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 }; 74 75 static inline struct request_sock *inet_reqsk(const struct sock *sk) 76 { 77 return (struct request_sock *)sk; 78 } 79 80 static inline struct sock *req_to_sk(struct request_sock *req) 81 { 82 return (struct sock *)req; 83 } 84 85 static inline struct request_sock * 86 reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener, 87 bool attach_listener) 88 { 89 struct request_sock *req; 90 91 req = kmem_cache_alloc(ops->slab, GFP_ATOMIC | __GFP_NOWARN); 92 if (!req) 93 return NULL; 94 req->rsk_listener = NULL; 95 if (attach_listener) { 96 if (unlikely(!refcount_inc_not_zero(&sk_listener->sk_refcnt))) { 97 kmem_cache_free(ops->slab, req); 98 return NULL; 99 } 100 req->rsk_listener = sk_listener; 101 } 102 req->rsk_ops = ops; 103 req_to_sk(req)->sk_prot = sk_listener->sk_prot; 104 sk_node_init(&req_to_sk(req)->sk_node); 105 sk_tx_queue_clear(req_to_sk(req)); 106 req->saved_syn = NULL; 107 req->num_timeout = 0; 108 req->num_retrans = 0; 109 req->sk = NULL; 110 refcount_set(&req->rsk_refcnt, 0); 111 112 return req; 113 } 114 115 static inline void __reqsk_free(struct request_sock *req) 116 { 117 req->rsk_ops->destructor(req); 118 if (req->rsk_listener) 119 sock_put(req->rsk_listener); 120 kfree(req->saved_syn); 121 kmem_cache_free(req->rsk_ops->slab, req); 122 } 123 124 static inline void reqsk_free(struct request_sock *req) 125 { 126 WARN_ON_ONCE(refcount_read(&req->rsk_refcnt) != 0); 127 __reqsk_free(req); 128 } 129 130 static inline void reqsk_put(struct request_sock *req) 131 { 132 if (refcount_dec_and_test(&req->rsk_refcnt)) 133 reqsk_free(req); 134 } 135 136 /* 137 * For a TCP Fast Open listener - 138 * lock - protects the access to all the reqsk, which is co-owned by 139 * the listener and the child socket. 140 * qlen - pending TFO requests (still in TCP_SYN_RECV). 141 * max_qlen - max TFO reqs allowed before TFO is disabled. 142 * 143 * XXX (TFO) - ideally these fields can be made as part of "listen_sock" 144 * structure above. But there is some implementation difficulty due to 145 * listen_sock being part of request_sock_queue hence will be freed when 146 * a listener is stopped. But TFO related fields may continue to be 147 * accessed even after a listener is closed, until its sk_refcnt drops 148 * to 0 implying no more outstanding TFO reqs. One solution is to keep 149 * listen_opt around until sk_refcnt drops to 0. But there is some other 150 * complexity that needs to be resolved. E.g., a listener can be disabled 151 * temporarily through shutdown()->tcp_disconnect(), and re-enabled later. 152 */ 153 struct fastopen_queue { 154 struct request_sock *rskq_rst_head; /* Keep track of past TFO */ 155 struct request_sock *rskq_rst_tail; /* requests that caused RST. 156 * This is part of the defense 157 * against spoofing attack. 158 */ 159 spinlock_t lock; 160 int qlen; /* # of pending (TCP_SYN_RECV) reqs */ 161 int max_qlen; /* != 0 iff TFO is currently enabled */ 162 163 struct tcp_fastopen_context __rcu *ctx; /* cipher context for cookie */ 164 }; 165 166 /** struct request_sock_queue - queue of request_socks 167 * 168 * @rskq_accept_head - FIFO head of established children 169 * @rskq_accept_tail - FIFO tail of established children 170 * @rskq_defer_accept - User waits for some data after accept() 171 * 172 */ 173 struct request_sock_queue { 174 spinlock_t rskq_lock; 175 u8 rskq_defer_accept; 176 177 u32 synflood_warned; 178 atomic_t qlen; 179 atomic_t young; 180 181 struct request_sock *rskq_accept_head; 182 struct request_sock *rskq_accept_tail; 183 struct fastopen_queue fastopenq; /* Check max_qlen != 0 to determine 184 * if TFO is enabled. 185 */ 186 }; 187 188 void reqsk_queue_alloc(struct request_sock_queue *queue); 189 190 void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req, 191 bool reset); 192 193 static inline bool reqsk_queue_empty(const struct request_sock_queue *queue) 194 { 195 return READ_ONCE(queue->rskq_accept_head) == NULL; 196 } 197 198 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue, 199 struct sock *parent) 200 { 201 struct request_sock *req; 202 203 spin_lock_bh(&queue->rskq_lock); 204 req = queue->rskq_accept_head; 205 if (req) { 206 sk_acceptq_removed(parent); 207 WRITE_ONCE(queue->rskq_accept_head, req->dl_next); 208 if (queue->rskq_accept_head == NULL) 209 queue->rskq_accept_tail = NULL; 210 } 211 spin_unlock_bh(&queue->rskq_lock); 212 return req; 213 } 214 215 static inline void reqsk_queue_removed(struct request_sock_queue *queue, 216 const struct request_sock *req) 217 { 218 if (req->num_timeout == 0) 219 atomic_dec(&queue->young); 220 atomic_dec(&queue->qlen); 221 } 222 223 static inline void reqsk_queue_added(struct request_sock_queue *queue) 224 { 225 atomic_inc(&queue->young); 226 atomic_inc(&queue->qlen); 227 } 228 229 static inline int reqsk_queue_len(const struct request_sock_queue *queue) 230 { 231 return atomic_read(&queue->qlen); 232 } 233 234 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue) 235 { 236 return atomic_read(&queue->young); 237 } 238 239 #endif /* _REQUEST_SOCK_H */ 240