// ***************************************************************************// An 8051 Based Web Server// tcp.c: TCP protocol processing// By Mason Kidd 3/14/02// ***************************************************************************#include "packets.h"#include "ip.h"#include "tcp.h"#include "http.h"static struct tcp_TCB tcp_table[TCP_MAX_CONN];void tcp_init(void){	int i;	       for (i = 0; i < TCP_MAX_CONN; i++)       {       	tcp_table[i].local_port = 0;       	tcp_table[i].remote_port = 0;       	tcp_table[i].remote_addr[0] = 0;       	tcp_table[i].remote_addr[1] = 0;       	tcp_table[i].remote_addr[2] = 0;       	tcp_table[i].remote_addr[3] = 0;       	tcp_table[i].state = LISTEN;       	tcp_table[i].local_seq = 0;       	tcp_table[i].remote_seq = 0;       	       }}unsigned char tcp_get_TCB(unsigned char remote_addr[4], unsigned int remote_port, unsigned int local_port){	int i = 0;	unsigned char free_TCB = TCP_MAX_CONN;    	for (i = 0; i < TCP_MAX_CONN; i++)	{		if (tcp_table[i].remote_addr[0] == remote_addr[0] &&			tcp_table[i].remote_addr[0] == remote_addr[1] &&			tcp_table[i].remote_addr[0] == remote_addr[2] &&			tcp_table[i].remote_addr[0] == remote_addr[3] &&			tcp_table[i].remote_port == remote_port &&			tcp_table[i].local_port == local_port)			return i;		else if (tcp_table[i].state == LISTEN)			free_TCB = i;	}		if (free_TCB != TCP_MAX_CONN)	{		tcp_table[free_TCB].local_port = local_port;		tcp_table[free_TCB].remote_port = remote_port;		tcp_table[free_TCB].remote_addr[0] = remote_addr[0];		tcp_table[free_TCB].remote_addr[1] = remote_addr[1];		tcp_table[free_TCB].remote_addr[2] = remote_addr[2];		tcp_table[free_TCB].remote_addr[3] = remote_addr[3];		return free_TCB;	}		return 0;}void delete_TCB(unsigned char num_TCB){       	tcp_table[num_TCB].local_port = 0;       	tcp_table[num_TCB].remote_port = 0;       	tcp_table[num_TCB].remote_addr[0] = 0;       	tcp_table[num_TCB].remote_addr[1] = 0;       	tcp_table[num_TCB].remote_addr[2] = 0;       	tcp_table[num_TCB].remote_addr[3] = 0;       	tcp_table[num_TCB].state = LISTEN;       	tcp_table[num_TCB].local_seq = 0;       	tcp_table[num_TCB].remote_seq = 0;}void rx_tcp_packet(unsigned char *rx_buffer){	struct eth_hdr *rx_eth_hdr = (struct eth_hdr *)rx_buffer;	struct ip_hdr *rx_ip_hdr = (struct ip_hdr *)(rx_buffer + sizeof(struct eth_hdr));	struct tcp_hdr *rx_tcp_hdr = (struct tcp_hdr *)(rx_buffer + sizeof(struct eth_hdr) + sizeof(struct ip_hdr));	unsigned int *tcp_data = (unsigned int *)(rx_buffer + sizeof(struct eth_hdr) + sizeof(struct ip_hdr) + sizeof(struct tcp_hdr));	unsigned int *chksum_hdr = (unsigned int *)rx_ip_hdr->srcIP;	unsigned int tcp_len = rx_ip_hdr->totlen - sizeof(rx_ip_hdr);	unsigned int chksum = tcp_len + IP_TCP;	unsigned char current_TCB = 0;	bit process_data = 0;	int i;		for (i = 0; i < 8; i++)		chksum += *chksum_hdr;	chksum_hdr = (unsigned int *)rx_tcp_hdr;	// if the packet length is odd, pad it	if (tcp_len % 2)		*((unsigned char *)chksum_hdr + tcp_len) = 0;	tcp_len = (tcp_len + 1) >> 1;	for (i = 0; i < tcp_len; i++, chksum_hdr++)		if (i != 8)			chksum += *chksum_hdr;	chksum = ~chksum;	if (chksum == rx_tcp_hdr->checksum)	{		current_TCB = tcp_get_TCB(rx_ip_hdr->srcIP, rx_tcp_hdr->src_port, rx_tcp_hdr->dst_port);		if (current_TCB != 0) 		{			switch (tcp_table[current_TCB].state)			{				case LISTEN:					if (rx_tcp_hdr->cntrl_bits & TCP_CNTRL_SYN)					{						// received SYN, send SYN and ACK, enter SYN_RECVD	   					tcp_table[current_TCB].state = SYN_RECVD;						