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; /* True if 65 * 1) tcpopts needs to be encoded in 66 * TS of SYN+ACK 67 * 2) ACK is validated by BPF kfunc. 68 */ 69 u8 num_timeout:7; /* number of timeouts */ 70 u32 ts_recent; 71 struct timer_list rsk_timer; 72 const struct request_sock_ops *rsk_ops; 73 struct sock *sk; 74 struct saved_syn *saved_syn; 75 u32 secid; 76 u32 peer_secid; 77 u32 timeout; 78 }; 79 80 static inline struct request_sock *inet_reqsk(const struct sock *sk) 81 { 82 return (struct request_sock *)sk; 83 } 84 85 static inline struct sock *req_to_sk(struct request_sock *req) 86 { 87 return (struct sock *)req; 88 } 89 90 /** 91 * skb_steal_sock - steal a socket from an sk_buff 92 * @skb: sk_buff to steal the socket from 93 * @refcounted: is set to true if the socket is reference-counted 94 * @prefetched: is set to true if the socket was assigned from bpf 95 */ 96 static inline struct sock *skb_steal_sock(struct sk_buff *skb, 97 bool *refcounted, bool *prefetched) 98 { 99 struct sock *sk = skb->sk; 100 101 if (!sk) { 102 *prefetched = false; 103 *refcounted = false; 104 return NULL; 105 } 106 107 *prefetched = skb_sk_is_prefetched(skb); 108 if (*prefetched) { 109 #if IS_ENABLED(CONFIG_SYN_COOKIES) 110 if (sk->sk_state == TCP_NEW_SYN_RECV && inet_reqsk(sk)->syncookie) { 111 struct request_sock *req = inet_reqsk(sk); 112 113 *refcounted = false; 114 sk = req->rsk_listener; 115 req->rsk_listener = NULL; 116 return sk; 117 } 118 #endif 119 *refcounted = sk_is_refcounted(sk); 120 } else { 121 *refcounted = true; 122 } 123 124 skb->destructor = NULL; 125 skb->sk = NULL; 126 return sk; 127 } 128 129 static inline struct request_sock * 130 reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener, 131 bool attach_listener) 132 { 133 struct request_sock *req; 134 135 req = kmem_cache_alloc(ops->slab, GFP_ATOMIC | __GFP_NOWARN); 136 if (!req) 137 return NULL; 138 req->rsk_listener = NULL; 139 if (attach_listener) { 140 if (unlikely(!refcount_inc_not_zero(&sk_listener->sk_refcnt))) { 141 kmem_cache_free(ops->slab, req); 142 return NULL; 143 } 144 req->rsk_listener = sk_listener; 145 } 146 req->rsk_ops = ops; 147 req_to_sk(req)->sk_prot = sk_listener->sk_prot; 148 sk_node_init(&req_to_sk(req)->sk_node); 149 sk_tx_queue_clear(req_to_sk(req)); 150 req->saved_syn = NULL; 151 req->syncookie = 0; 152 req->timeout = 0; 153 req->num_timeout = 0; 154 req->num_retrans = 0; 155 req->sk = NULL; 156 refcount_set(&req->rsk_refcnt, 0); 157 158 return req; 159 } 160 161 static inline void __reqsk_free(struct request_sock *req) 162 { 163 req->rsk_ops->destructor(req); 164 if (req->rsk_listener) 165 sock_put(req->rsk_listener); 166 kfree(req->saved_syn); 167 kmem_cache_free(req->rsk_ops->slab, req); 168 } 169 170 static inline void reqsk_free(struct request_sock *req) 171 { 172 WARN_ON_ONCE(refcount_read(&req->rsk_refcnt) != 0); 173 __reqsk_free(req); 174 } 175 176 static inline void reqsk_put(struct request_sock *req) 177 { 178 if (refcount_dec_and_test(&req->rsk_refcnt)) 179 reqsk_free(req); 180 } 181 182 /* 183 * For a TCP Fast Open listener - 184 * lock - protects the access to all the reqsk, which is co-owned by 185 * the listener and the child socket. 186 * qlen - pending TFO requests (still in TCP_SYN_RECV). 187 * max_qlen - max TFO reqs allowed before TFO is disabled. 188 * 189 * XXX (TFO) - ideally these fields can be made as part of "listen_sock" 190 * structure above. But there is some implementation difficulty due to 191 * listen_sock being part of request_sock_queue hence will be freed when 192 * a listener is stopped. But TFO related fields may continue to be 193 * accessed even after a listener is closed, until its sk_refcnt drops 194 * to 0 implying no more outstanding TFO reqs. One solution is to keep 195 * listen_opt around until sk_refcnt drops to 0. But there is some other 196 * complexity that needs to be resolved. E.g., a listener can be disabled 197 * temporarily through shutdown()->tcp_disconnect(), and re-enabled later. 198 */ 199 struct fastopen_queue { 200 struct request_sock *rskq_rst_head; /* Keep track of past TFO */ 201 struct request_sock *rskq_rst_tail; /* requests that caused RST. 202 * This is part of the defense 203 * against spoofing attack. 204 */ 205 spinlock_t lock; 206 int qlen; /* # of pending (TCP_SYN_RECV) reqs */ 207 int max_qlen; /* != 0 iff TFO is currently enabled */ 208 209 struct tcp_fastopen_context __rcu *ctx; /* cipher context for cookie */ 210 }; 211 212 /** struct request_sock_queue - queue of request_socks 213 * 214 * @rskq_accept_head - FIFO head of established children 215 * @rskq_accept_tail - FIFO tail of established children 216 * @rskq_defer_accept - User waits for some data after accept() 217 * 218 */ 219 struct request_sock_queue { 220 spinlock_t rskq_lock; 221 u8 rskq_defer_accept; 222 223 u32 synflood_warned; 224 atomic_t qlen; 225 atomic_t young; 226 227 struct request_sock *rskq_accept_head; 228 struct request_sock *rskq_accept_tail; 229 struct fastopen_queue fastopenq; /* Check max_qlen != 0 to determine 230 * if TFO is enabled. 231 */ 232 }; 233 234 void reqsk_queue_alloc(struct request_sock_queue *queue); 235 236 void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req, 237 bool reset); 238 239 static inline bool reqsk_queue_empty(const struct request_sock_queue *queue) 240 { 241 return READ_ONCE(queue->rskq_accept_head) == NULL; 242 } 243 244 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue, 245 struct sock *parent) 246 { 247 struct request_sock *req; 248 249 spin_lock_bh(&queue->rskq_lock); 250 req = queue->rskq_accept_head; 251 if (req) { 252 sk_acceptq_removed(parent); 253 WRITE_ONCE(queue->rskq_accept_head, req->dl_next); 254 if (queue->rskq_accept_head == NULL) 255 queue->rskq_accept_tail = NULL; 256 } 257 spin_unlock_bh(&queue->rskq_lock); 258 return req; 259 } 260 261 static inline void reqsk_queue_removed(struct request_sock_queue *queue, 262 const struct request_sock *req) 263 { 264 if (req->num_timeout == 0) 265 atomic_dec(&queue->young); 266 atomic_dec(&queue->qlen); 267 } 268 269 static inline void reqsk_queue_added(struct request_sock_queue *queue) 270 { 271 atomic_inc(&queue->young); 272 atomic_inc(&queue->qlen); 273 } 274 275 static inline int reqsk_queue_len(const struct request_sock_queue *queue) 276 { 277 return atomic_read(&queue->qlen); 278 } 279 280 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue) 281 { 282 return atomic_read(&queue->young); 283 } 284 285 #endif /* _REQUEST_SOCK_H */ 286