icmp.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
// icmp.c: ICMP protocol processing
// By Mason Kidd 3/14/02
// ***************************************************************************

#include <string.h>
#include "packets.h"
#include "ip.h"
#include "icmp.h"

void tx_icmp_packet(unsigned char tx_type, unsigned char *szData, unsigned char nLength)
{
	unsigned char tx_buf[BUF_LEN];
	struct ip_hdr *tx_ip_hdr = (struct ip_hdr *)(tx_buf + sizeof(struct eth_hdr));
	struct icmp_hdr *tx_icmp_hdr = (struct icmp_hdr *)(tx_buf + sizeof(struct ip_hdr) + sizeof(struct eth_hdr));
	unsigned char *icmp_data = (unsigned char *)(tx_buf + sizeof(struct eth_hdr) + sizeof(struct ip_hdr) + sizeof(struct icmp_hdr));
	unsigned int *chksum_hdr = (unsigned int *)tx_icmp_hdr;
	int i;
	unsigned long chksum = 0;
	
	tx_icmp_hdr->type = tx_type;
	tx_icmp_hdr->sequence = 0x01;
	for (i = 0; i < nLength; i++)
	{
		*icmp_data = *szData;
		icmp_data++;
		szData++;
	}

	// Compute the checksum
	for (i = 0; i < 5; i++, chksum_hdr++)
		if (i != 1)
			chksum += *chksum_hdr;
	chksum = ~((chksum >> 16) + (chksum & 0xffff));
 	tx_icmp_hdr->checksum = (unsigned int)(chksum & 0xffff);

	tx_ip_packet(tx_buf, nLength + sizeof(struct icmp_hdr), IP_ICMP);
}

void rx_icmp_packet(unsigned char *rx_buffer)
{
	struct ip_hdr *rx_ip_hdr = (struct ip_hdr *)(rx_buffer + sizeof(struct eth_hdr));
	struct icmp_hdr *rx_icmp_hdr = (struct icmp_hdr *)(rx_buffer + sizeof(struct eth_hdr) + sizeof(struct ip_hdr));
	unsigned char *pszData = (unsigned char *)(rx_buffer + sizeof(struct eth_hdr) + sizeof(struct ip_hdr) + sizeof(struct icmp_hdr));
	unsigned int nDataLen = rx_ip_hdr->totlen - sizeof(struct icmp_hdr) - sizeof(struct ip_hdr);

	// if it's an echo request, send a reply
	if (rx_icmp_hdr->type == ICMP_ECHO)
	{
		// switch source and destination IP's
		memcpy(targetMAC, srcMAC, sizeof(unsigned char) * 6);
		memcpy(targetIP, srcIP, sizeof(unsigned char) * 4);

		tx_icmp_packet(ICMP_ECHOREPLY, pszData, nDataLen);
	}
	// else discard packet
}