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

[Hailiang Zhang <zhang.zhanghailiang@huawei.com>]

On 2015/11/27 19:39, Yang Hongyang wrote:
> 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);

Good catch, :)

>
>>       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
>

Hmm, Adding default filter is suggested by Jason, and yes, it still go
through the default filter though it does nothing, which is not graceful.

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

That's a good idea, and we should also show the off/on info for 'info network' command.

Thanks,
zhanghailiang

>>       return 0;
>>   }
>>
>>
>