1 # Unbound Recursive DNS Server with UCI
4 [Unbound](https://www.unbound.net/) is a validating, recursive, and caching DNS resolver. The C implementation of Unbound is developed and maintained by [NLnet Labs](https://www.nlnetlabs.nl/). It is based on ideas and algorithms taken from a java prototype developed by Verisign labs, Nominet, Kirei and ep.net. Unbound is designed as a set of modular components, so that also DNSSEC (secure DNS) validation and stub-resolvers (that do not run as a server, but are linked into an application) are easily possible.
7 OpenWrt default build uses [dnsmasq](http://www.thekelleys.org.uk/dnsmasq/docs/dnsmasq-man.html) for DNS forwarding and DHCP. With a forward only resolver, dependence on the upstream recursors may be cause for concern. They are often provided by the ISP, and some users have switched to public DNS providers. Either way may result in problems due to performance, "snoop-vertising", hijacking (MiM), and other causes. Running a recursive resolver or resolver capable of TLS may be a solution.
9 Unbound may be useful on consumer grade embedded hardware. It is fully DNSSEC and TLS capable. It is _intended_ to be a recursive resolver only. NLnet Labs [NSD](https://www.nlnetlabs.nl/projects/nsd/) is _intended_ for the authoritative task. This is different than [ISC Bind](https://www.isc.org/downloads/bind/) and its inclusive functions. Unbound configuration effort and memory consumption may be easier to control. A consumer could have their own recursive resolver with 8/64 MB router, and remove potential issues from forwarding resolvers outside of their control.
11 This package builds on Unbounds capabilities with OpenWrt UCI. Not every Unbound option is in UCI, but rather, UCI simplifies the combination of related options. Unbounds native options are bundled and balanced within a smaller set of choices. Options include resources, DNSSEC, access control, and some TTL tweaking. The UCI also provides an escape option and works at the raw "unbound.conf" level.
13 ## HOW TO: Ad Blocking
14 The UCI scripts will work with [net/adblock](https://github.com/openwrt/packages/blob/master/net/adblock/files/README.md), if it is installed and enabled. Its all detected and integrated automatically. In brief, the adblock scripts create distinct local-zone files that are simply included in the unbound conf file during UCI generation. If you don't want this, then disable adblock or reconfigure adblock to not send these files to Unbound.
16 A few tweaks may be needed to enhance the realiability and effectiveness. Ad Block option for delay time may need to be set for upto one minute (adb_triggerdelay), because of boot up race conditions with interfaces calling Unbound restarts. Also many smart devices (TV, microwave, or refigerator) will also use public DNS servers either as a bypass or for certain connections in general. If you wish to force exclusive DNS to your router, then you will need a firewall rule for example:
18 **/etc/config/firewall**:
21 option name 'Block-Public-DNS'
25 option dest_port '53 853 5353'
28 option target 'REJECT'
31 ## HOW TO: Integrate with DHCP
32 Some UCI options and scripts help Unbound to work with DHCP servers to load the local DNS. The examples provided here are serial dnsmasq-unbound, parallel dnsmasq-unbound, and unbound scripted with odhcpd.
35 In this case, dnsmasq is not changed *much* with respect to the default [OpenWrt](https://openwrt.org/docs/guide-user/base-system/dns_configuration) configuration. Here dnsmasq is forced to use the local Unbound instance as the lone upstream DNS server, instead of your ISP. This may be the easiest implementation, but performance degradation can occur in high volume networks. Unbound and dnsmasq effectively have the same information in memory, and all transfers are double handled.
37 **/etc/config/unbound**:
40 option add_local_fqdn '0'
41 option add_wan_fqdn '0'
42 option dhcp_link 'none'
43 # dnsmasq should not forward your domain to unbound, but if...
