Fix multiple vulnerabilities in unbound.

[FreeBSD/FreeBSD.git] / contrib / unbound / doc / unbound.conf.5

.TH "unbound.conf" "5" "Jun 17, 2019" "NLnet Labs" "unbound 1.9.2"
.\"
.\" unbound.conf.5 -- unbound.conf manual
.\"
.\" Copyright (c) 2007, NLnet Labs. All rights reserved.
.\"
.\" See LICENSE for the license.
.\"
.\"
.SH "NAME"
.B unbound.conf
\- Unbound configuration file.
.SH "SYNOPSIS"
.B unbound.conf
.SH "DESCRIPTION"
.B unbound.conf
is used to configure
\fIunbound\fR(8).
The file format has attributes and values. Some attributes have attributes
inside them.
The notation is: attribute: value.
.P
Comments start with # and last to the end of line. Empty lines are
ignored as is whitespace at the beginning of a line.
.P
The utility
\fIunbound\-checkconf\fR(8)
can be used to check unbound.conf prior to usage.
.SH "EXAMPLE"
An example config file is shown below. Copy this to /etc/unbound/unbound.conf
and start the server with:
.P
.nf
        $ unbound \-c /etc/unbound/unbound.conf
.fi
.P
Most settings are the defaults. Stop the server with:
.P
.nf
        $ kill `cat /etc/unbound/unbound.pid`
.fi
.P
Below is a minimal config file. The source distribution contains an extensive
example.conf file with all the options.
.P
.nf
# unbound.conf(5) config file for unbound(8).
server:
        directory: "/etc/unbound"
        username: unbound
        # make sure 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/random /etc/unbound/dev/random
        # and  mount \-\-bind \-n /dev/log /etc/unbound/dev/log
        chroot: "/etc/unbound"
        # logfile: "/etc/unbound/unbound.log"  #uncomment to use logfile.
        pidfile: "/etc/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
.fi
.SH "FILE FORMAT"
There must be whitespace between keywords. Attribute keywords end with a colon ':'.
An attribute is followed by its containing attributes, or a value.
.P
Files can be included using the
.B 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 \fIglob\fR(7).
.SS "Server Options"
These options are part of the
.B server:
clause.
.TP
.B verbosity: \fI<number>
The verbosity number, level 0 means no verbosity, only errors. Level 1
gives operational information. Level 2 gives detailed operational
information. Level 3 gives query level information, output per query.
Level 4 gives algorithm level information.  Level 5 logs client
identification for cache misses.  Default is level 1.
The verbosity can also be increased from the commandline, see \fIunbound\fR(8).
.TP
.B statistics\-interval: \fI<seconds>
The number of seconds between printing statistics to the log for every thread.
Disable with value 0 or "". Default is disabled.  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.
.TP
.B statistics\-cumulative: \fI<yes or no>
If enabled, statistics are cumulative since starting unbound, without clearing
the statistics counters after logging the statistics. Default is no.
.TP
.B extended\-statistics: \fI<yes or no>
If enabled, extended statistics are printed from \fIunbound\-control\fR(8).
Default is off, because keeping track of more statistics takes time.  The
counters are listed in \fIunbound\-control\fR(8).
.TP
.B num\-threads: \fI<number>
The number of threads to create to serve clients. Use 1 for no threading.
.TP
.B port: \fI<port number>
The port number, default 53, on which the server responds to queries.
.TP
.B interface: \fI<ip address[@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 to localhost.
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
\fBport\fR) is used.
.TP
.B ip\-address: \fI<ip address[@port]>
Same as interface: (for ease of compatibility with nsd.conf).
.TP
.B interface\-automatic: \fI<yes or no>
Detect source interface on UDP queries and copy them to replies.  This
feature is experimental, and needs support in your OS for particular socket
options.  Default value is no.
.TP
.B outgoing\-interface: \fI<ip address or ip6 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
.B interface:
and
.B outgoing\-interface:
lines, the interfaces are then used for both purposes. Outgoing queries are
sent via a random outgoing interface to counter spoofing.
.IP
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 unbound, and requires OS support for unprivileged non-local binds
(currently only supported on Linux). Several netblocks may be specified with
multiple
.B 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
.B 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
.TP
.B outgoing\-range: \fI<number>
Number of ports to open. This number of file descriptors can be opened per
thread. Must be at least 1. Default depends on compile options. Larger
numbers need extra resources from the operating system.  For performance a
very large value is best, use libevent to make this possible.
.TP
.B outgoing\-port\-permit: \fI<port number or range>
Permit 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.
.IP
The \fBoutgoing\-port\-permit\fR and \fBoutgoing\-port\-avoid\fR 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.
.TP
.B outgoing\-port\-avoid: \fI<port number or range>
Do not permit unbound to open this port or range of ports for use to send
queries. Use this to make sure unbound does not grab a port that another
daemon needs. The port is avoided on all outgoing interfaces, both IP4 and IP6.
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.
.TP
.B outgoing\-num\-tcp: \fI<number>
Number of outgoing TCP buffers to allocate per thread. Default is 10. If
set to 0, or if do\-tcp is "no", no TCP queries to authoritative servers
are done.  For larger installations increasing this value is a good idea.
.TP
.B incoming\-num\-tcp: \fI<number>
Number of incoming TCP buffers to allocate per thread. Default is
10. If set to 0, or if do\-tcp is "no", no TCP queries from clients are
accepted. For larger installations increasing this value is a good idea.
.TP
.B edns\-buffer\-size: \fI<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).  Do
not set higher than that value.  Default is 4096 which is RFC recommended.
If you have fragmentation reassembly problems, usually seen as timeouts,
then a value of 1472 can fix it.  Setting to 512 bypasses even the most
stringent path MTU problems, but is seen as extreme, since the amount
of TCP fallback generated is excessive (probably also for this resolver,
consider tuning the outgoing tcp number).
.TP
.B max\-udp\-size: \fI<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 is 4096.
.TP
.B stream\-wait\-size: \fI<number>
Number of bytes size maximum to use for waiting stream buffers.  Default is
4 megabytes.  A plain number is in bytes, append 'k', 'm' or 'g' for kilobytes,
megabytes or gigabytes (1024*1024 bytes in a megabyte).  As 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.
.TP
.B msg\-buffer\-size: \fI<number>
Number of bytes size of the message buffers. Default is 65552 bytes, enough
for 64 Kb packets, the maximum DNS message size. No message larger than this
can be sent or received. 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.
.TP
.B msg\-cache\-size: \fI<number>
Number of bytes size of the message cache. Default is 4 megabytes.
A plain number is in bytes, append 'k', 'm' or 'g' for kilobytes, megabytes
or gigabytes (1024*1024 bytes in a megabyte).
.TP
.B msg\-cache\-slabs: \fI<number>
Number of slabs in the message cache. Slabs reduce lock contention by threads.
Must be set to a power of 2. Setting (close) to the number of cpus is a
reasonable guess.
.TP
.B num\-queries\-per\-thread: \fI<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 \fIjostle\-timeout\fR), then the queries are dropped. This forces
the client to resend after a timeout; allowing the server time to work on
the existing queries. Default depends on compile options, 512 or 1024.
.TP
.B jostle\-timeout: \fI<msec>
Timeout used when the server is very busy.  Set 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.  Default 200 milliseconds.
The effect is that the qps for long-lasting queries is about
(numqueriesperthread / 2) / (average time for such long queries) qps.
The qps for short queries can be about (numqueriesperthread / 2)
/ (jostletimeout in whole seconds) qps per thread, about (1024/2)*5 = 2560
qps by default.
.TP
.B delay\-close: \fI<msec>
Extra delay for timeouted UDP ports before they are closed, in msec.
Default is 0, and that disables it.  This prevents very delayed answer
packets from the upstream (recursive) servers from bouncing against
closed ports and setting off all sort of close-port counters, with
eg. 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.
.TP
.B unknown\-server\-time\-limit: \fI<msec>
The wait time in msec for waiting for an unknown server to reply.
Increase this if you are behind a slow satellite link, to eg. 1128.
That would then avoid re\-querying every initial query because it times out.
Default is 376 msec.
