3 <!DOCTYPE refentry PUBLIC
"-//OASIS//DTD DocBook XML V4.5//EN"
4 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
5 <!ENTITY % entities SYSTEM
"custom-entities.ent" >
8 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
10 <refentry id=
"org.freedesktop.resolve1" conditional='ENABLE_RESOLVE'
11 xmlns:
xi=
"http://www.w3.org/2001/XInclude">
13 <title>org.freedesktop.resolve1
</title>
14 <productname>systemd
</productname>
18 <refentrytitle>org.freedesktop.resolve1
</refentrytitle>
19 <manvolnum>5</manvolnum>
23 <refname>org.freedesktop.resolve1
</refname>
24 <refpurpose>The D-Bus interface of systemd-resolved
</refpurpose>
28 <title>Introduction
</title>
31 <citerefentry><refentrytitle>systemd-resolved.service
</refentrytitle><manvolnum>8</manvolnum></citerefentry>
32 is a system service that provides hostname resolution and caching using DNS, LLMNR, and mDNS. It also
33 does DNSSEC validation. This page describes the resolve semantics and the D-Bus interface.
</para>
35 <para>This page contains an API reference only. If you are looking for a longer explanation how to use
36 this API, please consult
37 <ulink url=
"https://wiki.freedesktop.org/www/Software/systemd/writing-network-configuration-managers">
38 Writing Network Configuration Managers
</ulink> and
39 <ulink url=
"https://wiki.freedesktop.org/www/Software/systemd/writing-resolver-clients">Writing Resolver
45 <title>The Manager Object
</title>
47 <para>The service exposes the following interfaces on the Manager object on the bus:
</para>
49 <programlisting executable=
"systemd-resolved" node=
"/org/freedesktop/resolve1" interface=
"org.freedesktop.resolve1.Manager">
50 node /org/freedesktop/resolve1 {
51 interface org.freedesktop.resolve1.Manager {
53 ResolveHostname(in i ifindex,
57 out a(iiay) addresses,
60 ResolveAddress(in i ifindex,
66 ResolveRecord(in i ifindex,
73 ResolveService(in i ifindex,
79 out a(qqqsa(iiay)s) srv_data,
83 out s canonical_domain,
87 SetLinkDNS(in i ifindex,
89 SetLinkDNSEx(in i ifindex,
90 in a(iayqs) addresses);
91 SetLinkDomains(in i ifindex,
93 SetLinkDefaultRoute(in i ifindex,
95 SetLinkLLMNR(in i ifindex,
97 SetLinkMulticastDNS(in i ifindex,
99 SetLinkDNSOverTLS(in i ifindex,
101 SetLinkDNSSEC(in i ifindex,
103 SetLinkDNSSECNegativeTrustAnchors(in i ifindex,
105 RevertLink(in i ifindex);
106 RegisterService(in s name,
110 in q service_priority,
112 in aa{say} txt_datas,
114 UnregisterService(in o service_path);
117 ResetServerFeatures();
119 readonly s LLMNRHostname = '...';
120 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
121 readonly s LLMNR = '...';
122 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
123 readonly s MulticastDNS = '...';
124 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
125 readonly s DNSOverTLS = '...';
126 readonly a(iiay) DNS = [...];
127 readonly a(iiayqs) DNSEx = [...];
128 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"const")
129 readonly a(iiay) FallbackDNS = [...];
130 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"const")
131 readonly a(iiayqs) FallbackDNSEx = [...];
132 readonly (iiay) CurrentDNSServer = ...;
133 readonly (iiayqs) CurrentDNSServerEx = ...;
134 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
135 readonly a(isb) Domains = [...];
136 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
137 readonly (tt) TransactionStatistics = ...;
138 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
139 readonly (ttt) CacheStatistics = ...;
140 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
141 readonly s DNSSEC = '...';
142 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
143 readonly (tttt) DNSSECStatistics = ...;
144 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
145 readonly b DNSSECSupported = ...;
146 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
147 readonly as DNSSECNegativeTrustAnchors = ['...', ...];
148 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
149 readonly s DNSStubListener = '...';
150 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
151 readonly s ResolvConfMode = '...';
153 interface org.freedesktop.DBus.Peer { ... };
154 interface org.freedesktop.DBus.Introspectable { ... };
155 interface org.freedesktop.DBus.Properties { ... };
159 <!--method RegisterService is not documented!-->
161 <!--method UnregisterService is not documented!-->
163 <!--method FlushCaches is not documented!-->
165 <!--method ResetServerFeatures is not documented!-->
167 <!--property DNSSECNegativeTrustAnchors is not documented!-->
169 <!--Autogenerated cross-references for systemd.directives, do not edit-->
171 <variablelist class=
"dbus-interface" generated=
"True" extra-ref=
"org.freedesktop.resolve1.Manager"/>
173 <variablelist class=
"dbus-interface" generated=
"True" extra-ref=
"org.freedesktop.resolve1.Manager"/>
175 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"ResolveHostname()"/>
177 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"ResolveAddress()"/>
179 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"ResolveRecord()"/>
181 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"ResolveService()"/>
183 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"GetLink()"/>
185 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetLinkDNS()"/>
187 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetLinkDNSEx()"/>
189 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetLinkDomains()"/>
191 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetLinkDefaultRoute()"/>
193 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetLinkLLMNR()"/>
195 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetLinkMulticastDNS()"/>
197 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetLinkDNSOverTLS()"/>
199 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetLinkDNSSEC()"/>
201 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetLinkDNSSECNegativeTrustAnchors()"/>
203 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"RevertLink()"/>
205 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"RegisterService()"/>
207 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"UnregisterService()"/>
209 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"ResetStatistics()"/>
211 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"FlushCaches()"/>
213 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"ResetServerFeatures()"/>
