vsock/virtio: add support for MSG_PEEK

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>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Tested-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 5bb70c692b1ee3ff40758304e6e74b2feb18f6ee..d31f1478c3da7a26dae94b70dcc47ae5fe4cb51d 100644 (file)
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -263,6 +263,55 @@ static int virtio_transport_send_credit_update(struct vsock_sock *vsk,
        return virtio_transport_send_pkt_info(vsk, &info);
 }
 
+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, total = 0, off;
+       int err = -EFAULT;
+
+       spin_lock_bh(&vvs->rx_lock);
+
+       list_for_each_entry(pkt, &vvs->rx_queue, list) {
+               off = pkt->off;
+
+               if (total == len)
+                       break;
+
+               while (total < len && off < pkt->len) {
+                       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;
+               }
+       }
+
+       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,
@@ -335,9 +384,9 @@ 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);