Re: [Qemu-devel] [PATCH v9 01/10] net: add a new object netfilter

[Stefan Hajnoczi <stefanha@redhat.com>]

On Tue, Sep 01, 2015 at 05:06:14PM +0800, Yang Hongyang wrote:
> Add the framework for a new netfilter object and a new
> -netfilter CLI option as a basis for the following patches.
> Note that the new added document in qemu-options.hx indicate that
> there's a buffer filter. This type of filter will be implemented
> in the following patches.

Adding Markus and Andreas for the command-line and QAPI perspective on
adding a new type of object to QEMU.

It seems you have followed how the net subsystem adds -netdev.  I think
that approach is not the preferred way of adding new types of objects...

> 
> Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
> CC: Paolo Bonzini <pbonzini@redhat.com>
> CC: Eric Blake <eblake@redhat.com>
> Reviewed-by: Thomas Huth <thuth@redhat.com>
> ---
> v9: Add documentation of buffer filter which will be implemented later
>     in this series.
> ---
>  include/net/filter.h    | 15 +++++++++++++++
>  include/sysemu/sysemu.h |  1 +
>  net/Makefile.objs       |  1 +
>  net/filter.c            | 27 +++++++++++++++++++++++++++
>  qemu-options.hx         | 21 +++++++++++++++++++++
>  vl.c                    | 13 +++++++++++++
>  6 files changed, 78 insertions(+)
>  create mode 100644 include/net/filter.h
>  create mode 100644 net/filter.c
> 
> diff --git a/include/net/filter.h b/include/net/filter.h
> new file mode 100644
> index 0000000..4242ded
> --- /dev/null
> +++ b/include/net/filter.h
> @@ -0,0 +1,15 @@
> +/*
> + * Copyright (c) 2015 FUJITSU LIMITED
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or
> + * later.  See the COPYING file in the top-level directory.
> + */
> +
> +#ifndef QEMU_NET_FILTER_H
> +#define QEMU_NET_FILTER_H
> +
> +#include "qemu-common.h"
> +
> +int net_init_filters(void);
> +
> +#endif /* QEMU_NET_FILTER_H */
> diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
> index 44570d1..15d6d00 100644
> --- a/include/sysemu/sysemu.h
> +++ b/include/sysemu/sysemu.h
> @@ -212,6 +212,7 @@ extern QemuOptsList qemu_chardev_opts;
>  extern QemuOptsList qemu_device_opts;
>  extern QemuOptsList qemu_netdev_opts;
>  extern QemuOptsList qemu_net_opts;
> +extern QemuOptsList qemu_netfilter_opts;
>  extern QemuOptsList qemu_global_opts;
>  extern QemuOptsList qemu_mon_opts;
>  
> diff --git a/net/Makefile.objs b/net/Makefile.objs
> index ec19cb3..914aec0 100644
> --- a/net/Makefile.objs
> +++ b/net/Makefile.objs
> @@ -13,3 +13,4 @@ common-obj-$(CONFIG_HAIKU) += tap-haiku.o
>  common-obj-$(CONFIG_SLIRP) += slirp.o
>  common-obj-$(CONFIG_VDE) += vde.o
>  common-obj-$(CONFIG_NETMAP) += netmap.o
> +common-obj-y += filter.o
> diff --git a/net/filter.c b/net/filter.c
> new file mode 100644
> index 0000000..4e40f08
> --- /dev/null
> +++ b/net/filter.c
> @@ -0,0 +1,27 @@
> +/*
> + * Copyright (c) 2015 FUJITSU LIMITED
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or
> + * later.  See the COPYING file in the top-level directory.
> + */
> +
> +#include "qemu-common.h"
> +#include "net/filter.h"
> +
> +int net_init_filters(void)
> +{
> +    return 0;
> +}
> +
> +QemuOptsList qemu_netfilter_opts = {
> +    .name = "netfilter",
> +    .implied_opt_name = "type",
> +    .head = QTAILQ_HEAD_INITIALIZER(qemu_netfilter_opts.head),
> +    .desc = {
> +        /*
> +         * no elements => accept any params
> +         * validation will happen later
> +         */
> +        { /* end of list */ }
> +    },
> +};

...because catch-alls like this make introspection impossible.

