* Acess2 IP Stack
* - TCP Handling
*/
-#define DEBUG 0
+#define DEBUG 1
#include "ipstack.h"
#include "ipv4.h"
#include "ipv6.h"
#include "tcp.h"
-#define USE_SELECT 1
#define HEXDUMP_INCOMING 0
#define HEXDUMP_OUTGOING 0
void TCP_Initialise(void);
void TCP_StartConnection(tTCPConnection *Conn);
void TCP_SendPacket(tTCPConnection *Conn, tTCPHeader *Header, size_t DataLen, const void *Data);
+void TCP_int_SendPacket(tInterface *Interface, const void *Dest, tTCPHeader *Header, size_t Length, const void *Data);
void TCP_GetPacket(tInterface *Interface, void *Address, int Length, void *Buffer);
void TCP_INT_HandleConnectionPacket(tTCPConnection *Connection, tTCPHeader *Header, int Length);
int TCP_INT_AppendRecieved(tTCPConnection *Connection, const void *Data, size_t Length);
int TCP_AllocatePort(Uint16 Port);
int TCP_DeallocatePort(Uint16 Port);
tTCPConnection *TCP_int_CreateConnection(tInterface *Interface, enum eTCPConnectionState State);
+void TCP_int_FreeTCB(tTCPConnection *Connection);
// --- Server
tVFS_Node *TCP_Server_Init(tInterface *Interface);
int TCP_Server_ReadDir(tVFS_Node *Node, int Pos, char Name[FILENAME_MAX]);
void TCP_Client_Close(tVFS_Node *Node);
// --- Helpers
int WrapBetween(Uint32 Lower, Uint32 Value, Uint32 Higher, Uint32 MaxValue);
+Uint32 GetRelative(Uint32 Base, Uint32 Value);
// === TEMPLATES ===
tSocketFile gTCP_ServerFile = {NULL, "tcps", TCP_Server_Init};
*/
void TCP_Initialise(void)
{
- giTCP_NextOutPort += rand()%32;
+ giTCP_NextOutPort += rand()%128;
IPStack_AddFile(&gTCP_ServerFile);
IPStack_AddFile(&gTCP_ClientFile);
IPv4_RegisterCallback(IP4PROT_TCP, TCP_GetPacket);
* \param Data Packet data (cast as a TCP Header)
*/
void TCP_SendPacket( tTCPConnection *Conn, tTCPHeader *Header, size_t Length, const void *Data )
+{
+ TCP_int_SendPacket(Conn->Interface, &Conn->RemoteIP, Header, Length, Data);
+}
+
+void TCP_int_SendPacket(tInterface *Interface, const void *Dest, tTCPHeader *Header, size_t Length, const void *Data )
{
tIPStackBuffer *buffer;
Uint16 checksum[3];
IPStack_Buffer_AppendSubBuffer(buffer, sizeof(*Header), 0, Header, NULL, NULL);
LOG("Sending %i+%i to %s:%i", sizeof(*Header), Length,
- IPStack_PrintAddress(Conn->Interface->Type, &Conn->RemoteIP),
- Conn->RemotePort
+ IPStack_PrintAddress(Interface->Type, Dest),
+ ntohs(Header->DestPort)
);
Header->Checksum = 0;
// TODO: Fragment packet
- switch( Conn->Interface->Type )
+ switch( Interface->Type )
{
case 4:
// Get IPv4 pseudo-header checksum
{
Uint32 buf[3];
- buf[0] = ((tIPv4*)Conn->Interface->Address)->L;
- buf[1] = Conn->RemoteIP.v4.L;
- buf[2] = (htons(packlen)<<16) | (6<<8) | 0;
+ buf[0] = ((tIPv4*)Interface->Address)->L;
+ buf[1] = ((tIPv4*)Dest)->L;
+ buf[2] = htonl( (packlen) | (IP4PROT_TCP<<16) | (0<<24) );
checksum[0] = htons( ~IPv4_Checksum(buf, sizeof(buf)) ); // Partial checksum
