virtio/vsock: support MSG_PEEK for SOCK_SEQPACKET

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>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 2ee4057..352d042 100644 (file)
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -460,6 +460,63 @@ out:
        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;
+}
+
 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);