blob: 1294af4e0127b7a9b98d6e9cfa9e3979c7d7086e [file] [log] [blame]
Stephen Hemminger317a76f2005-06-23 12:19:55 -07001/*
Fabian Frederickb92022f2014-11-04 20:25:38 +01002 * Pluggable TCP congestion control support and newReno
Stephen Hemminger317a76f2005-06-23 12:19:55 -07003 * congestion control.
Masanari Iida02582e92012-08-22 19:11:26 +09004 * Based on ideas from I/O scheduler support and Web100.
Stephen Hemminger317a76f2005-06-23 12:19:55 -07005 *
6 * Copyright (C) 2005 Stephen Hemminger <shemminger@osdl.org>
7 */
8
Joe Perchesafd465032012-03-12 07:03:32 +00009#define pr_fmt(fmt) "TCP: " fmt
10
Stephen Hemminger317a76f2005-06-23 12:19:55 -070011#include <linux/module.h>
12#include <linux/mm.h>
13#include <linux/types.h>
14#include <linux/list.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090015#include <linux/gfp.h>
Daniel Borkmannc5c6a8a2015-01-05 23:57:46 +010016#include <linux/jhash.h>
Stephen Hemminger317a76f2005-06-23 12:19:55 -070017#include <net/tcp.h>
18
19static DEFINE_SPINLOCK(tcp_cong_list_lock);
20static LIST_HEAD(tcp_cong_list);
21
22/* Simple linear search, don't expect many entries! */
23static struct tcp_congestion_ops *tcp_ca_find(const char *name)
24{
25 struct tcp_congestion_ops *e;
26
Stephen Hemminger5f8ef482005-06-23 20:37:36 -070027 list_for_each_entry_rcu(e, &tcp_cong_list, list) {
Stephen Hemminger317a76f2005-06-23 12:19:55 -070028 if (strcmp(e->name, name) == 0)
29 return e;
30 }
31
32 return NULL;
33}
34
Daniel Borkmannc5c6a8a2015-01-05 23:57:46 +010035/* Must be called with rcu lock held */
36static 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. */
51struct 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
Stephen Hemminger317a76f2005-06-23 12:19:55 -070063/*
Robert P. J. Dayd08df602007-02-17 19:07:33 +010064 * Attach new congestion control algorithm to the list
Stephen Hemminger317a76f2005-06-23 12:19:55 -070065 * of available options.
66 */
67int 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 */
Yuchung Chengc0402762016-09-19 23:39:21 -040072 if (!ca->ssthresh || !(ca->cong_avoid || ca->cong_control)) {
Joe Perchesafd465032012-03-12 07:03:32 +000073 pr_err("%s does not implement required ops\n", ca->name);
Stephen Hemminger317a76f2005-06-23 12:19:55 -070074 return -EINVAL;
75 }
76
Daniel Borkmannc5c6a8a2015-01-05 23:57:46 +010077 ca->key = jhash(ca->name, sizeof(ca->name), strlen(ca->name));
78
Stephen Hemminger317a76f2005-06-23 12:19:55 -070079 spin_lock(&tcp_cong_list_lock);
Daniel Borkmannc5c6a8a2015-01-05 23:57:46 +010080 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);
Stephen Hemminger317a76f2005-06-23 12:19:55 -070083 ret = -EEXIST;
84 } else {
Stephen Hemminger3d2573f2006-09-24 20:11:58 -070085 list_add_tail_rcu(&ca->list, &tcp_cong_list);
stephen hemmingerdb2855a2015-02-16 09:38:13 -050086 pr_debug("%s registered\n", ca->name);
Stephen Hemminger317a76f2005-06-23 12:19:55 -070087 }
88 spin_unlock(&tcp_cong_list_lock);
89
90 return ret;
91}
92EXPORT_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 */
100void 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);
Daniel Borkmannc5c6a8a2015-01-05 23:57:46 +0100105
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();
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700114}
115EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control);
116
Daniel Borkmannc3a8d942015-08-31 15:58:47 +0200117u32 tcp_ca_get_key_by_name(const char *name, bool *ecn_ca)
Daniel Borkmannc5c6a8a2015-01-05 23:57:46 +0100118{
119 const struct tcp_congestion_ops *ca;
