rbldnsd(8)                  System Manager's Manual                 rbldnsd(8)

       rbldnsd - DNS daemon suitable for running DNS-based blocklists

       rbldnsd options zone:dataset...

       rbldnsd is a small DNS-protocol daemon which is designed to handle
       queries to DNS-based IP-listing or NAME-listing services.  Such
       services are a simple way to share/publish a list of IP addresses or
       (domain) names which are "listed" for for some reason, for example in
       order to be able to refuse a service to a client which is "listed" in
       some blocklist.

       rbldnsd is not a general-purpose nameserver.  It will answer to A and
       TXT (and SOA and NS if such RRs are specified) queries, and has limited
       ability to answer to some other types of queries.

       rbldnsd tries to handle data from two different perspectives: given a
       set (or several) of "listed entries" (e.g. IP address ranges or domain
       names), it builds and serves a DNS zone.  Note the two are not the
       same: list of spammer's IPs is NOT a DNS zone, but may be represented
       and used as such, provided that some additional information necessary
       to build complete DNS zone (e.g. NS and SOA records, maybe A records
       necessary for http to work) is available.  In this context, rbldnsd is
       very different from other general-purpose nameservers such as BIND or
       NSD: rbldnsd operates with datasets (sets of entries - IP addresses or
       domain names, logically grouped together), while other general-purpose
       nameservers operates with zones.  The way how rbldnsd operates may be
       somewhat confusing to BIND experts.

       For rbldnsd, a building block is a dataset: e.g., set of
       insecure/abuseable hosts (IP addresses), set of network ranges that
       belongs to various spam operations (IP ranges), domain names that
       belong to spammers (RHSBL) and so on.  Usually, different kind of
       information is placed into separate file, for easy maintenance.  From a
       number of such datasets, rbldnsd constructs a number of DNS zones as
       specified on command line.  A single dataset may be used for several
       zones, and a single zone may be constructed from several datasets.

       rbldnsd will answer queries to DNS zones specified on the command line
       as a set of zone specifications.  Each zone specification consists of
       zone basename, dataset type and a comma-separated list of files that
       forms a given dataset: zone:type:file,file,...

       Several zones may be specified in command line, so that rbldnsd will
       answer queries to any of them.  Also, a single zone may be specified
       several times with different datasets, so it is possible to form a zone
       from a combination of several different dataset.  The same dataset may
       be reused for several zones too (and in this case, it will be read into
       memory only once).

       There are several dataset formats available, each is suitable and
       optimized (in terms of memory, speed and ease of use) for a specific
       task.  Available dataset types may be grouped into the following

              lists of IP addresses.  When a query is done to a zone with such
              data, query is interpreted as an IP address in a reverse form
              (similar to in-addr.arpa zone).  If the address is found in
              dataset data, rbldnsd will return A and TXT records specified in
              data for that IP.  This is a classical IP-based blocklist.

              lists of domain names.  Similar to list of IP addresses, but
              with generic domain names instead of IPs (wildcards allowed).
              This type of data may be used to form a blocklist of e.g.
              sender domain names.

              generic list of various types of records, as an auxilary data to
              form a complete nameserver.  This format is similar to
              bind-style datafiles, but very simplified.  One may specify A,
              TXT, NS and MX records here.

              combined set, different datasets from the list above combined in
              the single (set of) source files, for easy maintenance.

              acl, or Access Control List.  This is a pseudo dataset, that
              works by overweriting query results based on the requestor
              (peer) IP address.

       The following options may be specified:

       -u user[:group]
              rbldnsd will change its userid to the specified user, which
              defaults to rbldns, and group, which by default is the primary
              group of a user. rbldnsd will refuse to run as the root user,
              since this is insecure.

       -r rootdir
              rbldnsd will chroot to rootdir if specified.  Data files should
              be available inside rootdir.

       -w workdir
              rbldnsd will change its working directory to workdir (after
              chrooting to rootdir if -r option is also specified).  May be
              used to shorten filename paths.

       -b address/port
              This option is required.  rbldnsd will bind to specified address
              and port (port defaults to port 53, domain).  Either numeric IP
              address or a hostname may be specified, and either port number
              or service name is accepted.  It is possible to specify several
              addresses to listen on this way, by repeating -b option.
              Additionally, if there are several addresses listed for a
              hostname, rbldnsd will listen on all of them.  Note that rbldnsd
              will work slightly faster if only one listening address is
              specified.  Note the delimiter between host and port is a slash
              (/), not a colon, to be able to correctly handle IPv6 addresses.

       -4     Use IPv4 listening socket/transport, do not attempt to use IPv6
              (ignored if rbldnsd was built without IPv6 support).

       -6     Use IPv6 listening socket/transport, do not attempt to use IPv4
              (this option will be reported as error if IPv6 support was not
              compiled in).

