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
  54         struct request_sock             *dl_next;
  55         struct sock                     *rsk_listener;
  56         u16                             mss;
  57         u8                              num_retrans; /* number of retransmits */
  58         u8                              cookie_ts:1; /* syncookie: encode tcpopts in timestamp */
  59         u8                              num_timeout:7; /* number of timeouts */
  60         /* The following two fields can be easily recomputed I think -AK */
  61         u32                             window_clamp; /* window clamp at creation time */
  62         u32                             rcv_wnd;          /* rcv_wnd offered first time */
  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(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 {
  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                 sock_hold(sk_listener);
  92                 req->rsk_listener = sk_listener;
  93                 req_to_sk(req)->sk_prot = sk_listener->sk_prot;
  94                 sk_node_init(&req_to_sk(req)->sk_node);
  95                 req->saved_syn = NULL;
  96                 /* Following is temporary. It is coupled with debugging
  97                  * helpers in reqsk_put() & reqsk_free()
  98                  */
  99                 atomic_set(&req->rsk_refcnt, 0);
 100         }
 101         return req;
 102 }
 103
 104 static inline void reqsk_free(struct request_sock *req)
 105 {
 106         /* temporary debugging */
 107         WARN_ON_ONCE(atomic_read(&req->rsk_refcnt) != 0);
 108
 109         req->rsk_ops->destructor(req);
 110         if (req->rsk_listener)
 111                 sock_put(req->rsk_listener);
 112         kfree(req->saved_syn);
 113         kmem_cache_free(req->rsk_ops->slab, req);
 114 }
 115
 116 static inline void reqsk_put(struct request_sock *req)
 117 {
 118         if (atomic_dec_and_test(&req->rsk_refcnt))
 119                 reqsk_free(req);
 120 }
 121
 122 extern int sysctl_max_syn_backlog;
 123
 124 /*
 125  * For a TCP Fast Open listener -
 126  *      lock - protects the access to all the reqsk, which is co-owned by
 127  *              the listener and the child socket.
 128  *      qlen - pending TFO requests (still in TCP_SYN_RECV).
 129  *      max_qlen - max TFO reqs allowed before TFO is disabled.
 130  *
 131  *      XXX (TFO) - ideally these fields can be made as part of "listen_sock"
 132  *      structure above. But there is some implementation difficulty due to
 133  *      listen_sock being part of request_sock_queue hence will be freed when
 134  *      a listener is stopped. But TFO related fields may continue to be
 135  *      accessed even after a listener is closed, until its sk_refcnt drops
 136  *      to 0 implying no more outstanding TFO reqs. One solution is to keep
 137  *      listen_opt around until sk_refcnt drops to 0. But there is some other
 138  *      complexity that needs to be resolved. E.g., a listener can be disabled
 139  *      temporarily through shutdown()->tcp_disconnect(), and re-enabled later.
 140  */
 141 struct fastopen_queue {
 142         struct request_sock     *rskq_rst_head; /* Keep track of past TFO */
 143         struct request_sock     *rskq_rst_tail; /* requests that caused RST.
 144                                                  * This is part of the defense
 145                                                  * against spoofing attack.
 146                                                  */
 147         spinlock_t      lock;
 148         int             qlen;           /* # of pending (TCP_SYN_RECV) reqs */
 149         int             max_qlen;       /* != 0 iff TFO is currently enabled */
 150 };
 151
 152 /** struct request_sock_queue - queue of request_socks
 153  *
 154  * @rskq_accept_head - FIFO head of established children
 155  * @rskq_accept_tail - FIFO tail of established children
 156  * @rskq_defer_accept - User waits for some data after accept()
 157  *
 158  */
 159 struct request_sock_queue {
 160         spinlock_t              rskq_lock;
 161         u8                      rskq_defer_accept;
 162
 163         u32                     synflood_warned;
 164         atomic_t                qlen;
 165         atomic_t                young;
 166
 167         struct request_sock     *rskq_accept_head;
 168         struct request_sock     *rskq_accept_tail;
 169         struct fastopen_queue   fastopenq;  /* Check max_qlen != 0 to determine
 170                                              * if TFO is enabled.
 171                                              */
 172 };
 173
 174 void reqsk_queue_alloc(struct request_sock_queue *queue);
 175
 176 void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
 177                            bool reset);
 178
 179 static inline bool reqsk_queue_empty(const struct request_sock_queue *queue)
 180 {
 181         return queue->rskq_accept_head == NULL;
 182 }
 183
 184 static inline void reqsk_queue_add(struct request_sock_queue *queue,
 185                                    struct request_sock *req,
 186                                    struct sock *parent,
 187                                    struct sock *child)
 188 {
 189         spin_lock(&queue->rskq_lock);
 190         req->sk = child;
 191         sk_acceptq_added(parent);
 192
 193         if (queue->rskq_accept_head == NULL)
 194                 queue->rskq_accept_head = req;
 195         else
 196                 queue->rskq_accept_tail->dl_next = req;
 197
 198         queue->rskq_accept_tail = req;
 199         req->dl_next = NULL;
 200         spin_unlock(&queue->rskq_lock);
 201 }
 202
 203 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue,
 204                                                       struct sock *parent)
 205 {
 206         struct request_sock *req;
 207
 208         spin_lock_bh(&queue->rskq_lock);
 209         req = queue->rskq_accept_head;
 210         if (req) {
 211                 sk_acceptq_removed(parent);
 212                 queue->rskq_accept_head = req->dl_next;
 213                 if (queue->rskq_accept_head == NULL)
 214                         queue->rskq_accept_tail = NULL;
 215         }
 216         spin_unlock_bh(&queue->rskq_lock);
 217         return req;
 218 }
 219
 220 static inline void reqsk_queue_removed(struct request_sock_queue *queue,
 221                                        const struct request_sock *req)
 222 {
 223         if (req->num_timeout == 0)
 224                 atomic_dec(&queue->young);
 225         atomic_dec(&queue->qlen);
 226 }
 227
 228 static inline void reqsk_queue_added(struct request_sock_queue *queue)
 229 {
 230         atomic_inc(&queue->young);
 231         atomic_inc(&queue->qlen);
 232 }
 233
 234 static inline int reqsk_queue_len(const struct request_sock_queue *queue)
 235 {
 236         return atomic_read(&queue->qlen);
 237 }
 238
 239 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
 240 {
 241         return atomic_read(&queue->young);
 242 }
 243
 244 #endif /* _REQUEST_SOCK_H */