Re: [ethtool PATCH 2/2] Add RX packet classification interface

On Mon, 2011-03-07 at 10:22 -0800, Dimitris Michailidis wrote:

Ben Hutchings wrote:

quoted

On Mon, 2011-03-07 at 09:04 -0800, Alexander Duyck wrote:

quoted

The only time where location really matters is if you are attempting to 
overwrite an existing rule and I am not sure how that would be handled 
in ntuple anyway since right now adding additional rules via ntuple for 
ixgbe just results in duplicate rules being defined.

As I understand it, the location also determines the *priority* for the
rule.

This is true, at least for TCAMs.  But it's relevant only when multiple 
filters would match a packet.  People often use non-overlapping filters, for 
these adding the filter at any available slot is OK.

Right.  But ethtool would have to determine that the filter was non-
overlapping, before ignoring the location.  Also it cannot allow
deletion by location if it ever ignores the location on insertion.  We
should make the location optional at both the command-line and API
level, but never ignore it.

quoted

Which is why I wrote that "@fs.@location specifies the index to
use and must not be ignored."

To support hardware where the filter table is hash-based rather than a
TCAM, we would need some kind of flag or special value of location that
means 'wherever'.

I'd find the 'wherever' option useful for TCAMs too.  Maybe even have a few 
of those, like 'first available', 'any', and 'last available'.  The last one 
is quite useful for catch-all rules without requiring one to know the TCAM size.

Agreed.

Ben.

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