Re: [Qemu-devel] [PATCH] net/filter: Fix the output information for command 'info network'

[Hailiang Zhang]

On 2016/1/26 4:49, Eric Blake wrote:
> On 01/25/2016 02:12 AM, zhanghailiang wrote:
> > The properties of netfilter object could be changed by 'qom-set'
> > command, but the output of 'info network' command is not updated,
> > because it got the old information through nf->info_str, it will
> > not be updated while we change the value of netfilter's property.
> >
> > Here we split a helper function that could colletct the output
>
> s/colletct/collect/

> > information for filter, and also remove the useless member
> > 'info_str' from struct NetFilterState.
> >
> > Signed-off-by: zhanghailiang <address@hidden>
> > Cc: Jason Wang <address@hidden>
> > Cc: Eric Blake <address@hidden>
> > Cc: Markus Armbruster <address@hidden>
> > Cc: Yang Hongyang <address@hidden>
> > ---
> >   include/net/filter.h |  3 ++-
> >   net/filter.c         | 47 ++++++++++++++++++++++++++---------------------
> >   net/net.c            |  5 ++++-
> >   3 files changed, 32 insertions(+), 23 deletions(-)
>
> > +++ b/include/net/filter.h
> > @@ -55,7 +55,6 @@ struct NetFilterState {
> >       char *netdev_id;
> >       NetClientState *netdev;
> >       NetFilterDirection direction;
> > -    char info_str[256];
>
> Fixed size buffer...

> >       QTAILQ_ENTRY(NetFilterState) next;
> >   };
> >
> > @@ -74,4 +73,6 @@ ssize_t qemu_netfilter_pass_to_next(NetClientState *sender,
> >                                       int iovcnt,
> >                                       void *opaque);
> >
> > +void netfilter_print_info(NetFilterState *nf, char *output_str, int size);
> > +
> >   #endif /* QEMU_NET_FILTER_H */
> > diff --git a/net/filter.c b/net/filter.c
> > index 5d90f83..40254bd 100644
> > --- a/net/filter.c
> > +++ b/net/filter.c
> > @@ -128,6 +128,31 @@ static void netfilter_init(Object *obj)
> >                                NULL);
> >   }
> >
> > +void netfilter_print_info(NetFilterState *nf, char *output_str, int size)
> > +{
> > +    char *str, *info;
> > +    ObjectProperty *prop;
> > +    ObjectPropertyIterator iter;
> > +    StringOutputVisitor *ov;
> > +
> > +    /* generate info str */
> > +    object_property_iter_init(&iter, OBJECT(nf));
> > +    while ((prop = object_property_iter_next(&iter))) {
> > +        if (!strcmp(prop->name, "type")) {
> > +            continue;
> > +        }
> > +        ov = string_output_visitor_new(false);
> > +        object_property_get(OBJECT(nf), string_output_get_visitor(ov),
> > +                            prop->name, NULL);
> > +        str = string_output_get_string(ov);
> > +        string_output_visitor_cleanup(ov);
> > +        info = g_strdup_printf(",%s=%s", prop->name, str);
>
> ...but variable-sized print collection.  Why not just rewrite the
> function to malloc the entire string, and ditch the fixed-size buffer
> and size parameters altogether, while at it?

Yes, that is not elegant. It is inherited from the old codes.

> > +        g_strlcat(output_str, info, size);
> > +        g_free(str);
> > +        g_free(info);
> > +    }
> > +}
> > +
>
> > +++ b/net/net.c
> > @@ -1198,9 +1198,12 @@ void print_net_client(Monitor *mon, NetClientState *nc)
> >       }
> >       QTAILQ_FOREACH(nf, &nc->filters, next) {
> >           char *path = object_get_canonical_path_component(OBJECT(nf));
> > +        char info[256] = { 0 };
> > +
> > +        netfilter_print_info(nf, info, sizeof(info));
> >           monitor_printf(mon, "  - %s: type=%s%s\n", path,
> >                          object_get_typename(OBJECT(nf)),
> > -                       nf->info_str);
> > +                       info);
>
> Or, instead of printing into a temporary string just to then replay that
> string to monitor_printf(), why not have netfilter_print_info() directly
> write to the monitor (that is, use monitor_printf() directly in the
> helper function, instead of g_strlcat() into a temporary string).

Good idea, i will fix it like that in next version, thanks.