path: root/dht/OnionRouter.hs

{-# LANGUAGE LambdaCase               #-}
{-# LANGUAGE NondecreasingIndentation #-}
{-# LANGUAGE RankNTypes               #-}
module OnionRouter where

import Control.Concurrent.ThreadUtil
import Crypto.Tox
import Network.Address
import Network.Kademlia
import Network.Kademlia.Bootstrap
import Network.Kademlia.Routing as R
import Network.Kademlia.Search
import Network.QueryResponse
import Network.QueryResponse.TCP
import Network.Tox.NodeId
import Network.Tox.Onion.Transport as Onion
import qualified Data.Tox.Relay as TCP
import qualified Network.Tox.TCP as TCP
import qualified TCPProber as TCP

import Control.Arrow
import Control.Concurrent.STM
import Control.Concurrent.STM.TArray
import Control.Monad
import Crypto.Random
import Data.Array.MArray
import Data.Bits
import Data.Bool
import Data.List
import qualified Data.ByteString     as B
import Data.Functor.Identity
import Data.Hashable
import qualified Data.HashMap.Strict as HashMap
         ;import Data.HashMap.Strict (HashMap)
import qualified Data.IntMap         as IntMap
         ;import Data.IntMap         (IntMap)
import Data.Maybe
import Data.Ord
import qualified Data.Serialize      as S
import Data.Time.Clock.POSIX
import Data.Typeable
import Data.Word
import qualified Data.Word64Map      as W64
         ;import Data.Word64Map      (Word64Map, fitsInInt)
import Network.Socket
import System.Endian
import System.Timeout

-- Toxcore saves a maximum of 12 paths: 6 paths are reserved for announcing
-- ourselves and 6 others are used to search for friends.
--
-- Note: This is pointless because a man-in-the-middle attack currently makes
-- it trivial to glean friend relationships: the storing node can swap the
-- published to-route key with his own giving him access to one layer of
-- encryption and thus the real public key of the sender. TODO:
-- Counter-measures.
--
-- Unlike toxcore, we don't currently reserve paths for only-searching or
-- only-announcing.  Instead, we maintain 12 multi-purpose routes.
data OnionRouter = OnionRouter
    { -- | For every query, we remember the destination and source keys
      -- so we can decrypt the response.
      pendingQueries  :: TVar (Word64Map PendingQuery)
      -- | The current 12 routes that may be assigned to outgoing packets.
    , routeMap        :: TArray Int (Maybe RouteRecord)
      -- | A set of nodes used to query for random route nodes. These aren't
      -- used directly in onion routes, they are queried for route nodes that
      -- are nearby randomly selected ids.
    , trampolinesUDP :: TrampolineSet NodeInfo
      -- | A set for TCP relays to use as trampolines when UDP is not available.
    , trampolinesTCP :: TrampolineSet TCP.NodeInfo
      -- | True when we need to rely on TCP relays because UDP is apparently unavailable.
    , tcpMode :: TVar Bool
      -- | The pseudo-random generator used to select onion routes.
    , onionDRG        :: TVar ChaChaDRG
      -- | Building onion routes happens in a dedicated thread. See 'forkRouteBuilder'.
    , routeThread     :: ThreadId
      -- | Each of the 12 routes has a version number here that is set larger
      -- than the 'routeVersion' set in 'routeMap' when the route should be
      -- discarded and replaced with a fresh one.
    , pendingRoutes   :: TArray Int Int
      -- | Parameters used to implement Kademlia for TCP relays.
    , tcpKademliaClient :: TCP.TCPClient String Nonce8
      -- | This thread maintains the TCP relay table.
    , tcpKademliaThread :: ThreadId
    , tcpProberState :: TCPCache (SessionProtocol TCP.RelayPacket TCP.RelayPacket)
    , tcpProber :: TCP.TCPProber
    , tcpProberThread :: ThreadId
      -- | Kademlia table of TCP relays.
    , tcpBucketRefresher :: BucketRefresher NodeId TCP.NodeInfo
      -- | Debug prints are written to this channel which is then flushed to
      -- 'routeLogger'.
    , routeLog        :: TChan String
      -- | User supplied log function.
    , routeLogger     :: String -> IO ()
    }

data PendingQuery = PendingQuery
    { pendingVersion     :: !Int -- ^ Remembered version number so timeouts can signal a rebuild.
    , pendingDestination :: OnionDestination RouteId
    }
 deriving Show

data RouteRecord = RouteRecord
    { storedRoute    :: OnionRoute
    , responseCount  :: !Int
    , timeoutCount   :: !Int
    , routeVersion   :: !Int
    , routeBirthTime :: !POSIXTime
    }
 deriving Show

