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;
}
转自:http://hi.baidu.com/henujava/blog/item/20ea29c2c4ecf6c9d0006074.html
