[Winpcap-users] Portable way of implementing the reading of several interfaces with Pcap/WinPcap

[Asier Martínez]

Thank you very much for your time Guy, you are always ready to answer this
kind of questions.


2013/5/27 Guy Harris <guy at alum.mit.edu>

>
> On May 27, 2013, at 7:26 AM, Asier Martínez <axierr at gmail.com> wrote:
>
> > I'm trying to achieve a portable way of reading from multiple pcap
> devices in non blocking.
> > As far as I know, on Windows select() function it's nos usable with
> Winpcap because there is no file descriptor for that purposes available
> into the library, and this functionality must be implemented obtain a win32
> HANDLE with pcap_getevent() and wait on it with
> WaitForSingleObject/MultipleObjects(Ex).
>
> That's the correct way to do that on Windows.
>
> > On the other hand, I read on release changelog on Winpcap.org:
> >
> > Version 3.01 alpha
> >       • pcap_fileno returns a valid description also in case of a remote
> capture, so that the'select()' function can be used to check if packets are
> waiting to be read
>
> WinPcap is a port of libpcap to Windows, and shares a lot of code with
> libpcap; the remote capture code can work on UN*X as well as on Windows.
>
> That particular changelog item probably refers to the remote capture code
> on UN*X.
>
> > ¿What is the most portable ( and correct ) approach to read from
> multiple interfaces with winpcap ?
>
> There isn't one.  There's one that works on UN*X (except when it doesn't,
> e.g. BPF only works with select() with newer versions of the various *BSDs
> and OS X, and in some OS versions, the workaround for that doesn't work),
> namely using select(), and and there's one that works on Windows, namely
> WaitFor....
>
> > pcap_fileno returns a valid descriptor or not?
>
> On Windows, it happens to return a HANDLE (assuming a HANDLE fits in an
> int), but it's not necessarily the HANDLE for something on which you can do
> a WaitFor....
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