LXR linux/include/net/request

   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
  30struct request_sock_ops {
  31        int             family;
  32        int             obj_size;
  33        struct kmem_cache       *slab;
  34        char            *slab_name;
  35        int             (*rtx_syn_ack)(const struct sock *sk,
  36                                       struct request_sock *req);
  37        void            (*send_ack)(const struct sock *sk, struct sk_buff *skb,
  38                                    struct request_sock *req);
  39        void            (*send_reset)(const struct sock *sk,
  40                                      struct sk_buff *skb);
  41        void            (*destructor)(struct request_sock *req);
  42        void            (*syn_ack_timeout)(const struct request_sock *req);
  43};
  44
  45int inet_rtx_syn_ack(const struct sock *parent, struct request_sock *req);
  46
  47/* struct request_sock - mini sock to represent a connection request
  48 */
  49struct request_sock {
  50        struct sock_common              __req_common;
  51#define rsk_refcnt                      __req_common.skc_refcnt
  52#define rsk_hash                        __req_common.skc_hash
  53#define rsk_listener                    __req_common.skc_listener
  54#define rsk_window_clamp                __req_common.skc_window_clamp
  55#define rsk_rcv_wnd                     __req_common.skc_rcv_wnd
  56
  57        struct request_sock             *dl_next;
  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        u32                             ts_recent;
  63        struct timer_list               rsk_timer;
  64        const struct request_sock_ops   *rsk_ops;
  65        struct sock                     *sk;
  66        u32                             *saved_syn;
  67        u32                             secid;
  68        u32                             peer_secid;
  69};
  70
  71static inline struct request_sock *inet_reqsk(const struct sock *sk)
  72{
  73        return (struct request_sock *)sk;
  74}
  75
  76static inline struct sock *req_to_sk(struct request_sock *req)
  77{
  78        return (struct sock *)req;
  79}
  80
  81static inline struct request_sock *
  82reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener,
  83            bool attach_listener)
  84{
  85        struct request_sock *req;
  86
  87        req = kmem_cache_alloc(ops->slab, GFP_ATOMIC | __GFP_NOWARN);
  88        if (!req)
  89                return NULL;
  90        req->rsk_listener = NULL;
  91        if (attach_listener) {
  92                if (unlikely(!atomic_inc_not_zero(&sk_listener->sk_refcnt))) {
  93                        kmem_cache_free(ops->slab, req);
  94                        return NULL;
  95                }
  96                req->rsk_listener = sk_listener;
  97        }
  98        req->rsk_ops = ops;
  99        req_to_sk(req)->sk_prot = sk_listener->sk_prot;
 100        sk_node_init(&req_to_sk(req)->sk_node);
 101        sk_tx_queue_clear(req_to_sk(req));
 102        req->saved_syn = NULL;
 103        atomic_set(&req->rsk_refcnt, 0);
 104
 105        return req;
 106}
 107
 108static inline void reqsk_free(struct request_sock *req)
 109{
 110        /* temporary debugging */
 111        WARN_ON_ONCE(atomic_read(&req->rsk_refcnt) != 0);
 112
 113        req->rsk_ops->destructor(req);
 114        if (req->rsk_listener)
 115                sock_put(req->rsk_listener);
 116        kfree(req->saved_syn);
 117        kmem_cache_free(req->rsk_ops->slab, req);
 118}
 119
 120static inline void reqsk_put(struct request_sock *req)
 121{
 122        if (atomic_dec_and_test(&req->rsk_refcnt))
 123                reqsk_free(req);
 124}
 125
 126/*
 127 * For a TCP Fast Open listener -
 128 *      lock - protects the access to all the reqsk, which is co-owned by
 129 *              the listener and the child socket.
 130 *      qlen - pending TFO requests (still in TCP_SYN_RECV).
 131 *      max_qlen - max TFO reqs allowed before TFO is disabled.
 132 *
 133 *      XXX (TFO) - ideally these fields can be made as part of "listen_sock"
 134 *      structure above. But there is some implementation difficulty due to
 135 *      listen_sock being part of request_sock_queue hence will be freed when
 136 *      a listener is stopped. But TFO related fields may continue to be
 137 *      accessed even after a listener is closed, until its sk_refcnt drops
 138 *      to 0 implying no more outstanding TFO reqs. One solution is to keep
 139 *      listen_opt around until sk_refcnt drops to 0. But there is some other
 140 *      complexity that needs to be resolved. E.g., a listener can be disabled
 141 *      temporarily through shutdown()->tcp_disconnect(), and re-enabled later.
 142 */
 143struct fastopen_queue {
 144        struct request_sock     *rskq_rst_head; /* Keep track of past TFO */
 145        struct request_sock     *rskq_rst_tail; /* requests that caused RST.
 146                                                 * This is part of the defense
 147                                                 * against spoofing attack.
 148                                                 */
 149        spinlock_t      lock;
 150        int             qlen;           /* # of pending (TCP_SYN_RECV) reqs */
 151        int             max_qlen;       /* != 0 iff TFO is currently enabled */
 152};
 153
 154/** struct request_sock_queue - queue of request_socks
 155 *
 156 * @rskq_accept_head - FIFO head of established children
 157 * @rskq_accept_tail - FIFO tail of established children
 158 * @rskq_defer_accept - User waits for some data after accept()
 159 *
 160 */
 161struct request_sock_queue {
 162        spinlock_t              rskq_lock;
 163        u8                      rskq_defer_accept;
 164
 165        u32                     synflood_warned;
 166        atomic_t                qlen;
 167        atomic_t                young;
 168
 169        struct request_sock     *rskq_accept_head;
 170        struct request_sock     *rskq_accept_tail;
 171        struct fastopen_queue   fastopenq;  /* Check max_qlen != 0 to determine
 172                                             * if TFO is enabled.
 173                                             */
 174};
 175
 176void reqsk_queue_alloc(struct request_sock_queue *queue);
 177
 178void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
 179                           bool reset);
 180
 181static inline bool reqsk_queue_empty(const struct request_sock_queue *queue)
 182{
 183        return queue->rskq_accept_head == NULL;
 184}
 185
 186static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue,
 187                                                      struct sock *parent)
 188{
 189        struct request_sock *req;
 190
 191        spin_lock_bh(&queue->rskq_lock);
 192        req = queue->rskq_accept_head;
 193        if (req) {
 194                sk_acceptq_removed(parent);
 195                queue->rskq_accept_head = req->dl_next;
 196                if (queue->rskq_accept_head == NULL)
 197                        queue->rskq_accept_tail = NULL;
 198        }
 199        spin_unlock_bh(&queue->rskq_lock);
 200        return req;
 201}
 202
 203static inline void reqsk_queue_removed(struct request_sock_queue *queue,
 204                                       const struct request_sock *req)
 205{
 206        if (req->num_timeout == 0)
 207                atomic_dec(&queue->young);
 208        atomic_dec(&queue->qlen);
 209}
 210
 211static inline void reqsk_queue_added(struct request_sock_queue *queue)
 212{
 213        atomic_inc(&queue->young);
 214        atomic_inc(&queue->qlen);
 215}
 216
 217static inline int reqsk_queue_len(const struct request_sock_queue *queue)
 218{
 219        return atomic_read(&queue->qlen);
 220}
 221
 222static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
 223{
 224        return atomic_read(&queue->young);
 225}
 226
 227#endif /* _REQUEST_SOCK_H */
 228