processes to ascertain that the server is running.

       do-ip4: <yes or no>
              If yes, NSD listens to IPv4 connections.  Default yes.

       do-ip6: <yes or no>
              If yes, NSD listens to IPv6 connections.  Default yes.

       database: <filename>
              By  default  '/var/db/nsd/nsd.db' is used. The specified file is
              used to store the compiled zone information. Same as commandline
              option  -f.   If  set to "" then no database is used.  This uses
              less memory but zone updates are not  (immediately)  spooled  to
              disk.

       zonelistfile: <filename>
              By  default /var/db/nsd/zone.list is used. The specified file is
              used to store the dynamically added list of zones.  The list  is
              written  to  by  NSD to add and delete zones.  It is a text file
              with a zone-name and pattern-name on each line.   This  file  is
              used for the nsd-control addzone and delzone commands.

       identity: <string>
              Returns  the specified identity when asked for CH TXT ID.SERVER.
              Default is the name as returned by gethostname(3). Same as  com-
              mandline  option -i.  See hide-identity to set the server to not
              respond to such queries.

       version: <string>
              Returns the specified version string when asked for CH TXT  ver-
              sion.server,  and version.bind queries.  Default is the compiled
              package version.  See hide-version to  set  the  server  to  not
              respond to such queries.

       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.  Same
              as commandline option -I.

       logfile: <filename>
              Log messages to the logfile. The default is to log to stderr and
              syslog  (with  facility  LOG_DAEMON). Same as commandline option
              -l.

       server-count: <number>
              Start this many NSD servers. Default is 1. Same  as  commandline
              option -N.

       cpu-affinity: <number> <number> ...
              Overall  CPU affinity for NSD server(s). Default is no affinity.
              -n.

       server-N-cpu-affinity: <number>
              Bind NSD server specified by N to a specific core. Default is to
              have  affinity set to every core specified in cpu-affinity. This
              setting only takes effect if cpu-affinity is enabled.  -n

       xfrd-cpu-affinity: <number>
              Bind xfrd to a specific core. Default is to have affinity set to
              every  core  specified  in cpu-affinity. This setting only takes
              effect if cpu-affinity is enabled.  -n

       tcp-count: <number>
              The maximum number of concurrent, active TCP connections by each
              server.  Default is 100. Same as commandline option -n.

       tcp-reject-overflow: <yes or no>
              If  set  to  yes, TCP connections made beyond the maximum set by
              tcp-count will be dropped  immediately  (accepted  and  closed).
              Default is no.

       tcp-query-count: <number>
              The maximum number of queries served on a single TCP connection.
              Default is 0, meaning there is no maximum.

       tcp-timeout: <number>
              Overrides the default TCP timeout. This also affects zone trans-
              fers over TCP.

       tcp-mss: <number>
              Maximum  segment  size  (MSS)  of TCP socket on which the server
              responds to queries. Value lower than  common  MSS  on  Ethernet
              (1220 for example) will address path MTU problem.  Note that not
              all platform supports socket option  to  set  MSS  (TCP_MAXSEG).
              Default  is  system  default MSS determined by interface MTU and
              negotiation between server and client.

       outgoing-tcp-mss: <number>
              Maximum segment size  (MSS)  of  TCP  socket  for  outgoing  XFR
              request to other namesevers. Value lower than common MSS on Eth-
              ernet (1220 for example) will address path  MTU  problem.   Note
              that  not  all  platform  supports  socket  option  to  set  MSS
              (TCP_MAXSEG).  Default  is  system  default  MSS  determined  by
              interface MTU and negotiation between NSD and other servers.

       ipv4-edns-size: <number>
              Preferred EDNS buffer size for IPv4.  Default 4096.

       ipv6-edns-size: <number>
              Preferred EDNS buffer size for IPv6.  Default 4096.

       pidfile: <filename>
              Use  the pid file instead of the platform specific default, usu-
              ally /var/run/nsd.pid.  Same as commandline option -P.  With  ""
              there is no pidfile, for some startup management setups, where a
              pidfile is not useful to have.

       port: <number>
              Answer queries on the specified port. Default  is  53.  Same  as
              commandline option -p.

