Provided by: systemd-resolved_256.5-2ubuntu4_amd64 
NAME
org.freedesktop.resolve1 - The D-Bus interface of systemd-resolved
INTRODUCTION
systemd-resolved.service(8) is a system service that provides hostname resolution and
caching using DNS, LLMNR, and mDNS. It also does DNSSEC validation. This page describes
the resolve semantics and the D-Bus interface.
This page contains an API reference only. If you are looking for a longer explanation how
to use this API, please consult Writing Network Configuration Managers[1] and Writing
Resolver Clients[2].
THE MANAGER OBJECT
The service exposes the following interfaces on the Manager object on the bus:
node /org/freedesktop/resolve1 {
interface org.freedesktop.resolve1.Manager {
methods:
ResolveHostname(in i ifindex,
in s name,
in i family,
in t flags,
out a(iiay) addresses,
out s canonical,
out t flags);
ResolveAddress(in i ifindex,
in i family,
in ay address,
in t flags,
out a(is) names,
out t flags);
ResolveRecord(in i ifindex,
in s name,
in q class,
in q type,
in t flags,
out a(iqqay) records,
out t flags);
ResolveService(in i ifindex,
in s name,
in s type,
in s domain,
in i family,
in t flags,
out a(qqqsa(iiay)s) srv_data,
out aay txt_data,
out s canonical_name,
out s canonical_type,
out s canonical_domain,
out t flags);
GetLink(in i ifindex,
out o path);
SetLinkDNS(in i ifindex,
in a(iay) addresses);
SetLinkDNSEx(in i ifindex,
in a(iayqs) addresses);
SetLinkDomains(in i ifindex,
in a(sb) domains);
SetLinkDefaultRoute(in i ifindex,
in b enable);
SetLinkLLMNR(in i ifindex,
in s mode);
SetLinkMulticastDNS(in i ifindex,
in s mode);
SetLinkDNSOverTLS(in i ifindex,
in s mode);
SetLinkDNSSEC(in i ifindex,
in s mode);
SetLinkDNSSECNegativeTrustAnchors(in i ifindex,
in as names);
RevertLink(in i ifindex);
RegisterService(in s id,
in s name_template,
in s type,
in q service_port,
in q service_priority,
in q service_weight,
in aa{say} txt_datas,
out o service_path);
UnregisterService(in o service_path);
ResetStatistics();
FlushCaches();
ResetServerFeatures();
properties:
readonly s LLMNRHostname = '...';
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly s LLMNR = '...';
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly s MulticastDNS = '...';
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly s DNSOverTLS = '...';
readonly a(iiay) DNS = [...];
readonly a(iiayqs) DNSEx = [...];
@org.freedesktop.DBus.Property.EmitsChangedSignal("const")
readonly a(iiay) FallbackDNS = [...];
@org.freedesktop.DBus.Property.EmitsChangedSignal("const")
readonly a(iiayqs) FallbackDNSEx = [...];
readonly (iiay) CurrentDNSServer = ...;
readonly (iiayqs) CurrentDNSServerEx = ...;
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly a(isb) Domains = [...];
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly (tt) TransactionStatistics = ...;
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly (ttt) CacheStatistics = ...;
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly s DNSSEC = '...';
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly (tttt) DNSSECStatistics = ...;
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly b DNSSECSupported = ...;
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly as DNSSECNegativeTrustAnchors = ['...', ...];
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly s DNSStubListener = '...';
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly s ResolvConfMode = '...';
};
interface org.freedesktop.DBus.Peer { ... };
interface org.freedesktop.DBus.Introspectable { ... };
interface org.freedesktop.DBus.Properties { ... };
};
Methods
ResolveHostname() takes a hostname and resolves it to one or more IP addresses. As
parameters it takes the Linux network interface index to execute the query on, or 0 if it
may be done on any suitable interface. The name parameter specifies the hostname to
resolve. Note that if required, IDNA conversion is applied to this name unless it is
resolved via LLMNR or MulticastDNS. The family parameter limits the results to a specific
address family. It may be AF_INET, AF_INET6 or AF_UNSPEC. If AF_UNSPEC is specified
(recommended), both kinds are retrieved, subject to local network configuration (i.e. if
no local, routable IPv6 address is found, no IPv6 address is retrieved; and similarly for
IPv4). A 64-bit flags field may be used to alter the behaviour of the resolver operation
(see below). The method returns an array of address records. Each address record consists
of the interface index the address belongs to, an address family as well as a byte array
with the actual IP address data (which either has 4 or 16 elements, depending on the
address family). The returned address family will be one of AF_INET or AF_INET6. For IPv6,
the returned address interface index should be used to initialize the .sin6_scope_id field
of a struct sockaddr_in6 instance to permit support for resolution to link-local IP
addresses. The address array is followed by the canonical name of the host, which may or
may not be identical to the resolved hostname. Finally, a 64-bit flags field is returned
that is defined similarly to the flags field that was passed in, but contains information
about the resolved data (see below). If the hostname passed in is an IPv4 or IPv6 address
formatted as string, it is parsed, and the result is returned. In this case, no network
communication is done.
