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 extern int inet_rtx_syn_ack(struct sock *parent, struct request_sock *req); 53 54 /* struct request_sock - mini sock to represent a connection request 55 */ 56 struct request_sock { 57 struct request_sock *dl_next; /* Must be first member! */ 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 /* The following two fields can be easily recomputed I think -AK */ 63 u32 window_clamp; /* window clamp at creation time */ 64 u32 rcv_wnd; /* rcv_wnd offered first time */ 65 u32 ts_recent; 66 unsigned long expires; 67 const struct request_sock_ops *rsk_ops; 68 struct sock *sk; 69 u32 secid; 70 u32 peer_secid; 71 }; 72 73 static inline struct request_sock *reqsk_alloc(const struct request_sock_ops *ops) 74 { 75 struct request_sock *req = kmem_cache_alloc(ops->slab, GFP_ATOMIC); 76 77 if (req != NULL) 78 req->rsk_ops = ops; 79 80 return req; 81 } 82 83 static inline void __reqsk_free(struct request_sock *req) 84 { 85 kmem_cache_free(req->rsk_ops->slab, req); 86 } 87 88 static inline void reqsk_free(struct request_sock *req) 89 { 90 req->rsk_ops->destructor(req); 91 __reqsk_free(req); 92 } 93 94 extern int sysctl_max_syn_backlog; 95 96 /** struct listen_sock - listen state 97 * 98 * @max_qlen_log - log_2 of maximal queued SYNs/REQUESTs 99 */ 100 struct listen_sock { 101 u8 max_qlen_log; 102 u8 synflood_warned; 103 /* 2 bytes hole, try to use */ 104 int qlen; 105 int qlen_young; 106 int clock_hand; 107 u32 hash_rnd; 108 u32 nr_table_entries; 109 struct request_sock *syn_table[0]; 110 }; 111 112 /* 113 * For a TCP Fast Open listener - 114 * lock - protects the access to all the reqsk, which is co-owned by 115 * the listener and the child socket. 116 * qlen - pending TFO requests (still in TCP_SYN_RECV). 117 * max_qlen - max TFO reqs allowed before TFO is disabled. 118 * 119 * XXX (TFO) - ideally these fields can be made as part of "listen_sock" 120 * structure above. But there is some implementation difficulty due to 121 * listen_sock being part of request_sock_queue hence will be freed when 122 * a listener is stopped. But TFO related fields may continue to be 123 * accessed even after a listener is closed, until its sk_refcnt drops 124 * to 0 implying no more outstanding TFO reqs. One solution is to keep 125 * listen_opt around until sk_refcnt drops to 0. But there is some other 126 * complexity that needs to be resolved. E.g., a listener can be disabled 127 * temporarily through shutdown()->tcp_disconnect(), and re-enabled later. 128 */ 129 struct fastopen_queue { 130 struct request_sock *rskq_rst_head; /* Keep track of past TFO */ 131 struct request_sock *rskq_rst_tail; /* requests that caused RST. 132 * This is part of the defense 133 * against spoofing attack. 134 */ 135 spinlock_t lock; 136 int qlen; /* # of pending (TCP_SYN_RECV) reqs */ 137 int max_qlen; /* != 0 iff TFO is currently enabled */ 138 }; 139 140 /** struct request_sock_queue - queue of request_socks 141 * 142 * @rskq_accept_head - FIFO head of established children 143 * @rskq_accept_tail - FIFO tail of established children 144 * @rskq_defer_accept - User waits for some data after accept() 145 * @syn_wait_lock - serializer 146 * 147 * %syn_wait_lock is necessary only to avoid proc interface having to grab the main 148 * lock sock while browsing the listening hash (otherwise it's deadlock prone). 