6. Configuration¶
6.1. Configuration File Elements¶
Following is a list of elements used throughout the Loop configuration file documentation:
|
The name of an |
``address_match_list `` |
A list of one or more |
|
A named list of one or more |
|
A quoted string which will be used as a DNS
name, for example " |
|
A list of one or more |
|
One to four integers valued 0 through 255
separated by dots (.'), such as ``123`,
|
|
An IPv4 address with exactly four elements in
|
|
An IPv6 address, such as |
|
An |
|
A |
|
An IP port |
|
An IP network specified as an When specifying a prefix involving a IPv6 scoped address the scope may be omitted. In that case the prefix will match packets from any scope. |
|
A |
|
A list of one or more |
|
A non-negative 32-bit integer (i.e., a number between 0 and 4294967295, inclusive). Its acceptable value might be further limited by the context in which it is used. |
|
A non-negative real number that can be specified to the nearest one hundredth. Up to five digits can be specified before a decimal point, and up to two digits after, so the maximum value is 99999.99. Acceptable values might be further limited by the context in which it is used. |
|
A quoted string which will be used as a
pathname, such as
|
|
A list of an |
|
A 64-bit unsigned integer, or the keywords
Integers may take values 0 <= value <=
18446744073709551615, though certain
parameters (such as Numeric values can optionally be followed by
a scaling factor:
|
|
Either |
|
One of |
6.1.1. Address Match Lists¶
6.1.1.1. Syntax¶
address_match_list = address_match_list_element ; ...
address_match_list_element = [ ! ] ( ip_address | ip_prefix |
key key_id | acl_name | { address_match_list } )
6.1.1.2. Definition and Usage¶
Address match lists are primarily used to determine access control for
various server operations. They are also used in the listen-on
statement. The elements which constitute an address match list can be
any of the following:
an IP address (IPv4 or IPv6)
an IP prefix (in `/' notation)
a key ID, as defined by the
key
statementthe name of an address match list defined with the
acl
statementa nested address match list enclosed in braces
Elements can be negated with a leading exclamation mark (`!'), and the match list names "any", "none", "localhost", and "localnets" are predefined. More information on those names can be found in the description of the acl statement.
The addition of the key clause made the name of this syntactic element something of a misnomer, since security keys can be used to validate access without regard to a host or network address. Nonetheless, the term "address match list" is still used throughout the documentation.
When a given IP address or prefix is compared to an address match list, the comparison takes place in approximately O(1) time. However, key comparisons require that the list of keys be traversed until a matching key is found, and therefore may be somewhat slower.
The interpretation of a match depends on whether the list is being used
for access control, or defining listen-on
ports, and whether the
element was negated.
When used as an access control list, a non-negated match allows access
and a negated match denies access. If there is no match, access is
denied. The clauses allow-notify
, allow-recursion
,
allow-recursion-on
, allow-query
, allow-query-on
,
allow-query-cache
, allow-query-cache-on
, allow-transfer
,
allow-update
, allow-update-forwarding
, and blackhole
all use
address match lists. Similarly, the listen-on
option will cause the
server to refuse queries on any of the machine's addresses which do not
match the list.
Order of insertion is significant. If more than one element in an ACL is
found to match a given IP address or prefix, preference will be given to
the one that came first in the ACL definition. Because of this
first-match behavior, an element that defines a subset of another
element in the list should come before the broader element, regardless
of whether either is negated. For example, in 1.2.3/24; ! 1.2.3.13;
the 1.2.3.13 element is completely useless because the algorithm will
match any lookup for 1.2.3.13 to the 1.2.3/24 element. Using
! 1.2.3.13; 1.2.3/24
fixes that problem by having 1.2.3.13 blocked
by the negation, but all other 1.2.3.* hosts fall through.
6.1.2. Comment Syntax¶
The Loop comment syntax allows for comments to appear anywhere that whitespace may appear in a Loop configuration file. To appeal to programmers of all kinds, they can be written in the C, C++, or shell/perl style.
6.1.2.1. Syntax¶
/* This is a Loop comment as in C */
// This is a Loop comment as in C++
# This is a Loop comment as in common UNIX shells
# and perl
6.1.2.2. Definition and Usage¶
Comments may appear anywhere that whitespace may appear in a Loop configuration file.
C-style comments start with the two characters /* (slash, star) and end with */ (star, slash). Because they are completely delimited with these characters, they can be used to comment only a portion of a line or to span multiple lines.
C-style comments cannot be nested. For example, the following is not valid because the entire comment ends with the first */:
/* This is the start of a comment.
This is still part of the comment.
/* This is an incorrect attempt at nesting a comment. */
This is no longer in any comment. */
C++-style comments start with the two characters // (slash, slash) and continue to the end of the physical line. They cannot be continued across multiple physical lines; to have one logical comment span multiple lines, each line must use the // pair. For example:
// This is the start of a comment. The next line
// is a new comment, even though it is logically
// part of the previous comment.
Shell-style (or perl-style, if you prefer) comments start with the
character #
(number sign) and continue to the end of the physical
line, as in C++ comments. For example:
# This is the start of a comment. The next line
# is a new comment, even though it is logically
# part of the previous comment.
Warning
You cannot use the semicolon (`;') character to start a comment such as you would in a zone file. The semicolon indicates the end of a configuration statement.
6.2. Configuration File Grammar¶
A Loop configuration consists of statements and comments. Statements end with a semicolon. Statements and comments are the only elements that can appear without enclosing braces. Many statements contain a block of sub-statements, which are also terminated with a semicolon.
The following statements are supported:
|
defines a named IP address matching list, for access control and other uses. |
|
declares control channels to be used by the
|
|
includes a file. |
|
specifies key information for use in authentication and authorization using TSIG. |
|
specifies what the server logs, and where the log messages are sent. |
|
defines a named masters list for inclusion in stub
and slave zones' |
|
controls global server configuration options and sets defaults for other statements. |
|
sets certain configuration options on a per-server basis. |
|
declares communication channels to get access to
|
``trusted-keys` ` |
defines trusted DNSSEC keys. |
``managed-keys` ` |
lists DNSSEC keys to be kept up to date using RFC 5011 trust anchor maintenance. |
|
defines a view. |
|
defines a zone. |
The logging
and options
statements may only occur once per
configuration.
6.2.1. acl
Statement Grammar¶
acl acl-name {
address_match_list
};
6.2.2. acl
Statement Definition and Usage¶
The acl
statement assigns a symbolic name to an address match list.
It gets its name from a primary use of address match lists: Access
Control Lists (ACLs).
The following ACLs are built-in:
|
Matches all hosts. |
|
Matches no hosts. |
``localhost` ` |
Matches the IPv4 and IPv6 addresses of all network
interfaces on the system. When addresses are added or
removed, the |
``localnets` ` |
Matches any host on an IPv4 or IPv6 network for which
the system has an interface. When addresses are added
or removed, the |
6.2.3. controls
Statement Grammar¶
controls {
[ inet ( ip_addr | * ) [ port ip_port ] allow { address_match_list }
[ keys { key_list } ]
[ read-only yes_or_no ] ; ]
[ ...; ]
};
6.2.4. controls
Statement Definition and Usage¶
The controls
statement declares control channels to be used by
system administrators to control the operation of the name server. These
control channels are used by the rndc
utility to send commands to
and retrieve non-DNS results from a name server.
An inet
control channel is a TCP socket listening at the specified
ip_port
on the specified ip_addr
, which can be an IPv4 or IPv6
address. An ip_addr
of *
(asterisk) is interpreted as the IPv4
wildcard address; connections will be accepted on any of the system's
IPv4 addresses. To listen on the IPv6 wildcard address, use an
ip_addr
of ::
. If you will only use rndc
on the local host,
using the loopback address (127.0.0.1
or ::1
) is recommended for
maximum security.
If no port is specified, port 953 is used. The asterisk "*
" cannot
be used for ip_port
.
The ability to issue commands over the control channel is restricted by
the allow
and keys
clauses. Connections to the control channel
are permitted based on the address_match_list
. This is for simple IP
address based filtering only; any key_id
elements of the
address_match_list
are ignored.
The primary authorization mechanism of the command channel is the
key_list
, which contains a list of key_id
s. Each key_id
in
the key_list
is authorized to execute commands over the control
channel. See Remote Name Daemon Control application in
section_title) for information about configuring keys
in rndc
.
If no controls
statement is present, named
will set up a default
control channel listening on the loopback address 127.0.0.1 and its IPv6
counterpart ::1. In this case, and also when the controls
statement
is present but does not have a keys
clause, named
will attempt
to load the command channel key from the file rndc.key
in
/etc
. To create a rndc.key
file, run rndc-confgen -a
.
The rndc.key
feature does not have a high degree of
configurability. You cannot easily change the key name or the size of
the secret, so you should make a rndc.conf
with your own key if you
wish to change those things. The rndc.key
file also has its
permissions set such that only the owner of the file (the user that
named
is running as) can access it. If you desire greater
flexibility in allowing other users to access rndc
commands, then
you need to create a rndc.conf
file and make it group readable by a
group that contains the users who should have access.
To disable the command channel, use an empty controls
statement:
controls { };
.
6.2.5. include
Statement Grammar¶
include filename;
6.2.6. include
Statement Definition and Usage¶
The include
statement inserts the specified file at the point where
the include
statement is encountered. The include
statement
facilitates the administration of configuration files by permitting the
reading or writing of some things but not others. For example, the
statement could include private keys that are readable only by the name
server.
6.2.7. key
Statement Grammar¶
key key_id {
algorithm algorithm_id;
secret secret_string;
};
6.2.8. key
Statement Definition and Usage¶
The key
statement defines a shared secret key for use with TSIG (see
section_title) or the command channel (see
section_title).
The key
statement can occur at the top level of the configuration
file or inside a view
statement. Keys defined in top-level key
statements can be used in all views. Keys intended for use in a
controls
statement (see
section_title) must be
defined at the top level.
The key_id, also known as the key name, is a domain name uniquely
identifying the key. It can be used in a server
statement to cause
requests sent to that server to be signed with this key, or in address
match lists to verify that incoming requests have been signed with a key
matching this name, algorithm, and secret.
The algorithm_id is a string that specifies a security/authentication
algorithm. Named supports hmac-md5
, hmac-sha1
, hmac-sha224
,
hmac-sha256
, hmac-sha384
and hmac-sha512
TSIG
authentication. Truncated hashes are supported by appending the minimum
number of required bits preceded by a dash, e.g. hmac-sha1-80
. The
secret_string is the secret to be used by the algorithm, and is treated
as a Base64 encoded string.
6.2.9. logging
Statement Grammar¶
logging {
[ channel channel_name {
( ( file path_name
[ versions ( number | unlimited ) ]
[ size size_spec ] )
| syslog syslog_facility
| stderr
| null ) ;
[ severity ( critical | error | warning | notice |
info | debug [ level ] | dynamic ) ; ]
[ print-category yes_or_no ; ]
[ print-severity yes_or_no ; ]
[ print-time yes_or_no ; ]
}; ]
[ category category_name {
channel_name ; ...
}; ]
...
};
6.2.10. logging
Statement Definition and Usage¶
The logging
statement configures a wide variety of logging options
for the name server. Its channel
phrase associates output methods,
format options and severity levels with a name that can then be used
with the category
phrase to select how various classes of messages
are logged.
Only one logging
statement is used to define as many channels and
categories as are wanted. If there is no logging
statement, the
logging configuration will be:
logging {
category default { default_syslog; default_debug; };
category unmatched { null; };
};
In Loop, the logging configuration is only established when the entire
configuration file has been parsed. When the server is starting up, all
logging messages regarding syntax errors in the configuration file go to
the default channels, or to standard error if the "-g
" option was
specified.
6.2.10.1. The channel
Phrase¶
All log output goes to one or more channels; you can make as many of them as you want.
Every channel definition must include a destination clause that says
whether messages selected for the channel go to a file, to a particular
syslog facility, to the standard error stream, or are discarded. It can
optionally also limit the message severity level that will be accepted
by the channel (the default is info
), and whether to include a
named
-generated time stamp, the category name and/or severity level
(the default is not to include any).
The null
destination clause causes all messages sent to the channel
to be discarded; in that case, other options for the channel are
meaningless.
The file
destination clause directs the channel to a disk file. It
can include limitations both on how large the file is allowed to become,
and how many versions of the file will be saved each time the file is
opened.
If you use the versions
log file option, then named
will retain
that many backup versions of the file by renaming them when opening. For
example, if you choose to keep three old versions of the file
lamers.log
, then just before it is opened lamers.log.1
is
renamed to lamers.log.2
, lamers.log.0
is renamed to
lamers.log.1
, and lamers.log
is renamed to lamers.log.0
. You
can say versions unlimited
to not limit the number of versions. If a
size
option is associated with the log file, then renaming is only
done when the file being opened exceeds the indicated size. No backup
versions are kept by default; any existing log file is simply appended.
The size
option for files is used to limit log growth. If the file
ever exceeds the size, then named
will stop writing to the file
unless it has a versions
option associated with it. If backup
versions are kept, the files are rolled as described above and a new one
begun. If there is no versions
option, no more data will be written
to the log until some out-of-band mechanism removes or truncates the log
to less than the maximum size. The default behavior is not to limit the
size of the file.
Example usage of the size
and versions
options:
channel an_example_channel {
file "example.log" versions 3 size 20m;
print-time yes;
print-category yes;
};
The syslog
destination clause directs the channel to the system log.
Its argument is a syslog facility as described in the syslog
man
page. Known facilities are kern
, user
, mail
, daemon
,
auth
, syslog
, lpr
, news
, uucp
, cron
,
authpriv
, ftp
, local0
, local1
, local2
, local3
,
local4
, local5
, local6
and local7
, however not all
facilities are supported on all operating systems. How syslog
will
handle messages sent to this facility is described in the
syslog.conf
man page. If you have a system which uses a very old
version of syslog
that only uses two arguments to the openlog()
function, then this clause is silently ignored.
The severity
clause works like syslog
's "priorities", except
that they can also be used if you are writing straight to a file rather
than using syslog
. Messages which are not at least of the severity
level given will not be selected for the channel; messages of higher
severity levels will be accepted.
If you are using syslog
, then the syslog.conf
priorities will
also determine what eventually passes through. For example, defining a
channel facility and severity as daemon
and debug
but only
logging daemon.warning
via syslog.conf
will cause messages of
severity info
and notice
to be dropped. If the situation were
reversed, with named
writing messages of only warning
or higher,
then syslogd
would print all messages it received from the channel.
The stderr
destination clause directs the channel to the server's
standard error stream. This is intended for use when the server is
running as a foreground process, for example when debugging a
configuration.
The server can supply extensive debugging information when it is in
debugging mode. If the server's global debug level is greater than zero,
then debugging mode will be active. The global debug level is set either
by starting the named
server with the -d
flag followed by a
positive integer, or by running rndc trace
. The global debug level
can be set to zero, and debugging mode turned off, by running rndc
notrace
. All debugging messages in the server have a debug level, and
higher debug levels give more detailed output. Channels that specify a
specific debug severity, for example:
channel specific_debug_level {
file "foo";
severity debug 3;
};
will get debugging output of level 3 or less any time the server is in
debugging mode, regardless of the global debugging level. Channels with
dynamic
severity use the server's global debug level to determine
what messages to print.
If print-time
has been turned on, then the date and time will be
logged. print-time
may be specified for a syslog
channel, but is
usually pointless since syslog
also logs the date and time. If
print-category
is requested, then the category of the message will
be logged as well. Finally, if print-severity
is on, then the
severity level of the message will be logged. The print-
options may
be used in any combination, and will always be printed in the following
order: time, category, severity. Here is an example where all three
print-
options are on:
28-Feb-2000 15:05:32.863 general: notice: running
There are four predefined channels that are used for named
's default
logging as follows. How they are used is described in
section_title.
channel default_syslog {
// send to syslog's daemon facility
syslog daemon;
// only send priority info and higher
severity info;
};
channel default_debug {
// write to named.run in the working directory
// Note: stderr is used instead of "named.run" if
// the server is started with the '-f' option.
file "named.run";
// log at the server's current debug level
severity dynamic;
};
channel default_stderr {
// writes to stderr
stderr;
// only send priority info and higher
severity info;
};
channel null {
// toss anything sent to this channel
null;
};
The default_debug
channel has the special property that it only
produces output when the server's debug level is nonzero. It normally
writes to a file called named.run
in the server's working directory.
For security reasons, when the "-u
" command line option is used, the
named.run
file is created only after named
has changed to the
new UID, and any debug output generated while named
is starting up
and still running as root is discarded. If you need to capture this
output, you must run the server with the "-g
" option and redirect
standard error to a file.
Once a channel is defined, it cannot be redefined. Thus you cannot alter the built-in channels directly, but you can modify the default logging by pointing categories at channels you have defined.
6.2.10.2. The category
Phrase¶
There are many categories, so you can send the logs you want to see
wherever you want, without seeing logs you don't want. If you don't
specify a list of channels for a category, then log messages in that
category will be sent to the default
category instead. If you don't
specify a default category, the following "default default" is used:
category default { default_syslog; default_debug; };
As an example, let's say you want to log security events to a file, but you also want keep the default logging behavior. You'd specify the following:
channel my_security_channel {
file "my_security_file";
severity info;
};
category security {
my_security_channel;
default_syslog;
default_debug;
};
To discard all messages in a category, specify the null
channel:
category xfer-out { null; };
category notify { null; };
Following are the available categories and brief descriptions of the types of log information they contain. More categories may be added in future Loop releases.
6.2.10.3. The query-errors
Category¶
The query-errors
category is specifically intended for debugging
purposes: To identify why and how specific queries result in responses
which indicate an error. Messages of this category are therefore only
logged with debug
levels.
At the debug levels of 1 or higher, each response with the rcode of SERVFAIL is logged as follows:
client 127.0.0.1#61502: query failed (SERVFAIL) for www.example.com/IN/AAAA at query.c:3880
This means an error resulting in SERVFAIL was detected at line 3880 of
source file query.c
. Log messages of this level will particularly
help identify the cause of SERVFAIL for an authoritative server.
At the debug levels of 2 or higher, detailed context information of recursive resolutions that resulted in SERVFAIL is logged. The log message will look like as follows:
fetch completed at resolver.c:2970 for www.example.com/A
in 30.000183: timed out/success [domain:example.com,
referral:2,restart:7,qrysent:8,timeout:5,lame:0,neterr:0,
badresp:1,adberr:0,findfail:0,valfail:0]
The first part before the colon shows that a recursive resolution for
AAAA records of www.example.com completed in 30.000183 seconds and the
final result that led to the SERVFAIL was determined at line 2970 of
source file resolver.c
.
The following part shows the detected final result and the latest result of DNSSEC validation. The latter is always success when no validation attempt is made. In this example, this query resulted in SERVFAIL probably because all name servers are down or unreachable, leading to a timeout in 30 seconds. DNSSEC validation was probably not attempted.