> diff --git a/qemu-options.hx b/qemu-options.hx
> index 77f5853..f1d42a1 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -1991,6 +1991,27 @@ override the default configuration (@option{-net nic -net user}) which
>  is activated if no @option{-net} options are provided.
>  ETEXI
>  
> +DEF("netfilter", HAS_ARG, QEMU_OPTION_netfilter,
> +    "-netfilter buffer,id=str,netdev=str[,chain=in|out|all,interval=t]\n"
> +    "                buffer network packets on netdev. if interval provided, will release\n"
> +    "                packets by interval. Interval scale: microsecond\n", QEMU_ARCH_ALL)

Perhaps the -object option should be used:

  -object netfilter-buffer,id=str,netdev=str[,chain=in|out|all,interval=t]

That is how IOThread and memory backends were recently added.

They are QOM objects (see include/qom/object.h) and eliminate the need
to write boilerplate code that adds new command-line options and
instantiates objects.

> +STEXI
> +@item -netfilter buffer,id=@var{id},netdev=@var{netdevid}[,chain=@var{in/out/all}][,interval=@var{t}]
> +Buffer network packets on netdev @var{netdevid}.
> +If interval @var{t} provided, will release packets by interval. Interval scale: microsecond.
> +If interval @var{t} not provided, you have to make sure the packets can be released,
> +either by manually remove this filter or call the release buffer API, otherwise,
> +the packets will be buffered forever. Use with caution.
> +
> +chain @var{in/out/all} is an option that can be applied to any netfilter, default is @option{all}.
> +
> +@option{in} means this filter will receive packets sent to the netdev
> +
> +@option{out} means this filter will receive packets sent from the netdev
> +
> +@option{all} means this filter will receive packets both sent to/from the netdev
> +ETEXI
> +
>  STEXI
>  @end table
>  ETEXI
> diff --git a/vl.c b/vl.c
> index 584ca88..aee931a 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -75,6 +75,7 @@ int main(int argc, char **argv)
>  #include "monitor/qdev.h"
>  #include "sysemu/bt.h"
>  #include "net/net.h"
> +#include "net/filter.h"
>  #include "net/slirp.h"
>  #include "monitor/monitor.h"
>  #include "ui/console.h"
> @@ -2998,6 +2999,7 @@ int main(int argc, char **argv, char **envp)
>      qemu_add_opts(&qemu_device_opts);
>      qemu_add_opts(&qemu_netdev_opts);
>      qemu_add_opts(&qemu_net_opts);
> +    qemu_add_opts(&qemu_netfilter_opts);
>      qemu_add_opts(&qemu_rtc_opts);
>      qemu_add_opts(&qemu_global_opts);
>      qemu_add_opts(&qemu_mon_opts);
> @@ -3284,6 +3286,13 @@ int main(int argc, char **argv, char **envp)
>                      exit(1);
>                  }
>                  break;
> +            case QEMU_OPTION_netfilter:
> +                opts = qemu_opts_parse_noisily(qemu_find_opts("netfilter"),
> +                                               optarg, true);
> +                if (!opts) {
> +                    exit(1);
> +                }
> +                break;
>  #ifdef CONFIG_LIBISCSI
>              case QEMU_OPTION_iscsi:
>                  opts = qemu_opts_parse_noisily(qemu_find_opts("iscsi"),
> @@ -4413,6 +4422,10 @@ int main(int argc, char **argv, char **envp)
>          exit(1);
>      }
>  
> +    if (net_init_filters() < 0) {
> +        exit(1);
> +    }
> +
>  #ifdef CONFIG_TPM
>      if (tpm_init() < 0) {
>          exit(1);
> -- 
> 1.9.1
>