1 /* SPDX-License-Identifier: GPL-2.0-or-later */ 2 /* 3 * NET Generic infrastructure for Network protocols. 4 * 5 * Definitions for request_sock 6 * 7 * Authors: Arnaldo Carvalho de Melo <acme@conectiva.com.br> 8 * 9 * From code originally in include/net/tcp.h 10 */ 11 #ifndef _REQUEST_SOCK_H 12 #define _REQUEST_SOCK_H 13 14 #include <linux/slab.h> 15 #include <linux/spinlock.h> 16 #include <linux/types.h> 17 #include <linux/bug.h> 18 #include <linux/refcount.h> 19 20 #include <net/sock.h> 21 22 struct request_sock; 23 struct sk_buff; 24 struct dst_entry; 25 struct proto; 26 27 struct request_sock_ops { 28 int family; 29 unsigned int obj_size; 30 struct kmem_cache *slab; 31 char *slab_name; 32 int (*rtx_syn_ack)(const struct sock *sk, 33 struct request_sock *req); 34 void (*send_ack)(const struct sock *sk, struct sk_buff *skb, 35 struct request_sock *req); 36 void (*send_reset)(const struct sock *sk, 37 struct sk_buff *skb); 38 void (*destructor)(struct request_sock *req); 39 void (*syn_ack_timeout)(const struct request_sock *req); 40 }; 41 42 int inet_rtx_syn_ack(const struct sock *parent, struct request_sock *req); 43 44 struct saved_syn { 45 u32 mac_hdrlen; 46 u32 network_hdrlen; 47 u32 tcp_hdrlen; 48 u8 data[]; 49 }; 50 51 /* struct request_sock - mini sock to represent a connection request 52 */ 53 struct request_sock { 54 struct sock_common __req_common; 55 #define rsk_refcnt __req_common.skc_refcnt 56 #define rsk_hash __req_common.skc_hash 57 #define rsk_listener __req_common.skc_listener 58 #define rsk_window_clamp __req_common.skc_window_clamp 59 #define rsk_rcv_wnd __req_common.skc_rcv_wnd 60 61 struct request_sock *dl_next; 62 u16 mss; 63 u8 num_retrans; /* number of retransmits */ 64 u8 syncookie:1; /* syncookie: encode tcpopts in timestamp */ 65 u8 num_timeout:7; /* number of timeouts */ 66 u32 ts_recent; 67 struct timer_list rsk_timer; 68 const struct request_sock_ops *rsk_ops; 69 struct sock *sk; 70 struct saved_syn *saved_syn; 71 u32 secid; 72 u32 peer_secid; 73 u32 timeout; 74 }; 75 76 static inline struct request_sock *inet_reqsk(const struct sock *sk) 77 { 78 return (struct request_sock *)sk; 79 } 80 81 static inline struct sock *req_to_sk(struct request_sock *req) 82 { 83 return (struct sock *)req; 84 } 85 86 static inline struct request_sock * 87 reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener, 88 bool attach_listener) 89 { 90 struct request_sock *req; 91 92 req = kmem_cache_alloc(ops->slab, GFP_ATOMIC | __GFP_NOWARN); 93 if (!req) 94 return NULL; 95 req->rsk_listener = NULL; 96 if (attach_listener) { 97 if (unlikely(!refcount_inc_not_zero(&sk_listener->sk_refcnt))) { 98 kmem_cache_free(ops->slab, req); 99 return NULL; 100 } 101 req->rsk_listener = sk_listener; 102 } 103 req->rsk_ops = ops; 104 req_to_sk(req)->sk_prot = sk_listener->sk_prot; 105 sk_node_init(&req_to_sk(req)->sk_node); 106 sk_tx_queue_clear(req_to_sk(req)); 107 req->saved_syn = NULL; 108 req->timeout = 0; 109 req->num_timeout = 0; 110 req->num_retrans = 0; 111 req->sk = NULL; 112 refcount_set(&req->rsk_refcnt, 0); 113 114 return req; 115 } 116 117 static inline void __reqsk_free(struct request_sock *req) 118 { 119 req->rsk_ops->destructor(req); 120 if (req->rsk_listener) 121 sock_put(req->rsk_listener); 122 kfree(req->saved_syn); 123 kmem_cache_free(req->rsk_ops->slab, req); 124 } 125 126 static inline void reqsk_free(struct request_sock *req) 127 { 128 WARN_ON_ONCE(refcount_read(&req->rsk_refcnt) != 0); 129 __reqsk_free(req); 130 } 131 132 static inline void reqsk_put(struct request_sock *req) 133 { 134 if (refcount_dec_and_test(&req->rsk_refcnt)) 135 reqsk_free(req); 136 } 137 138 /* 139 * For a TCP Fast Open listener - 140 * lock - protects the access to all the reqsk, which is co-owned by 141 * the listener and the child socket. 