Re: [Qemu-devel] [PATCH qemu v2] tap: Allow specifying a bridge

[Greg Kurz <groug@kaod.org>]

On Tue, 13 Sep 2016 17:11:54 +1000
Alexey Kardashevskiy <aik@ozlabs.ru> wrote:

> The tap backend is already using qemu-bridge-helper to attach tap
> interface to a bridge but (unlike the bridge backend) it always uses
> the default bridge name - br0.
> 
> This adds a "br" property support to the tap backend.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> --

Cool ! This allows to easily attach to virbr0 :)

Now that a consensus seems to have been reached for @br:

Reviewed-by: Greg Kurz <groug@kaod.org>
Tested-by: Greg Kurz <groug@kaod.org>

Also Cc'ing the tap device maintainer.

Cheers.

--
Greg

> Changes:
> v2:
> * documented a new member in json and hx
> ---
>  net/tap.c        |  4 +++-
>  qapi-schema.json |  3 +++
>  qemu-options.hx  | 12 +++++++-----
>  3 files changed, 13 insertions(+), 6 deletions(-)
> 
> diff --git a/net/tap.c b/net/tap.c
> index 6abb962..b6896a7 100644
> --- a/net/tap.c
> +++ b/net/tap.c
> @@ -857,7 +857,9 @@ free_fail:
>              return -1;
>          }
>  
> -        fd = net_bridge_run_helper(tap->helper, DEFAULT_BRIDGE_INTERFACE,
> +        fd = net_bridge_run_helper(tap->helper,
> +                                   tap->has_br ?
> +                                   tap->br : DEFAULT_BRIDGE_INTERFACE,
>                                     errp);
>          if (fd == -1) {
>              return -1;
> diff --git a/qapi-schema.json b/qapi-schema.json
> index c4f3674..dbb9f8f 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -2575,6 +2575,8 @@
>  #
>  # @downscript: #optional script to shut down the interface
>  #
> +# @br: #optional bridge name
> +#
>  # @helper: #optional command to execute to configure bridge
>  #
>  # @sndbuf: #optional send buffer limit. Understands [TGMKkb] suffixes.
> @@ -2604,6 +2606,7 @@
>      '*fds':        'str',
>      '*script':     'str',
>      '*downscript': 'str',
> +    '*br':         'str',
>      '*helper':     'str',
>      '*sndbuf':     'size',
>      '*vnet_hdr':   'bool',
> diff --git a/qemu-options.hx b/qemu-options.hx
> index a71aaf8..0b3ea42 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -1594,10 +1594,11 @@ DEF("netdev", HAS_ARG, QEMU_OPTION_netdev,
>      "                configure a host TAP network backend with ID 'str'\n"
>  #else
>      "-netdev tap,id=str[,fd=h][,fds=x:y:...:z][,ifname=name][,script=file][,downscript=dfile]\n"
> -    "         [,helper=helper][,sndbuf=nbytes][,vnet_hdr=on|off][,vhost=on|off]\n"
> +    "         [,br=bridge][,helper=helper][,sndbuf=nbytes][,vnet_hdr=on|off][,vhost=on|off]\n"
>      "         [,vhostfd=h][,vhostfds=x:y:...:z][,vhostforce=on|off][,queues=n]\n"
>      "         [,poll-us=n]\n"
>      "                configure a host TAP network backend with ID 'str'\n"
> +    "                connected to a bridge (default=" DEFAULT_BRIDGE_INTERFACE ")\n"
>      "                use network scripts 'file' (default=" DEFAULT_NETWORK_SCRIPT ")\n"
>      "                to configure it and 'dfile' (default=" DEFAULT_NETWORK_DOWN_SCRIPT ")\n"
>      "                to deconfigure it\n"
> @@ -1884,8 +1885,8 @@ processed and applied to -net user. Mixing them with the new configuration
>  syntax gives undefined results. Their use for new applications is discouraged
>  as they will be removed from future versions.
>  
> -@item -netdev tap,id=@var{id}[,fd=@var{h}][,ifname=@var{name}][,script=@var{file}][,downscript=@var{dfile}][,helper=@var{helper}]
> -@itemx -net tap[,vlan=@var{n}][,name=@var{name}][,fd=@var{h}][,ifname=@var{name}][,script=@var{file}][,downscript=@var{dfile}][,helper=@var{helper}]
> +@item -netdev tap,id=@var{id}[,fd=@var{h}][,ifname=@var{name}][,script=@var{file}][,downscript=@var{dfile}][,br=@var{bridge}][,helper=@var{helper}]
> +@itemx -net tap[,vlan=@var{n}][,name=@var{name}][,fd=@var{h}][,ifname=@var{name}][,script=@var{file}][,downscript=@var{dfile}][,br=@var{bridge}][,helper=@var{helper}]
>  Connect the host TAP network interface @var{name} to VLAN @var{n}.
>  
>  Use the network script @var{file} to configure it and the network script
> @@ -1896,8 +1897,9 @@ automatically provides one. The default network configure script is
>  to disable script execution.
>  
>  If running QEMU as an unprivileged user, use the network helper
> -@var{helper} to configure the TAP interface. The default network
> -helper executable is @file{/path/to/qemu-bridge-helper}.
> +@var{helper} to configure the TAP interface and attach it to the bridge.
> +The default network helper executable is @file{/path/to/qemu-bridge-helper}
> +and the default bridge device is @file{br0}.
>  
>  @option{fd}=@var{h} can be used to specify the handle of an already
>  opened host TAP interface.