-- Onion paths have different timeouts depending on whether the path is
-- confirmed or unconfirmed. Unconfirmed paths (paths that core has never
-- received any responses from) have a timeout of 4 seconds with 2 tries before
-- they are deemed non working. This is because, due to network conditions,
-- there may be a large number of newly created paths that do not work and so
-- trying them a lot would make finding a working path take much longer. The
-- timeout for a confirmed path (from which a response was received) is 12
-- seconds with 4 tries without a response. A confirmed path has a maximum
-- lifetime of 1200 seconds to make possible deanonimization attacks more
-- difficult.
timeoutForRoute :: RouteRecord -> Int
timeoutForRoute RouteRecord{ responseCount = 0 } = 4000000
timeoutForRoute RouteRecord{ responseCount = _ } = 12000000

freshRoute :: POSIXTime -> OnionRoute -> Maybe RouteRecord -> Maybe RouteRecord
freshRoute birthday r mrec = Just $ RouteRecord
    { storedRoute    = r
    , responseCount  = 0
    , timeoutCount   = 0
    , routeVersion   = maybe 0 succ $ routeVersion <$> mrec
    , routeBirthTime = birthday
    }

modifyArray :: TArray Int r -> (r -> r) -> Int -> STM ()
modifyArray a f i = do
    mx <- readArray a i
    writeArray a i $ f mx
{-# INLINE modifyArray #-}

gotResponse :: RouteRecord -> RouteRecord
gotResponse rr = rr
    { responseCount = succ $ responseCount rr
    , timeoutCount = 0
    }

gotTimeout :: RouteRecord -> RouteRecord
gotTimeout rr = rr
    { timeoutCount = succ $ timeoutCount rr
    }

newtype RouteEvent = BuildRoute RouteId

newOnionRouter :: TransportCrypto
                    -> (String -> IO ())
                    -> IO ( OnionRouter
                          , TVar ( ChaChaDRG
                                 , Word64Map (Either (Maybe (Bool,TCP.RelayPacket) -> IO ())
                                                     (Maybe (OnionMessage Identity) -> IO ()))))
newOnionRouter crypto perror = do
    drg0 <- drgNew
    (rlog,pq,rm) <- atomically $ do
        rlog <- newTChan
        pq <- newTVar W64.empty
        rm <- newArray (0,11) Nothing
        return (rlog,pq,rm)
    ((tbl,(tcptbl,tcpcons)),tcp) <- do
        (tcptbl, client) <- TCP.newClient crypto Left $ \case
            Left v  -> void . v . Just . (,) False
            Right v -> \case
                TCP.OnionPacketResponse x@(OnionAnnounceResponse n8 n24 _) -> do
                    mod <- lookupSender' pq rlog localhost4 n8
                    perror $ "TCP announce response from " ++ show mod
                    forM_ mod $ \od -> do
                        Onion.decrypt crypto x od >>= \case
                            Right (y,_) -> do perror $ "decrypted announce response, sending " ++ show y
                                              let
                                                RouteId rid = fromMaybe (routeId (nodeId (onionNodeInfo od)))
                                                                $ onionRouteSpec od
                                                Nonce8 w8 = n8
                                              atomically $ do
                                                modifyTVar' pq (W64.delete w8)
                                                modifyArray rm (fmap gotResponse) rid
                                              void $ v $ Just y
                            _           -> return ()
                x -> perror $ "Unexpected TCP query result: " ++ show x

