Release Notes

Introduction

BIND 9.20 is a stable branch, suitable for production use. This document summarizes significant changes since the last production release on the 9.18 branch.

Supported Platforms

See the Supported Platforms section in the Resource Requirements chapter.

Download

The latest versions of BIND 9 software can always be found at https://www.isc.org/download/. There you will find additional information about each release, and source code.

Known Issues

  • On some platforms, including FreeBSD, named must be run as root to use the rndc control channel on a privileged port (i.e., with a port number less than 1024; this includes the default rndc port, 953). Currently, using the named -u option to switch to an unprivileged user makes rndc unusable. This will be fixed in a future release; in the meantime, mac_portacl can be used as a workaround, as documented in https://kb.isc.org/docs/aa-00621. [GL #4793]

Notes for BIND 9.20.0

Note

This section only lists changes since BIND 9.18.28, the most recent release on the previous stable branch of BIND at the time of the publication of BIND 9.20.0.

New Features

  • The forwarders statement now supports the tls argument, to be used to forward queries to DoT-enabled servers. [GL #3726]

  • named now supports forwarding Dynamic DNS updates through DNS-over-TLS (DoT). [GL #3512]

  • The nsupdate tool now supports DNS-over-TLS (DoT). [GL !6752]

  • The tls block was extended with a new cipher-suites option that allows permitted cipher suites for TLSv1.3 to be set. Please consult the documentation for additional details. [GL #3504]

  • Initial support for the PROXYv2 protocol was added. named can now accept PROXYv2 headers over all currently implemented DNS transports and dig can insert these headers into the queries it sends. Please consult the related documentation (allow-proxy, allow-proxy-on, listen-on, and listen-on-v6 for named, dig +proxy and dig +proxy-plain for dig) for additional details. [GL #4388]

  • The client-side support of the EDNS EXPIRE option has been expanded to include IXFR and AXFR query types. This enhancement enables named to perform AXFR and IXFR queries while incorporating the EDNS EXPIRE option. [GL #4170]

  • A new configuration option require-cookie has been introduced. It specifies whether there should be a DNS COOKIE in the response for a given prefix; if not, named falls back to TCP. This is useful if it is known that a given server supports DNS COOKIE. It can also be used to force all non-DNS COOKIE responses to fall back to TCP. [GL #2295]

  • The check-svcb option has been added to control the checking of additional constraints on SVCB records. This change affects named, named-checkconf, named-checkzone, named-compilezone, and nsupdate. [GL #3576]

  • The new resolver-use-dns64 option enables named to apply dns64 rules to IPv4 server addresses when sending recursive queries, so that resolution can be performed over a NAT64 connection. [GL #608]

  • A new option to dnssec-policy has been added, cdnskey, that allows users to enable or disable the publication of CDNSKEY records. [GL #4050]

  • When using dnssec-policy, it is now possible to configure the digest type to use when CDS records need to be published with cds-digest-types. Also, publication of specific CDNSKEY/CDS records can now be set with dnssec-signzone -G. [GL #3837]

  • Support for multi-signer model 2 (RFC 8901) when using inline-signing was added. [GL #2710]

  • HSM support was added to dnssec-policy. Keys can now be configured with a key-store that allows users to set the directory where key files are stored and to set a PKCS#11 URI string. The latter requires OpenSSL 3 and a valid PKCS#11 provider to be configured for OpenSSL. [GL #1129]

  • A new DNSSEC tool dnssec-ksr has been added to create Key Signing Request (KSR) and Signed Key Response (SKR) files. [GL #1128]

  • dnssec-verify and dnssec-signzone now accept a -J option to specify a journal file to read when loading the zone to be verified or signed. [GL #2486]

  • dnssec-keygen now allows the options -k and -f to be used together. This allows the creation of keys for a given dnssec-policy that match only the KSK (-fK) or ZSK (-fZ) roles. [GL #1128]

  • The response-policy statement was extended with a new argument ede. It enables an RFC 8914 Extended DNS Error (EDE) code of choice to be set for responses which have been modified by a given RPZ. [GL #3410]

  • A new way of configuring the preferred source address when talking to remote servers, such as primaries and parental-agents, has been added: setting the source and/or source-v6 arguments for a given statement is now possible. This new approach is intended to eventually replace statements such as parental-source, parental-source-v6, transfer-source, etc. [GL #3762]

  • The new command-line delv +ns option activates name server mode, to more accurately reproduce the behavior of named when resolving a query. In this mode, delv uses an internal recursive resolver rather than an external server. All messages sent and received during the resolution and validation process are logged. This can be used in place of dig +trace. [GL #3842]

