171a5b7542
The general logic behind the addition of this new feature works as
folows:
When a client query arrives, the basic path (query.c / ns_query_recurse)
was to create a fetch, waiting for completion in fetch_callback.
With the introduction of stale-answer-client-timeout, a new event of
type DNS_EVENT_TRYSTALE may invoke fetch_callback, whenever stale
answers are enabled and the fetch took longer than
stale-answer-client-timeout to complete.
When an event of type DNS_EVENT_TRYSTALE triggers fetch_callback, we
must ensure that the folowing happens:
1. Setup a new query context with the sole purpose of looking up for
stale RRset only data, for that matters a new flag was added
'DNS_DBFIND_STALEONLY' used in database lookups.
. If a stale RRset is found, mark the original client query as
answered (with a new query attribute named NS_QUERYATTR_ANSWERED),
so when the fetch completion event is received later, we avoid
answering the client twice.
. If a stale RRset is not found, cleanup and wait for the normal
fetch completion event.
2. In ns_query_done, we must change this part:
/*
* If we're recursing then just return; the query will
* resume when recursion ends.
*/
if (RECURSING(qctx->client)) {
return (qctx->result);
}
To this:
if (RECURSING(qctx->client) && !QUERY_STALEONLY(qctx->client)) {
return (qctx->result);
}
Otherwise we would not proceed to answer the client if it happened
that a stale answer was found when looking up for stale only data.
When an event of type DNS_EVENT_FETCHDONE triggers fetch_callback, we
proceed as before, resuming query, updating stats, etc, but a few
exceptions had to be added, most important of which are two:
1. Before answering the client (ns_client_send), check if the query
wasn't already answered before.
2. Before detaching a client, e.g.
isc_nmhandle_detach(&client->reqhandle), ensure that this is the
fetch completion event, and not the one triggered due to
stale-answer-client-timeout, so a correct call would be:
if (!QUERY_STALEONLY(client)) {
isc_nmhandle_detach(&client->reqhandle);
}
Other than these notes, comments were added in code in attempt to make
these updates easier to follow.
|
||
|---|---|---|
| .gitlab/issue_templates | ||
| bin | ||
| cocci | ||
| conftools/perllib/dnsconf | ||
| contrib | ||
| doc | ||
| docutil | ||
| fuzz | ||
| lib | ||
| m4 | ||
| util | ||
| win32utils | ||
| .clang-format | ||
| .clang-format.headers | ||
| .dir-locals.el | ||
| .gitattributes | ||
| .gitignore | ||
| .gitlab-ci.yml | ||
| .lgtm.yml | ||
| .pylintrc | ||
| .uncrustify.cfg | ||
| AUTHORS | ||
| bind.keys | ||
| ChangeLog | ||
| CHANGES | ||
| CODE_OF_CONDUCT.md | ||
| config.h.win32 | ||
| configure.ac | ||
| CONTRIBUTING.md | ||
| COPYING | ||
| COPYRIGHT | ||
| dangerfile.py | ||
| HISTORY.md | ||
| LICENSE | ||
| Makefile.am | ||
| Makefile.docs | ||
| Makefile.tests | ||
| Makefile.top | ||
| NEWS | ||
| OPTIONS.md | ||
| PLATFORMS.md | ||
| README.md | ||
BIND 9
Contents
- Introduction
- Reporting bugs and getting help
- Contributing to BIND
- Building BIND
- macOS
- Dependencies
- Compile-time options
- Automated testing
- Documentation
- Change log
- Acknowledgments
Introduction
BIND (Berkeley Internet Name Domain) is a complete, highly portable implementation of the Domain Name System (DNS) protocol.
The BIND name server, named, can act as an authoritative name
server, recursive resolver, DNS forwarder, or all three simultaneously. It
implements views for split-horizon DNS, automatic DNSSEC zone signing and
key management, catalog zones to facilitate provisioning of zone data
throughout a name server constellation, response policy zones (RPZ) to
protect clients from malicious data, response rate limiting (RRL) and
recursive query limits to reduce distributed denial of service attacks,
and many other advanced DNS features. BIND also includes a suite of
administrative tools, including the dig and delv DNS lookup tools,
nsupdate for dynamic DNS zone updates, rndc for remote name server
administration, and more.
