📄 tcp.c
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//********************************************************************************************
//
// File : tcp.c implement for Transmission Control Protocol
//
//********************************************************************************************
//
// Copyright (C) 2007
//
// This program is free software; you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the Free Software
// Foundation; either version 2 of the License, or (at your option) any later
// version.
// This program is distributed in the hope that it will be useful, but
//
// WITHOUT ANY WARRANTY;
//
// without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
// PURPOSE. See the GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License along with
// this program; if not, write to the Free Software Foundation, Inc., 51
// Franklin St, Fifth Floor, Boston, MA 02110, USA
//
// http://www.gnu.de/gpl-ger.html
//
//********************************************************************************************
#include "includes.h"
//********************************************************************************************
//
// +------------+-----------+------------+----------+
// + MAC header + IP header + TCP header + Data ::: +
// +------------+-----------+------------+----------+
//
// TCP Header
//
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// +00+01+02+03+04+05+06+07+08+09+10+11+12+13+14+15+16+17+18+19+20+21+22+23+24+25+26+27+28+29+30+31+
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// + Source Port + Destination Port +
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// + Sequence Number +
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// + Acknowledgment Number +
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// +Data Offset+reserved+ ECN + Control Bits + Window size +
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// + Checksum + Urgent Pointer +
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// + Options and padding ::: +
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// + Data ::: +
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
//
//********************************************************************************************
// global variables ***********************************************************************
static BYTE seqnum=0xa; // my initial tcp sequence number
//static DWORD_BYTES tcp_sequence_number;
//*****************************************************************************************
//
// Function : tcp_get_dlength
// Description : claculate tcp received data length
//
//*****************************************************************************************
WORD tcp_get_dlength ( BYTE *rxtx_buffer )
{
int dlength, hlength;
dlength = ( rxtx_buffer[ IP_TOTLEN_H_P ] <<8 ) | ( rxtx_buffer[ IP_TOTLEN_L_P ] );
dlength -= sizeof(IP_HEADER);
hlength = (rxtx_buffer[ TCP_HEADER_LEN_P ]>>4) * 4; // generate len in bytes;
dlength -= hlength;
if ( dlength <= 0 )
dlength=0;
return ((WORD)dlength);
}
//*****************************************************************************************
//
// Function : tcp_get_hlength
// Description : claculate tcp received header length
//
//*****************************************************************************************
BYTE tcp_get_hlength ( BYTE *rxtx_buffer )
{
return ((rxtx_buffer[ TCP_HEADER_LEN_P ]>>4) * 4); // generate len in bytes;
}
//********************************************************************************************
//
// Function : tcp_puts_data_p
// Description : puts data from program memory to tx buffer
//
//********************************************************************************************
WORD tcp_puts_data_p ( BYTE *rxtx_buffer, PGM_P data, WORD offset )
{
BYTE ch;
while( (ch = pgm_read_byte(data++)) ) { rxtx_buffer[ TCP_DATA_P + offset ] = ch;
offset++; }
return offset;
}
//********************************************************************************************
//
// Function : tcp_puts_data
// Description : puts data from RAM to tx buffer
//
//********************************************************************************************
WORD tcp_puts_data ( BYTE *rxtx_buffer, BYTE *data, WORD offset )
{
while( *data ) { rxtx_buffer[ TCP_DATA_P + offset ] = *data++;
offset++; }
return offset;
}
//********************************************************************************************
//
// Function : tcp_send_packet
// Description : send tcp packet to network.