ResolveAddress() executes the reverse operation: it takes an IP address and acquires one
or more hostnames for it. As parameters it takes the interface index to execute the query
on, or 0 if all suitable interfaces are OK. The family parameter indicates the address
family of the IP address to resolve. It may be either AF_INET or AF_INET6. The address
parameter takes the raw IP address data (as either a 4 or 16 byte array). The flags input
parameter may be used to alter the resolver operation (see below). The method returns an
array of name records, each consisting of an interface index and a hostname. The flags
output field contains additional information about the resolver operation (see below).
ResolveRecord() takes a DNS resource record (RR) type, class and name, and retrieves the
full resource record set (RRset), including the RDATA, for it. As parameter it takes the
Linux network interface index to execute the query on, or 0 if it may be done on any
suitable interface. The name parameter specifies the RR domain name to look up (no IDNA
conversion is applied), followed by the 16-bit class and type fields (which may be ANY).
Finally, a flags field may be passed in to alter behaviour of the look-up (see below). On
completion, an array of RR items is returned. Each array entry consists of the network
interface index the RR was discovered on, the type and class field of the RR found, and a
byte array of the raw RR discovered. The raw RR data starts with the RR's domain name, in
the original casing, followed by the RR type, class, TTL and RDATA, in the binary format
documented in RFC 1035[3]. For RRs that support name compression in the payload (such as
MX or PTR), the compression is expanded in the returned data.
Note that currently, the class field has to be specified as IN or ANY. Specifying a
different class will return an error indicating that look-ups of this kind are
unsupported. Similarly, some special types are not supported either (AXFR, OPT, ...).
While systemd-resolved parses and validates resource records of many types, it is crucial
that clients using this API understand that the RR data originates from the network and
should be thoroughly validated before use.
ResolveService() may be used to resolve a DNS SRV service record, as well as the hostnames
referenced in it, and possibly an accompanying DNS-SD TXT record containing additional
service metadata. The primary benefit of using this method over ResolveRecord() specifying
the SRV type is that it will resolve the SRV and TXT RRs as well as the hostnames
referenced in the SRV in a single operation. As parameters it takes a Linux network
interface index, a service name, a service type and a service domain. This method may be
invoked in three different modes:
1. To resolve a DNS-SD service, specify the service name (e.g. "Lennart's Files"), the
service type (e.g. "_webdav._tcp") and the domain to search in (e.g. "local") as the
three service parameters. The service name must be in UTF-8 format, and no IDNA
conversion is applied to it in this mode (as mandated by the DNS-SD specifications).
However, if necessary, IDNA conversion is applied to the domain parameter.
2. To resolve a plain SRV record, set the service name parameter to the empty string and
set the service type and domain properly. (IDNA conversion is applied to the domain,
if necessary.)
3. Alternatively, leave both the service name and type empty and specify the full domain
name of the SRV record (i.e. prefixed with the service type) in the domain parameter.
