f623ab1fb3
The fetch loop detection occured in two places: when `dns_resolver_createfetch()` is invoked (looking up through the parent fetches chain and stops the fetch if a parent fetch is the same qname and qtype) and right after calling `dns_adb_findname()` in the resolver (stops the fetch if the current fetch is the same name from the ADB lookup, and ADB lookup needs to fetch it). Regarding fetch loop detection at the `dns_resulver_createfetch()` entry, there are case where both qname and qtype are similar but the zonecut is different. This will then query different name servers and get different responses. For instance, the following delegation parent-side (both for `foo.example.` and `dnshost.example.`): foo.example. 3600 NS ns.dnshost.example. dnshost.example. 3600 NS ns.dnshost.example. ns.dnshost.example. 3600 A 1.2.3.4 Then the child-side of `dnshost.example.`: dnshost.example. 300 NS ns.dnshost.example. ns.dnshost.example. 300 A 1.2.3.4 Then the child-side of `foo.example.`: foo.example 3600 NS ns.dnshost.example. a.foo.example 300 A 5.6.7.8 Obviously, there is a misconfiguration between the parent-side and the child-side of `dnshost.example` (the mismatch of the TTL), but, this happens... Because the resolver is currently child-centric, the parent-side delegation's glue of `dnshost.example.` will be overriden by the child-side of the delegation. Once both A records will expires, the resolver will attempt to find out the A RRs but will start from the `foo.example.` zonecut, as the delegation itself is still valid. Then the resolver will attempt to resolve `ns.dnshost.example.`, still using the `foo.example.` zonecut, which will immediately trigger another attempt to resolve `ns.foo.example.` (because the A RR is expired). This is, however _not_ a loop, because the second attempt will have `dnshost.example.` zonecut. And this changes everything, because the resolver detects the A name is in-domain, and pass a flag to ADB so `dns_view_find()` won't use the cache. As a result, the zonecut will be `.`, and the hints (root servers) will be queried instead. From that point, they'll return the parent-side delegation, which includes the glue for `ns.dnshost.example/A`, and the resolution can continue. Previously, this wouldn't be possible because a loop would be detected from the second attempt to looking `ns.foo.example/A` and would result in a SERVFAIL. Now, the loop detection is relaxed as the loop is detected if the qname, qtype _and_ zonecut are equals. This commit also changes the way the loop detection post `dns_adb_createfind()` works. From the same example above, there would be two ADB fetches with the same name, but with two different ADB flags (the first one without DNS_ADB_STARTATZONE, the second one with that flag). It means that there will be two fetches out of those two ADB lookups, both legit, and not a loop (i.e. it won't be stuck). To differenciate between a find which has a pending fetch (which could be from another find the current find has been attached to), a new find option `DNS_ADBFIND_STARTEDFETCH` is introduced, which tells that the current has did started a fetch. That way, if a find doesn't have `DNS_ADBFIND_STARTEDFETCH` option but has pending fetches, we know this is a find attached to a similar find so this is a loop. Otherwise, with `DNS_ADBFIND_STARTEDFETCH`, we know that even if there is a pending fetch, this is not a loop as the fetch has just been started |
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| .gitlab/issue_templates | ||
| .reuse/templates | ||
| bin | ||
| ci | ||
| cocci | ||
| contrib | ||
| doc | ||
| fuzz | ||
| lib | ||
| LICENSES | ||
| tests | ||
| util | ||
| .clang-format | ||
| .clang-format.headers | ||
| .dir-locals.el | ||
| .editorconfig | ||
| .git-blame-ignore-revs | ||
| .gitattributes | ||
| .gitchangelog.rc | ||
| .gitignore | ||
| .gitlab-ci.yml | ||
| .mailmap | ||
| .pylintrc | ||
| .readthedocs.yaml | ||
| .tsan-suppress | ||
| .uncrustify.cfg | ||
| AUTHORS | ||
| bind.keys | ||
| ChangeLog | ||
| CODE_OF_CONDUCT.md | ||
| CONTRIBUTING.md | ||
| COPYING | ||
| COPYRIGHT | ||
| dangerfile.py | ||
| dnstap.proto | ||
| gcovr.cfg | ||
| LICENSE | ||
| meson.build | ||
| meson.format | ||
| meson.options | ||
| NEWS | ||
| OPTIONS.md | ||
| README.md | ||
| REUSE.toml | ||
| SECURITY.md | ||
| sonar-project.properties | ||
| suppr-lsan.txt | ||
BIND 9
Contents
- Introduction
- Reporting bugs and getting help
- Contributing to BIND
- Building BIND
- Automated testing
- Documentation
- 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 detailed list of changes made throughout the history of BIND 9, see the changelog.
For up-to-date versions and release notes, see https://www.isc.org/download/.
For information about supported platforms, see the "Supported Platforms" section in the BIND 9 Administrator Reference Manual.
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.
For information about ISC's Security Vulnerability Disclosure Policy and
information about reporting potential security issues, please see
SECURITY.md.
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.
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
For information about building BIND 9, see the "Building BIND 9" section in the BIND 9 Administrator Reference Manual.
Automated testing
A system test suite can be run with pytest bin/tests/system. 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::IP 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 the option -Dcmocka=enabled. Execution of unit tests is done by the
meson's test functionality; run by meson test.
Documentation
The BIND 9 Administrator Reference Manual (ARM) is included with the source
distribution, and in .rst format, in the doc/arm
directory. The HTML version is automatically generated and can
be viewed at https://bind9.readthedocs.io/en/latest/index.html.
The PDF version can be built by running:
meson setup build
ninja -C build arm-pdf
The above requires TeX Live in order to work. The PDF will be written to
build/arm-pdf/latex/Bv9ARM.pdf.
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.
Bug report identifiers
Most notes in the ARM Changelog appendix 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).