//
//********************************************************************************************
void tcp_send_packet (
BYTE *rxtx_buffer,
WORD_BYTES dest_port,
WORD_BYTES src_port,
BYTE flags,
BYTE max_segment_size,
BYTE clear_seqack,
WORD next_ack_num,
WORD dlength,
BYTE *dest_mac,
BYTE *dest_ip )
{
BYTE i, tseq;
WORD_BYTES ck;
// generate ethernet header
eth_generate_header ( rxtx_buffer, (WORD_BYTES){ETH_TYPE_IP_V}, dest_mac );
// sequence numbers:
// add the rel ack num to SEQACK
if ( next_ack_num )
{
for( i=4; i>0; i-- )
{
next_ack_num = rxtx_buffer [ TCP_SEQ_P + i - 1] + next_ack_num;
tseq = rxtx_buffer [ TCP_SEQACK_P + i - 1];
rxtx_buffer [ TCP_SEQACK_P + i - 1] = 0xff & next_ack_num;
// copy the acknum sent to us into the sequence number
rxtx_buffer[ TCP_SEQ_P + i - 1 ] = tseq;
next_ack_num >>= 8;
}
}
// initial tcp sequence number
// setup maximum segment size
// require to setup first packet is receive or transmit only
if ( max_segment_size )
{
// initial sequence number
rxtx_buffer[ TCP_SEQ_P + 0 ] = 0; rxtx_buffer[ TCP_SEQ_P + 1 ] = 0; rxtx_buffer[ TCP_SEQ_P + 2 ] = seqnum; rxtx_buffer[ TCP_SEQ_P + 3 ] = 0; seqnum += 2;
// setup maximum segment size rxtx_buffer[ TCP_OPTIONS_P + 0 ] = 2;
rxtx_buffer[ TCP_OPTIONS_P + 1 ] = 4;
rxtx_buffer[ TCP_OPTIONS_P + 2 ] = HIGH(1408);
rxtx_buffer[ TCP_OPTIONS_P + 3 ] = LOW(1408);
// setup tcp header length 24 bytes: 6*32/8 = 24 rxtx_buffer[ TCP_HEADER_LEN_P ] = 0x60;
dlength += 4;
}
else
{
// no options: 20 bytes: 5*32/8 = 20 rxtx_buffer[ TCP_HEADER_LEN_P ] = 0x50;
}
// generate ip header and checksum
ip_generate_header ( rxtx_buffer, (WORD_BYTES){(sizeof(IP_HEADER) + sizeof(TCP_HEADER) + dlength)}, IP_PROTO_TCP_V, dest_ip );
// clear sequence ack number before send tcp SYN packet
if ( clear_seqack )
{
rxtx_buffer[ TCP_SEQACK_P + 0 ] = 0; rxtx_buffer[ TCP_SEQACK_P + 1 ] = 0; rxtx_buffer[ TCP_SEQACK_P + 2 ] = 0; rxtx_buffer[ TCP_SEQACK_P + 3 ] = 0;
}
// setup tcp flags
rxtx_buffer [ TCP_FLAGS_P ] = flags;
// setup destination port
rxtx_buffer [ TCP_DST_PORT_H_P ] = dest_port.byte.high;
rxtx_buffer [ TCP_DST_PORT_L_P ] = dest_port.byte.low;
// setup source port
rxtx_buffer [ TCP_SRC_PORT_H_P ] = src_port.byte.high;
rxtx_buffer [ TCP_SRC_PORT_L_P ] = src_port.byte.low;
// setup maximum windows size
rxtx_buffer [ TCP_WINDOWSIZE_H_P ] = HIGH((MAX_RX_BUFFER-sizeof(IP_HEADER)-sizeof(ETH_HEADER)));
rxtx_buffer [ TCP_WINDOWSIZE_L_P ] = LOW((MAX_RX_BUFFER-sizeof(IP_HEADER)-sizeof(ETH_HEADER)));
// setup urgend pointer (not used -> 0)
rxtx_buffer[ TCP_URGENT_PTR_H_P ] = 0;
rxtx_buffer[ TCP_URGENT_PTR_L_P ] = 0;
// clear old checksum and calculate new checksum
rxtx_buffer[ TCP_CHECKSUM_H_P ] = 0;
rxtx_buffer[ TCP_CHECKSUM_L_P ] = 0;
// This is computed as the 16-bit one's complement of the one's complement
// sum of a pseudo header of information from the
// IP header, the TCP header, and the data, padded
// as needed with zero bytes at the end to make a multiple of two bytes.
// The pseudo header contains the following fields:
//
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// +00+01+02+03+04+05+06+07+08+09+10+11+12+13+14+15+16+17+18+19+20+21+22+23+24+25+26+27+28+29+30+31+
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// + Source IP address +
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// + Destination IP address +
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// + 0 + IP Protocol + Total length +
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
ck.word = software_checksum( &rxtx_buffer[IP_SRC_IP_P], sizeof(TCP_HEADER)+dlength+8, IP_PROTO_TCP_V + sizeof(TCP_HEADER) + dlength );
rxtx_buffer[ TCP_CHECKSUM_H_P ] = ck.byte.high;
rxtx_buffer[ TCP_CHECKSUM_L_P ] = ck.byte.low;
// send packet to ethernet media
enc28j60_packet_send ( rxtx_buffer, sizeof(ETH_HEADER)+sizeof(IP_HEADER)+sizeof(TCP_HEADER)+dlength );
}
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