.TP
.B so\-rcvbuf: \fI<number>
If not 0, then set the SO_RCVBUF socket option to get more buffer
space on UDP port 53 incoming queries.  So that short spikes on busy
servers do not drop packets (see counter in netstat \-su).  Default is
0 (use system value).  Otherwise, the number of bytes to ask for, try
"4m" on a busy server.  The OS caps it at a maximum, on linux 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 header and recompile kernel. On Solaris ndd \-set
/dev/udp udp_max_buf 8388608.
.TP
.B so\-sndbuf: \fI<number>
If not 0, then set the SO_SNDBUF socket option to get more buffer space on
UDP port 53 outgoing queries.  This for very busy servers handles spikes
in answer traffic, otherwise 'send: resource temporarily unavailable'
can get logged, the buffer overrun is also visible by netstat \-su.
Default is 0 (use system value).  Specify the number of bytes to ask
for, try "4m" on a very busy server.  The OS caps it at a maximum, on
linux 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.
.TP
.B so\-reuseport: \fI<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.  Default is yes.
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).
.TP
.B ip\-transparent: \fI<yes or no>
If yes, then use IP_TRANSPARENT socket option on sockets where unbound
is listening for incoming traffic.  Default no.  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 unbound
provides service on.  This option needs unbound to be started with root
permissions on some systems.  The option uses IP_BINDANY on FreeBSD systems
and SO_BINDANY on OpenBSD systems.
.TP
.B ip\-freebind: \fI<yes or no>
If yes, then use IP_FREEBIND socket option on sockets where unbound
is listening to incoming traffic.  Default no.  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.
.TP
.B rrset\-cache\-size: \fI<number>
Number of bytes size of the RRset cache. Default is 4 megabytes.
A plain number is in bytes, append 'k', 'm' or 'g' for kilobytes, megabytes
or gigabytes (1024*1024 bytes in a megabyte).
.TP
.B rrset\-cache\-slabs: \fI<number>
Number of slabs in the RRset cache. Slabs reduce lock contention by threads.
Must be set to a power of 2.
.TP
.B cache\-max\-ttl: \fI<seconds>
Time to live maximum for RRsets and messages in the cache. Default is
86400 seconds (1 day).  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.
.TP
.B cache\-min\-ttl: \fI<seconds>
Time to live minimum for RRsets and messages in the cache. Default is 0.
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.
.TP
.B cache\-max\-negative\-ttl: \fI<seconds>
Time to live maximum for negative responses, these have a SOA in the
authority section that is limited in time.  Default is 3600.
This applies to nxdomain and nodata answers.
.TP
.B infra\-host\-ttl: \fI<seconds>
Time to live for entries in the host cache. The host cache contains
roundtrip timing, lameness and EDNS support information. Default is 900.
.TP
.B infra\-cache\-slabs: \fI<number>
Number of slabs in the infrastructure cache. Slabs reduce lock contention
by threads. Must be set to a power of 2.
.TP
.B infra\-cache\-numhosts: \fI<number>
Number of hosts for which information is cached. Default is 10000.
.TP
.B infra\-cache\-min\-rtt: \fI<msec>
Lower limit for dynamic retransmit timeout calculation in infrastructure
cache. Default is 50 milliseconds. Increase this value if using forwarders
needing more time to do recursive name resolution.
.TP
.B define\-tag: \fI<"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.
.TP
.B do\-ip4: \fI<yes or no>
Enable or disable whether ip4 queries are answered or issued. Default is yes.
.TP
.B do\-ip6: \fI<yes or no>
Enable or disable whether ip6 queries are answered or issued. Default is yes.
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 ip4 and ip6 addresses in it.
.TP
.B prefer\-ip6: \fI<yes or no>
If enabled, prefer IPv6 transport for sending DNS queries to internet
nameservers. Default is no.
.TP
.B do\-udp: \fI<yes or no>
Enable or disable whether UDP queries are answered or issued. Default is yes.
.TP
.B do\-tcp: \fI<yes or no>
Enable or disable whether TCP queries are answered or issued. Default is yes.
.TP
.B tcp\-mss: \fI<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.
.TP
.B outgoing\-tcp\-mss: \fI<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 Unbound and other servers.
.TP
.B tcp-idle-timeout: \fI<msec>\fR
The period Unbound will wait for a query on a TCP connection.
If this timeout expires Unbound closes the connection.
This option defaults to 30000 milliseconds.
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.
.TP
.B edns-tcp-keepalive: \fI<yes or no>\fR
Enable or disable EDNS TCP Keepalive. Default is no.
.TP
.B edns-tcp-keepalive-timeout: \fI<msec>\fR
The period Unbound will wait for a query on a TCP connection when
EDNS TCP Keepalive is active. If this timeout expires Unbound closes
the connection. If the client supports the EDNS TCP Keepalive option,
Unbound sends the timeout value to the client to encourage it to
close the connection before the server times out.
This option defaults to 120000 milliseconds.
When the number of free incoming TCP buffers falls below 50% of
the total number configured, the advertised timeout is progressively
reduced 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 actual timeout of 200 milliseconds is observed regardless of the
advertised timeout.
.TP
.B tcp\-upstream: \fI<yes or no>
Enable or disable whether the upstream queries use TCP only for transport.
Default is no.  Useful in tunneling scenarios.
.TP
.B udp\-upstream\-without\-downstream: \fI<yes or no>
Enable udp upstream even if do-udp is no.  Default is no, and this does not
change anything.  Useful for TLS service providers, that want no udp downstream
but use udp to fetch data upstream.
.TP
.B tls\-upstream: \fI<yes or no>
Enabled or disable whether the upstream queries use TLS only for transport.
Default is no.  Useful in tunneling scenarios.  The TLS contains plain DNS in
TCP wireformat.  The other server must support this (see
\fBtls\-service\-key\fR).
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.
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.
.TP
.B ssl\-upstream: \fI<yes or no>
Alternate syntax for \fBtls\-upstream\fR.  If both are present in the config
file the last is used.
.TP
.B tls\-service\-key: \fI<file>
If enabled, the server provides TLS service on the TCP ports marked
implicitly or explicitly for TLS service with tls\-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.  The default is "", turned off.  Enabling or disabling
this service requires a restart (a reload is not enough), because the
key is read while root permissions are held and before chroot (if any).
The ports enabled implicitly or explicitly via \fBtls\-port:\fR do not provide
normal DNS TCP service.
.TP
.B ssl\-service\-key: \fI<file>
Alternate syntax for \fBtls\-service\-key\fR.
.TP
.B tls\-service\-pem: \fI<file>
The public key certificate pem file for the tls service.  Default is "",
turned off.
.TP
.B ssl\-service\-pem: \fI<file>
Alternate syntax for \fBtls\-service\-pem\fR.
.TP
.B tls\-port: \fI<number>
The port number on which to provide TCP TLS service, default 853, only
interfaces configured with that port number as @number get the TLS service.
.TP
.B ssl\-port: \fI<number>
Alternate syntax for \fBtls\-port\fR.
.TP
.B tls\-cert\-bundle: \fI<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.
.TP
.B ssl\-cert\-bundle: \fI<file>
Alternate syntax for \fBtls\-cert\-bundle\fR.
.TP
.B tls\-win\-cert: \fI<yes or no>
Add the system certificates to the cert bundle certificates for authentication.
If no cert bundle, it uses only these certificates.  Default is no.
On windows this option uses the certificates from the cert store.  Use
the tls\-cert\-bundle option on other systems.
.TP
.B tls\-additional\-port: \fI<portnr>
List portnumbers 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.
.TP
.B tls-session-ticket-keys: \fI<file>
If not "", lists files with 80 bytes of random contents that are used to
perform TLS session resumption for clients using the unbound server.
These files contain the secret key for the TLS session tickets.
First key use to encrypt and decrypt TLS session tickets.
Other keys use 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.
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.
.TP
.B tls\-ciphers: \fI<string with cipher list>
Set the list of ciphers to allow when serving TLS.  Use "" for defaults,
and that is the default.
.TP
.B tls\-ciphersuites: \fI<string with ciphersuites list>
Set the list of ciphersuites to allow when serving TLS.  This is for newer
TLS 1.3 connections.  Use "" for defaults, and that is the default.
.TP
.B use\-systemd: \fI<yes or no>
Enable or disable systemd socket activation.
