2 * NET Generic infrastructure for Network protocols.
4 * Definitions for request_sock
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 extern 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 request_sock *dl_next;
53 u8 num_retrans; /* number of retransmits */
54 u8 cookie_ts:1; /* syncookie: encode tcpopts in timestamp */
55 u8 num_timeout:7; /* number of timeouts */
56 /* The following two fields can be easily recomputed I think -AK */
57 u32 window_clamp; /* window clamp at creation time */
58 u32 rcv_wnd; /* rcv_wnd offered first time */
60 unsigned long expires;
61 const struct request_sock_ops *rsk_ops;
67 static inline struct request_sock *reqsk_alloc(const struct request_sock_ops *ops)
69 struct request_sock *req = kmem_cache_alloc(ops->slab, GFP_ATOMIC);
77 static inline void __reqsk_free(struct request_sock *req)
79 kmem_cache_free(req->rsk_ops->slab, req);
82 static inline void reqsk_free(struct request_sock *req)
84 req->rsk_ops->destructor(req);
88 extern int sysctl_max_syn_backlog;
90 /** struct listen_sock - listen state
92 * @max_qlen_log - log_2 of maximal queued SYNs/REQUESTs
97 /* 2 bytes hole, try to use */
102 u32 nr_table_entries;
103 struct request_sock *syn_table[0];
107 * For a TCP Fast Open listener -
108 * lock - protects the access to all the reqsk, which is co-owned by
109 * the listener and the child socket.
110 * qlen - pending TFO requests (still in TCP_SYN_RECV).
111 * max_qlen - max TFO reqs allowed before TFO is disabled.
113 * XXX (TFO) - ideally these fields can be made as part of "listen_sock"
114 * structure above. But there is some implementation difficulty due to
115 * listen_sock being part of request_sock_queue hence will be freed when
116 * a listener is stopped. But TFO related fields may continue to be
117 * accessed even after a listener is closed, until its sk_refcnt drops
118 * to 0 implying no more outstanding TFO reqs. One solution is to keep
119 * listen_opt around until sk_refcnt drops to 0. But there is some other
120 * complexity that needs to be resolved. E.g., a listener can be disabled
121 * temporarily through shutdown()->tcp_disconnect(), and re-enabled later.
123 struct fastopen_queue {
124 struct request_sock *rskq_rst_head; /* Keep track of past TFO */
125 struct request_sock *rskq_rst_tail; /* requests that caused RST.
126 * This is part of the defense
127 * against spoofing attack.
130 int qlen; /* # of pending (TCP_SYN_RECV) reqs */
131 int max_qlen; /* != 0 iff TFO is currently enabled */
134 /** struct request_sock_queue - queue of request_socks
136 * @rskq_accept_head - FIFO head of established children
137 * @rskq_accept_tail - FIFO tail of established children
138 * @rskq_defer_accept - User waits for some data after accept()
139 * @syn_wait_lock - serializer
141 * %syn_wait_lock is necessary only to avoid proc interface having to grab the main
142 * lock sock while browsing the listening hash (otherwise it's deadlock prone).
144 * This lock is acquired in read mode only from listening_get_next() seq_file
145 * op and it's acquired in write mode _only_ from code that is actively
146 * changing rskq_accept_head. All readers that are holding the master sock lock
147 * don't need to grab this lock in read mode too as rskq_accept_head. writes
148 * are always protected from the main sock lock.
150 struct request_sock_queue {
151 struct request_sock *rskq_accept_head;
152 struct request_sock *rskq_accept_tail;
153 rwlock_t syn_wait_lock;
154 u8 rskq_defer_accept;
155 /* 3 bytes hole, try to pack */
156 struct listen_sock *listen_opt;
157 struct fastopen_queue *fastopenq; /* This is non-NULL iff TFO has been
158 * enabled on this listener. Check
159 * max_qlen != 0 in fastopen_queue
160 * to determine if TFO is enabled
161 * right at this moment.
165 extern int reqsk_queue_alloc(struct request_sock_queue *queue,
166 unsigned int nr_table_entries);
168 extern void __reqsk_queue_destroy(struct request_sock_queue *queue);
169 extern void reqsk_queue_destroy(struct request_sock_queue *queue);
170 extern void reqsk_fastopen_remove(struct sock *sk,
171 struct request_sock *req, bool reset);
173 static inline struct request_sock *
174 reqsk_queue_yank_acceptq(struct request_sock_queue *queue)
176 struct request_sock *req = queue->rskq_accept_head;
178 queue->rskq_accept_head = NULL;
182 static inline int reqsk_queue_empty(struct request_sock_queue *queue)
184 return queue->rskq_accept_head == NULL;
187 static inline void reqsk_queue_unlink(struct request_sock_queue *queue,
188 struct request_sock *req,
189 struct request_sock **prev_req)
191 write_lock(&queue->syn_wait_lock);
192 *prev_req = req->dl_next;
193 write_unlock(&queue->syn_wait_lock);
196 static inline void reqsk_queue_add(struct request_sock_queue *queue,
197 struct request_sock *req,
202 sk_acceptq_added(parent);
204 if (queue->rskq_accept_head == NULL)
205 queue->rskq_accept_head = req;
207 queue->rskq_accept_tail->dl_next = req;
209 queue->rskq_accept_tail = req;
213 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue)
215 struct request_sock *req = queue->rskq_accept_head;
217 WARN_ON(req == NULL);
219 queue->rskq_accept_head = req->dl_next;
220 if (queue->rskq_accept_head == NULL)
221 queue->rskq_accept_tail = NULL;
226 static inline int reqsk_queue_removed(struct request_sock_queue *queue,
227 struct request_sock *req)
229 struct listen_sock *lopt = queue->listen_opt;
231 if (req->num_timeout == 0)
237 static inline int reqsk_queue_added(struct request_sock_queue *queue)
239 struct listen_sock *lopt = queue->listen_opt;
240 const int prev_qlen = lopt->qlen;
247 static inline int reqsk_queue_len(const struct request_sock_queue *queue)
249 return queue->listen_opt != NULL ? queue->listen_opt->qlen : 0;
252 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
254 return queue->listen_opt->qlen_young;
257 static inline int reqsk_queue_is_full(const struct request_sock_queue *queue)
259 return queue->listen_opt->qlen >> queue->listen_opt->max_qlen_log;
262 static inline void reqsk_queue_hash_req(struct request_sock_queue *queue,
263 u32 hash, struct request_sock *req,
264 unsigned long timeout)
266 struct listen_sock *lopt = queue->listen_opt;
268 req->expires = jiffies + timeout;
269 req->num_retrans = 0;
270 req->num_timeout = 0;
272 req->dl_next = lopt->syn_table[hash];
274 write_lock(&queue->syn_wait_lock);
275 lopt->syn_table[hash] = req;
276 write_unlock(&queue->syn_wait_lock);
279 #endif /* _REQUEST_SOCK_H */