X-Git-Url: https://git.rkrishnan.org/?a=blobdiff_plain;f=src%2FFuncTorrent%2FPeer.hs;h=4396c1c004bd5364c9a75deecb34b862d3c10dc7;hb=d80bf91010f9f2f8653c55bb902ec83bf1f034a2;hp=c833c061bd4285be88f3754e62e5b83774c1d806;hpb=08f3238a8162039a1b77f4fb8825a56a34203c02;p=functorrent.git diff --git a/src/FuncTorrent/Peer.hs b/src/FuncTorrent/Peer.hs index c833c06..4396c1c 100644 --- a/src/FuncTorrent/Peer.hs +++ b/src/FuncTorrent/Peer.hs @@ -20,20 +20,21 @@ {-# LANGUAGE OverloadedStrings #-} module FuncTorrent.Peer - (PieceMap, - handlePeerMsgs + (handlePeerMsgs ) where import Prelude hiding (lookup, concat, replicate, splitAt, take, drop) +import Control.Concurrent.MVar (MVar, readMVar, putMVar, takeMVar) import Control.Monad.State -import Data.ByteString (ByteString, unpack, concat, hGet, hPut, take, drop, empty) +import Data.ByteString (ByteString, unpack, concat, hGet, hPut, take, drop, empty, singleton) import Data.Bits import Data.Word (Word8) -import Data.Map ((!), adjust) +import Data.Map (Map, (!), adjust, fromList, insert) import Network (connectTo, PortID(..)) import System.IO (Handle, BufferMode(..), hSetBuffering, hClose) +import FuncTorrent.Bencode(BVal(..), encode, decode, decodeWithLeftOvers) import FuncTorrent.Metainfo (Metainfo(..)) import FuncTorrent.PeerMsgs (Peer(..), PeerMsg(..), sendMsg, getMsg, genHandshakeMsg) import FuncTorrent.Utils (splitNum, verifyHash) @@ -47,6 +48,11 @@ data PState = PState { handle :: Handle , heChoking :: Bool , heInterested :: Bool} +data InfoPieceMap = InfoPieceMap { infoLength :: Integer + , infoMap :: Map Integer (Maybe ByteString) } + +newtype InfoState = InfoState (MVar InfoPieceMap) + havePiece :: PieceMap -> Integer -> Bool havePiece pm index = dlstate (pm ! index) == Have @@ -57,18 +63,25 @@ connectToPeer (Peer ip port) = do hSetBuffering h LineBuffering return h + doHandshake :: Bool -> Handle -> Peer -> ByteString -> String -> IO () doHandshake True h p infohash peerid = do let hs = genHandshakeMsg infohash peerid hPut h hs putStrLn $ "--> handhake to peer: " ++ show p - _ <- hGet h (length (unpack hs)) + hsMsg <- hGet h (length (unpack hs)) putStrLn $ "<-- handshake from peer: " ++ show p return () + -- if doesPeerSupportExtendedMsg hsMsg + -- then + -- return doExtendedHandshake h + -- else + -- return Nothing doHandshake False h p infohash peerid = do let hs = genHandshakeMsg infohash peerid putStrLn "waiting for a handshake" - hsMsg <- hGet h (length (unpack hs)) + -- read 28 bytes. '19' ++ 'BitTorrent Protocol' ++ 8 reserved bytes + hsMsg <- hGet h 28 putStrLn $ "<-- handshake from peer: " ++ show p let rxInfoHash = take 20 $ drop 28 hsMsg if rxInfoHash /= infohash @@ -79,7 +92,12 @@ doHandshake False h p infohash peerid = do else do _ <- hPut h hs putStrLn $ "--> handhake to peer: " ++ show p - return () + -- if doesPeerSupportExtendedMsg hsMsg + -- then do + -- doExtendedHandshake h + -- else + -- return Nothing + bitfieldToList :: [Word8] -> [Integer] bitfieldToList bs = go bs 0 @@ -200,3 +218,135 @@ downloadPiece h index pieceLength = do putStrLn $ "ignoring irrelevant msg: " ++ show msg return empty) + +{- + -- Extension messages support (BEP-0010) -- + + + In the regular peer handshake, adventise support for extension protocol. Protocol + extensions are done via the reserved bytes (8 of them) in the handshake message + as detailed in BEP-0003. For this particular "Extension Protocol" extension, we use + 20th bit (counted from the right, from 0) is set to 1. + + Once support for the extension protocol is established by the peer, the Peer is supposed + to support one message with the ID 20. This is sent like a regular message with 4-byte + length prefix and the msg id (20) in this case. + + First byte of the payload of this message is either 0, which means it is a handshake + msg. + + The rest of the payload is a dictionary with various keys. All of them are optional. The + one of interest at the moment for me is the one with key 'm' whose value is another + dictionary of all supported extensions. + + Here is where it gets interesting for us (to support magneturi. When the torrent client + has only got a magneturi to look at, it has only got the list of trackers with it (we + are not looking at the DHT case for the time being). So, it somehow needs to get the info + dictionary. It gets this by talking to another peer in the network. To do that, the client + needs to talk tracker protocol, get the list of peers and talk to