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)(struct sock *sk,
43					   struct request_sock *req);
44};
45
46int inet_rtx_syn_ack(struct sock *parent, struct request_sock *req);
47
48/* struct request_sock - mini sock to represent a connection request
49 */
50struct request_sock {
51	struct sock_common		__req_common;
52	struct request_sock		*dl_next;
53	u16				mss;
54	u8				num_retrans; /* number of retransmits */
55	u8				cookie_ts:1; /* syncookie: encode tcpopts in timestamp */
56	u8				num_timeout:7; /* number of timeouts */
57	/* The following two fields can be easily recomputed I think -AK */
58	u32				window_clamp; /* window clamp at creation time */
59	u32				rcv_wnd;	  /* rcv_wnd offered first time */
60	u32				ts_recent;
61	unsigned long			expires;
62	const struct request_sock_ops	*rsk_ops;
63	struct sock			*sk;
64	u32				secid;
65	u32				peer_secid;
66};
67
68static inline struct request_sock *reqsk_alloc(const struct request_sock_ops *ops)
69{
70	struct request_sock *req = kmem_cache_alloc(ops->slab, GFP_ATOMIC);
71
72	if (req != NULL)
73		req->rsk_ops = ops;
74
75	return req;
76}
77
78static inline void __reqsk_free(struct request_sock *req)
79{
80	kmem_cache_free(req->rsk_ops->slab, req);
81}
82
83static inline void reqsk_free(struct request_sock *req)
84{
85	req->rsk_ops->destructor(req);
86	__reqsk_free(req);
87}
88
89extern int sysctl_max_syn_backlog;
90
91/** struct listen_sock - listen state
92 *
93 * @max_qlen_log - log_2 of maximal queued SYNs/REQUESTs
94 */
95struct listen_sock {
96	u8			max_qlen_log;
97	u8			synflood_warned;
98	/* 2 bytes hole, try to use */
99	int			qlen;
100	int			qlen_young;
101	int			clock_hand;
102	u32			hash_rnd;
103	u32			nr_table_entries;
104	struct request_sock	*syn_table[0];
105};
106
107/*
108 * For a TCP Fast Open listener -
109 *	lock - protects the access to all the reqsk, which is co-owned by
110 *		the listener and the child socket.
111 *	qlen - pending TFO requests (still in TCP_SYN_RECV).
112 *	max_qlen - max TFO reqs allowed before TFO is disabled.
113 *
114 *	XXX (TFO) - ideally these fields can be made as part of "listen_sock"
115 *	structure above. But there is some implementation difficulty due to
116 *	listen_sock being part of request_sock_queue hence will be freed when
117 *	a listener is stopped. But TFO related fields may continue to be
118 *	accessed even after a listener is closed, until its sk_refcnt drops
119 *	to 0 implying no more outstanding TFO reqs. One solution is to keep
120 *	listen_opt around until	sk_refcnt drops to 0. But there is some other
121 *	complexity that needs to be resolved. E.g., a listener can be disabled
122 *	temporarily through shutdown()->tcp_disconnect(), and re-enabled later.
123 */
124struct fastopen_queue {
125	struct request_sock	*rskq_rst_head; /* Keep track of past TFO */
126	struct request_sock	*rskq_rst_tail; /* requests that caused RST.
127						 * This is part of the defense
128						 * against spoofing attack.
129						 */
130	spinlock_t	lock;
131	int		qlen;		/* # of pending (TCP_SYN_RECV) reqs */
132	int		max_qlen;	/* != 0 iff TFO is currently enabled */
133};
134
135/** struct request_sock_queue - queue of request_socks
136 *
137 * @rskq_accept_head - FIFO head of established children
138 * @rskq_accept_tail - FIFO tail of established children
139 * @rskq_defer_accept - User waits for some data after accept()
140 * @syn_wait_lock - serializer
141 *
142 * %syn_wait_lock is necessary only to avoid proc interface having to grab the main
143 * lock sock while browsing the listening hash (otherwise it's deadlock prone).
144 *
145 * This lock is acquired in read mode only from listening_get_next() seq_file
146 * op and it's acquired in write mode _only_ from code that is actively
147 * changing rskq_accept_head. All readers that are holding the master sock lock
148 * don't need to grab this lock in read mode too as rskq_accept_head. writes
149 * are always protected from the main sock lock.