       -t defttl:minttl:maxttl
              Set default reply time-to-live (TTL) value to be defttl, and set
              constraints for TTL to minttl and maxttl.  Default applies when
              there's no TTL defined in a given scope (in data file), and
              constraints are applied when such value provided in data.  Any
              of the values may be omitted, including trailing colon (:)
              characters, e.g. "-t 30" set default TTL to be 30 secound, and
              "-t ::120" or "-t ::2m" sets maximum allowed TTL to 2 minutes.
              All 3 values are in time units, with optional suffix: s
              (secounds, default), m (minutes), h (hours), d (days) or w
              (weeks).  Zero minttl or maxttl means no corresponding
              constraint will be enforced.  Default defttl is 35m.

       -c check
              Set interval between checking for zone file changes to be check,
              default is 1m (one minute).  rbldnsd will check zone file's last
              modification time every so often, and if it detects a change,
              zone will be automatically reloaded.  Setting this value to 0
              disables automatic zone change detection.  This procedure may
              also be triggered by sending a SIGHUP signal to rbldnsd (see
              SIGNALS section below).

       -e     Allow non-network addresses to be used in CIDR ranges.
              Normally, rbldnsd rejects addresses such as, where
              prefix is not within the network mask derived from bit number
              (in this case, correct form is, note the trailing
              zero in prefix).  This is done in order to catch possible typos
              in zones (rbldnsd will warn about a problem and will ignore such
              entry).  This option disables checking whether the CIDR prefix
              fits within the network mask.

       -q     Quick and quiet start.  Normally, rbldnsd does socket
              initialization and zone load in foreground, writing progress and
              statistic to standard output, and aborts in case of any errors.
              With this flag, nothing will be printed and first zone load will
              be done in background (unless -n option is also given), and zone
              load errors will be non-fatal.

       -p pidfile
              Write rbldnsd's pid to the specified pidfile, so it will be
              easily findable.  This file gets written before entering a
              chroot jail (if specified) and before changing userid, so it's
              ok to specify e.g. /var/run/rbldnsd.pid here.

       -l logfile
              Specifies a file to which log all requests made.  This file is
              created after entering a chroot jail and becoming a user.
              Logfiles may be quite large, esp. on busy sites (rbldnsd will
              log every recognized request if this option is specified).  This
              option is mainly intended for debugging purposes.  Upon
              receiption of SIGHUP signal, rbldnsd reopens its logfile.  If
              logfile prefixed with a plus sign (+), logging will not be
              buffered (i.e. each line will be flushed to disk); by default,
              logging is buffered to reduce system load.  Specify a single
              hyphen (-) as a filename to log to standard output
              (filedescriptor 1), either buffered by default, or line-buffered
              if specified as `+-' (standard output will not be "reopened"
              upon receiving SIGHUP signal, but will be flushed in case
              logging is buffered).

       -s statsfile
              Specifies a file where rbldnsd will write a line with short
              statistic summary of queries made per zone, every check (-c)
              interval.  Format of each line is:
                timestamp zone:qtot:qok:qnxd:bin:bout zone:...
              where timestamp is unix time (secounds since epoch), zone is the
              name of the base zone, qtot is the total number of queries
              received, qok - number of positive replies, qnxd - number of
              NXDOMAIN replies, bin is the total number of bytes read from
              network (excluding IP/UDP overhead and dropped packets), bout is
              the total number of bytes written to network.  Ther are as many
              such tuples as there are zones, and one extra, total typle at
              the end, with zone being "*", like:
                1234 bl1.ex:10:5:4:311:432 bl2.ex:24:13:7:248:375 *:98:35:12:820:987
              Note the total values may be larger than the sum of per-zone
              values, due to queries made against unlisted zones, or
              bad/broken packets.

              Rbldnsd will write bare timestamp to statsfile when it is
              starting up, shutting down or when statistic counters are being
              reset after receiving SIGUSR2 signal (see below), to indicate
              the points where the counters are starting back from zero.

              By default, rbldnsd writes absolute counter values into
              statsfile (number of packets (bytes) since startup or last
              reset).  statsfile may be prefixed with plus sign (+), in which
              case rbldnsd will write delta values, that is, number of packets
              or bytes since last write, or number of packets (bytes) per unit
              of time ("incremental" mode, hence the "+" sign).

       -n     Do not become a daemon.  Normally, rbldnsd will fork and go to
              the background after successful initialization.  This option
              disables this behaviour.

       -f     Request rbldnsd to continue processing requests during data
              reloads.  Rbldnsd forks a child process to handle requests while
              parent reloads the data.  This ensures smooth operations, but
              requires more memory, since two copies of data is keept in
              memory during reload process.

       -d     Dump all zones to stdout in BIND format and exit.  This may be
              suitable to convert easily editable rbldnsd-style data into BIND
              zone.  rbldnsd dumps all zones as one stream, so one may want to
              specify only one zone with -d.  Zone file will have appropriate
              $ORIGIN tags.  Note that data generated may be really huge (as
              BIND format isn't appropriate for this sort of things), and some
              entries may not be really the same in BIND as in rbldnsd (e.g.,
              IP netblocks of large size will be represented as wildcard
              entries - will become *.10; excluded entries will be
              represented by a CNAME to `excluded' name, so such name should
              not be present in a data set).  In this mode, rbldnsd ignores -r
              (root directory) option.

