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/*
* lib/route/qdisc/plug.c PLUG Qdisc
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation version 2.1
* of the License.
*
* Copyright (c) 2012 Shriram Rajagopalan <rshriram@cs.ubc.ca>
*/
/**
* @ingroup qdisc
* @defgroup qdisc_plug Plug/Unplug Traffic (PLUG)
* @brief
*
* Queue traffic until an explicit release command.
*
* There are two ways to use this qdisc:
* 1. A simple "instantaneous" plug/unplug operation, by issuing an alternating
* sequence of TCQ_PLUG_BUFFER & TCQ_PLUG_RELEASE_INDEFINITE commands.
*
* 2. For network output buffering (a.k.a output commit) functionality.
* Output commit property is commonly used by applications using checkpoint
* based fault-tolerance to ensure that the checkpoint from which a system
* is being restored is consistent w.r.t outside world.
*
* Consider for e.g. Remus - a Virtual Machine checkpointing system,
* wherein a VM is checkpointed, say every 50ms. The checkpoint is replicated
* asynchronously to the backup host, while the VM continues executing the
* next epoch speculatively.
*
* The following is a typical sequence of output buffer operations:
* 1.At epoch i, start_buffer(i)
* 2. At end of epoch i (i.e. after 50ms):
* 2.1 Stop VM and take checkpoint(i).
* 2.2 start_buffer(i+1) and Resume VM
* 3. While speculatively executing epoch(i+1), asynchronously replicate
* checkpoint(i) to backup host.
* 4. When checkpoint_ack(i) is received from backup, release_buffer(i)
* Thus, this Qdisc would receive the following sequence of commands:
* TCQ_PLUG_BUFFER (epoch i)
* .. TCQ_PLUG_BUFFER (epoch i+1)
* ....TCQ_PLUG_RELEASE_ONE (epoch i)
* ......TCQ_PLUG_BUFFER (epoch i+2)
* ........
*
*
* State of the queue, when used for network output buffering:
*
* plug(i+1) plug(i) head
* ------------------+--------------------+---------------->
* | |
* | |
* pkts_current_epoch| pkts_last_epoch |pkts_to_release
* ----------------->|<--------+--------->|+--------------->
* v v
*
*
* @{
*/
#include <netlink-private/netlink.h>
#include <netlink-private/tc.h>
#include <netlink/netlink.h>
#include <netlink/utils.h>
#include <netlink-private/route/tc-api.h>
#include <netlink/route/qdisc/plug.h>
static int plug_msg_fill(struct rtnl_tc *tc, void *data, struct nl_msg *msg)
{
struct rtnl_plug *plug = data;
struct tc_plug_qopt opts;
if (!plug)
return -NLE_INVAL;
opts.action = plug->action;
opts.limit = plug->limit;
return nlmsg_append(msg, &opts, sizeof(opts), NL_DONTPAD);
}
/**
* @name Attribute Modification
* @{
*/
/**
* Insert a plug into the qdisc and buffer any incoming
* network traffic.
* @arg qdisc PLUG qdisc to be modified.
*/
int rtnl_qdisc_plug_buffer(struct rtnl_qdisc *qdisc)
{
struct rtnl_plug *plug;
if (!(plug = rtnl_tc_data(TC_CAST(qdisc))))
return -NLE_NOMEM;
plug->action = TCQ_PLUG_BUFFER;
return 0;
}
/**
* Unplug the qdisc, releasing packets from queue head
* to the last complete buffer, while new traffic
* continues to be buffered.
* @arg qdisc PLUG qdisc to be modified.
*/
int rtnl_qdisc_plug_release_one(struct rtnl_qdisc *qdisc)
{
struct rtnl_plug *plug;
if (!(plug = rtnl_tc_data(TC_CAST(qdisc))))
return -NLE_NOMEM;
plug->action = TCQ_PLUG_RELEASE_ONE;
return 0;
}
/**
* Indefinitely unplug the qdisc, releasing all packets.
* Network traffic will not be buffered until the next
* buffer command is issued.
* @arg qdisc PLUG qdisc to be modified.
*/
int rtnl_qdisc_plug_release_indefinite(struct rtnl_qdisc *qdisc)
{
struct rtnl_plug *plug;
if (!(plug = rtnl_tc_data(TC_CAST(qdisc))))
return -NLE_NOMEM;
plug->action = TCQ_PLUG_RELEASE_INDEFINITE;
return 0;
}
/**
* Set limit of PLUG qdisc.
* @arg qdisc PLUG qdisc to be modified.
* @arg limit New limit.
* @return 0 on success or a negative error code.
*/
int rtnl_qdisc_plug_set_limit(struct rtnl_qdisc *qdisc, int limit)
{
struct rtnl_plug *plug;
if (!(plug = rtnl_tc_data(TC_CAST(qdisc))))
return -NLE_NOMEM;
plug->action = TCQ_PLUG_LIMIT;
plug->limit = limit;
return 0;
}
/** @} */
static struct rtnl_tc_ops plug_ops = {
.to_kind = "plug",
.to_type = RTNL_TC_TYPE_QDISC,
.to_size = sizeof(struct rtnl_plug),
.to_msg_fill = plug_msg_fill,
};
static void __init plug_init(void)
{
rtnl_tc_register(&plug_ops);
}
static void __exit plug_exit(void)
{
rtnl_tc_unregister(&plug_ops);
}
/** @} */
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