p14.2.c

linux编程源代码,其中是由大量的实例

#include <stdio.h>
#include <pcap.h>
#include <netinet/if_ether.h>

int main(void)
{
	pcap_t *sniffer_des;
	char errbuf[PCAP_ERRBUF_SIZE];
	char *net_dev;
	bpf_u_int32 netp;
	bpf_u_int32 maskp;
	struct bpf_program fp;
	const u_char *packet;
	struct pcap_pkthdr hdr;
	struct ether_header *eth_header;
	u_char *ptr;
	
	char filter_exp[]="port 22";

	net_dev=pcap_lookupdev(errbuf);
	if(net_dev==NULL){
		printf("cannot get the network device info: %s\n",errbuf);
		return 1;
	}	

	if(pcap_lookupnet(net_dev,&netp,&maskp,errbuf)==-1){
		printf("cannot get the network device ip info:%s\n",errbuf);
		return 1;
	}

	sniffer_des=pcap_open_live(net_dev, 65535, 1, 1000, errbuf);
	if(sniffer_des==NULL){
		printf("cannot open the network device: %s\n",errbuf);
		return 1;
	}

	if(pcap_compile(sniffer_des, &fp, filter_exp, 0, maskp)==-1){
		printf("cannot compile the filter rule\n");
		return 1;
	}

	if(pcap_setfilter(sniffer_des,&fp)==-1){
		printf("cannot set the filter to the network device\n");
		return 1;
	}
	
	packet=pcap_next(sniffer_des,&hdr);
	if(packet==NULL){
		printf("cannot get the packet\n");
		return 1;
	}

	printf("Packet length: %d\n",hdr.len);
	printf("Sniffer time: %s\n",ctime((const time_t*)&hdr.ts.tv_sec));
	printf("length of portion present: %d\n",hdr.caplen);

	eth_header=(struct ether_header*)packet;
	if(ntohs(eth_header->ether_type)!=ETHERTYPE_IP){
		printf("not ethernet packet\n ");
		return 1;
	}

	ptr=eth_header->ether_dhost;
	int i;
	i=0;
	printf("destination address(MAC):");
	while(i<ETHER_ADDR_LEN){
		printf(" %x ",*ptr++);
		i++;
	}
	
	printf("\nsource address(MAC):");
	ptr=eth_header->ether_shost;
	i=0;
	while(i<ETHER_ADDR_LEN){
		printf(" %x ",*ptr++);
		i++;
	}

	printf("\n");
	return 0;
}