(No IDNA conversion is applied in this mode.)
The family parameter of the ResolveService() method encodes the desired family of the
addresses to resolve (use AF_INET, AF_INET6, or AF_UNSPEC). If this is enabled (Use the
NO_ADDRESS flag to turn address resolution off, see below). The flags parameter takes a
couple of flags that may be used to alter the resolver operation.
On completion, ResolveService() returns an array of SRV record structures. Each items
consisting of the priority, weight and port fields as well as the hostname to contact, as
encoded in the SRV record. Immediately following is an array of the addresses of this
hostname, with each item consisting of the interface index, the address family and the
address data in a byte array. This address array is followed by the canonicalized
hostname. After this array of SRV record structures an array of byte arrays follows that
encodes the TXT RR strings, in case DNS-SD look-ups are enabled. The next parameters are
the canonical service name, type and domain. This may or may not be identical to the
parameters passed in. Finally, a flags field is returned that contains information about
the resolver operation performed.
The ResetStatistics() method resets the various statistics counters that systemd-resolved
maintains to zero. (For details, see the statistics properties below.)
The GetLink() method takes a network interface index and returns the object path to the
org.freedesktop.resolve1.Link object corresponding to it.
The SetLinkDNS() method sets the DNS servers to use on a specific interface. This method
(and the following ones) may be used by network management software to configure
per-interface DNS settings. It takes a network interface index as well as an array of DNS
server IP address records. Each array item consists of an address family (either AF_INET
or AF_INET6), followed by a 4-byte or 16-byte array with the raw address data. This method
is a one-step shortcut for retrieving the Link object for a network interface using
GetLink() (see above) and then invoking the SetDNS() method (see below) on it.
SetLinkDNSEx() is similar to SetLinkDNS(), but allows an IP port (instead of the default
53) and DNS name to be specified for each DNS server. The server name is used for Server
Name Indication (SNI), which is useful when DNS-over-TLS is used. C.f. DNS= in
resolved.conf(5).
SetLinkDefaultRoute() specifies whether the link shall be used as the default route for
name queries. See the description of name routing in systemd-resolved.service(8) for
details.
The SetLinkDomains() method sets the search and routing domains to use on a specific
network interface for DNS look-ups. It takes a network interface index and an array of
domains, each with a boolean parameter indicating whether the specified domain shall be
used as a search domain (false), or just as a routing domain (true). Search domains are
used for qualifying single-label names into FQDN when looking up hostnames, as well as for
making routing decisions on which interface to send queries ending in the domain to.
Routing domains are only used for routing decisions and not used for single-label name
qualification. Pass the search domains in the order they should be used.
The SetLinkLLMNR() method enables or disables LLMNR support on a specific network
interface. It takes a network interface index as well as a string that may either be empty
or one of "yes", "no" or "resolve". If empty, the systemd-wide default LLMNR setting is
used. If "yes", LLMNR is used for resolution of single-label names and the local hostname
is registered on all local LANs for LLMNR resolution by peers. If "no", LLMNR is turned
off fully on this interface. If "resolve", LLMNR is only enabled for resolving names, but
the local hostname is not registered for other peers to use.
Similarly, the SetLinkMulticastDNS() method enables or disables MulticastDNS support on a
specific interface. It takes the same parameters as SetLinkLLMNR() described above.
The SetLinkDNSSEC() method enables or disables DNSSEC validation on a specific network
interface. It takes a network interface index as well as a string that may either be empty
or one of "yes", "no", or "allow-downgrade". When empty, the system-wide default DNSSEC
setting is used. If "yes", full DNSSEC validation is done for all look-ups. If the
selected DNS server does not support DNSSEC, look-ups will fail if this mode is used. If
"no", DNSSEC validation is fully disabled. If "allow-downgrade", DNSSEC validation is
enabled, but is turned off automatically if the selected server does not support it (thus
opening up behaviour to downgrade attacks). Note that DNSSEC only applies to traditional
DNS, not to LLMNR or MulticastDNS.
