netstat(1) -s -f is broken

[神明達哉]

At Fri, 4 May 2018 13:19:57 +0300,
"Andrey V. Elsukov" <bu7cher at yandex.ru> wrote:

> > Doesn't work with -p either.
> > netstat -I lo0 -s -p udp
> > :udp: no per-interface stats routine
> >
> > It would be very useful if this actually worked.

> Only IPv6 and ICMPv6 have per-interface statistics counters. Other
> protocols don't have such support.

That's how I remember why per-interface statistics was originally
provided only for IPv6, but RFC4293 extended the concept to IPv4
(interestingly RFC4293 also seems to effectively deprecate
per-interface ICMPv6 statistics).  So it would make sense to make
'-I <ifname> -s -f inet' now works.

The UDP case is totally different - as far as I remember there has
never been per-interface UDP statistics defined in the form of RFC
MIBs, so it's actually reasonable to emit an error against
'-I <ifname> -s -p udp'.

--
JINMEI, Tatuya