.\" $Id: rbldnsd.8,v 1.61 2004/07/01 16:23:46 mjt Exp $
.\" rbldnsd manpage
.\"
.TH rbldnsd 8 "Jul 2004"
.SH NAME
rbldnsd \- DNS daemon suitable for running DNS\-based blocklists
.SH SYNOPSIS
.B rbldnsd
options
.IR zone : dataset ...

.SH DESCRIPTION
.PP
.B 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.

.PP
.B 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.

.PP
.B 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, \fBrbldnsd\fR is very
different from other general\-purpose nameservers such as BIND
or NSD: \fBrbldnsd\fR operates with \fIdatasets\fR (sets of
entries \- IP addresses or domain names, logically grouped
together), while other general\-purpose nameservers operates
with zones.  The way how \fBrbldnsd\fR operates may be somewhat
confusing to BIND experts.

.PP
For \fBrbldnsd\fR, 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, \fBrbldnsd\fR
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.

.PP
.B 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:
.IR   zone : type : file , file ,...

.PP
Several zones may be specified in command line, so that
.B 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).

.PP
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 3 categories:
.IP
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,
.B rbldnsd
will return A and TXT records specified in data for that IP.
This is a classical IP\-based blocklist.
.IP
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.
.IP
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.

.SH OPTIONS

.PP
The following options may be specified:

.IP "\fB\-u\fR \fIuser\fR[:\fIgroup\fR]"
\fBrbldnsd\fR will change its userid to the specified \fIuser\fR, which
defaults to \fBrbldns\fR, and \fIgroup\fR, which by default is the
primary group of a \fIuser\fR. \fBrbldnsd\fR will refuse to run as the root
user, since this is insecure.

.IP "\fB\-r\fR \fIrootdir\fR"
\fBrbldnsd\fR will chroot to \fIrootdir\fR if specified.  Data files
should be available inside \fIrootdir\fR.

.IP "\fB\-w\fR \fIworkdir\fR"
\fBrbldnsd\fR will change its working directory to \fIworkdir\fR
(after chrooting to \fIrootdir\fR if \fB\-r\fR option is also specified).
May be used to shorten filename paths.

.IP "\fB\-b\fR \fIaddress\fR/\fIport\fR"
This option is \fIrequired\fR.  \fBrbldnsd\fR will bind to specified
\fIaddress\fR and \fIport\fR (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 \fB\-b\fR option.  Additionally, if there are several addresses
listed for a hostname, \fBrbldnsd\fR will listen on all of them.
Note that \fBrbldnsd\fR 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.

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

.IP \fB\-6\fR
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).

.IP "\fB\-t\fR \fIdefttl\fR:\fIminttl\fR:\fImaxttl\fR"
Set default reply time\-to\-live (TTL) value to be \fIdefttl\fR,
and set constraints for TTL to \fIminttl\fR and \fImaxttl\fR.  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. "\fB\-t\fR\ 30" set default TTL to be 30 secound, and "\fB\-t\fR\ ::120"
or "\fB\-t\fR\ ::2m" sets maximum allowed TTL to 2 minutes.
All 3 values are in time units, with optional suffix:
\fBs\fR (secounds, default), \fBm\fR (minutes), \fBh\fR (hours),
\fBd\fR (days) or \fBw\fR (weeks).  Zero \fIminttl\fR or \fRmaxttl\fR
means no corresponding constraint will be enforced.
Default \fIdefttl\fR is 35m.

.IP "\fB\-c\fR \fIcheck\fR"
Set interval between checking for zone file changes to be \fIcheck\fR,
default is 1m (one minute).  \fBrbldnsd\fR 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 \fBrbldnsd\fR (see SIGNALS section below).

.IP \fB\-e\fR
Allow non\-network addresses to be used in CIDR ranges.  Normally,
\fBrbldnsd\fR rejects addresses such as 127.2.3.4/24, where prefix
is not within the network mask derived from bit number (in this
case, correct form is 127.2.3.0/24, note the trailing zero in prefix).
This is done in order to catch possible typos in zones (\fBrbldnsd\fR
will warn about a problem and will ignore such entry).  This option
disables checking whether the CIDR prefix fits within the network mask.

