{-# LANGUAGE CPP #-} -- | DNS Resolver and generic (lower-level) lookup functions. module Network.DNS.Resolver ( -- * Documentation -- ** Configuration for resolver FileOrNumericHost(..), ResolvConf(..), defaultResolvConf -- ** Intermediate data type for resolver , ResolvSeed, makeResolvSeed -- ** Type and function for resolver , Resolver(..), withResolver -- ** Looking up functions , lookup, lookupAuth, lookupRaw ) where import Control.Applicative import Control.Exception import Data.Char import Data.Int import Data.List hiding (find, lookup) import Network.BSD import Network.DNS.Decode import Network.DNS.Encode import Network.DNS.Internal import Network.Socket hiding (send, sendTo, recv, recvFrom) import Network.Socket.ByteString.Lazy import Prelude hiding (lookup) import System.Random import System.Timeout #if mingw32_HOST_OS == 1 import Network.Socket (send) import qualified Data.ByteString.Lazy.Char8 as LB import Control.Monad (when) #endif ---------------------------------------------------------------- -- | Union type for 'FilePath' and 'HostName'. Specify 'FilePath' to -- \"resolv.conf\" or numeric IP address in 'String' form. -- -- /Warning/: Only numeric IP addresses are valid @RCHostName@s. -- -- Example (using Google's public DNS cache): -- -- >>> let cache = RCHostName "8.8.8.8" -- data FileOrNumericHost = RCFilePath FilePath | RCHostName HostName -- | Type for resolver configuration. The easiest way to construct a -- @ResolvConf@ object is to modify the 'defaultResolvConf'. data ResolvConf = ResolvConf { resolvInfo :: FileOrNumericHost , resolvTimeout :: Int -- | This field was obsoleted. , resolvBufsize :: Integer } -- | Return a default 'ResolvConf': -- -- * 'resolvInfo' is 'RCFilePath' \"\/etc\/resolv.conf\". -- -- * 'resolvTimeout' is 3,000,000 micro seconds. -- -- * 'resolvBufsize' is 512. (obsoleted) -- -- Example (use Google's public DNS cache instead of resolv.conf): -- -- >>> let cache = RCHostName "8.8.8.8" -- >>> let rc = defaultResolvConf { resolvInfo = cache } -- defaultResolvConf :: ResolvConf defaultResolvConf = ResolvConf { resolvInfo = RCFilePath "/etc/resolv.conf" , resolvTimeout = 3 * 1000 * 1000 , resolvBufsize = 512 } ---------------------------------------------------------------- -- | Abstract data type of DNS Resolver seed data ResolvSeed = ResolvSeed { addrInfo :: AddrInfo , rsTimeout :: Int , rsBufsize :: Integer } -- | Abstract data type of DNS Resolver data Resolver = Resolver { genId :: IO Int , dnsSock :: Socket , dnsTimeout :: Int , dnsBufsize :: Integer } ---------------------------------------------------------------- -- | Make a 'ResolvSeed' from a 'ResolvConf'. -- -- Examples: -- -- >>> rs <- makeResolvSeed defaultResolvConf -- makeResolvSeed :: ResolvConf -> IO ResolvSeed makeResolvSeed conf = ResolvSeed <$> addr <*> pure (resolvTimeout conf) <*> pure (resolvBufsize conf) where addr = case resolvInfo conf of RCHostName numhost -> makeAddrInfo numhost RCFilePath file -> toAddr <$> readFile file >>= makeAddrInfo toAddr cs = let l:_ = filter ("nameserver" `isPrefixOf`) $ lines cs in extract l extract = reverse . dropWhile isSpace . reverse . dropWhile isSpace . drop 11 makeAddrInfo :: HostName -> IO AddrInfo makeAddrInfo addr = do proto <- getProtocolNumber "udp" let hints = defaultHints { addrFlags = [AI_ADDRCONFIG, AI_NUMERICHOST, AI_PASSIVE] , addrSocketType = Datagram , addrProtocol = proto } a:_ <- getAddrInfo (Just hints) (Just addr) (Just "domain") return a ---------------------------------------------------------------- -- | Giving a thread-safe 'Resolver' to the function of the second -- argument. 