tcp.c

ENC28J60 System HTTP

/*
,-----------------------------------------------------------------------------------------.
| net/tcp
|-----------------------------------------------------------------------------------------
| this file implements a very basic tcp protocol
| - very basic
|
| KNOWN PROBLEMS:
| - it does not yet check the tcp checksum of incoming packets!!
| - something with the seq/ack calc might be buggy
|   -> must be checked by sending bad tcp packets/re-request etc [[TODO!]]
|
| Author   : {{removed according to contest rules}}
|            -> circuitcellar.com avr design contest 2006
|            -> Entry #AT2616
|
|-----------------------------------------------------------------------------------------
| License:
| 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 "tcp.h"

//ACTIVATE DEBUG by editing this file:
#include "debug.h"

struct tcp_socket tcp_sockets[TCP_SOCKET_COUNT];

//initialise all sockets to closed state:
void tcp_init(){
	unsigned char i = 0;
	for(i=0; i<TCP_SOCKET_COUNT; i++){
		tcp_close_socket(i);
	}
}

unsigned char tcp_find_free_socket(){
	unsigned char i;
	for(i=0; i<TCP_SOCKET_COUNT; i++){
		if (tcp_sockets[i].state == TCP_STATE_CLOSED)
			return i;
	}

	//no free closed socket fount! -> kick an TIMED_WAIT socket
	for(i=0; i<TCP_SOCKET_COUNT; i++){
		if (tcp_sockets[i].state == TCP_STATE_TIMED_WAIT){
			tcp_close_socket(i);
			return i;
		}
	}

	//no more free sockets ... return invalid val	
	return(TCP_SOCKET_COUNT);
}

void tcp_packet_in(unsigned char *buffer, unsigned int len){
	unsigned char tcp_header_flags;
	unsigned int  source_port;
	unsigned int  dest_port;
	unsigned int  datalen;
	unsigned int  datapos;
	unsigned long source_ip;
	unsigned long longtmp;
	unsigned char socketnum;
	//unsigned char i;

	//read header:
	//source ip:
	source_ip   = nic_buffer_to_ip(&buffer[IP_POS_SRC_IP]);
	//source port:
	source_port = (buffer[TCP_POS_SRC_PORT]<<8) | buffer[TCP_POS_SRC_PORT+1];
	//dest port
	dest_port   = (buffer[TCP_POS_DST_PORT]<<8) | buffer[TCP_POS_DST_PORT+1];
	//flags:
	tcp_header_flags = buffer[TCP_POS_HEADERFLAGS] & 0x3F;

	//check if target ip matches:
	if (nic_buffer_to_ip(&buffer[IP_POS_DST_IP]) != nic_ip){
		#if TCP_DEBUG
		softuart_puts_progmem("TCP : ignoring packet for ip ");
		softuart_put_ip(nic_buffer_to_ip(&buffer[IP_POS_DST_IP]));
		softuart_putnewline();
		#endif
		return; //no, not for us !
	}

	//do we have an open socket for this connection ?!
	for(socketnum=0; socketnum<TCP_SOCKET_COUNT; socketnum++){
		//check every not closed socket
		if (tcp_sockets[socketnum].state != TCP_STATE_CLOSED){
			//compare source port (faster check than source ip
			if(tcp_sockets[socketnum].source_port == source_port){
				//now compare the source ip:
				if(tcp_sockets[socketnum].source_ip == source_ip){
					/// yes, this is for us !
					//handle packet
					#if TCP_DEBUG
					softuart_puts_progmem("TCP : socket[");
					softuart_put_uint8(socketnum);
					softuart_puts_progmem("] ACK: ");
					softuart_put_uint16(nic_buffer_to_seq(&buffer[TCP_POS_ACK])&0xFFFF);
					softuart_puts_progmem(" SEQ: ");
					softuart_put_uint16(nic_buffer_to_seq(&buffer[TCP_POS_SEQ])&0xFFFF);
					softuart_puts_progmem(" -> ");
					#endif

					//reset TTL:
					tcp_sockets[socketnum].ttl = TCP_TTL_TIMEOUT;

					//check for connection abort (RST flag)
					if (tcp_header_flags & TCP_RST_FLAG){
						//client wants to terminate ! accept this...
						tcp_close_socket(socketnum);
						//tcp_sockets[socketnum].ack = nic_buffer_to_seq(&buffer[TCP_POS_SEQ]) + 1;
						//tcp_sockets[socketnum].seq = nic_buffer_to_seq(&buffer[TCP_POS_ACK]);
						//FIXME: what is the correct response to an RST packet ?!

