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)(struct sock *sk, 36 struct request_sock *req); 37 void (*send_ack)(struct sock *sk, struct sk_buff *skb, 38 struct request_sock *req); 39 void (*send_reset)(struct sock *sk, 40 struct sk_buff *skb); 41 void (*destructor)(struct request_sock *req); 42 void (*syn_ack_timeout)(struct sock *sk, 43 struct request_sock *req); 44 }; 45 46 extern int inet_rtx_syn_ack(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 request_sock *dl_next; 52 u16 mss; 53 u8 num_retrans; /* number of retransmits */ 54 u8 cookie_ts:1; /* syncookie: encode tcpopts in timestamp */ 55 u8 num_timeout:7; /* number of timeouts */ 56 /* The following two fields can be easily recomputed I think -AK */ 57 u32 window_clamp; /* window clamp at creation time */ 58 u32 rcv_wnd; /* rcv_wnd offered first time */ 59 u32 ts_recent; 60 unsigned long expires; 61 const struct request_sock_ops *rsk_ops; 62 struct sock *sk; 63 u32 secid; 64 u32 peer_secid; 65 }; 66 67 static inline struct request_sock *reqsk_alloc(const struct request_sock_ops *ops) 68 { 69 struct request_sock *req = kmem_cache_alloc(ops->slab, GFP_ATOMIC); 70 71 if (req != NULL) 72 req->rsk_ops = ops; 73 74 return req; 75 } 76 77 static inline void __reqsk_free(struct request_sock *req) 78 { 79 kmem_cache_free(req->rsk_ops->slab, req); 80 } 81 82 static inline void reqsk_free(struct request_sock *req) 83 { 84 req->rsk_ops->destructor(req); 85 __reqsk_free(req); 86 } 87 88 extern int sysctl_max_syn_backlog; 89 90 /** struct listen_sock - listen state 91 * 92 * @max_qlen_log - log_2 of maximal queued SYNs/REQUESTs 93 */ 94 struct listen_sock { 95 u8 max_qlen_log; 96 u8 synflood_warned; 97 /* 2 bytes hole, try to use */ 98 int qlen; 99 int qlen_young; 100 int clock_hand; 101 u32 hash_rnd; 102 u32 nr_table_entries; 103 struct request_sock *syn_table[0]; 104 }; 105 106 /* 107 * For a TCP Fast Open listener - 108 * lock - protects the access to all the reqsk, which is co-owned by 109 * the listener and the child socket. 110 * qlen - pending TFO requests (still in TCP_SYN_RECV). 111 * max_qlen - max TFO reqs allowed before TFO is disabled. 112 * 113 * XXX (TFO) - ideally these fields can be made as part of "listen_sock" 114 * structure above. But there is some implementation difficulty due to 115 * listen_sock being part of request_sock_queue hence will be freed when 116 * a listener is stopped. But TFO related fields may continue to be 117 * accessed even after a listener is closed, until its sk_refcnt drops 118 * to 0 implying no more outstanding TFO reqs. One solution is to keep 119 * listen_opt around until sk_refcnt drops to 0. But there is some other 120 * complexity that needs to be resolved. E.g., a listener can be disabled 121 * temporarily through shutdown()->tcp_disconnect(), and re-enabled later. 122 */ 123 struct fastopen_queue { 124 struct request_sock *rskq_rst_head; /* Keep track of past TFO */ 125 struct request_sock *rskq_rst_tail; /* requests that caused RST. 126 * This is part of the defense 127 * against spoofing attack. 128 */ 129 spinlock_t lock; 130 int qlen; /* # of pending (TCP_SYN_RECV) reqs */ 131 int max_qlen; /* != 0 iff TFO is currently enabled */ 132 }; 133 134 /** struct request_sock_queue - queue of request_socks 135 * 136 * @rskq_accept_head - FIFO head of established children 137 * @rskq_accept_tail - FIFO tail of established children 138 * @rskq_defer_accept - User waits for some data after accept() 139 * @syn_wait_lock - serializer 140 * 141 * %syn_wait_lock is necessary only to avoid proc interface having to grab the main 142 * lock sock while browsing the listening hash (otherwise it's deadlock prone). 