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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
  22 #include <net/sock.h>
  23
  24 struct request_sock;
  25 struct sk_buff;
  26 struct dst_entry;
  27 struct proto;
  28
  29 struct request_sock_ops {
  30         int             family;
  31         kmem_cache_t    *slab;
  32         int             obj_size;
  33         int             (*rtx_syn_ack)(struct sock *sk,
  34                                        struct request_sock *req,
  35                                        struct dst_entry *dst);
  36         void            (*send_ack)(struct sk_buff *skb,
  37                                     struct request_sock *req);
  38         void            (*send_reset)(struct sk_buff *skb);
  39         void            (*destructor)(struct request_sock *req);
  40 };
  41
  42 /* struct request_sock - mini sock to represent a connection request
  43  */
  44 struct request_sock {
  45         struct request_sock             *dl_next; /* Must be first member! */
  46         u16                             mss;
  47         u8                              retrans;
  48         u8                              __pad;
  49         /* The following two fields can be easily recomputed I think -AK */
  50         u32                             window_clamp; /* window clamp at creation time */
  51         u32                             rcv_wnd;          /* rcv_wnd offered first time */
  52         u32                             ts_recent;
  53         unsigned long                   expires;
  54         struct request_sock_ops         *rsk_ops;
  55         struct sock                     *sk;
  56 };
  57
  58 static inline struct request_sock *reqsk_alloc(struct request_sock_ops *ops)
  59 {
  60         struct request_sock *req = kmem_cache_alloc(ops->slab, SLAB_ATOMIC);
  61
  62         if (req != NULL)
  63                 req->rsk_ops = ops;
  64
  65         return req;
  66 }
  67
  68 static inline void __reqsk_free(struct request_sock *req)
  69 {
  70         kmem_cache_free(req->rsk_ops->slab, req);
  71 }
  72
  73 static inline void reqsk_free(struct request_sock *req)
  74 {
  75         req->rsk_ops->destructor(req);
  76         __reqsk_free(req);
  77 }
  78
  79 extern int sysctl_max_syn_backlog;
  80
  81 /** struct listen_sock - listen state
  82  *
  83  * @max_qlen_log - log_2 of maximal queued SYNs/REQUESTs
  84  */
  85 struct listen_sock {
  86         u8                      max_qlen_log;
  87         /* 3 bytes hole, try to use */
  88         int                     qlen;
  89         int                     qlen_young;
  90         int                     clock_hand;
  91         u32                     hash_rnd;
  92         u32                     nr_table_entries;
  93         struct request_sock     *syn_table[0];
  94 };
  95
  96 /** struct request_sock_queue - queue of request_socks
  97  *
  98  * @rskq_accept_head - FIFO head of established children
  99  * @rskq_accept_tail - FIFO tail of established children
 100  * @rskq_defer_accept - User waits for some data after accept()
 101  * @syn_wait_lock - serializer
 102  *
 103  * %syn_wait_lock is necessary only to avoid proc interface having to grab the main
 104  * lock sock while browsing the listening hash (otherwise it's deadlock prone).
 105  *
 106  * This lock is acquired in read mode only from listening_get_next() seq_file
 107  * op and it's acquired in write mode _only_ from code that is actively
 108  * changing rskq_accept_head. All readers that are holding the master sock lock
 109  * don't need to grab this lock in read mode too as rskq_accept_head. writes
 110  * are always protected from the main sock lock.
