UNBOUND.CONF(5)

📦

version 15.1 · 2 versions

15.1 · freebsd 15.1 (latest)
14.5 · freebsd 14.5

💖 unbound.conf(5) 💖

Bestie, welcome to the UNBOUND.CONF(5) manual page — this is the config-file moment for Local-unbound 1.25.1. Yes, the whole page is about one file, and it's honestly iconic. 🎀

✨ NAME ✨

unbound.conf — Local-unbound 1.25.1 configuration file.

🎀 SYNOPSIS 🎀

unbound.conf

That's it. That's the synopsis. The file name is the main character. 💅

🦋 DESCRIPTION 🦋

unbound.conf is used to configure local-unbound(8). No cap — this is the file that tells the daemon how to act. 💖

Before you actually use it, local-unbound-checkconf(8) can be used to check unbound.conf prior to usage. Think of it as the pre-game vibe check for your config. ✨

🌸 FILE FORMAT 🌸

Okay so, the file format is pretty chill:

Whitespace is used to separate keywords.
Whitespace indentation is insignificant, but it's still recommended for visual clarity.
Comments start with # and last to the end of line.
Empty lines are ignored, as is whitespace at the beginning of a line.

Attribute keywords end with a colon (:) and they are either options or section clauses (group options together).

The configuration file is logically divided into sections where each section is introduced by a section clause.

💖 EXAMPLE 💖

An example minimal config file is shown below; most settings are the defaults. Copy this to /var/unbound/unbound.conf and start the server with:

$ local-unbound -c /var/unbound/unbound.conf

Stop the server with:

$ kill `cat /var/unbound/unbound.pid`

The source distribution contains an extensive example.conf file with all the options.

# unbound.conf(5) config file for local-unbound(8).
server:
    directory: "/var/unbound"
    username: unbound
    # make sure local-unbound can access entropy from inside the chroot.
    # e.g. on linux the use these commands (on BSD, devfs(8) is used):
    #      mount --bind -n /dev/urandom /var/unbound/dev/urandom
    # and  mount --bind -n /dev/log /var/unbound/dev/log
    chroot: "/var/unbound"
    # logfile: "/var/unbound/unbound.log"  #uncomment to use logfile.
    pidfile: "/var/unbound/unbound.pid"
    # verbosity: 1      # uncomment and increase to get more logging.
    # listen on all interfaces, answer queries from the local subnet.
    interface: 0.0.0.0
    interface: ::0
    access-control: 10.0.0.0/8 allow
    access-control: 2001:db8::/64 allow

This minimal config is giving "just enough to get started" energy. 🌈

🦋 SECTION CLAUSES 🦋

The recognized section clauses are:

server: — Most of the configuration is found in this section.
remote-control: — Configuration for the facility used by local-unbound-control(8).
stub-zone: — Configuration for a zone that redirects to specific authoritative name servers, e.g. for zones not generally available on the greater Internet.
forward-zone: — Configuration for a zone that forwards to specific DNS resolvers.
auth-zone: — Configuration for local authoritative zones.
view: — Overriding a small subset of configuration for incoming requests. Requests are mapped to views with access-control-view and interface-view.
python: — Configuration for the optional python script module.
dynlib: — Configuration for the optional dynlib module that loads dynamic libraries into Unbound.
dnscrypt: — Configuration for the optional DNSCrypt feature.
cachedb: — Configuration for the optional cachedb module that can interface with second level caches, currently Redis or Redis-complatible databases.
dnstap: — Configuration of the optional dnstap logging feature; a flexible, structured binary log format for DNS software.
rpz: — Configuration for Response Policy Zones that allows for DNS filtering. Requires the respip module.

Section clauses can be repeated throughout the file (or included files) to logically group options in one visually cohesive group. This may be particularly useful for the server: clause with its myriad of options.

🌈 INCLUDING FILES 🌈

Files can be included using the include: directive. It can appear anywhere, it accepts a single file name as argument. Processing continues as if the text from the included file was copied into the config file at that point.

If also using chroot, using full path names for the included files works, relative pathnames for the included names work if the directory where the daemon is started equals its chroot/working directory or is specified before the include statement with directory: dir. Wildcards can be used to include multiple files, see glob(7).

For a more structural include option, the include-toplevel: directive can be used. This closes whatever section clause is currently active (if any) and forces the use of section clauses in the included files and right after this directive.

🔥 SERVER OPTIONS 🔥

These options are part of the server: section.

verbosity: <number> — The verbosity level. It's the dial for how much logging you get.
- Level 0 — No verbosity, only errors.
- Level 1 — Gives operational information.
- Level 2 — Gives detailed operational information including short information per query.
- Level 3 — Gives query level information, output per query.
- Level 4 — Gives algorithm level information.
- Level 5 — Logs client identification for cache misses.

The verbosity can also be increased from the command line and during run time via remote control. See local-unbound(8) and local-unbound-control(8) respectively.

Default: 1

statistics-interval: <seconds> — The number of seconds between printing statistics to the log for every thread. Disable with value 0 or "". The histogram statistics are only printed if replies were sent during the statistics interval, requestlist statistics are printed for every interval (but can be 0). This is because the median calculation requires data to be present.

Default: 0 (disabled)

statistics-cumulative: <yes or no> — If enabled, statistics are cumulative since starting Local-unbound, without clearing the statistics counters after logging the statistics.

Default: no

extended-statistics: <yes or no> — If enabled, extended statistics are printed from local-unbound-control(8). The counters are listed in local-unbound-control(8). Keeping track of more statistics takes time.

Default: no

statistics-inhibit-zero: <yes or no> — If enabled, selected extended statistics with a value of 0 are inhibited from printing with local-unbound-control(8). These are query types, query classes, query opcodes, answer rcodes (except NOERROR, FORMERR, SERVFAIL, NXDOMAIN, NOTIMPL, REFUSED) and PRZ actions.

Default: yes

num-threads: <number> — The number of threads to create to serve clients. Use 1 for no threading.

Default: 1

port: <port number> — The port number on which the server responds to queries.

Default: 53

interface: <IP address or interface name[@port]> — Interface to use to connect to the network. This interface is listened to for queries from clients, and answers to clients are given from it. Can be given multiple times to work on several interfaces. If none are given the default is to listen on localhost.

If an interface name is used instead of an IP address, the list of IP addresses on that interface are used. Heads up: the interfaces are not changed on a reload (kill -HUP) but only on restart.

A port number can be specified with @port (without spaces between interface and port number), if not specified the default port (from port) is used.

ip-address: <IP address or interface name[@port]> — Same as interface (for ease of compatibility with nsd.conf(5)).
interface-automatic: <yes or no> — Listen on all addresses on all (current and future) interfaces, detect the source interface on UDP queries and copy them to replies. This is a lot like ip-transparent, but this option services all interfaces whilst with ip-transparent you can select which (future) interfaces Local-unbound provides service on.

🚨 This feature is experimental, and needs support in your OS for particular socket options.

Default: no

interface-automatic-ports: "<string>" — List the port numbers that interface-automatic listens on. If empty, the default port is listened on. The port numbers are separated by spaces in the string.

This can be used to have interface automatic to deal with the interface, and listen on the normal port number, by including it in the list, and also HTTPS or DNS-over-TLS port numbers by putting them in the list as well.

Default: ""

outgoing-interface: <IPv4/IPv6 address or IPv6 netblock> — Interface to use to connect to the network. This interface is used to send queries to authoritative servers and receive their replies. Can be given multiple times to work on several interfaces. If none are given the default (all) is used. You can specify the same interfaces in interface and outgoing-interface lines, the interfaces are then used for both purposes. Outgoing queries are sent via a random outgoing interface to counter spoofing.

If an IPv6 netblock is specified instead of an individual IPv6 address, outgoing UDP queries will use a randomised source address taken from the netblock to counter spoofing. Requires the IPv6 netblock to be routed to the host running Local-unbound, and requires OS support for unprivileged non-local binds (currently only supported on Linux). Several netblocks may be specified with multiple outgoing-interface options, but do not specify both an individual IPv6 address and an IPv6 netblock, or the randomisation will be compromised. Consider combining with prefer-ip6: yes to increase the likelihood of IPv6 nameservers being selected for queries. On Linux you need these two commands to be able to use the freebind socket option to receive traffic for the ip6 netblock:

ip -6 addr add mynetblock/64 dev lo && \
ip -6 route add local mynetblock/64 dev lo

okay we're still deep in options territory, bestie — this is the networking-nerd section and it's honestly giving main character energy 🔥 let's go 🫶

outgoing-range: <number> — how many ports to open. This number of file descriptors can be opened per thread, and it must be at least 1. The default depends on compile options. Bigger numbers need extra resources from the operating system. For performance, a very large value is best — use libevent to make this possible ✨. It should be higher (preferably double) than the value of num-queries-per-thread to account for cases where the request list is full and to avoid file descriptor starvation. Default: 4096 (libevent) / 960 (minievent) / 48 (windows)
outgoing-port-permit: <port number or range> — permits Local-unbound to open this port or range of ports for use to send queries. A larger number of permitted outgoing ports increases resilience against spoofing attempts 💪. Make sure these ports are not needed by other daemons. By default only ports above 1024 that have not been assigned by IANA are used. Give a port number or a range of the form "low-high", without spaces.

The outgoing-port-permit and outgoing-port-avoid statements are processed in the line order of the config file, adding the permitted ports and subtracting the avoided ports from the set of allowed ports. The processing starts with the non-IANA allocated ports above 1024 in the set of allowed ports.

outgoing-port-avoid: <port number or range> — do not permit Local-unbound to open this port or range of ports for use to send queries. Use this to make sure Local-unbound does not grab a port that another daemon needs 🙈. The port is avoided on all outgoing interfaces, both IPv4 and IPv6. By default only ports above 1024 that have not been assigned by IANA are used. Give a port number or a range of the form "low-high", without spaces.
outgoing-num-tcp: <number> — number of outgoing TCP buffers to allocate per thread. If set to 0, or if do-tcp: no is set, no TCP queries to authoritative servers are done. For larger installations, increasing this value is a good idea 👑. Default: 10
incoming-num-tcp: <number> — number of incoming TCP buffers to allocate per thread. If set to 0, or if do-tcp: no is set, no TCP queries from clients are accepted. For larger installations, increasing this value is a good idea 👑. Default: 10
edns-buffer-size: <number> — number of bytes size to advertise as the EDNS reassembly buffer size. This is the value put into datagrams over UDP towards peers. The actual buffer size is determined by msg-buffer-size (both for TCP and UDP), so do not set this higher than that value 🚨. Setting it to 512 bypasses even the most stringent path MTU problems, but it's seen as extreme, since the amount of TCP fallback generated is excessive (probably also for this resolver — consider tuning outgoing-num-tcp). Default: 1232 (DNS Flag Day 2020 recommendation)
max-udp-size: <number> — maximum UDP response size (not applied to TCP response). 65536 disables the UDP response size maximum and uses the choice from the client, always. Suggested values are 512 to 4096. Default: 1232 (same as edns-buffer-size)
stream-wait-size: <number> — number of bytes size maximum to use for waiting stream buffers. A plain number is in bytes; append 'k', 'm' or 'g' for kilobytes, megabytes or gigabytes (1024*1024 bytes in a megabyte). Because TCP and TLS streams queue up multiple results, the amount of memory used for these buffers does not exceed this number — otherwise the responses are dropped 💀. This manages the total memory usage of the server (under heavy use); the number of requests that can be queued up per connection is also limited, with further requests waiting in TCP buffers. Default: 4m
msg-buffer-size: <number> — number of bytes size of the message buffers. The default is 65552 bytes, enough for 64 Kb packets, the maximum DNS message size. No message larger than this can be sent or received 🙅. It can be reduced to use less memory, but some requests for DNS data, such as for huge resource records, will result in a SERVFAIL reply to the client. Default: 65552
msg-cache-size: <number> — number of bytes size of the message cache. A plain number is in bytes; append 'k', 'm' or 'g' for kilobytes, megabytes or gigabytes (1024*1024 bytes in a megabyte). Default: 4m
msg-cache-slabs: <number> — number of slabs in the message cache. Slabs reduce lock contention by threads 🧚. Must be set to a power of 2. Setting it (close) to the number of cpus is a fairly good setting. If left unconfigured, it will be configured automatically to be a power of 2 close to the number of configured threads in multi-threaded environments. Default: (unconfigured)
num-queries-per-thread: <number> — the number of queries that every thread will service simultaneously. If more queries arrive that need servicing, and no queries can be jostled out (see jostle-timeout), then the queries are dropped 💅. This forces the client to resend after a timeout, allowing the server time to work on the existing queries. The default depends on compile options. Default: 2048 (libevent) / 512 (minievent) / 24 (windows)
jostle-timeout: <msec> — timeout used when the server is very busy. Set it to a value that usually results in one roundtrip to the authority servers.

If too many queries arrive, then 50% of the queries are allowed to run to completion, and the other 50% are replaced with the new incoming query if they have already spent more than their allowed time. This protects against denial of service by slow queries or high query rates 🛡️.

The effect is that the qps for long-lasting queries is about:

(num-queries-per-thread / 2) / (average time for such long queries) qps

The qps for short queries can be about:

(num-queries-per-thread / 2) / (jostle-timeout in whole seconds) qps per thread

about (2048/2)*5 = 5120 qps by default.

Default: 200

delay-close: <msec> — extra delay for timeouted UDP ports before they are closed, in msec. This prevents very delayed answer packets from the upstream (recursive) servers from bouncing against closed ports and setting off all sorts of close-port counters — with e.g. 1500 msec. When timeouts happen you need extra sockets; it checks the ID and remote IP of packets, and unwanted packets are added to the unwanted packet counter. Default: 0 (disabled)
udp-connect: <yes or no> — perform connect(2) for UDP sockets, which mitigates ICMP side channel leakage. Default: yes
unknown-server-time-limit: <msec> — the wait time in msec for waiting for an unknown server to reply. Increase this if you're behind a slow satellite link, to e.g. 1128. That would then avoid re-querying every initial query because it times out 🛰️. Default: 376
discard-timeout: <msec> — the wait time in msec where recursion requests are dropped. This is to stop a large number of replies from accumulating 💀. They receive no reply, and the work item continues to recurse. For UDP the replies are dropped; for stream connections the reply is not dropped if the stream connection is still open ready to receive answers. It's nice to be a bit larger than serve-expired-client-timeout if that is enabled. A value of 1900 msec is suggested. The value 0 disables it. Default: 1900
wait-limit: <number> — the number of replies that can wait for recursion, for an IP address. This makes a ratelimit per IP address of waiting replies for recursion. It stops very large amounts of queries waiting to be returned to one destination 🙅. The value 0 disables all wait limits. Default: 1000
wait-limit-cookie: <number> — the number of replies that can wait for recursion, for an IP address that sent the query with a valid DNS Cookie 🍪. Since the cookie already validates the client address, this option lets you override a configured wait-limit value, usually with a higher one, for cookie validated queries. The value 0 disables wait limits for cookie validated queries. Default: 10000
wait-limit-netblock: <netblock> <number> — the wait limit for the netblock. If not given, the wait-limit value is used. The most specific netblock is used to determine the limit. Useful for overriding the default for a specific group or individual server. The value -1 disables wait limits for the netblock. By default the loopback has a wait limit netblock of -1; it is not limited, because it is separated from the rest of the network for spoofed packets. The loopback addresses 127.0.0.0/8 and ::1/128 are default at -1. Default: (none)
wait-limit-cookie-netblock: <netblock> <number> — the wait limit for the netblock, when the query has a DNS Cookie 🍪. If not given, the wait-limit-cookie value is used. The value -1 disables wait limits for the netblock. The loopback addresses 127.0.0.0/8 and ::1/128 are default at -1. Default: (none)
so-rcvbuf: <number> — if not 0, then set the SO_RCVBUF socket option to get more buffer space on UDP port 53 incoming queries. That way short spikes on busy servers don't drop packets (see the counter in netstat -su). Otherwise, this is the number of bytes to ask for — try "4m" on a busy server.

The OS caps it at a maximum. On linux, Local-unbound needs root permission to bypass the limit, or the admin can use sysctl net.core.rmem_max.

On BSD change kern.ipc.maxsockbuf in /etc/sysctl.conf.

On OpenBSD change the header and recompile the kernel.

On Solaris ndd -set /dev/udp udp_max_buf 8388608.

Default: 0 (use system value)

so-sndbuf: <number> — if not 0, then set the SO_SNDBUF socket option to get more buffer space on UDP port 53 outgoing queries. For very busy servers this handles spikes in answer traffic, otherwise:

send: resource temporarily unavailable

…can get logged, and ngl the buffer overrun is also visible by netstat -su. If set to 0 it uses the system value. Specify the number of bytes to ask for, try "8m" on a very busy server. 💅

It needs some space to be able to deal with packets that wait for local address resolution — think ARP and NDP discovery — before they’re sent out, hence it is elevated above the system default by default. ✨

The OS caps it at a maximum, on linux Local-unbound needs root permission to bypass the limit, or the admin can use sysctl net.core.wmem_max. 🫶

On BSD, Solaris changes are similar to so-rcvbuf.