The SetLinkDNSSECNegativeTrustAnchors() method may be used to configure DNSSEC Negative
Trust Anchors (NTAs) for a specific network interface. It takes a network interface index
and a list of domains as arguments.
The SetLinkDNSOverTLS() method enables or disables DNS-over-TLS. C.f. DNSOverTLS= in
systemd-resolved.service(8) for details.
Network management software integrating with systemd-resolved should call SetLinkDNS() or
SetLinkDNSEx(), SetLinkDefaultRoute(), SetLinkDomains() and others after the interface
appeared in the kernel (and thus after a network interface index has been assigned), but
before the network interfaces is activated (IFF_UP set) so that all settings take effect
during the full time the network interface is up. It is safe to alter settings while the
interface is up, however. Use RevertLink() (described below) to reset all per-interface
settings.
The RevertLink() method may be used to revert all per-link settings described above to the
defaults.
The FlushCaches() flushes all resource record caches maintained by the resolver, and
ensures that any subsequent lookups re-request their responses from their sources.
The ResetServerFeatures() flushes any feature information learned about remote DNS
servers. This ensures that subsequent lookups will be initially attempted at the highest
DNS protocol feature level again, possibly requiring a (potentially slow) downgrade cycle
to recognize the supported feature level again.
The RegisterService() method may be used to register a DNS-SD service on the host. This
functionality is closely related to the functionality provided by systemd.dnssd(5) files.
It takes a server identifier string as first parameter (this is just a local identifier,
and should be chosen so that it neither collides with the basename of *.dnssd files nor
with names chosen by other IPC clients). It also takes a name template string for the
DNS-SD service name visible on the network. This string is subject to specifier
expansation, as documented for the Name= setting in *.dnssd files. It also takes a service
type string containing the DNS-SD service type, as well as an IP port, a priority/weight
pair for the DNS-SD SRV record. Finally, it takes an array of TXT record data. It returns
an object path which may be used as handle to the registered service.
The UnregisterService() method undoes the effect of RegisterService() and deletes a DNS-SD
service previously created via IPC again.
The Flags Parameter
The four methods above accept and return a 64-bit flags value. In most cases passing 0
is sufficient and recommended. However, the following flags are defined to alter the
look-up:
/* Input+Output: Protocol/scope */
#define SD_RESOLVED_DNS (UINT64_C(1) << 0)
#define SD_RESOLVED_LLMNR_IPV4 (UINT64_C(1) << 1)
#define SD_RESOLVED_LLMNR_IPV6 (UINT64_C(1) << 2)
#define SD_RESOLVED_MDNS_IPV4 (UINT64_C(1) << 3)
#define SD_RESOLVED_MDNS_IPV6 (UINT64_C(1) << 4)
/* Input: Restrictions */
#define SD_RESOLVED_NO_CNAME (UINT64_C(1) << 5)
#define SD_RESOLVED_NO_TXT (UINT64_C(1) << 6)
#define SD_RESOLVED_NO_ADDRESS (UINT64_C(1) << 7)
#define SD_RESOLVED_NO_SEARCH (UINT64_C(1) << 8)
#define SD_RESOLVED_NO_VALIDATE (UINT64_C(1) << 10)
#define SD_RESOLVED_NO_SYNTHESIZE (UINT64_C(1) << 11)
#define SD_RESOLVED_NO_CACHE (UINT64_C(1) << 12)
#define SD_RESOLVED_NO_ZONE (UINT64_C(1) << 13)
#define SD_RESOLVED_NO_TRUST_ANCHOR (UINT64_C(1) << 14)
#define SD_RESOLVED_NO_NETWORK (UINT64_C(1) << 15)
#define SD_RESOLVED_NO_STALE (UINT64_C(1) << 24)
#define SD_RESOLVED_RELAX_SINGLE_LABEL (UINT64_C(1) << 25)
/* Output: Security */
#define SD_RESOLVED_AUTHENTICATED (UINT64_C(1) << 9)
#define SD_RESOLVED_CONFIDENTIAL (UINT64_C(1) << 18)
/* Output: Origin */
#define SD_RESOLVED_SYNTHETIC (UINT64_C(1) << 19)
#define SD_RESOLVED_FROM_CACHE (UINT64_C(1) << 20)
#define SD_RESOLVED_FROM_ZONE (UINT64_C(1) << 21)
#define SD_RESOLVED_FROM_TRUST_ANCHOR (UINT64_C(1) << 22)
