From ffd10e5a24bf7ece97b90dcebd64250b380ce16b Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= Date: Thu, 9 Apr 2020 21:57:16 +0200 Subject: [PATCH] man: import org.freedesktop.resolve1(3) from the wiki --- man/org.freedesktop.resolve1.xml | 567 +++++++++++++++++++++++++++++++ man/rules/meson.build | 1 + man/systemd-resolved.service.xml | 11 +- 3 files changed, 574 insertions(+), 5 deletions(-) create mode 100644 man/org.freedesktop.resolve1.xml diff --git a/man/org.freedesktop.resolve1.xml b/man/org.freedesktop.resolve1.xml new file mode 100644 index 0000000000..f0cf668f19 --- /dev/null +++ b/man/org.freedesktop.resolve1.xml @@ -0,0 +1,567 @@ + + + +%entities; +]> + + + + + org.freedesktop.resolve1 + systemd + + + + org.freedesktop.resolve1 + 5 + + + + org.freedesktop.resolve1 + The D-Bus interface of systemd-resolved + + + + Introduction + + + systemd-resolved.service8 + is a system service that provides host name 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 + and + Writing Resolver + Clients. + + + + + The Manager Object + + The service exposes the following interfaces on the Manager object on the bus: + + +$ gdbus introspect --system \ + --dest org.freedesktop.resolve1 \ + --object-path /org/freedesktop/resolve1 + +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); + ResetStatistics(); + GetLink(in i ifindex, + out o path); + SetLinkDNS(in i ifindex, + in a(iay) addresses); + SetLinkDomains(in i ifindex, + in a(sb) domains); + SetLinkLLMNR(in i ifindex, + in s mode); + SetLinkMulticastDNS(in i ifindex, + in s mode); + SetLinkDNSSEC(in i ifindex, + in s mode); + SetLinkDNSSECNegativeTrustAnchors(in i ifindex, + in as names); + RevertLink(in i ifindex); + properties: + readonly s LLMNRHostname = 'delta'; + readonly a(iiay) DNS = [(0, 2, [0xac, 0x1f, 0x00, 0x01])]; + readonly a(isb) Domains = [(0, 'fritz.box', false)]; + readonly (tt) TransactionStatistics = (0, 846); + readonly (ttt) CacheStatistics = (55, 406, 439); + readonly (tttt) DNSSECStatistics = (0, 0, 0, 0); + readonly b DNSSECSupported = false; + }; + interface org.freedesktop.DBus.Peer { + }; + interface org.freedesktop.DBus.Introspectable { + }; + interface org.freedesktop.DBus.Properties { + }; +}; + + + + Methods + + ResolveHostname() takes a hostname and acquires one or more IP addresses for + it. 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 IDNA conversion is applied to this name when necessary, and when it is resolved via + Unicast DNS, but not for resolution via LLMNR or MulticastDNS. The family parameter + specifies the address family of the IP address to retrieve. It may be AF_INET, + AF_INET6 or AF_UNSPEC, to request addresses of a specific + family. 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 + behaviour of the resolver operation (see below). The method returns an array of address records. Each + address record consists of an 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, 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 name looked up. 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 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 4 or 16 byte array). The flags input + parameter may be used to alter the resolver operation (see below). The call returns an array of name + records, consisting of an interface index plus the name each. 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 return 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. For RRs that support name + compression in the payload (such as MX or PTR), the compression is expanded in the returned + data. + + Note that the class field has to be specified as IN or ANY currently, and 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 systmed-resolved parses and validates resource + record 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 the + hostnames referenced in it, and possibly an accompanying DNS-SD TXT record containing additional + service metadata. The primary benefit of using this call 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. The call may be invoked in three different modes: + + + 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) in 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. + + + 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.) + + 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 + coversion is applied in this mode.) + + + The family parameter of the ResolveService() call encodes + the desired family of the addresses to resolve (use AF_INET, + AF_INET6, 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 return, ResolveService() returns an array of SRV record structures. Each + item consists of the priority, weight and port fields and the hostname to contact, as encoded in the SRV + record. Immediately following is an array with 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 with 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 to zero the various statistics counters + systmed-resolved maintains. (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 call (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 + call is a one-call shortcut for retrieving the Link object for a network interface using + GetLink() (see above) and then invoking the SetDNS() call + (see below) on it. + + + Network management software integrating with systmed-resolved is recommended + to invoke this method (and the five below) after the interface appeared in the kernel (and thus after a + network interface index has been assigned), but before the network interfaces is activated (set + IFF_UP on) 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 the + RevertLink() (described below) to reset all per-interface settings. + + The SetLinkDomains() method sets the search and routing domains to use on a + specific network interface for DNS look-ups. It take a network interface index plus an array of domains, + each with a boolean parameter indicating whether the specified domain shall be used as search domain + (false), or just as 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 not used for single-label name qualification, and + are only used for routing decisions. Pass the search domains in the order they shall 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 either may be empty, + 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 host name 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 either may be + empty, yes, no or allow-downgrade. If 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 parameters. + + The RevertLink() method may be used to revert all per-link settings done with + the six calls described above to the defaults again. + + + The Flags Parameter + + The four calls 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: + + +#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) +#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_AUTHENTICATED (UINT64_C(1) << 9) + + + 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, systmed-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 multicasting. + + On output these five flags indicate which protocol was used to execute the operation, and hence + where the data was found. + + The