44 option domain 'yourdomain'
45 option domain_type 'refuse'
46 option listen_port '1053'
53 option domain 'yourdomain'
55 option resolvfile '/tmp/resolv.conf.auto'
57 list server '127.0.0.1#1053'
58 list server '::1#1053'
63 In this case, Unbound serves your local network directly for all purposes. It will look over to dnsmasq for DHCP-DNS resolution. Unbound is generally accessible on port 53, and dnsmasq is only accessed at 127.0.0.1:1053 by Unbound. Although you can dig/drill/nslookup remotely with the proper directives.
65 **/etc/config/unbound**:
68 option dhcp_link 'dnsmasq'
69 option listen_port '53'
76 option domain 'yourdomain'
78 option resolvfile '/tmp/resolv.conf.auto'
83 # dnsmasq may not issue DNS option if not std. configuration
84 list dhcp_option 'option:dns-server,0.0.0.0'
88 ### Unbound and odhcpd
89 You may ask, "can Unbound replace dnsmasq?" You can have DHCP-DNS records with Unbound and [odhcpd](https://github.com/openwrt/odhcpd/blob/master/README) only. The UCI scripts will allow Unbound to act like dnsmasq. When odhcpd configures each DHCP lease, it will call a script. The script provided with Unbound will read the lease file for DHCP-DNS records. The unbound-control application is required, because simply rewriting conf-files and restarting unbound is too much overhead.
90 - Default OpenWrt has dnsmasq+odhcpd with `odhcpd-ipv6only` limited to DHCPv6.
91 - If you use dnsmasq+odhcpd together, then use dnsmasq serial or parallel methods above.
92 - You must install package `odhcpd` (full) to use odhcpd alone.
93 - You must install package `unbound-control` to load and unload leases.
94 - Remember to uninstall (or disable) dnsmasq when you won't use it.
96 **/etc/config/unbound**:
99 # name your router in DNS
100 option add_local_fqdn '1'
101 option add_wan_fqdn '1'
102 option dhcp_link 'odhcpd'
103 # add SLAAC inferred from DHCPv4
104 option dhcp4_slaac6 '1'
106 option domain_type 'static'
107 option listen_port '53'
108 option rebind_protection '1'
109 # install unbound-control and set this
110 option unbound_control '1'
114 **/etc/config/dhcp**:
117 option dhcpv4 'server'
118 option dhcpv6 'server'
119 option interface 'lan'
120 option leasetime '12h'
122 option ra_management '1'
125 config odhcpd 'odhcpd'
127 option leasefile '/var/lib/odhcpd/dhcp.leases'
128 # this is where the magic happens
129 option leasetrigger '/usr/lib/unbound/odhcpd.sh'
132 ## HOW TO: Manual Override
133 Yes, there is a UCI to disable the rest of Unbound UCI. However, OpenWrt or LEDE are targeted at embedded machines with flash ROM. The initialization scripts do a few things to protect flash ROM.
135 ### Completely Manual (almost)
136 All of `/etc/unbound` (persistent, ROM) is copied to `/var/lib/unbound` (tmpfs, RAM). Edit your manual `/etc/unbound/unbound.conf` to reference this `/var/lib/unbound` location for included files. Note in preparation for a jail, `/var/lib/unbound` is `chown unbound`. Configure for security in`/etc/unbound/unbound.conf` with options `username:unbound` and `chroot:/var/lib/unbound`.
138 Keep the DNSKEY updated with your choice of flash activity. `root.key` maintenance for DNSKEY RFC5011 would be hard on flash. Unbound natively updates frequently. It also creates and destroys working files in the process. In `/var/lib/unbound` this is no problem, but it would be gone at the next reboot. If you have DNSSEC (validator) active, then you should consider the age UCI option. Choose how many days to copy from `/var/lib/unbound/root.key` (tmpfs) to `/etc/unbound/root.key` (flash).
140 **/etc/config/unbound**:
143 option manual_conf '1'
148 ### Hybrid Manual/UCI
149 You like the UCI. Yet, you need to add some difficult to standardize options, or just are not ready to make a UCI request yet. The files `/etc/unbound/unbound_srv.conf` and `/etc/unbound/unbound_ext.conf` will be copied to Unbounds chroot directory and included during auto generation.
