blob: 3a6be23d222f382c32dcd1e3acc5e55b97594797 [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
John Heffner886236c2007-03-25 19:21:45 -070015int sysctl_tcp_max_ssthresh = 0;
16
Stephen Hemminger317a76f2005-06-23 12:19:55 -070017static DEFINE_SPINLOCK(tcp_cong_list_lock);
18static LIST_HEAD(tcp_cong_list);
19
20/* Simple linear search, don't expect many entries! */
21static struct tcp_congestion_ops *tcp_ca_find(const char *name)
22{
23 struct tcp_congestion_ops *e;
24
Stephen Hemminger5f8ef482005-06-23 20:37:36 -070025 list_for_each_entry_rcu(e, &tcp_cong_list, list) {
Stephen Hemminger317a76f2005-06-23 12:19:55 -070026 if (strcmp(e->name, name) == 0)
27 return e;
28 }
29
30 return NULL;
31}
32
33/*
Robert P. J. Dayd08df602007-02-17 19:07:33 +010034 * Attach new congestion control algorithm to the list
Stephen Hemminger317a76f2005-06-23 12:19:55 -070035 * of available options.
36 */
37int tcp_register_congestion_control(struct tcp_congestion_ops *ca)
38{
39 int ret = 0;
40
41 /* all algorithms must implement ssthresh and cong_avoid ops */
Stephen Hemminger72dc5b92006-06-05 17:30:08 -070042 if (!ca->ssthresh || !ca->cong_avoid) {
Stephen Hemminger317a76f2005-06-23 12:19:55 -070043 printk(KERN_ERR "TCP %s does not implement required ops\n",
44 ca->name);
45 return -EINVAL;
46 }
47
48 spin_lock(&tcp_cong_list_lock);
49 if (tcp_ca_find(ca->name)) {
50 printk(KERN_NOTICE "TCP %s already registered\n", ca->name);
51 ret = -EEXIST;
52 } else {
Stephen Hemminger3d2573f2006-09-24 20:11:58 -070053 list_add_tail_rcu(&ca->list, &tcp_cong_list);
Stephen Hemminger317a76f2005-06-23 12:19:55 -070054 printk(KERN_INFO "TCP %s registered\n", ca->name);
55 }
56 spin_unlock(&tcp_cong_list_lock);
57
58 return ret;
59}
60EXPORT_SYMBOL_GPL(tcp_register_congestion_control);
61
62/*
63 * Remove congestion control algorithm, called from
64 * the module's remove function. Module ref counts are used
65 * to ensure that this can't be done till all sockets using
66 * that method are closed.
67 */
68void tcp_unregister_congestion_control(struct tcp_congestion_ops *ca)
69{
70 spin_lock(&tcp_cong_list_lock);
71 list_del_rcu(&ca->list);
72 spin_unlock(&tcp_cong_list_lock);
73}
74EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control);
75
76/* Assign choice of congestion control. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -030077void tcp_init_congestion_control(struct sock *sk)
Stephen Hemminger317a76f2005-06-23 12:19:55 -070078{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -030079 struct inet_connection_sock *icsk = inet_csk(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -070080 struct tcp_congestion_ops *ca;
81
Stephen Hemminger4d4d3d12007-04-23 22:32:11 -070082 /* if no choice made yet assign the current value set as default */
83 if (icsk->icsk_ca_ops == &tcp_init_congestion_ops) {
84 rcu_read_lock();
85 list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
86 if (try_module_get(ca->owner)) {
87 icsk->icsk_ca_ops = ca;
88 break;
89 }
Stephen Hemminger5f8ef482005-06-23 20:37:36 -070090
Stephen Hemminger4d4d3d12007-04-23 22:32:11 -070091 /* fallback to next available */
Stephen Hemminger317a76f2005-06-23 12:19:55 -070092 }
Stephen Hemminger4d4d3d12007-04-23 22:32:11 -070093 rcu_read_unlock();
Stephen Hemminger317a76f2005-06-23 12:19:55 -070094 }
Stephen Hemminger317a76f2005-06-23 12:19:55 -070095
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -030096 if (icsk->icsk_ca_ops->init)
97 icsk->icsk_ca_ops->init(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -070098}
99
100/* Manage refcounts on socket close. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300101void tcp_cleanup_congestion_control(struct sock *sk)
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700102{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300103 struct inet_connection_sock *icsk = inet_csk(sk);
104
105 if (icsk->icsk_ca_ops->release)
106 icsk->icsk_ca_ops->release(sk);
107 module_put(icsk->icsk_ca_ops->owner);
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700108}
109
110/* Used by sysctl to change default congestion control */
111int tcp_set_default_congestion_control(const char *name)
112{
113 struct tcp_congestion_ops *ca;
114 int ret = -ENOENT;
115
116 spin_lock(&tcp_cong_list_lock);
117 ca = tcp_ca_find(name);
118#ifdef CONFIG_KMOD
