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 #include <linux/refcount.h>
23 
24 #include <net/sock.h>
25 
26 struct request_sock;
27 struct sk_buff;
28 struct dst_entry;
29 struct proto;
30 
31 struct request_sock_ops {
32 	int		family;
33 	unsigned int	obj_size;
34 	struct kmem_cache	*slab;
35 	char		*slab_name;
36 	int		(*rtx_syn_ack)(const struct sock *sk,
37 				       struct request_sock *req);
38 	void		(*send_ack)(const struct sock *sk, struct sk_buff *skb,
39 				    struct request_sock *req);
40 	void		(*send_reset)(const struct sock *sk,
41 				      struct sk_buff *skb);
42 	void		(*destructor)(struct request_sock *req);
43 	void		(*syn_ack_timeout)(const struct request_sock *req);
44 };
45 
46 int inet_rtx_syn_ack(const struct sock *parent, struct request_sock *req);
47 
48 /* struct request_sock - mini sock to represent a connection request
49  */
50 struct request_sock {
51 	struct sock_common		__req_common;
52 #define rsk_refcnt			__req_common.skc_refcnt
53 #define rsk_hash			__req_common.skc_hash
54 #define rsk_listener			__req_common.skc_listener
55 #define rsk_window_clamp		__req_common.skc_window_clamp
56 #define rsk_rcv_wnd			__req_common.skc_rcv_wnd
57 
58 	struct request_sock		*dl_next;
59 	u16				mss;
60 	u8				num_retrans; /* number of retransmits */
61 	u8				cookie_ts:1; /* syncookie: encode tcpopts in timestamp */
62 	u8				num_timeout:7; /* number of timeouts */
63 	u32				ts_recent;
64 	struct timer_list		rsk_timer;
65 	const struct request_sock_ops	*rsk_ops;
66 	struct sock			*sk;
67 	u32				*saved_syn;
68 	u32				secid;
69 	u32				peer_secid;
70 };
71 
inet_reqsk(const struct sock * sk)72 static inline struct request_sock *inet_reqsk(const struct sock *sk)
73 {
74 	return (struct request_sock *)sk;
75 }
76 
req_to_sk(struct request_sock * req)77 static inline struct sock *req_to_sk(struct request_sock *req)
78 {
79 	return (struct sock *)req;
80 }
81 
82 static inline struct request_sock *
reqsk_alloc(const struct request_sock_ops * ops,struct sock * sk_listener,bool attach_listener)83 reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener,
84 	    bool attach_listener)
85 {
86 	struct request_sock *req;
87 
88 	req = kmem_cache_alloc(ops->slab, GFP_ATOMIC | __GFP_NOWARN);
89 	if (!req)
90 		return NULL;
91 	req->rsk_listener = NULL;
92 	if (attach_listener) {
93 		if (unlikely(!refcount_inc_not_zero(&sk_listener->sk_refcnt))) {
94 			kmem_cache_free(ops->slab, req);
95 			return NULL;
96 		}
97 		req->rsk_listener = sk_listener;
98 	}
99 	req->rsk_ops = ops;
100 	req_to_sk(req)->sk_prot = sk_listener->sk_prot;
101 	sk_node_init(&req_to_sk(req)->sk_node);
102 	sk_tx_queue_clear(req_to_sk(req));
103 	req->saved_syn = NULL;
104 	refcount_set(&req->rsk_refcnt, 0);
105 
106 	return req;
107 }
108 
reqsk_free(struct request_sock * req)109 static inline void reqsk_free(struct request_sock *req)
110 {
111 	/* temporary debugging */
112 	WARN_ON_ONCE(refcount_read(&req->rsk_refcnt) != 0);
113 
114 	req->rsk_ops->destructor(req);
115 	if (req->rsk_listener)
116 		sock_put(req->rsk_listener);
117 	kfree(req->saved_syn);
118 	kmem_cache_free(req->rsk_ops->slab, req);
119 }
120 
reqsk_put(struct request_sock * req)121 static inline void reqsk_put(struct request_sock *req)
122 {
123 	if (refcount_dec_and_test(&req->rsk_refcnt))
124 		reqsk_free(req);
125 }
126 
127 /*
128  * For a TCP Fast Open listener -
129  *	lock - protects the access to all the reqsk, which is co-owned by
130  *		the listener and the child socket.
