module Network.DNS.Decode (
decode
, receive
) where
import Control.Applicative
import Control.Monad
import Data.Bits
import Data.ByteString (ByteString)
import qualified Data.ByteString.Char8 as BS
import qualified Data.ByteString.Lazy as BL
import Data.Conduit
import Data.Conduit.Network
import Data.IP
import Data.Maybe
import Network
import Network.DNS.Internal
import Network.DNS.StateBinary
receive :: Socket -> IO DNSFormat
receive sock = receiveDNSFormat $ sourceSocket sock
decode :: BL.ByteString -> Either String DNSFormat
decode bs = fst <$> runSGet decodeResponse bs
receiveDNSFormat :: Source (ResourceT IO) ByteString -> IO DNSFormat
receiveDNSFormat src = fst <$> runResourceT (src $$ sink)
where
sink = sinkSGet decodeResponse
decodeResponse :: SGet DNSFormat
decodeResponse = do
hd <- decodeHeader
DNSFormat hd <$> decodeQueries (qdCount hd)
<*> decodeRRs (anCount hd)
<*> decodeRRs (nsCount hd)
<*> decodeRRs (arCount hd)
decodeFlags :: SGet DNSFlags
decodeFlags = toFlags <$> get16
where
toFlags flgs = DNSFlags (getQorR flgs)
(getOpcode flgs)
(getAuthAnswer flgs)
(getTrunCation flgs)
(getRecDesired flgs)
(getRecAvailable flgs)
(getRcode flgs)
getQorR w = if testBit w 15 then QR_Response else QR_Query
getOpcode w = toEnum $ fromIntegral $ shiftR w 11 .&. 0x0f
getAuthAnswer w = testBit w 10
getTrunCation w = testBit w 9
getRecDesired w = testBit w 8
getRecAvailable w = testBit w 7
getRcode w = toEnum $ fromIntegral $ w .&. 0x0f
decodeHeader :: SGet DNSHeader
decodeHeader = DNSHeader <$> decodeIdentifier
<*> decodeFlags
<*> decodeQdCount
<*> decodeAnCount
<*> decodeNsCount
<*> decodeArCount
where
decodeIdentifier = getInt16
decodeQdCount = getInt16
decodeAnCount = getInt16
decodeNsCount = getInt16
decodeArCount = getInt16
decodeQueries :: Int -> SGet [Question]
decodeQueries n = replicateM n decodeQuery
decodeType :: SGet TYPE
decodeType = intToType <$> getInt16
decodeQuery :: SGet Question
decodeQuery = Question <$> decodeDomain
<*> (decodeType <* ignoreClass)
decodeRRs :: Int -> SGet [ResourceRecord]
decodeRRs n = replicateM n decodeRR
decodeRR :: SGet ResourceRecord
decodeRR = do
Question dom typ <- decodeQuery
ttl <- decodeTTL
len <- decodeRLen
dat <- decodeRData typ len
return ResourceRecord { rrname = dom
, rrtype = typ
, rrttl = ttl
, rdlen = len
, rdata = dat
}
where
decodeTTL = fromIntegral <$> get32
decodeRLen = getInt16
decodeRData :: TYPE -> Int -> SGet RDATA
decodeRData NS _ = RD_NS <$> decodeDomain
decodeRData MX _ = RD_MX <$> decodePreference <*> decodeDomain
where
decodePreference = getInt16
decodeRData CNAME _ = RD_CNAME <$> decodeDomain
decodeRData TXT len = (RD_TXT . ignoreLength) <$> getNByteString len
where
ignoreLength = BS.tail
decodeRData A len = (RD_A . toIPv4) <$> getNBytes len
decodeRData AAAA len = (RD_AAAA . toIPv6 . combine) <$> getNBytes len
where
combine [] = []
combine [_] = error "combine"
combine (a:b:cs) = a * 256 + b : combine cs
decodeRData SOA _ = RD_SOA <$> decodeDomain
<*> decodeDomain
<*> decodeSerial
<*> decodeRefesh
<*> decodeRetry
<*> decodeExpire
<*> decodeMinumun
where
decodeSerial = getInt32
decodeRefesh = getInt32
decodeRetry = getInt32
decodeExpire = getInt32
decodeMinumun = getInt32
decodeRData PTR _ = RD_PTR <$> decodeDomain
decodeRData SRV _ = RD_SRV <$> decodePriority
<*> decodeWeight
<*> decodePort
<*> decodeDomain
where
decodePriority = getInt16
decodeWeight = getInt16
decodePort = getInt16
decodeRData _ len = RD_OTH <$> getNBytes len
decodeDomain :: SGet Domain
decodeDomain = do
pos <- getPosition
c <- getInt8
if c == 0 then
return ""
else do
let n = getValue c
if isPointer c then do
d <- getInt8
let offset = n * 256 + d
fromMaybe (error $ "decodeDomain: " ++ show offset) <$> pop offset
else do
hs <- getNByteString n
ds <- decodeDomain
let dom = hs `BS.append` "." `BS.append` ds
push pos dom
return dom
where
getValue c = c .&. 0x3f
isPointer c = testBit c 7 && testBit c 6
ignoreClass :: SGet ()
ignoreClass = () <$ get16