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 extern int inet_rtx_syn_ack(struct sock *parent, struct request_sock *req);
  53
  54 /* struct request_sock - mini sock to represent a connection request
  55  */
  56 struct request_sock {
  57         struct request_sock             *dl_next; /* Must be first member! */
  58         u16                             mss;
  59         u8                              num_retrans; /* number of retransmits */
  60         u8                              cookie_ts:1; /* syncookie: encode tcpopts in timestamp */
  61         u8                              num_timeout:7; /* number of timeouts */
  62         /* The following two fields can be easily recomputed I think -AK */
  63         u32                             window_clamp; /* window clamp at creation time */
  64         u32                             rcv_wnd;          /* rcv_wnd offered first time */
  65         u32                             ts_recent;
  66         unsigned long                   expires;
  67         const struct request_sock_ops   *rsk_ops;
  68         struct sock                     *sk;
  69         u32                             secid;
  70         u32                             peer_secid;
  71 };
  72
  73 static inline struct request_sock *reqsk_alloc(const struct request_sock_ops *ops)
  74 {
  75         struct request_sock *req = kmem_cache_alloc(ops->slab, GFP_ATOMIC);
  76
  77         if (req != NULL)
  78                 req->rsk_ops = ops;
  79
  80         return req;
  81 }
  82
  83 static inline void __reqsk_free(struct request_sock *req)
  84 {
  85         kmem_cache_free(req->rsk_ops->slab, req);
  86 }
  87
  88 static inline void reqsk_free(struct request_sock *req)
  89 {
  90         req->rsk_ops->destructor(req);
  91         __reqsk_free(req);
  92 }
  93
  94 extern int sysctl_max_syn_backlog;
  95
  96 /** struct listen_sock - listen state
  97  *
  98  * @max_qlen_log - log_2 of maximal queued SYNs/REQUESTs
  99  */
 100 struct listen_sock {
 101         u8                      max_qlen_log;
 102         u8                      synflood_warned;
 103         /* 2 bytes hole, try to use */
 104         int                     qlen;
 105         int                     qlen_young;
 106         int                     clock_hand;
 107         u32                     hash_rnd;
 108         u32                     nr_table_entries;
 109         struct request_sock     *syn_table[0];
 110 };
 111
 112 /*
 113  * For a TCP Fast Open listener -
 114  *      lock - protects the access to all the reqsk, which is co-owned by
 115  *              the listener and the child socket.
 116  *      qlen - pending TFO requests (still in TCP_SYN_RECV).
 117  *      max_qlen - max TFO reqs allowed before TFO is disabled.
 118  *
 119  *      XXX (TFO) - ideally these fields can be made as part of "listen_sock"
 120  *      structure above. But there is some implementation difficulty due to
 121  *      listen_sock being part of request_sock_queue hence will be freed when
 122  *      a listener is stopped. But TFO related fields may continue to be
 123  *      accessed even after a listener is closed, until its sk_refcnt drops
 124  *      to 0 implying no more outstanding TFO reqs. One solution is to keep
 125  *      listen_opt around until sk_refcnt drops to 0. But there is some other
 126  *      complexity that needs to be resolved. E.g., a listener can be disabled
 127  *      temporarily through shutdown()->tcp_disconnect(), and re-enabled later.
 128  */
 129 struct fastopen_queue {
 130         struct request_sock     *rskq_rst_head; /* Keep track of past TFO */
 131         struct request_sock     *rskq_rst_tail; /* requests that caused RST.
 132                                                  * This is part of the defense
 133                                                  * against spoofing attack.
 134                                                  */
 135         spinlock_t      lock;
 136         int             qlen;           /* # of pending (TCP_SYN_RECV) reqs */
 137         int             max_qlen;       /* != 0 iff TFO is currently enabled */
 138 };
 139
 140 /** struct request_sock_queue - queue of request_socks
 141  *
 142  * @rskq_accept_head - FIFO head of established children
 143  * @rskq_accept_tail - FIFO tail of established children
 144  * @rskq_defer_accept - User waits for some data after accept()
 145  * @syn_wait_lock - serializer
 146  *
 147  * %syn_wait_lock is necessary only to avoid proc interface having to grab the main
 148  * lock sock while browsing the listening hash (otherwise it's deadlock prone).
 149  *
 150  * This lock is acquired in read mode only from listening_get_next() seq_file
 151  * op and it's acquired in write mode _only_ from code that is actively
 152  * changing rskq_accept_head. All readers that are holding the master sock lock
 153  * don't need to grab this lock in read mode too as rskq_accept_head. writes
 154  * are always protected from the main sock lock.