       statistics: <number>
              If not present no statistics are dumped. Statistics are produced
              every number seconds. Same as commandline option -s.

       chroot: <directory>
              NSD will chroot on startup to the specified directory. Note that
              if  elsewhere in the configuration you specify an absolute path-
              name to a file inside the chroot, you have to prepend the chroot
              path.  That  way,  you  can  switch the chroot option on and off
              without having to modify anything else in the configuration. Set
              the  value  to  ""  (the empty string) to disable the chroot. By
              default "" is used. Same as commandline option -t.

       username: <username>
              After binding the socket, drop user privileges  and  assume  the
              username.  Can  be  username,  id or id.gid. Same as commandline
              option -u.

       zonesdir: <directory>
              Change the working directory to the specified  directory  before
              accessing  zone files. Also, NSD will access database, zonelist-
              file,  logfile,  pidfile,  xfrdfile,  xfrdir,   server-key-file,
              server-cert-file,  control-key-file  and control-cert-file rela-
              tive to this directory. Set the value to "" (the  empty  string)
              to   disable   the  change  of  working  directory.  By  default
              "/etc/nsd" is used.

       difffile: <filename>
              Ignored, for compatibility with NSD3 config files.

       xfrdfile: <filename>
              The soa timeout and zone transfer daemon in NSD  will  save  its
              state  to  this  file.  State  is read back after a restart. The
              state file can be deleted without too much harm, but  timestamps
              of  zones  will  be  gone.  If it is configured as "", the state
              file is not used, all slave zones are checked for  updates  upon
              startup.  For more details see the section on zone expiry behav-
              ior of NSD. Default is /var/db/nsd/xfrd.state.

       xfrdir: <directory>
              The zone transfers are stored here before they are processed.  A
              directory  is  created  here  that  is  removed  when NSD exits.
              Default is /tmp.

       xfrd-reload-timeout: <number>
              If this value is -1, xfrd will not trigger a reload after a zone
              transfer.  If  positive  xfrd will trigger a reload after a zone
              transfer, then it will wait for the number of seconds before  it
              will  trigger  a  new  reload.  Setting this value throttles the
              reloads to once per the number of seconds. The default is 1 sec-
              ond.

       verbosity: <level>
              This  value  specifies  the verbosity level for (non-debug) log-
              ging.  Default is 0. 1 gives  more  information  about  incoming
              notifies  and  zone  transfers.  2  lists soft warnings that are
              encountered. 3 prints more information.

              Verbosity 0 will print warnings and  errors,  and  other  events
              that are important to keep NSD running.

              Verbosity  1 prints additionally messages of interest.  Success-
              ful notifies, successful incoming zone  transfer  (the  zone  is
              updated),  failed  incoming  zone  transfers or the inability to
              process zone updates.

              Verbosity 2 prints additionally  soft  errors,  like  connection
              resets over TCP.  And notify refusal, and axfr request refusals.

       hide-version: <yes or no>
              Prevent NSD from replying with the version string on CHAOS class
              queries.  Default is no.

       hide-identity: <yes or no>
              Prevent NSD from replying with  the  identity  string  on  CHAOS
              class queries.  Default is no.

       drop-updates: <yes or no>
              If set to yes, drop received packets with the UPDATE opcode.

       use-systemd: <yes or no>
              This option is deprecated and ignored.  If compiled with libsys-
              temd, NSD signals readiness to systemd and use of the option  is
              not necessary.

       log-time-ascii: <yes or no>
              Log  time  in  ascii, if "no" then in seconds epoch.  Default is
              yes.  This chooses the format when logging to file.  The  print-
              out via syslog has a timestamp formatted by syslog.

       round-robin: <yes or no>
              Enable  round  robin  rotation  of  records in the answer.  This
              changes the order of records in the answer and this may  balance
              load across them.  The default is no.

       minimal-responses: <yes or no>
              Enable  minimal responses for smaller answers.  This makes pack-
              ets smaller.  Extra data is only added for referrals, when it is
              really  necessary.  This is different from the --enable-minimal-
              responses configure  time  option,  that  reduces  packets,  but
              exactly to the fragmentation length, the nsd.conf option reduces
              packets as small as possible.  The default is no.