149 * 150 * This lock is acquired in read mode only from listening_get_next() seq_file 151 * op and it's acquired in write mode _only_ from code that is actively 152 * changing rskq_accept_head. All readers that are holding the master sock lock 153 * don't need to grab this lock in read mode too as rskq_accept_head. writes 154 * are always protected from the main sock lock. 155 */ 156 struct request_sock_queue { 157 struct request_sock *rskq_accept_head; 158 struct request_sock *rskq_accept_tail; 159 rwlock_t syn_wait_lock; 160 u8 rskq_defer_accept; 161 /* 3 bytes hole, try to pack */ 162 struct listen_sock *listen_opt; 163 struct fastopen_queue *fastopenq; /* This is non-NULL iff TFO has been 164 * enabled on this listener. Check 165 * max_qlen != 0 in fastopen_queue 166 * to determine if TFO is enabled 167 * right at this moment. 168 */ 169 }; 170 171 extern int reqsk_queue_alloc(struct request_sock_queue *queue, 172 unsigned int nr_table_entries); 173 174 extern void __reqsk_queue_destroy(struct request_sock_queue *queue); 175 extern void reqsk_queue_destroy(struct request_sock_queue *queue); 176 extern void reqsk_fastopen_remove(struct sock *sk, 177 struct request_sock *req, bool reset); 178 179 static inline struct request_sock * 180 reqsk_queue_yank_acceptq(struct request_sock_queue *queue) 181 { 182 struct request_sock *req = queue->rskq_accept_head; 183 184 queue->rskq_accept_head = NULL; 185 return req; 186 } 187 188 static inline int reqsk_queue_empty(struct request_sock_queue *queue) 189 { 190 return queue->rskq_accept_head == NULL; 191 } 192 193 static inline void reqsk_queue_unlink(struct request_sock_queue *queue, 194 struct request_sock *req, 195 struct request_sock **prev_req) 196 { 197 write_lock(&queue->syn_wait_lock); 198 *prev_req = req->dl_next; 199 write_unlock(&queue->syn_wait_lock); 200 } 201 202 static inline void reqsk_queue_add(struct request_sock_queue *queue, 203 struct request_sock *req, 204 struct sock *parent, 205 struct sock *child) 206 { 207 req->sk = child; 208 sk_acceptq_added(parent); 209 210 if (queue->rskq_accept_head == NULL) 211 queue->rskq_accept_head = req; 212 else 213 queue->rskq_accept_tail->dl_next = req; 214 215 queue->rskq_accept_tail = req; 216 req->dl_next = NULL; 217 } 218 219 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue) 220 { 221 struct request_sock *req = queue->rskq_accept_head; 222 223 WARN_ON(req == NULL); 224 225 queue->rskq_accept_head = req->dl_next; 226 if (queue->rskq_accept_head == NULL) 227 queue->rskq_accept_tail = NULL; 228 229 return req; 230 } 231 232 static inline int reqsk_queue_removed(struct request_sock_queue *queue, 233 struct request_sock *req) 234 { 235 struct listen_sock *lopt = queue->listen_opt; 236 237 if (req->num_timeout == 0) 238 --lopt->qlen_young; 239 240 return --lopt->qlen; 241 } 242 243 static inline int reqsk_queue_added(struct request_sock_queue *queue) 244 { 245 struct listen_sock *lopt = queue->listen_opt; 246 const int prev_qlen = lopt->qlen; 247 248 lopt->qlen_young++; 249 lopt->qlen++; 250 return prev_qlen; 251 } 252 253 static inline int reqsk_queue_len(const struct request_sock_queue *queue) 254 { 255 return queue->listen_opt != NULL ? queue->listen_opt->qlen : 0; 256 } 257 258 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue) 259 { 260 return queue->listen_opt->qlen_young; 261 } 262 263 static inline int reqsk_queue_is_full(const struct request_sock_queue *queue) 264 { 265 return queue->listen_opt->qlen >> queue->listen_opt->max_qlen_log; 266 } 267 268 static inline void reqsk_queue_hash_req(struct request_sock_queue *queue, 269 u32 hash, struct request_sock *req, 270 unsigned long timeout) 271 { 272 struct listen_sock *lopt = queue->listen_opt; 273 274 req->expires = jiffies + timeout; 275 req->num_retrans = 0; 276 req->num_timeout = 0; 277 req->sk = NULL; 278 req->dl_next = lopt->syn_table[hash]; 279 280 write_lock(&queue->syn_wait_lock); 281 lopt->syn_table[hash] = req; 282 write_unlock(&queue->syn_wait_lock); 283 } 284 285 #endif /* _REQUEST_SOCK_H */ 286