}
// - Combine checksums
Header->Checksum = htons( IPv4_Checksum(checksum, sizeof(checksum)) );
- IPv4_SendPacket(Conn->Interface, Conn->RemoteIP.v4, IP4PROT_TCP, 0, buffer);
+ IPv4_SendPacket(Interface, *(tIPv4*)Dest, IP4PROT_TCP, 0, buffer);
break;
case 6:
// Append IPv6 Pseudo Header
{
Uint32 buf[4+4+1+1];
- memcpy(buf, Conn->Interface->Address, 16);
- memcpy(&buf[4], &Conn->RemoteIP, 16);
+ memcpy(buf, Interface->Address, 16);
+ memcpy(&buf[4], Dest, 16);
buf[8] = htonl(packlen);
- buf[9] = htonl(6);
+ buf[9] = htonl(IP4PROT_TCP);
checksum[0] = htons( ~IPv4_Checksum(buf, sizeof(buf)) ); // Partial checksum
}
Header->Checksum = htons( IPv4_Checksum(checksum, sizeof(checksum)) ); // Combine the two
- IPv6_SendPacket(Conn->Interface, Conn->RemoteIP.v6, IP4PROT_TCP, Length, Data);
+ IPv6_SendPacket(Interface, *(tIPv6*)Dest, IP4PROT_TCP, buffer);
break;
}
}
+void TCP_int_SendRSTTo(tInterface *Interface, void *Address, size_t Length, const tTCPHeader *Header)
+{
+ tTCPHeader out_hdr = {0};
+
+ out_hdr.DataOffset = (sizeof(out_hdr)/4) << 4;
+ out_hdr.DestPort = Header->SourcePort;
+ out_hdr.SourcePort = Header->DestPort;
+
+ size_t data_len = Length - (Header->DataOffset>>4)*4;
+ out_hdr.AcknowlegementNumber = htonl( ntohl(Header->SequenceNumber) + data_len );
+ if( Header->Flags & TCP_FLAG_ACK ) {
+ out_hdr.Flags = TCP_FLAG_RST;
+ out_hdr.SequenceNumber = Header->AcknowlegementNumber;
+ }
+ else {
+ out_hdr.Flags = TCP_FLAG_RST|TCP_FLAG_ACK;
+ out_hdr.SequenceNumber = 0;
+ }
+ TCP_int_SendPacket(Interface, Address, &out_hdr, 0, NULL);
+}
+
/**
* \brief Handles a packet from the IP Layer
* \param Interface Interface the packet arrived from
void TCP_GetPacket(tInterface *Interface, void *Address, int Length, void *Buffer)
{
tTCPHeader *hdr = Buffer;
- tTCPListener *srv;
- tTCPConnection *conn;
#if TCP_DEBUG
Log_Log("TCP", "TCP_GetPacket: <Local>:%i from [%s]:%i, Flags = %s%s%s%s%s%s%s%s",
}
// Check Servers
- for( srv = gTCP_Listeners; srv; srv = srv->Next )
+ for( tTCPListener *srv = gTCP_Listeners; srv; srv = srv->Next )
{
// Check if the server is active
if(srv->Port == 0) continue;
Log_Log("TCP", "TCP_GetPacket: Matches server %p", srv);
// Is this in an established connection?
- for( conn = srv->Connections; conn; conn = conn->Next )
+ for( tTCPConnection *conn = srv->Connections; conn; conn = conn->Next )
{
// Check that it is coming in on the same interface
if(conn->Interface != Interface) continue;
return;
}
- Log_Log("TCP", "TCP_GetPacket: Opening Connection");
- // Open a new connection (well, check that it's a SYN)
- if(hdr->Flags != TCP_FLAG_SYN) {
- Log_Log("TCP", "TCP_GetPacket: Packet is not a SYN");
+
+ if( hdr->Flags & TCP_FLAG_RST ) {
+ LOG("RST, ignore");
+ return ;
+ }
+ else if( hdr->Flags & TCP_FLAG_ACK ) {
+ LOG("ACK, send RST");
