include/net/request_sock.h

   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
  23 #include <net/sock.h>
  24
  25 struct request_sock;
  26 struct sk_buff;
  27 struct dst_entry;
  28 struct proto;
  29
  30 /* empty to "strongly type" an otherwise void parameter.
  31  */
  32 struct request_values {
  33 };
  34
  35 struct request_sock_ops {
  36         int             family;
  37         int             obj_size;
  38         struct kmem_cache       *slab;
  39         char            *slab_name;
  40         int             (*rtx_syn_ack)(struct sock *sk,
  41                                        struct request_sock *req,
  42                                        struct request_values *rvp);
  43         void            (*send_ack)(struct sock *sk, struct sk_buff *skb,
  44                                     struct request_sock *req);
  45         void            (*send_reset)(struct sock *sk,
  46                                       struct sk_buff *skb);
  47         void            (*destructor)(struct request_sock *req);
  48         void            (*syn_ack_timeout)(struct sock *sk,
  49                                            struct request_sock *req);
  50 };
  51
  52 /* struct request_sock - mini sock to represent a connection request
  53  */
  54 struct request_sock {
  55         struct request_sock             *dl_next; /* Must be first member! */
  56         u16                             mss;
  57         u8                              retrans;
  58         u8                              cookie_ts; /* syncookie: encode tcpopts in timestamp */
  59         /* The following two fields can be easily recomputed I think -AK */
  60         u32                             window_clamp; /* window clamp at creation time */
  61         u32                             rcv_wnd;          /* rcv_wnd offered first time */
  62         u32                             ts_recent;
  63         unsigned long                   expires;
  64         const struct request_sock_ops   *rsk_ops;
  65         struct sock                     *sk;
  66         u32                             secid;
  67         u32                             peer_secid;
  68 };
  69
  70 static inline struct request_sock *reqsk_alloc(const struct request_sock_ops *ops)
  71 {
  72         struct request_sock *req = kmem_cache_alloc(ops->slab, GFP_ATOMIC);
  73
  74         if (req != NULL)
  75                 req->rsk_ops = ops;
  76
  77         return req;
  78 }
  79
  80 static inline void __reqsk_free(struct request_sock *req)
  81 {
  82         kmem_cache_free(req->rsk_ops->slab, req);
  83 }
  84
  85 static inline void reqsk_free(struct request_sock *req)
  86 {
  87         req->rsk_ops->destructor(req);
  88         __reqsk_free(req);
  89 }
  90
  91 extern int sysctl_max_syn_backlog;
  92
  93 /** struct listen_sock - listen state
  94  *
  95  * @max_qlen_log - log_2 of maximal queued SYNs/REQUESTs
  96  */
  97 struct listen_sock {
  98         u8                      max_qlen_log;
  99         u8                      synflood_warned;
 100         /* 2 bytes hole, try to use */
 101         int                     qlen;
 102         int                     qlen_young;
 103         int                     clock_hand;
 104         u32                     hash_rnd;
 105         u32                     nr_table_entries;
 106         struct request_sock     *syn_table[0];
 107 };
 108
 109 /*
 110  * For a TCP Fast Open listener -
 111  *      lock - protects the access to all the reqsk, which is co-owned by
 112  *              the listener and the child socket.
 113  *      qlen - pending TFO requests (still in TCP_SYN_RECV).
 114  *      max_qlen - max TFO reqs allowed before TFO is disabled.
 115  *
 116  *      XXX (TFO) - ideally these fields can be made as part of "listen_sock"
 117  *      structure above. But there is some implementation difficulty due to
 118  *      listen_sock being part of request_sock_queue hence will be freed when
 119  *      a listener is stopped. But TFO related fields may continue to be
 120  *      accessed even after a listener is closed, until its sk_refcnt drops
 121  *      to 0 implying no more outstanding TFO reqs. One solution is to keep
 122  *      listen_opt around until sk_refcnt drops to 0. But there is some other
 123  *      complexity that needs to be resolved. E.g., a listener can be disabled
 124  *      temporarily through shutdown()->tcp_disconnect(), and re-enabled later.
 125  */
 126 struct fastopen_queue {
 127         struct request_sock     *rskq_rst_head; /* Keep track of past TFO */
 128         struct request_sock     *rskq_rst_tail; /* requests that caused RST.
 129                                                  * This is part of the defense
 130                                                  * against spoofing attack.
 131                                                  */
 132         spinlock_t      lock;
 133         int             qlen;           /* # of pending (TCP_SYN_RECV) reqs */
 134         int             max_qlen;       /* != 0 iff TFO is currently enabled */
 135 };
 136
 137 /** struct request_sock_queue - queue of request_socks
 138  *
 139  * @rskq_accept_head - FIFO head of established children
 140  * @rskq_accept_tail - FIFO tail of established children
 141  * @rskq_defer_accept - User waits for some data after accept()
 142  * @syn_wait_lock - serializer
 143  *
 144  * %syn_wait_lock is necessary only to avoid proc interface having to grab the main
 145  * lock sock while browsing the listening hash (otherwise it's deadlock prone).
