Re: [Qemu-devel] [PATCH v3 10/12] netfilter: add a netbuffer filter

[Yang Hongyang]

On 08/04/2015 02:30 PM, Jason Wang wrote:
> On 08/04/2015 02:05 PM, Yang Hongyang wrote:
> > On 08/04/2015 01:03 PM, Jason Wang wrote:
> > > On 08/03/2015 04:30 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 <address@hidden>
> > > > ---
> > > > v3: check packet's sender and sender->peer when flush it
> > > > ---
> > > >    net/Makefile.objs   |   1 +
> > > >    net/filter-buffer.c | 162
> > > > ++++++++++++++++++++++++++++++++++++++++++++++++++++
> > > >    net/filter.c        |   2 +
> > > >    net/filters.h       |  17 ++++++
> > > >    qapi-schema.json    |  18 +++++-
> > > >    5 files changed, 199 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..1547765
> > > > --- /dev/null
> > > > +++ b/net/filter-buffer.c
> > > > @@ -0,0 +1,162 @@
> > > > +/*
> > > > + * Copyright (c) 2015 FUJITSU LIMITED
> > > > + * Author: Yang Hongyang <address@hidden>
> > > > + *
> > > > + * 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--;
> > > > +
> > > > +        if (packet->sender && packet->sender->peer) {
> > > > +            qemu_net_queue_send(packet->sender->peer->incoming_queue,
> > > > +                                packet->sender,
> > > > +                                packet->flags,
> > > > +                                packet->data,
> > > > +                                packet->size,
> > > > +                                packet->sent_cb);
> > > > +        }
> > > > +
> > > > +        /*
> > > > +         * now that we pass the packet to
> > > > sender->peer->incoming_queue, we
> > > > +         * don't care the reture value here, because the peer's
> > > > queue will
> > > > +         * take care of this packet
> > > > +         */
> > > > +        g_free(packet);
> > >
> > > So looks like the packet was still not passed to next filter?
> >
> > I didn't get your suggestion last time, sorry, will add it in next
> > version.
> > Just to confirm, do you mean we need to pass the packet to next filter
> > instead of pass to the receiver's incoming_queue?
>
> Yes, consider you may have two filters. First is dump and second is
> buffer, I believe you still want to buffer the packet even if it has
> been dumped.
>
> > and even if we pass to next
> > filter, the check of sender and it's peer is still needed, because if
> > there's no receiver, it's nonsense to pass it further?
>
> Yes.

thanks.

> > > > +    }
> > > > +
> > > > +    g_free(queue);
> > > > +    s->inflight_queue = NULL;
> > > > +}
> > > > +
> > > > +static void filter_buffer_flush_bh(void *opaque)
> > > > +{
> > > > +    FILTERBUFFERState *s = opaque;
> > > > +    NetFilterState *nf = &s->nf;
> > > > +    filter_buffer_flush(nf);
> > > > +}
> > > > +
> > > > +static void filter_buffer_release_one(NetFilterState *nf)
> > > > +{
> > > > +    FILTERBUFFERState *s = DO_UPCAST(FILTERBUFFERState, nf, nf);
> > > > +
> > > > +    /* flush inflight packets */
> > > > +    if (s->inflight_queue) {
> > > > +        filter_buffer_flush(nf);
> > > > +    }
> > > > +
> > > > +    s->inflight_queue = s->incoming_queue;
> > > > +    s->incoming_queue = qemu_new_net_queue(nf);
> > >
> > > So this in fact flush a brunch of packets. If yes, the name of function
> > > is confusing
> >
> > maybe filter_buffer_release ?
>
> Right.

By removing bh, this function can be dropped, just call filter_buffer_flush.
thanks.

> > > > +    qemu_bh_schedule(s->flush_bh);
> > >
> > > Don't get why a bh is needed. If we could get rid of it, there's
> > > probably no need for inflight_queue, and we can just drain
> > > incoming_queue here.
> >
> > Seems we can get rid of bh, will do, thanks.
>
> .

--
Thanks,
Yang.