Loading...
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Pluggable TCP congestion control support and newReno
4 * congestion control.
5 * Based on ideas from I/O scheduler support and Web100.
6 *
7 * Copyright (C) 2005 Stephen Hemminger <shemminger@osdl.org>
8 */
9
10#define pr_fmt(fmt) "TCP: " fmt
11
12#include <linux/module.h>
13#include <linux/mm.h>
14#include <linux/types.h>
15#include <linux/list.h>
16#include <linux/gfp.h>
17#include <linux/jhash.h>
18#include <net/tcp.h>
19#include <trace/events/tcp.h>
20
21static DEFINE_SPINLOCK(tcp_cong_list_lock);
22static LIST_HEAD(tcp_cong_list);
23
24/* Simple linear search, don't expect many entries! */
25struct tcp_congestion_ops *tcp_ca_find(const char *name)
26{
27 struct tcp_congestion_ops *e;
28
29 list_for_each_entry_rcu(e, &tcp_cong_list, list) {
30 if (strcmp(e->name, name) == 0)
31 return e;
32 }
33
34 return NULL;
35}
36
37void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
38{
39 struct inet_connection_sock *icsk = inet_csk(sk);
40
41 trace_tcp_cong_state_set(sk, ca_state);
42
43 if (icsk->icsk_ca_ops->set_state)
44 icsk->icsk_ca_ops->set_state(sk, ca_state);
45 icsk->icsk_ca_state = ca_state;
46}
47
48/* Must be called with rcu lock held */
49static struct tcp_congestion_ops *tcp_ca_find_autoload(struct net *net,
50 const char *name)
51{
52 struct tcp_congestion_ops *ca = tcp_ca_find(name);
53
54#ifdef CONFIG_MODULES
55 if (!ca && capable(CAP_NET_ADMIN)) {
56 rcu_read_unlock();
57 request_module("tcp_%s", name);
58 rcu_read_lock();
59 ca = tcp_ca_find(name);
60 }
61#endif
62 return ca;
63}
64
65/* Simple linear search, not much in here. */
66struct tcp_congestion_ops *tcp_ca_find_key(u32 key)
67{
68 struct tcp_congestion_ops *e;
69
70 list_for_each_entry_rcu(e, &tcp_cong_list, list) {
71 if (e->key == key)
72 return e;
73 }
74
75 return NULL;
76}
77
78int tcp_validate_congestion_control(struct tcp_congestion_ops *ca)
79{
80 /* all algorithms must implement these */
81 if (!ca->ssthresh || !ca->undo_cwnd ||
82 !(ca->cong_avoid || ca->cong_control)) {
83 pr_err("%s does not implement required ops\n", ca->name);
84 return -EINVAL;
85 }
86
87 return 0;
88}
89
90/* Attach new congestion control algorithm to the list
91 * of available options.
92 */
93int tcp_register_congestion_control(struct tcp_congestion_ops *ca)
94{
95 int ret;
96
97 ret = tcp_validate_congestion_control(ca);
98 if (ret)
99 return ret;
100
101 ca->key = jhash(ca->name, sizeof(ca->name), strlen(ca->name));
102
103 spin_lock(&tcp_cong_list_lock);
104 if (ca->key == TCP_CA_UNSPEC || tcp_ca_find_key(ca->key)) {
105 pr_notice("%s already registered or non-unique key\n",
106 ca->name);
107 ret = -EEXIST;
108 } else {
109 list_add_tail_rcu(&ca->list, &tcp_cong_list);
110 pr_debug("%s registered\n", ca->name);
111 }
112 spin_unlock(&tcp_cong_list_lock);
113
114 return ret;
115}
116EXPORT_SYMBOL_GPL(tcp_register_congestion_control);
117
118/*
119 * Remove congestion control algorithm, called from
120 * the module's remove function. Module ref counts are used
121 * to ensure that this can't be done till all sockets using
122 * that method are closed.
123 */
124void tcp_unregister_congestion_control(struct tcp_congestion_ops *ca)
125{
126 spin_lock(&tcp_cong_list_lock);
127 list_del_rcu(&ca->list);
128 spin_unlock(&tcp_cong_list_lock);
129
130 /* Wait for outstanding readers to complete before the
131 * module gets removed entirely.
