libnl: /data/src/libnl/lib/route/qdisc/plug.c Source File

libnl 3.12.0

plug.c
1/* SPDX-License-Identifier: LGPL-2.1-only */
2/*
3 * Copyright (c) 2012 Shriram Rajagopalan <rshriram@cs.ubc.ca>
4 */
5
6/**
7 * @ingroup qdisc
8 * @defgroup qdisc_plug Plug/Unplug Traffic (PLUG)
9 * @brief
10 *
11 * Queue traffic until an explicit release command.
12 *
13 * There are two ways to use this qdisc:
14 * 1. A simple "instantaneous" plug/unplug operation, by issuing an alternating
15 * sequence of TCQ_PLUG_BUFFER & TCQ_PLUG_RELEASE_INDEFINITE commands.
16 *
17 * 2. For network output buffering (a.k.a output commit) functionality.
18 * Output commit property is commonly used by applications using checkpoint
19 * based fault-tolerance to ensure that the checkpoint from which a system
20 * is being restored is consistent w.r.t outside world.
21 *
22 * Consider for e.g. Remus - a Virtual Machine checkpointing system,
23 * wherein a VM is checkpointed, say every 50ms. The checkpoint is replicated
24 * asynchronously to the backup host, while the VM continues executing the
25 * next epoch speculatively.
26 *
27 * The following is a typical sequence of output buffer operations:
28 * 1.At epoch i, start_buffer(i)
29 * 2. At end of epoch i (i.e. after 50ms):
30 * 2.1 Stop VM and take checkpoint(i).
31 * 2.2 start_buffer(i+1) and Resume VM
32 * 3. While speculatively executing epoch(i+1), asynchronously replicate
33 * checkpoint(i) to backup host.
34 * 4. When checkpoint_ack(i) is received from backup, release_buffer(i)
35 * Thus, this Qdisc would receive the following sequence of commands:
36 * TCQ_PLUG_BUFFER (epoch i)
37 * .. TCQ_PLUG_BUFFER (epoch i+1)
38 * ....TCQ_PLUG_RELEASE_ONE (epoch i)
39 * ......TCQ_PLUG_BUFFER (epoch i+2)
40 * ........
41 *
42 *
43 * State of the queue, when used for network output buffering:
44 *
45 * plug(i+1) plug(i) head
46 * ------------------+--------------------+---------------->
47 * | |
48 * | |
49 * pkts_current_epoch| pkts_last_epoch |pkts_to_release
50 * ----------------->|<--------+--------->|+--------------->
51 * v v
52 *
53 *
54 * @{
55 */
56
57#include "nl-default.h"
58
59#include <netlink/netlink.h>
60#include <netlink/utils.h>
61#include <netlink/route/qdisc/plug.h>
62
63#include "tc-api.h"
64
65 struct rtnl_plug {
66 int action;
67 uint32_t limit;
68};
69
70static int plug_msg_fill(struct rtnl_tc *tc, void *data, struct nl_msg *msg)
71{
72 struct rtnl_plug *plug = data;
73 struct tc_plug_qopt opts;
74
75 if (!plug)
76 return -NLE_INVAL;
77
78 opts.action = plug->action;
79 opts.limit = plug->limit;
80
81 return nlmsg_append(msg, &opts, sizeof(opts), NL_DONTPAD);
82}
83
84/**
85 * @name Attribute Modification
86 * @{
87 */
88
89/**
90 * Insert a plug into the qdisc and buffer any incoming
91 * network traffic.
92 * @arg qdisc PLUG qdisc to be modified.
93 */
94 int rtnl_qdisc_plug_buffer(struct rtnl_qdisc *qdisc)
95{
96 struct rtnl_plug *plug;
97
98 if (!(plug = rtnl_tc_data(TC_CAST(qdisc))))
99 return -NLE_NOMEM;
100
101 plug->action = TCQ_PLUG_BUFFER;
102 return 0;
103}
104
105/**
106 * Unplug the qdisc, releasing packets from queue head
107 * to the last complete buffer, while new traffic
108 * continues to be buffered.