       -v     Do not show exact version information in response to
              version.bind CH TXT queries (by default rbldnsd responds to such
              queries since version 0.98).  With single -v, rbldnsd will only
              return "rbldnsd" to the caller, without the version number.
              Second -v disables providing any information in response to such
              requests, i.e. rbldnsd will return REFUSE code.

       -C     Disable automatic on-the-fly uncompression of data files if this
              feature is compiled in (see below).


       -a     Controls "laziness" of rbldnsd when constructing replies.  With
              -a specified, rbldnsd does not add AUTH section (containing NS
              records) to replies unless explicitly asked for NS records.  It
              is equivalent to BIND9 "minimal-answers" configuration setting.
              While with -A specified, rbldnsd will always fill in AUTH
              section, increasing size of replies dramatically but allowing
              (caching) resolver clients to react faster to changes in
              nameserver lists.  Currently (as of 0.998 version), non-lazy (as
              with -A) mode is the default, but it will change in future

       -x extension
              Load the given extension file (a dynamically-linked library,
              usually with ".so" suffix).  This allows to gather custom
              statistics or perform other custom tasks.  See separate document
              for details about building and using extensions.  This feature
              is not available on all platforms, and can be disabled at
              compile time.

       -X extarg
              Pass the given argument, extarg, to the extension loaded with

       Dataset files are text files which are interpreted depending on type
       specified in command line.  Empty lines and lines starting with hash
       character (#) or semicolon (;) are ignored, except for a special case
       outlined below in section titled "Special Entries".

       A (comma-separated) list of files in dataset specification (in
       type:file,file,...) is interpreted as if all files where logically
       combined into one single file.

       When compiled with zlib support, rbldnsd is able to read
       gzip-compressed data files.  So, every file in dataset specification
       can be compressed with gzip(1), and rbldnsd will read such a file
       decompressing it on-the-fly.  This feature may be turned off by
       specifying -C option.

       rbldnsd is designed to service a DNSBL, where each entry have single A
       record and optional TXT record assotiated with it.  rbldnsd allows to
       specify A value and TXT template either for each entry individually, or
       to use default A value and TXT template pair for a group of entries.
       See section "Resulting A values and TXT templates" below for a way to
       specify them.

   Special Entries
       If a line starts with a dollar sign ($), hash character and a dollar
       sign (#$), semicolon and dollar sign (;#) or colon and a dollar sign
       (:$), it is interpreted in a special way, regardless of dataset type
       (this is one exception where a line starting with hash character is not
       ignored - to be able to use zone files for both rbldnsd and for DJB's
       rbldns). The following keywords, following a dollar sign, are

       $SOA ttl origindn persondn serial refresh retry expire minttl
              Specifies SOA (Start Of Authority) record for all zones using
              this dataset.  Only first SOA record is interpreted.  This is
              the only way to specify SOA - by default, rbldnsd will not add
              any SOA record into answers, and will REFUSE to answer to
              certain queries (notably, SOA query to zone's base domain name).
              It is recommended, but not mandatory to specify SOA record for
              every zone.  If no SOA is given, negative replies will not be
              cacheable by caching nameservers.  Only one, first $SOA line is
              recognized in every dataset (all subsequent $SOA lines
              encountered in the same dataset are silently ignored).  When
              constructing a zone, SOA will be taken from first dataset where
              $SOA line is found, in an order as specified in command line,
              subsequent $SOA lines, if any, are ignored.  This way, one may
              overwrite $SOA found in 3rd party data by prepending small local
              file to the dataset in question, listing it before any other

              If serial value specified is zero, timestamp of most recent
              modified file will be substituted as serial.

              If ttl field is zero, default ttl (-t option or last $TTL value,
              see below) will be used.

              All time fields (ttl, refresh, retry, expire, minttl) may be
              specified in time units.  See -t option for details.

       $NS ttl nameserverdn nameserverdn...
              Specifies NS (Name Server) records for all zones using this
              dataset.  Only first $NS line in a dataset is recognized, all
              subsequent lines are silently ignored.  When constructing a zone
              from several datasets, rbldnsd uses nameservers from $NS line in
              only first dataset where $NS line is given, in command-line
              order, just like for $SOA record.  Only first 32 namservers are
              recognized.  Individual nameserver(s) may be prefixed with a
              minus sign (-), which means this single nameserver will be
              ignored by rbldnsd.  This is useful to temporary comment out one
              nameserver entry without removing it from the list.  If ttl is
              zero, default ttl will be used.  The list of NS records, just
              like $SOA value, are taken from the first data file in a dataset
              where the $NS line is found, subsequent $NS lines, if any, are

       $TTL time-to-live
              Specifies TTL (time-to-live) value for all records in current
              dataset.  See also -t option.  $TTL special overrides -t value
              on a per-dataset basis.