131  *	qlen - pending TFO requests (still in TCP_SYN_RECV).
132  *	max_qlen - max TFO reqs allowed before TFO is disabled.
133  *
134  *	XXX (TFO) - ideally these fields can be made as part of "listen_sock"
135  *	structure above. But there is some implementation difficulty due to
136  *	listen_sock being part of request_sock_queue hence will be freed when
137  *	a listener is stopped. But TFO related fields may continue to be
138  *	accessed even after a listener is closed, until its sk_refcnt drops
139  *	to 0 implying no more outstanding TFO reqs. One solution is to keep
140  *	listen_opt around until	sk_refcnt drops to 0. But there is some other
141  *	complexity that needs to be resolved. E.g., a listener can be disabled
142  *	temporarily through shutdown()->tcp_disconnect(), and re-enabled later.
143  */
144 struct fastopen_queue {
145 	struct request_sock	*rskq_rst_head; /* Keep track of past TFO */
146 	struct request_sock	*rskq_rst_tail; /* requests that caused RST.
147 						 * This is part of the defense
148 						 * against spoofing attack.
149 						 */
150 	spinlock_t	lock;
151 	int		qlen;		/* # of pending (TCP_SYN_RECV) reqs */
152 	int		max_qlen;	/* != 0 iff TFO is currently enabled */
153 
154 	struct tcp_fastopen_context __rcu *ctx; /* cipher context for cookie */
155 };
156 
157 /** struct request_sock_queue - queue of request_socks
158  *
159  * @rskq_accept_head - FIFO head of established children
160  * @rskq_accept_tail - FIFO tail of established children
161  * @rskq_defer_accept - User waits for some data after accept()
162  *
163  */
164 struct request_sock_queue {
165 	spinlock_t		rskq_lock;
166 	u8			rskq_defer_accept;
167 
168 	u32			synflood_warned;
169 	atomic_t		qlen;
170 	atomic_t		young;
171 
172 	struct request_sock	*rskq_accept_head;
173 	struct request_sock	*rskq_accept_tail;
174 	struct fastopen_queue	fastopenq;  /* Check max_qlen != 0 to determine
175 					     * if TFO is enabled.
176 					     */
177 };
178 
179 void reqsk_queue_alloc(struct request_sock_queue *queue);
180 
181 void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
182 			   bool reset);
183 
reqsk_queue_empty(const struct request_sock_queue * queue)184 static inline bool reqsk_queue_empty(const struct request_sock_queue *queue)
185 {
186 	return READ_ONCE(queue->rskq_accept_head) == NULL;
187 }
188 
reqsk_queue_remove(struct request_sock_queue * queue,struct sock * parent)189 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue,
190 						      struct sock *parent)
191 {
192 	struct request_sock *req;
193 
194 	spin_lock_bh(&queue->rskq_lock);
195 	req = queue->rskq_accept_head;
196 	if (req) {
197 		sk_acceptq_removed(parent);
198 		WRITE_ONCE(queue->rskq_accept_head, req->dl_next);
199 		if (queue->rskq_accept_head == NULL)
200 			queue->rskq_accept_tail = NULL;
201 	}
202 	spin_unlock_bh(&queue->rskq_lock);
203 	return req;
204 }
205 
reqsk_queue_removed(struct request_sock_queue * queue,const struct request_sock * req)206 static inline void reqsk_queue_removed(struct request_sock_queue *queue,
207 				       const struct request_sock *req)
208 {
209 	if (req->num_timeout == 0)
210 		atomic_dec(&queue->young);
211 	atomic_dec(&queue->qlen);
212 }
213 
reqsk_queue_added(struct request_sock_queue * queue)214 static inline void reqsk_queue_added(struct request_sock_queue *queue)
215 {
216 	atomic_inc(&queue->young);
217 	atomic_inc(&queue->qlen);
218 }
219 
reqsk_queue_len(const struct request_sock_queue * queue)220 static inline int reqsk_queue_len(const struct request_sock_queue *queue)
221 {
222 	return atomic_read(&queue->qlen);
223 }
224 
reqsk_queue_len_young(const struct request_sock_queue * queue)225 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
226 {
227 	return atomic_read(&queue->young);
228 }
229 
230 #endif /* _REQUEST_SOCK_H */
231