Re: [Qemu-devel] [PATCH COLO-Frame v11 34/39] net/filter-buffer: Add default filter-buffer for each netdev

[Yang Hongyang <hongyang.yang@easystack.cn>]

On 2015年11月24日 17:25, zhanghailiang wrote:
> We add each netdev a default filter-buffer, which will be used for COLO
> or Micro-checkpoint to buffer VM's packets. The name of default filter-buffer
> is 'nop'.
> For the default filter-buffer, it will not buffer any packets in default.
> So it has no side effect for the netdev.
>
> Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
> Cc: Jason Wang <jasowang@redhat.com>
> Cc: Yang Hongyang <hongyang.yang@easystack.cn>
> ---
> v11:
> - New patch
> ---
[...]
>   static void filter_buffer_flush(NetFilterState *nf)
> @@ -65,6 +73,10 @@ static ssize_t filter_buffer_receive_iov(NetFilterState *nf,
>   {
>       FilterBufferState *s = FILTER_BUFFER(nf);
>
> +    /* Don't buffer any packets if the filter is not enabled */
> +    if (!s->enable_buffer) {
> +        return 0;
> +    }
>       /*
>        * We return size when buffer a packet, the sender will take it as
>        * a already sent packet, so sent_cb should not be called later.
> @@ -102,6 +114,7 @@ static void filter_buffer_cleanup(NetFilterState *nf)
>   static void filter_buffer_setup(NetFilterState *nf, Error **errp)
>   {
>       FilterBufferState *s = FILTER_BUFFER(nf);
> +    char *path = object_get_canonical_path_component(OBJECT(nf));

path should be freed after use.

>
>       /*
>        * We may want to accept zero interval when VM FT solutions like MC
> @@ -114,6 +127,7 @@ static void filter_buffer_setup(NetFilterState *nf, Error **errp)
>       }
>
>       s->incoming_queue = qemu_new_net_queue(qemu_netfilter_pass_to_next, nf);
> +    s->is_default = !strcmp(path, "nop");

free(path);

>       if (s->interval) {
>           timer_init_us(&s->release_timer, QEMU_CLOCK_VIRTUAL,
>                         filter_buffer_release_timer, nf);
> @@ -163,6 +177,66 @@ out:
>       error_propagate(errp, local_err);
>   }
>
> +/*
> +* This will be used by COLO or MC FT, for which they will need
> +* to buffer the packets of VM's net devices, Here we add a default
> +* buffer filter for each netdev. The name of default buffer filter is
> +* 'nop'
> +*/
> +void netdev_add_default_filter_buffer(const char *netdev_id,
> +                                      NetFilterDirection direction,
> +                                      Error **errp)
> +{
> +    QmpOutputVisitor *qov;
> +    QmpInputVisitor *qiv;
> +    Visitor *ov, *iv;
> +    QObject *obj = NULL;
> +    QDict *qdict;
> +    void *dummy = NULL;
> +    const char *id = "nop";
> +    char *queue = g_strdup(NetFilterDirection_lookup[direction]);
> +    NetClientState *nc = qemu_find_netdev(netdev_id);
> +    Error *err = NULL;
> +
> +    /* FIXME: Not support multiple queues */
> +    if (!nc || nc->queue_index > 1) {
> +        return;
> +    }
> +    qov = qmp_output_visitor_new();
> +    ov = qmp_output_get_visitor(qov);
> +    visit_start_struct(ov,  &dummy, NULL, NULL, 0, &err);
> +    if (err) {
> +        goto out;
> +    }
> +    visit_type_str(ov, &nc->name, "netdev", &err);
> +    if (err) {
> +        goto out;
> +    }
> +    visit_type_str(ov, &queue, "queue", &err);
> +    if (err) {
> +        goto out;
> +    }
> +    visit_end_struct(ov, &err);
> +    if (err) {
> +        goto out;
> +    }
> +    obj = qmp_output_get_qobject(qov);
> +    g_assert(obj != NULL);
> +    qdict = qobject_to_qdict(obj);
> +    qmp_output_visitor_cleanup(qov);
> +
> +    qiv = qmp_input_visitor_new(obj);
> +    iv = qmp_input_get_visitor(qiv);
> +    object_add(TYPE_FILTER_BUFFER, id, qdict, iv, &err);
> +    qmp_input_visitor_cleanup(qiv);
> +    qobject_decref(obj);
> +out:
> +    g_free(queue);
> +    if (err) {
> +        error_propagate(errp, err);
> +    }
> +}
> +
>   static void filter_buffer_init(Object *obj)
>   {
>       object_property_add(obj, "interval", "int",
> diff --git a/net/net.c b/net/net.c
> index ade6051..b36d49f 100644
> --- a/net/net.c
> +++ b/net/net.c
> @@ -1028,6 +1028,14 @@ static int net_client_init1(const void *object, int is_netdev, Error **errp)
>           }
>           return -1;
>       }
> +
> +    if (is_netdev) {
> +        const Netdev *netdev = object;
> +
> +        netdev_add_default_filter_buffer(netdev->id,
> +                                         NET_FILTER_DIRECTION_RX,
> +                                         errp);
> +    }

I'm not sure if add this default to all netdev is a good idea, because
in most cases, they do not need the default filter, although it is a
nop, it still go though the filter. Maybe we can add a argument to
netdev to easily turn if on, for example,
   -netdev default-filter=true

if not supplied, default to off, that is, by default no default filter
will be attached to the netdev.

>       return 0;
>   }
>
>

-- 
Thanks,
Yang