Stephen Hemminger35bfbc92006-11-09 16:36:36 -0800119 if (!ca && capable(CAP_SYS_MODULE)) {
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700120 spin_unlock(&tcp_cong_list_lock);
121
122 request_module("tcp_%s", name);
123 spin_lock(&tcp_cong_list_lock);
124 ca = tcp_ca_find(name);
125 }
126#endif
127
128 if (ca) {
Stephen Hemminger164891a2007-04-23 22:26:16 -0700129 ca->flags |= TCP_CONG_NON_RESTRICTED; /* default is always allowed */
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700130 list_move(&ca->list, &tcp_cong_list);
131 ret = 0;
132 }
133 spin_unlock(&tcp_cong_list_lock);
134
135 return ret;
136}
137
Stephen Hemmingerb1736a72006-10-31 17:31:33 -0800138/* Set default value from kernel configuration at bootup */
139static int __init tcp_congestion_default(void)
140{
141 return tcp_set_default_congestion_control(CONFIG_DEFAULT_TCP_CONG);
142}
143late_initcall(tcp_congestion_default);
144
145
Stephen Hemminger3ff825b2006-11-09 16:32:06 -0800146/* Build string with list of available congestion control values */
147void tcp_get_available_congestion_control(char *buf, size_t maxlen)
148{
149 struct tcp_congestion_ops *ca;
150 size_t offs = 0;
151
152 rcu_read_lock();
153 list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
154 offs += snprintf(buf + offs, maxlen - offs,
155 "%s%s",
156 offs == 0 ? "" : " ", ca->name);
157
158 }
159 rcu_read_unlock();
160}
161
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700162/* Get current default congestion control */
163void tcp_get_default_congestion_control(char *name)
164{
165 struct tcp_congestion_ops *ca;
166 /* We will always have reno... */
167 BUG_ON(list_empty(&tcp_cong_list));
168
169 rcu_read_lock();
170 ca = list_entry(tcp_cong_list.next, struct tcp_congestion_ops, list);
171 strncpy(name, ca->name, TCP_CA_NAME_MAX);
172 rcu_read_unlock();
173}
174
Stephen Hemmingerce7bc3b2006-11-09 16:35:15 -0800175/* Built list of non-restricted congestion control values */
176void tcp_get_allowed_congestion_control(char *buf, size_t maxlen)
177{
178 struct tcp_congestion_ops *ca;
179 size_t offs = 0;
180
181 *buf = '\0';
182 rcu_read_lock();
183 list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
Stephen Hemminger164891a2007-04-23 22:26:16 -0700184 if (!(ca->flags & TCP_CONG_NON_RESTRICTED))
Stephen Hemmingerce7bc3b2006-11-09 16:35:15 -0800185 continue;
186 offs += snprintf(buf + offs, maxlen - offs,
187 "%s%s",
188 offs == 0 ? "" : " ", ca->name);
189
190 }
191 rcu_read_unlock();
192}
193
194/* Change list of non-restricted congestion control */
195int tcp_set_allowed_congestion_control(char *val)
196{
197 struct tcp_congestion_ops *ca;
198 char *clone, *name;
199 int ret = 0;
200
201 clone = kstrdup(val, GFP_USER);
202 if (!clone)
203 return -ENOMEM;
204
205 spin_lock(&tcp_cong_list_lock);
206 /* pass 1 check for bad entries */
207 while ((name = strsep(&clone, " ")) && *name) {
208 ca = tcp_ca_find(name);
209 if (!ca) {
210 ret = -ENOENT;
211 goto out;
212 }
213 }
214
Stephen Hemminger164891a2007-04-23 22:26:16 -0700215 /* pass 2 clear old values */
Stephen Hemmingerce7bc3b2006-11-09 16:35:15 -0800216 list_for_each_entry_rcu(ca, &tcp_cong_list, list)
Stephen Hemminger164891a2007-04-23 22:26:16 -0700217 ca->flags &= ~TCP_CONG_NON_RESTRICTED;
Stephen Hemmingerce7bc3b2006-11-09 16:35:15 -0800218
219 /* pass 3 mark as allowed */
220 while ((name = strsep(&val, " ")) && *name) {
221 ca = tcp_ca_find(name);
222 WARN_ON(!ca);
223 if (ca)
Stephen Hemminger164891a2007-04-23 22:26:16 -0700224 ca->flags |= TCP_CONG_NON_RESTRICTED;
Stephen Hemmingerce7bc3b2006-11-09 16:35:15 -0800225 }
226out:
227 spin_unlock(&tcp_cong_list_lock);
228
229 return ret;
230}
231
232
Stephen Hemminger5f8ef482005-06-23 20:37:36 -0700233/* Change congestion control for socket */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300234int tcp_set_congestion_control(struct sock *sk, const char *name)
Stephen Hemminger5f8ef482005-06-23 20:37:36 -0700235{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300236 struct inet_connection_sock *icsk = inet_csk(sk);
Stephen Hemminger5f8ef482005-06-23 20:37:36 -0700237 struct tcp_congestion_ops *ca;
238 int err = 0;
239
240 rcu_read_lock();
241 ca = tcp_ca_find(name);
Stephen Hemminger4d4d3d12007-04-23 22:32:11 -0700242