        let addr = SockAddrInet 0 0
            tentative_udp = NodeInfo
                { nodeId   = key2id $ transportPublic crypto
                , nodeIP   = fromMaybe (toEnum 0) (fromSockAddr addr)
                , nodePort = fromMaybe 0 $ sockAddrPort addr
                }
            tentative_info = TCP.NodeInfo tentative_udp (fromIntegral 443)
        tbl <- atomically $ newTVar
                          $ R.nullTable (comparing TCP.nodeId)
                                        (\s -> hashWithSalt s . TCP.nodeId)
                                        tentative_info
                                        R.defaultBucketCount
        return $ (,) (tbl,tcptbl) TCP.TCPClient
            { tcpCrypto     = crypto
            , tcpClient     = client
            , tcpGetGateway = \ni -> do
                gw <- selectGateway tbl ni
                writeTChan rlog $ unwords ["Selected TCP Gateway:",show ni,"via",show gw]
                return gw
            }
    or <- atomically $ do
        -- chan <- newTChan
        drg <- newTVar drg0
        -- forM_ [0..11] $ \n -> writeTChan chan $ BuildRoute (RouteId n)
        tn <- newTVar IntMap.empty
        ti <- newTVar HashMap.empty
        tc <- newTVar 0
        ttn <- newTVar IntMap.empty
        tti <- newTVar HashMap.empty
        ttc <- newTVar 0
        pr <- newArray (0,11) 0
        prober <- TCP.newProber
        refresher <- newBucketRefresher
                            tbl
                            (TCP.nodeSearch prober tcp)
                            (fmap (maybe False $ const True) . TCP.tcpPing (TCP.tcpClient tcp))
        tcpmode <- newTVar True
        let o = OnionRouter
                { pendingRoutes  = pr
                , onionDRG       = drg
                , pendingQueries = pq
                , routeMap       = rm
                , trampolinesUDP = TrampolineSet
                    { setNodes     = tn
                    , setCount     = tc
                    , setNodeClass = nodeClass
                    , setIDs       = ti
                    }
                , trampolinesTCP = TrampolineSet
                    { setNodes     = ttn
                    , setCount     = ttc
                    , setNodeClass = nodeClass . TCP.udpNodeInfo
                    , setIDs       = tti
                    }
                , tcpMode = tcpmode
                , tcpKademliaClient = tcp
                    { TCP.tcpClient =
                        let c = TCP.tcpClient tcp
                        in c { clientNet = addHandler perror (handleMessage c)
                                            $ onInbound (updateTCP o)
                                            $ clientNet c }
                    }
                , tcpBucketRefresher = refresher
                , routeLog           = rlog
                , routeThread        = error "forkRouteBuilder not invoked (missing onion route builder thread)."
                , tcpKademliaThread  = error "forkRouteBuilder not invoked (missing TCP bucket maintenance thread)."
                , tcpProberState     = tcpcons
                , tcpProber          = prober
                , tcpProberThread    = error "forkRouteBuilder not invoked (missing TCP probe thread)."
                , routeLogger        = perror
                }
        return o
    return (or,tcptbl)

updateTCP :: OnionRouter -> TCP.NodeInfo -> p -> IO ()
updateTCP or addr x =
    let refresher = tcpBucketRefresher or
        kademlia0 = refreshKademlia refresher
        kademlia = kademlia0 { kademIO = (kademIO kademlia0)
                                { tblTransition = \tr -> do
                                    case refresher of
                                        BucketRefresher { refreshSearch = sch } -> do
                                            let spc = searchSpace sch
                                                bkts = refreshBuckets refresher
                                            hookBucketList spc bkts or (trampolinesTCP or) tr
                                    tblTransition (kademIO kademlia0) tr
                                }
                             }
    in insertNode kademlia addr

selectGateway :: TVar (R.BucketList TCP.NodeInfo) -> NodeInfo -> STM (Maybe TCP.NodeInfo)
selectGateway tbl ni = do
    ns <- kclosest TCP.tcpSpace 2 (nodeId ni) <$> readTVar tbl
    return $ listToMaybe ns -- $ dropWhile (\n -> TCP.nodeId n == nodeId ni) ns

quitRouteBuilder :: OnionRouter -> IO ()
quitRouteBuilder or = do
    killThread (routeThread or)
    killThread (tcpKademliaThread or)
    killThread (tcpProberThread or)