Daniel Borkmannc3a8d942015-08-31 15:58:47 +0200120 u32 key = TCP_CA_UNSPEC;
Daniel Borkmannc5c6a8a2015-01-05 23:57:46 +0100121
122 might_sleep();
123
124 rcu_read_lock();
125 ca = __tcp_ca_find_autoload(name);
Daniel Borkmannc3a8d942015-08-31 15:58:47 +0200126 if (ca) {
127 key = ca->key;
128 *ecn_ca = ca->flags & TCP_CONG_NEEDS_ECN;
129 }
Daniel Borkmannc5c6a8a2015-01-05 23:57:46 +0100130 rcu_read_unlock();
131
132 return key;
133}
134EXPORT_SYMBOL_GPL(tcp_ca_get_key_by_name);
135
136char *tcp_ca_get_name_by_key(u32 key, char *buffer)
137{
138 const struct tcp_congestion_ops *ca;
139 char *ret = NULL;
140
141 rcu_read_lock();
142 ca = tcp_ca_find_key(key);
143 if (ca)
144 ret = strncpy(buffer, ca->name,
145 TCP_CA_NAME_MAX);
146 rcu_read_unlock();
147
148 return ret;
149}
150EXPORT_SYMBOL_GPL(tcp_ca_get_name_by_key);
151
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700152/* Assign choice of congestion control. */
Florian Westphal55d86942014-09-26 22:37:32 +0200153void tcp_assign_congestion_control(struct sock *sk)
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700154{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300155 struct inet_connection_sock *icsk = inet_csk(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700156 struct tcp_congestion_ops *ca;
157
Florian Westphal55d86942014-09-26 22:37:32 +0200158 rcu_read_lock();
159 list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
160 if (likely(try_module_get(ca->owner))) {
161 icsk->icsk_ca_ops = ca;
162 goto out;
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700163 }
Florian Westphal55d86942014-09-26 22:37:32 +0200164 /* Fallback to next available. The last really
165 * guaranteed fallback is Reno from this list.
166 */
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700167 }
Florian Westphal55d86942014-09-26 22:37:32 +0200168out:
169 rcu_read_unlock();
170
171 /* Clear out private data before diag gets it and
172 * the ca has not been initialized.
173 */
174 if (ca->get_info)
175 memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));
Eric Dumazet6ac705b2015-09-25 07:39:18 -0700176 if (ca->flags & TCP_CONG_NEEDS_ECN)
177 INET_ECN_xmit(sk);
178 else
179 INET_ECN_dontxmit(sk);
Florian Westphal55d86942014-09-26 22:37:32 +0200180}
181
182void tcp_init_congestion_control(struct sock *sk)
183{
184 const struct inet_connection_sock *icsk = inet_csk(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700185
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300186 if (icsk->icsk_ca_ops->init)
187 icsk->icsk_ca_ops->init(sk);
Eric Dumazet6ac705b2015-09-25 07:39:18 -0700188 if (tcp_ca_needs_ecn(sk))
189 INET_ECN_xmit(sk);
190 else
191 INET_ECN_dontxmit(sk);
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700192}
193
Daniel Borkmann29ba4fff2015-01-05 23:57:45 +0100194static void tcp_reinit_congestion_control(struct sock *sk,
195 const struct tcp_congestion_ops *ca)
196{
197 struct inet_connection_sock *icsk = inet_csk(sk);
198
199 tcp_cleanup_congestion_control(sk);
200 icsk->icsk_ca_ops = ca;
Neal Cardwell9f950412015-05-29 13:47:07 -0400201 icsk->icsk_ca_setsockopt = 1;
Daniel Borkmann29ba4fff2015-01-05 23:57:45 +0100202
Eric Dumazet6ac705b2015-09-25 07:39:18 -0700203 if (sk->sk_state != TCP_CLOSE)
204 tcp_init_congestion_control(sk);
Daniel Borkmann29ba4fff2015-01-05 23:57:45 +0100205}
206
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700207/* Manage refcounts on socket close. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300208void tcp_cleanup_congestion_control(struct sock *sk)
