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

Jesse Gross jesse at nicira.com
Thu Apr 24 21:22:45 UTC 2014


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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