[ovs-discuss] OVS not forwarding packets to port

Chris Picton chris at picton.nom.za
Wed Mar 18 06:47:19 UTC 2015

On 03/18/15 01:05, Ben Pfaff wrote:
> On Tue, Mar 17, 2015 at 11:05:54PM +0200, Chris Picton wrote:
>> On 2015/03/17 10:21 PM, Ben Pfaff wrote:
>>> On Tue, Mar 17, 2015 at 10:17:03PM +0200, Chris Picton wrote:
>>>> At layer3, I can use the 'ip route get *' commands to determine how
>>>> the kernel will route a packet.  Is there any equivalent command to
>>>> inspect the ovs behaviour.  I would like to ask ovs: 'If I send a
>>>> packet with src mac 00:15:17:91:05:4c which came in on interface
>>>> bondV tagged with vlan 3, destined to mac 52:54:00:60:29:8c, what
>>>> port would it be forwarded to?'
>>> Yes, you can use "ovs-appctl ofproto/trace", please see
>>> ovs-vswitchd(8) for more details.
>> Thanks for the speedy reply - I get the results as below:
>> What I can see is that on both cases, OVS says it should be
>> forwarding via a datapath and popping the vlan tag.  The datapath
>> for ports veth-carbon1-3 (working) and vnet0 (not working) appear to
>> be similar.
> Huh.
> Check what the kernel actually says it's doing for installed flows,
> with "ovs-dpctl dump-flows".
Hi Ben

My terminology may not be 100% correct - I am new at this  :)

I has included the output from ovs-dpctl in my previous mail.  The 
relevant flow is:
packets:2, bytes:120, used:0.014s, actions:pop_vlan,7

I can't find any definitive documentation for an action element 
consisting purely of a number - in this case "7".  If I assume it means 
to forward to a numbered port, then that port does match the correct one 
from "ovs-dpctl show": port 7: vnet0

So the action appears to be correct, but my original problem still 
remains: the packet does not appear on the vnet0 when I run a tcpdump.

Where else should I be looking to try find the culprit here?

# ovs-dpctl show
system at ovs-system:
     lookups: hit:295139464 missed:8880738 lost:0
     flows: 76
     masks: hit:356499657 total:6 hit/pkt:1.17
     port 0: ovs-system (internal)
     port 1: vbr0 (internal)
     port 2: bondV
     port 3: vlan1 (internal)
     port 4: vlan108 (internal)
     port 5: vlan109 (internal)
     port 6: veth-carbon1-3
     port 7: vnet0
     port 8: vnet1
     port 9: vnet2
     port 10: vnet3
     port 11: vnet4
     port 12: vnet5
     port 13: vnet6
     port 17: vnet10
     port 18: vnet11
     port 19: vnet12
     port 20: vnet13
     port 21: vnet14
     port 22: vnet15
     port 23: vnet16
     port 24: vnet17
     port 25: vnet18
     port 26: vnet19
     port 27: vnet20
     port 28: vnet21

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