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)(struct sock *sk,
36 struct request_sock *req);
37 void (*send_ack)(struct sock *sk, struct sk_buff *skb,
38 struct request_sock *req);
39 void (*send_reset)(struct sock *sk,
41 void (*destructor)(struct request_sock *req);
42 void (*syn_ack_timeout)(struct sock *sk,
43 struct request_sock *req);
46 int inet_rtx_syn_ack(struct sock *parent, struct request_sock *req);
48 /* struct request_sock - mini sock to represent a connection request
51 struct sock_common __req_common;
52 #define rsk_refcnt __req_common.skc_refcnt
53 #define rsk_hash __req_common.skc_hash
55 struct request_sock *dl_next;
56 struct sock *rsk_listener;
58 u8 num_retrans; /* number of retransmits */
59 u8 cookie_ts:1; /* syncookie: encode tcpopts in timestamp */
60 u8 num_timeout:7; /* number of timeouts */
61 /* The following two fields can be easily recomputed I think -AK */
62 u32 window_clamp; /* window clamp at creation time */
63 u32 rcv_wnd; /* rcv_wnd offered first time */
65 struct timer_list rsk_timer;
66 const struct request_sock_ops *rsk_ops;
72 static inline struct request_sock *
73 reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener)
75 struct request_sock *req = kmem_cache_alloc(ops->slab, GFP_ATOMIC);
79 sock_hold(sk_listener);
80 req->rsk_listener = sk_listener;
82 /* Following is temporary. It is coupled with debugging
83 * helpers in reqsk_put() & reqsk_free()
85 atomic_set(&req->rsk_refcnt, 0);
90 static inline struct request_sock *inet_reqsk(struct sock *sk)
92 return (struct request_sock *)sk;
95 static inline struct sock *req_to_sk(struct request_sock *req)
97 return (struct sock *)req;
100 static inline void reqsk_free(struct request_sock *req)
102 /* temporary debugging */
103 WARN_ON_ONCE(atomic_read(&req->rsk_refcnt) != 0);
105 req->rsk_ops->destructor(req);
106 if (req->rsk_listener)
107 sock_put(req->rsk_listener);
108 kmem_cache_free(req->rsk_ops->slab, req);
111 static inline void reqsk_put(struct request_sock *req)
113 if (atomic_dec_and_test(&req->rsk_refcnt))
117 extern int sysctl_max_syn_backlog;
119 /** struct listen_sock - listen state
121 * @max_qlen_log - log_2 of maximal queued SYNs/REQUESTs
124 int qlen_inc; /* protected by listener lock */
125 int young_inc;/* protected by listener lock */
127 /* following fields can be updated by timer */
128 atomic_t qlen_dec; /* qlen = qlen_inc - qlen_dec */
131 u8 max_qlen_log ____cacheline_aligned_in_smp;
133 /* 2 bytes hole, try to use */
135 u32 nr_table_entries;
136 struct request_sock *syn_table[0];
140 * For a TCP Fast Open listener -
141 * lock - protects the access to all the reqsk, which is co-owned by
142 * the listener and the child socket.
143 * qlen - pending TFO requests (still in TCP_SYN_RECV).
144 * max_qlen - max TFO reqs allowed before TFO is disabled.
146 * XXX (TFO) - ideally these fields can be made as part of "listen_sock"
147 * structure above. But there is some implementation difficulty due to
148 * listen_sock being part of request_sock_queue hence will be freed when
149 * a listener is stopped. But TFO related fields may continue to be
150 * accessed even after a listener is closed, until its sk_refcnt drops
151 * to 0 implying no more outstanding TFO reqs. One solution is to keep
152 * listen_opt around until sk_refcnt drops to 0. But there is some other
153 * complexity that needs to be resolved. E.g., a listener can be disabled
154 * temporarily through shutdown()->tcp_disconnect(), and re-enabled later.
156 struct fastopen_queue {
157 struct request_sock *rskq_rst_head; /* Keep track of past TFO */
158 struct request_sock *rskq_rst_tail; /* requests that caused RST.
159 * This is part of the defense
160 * against spoofing attack.
