Re: [RFC PATCH v5 11/19] virtio/vsock: dequeue callback for SOCK_SEQPACKET

Michael S. Tsirkin
2021-02-23T14:18:47Z

On Thu, Feb 18, 2021 at 08:39:37AM +0300, Arseny Krasnov wrote:
> This adds transport callback and it's logic for SEQPACKET dequeue.
> Callback fetches RW packets from rx queue of socket until whole record
> is copied(if user's buffer is full, user is not woken up). This is done
> to not stall sender, because if we wake up user and it leaves syscall,
> nobody will send credit update for rest of record, and sender will wait
> for next enter of read syscall at receiver's side. So if user buffer is
> full, we just send credit update and drop data. If during copy SEQ_BEGIN
> was found(and not all data was copied), copying is restarted by reset
> user's iov iterator(previous unfinished data is dropped).
>
> Signed-off-by: Arseny Krasnov <arseny.krasnov@kaspersky.com>
> ---
> include/linux/virtio_vsock.h | 10 +++
> include/uapi/linux/virtio_vsock.h | 16 ++++
> net/vmw_vsock/virtio_transport_common.c | 114 ++++++++++++++++++++++++
> 3 files changed, 140 insertions(+)
>
> diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
> index dc636b727179..003d06ae4a85 100644
> --- a/include/linux/virtio_vsock.h
> +++ b/include/linux/virtio_vsock.h
> @@ -36,6 +36,11 @@ struct virtio_vsock_sock {
> u32 rx_bytes;
> u32 buf_alloc;
> struct list_head rx_queue;
> +
> + /* For SOCK_SEQPACKET */
> + u32 user_read_seq_len;
> + u32 user_read_copied;
> + u32 curr_rx_msg_cnt;

wrap these in a struct to make it's clearer they
are related?

> };
>
> struct virtio_vsock_pkt {
> @@ -80,6 +85,11 @@ virtio_transport_dgram_dequeue(struct vsock_sock *vsk,
> struct msghdr *msg,
> size_t len, int flags);
>
> +int
> +virtio_transport_seqpacket_dequeue(struct vsock_sock *vsk,
> + struct msghdr *msg,
> + int flags,
> + bool *msg_ready);
> s64 virtio_transport_stream_has_data(struct vsock_sock *vsk);
> s64 virtio_transport_stream_has_space(struct vsock_sock *vsk);
>
> diff --git a/include/uapi/linux/virtio_vsock.h b/include/uapi/linux/virtio_vsock.h
> index 1d57ed3d84d2..cf9c165e5cca 100644
> --- a/include/uapi/linux/virtio_vsock.h
> +++ b/include/uapi/linux/virtio_vsock.h
> @@ -63,8 +63,14 @@ struct virtio_vsock_hdr {
> __le32 fwd_cnt;
> } __attribute__((packed));
>
> +struct virtio_vsock_seq_hdr {
> + __le32 msg_cnt;
> + __le32 msg_len;
> +} __attribute__((packed));
> +
> enum virtio_vsock_type {
> VIRTIO_VSOCK_TYPE_STREAM = 1,
> + VIRTIO_VSOCK_TYPE_SEQPACKET = 2,
> };
>
> enum virtio_vsock_op {
> @@ -83,6 +89,11 @@ enum virtio_vsock_op {
> VIRTIO_VSOCK_OP_CREDIT_UPDATE = 6,
> /* Request the peer to send the credit info to us */
> VIRTIO_VSOCK_OP_CREDIT_REQUEST = 7,
> +
> + /* Record begin for SOCK_SEQPACKET */
> + VIRTIO_VSOCK_OP_SEQ_BEGIN = 8,
> + /* Record end for SOCK_SEQPACKET */
> + VIRTIO_VSOCK_OP_SEQ_END = 9,
> };
>
> /* VIRTIO_VSOCK_OP_SHUTDOWN flags values */
> @@ -91,4 +102,9 @@ enum virtio_vsock_shutdown {
> VIRTIO_VSOCK_SHUTDOWN_SEND = 2,
> };
>
> +/* VIRTIO_VSOCK_OP_RW flags values */
> +enum virtio_vsock_rw {
> + VIRTIO_VSOCK_RW_EOR = 1,
> +};
> +
> #endif /* _UAPI_LINUX_VIRTIO_VSOCK_H */

Probably a good idea to also have a feature bit gating
this functionality.

--
MST