#include <stdio.h>#include <pcap.h>#include <netinet/if_ether.h>void deal_with_packet(u_char *user, const struct pcap_pkthdr *hdr, const u_char *packet){      	static int count=0;	struct ether_header *eth_header;        u_char *ptr; 		printf("Packet length: %d\n",hdr->len);        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 ;        }        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");		printf("finish deal with %d packet\n",count);	count++;}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;	int ret;		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;	}		ret=pcap_loop(sniffer_des,3,deal_with_packet,NULL);	if(ret==-1 || ret==-2){		printf("cannot get the packet\n");		return 1;	}	printf("finish processing packets....\n");	return 0;}