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 const struct tcp_ulp_ops *__tcp_ulp_find_autoload(const char *name)
  33 {
  34         const struct tcp_ulp_ops *ulp = NULL;
  35
  36         rcu_read_lock();
  37         ulp = tcp_ulp_find(name);
  38
  39 #ifdef CONFIG_MODULES
  40         if (!ulp && capable(CAP_NET_ADMIN)) {
  41                 rcu_read_unlock();
  42                 request_module("%s", name);
  43                 rcu_read_lock();
  44                 ulp = tcp_ulp_find(name);
  45         }
  46 #endif
  47         if (!ulp || !try_module_get(ulp->owner))
  48                 ulp = NULL;
  49
  50         rcu_read_unlock();
  51         return ulp;
  52 }
  53
  54 /* Attach new upper layer protocol to the list
  55  * of available protocols.
  56  */
  57 int tcp_register_ulp(struct tcp_ulp_ops *ulp)
  58 {
  59         int ret = 0;
  60
  61         spin_lock(&tcp_ulp_list_lock);
  62         if (tcp_ulp_find(ulp->name)) {
  63                 pr_notice("%s already registered or non-unique name\n",
  64                           ulp->name);
  65                 ret = -EEXIST;
  66         } else {
  67                 list_add_tail_rcu(&ulp->list, &tcp_ulp_list);
  68         }
  69         spin_unlock(&tcp_ulp_list_lock);
  70
  71         return ret;
  72 }
  73 EXPORT_SYMBOL_GPL(tcp_register_ulp);
  74
  75 void tcp_unregister_ulp(struct tcp_ulp_ops *ulp)
  76 {
  77         spin_lock(&tcp_ulp_list_lock);
  78         list_del_rcu(&ulp->list);
  79         spin_unlock(&tcp_ulp_list_lock);
  80
  81         synchronize_rcu();
  82 }
  83 EXPORT_SYMBOL_GPL(tcp_unregister_ulp);
  84
  85 /* Build string with list of available upper layer protocl values */
  86 void tcp_get_available_ulp(char *buf, size_t maxlen)
  87 {
  88         struct tcp_ulp_ops *ulp_ops;
  89         size_t offs = 0;
  90
  91         *buf = '\0';
  92         rcu_read_lock();
  93         list_for_each_entry_rcu(ulp_ops, &tcp_ulp_list, list) {
  94                 offs += snprintf(buf + offs, maxlen - offs,
  95                                  "%s%s",
  96                                  offs == 0 ? "" : " ", ulp_ops->name);
  97         }
  98         rcu_read_unlock();
  99 }
 100
 101 void tcp_cleanup_ulp(struct sock *sk)
 102 {
 103         struct inet_connection_sock *icsk = inet_csk(sk);
 104
 105         if (!icsk->icsk_ulp_ops)
 106                 return;
 107
 108         if (icsk->icsk_ulp_ops->release)
 109                 icsk->icsk_ulp_ops->release(sk);
 110         module_put(icsk->icsk_ulp_ops->owner);
 111 }
 112
 113 /* Change upper layer protocol for socket */
 114 int tcp_set_ulp(struct sock *sk, const char *name)
 115 {
 116         struct inet_connection_sock *icsk = inet_csk(sk);
 117         const struct tcp_ulp_ops *ulp_ops;
 118         int err = 0;
 119
 120         if (icsk->icsk_ulp_ops)
 121                 return -EEXIST;
 122
 123         ulp_ops = __tcp_ulp_find_autoload(name);
 124         if (!ulp_ops)
 125                 return -ENOENT;
 126
 127         err = ulp_ops->init(sk);
 128         if (err) {
 129                 module_put(ulp_ops->owner);
 130                 return err;
 131         }
 132
 133         icsk->icsk_ulp_ops = ulp_ops;
 134         return 0;
 135 }