和我一起学libpcap(2)

2.2 现在的程序(C++)

文件名p.cxx

#ifdef __cplusplus
extern ""C"" {
#endif
#include
#ifdef __cplusplus
}
#endif

void printer(u_char * user, const struct pcap_pkthdr * h, const u_char * p)
{
printf(""I get one packet! "");
/* 哈哈,我都想喝一杯庆祝一下了! */
}

#define DEFAULT_SNAPLEN 68
/* 别问我为什么是68,我从tcpdump看来的 */

int main()
{
char ebuf[PCAP_ERRBUF_SIZE];
char *device = pcap_lookupdev(ebuf);

bpf_u_int32 localnet, netmask;
pcap_lookupnet(device, &localnet, &netmask, ebuf);
printf(""%u.%u.%u.%u"", localnet&0xff, localnet>>8&0xff,
localnet>>16&0xff, localnet>>24&0xff);
printf("":%d.%d.%d.%d "", netmask&0xff, netmask>>8&0xff,
netmask>>16&0xff, netmask>>24&0xff);

struct pcap_t *pd = pcap_open_live(device, DEFAULT_SNAPLEN, 0, 1000, ebuf);

if(pcap_datalink(pd) == DLT_EN10MB)
printf(""10Mb以太网 "");

struct bpf_program fcode;
pcap_compile(pd, &fcode, NULL, 1, 0);

pcap_setfilter(pd, &fcode);

pcap_loop(pd, 10, printer, NULL);

struct pcap_stat stat;
pcap_stats(pd, &stat);
printf(""recv %d, drop %d. "", stat.ps_recv, stat.ps_drop);

pcap_close(pd);
}

#gcc p.cxx -lpcap
#./a.out
166.111.168.0:255.255.252.0
10Mb以太网
I get one packet!
I get one packet!
I get one packet!
I get one packet!
I get one packet!
I get one packet!
I get one packet!
I get one packet!
I get one packet!
I get one packet!
recv 10, drop 0.
#

重要提示: libpcap 程序需要root权限

费了半天劲显示网段和掩码,抓了10个包,值得吗?