Re: [Qemu-devel] [PATCH V2] net/traffic-mirror:Add traffic-mirror

[Jason Wang <jasowang@redhat.com>]

On 01/27/2016 10:40 AM, Zhang Chen wrote:
> From: ZhangChen <zhangchen.fnst@cn.fujitsu.com>
>
> Traffic-mirror is a netfilter plugin.
> It gives qemu the ability to copy and mirror guest's
> net packet. we output packet to chardev.
>
> usage:
>
> -netdev tap,id=hn0
> -chardev socket,id=mirror0,host=ip_primary,port=X,server,nowait
> -traffic-mirror,id=m0,netdev=hn0,queue=tx/rx/all,outdev=mirror0
>
> Signed-off-by: ZhangChen <zhangchen.fnst@cn.fujitsu.com>
> Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
> Reviewed-by: Yang Hongyang <hongyang.yang@easystack.cn>

Thanks for the patch. Several questions:

- I'm curious about how the patch was tested? Simple setup e.g:

-netdev tap,id=hn0 -device virtio-net-pci,netdev=hn0 -chardev
socket,id=c0,host=localhost,port=4444,server,nowait -object
traffic-mirror,netdev=hn0,outdev=c0,id=f0 -netdev
socket,id=s0,connect=127.0.0.1:4444 -device e1000,netdev=s0

does not works for me.

- Is a reliable mirroring (e.g no packet drops during mirroring) is
needed for COLO? If yes, this patch seems could not guarantee this.
- Please consider to write a unit test for this patch.

And see comments below.

Thanks


> ---
>  net/Makefile.objs    |   1 +
>  net/traffic-mirror.c | 173 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  qemu-options.hx      |   5 ++
>  vl.c                 |   3 +-
>  4 files changed, 181 insertions(+), 1 deletion(-)
>  create mode 100644 net/traffic-mirror.c
>
> diff --git a/net/Makefile.objs b/net/Makefile.objs
> index 5fa2f97..de06ebe 100644
> --- a/net/Makefile.objs
> +++ b/net/Makefile.objs
> @@ -15,3 +15,4 @@ common-obj-$(CONFIG_VDE) += vde.o
>  common-obj-$(CONFIG_NETMAP) += netmap.o
>  common-obj-y += filter.o
>  common-obj-y += filter-buffer.o
> +common-obj-y += traffic-mirror.o

Let's s/traffic-mirror/filter-mirror/g to be consistent with other filters.

> diff --git a/net/traffic-mirror.c b/net/traffic-mirror.c
> new file mode 100644
> index 0000000..bed915c
> --- /dev/null
> +++ b/net/traffic-mirror.c
> @@ -0,0 +1,173 @@
> +/*
> + * Copyright (c) 2016 HUAWEI TECHNOLOGIES CO., LTD.
> + * Copyright (c) 2016 FUJITSU LIMITED
> + * Copyright (c) 2016 Intel Corporation
> + *
> + * Author: Zhang Chen <zhangchen.fnst@cn.fujitsu.com>
> + *
> + * 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 "net/filter.h"
> +#include "net/net.h"
> +#include "qemu-common.h"
> +#include "qapi/qmp/qerror.h"
> +#include "qapi-visit.h"
> +#include "qom/object.h"
> +#include "qemu/main-loop.h"
> +#include "qemu/error-report.h"
> +#include "trace.h"
> +#include "sysemu/char.h"
> +#include "qemu/iov.h"
> +
> +#define FILTER_TRAFFIC_MIRROR(obj) \
> +    OBJECT_CHECK(MirrorState, (obj), TYPE_FILTER_TRAFFIC_MIRROR)
> +
> +#define TYPE_FILTER_TRAFFIC_MIRROR "traffic-mirror"
> +
> +typedef struct MirrorState {
> +    NetFilterState parent_obj;
> +    char *outdev;
> +    CharDriverState *chr_out;
> +
> +} MirrorState;
> +
> +static ssize_t traffic_mirror_send(NetFilterState *nf,
> +                                   const struct iovec *iov,
> +                                   int iovcnt)
> +{
> +    MirrorState *s = FILTER_TRAFFIC_MIRROR(nf);
> +    ssize_t ret = 0;
> +    ssize_t size = 0;
> +    char *buf;
> +
> +    size = iov_size(iov, iovcnt);
> +    if (!size) {
> +        return 0;
> +    }
> +
> +    buf = g_malloc0(size);
> +    iov_to_buf(iov, iovcnt, 0, buf, size);
> +    ret = qemu_chr_fe_write(s->chr_out, (uint8_t *)&size, sizeof(size));

htonl(size)?

> +    if (ret < 0) {

This check is not sufficient, for some reason, only part of the packets
maybe sent by the socket. Need to handle this properly, otherwise it may
confuse receiver.

> +        g_free(buf);
> +        return ret;
> +    }
> +
> +    ret = qemu_chr_fe_write(s->chr_out, (uint8_t *)buf, size);
> +    g_free(buf);
> +    return ret;

Ditto.

> +}
> +
> +static ssize_t traffic_mirror_receive_iov(NetFilterState *nf,
> +                                         NetClientState *sender,
> +                                         unsigned flags,
> +                                         const struct iovec *iov,
> +                                         int iovcnt,
> +                                         NetPacketSent *sent_cb)
> +{
> +    /*
> +     * We copy and mirror packet to outdev,
> +     * then put back the packet.
> +     */

The code could explain itself, so the comment is unnecessary.

> +    ssize_t ret = 0;
> +
> +    ret = traffic_mirror_send(nf, iov, iovcnt);
> +    if (ret < 0) {
> +        error_report("traffic_mirror_send failed");

Monitor could be flooded by this.

> +    }
> +
> +    return 0;
> +}
> +

Other looks good.