On Tue, Jun 30, 2015 at 10:42:37AM +0800, Fam Zheng wrote: > This is necessary because once we return false from .can_receive, we > need to flush the queue when the .can_receive conditions become true > again, (for example when more buffer is available). > > We can rely on net_rx_packet (which checks the same conditions) to drop > the packet if the device is not ready, so drop net_xen_info.can_receive.
This patch changes behavior:
Previously can_receive() false meant packets are queued.
Now those same conditions result in net_rx_packet() returning -1, so
packets are discarded.
In order to keep the spirit of the queuing mechanism - where we tell a
sender to hold off until more rx buffers become available - I think the
following line in net_rx_packet() needs to be changed:
if (rc == rp || RING_REQUEST_CONS_OVERFLOW(&netdev->rx_ring, rc)) {
xen_be_printf(&netdev->xendev, 2, "no buffer, drop packet\n");
return -1; <-- this should be changed to return 0
}
That change assumes that net_event()'s flush is always called when the
rx ring gets more free space.
Any thoughts from Xen folks?
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