Re: [Qemu-devel] [PATCH v2] virtio-net: add a field to indicate if vlan table is used

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Feb 20, 2014 at 12:46:14PM -0500, Vlad Yasevich wrote:
> On 02/20/2014 11:38 AM, Amos Kong wrote:
> > Stefan Fritsch just fixed a virtio-net driver bug [1], virtio-net won't
> > filter out VLAN-tagged packets if VIRTIO_NET_F_CTRL_VLAN isn't negotiated.
> > 
> > This patch added a new field to @RxFilterInfo to indicate if management
> > uses the vlan table.
> > 
> > [1] http://lists.nongnu.org/archive/html/qemu-devel/2014-02/msg02604.html
> > 
> > Signed-off-by: Amos Kong <akong@redhat.com>
> > ---
> > V2: don't make vlan-table optional, add a flag to indicate
> >     if vlan table is used by management
> > ---
> >  hw/net/virtio-net.c | 38 +++++++++++++++++++++++++-------------
> >  qapi-schema.json    |  3 +++
> >  qmp-commands.hx     |  2 ++
> >  3 files changed, 30 insertions(+), 13 deletions(-)
> > 
> > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> > index 3626608..f591f4e 100644
> > --- a/hw/net/virtio-net.c
> > +++ b/hw/net/virtio-net.c
> > @@ -222,13 +222,33 @@ static char *mac_strdup_printf(const uint8_t *mac)
> >                              mac[1], mac[2], mac[3], mac[4], mac[5]);
> >  }
> >  
> > +static intList *get_vlan_table(VirtIONet *n)
> > +{
> > +    intList *list, *entry;
> > +    int i, j;
> > +
> > +    list = NULL;
> > +    for (i = 0; i < MAX_VLAN >> 5; i++) {
> > +        for (j = 0; n->vlans[i] && j < 0x1f; j++) {
> > +            if (n->vlans[i] & (1U << j)) {
> > +                entry = g_malloc0(sizeof(*entry));
> > +                entry->value = (i << 5) + j;
> > +                entry->next = list;
> > +                list = entry;
> > +            }
> > +        }
> > +    }
> > +
> > +    return list;
> > +}
> > +
> >  static RxFilterInfo *virtio_net_query_rxfilter(NetClientState *nc)
> >  {
> >      VirtIONet *n = qemu_get_nic_opaque(nc);
> > +    VirtIODevice *vdev = VIRTIO_DEVICE(n);
> >      RxFilterInfo *info;
> >      strList *str_list, *entry;
> > -    intList *int_list, *int_entry;
> > -    int i, j;
> > +    int i;
> >  
> >      info = g_malloc0(sizeof(*info));
> >      info->name = g_strdup(nc->name);
> > @@ -273,19 +293,11 @@ static RxFilterInfo *virtio_net_query_rxfilter(NetClientState *nc)
> >          str_list = entry;
> >      }
> >      info->multicast_table = str_list;
> > +    info->vlan_table = get_vlan_table(n);
> >  
> > -    int_list = NULL;
> > -    for (i = 0; i < MAX_VLAN >> 5; i++) {
> > -        for (j = 0; n->vlans[i] && j < 0x1f; j++) {
> > -            if (n->vlans[i] & (1U << j)) {
> > -                int_entry = g_malloc0(sizeof(*int_entry));
> > -                int_entry->value = (i << 5) + j;
> > -                int_entry->next = int_list;
> > -                int_list = int_entry;
> > -            }
> > -        }
> > +    if ((1 << VIRTIO_NET_F_CTRL_VLAN) & vdev->guest_features) {
> > +        info->vlan = true;
> >      }
> 
> So, in the case that vlan filtering is not supported in the guest
> we get:
>              "vlan": false,
>              "vlan-table": [
>                  0,
>                  1,
>                  2,
>                  ...
>                  4095
>             ]
> since virtio_net now initializes the table to all 1s.
> Seems a bit awkward.  We are providing a lot of data that
> is simply going to be ignored.

Yes - old qemu gave an empty table anyway, so I think
we should keep doing that: giving an all-vlans list
would help old libvirt work better with new qemu
but perpetuates the bug.

> > -    info->vlan_table = int_list;
> >  
> >      /* enable event notification after query */
> >      nc->rxfilter_notify_enabled = 1;
> > diff --git a/qapi-schema.json b/qapi-schema.json
> > index 7cfb5e5..5b54e94 100644
> > --- a/qapi-schema.json
> > +++ b/qapi-schema.json
> > @@ -4032,6 +4032,8 @@
> >  #
> >  # @unicast-overflow: unicast table is overflowed or not
> >  #
> > +# @vlan: whether management uses the vlan table
> > +#
> 
> The above description seems a bit confusing to me.  The value
> we are returning describes whether or not qemu is performing
> vlan filtering.  I am not sure if it has any bearing on what
> management may be doing.
> 
> I think the idea is that management, in the future, would look at
> this value and make some decision about applying provided filter
> to the current host configuration.
> 
> >  # @main-mac: the main macaddr string
> >  #
> >  # @vlan-table: a list of active vlan id
> > @@ -4052,6 +4054,7 @@
> >      'broadcast-allowed':  'bool',
> >      'multicast-overflow': 'bool',
> >      'unicast-overflow':   'bool',
> > +    'vlan':               'bool',
> 
> Not terribly descriptive.  May be call it vlan-filter?
> 
> Thanks
> -vlad
> >      'main-mac':           'str',
> >      'vlan-table':         ['int'],
> >      'unicast-table':      ['str'],
> > diff --git a/qmp-commands.hx b/qmp-commands.hx
> > index cce6b81..b170c79 100644
> > --- a/qmp-commands.hx
> > +++ b/qmp-commands.hx
> > @@ -3307,6 +3307,7 @@ Each array entry contains the following:
> >  - "broadcast-allowed": allow to receive broadcast (json-bool)
> >  - "multicast-overflow": multicast table is overflowed (json-bool)
> >  - "unicast-overflow": unicast table is overflowed (json-bool)
> > +- "vlan": management uses the vlan table (json-bool)
> >  - "main-mac": main macaddr string (json-string)
> >  - "vlan-table": a json-array of active vlan id
> >  - "unicast-table": a json-array of unicast macaddr string
> > @@ -3321,6 +3322,7 @@ Example:
> >              "name": "vnet0",
> >              "main-mac": "52:54:00:12:34:56",
> >              "unicast": "normal",
> > +            "vlan": true,
> >              "vlan-table": [
> >                  4,
> >                  0
> > 
>