						#if TCP_DEBUG
						softuart_puts_progmem(" RST FLAG received -> socket CLOSED.\r\n");
						#endif
						return;
					}

					switch (tcp_sockets[socketnum].state){
						///SNY_RECEIVED
						case(TCP_STATE_SYN_RECEIVED):
							if (tcp_header_flags == TCP_ACK_FLAG){
								//ok, this connection is established:
								//we do not need to send any data now)
								tcp_sockets[socketnum].state = TCP_STATE_ESTABLISHED;

								#if TCP_DEBUG
								softuart_puts_progmem("ESTABLISHED");
								#endif
							}else{
								//invalid packet or TCP_RST_FLAG for example ...
								//connection reset -> close socket
								tcp_close_socket(socketnum);
								#if TCP_DEBUG
								softuart_puts_progmem("CLOSED");
								#endif
							}
							break;
	
						///ESTABLISHED
						case(TCP_STATE_ESTABLISHED):
							if (tcp_header_flags & TCP_FIN_FLAG){
								//connection close request
								//-------send ACK & goto CLOSE_WAIT---- no do this:
								//send ACK+FIN and goto LAST ACK:
								tcp_sockets[socketnum].state = TCP_STATE_LAST_ACK;
								tcp_sockets[socketnum].ack = nic_buffer_to_seq(&buffer[TCP_POS_SEQ]) + 1;
								tcp_sockets[socketnum].seq = nic_buffer_to_seq(&buffer[TCP_POS_ACK]);

								tcp_send_packet(buffer, socketnum, (TCP_FIN_FLAG|TCP_ACK_FLAG), 0);
								#if TCP_DEBUG
								softuart_puts_progmem("LAST_ACK");
								#endif
							}else{
								//this is data for application!
								//check for error & send packet to correct application

								///OUTGOING DATA HANDLING:
								//which databyte was acked ?
								longtmp = nic_buffer_to_seq(&buffer[TCP_POS_ACK]);
								//the last packet we have sent was tcp_sockets[socketnum].seq,
								//check it:
								if ((longtmp != tcp_sockets[socketnum].seq) && (longtmp != 1)){
									#if TCP_DEBUG
									softuart_puts_progmem("TCP : ack != last seqnum! retransmit : ");
									softuart_put_uint16(longtmp&0xFFFF);
									softuart_putc(' ');
									softuart_put_uint16(tcp_sockets[socketnum].seq&0xFFFF);
									softuart_putc(' ');
									softuart_putnewline();
									#endif
									//overwrite seq num -> send acked data !
									tcp_sockets[socketnum].seq = longtmp;
								}

								//update our seq counter, we should send now
								//databyte longtmp-1 (1 = initval of seq counter)
								//tcp_sockets[socketnum].seq = longtmp;


								///INCOMING DATA HANDLING:
								//check if this is the data we expect:
								longtmp = nic_buffer_to_seq(&buffer[TCP_POS_SEQ]);

								//extract data pos:
								datapos = (14 + ((buffer[IP_POS_VERSION] & 0x0F) << 2) + ((buffer[TCP_POS_DATA_OFFSET] & 0xF0) >>2));
								datalen = ((buffer[IP_POS_PKTLEN+0]<<8) | buffer[IP_POS_PKTLEN+1])-datapos+14;

