On 2020-10-19 11:18 a.m., Vlad Buslov wrote:

On Mon 19 Oct 2020 at 16:48, Jamal Hadi Salim [off-list ref] wrote:

quoted

On 2020-10-18 8:16 a.m., Vlad Buslov wrote:

[..]

quoted

That could be a good thing, no? you get to see the action name with the
error. Its really not a big deal if you decide to do a->terse_print()
instead.

Maybe. Just saying that this change would also change user-visible
iproute2 behavior.

You are right(for the non-terse output). tbh, not sure if it is a big
deal given it happens only for the error case (where scripts look
for exit codes typically); having said that:
a ->terse_print() would be ok

It is not a trivial change. To get this data we need to call
tc_action_ops->dump() which puts bunch of other unrelated info in
TCA_OPTIONS nested attr. This hurts both dump size and runtime
performance. Even if we add another argument to dump "terse dump, print
only index", index is still part of larger options structure which
includes at least following fields:

#define tc_gen \
	__u32                 index; \
	__u32                 capab; \
	int                   action; \
	int                   refcnt; \
	int                   bindcnt

index is the _only_ important field for analytics purposes in that list.
i.e if i know the index i can correlate stats with one or more
filters (whether shared or not).
My worry is you have a very specific use case for your hardware or
maybe it is ovs - where counters are uniquely tied to filters and
there is no sharing. And possibly maybe only one counter can be tied
to a filter (was not sure if you could handle more than one action
in the terse from looking at the code).
Our assumptions so far had no such constraints.
Maybe a new TERSE_OPTIONS TLV, and then add an extra flag
to indicate interest in the tlv? Peharps store the stats in it as well.

This wouldn't be much of a terse dump anymore. What prevents user that
needs all action info from calling regular dump? It is not like terse
dump substitutes it or somehow makes it harder to use.

Both scaling and correctness are important. You have the cookie
in the terse dump, thats a lot of data.
In our case we totally bypass filters to reduce the amount of data
crossing to user space (tc action ls). Theres still a lot of data
crossing which we could trim with a terse dump. All we are interested
in are stats. Another alternative is perhaps to introduce the index for
the direct dump.

cheers,
jamal