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 req->rsk_ops->destructor(req); 112 if (req->rsk_listener) 113 sock_put(req->rsk_listener); 114 kfree(req->saved_syn); 115 kmem_cache_free(req->rsk_ops->slab, req); 116 } 117 118 static inline void reqsk_free(struct request_sock *req) 119 { 120 WARN_ON_ONCE(refcount_read(&req->rsk_refcnt) != 0); 121 __reqsk_free(req); 122 } 123 124 static inline void reqsk_put(struct request_sock *req) 125 { 126 if (refcount_dec_and_test(&req->rsk_refcnt)) 127 reqsk_free(req); 128 } 129 130 /* 131 * For a TCP Fast Open listener - 132 * lock - protects the access to all the reqsk, which is co-owned by 133 * the listener and the child socket. 134 * qlen - pending TFO requests (still in TCP_SYN_RECV). 135 * max_qlen - max TFO reqs allowed before TFO is disabled. 136 * 137 * XXX (TFO) - ideally these fields can be made as part of "listen_sock" 138 * structure above. But there is some implementation difficulty due to 139 * listen_sock being part of request_sock_queue hence will be freed when 140 * a listener is stopped. But TFO related fields may continue to be 141 * accessed even after a listener is closed, until its sk_refcnt drops 142 * to 0 implying no more outstanding TFO reqs. One solution is to keep 143 * listen_opt around until sk_refcnt drops to 0. But there is some other 144 * complexity that needs to be resolved. E.g., a listener can be disabled 145 * temporarily through shutdown()->tcp_disconnect(), and re-enabled later. 146 */ 147 struct fastopen_queue { 148 struct request_sock *rskq_rst_head; /* Keep track of past TFO */ 149 struct request_sock *rskq_rst_tail; /* requests that caused RST. 150 * This is part of the defense 151 * against spoofing attack. 152 */ 153 spinlock_t lock; 154 int qlen; /* # of pending (TCP_SYN_RECV) reqs */ 155 int max_qlen; /* != 0 iff TFO is currently enabled */ 156 157 struct tcp_fastopen_context __rcu *ctx; /* cipher context for cookie */ 158 }; 159 160 /** struct request_sock_queue - queue of request_socks 161 * 162 * @rskq_accept_head - FIFO head of established children 163 * @rskq_accept_tail - FIFO tail of established children 164 * @rskq_defer_accept - User waits for some data after accept() 165 * 166 */ 167 struct request_sock_queue { 168 spinlock_t rskq_lock; 169 u8 rskq_defer_accept; 170 171 u32 synflood_warned; 172 atomic_t qlen; 173 atomic_t young; 174 175 struct request_sock *rskq_accept_head; 176 struct request_sock *rskq_accept_tail; 177 struct fastopen_queue fastopenq; /* Check max_qlen != 0 to determine 178 * if TFO is enabled. 179 */ 180 }; 181 182 void reqsk_queue_alloc(struct request_sock_queue *queue); 183 184 void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req, 185 bool reset); 186 187 static inline bool reqsk_queue_empty(const struct request_sock_queue *queue) 188 { 189 return queue->rskq_accept_head == NULL; 190 } 191 192 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue, 193 struct sock *parent) 194 { 195 struct request_sock *req; 196 197 spin_lock_bh(&queue->rskq_lock); 198 req = queue->rskq_accept_head; 199 if (req) { 200 sk_acceptq_removed(parent); 201 queue->rskq_accept_head = req->dl_next; 202 if (queue->rskq_accept_head == NULL) 203 queue->rskq_accept_tail = NULL; 204 } 205 spin_unlock_bh(&queue->rskq_lock); 206 return req; 207 } 208 209 static inline void reqsk_queue_removed(struct request_sock_queue *queue, 210 const struct request_sock *req) 211 { 212 if (req->num_timeout == 0) 213 atomic_dec(&queue->young); 214 atomic_dec(&queue->qlen); 215 } 216 217 static inline void reqsk_queue_added(struct request_sock_queue *queue) 218 { 219 atomic_inc(&queue->young); 220 atomic_inc(&queue->qlen); 221 } 222 223 static inline int reqsk_queue_len(const struct request_sock_queue *queue) 224 { 225 return atomic_read(&queue->qlen); 226 } 227 228 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue) 229 { 230 return atomic_read(&queue->young); 231 } 232 233 #endif /* _REQUEST_SOCK_H */ 234