Combinatorrent-0.3.2: src/Process/Tracker.hs
-- | The TrackerP module is responsible for keeping in touch with the Tracker of a torrent.
-- The tracker is contacted periodically, and we exchange information with it. Specifically,
-- we tell the tracker how much we have downloaded, uploaded and what is left. We also
-- tell it about our current state (i.e., are we a seeder or a leecher?).
--
-- The tracker responds to us with a new set of Peers and general information about the
-- torrent in question. It may also respond with an error in which case we should present
-- it to the user.
--
module Process.Tracker
( start
)
where
import Control.Applicative
import Control.Concurrent
import Control.Concurrent.STM
import Control.Monad.Reader
import Control.Monad.State
import Data.Bits
import Data.Char (ord, chr)
import Data.List (intersperse)
import qualified Data.ByteString as B
import Data.Word
import Network.Socket as S
import Network.HTTP hiding (port)
import Network.URI hiding (unreserved)
import Numeric (showHex)
import Protocol.BCode as BCode hiding (encode)
import Process
import Channels
import Supervisor
import Torrent
import qualified Process.Status as Status
import qualified Process.PeerMgr as PeerMgr
import qualified Process.Timer as Timer
-- | The tracker state is used to tell the tracker our current state. In order
-- to output it correctly, we override the default show instance with the
-- version below. This may be wrong to do in the long run, but for now it works
-- fine.
--
-- The state is either started or stopped upon the client starting. The
-- tracker will create an entry for us if we tell it that we started, and it
-- will tear down this entry if we tell it that we stopped. It will know if
-- we are a seeder or a leecher based on how much data is left for us to
-- download.
--
-- the 'Completed' entry is used once in the lifetime of a torrent. It
-- explains to the tracker that we completed the torrent in question.
data TrackerEvent = Started | Stopped | Completed | Running
deriving Eq
-- | The tracker will in general respond with a BCoded dictionary. In our world, this is
-- not the data structure we would like to work with. Hence, we parse the structure into
-- the ADT below.
data TrackerResponse = ResponseOk { newPeers :: [PeerMgr.Peer],
completeR :: Maybe Integer,
incompleteR :: Maybe Integer,
timeoutInterval :: Integer,
timeoutMinInterval :: Maybe Integer }
| ResponseDecodeError B.ByteString
| ResponseWarning B.ByteString
| ResponseError B.ByteString
-- | If we fail to contact the tracker, we will wait for 15 minutes. The number is quite arbitrarily chosen
failTimerInterval :: Integer
failTimerInterval = 15 * 60
-- | Configuration of the tracker process
data CF = CF {
statusPCh :: Status.StatusChannel
, trackerMsgCh :: TrackerChannel
, peerMgrCh :: PeerMgr.PeerMgrChannel
, cfInfoHash :: InfoHash
}
instance Logging CF where
logName _ = "Process.Tracker"
-- | Internal state of the tracker CHP process
data ST = ST {
torrentInfo :: TorrentInfo
, peerId :: PeerId
, state :: TrackerEvent
, localPort :: Word16
, nextTick :: Integer
}
start :: InfoHash -> TorrentInfo -> PeerId -> Word16
-> Status.StatusChannel -> TrackerChannel -> PeerMgr.PeerMgrChannel
-> SupervisorChannel -> IO ThreadId
start ih ti pid port statusC msgC pc supC =
spawnP (CF statusC msgC pc ih) (ST ti pid Stopped port 0)