132 *
133 * A try_module_get() should fail by now as our module is
134 * in "going" state since no refs are held anymore and
135 * module_exit() handler being called.
136 */
137 synchronize_rcu();
138}
139EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control);
140
141/* Replace a registered old ca with a new one.
142 *
143 * The new ca must have the same name as the old one, that has been
144 * registered.
145 */
146int tcp_update_congestion_control(struct tcp_congestion_ops *ca, struct tcp_congestion_ops *old_ca)
147{
148 struct tcp_congestion_ops *existing;
149 int ret;
150
151 ret = tcp_validate_congestion_control(ca);
152 if (ret)
153 return ret;
154
155 ca->key = jhash(ca->name, sizeof(ca->name), strlen(ca->name));
156
157 spin_lock(&tcp_cong_list_lock);
158 existing = tcp_ca_find_key(old_ca->key);
159 if (ca->key == TCP_CA_UNSPEC || !existing || strcmp(existing->name, ca->name)) {
160 pr_notice("%s not registered or non-unique key\n",
161 ca->name);
162 ret = -EINVAL;
163 } else if (existing != old_ca) {
164 pr_notice("invalid old congestion control algorithm to replace\n");
165 ret = -EINVAL;
166 } else {
167 /* Add the new one before removing the old one to keep
168 * one implementation available all the time.
169 */
170 list_add_tail_rcu(&ca->list, &tcp_cong_list);
171 list_del_rcu(&existing->list);
172 pr_debug("%s updated\n", ca->name);
173 }
174 spin_unlock(&tcp_cong_list_lock);
175
176 /* Wait for outstanding readers to complete before the
177 * module or struct_ops gets removed entirely.
178 */
179 if (!ret)
180 synchronize_rcu();
181
182 return ret;
183}
184
185u32 tcp_ca_get_key_by_name(struct net *net, const char *name, bool *ecn_ca)
186{
187 const struct tcp_congestion_ops *ca;
188 u32 key = TCP_CA_UNSPEC;
189
190 might_sleep();
191
192 rcu_read_lock();
193 ca = tcp_ca_find_autoload(net, name);
194 if (ca) {
195 key = ca->key;
196 *ecn_ca = ca->flags & TCP_CONG_NEEDS_ECN;
197 }
198 rcu_read_unlock();
199
200 return key;
201}
202
203char *tcp_ca_get_name_by_key(u32 key, char *buffer)
204{
205 const struct tcp_congestion_ops *ca;
206 char *ret = NULL;
207
208 rcu_read_lock();
209 ca = tcp_ca_find_key(key);
210 if (ca)
211 ret = strncpy(buffer, ca->name,
212 TCP_CA_NAME_MAX);
213 rcu_read_unlock();
214
215 return ret;
216}
217
218/* Assign choice of congestion control. */
219void tcp_assign_congestion_control(struct sock *sk)
220{
221 struct net *net = sock_net(sk);
222 struct inet_connection_sock *icsk = inet_csk(sk);
223 const struct tcp_congestion_ops *ca;
224
225 rcu_read_lock();
226 ca = rcu_dereference(net->ipv4.tcp_congestion_control);
227 if (unlikely(!bpf_try_module_get(ca, ca->owner)))
228 ca = &tcp_reno;
229 icsk->icsk_ca_ops = ca;
230 rcu_read_unlock();
231
232 memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));
233 if (ca->flags & TCP_CONG_NEEDS_ECN)
234 INET_ECN_xmit(sk);
235 else
236 INET_ECN_dontxmit(sk);
237}
238
239void tcp_init_congestion_control(struct sock *sk)
240{
241 struct inet_connection_sock *icsk = inet_csk(sk);
242
243 tcp_sk(sk)->prior_ssthresh = 0;
244 if (icsk->icsk_ca_ops->init)
245 icsk->icsk_ca_ops->init(sk);
246 if (tcp_ca_needs_ecn(sk))
247 INET_ECN_xmit(sk);
248 else
249 INET_ECN_dontxmit(sk);
250 icsk->icsk_ca_initialized = 1;
251}
252
253static void tcp_reinit_congestion_control(struct sock *sk,
254 const struct tcp_congestion_ops *ca)
255{
256 struct inet_connection_sock *icsk = inet_csk(sk);
257
258 tcp_cleanup_congestion_control(sk);
259 icsk->icsk_ca_ops = ca;
260 icsk->icsk_ca_setsockopt = 1;
261 memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));
262
263 if (ca->flags & TCP_CONG_NEEDS_ECN)
264 INET_ECN_xmit(sk);
265 else
266 INET_ECN_dontxmit(sk);
267
268 if (!((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)))
269 tcp_init_congestion_control(sk);
270}
271
272/* Manage refcounts on socket close. */