forkRouteBuilder :: OnionRouter -> (NodeId -> NodeInfo -> IO (Maybe [NodeInfo])) -> IO OnionRouter
forkRouteBuilder or getnodes = do
    bktsThread <- forkPollForRefresh $ tcpBucketRefresher or
    tcpprobe <- forkIO $ TCP.runProbeQueue (tcpProber or)
                                           (TCP.tcpClient $ tcpKademliaClient or)
                                           12
    labelThread tcpprobe "tcp-probe"
    tid <- forkIO $ do
        me <- myThreadId
        labelThread me "OnionRouter"
        forever $ do
            let checkRebuild :: Int -> Int -> STM RouteEvent
                checkRebuild rid wanted_ver = do
                    current_ver <- fmap routeVersion <$> readArray (routeMap or) rid
                    writeTChan (routeLog or) $ "ONION checkRebuild "++show(current_ver,wanted_ver)
                    check $ maybe True (< wanted_ver) current_ver
                    return $ BuildRoute $ RouteId rid
            io <- atomically $ {-# SCC "forkRouteBuilder.log" #-}
                   (readTChan (routeLog or) >>= return . routeLogger or)
                `orElse` {-# SCC "forkRouteBuilder.checkRebuild" #-}
                   (let stms = map (\rid -> checkRebuild rid =<< readArray (pendingRoutes or) rid)
                                   [0..11]
                        in do event <- foldr1 orElse stms
                              return $ handleEvent getnodes or { routeThread = me } event)
            io
    return or { routeThread       = tid
              , tcpKademliaThread = bktsThread
              , tcpProberThread   = tcpprobe }

generateNodeId :: MonadRandom m => m NodeId
generateNodeId = either (error "unable to make random nodeid")
                        id
                 . S.decode <$> getRandomBytes 32

distinct3by :: Eq t => (a -> t) -> a -> a -> a -> Bool
distinct3by f a b c = f a /= f b && f b /= f c && f c /= f a

-- The two integer functions below take an [inclusive,inclusive] range.
randomR :: (DRG g, Integral a) => (a, a) -> g -> (a, g)
randomR (l,h) = randomIvalInteger (toInteger l, toInteger h)

next :: DRG g => g -> (Int,g)
next g = withDRG g $ do bs <- getRandomBytes $ if fitsInInt (Proxy :: Proxy Word64)
                                                then 8
                                                else 4
                        either (return . error) return $ S.decode bs

randomIvalInteger :: (DRG g, Num a) => (Integer, Integer) -> g -> (a, g)
randomIvalInteger (l,h) rng
 | l > h     = randomIvalInteger (h,l) rng
 | otherwise = case (f 1 0 rng) of (v, rng') -> (fromInteger (l + v `mod` k), rng')
     where
       (genlo, genhi) = (minBound :: Int, maxBound :: Int) -- genRange :: RandomGen g => g -> (Int, Int)
       b = fromIntegral genhi - fromIntegral genlo + 1

       -- Probabilities of the most likely and least likely result
       -- will differ at most by a factor of (1 +- 1/q).  Assuming the RandomGen
       -- is uniform, of course

       -- On average, log q / log b more random values will be generated
       -- than the minimum
       q = 1000
       k = h - l + 1
       magtgt = k * q

       -- generate random values until we exceed the target magnitude
       f mag v g | mag >= magtgt = (v, g)
                 | otherwise = v' `seq`f (mag*b) v' g' where
                        (x,g') = next g -- next :: RandomGen g => g -> (Int, g)
                        v' = (v * b + (fromIntegral x - fromIntegral genlo))

-- Repeatedly attempt to select 3 nodes as a secure onion route letting 1 second
-- elapse between retries.
--
-- Only the DRG random seed is updated.  Hopefully another thread will change the
-- trampolineNodes set so that selection can succeed.
selectTrampolines :: OnionRouter -> IO (Either [TCP.NodeInfo] [NodeInfo])
selectTrampolines or = do
    myThreadId >>= flip labelThread ("OnionRouter.selectTrampolines")
    let tset :: (forall x. TrampolineSet x -> STM (Either [x] [x]))
                -> STM (Either (Either [TCP.NodeInfo] [NodeInfo])
                               (Either [TCP.NodeInfo] [NodeInfo]))
        tset f = bool (left Right . right Right <$> f (trampolinesUDP or))
                      (left Left  . right Left  <$> f (trampolinesTCP or))
                      =<< readTVar (tcpMode or)
    atomically (tset $ internalSelectTrampolines (onionDRG or)) >>= \case
        Left ns -> do
            -- atomically $ writeTChan (routeLog or)
            routeLogger or $ unwords
                ( "ONION Discarding insecure trampolines:" : (either (map show) (map show) ns))
            myThreadId >>= flip labelThread ("OnionRouter.selectTrampolines.sleep")
            case ns of
                Left  [_,_,_] -> threadDelay 1000000 -- (tcp) wait 1 second if we failed the distinct3by predicate.
                Right [_,_,_] -> threadDelay 1000000 -- (udp) wait 1 second if we failed the distinct3by predicate.
                _             -> threadDelay 5000000 -- wait 5 seconds if insufficient nodes.
            myThreadId >>= flip labelThread ("OnionRouter.selectTrampolines")
            selectTrampolines or
        Right ns -> do
            myThreadId >>= flip labelThread ("OnionRouter")
            return ns

