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.TH dsc.conf 5 "@PACKAGE_VERSION@" "DNS Statistics Collector"
.SH NAME
dsc.conf \- Configuration for the DNS Statistics Collector
.SH DESCRIPTION
The file
.I dsc.conf
contains defaults for the program
.B dsc(1) .
Each line is a configuration option and may have arguments in the form
.IR "option value;" .
Comment lines must have a hash sign (#) in the first column.

Since
.B dsc(1)
version 2.2.0, a configuration line may not be divided with CR/LF and
quoted characters are not understood (\\quote).
.SH CONFIGURATION
.TP
\fBlocal_address\fR IP [ MASK / BITS ] ;
Specifies the DNS server's local IP address with an optional mask/bits
for local networks.
It is used to determine the direction of an IP packet: sending, receiving,
or other.
You may specify multiple local addresses by repeating the
\fBlocal_address\fR line any number of times.
.TP
\fBrun_dir\fR PATH ;
A directory that will become
.I dsc
current directory after it starts.
Output files will be written here, as will any core dumps.
.TP
\fBminfree_bytes\fR BYTES ;
If the filesystem where
.I dsc
writes its output files does not have at least this much free space, then
.I dsc
will not write the files.
This prevents
.I dsc
from filling up the filesystem.
The files that would have been written are simply lost and cannot be
recovered.
Output files will be written again when the filesystem has the necessary
free space.
.TP
\fBpid_file\fR " FILE " ;
The file where
.I dsc
will store its process id.
.TP
\fBbpf_program\fR " RULE " ;
A Berkeley Packet Filter program string.
You may use this to further restrict the traffic seen but note that
.I dsc
currently has one indexer that looks at all IP packets.
If you specify something like \fBudp port 53\fR that indexer will not work.

However, if you want to monitor multiple DNS servers with separate
.I dsc
instances on one collector box, then you may need to use
\fBbpf_program\fR to make sure that each
.I dsc
process sees only the traffic it should see.

Note that this directive must go before the \fBinterface\fR directive
because
.I dsc
makes only one pass through the configuration file and the BPF filter
is set when the interface is initialized.
.TP
\fBdns_port\fR NUMBER ;
.I dsc
will only parse traffic coming to or leaving the DNS port (default 53),
this option lets you control which port that is in case it's not standard.
.TP
\fBpcap_buffer_size\fR NUMBER ;
Set the buffer size (in bytes) for pcap, increasing this may help
if you see dropped packets by the kernel but increasing it too much
may have other side effects.

Note that this directive must go before the \fBinterface\fR
directive because
.I dsc
makes only one pass through the configuration file and the pcap buffer
size is set when the interface is initialized.
.TP
\fBpcap_thread_timeout\fR MILLISECONDS ;
Set the internal timeout pcap-thread uses when waiting for packets, the
default is 100 ms.

Note that this directive must go before the \fBinterface\fR directive.
.TP
\fBdrop_ip_fragments\fR ;
Drop all packets that are fragments.

Note that this directive must go before the \fBinterface\fR directive.
.TP
\fBinterface\fR IFACE | FILE ;
The interface name to sniff packets from or a pcap file to read packets
from.
You may specify multiple interfaces by repeating the \fBinterface\fR line
any number of times.

Under Linux (kernel v2.2+) libpcap can use an "any" interface which
will include any interfaces the host has but these interfaces will
not be put into promiscuous mode which may prevent capturing traffic
that is not directly related to the host.
.TP
\fBdnstap_file\fR FILE ;
.TQ
\fBdnstap_unixsock\fR FILE [ USER ][ :GROUP ] [ UMASK ] ;
.TQ
\fBdnstap_tcp\fR IP PORT ;
.TQ
\fBdnstap_udp\fR IP PORT ;
Specify DNSTAP input from a file, UNIX socket, UDP or TCP connections (dsc
will listen for incoming connections).
This type of input is delivered directly from the DNS software itself
as encapsulated DNS packets as seen or as made by the software.
See
.UR https://dnstap.info
https://dnstap.info
.UE
for more information about DNSTAP.

For UNIX sockets there are additional optional options to control access
to it.
The user and group access are specified together as strings (USER:GROUP),
separated with a colon if a group is specified.
The file permissions are controlled by a file mode creation mask (UMASK,
must being with 0) which is set temporarily during socket creation.
It is not necessary to specify all options, you can specify only USER,
only :GROUP or only UMASK.

Example below shows how to give read and write access to somegroup,
remove permissions for others and how the resulting socket file permissions
would be:

.EX
  dnstap_unixsock /path/to/file.sock :somegroup 0007;

  srwxrwx--- 1 root somegroup    0 Date dd HH:MM /path/to/file.sock
.EE

NOTE:
.RS
.IP -
Only one DNSTAP input can be specified at a time currently.
.IP -
Configuration needs to match that of the DNS software.
.RE
.TP
\fBdnstap_network\fR IPV4 IPV6 PORT ;
Specify DNSTAP network information.