Default: 4m

so-reuseport: <yes or no> — if yes, then open dedicated listening sockets for incoming queries for each thread and try to set the SO_REUSEPORT socket option on each socket. May distribute incoming queries to threads more evenly. On Linux it is supported in kernels >= 3.9. On other systems, FreeBSD, OSX it may also work. You can enable it (on any platform and kernel), it then attempts to open the port and passes the option if it was available at compile time; if that works it is used, if it fails it continues silently (unless verbosity 3) without the option. At extreme load it could be better to turn it off to distribute the queries evenly, reported for Linux systems (4.4.x). Default: yes
ip-transparent: <yes or no> — if yes, then use the IP_TRANSPARENT socket option on sockets where Local-unbound is listening for incoming traffic. Allows you to bind to non-local interfaces. For example, for non-existent IP addresses that are going to exist later on, with host failover configuration. This is a lot like interface-automatic, but that one services all interfaces and with this option you can select which (future) interfaces Local-unbound provides service on. This option needs Local-unbound to be started with root permissions on some systems. The option uses IP_BINDANY on FreeBSD systems and SO_BINDANY on OpenBSD systems. Default: no
ip-freebind: <yes or no> — if yes, then use the IP_FREEBIND socket option on sockets where Local-unbound is listening to incoming traffic. Allows you to bind to IP addresses that are nonlocal or do not exist, like when the network interface or IP address is down. Exists only on Linux, where the similar ip-transparent option is also available. Default: no
ip-dscp: <number> — the value of the Differentiated Services Codepoint (DSCP) in the differentiated services field (DS) of the outgoing IP packet headers. The field replaces the outdated IPv4 Type-Of-Service field and the IPv6 traffic class field. 👑
rrset-cache-size: <number> — number of bytes size of the RRset cache. A plain number is in bytes, append 'k', 'm' or 'g' for kilobytes, megabytes or gigabytes (1024*1024 bytes in a megabyte). Default: 4m
rrset-cache-slabs: <number> — number of slabs in the RRset cache. Slabs reduce lock contention by threads. Must be set to a power of 2. Setting (close) to the number of cpus is a fairly good setting. If left unconfigured, it will be configured automatically to be a power of 2 close to the number of configured threads in multi-threaded environments. Default: (unconfigured)
cache-max-ttl: <seconds> — time to live maximum for RRsets and messages in the cache. When the TTL expires, the cache item has expired. Can be set lower to force the resolver to query for data often, and not trust (very large) TTL values. Downstream clients also see the lower TTL. Default: 86400 (1 day)
cache-min-ttl: <seconds> — time to live minimum for RRsets and messages in the cache. If the minimum kicks in, the data is cached for longer than the domain owner intended, and thus less queries are made to look up the data. Zero makes sure the data in the cache is as the domain owner intended; higher values, especially more than an hour or so, can lead to trouble as the data in the cache does not match up with the actual data any more. 😭 Default: 0 (disabled)
cache-max-negative-ttl: <seconds> — time to live maximum for negative responses; these have a SOA in the authority section that is limited in time. This applies to NXDOMAIN and NODATA answers. Default: 3600
cache-min-negative-ttl: <seconds> — time to live minimum for negative responses; these have a SOA in the authority section that is limited in time. If this is disabled and cache-min-ttl is configured, it will take effect instead. In that case you can set this to 1 to honor the upstream TTL. This applies to NXDOMAIN and NODATA answers. Default: 0 (disabled)
infra-host-ttl: <seconds> — time to live for entries in the host cache. The host cache contains roundtrip timing, lameness and EDNS support information. Default: 900
infra-cache-slabs: <number> — number of slabs in the infrastructure cache. Slabs reduce lock contention by threads. Must be set to a power of 2. Setting (close) to the number of cpus is a fairly good setting. If left unconfigured, it will be configured automatically to be a power of 2 close to the number of configured threads in multi-threaded environments. Default: (unconfigured)
infra-cache-numhosts: <number> — number of hosts for which information is cached. Default: 10000
infra-cache-min-rtt: <msec> — lower limit for dynamic retransmit timeout calculation in infrastructure cache. Increase this value if using forwarders needing more time to do recursive name resolution. Default: 50
infra-cache-max-rtt: <msec> — upper limit for dynamic retransmit timeout calculation in infrastructure cache. Default: 120000 (2 minutes)
infra-keep-probing: <yes or no> — if enabled the server keeps probing hosts that are down, in the one probe at a time regime. Hosts that are down, eg. they did not respond during the one probe at a time period, are marked as down and it may take infra-host-ttl time to get probed again. Default: no
define-tag: "<list of tags>" — define the tags that can be used with local-zone and access-control. Enclose the list between quotes ("") and put spaces between tags. 🎀
do-ip4: <yes or no> — enable or disable whether IPv4 queries are answered or issued. Default: yes
do-ip6: <yes or no> — enable or disable whether IPv6 queries are answered or issued. If disabled, queries are not answered on IPv6, and queries are not sent on IPv6 to the internet nameservers. With this option you can disable the IPv6 transport for sending DNS traffic; it does not impact the contents of the DNS traffic, which may have IPv4 (A) and IPv6 (AAAA) addresses in it. Default: yes
prefer-ip4: <yes or no> — if enabled, prefer IPv4 transport for sending DNS queries to internet nameservers. Useful if the IPv6 netblock the server has, the entire /64 of that is not owned by one operator and the reputation of the netblock /64 is an issue; using IPv4 then uses the IPv4 filters that the upstream servers have. Default: no
prefer-ip6: <yes or no> — if enabled, prefer IPv6 transport for sending DNS queries to internet nameservers. Default: no
do-udp: <yes or no> — enable or disable whether UDP queries are answered or issued. Default: yes
do-tcp: <yes or no> — enable or disable whether TCP queries are answered or issued. Default: yes
tcp-mss: <number> — maximum segment size (MSS) of TCP socket on which the server responds to queries. Value lower than common MSS on Ethernet (1220 for example) will address path MTU problem. Note that not all platform supports socket option to set MSS (TCP_MAXSEG). Default is system default MSS determined by interface MTU and negotiation between server and client. 🦋
outgoing-tcp-mss: <number> — maximum segment size (MSS) of TCP socket for outgoing queries (from Unbound to other servers). Value lower than common MSS on Ethernet (1220 for example) will address path MTU problem. Note that not all platform supports socket option to set MSS (TCP_MAXSEG). Default is system default MSS determined by interface MTU and negotiation between Local-unbound and other servers. ✨
tcp-idle-timeout: <msec> — the period Local-unbound will wait for a query on a TCP connection. If this timeout expires Local-unbound closes the connection. When the number of free incoming TCP buffers falls below 50% of the total number configured, the option value used is progressively reduced, first to 1% of the configured value, then to 0.2% of the configured value if the number of free buffers falls below 35% of the total number configured, and finally to 0 if the number of free buffers falls below 20% of the total number configured. A minimum timeout of 200 milliseconds is observed regardless of the option value used. It will be overridden by edns-tcp-keepalive-timeout if edns-tcp-keepalive is enabled. Default: 30000 (30 seconds)
tcp-reuse-timeout: <msec> — the period Local-unbound will keep TCP persistent connections open to authority servers. Default: 60000 (60 seconds)
max-reuse-tcp-queries: <number> — the maximum number of queries that can be sent on a persistent TCP connection. Default: 200
tcp-auth-query-timeout: <number> — timeout in milliseconds for TCP queries to auth servers. Default: 3000 (3 seconds)
edns-tcp-keepalive: <yes or no> — enable or disable EDNS TCP Keepalive. Default: no
edns-tcp-keepalive-timeout: <msec> — this one overrides tcp-idle-timeout whenever edns-tcp-keepalive is enabled. So if the client supports the EDNS TCP Keepalive option, Local-unbound straight up sends the timeout value over to the client, like "hey bestie close this connection before I time out, mwah 💋".
- Default: 120000 (2 minutes)
sock-queue-timeout: <sec> — ngl UDP queries that have been chilling in the socket buffer for way too long can just get dropped. The time is in seconds, and 3 could be a good value to ignore old queries that the client probably doesn't even want a reply for anymore. This could happen if the host hasn't been able to service the queries for a while — like, Local-unbound isn't running, and then it gets enabled again. It uses timestamp socket options. The socket option is available on the Linux and FreeBSD platforms.
- Default: 0 (disabled)
tcp-upstream: <yes or no> — turn this on/off to decide whether upstream queries use TCP only for transport. Lowkey useful in tunneling scenarios. If set to no you can specify TCP transport only for selected forward or stub zones using forward-tcp-upstream or stub-tcp-upstream respectively.
- Default: no
udp-upstream-without-downstream: <yes or no> — enables UDP upstream even if do-udp: no is set. Super useful for TLS service providers that want no UDP downstream but use UDP to fetch data upstream.
- Default: no (no changes)
tls-upstream: <yes or no> — enables or disables whether the upstream queries use TLS only for transport. Useful in tunneling scenarios. The TLS contains plain DNS in TCP wireformat. The other server must support this (see tls-service-key).

Okay and fr fr on this next bit: if you enable this, also configure a tls-cert-bundle or use tls-win-cert or tls-system-cert to load CA certs, otherwise the connections cannot be authenticated. No cap, they just won't work 🫠

This option enables TLS for all of them, but if you do not set this you can configure TLS specifically for some forward zones with forward-tls-upstream. And also with stub-tls-upstream. If the tls-upstream option is enabled, it is for all the forwards and stubs, where the forward-tls-upstream and stub-tls-upstream options are ignored, as if they had been set to yes.

Default: no

ssl-upstream: <yes or no> — alternate syntax for tls-upstream. If both are present in the config file the last is used. Last one wins, periodt 💅
tls-service-key: <file> — if enabled, the server provides DNS-over-TLS or DNS-over-HTTPS service on the TCP ports marked implicitly or explicitly for these services with tls-port or https-port. The file must contain the private key for the TLS session, the public certificate is in the tls-service-pem file and it must also be specified if tls-service-key is specified.

Here's the tea though ☕ if the key is stored with root permissions or outside of chroot, then a change or enabling or disabling requires a restart (a reload is not enough 🙅). But if the key file (and tls-service-pem file) are accessible, then they are read in on reload, and fast_reload. The server checks the modification time of the file (and the filename) to see if the file has changed for reload. The ports enabled implicitly or explicitly via tls-port and https-port do not provide normal DNS TCP service.

NOTE: Local-unbound needs to be compiled with libnghttp2 in order to provide DNS-over-HTTPS.

Default: "" (disabled)

ssl-service-key: <file> — alternate syntax for tls-service-key.
tls-service-pem: <file> — the public key certificate pem file for the tls service. That's her 🎀
- Default: "" (disabled)
ssl-service-pem: <file> — alternate syntax for tls-service-pem.
tls-port: <number> — the port number on which to provide TCP TLS service. Only interfaces configured with that port number as @number get the TLS service.
- Default: 853
ssl-port: <number> — alternate syntax for tls-port.
tls-cert-bundle: <file> — if null or "", no file is used. Set it to the certificate bundle file, for example /etc/pki/tls/certs/ca-bundle.crt. These certificates are used for authenticating connections made to outside peers. For example auth-zone urls, and also DNS-over-TLS connections. It is read at start up before permission drop and chroot.
- Default: "" (disabled)
ssl-cert-bundle: <file> — alternate syntax for tls-cert-bundle.
tls-win-cert: <yes or no> — adds the system certificates to the cert bundle certificates for authentication. If no cert bundle, it uses only these certificates. On windows this option uses the certificates from the cert store. Use the tls-cert-bundle option on other systems. On other systems, this option enables the system certificates.
- Default: no
tls-system-cert: <yes or no> — this is the same as the tls-win-cert option, under a different name. Because it is not windows specific, bestie 💀
tls-additional-port: <portnr> — list port numbers as tls-additional-port, and when interfaces are defined, eg. with the @port suffix, as this port number, they provide DNS-over-TLS service. Can list multiple, each on a new statement.
tls-session-ticket-keys: <file> — if not "", lists files with 80 bytes of random contents that are used to perform TLS session resumption for clients using the Local-unbound server. These files contain the secret key for the TLS session tickets. The first key is used to encrypt and decrypt TLS session tickets. The other keys are used to decrypt only.

With this you can roll over to new keys, by generating a new first file and allowing decrypt of the old file by listing it after the first file for some time — after the wait, clients are not using the old key any more and the old key can be removed. Obsessed with a clean key rotation ngl 🌸

One way to create the file is:

dd if=/dev/random bs=1 count=80 of=ticket.dat

The first 16 bytes should be different from the old one if you create a second key, that is the name used to identify the key. Then there is 32 bytes random data for an AES key and then 32 bytes random data for the HMAC key.

Default: ""

tls-ciphers: <string with cipher list> — sets the list of ciphers to allow when serving TLS. Use "" for default ciphers.
- Default: ""
tls-ciphersuites: <string with ciphersuites list> — sets the list of ciphersuites to allow when serving TLS. This is for newer TLS 1.3 connections. Use "" for default ciphersuites.
- Default: ""
tls-use-sni: <yes or no> — enable or disable sending the SNI extension on TLS connections.

NOTE: Changing the value requires a restart.

Default: yes

tls-protocols: "<list of protocols>" — specify the allowed TLS protocol versions to use, in no particular order. Possible values are TLSv1.2 and TLSv1.3. Enclose the list of protocols in quotes ("") and put spaces between them.

NOTE: Changing the value requires a restart.

Default: "TLSv1.2 TLSv1.3"

pad-responses: <yes or no> — if enabled, TLS serviced queries that contained an EDNS Padding option will cause responses padded to the closest multiple of the size specified in pad-responses-block-size. Padding is literally the glow-up ✨
- Default: yes
pad-responses-block-size: <number> — the block size with which to pad responses serviced over TLS. Only responses to padded queries will be padded.
- Default: 468
pad-queries: <yes or no> — if enabled, all queries sent over TLS upstreams will be padded to the closest multiple of the size specified in pad-queries-block-size.
- Default: yes
pad-queries-block-size: <number> — the block size with which to pad queries sent over TLS upstreams.
- Default: 128
https-port: <number> — the port number on which to provide DNS-over-HTTPS service. Only interfaces configured with that port number as @number get the HTTPS service.
- Default: 443
http-endpoint: <endpoint string> — the HTTP endpoint to provide DNS-over-HTTPS service on.
- Default: /dns-query
http-max-streams: <number of streams> — number used in the SETTINGS_MAX_CONCURRENT_STREAMS parameter in the HTTP/2 SETTINGS frame for DNS-over-HTTPS connections.
- Default: 100
http-query-buffer-size: <size in bytes> — maximum number of bytes used for all HTTP/2 query buffers combined. These buffers contain (partial) DNS queries waiting for request stream completion. An RST_STREAM frame will be send to streams exceeding this limit. A plain number is in bytes, append k, m or g for kilobytes, megabytes or gigabytes (1024*1024 bytes in a megabyte).
- Default: 4m
http-response-buffer-size: <size in bytes> — maximum number of bytes used for all HTTP/2 response buffers combined. These buffers contain DNS responses waiting to be written back to the clients. An RST_STREAM frame will be send to streams exceeding this limit. A plain number is in bytes, append k, m or g for kilobytes, megabytes or gigabytes (1024*1024 bytes in a megabyte).
- Default: 4m
http-nodelay: <yes or no> — set the TCP_NODELAY socket option on sockets used to provide DNS-over-HTTPS service. Ignored if the option is not available.
- Default: yes
http-notls-downstream: <yes or no> — disable use of TLS for the downstream DNS-over-HTTP connections. Useful for local back end servers.
- Default: no
proxy-protocol-port: <portnr> — list port numbers as proxy-protocol-port, and when interfaces are defined, eg. with the @port suffix, as this port number, they support and expect PROXYv2.

In this case the proxy address will only be used for the network communication and initial ACL (check if the proxy itself is denied/refused by configuration).

The proxied address (if any) will then be used as the true client address and will be used where applicable for logging, ACL, DNSTAP, RPZ and IP ratelimiting. So the real one gets the main character energy 👑

PROXYv2 is supported for UDP and TCP/TLS listening interfaces. 💅

There is no support for PROXYv2 on a DoH, DoQ or DNSCrypt listening interface. Sad but true, bestie. 😭

You can list multiple, each one on a new statement.

quic-port: <number> — the port number where you're serving DNS-over-QUIC 🦋. Only interfaces that were configured with that port number as @number get the QUIC service, okay? The interface then uses QUIC for the UDP traffic on that port number. If you set it to 0, the server does not init QUIC code and QUIC is disabled — it's basically like QUIC isn't in use, except, like, explicitly. Default: 853
quic-size: <size in bytes> — the maximum number of bytes for all QUIC buffers and data combined 🎀. A plain number is in bytes; append 'k', 'm' or 'g' for kilobytes, megabytes or gigabytes (1024*1024 bytes in a megabyte, iykyk). New connections get connection refused when the limit is exceeded, and new streams get reset when the limit is exceeded. Default: 8m
use-systemd: <yes or no> — turn systemd socket activation on or off ✨. Default: no
do-daemonize: <yes or no> — enable or disable whether the Local-unbound server forks into the background as a daemon 🌸. Set the value to no when Local-unbound runs as a systemd service. Default: yes
tcp-connection-limit: <IP netblock> <limit> — allow up to limit simultaneous TCP connections from the given netblock 🫶. When you're at the limit, further connections are accepted but closed immediately. Heads up: this option is experimental at this time, ngl. Default: (disabled)
access-control: <IP netblock> <action> — specify the treatment of incoming queries based on their originating IP address 👑. Queries can be allowed access to this server that gives DNS answers, or refused, and other actions are possible too. The IP address range can be specified as a netblock, and you can give the statement several times to specify the treatment of different netblocks. The netblock is given as an IPv4 or IPv6 address with /size appended for a classless network block. The most specific netblock match is used, and if none match, refuse is used. So the order of the access-control statements literally does not matter 💅. The action can be deny, refuse, allow, allow_setrd, allow_snoop, allow_cookie, deny_non_local or refuse_non_local.
- deny — stops queries from hosts from that netblock. Periodt. 🚫
- refuse — stops queries too, but sends a DNS rcode REFUSED error message back.
- allow — gives access to clients from that netblock 💖. It gives only access for recursion clients (which is what almost all clients need). Non-recursive queries are refused.

The allow action does allow non-recursive queries to access the local-data that is configured. The reason is that this doesn't involve the Local-unbound server recursive lookup algorithm, and static data is served in the reply. This supports normal operations where non-recursive queries are made for the authoritative data. For non-recursive queries, any replies from the dynamic cache are refused.

allow_setrd — ignores the recursion desired (RD) bit and treats all requests as if the recursion desired bit is set 🙈.

