pcap_sniff.c - TCP Packet Sniffing Program (Using libpcap)

/**
 * [pcap_sniff.c]
 *
 * A TCP sniffing program, using raw sockets, @ the sub-Session (5) layer of the OSI model.  It
 * utilizes libpcap to handle raw sockets more accurately.
 *
 * compile with:
 * gcc -o pcap_sniff pcap_sniff.c -l pcap
 */

#include <pcap.h>

#include "hacking.h"


/**
 * The pcap_fatal() function:
 */
void pcap_fatal(const char *failed_in, const char *errBuf)
{
    printf("Fatal error in %s: %s\n", failed_in, errBuf);

    exit(1);
}


/**
 * The main() function:
 */
int main(void)
{
            struct  pcap_pkthdr header;
    const   u_char  *packet;
            char    errBuf[PCAP_ERRBUF_SIZE];
            char    *device;
            pcap_t  *pcap_handle;                                   /* Similar to a file descriptor; referencing a packet-capturing object. */
            int     i;

    /**
     * Find a suitable device to sniff on:
     */
    device = pcap_lookupdev(errBuf);

        if(device == NULL)
            pcap_fatal("pcap_lookupdev", errBuf);

    printf("Sniffing on device %s\n", device);


    /**
     * Open the packet-capturing device:
     */
    pcap_handle = pcap_open_live(device, 4096, 1, 0, errBuf);

        if(pcap_handle == NULL)
            pcap_fatal("pcap_open_live", errBuf);


        /**
         * Capture the (desired) packets (using a packet capture loop):
         */
        for(i = 0; i < 3; i++)
        {
            packet = pcap_next(pcap_handle, &header);

            printf("Got a %d byte packet\n", header.len);
            dump(packet, header.len);
        }


    /**
     * Close the packet capture interface:
     */
    pcap_close(pcap_handle);

    return 0;
}