215 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"LLMNRHostname"/>
217 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"LLMNR"/>
219 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"MulticastDNS"/>
221 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"DNSOverTLS"/>
223 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"DNS"/>
225 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"DNSEx"/>
227 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"FallbackDNS"/>
229 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"FallbackDNSEx"/>
231 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"CurrentDNSServer"/>
233 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"CurrentDNSServerEx"/>
235 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"Domains"/>
237 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"TransactionStatistics"/>
239 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"CacheStatistics"/>
241 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"DNSSEC"/>
243 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"DNSSECStatistics"/>
245 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"DNSSECSupported"/>
247 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"DNSSECNegativeTrustAnchors"/>
249 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"DNSStubListener"/>
251 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"ResolvConfMode"/>
253 <!--End of Autogenerated section-->
256 <title>Methods
</title>
258 <para><function>ResolveHostname()
</function> takes a hostname and resolves it to one or more IP
259 addresses. As parameters it takes the Linux network interface index to execute the query on, or
0 if
260 it may be done on any suitable interface. The
<varname>name
</varname> parameter specifies the hostname
261 to resolve. Note that if required, IDNA conversion is applied to this name unless it is resolved via
262 LLMNR or MulticastDNS. The
<varname>family
</varname> parameter limits the results to a specific address
263 family. It may be
<constant>AF_INET
</constant>,
<constant>AF_INET6
</constant> or
264 <constant>AF_UNSPEC
</constant>. If
<constant>AF_UNSPEC
</constant> is specified (recommended), both
265 kinds are retrieved, subject to local network configuration (i.e. if no local, routable IPv6 address is
266 found, no IPv6 address is retrieved; and similarly for IPv4). A
64-bit
<varname>flags
</varname> field
267 may be used to alter the behaviour of the resolver operation (see below). The method returns an array
268 of address records. Each address record consists of the interface index the address belongs to, an
269 address family as well as a byte array with the actual IP address data (which either has
4 or
16
270 elements, depending on the address family). The returned address family will be one of
271 <constant>AF_INET
</constant> or
<constant>AF_INET6
</constant>. For IPv6, the returned address interface
272 index should be used to initialize the .sin6_scope_id field of a
273 <structname>struct sockaddr_in6
</structname> instance to permit support for resolution to link-local IP
274 addresses. The address array is followed by the canonical name of the host, which may or may not be
275 identical to the resolved hostname. Finally, a
64-bit
<varname>flags
</varname> field is returned that
276 is defined similarly to the
<varname>flags
</varname> field that was passed in, but contains information
277 about the resolved data (see below). If the hostname passed in is an IPv4 or IPv6 address formatted as
278 string, it is parsed, and the result is returned. In this case, no network communication is
281 <para><function>ResolveAddress()
</function> executes the reverse operation: it takes an IP address and
282 acquires one or more hostnames for it. As parameters it takes the interface index to execute the query
283 on, or
<constant>0</constant> if all suitable interfaces are OK. The
<varname>family
</varname>
284 parameter indicates the address family of the IP address to resolve. It may be either
285 <constant>AF_INET
</constant> or
<constant>AF_INET6
</constant>. The
<varname>address
</varname> parameter
286 takes the raw IP address data (as either a
4 or
16 byte array). The
<varname>flags
</varname> input
287 parameter may be used to alter the resolver operation (see below). The method returns an array of name
288 records, each consisting of an interface index and a hostname. The
<varname>flags
</varname> output
289 field contains additional information about the resolver operation (see below).
</para>
291 <para><function>ResolveRecord()
</function> takes a DNS resource record (RR) type, class and name, and
292 retrieves the full resource record set (RRset), including the RDATA, for it. As parameter it takes the
293 Linux network interface index to execute the query on, or
<constant>0</constant> if it may be done on
294 any suitable interface. The
<varname>name
</varname> parameter specifies the RR domain name to look up
295 (no IDNA conversion is applied), followed by the
16-bit class and type fields (which may be
296 ANY). Finally, a
<varname>flags
</varname> field may be passed in to alter behaviour of the look-up (see
297 below). On completion, an array of RR items is returned. Each array entry consists of the network interface
298 index the RR was discovered on, the type and class field of the RR found, and a byte array of the raw
299 RR discovered. The raw RR data starts with the RR's domain name, in the original casing, followed
300 by the RR type, class, TTL and RDATA, in the binary format documented in
301 <ulink url=
"https://www.ietf.org/rfc/rfc1035.txt">RFC
1035</ulink>. For RRs that support name
302 compression in the payload (such as MX or PTR), the compression is expanded in the returned
305 <para>Note that currently, the class field has to be specified as IN or ANY. Specifying a different
306 class will return an error indicating that look-ups of this kind are unsupported. Similarly, some
307 special types are not supported either (AXFR, OPT, …). While
<filename>systemd-resolved
</filename> parses and validates resource
308 records of many types, it is crucial that clients using this API understand that the RR data originates
309 from the network and should be thoroughly validated before use.