#define SD_RESOLVED_FROM_NETWORK (UINT64_C(1) << 23)
On input, the first five flags control the protocols to use for the look-up. They
refer to classic unicast DNS, LLMNR via IPv4/UDP and IPv6/UDP respectively, as well as
MulticastDNS via IPv4/UDP and IPv6/UDP. If all of these five bits are off on input
(which is strongly recommended) the look-up will be done via all suitable protocols
for the specific look-up. Note that these flags operate as filter only, but cannot
force a look-up to be done via a protocol. Specifically, systemd-resolved will only
route look-ups within the .local TLD to MulticastDNS (plus some reverse look-up
address domains), and single-label names to LLMNR (plus some reverse address lookup
domains). It will route neither of these to Unicast DNS servers. Also, it will do
LLMNR and Multicast DNS only on interfaces suitable for multicast.
On output, these five flags indicate which protocol was used to execute the operation,
and hence where the data was found.
The primary use cases for these five flags are follow-up look-ups based on DNS data
retrieved earlier. In this case it is often a good idea to limit the follow-up look-up
to the protocol that was used to discover the first DNS result.
The NO_CNAME flag controls whether CNAME/DNAME resource records shall be followed
during the look-up. This flag is only available at input, none of the functions will
return it on output. If a CNAME/DNAME RR is discovered while resolving a hostname, an
error is returned instead. By default, when the flag is off, CNAME/DNAME RRs are
followed.
The NO_TXT and NO_ADDRESS flags only influence operation of the ResolveService()
method. They are only defined for input, not output. If NO_TXT is set, the DNS-SD TXT
RR look-up is not done in the same operation. If NO_ADDRESS is set, the discovered
hostnames are not implicitly translated to their addresses.
The NO_SEARCH flag turns off the search domain logic. It is only defined for input in
ResolveHostname(). When specified, single-label hostnames are not qualified using
defined search domains, if any are configured. Note that ResolveRecord() will never
qualify single-label domain names using search domains. Also note that multi-label
hostnames are never subject to search list expansion.
NO_VALIDATE can be set to disable validation via DNSSEC even if it would normally be
used.
The next six flags allow disabling certain sources during resolution. NO_SYNTHESIZE
disables synthetic records, e.g. the local host name, see section SYNTHETIC RECORDS in
systemd-resolved.service(8) for more information. NO_CACHE disables the use of the
cache of previously resolved records. NO_ZONE disables answers using locally
registered public LLMNR/mDNS resource records. NO_TRUST_ANCHOR disables answers using
locally configured trust anchors. NO_NETWORK requires all answers to be provided
without using the network, i.e. either from local sources or the cache. NO_STALE flag
can be set to disable answering request with stale records.
The AUTHENTICATED bit is defined only in the output flags of the four functions. If
set, the returned data has been fully authenticated. Specifically, this bit is set for
all DNSSEC-protected data for which a full trust chain may be established to a trusted
domain anchor. It is also set for locally synthesized data, such as "localhost" or
data from /etc/hosts. Moreover, it is set for all LLMNR or mDNS RRs which originate
from the local host. Applications that require authenticated RR data for operation
should check this flag before trusting the data. Note that systemd-resolved will never
return invalidated data, hence this flag simply allows one to discern the cases where
data is known to be trusted, or where there is proof that the data is "rightfully"
unauthenticated (which includes cases where the underlying protocol or server does not
support authenticating data).
CONFIDENTIAL means the query was resolved via encrypted channels or never left this
system.
