Difference between revisions of "Unit TCP"

Revision as of 04:34, 18 December 2016

Return to Unit Reference

Description

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

To be documented

Type definitions

To be documented

Public variables

To be documented

Function declarations

Initialization functions

procedure TCPInit;

TCP functions

function CheckTCP(AFamily:Word; ABuffer:Pointer):Boolean;

function GetTCPHeaderOffset(AFamily:Word; ABuffer:Pointer):Word;

function GetTCPHeaderLength(AFamily:Word; ABuffer:Pointer):Word;

function GetTCPOptionsLength(AFamily:Word; ABuffer:Pointer):Word;

function GetTCPDataOffset(AFamily:Word; ABuffer:Pointer):Word;

function GetTCPDataLength(AFamily:Word; ABuffer:Pointer):Word;

function ChecksumTCPRecv(AFamily:Word; APseudo:PIPPseudo; ABuffer:Pointer; AOffset,ALength:Word):Word;

function ChecksumTCPSend(AFamily:Word; APseudo:PIPPseudo; AHeader:PTCPHeader; AOptions,AData:Pointer; AOptionsLength,ADataLength:Word):Word;

Return to Unit Reference