RE: [E1000-devel] [PATCH 1/2] if_link: Add VF multicast promiscuous mode control

[David Laight]

From: Hiroshi Shimamoto
> My concern is what is the real issue that VF multicast promiscuous mode can cause.
> I think there is the 4k entries to filter multicast address, and the current ixgbe/ixgbevf
> can turn all bits on from VM. That is almost same as enabling multicast promiscuous mode.
> I mean that we can receive all multicast addresses by an onerous operation in untrusted VM.
> I think we should clarify what is real security issue in this context.

If you are worried about passing un-enabled multicasts to users then
what about doing a software hash of received multicasts and checking
against an actual list of multicasts enabled for that hash entry.
Under normal conditions there is likely to be only a single address to check.

It may (or may not) be best to use the same hash as any hashing hardware
filter uses.

	David