143 * 144 * This lock is acquired in read mode only from listening_get_next() seq_file 145 * op and it's acquired in write mode _only_ from code that is actively 146 * changing rskq_accept_head. All readers that are holding the master sock lock 147 * don't need to grab this lock in read mode too as rskq_accept_head. writes 148 * are always protected from the main sock lock. 149 */ 150 struct request_sock_queue { 151 struct request_sock *rskq_accept_head; 152 struct request_sock *rskq_accept_tail; 153 rwlock_t syn_wait_lock; 154 u8 rskq_defer_accept; 155 /* 3 bytes hole, try to pack */ 156 struct listen_sock *listen_opt; 157 struct fastopen_queue *fastopenq; /* This is non-NULL iff TFO has been 158 * enabled on this listener. Check 159 * max_qlen != 0 in fastopen_queue 160 * to determine if TFO is enabled 161 * right at this moment. 162 */ 163 }; 164 165 extern int reqsk_queue_alloc(struct request_sock_queue *queue, 166 unsigned int nr_table_entries); 167 168 extern void __reqsk_queue_destroy(struct request_sock_queue *queue); 169 extern void reqsk_queue_destroy(struct request_sock_queue *queue); 170 extern void reqsk_fastopen_remove(struct sock *sk, 171 struct request_sock *req, bool reset); 172 173 static inline struct request_sock * 174 reqsk_queue_yank_acceptq(struct request_sock_queue *queue) 175 { 176 struct request_sock *req = queue->rskq_accept_head; 177 178 queue->rskq_accept_head = NULL; 179 return req; 180 } 181 182 static inline int reqsk_queue_empty(struct request_sock_queue *queue) 183 { 184 return queue->rskq_accept_head == NULL; 185 } 186 187 static inline void reqsk_queue_unlink(struct request_sock_queue *queue, 188 struct request_sock *req, 189 struct request_sock **prev_req) 190 { 191 write_lock(&queue->syn_wait_lock); 192 *prev_req = req->dl_next; 193 write_unlock(&queue->syn_wait_lock); 194 } 195 196 static inline void reqsk_queue_add(struct request_sock_queue *queue, 197 struct request_sock *req, 198 struct sock *parent, 199 struct sock *child) 200 { 201 req->sk = child; 202 sk_acceptq_added(parent); 203 204 if (queue->rskq_accept_head == NULL) 205 queue->rskq_accept_head = req; 206 else 207 queue->rskq_accept_tail->dl_next = req; 208 209 queue->rskq_accept_tail = req; 210 req->dl_next = NULL; 211 } 212 213 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue) 214 { 215 struct request_sock *req = queue->rskq_accept_head; 216 217 WARN_ON(req == NULL); 218 219 queue->rskq_accept_head = req->dl_next; 220 if (queue->rskq_accept_head == NULL) 221 queue->rskq_accept_tail = NULL; 222 223 return req; 224 } 225 226 static inline int reqsk_queue_removed(struct request_sock_queue *queue, 227 struct request_sock *req) 228 { 229 struct listen_sock *lopt = queue->listen_opt; 230 231 if (req->num_timeout == 0) 232 --lopt->qlen_young; 233 234 return --lopt->qlen; 235 } 236 237 static inline int reqsk_queue_added(struct request_sock_queue *queue) 238 { 239 struct listen_sock *lopt = queue->listen_opt; 240 const int prev_qlen = lopt->qlen; 241 242 lopt->qlen_young++; 243 lopt->qlen++; 244 return prev_qlen; 245 } 246 247 static inline int reqsk_queue_len(const struct request_sock_queue *queue) 248 { 249 return queue->listen_opt != NULL ? queue->listen_opt->qlen : 0; 250 } 251 252 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue) 253 { 254 return queue->listen_opt->qlen_young; 255 } 256 257 static inline int reqsk_queue_is_full(const struct request_sock_queue *queue) 258 { 259 return queue->listen_opt->qlen >> queue->listen_opt->max_qlen_log; 260 } 261 262 static inline void reqsk_queue_hash_req(struct request_sock_queue *queue, 263 u32 hash, struct request_sock *req, 264 unsigned long timeout) 265 { 266 struct listen_sock *lopt = queue->listen_opt; 267 268 req->expires = jiffies + timeout; 269 req->num_retrans = 0; 270 req->num_timeout = 0; 271 req->sk = NULL; 272 req->dl_next = lopt->syn_table[hash]; 273 274 write_lock(&queue->syn_wait_lock); 275 lopt->syn_table[hash] = req; 276 write_unlock(&queue->syn_wait_lock); 277 } 278 279 #endif /* _REQUEST_SOCK_H */ 280