BIND 9 began as a complete rewrite of the BIND architecture that was used in versions 4 and 8. Internet Systems Consortium (https://www.isc.org), a 501(c)(3) US public benefit corporation dedicated to providing software and services in support of the Internet infrastructure, developed BIND 9 and is responsible for its ongoing maintenance and improvement. BIND is open source software licensed under the terms of the Mozilla Public License, version 2.0.
For a summary of features introduced in past major releases of BIND, see the file HISTORY.
For a detailed list of changes made throughout the history of BIND 9, see the file CHANGES. See below for details on the CHANGES file format.
For up-to-date versions and release notes, see https://www.isc.org/download/.
For information about supported platforms, see PLATFORMS.
Reporting bugs and getting help
To report non-security-sensitive bugs or request new features, you may open an issue in the BIND 9 project on the ISC GitLab server at https://gitlab.isc.org/isc-projects/bind9.
Please note that, unless you explicitly mark the newly created issue as
"confidential," it will be publicly readable. Please do not include any
information in bug reports that you consider to be confidential unless
the issue has been marked as such. In particular, if submitting the
contents of your configuration file in a non-confidential issue, it is
advisable to obscure key secrets; this can be done automatically by
using named-checkconf -px.
If you are reporting a bug that is a potential security issue, such as an
assertion failure or other crash in named, please do NOT use GitLab to
report it. Instead, send mail to
security-officer@isc.org using our
OpenPGP key to secure your message. (Information about OpenPGP and links
to our key can be found at
https://www.isc.org/pgpkey.) Please do not
discuss the bug on any public mailing list.
For a general overview of ISC security policies, read the Knowledgebase article at https://kb.isc.org/docs/aa-00861.
Professional support and training for BIND are available from ISC. Contact us at https://www.isc.org/contact for more information.
To join the BIND Users mailing list, or view the archives, visit https://lists.isc.org/mailman/listinfo/bind-users.
If you're planning on making changes to the BIND 9 source code, you may also want to join the BIND Workers mailing list, at https://lists.isc.org/mailman/listinfo/bind-workers.
Contributing to BIND
ISC maintains a public git repository for BIND; details can be found at https://www.isc.org/sourceaccess/.
Information for BIND contributors can be found in the following files:
- General information: CONTRIBUTING.md
- Code of Conduct: CODE_OF_CONDUCT.md
- BIND 9 code style: doc/dev/style.md
- BIND architecture and developer guide: doc/dev/dev.md
Patches for BIND may be submitted as merge requests on the ISC GitLab server.
By default, external contributors do not have the ability to fork BIND on the GitLab server; if you wish to contribute code to BIND, you may request permission to do so. Thereafter, you can create git branches and directly submit requests that they be reviewed and merged.
If you prefer, you may also submit code by opening a
GitLab issue and
including your patch as an attachment, preferably generated by
git format-patch.
Building BIND 9
At a minimum, BIND requires a Unix or Linux system with an ANSI C compiler,
basic POSIX support, and a 64-bit integer type. BIND also requires the
libuv asynchronous I/O library, and a cryptography provider library
such as OpenSSL or a hardware service module supporting PKCS#11. On
Linux, BIND requires the libcap library to set process privileges,
though this requirement can be overridden by disabling capability
support at compile time. See Compile-time options below
for details on other libraries that may be required to support
optional features.
Successful builds have been observed on many versions of Linux and Unix, including RHEL/CentOS, Fedora, Debian, Ubuntu, SLES, openSUSE, Slackware, Alpine, FreeBSD, NetBSD, OpenBSD, macOS, Solaris, OpenIndiana, OmniOS CE, HP-UX, and OpenWRT.
BIND 9 is also available for Windows Server 2012 R2 and higher. See
win32utils/build.txt for details on building for Windows
systems.
To build on a Unix or Linux system, use:
$ autoreconf -fi (if you are building in the git repository)
$ ./configure
$ make
If you're using Emacs, you might find make tags helpful.