  • The read timeout in rndc can now be specified on the command line using the -t option, allowing commands that take a long time to complete sufficient time to do so. [GL #4046]

  • The statistics channel now includes information about incoming zone transfers that are currently in progress. [GL #3883]

  • Information on incoming zone transfers in the statistics channel now also shows the zones’ “first refresh” flag, which indicates that a zone is not fully ready and that its first ever refresh is pending or is in progress. The number of such zones is now also exposed by the rndc status command. [GL #4241]

  • Added a new statistics variable recursive high-water that reports the maximum number of simultaneous recursive clients BIND has handled while running. [GL #4668]

  • A new command, rndc fetchlimit, prints a list of name server addresses that are currently rate-limited due to fetches-per-server and domain names that are rate-limited due to fetches-per-zone. [GL #665]

  • Queries and responses now emit distinct dnstap entries for DNS-over-TLS (DoT) and DNS-over-HTTPS (DoH), and dnstap-read understands these entries. [GL #4523]

  • dnstap-read can now print long timestamps with millisecond precision. [GL #2360]

  • Support for libsystemd’s sd_notify() function was added, enabling named to report its status to the init system. This allows systemd to wait until named is fully ready before starting other services that depend on name resolution. [GL #1176]

  • Support for User Statically Defined Tracing (USDT) probes has been added. These probes enable fine-grained application tracing and introduce no overhead when they are not enabled. [GL #4041]

Removed Features

  • Support for Red Hat Enterprise Linux version 7 (and clones) has been dropped. A C11-compliant compiler is now required to compile BIND 9. [GL #3729]

  • Compiling with jemalloc versions older than 4.0.0 is no longer supported; those versions do not provide the features required by current BIND 9 releases. [GL #4296]

  • The auto-dnssec configuration statement has been removed. Please use dnssec-policy or manual signing instead. See article how to migrate from auto-dnssec to dnssec-policy.

    The following statements have become obsolete: dnskey-sig-validity, dnssec-dnskey-kskonly, dnssec-update-mode, sig-validity-interval, and update-check-ksk. [GL #3672]

  • Dynamic updates that add and remove DNSKEY and NSEC3PARAM records no longer trigger key rollovers and denial-of-existence operations. This also means that the dnssec-secure-to-insecure option has been obsoleted. [GL #3686]

  • The glue-cache option has been removed. The glue cache feature still works and is now permanently enabled. [GL #2147]

  • Configuring the control channel to use a Unix domain socket has been a fatal error since BIND 9.18. The feature has now been completely removed and named-checkconf now reports it as a configuration error. [GL #4311]

  • The statements setting alternate local addresses for inbound zone transfers (alt-transfer-source, alt-transfer-source-v6, and use-alt-transfer-source) have been removed. [GL #3714]

  • The resolver-nonbackoff-tries and resolver-retry-interval statements have been removed. Using them is now a fatal error. [GL #4405]

  • BIND 9 no longer supports non-zero stale-answer-client-timeout values, when the feature is turned on. When using a non-zero value, named now generates a warning log message, and treats the value as 0. [GL #4447]

  • The Differentiated Services Code Point (DSCP) feature has been removed: configuring DSCP values in named.conf is now a configuration error. [GL #3789]

  • The keep-response-order option has been declared obsolete and the functionality has been removed. named expects DNS clients to be fully compliant with RFC 7766. [GL #3140]

  • Zone type delegation-only, and the delegation-only and root-delegation-only statements, have been removed. Using them is a configuration error.

    These statements were created to address the SiteFinder controversy, in which certain top-level domains redirected misspelled queries to other sites instead of returning NXDOMAIN responses. Since top-level domains are now DNSSEC-signed, and DNSSEC validation is active by default, the statements are no longer needed. [GL #3953]

  • The coresize, datasize, files, and stacksize options have been removed. The limits these options set should be enforced externally, either by manual configuration (e.g. using ulimit) or via the process supervisor (e.g. systemd). [GL #3676]

  • Support for using AES as the DNS COOKIE algorithm (cookie-algorithm aes;) has been removed. The only supported DNS COOKIE algorithm is now the current default, SipHash-2-4. [GL #4421]

  • The TKEY Mode 2 (Diffie-Hellman Exchanged Keying Mode) has been removed and using TKEY Mode 2 is now a fatal error. Users are advised to switch to TKEY Mode 3 (GSS-API). [GL #3905]

