Commit | Line | Data |
---|---|---|
317a76f9 | 1 | /* |
b92022f3 | 2 | * Pluggable TCP congestion control support and newReno |
317a76f9 | 3 | * congestion control. |
02582e9b | 4 | * Based on ideas from I/O scheduler support and Web100. |
317a76f9 SH |
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> |
c5c6a8ab | 16 | #include <linux/jhash.h> |
317a76f9 SH |
17 | #include <net/tcp.h> |
18 | ||
19 | static DEFINE_SPINLOCK(tcp_cong_list_lock); | |
20 | static LIST_HEAD(tcp_cong_list); | |
21 | ||
22 | /* Simple linear search, don't expect many entries! */ | |
23 | static struct tcp_congestion_ops *tcp_ca_find(const char *name) | |
24 | { | |
25 | struct tcp_congestion_ops *e; | |
26 | ||
5f8ef48d | 27 | list_for_each_entry_rcu(e, &tcp_cong_list, list) { |
317a76f9 SH |
28 | if (strcmp(e->name, name) == 0) |
29 | return e; | |
30 | } | |
31 | ||
32 | return NULL; | |
33 | } | |
34 | ||
c5c6a8ab DB |
35 | /* Must be called with rcu lock held */ |
36 | static const struct tcp_congestion_ops *__tcp_ca_find_autoload(const char *name) | |
37 | { | |
38 | const struct tcp_congestion_ops *ca = tcp_ca_find(name); | |
39 | #ifdef CONFIG_MODULES | |
40 | if (!ca && capable(CAP_NET_ADMIN)) { | |
41 | rcu_read_unlock(); | |
42 | request_module("tcp_%s", name); | |
43 | rcu_read_lock(); | |
44 | ca = tcp_ca_find(name); | |
45 | } | |
46 | #endif | |
47 | return ca; | |
48 | } | |
49 | ||
50 | /* Simple linear search, not much in here. */ | |
51 | struct tcp_congestion_ops *tcp_ca_find_key(u32 key) | |
52 | { | |
53 | struct tcp_congestion_ops *e; | |
54 | ||
55 | list_for_each_entry_rcu(e, &tcp_cong_list, list) { | |
56 | if (e->key == key) | |
57 | return e; | |
58 | } | |
59 | ||
60 | return NULL; | |
61 | } | |
62 | ||
317a76f9 | 63 | /* |
d08df601 | 64 | * Attach new congestion control algorithm to the list |
317a76f9 SH |
65 | * of available options. |
66 | */ | |
67 | int tcp_register_congestion_control(struct tcp_congestion_ops *ca) | |
68 | { | |
69 | int ret = 0; | |
70 | ||
71 | /* all algorithms must implement ssthresh and cong_avoid ops */ | |
72dc5b92 | 72 | if (!ca->ssthresh || !ca->cong_avoid) { |
afd46503 | 73 | pr_err("%s does not implement required ops\n", ca->name); |
317a76f9 SH |
74 | return -EINVAL; |
75 | } | |
76 | ||
c5c6a8ab DB |
77 | ca->key = jhash(ca->name, sizeof(ca->name), strlen(ca->name)); |
78 | ||
317a76f9 | 79 | spin_lock(&tcp_cong_list_lock); |
c5c6a8ab DB |
80 | if (ca->key == TCP_CA_UNSPEC || tcp_ca_find_key(ca->key)) { |
81 | pr_notice("%s already registered or non-unique key\n", | |
82 | ca->name); | |
317a76f9 SH |
83 | ret = -EEXIST; |
84 | } else { | |
3d2573f7 | 85 | list_add_tail_rcu(&ca->list, &tcp_cong_list); |
afd46503 | 86 | pr_info("%s registered\n", ca->name); |
317a76f9 SH |
87 | } |
88 | spin_unlock(&tcp_cong_list_lock); | |
89 | ||
90 | return ret; | |
91 | } | |
92 | EXPORT_SYMBOL_GPL(tcp_register_congestion_control); | |
93 | ||
94 | /* | |
95 | * Remove congestion control algorithm, called from | |
96 | * the module's remove function. Module ref counts are used | |
97 | * to ensure that this can't be done till all sockets using | |