273void tcp_cleanup_congestion_control(struct sock *sk)
274{
275 struct inet_connection_sock *icsk = inet_csk(sk);
276
277 if (icsk->icsk_ca_ops->release)
278 icsk->icsk_ca_ops->release(sk);
279 bpf_module_put(icsk->icsk_ca_ops, icsk->icsk_ca_ops->owner);
280}
281
282/* Used by sysctl to change default congestion control */
283int tcp_set_default_congestion_control(struct net *net, const char *name)
284{
285 struct tcp_congestion_ops *ca;
286 const struct tcp_congestion_ops *prev;
287 int ret;
288
289 rcu_read_lock();
290 ca = tcp_ca_find_autoload(net, name);
291 if (!ca) {
292 ret = -ENOENT;
293 } else if (!bpf_try_module_get(ca, ca->owner)) {
294 ret = -EBUSY;
295 } else if (!net_eq(net, &init_net) &&
296 !(ca->flags & TCP_CONG_NON_RESTRICTED)) {
297 /* Only init netns can set default to a restricted algorithm */
298 ret = -EPERM;
299 } else {
300 prev = xchg(&net->ipv4.tcp_congestion_control, ca);
301 if (prev)
302 bpf_module_put(prev, prev->owner);
303
304 ca->flags |= TCP_CONG_NON_RESTRICTED;
305 ret = 0;
306 }
307 rcu_read_unlock();
308
309 return ret;
310}
311
312/* Set default value from kernel configuration at bootup */
313static int __init tcp_congestion_default(void)
314{
315 return tcp_set_default_congestion_control(&init_net,
316 CONFIG_DEFAULT_TCP_CONG);
317}
318late_initcall(tcp_congestion_default);
319
320/* Build string with list of available congestion control values */
321void tcp_get_available_congestion_control(char *buf, size_t maxlen)
322{
323 struct tcp_congestion_ops *ca;
324 size_t offs = 0;
325
326 rcu_read_lock();
327 list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
328 offs += snprintf(buf + offs, maxlen - offs,
329 "%s%s",
330 offs == 0 ? "" : " ", ca->name);
331
332 if (WARN_ON_ONCE(offs >= maxlen))
333 break;
334 }
335 rcu_read_unlock();
336}
337
338/* Get current default congestion control */
339void tcp_get_default_congestion_control(struct net *net, char *name)
340{
341 const struct tcp_congestion_ops *ca;
342
343 rcu_read_lock();
344 ca = rcu_dereference(net->ipv4.tcp_congestion_control);
345 strncpy(name, ca->name, TCP_CA_NAME_MAX);
346 rcu_read_unlock();
347}
348
349/* Built list of non-restricted congestion control values */
350void tcp_get_allowed_congestion_control(char *buf, size_t maxlen)
351{
352 struct tcp_congestion_ops *ca;
353 size_t offs = 0;
354
355 *buf = '\0';
356 rcu_read_lock();
357 list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
358 if (!(ca->flags & TCP_CONG_NON_RESTRICTED))
359 continue;
360 offs += snprintf(buf + offs, maxlen - offs,
361 "%s%s",
362 offs == 0 ? "" : " ", ca->name);
363
364 if (WARN_ON_ONCE(offs >= maxlen))
365 break;
366 }
367 rcu_read_unlock();
368}
369
370/* Change list of non-restricted congestion control */
371int tcp_set_allowed_congestion_control(char *val)
372{
373 struct tcp_congestion_ops *ca;
374 char *saved_clone, *clone, *name;
375 int ret = 0;
376
377 saved_clone = clone = kstrdup(val, GFP_USER);
378 if (!clone)
379 return -ENOMEM;
380
381 spin_lock(&tcp_cong_list_lock);
382 /* pass 1 check for bad entries */
383 while ((name = strsep(&clone, " ")) && *name) {
384 ca = tcp_ca_find(name);
385 if (!ca) {
386 ret = -ENOENT;
387 goto out;
388 }
389 }
390
391 /* pass 2 clear old values */
392 list_for_each_entry_rcu(ca, &tcp_cong_list, list)
393 ca->flags &= ~TCP_CONG_NON_RESTRICTED;
394
395 /* pass 3 mark as allowed */
396 while ((name = strsep(&val, " ")) && *name) {
397 ca = tcp_ca_find(name);
398 WARN_ON(!ca);
399 if (ca)
400 ca->flags |= TCP_CONG_NON_RESTRICTED;
401 }
402out:
403 spin_unlock(&tcp_cong_list_lock);
404 kfree(saved_clone);
405
406 return ret;
407}
408
409/* Change congestion control for socket. If load is false, then it is the
410 * responsibility of the caller to call tcp_init_congestion_control or
411 * tcp_reinit_congestion_control (if the current congestion control was
412 * already initialized.
