[ovs-dev] Datapath kern log msg key attribute error

Andy Zhou azhou at nicira.com
Thu Apr 24 21:33:58 UTC 2014


I am sure it can be done and most likely involving some netlink
changes.  Since netlink message design is your forte, any suggestions?

On Thu, Apr 24, 2014 at 2:22 PM, Jesse Gross <jesse at nicira.com> wrote:
> That's a good point, I didn't think about that. I wonder if there is a
> way to avoid the error message in these cases since it's likely to
> cause confusion given that it is logged by default.
>
> On Thu, Apr 24, 2014 at 1:57 PM, Andy Zhou <azhou at nicira.com> wrote:
>> Whenever we instantiate a new ofproto (i.e. bridge), we probe datapath
>> to detect if it supports MPLS, and if yes, how many labels it can
>> support.  The probing produces similar error messages on my system.
>> It should only appear when you add the bridge, but not afterwards.
>>
>> On Thu, Apr 24, 2014 at 12:27 PM, Thomas F Herbert
>> <thomasfherbert at gmail.com> wrote:
>>> On 4/24/2014 1:47 PM, Jesse Gross wrote:
>>>>
>>>> On Thu, Apr 24, 2014 at 8:38 AM, Thomas F Herbert
>>>> <thomasfherbert at gmail.com> wrote:
>>>>>
>>>>> Hi,
>>>>>
>>>>> I think there is a problem with parsing out the OVS ATTRIBUTE nesting in
>>>>> the
>>>>> NL message in the datapath and I am having trouble finding the cause. I
>>>>> think the nl msg is built up wrong in the case of the vlan push action.
>>>>>
>>>>> I first saw the problem while testing my patch for 802.1ad. However, I
>>>>> also
>>>>> see the same problem WITHOUT the patch on commits in the master branch.
>>>>>
>>>>> The message appears in the kern log for commit dcbe78 and subsequent
>>>>> commits
>>>>> on the master branch. The message does NOT appear in the 2.1 release
>>>>> branch.
>>>>>
>>>>> Apr 23 07:50:11 lubuntu-12 kernel: [ 1009.493608] openvswitch: netlink:
>>>>> Key
>>>>> attribute has unexpected length (type=62, length=4, expected=0).
>>>>>
>>>>> Message is from line 300 in datapath/flow_netlink.c
>>>>>
>>>>> It is interesting that type 62 is the maximum key attribute value.
>>>>>
>>>>> The problem can be also  reproduced with the following command with
>>>>> commit
>>>>> f487a:
>>>>>
>>>>> ovs-ofctl -vdbg --protocols=OpenFlow11 add-flow br0
>>>>> in_port=1,actions=push_vlan:0x8100,load:0x64-\>OXM_OF_VLAN_VID[],output:2
>>>>
>>>> This attribute is for MPLS, which userspace supports but the kernel
>>>> doesn't. This shouldn't be generated in any case but is there any MPLS
>>>> traffic here?
>>>
>>> There is no traffic at all when the message appears.
>>>
>>>>
>>>> You could try bisecting since you have points in the code where it is
>>>> working and not. It might also be worth setting the log level to debug
>>>> to watch the upcalls and flow installations.
>>>
>>> OK, Jesse, I will debug by bisecting the commit history to see where it
>>> first appeared and get back to you when I find it.
>>>
>>> There is no traffic yet and it occurs before any flows are pushed. The
>>> message appears when the bridge is initially set up with the following
>>> command.
>>>
>>> ovs-vsctl add-br br0
>>>
>>>
>>>
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