98 | * that method are closed. | |
99 | */ | |
100 | void tcp_unregister_congestion_control(struct tcp_congestion_ops *ca) | |
101 | { | |
102 | spin_lock(&tcp_cong_list_lock); | |
103 | list_del_rcu(&ca->list); | |
104 | spin_unlock(&tcp_cong_list_lock); | |
c5c6a8ab DB |
105 | |
106 | /* Wait for outstanding readers to complete before the | |
107 | * module gets removed entirely. | |
108 | * | |
109 | * A try_module_get() should fail by now as our module is | |
110 | * in "going" state since no refs are held anymore and | |
111 | * module_exit() handler being called. | |
112 | */ | |
113 | synchronize_rcu(); | |
317a76f9 SH |
114 | } |
115 | EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control); | |
116 | ||
c5c6a8ab DB |
117 | u32 tcp_ca_get_key_by_name(const char *name) |
118 | { | |
119 | const struct tcp_congestion_ops *ca; | |
120 | u32 key; | |
121 | ||
122 | might_sleep(); | |
123 | ||
124 | rcu_read_lock(); | |
125 | ca = __tcp_ca_find_autoload(name); | |
126 | key = ca ? ca->key : TCP_CA_UNSPEC; | |
127 | rcu_read_unlock(); | |
128 | ||
129 | return key; | |
130 | } | |
131 | EXPORT_SYMBOL_GPL(tcp_ca_get_key_by_name); | |
132 | ||
133 | char *tcp_ca_get_name_by_key(u32 key, char *buffer) | |
134 | { | |
135 | const struct tcp_congestion_ops *ca; | |
136 | char *ret = NULL; | |
137 | ||
138 | rcu_read_lock(); | |
139 | ca = tcp_ca_find_key(key); | |
140 | if (ca) | |
141 | ret = strncpy(buffer, ca->name, | |
142 | TCP_CA_NAME_MAX); | |
143 | rcu_read_unlock(); | |
144 | ||
145 | return ret; | |
146 | } | |
147 | EXPORT_SYMBOL_GPL(tcp_ca_get_name_by_key); | |
148 | ||
317a76f9 | 149 | /* Assign choice of congestion control. */ |
55d8694f | 150 | void tcp_assign_congestion_control(struct sock *sk) |
317a76f9 | 151 | { |
6687e988 | 152 | struct inet_connection_sock *icsk = inet_csk(sk); |
317a76f9 SH |
153 | struct tcp_congestion_ops *ca; |
154 | ||
55d8694f FW |
155 | rcu_read_lock(); |
156 | list_for_each_entry_rcu(ca, &tcp_cong_list, list) { | |
157 | if (likely(try_module_get(ca->owner))) { | |
158 | icsk->icsk_ca_ops = ca; | |
159 | goto out; | |
317a76f9 | 160 | } |
55d8694f FW |
161 | /* Fallback to next available. The last really |
162 | * guaranteed fallback is Reno from this list. | |
163 | */ | |
317a76f9 | 164 | } |
55d8694f FW |
165 | out: |
166 | rcu_read_unlock(); | |
167 | ||
168 | /* Clear out private data before diag gets it and | |
169 | * the ca has not been initialized. | |
170 | */ | |
171 | if (ca->get_info) | |
172 | memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv)); | |
173 | } | |
174 | ||
175 | void tcp_init_congestion_control(struct sock *sk) | |
176 | { | |
177 | const struct inet_connection_sock *icsk = inet_csk(sk); | |
317a76f9 | 178 | |
6687e988 ACM |
179 | if (icsk->icsk_ca_ops->init) |
180 | icsk->icsk_ca_ops->init(sk); | |
317a76f9 SH |
181 | } |
182 | ||
29ba4fff DB |
183 | static void tcp_reinit_congestion_control(struct sock *sk, |
184 | const struct tcp_congestion_ops *ca) | |
185 | { | |
186 | struct inet_connection_sock *icsk = inet_csk(sk); | |
187 | ||
188 | tcp_cleanup_congestion_control(sk); | |