Per DNSTAP specification, some information may be not included such as
receiver or sender of DNS.
To be able to produce statistics,
.I dsc
needs to know what to put in place when that information is missing.
This is configured by
.I dnstap_network
and should be the primary IP addresses and port of the DNS software.

Default values are
.BR "127.0.0.1 ::1 53" .
.TP
\fBqname_filter\fR NAME FILTER ;
This directive allows you to define custom filters to match query names
in DNS messages.
Please see section QNAME FILTERS for more information.
.TP
\fBdatasets\fR NAME TYPE LABEL:FIRST LABEL:SECOND FILTERS [ PARAMETERS ] ;
This directive is the heart of \fBdsc\fR.
However, it is also the most complex (see section DATASETS).

See section EXAMPLE for a set of defined good datasets which is also
installed as \fBdsc.conf.sample\fR.
.TP
\fBbpf_vlan_tag_byte_order\fR TYPE ;
.I dsc
knows about VLAN tags.
Some operating systems (FreeBSD-4.x) have a bug whereby the VLAN tag id
is byte-swapped.
Valid values for this directive are \fBhost\fR and \fBnet\fR (the default).
Set this to \fBhost\fR if you suspect your operating system has the VLAN
tag byte order bug.
.TP
\fBmatch_vlan\fR ID [ ID ... ] ;
A white-space separated list of VLAN identifiers.
If set, only the packets belonging to these VLANs are analyzed.
.TP
\fBstatistics_interval\fR SECONDS ;
Specify how often \fBdsc\fR should write statistics, default to 60 seconds.
.TP
\fBno_wait_interval\fR ;
Do not wait on interval sync to start capturing, normally DSC will
sleep for time() % statistics_interval to align with the minute
(as was the default interval before) but now if you change the interval
to more then a minute you can use with option to begin capture right
away.
.TP
\fBoutput_format\fR FORMAT ;
Specify the output format.
You may specify multiple formats by repeating the \fBoutput_format\fR line
any number of times.
Default output format is XML, see section DATA FORMATS and FILE NAMING
CONVENTIONS.
.TP
\fBoutput_user\fR USER ;
Specify which user should own the output file, default to the user running
.IR dsc .
.TP
\fBoutput_group\fR GROUP ;
Specify which group should own the output file, default to the group of the
user running
.IR dsc .
.TP
\fBoutput_mod\fR FILE_MODE_BITS ;
Specify the file mode bits (in octal) for the output file permissions,
default to 0664.
.TP
\fBdump_reports_on_exit\fR ;
Dump any remaining report before exiting.

NOTE: Timing in the data files will be off!
.TP
\fBgeoip_v4_dat\fR " FILE " [ OPTION ... ] ;
Specify the GeoIP dat file to open for IPv4 country lookup, see section
GEOIP for options.
.TP
\fBgeoip_v6_dat\fR " FILE " [ OPTION ... ] ;
Specify the GeoIP dat file to open for IPv6 country lookup, see section
GEOIP for options.
.TP
\fBgeoip_asn_v4_dat\fR " FILE " [ OPTION ... ] ;
Specify the GeoIP dat file to open for IPv4 AS number lookup, see section
GEOIP for options.
.TP
\fBgeoip_asn_v6_dat\fR " FILE " [ OPTION ... ] ;
Specify the GeoIP dat file to open for IPv6 AS number lookup, see section
GEOIP for options.
.TP
\fBasn_indexer_backend\fR BACKEND ;
Specify what backend to use for the ASN indexer, either "geoip" for GeoIP
Legacy or "maxminddb" for MaxMind DB (GeoIP2).
.TP
\fBcountry_indexer_backend\fR BACKEND ;
Specify what backend to use for the country indexer, either "geoip" for GeoIP
Legacy or "maxminddb" for MaxMind DB (GeoIP2).
.TP
\fBmaxminddb_asn\fR " FILE " ;
Specify the MaxMind DB file to use for ASN lookups.
.TP
\fBmaxminddb_country\fR " FILE " ;
Specify the MaxMind DB file to use for country lookups.
.TP
\fBclient_v4_mask\fR NETMASK ;
Set the IPv4 MASK for client_subnet INDEXERS.
.TP
\fBclient_v6_mask\fR NETMASK ;
Set the IPv6 MASK for client_subnet INDEXERS.
.TP
\fBresponse_time_mode\fR MODE ;
Set the output MODE of the response time indexer:
.RS
.TP
\fBbucket\fR
Count response time in buckets of microseconds, see \fBresponse_time_bucket_size\fR
for setting the size of the buckets.
.TP
\fBlog10\fR
Count response time in logarithmic scale with base 10.
.TP
\fBlog2\fR
Count response time in logarithmic scale with base 2.
.RE
.TP
\fBresponse_time_max_queries\fR NUMBER ;
Set the maximum number of queries to keep track of.
.TP
\fBresponse_time_full_mode\fR MODE ;
If the number of queries tracked exceeds \fBresponse_time_max_queries\fR the
MODE will control how to handle it:
.RS
.TP
\fBdrop_query\fR
Drop the incoming query.
.TP
\fBdrop_oldest\fR
Drop the oldest query being tracked and accept the incoming one.
.RE
.TP
\fBresponse_time_max_seconds\fR SECONDS ;
Set the maximum seconds to keep a query but a query can still be matched to
a response while being outside this limit, see \fBresponse_time_max_sec_mode\fR
on how to handle those situations.
.TP
\fBresponse_time_max_sec_mode\fR MODE ;
Control how to handle queries and responses which are match successfully but
exceeds \fBresponse_time_max_seconds\fR:
.RS
.TP
\fBceil\fR
The query will be counted as successful but the time it took will be the
maximum seconds (think ceiling, or ceil()).
.TP
\fBtimed_out\fR
The query will be counted as timed out.
.RE
.TP
\fBresponse_time_bucket_size\fR SIZE ;
Control the size of bucket (microseconds) in bucket mode.
.TP
\fBknowntlds_file\fR FILE ;
Load known TLDs from FILE, this should be or have the same format as
.IR https://data.iana.org/TLD/tlds-alpha-by-domain.txt .
.TP
\fBtld_list\fR FILE ;
This option changes what DSC considers a TLD (similar to Public Suffix List)
and affects any indexers that gathers statistics on TLDs, such as the
.IR tld ,
.I second_ld
and
.I third_ld
indexers.
The file format is simply one line per suffix and supports commenting out
lines with
.BR # .
You can use
.B dsc-psl-convert
to convert the Public Suffix List to this format, see
.IR dsc-psl-convert (5)
for more information and examples on how to setup.
.SH DATASETS
A \fBdataset\fR is a 2-D array of counters.
For example, you might have a dataset with \*(lqQuery Type\*(rq along one
dimension and \*(lqQuery Name Length\*(rq on the other.
The result is a table that shows the distribution of query name lengths
for each query type.

