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 /* empty to "strongly type" an otherwise void parameter. 31 */ 32 struct request_values { 33 }; 34 35 struct request_sock_ops { 36 int family; 37 int obj_size; 38 struct kmem_cache *slab; 39 char *slab_name; 40 int (*rtx_syn_ack)(struct sock *sk, 41 struct request_sock *req, 42 struct request_values *rvp); 43 void (*send_ack)(struct sock *sk, struct sk_buff *skb, 44 struct request_sock *req); 45 void (*send_reset)(struct sock *sk, 46 struct sk_buff *skb); 47 void (*destructor)(struct request_sock *req); 48 void (*syn_ack_timeout)(struct sock *sk, 49 struct request_sock *req); 50 }; 51 52 /* struct request_sock - mini sock to represent a connection request 53 */ 54 struct request_sock { 55 struct request_sock *dl_next; /* Must be first member! */ 56 u16 mss; 57 u8 retrans; 58 u8 cookie_ts; /* syncookie: encode tcpopts in timestamp */ 59 /* The following two fields can be easily recomputed I think -AK */ 60 u32 window_clamp; /* window clamp at creation time */ 61 u32 rcv_wnd; /* rcv_wnd offered first time */ 62 u32 ts_recent; 63 unsigned long expires; 64 const struct request_sock_ops *rsk_ops; 65 struct sock *sk; 66 u32 secid; 67 u32 peer_secid; 68 }; 69 70 static inline struct request_sock *reqsk_alloc(const struct request_sock_ops *ops) 71 { 72 struct request_sock *req = kmem_cache_alloc(ops->slab, GFP_ATOMIC); 73 74 if (req != NULL) 75 req->rsk_ops = ops; 76 77 return req; 78 } 79 80 static inline void __reqsk_free(struct request_sock *req) 81 { 82 kmem_cache_free(req->rsk_ops->slab, req); 83 } 84 85 static inline void reqsk_free(struct request_sock *req) 86 { 87 req->rsk_ops->destructor(req); 88 __reqsk_free(req); 89 } 90 91 extern int sysctl_max_syn_backlog; 92 93 /** struct listen_sock - listen state 94 * 95 * @max_qlen_log - log_2 of maximal queued SYNs/REQUESTs 96 */ 97 struct listen_sock { 98 u8 max_qlen_log; 99 u8 synflood_warned; 100 /* 2 bytes hole, try to use */ 101 int qlen; 102 int qlen_young; 103 int clock_hand; 104 u32 hash_rnd; 105 u32 nr_table_entries; 106 struct request_sock *syn_table[0]; 107 }; 108 109 /* 110 * For a TCP Fast Open listener - 111 * lock - protects the access to all the reqsk, which is co-owned by 112 * the listener and the child socket. 113 * qlen - pending TFO requests (still in TCP_SYN_RECV). 114 * max_qlen - max TFO reqs allowed before TFO is disabled. 115 * 116 * XXX (TFO) - ideally these fields can be made as part of "listen_sock" 117 * structure above. But there is some implementation difficulty due to 118 * listen_sock being part of request_sock_queue hence will be freed when 119 * a listener is stopped. But TFO related fields may continue to be 120 * accessed even after a listener is closed, until its sk_refcnt drops 121 * to 0 implying no more outstanding TFO reqs. One solution is to keep 122 * listen_opt around until sk_refcnt drops to 0. But there is some other 123 * complexity that needs to be resolved. E.g., a listener can be disabled 124 * temporarily through shutdown()->tcp_disconnect(), and re-enabled later. 125 */ 126 struct fastopen_queue { 127 struct request_sock *rskq_rst_head; /* Keep track of past TFO */ 128 struct request_sock *rskq_rst_tail; /* requests that caused RST. 129 * This is part of the defense 130 * against spoofing attack. 131 */ 132 spinlock_t lock; 133 int qlen; /* # of pending (TCP_SYN_RECV) reqs */ 134 int max_qlen; /* != 0 iff TFO is currently enabled */ 135 }; 136 137 /** struct request_sock_queue - queue of request_socks 138 * 139 * @rskq_accept_head - FIFO head of established children 140 * @rskq_accept_tail - FIFO tail of established children 141 * @rskq_defer_accept - User waits for some data after accept() 142 * @syn_wait_lock - serializer 143 * 144 * %syn_wait_lock is necessary only to avoid proc interface having to grab the main 145 * lock sock while browsing the listening hash (otherwise it's deadlock prone). 