       confine-to-zone: <yes or no>
              If set to yes, additional information will not be added  to  the
              response if the apex zone of the additional information does not
              match the apex zone of the initial  query  (E.G.  CNAME  resolu-
              tion). Default is no.

       refuse-any: <yes or no>
              Refuse queries of type ANY.  This is useful to stop query floods
              trying to get large responses.  Note that rrl ratelimiting  also
              has  type  ANY  as  a ratelimiting type.  It sends truncation in
              response to UDP type ANY queries, and it  allows  TCP  type  ANY
              queries like normal.  The default is no.

       zonefiles-check: <yes or no>
              Make  NSD check the mtime of zone files on start and sighup.  If
              you disable it it starts faster (less disk activity in case of a
              lot of zones).  The default is yes.  The nsd-control reload com-
              mand reloads zone files regardless of this option.

       zonefiles-write: <seconds>
              Write changed secondary zones to their zonefile every N seconds.
              If  the  zone (pattern) configuration has "" zonefile, it is not
              written.  Zones that have received  zone  transfer  updates  are
              written  to  their zonefile.  Default is 0 (disabled) when there
              is a database, and 3600 (1 hour) when database is "".  The data-
              base  also commits zone transfer contents.  You can configure it
              away from the default by putting the config statement for  zone-
              files-write: after the database: statement in the config file.

       rrl-size: <numbuckets>
              This  option  gives  the size of the hashtable. Default 1000000.
              More buckets use more memory, and reduce the chance of hash col-
              lisions.

       rrl-ratelimit: <qps>
              The max qps allowed (from one query source). Default is on (with
              a suggested 200 qps). If set to 0 then it is disabled (unlimited
              rate),  also  set  the whitelist-ratelimit to 0 to disable rate-
              limit processing.  If you set verbosity to  2  the  blocked  and
              unblocked  subnets  are logged.  Blocked queries are blocked and
              some receive TCP fallback  replies.   Once  the  rate  limit  is
              reached,  NSD  begins  dropping responses. However, one in every
              "rrl-slip" number of responses is allowed, with the TC bit  set.
              If  slip is set to 2, the outgoing response rate will be halved.
              If it's set to 3, the outgoing response rate will be  one-third,
              and  so  on.   If  you set rrl-slip to 10, traffic is reduced to
              1/10th.    Ratelimit   options   rrl-ratelimit,   rrl-size   and
              rrl-whitelist-ratelimit are updated when nsd-control reconfig is
              done (also the zone-specific ratelimit options are updated).

       rrl-slip: <numpackets>
              This option controls the number of packets discarded  before  we
              send  back  a SLIP response (a response with "truncated" bit set
              to one). 0 disables the sending of SLIP packets, 1  means  every
              query  will  get a SLIP response.  Default is 2, cuts traffic in
              half and legit users have a fair chance to get a +TC response.

       rrl-ipv4-prefix-length: <subnet>
              IPv4 prefix length. Addresses are grouped by netblock.   Default
              24.

       rrl-ipv6-prefix-length: <subnet>
              IPv6  prefix length. Addresses are grouped by netblock.  Default
              64.

       rrl-whitelist-ratelimit: <qps>
              The max qps for query  sorts  for  a  source,  which  have  been
              whitelisted.  Default  on  (with a suggested 2000 qps). With the
              rrl-whitelist option you can set  specific  queries  to  receive
              this  qps  limit  instead of the normal limit.  With the value 0
              the rate is unlimited.

       tls-service-key: <filename>
              If enabled, the server provides TLS service on TCP sockets  with
              the  TLS  service port number.  The port number (853) is config-
              ured with tls-port.  To turn it on, create an interface:  option
              line in config with @port appended to the IP-address.  This cre-
              ates the extra socket on which the DNS over TLS service is  pro-
              vided.