Default is no.
.TP
.B do\-daemonize: \fI<yes or no>
Enable or disable whether the unbound server forks into the background as
a daemon.  Set the value to \fIno\fR when unbound runs as systemd service.
Default is yes.
.TP
.B tcp\-connection\-limit: \fI<IP netblock> <limit>
Allow up to \fIlimit\fR simultaneous TCP connections from the given netblock.
When at the limit, further connections are accepted but closed immediately.
This option is experimental at this time.
.TP
.B access\-control: \fI<IP netblock> <action>
The netblock is given as an IP4 or IP6 address with /size appended for a
classless network block. The action can be \fIdeny\fR, \fIrefuse\fR,
\fIallow\fR, \fIallow_setrd\fR, \fIallow_snoop\fR, \fIdeny_non_local\fR or
\fIrefuse_non_local\fR.
The most specific netblock match is used, if none match \fIdeny\fR is used.
The order of the access\-control statements therefore does not matter.
.IP
The action \fIdeny\fR stops queries from hosts from that netblock.
.IP
The action \fIrefuse\fR stops queries too, but sends a DNS rcode REFUSED
error message back.
.IP
The action \fIallow\fR gives access to clients from that netblock.
It gives only access for recursion clients (which is
what almost all clients need).  Nonrecursive queries are refused.
.IP
The \fIallow\fR action does allow nonrecursive queries to access the
local\-data that is configured.  The reason is that this does not involve
the unbound server recursive lookup algorithm, and static data is served
in the reply.  This supports normal operations where nonrecursive queries
are made for the authoritative data.  For nonrecursive queries any replies
from the dynamic cache are refused.
.IP
The \fIallow_setrd\fR action 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.
.IP
The action \fIallow_snoop\fR gives nonrecursive access too.  This give
both recursive and non recursive access.  The name \fIallow_snoop\fR refers
to cache snooping, a technique to use nonrecursive queries to examine
the cache contents (for malicious acts).  However, nonrecursive queries can
also be a valuable debugging tool (when you want to examine the cache
contents). In that case use \fIallow_snoop\fR for your administration host.
.IP
By default only localhost is \fIallow\fRed, the rest is \fIrefuse\fRd.
The default is \fIrefuse\fRd, 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.
.IP
The deny_non_local and refuse_non_local settings are for hosts that are
only allowed to query for the authoritative local\-data, they are not
allowed full recursion but only the static data.  With deny_non_local,
messages that are disallowed are dropped, with refuse_non_local they
receive error code REFUSED.
.TP
.B access\-control\-tag: \fI<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 \fIdefine\-tags\fR.  Enclose 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
\fIallow\fR is configured for this netblock.
.TP
.B access\-control\-tag\-action: \fI<IP netblock> <tag> <action>
Set action for particular tag for given access control element. If you have
multiple tag values, the tag used to lookup 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.
.TP
.B access\-control\-tag\-data: \fI<IP netblock> <tag> <"resource record string">
Set redirect data for particular tag for given access control element.
.TP
.B access\-control\-view: \fI<IP netblock> <view name>
Set view for given access control element.
.TP
.B chroot: \fI<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 to be able to reread the config after a reload.
.IP
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.
.IP
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. This allows the pidfile to be
/var/run/unbound.pid and the chroot to be /var/unbound, for example.
.IP
Additionally, unbound may need to access /dev/random (for entropy)
from inside the chroot.
.IP
If given a chroot is done to the given directory. By default chroot is
enabled and the default is "/var/unbound". If you give "" no
chroot is performed.
.TP
.B username: \fI<name>
If given, after binding the port the user privileges are dropped. Default is
"unbound". If you give username: "" no user change is performed.
.IP
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.
.TP
.B directory: \fI<directory>
Sets the working directory for the program. Default is "/var/unbound".
On Windows the string "%EXECUTABLE%" tries to change to the directory
that unbound.exe resides in.
If you give a server: directory: dir before include: file statements
then those includes can be relative to the working directory.
.TP
.B logfile: \fI<filename>
If "" is given, logging goes to stderr, or nowhere once daemonized.
The logfile is appended to, in the following format:
.nf
[seconds since 1970] unbound[pid:tid]: type: message.
.fi
If this option is given, the use\-syslog is option is set to "no".
The logfile is reopened (for append) when the config file is reread, on
SIGHUP.
.TP
.B use\-syslog: \fI<yes or no>
Sets unbound to send log messages to the syslogd, using
\fIsyslog\fR(3).
The log facility LOG_DAEMON is used, with identity "unbound".
The logfile setting is overridden when use\-syslog is turned on.
The default is to log to syslog.
.TP
.B log\-identity: \fI<string>
If "" is given (default), 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
unbound, with different configurations, so that the logs can be easily
distinguished against.
.TP
.B log\-time\-ascii: \fI<yes or no>
Sets logfile lines to use a timestamp in UTC ascii. Default is no, which
prints the seconds since 1970 in brackets. No effect if using syslog, in
that case syslog formats the timestamp printed into the log files.
.TP
.B log\-queries: \fI<yes or no>
Prints one line per query to the log, with the log timestamp and IP address,
name, type and class.  Default is no.  Note that it takes time to print these
lines which makes the server (significantly) slower.  Odd (nonprintable)
characters in names are printed as '?'.
.TP
.B log\-replies: \fI<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.
Default is no.  Note that it takes time to print these
lines which makes the server (significantly) slower.  Odd (nonprintable)
characters in names are printed as '?'.
.TP
.B log\-tag\-queryreply: \fI<yes or no>
Prints the word 'query' and 'reply' with log\-queries and log\-replies.
This makes filtering logs easier.  The default is off (for backwards
compatibility).
.TP
.B log\-local\-actions: \fI<yes or no>
Print log lines to inform about local zone actions.  These lines are like the
local\-zone type inform prints out, but they are also printed for the other
types of local zones.
.TP
.B log\-servfail: \fI<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.
.TP
.B pidfile: \fI<filename>
The process id is written to the file. Default is "/var/unbound/unbound.pid".
So,
.nf
kill \-HUP `cat /var/unbound/unbound.pid`
.fi
triggers a reload,
.nf
kill \-TERM `cat /var/unbound/unbound.pid`
.fi
gracefully terminates.
.TP
.B root\-hints: \fI<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, therefore it is good practice to use a root\-hints file.
.TP
.B hide\-identity: \fI<yes or no>
If enabled id.server and hostname.bind queries are refused.
.TP
.B identity: \fI<string>
Set the identity to report. If set to "", the default, then the hostname
of the server is returned.
.TP
.B hide\-version: \fI<yes or no>
If enabled version.server and version.bind queries are refused.
.TP
.B version: \fI<string>
Set the version to report. If set to "", the default, then the package
version is returned.
.TP
.B hide\-trustanchor: \fI<yes or no>
If enabled trustanchor.unbound queries are refused.
.TP
.B target\-fetch\-policy: \fI<"list of numbers">
Set the target fetch policy used by unbound to determine if it should fetch
nameserver target addresses opportunistically. The policy is described per
dependency depth.
.IP
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.
.IP
Enclose the list between quotes ("") and put spaces between numbers.
The default is "3 2 1 0 0". 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.
.TP
.B harden\-short\-bufsize: \fI<yes or no>
Very small EDNS buffer sizes from queries are ignored. Default is off, since
it is legal protocol wise to send these, and unbound tries to give very
small answers to these queries, where possible.
.TP
.B harden\-large\-queries: \fI<yes or no>
Very large queries are ignored. Default is off, since it is legal protocol
wise to send these, and could be necessary for operation if TSIG or EDNS
payload is very large.
.TP
.B harden\-glue: \fI<yes or no>
Will trust glue only if it is within the servers authority. Default is on.
.TP
.B harden\-dnssec\-stripped: \fI<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 is on.
.TP
.B harden\-below\-nxdomain: \fI<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.  Default is on.
The nxdomain must be secure, this means nsec3 with optout is insufficient.
.TP
.B harden\-referral\-path: \fI<yes or no>
Harden the referral path by performing additional queries for
infrastructure data.  Validates the replies if trust anchors are configured
and the zones are signed.  This enforces DNSSEC validation on nameserver
NS sets and the nameserver addresses that are encountered on the referral
path to the answer.
