Sniffer packets x Programming

功用

Used to Sniffer packets. You can specify which kind of packets should be handled.

Library

pcap.a

Example 

void nami_pcap_example_main(char *dev_name_arg )

{

    char *dev_name, errbuf[PCAP_ERRBUF_SIZE];

    bpf_u_int32    net, mask; 

    pcap_t                      *pcap_handler;

    struct bpf_program    pcap_fp;

    struct pcap_pkthdr    header;

    if( dev_name_arg == NULL )

   {

        /* use pcap_lookupdev to get a default device */ 

        dev_name = pcap_lookupdev(errubuf);

        if ( dev_name == NULL ) {    /* error handler */    }

    } else 

    {

        dev_name = dev_name_arg;

    }

    

    /* get the IP and mask of the iface, if net and mask is not required, can skip this step */

    if ( pcap_lookupnet( dev, &net, &mask, errbuf ) < 0 ) {    /* error handler */    }

    /* open a device for capturing */

    pcap_handler = pcap_open_live( dev, /* snaplen: snapshot len */ 1518, 

             /* promisc:  specifies if the interface is to be put into promiscuous mode*/ 1, 

             /* to_ms: the read timeout in milliseconds */ 1000, errbuf );

    if ( pcap_handler == NULL ) {    /* error handler */    }

    if ( pcap_compile( pcap_handler, &pcap_fp, pcap_filter_exp, 0, 

         PCAP_NETMASK_UNKNOWN) < 0 ) {    /* errbuf */    }

    if ( pcap_setfilter( pcap_hander, &pcap_fp ) < 0 ) {    /* error handler */    }

    pcap_loop ( pcap_handler, -1, nami_sniffer_handler, NULL );

    return ;

}

void 

Reference 

http://linux.die.net/man/3/pcap_compile