Unit TCP
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Description
Ultibo TCP (Transmission Control Protocol) unit
Notes:
Segment handling:
Send adds new segments to the end of the list only accepts ACKs for whole segments.
Recv adds/inserts segments in correct SEQ order accepts overlapping segments only sends ACKs for whole segments.
Send will coalesce small data writes into larger segments if options allow this.
Recv will store the segments exactly as received.
TCP Send and Recv do not use a block buffer as per UDP etc. Instead the data for each Segment is stored in memory (TCP_MAX_MSS) allocated with the Segment. The Free and Used values still track the amount of data in the buffer but this method allows OOB data to be handled correctly.
TCP Sequence numbers are compared using modulo 2^32 arithmetic. The following calculations provide the neccessary handling of wraparound etc.
LT = (A - B) < 0
LEQ = (A - B) <= 0
GT = (A - B) > 0
GEQ = (A - B) >= 0
See GlobalSock.pas for actual functions that implement this.
Constants
TCP specific constants
TCP_* | Note: Some TCP definitions are in the Protocol or IP modules | |
TCP_PROTOCOL_NAME = 'TCP';
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TCP_TIMER_INTERVAL = 1;
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1ms timer interval for TCP |
MIN_TCP_PACKET = 20;
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Not Counting Adapter and Transport Header |
MAX_TCP_PACKET = 1480;
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Not Counting Adapter and Transport Header |
TCP_DEFAULT_MSS = 536;
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Default Segment Size for TCP (576 - TCP - IP) |
TCP_MAX_MSS = 1460;
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Max Segment Size for TCP (1500 - TCP - IP) |
TCP_MAX_LIFETIME = 120000;
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Max Segment Lifetime (2 minutes) |
TCP_TIMEOUT = 0;
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Wait forever on a TCP Read/Write |
TCP_BUFFER_SIZE = 262144;
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65536; TCP Send/Receive Buffer Sizes |
TCP_WINDOW_SIZE = 16060;
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64240; Sliding Window Receive Size (44 x MSS) |
TCP_INITIAL_WINDOW = 8192;
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Initial Window to advertise in SYN packet |
TCP_WINDOW_TIMEOUT = 300;
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Time to wait before probing small/zero Window |
TCP_ACK_TIMEOUT = 200;
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Max Delayed Ack Time |
TCP_CONNECT_COUNT = 3;
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Number of Connect retries (on RST) before Failure |
TCP_RESTART_TIMEOUT = 400;
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Timeout between Connect retries (Milliseconds) |
TCP_RETRY_COUNT = 10;
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Number of Retransmits before Reset |
TCP_RETRY_TIMEOUT:array[1..TCP_RETRY_COUNT] of LongWord = (250,500,1000,2000,4000,8000,15000,30000,60000,120000);
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TCP_KEEPALIVE_COUNT = 3;
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Number of Failed Keepalives before Reset |
TCP_KEEPALIVE_TIMEOUT:array[1..TCP_KEEPALIVE_COUNT] of LongWord = (600000,60000,60000);
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TCP_MAX_PORT = 65536;
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TCP_HEADER_SIZE = 20;
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SizeOf(TTCPHeader); Does Not Allow for Options |
TCP_OPTIONS_SIZE = 40;
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Maximum Allowed Options |
TCP_SEGMENT_SIZE = 48;
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SizeOf(TTCPSegment) |
TCP socket state constants
TCP_STATE_* TCP_STATE_LISTEN = 0;
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listening for connection |
TCP_STATE_SYNSENT = 1;
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SYN sent, active open |
TCP_STATE_SYNREC = 2;
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SYN received, SYNACK sent |
TCP_STATE_ESTAB = 3;
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established |
TCP_STATE_FINWAIT1 = 4;
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sent FIN |
TCP_STATE_FINWAIT2 = 5;
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sent FIN, received FINACK |
TCP_STATE_CLOSWAIT = 6;
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received FIN waiting for close |
TCP_STATE_CLOSING = 7;
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sent FIN, received FIN (waiting for FINACK) |
TCP_STATE_LASTACK = 8;
