Commit | Line | Data |
---|---|---|
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 | ||
afd46503 JP |
9 | #define pr_fmt(fmt) "TCP: " fmt |
10 | ||
317a76f9 SH |
11 | #include <linux/module.h> |
12 | #include <linux/mm.h> | |
13 | #include <linux/types.h> | |
14 | #include <linux/list.h> | |
5a0e3ad6 | 15 | #include <linux/gfp.h> |
317a76f9 SH |
16 | #include <net/tcp.h> |
17 | ||
886236c1 JH |
18 | int sysctl_tcp_max_ssthresh = 0; |
19 | ||
317a76f9 SH |
20 | static DEFINE_SPINLOCK(tcp_cong_list_lock); |
21 | static LIST_HEAD(tcp_cong_list); | |
22 | ||
23 | /* Simple linear search, don't expect many entries! */ | |
24 | static struct tcp_congestion_ops *tcp_ca_find(const char *name) | |
25 | { | |
26 | struct tcp_congestion_ops *e; | |
27 | ||
5f8ef48d | 28 | list_for_each_entry_rcu(e, &tcp_cong_list, list) { |
317a76f9 SH |
29 | if (strcmp(e->name, name) == 0) |
30 | return e; | |
31 | } | |
32 | ||
33 | return NULL; | |
34 | } | |
35 | ||
36 | /* | |
d08df601 | 37 | * Attach new congestion control algorithm to the list |
317a76f9 SH |
38 | * of available options. |
39 | */ | |
40 | int tcp_register_congestion_control(struct tcp_congestion_ops *ca) | |
41 | { | |
42 | int ret = 0; | |
43 | ||
44 | /* all algorithms must implement ssthresh and cong_avoid ops */ | |
72dc5b92 | 45 | if (!ca->ssthresh || !ca->cong_avoid) { |
afd46503 | 46 | pr_err("%s does not implement required ops\n", ca->name); |
317a76f9 SH |
47 | return -EINVAL; |
48 | } | |
49 | ||
50 | spin_lock(&tcp_cong_list_lock); | |
51 | if (tcp_ca_find(ca->name)) { | |
afd46503 | 52 | pr_notice("%s already registered\n", ca->name); |
317a76f9 SH |
53 | ret = -EEXIST; |
54 | } else { | |
3d2573f7 | 55 | list_add_tail_rcu(&ca->list, &tcp_cong_list); |
afd46503 | 56 | pr_info("%s registered\n", ca->name); |
317a76f9 SH |
57 | } |
58 | spin_unlock(&tcp_cong_list_lock); | |
59 | ||
60 | return ret; | |
61 | } | |
62 | EXPORT_SYMBOL_GPL(tcp_register_congestion_control); | |
63 | ||
64 | /* | |
65 | * Remove congestion control algorithm, called from | |
66 | * the module's remove function. Module ref counts are used | |
67 | * to ensure that this can't be done till all sockets using | |
68 | * that method are closed. | |
69 | */ | |
70 | void tcp_unregister_congestion_control(struct tcp_congestion_ops *ca) | |
71 | { | |
72 | spin_lock(&tcp_cong_list_lock); | |
73 | list_del_rcu(&ca->list); | |
74 | spin_unlock(&tcp_cong_list_lock); | |
75 | } | |
76 | EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control); | |
77 | ||
78 | /* Assign choice of congestion control. */ | |
6687e988 | 79 | void tcp_init_congestion_control(struct sock *sk) |
317a76f9 | 80 | { |
6687e988 | 81 | struct inet_connection_sock *icsk = inet_csk(sk); |
317a76f9 SH |
82 | struct tcp_congestion_ops *ca; |
83 | ||
4d4d3d1e SH |
84 | /* if no choice made yet assign the current value set as default */ |
85 | if (icsk->icsk_ca_ops == &tcp_init_congestion_ops) { | |
86 | rcu_read_lock(); | |
87 | list_for_each_entry_rcu(ca, &tcp_cong_list, list) { | |
88 | if (try_module_get(ca->owner)) { | |
89 | icsk->icsk_ca_ops = ca; | |
90 | break; | |