Stephen Hemminger35bfbc92006-11-09 16:36:36 -0800243 /* no change asking for existing value */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300244 if (ca == icsk->icsk_ca_ops)
Stephen Hemminger5f8ef482005-06-23 20:37:36 -0700245 goto out;
246
Stephen Hemminger35bfbc92006-11-09 16:36:36 -0800247#ifdef CONFIG_KMOD
248 /* not found attempt to autoload module */
249 if (!ca && capable(CAP_SYS_MODULE)) {
250 rcu_read_unlock();
251 request_module("tcp_%s", name);
252 rcu_read_lock();
253 ca = tcp_ca_find(name);
254 }
255#endif
Stephen Hemminger5f8ef482005-06-23 20:37:36 -0700256 if (!ca)
257 err = -ENOENT;
258
Stephen Hemminger164891a2007-04-23 22:26:16 -0700259 else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) || capable(CAP_NET_ADMIN)))
Stephen Hemmingerce7bc3b2006-11-09 16:35:15 -0800260 err = -EPERM;
261
Stephen Hemminger5f8ef482005-06-23 20:37:36 -0700262 else if (!try_module_get(ca->owner))
263 err = -EBUSY;
264
265 else {
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300266 tcp_cleanup_congestion_control(sk);
267 icsk->icsk_ca_ops = ca;
Stephen Hemminger4d4d3d12007-04-23 22:32:11 -0700268
269 if (sk->sk_state != TCP_CLOSE && icsk->icsk_ca_ops->init)
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300270 icsk->icsk_ca_ops->init(sk);
Stephen Hemminger5f8ef482005-06-23 20:37:36 -0700271 }
272 out:
273 rcu_read_unlock();
274 return err;
275}
276
Ilpo Järvinencea14e02008-01-12 03:19:12 -0800277/* RFC2861 Check whether we are limited by application or congestion window
278 * This is the inverse of cwnd check in tcp_tso_should_defer
279 */
280int tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight)
281{
282 const struct tcp_sock *tp = tcp_sk(sk);
283 u32 left;
284
285 if (in_flight >= tp->snd_cwnd)
286 return 1;
287
288 if (!sk_can_gso(sk))
289 return 0;
290
291 left = tp->snd_cwnd - in_flight;
292 if (sysctl_tcp_tso_win_divisor)
293 return left * sysctl_tcp_tso_win_divisor < tp->snd_cwnd;
294 else
295 return left <= tcp_max_burst(tp);
296}
297EXPORT_SYMBOL_GPL(tcp_is_cwnd_limited);
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800298
299/*
Stephen Hemmingera02ba042007-05-17 00:04:18 -0700300 * Slow start is used when congestion window is less than slow start
301 * threshold. This version implements the basic RFC2581 version
302 * and optionally supports:
303 * RFC3742 Limited Slow Start - growth limited to max_ssthresh
304 * RFC3465 Appropriate Byte Counting - growth limited by bytes acknowledged
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800305 */
306void tcp_slow_start(struct tcp_sock *tp)
307{
Stephen Hemmingera02ba042007-05-17 00:04:18 -0700308 int cnt; /* increase in packets */
John Heffner886236c2007-03-25 19:21:45 -0700309
Stephen Hemmingera02ba042007-05-17 00:04:18 -0700310 /* RFC3465: ABC Slow start
311 * Increase only after a full MSS of bytes is acked
312 *
313 * TCP sender SHOULD increase cwnd by the number of
314 * previously unacknowledged bytes ACKed by each incoming
315 * acknowledgment, provided the increase is not more than L
316 */
317 if (sysctl_tcp_abc && tp->bytes_acked < tp->mss_cache)
318 return;
John Heffner886236c2007-03-25 19:21:45 -0700319
Stephen Hemmingera02ba042007-05-17 00:04:18 -0700320 if (sysctl_tcp_max_ssthresh > 0 && tp->snd_cwnd > sysctl_tcp_max_ssthresh)
321 cnt = sysctl_tcp_max_ssthresh >> 1; /* limited slow start */
John Heffner886236c2007-03-25 19:21:45 -0700322 else
Stephen Hemmingera02ba042007-05-17 00:04:18 -0700323 cnt = tp->snd_cwnd; /* exponential increase */
John Heffner886236c2007-03-25 19:21:45 -0700324
Stephen Hemmingera02ba042007-05-17 00:04:18 -0700325 /* RFC3465: ABC
326 * We MAY increase by 2 if discovered delayed ack
327 */
John Heffner886236c2007-03-25 19:21:45 -0700328 if (sysctl_tcp_abc > 1 && tp->bytes_acked >= 2*tp->mss_cache)
329 cnt <<= 1;
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800330 tp->bytes_acked = 0;
331
John Heffner886236c2007-03-25 19:21:45 -0700332 tp->snd_cwnd_cnt += cnt;
333 while (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
334 tp->snd_cwnd_cnt -= tp->snd_cwnd;
335 if (tp->snd_cwnd < tp->snd_cwnd_clamp)
336 tp->snd_cwnd++;
337 }
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800338}
339EXPORT_SYMBOL_GPL(tcp_slow_start);
340
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700341/*
342 * TCP Reno congestion control
343 * This is special case used for fallback as well.
