netdev - Re: [PATCH net-next] gso: enable udp gso for virtual devices

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Date:   Fri, 9 Aug 2019 11:58:03 -0700
From:   Josh Hunt <johunt@...mai.com>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Jason Baron <jbaron@...mai.com>
Cc:     Alexander Duyck <alexander.duyck@...il.com>,
        David Miller <davem@...emloft.net>,
        Netdev <netdev@...r.kernel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH net-next] gso: enable udp gso for virtual devices

On 6/26/19 4:41 PM, Willem de Bruijn wrote:
> On Wed, Jun 26, 2019 at 3:17 PM Jason Baron <jbaron@...mai.com> wrote:
>>
>>
>>
>> On 6/14/19 4:53 PM, Jason Baron wrote:
>>>
>>>
>>> On 6/13/19 5:20 PM, Willem de Bruijn wrote:
>>>>>>> @@ -237,6 +237,7 @@ static inline int find_next_netdev_feature(u64 feature, unsigned long start)
>>>>>>>                                   NETIF_F_GSO_GRE_CSUM |                 \
>>>>>>>                                   NETIF_F_GSO_IPXIP4 |                   \
>>>>>>>                                   NETIF_F_GSO_IPXIP6 |                   \
>>>>>>> +                                NETIF_F_GSO_UDP_L4 |                   \
>>>>>>>                                   NETIF_F_GSO_UDP_TUNNEL |               \
>>>>>>>                                   NETIF_F_GSO_UDP_TUNNEL_CSUM)
>>>>>>
>>>>>> Are you adding this to NETIF_F_GSO_ENCAP_ALL? Wouldn't it make more
>>>>>> sense to add it to NETIF_F_GSO_SOFTWARE?
>>>>>>
>>>>>
>>>>> Yes, I'm adding to NETIF_F_GSO_ENCAP_ALL (not very clear from the
>>>>> context). I will fix the commit log.
>>>>>
>>>>> In: 83aa025 udp: add gso support to virtual devices, the support was
>>>>> also added to NETIF_F_GSO_ENCAP_ALL (although subsequently reverted due
>>>>> to UDP GRO not being in place), so I wonder what the reason was for that?
>>>>
>>>> That was probably just a bad choice on my part.
>>>>
>>>> It worked in practice, but if NETIF_F_GSO_SOFTWARE works the same
>>>> without unexpected side effects, then I agree that it is the better choice.
>>>>
>>>> That choice does appear to change behavior when sending over tunnel
>>>> devices. Might it send tunneled GSO packets over loopback?
>>>>
>>>>
>>>
>>> I set up a test case using fou tunneling through a bridge device using
>>> the udpgso_bench_tx test where packets are not received correctly if
>>> NETIF_F_GSO_UDP_L4 is added to NETIF_F_GSO_SOFTWARE. If I have it added
>>> to NETIF_F_GSO_ENCAP_ALL, it does work correctly. So there are more
>>> fixes required to include it in NETIF_F_GSO_SOFTWARE.
>>>
>>> The use-case I have only requires it to be in NETIF_F_GSO_ENCAP_ALL, but
>>> if it needs to go in NETIF_F_GSO_SOFTWARE, I can look at what's required
>>> more next week.
>>>
>>
>> Hi,
>>
>> I haven't had a chance to investigate what goes wrong with including
>> NETIF_F_GSO_UDP_L4 in NETIF_F_GSO_SOFTWARE - but I was just wondering if
>> people are ok with NETIF_F_GSO_UDP_L4 being added to
>> NETIF_F_GSO_ENCAP_ALL and not NETIF_F_GSO_SOFTWARE (ie the original
>> patch as posted)?
>>
>> As I mentioned that is sufficient for my use-case, and its how Willem
>> originally proposed this.
> 
> Indeed, based on the previous discussion this sounds fine to me.
> 

Willem

Are you OK to ACK this? If not, is there something else you'd rather see 
here?

Thanks
Josh