Note that this behavior violates RFC 1034, which states that a name server should never perform recursive service unless asked via the RD bit, since this interferes with trouble shooting of name servers and their databases. This prohibited behavior may be useful if another DNS server must forward requests for specific zones to a resolver DNS server, but only supports stub domains and sends queries to the resolver DNS server with the RD bit cleared. 💀

allow_snoop — gives non-recursive access too 🔥. This gives both recursive and non-recursive access. The name allow_snoop refers to cache snooping, a technique to use non-recursive queries to examine the cache contents (for malicious acts). However, non-recursive queries can also be a valuable debugging tool (when you want to examine the cache contents).

In that case, use allow_snoop for your administration host. 🎀

allow_cookie — allows access only to UDP queries that contain a valid DNS Cookie as specified in RFC 7873 and RFC 9018, when the answer-cookie option is enabled 🍓. UDP queries containing only a DNS Client Cookie and no Server Cookie, or an invalid DNS Cookie, will receive a BADCOOKIE response including a newly generated DNS Cookie, allowing clients to retry with that DNS Cookie. The allow_cookie action will also accept requests over stateful transports, regardless of the presence of a DNS Cookie and regardless of the answer-cookie setting. UDP queries without a DNS Cookie receive REFUSED responses with the TC flag set, which may trigger fall back to TCP for those clients.
deny_non_local — the deny_non_local action is for hosts that are only allowed to query for the authoritative local-data 💜. They're not allowed full recursion, only the static data. Messages that are disallowed are dropped.
refuse_non_local — the refuse_non_local action is for hosts that are only allowed to query for the authoritative local-data 🌈. They're not allowed full recursion, only the static data. Messages that are disallowed receive error code REFUSED.

By default, only localhost (the 127.0.0.0/8 IP netblock, not the loopback interface) is implicitly allowed; the rest is refused. The default is refused because that is protocol-friendly 🔥. The DNS protocol is not designed to handle dropped packets due to policy, and dropping may result in (possibly excessive) retried queries.

access-control-tag: <IP netblock> "<list of tags>" — assign tags to access-control elements 🏷️. Clients using this access control element use localzones that are tagged with one of these tags.

Tags must be defined in define-tag. Enclose the list of tags in quotes ("") and put spaces between tags.

If access-control-tag is configured for a netblock that does not have an access-control, an access-control element with action allow is configured for this netblock ✨.

access-control-tag-action: <IP netblock> <tag> <action> — set the action for a particular tag for the given access control element 🎀. If you have multiple tag values, the tag used to look up the action is the first tag match between access-control-tag and local-zone-tag, where "first" comes from the order of the define-tag values.
access-control-tag-data: <IP netblock> <tag> "<resource record string>" — set redirect data for a particular tag for the given access control element 💖.
access-control-view: <IP netblock> <view name> — set the view for the given access control element 🦋.
interface-action: <ip address or interface name [@port]> <action> — similar to access-control but for interfaces 👑.

The action is the same as the ones defined under access-control.

Default action for interfaces is refuse. By default only localhost (the 127.0.0.0/8 IP netblock, not the loopback interface) is implicitly allowed through the default access-control behavior. This also means that any attempt to use the interface-*: options for the loopback interface will not work, as they will be overridden by the implicit default "access-control: 127.0.0.0/8 allow" option 😭.

NOTE: The interface needs to be already specified with interface, and any access-control*: option overrides all interface-*: options for targeted clients 💀

interface-tag: <ip address or interface name [@port]> <"list of tags"> — similar to access-control-tag but for interfaces 🌸.

NOTE: The interface needs to be already specified with interface, and any access-control*: option overrides all interface-*: options for targeted clients 💀

interface-tag-action: <ip address or interface name [@port]> <tag> <action> — similar to access-control-tag-action but for interfaces 🫶.

NOTE: The interface needs to be already specified with interface, and any access-control*: option overrides all interface-*: options for targeted clients 💀

interface-tag-data: <ip address or interface name [@port]> <tag> "<resource record string>" — similar to access-control-tag-data but for interfaces 🍓.

NOTE: The interface needs to be already specified with interface, and any access-control*: option overrides all interface-*: options for targeted clients 💀

interface-view: <ip address or interface name [@port]> <view name> — similar to access-control-view but for interfaces 🌈.

NOTE: The interface needs to be already specified with interface, and any access-control*: option overrides all interface-*: options for targeted clients 💀

chroot: <directory> — if chroot is enabled, you should pass the configfile (from the commandline) as a full path from the original root 🔒. After the chroot has been performed, the now defunct portion of the config file path is removed so it's able to reread the config after a reload.

All other file paths (working dir, logfile, roothints, and key files) can be specified in several ways 💅: as an absolute path relative to the new root, as a relative path to the working directory, or as an absolute path relative to the original root. In the last case the path is adjusted to remove the unused portion.

okay so bestie, the pidfile can be either a relative path to the working directory, or an absolute path relative to the original root. It is written just prior to chroot and dropping permissions — which is exactly how you can have the pidfile at /var/run/unbound.pid and the chroot at /var/unbound, for example. 🫶 Note that Local-unbound is not able to remove the pidfile after termination when it is located outside of the chroot directory. 😭

Also, Local-unbound may need to access /dev/urandom (for entropy) from inside the chroot.

If given, a chroot(2) is done to the given directory. If you give "" no chroot(2) is performed.

Default: /var/unbound.

Now the options, one by one, no cap:

username: <name> — if given, after binding the port the user privileges are dropped. If you give username: "" no user change is performed. If this user is not capable of binding the port, reloads (by signal HUP) will still retain the opened ports. If you change the port number in the config file, and that new port number requires privileges, then a reload will fail; a restart is needed. Default: unbound.
directory: <directory> — sets the working directory for the program. On Windows the string %EXECUTABLE% tries to change to the directory that unbound.exe resides in. If you give a server: directory: <directory> before include file statements then those includes can be relative to the working directory. Default: /var/unbound.
logfile: <filename> — if "" is given, logging goes to stderr, or nowhere once daemonized. The logfile is appended to, in the following format: [seconds since 1970] local-unbound[pid:tid]: type: message. If this option is given, the use-syslog option is internally set to no. The logfile is reopened (for append) when the config file is reread, on SIGHUP. Default: "" (disabled).
use-syslog: <yes or no> — sets Local-unbound to send log messages to the syslogd, using syslog(3). The log facility LOG_DAEMON is used, with identity "unbound". The logfile setting is overridden when use-syslog: yes is set. Default: yes.
log-identity: <string> — if "" is given, then the name of the executable, usually "unbound" is used to report to the log. Enter a string to override it with that, which is useful on systems that run more than one instance of Local-unbound, with different configurations, so that the logs can be easily distinguished against. Default: "".
log-time-ascii: <yes or no> — sets logfile lines to use a timestamp in UTC ASCII. No effect if using syslog, in that case syslog formats the timestamp printed into the log files. Default: no (prints the seconds since 1970 in brackets).
log-time-iso: <yes or no> — log time in ISO8601 format, if log-time-ascii: yes is also set. Default: no.
log-queries: <yes or no> — prints one line per query to the log, with the log timestamp and IP address, name, type and class. Note that it takes time to print these lines which makes the server (significantly) slower. Odd (nonprintable) characters in names are printed as '?'. Default: no.
log-replies: <yes or no> — prints one line per reply to the log, with the log timestamp and IP address, name, type, class, return code, time to resolve, from cache and response size. Note that it takes time to print these lines which makes the server (significantly) slower. Odd (nonprintable) characters in names are printed as '?'. Default: no.
log-tag-queryreply: <yes or no> — prints the word 'query' and 'reply' with log-queries and log-replies. This makes filtering logs easier. Default: no (backwards compatible).
log-destaddr: <yes or no> — prints the destination address, port and type in the log-replies output. This disambiguates what type of traffic, eg. UDP or TCP, and to what local port the traffic was sent to. Default: no.
log-local-actions: <yes or no> — print log lines to inform about local zone actions. These lines are like the local-zone type inform print outs, but they are also printed for the other types of local zones. Default: no.
log-servfail: <yes or no> — print log lines that say why queries return SERVFAIL to clients. This is separate from the verbosity debug logs, much smaller, and printed at the error level, not the info level of debug info from verbosity. Default: no.
log-thread-id: <yes or no> — (only on Linux and only when threads are available) logs the system-wide Linux thread ID instead of Local-unbound's internal thread counter. Can be useful when debugging with system tools. Default: no.
pidfile: <filename> — the process id is written to the file. Default is /var/unbound/unbound.pid. So,

kill -HUP `cat /var/unbound/unbound.pid`

triggers a reload,

kill -TERM `cat /var/unbound/unbound.pid`

gracefully terminates.

Default: /var/unbound/unbound.pid.

root-hints: <filename> — read the root hints from this file. Default is nothing, using builtin hints for the IN class. The file has the format of zone files, with root nameserver names and addresses only. The default may become outdated, when servers change, and then it is possible to use a root hints file with specific servers. Default: "".
hide-identity: <yes or no> — if enabled 'id.server' and 'hostname.bind' queries are REFUSED. Default: no.
identity: <string> — set the identity to report. If set to "", then the hostname of the server is returned. Default: "".
hide-version: <yes or no> — if enabled 'version.server' and 'version.bind' queries are REFUSED. Default: no.
version: <string> — set the version to report. If set to "", then the package version is returned. Default: "".
hide-http-user-agent: <yes or no> — if enabled the HTTP header User-Agent is not set. Use with caution as some webserver configurations may reject HTTP requests lacking this header. If needed, it is better to explicitly set the http-user-agent below. Default: no.
http-user-agent: <string> — set the HTTP User-Agent header for outgoing HTTP requests. If set to "", then the package name and version are used. Default: "".
nsid: <string> — add the specified nsid to the EDNS section of the answer when queried with an NSID EDNS enabled packet. As a sequence of hex characters or with 'ascii_' prefix and then an ASCII string. Default: (disabled).
hide-trustanchor: <yes or no> — if enabled 'trustanchor.local-unbound' queries are REFUSED. Default: no.
target-fetch-policy: <"list of numbers"> — set the target fetch policy used by Local-unbound to determine if it should fetch nameserver target addresses opportunistically. The policy is described per dependency depth. The number of values determines the maximum dependency depth that Unbound will pursue in answering a query. A value of -1 means to fetch all targets opportunistically for that dependency depth. A value of 0 means to fetch on demand only. A positive value fetches that many targets opportunistically. Enclose the list between quotes ("") and put spaces between numbers. Setting all zeroes, "0 0 0 0 0" gives behaviour closer to that of BIND 9, while setting "-1 -1 -1 -1 -1" gives behaviour rumoured to be closer to that of BIND 8. Default: "3 2 1 0 0".
harden-short-bufsize: <yes or no> — very small EDNS buffer sizes from queries are ignored. Default: yes (per RFC 6891).
harden-large-queries: <yes or no> — very large queries are ignored. Default is no, since it is legal protocol wise to send these, and could be necessary for operation if TSIG or EDNS payload is very large. Default: no.
harden-glue: <yes or no> — will trust glue only if it is within the servers authority. Default: yes.
harden-unverified-glue: <yes or no> — will trust only in-zone glue. Will try to resolve all out of zone (unverified) glue. Will fallback to the original glue if unable to resolve. Default: no.
harden-dnssec-stripped: <yes or no> — require DNSSEC data for trust-anchored zones, if such data is absent, the zone becomes bogus. If turned off, and no DNSSEC data is received (or the DNSKEY data fails to validate), then the zone is made insecure, this behaves like there is no trust anchor. You could turn this off if you are sometimes behind an intrusive firewall (of some sort) that removes DNSSEC data from packets, or a zone changes from signed to unsigned to badly signed often.

If turned off you run the risk of a downgrade attack that disables security for a zone.

Default: yes.

harden-below-nxdomain: <yes or no> — from RFC 8020 (with title "NXDOMAIN: There Really Is Nothing Underneath"), returns NXDOMAIN to queries for a name below another name that is already known to be NXDOMAIN. DNSSEC mandates NOERROR for empty nonterminals, hence this is possible. Very old software might return NXDOMAIN for empty nonterminals (that usually happen for reverse IP address lookups), and thus may be incompatible with this. To try to avoid this only DNSSEC-secure NXDOMAINs are used, because the old software does not have DNSSEC.

NOTE: The NXDOMAIN must be secure, this means NSEC3 with optout is insufficient.

Default: yes periodt ✨

harden-referral-path: <yes or no> — ok so this one hardens the referral path by doing extra queries for infrastructure data 🕵️♀️. It validates replies if trust anchors are configured and the zones are signed, and it enforces DNSSEC validation on nameserver NS sets and the nameserver addresses that get encountered on the referral path to the answer. Default is off, and like... for good reason: it burdens the authority servers, it's not RFC standard, and it could lead to performance problems because of the extra query load that gets generated. Experimental option, bestie. If you enable it, consider adding more numbers after the target-fetch-policy to increase the max depth that is checked to.

Default: no

harden-algo-downgrade: <yes or no> — harden against algorithm downgrade when multiple algorithms are advertised in the DS record 💅. The way this works: first it chooses only the strongest DS digest type as per RFC 4509 (Local-unbound treats the highest algorithm as the strongest), and then it expects signatures from all the advertised signing algorithms from the chosen DS(es) to be present. If no, it allows any one supported algorithm to validate the zone, even if other advertised algorithms are broken. RFC 6840 mandates that zone signers must produce zones signed with all advertised algorithms, but sometimes they do not 😬. RFC 6840 also clarifies that this requirement is not for validators, and validators should accept any single valid path. So it should thus be explicitly noted that this option violates RFC 6840 for DNSSEC validation and should only be used to perform a signature completeness test to support troubleshooting.

WARNING: Using this option may break DNSSEC resolution with non RFC 6840 conforming signers and/or in multi-signer configurations that don't send all the advertised signatures.

Default: no

harden-unknown-additional: <yes or no> — hardens against unknown records in the authority section and additional section 🛡️. If no, such records are copied from the upstream and presented to the client together with the answer. If yes, it could hamper future protocol developments that want to add records.

Default: no

use-caps-for-id: <yes or no> — uses 0x20-encoded random bits in the query to foil spoof attempts ✨. It perturbs the lowercase and uppercase of query names sent to authority servers and checks if the reply still has the correct casing. This feature is an experimental implementation of draft dns-0x20.

Default: no

caps-exempt: <domain> — exempts the domain so it does not receive caps-for-id perturbed queries 🙅♀️. For domains that do not support 0x20 and also fail with fallback because they keep sending different answers, like some load balancers. Can be given multiple times, for different domains.
caps-whitelist: <domain> — alternate syntax for caps-exempt.
qname-minimisation: <yes or no> — send the minimum amount of information to upstream servers to enhance privacy 🤫. Only send the minimum required labels of the QNAME and set QTYPE to A when possible. Best effort approach; the full QNAME and original QTYPE will be sent when upstream replies with a RCODE other than NOERROR, except when receiving NXDOMAIN from a DNSSEC signed zone.

Default: yes

qname-minimisation-strict: <yes or no> — QNAME minimisation in strict mode 🫣. Do not fall back to sending the full QNAME to potentially broken nameservers. A lot of domains will not be resolvable when this option is enabled. Only use if you know what you are doing. This option only has effect when qname-minimisation is enabled.

Default: no

aggressive-nsec: <yes or no> — aggressive NSEC uses the DNSSEC NSEC chain to synthesize NXDOMAIN and other denials, using information from previous NXDOMAIN answers 🔥. It helps reduce the query rate towards targets that get a very high nonexistent name lookup rate.

Default: yes

private-address: <IP address or subnet> — give IPv4 or IPv6 addresses or classless subnets 🏠. These are addresses on your private network, and they're not allowed to be returned for public internet names. Any occurrence of such addresses gets removed from DNS answers. Additionally, the DNSSEC validator may mark the answers bogus 😭. This protects against so-called DNS Rebinding, where a user browser is turned into a network proxy, allowing remote access through the browser to other parts of your private network.

The option removes resource records of types A, AAAA, SVCB and HTTPS that match the filter. Inside the SVCB and HTTPS records, the svcparams of type ipv4hint and ipv6hint are checked for matches.

Some names can be allowed to contain your private addresses — by default all the local-data that you configured is allowed to, and you can specify additional names using private-domain. No private addresses are enabled by default.

We consider enabling this for the RFC 1918 private IP address space by default in later releases 👀. That would enable private addresses for 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, 169.254.0.0/16, fd00::/8 and fe80::/10, since the RFC standards say these addresses should not be visible on the public internet.

Turning on 127.0.0.0/8 would hinder many spamblocklists as they use that. Adding ::ffff:0:0/96 stops IPv4-mapped IPv6 addresses from bypassing the filter 💀.

private-domain: <domain name> — allow this domain, and all its subdomains, to contain private addresses 🫶. Give it multiple times to allow multiple domain names to contain private addresses.

Default: (none)

unwanted-reply-threshold: <number> — if set, a total number of unwanted replies is kept track of in every thread 🧮. When it reaches the threshold, a defensive action is taken and a warning is printed to the log. The defensive action is to clear the rrset and message caches, hopefully flushing away any poison. A value of 10 million is suggested.

Default: 0 (disabled)

do-not-query-address: <IP address> — do not query the given IP address 🚫. Can be IPv4 or IPv6. Append /num to indicate a classless delegation netblock, for example like 10.2.3.4/24 or 2001::11/64.

Default: (none)

do-not-query-localhost: <yes or no> — if yes, localhost is added to the do-not-query-address entries, both IPv6 ::1 and IPv4 127.0.0.1/8 💅. If no, then localhost can be used to send queries to.

Default: yes

prefetch: <yes or no> — if yes, cache hits on message cache elements that are on their last 10 percent of their TTL value trigger a prefetch to keep the cache up to date ⏰. Turning it on gives about 10 percent more traffic and load on the machine, but popular items do not expire from the cache.

