Re: [PATCH] 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 <redacted>
---
 net/vmw_vsock/virtio_transport_common.c | 50 +++++++++++++++++++++++++++++++--
 1 file changed, 47 insertions(+), 3 deletions(-)

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 94cc0fa..938f2ed 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c

@@ -264,6 +264,50 @@ 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, total = 0;
+	int err = -EFAULT;
+
+	spin_lock_bh(&vvs->rx_lock);
+
+	list_for_each_entry(pkt, &vvs->rx_queue, list) {
+		if (total == len)
+			break;
+
+		bytes = len - total;
+		if (bytes > pkt->len - pkt->off)
+			bytes = pkt->len - pkt->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 + pkt->off, bytes);
+		if (err)
+			goto out;
+
+		spin_lock_bh(&vvs->rx_lock);
+
+		total += bytes;
+	}
+
+	spin_unlock_bh(&vvs->rx_lock);
+
+	return total;
+
+out:
+	if (total)
+		err = total;
+	return err;
+}