/**
* <code>
* 2) Authenticate the State Cookie as one that it previously generated
* by comparing the computed MAC against the one carried in the
* State Cookie. If this comparison fails, the SCTP packet,
* including the COOKIE ECHO and any DATA chunks, should be silently
* discarded,
*
* 3) Compare the port numbers and the Verification Tag contained
* within the COOKIE ECHO chunk to the actual port numbers and the
* Verification Tag within the SCTP common header of the received
* packet. If these values do not match, the packet MUST be
* silently discarded.
*
* 4) Compare the creation timestamp in the State Cookie to the current
* local time. If the elapsed time is longer than the lifespan
* carried in the State Cookie, then the packet, including the
* COOKIE ECHO and any attached DATA chunks, SHOULD be discarded,
* and the endpoint MUST transmit an ERROR chunk with a "Stale
* Cookie" error cause to the peer endpoint.
*
* 5) If the State Cookie is valid, create an association to the sender
* of the COOKIE ECHO chunk with the information in the TCB data
* carried in the COOKIE ECHO and enter the ESTABLISHED state.
*
* 6) Send a COOKIE ACK chunk to the peer acknowledging receipt of the
* COOKIE ECHO. The COOKIE ACK MAY be bundled with an outbound DATA
* chunk or SACK chunk; however, the COOKIE ACK MUST be the first
* chunk in the SCTP packet.
*
* 7) Immediately acknowledge any DATA chunk bundled with the COOKIE
* ECHO with a SACK (subsequent DATA chunk acknowledgement should
* follow the rules defined in Section 6.2). As mentioned in step
* 6, if the SACK is bundled with the COOKIE ACK, the COOKIE ACK
* MUST appear first in the SCTP packet.
* </code>
*/
private Chunk[] cookieEchoDeal(CookieEchoChunk echo)
{
Chunk[] reply = new Chunk[0];
if (_state == State.CLOSED || _state == State.COOKIEWAIT || _state == State.COOKIEECHOED)
{
// Authenticate the State Cookie
CookieHolder cookie;
if (null != (cookie = checkCookieEcho(echo.getCookieData())))
{
// Compare the creation timestamp in the State Cookie to the current local time.
uint howStale = howStaleIsMyCookie(cookie);
if (howStale == 0)
{
//enter the ESTABLISHED state
_state = State.ESTABLISHED;
/*
* Send a COOKIE ACK chunk to the peer acknowledging receipt of the
* COOKIE ECHO. The COOKIE ACK MAY be bundled with an outbound DATA
* chunk or SACK chunk; however, the COOKIE ACK MUST be the first
* chunk in the SCTP packet.
*/
reply = new Chunk[1];
reply[0] = new CookieAckChunk();
}
else
{
reply = new Chunk[1];
/* If the elapsed time is longer than the lifespan
* carried in the State Cookie, then the packet, including the
* COOKIE ECHO and any attached DATA chunks, SHOULD be discarded,
* and the endpoint MUST transmit an ERROR chunk with a "Stale
* Cookie" error cause to the peer endpoint.*/
StaleCookieError sce = new StaleCookieError();
sce.setMeasure(howStale * 1000);
ErrorChunk ec = new ErrorChunk(sce);
reply[0] = ec;
}
}
else
{
logger.LogError("Got a COOKIE_ECHO that doesn't match any we sent. ?!?");
}
}
else
{
logger.LogDebug("Got an COOKIE_ECHO when not closed - ignoring it");
}
return(reply);
}
public static Chunk mkChunk(ByteBuffer pkt)
{
Chunk ret = null;
if (pkt.remaining() >= 4)
{
ChunkType type = (ChunkType)pkt.GetByte();
byte flags = pkt.GetByte();
int length = pkt.GetUShort();
switch (type)
{
case ChunkType.DATA:
ret = new DataChunk(flags, length, pkt);
break;
case ChunkType.INIT:
ret = new InitChunk(type, flags, length, pkt);
break;
case ChunkType.SACK:
ret = new SackChunk(type, flags, length, pkt);
break;
case ChunkType.INITACK:
ret = new InitAckChunk(type, flags, length, pkt);
break;
case ChunkType.COOKIE_ECHO:
ret = new CookieEchoChunk(type, flags, length, pkt);
break;
case ChunkType.COOKIE_ACK:
ret = new CookieAckChunk(type, flags, length, pkt);
break;
case ChunkType.ABORT:
ret = new AbortChunk(type, flags, length, pkt);
break;
case ChunkType.HEARTBEAT:
ret = new HeartBeatChunk(type, flags, length, pkt);
break;
case ChunkType.RE_CONFIG:
ret = new ReConfigChunk(type, flags, length, pkt);
break;
case ChunkType.ERROR:
ret = new ErrorChunk(type, flags, length, pkt);
break;
default:
logger.LogWarning($"SCTP unknown chunk type received {type}.");
ret = new FailChunk(type, flags, length, pkt);
break;
}
if (ret != null)
{
if (pkt.hasRemaining())
{
int mod = ret.getLength() % 4;
if (mod != 0)
{
for (int pad = mod; pad < 4; pad++)
{
pkt.GetByte();
}
}
}
}
}
return(ret);
}