netfilter: add a netbuffer filter

This filter is to buffer/release packets. Can be used when using
MicroCheckpointing or other Remus like VM FT solutions.
You can also use it to crudely simulate network delay.  Doesn't
actually delay individual packets, but batches them together, which is
a delay of sorts.

Usage:
 -netdev tap,id=bn0
 -object filter-buffer,id=f0,netdev=bn0,queue=rx,interval=1000

NOTE:
 Interval is in microseconds, it can't be omitted currently, and can't be 0.

Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/qemu-options.hx b/qemu-options.hx
index 328404c..2485b94 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3643,6 +3643,23 @@ in PEM format, in filenames @var{ca-cert.pem}, @var{ca-crl.pem} (optional),
 @var{server-cert.pem} (only servers), @var{server-key.pem} (only servers),
 @var{client-cert.pem} (only clients), and @var{client-key.pem} (only clients).
 
+@item -object filter-buffer,id=@var{id},netdev=@var{netdevid},interval=@var{t}[,queue=@var{all|rx|tx}]
+
+Interval @var{t} can't be 0, this filter batches the packet delivery: all
+packets arriving in a given interval on netdev @var{netdevid} are delayed
+until the end of the interval. Interval is in microseconds.
+
+queue @var{all|rx|tx} is an option that can be applied to any netfilter.
+
+@option{all}: the filter is attached both to the receive and the transmit
+              queue of the netdev (default).
+
+@option{rx}: the filter is attached to the receive queue of the netdev,
+             where it will receive packets sent to the netdev.
+
+@option{tx}: the filter is attached to the transmit queue of the netdev,
+             where it will receive packets sent by the netdev.
+
 @end table
 
 ETEXI