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Linux/net/ipv4/tcp_ulp.c

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  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 }
185 

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