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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)(const struct sock *sk,
36 struct request_sock *req);
37 void (*send_ack)(const struct sock *sk, struct sk_buff *skb,
38 struct request_sock *req);
39 void (*send_reset)(const struct sock *sk,
40 struct sk_buff *skb);
41 void (*destructor)(struct request_sock *req);
42 void (*syn_ack_timeout)(const struct request_sock *req);
43};
44
45int inet_rtx_syn_ack(const struct sock *parent, struct request_sock *req);
46
47/* struct request_sock - mini sock to represent a connection request
48 */
49struct request_sock {
50 struct sock_common __req_common;
51#define rsk_refcnt __req_common.skc_refcnt
52#define rsk_hash __req_common.skc_hash
53#define rsk_listener __req_common.skc_listener
54#define rsk_window_clamp __req_common.skc_window_clamp
55#define rsk_rcv_wnd __req_common.skc_rcv_wnd
56
57 struct request_sock *dl_next;
58 u16 mss;
59 u8 num_retrans; /* number of retransmits */
60 u8 cookie_ts:1; /* syncookie: encode tcpopts in timestamp */
61 u8 num_timeout:7; /* number of timeouts */
62 u32 ts_recent;
63 struct timer_list rsk_timer;
64 const struct request_sock_ops *rsk_ops;
65 struct sock *sk;
66 u32 *saved_syn;
67 u32 secid;
68 u32 peer_secid;
69};
70
71static inline struct request_sock *inet_reqsk(const struct sock *sk)
72{
73 return (struct request_sock *)sk;
74}
75
76static inline struct sock *req_to_sk(struct request_sock *req)
77{
78 return (struct sock *)req;
79}
80
81static inline struct request_sock *
82reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener,
83 bool attach_listener)
84{
85 struct request_sock *req;
86
87 req = kmem_cache_alloc(ops->slab, GFP_ATOMIC | __GFP_NOWARN);
88
89 if (req) {
90 req->rsk_ops = ops;
91 if (attach_listener) {
92 sock_hold(sk_listener);
93 req->rsk_listener = sk_listener;
94 } else {
95 req->rsk_listener = NULL;
96 }
97 req_to_sk(req)->sk_prot = sk_listener->sk_prot;
98 sk_node_init(&req_to_sk(req)->sk_node);
99 sk_tx_queue_clear(req_to_sk(req));
100 req->saved_syn = NULL;
101 /* Following is temporary. It is coupled with debugging
102 * helpers in reqsk_put() & reqsk_free()
103 */
104 atomic_set(&req->rsk_refcnt, 0);
105 }
106 return req;
107}
108
109static inline void reqsk_free(struct request_sock *req)
110{
111 /* temporary debugging */
112 WARN_ON_ONCE(atomic_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
121static inline void reqsk_put(struct request_sock *req)
122{
123 if (atomic_dec_and_test(&req->rsk_refcnt))
124 reqsk_free(req);
125}
126
127extern int sysctl_max_syn_backlog;
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 */
146struct 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
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 */
164struct 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
179void reqsk_queue_alloc(struct request_sock_queue *queue);
180
181void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
182 bool reset);
183
184static inline bool reqsk_queue_empty(const struct request_sock_queue *queue)
185{
186 return queue->rskq_accept_head == NULL;
187}
188
189static 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 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
206static 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
214static inline void reqsk_queue_added(struct request_sock_queue *queue)
215{
216 atomic_inc(&queue->young);
217 atomic_inc(&queue->qlen);
218}
219
220static inline int reqsk_queue_len(const struct request_sock_queue *queue)
221{
222 return atomic_read(&queue->qlen);
223}
224
225static 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 */