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 };
74
inet_reqsk(const struct sock * sk)75 static inline struct request_sock *inet_reqsk(const struct sock *sk)
76 {
77 return (struct request_sock *)sk;
78 }
79
req_to_sk(struct request_sock * req)80 static inline struct sock *req_to_sk(struct request_sock *req)
81 {
82 return (struct sock *)req;
83 }
84
85 static inline struct request_sock *
reqsk_alloc(const struct request_sock_ops * ops,struct sock * sk_listener,bool attach_listener)86 reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener,
87 bool attach_listener)
88 {
89 struct request_sock *req;
90
91 req = kmem_cache_alloc(ops->slab, GFP_ATOMIC | __GFP_NOWARN);
92 if (!req)
93 return NULL;
94 req->rsk_listener = NULL;
95 if (attach_listener) {
96 if (unlikely(!refcount_inc_not_zero(&sk_listener->sk_refcnt))) {
97 kmem_cache_free(ops->slab, req);
98 return NULL;
99 }
100 req->rsk_listener = sk_listener;
101 }
102 req->rsk_ops = ops;
103 req_to_sk(req)->sk_prot = sk_listener->sk_prot;
104 sk_node_init(&req_to_sk(req)->sk_node);
105 sk_tx_queue_clear(req_to_sk(req));
106 req->saved_syn = NULL;
107 req->num_timeout = 0;
108 req->num_retrans = 0;
109 req->sk = NULL;
110 refcount_set(&req->rsk_refcnt, 0);
111
112 return req;
113 }
114
__reqsk_free(struct request_sock * req)115 static inline void __reqsk_free(struct request_sock *req)
116 {
117 req->rsk_ops->destructor(req);
118 if (req->rsk_listener)
119 sock_put(req->rsk_listener);
120 kfree(req->saved_syn);
121 kmem_cache_free(req->rsk_ops->slab, req);
122 }
123
reqsk_free(struct request_sock * req)124 static inline void reqsk_free(struct request_sock *req)
125 {
126 WARN_ON_ONCE(refcount_read(&req->rsk_refcnt) != 0);
127 __reqsk_free(req);
128 }
129
reqsk_put(struct request_sock * req)130 static inline void reqsk_put(struct request_sock *req)
131 {
132 if (refcount_dec_and_test(&req->rsk_refcnt))
133 reqsk_free(req);
134 }
135
136 /*
137 * For a TCP Fast Open listener -
138 * lock - protects the access to all the reqsk, which is co-owned by
139 * the listener and the child socket.
140 * qlen - pending TFO requests (still in TCP_SYN_RECV).
141 * max_qlen - max TFO reqs allowed before TFO is disabled.
142 *
143 * XXX (TFO) - ideally these fields can be made as part of "listen_sock"
144 * structure above. But there is some implementation difficulty due to
145 * listen_sock being part of request_sock_queue hence will be freed when
146 * a listener is stopped. But TFO related fields may continue to be
147 * accessed even after a listener is closed, until its sk_refcnt drops
148 * to 0 implying no more outstanding TFO reqs. One solution is to keep
149 * listen_opt around until sk_refcnt drops to 0. But there is some other
150 * complexity that needs to be resolved. E.g., a listener can be disabled
151 * temporarily through shutdown()->tcp_disconnect(), and re-enabled later.
152 */
153 struct fastopen_queue {
154 struct request_sock *rskq_rst_head; /* Keep track of past TFO */
155 struct request_sock *rskq_rst_tail; /* requests that caused RST.
156 * This is part of the defense
157 * against spoofing attack.
158 */
159 spinlock_t lock;
160 int qlen; /* # of pending (TCP_SYN_RECV) reqs */
161 int max_qlen; /* != 0 iff TFO is currently enabled */
162
163 struct tcp_fastopen_context __rcu *ctx; /* cipher context for cookie */
164 };
165
166 /** struct request_sock_queue - queue of request_socks
167 *
168 * @rskq_accept_head - FIFO head of established children
169 * @rskq_accept_tail - FIFO tail of established children
170 * @rskq_defer_accept - User waits for some data after accept()
171 *
172 */
173 struct request_sock_queue {
174 spinlock_t rskq_lock;
175 u8 rskq_defer_accept;
176
177 u32 synflood_warned;
178 atomic_t qlen;
179 atomic_t young;
180
181 struct request_sock *rskq_accept_head;
182 struct request_sock *rskq_accept_tail;
183 struct fastopen_queue fastopenq; /* Check max_qlen != 0 to determine
184 * if TFO is enabled.
185 */
186 };
187
188 void reqsk_queue_alloc(struct request_sock_queue *queue);
189
190 void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
191 bool reset);
192
reqsk_queue_empty(const struct request_sock_queue * queue)193 static inline bool reqsk_queue_empty(const struct request_sock_queue *queue)
194 {
195 return READ_ONCE(queue->rskq_accept_head) == NULL;
196 }
197
reqsk_queue_remove(struct request_sock_queue * queue,struct sock * parent)198 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue,
199 struct sock *parent)
200 {
201 struct request_sock *req;
202
203 spin_lock_bh(&queue->rskq_lock);
204 req = queue->rskq_accept_head;
205 if (req) {
206 sk_acceptq_removed(parent);
207 WRITE_ONCE(queue->rskq_accept_head, req->dl_next);
208 if (queue->rskq_accept_head == NULL)
209 queue->rskq_accept_tail = NULL;
210 }
211 spin_unlock_bh(&queue->rskq_lock);
212 return req;
213 }
214
reqsk_queue_removed(struct request_sock_queue * queue,const struct request_sock * req)215 static inline void reqsk_queue_removed(struct request_sock_queue *queue,
216 const struct request_sock *req)
217 {
218 if (req->num_timeout == 0)
219 atomic_dec(&queue->young);
220 atomic_dec(&queue->qlen);
221 }
222
reqsk_queue_added(struct request_sock_queue * queue)223 static inline void reqsk_queue_added(struct request_sock_queue *queue)
224 {
225 atomic_inc(&queue->young);
226 atomic_inc(&queue->qlen);
227 }
228
reqsk_queue_len(const struct request_sock_queue * queue)229 static inline int reqsk_queue_len(const struct request_sock_queue *queue)
230 {
231 return atomic_read(&queue->qlen);
232 }
233
reqsk_queue_len_young(const struct request_sock_queue * queue)234 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
235 {
236 return atomic_read(&queue->young);
237 }
238
239 #endif /* _REQUEST_SOCK_H */
240