* We'll send one ICMP ECHO request packet to the target host.
     * If ICMP ECHO REPLY is received, the target is UP.
     * If ICMP HOST UNREACHABLE is received, the target is UNREACHABLE.
     * If the REQUEST timed out, the target is assumed to be OFFLINE.
     */

    /* set the filter */
    pcap_cfg.f_code = ( char * ) malloc( 100 );
    sprintf(pcap_cfg.f_code, "src host %s and dst host %s and icmp\0",
                             libnet_addr2name4( target_ip, LIBNET_DONT_RESOLVE ),
                             libnet_addr2name4( local_ip_addr, LIBNET_DONT_RESOLVE ) );
	
    /* compile the filter */
    if( pcap_compile( pcap_cfg.p, &pcap_cfg.f_program,
                      pcap_cfg.f_code, 1, pcap_cfg.netmask ) == -1 )
    {
        printf("Cannot compile the filter code: %s\n", pcap_geterr( pcap_cfg.p ) );
        pcap_close( pcap_cfg.p );
        exit( EXIT_FAILURE );
    }
    free( pcap_cfg.f_code );

    /* Set the filter program on the interface */
    dps_set_filter( pcap_cfg.f_program );

    /* build the ICMP ECHO REQUEST packet */
    dps_build_icmp( local_ip_addr, target_ip, local_eth_addr, remote_eth );

    /* write the packet */
    dps_write_packet();

    /* listen for the response */
    start_time = time( NULL );

    while( start_time + PING_TIMEOUT > time( NULL ) )
    {
        rcv_packet = ( u_int8_t * ) pcap_next( pcap_cfg.p, &header );
        if( rcv_packet == NULL || rcv_packet == 0 )
            continue;

        ip_hl = ( rcv_packet[ LIBNET_ETH_H ] & 0X0F ) << 0X02;

        icmp = ( struct libnet_icmp_hdr * ) ( rcv_packet + LIBNET_ETH_H + ip_hl );
		
        if( icmp->icmp_type != ICMP_ECHOREPLY || icmp->icmp_code != 0 )
            continue;

        if( ntohs( icmp->icmp_id ) != 0X2233 || ntohs( icmp->icmp_seq ) != 0X5544 )
            continue;

        return 1;
    }

    /* the host is not PINGable */
    return 0;
}

void dps_build_icmp( u_int32_t src_ip, u_int32_t dst_ip,
                     u_int8_t *src_eth, u_int8_t *dst_eth )
{
    libnet_cfg.icmp = libnet_build_icmpv4_echo(
                       ICMP_ECHO,     /* ICMP type */
                       0,             /* ICMP code */
                       0,             /* checksum */
                       0X2233,        /* Identification (arbitrary) */
                       0X5544,        /* ICMP ECHO sequence number (arbitrary) */
                       NULL,          /* optional payload */
                       0,             /* payload size */
                       libnet_cfg.l,  /* libnet handle */
                       0              /* libnet protocol tag */
                       );
    if( libnet_cfg.icmp == -1 )
    {
        printf("Cannot build ICMP ECHO header\n");
        exit( EXIT_FAILURE );
    }

    libnet_cfg.ip = libnet_build_ipv4(
                     ICMPIP_LEN,
                     TOS,
                     ID,
                     0,
                     TTL,
                     IPPROTO_ICMP,
                     0,
                     src_ip,
                     dst_ip,
                     NULL,
                     0,
                     libnet_cfg.l,
                     0
                     );
    if( libnet_cfg.ip == -1 )
    {
        printf("Cannot build IP header\n");
        exit( EXIT_FAILURE );
    }

    libnet_cfg.eth = libnet_build_ethernet(
                      dst_eth,       /* Ethernet destinatin address */
                      src_eth,       /* Ethernet source address */
                      ETHERTYPE_IP,  /* protocol type */
                      NULL,          /* optional payload */
                      0,             /* payload size */
                      libnet_cfg.l,  /* libnet handle */
                      0              /* libnet protocol tag */
                      );
    if( libnet_cfg.eth == -1 )
    {
        printf("Cannot build Ethernet header\n");
        exit( EXIT_FAILURE );
    }
}

void dps_write_packet()
{
    int c;

    /* inject the packet in libnet_cfg.l */
    c = libnet_write( libnet_cfg.l );

    if( c == -1 )
    {
        printf("Cannot write packet\n");
        exit( EXIT_FAILURE );
    }

    /* clear the packet */
    libnet_clear_packet( libnet_cfg.l );
}

void dps_set_filter( struct bpf_program program )
{
    int c;

