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 #include <linux/refcount.h>
23
24 #include <net/sock.h>
25
26 struct request_sock;
27 struct sk_buff;
28 struct dst_entry;
29 struct proto;
30
31 struct request_sock_ops {
32 int family;
33 unsigned int obj_size;
34 struct kmem_cache *slab;
35 char *slab_name;
36 int (*rtx_syn_ack)(const struct sock *sk,
37 struct request_sock *req);
38 void (*send_ack)(const struct sock *sk, struct sk_buff *skb,
39 struct request_sock *req);
40 void (*send_reset)(const struct sock *sk,
41 struct sk_buff *skb);
42 void (*destructor)(struct request_sock *req);
43 void (*syn_ack_timeout)(const struct request_sock *req);
44 };
45
46 int inet_rtx_syn_ack(const 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 sock_common __req_common;
52 #define rsk_refcnt __req_common.skc_refcnt
53 #define rsk_hash __req_common.skc_hash
54 #define rsk_listener __req_common.skc_listener
55 #define rsk_window_clamp __req_common.skc_window_clamp
56 #define rsk_rcv_wnd __req_common.skc_rcv_wnd
57
58 struct request_sock *dl_next;
59 u16 mss;
60 u8 num_retrans; /* number of retransmits */
61 u8 cookie_ts:1; /* syncookie: encode tcpopts in timestamp */
62 u8 num_timeout:7; /* number of timeouts */
63 u32 ts_recent;
64 struct timer_list rsk_timer;
65 const struct request_sock_ops *rsk_ops;
66 struct sock *sk;
67 u32 *saved_syn;
68 u32 secid;
69 u32 peer_secid;
70 };
71
inet_reqsk(const struct sock * sk)72 static inline struct request_sock *inet_reqsk(const struct sock *sk)
73 {
74 return (struct request_sock *)sk;
75 }
76
req_to_sk(struct request_sock * req)77 static inline struct sock *req_to_sk(struct request_sock *req)
78 {
79 return (struct sock *)req;
80 }
81
82 static inline struct request_sock *
reqsk_alloc(const struct request_sock_ops * ops,struct sock * sk_listener,bool attach_listener)83 reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener,
84 bool attach_listener)
85 {
86 struct request_sock *req;
87
88 req = kmem_cache_alloc(ops->slab, GFP_ATOMIC | __GFP_NOWARN);
89 if (!req)
90 return NULL;
91 req->rsk_listener = NULL;
92 if (attach_listener) {
93 if (unlikely(!refcount_inc_not_zero(&sk_listener->sk_refcnt))) {
94 kmem_cache_free(ops->slab, req);
95 return NULL;
96 }
97 req->rsk_listener = sk_listener;
98 }
99 req->rsk_ops = ops;
100 req_to_sk(req)->sk_prot = sk_listener->sk_prot;
101 sk_node_init(&req_to_sk(req)->sk_node);
102 sk_tx_queue_clear(req_to_sk(req));
103 req->saved_syn = NULL;
104 refcount_set(&req->rsk_refcnt, 0);
105
106 return req;
107 }
108
reqsk_free(struct request_sock * req)109 static inline void reqsk_free(struct request_sock *req)
110 {
111 /* temporary debugging */
112 WARN_ON_ONCE(refcount_read(&req->rsk_refcnt) != 0);
113
114 req->rsk_ops->destructor(req);
115 if (req->rsk_listener)
116 sock_put(req->rsk_listener);
117 kfree(req->saved_syn);
118 kmem_cache_free(req->rsk_ops->slab, req);
119 }
120
reqsk_put(struct request_sock * req)121 static inline void reqsk_put(struct request_sock *req)
122 {
123 if (refcount_dec_and_test(&req->rsk_refcnt))
124 reqsk_free(req);
125 }
126
127 /*
128 * For a TCP Fast Open listener -
129 * lock - protects the access to all the reqsk, which is co-owned by
130 * the listener and the child socket.
131 * qlen - pending TFO requests (still in TCP_SYN_RECV).