142 * qlen - pending TFO requests (still in TCP_SYN_RECV). 143 * max_qlen - max TFO reqs allowed before TFO is disabled. 144 * 145 * XXX (TFO) - ideally these fields can be made as part of "listen_sock" 146 * structure above. But there is some implementation difficulty due to 147 * listen_sock being part of request_sock_queue hence will be freed when 148 * a listener is stopped. But TFO related fields may continue to be 149 * accessed even after a listener is closed, until its sk_refcnt drops 150 * to 0 implying no more outstanding TFO reqs. One solution is to keep 151 * listen_opt around until sk_refcnt drops to 0. But there is some other 152 * complexity that needs to be resolved. E.g., a listener can be disabled 153 * temporarily through shutdown()->tcp_disconnect(), and re-enabled later. 154 */ 155 struct fastopen_queue { 156 struct request_sock *rskq_rst_head; /* Keep track of past TFO */ 157 struct request_sock *rskq_rst_tail; /* requests that caused RST. 158 * This is part of the defense 159 * against spoofing attack. 160 */ 161 spinlock_t lock; 162 int qlen; /* # of pending (TCP_SYN_RECV) reqs */ 163 int max_qlen; /* != 0 iff TFO is currently enabled */ 164 165 struct tcp_fastopen_context __rcu *ctx; /* cipher context for cookie */ 166 }; 167 168 /** struct request_sock_queue - queue of request_socks 169 * 170 * @rskq_accept_head - FIFO head of established children 171 * @rskq_accept_tail - FIFO tail of established children 172 * @rskq_defer_accept - User waits for some data after accept() 173 * 174 */ 175 struct request_sock_queue { 176 spinlock_t rskq_lock; 177 u8 rskq_defer_accept; 178 179 u32 synflood_warned; 180 atomic_t qlen; 181 atomic_t young; 182 183 struct request_sock *rskq_accept_head; 184 struct request_sock *rskq_accept_tail; 185 struct fastopen_queue fastopenq; /* Check max_qlen != 0 to determine 186 * if TFO is enabled. 187 */ 188 }; 189 190 void reqsk_queue_alloc(struct request_sock_queue *queue); 191 192 void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req, 193 bool reset); 194 195 static inline bool reqsk_queue_empty(const struct request_sock_queue *queue) 196 { 197 return READ_ONCE(queue->rskq_accept_head) == NULL; 198 } 199 200 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue, 201 struct sock *parent) 202 { 203 struct request_sock *req; 204 205 spin_lock_bh(&queue->rskq_lock); 206 req = queue->rskq_accept_head; 207 if (req) { 208 sk_acceptq_removed(parent); 209 WRITE_ONCE(queue->rskq_accept_head, req->dl_next); 210 if (queue->rskq_accept_head == NULL) 211 queue->rskq_accept_tail = NULL; 212 } 213 spin_unlock_bh(&queue->rskq_lock); 214 return req; 215 } 216 217 static inline void reqsk_queue_removed(struct request_sock_queue *queue, 218 const struct request_sock *req) 219 { 220 if (req->num_timeout == 0) 221 atomic_dec(&queue->young); 222 atomic_dec(&queue->qlen); 223 } 224 225 static inline void reqsk_queue_added(struct request_sock_queue *queue) 226 { 227 atomic_inc(&queue->young); 228 atomic_inc(&queue->qlen); 229 } 230 231 static inline int reqsk_queue_len(const struct request_sock_queue *queue) 232 { 233 return atomic_read(&queue->qlen); 234 } 235 236 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue) 237 { 238 return atomic_read(&queue->young); 239 } 240 241 #endif /* _REQUEST_SOCK_H */ 242