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diff --git a/doc/arm/Bv9ARM-book.xml b/doc/arm/Bv9ARM-book.xml new file mode 100644 index 0000000..719b074 --- /dev/null +++ b/doc/arm/Bv9ARM-book.xml @@ -0,0 +1,18117 @@ +<!-- + - Copyright (C) Internet Systems Consortium, Inc. ("ISC") + - + - This Source Code Form is subject to the terms of the Mozilla Public + - License, v. 2.0. If a copy of the MPL was not distributed with this + - file, You can obtain one at http://mozilla.org/MPL/2.0/. + - + - See the COPYRIGHT file distributed with this work for additional + - information regarding copyright ownership. +--> + +<!-- Converted by db4-upgrade version 1.0 --> +<book xmlns:db="http://docbook.org/ns/docbook" version="5.0"> + <info> + <title>BIND 9 Administrator Reference Manual</title> + <!-- insert copyright start --> + <copyright> + <year>2000</year> + <year>2001</year> + <year>2002</year> + <year>2003</year> + <year>2004</year> + <year>2005</year> + <year>2006</year> + <year>2007</year> + <year>2008</year> + <year>2009</year> + <year>2010</year> + <year>2011</year> + <year>2012</year> + <year>2013</year> + <year>2014</year> + <year>2015</year> + <year>2016</year> + <year>2017</year> + <year>2018</year> + <year>2019</year> + <holder>Internet Systems Consortium, Inc. ("ISC")</holder> + </copyright> + <!-- insert copyright end --> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="releaseinfo.xml"/> + </info> + + <chapter xml:id="Bv9ARM.ch01"><info><title>Introduction</title></info> + + <para> + The Internet Domain Name System (<acronym>DNS</acronym>) + consists of the syntax + to specify the names of entities in the Internet in a hierarchical + manner, the rules used for delegating authority over names, and the + system implementation that actually maps names to Internet + addresses. <acronym>DNS</acronym> data is maintained in a + group of distributed + hierarchical databases. + </para> + + <section xml:id="doc_scope"><info><title>Scope of Document</title></info> + + <para> + The Berkeley Internet Name Domain + (<acronym>BIND</acronym>) implements a + domain name server for a number of operating systems. This + document provides basic information about the installation and + care of the Internet Systems Consortium (<acronym>ISC</acronym>) + <acronym>BIND</acronym> version 9 software package for + system administrators. + </para> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="pkgversion.xml"/> + </section> + + <section xml:id="organization"><info><title>Organization of This Document</title></info> + + <para> + In this document, <emphasis>Chapter 1</emphasis> introduces + the basic <acronym>DNS</acronym> and <acronym>BIND</acronym> concepts. <emphasis>Chapter 2</emphasis> + describes resource requirements for running <acronym>BIND</acronym> in various + environments. Information in <emphasis>Chapter 3</emphasis> is + <emphasis>task-oriented</emphasis> in its presentation and is + organized functionally, to aid in the process of installing the + <acronym>BIND</acronym> 9 software. The task-oriented + section is followed by + <emphasis>Chapter 4</emphasis>, which contains more advanced + concepts that the system administrator may need for implementing + certain options. <emphasis>Chapter 5</emphasis> + describes the <acronym>BIND</acronym> 9 lightweight + resolver. The contents of <emphasis>Chapter 6</emphasis> are + organized as in a reference manual to aid in the ongoing + maintenance of the software. <emphasis>Chapter 7</emphasis> addresses + security considerations, and + <emphasis>Chapter 8</emphasis> contains troubleshooting help. The + main body of the document is followed by several + <emphasis>appendices</emphasis> which contain useful reference + information, such as a <emphasis>bibliography</emphasis> and + historic information related to <acronym>BIND</acronym> + and the Domain Name + System. + </para> + </section> + <section xml:id="conventions"><info><title>Conventions Used in This Document</title></info> + + <para> + In this document, we use the following general typographic + conventions: + </para> + + <informaltable> + <tgroup cols="2"> + <colspec colname="1" colnum="1" colwidth="3.000in"/> + <colspec colname="2" colnum="2" colwidth="2.625in"/> + <tbody> + <row> + <entry colname="1"> + <para> + <emphasis>To describe:</emphasis> + </para> + </entry> + <entry colname="2"> + <para> + <emphasis>We use the style:</emphasis> + </para> + </entry> + </row> + <row> + <entry colname="1"> + <para> + a pathname, filename, URL, hostname, + mailing list name, or new term or concept + </para> + </entry> + <entry colname="2"> + <para> + <filename>Fixed width</filename> + </para> + </entry> + </row> + <row> + <entry colname="1"> + <para> + literal user + input + </para> + </entry> + <entry colname="2"> + <para> + <userinput>Fixed Width Bold</userinput> + </para> + </entry> + </row> + <row> + <entry colname="1"> + <para> + program output + </para> + </entry> + <entry colname="2"> + <para> + <computeroutput>Fixed Width</computeroutput> + </para> + </entry> + </row> + </tbody> + </tgroup> + </informaltable> + + <para> + The following conventions are used in descriptions of the + <acronym>BIND</acronym> configuration file:<informaltable colsep="0" frame="all" rowsep="0"> + <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="2Level-table"> + <colspec colname="1" colnum="1" colsep="0" colwidth="3.000in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="2.625in"/> + <tbody> + <row rowsep="0"> + <entry colname="1" colsep="1" rowsep="1"> + <para> + <emphasis>To describe:</emphasis> + </para> + </entry> + <entry colname="2" rowsep="1"> + <para> + <emphasis>We use the style:</emphasis> + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1" colsep="1" rowsep="1"> + <para> + keywords + </para> + </entry> + <entry colname="2" rowsep="1"> + <para> + <literal>Fixed Width</literal> + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1" colsep="1" rowsep="1"> + <para> + variables + </para> + </entry> + <entry colname="2" rowsep="1"> + <para> + <varname>Fixed Width</varname> + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1" colsep="1"> + <para> + Optional input + </para> + </entry> + <entry colname="2"> + <para> + <optional>Text is enclosed in square brackets</optional> + </para> + </entry> + </row> + </tbody> + </tgroup> + </informaltable> + </para> + </section> + <section xml:id="dns_overview"><info><title>The Domain Name System (<acronym>DNS</acronym>)</title></info> + + <para> + The purpose of this document is to explain the installation + and upkeep of the <acronym>BIND</acronym> (Berkeley Internet + Name Domain) software package, and we + begin by reviewing the fundamentals of the Domain Name System + (<acronym>DNS</acronym>) as they relate to <acronym>BIND</acronym>. + </para> + + <section xml:id="dns_fundamentals"><info><title>DNS Fundamentals</title></info> + + <para> + The Domain Name System (DNS) is a hierarchical, distributed + database. It stores information for mapping Internet host names to + IP + addresses and vice versa, mail routing information, and other data + used by Internet applications. + </para> + + <para> + Clients look up information in the DNS by calling a + <emphasis>resolver</emphasis> library, which sends queries to one or + more <emphasis>name servers</emphasis> and interprets the responses. + The <acronym>BIND</acronym> 9 software distribution + contains a name server, <command>named</command>, and a + resolver library, <command>liblwres</command>. + </para> + + </section> + <section xml:id="domain_names"><info><title>Domains and Domain Names</title></info> + + <para> + The data stored in the DNS is identified by <emphasis>domain names</emphasis> that are organized as a tree according to + organizational or administrative boundaries. Each node of the tree, + called a <emphasis>domain</emphasis>, is given a label. The domain + name of the + node is the concatenation of all the labels on the path from the + node to the <emphasis>root</emphasis> node. This is represented + in written form as a string of labels listed from right to left and + separated by dots. A label need only be unique within its parent + domain. + </para> + + <para> + For example, a domain name for a host at the + company <emphasis>Example, Inc.</emphasis> could be + <literal>ourhost.example.com</literal>, + where <literal>com</literal> is the + top level domain to which + <literal>ourhost.example.com</literal> belongs, + <literal>example</literal> is + a subdomain of <literal>com</literal>, and + <literal>ourhost</literal> is the + name of the host. + </para> + + <para> + For administrative purposes, the name space is partitioned into + areas called <emphasis>zones</emphasis>, each starting at a node and + extending down to the leaf nodes or to nodes where other zones + start. + The data for each zone is stored in a <emphasis>name server</emphasis>, which answers queries about the zone using the + <emphasis>DNS protocol</emphasis>. + </para> + + <para> + The data associated with each domain name is stored in the + form of <emphasis>resource records</emphasis> (<acronym>RR</acronym>s). + Some of the supported resource record types are described in + <xref linkend="types_of_resource_records_and_when_to_use_them"/>. + </para> + + <para> + For more detailed information about the design of the DNS and + the DNS protocol, please refer to the standards documents listed in + <xref linkend="rfcs"/>. + </para> + </section> + + <section xml:id="zones"><info><title>Zones</title></info> + + <para> + To properly operate a name server, it is important to understand + the difference between a <emphasis>zone</emphasis> + and a <emphasis>domain</emphasis>. + </para> + + <para> + As stated previously, a zone is a point of delegation in + the <acronym>DNS</acronym> tree. A zone consists of + those contiguous parts of the domain + tree for which a name server has complete information and over which + it has authority. It contains all domain names from a certain point + downward in the domain tree except those which are delegated to + other zones. A delegation point is marked by one or more + <emphasis>NS records</emphasis> in the + parent zone, which should be matched by equivalent NS records at + the root of the delegated zone. + </para> + + <para> + For instance, consider the <literal>example.com</literal> + domain which includes names + such as <literal>host.aaa.example.com</literal> and + <literal>host.bbb.example.com</literal> even though + the <literal>example.com</literal> zone includes + only delegations for the <literal>aaa.example.com</literal> and + <literal>bbb.example.com</literal> zones. A zone can + map + exactly to a single domain, but could also include only part of a + domain, the rest of which could be delegated to other + name servers. Every name in the <acronym>DNS</acronym> + tree is a + <emphasis>domain</emphasis>, even if it is + <emphasis>terminal</emphasis>, that is, has no + <emphasis>subdomains</emphasis>. Every subdomain is a domain and + every domain except the root is also a subdomain. The terminology is + not intuitive and we suggest that you read RFCs 1033, 1034 and 1035 + to + gain a complete understanding of this difficult and subtle + topic. + </para> + + <para> + Though <acronym>BIND</acronym> is called a "domain name + server", + it deals primarily in terms of zones. The master and slave + declarations in the <filename>named.conf</filename> file + specify + zones, not domains. When you ask some other site if it is willing to + be a slave server for your <emphasis>domain</emphasis>, you are + actually asking for slave service for some collection of zones. + </para> + </section> + + <section xml:id="auth_servers"><info><title>Authoritative Name Servers</title></info> + + <para> + Each zone is served by at least + one <emphasis>authoritative name server</emphasis>, + which contains the complete data for the zone. + To make the DNS tolerant of server and network failures, + most zones have two or more authoritative servers, on + different networks. + </para> + + <para> + Responses from authoritative servers have the "authoritative + answer" (AA) bit set in the response packets. This makes them + easy to identify when debugging DNS configurations using tools like + <command>dig</command> (<xref linkend="diagnostic_tools"/>). + </para> + + <section xml:id="primary_master"><info><title>The Primary Master</title></info> + + <para> + The authoritative server where the master copy of the zone + data is maintained is called the + <emphasis>primary master</emphasis> server, or simply the + <emphasis>primary</emphasis>. Typically it loads the zone + contents from some local file edited by humans or perhaps + generated mechanically from some other local file which is + edited by humans. This file is called the + <emphasis>zone file</emphasis> or + <emphasis>master file</emphasis>. + </para> + + <para> + In some cases, however, the master file may not be edited + by humans at all, but may instead be the result of + <emphasis>dynamic update</emphasis> operations. + </para> + </section> + + <section xml:id="slave_server"><info><title>Slave Servers</title></info> + + <para> + The other authoritative servers, the <emphasis>slave</emphasis> + servers (also known as <emphasis>secondary</emphasis> servers) + load the zone contents from another server using a replication + process known as a <emphasis>zone transfer</emphasis>. + Typically the data are transferred directly from the primary + master, but it is also possible to transfer it from another + slave. In other words, a slave server may itself act as a + master to a subordinate slave server. + </para> + <para> + Periodically, the slave server must send a refresh query to + determine whether the zone contents have been updated. This + is done by sending a query for the zone's SOA record and + checking whether the SERIAL field has been updated; if so, + a new transfer request is initiated. The timing of these + refresh queries is controlled by the SOA REFRESH and RETRY + fields, but can be overrridden with the + <command>max-refresh-time</command>, + <command>min-refresh-time</command>, + <command>max-retry-time</command>, and + <command>min-retry-time</command> options. + </para> + <para> + If the zone data cannot be updated within the time specified + by the SOA EXPIRE option (up to a hard-coded maximum of + 24 weeks) then the slave zone expires and will no longer + respond to queries. + </para> + </section> + + <section xml:id="stealth_server"><info><title>Stealth Servers</title></info> + + <para> + Usually all of the zone's authoritative servers are listed in + NS records in the parent zone. These NS records constitute + a <emphasis>delegation</emphasis> of the zone from the parent. + The authoritative servers are also listed in the zone file itself, + at the <emphasis>top level</emphasis> or <emphasis>apex</emphasis> + of the zone. You can list servers in the zone's top-level NS + records that are not in the parent's NS delegation, but you cannot + list servers in the parent's delegation that are not present at + the zone's top level. + </para> + + <para> + A <emphasis>stealth server</emphasis> is a server that is + authoritative for a zone but is not listed in that zone's NS + records. Stealth servers can be used for keeping a local copy of + a + zone to speed up access to the zone's records or to make sure that + the + zone is available even if all the "official" servers for the zone + are + inaccessible. + </para> + + <para> + A configuration where the primary master server itself is a + stealth server is often referred to as a "hidden primary" + configuration. One use for this configuration is when the primary + master + is behind a firewall and therefore unable to communicate directly + with the outside world. + </para> + + </section> + + </section> + <section xml:id="cache_servers"><info><title>Caching Name Servers</title></info> + + <!-- + - Terminology here is inconsistent. Probably ought to + - convert to using "recursive name server" everywhere + - with just a note about "caching" terminology. + --> + + <para> + The resolver libraries provided by most operating systems are + <emphasis>stub resolvers</emphasis>, meaning that they are not + capable of + performing the full DNS resolution process by themselves by talking + directly to the authoritative servers. Instead, they rely on a + local + name server to perform the resolution on their behalf. Such a + server + is called a <emphasis>recursive</emphasis> name server; it performs + <emphasis>recursive lookups</emphasis> for local clients. + </para> + + <para> + To improve performance, recursive servers cache the results of + the lookups they perform. Since the processes of recursion and + caching are intimately connected, the terms + <emphasis>recursive server</emphasis> and + <emphasis>caching server</emphasis> are often used synonymously. + </para> + + <para> + The length of time for which a record may be retained in + the cache of a caching name server is controlled by the + Time To Live (TTL) field associated with each resource record. + </para> + + <section xml:id="forwarder"><info><title>Forwarding</title></info> + + <para> + Even a caching name server does not necessarily perform + the complete recursive lookup itself. Instead, it can + <emphasis>forward</emphasis> some or all of the queries + that it cannot satisfy from its cache to another caching name + server, + commonly referred to as a <emphasis>forwarder</emphasis>. + </para> + + <para> + There may be one or more forwarders, + and they are queried in turn until the list is exhausted or an + answer + is found. Forwarders are typically used when you do not + wish all the servers at a given site to interact directly with the + rest of + the Internet servers. A typical scenario would involve a number + of internal <acronym>DNS</acronym> servers and an + Internet firewall. Servers unable + to pass packets through the firewall would forward to the server + that can do it, and that server would query the Internet <acronym>DNS</acronym> servers + on the internal server's behalf. + </para> + </section> + + </section> + + <section xml:id="multi_role"><info><title>Name Servers in Multiple Roles</title></info> + + <para> + The <acronym>BIND</acronym> name server can + simultaneously act as + a master for some zones, a slave for other zones, and as a caching + (recursive) server for a set of local clients. + </para> + + <para> + However, since the functions of authoritative name service + and caching/recursive name service are logically separate, it is + often advantageous to run them on separate server machines. + + A server that only provides authoritative name service + (an <emphasis>authoritative-only</emphasis> server) can run with + recursion disabled, improving reliability and security. + + A server that is not authoritative for any zones and only provides + recursive service to local + clients (a <emphasis>caching-only</emphasis> server) + does not need to be reachable from the Internet at large and can + be placed inside a firewall. + </para> + + </section> + </section> + + </chapter> + + <chapter xml:id="Bv9ARM.ch02"><info><title><acronym>BIND</acronym> Resource Requirements</title></info> + + <section xml:id="hw_req"><info><title>Hardware requirements</title></info> + <para> + <acronym>DNS</acronym> hardware requirements have + traditionally been quite modest. + For many installations, servers that have been pensioned off from + active duty have performed admirably as <acronym>DNS</acronym> servers. + </para> + <para> + The DNSSEC features of <acronym>BIND</acronym> 9 + may prove to be quite + CPU intensive however, so organizations that make heavy use of these + features may wish to consider larger systems for these applications. + <acronym>BIND</acronym> 9 is fully multithreaded, allowing + full utilization of + multiprocessor systems for installations that need it. + </para> + </section> + <section xml:id="cpu_req"><info><title>CPU Requirements</title></info> + <para> + CPU requirements for <acronym>BIND</acronym> 9 range from + i486-class machines + for serving of static zones without caching, to enterprise-class + machines if you intend to process many dynamic updates and DNSSEC + signed zones, serving many thousands of queries per second. + </para> + </section> + <section xml:id="mem_req"><info><title>Memory Requirements</title></info> + <para> + The memory of the server has to be large enough to fit the + cache and zones loaded off disk. The <command>max-cache-size</command> + option can be used to limit the amount of memory used by the cache, + at the expense of reducing cache hit rates and causing more <acronym>DNS</acronym> + traffic. + Additionally, if additional section caching + (<xref linkend="acache"/>) is enabled, + the <command>max-acache-size</command> option can be used to + limit the amount + of memory used by the mechanism. + It is still good practice to have enough memory to load + all zone and cache data into memory — unfortunately, the best + way + to determine this for a given installation is to watch the name server + in operation. After a few weeks the server process should reach + a relatively stable size where entries are expiring from the cache as + fast as they are being inserted. + </para> + <!-- + - Add something here about leaving overhead for attacks? + - How much overhead? Percentage? + --> + </section> + + <section xml:id="intensive_env"><info><title>Name Server Intensive Environment Issues</title></info> + + <para> + For name server intensive environments, there are two alternative + configurations that may be used. The first is where clients and + any second-level internal name servers query a main name server, which + has enough memory to build a large cache. This approach minimizes + the bandwidth used by external name lookups. The second alternative + is to set up second-level internal name servers to make queries + independently. + In this configuration, none of the individual machines needs to + have as much memory or CPU power as in the first alternative, but + this has the disadvantage of making many more external queries, + as none of the name servers share their cached data. + </para> + </section> + + <section xml:id="supported_os"><info><title>Supported Operating Systems</title></info> + + <para> + ISC <acronym>BIND</acronym> 9 compiles and runs on a large + number + of Unix-like operating systems and on + Microsoft Windows Server 2003 and 2008, and Windows XP and Vista. + For an up-to-date + list of supported systems, see the README file in the top level + directory + of the BIND 9 source distribution. + </para> + </section> + </chapter> + + <chapter xml:id="Bv9ARM.ch03"><info><title>Name Server Configuration</title></info> + + <para> + In this chapter we provide some suggested configurations along + with guidelines for their use. We suggest reasonable values for + certain option settings. + </para> + + <section xml:id="sample_configuration"><info><title>Sample Configurations</title></info> + + <section xml:id="cache_only_sample"><info><title>A Caching-only Name Server</title></info> + + <para> + The following sample configuration is appropriate for a caching-only + name server for use by clients internal to a corporation. All + queries + from outside clients are refused using the <command>allow-query</command> + option. Alternatively, the same effect could be achieved using + suitable + firewall rules. + </para> + +<programlisting> +// Two corporate subnets we wish to allow queries from. +acl corpnets { 192.168.4.0/24; 192.168.7.0/24; }; +options { + // Working directory + directory "/etc/namedb"; + + allow-query { corpnets; }; +}; +// Provide a reverse mapping for the loopback +// address 127.0.0.1 +zone "0.0.127.in-addr.arpa" { + type master; + file "localhost.rev"; + notify no; +}; +</programlisting> + + </section> + + <section xml:id="auth_only_sample"><info><title>An Authoritative-only Name Server</title></info> + + <para> + This sample configuration is for an authoritative-only server + that is the master server for "<filename>example.com</filename>" + and a slave for the subdomain "<filename>eng.example.com</filename>". + </para> + +<programlisting> +options { + // Working directory + directory "/etc/namedb"; + // Do not allow access to cache + allow-query-cache { none; }; + // This is the default + allow-query { any; }; + // Do not provide recursive service + recursion no; +}; + +// Provide a reverse mapping for the loopback +// address 127.0.0.1 +zone "0.0.127.in-addr.arpa" { + type master; + file "localhost.rev"; + notify no; +}; +// We are the master server for example.com +zone "example.com" { + type master; + file "example.com.db"; + // IP addresses of slave servers allowed to + // transfer example.com + allow-transfer { + 192.168.4.14; + 192.168.5.53; + }; +}; +// We are a slave server for eng.example.com +zone "eng.example.com" { + type slave; + file "eng.example.com.bk"; + // IP address of eng.example.com master server + masters { 192.168.4.12; }; +}; +</programlisting> + + </section> + </section> + + <section xml:id="load_balancing"><info><title>Load Balancing</title></info> + + <!-- + - Add explanation of why load balancing is fragile at best + - and completely pointless in the general case. + --> + + <para> + A primitive form of load balancing can be achieved in + the <acronym>DNS</acronym> by using multiple records + (such as multiple A records) for one name. + </para> + + <para> + For example, if you have three WWW servers with network addresses + of 10.0.0.1, 10.0.0.2 and 10.0.0.3, a set of records such as the + following means that clients will connect to each machine one third + of the time: + </para> + + <informaltable colsep="0" rowsep="0"> + <tgroup cols="5" colsep="0" rowsep="0" tgroupstyle="2Level-table"> + <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="0.500in"/> + <colspec colname="3" colnum="3" colsep="0" colwidth="0.750in"/> + <colspec colname="4" colnum="4" colsep="0" colwidth="0.750in"/> + <colspec colname="5" colnum="5" colsep="0" colwidth="2.028in"/> + <tbody> + <row rowsep="0"> + <entry colname="1"> + <para> + Name + </para> + </entry> + <entry colname="2"> + <para> + TTL + </para> + </entry> + <entry colname="3"> + <para> + CLASS + </para> + </entry> + <entry colname="4"> + <para> + TYPE + </para> + </entry> + <entry colname="5"> + <para> + Resource Record (RR) Data + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <literal>www</literal> + </para> + </entry> + <entry colname="2"> + <para> + <literal>600</literal> + </para> + </entry> + <entry colname="3"> + <para> + <literal>IN</literal> + </para> + </entry> + <entry colname="4"> + <para> + <literal>A</literal> + </para> + </entry> + <entry colname="5"> + <para> + <literal>10.0.0.1</literal> + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para/> + </entry> + <entry colname="2"> + <para> + <literal>600</literal> + </para> + </entry> + <entry colname="3"> + <para> + <literal>IN</literal> + </para> + </entry> + <entry colname="4"> + <para> + <literal>A</literal> + </para> + </entry> + <entry colname="5"> + <para> + <literal>10.0.0.2</literal> + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para/> + </entry> + <entry colname="2"> + <para> + <literal>600</literal> + </para> + </entry> + <entry colname="3"> + <para> + <literal>IN</literal> + </para> + </entry> + <entry colname="4"> + <para> + <literal>A</literal> + </para> + </entry> + <entry colname="5"> + <para> + <literal>10.0.0.3</literal> + </para> + </entry> + </row> + </tbody> + </tgroup> + </informaltable> + <para> + When a resolver queries for these records, <acronym>BIND</acronym> will rotate + them and respond to the query with the records in a different + order. In the example above, clients will randomly receive + records in the order 1, 2, 3; 2, 3, 1; and 3, 1, 2. Most clients + will use the first record returned and discard the rest. + </para> + <para> + For more detail on ordering responses, check the + <command>rrset-order</command> sub-statement in the + <command>options</command> statement, see + <xref endterm="rrset_ordering_title" linkend="rrset_ordering"/>. + </para> + + </section> + + <section xml:id="ns_operations"><info><title>Name Server Operations</title></info> + + <section xml:id="tools"><info><title>Tools for Use With the Name Server Daemon</title></info> + <para> + This section describes several indispensable diagnostic, + administrative and monitoring tools available to the system + administrator for controlling and debugging the name server + daemon. + </para> + <section xml:id="diagnostic_tools"><info><title>Diagnostic Tools</title></info> + <para> + The <command>dig</command>, <command>host</command>, and + <command>nslookup</command> programs are all command + line tools + for manually querying name servers. They differ in style and + output format. + </para> + + <variablelist> + <varlistentry> + <term xml:id="dig"><command>dig</command></term> + <listitem> + <para> + <command>dig</command> + is the most versatile and complete of these lookup tools. + It has two modes: simple interactive + mode for a single query, and batch mode which executes a + query for + each in a list of several query lines. All query options are + accessible + from the command line. + </para> + <cmdsynopsis label="Usage" sepchar=" "> + <command>dig</command> + <arg choice="opt" rep="norepeat">@<replaceable>server</replaceable></arg> + <arg choice="plain" rep="norepeat"><replaceable>domain</replaceable></arg> + <arg choice="opt" rep="norepeat"><replaceable>query-type</replaceable></arg> + <arg choice="opt" rep="norepeat"><replaceable>query-class</replaceable></arg> + <arg choice="opt" rep="norepeat">+<replaceable>query-option</replaceable></arg> + <arg choice="opt" rep="norepeat">-<replaceable>dig-option</replaceable></arg> + <arg choice="opt" rep="norepeat">%<replaceable>comment</replaceable></arg> + </cmdsynopsis> + <para> + The usual simple use of <command>dig</command> will take the form + </para> + <simpara> + <command>dig @server domain query-type query-class</command> + </simpara> + <para> + For more information and a list of available commands and + options, see the <command>dig</command> man + page. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>host</command></term> + <listitem> + <para> + The <command>host</command> utility emphasizes + simplicity + and ease of use. By default, it converts + between host names and Internet addresses, but its + functionality + can be extended with the use of options. + </para> + <cmdsynopsis label="Usage" sepchar=" "> + <command>host</command> + <arg choice="opt" rep="norepeat">-aCdlnrsTwv</arg> + <arg choice="opt" rep="norepeat">-c <replaceable>class</replaceable></arg> + <arg choice="opt" rep="norepeat">-N <replaceable>ndots</replaceable></arg> + <arg choice="opt" rep="norepeat">-t <replaceable>type</replaceable></arg> + <arg choice="opt" rep="norepeat">-W <replaceable>timeout</replaceable></arg> + <arg choice="opt" rep="norepeat">-R <replaceable>retries</replaceable></arg> + <arg choice="opt" rep="norepeat">-m <replaceable>flag</replaceable></arg> + <arg choice="opt" rep="norepeat">-4</arg> + <arg choice="opt" rep="norepeat">-6</arg> + <arg choice="plain" rep="norepeat"><replaceable>hostname</replaceable></arg> + <arg choice="opt" rep="norepeat"><replaceable>server</replaceable></arg> + </cmdsynopsis> + <para> + For more information and a list of available commands and + options, see the <command>host</command> man + page. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>nslookup</command></term> + <listitem> + <para><command>nslookup</command> + has two modes: interactive and + non-interactive. Interactive mode allows the user to + query name servers for information about various + hosts and domains or to print a list of hosts in a + domain. Non-interactive mode is used to print just + the name and requested information for a host or + domain. + </para> + <cmdsynopsis label="Usage" sepchar=" "> + <command>nslookup</command> + <arg rep="repeat" choice="opt">-option</arg> + <group choice="opt" rep="norepeat"> + <arg choice="opt" rep="norepeat"><replaceable>host-to-find</replaceable></arg> + <arg choice="opt" rep="norepeat">- <arg choice="opt" rep="norepeat">server</arg></arg> + </group> + </cmdsynopsis> + <para> + Interactive mode is entered when no arguments are given (the + default name server will be used) or when the first argument + is a + hyphen (`-') and the second argument is the host name or + Internet address + of a name server. + </para> + <para> + Non-interactive mode is used when the name or Internet + address + of the host to be looked up is given as the first argument. + The + optional second argument specifies the host name or address + of a name server. + </para> + <para> + Due to its arcane user interface and frequently inconsistent + behavior, we do not recommend the use of <command>nslookup</command>. + Use <command>dig</command> instead. + </para> + </listitem> + + </varlistentry> + </variablelist> + </section> + + <section xml:id="admin_tools"><info><title>Administrative Tools</title></info> + <para> + Administrative tools play an integral part in the management + of a server. + </para> + <variablelist> + <varlistentry xml:id="named-checkconf" xreflabel="Named Configuration Checking application"> + + <term><command>named-checkconf</command></term> + <listitem> + <para> + The <command>named-checkconf</command> program + checks the syntax of a <filename>named.conf</filename> file. + </para> + <cmdsynopsis label="Usage" sepchar=" "> + <command>named-checkconf</command> + <arg choice="opt" rep="norepeat">-jvz</arg> + <arg choice="opt" rep="norepeat">-t <replaceable>directory</replaceable></arg> + <arg choice="opt" rep="norepeat"><replaceable>filename</replaceable></arg> + </cmdsynopsis> + </listitem> + </varlistentry> + <varlistentry xml:id="named-checkzone" xreflabel="Zone Checking application"> + + <term><command>named-checkzone</command></term> + <listitem> + <para> + The <command>named-checkzone</command> program + checks a master file for + syntax and consistency. + </para> + <cmdsynopsis label="Usage" sepchar=" "> + <command>named-checkzone</command> + <arg choice="opt" rep="norepeat">-djqvD</arg> + <arg choice="opt" rep="norepeat">-c <replaceable>class</replaceable></arg> + <arg choice="opt" rep="norepeat">-o <replaceable>output</replaceable></arg> + <arg choice="opt" rep="norepeat">-t <replaceable>directory</replaceable></arg> + <arg choice="opt" rep="norepeat">-w <replaceable>directory</replaceable></arg> + <arg choice="opt" rep="norepeat">-k <replaceable>(ignore|warn|fail)</replaceable></arg> + <arg choice="opt" rep="norepeat">-n <replaceable>(ignore|warn|fail)</replaceable></arg> + <arg choice="opt" rep="norepeat">-W <replaceable>(ignore|warn)</replaceable></arg> + <arg choice="plain" rep="norepeat"><replaceable>zone</replaceable></arg> + <arg choice="opt" rep="norepeat"><replaceable>filename</replaceable></arg> + </cmdsynopsis> + </listitem> + </varlistentry> + <varlistentry xml:id="named-compilezone" xreflabel="Zone Compilation application"> + <term><command>named-compilezone</command></term> + <listitem> + <para> + Similar to <command>named-checkzone,</command> but + it always dumps the zone content to a specified file + (typically in a different format). + </para> + </listitem> + </varlistentry> + <varlistentry xml:id="rndc" xreflabel="Remote Name Daemon Control application"> + + <term><command>rndc</command></term> + <listitem> + <para> + The remote name daemon control + (<command>rndc</command>) program allows the + system + administrator to control the operation of a name server. + Since <acronym>BIND</acronym> 9.2, <command>rndc</command> + supports all the commands of the BIND 8 <command>ndc</command> + utility except <command>ndc start</command> and + <command>ndc restart</command>, which were also + not supported in <command>ndc</command>'s + channel mode. + If you run <command>rndc</command> without any + options + it will display a usage message as follows: + </para> + <cmdsynopsis label="Usage" sepchar=" "> + <command>rndc</command> + <arg choice="opt" rep="norepeat">-c <replaceable>config</replaceable></arg> + <arg choice="opt" rep="norepeat">-s <replaceable>server</replaceable></arg> + <arg choice="opt" rep="norepeat">-p <replaceable>port</replaceable></arg> + <arg choice="opt" rep="norepeat">-y <replaceable>key</replaceable></arg> + <arg choice="plain" rep="norepeat"><replaceable>command</replaceable></arg> + <arg rep="repeat" choice="opt"><replaceable>command</replaceable></arg> + </cmdsynopsis> + + <para>See <xref linkend="man.rndc"/> for details of + the available <command>rndc</command> commands. + </para> + + <para> + <command>rndc</command> requires a configuration file, + since all + communication with the server is authenticated with + digital signatures that rely on a shared secret, and + there is no way to provide that secret other than with a + configuration file. The default location for the + <command>rndc</command> configuration file is + <filename>/etc/rndc.conf</filename>, but an + alternate + location can be specified with the <option>-c</option> + option. If the configuration file is not found, + <command>rndc</command> will also look in + <filename>/etc/rndc.key</filename> (or whatever + <varname>sysconfdir</varname> was defined when + the <acronym>BIND</acronym> build was + configured). + The <filename>rndc.key</filename> file is + generated by + running <command>rndc-confgen -a</command> as + described in + <xref linkend="controls_statement_definition_and_usage"/>. + </para> + + <para> + The format of the configuration file is similar to + that of <filename>named.conf</filename>, but + limited to + only four statements, the <command>options</command>, + <command>key</command>, <command>server</command> and + <command>include</command> + statements. These statements are what associate the + secret keys to the servers with which they are meant to + be shared. The order of statements is not + significant. + </para> + + <para> + The <command>options</command> statement has + three clauses: + <command>default-server</command>, <command>default-key</command>, + and <command>default-port</command>. + <command>default-server</command> takes a + host name or address argument and represents the server + that will + be contacted if no <option>-s</option> + option is provided on the command line. + <command>default-key</command> takes + the name of a key as its argument, as defined by a <command>key</command> statement. + <command>default-port</command> specifies the + port to which + <command>rndc</command> should connect if no + port is given on the command line or in a + <command>server</command> statement. + </para> + + <para> + The <command>key</command> statement defines a + key to be used + by <command>rndc</command> when authenticating + with + <command>named</command>. Its syntax is + identical to the + <command>key</command> statement in <filename>named.conf</filename>. + The keyword <userinput>key</userinput> is + followed by a key name, which must be a valid + domain name, though it need not actually be hierarchical; + thus, + a string like "<userinput>rndc_key</userinput>" is a valid + name. + The <command>key</command> statement has two + clauses: + <command>algorithm</command> and <command>secret</command>. + While the configuration parser will accept any string as the + argument + to algorithm, currently only the strings + "<userinput>hmac-md5</userinput>", + "<userinput>hmac-sha1</userinput>", + "<userinput>hmac-sha224</userinput>", + "<userinput>hmac-sha256</userinput>", + "<userinput>hmac-sha384</userinput>" + and "<userinput>hmac-sha512</userinput>" + have any meaning. The secret is a Base64 encoded string + as specified in RFC 3548. + </para> + + <para> + The <command>server</command> statement + associates a key + defined using the <command>key</command> + statement with a server. + The keyword <userinput>server</userinput> is followed by a + host name or address. The <command>server</command> statement + has two clauses: <command>key</command> and <command>port</command>. + The <command>key</command> clause specifies the + name of the key + to be used when communicating with this server, and the + <command>port</command> clause can be used to + specify the port <command>rndc</command> should + connect + to on the server. + </para> + + <para> + A sample minimal configuration file is as follows: + </para> + +<programlisting> +key rndc_key { + algorithm "hmac-sha256"; + secret + "c3Ryb25nIGVub3VnaCBmb3IgYSBtYW4gYnV0IG1hZGUgZm9yIGEgd29tYW4K"; +}; +options { + default-server 127.0.0.1; + default-key rndc_key; +}; +</programlisting> + + <para> + This file, if installed as <filename>/etc/rndc.conf</filename>, + would allow the command: + </para> + + <para> + <prompt>$ </prompt><userinput>rndc reload</userinput> + </para> + + <para> + to connect to 127.0.0.1 port 953 and cause the name server + to reload, if a name server on the local machine were + running with + following controls statements: + </para> + +<programlisting> +controls { + inet 127.0.0.1 + allow { localhost; } keys { rndc_key; }; +}; +</programlisting> + + <para> + and it had an identical key statement for + <literal>rndc_key</literal>. + </para> + + <para> + Running the <command>rndc-confgen</command> + program will + conveniently create a <filename>rndc.conf</filename> + file for you, and also display the + corresponding <command>controls</command> + statement that you need to + add to <filename>named.conf</filename>. + Alternatively, + you can run <command>rndc-confgen -a</command> + to set up + a <filename>rndc.key</filename> file and not + modify + <filename>named.conf</filename> at all. + </para> + + </listitem> + </varlistentry> + </variablelist> + + </section> + </section> + + <section xml:id="signals"><info><title>Signals</title></info> + <para> + Certain UNIX signals cause the name server to take specific + actions, as described in the following table. These signals can + be sent using the <command>kill</command> command. + </para> + <informaltable frame="all"> + <tgroup cols="2"> + <colspec colname="1" colnum="1" colsep="0" colwidth="1.125in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="4.000in"/> + <tbody> + <row rowsep="0"> + <entry colname="1"> + <para><command>SIGHUP</command></para> + </entry> + <entry colname="2"> + <para> + Causes the server to read <filename>named.conf</filename> and + reload the database. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>SIGTERM</command></para> + </entry> + <entry colname="2"> + <para> + Causes the server to clean up and exit. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>SIGINT</command></para> + </entry> + <entry colname="2"> + <para> + Causes the server to clean up and exit. + </para> + </entry> + </row> + </tbody> + </tgroup> + </informaltable> + </section> + </section> + </chapter> + + <chapter xml:id="Bv9ARM.ch04"><info><title>Advanced DNS Features</title></info> + + <section xml:id="notify"><info><title>Notify</title></info> + <para> + <acronym>DNS</acronym> NOTIFY is a mechanism that allows master + servers to notify their slave servers of changes to a zone's data. In + response to a <command>NOTIFY</command> from a master server, the + slave will check to see that its version of the zone is the + current version and, if not, initiate a zone transfer. + </para> + + <para> + For more information about <acronym>DNS</acronym> + <command>NOTIFY</command>, see the description of the + <command>notify</command> option in <xref linkend="boolean_options"/> and + the description of the zone option <command>also-notify</command> in + <xref linkend="zone_transfers"/>. The <command>NOTIFY</command> + protocol is specified in RFC 1996. + </para> + + <note><simpara> + As a slave zone can also be a master to other slaves, <command>named</command>, + by default, sends <command>NOTIFY</command> messages for every zone + it loads. Specifying <command>notify master-only;</command> will + cause <command>named</command> to only send <command>NOTIFY</command> for master + zones that it loads. + </simpara></note> + + </section> + + <section xml:id="dynamic_update"><info><title>Dynamic Update</title></info> + + <para> + Dynamic Update is a method for adding, replacing or deleting + records in a master server by sending it a special form of DNS + messages. The format and meaning of these messages is specified + in RFC 2136. + </para> + + <para> + Dynamic update is enabled by including an + <command>allow-update</command> or an <command>update-policy</command> + clause in the <command>zone</command> statement. + </para> + + <para> + If the zone's <command>update-policy</command> is set to + <userinput>local</userinput>, updates to the zone + will be permitted for the key <varname>local-ddns</varname>, + which will be generated by <command>named</command> at startup. + See <xref linkend="dynamic_update_policies"/> for more details. + </para> + + <para> + Dynamic updates using Kerberos signed requests can be made + using the TKEY/GSS protocol by setting either the + <command>tkey-gssapi-keytab</command> option, or alternatively + by setting both the <command>tkey-gssapi-credential</command> + and <command>tkey-domain</command> options. Once enabled, + Kerberos signed requests will be matched against the update + policies for the zone, using the Kerberos principal as the + signer for the request. + </para> + + <para> + Updating of secure zones (zones using DNSSEC) follows RFC + 3007: RRSIG, NSEC and NSEC3 records affected by updates are + automatically regenerated by the server using an online + zone key. Update authorization is based on transaction + signatures and an explicit server policy. + </para> + + <section xml:id="journal"><info><title>The journal file</title></info> + + <para> + All changes made to a zone using dynamic update are stored + in the zone's journal file. This file is automatically created + by the server when the first dynamic update takes place. + The name of the journal file is formed by appending the extension + <filename>.jnl</filename> to the name of the + corresponding zone + file unless specifically overridden. The journal file is in a + binary format and should not be edited manually. + </para> + + <para> + The server will also occasionally write ("dump") + the complete contents of the updated zone to its zone file. + This is not done immediately after + each dynamic update, because that would be too slow when a large + zone is updated frequently. Instead, the dump is delayed by + up to 15 minutes, allowing additional updates to take place. + During the dump process, transient files will be created + with the extensions <filename>.jnw</filename> and + <filename>.jbk</filename>; under ordinary circumstances, these + will be removed when the dump is complete, and can be safely + ignored. + </para> + + <para> + When a server is restarted after a shutdown or crash, it will replay + the journal file to incorporate into the zone any updates that + took + place after the last zone dump. + </para> + + <para> + Changes that result from incoming incremental zone transfers are + also + journalled in a similar way. + </para> + + <para> + The zone files of dynamic zones cannot normally be edited by + hand because they are not guaranteed to contain the most recent + dynamic changes — those are only in the journal file. + The only way to ensure that the zone file of a dynamic zone + is up to date is to run <command>rndc stop</command>. + </para> + + <para> + If you have to make changes to a dynamic zone + manually, the following procedure will work: + Disable dynamic updates to the zone using + <command>rndc freeze <replaceable>zone</replaceable></command>. + This will update the zone's master file with the changes + stored in its <filename>.jnl</filename> file. + Edit the zone file. Run + <command>rndc thaw <replaceable>zone</replaceable></command> + to reload the changed zone and re-enable dynamic updates. + </para> + + <para> + <command>rndc sync <replaceable>zone</replaceable></command> + will update the zone file with changes from the journal file + without stopping dynamic updates; this may be useful for viewing + the current zone state. To remove the <filename>.jnl</filename> + file after updating the zone file, use + <command>rndc sync -clean</command>. + </para> + + </section> + + </section> + + <section xml:id="incremental_zone_transfers"><info><title>Incremental Zone Transfers (IXFR)</title></info> + + <para> + The incremental zone transfer (IXFR) protocol is a way for + slave servers to transfer only changed data, instead of having to + transfer the entire zone. The IXFR protocol is specified in RFC + 1995. See <xref linkend="proposed_standards"/>. + </para> + + <para> + When acting as a master, <acronym>BIND</acronym> 9 + supports IXFR for those zones + where the necessary change history information is available. These + include master zones maintained by dynamic update and slave zones + whose data was obtained by IXFR. For manually maintained master + zones, and for slave zones obtained by performing a full zone + transfer (AXFR), IXFR is supported only if the option + <command>ixfr-from-differences</command> is set + to <userinput>yes</userinput>. + </para> + + <para> + When acting as a slave, <acronym>BIND</acronym> 9 will + attempt to use IXFR unless + it is explicitly disabled. For more information about disabling + IXFR, see the description of the <command>request-ixfr</command> clause + of the <command>server</command> statement. + </para> + </section> + + <section xml:id="split_dns"><info><title>Split DNS</title></info> + + <para> + Setting up different views, or visibility, of the DNS space to + internal and external resolvers is usually referred to as a + <emphasis>Split DNS</emphasis> setup. There are several + reasons an organization would want to set up its DNS this way. + </para> + <para> + One common reason for setting up a DNS system this way is + to hide "internal" DNS information from "external" clients on the + Internet. There is some debate as to whether or not this is actually + useful. + Internal DNS information leaks out in many ways (via email headers, + for example) and most savvy "attackers" can find the information + they need using other means. + However, since listing addresses of internal servers that + external clients cannot possibly reach can result in + connection delays and other annoyances, an organization may + choose to use a Split DNS to present a consistent view of itself + to the outside world. + </para> + <para> + Another common reason for setting up a Split DNS system is + to allow internal networks that are behind filters or in RFC 1918 + space (reserved IP space, as documented in RFC 1918) to resolve DNS + on the Internet. Split DNS can also be used to allow mail from outside + back in to the internal network. + </para> + <section xml:id="split_dns_sample"><info><title>Example split DNS setup</title></info> + <para> + Let's say a company named <emphasis>Example, Inc.</emphasis> + (<literal>example.com</literal>) + has several corporate sites that have an internal network with + reserved + Internet Protocol (IP) space and an external demilitarized zone (DMZ), + or "outside" section of a network, that is available to the public. + </para> + <para> + <emphasis>Example, Inc.</emphasis> wants its internal clients + to be able to resolve external hostnames and to exchange mail with + people on the outside. The company also wants its internal resolvers + to have access to certain internal-only zones that are not available + at all outside of the internal network. + </para> + <para> + In order to accomplish this, the company will set up two sets + of name servers. One set will be on the inside network (in the + reserved + IP space) and the other set will be on bastion hosts, which are + "proxy" + hosts that can talk to both sides of its network, in the DMZ. + </para> + <para> + The internal servers will be configured to forward all queries, + except queries for <filename>site1.internal</filename>, <filename>site2.internal</filename>, <filename>site1.example.com</filename>, + and <filename>site2.example.com</filename>, to the servers + in the + DMZ. These internal servers will have complete sets of information + for <filename>site1.example.com</filename>, <filename>site2.example.com</filename>, <filename>site1.internal</filename>, + and <filename>site2.internal</filename>. + </para> + <para> + To protect the <filename>site1.internal</filename> and <filename>site2.internal</filename> domains, + the internal name servers must be configured to disallow all queries + to these domains from any external hosts, including the bastion + hosts. + </para> + <para> + The external servers, which are on the bastion hosts, will + be configured to serve the "public" version of the <filename>site1</filename> and <filename>site2.example.com</filename> zones. + This could include things such as the host records for public servers + (<filename>www.example.com</filename> and <filename>ftp.example.com</filename>), + and mail exchange (MX) records (<filename>a.mx.example.com</filename> and <filename>b.mx.example.com</filename>). + </para> + <para> + In addition, the public <filename>site1</filename> and <filename>site2.example.com</filename> zones + should have special MX records that contain wildcard (`*') records + pointing to the bastion hosts. This is needed because external mail + servers do not have any other way of looking up how to deliver mail + to those internal hosts. With the wildcard records, the mail will + be delivered to the bastion host, which can then forward it on to + internal hosts. + </para> + <para> + Here's an example of a wildcard MX record: + </para> + <programlisting>* IN MX 10 external1.example.com.</programlisting> + <para> + Now that they accept mail on behalf of anything in the internal + network, the bastion hosts will need to know how to deliver mail + to internal hosts. In order for this to work properly, the resolvers + on + the bastion hosts will need to be configured to point to the internal + name servers for DNS resolution. + </para> + <para> + Queries for internal hostnames will be answered by the internal + servers, and queries for external hostnames will be forwarded back + out to the DNS servers on the bastion hosts. + </para> + <para> + In order for all this to work properly, internal clients will + need to be configured to query <emphasis>only</emphasis> the internal + name servers for DNS queries. This could also be enforced via + selective + filtering on the network. + </para> + <para> + If everything has been set properly, <emphasis>Example, Inc.</emphasis>'s + internal clients will now be able to: + </para> + <itemizedlist> + <listitem> + <simpara> + Look up any hostnames in the <literal>site1</literal> + and + <literal>site2.example.com</literal> zones. + </simpara> + </listitem> + <listitem> + <simpara> + Look up any hostnames in the <literal>site1.internal</literal> and + <literal>site2.internal</literal> domains. + </simpara> + </listitem> + <listitem> + <simpara>Look up any hostnames on the Internet.</simpara> + </listitem> + <listitem> + <simpara>Exchange mail with both internal and external people.</simpara> + </listitem> + </itemizedlist> + <para> + Hosts on the Internet will be able to: + </para> + <itemizedlist> + <listitem> + <simpara> + Look up any hostnames in the <literal>site1</literal> + and + <literal>site2.example.com</literal> zones. + </simpara> + </listitem> + <listitem> + <simpara> + Exchange mail with anyone in the <literal>site1</literal> and + <literal>site2.example.com</literal> zones. + </simpara> + </listitem> + </itemizedlist> + + <para> + Here is an example configuration for the setup we just + described above. Note that this is only configuration information; + for information on how to configure your zone files, see <xref linkend="sample_configuration"/>. + </para> + + <para> + Internal DNS server config: + </para> + +<programlisting> + +acl internals { 172.16.72.0/24; 192.168.1.0/24; }; + +acl externals { <varname>bastion-ips-go-here</varname>; }; + +options { + ... + ... + forward only; + // forward to external servers + forwarders { + <varname>bastion-ips-go-here</varname>; + }; + // sample allow-transfer (no one) + allow-transfer { none; }; + // restrict query access + allow-query { internals; externals; }; + // restrict recursion + allow-recursion { internals; }; + ... + ... +}; + +// sample master zone +zone "site1.example.com" { + type master; + file "m/site1.example.com"; + // do normal iterative resolution (do not forward) + forwarders { }; + allow-query { internals; externals; }; + allow-transfer { internals; }; +}; + +// sample slave zone +zone "site2.example.com" { + type slave; + file "s/site2.example.com"; + masters { 172.16.72.3; }; + forwarders { }; + allow-query { internals; externals; }; + allow-transfer { internals; }; +}; + +zone "site1.internal" { + type master; + file "m/site1.internal"; + forwarders { }; + allow-query { internals; }; + allow-transfer { internals; } +}; + +zone "site2.internal" { + type slave; + file "s/site2.internal"; + masters { 172.16.72.3; }; + forwarders { }; + allow-query { internals }; + allow-transfer { internals; } +}; +</programlisting> + + <para> + External (bastion host) DNS server config: + </para> + +<programlisting> +acl internals { 172.16.72.0/24; 192.168.1.0/24; }; + +acl externals { bastion-ips-go-here; }; + +options { + ... + ... + // sample allow-transfer (no one) + allow-transfer { none; }; + // default query access + allow-query { any; }; + // restrict cache access + allow-query-cache { internals; externals; }; + // restrict recursion + allow-recursion { internals; externals; }; + ... + ... +}; + +// sample slave zone +zone "site1.example.com" { + type master; + file "m/site1.foo.com"; + allow-transfer { internals; externals; }; +}; + +zone "site2.example.com" { + type slave; + file "s/site2.foo.com"; + masters { another_bastion_host_maybe; }; + allow-transfer { internals; externals; } +}; +</programlisting> + + <para> + In the <filename>resolv.conf</filename> (or equivalent) on + the bastion host(s): + </para> + +<programlisting> +search ... +nameserver 172.16.72.2 +nameserver 172.16.72.3 +nameserver 172.16.72.4 +</programlisting> + + </section> + </section> + <section xml:id="tsig"><info><title>TSIG</title></info> + + <para> + TSIG (Transaction SIGnatures) is a mechanism for authenticating DNS + messages, originally specified in RFC 2845. It allows DNS messages + to be cryptographically signed using a shared secret. TSIG can + be used in any DNS transaction, as a way to restrict access to + certain server functions (e.g., recursive queries) to authorized + clients when IP-based access control is insufficient or needs to + be overridden, or as a way to ensure message authenticity when it + is critical to the integrity of the server, such as with dynamic + UPDATE messages or zone transfers from a master to a slave server. + </para> + <para> + This is a guide to setting up TSIG in <acronym>BIND</acronym>. + It describes the configuration syntax and the process of creating + TSIG keys. + </para> + <para> + <command>named</command> supports TSIG for server-to-server + communication, and some of the tools included with + <acronym>BIND</acronym> support it for sending messages to + <command>named</command>: + <itemizedlist> + <listitem> + <xref linkend="man.nsupdate"/> supports TSIG via the + <option>-k</option>, <option>-l</option> and + <option>-y</option> command line options, or via + the <command>key</command> command when running + interactively. + </listitem> + <listitem> + <xref linkend="man.dig"/> supports TSIG via the + <option>-k</option> and <option>-y</option> command + line options. + </listitem> + </itemizedlist> + </para> + + <section><info><title>Generating a Shared Key</title></info> + <para> + TSIG keys can be generated using the <command>tsig-keygen</command> + command; the output of the command is a <command>key</command> directive + suitable for inclusion in <filename>named.conf</filename>. The + key name, algorithm and size can be specified by command line parameters; + the defaults are "tsig-key", HMAC-SHA256, and 256 bits, respectively. + </para> + <para> + Any string which is a valid DNS name can be used as a key name. + For example, a key to be shared between servers called + <emphasis>host1</emphasis> and <emphasis>host2</emphasis> could + be called "host1-host2.", and this key could be generated using: + </para> +<programlisting> + $ tsig-keygen host1-host2. > host1-host2.key +</programlisting> + <para> + This key may then be copied to both hosts. The key name and secret + must be identical on both hosts. + (Note: copying a shared secret from one server to another is beyond + the scope of the DNS. A secure transport mechanism should be used: + secure FTP, SSL, ssh, telephone, encrypted email, etc.) + </para> + <para> + <command>tsig-keygen</command> can also be run as + <command>ddns-confgen</command>, in which case its output includes + additional configuration text for setting up dynamic DNS in + <command>named</command>. See <xref linkend="man.ddns-confgen"/> + for details. + </para> + </section> + + <section><info><title>Loading A New Key</title></info> + <para> + For a key shared between servers called + <emphasis>host1</emphasis> and <emphasis>host2</emphasis>, + the following could be added to each server's + <filename>named.conf</filename> file: + </para> +<programlisting> +key "host1-host2." { + algorithm hmac-sha256; + secret "DAopyf1mhCbFVZw7pgmNPBoLUq8wEUT7UuPoLENP2HY="; +}; +</programlisting> + <para> + (This is the same key generated above using + <command>tsig-keygen</command>.) + </para> + <para> + Since this text contains a secret, it + is recommended that either <filename>named.conf</filename> not be + world-readable, or that the <command>key</command> directive + be stored in a file which is not world-readable, and which is + included in <filename>named.conf</filename> via the + <command>include</command> directive. + </para> + <para> + Once a key has been added to <filename>named.conf</filename> and the + server has been restarted or reconfigured, the server can recognize + the key. If the server receives a message signed by the + key, it will be able to verify the signature. If the signature + is valid, the response will be signed using the same key. + </para> + <para> + TSIG keys that are known to a server can be listed using the + command <command>rndc tsig-list</command>. + </para> + </section> + + <section><info><title>Instructing the Server to Use a Key</title></info> + <para> + A server sending a request to another server must be told whether + to use a key, and if so, which key to use. + </para> + <para> + For example, a key may be specified for each server in the + <command>masters</command> statement in the definition of a + slave zone; in this case, all SOA QUERY messages, NOTIFY + messages, and zone transfer requests (AXFR or IXFR) will be + signed using the specified key. Keys may also be specified + in the <command>also-notify</command> statement of a master + or slave zone, causing NOTIFY messages to be signed using + the specified key. + </para> + <para> + Keys can also be specified in a <command>server</command> + directive. Adding the following on <emphasis>host1</emphasis>, + if the IP address of <emphasis>host2</emphasis> is 10.1.2.3, would + cause <emphasis>all</emphasis> requests from <emphasis>host1</emphasis> + to <emphasis>host2</emphasis>, including normal DNS queries, to be + signed using the <command>host1-host2.