1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /*
3 * NET Generic infrastructure for Network protocols.
4 *
5 * Definitions for request_sock
6 *
7 * Authors: Arnaldo Carvalho de Melo <acme@conectiva.com.br>
8 *
9 * From code originally in include/net/tcp.h
10 */
11 #ifndef _REQUEST_SOCK_H
12 #define _REQUEST_SOCK_H
13
14 #include <linux/slab.h>
15 #include <linux/spinlock.h>
16 #include <linux/types.h>
17 #include <linux/bug.h>
18 #include <linux/refcount.h>
19
20 #include <net/sock.h>
21
22 struct request_sock;
23 struct sk_buff;
24 struct dst_entry;
25 struct proto;
26
27 struct request_sock_ops {
28 int family;
29 unsigned int obj_size;
30 struct kmem_cache *slab;
31 char *slab_name;
32 int (*rtx_syn_ack)(const struct sock *sk,
33 struct request_sock *req);
34 void (*send_ack)(const struct sock *sk, struct sk_buff *skb,
35 struct request_sock *req);
36 void (*send_reset)(const struct sock *sk,
37 struct sk_buff *skb);
38 void (*destructor)(struct request_sock *req);
39 void (*syn_ack_timeout)(const struct request_sock *req);
40 };
41
42 int inet_rtx_syn_ack(const struct sock *parent, struct request_sock *req);
43
44 struct saved_syn {
45 u32 mac_hdrlen;
46 u32 network_hdrlen;
47 u32 tcp_hdrlen;
48 u8 data[];
49 };
50
51 /* struct request_sock - mini sock to represent a connection request
52 */
53 struct request_sock {
54 struct sock_common __req_common;
55 #define rsk_refcnt __req_common.skc_refcnt
56 #define rsk_hash __req_common.skc_hash
57 #define rsk_listener __req_common.skc_listener
58 #define rsk_window_clamp __req_common.skc_window_clamp
59 #define rsk_rcv_wnd __req_common.skc_rcv_wnd
60
61 struct request_sock *dl_next;
62 u16 mss;
63 u8 num_retrans; /* number of retransmits */
64 u8 syncookie:1; /* syncookie: encode tcpopts in timestamp */
65 u8 num_timeout:7; /* number of timeouts */
66 u32 ts_recent;
67 struct timer_list rsk_timer;
68 const struct request_sock_ops *rsk_ops;
69 struct sock *sk;
70 struct saved_syn *saved_syn;
71 u32 secid;
72 u32 peer_secid;
73 u32 timeout;
74 };
75
inet_reqsk(const struct sock * sk)76 static inline struct request_sock *inet_reqsk(const struct sock *sk)
77 {
78 return (struct request_sock *)sk;
79 }
80
req_to_sk(struct request_sock * req)81 static inline struct sock *req_to_sk(struct request_sock *req)
82 {
83 return (struct sock *)req;
84 }
85
86 static inline struct request_sock *
reqsk_alloc(const struct request_sock_ops * ops,struct sock * sk_listener,bool attach_listener)87 reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener,
88 bool attach_listener)
89 {
90 struct request_sock *req;
91
92 req = kmem_cache_alloc(ops->slab, GFP_ATOMIC | __GFP_NOWARN);
93 if (!req)
94 return NULL;
95 req->rsk_listener = NULL;
96 if (attach_listener) {
97 if (unlikely(!refcount_inc_not_zero(&sk_listener->sk_refcnt))) {
98 kmem_cache_free(ops->slab, req);
99 return NULL;
100 }
101 req->rsk_listener = sk_listener;
102 }
103 req->rsk_ops = ops;
104 req_to_sk(req)->sk_prot = sk_listener->sk_prot;
105 sk_node_init(&req_to_sk(req)->sk_node);
106 sk_tx_queue_clear(req_to_sk(req));
107 req->saved_syn = NULL;
108 req->timeout = 0;
109 req->num_timeout = 0;
110 req->num_retrans = 0;
111 req->sk = NULL;
112 refcount_set(&req->rsk_refcnt, 0);
113
114 return req;
115 }
116
__reqsk_free(struct request_sock * req)117 static inline void __reqsk_free(struct request_sock *req)
118 {
119 req->rsk_ops->destructor(req);
120 if (req->rsk_listener)
121 sock_put(req->rsk_listener);
122 kfree(req->saved_syn);
123 kmem_cache_free(req->rsk_ops->slab, req);
124 }
125
reqsk_free(struct request_sock * req)126 static inline void reqsk_free(struct request_sock *req)
127 {
128 WARN_ON_ONCE(refcount_read(&req->rsk_refcnt) != 0);
129 __reqsk_free(req);
130 }
131
reqsk_put(struct request_sock * req)132 static inline void reqsk_put(struct request_sock *req)
133 {
134 if (refcount_dec_and_test(&req->rsk_refcnt))
135 reqsk_free(req);
136 }
137
138 /*
139 * For a TCP Fast Open listener -
140 * lock - protects the access to all the reqsk, which is co-owned by
141 * the listener and the child socket.