 155  */
 156 struct request_sock_queue {
 157         struct request_sock     *rskq_accept_head;
 158         struct request_sock     *rskq_accept_tail;
 159         rwlock_t                syn_wait_lock;
 160         u8                      rskq_defer_accept;
 161         /* 3 bytes hole, try to pack */
 162         struct listen_sock      *listen_opt;
 163         struct fastopen_queue   *fastopenq; /* This is non-NULL iff TFO has been
 164                                              * enabled on this listener. Check
 165                                              * max_qlen != 0 in fastopen_queue
 166                                              * to determine if TFO is enabled
 167                                              * right at this moment.
 168                                              */
 169 };
 170
 171 extern int reqsk_queue_alloc(struct request_sock_queue *queue,
 172                              unsigned int nr_table_entries);
 173
 174 extern void __reqsk_queue_destroy(struct request_sock_queue *queue);
 175 extern void reqsk_queue_destroy(struct request_sock_queue *queue);
 176 extern void reqsk_fastopen_remove(struct sock *sk,
 177                                   struct request_sock *req, bool reset);
 178
 179 static inline struct request_sock *
 180         reqsk_queue_yank_acceptq(struct request_sock_queue *queue)
 181 {
 182         struct request_sock *req = queue->rskq_accept_head;
 183
 184         queue->rskq_accept_head = NULL;
 185         return req;
 186 }
 187
 188 static inline int reqsk_queue_empty(struct request_sock_queue *queue)
 189 {
 190         return queue->rskq_accept_head == NULL;
 191 }
 192
 193 static inline void reqsk_queue_unlink(struct request_sock_queue *queue,
 194                                       struct request_sock *req,
 195                                       struct request_sock **prev_req)
 196 {
 197         write_lock(&queue->syn_wait_lock);
 198         *prev_req = req->dl_next;
 199         write_unlock(&queue->syn_wait_lock);
 200 }
 201
 202 static inline void reqsk_queue_add(struct request_sock_queue *queue,
 203                                    struct request_sock *req,
 204                                    struct sock *parent,
 205                                    struct sock *child)
 206 {
 207         req->sk = child;
 208         sk_acceptq_added(parent);
 209
 210         if (queue->rskq_accept_head == NULL)
 211                 queue->rskq_accept_head = req;
 212         else
 213                 queue->rskq_accept_tail->dl_next = req;
 214
 215         queue->rskq_accept_tail = req;
 216         req->dl_next = NULL;
 217 }
 218
 219 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue)
 220 {
 221         struct request_sock *req = queue->rskq_accept_head;
 222
 223         WARN_ON(req == NULL);
 224
 225         queue->rskq_accept_head = req->dl_next;
 226         if (queue->rskq_accept_head == NULL)
 227                 queue->rskq_accept_tail = NULL;
 228
 229         return req;
 230 }
 231
 232 static inline int reqsk_queue_removed(struct request_sock_queue *queue,
 233                                       struct request_sock *req)
 234 {
 235         struct listen_sock *lopt = queue->listen_opt;
 236
 237         if (req->num_timeout == 0)
 238                 --lopt->qlen_young;
 239
 240         return --lopt->qlen;
 241 }
 242
 243 static inline int reqsk_queue_added(struct request_sock_queue *queue)
 244 {
 245         struct listen_sock *lopt = queue->listen_opt;
 246         const int prev_qlen = lopt->qlen;
 247
 248         lopt->qlen_young++;
 249         lopt->qlen++;
 250         return prev_qlen;
 251 }
 252
 253 static inline int reqsk_queue_len(const struct request_sock_queue *queue)
 254 {
 255         return queue->listen_opt != NULL ? queue->listen_opt->qlen : 0;
 256 }
 257
 258 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
 259 {
 260         return queue->listen_opt->qlen_young;
 261 }
 262
 263 static inline int reqsk_queue_is_full(const struct request_sock_queue *queue)
 264 {
 265         return queue->listen_opt->qlen >> queue->listen_opt->max_qlen_log;
 266 }
 267
 268 static inline void reqsk_queue_hash_req(struct request_sock_queue *queue,
 269                                         u32 hash, struct request_sock *req,
 270                                         unsigned long timeout)
 271 {
 272         struct listen_sock *lopt = queue->listen_opt;
 273
 274         req->expires = jiffies + timeout;
 275         req->num_retrans = 0;
 276         req->num_timeout = 0;
 277         req->sk = NULL;
 278         req->dl_next = lopt->syn_table[hash];
 279
 280         write_lock(&queue->syn_wait_lock);
 281         lopt->syn_table[hash] = req;
 282         write_unlock(&queue->syn_wait_lock);
 283 }
 284
 285 #endif /* _REQUEST_SOCK_H */