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700209{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300210 struct inet_connection_sock *icsk = inet_csk(sk);
211
212 if (icsk->icsk_ca_ops->release)
213 icsk->icsk_ca_ops->release(sk);
214 module_put(icsk->icsk_ca_ops->owner);
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700215}
216
217/* Used by sysctl to change default congestion control */
218int tcp_set_default_congestion_control(const char *name)
219{
220 struct tcp_congestion_ops *ca;
221 int ret = -ENOENT;
222
223 spin_lock(&tcp_cong_list_lock);
224 ca = tcp_ca_find(name);
Johannes Berg95a5afc2008-10-16 15:24:51 -0700225#ifdef CONFIG_MODULES
Eric Parisa8f80e82009-08-13 09:44:51 -0400226 if (!ca && capable(CAP_NET_ADMIN)) {
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700227 spin_unlock(&tcp_cong_list_lock);
228
229 request_module("tcp_%s", name);
230 spin_lock(&tcp_cong_list_lock);
231 ca = tcp_ca_find(name);
232 }
233#endif
234
235 if (ca) {
Stephen Hemminger164891a2007-04-23 22:26:16 -0700236 ca->flags |= TCP_CONG_NON_RESTRICTED; /* default is always allowed */
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700237 list_move(&ca->list, &tcp_cong_list);
238 ret = 0;
239 }
240 spin_unlock(&tcp_cong_list_lock);
241
242 return ret;
243}
244
Stephen Hemmingerb1736a72006-10-31 17:31:33 -0800245/* Set default value from kernel configuration at bootup */
246static int __init tcp_congestion_default(void)
247{
248 return tcp_set_default_congestion_control(CONFIG_DEFAULT_TCP_CONG);
249}
250late_initcall(tcp_congestion_default);
251
Stephen Hemminger3ff825b2006-11-09 16:32:06 -0800252/* Build string with list of available congestion control values */
253void tcp_get_available_congestion_control(char *buf, size_t maxlen)
254{
255 struct tcp_congestion_ops *ca;
256 size_t offs = 0;
257
258 rcu_read_lock();
259 list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
260 offs += snprintf(buf + offs, maxlen - offs,
261 "%s%s",
262 offs == 0 ? "" : " ", ca->name);
Stephen Hemminger3ff825b2006-11-09 16:32:06 -0800263 }
264 rcu_read_unlock();
265}
266
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700267/* Get current default congestion control */
268void tcp_get_default_congestion_control(char *name)
269{
270 struct tcp_congestion_ops *ca;
271 /* We will always have reno... */
272 BUG_ON(list_empty(&tcp_cong_list));
273
274 rcu_read_lock();
275 ca = list_entry(tcp_cong_list.next, struct tcp_congestion_ops, list);
276 strncpy(name, ca->name, TCP_CA_NAME_MAX);
277 rcu_read_unlock();
278}
279
Stephen Hemmingerce7bc3b2006-11-09 16:35:15 -0800280/* Built list of non-restricted congestion control values */
281void tcp_get_allowed_congestion_control(char *buf, size_t maxlen)
282{
283 struct tcp_congestion_ops *ca;
284 size_t offs = 0;
285
286 *buf = '\0';
287 rcu_read_lock();
288 list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
Stephen Hemminger164891a2007-04-23 22:26:16 -0700289 if (!(ca->flags & TCP_CONG_NON_RESTRICTED))
Stephen Hemmingerce7bc3b2006-11-09 16:35:15 -0800290 continue;
291 offs += snprintf(buf + offs, maxlen - offs,
292 "%s%s",
293 offs == 0 ? "" : " ", ca->name);
Stephen Hemmingerce7bc3b2006-11-09 16:35:15 -0800294 }
295 rcu_read_unlock();
296}
297
298/* Change list of non-restricted congestion control */
299int tcp_set_allowed_congestion_control(char *val)
300{
301 struct tcp_congestion_ops *ca;
Julia Lawallc34186e2010-08-27 19:31:56 -0700302 char *saved_clone, *clone, *name;
Stephen Hemmingerce7bc3b2006-11-09 16:35:15 -0800303 int ret = 0;
304