</para>
311 <para><function>ResolveService()
</function> may be used to resolve a DNS SRV service record, as well as the
312 hostnames referenced in it, and possibly an accompanying DNS-SD TXT record containing additional
313 service metadata. The primary benefit of using this method over
<function>ResolveRecord()
</function>
314 specifying the SRV type is that it will resolve the SRV and TXT RRs as well as the hostnames referenced
315 in the SRV in a single operation. As parameters it takes a Linux network interface index, a service
316 name, a service type and a service domain. This method may be invoked in three different modes:
</para>
319 <listitem><para>To resolve a DNS-SD service, specify the service name (e.g.
<literal>Lennart's
320 Files
</literal>), the service type (e.g.
<literal>_webdav._tcp
</literal>) and the domain to search in
321 (e.g.
<literal>local
</literal>) as the three service parameters. The service name must be in UTF-
8
322 format, and no IDNA conversion is applied to it in this mode (as mandated by the DNS-SD
323 specifications). However, if necessary, IDNA conversion is applied to the domain parameter.
</para>
326 <listitem><para>To resolve a plain SRV record, set the service name parameter to the empty string
327 and set the service type and domain properly. (IDNA conversion is applied to the domain, if
328 necessary.)
</para></listitem>
330 <listitem><para>Alternatively, leave both the service name and type empty and specify the full
331 domain name of the SRV record (i.e. prefixed with the service type) in the domain parameter. (No IDNA
332 coversion is applied in this mode.)
</para></listitem>
335 <para>The
<varname>family
</varname> parameter of the
<function>ResolveService()
</function> method encodes
336 the desired family of the addresses to resolve (use
<constant>AF_INET
</constant>,
337 <constant>AF_INET6
</constant>, or
<constant>AF_UNSPEC
</constant>). If this is enabled (Use the
338 <constant>NO_ADDRESS
</constant> flag to turn address resolution off, see below). The
339 <varname>flags
</varname> parameter takes a couple of flags that may be used to alter the resolver
342 <para>On completion,
<function>ResolveService()
</function> returns an array of SRV record structures. Each
343 items consisting of the priority, weight and port fields as well as the hostname to contact, as encoded in the SRV
344 record. Immediately following is an array of the addresses of this hostname, with each item consisting
345 of the interface index, the address family and the address data in a byte array. This address array is
346 followed by the canonicalized hostname. After this array of SRV record structures an array of byte
347 arrays follows that encodes the TXT RR strings, in case DNS-SD look-ups are enabled. The next parameters
348 are the canonical service name, type and domain. This may or may not be identical to the parameters
349 passed in. Finally, a
<varname>flags
</varname> field is returned that contains information about the
350 resolver operation performed.
</para>
352 <para>The
<function>ResetStatistics()
</function> method resets the various statistics counters that
353 <filename>systemd-resolved
</filename> maintains to zero. (For details, see the statistics properties below.)
</para>
355 <para>The
<function>GetLink()
</function> method takes a network interface index and returns the object
356 path to the
<interfacename>org.freedesktop.resolve1.Link
</interfacename> object corresponding to it.
359 <para>The
<function>SetLinkDNS()
</function> method sets the DNS servers to use on a specific
360 interface. This method (and the following ones) may be used by network management software to configure
361 per-interface DNS settings. It takes a network interface index as well as an array of DNS server IP
362 address records. Each array item consists of an address family (either
<constant>AF_INET
</constant> or
363 <constant>AF_INET6
</constant>), followed by a
4-byte or
16-byte array with the raw address data. This
364 method is a one-step shortcut for retrieving the Link object for a network interface using
365 <function>GetLink()
</function> (see above) and then invoking the
<function>SetDNS()
</function> method
366 (see below) on it.
</para>
368 <para><function>SetLinkDNSEx()
</function> is similar to
<function>SetLinkDNS()
</function>, but allows
369 an IP port (instead of the default
53) and DNS name to be specified for each DNS server. The server
370 name is used for Server Name Indication (SNI), which is useful when DNS-over-TLS is
371 used. C.f.
