[ovs-discuss] OVS not forwarding packets to port

Chris Picton chris at picton.nom.za
Tue Mar 17 21:05:54 UTC 2015

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.

Working ofproto/trace action:
Datapath actions: pop_vlan,6

Non-working ofproto/trace action:
Datapath actions: pop_vlan,7

If I run ovs-dpctl dump-flows | grep 0x0806 | egrep 
'52:54:00:60:29:8c|52:54:00:14:54:c6', I get (immediately after dropping 
the arp entry from the working guest):

packets:2, bytes:120, used:1.669s, actions:pop_vlan,7
packets:0, bytes:0, used:never, actions:pop_vlan,6

The non-working port's output above entry has "used:never"

My request for help now becomes:

How can I determine why the packets are not appearing on vnet0, when the 
output of the commands below appear to indicate that they should?

The full ofproto/trace commands are below:

Working guest:
  # ovs-appctl ofproto/trace vbr0 "in_port=1" 
Bridge: vbr0
Rule: table=0 cookie=0 priority=0
OpenFlow actions=NORMAL
forwarding to learned port

Final flow: unchanged
Datapath actions: pop_vlan,6

Non-working guest:
ovs-appctl ofproto/trace vbr0 "in_port=1" 
Bridge: vbr0
Rule: table=0 cookie=0 priority=0
OpenFlow actions=NORMAL
forwarding to learned port

Final flow: unchanged
Datapath actions: pop_vlan,7

  # ovs-ofctl dump-flows vbr0
NXST_FLOW reply (xid=0x4):
  cookie=0x0, duration=486871.278s, table=0, n_packets=283716961, 
n_bytes=345708309931, idle_age=0, hard_age=65534, priority=0 actions=NORMAL

  # ovs-appctl dpif/show
system at ovs-system: hit:275109913 missed:8254378
                 bondV 1/2: (system)
                 vbr0 65534/1: (internal)
                 veth-carbon1-3 5/6: (system)
                 vlan1 2/3: (internal)
                 vlan108 3/4: (internal)
                 vlan109 4/5: (internal)
                 vnet0 6/7: (system)
                 vnet1 7/8: (system)
                 vnet10 16/17: (system)
                 vnet11 17/18: (system)
                 vnet12 18/19: (system)
                 vnet13 19/20: (system)
                 vnet14 20/21: (system)
                 vnet15 21/22: (system)
                 vnet16 22/23: (system)
                 vnet17 23/24: (system)
                 vnet18 24/25: (system)
                 vnet19 25/26: (system)
                 vnet2 8/9: (system)
                 vnet20 26/27: (system)
                 vnet21 27/28: (system)
                 vnet3 9/10: (system)
                 vnet4 10/11: (system)
                 vnet5 11/12: (system)
                 vnet6 12/13: (system)

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