The next five bits flags are used in output and provide information about the origin
of the answer. FROM_SYNTHETIC means the query was (at least partially) synthesized
locally. FROM_CACHE means the query was answered (at least partially) using the cache.
FROM_ZONE means the query was answered (at least partially) based on public, locally
registered records. FROM_TRUST_ANCHOR means the query was answered (at least
partially) using local trust anchors. FROM_NETWORK means the query was answered (at
least partially) using the network.
Properties
The LLMNR and MulticastDNS properties report whether LLMNR and MulticastDNS are (globally)
enabled. Each may be one of "yes", "no", and "resolve". See SetLinkLLMNR() and
SetLinkMulticastDNS() above.
LLMNRHostname contains the hostname currently exposed on the network via LLMNR. It usually
follows the system hostname as may be queried via gethostname(3), but may differ if a
conflict is detected on the network.
DNS and DNSEx contain arrays of all DNS servers currently used by systemd-resolved. DNS
contains information similar to the DNS server data in /run/systemd/resolve/resolv.conf.
Each structure in the array consists of a numeric network interface index, an address
family, and a byte array containing the DNS server address (either 4 bytes in length for
IPv4 or 16 bytes in lengths for IPv6). DNSEx is similar, but additionally contains the IP
port and server name (used for Server Name Indication, SNI). Both arrays contain DNS
servers configured system-wide, including those possibly read from a foreign
/etc/resolv.conf or the DNS= setting in /etc/systemd/resolved.conf, as well as
per-interface DNS server information either retrieved from systemd-networkd(8), or
configured by external software via SetLinkDNS() or SetLinkDNSEx() (see above). The
network interface index will be 0 for the system-wide configured services and non-zero for
the per-link servers.
FallbackDNS and FallbackDNSEx contain arrays of all DNS servers configured as fallback
servers, if any, using the same format as DNS and DNSEx described above. See the
description of FallbackDNS= in resolved.conf(5) for the description of when those servers
are used.
CurrentDNSServer and CurrentDNSServerEx specify the server that is currently used for
query resolution, in the same format as a single entry in the DNS and DNSEx arrays
described above.
Similarly, the Domains property contains an array of all search and routing domains
currently used by systemd-resolved. Each entry consists of a network interface index
(again, 0 encodes system-wide entries), the actual domain name, and whether the entry is
used only for routing (true) or for both routing and searching (false).
The TransactionStatistics property contains information about the number of transactions
systemd-resolved has processed. It contains a pair of unsigned 64-bit counters, the first
containing the number of currently ongoing transactions, the second the number of total
transactions systemd-resolved is processing or has processed. The latter value may be
reset using the ResetStatistics() method described above. Note that the number of
transactions does not directly map to the number of issued resolver bus method calls.
While simple look-ups usually require a single transaction only, more complex look-ups
might result in more, for example when CNAMEs or DNSSEC are in use.
The CacheStatistics property contains information about the executed cache operations so
far. It exposes three 64-bit counters: the first being the total number of current cache
entries (both positive and negative), the second the number of cache hits, and the third
the number of cache misses. The latter counters may be reset using ResetStatistics() (see
above).
The DNSSEC property specifies current status of DNSSEC validation. It is one of "yes"
(validation is enforced), "no" (no validation is done), "allow-downgrade" (validation is
done if the current DNS server supports it). See the description of DNSSEC= in
resolved.conf(5).
The DNSSECStatistics property contains information about the DNSSEC validations executed
so far. It contains four 64-bit counters: the number of secure, insecure, bogus, and
indeterminate DNSSEC validations so far. The counters are increased for each validated
RRset, and each non-existence proof. The secure counter is increased for each operation
that successfully verified a signed reply, the insecure counter is increased for each
operation that successfully verified that an unsigned reply is rightfully unsigned. The
bogus counter is increased for each operation where the validation did not check out and
the data is likely to have been tempered with. Finally the indeterminate counter is
increased for each operation which did not complete because the necessary keys could not
be acquired or the cryptographic algorithms were unknown.