       $TIMESTAMP dstamp [expires]
              (experimental) Specifies the data timestamp dstamp when the data
              has been generated, and optionally when it will expire.  The
              timestamps are in form yyyy:mm:dd[:hh[:mi[:ss]]], where yyyy is
              the year like 2005, mm is the month number (01..12), dd is the
              month day number (01..31), hh is hour (00..23), mi and ss are
              minutes and secounds (00.59); hours, minutes and secounds are
              optional and defaults to 0; the delimiters (either colon or dash
              may be used) are optional too, but are allowed for readability.
              Also, single zero (0) or dash (-) may be used as dstamp and/or
              expires, indicating the value is not given.  expires may also be
              specified as +rel, where rel is a time specification (probably
              with suffix like s, m, h, d) as an offset to dstamp.  rbldnsd
              compares dstamp with current timestamp and refuses to load the
              file if dstamp specifies time in the future.  And if expires is
              specified, rbldnsd will refuse to service requests for that data
              if current time is greather than the value specified in expires

              Note that rbldnsd will check the data expiry time every time it
              checks for data file updates (when receiving SIGHUP signal or
              every -c interval).  If automatic data reload timer (-c option)
              is disabled, zones will not be exipired automatically.

       $MAXRANGE4 range-size
              Specifies maximum size of IPv4 range allowed for IPv4-based
              datasets.  If an entry covers more IP addresses than range-size,
              it will be ignored (and a warning will be logged).  range-size
              may be specified as a number of hosts, like 256, or as network
              prefix lenght, like /24 (the two are the same):
                $MAXRANGE4 /24
                $MAXRANGE4 256
              This constraint is active for a dataset it is specified in, and
              can be owerwritten (by subsequent $MAXRANGE statement) by a
              smaller value, but can not be increased.

       $n text
              (n is a single digit).  Specifies a substitution variable for
              use as $n placeholders (the $n entries are ignored in generic
              daaset).  See section "Resulting A values and TXT templates"
              below for description and usage examples.

       $= text
              Set the base template for all individual TXT records.  See
              section "Resulting A values and TXT templates" below for more

   ip4set Dataset
       A set of IP addresses or CIDR address ranges, together with A and TXT
       resulting values.  IP addresses are specified one per line, by an IP
       address prefix (initial octets), complete IP address, CIDR range, or IP
       prefix range (two IP prefixes or complete addresses delimited by a
       dash, inclusive).  Examples, to specify
       to specify
       Note that in prefix range, last boundary is completed with all-ones
       (255), not all-zeros line with first boundary and a prefix alone.  In
       prefix ranges, if last boundary is only one octet (127.16-31), it is
       treated as "suffix", as value of last specified octet of the first
       boundary prefix (127.16.0-31 is treated as,

       After an IP address range, A and TXT values for a given entry may be
       specified.  If none given, default values in current scope (see below)
       applies.  If a value starts with a colon, it is interpreted as a pair
       of A record and TXT template, delimited by colon (: entry
       is listed).  If a value does not start with a colon, it is interpreted
       as TXT template only, with A record defaulting to the default A value
       in current scope.

       IP address range may be followed by a comment char (either hash
       character (#) or semicolon (;)), e.g.:
         127/8 ; loopback network
       In this case all characters up to the end of line are ignored, and
       default A and TXT values will be used for this IP range.

       Every IP address that fits within any of specified ranges is "listed",
       and rbldnsd will respond to reverse queries against it within specified
       zone with positive results.  In contrast, if an entry starts with an
       exclamation sign (!), this is an exclusion entry, i.e. corresponding
       address range is excluded from being listed (and any value for this
       record is ignored).  This may be used to specify large range except
       some individual addresses, in a compact form.

       If a line starts with a colon (:), this line specifies the default A
       value and TXT template to return (see below) for all subsequent entries
       up to end of current file.  If no default entry specified, and no value
       specified for a given record, rbldnsd will return for
       matching A queries and no record for matching TXT queries.  If TXT
       record template is specified and contains occurences of of dollar sign
       ($), every such occurence is replaced with an IP address in question,
       so singe TXT template may be used to e.g. refer to a webpage for an
       additional information for a specific IP address.

   ip4trie Dataset
       Set of IP4 CIDR ranges with corresponding (A, TXT) values.  This
       dataset is similar to ip4set, but uses a different internal
       representation.  It accepts CIDR ranges only (not a.b.c.d-e.f.g.h), and
       allows for the specification of A/TXT values on a per CIDR range basis.
       (If multiple CIDR ranges match a query, the value for longest matching
       prefix is returned.)  Exclusions are supported too.

       This dataset is not particularly memory-efficient for storing many
       single IP addresses — it uses about 50% more memory than the ip4set
       dataset in that case.  The ip4trie dataset is better adapted, however,
       for listing CIDR ranges (whose lengths are not a multiple of 8 bits.)

   ip4tset Dataset
       "trivial" ip4set: a set of single IP addresses (one per line), with the
       same A+TXT template.  This dataset type is more efficient than ip4set
       (in both memory usage and access times), but have obvious limitation.
       It is intended for DNSBLs like DSBL.org, ORDB.org and similar, where
       each entry uses the same default A+TXT template.  This dataset uses
       only half a memory for the same list of IP addresses compared to

   ip6trie Dataset
       Set of IP6 CIDR ranges.  This is the IP6 equivalent of the ip4trie
       dataset.  It allows the sepecification of individual A/TXT values for
       each CIDR range and supports exclusions.  Compressed ("::") ip6
       notation is supported.

