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