Adding Flow Director sysctls to ixgbe(4)

[Ben Hutchings]

On Thu, 2011-09-08 at 11:06 -0400, John Baldwin wrote:
> On Thursday, September 08, 2011 10:48:25 am K. Macy wrote:
> > On Thu, Sep 8, 2011 at 2:34 PM, John Baldwin <jhb at freebsd.org> wrote:
> > > On Monday, September 05, 2011 7:21:12 am Ben Hutchings wrote:
> > >> On Mon, 2011-09-05 at 15:51 +0900, Takuya ASADA wrote:
> > >> > Hi,
> > >> >
> > >> > I implemented Ethernet Flow Director sysctls to ixgbe(4), here's a detail:
> > >> >
> > >> > - Adding removing signature filter
> > >> > On linux version of ixgbe driver, it has ability to set/remove perfect
> > >> > filter from userland using ethtool command.
> > >> > I implemented similar feature, but on sysctl, and not perfect filter
> > >> > but signature filter(which means hash collision may occurs).
> > >> [...]
> > >>
> > >> Linux also has a generic interface to RX filtering and hashing
> > >> (ethtool_rxnfc) which ixgbe supports; wouldn't it be better for FreeBSD
> > >> to support something like that?
> > >
> > > Some sort of shared interface might be nice.  The cxgb(4) and cxgbe(4) drivers
> > > both provide their own tools to manipulate filters, though they do not
> > > provide explicit steering IIRC.
> > >
> > > We would need to come up with some sort of standard interface (ioctls?) for
> > > adding filters however.
> > 
> > I know this must sound like nitpicking, but please don't add more
> > ioctls if you can avoid it. If you want to add new interfaces try to
> > stick with sysctl as it tends to be less prone to breakage across
> > releases.
> 
> Passing strings in via sysctls isn't an ideal interface.  Passing in some sort
> of structure via ioctl would be far more typical, and it is possible to provide
> API compat since the size of the structure is encoded in the ioctl itself.

Whatever the mechanism is, the interface should allow for:

- Flexible matching on layer 2, 3 and 4 header fields
- Masking out some bits before matching (e.g. ignoring priority bits of
  VLAN tag or least significant bits of IPv4 address)
- Priority of rules in case several match a single flow.  This may
  need to be combined with location, since in a TCAM location may
  determine priority.
- Requesting packets to be dropped, steered to a single RX queue, or
  steered to a range of RX queues (using a flow hash and indirection
  table)
- Use of multiple hash indirection tables

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.