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 struct request_sock_ops {
  31         int             family;
  32         int             obj_size;
  33         struct kmem_cache       *slab;
  34         char            *slab_name;
  35         int             (*rtx_syn_ack)(struct sock *sk,
  36                                        struct request_sock *req);
  37         void            (*send_ack)(struct sock *sk, struct sk_buff *skb,
  38                                     struct request_sock *req);
  39         void            (*send_reset)(struct sock *sk,
  40                                       struct sk_buff *skb);
  41         void            (*destructor)(struct request_sock *req);
  42         void            (*syn_ack_timeout)(struct sock *sk,
  43                                            struct request_sock *req);
  44 };
  45
  46 int inet_rtx_syn_ack(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         struct request_sock             *dl_next;
  53         u16                             mss;
  54         u8                              num_retrans; /* number of retransmits */
  55         u8                              cookie_ts:1; /* syncookie: encode tcpopts in timestamp */
  56         u8                              num_timeout:7; /* number of timeouts */
  57         /* The following two fields can be easily recomputed I think -AK */
  58         u32                             window_clamp; /* window clamp at creation time */
  59         u32                             rcv_wnd;          /* rcv_wnd offered first time */
  60         u32                             ts_recent;
  61         unsigned long                   expires;
  62         const struct request_sock_ops   *rsk_ops;
  63         struct sock                     *sk;
  64         u32                             secid;
  65         u32                             peer_secid;
  66 };
  67
  68 static inline struct request_sock *reqsk_alloc(const struct request_sock_ops *ops)
  69 {
  70         struct request_sock *req = kmem_cache_alloc(ops->slab, GFP_ATOMIC);
  71
  72         if (req != NULL)
  73                 req->rsk_ops = ops;
  74
  75         return req;
  76 }
  77
  78 static inline void __reqsk_free(struct request_sock *req)
  79 {
  80         kmem_cache_free(req->rsk_ops->slab, req);
  81 }
  82
  83 static inline void reqsk_free(struct request_sock *req)
  84 {
  85         req->rsk_ops->destructor(req);
  86         __reqsk_free(req);
  87 }
  88
  89 extern int sysctl_max_syn_backlog;
  90
  91 /** struct listen_sock - listen state
  92  *
  93  * @max_qlen_log - log_2 of maximal queued SYNs/REQUESTs
  94  */
  95 struct listen_sock {
  96         u8                      max_qlen_log;
  97         u8                      synflood_warned;
  98         /* 2 bytes hole, try to use */
  99         int                     qlen;
 100         int                     qlen_young;
 101         int                     clock_hand;
 102         u32                     hash_rnd;
 103         u32                     nr_table_entries;
 104         struct request_sock     *syn_table[0];
 105 };
 106
 107 /*
 108  * For a TCP Fast Open listener -
 109  *      lock - protects the access to all the reqsk, which is co-owned by
 110  *              the listener and the child socket.
 111  *      qlen - pending TFO requests (still in TCP_SYN_RECV).
 112  *      max_qlen - max TFO reqs allowed before TFO is disabled.
 113  *
 114  *      XXX (TFO) - ideally these fields can be made as part of "listen_sock"
 115  *      structure above. But there is some implementation difficulty due to
 116  *      listen_sock being part of request_sock_queue hence will be freed when
 117  *      a listener is stopped. But TFO related fields may continue to be
 118  *      accessed even after a listener is closed, until its sk_refcnt drops
 119  *      to 0 implying no more outstanding TFO reqs. One solution is to keep
 120  *      listen_opt around until sk_refcnt drops to 0. But there is some other
 121  *      complexity that needs to be resolved. E.g., a listener can be disabled
 122  *      temporarily through shutdown()->tcp_disconnect(), and re-enabled later.
 123  */
 124 struct fastopen_queue {
 125         struct request_sock     *rskq_rst_head; /* Keep track of past TFO */
 126         struct request_sock     *rskq_rst_tail; /* requests that caused RST.
 127                                                  * This is part of the defense
 128                                                  * against spoofing attack.
 129                                                  */
 130         spinlock_t      lock;
 131         int             qlen;           /* # of pending (TCP_SYN_RECV) reqs */
 132         int             max_qlen;       /* != 0 iff TFO is currently enabled */
 133 };
 134
 135 /** struct request_sock_queue - queue of request_socks
 136  *
 137  * @rskq_accept_head - FIFO head of established children
 138  * @rskq_accept_tail - FIFO tail of established children
 139  * @rskq_defer_accept - User waits for some data after accept()
 140  * @syn_wait_lock - serializer
 141  *
 142  * %syn_wait_lock is necessary only to avoid proc interface having to grab the main
 143  * lock sock while browsing the listening hash (otherwise it's deadlock prone).
