net/ipv4/tcp_ulp.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Pluggable TCP upper layer protocol support.
   4  *
   5  * Copyright (c) 2016-2017, Mellanox Technologies. All rights reserved.
   6  * Copyright (c) 2016-2017, Dave Watson <davejwatson@fb.com>. All rights reserved.
   7  *
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/mm.h>
  12 #include <linux/types.h>
  13 #include <linux/list.h>
  14 #include <linux/gfp.h>
  15 #include <net/tcp.h>
  16
  17 static DEFINE_SPINLOCK(tcp_ulp_list_lock);
  18 static LIST_HEAD(tcp_ulp_list);
  19
  20 /* Simple linear search, don't expect many entries! */
  21 static struct tcp_ulp_ops *tcp_ulp_find(const char *name)
  22 {
  23         struct tcp_ulp_ops *e;
  24
  25         list_for_each_entry_rcu(e, &tcp_ulp_list, list) {
  26                 if (strcmp(e->name, name) == 0)
  27                         return e;
  28         }
  29
  30         return NULL;
  31 }
  32
  33 static const struct tcp_ulp_ops *__tcp_ulp_find_autoload(const char *name)
  34 {
  35         const struct tcp_ulp_ops *ulp = NULL;
  36
  37         rcu_read_lock();
  38         ulp = tcp_ulp_find(name);
  39
  40 #ifdef CONFIG_MODULES
  41         if (!ulp && capable(CAP_NET_ADMIN)) {
  42                 rcu_read_unlock();
  43                 request_module("tcp-ulp-%s", name);
  44                 rcu_read_lock();
  45                 ulp = tcp_ulp_find(name);
  46         }
  47 #endif
  48         if (!ulp || !try_module_get(ulp->owner))
  49                 ulp = NULL;
  50
  51         rcu_read_unlock();
  52         return ulp;
  53 }
  54
  55 /* Attach new upper layer protocol to the list
  56  * of available protocols.
  57  */
  58 int tcp_register_ulp(struct tcp_ulp_ops *ulp)
  59 {
  60         int ret = 0;
  61
  62         spin_lock(&tcp_ulp_list_lock);
  63         if (tcp_ulp_find(ulp->name))
  64                 ret = -EEXIST;
  65         else
  66                 list_add_tail_rcu(&ulp->list, &tcp_ulp_list);
  67         spin_unlock(&tcp_ulp_list_lock);
  68
  69         return ret;
  70 }
  71 EXPORT_SYMBOL_GPL(tcp_register_ulp);
  72
  73 void tcp_unregister_ulp(struct tcp_ulp_ops *ulp)
  74 {
  75         spin_lock(&tcp_ulp_list_lock);
  76         list_del_rcu(&ulp->list);
  77         spin_unlock(&tcp_ulp_list_lock);
  78
  79         synchronize_rcu();
  80 }
  81 EXPORT_SYMBOL_GPL(tcp_unregister_ulp);
  82
  83 /* Build string with list of available upper layer protocl values */
  84 void tcp_get_available_ulp(char *buf, size_t maxlen)
  85 {
  86         struct tcp_ulp_ops *ulp_ops;
  87         size_t offs = 0;
  88
  89         *buf = '\0';
  90         rcu_read_lock();
  91         list_for_each_entry_rcu(ulp_ops, &tcp_ulp_list, list) {
  92                 offs += snprintf(buf + offs, maxlen - offs,
  93                                  "%s%s",
  94                                  offs == 0 ? "" : " ", ulp_ops->name);
  95
  96                 if (WARN_ON_ONCE(offs >= maxlen))
  97                         break;
  98         }
  99         rcu_read_unlock();
 100 }
 101
 102 void tcp_update_ulp(struct sock *sk, struct proto *proto,
 103                     void (*write_space)(struct sock *sk))
 104 {
 105         struct inet_connection_sock *icsk = inet_csk(sk);
 106
 107         if (!icsk->icsk_ulp_ops) {
 108                 sk->sk_write_space = write_space;
 109                 sk->sk_prot = proto;
 110                 return;
 111         }
 112
 113         if (icsk->icsk_ulp_ops->update)
 114                 icsk->icsk_ulp_ops->update(sk, proto, write_space);
 115 }
 116
 117 void tcp_cleanup_ulp(struct sock *sk)
 118 {
 119         struct inet_connection_sock *icsk = inet_csk(sk);
 120
 121         /* No sock_owned_by_me() check here as at the time the
 122          * stack calls this function, the socket is dead and
 123          * about to be destroyed.
 124          */
 125         if (!icsk->icsk_ulp_ops)
 126                 return;
 127
 128         if (icsk->icsk_ulp_ops->release)
 129                 icsk->icsk_ulp_ops->release(sk);
 130         module_put(icsk->icsk_ulp_ops->owner);
 131
 132         icsk->icsk_ulp_ops = NULL;
 133 }
 134
 135 static int __tcp_set_ulp(struct sock *sk, const struct tcp_ulp_ops *ulp_ops)
 136 {
 137         struct inet_connection_sock *icsk = inet_csk(sk);
 138         int err;
 139
 140         err = -EEXIST;
 141         if (icsk->icsk_ulp_ops)
 142                 goto out_err;
 143
 144         err = ulp_ops->init(sk);
 145         if (err)
 146                 goto out_err;
 147
 148         icsk->icsk_ulp_ops = ulp_ops;
 149         return 0;
 150 out_err:
 151         module_put(ulp_ops->owner);
 152         return err;
 153 }
 154
 155 int tcp_set_ulp(struct sock *sk, const char *name)
 156 {
 157         const struct tcp_ulp_ops *ulp_ops;
 158
 159         sock_owned_by_me(sk);
 160
 161         ulp_ops = __tcp_ulp_find_autoload(name);
 162         if (!ulp_ops)
 163                 return -ENOENT;
 164
 165         return __tcp_set_ulp(sk, ulp_ops);
 166 }