189 | icsk->icsk_ca_ops = ca; | |
190 | ||
191 | if (sk->sk_state != TCP_CLOSE && icsk->icsk_ca_ops->init) | |
192 | icsk->icsk_ca_ops->init(sk); | |
193 | } | |
194 | ||
317a76f9 | 195 | /* Manage refcounts on socket close. */ |
6687e988 | 196 | void tcp_cleanup_congestion_control(struct sock *sk) |
317a76f9 | 197 | { |
6687e988 ACM |
198 | struct inet_connection_sock *icsk = inet_csk(sk); |
199 | ||
200 | if (icsk->icsk_ca_ops->release) | |
201 | icsk->icsk_ca_ops->release(sk); | |
202 | module_put(icsk->icsk_ca_ops->owner); | |
317a76f9 SH |
203 | } |
204 | ||
205 | /* Used by sysctl to change default congestion control */ | |
206 | int tcp_set_default_congestion_control(const char *name) | |
207 | { | |
208 | struct tcp_congestion_ops *ca; | |
209 | int ret = -ENOENT; | |
210 | ||
211 | spin_lock(&tcp_cong_list_lock); | |
212 | ca = tcp_ca_find(name); | |
95a5afca | 213 | #ifdef CONFIG_MODULES |
a8f80e8f | 214 | if (!ca && capable(CAP_NET_ADMIN)) { |
317a76f9 SH |
215 | spin_unlock(&tcp_cong_list_lock); |
216 | ||
217 | request_module("tcp_%s", name); | |
218 | spin_lock(&tcp_cong_list_lock); | |
219 | ca = tcp_ca_find(name); | |
220 | } | |
221 | #endif | |
222 | ||
223 | if (ca) { | |
164891aa | 224 | ca->flags |= TCP_CONG_NON_RESTRICTED; /* default is always allowed */ |
317a76f9 SH |
225 | list_move(&ca->list, &tcp_cong_list); |
226 | ret = 0; | |
227 | } | |
228 | spin_unlock(&tcp_cong_list_lock); | |
229 | ||
230 | return ret; | |
231 | } | |
232 | ||
b1736a71 SH |
233 | /* Set default value from kernel configuration at bootup */ |
234 | static int __init tcp_congestion_default(void) | |
235 | { | |
236 | return tcp_set_default_congestion_control(CONFIG_DEFAULT_TCP_CONG); | |
237 | } | |
238 | late_initcall(tcp_congestion_default); | |
239 | ||
3ff825b2 SH |
240 | /* Build string with list of available congestion control values */ |
241 | void tcp_get_available_congestion_control(char *buf, size_t maxlen) | |
242 | { | |
243 | struct tcp_congestion_ops *ca; | |
244 | size_t offs = 0; | |
245 | ||
246 | rcu_read_lock(); | |
247 | list_for_each_entry_rcu(ca, &tcp_cong_list, list) { | |
248 | offs += snprintf(buf + offs, maxlen - offs, | |
249 | "%s%s", | |
250 | offs == 0 ? "" : " ", ca->name); | |
3ff825b2 SH |
251 | } |
252 | rcu_read_unlock(); | |
253 | } | |
254 | ||
317a76f9 SH |
255 | /* Get current default congestion control */ |
256 | void tcp_get_default_congestion_control(char *name) | |
257 | { | |
258 | struct tcp_congestion_ops *ca; | |
259 | /* We will always have reno... */ | |
260 | BUG_ON(list_empty(&tcp_cong_list)); | |
261 | ||
262 | rcu_read_lock(); | |
263 | ca = list_entry(tcp_cong_list.next, struct tcp_congestion_ops, list); | |
264 | strncpy(name, ca->name, TCP_CA_NAME_MAX); | |
265 | rcu_read_unlock(); | |
266 | } | |
267 | ||
ce7bc3bf SH |
268 | /* Built list of non-restricted congestion control values */ |
269 | void tcp_get_allowed_congestion_control(char *buf, size_t maxlen) | |
270 | { | |
271 | struct tcp_congestion_ops *ca; | |
272 | size_t offs = 0; | |
273 | ||
274 | *buf = '\0'; | |
275 | rcu_read_lock(); | |
