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! */
tcp_ulp_find(const char * name)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 lockdep_is_held(&tcp_ulp_list_lock)) {
27 if (strcmp(e->name, name) == 0)
28 return e;
29 }
30
31 return NULL;
32 }
33
__tcp_ulp_find_autoload(const char * name)34 static const struct tcp_ulp_ops *__tcp_ulp_find_autoload(const char *name)
35 {
36 const struct tcp_ulp_ops *ulp = NULL;
37
38 rcu_read_lock();
39 ulp = tcp_ulp_find(name);
40
41 #ifdef CONFIG_MODULES
42 if (!ulp && capable(CAP_NET_ADMIN)) {
43 rcu_read_unlock();
44 request_module("tcp-ulp-%s", name);
45 rcu_read_lock();
46 ulp = tcp_ulp_find(name);
47 }
48 #endif
49 if (!ulp || !try_module_get(ulp->owner))
50 ulp = NULL;
51
52 rcu_read_unlock();
53 return ulp;
54 }
55
56 /* Attach new upper layer protocol to the list
57 * of available protocols.
58 */
tcp_register_ulp(struct tcp_ulp_ops * ulp)59 int tcp_register_ulp(struct tcp_ulp_ops *ulp)
60 {
61 int ret = 0;
62
63 spin_lock(&tcp_ulp_list_lock);
64 if (tcp_ulp_find(ulp->name))
65 ret = -EEXIST;
66 else
67 list_add_tail_rcu(&ulp->list, &tcp_ulp_list);
68 spin_unlock(&tcp_ulp_list_lock);
69
70 return ret;
71 }
72 EXPORT_SYMBOL_GPL(tcp_register_ulp);
73
tcp_unregister_ulp(struct tcp_ulp_ops * ulp)74 void tcp_unregister_ulp(struct tcp_ulp_ops *ulp)
75 {
76 spin_lock(&tcp_ulp_list_lock);
77 list_del_rcu(&ulp->list);
78 spin_unlock(&tcp_ulp_list_lock);
79
80 synchronize_rcu();
81 }
82 EXPORT_SYMBOL_GPL(tcp_unregister_ulp);
83
84 /* Build string with list of available upper layer protocl values */
tcp_get_available_ulp(char * buf,size_t maxlen)85 void tcp_get_available_ulp(char *buf, size_t maxlen)
86 {
87 struct tcp_ulp_ops *ulp_ops;
88 size_t offs = 0;
89
90 *buf = '\0';
91 rcu_read_lock();
92 list_for_each_entry_rcu(ulp_ops, &tcp_ulp_list, list) {
93 offs += snprintf(buf + offs, maxlen - offs,
94 "%s%s",
95 offs == 0 ? "" : " ", ulp_ops->name);
96
97 if (WARN_ON_ONCE(offs >= maxlen))
98 break;
99 }
100 rcu_read_unlock();
101 }
102
tcp_update_ulp(struct sock * sk,struct proto * proto,void (* write_space)(struct sock * sk))103 void tcp_update_ulp(struct sock *sk, struct proto *proto,
104 void (*write_space)(struct sock *sk))
105 {
106 struct inet_connection_sock *icsk = inet_csk(sk);
107
108 if (icsk->icsk_ulp_ops->update)
109 icsk->icsk_ulp_ops->update(sk, proto, write_space);
110 }
111
tcp_cleanup_ulp(struct sock * sk)112 void tcp_cleanup_ulp(struct sock *sk)
113 {
114 struct inet_connection_sock *icsk = inet_csk(sk);
115
116 /* No sock_owned_by_me() check here as at the time the
117 * stack calls this function, the socket is dead and
118 * about to be destroyed.
119 */
120 if (!icsk->icsk_ulp_ops)
121 return;
122
123 if (icsk->icsk_ulp_ops->release)
124 icsk->icsk_ulp_ops->release(sk);
125 module_put(icsk->icsk_ulp_ops->owner);
126
127 icsk->icsk_ulp_ops = NULL;
128 }
129
__tcp_set_ulp(struct sock * sk,const struct tcp_ulp_ops * ulp_ops)130 static int __tcp_set_ulp(struct sock *sk, const struct tcp_ulp_ops *ulp_ops)
131 {
132 struct inet_connection_sock *icsk = inet_csk(sk);
133 int err;
134
135 err = -EEXIST;
136 if (icsk->icsk_ulp_ops)
137 goto out_err;
138
139 err = ulp_ops->init(sk);
140 if (err)
141 goto out_err;
142
143 icsk->icsk_ulp_ops = ulp_ops;
144 return 0;
145 out_err:
146 module_put(ulp_ops->owner);
147 return err;
148 }
149
tcp_set_ulp(struct sock * sk,const char * name)150 int tcp_set_ulp(struct sock *sk, const char *name)
151 {
152 const struct tcp_ulp_ops *ulp_ops;
153
154 sock_owned_by_me(sk);
155
156 ulp_ops = __tcp_ulp_find_autoload(name);
157 if (!ulp_ops)
158 return -ENOENT;
159
160 return __tcp_set_ulp(sk, ulp_ops);
161 }
162