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