blob: c1b34f1edb32740fa38dc724f6792f5998118a54 [file] [log] [blame]
Stephen Hemminger317a76f2005-06-23 12:19:55 -07001/*
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
Stephen Hemminger317a76f2005-06-23 12:19:55 -07009#include <linux/module.h>
10#include <linux/mm.h>
11#include <linux/types.h>
12#include <linux/list.h>
13#include <net/tcp.h>
14
15static DEFINE_SPINLOCK(tcp_cong_list_lock);
16static LIST_HEAD(tcp_cong_list);
17
18/* Simple linear search, don't expect many entries! */
19static struct tcp_congestion_ops *tcp_ca_find(const char *name)
20{
21 struct tcp_congestion_ops *e;
22
Stephen Hemminger5f8ef482005-06-23 20:37:36 -070023 list_for_each_entry_rcu(e, &tcp_cong_list, list) {
Stephen Hemminger317a76f2005-06-23 12:19:55 -070024 if (strcmp(e->name, name) == 0)
25 return e;
26 }
27
28 return NULL;
29}
30
31/*
32 * Attach new congestion control algorthim to the list
33 * of available options.
34 */
35int tcp_register_congestion_control(struct tcp_congestion_ops *ca)
36{
37 int ret = 0;
38
39 /* all algorithms must implement ssthresh and cong_avoid ops */
Stephen Hemminger72dc5b92006-06-05 17:30:08 -070040 if (!ca->ssthresh || !ca->cong_avoid) {
Stephen Hemminger317a76f2005-06-23 12:19:55 -070041 printk(KERN_ERR "TCP %s does not implement required ops\n",
42 ca->name);
43 return -EINVAL;
44 }
45
46 spin_lock(&tcp_cong_list_lock);
47 if (tcp_ca_find(ca->name)) {
48 printk(KERN_NOTICE "TCP %s already registered\n", ca->name);
49 ret = -EEXIST;
50 } else {
Stephen Hemminger3d2573f2006-09-24 20:11:58 -070051 list_add_tail_rcu(&ca->list, &tcp_cong_list);
Stephen Hemminger317a76f2005-06-23 12:19:55 -070052 printk(KERN_INFO "TCP %s registered\n", ca->name);
53 }
54 spin_unlock(&tcp_cong_list_lock);
55
56 return ret;
57}
58EXPORT_SYMBOL_GPL(tcp_register_congestion_control);
59
60/*
61 * Remove congestion control algorithm, called from
62 * the module's remove function. Module ref counts are used
63 * to ensure that this can't be done till all sockets using
64 * that method are closed.
65 */
66void tcp_unregister_congestion_control(struct tcp_congestion_ops *ca)
67{
68 spin_lock(&tcp_cong_list_lock);
69 list_del_rcu(&ca->list);
70 spin_unlock(&tcp_cong_list_lock);
71}
72EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control);
73
74/* Assign choice of congestion control. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -030075void tcp_init_congestion_control(struct sock *sk)
Stephen Hemminger317a76f2005-06-23 12:19:55 -070076{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -030077 struct inet_connection_sock *icsk = inet_csk(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -070078 struct tcp_congestion_ops *ca;
79
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -030080 if (icsk->icsk_ca_ops != &tcp_init_congestion_ops)
Stephen Hemminger5f8ef482005-06-23 20:37:36 -070081 return;
82
Stephen Hemminger317a76f2005-06-23 12:19:55 -070083 rcu_read_lock();
84 list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
85 if (try_module_get(ca->owner)) {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -030086 icsk->icsk_ca_ops = ca;
Stephen Hemminger317a76f2005-06-23 12:19:55 -070087 break;
88 }
89
90 }
91 rcu_read_unlock();
92
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -030093 if (icsk->icsk_ca_ops->init)
94 icsk->icsk_ca_ops->init(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -070095}
96
97/* Manage refcounts on socket close. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -030098void tcp_cleanup_congestion_control(struct sock *sk)
Stephen Hemminger317a76f2005-06-23 12:19:55 -070099{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300100 struct inet_connection_sock *icsk = inet_csk(sk);
101
102 if (icsk->icsk_ca_ops->release)
103 icsk->icsk_ca_ops->release(sk);
104 module_put(icsk->icsk_ca_ops->owner);
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700105}
106
107/* Used by sysctl to change default congestion control */
108int tcp_set_default_congestion_control(const char *name)
109{
110 struct tcp_congestion_ops *ca;
111 int ret = -ENOENT;
112
113 spin_lock(&tcp_cong_list_lock);
114 ca = tcp_ca_find(name);
115#ifdef CONFIG_KMOD
Stephen Hemminger35bfbc92006-11-09 16:36:36 -0800116 if (!ca && capable(CAP_SYS_MODULE)) {
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700117 spin_unlock(&tcp_cong_list_lock);
118
119 request_module("tcp_%s", name);
120 spin_lock(&tcp_cong_list_lock);
121 ca = tcp_ca_find(name);
122 }
123#endif
124
125 if (ca) {
Stephen Hemmingerce7bc3b2006-11-09 16:35:15 -0800126 ca->non_restricted = 1; /* default is always allowed */
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700127 list_move(&ca->list, &tcp_cong_list);
128 ret = 0;
129 }
130 spin_unlock(&tcp_cong_list_lock);
131
132 return ret;
133}
134
Stephen Hemmingerb1736a72006-10-31 17:31:33 -0800135/* Set default value from kernel configuration at bootup */
136static int __init tcp_congestion_default(void)
137{
138 return tcp_set_default_congestion_control(CONFIG_DEFAULT_TCP_CONG);
139}
140late_initcall(tcp_congestion_default);
141
142
