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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 | ||
317a76f9 SH |
9 | #include <linux/module.h> |
10 | #include <linux/mm.h> | |
11 | #include <linux/types.h> | |
12 | #include <linux/list.h> | |
5a0e3ad6 | 13 | #include <linux/gfp.h> |
317a76f9 SH |
14 | #include <net/tcp.h> |
15 | ||
886236c1 JH |
16 | int sysctl_tcp_max_ssthresh = 0; |
17 | ||
317a76f9 SH |
18 | static DEFINE_SPINLOCK(tcp_cong_list_lock); |
19 | static LIST_HEAD(tcp_cong_list); | |
20 | ||
21 | /* Simple linear search, don't expect many entries! */ | |
22 | static struct tcp_congestion_ops *tcp_ca_find(const char *name) | |
23 | { | |
24 | struct tcp_congestion_ops *e; | |
25 | ||
5f8ef48d | 26 | list_for_each_entry_rcu(e, &tcp_cong_list, list) { |
317a76f9 SH |
27 | if (strcmp(e->name, name) == 0) |
28 | return e; | |
29 | } | |
30 | ||
31 | return NULL; | |
32 | } | |
33 | ||
34 | /* | |
d08df601 | 35 | * Attach new congestion control algorithm to the list |
317a76f9 SH |
36 | * of available options. |
37 | */ | |
38 | int tcp_register_congestion_control(struct tcp_congestion_ops *ca) | |
39 | { | |
40 | int ret = 0; | |
41 | ||
42 | /* all algorithms must implement ssthresh and cong_avoid ops */ | |
72dc5b92 | 43 | if (!ca->ssthresh || !ca->cong_avoid) { |
317a76f9 SH |
44 | printk(KERN_ERR "TCP %s does not implement required ops\n", |
45 | ca->name); | |
46 | return -EINVAL; | |
47 | } | |
48 | ||
49 | spin_lock(&tcp_cong_list_lock); | |
50 | if (tcp_ca_find(ca->name)) { | |
51 | printk(KERN_NOTICE "TCP %s already registered\n", ca->name); | |
52 | ret = -EEXIST; | |
53 | } else { | |
3d2573f7 | 54 | list_add_tail_rcu(&ca->list, &tcp_cong_list); |
317a76f9 SH |
55 | printk(KERN_INFO "TCP %s registered\n", ca->name); |
56 | } | |
57 | spin_unlock(&tcp_cong_list_lock); | |
58 | ||
59 | return ret; | |
60 | } | |
61 | EXPORT_SYMBOL_GPL(tcp_register_congestion_control); | |
62 | ||
63 | /* | |
64 | * Remove congestion control algorithm, called from | |
65 | * the module's remove function. Module ref counts are used | |
66 | * to ensure that this can't be done till all sockets using | |
67 | * that method are closed. | |
68 | */ | |
69 | void tcp_unregister_congestion_control(struct tcp_congestion_ops *ca) | |
70 | { | |
71 | spin_lock(&tcp_cong_list_lock); | |
72 | list_del_rcu(&ca->list); | |
73 | spin_unlock(&tcp_cong_list_lock); | |
74 | } | |
75 | EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control); | |
76 | ||
77 | /* Assign choice of congestion control. */ | |
6687e988 | 78 | void tcp_init_congestion_control(struct sock *sk) |
317a76f9 | 79 | { |
6687e988 | 80 | struct inet_connection_sock *icsk = inet_csk(sk); |
317a76f9 SH |
81 | struct tcp_congestion_ops *ca; |
82 | ||
4d4d3d1e SH |
83 | /* if no choice made yet assign the current value set as default */ |
84 | if (icsk->icsk_ca_ops == &tcp_init_congestion_ops) { | |