tcp_table[current_TCB].local_seq = TCP_START_SEQ;						tcp_table[current_TCB].remote_seq = rx_tcp_hdr->seq;						tx_tcp_packet(current_TCB, TCP_CNTRL_ACK | TCP_CNTRL_SYN, 0, 0);					}					break;				case SYN_SENT:					if (rx_tcp_hdr->cntrl_bits & (TCP_CNTRL_ACK || TCP_CNTRL_SYN))					{   						// received SYN and ACK, enter ESTABLISHED, send ACK						tcp_table[current_TCB].state = ESTABLISHED;						tcp_table[current_TCB].remote_seq = rx_tcp_hdr->seq;   						tx_tcp_packet(current_TCB, TCP_CNTRL_ACK, 0, 0);					}					else if (rx_tcp_hdr->cntrl_bits & TCP_CNTRL_SYN)					{	   					// received SYN, enter SYN_RECVD, send ACK						tcp_table[current_TCB].remote_seq = rx_tcp_hdr->seq;						tcp_table[current_TCB].state = SYN_RECVD;   						tx_tcp_packet(current_TCB, TCP_CNTRL_ACK, 0, 0);					}					break;				case SYN_RECVD:  					if (rx_tcp_hdr->cntrl_bits & TCP_CNTRL_ACK)   	 				{   	   					// received ACK, enter ESTABLISHED						tcp_table[current_TCB].remote_seq = rx_tcp_hdr->seq;						tcp_table[current_TCB].state = ESTABLISHED;   		   			}					break;				case ESTABLISHED:					if (rx_tcp_hdr->cntrl_bits & TCP_CNTRL_FIN)					{   						// received FIN, send ACK, close connection   	   					// skip the CLOSE_WAIT state						tcp_table[current_TCB].state = LAST_ACK;						tx_tcp_packet(current_TCB, TCP_CNTRL_ACK | TCP_CNTRL_FIN, 0, 0);					}					else						process_data = 1;   					break;				case CLOSE_WAIT:					break;				case FIN_WAIT_1:					break;				case FIN_WAIT_2:					break;				case CLOSING:					break;				case LAST_ACK:					if (rx_tcp_hdr->cntrl_bits & TCP_CNTRL_ACK)					{						tcp_table[current_TCB].state = CLOSED;					}				case CLOSED:  					delete_TCB(current_TCB);					break;				case TIME_WAIT:					break;			}			// connection is established, send data to correct socket			if (process_data == 1)				switch (rx_tcp_hdr->dst_port)				{					case TCP_PORT_HTTP:						rx_http_packet((unsigned char *)tcp_data, tcp_len - sizeof(struct tcp_hdr), current_TCB);						break;				}		} 	}	// else discard packet}void tx_tcp_packet(unsigned char current_TCB, unsigned char control_bits, unsigned char *szData, unsigned int nLength){	unsigned char tx_buf[BUF_LEN];	struct ip_hdr *tx_ip_hdr = (struct ip_hdr *)(tx_buf + sizeof(struct eth_hdr));	struct tcp_hdr *tx_tcp_hdr = (struct tcp_hdr *)(tx_buf + sizeof(struct ip_hdr) + sizeof(struct eth_hdr));	unsigned char *tcp_data = (unsigned char *)(tx_buf + sizeof(struct eth_hdr) + sizeof(struct ip_hdr) + sizeof(struct tcp_hdr));	unsigned int *chksum_hdr = (unsigned int *)tx_ip_hdr->srcIP;	unsigned int tcp_len = nLength + sizeof(struct tcp_hdr);	unsigned long chksum = tcp_len + IP_TCP;	int i;		for (i = 0; i < nLength; i++)	{		*tcp_data = szData[i]; 		tcp_data++;	}	    tx_tcp_hdr->src_port = tcp_table[current_TCB].local_port;    tx_tcp_hdr->dst_port = tcp_table[current_TCB].remote_port;    tx_tcp_hdr->seq = tcp_table[current_TCB].local_seq++;    if (control_bits & TCP_CNTRL_ACK)	    tx_tcp_hdr->ack = tcp_table[current_TCB].remote_seq;	tx_tcp_hdr->cntrl_bits = control_bits;	   	for (i = 0; i < 8; i++)		chksum += *chksum_hdr;	chksum_hdr = (unsigned int *)tx_tcp_hdr;	// if the packet length is odd, pad it	if (tcp_len % 2)		*((unsigned char *)chksum_hdr + tcp_len) = 0;	tcp_len = (tcp_len + 1) >> 1;	for (i = 0; i < tcp_len; i++, chksum_hdr++)		if (i != 8)			chksum += *chksum_hdr;	chksum = ~((chksum >> 16) + (chksum & 0xffff));	tx_tcp_hdr->checksum = (unsigned int)(chksum & 0xffff);	tx_ip_packet(tx_buf, nLength + sizeof(struct tcp_hdr), IP_TCP);}