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
22struct request_sock;
23struct sk_buff;
24struct dst_entry;
25struct proto;
26
27struct 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
42int inet_rtx_syn_ack(const struct sock *parent, struct request_sock *req);
43
44struct 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 */
53struct 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; /* True if
65						      * 1) tcpopts needs to be encoded in
66						      *    TS of SYN+ACK
67						      * 2) ACK is validated by BPF kfunc.
68						      */
69	u8				num_timeout:7; /* number of timeouts */
70	u32				ts_recent;
71	struct timer_list		rsk_timer;
72	const struct request_sock_ops	*rsk_ops;
73	struct sock			*sk;
74	struct saved_syn		*saved_syn;
75	u32				secid;
76	u32				peer_secid;
77	u32				timeout;
78};
79
80static inline struct request_sock *inet_reqsk(const struct sock *sk)
81{
82	return (struct request_sock *)sk;
83}
84
85static inline struct sock *req_to_sk(struct request_sock *req)
86{
87	return (struct sock *)req;
88}
89
90/**
91 * skb_steal_sock - steal a socket from an sk_buff
92 * @skb: sk_buff to steal the socket from
93 * @refcounted: is set to true if the socket is reference-counted
94 * @prefetched: is set to true if the socket was assigned from bpf
95 */
96static inline struct sock *skb_steal_sock(struct sk_buff *skb,
97					  bool *refcounted, bool *prefetched)
98{
99	struct sock *sk = skb->sk;
100
101	if (!sk) {
102		*prefetched = false;
103		*refcounted = false;
104		return NULL;
105	}
106
107	*prefetched = skb_sk_is_prefetched(skb);
108	if (*prefetched) {
109#if IS_ENABLED(CONFIG_SYN_COOKIES)
110		if (sk->sk_state == TCP_NEW_SYN_RECV && inet_reqsk(sk)->syncookie) {
111			struct request_sock *req = inet_reqsk(sk);
112
113			*refcounted = false;
114			sk = req->rsk_listener;
115			req->rsk_listener = NULL;
116			return sk;
117		}
118#endif
119		*refcounted = sk_is_refcounted(sk);
120	} else {
121		*refcounted = true;
122	}
123
124	skb->destructor = NULL;
125	skb->sk = NULL;
126	return sk;
127}
128
129static inline struct request_sock *
130reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener,
131	    bool attach_listener)
132{
133	struct request_sock *req;
134
135	req = kmem_cache_alloc(ops->slab, GFP_ATOMIC | __GFP_NOWARN);
136	if (!req)
137		return NULL;
138	req->rsk_listener = NULL;
139	if (attach_listener) {
140		if (unlikely(!refcount_inc_not_zero(&sk_listener->sk_refcnt))) {
141			kmem_cache_free(ops->slab, req);
142			return NULL;
143		}
144		req->rsk_listener = sk_listener;
145	}
146	req->rsk_ops = ops;
147	req_to_sk(req)->sk_prot = sk_listener->sk_prot;
148	sk_node_init(&req_to_sk(req)->sk_node);
149	sk_tx_queue_clear(req_to_sk(req));
150	req->saved_syn = NULL;
151	req->syncookie = 0;
152	req->timeout = 0;
153	req->num_timeout = 0;
154	req->num_retrans = 0;
155	req->sk = NULL;
156	refcount_set(&req->rsk_refcnt, 0);
157
158	return req;
159}
160
161static inline void __reqsk_free(struct request_sock *req)
162{
163	req->rsk_ops->destructor(req);
164	if (req->rsk_listener)
165		sock_put(req->rsk_listener);
166	kfree(req->saved_syn);
167	kmem_cache_free(req->rsk_ops->slab, req);
168}
169
170static inline void reqsk_free(struct request_sock *req)
171{
172	WARN_ON_ONCE(refcount_read(&req->rsk_refcnt) != 0);
173	__reqsk_free(req);
174}
175
176static inline void reqsk_put(struct request_sock *req)
177{
178	if (refcount_dec_and_test(&req->rsk_refcnt))
179		reqsk_free(req);
180}
181
182/*
183 * For a TCP Fast Open listener -
184 *	lock - protects the access to all the reqsk, which is co-owned by
185 *		the listener and the child socket.
