GHC 10.0.0.20260917 · lts/ghc-10.0.x · 77a8662 · 2026-10-31
Moduleresolv-0.2.0.3Haskell2010
This module implements an API for accessing
the Domain Name Service (DNS)
resolver service via the standard libresolv system library
on Unix systems.
Query A record (see RFC 1035, section 3.4.1).
This query returns only exact matches (modulo foldCaseName).
E.g. in case of CNAME responses even if the
answer section would contain A records for the hostnames pointed
to by the CNAME. You can use query if you need more control.
queryA (Name "www.google.com")[(TTL 72,IPv4 0xd83acde4)]
Query AAAA records (see RFC 3596).
This query returns only exact matches (modulo foldCaseName).
E.g. in case of CNAME responses even if the answer section would
contain A records for the hostnames pointed to by the
CNAME. You can use query if you need more control.
queryAAAA (Name "www.google.com")[(TTL 299,IPv6 0x2a0014504001081e 0x2004)]
Query CNAME records (see RFC 1035, section 3.3.1).
queryCNAME (Name "hackage.haskell.org")[(TTL 299,Name "j.global-ssl.fastly.net.")]
Query PTR records (see RFC 1035, section 3.3.12).
queryPTR (Name "4.4.8.8.in-addr.arpa.")[(TTL 14390,Name "dns.google.")]
See also arpaIPv6 and arpaIPv4 for converting IPv6 and IPv4 values to the respective .arpa." domain name for reverse lookups.
Query SRV records (see RFC 2782).
querySRV (Name "_imap._tcp.gmail.com")[(TTL 21599,SRV {srvPriority = 0, srvWeight = 0, srvPort = 0, srvTarget = Name "."})]
Query TXT records (see RFC 1035, section 3.3.14).
queryTXT (Name "_mirrors.hackage.haskell.org")[(TTL 299,["0.urlbase=http://hackage.fpcomplete.com/", "1.urlbase=http://objects-us-west-1.dream.io/hackage-mirror/"])]
Send a query via res_query(3) and decode its response into a Msg
Throws DnsException in case of resolving or encoding/decoding errors. May throw other IO exceptions in case of network errors.
query classIN (Name "_mirrors.hackage.haskell.org") TypeTXTJust (Msg{msgHeader = MsgHeader{mhId = 56694, mhFlags = MsgHeaderFlags{mhQR = IsResponse, mhOpcode = 0, mhAA = False, mhTC = False, mhRD = True, mhRA = True, mhZ = False, mhAD = False, mhCD = False, mhRCode = 0}, mhQDCount = 1, mhANCount = 1, mhNSCount = 0, mhARCount = 1}, msgQD = [MsgQuestion (Name "_mirrors.hackage.haskell.org.") (Type 16) (Class 1)], msgAN = [MsgRR{rrName = Name "_mirrors.hackage.haskell.org.", rrClass = Class 1, rrTTL = TTL 299, rrData = RDataTXT ["0.urlbase=http://hackage.fpcomplete.com/", "1.urlbase=http://objects-us-west-1.dream.io/hackage-mirror/"]}], msgNS = [], msgAR = [MsgRR{rrName = Name ".", rrClass = Class 512, rrTTL = TTL 32768, rrData = RDataOPT ""}] })
Exception thrown in case of errors while resolving or encoding/decoding into a Msg.
DnsEncodeExceptionDnsDecodeExceptionDnsHostNotFoundNo such domain (authoritative)
DnsNoDataNo record for requested type
DnsNoRecoveryNon recoverable errors, REFUSED, NOTIMP
DnsTryAgainNo such domain (non-authoritative) or SERVERFAIL
Eq DnsExceptionDefined in resolv-0.2.0.3 · Network.DNSShow DnsExceptionDefined in resolv-0.2.0.3 · Network.DNSException DnsExceptionDefined in resolv-0.2.0.3 · Network.DNSWhether the reentrant DNS resolver C API (e.g. res_nquery(3), res_nsend(3)) is being used.
If this this False, then as a fall-back
res_query(3)/res_send(3) are used, protected by a global mutex.
Send a query via res_query(3), the return value is the raw binary response message.
You can use decodeMessage to decode the response message.
