Kea 1.9.4, January 27th 2021, Release Notes
Welcome to Kea 1.9.4, the fifth monthly release of the 1.9 development branch. As with any other development release, use this with caution: development releases are not recommended for production use.
This release adds new features, improves existing features, clarifies documentation and fixes a few bugs. The most notable changes introduced in this version are:
Experiments with TLS support. Kea has never supported TLS, so we have always recommended that more security-conscious deployments set up a reverse HTTPS proxy to secure access. This is inconvenient and can introduce additional problems. We finally got the necessary resources (and courage) to tackle the problem of implementing native TLS support in Kea. We did several experiments with the Boost.SSL library, which provides a nice C++/ASIO abstraction over the OpenSSL layer. We now have a working proof of concept (PoC). The code for the PoC is not included in this release as it is not yet production quality, but you can find it in our open GitLab repo. Adding native TLS support is a fairly big project and will take more than one monthly development cycle to complete. The plan is to turn this PoC into production-quality code in the coming releases. Stay tuned! #1619 (closed).
Cache threshold. The renew-timer governs when the devices are supposed to renew their leases. Clients sometimes renew earlier than specified, either because they are ignoring the timer or because they are broken. Frequent early renewals put an extra burden on the server, which has to write updated leases, even though they may have been already renewed seconds earlier. The
cache-threshold (expressed as a percentage) and
cache-max-age (expressed in seconds) parameters help reduce that extra burden on Kea. Kea still responds to the client but merely resends the existing lease lifetime, thus eliminating the need to update the lease database. Cache threshold is a popular feature of ISC DHCP that so far was missing in Kea. The implementation is considered experimental, as we were unable to test it properly by release time. If you're willing to test it, please do report your findings. #1418 (closed)
HA improvement: responsive when recovering from communication failure. The failover procedure in the Kea High Availability library has been improved by introducing a new communication-recovery state. In this state, the load balancing servers remain responsive to DHCP queries when the communication between them is interrupted. The new feature is controlled using the
delayed-updates-limit configuration parameter. #1402 (closed)
HA improvement: dhcp-enable/dhcp-disable upgrades. The DHCP service can be independently enabled or disabled by a user command, by the database connection mechanics, or by the HA library. The DHCP service is disabled when any of those originators disable the service, and it is enabled when all those that previously disabled the service enable it. The
dhcp-disable commands accept an "origin" parameter with valid values of "user," which is the default and indicates a user-generated command, and "ha-partner," which is used internally by the HA library. #1601 (closed)
Small performance improvement in host backend. The host retrieval algorithm has been optimized slightly when retrieving host data from a database: in certain situations, a single query can retrieve multiple reservations. This should improve performance a bit, especially in cases with shared networks and many reservations. #1458 (closed)
Documentation updates. Vendor option examples (options 43 and 125) were added. We also detected several oddities in the option handling, so we plan to add more code fixes and examples in the near future. #1546 (closed) The Administrator Reference Manual (ARM) has been updated to clarify that the lease sanitizer fixes lease records in memory only. Kea only reads stored lease files when starting. #1618 (closed) The section about running Kea as a non-root user has been corrected. #1629 (closed) The example in Section 8.2.12 has been corrected by removing unbalanced parentheses. #1589 (closed) In some cases, Kea does not adhere to RFC standards. The new ARM section dedicated to RFC conformance exceptions mentions two such cases and explains why they exist. Usually, the practical aspects of supporting real-life non-conformant devices outweigh the compliance benefits. The two documented exceptions are: 1) a DECLINE packet with a missing mandatory "server id" option is handled #1615 (closed), and 2) on REQUEST, for a packet with no
requested IP address Kea should respond with NAK. #1608 (closed)
Build improvements. Hammer, our build automation tool, has been extended with support for recently released Fedora 33 and Ubuntu 20.10 systems. This is the first step towards building packages. #1527 (closed), #1528 (closed) The Perfdhcp build system was overly strict. #1637 (closed) Hammer exception handling was improved. It now handles the scenario in which required tools are missing in a gentler way. #1512 (closed)
Bug fixes. A handful of bugs were fixed in this release. When using the configuration backend, the server converts the old
reservation-mode global parameter internally to new reservation flags. The new flags are listed when issuing the
config-get command. #1598 (closed) Kea previously did not handle sub-options with option code 125 well, incorrectly assuming that 125 was always a vendor option. That is now fixed. If you previously experienced problems with Kea misinterpreting sub-options, your problem may have been fixed as well. #1585 (closed) The Kea-LFC (lease file cleanup) tool now processes all lines, even if the last trailing blank line is missing. #1603 (closed)