<varname>DNS=
</varname> in
372 <citerefentry><refentrytitle>resolved.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
375 <para><function>SetLinkDefaultRoute()
</function> specifies whether the link shall be used as the
376 default route for name queries. See the description of name routing in
377 <citerefentry><refentrytitle>systemd-resolved.service
</refentrytitle><manvolnum>8</manvolnum></citerefentry>
380 <para>The
<function>SetLinkDomains()
</function> method sets the search and routing domains to use on a
381 specific network interface for DNS look-ups. It takes a network interface index and an array of domains,
382 each with a boolean parameter indicating whether the specified domain shall be used as a search domain
383 (false), or just as a routing domain (true). Search domains are used for qualifying single-label names into
384 FQDN when looking up hostnames, as well as for making routing decisions on which interface to send
385 queries ending in the domain to. Routing domains are only used for routing decisions and not used for single-label
386 name qualification. Pass the search domains in the order they should be used.
</para>
388 <para>The
<function>SetLinkLLMNR()
</function> method enables or disables LLMNR support on a specific
389 network interface. It takes a network interface index as well as a string that may either be empty or one of
390 <literal>yes
</literal>,
<literal>no
</literal> or
<literal>resolve
</literal>. If empty, the systemd-wide
391 default LLMNR setting is used. If
<literal>yes
</literal>, LLMNR is used for resolution of single-label
392 names and the local hostname is registered on all local LANs for LLMNR resolution by peers. If
393 <literal>no
</literal>, LLMNR is turned off fully on this interface. If
<literal>resolve
</literal>, LLMNR
394 is only enabled for resolving names, but the local hostname is not registered for other peers to
397 <para>Similarly, the
<function>SetLinkMulticastDNS()
</function> method enables or disables MulticastDNS
398 support on a specific interface. It takes the same parameters as
<function>SetLinkLLMNR()
</function>
399 described above.
</para>
401 <para>The
<function>SetLinkDNSSEC()
</function> method enables or disables DNSSEC validation on a
402 specific network interface. It takes a network interface index as well as a string that may either be
403 empty or one of
<literal>yes
</literal>,
<literal>no
</literal>, or
<literal>allow-downgrade
</literal>. When
404 empty, the system-wide default DNSSEC setting is used. If
<literal>yes
</literal>, full DNSSEC validation
405 is done for all look-ups. If the selected DNS server does not support DNSSEC, look-ups will fail if this
406 mode is used. If
<literal>no
</literal>, DNSSEC validation is fully disabled. If
407 <literal>allow-downgrade
</literal>, DNSSEC validation is enabled, but is turned off automatically if the
408 selected server does not support it (thus opening up behaviour to downgrade attacks). Note that DNSSEC
409 only applies to traditional DNS, not to LLMNR or MulticastDNS.
</para>
411 <para>The
<function>SetLinkDNSSECNegativeTrustAnchors()
</function> method may be used to configure DNSSEC
412 Negative Trust Anchors (NTAs) for a specific network interface. It takes a network interface index and a
413 list of domains as arguments.
</para>
415 <para>The
<function>SetLinkDNSOverTLS()
</function> method enables or disables DNS-over-TLS.
416 C.f.
<varname>DNSOverTLS=
</varname> in
417 <citerefentry><refentrytitle>systemd-resolved.service
</refentrytitle><manvolnum>8</manvolnum></citerefentry>
420 <para>Network management software integrating with
<filename>systemd-resolved
</filename> should call
421 <function>SetLinkDNS()
</function> or
<function>SetLinkDNSEx()
</function>,
422 <function>SetLinkDefaultRoute()
</function>,
<function>SetLinkDomains()
</function> and others after the
423 interface appeared in the kernel (and thus after a network interface index has been assigned), but
424 before the network interfaces is activated (
<constant>IFF_UP
</constant> set) so that all settings take
425 effect during the full time the network interface is up. It is safe to alter settings while the
426 interface is up, however. Use
<function>RevertLink()
</function> (described below) to reset all
427 per-interface settings.
</para>
429 <para>The
<function>RevertLink()
</function> method may be used to revert all per-link settings
430 described above to the defaults.
</para>
433 <title>The Flags Parameter
</title>
435 <para>The four methods above accept and return a
64-bit flags value. In most cases passing
0 is sufficient
436 and recommended. However, the following flags are defined to alter the look-up:
</para>
439 #define SD_RESOLVED_DNS (UINT64_C(
1)
<< 0)
440 #define SD_RESOLVED_LLMNR_IPV4 (UINT64_C(
1)
<< 1)
441 #define SD_RESOLVED_LLMNR_IPV6 (UINT64_C(
1)
<< 2)
442 #define SD_RESOLVED_MDNS_IPV4 (UINT64_C(
1)
<< 3)
443 #define SD_RESOLVED_MDNS_IPV6 (UINT64_C(
1)
<< 4)
444 #define SD_RESOLVED_NO_CNAME (UINT64_C(
1)
<< 5)
445 #define SD_RESOLVED_NO_TXT (UINT64_C(
1)
<< 6)
446 #define SD_RESOLVED_NO_ADDRESS (UINT64_C(
1)
<< 7)
447 #define SD_RESOLVED_NO_SEARCH (UINT64_C(
1)
<< 8)
448 #define SD_RESOLVED_AUTHENTICATED (UINT64_C(
1)
<< 9)
451 <para>On input, the first five flags control the protocols to use for the look-up. They refer to
452 classic unicast DNS, LLMNR via IPv4/UDP and IPv6/UDP respectively, as well as MulticastDNS via
453 IPv4/UDP and IPv6/UDP. If all of these five bits are off on input (which is strongly recommended) the
454 look-up will be done via all suitable protocols for the specific look-up. Note that these flags
455 operate as filter only, but cannot force a look-up to be done via a protocol. Specifically,
456 <filename>systemd-resolved
</filename> will only route look-ups within the .local TLD to MulticastDNS
457 (plus some reverse look-up address domains), and single-label names to LLMNR (plus some reverse
458 address lookup domains). It will route neither of these to Unicast DNS servers. Also, it will do
