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)(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
45 int 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 */
49 struct 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
inet_reqsk(const struct sock * sk)71 static inline struct request_sock *inet_reqsk(const struct sock *sk)
72 {
73 return (struct request_sock *)sk;
74 }
75
req_to_sk(struct request_sock * req)76 static inline struct sock *req_to_sk(struct request_sock *req)
77 {
78 return (struct sock *)req;
79 }
80
81 static inline struct request_sock *
reqsk_alloc(const struct request_sock_ops * ops,struct sock * sk_listener,bool attach_listener)82 reqsk_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 if (!req)
89 return NULL;
90 req->rsk_listener = NULL;
91 if (attach_listener) {
92 if (unlikely(!atomic_inc_not_zero(&sk_listener->sk_refcnt))) {
93 kmem_cache_free(ops->slab, req);
94 return NULL;
95 }
96 req->rsk_listener = sk_listener;
97 }
98 req->rsk_ops = ops;
99 req_to_sk(req)->sk_prot = sk_listener->sk_prot;
100 sk_node_init(&req_to_sk(req)->sk_node);
101 sk_tx_queue_clear(req_to_sk(req));
102 req->saved_syn = NULL;
103 atomic_set(&req->rsk_refcnt, 0);
104
105 return req;
106 }
107
reqsk_free(struct request_sock * req)108 static inline void reqsk_free(struct request_sock *req)
109 {
110 /* temporary debugging */
111 WARN_ON_ONCE(atomic_read(&req->rsk_refcnt) != 0);
112
113 req->rsk_ops->destructor(req);
114 if (req->rsk_listener)
115 sock_put(req->rsk_listener);
116 kfree(req->saved_syn);
117 kmem_cache_free(req->rsk_ops->slab, req);
118 }
119
reqsk_put(struct request_sock * req)120 static inline void reqsk_put(struct request_sock *req)
121 {
122 if (atomic_dec_and_test(&req->rsk_refcnt))
123 reqsk_free(req);
124 }
125
126 extern int sysctl_max_syn_backlog;
127
128 /*
129 * For a TCP Fast Open listener -
130 * lock - protects the access to all the reqsk, which is co-owned by
131 * the listener and the child socket.
132 * qlen - pending TFO requests (still in TCP_SYN_RECV).
133 * max_qlen - max TFO reqs allowed before TFO is disabled.
134 *
135 * XXX (TFO) - ideally these fields can be made as part of "listen_sock"
136 * structure above. But there is some implementation difficulty due to
137 * listen_sock being part of request_sock_queue hence will be freed when
138 * a listener is stopped. But TFO related fields may continue to be
139 * accessed even after a listener is closed, until its sk_refcnt drops
140 * to 0 implying no more outstanding TFO reqs. One solution is to keep
141 * listen_opt around until sk_refcnt drops to 0. But there is some other
142 * complexity that needs to be resolved. E.g., a listener can be disabled
143 * temporarily through shutdown()->tcp_disconnect(), and re-enabled later.
144 */
145 struct fastopen_queue {
146 struct request_sock *rskq_rst_head; /* Keep track of past TFO */
147 struct request_sock *rskq_rst_tail; /* requests that caused RST.
148 * This is part of the defense
149 * against spoofing attack.
150 */
151 spinlock_t lock;
152 int qlen; /* # of pending (TCP_SYN_RECV) reqs */
153 int max_qlen; /* != 0 iff TFO is currently enabled */
154 };
155
156 /** struct request_sock_queue - queue of request_socks
157 *
158 * @rskq_accept_head - FIFO head of established children
159 * @rskq_accept_tail - FIFO tail of established children
160 * @rskq_defer_accept - User waits for some data after accept()
161 *
162 */
163 struct request_sock_queue {
164 spinlock_t rskq_lock;
165 u8 rskq_defer_accept;
166
167 u32 synflood_warned;
168 atomic_t qlen;
169 atomic_t young;
170
171 struct request_sock *rskq_accept_head;
172 struct request_sock *rskq_accept_tail;
173 struct fastopen_queue fastopenq; /* Check max_qlen != 0 to determine
174 * if TFO is enabled.
175 */
176 };
177
178 void reqsk_queue_alloc(struct request_sock_queue *queue);
179
180 void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
181 bool reset);
182
reqsk_queue_empty(const struct request_sock_queue * queue)183 static inline bool reqsk_queue_empty(const struct request_sock_queue *queue)
184 {
185 return queue->rskq_accept_head == NULL;
186 }
187
reqsk_queue_remove(struct request_sock_queue * queue,struct sock * parent)188 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue,
189 struct sock *parent)
190 {
191 struct request_sock *req;
192
193 spin_lock_bh(&queue->rskq_lock);
194 req = queue->rskq_accept_head;
195 if (req) {
196 sk_acceptq_removed(parent);
197 queue->rskq_accept_head = req->dl_next;
198 if (queue->rskq_accept_head == NULL)
199 queue->rskq_accept_tail = NULL;
200 }
201 spin_unlock_bh(&queue->rskq_lock);
202 return req;
203 }
204
reqsk_queue_removed(struct request_sock_queue * queue,const struct request_sock * req)205 static inline void reqsk_queue_removed(struct request_sock_queue *queue,
206 const struct request_sock *req)
207 {
208 if (req->num_timeout == 0)
209 atomic_dec(&queue->young);
210 atomic_dec(&queue->qlen);
211 }
212
reqsk_queue_added(struct request_sock_queue * queue)213 static inline void reqsk_queue_added(struct request_sock_queue *queue)
214 {
215 atomic_inc(&queue->young);
216 atomic_inc(&queue->qlen);
217 }
218
reqsk_queue_len(const struct request_sock_queue * queue)219 static inline int reqsk_queue_len(const struct request_sock_queue *queue)
220 {
221 return atomic_read(&queue->qlen);
222 }
223
reqsk_queue_len_young(const struct request_sock_queue * queue)224 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
225 {
226 return atomic_read(&queue->young);
227 }
228
229 #endif /* _REQUEST_SOCK_H */
230