+ TCP_int_SendRSTTo(Interface, Address, Length, hdr);
return ;
}
+ else if( !(hdr->Flags & TCP_FLAG_SYN) ) {
+ LOG("Other, ignore");
+ return ;
+ }
+ Log_Log("TCP", "TCP_GetPacket: Opening Connection");
// TODO: Check for halfopen max
- conn = TCP_int_CreateConnection(Interface, TCP_ST_SYN_RCVD);
+ tTCPConnection *conn = TCP_int_CreateConnection(Interface, TCP_ST_SYN_RCVD);
conn->LocalPort = srv->Port;
conn->RemotePort = ntohs(hdr->SourcePort);
{
case 4: conn->RemoteIP.v4 = *(tIPv4*)Address; break;
case 6: conn->RemoteIP.v6 = *(tIPv6*)Address; break;
+ default: ASSERTC(Interface->Type,==,4); return;
}
conn->NextSequenceRcv = ntohl( hdr->SequenceNumber ) + 1;
conn->HighestSequenceRcvd = conn->NextSequenceRcv;
conn->NextSequenceSend = rand();
+ conn->LastACKSequence = ntohl( hdr->SequenceNumber );
conn->Node.ImplInt = srv->NextID ++;
// Oh, wait, there is a case where a wildcard can be used
// (srv->Interface == NULL) so having the lock is a good idea
SHORTLOCK(&srv->lConnections);
- if( !srv->Connections )
- srv->Connections = conn;
- else
+ conn->Server = srv;
+ conn->Prev = srv->ConnectionsTail;
+ if(srv->Connections) {
+ ASSERT(srv->ConnectionsTail);
srv->ConnectionsTail->Next = conn;
+ }
+ else {
+ ASSERT(!srv->ConnectionsTail);
+ srv->Connections = conn;
+ }
srv->ConnectionsTail = conn;
if(!srv->NewConnections)
srv->NewConnections = conn;
// Check Open Connections
{
- for( conn = gTCP_OutbountCons; conn; conn = conn->Next )
+ for( tTCPConnection *conn = gTCP_OutbountCons; conn; conn = conn->Next )
{
// Check that it is coming in on the same interface
if(conn->Interface != Interface) continue;
}
Log_Log("TCP", "TCP_GetPacket: No Match");
+ // If not a RST, send a RST
+ if( !(hdr->Flags & TCP_FLAG_RST) )
+ {
+ TCP_int_SendRSTTo(Interface, Address, Length, hdr);
+ }
}
/**
Log_Log("TCP", "ACKing SYN-ACK");
Connection->State = TCP_ST_OPEN;
VFS_MarkFull(&Connection->Node, 0);
+ TCP_INT_SendACK(Connection, "SYN-ACK");
}
else
{
Log_Log("TCP", "ACKing SYN");
Connection->State = TCP_ST_SYN_RCVD;
+ TCP_INT_SendACK(Connection, "SYN");
}
- Header->DestPort = Header->SourcePort;
- Header->SourcePort = htons(Connection->LocalPort);
- Header->AcknowlegementNumber = htonl(Connection->NextSequenceRcv);
- Header->SequenceNumber = htonl(Connection->NextSequenceSend);
- Header->WindowSize = htons(TCP_WINDOW_SIZE);
- Header->Flags = TCP_FLAG_ACK;
- Header->DataOffset = (sizeof(tTCPHeader)/4) << 4;
- TCP_SendPacket( Connection, Header, 0, NULL );
}
break;
if( Header->Flags & TCP_FLAG_FIN ) {
Log_Log("TCP", "Conn %p closed, recieved FIN", Connection);
VFS_MarkError(&Connection->Node, 1);
+ Connection->NextSequenceRcv ++;
+ TCP_INT_SendACK(Connection, "FIN Received");
Connection->State = TCP_ST_CLOSE_WAIT;
-// Header->Flags &= ~TCP_FLAG_FIN;
- // CLOSE WAIT requires the client to close (or does it?)
