include/net/request_sock.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /*
   3  * NET          Generic infrastructure for Network protocols.
   4  *
   5  *              Definitions for request_sock
   6  *
   7  * Authors:     Arnaldo Carvalho de Melo <acme@conectiva.com.br>
   8  *
   9  *              From code originally in include/net/tcp.h
  10  */
  11 #ifndef _REQUEST_SOCK_H
  12 #define _REQUEST_SOCK_H
  13
  14 #include <linux/slab.h>
  15 #include <linux/spinlock.h>
  16 #include <linux/types.h>
  17 #include <linux/bug.h>
  18 #include <linux/refcount.h>
  19
  20 #include <net/sock.h>
  21
  22 struct request_sock;
  23 struct sk_buff;
  24 struct dst_entry;
  25 struct proto;
  26
  27 struct request_sock_ops {
  28         int             family;
  29         unsigned int    obj_size;
  30         struct kmem_cache       *slab;
  31         char            *slab_name;
  32         int             (*rtx_syn_ack)(const struct sock *sk,
  33                                        struct request_sock *req);
  34         void            (*send_ack)(const struct sock *sk, struct sk_buff *skb,
  35                                     struct request_sock *req);
  36         void            (*send_reset)(const struct sock *sk,
  37                                       struct sk_buff *skb);
  38         void            (*destructor)(struct request_sock *req);
  39         void            (*syn_ack_timeout)(const struct request_sock *req);
  40 };
  41
  42 int inet_rtx_syn_ack(const struct sock *parent, struct request_sock *req);
  43
  44 /* struct request_sock - mini sock to represent a connection request
  45  */
  46 struct request_sock {
  47         struct sock_common              __req_common;
  48 #define rsk_refcnt                      __req_common.skc_refcnt
  49 #define rsk_hash                        __req_common.skc_hash
  50 #define rsk_listener                    __req_common.skc_listener
  51 #define rsk_window_clamp                __req_common.skc_window_clamp
  52 #define rsk_rcv_wnd                     __req_common.skc_rcv_wnd
  53
  54         struct request_sock             *dl_next;
  55         u16                             mss;
  56         u8                              num_retrans; /* number of retransmits */
  57         u8                              cookie_ts:1; /* syncookie: encode tcpopts in timestamp */
  58         u8                              num_timeout:7; /* number of timeouts */
  59         u32                             ts_recent;
  60         struct timer_list               rsk_timer;
  61         const struct request_sock_ops   *rsk_ops;
  62         struct sock                     *sk;
  63         u32                             *saved_syn;
  64         u32                             secid;
  65         u32                             peer_secid;
  66 };
  67
  68 static inline struct request_sock *inet_reqsk(const struct sock *sk)
  69 {
  70         return (struct request_sock *)sk;
  71 }
  72
  73 static inline struct sock *req_to_sk(struct request_sock *req)
  74 {
  75         return (struct sock *)req;
  76 }
  77
  78 static inline struct request_sock *
  79 reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener,
  80             bool attach_listener)
  81 {
  82         struct request_sock *req;
  83
  84         req = kmem_cache_alloc(ops->slab, GFP_ATOMIC | __GFP_NOWARN);
  85         if (!req)
  86                 return NULL;
  87         req->rsk_listener = NULL;
  88         if (attach_listener) {
  89                 if (unlikely(!refcount_inc_not_zero(&sk_listener->sk_refcnt))) {
  90                         kmem_cache_free(ops->slab, req);
  91                         return NULL;
  92                 }
  93                 req->rsk_listener = sk_listener;
  94         }
  95         req->rsk_ops = ops;
  96         req_to_sk(req)->sk_prot = sk_listener->sk_prot;
  97         sk_node_init(&req_to_sk(req)->sk_node);
  98         sk_tx_queue_clear(req_to_sk(req));
  99         req->saved_syn = NULL;
 100         req->num_timeout = 0;
 101         req->num_retrans = 0;
 102         req->sk = NULL;
 103         refcount_set(&req->rsk_refcnt, 0);
 104
 105         return req;
 106 }
 107
 108 static inline void __reqsk_free(struct request_sock *req)
 109 {
 110         req->rsk_ops->destructor(req);
 111         if (req->rsk_listener)
 112                 sock_put(req->rsk_listener);
 113         kfree(req->saved_syn);
 114         kmem_cache_free(req->rsk_ops->slab, req);
 115 }
 116
 117 static inline void reqsk_free(struct request_sock *req)
 118 {
 119         WARN_ON_ONCE(refcount_read(&req->rsk_refcnt) != 0);
 120         __reqsk_free(req);
 121 }
 122
 123 static inline void reqsk_put(struct request_sock *req)
 124 {
 125         if (refcount_dec_and_test(&req->rsk_refcnt))
 126                 reqsk_free(req);
 127 }
 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         struct tcp_fastopen_context __rcu *ctx; /* cipher context for cookie */
 157 };
 158
 159 /** struct request_sock_queue - queue of request_socks
 160  *
 161  * @rskq_accept_head - FIFO head of established children
 162  * @rskq_accept_tail - FIFO tail of established children
 163  * @rskq_defer_accept - User waits for some data after accept()
 164  *
 165  */
 166 struct request_sock_queue {
 167         spinlock_t              rskq_lock;
 168         u8                      rskq_defer_accept;
 169
 170         u32                     synflood_warned;
 171         atomic_t                qlen;
 172         atomic_t                young;
 173
 174         struct request_sock     *rskq_accept_head;
 175         struct request_sock     *rskq_accept_tail;
 176         struct fastopen_queue   fastopenq;  /* Check max_qlen != 0 to determine
 177                                              * if TFO is enabled.
 178                                              */
 179 };
 180
 181 void reqsk_queue_alloc(struct request_sock_queue *queue);
 182
 183 void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
 184                            bool reset);
 185
 186 static inline bool reqsk_queue_empty(const struct request_sock_queue *queue)
 187 {
 188         return READ_ONCE(queue->rskq_accept_head) == NULL;
 189 }
 190
 191 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue,
 192                                                       struct sock *parent)
 193 {
 194         struct request_sock *req;
 195
 196         spin_lock_bh(&queue->rskq_lock);
 197         req = queue->rskq_accept_head;
 198         if (req) {
 199                 sk_acceptq_removed(parent);
 200                 WRITE_ONCE(queue->rskq_accept_head, req->dl_next);
 201                 if (queue->rskq_accept_head == NULL)
 202                         queue->rskq_accept_tail = NULL;
 203         }
 204         spin_unlock_bh(&queue->rskq_lock);
 205         return req;
 206 }
 207
 208 static inline void reqsk_queue_removed(struct request_sock_queue *queue,
 209                                        const struct request_sock *req)
 210 {
 211         if (req->num_timeout == 0)
 212                 atomic_dec(&queue->young);
 213         atomic_dec(&queue->qlen);
 214 }
 215
 216 static inline void reqsk_queue_added(struct request_sock_queue *queue)
 217 {
 218         atomic_inc(&queue->young);
 219         atomic_inc(&queue->qlen);
 220 }
 221
 222 static inline int reqsk_queue_len(const struct request_sock_queue *queue)
 223 {
 224         return atomic_read(&queue->qlen);
 225 }
 226
 227 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
 228 {
 229         return atomic_read(&queue->young);
 230 }
 231
 232 #endif /* _REQUEST_SOCK_H */