net/mptcp/sched.c

   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
  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 */
  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  */
  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
  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
  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
 101 void mptcp_sched_init(void)
 102 {
 103         mptcp_register_scheduler(&mptcp_sched_default);
 104 }
 105
 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
 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
 138 void mptcp_subflow_set_scheduled(struct mptcp_subflow_context *subflow,
 139                                  bool scheduled)
 140 {
 141         WRITE_ONCE(subflow->scheduled, scheduled);
 142 }
 143
 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
 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 }