Re: Port mirroring (RFC)

On Tue, Dec 14, 2021 at 08:47:12AM -0600, Alex Elder wrote:

I am implementing what amounts to port mirroring functionality
for the IPA driver.

The IPA hardware isn't exactly a network switch (it's sort of
more than that), but it has the ability to supply replicas of
packets transferred within it to a special (read only) interface.

I think you need to explain "within it" in a bit more detail. Where
are these packets coming from/going to?

My plan is to implement this using a new "ipa_mirror" network
device, so it could be used with a raw socket to capture the
arriving packets.  There currently exists one other netdev,
which represents access through a modem to a WWAN network.

I would like some advice on how to proceed with this.  I want
the result to match "best practice" upstream, and would like
this to be as well integrated possible with existing network
tools.

A few details about the stream of packets that arrive on
this hardware interface:
- Packet data is truncated if it's larger than a certain size
- Each packet is preceded by a fixed-size header describing it
- Packets (and their headers) are aggregated into a buffer; i.e.
  a single receive might carry a dozen (truncated) packets

So this sounds something more like what you would attach pcap/tcpdump
to.  I'm not sure port mirroring is the correct model here. Maybe take
a look at wifi adaptors and their monitor mode? See if that fits
better?
 
	Andrew