The last part enclosed in square brackets shows statistics information
collected for this particular resolution attempt. The domain
field
shows the deepest zone that the resolver reached; it is the zone where
the error was finally detected. The meaning of the other fields is
summarized in the following table.
|
The number of referrals the resolver received throughout the resolution process. In the above example this is 2, which are most likely com and example.com. |
|
The number of cycles that the resolver tried
remote servers at the |
|
The number of queries the resolver sent at the
|
|
The number of timeouts since the resolver received the last response. |
|
The number of lame servers the resolver detected
at the |
|
The number of erroneous results that the resolver
encountered in sending queries at the |
|
The number of unexpected responses (other than
|
|
Failures in finding remote server addresses of the
|
|
Failures of resolving remote server addresses. This is a total number of failures throughout the resolution process. |
|
Failures of DNSSEC validation. Validation failures
are counted throughout the resolution process (not
limited to the |
At the debug levels of 3 or higher, the same messages as those at the debug 1 level are logged for other errors than SERVFAIL. Note that negative responses such as NXDOMAIN are not regarded as errors here.
At the debug levels of 4 or higher, the same messages as those at the debug 2 level are logged for other errors than SERVFAIL. Unlike the above case of level 3, messages are logged for negative responses. This is because any unexpected results can be difficult to debug in the recursion case.
6.2.11. masters
Statement Grammar¶
masters name [ port ip_port ] [ dscp ip_dscp ] {
( masters_list ; ) |
( ip_addr [ port ip_port ] [ key key ] ; )
...
};
6.2.12. masters
Statement Definition and Usage¶
masters
lists allow for a common set of masters to be easily used by
multiple stub and slave zones in their masters
or also-notify
lists.
6.2.13. options
Statement Grammar¶
This is the grammar of the options
statement in the named.conf
file:
options {
[ attach-cache cache_name ; ]
[ version version_string ; ]
[ hostname hostname_string ; ]
[ server-id server_id_string ; ]
[ directory path_name ; ]
[ key-directory path_name ; ]
[ managed-keys-directory path_name ; ]
[ tkey-domain domain_name ; ]
[ tkey-dhkey key_name key_tag ; ]
[ cache-file path_name ; ]
[ dump-file path_name ; ]
[ dnssec-keys-file path_name ; ]
[ license-file path_name ; ]
[ secroots-file path_name ; ]
[ session-keyfile path_name ; ]
[ session-keyname key_name ; ]
[ session-keyalg algorithm_id ; ]
[ pid-file path_name ; ]
[ recursing-file path_name ; ]
[ statistics-file path_name ; ]
[ zone-statistics ( full | terse | none ) ; ]
[ auth-nxdomain yes_or_no ; ]
[ deallocate-on-exit yes_or_no ; ]
[ dialup dialup_option ; ]
[ flush-zones-on-shutdown yes_or_no ; ]
[ has-old-clients yes_or_no ; ]
[ minimal-responses yes_or_no ; ]
[ notify ( yes_or_no | explicit | master-only ) ; ]
[ recursion yes_or_no ; ]
[ request-cookie yes_or_no ; ]
[ nocookie-udp-size number ; ]
[ cookie-secret secret_string ; ]
[ request-nsid yes_or_no ; ]
[ ixfr-from-differences ( yes_or_no | master | slave ) ; ]
[ auto-dnssec ( allow | maintain | off ) ; ]
[ inline-signing yes_or_no ; ]
[ dnssec-enable yes_or_no ; ]
[ dnssec-validation ( yes_or_no | auto ) ; ]
[ dnssec-must-be-secure domain yes_or_no ; ]
[ forward ( only | first ) ; ]
[ forwarders {
( ip_addr [ port ip_port ] [ dscp ip_dscp ] ; )
...
} ; ]
[ dual-stack-servers [ port ip_port ] [ dscp ip_dscp ] {
( ( domain_name | ip_addr ) [ port ip_port ] [ dscp ip_dscp ] ; )
...
} ; ]
[ check-names ( master | slave | response )
( warn | fail | ignore ) ; ]
[ check-dup-records ( warn | fail | ignore ) ; ]
[ check-mx ( warn | fail | ignore ) ; ]
[ check-wildcard yes_or_no ; ]
[ check-integrity yes_or_no ; ]
[ check-mx-cname ( warn | fail | ignore ) ; ]
[ check-srv-cname ( warn | fail | ignore ) ; ]
[ check-sibling yes_or_no ; ]
[ check-spf ( warn | ignore ) ; ]
[ allow-new-zones yes_or_no ; ]
[ allow-notify { address_match_list } ; ]
[ allow-query { address_match_list } ; ]
[ allow-query-on { address_match_list } ; ]
[ allow-query-cache { address_match_list } ; ]
[ allow-query-cache-on { address_match_list } ; ]
[ allow-transfer { address_match_list } ; ]
[ allow-recursion { address_match_list } ; ]
[ allow-recursion-on { address_match_list } ; ]
[ allow-update { address_match_list } ]
[ allow-update-forwarding { address_match_list } ; ]
[ automatic-interface-scan yes_or_no ; ]
[ update-check-ksk yes_or_no ; ]
[ dnssec-update-mode ( maintain | no-resign ) ; ]
[ dnssec-dnskey-kskonly yes_or_no ; ]
[ dnssec-loadkeys-interval number ; ]
[ dnssec-secure-to-insecure yes_or_no ; ]
[ try-tcp-refresh yes_or_no ; ]
[ allow-v6-synthesis { address_match_list } ; ]
[ blackhole { address_match_list } ; ]
[ no-case-compress { address_match_list } ; ]
[ use-v4-udp-ports { port_list } ; ]
[ avoid-v4-udp-ports { port_list } ; ]
[ use-v6-udp-ports { port_list } ; ]
[ avoid-v6-udp-ports { port_list } ; ]
[ listen-on [ port ip_port ] [ dscp ip_dscp ] { address_match_list } ; ]
[ listen-on-v6 [ port ip_port ] [ dscp ip_dscp ] { address_match_list } ; ]
[ query-source ( [ address ] ( ip4_addr | * ) )
[ port ( ip_port | * ) ] [ dscp ip_dscp ] ] ;
[ query-source-v6 ( [ address ] ( ip6_addr | * ) )
[ port ( ip_port | * ) ] [ dscp ip_dscp ] ] ;
[ use-queryport-pool yes_or_no ; ]
[ queryport-pool-ports number ; ]
[ queryport-pool-updateinterval number ; ]
[ max-records number ; ]
[ max-transfer-time-in number ; ]
[ max-transfer-time-out number ; ]
[ max-transfer-idle-in number ; ]
[ max-transfer-idle-out number ; ]
[ reserved-sockets number ; ]
[ recursive-clients number ; ]
[ tcp-clients number ; ]
[ clients-per-query number ; ]
[ max-clients-per-query number ; ]
[ fetches-per-server number [ ( drop | fail ) ] ; ]
[ fetches-per-zone number [ ( drop | fail ) ] ; ]
[ fetch-quota-params number fixedpoint fixedpoint fixedpoint ; ]
[ serial-query-rate number ; ]
[ tcp-listen-queue number ; ]
[ transfers-in number ; ]
[ transfers-out number ; ]
[ transfers-per-ns number ; ]
[ transfer-source ( ip4_addr | * )
[ port ip_port ] [ dscp ip_dscp ] ; ]
[ transfer-source-v6 ( ip6_addr | * )
[ port ip_port ] [ dscp ip_dscp ] ; ]
[ alt-transfer-source ( ip4_addr | * )
[ port ip_port ] [ dscp ip_dscp ] ; ]
[ alt-transfer-source-v6 ( ip6_addr | * )
[ port ip_port ] [ dscp ip_dscp ] ; ]
[ use-alt-transfer-source yes_or_no ; ]
[ notify-delay seconds ; ]
[ notify-source ( ip4_addr | * )
[ port ip_port ] [ dscp ip_dscp ] ; ]
[ notify-source-v6 ( ip6_addr | * )
[ port ip_port ] [ dscp ip_dscp ] ; ]
[ notify-to-soa yes_or_no ; ]
[ also-notify [ port ip_port] [ dscp ip_dscp] {
( masters | ip_addr [ port ip_port ] ) [ key key_name ] ;
...
} ; ]
[ max-journal-size size_spec ; ]
[ coresize size_spec ; ]
[ datasize size_spec ; ]
[ files size_spec ; ]
[ stacksize size_spec ; ]
[ heartbeat-interval number ; ]
[ interface-interval number ; ]
[ rrset-order { order_spec ; ... } ; ]
[ lame-ttl number ; ]
[ max-ncache-ttl number ; ]
[ max-cache-ttl number ; ]
[ max-zone-ttl ( unlimited | number ) ; ]
[ serial-update-method ( increment | unixtime ) ; ]
[ sig-validity-interval number [number] ; ]
[ sig-signing-nodes number ; ]
[ sig-signing-signatures number ; ]
[ sig-signing-type number ; ]
[ provide-ixfr yes_or_no ; ]
[ request-ixfr yes_or_no ; ]
[ min-refresh-time number ; ]
[ max-refresh-time number ; ]
[ min-retry-time number ; ]
[ max-retry-time number ; ]
[ port ip_port ; ]
[ dscp ip_dscp ; ]
[ max-cache-size size_spec ; ]
[ match-mapped-addresses yes_or_no ; ]
[ dns64 ipv6-prefix {
[ clients { address_match_list } ; ]
[ mapped { address_match_list } ; ]
[ exclude { address_match_list } ; ]
[ suffix ip6-address ; ]
[ recursive-only yes_or_no ; ]
[ break-dnssec yes_or_no ; ]
} ; ]
[ dns64-server name ]
[ dns64-contact name ]
[ preferred-glue ( A | AAAA | none ); ]
[ edns-udp-size number ; ]
[ max-udp-size number ; ]
[ max-rsa-exponent-size number ; ]
[ root-delegation-only [ exclude { namelist } ] ; ]
[ querylog yes_or_no ; ]
[ disable-algorithms domain { algorithm ; ... } ; ]
[ disable-ds-digests domain { digest_type ; ... } ; ]
[ max-recursion-depth number ; ]
[ max-recursion-queries number ; ]
[ empty-server name ; ]
[ empty-contact name ; ]
[ empty-zones-enable yes_or_no ; ]
[ disable-empty-zone zone_name ; ]
[ zero-no-soa-ttl yes_or_no ; ]
[ zero-no-soa-ttl-cache yes_or_no ; ]
[ resolver-query-timeout number ; ]
[ deny-answer-addresses { address_match_list }
[ except-from { namelist } ] ; ]
[ deny-answer-aliases { namelist }
[ except-from { namelist } ] ; ]
[ prefetch number [ number ] ; ]
[ rate-limit {
[ responses-per-second number ; ]
[ referrals-per-second number ; ]
[ nodata-per-second number ; ]
[ nxdomains-per-second number ; ]
[ errors-per-second number ; ]
[ all-per-second number ; ]
[ window number ; ]
[ log-only yes_or_no ; ]
[ qps-scale number ; ]
[ ipv4-prefix-length number ; ]
[ ipv6-prefix-length number ; ]
[ slip number ; ]
[ exempt-clients { address_match_list } ; ]
[ max-table-size number ; ]
[ min-table-size number ; ]
} ; ]
[ response-policy {
zone zone_name
[ policy ( given | disabled | passthru | drop |
tcp-only | nxdomain | nodata | cname domain ) ]
[ recursive-only yes_or_no ]
[ max-policy-ttl number ] ;
...
}
[ recursive-only yes_or_no ]
[ max-policy-ttl number ]
[ break-dnssec yes_or_no ]
[ min-ns-dots number ]
[ qname-wait-recurse yes_or_no ] ; ]
} ; ]
6.2.14. options
Statement Definition and Usage¶
The options
statement sets up global options to be used by Loop.
This statement may appear only once in a configuration file. If there is
no options
statement, an options block with each option set to its
default will be used.
attach-cache
Allows multiple views to share a single cache database. Each view has its own cache database by default, but if multiple views have the same operational policy for name resolution and caching, those views can share a single cache to save memory and possibly improve resolution efficiency by using this option.
The
attach-cache
option may also be specified inview
statements, in which case it overrides the globalattach-cache
option.The cache_name specifies the cache to be shared. When the
named
server configures views which are supposed to share a cache, it creates a cache with the specified name for the first view of these sharing views. The rest of the views will simply refer to the already created cache.One common configuration to share a cache would be to allow all views to share a single cache. This can be done by specifying the
attach-cache
as a global option with an arbitrary name.Another possible operation is to allow a subset of all views to share a cache while the others to retain their own caches. For example, if there are three views A, B, and C, and only A and B should share a cache, specify the
attach-cache
option as a view A (or B)'s option, referring to the other view name:view "A" { // this view has its own cache ... }; view "B" { // this view refers to A's cache attach-cache "A"; }; view "C" { // this view has its own cache ... };
Views that share a cache must have the same policy on configurable parameters that may affect caching. The current implementation requires the following configurable options be consistent among these views:
check-names
,dnssec-validation
,max-cache-ttl
,max-ncache-ttl
,max-cache-size
, andzero-no-soa-ttl
.Note that there may be other parameters that may cause confusion if they are inconsistent for different views that share a single cache. For example, if these views define different sets of forwarders that can return different answers for the same question, sharing the answer does not make sense or could even be harmful. It is administrator's responsibility to ensure configuration differences in different views do not cause disruption with a shared cache.
directory
The working directory of the server. Any non-absolute pathnames in the configuration file will be taken as relative to this directory. The default location for most server output files (e.g.
named.run
) is this directory. If a directory is not specified, the working directory defaults to `.
', the directory from which the server was started. The directory specified should be an absolute path. It is strongly recommended that the directory be writable by the effective user ID of thenamed
process.key-directory
When performing dynamic update of secure zones, the directory where the public and private DNSSEC key files should be found, if different than the current working directory. (Note that this option has no effect on the paths for files containing non-DNSSEC keys such as
rndc.key
orsession.key
.)managed-keys-directory
Specifies the directory in which to store the files that track managed DNSSEC keys. By default, this is the working directory. The directory must be writable by the effective user ID of the
named
process.If
named
is not configured to use views, then managed keys for the server will be tracked in a single file calledmanaged-keys.loop
. Otherwise, managed keys will be tracked in separate files, one file per view; each file name will be the SHA256 hash of the view name, followed by the extension.mkeys
.tkey-domain
The domain appended to the names of all shared keys generated with
TKEY
. When a client requests aTKEY
exchange, it may or may not specify the desired name for the key. If present, the name of the shared key will beclient specified part
+tkey-domain
. Otherwise, the name of the shared key will be ``random hexdigits`` +
tkey-domain
. In most cases, thedomainname
should be the server's domain name, or an otherwise non-existent subdomain like "_tkey.``domainname``".tkey-dhkey
The Diffie-Hellman key used by the server to generate shared keys with clients using the Diffie-Hellman mode of
TKEY
. The server must be able to load the public and private keys from files in the working directory. In most cases, thekey_name
should be the server's host name.cache-file
This is for testing only. Do not use.
dump-file
The pathname of the file the server dumps the database to when instructed to do so with
rndc dumpdb
. If not specified, the default isnamed_dump.db
.pid-file
The pathname of the file the server writes its process ID in. If not specified, the default is
/var/run/loop/named.pid
. The PID file is used by programs that want to send signals to the running name server. Specifyingpid-file none
disables the use of a PID file --- no file will be written and any existing one will be removed. Note thatnone
is a keyword, not a filename, and therefore is not enclosed in double quotes.recursing-file
The pathname of the file the server dumps the queries that are currently recursing when instructed to do so with
rndc recursing
. If not specified, the default isnamed.recursing
.statistics-file
The pathname of the file the server appends statistics to when instructed to do so using
rndc stats
. If not specified, the default isnamed.stats
in the server's current directory. The format of the file is described in section_title.dnssec-keys-file
The pathname of a file to override the built-in DNSSEC trust anchors provided by
named
. See the discussion ofdnssec-validation
for details.license-file
The pathname of a file to override the Loop subscription license information file path. The default is
/etc/loop/loop-license.conf
. See the loop-license.conf(5) manpage for more details.secroots-file
The pathname of the file the server dumps security roots to when instructed to do so with
rndc secroots
. If not specified, the default isnamed.secroots
.session-keyfile
The pathname of the file into which to write a TSIG session key generated by
named
for use bynsupdate -l
. If not specified, the default is/var/run/loop/session.key
. (See section_title, and in particular the discussion of theupdate-policy
statement'slocal
option for more information about this feature.)session-keyname
The key name to use for the TSIG session key. If not specified, the default is "local-ddns".
session-keyalg
The algorithm to use for the TSIG session key. Valid values are hmac-sha1, hmac-sha224, hmac-sha256, hmac-sha384, hmac-sha512 and hmac-md5. If not specified, the default is hmac-sha256.
port
The UDP/TCP port number the server uses for receiving and sending DNS protocol traffic. The default is 53. This option is mainly intended for server testing; a server using a port other than 53 will not be able to communicate with the global DNS.
dscp
The global Differentiated Services Code Point (DSCP) value to classify outgoing DNS traffic on operating systems that support DSCP. Valid values are 0 through 63. It is not configured by default.
preferred-glue
If specified, the listed type (A or AAAA) will be emitted before other glue in the additional section of a query response. The default is to prefer A records when responding to queries that arrived via IPv4 and AAAA when responding to queries that arrived via IPv6.
root-delegation-only
Turn on enforcement of delegation-only in TLDs (top level domains) and root zones with an optional exclude list.
DS queries are expected to be made to and be answered by delegation only zones. Such queries and responses are treated as an exception to delegation-only processing and are not converted to NXDOMAIN responses provided a CNAME is not discovered at the query name.
If a delegation only zone server also serves a child zone it is not always possible to determine whether an answer comes from the delegation only zone or the child zone. SOA NS and DNSKEY records are apex only records and a matching response that contains these records or DS is treated as coming from a child zone. RRSIG records are also examined to see if they are signed by a child zone or not. The authority section is also examined to see if there is evidence that the answer is from the child zone. Answers that are determined to be from a child zone are not converted to NXDOMAIN responses. Despite all these checks there is still a possibility of false negatives when a child zone is being served.
Similarly false positives can arise from empty nodes (no records at the name) in the delegation only zone when the query type is not ANY.