.IP \fB\-q\fR
Quick and quiet start.  Normally,
.B 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 \fB\-n\fR option is also given), and zone load
errors will be non\-fatal.

.IP "\fB\-p\fR \fIpidfile\fR"
Write rbldnsd's pid to the specified \fIpidfile\fR, 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.

.IP "\fB\-l\fR \fIlogfile\fR"
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 (\fBrbldnsd\fR will log \fIevery\fR recognized
request if this option is specified).  This option is mainly intended for
debugging purposes.  Upon receiption of SIGHUP signal, \fBrbldnsd\fR
reopens its logfile.  If \fIlogfile\fR 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).

.IP "\fB\-s\fR \fIstatsfile\fR"
Specifies a file where \fBrbldnsd\fR will write a line with short statistic
summary of queries made per zone, every check (\fB\-c\fR) interval.
Format of each line is:
.nf
  \fItimestamp\fR \fIzone\fR:\fIqtot\fR:\fIqok\fR:\fIqnxd\fR:\fIbin\fR:\fIbout\fR \fIzone\fR:...
.fi
where
\fItimestamp\fR is unix time (secounds since epoch),
\fIzone\fR is the name of the base zone,
\fIqtot\fR is the total number of queries received,
\fIqok\fR \- number of positive replies,
\fIqnxd\fR \- number of NXDOMAIN replies,
\fIbin\fR is the total number of bytes read from network
(excluding IP/UDP overhead and dropped packets),
\fIbout\fR 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 \fIzone\fR being "*", like:
.nf
  1234 bl1.ex:10:5:4:311:432 bl2.ex:24:13:7:248:375 *:98:35:12:820:987
.fi
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.

\fBRbldnsd\fR will write bare timestamp to \fIstatsfile\fR 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, \fBrbldnsd\fR writes absolute counter values into
\fIstatsfile\fR (number of packets (bytes) since startup or
last reset).  \fIstatsfile\fR may be prefixed with plus sign (+),
in which case \fBrbldnsd\fR 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).

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

.IP \fB\-f\fR
Request \fBrbldnsd\fR to continue processing requests during data reloads.
\fBRbldnsd\fR 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.

.IP \fB\-d\fR
Dump all zones to stdout in BIND format and exit.  This may be suitable
to convert easily editable rbldnsd-style data into BIND zone.  \fBrbldnsd\fR
dumps all zones as one stream, so one may want to specify only one zone
with \fB\-d\fR.  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 \fBrbldnsd\fR (e.g., IP netblocks of large size will be
represented as wildcard entries \- 10.0.0.0/8 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, \fBrbldnsd\fR ignores
\fB\-r\fR (root directory) option.

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

.SH "DATASET TYPES AND FORMATS"

.PP
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".

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

.PP
.B rbldnsd
is designed to service a DNSBL, where each entry have single
A record and optional TXT record assotiated with it.
.B rbldnsd
allows to specify A value and TXT \fItemplate\fR 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.

.SS "Special Entries"
.PP
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 \fBrbldnsd\fR and
for DJB's rbldns). The following keywords, following a dollar sign,
are recognized:

.IP "\fB$SOA\fR \fIttl 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, \fBrbldnsd\fR 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 \fIfirst\fR 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 $SOA found in 3rd party data by \fIprepending\fR
small local file to the dataset in question, listing it before any other
files.
.IP
If \fIserial\fR value specified is zero, timestamp of most recent
modified file will be substituted as \fIserial\fR.
.IP
If \fIttl\fR field is zero, default ttl (\fB\-t\fR option or last \fB$TTL\fR
value, see below) will be used.
.IP
All time fields (ttl, refresh, retry, expire, minttl) may be specified
in time units.  See \fB\-t\fR option for details.

