Re: supporting extend 'open live capture' parametes

["Abeni Paolo" <paolo.abeni () telecomitalia it>]

hi all,

on 2008-01-13 23:33:55 Michael Richardson wrote:
> we should instead have a new pcap_open() call, and then we should
> have a serious of calls that set various options or ask for various
> things based upon that handle

> From a mere implementation POV, this looks like the easier solution. There could be some concerns about:

- the (possibly high) number of new API that need to be added in order to support all required/wanted options for the 
open call
- if we use the pcap struct to store all the supplied options (witch seams a reasonable choice, at least to me) it need 
to be changed/updated every time a new option need to be added. Can this scenario possibly leads to ABI compatibility 
issue ?!?

The first concern can be coped with a generic method to set the required option:

int pcap_set_property(pcap_t *pcap, int type, void* data);

This function should interpret data for known type and copy it's value into the appropriate pcap field. 

    Guy> 2) allow a application to inquire which particular options are
    Guy> available for a particular device, so it could, for example,
    Guy> not present UI for turning on 802.11 monitor mode if it's not

> so maybe you have to have pcap_get_prop() on the pt too.

Something like:

int pcap_get_property(pcap_t *pcap, int type, void* data, int len);

could be implemented with very little platform specific code, if upon complete initialization allowed option/values are 
stored into the pcap handle. 
Moreover, since the caller knows the parameter is requesting, it could be inferred it know also the parameter's size: 
any others APIs to request this information should not be required.

I would like to try to implement the new API this way and post some code, even in very experimental form, in the hope 
to make the discussion/analysis easier (at least to me...). What do you think?

cheers,

Paolo
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