Re: [Qemu-devel] [PATCH v4 09/11] netfilter: add a netbuffer filter

[Yang Hongyang <yanghy@cn.fujitsu.com>]

On 08/06/2015 03:21 PM, Jason Wang wrote:
>
>
> On 08/04/2015 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 <yanghy@cn.fujitsu.com>
>> ---
>> v4: remove bh
>>      pass the packet to next filter instead of receiver
>> v3: check packet's sender and sender->peer when flush it
>> ---
>>   net/Makefile.objs   |   1 +
>>   net/filter-buffer.c | 120 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>>   net/filter.c        |   2 +
>>   net/filters.h       |  17 ++++++++
>>   qapi-schema.json    |  18 +++++++-
>>   5 files changed, 157 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..fd467db
>> --- /dev/null
>> +++ b/net/filter-buffer.c
>> @@ -0,0 +1,120 @@
>> +/*
>> + * 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/timer.h"
>> +#include "qemu/iov.h"
>> +
>> +typedef struct FILTERBUFFERState {
>> +    NetFilterState nf;
>> +    NetQueue *incoming_queue;
>> +    int64_t interval;
>
> Can interval be negative?

No.

> If not please uint. And not sure you really
> need a 64 bit integer, if not, please use uint32_t.

Ok, will use uint32_t instead.

>
>> +    QEMUTimer release_timer;
>> +} FILTERBUFFERState;
>
> Filter buffer is not abbreviation. So better name it as FilterBufferState.

Ok, thanks.

>
>> +
>> +static void packet_send_completed(NetClientState *nc, ssize_t len)
>> +{
>> +    return;
>> +}
>
> Why need a dummy sent cb?

Need to work around with queue_append, if there's no sent_cb, queue_append
will simply drop the packet...Even we provide a sent_cb param to receive_iov,
this dummy might still be needed because sent_cb might be null.

>
>> +
>> +static void filter_buffer_flush(NetFilterState *nf)
>> +{
>> +    FILTERBUFFERState *s = DO_UPCAST(FILTERBUFFERState, nf, nf);
>> +    NetQueue *queue = s->incoming_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_netfilter_pass_to_next(nf, packet->sender, packet->flags,
>> +                                        packet->data, packet->size);
>> +        }
>> +
>> +        /*
>> +         * now that we pass the packet to next filter, we don't care the
>> +         * reture value here, because the filter layer or other filter
>> +         * will take care of this packet
>> +         */
>> +        g_free(packet);
>
> This seems wrong, since packet could be queued into incoming queue.
> Doing this may cause use after free.

The incoming queue will make a copy of packet data when queued a packet.
So I think it's ok to free this packet here...because this packet is
alloced by this filter when calling qemu_net_queue_append_iov.

>
>> +    }
>> +}
>> +
>> +static void filter_buffer_release_timer(void *opaque)
>> +{
>> +    FILTERBUFFERState *s = opaque;
>> +    filter_buffer_flush(&s->nf);
>> +    timer_mod(&s->release_timer,
>> +              qemu_clock_get_us(QEMU_CLOCK_VIRTUAL) + s->interval);
>> +}
>> +
>> +/* filter APIs */
>> +static ssize_t filter_buffer_receive_iov(NetFilterState *nf,
>> +                                         NetClientState *sender,
>> +                                         unsigned flags,
>> +                                         const struct iovec *iov,
>> +                                         int iovcnt)
>> +{
>> +    FILTERBUFFERState *s = DO_UPCAST(FILTERBUFFERState, nf, nf);
>> +    NetQueue *queue = s->incoming_queue;
>> +
>> +    qemu_net_queue_append_iov(queue, sender, flags, iov, iovcnt,
>> +                              packet_send_completed);
>> +    return iov_size(iov, iovcnt);
>
> So if interval is zero, packet will be blocked forever and memory will
> be exhausted.

Yes, but this supposed to be used by FT solutions, so it will
be released periodically. Currently only used with interval makes sense.