  • Special-case code that was originally added to allow GSS-TSIG to work around bugs in the Windows 2000 version of Active Directory has now been removed, since Windows 2000 is long past end-of-life. The -o option and the oldgsstsig command to nsupdate have been deprecated, and are now treated as synonyms for -g and gsstsig respectively. [GL #4012]

  • Support for the lock-file statement and the named -X command-line option has been removed. An external process supervisor should be used instead. [GL #4391]

    Alternatively, the flock utility (part of util-linux) can be used on Linux systems to achieve the same effect as lock-file or named -X:

    flock -n -x <directory>/named.lock <path>/named <arguments>

  • The named command-line option -U, which specified the number of UDP dispatches, has been removed. Using it now returns a warning. [GL #1879]

  • The --with-tuning option for configure has been removed. Each of the compile-time settings that required different values based on the “workload” (which were previously affected by the value of the --with-tuning option) has either been removed or changed to a sensible default. [GL #3664]

  • The functions that were in the libbind9 shared library have been moved to the libisc and libisccfg libraries. The now-empty libbind9 has been removed and is no longer installed. [GL #3903]

  • The irs_resconf module has been moved to the libdns shared library. The now-empty libirs library has been removed and is no longer installed. [GL #3904]

Deprecated Features

Features listed in this section still work but are scheduled for eventual removal.

  • The use of the max-zone-ttl option in options and zone blocks has been deprecated; it should now be configured as part of dnssec-policy. A warning is logged if this option is used in options or zone blocks. In a future release, it will become nonoperational. [GL #2918]

  • The sortlist option has been deprecated and will be removed in a future BIND 9.21.x release. Users should not rely on a specific order of resource records in DNS messages. [GL #4593]

  • The fixed value for the rrset-order option and the corresponding configure script option have been deprecated and will be removed in a future BIND 9.21.x release. Users should not rely on a specific order of resource records in DNS messages. [GL #4446]

Feature Changes

  • BIND now depends on liburcu, Userspace RCU, for lock-free data structures. [GL #3934]

  • On Linux, libcap is now a required dependency to help named keep needed privileges. [GL #3583]

  • Compiling BIND 9 now requires at least libuv version 1.34.0 or higher. libuv should be available on all supported platforms either as a native package or as a backport. [GL #3567]

  • Outgoing zone transfers are no longer enabled by default. An explicit allow-transfer ACL must now be set at the zone, view, or options level to enable outgoing transfers. [GL #4728]

  • DNS zones signed using dnssec-policy now automatically detect their parent servers, and BIND queries them to check the content of the DS RRset. This allows DNSSEC key rollovers to safely and automatically proceed when the parent zone is updated with new DNSSEC keys, i.e. using the CDS/CDNSKEY mechanism. This behavior is facilitated by the new checkds feature, which automatically populates parental-agents by resolving the parent NS records. These parent name servers are queried to check the DS RRset during a KSK rollover initiated by dnssec-policy. [GL #3901]

  • The responsiveness of named was improved, when serving as an authoritative DNS server for a delegation-heavy zone(s) shortly after loading such zone(s). [GL #4045]

  • To improve query-processing latency under load, the uninterrupted time spent on resolving long chains of cached domain names has been reduced. [GL #4185]

  • QNAME minimization is now used when looking up the addresses of name servers during the recursive resolution process. [GL #4209]

  • BIND now returns BADCOOKIE for out-of-date or otherwise bad but well-formed DNS server cookies. [GL #4194]

  • The DNS name compression algorithm used in BIND 9 has been revised: it now compresses more thoroughly than before, so responses containing names with many labels might have a smaller encoding than before. [GL #3661]

  • Processing large incremental transfers (IXFR) has been offloaded to a separate work thread so that it does not prevent networking threads from processing regular traffic in the meantime. [GL #4367]

  • Querying the statistics channel no longer blocks DNS communication on the networking event loop level. [GL #4680]

  • The inline-signing zone option is now ignored if there is no dnssec-policy configured for the zone. This means that unsigned zones no longer create redundant signed versions of the zone. [GL #4349]

  • The inline-signing statement can now also be set inside dnssec-policy. The built-in policies default and insecure enable the use of inline-signing. If inline-signing is set at the zone level, it overrides the value set in dnssec-policy. [GL #3677]

  • Following RFC 9276 recommendations, dnssec-policy now only allows an NSEC3 iteration count of 0 for the DNSSEC-signed zones using NSEC3 that the policy manages. [GL #4363]

  • The maximum number of NSEC3 iterations allowed for validation purposes has been lowered from 150 to 50. DNSSEC responses containing NSEC3 records with iteration counts greater than 50 are now treated as insecure. [GL #4363]