Default: no

prefetch-key: <yes or no> — if yes, fetch the DNSKEYs earlier in the validation process, when a DS record is encountered 🔑. This lowers the latency of requests. It does use a little more CPU. Also if the cache is set to 0, it is no use.

Default: no

deny-any: <yes or no> — if yes, deny queries of type ANY with an empty response 🙃. If disabled, Local-unbound responds with a short list of resource records if some can be found in the cache and makes the upstream type ANY query if there are none.

Default: no

rrset-roundrobin: <yes or no> — if yes, Local-unbound rotates RRSet order in response (the random number is taken from the query ID, for speed and thread safety) 🔄.

Default: yes

minimal-responses: <yes or no> — if yes, Local-unbound does not insert authority/additional sections into response messages when those sections are not required 🪄. This reduces response size significantly, and may avoid TCP fallback for some responses, which may cause a slight speedup. The default is yes, even though the DNS protocol RFCs mandate these sections, and the additional content could save roundtrips for clients that use the additional content. However these sections are hardly used by clients. Enabling prefetch can benefit clients that need the additional content by trying to keep that content fresh in the cache.

Default: yes

disable-dnssec-lame-check: <yes or no> — if yes, disables the DNSSEC lameness check in the iterator 😴. This check sees if RRSIGs are present in the answer, when DNSSEC is expected, and retries another authority if RRSIGs are unexpectedly missing. The validator will insist in RRSIGs for DNSSEC signed domains regardless of this setting, if a trust anchor is loaded.

Default: no

module-config: "<module names>" — module configuration, a list of module names separated by spaces, surround the string with quotes ("") 🧩. The modules can be respip, validator, or iterator (and possibly more, see below).

NOTE: The ordering of the modules is significant — the order decides the order of processing.

Setting this to just "iterator" will result in a non-validating server. Setting this to "validator iterator" will turn on DNSSEC validation.

NOTE: You must also set trust-anchors for validation to be useful.

Adding respip to the front will cause RPZ processing to be done on all queries 👑

Most modules that need to be listed here have to be listed at the beginning of the line.

The subnetcache module has to be listed just before the iterator.

The python module can be listed in different places — it then processes the output of the module it is just before.

The dynlib module can be listed pretty much anywhere, it is only a very thin wrapper that allows dynamic libraries to run in its place.

Default: "validator iterator"

trust-anchor-file: <filename> — file with trusted keys for validation 🔐. Both DS and DNSKEY entries can appear in the file. The format of the file is the standard DNS Zone file format.

Default: "" (no trust anchor file) — that's the tail end of trust-anchor-file from before, bestie, just closing the loop 💖

auto-trust-anchor-file: <filename> — a file holding a trust anchor for one zone, and Local-unbound keeps it fresh with RFC 5011 probes ✨ Heads up: those probes run several times per month, so the machine genuinely has to be online a lot. The starting file can be one with the contents described in trust-anchor-file. The file gets written to whenever the anchor updates, so the Local-unbound user must have write permission. And not just on the file — write permission on the directory it lives in too (that's so it can create a temporary file, which is necessary to deal with filesystem-full events). It also has to be inside the chroot if you're using one. Default: "" (no auto trust anchor file).
trust-anchor: "<Resource Record>" — a DS or DNSKEY RR for a key to use for validation 👑 You can hand it multiple entries to specify multiple trusted keys, in addition to trust-anchor-file. The resource record goes in the same format that dig(1) or drill(1) prints them — same format as in the zone file, periodt. It has to be on a single line, wrapped in "". You can put a TTL in there for ease of cut and paste, but it's ignored, so don't stress. You can specify a class too, but class IN is the default. Default: (none).
trusted-keys-file: <filename> — a file with trusted keys for validation 🗝️ Want more than one? Give several entries, one file per entry. It's like trust-anchor-file but with a different file format — this one is BIND-9 style, so the trusted-keys { name flag proto algo "key"; }; clauses get read. Wildcards work with this statement too, and the wildcard is expanded on start and on reload. Default: "" (no trusted keys file).
trust-anchor-signaling: <yes or no> — send the RFC 8145 key tag query after trust anchor priming 📡 Default: yes.
root-key-sentinel: <yes or no> — root key trust anchor sentinel 🛡️ Default: yes.
domain-insecure: <domain name> — marks domain name as insecure, so the DNSSEC chain of trust gets ignored all the way down to it. Meaning: a trust anchor above the domain name can't make that domain secure with a DS record — that DS record just gets ignored. You can give this multiple times to list multiple domains treated as if they were unsigned. But if you set trust anchors for the domain, those override this setting (and the domain is secured). Super useful when you want to make sure a trust anchor for external lookups doesn't mess with an (unsigned) internal domain — because a DS record on the outside can absolutely create validation failures for that internal domain 😭 Default: (none).
val-override-date: <rrsig-style date spec> — give it an RRSIG-style date and that date gets used for verifying RRSIG inception and expiration dates instead of the current date 🕰️

⚠️ WARNING: Debugging feature! Do not set this unless you're literally debugging signature inception and expiration, no cap. The value -1 ignores the date altogether, which is useful for some special applications.

Default: 0 (disabled)

val-sig-skew-min: <seconds> — the minimum number of seconds of clock skew to apply to validated signatures. It uses 10% of the signature lifetime (expiration - inception), capped by this setting. Default is 3600 (1 hour) and that's what allows for daylight savings differences 🌸 Lower this value if you want stricter checking of short-lived signatures. Default: 3600 (1 hour).
val-sig-skew-max: <seconds> — the maximum number of seconds of clock skew to apply to validated signatures. Same deal: 10% of the signature lifetime (expiration - inception), capped by this setting. Default is 86400 (24 hours), which allows for timezone-setting problems in stable domains 🌍 Setting both min and max very low disables the clock skew allowances entirely. Setting both min and max very high makes the validator check signature timestamps less strictly. Default: 86400 (24 hours).
val-max-restart: <number> — how many times the validator is allowed to restart validation with another authority when validation fails 🔁 Default: 5.
val-bogus-ttl: <seconds> — the TTL for bogus data, i.e. data that failed validation because of invalid signatures or other checks 💀 The TTL from that data can't be trusted, so this value is used instead. The time interval is what prevents repeated revalidation of bogus data. Default: 60.
val-clean-additional: <yes or no> — tells the validator to strip out data from the additional section of secure messages that isn't signed properly 🧹 Messages that are insecure, bogus, indeterminate or unchecked are not affected. Use this to protect users who rely on this validator for authentication from potentially bad data in the additional section. Default: yes.
val-log-level: <number> — makes the validator print validation failures to the log, regardless of the verbosity setting 📝 At 1, a line gets printed for every user query that fails, so you can actually monitor what's happening with validation — and then use a diagnosis tool like dig or drill to find out why those queries are failing. At 2, you don't just get the failed query, you also get the reason why Local-unbound thought it was wrong and which server sent the faulty data. Default: 0 (disabled).
val-permissive-mode: <yes or no> — instructs the validator to mark bogus messages as indeterminate 🙈 The security checks still happen, but if the result is bogus (failed security), the reply is not withheld from the client with SERVFAIL like usual — the client just receives the bogus data. For messages that are found to be secure, the AD bit is set in replies. Logging also happens same as for full validation. Default: no.
ignore-cd-flag: <yes or no> — tells Local-unbound to ignore the CD flag from clients and refuse to give them bogus answers 🚫 So the CD (Checking Disabled) flag doesn't disable checking anymore. Handy when the clients are legacy (w2008) servers that set the CD flag but can't validate DNSSEC themselves — then Local-unbound still gives them DNSSEC protection. Default: no.
disable-edns-do: <yes or no> — disables the EDNS DO flag in upstream requests 💅 Slight problem: it breaks DNSSEC validation for Local-unbound's clients. Upstream name servers end up not including DNSSEC records in their replies, which can be helpful for devices that can't handle DNSSEC information. When this option is enabled, clients that set the DO flag receive no EDNS record in the response, to indicate the lack of support to them. And here's the twist: if this option is enabled but Local-unbound is already configured for DNSSEC validation (i.e. the validator module is enabled; that's the default), this option is implicitly turned off with a warning so as to not break DNSSEC validation in Unbound. Default: no.
serve-expired: <yes or no> — if enabled, Local-unbound tries to serve old responses from cache with a TTL of serve-expired-reply-ttl in the response ⏳ By default the expired answer is used after a resolution attempt errored out or is taking more than serve-expired-client-timeout to resolve. Default: no.
serve-expired-ttl: <seconds> — caps how long past expiration you'll keep serving expired responses, in seconds. 0 disables the limit 🎀 This option only applies when serve-expired is enabled. Per RFC 8767, a suggested value is between 86400 (1 day) and 259200 (3 days). Default: 86400.
serve-expired-ttl-reset: <yes or no> — sets the TTL of expired records to the serve-expired-ttl value after a failed attempt to retrieve the record from upstream 🔄 This makes sure the expired records keep getting served for as long as there are queries for them. Default: no.
serve-expired-reply-ttl: <seconds> — the TTL value to use when replying with expired data 📬 If serve-expired-client-timeout is also in play, then it's RECOMMENDED to use 30 as the value (RFC 8767). This value is capped by the original TTL of the record — so records with a higher original TTL than this value use this value for expired replies, and records with a lower original TTL than this value use their own original TTL for expired replies. Default: 30.
serve-expired-client-timeout: <msec> — time in milliseconds before replying to the client with expired data ⏱️ This basically turns on the serve-stale behavior from RFC 8767, where it first tries to resolve before immediately responding with expired data. Setting it to 0 disables that behavior and instead serves the expired record immediately from cache, before even attempting to refresh it via resolution. Default: 1800.
serve-original-ttl: <yes or no> — if enabled, Local-unbound always returns the original TTL as received from the upstream name server, instead of the decrementing TTL stored in the cache 👑 This can be useful if Local-unbound serves as a front-end to a hidden authoritative name server. Enabling it does not impact cache expiry — it only changes the TTL Local-unbound embeds in responses to queries. Default: no.

NOTE: Enabling this feature implicitly disables enforcement of the configured minimum and maximum TTL, since it's assumed that users who enable this don't want Local-unbound changing the TTL it got from an upstream server.

NOTE: The values set using cache-min-ttl and cache-max-ttl are ignored.

val-nsec3-keysize-iterations: <"list of values"> — okay so this is a list of keysize and iteration count values, separated by spaces and surrounded by quotes. It decides the maximum allowed NSEC3 iteration count before a message is just marked insecure instead of doing all those many hashing iterations. The list has to be in ascending order and have at least one entry. If you set it to "1024 65535", there's no restriction to NSEC3 iteration values. ✨
- NOTE: this table has to be kept short, bestie — a very long list could cause slower operation. 😭
- Default: "1024 150 2048 150 4096 150"
zonemd-permissive-mode: <yes or no> — if enabled, ZONEMD verification failures are only logged and don't cause the zone to be blocked, and they only return servfail. Useful for testing out if it works, or if the operator just wants to be notified of a problem without disrupting service. 🫶
- Default: no
add-holddown: <seconds> — tells the auto-trust-anchor-file probe mechanism for RFC 5011 autotrust updates to add new trust anchors only after they've been visible for this long. ⏳
- Default: 2592000 (30 days as per the RFC)
del-holddown: <seconds> — tells the auto-trust-anchor-file probe mechanism for RFC 5011 autotrust updates to remove revoked trust anchors after they've been kept in the revoked list for this long. 🗑️
- Default: 2592000 (30 days as per the RFC)
keep-missing: <seconds> — tells the auto-trust-anchor-file probe mechanism for RFC 5011 autotrust updates to remove missing trust anchors after they've been unseen for this long. This cleans up the state file if the target zone doesn't perform trust anchor revocation, so it makes the auto probe mechanism work with zones that perform regular (non-5011) rollovers. The value 0 does not remove missing anchors, as per the RFC. 👀
- Default: 31622400 (366 days)
permit-small-holddown: <yes or no> — debug option that allows the autotrust 5011 rollover timers to assume very small values. 🧪
- Default: no
key-cache-size: <number> — number of bytes size of the key cache. A plain number is in bytes; append 'k', 'm' or 'g' for kilobytes, megabytes or gigabytes (1024*1024 bytes in a megabyte). 💾
- Default: 4m
key-cache-slabs: <number> — number of slabs in the key cache. Slabs reduce lock contention by threads. Must be set to a power of 2. Setting (close) to the number of cpus is a fairly good setting. If left unconfigured, it will be configured automatically to be a power of 2 close to the number of configured threads in multi-threaded environments. 🧩
- Default: (unconfigured)
neg-cache-size: <number> — number of bytes size of the aggressive negative cache. A plain number is in bytes; append 'k', 'm' or 'g' for kilobytes, megabytes or gigabytes (1024*1024 bytes in a megabyte). 🚫
- Default: 1m
unblock-lan-zones: <yes or no> — if enabled, then for private address space the reverse lookups are no longer filtered. This allows Local-unbound, when running as dns service on a host where it provides service for that host, to put out all of the queries for the 'lan' upstream. When enabled, only localhost, 127.0.0.1 reverse and ::1 reverse zones are configured with default local zones. Disable the option when Local-unbound is running as a (DHCP-) DNS network resolver for a group of machines, where such lookups should be filtered (RFC compliance) — this also stops potential data leakage about the local network to the upstream DNS servers. 🏠
- Default: no
insecure-lan-zones: <yes or no> — if enabled, then reverse lookups in private address space are not validated. This is usually required whenever unblock-lan-zones is used. 🙈
- Default: no
local-zone: <zone> <type> — configure a local zone, bestie. The <type> determines the answer to give if there's no match from local-data. The types are deny, refuse, static, transparent, redirect, nodefault, typetransparent, inform, inform_deny, inform_redirect, always_transparent, block_a, always_refuse, always_nxdomain, always_null, noview, and they're all explained below. After that the default settings are listed. Use local-data to enter data into the local zone. Answers for local zones are authoritative DNS answers. By default the zones are class IN. 👑

If you need more complicated authoritative data — with referrals, wildcards, CNAME/DNAME support, or DNSSEC authoritative service — set up a stub-zone for it as detailed in the stub zone section below. A stub-zone can be used to have unbound send queries to another server, an authoritative server, to fetch the information. With a forward-zone, local-unbound sends queries to a server that is a recursive server to fetch the information. With an auth-zone a zone can be loaded from file and used; it can be used like a local zone for users downstream, or the auth-zone information can be used to fetch information from when resolving like it's an upstream server. The forward-zone and auth-zone options are described in their sections below. If you want to perform filtering of the information that the users can fetch, the local-zone and local-data statements allow for this, but the rpz functionality can also be used, described in the RPZ section. 🌈

deny — do not send an answer, drop the query. If there's a match from local data, the query is answered.
refuse — send an error message reply, with rcode REFUSED. If there's a match from local data, the query is answered.
static — if there's a match from local data, the query is answered. Otherwise the query is answered with NODATA or NXDOMAIN. For a negative answer a SOA is included in the answer if present as local-data for the zone apex domain.
transparent — if there's a match from local-data, the query is answered. Otherwise, if the query has a different name, the query is resolved normally. If the query is for a name given in local-data but no such type of data is given in local-data, then a NOERROR NODATA answer is returned. If no local-zone is given, local-data causes a transparent zone to be created by default.
typetransparent — if there's a match from local data, the query is answered. If the query is for a different name, or for the same name but for a different type, the query is resolved normally. So, similar to transparent but types that aren't listed in local data are resolved normally, so if an A record is in the local data that doesn't cause a NODATA reply for AAAA queries. 💅
redirect — the query is answered from the local data for the zone name. There may be no local data beneath the zone name. This answers queries for the zone, and all subdomains of the zone, with the local data for the zone. It can be used to redirect a domain to return a different address record to the end user, with:

local-zone: "example.com." redirect
local-data: "example.com. A 127.0.0.1"

queries for www.example.com and www.foo.example.com are redirected, so that users with web browsers cannot access sites with suffix example.com. 🕸️

A CNAME record can also be provided via local-data:

local-zone: "example.com." redirect
local-data: "example.com. CNAME www.example.org."

In that case, the CNAME is resolved and the answer includes resolved target records as well. The CNAME record has to be with the zone name of the local-zone, and there can be one CNAME, not more. The CNAME record has to be at the zone apex of the redirect zone, then it's used for redirection. The resolution proceeds with upstream DNS resolution, and that does not include the lookup in local zones. So the record is not able to point in local zones, but it can point to upstream DNS answers. 😮

CNAME resolution is supported only in type redirect local-zone, and in type inform_redirect local-zone.

As different from CNAME records that are used elsewhere, in the redirect type local-zone, it's supported that in the target of the record a wildcard label gets expanded to the query name, with for example: example.com. CNAME *.foo.net. gets expanded to www.example.com. CNAME www.example.com.foo.net.. 🦋

inform — the query is answered normally, same as transparent. The client IP address (@portnumber) is printed to the logfile. The log message is:

timestamp, local-unbound-pid, info: zonename inform IP@port queryname type class.

This option can be used for normal resolution, but machines looking up infected names are logged, eg. to run antivirus on them. 🦠

inform_deny — the query is dropped, like deny, and logged, like inform. Ie. find infected machines without answering the queries.
inform_redirect — the query is redirected, like redirect, and logged, like inform. Ie. answer queries with fixed data and also log the machines that ask. 📝
always_transparent — like transparent, but ignores local data and resolves normally.
block_a — like transparent, but ignores local data and resolves normally all query types excluding A. For A queries it unconditionally returns NODATA. Useful in cases when there's a need to explicitly force all apps to use IPv6 protocol and avoid any queries to IPv4. 🚫

always_refuse — okay so this is like refuse, but it ignores local data and refuses the query. It also blocks queries of type DS for the zone name. That can break the DNSSEC chain of trust, but it is refused anyway. The block for type DS assists in more completely blocking the zone.
always_nxdomain — like static, but it ignores local data and returns NXDOMAIN for the query.
always_nodata — like static, but it ignores local data and returns NODATA for the query.
always_deny — like deny, but it ignores local data and drops the query.
always_null — always returns 0.0.0.0 or ::0 for every name in the zone. It's like redirect with zero data for A and AAAA. It ignores local data in the zone. Used for some block lists.
noview — breaks out of that view and moves towards the global local zones for an answer to the query. If view-first is no, it'll resolve normally. If view-first is enabled, it'll break perform that step and check the global answers. For when the view has view specific overrides but some zone has to be answered from global local zone contents.
nodefault — used to turn off default contents for AS112 zones. The other types also turn off default contents for the zone. The nodefault option has no other effect than turning off default contents for the given zone. Use nodefault if you use exactly that zone; if you want to use a subzone, use transparent.