({-# SCC "Tracker" #-} cleanupP loop
(defaultStopHandler supC)
stopEvent)
where
stopEvent :: Process CF ST ()
stopEvent = do
debugP "Stopping... telling tracker"
modify (\s -> s { state = Stopped }) >> talkTracker
loop :: Process CF ST ()
loop = do
ch <- asks trackerMsgCh
msg <- liftIO . atomically $ readTChan ch
debugP $ "Got tracker event"
case msg of
TrackerTick x ->
do t <- gets nextTick
when (x+1 == t) talkTracker
Stop ->
modify (\s -> s { state = Stopped }) >> talkTracker
Start ->
modify (\s -> s { state = Started }) >> talkTracker
Complete ->
modify (\s -> s { state = Completed }) >> talkTracker
loop
talkTracker = pokeTracker >>= timerUpdate
eventTransition :: Process CF ST ()
eventTransition = do
st <- gets state
modify (\s -> s { state = newS st})
where newS st =
case st of
Running -> Running
Stopped -> Stopped
Completed -> Running
Started -> Running
-- | Poke the tracker. It returns the new timer intervals to use
pokeTracker :: Process CF ST (Integer, Maybe Integer)
pokeTracker = do
v <- liftIO $ newEmptyTMVarIO
ih <- asks cfInfoHash
asks statusPCh >>= (\ch -> liftIO . atomically $ writeTChan ch (Status.RequestStatus ih v))
upDownLeft <- liftIO . atomically $ takeTMVar v
url <- buildRequestURL upDownLeft
debugP $ "Request URL: " ++ url
uri <- case parseURI url of
Nothing -> fail $ "Could not parse the url " ++ url
Just u -> return u
resp <- trackerRequest uri
case resp of
Left err -> do infoP $ "Tracker HTTP Error: " ++ err
return (failTimerInterval, Just failTimerInterval)
Right (ResponseWarning wrn) ->
do infoP $ "Tracker Warning Response: " ++ fromBS wrn
return (failTimerInterval, Just failTimerInterval)
Right (ResponseError err) ->
do infoP $ "Tracker Error Response: " ++ fromBS err
return (failTimerInterval, Just failTimerInterval)
Right (ResponseDecodeError err) ->
do infoP $ "Response Decode error: " ++ fromBS err
return (failTimerInterval, Just failTimerInterval)
Right bc -> do
c <- asks peerMgrCh
liftIO . atomically $ writeTChan c (PeerMgr.PeersFromTracker ih $ newPeers bc)
let trackerStats = Status.TrackerStat
{ Status.trackInfoHash = ih
, Status.trackComplete = completeR bc
, Status.trackIncomplete = incompleteR bc }
asks statusPCh >>= \ch -> liftIO . atomically $ writeTChan ch trackerStats
eventTransition
return (timeoutInterval bc, timeoutMinInterval bc)
timerUpdate :: (Integer, Maybe Integer) -> Process CF ST ()
timerUpdate (timeout, _minTimeout) = do
st <- gets state
when (st == Running)
(do t <- tick
ch <- asks trackerMsgCh
_ <- Timer.registerSTM (fromIntegral timeout) ch (TrackerTick t)
debugP $ "Set timer to: " ++ show timeout)
where tick = do t <- gets nextTick
modify (\s -> s { nextTick = t + 1 })
return t
-- Process a result dict into a tracker response object.
processResultDict :: BCode -> TrackerResponse
processResultDict d =
case BCode.trackerError d of
Just err -> ResponseError err
Nothing -> case BCode.trackerWarning d of
Just warn -> ResponseWarning warn
Nothing -> case decodeOk of
Nothing -> ResponseDecodeError . toBS $ "Could not decode response properly"
Just rok -> rok
where decodeOk =
ResponseOk <$> (decodeIps <$> BCode.trackerPeers d)
<*> (pure $ BCode.trackerComplete d)
<*> (pure $ BCode.trackerIncomplete d)
<*> (BCode.trackerInterval d)
<*> (pure $ BCode.trackerMinInterval d)
decodeIps :: (B.ByteString, B.ByteString) -> [PeerMgr.Peer]
decodeIps (ipv4, ipv6) = decodeIps4 ipv4 ++ decodeIps6 ipv6