       Example zone data:
         # Default A and TXT template valuse
         : Listed, see http://example.com/lookup?$

         # A listing, note that trailing :0s can be omitted

         # /64 range with non-default A and TXT values
         2001:21ab:def7:4242 : This one smells funny

         # compressed notation
         ::1                   # localhost
         !2605:6001:42::bead   # exclusion

   ip6tset Dataset
       "Trivial" ip6 dataset: a set of /64 IP6 CIDR ranges (one per line), all
       sharing a single A+TXT template.  Exclusions of single IP6 (/128)
       addresses are also supported.  This dataset type is quite memory-
       efficient — it uses about 40% of the memory that the ip6trie dataset
       would use — but has obvious limitations.

       This dataset wants the /64s listed as four ip6 words, for example:
       Exclusions are denoted with a leading exclamation mark.  You may also
       use compressed "::" notation for excluded addresses.  E.g.:

   dnset Dataset
       Set of (possible wildcarded) domain names with associated A and TXT
       values.  Similar to ip4set, but instead of IP addresses, data consists
       of domain names (not in reverse form).  One domain name per line,
       possible starting with wildcard (either with star-dot (*.) or just a
       dot).  Entry starting with exclamation sign is exclusion.  Default
       value for all subsequent lines may be specified by a line starting with
       a colon.

       Wildcards are interpreted as follows:

              only example.com domain is listed, not subdomains thereof.  Not
              a wildcard entry.

              all subdomains of example.com are listed, but not example.com

              all subdomains of example.com and example.com itself are listed.
              This is a shortcut: to list a domain name itself and all it's
              subdomains, one may either specify two lines (example.com and
              *.example.com), or one line (.example.com).

       This dataset type may be used instead of ip4set, provided all CIDR
       ranges are expanded and reversed (but in this case, TXT template will
       be expanded differently).

   generic Dataset
       Generic type, simplified bind-style format.  Every record should be on
       one line (line continuations are not supported), and should be
       specified completely (i.e. all domain names in values should be
       fully-qualified, entry name may not be omitted).  No wildcards are
       accepted.  Only A, TXT, and MX records are recognized.  TTL value may
       be specified before record type.  Examples:

               # bl.ex.com
               # specify some values for current zone
               $NS 0 ns1.ex.com ns2.ex.com
               # record with TTL
               www 3000 A
               about TXT "ex.com combined blocklist"

   combined Dataset
       This is a special dataset that stores no data by itself but acts like a
       container for several other datasets of any type except of combined
       type itself.  The data file contains an optional common section, where
       various specials are recognized like $NS, $SOA, $TTL (see above), and a
       series of sections, each of which defines one (nested) dataset and
       several subzones of the base zone, for which this dataset should be
       consulted.  New (nested) dataset starts with a line
         $DATASET type[:name] subzone subzone...
       and all subsequent lines up to the end of current file or to next
       $DATASET line are interpreted as a part of dataset of type type, with
       optional name (name is used for logging purposes only, and the whole
       ":name" (without quotes or square brackets) part is optional).  Note
       that combined datasets cannot be nested.  Every subzone will always be
       relative to the base zone name specified on command line.  If subzone
       specified as single character "@", dataset will be connected to the
       base zone itself.

       This dataset type aims to simplify subzone maintenance, in order to be
       able to include several subzones in one file for easy data transfer,
       atomic operations and to be able to modify list of subzones on remote
       secondary nameservers.

       Example of a complete dataset that contains subzone `proxies' with a
       list of open proxies, subzone `relays' with a list of open relays,
       subzone `multihop' with output IPs of multihop open relays, and the
       base zone itself includes proxies and relays but not multihops:
         # common section
         $NS 1w ns1.ex.com ns2.ex.com
         $SOA 1w ns1.ex.com admin.ex.com 0 2h 2h 1w 1h
         # list of open proxies,
         # in `proxies' subzone and in base zone
         $DATASET ip4set:proxy proxies @
         :2:Open proxy, see http://bl.ex.com/proxy/$
         # list of open relays,
         # in `relays' subzone and in base zone
         $DATASET ip4set:relay relays @
         :3:Open relay, see http://bl.ex.com/relay/$
         # list of optputs of multistage relays,
         # in `multihop' subzone only
         $DATASET ip4set:multihop-relay multihop
         :4:Multihop open relay, see http://bl.ex.com/relay/$
         # for the base zone and all subzones,
         # include several additional records
         $DATASET generic:common proxies relays multihop @
         @ A
         www A
         @ MX 10 mx.ex.com
         # the above results in having the following records
         # (provided that the base zone specified is bl.ex.com):
         #  proxies.bl.ex.com A
         #  www.proxies.bl.ex.com
         #  relays.bl.ex.com A
         #  www.relays.bl.ex.com
         #  multihop.bl.ex.com A
         #  www.multihop.bl.ex.com
         #  bl.ex.com A
         #  www.bl.ex.com

