Re: supporting extend 'open live capture' parametes

[Andy Howell <AndyHowell () raitechnology com>]

Abeni Paolo wrote:
> hello,
>
> I assume that the my initial suggestion is going to be dismissed,
> right ?!?
>
> on Thu 1/10/2008 10:47 AM  Guy Harris wrote:
> > There'd also be an API to ask which parameters a particular adapter
> >  supports (and possibly which values it supports for those
> > parameters, e.g. if one of the parameters is a DLT_ type or an
> > 802.11 channel).
>
> I think that a complete solution can be pretty complicated; such
> information could be provided with a buffer filled with TLV items,
> much like the 'extened open live capture' call. Supported values for
> each parameter could be inserted in the corresponding 'value' part of
> each item, putting all the supported values in the same item. A
> possible API could be:
>
> int pcap_get_capabilities(const char* device_name, char* optbuf,
> unsigned size); /* fill optbuf up to size bytes with TLVs and returns
> error code or the number of bytes used */
>
> There is an issue: optbuf can be not large enough to handle all
> supported parameters/values; we can enforce a reasonable upper bound
> for the TLVs buffer or we can use a TLV entry to specify the required
> buffer len.
>
> To completed the picture, in extended open live capture the timeout
> parameter could be provided via the TLV buffer, since is not
> supported by all platform:
>
> int pcap_open_live_ex(const char *device, int snaplen, int promisc,
> const char * optbuf, char *errbuf);
>
> What do you think?
Paolo,

How about having a generic list of options? Something like:

typedef enum {
  END_OF_OPTS,
  PARAM_1,
  PARAM_2,
} pcap_opts;

typedef union {
  void           *p;
  unsigned int   u;
} pcap_opt_value;

typedef struct {
  pcap_opts       option;
  pcap_opt_value  value;
} pcap_opt_item;

int pcap_open_live_ex(const char *device, int snaplen, int promisc,
                      pcap_opt_item *options, char *errbuf);
main()
{
  char *strOpt="blah";
  char errbuf[ PCAP_ERRBUF_SIZE ];

  pcap_opt_item my_opts[] = {
    { PARAM_1, .value.u = 1 },
    { PARAM_2, .value.p = strOpt },
    { END_OF_OPTS  },
  };
  pcap_open_live_ex( "eth0", 0, 0, my_opts, errbuf );
}

The list of options could easily be extended. We would probably want a 
functions that returns the valid options for a device.

Regards,

        Andy
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