Send a raw preformatted query via res_send(3).
Use res_mkquery(3) to construct a DNS query message.
Decode a raw DNS message (query or response)
Returns Nothing on decoding failures.
Construct a raw DNS message (query or response)
May return Nothing in input parameters are detected to be invalid.
Construct a DNS query Msg in the style of mkQueryRaw
A DNS Label
Must be non-empty and at most 63 octets.
A domain-name as per RFC 1035, section 3.3 expressed as list of Labels.
See also Name
Types that represent domain-name as per RFC 1035, section 3.3 and can be converted to and from Labels.
toLabels :: s -> Maybe LabelsfromLabels :: Labels -> s<domain-name> as per RFC 1035, section 3.3.
A domain-name represented as a series of labels separated by dots.
See also Labels for list-based representation.
NOTE: The Labels type is able to properly represent domain names whose components contain dots which the Name representation cannot.
Normalise Name
This function case folds Names as described in
in RFC 4343, section 3
by subtracting 0x20 from all octets in the inclusive range
[0x61..0x7A] (i.e. mapping [ to a..z][).A..Z]
This operation is idempotent.
<character-string> as per RFC 1035, section 3.3.
A sequence of up to 255 octets
The limit of 255 octets is caused by the encoding which uses by a prefixed octet denoting the length.
Eq CharStrDefined in resolv-0.2.0.3 · Network.DNS.MessageOrd CharStrDefined in resolv-0.2.0.3 · Network.DNS.MessageRead CharStrDefined in resolv-0.2.0.3 · Network.DNS.MessageShow CharStrDefined in resolv-0.2.0.3 · Network.DNS.MessageIsString CharStrDefined in resolv-0.2.0.3 · Network.DNS.MessageBinary CharStrDefined in resolv-0.2.0.3 · Network.DNS.MessageAn IPv4 address
The IP address is represented in network order, i.e. 127.0.0.1 is
represented as (IPv4 0x7f000001).
Convert IPv4 address to in-addr.arpa. Name (see RFC 1035, section 3.5).
arpaIPv4 (IPv4 0x8080404)Name "4.4.8.8.in-addr.arpa."
An IPv6 address
The IP address is represented in network order,
i.e. 2606:2800:220:1:248:1893:25c8:1946 is
represented as (IPv6 0x2606280002200001 0x248189325c81946).
Convert IPv4 address to ip6.arpa. Name (see RFC 3596, section 2.5).
arpaIPv6 (IPv6 0x2001486048600000 0x8844)Name "4.4.8.8.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.6.8.4.0.6.8.4.1.0.0.2.ip6.arpa."
DNS CLASS code as per RFC 1035, section 3.2.4
The most commonly used value is classIN.
The Class constant for IN (Internet)
Symbolic DNS record type
Bounded TypeSymDefined in resolv-0.2.0.3 · Network.DNS.MessageEnum TypeSymDefined in resolv-0.2.0.3 · Network.DNS.MessageEq TypeSymDefined in resolv-0.2.0.3 · Network.DNS.MessageOrd TypeSymDefined in resolv-0.2.0.3 · Network.DNS.MessageRead TypeSymDefined in resolv-0.2.0.3 · Network.DNS.MessageShow TypeSymDefined in resolv-0.2.0.3 · Network.DNS.MessageRepresents a DNS message as per RFC 1035
Functor MsgDefined in resolv-0.2.0.3 · Network.DNS.MessageFoldable MsgDefined in resolv-0.2.0.3 · Network.DNS.MessageTraversable MsgDefined in resolv-0.2.0.3 · Network.DNS.MessageRead l => Read (Msg l)Defined in resolv-0.2.0.3 · Network.DNS.MessageShow l => Show (Msg l)Defined in resolv-0.2.0.3 · Network.DNS.MessageBinary l => Binary (Msg l)Defined in resolv-0.2.0.3 · Network.DNS.MessageDNS message header section as per RFC 1035, section 4.1.1
