Il 22/04/2013 17:27, Fedorov Sergey ha scritto: > > E.g. network hub has 3 ports. Suppose when iterating through port list > in net_hub_port_can_receive() a packet is successfully delivered to the > first port, and then is queued in the source port queue because the > second port cannot receive packets. Later net_hub_flush() will flush the > packet from the source port queue and it will be delivered in every > port. But it had been already delivered to one of them. So it will be > delivered twice to some ports. Moreover there is less chance to dequeue > the packet if several clients can't receive periodically.
Perhaps it is indeed wrong to do this blocking in can_receive()... You're right that a hubport can always receive, but the hub itself should have a queue. If one port cannot receive, the packet should be appended to the hub's queue. And net_hub_flush will just go through the hub's queue. > Anyway, actually there is no need in net_hub_port_can_receive() as the > network hub can always receive packets and pass it to its port network > clients with qemu_send_packet(). I think it's more natural solution. I think the point was to keep dumps in sync with what actually happened on the other ports. Otherwise a "-net dump" port will show the packet immediately, even though it hasn't been delivered yet. Paolo