 144  *
 145  * This lock is acquired in read mode only from listening_get_next() seq_file
 146  * op and it's acquired in write mode _only_ from code that is actively
 147  * changing rskq_accept_head. All readers that are holding the master sock lock
 148  * don't need to grab this lock in read mode too as rskq_accept_head. writes
 149  * are always protected from the main sock lock.
 150  */
 151 struct request_sock_queue {
 152         struct request_sock     *rskq_accept_head;
 153         struct request_sock     *rskq_accept_tail;
 154         rwlock_t                syn_wait_lock;
 155         u8                      rskq_defer_accept;
 156         /* 3 bytes hole, try to pack */
 157         struct listen_sock      *listen_opt;
 158         struct fastopen_queue   *fastopenq; /* This is non-NULL iff TFO has been
 159                                              * enabled on this listener. Check
 160                                              * max_qlen != 0 in fastopen_queue
 161                                              * to determine if TFO is enabled
 162                                              * right at this moment.
 163                                              */
 164 };
 165
 166 int reqsk_queue_alloc(struct request_sock_queue *queue,
 167                       unsigned int nr_table_entries);
 168
 169 void __reqsk_queue_destroy(struct request_sock_queue *queue);
 170 void reqsk_queue_destroy(struct request_sock_queue *queue);
 171 void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
 172                            bool reset);
 173
 174 static inline struct request_sock *
 175         reqsk_queue_yank_acceptq(struct request_sock_queue *queue)
 176 {
 177         struct request_sock *req = queue->rskq_accept_head;
 178
 179         queue->rskq_accept_head = NULL;
 180         return req;
 181 }
 182
 183 static inline int reqsk_queue_empty(struct request_sock_queue *queue)
 184 {
 185         return queue->rskq_accept_head == NULL;
 186 }
 187
 188 static inline void reqsk_queue_unlink(struct request_sock_queue *queue,
 189                                       struct request_sock *req,
 190                                       struct request_sock **prev_req)
 191 {
 192         write_lock(&queue->syn_wait_lock);
 193         *prev_req = req->dl_next;
 194         write_unlock(&queue->syn_wait_lock);
 195 }
 196
 197 static inline void reqsk_queue_add(struct request_sock_queue *queue,
 198                                    struct request_sock *req,
 199                                    struct sock *parent,
 200                                    struct sock *child)
 201 {
 202         req->sk = child;
 203         sk_acceptq_added(parent);
 204
 205         if (queue->rskq_accept_head == NULL)
 206                 queue->rskq_accept_head = req;
 207         else
 208                 queue->rskq_accept_tail->dl_next = req;
 209
 210         queue->rskq_accept_tail = req;
 211         req->dl_next = NULL;
 212 }
 213
 214 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue)
 215 {
 216         struct request_sock *req = queue->rskq_accept_head;
 217
 218         WARN_ON(req == NULL);
 219
 220         queue->rskq_accept_head = req->dl_next;
 221         if (queue->rskq_accept_head == NULL)
 222                 queue->rskq_accept_tail = NULL;
 223
 224         return req;
 225 }
 226
 227 static inline int reqsk_queue_removed(struct request_sock_queue *queue,
 228                                       struct request_sock *req)
 229 {
 230         struct listen_sock *lopt = queue->listen_opt;
 231
 232         if (req->num_timeout == 0)
 233                 --lopt->qlen_young;
 234
 235         return --lopt->qlen;
 236 }
 237
 238 static inline int reqsk_queue_added(struct request_sock_queue *queue)
 239 {
 240         struct listen_sock *lopt = queue->listen_opt;
 241         const int prev_qlen = lopt->qlen;
 242
 243         lopt->qlen_young++;
 244         lopt->qlen++;
 245         return prev_qlen;
 246 }
 247
 248 static inline int reqsk_queue_len(const struct request_sock_queue *queue)
 249 {
 250         return queue->listen_opt != NULL ? queue->listen_opt->qlen : 0;
 251 }
 252
 253 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
 254 {
 255         return queue->listen_opt->qlen_young;
 256 }
 257
 258 static inline int reqsk_queue_is_full(const struct request_sock_queue *queue)
 259 {
 260         return queue->listen_opt->qlen >> queue->listen_opt->max_qlen_log;
 261 }
 262
 263 static inline void reqsk_queue_hash_req(struct request_sock_queue *queue,
 264                                         u32 hash, struct request_sock *req,
 265                                         unsigned long timeout)
 266 {
 267         struct listen_sock *lopt = queue->listen_opt;
 268
 269         req->expires = jiffies + timeout;
 270         req->num_retrans = 0;
 271         req->num_timeout = 0;
 272         req->sk = NULL;
 273         req->dl_next = lopt->syn_table[hash];
 274
 275         write_lock(&queue->syn_wait_lock);
 276         lopt->syn_table[hash] = req;
 277         write_unlock(&queue->syn_wait_lock);
 278 }
 279
 280 #endif /* _REQUEST_SOCK_H */