data TrampolineSet ni = TrampolineSet
    { -- | A set of nodes used to query for random route nodes. These aren't
      -- used directly in onion routes, they are queried for route nodes that
      -- are nearby randomly selected ids.
      --
      -- These nodes are chosen from the kademlia buckets and when one of them
      -- is evicted from a bucket, it is no longer used as a trampoline node.
      setNodes     :: TVar (IntMap ni)
      -- | Indicates the current size of 'setNodes'.
    , setCount     :: TVar Int
      -- | In order to reduce the likelihood that an attacker will control all
      -- nodes in a route, we color the nodes with 'IPClass' and require
      -- distinct colors for each of the hops.
    , setNodeClass :: ni -> IPClass
      -- | This map associates 'NodeId' values with the corresponding
      -- 'trampolineNodes' index.
    , setIDs       :: TVar (HashMap NodeId Int)
    }

choose3 :: (Integral a, DRG drg) => drg -> a -> ([a], drg)
choose3 drg0 cnt = ([a,b,c], drg)
 where
        (a, drg1) = randomR (0,cnt - 1) drg0
        (b0, drg2) = randomR (0,cnt - 2) drg1
        (c0, drg ) = randomR (0,cnt - 3) drg2
        b | b0 < a    = b0
          | otherwise = b0 + 1
        [ac,bc] = sort [a,b]
        c1 | c0 < ac    = c0
           | otherwise  = c0 + 1
        c | c1 < bc   = c1
          | otherwise = c1 + 1

-- Select 3 indices into the trampolineNodes set and returns the associated
-- nodes provided they are suitable for use in an onion route.  Otherwise, it
-- returns Left with the nodes that were selected.
--
-- The only write this function does to STM state is that the onionDRG random
-- seed will be updated.
internalSelectTrampolines :: TVar ChaChaDRG -> TrampolineSet ni -> STM (Either [ni] [ni])
internalSelectTrampolines setDRG TrampolineSet{..} = do
    cnt <- readTVar setCount
    ts <- readTVar setNodes
    drg0 <- readTVar setDRG
    let ([a,b,c],drg) = choose3 drg0 cnt
        ns = mapMaybe (\n -> IntMap.lookup n ts) [a,b,c]
    ns' <- case ns of
            [an,bn,cn] | distinct3by setNodeClass an bn cn
                       -> return $ Right ns
            _          -> return $ Left ns
    writeTVar setDRG drg
    return ns'