459 LLMNR and Multicast DNS only on interfaces suitable for multicast.
</para>
461 <para>On output, these five flags indicate which protocol was used to execute the operation, and hence
462 where the data was found.
</para>
464 <para>The primary use cases for these five flags are follow-up look-ups based on DNS data retrieved
465 earlier. In this case it is often a good idea to limit the follow-up look-up to the protocol that was
466 used to discover the first DNS result.
</para>
468 <para>The NO_CNAME flag controls whether CNAME/DNAME resource records shall be followed during the
469 look-up. This flag is only available at input, none of the functions will return it on output. If a
470 CNAME/DNAME RR is discovered while resolving a hostname, an error is returned instead. By default,
471 when the flag is off, CNAME/DNAME RRs are followed.
</para>
473 <para>The NO_TXT and NO_ADDRESS flags only influence operation of the
474 <function>ResolveService()
</function> method. They are only defined for input, not output. If
475 NO_TXT set, the DNS-SD TXT RR look-up is not done in the same operation. If NO_ADDRESS is specified,
476 the hostnames discovered are not implicitly translated to their addresses.
</para>
478 <para>The NO_SEARCH flag turns off the search domain logic. It is only defined for input in
479 <function>ResolveHostname()
</function>. When specified, single-label hostnames are not qualified
480 using defined search domains, if any are configured. Note that
<function>ResolveRecord()
</function>
481 will never qualify single-label domain names using search domains. Also note that
482 multi-label hostnames are never subject to search list expansion.
</para>
484 <para>The AUTHENTICATED bit is defined only in the output flags of the four functions. If set, the
485 returned data has been fully authenticated. Specifically, this bit is set for all DNSSEC-protected data
486 for which a full trust chain may be established to a trusted domain anchor. It is also set for locally
487 synthesized data, such as
<literal>localhost
</literal> or data from
488 <filename>/etc/hosts
</filename>. Moreover, it is set for all LLMNR or mDNS RRs which originate from the
489 local host. Applications that require authenticated RR data for operation should check this flag before
490 trusting the data. Note that
<filename>systemd-resolved
</filename> will never return invalidated data, hence this flag
491 simply allows to discern the cases where data is known to be trustable, or where there is proof that
492 the data is
"rightfully" unauthenticated (which includes cases where the underlying protocol or server
493 does not support authenticating data).
</para>
498 <title>Properties
</title>
500 <para>The
<varname>LLMNR
</varname> and
<varname>MulticastDNS
</varname> properties report whether LLMNR
501 and MulticastDNS are (globally) enabled. Each may be one of
<literal>yes
</literal>,
502 <literal>no
</literal>, and
<literal>resolve
</literal>. See
<function>SetLinkLLMNR()
</function>
503 and
<function>SetLinkMulticastDNS()
</function> above.
</para>
505 <para><varname>LLMNRHostname
</varname> contains the hostname currently exposed on the network via
506 LLMNR. It usually follows the system hostname as may be queried via
507 <citerefentry project=
"man-pages"><refentrytitle>gethostname
</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
508 but may differ if a conflict is detected on the network.
</para>
510 <para><varname>DNS
</varname> and
<varname>DNSEx
</varname> contain arrays of all DNS servers currently
511 used by
<filename>systemd-resolved
</filename>.
<varname>DNS
</varname> contains information similar to
512 the DNS server data in
<filename>/run/systemd/resolve/resolv.conf
</filename>. Each structure in the
513 array consists of a numeric network interface index, an address family, and a byte array containing the
514 DNS server address (either
4 bytes in length for IPv4 or
16 bytes in lengths for IPv6).
515 <varname>DNSEx
</varname> is similar, but additionally contains the IP port and server name (used for
516 Server Name Indication, SNI). Both arrays contain DNS servers configured system-wide, including those
517 possibly read from a foreign
<filename>/etc/resolv.conf
</filename> or the
<varname>DNS=
</varname>
518 setting in
<filename>/etc/systemd/resolved.conf
</filename>, as well as per-interface DNS server
519 information either retrieved from
520 <citerefentry><refentrytitle>systemd-networkd
</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
521 or configured by external software via
<function>SetLinkDNS()
</function> or
522 <function>SetLinkDNSEx()
</function> (see above). The network interface index will be
0 for the
523 system-wide configured services and non-zero for the per-link servers.
