Re: [iproute PATCH] tc: u32: Fix key folding in sample option

Jamal,

On Thu, Feb 04, 2021 at 08:19:55AM -0500, Jamal Hadi Salim wrote:

I couldnt tell by inspection if what used to work before continues to.
In particular the kernel version does consider the divisor when folding.

That's correct. And so does tc. What's the matter?

Two examples that currently work, if you can try them:

Both lack information about the used hashkey and divisor.

Most used scheme:
---
tc filter add dev $DEV parent 999:0  protocol ip prio 10 u32 \
ht 2:: \
sample ip protocol 1 0xff match ip src 1.2.3.4/32 flowid 1:10 \
action ok
----

htid before: 0x201000
htid after: 0x201000

and this i also found in one of my scripts:
----
tc filter add dev $DEV parent 999:0  protocol ip prio 10 u32 \
ht 2:: \
sample u32 0x00000806 0x0000ffff at 12 \
match u32 0x00000800 0x0000ff00 at 12 flowid 1:10 \
action ok
----

htid before: 0x20e000 (0x8 ^ 0x6 = 0xe)
htid after: 0x206000

Are you sure this still works with current kernel and iproute2
(excluding my patch)? What divisor and hashkey is used?

Probably a simple meaning of "working" is:
the values before and after (your changes) are consistent.

If also you will do us a kindness and add maybe a testcase in tdc?
This way next person wanting to fix it can run the tests first before
posting a patch.

What is "tdc"?

Cheers, Phil