path: root/include
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authorShriram Rajagopalan <>2012-02-05 13:51:32 +0000
committerDavid S. Miller <>2012-02-07 12:54:56 -0500
commitc3059be16c9ef29c05f0876a9df5fea21f29724f (patch)
tree18e5635982b69c7d8369e441d3233c437d2262df /include
parent17b8a74f00474fb4fe6154aa426a80bcf1220997 (diff)
net/sched: sch_plug - Queue traffic until an explicit release command
The qdisc supports two operations - plug and unplug. When the qdisc receives a plug command via netlink request, packets arriving henceforth are buffered until a corresponding unplug command is received. Depending on the type of unplug command, the queue can be unplugged indefinitely or selectively. This qdisc can be used to implement output buffering, an essential functionality required for consistent recovery in checkpoint based fault-tolerance systems. Output buffering enables speculative execution by allowing generated network traffic to be rolled back. It is used to provide network protection for Xen Guests in the Remus high availability project, available as part of Xen. This module is generic enough to be used by any other system that wishes to add speculative execution and output buffering to its applications. This module was originally available in the linux 2.6.32 PV-OPS tree, used as dom0 for Xen. For more information, please refer to and Changes in V3: * Removed debug output (printk) on queue overflow * Added TCQ_PLUG_RELEASE_INDEFINITE - that allows the user to use this qdisc, for simple plug/unplug operations. * Use of packet counts instead of pointers to keep track of the buffers in the queue. Signed-off-by: Shriram Rajagopalan <> Signed-off-by: Brendan Cully <> [author of the code in the linux 2.6.32 pvops tree] Signed-off-by: David S. Miller <>
Diffstat (limited to 'include')
1 files changed, 21 insertions, 0 deletions
diff --git a/include/linux/pkt_sched.h b/include/linux/pkt_sched.h
index 0d5b79365d0..410b33d014d 100644
--- a/include/linux/pkt_sched.h
+++ b/include/linux/pkt_sched.h
@@ -127,6 +127,27 @@ struct tc_multiq_qopt {
__u16 max_bands; /* Maximum number of queues */
+/* PLUG section */
+#define TCQ_PLUG_BUFFER 0
+#define TCQ_PLUG_LIMIT 3
+struct tc_plug_qopt {
+ /* TCQ_PLUG_BUFFER: Inset a plug into the queue and
+ * buffer any incoming packets
+ * TCQ_PLUG_RELEASE_ONE: Dequeue packets from queue head
+ * to beginning of the next plug.
+ * TCQ_PLUG_RELEASE_INDEFINITE: Dequeue all packets from queue.
+ * Stop buffering packets until the next TCQ_PLUG_BUFFER
+ * command is received (just act as a pass-thru queue).
+ * TCQ_PLUG_LIMIT: Increase/decrease queue size
+ */
+ int action;
+ __u32 limit;
/* TBF section */
struct tc_tbf_qopt {