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         rcu_read_unlock();
  97 }
  98
  99 void tcp_cleanup_ulp(struct sock *sk)
 100 {
 101         struct inet_connection_sock *icsk = inet_csk(sk);
 102
 103         /* No sock_owned_by_me() check here as at the time the
 104          * stack calls this function, the socket is dead and
 105          * about to be destroyed.
 106          */
 107         if (!icsk->icsk_ulp_ops)
 108                 return;
 109
 110         if (icsk->icsk_ulp_ops->release)
 111                 icsk->icsk_ulp_ops->release(sk);
 112         module_put(icsk->icsk_ulp_ops->owner);
 113
 114         icsk->icsk_ulp_ops = NULL;
 115 }
 116
 117 static int __tcp_set_ulp(struct sock *sk, const struct tcp_ulp_ops *ulp_ops)
 118 {
 119         struct inet_connection_sock *icsk = inet_csk(sk);
 120         int err;
 121
 122         err = -EEXIST;
 123         if (icsk->icsk_ulp_ops)
 124                 goto out_err;
 125
 126         err = ulp_ops->init(sk);
 127         if (err)
 128                 goto out_err;
 129
 130         icsk->icsk_ulp_ops = ulp_ops;
 131         return 0;
 132 out_err:
 133         module_put(ulp_ops->owner);
 134         return err;
 135 }
 136
 137 int tcp_set_ulp(struct sock *sk, const char *name)
 138 {
 139         const struct tcp_ulp_ops *ulp_ops;
 140
 141         sock_owned_by_me(sk);
 142
 143         ulp_ops = __tcp_ulp_find_autoload(name);
 144         if (!ulp_ops)
 145                 return -ENOENT;
 146
 147         return __tcp_set_ulp(sk, ulp_ops);
 148 }