staging: usbip: vhci: handle EAGAIN from SO_RCVTIMEO

If there is a receive timeout without any active
requests, we can tell the connection was idle and
ignore the timeout.

If there are active requests for which we expect
to receive a reply we close the connection.

This makes it possible to set an upper bound on
the time a usbip device may be unresponsive.

This is a workaround for the lack of heart-beat
messages in the USBIP protocol.

Extending the protocol would break compatibility
with all previous stub versions, so this seems like
the lesser evil.

Signed-off-by: Max Vozeler <max@vozeler.com>
Tested-by: Mark Wehby <MWehby@luxotticaRetail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/staging/usbip/vhci_rx.c b/drivers/staging/usbip/vhci_rx.c
index ac15cea753960fff7cfbd25db00e5e07317b11a2..bf69914709410cf054825933a638b7dd7060180a 100644 (file)
--- a/drivers/staging/usbip/vhci_rx.c
+++ b/drivers/staging/usbip/vhci_rx.c
@@ -193,6 +193,19 @@ static void vhci_recv_ret_unlink(struct vhci_device *vdev,
        return;
 }
 
+static int vhci_priv_tx_empty(struct vhci_device *vdev)
+{
+       int empty = 0;
+
+       spin_lock(&vdev->priv_lock);
+
+       empty = list_empty(&vdev->priv_rx);
+
+       spin_unlock(&vdev->priv_lock);
+
+       return empty;
+}
+
 /* recv a pdu */
 static void vhci_rx_pdu(struct usbip_device *ud)
 {
@@ -210,8 +223,14 @@ static void vhci_rx_pdu(struct usbip_device *ud)
        if (ret < 0) {
                if (ret == -ECONNRESET)
                        usbip_uinfo("connection reset by peer\n");
-               else if (ret != -ERESTARTSYS)
+               else if (ret == -EAGAIN) {
+                       /* ignore if connection was idle */
+                       if (vhci_priv_tx_empty(vdev))
+                               return;
+                       usbip_uinfo("connection timed out with pending urbs\n");
+               } else if (ret != -ERESTARTSYS)
                        usbip_uinfo("xmit failed %d\n", ret);
+
                usbip_event_add(ud, VDEV_EVENT_ERROR_TCP);
                return;
        }