Several environment variables, which can be set before running configure,
affect compilation. Significant ones are:
| Variable | Description |
|---|---|
CC |
The C compiler to use. configure tries to figure out the right one for supported systems. |
CFLAGS |
C compiler flags. Defaults to include -g and/or -O2 as supported by the compiler. Please include '-g' if you need to set CFLAGS. |
LDFLAGS |
Linker flags. Defaults to empty string. |
Additional environment variables affecting the build are listed at the
end of the configure help text, which can be obtained by running the
command:
$ ./configure --help
macOS
Building on macOS assumes that the "Command Tools for Xcode" are installed.
These can be downloaded from
https://developer.apple.com/download/more/
or, if you have Xcode already installed, you can run xcode-select --install.
(Note that an Apple ID may be required to access the download page.)
Dependencies
To build BIND you need to have the following packages installed:
libuv
pkg-config / pkgconfig / pkgconf
To build BIND from the git repository, you need the following tools installed:
autoconf (includes autoreconf)
automake
libtool
Compile-time options
To see a full list of configuration options, run configure --help.
For the server to support DNSSEC, you need to build it with crypto support.
To use OpenSSL, you should have OpenSSL 1.0.2e or newer installed. If the
OpenSSL library is installed in a nonstandard location, specify the prefix
using --with-openssl=<PREFIX> on the configure command line. To use a
PKCS#11 hardware service module for cryptographic operations, specify the
path to the PKCS#11 provider library using --with-pkcs11=<PREFIX>, and
configure BIND with --enable-native-pkcs11.
To support the HTTP statistics channel, the server must be linked with at
least one of the following libraries: libxml2
http://xmlsoft.org or json-c
https://github.com/json-c/json-c.
If these are installed at a nonstandard location, then:
- for
libxml2, specify the prefix using--with-libxml2=/prefix. - for
json-c, adjustPKG_CONFIG_PATH.
To support compression on the HTTP statistics channel, the server must be
linked against libzlib. If this is installed in a nonstandard location,
specify the prefix using --with-zlib=/prefix.
To support storing configuration data for runtime-added zones in an LMDB
database, the server must be linked with liblmdb. If this is installed in a
nonstandard location, specify the prefix using with-lmdb=/prefix.
To support MaxMind GeoIP2 location-based ACLs, the server must be linked
with libmaxminddb. This is turned on by default if the library is
found; if the library is installed in a nonstandard location,
specify the prefix using --with-maxminddb=/prefix. GeoIP2 support
can be switched off with --disable-geoip.
For DNSTAP packet logging, you must have installed libfstrm
https://github.com/farsightsec/fstrm
and libprotobuf-c
https://developers.google.com/protocol-buffers,
and BIND must be configured with --enable-dnstap.
Certain compiled-in constants and default settings can be decreased to
values better suited to small machines, e.g. OpenWRT boxes, by specifying
--with-tuning=small on the configure command line. This decreases
memory usage by using smaller structures, but degrades performance.
On Linux, process capabilities are managed in user space using
the libcap library, which can be installed on most Linux systems via
the libcap-dev or libcap-devel package. Process capability support can
also be disabled by configuring with --disable-linux-caps.
On some platforms it is necessary to explicitly request large file support
to handle files bigger than 2GB. This can be done by using
--enable-largefile on the configure command line.
Support for the "fixed" rrset-order option can be enabled or disabled by
specifying --enable-fixed-rrset or --disable-fixed-rrset on the
configure command line. By default, fixed rrset-order is disabled to
reduce memory footprint.
The --enable-querytrace option causes named to log every step of
processing every query. The --enable-singletrace option turns on the
same verbose tracing, but allows an individual query to be separately
traced by setting its query ID to 0. These options should only be enabled
when debugging, because they have a significant negative impact on query
performance.
make install installs named and the various BIND 9 libraries. By
default, installation is into /usr/local, but this can be changed with the
--prefix option when running configure.