142 * qlen - pending TFO requests (still in TCP_SYN_RECV).
143 * max_qlen - max TFO reqs allowed before TFO is disabled.
144 *
145 * XXX (TFO) - ideally these fields can be made as part of "listen_sock"
146 * structure above. But there is some implementation difficulty due to
147 * listen_sock being part of request_sock_queue hence will be freed when
148 * a listener is stopped. But TFO related fields may continue to be
149 * accessed even after a listener is closed, until its sk_refcnt drops
150 * to 0 implying no more outstanding TFO reqs. One solution is to keep
151 * listen_opt around until sk_refcnt drops to 0. But there is some other
152 * complexity that needs to be resolved. E.g., a listener can be disabled
153 * temporarily through shutdown()->tcp_disconnect(), and re-enabled later.
154 */
155 struct fastopen_queue {
156 struct request_sock *rskq_rst_head; /* Keep track of past TFO */
157 struct request_sock *rskq_rst_tail; /* requests that caused RST.
158 * This is part of the defense
159 * against spoofing attack.
160 */
161 spinlock_t lock;
162 int qlen; /* # of pending (TCP_SYN_RECV) reqs */
163 int max_qlen; /* != 0 iff TFO is currently enabled */
164
165 struct tcp_fastopen_context __rcu *ctx; /* cipher context for cookie */
166 };
167
168 /** struct request_sock_queue - queue of request_socks
169 *
170 * @rskq_accept_head - FIFO head of established children
171 * @rskq_accept_tail - FIFO tail of established children
172 * @rskq_defer_accept - User waits for some data after accept()
173 *
174 */
175 struct request_sock_queue {
176 spinlock_t rskq_lock;
177 u8 rskq_defer_accept;
178
179 u32 synflood_warned;
180 atomic_t qlen;
181 atomic_t young;
182
183 struct request_sock *rskq_accept_head;
184 struct request_sock *rskq_accept_tail;
185 struct fastopen_queue fastopenq; /* Check max_qlen != 0 to determine
186 * if TFO is enabled.
187 */
188 };
189
190 void reqsk_queue_alloc(struct request_sock_queue *queue);
191
192 void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
193 bool reset);
194
reqsk_queue_empty(const struct request_sock_queue * queue)195 static inline bool reqsk_queue_empty(const struct request_sock_queue *queue)
196 {
197 return READ_ONCE(queue->rskq_accept_head) == NULL;
198 }
199
reqsk_queue_remove(struct request_sock_queue * queue,struct sock * parent)200 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue,
201 struct sock *parent)
202 {
203 struct request_sock *req;
204
205 spin_lock_bh(&queue->rskq_lock);
206 req = queue->rskq_accept_head;
207 if (req) {
208 sk_acceptq_removed(parent);
209 WRITE_ONCE(queue->rskq_accept_head, req->dl_next);
210 if (queue->rskq_accept_head == NULL)
211 queue->rskq_accept_tail = NULL;
212 }
213 spin_unlock_bh(&queue->rskq_lock);
214 return req;
215 }
216
reqsk_queue_removed(struct request_sock_queue * queue,const struct request_sock * req)217 static inline void reqsk_queue_removed(struct request_sock_queue *queue,
218 const struct request_sock *req)
219 {
220 if (req->num_timeout == 0)
221 atomic_dec(&queue->young);
222 atomic_dec(&queue->qlen);
223 }
224
reqsk_queue_added(struct request_sock_queue * queue)225 static inline void reqsk_queue_added(struct request_sock_queue *queue)
226 {
227 atomic_inc(&queue->young);
228 atomic_inc(&queue->qlen);
229 }
230
reqsk_queue_len(const struct request_sock_queue * queue)231 static inline int reqsk_queue_len(const struct request_sock_queue *queue)
232 {
233 return atomic_read(&queue->qlen);
234 }
235
reqsk_queue_len_young(const struct request_sock_queue * queue)236 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
237 {
238 return atomic_read(&queue->young);
239 }
240
241 #endif /* _REQUEST_SOCK_H */
242