The DNSSECSupported boolean property reports whether DNSSEC is enabled and the selected
DNS servers support it. It combines information about system-wide and per-link DNS
settings (see below), and only reports true if DNSSEC is enabled and supported on every
interface for which DNS is configured and for the system-wide settings if there are any.
Note that systemd-resolved assumes DNSSEC is supported by DNS servers until it verifies
that this is not the case. Thus, the reported value may initially be true, until the first
transactions are executed.
The DNSOverTLS boolean property reports whether DNS-over-TLS is enabled.
The ResolvConfMode property exposes how /etc/resolv.conf is managed on the host.
Currently, the values "uplink", "stub", "static" (these three correspond to the three
different files systemd-resolved.service provides), "foreign" (the file is managed by
admin or another service, systemd-resolved.service just consumes it), "missing"
(/etc/resolv.conf is missing).
The DNSStubListener property reports whether the stub listener on port 53 is enabled.
Possible values are "yes" (enabled), "no" (disabled), "udp" (only the UDP listener is
enabled), and "tcp" (only the TCP listener is enabled).
The DNSSECNegativeTrustAnchors property contains a list of recognized DNSSEC negative
trust anchors and contains a list of domains.
LINK OBJECT
node /org/freedesktop/resolve1/link/_1 {
interface org.freedesktop.resolve1.Link {
methods:
SetDNS(in a(iay) addresses);
SetDNSEx(in a(iayqs) addresses);
SetDomains(in a(sb) domains);
SetDefaultRoute(in b enable);
SetLLMNR(in s mode);
SetMulticastDNS(in s mode);
SetDNSOverTLS(in s mode);
SetDNSSEC(in s mode);
SetDNSSECNegativeTrustAnchors(in as names);
Revert();
properties:
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly t ScopesMask = ...;
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly a(iay) DNS = [...];
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly a(iayqs) DNSEx = [...];
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly (iay) CurrentDNSServer = ...;
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly (iayqs) CurrentDNSServerEx = ...;
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly a(sb) Domains = [...];
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly b DefaultRoute = ...;
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly s LLMNR = '...';
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly s MulticastDNS = '...';
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly s DNSOverTLS = '...';
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly s DNSSEC = '...';
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly as DNSSECNegativeTrustAnchors = ['...', ...];
@org.freedesktop.DBus.Property.EmitsChangedSignal("false")
readonly b DNSSECSupported = ...;
};
interface org.freedesktop.DBus.Peer { ... };
interface org.freedesktop.DBus.Introspectable { ... };
interface org.freedesktop.DBus.Properties { ... };
};
For each Linux network interface a "Link" object is created which exposes per-link DNS
configuration and state. Use GetLink() on the Manager interface to retrieve the object
path for a link object given the network interface index (see above).
Methods
The various methods exposed by the Link interface are equivalent to their similarly named
counterparts on the Manager interface. e.g. SetDNS() on the Link object maps to
SetLinkDNS() on the Manager object, the main difference being that the later expects an
interface index to be specified. Invoking the methods on the Manager interface has the
benefit of reducing roundtrips, as it is not necessary to first request the Link object
path via GetLink() before invoking the methods. The same relationship holds for
SetDNSEx(), SetDomains(), SetDefaultRoute(), SetLLMNR(), SetMulticastDNS(),
SetDNSOverTLS(), SetDNSSEC(), SetDNSSECNegativeTrustAnchors(), and Revert(). For further
details on these methods see the Manager documentation above.
Properties
ScopesMask defines which resolver scopes are currently active on this interface. This
64-bit unsigned integer field is a bit mask consisting of a subset of the bits of the
flags parameter describe above. Specifically, it may have the DNS, LLMNR and MDNS bits
(the latter in IPv4 and IPv6 flavours) set. Each individual bit is set when the protocol
applies to a specific interface and is enabled for it. It is unset otherwise.
