1/*
2 * NET		Generic infrastructure for Network protocols.
3 *
4 *		Definitions for request_sock
5 *
6 * Authors:	Arnaldo Carvalho de Melo <acme@conectiva.com.br>
7 *
8 * 		From code originally in include/net/tcp.h
9 *
10 *		This program is free software; you can redistribute it and/or
11 *		modify it under the terms of the GNU General Public License
12 *		as published by the Free Software Foundation; either version
13 *		2 of the License, or (at your option) any later version.
14 */
15#ifndef _REQUEST_SOCK_H
16#define _REQUEST_SOCK_H
17
18#include <linux/slab.h>
19#include <linux/spinlock.h>
20#include <linux/types.h>
21#include <linux/bug.h>
22
23#include <net/sock.h>
24
25struct request_sock;
26struct sk_buff;
27struct dst_entry;
28struct proto;
29
30struct request_sock_ops {
31	int		family;
32	int		obj_size;
33	struct kmem_cache	*slab;
34	char		*slab_name;
35	int		(*rtx_syn_ack)(struct sock *sk,
36				       struct request_sock *req);
37	void		(*send_ack)(struct sock *sk, struct sk_buff *skb,
38				    struct request_sock *req);
39	void		(*send_reset)(struct sock *sk,
40				      struct sk_buff *skb);
41	void		(*destructor)(struct request_sock *req);
42	void		(*syn_ack_timeout)(const struct request_sock *req);
43};
44
45int inet_rtx_syn_ack(struct sock *parent, struct request_sock *req);
46
47/* struct request_sock - mini sock to represent a connection request
48 */
49struct request_sock {
50	struct sock_common		__req_common;
51#define rsk_refcnt			__req_common.skc_refcnt
52#define rsk_hash			__req_common.skc_hash
53
54	struct request_sock		*dl_next;
55	struct sock			*rsk_listener;
56	u16				mss;
57	u8				num_retrans; /* number of retransmits */
58	u8				cookie_ts:1; /* syncookie: encode tcpopts in timestamp */
59	u8				num_timeout:7; /* number of timeouts */
60	/* The following two fields can be easily recomputed I think -AK */
61	u32				window_clamp; /* window clamp at creation time */
62	u32				rcv_wnd;	  /* rcv_wnd offered first time */
63	u32				ts_recent;
64	struct timer_list		rsk_timer;
65	const struct request_sock_ops	*rsk_ops;
66	struct sock			*sk;
67	u32				secid;
68	u32				peer_secid;
69};
70
71static inline struct request_sock *
72reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener)
73{
74	struct request_sock *req = kmem_cache_alloc(ops->slab, GFP_ATOMIC);
75
76	if (req) {
77		req->rsk_ops = ops;
78		sock_hold(sk_listener);
79		req->rsk_listener = sk_listener;
80
81		/* Following is temporary. It is coupled with debugging
82		 * helpers in reqsk_put() & reqsk_free()
83		 */
84		atomic_set(&req->rsk_refcnt, 0);
85	}
86	return req;
87}
88
89static inline struct request_sock *inet_reqsk(struct sock *sk)
90{
91	return (struct request_sock *)sk;
92}
93
94static inline struct sock *req_to_sk(struct request_sock *req)
95{
96	return (struct sock *)req;
97}
98
99static inline void reqsk_free(struct request_sock *req)
100{
101	/* temporary debugging */
102	WARN_ON_ONCE(atomic_read(&req->rsk_refcnt) != 0);
103
104	req->rsk_ops->destructor(req);
105	if (req->rsk_listener)
106		sock_put(req->rsk_listener);
107	kmem_cache_free(req->rsk_ops->slab, req);
108}
109
110static inline void reqsk_put(struct request_sock *req)
111{
112	if (atomic_dec_and_test(&req->rsk_refcnt))
113		reqsk_free(req);
114}
115
116extern int sysctl_max_syn_backlog;
117
118/** struct listen_sock - listen state
119 *
120 * @max_qlen_log - log_2 of maximal queued SYNs/REQUESTs
121 */
122struct listen_sock {
123	int			qlen_inc; /* protected by listener lock */
124	int			young_inc;/* protected by listener lock */
125
126	/* following fields can be updated by timer */
127	atomic_t		qlen_dec; /* qlen = qlen_inc - qlen_dec */
128	atomic_t		young_dec;
129
130	u8			max_qlen_log ____cacheline_aligned_in_smp;
131	u8			synflood_warned;
132	/* 2 bytes hole, try to use */
133	u32			hash_rnd;
134	u32			nr_table_entries;
135	struct request_sock	*syn_table[0];
136};
137
138/*
139 * For a TCP Fast Open listener -
140 *	lock - protects the access to all the reqsk, which is co-owned by
141 *		the listener and the child socket.
142 *	qlen - pending TFO requests (still in TCP_SYN_RECV).
143 *	max_qlen - max TFO reqs allowed before TFO is disabled.
