#include <stdio.h>
#include <stdlib.h>
#include <pcap.h>
#include <errno.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h> int main(int argc, char **argv)
{
char *dev;
char *net;
char *mask;
int ret;
char errbuf[PCAP_ERRBUF_SIZE];
bpf_u_int32 netp;
bpf_u_int32 maskp;
struct in_addr addr; dev = pcap_lookupdev(errbuf); if(dev == NULL)
{
printf("%s\n",errbuf);
exit();
} printf("DEV: %s\n",dev); ret = pcap_lookupnet(dev,&netp,&maskp,errbuf); if(ret == -)
{
printf("%s\n",errbuf);
exit();
} addr.s_addr = netp;
net = inet_ntoa(addr); if(net == NULL)
{
perror("inet_ntoa");
exit();
} printf("NET: %s\n",net); addr.s_addr = maskp;
mask = inet_ntoa(addr); if(mask == NULL)
{
perror("inet_ntoa");
exit();
} printf("MASK: %s\n",mask); return ;
}
然后gcc -o pcap_1 pcap_1.c -lpcap（一定要-lpcap参数）
编译ok~，执行./pcap_1，可以看到：
DEV: eth0
NET: 192.168.12.0
MASK: 255.255.255.0
好了，第一个pcap程序出炉了。。。。。 但是（当然有但是了，要不然我后面写啥），上面那个程序除了向我们展现pcap_lookupdev和pcap_lookupnet之外什么都没有干，好，我们接着来，动手编写我们的第一个抓包程序。 #include <stdio.h>
#include <stdlib.h>
#include <pcap.h>
#include <errno.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netinet/if_ether.h> int main(int argc, char **argv)
{
int i;
char *dev;
char errbuf[PCAP_ERRBUF_SIZE];
pcap_t* descr;
const u_char *packet;
struct pcap_pkthdr hdr;
struct ether_header *eptr; u_char *ptr; dev = pcap_lookupdev(errbuf); if(dev == NULL)
{
printf("%s\n",errbuf);
exit();
} printf("DEV: %s\n",dev); descr = pcap_open_live(dev,BUFSIZ,,-,errbuf); if(descr == NULL)
{
printf("pcap_open_live(): %s\n",errbuf);
exit();
} packet = pcap_next(descr,&hdr); if(packet == NULL)
{
printf("Didn't grab packet\n");
exit();
} printf("Grabbed packet of length %d\n",hdr.len);
printf("Recieved at ..... %s\n",ctime((const time_t*)&hdr.ts.tv_sec));
printf("Ethernet address length is %d\n",ETHER_HDR_LEN); eptr = (struct ether_header *) packet; if (ntohs (eptr->ether_type) == ETHERTYPE_IP)
{
printf("Ethernet type hex:%x dec:%d is an IP packet\n",
ntohs(eptr->ether_type),
ntohs(eptr->ether_type));
}else if (ntohs (eptr->ether_type) == ETHERTYPE_ARP)
{
printf("Ethernet type hex:%x dec:%d is an ARP packet\n",
ntohs(eptr->ether_type),
ntohs(eptr->ether_type));
}else {
printf("Ethernet type %x not IP", ntohs(eptr->ether_type));
exit();
} ptr = eptr->ether_dhost;
i = ETHER_ADDR_LEN;
printf(" Destination Address: ");
do{
printf("%s%x",(i == ETHER_ADDR_LEN) ? " " : ":",*ptr++);
}while(--i>);
printf("\n"); ptr = eptr->ether_shost;
i = ETHER_ADDR_LEN;
printf(" Source Address: ");
do{
printf("%s%x",(i == ETHER_ADDR_LEN) ? " " : ":",*ptr++);
}while(--i>);
printf("\n"); return ;
} 好了,编译运行!