</command> key: + </para> +<programlisting> +server 10.1.2.3 { + keys { host1-host2. ;}; +}; +</programlisting> + <para> + Multiple keys may be present in the <command>keys</command> + statement, but only the first one is used. As this directive does + not contain secrets, it can be used in a world-readable file. + </para> + <para> + Requests sent by <emphasis>host2</emphasis> to <emphasis>host1</emphasis> + would <emphasis>not</emphasis> be signed, unless a similar + <command>server</command> directive were in <emphasis>host2</emphasis>'s + configuration file. + </para> + <para> + Whenever any server sends a TSIG-signed DNS request, it will expect + the response to be signed with the same key. If a response is not + signed, or if the signature is not valid, the response will be + rejected. + </para> + </section> + + <section><info><title>TSIG-Based Access Control</title></info> + <para> + TSIG keys may be specified in ACL definitions and ACL directives + such as <command>allow-query</command>, <command>allow-transfer</command> + and <command>allow-update</command>. + The above key would be denoted in an ACL element as + <command>key host1-host2.</command> + </para> + <para> + An example of an <command>allow-update</command> directive using + a TSIG key: + </para> +<programlisting> +allow-update { !{ !localnets; any; }; key host1-host2. ;}; +</programlisting> + <para> + This allows dynamic updates to succeed only if the UPDATE + request comes from an address in <command>localnets</command>, + <emphasis>and</emphasis> if it is signed using the + <command>host1-host2.</command> key. + </para> + <para> + See <xref linkend="dynamic_update_policies"/> for a discussion of + the more flexible <command>update-policy</command> statement. + </para> + </section> + + <section><info><title>Errors</title></info> + <para> + Processing of TSIG-signed messages can result in several errors: + <itemizedlist> + <listitem> + If a TSIG-aware server receives a message signed by an + unknown key, the response will be unsigned, with the TSIG + extended error code set to BADKEY. + </listitem> + <listitem> + If a TSIG-aware server receives a message from a known key + but with an invalid signature, the response will be unsigned, + with the TSIG extended error code set to BADSIG. + </listitem> + <listitem> + If a TSIG-aware server receives a message with a time + outside of the allowed range, the response will be signed, with + the TSIG extended error code set to BADTIME, and the time values + will be adjusted so that the response can be successfully + verified. + </listitem> + </itemizedlist> + In all of the above cases, the server will return a response code + of NOTAUTH (not authenticated). + </para> + </section> + </section> + + <section xml:id="tkey"><info><title>TKEY</title></info> + + <para> + TKEY (Transaction KEY) is a mechanism for automatically negotiating + a shared secret between two hosts, originally specified in RFC 2930. + </para> + <para> + There are several TKEY "modes" that specify how a key is to be + generated or assigned. <acronym>BIND</acronym> 9 implements only + one of these modes: Diffie-Hellman key exchange. Both hosts are + required to have a KEY record with algorithm DH (though this + record is not required to be present in a zone). + </para> + <para> + The TKEY process is initiated by a client or server by sending + a query of type TKEY to a TKEY-aware server. The query must include + an appropriate KEY record in the additional section, and + must be signed using either TSIG or SIG(0) with a previously + established key. The server's response, if successful, will + contain a TKEY record in its answer section. After this transaction, + both participants will have enough information to calculate a + shared secret using Diffie-Hellman key exchange. The shared secret + can then be used by to sign subsequent transactions between the + two servers. + </para> + <para> + TSIG keys known by the server, including TKEY-negotiated keys, can + be listed using <command>rndc tsig-list</command>. + </para> + <para> + TKEY-negotiated keys can be deleted from a server using + <command>rndc tsig-delete</command>. This can also be done via + the TKEY protocol itself, by sending an authenticated TKEY query + specifying the "key deletion" mode. + </para> + + </section> + <section xml:id="sig0"><info><title>SIG(0)</title></info> + + <para> + <acronym>BIND</acronym> partially supports DNSSEC SIG(0) + transaction signatures as specified in RFC 2535 and RFC 2931. + SIG(0) uses public/private keys to authenticate messages. Access control + is performed in the same manner as TSIG keys; privileges can be + granted or denied in ACL directives based on the key name. + </para> + <para> + When a SIG(0) signed message is received, it will only be + verified if the key is known and trusted by the server. The + server will not attempt to recursively fetch or validate the + key. + </para> + <para> + SIG(0) signing of multiple-message TCP streams is not supported. + </para> + <para> + The only tool shipped with <acronym>BIND</acronym> 9 that + generates SIG(0) signed messages is <command>nsupdate</command>. + </para> + </section> + + <section xml:id="DNSSEC"><info><title>DNSSEC</title></info> + <para> + Cryptographic authentication of DNS information is possible + through the DNS Security (<emphasis>DNSSEC-bis</emphasis>) extensions, + defined in RFC 4033, RFC 4034, and RFC 4035. + This section describes the creation and use of DNSSEC signed zones. + </para> + + <para> + In order to set up a DNSSEC secure zone, there are a series + of steps which must be followed. <acronym>BIND</acronym> + 9 ships + with several tools + that are used in this process, which are explained in more detail + below. In all cases, the <option>-h</option> option prints a + full list of parameters. Note that the DNSSEC tools require the + keyset files to be in the working directory or the + directory specified by the <option>-d</option> option, and + that the tools shipped with BIND 9.2.x and earlier are not compatible + with the current ones. + </para> + + <para> + There must also be communication with the administrators of + the parent and/or child zone to transmit keys. A zone's security + status must be indicated by the parent zone for a DNSSEC capable + resolver to trust its data. This is done through the presence + or absence of a <literal>DS</literal> record at the + delegation + point. + </para> + + <para> + For other servers to trust data in this zone, they must + either be statically configured with this zone's zone key or the + zone key of another zone above this one in the DNS tree. + </para> + + <section xml:id="dnssec_keys"><info><title>Generating Keys</title></info> + + <para> + The <command>dnssec-keygen</command> program is used to + generate keys. + </para> + + <para> + A secure zone must contain one or more zone keys. The + zone keys will sign all other records in the zone, as well as + the zone keys of any secure delegated zones. Zone keys must + have the same name as the zone, a name type of + <command>ZONE</command>, and must be usable for + authentication. + It is recommended that zone keys use a cryptographic algorithm + designated as "mandatory to implement" by the IETF; currently + the only one is RSASHA1. + </para> + + <para> + The following command will generate a 768-bit RSASHA1 key for + the <filename>child.example</filename> zone: + </para> + + <para> + <userinput>dnssec-keygen -a RSASHA1 -b 768 -n ZONE child.example.</userinput> + </para> + + <para> + Two output files will be produced: + <filename>Kchild.example.+005+12345.key</filename> and + <filename>Kchild.example.+005+12345.private</filename> + (where + 12345 is an example of a key tag). The key filenames contain + the key name (<filename>child.example.</filename>), + algorithm (3 + is DSA, 1 is RSAMD5, 5 is RSASHA1, etc.), and the key tag (12345 in + this case). + The private key (in the <filename>.private</filename> + file) is + used to generate signatures, and the public key (in the + <filename>.key</filename> file) is used for signature + verification. + </para> + + <para> + To generate another key with the same properties (but with + a different key tag), repeat the above command. + </para> + + <para> + The <command>dnssec-keyfromlabel</command> program is used + to get a key pair from a crypto hardware and build the key + files. Its usage is similar to <command>dnssec-keygen</command>. + </para> + + <para> + The public keys should be inserted into the zone file by + including the <filename>.key</filename> files using + <command>$INCLUDE</command> statements. + </para> + + </section> + <section xml:id="dnssec_signing"><info><title>Signing the Zone</title></info> + + <para> + The <command>dnssec-signzone</command> program is used + to sign a zone. + </para> + + <para> + Any <filename>keyset</filename> files corresponding to + secure subzones should be present. The zone signer will + generate <literal>NSEC</literal>, <literal>NSEC3</literal> + and <literal>RRSIG</literal> records for the zone, as + well as <literal>DS</literal> for the child zones if + <literal>'-g'</literal> is specified. If <literal>'-g'</literal> + is not specified, then DS RRsets for the secure child + zones need to be added manually. + </para> + + <para> + The following command signs the zone, assuming it is in a + file called <filename>zone.child.example</filename>. By + default, all zone keys which have an available private key are + used to generate signatures. + </para> + + <para> + <userinput>dnssec-signzone -o child.example zone.child.example</userinput> + </para> + + <para> + One output file is produced: + <filename>zone.child.example.signed</filename>. This + file + should be referenced by <filename>named.conf</filename> + as the + input file for the zone. + </para> + + <para><command>dnssec-signzone</command> + will also produce a keyset and dsset files and optionally a + dlvset file. These are used to provide the parent zone + administrators with the <literal>DNSKEYs</literal> (or their + corresponding <literal>DS</literal> records) that are the + secure entry point to the zone. + </para> + + </section> + + <section xml:id="dnssec_config"><info><title>Configuring Servers</title></info> + + <para> + To enable <command>named</command> to respond appropriately + to DNS requests from DNSSEC aware clients, + <command>dnssec-enable</command> must be set to yes. + (This is the default setting.) + </para> + + <para> + To enable <command>named</command> to validate answers from + other servers, the <command>dnssec-enable</command> option + must be set to <userinput>yes</userinput>, and the + <command>dnssec-validation</command> options must be set to + <userinput>yes</userinput> or <userinput>auto</userinput>. + </para> + + <para> + If <command>dnssec-validation</command> is set to + <userinput>auto</userinput>, then a default + trust anchor for the DNS root zone will be used. + If it is set to <userinput>yes</userinput>, however, + then at least one trust anchor must be configured + with a <command>trusted-keys</command> or + <command>managed-keys</command> statement in + <filename>named.conf</filename>, or DNSSEC validation + will not occur. The default setting is + <userinput>yes</userinput>. + </para> + + <para> + <command>trusted-keys</command> are copies of DNSKEY RRs + for zones that are used to form the first link in the + cryptographic chain of trust. All keys listed in + <command>trusted-keys</command> (and corresponding zones) + are deemed to exist and only the listed keys will be used + to validated the DNSKEY RRset that they are from. + </para> + + <para> + <command>managed-keys</command> are trusted keys which are + automatically kept up to date via RFC 5011 trust anchor + maintenance. + </para> + + <para> + <command>trusted-keys</command> and + <command>managed-keys</command> are described in more detail + later in this document. + </para> + + <para> + Unlike <acronym>BIND</acronym> 8, <acronym>BIND</acronym> + 9 does not verify signatures on load, so zone keys for + authoritative zones do not need to be specified in the + configuration file. + </para> + + <para> + After DNSSEC gets established, a typical DNSSEC configuration + will look something like the following. It has one or + more public keys for the root. This allows answers from + outside the organization to be validated. It will also + have several keys for parts of the namespace the organization + controls. These are here to ensure that <command>named</command> + is immune to compromises in the DNSSEC components of the security + of parent zones. + </para> + +<programlisting> +managed-keys { + /* Root Key */ + "." initial-key 257 3 3 "BNY4wrWM1nCfJ+CXd0rVXyYmobt7sEEfK3clRbGaTwS + JxrGkxJWoZu6I7PzJu/E9gx4UC1zGAHlXKdE4zYIpRh + aBKnvcC2U9mZhkdUpd1Vso/HAdjNe8LmMlnzY3zy2Xy + 4klWOADTPzSv9eamj8V18PHGjBLaVtYvk/ln5ZApjYg + hf+6fElrmLkdaz MQ2OCnACR817DF4BBa7UR/beDHyp + 5iWTXWSi6XmoJLbG9Scqc7l70KDqlvXR3M/lUUVRbke + g1IPJSidmK3ZyCllh4XSKbje/45SKucHgnwU5jefMtq + 66gKodQj+MiA21AfUVe7u99WzTLzY3qlxDhxYQQ20FQ + 97S+LKUTpQcq27R7AT3/V5hRQxScINqwcz4jYqZD2fQ + dgxbcDTClU0CRBdiieyLMNzXG3"; +}; + +trusted-keys { + /* Key for our organization's forward zone */ + example.com. 257 3 5 "AwEAAaxPMcR2x0HbQV4WeZB6oEDX+r0QM6 + 5KbhTjrW1ZaARmPhEZZe3Y9ifgEuq7vZ/z + GZUdEGNWy+JZzus0lUptwgjGwhUS1558Hb + 4JKUbbOTcM8pwXlj0EiX3oDFVmjHO444gL + kBOUKUf/mC7HvfwYH/Be22GnClrinKJp1O + g4ywzO9WglMk7jbfW33gUKvirTHr25GL7S + TQUzBb5Usxt8lgnyTUHs1t3JwCY5hKZ6Cq + FxmAVZP20igTixin/1LcrgX/KMEGd/biuv + F4qJCyduieHukuY3H4XMAcR+xia2nIUPvm + /oyWR8BW/hWdzOvnSCThlHf3xiYleDbt/o + 1OTQ09A0="; + + /* Key for our reverse zone. */ + 2.0.192.IN-ADDRPA.NET. 257 3 5 "AQOnS4xn/IgOUpBPJ3bogzwc + xOdNax071L18QqZnQQQAVVr+i + LhGTnNGp3HoWQLUIzKrJVZ3zg + gy3WwNT6kZo6c0tszYqbtvchm + gQC8CzKojM/W16i6MG/eafGU3 + siaOdS0yOI6BgPsw+YZdzlYMa + IJGf4M4dyoKIhzdZyQ2bYQrjy + Q4LB0lC7aOnsMyYKHHYeRvPxj + IQXmdqgOJGq+vsevG06zW+1xg + YJh9rCIfnm1GX/KMgxLPG2vXT + D/RnLX+D3T3UL7HJYHJhAZD5L + 59VvjSPsZJHeDCUyWYrvPZesZ + DIRvhDD52SKvbheeTJUm6Ehkz + ytNN2SN96QRk8j/iI8ib"; +}; + +options { + ... + dnssec-enable yes; + dnssec-validation yes; +}; +</programlisting> + + <note><simpara> + None of the keys listed in this example are valid. In particular, + the root key is not valid. + </simpara></note> + + <para> + When DNSSEC validation is enabled and properly configured, + the resolver will reject any answers from signed, secure zones + which fail to validate, and will return SERVFAIL to the client. + </para> + + <para> + Responses may fail to validate for any of several reasons, + including missing, expired, or invalid signatures, a key which + does not match the DS RRset in the parent zone, or an insecure + response from a zone which, according to its parent, should have + been secure. + </para> + + <note> + <para> + When the validator receives a response from an unsigned zone + that has a signed parent, it must confirm with the parent + that the zone was intentionally left unsigned. It does + this by verifying, via signed and validated NSEC/NSEC3 records, + that the parent zone contains no DS records for the child. + </para> + <para> + If the validator <emphasis>can</emphasis> prove that the zone + is insecure, then the response is accepted. However, if it + cannot, then it must assume an insecure response to be a + forgery; it rejects the response and logs an error. + </para> + <para> + The logged error reads "insecurity proof failed" and + "got insecure response; parent indicates it should be secure". + </para> + </note> + </section> + </section> + + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="dnssec.xml"/> + + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="managed-keys.xml"/> + + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="pkcs11.xml"/> + + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="dlz.xml"/> + + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="dyndb.xml"/> + + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="catz.xml"/> + + <section xml:id="ipv6"><info><title>IPv6 Support in <acronym>BIND</acronym> 9</title></info> + <para> + <acronym>BIND</acronym> 9 fully supports all currently + defined forms of IPv6 name to address and address to name + lookups. It will also use IPv6 addresses to make queries when + running on an IPv6 capable system. + </para> + + <para> + For forward lookups, <acronym>BIND</acronym> 9 supports + only AAAA records. RFC 3363 deprecated the use of A6 records, + and client-side support for A6 records was accordingly removed + from <acronym>BIND</acronym> 9. + However, authoritative <acronym>BIND</acronym> 9 name servers still + load zone files containing A6 records correctly, answer queries + for A6 records, and accept zone transfer for a zone containing A6 + records. + </para> + + <para> + For IPv6 reverse lookups, <acronym>BIND</acronym> 9 supports + the traditional "nibble" format used in the + <emphasis>ip6.arpa</emphasis> domain, as well as the older, deprecated + <emphasis>ip6.int</emphasis> domain. + Older versions of <acronym>BIND</acronym> 9 + supported the "binary label" (also known as "bitstring") format, + but support of binary labels has been completely removed per + RFC 3363. + Many applications in <acronym>BIND</acronym> 9 do not understand + the binary label format at all any more, and will return an + error if given. + In particular, an authoritative <acronym>BIND</acronym> 9 + name server will not load a zone file containing binary labels. + </para> + + <para> + For an overview of the format and structure of IPv6 addresses, + see <xref linkend="ipv6addresses"/>. + </para> + + <section><info><title>Address Lookups Using AAAA Records</title></info> + + <para> + The IPv6 AAAA record is a parallel to the IPv4 A record, + and, unlike the deprecated A6 record, specifies the entire + IPv6 address in a single record. For example, + </para> + +<programlisting> +$ORIGIN example.com. +host 3600 IN AAAA 2001:db8::1 +</programlisting> + + <para> + Use of IPv4-in-IPv6 mapped addresses is not recommended. + If a host has an IPv4 address, use an A record, not + a AAAA, with <literal>::ffff:192.168.42.1</literal> as + the address. + </para> + </section> + <section><info><title>Address to Name Lookups Using Nibble Format</title></info> + + <para> + When looking up an address in nibble format, the address + components are simply reversed, just as in IPv4, and + <literal>ip6.arpa.</literal> is appended to the + resulting name. + For example, the following would provide reverse name lookup for + a host with address + <literal>2001:db8::1</literal>. + </para> + +<programlisting> +$ORIGIN 0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa. +1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0 14400 IN PTR ( + host.example.com. ) +</programlisting> + + </section> + </section> + </chapter> + + <chapter xml:id="Bv9ARM.ch05"><info><title>The <acronym>BIND</acronym> 9 Lightweight Resolver</title></info> + + <section xml:id="lightweight_resolver"><info><title>The Lightweight Resolver Library</title></info> + + <para> + Traditionally applications have been linked with a stub resolver + library that sends recursive DNS queries to a local caching name + server. + </para> + <para> + IPv6 once introduced new complexity into the resolution process, + such as following A6 chains and DNAME records, and simultaneous + lookup of IPv4 and IPv6 addresses. Though most of the complexity was + then removed, these are hard or impossible + to implement in a traditional stub resolver. + </para> + <para> + <acronym>BIND</acronym> 9 therefore can also provide resolution + services to local clients + using a combination of a lightweight resolver library and a resolver + daemon process running on the local host. These communicate using + a simple UDP-based protocol, the "lightweight resolver protocol" + that is distinct from and simpler than the full DNS protocol. + </para> + </section> + <section xml:id="lwresd"><info><title>Running a Resolver Daemon</title></info> + + <para> + To use the lightweight resolver interface, the system must + run the resolver daemon <command>lwresd</command> or a + local + name server configured with a <command>lwres</command> + statement. + </para> + + <para> + By default, applications using the lightweight resolver library will + make + UDP requests to the IPv4 loopback address (127.0.0.1) on port 921. + The + address can be overridden by <command>lwserver</command> + lines in + <filename>/etc/resolv.conf</filename>. + </para> + + <para> + The daemon currently only looks in the DNS, but in the future + it may use other sources such as <filename>/etc/hosts</filename>, + NIS, etc. + </para> + + <para> + The <command>lwresd</command> daemon is essentially a + caching-only name server that responds to requests using the + lightweight + resolver protocol rather than the DNS protocol. Because it needs + to run on each host, it is designed to require no or minimal + configuration. + Unless configured otherwise, it uses the name servers listed on + <command>nameserver</command> lines in <filename>/etc/resolv.conf</filename> + as forwarders, but is also capable of doing the resolution + autonomously if + none are specified. + </para> + <para> + The <command>lwresd</command> daemon may also be + configured with a + <filename>named.conf</filename> style configuration file, + in + <filename>/etc/lwresd.conf</filename> by default. A name + server may also + be configured to act as a lightweight resolver daemon using the + <command>lwres</command> statement in <filename>named.conf</filename>. + </para> + <para> + The number of client queries that the <command>lwresd</command> + daemon is able to serve can be set using the + <option>lwres-tasks</option> and <option>lwres-clients</option> + statements in the configuration. + </para> + </section> + </chapter> + + <chapter xml:id="Bv9ARM.ch06"><info><title><acronym>BIND</acronym> 9 Configuration Reference</title></info> + + <para> + <acronym>BIND</acronym> 9 configuration is broadly similar + to <acronym>BIND</acronym> 8; however, there are a few new + areas + of configuration, such as views. <acronym>BIND</acronym> + 8 configuration files should work with few alterations in <acronym>BIND</acronym> + 9, although more complex configurations should be reviewed to check + if they can be more efficiently implemented using the new features + found in <acronym>BIND</acronym> 9. + </para> + + <para> + <acronym>BIND</acronym> 4 configuration files can be + converted to the new format + using the shell script + <filename>contrib/named-bootconf/named-bootconf.sh</filename>. + </para> + <section xml:id="configuration_file_elements"><info><title>Configuration File Elements</title></info> + + <para> + Following is a list of elements used throughout the <acronym>BIND</acronym> configuration + file documentation: + </para> + <informaltable colsep="0" rowsep="0"> + <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="2Level-table"> + <colspec colname="1" colnum="1" colsep="0" colwidth="1.855in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="3.770in"/> + <tbody> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>acl_name</varname> + </para> + </entry> + <entry colname="2"> + <para> + The name of an <varname>address_match_list</varname> as + defined by the <command>acl</command> statement. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>address_match_list</varname> + </para> + </entry> + <entry colname="2"> + <para> + A list of one or more + <varname>ip_addr</varname>, + <varname>ip_prefix</varname>, <varname>key_id</varname>, + or <varname>acl_name</varname> elements, see + <xref linkend="address_match_lists"/>. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>masters_list</varname> + </para> + </entry> + <entry colname="2"> + <para> + A named list of one or more <varname>ip_addr</varname> + with optional <varname>key_id</varname> and/or + <varname>ip_port</varname>. + A <varname>masters_list</varname> may include other + <varname>masters_lists</varname>. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>domain_name</varname> + </para> + </entry> + <entry colname="2"> + <para> + A quoted string which will be used as + a DNS name, for example "<literal>my.test.domain</literal>". + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>namelist</varname> + </para> + </entry> + <entry colname="2"> + <para> + A list of one or more <varname>domain_name</varname> + elements. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>dotted_decimal</varname> + </para> + </entry> + <entry colname="2"> + <para> + One to four integers valued 0 through + 255 separated by dots (`.'), such as <command>123</command>, + <command>45.67</command> or <command>89.123.45.67</command>. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>ip4_addr</varname> + </para> + </entry> + <entry colname="2"> + <para> + An IPv4 address with exactly four elements + in <varname>dotted_decimal</varname> notation. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>ip6_addr</varname> + </para> + </entry> + <entry colname="2"> + <para> + An IPv6 address, such as <command>2001:db8::1234</command>. + IPv6 scoped addresses that have ambiguity on their + scope zones must be disambiguated by an appropriate + zone ID with the percent character (`%') as + delimiter. It is strongly recommended to use + string zone names rather than numeric identifiers, + in order to be robust against system configuration + changes. However, since there is no standard + mapping for such names and identifier values, + currently only interface names as link identifiers + are supported, assuming one-to-one mapping between + interfaces and links. For example, a link-local + address <command>fe80::1</command> on the link + attached to the interface <command>ne0</command> + can be specified as <command>fe80::1%ne0</command>. + Note that on most systems link-local addresses + always have the ambiguity, and need to be + disambiguated. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>ip_addr</varname> + </para> + </entry> + <entry colname="2"> + <para> + An <varname>ip4_addr</varname> or <varname>ip6_addr</varname>. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>ip_dscp</varname> + </para> + </entry> + <entry colname="2"> + <para> + A <varname>number</varname> between 0 and 63, used + to select a differentiated services code point (DSCP) + value for use with outgoing traffic on operating systems + that support DSCP. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>ip_port</varname> + </para> + </entry> + <entry colname="2"> + <para> + An IP port <varname>number</varname>. + The <varname>number</varname> is limited to 0 + through 65535, with values + below 1024 typically restricted to use by processes running + as root. + In some cases, an asterisk (`*') character can be used as a + placeholder to + select a random high-numbered port. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>ip_prefix</varname> + </para> + </entry> + <entry colname="2"> + <para> + An IP network specified as an <varname>ip_addr</varname>, + followed by a slash (`/') and then the number of bits in the + netmask. + Trailing zeros in a <varname>ip_addr</varname> + may omitted. + For example, <command>127/8</command> is the + network <command>127.0.0.0</command> with + netmask <command>255.0.0.0</command> and <command>1.2.3.0/28</command> is + network <command>1.2.3.0</command> with netmask <command>255.255.255.240</command>. + </para> + <para> + 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. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>key_id</varname> + </para> + </entry> + <entry colname="2"> + <para> + A <varname>domain_name</varname> representing + the name of a shared key, to be used for transaction + security. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>key_list</varname> + </para> + </entry> + <entry colname="2"> + <para> + A list of one or more + <varname>key_id</varname>s, + separated by semicolons and ending with a semicolon. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>number</varname> + </para> + </entry> + <entry colname="2"> + <para> + 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. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>fixedpoint</varname> + </para> + </entry> + <entry colname="2"> + <para> + 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. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>path_name</varname> + </para> + </entry> + <entry colname="2"> + <para> + A quoted string which will be used as + a pathname, such as <filename>zones/master/my.test.domain</filename>. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>port_list</varname> + </para> + </entry> + <entry colname="2"> + <para> + A list of an <varname>ip_port</varname> or a port + range. + A port range is specified in the form of + <userinput>range</userinput> followed by + two <varname>ip_port</varname>s, + <varname>port_low</varname> and + <varname>port_high</varname>, which represents + port numbers from <varname>port_low</varname> through + <varname>port_high</varname>, inclusive. + <varname>port_low</varname> must not be larger than + <varname>port_high</varname>. + For example, + <userinput>range 1024 65535</userinput> represents + ports from 1024 through 65535. + In either case an asterisk (`*') character is not + allowed as a valid <varname>ip_port</varname>. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>size_spec</varname> + </para> + </entry> + <entry colname="2"> + <para> + A 64-bit unsigned integer, or the keywords + <userinput>unlimited</userinput> or + <userinput>default</userinput>. + </para> + <para> + Integers may take values + 0 <= value <= 18446744073709551615, though + certain parameters + (such as <command>max-journal-size</command>) may + use a more limited range within these extremes. + In most cases, setting a value to 0 does not + literally mean zero; it means "undefined" or + "as big as possible", depending on the context. + See the explanations of particular parameters + that use <varname>size_spec</varname> + for details on how they interpret its use. + </para> + <para> + Numeric values can optionally be followed by a + scaling factor: + <userinput>K</userinput> or <userinput>k</userinput> + for kilobytes, + <userinput>M</userinput> or <userinput>m</userinput> + for megabytes, and + <userinput>G</userinput> or <userinput>g</userinput> + for gigabytes, which scale by 1024, 1024*1024, and + 1024*1024*1024 respectively. + </para> + <para> + <varname>unlimited</varname> generally means + "as big as possible", and is usually the best + way to safely set a very large number. + </para> + <para> + <varname>default</varname> + uses the limit that was in force when the server was started. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>size_or_percent</varname> + </para> + </entry> + <entry colname="2"> + <para> + <varname>size_spec</varname> or integer value + followed by '%' to represent percents. + </para> + <para> + The behavior is exactly the same as + <varname>size_spec</varname>, but + <varname>size_or_percent</varname> allows also + to specify a positive integer value followed by + '%' sign to represent percents. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>yes_or_no</varname> + </para> + </entry> + <entry colname="2"> + <para> + Either <userinput>yes</userinput> or <userinput>no</userinput>. + The words <userinput>true</userinput> and <userinput>false</userinput> are + also accepted, as are the numbers <userinput>1</userinput> + and <userinput>0</userinput>. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>dialup_option</varname> + </para> + </entry> + <entry colname="2"> + <para> + One of <userinput>yes</userinput>, + <userinput>no</userinput>, <userinput>notify</userinput>, + <userinput>notify-passive</userinput>, <userinput>refresh</userinput> or + <userinput>passive</userinput>. + When used in a zone, <userinput>notify-passive</userinput>, + <userinput>refresh</userinput>, and <userinput>passive</userinput> + are restricted to slave and stub zones. + </para> + </entry> + </row> + </tbody> + </tgroup> + </informaltable> + <section xml:id="address_match_lists"><info><title>Address Match Lists</title></info> + + <section><info><title>Syntax</title></info> + +<programlisting><replaceable>address_match_list</replaceable> = <replaceable>address_match_list_element</replaceable> <command>;</command> ... + +<replaceable>address_match_list_element</replaceable> = [ <command>!</command> ] ( <replaceable>ip_address</replaceable> | <replaceable>ip_prefix</replaceable> | + <command>key</command> <replaceable>key_id</replaceable> | <replaceable>acl_name</replaceable> | <command>{</command> <replaceable>address_match_list</replaceable> <command>}</command> ) +</programlisting> + + </section> + <section><info><title>Definition and Usage</title></info> + + <para> + Address match lists are primarily used to determine access + control for various server operations. They are also used in + the <command>listen-on</command> and <command>sortlist</command> + statements. The elements which constitute an address match + list can be any of the following: + </para> + <itemizedlist> + <listitem> + <simpara>an IP address (IPv4 or IPv6)</simpara> + </listitem> + <listitem> + <simpara>an IP prefix (in `/' notation)</simpara> + </listitem> + <listitem> + <simpara> + a key ID, as defined by the <command>key</command> + statement + </simpara> + </listitem> + <listitem> + <simpara>the name of an address match list defined with + the <command>acl</command> statement + </simpara> + </listitem> + <listitem> + <simpara>a nested address match list enclosed in braces</simpara> + </listitem> + </itemizedlist> + + <para> + 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. + </para> + + <para> + 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. + </para> + + <para> + 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. + </para> + + <para> + The interpretation of a match depends on whether the list is being + used for access control, defining <command>listen-on</command> ports, or in a + <command>sortlist</command>, and whether the element was negated. + </para> + + <para> + 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 + <command>allow-notify</command>, + <command>allow-recursion</command>, + <command>allow-recursion-on</command>, + <command>allow-query</command>, + <command>allow-query-on</command>, + <command>allow-query-cache</command>, + <command>allow-query-cache-on</command>, + <command>allow-transfer</command>, + <command>allow-update</command>, + <command>allow-update-forwarding</command>, + <command>blackhole</command>, and + <command>keep-response-order</command> all use address match + lists. Similarly, the <command>listen-on</command> option will cause the + server to refuse queries on any of the machine's + addresses which do not match the list. + </para> + + <para> + 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 + <emphasis>first</emphasis> 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 + <command>1.2.3/24; ! 1.2.3.13;</command> + 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 <command>! 1.2.3.13; 1.2.3/24</command> fixes + that problem by having 1.2.3.13 blocked by the negation, but + all other 1.2.3.* hosts fall through. + </para> + </section> + </section> + + <section xml:id="comment_syntax"><info><title>Comment Syntax</title></info> + + <para> + The <acronym>BIND</acronym> 9 comment syntax allows for + comments to appear + anywhere that whitespace may appear in a <acronym>BIND</acronym> configuration + file. To appeal to programmers of all kinds, they can be written + in the C, C++, or shell/perl style. + </para> + + <section><info><title>Syntax</title></info> + + <para> + <programlisting>/* This is a <acronym>BIND</acronym> comment as in C */</programlisting> + <programlisting>// This is a <acronym>BIND</acronym> comment as in C++</programlisting> + <programlisting># This is a <acronym>BIND</acronym> comment as in common UNIX shells +# and perl</programlisting> + </para> + </section> + <section><info><title>Definition and Usage</title></info> + + <para> + Comments may appear anywhere that whitespace may appear in + a <acronym>BIND</acronym> configuration file. + </para> + <para> + 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. + </para> + <para> + C-style comments cannot be nested. For example, the following + is not valid because the entire comment ends with the first */: + </para> + <para> + +<programlisting>/* 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. */ +</programlisting> + + </para> + + <para> + 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: + </para> + <para> + +<programlisting>// This is the start of a comment. The next line +// is a new comment, even though it is logically +// part of the previous comment. +</programlisting> + + </para> + <para> + Shell-style (or perl-style, if you prefer) comments start + with the character <literal>#</literal> (number sign) + and continue to the end of the + physical line, as in C++ comments. + For example: + </para> + + <para> + +<programlisting># This is the start of a comment. The next line +# is a new comment, even though it is logically +# part of the previous comment. +</programlisting> + + </para> + + <warning> + <para> + 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. + </para> + </warning> + </section> + </section> + </section> + + <section xml:id="Configuration_File_Grammar"><info><title>Configuration File Grammar</title></info> + + <para> + A <acronym>BIND</acronym> 9 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. + </para> + + <para> + The following statements are supported: + </para> + + <informaltable colsep="0" rowsep="0"> + <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="2Level-table"> + <colspec colname="1" colnum="1" colsep="0" colwidth="1.336in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="3.778in"/> + <tbody> + <row rowsep="0"> + <entry colname="1"> + <para><command>acl</command></para> + </entry> + <entry colname="2"> + <para> + defines a named IP address + matching list, for access control and other uses. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>controls</command></para> + </entry> + <entry colname="2"> + <para> + declares control channels to be used + by the <command>rndc</command> utility. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>include</command></para> + </entry> + <entry colname="2"> + <para> + includes a file. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>key</command></para> + </entry> + <entry colname="2"> + <para> + specifies key information for use in + authentication and authorization using TSIG. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>logging</command></para> + </entry> + <entry colname="2"> + <para> + specifies what the server logs, and where + the log messages are sent. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>lwres</command></para> + </entry> + <entry colname="2"> + <para> + configures <command>named</command> to + also act as a light-weight resolver daemon (<command>lwresd</command>). + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>masters</command></para> + </entry> + <entry colname="2"> + <para> + defines a named masters list for + inclusion in stub and slave zones' + <command>masters</command> or + <command>also-notify</command> lists. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>options</command></para> + </entry> + <entry colname="2"> + <para> + controls global server configuration + options and sets defaults for other statements. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>server</command></para> + </entry> + <entry colname="2"> + <para> + sets certain configuration options on + a per-server basis. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>statistics-channels</command></para> + </entry> + <entry colname="2"> + <para> + declares communication channels to get access to + <command>named</command> statistics. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>trusted-keys</command></para> + </entry> + <entry colname="2"> + <para> + defines trusted DNSSEC keys. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>managed-keys</command></para> + </entry> + <entry colname="2"> + <para> + lists DNSSEC keys to be kept up to date + using RFC 5011 trust anchor maintenance. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>view</command></para> + </entry> + <entry colname="2"> + <para> + defines a view. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>zone</command></para> + </entry> + <entry colname="2"> + <para> + defines a zone. + </para> + </entry> + </row> + </tbody> + </tgroup> + </informaltable> + + <para> + The <command>logging</command> and + <command>options</command> statements may only occur once + per + configuration. + </para> + + <section xml:id="acl_grammar"><info><title><command>acl</command> Statement Grammar</title></info> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="acl.grammar.xml"/> + </section> + <section xml:id="acl"><info><title><command>acl</command> Statement Definition and + Usage</title></info> + + <para> + The <command>acl</command> 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). + </para> + + <para> + The following ACLs are built-in: + </para> + + <informaltable colsep="0" rowsep="0"> + <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table"> + <colspec colname="1" colnum="1" colsep="0" colwidth="1.130in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="4.000in"/> + <tbody> + <row rowsep="0"> + <entry colname="1"> + <para><command>any</command></para> + </entry> + <entry colname="2"> + <para> + Matches all hosts. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>none</command></para> + </entry> + <entry colname="2"> + <para> + Matches no hosts. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>localhost</command></para> + </entry> + <entry colname="2"> + <para> + Matches the IPv4 and IPv6 addresses of all network + interfaces on the system. When addresses are + added or removed, the <command>localhost</command> + ACL element is updated to reflect the changes. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>localnets</command></para> + </entry> + <entry colname="2"> + <para> + Matches any host on an IPv4 or IPv6 network + for which the system has an interface. + When addresses are added or removed, + the <command>localnets</command> + ACL element is updated to reflect the changes. + Some systems do not provide a way to determine the prefix + lengths of + local IPv6 addresses. + In such a case, <command>localnets</command> + only matches the local + IPv6 addresses, just like <command>localhost</command>. + </para> + </entry> + </row> + </tbody> + </tgroup> + </informaltable> + </section> + <section xml:id="controls_grammar"><info><title><command>controls</command> Statement Grammar</title></info> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="controls.grammar.xml"/> + </section> + + <section xml:id="controls_statement_definition_and_usage"><info><title><command>controls</command> Statement Definition and + Usage</title></info> + + <para> + The <command>controls</command> 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 <command>rndc</command> utility to send + commands to and retrieve non-DNS results from a name server. + </para> + + <para> + An <command>inet</command> control channel is a TCP socket + listening at the specified <command>ip_port</command> on the + specified <command>ip_addr</command>, which can be an IPv4 or IPv6 + address. An <command>ip_addr</command> of <literal>*</literal> (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 <command>ip_addr</command> of <literal>::</literal>. + If you will only use <command>rndc</command> on the local host, + using the loopback address (<literal>127.0.0.1</literal> + or <literal>::1</literal>) is recommended for maximum security. + </para> + + <para> + If no port is specified, port 953 is used. The asterisk + "<literal>*</literal>" cannot be used for <command>ip_port</command>. + </para> + + <para> + The ability to issue commands over the control channel is + restricted by the <command>allow</command> and + <command>keys</command> clauses. + Connections to the control channel are permitted based on the + <command>address_match_list</command>. This is for simple + IP address based filtering only; any <command>key_id</command> + elements of the <command>address_match_list</command> + are ignored. + </para> + + <para> + A <command>unix</command> control channel is a UNIX domain + socket listening at the specified path in the file system. + Access to the socket is specified by the <command>perm</command>, + <command>owner</command> and <command>group</command> clauses. + Note on some platforms (SunOS and Solaris) the permissions + (<command>perm</command>) are applied to the parent directory + as the permissions on the socket itself are ignored. + </para> + + <para> + The primary authorization mechanism of the command + channel is the <command>key_list</command>, which + contains a list of <command>key_id</command>s. + Each <command>key_id</command> in the <command>key_list</command> + is authorized to execute commands over the control channel. + See <xref linkend="rndc"/> in <xref linkend="admin_tools"/>) + for information about configuring keys in <command>rndc</command>. + </para> + + <para> + If the <command>read-only</command> clause is enabled, the + control channel is limited to the following set of read-only + commands: <command>nta -dump</command>, + <command>null</command>, <command>status</command>, + <command>showzone</command>, <command>testgen</command>, and + <command>zonestatus</command>. By default, + <command>read-only</command> is not enabled and the control + channel allows read-write access. + </para> + + <para> + If no <command>controls</command> statement is present, + <command>named</command> 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 <command>controls</command> statement + is present but does not have a <command>keys</command> clause, + <command>named</command> will attempt to load the command channel key + from the file <filename>rndc.key</filename> in + <filename>/etc</filename> (or whatever <varname>sysconfdir</varname> + was specified as when <acronym>BIND</acronym> was built). + To create a <filename>rndc.key</filename> file, run + <userinput>rndc-confgen -a</userinput>. + </para> + + <para> + The <filename>rndc.key</filename> feature was created to + ease the transition of systems from <acronym>BIND</acronym> 8, + which did not have digital signatures on its command channel + messages and thus did not have a <command>keys</command> clause. + + It makes it possible to use an existing <acronym>BIND</acronym> 8 + configuration file in <acronym>BIND</acronym> 9 unchanged, + and still have <command>rndc</command> work the same way + <command>ndc</command> worked in BIND 8, simply by executing the + command <userinput>rndc-confgen -a</userinput> after BIND 9 is + installed. + </para> + + <para> + Since the <filename>rndc.key</filename> feature + is only intended to allow the backward-compatible usage of + <acronym>BIND</acronym> 8 configuration files, this + 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 + <filename>rndc.conf</filename> with your own key if you + wish to change + those things. The <filename>rndc.key</filename> file + also has its + permissions set such that only the owner of the file (the user that + <command>named</command> is running as) can access it. + If you + desire greater flexibility in allowing other users to access + <command>rndc</command> commands, then you need to create + a + <filename>rndc.conf</filename> file and make it group + readable by a group + that contains the users who should have access. + </para> + + <para> + To disable the command channel, use an empty + <command>controls</command> statement: + <command>controls { };</command>. + </para> + + </section> + <section xml:id="include_grammar"><info><title><command>include</command> Statement Grammar</title></info> + + <programlisting><command>include</command> <replaceable>filename</replaceable><command>;</command></programlisting> + </section> + <section xml:id="include_statement"><info><title><command>include</command> Statement Definition and Usage</title></info> + + <para> + The <command>include</command> statement inserts the + specified file at the point where the <command>include</command> + statement is encountered. The <command>include</command> + 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. + </para> + + </section> + <section xml:id="key_grammar"><info><title><command>key</command> Statement Grammar</title></info> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="key.grammar.xml"/> + </section> + + <section xml:id="key_statement"><info><title><command>key</command> Statement Definition and Usage</title></info> + + <para> + The <command>key</command> statement defines a shared + secret key for use with TSIG (see <xref linkend="tsig"/>) + or the command channel + (see <xref linkend="controls_statement_definition_and_usage"/>). + </para> + + <para> + The <command>key</command> statement can occur at the + top level + of the configuration file or inside a <command>view</command> + statement. Keys defined in top-level <command>key</command> + statements can be used in all views. Keys intended for use in + a <command>controls</command> statement + (see <xref linkend="controls_statement_definition_and_usage"/>) + must be defined at the top level. + </para> + + <para> + The <replaceable>key_id</replaceable>, also known as the + key name, is a domain name uniquely identifying the key. It can + be used in a <command>server</command> + 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. + </para> + + <para> + The <replaceable>algorithm_id</replaceable> is a string + that specifies a security/authentication algorithm. The + <command>named</command> server supports <literal>hmac-md5</literal>, + <literal>hmac-sha1</literal>, <literal>hmac-sha224</literal>, + <literal>hmac-sha256</literal>, <literal>hmac-sha384</literal> + and <literal>hmac-sha512</literal> TSIG authentication. + Truncated hashes are supported by appending the minimum + number of required bits preceded by a dash, e.g. + <literal>hmac-sha1-80</literal>. The + <replaceable>secret_string</replaceable> is the secret + to be used by the algorithm, and is treated as a Base64 + encoded string. + </para> + + </section> + <section xml:id="logging_grammar"><info><title><command>logging</command> Statement Grammar</title></info> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="logging.grammar.xml"/> + </section> + + <section xml:id="logging_statement"><info><title><command>logging</command> Statement Definition and Usage</title></info> + + <para> + The <command>logging</command> statement configures a + wide + variety of logging options for the name server. Its <command>channel</command> phrase + associates output methods, format options and severity levels with + a name that can then be used with the <command>category</command> phrase + to select how various classes of messages are logged. + </para> + <para> + Only one <command>logging</command> statement is used to + define + as many channels and categories as are wanted. If there is no <command>logging</command> statement, + the logging configuration will be: + </para> + +<programlisting>logging { + category default { default_syslog; default_debug; }; + category unmatched { null; }; +}; +</programlisting> + + <para> + If <command>named</command> is started with the + <option>-L</option> option, it logs to the specified file + at startup, instead of using syslog. In this case the logging + configuration will be: + </para> + +<programlisting>logging { + category default { default_logfile; default_debug; }; + category unmatched { null; }; +}; +</programlisting> + + <para> + In <acronym>BIND</acronym> 9, the logging configuration + is only established when + the entire configuration file has been parsed. In <acronym>BIND</acronym> 8, it was + established as soon as the <command>logging</command> + statement + was 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 <option>-g</option> option + was specified. + </para> + + <section xml:id="channel"><info><title>The <command>channel</command> Phrase</title></info> + + <para> + All log output goes to one or more <emphasis>channels</emphasis>; + you can make as many of them as you want. + </para> + + <para> + 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 + <command>info</command>), and whether to include a + <command>named</command>-generated time stamp, the + category name + and/or severity level (the default is not to include any). + </para> + + <para> + The <command>null</command> destination clause + causes all messages sent to the channel to be discarded; + in that case, other options for the channel are meaningless. + </para> + + <para> + The <command>file</command> 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. + </para> + + <para> + If you use the <command>versions</command> log file + option, then + <command>named</command> 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 <filename>lamers.log</filename>, then just + before it is opened + <filename>lamers.log.1</filename> is renamed to + <filename>lamers.log.2</filename>, <filename>lamers.log.0</filename> is renamed + to <filename>lamers.log.1</filename>, and <filename>lamers.log</filename> is + renamed to <filename>lamers.log.0</filename>. + You can say <command>versions unlimited</command> to + not limit + the number of versions. + If a <command>size</command> 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. + </para> + + <para> + The <command>size</command> option for files is used + to limit log + growth. If the file ever exceeds the size, then <command>named</command> will + stop writing to the file unless it has a <command>versions</command> 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 + <command>versions</command> 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. + </para> + + <para> + Example usage of the <command>size</command> and + <command>versions</command> options: + </para> + +<programlisting>channel an_example_channel { + file "example.log" versions 3 size 20m; + print-time yes; + print-category yes; +}; +</programlisting> + + <para> + The <command>syslog</command> destination clause + directs the + channel to the system log. Its argument is a + syslog facility as described in the <command>syslog</command> man + page. Known facilities are <command>kern</command>, <command>user</command>, + <command>mail</command>, <command>daemon</command>, <command>auth</command>, + <command>syslog</command>, <command>lpr</command>, <command>news</command>, + <command>uucp</command>, <command>cron</command>, <command>authpriv</command>, + <command>ftp</command>, <command>local0</command>, <command>local1</command>, + <command>local2</command>, <command>local3</command>, <command>local4</command>, + <command>local5</command>, <command>local6</command> and + <command>local7</command>, however not all facilities + are supported on + all operating systems. + How <command>syslog</command> will handle messages + sent to + this facility is described in the <command>syslog.conf</command> man + page. If you have a system which uses a very old version of <command>syslog</command> that + only uses two arguments to the <command>openlog()</command> function, + then this clause is silently ignored. + </para> + <para> + On Windows machines syslog messages are directed to the EventViewer. + </para> + <para> + The <command>severity</command> clause works like <command>syslog</command>'s + "priorities", except that they can also be used if you are writing + straight to a file rather than using <command>syslog</command>. + 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. + </para> + <para> + If you are using <command>syslog</command>, then the <command>syslog.conf</command> priorities + will also determine what eventually passes through. For example, + defining a channel facility and severity as <command>daemon</command> and <command>debug</command> but + only logging <command>daemon.warning</command> via <command>syslog.conf</command> will + cause messages of severity <command>info</command> and + <command>notice</command> to + be dropped. If the situation were reversed, with <command>named</command> writing + messages of only <command>warning</command> or higher, + then <command>syslogd</command> would + print all messages it received from the channel. + </para> + + <para> + The <command>stderr</command> 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. + </para> + + <para> + 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 <command>named</command> server + with the <option>-d</option> flag followed by a positive integer, + or by running <command>rndc trace</command>. + The global debug level + can be set to zero, and debugging mode turned off, by running <command>rndc +notrace</command>. 