413 */
414int tcp_set_congestion_control(struct sock *sk, const char *name, bool load,
415 bool cap_net_admin)
416{
417 struct inet_connection_sock *icsk = inet_csk(sk);
418 const struct tcp_congestion_ops *ca;
419 int err = 0;
420
421 if (icsk->icsk_ca_dst_locked)
422 return -EPERM;
423
424 rcu_read_lock();
425 if (!load)
426 ca = tcp_ca_find(name);
427 else
428 ca = tcp_ca_find_autoload(sock_net(sk), name);
429
430 /* No change asking for existing value */
431 if (ca == icsk->icsk_ca_ops) {
432 icsk->icsk_ca_setsockopt = 1;
433 goto out;
434 }
435
436 if (!ca)
437 err = -ENOENT;
438 else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) || cap_net_admin))
439 err = -EPERM;
440 else if (!bpf_try_module_get(ca, ca->owner))
441 err = -EBUSY;
442 else
443 tcp_reinit_congestion_control(sk, ca);
444 out:
445 rcu_read_unlock();
446 return err;
447}
448
449/* Slow start is used when congestion window is no greater than the slow start
450 * threshold. We base on RFC2581 and also handle stretch ACKs properly.
451 * We do not implement RFC3465 Appropriate Byte Counting (ABC) per se but
452 * something better;) a packet is only considered (s)acked in its entirety to
453 * defend the ACK attacks described in the RFC. Slow start processes a stretch
454 * ACK of degree N as if N acks of degree 1 are received back to back except
455 * ABC caps N to 2. Slow start exits when cwnd grows over ssthresh and
456 * returns the leftover acks to adjust cwnd in congestion avoidance mode.
457 */
458__bpf_kfunc u32 tcp_slow_start(struct tcp_sock *tp, u32 acked)
459{
460 u32 cwnd = min(tcp_snd_cwnd(tp) + acked, tp->snd_ssthresh);
461
462 acked -= cwnd - tcp_snd_cwnd(tp);
463 tcp_snd_cwnd_set(tp, min(cwnd, tp->snd_cwnd_clamp));
464
465 return acked;
466}
467EXPORT_SYMBOL_GPL(tcp_slow_start);
468
469/* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd (or alternative w),
470 * for every packet that was ACKed.
471 */
472__bpf_kfunc void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked)
473{
474 /* If credits accumulated at a higher w, apply them gently now. */
475 if (tp->snd_cwnd_cnt >= w) {
476 tp->snd_cwnd_cnt = 0;
477 tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) + 1);
478 }
479
480 tp->snd_cwnd_cnt += acked;
481 if (tp->snd_cwnd_cnt >= w) {
482 u32 delta = tp->snd_cwnd_cnt / w;
483
484 tp->snd_cwnd_cnt -= delta * w;
485 tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) + delta);
486 }
487 tcp_snd_cwnd_set(tp, min(tcp_snd_cwnd(tp), tp->snd_cwnd_clamp));
488}
489EXPORT_SYMBOL_GPL(tcp_cong_avoid_ai);
490
491/*
492 * TCP Reno congestion control
493 * This is special case used for fallback as well.