Test improvements. We continue our efforts to improve testing capabilities. Investments in testing infrastructure make the code more stable and more maintainable in the long term. Unit tests for HA running with thread sanitizer (#1627 (closed)), lfc timer, and shell tests were improved. #1630 (closed) A tricky off-by-one error was fixed in HA failover tests. #1578 (closed) The shell tests now report their results in an XML file, similar to Google tests. #437 (closed) A unit test failure on FreeBSD 12.0 is now fixed. #673 (closed) One Cassandra test (cql_update_hosts) has been fixed. #1616 (closed) Jenkins, our testing and build farm, did not report crashes under some circumstances. This is now fixed. #1519 (closed)
Developer tools. Our team also spent some time improving our processes. Code formatting is now automated using
clang-format. #1455 (closed) The kea-msg-compiler tool no longer adds dates to generated files, which will reduce commits in Kea's git history. #1511 (closed) We added a script to check for duplicate includes, which are mostly harmless but which slow down the compilation a bit. #1602 (closed) A new section about best practices for maintaining and developing shell scripts was added to the Developer's Guide. #1610 (closed)
This release introduces one incompatible change:
config-getcommand now returns the reservation mode using the new syntax. This affects only people who implemented specific code that relies on the now obsolete
reservation-modeas returned by Kea. The parameter is deprecated, but is still supported when setting the config or reading the configuration from a file.
For details on known issues, visit:
And the list of issues marked as bug:
The Kea project has a significant production deployment base with users who are looking for stability, rather than a constant stream of new "bleeding-edge" features. At the same time, we want to continue developing the software and add some new powerful, but difficult-to-implement, features. To meet both of these requirements we have both Stable and Development branches.
Stable releases are what you would expect: stable, released infrequently, without new features or significant changes, very well-tested. These can be identified by an even-numbered minor version number. The current stable releases are 1.8.2. The older stable version of 1.6.3 is also available. If we discover important bugs that require fixing, we may release additional maintenance versions on the 1.8 branch, but that will be determined on a case-by-case basis. The next major stable version will be 2.0.0.
Development releases can be easily identified by an odd minor version number: for example, 1.9.0 is a development release. Subsequent releases on the same minor release branch get numbered with 1.9.1, 1.9.2, and so on.
Our goal is to make the development release available on the last Wednesday of each month. There may be exceptions (such as during holidays), but that's the general plan.
We encourage users to test the development releases and report back their findings.
For more details on the plan, see ISC's Software Support Policy at:
Kea is a DHCP implementation developed by Internet Systems Consortium, Inc. that features fully functional DHCPv4 and DHCPv6 servers, a dynamic DNS update daemon, a Control Agent (CA) that provides a REST API to control the DHCP and DNS update servers, an example shell client to connect to the CA, a daemon that is able to retrieve YANG configuration and updates from Sysrepo, and a DHCP performance-measurement tool. Both DHCP servers support server discovery, address assignment, renewal, rebinding, release, decline, information request, DNS updates, client classification, and host reservations. The DHCPv6 server also supports prefix delegation. Lease information is stored in a CSV file by default; it can optionally be stored in a MySQL, PostgreSQL, or Cassandra database instead. Host reservations can be stored in a configuration file, or in a MySQL, PostgreSQL, or Cassandra database. They can also be retrieved from a RADIUS server, although this functionality is somewhat limited. Kea DHCPv4 and DHCPv6 daemons provide support for YANG models, which are stored in a Sysrepo datastore and can be configured via the NETCONF protocol.
This text references issue numbers. For more details, visit the Kea GitLab page at:
This version of Kea is released under the Mozilla Public License, version 2.0.
The premium and subscriber-only hooks libraries are provided in source code form, under the terms of an End User License Agreement (you will get the source code that you can modify freely, but you are not permitted to redistribute it).
Pre-built ISC packages for current versions of the most popular Linux operating systems are available at:
The Kea source and PGP signature for this release may be downloaded from:
The signature was generated with the ISC code-signing key which is available at:
ISC provides detailed documentation, including installation instructions and usage tutorials, in the Kea Administrator Reference Manual. Documentation is included with the installation, at:
- or via https://kb.isc.org/docs/kea-administrator-reference-manual in HTML, plain text, or PDF formats
ISC maintains a public open source code tree, a wiki, an issue tracking system, milestone planning, and a roadmap at:
We ask users of this software to please let us know how it worked for you and what operating system you tested on. Feel free to share your feedback on the Kea Users mailing list at:
We would also like to hear whether the documentation is adequate and accurate. Please open tickets in the Kea GitLab project for bugs, documentation omissions and errors, and enhancement requests. We want to hear from you even if everything worked.