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: + </para> + +<programlisting>channel specific_debug_level { + file "foo"; + severity debug 3; +}; +</programlisting> + + <para> + 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 <command>dynamic</command> + severity use the + server's global debug level to determine what messages to print. + </para> + <para> + If <command>print-time</command> has been turned on, + then + the date and time will be logged. <command>print-time</command> may + be specified for a <command>syslog</command> channel, + but is usually + pointless since <command>syslog</command> also logs + the date and + time. If <command>print-category</command> is + requested, then the + category of the message will be logged as well. Finally, if <command>print-severity</command> is + on, then the severity level of the message will be logged. The <command>print-</command> 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 <command>print-</command> options + are on: + </para> + + <para> + <computeroutput>28-Feb-2000 15:05:32.863 general: notice: running</computeroutput> + </para> + + <para> + If <command>buffered</command> has been turned on the output + to files will not be flushed after each log entry. By default + all log messages are flushed. + </para> + + <para> + There are four predefined channels that are used for + <command>named</command>'s default logging as follows. + If <command>named</command> is started with the + <option>-L</option> then a + fifth channel <command>default_logfile</command> is added. + How they are + used is described in <xref linkend="the_category_phrase"/>. + </para> + +<programlisting>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 '-g' 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; +}; + +channel default_logfile { + // this channel is only present if named is + // started with the -L option, whose argument + // provides the file name + file "..."; + // log at the server's current debug level + severity dynamic; +}; +</programlisting> + + <para> + The <command>default_debug</command> 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 <filename>named.run</filename> + in the server's working directory. + </para> + + <para> + For security reasons, when the <option>-u</option> + command line option is used, the <filename>named.run</filename> file + is created only after <command>named</command> has + changed to the + new UID, and any debug output generated while <command>named</command> is + starting up and still running as root is discarded. If you need + to capture this output, you must run the server with the <option>-L</option> + option to specify a default logfile, or the <option>-g</option> + option to log to standard error which you can redirect to a file. + </para> + + <para> + 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. + </para> + </section> + + <section xml:id="the_category_phrase"><info><title>The <command>category</command> Phrase</title></info> + + <para> + 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 <command>default</command> category + instead. If you don't specify a default category, the following + "default default" is used: + </para> + +<programlisting>category default { default_syslog; default_debug; }; +</programlisting> + + <para> + If you start <command>named</command> with the + <option>-L</option> option then the default category is: + </para> + +<programlisting>category default { default_logfile; default_debug; }; +</programlisting> + + <para> + 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: + </para> + +<programlisting>channel my_security_channel { + file "my_security_file"; + severity info; +}; +category security { + my_security_channel; + default_syslog; + default_debug; +};</programlisting> + + <para> + To discard all messages in a category, specify the <command>null</command> channel: + </para> + +<programlisting>category xfer-out { null; }; +category notify { null; }; +</programlisting> + + <para> + Following are the available categories and brief descriptions + of the types of log information they contain. More + categories may be added in future <acronym>BIND</acronym> releases. + </para> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="logging-categories.xml"/> + </section> + <section xml:id="query_errors"><info><title>The <command>query-errors</command> Category</title></info> + <para> + The <command>query-errors</command> 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 <command>debug</command> levels. + </para> + + <para> + At the debug levels of 1 or higher, each response with the + rcode of SERVFAIL is logged as follows: + </para> + <para> + <computeroutput>client 127.0.0.1#61502: query failed (SERVFAIL) for www.example.com/IN/AAAA at query.c:3880</computeroutput> + </para> + <para> + This means an error resulting in SERVFAIL was + detected at line 3880 of source file + <filename>query.c</filename>. + Log messages of this level will particularly + help identify the cause of SERVFAIL for an + authoritative server. + </para> + <para> + 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: + </para> + <para> +<!-- NOTE: newlines and some spaces added so this would fit on page --> + <programlisting> +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] + </programlisting> + </para> + <para> + 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 + <filename>resolver.c</filename>. + </para> + <para> + 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. + </para> + <para> + The last part enclosed in square brackets shows statistics + information collected for this particular resolution + attempt. + The <varname>domain</varname> 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. + </para> + + <informaltable colsep="0" rowsep="0"> + <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table"> + <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="3.350in"/> + <tbody> + <row rowsep="0"> + <entry colname="1"> + <para><varname>referral</varname></para> + </entry> + <entry colname="2"> + <para> + 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. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><varname>restart</varname></para> + </entry> + <entry colname="2"> + <para> + The number of cycles that the resolver tried + remote servers at the <varname>domain</varname> + zone. + In each cycle the resolver sends one query + (possibly resending it, depending on the response) + to each known name server of + the <varname>domain</varname> zone. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><varname>qrysent</varname></para> + </entry> + <entry colname="2"> + <para> + The number of queries the resolver sent at the + <varname>domain</varname> zone. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><varname>timeout</varname></para> + </entry> + <entry colname="2"> + <para> + The number of timeouts since the resolver + received the last response. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><varname>lame</varname></para> + </entry> + <entry colname="2"> + <para> + The number of lame servers the resolver detected + at the <varname>domain</varname> zone. + A server is detected to be lame either by an + invalid response or as a result of lookup in + BIND9's address database (ADB), where lame + servers are cached. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><varname>neterr</varname></para> + </entry> + <entry colname="2"> + <para> + The number of erroneous results that the + resolver encountered in sending queries + at the <varname>domain</varname> zone. + One common case is the remote server is + unreachable and the resolver receives an ICMP + unreachable error message. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><varname>badresp</varname></para> + </entry> + <entry colname="2"> + <para> + The number of unexpected responses (other than + <varname>lame</varname>) to queries sent by the + resolver at the <varname>domain</varname> zone. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><varname>adberr</varname></para> + </entry> + <entry colname="2"> + <para> + Failures in finding remote server addresses + of the <varname>domain</varname> zone in the ADB. + One common case of this is that the remote + server's name does not have any address records. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><varname>findfail</varname></para> + </entry> + <entry colname="2"> + <para> + Failures of resolving remote server addresses. + This is a total number of failures throughout + the resolution process. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><varname>valfail</varname></para> + </entry> + <entry colname="2"> + <para> + Failures of DNSSEC validation. + Validation failures are counted throughout + the resolution process (not limited to + the <varname>domain</varname> zone), but should + only happen in <varname>domain</varname>. + </para> + </entry> + </row> + </tbody> + </tgroup> + </informaltable> + <para> + 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. + </para> + <para> + 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. + </para> + </section> + </section> + + <section xml:id="lwres_grammar"><info><title><command>lwres</command> Statement Grammar</title></info> + + <para> + This is the grammar of the <command>lwres</command> + statement in the <filename>named.conf</filename> file: + </para> + +<programlisting><command>lwres {</command> + [ <command>listen-on {</command> + ( <replaceable>ip_addr</replaceable> [ <command>port</command> <replaceable>ip_port</replaceable> ] [ <command>dscp</command> <replaceable>ip_dscp</replaceable> ] <command>;</command> ) + ... + <command>};</command> ] + [ <command>view</command> <replaceable>view_name</replaceable><command>;</command> ] + [ <command>search {</command> <replaceable>domain_name</replaceable> <command>;</command> ... <command>};</command> ] + [ <command>ndots</command> <replaceable>number</replaceable><command>;</command> ] + [ <command>lwres-tasks</command> <replaceable>number</replaceable><command>;</command> ] + [ <command>lwres-clients</command> <replaceable>number</replaceable><command>;</command> ] +<command>};</command> +</programlisting> + + </section> + <section xml:id="lwres_statement"><info><title><command>lwres</command> Statement Definition and Usage</title></info> + + <para> + The <command>lwres</command> statement configures the + name + server to also act as a lightweight resolver server. (See + <xref linkend="lwresd"/>.) There may be multiple + <command>lwres</command> statements configuring + lightweight resolver servers with different properties. + </para> + + <para> + The <command>listen-on</command> statement specifies a + list of + IPv4 addresses (and ports) that this instance of a lightweight + resolver daemon + should accept requests on. If no port is specified, port 921 is + used. + If this statement is omitted, requests will be accepted on + 127.0.0.1, + port 921. + </para> + + <para> + The <command>view</command> statement binds this + instance of a + lightweight resolver daemon to a view in the DNS namespace, so that + the + response will be constructed in the same manner as a normal DNS + query + matching this view. If this statement is omitted, the default view + is + used, and if there is no default view, an error is triggered. + </para> + + <para> + The <command>search</command> statement is equivalent to + the + <command>search</command> statement in + <filename>/etc/resolv.conf</filename>. It provides a + list of domains + which are appended to relative names in queries. + </para> + + <para> + The <command>ndots</command> statement is equivalent to + the + <command>ndots</command> statement in + <filename>/etc/resolv.conf</filename>. It indicates the + minimum + number of dots in a relative domain name that should result in an + exact match lookup before search path elements are appended. + </para> + <para> + The <option>lwres-tasks</option> statement specifies the number + of worker threads the lightweight resolver will dedicate to serving + clients. By default the number is the same as the number of CPUs on + the system; this can be overridden using the <option>-n</option> + command line option when starting the server. + </para> + <para> + The <option>lwres-clients</option> specifies + the number of client objects per thread the lightweight + resolver should create to serve client queries. + By default, if the lightweight resolver runs as a part + of <command>named</command>, 256 client objects are + created for each task; if it runs as <command>lwresd</command>, + 1024 client objects are created for each thread. The maximum + value is 32768; higher values will be silently ignored and + the maximum will be used instead. + Note that setting too high a value may overconsume + system resources. + </para> + <para> + The maximum number of client queries that the lightweight + resolver can handle at any one time equals + <option>lwres-tasks</option> times <option>lwres-clients</option>. + </para> + </section> + <section xml:id="masters_grammar"><info><title><command>masters</command> Statement Grammar</title></info> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="masters.grammar.xml"/> + </section> + + <section xml:id="masters_statement"><info><title><command>masters</command> Statement Definition and + Usage</title></info> + + <para><command>masters</command> + lists allow for a common set of masters to be easily used by + multiple stub and slave zones in their <command>masters</command> + or <command>also-notify</command> lists. + </para> + </section> + + <section xml:id="options_grammar"><info><title><command>options</command> Statement Grammar</title></info> + + <para> + This is the grammar of the <command>options</command> + statement in the <filename>named.conf</filename> file: + </para> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="options.grammar.xml"/> + </section> + + <section xml:id="options"><info><title><command>options</command> Statement Definition and + Usage</title></info> + + <para> + The <command>options</command> statement sets up global + options + to be used by <acronym>BIND</acronym>. This statement + may appear only + once in a configuration file. If there is no <command>options</command> + statement, an options block with each option set to its default will + be used. + </para> + + <variablelist> + + <varlistentry> + <term><command>attach-cache</command></term> + <listitem> + <para> + 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. + </para> + + <para> + The <command>attach-cache</command> option + may also be specified in <command>view</command> + statements, in which case it overrides the + global <command>attach-cache</command> option. + </para> + + <para> + The <replaceable>cache_name</replaceable> specifies + the cache to be shared. + When the <command>named</command> 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. + </para> + + <para> + 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 <command>attach-cache</command> as a global + option with an arbitrary name. + </para> + + <para> + 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 + <command>attach-cache</command> option as a view A (or + B)'s option, referring to the other view name: + </para> + +<programlisting> + 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 + ... + }; +</programlisting> + + <para> + 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: + <command>check-names</command>, + <command>cleaning-interval</command>, + <command>dnssec-accept-expired</command>, + <command>dnssec-validation</command>, + <command>max-cache-ttl</command>, + <command>max-ncache-ttl</command>, + <command>max-cache-size</command>, and + <command>zero-no-soa-ttl</command>. + </para> + + <para> + 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. + </para> + </listitem> + + </varlistentry> + + <varlistentry> + <term><command>directory</command></term> + <listitem> + <para> + 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. <filename>named.run</filename>) is this directory. + If a directory is not specified, the working directory + defaults to `<filename>.</filename>', the directory from + which the server was started. The directory specified + should be an absolute path. It is + <emphasis>strongly recommended</emphasis> + that the directory be writable by the effective user + ID of the <command>named</command> process. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>dnstap</command></term> + <listitem> + <para> + <command>dnstap</command> is a fast, flexible method + for capturing and logging DNS traffic. Developed by + Robert Edmonds at Farsight Security, Inc., and supported + by multiple DNS implementations, <command>dnstap</command> + uses + <command>libfstrm</command> (a lightweight high-speed + framing library, see + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://github.com/farsightsec/fstrm">https://github.com/farsightsec/fstrm</link>) to send + event payloads which are encoded using Protocol Buffers + (<command>libprotobuf-c</command>, a mechanism for + serializing structured data developed + by Google, Inc.; see + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://developers.google.com/protocol-buffers/">https://developers.google.com/protocol-buffers</link>). + </para> + <para> + To enable <command>dnstap</command> at compile time, + the <command>fstrm</command> and <command>protobuf-c</command> + libraries must be available, and BIND must be configured with + <option>--enable-dnstap</option>. + </para> + <para> + The <command>dnstap</command> option is a bracketed list + of message types to be logged. These may be set differently + for each view. Supported types are <literal>client</literal>, + <literal>auth</literal>, <literal>resolver</literal>, and + <literal>forwarder</literal>. Specifying type + <literal>all</literal> will cause all <command>dnstap</command> + messages to be logged, regardless of type. + </para> + <para> + Each type may take an additional argument to indicate whether + to log <literal>query</literal> messages or + <literal>response</literal> messages; if not specified, + both queries and responses are logged. + </para> + <para> + Example: To log all authoritative queries and responses, + recursive client responses, and upstream queries sent by + the resolver, use: +<programlisting>dnstap { + auth; + client response; + resolver query; +}; +</programlisting> + </para> + <para> + Logged <command>dnstap</command> messages can be parsed + using the <command>dnstap-read</command> utility (see + <xref linkend="man.dnstap-read"/> for details). + </para> + <para> + For more information on <command>dnstap</command>, see + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://dnstap.info">http://dnstap.info</link>. + </para> + <para> + The fstrm library has a number of tunables that are exposed + in <filename>named.conf</filename>, and can be modified + if necessary to improve performance or prevent loss of data. + These are: + </para> + <itemizedlist> + <listitem> + <simpara> + <command>fstrm-set-buffer-hint</command>: The + threshold number of bytes to accumulate in the output + buffer before forcing a buffer flush. The minimum is + 1024, the maximum is 65536, and the default is 8192. + </simpara> + </listitem> + <listitem> + <simpara> + <command>fstrm-set-flush-timeout</command>: The number + of seconds to allow unflushed data to remain in the + output buffer. The minimum is 1 second, the maximum is + 600 seconds (10 minutes), and the default is 1 second. + </simpara> + </listitem> + <listitem> + <simpara> + <command>fstrm-set-output-notify-threshold</command>: + The number of outstanding queue entries to allow on + an input queue before waking the I/O thread. + The minimum is 1 and the default is 32. + </simpara> + </listitem> + <listitem> + <simpara> + <command>fstrm-set-output-queue-model</command>: + Controls the queuing semantics to use for queue + objects. The default is <literal>mpsc</literal> + (multiple producer, single consumer); the other + option is <literal>spsc</literal> (single producer, + single consumer). + </simpara> + </listitem> + <listitem> + <simpara> + <command>fstrm-set-input-queue-size</command>: The + number of queue entries to allocate for each + input queue. This value must be a power of 2. + The minimum is 2, the maximum is 16384, and + the default is 512. + </simpara> + </listitem> + <listitem> + <simpara> + <command>fstrm-set-output-queue-size</command>: + The number of queue entries to allocate for each + output queue. The minimum is 2, the maximum is + system-dependent and based on <option>IOV_MAX</option>, + and the default is 64. + </simpara> + </listitem> + <listitem> + <simpara> + <command>fstrm-set-reopen-interval</command>: + The number of seconds to wait between attempts to + reopen a closed output stream. The minimum is 1 second, + the maximum is 600 seconds (10 minutes), and the default + is 5 seconds. + </simpara> + </listitem> + </itemizedlist> + <para> + Note that all of the above minimum, maximum, and default + values are set by the <command>libfstrm</command> library, + and may be subject to change in future versions of the + library. See the <command>libfstrm</command> documentation + for more information. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>dnstap-output</command></term> + <listitem> + <para> + Configures the path to which the <command>dnstap</command> + frame stream will be sent if <command>dnstap</command> + is enabled at compile time and active. + </para> + <para> + The first argument is either <literal>file</literal> or + <literal>unix</literal>, indicating whether the destination + is a file or a UNIX domain socket. The second argument + is the path of the file or socket. (Note: when using a + socket, <command>dnstap</command> messages will + only be sent if another process such as + <command>fstrm_capture</command> + (provided with <command>libfstrm</command>) is listening on + the socket.) + </para> + <para> + <command>dnstap-output</command> can only be set globally + in <command>options</command>. Currently, it can only be + set once while <command>named</command> is running; + once set, it cannot be changed by + <command>rndc reload</command> or + <command>rndc reconfig</command>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>dnstap-identity</command></term> + <listitem> + <para> + Specifies an <command>identity</command> string to send in + <command>dnstap</command> messages. If set to + <literal>hostname</literal>, which is the default, the + server's hostname will be sent. If set to + <literal>none</literal>, no identity string will be sent. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>dnstap-version</command></term> + <listitem> + <para> + Specifies a <command>version</command> string to send in + <command>dnstap</command> messages. The default is the + version number of the BIND release. If set to + <literal>none</literal>, no version string will be sent. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>geoip-directory</command></term> + <listitem> + <para> + Specifies the directory containing GeoIP + <filename>.dat</filename> database files for GeoIP + initialization. By default, this option is unset + and the GeoIP support will use libGeoIP's + built-in directory. + (For details, see <xref linkend="acl"/> about the + <command>geoip</command> ACL.) + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>key-directory</command></term> + <listitem> + <para> + 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 + <filename>bind.keys</filename>, + <filename>rndc.key</filename> or + <filename>session.key</filename>.) + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>lmdb-mapsize</command></term> + <listitem> + <para> + When <command>named</command> is built with liblmdb, + this option sets a maximum size for the memory map of + the new-zone database (NZD) in LMDB database format. + This database is used to store configuration information + for zones added using <command>rndc addzone</command>. + Note that this is not the NZD database file size, but + the largest size that the database may grow to. + </para> + <para> + Because the database file is memory mapped, its size is + limited by the address space of the named process. The + default of 32 megabytes was chosen to be usable with + 32-bit <command>named</command> builds. The largest + permitted value is 1 terabyte. Given typical zone + configurations without elaborate ACLs, a 32 MB NZD file + ought to be able to hold configurations of about 100,000 + zones. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>managed-keys-directory</command></term> + <listitem> + <para> + Specifies the directory in which to store the files that + track managed DNSSEC keys. By default, this is the working + directory. The directory <emphasis>must</emphasis> + be writable by the effective user ID of the + <command>named</command> process. + </para> + <para> + If <command>named</command> is not configured to use views, + then managed keys for the server will be tracked in a single + file called <filename>managed-keys.bind</filename>. + Otherwise, managed keys will be tracked in separate files, + one file per view; each file name will be the view name + (or, if it contains characters that are incompatible with + use as a file name, the SHA256 hash of the view name), + followed by the extension + <filename>.mkeys</filename>. + </para> + <para> + (Note: in previous releases, file names for views + always used the SHA256 hash of the view name. To ensure + compatibility after upgrade, if a file using the old + name format is found to exist, it will be used instead + of the new format.) + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>named-xfer</command></term> + <listitem> + <para> + <emphasis>This option is obsolete.</emphasis> It + was used in <acronym>BIND</acronym> 8 to specify + the pathname to the <command>named-xfer</command> + program. In <acronym>BIND</acronym> 9, no separate + <command>named-xfer</command> program is needed; + its functionality is built into the name server. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>tkey-gssapi-keytab</command></term> + <listitem> + <para> + The KRB5 keytab file to use for GSS-TSIG updates. If + this option is set and tkey-gssapi-credential is not + set, then updates will be allowed with any key + matching a principal in the specified keytab. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>tkey-gssapi-credential</command></term> + <listitem> + <para> + The security credential with which the server should + authenticate keys requested by the GSS-TSIG protocol. + Currently only Kerberos 5 authentication is available + and the credential is a Kerberos principal which the + server can acquire through the default system key + file, normally <filename>/etc/krb5.keytab</filename>. + The location keytab file can be overridden using the + tkey-gssapi-keytab option. Normally this principal is + of the form "<userinput>DNS/</userinput><varname>server.domain</varname>". + To use GSS-TSIG, <command>tkey-domain</command> must + also be set if a specific keytab is not set with + tkey-gssapi-keytab. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>tkey-domain</command></term> + <listitem> + <para> + The domain appended to the names of all shared keys + generated with <command>TKEY</command>. When a + client requests a <command>TKEY</command> exchange, + it may or may not specify the desired name for the + key. If present, the name of the shared key will + be <varname>client specified part</varname> + + <varname>tkey-domain</varname>. Otherwise, the + name of the shared key will be <varname>random hex + digits</varname> + <varname>tkey-domain</varname>. + In most cases, the <command>domainname</command> + should be the server's domain name, or an otherwise + non-existent subdomain like + "_tkey.<varname>domainname</varname>". If you are + using GSS-TSIG, this variable must be defined, unless + you specify a specific keytab using tkey-gssapi-keytab. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>tkey-dhkey</command></term> + <listitem> + <para> + The Diffie-Hellman key used by the server + to generate shared keys with clients using the Diffie-Hellman + mode + of <command>TKEY</command>. The server must be + able to load the + public and private keys from files in the working directory. + In + most cases, the <varname>key_name</varname> should be the server's host name. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>cache-file</command></term> + <listitem> + <para> + This is for testing only. Do not use. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>dump-file</command></term> + <listitem> + <para> + The pathname of the file the server dumps + the database to when instructed to do so with + <command>rndc dumpdb</command>. + If not specified, the default is <filename>named_dump.db</filename>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>memstatistics-file</command></term> + <listitem> + <para> + The pathname of the file the server writes memory + usage statistics to on exit. If not specified, + the default is <filename>named.memstats</filename>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>lock-file</command></term> + <listitem> + <para> + The pathname of a file on which <command>named</command> will + attempt to acquire a file lock when starting up for + the first time; if unsuccessful, the server will + will terminate, under the assumption that another + server is already running. If not specified, the default is + <filename>/var/run/named/named.lock</filename>. + </para> + <para> + Specifying <command>lock-file none</command> disables the + use of a lock file. <command>lock-file</command> is + ignored if <command>named</command> was run using the <option>-X</option> + option, which overrides it. Changes to + <command>lock-file</command> are ignored if + <command>named</command> is being reloaded or + reconfigured; it is only effective when the server is + first started up. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>pid-file</command></term> + <listitem> + <para> + The pathname of the file the server writes its process ID + in. If not specified, the default is + <filename>/var/run/named/named.pid</filename>. + The PID file is used by programs that want to send signals to + the running + name server. Specifying <command>pid-file none</command> disables the + use of a PID file — no file will be written and any + existing one will be removed. Note that <command>none</command> + is a keyword, not a filename, and therefore is not enclosed + in + double quotes. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>recursing-file</command></term> + <listitem> + <para> + The pathname of the file the server dumps + the queries that are currently recursing when instructed + to do so with <command>rndc recursing</command>. + If not specified, the default is <filename>named.recursing</filename>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>statistics-file</command></term> + <listitem> + <para> + The pathname of the file the server appends statistics + to when instructed to do so using <command>rndc stats</command>. + If not specified, the default is <filename>named.stats</filename> in the + server's current directory. The format of the file is + described + in <xref linkend="statsfile"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>bindkeys-file</command></term> + <listitem> + <para> + The pathname of a file to override the built-in trusted + keys provided by <command>named</command>. + See the discussion of <command>dnssec-validation</command> + for details. If not specified, the default is + <filename>/etc/bind.keys</filename>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>secroots-file</command></term> + <listitem> + <para> + The pathname of the file the server dumps + security roots to when instructed to do so with + <command>rndc secroots</command>. + If not specified, the default is + <filename>named.secroots</filename>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>session-keyfile</command></term> + <listitem> + <para> + The pathname of the file into which to write a TSIG + session key generated by <command>named</command> for use by + <command>nsupdate -l</command>. If not specified, the + default is <filename>/var/run/named/session.key</filename>. + (See <xref linkend="dynamic_update_policies"/>, and in + particular the discussion of the + <command>update-policy</command> statement's + <userinput>local</userinput> option for more + information about this feature.) + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>session-keyname</command></term> + <listitem> + <para> + The key name to use for the TSIG session key. + If not specified, the default is "local-ddns". + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>session-keyalg</command></term> + <listitem> + <para> + 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>port</command></term> + <listitem> + <para> + 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>dscp</command></term> + <listitem> + <para> + 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>random-device</command></term> + <listitem> + <para> + The source of entropy to be used by the server. Entropy is + primarily needed + for DNSSEC operations, such as TKEY transactions and dynamic + update of signed + zones. This options specifies the device (or file) from which + to read + entropy. If this is a file, operations requiring entropy will + fail when the + file has been exhausted. If not specified, the default value + is + <filename>/dev/random</filename> + (or equivalent) when present, and none otherwise. The + <command>random-device</command> option takes + effect during + the initial configuration load at server startup time and + is ignored on subsequent reloads. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>preferred-glue</command></term> + <listitem> + <para> + 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. + </para> + </listitem> + </varlistentry> + + <varlistentry xml:id="root_delegation_only"> + <term><command>root-delegation-only</command></term> + <listitem> + <para> + Turn on enforcement of delegation-only in TLDs + (top level domains) and root zones with an optional + exclude list. + </para> + <para> + 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. + </para> + <para> + 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. + </para> + <para> + 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. + </para> + <para> + Note some TLDs are not delegation only (e.g. "DE", "LV", + "US" and "MUSEUM"). This list is not exhaustive. + </para> + +<programlisting> +options { + root-delegation-only exclude { "de"; "lv"; "us"; "museum"; }; +}; +</programlisting> + + </listitem> + </varlistentry> + + <varlistentry> + <term><command>disable-algorithms</command></term> + <listitem> + <para> + Disable the specified DNSSEC algorithms at and below the + specified name. + Multiple <command>disable-algorithms</command> + statements are allowed. + Only the best match <command>disable-algorithms</command> + clause will be used to determine which algorithms are used. + </para> + <para> + If all supported algorithms are disabled, the zones covered + by the <command>disable-algorithms</command> will be treated + as insecure. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>disable-ds-digests</command></term> + <listitem> + <para> + Disable the specified DS/DLV digest types at and below the + specified name. + Multiple <command>disable-ds-digests</command> + statements are allowed. + Only the best match <command>disable-ds-digests</command> + clause will be used to determine which digest types are used. + </para> + <para> + If all supported digest types are disabled, the zones covered + by the <command>disable-ds-digests</command> will be treated + as insecure. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>dnssec-lookaside</command></term> + <listitem> + <para> + When set, <command>dnssec-lookaside</command> provides the + validator with an alternate method to validate DNSKEY + records at the top of a zone. When a DNSKEY is at or + below a domain specified by the deepest + <command>dnssec-lookaside</command>, and the normal DNSSEC + validation has left the key untrusted, the trust-anchor + will be appended to the key name and a DLV record will be + looked up to see if it can validate the key. If the DLV + record validates a DNSKEY (similarly to the way a DS + record does) the DNSKEY RRset is deemed to be trusted. + </para> + <para> + If <command>dnssec-lookaside</command> is set to + <userinput>no</userinput>, then dnssec-lookaside + is not used. + </para> + <para> + NOTE: The ISC-provided DLV service at + <literal>dlv.isc.org</literal>, has been shut down. + The <command>dnssec-lookaside auto;</command> + configuration option, which set <command>named</command> + up to use ISC DLV with minimal configuration, has + accordingly been removed. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>dnssec-must-be-secure</command></term> + <listitem> + <para> + Specify hierarchies which must be or may not be secure + (signed and validated). If <userinput>yes</userinput>, + then <command>named</command> will only accept answers if + they are secure. If <userinput>no</userinput>, then normal + DNSSEC validation applies allowing for insecure answers to + be accepted. The specified domain must be under a + <command>trusted-keys</command> or + <command>managed-keys</command> statement, or + <command>dnssec-validation auto</command> must be active. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>dns64</command></term> + <listitem> + <para> + This directive instructs <command>named</command> 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. Each + <command>dns64</command> defines one DNS64 prefix. + Multiple DNS64 prefixes can be defined. + </para> + <para> + Compatible IPv6 prefixes have lengths of 32, 40, 48, 56, + 64 and 96 as per RFC 6052. + </para> + <para> + 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. <command>dns64-server</command> and + <command>dns64-contact</command> 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. + </para> + <para> + Each <command>dns64</command> supports an optional + <command>clients</command> ACL that determines which + clients are affected by this directive. If not defined, + it defaults to <userinput>any;</userinput>. + </para> + <para> + Each <command>dns64</command> supports an optional + <command>mapped</command> ACL that selects which + IPv4 addresses are to be mapped in the corresponding + A RRset. If not defined it defaults to + <userinput>any;</userinput>. + </para> + <para> + Normally, DNS64 won't apply to a domain name that + owns one or more AAAA records; these records will + simply be returned. The optional + <command>exclude</command> 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, <command>exclude</command> + defaults to ::ffff:0.0.0.0/96. + </para> + <para> + A optional <command>suffix</command> can also + be defined to set the bits trailing the mapped + IPv4 address bits. By default these bits are + set to <userinput>::</userinput>. The bits + matching the prefix and mapped IPv4 address + must be zero. + </para> + <para> + If <command>recursive-only</command> is set to + <command>yes</command> the DNS64 synthesis will + only happen for recursive queries. The default + is <command>no</command>. + </para> + <para> + If <command>break-dnssec</command> is set to + <command>yes</command> the DNS64 synthesis will + happen even if the result, if validated, would + cause a DNSSEC validation failure. If this option + is set to <command>no</command> (the default), the DO + is set on the incoming query, and there are RRSIGs on + the applicable records, then synthesis will not happen. + </para> +<programlisting> + 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 ::; + }; +</programlisting> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>dnssec-loadkeys-interval</command></term> + <listitem> + <para> + When a zone is configured with <command>auto-dnssec + maintain;</command> 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 <xref linkend="man.dnssec-keygen"/> and + <xref linkend="man.dnssec-settime"/>). The + <command>dnssec-loadkeys-interval</command> option + sets the frequency of automatic repository checks, in + minutes. The default is <literal>60</literal> (1 hour), + the minimum is <literal>1</literal> (1 minute), and the + maximum is <literal>1440</literal> (24 hours); any higher + value is silently reduced. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>dnssec-update-mode</command></term> + <listitem> + <para> + If this option is set to its default value of + <literal>maintain</literal> in a zone of type + <literal>master</literal> which is DNSSEC-signed + and configured to allow dynamic updates (see + <xref linkend="dynamic_update_policies"/>), and + if <command>named</command> has access to the + private signing key(s) for the zone, then + <command>named</command> will automatically sign all new + or changed records and maintain signatures for the zone + by regenerating RRSIG records whenever they approach + their expiration date. + </para> + <para> + If the option is changed to <literal>no-resign</literal>, + then <command>named</command> will sign all new or + changed records, but scheduled maintenance of + signatures is disabled. + </para> + <para> + With either of these settings, <command>named</command> + will reject updates to a DNSSEC-signed zone when the + signing keys are inactive or unavailable to + <command>named</command>. (A planned third option, + <literal>external</literal>, will disable all automatic + signing and allow DNSSEC data to be submitted into a zone + via dynamic update; this is not yet implemented.) + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>nta-lifetime</command></term> + <listitem> + <para> + Species the default lifetime, in seconds, + that will be used for negative trust anchors added + via <command>rndc nta</command>. + </para> + <para> + A negative trust anchor selectively disables + DNSSEC validation for zones that are known to be + failing because of misconfiguration rather than + an attack. When data to be validated is + at or below an active NTA (and above any other + configured trust anchors), <command>named</command> will + abort the DNSSEC validation process and treat the data as + insecure rather than bogus. This continues until the + NTA's lifetime is elapsed. NTAs persist + across <command>named</command> restarts. + </para> + <para> + For convenience, TTL-style time unit suffixes can be + used to specify the NTA lifetime in seconds, minutes + or hours. <option>nta-lifetime</option> defaults to + one hour. It cannot exceed one week. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>nta-recheck</command></term> + <listitem> + <para> + Species how often to check whether negative + trust anchors added via <command>rndc nta</command> + are still necessary. + </para> + <para> + A negative trust anchor is normally used when a + domain has stopped validating due to operator error; + it temporarily disables DNSSEC validation for that + domain. In the interest of ensuring that DNSSEC + validation is turned back on as soon as possible, + <command>named</command> will periodically send a + query to the domain, ignoring negative trust anchors, + to find out whether it can now be validated. If so, + the negative trust anchor is allowed to expire early. + </para> + <para> + Validity checks can be disabled for an individual + NTA by using <command>rndc nta -f</command>, or + for all NTAs by setting <option>nta-recheck</option> + to zero. + </para> + <para> + For convenience, TTL-style time unit suffixes can be + used to specify the NTA recheck interval in seconds, + minutes or hours. The default is five minutes. It + cannot be longer than <option>nta-lifetime</option> + (which cannot be longer than a week). + </para> + </listitem> + </varlistentry> + + + <varlistentry> + <term><command>max-zone-ttl</command></term> + <listitem> + <para> + Specifies a maximum permissible TTL value in seconds. + For convenience, TTL-style time unit suffixes may be + used to specify the maximum value. + When loading a zone file using a + <option>masterfile-format</option> of + <constant>text</constant> or <constant>raw</constant>, + any record encountered with a TTL higher than + <option>max-zone-ttl</option> will cause the zone to + be rejected. + </para> + <para> + 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 <option>max-zone-ttl</option> option guarantees + that the largest TTL in the zone will be no higher + than the set value. + </para> + <para> + (NOTE: Because <constant>map</constant>-format files + load directly into memory, this option cannot be + used with them.) + </para> + <para> + The default value is <constant>unlimited</constant>. + A <option>max-zone-ttl</option> of zero is treated as + <constant>unlimited</constant>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>serial-update-method</command></term> + <listitem> + <para> + 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. + </para> + <para> + With the default setting of + <command>serial-update-method increment;</command>, the + SOA serial number will be incremented by one each time + the zone is updated. + </para> + <para> + When set to + <command>serial-update-method unixtime;</command>, 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. + </para> + <para> + When set to + <command>serial-update-method date;</command>, the + new SOA serial number will be the current date + in the form "YYYYMMDD", followed by two zeroes, + unless the existing serial number is already greater + than or equal to that value, in which case it is + incremented by one. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>zone-statistics</command></term> + <listitem> + <para> + If <userinput>full</userinput>, the server will collect + statistical data on all zones (unless specifically + turned off on a per-zone basis by specifying + <command>zone-statistics terse</command> or + <command>zone-statistics none</command> + in the <command>zone</command> statement). + The default is <userinput>terse</userinput>, providing + minimal statistics on zones (including name and + current serial number, but not query type + counters). + </para> + <para> + These statistics may be accessed via the + <command>statistics-channel</command> or + using <command>rndc stats</command>, which + will dump them to the file listed + in the <command>statistics-file</command>. See + also <xref linkend="statsfile"/>. + </para> + <para> + For backward compatibility with earlier versions + of BIND 9, the <command>zone-statistics</command> + option can also accept <userinput>yes</userinput> + or <userinput>no</userinput>; <userinput>yes</userinput> + has the same meaning as <userinput>full</userinput>. + As of <acronym>BIND</acronym> 9.10, + <userinput>no</userinput> has the same meaning + as <userinput>none</userinput>; previously, it + was the same as <userinput>terse</userinput>. + </para> + </listitem> + </varlistentry> + </variablelist> + + <section xml:id="boolean_options"><info><title>Boolean Options</title></info> + + <variablelist> + + <varlistentry> + <term><command>automatic-interface-scan</command></term> + <listitem> + <para> + If <userinput>yes</userinput> and supported by the OS, + automatically rescan network interfaces when the interface + addresses are added or removed. The default is + <userinput>yes</userinput>. + </para> + <para> + Currently the OS needs to support routing sockets for + <command>automatic-interface-scan</command> to be + supported. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>allow-new-zones</command></term> + <listitem> + <para> + If <userinput>yes</userinput>, then zones can be + added at runtime via <command>rndc addzone</command>. + The default is <userinput>no</userinput>. + </para> + <para> + Newly added zones' configuration parameters + are stored so that they can persist after the + server is restarted. The configuration information + is saved in a file called + <filename><replaceable>viewname</replaceable>.nzf</filename> + (or, if <command>named</command> is compiled with + liblmdb, in an LMDB database file called + <filename><replaceable>viewname</replaceable>.nzd</filename>). + <replaceable>viewname</replaceable> is the name of the + view, unless the view name contains characters that are + incompatible with use as a file name, in which case a + cryptographic hash of the view name is used instead. + </para> + <para> + Zones added at runtime will have their configuration + stored either in a new-zone file (NZF) or a new-zone + database (NZD) depending on whether + <command>named</command> was linked with + liblmdb at compile time. + See <xref linkend="man.rndc"/> for further details + about <command>rndc addzone</command>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>auth-nxdomain</command></term> + <listitem> + <para> + If <userinput>yes</userinput>, then the <command>AA</command> bit + is always set on NXDOMAIN responses, even if the server is + not actually + authoritative. The default is <userinput>no</userinput>; + this is + a change from <acronym>BIND</acronym> 8. If you + are using very old DNS software, you + may need to set it to <userinput>yes</userinput>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>deallocate-on-exit</command></term> + <listitem> + <para> + This option was used in <acronym>BIND</acronym> + 8 to enable checking + for memory leaks on exit. <acronym>BIND</acronym> 9 ignores the option and always performs + the checks. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>memstatistics</command></term> + <listitem> + <para> + Write memory statistics to the file specified by + <command>memstatistics-file</command> at exit. + The default is <userinput>no</userinput> unless + '-m record' is specified on the command line in + which case it is <userinput>yes</userinput>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>dialup</command></term> + <listitem> + <para> + If <userinput>yes</userinput>, 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 every <command>heartbeat-interval</command> and + hopefully during the one call. It also suppresses some of + the normal + zone maintenance traffic. The default is <userinput>no</userinput>. + </para> + <para> + The <command>dialup</command> option + may also be specified in the <command>view</command> and + <command>zone</command> statements, + in which case it overrides the global <command>dialup</command> + option. + </para> + <para> + 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 + <command>notify</command> and <command>also-notify</command>. + </para> + <para> + 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 + <command>heartbeat-interval</command> expires in + addition to sending + NOTIFY requests. + </para> + <para> + Finer control can be achieved by using + <userinput>notify</userinput> which only sends NOTIFY + messages, + <userinput>notify-passive</userinput> which sends NOTIFY + messages and + suppresses the normal refresh queries, <userinput>refresh</userinput> + which suppresses normal refresh processing and sends refresh + queries + when the <command>heartbeat-interval</command> + expires, and + <userinput>passive</userinput> which just disables normal + refresh + processing. + </para> + + <informaltable colsep="0" rowsep="0"> + <tgroup cols="4" colsep="0" rowsep="0" tgroupstyle="4Level-table"> + <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="1.150in"/> + <colspec colname="3" colnum="3" colsep="0" colwidth="1.150in"/> + <colspec colname="4" colnum="4" colsep="0" colwidth="1.150in"/> + <tbody> + <row rowsep="0"> + <entry colname="1"> + <para> + dialup mode + </para> + </entry> + <entry colname="2"> + <para> + normal refresh + </para> + </entry> + <entry colname="3"> + <para> + heart-beat refresh + </para> + </entry> + <entry colname="4"> + <para> + heart-beat notify + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>no</command> (default)</para> + </entry> + <entry colname="2"> + <para> + yes + </para> + </entry> + <entry colname="3"> + <para> + no + </para> + </entry> + <entry colname="4"> + <para> + no + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>yes</command></para> + </entry> + <entry colname="2"> + <para> + no + </para> + </entry> + <entry colname="3"> + <para> + yes + </para> + </entry> + <entry colname="4"> + <para> + yes + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>notify</command></para> + </entry> + <entry colname="2"> + <para> + yes + </para> + </entry> + <entry colname="3"> + <para> + no + </para> + </entry> + <entry colname="4"> + <para> + yes + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>refresh</command></para> + </entry> + <entry colname="2"> + <para> + no + </para> + </entry> + <entry colname="3"> + <para> + yes + </para> + </entry> + <entry colname="4"> + <para> + no + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>passive</command></para> + </entry> + <entry colname="2"> + <para> + no + </para> + </entry> + <entry colname="3"> + <para> + no + </para> + </entry> + <entry colname="4"> + <para> + no + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>notify-passive</command></para> + </entry> + <entry colname="2"> + <para> + no + </para> + </entry> + <entry colname="3"> + <para> + no + </para> + </entry> + <entry colname="4"> + <para> + yes + </para> + </entry> + </row> + </tbody> + </tgroup> + </informaltable> + + <para> + Note that normal NOTIFY processing is not affected by + <command>dialup</command>. + </para> + + </listitem> + </varlistentry> + + <varlistentry> + <term><command>fake-iquery</command></term> + <listitem> + <para> + In <acronym>BIND</acronym> 8, this option + enabled simulating the obsolete DNS query type + IQUERY. <acronym>BIND</acronym> 9 never does + IQUERY simulation. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>fetch-glue</command></term> + <listitem> + <para> + This option is obsolete. + In BIND 8, <userinput>fetch-glue yes</userinput> + caused the server to attempt to fetch glue resource records + it + didn't have when constructing the additional + data section of a response. This is now considered a bad + idea + and BIND 9 never does it. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>flush-zones-on-shutdown</command></term> + <listitem> + <para> + When the nameserver exits due receiving SIGTERM, + flush or do not flush any pending zone writes. The default + is + <command>flush-zones-on-shutdown</command> <userinput>no</userinput>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>geoip-use-ecs</command></term> + <listitem> + <para> + When BIND is compiled with GeoIP support and configured + with "geoip" ACL elements, this option indicates whether + the EDNS Client Subnet option, if present in a request, + should be used for matching against the GeoIP database. + The default is + <command>geoip-use-ecs</command> <userinput>yes</userinput>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>has-old-clients</command></term> + <listitem> + <para> + This option was incorrectly implemented + in <acronym>BIND</acronym> 8, and is ignored by <acronym>BIND</acronym> 9. + To achieve the intended effect + of + <command>has-old-clients</command> <userinput>yes</userinput>, specify + the two separate options <command>auth-nxdomain</command> <userinput>yes</userinput> + and <command>rfc2308-type1</command> <userinput>no</userinput> instead. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>host-statistics</command></term> + <listitem> + <para> + In BIND 8, this enabled keeping of + statistics for every host that the name server interacts + with. + Not implemented in BIND 9. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>root-key-sentinel</command></term> + <listitem> + <para> + Respond to root key sentinel probes as described in + draft-ietf-dnsop-kskroll-sentinel-08. The default is + <userinput>yes</userinput>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>maintain-ixfr-base</command></term> + <listitem> + <para> + <emphasis>This option is obsolete</emphasis>. + It was used in <acronym>BIND</acronym> 8 to + determine whether a transaction log was + kept for Incremental Zone Transfer. <acronym>BIND</acronym> 9 maintains a transaction + log whenever possible. If you need to disable outgoing + incremental zone + transfers, use <command>provide-ixfr</command> <userinput>no</userinput>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>message-compression</command></term> <listitem> + <para> + If <userinput>yes</userinput>, DNS name compression is + used in responses to regular queries (not including + AXFR or IXFR, which always uses compression). Setting + this option to <userinput>no</userinput> reduces CPU + usage on servers and may improve throughput. However, + it increases response size, which may cause more queries + to be processed using TCP; a server with compression + disabled is out of compliance with RFC 1123 Section + 6.1.3.2. The default is <userinput>yes</userinput>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>minimal-responses</command></term> + <listitem> + <para> + If set to <userinput>yes</userinput>, 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. + </para> + <para> + When set to <userinput>no-auth</userinput>, the + server will omit records from the authority section + unless they are required, but it may still add + records to the additional section. When set to + <userinput>no-auth-recursive</userinput>, this + is only done if the query is recursive. These + settings are useful when answering stub clients, + which usually ignore the authority section. + <userinput>no-auth-recursive</userinput> is + designed for mixed-mode servers which handle + both authoritative and recursive queries. + </para> + <para> + The default is <userinput>no</userinput>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>minimal-any</command></term> + <listitem> + <para> + If set to <userinput>yes</userinput>, then when + generating a positive response to a query of type + ANY over UDP, the server will reply with only one + of the RRsets for the query name, and its covering + RRSIGs if any, instead of replying with all known + RRsets for the name. Similarly, a query for type + RRSIG will be answered with the RRSIG records covering + only one type. This can reduce the impact of some kinds + of attack traffic, without harming legitimate + clients. (Note, however, that the RRset returned is the + first one found in the database; it is not necessarily + the smallest available RRset.) + Additionally, <option>minimal-responses</option> is + turned on for these queries, so no unnecessary records + will be added to the authority or additional sections. + The default is <userinput>no</userinput>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>multiple-cnames</command></term> + <listitem> + <para> + This option was used in <acronym>BIND</acronym> 8 to allow + a domain name to have multiple CNAME records in violation of + the DNS standards. <acronym>BIND</acronym> 9.2 onwards + always strictly enforces the CNAME rules both in master + files and dynamic updates. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>notify</command></term> + <listitem> + <para> + If <userinput>yes</userinput> (the default), + DNS NOTIFY messages are sent when a zone the server is + authoritative for + changes, see <xref linkend="notify"/>. 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 the + <command>also-notify</command> option. + </para> + <para> + If <userinput>master-only</userinput>, notifies are only + sent + for master zones. + If <userinput>explicit</userinput>, notifies are sent only + to + servers explicitly listed using <command>also-notify</command>. + If <userinput>no</userinput>, no notifies are sent. + </para> + <para> + The <command>notify</command> option may also be + specified in the <command>zone</command> + statement, + in which case it overrides the <command>options notify</command> statement. + It would only be necessary to turn off this option if it + caused slaves + to crash. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>notify-to-soa</command></term> + <listitem> + <para> + If <userinput>yes</userinput> 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>recursion</command></term> + <listitem> + <para> + If <userinput>yes</userinput>, 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 is + <userinput>yes</userinput>. + Note that setting <command>recursion no</command> 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>request-nsid</command></term> + <listitem> + <para> + If <userinput>yes</userinput>, 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 + the <command>resolver</command> category at level + <command>info</command>. + The default is <userinput>no</userinput>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>request-sit</command></term> + <listitem> + <para> + This experimental option is obsolete. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>require-server-cookie</command></term> + <listitem> + <para> + Require a valid server cookie before sending a full + response to a UDP request from a cookie aware client. + BADCOOKIE is sent if there is a bad or no existent + server cookie. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>answer-cookie</command></term> + <listitem> + <para> + When set to the default value of <userinput>yes</userinput>, + COOKIE EDNS options will be sent when applicable in + replies to client queries. If set to + <userinput>no</userinput>, COOKIE EDNS options will not + be sent in replies. This can only be set at the global + options level, not per-view. + </para> + <para> + <command>answer-cookie no</command> is only intended as a + temporary measure, for use when <command>named</command> + shares an IP address with other servers that do not yet + support DNS COOKIE. A mismatch between servers on the + same address is not expected to cause operational + problems, but the option to disable COOKIE responses so + that all servers have the same behavior is provided out + of an abundance of caution. DNS COOKIE is an important + security mechanism, and should not be disabled unless + absolutely necessary. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>send-cookie</command></term> + <listitem> + <para> + If <userinput>yes</userinput>, then a 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 the + <command>nocookie-udp-size</command> option. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>nocookie-udp-size</command></term> + <listitem> + <para> + Sets the maximum size of UDP responses that will be + sent to queries without a valid server COOKIE. A value + below 128 will be silently raised to 128. The default + value is 4096, but the <command>max-udp-size</command> + option may further limit the response size. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>sit-secret</command></term> + <listitem> + <para> + This experimental option is obsolete. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>cookie-algorithm</command></term> + <listitem> + <para> + Set the algorithm to be used when generating the + server cookie. One of "aes", "sha1" or "sha256". + The default is "aes" if supported by the cryptographic + library or otherwise "sha256". + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>cookie-secret</command></term> + <listitem> + <para> + If set, this is a shared secret used for generating + and verifying EDNS COOKIE 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 128 bits for AES128, 160 bits for SHA1 and + 256 bits for SHA256. + </para> + <para> + If there are multiple secrets specified, the first + one listed in <filename>named.conf</filename> is + used to generate new server cookies. The others + will only be used to verify returned cookies. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>rfc2308-type1</command></term> + <listitem> + <para> + Setting this to <userinput>yes</userinput> will + cause the server to send NS records along with the SOA + record for negative + answers. The default is <userinput>no</userinput>. + </para> + <note> + <simpara> + Not yet implemented in <acronym>BIND</acronym> + 9. + </simpara> + </note> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>trust-anchor-telemetry</command></term> + <listitem> + <para> + Causes <command>named</command> to send specially-formed + queries once per day to domains for which trust anchors + have been configured via <command>trusted-keys</command>, + <command>managed-keys</command>, or + <command>dnssec-validation auto</command>. + </para> + <para> + The query name used for these queries has the + form "_ta-xxxx(-xxxx)(...)".<domain>, where + each "xxxx" is a group of four hexadecimal digits + representing the key ID of a trusted DNSSEC key. + The key IDs for each domain are sorted smallest + to largest prior to encoding. The query type is NULL. + </para> + <para> + By monitoring these queries, zone operators will + be able to see which resolvers have been updated to + trust a new key; this may help them decide when it + is safe to remove an old one. + </para> + <para> + The default is <userinput>yes</userinput>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>use-id-pool</command></term> + <listitem> + <para> + <emphasis>This option is obsolete</emphasis>. + <acronym>BIND</acronym> 9 always allocates query + IDs from a pool. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>use-ixfr</command></term> + <listitem> + <para> + <emphasis>This option is obsolete</emphasis>. + If you need to disable IXFR to a particular server or + servers, see + the information on the <command>provide-ixfr</command> option + in <xref linkend="server_statement_definition_and_usage"/>. + See also + <xref linkend="incremental_zone_transfers"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>provide-ixfr</command></term> + <listitem> + <para> + See the description of + <command>provide-ixfr</command> in + <xref linkend="server_statement_definition_and_usage"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>request-ixfr</command></term> + <listitem> + <para> + See the description of + <command>request-ixfr</command> in + <xref linkend="server_statement_definition_and_usage"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>request-expire</command></term> + <listitem> + <para> + See the description of + <command>request-expire</command> in + <xref linkend="server_statement_definition_and_usage"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>treat-cr-as-space</command></term> + <listitem> + <para> + This option was used in <acronym>BIND</acronym> + 8 to make + the server treat carriage return ("<command>\r</command>") characters the same way + as a space or tab character, + to facilitate loading of zone files on a UNIX system that + were generated + on an NT or DOS machine. In <acronym>BIND</acronym> 9, both UNIX "<command>\n</command>" + and NT/DOS "<command>\r\n</command>" newlines + are always accepted, + and the option is ignored. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>additional-from-auth</command></term> + <term><command>additional-from-cache</command></term> + <listitem> + + <para> + These options control the behavior of an authoritative + server when + answering queries which have additional data, or when + following CNAME + and DNAME chains. + </para> + + <para> + When both of these options are set to <userinput>yes</userinput> + (the default) and a + query is being answered from authoritative data (a zone + configured into the server), the additional data section of + the + reply will be filled in using data from other authoritative + zones + and from the cache. In some situations this is undesirable, + such + as when there is concern over the correctness of the cache, + or + in servers where slave zones may be added and modified by + untrusted third parties. Also, avoiding + the search for this additional data will speed up server + operations + at the possible expense of additional queries to resolve + what would + otherwise be provided in the additional section. + </para> + + <para> + For example, if a query asks for an MX record for host <literal>foo.example.com</literal>, + and the record found is "<literal>MX 10 mail.example.net</literal>", normally the address + records (A and AAAA) for <literal>mail.example.net</literal> will be provided as well, + if known, even though they are not in the example.com zone. + Setting these options to <command>no</command> + disables this behavior and makes + the server only search for additional data in the zone it + answers from. + </para> + + <para> + These options are intended for use in authoritative-only + servers, or in authoritative-only views. Attempts to set + them to <command>no</command> without also + specifying + <command>recursion no</command> will cause the + server to + ignore the options and log a warning message. + </para> + + <para> + Specifying <command>additional-from-cache no</command> actually + disables the use of the cache not only for additional data + lookups + but also when looking up the answer. This is usually the + desired + behavior in an authoritative-only server where the + correctness of + the cached data is an issue. + </para> + + <para> + When a name server is non-recursively queried for a name + that is not + below the apex of any served zone, it normally answers with + an + "upwards referral" to the root servers or the servers of + some other + known parent of the query name. Since the data in an + upwards referral + comes from the cache, the server will not be able to provide + upwards + referrals when <command>additional-from-cache no</command> + has been specified. Instead, it will respond to such + queries + with REFUSED. This should not cause any problems since + upwards referrals are not required for the resolution + process. + </para> + + </listitem> + </varlistentry> + + <varlistentry> + <term><command>match-mapped-addresses</command></term> + <listitem> + <para> + If <userinput>yes</userinput>, then an + IPv4-mapped IPv6 address will match any address match + list entries that match the corresponding IPv4 address. + </para> + <para> + 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, + <command>named</command> now solves this problem + internally. The use of this option is discouraged. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>filter-aaaa-on-v4</command></term> + <listitem> + <para> + This option is only available when + <acronym>BIND</acronym> 9 is compiled with the + <userinput>--enable-filter-aaaa</userinput> option on the + "configure" command line. It is intended to help the + transition from IPv4 to IPv6 by not giving IPv6 addresses + to DNS clients unless they have connections to the IPv6 + Internet. This is not recommended unless absolutely + necessary. The default is <userinput>no</userinput>. + The <command>filter-aaaa-on-v4</command> option + may also be specified in <command>view</command> statements + to override the global <command>filter-aaaa-on-v4</command> + option. + </para> + <para> + If <userinput>yes</userinput>, + the DNS client is at an IPv4 address, in <command>filter-aaaa</command>, + and if the response does not include DNSSEC signatures, + then all AAAA records are deleted from the response. + This filtering applies to all responses and not only + authoritative responses. + </para> + <para> + If <userinput>break-dnssec</userinput>, + then AAAA records are deleted even when DNSSEC is enabled. + As suggested by the name, this makes the response not verify, + because the DNSSEC protocol is designed detect deletions. + </para> + <para> + This mechanism can erroneously cause other servers to + not give AAAA records to their clients. + A recursing server with both IPv6 and IPv4 network connections + that queries an authoritative server using this mechanism + via IPv4 will be denied AAAA records even if its client is + using IPv6. + </para> + <para> + This mechanism is applied to authoritative as well as + non-authoritative records. + A client using IPv4 that is not allowed recursion can + erroneously be given AAAA records because the server is not + allowed to check for A records. + </para> + <para> + Some AAAA records are given to IPv4 clients in glue records. + IPv4 clients that are servers can then erroneously + answer requests for AAAA records received via IPv4. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>filter-aaaa-on-v6</command></term> + <listitem> + <para> + Identical to <command>filter-aaaa-on-v4</command>, + except it filters AAAA responses to queries from IPv6 + clients instead of IPv4 clients. To filter all + responses, set both options to <userinput>yes</userinput>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>ixfr-from-differences</command></term> + <listitem> + <para> + When <userinput>yes</userinput> 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. + </para> + <para> + 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. + </para> + <para><command>ixfr-from-differences</command> + also accepts <command>master</command> and + <command>slave</command> at the view and options + levels which causes + <command>ixfr-from-differences</command> to be enabled for + all <command>master</command> or + <command>slave</command> zones respectively. + It is off by default. + </para> + <para> + Note: if inline signing is enabled for a zone, the + user-provided <command>ixfr-from-differences</command> + setting is ignored for that zone. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>multi-master</command></term> + <listitem> + <para> + This should be set when you have multiple masters for a zone + and the + addresses refer to different machines. If <userinput>yes</userinput>, <command>named</command> will + not log + when the serial number on the master is less than what <command>named</command> + currently + has. The default is <userinput>no</userinput>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>auto-dnssec</command></term> + <listitem> + <para> + Zones configured for dynamic DNS may use this + option to allow varying levels of automatic DNSSEC key + management. There are three possible settings: + </para> + <para> + <command>auto-dnssec allow;</command> permits + keys to be updated and the zone fully re-signed + whenever the user issues the command <command>rndc sign + <replaceable>zonename</replaceable></command>. + </para> + <para> + <command>auto-dnssec maintain;</command> includes the + above, but also automatically adjusts the zone's DNSSEC + keys on schedule, according to the keys' timing metadata + (see <xref linkend="man.dnssec-keygen"/> and + <xref linkend="man.dnssec-settime"/>). The command + <command>rndc sign + <replaceable>zonename</replaceable></command> causes + <command>named</command> to load keys from the key + repository and sign the zone with all keys that are + active. + <command>rndc loadkeys + <replaceable>zonename</replaceable></command> causes + <command>named</command> to load keys from the key + repository 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 + <command>rndc loadkeys</command> is used. The recheck + interval is defined by + <command>dnssec-loadkeys-interval</command>.) + </para> + <para> + The default setting is <command>auto-dnssec off</command>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>dnssec-enable</command></term> + <listitem> + <para> + This indicates whether DNSSEC-related resource + records are to be returned by <command>named</command>. + If set to <userinput>no</userinput>, + <command>named</command> will not return DNSSEC-related + resource records unless specifically queried for. + The default is <userinput>yes</userinput>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>dnssec-validation</command></term> + <listitem> + <para> + Enable DNSSEC validation in <command>named</command>. + Note <command>dnssec-enable</command> also needs to be + set to <userinput>yes</userinput> to be effective. + If set to <userinput>no</userinput>, DNSSEC validation + is disabled. + </para> + <para> + If set to <userinput>auto</userinput>, DNSSEC validation + is enabled, and a default trust anchor for the DNS root + zone is used. If set to <userinput>yes</userinput>, + DNSSEC validation is enabled, but a trust anchor must be + manually configured using a <command>trusted-keys</command> + or <command>managed-keys</command> statement. The default + is <userinput>yes</userinput>. + </para> + <para> + The default root trust anchor is stored in the file + <filename>bind.keys</filename>. + <command>named</command> will load that key at + startup if <command>dnssec-validation</command> is + set to <constant>auto</constant>. A copy of the file is + installed along with BIND 9, and is current as of the + release date. If the root key expires, a new copy of + <filename>bind.keys</filename> can be downloaded + from <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://www.isc.org/bind-keys">https://www.isc.org/bind-keys</link>. + </para> + <para> + To prevent problems if <filename>bind.keys</filename> is + not found, the current trust anchor is also compiled in + to <command>named</command>. Relying on this is not + recommended, however, as it requires <command>named</command> + to be recompiled with a new key when the root key expires.) + </para> + <note> + <para> + <command>named</command> <emphasis>only</emphasis> + loads the root key from <filename>bind.keys</filename>. + The file cannot be used to store keys for other zones. + The root key in <filename>bind.keys</filename> is ignored + if <command>dnssec-validation auto</command> is not in + use. + </para> + <para> + 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 + <command>dnssec-validation</command> is off. + </para> + </note> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>dnssec-accept-expired</command></term> + <listitem> + <para> + Accept expired signatures when verifying DNSSEC signatures. + The default is <userinput>no</userinput>. + Setting this option to <userinput>yes</userinput> + leaves <command>named</command> vulnerable to + replay attacks. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>querylog</command></term> + <listitem> + <para> + Specify whether query logging should be started when <command>named</command> + starts. + If <command>querylog</command> is not specified, + then the query logging + is determined by the presence of the logging category <command>queries</command>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>check-names</command></term> + <listitem> + <para> + 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 + <command>master</command> zones the default is <command>fail</command>. + For <command>slave</command> zones the default + is <command>warn</command>. + For answers received from the network (<command>response</command>) + the default is <command>ignore</command>. + </para> + <para> + The rules for legal hostnames and mail domains are derived + from RFC 952 and RFC 821 as modified by RFC 1123. + </para> + <para><command>check-names</command> + 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). + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>check-dup-records</command></term> + <listitem> + <para> + Check master zones for records that are treated as different + by DNSSEC but are semantically equal in plain DNS. The + default is to <command>warn</command>. Other possible + values are <command>fail</command> and + <command>ignore</command>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>check-mx</command></term> + <listitem> + <para> + Check whether the MX record appears to refer to a IP address. + The default is to <command>warn</command>. Other possible + values are <command>fail</command> and + <command>ignore</command>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>check-wildcard</command></term> + <listitem> + <para> + 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 (<command>yes</command>) is to check + for non-terminal wildcards and issue a warning. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>check-integrity</command></term> + <listitem> + <para> + 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 + <command>named-checkzone</command>). + For NS records only names below top of zone are + checked (for out-of-zone names and glue consistency + checks use <command>named-checkzone</command>). + The default is <command>yes</command>. + </para> + <para> + 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 + <command>check-spf</command>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>check-mx-cname</command></term> + <listitem> + <para> + If <command>check-integrity</command> is set then + fail, warn or ignore MX records that refer + to CNAMES. The default is to <command>warn</command>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>check-srv-cname</command></term> + <listitem> + <para> + If <command>check-integrity</command> is set then + fail, warn or ignore SRV records that refer + to CNAMES. The default is to <command>warn</command>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>check-sibling</command></term> + <listitem> + <para> + When performing integrity checks, also check that + sibling glue exists. The default is <command>yes</command>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>check-spf</command></term> + <listitem> + <para> + If <command>check-integrity</command> 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 is + <command>warn</command>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>zero-no-soa-ttl</command></term> + <listitem> + <para> + 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 <command>yes</command>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>zero-no-soa-ttl-cache</command></term> + <listitem> + <para> + When caching a negative response to a SOA query + set the TTL to zero. + The default is <command>no</command>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>update-check-ksk</command></term> + <listitem> + <para> + When set to the default value of <literal>yes</literal>, + check the KSK bit in each key to determine how the key + should be used when generating RRSIGs for a secure zone. + </para> + <para> + 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 <literal>no</literal>, + 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 the <command>dnssec-signzone -z</command> + command line option. + </para> + <para> + When this option is set to <literal>yes</literal>, 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>dnssec-dnskey-kskonly</command></term> + <listitem> + <para> + When this option and <command>update-check-ksk</command> + are both set to <literal>yes</literal>, 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 the + <command>dnssec-signzone -x</command> command line option. + </para> + <para> + The default is <command>no</command>. If + <command>update-check-ksk</command> is set to + <literal>no</literal>, this option is ignored. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>try-tcp-refresh</command></term> + <listitem> + <para> + Try to refresh the zone using TCP if UDP queries fail. + For BIND 8 compatibility, the default is + <command>yes</command>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>dnssec-secure-to-insecure</command></term> + <listitem> + <para> + 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 <command>no</command>. + If set to <command>yes</command>, and if the DNSKEY RRset + at the zone apex is deleted, all RRSIG and NSEC records + will be removed from the zone as well. + </para> + <para> + 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.) + </para> + <para> + Note that if a zone has been configured with + <command>auto-dnssec maintain</command> and the + private keys remain accessible in the key repository, + then the zone will be automatically signed again the + next time <command>named</command> is started. + </para> + </listitem> + </varlistentry> + + </variablelist> + + </section> + + <section xml:id="forwarding"><info><title>Forwarding</title></info> + + <para> + 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. + </para> + + <variablelist> + <varlistentry> + <term><command>forward</command></term> + <listitem> + <para> + This option is only meaningful if the + forwarders list is not empty. A value of <varname>first</varname>, + 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. If <varname>only</varname> is + specified, the + server will only query the forwarders. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>forwarders</command></term> + <listitem> + <para> + Specifies the IP addresses to be used + for forwarding. The default is the empty list (no + forwarding). + </para> + </listitem> + </varlistentry> + + </variablelist> + + <para> + 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 <command>forward only/first</command> behavior, + or not forward at all, see <xref linkend="zone_statement_grammar"/>. + </para> + </section> + + <section xml:id="dual_stack"><info><title>Dual-stack Servers</title></info> + + <para> + 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. + </para> + + <variablelist> + <varlistentry> + <term><command>dual-stack-servers</command></term> + <listitem> + <para> + 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 <command>dual-stack-servers</command> have no effect unless + access to a transport has been disabled on the command line + (e.g. <command>named -4</command>). + </para> + </listitem> + </varlistentry> + </variablelist> + </section> + + <section xml:id="access_control"><info><title>Access Control</title></info> + + + <para> + Access to the server can be restricted based on the IP address + of the requesting system. See <xref linkend="address_match_lists"/> for + details on how to specify IP address lists. + </para> + + <variablelist> + + <varlistentry> + <term><command>allow-notify</command></term> + <listitem> + <para> + Specifies which hosts are allowed to + notify this server, a slave, of zone changes in addition + to the zone masters. + <command>allow-notify</command> may also be + specified in the + <command>zone</command> statement, in which case + it overrides the + <command>options allow-notify</command> + 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>allow-query</command></term> + <listitem> + <para> + Specifies which hosts are allowed to ask ordinary + DNS questions. <command>allow-query</command> may + also be specified in the <command>zone</command> + statement, in which case it overrides the + <command>options allow-query</command> statement. + If not specified, the default is to allow queries + from all hosts. + </para> + <note> + <para> + <command>allow-query-cache</command> is now + used to specify access to the cache. + </para> + </note> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>allow-query-on</command></term> + <listitem> + <para> + 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. + </para> + <para> + Note that <command>allow-query-on</command> is only + checked for queries that are permitted by + <command>allow-query</command>. A query must be + allowed by both ACLs, or it will be refused. + </para> + <para> + <command>allow-query-on</command> may + also be specified in the <command>zone</command> + statement, in which case it overrides the + <command>options allow-query-on</command> statement. + </para> + <para> + If not specified, the default is to allow queries + on all addresses. + </para> + <note> + <para> + <command>allow-query-cache</command> is + used to specify access to the cache. + </para> + </note> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>allow-query-cache</command></term> + <listitem> + <para> + Specifies which hosts are allowed to get answers + from the cache. If <command>allow-query-cache</command> + is not set then <command>allow-recursion</command> + is used if set, otherwise <command>allow-query</command> + is used if set unless <command>recursion no;</command> is + set in which case <command>none;</command> is used, + otherwise the default (<command>localnets;</command> + <command>localhost;</command>) is used. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>allow-query-cache-on</command></term> + <listitem> + <para> + Specifies which local addresses can give answers + from the cache. If not specified, the default is + to allow cache queries on any address, + <command>localnets</command> and + <command>localhost</command>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>allow-recursion</command></term> + <listitem> + <para> + Specifies which hosts are allowed to make recursive + queries through this server. If + <command>allow-recursion</command> is not set + then <command>allow-query-cache</command> is + used if set, otherwise <command>allow-query</command> + is used if set, otherwise the default + (<command>localnets;</command> + <command>localhost;</command>) is used. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>allow-recursion-on</command></term> + <listitem> + <para> + Specifies which local addresses can accept recursive + queries. If not specified, the default is to allow + recursive queries on all addresses. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>allow-update</command></term> + <listitem> + <para> + 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 + <xref linkend="dynamic_update_security"/> for details. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>allow-update-forwarding</command></term> + <listitem> + <para> + Specifies which hosts are allowed to + submit Dynamic DNS updates to slave zones to be forwarded to + the + master. The default is <userinput>{ none; }</userinput>, + which + means that no update forwarding will be performed. To + enable + update forwarding, specify + <userinput>allow-update-forwarding { any; };</userinput>. + Specifying values other than <userinput>{ none; }</userinput> or + <userinput>{ any; }</userinput> is usually + counterproductive, since + the responsibility for update access control should rest + with the + master server, not the slaves. + </para> + <para> + 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 <xref linkend="dynamic_update_security"/> + for more details. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>allow-v6-synthesis</command></term> + <listitem> + <para> + 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>allow-transfer</command></term> + <listitem> + <para> + Specifies which hosts are allowed to + receive zone transfers from the server. <command>allow-transfer</command> may + also be specified in the <command>zone</command> + statement, in which + case it overrides the <command>options allow-transfer</command> statement. + If not specified, the default is to allow transfers to all + hosts. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>blackhole</command></term> + <listitem> + <para> + 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 <userinput>none</userinput>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>filter-aaaa</command></term> + <listitem> + <para> + Specifies a list of addresses to which + <command>filter-aaaa-on-v4</command> + and <command>filter-aaaa-on-v6</command> + apply. The default is <userinput>any</userinput>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>keep-response-order</command></term> + <listitem> + <para> + Specifies a list of addresses to which the server + will send responses to TCP queries in the same order + in which they were received. This disables the + processing of TCP queries in parallel. The default + is <userinput>none</userinput>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>no-case-compress</command></term> <listitem> + <para> + Specifies a list of addresses which require responses + to use case-insensitive compression. This ACL can be + used when <command>named</command> 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. + </para> + <para> + If left undefined, the ACL defaults to + <command>none</command>: 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. + </para> + <para> + 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. + </para> + <para> + Case-insensitive compression is <emphasis>always</emphasis> + used in AXFR and IXFR responses, regardless of whether + the client matches this ACL. + </para> + <para> + There are circumstances in which <command>named</command> + 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 <emphasis>first</emphasis> 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>resolver-query-timeout</command></term> + <listitem> + <para> + The amount of time in seconds that the resolver + will spend attempting to resolve a recursive + query before failing. The default and minimum + is <literal>10</literal> and the maximum is + <literal>30</literal>. Setting it to + <literal>0</literal> will result in the default + being used. + </para> + </listitem> + </varlistentry> + </variablelist> + + </section> + + <section xml:id="interfaces"><info><title>Interfaces</title></info> + + <para> + The interfaces and ports that the server will answer queries + from may be specified using the <command>listen-on</command> option. <command>listen-on</command> takes + an optional port and an <varname>address_match_list</varname> + 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. + </para> + <para> + Multiple <command>listen-on</command> statements are + allowed. + For example, + </para> + +<programlisting>listen-on { 5.6.7.8; }; +listen-on port 1234 { !1.2.3.4; 1.2/16; }; +</programlisting> + + <para> + 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. + </para> + + <para> + If no <command>listen-on</command> is specified, the + server will listen on port 53 on all IPv4 interfaces. + </para> + + <para> + The <command>listen-on-v6</command> 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. + </para> + + <para> + When <programlisting>{ any; }</programlisting> is + specified + as the <varname>address_match_list</varname> for the + <command>listen-on-v6</command> 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. + </para> + + <para> + 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 <command>listen-on-v6</command> + will be ignored, with a logged warning. + </para> + + <para> + Multiple <command>listen-on-v6</command> options can + be used. + For example, + </para> + +<programlisting>listen-on-v6 { any; }; +listen-on-v6 port 1234 { !2001:db8::/32; any; }; +</programlisting> + + <para> + 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.) + </para> + + <para> + To make the server not listen on any IPv6 address, use + </para> + +<programlisting>listen-on-v6 { none; }; +</programlisting> + + </section> + + <section xml:id="query_address"><info><title>Query Address</title></info> + + <para> + If the server doesn't know the answer to a question, it will + query other name servers. <command>query-source</command> specifies + the address and port used for such queries. For queries sent over + IPv6, there is a separate <command>query-source-v6</command> option. + If <command>address</command> is <command>*</command> (asterisk) or is omitted, + a wildcard IP address (<command>INADDR_ANY</command>) + will be used. + </para> + + <para> + If <command>port</command> is <command>*</command> 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 <command>use-v4-udp-ports</command> (for IPv4) + and <command>use-v6-udp-ports</command> (for IPv6) + options, excluding the ranges specified in + the <command>avoid-v4-udp-ports</command> + and <command>avoid-v6-udp-ports</command> options, respectively. + </para> + + <para> + The defaults of the <command>query-source</command> and + <command>query-source-v6</command> options + are: + </para> + +<programlisting>query-source address * port *; +query-source-v6 address * port *; +</programlisting> + + <para> + If <command>use-v4-udp-ports</command> or + <command>use-v6-udp-ports</command> is unspecified, + <command>named</command> 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, + <command>named</command> will use the corresponding system + default range; otherwise, it will use its own defaults: + </para> + +<programlisting>use-v4-udp-ports { range 1024 65535; }; +use-v6-udp-ports { range 1024 65535; }; +</programlisting> + + <para> + 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 <command>named</command> is running; the new + range will automatically be applied when <command>named</command> + is reloaded. + It is encouraged to + configure <command>use-v4-udp-ports</command> and + <command>use-v6-udp-ports</command> explicitly so that the + ranges are sufficiently large and are reasonably + independent from the ranges used by other applications. + </para> + + <para> + Note: the operational configuration + where <command>named</command> runs may prohibit the use + of some ports. For example, UNIX systems will not allow + <command>named</command> 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. + </para> + + <para> + The defaults of the <command>avoid-v4-udp-ports</command> and + <command>avoid-v6-udp-ports</command> options + are: + </para> + +<programlisting>avoid-v4-udp-ports {}; +avoid-v6-udp-ports {}; +</programlisting> + + <para> + Note: BIND 9.5.0 introduced + the <command>use-queryport-pool</command> + option to support a pool of such random ports, but this + option is now obsolete because reusing the same ports in + the pool may not be sufficiently secure. + For the same reason, it is generally strongly discouraged to + specify a particular port for the + <command>query-source</command> or + <command>query-source-v6</command> options; + it implicitly disables the use of randomized port numbers. + </para> + + <variablelist> + <varlistentry> + <term><command>use-queryport-pool</command></term> + <listitem> + <para> + This option is obsolete. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>queryport-pool-ports</command></term> + <listitem> + <para> + This option is obsolete. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>queryport-pool-updateinterval</command></term> + <listitem> + <para> + This option is obsolete. + </para> + </listitem> + </varlistentry> + + </variablelist> + <note> + <para> + The address specified in the <command>query-source</command> 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. + </para> + </note> + <note> + <para> + Solaris 2.5.1 and earlier does not support setting the source + address for TCP sockets. + </para> + </note> + <note> + <para> + See also <command>transfer-source</command> and + <command>notify-source</command>. + </para> + </note> + </section> + + <section xml:id="zone_transfers"><info><title>Zone Transfers</title></info> + + <para> + <acronym>BIND</acronym> 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. + </para> + + <variablelist> + + <varlistentry> + <term><command>also-notify</command></term> + <listitem> + <para> + 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 + <command>also-notify</command> 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 named + <command>masters</command> lists can be used. + </para> + <para> + If an <command>also-notify</command> list + is given in a <command>zone</command> statement, + it will override + the <command>options also-notify</command> + statement. When a <command>zone notify</command> + statement + is set to <command>no</command>, the IP + addresses in the global <command>also-notify</command> list will + not be sent NOTIFY messages for that zone. The default is + the empty + list (no global notification list). + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>max-transfer-time-in</command></term> + <listitem> + <para> + 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). + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>max-transfer-idle-in</command></term> + <listitem> + <para> + 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). + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>max-transfer-time-out</command></term> + <listitem> + <para> + 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). + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>max-transfer-idle-out</command></term> + <listitem> + <para> + 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). + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>notify-rate</command></term> + <listitem> + <para> + The rate at which NOTIFY requests will be sent + during normal zone maintenance operations. (NOTIFY + requests due to initial zone loading are subject + to a separate rate limit; see below.) 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>startup-notify-rate</command></term> + <listitem> + <para> + The rate at which NOTIFY requests will be sent + when the name server is first starting up, or when + zones have been newly added to the nameserver. + 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>serial-query-rate</command></term> + <listitem> + <para> + 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, BIND 9 limits the + rate at which queries are sent. The value of the + <command>serial-query-rate</command> 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>serial-queries</command></term> + <listitem> + <para> + In BIND 8, the <command>serial-queries</command> + option + set the maximum number of concurrent serial number queries + allowed to be outstanding at any given time. + BIND 9 does not limit the number of outstanding + serial queries and ignores the <command>serial-queries</command> option. + Instead, it limits the rate at which the queries are sent + as defined using the <command>serial-query-rate</command> option. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>transfer-format</command></term> + <listitem> + + <para> + Zone transfers can be sent using two different formats, + <command>one-answer</command> and + <command>many-answers</command>. + The <command>transfer-format</command> option is used + on the master server to determine which format it sends. + <command>one-answer</command> uses one DNS message per + resource record transferred. + <command>many-answers</command> packs as many resource + records as possible into a message. + <command>many-answers</command> is more efficient, but is + only supported by relatively new slave servers, + such as <acronym>BIND</acronym> 9, <acronym>BIND</acronym> + 8.x and <acronym>BIND</acronym> 4.9.5 onwards. + The <command>many-answers</command> format is also supported by + recent Microsoft Windows nameservers. + The default is <command>many-answers</command>. + <command>transfer-format</command> may be overridden on a + per-server basis by using the <command>server</command> + statement. + </para> + + </listitem> + </varlistentry> + + <varlistentry> + <term><command>transfer-message-size</command></term> + <listitem> + <para> + This is an upper bound on the uncompressed size of DNS + messages used in zone transfers over TCP. If a message + grows larger than this size, additional messages will be + used to complete the zone transfer. (Note, however, + that this is a hint, not a hard limit; if a message + contains a single resource record whose RDATA does not + fit within the size limit, a larger message will be + permitted so the record can be transferred.) + </para> + <para> + Valid values are between 512 and 65535 octets, and any + values outside that range will be adjusted to the nearest + value within it. The default is <literal>20480</literal>, + which was selected to improve message compression: + most DNS messages of this size will compress to less + than 16536 bytes. Larger messages cannot be compressed + as effectively, because 16536 is the largest permissible + compression offset pointer in a DNS message. + </para> + <para> + This option is mainly intended for server testing; + there is rarely any benefit in setting a value other + than the default. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>transfers-in</command></term> + <listitem> + <para> + The maximum number of inbound zone transfers + that can be running concurrently. The default value is <literal>10</literal>. + Increasing <command>transfers-in</command> may + speed up the convergence + of slave zones, but it also may increase the load on the + local system. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>transfers-out</command></term> + <listitem> + <para> + 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 <literal>10</literal>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>transfers-per-ns</command></term> + <listitem> + <para> + The maximum number of inbound zone transfers + that can be concurrently transferring from a given remote + name server. + The default value is <literal>2</literal>. + Increasing <command>transfers-per-ns</command> + may + speed up the convergence of slave zones, but it also may + increase + the load on the remote name server. <command>transfers-per-ns</command> may + be overridden on a per-server basis by using the <command>transfers</command> phrase + of the <command>server</command> statement. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>transfer-source</command></term> + <listitem> + <para><command>transfer-source</command> + 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's + <command>allow-transfer</command> option for the + zone being transferred, if one is specified. This + statement sets the + <command>transfer-source</command> for all zones, + but can be overridden on a per-view or per-zone + basis by including a + <command>transfer-source</command> statement within + the <command>view</command> or + <command>zone</command> block in the configuration + file. + </para> + <note> + <para> + Solaris 2.5.1 and earlier does not support setting the + source address for TCP sockets. + </para> + </note> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>transfer-source-v6</command></term> + <listitem> + <para> + The same as <command>transfer-source</command>, + except zone transfers are performed using IPv6. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>alt-transfer-source</command></term> + <listitem> + <para> + An alternate transfer source if the one listed in + <command>transfer-source</command> fails and + <command>use-alt-transfer-source</command> is + set. + </para> + <note><simpara> + If you do not wish the alternate transfer source + to be used, you should set + <command>use-alt-transfer-source</command> + appropriately and you should not depend upon + getting an answer back to the first refresh + query. + </simpara></note> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>alt-transfer-source-v6</command></term> + <listitem> + <para> + An alternate transfer source if the one listed in + <command>transfer-source-v6</command> fails and + <command>use-alt-transfer-source</command> is + set. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>use-alt-transfer-source</command></term> + <listitem> + <para> + Use the alternate transfer sources or not. If views are + specified this defaults to <command>no</command> + otherwise it defaults to + <command>yes</command> (for BIND 8 + compatibility). + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>notify-source</command></term> + <listitem> + <para><command>notify-source</command> + determines which local source address, and + optionally UDP port, will be used to send NOTIFY + messages. This address must appear in the slave + server's <command>masters</command> zone clause or + in an <command>allow-notify</command> clause. This + statement sets the <command>notify-source</command> + for all zones, but can be overridden on a per-zone or + per-view basis by including a + <command>notify-source</command> statement within + the <command>zone</command> or + <command>view</command> block in the configuration + file. + </para> + <note> + <para> + Solaris 2.5.1 and earlier does not support setting the + source address for TCP sockets. + </para> + </note> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>notify-source-v6</command></term> + <listitem> + <para> + Like <command>notify-source</command>, + but applies to notify messages sent to IPv6 addresses. + </para> + </listitem> + </varlistentry> + + </variablelist> + + </section> + + <section xml:id="port_lists"><info><title>UDP Port Lists</title></info> + + <para> + <command>use-v4-udp-ports</command>, + <command>avoid-v4-udp-ports</command>, + <command>use-v6-udp-ports</command>, and + <command>avoid-v6-udp-ports</command> + specify a list of IPv4 and IPv6 UDP ports that will be + used or not used as source ports for UDP messages. + See <xref linkend="query_address"/> about how the + available ports are determined. + For example, with the following configuration + </para> + +<programlisting> +use-v6-udp-ports { range 32768 65535; }; +avoid-v6-udp-ports { 40000; range 50000 60000; }; +</programlisting> + + <para> + UDP ports of IPv6 messages sent + from <command>named</command> will be in one + of the following ranges: 32768 to 39999, 40001 to 49999, + and 60001 to 65535. + </para> + + <para> + <command>avoid-v4-udp-ports</command> and + <command>avoid-v6-udp-ports</command> can be used + to prevent <command>named</command> 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 + <command>use-v4-udp-ports</command> and + <command>use-v6-udp-ports</command>, and the + <command>avoid-</command> options are redundant in that + sense; they are provided for backward compatibility and + to possibly simplify the port specification. + </para> + </section> + + <section xml:id="resource_limits"><info><title>Operating System Resource Limits</title></info> + + <para> + The server's usage of many system resources can be limited. + Scaled values are allowed when specifying resource limits. For + example, <command>1G</command> can be used instead of + <command>1073741824</command> to specify a limit of + one + gigabyte. <command>unlimited</command> requests + unlimited use, or the + maximum available amount. <command>default</command> + uses the limit + that was in force when the server was started. See the description + of <command>size_spec</command> in <xref linkend="configuration_file_elements"/>. + </para> + + <para> + 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. + </para> + + <variablelist> + + <varlistentry> + <term><command>coresize</command></term> + <listitem> + <para> + The maximum size of a core dump. The default + is <literal>default</literal>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>datasize</command></term> + <listitem> + <para> + The maximum amount of data memory the server + may use. The default is <literal>default</literal>. + 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 the + <command>max-cache-size</command> and + <command>recursive-clients</command> + options instead. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>files</command></term> + <listitem> + <para> + The maximum number of files the server + may have open concurrently. The default is <literal>unlimited</literal>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>stacksize</command></term> + <listitem> + <para> + The maximum amount of stack memory the server + may use. The default is <literal>default</literal>. + </para> + </listitem> + </varlistentry> + + </variablelist> + + </section> + + <section xml:id="server_resource_limits"><info><title>Server Resource Limits</title></info> + + <para> + The following options set limits on the server's + resource consumption that are enforced internally by the + server rather than the operating system. + </para> + + <variablelist> + + <varlistentry> + <term><command>max-ixfr-log-size</command></term> + <listitem> + <para> + This option is obsolete; it is accepted + and ignored for BIND 8 compatibility. The option + <command>max-journal-size</command> performs a + similar function in BIND 9. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>max-journal-size</command></term> + <listitem> + <para> + Sets a maximum size for each journal file + (see <xref linkend="journal"/>). 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 + <literal>unlimited</literal>, which also + means 2 gigabytes. + This may also be set on a per-zone basis. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>max-records</command></term> + <listitem> + <para> + The maximum number of records permitted in a zone. + The default is zero which means unlimited. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>host-statistics-max</command></term> + <listitem> + <para> + In BIND 8, specifies the maximum number of host statistics + entries to be kept. + Not implemented in BIND 9. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>recursive-clients</command></term> + <listitem> + <para> + The maximum number ("hard quota") of simultaneous + recursive lookups the server will perform on behalf + of clients. The default is + <literal>1000</literal>. Because each recursing + client uses a fair + bit of memory (on the order of 20 kilobytes), the + value of the + <command>recursive-clients</command> option may + have to be decreased on hosts with limited memory. + </para> + <para> + <option>recursive-clients</option> 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. + </para> + <para> + 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 <option>recursive-clients</option> is greater than + 1000, the soft quota is set to + <option>recursive-clients</option> minus 100; + otherwise it is set to 90% of + <option>recursive-clients</option>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>tcp-clients</command></term> + <listitem> + <para> + The maximum number of simultaneous client TCP + connections that the server will accept. + The default is <literal>150</literal>. + </para> + </listitem> + </varlistentry> + + <varlistentry xml:id="clients-per-query"> + <term xml:id="cpq_term"><command>clients-per-query</command></term> + <term><command>max-clients-per-query</command></term> + <listitem> + <para>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. <command>named</command> will attempt to + self tune this value and changes will be logged. The + default values are 10 and 100. + </para> + <para> + 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, <command>named</command> 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. + </para> + <para> + If <command>clients-per-query</command> is set to zero, + then there is no limit on the number of clients per query + and no queries will be dropped. + </para> + <para> + If <command>max-clients-per-query</command> is set to zero, + then there is no upper bound other than imposed by + <command>recursive-clients</command>. + </para> + </listitem> + </varlistentry> + + <varlistentry xml:id="fetches-per-zone"> + <term><command>fetches-per-zone</command></term> + <listitem> + <para> + 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 <option>recursive-clients</option>. + </para> + <para> + When many clients simultaneously query for the + same name and type, the clients will all be attached + to the same fetch, up to the + <option>max-clients-per-query</option> limit, + and only one iterative query will be sent. + However, when clients are simultaneously + querying for <emphasis>different</emphasis> names + or types, multiple queries will be sent and + <option>max-clients-per-query</option> is not + effective as a limit. + </para> + <para> + Optionally, this value may be followed by the keyword + <literal>drop</literal> or <literal>fail</literal>, + indicating whether queries which exceed the fetch + quota for a zone will be dropped with no response, + or answered with SERVFAIL. The default is + <literal>drop</literal>. + </para> + <para> + If <command>fetches-per-zone</command> 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. + </para> + <para> + The current list of active fetches can be dumped by + running <command>rndc recursing</command>. 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 the + <option>fetches-per-zone</option> 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.) + </para> + </listitem> + </varlistentry> + + <varlistentry xml:id="fetches-per-server"> + <term><command>fetches-per-server</command></term> + <listitem> + <para> + 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 <option>recursive-clients</option>. + </para> + <para> + Optionally, this value may be followed by the keyword + <literal>drop</literal> or <literal>fail</literal>, + 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 is + <literal>fail</literal>. + </para> + <para> + If <command>fetches-per-server</command> 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. + </para> + <para> + The <command>fetches-per-server</command> 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, then <command>fetches-per-server</command> + is reduced for that server. If the timeout ratio + drops below a "low" threshold, then + <command>fetches-per-server</command> is increased. + The <command>fetch-quota-params</command> options + can be used to adjust the parameters for this + calculation. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>fetch-quota-params</command></term> + <listitem> + <para> + Sets the parameters to use for dynamic resizing of + the <option>fetches-per-server</option> quota in + response to detected congestion. + </para> + <para> + 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. + </para> + <para> + 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>reserved-sockets</command></term> + <listitem> + <para> + The number of file descriptors reserved for TCP, stdio, + etc. This needs to be big enough to cover the number of + interfaces <command>named</command> listens on, <command>tcp-clients</command> as well as + to provide room for outgoing TCP queries and incoming zone + transfers. The default is <literal>512</literal>. + The minimum value is <literal>128</literal> and the + maximum value is <literal>128</literal> less than + maxsockets (-S). This option may be removed in the future. + </para> + <para> + This option has little effect on Windows. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>max-cache-size</command></term> + <listitem> + <para> + The maximum amount of memory to use for the + server's cache, in bytes or % of total physical memory. + 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 <userinput>unlimited</userinput>, + 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 is <userinput>90%</userinput>. + On systems where detection of amount of physical + memory is not supported values represented as % + fall back to unlimited. + Note that the detection of physical memory is done only + once at startup, so <command>named</command> will not + adjust the cache size if the amount of physical memory + is changed during runtime. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>tcp-listen-queue</command></term> + <listitem> + <para> + 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. + </para> + </listitem> + </varlistentry> + + </variablelist> + + </section> + + <section xml:id="intervals"><info><title>Periodic Task Intervals</title></info> + + <variablelist> + + <varlistentry> + <term><command>cleaning-interval</command></term> + <listitem> + <para> + This interval is effectively obsolete. Previously, + the server would remove expired resource records + from the cache every <command>cleaning-interval</command> minutes. + <acronym>BIND</acronym> 9 now manages cache + memory in a more sophisticated manner and does not + rely on the periodic cleaning any more. + Specifying this option therefore has no effect on + the server's behavior. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>heartbeat-interval</command></term> + <listitem> + <para> + The server will perform zone maintenance tasks + for all zones marked as <command>dialup</command> 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>interface-interval</command></term> + <listitem> + <para> + The server will scan the network interface list + every <command>interface-interval</command> + 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 the + <command>listen-on</command> configuration), and + will + stop listening on interfaces that have gone away. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>statistics-interval</command></term> + <listitem> + <para> + Name server statistics will be logged + every <command>statistics-interval</command> + minutes. The default is + 60. The maximum value is 28 days (40320 minutes). + If set to 0, no statistics will be logged. + </para><note> + <simpara> + Not yet implemented in + <acronym>BIND</acronym> 9. + </simpara> + </note> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>topology</command></term> + <listitem> + <para> + In BIND 8, this option indicated network topology + so that preferential treatment could be given to + the topologicaly closest name servers when sending + queries. It is not implemented in BIND 9. + </para> + </listitem> + </varlistentry> + + </variablelist> + + </section> + + <section xml:id="the_sortlist_statement"><info><title>The <command>sortlist</command> Statement</title></info> + + <para> + The response to a DNS query may consist of multiple resource + records (RRs) forming a resource record set (RRset). The name + server will normally return the RRs within the RRset in an + indeterminate order (but see the <command>rrset-order</command> + statement in <xref linkend="rrset_ordering"/>). The client + resolver code should rearrange the RRs as appropriate, that is, + using any addresses on the local net in preference to other + addresses. However, not all resolvers can do this or are + correctly configured. When a client is using a local server, + the sorting can be performed in the server, based on the + client's address. This only requires configuring the name + servers, not all the clients. + </para> + + <para> + The <command>sortlist</command> statement (see below) takes an + <command>address_match_list</command> and interprets it in a + special way. Each top level statement in the + <command>sortlist</command> must itself be an explicit + <command>address_match_list</command> with one or two elements. + The first element (which may be an IP address, an IP prefix, an + ACL name or a nested <command>address_match_list</command>) of + each top level list is checked against the source address of + the query until a match is found. + </para> + <para> + Once the source address of the query has been matched, if the + top level statement contains only one element, the actual + primitive element that matched the source address is used to + select the address in the response to move to the beginning of + the response. If the statement is a list of two elements, then + the second element is interpreted as a topology preference + list. Each top level element is assigned a distance and the + address in the response with the minimum distance is moved to + the beginning of the response. + </para> + <para> + In the following example, any queries received from any of the + addresses of the host itself will get responses preferring + addresses on any of the locally connected networks. Next most + preferred are addresses on the 192.168.1/24 network, and after + that either the 192.168.2/24 or 192.168.3/24 network with no + preference shown between these two networks. Queries received + from a host on the 192.168.1/24 network will prefer other + addresses on that network to the 192.168.2/24 and 192.168.3/24 + networks. Queries received from a host on the 192.168.4/24 or + the 192.168.5/24 network will only prefer other addresses on + their directly connected networks. + </para> + +<programlisting>sortlist { + // IF the local host + // THEN first fit on the following nets + { localhost; + { localnets; + 192.168.1/24; + { 192.168.2/24; 192.168.3/24; }; }; }; + // IF on class C 192.168.1 THEN use .1, or .2 or .3 + { 192.168.1/24; + { 192.168.1/24; + { 192.168.2/24; 192.168.3/24; }; }; }; + // IF on class C 192.168.2 THEN use .2, or .1 or .3 + { 192.168.2/24; + { 192.168.2/24; + { 192.168.1/24; 192.168.3/24; }; }; }; + // IF on class C 192.168.3 THEN use .3, or .1 or .2 + { 192.168.3/24; + { 192.168.3/24; + { 192.168.1/24; 192.168.2/24; }; }; }; + // IF .4 or .5 THEN prefer that net + { { 192.168.4/24; 192.168.5/24; }; + }; +};</programlisting> + + <para> + The following example will give reasonable behavior for the + local host and hosts on directly connected networks. It is + similar to the behavior of the address sort in + <acronym>BIND</acronym> 4.9.x. Responses sent to queries from + the local host will favor any of the directly connected + networks. Responses sent to queries from any other hosts on a + directly connected network will prefer addresses on that same + network. Responses to other queries will not be sorted. + </para> + +<programlisting>sortlist { + { localhost; localnets; }; + { localnets; }; +}; +</programlisting> + + </section> + <section xml:id="rrset_ordering"><info><title xml:id="rrset_ordering_title">RRset Ordering</title></info> + + <para> + When multiple records are returned in an answer it may be + useful to configure the order of the records placed into the + response. + The <command>rrset-order</command> statement permits + configuration + of the ordering of the records in a multiple record response. + See also the <command>sortlist</command> statement, + <xref linkend="the_sortlist_statement"/>. + </para> + + <para> + An <command>order_spec</command> is defined as + follows: + </para> + <para> + <optional>class <replaceable>class_name</replaceable></optional> + <optional>type <replaceable>type_name</replaceable></optional> + <optional>name <replaceable>"domain_name"</replaceable></optional> + order <replaceable>ordering</replaceable> + </para> + <para> + If no class is specified, the default is <command>ANY</command>. + If no type is specified, the default is <command>ANY</command>. + If no name is specified, the default is "<command>*</command>" (asterisk). + </para> + <para> + The legal values for <command>ordering</command> are: + </para> + <informaltable colsep="0" rowsep="0"> + <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table"> + <colspec colname="1" colnum="1" colsep="0" colwidth="0.750in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="3.750in"/> + <tbody> + <row rowsep="0"> + <entry colname="1"> + <para><command>fixed</command></para> + </entry> + <entry colname="2"> + <para> + Records are returned in the order they + are defined in the zone file. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>random</command></para> + </entry> + <entry colname="2"> + <para> + Records are returned in some random order. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>cyclic</command></para> + </entry> + <entry colname="2"> + <para> + Records are returned in a cyclic round-robin order. + </para> + <para> + If <acronym>BIND</acronym> is configured with the + "--enable-fixed-rrset" option at compile time, then + the initial ordering of the RRset will match the + one specified in the zone file. + </para> + </entry> + </row> + </tbody> + </tgroup> + </informaltable> + <para> + For example: + </para> + +<programlisting>rrset-order { + class IN type A name "host.example.com" order random; + order cyclic; +}; +</programlisting> + + <para> + will cause any responses for type A records in class IN that + have "<literal>host.example.com</literal>" as a + suffix, to always be returned + in random order. All other records are returned in cyclic order. + </para> + <para> + If multiple <command>rrset-order</command> statements + appear, they are not combined — the last one applies. + </para> + <para> + By default, all records are returned in random order. + </para> + + <note> + <simpara> + In this release of <acronym>BIND</acronym> 9, the + <command>rrset-order</command> statement does not support + "fixed" ordering by default. Fixed ordering can be enabled + at compile time by specifying "--enable-fixed-rrset" on + the "configure" command line. + </simpara> + </note> + </section> + + <section xml:id="tuning"><info><title>Tuning</title></info> + + <variablelist> + + <varlistentry> + <term><command>lame-ttl</command></term> + <listitem> + <para> + Sets the number of seconds to cache a + lame server indication. 0 disables caching. (This is + <emphasis role="bold">NOT</emphasis> recommended.) + The default is <literal>600</literal> (10 minutes) and the + maximum value is + <literal>1800</literal> (30 minutes). + </para> + + </listitem> + </varlistentry> + + <varlistentry> + <term><command>servfail-ttl</command></term> + <listitem> + <para> + Sets the number of seconds to cache a + SERVFAIL response due to DNSSEC validation failure or + other general server failure. If set to + <literal>0</literal>, SERVFAIL caching is disabled. + The SERVFAIL cache is not consulted if a query has + the CD (Checking Disabled) bit set; this allows a + query that failed due to DNSSEC validation to be retried + without waiting for the SERVFAIL TTL to expire. + </para> + <para> + The maximum value is <literal>30</literal> + seconds; any higher value will be silently + reduced. The default is <literal>1</literal> + second. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>max-ncache-ttl</command></term> + <listitem> + <para> + To reduce network traffic and increase performance, + the server stores negative answers. <command>max-ncache-ttl</command> is + used to set a maximum retention time for these answers in + the server + in seconds. The default + <command>max-ncache-ttl</command> is <literal>10800</literal> seconds (3 hours). + <command>max-ncache-ttl</command> cannot exceed + 7 days and will + be silently truncated to 7 days if set to a greater value. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>max-cache-ttl</command></term> + <listitem> + <para> + Sets the maximum time for which the server will + cache ordinary (positive) answers in seconds. + The default is 604800 (one week). + 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>min-roots</command></term> + <listitem> + <para> + The minimum number of root servers that + is required for a request for the root servers to be + accepted. The default + is <userinput>2</userinput>. + </para> + <note> + <simpara> + Not implemented in <acronym>BIND</acronym> 9. + </simpara> + </note> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>sig-validity-interval</command></term> + <listitem> + <para> + Specifies the number of days into the future when + DNSSEC signatures automatically generated as a + result of dynamic updates (<xref linkend="dynamic_update"/>) 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 <literal>30</literal> days + giving a re-signing interval of 7 1/2 days. The maximum + values are 10 years (3660 days). + </para> + <para> + The signature inception time is unconditionally + set to one hour before the current time to allow + for a limited amount of clock skew. + </para> + <para> + The <command>sig-validity-interval</command> + should be, at least, several multiples of the SOA + expire interval to allow for reasonable interaction + between the various timer and expiry dates. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>sig-signing-nodes</command></term> + <listitem> + <para> + Specify the maximum number of nodes to be + examined in each quantum when signing a zone with + a new DNSKEY. The default is + <literal>100</literal>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>sig-signing-signatures</command></term> + <listitem> + <para> + Specify a threshold number of signatures that + will terminate processing a quantum when signing + a zone with a new DNSKEY. The default is + <literal>10</literal>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>sig-signing-type</command></term> + <listitem> + <para> + Specify a private RDATA type to be used when generating + signing state records. The default is + <literal>65534</literal>. + </para> + <para> + It is expected that this parameter may be removed + in a future version once there is a standard type. + </para> + <para> + Signing state records are used to internally by + <command>named</command> 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 command + <command>rndc signing -list <replaceable>zone</replaceable></command>. + Once <command>named</command> has finished signing + a zone with a particular key, the signing state + record associated with that key can be removed from + the zone by running + <command>rndc signing -clear <replaceable>keyid/algorithm</replaceable> <replaceable>zone</replaceable></command>. + To clear all of the completed signing state + records for a zone, use + <command>rndc signing -clear all <replaceable>zone</replaceable></command>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>min-refresh-time</command></term> + <term><command>max-refresh-time</command></term> + <term><command>min-retry-time</command></term> + <term><command>max-retry-time</command></term> + <listitem> + <para> + 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. + </para> + <para> + These options allow the administrator to set a minimum and + maximum refresh and retry time in seconds 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. + </para> + <para> + The following defaults apply. + <command>min-refresh-time</command> 300 seconds, + <command>max-refresh-time</command> 2419200 seconds + (4 weeks), <command>min-retry-time</command> 500 seconds, + and <command>max-retry-time</command> 1209600 seconds + (2 weeks). + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>edns-udp-size</command></term> + <listitem> + <para> + 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. + </para> + <para> + The usual reason for setting + <command>edns-udp-size</command> 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. + </para> + <para> + When <command>named</command> 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. + </para> + <para> + If the initial response times out, <command>named</command> + 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, <command>named</command> + will default to plain DNS for future communications + with that server. (Periodically, <command>named</command> + will send an EDNS query to see if the situation has + improved.) + </para> + <para> + However, if the initial query is successful with + EDNS advertising a buffer size of 512, then + <command>named</command> will advertise progressively + larger buffer sizes on successive queries, until + responses begin timing out or + <command>edns-udp-size</command> is reached. + </para> + <para> + The default buffer sizes used by <command>named</command> + are 512, 1232, 1432, and 4096, but never exceeding + <command>edns-udp-size</command>. (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.) + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>max-udp-size</command></term> + <listitem> + <para> + Sets the maximum EDNS UDP message size + <command>named</command> 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. + </para> + <para> + This value applies to responses sent by a server; to + set the advertised buffer size in queries, see + <command>edns-udp-size</command>. + </para> + <para> + The usual reason for setting + <command>max-udp-size</command> 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 (<command>edns-udp-size</command>). + </para> + <para> + Setting this to a low value will encourage additional + TCP traffic to the nameserver. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>masterfile-format</command></term> + <listitem> + <para>Specifies + the file format of zone files (see + <xref linkend="zonefile_format"/>). + The default value is <constant>text</constant>, which is the + standard textual representation, except for slave zones, + in which the default value is <constant>raw</constant>. + Files in other formats than <constant>text</constant> are + typically expected to be generated by the + <command>named-compilezone</command> tool, or dumped by + <command>named</command>. + </para> + <para> + Note that when a zone file in a different format than + <constant>text</constant> is loaded, <command>named</command> + may omit some of the checks which would be performed for a + file in the <constant>text</constant> format. In particular, + <command>check-names</command> checks do not apply + for the <constant>raw</constant> format. This means + a zone file in the <constant>raw</constant> format + must be generated with the same check level as that + specified in the <command>named</command> configuration + file. Also, <constant>map</constant> format files are + loaded directly into memory via memory mapping, with only + minimal checking. + </para> + <para> + This statement sets the + <command>masterfile-format</command> for all zones, + but can be overridden on a per-zone or per-view basis + by including a <command>masterfile-format</command> + statement within the <command>zone</command> or + <command>view</command> block in the configuration + file. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>masterfile-style</command></term> + <listitem> + <para> + Specifies the formatting of zone files during dump + when the <option>masterfile-format</option> is + <constant>text</constant>. (This option is ignored + with any other <option>masterfile-format</option>.) + </para> + <para> + When set to <constant>relative</constant>, + records are printed in a multi-line format with owner + names expressed relative to a shared origin. When set + to <constant>full</constant>, records are printed in + a single-line format with absolute owner names. + The <constant>full</constant> format is most suitable + when a zone file needs to be processed automatically + by a script. The <constant>relative</constant> format + is more human-readable, and is thus suitable when a + zone is to be edited by hand. The default is + <constant>relative</constant>. + </para> + </listitem> + </varlistentry> + + <varlistentry xml:id="max-recursion-depth"> + <term><command>max-recursion-depth</command></term> + <listitem> + <para> + 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. + </para> + </listitem> + </varlistentry> + + <varlistentry xml:id="max-recursion-queries"> + <term><command>max-recursion-queries</command></term> + <listitem> + <para> + 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 domains such as "com" and "net" + and the DNS root zone are exempt from this limitation. + The default is 75. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>notify-delay</command></term> + <listitem> + <para> + The delay, in seconds, between sending sets of notify + messages for a zone. The default is five (5) seconds. + </para> + <para> + The overall rate that NOTIFY messages are sent for all + zones is controlled by <command>serial-query-rate</command>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>max-rsa-exponent-size</command></term> + <listitem> + <para> + 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>prefetch</command></term> + <listitem> + <para> + When a query is received for cached data which + is to expire shortly, <command>named</command> can + refresh the data from the authoritative server + immediately, ensuring that the cache always has an + answer available. + </para> + <para> + The <option>prefetch</option> 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 is <literal>2</literal>. + </para> + <para> + An optional second argument specifies the "eligibility" + TTL: the smallest <emphasis>original</emphasis> + 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, <command>named</command> will silently + adjust it upward. + The default eligibility TTL is <literal>9</literal>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>v6-bias</command></term> + <listitem> + <para> + When determining the next nameserver to try + preference IPv6 nameservers by this many milliseconds. + The default is <literal>50</literal> milliseconds. + </para> + </listitem> + </varlistentry> + </variablelist> + + </section> + + <section xml:id="builtin"><info><title>Built-in server information zones</title></info> + + <para> + The server provides some helpful diagnostic information + through a number of built-in zones under the + pseudo-top-level-domain <literal>bind</literal> in the + <command>CHAOS</command> class. These zones are part + of a + built-in view (see <xref linkend="view_statement_grammar"/>) of + class + <command>CHAOS</command> which is separate from the + default view of class <command>IN</command>. Most global + configuration options (<command>allow-query</command>, + etc) will apply to this view, but some are locally + overridden: <command>notify</command>, + <command>recursion</command> and + <command>allow-new-zones</command> are + always set to <userinput>no</userinput>, and + <command>rate-limit</command> is set to allow + three responses per second. + </para> + <para> + If you need to disable these zones, use the options + below, or hide the built-in <command>CHAOS</command> + view by + defining an explicit view of class <command>CHAOS</command> + that matches all clients. + </para> + + <variablelist> + + <varlistentry> + <term><command>version</command></term> + <listitem> + <para> + The version the server should report + via a query of the name <literal>version.bind</literal> + with type <command>TXT</command>, class <command>CHAOS</command>. + The default is the real version number of this server. + Specifying <command>version none</command> + disables processing of the queries. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>hostname</command></term> + <listitem> + <para> + The hostname the server should report via a query of + the name <filename>hostname.bind</filename> + with type <command>TXT</command>, class <command>CHAOS</command>. + This defaults to the hostname of the machine hosting the + name server as + found by the gethostname() function. The primary purpose of such queries + is to + identify which of a group of anycast servers is actually + answering your queries. Specifying <command>hostname none;</command> + disables processing of the queries. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>server-id</command></term> + <listitem> + <para> + The ID the server should report when receiving a Name + Server Identifier (NSID) query, or a query of the name + <filename>ID.SERVER</filename> with type + <command>TXT</command>, class <command>CHAOS</command>. + The primary purpose of such queries is to + identify which of a group of anycast servers is actually + answering your queries. Specifying <command>server-id none;</command> + disables processing of the queries. + Specifying <command>server-id hostname;</command> will cause <command>named</command> to + use the hostname as found by the gethostname() function. + The default <command>server-id</command> is <command>none</command>. + </para> + </listitem> + </varlistentry> + + </variablelist> + + </section> + + <section xml:id="empty"><info><title>Built-in Empty Zones</title></info> + + <para> + The <command>named</command> server 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. + </para> + <para> + The server 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. + </para> + <para> + The current list of empty zones is: + <itemizedlist> + <listitem>10.IN-ADDR.ARPA</listitem> + <listitem>16.172.IN-ADDR.ARPA</listitem> + <listitem>17.172.IN-ADDR.ARPA</listitem> + <listitem>18.172.IN-ADDR.ARPA</listitem> + <listitem>19.172.IN-ADDR.ARPA</listitem> + <listitem>20.172.IN-ADDR.ARPA</listitem> + <listitem>21.172.IN-ADDR.ARPA</listitem> + <listitem>22.172.IN-ADDR.ARPA</listitem> + <listitem>23.172.IN-ADDR.ARPA</listitem> + <listitem>24.172.IN-ADDR.ARPA</listitem> + <listitem>25.172.IN-ADDR.ARPA</listitem> + <listitem>26.172.IN-ADDR.ARPA</listitem> + <listitem>27.172.IN-ADDR.ARPA</listitem> + <listitem>28.172.IN-ADDR.ARPA</listitem> + <listitem>29.172.IN-ADDR.ARPA</listitem> + <listitem>30.172.IN-ADDR.ARPA</listitem> + <listitem>31.172.IN-ADDR.ARPA</listitem> + <listitem>168.192.IN-ADDR.ARPA</listitem> + <listitem>64.100.IN-ADDR.ARPA</listitem> + <listitem>65.100.IN-ADDR.ARPA</listitem> + <listitem>66.100.IN-ADDR.ARPA</listitem> + <listitem>67.100.IN-ADDR.ARPA</listitem> + <listitem>68.100.IN-ADDR.ARPA</listitem> + <listitem>69.100.IN-ADDR.ARPA</listitem> + <listitem>70.100.IN-ADDR.ARPA</listitem> + <listitem>71.100.IN-ADDR.ARPA</listitem> + <listitem>72.100.IN-ADDR.ARPA</listitem> + <listitem>73.100.IN-ADDR.ARPA</listitem> + <listitem>74.100.IN-ADDR.ARPA</listitem> + <listitem>75.100.IN-ADDR.ARPA</listitem> + <listitem>76.100.IN-ADDR.ARPA</listitem> + <listitem>77.100.IN-ADDR.ARPA</listitem> + <listitem>78.100.IN-ADDR.ARPA</listitem> + <listitem>79.100.IN-ADDR.ARPA</listitem> + <listitem>80.100.IN-ADDR.ARPA</listitem> + <listitem>81.100.IN-ADDR.ARPA</listitem> + <listitem>82.100.IN-ADDR.ARPA</listitem> + <listitem>83.100.IN-ADDR.ARPA</listitem> + <listitem>84.100.IN-ADDR.ARPA</listitem> + <listitem>85.100.IN-ADDR.ARPA</listitem> + <listitem>86.100.IN-ADDR.ARPA</listitem> + <listitem>87.100.IN-ADDR.ARPA</listitem> + <listitem>88.100.IN-ADDR.ARPA</listitem> + <listitem>89.100.IN-ADDR.ARPA</listitem> + <listitem>90.100.IN-ADDR.ARPA</listitem> + <listitem>91.100.IN-ADDR.ARPA</listitem> + <listitem>92.100.IN-ADDR.ARPA</listitem> + <listitem>93.100.IN-ADDR.ARPA</listitem> + <listitem>94.100.IN-ADDR.ARPA</listitem> + <listitem>95.100.IN-ADDR.ARPA</listitem> + <listitem>96.100.IN-ADDR.ARPA</listitem> + <listitem>97.100.IN-ADDR.ARPA</listitem> + <listitem>98.100.IN-ADDR.ARPA</listitem> + <listitem>99.100.IN-ADDR.ARPA</listitem> + <listitem>100.100.IN-ADDR.ARPA</listitem> + <listitem>101.100.IN-ADDR.ARPA</listitem> + <listitem>102.100.IN-ADDR.ARPA</listitem> + <listitem>103.100.IN-ADDR.ARPA</listitem> + <listitem>104.100.IN-ADDR.ARPA</listitem> + <listitem>105.100.IN-ADDR.ARPA</listitem> + <listitem>106.100.IN-ADDR.ARPA</listitem> + <listitem>107.100.IN-ADDR.ARPA</listitem> + <listitem>108.100.IN-ADDR.ARPA</listitem> + <listitem>109.100.IN-ADDR.ARPA</listitem> + <listitem>110.100.IN-ADDR.ARPA</listitem> + <listitem>111.100.IN-ADDR.ARPA</listitem> + <listitem>112.100.IN-ADDR.ARPA</listitem> + <listitem>113.100.IN-ADDR.ARPA</listitem> + <listitem>114.100.IN-ADDR.ARPA</listitem> + <listitem>115.100.IN-ADDR.ARPA</listitem> + <listitem>116.100.IN-ADDR.ARPA</listitem> + <listitem>117.100.IN-ADDR.ARPA</listitem> + <listitem>118.100.IN-ADDR.ARPA</listitem> + <listitem>119.100.IN-ADDR.ARPA</listitem> + <listitem>120.100.IN-ADDR.ARPA</listitem> + <listitem>121.100.IN-ADDR.ARPA</listitem> + <listitem>122.100.IN-ADDR.ARPA</listitem> + <listitem>123.100.IN-ADDR.ARPA</listitem> + <listitem>124.100.IN-ADDR.ARPA</listitem> + <listitem>125.100.IN-ADDR.ARPA</listitem> + <listitem>126.100.IN-ADDR.ARPA</listitem> + <listitem>127.100.IN-ADDR.ARPA</listitem> + <listitem>0.IN-ADDR.ARPA</listitem> + <listitem>127.IN-ADDR.ARPA</listitem> + <listitem>254.169.IN-ADDR.ARPA</listitem> + <listitem>2.0.192.IN-ADDR.ARPA</listitem> + <listitem>100.51.198.IN-ADDR.ARPA</listitem> + <listitem>113.0.203.IN-ADDR.ARPA</listitem> + <listitem>255.255.255.255.IN-ADDR.ARPA</listitem> + <listitem>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</listitem> + <listitem>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</listitem> + <listitem>8.B.D.0.1.0.0.2.IP6.ARPA</listitem> + <listitem>D.F.IP6.ARPA</listitem> + <listitem>8.E.F.IP6.ARPA</listitem> + <listitem>9.E.F.IP6.ARPA</listitem> + <listitem>A.E.F.IP6.ARPA</listitem> + <listitem>B.E.F.IP6.ARPA</listitem> + <listitem>EMPTY.AS112.ARPA</listitem> + <listitem>HOME.ARPA</listitem> + </itemizedlist> + </para> + <para> + 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: +<programlisting> + disable-empty-zone "."; +</programlisting> + </para> + <para> + 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. + </para> + <note><simpara> + 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. + </simpara></note> + <variablelist> + <varlistentry> + <term><command>empty-server</command></term> + <listitem> + <para> + 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>empty-contact</command></term> + <listitem> + <para> + Specify what contact name will appear in the returned + SOA record for empty zones. If none is specified, then + "." will be used. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>empty-zones-enable</command></term> + <listitem> + <para> + Enable or disable all empty zones. By default, they + are enabled. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>disable-empty-zone</command></term> + <listitem> + <para> + Disable individual empty zones. By default, none are + disabled. This option can be specified multiple times. + </para> + </listitem> + </varlistentry> + </variablelist> + </section> + + <section xml:id="acache"><info><title>Additional Section Caching</title></info> + + + <para> + The additional section cache, also called <command>acache</command>, + is an internal cache to improve the response performance of BIND 9. + When additional section caching is enabled, BIND 9 will + cache an internal short-cut to the additional section content for + each answer RR. + Note that <command>acache</command> is an internal caching + mechanism of BIND 9, and is not related to the DNS caching + server function. + </para> + + <para> + Additional section caching does not change the + response content (except the RRsets ordering of the additional + section, see below), but can improve the response performance + significantly. + It is particularly effective when BIND 9 acts as an authoritative + server for a zone that has many delegations with many glue RRs. + </para> + + <para> + In order to obtain the maximum performance improvement + from additional section caching, setting + <command>additional-from-cache</command> + to <command>no</command> is recommended, since the current + implementation of <command>acache</command> + does not short-cut of additional section information from the + DNS cache data. + </para> + + <para> + One obvious disadvantage of <command>acache</command> is + that it requires much more + memory for the internal cached data. + Thus, if the response performance does not matter and memory + consumption is much more critical, the + <command>acache</command> mechanism can be + disabled by setting <command>acache-enable</command> to + <command>no</command>. + It is also possible to specify the upper limit of memory + consumption + for acache by using <command>max-acache-size</command>. + </para> + + <para> + Additional section caching also has a minor effect on the + RRset ordering in the additional section. + Without <command>acache</command>, + <command>cyclic</command> order is effective for the additional + section as well as the answer and authority sections. + However, additional section caching fixes the ordering when it + first caches an RRset for the additional section, and the same + ordering will be kept in succeeding responses, regardless of the + setting of <command>rrset-order</command>. + The effect of this should be minor, however, since an + RRset in the additional section + typically only contains a small number of RRs (and in many cases + it only contains a single RR), in which case the + ordering does not matter much. + </para> + + <para> + The following is a summary of options related to + <command>acache</command>. + </para> + + <variablelist> + + <varlistentry> + <term><command>acache-enable</command></term> + <listitem> + <para> + If <command>yes</command>, additional section caching is + enabled. The default value is <command>no</command>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>acache-cleaning-interval</command></term> + <listitem> + <para> + The server will remove stale cache entries, based on an LRU + based + algorithm, every <command>acache-cleaning-interval</command> minutes. + The default is 60 minutes. + If set to 0, no periodic cleaning will occur. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>max-acache-size</command></term> + <listitem> + <para> + The maximum amount of memory in bytes to use for the server's acache. + When the amount of data in the acache reaches this limit, + the server + will clean more aggressively so that the limit is not + exceeded. + In a server with multiple views, the limit applies + separately to the + acache of each view. + The default is <literal>16M</literal>. + </para> + </listitem> + </varlistentry> + + </variablelist> + + </section> + + <section xml:id="content_filtering"><info><title>Content Filtering</title></info> + + <para> + <acronym>BIND</acronym> 9 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 + <varname>address_match_list</varname> of the + <command>deny-answer-addresses</command> 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 <varname>namelist</varname> of the + <command>deny-answer-aliases</command> option, where + "match" means the alias name is a subdomain of one of + the <varname>name_list</varname> elements. + If the optional <varname>namelist</varname> is specified + with <command>except-from</command>, 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 <command>deny-answer-aliases</command> + filter will not apply; + for example, even if "example.com" is specified for + <command>deny-answer-aliases</command>, + </para> +<programlisting>www.example.com. CNAME xxx.example.com.</programlisting> + + <para> + returned by an "example.com" server will be accepted. + </para> + + <para> + In the <varname>address_match_list</varname> of the + <command>deny-answer-addresses</command> option, only + <varname>ip_addr</varname> + and <varname>ip_prefix</varname> + are meaningful; + any <varname>key_id</varname> will be silently ignored. + </para> + + <para> + 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. + </para> + + <para> + 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 + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://portal.acm.org/citation.cfm?id=1315245.1315298"> + http://portal.acm.org/citation.cfm?id=1315245.1315298 + </link> + for more details about the attacks. + </para> + + <para> + 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: + </para> + +<programlisting>deny-answer-addresses { 192.0.2.0/24; } except-from { "example.net"; }; +deny-answer-aliases { "example.net"; }; +</programlisting> + + <para> + 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: + </para> + +<programlisting>attacker.example.com. A 192.0.2.1</programlisting> + + <para> + 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. + </para> + + <para> + 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 <acronym>BIND</acronym> 9 server + </para> + +<programlisting>www.example.net. A 192.0.2.2</programlisting> + + <para> + it will be accepted since the owner name "www.example.net" + matches the <command>except-from</command> element, + "example.net". + </para> + + <para> + 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. + </para> + + <para> + 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. + </para> + </section> + + <section xml:id="rpz"><info><title>Response Policy Zone (RPZ) Rewriting</title></info> + + <para> + <acronym>BIND</acronym> 9 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. + </para> + + <para> + Response policy zones are named in the + <command>response-policy</command> 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 + <command>allow-query { localhost; };</command>. + Note that zones using <command>masterfile-format map</command> + cannot be used as policy zones. + </para> + + <para> + A <command>response-policy</command> 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 <command>response-policy</command> option; more + than that is a configuration error. + </para> + + <para> + Five policy triggers can be encoded in RPZ records. + <variablelist> + <varlistentry> + <term><command>RPZ-CLIENT-IP</command></term> + <listitem> + <para> + 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 + <command>rpz-client-ip</command> relativized to the + policy zone origin name + and encode an address or address block. + IPv4 addresses are represented as + <userinput>prefixlength.B4.B3.B2.B1.rpz-client-ip</userinput>. + 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. + </para> + + <para> + IPv6 addresses are encoded in a format similar + to the standard IPv6 text representation, + <userinput>prefixlength.W8.W7.W6.W5.W4.W3.W2.W1.rpz-client-ip</userinput>. + 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 <userinput>.zz.</userinput> + analogous to double colons (::) in standard IPv6 text + encodings. + The IPv6 prefix length must be between 1 and 128. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>QNAME</command></term> + <listitem> + <para> + 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>RPZ-IP</command></term> + <listitem> + <para> + 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 <command>rpz-ip</command>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>RPZ-NSDNAME</command></term> + <listitem> + <para> + 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 + <command>rpz-nsdname</command> 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>RPZ-NSIP</command></term> + <listitem> + <para> + NSIP triggers match the IP addresses of authoritative + servers. They are enncoded like IP triggers, except as + subdomains of <command>rpz-nsip</command>. + NSDNAME and NSIP triggers are checked only for names with at + least <command>min-ns-dots</command> dots. + The default value of <command>min-ns-dots</command> is + 1, to exclude top level domains. + </para> + <para> + If a name server's IP address is not yet known, + <command>named</command> will recursively look up + the IP address before applying an RPZ-NSIP rule. + This can cause a processing delay. To speed up + processing at the cost of precision, the + <command>nsip-wait-recurse</command> option + can be used: when set to <userinput>no</userinput>, + RPZ-NSIP rules will only be applied when a name + servers's IP address has already been looked up and + cached. If a server's IP address is not in the + cache, then the RPZ-NSIP rule will be ignored, + but the address will be looked up in the + background, and the rule will be applied + to subsequent queries. The default is + <userinput>yes</userinput>, meaning RPZ-NSIP + rules should always be applied even if an + address needs to be looked up first. + </para> + </listitem> + </varlistentry> + </variablelist> + </para> + + <para> + 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 + <command>DISABLED</command> actions) must be chosen. + Triggers or the records that encode them are chosen for the + rewriting in the following order: + <orderedlist inheritnum="ignore" continuation="restarts"> + <listitem>Choose the triggered record in the zone that appears + first in the <command>response-policy</command> option. + </listitem> + <listitem>Prefer CLIENT-IP to QNAME to IP to NSDNAME to NSIP + triggers in a single zone. + </listitem> + <listitem>Among NSDNAME triggers, prefer the + trigger that matches the smallest name under the DNSSEC ordering. + </listitem> + <listitem>Among IP or NSIP triggers, prefer the trigger + with the longest prefix. + </listitem> + <listitem>Among triggers with the same prefix length, + prefer the IP or NSIP trigger that matches + the smallest IP address. + </listitem> + </orderedlist> + </para> + + <para> + 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. + </para> + + <para> + 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 <command>TCP-only</command> policy is + commonly used with <command>client-IP</command> triggers, + it can be used with any type of trigger to force the use of + TCP for responses with owner names in a zone. + <variablelist> + <varlistentry> + <term><command>PASSTHRU</command></term> + <listitem> + <para> + The whitelist policy is specified + by a CNAME whose target is <command>rpz-passthru</command>. + It causes the response to not be rewritten + and is most often used to "poke holes" in policies for + CIDR blocks. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>DROP</command></term> + <listitem> + <para> + The blacklist policy is specified + by a CNAME whose target is <command>rpz-drop</command>. + It causes the response to be discarded. + Nothing is sent to the DNS client. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>TCP-Only</command></term> + <listitem> + <para> + The "slip" policy is specified + by a CNAME whose target is <command>rpz-tcp-only</command>. + 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>NXDOMAIN</command></term> + <listitem> + <para> + The domain undefined response is encoded + by a CNAME whose target is the root domain (.) + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>NODATA</command></term> + <listitem> + <para> + 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>Local Data</command></term> + <listitem> + <para> + A set of ordinary DNS records can be used to answer queries. + Queries for record types not the set are answered with + NODATA. + </para> + + <para> + 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 asterisk (*) + has been replaced with the query name. + The purpose for this special form is query logging in the + walled garden's authority DNS server. + </para> + </listitem> + </varlistentry> + </variablelist> + </para> + + <para> + All of the actions specified in all of the individual records + in a policy zone + can be overridden with a <command>policy</command> clause in the + <command>response-policy</command> option. + An organization using a policy zone provided by another + organization might use this mechanism to redirect domains + to its own walled garden. + <variablelist> + <varlistentry> + <term><command>GIVEN</command></term> + <listitem> + <para>The placeholder policy says "do not override but + perform the action specified in the zone." + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>DISABLED</command></term> + <listitem> + <para> + 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>PASSTHRU</command></term>, + <term><command>DROP</command></term>, + <term><command>TCP-Only</command></term>, + <term><command>NXDOMAIN</command></term>, + and + <term><command>NODATA</command></term> + <listitem> + <para> + override with the corresponding per-record policy. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>CNAME domain</command></term> + <listitem> + <para> + causes all RPZ policy records to act as if they were + "cname domain" records. + </para> + </listitem> + </varlistentry> + </variablelist> + </para> + + <para> + 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 <command>recursive-only no</command> 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. + </para> + + <para> + 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 + <command>break-dnssec yes</command> 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. + </para> + + <para> + 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 <command>qname-wait-recurse no</command> 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 <command>break-dnssec yes</command> + 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. + </para> + + <para> + 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 <command>max-policy-ttl</command> clause changes the + maximum seconds from its default of 5. + </para> + + <para> + For example, you might use this option statement + </para> +<programlisting> response-policy { zone "badlist"; };</programlisting> + <para> + and this zone statement + </para> +<programlisting> zone "badlist" {type master; file "master/badlist"; allow-query {none;}; };</programlisting> + <para> + with this zone file + </para> +<programlisting>$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. + +</programlisting> + <para> + 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 <acronym>BIND9</acronym> 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. + </para> + + <para> + Responses rewritten by RPZ are counted in the + <command>RPZRewrites</command> statistics. + </para> + + <para> + The <command>log</command> clause can be used to optionally + turn off rewrite logging for a particular response policy + zone. By default, all rewrites are logged. + </para> + </section> + + <section xml:id="rrl"><info><title>Response Rate Limiting</title></info> + + <para> + Excessive almost identical UDP <emphasis>responses</emphasis> + can be controlled by configuring a + <command>rate-limit</command> clause in an + <command>options</command> or <command>view</command> statement. + This mechanism keeps authoritative BIND 9 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. + </para> + + <para> + 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. + </para> + + <para> + 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 <command>window</command> 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 <command>window</command> + 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. + </para> + + <para> + 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 <command>ipv4-prefix-length</command> (default 24) + and <command>ipv6-prefix-length</command> (default 56). + </para> + + <para> + All non-empty responses for a valid domain name (qname) + and record type (qtype) are identical and have a limit specified + with <command>responses-per-second</command> + (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 + <command>nodata-per-second</command> + (default <command>responses-per-second</command>). + 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 <command>nxdomains-per-second</command> + (default <command>responses-per-second</command>). + 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 + <command>referrals-per-second</command> + (default <command>responses-per-second</command>). + </para> + + <para> + 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. + </para> + + <para> + 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 + <command>responses-per-second</command> value, + but it can be set separately with + <command>errors-per-second</command>. + </para> + + <para> + Many attacks using DNS involve UDP requests with forged source + addresses. + Rate limiting prevents the use of BIND 9 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 <command>slip</command> 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. + <command>slip</command> 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 <command>slip</command> rate. + </para> + + <para> + (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 + <command>slip</command> to 1, causing all rate-limited + responses to be truncated rather than dropped. This reduces + the effectiveness of rate-limiting against reflection attacks.) + </para> + + <para> + When the approximate query per second rate exceeds + the <command>qps-scale</command> value, + then the <command>responses-per-second</command>, + <command>errors-per-second</command>, + <command>nxdomains-per-second</command> and + <command>all-per-second</command> values are reduced by the + ratio of the current rate to the <command>qps-scale</command> value. + This feature can tighten defenses during attacks. + For example, with + <command>qps-scale 250; responses-per-second 20;</command> 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. + </para> + + <para> + Rate limiters for different name spaces maintain + separate counters: If, for example, there is a + <command>rate-limit</command> statement for "com" and + another for "example.com", queries matching "example.com" + will not be debited against the rate limiter for "com". + </para> + + <para> + If a <command>rate-limit</command> statement does not specify a + <command>domain</command>, then it applies to the root domain + (".") and thus affects the entire DNS namespace, except those + portions covered by other <command>rate-limit</command> + statements. + </para> + + <para> + Communities of DNS clients can be given their own parameters or no + rate limiting by putting + <command>rate-limit</command> statements in <command>view</command> + statements instead of the global <command>option</command> + statement. + A <command>rate-limit</command> statement in a view replaces, + rather than supplementing, a <command>rate-limit</command> + statement among the main options. + DNS clients within a view can be exempted from rate limits + with the <command>exempt-clients</command> clause. + </para> + + <para> + UDP responses of all kinds can be limited with the + <command>all-per-second</command> phrase. This rate + limiting is unlike the rate limiting provided by + <command>responses-per-second</command>, + <command>errors-per-second</command>, and + <command>nxdomains-per-second</command> 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 <command>all-per-second</command> limit + are always dropped; the <command>slip</command> value + has no effect. An <command>all-per-second</command> + 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 <command>Mail From</command> + command. Web browsers often repeatedly resolve the + same names that are repeated in HTML <IMG> tags + in a page. <command>all-per-second</command> 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 make TCP connections + or parsing DNS requests, but that rate limiting must + be done before the DNS server sees the requests. + </para> + + <para> + The maximum size of the table used to track requests and + rate limit responses is set with <command>max-table-size</command>. + 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, + <command>min-table-size</command> (default 500) + can set the minimum table size. + Enable <command>rate-limit</command> category logging to monitor + expansions of the table and inform + choices for the initial and maximum table size. + </para> + + <para> + Use <command>log-only yes</command> to test rate limiting parameters + without actually dropping any requests. + </para> + + <para> + Responses dropped by rate limits are included in the + <command>RateDropped</command> and <command>QryDropped</command> + statistics. + Responses that truncated by rate limits are included in + <command>RateSlipped</command> and <command>RespTruncated</command>. + </para> + </section> + + <section title="NXDOMAIN Redirection"><info/> + <para> + Named supports NXDOMAIN redirection via two methods: + <itemizedlist> + <listitem>Redirect zone <xref linkend="zone_statement_grammar"/></listitem> + <listitem>Redirect namespace</listitem> + </itemizedlist> + </para> + <para> + With both methods when named gets a NXDOMAIN response + it examines a separate namespace to see if the NXDOMAIN + response should be replaced with an alternative response. + </para> + <para> + With a redirect zone (<command>zone "." { type redirect; };</command>), the + data used to replace the NXDOMAIN is held in a single + zone which is not part of the normal namespace. All the + redirect information is contained in the zone; there are + no delegations. + </para> + <para> + With a redirect namespace (<command>option { nxdomain-redirect + <suffix> };</command>) the data used to replace the + NXDOMAIN is part of the normal namespace and is looked up by + appending the specified suffix to the original query name. + This roughly doubles the cache required to process NXDOMAIN + responses as you have the original NXDOMAIN response and + the replacement data or a NXDOMAIN indicating that there + is no replacement. + </para> + <para> + If both a redirect zone and a redirect namespace are configured, + the redirect zone is tried first. + </para> + </section> + </section> + + <section xml:id="server_statement_grammar"><info><title><command>server</command> Statement Grammar</title></info> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="server.grammar.xml"/> + </section> + + <section xml:id="server_statement_definition_and_usage"><info><title><command>server</command> Statement Definition and + Usage</title></info> + + <para> + The <command>server</command> 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 + <filename>named.conf</filename>. + </para> + + <para> + The <command>server</command> statement can occur at + the top level of the + configuration file or inside a <command>view</command> + statement. + If a <command>view</command> statement contains + one or more <command>server</command> statements, only + those + apply to the view and any top-level ones are ignored. + If a view contains no <command>server</command> + statements, + any top-level <command>server</command> statements are + used as + defaults. + </para> + + <para> + 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 <command>bogus</command> is <command>no</command>. + </para> + <para> + The <command>provide-ixfr</command> 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 <command>yes</command>, incremental transfer + will be provided + whenever possible. If set to <command>no</command>, + all transfers + to the remote server will be non-incremental. If not set, the + value + of the <command>provide-ixfr</command> option in the + view or + global options block is used as a default. + </para> + + <para> + The <command>request-ixfr</command> 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 <command>request-ixfr</command> 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. + </para> + + <para> + 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 <command>yes</command> should always work. + The purpose of the <command>provide-ixfr</command> and + <command>request-ixfr</command> 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. + </para> + + <para> + The <command>request-expire</command> clause determines + whether the local server, when acting as a slave, will + request the EDNS EXPIRE value. The EDNS EXPIRE value + indicates the remaining time before the zone data will + expire and need to be be refreshed. This is used + when a secondary server transfers a zone from another + secondary server; when transferring from the primary, the + expiration timer is set from the EXPIRE field of the SOA + record instead. + The default is <command>yes</command>. + </para> + + <para> + The <command>edns</command> clause determines whether + the local server will attempt to use EDNS when communicating + with the remote server. The default is <command>yes</command>. + </para> + + <para> + The <command>edns-udp-size</command> option sets the + EDNS UDP size that is advertised by <command>named</command> + 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; <command>named</command> will not deviate from + this value. This differs from the behavior of + <command>edns-udp-size</command> in <command>options</command> + or <command>view</command> statements, where it specifies + a maximum value. The <command>server</command> statement + behavior may be brought into conformance with the + <command>options/view</command> behavior in future releases.) + </para> + + <para> + The <command>edns-version</command> option sets the + maximum EDNS VERSION that will be sent to the server(s) + by the resolver. The actual EDNS version sent is still + subject to normal EDNS version negotiation rules (see + RFC 6891), the maximum EDNS version supported by the + server, and any other heuristics that indicate that a + lower version should be sent. This option is intended + to be used when a remote server reacts badly to a given + EDNS version or higher; it should be set to the highest + version the remote server is known to support. Valid + values are 0 to 255; higher values will be silently + adjusted. This option will not be needed until higher + EDNS versions than 0 are in use. + </para> + + <para> + The <command>max-udp-size</command> option sets the + maximum EDNS UDP message size <command>named</command> + 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 <command>named</command>. + </para> + + <para> + The <command>tcp-only</command> 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. + </para> + + <para> + The server supports two zone transfer methods. The first, <command>one-answer</command>, + uses one DNS message per resource record transferred. <command>many-answers</command> packs + as many resource records as possible into a message. <command>many-answers</command> is + more efficient, but is only known to be understood by <acronym>BIND</acronym> 9, <acronym>BIND</acronym> + 8.x, and patched versions of <acronym>BIND</acronym> + 4.9.5. You can specify which method + to use for a server with the <command>transfer-format</command> option. + If <command>transfer-format</command> is not + specified, the <command>transfer-format</command> + specified + by the <command>options</command> statement will be + used. + </para> + + <para><command>transfers</command> + is used to limit the number of concurrent inbound zone + transfers from the specified server. If no + <command>transfers</command> clause is specified, the + limit is set according to the + <command>transfers-per-ns</command> option. + </para> + + <para> + The <command>keys</command> clause identifies a + <command>key_id</command> defined by the <command>key</command> statement, + to be used for transaction security (TSIG, <xref linkend="tsig"/>) + 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. + </para> + + <para> + Only a single key per server is currently supported. + </para> + + <para> + The <command>transfer-source</command> and + <command>transfer-source-v6</command> 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 <command>transfer-source</command> can + be specified. + Similarly, for an IPv6 remote server, only + <command>transfer-source-v6</command> can be + specified. + For more details, see the description of + <command>transfer-source</command> and + <command>transfer-source-v6</command> in + <xref linkend="zone_transfers"/>. + </para> + + <para> + The <command>notify-source</command> and + <command>notify-source-v6</command> 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 <command>notify-source</command> + can be specified. Similarly, for an IPv6 remote server, + only <command>notify-source-v6</command> can be specified. + </para> + + <para> + The <command>query-source</command> and + <command>query-source-v6</command> clauses specify the + IPv4 and IPv6 source address to be used for queries + sent to remote servers, respectively. For an IPv4 + remote server, only <command>query-source</command> can + be specified. Similarly, for an IPv6 remote server, + only <command>query-source-v6</command> can be specified. + </para> + + <para> + The <command>request-nsid</command> clause determines + whether the local server will add a NSID EDNS option + to requests sent to the server. This overrides + <command>request-nsid</command> set at the view or + option level. + </para> + + <para> + The <command>send-cookie</command> clause determines + whether the local server will add a COOKIE EDNS option + to requests sent to the server. This overrides + <command>send-cookie</command> set at the view or + option level. The <command>named</command> server may + determine that COOKIE is not supported by the remote server + and not add a COOKIE EDNS option to requests. + </para> + </section> + + <section xml:id="statschannels"><info><title><command>statistics-channels</command> Statement Grammar</title></info> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="statistics-channels.grammar.xml"/> + </section> + + <section xml:id="statistics_channels"><info><title><command>statistics-channels</command> Statement Definition and + Usage</title></info> + + <para> + The <command>statistics-channels</command> statement + declares communication channels to be used by system + administrators to get access to statistics information of + the name server. + </para> + + <para> + This statement intends to be flexible to support multiple + communication protocols in the future, but currently only + HTTP access is supported. + It requires that BIND 9 be compiled with libxml2 and/or + json-c (also known as libjson0); the + <command>statistics-channels</command> statement is + still accepted even if it is built without the library, + but any HTTP access will fail with an error. + </para> + + <para> + An <command>inet</command> control channel is a TCP socket + listening at the specified <command>ip_port</command> on the + specified <command>ip_addr</command>, which can be an IPv4 or IPv6 + address. An <command>ip_addr</command> of <literal>*</literal> + (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 <command>ip_addr</command> of <literal>::</literal>. + </para> + + <para> + If no port is specified, port 80 is used for HTTP channels. + The asterisk "<literal>*</literal>" cannot be used for + <command>ip_port</command>. + </para> + + <para> + The attempt of opening a statistics channel is + restricted by the optional <command>allow</command> clause. + Connections to the statistics channel are permitted based on the + <command>address_match_list</command>. + If no <command>allow</command> clause is present, + <command>named</command> accepts connection + attempts from any address; since the statistics may + contain sensitive internal information, it is highly + recommended to restrict the source of connection requests + appropriately. + </para> + + <para> + If no <command>statistics-channels</command> statement is present, + <command>named</command> will not open any communication channels. + </para> + + <para> + The statistics are available in various formats and views + depending on the URI used to access them. For example, if + the statistics channel is configured to listen on 127.0.0.1 + port 8888, then the statistics are accessible in XML format at + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://127.0.0.1:8888/">http://127.0.0.1:8888/</link> or + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://127.0.0.1:8888/xml">http://127.0.0.1:8888/xml</link>. A CSS file is + included which can format the XML statistics into tables + when viewed with a stylesheet-capable browser, and into + charts and graphs using the Google Charts API when using a + javascript-capable browser. + </para> + + <para> + Applications that depend on a particular XML schema + can request + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://127.0.0.1:8888/xml/v2">http://127.0.0.1:8888/xml/v2</link> for version 2 + of the statistics XML schema or + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://127.0.0.1:8888/xml/v3">http://127.0.0.1:8888/xml/v3</link> for version 3. + If the requested schema is supported by the server, then + it will respond; if not, it will return a "page not found" + error. + </para> + + <para> + Broken-out subsets of the statistics can be viewed at + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://127.0.0.1:8888/xml/v3/status">http://127.0.0.1:8888/xml/v3/status</link> + (server uptime and last reconfiguration time), + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://127.0.0.1:8888/xml/v3/server">http://127.0.0.1:8888/xml/v3/server</link> + (server and resolver statistics), + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://127.0.0.1:8888/xml/v3/zones">http://127.0.0.1:8888/xml/v3/zones</link> + (zone statistics), + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://127.0.0.1:8888/xml/v3/net">http://127.0.0.1:8888/xml/v3/net</link> + (network status and socket statistics), + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://127.0.0.1:8888/xml/v3/mem">http://127.0.0.1:8888/xml/v3/mem</link> + (memory manager statistics), + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://127.0.0.1:8888/xml/v3/tasks">http://127.0.0.1:8888/xml/v3/tasks</link> + (task manager statistics), and + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://127.0.0.1:8888/xml/v3/traffic">http://127.0.0.1:8888/xml/v3/traffic</link> + (traffic sizes). + </para> + + <para> + The full set of statistics can also be read in JSON format at + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://127.0.0.1:8888/json">http://127.0.0.1:8888/json</link>, + with the broken-out subsets at + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://127.0.0.1:8888/json/v1/status">http://127.0.0.1:8888/json/v1/status</link> + (server uptime and last reconfiguration time), + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://127.0.0.1:8888/json/v1/server">http://127.0.0.1:8888/json/v1/server</link> + (server and resolver statistics), + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://127.0.0.1:8888/json/v1/zones">http://127.0.0.1:8888/json/v1/zones</link> + (zone statistics), + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://127.0.0.1:8888/json/v1/net">http://127.0.0.1:8888/json/v1/net</link> + (network status and socket statistics), + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://127.0.0.1:8888/json/v1/mem">http://127.0.0.1:8888/json/v1/mem</link> + (memory manager statistics), + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://127.0.0.1:8888/json/v1/tasks">http://127.0.0.1:8888/json/v1/tasks</link> + (task manager statistics), and + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://127.0.0.1:8888/json/v1/traffic">http://127.0.0.1:8888/json/v1/traffic</link> + (traffic sizes). + </para> + </section> + + <section xml:id="trusted-keys"><info><title><command>trusted-keys</command> Statement Grammar</title></info> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="trusted-keys.grammar.xml"/> + </section> + <section xml:id="trusted_keys"><info><title><command>trusted-keys</command> Statement Definition + and Usage</title></info> + + <para> + The <command>trusted-keys</command> statement defines + DNSSEC security roots. DNSSEC is described in <xref linkend="DNSSEC"/>. 