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SubjectRe: [RFC PATCH v1 2/4] virtio/vsock: support MSG_PEEK for SOCK_SEQPACKET
On Sun, Jun 18, 2023 at 09:24:49AM +0300, Arseniy Krasnov wrote:
>This adds support of MSG_PEEK flag for SOCK_SEQPACKET type of socket.
>Difference with SOCK_STREAM is that this callback returns either length
>of the message or error.
>
>Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>---
> net/vmw_vsock/virtio_transport_common.c | 63 +++++++++++++++++++++++--
> 1 file changed, 60 insertions(+), 3 deletions(-)
>
>diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>index 2ee40574c339..352d042b130b 100644
>--- a/net/vmw_vsock/virtio_transport_common.c
>+++ b/net/vmw_vsock/virtio_transport_common.c
>@@ -460,6 +460,63 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
> return err;
> }
>
>+static ssize_t
>+virtio_transport_seqpacket_do_peek(struct vsock_sock *vsk,
>+ struct msghdr *msg)
>+{
>+ struct virtio_vsock_sock *vvs = vsk->trans;
>+ struct sk_buff *skb;
>+ size_t total, len;
>+
>+ spin_lock_bh(&vvs->rx_lock);
>+
>+ if (!vvs->msg_count) {
>+ spin_unlock_bh(&vvs->rx_lock);
>+ return 0;
>+ }
>+
>+ total = 0;
>+ len = msg_data_left(msg);
>+
>+ skb_queue_walk(&vvs->rx_queue, skb) {
>+ struct virtio_vsock_hdr *hdr;
>+
>+ if (total < len) {
>+ size_t bytes;
>+ int err;
>+
>+ bytes = len - total;
>+ if (bytes > skb->len)
>+ bytes = skb->len;
>+
>+ spin_unlock_bh(&vvs->rx_lock);
>+
>+ /* sk_lock is held by caller so no one else can dequeue.
>+ * Unlock rx_lock since memcpy_to_msg() may sleep.
>+ */
>+ err = memcpy_to_msg(msg, skb->data, bytes);
>+ if (err)
>+ return err;
>+
>+ spin_lock_bh(&vvs->rx_lock);
>+ }
>+
>+ total += skb->len;
>+ hdr = virtio_vsock_hdr(skb);
>+
>+ if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SEQ_EOM) {
>+ if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SEQ_EOR)
>+ msg->msg_flags |= MSG_EOR;
>+
>+ break;
>+ }
>+ }
>+
>+ spin_unlock_bh(&vvs->rx_lock);
>+
>+ return total;

Should we return the minimum between total and len?

Thanks,
Stefano

>+}
>+
> static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk,
> struct msghdr *msg,
> int flags)
>@@ -554,9 +611,9 @@ virtio_transport_seqpacket_dequeue(struct vsock_sock *vsk,
> int flags)
> {
> if (flags & MSG_PEEK)
>- return -EOPNOTSUPP;
>-
>- return virtio_transport_seqpacket_do_dequeue(vsk, msg, flags);
>+ return virtio_transport_seqpacket_do_peek(vsk, msg);
>+ else
>+ return virtio_transport_seqpacket_do_dequeue(vsk, msg, flags);
> }
> EXPORT_SYMBOL_GPL(virtio_transport_seqpacket_dequeue);
>
>--
>2.25.1
>

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