net/ipv4/tcp_ulp.c

   1 /*
   2  * Pluggable TCP upper layer protocol support.
   3  *
   4  * Copyright (c) 2016-2017, Mellanox Technologies. All rights reserved.
   5  * Copyright (c) 2016-2017, Dave Watson <davejwatson@fb.com>. All rights reserved.
   6  *
   7  */
   8
   9 #include<linux/module.h>
  10 #include <linux/mm.h>
  11 #include <linux/types.h>
  12 #include <linux/list.h>
  13 #include <linux/gfp.h>
  14 #include <net/tcp.h>
  15
  16 static DEFINE_SPINLOCK(tcp_ulp_list_lock);
  17 static LIST_HEAD(tcp_ulp_list);
  18
  19 /* Simple linear search, don't expect many entries! */
  20 static struct tcp_ulp_ops *tcp_ulp_find(const char *name)
  21 {
  22         struct tcp_ulp_ops *e;
  23
  24         list_for_each_entry_rcu(e, &tcp_ulp_list, list) {
  25                 if (strcmp(e->name, name) == 0)
  26                         return e;
  27         }
  28
  29         return NULL;
  30 }
  31
  32 static struct tcp_ulp_ops *tcp_ulp_find_id(const int ulp)
  33 {
  34         struct tcp_ulp_ops *e;
  35
  36         list_for_each_entry_rcu(e, &tcp_ulp_list, list) {
  37                 if (e->uid == ulp)
  38                         return e;
  39         }
  40
  41         return NULL;
  42 }
  43
  44 static const struct tcp_ulp_ops *__tcp_ulp_find_autoload(const char *name)
  45 {
  46         const struct tcp_ulp_ops *ulp = NULL;
  47
  48         rcu_read_lock();
  49         ulp = tcp_ulp_find(name);
  50
  51 #ifdef CONFIG_MODULES
  52         if (!ulp && capable(CAP_NET_ADMIN)) {
  53                 rcu_read_unlock();
  54                 request_module("%s", name);
  55                 rcu_read_lock();
  56                 ulp = tcp_ulp_find(name);
  57         }
  58 #endif
  59         if (!ulp || !try_module_get(ulp->owner))
  60                 ulp = NULL;
  61
  62         rcu_read_unlock();
  63         return ulp;
  64 }
  65
  66 static const struct tcp_ulp_ops *__tcp_ulp_lookup(const int uid)
  67 {
  68         const struct tcp_ulp_ops *ulp;
  69
  70         rcu_read_lock();
  71         ulp = tcp_ulp_find_id(uid);
  72         if (!ulp || !try_module_get(ulp->owner))
  73                 ulp = NULL;
  74         rcu_read_unlock();
  75         return ulp;
  76 }
  77
  78 /* Attach new upper layer protocol to the list
  79  * of available protocols.
  80  */
  81 int tcp_register_ulp(struct tcp_ulp_ops *ulp)
  82 {
  83         int ret = 0;
  84
  85         spin_lock(&tcp_ulp_list_lock);
  86         if (tcp_ulp_find(ulp->name))
  87                 ret = -EEXIST;
  88         else
  89                 list_add_tail_rcu(&ulp->list, &tcp_ulp_list);
  90         spin_unlock(&tcp_ulp_list_lock);
  91
  92         return ret;
  93 }
  94 EXPORT_SYMBOL_GPL(tcp_register_ulp);
  95
  96 void tcp_unregister_ulp(struct tcp_ulp_ops *ulp)
  97 {
  98         spin_lock(&tcp_ulp_list_lock);
  99         list_del_rcu(&ulp->list);
 100         spin_unlock(&tcp_ulp_list_lock);
 101
 102         synchronize_rcu();
 103 }
 104 EXPORT_SYMBOL_GPL(tcp_unregister_ulp);
 105
 106 /* Build string with list of available upper layer protocl values */
 107 void tcp_get_available_ulp(char *buf, size_t maxlen)
 108 {
 109         struct tcp_ulp_ops *ulp_ops;
 110         size_t offs = 0;
 111
 112         *buf = '\0';
 113         rcu_read_lock();
 114         list_for_each_entry_rcu(ulp_ops, &tcp_ulp_list, list) {
 115                 offs += snprintf(buf + offs, maxlen - offs,
 116                                  "%s%s",
 117                                  offs == 0 ? "" : " ", ulp_ops->name);
 118         }
 119         rcu_read_unlock();
 120 }
 121
 122 void tcp_cleanup_ulp(struct sock *sk)
 123 {
 124         struct inet_connection_sock *icsk = inet_csk(sk);
 125
 126         if (!icsk->icsk_ulp_ops)
 127                 return;
 128
 129         if (icsk->icsk_ulp_ops->release)
 130                 icsk->icsk_ulp_ops->release(sk);
 131         module_put(icsk->icsk_ulp_ops->owner);
 132 }
 133
 134 /* Change upper layer protocol for socket */
 135 int tcp_set_ulp(struct sock *sk, const char *name)
 136 {
 137         struct inet_connection_sock *icsk = inet_csk(sk);
 138         const struct tcp_ulp_ops *ulp_ops;
 139         int err = 0;
 140
 141         if (icsk->icsk_ulp_ops)
 142                 return -EEXIST;
 143
 144         ulp_ops = __tcp_ulp_find_autoload(name);
 145         if (!ulp_ops)
 146                 return -ENOENT;
 147
 148         if (!ulp_ops->user_visible) {
 149                 module_put(ulp_ops->owner);
 150                 return -ENOENT;
 151         }
 152
 153         err = ulp_ops->init(sk);
 154         if (err) {
 155                 module_put(ulp_ops->owner);
 156                 return err;
 157         }
 158
 159         icsk->icsk_ulp_ops = ulp_ops;
 160         return 0;
 161 }
 162
 163 int tcp_set_ulp_id(struct sock *sk, int ulp)
 164 {
 165         struct inet_connection_sock *icsk = inet_csk(sk);
 166         const struct tcp_ulp_ops *ulp_ops;
 167         int err;
 168
 169         if (icsk->icsk_ulp_ops)
 170                 return -EEXIST;
 171
 172         ulp_ops = __tcp_ulp_lookup(ulp);
 173         if (!ulp_ops)
 174                 return -ENOENT;
 175
 176         err = ulp_ops->init(sk);
 177         if (err) {
 178                 module_put(ulp_ops->owner);
 179                 return err;
 180         }
 181
 182         icsk->icsk_ulp_ops = ulp_ops;
 183         return 0;
 184 }