You may specify the option --sysconfdir to set the directory where
configuration files like named.conf go by default, and --localstatedir
to set the default parent directory of run/named.pid. --sysconfdir
defaults to $prefix/etc and --localstatedir defaults to $prefix/var.
Automated testing
A system test suite can be run with make check. The system tests require
you to configure a set of virtual IP addresses on your system (this allows
multiple servers to run locally and communicate with each other). These
IP addresses can be configured by running the command
bin/tests/system/ifconfig.sh up as root.
Some tests require Perl and the Net::DNS and/or IO::Socket::INET6 modules,
and are skipped if these are not available. Some tests require Python
and the dnspython module and are skipped if these are not available.
See bin/tests/system/README for further details.
Unit tests are implemented using the CMocka unit testing framework. To build
them, use configure --with-cmocka. Execution of tests is done by the automake
parallel test driver; unit tests are also run by make check.
Documentation
The BIND 9 Administrator Reference Manual (ARM) is included with the source
distribution, and in .rst format, in the doc/arm
directory. HTML and PDF versions are automatically generated and can
be viewed at https://bind9.readthedocs.io/en/latest/index.html.
Man pages for some of the programs in the BIND 9 distribution are also included in the BIND ARM.
Frequently (and not-so-frequently) asked questions and their answers can be found in the ISC Knowledgebase at https://kb.isc.org.
Additional information on various subjects can be found in other
README files throughout the source tree.
Change log
A detailed list of all changes that have been made throughout the development of BIND 9 is included in the file CHANGES, with the most recent changes listed first. Change notes include tags indicating the category of the change that was made; these categories are:
| Category | Description |
|---|---|
| [func] | New feature |
| [bug] | General bug fix |
| [security] | Fix for a significant security flaw |
| [experimental] | Used for new features when the syntax or other aspects of the design are still in flux and may change |
| [port] | Portability enhancement |
| [maint] | Updates to built-in data such as root server addresses and keys |
| [tuning] | Changes to built-in configuration defaults and constants to improve performance |
| [performance] | Other changes to improve server performance |
| [protocol] | Updates to the DNS protocol such as new RR types |
| [test] | Changes to the automatic tests, not affecting server functionality |
| [cleanup] | Minor corrections and refactoring |
| [doc] | Documentation |
| [contrib] | Changes to the contributed tools and libraries in the 'contrib' subdirectory |
| [placeholder] | Used in the main development branch to reserve change numbers for use in other branches, e.g., when fixing a bug that only exists in older releases |
In general, [func] and [experimental] tags only appear in new-feature releases (i.e., those with version numbers ending in zero). Some new functionality may be backported to older releases on a case-by-case basis. All other change types may be applied to all currently supported releases.
Bug report identifiers
Most notes in the CHANGES file include a reference to a bug report or
issue number. Prior to 2018, these were usually of the form [RT #NNN]
and referred to entries in the "bind9-bugs" RT database, which was not open
to the public. More recent entries use the form [GL #NNN] or, less often,
[GL !NNN], which, respectively, refer to issues or merge requests in the
GitLab database. Most of these are publicly readable, unless they include
information which is confidential or security-sensitive.
To look up a GitLab issue by its number, use the URL https://gitlab.isc.org/isc-projects/bind9/issues/NNN. To look up a merge request, use https://gitlab.isc.org/isc-projects/bind9/merge_requests/NNN.
In rare cases, an issue or merge request number may be followed with the letter "P". This indicates that the information is in the private ISC GitLab instance, which is not visible to the public.
Acknowledgments
-
The original development of BIND 9 was underwritten by the following organizations:
Sun Microsystems, Inc. Hewlett Packard Compaq Computer Corporation IBM Process Software Corporation Silicon Graphics, Inc. Network Associates, Inc. U.S. Defense Information Systems Agency USENIX Association Stichting NLnet - NLnet Foundation Nominum, Inc. -
This product includes software developed by the OpenSSL Project for use in the OpenSSL Toolkit. https://www.OpenSSL.org/
-
This product includes cryptographic software written by Eric Young (eay@cryptsoft.com).
-
This product includes software written by Tim Hudson (tjh@cryptsoft.com).