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|
{-|
DNS Resolver and lookup functions.
Sample code:
@
import qualified Network.DNS as DNS (lookup)
import Network.DNS hiding (lookup)
main :: IO ()
main = do
rs <- makeResolvSeed defaultResolvConf
withResolver rs $ \\resolver -> do
DNS.lookup resolver \"www.example.com\" A >>= print
@
-}
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, 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
----------------------------------------------------------------
{-|
Union type for 'FilePath' and 'HostName'. Specify 'FilePath' to
\"resolv.conf\" or numeric IP address in 'String' form.
-}
data FileOrNumericHost = RCFilePath FilePath | RCHostName HostName
{-|
Type for resolver configuration
-}
data ResolvConf = ResolvConf {
resolvInfo :: FileOrNumericHost
, resolvTimeout :: Int
, resolvBufsize :: Integer
}
{-|
Default 'ResolvConf'.
'resolvInfo' is 'RCFilePath' \"\/etc\/resolv.conf\".
'resolvTimeout' is 3,000,000 micro seconds.
'resolvBufsize' is 512.
-}
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
}
----------------------------------------------------------------
{-|
Making 'ResolvSeed' from an IP address of a DNS cache server.
-}
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'.
-}
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.
-}
lookup :: Resolver -> Domain -> TYPE -> IO (Maybe [RDATA])
lookup rlv dom typ = (>>= toRDATA) <$> lookupRaw rlv dom typ
where
{- CNAME hack
dom' = if "." `isSuffixOf` dom
then dom
else dom ++ "."
correct r = rrname r == dom' && rrtype r == typ
-}
correct r = rrtype r == typ
listToMaybe [] = Nothing
listToMaybe xs = Just xs
toRDATA = listToMaybe . map rdata . filter correct . answer
{-|
Looking up a domain and returning an entire DNS Response.
-}
lookupRaw :: Resolver -> Domain -> TYPE -> IO (Maybe DNSFormat)
lookupRaw rlv dom typ = do
seqno <- genId rlv
sendAll sock (composeQuery seqno [q])
(>>= check seqno) <$> timeout tm (receive sock bufsize)
where
sock = dnsSock rlv
bufsize = dnsBufsize rlv
tm = dnsTimeout rlv
q = makeQuestion dom typ
check seqno res = do
let hdr = header res
if identifier hdr == seqno
then Just res
else Nothing
|