151 The file `unbound_srv.conf` will be added into the `server:` clause. The file `unbound_ext.conf` will be added to the end of all configuration. It is for extended `forward-zone:`, `stub-zone:`, `auth-zone:`, and `view:` clauses. You can also disable unbound-control in the UCI which only allows "localhost" connections unencrypted, and then add an encrypted remote `control:` clause.
153 ## HOW TO: Cache Zone Files
154 Unbound has the ability to AXFR a whole zone from an authoritative server to prefetch the zone. This can speed up access to common zones. Some may have special bandwidth concerns for DNSSEC overhead. The following is a generic example. UCI defaults include the [root](https://www.internic.net/domain/) zone, but it is disabled as a ready to go example.
156 **/etc/config/unbound**:
161 option url_dir 'https://asset-management.it.example.com/zones/'
162 option zone_type 'auth_zone'
163 list server 'ns1.it.example.com'
164 list server 'ns2.it.example.com'
165 list zone_name 'example.com'
168 ## HOW TO: TLS Over DNS
169 Unbound can use TLS as a client or server. UCI supports Unbound as a forwarding client with TLS. Servers are more complex and need manual configuration. This may be desired for privacy against stealth tracking. Some public DNS servers seem to advertise help in this quest. If your looking for a better understanding, then some information can be found at [Cloudflare](https://www.cloudflare.com/) DNS [1.1.1.1](https://1.1.1.1/). The following is a generic example. You can mix providers by using complete server specificaiton to override the zones common port and certificate domain index.
171 **NOTICE:** Unbound requires openssl-1.1.0 to verify host certificates. OpenWrt at present is configured with openssl-1.0.2. Connections will be over TLS, but theoretically, certificates may not be from a trusted source. See report [Unbound #658](https://www.nlnetlabs.nl/bugs-script/show_bug.cgi?id=658). When this is resolved, it will be recommended again to install `ca-bundle`, maintain it, and be sure to include the TLS certificate domain index with the host addresses.
173 **/etc/config/unbound**:
177 # question: do you want to recurse when TLS fails or not?
179 option tls_index 'dns.example.net'
180 option tls_port '853'
181 option tls_upstream '1'
182 option zone_type 'forward_zone'
183 # these servers assume a common TLS port/index
184 list server '192.0.2.53'
185 list server '2001:db8::53'
186 # this alternate server is fully specified inline
187 list server '192.0.2.153@443#dns.alternate.example.org'
191 ## Complete List of UCI Options
192 **/etc/config/unbound**:
195 Currently only one instance is supported.
197 option add_extra_dns '0'
198 Level. Execute traditional DNS overrides found in `/etc/config/dhcp`.
199 Optional so you may use other Unbound conf or redirect to NSD instance.
200 0 - Ignore `/etc/config/dhcp`
201 1 - Use only 'domain' clause (host records)
202 2 - Use 'domain', 'mxhost', and 'srvhost' clauses
203 3 - Use all of 'domain', 'mxhost', 'srvhost', and 'cname' clauses
205 option add_local_fqdn '0'
206 Level. This puts your routers host name in the LAN (local) DNS.
207 Each level is more detailed and comprehensive.
209 1 - Host Name on only the primary address
210 2 - Host Name on all addresses found (except link)
211 3 - FQDN and host name on all addresses (except link)
212 4 - Above and interfaces named <iface>.<hostname>.<domain>
214 option add_wan_fqdn '0'
215 Level. Same as previous option only this applies to the WAN. WAN
216 are inferred by a UCI `config dhcp` entry that contains the line
220 Boolean. Enable DNS64 through Unbound in order to bridge networks
221 that are IPV6 only and IPV4 only (see RFC6052).
223 option dns64_prefix '64:ff9b::/96'
224 IPV6 Prefix. The IPV6 prefix wrapped on the IPV4 address for DNS64.
225 You should use RFC6052 "well known" address, unless you also
226 redirect to a proxy or gateway for your NAT64.