85 | rcu_read_lock(); | |
86 | list_for_each_entry_rcu(ca, &tcp_cong_list, list) { | |
87 | if (try_module_get(ca->owner)) { | |
88 | icsk->icsk_ca_ops = ca; | |
89 | break; | |
90 | } | |
5f8ef48d | 91 | |
4d4d3d1e | 92 | /* fallback to next available */ |
317a76f9 | 93 | } |
4d4d3d1e | 94 | rcu_read_unlock(); |
317a76f9 | 95 | } |
317a76f9 | 96 | |
6687e988 ACM |
97 | if (icsk->icsk_ca_ops->init) |
98 | icsk->icsk_ca_ops->init(sk); | |
317a76f9 SH |
99 | } |
100 | ||
101 | /* Manage refcounts on socket close. */ | |
6687e988 | 102 | void tcp_cleanup_congestion_control(struct sock *sk) |
317a76f9 | 103 | { |
6687e988 ACM |
104 | struct inet_connection_sock *icsk = inet_csk(sk); |
105 | ||
106 | if (icsk->icsk_ca_ops->release) | |
107 | icsk->icsk_ca_ops->release(sk); | |
108 | module_put(icsk->icsk_ca_ops->owner); | |
317a76f9 SH |
109 | } |
110 | ||
111 | /* Used by sysctl to change default congestion control */ | |
112 | int tcp_set_default_congestion_control(const char *name) | |
113 | { | |
114 | struct tcp_congestion_ops *ca; | |
115 | int ret = -ENOENT; | |
116 | ||
117 | spin_lock(&tcp_cong_list_lock); | |
118 | ca = tcp_ca_find(name); | |
95a5afca | 119 | #ifdef CONFIG_MODULES |
a8f80e8f | 120 | if (!ca && capable(CAP_NET_ADMIN)) { |
317a76f9 SH |
121 | spin_unlock(&tcp_cong_list_lock); |
122 | ||
123 | request_module("tcp_%s", name); | |
124 | spin_lock(&tcp_cong_list_lock); | |
125 | ca = tcp_ca_find(name); | |
126 | } | |
127 | #endif | |
128 | ||
129 | if (ca) { | |
164891aa | 130 | ca->flags |= TCP_CONG_NON_RESTRICTED; /* default is always allowed */ |
317a76f9 SH |
131 | list_move(&ca->list, &tcp_cong_list); |
132 | ret = 0; | |
133 | } | |
134 | spin_unlock(&tcp_cong_list_lock); | |
135 | ||
136 | return ret; | |
137 | } | |
138 | ||
b1736a71 SH |
139 | /* Set default value from kernel configuration at bootup */ |
140 | static int __init tcp_congestion_default(void) | |
141 | { | |
142 | return tcp_set_default_congestion_control(CONFIG_DEFAULT_TCP_CONG); | |
143 | } | |
144 | late_initcall(tcp_congestion_default); | |
145 | ||
146 | ||
3ff825b2 SH |
147 | /* Build string with list of available congestion control values */ |
148 | void tcp_get_available_congestion_control(char *buf, size_t maxlen) | |
149 | { | |
150 | struct tcp_congestion_ops *ca; | |
151 | size_t offs = 0; | |
152 | ||
153 | rcu_read_lock(); | |
154 | list_for_each_entry_rcu(ca, &tcp_cong_list, list) { | |
155 | offs += snprintf(buf + offs, maxlen - offs, | |
156 | "%s%s", | |
157 | offs == 0 ? "" : " ", ca->name); | |
158 | ||
159 | } | |
160 | rcu_read_unlock(); | |
161 | } | |
162 | ||
317a76f9 SH |
163 | /* Get current default congestion control */ |
164 | void tcp_get_default_congestion_control(char *name) | |
165 | { | |
166 | struct tcp_congestion_ops *ca; | |
167 | /* We will always have reno... */ | |
168 | BUG_ON(list_empty(&tcp_cong_list)); | |
169 | ||
170 | rcu_read_lock(); | |