       Note that $NS and $SOA values applies to the base zone only, regardless
       of the placement in the file.  Unlike the $TTL values and $n
       substitutions, which may be both global and local for a given

   Resulting A values and TXT templates
       In all zone file types except generic, A values and TXT templates are
       specified as following:
         : http://example.com/bl?$
       If a line starts with a colon, it specifies default A and TXT for all
       subsequent entries in this dataset.  Similar format is used to specify
       values for individual records, with the A value (enclosed by colons)
       being optional: : http://example.com/bl?$
       or, without specific A value: Blacklisted: http://example.com/bl?$

       Two parts of a line, delimited by second colon, specifies A and TXT
       record values.  Both are optional.  By default (either if no default
       line specified, or no IP address within that line), rbldnsd will return as A record.  127.0.0 prefix for A value may be omitted, so
       the above example may be simplified to:
         :2:Blacklisted: http://example.com/bl?$
       There is no default TXT value, so rbldnsd will not return anything for
       TXT queries it TXT isn't specified.

       When A value is specified for a given entry, but TXT template is
       omitted, there may be two cases interpreted differently, namely,
       whenever there's a second semicolon (:) after the A value.  If there's
       no second semicolon, default TXT value for this scope will be used.  In
       contrast, when second semicolon is present, no TXT template will be
       generated at all.  All possible cases are outlined in the following

         # default A value and TXT template
         : address $ is listed
         # will use default A and TXT
         # will use specific A and default TXT :5
         # will use specific a and no TXT :6:
         # will use default A and specific TXT IP address $ running an open relay

       In a TXT template, references to substitution variables are replaced
       with values of that variables.  In particular, single dollar sign ($)
       is replaced by a listed entry (an IP address in question for IP-based
       datasets and the domain name for domain-based datasets).  $n-style
       constructs, where n is a single digit, are replaced by a substitution
       variable $n defined for this dataset in current scope (see section
       "Special Entries" above).  To specify a dollar sign as-is, use $$.

       For example, the following lines:
         $1 See http://www.example.com/bl
         $2 for details  $1/spammer/$ $2  $1/relay/$ $2  This spammer wants some $$$$.  $1/$
       will result in the following text to be generated:
         See http://www.example.com/bl/spammer/ for details
         See http://www.example.com/bl/relay/ for details
         This spammer wants some $$.  See http://www.example.com/bl/

       If the "base template" ($= variable) is defined, this template is used
       for expansion, instead of the one specified for an entry being queried.
       Inside the base template, $= construct is substituted with the text
       given for individual entries. In order to stop usage of base template
       $= for a single record, start it with = (which will be omitted from the
       resulting TXT value).  For example,
         $0 See http://www.example.com/bl?$= ($) for details    r123    =See other blocklists for details about $
       produces the following TXT records:
         See http://www.example.com/bl?r123 ( for details
         See http://www.example.com/bl? ( for details
         See other blocklists for details about

   acl Dataset
       This is not a real dataset, while the syntax and usage is the same as
       with other datasets.  Instead of defining which records exists in a
       given zone and which do not, the acl dataset specifies which client
       hosts (peers) are allowed to query the given zone.  The dataset
       specifies a set of IPv4 and/or IPv6 CIDR ranges (with the syntax
       exactly the same as understood by the ip4trie and ip6trie datasets),
       together with action specifiers.  When a query is made from an IP
       address listed (not for the IP address), the specified action changes
       rules used to construct the reply.  Possible actions and their meanings

              ignore all queries from this IP address altogether.  rbldnsd
              acts like there was no query received at all.  This is the
              default action.

              refuse all queries from the IP in question.  rbldnsd will always
              return REFUSED DNS response code.

       :empty pretend there's no data in all other datasets for the given
              zone.  This means that all the clients in question will always
              receive reply from rbldnsd telling that the requested IP address
              or domain name is not listed in a given DNSBL.  rbldnsd still
              replies to metadata queries (SOA and NS records, and to all
              queries satisfied by generic dataset if specified for the given
              zone) as usual.

       :pass  process the request as usual.  This may be used to add a
              "whitelisting" entry for a network/host bloked by another
              (larger) ACL entry.

              usual A+TXT template as used by other datasets.  This means that
              rbldnsd will reply to any valid DNSBL query with "it is listed"
              answer, so that the client in question will see every IP address
              or domain name is listed in a given DNSBL.  TXT record used in
              the reply is taken from the acl dataset instead of real
              datasets.  Again, just like with empty case, rbldnsd will
              continue replying to metadata queries (including generic
              datasets if any) as usual.

