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 #include <linux/refcount.h>
  23
  24 #include <net/sock.h>
  25
  26 struct request_sock;
  27 struct sk_buff;
  28 struct dst_entry;
  29 struct proto;
  30
  31 struct request_sock_ops {
  32         int             family;
  33         unsigned int    obj_size;
  34         struct kmem_cache       *slab;
  35         char            *slab_name;
  36         int             (*rtx_syn_ack)(const struct sock *sk,
  37                                        struct request_sock *req);
  38         void            (*send_ack)(const struct sock *sk, struct sk_buff *skb,
  39                                     struct request_sock *req);
  40         void            (*send_reset)(const struct sock *sk,
  41                                       struct sk_buff *skb);
  42         void            (*destructor)(struct request_sock *req);
  43         void            (*syn_ack_timeout)(const struct request_sock *req);
  44 };
  45
  46 int inet_rtx_syn_ack(const 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 #define rsk_refcnt                      __req_common.skc_refcnt
  53 #define rsk_hash                        __req_common.skc_hash
  54 #define rsk_listener                    __req_common.skc_listener
  55 #define rsk_window_clamp                __req_common.skc_window_clamp
  56 #define rsk_rcv_wnd                     __req_common.skc_rcv_wnd
  57
  58         struct request_sock             *dl_next;
  59         u16                             mss;
  60         u8                              num_retrans; /* number of retransmits */
  61         u8                              cookie_ts:1; /* syncookie: encode tcpopts in timestamp */
  62         u8                              num_timeout:7; /* number of timeouts */
  63         u32                             ts_recent;
  64         struct timer_list               rsk_timer;
  65         const struct request_sock_ops   *rsk_ops;
  66         struct sock                     *sk;
  67         u32                             *saved_syn;
  68         u32                             secid;
  69         u32                             peer_secid;
  70 };
  71
  72 static inline struct request_sock *inet_reqsk(const struct sock *sk)
  73 {
  74         return (struct request_sock *)sk;
  75 }
  76
  77 static inline struct sock *req_to_sk(struct request_sock *req)
  78 {
  79         return (struct sock *)req;
  80 }
  81
  82 static inline struct request_sock *
  83 reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener,
  84             bool attach_listener)
  85 {
  86         struct request_sock *req;
  87
  88         req = kmem_cache_alloc(ops->slab, GFP_ATOMIC | __GFP_NOWARN);
  89         if (!req)
  90                 return NULL;
  91         req->rsk_listener = NULL;
  92         if (attach_listener) {
  93                 if (unlikely(!refcount_inc_not_zero(&sk_listener->sk_refcnt))) {
  94                         kmem_cache_free(ops->slab, req);
  95                         return NULL;
  96                 }
  97                 req->rsk_listener = sk_listener;
  98         }
  99         req->rsk_ops = ops;
 100         req_to_sk(req)->sk_prot = sk_listener->sk_prot;
 101         sk_node_init(&req_to_sk(req)->sk_node);
 102         sk_tx_queue_clear(req_to_sk(req));
 103         req->saved_syn = NULL;
 104         refcount_set(&req->rsk_refcnt, 0);
 105
 106         return req;
 107 }
 108
 109 static inline void reqsk_free(struct request_sock *req)
 110 {
 111         /* temporary debugging */
 112         WARN_ON_ONCE(refcount_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
 121 static inline void reqsk_put(struct request_sock *req)
 122 {
 123         if (refcount_dec_and_test(&req->rsk_refcnt))
 124                 reqsk_free(req);
 125 }
 126
 127 /*
 128  * For a TCP Fast Open listener -
 129  *      lock - protects the access to all the reqsk, which is co-owned by
 130  *              the listener and the child socket.
 131  *      qlen - pending TFO requests (still in TCP_SYN_RECV).
 132  *      max_qlen - max TFO reqs allowed before TFO is disabled.
 133  *
 134  *      XXX (TFO) - ideally these fields can be made as part of "listen_sock"
 135  *      structure above. But there is some implementation difficulty due to
 136  *      listen_sock being part of request_sock_queue hence will be freed when
 137  *      a listener is stopped. But TFO related fields may continue to be
 138  *      accessed even after a listener is closed, until its sk_refcnt drops
 139  *      to 0 implying no more outstanding TFO reqs. One solution is to keep
 140  *      listen_opt around until sk_refcnt drops to 0. But there is some other
 141  *      complexity that needs to be resolved. E.g., a listener can be disabled
 142  *      temporarily through shutdown()->tcp_disconnect(), and re-enabled later.
 143  */
 144 struct fastopen_queue {
 145         struct request_sock     *rskq_rst_head; /* Keep track of past TFO */
 146         struct request_sock     *rskq_rst_tail; /* requests that caused RST.
 147                                                  * This is part of the defense
 148                                                  * against spoofing attack.
 149                                                  */
 150         spinlock_t      lock;
 151         int             qlen;           /* # of pending (TCP_SYN_RECV) reqs */
 152         int             max_qlen;       /* != 0 iff TFO is currently enabled */
 153 };
 154
 155 /** struct request_sock_queue - queue of request_socks
 156  *
 157  * @rskq_accept_head - FIFO head of established children
 158  * @rskq_accept_tail - FIFO tail of established children
 159  * @rskq_defer_accept - User waits for some data after accept()
 160  *
 161  */
 162 struct request_sock_queue {
 163         spinlock_t              rskq_lock;
 164         u8                      rskq_defer_accept;
 165
 166         u32                     synflood_warned;
 167         atomic_t                qlen;
 168         atomic_t                young;
 169
 170         struct request_sock     *rskq_accept_head;
 171         struct request_sock     *rskq_accept_tail;
 172         struct fastopen_queue   fastopenq;  /* Check max_qlen != 0 to determine
 173                                              * if TFO is enabled.
 174                                              */
 175 };
 176
 177 void reqsk_queue_alloc(struct request_sock_queue *queue);
 178
 179 void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
 180                            bool reset);
 181
 182 static inline bool reqsk_queue_empty(const struct request_sock_queue *queue)
 183 {
 184         return queue->rskq_accept_head == NULL;
 185 }
 186
 187 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue,
 188                                                       struct sock *parent)
 189 {
 190         struct request_sock *req;
 191
 192         spin_lock_bh(&queue->rskq_lock);
 193         req = queue->rskq_accept_head;
 194         if (req) {
 195                 sk_acceptq_removed(parent);
 196                 queue->rskq_accept_head = req->dl_next;
 197                 if (queue->rskq_accept_head == NULL)
 198                         queue->rskq_accept_tail = NULL;
 199         }
 200         spin_unlock_bh(&queue->rskq_lock);
 201         return req;
 202 }
 203
 204 static inline void reqsk_queue_removed(struct request_sock_queue *queue,
 205                                        const struct request_sock *req)
 206 {
 207         if (req->num_timeout == 0)
 208                 atomic_dec(&queue->young);
 209         atomic_dec(&queue->qlen);
 210 }
 211
 212 static inline void reqsk_queue_added(struct request_sock_queue *queue)
 213 {
 214         atomic_inc(&queue->young);
 215         atomic_inc(&queue->qlen);
 216 }
 217
 218 static inline int reqsk_queue_len(const struct request_sock_queue *queue)
 219 {
 220         return atomic_read(&queue->qlen);
 221 }
 222
 223 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
 224 {
 225         return atomic_read(&queue->young);
 226 }
 227
 228 #endif /* _REQUEST_SOCK_H */