/// <summary>
/// Gets an SCTP packet for a control (non-data) chunk.
/// </summary>
/// <param name="chunk">The control chunk to get a packet for.</param>
/// <returns>A single control chunk SCTP packet.</returns>
public SctpPacket GetControlPacket(SctpChunk chunk)
{
SctpPacket pkt = new SctpPacket(
_sctpSourcePort,
_sctpDestinationPort,
_remoteVerificationTag);
pkt.AddChunk(chunk);
return(pkt);
}
/// <summary>
/// Sends a SCTP chunk to the remote party.
/// </summary>
/// <param name="chunk">The chunk to send.</param>
internal void SendChunk(SctpChunk chunk)
{
if (!_wasAborted)
{
SctpPacket pkt = new SctpPacket(
_sctpSourcePort,
_sctpDestinationPort,
_remoteVerificationTag);
pkt.AddChunk(chunk);
byte[] buffer = pkt.GetBytes();
_sctpTransport.Send(ID, buffer, 0, buffer.Length);
}
}
/// <summary>
/// Creates the INIT ACK chunk and packet to send as a response to an SCTP
/// packet containing an INIT chunk.
/// </summary>
/// <param name="initPacket">The received packet containing the INIT chunk.</param>
/// <param name="remoteEP">Optional. The remote IP end point the INIT packet was
/// received on. For transports that don't use an IP transport directly this parameter
/// can be set to null and it will not form part of the COOKIE ECHO checks.</param>
/// <returns>An SCTP packet with a single INIT ACK chunk.</returns>
protected SctpPacket GetInitAck(SctpPacket initPacket, IPEndPoint remoteEP)
{
SctpInitChunk initChunk = initPacket.Chunks.Single(x => x.KnownType == SctpChunkType.INIT) as SctpInitChunk;
SctpPacket initAckPacket = new SctpPacket(
initPacket.Header.DestinationPort,
initPacket.Header.SourcePort,
initChunk.InitiateTag);
var cookie = GetInitAckCookie(
initPacket.Header.DestinationPort,
initPacket.Header.SourcePort,
initChunk.InitiateTag,
initChunk.InitialTSN,
initChunk.ARwnd,
remoteEP != null ? remoteEP.ToString() : string.Empty,
(int)(initChunk.CookiePreservative / 1000));
var json = cookie.ToJson();
var jsonBuffer = Encoding.UTF8.GetBytes(json);
using (HMACSHA256 hmac = new HMACSHA256(_hmacKey))
{
var result = hmac.ComputeHash(jsonBuffer);
cookie.HMAC = result.HexStr();
}
var jsonWithHMAC = cookie.ToJson();
var jsonBufferWithHMAC = Encoding.UTF8.GetBytes(jsonWithHMAC);
SctpInitChunk initAckChunk = new SctpInitChunk(
SctpChunkType.INIT_ACK,
cookie.Tag,
cookie.TSN,
cookie.ARwnd,
SctpAssociation.DEFAULT_NUMBER_OUTBOUND_STREAMS,
SctpAssociation.DEFAULT_NUMBER_INBOUND_STREAMS);
initAckChunk.StateCookie = jsonBufferWithHMAC;
initAckChunk.UnrecognizedPeerParameters = initChunk.UnrecognizedPeerParameters;
initAckPacket.AddChunk(initAckChunk);
return(initAckPacket);
}
/// <summary>
/// Send an SCTP packet with one of the error type chunks (ABORT or ERROR) to the remote peer.
/// </summary>
/// <param name=isAbort">Set to true to use an ABORT chunk otherwise an ERROR chunk will be used.</param>
/// <param name="desintationPort">The SCTP destination port.</param>
/// <param name="sourcePort">The SCTP source port.</param>
/// <param name="initiateTag">If available the initial tag for the remote peer.</param>
/// <param name="error">The error to send.</param>
private void SendError(
bool isAbort,
ushort destinationPort,
ushort sourcePort,
uint initiateTag,
ISctpErrorCause error)
{
SctpPacket errorPacket = new SctpPacket(
destinationPort,
sourcePort,
initiateTag);
SctpErrorChunk errorChunk = isAbort ? new SctpAbortChunk(true) : new SctpErrorChunk();
errorChunk.AddErrorCause(error);
errorPacket.AddChunk(errorChunk);
var buffer = errorPacket.GetBytes();
Send(null, buffer, 0, buffer.Length);
}
/// <summary>
/// Attempts to create an association with a remote party by sending an initialisation
/// control chunk.
/// </summary>
private void SendInit()
{
if (!_wasAborted)
{
// A packet containing an INIT chunk MUST have a zero Verification Tag (RFC4960 Pg 15).
SctpPacket init = new SctpPacket(_sctpSourcePort, _sctpDestinationPort, 0);
SctpInitChunk initChunk = new SctpInitChunk(
SctpChunkType.INIT,
VerificationTag,
TSN,
ARwnd,
_numberOutboundStreams,
_numberInboundStreams);
init.AddChunk(initChunk);
SetState(SctpAssociationState.CookieWait);
byte[] buffer = init.GetBytes();
_sctpTransport.Send(ID, buffer, 0, buffer.Length);
_t1Init = new Timer(T1InitTimerExpired, init, T1_INIT_TIMER_MILLISECONDS, T1_INIT_TIMER_MILLISECONDS);
}
}