 111  */
 112 struct request_sock_queue {
 113         struct request_sock     *rskq_accept_head;
 114         struct request_sock     *rskq_accept_tail;
 115         rwlock_t                syn_wait_lock;
 116         u8                      rskq_defer_accept;
 117         /* 3 bytes hole, try to pack */
 118         struct listen_sock      *listen_opt;
 119 };
 120
 121 extern int reqsk_queue_alloc(struct request_sock_queue *queue,
 122                              const int nr_table_entries);
 123
 124 static inline struct listen_sock *reqsk_queue_yank_listen_sk(struct request_sock_queue *queue)
 125 {
 126         struct listen_sock *lopt;
 127
 128         write_lock_bh(&queue->syn_wait_lock);
 129         lopt = queue->listen_opt;
 130         queue->listen_opt = NULL;
 131         write_unlock_bh(&queue->syn_wait_lock);
 132
 133         return lopt;
 134 }
 135
 136 static inline void __reqsk_queue_destroy(struct request_sock_queue *queue)
 137 {
 138         kfree(reqsk_queue_yank_listen_sk(queue));
 139 }
 140
 141 extern void reqsk_queue_destroy(struct request_sock_queue *queue);
 142
 143 static inline struct request_sock *
 144         reqsk_queue_yank_acceptq(struct request_sock_queue *queue)
 145 {
 146         struct request_sock *req = queue->rskq_accept_head;
 147
 148         queue->rskq_accept_head = NULL;
 149         return req;
 150 }
 151
 152 static inline int reqsk_queue_empty(struct request_sock_queue *queue)
 153 {
 154         return queue->rskq_accept_head == NULL;
 155 }
 156
 157 static inline void reqsk_queue_unlink(struct request_sock_queue *queue,
 158                                       struct request_sock *req,
 159                                       struct request_sock **prev_req)
 160 {
 161         write_lock(&queue->syn_wait_lock);
 162         *prev_req = req->dl_next;
 163         write_unlock(&queue->syn_wait_lock);
 164 }
 165
 166 static inline void reqsk_queue_add(struct request_sock_queue *queue,
 167                                    struct request_sock *req,
 168                                    struct sock *parent,
 169                                    struct sock *child)
 170 {
 171         req->sk = child;
 172         sk_acceptq_added(parent);
 173
 174         if (queue->rskq_accept_head == NULL)
 175                 queue->rskq_accept_head = req;
 176         else
 177                 queue->rskq_accept_tail->dl_next = req;
 178
 179         queue->rskq_accept_tail = req;
 180         req->dl_next = NULL;
 181 }
 182
 183 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue)
 184 {
 185         struct request_sock *req = queue->rskq_accept_head;
 186
 187         BUG_TRAP(req != NULL);
 188
 189         queue->rskq_accept_head = req->dl_next;
 190         if (queue->rskq_accept_head == NULL)
 191                 queue->rskq_accept_tail = NULL;
 192
 193         return req;
 194 }
 195
 196 static inline struct sock *reqsk_queue_get_child(struct request_sock_queue *queue,
 197                                                  struct sock *parent)
 198 {
 199         struct request_sock *req = reqsk_queue_remove(queue);
 200         struct sock *child = req->sk;
 201
 202         BUG_TRAP(child != NULL);
 203
 204         sk_acceptq_removed(parent);
 205         __reqsk_free(req);
 206         return child;
 207 }
 208
 209 static inline int reqsk_queue_removed(struct request_sock_queue *queue,
 210                                       struct request_sock *req)
 211 {
 212         struct listen_sock *lopt = queue->listen_opt;
 213
 214         if (req->retrans == 0)
 215                 --lopt->qlen_young;
 216
 217         return --lopt->qlen;
 218 }
 219
 220 static inline int reqsk_queue_added(struct request_sock_queue *queue)
 221 {
 222         struct listen_sock *lopt = queue->listen_opt;
 223         const int prev_qlen = lopt->qlen;
 224
 225         lopt->qlen_young++;
 226         lopt->qlen++;
 227         return prev_qlen;
 228 }
 229
 230 static inline int reqsk_queue_len(const struct request_sock_queue *queue)
 231 {
 232         return queue->listen_opt != NULL ? queue->listen_opt->qlen : 0;
 233 }
 234
 235 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
 236 {
 237         return queue->listen_opt->qlen_young;
 238 }
 239
 240 static inline int reqsk_queue_is_full(const struct request_sock_queue *queue)
 241 {
 242         return queue->listen_opt->qlen >> queue->listen_opt->max_qlen_log;
 243 }
 244
 245 static inline void reqsk_queue_hash_req(struct request_sock_queue *queue,
 246                                         u32 hash, struct request_sock *req,
 247                                         unsigned long timeout)
 248 {
 249         struct listen_sock *lopt = queue->listen_opt;
 250
 251         req->expires = jiffies + timeout;
 252         req->retrans = 0;
 253         req->sk = NULL;
 254         req->dl_next = lopt->syn_table[hash];
 255
 256         write_lock(&queue->syn_wait_lock);
 257         lopt->syn_table[hash] = req;
 258         write_unlock(&queue->syn_wait_lock);
 259 }
 260
 261 #endif /* _REQUEST_SOCK_H */