</para>
525 <para><varname>FallbackDNS
</varname> and
<varname>FallbackDNSEx
</varname> contain arrays of all DNS
526 servers configured as fallback servers, if any, using the same format as
<varname>DNS
</varname> and
527 <varname>DNSEx
</varname> described above. See the description of
<varname>FallbackDNS=
</varname> in
528 <citerefentry><refentrytitle>resolved.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
529 the description of when those servers are used.
</para>
531 <para><varname>CurrentDNSServer
</varname> and
<varname>CurrentDNSServerEx
</varname> specify the server
532 that is currently used for query resolution, in the same format as a single entry in the
533 <varname>DNS
</varname> and
<varname>DNSEx
</varname> arrays described above.
</para>
535 <para>Similarly, the
<varname>Domains
</varname> property contains an array of all search and routing
536 domains currently used by
<filename>systemd-resolved
</filename>. Each entry consists of a network
537 interface index (again,
0 encodes system-wide entries), the actual domain name, and whether the entry
538 is used only for routing (true) or for both routing and searching (false).
</para>
540 <para>The
<varname>TransactionStatistics
</varname> property contains information about the number of
541 transactions
<filename>systemd-resolved
</filename> has processed. It contains a pair of unsigned
64-bit counters, the first
542 containing the number of currently ongoing transactions, the second the number of total transactions
543 <filename>systemd-resolved
</filename> is processing or has processed. The latter value may be reset using the
544 <function>ResetStatistics()
</function> method described above. Note that the number of transactions does
545 not directly map to the number of issued resolver bus method calls. While simple look-ups usually require a
546 single transaction only, more complex look-ups might result in more, for example when CNAMEs or DNSSEC
549 <para>The
<varname>CacheStatistics
</varname> property contains information about the executed cache
550 operations so far. It exposes three
64-bit counters: the first being the total number of current cache
551 entries (both positive and negative), the second the number of cache hits, and the third the number of
552 cache misses. The latter counters may be reset using
<function>ResetStatistics()
</function> (see
555 <para>The
<varname>DNSSEC
</varname> property specifies current status of DNSSEC validation. It is one
556 of
<literal>yes
</literal> (validation is enforced),
<literal>no
</literal> (no validation is done),
557 <literal>allow-downgrade
</literal> (validation is done if the current DNS server supports it). See the
558 description of
<varname>DNSSEC=
</varname> in
559 <citerefentry><refentrytitle>resolved.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
562 <para>The
<varname>DNSSECStatistics
</varname> property contains information about the DNSSEC
563 validations executed so far. It contains four
64-bit counters: the number of secure, insecure, bogus,
564 and indeterminate DNSSEC validations so far. The counters are increased for each validated RRset, and
565 each non-existance proof. The secure counter is increased for each operation that successfully verified
566 a signed reply, the insecure counter is increased for each operation that successfully verified that an
567 unsigned reply is rightfully unsigned. The bogus counter is increased for each operation where the
568 validation did not check out and the data is likely to have been tempered with. Finally the
569 indeterminate counter is increased for each operation which did not complete because the necessary keys
570 could not be acquired or the cryptographic algorithms were unknown.
</para>
572 <para>The
<varname>DNSSECSupported
</varname> boolean property reports whether DNSSEC is enabled and
573 the selected DNS servers support it. It combines information about system-wide and per-link DNS
574 settings (see below), and only reports true if DNSSEC is enabled and supported on every interface for
575 which DNS is configured and for the system-wide settings if there are any. Note that
<filename>systemd-resolved
</filename> assumes
576 DNSSEC is supported by DNS servers until it verifies that this is not the case. Thus, the reported
577 value may initially be true, until the first transactions are executed.
</para>
579 <para>The
<varname>DNSOverTLS
</varname> boolean property reports whether DNS-over-TLS is enabled.
582 <para>The
<varname>ResolvConfMode
</varname> property exposes how
<filename>/etc/resolv.conf
</filename>
583 is managed on the host. Currently, the values
<literal>uplink
</literal>,
<literal>stub
</literal>,
584 <literal>static
</literal> (these three correspond to the three different files
585 <filename>systemd-resolved.service
</filename> provides),
<literal>foreign
</literal> (the file is
586 managed by admin or another service,
<filename>systemd-resolved.service
</filename> just consumes it),
587 <literal>missing
</literal> (
<filename>/etc/resolv.conf
</filename> is missing).
</para>
589 <para>The
<varname>DNSStubListener
</varname> property reports whether the stub listener on port
53 is
590 enabled. Possible values are
<literal>yes
</literal> (enabled),
<literal>no
</literal> (disabled),
591 <literal>udp
</literal> (only the UDP listener is enabled), and
<literal>tcp
</literal> (only the TCP
592 listener is enabled).