.IP "\fB$NS\fR \fIttl\fR \fInameserverdn\fR \fInameserverdn\fI..."
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 20 namservers are recognized.
Individual nameserver(s) may be prefixed with a minus sign (\-), which
means this single nameserver will be ignored by \fBrbldnsd\fR.  This
is useful to temporary comment out one nameserver entry without removing
it from the list.  If \fIttl\fR is zero, default ttl will be used.
The list of NS records, just like $SOA value, are taken from the \fIfirst\fR
data file in a dataset where the $NS line is found, subsequent $NS lines,
if any, are ignored.

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

.IP "\fB$MAXRANGE4\fR \fIrange-size\fR"
Specifies maximum size of IPv4 range allowed for IPv4\-based datasets.
If an entry covers more IP addresses than \fIrange-size\fR, it will
be ignored (and a warning will be logged).  \fIrange-size\fR may be
specified as a number of hosts, like 256, or as network prefix lenght,
like /24 (the two are the same):
.nf
  $MAXRANGE4 /24
  $MAXRANGE4 256
.fi
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.

.IP "\fB$\fIn\fR \fItext\fR"
(\fIn\fR is a single digit).
Specifies a \fIsubstitution variable\fR for use as $\fIn\fR placeholders
(the \fB$\fIn\fR entries are ignored in generic daaset).
See section "Resulting A values and TXT templates" below for description
and usage examples.

.SS "ip4set Dataset"
.PP
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:
.nf
  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
.fi
to specify 127.16.0.0\-127.31.255.255:
.nf
  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
.fi
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 \fIspecified\fR 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).
.PP
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.
.PP
IP address range may be followed by a comment char (either hash character (#)
or semicolon (;)), e.g.:
.nf
  127/8 ; loopback network
.fi
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.
.PP
Every IP address that fits within any of specified ranges is "listed", and
.B 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
.I 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.
.PP
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, \fBrbldnsd\fR 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.

.SS "ip4trie Dataset"
.PP
Set of IP4 CIDR ranges with corresponding (A, TXT) values.  Similar to
ip4set, but uses different internal representation (implemented as a
patricia trie), accepts CIDR ranges only (not a.b.c.d\-e.f.g.h), allows
to specify only one value per CIDR range, and returns only one, most
close matching, entry on queries.  Exclusions are supported too.  This
dataset is not memory-efficient to store many single IP addresses, but
it is ok to use it to store many possible wide CIDR ranges.

.SS "ip4tset Dataset"
.PP
"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 \fBip4set\fR.

.SS "dnset Dataset"
.PP
Set of (possible wildcarded) domain names with associated A and TXT values.
Similar to \fBip4set\fR, but instead of IP addresses, data consists of
domain names (\fInot\fR 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.
.PP
Wildcards are interpreted as follows:
.IP example.com
only example.com domain is listed, not subdomains thereof.  Not a wildcard
entry.
.IP *.example.com
all subdomains of example.com are listed, but not example.com itself.
.IP .example.com
all subdomains of example.com \fIand\fR 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).
.PP
This dataset type may be used instead of \fBip4set\fR,
provided all CIDR ranges are expanded and reversed (but in
this case, TXT template will be expanded differently).

.SS "generic Dataset"
.PP
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:
.IP
.nf
 # 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"
.fi

.SS "combined Dataset"
.PP
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
.nf
  $DATASET \fItype\fR[:\fIname\fR] \fIsubzone\fR \fIsubzone\fR...
.fi
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 \fItype\fR,
with optional \fIname\fR (name is used for logging purposes only,
and the whole ":\fIname\fR" (without quotes or square brackets)
part is optional).  Note that combined datasets cannot be nested.
Every \fIsubzone\fR will always be relative to the base zone name
specified on command line.  If \fIsubzone\fR specified as single
character "@", dataset will be connected to the base zone itself.
.PP
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.
.PP
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:
.nf
  # 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
.fi
.PP
Note that $NS and $SOA values applies to the base zone \fIonly\fR,
regardless of the placement in the file.  Unlike the $TTL values and
$\fIn\fR substitutions, which may be both global and local for a
given (sub\-)dataset.