163 int qlen; /* # of pending (TCP_SYN_RECV) reqs */
164 int max_qlen; /* != 0 iff TFO is currently enabled */
167 /** struct request_sock_queue - queue of request_socks
169 * @rskq_accept_head - FIFO head of established children
170 * @rskq_accept_tail - FIFO tail of established children
171 * @rskq_defer_accept - User waits for some data after accept()
172 * @syn_wait_lock - serializer
174 * %syn_wait_lock is necessary only to avoid proc interface having to grab the main
175 * lock sock while browsing the listening hash (otherwise it's deadlock prone).
177 * This lock is acquired in read mode only from listening_get_next() seq_file
178 * op and it's acquired in write mode _only_ from code that is actively
179 * changing rskq_accept_head. All readers that are holding the master sock lock
180 * don't need to grab this lock in read mode too as rskq_accept_head. writes
181 * are always protected from the main sock lock.
183 struct request_sock_queue {
184 struct request_sock *rskq_accept_head;
185 struct request_sock *rskq_accept_tail;
186 u8 rskq_defer_accept;
187 struct listen_sock *listen_opt;
188 struct fastopen_queue *fastopenq; /* This is non-NULL iff TFO has been
189 * enabled on this listener. Check
190 * max_qlen != 0 in fastopen_queue
191 * to determine if TFO is enabled
192 * right at this moment.
195 /* temporary alignment, our goal is to get rid of this lock */
196 rwlock_t syn_wait_lock ____cacheline_aligned_in_smp;
199 int reqsk_queue_alloc(struct request_sock_queue *queue,
200 unsigned int nr_table_entries);
202 void __reqsk_queue_destroy(struct request_sock_queue *queue);
203 void reqsk_queue_destroy(struct request_sock_queue *queue);
204 void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
207 static inline struct request_sock *
208 reqsk_queue_yank_acceptq(struct request_sock_queue *queue)
210 struct request_sock *req = queue->rskq_accept_head;
212 queue->rskq_accept_head = NULL;
216 static inline int reqsk_queue_empty(struct request_sock_queue *queue)
218 return queue->rskq_accept_head == NULL;
221 static inline void reqsk_queue_unlink(struct request_sock_queue *queue,
222 struct request_sock *req)
224 struct listen_sock *lopt = queue->listen_opt;
225 struct request_sock **prev;
227 write_lock(&queue->syn_wait_lock);
229 prev = &lopt->syn_table[req->rsk_hash];
231 prev = &(*prev)->dl_next;
232 *prev = req->dl_next;
234 write_unlock(&queue->syn_wait_lock);
235 if (del_timer(&req->rsk_timer))
239 static inline void reqsk_queue_add(struct request_sock_queue *queue,
240 struct request_sock *req,
245 sk_acceptq_added(parent);
247 if (queue->rskq_accept_head == NULL)
248 queue->rskq_accept_head = req;
250 queue->rskq_accept_tail->dl_next = req;
252 queue->rskq_accept_tail = req;
256 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue)
258 struct request_sock *req = queue->rskq_accept_head;
260 WARN_ON(req == NULL);
262 queue->rskq_accept_head = req->dl_next;
263 if (queue->rskq_accept_head == NULL)
264 queue->rskq_accept_tail = NULL;
269 static inline void reqsk_queue_removed(struct request_sock_queue *queue,
270 const struct request_sock *req)
272 struct listen_sock *lopt = queue->listen_opt;
274 if (req->num_timeout == 0)
275 atomic_inc(&lopt->young_dec);
276 atomic_inc(&lopt->qlen_dec);
279 static inline void reqsk_queue_added(struct request_sock_queue *queue)
281 struct listen_sock *lopt = queue->listen_opt;
287 static inline int listen_sock_qlen(const struct listen_sock *lopt)
289 return lopt->qlen_inc - atomic_read(&lopt->qlen_dec);
292 static inline int listen_sock_young(const struct listen_sock *lopt)
294 return lopt->young_inc - atomic_read(&lopt->young_dec);
297 static inline int reqsk_queue_len(const struct request_sock_queue *queue)
299 const struct listen_sock *lopt = queue->listen_opt;
301 return lopt ? listen_sock_qlen(lopt) : 0;
304 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
306 return listen_sock_young(queue->listen_opt);
309 static inline int reqsk_queue_is_full(const struct request_sock_queue *queue)
311 return reqsk_queue_len(queue) >> queue->listen_opt->max_qlen_log;
314 void reqsk_queue_hash_req(struct request_sock_queue *queue,
315 u32 hash, struct request_sock *req,
316 unsigned long timeout);
318 #endif /* _REQUEST_SOCK_H */