'withResolver' should be passed to 'forkIO'. For -- examples, see "Network.DNS.Lookup". withResolver :: ResolvSeed -> (Resolver -> IO a) -> IO a withResolver seed func = do let ai = addrInfo seed sock <- socket (addrFamily ai) (addrSocketType ai) (addrProtocol ai) connect sock (addrAddress ai) let resolv = Resolver { genId = getRandom , dnsSock = sock , dnsTimeout = rsTimeout seed , dnsBufsize = rsBufsize seed } func resolv `finally` sClose sock getRandom :: IO Int getRandom = getStdRandom (randomR (0,65535)) ---------------------------------------------------------------- -- | Looking up resource records of a domain. The first parameter is one of -- the field accessors of the 'DNSFormat' type -- this allows you to -- choose which section (answer, authority, or additional) you would like -- to inspect for the result. lookupSection :: (DNSFormat -> [ResourceRecord]) -> Resolver -> Domain -> TYPE -> IO (Either DNSError [RDATA]) lookupSection section rlv dom typ = (>>= toRDATA) <$> lookupRaw rlv dom typ where {- CNAME hack dom' = if "." `isSuffixOf` dom then dom else dom ++ "." correct r = rrname r == dom' && rrtype r == typ -} correct r = rrtype r == typ toRDATA = Right . map rdata . filter correct . section -- | Look up resource records for a domain, collecting the results -- from the ANSWER section of the response. -- -- We repeat an example from "Network.DNS.Lookup": -- -- >>> let hostname = Data.ByteString.Char8.pack "www.example.com" -- >>> rs <- makeResolvSeed defaultResolvConf -- >>> withResolver rs $ \resolver -> lookup resolver hostname A -- Right [93.184.216.119] -- lookup :: Resolver -> Domain -> TYPE -> IO (Either DNSError [RDATA]) lookup = lookupSection answer -- | Look up resource records for a domain, collecting the results -- from the AUTHORITY section of the response. lookupAuth :: Resolver -> Domain -> TYPE -> IO (Either DNSError [RDATA]) lookupAuth = lookupSection authority -- | Look up a name and return the entire DNS Response. Sample output -- is included below, however it is /not/ tested -- the sequence -- number is unpredictable (it has to be!). -- -- The example code: -- -- @ -- let hostname = Data.ByteString.Char8.pack \"www.example.com\" -- rs <- makeResolvSeed defaultResolvConf -- withResolver rs $ \resolver -> lookupRaw resolver hostname A -- @ -- -- And the (formatted) expected output: -- -- @ -- Right (DNSFormat -- { header = DNSHeader -- { identifier = 1, -- flags = DNSFlags -- { qOrR = QR_Response, -- opcode = OP_STD, -- authAnswer = False, -- trunCation = False, -- recDesired = True, -- recAvailable = True, -- rcode = NoErr }, -- qdCount = 1, -- anCount = 1, -- nsCount = 0, -- arCount = 0}, -- question = [Question { qname = \"www.example.com.\", -- qtype = A}], -- answer = [ResourceRecord {rrname = \"www.example.com.\", -- rrtype = A, -- rrttl = 800, -- rdlen = 4, -- rdata = 93.184.216.119}], -- authority = [], -- additional = []}) -- @ -- lookupRaw :: Resolver -> Domain -> TYPE -> IO (Either DNSError DNSFormat) lookupRaw rlv dom typ = do seqno <- genId rlv sendAll sock (composeQuery seqno [q]) response <- timeout tm (receive sock) return $ case response of Nothing -> Left TimeoutExpired Just y -> check seqno y where sock = dnsSock rlv tm = dnsTimeout rlv q = makeQuestion dom typ check seqno res = do let hdr = header res if identifier hdr == seqno then Right res else Left SequenceNumberMismatch #if mingw32_HOST_OS == 1 -- Windows does not support sendAll in Network.ByteString.Lazy. -- This implements sendAll with Haskell Strings. sendAll sock bs = do sent <- send sock (LB.unpack bs) when (sent < fromIntegral (LB.length bs)) $ sendAll sock (LB.drop (fromIntegral sent) bs) #endif