Note some TLDs are not delegation only (e.g. "DE", "LV", "US" and "MUSEUM"). This list is not exhaustive.
options { root-delegation-only exclude { "de"; "lv"; "us"; "museum"; }; };
disable-algorithms
Disable the specified DNSSEC algorithms at and below the specified name. Multiple
disable-algorithms
statements are allowed. Only the best matchdisable-algorithms
clause will be used to determine which algorithms are used.If all supported algorithms are disabled, the zones covered by the
disable-algorithms
will be treated as insecure.disable-ds-digests
Disable the specified DS/DLV digest types at and below the specified name. Multiple
disable-ds-digests
statements are allowed. Only the best matchdisable-ds-digests
clause will be used to determine which digest types are used.If all supported digest types are disabled, the zones covered by the
disable-ds-digests
will be treated as insecure.dnssec-must-be-secure
Specify hierarchies which must be or may not be secure (signed and validated). If
yes
, thennamed
will only accept answers if they are secure. Ifno
, then normal DNSSEC validation applies allowing for insecure answers to be accepted. The specified domain must be under atrusted-keys
ormanaged-keys
statement, ordnssec-validation auto
must be active.dns64
This directive instructs
named
to return mapped IPv4 addresses to AAAA queries when there are no AAAA records. It is intended to be used in conjunction with a NAT64. Eachdns64
defines one DNS64 prefix. Multiple DNS64 prefixes can be defined.Compatible IPv6 prefixes have lengths of 32, 40, 48, 56, 64 and 96 as per RFC 6052.
Additionally a reverse IP6.ARPA zone will be created for the prefix to provide a mapping from the IP6.ARPA names to the corresponding IN-ADDR.ARPA names using synthesized CNAMEs.
dns64-server
anddns64-contact
can be used to specify the name of the server and contact for the zones. These are settable at the view / options level. These are not settable on a per-prefix basis.Each
dns64
supports an optionalclients
ACL that determines which clients are affected by this directive. If not defined, it defaults toany;
.Each
dns64
supports an optionalmapped
ACL that selects which IPv4 addresses are to be mapped in the corresponding A RRset. If not defined it defaults toany;
.Normally, DNS64 won't apply to a domain name that owns one or more AAAA records; these records will simply be returned. The optional
exclude
ACL allows specification of a list of IPv6 addresses that will be ignored if they appear in a domain name's AAAA records, and DNS64 will be applied to any A records the domain name owns. If not defined,exclude
defaults to ::ffff:0.0.0.0/96.A optional
suffix
can also be defined to set the bits trailing the mapped IPv4 address bits. By default these bits are set to::
. The bits matching the prefix and mapped IPv4 address must be zero.If
recursive-only
is set toyes
the DNS64 synthesis will only happen for recursive queries. The default isno
.If
break-dnssec
is set toyes
the DNS64 synthesis will happen even if the result, if validated, would cause a DNSSEC validation failure. If this option is set tono
(the default), the DO is set on the incoming query, and there are RRSIGs on the applicable records, then synthesis will not happen.acl rfc1918 { 10/8; 192.168/16; 172.16/12; }; dns64 64:FF9B::/96 { clients { any; }; mapped { !rfc1918; any; }; exclude { 64:FF9B::/96; ::ffff:0000:0000/96; }; suffix ::; };
dnssec-loadkeys-interval
When a zone is configured with
auto-dnssec maintain
its key repository must be checked periodically to see if any new keys have been added or any existing keys' timing metadata has been updated (see ??? and ???). Thednssec-loadkeys-interval
option sets the frequency of automatic repository checks, in minutes. The default is60
(1 hour), the minimum is1
(1 minute), and the maximum is1440
(24 hours); any higher value is silently reduced.dnssec-update-mode
If this option is set to its default value of
maintain
in a zone of typemaster
which is DNSSEC-signed and configured to allow dynamic updates (see section_title), and ifnamed
has access to the private signing key(s) for the zone, thennamed
will automatically sign all new or changed records and maintain signatures for the zone by regenerating RRSIG records whenever they approach their expiration date.If the option is changed to
no-resign
, thennamed
will sign all new or changed records, but scheduled maintenance of signatures is disabled.With either of these settings,
named
will reject updates to a DNSSEC-signed zone when the signing keys are inactive or unavailable tonamed
. (A planned third option,external
, will disable all automatic signing and allow DNSSEC data to be submitted into a zone via dynamic update; this is not yet implemented.)max-zone-ttl
Specifies a maximum permissible TTL value. When loading a zone file, any record encountered with a TTL higher than
max-zone-ttl
will cause the zone to be rejected.This is useful in DNSSEC-signed zones because when rolling to a new DNSKEY, the old key needs to remain available until RRSIG records have expired from caches. The
max-zone-ttl
option guarantees that the largest TTL in the zone will be no higher the set value.The default value is
unlimited
. Amax-zone-ttl
of zero is treated asunlimited
.serial-update-method
Zones configured for dynamic DNS may use this option to set the update method that will be used for the zone serial number in the SOA record.
With the default setting of
serial-update-method increment;
, the SOA serial number will be incremented by one each time the zone is updated.When set to
serial-update-method unixtime;
, the SOA serial number will be set to the number of seconds since the UNIX epoch, unless the serial number is already greater than or equal to that value, in which case it is simply incremented by one.zone-statistics
If
full
, the server will collect statistical data on all zones (unless specifically turned off on a per-zone basis by specifyingzone-statistics terse
orzone-statistics none
in thezone
statement). The default isterse
, providing minimal statistics on zones (including name and current serial number, but not query type counters).These statistics may be accessed via the
statistics-channel
or usingrndc stats
, which will dump them to the file listed in thestatistics-file
. See also section_title.The
zone-statistics
option can also acceptyes
orno
;yes
has the same meaning asfull
.no
has the same meaning asnone
.
6.2.14.1. Boolean Options¶
automatic-interface-scan
If
yes
and supported by the OS, automatically rescan network interfaces when the interface addresses are added or removed. The default isyes
.Currently the OS needs to support routing sockets for
automatic-interface-scan
to be supported.allow-new-zones
If
yes
, then zones can be added at runtime viarndc addzone
or deleted viarndc delzone
. The default isno
.auth-nxdomain
If
yes
, then theAA
bit is always set on NXDOMAIN responses, even if the server is not actually authoritative. The default isno
. If you are using very old DNS software, you may need to set it toyes
.dialup
If
yes
, then the server treats all zones as if they are doing zone transfers across a dial-on-demand dialup link, which can be brought up by traffic originating from this server. This has different effects according to zone type and concentrates the zone maintenance so that it all happens in a short interval, once everyheartbeat-interval
and hopefully during the one call. It also suppresses some of the normal zone maintenance traffic. The default isno
.The
dialup
option may also be specified in theview
andzone
statements, in which case it overrides the globaldialup
option.If the zone is a master zone, then the server will send out a NOTIFY request to all the slaves (default). This should trigger the zone serial number check in the slave (providing it supports NOTIFY) allowing the slave to verify the zone while the connection is active. The set of servers to which NOTIFY is sent can be controlled by
notify
andalso-notify
.If the zone is a slave or stub zone, then the server will suppress the regular "zone up to date" (refresh) queries and only perform them when the
heartbeat-interval
expires in addition to sending NOTIFY requests.Finer control can be achieved by using
notify
which only sends NOTIFY messages,notify-passive
which sends NOTIFY messages and suppresses the normal refresh queries,refresh
which suppresses normal refresh processing and sends refresh queries when theheartbeat-interval
expires, andpassive
which just disables normal refresh processing.dialup mode
normal refresh
heart-beat refresh
heart-beat notify
no
(default)yes
no
no
yes
no
yes
yes
notify
yes
no
yes
refresh
no
yes
no
passive
no
no
no
notify-passiv e
no
no
yes
Note that normal NOTIFY processing is not affected by
dialup
.flush-zones-on-shutdown
When the nameserver exits due receiving SIGTERM, flush or do not flush any pending zone writes. The default is
flush-zones-on-shutdown
no
.minimal-responses
If
yes
, then when generating responses the server will only add records to the authority and additional data sections when they are required (e.g. delegations, negative responses). This may improve the performance of the server. The default isno
.notify
If
yes
(the default), DNS NOTIFY messages are sent when a zone the server is authoritative for changes, see section_title. The messages are sent to the servers listed in the zone's NS records (except the master server identified in the SOA MNAME field), and to any servers listed in thealso-notify
option.If
master-only
, notifies are only sent for master zones. Ifexplicit
, notifies are sent only to servers explicitly listed usingalso-notify
. Ifno
, no notifies are sent.The
notify
option may also be specified in thezone
statement, in which case it overrides theoptions notify
statement. It would only be necessary to turn off this option if it caused slaves to crash.notify-to-soa
If
yes
do not check the nameservers in the NS RRset against the SOA MNAME. Normally a NOTIFY message is not sent to the SOA MNAME (SOA ORIGIN) as it is supposed to contain the name of the ultimate master. Sometimes, however, a slave is listed as the SOA MNAME in hidden master configurations and in that case you would want the ultimate master to still send NOTIFY messages to all the nameservers listed in the NS RRset.recursion
If
yes
, and a DNS query requests recursion, then the server will attempt to do all the work required to answer the query. If recursion is off and the server does not already know the answer, it will return a referral response. The default isyes
. Note that settingrecursion no
does not prevent clients from getting data from the server's cache; it only prevents new data from being cached as an effect of client queries. Caching may still occur as an effect the server's internal operation, such as NOTIFY address lookups.request-nsid
If
yes
, then an empty EDNS(0) NSID (Name Server Identifier) option is sent with all queries to authoritative name servers during iterative resolution. If the authoritative server returns an NSID option in its response, then its contents are logged in theresolver
category at levelinfo
. The default isno
.request-cookie
If
yes
, then a DNS COOKIE EDNS option is sent along with the query. If the resolver has previously talked to the server, the cookie returned in the previous transaction is sent. This is used by the server to determine whether the resolver has talked to it before. A resolver sending the correct cookie is assumed not to be an off-path attacker sending a spoofed-source query; the query is therefore unlikely to be part of a reflection/amplification attack, so resolvers sending a correct COOKIE option are not subject to response rate limiting (RRL). Resolvers which do not send a correct COOKIE option may be limited to receiving smaller responses via thenocookie-udp-size
option.nocookie-udp-size
Sets the maximum size of UDP responses that will be sent to queries without a valid DNS COOKIE. A value below 128 will be silently raised to 128. The default value is 4096, but the
max-udp-size
option may further limit the response size.cookie-secret
If set, this is a shared secret used for generating and verifying DNS COOKIE EDNS options within an anycast cluster. If not set the system will generate a random secret at startup. The shared secret is encoded as a hex string and needs to be 512 bits for hmac-sha256 algorithm and 64 bits long for siphash algorithm.
provide-ixfr
See the description of
provide-ixfr
in section_title.request-ixfr
See the description of
request-ixfr
in section_title.match-mapped-addresses
If
yes
, then an IPv4-mapped IPv6 address will match any address match list entries that match the corresponding IPv4 address.This option was introduced to work around a kernel quirk in some operating systems that causes IPv4 TCP connections, such as zone transfers, to be accepted on an IPv6 socket using mapped addresses. This caused address match lists designed for IPv4 to fail to match. However,
named
now solves this problem internally. The use of this option is discouraged.ixfr-from-differences
When
yes
and the server loads a new version of a master zone from its zone file or receives a new version of a slave file via zone transfer, it will compare the new version to the previous one and calculate a set of differences. The differences are then logged in the zone's journal file such that the changes can be transmitted to downstream slaves as an incremental zone transfer.By allowing incremental zone transfers to be used for non-dynamic zones, this option saves bandwidth at the expense of increased CPU and memory consumption at the master. In particular, if the new version of a zone is completely different from the previous one, the set of differences will be of a size comparable to the combined size of the old and new zone version, and the server will need to temporarily allocate memory to hold this complete difference set.
ixfr-from-differences
also acceptsmaster
andslave
at the view and options levels which causesixfr-from-differences
to be enabled for allmaster
orslave
zones respectively. It is off by default.multi-master
This should be set when you have multiple masters for a zone and the addresses refer to different machines. If
yes
,named
will not log when the serial number on the master is less than whatnamed
currently has. The default isno
.auto-dnssec
Zones configured for dynamic DNS may use this option to allow varying levels of automatic DNSSEC key management. There are three possible settings:
auto-dnssec allow;
permits keys to be updated and the zone fully re-signed whenever the user issues the command ``rndc signzonename``.
auto-dnssec maintain;
includes the above, but also automatically adjusts the zone's DNSSEC keys on schedule, according to the keys' timing metadata (see ??? and ???). The command ``rndc signzonename`` causes
named
to load keys from the keyrepository and sign the zone with all keys that are active. ``rndc loadkeys
zonename`` causes
named
to load keys from the keyrepository and schedule key maintenance events to occur in the future, but it does not sign the full zone immediately. Note: once keys have been loaded for a zone the first time, the repository will be searched for changes periodically, regardless of whether
rndc loadkeys
is used. The recheck interval is defined bydnssec-loadkeys-interval
.)The default setting is
auto-dnssec off
.dnssec-enable
This indicates whether DNSSEC-related resource records are to be returned by
named
. If set tono
,named
will not return DNSSEC-related resource records unless specifically queried for. The default isyes
.dnssec-validation
Enable DNSSEC validation in
named
. Notednssec-enable
also needs to be set toyes
to be effective. If set tono
, DNSSEC validation is disabled.If set to
auto
, DNSSEC validation is enabled, and a default trust anchor for the DNS root zone is used. If set toyes
, DNSSEC validation is enabled, but a trust anchor must be manually configured using atrusted-keys
ormanaged-keys
statement. The default isyes
.The default root DNSSEC trust anchors are built-in
named
will load them at startup ifdnssec-validation
is set toauto
. The built-in trust anchors are current as of the software release date. If the root DNSSEC trust anchors expire, updated trust anchors may be provided using thednssec-keys-file
config option. Keeping the Loop software up-to-date is recommended instead, whereby the latest trust anchors will always be built-in. The use ofdnssec-keys-file
is discouraged.Note
named
only loads the root key fromdnssec-keys-file
. The file cannot be used to store keys for other zones. The root key indnssec-keys-file
is ignored ifdnssec-validation auto
is not in use.Whenever the resolver sends out queries to an EDNS-compliant server, it always sets the DO bit indicating it can support DNSSEC responses even if
dnssec-validation
is off.querylog
Specify whether query logging should be started when
named
starts. Ifquerylog
is not specified, then the query logging is determined by the presence of the logging categoryqueries
.check-names
This option is used to restrict the character set and syntax of certain domain names in master files and/or DNS responses received from the network. The default varies according to usage area. For
master
zones the default isfail
. Forslave
zones the default iswarn
. For answers received from the network (response
) the default isignore
.The rules for legal hostnames and mail domains are derived from RFC 952 and RFC 821 as modified by RFC 1123.
check-names
applies to the owner names of A, AAAA and MX records. It also applies to the domain names in the RDATA of NS, SOA, MX, and SRV records. It also applies to the RDATA of PTR records where the owner name indicated that it is a reverse lookup of a hostname (the owner name ends in IN-ADDR.ARPA, IP6.ARPA, or IP6.INT).check-dup-records
Check master zones for records that are treated as different by DNSSEC but are semantically equal in plain DNS. The default is to
warn
. Other possible values arefail
andignore
.check-mx
Check whether the MX record appears to refer to a IP address. The default is to
warn
. Other possible values arefail
andignore
.check-wildcard
This option is used to check for non-terminal wildcards. The use of non-terminal wildcards is almost always as a result of a failure to understand the wildcard matching algorithm (RFC 1034). This option affects master zones. The default (
yes
) is to check for non-terminal wildcards and issue a warning.check-integrity
Perform post load zone integrity checks on master zones. This checks that MX and SRV records refer to address (A or AAAA) records and that glue address records exist for delegated zones. For MX and SRV records only in-zone hostnames are checked (for out-of-zone hostnames use
named-checkzone
). For NS records only names below top of zone are checked (for out-of-zone names and glue consistency checks usenamed-checkzone
). The default isyes
.The use of the SPF record for publishing Sender Policy Framework is deprecated as the migration from using TXT records to SPF records was abandoned. Enabling this option also checks that a TXT Sender Policy Framework record exists (starts with "v=spf1") if there is an SPF record. Warnings are emitted if the TXT record does not exist and can be suppressed with
check-spf
.check-mx-cname
If
check-integrity
is set then fail, warn or ignore MX records that refer to CNAMES. The default is towarn
.check-srv-cname
If
check-integrity
is set then fail, warn or ignore SRV records that refer to CNAMES. The default is towarn
.check-sibling
When performing integrity checks, also check that sibling glue exists. The default is
yes
.check-spf
If
check-integrity
is set then check that there is a TXT Sender Policy Framework record present (starts with "v=spf1") if there is an SPF record present. The default iswarn
.zero-no-soa-ttl
When returning authoritative negative responses to SOA queries set the TTL of the SOA record returned in the authority section to zero. The default is
yes
.zero-no-soa-ttl-cache
When caching a negative response to a SOA query set the TTL to zero. The default is
no
.update-check-ksk
When set to the default value of
yes
, check the KSK bit in each key to determine how the key should be used when generating RRSIGs for a secure zone.Ordinarily, zone-signing keys (that is, keys without the KSK bit set) are used to sign the entire zone, while key-signing keys (keys with the KSK bit set) are only used to sign the DNSKEY RRset at the zone apex. However, if this option is set to
no
, then the KSK bit is ignored; KSKs are treated as if they were ZSKs and are used to sign the entire zone. This is similar to thednssec-signzone -z
command line option.When this option is set to
yes
, there must be at least two active keys for every algorithm represented in the DNSKEY RRset: at least one KSK and one ZSK per algorithm. If there is any algorithm for which this requirement is not met, this option will be ignored for that algorithm.dnssec-dnskey-kskonly
When this option and
update-check-ksk
are both set toyes
, only key-signing keys (that is, keys with the KSK bit set) will be used to sign the DNSKEY RRset at the zone apex. Zone-signing keys (keys without the KSK bit set) will be used to sign the remainder of the zone, but not the DNSKEY RRset. This is similar to thednssec-signzone -x
command line option.The default is
no
. Ifupdate-check-ksk
is set tono
, this option is ignored.try-tcp-refresh
Try to refresh the zone using TCP if UDP queries fail. The default is
yes
.dnssec-secure-to-insecure
Allow a dynamic zone to transition from secure to insecure (i.e., signed to unsigned) by deleting all of the DNSKEY records. The default is
no
. If set toyes
, and if the DNSKEY RRset at the zone apex is deleted, all RRSIG and NSEC records will be removed from the zone as well.If the zone uses NSEC3, then it is also necessary to delete the NSEC3PARAM RRset from the zone apex; this will cause the removal of all corresponding NSEC3 records. (It is expected that this requirement will be eliminated in a future release.)
Note that if a zone has been configured with
auto-dnssec maintain
and the private keys remain accessible in the key repository, then the zone will be automatically signed again the next timenamed
is started.
6.2.14.2. Forwarding¶
The forwarding facility can be used to create a large site-wide cache on a few servers, reducing traffic over links to external name servers. It can also be used to allow queries by servers that do not have direct access to the Internet, but wish to look up exterior names anyway. Forwarding occurs only on those queries for which the server is not authoritative and does not have the answer in its cache.
forward
This option is only meaningful if the forwarders list is not empty. A value of
first
, the default, causes the server to query the forwarders first — and if that doesn't answer the question, the server will then look for the answer itself. Ifonly
is specified, the server will only query the forwarders.forwarders
Specifies the IP addresses to be used for forwarding. The default is the empty list (no forwarding).
