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Subject[RFC] VSOCK: add support for MSG_PEEK
Date
This patch adds support for MSG_PEEK. In such a case, packets are not
removed from the rx_queue and credit updates are not sent.

Signed-off-by: Matias Ezequiel Vara Larsen <matiasevara@gmail.com>
---
net/vmw_vsock/virtio_transport_common.c | 59 +++++++++++++++++++++++++++++++--
1 file changed, 56 insertions(+), 3 deletions(-)

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 94cc0fa..830e890 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -264,6 +264,59 @@ static int virtio_transport_send_credit_update(struct vsock_sock *vsk,
}

static ssize_t
+virtio_transport_stream_do_peek(struct vsock_sock *vsk,
+ struct msghdr *msg,
+ size_t len)
+{
+ struct virtio_vsock_sock *vvs = vsk->trans;
+ struct virtio_vsock_pkt *pkt;
+ size_t bytes, off = 0, total = 0;
+ int err = -EFAULT;
+
+ spin_lock_bh(&vvs->rx_lock);
+
+ if (list_empty(&vvs->rx_queue)) {
+ spin_unlock_bh(&vvs->rx_lock);
+ return 0;
+ }
+
+ pkt = list_first_entry(&vvs->rx_queue,
+ struct virtio_vsock_pkt, list);
+ do {
+ bytes = len - total;
+ if (bytes > pkt->len - off)
+ bytes = pkt->len - off;
+
+ /* sk_lock is held by caller so no one else can dequeue.
+ * Unlock rx_lock since memcpy_to_msg() may sleep.
+ */
+ spin_unlock_bh(&vvs->rx_lock);
+
+ err = memcpy_to_msg(msg, pkt->buf + off, bytes);
+ if (err)
+ goto out;
+
+ spin_lock_bh(&vvs->rx_lock);
+
+ total += bytes;
+ off += bytes;
+ if (off == pkt->len) {
+ pkt = list_next_entry(pkt, list);
+ off = 0;
+ }
+ } while ((total < len) && !list_is_first(&pkt->list, &vvs->rx_queue));
+
+ spin_unlock_bh(&vvs->rx_lock);
+
+ return total;
+
+out:
+ if (total)
+ err = total;
+ return err;
+}
+
+static ssize_t
virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
struct msghdr *msg,
size_t len)
@@ -330,9 +383,9 @@ virtio_transport_stream_dequeue(struct vsock_sock *vsk,
size_t len, int flags)
{
if (flags & MSG_PEEK)
- return -EOPNOTSUPP;
-
- return virtio_transport_stream_do_dequeue(vsk, msg, len);
+ return virtio_transport_stream_do_peek(vsk, msg, len);
+ else
+ return virtio_transport_stream_do_dequeue(vsk, msg, len);
}
EXPORT_SYMBOL_GPL(virtio_transport_stream_dequeue);

--
2.7.4
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