/// <summary>
/// Parses the chunks from a serialised SCTP packet.
/// </summary>
/// <param name="buffer">The buffer holding the serialised packet.</param>
/// <param name="offset">The position in the buffer of the packet.</param>
/// <param name="length">The length of the serialised packet in the buffer.</param>
/// <returns>The lsit of parsed chunks and a list of unrecognised chunks that were not de-serialised.</returns>
private static (List <SctpChunk> chunks, List <byte[]> unrecognisedChunks) ParseChunks(byte[] buffer, int offset, int length)
{
List <SctpChunk> chunks = new List <SctpChunk>();
List <byte[]> unrecognisedChunks = new List <byte[]>();
int posn = offset + SctpHeader.SCTP_HEADER_LENGTH;
bool stop = false;
while (posn < length)
{
byte chunkType = buffer[posn];
if (Enum.IsDefined(typeof(SctpChunkType), chunkType))
{
var chunk = SctpChunk.Parse(buffer, posn);
chunks.Add(chunk);
}
else
{
switch (SctpChunk.GetUnrecognisedChunkAction(chunkType))
{
case SctpUnrecognisedChunkActions.Stop:
stop = true;
break;
case SctpUnrecognisedChunkActions.StopAndReport:
stop = true;
unrecognisedChunks.Add(SctpChunk.CopyUnrecognisedChunk(buffer, posn));
break;
case SctpUnrecognisedChunkActions.Skip:
break;
case SctpUnrecognisedChunkActions.SkipAndReport:
unrecognisedChunks.Add(SctpChunk.CopyUnrecognisedChunk(buffer, posn));
break;
}
}
if (stop)
{
logger.LogWarning($"SCTP unrecognised chunk type {chunkType} indicated no further chunks should be processed.");
break;
}
posn += (int)SctpChunk.GetChunkLengthFromHeader(buffer, posn, true);
}
return(chunks, unrecognisedChunks);
}
/// <summary>
/// Copies an unrecognised chunk to a byte buffer and returns it. This method is
/// used to assist in reporting unrecognised chunk types.
/// </summary>
/// <param name="buffer">The buffer containing the chunk.</param>
/// <param name="posn">The position in the buffer that the unrecognised chunk starts.</param>
/// <returns>A new buffer containing a copy of the chunk.</returns>
public static byte[] CopyUnrecognisedChunk(byte[] buffer, int posn)
{
byte[] unrecognised = new byte[SctpChunk.GetChunkLengthFromHeader(buffer, posn, true)];
Buffer.BlockCopy(buffer, posn, unrecognised, 0, unrecognised.Length);
return(unrecognised);
}