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FIN received, FINACK + FIN sent |
TCP_STATE_TIMEWAIT = 9;
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dally after sending final FINACK |
TCP_STATE_CLOSED = 10;
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FINACK received |
TCP header option constants
TCPOPT_* TCPOPT_EOL = 0;
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end-of-option list |
TCPOPT_NOP = 1;
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no-operation |
TCPOPT_MAXSEG = 2;
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maximum segment size |
TCPOPT_WINDOW = 3;
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window scale factor (rfc1072) |
TCPOPT_SACKOK = 4;
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selective ack ok (rfc1072) |
TCPOPT_SACK = 5;
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selective ack (rfc1072) |
TCPOPT_ECHO = 6;
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echo (rfc1072) |
TCPOPT_ECHOREPLY = 7;
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echo (rfc1072) |
TCPOPT_TIMESTAMP = 8;
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timestamps (rfc1323) |
TCPOPT_CC = 11;
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T/TCP CC options (rfc1644) |
TCPOPT_CCNEW = 12;
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T/TCP CC options (rfc1644) |
TCPOPT_CCECHO = 13;
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T/TCP CC options (rfc1644) |
TCP header flag constants
TCP_FLAG_* TCP_FLAG_FIN = $01;
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TCP_FLAG_SYN = $02;
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TCP_FLAG_RST = $04;
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TCP_FLAG_PUSH = $08;
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TCP_FLAG_ACK = $10;
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TCP_FLAG_URG = $20;
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TCP_FLAG_MASK = $3F;
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| Van Jacobson's Algorithm; max std. average and std. deviation | |
MAX_VJSA = 80000;
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MAX_VJSD = 20000;
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INIT_VJSA = 220;
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TCP port constants
TCP_PORT_* TCP_PORT_START = 49152;
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First dynamic port (Previously 1024) As per IANA assignment |
TCP_PORT_STOP = 65534;
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Last dynamic port (Previously 5000) Short of IANA assignment to allow for rollover |
Type definitions
To be documented
Public variables
None defined
Function declarations
Initialization functions
procedure TCPInit;
Description: To be documented
| Note | None documented |
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TCP functions
function CheckTCP(AFamily:Word; ABuffer:Pointer):Boolean;
Description: Verify that the packet is a valid TCP packet
| Buffer | The complete packet including Transport header |
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function GetTCPHeaderOffset(AFamily:Word; ABuffer:Pointer):Word;
Description: To be documented
| Buffer | The complete packet including Transport header |
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function GetTCPHeaderLength(AFamily:Word; ABuffer:Pointer):Word;
Description: TO be documented
| Buffer | The complete packet including Transport header |
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function GetTCPOptionsLength(AFamily:Word; ABuffer:Pointer):Word;
Description: To be documented
| Buffer | The complete packet including Transport header |
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function GetTCPDataOffset(AFamily:Word; ABuffer:Pointer):Word;
Description: To be documented
| Buffer | The complete packet including Transport header |
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function GetTCPDataLength(AFamily:Word; ABuffer:Pointer):Word;
Description: To be documented
| Buffer | The complete packet including Transport header |
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function ChecksumTCPRecv(AFamily:Word; APseudo:PIPPseudo; ABuffer:Pointer; AOffset,ALength:Word):Word;
Description: Validate the Checksum of TCP Pseudo, Header and Data on Receive
| Note | None documented |
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function ChecksumTCPSend(AFamily:Word; APseudo:PIPPseudo; AHeader:PTCPHeader; AOptions,AData:Pointer; AOptionsLength,ADataLength:Word):Word;
Description: Checksum the TCP Pseudo, Header, Options and Data on Send
| Note | None documented |
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