[ovs-dev] [PATCH V2 1/1] dpif-netlink: Log eth type 0x1234 not offloadable

Paul Blakey paulb at mellanox.com
Tue Jul 30 13:50:47 UTC 2019

On 7/30/2019 3:19 PM, Ilya Maximets wrote:
> On 30.07.2019 13:30, Ilya Maximets wrote:
>> On 30.07.2019 13:23, Eli Britstein wrote:
>>> On 7/30/2019 1:10 PM, Ilya Maximets wrote:
>>>> On 03.07.2019 7:58, Eli Britstein wrote:
>>>>> Ethernet type 0x1234 is used for testing and not being offloadable. For
>>>>> testing offloadable features, log about using this value.
>>>>> Signed-off-by: Eli Britstein <elibr at mellanox.com>
>>>>> Acked-by: Roi Dayan <roid at mellanox.com>
>>>>> Signed-off-by: Eli Britstein <elibr at mellanox.com>
>>>>> Acked-by: Ben Pfaff <blp at ovn.org>
>>>>> ---
>>>>>    lib/dpif-netlink.c | 1 +
>>>>>    1 file changed, 1 insertion(+)
>>>>> diff --git a/lib/dpif-netlink.c b/lib/dpif-netlink.c
>>>>> index ba80a0079..a0d51ae61 100644
>>>>> --- a/lib/dpif-netlink.c
>>>>> +++ b/lib/dpif-netlink.c
>>>>> @@ -2007,6 +2007,7 @@ parse_flow_put(struct dpif_netlink *dpif, struct dpif_flow_put *put)
>>>>>        /* When we try to install a dummy flow from a probed feature. */
>>>>>        if (match.flow.dl_type == htons(0x1234)) {
>>>>> +        VLOG_INFO_RL(&rl, "eth 0x1234 is special and not offloadable");
>>>>>            return EOPNOTSUPP;
>>>>>        }
>>>> But what is the purpose of this patch?  What is the use case?
>>> RH wanted to test that dl_type is offloaded. Coincidentally, they used
>>> 0x1234, and it was not offloaded, and they didn't understand why, and
>>> suggested a log message.
>> I'll take a closer look, but it seems that we just need to remove this
>> 'if' statement and allow oflloading.
> 'dpif_probe_feature' always has DPIF_FP_PROBE flag set. Other probing code uses
> dpif_execute() which uses DPIF_OP_EXECUTE, hence never calls parse_flow_put().
> So, this 'if' statement is wrong and should be deleted as it only forbids
> offloading of the real legitimate flows with dl_type 0x1234. Dummy flows never
> reaches this code.

Couldn't find any reason for it, I even looked at diff from my commit 
that introduced it.

Seems safe to remove it.

>>>> Actually, it looks like we need to just remove above 'if' statement
>>>> entirely.  Just a few lines above there is a check if we are probing
>>>> or installing real flow:
>>>>      if (put->flags & DPIF_FP_PROBE) {
>>>>          return EOPNOTSUPP;
>>>>      }
>>>> So, we will never get there while probing.  But why we're restricting
>>>> this flow type from being offloaded?  'netdev_flow_put' will refuse
>>>> to offload if it doesn't know that flow type, but this shouldn't be
>>>> done here.
>>>> In case we have a dummy flow without DPIF_FP_PROBE flag set, we need
>>>> to fix upper layers.  Is it the case?
>>> I didn't look into it why we restrict it and if there is a real reason
>>> why in this layer. You may be right, but I don't know.
>>>> Best regards, Ilya Maximets.

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