171 | ca = list_entry(tcp_cong_list.next, struct tcp_congestion_ops, list); | |
172 | strncpy(name, ca->name, TCP_CA_NAME_MAX); | |
173 | rcu_read_unlock(); | |
174 | } | |
175 | ||
ce7bc3bf SH |
176 | /* Built list of non-restricted congestion control values */ |
177 | void tcp_get_allowed_congestion_control(char *buf, size_t maxlen) | |
178 | { | |
179 | struct tcp_congestion_ops *ca; | |
180 | size_t offs = 0; | |
181 | ||
182 | *buf = '\0'; | |
183 | rcu_read_lock(); | |
184 | list_for_each_entry_rcu(ca, &tcp_cong_list, list) { | |
164891aa | 185 | if (!(ca->flags & TCP_CONG_NON_RESTRICTED)) |
ce7bc3bf SH |
186 | continue; |
187 | offs += snprintf(buf + offs, maxlen - offs, | |
188 | "%s%s", | |
189 | offs == 0 ? "" : " ", ca->name); | |
190 | ||
191 | } | |
192 | rcu_read_unlock(); | |
193 | } | |
194 | ||
195 | /* Change list of non-restricted congestion control */ | |
196 | int tcp_set_allowed_congestion_control(char *val) | |
197 | { | |
198 | struct tcp_congestion_ops *ca; | |
c34186ed | 199 | char *saved_clone, *clone, *name; |
ce7bc3bf SH |
200 | int ret = 0; |
201 | ||
c34186ed | 202 | saved_clone = clone = kstrdup(val, GFP_USER); |
ce7bc3bf SH |
203 | if (!clone) |
204 | return -ENOMEM; | |
205 | ||
206 | spin_lock(&tcp_cong_list_lock); | |
207 | /* pass 1 check for bad entries */ | |
208 | while ((name = strsep(&clone, " ")) && *name) { | |
209 | ca = tcp_ca_find(name); | |
210 | if (!ca) { | |
211 | ret = -ENOENT; | |
212 | goto out; | |
213 | } | |
214 | } | |
215 | ||
164891aa | 216 | /* pass 2 clear old values */ |
ce7bc3bf | 217 | list_for_each_entry_rcu(ca, &tcp_cong_list, list) |
164891aa | 218 | ca->flags &= ~TCP_CONG_NON_RESTRICTED; |
ce7bc3bf SH |
219 | |
220 | /* pass 3 mark as allowed */ | |
221 | while ((name = strsep(&val, " ")) && *name) { | |
222 | ca = tcp_ca_find(name); | |
223 | WARN_ON(!ca); | |
224 | if (ca) | |
164891aa | 225 | ca->flags |= TCP_CONG_NON_RESTRICTED; |
ce7bc3bf SH |
226 | } |
227 | out: | |
228 | spin_unlock(&tcp_cong_list_lock); | |
c34186ed | 229 | kfree(saved_clone); |
ce7bc3bf SH |
230 | |
231 | return ret; | |
232 | } | |
233 | ||
234 | ||
5f8ef48d | 235 | /* Change congestion control for socket */ |
6687e988 | 236 | int tcp_set_congestion_control(struct sock *sk, const char *name) |
5f8ef48d | 237 | { |
6687e988 | 238 | struct inet_connection_sock *icsk = inet_csk(sk); |
5f8ef48d SH |
239 | struct tcp_congestion_ops *ca; |
240 | int err = 0; | |
241 | ||
242 | rcu_read_lock(); | |
243 | ca = tcp_ca_find(name); | |
4d4d3d1e | 244 | |
35bfbc94 | 245 | /* no change asking for existing value */ |
6687e988 | 246 | if (ca == icsk->icsk_ca_ops) |
5f8ef48d SH |
247 | goto out; |
248 | ||
95a5afca | 249 | #ifdef CONFIG_MODULES |
35bfbc94 | 250 | /* not found attempt to autoload module */ |
a8f80e8f | 251 | if (!ca && capable(CAP_NET_ADMIN)) { |
35bfbc94 SH |
252 | rcu_read_unlock(); |
253 | request_module("tcp_%s", name); | |
