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 | 35 | /* Must be called with rcu lock held */ |
6670e152 SH |
36 | static struct tcp_congestion_ops *tcp_ca_find_autoload(struct net *net, |
37 | const char *name) | |
c5c6a8ab | 38 | { |
6670e152 SH |
39 | struct tcp_congestion_ops *ca = tcp_ca_find(name); |
40 | ||
c5c6a8ab DB |
41 | #ifdef CONFIG_MODULES |
42 | if (!ca && capable(CAP_NET_ADMIN)) { | |
43 | rcu_read_unlock(); | |
44 | request_module("tcp_%s", name); | |
45 | rcu_read_lock(); | |
46 | ca = tcp_ca_find(name); | |
47 | } | |
48 | #endif | |
49 | return ca; | |
50 | } | |
51 | ||
52 | /* Simple linear search, not much in here. */ | |
53 | struct tcp_congestion_ops *tcp_ca_find_key(u32 key) | |
54 | { | |
55 | struct tcp_congestion_ops *e; | |
56 | ||
57 | list_for_each_entry_rcu(e, &tcp_cong_list, list) { | |
58 | if (e->key == key) | |
59 | return e; | |
60 | } | |
61 | ||
62 | return NULL; | |
63 | } | |
64 | ||
317a76f9 | 65 | /* |
d08df601 | 66 | * Attach new congestion control algorithm to the list |
317a76f9 SH |
67 | * of available options. |
68 | */ | |
69 | int tcp_register_congestion_control(struct tcp_congestion_ops *ca) | |
70 | { | |
71 | int ret = 0; | |
72 | ||
e9799183 FW |
73 | /* all algorithms must implement these */ |
74 | if (!ca->ssthresh || !ca->undo_cwnd || | |
75 | !(ca->cong_avoid || ca->cong_control)) { | |
afd46503 | 76 | pr_err("%s does not implement required ops\n", ca->name); |
317a76f9 SH |
77 | return -EINVAL; |
78 | } | |
79 | ||
c5c6a8ab DB |
80 | ca->key = jhash(ca->name, sizeof(ca->name), strlen(ca->name)); |
81 | ||
317a76f9 | 82 | spin_lock(&tcp_cong_list_lock); |
c5c6a8ab DB |
83 | if (ca->key == TCP_CA_UNSPEC || tcp_ca_find_key(ca->key)) { |
84 | pr_notice("%s already registered or non-unique key\n", | |
85 | ca->name); | |
317a76f9 SH |
86 | ret = -EEXIST; |
87 | } else { | |
3d2573f7 | 88 | list_add_tail_rcu(&ca->list, &tcp_cong_list); |
db2855ae | 89 | pr_debug("%s registered\n", ca->name); |
317a76f9 SH |
90 | } |
91 | spin_unlock(&tcp_cong_list_lock); | |
92 | ||
93 | return ret; | |
94 | } | |
95 | EXPORT_SYMBOL_GPL(tcp_register_congestion_control); | |
96 | ||
97 | /* | |
98 | * Remove congestion control algorithm, called from | |
99 | * the module's remove function. Module ref counts are used | |
100 | * to ensure that this can't be done till all sockets using | |
101 | * that method are closed. | |
102 | */ | |
103 | void tcp_unregister_congestion_control(struct tcp_congestion_ops *ca) | |
104 | { | |
105 | spin_lock(&tcp_cong_list_lock); | |
106 | list_del_rcu(&ca->list); | |
107 | spin_unlock(&tcp_cong_list_lock); | |
c5c6a8ab DB |
108 | |
109 | /* Wait for outstanding readers to complete before the | |
110 | * module gets removed entirely. | |
111 | * | |
112 | * A try_module_get() should fail by now as our module is | |
113 | * in "going" state since no refs are held anymore and | |
114 | * module_exit() handler being called. | |
115 | */ | |
116 | synchronize_rcu(); | |
317a76f9 SH |
117 | } |
118 | EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control); | |
119 | ||
6670e152 | 120 | u32 tcp_ca_get_key_by_name(struct net *net, const char *name, bool *ecn_ca) |
c5c6a8ab DB |
121 | { |
122 | const struct tcp_congestion_ops *ca; | |
c3a8d947 | 123 | u32 key = TCP_CA_UNSPEC; |
c5c6a8ab DB |
124 | |