A dataset has the following format:

\fBdatasets\fR NAME TYPE LABEL:FIRST LABEL:SECOND FILTERS [ PARAMETERS ] ;

.TP
\fBNAME\fR
The name of the dataset, this must be unique and is used in the filename
for the output files.
.TP
\fBTYPE\fR
The protocol layer, available layers are:
.nf
    ip
    dns
.fi
.TP
\fBLABEL\fR
The label of the dimensions.
.TP
\fBFIRST\fR
The indexer for the first dimension, see INDEXERS sections.
.TP
\fBSECOND\fR
The indexer for the second dimension, see INDEXERS sections.
.TP
\fBFILTERS\fR
One or more filters, see FILTERS sections.
.TP
\fBPARAMETERS\fR
Zero or more parameters, see section PARAMETERS.
.LP
.SH "INDEXERS AND FILTERS"
An
.I indexer
is simply a function that transforms the attributes of an IP/DNS message
into an array index.
For some attributes the transformation is straightforward.
For example, the \*(lqQuery Type\*(rq indexer simply extracts the query
type value from a DNS message and uses this 16-bit value as the array index.

Other attributes are slightly more complicated.
For example, the \*(lqTLD\*(rq indexer extracts the TLD of the QNAME field
of a DNS message and maps it to an integer.
The indexer maintains a simple internal table of TLD-to-integer mappings.
The actual integer values are unimportant because the TLD strings, not the
integers, appear in the resulting data.

When you specify an indexer on a \fBdataset\fR line, you must provide both
the name of the indexer and a label.
The Label appears as an attribute in the output.

For example the following line:

.nf
    dataset the_dataset dns Foo:foo Bar:bar queries-only;
.fi

Would produce the following XML output:

.nf
    <array name="the_dataset" dimensions="2" start_time="1091663940" ...
      <dimension number="1" type="Foo"/>
      <dimension number="2" type="Bar"/>
      <data>
        <Foo val="1">
          <Bar val="0" count="4"/>
          ...
          <Bar val="100" count="41"/>
        </Foo>
        <Foo val="2">
          ...
        </Foo>
      </data>
    </array>
.fi
.SH "IP INDEXERS"
.I dsc
includes only minimal support for collecting IP-layer stats.
Mostly we are interested in finding out the mix of IP protocols received
by the DNS server.
It can also show us if/when the DNS server is the subject of
denial-of-service attack.
.TP
\fBip_direction\fR
One of three values: \fBsent\fR, \fBrecv\fR or \fBelse\fR.
Direction is determined based on the setting for \fBlocal_address\fR in
the configuration file.
.TP
\fBip_proto\fR
The IP protocol type, e.g.: \fBtcp\fR, \fBudp\fR or \fBicmp\fR.
Note that the \fBbpf_program\fR setting affects all traffic seen.
If the program contains the word \*(lqudp\*(rq then you won't see any
counts for non-UDP traffic.
.TP
\fBip_version\fR
The IP version number, e.g.: \fB4\fR or \fB6\fR.
Can be used to compare how much traffic comes in via IPv6 compared to IPv4.
.SH "IP FILTERS"
Currently there is only one IP protocol filter: \fBany\fR.
It includes all received packets.
.SH "DNS INDEXERS"
.TP
\fBcertain_qnames\fR
This indexer isolates the two most popular query names seen
by DNS root servers: \fIlocalhost\fR and \fI[a--m].root-servers.net\fR.
.TP
\fBclient_subnet\fR
Groups DNS messages together by the subnet of the client's IP address.
The subnet is masked by /24 for IPv4 and by /96 for IPv6.
We use this to make datasets with large, diverse client populations more
manageable and to provide a small amount of privacy and anonymization.
.TP
\fBclient\fR
The IP (v4 and v6) address of the DNS client.
.TP
\fBserver\fR
The IP (v4 and v6) address of the DNS server.
.TP
\fBcountry\fR
The country code of the IP (v4 and v6), see section GEOIP.
.TP
\fBasn\fR
The AS (autonomous system) number of the IP (v4 and v6), see section GEOIP.
.TP
\fBdo_bit\fR
This indexer has only two values: 0 or 1.
It indicates whether or not the \*(lqDO\*(rq bit is set in a DNS query.
According to RFC 2335: \fISetting the DO bit to one in a query indicates
to the server that the resolver is able to accept DNSSEC security RRs.\fR
.TP
\fBedns_version\fR
The EDNS version number, if any, in a DNS query.
EDNS Version 0 is documented in RFC 2671.
.TP
\fBedns_bufsiz\fR
The EDNS buffer size per 512 chunks (0-511, 512-1023 etc).
.TP
\fBedns_cookie\fR
Indicates whether or not a EDNS(0) Cookie (RFC7873) was present with "yes" or "no".
.TP
\fBedns_cookie_len\fR
The combined length of the EDNS(0) client and server cookies.
.TP
\fBedns_cookie_client\fR
The EDNS(0) Client Cookie bytes as a hexadecimal string.
.TP
\fBedns_cookie_server\fR
The EDNS(0) Server Cookie bytes as a hexadecimal string.
.TP
\fBedns_ecs\fR
Indicates whether or not a EDNS(0) Client Subnet (RFC7871) was present with "yes" or "no".
.TP
\fBedns_ecs_family\fR
The EDNS(0) Client Subnet address family.
.TP
\fBedns_ecs_source_prefix\fR
The EDNS(0) Client Subnet source prefix-length.
.TP
\fBedns_ecs_scope_prefix\fR
The EDNS(0) Client Subnet scope prefix-length.
.TP
\fBedns_ecs_address\fR
The EDNS(0) Client Subnet address bytes as a hexadecimal string.
.TP
\fBedns_ecs_subnet\fR
The EDNS(0) Client Subnet address as an IPv4/IPv6 textual address.
.TP
\fBedns_ede\fR
Indicates whether or not a EDNS(0) Extended DNS Errors (RFC8914) was present with "yes" or "no".
.TP
\fBedns_ede_code\fR
The EDNS(0) Extended DNS Errors code.
.TP
\fBedns_ede_textlen\fR
The length of the EDNS(0) Extended DNS Errors extra-text.
.TP
\fBedns_ede_text\fR
The EDNS(0) Extended DNS Errors extra-text.
.TP
\fBedns_nsid\fR
Indicates whether or not a EDNS(0) DNS Name Server Identifier (RFC5001) was present with "yes" or "no".
.TP
\fBedns_nsid_len\fR
The length of the EDNS(0) DNS Name Server Identifier (NSID).
.TP
\fBedns_nsid_data\fR
The EDNS(0) DNS Name Server Identifier (NSID) bytes as a hexadecimal string.
.TP
\fBedns_nsid_text\fR
The EDNS(0) DNS Name Server Identifier (NSID) as a string of printable characters.
Unprintable characters are replaced with ".".
.TP
\fBidn_qname\fR
This indexer has only two values: 0 or 1.
It returns 1 when the first QNAME in the DNS message question section
is an internationalized domain name (i.e., containing non-ASCII characters).
Such QNAMEs begin with the string \fIxn--\fR.
This convention is documented in RFC 3490.
.TP
\fBmsglen\fR
The overall length (size) of the DNS message.
.TP
\fBnull\fR
A \*(lqno-op\*(rq indexer that always returns the same value.
This can be used to effectively turn the 2-D table into a
1-D array.
.TP
\fBopcode\fR
The DNS message opcode is a four-bit field.
QUERY is the most common opcode.
Additional currently defined opcodes include: IQUERY, STATUS, NOTIFY,
and UPDATE.
.TP
\fBqclass\fR
The DNS message query class (QCLASS) is a 16-bit value.
IN is the most common query class.
Additional currently defined query class values include: CHAOS, HS, NONE,
and ANY.
.TP
\fBqname\fR
The full QNAME string from the first (and usually only) QNAME in the
question section of a DNS message.
.TP
\fBqnamelen\fR
The length of the first (and usually only) QNAME in a DNS message question
section.
Note this is the \*(lqexpanded\*(rq length if the message happens to take
advantage of DNS message \*(lqcompression\*(rq.
.TP
\fBlabel_count\fR
The number of labels (between "." dots) in the first (and usually only)
QNAME in a DNS message question section.
Note that a value of 0 (zero) means DNS root (.).
.TP
\fBqtype\fR
The query type (QTYPE) for the first QNAME in the DNS message question
section.
Well-known query types include: A, AAAA, A6, CNAME, PTR, MX, NS, SOA,
and ANY.
.TP
\fBquery_classification\fR
A stateless classification of \*(lqbogus\*(rq queries:
.RS
.TP
non-auth-tld
When the TLD is not one of the IANA-approved TLDs.
.TP
root-servers.net
A query for a root server IP address.
.TP
localhost
A query for the localhost IP address.
.TP
a-for-root
An \*(lqA\*(rq query for the DNS root (.).
.TP
a-for-a
An \*(lqA\*(rq query for an IPv4 address.
.TP
rfc1918-ptr
A PTR query for an RFC 1918 address.
.TP
funny-class
A query with an unknown/undefined query class.
.TP
funny-qtype
A query with an unknown/undefined query type.
.TP
src-port-zero
When the UDP message's source port equals zero.
.TP
malformed
A malformed DNS message that could not be entirely parsed.
.RE
.TP
\fBrcode\fR
The RCODE value in a DNS response.
The most common response codes are 0 (NO ERROR) and 3 (NXDOMAIN).
.TP
\fBrd_bit\fR
This indexer returns 1 if the RD (recursion desired) bit is set in the
query.
Usually only stub resolvers set the RD bit.
Usually authoritative servers do not offer recursion to their clients.
.TP
\fBtc_bit\fR
This indexer returns 1 if the TC (truncated) bit is set (in a response).
An authoritative server sets the TC bit when the entire response won't
fit into a UDP message.
.TP
\fBtld\fR
The TLD of the first QNAME in a DNS message's question section.
.TP
\fBsecond_ld\fR
The Second LD of the first QNAME in a DNS message's question section.
.TP
\fBthird_ld\fR
The Third LD of the first QNAME in a DNS message's question section.
.TP
\fBtransport\fR
Indicates whether the DNS message is carried via UDP or TCP.
.TP
\fBdns_ip_version\fR
The IP version number that carried the DNS message.
.TP
\fBdns_source_port\fR
The source port of the DNS message.
.TP
\fBdns_sport_range\fR
The source port of the DNS message per 1024 chunks (0-1023, 1024-2047 etc).
.TP
\fBqr_aa_bits\fR
The "qr_aa_bits" dataset may be useful when \fBdsc\fR is monitoring
an authoritative name server.
This dataset counts the number of DNS messages received with each
combination of QR,AA bits.
Normally the authoritative name server should *receive* only *queries*.
If the name server is the target of a DNS reflection attack, it will
probably receive DNS *responses* which have the QR bit set.
.TP
\fBresponse_time\fR
An indexer to track queries and return the response time in buckets along with
other state buckets for timeouts, missing queries (received a response but
have never seen the query), dropped queries (due to memory limitations) and
internal errors.
Queries are matched against responses by checking (in this order) the DNS ID,
the IP version and protocol, client IP, client port, server IP and last server
port.
There are a few configuration options to control how response time statistics
are gathered and handled, please see CONFIGURATION.
NOTE: Only one instance of this indexer can be used in a dataset, this is due
to the state to stores and the design of DSC.
.TP
\fBencryption\fR
Indicates whether the DNS message was carried over an encrypted connection
or not, and if so over which.
For example "unencrypted", "dot" (DNS-over-TLS), "doh" (DNS-over-HTTPS).
This information is only available via DNSTAP and if supported by the
software generating it.
.SH "DNS FILTERS"
You must specify one or more of the following filters (separated by commas)
on the \fBdataset\fR line.
Note that multiple filters are \fIAND\fRed together.
That is, they narrow the input stream, rather than broaden it.
.TP
\fBany\fR
The no-op filter, counts all messages.
.TP
\fBqueries-only\fR
Count only DNS query messages.
A query is a DNS message where the QR bit is set to 0.
.TP
\fBreplies-only\fR
Count only DNS response messages.
A response is a DNS message where the QR bit is set to 1.
.TP
\fBnxdomains-only\fR
Count only NXDOMAIN responses.
.TP
\fBpopular-qtypes\fR
Count only DNS messages where the query type is one of: A, NS, CNAME, SOA,
PTR, MX, AAAA, A6, ANY.
.TP
\fBidn-only\fR
Count only DNS messages where the query name is in the internationalized
domain name format.
.TP
\fBaaaa-or-a6-only\fR
Count only DNS messages where the query type is AAAA or A6.
.TP
\fBroot-servers-net-only\fR
Count only DNS messages where the query name is within the
\fIroot-servers.net\fR domain.
.TP
\fBchaos-class\fR
Counts only DNS messages where QCLASS is equal to CHAOS (3).
The CHAOS class is generally used for only the special \fIhostname.bind\fR
and \fIversion.bind\fR queries.
.TP
\fBpriming-query\fR
Count only DNS messages where the query type is NS and QNAME is \*(lq.\*(rq.
.TP
\fBservfail-only\fR
Count only SERVFAIL responses.
.TP
\fBauthentic-data-only\fR
Count only DNS messages with the AD bit is set.
.TP
\fBedns0-only\fR
Count only DNS messages with EDNS(0) options.
.TP
\fBedns0-cookie-only\fR
Count only DNS messages with EDNS(0) Cookie option.
.TP
\fBedns0-nsid-only\fR
Count only DNS messages with EDNS(0) DNS Name Server Identifier option.
.TP
\fBedns0-ede-only\fR
Count only DNS messages with EDNS(0) Extended DNS Errors option.
.TP
\fBedns0-ecs-only\fR
Count only DNS messages with EDNS(0) Client Subnet option.
.SH "QNAME FILTERS"
Defines a custom QNAME-based filter for DNS messages.
If you refer to this named filter on a dataset line, then only queries
or replies for matching QNAMEs will be counted.
The QNAME argument is a regular expression.
For example:

.nf
    qname_filter WWW-Only ^www\. ;
    dataset qtype dns All:null Qtype:qtype queries-only,WWW-Only ;
.fi
.SH PARAMETERS
.I dsc
currently supports the following optional parameters:
.TP
\fBmin-count\fR=NN
Cells with counts less than \fBNN\fR are not included in the output.
Instead, they are aggregated into the special values \fI-:SKIPPED:-\fR
and \fI-:SKIPPED_SUM:-\fR.
This helps reduce the size of datasets with a large number of small counts.
.TP
\fBmax-cells\fR=NN
A different, perhaps better, way of limiting the size of a dataset.
Instead of trying to determine an appropriate \fBmin-count\fR value in
advance, \fBmax-cells\fR allows you put a limit on the number of cells to
include for the second dataset dimension.
If the dataset has 9 possible first-dimension values, and you specify
a \fBmax-cell\fR count of 100, then the dataset will not have more than 900
total values.
The cell values are sorted and the top \fBmax-cell\fR values are output.
Values that fall below the limit are aggregated into the special
\fI-:SKIPPED:-\fR and \fI-:SKIPPED_SUM:-\fR entries.
.SH "FILE NAMING CONVENTIONS"
The filename is in the format:
.nf
    ${timestamp}.dscdata.${format}
.fi