254 | rcu_read_lock(); | |
255 | ca = tcp_ca_find(name); | |
256 | } | |
257 | #endif | |
5f8ef48d SH |
258 | if (!ca) |
259 | err = -ENOENT; | |
260 | ||
164891aa | 261 | else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) || capable(CAP_NET_ADMIN))) |
ce7bc3bf SH |
262 | err = -EPERM; |
263 | ||
5f8ef48d SH |
264 | else if (!try_module_get(ca->owner)) |
265 | err = -EBUSY; | |
266 | ||
267 | else { | |
6687e988 ACM |
268 | tcp_cleanup_congestion_control(sk); |
269 | icsk->icsk_ca_ops = ca; | |
4d4d3d1e SH |
270 | |
271 | if (sk->sk_state != TCP_CLOSE && icsk->icsk_ca_ops->init) | |
6687e988 | 272 | icsk->icsk_ca_ops->init(sk); |
5f8ef48d SH |
273 | } |
274 | out: | |
275 | rcu_read_unlock(); | |
276 | return err; | |
277 | } | |
278 | ||
cea14e0e IJ |
279 | /* RFC2861 Check whether we are limited by application or congestion window |
280 | * This is the inverse of cwnd check in tcp_tso_should_defer | |
281 | */ | |
282 | int tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight) | |
283 | { | |
284 | const struct tcp_sock *tp = tcp_sk(sk); | |
285 | u32 left; | |
286 | ||
287 | if (in_flight >= tp->snd_cwnd) | |
288 | return 1; | |
289 | ||
cea14e0e | 290 | left = tp->snd_cwnd - in_flight; |
ce447eb9 | 291 | if (sk_can_gso(sk) && |
246eb2af JH |
292 | left * sysctl_tcp_tso_win_divisor < tp->snd_cwnd && |
293 | left * tp->mss_cache < sk->sk_gso_max_size) | |
ce447eb9 | 294 | return 1; |
6b5a5c0d | 295 | return left <= tcp_max_tso_deferred_mss(tp); |
cea14e0e IJ |
296 | } |
297 | EXPORT_SYMBOL_GPL(tcp_is_cwnd_limited); | |
40efc6fa SH |
298 | |
299 | /* | |
a02ba041 SH |
300 | * 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 | |
40efc6fa SH |
305 | */ |
306 | void tcp_slow_start(struct tcp_sock *tp) | |
307 | { | |
a02ba041 SH |
308 | int cnt; /* increase in packets */ |
309 | ||
310 | /* 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; | |
319 | ||
320 | if (sysctl_tcp_max_ssthresh > 0 && tp->snd_cwnd > sysctl_tcp_max_ssthresh) | |
321 | cnt = sysctl_tcp_max_ssthresh >> 1; /* limited slow start */ | |
886236c1 | 322 | else |
a02ba041 | 323 | cnt = tp->snd_cwnd; /* exponential increase */ |
886236c1 | 324 | |
a02ba041 SH |
325 | /* RFC3465: ABC |
326 | * We MAY increase by 2 if discovered delayed ack | |
327 | */ | |
886236c1 JH |
328 | if (sysctl_tcp_abc > 1 && tp->bytes_acked >= 2*tp->mss_cache) |
329 | cnt <<= 1; | |
40efc6fa SH |
330 | tp->bytes_acked = 0; |
331 | ||
886236c1 JH |
332 | 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 | } | |
40efc6fa SH |
338 | } |
339 | EXPORT_SYMBOL_GPL(tcp_slow_start); | |
340 | ||
758ce5c8 IJ |
341 | /* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd (or alternative w) */ |
342 | void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w) | |
343 | { | |
344 | if (tp->snd_cwnd_cnt >= w) { | |
345 | if (tp->snd_cwnd < tp->snd_cwnd_clamp) | |
346 | tp->snd_cwnd++; | |
347 | tp->snd_cwnd_cnt = 0; | |
348 | } else { | |