276 | list_for_each_entry_rcu(ca, &tcp_cong_list, list) { | |
164891aa | 277 | if (!(ca->flags & TCP_CONG_NON_RESTRICTED)) |
ce7bc3bf SH |
278 | continue; |
279 | offs += snprintf(buf + offs, maxlen - offs, | |
280 | "%s%s", | |
281 | offs == 0 ? "" : " ", ca->name); | |
ce7bc3bf SH |
282 | } |
283 | rcu_read_unlock(); | |
284 | } | |
285 | ||
286 | /* Change list of non-restricted congestion control */ | |
287 | int tcp_set_allowed_congestion_control(char *val) | |
288 | { | |
289 | struct tcp_congestion_ops *ca; | |
c34186ed | 290 | char *saved_clone, *clone, *name; |
ce7bc3bf SH |
291 | int ret = 0; |
292 | ||
c34186ed | 293 | saved_clone = clone = kstrdup(val, GFP_USER); |
ce7bc3bf SH |
294 | if (!clone) |
295 | return -ENOMEM; | |
296 | ||
297 | spin_lock(&tcp_cong_list_lock); | |
298 | /* pass 1 check for bad entries */ | |
299 | while ((name = strsep(&clone, " ")) && *name) { | |
300 | ca = tcp_ca_find(name); | |
301 | if (!ca) { | |
302 | ret = -ENOENT; | |
303 | goto out; | |
304 | } | |
305 | } | |
306 | ||
164891aa | 307 | /* pass 2 clear old values */ |
ce7bc3bf | 308 | list_for_each_entry_rcu(ca, &tcp_cong_list, list) |
164891aa | 309 | ca->flags &= ~TCP_CONG_NON_RESTRICTED; |
ce7bc3bf SH |
310 | |
311 | /* pass 3 mark as allowed */ | |
312 | while ((name = strsep(&val, " ")) && *name) { | |
313 | ca = tcp_ca_find(name); | |
314 | WARN_ON(!ca); | |
315 | if (ca) | |
164891aa | 316 | ca->flags |= TCP_CONG_NON_RESTRICTED; |
ce7bc3bf SH |
317 | } |
318 | out: | |
319 | spin_unlock(&tcp_cong_list_lock); | |
c34186ed | 320 | kfree(saved_clone); |
ce7bc3bf SH |
321 | |
322 | return ret; | |
323 | } | |
324 | ||
5f8ef48d | 325 | /* Change congestion control for socket */ |
6687e988 | 326 | int tcp_set_congestion_control(struct sock *sk, const char *name) |
5f8ef48d | 327 | { |
6687e988 | 328 | struct inet_connection_sock *icsk = inet_csk(sk); |
c5c6a8ab | 329 | const struct tcp_congestion_ops *ca; |
5f8ef48d SH |
330 | int err = 0; |
331 | ||
c5c6a8ab DB |
332 | if (icsk->icsk_ca_dst_locked) |
333 | return -EPERM; | |
4d4d3d1e | 334 | |
c5c6a8ab DB |
335 | rcu_read_lock(); |
336 | ca = __tcp_ca_find_autoload(name); | |
337 | /* No change asking for existing value */ | |
6687e988 | 338 | if (ca == icsk->icsk_ca_ops) |
5f8ef48d | 339 | goto out; |
5f8ef48d SH |
340 | if (!ca) |
341 | err = -ENOENT; | |
52e804c6 EB |
342 | else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) || |
343 | ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN))) | |
ce7bc3bf | 344 | err = -EPERM; |
5f8ef48d SH |
345 | else if (!try_module_get(ca->owner)) |
346 | err = -EBUSY; | |
29ba4fff DB |
347 | else |
348 | tcp_reinit_congestion_control(sk, ca); | |
5f8ef48d SH |
349 | out: |
350 | rcu_read_unlock(); | |
351 | return err; | |
352 | } | |
353 | ||
9f9843a7 YC |
354 | /* Slow start is used when congestion window is no greater than the slow start |
355 | * threshold. We base on RFC2581 and also handle stretch ACKs properly. | |
356 | * We do not implement RFC3465 Appropriate Byte Counting (ABC) per se but | |
357 | * something better;) a packet is only considered (s)acked in its entirety to | |
