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

[Stathis Voukelatos]

On 23/01/15 11:20, Daniel Borkmann wrote:
> On 01/23/2015 11:07 AM, Stathis Voukelatos wrote:
> > This patch adds support the Ethernet Packet Sniffer H/W module
> > developed by Linn Products Ltd and found in the IMG Pistachio SoC.
> > The module allows Ethernet packets to be parsed, matched against
> > a user-defined pattern and timestamped. It sits between a 100M
> > Ethernet MAC and PHY and is completely passive with respect to
> > Ethernet frames.
> >
> > Matched packet bytes and timestamp values are returned through a
> > FIFO. Timestamps are provided to the module through an externally
> > generated Gray-encoded counter.
> >
> > The command pattern for packet matching is stored in module RAM
> > and consists of a sequence of 16-bit entries. Each entry includes
> > an 8-bit command code and and 8-bit data value. Valid command
> > codes are:
> > 0 - Don't care
> > 1 - Match: packet data must match command string byte
> > 2 - Copy: packet data will be copied to FIFO
> > 3 - Match/Stamp: if packet data matches string byte, a timestamp
> >                    is copied into the FIFO
> > 4 - Copy/Done: packet data will be copied into the FIFO.
> >                  This command terminates the command string.
> >
> > The driver consists of two modules:
> > - Core: it provides an API to user space using the Generic Netlink
> >           framework. Specific backend implementations, like the
> >           Ethernet Packet Sniffer, register one or more channels
> >           with the Core. For each channel a Genl family is created.
> >           User space can access a channel by sending Genl messages
> >           to the Genl family associated with the channel. Packet
> >           matching events are multicast.
> >
> > - Ethernet Packet Sniffer backend: provides the driver for the
> >           Linn Ethernet Packet Sniffer H/W modules.
> >
> > The split between a core and backend modules allows software-only
> > implementations to be added for platforms where no H/W support
> > is available.
> >
> > Based on 3.19-rc5
> >
> > Signed-off-by: Stathis Voukelatos <stathis.voukelatos@xxxxxxxxxx>
> Please have a look at packet sockets, they offer already all the
> functionality (if not more) your driver interface to the user space
> resembles, are transparent to the underlying hardware, and easily
> can cope with 100Mbit.
>
> If I understand this correctly, you are effectively introducing a
> parallel API *next* to packet sockets to user space that we have to
> maintain forever ...
>
> Thanks !

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.

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