Default no, because it burdens the authority servers, and it is
not RFC standard, and could lead to performance problems because of the
extra query load that is generated.  Experimental option.
If you enable it consider adding more numbers after the target\-fetch\-policy
to increase the max depth that is checked to.
.TP
.B harden\-algo\-downgrade: \fI<yes or no>
Harden against algorithm downgrade when multiple algorithms are
advertised in the DS record.  If no, allows the weakest algorithm to
validate the zone.  Default is no.  Zone signers must produce zones
that allow this feature to work, but sometimes they do not, and turning
this option off avoids that validation failure.
.TP
.B use\-caps\-for\-id: \fI<yes or no>
Use 0x20\-encoded random bits in the query to foil spoof attempts.
This perturbs the lowercase and uppercase of query names sent to
authority servers and checks if the reply still has the correct casing.
Disabled by default.
This feature is an experimental implementation of draft dns\-0x20.
.TP
.B caps\-whitelist: \fI<domain>
Whitelist the domain so that 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.
.TP
.B qname\-minimisation: \fI<yes or no>
Send minimum amount of information to upstream servers to enhance privacy.
Only send minimum required labels of the QNAME and set QTYPE to A when
possible. Best effort approach; 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 is yes.
.TP
.B qname\-minimisation\-strict: \fI<yes or no>
QNAME minimisation in strict mode. Do not fall-back to sending full QNAME to
potentially broken nameservers. A lot of domains will not be resolvable when
this option in enabled. Only use if you know what you are doing.
This option only has effect when qname-minimisation is enabled. Default is off.
.TP
.B aggressive\-nsec: \fI<yes or no>
Aggressive NSEC uses the DNSSEC NSEC chain to synthesize NXDOMAIN
and other denials, using information from previous NXDOMAINs answers.
Default is no.  It helps to reduce the query rate towards targets that get
a very high nonexistent name lookup rate.
.TP
.B private\-address: \fI<IP address or subnet>
Give IPv4 of IPv6 addresses or classless subnets. These are addresses
on your private network, and are not allowed to be returned for
public internet names.  Any occurrence of such addresses are 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.  Some names
can be allowed to contain your private addresses, by default all the
\fBlocal\-data\fR that you configured is allowed to, and you can specify
additional names using \fBprivate\-domain\fR.  No private addresses are
enabled by default.  We consider to enable this for the RFC1918 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.
.TP
.B private\-domain: \fI<domain name>
Allow this domain, and all its subdomains to contain private addresses.
Give multiple times to allow multiple domain names to contain private
addresses. Default is none.
.TP
.B unwanted\-reply\-threshold: \fI<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 is 0 (turned off).
.TP
.B do\-not\-query\-address: \fI<IP address>
Do not query the given IP address. Can be IP4 or IP6. Append /num to
indicate a classless delegation netblock, for example like
10.2.3.4/24 or 2001::11/64.
.TP
.B do\-not\-query\-localhost: \fI<yes or no>
If yes, localhost is added to the do\-not\-query\-address entries, both
IP6 ::1 and IP4 127.0.0.1/8. If no, then localhost can be used to send
queries to. Default is yes.
.TP
.B prefetch: \fI<yes or no>
If yes, message cache elements are prefetched before they expire to
keep the cache up to date.  Default is no.  Turning it on gives about
10 percent more traffic and load on the machine, but popular items do
not expire from the cache.
.TP
.B prefetch\-key: \fI<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 is no.
.TP
.B deny\-any: \fI<yes or no>
If yes, deny queries of type ANY with an empty response.  Default is no.
If disabled, 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.
.TP
.B rrset\-roundrobin: \fI<yes or no>
If yes, Unbound rotates RRSet order in response (the random number is taken
from the query ID, for speed and thread safety).  Default is no.
.TP
.B minimal-responses: \fI<yes or no>
If yes, Unbound doesn't 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.
This may cause a slight speedup.  The default is yes, even though the DNS
protocol RFCs mandate these sections, and the additional content could
be of use and save roundtrips for clients.  Because they are not used,
and the saved roundtrips are easier saved with prefetch, whilst this is
faster.
.TP
.B disable-dnssec-lame-check: \fI<yes or no>
If true, 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.
.TP
.B module\-config: \fI<"module names">
Module configuration, a list of module names separated by spaces, surround
the string with quotes (""). The modules can be validator, iterator.
Setting this to "iterator" will result in a non\-validating server.
Setting this to "validator iterator" will turn on DNSSEC validation.
The ordering of the modules is important.
You must also set trust\-anchors for validation to be useful.
The default is "validator iterator".  When the server is built with
EDNS client subnet support the default is "subnetcache validator iterator".
Most modules that need to be listed here have to be listed at the beginning
of the line.  The cachedb 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.
.TP
.B trust\-anchor\-file: \fI<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 is "", or no trust anchor file.
.TP
.B auto\-trust\-anchor\-file: \fI<filename>
File with trust anchor for one zone, which is tracked with RFC5011 probes.
The probes are several times per month, thus the machine must be online
frequently.  The initial file can be one with contents as described in
\fBtrust\-anchor\-file\fR.  The file is written to when the anchor is updated,
so the unbound user must have write permission.  Write permission to the file,
but also to the directory it is in (to create a temporary file, which is
necessary to deal with filesystem full events), it must also be inside the
chroot (if that is used).
.TP
.B trust\-anchor: \fI<"Resource Record">
A DS or DNSKEY RR for a key to use for validation. Multiple entries can be
given to specify multiple trusted keys, in addition to the trust\-anchor\-files.
The resource record is entered in the same format as 'dig' or 'drill' prints
them, the same format as in the zone file. Has to be on a single line, with
"" around it. A TTL can be specified for ease of cut and paste, but is ignored.
A class can be specified, but class IN is default.
.TP
.B trusted\-keys\-file: \fI<filename>
File with trusted keys for validation. Specify more than one file
with several entries, one file per entry. Like \fBtrust\-anchor\-file\fR
but has a different file format. Format is BIND\-9 style format,
the trusted\-keys { name flag proto algo "key"; }; clauses are read.
It is possible to use wildcards with this statement, the wildcard is
expanded on start and on reload.
.TP
.B trust\-anchor\-signaling: \fI<yes or no>
Send RFC8145 key tag query after trust anchor priming. Default is on.
.TP
.B root\-key\-sentinel: \fI<yes or no>
Root key trust anchor sentinel. Default is on.
.TP
.B dlv\-anchor\-file: \fI<filename>
This option was used during early days DNSSEC deployment when no parent-side
DS record registrations were easily available.  Nowadays, it is best to have
DS records registered with the parent zone (many top level zones are signed).
File with trusted keys for DLV (DNSSEC Lookaside Validation). Both DS and
DNSKEY entries can be used in the file, in the same format as for
\fItrust\-anchor\-file:\fR statements. Only one DLV can be configured, more
would be slow. The DLV configured is used as a root trusted DLV, this
means that it is a lookaside for the root. Default is "", or no dlv anchor
file. DLV is going to be decommissioned.  Please do not use it any more.
.TP
.B dlv\-anchor: \fI<"Resource Record">
Much like trust\-anchor, this is a DLV anchor with the DS or DNSKEY inline.
DLV is going to be decommissioned.  Please do not use it any more.
.TP
.B domain\-insecure: \fI<domain name>
Sets domain name to be insecure, DNSSEC chain of trust is ignored towards
the domain name.  So a trust anchor above the domain name can not make the
domain secure with a DS record, such a DS record is then ignored.
Also keys from DLV are ignored for the domain.  Can be given multiple times
to specify multiple domains that are treated as if unsigned.  If you set
trust anchors for the domain they override this setting (and the domain
is secured).
.IP
This can be useful if you want to make sure a trust anchor for external
lookups does not affect an (unsigned) internal domain.  A DS record
externally can create validation failures for that internal domain.
.TP
.B val\-override\-date: \fI<rrsig\-style date spec>
Default is "" or "0", which disables this debugging feature. If enabled by
giving a RRSIG style date, that date is used for verifying RRSIG inception
and expiration dates, instead of the current date. Do not set this unless
you are debugging signature inception and expiration. The value \-1 ignores
the date altogether, useful for some special applications.