150 */
151struct request_sock_queue {
152	struct request_sock	*rskq_accept_head;
153	struct request_sock	*rskq_accept_tail;
154	rwlock_t		syn_wait_lock;
155	u8			rskq_defer_accept;
156	/* 3 bytes hole, try to pack */
157	struct listen_sock	*listen_opt;
158	struct fastopen_queue	*fastopenq; /* This is non-NULL iff TFO has been
159					     * enabled on this listener. Check
160					     * max_qlen != 0 in fastopen_queue
161					     * to determine if TFO is enabled
162					     * right at this moment.
163					     */
164};
165
166int reqsk_queue_alloc(struct request_sock_queue *queue,
167		      unsigned int nr_table_entries);
168
169void __reqsk_queue_destroy(struct request_sock_queue *queue);
170void reqsk_queue_destroy(struct request_sock_queue *queue);
171void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
172			   bool reset);
173
174static inline struct request_sock *
175	reqsk_queue_yank_acceptq(struct request_sock_queue *queue)
176{
177	struct request_sock *req = queue->rskq_accept_head;
178
179	queue->rskq_accept_head = NULL;
180	return req;
181}
182
183static inline int reqsk_queue_empty(struct request_sock_queue *queue)
184{
185	return queue->rskq_accept_head == NULL;
186}
187
188static inline void reqsk_queue_unlink(struct request_sock_queue *queue,
189				      struct request_sock *req,
190				      struct request_sock **prev_req)
191{
192	write_lock(&queue->syn_wait_lock);
193	*prev_req = req->dl_next;
194	write_unlock(&queue->syn_wait_lock);
195}
196
197static inline void reqsk_queue_add(struct request_sock_queue *queue,
198				   struct request_sock *req,
199				   struct sock *parent,
200				   struct sock *child)
201{
202	req->sk = child;
203	sk_acceptq_added(parent);
204
205	if (queue->rskq_accept_head == NULL)
206		queue->rskq_accept_head = req;
207	else
208		queue->rskq_accept_tail->dl_next = req;
209
210	queue->rskq_accept_tail = req;
211	req->dl_next = NULL;
212}
213
214static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue)
215{
216	struct request_sock *req = queue->rskq_accept_head;
217
218	WARN_ON(req == NULL);
219
220	queue->rskq_accept_head = req->dl_next;
221	if (queue->rskq_accept_head == NULL)
222		queue->rskq_accept_tail = NULL;
223
224	return req;
225}
226
227static inline int reqsk_queue_removed(struct request_sock_queue *queue,
228				      struct request_sock *req)
229{
230	struct listen_sock *lopt = queue->listen_opt;
231
232	if (req->num_timeout == 0)
233		--lopt->qlen_young;
234
235	return --lopt->qlen;
236}
237
238static inline int reqsk_queue_added(struct request_sock_queue *queue)
239{
240	struct listen_sock *lopt = queue->listen_opt;
241	const int prev_qlen = lopt->qlen;
242
243	lopt->qlen_young++;
244	lopt->qlen++;
245	return prev_qlen;
246}
247
248static inline int reqsk_queue_len(const struct request_sock_queue *queue)
249{
250	return queue->listen_opt != NULL ? queue->listen_opt->qlen : 0;
251}
252
253static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
254{
255	return queue->listen_opt->qlen_young;
256}
257
258static inline int reqsk_queue_is_full(const struct request_sock_queue *queue)
259{
260	return queue->listen_opt->qlen >> queue->listen_opt->max_qlen_log;
261}
262
263static inline void reqsk_queue_hash_req(struct request_sock_queue *queue,
264					u32 hash, struct request_sock *req,
265					unsigned long timeout)
266{
267	struct listen_sock *lopt = queue->listen_opt;
268
269	req->expires = jiffies + timeout;
270	req->num_retrans = 0;
271	req->num_timeout = 0;
272	req->sk = NULL;
273	req->dl_next = lopt->syn_table[hash];
274
275	write_lock(&queue->syn_wait_lock);
276	lopt->syn_table[hash] = req;
277	write_unlock(&queue->syn_wait_lock);
278}
279
280#endif /* _REQUEST_SOCK_H */
281