linux下网络监听与发送数据包的方法(即libpcap、libnet两种类库的使用方法)

linux下可以用libpcap函数库实现监听数据包，使用libnet 函数库发送数据包

安装:

在命令行下apt-get install 就可以了

libpcap的使用:

/*
author hjj
date 2011-1-21
function:capture packet with the ruler and output the packet information
modify 2011-1-23
function:get dns packet
*/
#include<stdio.h>
#include<sys/socket.h>
#include<sys/types.h>
#include<pcap.h>
#include<netinet/in.h>
#include<netinet/tcp.h>
#include<string.h>
#include<stdlib.h>
#include<arpa/inet.h>
#define ETHER_ADDR_LEN 6
/*以太网头*/
struct sniff_ethernet
{
        u_char ether_dhost[ETHER_ADDR_LEN];
        u_char ether_shost[ETHER_ADDR_LEN];
        u_short ether_type;
};
/*IP头*/
struct sniff_ip
{
        u_char ip_vhl;
        u_char ip_tos;
        u_short ip_len;
        u_short ip_id;
        u_short ip_off;
        #define IP_RF 0x8000
        #define IP_DF 0x4000
        #define IP_MF 0x2000
        #define IP_OFFMASK 0x1fff
        u_char ip_ttl;
         u_char ip_p;
        u_short ip_sum;
        struct in_addr ip_src,ip_dst;
};
/*TCP头*/
typedef u_int tcp_seq;
struct sniff_tcp
{
        u_short th_sport;
        u_short th_dport;
        tcp_seq th_seq;
        tcp_seq th_ack;

        u_char th_offx2;
        u_char th_flags;

        u_short th_win;
        u_short th_sum;
        u_short th_urp;
};
/*UDP报头*/
struct sniff_udp
{
        u_short udp_sport;
        u_short udp_dport;
        u_short udp_len;
        u_short udp_sum;
};
/*DNS报头*/
struct sniff_dns
{
        u_short dns_id;
        u_short dns_flag;
        u_short dns_ques;
        u_short dns_ans;
        u_short dns_auth;

        u_short dns_add;
        u_int8_t *dsn_data;
};
//数据包到达回调函数
void packetcall(u_char *user,const struct pcap_pkthdr *pcap_head,const u_char *packet);
char *ipstr(struct in_addr s_addr);
char* getpackettype(u_short packet_type);
char* toString(u_long s);
//由u_char[6]获取网卡地址字符串
char *getMac(u_char *host);
int main(int argc,char **argv)
{
        char *dev,errbuf[PCAP_ERRBUF_SIZE];
        pcap_t *handler;
        struct bpf_program fp;
        char filter_exp[50]="ip and dst 172.20.92.118";
        if(argc==3)
        {
                sprintf(filter_exp,"dst %s and dst port %s",argv[1],argv[2]);
        }
        if(argc==5)
        {
                sprintf(filter_exp,"dst %s and dst port %s or src %s and src port %s",argv[1],argv[2],argv[3],argv[4]);
        }
        bpf_u_int32 mask;
        bpf_u_int32 net;
        struct pcap_pkthdr header;
        const u_char *packet;

        dev=pcap_lookupdev(errbuf);
        if(dev==NULL)
        {
                fprintf(stderr,"could not find default device:%s\n",errbuf);
                return 2;
        }
        printf("device:%s\n",dev);
      if(pcap_lookupnet(dev,&net,&mask,errbuf)==-1)
        {
                fprintf(stderr,"counld not get netmask for device %s;%s\n",dev,errbuf);
                net=0;
                mask=0;
        }
        handler=pcap_open_live(dev,BUFSIZ,1,10000,errbuf);

        if(handler==NULL)
        {
                fprintf(stderr,"could not open device %s;%s",dev,errbuf);
                return 2;
        }

        if(pcap_compile(handler,&fp,filter_exp,0,net)==-1)
        {
                fprintf(stderr,"counld not parse filter %s;%s\n",filter_exp,pcap_geterr(handler));
                return 2;
        }

        if(pcap_setfilter(handler,&fp)==-1)
        {
                fprintf(stderr,"counld not install filter %s;%s\n",filter_exp,pcap_geterr(handler));
                return 2;
        }
        //捕获数据包
        int packetnums=20;
        packet=pcap_loop(handler,packetnums,packetcall,NULL);
        pcap_close(handler);
        return 0;
}
//数据包到达回调函数
void packetcall(u_char *user,const struct pcap_pkthdr *pcap_head,const u_char *packet)
{
        static int count=1;//数据包计数
        struct sniff_ethernet *ethernet;//以太网包头

        struct sniff_ip *ip;//ip包头

        struct sniff_udp *udp;//udp包头

        struct sniff_dns *dns;//dns报头

        const u_char *payload;//数据包负载的数据

        int pay_size;//数据包负载的数据大小

        ethernet=(struct sniff_ethernet*)(packet);

        ip=(struct sniff_ip*)(packet + sizeof(struct sniff_ethernet));

        udp=(struct sniff_udp*)(packet + sizeof(struct sniff_ethernet)+sizeof(struct sniff_ip));

