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
16 static DEFINE_SPINLOCK(mptcp_sched_list_lock);
17 static LIST_HEAD(mptcp_sched_list);
18
mptcp_sched_default_get_subflow(struct mptcp_sock * msk,struct mptcp_sched_data * data)19 static int mptcp_sched_default_get_subflow(struct mptcp_sock *msk,
20 struct mptcp_sched_data *data)
21 {
22 struct sock *ssk;
23
24 ssk = data->reinject ? mptcp_subflow_get_retrans(msk) :
25 mptcp_subflow_get_send(msk);
26 if (!ssk)
27 return -EINVAL;
28
29 mptcp_subflow_set_scheduled(mptcp_subflow_ctx(ssk), true);
30 return 0;
31 }
32
33 static struct mptcp_sched_ops mptcp_sched_default = {
34 .get_subflow = mptcp_sched_default_get_subflow,
35 .name = "default",
36 .owner = THIS_MODULE,
37 };
38
39 /* Must be called with rcu read lock held */
mptcp_sched_find(const char * name)40 struct mptcp_sched_ops *mptcp_sched_find(const char *name)
41 {
42 struct mptcp_sched_ops *sched, *ret = NULL;
43
44 list_for_each_entry_rcu(sched, &mptcp_sched_list, list) {
45 if (!strcmp(sched->name, name)) {
46 ret = sched;
47 break;
48 }
49 }
50
51 return ret;
52 }
53
54 /* Build string with list of available scheduler values.
55 * Similar to tcp_get_available_congestion_control()
56 */
mptcp_get_available_schedulers(char * buf,size_t maxlen)57 void mptcp_get_available_schedulers(char *buf, size_t maxlen)
58 {
59 struct mptcp_sched_ops *sched;
60 size_t offs = 0;
61
62 rcu_read_lock();
63 list_for_each_entry_rcu(sched, &mptcp_sched_list, list) {
64 offs += snprintf(buf + offs, maxlen - offs,
65 "%s%s",
66 offs == 0 ? "" : " ", sched->name);
67
68 if (WARN_ON_ONCE(offs >= maxlen))
69 break;
70 }
71 rcu_read_unlock();
72 }
73
mptcp_register_scheduler(struct mptcp_sched_ops * sched)74 int mptcp_register_scheduler(struct mptcp_sched_ops *sched)
75 {
76 if (!sched->get_subflow)
77 return -EINVAL;
78
79 spin_lock(&mptcp_sched_list_lock);
80 if (mptcp_sched_find(sched->name)) {
81 spin_unlock(&mptcp_sched_list_lock);
82 return -EEXIST;
83 }
84 list_add_tail_rcu(&sched->list, &mptcp_sched_list);
85 spin_unlock(&mptcp_sched_list_lock);
86
87 pr_debug("%s registered\n", sched->name);
88 return 0;
89 }
90
mptcp_unregister_scheduler(struct mptcp_sched_ops * sched)91 void mptcp_unregister_scheduler(struct mptcp_sched_ops *sched)
92 {
93 if (sched == &mptcp_sched_default)
94 return;
95
96 spin_lock(&mptcp_sched_list_lock);
97 list_del_rcu(&sched->list);
98 spin_unlock(&mptcp_sched_list_lock);
99 }
100
mptcp_sched_init(void)101 void mptcp_sched_init(void)
102 {
103 mptcp_register_scheduler(&mptcp_sched_default);
104 }
105
mptcp_init_sched(struct mptcp_sock * msk,struct mptcp_sched_ops * sched)106 int mptcp_init_sched(struct mptcp_sock *msk,
107 struct mptcp_sched_ops *sched)
108 {
109 if (!sched)
110 sched = &mptcp_sched_default;
111
112 if (!bpf_try_module_get(sched, sched->owner))
113 return -EBUSY;
114
115 msk->sched = sched;
116 if (msk->sched->init)
117 msk->sched->init(msk);
118
119 pr_debug("sched=%s\n", msk->sched->name);
120
121 return 0;
122 }
123
mptcp_release_sched(struct mptcp_sock * msk)124 void mptcp_release_sched(struct mptcp_sock *msk)
125 {
126 struct mptcp_sched_ops *sched = msk->sched;
127
128 if (!sched)
129 return;
130
131 msk->sched = NULL;
132 if (sched->release)
133 sched->release(msk);
134
135 bpf_module_put(sched, sched->owner);
136 }
137
mptcp_subflow_set_scheduled(struct mptcp_subflow_context * subflow,bool scheduled)138 void mptcp_subflow_set_scheduled(struct mptcp_subflow_context *subflow,
139 bool scheduled)
140 {
141 WRITE_ONCE(subflow->scheduled, scheduled);
142 }
143
mptcp_sched_get_send(struct mptcp_sock * msk)144 int mptcp_sched_get_send(struct mptcp_sock *msk)
145 {
146 struct mptcp_subflow_context *subflow;
147 struct mptcp_sched_data data;
148
149 msk_owned_by_me(msk);
150
151 /* the following check is moved out of mptcp_subflow_get_send */
152 if (__mptcp_check_fallback(msk)) {
153 if (msk->first &&
154 __tcp_can_send(msk->first) &&
155 sk_stream_memory_free(msk->first)) {
156 mptcp_subflow_set_scheduled(mptcp_subflow_ctx(msk->first), true);
157 return 0;
158 }
159 return -EINVAL;
160 }
161
162 mptcp_for_each_subflow(msk, subflow) {
163 if (READ_ONCE(subflow->scheduled))
164 return 0;
165 }
166
167 data.reinject = false;
168 if (msk->sched == &mptcp_sched_default || !msk->sched)
169 return mptcp_sched_default_get_subflow(msk, &data);
170 return msk->sched->get_subflow(msk, &data);
171 }
172
mptcp_sched_get_retrans(struct mptcp_sock * msk)173 int mptcp_sched_get_retrans(struct mptcp_sock *msk)
174 {
175 struct mptcp_subflow_context *subflow;
176 struct mptcp_sched_data data;
177
178 msk_owned_by_me(msk);
179
180 /* the following check is moved out of mptcp_subflow_get_retrans */
181 if (__mptcp_check_fallback(msk))
182 return -EINVAL;
183
184 mptcp_for_each_subflow(msk, subflow) {
185 if (READ_ONCE(subflow->scheduled))
186 return 0;
187 }
188
189 data.reinject = true;
190 if (msk->sched == &mptcp_sched_default || !msk->sched)
191 return mptcp_sched_default_get_subflow(msk, &data);
192 return msk->sched->get_subflow(msk, &data);
193 }
194