91 | } | |
5f8ef48d | 92 | |
4d4d3d1e | 93 | /* fallback to next available */ |
317a76f9 | 94 | } |
4d4d3d1e | 95 | rcu_read_unlock(); |
317a76f9 | 96 | } |
317a76f9 | 97 | |
6687e988 ACM |
98 | if (icsk->icsk_ca_ops->init) |
99 | icsk->icsk_ca_ops->init(sk); | |
317a76f9 SH |
100 | } |
101 | ||
102 | /* Manage refcounts on socket close. */ | |
6687e988 | 103 | void tcp_cleanup_congestion_control(struct sock *sk) |
317a76f9 | 104 | { |
6687e988 ACM |
105 | struct inet_connection_sock *icsk = inet_csk(sk); |
106 | ||
107 | if (icsk->icsk_ca_ops->release) | |
108 | icsk->icsk_ca_ops->release(sk); | |
109 | module_put(icsk->icsk_ca_ops->owner); | |
317a76f9 SH |
110 | } |
111 | ||
112 | /* Used by sysctl to change default congestion control */ | |
113 | int tcp_set_default_congestion_control(const char *name) | |
114 | { | |
115 | struct tcp_congestion_ops *ca; | |
116 | int ret = -ENOENT; | |
117 | ||
118 | spin_lock(&tcp_cong_list_lock); | |
119 | ca = tcp_ca_find(name); | |
95a5afca | 120 | #ifdef CONFIG_MODULES |
a8f80e8f | 121 | if (!ca && capable(CAP_NET_ADMIN)) { |
317a76f9 SH |
122 | spin_unlock(&tcp_cong_list_lock); |
123 | ||
124 | request_module("tcp_%s", name); | |
125 | spin_lock(&tcp_cong_list_lock); | |
126 | ca = tcp_ca_find(name); | |
127 | } | |
128 | #endif | |
129 | ||
130 | if (ca) { | |
164891aa | 131 | ca->flags |= TCP_CONG_NON_RESTRICTED; /* default is always allowed */ |
317a76f9 SH |
132 | list_move(&ca->list, &tcp_cong_list); |
133 | ret = 0; | |
134 | } | |
135 | spin_unlock(&tcp_cong_list_lock); | |
136 | ||
137 | return ret; | |
138 | } | |
139 | ||
b1736a71 SH |
140 | /* Set default value from kernel configuration at bootup */ |
141 | static int __init tcp_congestion_default(void) | |
142 | { | |
143 | return tcp_set_default_congestion_control(CONFIG_DEFAULT_TCP_CONG); | |
144 | } | |
145 | late_initcall(tcp_congestion_default); | |
146 | ||
147 | ||
3ff825b2 SH |
148 | /* Build string with list of available congestion control values */ |
149 | void tcp_get_available_congestion_control(char *buf, size_t maxlen) | |
150 | { | |
151 | struct tcp_congestion_ops *ca; | |
152 | size_t offs = 0; | |
153 | ||
154 | rcu_read_lock(); | |
155 | list_for_each_entry_rcu(ca, &tcp_cong_list, list) { | |
156 | offs += snprintf(buf + offs, maxlen - offs, | |
157 | "%s%s", | |
158 | offs == 0 ? "" : " ", ca->name); | |
159 | ||
160 | } | |
161 | rcu_read_unlock(); | |
162 | } | |
163 | ||
317a76f9 SH |
164 | /* Get current default congestion control */ |
165 | void tcp_get_default_congestion_control(char *name) | |
166 | { | |
167 | struct tcp_congestion_ops *ca; | |
168 | /* We will always have reno... */ | |
169 | BUG_ON(list_empty(&tcp_cong_list)); | |
170 | ||
171 | rcu_read_lock(); | |
172 | ca = list_entry(tcp_cong_list.next, struct tcp_congestion_ops, list); | |
173 | strncpy(name, ca->name, TCP_CA_NAME_MAX); | |
174 | rcu_read_unlock(); | |
175 | } | |
176 | ||
ce7bc3bf SH |
177 | /* Built list of non-restricted congestion control values */ |
178 | void tcp_get_allowed_congestion_control(char *buf, size_t maxlen) | |
179 | { | |