For example:
.nf
    1154649660.dscdata.xml
.fi
.SH "DATA FORMATS"
.TP
\fBXML\fR
A dataset XML file has the following structure:
.RE

.nf
<array name="dataset-name" dimensions="2" start_time="unix-seconds"
        stop_time="unix-seconds">
  <dimension number="1" type="Label1"/>
  <dimension number="2" type="Label2"/>
  <data>
    <Label1 val="D1-V1">
      <Label2 val="D2-V1" count="N1"/>
      <Label2 val="D2-V2" count="N2"/>
      <Label2 val="D2-V3" count="N3"/>
    </Label1>
    <Label1 val="D1-V2">
      <Label2 val="D2-V1" count="N1"/>
      <Label2 val="D2-V2" count="N2"/>
      <Label2 val="D2-V3" count="N3"/>
    </Label1>
  </data>
</array>
.fi
.TP
\fBJSON\fR
A dataset JSON file has the following structure:
.RE

.nf
{
  "name": "dataset-name",
  "start_time": unix-seconds,
  "stop_time": unix-seconds,
  "dimensions": [ "Label1", "Label2" ],
  "data": [
    {
      "Label1": "D1-V1",
      "Label2": [
        { "val": "D2-V1", "count": N1 },
        { "val": "D2-V2", "count": N2 },
        { "val": "D2-V3", "count": N3 }
      ]
    },
    {
      "Label1": "D1-V2-base64",
      "base64": true,
      "Label2": [
        { "val": "D2-V1", "count": N1 },
        { "val": "D2-V2-base64", "base64": true, "count": N2 },
        { "val": "D2-V3", "count": N3 }
      ]
    }
  ]
}
.fi

\fBdataset-name\fR, \fBLabel1\fR, and \fBLabel2\fR come from the dataset
definition.