								//we are waiting for a packet with seq = <tcp_sockets[socketnum].ack>
								//-> we sent an ack for packet byte n, now the seq counter of incoming
								//   packet has to be <n>
								if ((longtmp != tcp_sockets[socketnum].ack) && (tcp_sockets[socketnum].ack != 0)){
									//there was an error, check what to do next:
									if (longtmp < tcp_sockets[socketnum].ack){
										//we expected data x to y but we got (x-n) to y
										//we onlny need x to y, so discard n bytes:
										longtmp = (tcp_sockets[socketnum].ack - longtmp);
										datapos = datapos + longtmp;
										datalen = datalen - longtmp;
										#if TCP_DEBUG
										softuart_puts_progmem(" WARN: tcp data dup! ignoring duplicate data. ");
										#endif
									}else{ //longtmp > tcp....
										//uups one packet was lost during transfer !
										//re request this packet, send an ack for expected <seq>:
										#if TCP_DEBUG
										softuart_puts_progmem(" ERR : tcp packet lost! re-requesting. ");
										#endif
										tcp_send_packet(buffer, socketnum, (TCP_ACK_FLAG), 0);
										return;
									}
								}

								//protect buffer:
								if (datapos > NIC_BUFFERSIZE)
									datapos = NIC_BUFFERSIZE;
								if ((datapos + datalen) > NIC_BUFFERSIZE)
									datalen = 0;

								//limit datalength to length that fits into our buffer:
								if (datalen > (NIC_BUFFERSIZE-datapos))
									datalen = (NIC_BUFFERSIZE-datapos);

								//next ack packet we will send must ack data byte n+datalen:
								tcp_sockets[socketnum].ack = tcp_sockets[socketnum].ack + (datalen);

								#if TCP_DEBUG
								softuart_put_uint16(datalen);
								softuart_puts_progmem(" bytes in ");
								/*if (datalen>0)
									softuart_putnewline();
								for(int d=datapos; d<datapos+datalen; d++){
									softuart_putc(buffer[d]);
								}*/
								softuart_putnewline();
								#endif

								//now call the application
								unsigned char appstate = TCP_APPSTATE_NONE;
								unsigned int  data_tx_count = 0;
								if ((tcp_sockets[socketnum].dest_port == IP_PORT_HTTPD)||(tcp_sockets[socketnum].dest_port == 3333)){
									data_tx_count = httpd_data_in(buffer, datapos, datalen, socketnum, &appstate);
								//}else{
								//	data_tx_count = http_client_data_in(buffer, datapos, datalen, socketnum, &appstate);
								}

								//application modified appstate
								switch(appstate){
									case (TCP_APPSTATE_EMPTYACK):
										tcp_send_packet(buffer, socketnum, (TCP_ACK_FLAG), 0);
										tcp_sockets[socketnum].seq = tcp_sockets[socketnum].seq;

										break;
									case (TCP_APPSTATE_HAS_TXDATA):
										//send data
										tcp_send_packet(buffer, socketnum, (TCP_ACK_FLAG), data_tx_count);
										//seq counter update:
										tcp_sockets[socketnum].seq = tcp_sockets[socketnum].seq + data_tx_count;
										#if TCP_DEBUG
										softuart_puts_progmem("TCP : last byte sent = ");
										softuart_put_uint16(tcp_sockets[socketnum].seq&0xFFFF);
										softuart_putc(' ');
										#endif
									
										break;
									case (TCP_APPSTATE_FINISHED):
										#if TCP_DEBUG
										softuart_puts_progmem("TCP : app closed socket ");
										softuart_put_uint8(socketnum);
										#endif
										tcp_sockets[socketnum].state = TCP_STATE_FIN_WAIT1;
										tcp_send_packet(buffer, socketnum, (TCP_FIN_FLAG|TCP_PSH_FLAG|TCP_ACK_FLAG), 0);
										//seq counter update:
										tcp_sockets[socketnum].seq = tcp_sockets[socketnum].seq + 1;
										break;
									default:
										//do nothing... should not happen!
										break;
								}
							}
							break;

						///CLOSE WAIT
						case(TCP_STATE_CLOSE_WAIT):
							//goto last_ack & send FIN packet
							tcp_sockets[socketnum].state = TCP_STATE_LAST_ACK;
							tcp_sockets[socketnum].ack = nic_buffer_to_seq(&buffer[TCP_POS_SEQ])+1;