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(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 */ 231