494 */
495/* This is Jacobson's slow start and congestion avoidance.
496 * SIGCOMM '88, p. 328.
497 */
498__bpf_kfunc void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked)
499{
500 struct tcp_sock *tp = tcp_sk(sk);
501
502 if (!tcp_is_cwnd_limited(sk))
503 return;
504
505 /* In "safe" area, increase. */
506 if (tcp_in_slow_start(tp)) {
507 acked = tcp_slow_start(tp, acked);
508 if (!acked)
509 return;
510 }
511 /* In dangerous area, increase slowly. */
512 tcp_cong_avoid_ai(tp, tcp_snd_cwnd(tp), acked);
513}
514EXPORT_SYMBOL_GPL(tcp_reno_cong_avoid);
515
516/* Slow start threshold is half the congestion window (min 2) */
517__bpf_kfunc u32 tcp_reno_ssthresh(struct sock *sk)
518{
519 const struct tcp_sock *tp = tcp_sk(sk);
520
521 return max(tcp_snd_cwnd(tp) >> 1U, 2U);
522}
523EXPORT_SYMBOL_GPL(tcp_reno_ssthresh);
524
525__bpf_kfunc u32 tcp_reno_undo_cwnd(struct sock *sk)
526{
527 const struct tcp_sock *tp = tcp_sk(sk);
528
529 return max(tcp_snd_cwnd(tp), tp->prior_cwnd);
530}
531EXPORT_SYMBOL_GPL(tcp_reno_undo_cwnd);
532
533struct tcp_congestion_ops tcp_reno = {
534 .flags = TCP_CONG_NON_RESTRICTED,
535 .name = "reno",
536 .owner = THIS_MODULE,
537 .ssthresh = tcp_reno_ssthresh,
538 .cong_avoid = tcp_reno_cong_avoid,
539 .undo_cwnd = tcp_reno_undo_cwnd,
540};
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
9#define pr_fmt(fmt) "TCP: " fmt
10
11#include <linux/module.h>
12#include <linux/mm.h>
13#include <linux/types.h>
14#include <linux/list.h>
15#include <linux/gfp.h>
16#include <net/tcp.h>
17
18int sysctl_tcp_max_ssthresh = 0;
19
20static DEFINE_SPINLOCK(tcp_cong_list_lock);
21static LIST_HEAD(tcp_cong_list);
22
23/* Simple linear search, don't expect many entries! */
24static struct tcp_congestion_ops *tcp_ca_find(const char *name)
25{
26 struct tcp_congestion_ops *e;
27
28 list_for_each_entry_rcu(e, &tcp_cong_list, list) {
29 if (strcmp(e->name, name) == 0)
30 return e;
31 }
32
33 return NULL;
34}
35
36/*
37 * Attach new congestion control algorithm to the list
38 * of available options.
