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TOMOYO Linux Cross Reference
Linux/include/net/request_sock.h

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  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 
 72 static inline struct request_sock *inet_reqsk(const struct sock *sk)
 73 {
 74         return (struct request_sock *)sk;
 75 }
 76 
 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 *
 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 
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 
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 
155 /** struct request_sock_queue - queue of request_socks
156  *
157  * @rskq_accept_head - FIFO head of established children
158  * @rskq_accept_tail - FIFO tail of established children
159  * @rskq_defer_accept - User waits for some data after accept()
160  *
161  */
162 struct request_sock_queue {
163         spinlock_t              rskq_lock;
164         u8                      rskq_defer_accept;
165 
166         u32                     synflood_warned;
167         atomic_t                qlen;
168         atomic_t                young;
169 
170         struct request_sock     *rskq_accept_head;
171         struct request_sock     *rskq_accept_tail;
172         struct fastopen_queue   fastopenq;  /* Check max_qlen != 0 to determine
173                                              * if TFO is enabled.
174                                              */
175 };
176 
177 void reqsk_queue_alloc(struct request_sock_queue *queue);
178 
179 void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
180                            bool reset);
181 
182 static inline bool reqsk_queue_empty(const struct request_sock_queue *queue)
183 {
184         return queue->rskq_accept_head == NULL;
185 }
186 
187 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue,
188                                                       struct sock *parent)
189 {
190         struct request_sock *req;
191 
192         spin_lock_bh(&queue->rskq_lock);
193         req = queue->rskq_accept_head;
194         if (req) {
195                 sk_acceptq_removed(parent);
196                 queue->rskq_accept_head = req->dl_next;
197                 if (queue->rskq_accept_head == NULL)
198                         queue->rskq_accept_tail = NULL;
199         }
200         spin_unlock_bh(&queue->rskq_lock);
201         return req;
202 }
203 
204 static inline void reqsk_queue_removed(struct request_sock_queue *queue,
205                                        const struct request_sock *req)
206 {
207         if (req->num_timeout == 0)
208                 atomic_dec(&queue->young);
209         atomic_dec(&queue->qlen);
210 }
211 
212 static inline void reqsk_queue_added(struct request_sock_queue *queue)
213 {
214         atomic_inc(&queue->young);
215         atomic_inc(&queue->qlen);
216 }
217 
218 static inline int reqsk_queue_len(const struct request_sock_queue *queue)
219 {
220         return atomic_read(&queue->qlen);
221 }
222 
223 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
224 {
225         return atomic_read(&queue->young);
226 }
227 
228 #endif /* _REQUEST_SOCK_H */
229 

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