344 */
345/* This is Jacobson's slow start and congestion avoidance.
346 * SIGCOMM '88, p. 328.
347 */
Ilpo Järvinenc3a05c62007-12-02 00:47:59 +0200348void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700349{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300350 struct tcp_sock *tp = tcp_sk(sk);
351
Stephen Hemmingerf4805ed2005-11-10 16:53:30 -0800352 if (!tcp_is_cwnd_limited(sk, in_flight))
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700353 return;
354
Stephen Hemminger7faffa12005-11-10 17:07:24 -0800355 /* In "safe" area, increase. */
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900356 if (tp->snd_cwnd <= tp->snd_ssthresh)
Stephen Hemminger7faffa12005-11-10 17:07:24 -0800357 tcp_slow_start(tp);
Stephen Hemminger9772efb2005-11-10 17:09:53 -0800358
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900359 /* In dangerous area, increase slowly. */
Stephen Hemminger9772efb2005-11-10 17:09:53 -0800360 else if (sysctl_tcp_abc) {
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900361 /* RFC3465: Appropriate Byte Count
362 * increase once for each full cwnd acked
363 */
364 if (tp->bytes_acked >= tp->snd_cwnd*tp->mss_cache) {
365 tp->bytes_acked -= tp->snd_cwnd*tp->mss_cache;
366 if (tp->snd_cwnd < tp->snd_cwnd_clamp)
367 tp->snd_cwnd++;
368 }
369 } else {
370 /* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd */
371 if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
372 if (tp->snd_cwnd < tp->snd_cwnd_clamp)
373 tp->snd_cwnd++;
374 tp->snd_cwnd_cnt = 0;
375 } else
376 tp->snd_cwnd_cnt++;
377 }
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700378}
379EXPORT_SYMBOL_GPL(tcp_reno_cong_avoid);
380
381/* Slow start threshold is half the congestion window (min 2) */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300382u32 tcp_reno_ssthresh(struct sock *sk)
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700383{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300384 const struct tcp_sock *tp = tcp_sk(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700385 return max(tp->snd_cwnd >> 1U, 2U);
386}
387EXPORT_SYMBOL_GPL(tcp_reno_ssthresh);
388
Stephen Hemminger72dc5b92006-06-05 17:30:08 -0700389/* Lower bound on congestion window with halving. */
390u32 tcp_reno_min_cwnd(const struct sock *sk)
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700391{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300392 const struct tcp_sock *tp = tcp_sk(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700393 return tp->snd_ssthresh/2;
394}
395EXPORT_SYMBOL_GPL(tcp_reno_min_cwnd);
396
397struct tcp_congestion_ops tcp_reno = {
Stephen Hemminger164891a2007-04-23 22:26:16 -0700398 .flags = TCP_CONG_NON_RESTRICTED,
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700399 .name = "reno",
400 .owner = THIS_MODULE,
401 .ssthresh = tcp_reno_ssthresh,
402 .cong_avoid = tcp_reno_cong_avoid,
403 .min_cwnd = tcp_reno_min_cwnd,
404};
405
Stephen Hemminger5f8ef482005-06-23 20:37:36 -0700406/* Initial congestion control used (until SYN)
407 * really reno under another name so we can tell difference
408 * during tcp_set_default_congestion_control
409 */
410struct tcp_congestion_ops tcp_init_congestion_ops = {
411 .name = "",
412 .owner = THIS_MODULE,
413 .ssthresh = tcp_reno_ssthresh,
414 .cong_avoid = tcp_reno_cong_avoid,
415 .min_cwnd = tcp_reno_min_cwnd,
416};
417EXPORT_SYMBOL_GPL(tcp_init_congestion_ops);