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
25 struct request_sock;
26 struct sk_buff;
27 struct dst_entry;
28 struct proto;
29
30 struct request_sock_ops {
31 int family;
32 int obj_size;
33 struct kmem_cache *slab;
34 char *slab_name;
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,
40 struct sk_buff *skb);
41 void (*destructor)(struct request_sock *req);
42 void (*syn_ack_timeout)(struct sock *sk,
43 struct request_sock *req);
44 };
45
46 extern int inet_rtx_syn_ack(struct sock *parent, struct request_sock *req);
47
48 /* struct request_sock - mini sock to represent a connection request
49 */
50 struct request_sock {
51 struct request_sock *dl_next;
52 u16 mss;
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 */
59 u32 ts_recent;
60 unsigned long expires;
61 const struct request_sock_ops *rsk_ops;
62 struct sock *sk;
63 u32 secid;
64 u32 peer_secid;
65 };
66
reqsk_alloc(const struct request_sock_ops * ops)67 static inline struct request_sock *reqsk_alloc(const struct request_sock_ops *ops)
68 {
69 struct request_sock *req = kmem_cache_alloc(ops->slab, GFP_ATOMIC);
70
71 if (req != NULL)
72 req->rsk_ops = ops;
73
74 return req;
75 }
76
__reqsk_free(struct request_sock * req)77 static inline void __reqsk_free(struct request_sock *req)
78 {
79 kmem_cache_free(req->rsk_ops->slab, req);
80 }
81
reqsk_free(struct request_sock * req)82 static inline void reqsk_free(struct request_sock *req)
83 {
84 req->rsk_ops->destructor(req);
85 __reqsk_free(req);
86 }
87
88 extern int sysctl_max_syn_backlog;
89
90 /** struct listen_sock - listen state
91 *
92 * @max_qlen_log - log_2 of maximal queued SYNs/REQUESTs
93 */
94 struct listen_sock {
95 u8 max_qlen_log;
96 u8 synflood_warned;
97 /* 2 bytes hole, try to use */
98 int qlen;
99 int qlen_young;
100 int clock_hand;
101 u32 hash_rnd;
102 u32 nr_table_entries;
103 struct request_sock *syn_table[0];
104 };
105
106 /*
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.
112 *
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.
122 */
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.
128 */
129 spinlock_t lock;
130 int qlen; /* # of pending (TCP_SYN_RECV) reqs */
131 int max_qlen; /* != 0 iff TFO is currently enabled */
132 };
133
134 /** struct request_sock_queue - queue of request_socks
135 *
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
140 *
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).
143 *
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.
149 */
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.
162 */
163 };
164
165 extern int reqsk_queue_alloc(struct request_sock_queue *queue,
166 unsigned int nr_table_entries);
167
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);
172
173 static inline struct request_sock *
reqsk_queue_yank_acceptq(struct request_sock_queue * queue)174 reqsk_queue_yank_acceptq(struct request_sock_queue *queue)
175 {
176 struct request_sock *req = queue->rskq_accept_head;
177
178 queue->rskq_accept_head = NULL;
179 return req;
180 }
181
reqsk_queue_empty(struct request_sock_queue * queue)182 static inline int reqsk_queue_empty(struct request_sock_queue *queue)
183 {
184 return queue->rskq_accept_head == NULL;
185 }
186
reqsk_queue_unlink(struct request_sock_queue * queue,struct request_sock * req,struct request_sock ** prev_req)187 static inline void reqsk_queue_unlink(struct request_sock_queue *queue,
188 struct request_sock *req,
189 struct request_sock **prev_req)
190 {
191 write_lock(&queue->syn_wait_lock);
192 *prev_req = req->dl_next;
193 write_unlock(&queue->syn_wait_lock);
194 }
195
reqsk_queue_add(struct request_sock_queue * queue,struct request_sock * req,struct sock * parent,struct sock * child)196 static inline void reqsk_queue_add(struct request_sock_queue *queue,
197 struct request_sock *req,
198 struct sock *parent,
199 struct sock *child)
200 {
201 req->sk = child;
202 sk_acceptq_added(parent);
203
204 if (queue->rskq_accept_head == NULL)
205 queue->rskq_accept_head = req;
206 else
207 queue->rskq_accept_tail->dl_next = req;
208
209 queue->rskq_accept_tail = req;
210 req->dl_next = NULL;
211 }
212
reqsk_queue_remove(struct request_sock_queue * queue)213 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue)
214 {
215 struct request_sock *req = queue->rskq_accept_head;
216
217 WARN_ON(req == NULL);
218
219 queue->rskq_accept_head = req->dl_next;
220 if (queue->rskq_accept_head == NULL)
221 queue->rskq_accept_tail = NULL;
222
223 return req;
224 }
225
reqsk_queue_removed(struct request_sock_queue * queue,struct request_sock * req)226 static inline int reqsk_queue_removed(struct request_sock_queue *queue,
227 struct request_sock *req)
228 {
229 struct listen_sock *lopt = queue->listen_opt;
230
231 if (req->num_timeout == 0)
232 --lopt->qlen_young;
233
234 return --lopt->qlen;
235 }
236
reqsk_queue_added(struct request_sock_queue * queue)237 static inline int reqsk_queue_added(struct request_sock_queue *queue)
238 {
239 struct listen_sock *lopt = queue->listen_opt;
240 const int prev_qlen = lopt->qlen;
241
242 lopt->qlen_young++;
243 lopt->qlen++;
244 return prev_qlen;
245 }
246
reqsk_queue_len(const struct request_sock_queue * queue)247 static inline int reqsk_queue_len(const struct request_sock_queue *queue)
248 {
249 return queue->listen_opt != NULL ? queue->listen_opt->qlen : 0;
250 }
251
reqsk_queue_len_young(const struct request_sock_queue * queue)252 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
253 {
254 return queue->listen_opt->qlen_young;
255 }
256
reqsk_queue_is_full(const struct request_sock_queue * queue)257 static inline int reqsk_queue_is_full(const struct request_sock_queue *queue)
258 {
259 return queue->listen_opt->qlen >> queue->listen_opt->max_qlen_log;
260 }
261
reqsk_queue_hash_req(struct request_sock_queue * queue,u32 hash,struct request_sock * req,unsigned long timeout)262 static inline void reqsk_queue_hash_req(struct request_sock_queue *queue,
263 u32 hash, struct request_sock *req,
264 unsigned long timeout)
265 {
266 struct listen_sock *lopt = queue->listen_opt;
267
268 req->expires = jiffies + timeout;
269 req->num_retrans = 0;
270 req->num_timeout = 0;
271 req->sk = NULL;
272 req->dl_next = lopt->syn_table[hash];
273
274 write_lock(&queue->syn_wait_lock);
275 lopt->syn_table[hash] = req;
276 write_unlock(&queue->syn_wait_lock);
277 }
278
279 #endif /* _REQUEST_SOCK_H */
280