Re: [Qemu-devel] [PATCH v2 2/6] net: removing tap_using_vnet_hdr() function

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

On Tue, Jan 14, 2014 at 11:59:46AM +0100, Vincenzo Maffione wrote:
> This function was used to set the using_vnet_hdr field into the
> TAPState struct. However, it is always called immediately before
> (see virtio-net.c) or immediately after (see vmxnet3.c) the function
> tap_set_vnet_hdr_len(). It's therefore possible to set the
> using_vnet_hdr field directly in tap_set_vnet_hdr_len() and remove
> tap_using_vnet_hdr(), making the code simpler.
> 
> Signed-off-by: Vincenzo Maffione <v.maffione@gmail.com>


virtio net only calls tap_set_vnet_hdr_len if tap_has_vnet_hdr_len
returns true.
I think this patch will break old linux hosts which don't support
modifying vnet_hdr_len.

Also, the current API is quite ugly, but I don't think adding side
effects to tap_set_vnet_hdr_len is an improvement.

> ---
>  hw/net/virtio-net.c |  4 ----
>  hw/net/vmxnet3.c    |  2 --
>  include/net/tap.h   |  1 -
>  net/tap-win32.c     |  4 ----
>  net/tap.c           | 11 +----------
>  5 files changed, 1 insertion(+), 21 deletions(-)
> 
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index 3626608..ac8322d 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -1496,7 +1496,6 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp)
>      VirtIODevice *vdev = VIRTIO_DEVICE(dev);
>      VirtIONet *n = VIRTIO_NET(dev);
>      NetClientState *nc;
> -    int i;
>  
>      virtio_init(vdev, "virtio-net", VIRTIO_ID_NET, n->config_size);
>  
> @@ -1543,9 +1542,6 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp)
>  
>      peer_test_vnet_hdr(n);
>      if (peer_has_vnet_hdr(n)) {
> -        for (i = 0; i < n->max_queues; i++) {
> -            tap_using_vnet_hdr(qemu_get_subqueue(n->nic, i)->peer, true);
> -        }
>          n->host_hdr_len = sizeof(struct virtio_net_hdr);
>      } else {
>          n->host_hdr_len = 0;
> diff --git a/hw/net/vmxnet3.c b/hw/net/vmxnet3.c
> index 19687aa..096b598 100644
> --- a/hw/net/vmxnet3.c
> +++ b/hw/net/vmxnet3.c
> @@ -1937,8 +1937,6 @@ static void vmxnet3_net_init(VMXNET3State *s)
>      if (s->peer_has_vhdr) {
>          tap_set_vnet_hdr_len(qemu_get_queue(s->nic)->peer,
>              sizeof(struct virtio_net_hdr));
> -
> -        tap_using_vnet_hdr(qemu_get_queue(s->nic)->peer, 1);
>      }
>  
>      qemu_format_nic_info_str(qemu_get_queue(s->nic), s->conf.macaddr.a);
> diff --git a/include/net/tap.h b/include/net/tap.h
> index a3490a9..54974dc 100644
> --- a/include/net/tap.h
> +++ b/include/net/tap.h
> @@ -32,7 +32,6 @@
>  bool tap_has_ufo(NetClientState *nc);
>  bool tap_has_vnet_hdr(NetClientState *nc);
>  bool tap_has_vnet_hdr_len(NetClientState *nc, int len);
> -void tap_using_vnet_hdr(NetClientState *nc, bool using_vnet_hdr);
>  void tap_set_offload(NetClientState *nc, int csum, int tso4, int tso6, int ecn, int ufo);
>  void tap_set_vnet_hdr_len(NetClientState *nc, int len);
>  int tap_enable(NetClientState *nc);
> diff --git a/net/tap-win32.c b/net/tap-win32.c
> index edf26c4..f4cd002 100644
> --- a/net/tap-win32.c
> +++ b/net/tap-win32.c
> @@ -741,10 +741,6 @@ void tap_fd_set_vnet_hdr_len(int fd, int len)
>  {
>  }
>  
> -void tap_using_vnet_hdr(NetClientState *nc, bool using_vnet_hdr)
> -{
> -}
> -
>  void tap_set_offload(NetClientState *nc, int csum, int tso4,
>                       int tso6, int ecn, int ufo)
>  {
> diff --git a/net/tap.c b/net/tap.c
> index c805f3c..42f768c 100644
> --- a/net/tap.c
> +++ b/net/tap.c
> @@ -247,16 +247,7 @@ void tap_set_vnet_hdr_len(NetClientState *nc, int len)
>  
>      tap_fd_set_vnet_hdr_len(s->fd, len);
>      s->host_vnet_hdr_len = len;
> -}
> -
> -void tap_using_vnet_hdr(NetClientState *nc, bool using_vnet_hdr)
> -{
> -    TAPState *s = DO_UPCAST(TAPState, nc, nc);
> -
> -    assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_TAP);
> -    assert(!!s->host_vnet_hdr_len == using_vnet_hdr);
> -
> -    s->using_vnet_hdr = using_vnet_hdr;
> +    s->using_vnet_hdr = true;
>  }
>  
>  void tap_set_offload(NetClientState *nc, int csum, int tso4,
> -- 
> 1.8.5.2
>