- #if 0
-
- #endif
+ // CLOSE WAIT requires the client to close
+ return ;
}
// Check for an empty packet
#if 1
// - Only send an ACK if we've had a burst
- if( Connection->NextSequenceRcv > (Uint32)(TCP_DACK_THRESHOLD + Connection->LastACKSequence) )
+ Uint32 bytes_since_last_ack = Connection->NextSequenceRcv - Connection->LastACKSequence;
+ LOG("bytes_since_last_ack = 0x%x", bytes_since_last_ack);
+ if( bytes_since_last_ack > TCP_DACK_THRESHOLD )
{
TCP_INT_SendACK(Connection, "DACK Burst");
// - Extend TCP deferred ACK timer
#endif
}
// Check if the packet is in window
- else if( WrapBetween(Connection->NextSequenceRcv, sequence_num,
- Connection->NextSequenceRcv+TCP_WINDOW_SIZE, 0xFFFFFFFF) )
+ else if( sequence_num - Connection->NextSequenceRcv < TCP_WINDOW_SIZE )
{
Uint8 *dataptr = (Uint8*)Header + (Header->DataOffset>>4)*4;
- #if CACHE_FUTURE_PACKETS_IN_BYTES
- Uint32 index;
-
- index = sequence_num % TCP_WINDOW_SIZE;
+ Uint32 index = sequence_num % TCP_WINDOW_SIZE;
+ Uint32 max = Connection->NextSequenceRcv % TCP_WINDOW_SIZE;
+ if( !(Connection->FuturePacketValidBytes[index/8] & (1 << (index%8))) )
+ TCP_INT_SendACK(Connection, "Lost packet");
for( int i = 0; i < dataLen; i ++ )
{
Connection->FuturePacketValidBytes[index/8] |= 1 << (index%8);
// Do a wrap increment
index ++;
if(index == TCP_WINDOW_SIZE) index = 0;
+ if(index == max) break;
}
- #else
- tTCPStoredPacket *pkt, *tmp, *prev = NULL;
-
- // Allocate and fill cached packet
- pkt = malloc( sizeof(tTCPStoredPacket) + dataLen );
- pkt->Next = NULL;
- pkt->Sequence = ntohl(Header->SequenceNumber);
- pkt->Length = dataLen;
- memcpy(pkt->Data, dataptr, dataLen);
-
- Log_Log("TCP", "We missed a packet, caching",
- pkt->Sequence, Connection->NextSequenceRcv);
-
- // No? Well, let's cache it and look at it later
- SHORTLOCK( &Connection->lFuturePackets );
- for(tmp = Connection->FuturePackets;
- tmp;
- prev = tmp, tmp = tmp->Next)
- {
- if(tmp->Sequence >= pkt->Sequence) break;
- }
-
- // Add if before first, or sequences don't match
- if( !tmp || tmp->Sequence != pkt->Sequence )
- {
- if(prev)
- prev->Next = pkt;
- else
- Connection->FuturePackets = pkt;
- pkt->Next = tmp;
- }
- // Replace if larger
- else if(pkt->Length > tmp->Length)
- {
- if(prev)
- prev->Next = pkt;
- pkt->Next = tmp->Next;
- free(tmp);
- }
- else
+ Uint32 rel_highest = Connection->HighestSequenceRcvd - Connection->NextSequenceRcv;
+ Uint32 rel_this = index - Connection->NextSequenceRcv;
+ LOG("Updating highest this(0x%x) > highest(%x)", rel_this, rel_highest);
+ if( rel_this > rel_highest )
{
- free(pkt); // TODO: Find some way to remove this
+ Connection->HighestSequenceRcvd = index;
}
- SHORTREL( &Connection->lFuturePackets );
- #endif
}
// Badly out of sequence packet
else
{
Connection->State = TCP_ST_FINISHED; // Connection completed
Log_Log("TCP", "LAST-ACK to CLOSED - Connection remote closed");
- // TODO: Destrory the TCB
+ TCP_int_FreeTCB(Connection);
}
break;
Log_Debug("TCP", "Conn %p closed, sent FIN and recieved FIN", Connection);
VFS_MarkError(&Connection->Node, 1);
- // ACK Packet
- Header->DestPort = Header->SourcePort;
- Header->SourcePort = htons(Connection->LocalPort);
- Header->AcknowlegementNumber = Header->SequenceNumber;
- Header->SequenceNumber = htonl(Connection->NextSequenceSend);
- Header->WindowSize = htons(TCP_WINDOW_SIZE);
- Header->Flags = TCP_FLAG_ACK;
- TCP_SendPacket( Connection, Header, 0, NULL );
