1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
|
/*
* Plugable TCP congestion control support and newReno
* congestion control.
* Based on ideas from I/O scheduler suport and Web100.
*
* Copyright (C) 2005 Stephen Hemminger <shemminger@osdl.org>
*/
#include <linux/config.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/types.h>
#include <linux/list.h>
#include <net/tcp.h>
static DEFINE_SPINLOCK(tcp_cong_list_lock);
static LIST_HEAD(tcp_cong_list);
/* Simple linear search, don't expect many entries! */
static struct tcp_congestion_ops *tcp_ca_find(const char *name)
{
struct tcp_congestion_ops *e;
list_for_each_entry_rcu(e, &tcp_cong_list, list) {
if (strcmp(e->name, name) == 0)
return e;
}
return NULL;
}
/*
* Attach new congestion control algorthim to the list
* of available options.
*/
int tcp_register_congestion_control(struct tcp_congestion_ops *ca)
{
int ret = 0;
/* all algorithms must implement ssthresh and cong_avoid ops */
if (!ca->ssthresh || !ca->cong_avoid || !ca->min_cwnd) {
printk(KERN_ERR "TCP %s does not implement required ops\n",
ca->name);
return -EINVAL;
}
spin_lock(&tcp_cong_list_lock);
if (tcp_ca_find(ca->name)) {
printk(KERN_NOTICE "TCP %s already registered\n", ca->name);
ret = -EEXIST;
} else {
list_add_rcu(&ca->list, &tcp_cong_list);
printk(KERN_INFO "TCP %s registered\n", ca->name);
}
spin_unlock(&tcp_cong_list_lock);
return ret;
}
EXPORT_SYMBOL_GPL(tcp_register_congestion_control);
/*
* Remove congestion control algorithm, called from
* the module's remove function. Module ref counts are used
* to ensure that this can't be done till all sockets using
* that method are closed.
*/
void tcp_unregister_congestion_control(struct tcp_congestion_ops *ca)
{
spin_lock(&tcp_cong_list_lock);
list_del_rcu(&ca->list);
spin_unlock(&tcp_cong_list_lock);
}
EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control);
/* Assign choice of congestion control. */
void tcp_init_congestion_control(struct tcp_sock *tp)
{
struct tcp_congestion_ops *ca;
if (tp->ca_ops != &tcp_init_congestion_ops)
return;
rcu_read_lock();
list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
if (try_module_get(ca->owner)) {
tp->ca_ops = ca;
break;
}
}
rcu_read_unlock();
if (tp->ca_ops->init)
tp->ca_ops->init(tp);
}
/* Manage refcounts on socket close. */
void tcp_cleanup_congestion_control(struct tcp_sock *tp)
{
if (tp->ca_ops->release)
tp->ca_ops->release(tp);
module_put(tp->ca_ops->owner);
}
/* Used by sysctl to change default congestion control */
int tcp_set_default_congestion_control(const char *name)
{
struct tcp_congestion_ops *ca;
int ret = -ENOENT;
spin_lock(&tcp_cong_list_lock);
ca = tcp_ca_find(name);
#ifdef CONFIG_KMOD
if (!ca) {
spin_unlock(&tcp_cong_list_lock);
request_module("tcp_%s", name);
spin_lock(&tcp_cong_list_lock);
ca = tcp_ca_find(name);
}
#endif
if (ca) {
list_move(&ca->list, &tcp_cong_list);
ret = 0;
}
spin_unlock(&tcp_cong_list_lock);
return ret;
}
/* Get current default congestion control */
void tcp_get_default_congestion_control(char *name)
{
struct tcp_congestion_ops *ca;
/* We will always have reno... */
BUG_ON(list_empty(&tcp_cong_list));
rcu_read_lock();
ca = list_entry(tcp_cong_list.next, struct tcp_congestion_ops, list);
strncpy(name, ca->name, TCP_CA_NAME_MAX);
rcu_read_unlock();
}
/* Change congestion control for socket */
int tcp_set_congestion_control(struct tcp_sock *tp, const char *name)
{
struct tcp_congestion_ops *ca;
int err = 0;
rcu_read_lock();
ca = tcp_ca_find(name);
if (ca == tp->ca_ops)
goto out;
if (!ca)
err = -ENOENT;
else if (!try_module_get(ca->owner))
err = -EBUSY;
else {
tcp_cleanup_congestion_control(tp);
tp->ca_ops = ca;
if (tp->ca_ops->init)
tp->ca_ops->init(tp);
}
out:
rcu_read_unlock();
return err;
}
/*
* TCP Reno congestion control
* This is special case used for fallback as well.
*/
/* This is Jacobson's slow start and congestion avoidance.
* SIGCOMM '88, p. 328.
*/
void tcp_reno_cong_avoid(struct tcp_sock *tp, u32 ack, u32 rtt, u32 in_flight,
int flag)
{
if (in_flight < tp->snd_cwnd)
return;
if (tp->snd_cwnd <= tp->snd_ssthresh) {
/* In "safe" area, increase. */
if (tp->snd_cwnd < tp->snd_cwnd_clamp)
tp->snd_cwnd++;
} else {
/* In dangerous area, increase slowly.
* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd
*/
if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
if (tp->snd_cwnd < tp->snd_cwnd_clamp)
tp->snd_cwnd++;
tp->snd_cwnd_cnt = 0;
} else
tp->snd_cwnd_cnt++;
}
}
EXPORT_SYMBOL_GPL(tcp_reno_cong_avoid);
/* Slow start threshold is half the congestion window (min 2) */
u32 tcp_reno_ssthresh(struct tcp_sock *tp)
{
return max(tp->snd_cwnd >> 1U, 2U);
}
EXPORT_SYMBOL_GPL(tcp_reno_ssthresh);
/* Lower bound on congestion window. */
u32 tcp_reno_min_cwnd(struct tcp_sock *tp)
{
return tp->snd_ssthresh/2;
}
EXPORT_SYMBOL_GPL(tcp_reno_min_cwnd);
struct tcp_congestion_ops tcp_reno = {
.name = "reno",
.owner = THIS_MODULE,
.ssthresh = tcp_reno_ssthresh,
.cong_avoid = tcp_reno_cong_avoid,
.min_cwnd = tcp_reno_min_cwnd,
};
/* Initial congestion control used (until SYN)
* really reno under another name so we can tell difference
* during tcp_set_default_congestion_control
*/
struct tcp_congestion_ops tcp_init_congestion_ops = {
.name = "",
.owner = THIS_MODULE,
.ssthresh = tcp_reno_ssthresh,
.cong_avoid = tcp_reno_cong_avoid,
.min_cwnd = tcp_reno_min_cwnd,
};
EXPORT_SYMBOL_GPL(tcp_init_congestion_ops);
|