The default zones are localhost, reverse 127.0.0.1 and ::1, the home.arpa, resolver.arpa, service.arpa, onion, test, invalid and the AS112 zones. The AS112 zones are reverse DNS zones for private use and reserved IP addresses for which the servers on the internet cannot provide correct answers. They are configured by default to give NXDOMAIN (no reverse information) answers.

The defaults can be turned off by specifying your own local-zone of that name, or using the nodefault type. Below is a list of the default zone contents.

💖 localhost 💖

The IPv4 and IPv6 localhost information is given. NS and SOA records are provided for completeness and to satisfy some DNS update tools. Default content:

local-zone: "localhost." redirect
local-data: "localhost. 10800 IN NS localhost."
local-data: "localhost. 10800 IN SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
local-data: "localhost. 10800 IN A 127.0.0.1"
local-data: "localhost. 10800 IN AAAA ::1"

🌸 reverse IPv4 loopback 🌸

Default content:

local-zone: "127.in-addr.arpa." static
local-data: "127.in-addr.arpa. 10800 IN NS localhost."
local-data: "127.in-addr.arpa. 10800 IN SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
local-data: "1.0.0.127.in-addr.arpa. 10800 IN PTR localhost."

🦋 reverse IPv6 loopback 🦋

Default content:

local-zone: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa." static
local-data: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa. 10800 IN NS localhost."
local-data: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa. 10800 IN SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
local-data: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa. 10800 IN PTR localhost."

🎀 home.arpa (RFC 8375) 🎀

Default content:

local-zone: "home.arpa." static
local-data: "home.arpa. 10800 IN NS localhost."
local-data: "home.arpa. 10800 IN SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"

✨ resolver.arpa (RFC 9462) ✨

Default content:

local-zone: "resolver.arpa." static
local-data: "resolver.arpa. 10800 IN NS localhost."
local-data: "resolver.arpa. 10800 IN SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"

🌈 service.arpa (draft-ietf-dnssd-srp-25) 🌈

Default content:

local-zone: "service.arpa." static
local-data: "service.arpa. 10800 IN NS localhost."
local-data: "service.arpa. 10800 IN SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"

🧅 onion (RFC 7686) 🧅

Default content:

local-zone: "onion." static
local-data: "onion. 10800 IN NS localhost."
local-data: "onion. 10800 IN SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"

⭐ test (RFC 6761) ⭐

Default content:

local-zone: "test." static
local-data: "test. 10800 IN NS localhost."
local-data: "test. 10800 IN SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"

💀 invalid (RFC 6761) 💀

Default content:

local-zone: "invalid." static
local-data: "invalid. 10800 IN NS localhost."
local-data: "invalid. 10800 IN SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"

💜 reverse local use zones (RFC 1918) 💜

Reverse data for zones 10.in-addr.arpa, 16.172.in-addr.arpa to 31.172.in-addr.arpa, 168.192.in-addr.arpa. The local-zone is set static and as local-data SOA and NS records are provided.

🍓 special-use IPv4 Addresses (RFC 3330) 🍓

Reverse data for zones 0.in-addr.arpa (this), 254.169.in-addr.arpa (link-local), 2.0.192.in-addr.arpa (TEST NET 1), 100.51.198.in-addr.arpa (TEST NET 2), 113.0.203.in-addr.arpa (TEST NET 3), 255.255.255.255.in-addr.arpa (broadcast). And from 64.100.in-addr.arpa to 127.100.in-addr.arpa (Shared Address Space).

🌸 reverse IPv6 unspecified (RFC 4291) 🌸

Reverse data for zone 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa.

🦋 reverse IPv6 Locally Assigned Local Addresses (RFC 4193) 🦋

Reverse data for zone D.F.ip6.arpa.

🎀 reverse IPv6 Link Local Addresses (RFC 4291) 🎀

Reverse data for zones 8.E.F.ip6.arpa to B.E.F.ip6.arpa.

✨ reverse IPv6 Example Prefix ✨

Reverse data for zone 8.B.D.0.1.0.0.2.ip6.arpa. This zone is used for tutorials and examples. You can remove the block on this zone with:

local-zone: 8.B.D.0.1.0.0.2.ip6.arpa. nodefault

You can also selectively unblock a part of the zone by making that part transparent with a local-zone statement. This also works with the other default zones.

💅 `local-data: "<resource record string>"` 💅

Configure local data, which is served in reply to queries for it. The query has to match exactly unless you configure the local-zone as redirect. If not matched exactly, the local-zone type determines further processing. If local-data is configured that is not a subdomain of a local-zone, a transparent local-zone is configured. For record types such as TXT, use single quotes, as in:

local-data: 'example. TXT "text"'

NOTE: If you need more complicated authoritative data, with referrals, wildcards, CNAME/DNAME support, or DNSSEC authoritative service, setup a stub-zone for it as detailed in the stub zone section below.

🫶 `local-data-ptr: "IPaddr name"` 🫶

Configure local data shorthand for a PTR record with the reversed IPv4 or IPv6 address and the host name. For example "192.0.2.4 www.example.com". TTL can be inserted like this: "2001:db8::4 7200 www.example.com"

🌟 `local-zone-tag: <zone> <"list of tags">` 🌟

Assign tags to local zones. Tagged localzones will only be applied when the used access-control element has a matching tag. Tags must be defined in define-tag. Enclose list of tags in quotes ("") and put spaces between tags. When there are multiple tags it checks if the intersection of the list of tags for the query and local-zone-tag is non-empty.

🔥 `local-zone-override: <zone> <IP netblock> <type>` 🔥

Override the local zone type for queries from addresses matching netblock. Use this localzone type, regardless the type configured for the local zone (both tagged and untagged) and regardless the type configured using access-control-tag-action.

👑 `response-ip: <IP-netblock> <action>` 👑

This requires use of the respip module.

If the IP address in an AAAA or A RR in the answer section of a response matches the specified IP netblock, the specified action will apply. <action> has generally the same semantics as that for access-control-tag-action, but there are some exceptions.

Actions for response-ip are different from those for local-zone in that in case of the former there is no point of such conditions as "the query matches it but there is no local data". Because of this difference, the semantics of response-ip actions are modified or simplified as follows: The static, refuse, transparent, typetransparent, and nodefault actions are invalid for response-ip. Using any of these will cause the configuration to be rejected as faulty. The deny action is non-conditional, i.e. it always results in dropping the corresponding query. The resolution result before applying the deny action is still cached and can be used for other queries.

💖 `response-ip-data: <IP-netblock> <"resource record string">` 💖

This requires use of the respip module.

…and about that <"resource record string"> for response-ip-data when the action is "redirect" 💅 — it's basically the same shape as the one in access-control-tag-data, but it has to be an AAAA, A or CNAME type, no exceptions. If the <IP-netblock> is an IPv6 prefix, the record must be AAAA; if it's an IPv4 prefix, it must be A — unless it's a CNAME, which is the ✨iconic✨ exception that works for both versions of IP netblocks. But heads up: if it's a CNAME, you literally can't have more than one response-ip-data for the same <IP-netblock>, and CNAME + other types of records must not coexist for the same <IP-netblock> either — that's just the normal rules for CNAME records, respect them 🙏. Also, small cute detail: the textual domain name for the CNAME doesn't have to be explicitly terminated with a dot (".") — the root name is assumed to be the origin for the name.

response-ip-tag: <IP-netblock> <"list of tags"> — this one needs the respip module, bestie. It assigns tags to a response <IP-netblock>: if the IP address in an AAAA or A RR in the answer section of a response matches the specified <IP-netblock>, those tags get assigned to the IP address. Then, if an access-control-tag is defined for the client and it includes one of the tags for the response IP, the corresponding access-control-tag-action will apply. Tag matching rule is the same as the one for access-control-tag and local-zone. Unlike local-zone-tag, response-ip-tag can be defined for an <IP-netblock> even if no response-ip is defined for that netblock. And important: if multiple response-ip-tag options are specified for the same <IP-netblock> in different statements, all but the first will be ignored — which is not flagged as a configuration error 😭, it just silently... probably isn't what you intended.

Actions specified in an access-control-tag-action that has a matching tag with response-ip-tag can be those that are "invalid" for response-ip listed above, since access-control-tag-action can be shared with local zones. For these actions, if they behave differently depending on whether local data exists or not in the case of local zones, the behavior for response-ip-data will generally result in NOERROR/NODATA instead of NXDOMAIN, since the response-ip data are inherently type specific, and non-existence of data does not indicate anything about the existence or non-existence of the qname itself. For example, if the matching tag action is static but there is no data for the corresponding response-ip configuration, then the result will be NOERROR/NODATA. The only case where NXDOMAIN is returned is when an always_nxdomain action applies 🔥.

ratelimit: <number or 0> — turns on ratelimiting of queries sent to nameserver for performing recursion. 0 disables the feature. This option is experimental at this time 🧪.

The ratelimit is in queries per second that are allowed. More queries are turned away with an error (SERVFAIL). Cached responses are not ratelimited by this setting.

It stops recursive floods, eg. random query names, but not spoofed reflection floods. The zone of the query is determined by examining the nameservers for it, and the zone name is used to keep track of the rate. For example, 1000 may be a suitable value to stop the server from being overloaded with random names, and keeps local-unbound from sending traffic to the nameservers for those zones.

NOTE: Configured forwarders are excluded from ratelimiting 🫶

Default: 0

ratelimit-size: <memory size> — the size of the data structure that keeps track of the current ongoing rates. In bytes, or use m(mega), k(kilo), g(giga). The ratelimit structure is small, so this thing likely does not need to be large ✨.

Default: 4m

ratelimit-slabs: <number> — number of slabs in the ratelimit tracking data structure. Slabs reduce lock contention by threads. Must be set to a power of 2 💀. Setting it (close) to the number of cpus is a fairly good setting. If left unconfigured, it will be configured automatically to be a power of 2 close to the number of configured threads in multi-threaded environments.

Default: (unconfigured)

ratelimit-factor: <number> — sets the amount of queries to rate limit when the limit is exceeded. If set to 0, all queries are dropped for domains where the limit is exceeded. If set to another value, 1 in that number is allowed through to complete. Default is 10, allowing 1/10 traffic to flow normally. This can make ordinary queries complete (if repeatedly queried for), and enter the cache, whilst also mitigating the traffic flow by the factor given 👑

Default: 10

ratelimit-backoff: <yes or no> — if enabled, the ratelimit is treated as a hard failure instead of the default maximum allowed constant rate. When the limit is reached, traffic is ratelimited and demand continues to be kept track of for a 2 second rate window. No traffic is allowed, except for ratelimit-factor, until demand decreases below the configured ratelimit for a 2 second rate window. Useful to set ratelimit to a suspicious rate to aggressively limit unusually high traffic 🔥.

Default: no

ratelimit-for-domain: <domain> <number qps or 0> — overrides the global ratelimit for an exact match domain name with the listed number. You can give this for any number of names. For example, for a top-level-domain you may want to have a higher limit than other names. A value of 0 will disable ratelimiting for that domain.
ratelimit-below-domain: <domain> <number qps or 0> — overrides the global ratelimit for a domain name that ends in this name. You can give this multiple times; it then describes different settings in different parts of the namespace. The closest matching suffix is used to determine the qps limit. The rate for the exact matching domain name is not changed — use ratelimit-for-domain to set that, you might want to use different settings for a top-level-domain and subdomains 💡. A value of 0 will disable ratelimiting for domain names that end in this name.
ip-ratelimit: <number or 0> — enables global ratelimiting of queries accepted per ip address. This option is experimental at this time 🧪. The ratelimit is in queries per second that are allowed. More queries are completely dropped and will not receive a reply, SERVFAIL or otherwise 😭. IP ratelimiting happens before looking in the cache. This may be useful for mitigating amplification attacks. Clients with a valid DNS Cookie will bypass the ratelimit — and if a ratelimit for such clients is still needed, ip-ratelimit-cookie can be used instead.

Default: 0 (disabled)

ip-ratelimit-cookie: <number or 0> — enables global ratelimiting of queries accepted per IP address with a valid DNS Cookie. Also experimental at this time 🧪. The ratelimit is in queries per second that are allowed. More queries are completely dropped and will not receive a reply, SERVFAIL or otherwise. IP ratelimiting happens before looking in the cache. This option could be useful in combination with allow_cookie, in an attempt to mitigate other amplification attacks than UDP reflections (e.g., attacks targeting Local-unbound itself) which are already handled with DNS Cookies 🍪. If used, the value is suggested to be higher than ip-ratelimit e.g., tenfold.

Default: 0 (disabled)

ip-ratelimit-size: <memory size> — the size of the data structure in which the current ongoing rates are kept track of. In bytes or use m(mega), k(kilo), g(giga). The IP ratelimit structure is small, so this data structure likely does not need to be large 💖.

Default: 4m

ip-ratelimit-slabs: <number> — number of slabs in the ip ratelimit tracking data structure. Slabs reduce lock contention by threads. Must be set to a power of 2 ⭐. Setting it (close) to the number of cpus is a fairly good setting. If left unconfigured, it will be configured automatically to be a power of 2 close to the number of configured threads in multi-threaded environments.

Default: (unconfigured)

ip-ratelimit-factor: <number> — sets the amount of queries to rate limit when the limit is exceeded. If set to 0, all queries are dropped for addresses where the limit is exceeded. If set to another value, 1 in that number is allowed through to complete. Default is 10, allowing 1/10 traffic to flow normally. This can make ordinary queries complete (if repeatedly queried for), and enter the cache, whilst also mitigating the traffic flow by the factor given 🎀

Default: 10

ip-ratelimit-backoff: <yes or no> — if enabled, the rate limit is treated as a hard failure instead of the default maximum allowed constant rate. When the limit is reached, traffic is ratelimited and demand continues to be kept track of for a 2 second rate window. No traffic is allowed, except for ip-ratelimit-factor, until demand decreases below the configured ratelimit for a 2 second rate window. Useful to set ip-ratelimit to a suspicious rate to aggressively limit unusually high traffic 🔥.

Default: no

outbound-msg-retry: <number> — the number of retries, per upstream nameserver in a delegation, that Local-unbound will attempt in case a throwaway response is received. No response (timeout) contributes to the retry counter. If a forward/stub zone is used, this is the number of retries per nameserver in the zone.

Default: 5

max-sent-count: <number> — a hard limit on the number of outgoing queries Local-unbound will make while resolving a name, making sure large NS sets do not loop 🌀. Results in SERVFAIL when reached. It resets on query restarts (e.g., CNAME) and referrals.

Default: 32

max-query-restarts: <number> — hard cap on how many times Local-unbound can restart a query when it bumps into a CNAME record 😤 hit the limit and you get SERVFAIL, periodt. This counts chained CNAMEs, but not the sporadic ones that just kinda show up during the lifetime of a query's resolution effort. And the moment a CNAME chain wraps up, the counter tracking this limit gets reset 🔄. Change this value with caution bestie — a bigger number means long CNAME chains get accepted, and Local-unbound has to verify (resolve) every single link one by one 😭.

Default: 11

iter-scrub-ns: <number> — the max number of NS records allowed in an rrset of type NS, courtesy of the iterator scrubber 🧹. This is protecting the resolver's internals from NS sets that are, like, way too big.

Default: 20

iter-scrub-cname: <number> — max number of CNAME and DNAME records in an answer, again from the iterator scrubber, protecting the internals from indirection chains that go on forever 🌀. It literally clips off the rest of the reply packet at that point ✂️.

Default: 11

iter-scrub-rrsig: <number> — max RRSIGs allowed for an RRset, iterator scrubber again 🧹, and this one protects against an overly large number of RRSIGs. It clips off the remainder of the RRSIG list right there.

Default: 8

max-global-quota: <number> — cap on how many upstream queries get sent out for one incoming query plus its subqueries from recursion 🔥. Heads up: it is not reset during resolution. Blow past it and the query fails and the whole lookup process stops 🛑.

Default: 200

iter-scrub-promiscuous: <yes or no> — should the iterator scrubber remove promiscuous NS from positive answers? 💅 This protects against poisonous contents that could mess with names in the same zone as a spoofed packet 🙈.

Default: yes

fast-server-permil: <number> — tells you how many times out of 1000 to pick from the set of fastest servers ⚡. 0 turns the whole feature off. A value of 900 would pick from the fastest servers 90 percent of the time, and do normal exploration of random servers the rest of the time 🌈. When prefetch is enabled (or serve-expired), those prefetches are not sped up — there's literally nobody waiting on them 😴 — and it's actually a great moment to do some server exploration. The fast-server-num option sets the size of that fastest-servers set.

Default: 0

fast-server-num: <number> — sets how many servers should be used for fast server selection. You only use the fastest specified number of servers with the fast-server-permil option, which is what turns this on or off 🔘.

Default: 3

answer-cookie: <yes or no> — if enabled, Local-unbound will answer requests that contain DNS Cookies, exactly as specified in RFC 7873 and RFC 9018 🍪✨.

Default: no

cookie-secret: "<128 bit hex string>" — the server's secret for DNS Cookie generation 🔐. Super useful to explicitly set for servers in an anycast deployment that need to share the secret so they can verify each other's Server Cookies. An example hex string would be "000102030405060708090a0b0c0d0e0f".