        dns=(struct sniff_dns*)(packet + sizeof(struct sniff_ethernet) + sizeof(struct sniff_ip) + sizeof(struct sniff_udp));
        payload=(u_char *)(packet+sizeof(struct sniff_ethernet)+sizeof(struct sniff_ip)+sizeof(struct sniff_udp)+sizeof(struct sniff_dns));

        pay_size=ntohs(udp->udp_len)-sizeof(struct sniff_udp)-sizeof(struct sniff_dns);
        printf("-------------数据包:%d\n",count);
        printf("数据包类型:%s\n",getpackettype(ethernet->ether_type));
        printf("源地址:%X:%X:%X:%X:%X:%X\n",
                (ethernet->ether_shost)[0],
                (ethernet->ether_shost)[1],
                (ethernet->ether_shost)[2],
                (ethernet->ether_shost)[3],
                (ethernet->ether_shost)[4],
                (ethernet->ether_shost)[5]);
        printf("目的地址:%X:%X:%X:%X:%X:%X\n",
                (ethernet->ether_dhost)[0],
                (ethernet->ether_dhost)[1],
                (ethernet->ether_dhost)[2],
                (ethernet->ether_dhost)[3],
                (ethernet->ether_dhost)[4],
                (ethernet->ether_dhost)[5]);
        printf("From:%s\n",inet_ntoa(ip->ip_src));
        printf("To:%s\n",inet_ntoa(ip->ip_dst));
        printf("源端口:%d\n",ntohs(udp->udp_sport));
        printf("目的端口:%d\n",ntohs(udp->udp_dport));
        printf("DNS查询问题数%d\n",ntohs(dns->dns_ques));
        if(pay_size>0)
        {
                printf("Payload    data size %d\n",pay_size);
                const u_char *ch=payload;
                int i,j;
                for(i=0;i<ntohs(dns->dns_ques);i++)
                {
                        //获取各查询名
                        printf("第%d个查询名\n",i);
                        int k=1;//标志符号;
                        while(1)
                        {
                                if(*ch==0)
                                        break;
                                u_int8_t identify_size=*ch;
                                printf("\t第%d个标志符号\n",k);
                                ch++;
                                for(j=0;j<identify_size;j++,ch++)
                                {
                                        if(isprint(*ch))
                                        {
                                                printf("%c",*ch);
                                        }else
                                        {
                                                printf(".");
                                        }
                                }
                                k++;
                        }
                }
        }
        count++;
}

libnet的使用

/*
author hjj
date 2011-1-20
function: send an arp packet to all machine on local net
*/
#include<stdio.h>
#include<libnet.h>
#define MAC_ADDR_LEN 6
#define IP_ADDR_LEN 4
#define LIBNET_DNS_H 0xc
int main(int argc,char **argv)
{
        libnet_t *net_t=NULL;
        char *dev="eth0";
        char err_buf[LIBNET_ERRBUF_SIZE];
        libnet_ptag_t p_tag;
        unsigned char src_mac[MAC_ADDR_LEN]={0x00,0x00,0xf1,0xe8,0x0e,0xc8};//发送者网卡地址

        unsigned char dst_mac[MAC_ADDR_LEN]={0xff,0xff,0xff,0xff,0xff,0xff};//接收者网卡地址
        char *src_ip_str="172.20.92.117";
        if(argc==2)
        {
                if(strcmp(argv[1],"-h")==0||strcmp(argv[1],"--help")==0)
                {
                        printf("%s","help message");
                }else
                {
                        src_ip_str=argv[1];
                }
        }
        unsigned long src_ip,dst_ip=0;
        src_ip=libnet_name2addr4(net_t,src_ip_str,LIBNET_RESOLVE);//将字符串类型的ip转换为顺序网络字节流
        net_t=libnet_init(LIBNET_LINK_ADV,dev,err_buf);//初始化发送包结构
        if(net_t==NULL)
        {
                printf("libnet_init error\n");
                exit(0)

       }

        p_tag=libnet_build_arp(
                ARPHRD_ETHER,//hardware type ethernet
                ETHERTYPE_IP,//protocol type
                MAC_ADDR_LEN,//mac length
                IP_ADDR_LEN,//protocol length
                ARPOP_REPLY,//op type
                (u_int8_t*)src_mac,//source mac addr这里的作用是更新目的地的arp表
                (u_int8_t*)&src_ip,//source ip addr
                (u_int8_t*)dst_mac,//source mac addr
                (u_int8_t*)&dst_ip,//dest ip addr
                NULL,//payload
                0,//payload length
                net_t,//libnet context
                0//0 stands to build a new one
        );
        if(-1 == p_tag)
        {
                printf("libnet_build_arp error");
                exit(0);
        }

        //以太网头部
        p_tag=libnet_build_ethernet(//create ethernet header
        (u_int8_t*)dst_mac,//dest mac addr
        (u_int8_t*)src_mac,//source mac addr
        ETHERTYPE_ARP,//protocol type
        NULL,//payload
        0,//payload length
        net_t,//libnet context
        0//0 to build a new one
        );

        if(-1 == p_tag)
        {
                printf("libnet_build_ethernet error!\n");
                exit(1);
        }
        int res;
        if(-1==(res=libnet_write(net_t)))
        {
                printf("libnet_write error!\n");
                exit(1);
        }
        libnet_destroy(net_t);
        return 0;
}