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 request_sock - mini sock to represent a connection request
45 */
46 struct request_sock {
47 struct sock_common __req_common;
48 #define rsk_refcnt __req_common.skc_refcnt
49 #define rsk_hash __req_common.skc_hash
50 #define rsk_listener __req_common.skc_listener
51 #define rsk_window_clamp __req_common.skc_window_clamp
52 #define rsk_rcv_wnd __req_common.skc_rcv_wnd
53
54 struct request_sock *dl_next;
55 u16 mss;
56 u8 num_retrans; /* number of retransmits */
57 u8 cookie_ts:1; /* syncookie: encode tcpopts in timestamp */
58 u8 num_timeout:7; /* number of timeouts */
59 u32 ts_recent;
60 struct timer_list rsk_timer;
61 const struct request_sock_ops *rsk_ops;
62 struct sock *sk;
63 u32 *saved_syn;
64 u32 secid;
65 u32 peer_secid;
66 };
67
inet_reqsk(const struct sock * sk)68 static inline struct request_sock *inet_reqsk(const struct sock *sk)
69 {
70 return (struct request_sock *)sk;
71 }
72
req_to_sk(struct request_sock * req)73 static inline struct sock *req_to_sk(struct request_sock *req)
74 {
75 return (struct sock *)req;
76 }
77
78 static inline struct request_sock *
reqsk_alloc(const struct request_sock_ops * ops,struct sock * sk_listener,bool attach_listener)79 reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener,
80 bool attach_listener)
81 {
82 struct request_sock *req;
83
84 req = kmem_cache_alloc(ops->slab, GFP_ATOMIC | __GFP_NOWARN);
85 if (!req)
86 return NULL;
87 req->rsk_listener = NULL;
88 if (attach_listener) {
89 if (unlikely(!refcount_inc_not_zero(&sk_listener->sk_refcnt))) {
90 kmem_cache_free(ops->slab, req);
91 return NULL;
92 }
93 req->rsk_listener = sk_listener;
94 }
95 req->rsk_ops = ops;
96 req_to_sk(req)->sk_prot = sk_listener->sk_prot;
97 sk_node_init(&req_to_sk(req)->sk_node);
98 sk_tx_queue_clear(req_to_sk(req));
99 req->saved_syn = NULL;
100 req->num_timeout = 0;
101 req->num_retrans = 0;
102 req->sk = NULL;
103 refcount_set(&req->rsk_refcnt, 0);
104
105 return req;
106 }
107
__reqsk_free(struct request_sock * req)108 static inline void __reqsk_free(struct request_sock *req)
109 {
110 req->rsk_ops->destructor(req);
111 if (req->rsk_listener)
112 sock_put(req->rsk_listener);
113 kfree(req->saved_syn);
114 kmem_cache_free(req->rsk_ops->slab, req);
115 }
116
reqsk_free(struct request_sock * req)117 static inline void reqsk_free(struct request_sock *req)
118 {
119 WARN_ON_ONCE(refcount_read(&req->rsk_refcnt) != 0);
120 __reqsk_free(req);
121 }
122
reqsk_put(struct request_sock * req)123 static inline void reqsk_put(struct request_sock *req)
124 {
125 if (refcount_dec_and_test(&req->rsk_refcnt))
126 reqsk_free(req);
127 }
128
129 /*
130 * For a TCP Fast Open listener -
131 * lock - protects the access to all the reqsk, which is co-owned by
132 * the listener and the child socket.
133 * qlen - pending TFO requests (still in TCP_SYN_RECV).
134 * max_qlen - max TFO reqs allowed before TFO is disabled.
135 *
136 * XXX (TFO) - ideally these fields can be made as part of "listen_sock"
137 * structure above. But there is some implementation difficulty due to
138 * listen_sock being part of request_sock_queue hence will be freed when
139 * a listener is stopped. But TFO related fields may continue to be
140 * accessed even after a listener is closed, until its sk_refcnt drops
141 * to 0 implying no more outstanding TFO reqs. One solution is to keep
142 * listen_opt around until sk_refcnt drops to 0. But there is some other
143 * complexity that needs to be resolved. E.g., a listener can be disabled
144 * temporarily through shutdown()->tcp_disconnect(), and re-enabled later.
145 */
146 struct fastopen_queue {
147 struct request_sock *rskq_rst_head; /* Keep track of past TFO */
148 struct request_sock *rskq_rst_tail; /* requests that caused RST.
149 * This is part of the defense
150 * against spoofing attack.
151 */
152 spinlock_t lock;
153 int qlen; /* # of pending (TCP_SYN_RECV) reqs */
154 int max_qlen; /* != 0 iff TFO is currently enabled */
155
156 struct tcp_fastopen_context __rcu *ctx; /* cipher context for cookie */
157 };
158
159 /** struct request_sock_queue - queue of request_socks
160 *
161 * @rskq_accept_head - FIFO head of established children
162 * @rskq_accept_tail - FIFO tail of established children
163 * @rskq_defer_accept - User waits for some data after accept()
164 *
165 */
166 struct request_sock_queue {
167 spinlock_t rskq_lock;
168 u8 rskq_defer_accept;
169
170 u32 synflood_warned;
171 atomic_t qlen;
172 atomic_t young;
173
174 struct request_sock *rskq_accept_head;
175 struct request_sock *rskq_accept_tail;
176 struct fastopen_queue fastopenq; /* Check max_qlen != 0 to determine
177 * if TFO is enabled.
178 */
179 };
180
181 void reqsk_queue_alloc(struct request_sock_queue *queue);
182
183 void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
184 bool reset);
185
reqsk_queue_empty(const struct request_sock_queue * queue)186 static inline bool reqsk_queue_empty(const struct request_sock_queue *queue)
187 {
188 return READ_ONCE(queue->rskq_accept_head) == NULL;
189 }
190
reqsk_queue_remove(struct request_sock_queue * queue,struct sock * parent)191 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue,
192 struct sock *parent)
193 {
194 struct request_sock *req;
195
196 spin_lock_bh(&queue->rskq_lock);
197 req = queue->rskq_accept_head;
198 if (req) {
199 sk_acceptq_removed(parent);
200 WRITE_ONCE(queue->rskq_accept_head, req->dl_next);
201 if (queue->rskq_accept_head == NULL)
202 queue->rskq_accept_tail = NULL;
203 }
204 spin_unlock_bh(&queue->rskq_lock);
205 return req;
206 }
207
reqsk_queue_removed(struct request_sock_queue * queue,const struct request_sock * req)208 static inline void reqsk_queue_removed(struct request_sock_queue *queue,
209 const struct request_sock *req)
210 {
211 if (req->num_timeout == 0)
212 atomic_dec(&queue->young);
213 atomic_dec(&queue->qlen);
214 }
215
reqsk_queue_added(struct request_sock_queue * queue)216 static inline void reqsk_queue_added(struct request_sock_queue *queue)
217 {
218 atomic_inc(&queue->young);
219 atomic_inc(&queue->qlen);
220 }
221
reqsk_queue_len(const struct request_sock_queue * queue)222 static inline int reqsk_queue_len(const struct request_sock_queue *queue)
223 {
224 return atomic_read(&queue->qlen);
225 }
226
reqsk_queue_len_young(const struct request_sock_queue * queue)227 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
228 {
229 return atomic_read(&queue->young);
230 }
231
232 #endif /* _REQUEST_SOCK_H */
233