NOTE: this option is ignored if a cookie-secret-file is present 👀 — in that case the secrets from that file are the ones used in DNS Cookie calculations.

Default: 128 bits random secret generated at startup time

cookie-secret-file: <filename> — the file the secrets are read from, used in DNS Cookie calculations 📄. When this file exists, the secrets inside it get used and the secret from the cookie-secret option is ignored. Enable it by setting a filename, like "/usr/local/etc/unbound_cookiesecrets.txt". The content of this file must be manipulated with the add_cookie_secret, drop_cookie_secret and activate_cookie_secret commands to the local-unbound-control(8) tool 🛠️. Please see that manpage on how to do a safe cookie secret rollover, bestie, don't freestyle it 💀.

Default: "" (disabled)

edns-client-string: <IP netblock> <string> — includes an EDNS0 option containing the configured ASCII string in queries whose destination address matches the configured <IP netblock> 🎯. This config option can be used multiple times. The most specific match wins 👑.
edns-client-string-opcode: <opcode> — the EDNS0 option code for the edns-client-string option, from 0 to 65535. A value from the 'Reserved for Local/Experimental' range (65001-65534) should be used 🧪.

Default: 65001

ede: <yes or no> — if enabled, Local-unbound will respond with Extended DNS Error codes (RFC 8914) 🚨. These EDEs give you extra info alongside a response, mainly for DNS and DNSSEC errors (but not limited to those).

When the val-log-level option is also set to 2, responses with Extended DNS Errors about DNSSEC failures will also contain a descriptive text message explaining why the failure happened 📝.

Default: no

ede-serve-expired: <yes or no> — if enabled, Local-unbound attaches an Extended DNS Error (RFC 8914) Code 3 - Stale Answer as an EDNS0 option to the expired response 🕰️.

NOTE: ede: yes needs to be set as well for this to work, no cap.

Default: no

dns-error-reporting: <yes or no> — if enabled, Local-unbound will send DNS Error Reports (RFC 9567) 📮. The name servers need to express support by attaching the Report-Channel EDNS0 option on their replies, specifying the reporting agent for the zone. Any errors encountered during resolution that would result in Unbound generating an Extended DNS Error (RFC 8914) get reported to the zone's reporting agent.

The ede option does not need to be enabled for this to work 👏.

It is advised that the qname-minimisation option is also enabled to increase privacy on the outgoing reports 🕵️‍♀️.

Default: no

🎮 REMOTE CONTROL OPTIONS 🎮

These options are part of the remote-control: section and they're basically the declarations for the remote control facility 🕹️.

If this is enabled, the local-unbound-control(8) utility can be used to send commands to the running Local-unbound server 💌. The server uses these options to set up the TLS security for the connection 🔒. The local-unbound-control(8) utility also reads this remote-control: section for options. To set up the correct self-signed certificates, use the unbound-control-setup(8) utility 🎀.

control-enable: <yes or no> — this option is used to enable remote control. Turn it off and the server doesn't listen for control commands at all 🙅‍♀️.

Default: no

control-interface: <IP address or interface name[@port] or path> — give IPv4 or IPv6 addresses, or a local socket path, to listen on for control commands 👂. If you use an interface name instead of an IP address, the list of IP addresses on that interface gets used.

By default localhost (127.0.0.1 and ::1) is listened to. Use 0.0.0.0 and ::0 to listen on all interfaces 🌐. If you change this and permissions have already been dropped, you must restart the server for the change to take effect 🔁.

If you set it to an absolute path, a unix domain socket is used 🧦. This socket does not use the certificates and keys, so those files need not be present. To restrict access, Local-unbound sets permissions on the file to the user and group that is configured, and the access bits are set to allow the group members to access the control socket file. Put users that need to access the socket in that group 👥. Wanna restrict access further? Create a directory to put the control socket in and restrict access to that directory 🔐.

control-port: <port number> — the port number to listen on for IPv4 or IPv6 control interfaces 🔢.

NOTE: if you change this and permissions have been dropped, you must restart the server for the change to take effect.

Default: 8953

control-use-cert: <yes or no> — for a localhost control-interface you can disable TLS by setting this option to "no" 🙈. For local sockets, TLS is disabled and the value of this option is just ignored.

Default: yes

server-key-file: <private key file> — path to the server private key 🔑. This file is generated by the local-unbound-control-setup(8) utility. It's used by the Local-unbound server, but not by local-unbound-control(8).

Default: unbound_server.key

server-cert-file: <certificate file.pem> — path to the server self signed certificate 📜. Generated by the local-unbound-control-setup(8) utility. This one is used by the Local-unbound server, and also by local-unbound-control(8).

Default: unbound_server.pem

control-key-file: <private key file> — path to the control client private key 🗝️. Generated by the local-unbound-control-setup(8) utility. This file is used by local-unbound-control(8).

Default: unbound_control.key

control-cert-file: <certificate file.pem> — path to the control client certificate 📃. This certificate has to be signed with the server certificate. Generated by the local-unbound-control-setup(8) utility. This file is used by local-unbound-control(8).

Default: unbound_control.pem

🌸 STUB ZONE OPTIONS 🌸

okay so these are the options that live inside the stub-zone: section, and bestie, they're lowkey iconic for private zones. ✨

There may be multiple stub-zone: sections. Each with a name and zero or more hostnames or IP addresses. For the stub zone this list of nameservers is used. Class IN is assumed. The servers should be authority servers, not recursors — Local-unbound performs the recursive processing itself for stub zones. 💅

The stub zone can be used to configure authoritative data to be used by the resolver that cannot be accessed using the public internet servers. This is useful for company-local data or private zones. Setup an authoritative server on a different host (or different port). Enter a config entry for Local-unbound with:

stub-addr: <ip address of host[@port]>

The Local-unbound resolver can then access the data, without referring to the public internet for it. 🎀

This setup allows DNSSEC signed zones to be served by that authoritative server, in which case a trusted key entry with the public key can be put in config, so that Local-unbound can validate the data and set the AD bit on replies for the private zone (authoritative servers do not set the AD bit). This setup makes Local-unbound capable of answering queries for the private zone, and can even set the AD bit ('authentic'), but the AA ('authoritative') bit is not set on these replies. no cap, that's the whole vibe. 🦋

Consider adding server statements for domain-insecure and for local-zone: <name> nodefault for the zone if it is a locally served zone. The domain-insecure option stops DNSSEC from invalidating the zone. The local-zone: nodefault (or transparent) option makes the (reverse-) zone bypass Local-unbound's filtering of RFC 1918 zones. 💖

name: <domain name> — Name of the stub zone. This is the full domain name of the zone. 👑
stub-host: <domain name> — Name of stub zone nameserver. Is itself resolved before it is used.
- To use a non-default port for DNS communication append '@' with the port number.
- If TLS is enabled, then you can append a '#' and a name, then it'll check the TLS authentication certificates with that name.
- If you combine the '@' and '#', the '@' comes first. If only '#' is used the default port is the configured tls-port.

CAUTION: If the domain (or a subdomain) from this zone is used as the host, it will unavoidably introduce a circular dependency on retrieving the IP addresses of the name server. In that case, it is suggested to use stub-addr instead. Alternatively, stub-first: yes can also work around the circular dependency by trying resolution outside of this zone. However this has the caveat that it would allow escaping this zone when any resolution attempt fails within this zone. 😭 like, be careful bestie.

stub-addr: <IP address> — IP address of stub zone nameserver. Can be IPv4 or IPv6.
- To use a non-default port for DNS communication append '@' with the port number.
- If TLS is enabled, then you can append a '#' and a name, then it'll check the tls authentication certificates with that name.
- If you combine the '@' and '#', the '@' comes first. If only '#' is used the default port is the configured tls-port.
stub-prime: <yes or no> — If enabled it performs NS set priming, which is similar to root hints, where it starts using the list of nameservers currently published by the zone. Thus, if the hint list is slightly outdated, the resolver picks up a correct list online. 🧚
- Default: no
stub-first: <yes or no> — If enabled, a query is attempted without this stub section if it fails. The data could not be retrieved and would have caused SERVFAIL because the servers are unreachable, instead it is tried without this stub section. This can lead to using less specific configured forward/stub/auth zones if any, or end up to otherwise normal recursive resolution for that particular query. 💫
- Default: no
stub-tls-upstream: <yes or no> — Enable or disable whether the queries to this stub use TLS for transport. 🔥
- Default: no
stub-ssl-upstream: <yes or no> — Alternate syntax for stub-tls-upstream.
stub-tcp-upstream: <yes or no> — If it is set to "yes" then upstream queries use TCP only for transport regardless of global flag tcp-upstream.
- Default: no
stub-no-cache: <yes or no> — If enabled, data inside the stub is not cached. This is useful when you want immediate changes to be visible. 👀
- Default: no

🦋 FORWARD ZONE OPTIONS 🦋

These options are part of the forward-zone: section, and honestly? it's giving "just hand it off to someone else" energy. 💅

There may be multiple forward-zone: sections. Each with a name and zero or more hostnames or IP addresses. For the forward zone this list of nameservers is used to forward the queries to. The servers listed as forward-host and forward-addr have to handle further recursion for the query. Thus, those servers are not authority servers, but are (just like Local-unbound is) recursive servers too; Local-unbound does not perform recursion itself for the forward zone, it lets the remote server do it. Class IN is assumed. CNAMEs are chased by Local-unbound itself, asking the remote server for every name in the indirection chain, to protect the local cache from illegal indirect referenced items. A forward-zone entry with name "." and a forward-addr target will forward all queries to that other server (unless it can answer from the cache). ⭐

name: <domain name> — Name of the forward zone. This is the full domain name of the zone. 👑
forward-host: <domain name> — Name of server to forward to. Is itself resolved before it is used.
- To use a non-default port for DNS communication append '@' with the port number.
- If TLS is enabled, then you can append a '#' and a name, then it'll check the TLS authentication certificates with that name.
- If you combine the '@' and '#', the '@' comes first. If only '#' is used the default port is the configured tls-port.

CAUTION: If the domain (or a subdomain) from this zone is used as the host, it will unavoidably introduce a circular dependency on retrieving the IP addresses of the name server. In that case, it is suggested to use forward-addr instead. Alternatively, forward-first: yes can also work around the circular dependency by trying resolution outside of this zone. However this has the caveat that it would allow escaping this zone when any resolution attempt fails within this zone. 🙈 bestie pls read this one.

forward-addr: <IP address> — IP address of server to forward to. Can be IPv4 or IPv6.
- To use a non-default port for DNS communication append '@' with the port number.
- If TLS is enabled, then you can append a '#' and a name, then it'll check the TLS authentication certificates with that name.
- If you combine the '@' and '#', the '@' comes first. If only '#' is used the default port is the configured tls-port.
- At high verbosity it logs the TLS certificate, with TLS enabled. If you leave out the '#' and auth name from the forward-addr, any name is accepted. The cert must also match a CA from the tls-cert-bundle. 🔍
forward-first: <yes or no> — If a forwarded query is met with a SERVFAIL error and this option is enabled Local-unbound will fall back to less specific resolution. This can lead to using less specific configured forward/stub/auth zones if any, or end up to otherwise normal recursive resolution for that particular query. 💫
- Default: no
forward-tls-upstream: <yes or no> — Enable or disable whether the queries to this forwarder use TLS for transport. If you enable this, also configure a tls-cert-bundle or use tls-win-cert to load CA certs, otherwise the connections cannot be authenticated. 🔥
- Default: no
forward-ssl-upstream: <yes or no> — Alternate syntax for forward-tls-upstream.
forward-tcp-upstream: <yes or no> — If it is set to "yes" then upstream queries use TCP only for transport regardless of global flag tcp-upstream.
- Default: no
forward-no-cache: <yes or no> — If enabled, data inside the forward is not cached. This is useful when you want immediate changes to be visible. 👀
- Default: no

👑 AUTHORITY ZONE OPTIONS 👑

Okay so these options live inside the auth-zone: section. Authority zones are configured with auth-zone:, and every single one must have a name. You can have multiple ones by listing multiple auth-zone section clauses, each with a different name, pertaining to that part of the namespace. The authority zone with the name closest to the name looked up is used. Authority zones can be processed on two distinct, non-exclusive, configurable stages. periodt 💅

With for-downstream: yes (default), authority zones are processed after local-zones and before cache. When used in this manner, Local-unbound responds like an authority server with no further processing other than returning an answer from the zone contents. A notable example, in this case, is CNAME records which are returned verbatim to downstream clients without further resolution. iykyk ✨

With for-upstream: yes (default), authority zones are processed after the cache lookup, just before going to the network to fetch information for recursion. When used in this manner they provide a local copy of an authority server that speeds up lookups for that data during resolving. lowkey efficient 🦋

If both options are enabled (default), client queries for an authority zone are answered authoritatively from Local-unbound, while internal queries that require data from the authority zone consult the local zone data instead of going to the network.

An interesting configuration is for-downstream: no, for-upstream: yes that allows for hyperlocal behavior where both client and internal queries consult the local zone data while resolving. In this case, the aforementioned CNAME example will result in a thoroughly resolved answer. slay 🔥

Authority zones can be read from a zonefile. And can be kept updated via AXFR and IXFR. After update the zonefile is rewritten. The update mechanism uses the SOA timer values and performs SOA UDP queries to detect zone changes.

If the update fetch fails, the timers in the SOA record are used to time another fetch attempt. Until the SOA expiry timer is reached. Then the zone is expired. When a zone is expired, queries are SERVFAIL, and any new serial number is accepted from the primary (even if older), and if fallback is enabled, the fallback activates to fetch from the upstream instead of the SERVFAIL. not me getting stressed about expired zones 😭

name: <zone name> — Name of the authority zone. 🎀
primary: <IP address or host name> — Where to download a copy of the zone from, with AXFR and IXFR. Multiple primaries can be specified. They are all tried if one fails. To use a non-default port for DNS communication append '@' with the port number. You can append a '#' and a name, then AXFR over TLS can be used and the TLS authentication certificates will be checked with that name. If you combine the '@' and '#', the '@' comes first. If you point it at another Local-unbound instance, it would not work because that does not support AXFR/IXFR for the zone, but if you used url to download the zonefile as a text file from a webserver that would work. CAUTION: If you specify the hostname, you cannot use the domain from the zonefile, because it may not have that when retrieving that data, instead use a plain IP address to avoid a circular dependency on retrieving that IP address. bestie please read the caution 💀
master: <IP address or host name> — Alternate syntax for primary. same energy, different name 💚
url: <URL to zone file> — Where to download a zonefile for the zone. With HTTP or HTTPS. An example for the url is: http://www.example.com/example.org.zone. Multiple url statements can be given, they are tried in turn. If only urls are given the SOA refresh timer is used to wait for making new downloads. If also primaries are listed, the primaries are first probed with UDP SOA queries to see if the SOA serial number has changed, reducing the number of downloads. If none of the urls work, the primaries are tried with IXFR and AXFR. For HTTPS, the tls-cert-bundle and the hostname from the url are used to authenticate the connection. If you specify a hostname in the URL, you cannot use the domain from the zonefile, because it may not have that when retrieving that data, instead use a plain IP address to avoid a circular dependency on retrieving that IP address. Avoid dependencies on name lookups by using a notation like "http://192.0.2.1/unbound-primaries/example.com.zone", with an explicit IP address. URL lore but make it safe 🌸
allow-notify: <IP address or host name or netblockIP/prefix> — With allow-notify you can specify additional sources of notifies. When notified, the server attempts to first probe and then zone transfer. If the notify is from a primary, it first attempts that primary. Otherwise other primaries are attempted. If there are no primaries, but only urls, the file is downloaded when notified. NOTE: The primaries from primary and url statements are allowed notify by default. notify me bestie 🔔
fallback-enabled: <yes or no> — If enabled, Local-unbound falls back to querying the internet as a resolver for this zone when lookups fail. For example for DNSSEC validation failures. Default: no. fallback era 🍑
for-downstream: <yes or no> — If enabled, Local-unbound serves authority responses to downstream clients for this zone. This option makes Local-unbound behave, for the queries with names in this zone, like one of the authority servers for that zone. Turn it off if you want Local-unbound to provide recursion for the zone but have a local copy of zone data. If for-downstream: no and for-upstream: yes are set, then Local-unbound will DNSSEC validate the contents of the zone before serving the zone contents to clients and store validation results in the cache. Default: yes. downstream icon behavior 👑
for-upstream: <yes or no> — If enabled, Local-unbound fetches data from this data collection for answering recursion queries. Instead of sending queries over the internet to the authority servers for this zone, it'll fetch the data directly from the zone data. Turn it on when you want Local-unbound to provide recursion for downstream clients, and use the zone data as a local copy to speed up lookups. Default: yes. upstream main character energy ⭐
zonemd-check: <yes or no> — Enable this option to check ZONEMD records in the zone. The ZONEMD record is a checksum over the zone data. This includes glue in the zone and data from the zone file, and excludes comments from the zone file. When there is a DNSSEC chain of trust, DNSSEC signatures are checked too. Default: no. checksum vibe check 🧚
zonemd-reject-absence: <yes or no> — Enable this option to reject the absence of the ZONEMD record. Without it, when ZONEMD is not there it is not checked. It is useful to enable for a non-DNSSEC signed zone where the operator wants to require the verification of a ZONEMD, hence a missing ZONEMD is a failure. The action upon failure is controlled by the zonemd-permissive-mode option, for log only or also block the zone. Without the option, absence of a ZONEMD is only a failure when the zone is DNSSEC signed, and we have a trust anchor, and the DNSSEC verification of the absence of the ZONEMD fails. With the option enabled, the absence of a ZONEMD is always a failure, also for nonDNSSEC signed zones. Default: no. no ZONEMD? no thank you 🙈
zonefile: <filename> — The filename where the zone is stored. If not given then no zonefile is used. If the file does not exist or is empty, Local-unbound will attempt to fetch zone data (eg. from the primary servers). file goes here, data goes fetch 🍓

🦋 VIEW OPTIONS 🦋

These options are part of the view: section.

