On Sat, Feb 26, 2011 at 4:07 PM, David Miller [off-list ref] wrote:

From: Alexander Duyck <redacted>
Date: Fri, 25 Feb 2011 16:40:13 -0800

quoted

It cannot occur with any of the in-kernel drivers since they all set
the NETIF_F_NTUPLE flag and have the function defined.  However going
forward I would like to have the option of using the network flow
classifier interface instead of the set_rx_ntuple interface due to the
fact that it supports many of the features I needed.

This still doesn't explain to me why a driver would set the feature
flag, but not actually implement the feature.

Actually the reason I ran into this is because of the patches in the
RFC set.  Basically I was looking at moving the ntuple support in
ixgbe over to network flow classifier rules.  As such I was leaving
the ntuple flag set, but using set_rxnfc via the filter rules instead.
 If you recommend adding a new flag to do that I am fine with that.

I'm not applying this patch.

When you create the situation that causes the potentially NULL
dereference, then you can use that patch to show why this seemingly
illogical situation can indeed occur.

Until then no driver causes this issue, therefore the problem does
not exist.

I'll do some digging late next week to see if there are any other
means of encountering the issue and will get back to you if I find
anything.

Thanks,

Alex