180 | struct tcp_congestion_ops *ca; | |
181 | size_t offs = 0; | |
182 | ||
183 | *buf = '\0'; | |
184 | rcu_read_lock(); | |
185 | list_for_each_entry_rcu(ca, &tcp_cong_list, list) { | |
164891aa | 186 | if (!(ca->flags & TCP_CONG_NON_RESTRICTED)) |
ce7bc3bf SH |
187 | continue; |
188 | offs += snprintf(buf + offs, maxlen - offs, | |
189 | "%s%s", | |
190 | offs == 0 ? "" : " ", ca->name); | |
191 | ||
192 | } | |
193 | rcu_read_unlock(); | |
194 | } | |
195 | ||
196 | /* Change list of non-restricted congestion control */ | |
197 | int tcp_set_allowed_congestion_control(char *val) | |
198 | { | |
199 | struct tcp_congestion_ops *ca; | |
c34186ed | 200 | char *saved_clone, *clone, *name; |
ce7bc3bf SH |
201 | int ret = 0; |
202 | ||
c34186ed | 203 | saved_clone = clone = kstrdup(val, GFP_USER); |
ce7bc3bf SH |
204 | if (!clone) |
205 | return -ENOMEM; | |
206 | ||
207 | spin_lock(&tcp_cong_list_lock); | |
208 | /* pass 1 check for bad entries */ | |
209 | while ((name = strsep(&clone, " ")) && *name) { | |
210 | ca = tcp_ca_find(name); | |
211 | if (!ca) { | |
212 | ret = -ENOENT; | |
213 | goto out; | |
214 | } | |
215 | } | |
216 | ||
164891aa | 217 | /* pass 2 clear old values */ |
ce7bc3bf | 218 | list_for_each_entry_rcu(ca, &tcp_cong_list, list) |
164891aa | 219 | ca->flags &= ~TCP_CONG_NON_RESTRICTED; |
ce7bc3bf SH |
220 | |
221 | /* pass 3 mark as allowed */ | |
222 | while ((name = strsep(&val, " ")) && *name) { | |
223 | ca = tcp_ca_find(name); | |
224 | WARN_ON(!ca); | |
225 | if (ca) | |
164891aa | 226 | ca->flags |= TCP_CONG_NON_RESTRICTED; |
ce7bc3bf SH |
227 | } |
228 | out: | |
229 | spin_unlock(&tcp_cong_list_lock); | |
c34186ed | 230 | kfree(saved_clone); |
ce7bc3bf SH |
231 | |
232 | return ret; | |
233 | } | |
234 | ||
235 | ||
5f8ef48d | 236 | /* Change congestion control for socket */ |
6687e988 | 237 | int tcp_set_congestion_control(struct sock *sk, const char *name) |
5f8ef48d | 238 | { |
6687e988 | 239 | struct inet_connection_sock *icsk = inet_csk(sk); |
5f8ef48d SH |
240 | struct tcp_congestion_ops *ca; |
241 | int err = 0; | |
242 | ||
243 | rcu_read_lock(); | |
244 | ca = tcp_ca_find(name); | |
4d4d3d1e | 245 | |
35bfbc94 | 246 | /* no change asking for existing value */ |
6687e988 | 247 | if (ca == icsk->icsk_ca_ops) |
5f8ef48d SH |
248 | goto out; |
249 | ||
95a5afca | 250 | #ifdef CONFIG_MODULES |
35bfbc94 | 251 | /* not found attempt to autoload module */ |
a8f80e8f | 252 | if (!ca && capable(CAP_NET_ADMIN)) { |
35bfbc94 SH |
253 | rcu_read_unlock(); |
254 | request_module("tcp_%s", name); | |
255 | rcu_read_lock(); | |
256 | ca = tcp_ca_find(name); | |
257 | } | |
258 | #endif | |
5f8ef48d SH |
259 | if (!ca) |
260 | err = -ENOENT; | |
261 | ||
164891aa | 262 | else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) || capable(CAP_NET_ADMIN))) |
ce7bc3bf SH |
263 | err = -EPERM; |
264 | ||
5f8ef48d SH |
265 | else if (!try_module_get(ca->owner)) |
266 | err = -EBUSY; | |
267 | ||
268 | else { | |
6687e988 ACM |
269 | tcp_cleanup_congestion_control(sk); |
270 | icsk->icsk_ca_ops = ca; | |
4d4d3d1e SH |
271 | |
272 | if (sk->sk_state != TCP_CLOSE && icsk->icsk_ca_ops->init) | |