186 *	qlen - pending TFO requests (still in TCP_SYN_RECV).
187 *	max_qlen - max TFO reqs allowed before TFO is disabled.
188 *
189 *	XXX (TFO) - ideally these fields can be made as part of "listen_sock"
190 *	structure above. But there is some implementation difficulty due to
191 *	listen_sock being part of request_sock_queue hence will be freed when
192 *	a listener is stopped. But TFO related fields may continue to be
193 *	accessed even after a listener is closed, until its sk_refcnt drops
194 *	to 0 implying no more outstanding TFO reqs. One solution is to keep
195 *	listen_opt around until	sk_refcnt drops to 0. But there is some other
196 *	complexity that needs to be resolved. E.g., a listener can be disabled
197 *	temporarily through shutdown()->tcp_disconnect(), and re-enabled later.
198 */
199struct fastopen_queue {
200	struct request_sock	*rskq_rst_head; /* Keep track of past TFO */
201	struct request_sock	*rskq_rst_tail; /* requests that caused RST.
202						 * This is part of the defense
203						 * against spoofing attack.
204						 */
205	spinlock_t	lock;
206	int		qlen;		/* # of pending (TCP_SYN_RECV) reqs */
207	int		max_qlen;	/* != 0 iff TFO is currently enabled */
208
209	struct tcp_fastopen_context __rcu *ctx; /* cipher context for cookie */
210};
211
212/** struct request_sock_queue - queue of request_socks
213 *
214 * @rskq_accept_head - FIFO head of established children
215 * @rskq_accept_tail - FIFO tail of established children
216 * @rskq_defer_accept - User waits for some data after accept()
217 *
218 */
219struct request_sock_queue {
220	spinlock_t		rskq_lock;
221	u8			rskq_defer_accept;
222
223	u32			synflood_warned;
224	atomic_t		qlen;
225	atomic_t		young;
226
227	struct request_sock	*rskq_accept_head;
228	struct request_sock	*rskq_accept_tail;
229	struct fastopen_queue	fastopenq;  /* Check max_qlen != 0 to determine
230					     * if TFO is enabled.
231					     */
232};
233
234void reqsk_queue_alloc(struct request_sock_queue *queue);
235
236void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
237			   bool reset);
238
239static inline bool reqsk_queue_empty(const struct request_sock_queue *queue)
240{
241	return READ_ONCE(queue->rskq_accept_head) == NULL;
242}
243
244static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue,
245						      struct sock *parent)
246{
247	struct request_sock *req;
248
249	spin_lock_bh(&queue->rskq_lock);
250	req = queue->rskq_accept_head;
251	if (req) {
252		sk_acceptq_removed(parent);
253		WRITE_ONCE(queue->rskq_accept_head, req->dl_next);
254		if (queue->rskq_accept_head == NULL)
255			queue->rskq_accept_tail = NULL;
256	}
257	spin_unlock_bh(&queue->rskq_lock);
258	return req;
259}
260
261static inline void reqsk_queue_removed(struct request_sock_queue *queue,
262				       const struct request_sock *req)
263{
264	if (req->num_timeout == 0)
265		atomic_dec(&queue->young);
266	atomic_dec(&queue->qlen);
267}
268
269static inline void reqsk_queue_added(struct request_sock_queue *queue)
270{
271	atomic_inc(&queue->young);
272	atomic_inc(&queue->qlen);
273}
274
275static inline int reqsk_queue_len(const struct request_sock_queue *queue)
276{
277	return atomic_read(&queue->qlen);
278}
279
280static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
281{
282	return atomic_read(&queue->young);
283}
284
285#endif /* _REQUEST_SOCK_H */
286