1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /*
3  * NET		Generic infrastructure for Network protocols.
4  *
5  *		Definitions for request_sock
6  *
7  * Authors:	Arnaldo Carvalho de Melo <acme@conectiva.com.br>
8  *
9  * 		From code originally in include/net/tcp.h
10  */
11 #ifndef _REQUEST_SOCK_H
12 #define _REQUEST_SOCK_H
13 
14 #include <linux/slab.h>
15 #include <linux/spinlock.h>
16 #include <linux/types.h>
17 #include <linux/bug.h>
18 #include <linux/refcount.h>
19 
20 #include <net/sock.h>
21 
22 struct request_sock;
23 struct sk_buff;
24 struct dst_entry;
25 struct proto;
26 
27 struct request_sock_ops {
28 	int		family;
29 	unsigned int	obj_size;
30 	struct kmem_cache	*slab;
31 	char		*slab_name;
32 	int		(*rtx_syn_ack)(const struct sock *sk,
33 				       struct request_sock *req);
34 	void		(*send_ack)(const struct sock *sk, struct sk_buff *skb,
35 				    struct request_sock *req);
36 	void		(*send_reset)(const struct sock *sk,
37 				      struct sk_buff *skb);
38 	void		(*destructor)(struct request_sock *req);
39 	void		(*syn_ack_timeout)(const struct request_sock *req);
40 };
41 
42 int inet_rtx_syn_ack(const struct sock *parent, struct request_sock *req);
43 
44 struct saved_syn {
45 	u32 mac_hdrlen;
46 	u32 network_hdrlen;
47 	u32 tcp_hdrlen;
48 	u8 data[];
49 };
50 
51 /* struct request_sock - mini sock to represent a connection request
52  */
53 struct request_sock {
54 	struct sock_common		__req_common;
55 #define rsk_refcnt			__req_common.skc_refcnt
56 #define rsk_hash			__req_common.skc_hash
57 #define rsk_listener			__req_common.skc_listener
58 #define rsk_window_clamp		__req_common.skc_window_clamp
59 #define rsk_rcv_wnd			__req_common.skc_rcv_wnd
60 
61 	struct request_sock		*dl_next;
62 	u16				mss;
63 	u8				num_retrans; /* number of retransmits */
64 	u8				syncookie:1; /* syncookie: encode tcpopts in timestamp */
65 	u8				num_timeout:7; /* number of timeouts */
66 	u32				ts_recent;
67 	struct timer_list		rsk_timer;
68 	const struct request_sock_ops	*rsk_ops;
69 	struct sock			*sk;
70 	struct saved_syn		*saved_syn;
71 	u32				secid;
72 	u32				peer_secid;
73 	u32				timeout;
74 };
75 
inet_reqsk(const struct sock * sk)76 static inline struct request_sock *inet_reqsk(const struct sock *sk)
77 {
78 	return (struct request_sock *)sk;
79 }
80 
req_to_sk(struct request_sock * req)81 static inline struct sock *req_to_sk(struct request_sock *req)
82 {
83 	return (struct sock *)req;
84 }
85 
86 static inline struct request_sock *
reqsk_alloc(const struct request_sock_ops * ops,struct sock * sk_listener,bool attach_listener)87 reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener,
88 	    bool attach_listener)
89 {
90 	struct request_sock *req;
91 
92 	req = kmem_cache_alloc(ops->slab, GFP_ATOMIC | __GFP_NOWARN);
93 	if (!req)
94 		return NULL;
95 	req->rsk_listener = NULL;
96 	if (attach_listener) {
97 		if (unlikely(!refcount_inc_not_zero(&sk_listener->sk_refcnt))) {
98 			kmem_cache_free(ops->slab, req);
99 			return NULL;
100 		}
101 		req->rsk_listener = sk_listener;
102 	}
103 	req->rsk_ops = ops;
104 	req_to_sk(req)->sk_prot = sk_listener->sk_prot;
105 	sk_node_init(&req_to_sk(req)->sk_node);
106 	sk_tx_queue_clear(req_to_sk(req));
107 	req->saved_syn = NULL;
108 	req->timeout = 0;
109 	req->num_timeout = 0;
110 	req->num_retrans = 0;
111 	req->sk = NULL;
112 	refcount_set(&req->rsk_refcnt, 0);
113 