              The file is the private key for the TLS session. The public cer-
              tificate is in the tls-service-pem file. Default is  "",  turned
              off.  Requires  a  restart  (a reload is not enough) if changed,
              because the private key is read while root permissions are  held
              and before chroot (if any).

       tls-service-pem: <filename>
              The public key certificate pem file for the tls service. Default
              is "", turned off.

       tls-service-ocsp: <filename>
              The ocsp pem file  for  the  tls  service,  for  OCSP  stapling.
              Default  is  "",  turned  off.  An external process prepares and
              updates the OCSP stapling data.  Like this,
                openssl ocsp -no_nonce \
                   -respout /path/to/ocsp.pem \
                   -CAfile /path/to/ca_and_any_intermediate.pem \
                   -issuer /path/to/direct_issuer.pem \
                   -cert /path/to/cert.pem \
                   -url "$( openssl x509 -noout -text -in /path/to/cert.pem  |
                grep 'OCSP - URI:' | cut -d: -f2,3 )"

       tls-port: <number>
              The  port number on which to provide TCP TLS service, default is
              853, only interfaces configured with that port number as @number
              get DNS over TLS service.

   Remote Control
       The  remote-control:  clause  is  used  to  set  options  for using the
       nsd-control(8) tool to give commands to the running NSD server.  It  is
       disabled by default, and listens for localhost by default.  It uses TLS
       over TCP where the server and client authenticate to  each  other  with
       self-signed  certificates.   The self-signed certificates can be gener-
       ated with the nsd-control-setup tool.  The key files are  read  by  NSD
       before  the chroot and before dropping user permissions, so they can be
       outside the chroot and readable by the superuser only.

       control-enable: <yes or no>
              Enable remote control, default is no.

       control-interface: <ip4 or ip6>
              NSD will  bind  to  the  listed  addresses  to  service  control
              requests (on TCP).  Can be given multiple times to bind multiple
              ip-addresses.  Use 0.0.0.0  and  ::0  to  service  the  wildcard
              interface.   If  none  are  given  NSD  listens to the localhost
              127.0.0.1 and ::1 interfaces for control, if control is  enabled
              with control-enable.

              With  an absolute path, a unix local named pipe is used for con-
              trol.  The file is created with user and group that  is  config-
              ured  and  access  bits  are  set  to allow members of the group
              access.  Further access can be controlled by setting permissions
              on  the  directory  containing the control socket file.  The key
              and cert files are not used when control is via the named  pipe,
              because access control is via file and directory permission.

       control-port: <number>
              The port number for remote control service. 8952 by default.

       server-key-file: <filename>
              Path     to    the    server    private    key,    by    default
              /etc/nsd/nsd_server.key.  This file is generated by the nsd-con-
              trol-setup  utility.   This  file is used by the nsd server, but
              not by nsd-control.

       server-cert-file: <filename>
              Path  to  the  server  self  signed  certificate,   by   default
              /etc/nsd/nsd_server.pem.  This file is generated by the nsd-con-
              trol-setup utility.  This file is used by the  nsd  server,  and
              also by nsd-control.

       control-key-file: <filename>
              Path   to   the   control   client   private   key,  by  default
              /etc/nsd/nsd_control.key.   This  file  is  generated   by   the
              nsd-control-setup utility.  This file is used by nsd-control.

       control-cert-file: <filename>
              Path   to   the   control   client   certificate,   by   default
              /etc/nsd/nsd_control.pem.  This certificate  has  to  be  signed
              with  the  server  certificate.   This  file is generated by the
              nsd-control-setup utility.  This file is used by nsd-control.

   Pattern Options
       The pattern: clause is used to denote a set of options to apply to some
       zones.  The same zone options as for a zone are allowed.

       name: <string>
              The  name  of  the  pattern.  This is a (case sensitive) string.
              The pattern names that start with "_implicit_" are  used  inter-
              nally  for  zones  that  have  no  pattern  (they are defined in
              nsd.conf directly).

       include-pattern: <pattern-name>
              The options from the given pattern are included at this point in
              this pattern.  The referenced pattern must be defined above this
              one.

       <zone option>: <value>
              The zone options such as  zonefile,  allow-notify,  request-xfr,
              allow-axfr-fallback,  notify,  notify-retry, provide-xfr, zones-
              tats, and outgoing-interface can be given.  They are applied  to
              the patterns and zones that include this pattern.

   Zone Options
       For  every  zone  the options need to be specified in one zone: clause.
       The access control list elements can be given  multiple  times  to  add
       multiple servers. These elements need to be added explicitly.