.TP
.B val\-sig\-skew\-min: \fI<seconds>
Minimum number of seconds of clock skew to apply to validated signatures.
A value of 10% of the signature lifetime (expiration \- inception) is
used, capped by this setting.  Default is 3600 (1 hour) which allows for
daylight savings differences.  Lower this value for more strict checking
of short lived signatures.
.TP
.B val\-sig\-skew\-max: \fI<seconds>
Maximum number of seconds of clock skew to apply to validated signatures.
A value of 10% of the signature lifetime (expiration \- inception)
is used, 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.  Setting both
min and max very high makes the validator check the signature timestamps
less strictly.
.TP
.B val\-bogus\-ttl: \fI<number>
The time to live for bogus data. This is data that has failed validation;
due to invalid signatures or other checks. The TTL from that data cannot be
trusted, and this value is used instead. The value is in seconds, default 60.
The time interval prevents repeated revalidation of bogus data.
.TP
.B val\-clean\-additional: \fI<yes or no>
Instruct the validator to remove data from the additional section of secure
messages that are not signed properly. Messages that are insecure, bogus,
indeterminate or unchecked are not affected. Default is yes. Use this setting
to protect the users that rely on this validator for authentication from
potentially bad data in the additional section.
.TP
.B val\-log\-level: \fI<number>
Have the validator print validation failures to the log.  Regardless of
the verbosity setting.  Default is 0, off.  At 1, for every user query
that fails a line is printed to the logs.  This way you can monitor what
happens with validation.  Use a diagnosis tool, such as dig or drill,
to find out why validation is failing for these queries.  At 2, not only
the query that failed is printed but also the reason why unbound thought
it was wrong and which server sent the faulty data.
.TP
.B val\-permissive\-mode: \fI<yes or no>
Instruct the validator to mark bogus messages as indeterminate. The security
checks are performed, but if the result is bogus (failed security), the
reply is not withheld from the client with SERVFAIL as usual. The client
receives the bogus data. For messages that are found to be secure the AD bit
is set in replies. Also logging is performed as for full validation.
The default value is "no".
.TP
.B ignore\-cd\-flag: \fI<yes or no>
Instruct unbound to ignore the CD flag from clients and refuse to
return bogus answers to them.  Thus, the CD (Checking Disabled) flag
does not disable checking any more.  This is useful if legacy (w2008)
servers that set the CD flag but cannot validate DNSSEC themselves are
the clients, and then unbound provides them with DNSSEC protection.
The default value is "no".
.TP
.B serve\-expired: \fI<yes or no>
If enabled, unbound attempts to serve old responses from cache with a
TTL of 0 in the response without waiting for the actual resolution to finish.
The actual resolution answer ends up in the cache later on.  Default is "no".
.TP
.B serve\-expired\-ttl: \fI<seconds>
Limit serving of expired responses to configured seconds after expiration. 0
disables the limit. This option only applies when \fBserve\-expired\fR is
enabled. The default is 0.
.TP
.B serve\-expired\-ttl\-reset: \fI<yes or no>
Set the TTL of expired records to the \fBserve\-expired\-ttl\fR value after a
failed attempt to retrieve the record from upstream. This makes sure that the
expired records will be served as long as there are queries for it. Default is
"no".
.TP
.B val\-nsec3\-keysize\-iterations: \fI<"list of values">
List of keysize and iteration count values, separated by spaces, surrounded
by quotes. Default is "1024 150 2048 500 4096 2500". This determines the
maximum allowed NSEC3 iteration count before a message is simply marked
insecure instead of performing the many hashing iterations. The list must
be in ascending order and have at least one entry. If you set it to
"1024 65535" there is no restriction to NSEC3 iteration values.
This table must be kept short; a very long list could cause slower operation.
.TP
.B add\-holddown: \fI<seconds>
Instruct the \fBauto\-trust\-anchor\-file\fR probe mechanism for RFC5011
autotrust updates to add new trust anchors only after they have been
visible for this time.  Default is 30 days as per the RFC.
.TP
.B del\-holddown: \fI<seconds>
Instruct the \fBauto\-trust\-anchor\-file\fR probe mechanism for RFC5011
autotrust updates to remove revoked trust anchors after they have been
kept in the revoked list for this long.  Default is 30 days as per
the RFC.
.TP
.B keep\-missing: \fI<seconds>
Instruct the \fBauto\-trust\-anchor\-file\fR probe mechanism for RFC5011
autotrust updates to remove missing trust anchors after they have been
unseen for this long.  This cleans up the state file if the target zone
does not perform trust anchor revocation, so this makes the auto probe
mechanism work with zones that perform regular (non\-5011) rollovers.
The default is 366 days.  The value 0 does not remove missing anchors,
as per the RFC.
.TP
.B permit\-small\-holddown: \fI<yes or no>
Debug option that allows the autotrust 5011 rollover timers to assume
very small values.  Default is no.
.TP
.B key\-cache\-size: \fI<number>
Number of bytes size of the key cache. Default is 4 megabytes.
A plain number is in bytes, append 'k', 'm' or 'g' for kilobytes, megabytes
or gigabytes (1024*1024 bytes in a megabyte).
.TP
.B key\-cache\-slabs: \fI<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
reasonable guess.
.TP
.B neg\-cache\-size: \fI<number>
Number of bytes size of the aggressive negative cache. Default is 1 megabyte.
A plain number is in bytes, append 'k', 'm' or 'g' for kilobytes, megabytes
or gigabytes (1024*1024 bytes in a megabyte).
.TP
.B unblock\-lan\-zones: \fI<yes or no>
Default is disabled.  If enabled, then for private address space,
the reverse lookups are no longer filtered.  This allows 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 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.
.TP
.B insecure\-lan\-zones: \fI<yes or no>
Default is disabled.  If enabled, then reverse lookups in private
address space are not validated.  This is usually required whenever
\fIunblock\-lan\-zones\fR is used.
.TP
.B local\-zone: \fI<zone> <type>
Configure a local zone. The type determines the answer to give if
there is no match from local\-data. The types are deny, refuse, static,
transparent, redirect, nodefault, typetransparent, inform, inform_deny,
inform_redirect, always_transparent, always_refuse, always_nxdomain, noview,
and are 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.
.IP
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.
.TP 10
\h'5'\fIdeny\fR
Do not send an answer, drop the query.
If there is a match from local data, the query is answered.
.TP 10
\h'5'\fIrefuse\fR
Send an error message reply, with rcode REFUSED.
If there is a match from local data, the query is answered.
.TP 10
\h'5'\fIstatic\fR
If there is 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.
.TP 10
\h'5'\fItransparent\fR
If there is 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 localdata but no such type of data is
given in localdata, then a noerror nodata answer is returned.
If no local\-zone is given local\-data causes a transparent zone
to be created by default.
.TP 10
\h'5'\fItypetransparent\fR
If there is 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 are not listed in local data are resolved normally, so if an A record
is in the local data that does not cause a nodata reply for AAAA queries.
.TP 10
\h'5'\fIredirect\fR
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 and
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.
.TP 10
\h'5'\fIinform\fR
The query is answered normally, same as transparent.  The client IP
address (@portnumber) is printed to the logfile.  The log message is:
timestamp, 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.
.TP 10
\h'5'\fIinform_deny\fR
The query is dropped, like 'deny', and logged, like 'inform'.  Ie. find
infected machines without answering the queries.
.TP 10
\h'5'\fIinform_redirect\fR
The query is redirected, like 'redirect', and logged, like 'inform'.
Ie. answer queries with fixed data and also log the machines that ask.
.TP 10
\h'5'\fIalways_transparent\fR
Like transparent, but ignores local data and resolves normally.
.TP 10
\h'5'\fIalways_refuse\fR
Like refuse, but ignores local data and refuses the query.
.TP 10
\h'5'\fIalways_nxdomain\fR
Like static, but ignores local data and returns nxdomain for the query.
.TP 10
\h'5'\fInoview\fR
Breaks out of that view and moves towards the global local zones for answer
to the query.  If the 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. 
.TP 10
\h'5'\fInodefault\fR
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 \fInodefault\fR if you use exactly that zone, if you want to
use a subzone, use \fItransparent\fR.
.P
The default zones are localhost, reverse 127.0.0.1 and ::1, the 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.