132 * max_qlen - max TFO reqs allowed before TFO is disabled.
133 *
134 * XXX (TFO) - ideally these fields can be made as part of "listen_sock"
135 * structure above. But there is some implementation difficulty due to
136 * listen_sock being part of request_sock_queue hence will be freed when
137 * a listener is stopped. But TFO related fields may continue to be
138 * accessed even after a listener is closed, until its sk_refcnt drops
139 * to 0 implying no more outstanding TFO reqs. One solution is to keep
140 * listen_opt around until sk_refcnt drops to 0. But there is some other
141 * complexity that needs to be resolved. E.g., a listener can be disabled
142 * temporarily through shutdown()->tcp_disconnect(), and re-enabled later.
143 */
144 struct fastopen_queue {
145 struct request_sock *rskq_rst_head; /* Keep track of past TFO */
146 struct request_sock *rskq_rst_tail; /* requests that caused RST.
147 * This is part of the defense
148 * against spoofing attack.
149 */
150 spinlock_t lock;
151 int qlen; /* # of pending (TCP_SYN_RECV) reqs */
152 int max_qlen; /* != 0 iff TFO is currently enabled */
153
154 struct tcp_fastopen_context __rcu *ctx; /* cipher context for cookie */
155 };
156
157 /** struct request_sock_queue - queue of request_socks
158 *
159 * @rskq_accept_head - FIFO head of established children
160 * @rskq_accept_tail - FIFO tail of established children
161 * @rskq_defer_accept - User waits for some data after accept()
162 *
163 */
164 struct request_sock_queue {
165 spinlock_t rskq_lock;
166 u8 rskq_defer_accept;
167
168 u32 synflood_warned;
169 atomic_t qlen;
170 atomic_t young;
171
172 struct request_sock *rskq_accept_head;
173 struct request_sock *rskq_accept_tail;
174 struct fastopen_queue fastopenq; /* Check max_qlen != 0 to determine
175 * if TFO is enabled.
176 */
177 };
178
179 void reqsk_queue_alloc(struct request_sock_queue *queue);
180
181 void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
182 bool reset);
183
reqsk_queue_empty(const struct request_sock_queue * queue)184 static inline bool reqsk_queue_empty(const struct request_sock_queue *queue)
185 {
186 return READ_ONCE(queue->rskq_accept_head) == NULL;
187 }
188
reqsk_queue_remove(struct request_sock_queue * queue,struct sock * parent)189 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue,
190 struct sock *parent)
191 {
192 struct request_sock *req;
193
194 spin_lock_bh(&queue->rskq_lock);
195 req = queue->rskq_accept_head;
196 if (req) {
197 sk_acceptq_removed(parent);
198 WRITE_ONCE(queue->rskq_accept_head, req->dl_next);
199 if (queue->rskq_accept_head == NULL)
200 queue->rskq_accept_tail = NULL;
201 }
202 spin_unlock_bh(&queue->rskq_lock);
203 return req;
204 }
205
reqsk_queue_removed(struct request_sock_queue * queue,const struct request_sock * req)206 static inline void reqsk_queue_removed(struct request_sock_queue *queue,
207 const struct request_sock *req)
208 {
209 if (req->num_timeout == 0)
210 atomic_dec(&queue->young);
211 atomic_dec(&queue->qlen);
212 }
213
reqsk_queue_added(struct request_sock_queue * queue)214 static inline void reqsk_queue_added(struct request_sock_queue *queue)
215 {
216 atomic_inc(&queue->young);
217 atomic_inc(&queue->qlen);
218 }
219
reqsk_queue_len(const struct request_sock_queue * queue)220 static inline int reqsk_queue_len(const struct request_sock_queue *queue)
221 {
222 return atomic_read(&queue->qlen);
223 }
224
reqsk_queue_len_young(const struct request_sock_queue * queue)225 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
226 {
227 return atomic_read(&queue->young);
228 }
229
230 #endif /* _REQUEST_SOCK_H */
231