Re: code available: netmap support for libpcap

[Luigi Rizzo <rizzo () iet unipi it>]

On Thu, Feb 27, 2014 at 1:05 PM, Guy Harris <guy () alum mit edu> wrote:

> On Feb 27, 2014, at 12:57 PM, Luigi Rizzo <rizzo () iet unipi it> wrote:
>
> > this can be used to plumb things together.
>
> If you want to plumb things together, do you need libpcap?

the plumbing is done by netmap/vale/netmap pipes.

libpcap is "only" a shim layer that can be used by
tools that only speak libpcap so you do not need
to recompile them.

But it is a crucially important shim layer that
gives you a lot of flexibility.



> > Say you want to interconnect two VMs,
>
> Why would I use libpcap for that?
>
> > or a traffic generator and a firewall/ids/monitor
> > that you want to test for performance, etc.
>
> But wouldn't I create a netmap pipe using something other than libpcap,
> and only use libpcap if I want to watch the traffic on that pipe?
>
> I.e., what would be lost if, for example, libpcap only supported capturing
> on existing netmap devices, and didn't support creating new ones on the fly?

Well you would lose the ability to connect to a
VALE switch or a pipe (which only support dynamically
created endpoints).

Most importantly, you would need additional code to
disable the functionality, because if you look
at the pcap-netmap.c everything is handled in the
nm_open() call.

cheers
luigi



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