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

[Hailiang Zhang]

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 <address@hidden>
> > Cc: Jason Wang <address@hidden>
> > Cc: Yang Hongyang <address@hidden>
> > ---
> > 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;
> >   }