</para>
597 <title>Link Object
</title>
599 <programlisting executable=
"systemd-resolved" node=
"/org/freedesktop/resolve1/link/_1" interface=
"org.freedesktop.resolve1.Link">
600 node /org/freedesktop/resolve1/link/_1 {
601 interface org.freedesktop.resolve1.Link {
603 SetDNS(in a(iay) addresses);
604 SetDNSEx(in a(iayqs) addresses);
605 SetDomains(in a(sb) domains);
606 SetDefaultRoute(in b enable);
608 SetMulticastDNS(in s mode);
609 SetDNSOverTLS(in s mode);
610 SetDNSSEC(in s mode);
611 SetDNSSECNegativeTrustAnchors(in as names);
614 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
615 readonly t ScopesMask = ...;
616 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
617 readonly a(iay) DNS = [...];
618 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
619 readonly a(iayqs) DNSEx = [...];
620 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
621 readonly (iay) CurrentDNSServer = ...;
622 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
623 readonly (iayqs) CurrentDNSServerEx = ...;
624 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
625 readonly a(sb) Domains = [...];
626 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
627 readonly b DefaultRoute = ...;
628 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
629 readonly s LLMNR = '...';
630 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
631 readonly s MulticastDNS = '...';
632 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
633 readonly s DNSOverTLS = '...';
634 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
635 readonly s DNSSEC = '...';
636 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
637 readonly as DNSSECNegativeTrustAnchors = ['...', ...];
638 @org.freedesktop.DBus.Property.EmitsChangedSignal(
"false")
639 readonly b DNSSECSupported = ...;
641 interface org.freedesktop.DBus.Peer { ... };
642 interface org.freedesktop.DBus.Introspectable { ... };
643 interface org.freedesktop.DBus.Properties { ... };
647 <!--property DNSSECNegativeTrustAnchors is not documented!-->
649 <!--Autogenerated cross-references for systemd.directives, do not edit-->
651 <variablelist class=
"dbus-interface" generated=
"True" extra-ref=
"org.freedesktop.resolve1.Link"/>
653 <variablelist class=
"dbus-interface" generated=
"True" extra-ref=
"org.freedesktop.resolve1.Link"/>
655 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetDNS()"/>
657 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetDNSEx()"/>
659 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetDomains()"/>
661 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetDefaultRoute()"/>
663 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetLLMNR()"/>
665 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetMulticastDNS()"/>
667 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetDNSOverTLS()"/>
669 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetDNSSEC()"/>
671 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"SetDNSSECNegativeTrustAnchors()"/>
673 <variablelist class=
"dbus-method" generated=
"True" extra-ref=
"Revert()"/>
675 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"ScopesMask"/>
677 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"DNS"/>
679 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"DNSEx"/>
681 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"CurrentDNSServer"/>
683 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"CurrentDNSServerEx"/>
685 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"Domains"/>
687 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"DefaultRoute"/>
689 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"LLMNR"/>
691 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"MulticastDNS"/>
693 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"DNSOverTLS"/>
695 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"DNSSEC"/>
697 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"DNSSECNegativeTrustAnchors"/>
699 <variablelist class=
"dbus-property" generated=
"True" extra-ref=
"DNSSECSupported"/>
701 <!--End of Autogenerated section-->
703 <para>For each Linux network interface a
"Link" object is created which exposes per-link DNS
704 configuration and state. Use
<function>GetLink()
</function> on the Manager interface to retrieve the
705 object path for a link object given the network interface index (see above).
</para>
708 <title>Methods
</title>
710 <para>The various methods exposed by the Link interface are equivalent to their similarly named
711 counterparts on the Manager interface. e.g.
<function>SetDNS()
</function> on the Link object maps to
712 <function>SetLinkDNS()
</function> on the Manager object, the main difference being that the later
713 expects an interface index to be specified. Invoking the methods on the Manager interface has the
714 benefit of reducing roundtrips, as it is not necessary to first request the Link object path via
715 <function>GetLink()
</function> before invoking the methods. The same relationship holds for
716 <function>SetDNSEx()
</function>,
<function>SetDomains()
</function>,
717 <function>SetDefaultRoute()
</function>,
<function>SetLLMNR()
</function>,
718 <function>SetMulticastDNS()
</function>,
<function>SetDNSOverTLS()
</function>,
719 <function>SetDNSSEC()
</function>,
<function>SetDNSSECNegativeTrustAnchors()
</function>, and
720 <function>Revert()
</function>. For further details on these methods see the
721 <interfacename>Manager
</interfacename> documentation above.
</para>
725 <title>Properties
</title>
727 <para><varname>ScopesMask
</varname> defines which resolver scopes are currently active on this
728 interface. This
64-bit unsigned integer field is a bit mask consisting of a subset of the bits of the
729 flags parameter describe above. Specifically, it may have the DNS, LLMNR and MDNS bits (the latter in
730 IPv4 and IPv6 flavours) set. Each individual bit is set when the protocol applies to a specific
731 interface and is enabled for it. It is unset otherwise. Specifically, a multicast-capable interface in
732 the
"UP" state with an IP address is suitable for LLMNR or MulticastDNS, and any interface that is UP and
733 has an IP address is suitable for DNS. Note the relationship of the bits exposed here with the LLMNR
734 and MulticastDNS properties also exposed on the Link interface. The latter expose what is *configured*
735 to be used on the interface, the former expose what is actually used on the interface, taking into
736 account the abilities of the interface.