    /* Setting the filter */
    c = pcap_setfilter( pcap_cfg.p, &program );

    if( c == -1 )
    {
        printf("Cannot set the filter\n");
        pcap_close( pcap_cfg.p );
        exit( EXIT_FAILURE );
    }
}

void dps_print()
{
    int i;
    struct port_data *ptr;

    printf("=========================== SCAN RESULT ===========================\n");
    printf("Scanned Host: %s ", libnet_addr2name4( target_ip, LIBNET_DONT_RESOLVE ) );
    if( cfg.resolve )
        printf("(%s)", libnet_addr2name4( target_ip, LIBNET_RESOLVE ) );
    printf("\n");
    printf("Scan Type: %s\n", scan_type_str );
    printf("Total Scan Time: %d seconds\n", scan_time );
    printf("Number of scanned ports: %d\n", result.counter);
    printf("    { ");
    if( result.open )          printf("[open %d] ", result.open);
    if( result.closed )        printf("[closed %d] ", result.closed);
    if( result.filtered )      printf("[filtered %d] ", result.filtered);
    if( result.unfiltered )    printf("[unfiltered %d] ", result.unfiltered);
    if( result.open_filtered ) printf("[open|filtered %d]", result.open_filtered);
    printf(" }\n\n");
    if( !cfg.windows )
    {
        printf(" ----   ------        -------      ---------------\n");
        printf(" port   status        service      used spoofed IP\n");
        printf(" ----   ------        -------      ---------------\n");
    }
    else
    {
        printf(" ----   ------------- -----------   -------     ---------------\n");
        printf(" port   status(linux) status(win)   service     used spoofed IP\n");
        printf(" ----   ------------- -----------   -------     ---------------\n");
    }
    ptr = result.data;

    for( i = 0; i < result.counter; i++ )
    {
        printf(" %-7d", ptr->port );
        switch( ptr->status )
        {
            case PORT_OPEN:
                printf("%-14s", "open" );
                break;
            case PORT_CLOSED:
                printf("%-14s", "closed" );
                break;
            case PORT_FILTERED:
                printf("%-14s", "filtered" );
                break;
            case PORT_UNFILTERED:
                printf("%-14s", "unfiltered" );
                break;
            case PORT_OPEN + PORT_FILTERED:
                printf("%-14s", "open|filtered" );
                break;
        }
        if( cfg.windows )
        {
            switch( ptr->status_win )
            {
                case PORT_OPEN:
                    printf("%-14s", "open" );
                    break;
                case PORT_CLOSED:
                    printf("%-14s", "closed" );
                    break;
                case PORT_FILTERED:
                    printf("%-14s", "filtered" );
                    break;
                case PORT_UNFILTERED:
                    printf("%-14s", "unfiltered" );
                    break;
                case PORT_OPEN + PORT_CLOSED:
                    printf("%-14s", "open|closed" );
                    break;
                case PORT_OPEN + PORT_FILTERED:
                    printf("%-14s", "open|filtered" );
                    break;
            }
        }
        printf("%-12s", b_search( ptr->port ) );
        printf("%s ", libnet_addr2name4( ptr->spoofed_ip, LIBNET_DONT_RESOLVE ) );
        if( cfg.resolve )
            printf("(%s)", libnet_addr2name4( ptr->spoofed_ip, LIBNET_RESOLVE) );
        printf("\n");
        ptr = ptr->next;
    }
}

void dps_cleanup()
{
    struct port_data *ptr1;
    struct port_data *ptr2;

    /* free dynamically allocated pointers */
    if( cfg.scan_type )    free( cfg.scan_type );
    if( cfg.port_list )    free( cfg.port_list );
    if( cfg.source_ports ) free( cfg.source_ports );
    if( cfg.source_ips )   free( cfg.source_ips );
    if( cfg.target_ips )   free( cfg.target_ips );
    if( local_eth_addr )   free( local_eth_addr );
    if( remote_eth )       free( remote_eth );

    /* Free the Linked-List */
    ptr1 = result.data;
    while( ptr1 != NULL )
    {
        ptr2 = ptr1;
        ptr1 = ptr1->next;
        free( ptr2 );
    }

    /* Shutdown Libpcap and Libnet */
    pcap_close( pcap_cfg.p );
	libnet_plist_chain_free( libnet_cfg.plist );
    libnet_destroy( libnet_cfg.l );
}

int dps_catch_signal( int signo, void( *handler )() )
{
    struct sigaction action;

    /* set the action struct */
    action.sa_handler = handler;
    sigemptyset( &action.sa_mask );
    action.sa_flags = 0;

    /* assign the action to the signal */
    if( sigaction( signo, &action, NULL ) == -1 )
        return -1;
    else
        return 1;
}

void dps_signal_handler()
{
    /* signal is cought! */
    printf("Signal cought.. Shutting Down...\n");
    /* print whatever results there are */
    dps_print();

    /* cleanup before exiting */
    dps_cleanup();
}

void dps_usage( char *cmd )
{
    printf(
        "============================================================\n"
        BANNER "\n"
        COPYRIGHT "\n"
        "============================================================\n"
        "Usage:\n"
        "%s [options] hostname | ip\n"
        "options:\n"
        "  -t          Scan Type: (default: S)\n"
        "               N  NULL Scan    F  FIN Scan    S  SYN Scan\n"
        "               P  PSH Scan     A  ACK Scan    U  URG Scan\n"
        "               X  XMAS Scan    X1 XMAS2 Scan  X2 XMAS2 Scan\n"
        "               X3 XMAS3 Scan   U  UDP Scan\n"
        "  -p <ports>  Port list to scan (default: 1-1024)\n"
        "  -i <device> Device to use (optional)\n"
        "  -T <secs>   Scan time-out in seconds (default: 1 sec)\n"
        "  -P <no>     PINGing option: (default: 1)\n"
        "               0  DONT PING   1  PING\n"
        "  -d          Do NOT resolve hostname or lookup IP address\n"
        "  -w          Show port status if the scanned host is Windows\n"
        "  -h          Help (this menu)\n"
        "  -v[v]       Verbosity\n",
        cmd
        );
}

/* EOF */