       Only one ACL dataset can be specified for a given zone, and each zone
       must have at least one non-acl dataset.  It is also possible to specify
       one global ACL dataset, by specifying empty zone name (which is not
       allowed for other dataset types), like
         rbldnsd ... :acl:filename...
       In this case the ACL defined in filename applies to all zones.  If
       there are both global ACL and local zone-specific ACL specified, both
       will be consulted and actions taken in the order specified above, ie,
       if either ACL returns ignore for this IP, the request will be ignored,
       else if either ACL returns refuse, the query will be refused, and so
       on.  If both ACLs specifies "always listed" A+TXT template, the reply
       will contain A+TXT from global ACL.

       For this dataset type, only a few $-style specials are recognized.  In
       particular, $SOA and $NS keywords are not allowed.  When rbldnsd
       performs $ substitution in the TXT template returned from ACL dataset,
       it will use client IP address to substitute for a single $ character,
       instead of the IP address or domain name found in the original query.

       Rbldnsd handles the following signals:

       SIGHUP recheck zone files and reload any outdated ones.  This is done
              automatically if enabled, see -c option.  Additionally, rbldnsd
              will reopen logfile upon receiving SIGHUP, if specified (-l

              Terminate process.

              Log current statistic counters into syslog.  Rbldnsd collects
              how many packets it handled, how many bytes was received, sent,
              how many OK requests/replies (and how many answer records) was
              received/sent, how many NXDOMAIN answers was sent, and how many
              errors/refusals/etc was sent, in a period of time.

              The same as SIGUSR1, but reset all counters and start new sample

       Some unsorted usage notes follows.

   Generating and transferring data files
       When creating a data file for rbldnsd (and for anything else, it is a
       general advise), it is a good idea to create the data in temporary file
       and rename the temp file when all is done.  Never try to write to the
       main file directly, it is possible that at the same time, rbldnsd will
       try to read it and will get incomplete data as the result.  The same
       applies to copying data using cp(1) utility and similar (including
       scp(1)), that performs copying over existing data.  Even if you're sure
       noone is reading the data while you're copying or generating it,
       imagine what will happen if you will not be able to complete the
       process for whatever reason (interrupt, filesystem full, endless number
       of other reasons...).  In most cases is better to keep older but
       correct data instead of leaving incomplete/corrupt data in place.

         scp remote:data target.tmp && mv target.tmp target
         scp remote:data target
         ./generate.pl > target.tmp && mv target.tmp target
         ./generate.pl > target

       From this point of view, rsync(1) command seems to be safe, as it
       always creates temporary file and renames it to the destination only
       when all is ok (but note the --partial option, which is good for
       downloading something but may be wrong to transfer data files --
       usually you don't want partial files to be loaded).  In contrast,
       scp(1) command is not safe, as it performs direct copying.  You may
       still use scp(1) in a safe manner, as shown in the example above.

       Also try to eliminate a case when two (or more) processes performs data
       copying/generation at the same time to the same destination.  When your
       data is generated by a cron job, use file locking (create separate lock
       file (which should never be removed) and flock/fcntl it in exclusive
       mode without waiting, exiting if lock fails) before attempting to do
       other file manipulation.

   Absolute vs relative domain names
       All keys specified in dataset files are always relative to the zone
       base DN.  In contrast, all the values (NS and SOA records, MX records
       in generic dataset) are absolute.  This is different from BIND
       behaviour, where trailing dot indicates whenever this is an absolute or
       relative DN.  Trailing dots in domain names are ignored by rbldnsd.

   Aggregating datasets
       Several zones may be served by rbldnsd, every zone may consist of
       several datasets.  There are numerous ways to combine several data
       files into several zones.  For example, suppose you have a list of
       dialup ranges in file named `dialups', and a list of spammer's ip
       addresses in file named `spammers', and want to serve 3 zones with
       rbldnsd: dialups.bl.ex.com, spam.bl.ex.com and bl.ex.com which is a
       combination of the two.  There are two ways to do this:

        rbldnsd options... \
          dialups.bl.ex.com:ip4set:dialups \
          spam.bl.ex.com:ip4set:spammers \


        rbldnsd options... \
          dialups.bl.ex.com:ip4set:dialups \
          spam.bl.ex.com:ip4set:spammers \
          bl.ex.com:ip4set:dialups \

       (note you should specify combined bl.ex.com zone after all its subzones
       in a command line, or else subzones will not be consulted at all).

       In the first form, there will be 3 independent data sets, and every
       record will be stored 2 times in memory, but only one search in
       internal data structures will be needed to resolve queries for
       aggregate bl.ex.com.  In second form, there will be only 2 data sets,
       every record will be stored only once (both datasets will be reused),
       but 2 searches will be performed by rbldnsd to answer queries against
       aggregate zone (but difference in speed is almost unnoticeable).  Note
       that when aggregating several data files into one dataset, an exclusion
       entry in one file becomes exclusion entry in the whole dataset (which
       may be a problem when aggregating dialups, where exclusions are common,
       with open relays/proxies, where exclusions are rare if at all used).