>
>> +}
>> +
>> +static void filter_buffer_cleanup(NetFilterState *nf)
>> +{
>> +    FILTERBUFFERState *s = DO_UPCAST(FILTERBUFFERState, nf, nf);
>> +
>> +    if (s->interval) {
>> +        timer_del(&s->release_timer);
>> +    }
>> +
>> +    /* flush packets */
>> +    filter_buffer_flush(nf);
>> +    g_free(s->incoming_queue);
>> +    return;
>> +}
>> +
>> +static NetFilterInfo net_filter_buffer_info = {
>> +    .type = NET_FILTER_OPTIONS_KIND_BUFFER,
>> +    .size = sizeof(FILTERBUFFERState),
>> +    .receive_iov = filter_buffer_receive_iov,
>> +    .cleanup = filter_buffer_cleanup,
>> +};
>> +
>> +int net_init_filter_buffer(const NetFilterOptions *opts, const char *name,
>> +                           int chain, NetClientState *netdev, Error **errp)
>> +{
>> +    NetFilterState *nf;
>> +    FILTERBUFFERState *s;
>> +    const NetFilterBufferOptions *bufferopt;
>> +
>> +    assert(opts->kind == NET_FILTER_OPTIONS_KIND_BUFFER);
>> +    bufferopt = opts->buffer;
>> +
>> +    nf = qemu_new_net_filter(&net_filter_buffer_info,
>> +                             netdev, "buffer", name, chain);
>> +    s = DO_UPCAST(FILTERBUFFERState, nf, nf);
>> +    s->incoming_queue = qemu_new_net_queue(nf);
>> +    s->interval = bufferopt->has_interval ? bufferopt->interval : 0;
>> +    if (s->interval) {
>> +        timer_init_us(&s->release_timer, QEMU_CLOCK_VIRTUAL,
>> +                      filter_buffer_release_timer, s);
>> +        timer_mod(&s->release_timer,
>> +                  qemu_clock_get_us(QEMU_CLOCK_VIRTUAL) + s->interval);
>> +    }
>> +
>> +    return 0;
>> +}
>> diff --git a/net/filter.c b/net/filter.c
>> index 166b851..02f3e76 100644
>> --- a/net/filter.c
>> +++ b/net/filter.c
>> @@ -19,6 +19,7 @@
>>   #include "net/filter.h"
>>   #include "net/net.h"
>>   #include "net/queue.h"
>> +#include "filters.h"
>>
>>   static QTAILQ_HEAD(, NetFilterState) net_filters;
>>
>> @@ -179,6 +180,7 @@ typedef int (NetFilterInit)(const NetFilterOptions *opts,
>>
>>   static
>>   NetFilterInit * const net_filter_init_fun[NET_FILTER_OPTIONS_KIND_MAX] = {
>> +    [NET_FILTER_OPTIONS_KIND_BUFFER] = net_init_filter_buffer,
>>   };
>>
>>   static int net_filter_init1(const NetFilter *netfilter, Error **errp)
>> diff --git a/net/filters.h b/net/filters.h
>> new file mode 100644
>> index 0000000..3b546db
>> --- /dev/null
>> +++ b/net/filters.h
>> @@ -0,0 +1,17 @@
>> +/*
>> + * 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_FILTERS_H
>> +#define QEMU_NET_FILTERS_H
>> +
>> +#include "net/net.h"
>> +#include "net/filter.h"
>> +
>> +int net_init_filter_buffer(const NetFilterOptions *opts, const char *name,
>> +                           int chain, NetClientState *netdev, Error **errp);
>> +
>> +#endif /* QEMU_NET_FILTERS_H */
>> diff --git a/qapi-schema.json b/qapi-schema.json
>> index 9d97c21..e51bb59 100644
>> --- a/qapi-schema.json
>> +++ b/qapi-schema.json
>> @@ -2584,6 +2584,21 @@
>>   { 'command': 'netfilter_del', 'data': {'id': 'str'} }
>>
>>   ##
>> +# @NetFilterBufferOptions
>> +#
>> +# a netbuffer filter for network backend.
>> +#
>> +# @interval: #optional release packets by interval, if no interval supplied,
>> +#            will release packets when filter_buffer_release_all been called.
>> +#            scale: microsecond
>> +#
>> +# Since 2.5
>> +##
>> +{ 'struct': 'NetFilterBufferOptions',
>> +  'data': {
>> +    '*interval':     'int64' } }
>> +
>> +##
>>   # @NetFilterOptions
>>   #
>>   # A discriminated record of network filters.
>> @@ -2592,7 +2607,8 @@
>>   #
>>   ##
>>   { 'union': 'NetFilterOptions',
>> -  'data': { } }
>> +  'data': {
>> +    'buffer':     'NetFilterBufferOptions'} }
>>
>>   ##
>>   # @NetFilter
>
> .
>

-- 
Thanks,
Yang.