There may be multiple view: sections. Each with a name and zero or more local-zone and local-data options. Views can also contain view-first, response-ip, response-ip-data and local-data-ptr options. View can be mapped to requests by specifying the view name in an access-control-view option. Options from matching views will override global options. Global options will be used if no matching view is found, or when the matching view does not have the option specified. view matching is giving group chat rules 🫶

name: <view name> — Name of the view. Must be unique. This name is used in the access-control-view option. unique queen 💅
local-zone: <zone> <type> — View specific local zone elements. Has the same types and behaviour as the global local-zone elements. When there is at least one local-zone: specified and view-first: no is set, the default local-zones will be added to this view. Defaults can be disabled using the nodefault type. When view-first: yes is set or when a view does not have a local-zone, the global local-zone will be used including it's default zones. local zone but make it view-specific 🌈
local-data: "<resource record string>" — View specific local data elements. Has the same behaviour as the global local-data elements. data but for this view ✨
local-data-ptr: "IPaddr name" — View specific local-data-ptr elements. Has the same behaviour as the global local-data-ptr elements. ptr but private to the view 🦋
response-ip: <IP-netblock> <action> — This requires use of the respip module. Similar to response-ip but only applies to this view. respip module said view-only 💛
response-ip-data: <IP-netblock> <"resource record string"> — This requires use of the respip module. Similar to response-ip-data but only applies to this view. same respip energy, this view only 🍑
view-first: <yes or no> — If enabled, it attempts to use the global local-zone and local-data if there is no match in the view specific options. Default: no. fallback to global, but make it cute 🎀

✨ PYTHON MODULE OPTIONS ✨

okay so these options are part of the python: section, bestie. 💖

The python: section gives the settings for the python(1) script module. This module acts like the iterator and validator modules do, on queries and answers. To enable the script module it has to be compiled into the daemon, and the word python has to be put in the module-config option (usually first, or between the validator and iterator). Multiple instances of the python module are supported by adding the word python more than once. fr fr, it's giving plug-in energy. ✨

If the chroot option is enabled, you should make sure Python's library directory structure is bind mounted in the new root environment, see mount(8). Also the python-script path should be specified as an absolute path relative to the new root, or as a relative path to the working directory.

python-script: <python file> — the script file to load. Repeat this option for every python module instance added to the module-config option. 💜

🦋 DYNAMIC LIBRARY MODULE OPTIONS 🦋

These options are part of the dynlib: section.

The dynlib: section gives the settings for the dynlib module. This module is only a very small wrapper that allows dynamic modules to be loaded on runtime instead of being compiled into the application. To enable the dynlib module it has to be compiled into the daemon, and the word dynlib has to be put in the module-config option. Multiple instances of dynamic libraries are supported by adding the word dynlib more than once.

The dynlib-file path should be specified as an absolute path relative to the new path set by chroot, or as a relative path to the working directory.

dynlib-file: <dynlib file> — the dynamic library file to load. Repeat this option for every dynlib module instance added to the module-config option. 🌈

🔥 DNS64 MODULE OPTIONS 🔥

These options are part of the server: section.

The dns64 module must be configured in the module-config directive, e.g.:

module-config: "dns64 validator iterator"

and be compiled into the daemon to be enabled. 👑

NOTE: If combining the respip and dns64 modules, the respip module needs to appear before the dns64 module in the module-config configuration option so that response IP and/or RPZ feeds can properly filter responses regardless of DNS64 synthesis.

dns64-prefix: <IPv6 prefix> — this sets the DNS64 prefix to use to synthesize AAAA records with. It must be /96 or shorter.

Default: 64:ff9b::/96

dns64-synthall: <yes or no> — okay bestie, warning first:

WARNING: Debugging feature!

If enabled, synthesize all AAAA records despite the presence of actual AAAA records.

Default: no

dns64-ignore-aaaa: <domain name> — list domain for which the AAAA records are ignored and the A record is used by DNS64 processing instead. Can be entered multiple times, list a new domain for which it applies, one per line. Applies also to names underneath the name given. 💖

🌈 NAT64 OPTIONS 🌈

These options are part of the server: section.

NAT64 operation allows using a NAT64 prefix for outbound requests to IPv4-only servers.

do-nat64: <yes or no> — use NAT64 to reach IPv4-only servers. Consider also enabling prefer-ip6 to prefer native IPv6 connections to nameservers.

Default: no

nat64-prefix: <IPv6 prefix> — use a specific NAT64 prefix to reach IPv4-only servers. The prefix length must be one of /32, /40, /48, /56, /64 or /96.

The NAT64 prefix is allowed by the do-not-query-address option, so that there is a clear outcome of addresses in both; the NAT64 prefix is allowed. The IPv4 address could be filtered by the do-not-query-address option, if needed. Allowing the NAT64 prefix is useful when using do-not-query-address for a cluster of machines that is IPv6-only and uses NAT64, but does not have internet access.

Default: 64:ff9b::/96 (same as dns64-prefix)

💅 DNSCRYPT OPTIONS 💅

These options are part of the dnscrypt: section.

The dnscrypt: section gives the settings of the dnscrypt channel. While those options are available, they are only meaningful if Local-unbound was compiled with --enable-dnscrypt. Currently certificate and secret/public keys cannot be generated by Unbound. You can use dnscrypt-wrapper to generate those: https://github.com/cofyc/dnscrypt-wrapper/blob/master/README.md#usage 👑

dnscrypt-enable: <yes or no> — whether or not the dnscrypt config should be enabled. You may define configuration but not activate it.

Default: no

dnscrypt-port: <port number> — on which port dnscrypt should be activated.

NOTE: There should be a matching interface option defined in the server: section for this port.

dnscrypt-provider: <provider name> — the provider name to use to distribute certificates. This is of the form:

2.dnscrypt-cert.example.com.

IMPORTANT: The name MUST end with a dot.

dnscrypt-secret-key: <path to secret key file> — path to the time limited secret key file. This option may be specified multiple times.
dnscrypt-provider-cert: <path to cert file> — path to the certificate related to the dnscrypt-secret-key. This option may be specified multiple times.
dnscrypt-provider-cert-rotated: <path to cert file> — path to a certificate that we should be able to serve existing connection from but do not want to advertise over the dnscrypt-provider's TXT record certs distribution.

A typical use case is when rotating certificates, existing clients may still use the client magic from the old cert in their queries until they fetch and update the new cert. Likewise, it would allow one to prime the new cert/key without distributing the new cert yet, this can be useful when using a network of servers using anycast and on which the configuration may not get updated at the exact same time.

By priming the cert, the servers can handle both old and new certs traffic while distributing only one.

This option may be specified multiple times.

dnscrypt-shared-secret-cache-size: <memory size> — give the size of the data structure in which the shared secret keys are kept in. In bytes or use m (mega), k (kilo), g (giga). The shared secret cache is used when a same client is making multiple queries using the same public key. It saves a substantial amount of CPU.

Default: 4m

dnscrypt-shared-secret-cache-slabs: <number> — number of slabs in the dnscrypt shared secrets cache. Slabs reduce lock contention by threads. Must be set to a power of 2. Setting (close) to the number of cpus is a fairly good setting. If left unconfigured, it will be configured automatically to be a power of 2 close to the number of configured threads in multi-threaded environments.

Default: (unconfigured)

dnscrypt-nonce-cache-size: <memory size> — give the size of the data structure in which the client nonces are kept in. In bytes or use m (mega), k (kilo), g (giga). The nonce cache is used to prevent dnscrypt message replaying. Client nonce should be unique for any pair of client pk/server sk.

Default: 4m

dnscrypt-nonce-cache-slabs: <number> — number of slabs in the dnscrypt nonce cache. Slabs reduce lock contention by threads. Must be set to a power of 2. Setting (close) to the number of cpus is a fairly good setting. If left unconfigured, it will be configured automatically to be a power of 2 close to the number of configured threads in multi-threaded environments.

Default: (unconfigured)

🌸 EDNS CLIENT SUBNET MODULE OPTIONS 🌸

okay so these ECS options are part of the server: section, bestie. 💖

The ECS module has to be configured in the module-config directive, like this:

module-config: "subnetcache validator iterator"

and it also has to be compiled into the daemon to be enabled. no cap. ✨

If the destination address is allowed in the configuration, Local-unbound will add the EDNS0 option to the query containing the relevant part of the client's address. When an answer contains the ECS option, the response and the option are placed in a specialized cache. If the authority indicated no support, the response is stored in the regular cache. 💅

Additionally, when a client includes the option in its queries, Local-unbound will forward the option when sending the query to addresses that are explicitly allowed in the configuration using send-client-subnet. The option will always be forwarded, regardless of the allowed addresses, when client-subnet-always-forward: yes is set. In this case the lookup in the regular cache is skipped. 🫶

The maximum size of the ECS cache is controlled by msg-cache-size in the configuration file. On top of that, for each query only 100 different subnets are allowed to be stored for each address family. Exceeding that number, older entries will be purged from cache. 🧚

real talk: due to the nature of how EDNS Client Subnet works, by segregating the client IP space in order to try and have tailored responses for prefixes of unknown sizes, resolution and cache response performance are impacted as a result. Usage of the subnetcache module should only be enabled in installations that require such functionality where the resolver and the clients belong to different networks. An example of that is an open resolver installation. 👑

This module does not interact with the serve-expired* and prefetch options. 💀

send-client-subnet: <IP address> — Send client source address to this authority. Append /num to indicate a classless delegation netblock, for example like 10.2.3.4/24 or 2001::11/64. Can be given multiple times. Authorities not listed will not receive edns-subnet information, unless domain in query is specified in client-subnet-zone. ⭐
client-subnet-zone: <domain> — Send client source address in queries for this domain and its subdomains. Can be given multiple times. Zones not listed will not receive edns-subnet information, unless hosted by authority specified in send-client-subnet. 🦋
client-subnet-always-forward: <yes or no> — Specify whether the ECS address check (configured using send-client-subnet) is applied for all queries, even if the triggering query contains an ECS record, or only for queries for which the ECS record is generated using the querier address (and therefore did not contain ECS data in the client query). If enabled, the address check is skipped when the client query contains an ECS record. And the lookup in the regular cache is skipped. Default: no. 🌈
max-client-subnet-ipv6: <number> — Specifies the maximum prefix length of the client source address we are willing to expose to third parties for IPv6. Default: 56. 💖
max-client-subnet-ipv4: <number> — Specifies the maximum prefix length of the client source address we are willing to expose to third parties for IPv4. Default: 24. 💖
min-client-subnet-ipv6: <number> — Specifies the minimum prefix length of the IPv6 source mask we are willing to accept in queries. Shorter source masks result in REFUSED answers. Source mask of 0 is always accepted. Default: 0. 🎀
min-client-subnet-ipv4: <number> — Specifies the minimum prefix length of the IPv4 source mask we are willing to accept in queries. Shorter source masks result in REFUSED answers. Source mask of 0 is always accepted. Default: 0. 🎀
max-ecs-tree-size-ipv4: <number> — Specifies the maximum number of subnets ECS answers kept in the ECS radix tree. This number applies for each qname/qclass/qtype tuple. Default: 100. 🔥
max-ecs-tree-size-ipv6: <number> — Specifies the maximum number of subnets ECS answers kept in the ECS radix tree. This number applies for each qname/qclass/qtype tuple. Default: 100. 🔥

🧚 OPPORTUNISTIC IPSEC SUPPORT MODULE OPTIONS 🧚

These options are part of the server: section. ✨

The IPsec module must be configured in the module-config directive, e.g.:

module-config: "ipsecmod validator iterator"

and be compiled into Local-unbound by using --enable-ipsecmod to be enabled. 💖

When Local-unbound receives an A/AAAA query that is not in the cache and finds a valid answer, it will withhold returning the answer and instead will generate an IPSECKEY subquery for the same domain name. If an answer was found, Local-unbound will call an external hook passing the following arguments: 👑

QNAME — Domain name of the A/AAAA and IPSECKEY query. In string format.
IPSECKEY TTL — TTL of the IPSECKEY RRset.
A/AAAA — String of space separated IP addresses present in the A/AAAA RRset. The IP addresses are in string format.
IPSECKEY — String of space separated IPSECKEY RDATA present in the IPSECKEY RRset. The IPSECKEY RDATA are in DNS presentation format.

The A/AAAA answer is then cached and returned to the client. If the external hook was called the TTL changes to ensure it doesn't surpass ipsecmod-max-ttl. 🦋

The same procedure is also followed when prefetch: yes is set, but the A/AAAA answer is given to the client before the hook is called. ipsecmod-max-ttl ensures that the A/AAAA answer given from cache is still relevant for opportunistic IPsec. 🌈

ipsecmod-enabled: <yes or no> — Specifies whether the IPsec module is enabled or not. The IPsec module still needs to be defined in the module-config directive. This option facilitates turning on/off the module without restarting/reloading Unbound. Default: yes. ⭐
ipsecmod-hook: <filename> — Specifies the external hook that Local-unbound will call with system(3). The file can be specified as an absolute/relative path. The file needs the proper permissions to be able to be executed by the same user that runs Unbound. It must be present when the IPsec module is defined in the module-config directive. 🧚
ipsecmod-strict: <yes or no> — If enabled Local-unbound requires the external hook to return a success value of 0. Failing to do so Local-unbound will reply with SERVFAIL. The A/AAAA answer will also not be cached. Default: no. 💀
ipsecmod-max-ttl: <seconds> — Time to live maximum for A/AAAA cached records after calling the external hook. Default: 3600. 🎀
ipsecmod-ignore-bogus: <yes or no> — Specifies the behaviour of Local-unbound when the IPSECKEY answer is bogus. If set to yes, the hook will be called and the A/AAAA answer will be returned to the client. If set to no, the hook will not be called and the answer to the A/AAAA query will be SERVFAIL. Mainly used for testing. Default: no. 🙈
ipsecmod-allow: <domain> — Allow the IPsec module functionality for the domain so that the module logic will be executed. Can be given multiple times, for different domains. If the option is not specified, all domains are treated as being allowed (default). 👑
ipsecmod-whitelist: <domain> — Alternate syntax for ipsecmod-allow. 💅

💾 CACHE DB MODULE OPTIONS 💾

Okay bestie, these options are part of the cachedb: section. Yes, it's giving "second cache era" and honestly? Kinda iconic. 💅

The Cache DB module must be configured in the module-config directive, like this:

module-config: "validator cachedb iterator"

and it has to be compiled into the daemon with --enable-cachedb. No cap.

If this module is enabled and configured, the specified backend database works as a second level cache; when Local-unbound cannot find an answer to a query in its built-in in-memory cache, it consults the specified backend. If it finds a valid answer in the backend, Local-unbound uses it to respond to the query without performing iterative DNS resolution. If Local-unbound cannot even find an answer in the backend, it resolves the query as usual, and stores the answer in the backend. That's the whole little second-cache pipeline, bestie 💖

This module interacts with the serve-expired-* options and will reply with expired data if Local-unbound is configured for that. expired but still serving? it's giving ghost of DNS past 👻

If Local-unbound was built with --with-libhiredis on a system that has installed the hiredis C client library of Redis, then the redis backend can be used. This backend communicates with the specified Redis server over a TCP connection to store and retrieve cache data. It can be used as a persistent and/or shared cache backend. redis backend girlies, rise ✨

NOTE: Local-unbound never removes data stored in the Redis server, even if some data have expired in terms of DNS TTL or the Redis server has cached too much data; if necessary the Redis server must be configured to limit the cache size, preferably with some kind of least-recently-used eviction policy. like fr fr, Redis is not gonna clean up after itself here 💀

Additionally, the redis-expire-records option can be used in order to set the relative DNS TTL of the message as timeout to the Redis records; keep in mind that some additional memory is used per key and that the expire information is stored as absolute Unix timestamps in Redis (computer time must be stable). clock stability is not a vibe to skip, bestie 🕰️

This backend uses synchronous communication with the Redis server based on the assumption that the communication is stable and sufficiently fast. The thread waiting for a response from the Redis server cannot handle other DNS queries. Although the backend has the ability to reconnect to the server when the connection is closed unexpectedly and there is a configurable timeout in case the server is overly slow or hangs up, these cases are assumed to be very rare. If connection close or timeout happens too often, Local-unbound will be effectively unusable with this backend. It's the administrator's responsibility to make the assumption hold. so if Redis is flaky? yeah, that's gonna be a whole situation 😭

The cachedb: section gives custom settings of the cache DB module.

🎀 the main `cachedb:` settings 🎀

backend: <backend name> — Specify the backend database name. The default database is the in-memory backend named testframe, which, as the name suggests, is not of any practical use. Depending on the build-time configuration, redis backend may also be used as described above. Default: testframe.
secret-seed: "<secret string>" — Specify a seed to calculate a hash value from query information. This value will be used as the key of the corresponding answer for the backend database and can be customized if the hash should not be predictable operationally. If the backend database is shared by multiple Local-unbound instances, all instances must use the same secret seed. Default: "default". shared cache besties gotta match seeds, no exceptions 💖
cachedb-no-store: <yes or no> — If the backend should be read from, but not written to. This makes this instance not store dns messages in the backend. But if data is available it is retrieved. Default: no.
cachedb-check-when-serve-expired: <yes or no> — If enabled, the cachedb is checked before an expired response is returned. When serve-expired is enabled, without serve-expired-client-timeout, it then does not immediately respond with an expired response from cache, but instead first checks the cachedb for valid contents, and if so returns it. If the cachedb also has no valid contents, the serve expired response is sent. If also serve-expired-client-timeout is enabled, the expired response is delayed until the timeout expires. Unless the lookup succeeds within the timeout. Default: yes.

