Re: capturing on both interfaces simultaneously

[abhinav narain <abhinavnarain10 () gmail com>]

I used the FD_IFSET() way to fnd out the descriptor.
I have an issue,
For few time dispatch works fine, but after I write the stats to a file,
and the loop returns to phy0, the programs quits with switch condition of
-1.

I don't  see why ? I have the pcap{0,1} to non blocking. But this does not
work after sometime and I have an error displayed

: Interrupted system call


Abhinav
On Sun, Dec 11, 2011 at 3:21 AM, Guy Harris <guy () alum mit edu> wrote:

> On Dec 10, 2011, at 11:58 PM, Cedric Cellier wrote:
>
> > > I got it to work.
> > (...)
> > > > default:           /* We got traffic */
> > > > pcap_dispatch(pcap0,-1, (void *) packet_callback, NULL);
> > > > pcap_dispatch(pcap1,-1, (void *) packet_callback2, NULL);
> >
> > So that other may benefit from it in the future, I
> > guess your fixed version looks like:
> >
> > default:
> >  if (t==pcap0) pcap_dispatch(pcap0,...)
> >  else if (t==pcap1) pcap_dispatch(pcap1,...)
>
> I would not guess that, because select() returns a count of the number of
> descriptors that are ready to read - it does not return one of the
> descriptors that are ready to read - and because pcap0 and pcap1 are
> pointers to pcap_t structures, not descriptors.
>
> The right way to do this is
>
>  pcap0 = pcap_open_live(device0, BUFSIZ, 1, -1, errbuf);
>   if (pcap0 == NULL)
>    /* report failure */
>   pcap1 = pcap_open_live(device1, BUFSIZ, 1, -1, errbuf);
>   if (pcap1 == NULL)
>    /* report failure */
>  /*
>   * If this is being built with a version of libpcap that doesn't
>   * include pcap_get_selectable_fd(), use pcap_fileno(), but be
>   * prepared to be surprised if the devices don't happen to be
>   * selectable or if you're running on Windows.
>   */
>  pcapfd0 = pcap_get_selectable_fd(pcap0);
>  if (pcapfd0 == -1)
>    /* fail with an indication that you can't select on device0 */
>  pcapfd1 = pcap_get_selectable_fd(pcap1);
>  if (pcapfd1 == -1)
>    /* fail with an indication that you can't select on device1 */
>
>  for(;;)
>    {
>
>    /* If you include STDIN_FILENO, be sure to read from it when you get
>       traffic from it, or select will return every time it is called,
>       since there will still be traffic waiting there.
>    */
>
>    FD_ZERO(&fd_wait);
>    //FD_SET(STDIN_FILENO, &fd_wait);
>     FD_SET(pcapfd0, &fd_wait);
>    FD_SET(pcapfd1, &fd_wait);
>
>    st.tv_sec  = 1;
>    st.tv_usec = 0;   /* 1000 = 1 second */
>
>    t=select(FD_SETSIZE, &fd_wait, NULL, NULL, &st);
>    printf("t is %d\n",t);
>    switch(t)
>      {
>      case -1:      /* Something went really wrong */
>         printf("select failed: %s\n", strerror(errno));
>         exit(1);
>
>      case  0:      /* We timed out, no trafffic */
>        printf( " Time out ! \n");
>        break;
>
>       default:      /* We got traffic */
>         //if (FD_ISSET(STDIN_FILENO, &fd_wait))
>        //  process information from the standard input
>        if (FD_ISSET(pcapfd0, &fd_wait))
>          {
>          if (pcap_dispatch(pcap0,-1, (void *) packet_callback, NULL) == -1)
>            /* report an error processing packets from device0 */
>          }
>        if (FD_ISSET(pcapfd1, &fd_wait))
>          {
>          if (pcap_dispatch(pcap1,-1, (void *) packet_callback2, NULL) ==
> -1)
>            /* report an error processing packets from device0 */
>           }
>      }
>    }
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