Re: [PATCH] udp: increment UDP_MIB_NOPORTS in mcast receive

David Stevens
2012-10-03T14:25:37Z

Eric Dumazet <eric.dumazet@gmail.com> wrote on 10/03/2012 09:15:51 AM:

> So when a host receives an UDP datagram but there was no application
> at the destination port we should increment udpNoPorts, and its not
> an error but just a fact.

Of course. I think our difference is on the definition of
"receives".
I don't think a packet delivered locally due to promiscuous mode,
broadcast
or an imperfect multicast address filter match is a host UDP datagram
receive.
These packets really shouldn't be delivered to UDP at all; they are not
addressed to this host (at least the non-broadcast, no-membership ones).
A unicast UDP packet that doesn't match a local IP address does
not
increment this counter. A promiscuous mode multicast delivery is no
different,
except that the destination alone doesn't tell us if it is for us.

I think counting these will primarily lead to administrators
seeing
non-zero drops and wasting their time trying to track them down.

+-DLS