       For  zones  that  are configured in the nsd.conf config file their set-
       tings are hardcoded (in an implicit pattern for  themselves  only)  and
       they  cannot  be  deleted  via delzone, but remove them from the config
       file and repattern.

       name: <string>
              The name of the zone. This is the domain name of the apex of the
              zone.  May end with a '.' (in FQDN notation). For example "exam-
              ple.com", "sub.example.net.". This attribute must be present  in
              each zone.

       zonefile: <filename>
              The  file  containing the zone information. If this attribute is
              present it is used to read and write the zone contents.  If  the
              attribute is absent it prevents writing out of the zone.

              The  string  is  processed  so that one string can be used (in a
              pattern) for a lot of different zones.  If the label or  charac-
              ter  does  not  exist  the  percent-character is replaced with a
              period for output (i.e. for the third character in a two  letter
              domain name).

              %s is replaced with the zone name.

              %1 is replaced with the first character of the zone name.

              %2 is replaced with the second character of the zone name.

              %3 is replaced with the third character of the zone name.

              %z is replaced with the toplevel domain name of the zone.

              %y is replaced with the next label under the toplevel domain.

              %x  is  replaced  with  the  next-next  label under the toplevel
              domain.

       allow-notify: <ip-spec> <key-name | NOKEY | BLOCKED>
              Access control list. The listed (primary) address is allowed  to
              send notifies to this (secondary) server. Notifies from unlisted
              or specifically BLOCKED addresses are  discarded.  If  NOKEY  is
              given  no  TSIG signature is required.  BLOCKED supersedes other
              entries, other entries are scanned for a match in the  order  of
              the statements.

              The  ip-spec is either a plain IP address (IPv4 or IPv6), or can
              be  a  subnet  of  the   form   1.2.3.4/24,   or   masked   like
              1.2.3.4&255.255.255.0  or  a range of the form 1.2.3.4-1.2.3.25.
              A port number can be added using a suffix of @number, for  exam-
              ple  1.2.3.4@5300  or  1.2.3.4/24@5300  for port 5300.  Note the
              ip-spec ranges do not use spaces around the /, &, @ and  -  sym-
              bols.

       request-xfr: [AXFR|UDP] <ip-address> <key-name | NOKEY>
              Access  control list. The listed address (the master) is queried
              for AXFR/IXFR on update. A port number can be added using a suf-
              fix  of  @number, for example 1.2.3.4@5300. The specified key is
              used during AXFR/IXFR.

              If the AXFR option is given, the server will  not  be  contacted
              with  IXFR  queries  but  only AXFR requests will be made to the
              server. This allows an NSD secondary to  have  a  master  server
              that runs NSD. If the AXFR option is left out then both IXFR and
              AXFR requests are made to the master server.

              If the UDP option is given, the secondary will use UDP to trans-
              mit  the IXFR requests. You should deploy TSIG when allowing UDP
              transport, to authenticate notifies and zone  transfers.  Other-
              wise,  NSD is more vulnerable for Kaminsky-style attacks. If the
              UDP option is left out then IXFR will be transmitted using TCP.

       allow-axfr-fallback: <yes or no>
              This option should be accompanied by request-xfr. It (dis)allows
              NSD  (as  secondary)  to  fallback  to  AXFR if the primary name
              server does not support IXFR. Default is yes.

       size-limit-xfr: <number>
              This option should be accompanied by request-xfr.  It  specifies
              XFR  temporary  file  size  limit.   It can be used to stop very
              large zone retrieval, that could otherwise use up a lot of  mem-
              ory  and  disk  space.   If this option is 0, unlimited. Default
              value is 0.

       notify: <ip-address> <key-name | NOKEY>
              Access control list. The listed address (a secondary)  is  noti-
              fied of updates to this zone. A port number can be added using a
              suffix of @number, for example 1.2.3.4@5300. The  specified  key
              is  used  to  sign  the notify. Only on secondary configurations
              will NSD be able to detect zone updates  (as  it  gets  notified
              itself, or refreshes after a time).

       notify-retry: <number>
              This  option should be accompanied by notify. It sets the number
              of retries when sending notifies.

       provide-xfr: <ip-spec> <key-name | NOKEY | BLOCKED>
              Access control list. The listed address (a secondary) is allowed
              to  request AXFR from this server. Zone data will be provided to
              the address. The specified key is used during AXFR. For unlisted
              or  BLOCKED  addresses  no  data  is provided, requests are dis-
              carded.  BLOCKED supersedes other  entries,  other  entries  are
              scanned  for  a  match in the order of the statements.  NSD pro-
              vides AXFR for its secondaries,  but  IXFR  is  not  implemented
              (IXFR is implemented for request-xfr, but not for provide-xfr).