146 * 147 * This lock is acquired in read mode only from listening_get_next() seq_file 148 * op and it's acquired in write mode _only_ from code that is actively 149 * changing rskq_accept_head. All readers that are holding the master sock lock 150 * don't need to grab this lock in read mode too as rskq_accept_head. writes 151 * are always protected from the main sock lock. 152 */ 153 struct request_sock_queue { 154 struct request_sock *rskq_accept_head; 155 struct request_sock *rskq_accept_tail; 156 rwlock_t syn_wait_lock; 157 u8 rskq_defer_accept; 158 /* 3 bytes hole, try to pack */ 159 struct listen_sock *listen_opt; 160 struct fastopen_queue *fastopenq; /* This is non-NULL iff TFO has been 161 * enabled on this listener. Check 162 * max_qlen != 0 in fastopen_queue 163 * to determine if TFO is enabled 164 * right at this moment. 165 */ 166 }; 167 168 extern int reqsk_queue_alloc(struct request_sock_queue *queue, 169 unsigned int nr_table_entries); 170 171 extern void __reqsk_queue_destroy(struct request_sock_queue *queue); 172 extern void reqsk_queue_destroy(struct request_sock_queue *queue); 173 extern void reqsk_fastopen_remove(struct sock *sk, 174 struct request_sock *req, bool reset); 175 176 static inline struct request_sock * 177 reqsk_queue_yank_acceptq(struct request_sock_queue *queue) 178 { 179 struct request_sock *req = queue->rskq_accept_head; 180 181 queue->rskq_accept_head = NULL; 182 return req; 183 } 184 185 static inline int reqsk_queue_empty(struct request_sock_queue *queue) 186 { 187 return queue->rskq_accept_head == NULL; 188 } 189 190 static inline void reqsk_queue_unlink(struct request_sock_queue *queue, 191 struct request_sock *req, 192 struct request_sock **prev_req) 193 { 194 write_lock(&queue->syn_wait_lock); 195 *prev_req = req->dl_next; 196 write_unlock(&queue->syn_wait_lock); 197 } 198 199 static inline void reqsk_queue_add(struct request_sock_queue *queue, 200 struct request_sock *req, 201 struct sock *parent, 202 struct sock *child) 203 { 204 req->sk = child; 205 sk_acceptq_added(parent); 206 207 if (queue->rskq_accept_head == NULL) 208 queue->rskq_accept_head = req; 209 else 210 queue->rskq_accept_tail->dl_next = req; 211 212 queue->rskq_accept_tail = req; 213 req->dl_next = NULL; 214 } 215 216 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue) 217 { 218 struct request_sock *req = queue->rskq_accept_head; 219 220 WARN_ON(req == NULL); 221 222 queue->rskq_accept_head = req->dl_next; 223 if (queue->rskq_accept_head == NULL) 224 queue->rskq_accept_tail = NULL; 225 226 return req; 227 } 228 229 static inline int reqsk_queue_removed(struct request_sock_queue *queue, 230 struct request_sock *req) 231 { 232 struct listen_sock *lopt = queue->listen_opt; 233 234 if (req->retrans == 0) 235 --lopt->qlen_young; 236 237 return --lopt->qlen; 238 } 239 240 static inline int reqsk_queue_added(struct request_sock_queue *queue) 241 { 242 struct listen_sock *lopt = queue->listen_opt; 243 const int prev_qlen = lopt->qlen; 244 245 lopt->qlen_young++; 246 lopt->qlen++; 247 return prev_qlen; 248 } 249 250 static inline int reqsk_queue_len(const struct request_sock_queue *queue) 251 { 252 return queue->listen_opt != NULL ? queue->listen_opt->qlen : 0; 253 } 254 255 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue) 256 { 257 return queue->listen_opt->qlen_young; 258 } 259 260 static inline int reqsk_queue_is_full(const struct request_sock_queue *queue) 261 { 262 return queue->listen_opt->qlen >> queue->listen_opt->max_qlen_log; 263 } 264 265 static inline void reqsk_queue_hash_req(struct request_sock_queue *queue, 266 u32 hash, struct request_sock *req, 267 unsigned long timeout) 268 { 269 struct listen_sock *lopt = queue->listen_opt; 270 271 req->expires = jiffies + timeout; 272 req->retrans = 0; 273 req->sk = NULL; 274 req->dl_next = lopt->syn_table[hash]; 275 276 write_lock(&queue->syn_wait_lock); 277 lopt->syn_table[hash] = req; 278 write_unlock(&queue->syn_wait_lock); 279 } 280 281 #endif /* _REQUEST_SOCK_H */ 282