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.
Thanks,
-Jason
>
>> I agree that NETIF_F_GSO_SOFTWARE seems conceptually more logical and
>> further I think it adds support for more 'virtual' devices. For example,
>> I tested loopback with NETIF_F_GSO_UDP_L4 being added to
>> NETIF_F_GSO_SOFTWARE and it shows a nice performance gain, whereas
>> NETIF_F_GSO_ENCAP_ALL isn't included for loopback.
>>
>> Thanks,
>>
>> -Jason