Professional support for Kea is available from ISC. We encourage all professional users to consider this option; Kea development and maintenance are funded with support subscriptions. For more information on ISC's Kea and DHCP software support see:
Free best-effort support is provided by our user community via a mailing list. Information on all public email lists is available at:
If you have any comments or questions about working with Kea, please share them to the Kea Users List:
Bugs and feature requests may be submitted via GitLab at:
The following summarizes changes since the previous release of 1.9.3:
1860. [build] razvan Library version numbers bumped for Kea 1.9.4 development version. (Gitlab #1666) 1859. [doc] wlodek Added example files with configured Vendor Specific Information option (code 43) and Vendor-Identifying Vendor-specific Information option (code 125) with several suboptions each. (Gitlab #1546) 1858. [bug] razvan The DHCP service can be independently enabled or disabled by the user command, by the database connection mechanics or by the HA library. The DHCP service is disabled when any of those originators disables the service, and it is enabled when all those who previously disabled the service enable it. The 'dhcp-enable' and 'dhcp-disable' commands accept 'origin' parameter with valid values of 'user' (which is the default) indicating a user generated command and 'ha-partner' which is used internally by the HA library. (Gitlab #1601) 1857. [build] andrei Code format styles meant to be as close as possible to the recommended coding guidelines are now included with the Kea source repository in the form of .clang-format and .uncrustify.cfg. The clang-format.sh and uncrustify.sh scripts in the tools directory can be used to apply these styles to chosen files. See coding guidelines in CONTRIBUTING.md for more details. (Gitlab #1455) 1856. [bug] razvan When using the config backend, the server converts the old 'reservation-mode' global parameter internally to new reservation flags. The new flags are listed when issuing the config-get command. (Gitlab #1598) 1855. [func] marcin Improved failover procedure in Kea High Availability library by introducing new communication-recovery state. In this state the load balancing servers remain responsive to DHCP queries when the communication between them is interrupted. The new feature is controlled using the delayed-updates-limit configuration parameter. (Gitlab #1402) 1854. [func, perf] fdupont Implemented "lease caching", a feature similar to ISC DHCP's dhcp-cache-threshold. Lease caching is configured through two new parameters: cache-max-age and cache-threshold, and is supported by both kea-dhcp4 and kea-dhcp6. When enabled, lease-caching allows the server to skip updating lease storage, when a client is requesting it's own pre-existing lease whose age falls under the cache threshold and for which there are no substantive changes to lease values such as the hostname. (Gitlab #1418) 1853. [func] fdupont Populated the space field of option definitions. This solved reported bugs where a specific standard option processing was applied to an option from another space but sharing the same code. In particular, this fixes the problem reported with vendor suboption 125. (Gitlab #1585) 1852. [bug] razvan Corrected the value of unacked-clients-left returned in response to the status-get command and the corresponding log messages. The previously returned value was too low by 1. (Gitlab #1578) 1851. [func] fdupont Removed methods fetching leases by both client identifier and hardware addresses from the API. (Gitlab #1540) 1850. [build] andrei Add two scripts to help with code aesthetics, insight on how Kea is built or minor build optimizations: * ./tools/check-for-duplicate-includes.sh: warns you if there is a source file that includes the same header twice. While this wouldn't normally result in any errors, it is an unusual practice. If you feel that a header should be included twice in a file, add the file under "# Exceptions:" in the script. * ./tools/print-generated-files.sh: prints all the files that are generated which may or may not be part of the repository. These consist of messages, parser files, and "built sources" (as called in Makefile.am files). (Gitlab #1602) 1849. [doc] tomek Two known DHCPv4 RFC violations are now documented in the ARM. They are both cases where Kea deliberately deviates from the RFC to accommodate some common broken-client behaviors. (Gitlab #1608, #1615) 1848. [bug] razvan The cql upgrade script from schema v3.0 to v4.0 was broken in Kea-1.9.3 and has been fixed also enabling the unittest. (Gitlab #1616)
Thank you again to everyone who assisted us in making this release possible.
We look forward to receiving your feedback.