DNS message header flags as per RFC 1035, section 4.1.1
Read MsgHeaderFlagsDefined in resolv-0.2.0.3 · Network.DNS.MessageShow MsgHeaderFlagsDefined in resolv-0.2.0.3 · Network.DNS.MessageBinary MsgHeaderFlagsDefined in resolv-0.2.0.3 · Network.DNS.MessageEncodes whether message is a query or a response
DNS message header section as per RFC 1035, section 4.1.2
MsgQuestion !l !Type !ClassFunctor MsgQuestionDefined in resolv-0.2.0.3 · Network.DNS.MessageFoldable MsgQuestionDefined in resolv-0.2.0.3 · Network.DNS.MessageTraversable MsgQuestionDefined in resolv-0.2.0.3 · Network.DNS.MessageEq l => Eq (MsgQuestion l)Defined in resolv-0.2.0.3 · Network.DNS.MessageRead l => Read (MsgQuestion l)Defined in resolv-0.2.0.3 · Network.DNS.MessageShow l => Show (MsgQuestion l)Defined in resolv-0.2.0.3 · Network.DNS.MessageBinary l => Binary (MsgQuestion l)Defined in resolv-0.2.0.3 · Network.DNS.MessageDNS resource record section as per RFC 1035, section 4.1.3
Functor MsgRRDefined in resolv-0.2.0.3 · Network.DNS.MessageFoldable MsgRRDefined in resolv-0.2.0.3 · Network.DNS.MessageTraversable MsgRRDefined in resolv-0.2.0.3 · Network.DNS.MessageEq l => Eq (MsgRR l)Defined in resolv-0.2.0.3 · Network.DNS.MessageRead l => Read (MsgRR l)Defined in resolv-0.2.0.3 · Network.DNS.MessageShow l => Show (MsgRR l)Defined in resolv-0.2.0.3 · Network.DNS.MessageBinary l => Binary (MsgRR l)Defined in resolv-0.2.0.3 · Network.DNS.MessageRDataA !IPv4RDataAAAA !IPv6RDataCNAME !lRDataPTR !lRDataHINFO !CharStr !CharStrRDataNS !lRDataMX !Word16 !lRDataTXT ![CharStr]RDataSPF ![CharStr]RDataSOA !l !l !Word32 !Word32 !Word32 !Word32 !Word32RDataSRV !(SRV l)RDataAFSDB !Word16 !lRDataNAPTR !Word16 !Word16 !CharStr !CharStr !CharStr !lRDataURI !Word16 !Word16 !ByteStringRDataRRSIG !Word16 !Word8 !Word8 !Word32 !Word32 !Word32 !Word16 !l !ByteStringRDataDNSKEY !Word16 !Word8 !Word8 !ByteStringRDataDS !Word16 !Word8 !Word8 !ByteStringRDataNSEC !l !(Set Type)RDataSSHFP !Word8 !Word8 !ByteStringRDataNSEC3PARAM !Word8 !Word8 !Word16 !CharStrRDataNSEC3 !Word8 !Word8 !Word16 !CharStr !CharStr !(Set Type)RDataCAA !Word8 !CharStr !ByteStringRDataOPT !ByteStringRData !Type !ByteStringUnknown/undecoded resource record type
Functor RDataDefined in resolv-0.2.0.3 · Network.DNS.MessageFoldable RDataDefined in resolv-0.2.0.3 · Network.DNS.MessageTraversable RDataDefined in resolv-0.2.0.3 · Network.DNS.MessageEq l => Eq (RData l)Defined in resolv-0.2.0.3 · Network.DNS.MessageRead l => Read (RData l)Defined in resolv-0.2.0.3 · Network.DNS.MessageShow l => Show (RData l)Defined in resolv-0.2.0.3 · Network.DNS.MessageExtract the resource record type of a RData object
SRV Record data as per RFC 2782
Functor SRVDefined in resolv-0.2.0.3 · Network.DNS.MessageFoldable SRVDefined in resolv-0.2.0.3 · Network.DNS.MessageTraversable SRVDefined in resolv-0.2.0.3 · Network.DNS.MessageEq l => Eq (SRV l)Defined in resolv-0.2.0.3 · Network.DNS.MessageRead l => Read (SRV l)Defined in resolv-0.2.0.3 · Network.DNS.MessageShow l => Show (SRV l)Defined in resolv-0.2.0.3 · Network.DNS.MessageBinary l => Binary (SRV l)Defined in resolv-0.2.0.3 · Network.DNS.Message