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module Network.DNS.Response (parseResponse) where
import Control.Monad
import Data.Bits
import qualified Data.ByteString.Lazy.Char8 as L
import Data.Char
import Data.IP
import Data.Maybe
import Network.DNS.Internal
import Network.DNS.StateBinary
----------------------------------------------------------------
parseResponse :: L.ByteString -> DNSFormat
parseResponse = runSGet 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 = do
flgs <- get16
return $ DNSFlags (getQorR flgs)
(getOpcode flgs)
(getAuthAnswer flgs)
(getTrunCation flgs)
(getRecDesired flgs)
(getRecAvailable flgs)
(getRcode flgs)
where
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 = L.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 <$> decodeDomain
<*> decodeDomain
<*> decodeSerial
<*> decodeRefesh
<*> decodeRetry
<*> decodeExpire
<*> decodeMinumun
where
decodeSerial = getInt32
decodeRefesh = getInt32
decodeRetry = getInt32
decodeExpire = getInt32
decodeMinumun = getInt32
decodeRData _ len = RD_OTH <$> 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) <$> pop offset
else do
hs <- decodeString n
ds <- decodeDomain
let dom = hs ++ "." ++ ds
push pos dom
return dom
where
getValue c = c .&. 0x3f
isPointer c = testBit c 7 && testBit c 6
decodeString :: Int -> SGet String
decodeString n = map chr <$> getNBytes n
ignoreClass :: SGet ()
ignoreClass = () <$ get16
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