OpenVPN
schedule.h
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1 /*
2  * OpenVPN -- An application to securely tunnel IP networks
3  * over a single TCP/UDP port, with support for SSL/TLS-based
4  * session authentication and key exchange,
5  * packet encryption, packet authentication, and
6  * packet compression.
7  *
8  * Copyright (C) 2002-2018 OpenVPN Inc <sales@openvpn.net>
9  *
10  * This program is free software; you can redistribute it and/or modify
11  * it under the terms of the GNU General Public License version 2
12  * as published by the Free Software Foundation.
13  *
14  * This program is distributed in the hope that it will be useful,
15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17  * GNU General Public License for more details.
18  *
19  * You should have received a copy of the GNU General Public License along
20  * with this program; if not, write to the Free Software Foundation, Inc.,
21  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
22  */
23 
24 #ifndef SCHEDULE_H
25 #define SCHEDULE_H
26 
27 /*
28  * This code implements an efficient scheduler using
29  * a random treap binary tree.
30  *
31  * The scheduler is used by the server executive to
32  * keep track of which instances need service at a
33  * known time in the future. Instances need to
34  * schedule events for things such as sending
35  * a ping or scheduling a TLS renegotiation.
36  */
37 
38 /* define to enable a special test mode */
39 /*#define SCHEDULE_TEST*/
40 
41 #include "otime.h"
42 #include "error.h"
43 
45 {
46  struct timeval tv; /* wakeup time */
47  unsigned int pri; /* random treap priority */
48  struct schedule_entry *parent; /* treap (btree) links */
49  struct schedule_entry *lt;
50  struct schedule_entry *gt;
51 };
52 
53 struct schedule
54 {
55  struct schedule_entry *earliest_wakeup; /* cached earliest wakeup */
56  struct schedule_entry *root; /* the root of the treap (btree) */
57 };
58 
59 /* Public functions */
60 
61 struct schedule *schedule_init(void);
62 
63 void schedule_free(struct schedule *s);
64 
65 void schedule_remove_entry(struct schedule *s, struct schedule_entry *e);
66 
67 #ifdef SCHEDULE_TEST
68 void schedule_test(void);
69 
70 #endif
71 
72 /* Private Functions */
73 
74 /* is node already in tree? */
75 #define IN_TREE(e) ((e)->pri)
76 
78 
79 void schedule_add_modify(struct schedule *s, struct schedule_entry *e);
80 
81 void schedule_remove_node(struct schedule *s, struct schedule_entry *e);
82 
83 /* Public inline functions */
84 
85 /*
86  * Add a struct schedule_entry (whose storage is managed by
87  * caller) to the btree. tv signifies the wakeup time for
88  * a future event. sigma is a time interval measured
89  * in microseconds -- the event window being represented
90  * starts at (tv - sigma) and ends at (tv + sigma).
91  * Event signaling can occur anywere within this interval.
92  * Making the interval larger makes the scheduler more efficient,
93  * while making it smaller results in more precise scheduling.
94  * The caller should treat the passed struct schedule_entry as
95  * an opaque object.
96  */
97 static inline void
99  struct schedule_entry *e,
100  const struct timeval *tv,
101  unsigned int sigma)
102 {
103  if (!IN_TREE(e) || !sigma || !tv_within_sigma(tv, &e->tv, sigma))
104  {
105  e->tv = *tv;
106  schedule_add_modify(s, e);
107  s->earliest_wakeup = NULL; /* invalidate cache */
108  }
109 }
110 
111 /*
112  * Return the node with the earliest wakeup time. If two
113  * nodes have the exact same wakeup time, select based on
114  * the random priority assigned to each node (the priority
115  * is randomized every time an entry is re-added).
116  */
117 static inline struct schedule_entry *
119  struct timeval *wakeup)
120 {
121  struct schedule_entry *ret;
122 
123  /* cache result */
124  if (!s->earliest_wakeup)
125  {
127  }
128  ret = s->earliest_wakeup;
129  if (ret)
130  {
131  *wakeup = ret->tv;
132  }
133 
134  return ret;
135 }
136 
137 #endif /* ifndef SCHEDULE_H */
#define IN_TREE(e)
Definition: schedule.h:75
static void schedule_add_entry(struct schedule *s, struct schedule_entry *e, const struct timeval *tv, unsigned int sigma)
Definition: schedule.h:98
unsigned int pri
Definition: schedule.h:47
struct schedule_entry * earliest_wakeup
Definition: schedule.h:55
void schedule_add_modify(struct schedule *s, struct schedule_entry *e)
Definition: schedule.c:346
struct timeval tv
Definition: schedule.h:46
void schedule_free(struct schedule *s)
Definition: schedule.c:423
void schedule_remove_node(struct schedule *s, struct schedule_entry *e)
Definition: schedule.c:250
struct schedule_entry * root
Definition: schedule.h:56
void schedule_remove_entry(struct schedule *s, struct schedule_entry *e)
Definition: schedule.c:429
struct schedule_entry * gt
Definition: schedule.h:50
Definition: schedule.h:44
struct schedule_entry * parent
Definition: schedule.h:48
struct schedule_entry * lt
Definition: schedule.h:49
struct schedule_entry * schedule_find_least(struct schedule_entry *e)
Definition: schedule.c:386
static struct schedule_entry * schedule_get_earliest_wakeup(struct schedule *s, struct timeval *wakeup)
Definition: schedule.h:118
static bool tv_within_sigma(const struct timeval *t1, const struct timeval *t2, unsigned int sigma)
Definition: otime.h:280
struct schedule * schedule_init(void)
Definition: schedule.c:414