125 | might_sleep(); | |
126 | ||
127 | rcu_read_lock(); | |
6670e152 | 128 | ca = tcp_ca_find_autoload(net, name); |
c3a8d947 DB |
129 | if (ca) { |
130 | key = ca->key; | |
131 | *ecn_ca = ca->flags & TCP_CONG_NEEDS_ECN; | |
132 | } | |
c5c6a8ab DB |
133 | rcu_read_unlock(); |
134 | ||
135 | return key; | |
136 | } | |
137 | EXPORT_SYMBOL_GPL(tcp_ca_get_key_by_name); | |
138 | ||
139 | char *tcp_ca_get_name_by_key(u32 key, char *buffer) | |
140 | { | |
141 | const struct tcp_congestion_ops *ca; | |
142 | char *ret = NULL; | |
143 | ||
144 | rcu_read_lock(); | |
145 | ca = tcp_ca_find_key(key); | |
146 | if (ca) | |
147 | ret = strncpy(buffer, ca->name, | |
148 | TCP_CA_NAME_MAX); | |
149 | rcu_read_unlock(); | |
150 | ||
151 | return ret; | |
152 | } | |
153 | EXPORT_SYMBOL_GPL(tcp_ca_get_name_by_key); | |
154 | ||
317a76f9 | 155 | /* Assign choice of congestion control. */ |
55d8694f | 156 | void tcp_assign_congestion_control(struct sock *sk) |
317a76f9 | 157 | { |
6670e152 | 158 | struct net *net = sock_net(sk); |
6687e988 | 159 | struct inet_connection_sock *icsk = inet_csk(sk); |
6670e152 | 160 | const struct tcp_congestion_ops *ca; |
317a76f9 | 161 | |
55d8694f | 162 | rcu_read_lock(); |
6670e152 SH |
163 | ca = rcu_dereference(net->ipv4.tcp_congestion_control); |
164 | if (unlikely(!try_module_get(ca->owner))) | |
165 | ca = &tcp_reno; | |
166 | icsk->icsk_ca_ops = ca; | |
55d8694f FW |
167 | rcu_read_unlock(); |
168 | ||
6670e152 | 169 | memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv)); |
6ac705b1 ED |
170 | if (ca->flags & TCP_CONG_NEEDS_ECN) |
171 | INET_ECN_xmit(sk); | |
172 | else | |
173 | INET_ECN_dontxmit(sk); | |
55d8694f FW |
174 | } |
175 | ||
176 | void tcp_init_congestion_control(struct sock *sk) | |
177 | { | |
178 | const struct inet_connection_sock *icsk = inet_csk(sk); | |
317a76f9 | 179 | |
44abafc4 | 180 | tcp_sk(sk)->prior_ssthresh = 0; |
6687e988 ACM |
181 | if (icsk->icsk_ca_ops->init) |
182 | icsk->icsk_ca_ops->init(sk); | |
6ac705b1 ED |
183 | if (tcp_ca_needs_ecn(sk)) |
184 | INET_ECN_xmit(sk); | |
185 | else | |
186 | INET_ECN_dontxmit(sk); | |
317a76f9 SH |
187 | } |
188 | ||
ebfa00c5 SD |
189 | static void tcp_reinit_congestion_control(struct sock *sk, |
190 | const struct tcp_congestion_ops *ca) | |
29ba4fff DB |
191 | { |
192 | struct inet_connection_sock *icsk = inet_csk(sk); | |
193 | ||
194 | tcp_cleanup_congestion_control(sk); | |
195 | icsk->icsk_ca_ops = ca; | |
9f950415 | 196 | icsk->icsk_ca_setsockopt = 1; |
c1201444 | 197 | memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv)); |
29ba4fff | 198 | |
c1201444 | 199 | if (sk->sk_state != TCP_CLOSE) |
6ac705b1 | 200 | tcp_init_congestion_control(sk); |
29ba4fff DB |
201 | } |
202 | ||
317a76f9 | 203 | /* Manage refcounts on socket close. */ |
6687e988 | 204 | void tcp_cleanup_congestion_control(struct sock *sk) |
317a76f9 | 205 | { |
6687e988 ACM |
206 | struct inet_connection_sock *icsk = inet_csk(sk); |
207 | ||
208 | if (icsk->icsk_ca_ops->release) | |
209 | icsk->icsk_ca_ops->release(sk); | |
210 | module_put(icsk->icsk_ca_ops->owner); | |
317a76f9 SH |
211 | } |
212 | ||
213 | /* Used by sysctl to change default congestion control */ | |
6670e152 | 214 | int tcp_set_default_congestion_control(struct net *net, const char *name) |
317a76f9 SH |
215 | { |
