Problem capturing packets over the LAN using ICAP

[theumer]

Hi. I'm having a problem in my code to capture packets over the LAN using ICAP library. Apparently there doesn't seem to be any problem, but whenever I run the code, it gives to list of the devices (which is indeed required) but when I enter the device number, it says: "Segmentation fault". I don't understand what's the problem. Can anyone help? Here's the code:

int main(int argc, char **argv)
{
     
    char errbuf[PCAP_ERRBUF_SIZE];
    pcap_t* descr;
    const u_char *packet;
    struct pcap_pkthdr hdr;     /* pcap.h */
    struct ether_header *eptr;  /* net/ethernet.h */

    u_char *ptr; /* printing out hardware header info */

    /* grab a device to peak into... */
   /* dev = pcap_lookupdev(errbuf);

    if(dev == NULL)
    {
        printf("%s\n",errbuf);
        exit(1);
    }

    printf("DEV: %s\n",dev);*/

///////////////////////////////////////////////////////////////////////////////////////////////////////////



        pcap_if_t *alldevs;

        pcap_if_t *d;

        int i=0;


        pcap_t * fp;

       if (pcap_findalldevs(&alldevs, errbuf) == -1)

        {

                cout<<"Error in pcap_findalldevs "<<errbuf;

                exit(1);

        }

        /* Print the list */

        for(d= alldevs; d != NULL; d= d->next)

        {

                cout<<++i<<" "<<d->name;

                if (d->description)

                cout<<d->description<<endl;

                else

                cout<< "(No description available)\n";

        }

        if (i == 0)

        {

                cout<<"\nNo interfaces found! Make sure Pcap is installed.\n";

                return 1;

        }

       cout<<"Enter the interface number"<< (1-i);        

        int inum;

        cin>>inum;

        if(inum < 1 || inum > i)

        {

                cout<<"\nInterface number out of range.\n";


                // Free the device list /

                pcap_freealldevs(alldevs);

                return 1;

        }
	char *dev=d->name;

////////////////////////////////////////////////////////////////////////////////////////////////////


	cout<<"adada"<<endl;
    descr = pcap_open_live(dev,65536,1,0,errbuf);

    if(descr == NULL)
    {
      printf("pcap_open_live(): %s\n",errbuf);
      exit(1);
    }
	      
       struct pcap_pkthdr;                                 

       packet = pcap_next(descr,&hdr);

    if(packet == NULL)
    {
        printf("Didn't grab packet\n");
        exit(1);
    }


    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(1);
    }

    ptr = eptr->ether_dhost;
    i = ETHER_ADDR_LEN;
    printf(" Destination Address:  ");
    do{
        printf("%s%x",(i == ETHER_ADDR_LEN) ? " " : ":",*ptr++);
    }while(--i>0);
    printf("\n");

    ptr = eptr->ether_shost;
    i = ETHER_ADDR_LEN;
    printf(" Source Address:  ");
    do{
        printf("%s%x",(i == ETHER_ADDR_LEN) ? " " : ":",*ptr++);
    }while(--i>0);
    printf("\n");
    return 0;
}

[dE_logics]

I'm not sure what's your actual motive, but there're lots of applications available which allow you to do that. For e.g. hping which uses tcl for it's API -


while {1} {
puts [hping recv eth0]
}