🍒 the `cachedb:` options that are redis-backend-specific 🍒

The following cachedb: options are specific to the redis backend. redis girlies, this is your moment 💅

redis-server-host: <server address or name> — The IP (either v6 or v4) address or domain name of the Redis server. In general an IP address should be specified as otherwise Local-unbound will have to resolve the name of the server every time it establishes a connection to the server. Default: 127.0.0.1.
redis-server-port: <port number> — The TCP port number of the Redis server. Default: 6379.
redis-server-path: <unix socket path> — The unix socket path to connect to the Redis server. Unix sockets may have better throughput than the IP address option. Default: "" (disabled).
redis-server-password: "<password>" — The Redis AUTH password to use for the Redis server. Only relevant if Redis is configured for client password authorisation. Default: "" (disabled).
redis-timeout: <msec> — The period until when Local-unbound waits for a response from the Redis server. If this timeout expires Local-unbound closes the connection, treats it as if the Redis server does not have the requested data, and will try to re-establish a new connection later. Default: 100.
redis-command-timeout: <msec> — The timeout to use for Redis commands, in milliseconds. If 0, it uses the redis-timeout value. Default: 0.
redis-connect-timeout: <msec> — The timeout to use for Redis connection set up, in milliseconds. If 0, it uses the redis-timeout value. Default: 0.
redis-expire-records: <yes or no> — If Redis record expiration is enabled. If yes, Local-unbound sets timeout for Redis records so that Redis can evict keys that have expired automatically. If Local-unbound is configured with serve-expired and serve-expired-ttl: 0, this option is internally reverted to "no". Default: no.

NOTE: Redis "SET ... EX" support is required for this option (Redis >= 2.6.12). old Redis? not invited to this party 🙈

redis-logical-db: <logical database index> — The logical database in Redis to use. These are databases in the same Redis instance sharing the same configuration and persisted in the same RDB/AOF file. If unsure about using this option, Redis documentation (https://redis.io/commands/select/) suggests not to use a single Redis instance for multiple unrelated applications. The default database in Redis is 0 while other logical databases need to be explicitly SELECT'ed upon connecting. Default: 0.
redis-replica-server-host: <server address or name> — The IP (either v6 or v4) address or domain name of the Redis server. In general an IP address should be specified as otherwise Local-unbound will have to resolve the name of the server every time it establishes a connection to the server. This server is treated as a read-only replica server (the https://redis.io/docs/management/replication/#read-only-replica situation). If specified, all Redis read commands will go to this replica server, while the write commands will go to the redis-server-host. Default: "" (disabled).
redis-replica-server-port: <port number> — The TCP port number of the Redis replica server. Default: 6379.
redis-replica-server-path: <unix socket path> — The unix socket path to connect to the Redis replica server. Unix sockets may have better throughput than the IP address option. Default: "" (disabled).
redis-replica-server-password: "<password>" — The Redis AUTH password to use for the Redis server. Only relevant if Redis is configured for client password authorisation. Default: "" (disabled).
redis-replica-timeout: <msec> — The period until when Local-unbound waits for a response from the Redis replica server. If this timeout expires Local-unbound closes the connection, treats it as if the Redis server does not have the requested data, and will try to re-establish a new connection later. Default: 100.
redis-replica-command-timeout: <msec> — The timeout to use for Redis replica commands, in milliseconds. If 0, it uses the redis-replica-timeout value. Default: 0.
redis-replica-connect-timeout: <msec> — The timeout to use for Redis replica connection set up, in milliseconds. If 0, it uses the redis-replica-timeout value. Default: 0.
redis-replica-logical-db: <logical database index> — Same as redis-logical-db but for the Redis replica server. Default: 0.

🔥 DNSTAP OPTIONS 🔥

okay so these ones live inside the dnstap: section, bestie. dnstap is this super flexible, structured binary log format for DNS software, and when it's compiled in (you do that with --enable-dnstap 🫶) you can turn it on right here in the dnstap: section.

Here's the tea: this spins up an extra thread (when it's compiled with threading, that is) that writes the log info to wherever you point it. and ngl, if Local-unbound is compiled without threading, it doesn't spawn a thread at all — it just connects per-process to the destination instead. 💅

dnstap-enable: <yes or no> — whether dnstap is on at all. If yes, it connects to the DNSTAP server, and if any of the dnstap-log-..-messages: options are enabled it ships logs for those messages over to the server. slay.

Default: no

dnstap-bidirectional: <yes or no> — use frame streams in bidirectional mode to transfer DNSTAP messages. 🔄

Default: yes

dnstap-socket-path: <file name> — sets the unix socket file name for connecting to the server that's listening on that socket.

Default: (blank)

dnstap-ip: <IPaddress[@port]> — if "", the unix socket gets used; if you set it to an IP address (IPv4 or IPv6), that address is what's used to connect to the server. 👑

Default: ""

dnstap-tls: <yes or no> — set this to use TLS when connecting to the server specified in dnstap-ip. If you set it to no, plain TCP is what's used to connect instead.

Default: yes

dnstap-tls-server-name: <name of TLS authentication> — the TLS server name to authenticate the server with. used when dnstap-tls: yes is set. if it's "" it's just ignored 🙈

Default: ""

dnstap-tls-cert-bundle: <file name of cert bundle> — the pem file with certs to verify the TLS server certificate. if "", the server default cert bundle is used, or the windows cert bundle on windows.

Default: ""

dnstap-tls-client-key-file: <file name> — the client key file for TLS client authentication. if "", client authentication is not used.

Default: ""

dnstap-tls-client-cert-file: <file name> — the client cert file for TLS client authentication.

Default: ""

dnstap-send-identity: <yes or no> — if enabled, the server identity gets included in the log messages. 💖

Default: no

dnstap-send-version: <yes or no> — if enabled, the server version gets included in the log messages.

Default: no

dnstap-identity: <string> — the identity to send with messages; if "", the hostname is used.

Default: ""

dnstap-version: <string> — the version to send with messages; if "", the package version is used.

Default: ""

dnstap-sample-rate: <number> — the sample rate for logging messages, i.e. it logs only 1/N messages. with 0 it's disabled. this is genuinely so useful in a high volume environment, where the log functionality would otherwise not be reliable. like, 10 would spend only 1/10th the time on logging, and 100 would only spend a hundredth of the time on logging. math ate, fr fr. 🍓

Default: 0 (disabled)

dnstap-log-resolver-query-messages: <yes or no> — enable to log resolver query messages. these are messages from Local-unbound to upstream servers.

Default: no

dnstap-log-resolver-response-messages: <yes or no> — enable to log resolver response messages. these are replies from upstream servers to Unbound.

Default: no

dnstap-log-client-query-messages: <yes or no> — enable to log client query messages. these are client queries to Unbound.

Default: no

dnstap-log-client-response-messages: <yes or no> — enable to log client response messages. these are responses from Local-unbound to clients. 🌸

Default: no

dnstap-log-forwarder-query-messages: <yes or no> — enable to log forwarder query messages.

Default: no

dnstap-log-forwarder-response-messages: <yes or no> — enable to log forwarder response messages.

Default: no

💅 RESPONSE POLICY ZONE OPTIONS 💅

okay so these options are part of the rpz: section. RPZ stands for Response Policy Zones, and they're configured with rpz: section clauses — each one must have a name option. You can have multiple ones by listing multiple rpz: section clauses, each with a different name. They're applied in order of configuration, and any match from an earlier RPZ zone will terminate the RPZ lookup. Important: a PASSTHRU action is still considered a match.

The respip module needs to be added to the module-config, like this:

module-config: "respip validator iterator"

NOTE: If you combine the respip and dns64 modules, the respip module needs to appear before the dns64 module in the module-config configuration option so that response IP and/or RPZ feeds can properly filter responses regardless of DNS64 synthesis. fr fr, order matters here.

QNAME, Response IP Address, nsdname, nsip and clientip triggers are supported. Supported actions are: NXDOMAIN, NODATA, PASSTHRU, DROP, Local Data, tcp-only and drop. RPZ QNAME triggers are applied after any local-zone and before any auth-zone.

The RPZ zone is a regular DNS zone formatted with a SOA start record as usual. The items in the zone are entries that specify what to act on (the trigger) and what to do (the action). The trigger to act on is recorded in the name, and the action to do is recorded as the resource record. The names all end in the zone name, so you could type the trigger names without a trailing dot in the zonefile.

An example RPZ record that answers example.com with NXDOMAIN:

example.com CNAME .

The triggers are encoded in the name on the left:

name — query name
netblock.rpz-client-ip — client IP address
netblock.rpz-ip — response IP address in the answer
name.rpz-nsdname — nameserver name
netblock.rpz-nsip — nameserver IP address

The netblock is written as <netblocklen>.<ip address in reverse>. For IPv6 use 'zz' for '::'. Specify individual addresses with scope length of 32 or 128. For example, 24.10.100.51.198.rpz-ip is 198.51.100.10/24 and 32.10.zz.db8.2001.rpz-ip is 2001:db8:0:0:0:0:0:10/32. look at those reversed octets, iconic 💅

The actions are specified with the record on the right:

CNAME . — nxdomain reply
CNAME *. — nodata reply
CNAME rpz-passthru. — do nothing, allow to continue
CNAME rpz-drop. — the query is dropped
CNAME rpz-tcp-only. — answer over TCP
A 192.0.2.1 — answer with this IP address

Other records like AAAA, TXT and other CNAMEs (not rpz-..) can also be used to answer queries with that content. slay, flexible much?

name: <zone name> — Name of the authority zone.
primary: <IP address or host name> — Where to download a copy of the zone from, with AXFR and IXFR. Multiple primaries can be specified. They are all tried if one fails.
- To use a non-default port for DNS communication append '@' with the port number.
- You can append a '#' and a name, then AXFR over TLS can be used and the TLS authentication certificates will be checked with that name.
- If you combine the '@' and '#', the '@' comes first. If you point it at another Local-unbound instance, it would not work because that does not support AXFR/IXFR for the zone, but if you used url to download the zonefile as a text file from a webserver that would work.
- If you specify the hostname, you cannot use the domain from the zonefile, because it may not have that when retrieving that data; instead use a plain IP address to avoid a circular dependency on retrieving that IP address.
master: <IP address or host name> — Alternate syntax for primary.
url: <url to zonefile> — Where to download a zonefile for the zone. With HTTP or HTTPS. An example for the url is:

http://www.example.com/example.org.zone

Multiple url statements can be given, they are tried in turn.

If only urls are given the SOA refresh timer is used to wait for making new downloads. If also primaries are listed, the primaries are first probed with UDP SOA queries to see if the SOA serial number has changed, reducing the number of downloads. If none of the URLs work, the primaries are tried with IXFR and AXFR.

For HTTPS, the tls-cert-bundle and the hostname from the url are used to authenticate the connection. secure-ish bestie, we love an authenticated download.

allow-notify: <IP address or host name or netblockIP/prefix> — With allow-notify you can specify additional sources of notifies. When notified, the server attempts to first probe and then zone transfer. If the notify is from a primary, it first attempts that primary. Otherwise other primaries are attempted. If there are no primaries, but only urls, the file is downloaded when notified.

NOTE: The primaries from primary and url statements are allowed notify by default.

zonefile: <filename> — The filename where the zone is stored. If not given then no zonefile is used. If the file does not exist or is empty, Local-unbound will attempt to fetch zone data (eg. from the primary servers).
rpz-action-override: <action> — Always use this RPZ action for matching triggers from this zone. Possible actions are: nxdomain, nodata, passthru, drop, disabled and cname.
rpz-cname-override: <domain> — The CNAME target domain to use if the cname action is configured for rpz-action-override.
rpz-log: <yes or no> — Log all applied RPZ actions for this RPZ zone.

Default: no

rpz-log-name: <name> — Specify a string to be part of the log line, for easy referencing. so your greps stay cute and effective 💚
rpz-signal-nxdomain-ra: <yes or no> — Signal when a query is blocked by the RPZ with NXDOMAIN with an unset RA flag. This allows certain clients, like dnsmasq, to infer that the domain is externally blocked.

Default: no

for-downstream: <yes or no> — If enabled the zone is authoritatively answered for and queries for the RPZ zone information are answered to downstream clients. This is useful for monitoring scripts, that can then access the SOA information to check if the RPZ information is up to date.

Default: no

tags: "<list of tags>" — Limit the policies from this RPZ section to clients with a matching tag.

Tags need to be defined in define-tag and can be assigned to client addresses using access-control-tag or interface-tag. Enclose list of tags in quotes ("") and put spaces between tags.

If no tags are specified the policies from this section will be applied for all clients.

🧠 MEMORY CONTROL EXAMPLE 🧠

In the example config settings below memory usage is reduced. Some service levels are lower; notable very large data and a high TCP load are no longer supported. Very large data and high TCP loads are exceptional for the DNS. DNSSEC validation is enabled, just add trust anchors. If you do not have to worry about programs using more than 3 Mb of memory, the below example is not for you. Use the defaults to receive full service, which on BSD-32bit tops out at 30-40 Mb after heavy usage. basically: this is the low-memory era, not the main-character-everything-on era 🍑

# example settings that reduce memory usage
server:
    num-threads: 1
    outgoing-num-tcp: 1 # this limits TCP service, uses less buffers.
    incoming-num-tcp: 1
    outgoing-range: 60  # uses less memory, but less performance.
    msg-buffer-size: 8192   # note this limits service, 'no huge stuff'.
    msg-cache-size: 100k
    msg-cache-slabs: 1
    rrset-cache-size: 100k
    rrset-cache-slabs: 1
    infra-cache-numhosts: 200
    infra-cache-slabs: 1
    key-cache-size: 100k
    key-cache-slabs: 1
    neg-cache-size: 10k
    num-queries-per-thread: 30
    target-fetch-policy: "2 1 0 0 0 0"
    harden-large-queries: "yes"
    harden-short-bufsize: "yes"

📁 FILES 📁

/var/unbound — default Local-unbound working directory.
/var/unbound — default chroot(2) location. yes it's listed twice, that's the page, not me repeating myself 💜
/var/unbound/unbound.conf — Local-unbound configuration file.
/var/unbound/unbound.pid — default Local-unbound pidfile with process ID of the running daemon.
unbound.log — Local-unbound log file. Default is to log to syslog(3).

👀 SEE ALSO 👀

local-unbound(8)
local-unbound-checkonf(8) copying that exact, bestie — checkonf, not a typo I invented 😭

✍️ AUTHOR ✍️

Local-unbound developers are mentioned in the CREDITS file in the distribution. give them their flowers 💐

1999-2026, NLnet Labs

okay that's the whole page, and the footer-vibe sign-off is: source/version is UNBOUND.CONF(5), version 1.25.1, dated May 20, 2026 — periodt, go configure your RPZ and slay 💅🫶

📦 where this page comes from

freebsd 15.1: base 15.1
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash-1017 on 2026-11-04: a language model's rewrite of the original, under its terms

UNBOUND.CONF(5)

💖 unbound.conf(5) 💖

✨ NAME ✨

🎀 SYNOPSIS 🎀

🦋 DESCRIPTION 🦋

🌸 FILE FORMAT 🌸

💖 EXAMPLE 💖

🦋 SECTION CLAUSES 🦋

🌈 INCLUDING FILES 🌈

🔥 SERVER OPTIONS 🔥

💖 localhost 💖

🌸 reverse IPv4 loopback 🌸

🦋 reverse IPv6 loopback 🦋

🎀 home.arpa (RFC 8375) 🎀

✨ resolver.arpa (RFC 9462) ✨

🌈 service.arpa (draft-ietf-dnssd-srp-25) 🌈

🧅 onion (RFC 7686) 🧅

⭐ test (RFC 6761) ⭐

💀 invalid (RFC 6761) 💀

💜 reverse local use zones (RFC 1918) 💜

🍓 special-use IPv4 Addresses (RFC 3330) 🍓

🌸 reverse IPv6 unspecified (RFC 4291) 🌸

🦋 reverse IPv6 Locally Assigned Local Addresses (RFC 4193) 🦋

🎀 reverse IPv6 Link Local Addresses (RFC 4291) 🎀

✨ reverse IPv6 Example Prefix ✨

💅 local-data: "<resource record string>" 💅

🫶 local-data-ptr: "IPaddr name" 🫶

🌟 local-zone-tag: <zone> <"list of tags"> 🌟

🔥 local-zone-override: <zone> <IP netblock> <type> 🔥

👑 response-ip: <IP-netblock> <action> 👑

💖 response-ip-data: <IP-netblock> <"resource record string"> 💖

🎮 REMOTE CONTROL OPTIONS 🎮

🌸 STUB ZONE OPTIONS 🌸

🦋 FORWARD ZONE OPTIONS 🦋

👑 AUTHORITY ZONE OPTIONS 👑

🦋 VIEW OPTIONS 🦋

✨ PYTHON MODULE OPTIONS ✨

🦋 DYNAMIC LIBRARY MODULE OPTIONS 🦋

🔥 DNS64 MODULE OPTIONS 🔥

🌈 NAT64 OPTIONS 🌈

💅 DNSCRYPT OPTIONS 💅

🌸 EDNS CLIENT SUBNET MODULE OPTIONS 🌸

🧚 OPPORTUNISTIC IPSEC SUPPORT MODULE OPTIONS 🧚

💾 CACHE DB MODULE OPTIONS 💾

🎀 the main cachedb: settings 🎀

🍒 the cachedb: options that are redis-backend-specific 🍒

🔥 DNSTAP OPTIONS 🔥

💅 RESPONSE POLICY ZONE OPTIONS 💅

🧠 MEMORY CONTROL EXAMPLE 🧠

📁 FILES 📁

👀 SEE ALSO 👀

✍️ AUTHOR ✍️

©️ COPYRIGHT ©️

💅 `local-data: "<resource record string>"` 💅

🫶 `local-data-ptr: "IPaddr name"` 🫶

🌟 `local-zone-tag: <zone> <"list of tags">` 🌟

🔥 `local-zone-override: <zone> <IP netblock> <type>` 🔥

👑 `response-ip: <IP-netblock> <action>` 👑

💖 `response-ip-data: <IP-netblock> <"resource record string">` 💖

🎀 the main `cachedb:` settings 🎀

🍒 the `cachedb:` options that are redis-backend-specific 🍒