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 bool attach_listener) 85 { 86 struct request_sock *req; 87 88 req = kmem_cache_alloc(ops->slab, GFP_ATOMIC | __GFP_NOWARN); 89 90 if (req) { 91 req->rsk_ops = ops; 92 if (attach_listener) { 93 sock_hold(sk_listener); 94 req->rsk_listener = sk_listener; 95 } else { 96 req->rsk_listener = NULL; 97 } 98 req_to_sk(req)->sk_prot = sk_listener->sk_prot; 99 sk_node_init(&req_to_sk(req)->sk_node); 100 sk_tx_queue_clear(req_to_sk(req)); 101 req->saved_syn = NULL; 102 /* Following is temporary. It is coupled with debugging 103 * helpers in reqsk_put() & reqsk_free() 104 */ 105 atomic_set(&req->rsk_refcnt, 0); 106 } 107 return req; 108 } 109 110 static inline void reqsk_free(struct request_sock *req) 111 { 112 /* temporary debugging */ 113 WARN_ON_ONCE(atomic_read(&req->rsk_refcnt) != 0); 114 115 req->rsk_ops->destructor(req); 116 if (req->rsk_listener) 117 sock_put(req->rsk_listener); 118 kfree(req->saved_syn); 119 kmem_cache_free(req->rsk_ops->slab, req); 120 } 121 122 static inline void reqsk_put(struct request_sock *req) 123 { 124 if (atomic_dec_and_test(&req->rsk_refcnt)) 125 reqsk_free(req); 126 } 127 128 extern int sysctl_max_syn_backlog; 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 }; 157 158 /** struct request_sock_queue - queue of request_socks 159 * 160 * @rskq_accept_head - FIFO head of established children 161 * @rskq_accept_tail - FIFO tail of established children 162 * @rskq_defer_accept - User waits for some data after accept() 163 * 164 */ 165 struct request_sock_queue { 166 spinlock_t rskq_lock; 167 u8 rskq_defer_accept; 168 169 u32 synflood_warned; 170 atomic_t qlen; 171 atomic_t young; 172 173 struct request_sock *rskq_accept_head; 174 struct request_sock *rskq_accept_tail; 175 struct fastopen_queue fastopenq; /* Check max_qlen != 0 to determine 176 * if TFO is enabled. 177 */ 178 }; 179 180 void reqsk_queue_alloc(struct request_sock_queue *queue); 181 182 void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req, 183 bool reset); 184 185 static inline bool reqsk_queue_empty(const struct request_sock_queue *queue) 186 { 187 return queue->rskq_accept_head == NULL; 188 } 189 190 static inline void reqsk_queue_add(struct request_sock_queue *queue, 191 struct request_sock *req, 192 struct sock *parent, 193 struct sock *child) 194 { 195 spin_lock(&queue->rskq_lock); 196 req->sk = child; 197 sk_acceptq_added(parent); 198 199 if (queue->rskq_accept_head == NULL) 200 queue->rskq_accept_head = req; 201 else 202 queue->rskq_accept_tail->dl_next = req; 203 204 queue->rskq_accept_tail = req; 205 req->dl_next = NULL; 206 spin_unlock(&queue->rskq_lock); 207 } 208 209 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue, 210 struct sock *parent) 211 { 212 struct request_sock *req; 213 214 spin_lock_bh(&queue->rskq_lock); 215 req = queue->rskq_accept_head; 216 if (req) { 217 sk_acceptq_removed(parent); 218 queue->rskq_accept_head = req->dl_next; 219 if (queue->rskq_accept_head == NULL) 220 queue->rskq_accept_tail = NULL; 221 } 222 spin_unlock_bh(&queue->rskq_lock); 223 return req; 224 } 225 226 static inline void reqsk_queue_removed(struct request_sock_queue *queue, 227 const struct request_sock *req) 228 { 229 if (req->num_timeout == 0) 230 atomic_dec(&queue->young); 231 atomic_dec(&queue->qlen); 232 } 233 234 static inline void reqsk_queue_added(struct request_sock_queue *queue) 235 { 236 atomic_inc(&queue->young); 237 atomic_inc(&queue->qlen); 238 } 239 240 static inline int reqsk_queue_len(const struct request_sock_queue *queue) 241 { 242 return atomic_read(&queue->qlen); 243 } 244 245 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue) 246 { 247 return atomic_read(&queue->young); 248 } 249 250 #endif /* _REQUEST_SOCK_H */ 251