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Commit | Line | Data |
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317a76f9 SH |
1 | /* |
2 | * Plugable TCP congestion control support and newReno | |
3 | * congestion control. | |
4 | * Based on ideas from I/O scheduler suport and Web100. | |
5 | * | |
6 | * Copyright (C) 2005 Stephen Hemminger <shemminger@osdl.org> | |
7 | */ | |
8 | ||
9 | #include <linux/config.h> | |
10 | #include <linux/module.h> | |
11 | #include <linux/mm.h> | |
12 | #include <linux/types.h> | |
13 | #include <linux/list.h> | |
14 | #include <net/tcp.h> | |
15 | ||
16 | static DEFINE_SPINLOCK(tcp_cong_list_lock); | |
17 | static LIST_HEAD(tcp_cong_list); | |
18 | ||
19 | /* Simple linear search, don't expect many entries! */ | |
20 | static struct tcp_congestion_ops *tcp_ca_find(const char *name) | |
21 | { | |
22 | struct tcp_congestion_ops *e; | |
23 | ||
24 | list_for_each_entry(e, &tcp_cong_list, list) { | |
25 | if (strcmp(e->name, name) == 0) | |
26 | return e; | |
27 | } | |
28 | ||
29 | return NULL; | |
30 | } | |
31 | ||
32 | /* | |
33 | * Attach new congestion control algorthim to the list | |
34 | * of available options. | |
35 | */ | |
36 | int tcp_register_congestion_control(struct tcp_congestion_ops *ca) | |
37 | { | |
38 | int ret = 0; | |
39 | ||
40 | /* all algorithms must implement ssthresh and cong_avoid ops */ | |
41 | if (!ca->ssthresh || !ca->cong_avoid || !ca->min_cwnd) { | |
42 | printk(KERN_ERR "TCP %s does not implement required ops\n", | |
43 | ca->name); | |
44 | return -EINVAL; | |
45 | } | |
46 | ||
47 | spin_lock(&tcp_cong_list_lock); | |
48 | if (tcp_ca_find(ca->name)) { | |
49 | printk(KERN_NOTICE "TCP %s already registered\n", ca->name); | |
50 | ret = -EEXIST; | |
51 | } else { | |
52 | list_add_rcu(&ca->list, &tcp_cong_list); | |
53 | printk(KERN_INFO "TCP %s registered\n", ca->name); | |
54 | } | |
55 | spin_unlock(&tcp_cong_list_lock); | |
56 | ||
57 | return ret; | |
58 | } | |
59 | EXPORT_SYMBOL_GPL(tcp_register_congestion_control); | |
60 | ||
61 | /* | |
62 | * Remove congestion control algorithm, called from | |
63 | * the module's remove function. Module ref counts are used | |
64 | * to ensure that this can't be done till all sockets using | |
65 | * that method are closed. | |
66 | */ | |
67 | void tcp_unregister_congestion_control(struct tcp_congestion_ops *ca) | |
68 | { | |
69 | spin_lock(&tcp_cong_list_lock); | |
70 | list_del_rcu(&ca->list); | |
71 | spin_unlock(&tcp_cong_list_lock); | |
72 | } | |
73 | EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control); | |
74 | ||
75 | /* Assign choice of congestion control. */ | |
76 | void tcp_init_congestion_control(struct tcp_sock *tp) | |
77 | { | |
78 | struct tcp_congestion_ops *ca; | |
79 | ||
80 | rcu_read_lock(); | |
81 | list_for_each_entry_rcu(ca, &tcp_cong_list, list) { | |
82 | if (try_module_get(ca->owner)) { | |
83 | tp->ca_ops = ca; | |
84 | break; | |
85 | } | |
86 | ||
87 | } | |
88 | rcu_read_unlock(); | |
89 | ||
90 | if (tp->ca_ops->init) | |
91 | tp->ca_ops->init(tp); | |
92 | } | |
93 | ||
94 | /* Manage refcounts on socket close. */ | |
95 | void tcp_cleanup_congestion_control(struct tcp_sock *tp) | |