114 	return req;
115 }
116 
__reqsk_free(struct request_sock * req)117 static inline void __reqsk_free(struct request_sock *req)
118 {
119 	req->rsk_ops->destructor(req);
120 	if (req->rsk_listener)
121 		sock_put(req->rsk_listener);
122 	kfree(req->saved_syn);
123 	kmem_cache_free(req->rsk_ops->slab, req);
124 }
125 
reqsk_free(struct request_sock * req)126 static inline void reqsk_free(struct request_sock *req)
127 {
128 	WARN_ON_ONCE(refcount_read(&req->rsk_refcnt) != 0);
129 	__reqsk_free(req);
130 }
131 
reqsk_put(struct request_sock * req)132 static inline void reqsk_put(struct request_sock *req)
133 {
134 	if (refcount_dec_and_test(&req->rsk_refcnt))
135 		reqsk_free(req);
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  */
155 struct 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 	struct tcp_fastopen_context __rcu *ctx; /* cipher context for cookie */
166 };
167 
168 /** struct request_sock_queue - queue of request_socks
169  *
170  * @rskq_accept_head - FIFO head of established children
171  * @rskq_accept_tail - FIFO tail of established children
172  * @rskq_defer_accept - User waits for some data after accept()
173  *
174  */
175 struct request_sock_queue {
176 	spinlock_t		rskq_lock;
177 	u8			rskq_defer_accept;
178 
179 	u32			synflood_warned;
180 	atomic_t		qlen;
181 	atomic_t		young;
182 
183 	struct request_sock	*rskq_accept_head;
184 	struct request_sock	*rskq_accept_tail;
185 	struct fastopen_queue	fastopenq;  /* Check max_qlen != 0 to determine
186 					     * if TFO is enabled.
187 					     */
188 };
189 
190 void reqsk_queue_alloc(struct request_sock_queue *queue);
191 
192 void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
193 			   bool reset);
194 
reqsk_queue_empty(const struct request_sock_queue * queue)195 static inline bool reqsk_queue_empty(const struct request_sock_queue *queue)
196 {
197 	return READ_ONCE(queue->rskq_accept_head) == NULL;
198 }
199 
reqsk_queue_remove(struct request_sock_queue * queue,struct sock * parent)200 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue,
201 						      struct sock *parent)
202 {
203 	struct request_sock *req;
204 
205 	spin_lock_bh(&queue->rskq_lock);
206 	req = queue->rskq_accept_head;
207 	if (req) {
208 		sk_acceptq_removed(parent);
209 		WRITE_ONCE(queue->rskq_accept_head, req->dl_next);
210 		if (queue->rskq_accept_head == NULL)
211 			queue->rskq_accept_tail = NULL;
212 	}
213 	spin_unlock_bh(&queue->rskq_lock);
214 	return req;
215 }
216 
reqsk_queue_removed(struct request_sock_queue * queue,const struct request_sock * req)217 static inline void reqsk_queue_removed(struct request_sock_queue *queue,
218 				       const struct request_sock *req)
219 {
220 	if (req->num_timeout == 0)
221 		atomic_dec(&queue->young);
222 	atomic_dec(&queue->qlen);
223 }
224 
reqsk_queue_added(struct request_sock_queue * queue)225 static inline void reqsk_queue_added(struct request_sock_queue *queue)
226 {
227 	atomic_inc(&queue->young);
228 	atomic_inc(&queue->qlen);
229 }
230 
reqsk_queue_len(const struct request_sock_queue * queue)231 static inline int reqsk_queue_len(const struct request_sock_queue *queue)
232 {
233 	return atomic_read(&queue->qlen);
234 }
235 
reqsk_queue_len_young(const struct request_sock_queue * queue)236 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
237 {
238 	return atomic_read(&queue->young);
239 }
240 
241 #endif /* _REQUEST_SOCK_H */
242