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