144 *
145 *	XXX (TFO) - ideally these fields can be made as part of "listen_sock"
146 *	structure above. But there is some implementation difficulty due to
147 *	listen_sock being part of request_sock_queue hence will be freed when
148 *	a listener is stopped. But TFO related fields may continue to be
149 *	accessed even after a listener is closed, until its sk_refcnt drops
150 *	to 0 implying no more outstanding TFO reqs. One solution is to keep
151 *	listen_opt around until	sk_refcnt drops to 0. But there is some other
152 *	complexity that needs to be resolved. E.g., a listener can be disabled
153 *	temporarily through shutdown()->tcp_disconnect(), and re-enabled later.
154 */
155struct fastopen_queue {
156	struct request_sock	*rskq_rst_head; /* Keep track of past TFO */
157	struct request_sock	*rskq_rst_tail; /* requests that caused RST.
158						 * This is part of the defense
159						 * against spoofing attack.
160						 */
161	spinlock_t	lock;
162	int		qlen;		/* # of pending (TCP_SYN_RECV) reqs */
163	int		max_qlen;	/* != 0 iff TFO is currently enabled */
164};
165
166/** struct request_sock_queue - queue of request_socks
167 *
168 * @rskq_accept_head - FIFO head of established children
169 * @rskq_accept_tail - FIFO tail of established children
170 * @rskq_defer_accept - User waits for some data after accept()
171 * @syn_wait_lock - serializer
172 *
173 * %syn_wait_lock is necessary only to avoid proc interface having to grab the main
174 * lock sock while browsing the listening hash (otherwise it's deadlock prone).
175 *
176 */
177struct request_sock_queue {
178	struct request_sock	*rskq_accept_head;
179	struct request_sock	*rskq_accept_tail;
180	u8			rskq_defer_accept;
181	struct listen_sock	*listen_opt;
182	struct fastopen_queue	*fastopenq; /* This is non-NULL iff TFO has been
183					     * enabled on this listener. Check
184					     * max_qlen != 0 in fastopen_queue
185					     * to determine if TFO is enabled
186					     * right at this moment.
187					     */
188
189	/* temporary alignment, our goal is to get rid of this lock */
190	spinlock_t		syn_wait_lock ____cacheline_aligned_in_smp;
191};
192
193int reqsk_queue_alloc(struct request_sock_queue *queue,
194		      unsigned int nr_table_entries);
195
196void __reqsk_queue_destroy(struct request_sock_queue *queue);
197void reqsk_queue_destroy(struct request_sock_queue *queue);
198void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
199			   bool reset);
200
201static inline struct request_sock *
202	reqsk_queue_yank_acceptq(struct request_sock_queue *queue)
203{
204	struct request_sock *req = queue->rskq_accept_head;
205
206	queue->rskq_accept_head = NULL;
207	return req;
208}
209
210static inline int reqsk_queue_empty(struct request_sock_queue *queue)
211{
212	return queue->rskq_accept_head == NULL;
213}
214
215static inline void reqsk_queue_add(struct request_sock_queue *queue,
216				   struct request_sock *req,
217				   struct sock *parent,
218				   struct sock *child)
219{
220	req->sk = child;
221	sk_acceptq_added(parent);
222
223	if (queue->rskq_accept_head == NULL)
224		queue->rskq_accept_head = req;
225	else
226		queue->rskq_accept_tail->dl_next = req;
227
228	queue->rskq_accept_tail = req;
229	req->dl_next = NULL;
230}
231
232static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue)
233{
234	struct request_sock *req = queue->rskq_accept_head;
235
236	WARN_ON(req == NULL);
237
238	queue->rskq_accept_head = req->dl_next;
239	if (queue->rskq_accept_head == NULL)
240		queue->rskq_accept_tail = NULL;
241
242	return req;
243}
244
245static inline void reqsk_queue_removed(struct request_sock_queue *queue,
246				       const struct request_sock *req)
247{
248	struct listen_sock *lopt = queue->listen_opt;
249
250	if (req->num_timeout == 0)
251		atomic_inc(&lopt->young_dec);
252	atomic_inc(&lopt->qlen_dec);
253}
254
255static inline void reqsk_queue_added(struct request_sock_queue *queue)
256{
257	struct listen_sock *lopt = queue->listen_opt;
258
259	lopt->young_inc++;
260	lopt->qlen_inc++;
261}
262
263static inline int listen_sock_qlen(const struct listen_sock *lopt)
264{
265	return lopt->qlen_inc - atomic_read(&lopt->qlen_dec);
266}
267
268static inline int listen_sock_young(const struct listen_sock *lopt)
269{
270	return lopt->young_inc - atomic_read(&lopt->young_dec);
271}
272
273static inline int reqsk_queue_len(const struct request_sock_queue *queue)
274{
275	const struct listen_sock *lopt = queue->listen_opt;
276
277	return lopt ? listen_sock_qlen(lopt) : 0;
278}
279
280static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
281{
282	return listen_sock_young(queue->listen_opt);
283}
284
285static inline int reqsk_queue_is_full(const struct request_sock_queue *queue)
286{
287	return reqsk_queue_len(queue) >> queue->listen_opt->max_qlen_log;
288}
289
290void reqsk_queue_hash_req(struct request_sock_queue *queue,
291			  u32 hash, struct request_sock *req,
292			  unsigned long timeout);
293
294#endif /* _REQUEST_SOCK_H */
295