              The  ip-spec is either a plain IP address (IPv4 or IPv6), or can
              be  a  subnet  of  the   form   1.2.3.4/24,   or   masked   like
              1.2.3.4&255.255.255.0  or  a range of the form 1.2.3.4-1.2.3.25.
              A port number can be added using a suffix of @number, for  exam-
              ple  1.2.3.4@5300  or  1.2.3.4/24@5300  for  port 5300. Note the
              ip-spec ranges do not use spaces around the /, &, @ and  -  sym-
              bols.

       outgoing-interface: <ip-address>
              Access  control  list.  The  listed  address  is used to request
              AXFR|IXFR (in case of a secondary) or used to send notifies  (in
              case of a primary).

              The  ip-address  is  a  plain IP address (IPv4 or IPv6).  A port
              number can be added using  a  suffix  of  @number,  for  example
              1.2.3.4@5300.

       max-refresh-time: <seconds>
              Limit refresh time for secondary zones.  This is the timer which
              checks to see if the zone has to be refetched when  it  expires.
              Normally  the value from the SOA record is used, but this option
              restricts that value.

       min-refresh-time: <seconds>
              Limit refresh time for secondary zones.

       max-retry-time: <seconds>
              Limit retry time for secondary zones.  This is the timeout after
              a  failed  fetch  attempt for the zone.  Normally the value from
              the SOA record is used, but this option restricts that value.

       min-retry-time: <seconds>
              Limit retry time for secondary zones.

       zonestats: <name>
              When compiled with --enable-zone-stats NSD can  collect  statis-
              tics  per  zone.  This name gives the group where statistics are
              added to.  The groups are  output  from  nsd-control  stats  and
              stats_noreset.  Default is "".  You can use "%s" to use the name
              of the zone to track its statistics.  If not  compiled  in,  the
              option can be given but is ignored.

       include-pattern: <pattern-name>
              The  options  from the given pattern are included at this point.
              The referenced pattern must be defined above this zone.

       rrl-whitelist: <rrltype>
              This option causes queries of this rrltype  to  be  whitelisted,
              for  this  zone.  They  receive the whitelist-ratelimit. You can
              give  multiple  lines,  each  enables  a  new  rrltype   to   be
              whitelisted for the zone. Default has none whitelisted. The rrl-
              type is the query classification that the  NSD  RRL  employs  to
              make  different types not interfere with one another.  The types
              are logged in the loglines when a subnet  is  blocked  (in  ver-
              bosity  2).   The RRL classification types are: nxdomain, error,
              referral, any, rrsig, wildcard, nodata, dnskey, positive, all.

       multi-master-check: <yes or no>
              Default no.  If enabled, checks all masters for  the  last  ver-
              sion.  It uses the higher version of all the configured masters.
              Useful if you have multiple masters that have different  version
              numbers served.

   Key Declarations
       The  key:  clause establishes a key for use in access control lists. It
       has the following attributes.

       name: <string>
              The key name. Used to refer to this key in  the  access  control
              list.  The key name has to be correct for tsig to work.  This is
              because the key name is output on the wire.

       algorithm: <string>
              Authentication  algorithm  for  this  key.   Such  as  hmac-md5,
              hmac-sha1,    hmac-sha224,    hmac-sha256,    hmac-sha384    and
              hmac-sha512.  Can  also  be  abbreviated  as  'sha1',  'sha256'.
              Default is sha256.  Algorithms are only available when they were
              compiled in (available in the crypto library).

       secret: <base64 blob>
              The base64 encoded shared secret. It  is  possible  to  put  the
              secret: declaration (and base64 blob) into a different file, and
              then to include: that file. In this way the key secret  and  the
              rest  of  the configuration file, which may have different secu-
              rity policies, can be split apart.  The content of the secret is
              the  agreed base64 secret content.  To make it up, enter a pass-
              word (its length must be a multiple of 4 characters, A-Za-z0-9),
              or use dev-random output through a base64 encode filter.