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. + </para> + <para> + All keys (and corresponding zones) listed in + <command>trusted-keys</command> are deemed to exist regardless + of what parent zones say. Similarly for all keys listed in + <command>trusted-keys</command> only those keys are + used to validate the DNSKEY RRset. The parent's DS RRset + will not be used. + </para> + <para> + The <command>trusted-keys</command> 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. + </para> + <para> + <command>trusted-keys</command> may be set at the top level + of <filename>named.conf</filename> 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. + </para> + <para> + Validation below specified names can be temporarily disabled + by using <command>rndc nta</command>. + </para> + </section> + + <section xml:id="managed_keys"><info><title><command>managed-keys</command> Statement Grammar</title></info> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="managed-keys.grammar.xml"/> + </section> + <section xml:id="managed-keys"><info><title><command>managed-keys</command> Statement Definition + and Usage</title></info> + + <para> + The <command>managed-keys</command> statement, like + <command>trusted-keys</command>, defines DNSSEC + security roots. The difference is that + <command>managed-keys</command> can be kept up to date + automatically, without intervention from the resolver + operator. + </para> + <para> + 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 + <command>trusted-keys</command> 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 + <command>trusted-keys</command> statement with the new key. + </para> + <para> + If, however, the zone were listed in a + <command>managed-keys</command> statement instead, then the + zone owner could add a "stand-by" key to the zone in advance. + <command>named</command> would store the stand-by key, and + when the original key was revoked, <command>named</command> + 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. + </para> + <para> + A <command>managed-keys</command> 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 + <literal>initial-key</literal>. + This means the <command>managed-keys</command> statement must + contain a copy of the initializing key. (Future releases may + allow keys to be initialized by other methods, eliminating this + requirement.) + </para> + <para> + Consequently, a <command>managed-keys</command> statement + appears similar to a <command>trusted-keys</command>, differing + in the presence of the second field, containing the keyword + <literal>initial-key</literal>. The difference is, whereas the + keys listed in a <command>trusted-keys</command> continue to be + trusted until they are removed from + <filename>named.conf</filename>, an initializing key listed + in a <command>managed-keys</command> statement is only trusted + <emphasis>once</emphasis>: for as long as it takes to load the + managed key database and start the RFC 5011 key maintenance + process. + </para> + <para> + The first time <command>named</command> runs with a managed key + configured in <filename>named.conf</filename>, it fetches the + DNSKEY RRset directly from the zone apex, and validates it + using the key specified in the <command>managed-keys</command> + statement. If the DNSKEY RRset is validly signed, then it is + used as the basis for a new managed keys database. + </para> + <para> + From that point on, whenever <command>named</command> runs, it + sees the <command>managed-keys</command> 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 <command>managed-keys</command> + statement is not used to validate answers; it has been + superseded by the key or keys stored in the managed keys database. + </para> + <para> + The next time <command>named</command> runs after a name + has been <emphasis>removed</emphasis> from the + <command>managed-keys</command> 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. + </para> + <para> + In the current implementation, the managed keys database + is stored as a master-format zone file. + </para> + <para> + On servers which do not use views, this file is named + <filename>managed-keys.bind</filename>. When views are in + use, there will be a separate managed keys database for each + view; the filename will be the view name (or, if a view name + contains characters which would make it illegal as a filename, + a hash of the view name), followed by + the suffix <filename>.mkeys</filename>. + </para> + <para> + 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., + <filename>managed-keys.bind.jnl</filename> or + <filename>internal.mkeys.jnl</filename>. + Changes are committed to the master file as soon as + possible afterward; this will usually occur within 30 + seconds. So, whenever <command>named</command> 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 <command>named</command>.) + </para> + <para> + If the <command>dnssec-validation</command> option is + set to <userinput>auto</userinput>, <command>named</command> + will automatically initialize a managed key for the + root zone. The key that is used to initialize the key + maintenance process is stored in <filename>bind.keys</filename>; + the location of this file can be overridden with the + <command>bindkeys-file</command> option. As a fallback + in the event no <filename>bind.keys</filename> can be + found, the initializing key is also compiled directly + into <command>named</command>. + </para> + </section> + + <section xml:id="view_statement_grammar"><info><title><command>view</command> Statement Grammar</title></info> + +<programlisting><command>view</command> <replaceable>view_name</replaceable> [ <replaceable>class</replaceable> ] <command>{</command> + <command>match-clients {</command> <replaceable>address_match_list</replaceable> <command>}</command> ; + <command>match-destinations {</command> <replaceable>address_match_list</replaceable> <command>}</command> ; + <command>match-recursive-only</command> <replaceable>yes_or_no</replaceable> ; + [ <replaceable>view_option</replaceable> ; ... ] + [ <replaceable>zone_statement</replaceable> ; ... ] +<command>} </command>; +</programlisting> + + </section> + <section xml:id="view_statement"><info><title><command>view</command> Statement Definition and Usage</title></info> + + <para> + The <command>view</command> statement is a powerful + feature + of <acronym>BIND</acronym> 9 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. + </para> + + <para> + Each <command>view</command> 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 + <varname>address_match_list</varname> of the view's + <command>match-clients</command> clause and its + destination IP address matches + the <varname>address_match_list</varname> of the + view's + <command>match-destinations</command> clause. If not + specified, both + <command>match-clients</command> and <command>match-destinations</command> + default to matching all addresses. In addition to checking IP + addresses + <command>match-clients</command> and <command>match-destinations</command> + can also take <command>keys</command> which provide an + mechanism for the + client to select the view. A view can also be specified + as <command>match-recursive-only</command>, which + means that only recursive + requests from matching clients will match that view. + The order of the <command>view</command> statements is + significant — + a client request will be resolved in the context of the first + <command>view</command> that it matches. + </para> + + <para> + Zones defined within a <command>view</command> + statement will + only be accessible to clients that match the <command>view</command>. + 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. + </para> + + <para> + Many of the options given in the <command>options</command> statement + can also be used within a <command>view</command> + statement, and then + apply only when resolving queries with that view. When no + view-specific + value is given, the value in the <command>options</command> statement + is used as a default. Also, zone options can have default values + specified + in the <command>view</command> statement; these + view-specific defaults + take precedence over those in the <command>options</command> statement. + </para> + + <para> + 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. + </para> + + <para> + If there are no <command>view</command> statements in + the config + file, a default view that matches any client is automatically + created + in class IN. Any <command>zone</command> statements + specified on + the top level of the configuration file are considered to be part + of + this default view, and the <command>options</command> + statement will + apply to the default view. If any explicit <command>view</command> + statements are present, all <command>zone</command> + statements must + occur inside <command>view</command> statements. + </para> + + <para> + Here is an example of a typical split DNS setup implemented + using <command>view</command> statements: + </para> + +<programlisting>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"; + }; +}; +</programlisting> + + </section> + <section xml:id="zone_statement_grammar"><info><title><command>zone</command> + Statement Grammar</title></info> + +<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="master.zoneopt.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="slave.zoneopt.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="hint.zoneopt.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="stub.zoneopt.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="static-stub.zoneopt.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="forward.zoneopt.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="redirect.zoneopt.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="delegation-only.zoneopt.xml"/> +<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="in-view.zoneopt.xml"/> + + </section> + <section xml:id="zone_statement"><info><title><command>zone</command> Statement Definition and Usage</title></info> + + <section xml:id="zone_types"><info><title>Zone Types</title></info> + <para> + The <command>type</command> keyword is required + for the <command>zone</command> configuration unless + it is an <command>in-view</command> configuration. Its + acceptable values include: <varname>delegation-only</varname>, + <varname>forward</varname>, <varname>hint</varname>, + <varname>master</varname>, <varname>redirect</varname>, + <varname>slave</varname>, <varname>static-stub</varname>, + and <varname>stub</varname>. + </para> + + <informaltable colsep="0" rowsep="0"> + <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table"> + <!--colspec colname="1" colnum="1" colsep="0" colwidth="1.108in"/--> + <!--colspec colname="2" colnum="2" colsep="0" colwidth="4.017in"/--> + <colspec colname="1" colnum="1" colsep="0"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="4.017in"/> + <tbody> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>master</varname> + </para> + </entry> + <entry colname="2"> + <para> + The server has a master copy of the data + for the zone and will be able to provide authoritative + answers for + it. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>slave</varname> + </para> + </entry> + <entry colname="2"> + <para> + A slave zone is a replica of a master + zone. The <command>masters</command> list + specifies one or more IP addresses + of master servers that the slave contacts to update + its copy of the zone. + Masters list elements can also be names of other + masters lists. + By default, transfers are made from port 53 on the + servers; this can + be changed for all servers by specifying a port number + before the + list of IP addresses, or on a per-server basis after + the IP address. + Authentication to the master can also be done with + per-server TSIG keys. + If a file is specified, then the + replica will be written to this file whenever the zone + is changed, + and reloaded from this file on a server restart. Use + of a file is + recommended, since it often speeds server startup and + eliminates + a needless waste of bandwidth. Note that for large + numbers (in the + tens or hundreds of thousands) of zones per server, it + is best to + use a two-level naming scheme for zone filenames. For + example, + a slave server for the zone <literal>example.com</literal> might place + the zone contents into a file called + <filename>ex/example.com</filename> where <filename>ex/</filename> is + just the first two letters of the zone name. (Most + operating systems + behave very slowly if you put 100000 files into + a single directory.) + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>stub</varname> + </para> + </entry> + <entry colname="2"> + <para> + 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 <acronym>BIND</acronym> implementation. + </para> + + <para> + 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 <filename>named.conf</filename>. + This usage is not recommended for new configurations, + and BIND 9 + supports it only in a limited way. + In <acronym>BIND</acronym> 4/8, zone + transfers of a parent zone + included the NS records from stub children of that + zone. This meant + that, in some cases, users could get away with + configuring child stubs + only in the master server for the parent zone. <acronym>BIND</acronym> + 9 never mixes together zone data from different zones + in this + way. Therefore, if a <acronym>BIND</acronym> 9 master serving a parent + zone has child stub zones configured, all the slave + servers for the + parent zone also need to have the same child stub + zones + configured. + </para> + + <para> + 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 + <literal>10.in-addr.arpa</literal> + to use a set of internal name servers as the + authoritative + servers for that domain. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>static-stub</varname> + </para> + </entry> + <entry colname="2"> + <para> + 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. + </para> + <para> + Zone data is configured via the + <command>server-addresses</command> and + <command>server-names</command> zone options. + </para> + <para> + 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 <command>rndc dumpdb -all</command>. + The configured RRs are considered local configuration + parameters rather than public data. + Non recursive queries (i.e., those with the RD + bit off) to a static-stub zone are therefore + prohibited and will be responded with REFUSED. + </para> + <para> + 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. + </para> + <para> + Each static-stub zone is configured with + internally generated NS and (if necessary) + glue A or AAAA RRs + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>forward</varname> + </para> + </entry> + <entry colname="2"> + <para> + A "forward zone" is a way to configure + forwarding on a per-domain basis. A <command>zone</command> statement + of type <command>forward</command> can + contain a <command>forward</command> + and/or <command>forwarders</command> + statement, + which will apply to queries within the domain given by + the zone + name. If no <command>forwarders</command> + statement is present or + an empty list for <command>forwarders</command> is given, then no + forwarding will be done for the domain, canceling the + effects of + any forwarders in the <command>options</command> statement. Thus + if you want to use this type of zone to change the + behavior of the + global <command>forward</command> option + (that is, "forward first" + to, then "forward only", or vice versa, but want to + use the same + servers as set globally) you need to re-specify the + global forwarders. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>hint</varname> + </para> + </entry> + <entry colname="2"> + <para> + 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. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>redirect</varname> + </para> + </entry> + <entry colname="2"> + <para> + Redirect zones are used to provide answers to + queries when normal resolution would result in + NXDOMAIN being returned. + Only one redirect zone is supported + per view. <command>allow-query</command> can be + used to restrict which clients see these answers. + </para> + <para> + If the client has requested DNSSEC records (DO=1) and + the NXDOMAIN response is signed then no substitution + will occur. + </para> + <para> + To redirect all NXDOMAIN responses to + 100.100.100.2 and + 2001:ffff:ffff::100.100.100.2, one would + configure a type redirect zone named ".", + with the zone file containing wildcard records + that point to the desired addresses: + <literal>"*. IN A 100.100.100.2"</literal> + and + <literal>"*. IN AAAA 2001:ffff:ffff::100.100.100.2"</literal>. + </para> + <para> + To redirect all Spanish names (under .ES) one + would use similar entries but with the names + "*.ES." instead of "*.". To redirect all + commercial Spanish names (under COM.ES) one + would use wildcard entries called "*.COM.ES.". + </para> + <para> + Note that the redirect zone supports all + possible types; it is not limited to A and + AAAA records. + </para> + <para> + Because redirect zones are not referenced + directly by name, they are not kept in the + zone lookup table with normal master and slave + zones. Consequently, it is not currently possible + to use + <command>rndc reload + <replaceable>zonename</replaceable></command> + to reload a redirect zone. However, when using + <command>rndc reload</command> without specifying + a zone name, redirect zones will be reloaded along + with other zones. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>delegation-only</varname> + </para> + </entry> + <entry colname="2"> + <para> + 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. + </para> + <para> + <varname>delegation-only</varname> has no + effect on answers received from forwarders. + </para> + <para> + See caveats in <xref linkend="root_delegation_only"/>. + </para> + </entry> + </row> + </tbody> + </tgroup> + </informaltable> + </section> + + <section xml:id="class"><info><title>Class</title></info> + + <para> + The zone's name may optionally be followed by a class. If + a class is not specified, class <literal>IN</literal> (for <varname>Internet</varname>), + is assumed. This is correct for the vast majority of cases. + </para> + <para> + The <literal>hesiod</literal> 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 + <literal>HS</literal> is + a synonym for hesiod. + </para> + <para> + Another MIT development is Chaosnet, a LAN protocol created + in the mid-1970s. Zone data for it can be specified with the <literal>CHAOS</literal> class. + </para> + </section> + + <section xml:id="zone_options"><info><title>Zone Options</title></info> + + <variablelist> + + <varlistentry> + <term><command>allow-notify</command></term> + <listitem> + <para> + See the description of + <command>allow-notify</command> in <xref linkend="access_control"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>allow-query</command></term> + <listitem> + <para> + See the description of + <command>allow-query</command> in <xref linkend="access_control"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>allow-query-on</command></term> + <listitem> + <para> + See the description of + <command>allow-query-on</command> in <xref linkend="access_control"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>allow-transfer</command></term> + <listitem> + <para> + See the description of <command>allow-transfer</command> + in <xref linkend="access_control"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>allow-update</command></term> + <listitem> + <para> + See the description of <command>allow-update</command> + in <xref linkend="access_control"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>update-policy</command></term> + <listitem> + <para> + Specifies a "Simple Secure Update" policy. See + <xref linkend="dynamic_update_policies"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>allow-update-forwarding</command></term> + <listitem> + <para> + See the description of <command>allow-update-forwarding</command> + in <xref linkend="access_control"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>also-notify</command></term> + <listitem> + <para> + Only meaningful if <command>notify</command> + is + active for this zone. The set of machines that will + receive a + <literal>DNS NOTIFY</literal> 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 + with <command>also-notify</command>. A port + may be specified + with each <command>also-notify</command> + address to send the notify + messages to a port other than the default of 53. + A TSIG key may also be specified to cause the + <literal>NOTIFY</literal> to be signed by the + given key. + <command>also-notify</command> is not + meaningful for stub zones. + The default is the empty list. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>check-names</command></term> + <listitem> + <para> + 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 <command>master</command> zones the default is <command>fail</command>. For <command>slave</command> + zones the default is <command>warn</command>. + It is not implemented for <command>hint</command> zones. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>check-mx</command></term> + <listitem> + <para> + See the description of + <command>check-mx</command> in <xref linkend="boolean_options"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>check-spf</command></term> + <listitem> + <para> + See the description of + <command>check-spf</command> in <xref linkend="boolean_options"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>check-wildcard</command></term> + <listitem> + <para> + See the description of + <command>check-wildcard</command> in <xref linkend="boolean_options"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>check-integrity</command></term> + <listitem> + <para> + See the description of + <command>check-integrity</command> in <xref linkend="boolean_options"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>check-sibling</command></term> + <listitem> + <para> + See the description of + <command>check-sibling</command> in <xref linkend="boolean_options"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>zero-no-soa-ttl</command></term> + <listitem> + <para> + See the description of + <command>zero-no-soa-ttl</command> in <xref linkend="boolean_options"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>update-check-ksk</command></term> + <listitem> + <para> + See the description of + <command>update-check-ksk</command> in <xref linkend="boolean_options"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>dnssec-loadkeys-interval</command></term> + <listitem> + <para> + See the description of + <command>dnssec-loadkeys-interval</command> in <xref linkend="options"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>dnssec-update-mode</command></term> + <listitem> + <para> + See the description of + <command>dnssec-update-mode</command> in <xref linkend="options"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>dnssec-dnskey-kskonly</command></term> + <listitem> + <para> + See the description of + <command>dnssec-dnskey-kskonly</command> in <xref linkend="boolean_options"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>try-tcp-refresh</command></term> + <listitem> + <para> + See the description of + <command>try-tcp-refresh</command> in <xref linkend="boolean_options"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>database</command></term> + <listitem> + <para> + Specify the type of database to be used for storing the + zone data. The string following the <command>database</command> 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. + </para> + <para> + The default is <userinput>"rbt"</userinput>, BIND 9's + native in-memory + red-black-tree database. This database does not take + arguments. + </para> + <para> + 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>dialup</command></term> + <listitem> + <para> + See the description of + <command>dialup</command> in <xref linkend="boolean_options"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>delegation-only</command></term> + <listitem> + <para> + The flag only applies to forward, hint and stub + zones. If set to <userinput>yes</userinput>, + then the zone will also be treated as if it is + also a delegation-only type zone. + </para> + <para> + See caveats in <xref linkend="root_delegation_only"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>file</command></term> + <listitem> + <para> + Set the zone's filename. In <command>master</command>, + <command>hint</command>, and <command>redirect</command> + zones which do not have <command>masters</command> + defined, zone data is loaded from this file. In + <command>slave</command>, <command>stub</command>, and + <command>redirect</command> zones which do have + <command>masters</command> defined, zone data is + retrieved from another server and saved in this file. + This option is not applicable to other zone types. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>forward</command></term> + <listitem> + <para> + Only meaningful if the zone has a forwarders + list. The <command>only</command> value causes + the lookup to fail + after trying the forwarders and getting no answer, while <command>first</command> would + allow a normal lookup to be tried. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>forwarders</command></term> + <listitem> + <para> + Used to override the list of global forwarders. + If it is not specified in a zone of type <command>forward</command>, + no forwarding is done for the zone and the global options are + not used. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>ixfr-base</command></term> + <listitem> + <para> + Was used in <acronym>BIND</acronym> 8 to + specify the name + of the transaction log (journal) file for dynamic update + and IXFR. + <acronym>BIND</acronym> 9 ignores the option + and constructs the name of the journal + file by appending "<filename>.jnl</filename>" + to the name of the + zone file. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>ixfr-tmp-file</command></term> + <listitem> + <para> + Was an undocumented option in <acronym>BIND</acronym> 8. + Ignored in <acronym>BIND</acronym> 9. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>journal</command></term> + <listitem> + <para> + Allow the default journal's filename to be overridden. + The default is the zone's filename with "<filename>.jnl</filename>" appended. + This is applicable to <command>master</command> and <command>slave</command> zones. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>max-journal-size</command></term> + <listitem> + <para> + See the description of + <command>max-journal-size</command> in <xref linkend="server_resource_limits"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>max-records</command></term> + <listitem> + <para> + See the description of + <command>max-records</command> in <xref linkend="server_resource_limits"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>max-transfer-time-in</command></term> + <listitem> + <para> + See the description of + <command>max-transfer-time-in</command> in <xref linkend="zone_transfers"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>max-transfer-idle-in</command></term> + <listitem> + <para> + See the description of + <command>max-transfer-idle-in</command> in <xref linkend="zone_transfers"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>max-transfer-time-out</command></term> + <listitem> + <para> + See the description of + <command>max-transfer-time-out</command> in <xref linkend="zone_transfers"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>max-transfer-idle-out</command></term> + <listitem> + <para> + See the description of + <command>max-transfer-idle-out</command> in <xref linkend="zone_transfers"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>notify</command></term> + <listitem> + <para> + See the description of + <command>notify</command> in <xref linkend="boolean_options"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>notify-delay</command></term> + <listitem> + <para> + See the description of + <command>notify-delay</command> in <xref linkend="tuning"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>notify-to-soa</command></term> + <listitem> + <para> + See the description of + <command>notify-to-soa</command> in + <xref linkend="boolean_options"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>pubkey</command></term> + <listitem> + <para> + In <acronym>BIND</acronym> 8, this option was + intended for specifying + a public zone key for verification of signatures in DNSSEC + signed + zones when they are loaded from disk. <acronym>BIND</acronym> 9 does not verify signatures + on load and ignores the option. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>zone-statistics</command></term> + <listitem> + <para> + See the description of + <command>zone-statistics</command> in + <xref linkend="options"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>server-addresses</command></term> + <listitem> + <para> + 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. + </para> + <para> + For example, if "example.com" is configured as a + static-stub zone with 192.0.2.1 and 2001:db8::1234 + in a <command>server-addresses</command> option, + the following RRs will be internally configured. + </para> +<programlisting>example.com. NS example.com. +example.com. A 192.0.2.1 +example.com. AAAA 2001:db8::1234</programlisting> + <para> + 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>server-names</command></term> + <listitem> + <para> + 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 + <command>named</command> 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 the + <command>server-names</command> option, but + "ns.example.net" cannot, and will be rejected by + the configuration parser. + </para> + <para> + 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 <command>server-names</command> option, + the following RRs will be internally configured. + </para> +<programlisting>example.com. NS ns1.example.net. +example.com. NS ns2.example.net. +</programlisting> + <para> + 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. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>sig-validity-interval</command></term> + <listitem> + <para> + See the description of + <command>sig-validity-interval</command> in <xref linkend="tuning"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>sig-signing-nodes</command></term> + <listitem> + <para> + See the description of + <command>sig-signing-nodes</command> in <xref linkend="tuning"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>sig-signing-signatures</command></term> + <listitem> + <para> + See the description of + <command>sig-signing-signatures</command> in <xref linkend="tuning"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>sig-signing-type</command></term> + <listitem> + <para> + See the description of + <command>sig-signing-type</command> in <xref linkend="tuning"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>transfer-source</command></term> + <listitem> + <para> + See the description of + <command>transfer-source</command> in <xref linkend="zone_transfers"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>transfer-source-v6</command></term> + <listitem> + <para> + See the description of + <command>transfer-source-v6</command> in <xref linkend="zone_transfers"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>alt-transfer-source</command></term> + <listitem> + <para> + See the description of + <command>alt-transfer-source</command> in <xref linkend="zone_transfers"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>alt-transfer-source-v6</command></term> + <listitem> + <para> + See the description of + <command>alt-transfer-source-v6</command> in <xref linkend="zone_transfers"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>use-alt-transfer-source</command></term> + <listitem> + <para> + See the description of + <command>use-alt-transfer-source</command> in <xref linkend="zone_transfers"/>. + </para> + </listitem> + </varlistentry> + + + <varlistentry> + <term><command>notify-source</command></term> + <listitem> + <para> + See the description of + <command>notify-source</command> in <xref linkend="zone_transfers"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>notify-source-v6</command></term> + <listitem> + <para> + See the description of + <command>notify-source-v6</command> in <xref linkend="zone_transfers"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>min-refresh-time</command></term> + <term><command>max-refresh-time</command></term> + <term><command>min-retry-time</command></term> + <term><command>max-retry-time</command></term> + <listitem> + <para> + See the description in <xref linkend="tuning"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>ixfr-from-differences</command></term> + <listitem> + <para> + See the description of + <command>ixfr-from-differences</command> in <xref linkend="boolean_options"/>. + (Note that the <command>ixfr-from-differences</command> + <userinput>master</userinput> and + <userinput>slave</userinput> choices are not + available at the zone level.) + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>key-directory</command></term> + <listitem> + <para> + See the description of + <command>key-directory</command> in <xref linkend="options"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>auto-dnssec</command></term> + <listitem> + <para> + See the description of + <command>auto-dnssec</command> in + <xref linkend="options"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>serial-update-method</command></term> + <listitem> + <para> + See the description of + <command>serial-update-method</command> in + <xref linkend="options"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>inline-signing</command></term> + <listitem> + <para> + If <literal>yes</literal>, 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 + behavior is disabled by default. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>multi-master</command></term> + <listitem> + <para> + See the description of <command>multi-master</command> in + <xref linkend="boolean_options"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>masterfile-format</command></term> + <listitem> + <para> + See the description of <command>masterfile-format</command> + in <xref linkend="tuning"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>max-zone-ttl</command></term> + <listitem> + <para> + See the description of <command>max-zone-ttl</command> + in <xref linkend="options"/>. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>dnssec-secure-to-insecure</command></term> + <listitem> + <para> + See the description of + <command>dnssec-secure-to-insecure</command> in <xref linkend="boolean_options"/>. + </para> + </listitem> + </varlistentry> + + </variablelist> + + </section> + <section xml:id="dynamic_update_policies"><info><title>Dynamic Update Policies</title></info> + + <para><acronym>BIND</acronym> 9 supports two alternative + methods of granting clients the right to perform + dynamic updates to a zone, configured by the + <command>allow-update</command> and + <command>update-policy</command> option, respectively. + </para> + <para> + The <command>allow-update</command> clause is a simple + access control list. Any client that matches + the ACL is granted permission to update any record + in the zone. + </para> + <para> + The <command>update-policy</command> 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, <command>update-policy</command> rules + only apply to key-based identities. There is no way + to specify update permissions based on client source + address. + </para> + <para> + <command>update-policy</command> rules are only meaningful + for zones of type <command>master</command>, and are + not allowed in any other zone type. + It is a configuration error to specify both + <command>allow-update</command> and + <command>update-policy</command> at the same time. + </para> + <para> + A pre-defined <command>update-policy</command> rule can be + switched on with the command + <command>update-policy local;</command>. + Using this in a zone causes + <command>named</command> 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 + <command>named</command> is running. + By default, the session key is stored in the file + <filename>/var/run/named/session.key</filename>, the key name + is "local-ddns", and the key algorithm is HMAC-SHA256. + These values are configurable with the + <command>session-keyfile</command>, + <command>session-keyname</command> and + <command>session-keyalg</command> 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: + </para> + + <programlisting>update-policy { grant local-ddns zonesub any; }; + </programlisting> + + <para> + ...with the additional restriction that only clients + connecting from the local system will be permitted to send + updates. + </para> + <para> + Note that only one session key is generated by + <command>named</command>; all zones configured to use + <command>update-policy local</command> will accept the same key. + </para> + <para> + The command <command>nsupdate -l</command> implements this + feature, sending requests to localhost and signing them using + the key retrieved from the session key file. + </para> + + <para> + Other rule definitions look like this: + </para> + +<programlisting> +( <command>grant</command> | <command>deny</command> ) <replaceable>identity</replaceable> <replaceable>ruletype</replaceable> <optional> <replaceable>name</replaceable> </optional> <optional> <replaceable>types</replaceable> </optional> +</programlisting> + + <para> + Each rule grants or denies privileges. Rules are checked + in the order in which they are specified in the + <command>update-policy</command> 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 + <command>ruletype</command> field, and the interpretation + of other fields varies depending on the rule type. + </para> + <para> + In general, a rule is matched when the + key that signed an update request matches the + <command>identity</command> field, the name of the record + to be updated matches the <command>name</command> field + (in the manner specified by the <command>ruletype</command> + field), and the type of the record to be updated matches the + <command>types</command> field. Details for each rule type + are described below. + </para> + <para> + The <command>identity</command> 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 identities matching the client's Kerberos principal + (e.g, <userinput>"host/machine@REALM"</userinput>) or + Windows realm (<userinput>machine$@REALM</userinput>). + </para> + <para> + The <replaceable>name</replaceable> 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. + </para> + <para> + If no <command>types</command> 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. + </para> + <para> + The <replaceable>ruletype</replaceable> field has 16 + values: + <varname>name</varname>, <varname>subdomain</varname>, + <varname>wildcard</varname>, <varname>self</varname>, + <varname>selfsub</varname>, <varname>selfwild</varname>, + <varname>krb5-self</varname>, <varname>ms-self</varname>, + <varname>krb5-selfsub</varname>, <varname>ms-selfsub</varname>, + <varname>krb5-subdomain</varname>, + <varname>ms-subdomain</varname>, + <varname>tcp-self</varname>, <varname>6to4-self</varname>, + <varname>zonesub</varname>, and <varname>external</varname>. + </para> + <informaltable> + <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table"> + <colspec colname="1" colnum="1" colsep="0" colwidth="0.819in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="3.681in"/> + <tbody> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>name</varname> + </para> + </entry> <entry colname="2"> + <para> + Exact-match semantics. This rule matches + when the name being updated is identical + to the contents of the + <replaceable>name</replaceable> field. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>subdomain</varname> + </para> + </entry> <entry colname="2"> + <para> + This rule matches when the name being updated + is a subdomain of, or identical to, the + contents of the <replaceable>name</replaceable> + field. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>zonesub</varname> + </para> + </entry> <entry colname="2"> + <para> + This rule is similar to subdomain, except that + it matches when the name being updated is a + subdomain of the zone in which the + <command>update-policy</command> statement + appears. This obviates the need to type the zone + name twice, and enables the use of a standard + <command>update-policy</command> statement in + multiple zones without modification. + </para> + <para> + When this rule is used, the + <replaceable>name</replaceable> field is omitted. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>wildcard</varname> + </para> + </entry> <entry colname="2"> + <para> + The <replaceable>name</replaceable> field + is subject to DNS wildcard expansion, and + this rule matches when the name being updated + is a valid expansion of the wildcard. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>self</varname> + </para> + </entry> + <entry colname="2"> + <para> + This rule matches when the name of the record + being updated matches the contents of the + <replaceable>identity</replaceable> field. + The <replaceable>name</replaceable> field + is ignored. To avoid confusion, it is recommended + that this field be set to the same value as the + <replaceable>identity</replaceable> field or to + "." + </para> + <para> + The <varname>self</varname> rule type is + most useful when allowing one key per + name to update, where the key has the same + name as the record to be updated. In this case, + the <replaceable>identity</replaceable> field + can be specified as <constant>*</constant> + (an asterisk). + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>selfsub</varname> + </para> + </entry> <entry colname="2"> + <para> + This rule is similar to <varname>self</varname> + except that subdomains of <varname>self</varname> + can also be updated. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>selfwild</varname> + </para> + </entry> <entry colname="2"> + <para> + This rule is similar to <varname>self</varname> + except that only subdomains of + <varname>self</varname> can be updated. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>ms-self</varname> + </para> + </entry> <entry colname="2"> + <para> + When a client sends an UPDATE using a Windows + machine principal (for example, 'machine$@REALM'), + this rule allows records with the absolute name + of 'machine.REALM' to be updated. + </para> + <para> + The realm to be matched is specified in the + <replaceable>identity</replaceable> field. + </para> + <para> + The <replaceable>name</replaceable> field has + no effect on this rule; it should be set to "." + as a placeholder. + </para> + <para> + For example, + <userinput>grant EXAMPLE.COM ms-self . A AAAA</userinput> + allows any machine with a valid principal in + the realm <userinput>EXAMPLE.COM</userinput> to update + its own address records. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>ms-selfsub</varname> + </para> + </entry> <entry colname="2"> + <para> + This is similar to <command>ms-self</command> + except it also allows updates to any subdomain of + the name specified in the Windows machine + principal, not just to the name itself. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>ms-subdomain</varname> + </para> + </entry> <entry colname="2"> + <para> + When a client sends an UPDATE using a Windows + machine principal (for example, 'machine$@REALM'), + this rule allows any machine in the specified + realm to update any record in the zone or in a + specified subdomain of the zone. + </para> + <para> + The realm to be matched is specified in the + <replaceable>identity</replaceable> field. + </para> + <para> + The <replaceable>name</replaceable> field + specifies the subdomain that may be updated. + If set to "." (or any other name at or above + the zone apex), any name in the zone can be + updated. + </para> + <para> + For example, if <command>update-policy</command> + for the zone "example.com" includes + <userinput>grant EXAMPLE.COM ms-subdomain hosts.example.com. A AAAA</userinput>, + any machine with a valid principal in + the realm <userinput>EXAMPLE.COM</userinput> will + be able to update address records at or below + "hosts.example.com". + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>krb5-self</varname> + </para> + </entry> <entry colname="2"> + <para> + When a client sends an UPDATE using a + Kerberos machine principal (for example, + 'host/machine@REALM'), this rule allows + records with the absolute name of 'machine' + to be updated provided it has been authenticated + by REALM. This is similar but not identical + to <command>ms-self</command> due to the + 'machine' part of the Kerberos principal + being an absolute name instead of a unqualified + name. + </para> + <para> + The realm to be matched is specified in the + <replaceable>identity</replaceable> field. + </para> + <para> + The <replaceable>name</replaceable> field has + no effect on this rule; it should be set to "." + as a placeholder. + </para> + <para> + For example, + <userinput>grant EXAMPLE.COM krb5-self . A AAAA</userinput> + allows any machine with a valid principal in + the realm <userinput>EXAMPLE.COM</userinput> to update + its own address records. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>krb5-selfsub</varname> + </para> + </entry> <entry colname="2"> + <para> + This is similar to <command>krb5-self</command> + except it also allows updates to any subdomain of + the name specified in the 'machine' part of the + Kerberos principal, not just to the name itself. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>krb5-subdomain</varname> + </para> + </entry> <entry colname="2"> + <para> + This rule is identical to + <command>ms-subdomain</command>, except that it works + with Kerberos machine principals (i.e., + 'host/machine@REALM') rather than Windows machine + principals. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>tcp-self</varname> + </para> + </entry> <entry colname="2"> + <para> + This rule allows updates that have been sent via + TCP and for which the standard mapping from the + client's IP address into the + <literal>in-addr.arpa</literal> and + <literal>ip6.arpa</literal> + namespaces match the name to be updated. + The <command>identity</command> field must match + that name. The <command>name</command> field + should be set to ".". + Note that, since identity is based on the client's + IP address, it is not necessary for update request + messages to be signed. + </para> + <note> + It is theoretically possible to spoof these TCP + sessions. + </note> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>6to4-self</varname> + </para> + </entry> <entry colname="2"> + <para> + 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 <literal>ip6.arpa</literal> reverse tree. + </para> + <para> + The <command>identity</command> field must match + the 6to4 prefix in <literal>ip6.arpa</literal>. + The <command>name</command> field should + be set to ".". + Note that, since identity is based on the client's + IP address, it is not necessary for update request + messages to be signed. + </para> + <para> + In addition, if specified for an + <literal>ip6.arpa</literal> name outside of the + <literal>2.0.0.2.ip6.arpa</literal> namespace, + the corresponding /48 reverse name can be updated. + For example, TCP/IPv6 connections + from 2001:DB8:ED0C::/48 can update records at + <literal>C.0.D.E.8.B.D.0.1.0.0.2.ip6.arpa</literal>. + </para> + <note> + It is theoretically possible to spoof these TCP + sessions. + </note> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <varname>external</varname> + </para> + </entry> <entry colname="2"> + <para> + This rule allows <command>named</command> + to defer the decision of whether to allow a + given update to an external daemon. + </para> + <para> + The method of communicating with the daemon is + specified in the <replaceable>identity</replaceable> + field, the format of which is + "<constant>local:</constant><replaceable>path</replaceable>", + where <replaceable>path</replaceable> is the location + of a UNIX-domain socket. (Currently, "local" is the + only supported mechanism.) + </para> + <para> + Requests to the external daemon are sent over the + UNIX-domain socket as datagrams with the following + format: + </para> + <programlisting> + Protocol version number (4 bytes, network byte order, currently 1) + Request length (4 bytes, network byte order) + Signer (null-terminated string) + Name (null-terminated string) + TCP source address (null-terminated string) + Rdata type (null-terminated string) + Key (null-terminated string) + TKEY token length (4 bytes, network byte order) + TKEY token (remainder of packet)</programlisting> + <para> + 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. + </para> + </entry> + </row> + </tbody> + </tgroup> + </informaltable> + </section> + + <section xml:id="multiple_views"><info><title>Multiple views</title></info> + + <para> + 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 + <command>in-view</command> 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: + </para> + <programlisting> +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; + }; +}; + </programlisting> + <para> + An <command>in-view</command> option cannot refer to a view + that is configured later in the configuration file. + </para> + <para> + A <command>zone</command> statement which uses the + <command>in-view</command> option may not use any other + options with the exception of <command>forward</command> + and <command>forwarders</command>. (These options control + the behavior of the containing view, rather than changing + the zone object itself.) + </para> + <para> + 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. + </para> + <para> + An <command>in-view</command> zone cannot be used as a + response policy zone. + </para> + <para> + An <command>in-view</command> zone is not intended to reference + a <command>forward</command> zone. + </para> + </section> + + </section> + </section> + <section xml:id="zone_file"><info><title>Zone File</title></info> + + <section xml:id="types_of_resource_records_and_when_to_use_them"><info><title>Types of Resource Records and When to Use Them</title></info> + + <para> + This section, largely borrowed from RFC 1034, describes the + concept of a Resource Record (RR) and explains when each is used. + Since the publication of RFC 1034, several new RRs have been + identified + and implemented in the DNS. These are also included. + </para> + <section><info><title>Resource Records</title></info> + + <para> + A domain name identifies a node. Each node has a set of + resource information, which may be empty. The set of resource + information associated with a particular name is composed of + separate RRs. The order of RRs in a set is not significant and + need not be preserved by name servers, resolvers, or other + parts of the DNS. However, sorting of multiple RRs is + permitted for optimization purposes, for example, to specify + that a particular nearby server be tried first. See <xref linkend="the_sortlist_statement"/> and <xref linkend="rrset_ordering"/>. + </para> + + <para> + The components of a Resource Record are: + </para> + <informaltable colsep="0" rowsep="0"> + <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table"> + <colspec colname="1" colnum="1" colsep="0" colwidth="1.000in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="3.500in"/> + <tbody> + <row rowsep="0"> + <entry colname="1"> + <para> + owner name + </para> + </entry> + <entry colname="2"> + <para> + The domain name where the RR is found. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + type + </para> + </entry> + <entry colname="2"> + <para> + An encoded 16-bit value that specifies + the type of the resource record. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + TTL + </para> + </entry> + <entry colname="2"> + <para> + The time-to-live of the RR. This field + is a 32-bit integer in units of seconds, and is + primarily used by + resolvers when they cache RRs. The TTL describes how + long a RR can + be cached before it should be discarded. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + class + </para> + </entry> + <entry colname="2"> + <para> + An encoded 16-bit value that identifies + a protocol family or instance of a protocol. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + RDATA + </para> + </entry> + <entry colname="2"> + <para> + The resource data. The format of the + data is type (and sometimes class) specific. + </para> + </entry> + </row> + </tbody> + </tgroup> + </informaltable> + <para> + The following are <emphasis>types</emphasis> of valid RRs: + </para> + <informaltable colsep="0" rowsep="0"> + <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table"> + <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="3.625in"/> + <tbody> + <row rowsep="0"> + <entry colname="1"> + <para> + A + </para> + </entry> + <entry colname="2"> + <para> + A host address. In the IN class, this is a + 32-bit IP address. Described in RFC 1035. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + AAAA + </para> + </entry> + <entry colname="2"> + <para> + IPv6 address. Described in RFC 1886. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + A6 + </para> + </entry> + <entry colname="2"> + <para> + IPv6 address. This can be a partial + address (a suffix) and an indirection to the name + where the rest of the + address (the prefix) can be found. Experimental. + Described in RFC 2874. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + AFSDB + </para> + </entry> + <entry colname="2"> + <para> + Location of AFS database servers. + Experimental. Described in RFC 1183. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + APL + </para> + </entry> + <entry colname="2"> + <para> + Address prefix list. Experimental. + Described in RFC 3123. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + ATMA + </para> + </entry> + <entry colname="2"> + <para> + ATM Address. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + AVC + </para> + </entry> + <entry colname="2"> + <para> + Application Visibility and Control record. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + CAA + </para> + </entry> + <entry colname="2"> + <para> + Identifies which Certificate Authorities can issue + certificates for this domain and what rules they + need to follow when doing so. Defined in RFC 6844. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + CDNSKEY + </para> + </entry> + <entry colname="2"> + <para> + Identifies which DNSKEY records should be published + as DS records in the parent zone. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + CDS + </para> + </entry> + <entry colname="2"> + <para> + Contains the set of DS records that should be published + by the parent zone. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + CERT + </para> + </entry> + <entry colname="2"> + <para> + Holds a digital certificate. + Described in RFC 2538. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + CNAME + </para> + </entry> + <entry colname="2"> + <para> + Identifies the canonical name of an alias. + Described in RFC 1035. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + CSYNC + </para> + </entry> + <entry colname="2"> + <para> + Child-to-Parent Synchronization in DNS as described + in RFC 7477. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + DHCID + </para> + </entry> + <entry colname="2"> + <para> + Is used for identifying which DHCP client is + associated with this name. Described in RFC 4701. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + DLV + </para> + </entry> + <entry colname="2"> + <para> + A DNS Look-aside Validation record which contains + the records that are used as trust anchors for + zones in a DLV namespace. Described in RFC 4431. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + DNAME + </para> + </entry> + <entry colname="2"> + <para> + Replaces the domain name specified with + another name to be looked up, effectively aliasing an + entire + subtree of the domain name space rather than a single + record + as in the case of the CNAME RR. + Described in RFC 2672. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + DNSKEY + </para> + </entry> + <entry colname="2"> + <para> + Stores a public key associated with a signed + DNS zone. Described in RFC 4034. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + DOA + </para> + </entry> + <entry colname="2"> + <para> + Implements the Digital Object Architecture over + DNS. Experimental. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + DS + </para> + </entry> + <entry colname="2"> + <para> + Stores the hash of a public key associated with a + signed DNS zone. Described in RFC 4034. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + EID + </para> + </entry> + <entry colname="2"> + <para> + End Point Identifier. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + EUI48 + </para> + </entry> + <entry colname="2"> + <para> + A 48-bit EUI address. Described in RFC 7043. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + EUI64 + </para> + </entry> + <entry colname="2"> + <para> + A 64-bit EUI address. Described in RFC 7043. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + GID + </para> + </entry> + <entry colname="2"> + <para> + Reserved. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + GPOS + </para> + </entry> + <entry colname="2"> + <para> + Specifies the global position. Superseded by LOC. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + HINFO + </para> + </entry> + <entry colname="2"> + <para> + Identifies the CPU and OS used by a host. + Described in RFC 1035. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + HIP + </para> + </entry> + <entry colname="2"> + <para> + Host Identity Protocol Address. + Described in RFC 5205. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + IPSECKEY + </para> + </entry> + <entry colname="2"> + <para> + Provides a method for storing IPsec keying material in + DNS. Described in RFC 4025. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + ISDN + </para> + </entry> + <entry colname="2"> + <para> + Representation of ISDN addresses. + Experimental. Described in RFC 1183. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + KEY + </para> + </entry> + <entry colname="2"> + <para> + Stores a public key associated with a + DNS name. Used in original DNSSEC; replaced + by DNSKEY in DNSSECbis, but still used with + SIG(0). Described in RFCs 2535 and 2931. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + KX + </para> + </entry> + <entry colname="2"> + <para> + Identifies a key exchanger for this + DNS name. Described in RFC 2230. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + L32 + </para> + </entry> + <entry colname="2"> + <para> + Holds 32-bit Locator values for + Identifier-Locator Network Protocol. Described + in RFC 6742. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + L64 + </para> + </entry> + <entry colname="2"> + <para> + Holds 64-bit Locator values for + Identifier-Locator Network Protocol. Described + in RFC 6742. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + LOC + </para> + </entry> + <entry colname="2"> + <para> + For storing GPS info. Described in RFC 1876. + Experimental. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + LP + </para> + </entry> + <entry colname="2"> + <para> + Identifier-Locator Network Protocol. + Described in RFC 6742. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + MB + </para> + </entry> + <entry colname="2"> + <para> + Mail Box. Historical. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + MD + </para> + </entry> + <entry colname="2"> + <para> + Mail Destination. Historical. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + MF + </para> + </entry> + <entry colname="2"> + <para> + Mail Forwarder. Historical. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + MG + </para> + </entry> + <entry colname="2"> + <para> + Mail Group. Historical. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + MINFO + </para> + </entry> + <entry colname="2"> + <para> + Mail Information. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + MR + </para> + </entry> + <entry colname="2"> + <para> + Mail Rename. Historical. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + MX + </para> + </entry> + <entry colname="2"> + <para> + Identifies a mail exchange for the domain with + a 16-bit preference value (lower is better) + followed by the host name of the mail exchange. + Described in RFC 974, RFC 1035. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + NAPTR + </para> + </entry> + <entry colname="2"> + <para> + Name authority pointer. Described in RFC 2915. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + NID + </para> + </entry> + <entry colname="2"> + <para> + Holds values for Node Identifiers in + Identifier-Locator Network Protocol. Described + in RFC 6742. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + NINFO + </para> + </entry> + <entry colname="2"> + <para> + Contains zone status information. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + NIMLOC + </para> + </entry> + <entry colname="2"> + <para> + Nimrod Locator. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + NSAP + </para> + </entry> + <entry colname="2"> + <para> + A network service access point. + Described in RFC 1706. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + NSAP-PTR + </para> + </entry> + <entry colname="2"> + <para> + Historical. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + NS + </para> + </entry> + <entry colname="2"> + <para> + The authoritative name server for the + domain. Described in RFC 1035. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + NSEC + </para> + </entry> + <entry colname="2"> + <para> + Used in DNSSECbis to securely indicate that + RRs with an owner name in a certain name interval do + not exist in + a zone and indicate what RR types are present for an + existing name. + Described in RFC 4034. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + NSEC3 + </para> + </entry> + <entry colname="2"> + <para> + Used in DNSSECbis to securely indicate that + RRs with an owner name in a certain name + interval do not exist in a zone and indicate + what RR types are present for an existing + name. NSEC3 differs from NSEC in that it + prevents zone enumeration but is more + computationally expensive on both the server + and the client than NSEC. Described in RFC + 5155. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + NSEC3PARAM + </para> + </entry> + <entry colname="2"> + <para> + Used in DNSSECbis to tell the authoritative + server which NSEC3 chains are available to use. + Described in RFC 5155. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + NULL + </para> + </entry> + <entry colname="2"> + <para> + This is an opaque container. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + NXT + </para> + </entry> + <entry colname="2"> + <para> + Used in DNSSEC to securely indicate that + RRs with an owner name in a certain name interval do + not exist in + a zone and indicate what RR types are present for an + existing name. + Used in original DNSSEC; replaced by NSEC in + DNSSECbis. + Described in RFC 2535. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + OPENPGPKEY + </para> + </entry> + <entry colname="2"> + <para> + Used to hold an OPENPGPKEY. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + PTR + </para> + </entry> + <entry colname="2"> + <para> + A pointer to another part of the domain + name space. Described in RFC 1035. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + PX + </para> + </entry> + <entry colname="2"> + <para> + Provides mappings between RFC 822 and X.400 + addresses. Described in RFC 2163. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + RKEY + </para> + </entry> + <entry colname="2"> + <para> + Resource key. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + RP + </para> + </entry> + <entry colname="2"> + <para> + Information on persons responsible + for the domain. Experimental. Described in RFC 1183. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + RRSIG + </para> + </entry> + <entry colname="2"> + <para> + Contains DNSSECbis signature data. Described + in RFC 4034. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + RT + </para> + </entry> + <entry colname="2"> + <para> + Route-through binding for hosts that + do not have their own direct wide area network + addresses. + Experimental. Described in RFC 1183. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + SIG + </para> + </entry> + <entry colname="2"> + <para> + Contains DNSSEC signature data. Used in + original DNSSEC; replaced by RRSIG in + DNSSECbis, but still used for SIG(0). + Described in RFCs 2535 and 2931. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + SINK + </para> + </entry> + <entry colname="2"> + <para> + The kitchen sink record. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + SMIMEA + </para> + </entry> + <entry colname="2"> + <para> + The S/MIME Security Certificate Association. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + SOA + </para> + </entry> + <entry colname="2"> + <para> + Identifies the start of a zone of authority. + Described in RFC 1035. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + SPF + </para> + </entry> + <entry colname="2"> + <para> + Contains the Sender Policy Framework information + for a given email domain. Described in RFC 4408. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + SRV + </para> + </entry> + <entry colname="2"> + <para> + Information about well known network + services (replaces WKS). Described in RFC 2782. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + SSHFP + </para> + </entry> + <entry colname="2"> + <para> + Provides a way to securely publish a secure shell key's + fingerprint. Described in RFC 4255. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + TA + </para> + </entry> + <entry colname="2"> + <para> + Trust Anchor. Experimental. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + TALINK + </para> + </entry> + <entry colname="2"> + <para> + Trust Anchor Link. Experimental. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + TLSA + </para> + </entry> + <entry colname="2"> + <para> + Transport Layer Security Certificate Association. + Described in RFC 6698. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + TXT + </para> + </entry> + <entry colname="2"> + <para> + Text records. Described in RFC 1035. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + UID + </para> + </entry> + <entry colname="2"> + <para> + Reserved. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + UINFO + </para> + </entry> + <entry colname="2"> + <para> + Reserved. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + UNSPEC + </para> + </entry> + <entry colname="2"> + <para> + Reserved. Historical. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + URI + </para> + </entry> + <entry colname="2"> + <para> + Holds a URI. Described in RFC 7553. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + WKS + </para> + </entry> + <entry colname="2"> + <para> + Information about which well known + network services, such as SMTP, that a domain + supports. Historical. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + X25 + </para> + </entry> + <entry colname="2"> + <para> + Representation of X.25 network addresses. + Experimental. Described in RFC 1183. + </para> + </entry> + </row> + </tbody> + </tgroup> + </informaltable> + <para> + The following <emphasis>classes</emphasis> of resource records + are currently valid in the DNS: + </para> + <informaltable colsep="0" rowsep="0"><tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table"> + <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="3.625in"/> + <tbody> + + <row rowsep="0"> + <entry colname="1"> + <para> + IN + </para> + </entry> + <entry colname="2"> + <para> + The Internet. + </para> + </entry> + </row> + + <row rowsep="0"> + <entry colname="1"> + <para> + CH + </para> + </entry> + <entry colname="2"> + <para> + Chaosnet, a LAN protocol created at MIT in the + mid-1970s. + Rarely used for its historical purpose, but reused for + BIND's + built-in server information zones, e.g., + <literal>version.bind</literal>. + </para> + </entry> + </row> + + <row rowsep="0"> + <entry colname="1"> + <para> + HS + </para> + </entry> + <entry colname="2"> + <para> + Hesiod, an information service + developed by MIT's Project Athena. It is used to share + information + about various systems databases, such as users, + groups, printers + and so on. + </para> + </entry> + </row> + + </tbody> + </tgroup> + </informaltable> + + <para> + The owner name is often implicit, rather than forming an + integral + part of the RR. For example, many name servers internally form + tree + or hash structures for the name space, and chain RRs off nodes. + The remaining RR parts are the fixed header (type, class, TTL) + which is consistent for all RRs, and a variable part (RDATA) + that + fits the needs of the resource being described. + </para> + <para> + The meaning of the TTL field is a time limit on how long an + RR can be kept in a cache. This limit does not apply to + authoritative + data in zones; it is also timed out, but by the refreshing + policies + for the zone. The TTL is assigned by the administrator for the + zone where the data originates. While short TTLs can be used to + minimize caching, and a zero TTL prohibits caching, the + realities + of Internet performance suggest that these times should be on + the + order of days for the typical host. If a change can be + anticipated, + the TTL can be reduced prior to the change to minimize + inconsistency + during the change, and then increased back to its former value + following + the change. + </para> + <para> + The data in the RDATA section of RRs is carried as a combination + of binary strings and domain names. The domain names are + frequently + used as "pointers" to other data in the DNS. + </para> + </section> + <section xml:id="rr_text"><info><title>Textual expression of RRs</title></info> + + <para> + RRs are represented in binary form in the packets of the DNS + protocol, and are usually represented in highly encoded form + when + stored in a name server or resolver. In the examples provided + in + RFC 1034, a style similar to that used in master files was + employed + in order to show the contents of RRs. In this format, most RRs + are shown on a single line, although continuation lines are + possible + using parentheses. + </para> + <para> + The start of the line gives the owner of the RR. If a line + begins with a blank, then the owner is assumed to be the same as + that of the previous RR. Blank lines are often included for + readability. + </para> + <para> + Following the owner, we list the TTL, type, and class of the + RR. Class and type use the mnemonics defined above, and TTL is + an integer before the type field. In order to avoid ambiguity + in + parsing, type and class mnemonics are disjoint, TTLs are + integers, + and the type mnemonic is always last. The IN class and TTL + values + are often omitted from examples in the interests of clarity. + </para> + <para> + The resource data or RDATA section of the RR are given using + knowledge of the typical representation for the data. + </para> + <para> + For example, we might show the RRs carried in a message as: + </para> + <informaltable colsep="0" rowsep="0"><tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table"> + <colspec colname="1" colnum="1" colsep="0" colwidth="1.381in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="1.020in"/> + <colspec colname="3" colnum="3" colsep="0" colwidth="2.099in"/> + <tbody> + <row rowsep="0"> + <entry colname="1"> + <para> + <literal>ISI.EDU.</literal> + </para> + </entry> + <entry colname="2"> + <para> + <literal>MX</literal> + </para> + </entry> + <entry colname="3"> + <para> + <literal>10 VENERA.ISI.EDU.</literal> + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para/> + </entry> + <entry colname="2"> + <para> + <literal>MX</literal> + </para> + </entry> + <entry colname="3"> + <para> + <literal>10 VAXA.ISI.EDU</literal> + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <literal>VENERA.ISI.EDU</literal> + </para> + </entry> + <entry colname="2"> + <para> + <literal>A</literal> + </para> + </entry> + <entry colname="3"> + <para> + <literal>128.9.0.32</literal> + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para/> + </entry> + <entry colname="2"> + <para> + <literal>A</literal> + </para> + </entry> + <entry colname="3"> + <para> + <literal>10.1.0.52</literal> + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <literal>VAXA.ISI.EDU</literal> + </para> + </entry> + <entry colname="2"> + <para> + <literal>A</literal> + </para> + </entry> + <entry colname="3"> + <para> + <literal>10.2.0.27</literal> + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para/> + </entry> + <entry colname="2"> + <para> + <literal>A</literal> + </para> + </entry> + <entry colname="3"> + <para> + <literal>128.9.0.33</literal> + </para> + </entry> + </row> + </tbody> + </tgroup> + </informaltable> + <para> + The MX RRs have an RDATA section which consists of a 16-bit + number followed by a domain name. The address RRs use a + standard + IP address format to contain a 32-bit internet address. + </para> + <para> + The above example shows six RRs, with two RRs at each of three + domain names. + </para> + <para> + Similarly we might see: + </para> + <informaltable colsep="0" rowsep="0"><tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table"> + <colspec colname="1" colnum="1" colsep="0" colwidth="1.491in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="1.067in"/> + <colspec colname="3" colnum="3" colsep="0" colwidth="2.067in"/> + <tbody> + <row rowsep="0"> + <entry colname="1"> + <para> + <literal>XX.LCS.MIT.EDU.</literal> + </para> + </entry> + <entry colname="2"> + <para> + <literal>IN A</literal> + </para> + </entry> + <entry colname="3"> + <para> + <literal>10.0.0.44</literal> + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"/> + <entry colname="2"> + <para> + <literal>CH A</literal> + </para> + </entry> + <entry colname="3"> + <para> + <literal>MIT.EDU. 2420</literal> + </para> + </entry> + </row> + </tbody> + </tgroup> + </informaltable> + <para> + This example shows two addresses for + <literal>XX.LCS.MIT.EDU</literal>, each of a different class. + </para> + </section> + </section> + + <section xml:id="mx_records"><info><title>Discussion of MX Records</title></info> + + <para> + As described above, domain servers store information as a + series of resource records, each of which contains a particular + piece of information about a given domain name (which is usually, + but not always, a host). The simplest way to think of a RR is as + a typed pair of data, a domain name matched with a relevant datum, + and stored with some additional type information to help systems + determine when the RR is relevant. + </para> + + <para> + MX records are used to control delivery of email. The data + specified in the record is a priority and a domain name. The + priority + controls the order in which email delivery is attempted, with the + lowest number first. If two priorities are the same, a server is + chosen randomly. If no servers at a given priority are responding, + the mail transport agent will fall back to the next largest + priority. + Priority numbers do not have any absolute meaning — they are + relevant + only respective to other MX records for that domain name. The + domain + name given is the machine to which the mail will be delivered. + It <emphasis>must</emphasis> have an associated address record + (A or AAAA) — CNAME is not sufficient. + </para> + <para> + For a given domain, if there is both a CNAME record and an + MX record, the MX record is in error, and will be ignored. + Instead, + the mail will be delivered to the server specified in the MX + record + pointed to by the CNAME. + For example: + </para> + <informaltable colsep="0" rowsep="0"> + <tgroup cols="5" colsep="0" rowsep="0" tgroupstyle="3Level-table"> + <colspec colname="1" colnum="1" colsep="0" colwidth="1.708in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="0.444in"/> + <colspec colname="3" colnum="3" colsep="0" colwidth="0.444in"/> + <colspec colname="4" colnum="4" colsep="0" colwidth="0.976in"/> + <colspec colname="5" colnum="5" colsep="0" colwidth="1.553in"/> + <tbody> + <row rowsep="0"> + <entry colname="1"> + <para> + <literal>example.com.</literal> + </para> + </entry> + <entry colname="2"> + <para> + <literal>IN</literal> + </para> + </entry> + <entry colname="3"> + <para> + <literal>MX</literal> + </para> + </entry> + <entry colname="4"> + <para> + <literal>10</literal> + </para> + </entry> + <entry colname="5"> + <para> + <literal>mail.example.com.</literal> + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para/> + </entry> + <entry colname="2"> + <para> + <literal>IN</literal> + </para> + </entry> + <entry colname="3"> + <para> + <literal>MX</literal> + </para> + </entry> + <entry colname="4"> + <para> + <literal>10</literal> + </para> + </entry> + <entry colname="5"> + <para> + <literal>mail2.example.com.</literal> + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para/> + </entry> + <entry colname="2"> + <para> + <literal>IN</literal> + </para> + </entry> + <entry colname="3"> + <para> + <literal>MX</literal> + </para> + </entry> + <entry colname="4"> + <para> + <literal>20</literal> + </para> + </entry> + <entry colname="5"> + <para> + <literal>mail.backup.org.</literal> + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <literal>mail.example.com.</literal> + </para> + </entry> + <entry colname="2"> + <para> + <literal>IN</literal> + </para> + </entry> + <entry colname="3"> + <para> + <literal>A</literal> + </para> + </entry> + <entry colname="4"> + <para> + <literal>10.0.0.1</literal> + </para> + </entry> + <entry colname="5"> + <para/> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <literal>mail2.example.com.</literal> + </para> + </entry> + <entry colname="2"> + <para> + <literal>IN</literal> + </para> + </entry> + <entry colname="3"> + <para> + <literal>A</literal> + </para> + </entry> + <entry colname="4"> + <para> + <literal>10.0.0.2</literal> + </para> + </entry> + <entry colname="5"> + <para/> + </entry> + </row> + </tbody> + </tgroup> + </informaltable><para> + Mail delivery will be attempted to <literal>mail.example.com</literal> and + <literal>mail2.example.com</literal> (in + any order), and if neither of those succeed, delivery to <literal>mail.backup.org</literal> will + be attempted. + </para> + </section> + <section xml:id="Setting_TTLs"><info><title>Setting TTLs</title></info> + + <para> + The time-to-live of the RR field is a 32-bit integer represented + in units of seconds, and is primarily used by resolvers when they + cache RRs. The TTL describes how long a RR can be cached before it + should be discarded. The following three types of TTL are + currently + used in a zone file. + </para> + <informaltable colsep="0" rowsep="0"> + <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table"> + <colspec colname="1" colnum="1" colsep="0" colwidth="0.750in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="4.375in"/> + <tbody> + <row rowsep="0"> + <entry colname="1"> + <para> + SOA + </para> + </entry> + <entry colname="2"> + <para> + The last field in the SOA is the negative + caching TTL. This controls how long other servers will + cache no-such-domain + (NXDOMAIN) responses from you. + </para> + <para> + The maximum time for + negative caching is 3 hours (3h). + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + $TTL + </para> + </entry> + <entry colname="2"> + <para> + The $TTL directive at the top of the + zone file (before the SOA) gives a default TTL for every + RR without + a specific TTL set. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + RR TTLs + </para> + </entry> + <entry colname="2"> + <para> + Each RR can have a TTL as the second + field in the RR, which will control how long other + servers can cache it. + </para> + </entry> + </row> + </tbody> + </tgroup> + </informaltable> + <para> + All of these TTLs default to units of seconds, though units + can be explicitly specified, for example, <literal>1h30m</literal>. + </para> + </section> + <section xml:id="ipv4_reverse"><info><title>Inverse Mapping in IPv4</title></info> + + <para> + Reverse name resolution (that is, translation from IP address + to name) is achieved by means of the <emphasis>in-addr.arpa</emphasis> domain + and PTR records. Entries in the in-addr.arpa domain are made in + least-to-most significant order, read left to right. This is the + opposite order to the way IP addresses are usually written. Thus, + a machine with an IP address of 10.1.2.3 would have a + corresponding + in-addr.arpa name of + 3.2.1.10.in-addr.arpa. This name should have a PTR resource record + whose data field is the name of the machine or, optionally, + multiple + PTR records if the machine has more than one name. For example, + in the <optional>example.com</optional> domain: + </para> + <informaltable colsep="0" rowsep="0"> + <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table"> + <colspec colname="1" colnum="1" colsep="0" colwidth="1.125in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="4.000in"/> + <tbody> + <row rowsep="0"> + <entry colname="1"> + <para> + <literal>$ORIGIN</literal> + </para> + </entry> + <entry colname="2"> + <para> + <literal>2.1.10.in-addr.arpa</literal> + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para> + <literal>3</literal> + </para> + </entry> + <entry colname="2"> + <para> + <literal>IN PTR foo.example.com.</literal> + </para> + </entry> + </row> + </tbody> + </tgroup> + </informaltable> + <note> + <para> + The <command>$ORIGIN</command> lines in the examples + are for providing context to the examples only — they do not + necessarily + appear in the actual usage. They are only used here to indicate + that the example is relative to the listed origin. + </para> + </note> + </section> + <section xml:id="zone_directives"><info><title>Other Zone File Directives</title></info> + + <para> + The Master File Format was initially defined in RFC 1035 and + has subsequently been extended. While the Master File Format + itself + is class independent all records in a Master File must be of the + same + class. + </para> + <para> + Master File Directives include <command>$ORIGIN</command>, <command>$INCLUDE</command>, + and <command>$TTL.</command> + </para> + <section xml:id="atsign"><info><title>The <command>@</command> (at-sign)</title></info> + + <para> + When used in the label (or name) field, the asperand or + at-sign (@) symbol represents the current origin. + At the start of the zone file, it is the + <<varname>zone_name</varname>> (followed by + trailing dot). + </para> + </section> + <section xml:id="origin_directive"><info><title>The <command>$ORIGIN</command> Directive</title></info> + + <para> + Syntax: <command>$ORIGIN</command> + <replaceable>domain-name</replaceable> + <optional><replaceable>comment</replaceable></optional> + </para> + <para><command>$ORIGIN</command> + sets the domain name that will be appended to any + unqualified records. When a zone is first read in there + is an implicit <command>$ORIGIN</command> + <<varname>zone_name</varname>><command>.</command> + (followed by trailing dot). + The current <command>$ORIGIN</command> is appended to + the domain specified in the <command>$ORIGIN</command> + argument if it is not absolute. + </para> + +<programlisting> +$ORIGIN example.com. +WWW CNAME MAIN-SERVER +</programlisting> + + <para> + is equivalent to + </para> + +<programlisting> +WWW.EXAMPLE.COM. CNAME MAIN-SERVER.EXAMPLE.COM. +</programlisting> + + </section> + <section xml:id="include_directive"><info><title>The <command>$INCLUDE</command> Directive</title></info> + + <para> + Syntax: <command>$INCLUDE</command> + <replaceable>filename</replaceable> + <optional> +<replaceable>origin</replaceable> </optional> + <optional> <replaceable>comment</replaceable> </optional> + </para> + <para> + Read and process the file <filename>filename</filename> as + if it were included into the file at this point. If <command>origin</command> is + specified the file is processed with <command>$ORIGIN</command> set + to that value, otherwise the current <command>$ORIGIN</command> is + used. + </para> + <para> + The origin and the current domain name + revert to the values they had prior to the <command>$INCLUDE</command> once + the file has been read. + </para> + <note> + <para> + RFC 1035 specifies that the current origin should be restored + after + an <command>$INCLUDE</command>, but it is silent + on whether the current + domain name should also be restored. BIND 9 restores both of + them. + This could be construed as a deviation from RFC 1035, a + feature, or both. + </para> + </note> + </section> + <section xml:id="ttl_directive"><info><title>The <command>$TTL</command> Directive</title></info> + + <para> + Syntax: <command>$TTL</command> + <replaceable>default-ttl</replaceable> + <optional> +<replaceable>comment</replaceable> </optional> + </para> + <para> + Set the default Time To Live (TTL) for subsequent records + with undefined TTLs. Valid TTLs are of the range 0-2147483647 + seconds. + </para> + <para><command>$TTL</command> + is defined in RFC 2308. + </para> + </section> + </section> + <section xml:id="generate_directive"><info><title><acronym>BIND</acronym> Master File Extension: the <command>$GENERATE</command> Directive</title></info> + + <para> + Syntax: <command>$GENERATE</command> + <replaceable>range</replaceable> + <replaceable>lhs</replaceable> + <optional><replaceable>ttl</replaceable></optional> + <optional><replaceable>class</replaceable></optional> + <replaceable>type</replaceable> + <replaceable>rhs</replaceable> + <optional><replaceable>comment</replaceable></optional> + </para> + <para><command>$GENERATE</command> + is used to create a series of resource records that only + differ from each other by an + iterator. <command>$GENERATE</command> can be used to + easily generate the sets of records required to support + sub /24 reverse delegations described in RFC 2317: + Classless IN-ADDR.ARPA delegation. + </para> + +<programlisting>$ORIGIN 0.0.192.IN-ADDR.ARPA. +$GENERATE 1-2 @ NS SERVER$.EXAMPLE. +$GENERATE 1-127 $ CNAME $.0</programlisting> + + <para> + is equivalent to + </para> + +<programlisting>0.0.0.192.IN-ADDR.ARPA. NS SERVER1.EXAMPLE. +0.0.0.192.IN-ADDR.ARPA. NS SERVER2.EXAMPLE. +1.0.0.192.IN-ADDR.ARPA. CNAME 1.0.0.0.192.IN-ADDR.ARPA. +2.0.0.192.IN-ADDR.ARPA. CNAME 2.0.0.0.192.IN-ADDR.ARPA. +... +127.0.0.192.IN-ADDR.ARPA. CNAME 127.0.0.0.192.IN-ADDR.ARPA. +</programlisting> + + <para> + Generate a set of A and MX records. Note the MX's right hand + side is a quoted string. The quotes will be stripped when the + right hand side is processed. + </para> + +<programlisting> +$ORIGIN EXAMPLE. +$GENERATE 1-127 HOST-$ A 1.2.3.$ +$GENERATE 1-127 HOST-$ MX "0 ."</programlisting> + + <para> + is equivalent to + </para> + +<programlisting>HOST-1.EXAMPLE. A 1.2.3.1 +HOST-1.EXAMPLE. MX 0 . +HOST-2.EXAMPLE. A 1.2.3.2 +HOST-2.EXAMPLE. MX 0 . +HOST-3.EXAMPLE. A 1.2.3.3 +HOST-3.EXAMPLE. MX 0 . +... +HOST-127.EXAMPLE. A 1.2.3.127 +HOST-127.EXAMPLE. MX 0 . +</programlisting> + + <informaltable colsep="0" rowsep="0"> + <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table"> + <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="4.250in"/> + <tbody> + <row rowsep="0"> + <entry colname="1"> + <para><command>range</command></para> + </entry> + <entry colname="2"> + <para> + This can be one of two forms: start-stop + or start-stop/step. If the first form is used, then step + is set to 1. start, stop and step must be positive + integers between 0 and (2^31)-1. start must not be + larger than stop. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>lhs</command></para> + </entry> + <entry colname="2"> + <para>This + describes the owner name of the resource records + to be created. Any single <command>$</command> + (dollar sign) + symbols within the <command>lhs</command> string + are replaced by the iterator value. + + To get a $ in the output, you need to escape the + <command>$</command> using a backslash + <command>\</command>, + e.g. <command>\$</command>. The + <command>$</command> may optionally be followed + by modifiers which change the offset from the + iterator, field width and base. + + Modifiers are introduced by a + <command>{</command> (left brace) immediately following the + <command>$</command> as + <command>${offset[,width[,base]]}</command>. + For example, <command>${-20,3,d}</command> + subtracts 20 from the current value, prints the + result as a decimal in a zero-padded field of + width 3. + + Available output forms are decimal + (<command>d</command>), octal + (<command>o</command>), hexadecimal + (<command>x</command> or <command>X</command> + for uppercase) and nibble + (<command>n</command> or <command>N</command>\ + for uppercase). The default modifier is + <command>${0,0,d}</command>. If the + <command>lhs</command> is not absolute, the + current <command>$ORIGIN</command> is appended + to the name. + </para> + <para> + In nibble mode the value will be treated as + if it was a reversed hexadecimal string + with each hexadecimal digit as a separate + label. The width field includes the label + separator. + </para> + <para> + For compatibility with earlier versions, + <command>$$</command> is still recognized as + indicating a literal $ in the output. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>ttl</command></para> + </entry> + <entry colname="2"> + <para> + Specifies the time-to-live of the generated records. If + not specified this will be inherited using the + normal TTL inheritance rules. + </para> + <para><command>class</command> + and <command>ttl</command> can be + entered in either order. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>class</command></para> + </entry> + <entry colname="2"> + <para> + Specifies the class of the generated records. + This must match the zone class if it is + specified. + </para> + <para><command>class</command> + and <command>ttl</command> can be + entered in either order. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>type</command></para> + </entry> + <entry colname="2"> + <para> + Any valid type. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>rhs</command></para> + </entry> + <entry colname="2"> + <para> + <command>rhs</command>, optionally, quoted string. + </para> + </entry> + </row> + </tbody> + </tgroup> + </informaltable> + <para> + The <command>$GENERATE</command> directive is a <acronym>BIND</acronym> extension + and not part of the standard zone file format. + </para> + <para> + BIND 8 did not support the optional TTL and CLASS fields. + </para> + </section> + + <section xml:id="zonefile_format"><info><title>Additional File Formats</title></info> + + <para> + In addition to the standard textual format, BIND 9 + supports the ability to read or dump to zone files in + other formats. + </para> + <para> + The <constant>raw</constant> format is + a binary representation of zone data in a manner similar + to that used in zone transfers. Since it does not require + parsing text, load time is significantly reduced. + </para> + <para> + An even faster alternative is the <constant>map</constant> + format, which is an image of a <acronym>BIND</acronym> 9 + in-memory zone database; it is capable of being loaded + directly into memory via the <command>mmap()</command> + function; the zone can begin serving queries almost + immediately. + </para> + <para> + For a primary server, a zone file in + <constant>raw</constant> or <constant>map</constant> + format is expected to be generated from a textual zone + file by the <command>named-compilezone</command> command. + For a secondary server or for a dynamic zone, it is automatically + generated (if this format is specified by the + <command>masterfile-format</command> option) when + <command>named</command> dumps the zone contents after + zone transfer or when applying prior updates. + </para> + <para> + If a zone file in a binary format needs manual modification, + it first must be converted to a textual form by the + <command>named-compilezone</command> command. All + necessary modification should go to the text file, which + should then be converted to the binary form by the + <command>named-compilezone</command> command again. + </para> + <para> + Note that <command>map</command> format is extremely + architecture-specific. A <constant>map</constant> + file <emphasis>cannot</emphasis> be used on a system + with different pointer size, endianness or data alignment + than the system on which it was generated, and should in + general be used only inside a single system. + While <constant>raw</constant> format uses + network byte order and avoids architecture-dependent + data alignment so that it is as portable as + possible, it is also primarily expected to be used + inside the same single system. To export a + zone file in either <constant>raw</constant> or + <constant>map</constant> format, or make a + portable backup of such a file, conversion to + <constant>text</constant> format is recommended. + </para> + </section> + </section> + + <section xml:id="statistics"><info><title>BIND9 Statistics</title></info> + + <para> + <acronym>BIND</acronym> 9 maintains lots of statistics + information and provides several interfaces for users to + get access to the statistics. + The available statistics include all statistics counters + that were available in <acronym>BIND</acronym> 8 and + are meaningful in <acronym>BIND</acronym> 9, + and other information that is considered useful. + </para> + + <para> + The statistics information is categorized into the following + sections. + </para> + + <informaltable frame="all"> + <tgroup cols="2"> + <colspec colname="1" colnum="1" colsep="0" colwidth="3.300in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="2.625in"/> + <tbody> + + <row rowsep="0"> + <entry colname="1"> + <para>Incoming Requests</para> + </entry> + <entry colname="2"> + <para> + The number of incoming DNS requests for each OPCODE. + </para> + </entry> + </row> + + <row rowsep="0"> + <entry colname="1"> + <para>Incoming Queries</para> + </entry> + <entry colname="2"> + <para> + The number of incoming queries for each RR type. + </para> + </entry> + </row> + + <row rowsep="0"> + <entry colname="1"> + <para>Outgoing Queries</para> + </entry> + <entry colname="2"> + <para> + The number of outgoing queries for each RR + type sent from the internal resolver. + Maintained per view. + </para> + </entry> + </row> + + <row rowsep="0"> + <entry colname="1"> + <para>Name Server Statistics</para> + </entry> + <entry colname="2"> + <para> + Statistics counters about incoming request processing. + </para> + </entry> + </row> + + <row rowsep="0"> + <entry colname="1"> + <para>Zone Maintenance Statistics</para> + </entry> + <entry colname="2"> + <para> + Statistics counters regarding zone maintenance + operations such as zone transfers. + </para> + </entry> + </row> + + <row rowsep="0"> + <entry colname="1"> + <para>Resolver Statistics</para> + </entry> + <entry colname="2"> + <para> + Statistics counters about name resolution + performed in the internal resolver. + Maintained per view. + </para> + </entry> + </row> + + <row rowsep="0"> + <entry colname="1"> + <para>Cache DB RRsets</para> + </entry> + <entry colname="2"> + <para> + The number of RRsets per RR type and nonexistent + names stored in the cache database. + If the exclamation mark (!) is printed for a RR + type, it means that particular type of RRset is + known to be nonexistent (this is also known as + "NXRRSET"). If a hash mark (#) is present then + the RRset is marked for garbage collection. + Maintained per view. + </para> + </entry> + </row> + + <row rowsep="0"> + <entry colname="1"> + <para>Socket I/O Statistics</para> + </entry> + <entry colname="2"> + <para> + Statistics counters about network related events. + </para> + </entry> + </row> + + </tbody> + </tgroup> + </informaltable> + + <para> + A subset of Name Server Statistics is collected and shown + per zone for which the server has the authority when + <command>zone-statistics</command> is set to + <userinput>full</userinput> (or <userinput>yes</userinput> + for backward compatibility. See the description of + <command>zone-statistics</command> in <xref linkend="options"/> + for further details. + </para> + + <para> + These statistics counters are shown with their zone and + view names. The view name is omitted when the server is + not configured with explicit views.</para> + + <para> + There are currently two user interfaces to get access to the + statistics. + One is in the plain text format dumped to the file specified + by the <command>statistics-file</command> configuration option. + The other is remotely accessible via a statistics channel + when the <command>statistics-channels</command> statement + is specified in the configuration file + (see <xref linkend="statschannels"/>.) + </para> + + <section xml:id="statsfile"><info><title>The Statistics File</title></info> + + <para> + The text format statistics dump begins with a line, like: + </para> + <para> + <command>+++ Statistics Dump +++ (973798949)</command> + </para> + <para> + The number in parentheses is a standard + Unix-style timestamp, measured as seconds since January 1, 1970. + + Following + that line is a set of statistics information, which is categorized + as described above. + Each section begins with a line, like: + </para> + + <para> + <command>++ Name Server Statistics ++</command> + </para> + + <para> + Each section consists of lines, each containing the statistics + counter value followed by its textual description. + See below for available counters. + For brevity, counters that have a value of 0 are not shown + in the statistics file. + </para> + + <para> + The statistics dump ends with the line where the + number is identical to the number in the beginning line; for example: + </para> + <para> + <command>--- Statistics Dump --- (973798949)</command> + </para> + </section> + + <section xml:id="statistics_counters"><info><title>Statistics Counters</title></info> + + <para> + The following tables summarize statistics counters that + <acronym>BIND</acronym> 9 provides. + For each row of the tables, the leftmost column is the + abbreviated symbol name of that counter. + These symbols are shown in the statistics information + accessed via an HTTP statistics channel. + The rightmost column gives the description of the counter, + which is also shown in the statistics file + (but, in this document, possibly with slight modification + for better readability). + Additional notes may also be provided in this column. + When a middle column exists between these two columns, + it gives the corresponding counter name of the + <acronym>BIND</acronym> 8 statistics, if applicable. + </para> + + <section xml:id="stats_counters"><info><title>Name Server Statistics Counters</title></info> + + <informaltable colsep="0" rowsep="0"> + <tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table"> + <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="1.150in"/> + <colspec colname="3" colnum="3" colsep="0" colwidth="3.350in"/> + <tbody> + <row> + <entry colname="1"> + <para> + <emphasis>Symbol</emphasis> + </para> + </entry> + <entry colname="2"> + <para> + <emphasis>BIND8 Symbol</emphasis> + </para> + </entry> + <entry colname="3"> + <para> + <emphasis>Description</emphasis> + </para> + </entry> + </row> + + <row rowsep="0"> + <entry colname="1"> + <para><command>Requestv4</command></para> + </entry> + <entry colname="2"> + <para><command>RQ</command></para> + </entry> + <entry colname="3"> + <para> + IPv4 requests received. + Note: this also counts non query requests. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>Requestv6</command></para> + </entry> + <entry colname="2"> + <para><command>RQ</command></para> + </entry> + <entry colname="3"> + <para> + IPv6 requests received. + Note: this also counts non query requests. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>ReqEdns0</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Requests with EDNS(0) received. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>ReqBadEDNSVer</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Requests with unsupported EDNS version received. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>ReqTSIG</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Requests with TSIG received. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>ReqSIG0</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Requests with SIG(0) received. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>ReqBadSIG</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Requests with invalid (TSIG or SIG(0)) signature. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>ReqTCP</command></para> + </entry> + <entry colname="2"> + <para><command>RTCP</command></para> + </entry> + <entry colname="3"> + <para> + TCP requests received. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>AuthQryRej</command></para> + </entry> + <entry colname="2"> + <para><command>RUQ</command></para> + </entry> + <entry colname="3"> + <para> + Authoritative (non recursive) queries rejected. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>RecQryRej</command></para> + </entry> + <entry colname="2"> + <para><command>RURQ</command></para> + </entry> + <entry colname="3"> + <para> + Recursive queries rejected. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>XfrRej</command></para> + </entry> + <entry colname="2"> + <para><command>RUXFR</command></para> + </entry> + <entry colname="3"> + <para> + Zone transfer requests rejected. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>UpdateRej</command></para> + </entry> + <entry colname="2"> + <para><command>RUUpd</command></para> + </entry> + <entry colname="3"> + <para> + Dynamic update requests rejected. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>Response</command></para> + </entry> + <entry colname="2"> + <para><command>SAns</command></para> + </entry> + <entry colname="3"> + <para> + Responses sent. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>RespTruncated</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Truncated responses sent. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>RespEDNS0</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Responses with EDNS(0) sent. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>RespTSIG</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Responses with TSIG sent. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>RespSIG0</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Responses with SIG(0) sent. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>QrySuccess</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Queries resulted in a successful answer. + This means the query which returns a NOERROR response + with at least one answer RR. + This corresponds to the + <command>success</command> counter + of previous versions of + <acronym>BIND</acronym> 9. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>QryAuthAns</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Queries resulted in authoritative answer. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>QryNoauthAns</command></para> + </entry> + <entry colname="2"> + <para><command>SNaAns</command></para> + </entry> + <entry colname="3"> + <para> + Queries resulted in non authoritative answer. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>QryReferral</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Queries resulted in referral answer. + This corresponds to the + <command>referral</command> counter + of previous versions of + <acronym>BIND</acronym> 9. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>QryNxrrset</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Queries resulted in NOERROR responses with no data. + This corresponds to the + <command>nxrrset</command> counter + of previous versions of + <acronym>BIND</acronym> 9. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>QrySERVFAIL</command></para> + </entry> + <entry colname="2"> + <para><command>SFail</command></para> + </entry> + <entry colname="3"> + <para> + Queries resulted in SERVFAIL. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>QryFORMERR</command></para> + </entry> + <entry colname="2"> + <para><command>SFErr</command></para> + </entry> + <entry colname="3"> + <para> + Queries resulted in FORMERR. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>QryNXDOMAIN</command></para> + </entry> + <entry colname="2"> + <para><command>SNXD</command></para> + </entry> + <entry colname="3"> + <para> + Queries resulted in NXDOMAIN. + This corresponds to the + <command>nxdomain</command> counter + of previous versions of + <acronym>BIND</acronym> 9. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>QryRecursion</command></para> + </entry> + <entry colname="2"> + <para><command>RFwdQ</command></para> + </entry> + <entry colname="3"> + <para> + Queries which caused the server + to perform recursion in order to find the final answer. + This corresponds to the + <command>recursion</command> counter + of previous versions of + <acronym>BIND</acronym> 9. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>QryDuplicate</command></para> + </entry> + <entry colname="2"> + <para><command>RDupQ</command></para> + </entry> + <entry colname="3"> + <para> + Queries which the server attempted to + recurse but discovered an existing query with the same + IP address, port, query ID, name, type and class + already being processed. + This corresponds to the + <command>duplicate</command> counter + of previous versions of + <acronym>BIND</acronym> 9. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>QryDropped</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Recursive queries for which the server + discovered an excessive number of existing + recursive queries for the same name, type and + class and were subsequently dropped. + This is the number of dropped queries due to + the reason explained with the + <command>clients-per-query</command> + and + <command>max-clients-per-query</command> + options + (see the description about + <xref endterm="cpq_term" linkend="clients-per-query"/>.) + This corresponds to the + <command>dropped</command> counter + of previous versions of + <acronym>BIND</acronym> 9. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>QryFailure</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Other query failures. + This corresponds to the + <command>failure</command> counter + of previous versions of + <acronym>BIND</acronym> 9. + Note: this counter is provided mainly for + backward compatibility with the previous versions. + Normally a more fine-grained counters such as + <command>AuthQryRej</command> and + <command>RecQryRej</command> + that would also fall into this counter are provided, + and so this counter would not be of much + interest in practice. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>QryNXRedir</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Queries resulted in NXDOMAIN that were redirected. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>QryNXRedirRLookup</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Queries resulted in NXDOMAIN that were redirected + and resulted in a successful remote lookup. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>XfrReqDone</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Requested zone transfers completed. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>UpdateReqFwd</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Update requests forwarded. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>UpdateRespFwd</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Update responses forwarded. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>UpdateFwdFail</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Dynamic update forward failed. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>UpdateDone</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Dynamic updates completed. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>UpdateFail</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Dynamic updates failed. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>UpdateBadPrereq</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Dynamic updates rejected due to prerequisite failure. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>RateDropped</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Responses dropped by rate limits. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>RateSlipped</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Responses truncated by rate limits. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>RPZRewrites</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Response policy zone rewrites. + </para> + </entry> + </row> + </tbody> + </tgroup> + </informaltable> + </section> + + <section xml:id="zone_stats"><info><title>Zone Maintenance Statistics Counters</title></info> + + <informaltable colsep="0" rowsep="0"> + <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table"> + <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="3.350in"/> + <tbody> + <row> + <entry colname="1"> + <para> + <emphasis>Symbol</emphasis> + </para> + </entry> + <entry colname="2"> + <para> + <emphasis>Description</emphasis> + </para> + </entry> + </row> + + <row rowsep="0"> + <entry colname="1"> + <para><command>NotifyOutv4</command></para> + </entry> + <entry colname="2"> + <para> + IPv4 notifies sent. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>NotifyOutv6</command></para> + </entry> + <entry colname="2"> + <para> + IPv6 notifies sent. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>NotifyInv4</command></para> + </entry> + <entry colname="2"> + <para> + IPv4 notifies received. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>NotifyInv6</command></para> + </entry> + <entry colname="2"> + <para> + IPv6 notifies received. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>NotifyRej</command></para> + </entry> + <entry colname="2"> + <para> + Incoming notifies rejected. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>SOAOutv4</command></para> + </entry> + <entry colname="2"> + <para> + IPv4 SOA queries sent. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>SOAOutv6</command></para> + </entry> + <entry colname="2"> + <para> + IPv6 SOA queries sent. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>AXFRReqv4</command></para> + </entry> + <entry colname="2"> + <para> + IPv4 AXFR requested. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>AXFRReqv6</command></para> + </entry> + <entry colname="2"> + <para> + IPv6 AXFR requested. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>IXFRReqv4</command></para> + </entry> + <entry colname="2"> + <para> + IPv4 IXFR requested. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>IXFRReqv6</command></para> + </entry> + <entry colname="2"> + <para> + IPv6 IXFR requested. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>XfrSuccess</command></para> + </entry> + <entry colname="2"> + <para> + Zone transfer requests succeeded. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>XfrFail</command></para> + </entry> + <entry colname="2"> + <para> + Zone transfer requests failed. + </para> + </entry> + </row> + </tbody> + </tgroup> + </informaltable> + </section> + + <section xml:id="resolver_stats"><info><title>Resolver Statistics Counters</title></info> + + <informaltable colsep="0" rowsep="0"> + <tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table"> + <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="1.150in"/> + <colspec colname="3" colnum="3" colsep="0" colwidth="3.350in"/> + <tbody> + <row> + <entry colname="1"> + <para> + <emphasis>Symbol</emphasis> + </para> + </entry> + <entry colname="2"> + <para> + <emphasis>BIND8 Symbol</emphasis> + </para> + </entry> + <entry colname="3"> + <para> + <emphasis>Description</emphasis> + </para> + </entry> + </row> + + <row rowsep="0"> + <entry colname="1"> + <para><command>Queryv4</command></para> + </entry> + <entry colname="2"> + <para><command>SFwdQ</command></para> + </entry> + <entry colname="3"> + <para> + IPv4 queries sent. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>Queryv6</command></para> + </entry> + <entry colname="2"> + <para><command>SFwdQ</command></para> + </entry> + <entry colname="3"> + <para> + IPv6 queries sent. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>Responsev4</command></para> + </entry> + <entry colname="2"> + <para><command>RR</command></para> + </entry> + <entry colname="3"> + <para> + IPv4 responses received. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>Responsev6</command></para> + </entry> + <entry colname="2"> + <para><command>RR</command></para> + </entry> + <entry colname="3"> + <para> + IPv6 responses received. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>NXDOMAIN</command></para> + </entry> + <entry colname="2"> + <para><command>RNXD</command></para> + </entry> + <entry colname="3"> + <para> + NXDOMAIN received. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>SERVFAIL</command></para> + </entry> + <entry colname="2"> + <para><command>RFail</command></para> + </entry> + <entry colname="3"> + <para> + SERVFAIL received. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>FORMERR</command></para> + </entry> + <entry colname="2"> + <para><command>RFErr</command></para> + </entry> + <entry colname="3"> + <para> + FORMERR received. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>OtherError</command></para> + </entry> + <entry colname="2"> + <para><command>RErr</command></para> + </entry> + <entry colname="3"> + <para> + Other errors received. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>EDNS0Fail</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + EDNS(0) query failures. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>Mismatch</command></para> + </entry> + <entry colname="2"> + <para><command>RDupR</command></para> + </entry> + <entry colname="3"> + <para> + Mismatch responses received. + The DNS ID, response's source address, + and/or the response's source port does not + match what was expected. + (The port must be 53 or as defined by + the <command>port</command> option.) + This may be an indication of a cache + poisoning attempt. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>Truncated</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Truncated responses received. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>Lame</command></para> + </entry> + <entry colname="2"> + <para><command>RLame</command></para> + </entry> + <entry colname="3"> + <para> + Lame delegations received. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>Retry</command></para> + </entry> + <entry colname="2"> + <para><command>SDupQ</command></para> + </entry> + <entry colname="3"> + <para> + Query retries performed. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>QueryAbort</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Queries aborted due to quota control. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>QuerySockFail</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Failures in opening query sockets. + One common reason for such failures is a + failure of opening a new socket due to a + limitation on file descriptors. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>QueryTimeout</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Query timeouts. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>GlueFetchv4</command></para> + </entry> + <entry colname="2"> + <para><command>SSysQ</command></para> + </entry> + <entry colname="3"> + <para> + IPv4 NS address fetches invoked. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>GlueFetchv6</command></para> + </entry> + <entry colname="2"> + <para><command>SSysQ</command></para> + </entry> + <entry colname="3"> + <para> + IPv6 NS address fetches invoked. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>GlueFetchv4Fail</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + IPv4 NS address fetch failed. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>GlueFetchv6Fail</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + IPv6 NS address fetch failed. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>ValAttempt</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + DNSSEC validation attempted. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>ValOk</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + DNSSEC validation succeeded. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>ValNegOk</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + DNSSEC validation on negative information succeeded. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>ValFail</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + DNSSEC validation failed. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command>QryRTTnn</command></para> + </entry> + <entry colname="2"> + <para><command/></para> + </entry> + <entry colname="3"> + <para> + Frequency table on round trip times (RTTs) of + queries. + Each <command>nn</command> specifies the corresponding + frequency. + In the sequence of + <command>nn_1</command>, + <command>nn_2</command>, + ..., + <command>nn_m</command>, + the value of <command>nn_i</command> is the + number of queries whose RTTs are between + <command>nn_(i-1)</command> (inclusive) and + <command>nn_i</command> (exclusive) milliseconds. + For the sake of convenience we define + <command>nn_0</command> to be 0. + The last entry should be represented as + <command>nn_m+</command>, which means the + number of queries whose RTTs are equal to or over + <command>nn_m</command> milliseconds. + </para> + </entry> + </row> + </tbody> + </tgroup> + </informaltable> + + </section> + + <section xml:id="socket_stats"><info><title>Socket I/O Statistics Counters</title></info> + + <para> + Socket I/O statistics counters are defined per socket + types, which are + <command>UDP4</command> (UDP/IPv4), + <command>UDP6</command> (UDP/IPv6), + <command>TCP4</command> (TCP/IPv4), + <command>TCP6</command> (TCP/IPv6), + <command>Unix</command> (Unix Domain), and + <command>FDwatch</command> (sockets opened outside the + socket module). + In the following table <command><TYPE></command> + represents a socket type. + Not all counters are available for all socket types; + exceptions are noted in the description field. + </para> + + <informaltable colsep="0" rowsep="0"> + <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table"> + <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/> + <colspec colname="2" colnum="2" colsep="0" colwidth="3.350in"/> + <tbody> + <row> + <entry colname="1"> + <para> + <emphasis>Symbol</emphasis> + </para> + </entry> + <entry colname="2"> + <para> + <emphasis>Description</emphasis> + </para> + </entry> + </row> + + <row rowsep="0"> + <entry colname="1"> + <para><command><TYPE>Open</command></para> + </entry> + <entry colname="2"> + <para> + Sockets opened successfully. + This counter is not applicable to the + <command>FDwatch</command> type. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command><TYPE>OpenFail</command></para> + </entry> + <entry colname="2"> + <para> + Failures of opening sockets. + This counter is not applicable to the + <command>FDwatch</command> type. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command><TYPE>Close</command></para> + </entry> + <entry colname="2"> + <para> + Sockets closed. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command><TYPE>BindFail</command></para> + </entry> + <entry colname="2"> + <para> + Failures of binding sockets. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command><TYPE>ConnFail</command></para> + </entry> + <entry colname="2"> + <para> + Failures of connecting sockets. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command><TYPE>Conn</command></para> + </entry> + <entry colname="2"> + <para> + Connections established successfully. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command><TYPE>AcceptFail</command></para> + </entry> + <entry colname="2"> + <para> + Failures of accepting incoming connection requests. + This counter is not applicable to the + <command>UDP</command> and + <command>FDwatch</command> types. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command><TYPE>Accept</command></para> + </entry> + <entry colname="2"> + <para> + Incoming connections successfully accepted. + This counter is not applicable to the + <command>UDP</command> and + <command>FDwatch</command> types. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command><TYPE>SendErr</command></para> + </entry> + <entry colname="2"> + <para> + Errors in socket send operations. + This counter corresponds + to <command>SErr</command> counter of + <command>BIND</command> 8. + </para> + </entry> + </row> + <row rowsep="0"> + <entry colname="1"> + <para><command><TYPE>RecvErr</command></para> + </entry> + <entry colname="2"> + <para> + Errors in socket receive operations. + This includes errors of send operations on a + connected UDP socket notified by an ICMP error + message. + </para> + </entry> + </row> + </tbody> + </tgroup> + </informaltable> + </section> + + <section xml:id="bind8_compatibility"><info><title>Compatibility with <emphasis>BIND</emphasis> 8 Counters</title></info> + + <para> + Most statistics counters that were available + in <command>BIND</command> 8 are also supported in + <command>BIND</command> 9 as shown in the above tables. + Here are notes about other counters that do not appear + in these tables. + </para> + + <variablelist> + <varlistentry> + <term><command>RFwdR,SFwdR</command></term> + <listitem> + <para> + These counters are not supported + because <command>BIND</command> 9 does not adopt + the notion of <emphasis>forwarding</emphasis> + as <command>BIND</command> 8 did. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>RAXFR</command></term> + <listitem> + <para> + This counter is accessible in the Incoming Queries section. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>RIQ</command></term> + <listitem> + <para> + This counter is accessible in the Incoming Requests section. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term><command>ROpts</command></term> + <listitem> + <para> + This counter is not supported + because <command>BIND</command> 9 does not care + about IP options in the first place. + </para> + </listitem> + </varlistentry> + </variablelist> + </section> + </section> + </section> + + </chapter> + <chapter xml:id="Bv9ARM.ch07"><info><title><acronym>BIND</acronym> 9 Security Considerations</title></info> + + <section xml:id="Access_Control_Lists"><info><title>Access Control Lists</title></info> + + <para> + Access Control Lists (ACLs) are address match lists that + you can set up and nickname for future use in + <command>allow-notify</command>, <command>allow-query</command>, + <command>allow-query-on</command>, <command>allow-recursion</command>, + <command>blackhole</command>, <command>allow-transfer</command>, + <command>match-clients</command>, etc. + </para> + <para> + Using ACLs allows you to have finer control over who can access + your name server, without cluttering up your config files with huge + lists of IP addresses. + </para> + <para> + It is a <emphasis>good idea</emphasis> to use ACLs, and to + control access to your server. Limiting access to your server by + outside parties can help prevent spoofing and denial of service + (DoS) attacks against your server. + </para> + <para> + ACLs match clients on the basis of up to three characteristics: + 1) The client's IP address; 2) the TSIG or SIG(0) key that was + used to sign the request, if any; and 3) an address prefix + encoded in an EDNS Client Subnet option, if any. + </para> + <para> + Here is an example of ACLs based on client addresses: + </para> + +<programlisting> +// Set up an ACL named "bogusnets" that will block +// RFC1918 space and some reserved space, which is +// commonly used in spoofing attacks. +acl bogusnets { + 0.0.0.0/8; 192.0.2.0/24; 224.0.0.0/3; + 10.0.0.0/8; 172.16.0.0/12; 192.168.0.0/16; +}; + +// Set up an ACL called our-nets. Replace this with the +// real IP numbers. +acl our-nets { x.x.x.x/24; x.x.x.x/21; }; +options { + ... + ... + allow-query { our-nets; }; + allow-recursion { our-nets; }; + ... + blackhole { bogusnets; }; + ... +}; + +zone "example.com" { + type master; + file "m/example.com"; + allow-query { any; }; +}; +</programlisting> + + <para> + This allows authoritative queries for "example.com" from any + address, but recursive queries only from the networks specified + in "our-nets", and no queries at all from the networks + specified in "bogusnets". + </para> + <para> + In addition to network addresses and prefixes, which are + matched against the source address of the DNS request, ACLs + may include <option>key</option> elements, which specify the + name of a TSIG or SIG(0) key, or <option>ecs</option> + elements, which specify a network prefix but are only matched + if that prefix matches an EDNS client subnet option included + in the request. + </para> + <para> + The EDNS Client Subnet (ECS) option is used by a recursive + resolver to inform an authoritative name server of the network + address block from which the original query was received, enabling + authoritative servers to give different answers to the same + resolver for different resolver clients. An ACL containing + an element of the form + <command>ecs <replaceable>prefix</replaceable></command> + will match if a request arrives in containing an ECS option + encoding an address within that prefix. If the request has no + ECS option, then "ecs" elements are simply ignored. Addresses + in ACLs that are not prefixed with "ecs" are matched only + against the source address. + </para> + <note> + <simpara> + (Note: The authoritative ECS implementation in + <command>named</command> is based on an early version of the + specification, and is known to have incompatibilities with + other implementations. It is also inefficient, requiring + a separate view for each client subnet to be sent different + answers, and it is unable to correct for overlapping subnets in + the configuration. It can be used for testing purposes, but is + not recommended for production use.) + </simpara> + </note> + <para> + When <acronym>BIND</acronym> 9 is built with GeoIP support, + ACLs can also be used for geographic access restrictions. + This is done by specifying an ACL element of the form: + <command>geoip <optional>db <replaceable>database</replaceable></optional> <replaceable>field</replaceable> <replaceable>value</replaceable></command> + </para> + <para> + The <replaceable>field</replaceable> indicates which field + to search for a match. Available fields are "country", + "region", "city", "continent", "postal" (postal code), + "metro" (metro code), "area" (area code), "tz" (timezone), + "isp", "org", "asnum", "domain" and "netspeed". + </para> + <para> + <replaceable>value</replaceable> is the value to search + for within the database. A string may be quoted if it + contains spaces or other special characters. If this is + an "asnum" search, then the leading "ASNNNN" string can be + used, otherwise the full description must be used (e.g. + "ASNNNN Example Company Name"). If this is a "country" + search and the string is two characters long, then it must + be a standard ISO-3166-1 two-letter country code, and if it + is three characters long then it must be an ISO-3166-1 + three-letter country code; otherwise it is the full name + of the country. Similarly, if this is a "region" search + and the string is two characters long, then it must be a + standard two-letter state or province abbreviation; + otherwise it is the full name of the state or province. + </para> + <para> + The <replaceable>database</replaceable> field indicates which + GeoIP database to search for a match. In most cases this is + unnecessary, because most search fields can only be found in + a single database. However, searches for country can be + answered from the "city", "region", or "country" databases, + and searches for region (i.e., state or province) can be + answered from the "city" or "region" databases. For these + search types, specifying a <replaceable>database</replaceable> + will force the query to be answered from that database and no + other. If <replaceable>database</replaceable> is not + specified, then these queries will be answered from the "city", + database if it is installed, or the "region" database if it is + installed, or the "country" database, in that order. + </para> + <para> + By default, if a DNS query includes an EDNS Client Subnet (ECS) + option which encodes a non-zero address prefix, then GeoIP ACLs + will be matched against that address prefix. Otherwise, they + are matched against the source address of the query. To + prevent GeoIP ACLs from matching against ECS options, set + the <command>geoip-use-ecs</command> to <literal>no</literal>. + </para> + <para> + Some example GeoIP ACLs: + </para> + <programlisting>geoip country US; +geoip country JAP; +geoip db country country Canada; +geoip db region region WA; +geoip city "San Francisco"; +geoip region Oklahoma; +geoip postal 95062; +geoip tz "America/Los_Angeles"; +geoip org "Internet Systems Consortium"; +</programlisting> + + <para> + ACLs use a "first-match" logic rather than "best-match": + if an address prefix matches an ACL element, then that ACL + is considered to have matched even if a later element would + have matched more specifically. For example, the ACL + <command> { 10/8; !10.0.0.1; }</command> would actually + match a query from 10.0.0.1, because the first element + indicated that the query should be accepted, and the second + element is ignored. + </para> + <para> + When using "nested" ACLs (that is, ACLs included or referenced + within other ACLs), a negative match of a nested ACL will + the containing ACL to continue looking for matches. This + enables complex ACLs to be constructed, in which multiple + client characteristics can be checked at the same time. For + example, to construct an ACL which allows queries only when + it originates from a particular network <emphasis>and</emphasis> + only when it is signed with a particular key, use: + </para> + <programlisting> +allow-query { !{ !10/8; any; }; key example; }; +</programlisting> + <para> + Within the nested ACL, any address that is + <emphasis>not</emphasis> in the 10/8 network prefix will + be rejected, and this will terminate processing of the + ACL. Any address that <emphasis>is</emphasis> in the 10/8 + network prefix will be accepted, but this causes a negative + match of the nested ACL, so the containing ACL continues + processing. The query will then be accepted if it is signed + by the key "example", and rejected otherwise. The ACL, then, + will only matches when <emphasis>both</emphasis> conditions + are true. + </para> + </section> + + <section xml:id="chroot_and_setuid"><info><title><command>Chroot</command> and <command>Setuid</command></title></info> + + <para> + On UNIX servers, it is possible to run <acronym>BIND</acronym> + in a <emphasis>chrooted</emphasis> environment (using + the <command>chroot()</command> function) by specifying + the <option>-t</option> option for <command>named</command>. + This can help improve system security by placing + <acronym>BIND</acronym> in a "sandbox", which will limit + the damage done if a server is compromised. + </para> + <para> + Another useful feature in the UNIX version of <acronym>BIND</acronym> is the + ability to run the daemon as an unprivileged user ( <option>-u</option> <replaceable>user</replaceable> ). + We suggest running as an unprivileged user when using the <command>chroot</command> feature. + </para> + <para> + Here is an example command line to load <acronym>BIND</acronym> in a <command>chroot</command> sandbox, + <command>/var/named</command>, and to run <command>named</command> <command>setuid</command> to + user 202: + </para> + <para> + <userinput>/usr/local/sbin/named -u 202 -t /var/named</userinput> + </para> + + <section xml:id="chroot"><info><title>The <command>chroot</command> Environment</title></info> + + <para> + In order for a <command>chroot</command> environment + to work properly in a particular directory (for example, + <filename>/var/named</filename>), you will need to set + up an environment that includes everything + <acronym>BIND</acronym> needs to run. From + <acronym>BIND</acronym>'s point of view, + <filename>/var/named</filename> is the root of the + filesystem. You will need to adjust the values of + options like <command>directory</command> and + <command>pid-file</command> to account for this. + </para> + <para> + Unlike with earlier versions of BIND, you typically will + <emphasis>not</emphasis> need to compile <command>named</command> + statically nor install shared libraries under the new root. + However, depending on your operating system, you may need + to set up things like + <filename>/dev/zero</filename>, + <filename>/dev/random</filename>, + <filename>/dev/log</filename>, and + <filename>/etc/localtime</filename>. + </para> + </section> + + <section xml:id="setuid"><info><title>Using the <command>setuid</command> Function</title></info> + + <para> + Prior to running the <command>named</command> daemon, + use + the <command>touch</command> utility (to change file + access and + modification times) or the <command>chown</command> + utility (to + set the user id and/or group id) on files + to which you want <acronym>BIND</acronym> + to write. + </para> + <note><simpara> + If the <command>named</command> daemon is running as an + unprivileged user, it will not be able to bind to new restricted + ports if the server is reloaded. + </simpara></note> + </section> + </section> + + <section xml:id="dynamic_update_security"><info><title>Dynamic Update Security</title></info> + + <para> + Access to the dynamic + update facility should be strictly limited. In earlier versions of + <acronym>BIND</acronym>, the only way to do this was + based on the IP + address of the host requesting the update, by listing an IP address + or + network prefix in the <command>allow-update</command> + zone option. + This method is insecure since the source address of the update UDP + packet + is easily forged. Also note that if the IP addresses allowed by the + <command>allow-update</command> option include the + address of a slave + server which performs forwarding of dynamic updates, the master can + be + trivially attacked by sending the update to the slave, which will + forward it to the master with its own source IP address causing the + master to approve it without question. + </para> + + <para> + For these reasons, we strongly recommend that updates be + cryptographically authenticated by means of transaction signatures + (TSIG). That is, the <command>allow-update</command> + option should + list only TSIG key names, not IP addresses or network + prefixes. Alternatively, the new <command>update-policy</command> + option can be used. + </para> + + <para> + Some sites choose to keep all dynamically-updated DNS data + in a subdomain and delegate that subdomain to a separate zone. This + way, the top-level zone containing critical data such as the IP + addresses + of public web and mail servers need not allow dynamic update at + all. + </para> + + </section> + </chapter> + + <chapter xml:id="Bv9ARM.ch08"><info><title>Troubleshooting</title></info> + + <section xml:id="common_problems"><info><title>Common Problems</title></info> + + <section><info><title>It's not working; how can I figure out what's wrong?</title></info> + + <para> + The best solution to solving installation and + configuration issues is to take preventative measures by setting + up logging files beforehand. The log files provide a + source of hints and information that can be used to figure out + what went wrong and how to fix the problem. + </para> + + </section> + </section> + <section><info><title>Incrementing and Changing the Serial Number</title></info> + + <para> + Zone serial numbers are just numbers — they aren't + date related. A lot of people set them to a number that + represents a date, usually of the form YYYYMMDDRR. + Occasionally they will make a mistake and set them to a + "date in the future" then try to correct them by setting + them to the "current date". This causes problems because + serial numbers are used to indicate that a zone has been + updated. If the serial number on the slave server is + lower than the serial number on the master, the slave + server will attempt to update its copy of the zone. + </para> + + <para> + Setting the serial number to a lower number on the master + server than the slave server means that the slave will not perform + updates to its copy of the zone. + </para> + + <para> + The solution to this is to add 2147483647 (2^31-1) to the + number, reload the zone and make sure all slaves have updated to + the new zone serial number, then reset the number to what you want + it to be, and reload the zone again. + </para> + + </section> + <section xml:id="more_help"><info><title>Where Can I Get Help?</title></info> + + <para> + The Internet Systems Consortium + (<acronym>ISC</acronym>) offers a wide range + of support and service agreements for <acronym>BIND</acronym> and <acronym>DHCP</acronym> servers. Four + levels of premium support are available and each level includes + support for all <acronym>ISC</acronym> programs, + significant discounts on products + and training, and a recognized priority on bug fixes and + non-funded feature requests. In addition, <acronym>ISC</acronym> offers a standard + support agreement package which includes services ranging from bug + fix announcements to remote support. It also includes training in + <acronym>BIND</acronym> and <acronym>DHCP</acronym>. + </para> + + <para> + To discuss arrangements for support, contact + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="mailto:info@isc.org">info@isc.org</link> or visit the + <acronym>ISC</acronym> web page at + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.isc.org/services/support/">http://www.isc.org/services/support/</link> + to read more. + </para> + </section> + </chapter> + + <appendix xml:id="Bv9ARM.ch09"><info><title>Release Notes</title></info> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="notes.xml"/> + </appendix> + + <appendix xml:id="Bv9ARM.ch10"><info><title>A Brief History of the <acronym>DNS</acronym> and <acronym>BIND</acronym></title></info> + <para xml:id="historical_dns_information"> + Although the "official" beginning of the Domain Name + System occurred in 1984 with the publication of RFC 920, the + core of the new system was described in 1983 in RFCs 882 and + 883. From 1984 to 1987, the ARPAnet (the precursor to today's + Internet) became a testbed of experimentation for developing the + new naming/addressing scheme in a rapidly expanding, + operational network environment. New RFCs were written and + published in 1987 that modified the original documents to + incorporate improvements based on the working model. RFC 1034, + "Domain Names-Concepts and Facilities", and RFC 1035, "Domain + Names-Implementation and Specification" were published and + became the standards upon which all <acronym>DNS</acronym> implementations are + built. + </para> + + <para> + The first working domain name server, called "Jeeves", was + written in 1983-84 by Paul Mockapetris for operation on DEC + Tops-20 + machines located at the University of Southern California's + Information + Sciences Institute (USC-ISI) and SRI International's Network + Information + Center (SRI-NIC). A <acronym>DNS</acronym> server for + Unix machines, the Berkeley Internet + Name Domain (<acronym>BIND</acronym>) package, was + written soon after by a group of + graduate students at the University of California at Berkeley + under + a grant from the US Defense Advanced Research Projects + Administration + (DARPA). + </para> + <para> + Versions of <acronym>BIND</acronym> through + 4.8.3 were maintained by the Computer + Systems Research Group (CSRG) at UC Berkeley. Douglas Terry, Mark + Painter, David Riggle and Songnian Zhou made up the initial <acronym>BIND</acronym> + project team. After that, additional work on the software package + was done by Ralph Campbell. Kevin Dunlap, a Digital Equipment + Corporation + employee on loan to the CSRG, worked on <acronym>BIND</acronym> for 2 years, from 1985 + to 1987. Many other people also contributed to <acronym>BIND</acronym> development + during that time: Doug Kingston, Craig Partridge, Smoot + Carl-Mitchell, + Mike Muuss, Jim Bloom and Mike Schwartz. <acronym>BIND</acronym> maintenance was subsequently + handled by Mike Karels and Øivind Kure. + </para> + <para> + <acronym>BIND</acronym> versions 4.9 and 4.9.1 were + released by Digital Equipment + Corporation (now Compaq Computer Corporation). Paul Vixie, then + a DEC employee, became <acronym>BIND</acronym>'s + primary caretaker. He was assisted + by Phil Almquist, Robert Elz, Alan Barrett, Paul Albitz, Bryan + Beecher, Andrew + Partan, Andy Cherenson, Tom Limoncelli, Berthold Paffrath, Fuat + Baran, Anant Kumar, Art Harkin, Win Treese, Don Lewis, Christophe + Wolfhugel, and others. + </para> + <para> + In 1994, <acronym>BIND</acronym> version 4.9.2 was sponsored by + Vixie Enterprises. Paul + Vixie became <acronym>BIND</acronym>'s principal + architect/programmer. + </para> + <para> + <acronym>BIND</acronym> versions from 4.9.3 onward + have been developed and maintained + by the Internet Systems Consortium and its predecessor, + the Internet Software Consortium, with support being provided + by ISC's sponsors. + </para> + <para> + As co-architects/programmers, Bob Halley and + Paul Vixie released the first production-ready version of + <acronym>BIND</acronym> version 8 in May 1997. + </para> + <para> + BIND version 9 was released in September 2000 and is a + major rewrite of nearly all aspects of the underlying + BIND architecture. + </para> + <para> + BIND versions 4 and 8 are officially deprecated. + No additional development is done + on BIND version 4 or BIND version 8. + </para> + <para> + <acronym>BIND</acronym> development work is made + possible today by the sponsorship + of several corporations, and by the tireless work efforts of + numerous individuals. + </para> + </appendix> + + <appendix xml:id="Bv9ARM.ch11"><info><title>General <acronym>DNS</acronym> Reference Information</title></info> + + <section xml:id="ipv6addresses"><info><title>IPv6 addresses (AAAA)</title></info> + + <para> + IPv6 addresses are 128-bit identifiers for interfaces and + sets of interfaces which were introduced in the <acronym>DNS</acronym> to facilitate + scalable Internet routing. There are three types of addresses: <emphasis>Unicast</emphasis>, + an identifier for a single interface; + <emphasis>Anycast</emphasis>, + an identifier for a set of interfaces; and <emphasis>Multicast</emphasis>, + an identifier for a set of interfaces. Here we describe the global + Unicast address scheme. For more information, see RFC 3587, + "Global Unicast Address Format." + </para> + <para> + IPv6 unicast addresses consist of a + <emphasis>global routing prefix</emphasis>, a + <emphasis>subnet identifier</emphasis>, and an + <emphasis>interface identifier</emphasis>. + </para> + <para> + The global routing prefix is provided by the + upstream provider or ISP, and (roughly) corresponds to the + IPv4 <emphasis>network</emphasis> section + of the address range. + + The subnet identifier is for local subnetting, much the + same as subnetting an + IPv4 /16 network into /24 subnets. + + The interface identifier is the address of an individual + interface on a given network; in IPv6, addresses belong to + interfaces rather than to machines. + </para> + <para> + The subnetting capability of IPv6 is much more flexible than + that of IPv4: subnetting can be carried out on bit boundaries, + in much the same way as Classless InterDomain Routing + (CIDR), and the DNS PTR representation ("nibble" format) + makes setting up reverse zones easier. + </para> + <para> + The Interface Identifier must be unique on the local link, + and is usually generated automatically by the IPv6 + implementation, although it is usually possible to + override the default setting if necessary. A typical IPv6 + address might look like: + <command>2001:db8:201:9:a00:20ff:fe81:2b32</command> + </para> + <para> + IPv6 address specifications often contain long strings + of zeros, so the architects have included a shorthand for + specifying + them. The double colon (`::') indicates the longest possible + string + of zeros that can fit, and can be used only once in an address. + </para> + </section> + <section xml:id="bibliography"><info><title>Bibliography (and Suggested Reading)</title></info> + + <section xml:id="rfcs"><info><title>Request for Comments (RFCs)</title></info> + + <para> + Specification documents for the Internet protocol suite, including + the <acronym>DNS</acronym>, are published as part of + the Request for Comments (RFCs) + series of technical notes. The standards themselves are defined + by the Internet Engineering Task Force (IETF) and the Internet + Engineering Steering Group (IESG). RFCs can be obtained online via FTP at: + </para> + <para> + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ftp://www.isi.edu/in-notes/"> + ftp://www.isi.edu/in-notes/RFC<replaceable>xxxx</replaceable>.txt + </link> + </para> + <para> + (where <replaceable>xxxx</replaceable> is + the number of the RFC). RFCs are also available via the Web at: + </para> + <para> + <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.ietf.org/rfc/">http://www.ietf.org/rfc/</link>. + </para> + <bibliography> + <bibliodiv><info><title>Standards</title></info> + <!-- one of (BIBLIOENTRY BIBLIOMIXED) --> + + <biblioentry> + <abbrev>RFC974</abbrev> + <author><personname><surname>Partridge</surname><firstname>C.</firstname></personname></author> + <citetitle>Mail Routing and the Domain System</citetitle> + <pubdate>January 1986</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC1034</abbrev> + <author><personname><surname>Mockapetris</surname><firstname>P.V.</firstname></personname></author> + <citetitle>Domain Names — Concepts and Facilities</citetitle> + <pubdate>November 1987</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC1035</abbrev> + <author><personname><surname>Mockapetris</surname><firstname>P. V.</firstname></personname></author> <citetitle>Domain Names — Implementation and + Specification</citetitle> + <pubdate>November 1987</pubdate> + </biblioentry> + </bibliodiv> + <bibliodiv xml:id="proposed_standards" xreflabel="Proposed Standards"><info><title>Proposed Standards</title></info> + + <!-- one of (BIBLIOENTRY BIBLIOMIXED) --> + <biblioentry> + <abbrev>RFC2181</abbrev> + <author><personname><surname>Elz</surname><firstname>R., R. Bush</firstname></personname></author> + <citetitle>Clarifications to the <acronym>DNS</acronym> + Specification</citetitle> + <pubdate>July 1997</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2308</abbrev> + <author><personname><surname>Andrews</surname><firstname>M.</firstname></personname></author> + <citetitle>Negative Caching of <acronym>DNS</acronym> + Queries</citetitle> + <pubdate>March 1998</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC1995</abbrev> + <author><personname><surname>Ohta</surname><firstname>M.</firstname></personname></author> + <citetitle>Incremental Zone Transfer in <acronym>DNS</acronym></citetitle> + <pubdate>August 1996</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC1996</abbrev> + <author><personname><surname>Vixie</surname><firstname>P.</firstname></personname></author> + <citetitle>A Mechanism for Prompt Notification of Zone Changes</citetitle> + <pubdate>August 1996</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2136</abbrev> + <authorgroup> + <author><personname><surname>Vixie</surname><firstname>P.</firstname></personname></author> + <author><personname><firstname>S.</firstname><surname>Thomson</surname></personname></author> + <author><personname><firstname>Y.</firstname><surname>Rekhter</surname></personname></author> + <author><personname><firstname>J.</firstname><surname>Bound</surname></personname></author> + </authorgroup> + <citetitle>Dynamic Updates in the Domain Name System</citetitle> + <pubdate>April 1997</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2671</abbrev> + <authorgroup> + <author><personname><firstname>P.</firstname><surname>Vixie</surname></personname></author> + </authorgroup> + <citetitle>Extension Mechanisms for DNS (EDNS0)</citetitle> + <pubdate>August 1997</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2672</abbrev> + <authorgroup> + <author><personname><firstname>M.</firstname><surname>Crawford</surname></personname></author> + </authorgroup> + <citetitle>Non-Terminal DNS Name Redirection</citetitle> + <pubdate>August 1999</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2845</abbrev> + <authorgroup> + <author><personname><surname>Vixie</surname><firstname>P.</firstname></personname></author> + <author><personname><firstname>O.</firstname><surname>Gudmundsson</surname></personname></author> + <author><personname><firstname>D.</firstname><surname>Eastlake</surname><lineage>3rd</lineage></personname></author> + <author><personname><firstname>B.</firstname><surname>Wellington</surname></personname></author> + </authorgroup> + <citetitle>Secret Key Transaction Authentication for <acronym>DNS</acronym> (TSIG)</citetitle> + <pubdate>May 2000</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2930</abbrev> + <authorgroup> + <author><personname><firstname>D.</firstname><surname>Eastlake</surname><lineage>3rd</lineage></personname></author> + </authorgroup> + <citetitle>Secret Key Establishment for DNS (TKEY RR)</citetitle> + <pubdate>September 2000</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2931</abbrev> + <authorgroup> + <author><personname><firstname>D.</firstname><surname>Eastlake</surname><lineage>3rd</lineage></personname></author> + </authorgroup> + <citetitle>DNS Request and Transaction Signatures (SIG(0)s)</citetitle> + <pubdate>September 2000</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC3007</abbrev> + <authorgroup> + <author><personname><firstname>B.</firstname><surname>Wellington</surname></personname></author> + </authorgroup> + <citetitle>Secure Domain Name System (DNS) Dynamic Update</citetitle> + <pubdate>November 2000</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC3645</abbrev> + <authorgroup> + <author><personname><firstname>S.</firstname><surname>Kwan</surname></personname></author> + <author><personname><firstname>P.</firstname><surname>Garg</surname></personname></author> + <author><personname><firstname>J.</firstname><surname>Gilroy</surname></personname></author> + <author><personname><firstname>L.</firstname><surname>Esibov</surname></personname></author> + <author><personname><firstname>J.</firstname><surname>Westhead</surname></personname></author> + <author><personname><firstname>R.</firstname><surname>Hall</surname></personname></author> + </authorgroup> + <citetitle>Generic Security Service Algorithm for Secret + Key Transaction Authentication for DNS + (GSS-TSIG)</citetitle> + <pubdate>October 2003</pubdate> + </biblioentry> + </bibliodiv> + <bibliodiv><info><title><acronym>DNS</acronym> Security Proposed Standards</title></info> + + <biblioentry> + <abbrev>RFC3225</abbrev> + <authorgroup> + <author><personname><firstname>D.</firstname><surname>Conrad</surname></personname></author> + </authorgroup> + <citetitle>Indicating Resolver Support of DNSSEC</citetitle> + <pubdate>December 2001</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC3833</abbrev> + <authorgroup> + <author><personname><firstname>D.</firstname><surname>Atkins</surname></personname></author> + <author><personname><firstname>R.</firstname><surname>Austein</surname></personname></author> + </authorgroup> + <citetitle>Threat Analysis of the Domain Name System (DNS)</citetitle> + <pubdate>August 2004</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC4033</abbrev> + <authorgroup> + <author><personname><firstname>R.</firstname><surname>Arends</surname></personname></author> + <author><personname><firstname>R.</firstname><surname>Austein</surname></personname></author> + <author><personname><firstname>M.</firstname><surname>Larson</surname></personname></author> + <author><personname><firstname>D.</firstname><surname>Massey</surname></personname></author> + <author><personname><firstname>S.</firstname><surname>Rose</surname></personname></author> + </authorgroup> + <citetitle>DNS Security Introduction and Requirements</citetitle> + <pubdate>March 2005</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC4034</abbrev> + <authorgroup> + <author><personname><firstname>R.</firstname><surname>Arends</surname></personname></author> + <author><personname><firstname>R.</firstname><surname>Austein</surname></personname></author> + <author><personname><firstname>M.</firstname><surname>Larson</surname></personname></author> + <author><personname><firstname>D.</firstname><surname>Massey</surname></personname></author> + <author><personname><firstname>S.</firstname><surname>Rose</surname></personname></author> + </authorgroup> + <citetitle>Resource Records for the DNS Security Extensions</citetitle> + <pubdate>March 2005</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC4035</abbrev> + <authorgroup> + <author><personname><firstname>R.</firstname><surname>Arends</surname></personname></author> + <author><personname><firstname>R.</firstname><surname>Austein</surname></personname></author> + <author><personname><firstname>M.</firstname><surname>Larson</surname></personname></author> + <author><personname><firstname>D.</firstname><surname>Massey</surname></personname></author> + <author><personname><firstname>S.</firstname><surname>Rose</surname></personname></author> + </authorgroup> + <citetitle>Protocol Modifications for the DNS + Security Extensions</citetitle> + <pubdate>March 2005</pubdate> + </biblioentry> + </bibliodiv> + <bibliodiv><info><title>Other Important RFCs About <acronym>DNS</acronym> + Implementation</title></info> + + <biblioentry> + <abbrev>RFC1535</abbrev> + <author><personname><surname>Gavron</surname><firstname>E.</firstname></personname></author> + <citetitle>A Security Problem and Proposed Correction With Widely + Deployed <acronym>DNS</acronym> Software</citetitle> + <pubdate>October 1993</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC1536</abbrev> + <authorgroup> + <author><personname><surname>Kumar</surname><firstname>A.</firstname></personname></author> + <author><personname><firstname>J.</firstname><surname>Postel</surname></personname></author> + <author><personname><firstname>C.</firstname><surname>Neuman</surname></personname></author> + <author><personname><firstname>P.</firstname><surname>Danzig</surname></personname></author> + <author><personname><firstname>S.</firstname><surname>Miller</surname></personname></author> + </authorgroup> + <citetitle>Common <acronym>DNS</acronym> Implementation + Errors and Suggested Fixes</citetitle> + <pubdate>October 1993</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC1982</abbrev> + <authorgroup> + <author><personname><surname>Elz</surname><firstname>R.</firstname></personname></author> + <author><personname><firstname>R.</firstname><surname>Bush</surname></personname></author> + </authorgroup> + <citetitle>Serial Number Arithmetic</citetitle> + <pubdate>August 1996</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC4074</abbrev> + <authorgroup> + <author><personname><surname>Morishita</surname><firstname>Y.</firstname></personname></author> + <author><personname><firstname>T.</firstname><surname>Jinmei</surname></personname></author> + </authorgroup> + <citetitle>Common Misbehaviour Against <acronym>DNS</acronym> + Queries for IPv6 Addresses</citetitle> + <pubdate>May 2005</pubdate> + </biblioentry> + </bibliodiv> + <bibliodiv><info><title>Resource Record Types</title></info> + + <biblioentry> + <abbrev>RFC1183</abbrev> + <authorgroup> + <author><personname><surname>Everhart</surname><firstname>C.F.</firstname></personname></author> + <author><personname><firstname>L. A.</firstname><surname>Mamakos</surname></personname></author> + <author><personname><firstname>R.</firstname><surname>Ullmann</surname></personname></author> + <author><personname><firstname>P.</firstname><surname>Mockapetris</surname></personname></author> + </authorgroup> + <citetitle>New <acronym>DNS</acronym> RR Definitions</citetitle> + <pubdate>October 1990</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC1706</abbrev> + <authorgroup> + <author><personname><surname>Manning</surname><firstname>B.</firstname></personname></author> + <author><personname><firstname>R.</firstname><surname>Colella</surname></personname></author> + </authorgroup> + <citetitle><acronym>DNS</acronym> NSAP Resource Records</citetitle> + <pubdate>October 1994</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2168</abbrev> + <authorgroup> + <author><personname><surname>Daniel</surname><firstname>R.</firstname></personname></author> + <author><personname><firstname>M.</firstname><surname>Mealling</surname></personname></author> + </authorgroup> + <citetitle>Resolution of Uniform Resource Identifiers using + the Domain Name System</citetitle> + <pubdate>June 1997</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC1876</abbrev> + <authorgroup> + <author><personname><surname>Davis</surname><firstname>C.</firstname></personname></author> + <author><personname><firstname>P.</firstname><surname>Vixie</surname></personname></author> + <author><personname><firstname>T.</firstname><firstname>Goodwin</firstname></personname></author> + <author><personname><firstname>I.</firstname><surname>Dickinson</surname></personname></author> + </authorgroup> + <citetitle>A Means for Expressing Location Information in the + Domain + Name System</citetitle> + <pubdate>January 1996</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2052</abbrev> + <authorgroup> + <author><personname><surname>Gulbrandsen</surname><firstname>A.</firstname></personname></author> + <author><personname><firstname>P.</firstname><surname>Vixie</surname></personname></author> + </authorgroup> + <citetitle>A <acronym>DNS</acronym> RR for Specifying the + Location of + Services</citetitle> + <pubdate>October 1996</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2163</abbrev> + <author><personname><surname>Allocchio</surname><firstname>A.</firstname></personname></author> + <citetitle>Using the Internet <acronym>DNS</acronym> to + Distribute MIXER + Conformant Global Address Mapping</citetitle> + <pubdate>January 1998</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2230</abbrev> + <author><personname><surname>Atkinson</surname><firstname>R.</firstname></personname></author> + <citetitle>Key Exchange Delegation Record for the <acronym>DNS</acronym></citetitle> + <pubdate>October 1997</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2536</abbrev> + <author><personname><surname>Eastlake</surname><firstname>D.</firstname><lineage>3rd</lineage></personname></author> + <citetitle>DSA KEYs and SIGs in the Domain Name System (DNS)</citetitle> + <pubdate>March 1999</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2537</abbrev> + <author><personname><surname>Eastlake</surname><firstname>D.</firstname><lineage>3rd</lineage></personname></author> + <citetitle>RSA/MD5 KEYs and SIGs in the Domain Name System (DNS)</citetitle> + <pubdate>March 1999</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2538</abbrev> + <authorgroup> + <author><personname><surname>Eastlake</surname><firstname>D.</firstname><lineage>3rd</lineage></personname></author> + <author><personname><surname>Gudmundsson</surname><firstname>O.</firstname></personname></author> + </authorgroup> + <citetitle>Storing Certificates in the Domain Name System (DNS)</citetitle> + <pubdate>March 1999</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2539</abbrev> + <authorgroup> + <author><personname><surname>Eastlake</surname><firstname>D.</firstname><lineage>3rd</lineage></personname></author> + </authorgroup> + <citetitle>Storage of Diffie-Hellman Keys in the Domain Name System (DNS)</citetitle> + <pubdate>March 1999</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2540</abbrev> + <authorgroup> + <author><personname><surname>Eastlake</surname><firstname>D.</firstname><lineage>3rd</lineage></personname></author> + </authorgroup> + <citetitle>Detached Domain Name System (DNS) Information</citetitle> + <pubdate>March 1999</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2782</abbrev> + <author><personname><surname>Gulbrandsen</surname><firstname>A.</firstname></personname></author> + <author><personname><surname>Vixie</surname><firstname>P.</firstname></personname></author> + <author><personname><surname>Esibov</surname><firstname>L.</firstname></personname></author> + <citetitle>A DNS RR for specifying the location of services (DNS SRV)</citetitle> + <pubdate>February 2000</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2915</abbrev> + <author><personname><surname>Mealling</surname><firstname>M.</firstname></personname></author> + <author><personname><surname>Daniel</surname><firstname>R.</firstname></personname></author> + <citetitle>The Naming Authority Pointer (NAPTR) DNS Resource Record</citetitle> + <pubdate>September 2000</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC3110</abbrev> + <author><personname><surname>Eastlake</surname><firstname>D.</firstname><lineage>3rd</lineage></personname></author> + <citetitle>RSA/SHA-1 SIGs and RSA KEYs in the Domain Name System (DNS)</citetitle> + <pubdate>May 2001</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC3123</abbrev> + <author><personname><surname>Koch</surname><firstname>P.</firstname></personname></author> + <citetitle>A DNS RR Type for Lists of Address Prefixes (APL RR)</citetitle> + <pubdate>June 2001</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC3596</abbrev> + <authorgroup> + <author><personname><surname>Thomson</surname><firstname>S.</firstname></personname></author> + <author><personname><firstname>C.</firstname><surname>Huitema</surname></personname></author> + <author><personname><firstname>V.</firstname><surname>Ksinant</surname></personname></author> + <author><personname><firstname>M.</firstname><surname>Souissi</surname></personname></author> + </authorgroup> + <citetitle><acronym>DNS</acronym> Extensions to support IP + version 6</citetitle> + <pubdate>October 2003</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC3597</abbrev> + <author><personname><surname>Gustafsson</surname><firstname>A.</firstname></personname></author> + <citetitle>Handling of Unknown DNS Resource Record (RR) Types</citetitle> + <pubdate>September 2003</pubdate> + </biblioentry> + </bibliodiv> + <bibliodiv><info><title><acronym>DNS</acronym> and the Internet</title></info> + + <biblioentry> + <abbrev>RFC1101</abbrev> + <author><personname><surname>Mockapetris</surname><firstname>P. V.</firstname></personname></author> + <citetitle><acronym>DNS</acronym> Encoding of Network Names + and Other Types</citetitle> + <pubdate>April 1989</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC1123</abbrev> + <author><personname><surname>Braden</surname><surname>R.</surname></personname></author> + <citetitle>Requirements for Internet Hosts - Application and + Support</citetitle> + <pubdate>October 1989</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC1591</abbrev> + <author><personname><surname>Postel</surname><firstname>J.</firstname></personname></author> + <citetitle>Domain Name System Structure and Delegation</citetitle> + <pubdate>March 1994</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2317</abbrev> + <authorgroup> + <author><personname><surname>Eidnes</surname><firstname>H.</firstname></personname></author> + <author><personname><firstname>G.</firstname><surname>de Groot</surname></personname></author> + <author><personname><firstname>P.</firstname><surname>Vixie</surname></personname></author> + </authorgroup> + <citetitle>Classless IN-ADDR.ARPA Delegation</citetitle> + <pubdate>March 1998</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2826</abbrev> + <authorgroup> + <author><personname><surname>Internet Architecture Board</surname></personname></author> + </authorgroup> + <citetitle>IAB Technical Comment on the Unique DNS Root</citetitle> + <pubdate>May 2000</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2929</abbrev> + <authorgroup> + <author><personname><surname>Eastlake</surname><firstname>D.</firstname><lineage>3rd</lineage></personname></author> + <author><personname><surname>Brunner-Williams</surname><firstname>E.</firstname></personname></author> + <author><personname><surname>Manning</surname><firstname>B.</firstname></personname></author> + </authorgroup> + <citetitle>Domain Name System (DNS) IANA Considerations</citetitle> + <pubdate>September 2000</pubdate> + </biblioentry> + </bibliodiv> + <bibliodiv><info><title><acronym>DNS</acronym> Operations</title></info> + + <biblioentry> + <abbrev>RFC1033</abbrev> + <author><personname><surname>Lottor</surname><firstname>M.</firstname></personname></author> + <citetitle>Domain administrators operations guide</citetitle> + <pubdate>November 1987</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC1537</abbrev> + <author><personname><surname>Beertema</surname><firstname>P.</firstname></personname></author> + <citetitle>Common <acronym>DNS</acronym> Data File + Configuration Errors</citetitle> + <pubdate>October 1993</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC1912</abbrev> + <author><personname><surname>Barr</surname><firstname>D.</firstname></personname></author> + <citetitle>Common <acronym>DNS</acronym> Operational and + Configuration Errors</citetitle> + <pubdate>February 1996</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2010</abbrev> + <authorgroup> + <author><personname><surname>Manning</surname><firstname>B.</firstname></personname></author> + <author><personname><firstname>P.</firstname><surname>Vixie</surname></personname></author> + </authorgroup> + <citetitle>Operational Criteria for Root Name Servers</citetitle> + <pubdate>October 1996</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2219</abbrev> + <authorgroup> + <author><personname><surname>Hamilton</surname><firstname>M.</firstname></personname></author> + <author><personname><firstname>R.</firstname><surname>Wright</surname></personname></author> + </authorgroup> + <citetitle>Use of <acronym>DNS</acronym> Aliases for + Network Services</citetitle> + <pubdate>October 1997</pubdate> + </biblioentry> + </bibliodiv> + <bibliodiv><info><title>Internationalized Domain Names</title></info> + + <biblioentry> + <abbrev>RFC2825</abbrev> + <authorgroup> + <author><personname><surname>IAB</surname></personname></author> + <author><personname><surname>Daigle</surname><firstname>R.</firstname></personname></author> + </authorgroup> + <citetitle>A Tangled Web: Issues of I18N, Domain Names, + and the Other Internet protocols</citetitle> + <pubdate>May 2000</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC3490</abbrev> + <authorgroup> + <author><personname><surname>Faltstrom</surname><firstname>P.</firstname></personname></author> + <author><personname><surname>Hoffman</surname><firstname>P.</firstname></personname></author> + <author><personname><surname>Costello</surname><firstname>A.</firstname></personname></author> + </authorgroup> + <citetitle>Internationalizing Domain Names in Applications (IDNA)</citetitle> + <pubdate>March 2003</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC3491</abbrev> + <authorgroup> + <author><personname><surname>Hoffman</surname><firstname>P.</firstname></personname></author> + <author><personname><surname>Blanchet</surname><firstname>M.</firstname></personname></author> + </authorgroup> + <citetitle>Nameprep: A Stringprep Profile for Internationalized Domain Names</citetitle> + <pubdate>March 2003</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC3492</abbrev> + <authorgroup> + <author><personname><surname>Costello</surname><firstname>A.</firstname></personname></author> + </authorgroup> + <citetitle>Punycode: A Bootstring encoding of Unicode + for Internationalized Domain Names in + Applications (IDNA)</citetitle> + <pubdate>March 2003</pubdate> + </biblioentry> + </bibliodiv> + <bibliodiv><info><title>Other <acronym>DNS</acronym>-related RFCs</title></info> + + <note> + <para> + Note: the following list of RFCs, although + <acronym>DNS</acronym>-related, are not + concerned with implementing software. + </para> + </note> + <biblioentry> + <abbrev>RFC1464</abbrev> + <author><personname><surname>Rosenbaum</surname><firstname>R.</firstname></personname></author> + <citetitle>Using the Domain Name System To Store Arbitrary String + Attributes</citetitle> + <pubdate>May 1993</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC1713</abbrev> + <author><personname><surname>Romao</surname><firstname>A.</firstname></personname></author> + <citetitle>Tools for <acronym>DNS</acronym> Debugging</citetitle> + <pubdate>November 1994</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC1794</abbrev> + <author><personname><surname>Brisco</surname><firstname>T.</firstname></personname></author> + <citetitle><acronym>DNS</acronym> Support for Load + Balancing</citetitle> + <pubdate>April 1995</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2240</abbrev> + <author><personname><surname>Vaughan</surname><firstname>O.</firstname></personname></author> + <citetitle>A Legal Basis for Domain Name Allocation</citetitle> + <pubdate>November 1997</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2345</abbrev> + <authorgroup> + <author><personname><surname>Klensin</surname><firstname>J.</firstname></personname></author> + <author><personname><firstname>T.</firstname><surname>Wolf</surname></personname></author> + <author><personname><firstname>G.</firstname><surname>Oglesby</surname></personname></author> + </authorgroup> + <citetitle>Domain Names and Company Name Retrieval</citetitle> + <pubdate>May 1998</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2352</abbrev> + <author><personname><surname>Vaughan</surname><firstname>O.</firstname></personname></author> + <citetitle>A Convention For Using Legal Names as Domain Names</citetitle> + <pubdate>May 1998</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC3071</abbrev> + <authorgroup> + <author><personname><surname>Klensin</surname><firstname>J.</firstname></personname></author> + </authorgroup> + <citetitle>Reflections on the DNS, RFC 1591, and Categories of Domains</citetitle> + <pubdate>February 2001</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC3258</abbrev> + <authorgroup> + <author><personname><surname>Hardie</surname><firstname>T.</firstname></personname></author> + </authorgroup> + <citetitle>Distributing Authoritative Name Servers via + Shared Unicast Addresses</citetitle> + <pubdate>April 2002</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC3901</abbrev> + <authorgroup> + <author><personname><surname>Durand</surname><firstname>A.</firstname></personname></author> + <author><personname><firstname>J.</firstname><surname>Ihren</surname></personname></author> + </authorgroup> + <citetitle>DNS IPv6 Transport Operational Guidelines</citetitle> + <pubdate>September 2004</pubdate> + </biblioentry> + </bibliodiv> + <bibliodiv><info><title>Obsolete and Unimplemented Experimental RFC</title></info> + + <biblioentry> + <abbrev>RFC1712</abbrev> + <authorgroup> + <author><personname><surname>Farrell</surname><firstname>C.</firstname></personname></author> + <author><personname><firstname>M.</firstname><surname>Schulze</surname></personname></author> + <author><personname><firstname>S.</firstname><surname>Pleitner</surname></personname></author> + <author><personname><firstname>D.</firstname><surname>Baldoni</surname></personname></author> + </authorgroup> + <citetitle><acronym>DNS</acronym> Encoding of Geographical + Location</citetitle> + <pubdate>November 1994</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2673</abbrev> + <authorgroup> + <author><personname><surname>Crawford</surname><firstname>M.</firstname></personname></author> + </authorgroup> + <citetitle>Binary Labels in the Domain Name System</citetitle> + <pubdate>August 1999</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2874</abbrev> + <authorgroup> + <author><personname><surname>Crawford</surname><firstname>M.</firstname></personname></author> + <author><personname><surname>Huitema</surname><firstname>C.</firstname></personname></author> + </authorgroup> + <citetitle>DNS Extensions to Support IPv6 Address Aggregation + and Renumbering</citetitle> + <pubdate>July 2000</pubdate> + </biblioentry> + </bibliodiv> + <bibliodiv><info><title>Obsoleted DNS Security RFCs</title></info> + + <note> + <para> + Most of these have been consolidated into RFC4033, + RFC4034 and RFC4035 which collectively describe DNSSECbis. + </para> + </note> + <biblioentry> + <abbrev>RFC2065</abbrev> + <authorgroup> + <author><personname><surname>Eastlake</surname><lineage>3rd</lineage><firstname>D.</firstname></personname></author> + <author><personname><firstname>C.</firstname><surname>Kaufman</surname></personname></author> + </authorgroup> + <citetitle>Domain Name System Security Extensions</citetitle> + <pubdate>January 1997</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2137</abbrev> + <author><personname><surname>Eastlake</surname><lineage>3rd</lineage><firstname>D.</firstname></personname></author> + <citetitle>Secure Domain Name System Dynamic Update</citetitle> + <pubdate>April 1997</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC2535</abbrev> + <authorgroup> + <author><personname><surname>Eastlake</surname><lineage>3rd</lineage><firstname>D.</firstname></personname></author> + </authorgroup> + <citetitle>Domain Name System Security Extensions</citetitle> + <pubdate>March 1999</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC3008</abbrev> + <authorgroup> + <author><personname><surname>Wellington</surname><firstname>B.</firstname></personname></author> + </authorgroup> + <citetitle>Domain Name System Security (DNSSEC) + Signing Authority</citetitle> + <pubdate>November 2000</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC3090</abbrev> + <authorgroup> + <author><personname><surname>Lewis</surname><firstname>E.</firstname></personname></author> + </authorgroup> + <citetitle>DNS Security Extension Clarification on Zone Status</citetitle> + <pubdate>March 2001</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC3445</abbrev> + <authorgroup> + <author><personname><surname>Massey</surname><firstname>D.</firstname></personname></author> + <author><personname><surname>Rose</surname><firstname>S.</firstname></personname></author> + </authorgroup> + <citetitle>Limiting the Scope of the KEY Resource Record (RR)</citetitle> + <pubdate>December 2002</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC3655</abbrev> + <authorgroup> + <author><personname><surname>Wellington</surname><firstname>B.</firstname></personname></author> + <author><personname><surname>Gudmundsson</surname><firstname>O.</firstname></personname></author> + </authorgroup> + <citetitle>Redefinition of DNS Authenticated Data (AD) bit</citetitle> + <pubdate>November 2003</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC3658</abbrev> + <authorgroup> + <author><personname><surname>Gudmundsson</surname><firstname>O.</firstname></personname></author> + </authorgroup> + <citetitle>Delegation Signer (DS) Resource Record (RR)</citetitle> + <pubdate>December 2003</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC3755</abbrev> + <authorgroup> + <author><personname><surname>Weiler</surname><firstname>S.</firstname></personname></author> + </authorgroup> + <citetitle>Legacy Resolver Compatibility for Delegation Signer (DS)</citetitle> + <pubdate>May 2004</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC3757</abbrev> + <authorgroup> + <author><personname><surname>Kolkman</surname><firstname>O.</firstname></personname></author> + <author><personname><surname>Schlyter</surname><firstname>J.</firstname></personname></author> + <author><personname><surname>Lewis</surname><firstname>E.</firstname></personname></author> + </authorgroup> + <citetitle>Domain Name System KEY (DNSKEY) Resource Record + (RR) Secure Entry Point (SEP) Flag</citetitle> + <pubdate>April 2004</pubdate> + </biblioentry> + <biblioentry> + <abbrev>RFC3845</abbrev> + <authorgroup> + <author><personname><surname>Schlyter</surname><firstname>J.</firstname></personname></author> + </authorgroup> + <citetitle>DNS Security (DNSSEC) NextSECure (NSEC) RDATA Format</citetitle> + <pubdate>August 2004</pubdate> + </biblioentry> + </bibliodiv> + </bibliography> + </section> + <section xml:id="internet_drafts"><info><title>Internet Drafts</title></info> + + <para> + Internet Drafts (IDs) are rough-draft working documents of + the Internet Engineering Task Force. They are, in essence, RFCs + in the preliminary stages of development. Implementors are + cautioned not + to regard IDs as archival, and they should not be quoted or cited + in any formal documents unless accompanied by the disclaimer that + they are "works in progress." IDs have a lifespan of six months + after which they are deleted unless updated by their authors. + </para> + </section> + <section xml:id="more_about_bind"><info><title>Other Documents About <acronym>BIND</acronym></title></info> + + <para/> + <bibliography> + <biblioentry> + <authorgroup> + <author><personname><surname>Albitz</surname><firstname>Paul</firstname></personname></author> + <author><personname><firstname>Cricket</firstname><surname>Liu</surname></personname></author> + </authorgroup> + <citetitle><acronym>DNS</acronym> and <acronym>BIND</acronym></citetitle> + <copyright> + <year>1998</year> + <holder>Sebastopol, CA: O'Reilly and Associates</holder> + </copyright> + </biblioentry> + </bibliography> + </section> + </section> + </appendix> + + <appendix xml:id="Bv9ARM.ch12"><info><title>BIND 9 DNS Library Support</title></info> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="libdns.xml"/> + </appendix> + + <reference xml:id="Bv9ARM.ch13"><info><title>Manual pages</title></info> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/dig/dig.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/tools/mdig.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/dig/host.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/delv/delv.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/dig/nslookup.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/python/dnssec-checkds.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/python/dnssec-coverage.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/dnssec/dnssec-dsfromkey.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/dnssec/dnssec-importkey.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/dnssec/dnssec-keyfromlabel.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/dnssec/dnssec-keygen.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/python/dnssec-keymgr.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/dnssec/dnssec-revoke.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/dnssec/dnssec-settime.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/dnssec/dnssec-signzone.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/dnssec/dnssec-verify.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/named/lwresd.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/named/named.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/named/named.conf.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/check/named-checkconf.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/check/named-checkzone.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/tools/named-journalprint.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/tools/named-nzd2nzf.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/tools/named-rrchecker.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/nsupdate/nsupdate.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/rndc/rndc.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/rndc/rndc.conf.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/confgen/rndc-confgen.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/confgen/ddns-confgen.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/tools/arpaname.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/tools/dnstap-read.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/tools/genrandom.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/tools/isc-hmac-fixup.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/tools/nsec3hash.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/pkcs11/pkcs11-destroy.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/pkcs11/pkcs11-list.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/pkcs11/pkcs11-keygen.docbook"/> + <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/pkcs11/pkcs11-tokens.docbook"/> + </reference> + + </book> |