Re: [PATCH] net: Linn Ethernet Packet Sniffer driver

[Daniel Borkmann]

Hi Stathis,

On 01/27/2015 12:15 PM, Stathis Voukelatos wrote:
> On 26/01/15 10:10, Daniel Borkmann wrote:
> > > Hello Daniel. Thank you for your feedback.
> > > Packet sockets could also be used for the driver interface to
> > > user space, however I think that both approaches would require the same
> > > amount of maintenance. We need to maintain a protocol consisting of
> > > a set of messages or commands that user space can use to communicate
> > > with the driver in order to configure the H/W and retrieve results.
> > > We could use packet sockets to send those messages  too, but I thought
> > > netlink already provides a message exchange framework that we could
> > > make use of.
> >
> > When using packet sockets and your driver as a backend feeding them,
> > users can see that there's an extra capturing/monitoring netdev present,
> > all libpcap-based tools such as tcpdump et al would work out of the box
> > w/o adapting any code, and as an admin you can also see what users/tools
> > are making of use of the device through packet sockets. I couldn't parse
> > the exact motivation from the commit message of why avoiding all this is
> > better?
>
> Just wanted to clarify some implementation details for your approach.
> - The driver would need to create and register two net_device instances.
> One for sniffing Ethernet TX packets and one for RX.

Hm, I would represent the whole device as a single monitoring-only netdev.
I'm somehow still missing the big advantage of all this as compared to
using packet sockets on the normal netdev? I couldn't parse that from your
commit message.

> - Would the control interface for the sniffer in that case need to be
> through private socket ioctls (ie SIOCDEVPRIVATE + x ioctl ids)?

Nope, please have a look at Documentation/networking/packet_mmap.txt.
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