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|
{-# LANGUAGE TupleSections #-}
module DNSCache
( DNSCache
, reverseResolve
, forwardResolve
, newDNSCache
) where
import Control.Concurrent
import Control.Concurrent.STM
import Data.Text ( Text )
import Network.Socket ( SockAddr(..), AddrInfoFlag(..), defaultHints, getAddrInfo, AddrInfo(..) )
import Data.Time.Clock ( UTCTime, getCurrentTime, diffUTCTime )
import System.IO.Error ( isDoesNotExistError )
import System.Endian ( fromBE32, toBE32 )
import Control.Exception ( handle, ErrorCall(..) )
import Data.Map ( Map )
import qualified Data.Map as Map
import qualified Network.BSD as BSD
import qualified Data.Text as Text
import Control.Monad
import Data.List
import Data.Ord
import SockAddr ()
import ControlMaybe ( handleIO_ )
import GetHostByAddr ( getHostByAddr )
type TimeStamp = UTCTime
data DNSCache =
DNSCache
{ fcache :: TVar (Map Text [(TimeStamp, SockAddr)])
, rcache :: TVar (Map SockAddr [(TimeStamp, Text)])
}
newDNSCache :: IO DNSCache
newDNSCache = do
atomically $ do
fcache <- newTVar Map.empty
rcache <- newTVar Map.empty
return DNSCache { fcache=fcache, rcache=rcache }
equivBy f a b = f a == f b
updateCache :: Eq x =>
Bool -> TimeStamp -> [x] -> Maybe [(TimeStamp,x)] -> Maybe [(TimeStamp,x)]
updateCache withScrub utc xs mys = do
let ys = maybe [] id mys
ys' = filter scrub ys
ys'' = map (utc,) xs ++ ys'
minute = 60
scrub (t,x) | withScrub && diffUTCTime utc t < minute = False
scrub (t,x) | x `elem` xs = False
scrub _ = True
guard $ not (null ys'')
return ys''
dnsObserve :: DNSCache -> Bool -> TimeStamp -> [(Text,SockAddr)] -> STM ()
dnsObserve dns withScrub utc obs = do
f <- readTVar $ fcache dns
r <- readTVar $ rcache dns
let gs = do
g <- groupBy (equivBy fst) $ sortBy (comparing fst) obs
(n,_) <- take 1 g
return (n,map snd g)
f' = foldl' updatef f gs
hs = do
h <- groupBy (equivBy snd) $ sortBy (comparing snd) obs
(_,a) <- take 1 h
return (a,map fst h)
r' = foldl' updater r hs
writeTVar (fcache dns) f'
writeTVar (rcache dns) r'
where
updatef f (n,addrs) = Map.alter (updateCache withScrub utc addrs) n f
updater r (a,ns) = Map.alter (updateCache withScrub utc ns) a r
make6mapped4 addr@(SockAddrInet6 {}) = addr
make6mapped4 addr@(SockAddrInet port a) = SockAddrInet6 port 0 (0,0,0xFFFF,fromBE32 a) 0
rawForwardResolve dns fail timeout addrtext = do
r <- atomically newEmptyTMVar
mvar <- atomically newEmptyTMVar
rt <- forkOS $ resolver r mvar
tt <- forkIO $ timer (fail addrtext) timeout r rt
atomically $ putTMVar mvar tt
atomically $ readTMVar r
where
resolver r mvar = do
xs <- handle (\e -> let _ = isDoesNotExistError e in return [])
$ do fmap (nub . map (make6mapped4 . addrAddress)) $
getAddrInfo (Just $ defaultHints { addrFlags = [ AI_CANONNAME, AI_V4MAPPED ]})
(Just $ Text.unpack $ strip_brackets addrtext)
(Just "5269")
did <- atomically $ tryPutTMVar r xs
when did $ do
tt <- atomically $ readTMVar mvar
throwTo tt (ErrorCall "Interrupted delay")
utc <- getCurrentTime
atomically $ dnsObserve dns True utc $ map (addrtext,) xs
return ()
strip_brackets s =
case Text.uncons s of
Just ('[',t) -> Text.takeWhile (/=']') t
_ -> s
reportTimeout addrtext = do
putStrLn $ "timeout resolving: "++show addrtext
-- killThread rt
timer fail timeout r rt = do
handle (\(ErrorCall _)-> return ()) $ do
threadDelay timeout
did <- atomically $ tryPutTMVar r []
when did fail
unmap6mapped4 addr@(SockAddrInet6 port _ (0,0,0xFFFF,a) _) =
SockAddrInet port (toBE32 a)
unmap6mapped4 addr = addr
rawReverseResolve dns fail timeout addr = do
r <- atomically newEmptyTMVar
mvar <- atomically newEmptyTMVar
rt <- forkOS $ resolver r mvar
tt <- forkIO $ timer (fail addr) timeout r rt
atomically $ putTMVar mvar tt
atomically $ readTMVar r
where
resolver r mvar =
handleIO_ (return ()) $ do
ent <- getHostByAddr (unmap6mapped4 addr) -- AF_UNSPEC addr
let names = BSD.hostName ent : BSD.hostAliases ent
xs = map Text.pack $ nub names
forkIO $ do
utc <- getCurrentTime
atomically $ dnsObserve dns False utc $ map (,addr) xs
atomically $ putTMVar r xs
expiredReverse dns addr = do
utc <- getCurrentTime
es <- atomically $ do
r <- readTVar $ rcache dns
let ns = maybe [] id $ Map.lookup addr r
minute = 60 -- seconds
(es0,ns') = partition ( (>=minute) . flip diffUTCTime utc . fst ) ns
es = map snd es0
modifyTVar' (rcache dns) $ Map.insert addr ns'
f <- readTVar $ fcache dns
let f' = foldl' (flip $ Map.alter (expire utc)) f es
expire utc Nothing = Nothing
expire utc (Just as) = if null as' then Nothing else Just as'
where as' = filter ( (<minute) . flip diffUTCTime utc . fst) as
writeTVar (fcache dns) f'
return es
return es
cachedReverse dns addr = do
utc <- getCurrentTime
atomically $ do
r <- readTVar (rcache dns)
let ns = maybe [] id $ Map.lookup addr r
{-
ns' = filter ( (<minute) . flip diffUTCTime utc . fst) ns
minute = 60 -- seconds
modifyTVar' (rcache dns) $ Map.insert addr ns'
return $ map snd ns'
-}
return $ map snd ns
cachedForward dns n = do
utc <- getCurrentTime
atomically $ do
f <- readTVar (fcache dns)
let as = maybe [] id $ Map.lookup n f
as' = filter ( (<minute) . flip diffUTCTime utc . fst) as
minute = 60 -- seconds
modifyTVar' (fcache dns) $ Map.insert n as'
return $ map snd as'
reverseResolve dns addr = do
expired <- expiredReverse dns addr
forM_ expired $ \n -> forkIO $ do
rawForwardResolve dns (const $ return ()) 1000000 n
return ()
xs <- rawReverseResolve dns (const $ return ()) 1000000 addr
cs <- cachedReverse dns addr
return $ xs ++ filter (not . flip elem xs) cs
forwardResolve dns n = do
as <- rawForwardResolve dns (const $ return ()) 1000000 n
if null as
then cachedForward dns n
else return as
|
