/// <summary>
/// Requests a new association be created.
/// </summary>
/// <param name="destination">The UDP endpoint to attempt to create the association with.</param>
/// <param name="sourcePort">The SCTP source port.</param>
/// <param name="destinationPort">The SCTP destination port.</param>
/// <returns>An SCTP association.</returns>
public SctpAssociation Associate(
IPEndPoint destination,
ushort sourcePort,
ushort destinationPort,
ushort numberOutboundStreams = SctpAssociation.DEFAULT_NUMBER_OUTBOUND_STREAMS,
ushort numberInboundStreams = SctpAssociation.DEFAULT_NUMBER_INBOUND_STREAMS)
{
var association = new SctpAssociation(
this,
destination,
sourcePort,
destinationPort,
DEFAULT_UDP_MTU,
numberOutboundStreams,
numberInboundStreams);
if (_associations.TryAdd(association.ID, association))
{
association.Init();
return(association);
}
else
{
logger.LogWarning("SCTP transport failed to add association.");
association.Shutdown();
return(null);
}
}
/// <summary>
/// Event handler for a packet receive on the UDP encapsulation socket.
/// </summary>
/// <param name="receiver">The UDP receiver that received the packet.</param>
/// <param name="localPort">The local port the packet was received on.</param>
/// <param name="remoteEndPoint">The remote end point the packet was received from.</param>
/// <param name="packet">A buffer containing the packet.</param>
private void OnEncapsulationSocketPacketReceived(UdpReceiver receiver, int localPort, IPEndPoint remoteEndPoint, byte[] packet)
{
try
{
if (!SctpPacket.VerifyChecksum(packet, 0, packet.Length))
{
logger.LogWarning($"SCTP packet from UDP {remoteEndPoint} dropped due to invalid checksum.");
}
else
{
var sctpPacket = SctpPacket.Parse(packet, 0, packet.Length);
// Process packet.
if (sctpPacket.Header.VerificationTag == 0)
{
GotInit(sctpPacket, remoteEndPoint);
}
else if (sctpPacket.Chunks.Any(x => x.KnownType == SctpChunkType.COOKIE_ECHO))
{
// The COOKIE ECHO chunk is the 3rd step in the SCTP handshake when the remote party has
// requested a new association be created.
var cookie = base.GetCookie(sctpPacket);
if (cookie.IsEmpty())
{
logger.LogWarning($"SCTP error acquiring handshake cookie from COOKIE ECHO chunk.");
}
else
{
logger.LogDebug($"SCTP creating new association for {remoteEndPoint}.");
var association = new SctpAssociation(this, cookie, localPort);
if (_associations.TryAdd(association.ID, association))
{
if (sctpPacket.Chunks.Count > 1)
{
// There could be DATA chunks after the COOKIE ECHO chunk.
association.OnPacketReceived(sctpPacket);
}
}
else
{
logger.LogError($"SCTP failed to add new association to dictionary.");
}
}
}
else
{
// TODO: Lookup the existing association for the packet.
_associations.Values.First().OnPacketReceived(sctpPacket);
}
}
}
catch (Exception excp)
{
logger.LogError($"Exception SctpTransport.OnEncapsulationSocketPacketReceived. {excp}");
}
}