[root@norman libpcap]# ./pcap_2
DEV: eth0
Grabbed packet of length
Recieved at time..... Mon Mar :: Ethernet address length is
Ethernet type hex: dec: is an IP packet
Destination Address: :::d1:e8:
Source Address: :a0:cc::c2:
[root@pepe libpcap]# 可能有人等了半天都没有一个包过来，有个好办法，再开一个控制台，ping一下某个网站，比如google~~，呵呵
马上就有反应了~~ 这个程序是一个老外写的，大家看看注释应该没有问题吧~
但是大家也发现了一个问题，就是上面的程序只能捕捉一个包，要不停的捕捉包怎么办，用循环？？libpcap提供了一个更好的方法：
int pcap_loop(pcap_t *p, int cnt, pcap_handler callback, u_char *user);
这个函数能够不停的捕捉以太网的包，cnt就是捕捉的次数，callback是处理函数，这个处理函数怎么写，看看pcap_3.c就知道了。user参数是干什么的？不要问我，我也不知道。 #include <pcap.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netinet/if_ether.h> void my_callback(u_char *useless,const struct pcap_pkthdr* pkthdr,const u_char*
packet)
{
static int count = ;
fprintf(stdout,"%d, ",count);
if(count == )
fprintf(stdout,"Come on baby sayyy you love me!!! ");
if(count == )
fprintf(stdout,"Tiiimmmeesss!! ");
fflush(stdout);
count++;
} int main(int argc,char **argv)
{
int i;
char *dev;
char errbuf[PCAP_ERRBUF_SIZE];
pcap_t* descr;
const u_char *packet;
struct pcap_pkthdr hdr;
struct ether_header *eptr; if(argc != ){ fprintf(stdout,"Usage: %s numpackets\n",argv[]);return ;} dev = pcap_lookupdev(errbuf);
if(dev == NULL)
{ printf("%s\n",errbuf); exit(); } descr = pcap_open_live(dev,BUFSIZ,,-,errbuf);
if(descr == NULL)
{ printf("pcap_open_live(): %s\n",errbuf); exit(); } pcap_loop(descr,atoi(argv[]),my_callback,NULL); fprintf(stdout,"\nDone processing packets... wheew!\n");
return ;
} 运行./pcap_3
, , , , Come on baby sayyy you love me!!! , , , Tiiimmmeesss!!
Done processing packets... wheew! pcap_loop确实很好用,但是如果没有包包过来,只有干等在那里,pcap_dispatch就含有一个超时的功能，下面是man里面的一段话：
pcap_dispatch() is used to collect and process packets. cnt specifies the maximum number of packets to process before returning. A cnt of - processes all the packets received in one buffer. A cnt of processes all packets until an error occurs, EOF is reached, or the read times out (when doing live reads and a non-zero read timeout is specified). callback specifies a routine to be called with three arguments: a u_char pointer which is passed in from pcap_dispatch(), a pointer to the pcap_pkthdr struct (which precede the actual network headers and data), and a u_char pointer to the packet data. The number of packets read is returned. Zero is returned when EOF is reached in a ``savefile.'' A return of - indicates an error in which case pcap_perror() or pcap_geterr() may be used to display the error text. 另外的问题是，我们可能对抓取的包包太多而很头痛，可能很多都不是我们感兴趣的包，别急，pcap_compile和pcap_setfilter能帮我们解决问题。 #include <pcap.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netinet/if_ether.h> void my_callback(u_char *useless,const struct pcap_pkthdr* pkthdr,const u_char*
packet)
{
static int count = ;
fprintf(stdout,"%d, ",count);
fflush(stdout);
count++;
} int main(int argc,char **argv)
{
int i;
char *dev;
char errbuf[PCAP_ERRBUF_SIZE];
pcap_t* descr;
const u_char *packet;
struct pcap_pkthdr hdr;
struct ether_header *eptr;
struct bpf_program fp;
bpf_u_int32 maskp;
bpf_u_int32 netp; if(argc != ){ fprintf(stdout,"Usage: %s \"filter program\"\n"
,argv[]);return ;} dev = pcap_lookupdev(errbuf);
if(dev == NULL)
{ fprintf(stderr,"%s\n",errbuf); exit(); } pcap_lookupnet(dev,&netp,&maskp,errbuf); descr = pcap_open_live(dev,BUFSIZ,,-,errbuf);
if(descr == NULL)
{ printf("pcap_open_live(): %s\n",errbuf); exit(); } if(pcap_compile(descr,&fp,argv[],,netp) == -)
{ fprintf(stderr,"Error calling pcap_compile\n"); exit(); } if(pcap_setfilter(descr,&fp) == -)
{ fprintf(stderr,"Error setting filter\n"); exit(); } pcap_loop(descr,-,my_callback,NULL); return ;
} 运行./pcap_4.c "host www.google.com"
然后在另外一个控制台下面ping www.baidu.com
哈哈
没有反应吧
接着再ping www.google.com
就看到1, , , , , ,
ok
you got it!!
