linux/include/net/request_sock.h
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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#include <linux/bug.h>
  22
  23#include <net/sock.h>
  24
  25struct request_sock;
  26struct sk_buff;
  27struct dst_entry;
  28struct proto;
  29
  30/* empty to "strongly type" an otherwise void parameter.
  31 */
  32struct request_values {
  33};
  34
  35struct 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 */
  54struct 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
  70static 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
  80static inline void __reqsk_free(struct request_sock *req)
  81{
  82        kmem_cache_free(req->rsk_ops->slab, req);
  83}
  84
  85static inline void reqsk_free(struct request_sock *req)
  86{
  87        req->rsk_ops->destructor(req);
  88        __reqsk_free(req);
  89}
  90
  91extern 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 */
  97struct 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 */
 126struct 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 */
 153struct 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
 168extern int reqsk_queue_alloc(struct request_sock_queue *queue,
 169                             unsigned int nr_table_entries);
 170
 171extern void __reqsk_queue_destroy(struct request_sock_queue *queue);
 172extern void reqsk_queue_destroy(struct request_sock_queue *queue);
 173extern void reqsk_fastopen_remove(struct sock *sk,
 174                                  struct request_sock *req, bool reset);
 175
 176static 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
 185static inline int reqsk_queue_empty(struct request_sock_queue *queue)
 186{
 187        return queue->rskq_accept_head == NULL;
 188}
 189
 190static 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
 199static 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
 216static 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
 229static 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
 240static 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
 250static 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
 255static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
 256{
 257        return queue->listen_opt->qlen_young;
 258}
 259
 260static 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
 265static 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 */
 282
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