net: Flush queued packets when guest resumes

Since commit 6e99c63 "net/socket: Drop net_socket_can_send" and friends,
net queues need to be explicitly flushed after qemu_can_send_packet()
returns false, because the netdev side will disable the polling of fd.

This fixes the case of "cont" after "stop" (or migration).

Signed-off-by: Fam Zheng <famz@redhat.com>
Message-id: 1436232067-29144-1-git-send-email-famz@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 12 insertions, 7 deletions

diff --git a/net/net.c b/net/net.c
index 6ff7fec1bb..28a5597b8d 100644
--- a/net/net.c
+++ b/net/net.c
@@ -1257,14 +1257,19 @@ void qmp_set_link(const char *name, bool up, Error **errp)
 static void net_vm_change_state_handler(void *opaque, int running,
                                         RunState state)
 {
-    /* Complete all queued packets, to guarantee we don't modify
-     * state later when VM is not running.
-     */
-    if (!running) {
-        NetClientState *nc;
-        NetClientState *tmp;
+    NetClientState *nc;
+    NetClientState *tmp;
 
-        QTAILQ_FOREACH_SAFE(nc, &net_clients, next, tmp) {
+    QTAILQ_FOREACH_SAFE(nc, &net_clients, next, tmp) {
+        if (running) {
+            /* Flush queued packets and wake up backends. */
+            if (nc->peer && qemu_can_send_packet(nc)) {
+                qemu_flush_queued_packets(nc->peer);
+            }
+        } else {
+            /* Complete all queued packets, to guarantee we don't modify
+             * state later when VM is not running.
+             */
             qemu_flush_or_purge_queued_packets(nc, true);
         }
     }