6687e988 | 273 | icsk->icsk_ca_ops->init(sk); |
5f8ef48d SH |
274 | } |
275 | out: | |
276 | rcu_read_unlock(); | |
277 | return err; | |
278 | } | |
279 | ||
cea14e0e IJ |
280 | /* RFC2861 Check whether we are limited by application or congestion window |
281 | * This is the inverse of cwnd check in tcp_tso_should_defer | |
282 | */ | |
a2a385d6 | 283 | bool tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight) |
cea14e0e IJ |
284 | { |
285 | const struct tcp_sock *tp = tcp_sk(sk); | |
286 | u32 left; | |
287 | ||
288 | if (in_flight >= tp->snd_cwnd) | |
a2a385d6 | 289 | return true; |
cea14e0e | 290 | |
cea14e0e | 291 | left = tp->snd_cwnd - in_flight; |
ce447eb9 | 292 | if (sk_can_gso(sk) && |
246eb2af | 293 | left * sysctl_tcp_tso_win_divisor < tp->snd_cwnd && |
1485348d BH |
294 | left * tp->mss_cache < sk->sk_gso_max_size && |
295 | left < sk->sk_gso_max_segs) | |
a2a385d6 | 296 | return true; |
6b5a5c0d | 297 | return left <= tcp_max_tso_deferred_mss(tp); |
cea14e0e IJ |
298 | } |
299 | EXPORT_SYMBOL_GPL(tcp_is_cwnd_limited); | |
40efc6fa SH |
300 | |
301 | /* | |
a02ba041 SH |
302 | * Slow start is used when congestion window is less than slow start |
303 | * threshold. This version implements the basic RFC2581 version | |
304 | * and optionally supports: | |
305 | * RFC3742 Limited Slow Start - growth limited to max_ssthresh | |
306 | * RFC3465 Appropriate Byte Counting - growth limited by bytes acknowledged | |
40efc6fa SH |
307 | */ |
308 | void tcp_slow_start(struct tcp_sock *tp) | |
309 | { | |
a02ba041 | 310 | int cnt; /* increase in packets */ |
9dc27415 | 311 | unsigned int delta = 0; |
a02ba041 SH |
312 | |
313 | /* RFC3465: ABC Slow start | |
314 | * Increase only after a full MSS of bytes is acked | |
315 | * | |
316 | * TCP sender SHOULD increase cwnd by the number of | |
317 | * previously unacknowledged bytes ACKed by each incoming | |
318 | * acknowledgment, provided the increase is not more than L | |
319 | */ | |
320 | if (sysctl_tcp_abc && tp->bytes_acked < tp->mss_cache) | |
321 | return; | |
322 | ||
323 | if (sysctl_tcp_max_ssthresh > 0 && tp->snd_cwnd > sysctl_tcp_max_ssthresh) | |
324 | cnt = sysctl_tcp_max_ssthresh >> 1; /* limited slow start */ | |
886236c1 | 325 | else |
a02ba041 | 326 | cnt = tp->snd_cwnd; /* exponential increase */ |
886236c1 | 327 | |
a02ba041 SH |
328 | /* RFC3465: ABC |
329 | * We MAY increase by 2 if discovered delayed ack | |
330 | */ | |
886236c1 JH |
331 | if (sysctl_tcp_abc > 1 && tp->bytes_acked >= 2*tp->mss_cache) |
332 | cnt <<= 1; | |
40efc6fa SH |
333 | tp->bytes_acked = 0; |
334 | ||
886236c1 JH |
335 | tp->snd_cwnd_cnt += cnt; |
336 | while (tp->snd_cwnd_cnt >= tp->snd_cwnd) { | |
337 | tp->snd_cwnd_cnt -= tp->snd_cwnd; | |
9dc27415 | 338 | delta++; |
886236c1 | 339 | } |
9dc27415 | 340 | tp->snd_cwnd = min(tp->snd_cwnd + delta, tp->snd_cwnd_clamp); |
40efc6fa SH |
341 | } |
342 | EXPORT_SYMBOL_GPL(tcp_slow_start); | |
343 | ||
758ce5c8 IJ |
344 | /* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd (or alternative w) */ |
345 | void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w) | |
