[RFC v2 0/5] virtio/vsock: introduce SOCK_DGRAM support

[Jiang Wang <jiang.wang@bytedance.com>]

This patchset implements support of SOCK_DGRAM for virtio
transport.

Datagram sockets are connectionless and unreliable. To avoid unfair contention
with stream and other sockets, add two more virtqueues and
a new feature bit to indicate if those two new queues exist or not.

Dgram does not use the existing credit update mechanism for
stream sockets. When sending from the guest/driver, sending packets
synchronously, so the sender will get an error when the virtqueue is full.
When sending from the host/device, send packets asynchronously
because the descriptor memory belongs to the corresponding QEMU
process.

The virtio spec patch is here:
https://www.mail-archive.com/virtualization@lists.linux-foundation.org/msg47457.html

For those who prefer git repo, here is the link for the linux kernel：
https://github.com/Jiang1155/linux/tree/vsock-dgram-v2

qemu patch link:
https://lists.gnu.org/archive/html/qemu-devel/2021-09/msg03462.html


To do:
1. use skb when receiving packets
2. support multiple transport
3. support mergeable rx buffer
4. support disabling F_STREAM feature bit


v1 -> v2 :
  - fix migration bug in vhost-vsock
  - rename some variables
  - clean up some code in virtio-vsock
  - use le_to_cpu16 in virtio-vsock



Jiang Wang (5):
  virtio/vsock: add VIRTIO_VSOCK_F_DGRAM feature bit
  virtio/vsock: add support for virtio datagram
  vhost/vsock: add support for vhost dgram.
  vsock_test: add tests for vsock dgram
  virtio/vsock: add sysfs for rx buf len for dgram

 drivers/vhost/vsock.c                         | 220 +++++++--
 include/linux/virtio_vsock.h                  |   9 +
 include/net/af_vsock.h                        |   1 +
 .../events/vsock_virtio_transport_common.h    |   2 +
 include/uapi/linux/virtio_vsock.h             |   3 +
 net/vmw_vsock/af_vsock.c                      |  12 +
 net/vmw_vsock/virtio_transport.c              | 463 +++++++++++++++---
 net/vmw_vsock/virtio_transport_common.c       | 181 ++++++-
 tools/testing/vsock/util.c                    | 105 ++++
 tools/testing/vsock/util.h                    |   4 +
 tools/testing/vsock/vsock_test.c              | 195 ++++++++
 11 files changed, 1083 insertions(+), 112 deletions(-)

-- 
2.20.1