Re: [Qemu-devel] [PATCH RFC] net: add a flag to disable mac/vlan filtering

[Anthony Liguori]

On 03/09/2010 07:15 AM, Michael S. Tsirkin wrote:
> New bridge in linux 2.6.34 adds IGMP snooping support,
> after which bridge should not normally flood any packets.
> While we still need mac table to arm forwarding tables
> after migration, we can thus ignore it for rx datapath.
>
> For vlan, it's possible to do filtering down the
> stack simply by using bridge per guest and binding said bridge
> to vlan device, which some people do.
>
> Since qemu has no easy way to check IGMP snooping
> support in bridge or how it's connected, add options
> to disable rx filtering, so that management can set it
> as appropriate.
> Use these options to optimise virtio-net rx path.
> We still ask guest for the list of vlans/macs for
> migration.
>
> Signed-off-by: Michael S. Tsirkin<address@hidden>
>    

Can't this be achieved by just disabling the feature bits?  IOW,

ctrl_vq=0,ctrl_vlan=0?

Regards,

Anthony Liguori

> Cc: Alex Williamson<address@hidden>
> Cc: Andreas Plesner Jacobsen<address@hidden>
> ---
>   hw/virtio-net.c |   10 +++++++++-
>   net.h           |   12 +++++++++++-
>   2 files changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/hw/virtio-net.c b/hw/virtio-net.c
> index 5c0093e..01b45ed 100644
> --- a/hw/virtio-net.c
> +++ b/hw/virtio-net.c
> @@ -47,6 +47,7 @@ typedef struct VirtIONet
>       uint8_t nomulti;
>       uint8_t nouni;
>       uint8_t nobcast;
> +    uint32_t filtering;
>       struct {
>           int in_use;
>           int first_multi;
> @@ -475,12 +476,17 @@ static int receive_filter(VirtIONet *n, const uint8_t 
> *buf, int size)
>           ptr += sizeof(struct virtio_net_hdr);
>       }
>
> -    if (!memcmp(&ptr[12], vlan, sizeof(vlan))) {
> +    if ((n->filtering&  (0x1<<  NICCONF_F_VLAN_FILTERING))&&
> +        !memcmp(&ptr[12], vlan, sizeof(vlan))) {
>           int vid = be16_to_cpup((uint16_t *)(ptr + 14))&  0xfff;
>           if (!(n->vlans[vid>>  5]&  (1U<<  (vid&  0x1f))))
>               return 0;
>       }
>
> +    if (!(n->filtering&  (0x1<<  NICCONF_F_MAC_FILTERING))) {
> +            return 1;
> +    }
> +
>       if (ptr[0]&  1) { // multicast
>           if (!memcmp(ptr, bcast, sizeof(bcast))) {
>               return !n->nobcast;
> @@ -863,6 +869,8 @@ VirtIODevice *virtio_net_init(DeviceState *dev, NICConf 
> *conf)
>
>       n->mac_table.macs = qemu_mallocz(MAC_TABLE_ENTRIES * ETH_ALEN);
>
> +    n->filtering = conf->filtering;
> +
>       n->vlans = qemu_mallocz(MAX_VLAN>>  3);
>
>       register_savevm("virtio-net", virtio_net_id++, VIRTIO_NET_VM_VERSION,
> diff --git a/net.h b/net.h
> index 33a1eaf..459ede5 100644
> --- a/net.h
> +++ b/net.h
> @@ -18,12 +18,22 @@ typedef struct NICConf {
>       MACAddr macaddr;
>       VLANState *vlan;
>       VLANClientState *peer;
> +    uint32_t filtering;
>   } NICConf;
>
> +enum {
> +    NICCONF_F_MAC_FILTERING = 0,
> +    NICCONF_F_VLAN_FILTERING = 1
> +};
> +
>   #define DEFINE_NIC_PROPERTIES(_state, _conf)                            \
>       DEFINE_PROP_MACADDR("mac",   _state, _conf.macaddr),                \
>       DEFINE_PROP_VLAN("vlan",     _state, _conf.vlan),                   \
> -    DEFINE_PROP_NETDEV("netdev", _state, _conf.peer)
> +    DEFINE_PROP_NETDEV("netdev", _state, _conf.peer),                    \
> +    DEFINE_PROP_BIT("mac_filtering", _state, _conf.filtering,           \
> +                     NICCONF_F_MAC_FILTERING, true)                     \
> +    DEFINE_PROP_BIT("vlan_filtering", _state, _conf.filtering,          \
> +                     NICCONF_F_VLAN_FILTERING, true)                    \
>
>   /* VLANs support */
>
>