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Date: Tue, 22 Feb 2022 15:22:00 +0200
From: Andrew Melnichenko <andrew@...nix.com>
To: Jason Wang <jasowang@...hat.com>
Cc: "David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
"Michael S. Tsirkin" <mst@...hat.com>,
Network Development <netdev@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
virtualization <virtualization@...ts.linux-foundation.org>,
Yuri Benditovich <yuri.benditovich@...nix.com>,
Yan Vugenfirer <yan@...nix.com>
Subject: Re: [RFC PATCH 2/5] driver/net/tun: Added features for USO.
On Wed, Feb 9, 2022 at 6:39 AM Jason Wang <jasowang@...hat.com> 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@...nix.com>
> > ---
> > 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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