Forwarding can also be configured on a per-domain basis, allowing for
the global forwarding options to be overridden in a variety of ways. You
can set particular domains to use different forwarders, or have a
different forward only/first
behavior, or not forward at all, see
section_title.
6.2.14.3. Dual-stack Servers¶
Dual-stack servers are used as servers of last resort to work around problems in reachability due the lack of support for either IPv4 or IPv6 on the host machine.
dual-stack-servers
Specifies host names or addresses of machines with access to both IPv4 and IPv6 transports. If a hostname is used, the server must be able to resolve the name using only the transport it has. If the machine is dual stacked, then the
dual-stack-servers
have no effect unless access to a transport has been disabled on the command line (e.g.named -4
).
6.2.14.4. Access Control¶
Access to the server can be restricted based on the IP address of the requesting system. See section_title for details on how to specify IP address lists.
allow-notify
Specifies which hosts are allowed to notify this server, a slave, of zone changes in addition to the zone masters.
allow-notify
may also be specified in thezone
statement, in which case it overrides theoptions allow-notify
statement. It is only meaningful for a slave zone. If not specified, the default is to process notify messages only from a zone's master.allow-query
Specifies which hosts are allowed to ask ordinary DNS questions.
allow-query
may also be specified in thezone
statement, in which case it overrides theoptions allow-query
statement. If not specified, the default is to allow queries from all hosts.Note
allow-query-cache
is now used to specify access to the cache.allow-query-on
Specifies which local addresses can accept ordinary DNS questions. This makes it possible, for instance, to allow queries on internal-facing interfaces but disallow them on external-facing ones, without necessarily knowing the internal network's addresses.
Note that
allow-query-on
is only checked for queries that are permitted byallow-query
. A query must be allowed by both ACLs, or it will be refused.allow-query-on
may also be specified in thezone
statement, in which case it overrides theoptions allow-query-on
statement.If not specified, the default is to allow queries on all addresses.
Note
allow-query-cache
is used to specify access to the cache.allow-query-cache
Specifies which hosts are allowed to get answers from the cache. If
allow-query-cache
is not set thenallow-recursion
is used if set, otherwiseallow-query
is used if set unlessrecursion no;
is set in which casenone;
is used, otherwise the default (localnets;
localhost;
) is used.allow-query-cache-on
Specifies which local addresses can give answers from the cache. If not specified, the default is to allow cache queries on any address,
localnets
andlocalhost
.allow-recursion
Specifies which hosts are allowed to make recursive queries through this server. If
allow-recursion
is not set thenallow-query-cache
is used if set, otherwiseallow-query
is used if set, otherwise the default (localnets;
localhost;
) is used.allow-recursion-on
Specifies which local addresses can accept recursive queries. If not specified, the default is to allow recursive queries on all addresses.
allow-update
Specifies which hosts are allowed to submit Dynamic DNS updates for master zones. The default is to deny updates from all hosts. Note that allowing updates based on the requestor's IP address is insecure; see section_title for details.
allow-update-forwarding
Specifies which hosts are allowed to submit Dynamic DNS updates to slave zones to be forwarded to the master. The default is
{ none; }
, which means that no update forwarding will be performed. To enable update forwarding, specifyallow-update-forwarding { any; };
. Specifying values other than{ none; }
or{ any; }
is usually counterproductive, since the responsibility for update access control should rest with the master server, not the slaves.Note that enabling the update forwarding feature on a slave server may expose master servers relying on insecure IP address based access control to attacks; see section_title for more details.
allow-v6-synthesis
This option was introduced for the smooth transition from AAAA to A6 and from "nibble labels" to binary labels. However, since both A6 and binary labels were then deprecated, this option was also deprecated. It is now ignored with some warning messages.
allow-transfer
Specifies which hosts are allowed to receive zone transfers from the server.
allow-transfer
may also be specified in thezone
statement, in which case it overrides theoptions allow-transfer
statement. If not specified, the default is to allow transfers to all hosts.blackhole
Specifies a list of addresses that the server will not accept queries from or use to resolve a query. Queries from these addresses will not be responded to. The default is
none
.no-case-compress
Specifies a list of addresses which require responses to use case-insensitive compression. This ACL can be used when
named
needs to work with clients that do not comply with the requirement in RFC 1034 to use case-insensitive name comparisons when checking for matching domain names.If left undefined, the ACL defaults to
none
: case-insensitive compression will be used for all clients. If the ACL is defined and matches a client, then case will be ignored when compressing domain names in DNS responses sent to that client.This can result in slightly smaller responses: if a response contains the names "example.com" and "example.COM", case-insensitive compression would treat the second one as a duplicate. It also ensures that the case of the query name exactly matches the case of the owner names of returned records, rather than matching the case of the records entered in the zone file. This allows responses to exactly match the query, which is required by some clients due to incorrect use of case-sensitive comparisons.
Case-insensitive compression is always used in AXFR and IXFR responses, regardless of whether the client matches this ACL.
There are circumstances in which
named
will not preserve the case of owner names of records: if a zone file defines records of different types with the same name, but the capitalization of the name is different (e.g., "www.example.com/A" and "WWW.EXAMPLE.COM/AAAA"), then all responses for that name will use the first version of the name that was used in the zone file. This limitation may be addressed in a future release. However, domain names specified in the rdata of resource records (i.e., records of type NS, MX, CNAME, etc) will always have their case preserved unless the client matches this ACL.resolver-query-timeout
The amount of time the resolver will spend attempting to resolve a recursive query before failing. The default and minimum is
10
and the maximum is30
. Setting it to0
will result in the default being used.
6.2.14.5. Interfaces¶
The interfaces and ports that the server will answer queries from may be
specified using the listen-on
option. listen-on
takes an
optional port and an address_match_list
of IPv4 addresses. (IPv6
addresses are ignored, with a logged warning.) The server will listen on
all interfaces allowed by the address match list. If a port is not
specified, port 53 will be used.
Multiple listen-on
statements are allowed. For example,
listen-on { 5.6.7.8; };
listen-on port 1234 { !1.2.3.4; 1.2/16; };
will enable the name server on port 53 for the IP address 5.6.7.8, and on port 1234 of an address on the machine in net 1.2 that is not 1.2.3.4.
If no listen-on
is specified, the server will listen on port 53 on
all IPv4 interfaces.
The listen-on-v6
option is used to specify the interfaces and the
ports on which the server will listen for incoming queries sent using
IPv6. If not specified, the server will listen on port 53 on all IPv6
interfaces.
When
{ any; }
is specified as the address_match_list
for the listen-on-v6
option, the server does not bind a separate socket to each IPv6
interface address as it does for IPv4 if the operating system has enough
API support for IPv6 (specifically if it conforms to RFC 3493 and RFC
3542). Instead, it listens on the IPv6 wildcard address. If the system
only has incomplete API support for IPv6, however, the behavior is the
same as that for IPv4.
A list of particular IPv6 addresses can also be specified, in which case
the server listens on a separate socket for each specified address,
regardless of whether the desired API is supported by the system. IPv4
addresses specified in listen-on-v6
will be ignored, with a logged
warning.
Multiple listen-on-v6
options can be used. For example,
listen-on-v6 { any; };
listen-on-v6 port 1234 { !2001:db8::/32; any; };
will enable the name server on port 53 for any IPv6 addresses (with a single wildcard socket), and on port 1234 of IPv6 addresses that is not in the prefix 2001:db8::/32 (with separate sockets for each matched address.)
To make the server not listen on any IPv6 address, use
listen-on-v6 { none; };
6.2.14.6. Query Address¶
If the server doesn't know the answer to a question, it will query other
name servers. query-source
specifies the address and port used for
such queries. For queries sent over IPv6, there is a separate
query-source-v6
option. If address
is *
(asterisk) or is
omitted, a wildcard IP address (INADDR_ANY
) will be used.
If port
is *
or is omitted, a random port number from a
pre-configured range is picked up and will be used for each query. The
port range(s) is that specified in the use-v4-udp-ports
(for IPv4)
and use-v6-udp-ports
(for IPv6) options, excluding the ranges
specified in the avoid-v4-udp-ports
and avoid-v6-udp-ports
options, respectively.
The defaults of the query-source
and query-source-v6
options
are:
query-source address * port *;
query-source-v6 address * port *;
If use-v4-udp-ports
or use-v6-udp-ports
is unspecified,
named
will check if the operating system provides a programming
interface to retrieve the system's default range for ephemeral ports. If
such an interface is available, named
will use the corresponding
system default range; otherwise, it will use its own defaults:
use-v4-udp-ports { range 1024 65535; };
use-v6-udp-ports { range 1024 65535; };
Note: make sure the ranges be sufficiently large for security. A
desirable size depends on various parameters, but we generally recommend
it contain at least 16384 ports (14 bits of entropy). Note also that the
system's default range when used may be too small for this purpose, and
that the range may even be changed while named
is running; the new
range will automatically be applied when named
is reloaded. It is
encouraged to configure use-v4-udp-ports
and use-v6-udp-ports
explicitly so that the ranges are sufficiently large and are reasonably
independent from the ranges used by other applications.
Note: the operational configuration where named
runs may prohibit
the use of some ports. For example, UNIX systems will not allow
named
running without a root privilege to use ports less than 1024.
If such ports are included in the specified (or detected) set of query
ports, the corresponding query attempts will fail, resulting in
resolution failures or delay. It is therefore important to configure the
set of ports that can be safely used in the expected operational
environment.
The defaults of the avoid-v4-udp-ports
and avoid-v6-udp-ports
options are:
avoid-v4-udp-ports {};
avoid-v6-udp-ports {};
Note: It is generally strongly discouraged to specify a particular port
for the query-source
or query-source-v6
options; it implicitly
disables the use of randomized port numbers.
Note
The address specified in the
query-source
option is used for both UDP and TCP queries, but the port applies only to UDP queries. TCP queries always use a random unprivileged port.
Note
See also
transfer-source
andnotify-source
.
6.2.14.7. Zone Transfers¶
Loop has mechanisms in place to facilitate zone transfers and set limits on the amount of load that transfers place on the system. The following options apply to zone transfers.
also-notify
Defines a global list of IP addresses of name servers that are also sent NOTIFY messages whenever a fresh copy of the zone is loaded, in addition to the servers listed in the zone's NS records. This helps to ensure that copies of the zones will quickly converge on stealth servers. Optionally, a port may be specified with each
also-notify
address to send the notify messages to a port other than the default of 53. An optional TSIG key can also be specified with each address to cause the notify messages to be signed; this can be useful when sending notifies to multiple views. In place of explicit addresses, one or more namedmasters
lists can be used.If an
also-notify
list is given in azone
statement, it will override theoptions also-notify
statement. When azone notify
statement is set tono
, the IP addresses in the globalalso-notify
list will not be sent NOTIFY messages for that zone. The default is the empty list (no global notification list).max-transfer-time-in
Inbound zone transfers running longer than this many minutes will be terminated. The default is 120 minutes (2 hours). The maximum value is 28 days (40320 minutes).
max-transfer-idle-in
Inbound zone transfers making no progress in this many minutes will be terminated. The default is 60 minutes (1 hour). The maximum value is 28 days (40320 minutes).
max-transfer-time-out
Outbound zone transfers running longer than this many minutes will be terminated. The default is 120 minutes (2 hours). The maximum value is 28 days (40320 minutes).
max-transfer-idle-out
Outbound zone transfers making no progress in this many minutes will be terminated. The default is 60 minutes (1 hour). The maximum value is 28 days (40320 minutes).
serial-query-rate
Slave servers will periodically query master servers to find out if zone serial numbers have changed. Each such query uses a minute amount of the slave server's network bandwidth. To limit the amount of bandwidth used, Loop limits the rate at which queries are sent. The value of the
serial-query-rate
option, an integer, is the maximum number of queries sent per second. The default is 20 per second. The lowest possible rate is one per second; when set to zero, it will be silently raised to one.In addition to controlling the rate SOA refresh queries are issued at,
serial-query-rate
also controls the rate at which NOTIFY messages are sent from both master and slave zones.transfers-in
The maximum number of inbound zone transfers that can be running concurrently. The default value is
10
. Increasingtransfers-in
may speed up the convergence of slave zones, but it also may increase the load on the local system.transfers-out
The maximum number of outbound zone transfers that can be running concurrently. Zone transfer requests in excess of the limit will be refused. The default value is
10
.transfers-per-ns
The maximum number of inbound zone transfers that can be concurrently transferring from a given remote name server. The default value is
2
. Increasingtransfers-per-ns
may speed up the convergence of slave zones, but it also may increase the load on the remote name server.transfers-per-ns
may be overridden on a per-server basis by using thetransfers
phrase of theserver
statement.transfer-source
transfer-source
determines which local address will be bound to IPv4 TCP connections used to fetch zones transferred inbound by the server. It also determines the source IPv4 address, and optionally the UDP port, used for the refresh queries and forwarded dynamic updates. If not set, it defaults to a system controlled value which will usually be the address of the interface "closest to" the remote end. This address must appear in the remote end'sallow-transfer
option for the zone being transferred, if one is specified. This statement sets thetransfer-source
for all zones, but can be overridden on a per-view or per-zone basis by including atransfer-source
statement within theview
orzone
block in the configuration file.transfer-source-v6
The same as
transfer-source
, except zone transfers are performed using IPv6.alt-transfer-source
An alternate transfer source if the one listed in
transfer-source
fails anduse-alt-transfer-source
is set.Note
If you do not wish the alternate transfer source to be used, you should set
use-alt-transfer-source
appropriately and you should not depend upon getting an answer back to the first refresh query.alt-transfer-source-v6
An alternate transfer source if the one listed in
transfer-source-v6
fails anduse-alt-transfer-source
is set.use-alt-transfer-source
Use the alternate transfer sources or not. If views are specified this defaults to
no
otherwise it defaults toyes
.notify-source
notify-source
determines which local source address, and optionally UDP port, will be used to send NOTIFY messages. This address must appear in the slave server'smasters
zone clause or in anallow-notify
clause. This statement sets thenotify-source
for all zones, but can be overridden on a per-zone or per-view basis by including anotify-source
statement within thezone
orview
block in the configuration file.notify-source-v6
Like
notify-source
, but applies to notify messages sent to IPv6 addresses.
6.2.14.8. UDP Port Lists¶
use-v4-udp-ports
, avoid-v4-udp-ports
, use-v6-udp-ports
, and
avoid-v6-udp-ports
specify a list of IPv4 and IPv6 UDP ports that
will be used or not used as source ports for UDP messages. See
section_title about how the available ports are
determined. For example, with the following configuration
use-v6-udp-ports { range 32768 65535; };
avoid-v6-udp-ports { 40000; range 50000 60000; };
UDP ports of IPv6 messages sent from named
will be in one of the
following ranges: 32768 to 39999, 40001 to 49999, and 60001 to 65535.
avoid-v4-udp-ports
and avoid-v6-udp-ports
can be used to prevent
named
from choosing as its random source port a port that is blocked
by your firewall or a port that is used by other applications; if a
query went out with a source port blocked by a firewall, the answer
would not get by the firewall and the name server would have to query
again. Note: the desired range can also be represented only with
use-v4-udp-ports
and use-v6-udp-ports
, and the avoid-
options are redundant in that sense; they are provided for backward
compatibility and to possibly simplify the port specification.
6.2.14.9. Operating System Resource Limits¶
The server's usage of many system resources can be limited. Scaled
values are allowed when specifying resource limits. For example, 1G
can be used instead of 1073741824
to specify a limit of one
gigabyte. unlimited
requests unlimited use, or the maximum available
amount. default
uses the limit that was in force when the server was
started. See the description of size_spec
in
section_title.
The following options set operating system resource limits for the name server process. Some operating systems don't support some or any of the limits. On such systems, a warning will be issued if the unsupported limit is used.
coresize
The maximum size of a core dump. The default is
default
.datasize
The maximum amount of data memory the server may use. The default is
default
. This is a hard limit on server memory usage. If the server attempts to allocate memory in excess of this limit, the allocation will fail, which may in turn leave the server unable to perform DNS service. Therefore, this option is rarely useful as a way of limiting the amount of memory used by the server, but it can be used to raise an operating system data size limit that is too small by default. If you wish to limit the amount of memory used by the server, use themax-cache-size
andrecursive-clients
options instead.files
The maximum number of files the server may have open concurrently. The default is
unlimited
.stacksize
The maximum amount of stack memory the server may use. The default is
default
.
6.2.14.10. Server Resource Limits¶
The following options set limits on the server's resource consumption that are enforced internally by the server rather than the operating system.
max-journal-size
Sets a maximum size for each journal file (see section_title). When the journal file approaches the specified size, some of the oldest transactions in the journal will be automatically removed. The largest permitted value is 2 gigabytes. The default is
unlimited
, which also means 2 gigabytes. This may also be set on a per-zone basis.max-records
The maximum number of records permitted in a zone. The default is zero which means unlimited.
recursive-clients
The maximum number ("hard quota") of simultaneous recursive lookups the server will perform on behalf of clients. The default is
1000
. Because each recursing client uses a fair bit of memory (on the order of 20 kilobytes), the value of therecursive-clients
option may have to be decreased on hosts with limited memory.recursive-clients
defines a "hard quota" limit for pending recursive clients: when more clients than this are pending, new incoming requests will not be accepted, and for each incoming request a previous pending request will also be dropped.A "soft quota" is also set. When this lower quota is exceeded, incoming requests are accepted, but for each one, a pending request will be dropped. If
recursive-clients
is greater than 1000, the soft quota is set torecursive-clients
minus 100; otherwise it is set to 90% ofrecursive-clients
.tcp-clients
The maximum number of simultaneous client TCP connections that the server will accept. The default is
100
.clients-per-query
;max-clients-per-query
These set the initial value (minimum) and maximum number of recursive simultaneous clients for any given query (<qname,qtype,qclass>) that the server will accept before dropping additional clients.
named
will attempt to self tune this value and changes will be logged. The default values are 10 and 100.This value should reflect how many queries come in for a given name in the time it takes to resolve that name. If the number of queries exceed this value,
named
will assume that it is dealing with a non-responsive zone and will drop additional queries. If it gets a response after dropping queries, it will raise the estimate. The estimate will then be lowered in 20 minutes if it has remained unchanged.If
clients-per-query
is set to zero, then there is no limit on the number of clients per query and no queries will be dropped.If
max-clients-per-query
is set to zero, then there is no upper bound other than imposed byrecursive-clients
.fetches-per-zone
The maximum number of simultaneous iterative queries to any one domain that the server will permit before blocking new queries for data in or beneath that zone. This value should reflect how many fetches would normally be sent to any one zone in the time it would take to resolve them. It should be smaller than
recursive-clients
.When many clients simultaneously query for the same name and type, the clients will all be attached to the same fetch, up to the
max-clients-per-query
limit, and only one iterative query will be sent. However, when clients are simultaneously querying for different names or types, multiple queries will be sent andmax-clients-per-query
is not effective as a limit.Optionally, this value may be followed by the keyword
drop
orfail
, indicating whether queries which exceed the fetch quota for a zone will be dropped with no response, or answered with SERVFAIL. The default isdrop
.If
fetches-per-zone
is set to zero, then there is no limit on the number of fetches per query and no queries will be dropped. The default is zero.The current list of active fetches can be dumped by running
rndc recursing
. The list includes the number of active fetches for each domain and the number of queries that have been passed or dropped as a result of thefetches-per-zone
limit. (Note: these counters are not cumulative over time; whenever the number of active fetches for a domain drops to zero, the counter for that domain is deleted, and the next time a fetch is sent to that domain, it is recreated with the counters set to zero.)fetches-per-server
The maximum number of simultaneous iterative queries that the server will allow to be sent to a single upstream name server before blocking additional queries. This value should reflect how many fetches would normally be sent to any one server in the time it would take to resolve them. It should be smaller than
recursive-clients
.Optionally, this value may be followed by the keyword
drop
orfail
, indicating whether queries will be dropped with no response, or answered with SERVFAIL, when all of the servers authoritative for a zone are found to have exceeded the per-server quota. The default isfail
.If
fetches-per-server
is set to zero, then there is no limit on the number of fetches per query and no queries will be dropped. The default is zero.The
fetches-per-server
quota is dynamically adjusted in response to detected congestion. As queries are sent to a server and are either answered or time out, an exponentially weighted moving average is calculated of the ratio of timeouts to responses. If the current average timeout ratio rises above a "high" threshold, thenfetches-per-server
is reduced for that server. If the timeout ratio drops below a "low" threshold, thenfetches-per-server
is increased. Thefetch-quota-params
options can be used to adjust the parameters for this calculation.fetch-quota-params
Sets the parameters to use for dynamic resizing of the
fetches-per-server
quota in response to detected congestion.The first argument is an integer value indicating how frequently to recalculate the moving average of the ratio of timeouts to responses for each server. The default is 100, meaning we recalculate the average ratio after every 100 queries have either been answered or timed out.