handleEvent :: (NodeId -> NodeInfo -> IO (Maybe [NodeInfo])) -> OnionRouter -> RouteEvent -> IO ()
handleEvent getnodes or e@(BuildRoute (RouteId rid)) = do
    routeLogger or $ "ONION Rebuilding RouteId " ++ show rid
    mb <- do
        mts <- selectTrampolines or
        join . atomically $ do
        drg <- readTVar (onionDRG or)
        av <- newTVar Nothing
        bv <- newTVar Nothing
        cv <- newTVar Nothing
        let (getr, drg') = withDRG drg $ do
                asec <- generateSecretKey -- Three aliases
                bsec <- generateSecretKey
                csec <- generateSecretKey
                aq <- generateNodeId -- Three queries
                bq <- generateNodeId
                cq <- generateNodeId
                sel <- B.head <$> getRandomBytes 1 -- Three two-bit result selectors (6 bits)
                let asel = sel .&. 0x3
                    bsel = shiftR sel 2 .&. 0x3
                    csel = shiftR sel 4 .&. 0x3
                    cycle' [] = []
                    cycle' ns = cycle ns
                    sendq :: Word8 -> NodeId -> Int -> IO (Maybe NodeInfo)
                    sendq s q ni
                        | Right ts <- mts = (>>= (listToMaybe . drop (fromIntegral s) . cycle')) <$> getnodes q (ts !! ni)
                        | Left  ts <- mts = case ni of
                            0 -> return $ Just $ TCP.udpNodeInfo (ts !! 0)
                            n -> (>>= (listToMaybe . drop (fromIntegral s) . (\(ns,_,_)->cycle' ns)))
                                   <$> TCP.getUDPNodes (tcpKademliaClient or) q (TCP.udpNodeInfo $ ts !! n)
                    sendqs = do
                        forkLabeled "sendq.asel" $ sendq asel aq 0 >>= atomically . writeTVar av . Just
                        forkLabeled "sendq.bsel" $ sendq bsel bq 1 >>= atomically . writeTVar bv . Just
                        forkLabeled "sendq.csel" $ sendq csel cq 2 >>= atomically . writeTVar cv . Just
                        -- This timeout should be unnecessary... But I'm paranoid.
                        -- Note: 10 seconds should be sufficient for typical get-nodes queries.
                        tm <- timeout 30000000 $ atomically $ do -- Wait for all 3 results.
                            rs <- catMaybes <$> sequence [readTVar av,readTVar bv,readTVar cv]
                            case rs of [_,_,_] -> do
                                                    return $ catMaybes $ rs
                                                    -- self <- IntMap.lookup (-1) <$> readTVar (trampolineNodes or)
                                                    -- return $ maybe (catMaybes rs) (\x -> [x,x,x]) self
                                       _       -> retry
                        maybe (routeLogger or "ONION: Unexpected sendq timeout!" >> return [])
                              return
                              tm
                return $ do
                    myThreadId >>= flip labelThread ("OnionRouter.sendqs")
                    let mtcpport = either (Just . TCP.tcpPort . head) (const Nothing) mts
                    nodes <- case mts of
                        Right [_,_,_] -> sendqs
                        Left  [_,_,_] -> sendqs
                        _             -> return []
                    myThreadId >>= flip labelThread ("OnionRouter")
                    routeLogger or $ unlines
                        [ "ONION trampolines:   " ++ show mts
                        , "ONION query results: " ++ show nodes ]
                    case nodes of
                        [a,b,c] | distinct3by nodeClass a b c -> do
                            atomically $ do
                              writeTChan (routeLog or) $ unwords [ "ONION using route:"
                                                                 , show $ nodeAddr a
                                                                 , show $ nodeAddr b
                                                                 , show $ nodeAddr c ]
                            return $ Just OnionRoute
                                { routeAliasA = asec
                                , routeAliasB = bsec
                                , routeAliasC = csec
                                , routeNodeA = a
                                , routeNodeB = b
                                , routeNodeC = c
                                , routeRelayPort = mtcpport
                                }
                        [a,b,c] -> do
                            atomically $ writeTChan (routeLog or)
                                       $ unwords [ "ONION Discarding insecure route:"
                                                 , show $ nodeAddr a
                                                 , show $ nodeAddr b
                                                 , show $ nodeAddr c
                                                 ]
                            return Nothing
                        _ -> return Nothing
        writeTVar (onionDRG or) drg'
        return $ getr
    now <- getPOSIXTime
    atomically $ maybe (return ()) -- writeTVar (pendingRoutes or IntMap.! rid) True)
                       (\r -> do modifyArray (routeMap or)
                                             (freshRoute now r)
                                             rid
                                 v <- routeVersion . fromJust <$> readArray (routeMap or) rid
                                 writeArray (pendingRoutes or) rid v
                                 )
                       (mb :: Maybe OnionRoute)
    case mb of
        Just _  -> routeLogger or $ "ONION Finished RouteId " ++ show rid
        Nothing -> routeLogger or $ "ONION Failed RouteId " ++ show rid


lookupSender :: OnionRouter -> SockAddr -> Nonce8 -> IO (Maybe (OnionDestination RouteId))
lookupSender or = lookupSender' (pendingQueries or) (routeLog or)

lookupSender' :: TVar (Word64Map PendingQuery)
                       -> TChan String
                       -> SockAddr
                       -> Nonce8
                       -> IO (Maybe (OnionDestination RouteId))
lookupSender' pending log saddr (Nonce8 w8) = do
    result <- atomically $ do
        ks <- readTVar pending
        let r = W64.lookup w8 ks
        writeTChan log $ "ONION lookupSender " ++ unwords [show w8, "->", show r]
        return r
    return $ do
        od <- result
        let nid = nodeId $ onionNodeInfo $ pendingDestination od
        ni <- either (const Nothing) Just $ nodeInfo nid saddr
        Just (OnionDestination (onionAliasSelector $ pendingDestination od)
                               ni
                               (Just $ routeId nid))