.TP 10
\h'5'\fIlocalhost\fR
The IP4 and IP6 localhost information is given. NS and SOA records are provided
for completeness and to satisfy some DNS update tools. Default content:
.nf
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"
.fi
.TP 10
\h'5'\fIreverse IPv4 loopback\fR
Default content:
.nf
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."
.fi
.TP 10
\h'5'\fIreverse IPv6 loopback\fR
Default content:
.nf
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."
.fi
.TP 10
\h'5'\fIonion (RFC 7686)\fR
Default content:
.nf
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"
.fi
.TP 10
\h'5'\fItest (RFC 2606)\fR
Default content:
.nf
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"
.fi
.TP 10
\h'5'\fIinvalid (RFC 2606)\fR
Default content:
.nf
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"
.fi
.TP 10
\h'5'\fIreverse RFC1918 local use zones\fR
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 \fBlocal\-zone:\fR is set static and as \fBlocal\-data:\fR SOA and NS
records are provided.
.TP 10
\h'5'\fIreverse RFC3330 IP4 this, link\-local, testnet and broadcast\fR
Reverse data for zones 0.in\-addr.arpa, 254.169.in\-addr.arpa,
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.
And from 64.100.in\-addr.arpa to 127.100.in\-addr.arpa (Shared Address Space).
.TP 10
\h'5'\fIreverse RFC4291 IP6 unspecified\fR
Reverse data for zone
.nf
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.
.fi
.TP 10
\h'5'\fIreverse RFC4193 IPv6 Locally Assigned Local Addresses\fR
Reverse data for zone D.F.ip6.arpa.
.TP 10
\h'5'\fIreverse RFC4291 IPv6 Link Local Addresses\fR
Reverse data for zones 8.E.F.ip6.arpa to B.E.F.ip6.arpa.
.TP 10
\h'5'\fIreverse IPv6 Example Prefix\fR
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:
.nf
  local\-zone: 8.B.D.0.1.0.0.2.ip6.arpa. nodefault
.fi
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.
.\" End of local-zone listing.
.TP 5
.B local\-data: \fI"<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"'.
.IP
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.
.TP 5
.B local\-data\-ptr: \fI"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"
.TP 5
.B local\-zone\-tag: \fI<zone> <"list of tags">
Assign tags to localzones. Tagged localzones will only be applied when the
used access-control element has a matching tag. Tags must be defined in
\fIdefine\-tags\fR.  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.
.TP 5
.B local\-zone\-override: \fI<zone> <IP netblock> <type>
Override the localzone 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.
.TP 5
.B ratelimit: \fI<number or 0>
Enable ratelimiting of queries sent to nameserver for performing recursion.
If 0, the default, it is disabled.  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).  This stops recursive floods, eg. random
query names, but not spoofed reflection floods.  Cached responses are not
ratelimited by this setting.  The zone of the query is determined by examining
the nameservers for it, 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 unbound from sending traffic to the
nameservers for those zones.
.TP 5
.B ratelimit\-size: \fI<memory size>
Give the size of the data structure in which the current ongoing rates are
kept track in.  Default 4m.  In bytes or use m(mega), k(kilo), g(giga).
The ratelimit structure is small, so this data structure likely does
not need to be large.
.TP 5
.B ratelimit\-slabs: \fI<number>
Give power of 2 number of slabs, this is used to reduce lock contention
in the ratelimit tracking data structure.  Close to the number of cpus is
a fairly good setting.
.TP 5
.B ratelimit\-factor: \fI<number>
Set 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.
.TP 5
.B ratelimit\-for\-domain: \fI<domain> <number qps or 0>
Override 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.
.TP 5
.B ratelimit\-below\-domain: \fI<domain> <number qps or 0>
Override 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.
.TP 5
.B ip\-ratelimit: \fI<number or 0>
Enable global ratelimiting of queries accepted per ip address.
If 0, the default, it is disabled.  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.
.TP 5
.B ip\-ratelimit\-size: \fI<memory size>
Give the size of the data structure in which the current ongoing rates are
kept track in.  Default 4m.  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.
.TP 5
.B ip\-ratelimit\-slabs: \fI<number>
Give power of 2 number of slabs, this is used to reduce lock contention
in the ip ratelimit tracking data structure.  Close to the number of cpus is
a fairly good setting.
.TP 5
.B ip\-ratelimit\-factor: \fI<number>
Set 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.
.TP 5
.B fast\-server\-permil: \fI<number>
Specify how many times out of 1000 to pick from the set of fastest servers.
0 turns the feature off.  A value of 900 would pick from the fastest
servers 90 percent of the time, and would perform normal exploration of random
servers for the remaining time. When prefetch is enabled (or serve\-expired),
such prefetches are not sped up, because there is no one waiting for it, and it
presents a good moment to perform server exploration. The
\fBfast\-server\-num\fR option can be used to specify the size of the fastest
servers set. The default for fast\-server\-permil is 0.
.TP 5
.B fast\-server\-num: \fI<number>
Set the number of servers that should be used for fast server selection. Only
use the fastest specified number of servers with the fast\-server\-permil
option, that turns this on or off. The default is to use the fastest 3 servers.
.SS "Remote Control Options"
In the
.B remote\-control:
clause are the declarations for the remote control facility.  If this is
enabled, the \fIunbound\-control\fR(8) utility can be used to send
commands to the running unbound server.  The server uses these clauses
to setup TLSv1 security for the connection.  The
\fIunbound\-control\fR(8) utility also reads the \fBremote\-control\fR
section for options.  To setup the correct self\-signed certificates use the
\fIunbound\-control\-setup\fR(8) utility.
.TP 5
.B control\-enable: \fI<yes or no>
The option is used to enable remote control, default is "no".
If turned off, the server does not listen for control commands.
.TP 5
.B control\-interface: \fI<ip address or path>
Give IPv4 or IPv6 addresses or local socket path to listen on for
control commands.
By default localhost (127.0.0.1 and ::1) is listened to.
Use 0.0.0.0 and ::0 to listen to all interfaces.
If you change this and permissions have been dropped, you must restart
the server for the change to take effect.
.IP
If you set it to an absolute path, a local socket is used.  The local socket
does not use the certificates and keys, so those files need not be present.
To restrict access, unbound sets permissions on the file to the user and
group that is configured, 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 the that group.  To restrict access further, create a directory to put
the control socket in and restrict access to that directory.
.TP 5
.B control\-port: \fI<port number>
The port number to listen on for IPv4 or IPv6 control interfaces,
default is 8953.
If you change this and permissions have been dropped, you must restart
the server for the change to take effect.
.TP 5
.B control\-use\-cert: \fI<yes or no>
For localhost control-interface you can disable the use of TLS by setting
this option to "no", default is "yes".  For local sockets, TLS is disabled
and the value of this option is ignored.
.TP 5
.B server\-key\-file: \fI<private key file>
Path to the server private key, by default unbound_server.key.
This file is generated by the \fIunbound\-control\-setup\fR utility.
This file is used by the unbound server, but not by \fIunbound\-control\fR.
.TP 5
.B server\-cert\-file: \fI<certificate file.pem>
Path to the server self signed certificate, by default unbound_server.pem.
This file is generated by the \fIunbound\-control\-setup\fR utility.
This file is used by the unbound server, and also by \fIunbound\-control\fR.
.TP 5
.B control\-key\-file: \fI<private key file>
Path to the control client private key, by default unbound_control.key.
This file is generated by the \fIunbound\-control\-setup\fR utility.
This file is used by \fIunbound\-control\fR.
.TP 5
.B control\-cert\-file: \fI<certificate file.pem>
Path to the control client certificate, by default unbound_control.pem.
This certificate has to be signed with the server certificate.
This file is generated by the \fIunbound\-control\-setup\fR utility.
This file is used by \fIunbound\-control\fR.
.SS "Stub Zone Options"
.LP
There may be multiple
.B stub\-zone:
clauses. 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; unbound performs
the recursive processing itself for stub zones.
.P
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 unbound with
.B stub\-addr:
<ip address of host[@port]>.
The unbound resolver can then access the data, without referring to the
public internet for it.
.P
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 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 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.