Stephen Hemminger3ff825b2006-11-09 16:32:06 -0800143/* Build string with list of available congestion control values */
144void tcp_get_available_congestion_control(char *buf, size_t maxlen)
145{
146 struct tcp_congestion_ops *ca;
147 size_t offs = 0;
148
149 rcu_read_lock();
150 list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
151 offs += snprintf(buf + offs, maxlen - offs,
152 "%s%s",
153 offs == 0 ? "" : " ", ca->name);
154
155 }
156 rcu_read_unlock();
157}
158
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700159/* Get current default congestion control */
160void tcp_get_default_congestion_control(char *name)
161{
162 struct tcp_congestion_ops *ca;
163 /* We will always have reno... */
164 BUG_ON(list_empty(&tcp_cong_list));
165
166 rcu_read_lock();
167 ca = list_entry(tcp_cong_list.next, struct tcp_congestion_ops, list);
168 strncpy(name, ca->name, TCP_CA_NAME_MAX);
169 rcu_read_unlock();
170}
171
Stephen Hemmingerce7bc3b2006-11-09 16:35:15 -0800172/* Built list of non-restricted congestion control values */
173void tcp_get_allowed_congestion_control(char *buf, size_t maxlen)
174{
175 struct tcp_congestion_ops *ca;
176 size_t offs = 0;
177
178 *buf = '\0';
179 rcu_read_lock();
180 list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
181 if (!ca->non_restricted)
182 continue;
183 offs += snprintf(buf + offs, maxlen - offs,
184 "%s%s",
185 offs == 0 ? "" : " ", ca->name);
186
187 }
188 rcu_read_unlock();
189}
190
191/* Change list of non-restricted congestion control */
192int tcp_set_allowed_congestion_control(char *val)
193{
194 struct tcp_congestion_ops *ca;
195 char *clone, *name;
196 int ret = 0;
197
198 clone = kstrdup(val, GFP_USER);
199 if (!clone)
200 return -ENOMEM;
201
202 spin_lock(&tcp_cong_list_lock);
203 /* pass 1 check for bad entries */
204 while ((name = strsep(&clone, " ")) && *name) {
205 ca = tcp_ca_find(name);
206 if (!ca) {
207 ret = -ENOENT;
208 goto out;
209 }
210 }
211
212 /* pass 2 clear */
213 list_for_each_entry_rcu(ca, &tcp_cong_list, list)
214 ca->non_restricted = 0;
215
216 /* pass 3 mark as allowed */
217 while ((name = strsep(&val, " ")) && *name) {
218 ca = tcp_ca_find(name);
219 WARN_ON(!ca);
220 if (ca)
221 ca->non_restricted = 1;
222 }
223out:
224 spin_unlock(&tcp_cong_list_lock);
225
226 return ret;
227}
228
229
Stephen Hemminger5f8ef482005-06-23 20:37:36 -0700230/* Change congestion control for socket */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300231int tcp_set_congestion_control(struct sock *sk, const char *name)
Stephen Hemminger5f8ef482005-06-23 20:37:36 -0700232{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300233 struct inet_connection_sock *icsk = inet_csk(sk);
Stephen Hemminger5f8ef482005-06-23 20:37:36 -0700234 struct tcp_congestion_ops *ca;
235 int err = 0;
236
237 rcu_read_lock();
238 ca = tcp_ca_find(name);
Stephen Hemminger35bfbc92006-11-09 16:36:36 -0800239 /* no change asking for existing value */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300240 if (ca == icsk->icsk_ca_ops)
Stephen Hemminger5f8ef482005-06-23 20:37:36 -0700241 goto out;
242
Stephen Hemminger35bfbc92006-11-09 16:36:36 -0800243#ifdef CONFIG_KMOD
244 /* not found attempt to autoload module */
245 if (!ca && capable(CAP_SYS_MODULE)) {
246 rcu_read_unlock();
247 request_module("tcp_%s", name);
248 rcu_read_lock();
249 ca = tcp_ca_find(name);
250 }
251#endif
Stephen Hemminger5f8ef482005-06-23 20:37:36 -0700252 if (!ca)
253 err = -ENOENT;
254
Stephen Hemmingerce7bc3b2006-11-09 16:35:15 -0800255 else if (!(ca->non_restricted || capable(CAP_NET_ADMIN)))
256 err = -EPERM;
257
Stephen Hemminger5f8ef482005-06-23 20:37:36 -0700258 else if (!try_module_get(ca->owner))
259 err = -EBUSY;
260
261 else {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300262 tcp_cleanup_congestion_control(sk);
263 icsk->icsk_ca_ops = ca;
264 if (icsk->icsk_ca_ops->init)
265 icsk->icsk_ca_ops->init(sk);
Stephen Hemminger5f8ef482005-06-23 20:37:36 -0700266 }
267 out:
268 rcu_read_unlock();
269 return err;
270}
271
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800272
273/*
274 * Linear increase during slow start
275 */
276void tcp_slow_start(struct tcp_sock *tp)
277{
278 if (sysctl_tcp_abc) {
279 /* RFC3465: Slow Start
280 * TCP sender SHOULD increase cwnd by the number of
281 * previously unacknowledged bytes ACKed by each incoming
282 * acknowledgment, provided the increase is not more than L
283 */
284 if (tp->bytes_acked < tp->mss_cache)
285 return;
286
287 /* We MAY increase by 2 if discovered delayed ack */
Daikichi Osuga3fdf3f02006-08-29 02:01:44 -0700288 if (sysctl_tcp_abc > 1 && tp->bytes_acked >= 2*tp->mss_cache) {
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800289 if (tp->snd_cwnd < tp->snd_cwnd_clamp)
290 tp->snd_cwnd++;
291 }
292 }
293 tp->bytes_acked = 0;
294
295 if (tp->snd_cwnd < tp->snd_cwnd_clamp)
296 tp->snd_cwnd++;
297}
298EXPORT_SYMBOL_GPL(tcp_slow_start);
299
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700300/*
301 * TCP Reno congestion control
302 * This is special case used for fallback as well.