216 | struct tcp_congestion_ops *ca; | |
6670e152 SH |
217 | const struct tcp_congestion_ops *prev; |
218 | int ret; | |
317a76f9 | 219 | |
6670e152 SH |
220 | rcu_read_lock(); |
221 | ca = tcp_ca_find_autoload(net, name); | |
222 | if (!ca) { | |
223 | ret = -ENOENT; | |
224 | } else if (!try_module_get(ca->owner)) { | |
225 | ret = -EBUSY; | |
226 | } else { | |
227 | prev = xchg(&net->ipv4.tcp_congestion_control, ca); | |
228 | if (prev) | |
229 | module_put(prev->owner); | |
317a76f9 | 230 | |
6670e152 | 231 | ca->flags |= TCP_CONG_NON_RESTRICTED; |
317a76f9 SH |
232 | ret = 0; |
233 | } | |
6670e152 | 234 | rcu_read_unlock(); |
317a76f9 SH |
235 | |
236 | return ret; | |
237 | } | |
238 | ||
b1736a71 SH |
239 | /* Set default value from kernel configuration at bootup */ |
240 | static int __init tcp_congestion_default(void) | |
241 | { | |
6670e152 SH |
242 | return tcp_set_default_congestion_control(&init_net, |
243 | CONFIG_DEFAULT_TCP_CONG); | |
b1736a71 SH |
244 | } |
245 | late_initcall(tcp_congestion_default); | |
246 | ||
3ff825b2 SH |
247 | /* Build string with list of available congestion control values */ |
248 | void tcp_get_available_congestion_control(char *buf, size_t maxlen) | |
249 | { | |
250 | struct tcp_congestion_ops *ca; | |
251 | size_t offs = 0; | |
252 | ||
253 | rcu_read_lock(); | |
254 | list_for_each_entry_rcu(ca, &tcp_cong_list, list) { | |
255 | offs += snprintf(buf + offs, maxlen - offs, | |
256 | "%s%s", | |
257 | offs == 0 ? "" : " ", ca->name); | |
3ff825b2 SH |
258 | } |
259 | rcu_read_unlock(); | |
260 | } | |
261 | ||
317a76f9 | 262 | /* Get current default congestion control */ |
6670e152 | 263 | void tcp_get_default_congestion_control(struct net *net, char *name) |
317a76f9 | 264 | { |
6670e152 | 265 | const struct tcp_congestion_ops *ca; |
317a76f9 SH |
266 | |
267 | rcu_read_lock(); | |
6670e152 | 268 | ca = rcu_dereference(net->ipv4.tcp_congestion_control); |
317a76f9 SH |
269 | strncpy(name, ca->name, TCP_CA_NAME_MAX); |
270 | rcu_read_unlock(); | |
271 | } | |
272 | ||
ce7bc3bf SH |
273 | /* Built list of non-restricted congestion control values */ |
274 | void tcp_get_allowed_congestion_control(char *buf, size_t maxlen) | |
275 | { | |
276 | struct tcp_congestion_ops *ca; | |
277 | size_t offs = 0; | |
278 | ||
279 | *buf = '\0'; | |
280 | rcu_read_lock(); | |
281 | list_for_each_entry_rcu(ca, &tcp_cong_list, list) { | |
164891aa | 282 | if (!(ca->flags & TCP_CONG_NON_RESTRICTED)) |
ce7bc3bf SH |
283 | continue; |
284 | offs += snprintf(buf + offs, maxlen - offs, | |
285 | "%s%s", | |
286 | offs == 0 ? "" : " ", ca->name); | |
ce7bc3bf SH |
287 | } |
288 | rcu_read_unlock(); | |
289 | } | |
290 | ||
291 | /* Change list of non-restricted congestion control */ | |
292 | int tcp_set_allowed_congestion_control(char *val) | |
293 | { | |
294 | struct tcp_congestion_ops *ca; | |
c34186ed | 295 | char *saved_clone, *clone, *name; |
ce7bc3bf SH |
296 | int ret = 0; |
297 | ||
c34186ed | 298 | saved_clone = clone = kstrdup(val, GFP_USER); |
ce7bc3bf SH |
299 | if (!clone) |
300 | return -ENOMEM; | |
301 | ||
302 | spin_lock(&tcp_cong_list_lock); | |
303 | /* pass 1 check for bad entries */ | |
304 | while ((name = strsep(&clone, " ")) && *name) { | |
305 | ca = tcp_ca_find(name); | |
306 | if (!ca) { | |
307 | ret = -ENOENT; | |
