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>

1 files changed, 20 insertions, 1 deletions

diff --git a/drivers/staging/usbip/vhci_rx.c b/drivers/staging/usbip/vhci_rx.c
index ac15cea75396..bf6991470941 100644
--- 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;
         }