349 | tp->snd_cwnd_cnt++; | |
350 | } | |
351 | } | |
352 | EXPORT_SYMBOL_GPL(tcp_cong_avoid_ai); | |
353 | ||
317a76f9 SH |
354 | /* |
355 | * TCP Reno congestion control | |
356 | * This is special case used for fallback as well. | |
357 | */ | |
358 | /* This is Jacobson's slow start and congestion avoidance. | |
359 | * SIGCOMM '88, p. 328. | |
360 | */ | |
c3a05c60 | 361 | void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 in_flight) |
317a76f9 | 362 | { |
6687e988 ACM |
363 | struct tcp_sock *tp = tcp_sk(sk); |
364 | ||
f4805ede | 365 | if (!tcp_is_cwnd_limited(sk, in_flight)) |
317a76f9 SH |
366 | return; |
367 | ||
7faffa1c | 368 | /* In "safe" area, increase. */ |
e905a9ed | 369 | if (tp->snd_cwnd <= tp->snd_ssthresh) |
7faffa1c | 370 | tcp_slow_start(tp); |
9772efb9 | 371 | |
e905a9ed | 372 | /* In dangerous area, increase slowly. */ |
9772efb9 | 373 | else if (sysctl_tcp_abc) { |
e905a9ed YH |
374 | /* RFC3465: Appropriate Byte Count |
375 | * increase once for each full cwnd acked | |
376 | */ | |
377 | if (tp->bytes_acked >= tp->snd_cwnd*tp->mss_cache) { | |
378 | tp->bytes_acked -= tp->snd_cwnd*tp->mss_cache; | |
379 | if (tp->snd_cwnd < tp->snd_cwnd_clamp) | |
380 | tp->snd_cwnd++; | |
381 | } | |
382 | } else { | |
758ce5c8 | 383 | tcp_cong_avoid_ai(tp, tp->snd_cwnd); |
e905a9ed | 384 | } |
317a76f9 SH |
385 | } |
386 | EXPORT_SYMBOL_GPL(tcp_reno_cong_avoid); | |
387 | ||
388 | /* Slow start threshold is half the congestion window (min 2) */ | |
6687e988 | 389 | u32 tcp_reno_ssthresh(struct sock *sk) |
317a76f9 | 390 | { |
6687e988 | 391 | const struct tcp_sock *tp = tcp_sk(sk); |
317a76f9 SH |
392 | return max(tp->snd_cwnd >> 1U, 2U); |
393 | } | |
394 | EXPORT_SYMBOL_GPL(tcp_reno_ssthresh); | |
395 | ||
72dc5b92 SH |
396 | /* Lower bound on congestion window with halving. */ |
397 | u32 tcp_reno_min_cwnd(const struct sock *sk) | |
317a76f9 | 398 | { |
6687e988 | 399 | const struct tcp_sock *tp = tcp_sk(sk); |
317a76f9 SH |
400 | return tp->snd_ssthresh/2; |
401 | } | |
402 | EXPORT_SYMBOL_GPL(tcp_reno_min_cwnd); | |
403 | ||
404 | struct tcp_congestion_ops tcp_reno = { | |
164891aa | 405 | .flags = TCP_CONG_NON_RESTRICTED, |
317a76f9 SH |
406 | .name = "reno", |
407 | .owner = THIS_MODULE, | |
408 | .ssthresh = tcp_reno_ssthresh, | |
409 | .cong_avoid = tcp_reno_cong_avoid, | |
410 | .min_cwnd = tcp_reno_min_cwnd, | |
411 | }; | |
412 | ||
5f8ef48d SH |
413 | /* Initial congestion control used (until SYN) |
414 | * really reno under another name so we can tell difference | |
415 | * during tcp_set_default_congestion_control | |
416 | */ | |
417 | struct tcp_congestion_ops tcp_init_congestion_ops = { | |
418 | .name = "", | |
419 | .owner = THIS_MODULE, | |
420 | .ssthresh = tcp_reno_ssthresh, | |
421 | .cong_avoid = tcp_reno_cong_avoid, | |
422 | .min_cwnd = tcp_reno_min_cwnd, | |
423 | }; | |
424 | EXPORT_SYMBOL_GPL(tcp_init_congestion_ops); |