lookupRoute :: OnionRouter -> NodeInfo -> RouteId -> IO (Maybe OnionRoute)
lookupRoute or ni (RouteId rid) = do
    mb <- atomically $ readArray (routeMap or) rid
    return $ storedRoute <$> mb

lookupTimeout :: OnionRouter -> Nonce8 -> OnionDestination r -> STM (OnionDestination RouteId, Int)
lookupTimeout or n8 (OnionDestination asel ni Nothing) = do
    let RouteId rid = routeId (nodeId ni)
    mrr <- readArray (routeMap or) rid
    writeTChan (routeLog or) $ unwords ["ONION lookupTimeout " ,show rid]
    case mrr of
        Just rr -> return ( OnionDestination asel ni (Just $ RouteId rid), timeoutForRoute rr)
        Nothing -> return ( OnionDestination asel ni Nothing             , 0 )

hookQueries :: OnionRouter -> (tid -> Nonce8)
                           -> TransactionMethods d tid (OnionDestination RouteId) x
                           -> TransactionMethods d tid (OnionDestination RouteId) x
hookQueries or t8 tmethods = TransactionMethods
    { dispatchRegister = \getTimeout now mvar od d -> {-# SCC "hookQ.dispatchRegister" #-} do --  :: MVar x -> d -> STM (tid, d)
        let ni = onionNodeInfo od
            rid@(RouteId ridn) = fromMaybe (routeId (nodeId ni)) $ onionRouteSpec od
        wanted <- {-# SCC "hookQ.wanted" #-} (readArray (pendingRoutes or) ridn)
        mr <- {-# SCC "hookQ.mr_action" #-} (readArray (routeMap or) ridn)
        -- Block query until a route is ready.
        check $ fromMaybe False $ do
            RouteRecord{routeVersion=rv} <- {-# SCC "hookQ.mr" #-} mr
            return $ wanted <= rv
        ((tid,a,expiry),d') <- dispatchRegister tmethods getTimeout now mvar od d
        let Nonce8 w8 = t8 tid
            od' = case od of
                OnionDestination {} -> od { onionRouteSpec = Just rid }
                OnionToOwner a b    -> OnionToOwner a b -- Type cast.
        let pq = PendingQuery { pendingDestination = od'
                              , pendingVersion = maybe 0 routeVersion mr
                              }
        pqs <- readTVar (pendingQueries or)
        -- check $ W64.size pqs < 20
        modifyTVar' (pendingQueries or) (W64.insert w8 pq)
        writeTChan (routeLog or) $ "ONION query add " ++ unwords [ show (Just $ pendingVersion pq,w8), ":=", show ni ]
        return ((tid,a,expiry),d')
    , dispatchResponse = \tid x d -> {-# SCC "hookQ.dispatchResponse" #-} do -- :: tid -> x -> d -> STM (d, IO ())
        let Nonce8 w8 = t8 tid
        mb <- W64.lookup w8 <$> readTVar (pendingQueries or)
        modifyTVar' (pendingQueries or) (W64.delete w8)
        forM_ mb $ \pq -> do
            let od = pendingDestination pq
                RouteId rid = fromMaybe (routeId (nodeId (onionNodeInfo od)))
                                $ onionRouteSpec od
            modifyArray (routeMap or) (fmap gotResponse) rid
        writeTChan (routeLog or) $ "ONION query del " ++ show (fmap pendingVersion mb, w8)
        dispatchResponse tmethods tid x d
    , dispatchCancel = \tid d -> {-# SCC "hookQ.dispatchCancel" #-} do -- :: tid -> d -> STM d
        let Nonce8 w8 = t8 tid
        mb <- W64.lookup w8 <$> readTVar (pendingQueries or)
        modifyTVar' (pendingQueries or) (W64.delete w8)
        forM_ mb $ \pq -> do
            let od = pendingDestination pq
                RouteId rid = fromMaybe (routeId (nodeId (onionNodeInfo od)))
                                $ onionRouteSpec od
            mrr <- readArray (routeMap or) rid
            forM_ mrr $ \rr -> do
            when (routeVersion rr == pendingVersion pq) $ do
            let expireRoute = modifyArray (pendingRoutes or) expire rid
                expire ver | ver <= succ (pendingVersion pq) = succ (pendingVersion pq)
                           | otherwise                       = ver
            modifyArray (routeMap or) (fmap gotTimeout) rid
            case rr of
                RouteRecord{ responseCount = 0
                           , timeoutCount  = c
                           , routeVersion = v } | c >= 5 -> expireRoute
                RouteRecord{ responseCount = 1
                           , timeoutCount = c
                           , routeVersion = v } | c >= 10 -> expireRoute
                RouteRecord{ timeoutCount = c
                           , routeVersion = v } | c >= 20 -> expireRoute
                _ -> return ()
        writeTChan (routeLog or) $ "ONION query can " ++ show (fmap pendingVersion mb, w8)
        dispatchCancel tmethods tid d
    }