308 | goto out; | |
309 | } | |
310 | } | |
311 | ||
164891aa | 312 | /* pass 2 clear old values */ |
ce7bc3bf | 313 | list_for_each_entry_rcu(ca, &tcp_cong_list, list) |
164891aa | 314 | ca->flags &= ~TCP_CONG_NON_RESTRICTED; |
ce7bc3bf SH |
315 | |
316 | /* pass 3 mark as allowed */ | |
317 | while ((name = strsep(&val, " ")) && *name) { | |
318 | ca = tcp_ca_find(name); | |
319 | WARN_ON(!ca); | |
320 | if (ca) | |
164891aa | 321 | ca->flags |= TCP_CONG_NON_RESTRICTED; |
ce7bc3bf SH |
322 | } |
323 | out: | |
324 | spin_unlock(&tcp_cong_list_lock); | |
c34186ed | 325 | kfree(saved_clone); |
ce7bc3bf SH |
326 | |
327 | return ret; | |
328 | } | |
329 | ||
91b5b21c LB |
330 | /* Change congestion control for socket. If load is false, then it is the |
331 | * responsibility of the caller to call tcp_init_congestion_control or | |
332 | * tcp_reinit_congestion_control (if the current congestion control was | |
333 | * already initialized. | |
334 | */ | |
ebfa00c5 | 335 | int tcp_set_congestion_control(struct sock *sk, const char *name, bool load, bool reinit) |
5f8ef48d | 336 | { |
6687e988 | 337 | struct inet_connection_sock *icsk = inet_csk(sk); |
c5c6a8ab | 338 | const struct tcp_congestion_ops *ca; |
5f8ef48d SH |
339 | int err = 0; |
340 | ||
c5c6a8ab DB |
341 | if (icsk->icsk_ca_dst_locked) |
342 | return -EPERM; | |
4d4d3d1e | 343 | |
c5c6a8ab | 344 | rcu_read_lock(); |
91b5b21c LB |
345 | if (!load) |
346 | ca = tcp_ca_find(name); | |
347 | else | |
6670e152 SH |
348 | ca = tcp_ca_find_autoload(sock_net(sk), name); |
349 | ||
c5c6a8ab | 350 | /* No change asking for existing value */ |
9f950415 NC |
351 | if (ca == icsk->icsk_ca_ops) { |
352 | icsk->icsk_ca_setsockopt = 1; | |
5f8ef48d | 353 | goto out; |
9f950415 | 354 | } |
6670e152 | 355 | |
91b5b21c | 356 | if (!ca) { |
5f8ef48d | 357 | err = -ENOENT; |
91b5b21c | 358 | } else if (!load) { |
ebfa00c5 SD |
359 | const struct tcp_congestion_ops *old_ca = icsk->icsk_ca_ops; |
360 | ||
361 | if (try_module_get(ca->owner)) { | |
362 | if (reinit) { | |
363 | tcp_reinit_congestion_control(sk, ca); | |
364 | } else { | |
365 | icsk->icsk_ca_ops = ca; | |
366 | module_put(old_ca->owner); | |
367 | } | |
368 | } else { | |
91b5b21c | 369 | err = -EBUSY; |
ebfa00c5 | 370 | } |
91b5b21c LB |
371 | } else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) || |
372 | ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN))) { | |
ce7bc3bf | 373 | err = -EPERM; |
91b5b21c | 374 | } else if (!try_module_get(ca->owner)) { |
5f8ef48d | 375 | err = -EBUSY; |
91b5b21c | 376 | } else { |
29ba4fff | 377 | tcp_reinit_congestion_control(sk, ca); |
91b5b21c | 378 | } |
5f8ef48d SH |
379 | out: |
380 | rcu_read_unlock(); | |
381 | return err; | |
382 | } | |
383 | ||
9f9843a7 YC |
384 | /* Slow start is used when congestion window is no greater than the slow start |
385 | * threshold. We base on RFC2581 and also handle stretch ACKs properly. | |
386 | * We do not implement RFC3465 Appropriate Byte Counting (ABC) per se but | |
387 | * something better;) a packet is only considered (s)acked in its entirety to | |
388 | * defend the ACK attacks described in the RFC. Slow start processes a stretch | |
389 | * ACK of degree N as if N acks of degree 1 are received back to back except | |
390 | * ABC caps N to 2. Slow start exits when cwnd grows over ssthresh and | |