#include <stdio.h>
#include <stdlib.h>
#include <pcap.h>
#include <errno.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h> int main(int argc, char **argv)
{
char *dev;
char *net;
char *mask;
int ret;
char errbuf[PCAP_ERRBUF_SIZE];
bpf_u_int32 netp;
bpf_u_int32 maskp;
struct in_addr addr; dev = pcap_lookupdev(errbuf); if(dev == NULL)
{
printf("%s\n",errbuf);
exit();
} printf("DEV: %s\n",dev); ret = pcap_lookupnet(dev,&netp,&maskp,errbuf); if(ret == -)
{
printf("%s\n",errbuf);
exit();
} addr.s_addr = netp;
net = inet_ntoa(addr); if(net == NULL)
{
perror("inet_ntoa");
exit();
} printf("NET: %s\n",net); addr.s_addr = maskp;
mask = inet_ntoa(addr); if(mask == NULL)
{
perror("inet_ntoa");
exit();
} printf("MASK: %s\n",mask); return ;
}
然后gcc -o pcap_1 pcap_1.c -lpcap（一定要-lpcap参数）
编译ok~，执行./pcap_1，可以看到：
DEV: eth0
NET: 192.168.12.0
MASK: 255.255.255.0
好了，第一个pcap程序出炉了。。。。。 但是（当然有但是了，要不然我后面写啥），上面那个程序除了向我们展现pcap_lookupdev和pcap_lookupnet之外什么都没有干，好，我们接着来，动手编写我们的第一个抓包程序。 #include <stdio.h>
#include <stdlib.h>
#include <pcap.h>
#include <errno.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netinet/if_ether.h> int main(int argc, char **argv)
{
int i;
char *dev;
char errbuf[PCAP_ERRBUF_SIZE];
pcap_t* descr;
const u_char *packet;
struct pcap_pkthdr hdr;
struct ether_header *eptr; u_char *ptr; dev = pcap_lookupdev(errbuf); if(dev == NULL)
{
printf("%s\n",errbuf);
exit();
} printf("DEV: %s\n",dev); descr = pcap_open_live(dev,BUFSIZ,1,0,errbuf); if(descr == NULL)
{
printf("pcap_open_live(): %s\n",errbuf);
exit();
} packet = pcap_next(descr,&hdr); if(packet == NULL)
{
printf("Didn't grab packet\n");
exit();
} printf("Grabbed packet of length %d\n",hdr.len);
printf("Recieved at ..... %s\n",ctime((const time_t*)&hdr.ts.tv_sec));
printf("Ethernet address length is %d\n",ETHER_HDR_LEN); eptr = (struct ether_header *) packet; if (ntohs (eptr->ether_type) == ETHERTYPE_IP)
{
printf("Ethernet type hex:%x dec:%d is an IP packet\n",
ntohs(eptr->ether_type),
ntohs(eptr->ether_type));
}else if (ntohs (eptr->ether_type) == ETHERTYPE_ARP)
{
printf("Ethernet type hex:%x dec:%d is an ARP packet\n",
ntohs(eptr->ether_type),
ntohs(eptr->ether_type));
}else {
printf("Ethernet type %x not IP", ntohs(eptr->ether_type));
exit();
} ptr = eptr->ether_dhost;
i = ETHER_ADDR_LEN;
printf(" Destination Address: ");
do{
printf("%s%x",(i == ETHER_ADDR_LEN) ? " " : ":",*ptr++);
}while(--i>);
printf("\n"); ptr = eptr->ether_shost;
i = ETHER_ADDR_LEN;
printf(" Source Address: ");
do{
printf("%s%x",(i == ETHER_ADDR_LEN) ? " " : ":",*ptr++);
}while(--i>);
printf("\n"); return ;
} 好了,编译运行!