109 * @arg qdisc PLUG qdisc to be modified.
110 */
111 int rtnl_qdisc_plug_release_one(struct rtnl_qdisc *qdisc)
112{
113 struct rtnl_plug *plug;
114
115 if (!(plug = rtnl_tc_data(TC_CAST(qdisc))))
116 return -NLE_NOMEM;
117
118 plug->action = TCQ_PLUG_RELEASE_ONE;
119 return 0;
120}
121
122/**
123 * Indefinitely unplug the qdisc, releasing all packets.
124 * Network traffic will not be buffered until the next
125 * buffer command is issued.
126 * @arg qdisc PLUG qdisc to be modified.
127 */
128 int rtnl_qdisc_plug_release_indefinite(struct rtnl_qdisc *qdisc)
129{
130 struct rtnl_plug *plug;
131
132 if (!(plug = rtnl_tc_data(TC_CAST(qdisc))))
133 return -NLE_NOMEM;
134
135 plug->action = TCQ_PLUG_RELEASE_INDEFINITE;
136 return 0;
137}
138
139/**
140 * Set limit of PLUG qdisc.
141 * @arg qdisc PLUG qdisc to be modified.
142 * @arg limit New limit.
143 * @return 0 on success or a negative error code.
144 */
145 int rtnl_qdisc_plug_set_limit(struct rtnl_qdisc *qdisc, int limit)
146{
147 struct rtnl_plug *plug;
148
149 if (!(plug = rtnl_tc_data(TC_CAST(qdisc))))
150 return -NLE_NOMEM;
151
152 plug->action = TCQ_PLUG_LIMIT;
153 plug->limit = limit;
154
155 return 0;
156}
157
158/** @} */
159
160static struct rtnl_tc_ops plug_ops = {
161 .to_kind = "plug",
162 .to_type = RTNL_TC_TYPE_QDISC,
163 .to_size = sizeof(struct rtnl_plug),
164 .to_msg_fill = plug_msg_fill,
165};
166
167static void _nl_init plug_init(void)
168{
169 rtnl_tc_register(&plug_ops);
170}
171
172static void _nl_exit plug_exit(void)
173{
174 rtnl_tc_unregister(&plug_ops);
175}
176
177/** @} */
nlmsg_append
int nlmsg_append(struct nl_msg *n, void *data, size_t len, int pad)
Append data to tail of a netlink message.
Definition msg.c:456
rtnl_qdisc_plug_release_indefinite
int rtnl_qdisc_plug_release_indefinite(struct rtnl_qdisc *qdisc)
Indefinitely unplug the qdisc, releasing all packets.
Definition plug.c:128
rtnl_qdisc_plug_release_one
int rtnl_qdisc_plug_release_one(struct rtnl_qdisc *qdisc)
Unplug the qdisc, releasing packets from queue head to the last complete buffer, while new traffic co...
Definition plug.c:111
rtnl_qdisc_plug_buffer
int rtnl_qdisc_plug_buffer(struct rtnl_qdisc *qdisc)
Insert a plug into the qdisc and buffer any incoming network traffic.
Definition plug.c:94
rtnl_qdisc_plug_set_limit
int rtnl_qdisc_plug_set_limit(struct rtnl_qdisc *qdisc, int limit)
Set limit of PLUG qdisc.
Definition plug.c:145
TC_CAST
#define TC_CAST(ptr)
Macro to cast qdisc/class/classifier to tc object.
Definition tc.h:50
rtnl_tc_data
void * rtnl_tc_data(struct rtnl_tc *)
Return pointer to private data of traffic control object.
Definition tc.c:1079
rtnl_tc_register
int rtnl_tc_register(struct rtnl_tc_ops *)
Register a traffic control module.
Definition tc.c:1018
rtnl_tc_unregister
void rtnl_tc_unregister(struct rtnl_tc_ops *)
Unregister a traffic control module.
Definition tc.c:1052
rtnl_plug
Definition plug.c:65
rtnl_qdisc
Definition nl-route.h:119
rtnl_tc
Definition nl-route.h:115