.SS "Resulting A values and TXT templates"
.PP
In all zone file types except generic, A values and TXT templates are
specified as following:
.nf
  :127.0.0.2:Blacklisted: http://example.com/bl?$
.fi
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:
.nf
  127.0.0.2 :127.0.0.2:Blacklisted: http://example.com/bl?$
.fi
or, without specific A value:
.nf
  127.0.0.2 Blacklisted: http://example.com/bl?$
.fi

.PP
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), \fBrbldnsd\fR 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:
.nf
  :2:Blacklisted: http://example.com/bl?$
.fi
There is no default TXT value, so
.B rbldnsd
will not return anything for TXT queries it TXT isn't
specified.
.PP
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:
.PP
.nf
  # 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 \fIno\fR 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
.fi
.PP
In a TXT template, some references to substitution variables are
replaced with values of that variables.  In particular,
single dollar sign ($) is replaced by a listed entry (an IP address
in question for IP\-based datasets and the domain name for domain\-based
datasets).  \fB$\fIn\fR\-style constructs, where \fIn\fR is a single
digit, are replaced by a substitution variable $\fIn\fR defined for
this dataset in current scope (see section "Special Entries" above).
To specify a dollar sign as\-is, use \fB$$\fR.
.PP
For example, the following lines:
.nf
  $1 See http://www.example.com/bl
  $2 for details
  127.0.0.2  $1/spammer/$ $2
  127.0.0.3  $1/relay/$ $2
  127.0.0.4  This spammer wants some $$$$.  $1/$
.fi
will result in the following text to be generated:
.nf
  See http://www.example.com/bl/spammer/127.0.0.2 for details
  See http://www.example.com/bl/relay/127.0.0.3 for details
  This spammer wants some $$.  See http://www.example.com/bl/127.0.0.4
.fi

.SH SIGNALS

.B Rbldnsd
handles the following signals:

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

.IP "\fBSIGTERM\fR, \fBSIGINT\fR"
Terminate process.

.IP \fBSIGUSR1\fR
Log current statistic counters into syslog.
.B 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.

.IP \fBSIGUSR2\fR
The same as SIGUSR1, but reset all counters and start new sample
period.

.SH NOTES

.PP
Some unsorted usage notes follows.

.SS "Generating and transferring data files"
.PP
When creating a data file for \fBrbldnsd\fR (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.  \fINever\fR try to write to the main file directly,
it is possible that at the same time, \fBrbldnsd\fR will try
to read it and will get incomplete data as the result.  The
same applies to copying data using \fBcp\fR(1) utility and
similar (including \fBscp\fR(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.
.PP
Right:
.nf
  scp remote:data target.tmp && mv target.tmp target
.fi
\fIWrong\fR:
.nf
  scp remote:data target
.fi
Right:
.nf
  ./generate.pl > target.tmp && mv target.tmp target
.fi
\fIWrong\fR:
.nf
  ./generate.pl > target
.fi
.PP
From this point of view, \fBrsync\fR(1) command seems
to be safe, as it \fIalways\fR 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, \fBscp\fR(1) command is
\fInot\fR safe, as it performs direct copying.  You
may still use \fBscp\fR(1) in a safe manner, as shown
in the example above.

.PP
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.

.SS "Absolute vs relative domain names"

.PP
All \fIkeys\fR specified in dataset files are always relative
to the zone base DN.  In contrast, all the \fIvalues\fR (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 \fBrbldnsd\fR.

