1// SPDX-License-Identifier: GPL-2.0
2/* Multipath TCP
3 *
4 * Copyright (c) 2022, SUSE.
5 */
6
7#define pr_fmt(fmt) "MPTCP: " fmt
8
9#include <linux/kernel.h>
10#include <linux/module.h>
11#include <linux/list.h>
12#include <linux/rculist.h>
13#include <linux/spinlock.h>
14#include "protocol.h"
15
16static DEFINE_SPINLOCK(mptcp_sched_list_lock);
17static LIST_HEAD(mptcp_sched_list);
18
19static int mptcp_sched_default_get_send(struct mptcp_sock *msk)
20{
21 struct sock *ssk;
22
23 ssk = mptcp_subflow_get_send(msk);
24 if (!ssk)
25 return -EINVAL;
26
27 mptcp_subflow_set_scheduled(subflow: mptcp_subflow_ctx(sk: ssk), scheduled: true);
28 return 0;
29}
30
31static int mptcp_sched_default_get_retrans(struct mptcp_sock *msk)
32{
33 struct sock *ssk;
34
35 ssk = mptcp_subflow_get_retrans(msk);
36 if (!ssk)
37 return -EINVAL;
38
39 mptcp_subflow_set_scheduled(subflow: mptcp_subflow_ctx(sk: ssk), scheduled: true);
40 return 0;
41}
42
43static struct mptcp_sched_ops mptcp_sched_default = {
44 .get_send = mptcp_sched_default_get_send,
45 .get_retrans = mptcp_sched_default_get_retrans,
46 .name = "default",
47 .owner = THIS_MODULE,
48};
49
50/* Must be called with rcu read lock held */
51struct mptcp_sched_ops *mptcp_sched_find(const char *name)
52{
53 struct mptcp_sched_ops *sched, *ret = NULL;
54
55 list_for_each_entry_rcu(sched, &mptcp_sched_list, list) {
56 if (!strcmp(sched->name, name)) {
57 ret = sched;
58 break;
59 }
60 }
61
62 return ret;
63}
64
65/* Build string with list of available scheduler values.
66 * Similar to tcp_get_available_congestion_control()
67 */
68void mptcp_get_available_schedulers(char *buf, size_t maxlen)
69{
70 struct mptcp_sched_ops *sched;
71 size_t offs = 0;
72
73 rcu_read_lock();
74 list_for_each_entry_rcu(sched, &mptcp_sched_list, list) {
75 offs += snprintf(buf: buf + offs, size: maxlen - offs,
76 fmt: "%s%s",
77 offs == 0 ? "" : " ", sched->name);
78
79 if (WARN_ON_ONCE(offs >= maxlen))
80 break;
81 }
82 rcu_read_unlock();
83}
84
85int mptcp_validate_scheduler(struct mptcp_sched_ops *sched)
86{
87 if (!sched->get_send) {
88 pr_err("%s does not implement required ops\n", sched->name);
89 return -EINVAL;
90 }
91
92 return 0;
93}
94
95int mptcp_register_scheduler(struct mptcp_sched_ops *sched)
96{
97 int ret;
98
99 ret = mptcp_validate_scheduler(sched);
100 if (ret)
101 return ret;
102
103 spin_lock(lock: &mptcp_sched_list_lock);
104 if (mptcp_sched_find(name: sched->name)) {
105 spin_unlock(lock: &mptcp_sched_list_lock);
106 return -EEXIST;
107 }
108 list_add_tail_rcu(new: &sched->list, head: &mptcp_sched_list);
109 spin_unlock(lock: &mptcp_sched_list_lock);
110
111 pr_debug("%s registered\n", sched->name);
112 return 0;
113}
114
115void mptcp_unregister_scheduler(struct mptcp_sched_ops *sched)
116{
117 if (sched == &mptcp_sched_default)
118 return;
119
120 spin_lock(lock: &mptcp_sched_list_lock);
121 list_del_rcu(entry: &sched->list);
122 spin_unlock(lock: &mptcp_sched_list_lock);
123}
124
125void mptcp_sched_init(void)
126{
127 mptcp_register_scheduler(sched: &mptcp_sched_default);
128}
129
130int mptcp_init_sched(struct mptcp_sock *msk,
131 struct mptcp_sched_ops *sched)
132{
133 if (!sched)
134 sched = &mptcp_sched_default;
135
136 if (!bpf_try_module_get(data: sched, owner: sched->owner))
137 return -EBUSY;
138
139 msk->sched = sched;
140 if (msk->sched->init)
141 msk->sched->init(msk);
142
143 pr_debug("sched=%s\n", msk->sched->name);
144
145 return 0;
146}
147
148void mptcp_release_sched(struct mptcp_sock *msk)
149{
150 struct mptcp_sched_ops *sched = msk->sched;
151
152 if (!sched)
153 return;
154
155 msk->sched = NULL;
156 if (sched->release)
157 sched->release(msk);
158
159 bpf_module_put(data: sched, owner: sched->owner);
160}
161
162void mptcp_subflow_set_scheduled(struct mptcp_subflow_context *subflow,
163 bool scheduled)
164{
165 WRITE_ONCE(subflow->scheduled, scheduled);
166}
167
168int mptcp_sched_get_send(struct mptcp_sock *msk)
169{
170 struct mptcp_subflow_context *subflow;
171
172 msk_owned_by_me(msk);
173
174 /* the following check is moved out of mptcp_subflow_get_send */
175 if (__mptcp_check_fallback(msk)) {
176 if (msk->first &&
177 __tcp_can_send(ssk: msk->first) &&
178 sk_stream_memory_free(sk: msk->first)) {
179 mptcp_subflow_set_scheduled(subflow: mptcp_subflow_ctx(sk: msk->first), scheduled: true);
180 return 0;
181 }
182 return -EINVAL;
183 }
184
185 mptcp_for_each_subflow(msk, subflow) {
186 if (READ_ONCE(subflow->scheduled))
187 return 0;
188 }
189
190 if (msk->sched == &mptcp_sched_default || !msk->sched)
191 return mptcp_sched_default_get_send(msk);
192 return msk->sched->get_send(msk);
193}
194
195int mptcp_sched_get_retrans(struct mptcp_sock *msk)
196{
197 struct mptcp_subflow_context *subflow;
198
199 msk_owned_by_me(msk);
200
201 /* the following check is moved out of mptcp_subflow_get_retrans */
202 if (__mptcp_check_fallback(msk))
203 return -EINVAL;
204
205 mptcp_for_each_subflow(msk, subflow) {
206 if (READ_ONCE(subflow->scheduled))
207 return 0;
208 }
209
210 if (msk->sched == &mptcp_sched_default || !msk->sched)
211 return mptcp_sched_default_get_retrans(msk);
212 if (msk->sched->get_retrans)
213 return msk->sched->get_retrans(msk);
214 return msk->sched->get_send(msk);
215}
216

source code of linux/net/mptcp/sched.c