2 * NET Generic infrastructure for Network protocols.
4 * Definitions for request_sock
6 * Authors: Arnaldo Carvalho de Melo <acme@conectiva.com.br>
8 * From code originally in include/net/tcp.h
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.
15 #ifndef _REQUEST_SOCK_H
16 #define _REQUEST_SOCK_H
18 #include <linux/slab.h>
19 #include <linux/spinlock.h>
20 #include <linux/types.h>
21 #include <linux/bug.h>
30 struct request_sock_ops {
33 struct kmem_cache *slab;
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,
41 void (*destructor)(struct request_sock *req);
42 void (*syn_ack_timeout)(const struct request_sock *req);
45 int inet_rtx_syn_ack(const struct sock *parent, struct request_sock *req);
47 /* struct request_sock - mini sock to represent a connection request
50 struct sock_common __req_common;
51 #define rsk_refcnt __req_common.skc_refcnt
52 #define rsk_hash __req_common.skc_hash
54 struct request_sock *dl_next;
55 struct sock *rsk_listener;
57 u8 num_retrans; /* number of retransmits */
58 u8 cookie_ts:1; /* syncookie: encode tcpopts in timestamp */
59 u8 num_timeout:7; /* number of timeouts */
60 /* The following two fields can be easily recomputed I think -AK */
61 u32 window_clamp; /* window clamp at creation time */
62 u32 rcv_wnd; /* rcv_wnd offered first time */
64 struct timer_list rsk_timer;
65 const struct request_sock_ops *rsk_ops;
72 static inline struct request_sock *inet_reqsk(struct sock *sk)
74 return (struct request_sock *)sk;
77 static inline struct sock *req_to_sk(struct request_sock *req)
79 return (struct sock *)req;
82 static inline struct request_sock *
83 reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener)
85 struct request_sock *req;
87 req = kmem_cache_alloc(ops->slab, GFP_ATOMIC | __GFP_NOWARN);
91 sock_hold(sk_listener);
92 req->rsk_listener = sk_listener;
93 req_to_sk(req)->sk_prot = sk_listener->sk_prot;
94 sk_node_init(&req_to_sk(req)->sk_node);
95 sk_tx_queue_clear(req_to_sk(req));
96 req->saved_syn = NULL;
97 /* Following is temporary. It is coupled with debugging
98 * helpers in reqsk_put() & reqsk_free()
100 atomic_set(&req->rsk_refcnt, 0);
105 static inline void reqsk_free(struct request_sock *req)
107 /* temporary debugging */
108 WARN_ON_ONCE(atomic_read(&req->rsk_refcnt) != 0);
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);
117 static inline void reqsk_put(struct request_sock *req)
119 if (atomic_dec_and_test(&req->rsk_refcnt))
123 extern int sysctl_max_syn_backlog;
126 * For a TCP Fast Open listener -
127 * lock - protects the access to all the reqsk, which is co-owned by
128 * the listener and the child socket.
129 * qlen - pending TFO requests (still in TCP_SYN_RECV).
130 * max_qlen - max TFO reqs allowed before TFO is disabled.
132 * XXX (TFO) - ideally these fields can be made as part of "listen_sock"
133 * structure above. But there is some implementation difficulty due to
134 * listen_sock being part of request_sock_queue hence will be freed when
135 * a listener is stopped. But TFO related fields may continue to be
136 * accessed even after a listener is closed, until its sk_refcnt drops
137 * to 0 implying no more outstanding TFO reqs. One solution is to keep
138 * listen_opt around until sk_refcnt drops to 0. But there is some other
139 * complexity that needs to be resolved. E.g., a listener can be disabled
140 * temporarily through shutdown()->tcp_disconnect(), and re-enabled later.
142 struct fastopen_queue {
143 struct request_sock *rskq_rst_head; /* Keep track of past TFO */
144 struct request_sock *rskq_rst_tail; /* requests that caused RST.
145 * This is part of the defense
146 * against spoofing attack.
149 int qlen; /* # of pending (TCP_SYN_RECV) reqs */
150 int max_qlen; /* != 0 iff TFO is currently enabled */
153 /** struct request_sock_queue - queue of request_socks
155 * @rskq_accept_head - FIFO head of established children
156 * @rskq_accept_tail - FIFO tail of established children
157 * @rskq_defer_accept - User waits for some data after accept()
160 struct request_sock_queue {
161 spinlock_t rskq_lock;
162 u8 rskq_defer_accept;
168 struct request_sock *rskq_accept_head;
169 struct request_sock *rskq_accept_tail;
170 struct fastopen_queue fastopenq; /* Check max_qlen != 0 to determine
175 void reqsk_queue_alloc(struct request_sock_queue *queue);
177 void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
180 static inline bool reqsk_queue_empty(const struct request_sock_queue *queue)
182 return queue->rskq_accept_head == NULL;
185 static inline void reqsk_queue_add(struct request_sock_queue *queue,
186 struct request_sock *req,
190 spin_lock(&queue->rskq_lock);
192 sk_acceptq_added(parent);
194 if (queue->rskq_accept_head == NULL)
195 queue->rskq_accept_head = req;
197 queue->rskq_accept_tail->dl_next = req;
199 queue->rskq_accept_tail = req;
201 spin_unlock(&queue->rskq_lock);
204 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue,
207 struct request_sock *req;
209 spin_lock_bh(&queue->rskq_lock);
210 req = queue->rskq_accept_head;
212 sk_acceptq_removed(parent);
213 queue->rskq_accept_head = req->dl_next;
214 if (queue->rskq_accept_head == NULL)
215 queue->rskq_accept_tail = NULL;
217 spin_unlock_bh(&queue->rskq_lock);
221 static inline void reqsk_queue_removed(struct request_sock_queue *queue,
222 const struct request_sock *req)
224 if (req->num_timeout == 0)
225 atomic_dec(&queue->young);
226 atomic_dec(&queue->qlen);
229 static inline void reqsk_queue_added(struct request_sock_queue *queue)
231 atomic_inc(&queue->young);
232 atomic_inc(&queue->qlen);
235 static inline int reqsk_queue_len(const struct request_sock_queue *queue)
237 return atomic_read(&queue->qlen);
240 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
242 return atomic_read(&queue->young);
245 #endif /* _REQUEST_SOCK_H */