The \fBstart_time\fR and \fBstop_time\fR attributes are given in Unix
seconds.
They are normally 60-seconds apart.
.I dsc
usually starts a new measurement interval on 60 second boundaries.
That is:

.nf
    stop_time mod{60} == 0
.fi

The \fBLabel1\fR attributes (\fID1-V1\fR, \fID1-V2\fR) are values for the
first dimension indexer.
Similarly, the \fBLabel2\fR attributes (\fID2-V1\fR, \fID2-V2\fR \fID2-V3\fR)
are values for the second dimension indexer.
For some indexers these values are numeric, for others they are strings.
If the value contains certain non-printable characters, the string is
base64-encoded and the optional BASE64 attribute is set to 1/true.

There are two special \fBval\fRs that help keep large datasets down to a
reasonable size: \fI-:SKIPPED:-\fR and \fI-:SKIPPED_SUM:-\fR.
These may be present on datasets that use the \fImin-count\fR and
\fImax-cells\fR parameters (see section PARAMETERS).
\fI-:SKIPPED:-\fR is the number of cells that were not included in the
output.
\fI-:SKIPPED_SUM:-\fR, is the sum of the counts for all the skipped cells.

Note that \*(lqone-dimensional datasets\*(rq still use two dimensions in
the output.
The first dimension type and value will be \*(lqAll\*(rq as shown in the
example below:

.nf
    <array name="rcode" dimensions="2" start_time="1154649600"
            stop_time="1154649660">
      <dimension number="1" type="All"/>
      <dimension number="2" type="Rcode"/>
      <data>
        <All val="ALL">
          <Rcode val="0" count="70945"/>
          <Rcode val="3" count="50586"/>
          <Rcode val="4" count="121"/>
          <Rcode val="1" count="56"/>
          <Rcode val="5" count="44"/>
        </All>
      </data>
    </array>
.fi

The \fBcount\fR values are always integers.
If the count for a particular tuple is zero, it should not be included in
the output.

Note that the contents of the output do not indicate where it came from.
In particular, the server and node that it came from are not present.
.SH GEOIP
Country code and AS number lookup is available using MaxMind GeoIP Legacy
API if it was enabled during compilation.

Multiple options can be give to the database and are directly linked
to the options for \fIGeoIP_open()\fR but without the prefix of
\fBGEOIP_\fR, example:

.nf
    geoip_v4_dat "/usr/local/share/GeoIP/GeoIP.dat" STANDARD MEMORY_CACHE;
    geoip_asn_v6_dat "/usr/local/share/GeoIP/GeoIPASNumv6.dat" MEMORY_CACHE;
.fi

GeoIP documentation says:
.TP
\fBSTANDARD\fR
Read database from file system.
This uses the least memory.
.TP
\fBMEMORY_CACHE\fR
Load database into memory.
Provides faster performance but uses more memory.
.TP
\fBCHECK_CACHE\fR
Check for updated database.
If database has been updated, reload file handle and/or memory cache.
.TP
\fBINDEX_CACHE\fR
Cache only the the most frequently accessed index portion of the database,
resulting in faster lookups than GEOIP_STANDARD, but less memory usage
than GEOIP_MEMORY_CACHE.
This is useful for larger databases such as GeoIP Legacy Organization and
GeoIP Legacy City.
Note: for GeoIP Legacy Country, Region and Netspeed databases,
GEOIP_INDEX_CACHE is equivalent to GEOIP_MEMORY_CACHE.
.TP
\fBMMAP_CACHE\fR
Load database into mmap shared memory.
MMAP is not available for 32bit Windows.
.SH EXAMPLE
.nf
local_address 127.0.0.1;
local_address ::1;
#local_address 127.0.0.0 255.0.0.0;
#local_address 192.168.0.0 24;
#local_address 10.0.0.0 8;

run_dir "/var/lib/dsc";

minfree_bytes 5000000;

pid_file "/run/dsc.pid";

# Example filters
#
#bpf_program "udp port 53";
#bpf_program "tcp port 53 or udp port 53";

# Use this to see only DNS *queries*
#
#bpf_program "udp dst port 53 and udp[10:2] & 0x8000 = 0";

#dns_port 53;
#pcap_buffer_size 4194304;
#pcap_thread_timeout 100;
#drop_ip_fragments;
interface eth0;
#interface any;

