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* net_sched: sch_plug: plug_qdisc_ops is staticEric Dumazet2012-02-131-1/+1
| | | | | | | | net/sched/sch_plug.c:211:18: warning: symbol 'plug_qdisc_ops' was not declared. Should it be static? Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* net/sched: sch_plug - Queue traffic until an explicit release commandShriram Rajagopalan2012-02-071-0/+233
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 http://nss.cs.ubc.ca/remus/ and http://wiki.xensource.com/xenwiki/Remus 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 <rshriram@cs.ubc.ca> Signed-off-by: Brendan Cully <brendan@cs.ubc.ca> [author of the code in the linux 2.6.32 pvops tree] Signed-off-by: David S. Miller <davem@davemloft.net>