228 option dhcp_link 'none'
229 Program Name. Link to one of the supported programs we have scripts
230 for. You may also need to install a trigger script in the DHCP
231 servers configuration. See HOW TO above.
233 option dhcp4_slaac6 '0'
234 Boolean. Some DHCP servers do this natively (dnsmasq). Otherwise
235 the script provided with this package will try to fabricate SLAAC
236 IP6 addresses from DHCPv4 MAC records.
239 Unbound local-zone: <domain> <type>. This is used to suffix all
240 host records, and maintain a local zone. When dnsmasq is dhcp_link
241 however, then this option is ignored (dnsmasq does it all).
243 option domain_type 'static'
244 Unbound local-zone: <domain> <type>. This allows you to lock
245 down or allow forwarding of the local zone. Notable types:
246 static - typical single router setup much like OpenWrt dnsmasq default
247 refuse - to answer overtly with DNS code REFUSED
248 deny - to drop queries for the local zone
249 transparent - to use your manually added forward-zone: or stub-zone: clause
251 option edns_size '1280'
252 Bytes. Extended DNS is necessary for DNSSEC. However, it can run
253 into MTU issues. Use this size in bytes to manage drop outs.
255 option extended_stats '0'
256 Boolean. extended statistics are printed from unbound-control.
257 Keeping track of more statistics takes time.
259 option hide_binddata '1'
260 Boolean. If enabled version.server, version.bind, id.server, and
261 hostname.bind queries are refused.
263 option listen_port '53'
264 Port. Incoming. Where Unbound will listen for queries.
266 option localservice '1'
267 Boolean. Prevent DNS amplification attacks. Only provide access to
268 Unbound from subnets this machine has interfaces on.
270 option manual_conf '0'
271 Boolean. Skip all this UCI nonsense. Manually edit the
272 configuration. Make changes to /etc/unbound/unbound.conf.
274 option protocol 'mixed'
275 Unbound can limit its protocol used for recursive queries.
276 ip4_only - limit issues if you do not have native IPv6
277 ip6_only - test environment only; could cauase problems
278 ip6_prefer - both IPv4 and IPv6 but try IPv6 first
279 mixed - both IPv4 and IPv6
280 default - Unbound built-in defaults
282 option query_minimize '0'
283 Boolean. Enable a minor privacy option. Don't let each server know
284 the next recursion. Query one piece at a time.
286 option query_min_strict '0'
287 Boolean. Query minimize is best effort and will fall back to normal
288 when it must. This option prevents the fall back, but less than
289 standard name servers will fail to resolve their domains.
291 option rebind_localhost '0'
292 Boolean. Prevent loopback "127.0.0.0/8" or "::1/128" responses.
293 These may used by black hole servers for good purposes like
294 ad-blocking or parental access control. Obviously these responses
295 also can be used to for bad purposes.
297 option rebind_protection '1'
298 Level. Block your local address responses from global DNS. A poisoned
299 reponse within "192.168.0.0/24" or "fd00::/8" could turn a local browser
300 into an external attack proxy server. IP6 GLA may be vulnerable also.
302 1 - Only RFC 1918 and 4193 responses blocked
303 2 - Plus GLA /64 on designated interface(s)
304 3 - Plus DHCP-PD range passed down interfaces (not implemented)
306 option recursion 'passive'
307 Unbound has many options for recrusion but UCI is bundled for simplicity.
308 passive - slower until cache fills but kind on CPU load
309 default - Unbound built-in defaults
310 aggressive - uses prefetching to handle more requests quickly
312 option resource 'small'
313 Unbound has many options for resources but UCI is bundled for simplicity.
314 tiny - similar to published memory restricted configuration
315 small - about half of medium
316 medium - similar to default, but fixed for consistency
317 default - Unbound built-in defaults
318 large - about double of medium
321 Days. >90 Disables. Age limit for Unbound root data like root
322 DNSSEC key. Unbound uses RFC 5011 to manage root key. This could
323 harm flash ROM. This activity is mapped to "tmpfs," but every so
324 often it needs to be copied back to flash for the next reboot.