391 | * returns the leftover acks to adjust cwnd in congestion avoidance mode. | |
40efc6fa | 392 | */ |
e73ebb08 | 393 | u32 tcp_slow_start(struct tcp_sock *tp, u32 acked) |
40efc6fa | 394 | { |
76174004 | 395 | u32 cwnd = min(tp->snd_cwnd + acked, tp->snd_ssthresh); |
a02ba041 | 396 | |
e73ebb08 | 397 | acked -= cwnd - tp->snd_cwnd; |
9f9843a7 | 398 | tp->snd_cwnd = min(cwnd, tp->snd_cwnd_clamp); |
e73ebb08 NC |
399 | |
400 | return acked; | |
40efc6fa SH |
401 | } |
402 | EXPORT_SYMBOL_GPL(tcp_slow_start); | |
403 | ||
814d488c NC |
404 | /* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd (or alternative w), |
405 | * for every packet that was ACKed. | |
406 | */ | |
e73ebb08 | 407 | void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked) |
758ce5c8 | 408 | { |
9949afa4 NC |
409 | /* If credits accumulated at a higher w, apply them gently now. */ |
410 | if (tp->snd_cwnd_cnt >= w) { | |
411 | tp->snd_cwnd_cnt = 0; | |
412 | tp->snd_cwnd++; | |
413 | } | |
414 | ||
814d488c | 415 | tp->snd_cwnd_cnt += acked; |
758ce5c8 | 416 | if (tp->snd_cwnd_cnt >= w) { |
814d488c NC |
417 | u32 delta = tp->snd_cwnd_cnt / w; |
418 | ||
419 | tp->snd_cwnd_cnt -= delta * w; | |
420 | tp->snd_cwnd += delta; | |
758ce5c8 | 421 | } |
814d488c | 422 | tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_cwnd_clamp); |
758ce5c8 IJ |
423 | } |
424 | EXPORT_SYMBOL_GPL(tcp_cong_avoid_ai); | |
425 | ||
317a76f9 SH |
426 | /* |
427 | * TCP Reno congestion control | |
428 | * This is special case used for fallback as well. | |
429 | */ | |
430 | /* This is Jacobson's slow start and congestion avoidance. | |
431 | * SIGCOMM '88, p. 328. | |
432 | */ | |
24901551 | 433 | void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked) |
317a76f9 | 434 | { |
6687e988 ACM |
435 | struct tcp_sock *tp = tcp_sk(sk); |
436 | ||
24901551 | 437 | if (!tcp_is_cwnd_limited(sk)) |
317a76f9 SH |
438 | return; |
439 | ||
7faffa1c | 440 | /* In "safe" area, increase. */ |
071d5080 | 441 | if (tcp_in_slow_start(tp)) { |
c22bdca9 NC |
442 | acked = tcp_slow_start(tp, acked); |
443 | if (!acked) | |
444 | return; | |
445 | } | |
e905a9ed | 446 | /* In dangerous area, increase slowly. */ |
c22bdca9 | 447 | tcp_cong_avoid_ai(tp, tp->snd_cwnd, acked); |
317a76f9 SH |
448 | } |
449 | EXPORT_SYMBOL_GPL(tcp_reno_cong_avoid); | |
450 | ||
451 | /* Slow start threshold is half the congestion window (min 2) */ | |
6687e988 | 452 | u32 tcp_reno_ssthresh(struct sock *sk) |
317a76f9 | 453 | { |
6687e988 | 454 | const struct tcp_sock *tp = tcp_sk(sk); |
688d1945 | 455 | |
317a76f9 SH |
456 | return max(tp->snd_cwnd >> 1U, 2U); |
457 | } | |
458 | EXPORT_SYMBOL_GPL(tcp_reno_ssthresh); | |
459 | ||
e9799183 FW |
460 | u32 tcp_reno_undo_cwnd(struct sock *sk) |
461 | { | |
462 | const struct tcp_sock *tp = tcp_sk(sk); | |
463 | ||
4faf7839 | 464 | return max(tp->snd_cwnd, tp->prior_cwnd); |
e9799183 FW |
465 | } |
466 | EXPORT_SYMBOL_GPL(tcp_reno_undo_cwnd); | |
467 | ||
317a76f9 | 468 | struct tcp_congestion_ops tcp_reno = { |
164891aa | 469 | .flags = TCP_CONG_NON_RESTRICTED, |
317a76f9 SH |
470 | .name = "reno", |
471 | .owner = THIS_MODULE, | |
472 | .ssthresh = tcp_reno_ssthresh, | |
473 | .cong_avoid = tcp_reno_cong_avoid, | |
e9799183 | 474 | .undo_cwnd = tcp_reno_undo_cwnd, |
317a76f9 | 475 | }; |