libnl 3.5.0

plug.c
1 /*
2 * lib/route/qdisc/plug.c PLUG Qdisc
3 *
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Lesser General Public
6 * License as published by the Free Software Foundation version 2.1
7 * of the License.
8 *
9 * Copyright (c) 2012 Shriram Rajagopalan <rshriram@cs.ubc.ca>
10 */
11
12 /**
13 * @ingroup qdisc
14 * @defgroup qdisc_plug Plug/Unplug Traffic (PLUG)
15 * @brief
16 *
17 * Queue traffic until an explicit release command.
18 *
19 * There are two ways to use this qdisc:
20 * 1. A simple "instantaneous" plug/unplug operation, by issuing an alternating
21 * sequence of TCQ_PLUG_BUFFER & TCQ_PLUG_RELEASE_INDEFINITE commands.
22 *
23 * 2. For network output buffering (a.k.a output commit) functionality.
24 * Output commit property is commonly used by applications using checkpoint
25 * based fault-tolerance to ensure that the checkpoint from which a system
26 * is being restored is consistent w.r.t outside world.
27 *
28 * Consider for e.g. Remus - a Virtual Machine checkpointing system,
29 * wherein a VM is checkpointed, say every 50ms. The checkpoint is replicated
30 * asynchronously to the backup host, while the VM continues executing the
31 * next epoch speculatively.
32 *
33 * The following is a typical sequence of output buffer operations:
34 * 1.At epoch i, start_buffer(i)
35 * 2. At end of epoch i (i.e. after 50ms):
36 * 2.1 Stop VM and take checkpoint(i).
37 * 2.2 start_buffer(i+1) and Resume VM
38 * 3. While speculatively executing epoch(i+1), asynchronously replicate
39 * checkpoint(i) to backup host.
40 * 4. When checkpoint_ack(i) is received from backup, release_buffer(i)
41 * Thus, this Qdisc would receive the following sequence of commands:
42 * TCQ_PLUG_BUFFER (epoch i)
43 * .. TCQ_PLUG_BUFFER (epoch i+1)
44 * ....TCQ_PLUG_RELEASE_ONE (epoch i)
45 * ......TCQ_PLUG_BUFFER (epoch i+2)
46 * ........
47 *
48 *
49 * State of the queue, when used for network output buffering:
50 *
51 * plug(i+1) plug(i) head
52 * ------------------+--------------------+---------------->
53 * | |
54 * | |
55 * pkts_current_epoch| pkts_last_epoch |pkts_to_release
56 * ----------------->|<--------+--------->|+--------------->
57 * v v
58 *
59 *
60 * @{
61 */
62
63 #include <netlink-private/netlink.h>
64 #include <netlink-private/tc.h>
65 #include <netlink/netlink.h>
66 #include <netlink/utils.h>
67 #include <netlink-private/route/tc-api.h>
68 #include <netlink/route/qdisc/plug.h>
69
70 static 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
160 static 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
167 static void __init plug_init(void)
168 {
169 rtnl_tc_register(&plug_ops);
170 }
171
172 static void __exit plug_exit(void)
173 {
174 rtnl_tc_unregister(&plug_ops);
175 }
176
177 /** @} */
rtnl_tc_register
int rtnl_tc_register(struct rtnl_tc_ops *ops)
Register a traffic control module.
Definition: tc.c:1021
rtnl_tc_unregister
void rtnl_tc_unregister(struct rtnl_tc_ops *ops)
Unregister a traffic control module.
Definition: tc.c:1055
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:56
rtnl_tc_data
void * rtnl_tc_data(struct rtnl_tc *tc)
Return pointer to private data of traffic control object.
Definition: tc.c:1082
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:449
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_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_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