NSD CONFIGURATION FOR BIND9 HACKERS
       BIND9  is  a name server implementation with its own configuration file
       format, named.conf(5). BIND9 types zones as 'Master' or 'Slave'.

   Slave zones
       For a slave zone, the master servers are listed. The master servers are
       queried  for  zone  data, and are listened to for update notifications.
       In NSD these two properties need to be configured separately, by  list-
       ing the master address in allow-notify and request-xfr statements.

       In  BIND9  you only need to provide allow-notify elements for any extra
       sources of notifications  (i.e.  the  operators),  NSD  needs  to  have
       allow-notify  for  both  masters and operators. BIND9 allows additional
       transfer sources, in NSD you list those as request-xfr.

       Here is an example of a slave zone in BIND9 syntax.

       # Config file for example.org options {
            dnssec-enable yes;
       };

       key tsig.example.org. {
            algorithm hmac-md5;
            secret "aaaaaabbbbbbccccccdddddd";
       };

       server 162.0.4.49 {
            keys { tsig.example.org. ; };
       };

       zone "example.org" {
            type slave;
            file "secondary/example.org.signed";
            masters { 162.0.4.49; };
       };

       For NSD, DNSSEC is enabled automatically for zones that are signed. The
       dnssec-enable  statement  in  the  options clause is not needed. In NSD
       keys are associated with an IP  address  in  the  access  control  list
       statement, therefore the server{} statement is not needed. Below is the
       same example in an NSD config file.

       # Config file for example.org
       key:
            name: tsig.example.org.
            algorithm: hmac-md5
            secret: "aaaaaabbbbbbccccccdddddd"

       zone:
            name: "example.org"
            zonefile: "secondary/example.org.signed"
            # the master is allowed to notify and will provide zone data.
            allow-notify: 162.0.4.49 NOKEY
            request-xfr: 162.0.4.49 tsig.example.org.

       Notice that the master is listed twice, once to allow it to send  noti-
       fies  to  this  slave server and once to tell the slave server where to
       look for updates zone data. More allow-notify and request-xfr lines can
       be added to specify more masters.

       It  is  possible to specify extra allow-notify lines for addresses that
       are also allowed to send notifications to this slave server.

   Master zones
       For a master zone in BIND9, the slave servers are listed.  These  slave
       servers  are  sent  notifications of updated and are allowed to request
       transfer of the zone data. In NSD these two properties need to be  con-
       figured separately.

       Here is an example of a master zone in BIND9 syntax.

       zone "example.nl" {
            type master;
            file "example.nl";
       };

       In NSD syntax this becomes:

       zone:
            name: "example.nl"
            zonefile: "example.nl"
            # allow anybody to request xfr.
            provide-xfr: 0.0.0.0/0 NOKEY
            provide-xfr: ::0/0 NOKEY

            # to list a slave server you would in general give
            # provide-xfr: 1.2.3.4 tsig-key.name.
            # notify: 1.2.3.4 NOKEY

   Other
       NSD is an authoritative only DNS server. This means that it is meant as
       a primary or secondary server for zones,  providing  DNS  data  to  DNS
       resolvers  and  caches.  BIND9  can  function  as  an authoritative DNS
       server, the configuration options for that are compared with those  for
       NSD  in this section. However, BIND9 can also function as a resolver or
       cache. The configuration options that BIND9 has  for  the  resolver  or
       caching thus have no equivalents for NSD.

FILES
       "/var/db/nsd/nsd.db"
              default NSD database

       /etc/nsd/nsd.conf
              default NSD configuration file

SEE ALSO
       nsd(8), nsd-checkconf(8), nsd-control(8)

AUTHORS
       NSD was written by NLnet Labs and RIPE NCC joint team. Please see CRED-
       ITS file in the distribution for further details.

BUGS
       nsd.conf is parsed by a primitive parser, error messages may not be  to
       the point.



NLnet Labs                       Apr 16, 2020                      nsd.conf(5)