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

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Date:   Wed, 26 Jun 2019 19:41:34 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Jason Baron <jbaron@...mai.com>
Cc:     Alexander Duyck <alexander.duyck@...il.com>,
        David Miller <davem@...emloft.net>,
        Netdev <netdev@...r.kernel.org>, Joshua Hunt <johunt@...mai.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH net-next] gso: enable udp gso for virtual devices

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.