Re: [RFC PATCH 2/5] driver/net/tun: Added features for USO.

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On Wed, Feb 9, 2022 at 6:39 AM Jason Wang <jasowang@xxxxxxxxxx> wrote:
>
>
> 在 2022/1/25 下午4:46, Andrew Melnychenko 写道:
> > Added support for USO4 and USO6, also added code for new ioctl TUNGETSUPPORTEDOFFLOADS.
> > For now, to "enable" USO, it's required to set both USO4 and USO6 simultaneously.
> > USO enables NETIF_F_GSO_UDP_L4.
> >
> > Signed-off-by: Andrew Melnychenko <andrew@xxxxxxxxxx>
> > ---
> >   drivers/net/tap.c | 18 ++++++++++++++++--
> >   drivers/net/tun.c | 15 ++++++++++++++-
> >   2 files changed, 30 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/net/tap.c b/drivers/net/tap.c
> > index 8e3a28ba6b28..82d742ba78b1 100644
> > --- a/drivers/net/tap.c
> > +++ b/drivers/net/tap.c
> > @@ -940,6 +940,10 @@ static int set_offload(struct tap_queue *q, unsigned long arg)
> >                       if (arg & TUN_F_TSO6)
> >                               feature_mask |= NETIF_F_TSO6;
> >               }
> > +
> > +             /* TODO: for now USO4 and USO6 should work simultaneously */
> > +             if (arg & (TUN_F_USO4 | TUN_F_USO6) == (TUN_F_USO4 | TUN_F_USO6))
> > +                     features |= NETIF_F_GSO_UDP_L4;
>
>
> If kernel doesn't want to split the GSO_UDP features, I wonder how much
> value to keep separated features for TUN and virtio.
>
> Thanks
>

It's important for Windows guests that may request USO receive only
for IPv4 or IPv6.
Or there is possible to implement one feature and change its
"meanings" when "split" happens.
I think it's a good idea to implement an interface for iUSO4/USO6 and
do it right away.

>
> >       }
> >
> >       /* tun/tap driver inverts the usage for TSO offloads, where
> > @@ -950,7 +954,8 @@ static int set_offload(struct tap_queue *q, unsigned long arg)
> >        * When user space turns off TSO, we turn off GSO/LRO so that
> >        * user-space will not receive TSO frames.
> >        */
> > -     if (feature_mask & (NETIF_F_TSO | NETIF_F_TSO6))
> > +     if (feature_mask & (NETIF_F_TSO | NETIF_F_TSO6) ||
> > +         feature_mask & (TUN_F_USO4 | TUN_F_USO6) == (TUN_F_USO4 | TUN_F_USO6))
> >               features |= RX_OFFLOADS;
> >       else
> >               features &= ~RX_OFFLOADS;
> > @@ -979,6 +984,7 @@ static long tap_ioctl(struct file *file, unsigned int cmd,
> >       unsigned short u;
> >       int __user *sp = argp;
> >       struct sockaddr sa;
> > +     unsigned int supported_offloads;
> >       int s;
> >       int ret;
> >
> > @@ -1074,7 +1080,8 @@ static long tap_ioctl(struct file *file, unsigned int cmd,
> >       case TUNSETOFFLOAD:
> >               /* let the user check for future flags */
> >               if (arg & ~(TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
> > -                         TUN_F_TSO_ECN | TUN_F_UFO))
> > +                         TUN_F_TSO_ECN | TUN_F_UFO |
> > +                         TUN_F_USO4 | TUN_F_USO6))
> >                       return -EINVAL;
> >
> >               rtnl_lock();
> > @@ -1082,6 +1089,13 @@ static long tap_ioctl(struct file *file, unsigned int cmd,
> >               rtnl_unlock();
> >               return ret;
> >
> > +     case TUNGETSUPPORTEDOFFLOADS:
> > +             supported_offloads = TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
> > +                                             TUN_F_TSO_ECN | TUN_F_UFO | TUN_F_USO4 | TUN_F_USO6;
> > +             if (copy_to_user(&arg, &supported_offloads, sizeof(supported_offloads)))
> > +                     return -EFAULT;
> > +             return 0;
> > +
> >       case SIOCGIFHWADDR:
> >               rtnl_lock();
> >               tap = tap_get_tap_dev(q);
> > diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> > index fed85447701a..4f2105d1e6f1 100644
> > --- a/drivers/net/tun.c
> > +++ b/drivers/net/tun.c
> > @@ -185,7 +185,7 @@ struct tun_struct {
> >       struct net_device       *dev;
> >       netdev_features_t       set_features;
> >   #define TUN_USER_FEATURES (NETIF_F_HW_CSUM|NETIF_F_TSO_ECN|NETIF_F_TSO| \
> > -                       NETIF_F_TSO6)
> > +                       NETIF_F_TSO6 | NETIF_F_GSO_UDP_L4)
> >
> >       int                     align;
> >       int                     vnet_hdr_sz;
> > @@ -2821,6 +2821,12 @@ static int set_offload(struct tun_struct *tun, unsigned long arg)
> >               }
> >
> >               arg &= ~TUN_F_UFO;
> > +
> > +             /* TODO: for now USO4 and USO6 should work simultaneously */
> > +             if (arg & TUN_F_USO4 && arg & TUN_F_USO6) {
> > +                     features |= NETIF_F_GSO_UDP_L4;
> > +                     arg &= ~(TUN_F_USO4 | TUN_F_USO6);
> > +             }
> >       }
> >
> >       /* This gives the user a way to test for new features in future by
> > @@ -2991,6 +2997,7 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
> >       int sndbuf;
> >       int vnet_hdr_sz;
> >       int le;
> > +     unsigned int supported_offloads;
> >       int ret;
> >       bool do_notify = false;
> >
> > @@ -3154,6 +3161,12 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
> >       case TUNSETOFFLOAD:
> >               ret = set_offload(tun, arg);
> >               break;
> > +     case TUNGETSUPPORTEDOFFLOADS:
> > +             supported_offloads = TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
> > +                             TUN_F_TSO_ECN | TUN_F_UFO | TUN_F_USO4 | TUN_F_USO6;
> > +             if (copy_to_user(&arg, &supported_offloads, sizeof(supported_offloads)))
> > +                     ret = -EFAULT;
> > +             break;
> >
> >       case TUNSETTXFILTER:
> >               /* Can be set only for TAPs */
>
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