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From: Markus Armbruster <armbru@redhat.com>
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Date: Fri, 25 Sep 2015 17:13:25 +0200
In-Reply-To: <5605035D.7070801@redhat.com> (Jason Wang's message of "Fri, 25
	Sep 2015 16:18:37 +0800")
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Subject: Re: [Qemu-devel] [PATCH v11 09/12] netfilter: add a netbuffer filter
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To: Jason Wang <jasowang@redhat.com>
Cc: thuth@redhat.com, zhang.zhanghailiang@huawei.com, lizhijian@cn.fujitsu.com, qemu-devel@nongnu.org, stefanha@redhat.com, Yang Hongyang <yanghy@cn.fujitsu.com>

Jason Wang <jasowang@redhat.com> writes:

> On 09/25/2015 03:18 PM, Yang Hongyang wrote:
>>
>>
>> On 09/24/2015 05:12 PM, Markus Armbruster wrote:
>>> Yang Hongyang <yanghy@cn.fujitsu.com> writes:
[...]
>>>> +static ssize_t filter_buffer_receive_iov(NetFilterState *nf,
>>>> +                                         NetClientState *sender,
>>>> +                                         unsigned flags,
>>>> +                                         const struct iovec *iov,
>>>> +                                         int iovcnt,
>>>> +                                         NetPacketSent *sent_cb)
>>>> +{
>>>> +    FilterBufferState *s = FILTER_BUFFER(nf);
>>>> +
>>>> +    /*
>>>> +     * we return size when buffer a packet, the sender will take it as
>>>> +     * a already sent packet, so sent_cb should not be called later
[...]
>>>> +     * FIXME: even if guest can't receive packet for some reasons.
>>>> Filter
>>>> +     * can still accept packet until its internal queue is full.
>>>> +     */
>>>
>>> I'm not sure I understand the comment.
>>
>> This is taken from Jason's comments, may be he can have a better explain?
>
> For example. For some reason, receiver could not receive more packets
> (.can_receive() returns zero). Without a filter, at most one packet will
> be queued in incoming queue and sender's poll will be disabled unit its
> sent_cb() was called. With a filter, it will keep receive the packets
> without caring about the receiver. This is suboptimal. May need more
> thoughts (e.g keeping sent_cb).

Aha.  Perhaps you can work that explanation into the comment.