dnsjava

Overview

dnsjava is an implementation of DNS in Java. It supports almost all defined record
types (including the DNSSEC types), and unknown types. It can be used for
queries, zone transfers, and dynamic updates. It includes a cache which can be
used by clients, and an authoritative only server. It supports TSIG
authenticated messages, partial DNSSEC verification, and EDNS0. It is fully
thread safe.

dnsjava was started as an excuse to learn Java. It was useful for testing new
features in BIND without rewriting the C resolver. It was then cleaned up and
extended in order to be used as a testing framework for DNS interoperability
testing. The high level API and caching resolver were added to make it useful
to a wider audience. The authoritative only server was added as proof of
concept.

dnsjava on Github

This repository has been a mirror of the dnsjava project at Sourceforge
since 2014 to maintain the Maven build for publishing to
Maven Central.
As of 2019-05-15, Github is
officially
the new home of dnsjava.

Please use the Github issue tracker
and send - well tested - pull requests. The
dnsjava-users@lists.sourceforge.net
mailing list still exists.

Getting started

Config options

Some settings of dnsjava can be configured via
system properties:

dnsjava.options pairs

The dnsjava.options configuration options can also be set programmatically
through the Options class. Please refer to the Javadoc for details., Key, Type, Default, Explanation, ---, ----, -------, -----------, BINDTTL, Boolean, false, Print TTLs in BIND format, multiline, Boolean, false, Print records in multiline format, noPrintIN, Boolean, false, Don't print the class of a record if it's IN, tsigfudge, Integer, 300, Sets the default TSIG fudge value (in seconds), sig0validity, Integer, 300, Sets the default SIG(0) validity period (in seconds), ### Resolvers
dnsjava comes with several built-in resolvers:

• SimpleResolver: a basic resolver that uses UDP by default and falls back
  to TCP if required.
• ExtendedResolver: a resolver that uses multiple SimpleResolvers to send
  the queries. Can be configured to query the servers in a round-robin order.
  Blacklists a server if it times out.
• DohResolver: a very basic DNS over HTTP resolver, e.g. to use
  https://dns.google/query.

The project dnssecjava has a
resolver that validates responses with DNSSEC.

Migrating from version 2.1.x to v3

dnsjava 3 has significant API changes compared to version 2.1.x and is
neither source nor binary compatible. The most important changes are:

• The minimum supported version is Java 8
• Uses slf4j for logging and thus needs slf4j-api
  on the classpath
• The command line tools were moved to the org.xbill.DNS.tools
  package
• On Windows, JNA should be
  on the classpath for the search path
• The Resolver API for custom resolvers has changed to use
  CompletionStage<Message> for asynchronous resolving. The built-in
  resolvers are now fully non-blocking and do not start a thread per
  query anymore.
• Many methods return a List<T> instead of an array. Ideally, use a
  for-each loop. If this isn't possible, call size() instead of
  using length:
  • Cache#findAnyRecords
  • Cache#findRecords
  • Lookup#getDefaultSearchPath
  • Message#getSectionRRsets
  • SetResponse#answers
  • ResolverConfig
• RRset returns a List instead of an Iterator. Ideally, modify your
  code to use a for-each loop. If this is not possible, create an iterator
  on the returned list:
  • RRset#rrs
  • RRset#sigs
• Methods using java.util.Date are deprecated. Use the new versions with
  java.time.Instant or java.time.Duration instead
• The type hierarchy of SMIMEARecord changed, it now inherits from
  TLSARecord and constants are shared
• Records are no longer marked as Serializable. Use the RFC defined
  serialization formats:
  • toString(), rrToString() <-> fromString()
  • toWire() <-> fromWire(), newRecord()
• Message and Header properly supported clone()

Replacing the standard Java DNS functionality

Java versions from 1.4 to 8 can load DNS service providers at runtime. The
functionality was removed in JDK 9,
a replacement is requested,
but so far has not been implemented.

To load the dnsjava service provider, build dnsjava on JDK 8 and set the system property:

sun.net.spi.nameservice.provider.1=dns,dnsjava

This instructs the JVM to use the dnsjava service provide for DNS at the
highest priority.

Build

Run mvn package from the toplevel directory to build dnsjava. JDK 8
or higher is required.

Testing dnsjava

Matt Rutherford contributed a number of unit
tests, which are in the tests subdirectory. The hierarchy under tests
mirrors the org.xbill.DNS classes. To run the unit tests, execute
mvn test.

Limitations

There's no standard way to determine what the local nameserver or DNS search
path is at runtime from within the JVM. dnsjava attempts several methods
until one succeeds.

• The properties dns.server and dns.search (comma delimited lists) are
  checked. The servers can either be IP addresses or hostnames (which are
  resolved using Java's built in DNS support).
• On Unix/Solaris, /etc/resolv.conf is parsed.
• On Windows, if JNA is available
  on the classpath, the GetAdaptersAddresses API is used.
• On Android, depending on the SDK level, either the properties net.dns[1234]
  or the ConnectivityManager is used (requires initialization).
• The sun.net.dns.ResolverConfiguration class is queried if enabled.
• If available and no servers have been found yet,
  JNDI-DNS is used.
• As a last resort, localhost is used as the nameserver, and the search
  path is empty.

Additional documentation

Javadoc documentation can be built with mvn javadoc:javadoc or viewed online
at javadoc.io. See the
examples for some basic usage information.

License

dnsjava is placed under the BSD license. Several files are also under
additional licenses; see the individual files for details.

Authors

• Brian Wellington (@bwelling), March 12, 2004
• Various contributors, see Changelog
• Ingo Bauersachs (@ibauersachs), current maintainer

Final notes

• Thanks to Network Associates, Inc. for sponsoring some of the original
  dnsjava work in 1999-2000.
• Thanks to Nominum, Inc. for sponsoring some work on dnsjava from 2000 through 2017.