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
  89        if (req) {
  90                req->rsk_ops = ops;
  91                if (attach_listener) {
  92                        sock_hold(sk_listener);
  93                        req->rsk_listener = sk_listener;
  94                } else {
  95                        req->rsk_listener = NULL;
  96                }
  97                req_to_sk(req)->sk_prot = sk_listener->sk_prot;
  98                sk_node_init(&req_to_sk(req)->sk_node);
  99                sk_tx_queue_clear(req_to_sk(req));
 100                req->saved_syn = NULL;
 101                /* Following is temporary. It is coupled with debugging
 102                 * helpers in reqsk_put() & reqsk_free()
 103                 */
 104                atomic_set(&req->rsk_refcnt, 0);
 105        }
 106        return req;
 107}
 108
 109static inline void reqsk_free(struct request_sock *req)
 110{
 111        /* temporary debugging */
 112        WARN_ON_ONCE(atomic_read(&req->rsk_refcnt) != 0);
 113
 114        req->rsk_ops->destructor(req);
 115        if (req->rsk_listener)
 116                sock_put(req->rsk_listener);
 117        kfree(req->saved_syn);
 118        kmem_cache_free(req->rsk_ops->slab, req);
 119}
 120
 121static inline void reqsk_put(struct request_sock *req)
 122{
 123        if (atomic_dec_and_test(&req->rsk_refcnt))
 124                reqsk_free(req);
 125}
 126
 127extern int sysctl_max_syn_backlog;
 128
 129/*
 130 * For a TCP Fast Open listener -
 131 *      lock - protects the access to all the reqsk, which is co-owned by
 132 *              the listener and the child socket.
 133 *      qlen - pending TFO requests (still in TCP_SYN_RECV).
 134 *      max_qlen - max TFO reqs allowed before TFO is disabled.
 135 *
 136 *      XXX (TFO) - ideally these fields can be made as part of "listen_sock"
 137 *      structure above. But there is some implementation difficulty due to
 138 *      listen_sock being part of request_sock_queue hence will be freed when
 139 *      a listener is stopped. But TFO related fields may continue to be
 140 *      accessed even after a listener is closed, until its sk_refcnt drops
 141 *      to 0 implying no more outstanding TFO reqs. One solution is to keep
 142 *      listen_opt around until sk_refcnt drops to 0. But there is some other
 143 *      complexity that needs to be resolved. E.g., a listener can be disabled
 144 *      temporarily through shutdown()->tcp_disconnect(), and re-enabled later.
 145 */
 146struct fastopen_queue {
 147        struct request_sock     *rskq_rst_head; /* Keep track of past TFO */
 148        struct request_sock     *rskq_rst_tail; /* requests that caused RST.
 149                                                 * This is part of the defense
 150                                                 * against spoofing attack.
 151                                                 */
 152        spinlock_t      lock;
 153        int             qlen;           /* # of pending (TCP_SYN_RECV) reqs */
 154        int             max_qlen;       /* != 0 iff TFO is currently enabled */
 155};
 156
 157/** struct request_sock_queue - queue of request_socks
 158 *
 159 * @rskq_accept_head - FIFO head of established children
 160 * @rskq_accept_tail - FIFO tail of established children
 161 * @rskq_defer_accept - User waits for some data after accept()
 162 *
 163 */
 164struct request_sock_queue {
 165        spinlock_t              rskq_lock;
 166        u8                      rskq_defer_accept;
 167
 168        u32                     synflood_warned;
 169        atomic_t                qlen;
 170        atomic_t                young;
 171
 172        struct request_sock     *rskq_accept_head;
 173        struct request_sock     *rskq_accept_tail;
 174        struct fastopen_queue   fastopenq;  /* Check max_qlen != 0 to determine
 175                                             * if TFO is enabled.
 176                                             */
 177};
 178
 179void reqsk_queue_alloc(struct request_sock_queue *queue);
 180
 181void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
 182                           bool reset);
 183
 184static inline bool reqsk_queue_empty(const struct request_sock_queue *queue)
 185{
 186        return queue->rskq_accept_head == NULL;
 187}
 188
 189static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue,
 190                                                      struct sock *parent)
 191{
 192        struct request_sock *req;
 193
 194        spin_lock_bh(&queue->rskq_lock);
 195        req = queue->rskq_accept_head;
 196        if (req) {
 197                sk_acceptq_removed(parent);
 198                queue->rskq_accept_head = req->dl_next;
 199                if (queue->rskq_accept_head == NULL)
 200                        queue->rskq_accept_tail = NULL;
 201        }
 202        spin_unlock_bh(&queue->rskq_lock);
 203        return req;
 204}
 205
 206static inline void reqsk_queue_removed(struct request_sock_queue *queue,
 207                                       const struct request_sock *req)
 208{
 209        if (req->num_timeout == 0)
 210                atomic_dec(&queue->young);
 211        atomic_dec(&queue->qlen);
 212}
 213
 214static inline void reqsk_queue_added(struct request_sock_queue *queue)
 215{
 216        atomic_inc(&queue->young);
 217        atomic_inc(&queue->qlen);
 218}
 219
 220static inline int reqsk_queue_len(const struct request_sock_queue *queue)
 221{
 222        return atomic_read(&queue->qlen);
 223}
 224
 225static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
 226{
 227        return atomic_read(&queue->young);
 228}
 229
 230#endif /* _REQUEST_SOCK_H */
 231