+ TCP_INT_SendACK(Connection, "FINWAIT-1 FIN");
break ;
}
if( Header->Flags & TCP_FLAG_FIN )
{
Connection->State = TCP_ST_TIME_WAIT;
- Log_Debug("TCP", "FIN sent and recieved, ACKing and going into TIME WAIT %p FINWAIT-2 -> TIME WAIT", Connection);
- // Send ACK
- Header->DestPort = Header->SourcePort;
- Header->SourcePort = htons(Connection->LocalPort);
- Header->AcknowlegementNumber = Header->SequenceNumber;
- Header->SequenceNumber = htonl(Connection->NextSequenceSend);
- Header->WindowSize = htons(TCP_WINDOW_SIZE);
- Header->Flags = TCP_FLAG_ACK;
- TCP_SendPacket( Connection, Header, 0, NULL );
+ Log_Debug("TCP", "Conn %p FINWAIT-2 -> TIME WAIT", Connection);
+ TCP_INT_SendACK(Connection, "FINWAIT-2 FIN");
}
break;
*/
void TCP_INT_UpdateRecievedFromFuture(tTCPConnection *Connection)
{
- #if CACHE_FUTURE_PACKETS_IN_BYTES
// Calculate length of contiguous bytes
- int length = Connection->HighestSequenceRcvd - Connection->NextSequenceRcv;
+ const int length = Connection->HighestSequenceRcvd - Connection->NextSequenceRcv;
Uint32 index = Connection->NextSequenceRcv % TCP_WINDOW_SIZE;
- LOG("length=%i, index=%i", length, index);
+ size_t runlength = length;
+ LOG("length=%i, index=0x%x", length, index);
for( int i = 0; i < length; i ++ )
{
int bit = index % 8;
Uint8 bitfield_byte = Connection->FuturePacketValidBytes[index / 8];
if( (bitfield_byte & (1 << bit)) == 0 ) {
- length = i;
+ runlength = i;
+ LOG("Hit missing, break");
break;
}
}
index = Connection->NextSequenceRcv % TCP_WINDOW_SIZE;
+ Connection->NextSequenceRcv += runlength;
// Write data to to the ring buffer
- if( TCP_WINDOW_SIZE - index > length )
+ if( TCP_WINDOW_SIZE - index > runlength )
{
// Simple case
- RingBuffer_Write( Connection->RecievedBuffer, Connection->FuturePacketData + index, length );
+ RingBuffer_Write( Connection->RecievedBuffer, Connection->FuturePacketData + index, runlength );
}
else
{
int endLen = TCP_WINDOW_SIZE - index;
// 2-part case
RingBuffer_Write( Connection->RecievedBuffer, Connection->FuturePacketData + index, endLen );
- RingBuffer_Write( Connection->RecievedBuffer, Connection->FuturePacketData, endLen - length );
+ RingBuffer_Write( Connection->RecievedBuffer, Connection->FuturePacketData, endLen - runlength );
}
// Mark (now saved) bytes as invalid
// - Align index
- while(index % 8 && length > 0)
+ while(index % 8 && runlength > 0)
{
Connection->FuturePacketData[index] = 0;
Connection->FuturePacketValidBytes[index/8] &= ~(1 << (index%8));
index ++;
if(index > TCP_WINDOW_SIZE)
index -= TCP_WINDOW_SIZE;
- length --;
+ runlength --;
}
- while( length > 7 )
+ while( runlength > 7 )
{
Connection->FuturePacketData[index] = 0;
Connection->FuturePacketValidBytes[index/8] = 0;
- length -= 8;
+ runlength -= 8;
index += 8;
if(index > TCP_WINDOW_SIZE)
index -= TCP_WINDOW_SIZE;
}
- while(length)
+ while( runlength > 0)
{
Connection->FuturePacketData[index] = 0;
Connection->FuturePacketData[index/8] &= ~(1 << (index%8));
index ++;
if(index > TCP_WINDOW_SIZE)
index -= TCP_WINDOW_SIZE;
- length --;
+ runlength --;
}
-
- #else
- tTCPStoredPacket *pkt;
- for(;;)
- {
- SHORTLOCK( &Connection->lFuturePackets );
-
- // Clear out duplicates from cache
- // - If a packet has just been recieved, and it is expected, then
- // (since NextSequenceRcv = rcvd->Sequence + rcvd->Length) all
- // packets in cache that are smaller than the next expected
- // are now defunct.