  • The dnssec-validation yes option now requires an explicitly configured trust-anchors statement. If using manual trust anchors is not operationally required, then please consider using dnssec-validation auto instead. [GL #4373]

  • named-compilezone no longer performs zone integrity checks by default; this allows faster conversion of a zone file from one format to another. [GL #4364]

    Zone checks can be performed by running named-checkzone separately, or the previous default behavior can be restored by using:

    named-compilezone -i full -k fail -n fail -r warn -m warn -M warn -S warn -T warn -W warn -C check-svcb:fail

  • The red-black tree data structure used in the RBTDB (the default database implementation for cache and zone databases), has been replaced with QP-tries. This is expected to improve performance and scalability, though in the current implementation large zones require roughly 15% more memory than the old red-black tree data structure.

    A side effect of this change is that zone files that are created with masterfile-style relative - for example, the output of dnssec-signzone - will no longer have multiple different $ORIGIN statements. There should be no other changes to server behavior.

    The old RBT-based database still exists for now, and can be used by specifying database rbt in a zone statement in named.conf, or by compiling with configure --with-zonedb=rbt --with-cachedb=rbt. [GL #4411] [GL #4614]

  • Multiple RNDC messages are now processed when sent in a single TCP message.

    ISC would like to thank Dominik Thalhammer for reporting the issue and preparing the initial patch. [GL #4416]

  • The DNSSEC signing data included in zone statistics identified keys only by the key ID; this caused confusion when two keys using different algorithms had the same ID. Zone statistics now identify keys using the algorithm number, followed by “+”, followed by the key ID: for example, 8+54274. [GL #3525]

  • The TTL of the NSEC3PARAM record for every NSEC3-signed zone was previously set to 0. It is now changed to match the SOA MINIMUM value for the given zone. [GL #3570]

  • On startup, named now sets the limit on the number of open files to the maximum allowed by the operating system, instead of trying to set it to “unlimited”. [GL #3676]

  • When an international domain name is not valid according to IDNA2008, dig now tries to convert it according to IDNA2003 rules, or pass it through unchanged, instead of stopping with an error message. The idna2 utility can be used to check IDNA syntax. [GL #3527]

  • The memory statistics have been reduced to a single counter, InUse; Malloced is an alias that holds the same value. The other counters were usable with the old BIND 9 internal memory allocator, but they are unnecessary now that the latter has been removed. [GL #3718]

  • The log message resolver priming query complete has been moved from the INFO log level to the DEBUG(1) log level, to prevent delv from emitting that message when setting up its internal resolver. [GL #3842]

  • Worker threads’ event loops are now managed by a new “loop manager” API, significantly changing the architecture of the task, timer, and networking subsystems for improved performance and code flow. [GL #3508]

  • The code for DNS over TCP and DNS over TLS transports has been replaced with a new, unified transport implementation. [GL #3374]

Bug Fixes

  • When the same notify-source address and port number was configured for multiple destinations and zones, an unresponsive server could tie up the relevant network socket until it timed out; in the meantime, NOTIFY messages for other servers silently failed. named will now retry sending such NOTIFY messages over TCP. Furthermore, NOTIFY failures are now logged at the INFO level. [GL #4001] [GL #4002]

  • DNS compression is no longer applied to the root name (.) if it is repeatedly used in the same RRset. [GL #3423]

  • named could incorrectly return non-truncated, glueless referrals for responses whose size was close to the UDP packet size limit. This has been fixed. [GL #1967]

Known Issues

  • On some platforms, including FreeBSD, named must be run as root to use the rndc control channel on a privileged port (i.e., with a port number less than 1024; this includes the default rndc port, 953). Currently, using the named -u option to switch to an unprivileged user makes rndc unusable. This will be fixed in a future release; in the meantime, mac_portacl can be used as a workaround, as documented in https://kb.isc.org/docs/aa-00621. [GL #4793]

  • See above for a list of all known issues affecting this BIND 9 branch.

License

BIND 9 is open source software licensed under the terms of the Mozilla Public License, version 2.0 (see the COPYING file for the full text).

Those wishing to discuss license compliance may contact ISC at https://www.isc.org/contact/.

End of Life

BIND 9.20 is a stable branch, suitable for production use. After it has been in production use for a while it will be designated as an Extended Support Version (ESV). Until then, the current ESV is BIND 9.18, which will be supported until at least December 2025. See https://kb.isc.org/docs/aa-00896 for details of ISC’s software support policy.

Thank You

Thank you to everyone who assisted us in making this release possible.