Julia Lawallc34186e2010-08-27 19:31:56 -0700305 saved_clone = clone = kstrdup(val, GFP_USER);
Stephen Hemmingerce7bc3b2006-11-09 16:35:15 -0800306 if (!clone)
307 return -ENOMEM;
308
309 spin_lock(&tcp_cong_list_lock);
310 /* pass 1 check for bad entries */
311 while ((name = strsep(&clone, " ")) && *name) {
312 ca = tcp_ca_find(name);
313 if (!ca) {
314 ret = -ENOENT;
315 goto out;
316 }
317 }
318
Stephen Hemminger164891a2007-04-23 22:26:16 -0700319 /* pass 2 clear old values */
Stephen Hemmingerce7bc3b2006-11-09 16:35:15 -0800320 list_for_each_entry_rcu(ca, &tcp_cong_list, list)
Stephen Hemminger164891a2007-04-23 22:26:16 -0700321 ca->flags &= ~TCP_CONG_NON_RESTRICTED;
Stephen Hemmingerce7bc3b2006-11-09 16:35:15 -0800322
323 /* pass 3 mark as allowed */
324 while ((name = strsep(&val, " ")) && *name) {
325 ca = tcp_ca_find(name);
326 WARN_ON(!ca);
327 if (ca)
Stephen Hemminger164891a2007-04-23 22:26:16 -0700328 ca->flags |= TCP_CONG_NON_RESTRICTED;
Stephen Hemmingerce7bc3b2006-11-09 16:35:15 -0800329 }
330out:
331 spin_unlock(&tcp_cong_list_lock);
Julia Lawallc34186e2010-08-27 19:31:56 -0700332 kfree(saved_clone);
Stephen Hemmingerce7bc3b2006-11-09 16:35:15 -0800333
334 return ret;
335}
336
Stephen Hemminger5f8ef482005-06-23 20:37:36 -0700337/* Change congestion control for socket */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300338int tcp_set_congestion_control(struct sock *sk, const char *name)
Stephen Hemminger5f8ef482005-06-23 20:37:36 -0700339{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300340 struct inet_connection_sock *icsk = inet_csk(sk);
Daniel Borkmannc5c6a8a2015-01-05 23:57:46 +0100341 const struct tcp_congestion_ops *ca;
Stephen Hemminger5f8ef482005-06-23 20:37:36 -0700342 int err = 0;
343
Daniel Borkmannc5c6a8a2015-01-05 23:57:46 +0100344 if (icsk->icsk_ca_dst_locked)
345 return -EPERM;
Stephen Hemminger4d4d3d12007-04-23 22:32:11 -0700346
Daniel Borkmannc5c6a8a2015-01-05 23:57:46 +0100347 rcu_read_lock();
348 ca = __tcp_ca_find_autoload(name);
349 /* No change asking for existing value */
Neal Cardwell9f950412015-05-29 13:47:07 -0400350 if (ca == icsk->icsk_ca_ops) {
351 icsk->icsk_ca_setsockopt = 1;
Stephen Hemminger5f8ef482005-06-23 20:37:36 -0700352 goto out;
Neal Cardwell9f950412015-05-29 13:47:07 -0400353 }
Stephen Hemminger5f8ef482005-06-23 20:37:36 -0700354 if (!ca)
355 err = -ENOENT;
Eric W. Biederman52e804c2012-11-16 03:03:05 +0000356 else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) ||
357 ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN)))
Stephen Hemmingerce7bc3b2006-11-09 16:35:15 -0800358 err = -EPERM;
Stephen Hemminger5f8ef482005-06-23 20:37:36 -0700359 else if (!try_module_get(ca->owner))
360 err = -EBUSY;
Daniel Borkmann29ba4fff2015-01-05 23:57:45 +0100361 else
362 tcp_reinit_congestion_control(sk, ca);
Stephen Hemminger5f8ef482005-06-23 20:37:36 -0700363 out:
364 rcu_read_unlock();
365 return err;
366}
367
Yuchung Cheng9f9843a72013-10-31 11:07:31 -0700368/* Slow start is used when congestion window is no greater than the slow start
369 * threshold. We base on RFC2581 and also handle stretch ACKs properly.
370 * We do not implement RFC3465 Appropriate Byte Counting (ABC) per se but
371 * something better;) a packet is only considered (s)acked in its entirety to
372 * defend the ACK attacks described in the RFC. Slow start processes a stretch
373 * ACK of degree N as if N acks of degree 1 are received back to back except
374 * ABC caps N to 2. Slow start exits when cwnd grows over ssthresh and
375 * returns the leftover acks to adjust cwnd in congestion avoidance mode.