39 */
40int 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 */
45 if (!ca->ssthresh || !ca->cong_avoid) {
46 pr_err("%s does not implement required ops\n", ca->name);
47 return -EINVAL;
48 }
49
50 spin_lock(&tcp_cong_list_lock);
51 if (tcp_ca_find(ca->name)) {
52 pr_notice("%s already registered\n", ca->name);
53 ret = -EEXIST;
54 } else {
55 list_add_tail_rcu(&ca->list, &tcp_cong_list);
56 pr_info("%s registered\n", ca->name);
57 }
58 spin_unlock(&tcp_cong_list_lock);
59
60 return ret;
61}
62EXPORT_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 */
70void 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}
76EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control);
77
78/* Assign choice of congestion control. */
79void tcp_init_congestion_control(struct sock *sk)
80{
81 struct inet_connection_sock *icsk = inet_csk(sk);
82 struct tcp_congestion_ops *ca;
83
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 }
92
93 /* fallback to next available */
94 }
95 rcu_read_unlock();
96 }
97
98 if (icsk->icsk_ca_ops->init)
99 icsk->icsk_ca_ops->init(sk);
100}
101
102/* Manage refcounts on socket close. */
103void tcp_cleanup_congestion_control(struct sock *sk)
104{
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);
110}
111
112/* Used by sysctl to change default congestion control */
113int 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);
120#ifdef CONFIG_MODULES
121 if (!ca && capable(CAP_NET_ADMIN)) {
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) {
131 ca->flags |= TCP_CONG_NON_RESTRICTED; /* default is always allowed */
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
140/* Set default value from kernel configuration at bootup */
141static int __init tcp_congestion_default(void)
142{
143 return tcp_set_default_congestion_control(CONFIG_DEFAULT_TCP_CONG);
144}
145late_initcall(tcp_congestion_default);
146
147
148/* Build string with list of available congestion control values */
149void 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
164/* Get current default congestion control */
165void 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
177/* Built list of non-restricted congestion control values */
178void 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) {
186 if (!(ca->flags & TCP_CONG_NON_RESTRICTED))
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 */
197int tcp_set_allowed_congestion_control(char *val)
198{
199 struct tcp_congestion_ops *ca;
200 char *saved_clone, *clone, *name;
201 int ret = 0;
202
203 saved_clone = clone = kstrdup(val, GFP_USER);
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
217 /* pass 2 clear old values */
218 list_for_each_entry_rcu(ca, &tcp_cong_list, list)
219 ca->flags &= ~TCP_CONG_NON_RESTRICTED;
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)
226 ca->flags |= TCP_CONG_NON_RESTRICTED;
227 }
228out:
229 spin_unlock(&tcp_cong_list_lock);
230 kfree(saved_clone);
231
232 return ret;
233}
234
235
236/* Change congestion control for socket */
237int tcp_set_congestion_control(struct sock *sk, const char *name)
238{
239 struct inet_connection_sock *icsk = inet_csk(sk);
240 struct tcp_congestion_ops *ca;
241 int err = 0;
242
243 rcu_read_lock();
244 ca = tcp_ca_find(name);
245
246 /* no change asking for existing value */
247 if (ca == icsk->icsk_ca_ops)
248 goto out;
249
250#ifdef CONFIG_MODULES
251 /* not found attempt to autoload module */
252 if (!ca && capable(CAP_NET_ADMIN)) {
253 rcu_read_unlock();
254 request_module("tcp_%s", name);
255 rcu_read_lock();
256 ca = tcp_ca_find(name);
257 }
258#endif
259 if (!ca)
260 err = -ENOENT;
261
262 else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) || capable(CAP_NET_ADMIN)))
263 err = -EPERM;
264
265 else if (!try_module_get(ca->owner))
266 err = -EBUSY;
267
268 else {
269 tcp_cleanup_congestion_control(sk);
270 icsk->icsk_ca_ops = ca;
271
272 if (sk->sk_state != TCP_CLOSE && icsk->icsk_ca_ops->init)
273 icsk->icsk_ca_ops->init(sk);
274 }
275 out:
276 rcu_read_unlock();
277 return err;
278}
279
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 */
