Re: [PATCH 0/2] vhost: add port mirroring function in the vhost lib

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 5/11/23 10:59, Xia, Chenbo wrote:
>> -----Original Message-----
>> From: Jiang, Cheng1 <cheng1.jiang@intel.com>
>> Sent: Monday, May 8, 2023 8:23 PM
>> To: Maxime Coquelin <maxime.coquelin@redhat.com>; Xia, Chenbo
>> <chenbo.xia@intel.com>
>> Cc: dev@dpdk.org; Hu, Jiayu <jiayu.hu@intel.com>; Ding, Xuan
>> <xuan.ding@intel.com>; Ma, WenwuX <wenwux.ma@intel.com>; Wang, YuanX
>> <yuanx.wang@intel.com>; He, Xingguang <xingguang.he@intel.com>; David
>> Marchand <david.marchand@redhat.com>
>> Subject: RE: [PATCH 0/2] vhost: add port mirroring function in the vhost
>> lib
>>
>> Hi Maxime,
>>
>>> -----Original Message-----
>>> From: Maxime Coquelin <maxime.coquelin@redhat.com>
>>> Sent: Wednesday, May 3, 2023 5:37 PM
>>> To: Jiang, Cheng1 <cheng1.jiang@intel.com>; Xia, Chenbo
>>> <chenbo.xia@intel.com>
>>> Cc: dev@dpdk.org; Hu, Jiayu <jiayu.hu@intel.com>; Ding, Xuan
>>> <xuan.ding@intel.com>; Ma, WenwuX <wenwux.ma@intel.com>; Wang, YuanX
>>> <yuanx.wang@intel.com>; He, Xingguang <xingguang.he@intel.com>; David
>>> Marchand <david.marchand@redhat.com>
>>> Subject: Re: [PATCH 0/2] vhost: add port mirroring function in the vhost
>> lib
>>>
>>> Hi Cheng,
>>>
>>> On 4/21/23 03:09, Cheng Jiang wrote:
>>>> Similar to the port mirroring function on the switch or router, this
>>>> patch set implements such function on the Vhost lib. When data is sent
>>>> to a front-end, it will also send the data to its mirror front-end.
>>>> When data is received from a front-end, it will also send the data to
>>>> its mirror front-end.
>>>
>>> Why not just keeping mirroring in the switch/router?
>>> I am really not convinced this is the way to go:
>>> 1. API is too complex
>>> 2. It requires async support
>>> 3. There is too much code duplication, it increases  virtio-net.c by
>>>      30%, and it is without packed ring support.
>>> 4. If mirror port is down for any reason, packets to/from the original
>>>      port are dropped.
>>> 5. It seems to assume negotiated features of the two ports are
>>>      identical, e.g. Virtio-net header length? If so, that's not a
>>>      manageable solution.
>>
>> Thank you for your feedback.
>> I concur that placing the mirror function in the Vhost library is not
>> ideal. We are currently considering implementing either a mirror Vhost PMD,
>> or adding a function to TestPMD to handle this functionality.
>> Would you please share your thoughts on this plan and let us know which
>> option you prefer?
> 
> Based on current implementation, it seems that vhost lib could be ignorant
> of the mirroring usage. Making these logic into APP like testpmd seems to make
> more sense.

I agree with Chenbo, it should be done at the application level, which
would enable to also mirror non-Vhost ports.

Thanks,
Maxime

> Thanks,
> Chenbo
> 
>>
>> Thanks a lot,
>> Cheng
>>
>>
>>
>>>
>>> Regards,
>>> Maxime
>>>
>>>>
>>>> Cheng Jiang (2):
>>>>     vhost: add ingress API for port mirroring datapath
>>>>     vhost: add egress API for port mirroring datapath
>>>>
>>>>    lib/vhost/rte_vhost_async.h |   17 +
>>>>    lib/vhost/version.map       |    3 +
>>>>    lib/vhost/virtio_net.c      | 1266
>> +++++++++++++++++++++++++++++++++++
>>>>    3 files changed, 1286 insertions(+)
>>>>
>>>> --
>>>> 2.35.1
>>>>
>