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 recognized:

$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 files.

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 ignored.

$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 field.

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 information.

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 127.0.0.0/24:

  127.0.0.0/24


  127.0.0


  127/24


  127-127.0.0


  127.0.0.0-127.0.0.255


  127.0.0.1-255

to specify 127.16.0.0-127.31.255.255:

  127.16.0.0-127.31.255.255


  127.16.0-127.31.255


  127.16-127.31


  127.16-31


  127.16.0.0/12


  127.16.0/12


  127.16/12

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 127.16.0.0-127.16.31.255, i.e. 127.16.0.0/19).

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 (:127.0.0.2:This 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

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 127.0.0.2 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 ip4set.

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


  :127.0.1.2: Listed, see http://example.com/lookup?$


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


  2001:21ab:c000/36


  # /64 range with non-default A and TXT values


  2001:21ab:def7:4242 :127.0.1.3: This one smells funny


  # compressed notation


  2605:6001:42::/52


  ::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:

  2001:20fe:23:41ed


  abac:adab:ad00:42f

  !abac:adab:ad00:42f:face:0f:a:beef


  !abac:adab:ad00:42f::2

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:

example.com

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

*.example.com

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

.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 127.0.0.1


 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/$


  127.0.0.2


  127.0.0.10


  # list of open relays,


  # in `relays' subzone and in base zone


  $DATASET ip4set:relay relays @


  :3:Open relay, see http://bl.ex.com/relay/$


  127.0.0.2


  127.0.2.10


  # 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/$


  127.0.0.2


  127.0.9.12


  # for the base zone and all subzones,


  # include several additional records


  $DATASET generic:common proxies relays multihop @


  @ A 127.0.0.8


  www A 127.0.0.8


  @ 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 127.0.0.8


  #  www.proxies.bl.ex.com 127.0.0.8


  #  relays.bl.ex.com A 127.0.0.8


  #  www.relays.bl.ex.com 127.0.0.8


  #  multihop.bl.ex.com A 127.0.0.8


  #  www.multihop.bl.ex.com 127.0.0.8


  #  bl.ex.com A 127.0.0.8


  #  www.bl.ex.com 127.0.0.8

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 (sub-)dataset.

Resulting A values and TXT templates

In all zone file types except generic, A values and TXT templates are specified as following:

  :127.0.0.2:Blacklisted: 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:

  127.0.0.2 :127.0.0.2:Blacklisted: http://example.com/bl?$

or, without specific A value:

  127.0.0.2 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 127.0.0.2 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?$

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 example:

  # default A value and TXT template


  :127.0.0.2:IP address $ is listed


  # 127.0.0.4 will use default A and TXT


  127.0.0.4


  # 127.0.0.5 will use specific A and default TXT


  127.0.0.5 :5


  # 127.0.0.6 will use specific a and no TXT


  127.0.0.6 :6:


  # 127.0.0.7 will use default A and specific TXT


  127.0.0.7 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


  127.0.0.2  $1/spammer/$ $2


  127.0.0.3  $1/relay/$ $2


  127.0.0.4  This spammer wants some $$$$.  $1/$

  See http://www.example.com/bl/spammer/127.0.0.2 for details


  See http://www.example.com/bl/relay/127.0.0.3 for details


  This spammer wants some $$.  See http://www.example.com/bl/127.0.0.4

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


  127.0.0.2	r123


  127.0.0.3


  127.0.0.4	=See other blocklists for details about $

  See http://www.example.com/bl?r123 (127.0.0.2) for details


  See http://www.example.com/bl?127.0.0.3 (127.0.0.3) for details


  See other blocklists for details about 127.0.0.4

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 are:

:ignore

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

:refuse

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.

a_txt_template

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...

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.

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.

Right:

  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 \


   bl.ex.com:ip4set:dialups,spammers

or:

 rbldnsd options... \


   dialups.bl.ex.com:ip4set:dialups \


   spam.bl.ex.com:ip4set:spammers \


   bl.ex.com:ip4set:dialups \


   bl.ex.com:ip4set:spammers

(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 form

  proxies      TXT list of open proxies


  www.proxies  A 127.0.0.8


  relays       TXT list of open relays


  www.relays   A 127.0.0.9