On Tue, Sep 02, 2014 at 03:23:10PM +0100, Stefan Hajnoczi wrote:
> Do not modify guest memory or devices when the guest is stopped.
> Currently the netdevs still send packets while the guest is stopped if
> their file descriptor was being monitored for write (e.g. the socket
> write buffer filled before the guest was stopped).
>
> Netdevs call qemu_flush_queued_packets() when the file descriptor
> becomes writable again. Don't resume packet processing when this
> happens.
>
> Instead we flush queues when the guest resumes.
>
> Cc: qemu-sta...@nongnu.org
> Reported-by: Michael S. Tsirkin <m...@redhat.com>
> Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
Reviewed-by: Michael S. Tsirkin <m...@redhat.com>
> ---
> Note this fixes the transmit side. The receive side was recently fixed in
> "net: Forbid dealing with packets when VM is not running".
>
> net/net.c | 30 ++++++++++++++++++++++++++++++
> 1 file changed, 30 insertions(+)
>
> diff --git a/net/net.c b/net/net.c
> index 6d930ea..74ec07a 100644
> --- a/net/net.c
> +++ b/net/net.c
> @@ -47,6 +47,7 @@
> # define CONFIG_NET_BRIDGE
> #endif
>
> +static VMChangeStateEntry *net_change_state_entry;
> static QTAILQ_HEAD(, NetClientState) net_clients;
>
> const char *host_net_devices[] = {
> @@ -506,6 +507,11 @@ void qemu_purge_queued_packets(NetClientState *nc)
>
> void qemu_flush_queued_packets(NetClientState *nc)
> {
> + /* Guest memory and devices must not be modified while stopped */
> + if (!runstate_is_running()) {
> + return;
> + }
> +
> nc->receive_disabled = 0;
>
> if (nc->peer && nc->peer->info->type == NET_CLIENT_OPTIONS_KIND_HUBPORT)
> {
> @@ -1168,6 +1174,25 @@ void qmp_set_link(const char *name, bool up, Error
> **errp)
> }
> }
>
> +/* Kick net clients when guest resumes. If a file descriptor was monitored
> for
> + * writing before the guest was stopped, there will be nothing monitoring it
> + * right now so a kick is required to get packets flowing again.
> + */
> +static void net_vm_change_state_handler(void *opaque, int running,
> + RunState state)
> +{
> + NetClientState *nc;
> + NetClientState *tmp;
> +
> + if (!running) {
> + return;
> + }
> +
> + QTAILQ_FOREACH_SAFE(nc, &net_clients, next, tmp) {
> + qemu_flush_queued_packets(nc);
> + }
> +}
> +
> void net_cleanup(void)
> {
> NetClientState *nc;
> @@ -1183,6 +1208,8 @@ void net_cleanup(void)
> qemu_del_net_client(nc);
> }
> }
> +
> + qemu_del_vm_change_state_handler(net_change_state_entry);
> }
>
> void net_check_clients(void)
> @@ -1268,6 +1295,9 @@ int net_init_clients(void)
> #endif
> }
>
> + net_change_state_entry =
> + qemu_add_vm_change_state_handler(net_vm_change_state_handler, NULL);
> +
> QTAILQ_INIT(&net_clients);
>
> if (qemu_opts_foreach(qemu_find_opts("netdev"), net_init_netdev, NULL,
> 1) == -1)
> --
> 1.9.3
