netdev - Re: [PATCH] udp: increment UDP_MIB

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Date:	Wed, 3 Oct 2012 10:09:51 -0400
From:	David Stevens <dlstevens@...ibm.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	chris2553@...glemail.com, Dave Jones <davej@...hat.com>,
	David Miller <davem@...emloft.net>, gpiez@....de,
	Julian Anastasov <ja@....bg>, netdev@...r.kernel.org,
	netdev-owner@...r.kernel.org
Subject: Re: [PATCH] udp: increment UDP_MIB_NOPORTS in mcast receive

Eric Dumazet <eric.dumazet@...il.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


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