 146  *
 147  * This lock is acquired in read mode only from listening_get_next() seq_file
 148  * op and it's acquired in write mode _only_ from code that is actively
 149  * changing rskq_accept_head. All readers that are holding the master sock lock
 150  * don't need to grab this lock in read mode too as rskq_accept_head. writes
 151  * are always protected from the main sock lock.
 152  */
 153 struct request_sock_queue {
 154         struct request_sock     *rskq_accept_head;
 155         struct request_sock     *rskq_accept_tail;
 156         rwlock_t                syn_wait_lock;
 157         u8                      rskq_defer_accept;
 158         /* 3 bytes hole, try to pack */
 159         struct listen_sock      *listen_opt;
 160         struct fastopen_queue   *fastopenq; /* This is non-NULL iff TFO has been
 161                                              * enabled on this listener. Check
 162                                              * max_qlen != 0 in fastopen_queue
 163                                              * to determine if TFO is enabled
 164                                              * right at this moment.
 165                                              */
 166 };
 167
 168 extern int reqsk_queue_alloc(struct request_sock_queue *queue,
 169                              unsigned int nr_table_entries);
 170
 171 extern void __reqsk_queue_destroy(struct request_sock_queue *queue);
 172 extern void reqsk_queue_destroy(struct request_sock_queue *queue);
 173 extern void reqsk_fastopen_remove(struct sock *sk,
 174                                   struct request_sock *req, bool reset);
 175
 176 static inline struct request_sock *
 177         reqsk_queue_yank_acceptq(struct request_sock_queue *queue)
 178 {
 179         struct request_sock *req = queue->rskq_accept_head;
 180
 181         queue->rskq_accept_head = NULL;
 182         return req;
 183 }
 184
 185 static inline int reqsk_queue_empty(struct request_sock_queue *queue)
 186 {
 187         return queue->rskq_accept_head == NULL;
 188 }
 189
 190 static inline void reqsk_queue_unlink(struct request_sock_queue *queue,
 191                                       struct request_sock *req,
 192                                       struct request_sock **prev_req)
 193 {
 194         write_lock(&queue->syn_wait_lock);
 195         *prev_req = req->dl_next;
 196         write_unlock(&queue->syn_wait_lock);
 197 }
 198
 199 static inline void reqsk_queue_add(struct request_sock_queue *queue,
 200                                    struct request_sock *req,
 201                                    struct sock *parent,
 202                                    struct sock *child)
 203 {
 204         req->sk = child;
 205         sk_acceptq_added(parent);
 206
 207         if (queue->rskq_accept_head == NULL)
 208                 queue->rskq_accept_head = req;
 209         else
 210                 queue->rskq_accept_tail->dl_next = req;
 211
 212         queue->rskq_accept_tail = req;
 213         req->dl_next = NULL;
 214 }
 215
 216 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue)
 217 {
 218         struct request_sock *req = queue->rskq_accept_head;
 219
 220         WARN_ON(req == NULL);
 221
 222         queue->rskq_accept_head = req->dl_next;
 223         if (queue->rskq_accept_head == NULL)
 224                 queue->rskq_accept_tail = NULL;
 225
 226         return req;
 227 }
 228
 229 static inline int reqsk_queue_removed(struct request_sock_queue *queue,
 230                                       struct request_sock *req)
 231 {
 232         struct listen_sock *lopt = queue->listen_opt;
 233
 234         if (req->retrans == 0)
 235                 --lopt->qlen_young;
 236
 237         return --lopt->qlen;
 238 }
 239
 240 static inline int reqsk_queue_added(struct request_sock_queue *queue)
 241 {
 242         struct listen_sock *lopt = queue->listen_opt;
 243         const int prev_qlen = lopt->qlen;
 244
 245         lopt->qlen_young++;
 246         lopt->qlen++;
 247         return prev_qlen;
 248 }
 249
 250 static inline int reqsk_queue_len(const struct request_sock_queue *queue)
 251 {
 252         return queue->listen_opt != NULL ? queue->listen_opt->qlen : 0;
 253 }
 254
 255 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
 256 {
 257         return queue->listen_opt->qlen_young;
 258 }
 259
 260 static inline int reqsk_queue_is_full(const struct request_sock_queue *queue)
 261 {
 262         return queue->listen_opt->qlen >> queue->listen_opt->max_qlen_log;
 263 }
 264
 265 static inline void reqsk_queue_hash_req(struct request_sock_queue *queue,
 266                                         u32 hash, struct request_sock *req,
 267                                         unsigned long timeout)
 268 {
 269         struct listen_sock *lopt = queue->listen_opt;
 270
 271         req->expires = jiffies + timeout;
 272         req->retrans = 0;
 273         req->sk = NULL;
 274         req->dl_next = lopt->syn_table[hash];
 275
 276         write_lock(&queue->syn_wait_lock);
 277         lopt->syn_table[hash] = req;
 278         write_unlock(&queue->syn_wait_lock);
 279 }
 280
 281 #endif /* _REQUEST_SOCK_H */