.P
Consider adding \fBserver:\fR statements for \fBdomain\-insecure:\fR and
for \fBlocal\-zone:\fI name nodefault\fR for the zone if it is a locally
served zone.  The insecure clause stops DNSSEC from invalidating the
zone.  The local zone nodefault (or \fItransparent\fR) clause makes the
(reverse\-) zone bypass unbound's filtering of RFC1918 zones.
.TP
.B name: \fI<domain name>
Name of the stub zone.
.TP
.B stub\-host: \fI<domain name>
Name of stub zone nameserver. Is itself resolved before it is used.
.TP
.B stub\-addr: \fI<IP address>
IP address of stub zone nameserver. Can be IP 4 or IP 6.
To use a nondefault port for DNS communication append '@' with the port number.
.TP
.B stub\-prime: \fI<yes or no>
This option is by default 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.
.TP
.B stub\-first: \fI<yes or no>
If enabled, a query is attempted without the stub clause 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 clause.
The default is no.
.TP
.B stub\-tls\-upstream: \fI<yes or no>
Enabled or disable whether the queries to this stub use TLS for transport.
Default is no.
.TP
.B stub\-ssl\-upstream: \fI<yes or no>
Alternate syntax for \fBstub\-tls\-upstream\fR.
.TP
.B stub\-no\-cache: \fI<yes or no>
Default is no.  If enabled, data inside the stub is not cached.  This is
useful when you want immediate changes to be visible.
.SS "Forward Zone Options"
.LP
There may be multiple
.B forward\-zone:
clauses. Each with a \fBname:\fR 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 \fBforward\-host:\fR and
\fBforward\-addr:\fR have to handle further recursion for the query.  Thus,
those servers are not authority servers, but are (just like unbound is)
recursive servers too; 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 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).
.TP
.B name: \fI<domain name>
Name of the forward zone.
.TP
.B forward\-host: \fI<domain name>
Name of server to forward to. Is itself resolved before it is used.
.TP
.B forward\-addr: \fI<IP address>
IP address of server to forward to. Can be IP 4 or IP 6.
To use a nondefault 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.
.IP
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.
.TP
.B forward\-first: \fI<yes or no>
If a forwarded query is met with a SERVFAIL error, and this option is
enabled, unbound will fall back to normal recursive resolution for this
query as if no query forwarding had been specified.  The default is "no".
.TP
.B forward\-tls\-upstream: \fI<yes or no>
Enabled or disable whether the queries to this forwarder use TLS for transport.
Default is no.
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.
.TP
.B forward\-ssl\-upstream: \fI<yes or no>
Alternate syntax for \fBforward\-tls\-upstream\fR.
.TP
.B forward\-no\-cache: \fI<yes or no>
Default is no.  If enabled, data inside the forward is not cached.  This is
useful when you want immediate changes to be visible.
.SS "Authority Zone Options"
.LP
Authority zones are configured with \fBauth\-zone:\fR, and each one must
have a \fBname:\fR.  There can be multiple ones, by listing multiple auth\-zone 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 are processed after \fBlocal\-zones\fR and before
cache (\fBfor\-downstream:\fR \fIyes\fR), and when used in this manner
make unbound respond like an authority server.  Authority zones are also
processed after cache, just before going to the network to fetch
information for recursion (\fBfor\-upstream:\fR \fIyes\fR), and when used
in this manner provide a local copy of an authority server that speeds up
lookups of that data.
.LP
Authority zones can be read from 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.
.LP
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 master (even if older), and if
fallback is enabled, the fallback activates to fetch from the upstream instead
of the SERVFAIL.
.TP
.B name: \fI<zone name>
Name of the authority zone.
.TP
.B master: \fI<IP address or host name>
Where to download a copy of the zone from, with AXFR and IXFR.  Multiple
masters can be specified.  They are all tried if one fails.
With the "ip#name" notation a AXFR over TLS can be used.
.TP
.B url: \fI<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
masters are listed, the masters 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 masters are tried with IXFR and AXFR.
For https, the \fBtls\-cert\-bundle\fR and the hostname from the url are used
to authenticate the connection.
.TP
.B allow\-notify: \fI<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 master, it first attempts that master.  Otherwise
other masters are attempted.  If there are no masters, but only urls, the
file is downloaded when notified.  The masters from master: statements are
allowed notify by default.
.TP
.B fallback\-enabled: \fI<yes or no>
Default no.  If enabled, unbound falls back to querying the internet as
a resolver for this zone when lookups fail.  For example for DNSSEC
validation failures.
.TP
.B for\-downstream: \fI<yes or no>
Default yes.  If enabled, unbound serves authority responses to
downstream clients for this zone.  This option makes 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 unbound to provide recursion for the
zone but have a local copy of zone data.  If for\-downstream is no and
for\-upstream is yes, then unbound will DNSSEC validate the contents of the
zone before serving the zone contents to clients and store validation
results in the cache.
.TP
.B for\-upstream: \fI<yes or no>
Default yes.  If enabled, 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 unbound to provide recursion for
downstream clients, and use the zone data as a local copy to speed up lookups.
.TP
.B zonefile: \fI<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, unbound will attempt to fetch zone
data (eg. from the master servers).
.SS "View Options"
.LP
There may be multiple
.B view:
clauses. Each with a \fBname:\fR and zero or more \fBlocal\-zone\fR and
\fBlocal\-data\fR elements. Views can also contain view\-first, 
response\-ip, response\-ip\-data and local\-data\-ptr elements.
View can be mapped to requests by specifying the
view name in an \fBaccess\-control\-view\fR element. 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.
.TP
.B name: \fI<view name>
Name of the view. Must be unique. This name is used in access\-control\-view
elements.
.TP
.B local\-zone: \fI<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 is no, the default local-zones will be added to this view.
Defaults can be disabled using the nodefault type. When view\-first is yes or
when a view does not have a local\-zone, the global local\-zone will be used
including it's default zones.
.TP
.B local\-data: \fI"<resource record string>"
View specific local\-data elements. Has the same behaviour as the global
local\-data elements.
.TP
.B local\-data\-ptr: \fI"IPaddr name"
View specific local\-data\-ptr elements. Has the same behaviour as the global
local\-data\-ptr elements.
.TP
.B view\-first: \fI<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.
The default is no.
.SS "Python Module Options"
.LP
The
.B python:
clause gives the settings for the \fIpython\fR(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 \fBmodule\-config:\fR option
(usually first, or between the validator and iterator).
.LP
If the \fBchroot:\fR option is enabled, you should make sure Python's
library directory structure is bind mounted in the new root environment, see
\fImount\fR(8).  Also the \fBpython\-script:\fR path should be specified as an
absolute path relative to the new root, or as a relative path to the working
directory.
.TP
.B python\-script: \fI<python file>\fR
The script file to load.
.SS "DNS64 Module Options"
.LP
The dns64 module must be configured in the \fBmodule\-config:\fR "dns64
validator iterator" directive and be compiled into the daemon to be
enabled.  These settings go in the \fBserver:\fR section.
.TP
.B dns64\-prefix: \fI<IPv6 prefix>\fR
This sets the DNS64 prefix to use to synthesize AAAA records with.
It must be /96 or shorter.  The default prefix is 64:ff9b::/96.
.TP
.B dns64\-synthall: \fI<yes or no>\fR
Debug option, default no.  If enabled, synthesize all AAAA records
despite the presence of actual AAAA records.
.TP
.B dns64\-ignore\-aaaa: \fI<name>\fR
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.
.SS "DNSCrypt Options"
.LP
The
.B dnscrypt:
clause gives the settings of the dnscrypt channel. While those options are
available, they are only meaningful if unbound was compiled with
\fB\-\-enable\-dnscrypt\fR.
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
.TP
.B dnscrypt\-enable: \fI<yes or no>\fR
Whether or not the \fBdnscrypt\fR config should be enabled. You may define
configuration but not activate it.
The default is no.
.TP
.B dnscrypt\-port: \fI<port number>
On which port should \fBdnscrypt\fR should be activated. Note that you should
have a matching \fBinterface\fR option defined in the \fBserver\fR section for
this port.
.TP
.B dnscrypt\-provider: \fI<provider name>\fR
The provider name to use to distribute certificates. This is of the form:
\fB2.dnscrypt-cert.example.com.\fR. The name \fIMUST\fR end with a dot.