Specifically, a multicast-capable interface in the "UP" state with an IP address is
suitable for LLMNR or MulticastDNS, and any interface that is UP and has an IP address is
suitable for DNS. Note the relationship of the bits exposed here with the LLMNR and
MulticastDNS properties also exposed on the Link interface. The latter expose what is
*configured* to be used on the interface, the former expose what is actually used on the
interface, taking into account the abilities of the interface.
DNSSECSupported exposes a boolean field that indicates whether DNSSEC is currently
configured and in use on the interface. Note that if DNSSEC is enabled on an interface, it
is assumed available until it is detected that the configured server does not actually
support it. Thus, this property may initially report that DNSSEC is supported on an
interface.
DefaultRoute exposes a boolean field that indicates whether the interface will be used as
default route for name queries. See SetLinkDefaultRoute() above.
The other properties reflect the state of the various configuration settings for the link
which may be set with the various methods calls such as SetDNS() or SetLLMNR().
COMMON ERRORS
Many bus methods systemd-resolved exposes (in particular the resolver methods such as
ResolveHostname() on the Manager interface) may return some of the following errors:
org.freedesktop.resolve1.NoNameServers
No suitable DNS servers were found to resolve a request.
Added in version 246.
org.freedesktop.resolve1.InvalidReply
A response from the selected DNS server was not understood.
Added in version 246.
org.freedesktop.resolve1.NoSuchRR
The requested name exists, but there is no resource record of the requested type for
it. (This is the DNS NODATA case).
Added in version 246.
org.freedesktop.resolve1.CNameLoop
The look-up failed because a CNAME or DNAME loop was detected.
Added in version 246.
org.freedesktop.resolve1.Aborted
The look-up was aborted because the selected protocol became unavailable while the
operation was ongoing.
Added in version 246.
org.freedesktop.resolve1.NoSuchService
A service look-up was successful, but the SRV record reported that the service is not
available.
Added in version 246.
org.freedesktop.resolve1.DnssecFailed
The acquired response did not pass DNSSEC validation.
Added in version 246.
org.freedesktop.resolve1.NoTrustAnchor
No chain of trust could be established for the response to a configured DNSSEC trust
anchor.
Added in version 246.
org.freedesktop.resolve1.ResourceRecordTypeUnsupported
The requested resource record type is not supported on the selected DNS servers. This
error is generated for example when an RRSIG record is requested from a DNS server
that does not support DNSSEC.
Added in version 246.
org.freedesktop.resolve1.NoSuchLink
No network interface with the specified network interface index exists.
Added in version 246.
org.freedesktop.resolve1.LinkBusy
The requested configuration change could not be made because systemd-networkd(8),
already took possession of the interface and supplied configuration data for it.
Added in version 246.
org.freedesktop.resolve1.NetworkDown
The requested look-up failed because the system is currently not connected to any
suitable network.
Added in version 246.
org.freedesktop.resolve1.DnsError.NXDOMAIN, org.freedesktop.resolve1.DnsError.REFUSED, ...
The look-up failed with a DNS return code reporting a failure. The error names used as
suffixes here are defined in by IANA in DNS RCODEs[4].
Added in version 246.
EXAMPLES
Example 1. Introspect org.freedesktop.resolve1.Manager on the bus
$ gdbus introspect --system \
--dest org.freedesktop.resolve1 \
--object-path /org/freedesktop/resolve1
Example 2. Introspect org.freedesktop.resolve1.Link on the bus
$ gdbus introspect --system \
--dest org.freedesktop.resolve1 \
--object-path /org/freedesktop/resolve1/link/_11
VERSIONING
These D-Bus interfaces follow the usual interface versioning guidelines[5].
NOTES
1. Writing Network Configuration Managers
https://wiki.freedesktop.org/www/Software/systemd/writing-network-configuration-managers
2. Writing Resolver Clients
https://wiki.freedesktop.org/www/Software/systemd/writing-resolver-clients
3. RFC 1035
https://www.ietf.org/rfc/rfc1035.txt
4. DNS RCODEs
https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-6
5. the usual interface versioning guidelines
https://0pointer.de/blog/projects/versioning-dbus.html