decodeIps4 :: B.ByteString -> [PeerMgr.Peer]
decodeIps4 bs | B.null bs = []
| B.length bs >= 6 =
let (ip, r1) = B.splitAt 4 bs
(port, r2) = B.splitAt 2 r1
i' = cW32 ip
p' = PortNum $ cW16 port
in PeerMgr.Peer (S.SockAddrInet p' i') : decodeIps4 r2
| otherwise = [] -- Some trackers fail spectacularly
decodeIps6 :: B.ByteString -> [PeerMgr.Peer]
decodeIps6 bs | B.null bs = []
| B.length bs >= 18 =
let (ip6, r1) = B.splitAt 16 bs
(port, r2) = B.splitAt 2 r1
i' = cW128 ip6
p' = PortNum $ cW16 port
in PeerMgr.Peer (S.SockAddrInet6 p' 0 i' 0) : decodeIps6 r2
| otherwise = [] -- Some trackers fail spectacularly
cW32 :: B.ByteString -> Word32
cW32 bs = fromIntegral . sum $ s
where up = B.unpack bs
s = [ fromIntegral b `shiftL` sa | (b, sa) <- zip up [0,8,16,24]] :: [Word32]
cW16 :: B.ByteString -> Word16
cW16 bs = fromIntegral . sum $ s
where s = [ fromIntegral b `shiftL` sa | (b, sa) <- zip (B.unpack bs) [0,8]] :: [Word16]
cW128 :: B.ByteString -> (Word32, Word32, Word32, Word32)
cW128 bs =
let (q1, r1) = B.splitAt 4 bs
(q2, r2) = B.splitAt 4 r1
(q3, q4) = B.splitAt 4 r2
in (cW32 q1, cW32 q2, cW32 q3, cW32 q4)
trackerRequest :: URI -> Process CF ST (Either String TrackerResponse)
trackerRequest uri =
do resp <- liftIO $ simpleHTTP request
case resp of
Left x -> return $ Left ("Error connecting: " ++ show x)
Right r ->
case rspCode r of
(2,_,_) ->
case BCode.decode . toBS . rspBody $ r of
Left pe -> return $ Left (show pe)
Right bc -> do debugP $ "Response: " ++ BCode.prettyPrint bc
return $ Right $ processResultDict bc
(3,_,_) ->
case findHeader HdrLocation r of
Nothing -> return $ Left (show r)
Just newURL -> case parseURI newURL of
Nothing -> return $ Left (show newURL)
Just u -> trackerRequest u
_ -> return $ Left (show r)
where request = Request {rqURI = uri,
rqMethod = GET,
rqHeaders = [],
rqBody = ""}
-- Construct a new request URL. Perhaps this ought to be done with the HTTP client library
buildRequestURL :: Status.StatusState -> Process CF ST String
buildRequestURL ss = do ti <- gets torrentInfo
hdrs <- headers
let hl = concat $ hlist hdrs
return $ concat [fromBS $ announceURL ti, "?", hl]
where hlist x = intersperse "&" $ map (\(k,v) -> k ++ "=" ++ v) x
headers = do
s <- get
p <- prt
return $ [("info_hash", rfc1738Encode $
map (chr . fromIntegral) . B.unpack . infoHash . torrentInfo $ s),
("peer_id", rfc1738Encode $ peerId s),
("uploaded", show $ Status.uploaded ss),
("downloaded", show $ Status.downloaded ss),
("left", show $ Status.left ss),
("port", show p),
("compact", "1")] ++
(trackerfyEvent $ state s)
prt :: Process CF ST Integer
prt = do lp <- gets localPort
return $! fromIntegral lp
trackerfyEvent ev =
case ev of
Running -> []
Completed -> [("event", "completed")]
Started -> [("event", "started")]
Stopped -> [("event", "stopped")]
-- Carry out URL-encoding of a string. Note that the clients seems to do it the wrong way
-- so we explicitly code it up here in the same wrong way, jlouis.
rfc1738Encode :: String -> String
rfc1738Encode = concatMap (\c -> if unreserved c then [c] else encode c)
where unreserved = (`elem` chars)
-- I killed ~ from this list as the Mainline client doesn't announce it - jlouis
chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_./"
encode :: Char -> String
encode c = '%' : pHex c
pHex c =
let p = (showHex . ord $ c) ""
in if length p == 1 then '0' : p else p