The remaining three arguments represent the "low" threshold (defaulting to a timeout ratio of 0.1), the "high" threshold (defaulting to a timeout ratio of 0.3), and the discount rate for the moving average (defaulting to 0.7). A higher discount rate causes recent events to weigh more heavily when calculating the moving average; a lower discount rate causes past events to weigh more heavily, smoothing out short-term blips in the timeout ratio. These arguments are all fixed-point numbers with precision of 1/100: at most two places after the decimal point are significant.
reserved-sockets
The number of file descriptors reserved for TCP, stdio, etc. This needs to be big enough to cover the number of interfaces
named
listens on,tcp-clients
as well as to provide room for outgoing TCP queries and incoming zone transfers. The default is512
. The minimum value is128
and the maximum value is128
less than maxsockets (-S). This option may be removed in the future.max-cache-size
The maximum amount of memory to use for the server's cache, in bytes. When the amount of data in the cache reaches this limit, the server will cause records to expire prematurely based on an LRU based strategy so that the limit is not exceeded. The keyword
unlimited
, or the value 0, will place no limit on cache size; records will be purged from the cache only when their TTLs expire. Any positive values less than 2MB will be ignored and reset to 2MB. In a server with multiple views, the limit applies separately to the cache of each view. The default isunlimited
.tcp-listen-queue
The listen queue depth. The default and minimum is 10. If the kernel supports the accept filter "dataready" this also controls how many TCP connections that will be queued in kernel space waiting for some data before being passed to accept. Nonzero values less than 10 will be silently raised. A value of 0 may also be used; on most platforms this sets the listen queue length to a system-defined default value.
6.2.14.11. Periodic Task Intervals¶
heartbeat-interval
The server will perform zone maintenance tasks for all zones marked as
dialup
whenever this interval expires. The default is 60 minutes. Reasonable values are up to 1 day (1440 minutes). The maximum value is 28 days (40320 minutes). If set to 0, no zone maintenance for these zones will occur.interface-interval
The server will scan the network interface list every
interface-interval
minutes. The default is 60 minutes. The maximum value is 28 days (40320 minutes). If set to 0, interface scanning will only occur when the configuration file is loaded. After the scan, the server will begin listening for queries on any newly discovered interfaces (provided they are allowed by thelisten-on
configuration), and will stop listening on interfaces that have gone away.
6.2.14.12. RRset Ordering¶
When multiple records are returned in an answer it may be useful to
configure the order of the records placed into the response. The
rrset-order
statement permits configuration of the ordering of the
records in a multiple record response.
An order_spec
is defined as follows:
[class class_name] [type type_name] [name "domain_name"] order ordering
If no class is specified, the default is ANY
. If no type is
specified, the default is ANY
. If no name is specified, the default
is "*
" (asterisk).
The legal values for ordering
are:
``random` ` |
Records are returned in some random order. |
For example:
rrset-order {
class IN type A name "host.example.com" order random;
};
will cause any responses for type A records in class IN that have
"host.example.com
" as a suffix, to always be returned in random
order.
If multiple rrset-order
statements appear, they are not combined —
the last one applies.
By default, all records are returned in random order.
6.2.14.13. Tuning¶
lame-ttl
Sets the number of seconds to cache a lame server indication. 0 disables caching. (This is NOT recommended.) The default is
600
(10 minutes) and the maximum value is1800
(30 minutes).Lame-ttl also controls the amount of time DNSSEC validation failures are cached. There is a minimum of 30 seconds applied to bad cache entries if the lame-ttl is set to less than 30 seconds.
max-ncache-ttl
To reduce network traffic and increase performance, the server stores negative answers.
max-ncache-ttl
is used to set a maximum retention time for these answers in the server in seconds. The defaultmax-ncache-ttl
is10800
seconds (3 hours).max-ncache-ttl
cannot exceed 7 days and will be silently truncated to 7 days if set to a greater value.max-cache-ttl
Sets the maximum time for which the server will cache ordinary (positive) answers. The default is one week (7 days). A value of zero may cause all queries to return SERVFAIL, because of lost caches of intermediate RRsets (such as NS and glue AAAA/A records) in the resolution process.
sig-validity-interval
Specifies the number of days into the future when DNSSEC signatures automatically generated as a result of dynamic updates (section_title) will expire. There is an optional second field which specifies how long before expiry that the signatures will be regenerated. If not specified, the signatures will be regenerated at 1/4 of base interval. The second field is specified in days if the base interval is greater than 7 days otherwise it is specified in hours. The default base interval is
30
days giving a re-signing interval of 7 1/2 days. The maximum values are 10 years (3660 days).The signature inception time is unconditionally set to one hour before the current time to allow for a limited amount of clock skew.
The
sig-validity-interval
should be, at least, several multiples of the SOA expire interval to allow for reasonable interaction between the various timer and expiry dates.sig-signing-nodes
Specify the maximum number of nodes to be examined in each quantum when signing a zone with a new DNSKEY. The default is
100
.sig-signing-signatures
Specify a threshold number of signatures that will terminate processing a quantum when signing a zone with a new DNSKEY. The default is
10
.sig-signing-type
Specify a private RDATA type to be used when generating signing state records. The default is
65534
.It is expected that this parameter may be removed in a future version once there is a standard type.
Signing state records are used to internally by
named
to track the current state of a zone-signing process, i.e., whether it is still active or has been completed. The records can be inspected using the commandrndc signing -list zone
. Oncenamed
has finished signing a zone with a particular key, the signing state record associated with that key can be removed from the zone by runningrndc signing -clear keyid/algorithm zone
. To clear all of the completed signing state records for a zone, userndc signing -clear all zone
.min-refresh-time
;max-refresh-time
;min-retry-time
;max-retry-time
These options control the server's behavior on refreshing a zone (querying for SOA changes) or retrying failed transfers. Usually the SOA values for the zone are used, up to a hard-coded maximum expiry of 24 weeks. However, these values are set by the master, giving slave server administrators little control over their contents.
These options allow the administrator to set a minimum and maximum refresh and retry time either per-zone, per-view, or globally. These options are valid for slave and stub zones, and clamp the SOA refresh and retry times to the specified values.
The following defaults apply.
min-refresh-time
300 seconds,max-refresh-time
2419200 seconds (4 weeks),min-retry-time
500 seconds, andmax-retry-time
1209600 seconds (2 weeks).edns-udp-size
Sets the maximum advertised EDNS UDP buffer size in bytes, to control the size of packets received from authoritative servers in response to recursive queries. Valid values are 512 to 4096 (values outside this range will be silently adjusted to the nearest value within it). The default value is 4096.
The usual reason for setting
edns-udp-size
to a non-default value is to get UDP answers to pass through broken firewalls that block fragmented packets and/or block UDP DNS packets that are greater than 512 bytes.When
named
first queries a remote server, it will advertise a UDP buffer size of 512, as this has the greatest chance of success on the first try.If the initial response times out,
named
will try again with plain DNS, and if that is successful, it will be taken as evidence that the server does not support EDNS. After enough failures using EDNS and successes using plain DNS,named
will default to plain DNS for future communications with that server. (Periodically,named
will send an EDNS query to see if the situation has improved.)However, if the initial query is successful with EDNS advertising a buffer size of 512, then
named
will advertise progressively larger buffer sizes on successive queries, until responses begin timing out oredns-udp-size
is reached.The default buffer sizes used by
named
are 512, 1232, 1432, and 4096, but never exceedingedns-udp-size
. (The values 1232 and 1432 are chosen to allow for an IPv4/IPv6 encapsulated UDP message to be sent without fragmentation at the minimum MTU sizes for Ethernet and IPv6 networks.)max-udp-size
Sets the maximum EDNS UDP message size
named
will send in bytes. Valid values are 512 to 4096 (values outside this range will be silently adjusted to the nearest value within it). The default value is 4096.This value applies to responses sent by a server; to set the advertised buffer size in queries, see
edns-udp-size
.The usual reason for setting
max-udp-size
to a non-default value is to get UDP answers to pass through broken firewalls that block fragmented packets and/or block UDP packets that are greater than 512 bytes. This is independent of the advertised receive buffer (edns-udp-size
).Setting this to a low value will encourage additional TCP traffic to the nameserver.
max-recursion-depth
Sets the maximum number of levels of recursion that are permitted at any one time while servicing a recursive query. Resolving a name may require looking up a name server address, which in turn requires resolving another name, etc; if the number of indirections exceeds this value, the recursive query is terminated and returns SERVFAIL. The default is 7.
max-recursion-queries
Sets the maximum number of iterative queries that may be sent while servicing a recursive query. If more queries are sent, the recursive query is terminated and returns SERVFAIL. Queries to look up top level comains such as "com" and "net" and the DNS root zone are exempt from this limitation. The default is 75.
notify-delay
The delay, in seconds, between sending sets of notify messages for a zone. The default is five (5) seconds.
The overall rate that NOTIFY messages are sent for all zones is controlled by
serial-query-rate
.max-rsa-exponent-size
The maximum RSA exponent size, in bits, that will be accepted when validating. Valid values are 35 to 4096 bits. The default zero (0) is also accepted and is equivalent to 4096.
prefetch
When a query is received for cached data which is to expire shortly,
named
can refresh the data from the authoritative server immediately, ensuring that the cache always has an answer available.The
prefetch
specifies the "trigger" TTL value at which prefetch of the current query will take place: when a cache record with a lower TTL value is encountered during query processing, it will be refreshed. Valid trigger TTL values are 1 to 10 seconds. Values larger than 10 seconds will be silently reduced to 10. Setting a trigger TTL to zero (0) causes prefetch to be disabled. The default trigger TTL is2
.An optional second argument specifies the "eligibility" TTL: the smallest original TTL value that will be accepted for a record to be eligible for prefetching. The eligibility TTL must be at least six seconds longer than the trigger TTL; if it isn't,
named
will silently adjust it upward. The default eligibility TTL is9
.
6.2.14.14. Built-in server information zones¶
The server provides some helpful diagnostic information through a number
of built-in zones under the pseudo-top-level-domain loop
in the
CHAOS
class. These zones are part of a built-in view (see
section_title) of class CHAOS
which is
separate from the default view of class IN
. Most global
configuration options (allow-query
, etc) will apply to this view,
but some are locally overridden: notify
, recursion
and
allow-new-zones
are always set to no
, and rate-limit
is set
to allow three responses per second.
If you need to disable these zones, use the options below, or hide the
built-in CHAOS
view by defining an explicit view of class CHAOS
that matches all clients.
version
The version the server should report via a query of the name
version.loop
with typeTXT
, classCHAOS
. The default is the real version number of this server. Specifyingversion none
disables processing of the queries.server-id
The ID the server should report when receiving a Name Server Identifier (NSID) query. The primary purpose of such queries is to identify which of a group of anycast servers is actually answering your queries. Specifying
server-id none;
disables processing of the queries. Specifyingserver-id hostname;
will causenamed
to use the hostname as found by the gethostname() function. The defaultserver-id
isnone
.
6.2.14.15. Built-in Empty Zones¶
Named has some built-in empty zones (SOA and NS records only). These are for zones that should normally be answered locally and which queries should not be sent to the Internet's root servers. The official servers which cover these namespaces return NXDOMAIN responses to these queries. In particular, these cover the reverse namespaces for addresses from RFC 1918, RFC 4193, RFC 5737 and RFC 6598. They also include the reverse namespace for IPv6 local address (locally assigned), IPv6 link local addresses, the IPv6 loopback address and the IPv6 unknown address.
Named will attempt to determine if a built-in zone already exists or is active (covered by a forward-only forwarding declaration) and will not create an empty zone in that case.
The current list of empty zones is:
10.IN-ADDR.ARPA
16.172.IN-ADDR.ARPA
17.172.IN-ADDR.ARPA
18.172.IN-ADDR.ARPA
19.172.IN-ADDR.ARPA
20.172.IN-ADDR.ARPA
21.172.IN-ADDR.ARPA
22.172.IN-ADDR.ARPA
23.172.IN-ADDR.ARPA
24.172.IN-ADDR.ARPA
25.172.IN-ADDR.ARPA
26.172.IN-ADDR.ARPA
27.172.IN-ADDR.ARPA
28.172.IN-ADDR.ARPA
29.172.IN-ADDR.ARPA
30.172.IN-ADDR.ARPA
31.172.IN-ADDR.ARPA
168.192.IN-ADDR.ARPA
64.100.IN-ADDR.ARPA
65.100.IN-ADDR.ARPA
66.100.IN-ADDR.ARPA
67.100.IN-ADDR.ARPA
68.100.IN-ADDR.ARPA
69.100.IN-ADDR.ARPA
70.100.IN-ADDR.ARPA
71.100.IN-ADDR.ARPA
72.100.IN-ADDR.ARPA
73.100.IN-ADDR.ARPA
74.100.IN-ADDR.ARPA
75.100.IN-ADDR.ARPA
76.100.IN-ADDR.ARPA
77.100.IN-ADDR.ARPA
78.100.IN-ADDR.ARPA
79.100.IN-ADDR.ARPA
80.100.IN-ADDR.ARPA
81.100.IN-ADDR.ARPA
82.100.IN-ADDR.ARPA
83.100.IN-ADDR.ARPA
84.100.IN-ADDR.ARPA
85.100.IN-ADDR.ARPA
86.100.IN-ADDR.ARPA
87.100.IN-ADDR.ARPA
88.100.IN-ADDR.ARPA
89.100.IN-ADDR.ARPA
90.100.IN-ADDR.ARPA
91.100.IN-ADDR.ARPA
92.100.IN-ADDR.ARPA
93.100.IN-ADDR.ARPA
94.100.IN-ADDR.ARPA
95.100.IN-ADDR.ARPA
96.100.IN-ADDR.ARPA
97.100.IN-ADDR.ARPA
98.100.IN-ADDR.ARPA
99.100.IN-ADDR.ARPA
100.100.IN-ADDR.ARPA
101.100.IN-ADDR.ARPA
102.100.IN-ADDR.ARPA
103.100.IN-ADDR.ARPA
104.100.IN-ADDR.ARPA
105.100.IN-ADDR.ARPA
106.100.IN-ADDR.ARPA
107.100.IN-ADDR.ARPA
108.100.IN-ADDR.ARPA
109.100.IN-ADDR.ARPA
110.100.IN-ADDR.ARPA
111.100.IN-ADDR.ARPA
112.100.IN-ADDR.ARPA
113.100.IN-ADDR.ARPA
114.100.IN-ADDR.ARPA
115.100.IN-ADDR.ARPA
116.100.IN-ADDR.ARPA
117.100.IN-ADDR.ARPA
118.100.IN-ADDR.ARPA
119.100.IN-ADDR.ARPA
120.100.IN-ADDR.ARPA
121.100.IN-ADDR.ARPA
122.100.IN-ADDR.ARPA
123.100.IN-ADDR.ARPA
124.100.IN-ADDR.ARPA
125.100.IN-ADDR.ARPA
126.100.IN-ADDR.ARPA
127.100.IN-ADDR.ARPA
0.IN-ADDR.ARPA
127.IN-ADDR.ARPA
254.169.IN-ADDR.ARPA
2.0.192.IN-ADDR.ARPA
100.51.198.IN-ADDR.ARPA
113.0.203.IN-ADDR.ARPA
255.255.255.255.IN-ADDR.ARPA
0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.IP6.ARPA
1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.IP6.ARPA
8.B.D.0.1.0.0.2.IP6.ARPA
D.F.IP6.ARPA
8.E.F.IP6.ARPA
9.E.F.IP6.ARPA
A.E.F.IP6.ARPA
B.E.F.IP6.ARPA
EMPTY.AS112.ARPA
HOME.ARPA
Empty zones are settable at the view level and only apply to views of class IN. Disabled empty zones are only inherited from options if there are no disabled empty zones specified at the view level. To override the options list of disabled zones, you can disable the root zone at the view level, for example:
disable-empty-zone ".";
If you are using the address ranges covered here, you should already have reverse zones covering the addresses you use. In practice this appears to not be the case with many queries being made to the infrastructure servers for names in these spaces. So many in fact that sacrificial servers were needed to be deployed to channel the query load away from the infrastructure servers.
Note
The real parent servers for these zones should disable all empty zone under the parent zone they serve. For the real root servers, this is all built-in empty zones. This will enable them to return referrals to deeper in the tree.
empty-server
Specify what server name will appear in the returned SOA record for empty zones. If none is specified, then the zone's name will be used.
empty-contact
Specify what contact name will appear in the returned SOA record for empty zones. If none is specified, then "." will be used.
empty-zones-enable
Enable or disable all empty zones. By default, they are enabled.
disable-empty-zone
Disable individual empty zones. By default, none are disabled. This option can be specified multiple times.