327 Seconds. Minimum TTL in cache. Recursion can be expensive without
328 cache. A low TTL is normal for server migration. A low TTL can be
329 abused for snoop-vertising (DNS hit counts; recording query IP).
330 Typical to configure maybe 0~300, but 1800 is the maximum accepted.
332 option unbound_control '0'
333 Level. Enables unbound-control application access ports.
334 0 - No unbound-control Access, or add your own in 'unbound_ext.conf'
335 1 - Unencrypted Local Host Access
336 2 - SSL Local Host Access; auto unbound-control-setup if available
337 3 - SSL Network Access; auto unbound-control-setup if available
338 4 - SSL Network Access; static key/pem files must already exist
341 Boolean. Enable DNSSEC. Unbound names this the "validator" module.
343 option validator_ntp '1'
344 Boolean. Disable DNSSEC time checks at boot. Once NTP confirms
345 global real time, then DNSSEC is restarted at full strength. Many
346 embedded devices don't have a real time power off clock. NTP needs
347 DNS to resolve servers. This works around the chicken-and-egg.
350 Level. Sets Unbounds logging intensity.
352 list domain_insecure 'ntp.somewhere.org'
353 Domain. Domains that you wish to skip DNSSEC. It is one way around NTP
354 chicken and egg. Your DHCP servered domains are automatically included.
356 list trigger_interface 'lan' 'wan'
357 Interface (logical). This option is a work around for netifd/procd
358 interaction with WAN DHCPv6. Minor RA or DHCP changes in IP6 can
359 cause netifd to execute procd interface reload. Limit Unbound procd
360 triggers to LAN and WAN (IP4 only) to prevent restart @2-3 minutes.
364 Create Unbounds forward-zone:, stub-zone:, or auth-zone: clauses
367 Boolean. Enable the zone clause.
370 Boolean. Permit normal recursion when the narrowly selected servers
371 in this zone are unresponsive or return empty responses. Disable, if
372 there are security concerns (forward only internal to organization).
375 Port. Servers are contact on this port for plain DNS operations.
378 Boolean. Use "resolv.conf" as it was filled by the DHCP client. This
379 can be used to forward zones within your ISP (mail.example.net) or that
380 have co-located services (streamed-movies.example.com). Recursion may
381 not yield the most local result, but forwarding may instead.
383 option tls_index (n/a)
384 Domain. Name TLS certificates are signed for (dns.example.net). If this
385 option is ommitted, then Unbound will make the connection but not
389 Port. Servers are contact on this port for DNS over TLS operations.
391 option tls_upstream 0
392 Boolean. Use TLS to contact the zone server.
395 String. http or https path, directory part only, to the zone file for
396 auth_zone type only. Files "${zone_name}.zone" are expect in this path.
398 option zone_type (n/a)
399 State. Required field or the clause is effectively disabled. Check
400 Unbound documentation for clarity (unbound-conf).
401 auth_zone - prefetch whole zones from authoritative server (ICANN)
402 forward_zone - forward queries in these domains to the listed servers
403 stub_zone - force recursion of these domains to the listed servers
406 IP. Every zone must have one server. Stub and forward require IP to
407 prevent chicken and egg (due to UCI simplicity). Authoritative prefetch
408 may use a server name.
411 Domain. Every zone must represent some part of the DNS tree. It can be
412 all of it "." or you internal organization domain "example.com." Within
413 each zone clause all zone names will be matched to all servers.
417 config unbound / option prefetch_root
418 List the domains in a zone with type auth_zone and fill in the server
419 or url fields. Root zones are ready but disabled in default install UCI.
421 config unbound / list domain_forward
422 List the domains in a zone with type forward_zone and enable the
425 config unbound / list rebind_interface
426 Enable rebind_protection at 2 and all DHCP interfaces are also
427 protected for IPV6 GLA (parallel to subnets in add_local_fqdn).