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800376 */
Neal Cardwelle73ebb02015-01-28 20:01:35 -0500377u32 tcp_slow_start(struct tcp_sock *tp, u32 acked)
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800378{
Yuchung Cheng76174002015-07-09 13:16:30 -0700379 u32 cwnd = min(tp->snd_cwnd + acked, tp->snd_ssthresh);
Eric Dumazet973ec442013-02-02 05:23:16 +0000380
Neal Cardwelle73ebb02015-01-28 20:01:35 -0500381 acked -= cwnd - tp->snd_cwnd;
Yuchung Cheng9f9843a72013-10-31 11:07:31 -0700382 tp->snd_cwnd = min(cwnd, tp->snd_cwnd_clamp);
Neal Cardwelle73ebb02015-01-28 20:01:35 -0500383
384 return acked;
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800385}
386EXPORT_SYMBOL_GPL(tcp_slow_start);
387
Neal Cardwell814d4882015-01-28 20:01:36 -0500388/* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd (or alternative w),
389 * for every packet that was ACKed.
390 */
Neal Cardwelle73ebb02015-01-28 20:01:35 -0500391void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked)
Ilpo Järvinen758ce5c2009-02-28 04:44:37 +0000392{
Neal Cardwell9949afa2015-03-10 17:17:03 -0400393 /* If credits accumulated at a higher w, apply them gently now. */
394 if (tp->snd_cwnd_cnt >= w) {
395 tp->snd_cwnd_cnt = 0;
396 tp->snd_cwnd++;
397 }
398
Neal Cardwell814d4882015-01-28 20:01:36 -0500399 tp->snd_cwnd_cnt += acked;
Ilpo Järvinen758ce5c2009-02-28 04:44:37 +0000400 if (tp->snd_cwnd_cnt >= w) {
Neal Cardwell814d4882015-01-28 20:01:36 -0500401 u32 delta = tp->snd_cwnd_cnt / w;
402
403 tp->snd_cwnd_cnt -= delta * w;
404 tp->snd_cwnd += delta;
Ilpo Järvinen758ce5c2009-02-28 04:44:37 +0000405 }
Neal Cardwell814d4882015-01-28 20:01:36 -0500406 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_cwnd_clamp);
Ilpo Järvinen758ce5c2009-02-28 04:44:37 +0000407}
408EXPORT_SYMBOL_GPL(tcp_cong_avoid_ai);
409
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700410/*
411 * TCP Reno congestion control
412 * This is special case used for fallback as well.
413 */
414/* This is Jacobson's slow start and congestion avoidance.
415 * SIGCOMM '88, p. 328.
416 */
Eric Dumazet24901552014-05-02 21:18:05 -0700417void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked)
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700418{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300419 struct tcp_sock *tp = tcp_sk(sk);
420
Eric Dumazet24901552014-05-02 21:18:05 -0700421 if (!tcp_is_cwnd_limited(sk))
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700422 return;
423
Stephen Hemminger7faffa12005-11-10 17:07:24 -0800424 /* In "safe" area, increase. */
Yuchung Cheng071d5082015-07-09 13:16:29 -0700425 if (tcp_in_slow_start(tp)) {
Neal Cardwellc22bdca2015-01-28 20:01:37 -0500426 acked = tcp_slow_start(tp, acked);
427 if (!acked)
428 return;
429 }
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900430 /* In dangerous area, increase slowly. */
Neal Cardwellc22bdca2015-01-28 20:01:37 -0500431 tcp_cong_avoid_ai(tp, tp->snd_cwnd, acked);
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700432}
433EXPORT_SYMBOL_GPL(tcp_reno_cong_avoid);
434
435/* Slow start threshold is half the congestion window (min 2) */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300436u32 tcp_reno_ssthresh(struct sock *sk)
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700437{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300438 const struct tcp_sock *tp = tcp_sk(sk);
stephen hemminger688d1942014-08-29 23:32:05 -0700439
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700440 return max(tp->snd_cwnd >> 1U, 2U);
441}
442EXPORT_SYMBOL_GPL(tcp_reno_ssthresh);
443
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700444struct tcp_congestion_ops tcp_reno = {
Stephen Hemminger164891a2007-04-23 22:26:16 -0700445 .flags = TCP_CONG_NON_RESTRICTED,
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700446 .name = "reno",
447 .owner = THIS_MODULE,
448 .ssthresh = tcp_reno_ssthresh,
449 .cong_avoid = tcp_reno_cong_avoid,
Stephen Hemminger317a76f2005-06-23 12:19:55 -0700450};