primary use case 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 data look-up. + + 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 influence operation of the + ResolveService() call only. They are only defined for input, not output. If + NO_TXT set, the DNS-SD TXT RR look-up is not done in the same operation. If NO_ADDRESS is specified + the hostnames discovered 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 not qualify single-label domain names using search domains in any case. Also note that + multi-label hostnames are never subject to search list expansion. + + 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. Not that systmed-resolved will not return invalidated data in any case, hence this flag + simply allows to discern the cases where data is known to be trustable, 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). + + + + + + Properties + + LLMNRHostname contains the hostname currently exposed on the network via LLMNR. It + usually follows the system hostname as may be queried via + gethostname3, + but may differ if a conflict is detected on the network. + + DNS contains an array containing all DNS servers currently used by + systmed-resolved. It contains similar information as the DNS server data written to + /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). The array contains 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-networkd8, + or configured by external software via SetLinkDNS() (see above). The network + interface index will be 0 for the system-wide configured services, and non-zero for the per-link + servers. + + Similarly, the Domains property contains an array containing all search and + routing domains currently used by systmed-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 systmed-resolved has been processing. 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 + systmed-resolved is processing or has processed. The latter value may be reset using the + ResetStatistics() call described above. Note that the number of transaction does + not directly map to the number of resolver bus calls issued. 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 number of cache hits, and the third the number of + cache misses. The latter counters may be reset using ResetStatistics() (see + above). + + 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-existance 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 systmed-resolved assumes + DNSSEC is supported by DNS servers until it verified that this is not the case. Thus, the reported + value may initially be true, until the first transactions are executed. + + + + + Link Object + + +$ gdbus introspect --system \ + --dest org.freedesktop.resolve1 \ + --object-path /org/freedesktop/resolve1/link/_34 + +node /org/freedesktop/resolve1/link/_34 { + interface org.freedesktop.resolve1.Link { + methods: + SetDNS(in a(iay) arg_0); + SetDomains(in a(sb) arg_0); + SetLLMNR(in s arg_0); + SetMulticastDNS(in s arg_0); + SetDNSSEC(in s arg_0); + SetDNSSECNegativeTrustAnchors(in as arg_0); + Revert(); + signals: + properties: + readonly t ScopesMask = 6; + readonly a(iay) DNS = []; + readonly a(sb) Domains = []; + readonly s LLMNR = 'yes'; + readonly s MulticastDNS = 'no'; + readonly s DNSSEC = ''; + readonly as DNSSECNegativeTrustAnchors = []; + readonly b DNSSECSupported = true; + }; + 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 speicified. Invoking the calls 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. For further details on these calls 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 as 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 + "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. + + 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 calls systmed-resolved exposes (in particular the resolver calls such + as ResolveHostname() on the Manager interface) return + some of the following errors: + + + org.freedesktop.resolve1.NoNameServers + No suitable DNS servers have been found to resolve a request. + + + org.freedesktop.resolve1.InvalidReply + A response from the selected DNS server could not be understood. + + + 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). + + org.freedesktop.resolve1.CNameLoop + The look-up failed because a CNAME or DNAME loop was detected. + + + org.freedesktop.resolve1.Aborted + The look-up was aborted, because the selected protocol became unavailable while the + operation was ongoing. + + + org.freedesktop.resolve1.NoSuchService + A service look-up was successful, but the SRV record reported that the service is not + available. + + org.freedesktop.resolve1.DnssecFailed + The acquired response did not pass DNSSEC validation. + + + org.freedesktop.resolve1.NoTrustAnchor + No chain of trust could be established for the response, to a configured DNSSEC trust + anchor. + + + 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. + + + + org.freedesktop.resolve1.NoSuchLink + No network interface with the specified network interface index exists. + + + org.freedesktop.resolve1.LinkBusy + The requested configuration change can not be made, because + systemd-networkd8, + already took possession of the interface and supplied configuration data for it. + + + org.freedesktop.resolve1.NetworkDown + The requested look-up failed because the system is currently not connected to any + suitable network. + + 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. + + + + + + + Versioning + + These D-Bus interfaces follow + the usual interface versioning guidelines. + + diff --git a/man/rules/meson.build b/man/rules/meson.build index c881bae6cd..1552fe2d10 100644 --- a/man/rules/meson.build +++ b/man/rules/meson.build @@ -49,6 +49,7 @@ manpages = [ ['org.freedesktop.locale1', '5', [], 'ENABLE_LOCALED'], ['org.freedesktop.login1', '5', [], 'ENABLE_LOGIND'], ['org.freedesktop.machine1', '5', [], 'ENABLE_MACHINED'], + ['org.freedesktop.resolve1', '5', [], 'ENABLE_RESOLVE'], ['org.freedesktop.timedate1', '5', [], 'ENABLE_TIMEDATED'], ['os-release', '5', [], ''], ['pam_systemd', '8', [], 'HAVE_PAM'], diff --git a/man/systemd-resolved.service.xml b/man/systemd-resolved.service.xml index 53c46a1018..3fb0846157 100644 --- a/man/systemd-resolved.service.xml +++ b/man/systemd-resolved.service.xml @@ -34,11 +34,12 @@ resolver and responder. Local applications may submit network name resolution requests via three interfaces: - The native, fully-featured API systemd-resolved exposes on the bus. See the - API Documentation for - details. Usage of this API is generally recommended to clients as it is asynchronous and fully featured (for - example, properly returns DNSSEC validation status and interface scope for addresses as necessary for supporting - link-local networking). + The native, fully-featured API systemd-resolved exposes on the bus, + see + org.freedesktop.resolve15 + for details. Usage of this API is generally recommended to clients as it is asynchronous and fully + featured (for example, properly returns DNSSEC validation status and interface scope for addresses as + necessary for supporting link-local networking). The glibc getaddrinfo3 API as defined