- pkt = Connection->FuturePackets;
- while(pkt && pkt->Sequence < Connection->NextSequenceRcv)
- {
- tTCPStoredPacket *next = pkt->Next;
- free(pkt);
- pkt = next;
- }
-
- // If there's no packets left in cache, stop looking
- if(!pkt || pkt->Sequence > Connection->NextSequenceRcv) {
- SHORTREL( &Connection->lFuturePackets );
- return;
- }
-
- // Delete packet from future list
- Connection->FuturePackets = pkt->Next;
-
- // Release list
- SHORTREL( &Connection->lFuturePackets );
-
- // Looks like we found one
- TCP_INT_AppendRecieved(Connection, pkt->Data, pkt->Length);
- if( Connection->HighestSequenceRcvd == Connection->NextSequenceRcv )
- Connection->HighestSequenceRcvd += pkt->Length;
- Connection->NextSequenceRcv += pkt->Length;
- free(pkt);
- }
- #endif
}
void TCP_int_SendDelayedACK(void *ConnPtr)
return conn;
}
+void TCP_int_FreeTCB(tTCPConnection *Connection)
+{
+ ASSERTC(Connection->State, ==, TCP_ST_FINISHED);
+ ASSERTC(Connection->Node.ReferenceCount, ==, 0);
+
+ if( Connection->Server )
+ {
+ tTCPListener *srv = Connection->Server;
+ SHORTLOCK(&srv->lConnections);
+ if(Connection->Prev)
+ Connection->Prev->Next = Connection->Next;
+ else
+ srv->Connections = Connection->Next;
+ if(Connection->Next)
+ Connection->Next->Prev = Connection->Prev;
+ else {
+ ASSERT(srv->ConnectionsTail == Connection);
+ srv->ConnectionsTail = Connection->Prev;
+ }
+ SHORTREL(&srv->lConnections);
+ }
+ else
+ {
+ SHORTLOCK(&glTCP_OutbountCons);
+ if(Connection->Prev)
+ Connection->Prev->Next = Connection->Next;
+ else
+ gTCP_OutbountCons = Connection->Next;
+ if(Connection->Next)
+ Connection->Next->Prev = Connection->Prev;
+ else
+ ;
+ SHORTREL(&glTCP_OutbountCons);
+ }
+
+ RingBuffer_Free(Connection->RecievedBuffer);
+ Time_FreeTimer(Connection->DeferredACKTimer);
+ // TODO: Force VFS to close handles? (they should all be closed);
+ free(Connection);
+}
+
// --- Server
tVFS_Node *TCP_Server_Init(tInterface *Interface)
{
tTCPConnection *conn = TCP_int_CreateConnection(Interface, TCP_ST_CLOSED);
SHORTLOCK(&glTCP_OutbountCons);
+ conn->Server = NULL;
+ conn->Prev = NULL;
conn->Next = gTCP_OutbountCons;
+ gTCP_OutbountCons->Prev = conn;
gTCP_OutbountCons = conn;
SHORTREL(&glTCP_OutbountCons);
// - Stop Delayed ACK timer (as this data packet ACKs)
Time_RemoveTimer(Connection->DeferredACKTimer);
+
+ // TODO: Don't exceed window size
packet->SourcePort = htons(Connection->LocalPort);
packet->DestPort = htons(Connection->RemotePort);
LEAVE('-');
return ;
}
+ Node->ReferenceCount --;
if( conn->State == TCP_ST_CLOSE_WAIT || conn->State == TCP_ST_OPEN )
{
TCP_SendPacket( conn, &packet, 0, NULL );
}
+ Time_RemoveTimer(conn->DeferredACKTimer);
+
switch( conn->State )
{
case TCP_ST_CLOSED:
Log_Warning("TCP", "Closing connection that was never opened");
+ TCP_int_FreeTCB(conn);
break;
case TCP_ST_CLOSE_WAIT:
conn->State = TCP_ST_LAST_ACK;
break;
case TCP_ST_OPEN:
conn->State = TCP_ST_FIN_WAIT1;
- while( conn->State == TCP_ST_FIN_WAIT1 ) Threads_Yield();
+ while( conn->State == TCP_ST_FIN_WAIT1 )
+ Threads_Yield();
+ // No free, freed after TIME_WAIT
break;
default:
Log_Warning("TCP", "Unhandled connection state %i in TCP_Client_Close",
break;
}
- Time_RemoveTimer(conn->DeferredACKTimer);
- Time_FreeTimer(conn->DeferredACKTimer);
- free(conn);
-
LEAVE('-');
}
return 0;
}
+Uint32 GetRelative(Uint32 Base, Uint32 Value)
+{
+ if( Value < Base )
+ return Value - Base + 0xFFFFFFFF;
+ else
+ return Value - Base;
+}