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net: fix qemu_flush_queued_packets() in presence of a hub

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When frontend and backend are connected through a hub as below
(showing only one direction), and the frontend (or in general, all
output ports of the hub) cannot accept more traffic, the backend
queues packets in queue-A.

When the frontend (or in general, one output port) becomes ready again,
quemu tries to flush packets from queue-B, which is unfortunately empty.

  e1000.0 <--[queue B]-- hub0port0(hub)hub0port1 <--[queue A]-- tap.0

To fix this i propose to introduce a new function net_hub_flush()
which is called when trying to flush a queue connected to a hub.

Signed-off-by: Luigi Rizzo <rizzo@iet.unipi.it>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Luigi Rizzo 2013-02-05 17:53:31 +01:00 committed by Stefan Hajnoczi
parent ee24aaf356
commit 199ee608f0
3 changed files with 21 additions and 0 deletions
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14
net/hub.c
View File

@ -338,3 +338,17 @@ void net_hub_check_clients(void)
}
}
}
bool net_hub_flush(NetClientState *nc)
{
NetHubPort *port;
NetHubPort *source_port = DO_UPCAST(NetHubPort, nc, nc);
int ret = 0;
QLIST_FOREACH(port, &source_port->hub->ports, next) {
if (port != source_port) {
ret += qemu_net_queue_flush(port->nc.send_queue);
}
}
return ret ? true : false;
}

1
net/hub.h
View File

@ -21,5 +21,6 @@ NetClientState *net_hub_add_port(int hub_id, const char *name);
NetClientState *net_hub_find_client_by_name(int hub_id, const char *name);
void net_hub_info(Monitor *mon);
void net_hub_check_clients(void);
bool net_hub_flush(NetClientState *nc);
#endif /* NET_HUB_H */

6
net/net.c
View File

@ -441,6 +441,12 @@ void qemu_flush_queued_packets(NetClientState *nc)
{
nc->receive_disabled = 0;
if (nc->peer && nc->peer->info->type == NET_CLIENT_OPTIONS_KIND_HUBPORT) {
if (net_hub_flush(nc->peer)) {
qemu_notify_event();
}
return;
}
if (qemu_net_queue_flush(nc->send_queue)) {
/* We emptied the queue successfully, signal to the IO thread to repoll
* the file descriptor (for tap, for example).