-- hookBucketList :: KademliaSpace NodeId NodeInfo -> TVar (BucketList NodeInfo) ->  OnionRouter -> RoutingTransition NodeInfo -> STM ()
hookBucketList :: Show ni =>
                        KademliaSpace NodeId ni
                        -> TVar (BucketList ni)
                        -> OnionRouter
                        -> TrampolineSet ni
                        -> RoutingTransition ni
                        -> STM ()
hookBucketList kademlia bkts0 or TrampolineSet{..} (RoutingTransition ni Accepted) = do
    (s,antibias) <- do
        drg0 <- readTVar (onionDRG or)
        bkts <- readTVar bkts0
        let antibias = 2 ^ bucketNumber kademlia (kademliaLocation kademlia ni) bkts
            (s,drg)  = randomR (0,antibias - 1) drg0
        writeTVar (onionDRG or) drg
        {-
        do -- Store localhost as trampoline node (-1).
           -- This is potentionally useful for testing.
           let self = (thisNode bkts) { nodeIP = read "127.0.0.1" }
           modifyTVar' setNodes (IntMap.insert (-1) self)
        -}
        return (s::Int,antibias)
    -- debias via stochastic filter
    when (s == 0) $ do
    ns <- readTVar setIDs -- (trampolineIds or)
    case HashMap.lookup (kademliaLocation kademlia ni) ns of
        Just _ -> return ()
        Nothing -> do
            cnt <- readTVar setCount
            writeTChan (routeLog or) $ "ONION trampoline Accepted " ++ unwords ["s="++show (s,antibias),show cnt, show ni]
            modifyTVar' setIDs (HashMap.insert (kademliaLocation kademlia ni) cnt)
            modifyTVar' setNodes (IntMap.insert cnt ni)
            writeTVar setCount (succ cnt)
hookBucketList kademlia _ or TrampolineSet{..} (RoutingTransition ni Stranger) = do
    ns <- readTVar setIDs
    case HashMap.lookup (kademliaLocation kademlia ni) ns of
        Just n -> do writeTVar setIDs (HashMap.delete (kademliaLocation kademlia ni) ns)
                     cnt <- pred <$> readTVar setCount
                     writeTVar setCount cnt
                     case compare n cnt of
                        EQ -> modifyTVar' setNodes (IntMap.delete n)
                        LT -> do lastnode <- (IntMap.! cnt) <$> readTVar setNodes
                                 modifyTVar' setNodes
                                             (IntMap.insert n lastnode . IntMap.delete cnt)
                                 modifyTVar' setIDs
                                             (HashMap.delete (kademliaLocation kademlia ni)
                                                              . HashMap.insert (kademliaLocation kademlia lastnode) n)
                        GT -> writeTChan (routeLog or) $ "BUG!! Trampoline maps are out of sync."
                     writeTChan (routeLog or) $ "ONION trampoline Stranger " ++ unwords [show n,show ni]
        Nothing -> return ()
hookBucketList _ _ _ _ _ = return () -- ignore Applicant event.

newtype IPClass = IPClass Word32
 deriving Eq

ipkey :: IPClass -> Int
ipkey (IPClass k) = fromIntegral k

nodeClass :: NodeInfo -> IPClass
nodeClass = ipClass . nodeAddr

ipClass :: SockAddr -> IPClass
ipClass= either ipClass' ipClass' . either4or6

ipClass' :: SockAddr -> IPClass
ipClass' (SockAddrInet _ addr)                = IPClass (fromBE32 addr .&. 0xFF000000)
ipClass' (SockAddrInet6 _ _ (hiword,_,_,_) _) = IPClass hiword
ipClass' _                                    = IPClass 0 -- unreachable.