Re: [Qemu-devel] [PATCH v2 8/9] netfilter: add a netbuffer filter

[Jason Wang <jasowang@redhat.com>]

On 07/31/2015 12:13 PM, Yang Hongyang wrote:
> This filter is to buffer/release packets, this feature can be used
> when using MicroCheckpointing, or other Remus like VM FT solutions, you
> can also use it to simulate the network delay.
> It has an interval option, if supplied, this filter will release
> packets by interval.
>
> Usage:
>  -netdev tap,id=bn0
>  -netfilter buffer,id=f0,netdev=bn0,chain=in,interval=1000
>
> NOTE:
>  the scale of interval is microsecond.
>
> Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
> ---
>  net/Makefile.objs   |   1 +
>  net/filter-buffer.c | 160 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  net/filter.c        |   2 +
>  net/filters.h       |  17 ++++++
>  qapi-schema.json    |  18 +++++-
>  5 files changed, 197 insertions(+), 1 deletion(-)
>  create mode 100644 net/filter-buffer.c
>  create mode 100644 net/filters.h
>
> diff --git a/net/Makefile.objs b/net/Makefile.objs
> index 914aec0..5fa2f97 100644
> --- a/net/Makefile.objs
> +++ b/net/Makefile.objs
> @@ -14,3 +14,4 @@ common-obj-$(CONFIG_SLIRP) += slirp.o
>  common-obj-$(CONFIG_VDE) += vde.o
>  common-obj-$(CONFIG_NETMAP) += netmap.o
>  common-obj-y += filter.o
> +common-obj-y += filter-buffer.o
> diff --git a/net/filter-buffer.c b/net/filter-buffer.c
> new file mode 100644
> index 0000000..7f2b050
> --- /dev/null
> +++ b/net/filter-buffer.c
> @@ -0,0 +1,160 @@
> +/*
> + * Copyright (c) 2015 FUJITSU LIMITED
> + * Author: Yang Hongyang <yanghy@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/queue.h"
> +#include "filters.h"
> +#include "qemu-common.h"
> +#include "qemu/error-report.h"
> +#include "qemu/main-loop.h"
> +#include "qemu/timer.h"
> +#include "qemu/iov.h"
> +
> +typedef struct FILTERBUFFERState {
> +    NetFilterState nf;
> +    NetQueue *incoming_queue;
> +    NetQueue *inflight_queue;
> +    QEMUBH *flush_bh;
> +    int64_t interval;
> +    QEMUTimer release_timer;
> +} FILTERBUFFERState;
> +
> +static void packet_send_completed(NetClientState *nc, ssize_t len)
> +{
> +    return;
> +}
> +
> +static void filter_buffer_flush(NetFilterState *nf)
> +{
> +    FILTERBUFFERState *s = DO_UPCAST(FILTERBUFFERState, nf, nf);
> +    NetQueue *queue = s->inflight_queue;
> +    NetPacket *packet;
> +
> +    while (queue && !QTAILQ_EMPTY(&queue->packets)) {
> +        packet = QTAILQ_FIRST(&queue->packets);
> +        QTAILQ_REMOVE(&queue->packets, packet, entry);
> +        queue->nq_count--;
> +
> +        qemu_net_queue_send(packet->sender->peer->incoming_queue,
> +                            packet->sender,
> +                            packet->flags,
> +                            packet->data,
> +                            packet->size,
> +                            packet->sent_cb);

Need to check peer since it may be NULL e.g after it was deleted. And we
probably need to queue the packet into next filter.