peers using the above + extension protocol to get the infodict as payload. Let us see how we can do that now. + + If a peer already has the full infodict, then, the handshake message sent by that peer + is something like this: + + {'m': {'ut_metadata', 3}, 'metadata_size': 31235} + + Note that the 'metadata_size' is not part of the value of the key 'm'. + If we are a new client and are requesting the handshake to a peer, then we don't have + the infodict yet, in which case, we only send the first part: + + {'m': {'ut_metadata', 3}} + + This is bencoded and sent across the wire. The value "3" (integer) against the key + 'ut_metadata" is an ordered integer within a client that identifies the extention. + No two extension supported by the same client shares the same value. If the value is + '0', then the extension is unsupported. + + Here we use the BEP-0009, the metadata extension protocol. The metadata in this case + is the infodict. The infodict itself is divided into 16KB sized pieces. + + Here is a possible interaction between two peers: + + 1. Peer Pn comes up, gets the ip/ports of other peers, P0, P1.... Pn does not have the + size of the infodict. Pn has advertised itself as supporting the extension protocol. + It sends the handshake msg to other peers with this bit on in the reserved bytes. + 2. Let us say, P1 replied with a handshake. We check if it also supports the extension + mechanism. + 3. Now we get into the extension message passing so that we have the info dict. + To do that, we send the extension handshake (ut_metadata) m dict without the + metadata_size. We get back the extension handshake with metadata_size. We take + note of the size. + 4. We calculate the number of 16384 chunks in the total size of the metadata. That + gives us the number of pieces the metadata has. + 5. We send a "request" extension msg: + {'msg_type': 0, 'piece': 0} + 6. We recieve the "data" message. + {'msg_type': 1, 'piece': 0, 'total_size': 3425} in bencoded format, followed by + total_size bytes. total_size is 16KiB except perhaps for the last piece. + 7. If the peer does not have the requested piece, it sends the "reject" message. + {'msg_type': 2, 'piece': 0} + 8. Repeat 5, 6/7 for every piece. + + At this point, we have the infodict. + +-} + +{- +data InfoPieceMap = { infoLength :: Integer + , infoMap :: Map Integer (Maybe ByteString) + } + +newtype InfoState = InfoState (MVar InfoPieceMap) + +-} + + +metadataMsgLoop :: Handle -> InfoState -> IO () +metadataMsgLoop h (InfoState st) = do + infoState <- readMVar st + let metadataLen = infoLength infoState + -- send the handshake msg + metadata = encode (metadataMsg metadataLen) + sendMsg h (ExtendedMsg 0 metadata) + -- recv return msg from the peer. Will have 'metadata_size' + msg <- getMsg h + case msg of + ExtendedMsg 0 rBs -> do + -- decode rBs + let (Right (Bdict msgMap)) = decode rBs + (Bdict mVal) = msgMap ! "m" -- which is another dict + (Bint metadata_msgID) = mVal ! "ut_metadata" + (Bint metadata_size) = msgMap ! "metadata_size" + -- divide metadata_size into 16384 sized pieces, find number of pieces + (q, r) = metadata_size `divMod` 16384 + -- pNumLengthPairs = zip [0..q-1] (take q (repeat 16384)) ++ (q, r) + -- TODO: corner case where infodict size is a multiple of 16384 + -- and start sending request msg for each. + if metadataLen == 0 + then -- We don't have any piece. Send request msg for all pieces. + mapM_ (\n -> do + sendMsg h (ExtendedMsg metadata_msgID (encode (requestMsg n))) + dataOrRejectMsg <- getMsg h + case dataOrRejectMsg of + ExtendedMsg 3 payload -> do + -- bencoded dict followed by XXXXXX + infoState <- takeMVar st + let (Right (Bdict bval, pieceData)) = decodeWithLeftOvers payload + (Bint pieceIndex) = bval ! "piece" + payloadLen = length (unpack pieceData) + infoMapVal = infoMap infoState + putMVar st infoState { + infoMap = insert pieceIndex (Just payload) infoMapVal } + ) + [0..q] + else + return () -- TODO: reject for now + where + metadataMsg 0 = Bdict (fromList [("m", Bdict (fromList [("ut_metadata", (Bint 3))]))]) + metadataMsg l = Bdict (fromList [("m", Bdict (fromList [("ut_metadata", (Bint 3))])), + ("metadata_size", (Bint l))]) + requestMsg i = Bdict (fromList [("msg_type", (Bint 0)), ("piece", (Bint i))]) + rejectmsg i = Bdict (fromList [("msg_type", (Bint 2)), ("piece", (Bint i))]) + +doesPeerSupportExtendedMsg :: ByteString -> Bool +doesPeerSupportExtendedMsg bs = take 1 (drop 5 bs) == singleton 0x10