[Xorp-users] Multiple xorp instances performance improvements.

[Pavlin Radoslavov]

Ben Greear <greearb at candelatech.com> wrote:

> Pavlin Radoslavov wrote:
> 
> > I don't think you can apply BPF filters on raw IP sockets.

Sorry, I should have clarified that I was thinking within the pcap(3)
framework which internally might be using BPF (depends on the
system).

> Just FYI, it appears that we *can* apply filters to IP and other
> sockets, at least on Linux, so I'm adding this to my Xorp TODO list.

For portability reasons we are using pcap(3) (for I/O purpose)
instead of the OS-specific BPF.
With the PCAP API you get a pcap handler when you use, say,
pcap_open_live(). Then all pcap operations are with that handler.
If you need a file descriptor associated with that pcap handler,
then you use the apprpriate pcap_*() function.
Said that, it is pcap itself that gives you the file descriptor
hence you cannot apply it on pre-existing socket.

Indeed, in your case you wanted to use BPF for different purpose:
filtering incoming packets.
Again, I am yet to be convinced that this is the bottleneck and is
worth the extra complexity, so I wouldn't have it too high on the
TODO list.

Thanks,
Pavlin

> Thanks,
> Ben
> 
> -- 
> Ben Greear <greearb at candelatech.com>
> Candela Technologies Inc  http://www.candelatech.com
> 
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