</para>
738 <para><varname>DNSSECSupported
</varname> exposes a boolean field that indicates whether DNSSEC is
739 currently configured and in use on the interface. Note that if DNSSEC is enabled on an interface, it is
740 assumed available until it is detected that the configured server does not actually support it. Thus,
741 this property may initially report that DNSSEC is supported on an interface.
</para>
743 <para><varname>DefaultRoute
</varname> exposes a boolean field that indicates whether the interface will
744 be used as default route for name queries. See
<function>SetLinkDefaultRoute()
</function> above.
</para>
746 <para>The other properties reflect the state of the various configuration settings for the link which
747 may be set with the various methods calls such as
<function>SetDNS()
</function> or
748 <function>SetLLMNR()
</function>.
</para>
753 <title>Common Errors
</title>
755 <para>Many bus methods
<filename>systemd-resolved
</filename> exposes (in particular the resolver methods such
756 as
<function>ResolveHostname()
</function> on the
<interfacename>Manager
</interfacename> interface) may return
757 some of the following errors:
</para>
760 <varlistentry><term><constant>org.freedesktop.resolve1.NoNameServers
</constant></term>
761 <listitem><para>No suitable DNS servers were found to resolve a request.
</para></listitem>
764 <varlistentry><term><constant>org.freedesktop.resolve1.InvalidReply
</constant></term>
765 <listitem><para>A response from the selected DNS server was not understood.
</para></listitem>
768 <varlistentry><term><constant>org.freedesktop.resolve1.NoSuchRR
</constant></term>
769 <listitem><para>The requested name exists, but there is no resource record of the requested type for
770 it. (This is the DNS NODATA case).
</para></listitem></varlistentry>
772 <varlistentry><term><constant>org.freedesktop.resolve1.CNameLoop
</constant></term>
773 <listitem><para>The look-up failed because a CNAME or DNAME loop was detected.
</para></listitem>
776 <varlistentry><term><constant>org.freedesktop.resolve1.Aborted
</constant></term>
777 <listitem><para>The look-up was aborted because the selected protocol became unavailable while the
778 operation was ongoing.
</para></listitem>
781 <varlistentry><term><constant>org.freedesktop.resolve1.NoSuchService
</constant></term>
782 <listitem><para>A service look-up was successful, but the SRV record reported that the service is not
783 available.
</para></listitem></varlistentry>
785 <varlistentry><term><constant>org.freedesktop.resolve1.DnssecFailed
</constant></term>
786 <listitem><para>The acquired response did not pass DNSSEC validation.
</para></listitem>
789 <varlistentry><term><constant>org.freedesktop.resolve1.NoTrustAnchor
</constant></term>
790 <listitem><para>No chain of trust could be established for the response to a configured DNSSEC trust
791 anchor.
</para></listitem>
794 <varlistentry><term><constant>org.freedesktop.resolve1.ResourceRecordTypeUnsupported
</constant></term>
795 <listitem><para>The requested resource record type is not supported on the selected DNS servers. This
796 error is generated for example when an RRSIG record is requested from a DNS server that does not
797 support DNSSEC.
</para></listitem>
801 <varlistentry><term><constant>org.freedesktop.resolve1.NoSuchLink
</constant></term>
802 <listitem><para>No network interface with the specified network interface index exists.
803 </para></listitem></varlistentry>
805 <varlistentry><term><constant>org.freedesktop.resolve1.LinkBusy
</constant></term>
806 <listitem><para>The requested configuration change could not be made because
807 <citerefentry><refentrytitle>systemd-networkd
</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
808 already took possession of the interface and supplied configuration data for it.
</para></listitem>
811 <varlistentry><term><constant>org.freedesktop.resolve1.NetworkDown
</constant></term>
812 <listitem><para>The requested look-up failed because the system is currently not connected to any
813 suitable network.
</para></listitem></varlistentry>
815 <varlistentry><term><constant>org.freedesktop.resolve1.DnsError.NXDOMAIN
</constant></term>
816 <term><constant>org.freedesktop.resolve1.DnsError.REFUSED
</constant></term>
818 <listitem><para>The look-up failed with a DNS return code reporting a failure. The error names used as
819 suffixes here are defined in by IANA in
820 <ulink url=
"https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-6">DNS RCODEs
</ulink>.
827 <title>Examples
</title>
830 <title>Introspect
<interfacename>org.freedesktop.resolve1.Manager
</interfacename> on the bus
</title>
833 $ gdbus introspect --system \
834 --dest org.freedesktop.resolve1 \
835 --object-path /org/freedesktop/resolve1
840 <title>Introspect
<interfacename>org.freedesktop.resolve1.Link
</interfacename> on the bus
</title>
843 $ gdbus introspect --system \
844 --dest org.freedesktop.resolve1 \
845 --object-path /org/freedesktop/resolve1/link/_11
851 <title>Versioning
</title>
853 <para>These D-Bus interfaces follow
<ulink url=
"http://0pointer.de/blog/projects/versioning-dbus.html">
854 the usual interface versioning guidelines
</ulink>.
</para>