[ovs-discuss] IGMP fields added to the flow structure causes problem?

Tony van der Peet Tony.vanderPeet at alliedtelesis.co.nz
Fri Apr 24 19:14:09 UTC 2015

Just to get dates in order:

Jun/2014 - deliveries to master branch that introduce IGMP fields to flow structure
Sep/2014 - we update from tip of master
Apr/2014 - I notice this potential issue

I am running a simple ryu application (using code from https://github.com/samrussell/nss) and connecting my desktop PC to our main LAN. Flows with multicast addresses appear to come and go, but I suspect it's IGMPv3 Membership Reports (type 0x22) that are causing flows to be created that then persist.

In this application at least, matching is done purely on source and destination MAC, so the existence of these flows is probably not that much of a problem since the flows will cover many other packets that aren't Membership reports. It's not really that surprising that this might not be noticed since the switch is behaving perfectly normally and acceptably.

To your point of reproducing on unmodified OpenVSwitch, yes, I will do that, and report further. Time zones and public holidays mean that it won't be until next week.

From: Ben Pfaff <blp at nicira.com>
Sent: Friday, 24 April 2015 11:08 a.m.
To: Tony van der Peet
Cc: discuss at openvswitch.org
Subject: Re: [ovs-discuss] IGMP fields added to the flow structure causes problem?

On Thu, Apr 23, 2015 at 12:03:08AM +0000, Tony van der Peet wrote:
> I have been investigating some anomalous behaviour in a switch
> (developed by us, based on OpenVSwitch code). It appears that flows
> added as a result of receiving IGMP packets are never deleted. Here's
> one of the flows (this is a switch running a simple MAC learning
> application, so you don't see the upper level fields).
> recirc_id(0),in_port(2),eth(src=38:60:77:8b:d9:0a,dst=01:00:5e:00:00:16),eth_type(0x0800),ipv4(frag=no), packets:26, bytes:2236, used:9.600s, actions:1,6,5,4,3
> Here's a log message I'm seeing:
> 2015 Apr 23 12:33:23 awplus ovs-vswitchd: 02570|dpif(revalidator4)|WARN|system at ovs-system: failed to flow_del (No such file or directory)
>  skb_priority(0),skb_mark(0),recirc_id(0),dp_hash(0),in_port(2),eth(src=38:60:77:8b:d9:0a,dst=01:00:5e:00:00:16),eth_type(0x0800),ipv4(src=,dst=,proto=2,tos=0xc0,ttl=1,frag=no)

Thanks for the report.  I'm a little surprised to hear about this, since
that code is somewhat old (I think you said September 2014) and I don't
remember getting similar reports before.  Can you explain how to
reproduce the problem (with unmodified OVS)?

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