/// <summary>
/// Parses the SHUTDOWN chunk fields.
/// </summary>
/// <param name="buffer">The buffer holding the serialised chunk.</param>
/// <param name="posn">The position to start parsing at.</param>
public static SctpShutdownChunk ParseChunk(byte[] buffer, int posn)
{
var shutdownChunk = new SctpShutdownChunk();
shutdownChunk.CumulativeTsnAck = NetConvert.ParseUInt32(buffer, posn + SCTP_CHUNK_HEADER_LENGTH);
return(shutdownChunk);
}
/// <summary>
/// Parses an SCTP chunk from a buffer.
/// </summary>
/// <param name="buffer">The buffer holding the serialised chunk.</param>
/// <param name="posn">The position to start parsing at.</param>
/// <returns>An SCTP chunk instance.</returns>
public static SctpChunk Parse(byte[] buffer, int posn)
{
if (buffer.Length < posn + SCTP_CHUNK_HEADER_LENGTH)
{
throw new ApplicationException("Buffer did not contain the minimum of bytes for an SCTP chunk.");
}
byte chunkType = buffer[posn];
if (Enum.IsDefined(typeof(SctpChunkType), chunkType))
{
switch ((SctpChunkType)chunkType)
{
case SctpChunkType.ABORT:
return(SctpAbortChunk.ParseChunk(buffer, posn, true));
case SctpChunkType.DATA:
return(SctpDataChunk.ParseChunk(buffer, posn));
case SctpChunkType.ERROR:
return(SctpErrorChunk.ParseChunk(buffer, posn, false));
case SctpChunkType.SACK:
return(SctpSackChunk.ParseChunk(buffer, posn));
case SctpChunkType.COOKIE_ACK:
case SctpChunkType.COOKIE_ECHO:
case SctpChunkType.HEARTBEAT:
case SctpChunkType.HEARTBEAT_ACK:
case SctpChunkType.SHUTDOWN_ACK:
case SctpChunkType.SHUTDOWN_COMPLETE:
return(ParseBaseChunk(buffer, posn));
case SctpChunkType.INIT:
case SctpChunkType.INIT_ACK:
return(SctpInitChunk.ParseChunk(buffer, posn));
case SctpChunkType.SHUTDOWN:
return(SctpShutdownChunk.ParseChunk(buffer, posn));
default:
logger.LogDebug($"TODO: Implement parsing logic for well known chunk type {(SctpChunkType)chunkType}.");
return(ParseBaseChunk(buffer, posn));
}
}
// Shouldn't reach this point. The SCTP packet parsing logic checks if the chunk is
// recognised before attempting to parse it.
throw new ApplicationException($"SCTP chunk type of {chunkType} was not recognised.");
}
/// <summary>
/// Initiates the shutdown of the association by sending a shutdown
/// control chunk to the remote party.
/// </summary>
public void Shutdown()
{
if (!_wasAborted)
{
SetState(SctpAssociationState.ShutdownPending);
// TODO: Check outstanding data chunks.
// If no DATA chunks have been received use the initial TSN - 1 from
// the remote party. Seems weird to use the - 1, and couldn't find anything
// in the RFC that says to do it, but that's what usrsctp accepts.
uint?ackTSN = _dataReceiver.CumulativeAckTSN ?? _remoteInitialTSN - 1;
logger.LogTrace($"SCTP sending shutdown for association {ID}, ACK TSN {ackTSN}.");
SetState(SctpAssociationState.ShutdownSent);
SctpShutdownChunk shutdownChunk = new SctpShutdownChunk(ackTSN);
SendChunk(shutdownChunk);
_dataSender.Close();
}
}
