ip.c

网络单片机 让嵌入式系统上网,基于keil C. 文件名:microweb-keil-0.1

// ***************************************************************************
// An 8051 Based Web Server
// ip.c: IP protocol processing
// By Mason Kidd 4/18/02
// ***************************************************************************

#include <string.h>
#include "packets.h"
#include "csio.h"

unsigned char rx_ip_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));
	unsigned int *chksum_hdr = (unsigned int *)rx_ip_hdr;
	int i;
	unsigned long chksum = 0;
	
	// Make sure that the packet is destined for me or for broadcast
	if ((!memcmp(myIP, &rx_ip_hdr->destIP, sizeof(unsigned char) * 4)) || (!memcmp(myBCAST, &rx_ip_hdr->destIP, sizeof(unsigned char) * 4)))
	{
       	// Save the source MAC and IP for when I reply
       	memcpy(srcMAC, &rx_eth_hdr->shost, sizeof(unsigned char) * 6);
       	memcpy(srcIP, &rx_ip_hdr->srcIP, sizeof(unsigned char) * 4);
		
		// Compute the checksum
		for (i = 0; i < 10; i++, chksum_hdr++)
			if (i != 5)
				chksum += *chksum_hdr;
		chksum = ~((chksum >> 16) + (chksum & 0xffff));
 		
 		// packet is valid if they match
 		if ((chksum & 0xffff) == rx_ip_hdr->hdrchksum)
  		{
			return rx_ip_hdr->proto;
    	}
     	else
      		return 0;
	}
	return 0;
}

void tx_ip_packet(unsigned char *tx_buffer, unsigned char tx_length, unsigned char cProto)
{
	struct eth_hdr *tx_eth_hdr = (struct eth_hdr *)tx_buffer;
	struct ip_hdr *tx_ip_hdr = (struct ip_hdr *)(tx_buffer + sizeof(struct eth_hdr));
	unsigned int *chksum_hdr = (unsigned int *)tx_ip_hdr;
	int i;
	unsigned long chksum = 0;

    tx_ip_hdr->verIHL = 0x45;
    tx_ip_hdr->totlen = tx_length + sizeof(struct ip_hdr);
    tx_ip_hdr->TTL = 0x32;
    tx_ip_hdr->proto = cProto;
    
	memcpy(tx_ip_hdr->srcIP, myIP, sizeof(unsigned char) * 4);
	memcpy(tx_ip_hdr->destIP, targetIP, sizeof(unsigned char) * 4);
	
	chksum_hdr = (unsigned int *)tx_ip_hdr;

	// Compute the checksum
	for (i = 0; i < 10; i++, chksum_hdr++)
		if (i != 5)
			chksum += *chksum_hdr;
	chksum = ~((chksum >> 16) + (chksum & 0xffff));
	tx_ip_hdr->hdrchksum = (unsigned int)(chksum & 0xffff);

	tx_eth_hdr->type = ETHER_IP;
	memcpy(tx_eth_hdr->shost, myMAC, sizeof(unsigned char) * 6);
	memcpy(tx_eth_hdr->dhost, targetMAC, sizeof(unsigned char) * 6);
	
   	tx_packet(tx_buffer, tx_length);
}