[root@norman libpcap]# ./pcap_2
DEV: eth0
Grabbed packet of length
Recieved at time..... Mon Mar :: Ethernet address length is
Ethernet type hex: dec: is an IP packet
Destination Address: :::d1:e8:
Source Address: :a0:cc::c2:
[root@pepe libpcap]# 可能有人等了半天都没有一个包过来，有个好办法，再开一个控制台，ping一下某个网站，比如google~~，呵呵
马上就有反应了~~ 这个程序是一个老外写的，大家看看注释应该没有问题吧~
但是大家也发现了一个问题，就是上面的程序只能捕捉一个包，要不停的捕捉包怎么办，用循环？？libpcap提供了一个更好的方法：
int pcap_loop(pcap_t *p, int cnt, pcap_handler callback, u_char *user);
这个函数能够不停的捕捉以太网的包，cnt就是捕捉的次数，callback是处理函数，这个处理函数怎么写，看看pcap_3.c就知道了。user参数是干什么的？不要问我，我也不知道。 #include <pcap.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netinet/if_ether.h> void my_callback(u_char *useless,const struct pcap_pkthdr* pkthdr,const u_char*
packet)
{
static int count = ;
fprintf(stdout,"%d, ",count);
if(count == )
fprintf(stdout,"Come on baby sayyy you love me!!! ");
if(count == )
fprintf(stdout,"Tiiimmmeesss!! ");
fflush(stdout);
count++;
} int main(int argc,char **argv)
{
int i;
char *dev;
char errbuf[PCAP_ERRBUF_SIZE];
pcap_t* descr;
const u_char *packet;
struct pcap_pkthdr hdr;
struct ether_header *eptr; if(argc != ){ fprintf(stdout,"Usage: %s numpackets\n",argv[]);return ;} dev = pcap_lookupdev(errbuf);
if(dev == NULL)
{ printf("%s\n",errbuf); exit(); } descr = pcap_open_live(dev,BUFSIZ,,-,errbuf);
if(descr == NULL)
{ printf("pcap_open_live(): %s\n",errbuf); exit(); } pcap_loop(descr,atoi(argv[]),my_callback,NULL); fprintf(stdout,"\nDone processing packets... wheew!\n");
return ;
} 运行./pcap_3
, , , , Come on baby sayyy you love me!!! , , , Tiiimmmeesss!!
Done processing packets... wheew! pcap_loop确实很好用,但是如果没有包包过来,只有干等在那里,pcap_dispatch就含有一个超时的功能，下面是man里面的一段话：
pcap_dispatch() is used to collect and process packets. cnt specifies the maximum number of packets to process before returning. A cnt of - processes all the packets received in one buffer. A cnt of processes all packets until an error occurs, EOF is reached, or the read times out (when doing live reads and a non-zero read timeout is specified). callback specifies a routine to be called with three arguments: a u_char pointer which is passed in from pcap_dispatch(), a pointer to the pcap_pkthdr struct (which precede the actual network headers and data), and a u_char pointer to the packet data. The number of packets read is returned. Zero is returned when EOF is reached in a ``savefile.'' A return of - indicates an error in which case pcap_perror() or pcap_geterr() may be used to display the error text. 另外的问题是，我们可能对抓取的包包太多而很头痛，可能很多都不是我们感兴趣的包，别急，pcap_compile和pcap_setfilter能帮我们解决问题。 #include <pcap.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netinet/if_ether.h> void my_callback(u_char *useless,const struct pcap_pkthdr* pkthdr,const u_char*
packet)
{
static int count = ;
fprintf(stdout,"%d, ",count);
fflush(stdout);
count++;
} int main(int argc,char **argv)
{
int i;
char *dev;
char errbuf[PCAP_ERRBUF_SIZE];
pcap_t* descr;
const u_char *packet;
struct pcap_pkthdr hdr;
struct ether_header *eptr;
struct bpf_program fp;
bpf_u_int32 maskp;
bpf_u_int32 netp; if(argc != ){ fprintf(stdout,"Usage: %s \"filter program\"\n"
,argv[]);return ;} dev = pcap_lookupdev(errbuf);
if(dev == NULL)
{ fprintf(stderr,"%s\n",errbuf); exit(); } pcap_lookupnet(dev,&netp,&maskp,errbuf); descr = pcap_open_live(dev,BUFSIZ,,-,errbuf);
if(descr == NULL)
{ printf("pcap_open_live(): %s\n",errbuf); exit(); } if(pcap_compile(descr,&fp,argv[],,netp) == -)
{ fprintf(stderr,"Error calling pcap_compile\n"); exit(); } if(pcap_setfilter(descr,&fp) == -)
{ fprintf(stderr,"Error setting filter\n"); exit(); } pcap_loop(descr,-,my_callback,NULL); return ;
} 运行./pcap_4.c "host www.google.com"
然后在另外一个控制台下面ping www.baidu.com
哈哈
没有反应吧
接着再ping www.google.com
就看到1, , , , , ,
ok
you got it!!