if_lagg(4) accounting changes

[Alan Somers]

On Sat, Sep 13, 2014 at 5:19 PM, Alexander V. Chernikov
<melifaro at freebsd.org> wrote:
> Hello list.
>
> I'd like to commit some changes to lagg counters which might be worth
> discussion.
>
> Diff is available at https://reviews.freebsd.org/D781
> Quoting its summary:
>
>
> While counting packets using per-cpu counters might not introduce
> any significant overhead at current rates, we do not need to
> do such accounting at all.
>
> lagg in general is pure control-plane interface, its action on
> receive should be just to change packet src if pointer.
> Its action on transmit should be just selecting output interface
> based on flowid.
> It should not generate any errors on its own.
>
> In fact, RX lagg path can be skipped by setting correct ifp inside
> NIC driver. TX path should be handled by generic multipath L2 nexthops
> inside routing code.
>
> This is first step for implementing this scenario.
> One side effect is that we're now collecting all counters (including
> errors) from underlying interfaces. Generally most networking HW vendors
> implement this behavior for their equipment and this is really the
> reasonable thing to do.

Sounds interesting.  I'll give it a thorough review soon, but probably
not today.

-Alan