> Not sure that only one field is enough, cause
> we may have two states on bh execution start:
> 1. There are packets in vmnet buffer s->packets_buf
> that were rejected by qemu_send_async and waiting
> to be sent. If this happens, we should complete sending
> these waiting packets with qemu_send_async firstly,
> and after that we should call vmnet_read to get
> new ones and send them to QEMU;
> 2. There are no packets in s->packets_buf to be sent to
> qemu, we only need to get new packets from vmnet
> with vmnet_read and send them to QEMU
In case 1, you should just keep calling qemu_send_packet_async.
Actually
qemu_send_packet_async adds the packet to its internal queue and calls
the callback when it is consumed.
I'm not sure we can keep calling qemu_send_packet_async,
because as docs from net/queue.c says:
/* [...]
* If a sent callback is provided to send(), the caller must handle a
* zero return from the delivery handler by not sending any more packets
* until we have invoked the callback. Only in that case will we queue
* the packet.
*
* If a sent callback isn't provided, we just drop the packet to avoid
* unbounded queueing.
*/
So after we did vmnet_read and read N packets
into temporary s->packets_buf, we begin calling
qemu_send_packet_async. If it returns 0 - it says
"no more packets until sent_cb called please".
At this moment we have N packets in s->packets_buf
and already queued K < N of them. But, packets K..N
are not queued and keep waiting for sent_cb to be sent
with qemu_send_packet_async.
Thus when sent_cb called, we should finish
our transfer of packets K..N from s->packets_buf
to qemu calling qemu_send_packet_async.
I meant this.