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)(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
  45 int 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  */
  49 struct 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
  71 static inline struct request_sock *inet_reqsk(const struct sock *sk)
  72 {
  73         return (struct request_sock *)sk;
  74 }
  75
  76 static inline struct sock *req_to_sk(struct request_sock *req)
  77 {
  78         return (struct sock *)req;
  79 }
  80
  81 static inline struct request_sock *
  82 reqsk_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
 109 static 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
 121 static inline void reqsk_put(struct request_sock *req)
 122 {
 123         if (atomic_dec_and_test(&req->rsk_refcnt))
 124                 reqsk_free(req);
 125 }
 126
 127 extern 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  */
 146 struct 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  */
 164 struct 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
 179 void reqsk_queue_alloc(struct request_sock_queue *queue);
 180
 181 void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
 182                            bool reset);
 183
 184 static inline bool reqsk_queue_empty(const struct request_sock_queue *queue)
 185 {
 186         return queue->rskq_accept_head == NULL;
 187 }
 188
 189 static 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
 206 static 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
 214 static inline void reqsk_queue_added(struct request_sock_queue *queue)
 215 {
 216         atomic_inc(&queue->young);
 217         atomic_inc(&queue->qlen);
 218 }
 219
 220 static inline int reqsk_queue_len(const struct request_sock_queue *queue)
 221 {
 222         return atomic_read(&queue->qlen);
 223 }
 224
 225 static 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 */