346 | { | |
347 | if (tp->snd_cwnd_cnt >= w) { | |
348 | if (tp->snd_cwnd < tp->snd_cwnd_clamp) | |
349 | tp->snd_cwnd++; | |
350 | tp->snd_cwnd_cnt = 0; | |
351 | } else { | |
352 | tp->snd_cwnd_cnt++; | |
353 | } | |
354 | } | |
355 | EXPORT_SYMBOL_GPL(tcp_cong_avoid_ai); | |
356 | ||
317a76f9 SH |
357 | /* |
358 | * TCP Reno congestion control | |
359 | * This is special case used for fallback as well. | |
360 | */ | |
361 | /* This is Jacobson's slow start and congestion avoidance. | |
362 | * SIGCOMM '88, p. 328. | |
363 | */ | |
c3a05c60 | 364 | void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 in_flight) |
317a76f9 | 365 | { |
6687e988 ACM |
366 | struct tcp_sock *tp = tcp_sk(sk); |
367 | ||
f4805ede | 368 | if (!tcp_is_cwnd_limited(sk, in_flight)) |
317a76f9 SH |
369 | return; |
370 | ||
7faffa1c | 371 | /* In "safe" area, increase. */ |
e905a9ed | 372 | if (tp->snd_cwnd <= tp->snd_ssthresh) |
7faffa1c | 373 | tcp_slow_start(tp); |
9772efb9 | 374 | |
e905a9ed | 375 | /* In dangerous area, increase slowly. */ |
9772efb9 | 376 | else if (sysctl_tcp_abc) { |
e905a9ed YH |
377 | /* RFC3465: Appropriate Byte Count |
378 | * increase once for each full cwnd acked | |
379 | */ | |
380 | if (tp->bytes_acked >= tp->snd_cwnd*tp->mss_cache) { | |
381 | tp->bytes_acked -= tp->snd_cwnd*tp->mss_cache; | |
382 | if (tp->snd_cwnd < tp->snd_cwnd_clamp) | |
383 | tp->snd_cwnd++; | |
384 | } | |
385 | } else { | |
758ce5c8 | 386 | tcp_cong_avoid_ai(tp, tp->snd_cwnd); |
e905a9ed | 387 | } |
317a76f9 SH |
388 | } |
389 | EXPORT_SYMBOL_GPL(tcp_reno_cong_avoid); | |
390 | ||
391 | /* Slow start threshold is half the congestion window (min 2) */ | |
6687e988 | 392 | u32 tcp_reno_ssthresh(struct sock *sk) |
317a76f9 | 393 | { |
6687e988 | 394 | const struct tcp_sock *tp = tcp_sk(sk); |
317a76f9 SH |
395 | return max(tp->snd_cwnd >> 1U, 2U); |
396 | } | |
397 | EXPORT_SYMBOL_GPL(tcp_reno_ssthresh); | |
398 | ||
72dc5b92 SH |
399 | /* Lower bound on congestion window with halving. */ |
400 | u32 tcp_reno_min_cwnd(const struct sock *sk) | |
317a76f9 | 401 | { |
6687e988 | 402 | const struct tcp_sock *tp = tcp_sk(sk); |
317a76f9 SH |
403 | return tp->snd_ssthresh/2; |
404 | } | |
405 | EXPORT_SYMBOL_GPL(tcp_reno_min_cwnd); | |
406 | ||
407 | struct tcp_congestion_ops tcp_reno = { | |
164891aa | 408 | .flags = TCP_CONG_NON_RESTRICTED, |
317a76f9 SH |
409 | .name = "reno", |
410 | .owner = THIS_MODULE, | |
411 | .ssthresh = tcp_reno_ssthresh, | |
412 | .cong_avoid = tcp_reno_cong_avoid, | |
413 | .min_cwnd = tcp_reno_min_cwnd, | |
414 | }; | |
415 | ||
5f8ef48d SH |
416 | /* Initial congestion control used (until SYN) |
417 | * really reno under another name so we can tell difference | |
418 | * during tcp_set_default_congestion_control | |
419 | */ | |
420 | struct tcp_congestion_ops tcp_init_congestion_ops = { | |
421 | .name = "", | |
422 | .owner = THIS_MODULE, | |
423 | .ssthresh = tcp_reno_ssthresh, | |
424 | .cong_avoid = tcp_reno_cong_avoid, | |
425 | .min_cwnd = tcp_reno_min_cwnd, | |
426 | }; | |
427 | EXPORT_SYMBOL_GPL(tcp_init_congestion_ops); |