.TP
.B dnscrypt\-secret\-key: \fI<path to secret key file>\fR
Path to the time limited secret key file. This option may be specified multiple
times.
.TP
.B dnscrypt\-provider\-cert: \fI<path to cert file>\fR
Path to the certificate related to the \fBdnscrypt\-secret\-key\fRs.
This option may be specified multiple times.
.TP
.B dnscrypt\-provider\-cert\-rotated: \fI<path to cert file>\fR
Path to a certificate that we should be able to serve existing connection from
but do not want to advertise over \fBdnscrypt\-provider\fR'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.
.TP
.B dnscrypt\-shared\-secret\-cache\-size: \fI<memory size>
Give the size of the data structure in which the shared secret keys are kept
in.  Default 4m.  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.
.TP
.B dnscrypt\-shared\-secret\-cache\-slabs: \fI<number>
Give power of 2 number of slabs, this is used to reduce lock contention
in the dnscrypt shared secrets cache.  Close to the number of cpus is
a fairly good setting.
.TP
.B dnscrypt\-nonce\-cache\-size: \fI<memory size>
Give the size of the data structure in which the client nonces are kept in.
Default 4m. 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.
.TP
.B dnscrypt\-nonce\-cache\-slabs: \fI<number>
Give power of 2 number of slabs, this is used to reduce lock contention
in the dnscrypt nonce cache.  Close to the number of cpus is
a fairly good setting.
.SS "EDNS Client Subnet Module Options"
.LP
The ECS module must be configured in the \fBmodule\-config:\fR "subnetcache
validator iterator" directive and be compiled into the daemon to be
enabled.  These settings go in the \fBserver:\fR section.
.LP
If the destination address is whitelisted with 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.
.LP
Additionally, when a client includes the option in its queries, Unbound will
forward the option to the authority if present in the whitelist, or
\fBclient\-subnet\-always\-forward\fR is set to yes. In this case the lookup in
the regular cache is skipped.
.LP
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.
.TP
.B send\-client\-subnet: \fI<IP address>\fR
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 \fBclient\-subnet\-zone\fR.
.TP
.B client\-subnet\-zone: \fI<domain>\fR
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 \fBsend\-client\-subnet\fR.
.TP
.B client\-subnet\-always\-forward: \fI<yes or no>\fR
Specify whether the ECS whitelist check (configured using
\fBsend\-client\-subnet\fR) 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 whitelist check is skipped when the client
query contains an ECS record. Default is no.
.TP
.B max\-client\-subnet\-ipv6: \fI<number>\fR
Specifies the maximum prefix length of the client source address we are willing
to expose to third parties for IPv6.  Defaults to 56.
.TP
.B max\-client\-subnet\-ipv4: \fI<number>\fR
Specifies the maximum prefix length of the client source address we are willing
to expose to third parties for IPv4. Defaults to 24.
.TP
.B min\-client\-subnet\-ipv6: \fI<number>\fR
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 is 0.
.TP
.B min\-client\-subnet\-ipv4: \fI<number>\fR
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 is 0.
.TP
.B max\-ecs\-tree\-size\-ipv4: \fI<number>\fR
Specifies the maximum number of subnets ECS answers kept in the ECS radix tree.
This number applies for each qname/qclass/qtype tuple. Defaults to 100.
.TP
.B max\-ecs\-tree\-size\-ipv6: \fI<number>\fR
Specifies the maximum number of subnets ECS answers kept in the ECS radix tree.
This number applies for each qname/qclass/qtype tuple. Defaults to 100.
.SS "Opportunistic IPsec Support Module Options"
.LP
The IPsec module must be configured in the \fBmodule\-config:\fR "ipsecmod
validator iterator" directive and be compiled into the daemon to be
enabled.  These settings go in the \fBserver:\fR section.
.LP
When 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, unbound
will call an external hook passing the following arguments:
.TP 10
\h'5'\fIQNAME\fR
Domain name of the A/AAAA and IPSECKEY query.  In string format.
.TP 10
\h'5'\fIIPSECKEY TTL\fR
TTL of the IPSECKEY RRset.
.TP 10
\h'5'\fIA/AAAA\fR
String of space separated IP addresses present in the A/AAAA RRset.  The IP
addresses are in string format.
.TP 10
\h'5'\fIIPSECKEY\fR
String of space separated IPSECKEY RDATA present in the IPSECKEY RRset.  The
IPSECKEY RDATA are in DNS presentation format.
.LP
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
\fBipsecmod-max-ttl\fR.
.LP
The same procedure is also followed when \fBprefetch:\fR is used, but the
A/AAAA answer is given to the client before the hook is called.
\fBipsecmod-max-ttl\fR ensures that the A/AAAA answer given from cache is still
relevant for opportunistic IPsec.
.TP
.B ipsecmod-enabled: \fI<yes or no>\fR
Specifies whether the IPsec module is enabled or not.  The IPsec module still
needs to be defined in the \fBmodule\-config:\fR directive.  This option
facilitates turning on/off the module without restarting/reloading unbound.
Defaults to yes.
.TP
.B ipsecmod\-hook: \fI<filename>\fR
Specifies the external hook that unbound will call with \fIsystem\fR(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 \fBmodule\-config:\fR
directive.
.TP
.B ipsecmod-strict: \fI<yes or no>\fR
If enabled unbound requires the external hook to return a success value of 0.
Failing to do so unbound will reply with SERVFAIL.  The A/AAAA answer will also
not be cached.  Defaults to no.
.TP
.B ipsecmod\-max-ttl: \fI<seconds>\fR
Time to live maximum for A/AAAA cached records after calling the external hook.
Defaults to 3600.
.TP
.B ipsecmod-ignore-bogus: \fI<yes or no>\fR
Specifies the behaviour of 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.  Defaults to no.
.TP
.B ipsecmod\-whitelist: \fI<domain>\fR
Whitelist 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 whitelisted (default).
.SS "Cache DB Module Options"
.LP
The Cache DB module must be configured in the \fBmodule\-config:\fR
"validator cachedb iterator" directive and be compiled into the daemon
with \fB\-\-enable\-cachedb\fR.
If this module is enabled and configured, the specified backend database
works as a second level cache:
When 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, Unbound uses it to respond
to the query without performing iterative DNS resolution.
If Unbound cannot even find an answer in the backend, it resolves the
query as usual, and stores the answer in the backend.
.P
If Unbound was built with
\fB\-\-with\-libhiredis\fR
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.
It should be noted that 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.
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, Unbound will be
effectively unusable with this backend.
It's the administrator's responsibility to make the assumption hold.
.P
The
.B cachedb:
clause gives custom settings of the cache DB module.
.TP
.B backend: \fI<backend name>\fR
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.
.TP
.B secret-seed: \fI<"secret string">\fR
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 Unbound instances,
all instances must use the same secret seed.
This option defaults to "default".
.P
The following
.B cachedb
otions are specific to the redis backend.
.TP
.B redis-server-host: \fI<server address or name>\fR
The IP (either v6 or v4) address or domain name of the Redis server.
In general an IP address should be specified as otherwise Unbound will have to
resolve the name of the server every time it establishes a connection
to the server.
This option defaults to "127.0.0.1".
.TP
.B redis-server-port: \fI<port number>\fR
The TCP port number of the Redis server.
This option defaults to 6379.
.TP
.B redis-timeout: \fI<msec>\fR
The period until when Unbound waits for a response from the Redis sever.
If this timeout expires 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.
This option defaults to 100 milliseconds.
.SH "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.
.P
.nf
# 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"
.fi
.SH "FILES"
.TP
.I /var/unbound
default unbound working directory.
.TP
.I /var/unbound
default
\fIchroot\fR(2)
location.
.TP
.I /var/unbound/unbound.conf
unbound configuration file.
.TP
.I /var/unbound/unbound.pid
default unbound pidfile with process ID of the running daemon.
.TP
.I unbound.log
unbound log file. default is to log to
\fIsyslog\fR(3).
.SH "SEE ALSO"
\fIunbound\fR(8),
\fIunbound\-checkconf\fR(8).
.SH "AUTHORS"
.B Unbound
was written by NLnet Labs. Please see CREDITS file
in the distribution for further details.