       Similar effect may be achieved by using combined dataset type,
       sometimes more easily.  combined dataset results in every nested
       dataset to be used independantly, like in second form above.

       combined dataset requires rbldnsd to be the authoritative nameserver
       for the whole base zone.  Most important, one may specify SOA and NS
       records for the base zone only.  So, some DNSBLs which does not use a
       common subzone for the data, cannot use this dataset.  An example being
       DSBL.org DNSBL, where each of list.dsbl.org, multihop.dsbl.org and
       unconfirmed.dsbl.org zones are separate, independant zones with
       different set of nameservers.  But for DSBL.org, where each dataset is
       really independant and used only once (there's no (sub)zone that is as
       a combinations of other zones), combined dataset isn't necessary.  In
       contrast, SORBS.net zones, where several subzones used and main zone is
       a combination of several subzones, combined dataset is a way to go.

   All authoritative nameservers should be set up similarily
       When you have several nameservers for your zone, set them all in a
       similar way.  Namely, if one is set up using combined dataset, all the
       rest should be too, or else DNS meta-data will be broken.  This is
       because metadata (SOA and NS) records returned by nameservers using
       combined and other datasets will have different origin.  With combined
       dataset, rbldnsd return NS and SOA records for the base zone, not for
       any subzone defined inside the dataset.  Given the above example with
       dialups.bl.ex.com, spammers.bl.ex.com and aggregate bl.ex.com zones,
       and two nameservers, first is set up in any ways described above (using
       individual datasets for every of the 3 zones), and second is set up for
       the whole bl.ex.com zone using combined dataset.  In this case, for
       queries against dialups.bl.ex.com, first nameserver will return NS
       records like
         dialups.bl.ex.com. IN NS a.ns.ex.com.
       while second will always use base zone, and NS records will look like
         bl.ex.com. IN NS a.ns.ex.com.
       All authoritative nameservers for a zone must have consistent metadata
       records.  The only way to achieve this is to use similar configuration
       (combined or not) on all nameservers.  Have this in mind when using
       other software for a nameserver.

   Generic dataset usage
       generic dataset type is very rudimentary.  It's purpose is to
       complement all the other type to form complete nameserver that may
       answer to A, TXT and MX queries.  This is useful mostly to define A
       records for HTTP access (relays.bl.example.com A, www.bl.example.com A
       just in case), and maybe descriptive texts as a TXT record.

       Since rbldnsd only searches one, most closely matching (sub)zone for
       every request, one cannot specify a single e.g.  generic dataset in
         proxies      TXT list of open proxies
         www.proxies  A
         relays       TXT list of open relays
         www.relays   A
       for several (sub)zones, each of which are represented as a zone too
       (either in command line or as combined dataset).  Instead, several
       generic datasets should be specified, separate one for every (sub)zone.
       If the data for every subzone is the same, the same, single dataset may
       be used, but it should be specified for every zone it should apply to
       (see combined dataset usage example above).

       Most of the bugs outlined in this section aren't really bugs, but
       present due to non-standartized and thus unknown expected behaviour of
       a nameserver that serves a DNSBL zone.  rbldnsd matches BIND runtime
       behaviour where appropriate, but not always.

       rbldnsd lowercases some domain names (the ones that are lookup keys,
       e.g. in `generic' and `dnset' datasets) when loading, to speed up
       lookup operations.  This isn't a problem in most cases.

       There is no TCP mode.  If a resource record does not fit in UDP packet
       (512 bytes), it will be silently ignored.  For most usages, this isn't
       a problem, because there should be only a few RRs in an answer, and
       because one record is usually sufficient to decide whenever a given
       entry is "listed" or not.  rbldnsd isn't a full-featured nameserver,
       after all.

       rbldnsd will not always return a list of nameserver records in the
       AUTHORITY section of every positive answer: NS records will be provided
       (if given) only if there's a room for them in single UDP packet.  If
       records does not fit, AUTHORITY section will be empty.

       rbldnsd does not allow AXFR operations.  For DNSBLs, AXFR is the
       stupidiest yet common thing to do - use rsync for zone transfers
       instead.  This isn't a bug in rbldnsd itself, but in common practice of
       using AXFR and the like to transfer huge zones in a format which isn't
       suitable for such a task.  Perhaps in the future, if there will be some
       real demand, I'll implement AXFR "server" support (so that rbldnsd will
       be able to act as master for BIND nameservers, but not as secondary),
       but the note remains: use rsync.

       rbldnsd truncates all TXT records to be at most 255 bytes.  DNS specs
       allows longer TXTs, but long TXTs is something that should be avoided
       as much as possible - TXT record is used as SMTP rejection string.
       Note that DNS UDP packet is limited to 512 bytes.  rbldnsd will log a
       warning when such truncation occurs.

       This manpage corresponds to rbldnsd version 0.998.

       The rbldnsd daemon written by Michael Tokarev <mjt+rbldnsd@corpit.ru>,
       based on ideas by Dan Bernstein and his djbdns package, with excellent
       contributions by Geoffrey T. Dairiki <dairiki@dairiki.org>.

       Mostly GPL, with some code licensed under 3-clause BSD license.

                                   Dec 2015                         rbldnsd(8)