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
 17static DEFINE_SPINLOCK(tcp_ulp_list_lock);
 18static LIST_HEAD(tcp_ulp_list);
 19
 20/* Simple linear search, don't expect many entries! */
 21static 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
 34static 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 */
 59int 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}
 72EXPORT_SYMBOL_GPL(tcp_register_ulp);
 73
 74void 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}
 82EXPORT_SYMBOL_GPL(tcp_unregister_ulp);
 83
 84/* Build string with list of available upper layer protocl values */
 85void 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
103void 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
112void 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
130static 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;
145out_err:
146	module_put(ulp_ops->owner);
147	return err;
148}
149
150int 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}