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 /** 87 * skb_steal_sock - steal a socket from an sk_buff 88 * @skb: sk_buff to steal the socket from 89 * @refcounted: is set to true if the socket is reference-counted 90 * @prefetched: is set to true if the socket was assigned from bpf 91 */ 92 static inline struct sock *skb_steal_sock(struct sk_buff *skb, 93 bool *refcounted, bool *prefetched) 94 { 95 struct sock *sk = skb->sk; 96 97 if (!sk) { 98 *prefetched = false; 99 *refcounted = false; 100 return NULL; 101 } 102 103 *prefetched = skb_sk_is_prefetched(skb); 104 if (*prefetched) { 105 #if IS_ENABLED(CONFIG_SYN_COOKIES) 106 if (sk->sk_state == TCP_NEW_SYN_RECV && inet_reqsk(sk)->syncookie) { 107 struct request_sock *req = inet_reqsk(sk); 108 109 *refcounted = false; 110 sk = req->rsk_listener; 111 req->rsk_listener = NULL; 112 return sk; 113 } 114 #endif 115 *refcounted = sk_is_refcounted(sk); 116 } else { 117 *refcounted = true; 118 } 119 120 skb->destructor = NULL; 121 skb->sk = NULL; 122 return sk; 123 } 124 125 static inline struct request_sock * 126 reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener, 127 bool attach_listener) 128 { 129 struct request_sock *req; 130 131 req = kmem_cache_alloc(ops->slab, GFP_ATOMIC | __GFP_NOWARN); 132 if (!req) 133 return NULL; 134 req->rsk_listener = NULL; 135 if (attach_listener) { 136 if (unlikely(!refcount_inc_not_zero(&sk_listener->sk_refcnt))) { 137 kmem_cache_free(ops->slab, req); 138 return NULL; 139 } 140 req->rsk_listener = sk_listener; 141 } 142 req->rsk_ops = ops; 143 req_to_sk(req)->sk_prot = sk_listener->sk_prot; 144 sk_node_init(&req_to_sk(req)->sk_node); 145 sk_tx_queue_clear(req_to_sk(req)); 146 req->saved_syn = NULL; 147 req->timeout = 0; 148 req->num_timeout = 0; 149 req->num_retrans = 0; 150 req->sk = NULL; 151 refcount_set(&req->rsk_refcnt, 0); 152 153 return req; 154 } 155 156 static inline void __reqsk_free(struct request_sock *req) 157 { 158 req->rsk_ops->destructor(req); 159 if (req->rsk_listener) 160 sock_put(req->rsk_listener); 161 kfree(req->saved_syn); 162 kmem_cache_free(req->rsk_ops->slab, req); 163 } 164 165 static inline void reqsk_free(struct request_sock *req) 166 { 167 WARN_ON_ONCE(refcount_read(&req->rsk_refcnt) != 0); 168 __reqsk_free(req); 169 } 170 171 static inline void reqsk_put(struct request_sock *req) 172 { 173 if (refcount_dec_and_test(&req->rsk_refcnt)) 174 reqsk_free(req); 175 } 176 177 /* 178 * For a TCP Fast Open listener - 179 * lock - protects the access to all the reqsk, which is co-owned by 180 * the listener and the child socket. 181 * qlen - pending TFO requests (still in TCP_SYN_RECV). 182 * max_qlen - max TFO reqs allowed before TFO is disabled. 183 * 184 * XXX (TFO) - ideally these fields can be made as part of "listen_sock" 185 * structure above. But there is some implementation difficulty due to 186 * listen_sock being part of request_sock_queue hence will be freed when 187 * a listener is stopped. But TFO related fields may continue to be 188 * accessed even after a listener is closed, until its sk_refcnt drops 189 * to 0 implying no more outstanding TFO reqs. One solution is to keep 190 * listen_opt around until sk_refcnt drops to 0. But there is some other 191 * complexity that needs to be resolved. E.g., a listener can be disabled 192 * temporarily through shutdown()->tcp_disconnect(), and re-enabled later. 193 */ 194 struct fastopen_queue { 195 struct request_sock *rskq_rst_head; /* Keep track of past TFO */ 196 struct request_sock *rskq_rst_tail; /* requests that caused RST. 197 * This is part of the defense 198 * against spoofing attack. 199 */ 200 spinlock_t lock; 201 int qlen; /* # of pending (TCP_SYN_RECV) reqs */ 202 int max_qlen; /* != 0 iff TFO is currently enabled */ 203 204 struct tcp_fastopen_context __rcu *ctx; /* cipher context for cookie */ 205 }; 206 207 /** struct request_sock_queue - queue of request_socks 208 * 209 * @rskq_accept_head - FIFO head of established children 210 * @rskq_accept_tail - FIFO tail of established children 211 * @rskq_defer_accept - User waits for some data after accept() 212 * 213 */ 214 struct request_sock_queue { 215 spinlock_t rskq_lock; 216 u8 rskq_defer_accept; 217 218 u32 synflood_warned; 219 atomic_t qlen; 220 atomic_t young; 221 222 struct request_sock *rskq_accept_head; 223 struct request_sock *rskq_accept_tail; 224 struct fastopen_queue fastopenq; /* Check max_qlen != 0 to determine 225 * if TFO is enabled. 226 */ 227 }; 228 229 void reqsk_queue_alloc(struct request_sock_queue *queue); 230 231 void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req, 232 bool reset); 233 234 static inline bool reqsk_queue_empty(const struct request_sock_queue *queue) 235 { 236 return READ_ONCE(queue->rskq_accept_head) == NULL; 237 } 238 239 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue, 240 struct sock *parent) 241 { 242 struct request_sock *req; 243 244 spin_lock_bh(&queue->rskq_lock); 245 req = queue->rskq_accept_head; 246 if (req) { 247 sk_acceptq_removed(parent); 248 WRITE_ONCE(queue->rskq_accept_head, req->dl_next); 249 if (queue->rskq_accept_head == NULL) 250 queue->rskq_accept_tail = NULL; 251 } 252 spin_unlock_bh(&queue->rskq_lock); 253 return req; 254 } 255 256 static inline void reqsk_queue_removed(struct request_sock_queue *queue, 257 const struct request_sock *req) 258 { 259 if (req->num_timeout == 0) 260 atomic_dec(&queue->young); 261 atomic_dec(&queue->qlen); 262 } 263 264 static inline void reqsk_queue_added(struct request_sock_queue *queue) 265 { 266 atomic_inc(&queue->young); 267 atomic_inc(&queue->qlen); 268 } 269 270 static inline int reqsk_queue_len(const struct request_sock_queue *queue) 271 { 272 return atomic_read(&queue->qlen); 273 } 274 275 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue) 276 { 277 return atomic_read(&queue->young); 278 } 279 280 #endif /* _REQUEST_SOCK_H */ 281