303 */
304/* This is Jacobson's slow start and congestion avoidance.
305 * SIGCOMM '88, p. 328.
306 */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300307void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 rtt, u32 in_flight,
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700308 int flag)
309{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300310 struct tcp_sock *tp = tcp_sk(sk);
311
Stephen Hemmingerf4805ed2005-11-10 16:53:30 -0800312 if (!tcp_is_cwnd_limited(sk, in_flight))
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700313 return;
314
Stephen Hemminger7faffa12005-11-10 17:07:24 -0800315 /* In "safe" area, increase. */
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900316 if (tp->snd_cwnd <= tp->snd_ssthresh)
Stephen Hemminger7faffa12005-11-10 17:07:24 -0800317 tcp_slow_start(tp);
Stephen Hemminger9772efb2005-11-10 17:09:53 -0800318
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900319 /* In dangerous area, increase slowly. */
Stephen Hemminger9772efb2005-11-10 17:09:53 -0800320 else if (sysctl_tcp_abc) {
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900321 /* RFC3465: Appropriate Byte Count
322 * increase once for each full cwnd acked
323 */
324 if (tp->bytes_acked >= tp->snd_cwnd*tp->mss_cache) {
325 tp->bytes_acked -= tp->snd_cwnd*tp->mss_cache;
326 if (tp->snd_cwnd < tp->snd_cwnd_clamp)
327 tp->snd_cwnd++;
328 }
329 } else {
330 /* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd */
331 if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
332 if (tp->snd_cwnd < tp->snd_cwnd_clamp)
333 tp->snd_cwnd++;
334 tp->snd_cwnd_cnt = 0;
335 } else
336 tp->snd_cwnd_cnt++;
337 }
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700338}
339EXPORT_SYMBOL_GPL(tcp_reno_cong_avoid);
340
341/* Slow start threshold is half the congestion window (min 2) */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300342u32 tcp_reno_ssthresh(struct sock *sk)
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700343{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300344 const struct tcp_sock *tp = tcp_sk(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700345 return max(tp->snd_cwnd >> 1U, 2U);
346}
347EXPORT_SYMBOL_GPL(tcp_reno_ssthresh);
348
Stephen Hemminger72dc5b92006-06-05 17:30:08 -0700349/* Lower bound on congestion window with halving. */
350u32 tcp_reno_min_cwnd(const struct sock *sk)
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700351{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300352 const struct tcp_sock *tp = tcp_sk(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700353 return tp->snd_ssthresh/2;
354}
355EXPORT_SYMBOL_GPL(tcp_reno_min_cwnd);
356
357struct tcp_congestion_ops tcp_reno = {
358 .name = "reno",
Stephen Hemmingerce7bc3b2006-11-09 16:35:15 -0800359 .non_restricted = 1,
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700360 .owner = THIS_MODULE,
361 .ssthresh = tcp_reno_ssthresh,
362 .cong_avoid = tcp_reno_cong_avoid,
363 .min_cwnd = tcp_reno_min_cwnd,
364};
365
Stephen Hemminger5f8ef482005-06-23 20:37:36 -0700366/* Initial congestion control used (until SYN)
367 * really reno under another name so we can tell difference
368 * during tcp_set_default_congestion_control
369 */
370struct tcp_congestion_ops tcp_init_congestion_ops = {
371 .name = "",
372 .owner = THIS_MODULE,
373 .ssthresh = tcp_reno_ssthresh,
374 .cong_avoid = tcp_reno_cong_avoid,
375 .min_cwnd = tcp_reno_min_cwnd,
376};
377EXPORT_SYMBOL_GPL(tcp_init_congestion_ops);