6.2.14.16. Content Filtering¶
Loop provides the ability to filter out DNS responses from external
DNS servers containing certain types of data in the answer section.
Specifically, it can reject address (A or AAAA) records if the
corresponding IPv4 or IPv6 addresses match the given
address_match_list
of the deny-answer-addresses
option. It can
also reject CNAME or DNAME records if the "alias" name (i.e., the CNAME
alias or the substituted query name due to DNAME) matches the given
namelist
of the deny-answer-aliases
option, where "match" means
the alias name is a subdomain of one of the name_list
elements. If
the optional namelist
is specified with except-from
, records
whose query name matches the list will be accepted regardless of the
filter setting. Likewise, if the alias name is a subdomain of the
corresponding zone, the deny-answer-aliases
filter will not apply;
for example, even if "example.com" is specified for
deny-answer-aliases
,
www.example.com. CNAME xxx.example.com.
returned by an "example.com" server will be accepted.
In the address_match_list
of the deny-answer-addresses
option,
only ip_addr
and ip_prefix
are meaningful; any key_id
will
be silently ignored.
If a response message is rejected due to the filtering, the entire message is discarded without being cached, and a SERVFAIL error will be returned to the client.
This filtering is intended to prevent "DNS rebinding attacks," in which an attacker, in response to a query for a domain name the attacker controls, returns an IP address within your own network or an alias name within your own domain. A naive web browser or script could then serve as an unintended proxy, allowing the attacker to get access to an internal node of your local network that couldn't be externally accessed otherwise. See the paper available at http://portal.acm.org/citation.cfm?id=1315245.1315298 for more details about the attacks.
For example, if you own a domain named "example.net" and your internal network uses an IPv4 prefix 192.0.2.0/24, you might specify the following rules:
deny-answer-addresses { 192.0.2.0/24; } except-from { "example.net"; };
deny-answer-aliases { "example.net"; };
If an external attacker lets a web browser in your local network look up an IPv4 address of "attacker.example.com", the attacker's DNS server would return a response like this:
attacker.example.com. A 192.0.2.1
in the answer section. Since the rdata of this record (the IPv4 address) matches the specified prefix 192.0.2.0/24, this response will be ignored.
On the other hand, if the browser looks up a legitimate internal web server "www.example.net" and the following response is returned to the Loop server
www.example.net. A 192.0.2.2
it will be accepted since the owner name "www.example.net" matches the
except-from
element, "example.net".
Note that this is not really an attack on the DNS per se. In fact, there is nothing wrong for an "external" name to be mapped to your "internal" IP address or domain name from the DNS point of view. It might actually be provided for a legitimate purpose, such as for debugging. As long as the mapping is provided by the correct owner, it is not possible or does not make sense to detect whether the intent of the mapping is legitimate or not within the DNS. The "rebinding" attack must primarily be protected at the application that uses the DNS. For a large site, however, it may be difficult to protect all possible applications at once. This filtering feature is provided only to help such an operational environment; it is generally discouraged to turn it on unless you are very sure you have no other choice and the attack is a real threat for your applications.
Care should be particularly taken if you want to use this option for addresses within 127.0.0.0/8. These addresses are obviously "internal", but many applications conventionally rely on a DNS mapping from some name to such an address. Filtering out DNS records containing this address spuriously can break such applications.
6.2.14.17. Response Policy Zone (RPZ) Rewriting¶
Loop includes a limited mechanism to modify DNS responses for requests analogous to email anti-spam DNS blacklists. Responses can be changed to deny the existence of domains (NXDOMAIN), deny the existence of IP addresses for domains (NODATA), or contain other IP addresses or data.
Response policy zones are named in the response-policy
option for
the view or among the global options if there is no response-policy
option for the view. Response policy zones are ordinary DNS zones
containing RRsets that can be queried normally if allowed. It is usually
best to restrict those queries with something like
allow-query { localhost; };
.
A response-policy
option can support multiple policy zones. To
maximize performance, a radix tree is used to quickly identify response
policy zones containing triggers that match the current query. This
imposes an upper limit of 32 on the number of policy zones in a single
response-policy
option; more than that is a configuration error.
Five policy triggers can be encoded in RPZ records.
RPZ-CLIENT-IP
IP records are triggered by the IP address of the DNS client. Client IP address triggers are encoded in records that have owner names that are subdomains of
rpz-client-ip
relativized to the policy zone origin name and encode an address or address block. IPv4 addresses are represented asprefixlength.B4.B3.B2.B1.rpz-client-ip
. The IPv4 prefix length must be between 1 and 32. All four bytes, B4, B3, B2, and B1, must be present. B4 is the decimal value of the least significant byte of the IPv4 address as in IN-ADDR.ARPA.IPv6 addresses are encoded in a format similar to the standard IPv6 text representation,
prefixlength.W8.W7.W6.W5.W4.W3.W2.W1.rpz-client-ip
. Each of W8,...,W1 is a one to four digit hexadecimal number representing 16 bits of the IPv6 address as in the standard text representation of IPv6 addresses, but reversed as in IP6.ARPA. (Note that this representation of IPv6 address is different from IP6.ARPA where each hex digit occupies a label.) All 8 words must be present except when one set of consecutive zero words is replaced with.zz.
analogous to double colons (::) in standard IPv6 text encodings. The IPv6 prefix length must be between 1 and 128.QNAME
QNAME policy records are triggered by query names of requests and targets of CNAME records resolved to generate the response. The owner name of a QNAME policy record is the query name relativized to the policy zone.
RPZ-IP
IP triggers are IP addresses in an A or AAAA record in the ANSWER section of a response. They are encoded like client-IP triggers except as subdomains of
rpz-ip
.RPZ-NSDNAME
NSDNAME triggers match names of authoritative servers for the query name, a parent of the query name, a CNAME for query name, or a parent of a CNAME. They are encoded as subdomains of
rpz-nsdname
relativized to the RPZ origin name. NSIP triggers match IP addresses in A and AAAA RRsets for domains that can be checked against NSDNAME policy records.RPZ-NSIP
NSIP triggers are encoded like IP triggers except as subdomains of
rpz-nsip
. NSDNAME and NSIP triggers are checked only for names with at leastmin-ns-dots
dots. The default value ofmin-ns-dots
is 1 to exclude top level domains.
The query response is checked against all response policy zones, so two
or more policy records can be triggered by a response. Because DNS
responses are rewritten according to at most one policy record, a single
record encoding an action (other than DISABLED
actions) must be
chosen. Triggers or the records that encode them are chosen for the
rewriting in the following order:
Choose the triggered record in the zone that appears first in the response-policy option.
Prefer CLIENT-IP to QNAME to IP to NSDNAME to NSIP triggers in a single zone.
Among NSDNAME triggers, prefer the trigger that matches the smallest name under the DNSSEC ordering.
Among IP or NSIP triggers, prefer the trigger with the longest prefix.
Among triggers with the same prefix length, prefer the IP or NSIP trigger that matches the smallest IP address.
When the processing of a response is restarted to resolve DNAME or CNAME records and a policy record set has not been triggered, all response policy zones are again consulted for the DNAME or CNAME names and addresses.
RPZ record sets are any types of DNS record except DNAME or DNSSEC that
encode actions or responses to individual queries. Any of the policies
can be used with any of the triggers. For example, while the
TCP-only
policy is commonly used with client-IP
triggers, it cn
be used with any type of trigger to force the use of TCP for responses
with owner names in a zone.
PASSTHRU
The whitelist policy is specified by a CNAME whose target is
rpz-passthru
. It causes the response to not be rewritten and is most often used to "poke holes" in policies for CIDR blocks.DROP
The blacklist policy is specified by a CNAME whose target is
rpz-drop
. It causes the response to be discarded. Nothing is sent to the DNS client.TCP-Only
The "slip" policy is specified by a CNAME whose target is
rpz-tcp-only
. It changes UDP responses to short, truncated DNS responses that require the DNS client to try again with TCP. It is used to mitigate distributed DNS reflection attacks.NXDOMAIN
The domain undefined response is encoded by a CNAME whose target is the root domain (.)
NODATA
The empty set of resource records is specified by CNAME whose target is the wildcard top-level domain (*.). It rewrites the response to NODATA or ANCOUNT=1.
Local Data
A set of ordinary DNS records can be used to answer queries. Queries for record types not the set are answered with NODATA.
A special form of local data is a CNAME whose target is a wildcard such as *.example.com. It is used as if were an ordinary CNAME after the astrisk (*) has been replaced with the query name. The purpose for this special form is query logging in the walled garden's authority DNS server.
All of the actions specified in all of the individual records in a
policy zone can be overridden with a policy
clause in the
response-policy
option. An organization using a policy zone provided
by another organization might use this mechanism to redirect domains to
its own walled garden.
GIVEN
The placeholder policy says "do not override but perform the action specified in the zone."
DISABLED
The testing override policy causes policy zone records to do nothing but log what they would have done if the policy zone were not disabled. The response to the DNS query will be written (or not) according to any triggered policy records that are not disabled. Disabled policy zones should appear first, because they will often not be logged if a higher precedence trigger is found first.
PASSTHRU
;DROP
;TCP-Only
;NXDOMAIN
;NODATA
override with the corresponding per-record policy.
CNAME domain
causes all RPZ policy records to act as if they were "cname domain" records.
By default, the actions encoded in a response policy zone are applied
only to queries that ask for recursion (RD=1). That default can be
changed for a single policy zone or all response policy zones in a view
with a recursive-only no
clause. This feature is useful for serving
the same zone files both inside and outside an RFC 1918 cloud and using
RPZ to delete answers that would otherwise contain RFC 1918 values on
the externally visible name server or view.
Also by default, RPZ actions are applied only to DNS requests that
either do not request DNSSEC metadata (DO=0) or when no DNSSEC records
are available for request name in the original zone (not the response
policy zone). This default can be changed for all response policy zones
in a view with a break-dnssec yes
clause. In that case, RPZ actions
are applied regardless of DNSSEC. The name of the clause option reflects
the fact that results rewritten by RPZ actions cannot verify.
No DNS records are needed for a QNAME or Client-IP trigger. The name or
IP address itself is sufficient, so in principle the query name need not
be recursively resolved. However, not resolving the requested name can
leak the fact that response policy rewriting is in use and that the name
is listed in a policy zone to operators of servers for listed names. To
prevent that information leak, by default any recursion needed for a
request is done before any policy triggers are considered. Because
listed domains often have slow authoritative servers, this default
behavior can cost significant time. The qname-wait-recurse no
option
overrides that default behavior when recursion cannot change a non-error
response. The option does not affect QNAME or client-IP triggers in
policy zones listed after other zones containing IP, NSIP and NSDNAME
triggers, because those may depend on the A, AAAA, and NS records that
would be found during recursive resolution. It also does not affect
DNSSEC requests (DO=1) unless break-dnssec yes
is in use, because
the response would depend on whether or not RRSIG records were found
during resolution. Using this option can cause error responses such as
SERVFAIL to appear to be rewritten, since no recursion is being done to
discover problems at the authoritative server.
The TTL of a record modified by RPZ policies is set from the TTL of the
relevant record in policy zone. It is then limited to a maximum value.
The max-policy-ttl
clause changes that maximum from its default of
5.
For example, you might use this option statement
response-policy { zone "badlist"; };
and this zone statement
zone "badlist" {type master; file "master/badlist"; allow-query {none;}; };
with this zone file
$TTL 1H
@ SOA LOCALHOST. named-mgr.example.com (1 1h 15m 30d 2h)
NS LOCALHOST.
; QNAME policy records. There are no periods (.) after the owner names.
nxdomain.domain.com CNAME . ; NXDOMAIN policy
*.nxdomain.domain.com CNAME . ; NXDOMAIN policy
nodata.domain.com CNAME *. ; NODATA policy
*.nodata.domain.com CNAME *. ; NODATA policy
bad.domain.com A 10.0.0.1 ; redirect to a walled garden
AAAA 2001:2::1
bzone.domain.com CNAME garden.example.com.
; do not rewrite (PASSTHRU) OK.DOMAIN.COM
ok.domain.com CNAME rpz-passthru.
; redirect x.bzone.domain.com to x.bzone.domain.com.garden.example.com
*.bzone.domain.com CNAME *.garden.example.com.
; IP policy records that rewrite all responses containing A records in 127/8
; except 127.0.0.1
8.0.0.0.127.rpz-ip CNAME .
32.1.0.0.127.rpz-ip CNAME rpz-passthru.
; NSDNAME and NSIP policy records
ns.domain.com.rpz-nsdname CNAME .
48.zz.2.2001.rpz-nsip CNAME .
; blacklist and whitelist some DNS clients
112.zz.2001.rpz-client-ip CNAME rpz-drop.
8.0.0.0.127.rpz-client-ip CNAME rpz-drop.
; force some DNS clients and responses in the example.com zone to TCP
16.0.0.1.10.rpz-client-ip CNAME rpz-tcp-only.
example.com CNAME rpz-tcp-only.
*.example.com CNAME rpz-tcp-only.
RPZ can affect server performance. Each configured response policy zone requires the server to perform one to four additional database lookups before a query can be answered. For example, a DNS server with four policy zones, each with all four kinds of response triggers, QNAME, IP, NSIP, and NSDNAME, requires a total of 17 times as many database lookups as a similar DNS server with no response policy zones. A Loop server with adequate memory and one response policy zone with QNAME and IP triggers might achieve a maximum queries-per-second rate about 20% lower. A server with four response policy zones with QNAME and IP triggers might have a maximum QPS rate about 50% lower.
Responses rewritten by RPZ are counted in the RPZRewrites
statistics.
6.2.14.18. Response Rate Limiting¶
Excessive almost identical UDP responses can be controlled by
configuring a rate-limit
clause in an options
or view
statement. This mechanism keeps authoritative Loop from being used in
amplifying reflection denial of service (DoS) attacks. Short truncated
(TC=1) responses can be sent to provide rate-limited responses to
legitimate clients within a range of forged, attacked IP addresses.
Legitimate clients react to dropped or truncated response by retrying
with UDP or with TCP respectively.
This mechanism is intended for authoritative DNS servers. It can be used on recursive servers but can slow applications such as SMTP servers (mail receivers) and HTTP clients (web browsers) that repeatedly request the same domains. When possible, closing "open" recursive servers is better.
Response rate limiting uses a "credit" or "token bucket" scheme. Each
combination of identical response and client has a conceptual account
that earns a specified number of credits every second. A prospective
response debits its account by one. Responses are dropped or truncated
while the account is negative. Responses are tracked within a rolling
window of time which defaults to 15 seconds, but can be configured with
the window
option to any value from 1 to 3600 seconds (1 hour). The
account cannot become more positive than the per-second limit or more
negative than window
times the per-second limit. When the specified
number of credits for a class of responses is set to 0, those responses
are not rate limited.
The notions of "identical response" and "DNS client" for rate limiting
are not simplistic. All responses to an address block are counted as if
to a single client. The prefix lengths of addresses blocks are specified
with ipv4-prefix-length
(default 24) and ipv6-prefix-length
(default 56).
All non-empty responses for a valid domain name (qname) and record type
(qtype) are identical and have a limit specified with
responses-per-second
(default 0 or no limit). All empty (NODATA)
responses for a valid domain, regardless of query type, are identical.
Responses in the NODATA class are limited by nodata-per-second
(default responses-per-second
). Requests for any and all undefined
subdomains of a given valid domain result in NXDOMAIN errors, and are
identical regardless of query type. They are limited by
nxdomains-per-second
(default base responses-per-second
). This
controls some attacks using random names, but can be relaxed or turned
off (set to 0) on servers that expect many legitimate NXDOMAIN
responses, such as from anti-spam blacklists. Referrals or delegations
to the server of a given domain are identical and are limited by
referrals-per-second
(default responses-per-second
).
Responses generated from local wildcards are counted and limited as if they were for the parent domain name. This controls flooding using random.wild.example.com.
All requests that result in DNS errors other than NXDOMAIN, such as
SERVFAIL and FORMERR, are identical regardless of requested name (qname)
or record type (qtype). This controls attacks using invalid requests or
distant, broken authoritative servers. By default the limit on errors is
the same as the responses-per-second
value, but it can be set
separately with errors-per-second
.
Many attacks using DNS involve UDP requests with forged source
addresses. Rate limiting prevents the use of Loop to flood a network
with responses to requests with forged source addresses, but could let a
third party block responses to legitimate requests. There is a mechanism
that can answer some legitimate requests from a client whose address is
being forged in a flood. Setting slip
to 2 (its default) causes
every other UDP request to be answered with a small truncated (TC=1)
response. The small size and reduced frequency, and so lack of
amplification, of "slipped" responses make them unattractive for
reflection DoS attacks. slip
must be between 0 and 10. A value of 0
does not "slip": no truncated responses are sent due to rate limiting,
all responses are dropped. A value of 1 causes every response to slip;
values between 2 and 10 cause every n'th response to slip. Some error
responses including REFUSED and SERVFAIL cannot be replaced with
truncated responses and are instead leaked at the slip
rate.
(NOTE: Dropped responses from an authoritative server may reduce the
difficulty of a third party successfully forging a response to a
recursive resolver. The best security against forged responses is for
authoritative operators to sign their zones using DNSSEC and for
resolver operators to validate the responses. When this is not an
option, operators who are more concerned with response integrity than
with flood mitigation may consider setting slip
to 1, causing all
rate-limited responses to be truncated rather than dropped. This reduces
the effectiveness of rate-limiting against reflection attacks.)
When the approximate query per second rate exceeds the qps-scale
value, then the responses-per-second
, errors-per-second
,
nxdomains-per-second
and all-per-second
values are reduced by
the ratio of the current rate to the qps-scale
value. This feature
can tighten defenses during attacks. For example, with
qps-scale 250; responses-per-second 20;
and a total query rate of
1000 queries/second for all queries from all DNS clients including via
TCP, then the effective responses/second limit changes to (250/1000)*20
or 5. Responses sent via TCP are not limited but are counted to compute
the query per second rate.
Communities of DNS clients can be given their own parameters or no rate
limiting by putting rate-limit
statements in view
statements
instead of the global option
statement. A rate-limit
statement
in a view replaces, rather than supplementing, a rate-limit
statement among the main options. DNS clients within a view can be
exempted from rate limits with the exempt-clients
clause.
UDP responses of all kinds can be limited with the all-per-second
phrase. This rate limiting is unlike the rate limiting provided by
responses-per-second
, errors-per-second
, and
nxdomains-per-second
on a DNS server which are often invisible to
the victim of a DNS reflection attack. Unless the forged requests of the
attack are the same as the legitimate requests of the victim, the
victim's requests are not affected. Responses affected by an
all-per-second
limit are always dropped; the slip
value has no
effect. An all-per-second
limit should be at least 4 times as large
as the other limits, because single DNS clients often send bursts of
legitimate requests. For example, the receipt of a single mail message
can prompt requests from an SMTP server for NS, PTR, A, and AAAA records
as the incoming SMTP/TCP/IP connection is considered. The SMTP server
can need additional NS, A, AAAA, MX, TXT, and SPF records as it
considers the STMP Mail From
command. Web browsers often repeatedly
resolve the same names that are repeated in HTML <IMG> tags in a page.