#dnstap_file /path/to/file.dnstap;
#dnstap_unixsock /path/to/unix.sock;
#dnstap_tcp 127.0.0.1 5353;
#dnstap_udp 127.0.0.1 5353;
#dnstap_network 127.0.0.1 ::1 53;

dataset qtype dns All:null Qtype:qtype queries-only;
dataset rcode dns All:null Rcode:rcode replies-only;
dataset opcode dns All:null Opcode:opcode queries-only;
dataset rcode_vs_replylen dns Rcode:rcode ReplyLen:msglen replies-only;
dataset client_subnet dns All:null ClientSubnet:client_subnet queries-only max-cells=200;
dataset qtype_vs_qnamelen dns Qtype:qtype QnameLen:qnamelen queries-only;
dataset qtype_vs_tld dns Qtype:qtype TLD:tld queries-only,popular-qtypes max-cells=200;
dataset certain_qnames_vs_qtype dns CertainQnames:certain_qnames Qtype:qtype queries-only;
dataset client_subnet2 dns Class:query_classification ClientSubnet:client_subnet queries-only max-cells=200;
dataset client_addr_vs_rcode dns Rcode:rcode ClientAddr:client replies-only max-cells=50;
dataset chaos_types_and_names dns Qtype:qtype Qname:qname chaos-class,queries-only;
#dataset country_code dns All:null CountryCode:country queries-only;
#dataset asn_all dns IPVersion:dns_ip_version ASN:asn queries-only max-cells=200;
dataset idn_qname dns All:null IDNQname:idn_qname queries-only;
dataset edns_version dns All:null EDNSVersion:edns_version queries-only;
dataset edns_bufsiz dns All:null EDNSBufSiz:edns_bufsiz queries-only;
dataset do_bit dns All:null D0:do_bit queries-only;
dataset rd_bit dns All:null RD:rd_bit queries-only;
dataset idn_vs_tld dns All:null TLD:tld queries-only,idn-only;
dataset ipv6_rsn_abusers dns All:null ClientAddr:client queries-only,aaaa-or-a6-only,root-servers-net-only max-cells=50;
dataset transport_vs_qtype dns Transport:transport Qtype:qtype queries-only;
dataset client_port_range dns All:null PortRange:dns_sport_range queries-only;
#dataset second_ld_vs_rcode dns Rcode:rcode SecondLD:second_ld replies-only max-cells=50;
#dataset third_ld_vs_rcode dns Rcode:rcode ThirdLD:third_ld replies-only max-cells=50;
dataset direction_vs_ipproto ip Direction:ip_direction IPProto:ip_proto any;
#dataset dns_ip_version_vs_qtype dns IPVersion:dns_ip_version Qtype:qtype queries-only;
#dataset response_time dns All:null ResponseTime:response_time;
#dataset priming_queries dns Transport:transport EDNSBufSiz:edns_bufsiz priming-query,queries-only;
#dataset priming_responses dns All:null ReplyLen:msglen priming-query,replies-only;
#dataset qr_aa_bits dns Direction:ip_direction QRAABits:qr_aa_bits any;
#dataset servfail_qname dns ALL:null Qname:qname servfail-only,replies-only;
#dataset ad_qname dns ALL:null Qname:qname authentic-data-only,replies-only;
#dataset label_count dns All:null LabelCount:label_count any;
#dataset encryption dns All:null Encryption:encryption queries-only;

#statistics_interval 60;
#no_wait_interval;
output_format XML;
#output_format JSON;
#output_user root;
#output_group root;
#output_mod 0664;

#geoip_v4_dat "/usr/share/GeoIP/GeoIP.dat" STANDARD MEMORY_CACHE MMAP_CACHE;
#geoip_v6_dat "/usr/share/GeoIP/GeoIPv6.dat";
#geoip_asn_v4_dat "/usr/share/GeoIP/GeoIPASNum.dat" MEMORY_CACHE;
#geoip_asn_v6_dat "/usr/share/GeoIP/GeoIPASNumv6.dat" MEMORY_CACHE;

#asn_indexer_backend geoip;
#country_indexer_backend geoip;
#maxminddb_asn "/path/to/GeoLite2/ASN.mmdb";
#maxminddb_country "/path/to/GeoLite2/Country.mmdb";

#client_v4_mask 255.255.255.0;
#client_v6_mask ffff:ffff:ffff:ffff:ffff:ffff:0000:0000;

#response_time_mode log10;
#response_time_max_queries 1000000;
#response_time_full_mode drop_query;
#response_time_max_seconds 5;
#response_time_max_sec_mode ceil;
#response_time_bucket_size 100;

#knowntlds_file file;
.fi
.SH FILES
@etcdir@/dsc.conf
.br
@etcdir@/dsc.conf.sample
.SH "SEE ALSO"
dsc(1), dsc-psl-convert(1)
.SH AUTHORS
Jerry Lundström, DNS-OARC
.br
Duane Wessels, Measurement Factory / Verisign
.br
Ken Keys, Cooperative Association for Internet Data Analysis
.br
Sebastian Castro, New Zealand Registry Services
.LP
Maintained by DNS-OARC
.LP
.RS
.I https://www.dns-oarc.net/tools/dsc
.RE
.LP
.SH BUGS
For issues and feature requests please use:
.LP
.RS
\fI@PACKAGE_URL@\fP
.RE
.LP
For question and help please use:
.LP
.RS
\fI@PACKAGE_BUGREPORT@\fP
.RE
.LP