96 | { | |
97 | if (tp->ca_ops->release) | |
98 | tp->ca_ops->release(tp); | |
99 | module_put(tp->ca_ops->owner); | |
100 | } | |
101 | ||
102 | /* Used by sysctl to change default congestion control */ | |
103 | int tcp_set_default_congestion_control(const char *name) | |
104 | { | |
105 | struct tcp_congestion_ops *ca; | |
106 | int ret = -ENOENT; | |
107 | ||
108 | spin_lock(&tcp_cong_list_lock); | |
109 | ca = tcp_ca_find(name); | |
110 | #ifdef CONFIG_KMOD | |
111 | if (!ca) { | |
112 | spin_unlock(&tcp_cong_list_lock); | |
113 | ||
114 | request_module("tcp_%s", name); | |
115 | spin_lock(&tcp_cong_list_lock); | |
116 | ca = tcp_ca_find(name); | |
117 | } | |
118 | #endif | |
119 | ||
120 | if (ca) { | |
121 | list_move(&ca->list, &tcp_cong_list); | |
122 | ret = 0; | |
123 | } | |
124 | spin_unlock(&tcp_cong_list_lock); | |
125 | ||
126 | return ret; | |
127 | } | |
128 | ||
129 | /* Get current default congestion control */ | |
130 | void tcp_get_default_congestion_control(char *name) | |
131 | { | |
132 | struct tcp_congestion_ops *ca; | |
133 | /* We will always have reno... */ | |
134 | BUG_ON(list_empty(&tcp_cong_list)); | |
135 | ||
136 | rcu_read_lock(); | |
137 | ca = list_entry(tcp_cong_list.next, struct tcp_congestion_ops, list); | |
138 | strncpy(name, ca->name, TCP_CA_NAME_MAX); | |
139 | rcu_read_unlock(); | |
140 | } | |
141 | ||
142 | /* | |
143 | * TCP Reno congestion control | |
144 | * This is special case used for fallback as well. | |
145 | */ | |
146 | /* This is Jacobson's slow start and congestion avoidance. | |
147 | * SIGCOMM '88, p. 328. | |
148 | */ | |
149 | void tcp_reno_cong_avoid(struct tcp_sock *tp, u32 ack, u32 rtt, u32 in_flight, | |
150 | int flag) | |
151 | { | |
152 | if (in_flight < tp->snd_cwnd) | |
153 | return; | |
154 | ||
155 | if (tp->snd_cwnd <= tp->snd_ssthresh) { | |
156 | /* In "safe" area, increase. */ | |
157 | if (tp->snd_cwnd < tp->snd_cwnd_clamp) | |
158 | tp->snd_cwnd++; | |
159 | } else { | |
160 | /* In dangerous area, increase slowly. | |
161 | * In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd | |
162 | */ | |
163 | if (tp->snd_cwnd_cnt >= tp->snd_cwnd) { | |
164 | if (tp->snd_cwnd < tp->snd_cwnd_clamp) | |
165 | tp->snd_cwnd++; | |
166 | tp->snd_cwnd_cnt = 0; | |
167 | } else | |
168 | tp->snd_cwnd_cnt++; | |
169 | } | |
170 | } | |
171 | EXPORT_SYMBOL_GPL(tcp_reno_cong_avoid); | |
172 | ||
173 | /* Slow start threshold is half the congestion window (min 2) */ | |
174 | u32 tcp_reno_ssthresh(struct tcp_sock *tp) | |
175 | { | |
176 | return max(tp->snd_cwnd >> 1U, 2U); | |
177 | } | |
178 | EXPORT_SYMBOL_GPL(tcp_reno_ssthresh); | |
179 | ||
180 | /* Lower bound on congestion window. */ | |
181 | u32 tcp_reno_min_cwnd(struct tcp_sock *tp) | |
182 | { | |
183 | return tp->snd_ssthresh/2; | |
184 | } | |
185 | EXPORT_SYMBOL_GPL(tcp_reno_min_cwnd); | |
186 | ||
187 | struct tcp_congestion_ops tcp_reno = { | |
188 | .name = "reno", | |
189 | .owner = THIS_MODULE, | |
190 | .ssthresh = tcp_reno_ssthresh, | |
191 | .cong_avoid = tcp_reno_cong_avoid, | |
192 | .min_cwnd = tcp_reno_min_cwnd, | |
193 | }; | |
194 | ||
195 | EXPORT_SYMBOL_GPL(tcp_reno); |