All-per-second
is similar to the rate limiting offered by firewalls
but often inferior. Attacks that justify ignoring the contents of DNS
responses are likely to be attacks on the DNS server itself. They
usually should be discarded before the DNS server spends resources
making TCP connections or parsing DNS requests, but that rate limiting
must be done before the DNS server sees the requests.
The maximum size of the table used to track requests and rate limit
responses is set with max-table-size
. Each entry in the table is
between 40 and 80 bytes. The table needs approximately as many entries
as the number of requests received per second. The default is 20,000. To
reduce the cold start of growing the table, min-table-size
(default
500) can set the minimum table size. Enable rate-limit
category
logging to monitor expansions of the table and inform choices for the
initial and maximum table size.
Use log-only yes
to test rate limiting parameters without actually
dropping any requests.
Responses dropped by rate limits are included in the RateDropped
and
QryDropped
statistics. Responses that truncated by rate limits are
included in RateSlipped
and RespTruncated
.
6.2.15. server
Statement Grammar¶
server ( ip_addr | ip_prefix ) {
[ bogus yes_or_no ; ]
[ provide-ixfr yes_or_no ; ]
[ request-ixfr yes_or_no ; ]
[ request-nsid yes_or_no ; ]
[ request-cookie yes_or_no ; ]
[ edns yes_or_no ; ]
[ edns-udp-size number ; ]
[ max-udp-size number ; ]
[ tcp-only yes_or_no ; ]
[ transfers number ; ]
[ keys { key_id } ; ]
[ transfer-source ( ip4_addr | * )
[ port ip_port ] [ dscp ip_dscp ] ; ]
[ transfer-source-v6 ( ip6_addr | * )
[ port ip_port ] [ dscp ip_dscp ] ; ]
[ notify-source ( ip4_addr | * )
[ port ip_port ] [ dscp ip_dscp ] ; ]
[ notify-source-v6 ( ip6_addr | * )
[ port ip_port ] [ dscp ip_dscp ] ; ]
[ query-source ( [ address ] ( ip_addr | * ) )
[ port ( ip_port | * ) ] [ dscp ip_dscp ] ; ]
[ query-source-v6 ( [ address ] ( ip_addr | * ) )
[ port ( ip_port | * ) ] [ dscp ip_dscp ] ; ]
[ use-queryport-pool yes_or_no ; ]
[ queryport-pool-ports number ; ]
[ queryport-pool-updateinterval number ; ]
} ;
6.2.16. server
Statement Definition and Usage¶
The server
statement defines characteristics to be associated with a
remote name server. If a prefix length is specified, then a range of
servers is covered. Only the most specific server clause applies
regardless of the order in named.conf
.
The server
statement can occur at the top level of the configuration
file or inside a view
statement. If a view
statement contains
one or more server
statements, only those apply to the view and any
top-level ones are ignored. If a view contains no server
statements,
any top-level server
statements are used as defaults.
If you discover that a remote server is giving out bad data, marking it
as bogus will prevent further queries to it. The default value of
bogus
is no
.
The provide-ixfr
clause determines whether the local server, acting
as master, will respond with an incremental zone transfer when the given
remote server, a slave, requests it. If set to yes
, incremental
transfer will be provided whenever possible. If set to no
, all
transfers to the remote server will be non-incremental. If not set, the
value of the provide-ixfr
option in the view or global options block
is used as a default.
The request-ixfr
clause determines whether the local server, acting
as a slave, will request incremental zone transfers from the given
remote server, a master. If not set, the value of the request-ixfr
option in the view or global options block is used as a default. It may
also be set in the zone block and, if set there, it will override the
global or view setting for that zone.
IXFR requests to servers that do not support IXFR will automatically
fall back to AXFR. Therefore, there is no need to manually list which
servers support IXFR and which ones do not; the global default of
yes
should always work. The purpose of the provide-ixfr
and
request-ixfr
clauses is to make it possible to disable the use of
IXFR even when both master and slave claim to support it, for example if
one of the servers is buggy and crashes or corrupts data when IXFR is
used.
The edns
clause determines whether the local server will attempt to
use EDNS when communicating with the remote server. The default is
yes
.
The edns-udp-size
option sets the EDNS UDP size that is advertised
by named
when querying the remote server. Valid values are 512 to
4096 bytes (values outside this range will be silently adjusted to the
nearest value within it). This option is useful when you wish to
advertise a different value to this server than the value you advertise
globally, for example, when there is a firewall at the remote site that
is blocking large replies. (Note: Currently, this sets a single UDP size
for all packets sent to the server; named
will not deviate from this
value. This differs from the behavior of edns-udp-size
in
options
or view
statements, where it specifies a maximum value.
The server
statement behavior may be brought into conformance with
the options/view
behavior in future releases.)
The max-udp-size
option sets the maximum EDNS UDP message size
named
will send. Valid values are 512 to 4096 bytes (values outside
this range will be silently adjusted). This option is useful when you
know that there is a firewall that is blocking large replies from
named
.
The tcp-only
option sets the transport protocol to TCP. The default
is to use the UDP transport and to fallback on TCP only when a truncated
response is received.
transfers
is used to limit the number of concurrent inbound zone
transfers from the specified server. If no transfers
clause is
specified, the limit is set according to the transfers-per-ns
option.
The keys
clause identifies a key_id
defined by the key
statement, to be used for transaction security (TSIG,
section_title) when talking to the remote server. When a
request is sent to the remote server, a request signature will be
generated using the key specified here and appended to the message. A
request originating from the remote server is not required to be signed
by this key.
Only a single key per server is currently supported.
The transfer-source
and transfer-source-v6
clauses specify the
IPv4 and IPv6 source address to be used for zone transfer with the
remote server, respectively. For an IPv4 remote server, only
transfer-source
can be specified. Similarly, for an IPv6 remote
server, only transfer-source-v6
can be specified. For more details,
see the description of transfer-source
and transfer-source-v6
in
section_title.
The notify-source
and notify-source-v6
clauses specify the IPv4
and IPv6 source address to be used for notify messages sent to remote
servers, respectively. For an IPv4 remote server, only notify-source
can be specified. Similarly, for an IPv6 remote server, only
notify-source-v6
can be specified.
The query-source
and query-source-v6
clauses specify the IPv4
and IPv6 source address to be used for queries sent to remote servers,
respectively. For an IPv4 remote server, only query-source
can be
specified. Similarly, for an IPv6 remote server, only
query-source-v6
can be specified.
The request-nsid
clause determines whether the local server will add
a NSID EDNS option to requests sent to the server. This overrides
request-nsid
set at the view or option level.
The request-cookie
clause determines whether the local server will
add a DNS COOKIE EDNS option to requests sent to the server. This
overrides request-cookie
set at the view or option
level. named may determine that COOKIE is not supported by
the remote server and not add a COOKIE EDNS option to requests.
6.2.17. trusted-keys
Statement Grammar¶
trusted-keys {
( domain_name flags protocol algorithm key_data ; )
...
} ;
6.2.18. trusted-keys
Statement Definition and Usage¶
The trusted-keys
statement defines DNSSEC security roots. DNSSEC is
described in section_title. A security root is defined
when the public key for a non-authoritative zone is known, but cannot be
securely obtained through DNS, either because it is the DNS root zone or
because its parent zone is unsigned. Once a key has been configured as a
trusted key, it is treated as if it had been validated and proven
secure. The resolver attempts DNSSEC validation on all DNS data in
subdomains of a security root.
All keys (and corresponding zones) listed in trusted-keys
are deemed
to exist regardless of what parent zones say. Similarly for all keys
listed in trusted-keys
only those keys are used to validate the
DNSKEY RRset. The parent's DS RRset will not be used.
The trusted-keys
statement can contain multiple key entries, each
consisting of the key's domain name, flags, protocol, algorithm, and the
Base64 representation of the key data. Spaces, tabs, newlines and
carriage returns are ignored in the key data, so the configuration may
be split up into multiple lines.
trusted-keys
may be set at the top level of named.conf
or within
a view. If it is set in both places, they are additive: keys defined at
the top level are inherited by all views, but keys defined in a view are
only used within that view.
6.2.19. managed-keys
Statement Grammar¶
managed-keys {
( domain_name initial_key flags protocol algorithm key_data ; )
...
} ;
6.2.20. managed-keys
Statement Definition and Usage¶
The managed-keys
statement, like trusted-keys
, defines DNSSEC
security roots. The difference is that managed-keys
can be kept up
to date automatically, without intervention from the resolver operator.
Suppose, for example, that a zone's key-signing key was compromised, and
the zone owner had to revoke and replace the key. A resolver which had
the old key in a trusted-keys
statement would be unable to validate
this zone any longer; it would reply with a SERVFAIL response code. This
would continue until the resolver operator had updated the
trusted-keys
statement with the new key.
If, however, the zone were listed in a managed-keys
statement
instead, then the zone owner could add a "stand-by" key to the zone in
advance. named
would store the stand-by key, and when the original
key was revoked, named
would be able to transition smoothly to the
new key. It would also recognize that the old key had been revoked, and
cease using that key to validate answers, minimizing the damage that the
compromised key could do.
A managed-keys
statement contains a list of the keys to be managed,
along with information about how the keys are to be initialized for the
first time. The only initialization method currently supported is
initial-key
. This means the managed-keys
statement must contain
a copy of the initializing key. (Future releases may allow keys to be
initialized by other methods, eliminating this requirement.)
Consequently, a managed-keys
statement appears similar to a
trusted-keys
, differing in the presence of the second field,
containing the keyword initial-key
. The difference is, whereas the
keys listed in a trusted-keys
continue to be trusted until they are
removed from named.conf
, an initializing key listed in a
managed-keys
statement is only trusted once: for as long as it
takes to load the managed key database and start the RFC 5011 key
maintenance process.
The first time named
runs with a managed key configured in
named.conf
, it fetches the DNSKEY RRset directly from the zone apex,
and validates it using the key specified in the managed-keys
statement. If the DNSKEY RRset is validly signed, then it is used as the
basis for a new managed keys database.
From that point on, whenever named
runs, it sees the
managed-keys
statement, checks to make sure RFC 5011 key maintenance
has already been initialized for the specified domain, and if so, it
simply moves on. The key specified in the managed-keys
statement is
not used to validate answers; it has been superseded by the key or keys
stored in the managed keys database.
The next time named
runs after a name has been removed from the
managed-keys
statement, the corresponding zone will be removed from
the managed keys database, and RFC 5011 key maintenance will no longer
be used for that domain.
In the current implementation, the managed keys database is stored as a master-format zone file.
On servers which do not use views, this file is named
managed-keys.loop
. When views are in use, there will be a separate
managed keys database for each view; the filename will be a hash of the
view name followed by the suffix .mkeys
.
When the key database is changed, the zone is updated. As with any other
dynamic zone, changes will be written into a journal file, e.g.,
managed-keys.loop.jnl
. Changes are committed to the master file as
soon as possible afterward; this will usually occur within 30 seconds.
So, whenever named
is using automatic key maintenance, the zone file
and journal file can be expected to exist in the working directory. (For
this reason among others, the working directory should be always be
writable by named
.)
If the dnssec-validation
option is set to auto
, named
will
automatically initialize a managed key for the root zone. The key that
is used to initialize the key maintenance process is built-in and can be
overridden with the dnssec-keys-file
option.
6.2.21. view
Statement Grammar¶
view view_name [ class ] {
match-clients { address_match_list } ;
match-destinations { address_match_list } ;
match-recursive-only yes_or_no ;
[ view_option ; ... ]
[ zone_statement ; ... ]
} ;
6.2.22. view
Statement Definition and Usage¶
The view
statement is a powerful feature of Loop that lets a name
server answer a DNS query differently depending on who is asking. It is
particularly useful for implementing split DNS setups without having to
run multiple servers.
Each view
statement defines a view of the DNS namespace that will be
seen by a subset of clients. A client matches a view if its source IP
address matches the address_match_list
of the view's
match-clients
clause and its destination IP address matches the
address_match_list
of the view's match-destinations
clause. If
not specified, both match-clients
and match-destinations
default
to matching all addresses. In addition to checking IP addresses
match-clients
and match-destinations
can also take keys
which provide an mechanism for the client to select the view. A view can
also be specified as match-recursive-only
, which means that only
recursive requests from matching clients will match that view. The order
of the view
statements is significant — a client request will be
resolved in the context of the first view
that it matches.
Zones defined within a view
statement will only be accessible to
clients that match the view
. By defining a zone of the same name in
multiple views, different zone data can be given to different clients,
for example, "internal" and "external" clients in a split DNS setup.
Many of the options given in the options
statement can also be used
within a view
statement, and then apply only when resolving queries
with that view. When no view-specific value is given, the value in the
options
statement is used as a default. Also, zone options can have
default values specified in the view
statement; these view-specific
defaults take precedence over those in the options
statement.
Views are class specific. If no class is given, class IN is assumed. Note that all non-IN views must contain a hint zone, since only the IN class has compiled-in default hints.
If there are no view
statements in the config file, a default view
that matches any client is automatically created in class IN. Any
zone
statements specified on the top level of the configuration file
are considered to be part of this default view, and the options
statement will apply to the default view. If any explicit view
statements are present, all zone
statements must occur inside
view
statements.
Here is an example of a typical split DNS setup implemented using
view
statements:
view "internal" {
// This should match our internal networks.
match-clients { 10.0.0.0/8; };
// Provide recursive service to internal
// clients only.
recursion yes;
// Provide a complete view of the example.com
// zone including addresses of internal hosts.
zone "example.com" {
type master;
file "example-internal.db";
};
};
view "external" {
// Match all clients not matched by the
// previous view.
match-clients { any; };
// Refuse recursive service to external clients.
recursion no;
// Provide a restricted view of the example.com
// zone containing only publicly accessible hosts.
zone "example.com" {
type master;
file "example-external.db";
};
};
6.2.23. zone
Statement Grammar¶
zone zone_name [ class ] {
type master ;
[ allow-query { address_match_list } ; ]
[ allow-query-on { address_match_list } ; ]
[ allow-transfer { address_match_list } ; ]
[ allow-update { address_match_list } ; ]
[ update-check-ksk yes_or_no ; ]
[ dnssec-dnskey-kskonly yes_or_no ; ]
[ dnssec-loadkeys-interval number ; ]
[ update-policy local | { update_policy_rule ; ... } ; ]
[ also-notify [ port ip_port ] [ dscp ip_dscp ] {
( masters_list | ip_addr [ port ip_port ] ) [ key key_name ] ;
...
} ; ]
[ check-names ( warn | fail | ignore ) ; ]
[ check-mx ( warn | fail | ignore ) ; ]
[ check-wildcard yes_or_no ; ]
[ check-spf ( warn | ignore ); ]
[ check-integrity yes_or_no ; ]
[ dialup dialup_option ; ]
[ file string ; ]
[ journal string ; ]
[ max-journal-size size_spec ; ]
[ forward ( only | first ) ; ]
[ forwarders { [ ip_addr [ port ip_port ] [ dscp ip_dscp ] ; ... ] } ; ]
[ ixfr-from-differences yes_or_no ; ]
[ max-ixfr-log-size number ; ]
[ max-transfer-idle-out number ; ]
[ max-transfer-time-out number ; ]
[ notify yes_or_no | explicit | master-only ; ]
[ notify-delay seconds ; ]
[ notify-to-soa yes_or_no ; ]
[ notify-source ( ip4_addr | * )
[ port ip_port ] [ dscp ip_dscp ] ; ]
[ notify-source-v6 ( ip6_addr | * )
[ port ip_port ] [ dscp ip_dscp ] ; ]
[ zone-statistics ( full | terse | none ) ; ]
[ sig-validity-interval number [ number ] ; ]
[ sig-signing-nodes number ; ]
[ sig-signing-signatures number ; ]
[ sig-signing-type number ; ]
[ database string ; ]
[ min-refresh-time number ; ]
[ max-refresh-time number ; ]
[ min-retry-time number ; ]
[ max-retry-time number ; ]
[ key-directory path_name ; ]
[ auto-dnssec ( allow | maintain | off ) ; ]
[ inline-signing yes_or_no ; ]
[ zero-no-soa-ttl yes_or_no ; ]
[ serial-update-method ( increment | unixtime ) ; ]
[ max-zone-ttl number ; ]
} ;
zone zone_name [ class ] {
type slave ;
[ allow-notify { address_match_list } ; ]
[ allow-query { address_match_list } ; ]
[ allow-query-on { address_match_list } ; ]
[ allow-transfer { address_match_list } ; ]
[ allow-update-forwarding { address_match_list } ; ]
[ dnssec-update-mode ( maintain | no-resign ); ]
[ update-check-ksk yes_or_no ; ]
[ dnssec-dnskey-kskonly yes_or_no ; ]
[ dnssec-loadkeys-interval number ; ]
[ dnssec-secure-to-insecure yes_or_no ; ]
[ try-tcp-refresh yes_or_no ; ]
[ also-notify [ port ip_port ] [ dscp ip_dscp ] {
( masters_list | ip_addr [ port ip_port ] ) [ key key_name ] ;
...
} ; ]
[ check-names ( warn | fail | ignore ) ; ]
[ dialup dialup_option ; ]
[ file string ; ]
[ journal string ; ]
[ max-journal-size size_spec ; ]
[ forward ( only | first ) ; ]
[ forwarders { [ ip_addr [ port ip_port ] [ dscp ip_dscp ] ; ... } ; ]
[ ixfr-from-differences yes_or_no ; ]
[ request-ixfr yes_or_no ; ]
[ masters [ port ip_port ] [ dscp ip_dscp ] {
( masters_list | ip_addr [ port ip_port ] ) [ key key_name ] ;
...
} ; ]
[ max-ixfr-log-size number ; ]
[ max-transfer-idle-in number ; ]
[ max-transfer-idle-out number ; ]
[ max-transfer-time-in number ; ]
[ max-transfer-time-out number ; ]
[ notify ( yes_or_no | explicit | master-only ) ; ]
[ notify-delay seconds ; ]
[ notify-to-soa yes_or_no ; ]
[ transfer-source ( ip4_addr | * )
[ port ip_port ] [ dscp ip_dscp ] ; ]
[ transfer-source-v6 ( ip6_addr | * )
[ port ip_port ] [ dscp ip_dscp ] ; ]
[ alt-transfer-source ( ip4_addr | * )
[ port ip_port ] [ dscp ip_dscp ] ; ]
[ alt-transfer-source-v6 ( ip6_addr | * )
[ port ip_port ] [ dscp ip_dscp ] ; ]
[ use-alt-transfer-source yes_or_no ; ]
[ notify-source ( ip4_addr | * )
[ port ip_port ] [ dscp ip_dscp ] ; ]
[ notify-source-v6 ( ip6_addr | * )
[ port ip_port ] [ dscp ip_dscp ] ; ]
[ zone-statistics ( full | terse | none ) ; ]
[ sig-validity-interval number [ number ] ; ]
[ sig-signing-nodes number ; ]
[ sig-signing-signatures number ; ]
[ sig-signing-type number ; ]
[ database string ; ]
[ min-refresh-time number ; ]
[ max-refresh-time number ; ]
[ min-retry-time number ; ]
[ max-retry-time number ; ]
[ key-directory path_name ; ]
[ auto-dnssec ( allow | maintain | off ) ; ]
[ inline-signing yes_or_no ; ]
[ multi-master yes_or_no ; ]
[ zero-no-soa-ttl yes_or_no ; ]
} ;
zone zone_name [ class ] {
type hint;
file string ;
[ delegation-only yes_or_no ; ]
[ check-names ( warn | fail | ignore ) ; ] // Not Implemented.
