// Creates a human-readable formatting of the bencoded data.
public static string ToHuman(byte[] data)
{
var value = Bencoding.Decode(data);
var result = new StringBuilder();
toHuman(value, result, 0, 2);
return(result.ToString());
}
public static void SaveMetadata(byte[] bytes)
{
var info = Bencoding.DecodeDict(bytes);
var name = info.GetBytes("name");
var metainfo = Bencoding.Dict();
metainfo.Set("info", info);
var torrentFileData = Bencoding.Encode(metainfo);
string[] pathStrings = { Directory.GetCurrentDirectory(), "..", "..", "our-state", "metadata", name.FromUTF8() + ".torrent" };
var path = Path.Combine(pathStrings);
// if the file already exists, completely overwrite it.
using (var stream = File.Create(path))
{
stream.Write(torrentFileData, 0, torrentFileData.Length);
}
}
// For messages with msgType 0 (request) and 2 (reject)
private static byte[] ConstructMessage(int ourExtCode, int msgType, int piece)
{
var messageDict = new Dictionary <byte[], object>();
messageDict.Set("msg_type", msgType);
messageDict.Set("piece", piece);
var encodedMsg = Bencoding.Encode(messageDict);
var length = (encodedMsg.Length + 2).EncodeBytes();
var message = new byte[encodedMsg.Length + 6];
length.CopyTo(message, 0);
message[4] = 20;
message[5] = (byte)ourExtCode;
encodedMsg.CopyTo(message, 6);
return(message);
}
// ourExtCode refers to the value we have associated with ut_metadata
// theirExtCode refers to the value they have associated with ut_metadata
public byte[] GetMetadata(NetworkStream stream, TcpClient connection, byte ourExtCode, byte theirExtCode, byte[] infohash)
{
if (!connection.Connected)
{
throw new Exception("Disconnected from peer after handshake.");
}
var currentPiece = 0;
var info = new VerifiedBytes(infohash, (Int32)metadataLength, CommonPieceSizes.BEP9_METADATA);
using (logger.BeginScope($"Metadata request for {infohash.ToHex()} from {connection.Client.RemoteEndPoint}"))
{
// Request the first piece.
var initialRequest = ConstructRequestMessage(ourExtCode, 0);
logger.LogInformation(LoggingEvents.METADATA_REQUEST, "Sending request for first metadata piece: " + initialRequest.ToHuman());
stream.Write(initialRequest);
while (true)
{
Int32 theirLength = 0;
// Read lengths until we get a non-zero (non-keepalive) length.
while (theirLength == 0)
{
var theirPrefix = stream.ReadBytes(4);
theirLength = theirPrefix.Decode32BitInteger();
if (theirLength == 0)
{
logger.LogInformation(LoggingEvents.PEER_PROTOCOL_MSG, "Got keepalive. Let's send our own!");
stream.Write(new byte[4]);
}
}
logger.LogInformation(LoggingEvents.PEER_PROTOCOL_MSG, $"Got message with length {theirLength}.");
var peerResponse = stream.ReadBytes(theirLength);
var responseTypeId = peerResponse[0];
switch (responseTypeId)
{
case 20:
logger.LogInformation(LoggingEvents.EXTENSION_MESSAGE, "It's an extension message! Hurrah!");
var extensionId = peerResponse[1];
if (extensionId == theirExtCode)
{
logger.LogInformation(LoggingEvents.METADATA_RESPONSE_INCOMING, "It's a metadata exchange message!");
var data = peerResponse.Slice(2);
var dict = Bencoding.DecodeFirstDict(data, out Int64 dictSize);
var postDict = data.Slice((Int32)dictSize); // This is the metadata itself -- a bencoded dictionary of utf8 strings
if (dict.GetInt("piece") != currentPiece)
{
throw new Exception($"Expected piece {currentPiece}. Instead, received {dict.GetInt("piece")}");
}
logger.LogInformation(
LoggingEvents.METADATA_RESPONSE_INCOMING,
$"Got BEP-9 {Bencoding.ToHuman(Bencoding.Encode(dict))} followed by {postDict.Length} bytes of data.\nStoring...");
info.ProvidePiece(currentPiece, postDict);
currentPiece++;
if (currentPiece == info.PieceCount)
{
byte[] combinedPieces;
try {
combinedPieces = info.Result.Result;
} catch (BytesVerificationException ex) {
logger.LogWarning(LoggingEvents.METADATA_FAILURE, "metadata verification failed!", ex);
throw new MetadataException("Metadata verification failed -- try another peer.");
}
logger.LogInformation(LoggingEvents.DATA_STORAGE_ACTION, "metadata verified! saving...");
DataHandler.SaveMetadata(combinedPieces);
logger.LogInformation(LoggingEvents.DATA_STORAGE_ACTION, "metadata saved.");
return(combinedPieces);
}
var request = ConstructRequestMessage(ourExtCode, currentPiece);
logger.LogInformation(LoggingEvents.METADATA_REQUEST, "Requesting the next piece of metadata...");
stream.Write(request);
}
else
{
logger.LogWarning(LoggingEvents.PEER_UNEXPECTED_RESPONSE, $"It's an unexpected message type, ID {extensionId}.");
}
break;
case 0:
logger.LogInformation(LoggingEvents.PEER_PROTOCOL_MSG, "It's a choke message! :(");
break;
case 1:
logger.LogInformation(LoggingEvents.PEER_PROTOCOL_MSG, "It's an unchoke message! :D");
break;
case 2:
logger.LogInformation(LoggingEvents.PEER_PROTOCOL_MSG, "It's an interested message! <3");
break;
case 4:
logger.LogInformation(LoggingEvents.PEER_PROTOCOL_MSG, "It's a not interested message! </3");
break;
default:
logger.LogWarning(LoggingEvents.PEER_UNEXPECTED_RESPONSE, $"Unexpected message type {responseTypeId}; ignoring.");
break;
}
}
}
}