283bool tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight)
284{
285 const struct tcp_sock *tp = tcp_sk(sk);
286 u32 left;
287
288 if (in_flight >= tp->snd_cwnd)
289 return true;
290
291 left = tp->snd_cwnd - in_flight;
292 if (sk_can_gso(sk) &&
293 left * sysctl_tcp_tso_win_divisor < tp->snd_cwnd &&
294 left * tp->mss_cache < sk->sk_gso_max_size &&
295 left < sk->sk_gso_max_segs)
296 return true;
297 return left <= tcp_max_tso_deferred_mss(tp);
298}
299EXPORT_SYMBOL_GPL(tcp_is_cwnd_limited);
300
301/*
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
307 */
308void tcp_slow_start(struct tcp_sock *tp)
309{
310 int cnt; /* increase in packets */
311
312 /* RFC3465: ABC Slow start
313 * Increase only after a full MSS of bytes is acked
314 *
315 * TCP sender SHOULD increase cwnd by the number of
316 * previously unacknowledged bytes ACKed by each incoming
317 * acknowledgment, provided the increase is not more than L
318 */
319 if (sysctl_tcp_abc && tp->bytes_acked < tp->mss_cache)
320 return;
321
322 if (sysctl_tcp_max_ssthresh > 0 && tp->snd_cwnd > sysctl_tcp_max_ssthresh)
323 cnt = sysctl_tcp_max_ssthresh >> 1; /* limited slow start */
324 else
325 cnt = tp->snd_cwnd; /* exponential increase */
326
327 /* RFC3465: ABC
328 * We MAY increase by 2 if discovered delayed ack
329 */
330 if (sysctl_tcp_abc > 1 && tp->bytes_acked >= 2*tp->mss_cache)
331 cnt <<= 1;
332 tp->bytes_acked = 0;
333
334 tp->snd_cwnd_cnt += cnt;
335 while (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
336 tp->snd_cwnd_cnt -= tp->snd_cwnd;
337 if (tp->snd_cwnd < tp->snd_cwnd_clamp)
338 tp->snd_cwnd++;
339 }
340}
341EXPORT_SYMBOL_GPL(tcp_slow_start);
342
343/* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd (or alternative w) */
344void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w)
345{
346 if (tp->snd_cwnd_cnt >= w) {
347 if (tp->snd_cwnd < tp->snd_cwnd_clamp)
348 tp->snd_cwnd++;
349 tp->snd_cwnd_cnt = 0;
350 } else {
351 tp->snd_cwnd_cnt++;
352 }
353}
354EXPORT_SYMBOL_GPL(tcp_cong_avoid_ai);
355
356/*
357 * TCP Reno congestion control
358 * This is special case used for fallback as well.
359 */
360/* This is Jacobson's slow start and congestion avoidance.
361 * SIGCOMM '88, p. 328.
362 */
363void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
364{
365 struct tcp_sock *tp = tcp_sk(sk);
366
367 if (!tcp_is_cwnd_limited(sk, in_flight))
368 return;
369
370 /* In "safe" area, increase. */
371 if (tp->snd_cwnd <= tp->snd_ssthresh)
372 tcp_slow_start(tp);
373
374 /* In dangerous area, increase slowly. */
375 else if (sysctl_tcp_abc) {
376 /* RFC3465: Appropriate Byte Count
377 * increase once for each full cwnd acked
378 */
379 if (tp->bytes_acked >= tp->snd_cwnd*tp->mss_cache) {
380 tp->bytes_acked -= tp->snd_cwnd*tp->mss_cache;
381 if (tp->snd_cwnd < tp->snd_cwnd_clamp)
382 tp->snd_cwnd++;
383 }
384 } else {
385 tcp_cong_avoid_ai(tp, tp->snd_cwnd);
386 }
387}
388EXPORT_SYMBOL_GPL(tcp_reno_cong_avoid);
389
390/* Slow start threshold is half the congestion window (min 2) */
391u32 tcp_reno_ssthresh(struct sock *sk)
392{
393 const struct tcp_sock *tp = tcp_sk(sk);
394 return max(tp->snd_cwnd >> 1U, 2U);
395}
396EXPORT_SYMBOL_GPL(tcp_reno_ssthresh);
397
398/* Lower bound on congestion window with halving. */
399u32 tcp_reno_min_cwnd(const struct sock *sk)
400{
401 const struct tcp_sock *tp = tcp_sk(sk);
402 return tp->snd_ssthresh/2;
403}
404EXPORT_SYMBOL_GPL(tcp_reno_min_cwnd);
405
406struct tcp_congestion_ops tcp_reno = {
407 .flags = TCP_CONG_NON_RESTRICTED,
408 .name = "reno",
409 .owner = THIS_MODULE,
410 .ssthresh = tcp_reno_ssthresh,
411 .cong_avoid = tcp_reno_cong_avoid,
412 .min_cwnd = tcp_reno_min_cwnd,
413};
414
415/* Initial congestion control used (until SYN)
416 * really reno under another name so we can tell difference
417 * during tcp_set_default_congestion_control
418 */
419struct tcp_congestion_ops tcp_init_congestion_ops = {
420 .name = "",
421 .owner = THIS_MODULE,
422 .ssthresh = tcp_reno_ssthresh,
423 .cong_avoid = tcp_reno_cong_avoid,
424 .min_cwnd = tcp_reno_min_cwnd,
425};
426EXPORT_SYMBOL_GPL(tcp_init_congestion_ops);