.SS "Aggregating datasets"
.PP
Several zones may be served by \fBrbldnsd\fR,
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 \fBrbldnsd\fR:
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:
.PP
.nf
 rbldnsd \fIoptions...\fR \\
   dialups.bl.ex.com:ip4set:dialups \\
   spam.bl.ex.com:ip4set:spammers \\
   bl.ex.com:ip4set:dialups,spammers
.fi
.PP
or:
.PP
.nf
 rbldnsd \fIoptions...\fR \\
   dialups.bl.ex.com:ip4set:dialups \\
   spam.bl.ex.com:ip4set:spammers \\
   bl.ex.com:ip4set:dialups \\
   bl.ex.com:ip4set:spammers
.fi
.PP
(note you should specify combined bl.ex.com zone
.I after
all its subzones in a command line, or else subzones
will not be consulted at all).
.PP
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 \fBrbldnsd\fR 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).
.PP
Similar effect may be achieved by using \fBcombined\fR
dataset type, sometimes more easily.  \fBcombined\fR
dataset results in every nested dataset to be used
independantly, like in second form above.

.PP
\fBcombined\fR dataset requires \fBrbldnsd\fR to be the
authoritative nameserver for the whole base zone.  Most
important, one may specify SOA and NS records for the
base zone \fIonly\fR.  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), \fBcombined\fR dataset isn't necessary.  In contrast,
SORBS.net zones, where several subzones used and main zone is
a combination of several subzones, \fBcombined\fR dataset is a
way to go.

.SS "All authoritative nameservers should be set up similarily"
.PP
When you have several nameservers for your zone, set them
all in a similar way.  Namely, if one is set up using \fBcombined\fR
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 \fBcombined\fR and other datasets will have
different origin.  With \fRcombined\fR dataset, \fBrbldnsd\fR
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 \fBcombined\fR
dataset.  In this case, for queries against dialups.bl.ex.com, first
nameserver will return NS records like
.nf
  dialups.bl.ex.com. IN NS a.ns.ex.com.
.fi
while second will always use base zone, and NS records will
look like
.nf
  bl.ex.com. IN NS a.ns.ex.com.
.fi
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.

.SS "Generic dataset usage"
.PP
.B 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.

.PP
Since \fBrbldnsd\fR only searches \fIone\fR, most closely matching
(sub)zone for every request, one cannot specify a single e.g.
\fBgeneric\fR dataset in form
.nf
  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
.fi
for several (sub)zones, each of which are represented as a zone
too (either in command line or as \fBcombined\fR dataset).
Instead, several \fBgeneric\fR 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 \fBcombined\fR
dataset usage example above).

.SS "NS records belongs to separate zone"
.PP
.B Rbldnsd
does not insert A records for nameservers into the ADDITIONAL
section in replies, so NS records \fIshould not\fR point to the
zone served by \fBrbldnsd\fR, or else you will have chicken\-and\-eggs
problem and your zone will be broken from the DNS point of view.
In order to work around this problem, set up nameservers inside
another domain/zone that isn't handled by \fBrbldnsd\fR (and thus
\fBrbldnsd\fR is not authoritative for that zone), i.e. instead of
using quite natural ns0.bl.ex.com NS for bl.ex.com zone, use n0-bl.ex.com
or ns0.blns.ex.com (inside parent zone, not controlled by \fBrbldnsd\fR).
Since the parent zone is accessed much less frequently than the DNSBL
zone itself, it usually requires less nameservers.

.SH BUGS

.PP
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.
.B rbldnsd
matches BIND runtime behaviour where appropriate, but not
always.

.PP
.B 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.

.PP
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.
.B rbldnsd
isn't a full\-featured nameserver, after all.

.PP
.B 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.

.PP
Also, \fBrbldnsd\fR does not add A records for nameservers into
the ADDITIONAL section in replies.  See NOTES section above for
more details.

.PP
.B 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
.B 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
.B rbldnsd
will be able to act as master for BIND nameservers, but not
as secondary), but the note remains: use rsync.

.PP
.B 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.
.B rbldnsd
will log a warning when such truncation occurs.

.SH VERSION

This manpage corresponds to \fBrbldnsd\fR version \fB0.993\fR.

.SH AUTHOR

The \fBrbldnsd\fR daemon written by Michael Tokarev <mjt@corpit.ru>,
based on ideas by Dan Bernstein and his djbdns package.

.SH LICENCE
GPL.