[c-prog] Re: help with packet tracer

[John Matthews]

--- In c-prog@yahoogroups.com, "Tyler Littlefield" <ty...@...> wrote:
>
> I give it -c 5. The destination and source ports aren't valid.

I give it these arguments (running as root) and I get:

compiling
applying
creating loop

although it doesn't appear to do anything after that. Is that
different to what you get?

Tidied up code below.

int main(int argc, char* argv[])
{
    //check arg length:
    if (argc <=1)
    {
        PrintErr("You must provide an argument.");
        help(argv[0]);
        exit(EXIT_FAILURE);
    }

    char* dev = NULL;             //the device pointer
    char ebuff[PCAP_ERRBUF_SIZE]; //the error buffer
    bpf_u_int32 net_addr;         //the network address
    bpf_u_int32 mask_addr;        //network mask.
    in_addr addr;                 //used for translating addresses.
    int i = 0;                    //used for loops.
    string temp;                  //our temporary string.
    int loop = 0;                 //how many times will we loop?
    int wait = 1;                 //how long should we wait?
    pcap_t* handle;
    bool stop = true;             //should we continue after the arg
parsing?
    char filter[] = "port 22";    //our default filter
    bpf_program prog;             //used for applying the filter.
    
    //get the device name:
    if (!(dev = pcap_lookupdev(ebuff)))
    {
        PrintErr(ebuff);
        exit(EXIT_FAILURE);
    }

    //get the subnet mask and network mask:
    if ((pcap_lookupnet(dev, &net_addr, &mask_addr, ebuff)) == -1)
    {
        PrintErr(ebuff);
        exit(EXIT_FAILURE);
    }

    //loop through args:
    for (i = 1; i < argc; i++)
    {
        if ((temp = argv[i]) == "-i")
        {
            cout << "Interface: " << dev << endl; //print the
interface name
            addr.s_addr = mask_addr;
            cout << "Network mask: " << inet_ntoa(addr) << endl;
            addr.s_addr = net_addr;
            cout << "Network address: " << inet_ntoa(addr) << endl;
        }
        else if (temp == "-v")
        {
            version(argv[0]);
        }
        else if (temp=="-c") //the number of packets to capture:
        {
            if (argc == i)
            {
                PrintErr("-c takes an argument.");
                help(argv[0]);
                exit(EXIT_FAILURE);
            }

            loop = atoi(argv[i+1]);
            stop = false;
        }
    }

    //make sure we're not needlessly continuing.
    if (stop)
    {
        exit(EXIT_SUCCESS);
    }

    //here we open the device.
    //we'll set promisc to 0 so that this can be ran on non-root systems.
    if (!(handle = pcap_open_live(dev, BUFSIZ, 0, wait, ebuff)))
    {
        PrintErr(ebuff);
        exit(EXIT_FAILURE);
    }

    //now we "compile" our filter:
    cout << "compiling" << endl;

    if (pcap_compile(handle, &prog, filter, 1, net_addr) == -1)
    {
        PrintErr("Filter compilation error!");
        exit(EXIT_FAILURE);
    }

    //now we apply the filter:
    cout << "applying" << endl;

    if (pcap_setfilter(handle, &prog) == -1)
    {
        PrintErr("Error in applying filter!");
        exit(EXIT_FAILURE);
    }

    cout << "creating loop" << endl;

    pcap_loop(handle, loop, capt_h, NULL);
    pcap_close(handle);

    return 0;
}