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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         int             obj_size;
  32         struct kmem_cache       *slab;
  33         int             (*rtx_syn_ack)(struct sock *sk,
  34                                        struct request_sock *req);
  35         void            (*send_ack)(struct sk_buff *skb,
  36                                     struct request_sock *req);
  37         void            (*send_reset)(struct sock *sk,
  38                                       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                              cookie_ts; /* syncookie: encode tcpopts in timestamp */
  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         const struct request_sock_ops   *rsk_ops;
  55         struct sock                     *sk;
  56         u32                             secid;
  57         u32                             peer_secid;
  58 };
  59
  60 static inline struct request_sock *reqsk_alloc(const struct request_sock_ops *ops)
  61 {
  62         struct request_sock *req = kmem_cache_alloc(ops->slab, GFP_ATOMIC);
  63
  64         if (req != NULL)
  65                 req->rsk_ops = ops;
  66
  67         return req;
  68 }
  69
  70 static inline void __reqsk_free(struct request_sock *req)
  71 {
  72         kmem_cache_free(req->rsk_ops->slab, req);
  73 }
  74
  75 static inline void reqsk_free(struct request_sock *req)
  76 {
  77         req->rsk_ops->destructor(req);
  78         __reqsk_free(req);
  79 }
  80
  81 extern int sysctl_max_syn_backlog;
  82
  83 /** struct listen_sock - listen state
  84  *
  85  * @max_qlen_log - log_2 of maximal queued SYNs/REQUESTs
  86  */
  87 struct listen_sock {
  88         u8                      max_qlen_log;
  89         /* 3 bytes hole, try to use */
  90         int                     qlen;
  91         int                     qlen_young;
  92         int                     clock_hand;
  93         u32                     hash_rnd;
  94         u32                     nr_table_entries;
  95         struct request_sock     *syn_table[0];
  96 };
  97
  98 /** struct request_sock_queue - queue of request_socks
  99  *
 100  * @rskq_accept_head - FIFO head of established children
 101  * @rskq_accept_tail - FIFO tail of established children
 102  * @rskq_defer_accept - User waits for some data after accept()
 103  * @syn_wait_lock - serializer
 104  *
 105  * %syn_wait_lock is necessary only to avoid proc interface having to grab the main
 106  * lock sock while browsing the listening hash (otherwise it's deadlock prone).
 107  *
 108  * This lock is acquired in read mode only from listening_get_next() seq_file
 109  * op and it's acquired in write mode _only_ from code that is actively
 110  * changing rskq_accept_head. All readers that are holding the master sock lock
 111  * don't need to grab this lock in read mode too as rskq_accept_head. writes
 112  * are always protected from the main sock lock.
 113  */
 114 struct request_sock_queue {
 115         struct request_sock     *rskq_accept_head;
 116         struct request_sock     *rskq_accept_tail;
 117         rwlock_t                syn_wait_lock;
 118         u16                     rskq_defer_accept;
 119         /* 2 bytes hole, try to pack */
 120         struct listen_sock      *listen_opt;
 121 };
 122
 123 extern int reqsk_queue_alloc(struct request_sock_queue *queue,
 124                              unsigned int nr_table_entries);
 125
 126 extern void __reqsk_queue_destroy(struct request_sock_queue *queue);
 127 extern void reqsk_queue_destroy(struct request_sock_queue *queue);
 128
 129 static inline struct request_sock *
 130         reqsk_queue_yank_acceptq(struct request_sock_queue *queue)
 131 {
 132         struct request_sock *req = queue->rskq_accept_head;
 133
 134         queue->rskq_accept_head = NULL;
 135         return req;
 136 }
 137
 138 static inline int reqsk_queue_empty(struct request_sock_queue *queue)
 139 {
 140         return queue->rskq_accept_head == NULL;
 141 }
 142
 143 static inline void reqsk_queue_unlink(struct request_sock_queue *queue,
 144                                       struct request_sock *req,
 145                                       struct request_sock **prev_req)
 146 {
 147         write_lock(&queue->syn_wait_lock);
 148         *prev_req = req->dl_next;
 149         write_unlock(&queue->syn_wait_lock);
 150 }
 151
 152 static inline void reqsk_queue_add(struct request_sock_queue *queue,
 153                                    struct request_sock *req,
 154                                    struct sock *parent,
 155                                    struct sock *child)
 156 {
 157         req->sk = child;
 158         sk_acceptq_added(parent);
 159
 160         if (queue->rskq_accept_head == NULL)
 161                 queue->rskq_accept_head = req;
 162         else
 163                 queue->rskq_accept_tail->dl_next = req;
 164
 165         queue->rskq_accept_tail = req;
 166         req->dl_next = NULL;
 167 }
 168
 169 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue)
 170 {
 171         struct request_sock *req = queue->rskq_accept_head;
 172
 173         BUG_TRAP(req != NULL);
 174
 175         queue->rskq_accept_head = req->dl_next;
 176         if (queue->rskq_accept_head == NULL)
 177                 queue->rskq_accept_tail = NULL;
 178
 179         return req;
 180 }
 181
 182 static inline struct sock *reqsk_queue_get_child(struct request_sock_queue *queue,
 183                                                  struct sock *parent)
 184 {
 185         struct request_sock *req = reqsk_queue_remove(queue);
 186         struct sock *child = req->sk;
 187
 188         BUG_TRAP(child != NULL);
 189
 190         sk_acceptq_removed(parent);
 191         __reqsk_free(req);
 192         return child;
 193 }
 194
 195 static inline int reqsk_queue_removed(struct request_sock_queue *queue,
 196                                       struct request_sock *req)
 197 {
 198         struct listen_sock *lopt = queue->listen_opt;
 199
 200         if (req->retrans == 0)
 201                 --lopt->qlen_young;
 202
 203         return --lopt->qlen;
 204 }
 205
 206 static inline int reqsk_queue_added(struct request_sock_queue *queue)
 207 {
 208         struct listen_sock *lopt = queue->listen_opt;
 209         const int prev_qlen = lopt->qlen;
 210
 211         lopt->qlen_young++;
 212         lopt->qlen++;
 213         return prev_qlen;
 214 }
 215
 216 static inline int reqsk_queue_len(const struct request_sock_queue *queue)
 217 {
 218         return queue->listen_opt != NULL ? queue->listen_opt->qlen : 0;
 219 }
 220
 221 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
 222 {
 223         return queue->listen_opt->qlen_young;
 224 }
 225
 226 static inline int reqsk_queue_is_full(const struct request_sock_queue *queue)
 227 {
 228         return queue->listen_opt->qlen >> queue->listen_opt->max_qlen_log;
 229 }
 230
 231 static inline void reqsk_queue_hash_req(struct request_sock_queue *queue,
 232                                         u32 hash, struct request_sock *req,
 233                                         unsigned long timeout)
 234 {
 235         struct listen_sock *lopt = queue->listen_opt;
 236
 237         req->expires = jiffies + timeout;
 238         req->retrans = 0;
 239         req->sk = NULL;
 240         req->dl_next = lopt->syn_table[hash];
 241
 242         write_lock(&queue->syn_wait_lock);
 243         lopt->syn_table[hash] = req;
 244         write_unlock(&queue->syn_wait_lock);
 245 }
 246
 247 #endif /* _REQUEST_SOCK_H */