[RFC PATCH 0/5] TUN/VirtioNet USO features support.

[Andrew Melnychenko <andrew@daynix.com>]

Added new offloads for TUN devices TUN_F_USO4 and TUN_F_USO6.
Technically they enable NETIF_F_GSO_UDP_L4
(and only if USO4 & USO6 are set simultaneously).
It allows to transmission of large UDP packets.

Different features USO4 and USO6 are required for qemu where Windows guests can
enable disable USO receives for IPv4 and IPv6 separately.
On the other side, Linux can't really differentiate USO4 and USO6, for now.
For now, to enable USO for TUN it requires enabling USO4 and USO6 together.
In the future, there would be a mechanism to control UDP_L4 GSO separately.

Test it WIP Qemu https://github.com/daynix/qemu/tree/Dev_USOv2

New types for VirtioNet already on mailing:
https://lists.oasis-open.org/archives/virtio-comment/202110/msg00010.html

Also, there is a known issue with transmitting packages between two guests.
Without hacks with skb's GSO - packages are still segmented on the host's postrouting.

Andrew Melnychenko (5):
  uapi/linux/if_tun.h: Added new ioctl for tun/tap.
  driver/net/tun: Added features for USO.
  uapi/linux/virtio_net.h: Added USO types.
  linux/virtio_net.h: Added Support for GSO_UDP_L4 offload.
  drivers/net/virtio_net.c: Added USO support.

 drivers/net/tap.c               | 18 ++++++++++++++++--
 drivers/net/tun.c               | 15 ++++++++++++++-
 drivers/net/virtio_net.c        | 22 ++++++++++++++++++----
 include/linux/virtio_net.h      | 11 +++++++++++
 include/uapi/linux/if_tun.h     |  3 +++
 include/uapi/linux/virtio_net.h |  4 ++++
 6 files changed, 66 insertions(+), 7 deletions(-)

-- 
2.34.1