} ;
zone zone_name [ class ] {
type stub;
[ allow-query { address_match_list } ; ]
[ allow-query-on { address_match_list } ; ]
[ check-names ( warn | fail | ignore ) ; ]
[ dialup dialup_option ; ]
[ delegation-only yes_or_no ; ]
[ file string ; ]
[ forward ( only | first ) ; ]
[ forwarders { [ ip_addr [ port ip_port ] [ dscp ip_dscp ] ; ... ] } ; ]
[ masters [ port ip_port ] [ dscp ip_dscp ] {
( masters_list | ip_addr [ port ip_port ] ) [ key key_name ] ;
...
} ; ]
[ max-transfer-idle-in number ; ]
[ max-transfer-time-in number ; ]
[ transfer-source ( ip4_addr | * )
[ port ip_port ] [ dscp ip_dscp ] ; ]
[ transfer-source-v6 ( ip6_addr | * )
[ port ip_port ] [ dscp ip_dscp ] ; ]
[ alt-transfer-source ( ip4_addr | * )
[ port ip_port ] [ dscp ip_dscp ] ; ]
[ alt-transfer-source-v6 ( ip6_addr | * )
[ port ip_port ] [ dscp ip_dscp ] ; ]
[ use-alt-transfer-source yes_or_no ; ]
[ zone-statistics ( full | terse | none ) ; ]
[ database string ; ]
[ min-refresh-time number ; ]
[ max-refresh-time number ; ]
[ min-retry-time number ; ]
[ max-retry-time number ; ]
[ multi-master yes_or_no ; ]
} ;
zone zone_name [ class ] {
type static-stub;
[ allow-query { address_match_list } ; ]
[ server-addresses { [ ip_addr ; ... } ; ]
[ server-names { [ namelist ] } ; ]
[ zone-statistics ( full | terse | none ) ; ]
} ;
zone zone_name [ class ] {
type forward;
[ forward ( only | first ) ; ]
[ forwarders { [ ip_addr [ port ip_port ] [ dscp ip_dscp ] ; ... } ; ]
[ delegation-only yes_or_no ; ]
} ;
zone zone_name [ class ] {
type delegation-only;
} ;
zone zone_name [ class ] {
[ in-view string ; ]
} ;
6.2.24. zone
Statement Definition and Usage¶
6.2.24.1. Zone Types¶
The type
keyword is required for the zone
configuration unless
it is an in-view
configuration. Its acceptable values include:
delegation-only
, forward
, hint
, master
, slave
,
static-stub
, and stub
.
|
The server has a master copy of the data for the zone and will be able to provide authoritative answers for it. |
|
A slave zone is a replica of a
master zone. The |
|
A stub zone is similar to a slave zone, except that it replicates only the NS records of a master zone instead of the entire zone. Stub zones are not a standard part of the DNS; they are a feature specific to the Loop implementation. Stub zones can be used to
eliminate the need for glue NS
record in a parent zone at the
expense of maintaining a stub
zone entry and a set of name
server addresses in
Stub zones can also be used as a
way of forcing the resolution of
a given domain to use a
particular set of authoritative
servers. For example, the caching
name servers on a private network
using RFC1918 addressing may be
configured with stub zones for
|
|
A static-stub zone is similar to a stub zone with the following exceptions: the zone data is statically configured, rather than transferred from a master server; when recursion is necessary for a query that matches a static-stub zone, the locally configured data (nameserver names and glue addresses) is always used even if different authoritative information is cached. Zone data is configured via the
The zone data is maintained in
the form of NS and (if necessary)
glue A or AAAA RRs internally,
which can be seen by dumping zone
databases by
Since the data is statically configured, no zone maintenance action takes place for a static-stub zone. For example, there is no periodic refresh attempt, and an incoming notify message will be rejected with an rcode of NOTAUTH. Each static-stub zone is configured with internally generated NS and (if necessary) glue A or AAAA RRs |
|
A "forward zone" is a way to
configure forwarding on a
per-domain basis. A |
|
The initial set of root name servers is specified using a "hint zone". When the server starts up, it uses the root hints to find a root name server and get the most recent list of root name servers. If no hint zone is specified for class IN, the server uses a compiled-in default set of root servers hints. Classes other than IN have no built-in defaults hints. |
|
This is used to enforce the delegation-only status of infrastructure zones (e.g. COM, NET, ORG). Any answer that is received without an explicit or implicit delegation in the authority section will be treated as NXDOMAIN. This does not apply to the zone apex. This should not be applied to leaf zones.
See caveats in varlistentry_title. |
6.2.24.2. Class¶
The zone's name may optionally be followed by a class. If a class is not
specified, class IN
(for Internet
), is assumed. This is correct
for the vast majority of cases.
The hesiod
class is named for an information service from MIT's
Project Athena. It is used to share information about various systems
databases, such as users, groups, printers and so on. The keyword HS
is a synonym for hesiod.
Another MIT development is Chaosnet, a LAN protocol created in the
mid-1970s. Zone data for it can be specified with the CHAOS
class.
6.2.24.3. Zone Options¶
allow-notify
See the description of
allow-notify
in section_title.allow-query
See the description of
allow-query
in section_title.allow-query-on
See the description of
allow-query-on
in section_title.allow-transfer
See the description of
allow-transfer
in section_title.allow-update
See the description of
allow-update
in section_title.update-policy
Specifies a "Simple Secure Update" policy. See section_title.
allow-update-forwarding
See the description of
allow-update-forwarding
in section_title.also-notify
Only meaningful if
notify
is active for this zone. The set of machines that will receive aDNS NOTIFY
message for this zone is made up of all the listed name servers (other than the primary master) for the zone plus any IP addresses specified withalso-notify
. A port may be specified with eachalso-notify
address to send the notify messages to a port other than the default of 53. A TSIG key may also be specified to cause theNOTIFY
to be signed by the given key.also-notify
is not meaningful for stub zones. The default is the empty list.check-names
This option is used to restrict the character set and syntax of certain domain names in master files and/or DNS responses received from the network. The default varies according to zone type. For
master
zones the default isfail
. Forslave
zones the default iswarn
. It is not implemented forhint
zones.check-mx
See the description of
check-mx
in section_title.check-spf
See the description of
check-spf
in section_title.check-wildcard
See the description of
check-wildcard
in section_title.check-integrity
See the description of
check-integrity
in section_title.check-sibling
See the description of
check-sibling
in section_title.zero-no-soa-ttl
See the description of
zero-no-soa-ttl
in section_title.update-check-ksk
See the description of
update-check-ksk
in section_title.dnssec-loadkeys-interval
See the description of
dnssec-loadkeys-interval
in section_title.dnssec-update-mode
See the description of
dnssec-update-mode
in section_title.dnssec-dnskey-kskonly
See the description of
dnssec-dnskey-kskonly
in section_title.try-tcp-refresh
See the description of
try-tcp-refresh
in section_title.database
Specify the type of database to be used for storing the zone data. The string following the
database
keyword is interpreted as a list of whitespace-delimited words. The first word identifies the database type, and any subsequent words are passed as arguments to the database to be interpreted in a way specific to the database type.The default is
"rbt"
, Loop's native in-memory red-black-tree database. This database does not take arguments.Other values are possible if additional database drivers have been linked into the server. Some sample drivers are included with the distribution but none are linked in by default.
dialup
See the description of
dialup
in section_title.delegation-only
The flag only applies to forward, hint and stub zones. If set to
yes
, then the zone will also be treated as if it is also a delegation-only type zone.See caveats in varlistentry_title.
file
Set the zone's filename. In
master
andhint
zones which do not havemasters
defined, zone data is loaded from this file. Inslave
andstub
zones which do havemasters
defined, zone data is retrieved from another server and saved in this file. This option is not applicable to other zone types.forward
Only meaningful if the zone has a forwarders list. The
only
value causes the lookup to fail after trying the forwarders and getting no answer, whilefirst
would allow a normal lookup to be tried.forwarders
Used to override the list of global forwarders. If it is not specified in a zone of type
forward
, no forwarding is done for the zone and the global options are not used.journal
Allow the default journal's filename to be overridden. The default is the zone's filename with "
.jnl
" appended. This is applicable tomaster
andslave
zones.max-journal-size
See the description of
max-journal-size
in section_title.max-records
See the description of
max-records
in section_title.max-transfer-time-in
See the description of
max-transfer-time-in
in section_title.max-transfer-idle-in
See the description of
max-transfer-idle-in
in section_title.max-transfer-time-out
See the description of
max-transfer-time-out
in section_title.max-transfer-idle-out
See the description of
max-transfer-idle-out
in section_title.notify
See the description of
notify
in section_title.notify-delay
See the description of
notify-delay
in section_title.notify-to-soa
See the description of
notify-to-soa
in section_title.zone-statistics
See the description of
zone-statistics
in section_title.server-addresses
Only meaningful for static-stub zones. This is a list of IP addresses to which queries should be sent in recursive resolution for the zone. A non empty list for this option will internally configure the apex NS RR with associated glue A or AAAA RRs.
For example, if "example.com" is configured as a static-stub zone with 192.0.2.1 and 2001:db8::1234 in a
server-addresses
option, the following RRs will be internally configured.example.com. NS example.com. example.com. A 192.0.2.1 example.com. AAAA 2001:db8::1234
These records are internally used to resolve names under the static-stub zone. For instance, if the server receives a query for "www.example.com" with the RD bit on, the server will initiate recursive resolution and send queries to 192.0.2.1 and/or 2001:db8::1234.
server-names
Only meaningful for static-stub zones. This is a list of domain names of nameservers that act as authoritative servers of the static-stub zone. These names will be resolved to IP addresses when
named
needs to send queries to these servers. To make this supplemental resolution successful, these names must not be a subdomain of the origin name of static-stub zone. That is, when "example.net" is the origin of a static-stub zone, "ns.example" and "master.example.com" can be specified in theserver-names
option, but "ns.example.net" cannot, and will be rejected by the configuration parser.A non empty list for this option will internally configure the apex NS RR with the specified names. For example, if "example.com" is configured as a static-stub zone with "ns1.example.net" and "ns2.example.net" in a
server-names
option, the following RRs will be internally configured.example.com. NS ns1.example.net. example.com. NS ns2.example.net.
These records are internally used to resolve names under the static-stub zone. For instance, if the server receives a query for "www.example.com" with the RD bit on, the server initiate recursive resolution, resolve "ns1.example.net" and/or "ns2.example.net" to IP addresses, and then send queries to (one or more of) these addresses.
sig-validity-interval
See the description of
sig-validity-interval
in section_title.sig-signing-nodes
See the description of
sig-signing-nodes
in section_title.sig-signing-signatures
See the description of
sig-signing-signatures
in section_title.sig-signing-type
See the description of
sig-signing-type
in section_title.transfer-source
See the description of
transfer-source
in section_title.transfer-source-v6
See the description of
transfer-source-v6
in section_title.alt-transfer-source
See the description of
alt-transfer-source
in section_title.alt-transfer-source-v6
See the description of
alt-transfer-source-v6
in section_title.use-alt-transfer-source
See the description of
use-alt-transfer-source
in section_title.notify-source
See the description of
notify-source
in section_title.notify-source-v6
See the description of
notify-source-v6
in section_title.min-refresh-time
;max-refresh-time
;min-retry-time
;max-retry-time
See the description in section_title.
ixfr-from-differences
See the description of
ixfr-from-differences
in section_title. (Note that theixfr-from-differences
master
andslave
choices are not available at the zone level.)key-directory
See the description of
key-directory
in section_title.auto-dnssec
See the description of
auto-dnssec
in section_title.serial-update-method
See the description of
serial-update-method
in section_title.inline-signing
If
yes
, this enables "bump in the wire" signing of a zone, where a unsigned zone is transferred in or loaded from disk and a signed version of the zone is served, with possibly, a different serial number. This behaviour is disabled by default.multi-master
See the description of
multi-master
in section_title.max-zone-ttl
See the description of
max-zone-ttl
in section_title.dnssec-secure-to-insecure
See the description of
dnssec-secure-to-insecure
in section_title.
6.2.24.4. Dynamic Update Policies¶
Loop supports two alternative methods of granting clients the right to
perform dynamic updates to a zone, configured by the allow-update
and update-policy
option, respectively.
The allow-update
clause is a simple access control list. Any client
that matches the ACL is granted permission to update any record in the
zone.
The update-policy
clause allows more fine-grained control over what
updates are allowed. It specifies a set of rules, in which each rule
either grants or denies permission for one or more names in the zone to
be updated by one or more identities. Identity is determined by the key
that signed the update request using either TSIG or SIG(0). In most
cases, update-policy
rules only apply to key-based identities. There
is no way to specify update permissions based on client source address.
update-policy
rules are only meaningful for zones of type
master
, and are not allowed in any other zone type. It is a
configuration error to specify both allow-update
and
update-policy
at the same time.
A pre-defined update-policy
rule can be switched on with the command
update-policy local;
. Using this in a zone causes named
to
generate a TSIG session key when starting up and store it in a file;
this key can then be used by local clients to update the zone while
named
is running. By default, the session key is stored in the file
/var/run/loop/session.key
, the key name is
"local-ddns", and the key algorithm is HMAC-SHA256. These values are
configurable with the session-keyfile
, session-keyname
and
session-keyalg
options, respectively. A client running on the local
system, if run with appropriate permissions, may read the session key
from the key file and use it to sign update requests. The zone's update
policy will be set to allow that key to change any record within the
zone. Assuming the key name is "local-ddns", this policy is equivalent
to:
update-policy { grant local-ddns zonesub any; };
...with the additional restriction that only clients connecting from the local system will be permitted to send updates.
Note that only one session key is generated by named
; all zones
configured to use update-policy local
will accept the same key.
The command nsupdate -l
implements this feature, sending requests to
localhost and signing them using the key retrieved from the session key
file.
Other rule definitions look like this:
( grant | deny ) identity ruletype name types
Each rule grants or denies privileges. Rules are checked in the order in
which they are specified in the update-policy
statement. Once a
message has successfully matched a rule, the operation is immediately
granted or denied, and no further rules are examined. There are 13 types
of rules; the rule type is specified by the ruletype
field, and the
interpretation of other fields varies depending on the rule type.
In general, a rule is matched when the key that signed an update request
matches the identity
field, the name of the record to be updated
matches the name
field (in the manner specified by the ruletype
field), and the type of the record to be updated matches the types
field. Details for each rule type are described below.
The identity
field must be set to a fully-qualified domain name. In
most cases, this represensts the name of the TSIG or SIG(0) key that
must be used to sign the update request. If the specified name is a
wildcard, it is subject to DNS wildcard expansion, and the rule may
apply to multiple identities. When a TKEY exchange has been used to
create a shared secret, the identity of the key used to authenticate the
TKEY exchange will be used as the identity of the shared secret. Some
rule types use indentities matching the client's Kerberos principal
(e.g, "host/machine@REALM"
) or Windows realm (machine$@REALM
).
The name field also specifies a fully-qualified domain name. This often represents the name of the record to be updated. Interpretation of this field is dependent on rule type.
If no types
are explicitly specified, then a rule matches all types
except RRSIG, NS, SOA, NSEC and NSEC3. Types may be specified by name,
including "ANY" (ANY matches all types except NSEC and NSEC3, which can
never be updated). Note that when an attempt is made to delete all
records associated with a name, the rules are checked for each existing
record type.
The ruletype field has 13 values: name
, subdomain
, wildcard
,
self
, selfsub
, selfwild
, tcp-self
, 6to4-self
,
zonesub
, and external
.
|
Exact-match semantics. This rule matches when the name being updated is identical to the contents of the name field. |
|
This rule matches when the name being updated is a subdomain of, or identical to, the contents of the name field. |
``zonesub` ` |
This rule is similar to subdomain, except that it
matches when the name being updated is a subdomain of
the zone in which the When this rule is used, the name field is omitted. |
``wildcard `` |
The name field is subject to DNS wildcard expansion, and this rule matches when the name being updated is a valid expansion of the wildcard. |
|
This rule matches when the name of the record being updated matches the contents of the identity field. The name field is ignored. To avoid confusion, it is recommended that this field be set to the same value as the identity field or to "." The |
``selfsub` ` |
This rule is similar to |
``selfwild `` |
This rule is similar to |
``tcp-self `` |
This rule allows updates that have been sent via TCP
and for which the standard mapping from the client's IP
address into the
|
|
This allows the name matching a 6to4 IPv6 prefix, as
specified in RFC 3056, to be updated by any TCP
connection from either the 6to4 network or from the
corresponding IPv4 address. This is intended to allow
NS or DNAME RRsets to be added to the The In addition, if specified for an
|
``external `` |
This rule allows The method of communicating with the daemon is
specified in the identity field, the format of which is
" Requests to the external daemon are sent over the UNIX-domain socket as datagrams with the following format: Protocol version number (4 bytes, network byte o
The daemon replies with a four-byte value in network byte order, containing either 0 or 1; 0 indicates that the specified update is not permitted, and 1 indicates that it is. |
6.2.24.5. Multiple views¶
When multiple views are in use, a zone may be referenced by more than
one of them. Often, the views will contain different zones with the same
name, allowing different clients to receive different answers for the
same queries. At times, however, it is desirable for multiple views to
contain identical zones. The in-view
zone option provides an
efficient way to do this: it allows a view to reference a zone that was
defined in a previously configured view. Example:
view internal {
match-clients { 10/8; };
zone example.com {
type master;
file "example-external.db";
};
};
view external {
match-clients { any; };
zone example.com {
in-view internal;
};
};
An in-view
option cannot refer to a view that is configured later in
the configuration file.
A zone
statement which uses the in-view
option may not use any
other options with the exception of forward
and forwarders
.
(These options control the behavior of the containing view, rather than
changing the zone object itself.)
Zone level acls (e.g. allow-query, allow-transfer) and other configuration details of the zone are all set in the view the referenced zone is defined in. Care need to be taken to ensure that acls are wide enough for all views referencing the zone.
An in-view
zone cannot be used as a response policy zone.
An in-view
zone is not intended to reference a forward
zone.