arp.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
// arp.c: processing for ARP packets
// By Mason Kidd 4/18/02
// ***************************************************************************

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

void tx_arp_packet(unsigned int arp_oper)
{
	unsigned char tx_buffer[100];
	struct eth_hdr *tx_eth_hdr = (struct eth_hdr *)tx_buffer;
	struct eth_arp *tx_eth_arp = (struct eth_arp *)tx_buffer + sizeof(struct eth_hdr);
	unsigned char nLength, i;
	
	tx_eth_hdr->eth_arp_hdr.ar_op = arp_oper;
	tx_eth_hdr->eth_arp_hdr.ar_hrd = ARP_HRD_ETHER;
	tx_eth_hdr->eth_arp_hdr.ar_pro = ETHER_IP;
	tx_eth_hdr->eth_arp_hdr.ar_hln = mac_size;
	tx_eth_hdr->eth_arp_hdr.ar_pln = ip_size;
	
	memcpy(rx_eth_arp->ar_spa, myIP, sizeof(unsigned char) * ip_size);
	memcpy(rx_eth_arp->ar_sha, myMAC, sizeof(unsigned char) * mac_size);
	memcpy(rx_eth_arp->ar_tpa, targetIP, sizeof(unsigned char) * ip_size);
	memcpy(rx_eth_arp->ar_sha, targetMAC, sizeof(unsigned char) * mac_size);
	
	nLength = sizeof(struct eth_hdr) + sizeof(struct eth_arp);
	if (nLength < 60)
	{
		for (i = 0; i < (60 - nLength); i++)
			*(tx_eth_arp++) = 0x00;
		nLength = 60;
	}
	tx_packet(tx_buffer, nLength);
}

void rx_arp_packet(unsigned char *rx_buffer)
{
	struct eth_hdr *rx_eth_hdr = (struct eth_hdr *)rx_buffer;
	struct eth_arp *rx_eth_arp = (struct eth_arp *)(rx_buffer + sizeof(struct eth_hdr));
	
	// make sure the ARP packet is Ethernet and IP
	if ((rx_eth_arp->eth_arp_hdr.ar_hrd == ARP_HRD_ETHER) && (rx_eth_arp->eth_arp_hdr.ar_pro == ETHER_IP))
	{
		// make sure the ARP packet is a request destined for us
		if ((rx_eth_arp->eth_arp_hdr.ar_op == ARP_REQUEST) && (!memcmp(myIP, rx_eth_arp->ar_tpa, sizeof(unsigned char) * ip_size)))
		{
			// send a reply
			memcpy(targetIP, rx_eth_arp->ar_spa, sizeof(unsigned char) * ip_size);
			memcpy(targetMAC, rx_eth_arp->ar_sha, sizeof(unsigned char) * mac_size);
  			tx_arp_packet(ARP_REPLY);
		}
		// else discard packet
	}
	// else discard packet
}