358 | * defend the ACK attacks described in the RFC. Slow start processes a stretch | |
359 | * ACK of degree N as if N acks of degree 1 are received back to back except | |
360 | * ABC caps N to 2. Slow start exits when cwnd grows over ssthresh and | |
361 | * returns the leftover acks to adjust cwnd in congestion avoidance mode. | |
40efc6fa | 362 | */ |
e73ebb08 | 363 | u32 tcp_slow_start(struct tcp_sock *tp, u32 acked) |
40efc6fa | 364 | { |
9f9843a7 | 365 | u32 cwnd = tp->snd_cwnd + acked; |
a02ba041 | 366 | |
9f9843a7 YC |
367 | if (cwnd > tp->snd_ssthresh) |
368 | cwnd = tp->snd_ssthresh + 1; | |
e73ebb08 | 369 | acked -= cwnd - tp->snd_cwnd; |
9f9843a7 | 370 | tp->snd_cwnd = min(cwnd, tp->snd_cwnd_clamp); |
e73ebb08 NC |
371 | |
372 | return acked; | |
40efc6fa SH |
373 | } |
374 | EXPORT_SYMBOL_GPL(tcp_slow_start); | |
375 | ||
814d488c NC |
376 | /* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd (or alternative w), |
377 | * for every packet that was ACKed. | |
378 | */ | |
e73ebb08 | 379 | void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked) |
758ce5c8 | 380 | { |
814d488c | 381 | tp->snd_cwnd_cnt += acked; |
758ce5c8 | 382 | if (tp->snd_cwnd_cnt >= w) { |
814d488c NC |
383 | u32 delta = tp->snd_cwnd_cnt / w; |
384 | ||
385 | tp->snd_cwnd_cnt -= delta * w; | |
386 | tp->snd_cwnd += delta; | |
758ce5c8 | 387 | } |
814d488c | 388 | tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_cwnd_clamp); |
758ce5c8 IJ |
389 | } |
390 | EXPORT_SYMBOL_GPL(tcp_cong_avoid_ai); | |
391 | ||
317a76f9 SH |
392 | /* |
393 | * TCP Reno congestion control | |
394 | * This is special case used for fallback as well. | |
395 | */ | |
396 | /* This is Jacobson's slow start and congestion avoidance. | |
397 | * SIGCOMM '88, p. 328. | |
398 | */ | |
24901551 | 399 | void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked) |
317a76f9 | 400 | { |
6687e988 ACM |
401 | struct tcp_sock *tp = tcp_sk(sk); |
402 | ||
24901551 | 403 | if (!tcp_is_cwnd_limited(sk)) |
317a76f9 SH |
404 | return; |
405 | ||
7faffa1c | 406 | /* In "safe" area, increase. */ |
c22bdca9 NC |
407 | if (tp->snd_cwnd <= tp->snd_ssthresh) { |
408 | acked = tcp_slow_start(tp, acked); | |
409 | if (!acked) | |
410 | return; | |
411 | } | |
e905a9ed | 412 | /* In dangerous area, increase slowly. */ |
c22bdca9 | 413 | tcp_cong_avoid_ai(tp, tp->snd_cwnd, acked); |
317a76f9 SH |
414 | } |
415 | EXPORT_SYMBOL_GPL(tcp_reno_cong_avoid); | |
416 | ||
417 | /* Slow start threshold is half the congestion window (min 2) */ | |
6687e988 | 418 | u32 tcp_reno_ssthresh(struct sock *sk) |
317a76f9 | 419 | { |
6687e988 | 420 | const struct tcp_sock *tp = tcp_sk(sk); |
688d1945 | 421 | |
317a76f9 SH |
422 | return max(tp->snd_cwnd >> 1U, 2U); |
423 | } | |
424 | EXPORT_SYMBOL_GPL(tcp_reno_ssthresh); | |
425 | ||
317a76f9 | 426 | struct tcp_congestion_ops tcp_reno = { |
164891aa | 427 | .flags = TCP_CONG_NON_RESTRICTED, |
317a76f9 SH |
428 | .name = "reno", |
429 | .owner = THIS_MODULE, | |
430 | .ssthresh = tcp_reno_ssthresh, | |
431 | .cong_avoid = tcp_reno_cong_avoid, | |
317a76f9 | 432 | }; |