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 #include <net/rstreason.h> 22 23 struct request_sock; 24 struct sk_buff; 25 struct dst_entry; 26 struct proto; 27 28 struct request_sock_ops { 29 int family; 30 unsigned int obj_size; 31 struct kmem_cache *slab; 32 char *slab_name; 33 void (*send_ack)(const struct sock *sk, struct sk_buff *skb, 34 struct request_sock *req); 35 void (*send_reset)(const struct sock *sk, 36 struct sk_buff *skb, 37 enum sk_rst_reason reason); 38 void (*destructor)(struct request_sock *req); 39 }; 40 41 struct saved_syn { 42 u32 mac_hdrlen; 43 u32 network_hdrlen; 44 u32 tcp_hdrlen; 45 u8 data[]; 46 }; 47 48 /* struct request_sock - mini sock to represent a connection request 49 */ 50 struct request_sock { 51 struct sock_common __req_common; 52 #define rsk_refcnt __req_common.skc_refcnt 53 #define rsk_hash __req_common.skc_hash 54 #define rsk_listener __req_common.skc_listener 55 #define rsk_window_clamp __req_common.skc_window_clamp 56 #define rsk_rcv_wnd __req_common.skc_rcv_wnd 57 58 struct request_sock *dl_next; 59 u16 mss; 60 u8 num_retrans; /* number of retransmits */ 61 u8 syncookie:1; /* True if 62 * 1) tcpopts needs to be encoded in 63 * TS of SYN+ACK 64 * 2) ACK is validated by BPF kfunc. 65 */ 66 u8 num_timeout:7; /* number of timeouts */ 67 u32 ts_recent; 68 struct timer_list rsk_timer; 69 const struct request_sock_ops *rsk_ops; 70 struct sock *sk; 71 struct saved_syn *saved_syn; 72 u32 secid; 73 u32 peer_secid; 74 u32 timeout; 75 }; 76 77 static inline struct request_sock *inet_reqsk(const struct sock *sk) 78 { 79 return (struct request_sock *)sk; 80 } 81 82 static inline struct sock *req_to_sk(struct request_sock *req) 83 { 84 return (struct sock *)req; 85 } 86 87 /** 88 * skb_steal_sock - steal a socket from an sk_buff 89 * @skb: sk_buff to steal the socket from 90 * @refcounted: is set to true if the socket is reference-counted 91 * @prefetched: is set to true if the socket was assigned from bpf 92 */ 93 static inline struct sock *skb_steal_sock(struct sk_buff *skb, 94 bool *refcounted, bool *prefetched) 95 { 96 struct sock *sk = skb->sk; 97 98 if (!sk) { 99 *prefetched = false; 100 *refcounted = false; 101 return NULL; 102 } 103 104 *prefetched = skb_sk_is_prefetched(skb); 105 if (*prefetched) { 106 #if IS_ENABLED(CONFIG_SYN_COOKIES) 107 if (sk->sk_state == TCP_NEW_SYN_RECV && inet_reqsk(sk)->syncookie) { 108 struct request_sock *req = inet_reqsk(sk); 109 110 *refcounted = false; 111 sk = req->rsk_listener; 112 req->rsk_listener = NULL; 113 return sk; 114 } 115 #endif 116 *refcounted = sk_is_refcounted(sk); 117 } else { 118 *refcounted = true; 119 } 120 121 skb->destructor = NULL; 122 skb->sk = NULL; 123 return sk; 124 } 125 126 void __reqsk_free(struct request_sock *req); 127 128 static inline void reqsk_free(struct request_sock *req) 129 { 130 DEBUG_NET_WARN_ON_ONCE(refcount_read(&req->rsk_refcnt) != 0); 131 __reqsk_free(req); 132 } 133 134 static inline void reqsk_put(struct request_sock *req) 135 { 136 if (refcount_dec_and_test(&req->rsk_refcnt)) 137 __reqsk_free(req); 138 } 139 140 /* 141 * For a TCP Fast Open listener - 142 * lock - protects the access to all the reqsk, which is co-owned by 143 * the listener and the child socket. 144 * qlen - pending TFO requests (still in TCP_SYN_RECV). 145 * max_qlen - max TFO reqs allowed before TFO is disabled. 146 * 147 * XXX (TFO) - ideally these fields can be made as part of "listen_sock" 148 * structure above. But there is some implementation difficulty due to 149 * listen_sock being part of request_sock_queue hence will be freed when 150 * a listener is stopped. But TFO related fields may continue to be 151 * accessed even after a listener is closed, until its sk_refcnt drops 152 * to 0 implying no more outstanding TFO reqs. One solution is to keep 153 * listen_opt around until sk_refcnt drops to 0. But there is some other 154 * complexity that needs to be resolved. E.g., a listener can be disabled 155 * temporarily through shutdown()->tcp_disconnect(), and re-enabled later. 156 */ 157 struct fastopen_queue { 158 struct request_sock *rskq_rst_head; /* Keep track of past TFO */ 159 struct request_sock *rskq_rst_tail; /* requests that caused RST. 160 * This is part of the defense 161 * against spoofing attack. 162 */ 163 spinlock_t lock; 164 int qlen; /* # of pending (TCP_SYN_RECV) reqs */ 165 int max_qlen; /* != 0 iff TFO is currently enabled */ 166 167 struct tcp_fastopen_context __rcu *ctx; /* cipher context for cookie */ 168 }; 169 170 /** struct request_sock_queue - queue of request_socks 171 * 172 * @rskq_accept_head - FIFO head of established children 173 * @rskq_accept_tail - FIFO tail of established children 174 * @rskq_defer_accept - User waits for some data after accept() 175 * 176 */ 177 struct request_sock_queue { 178 spinlock_t rskq_lock; 179 u8 rskq_defer_accept; 180 u8 synflood_warned; 181 182 atomic_t qlen; 183 atomic_t young; 184 185 struct request_sock *rskq_accept_head; 186 struct request_sock *rskq_accept_tail; 187 struct fastopen_queue fastopenq; /* Check max_qlen != 0 to determine 188 * if TFO is enabled. 189 */ 190 }; 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 /* RFC 7323 2.3 Using the Window Scale Option 242 * The window field (SEG.WND) of every outgoing segment, with the 243 * exception of <SYN> segments, MUST be right-shifted by 244 * Rcv.Wind.Shift bits. 245 * 246 * This means the SEG.WND carried in SYNACK can not exceed 65535. 247 * We use this property to harden TCP stack while in NEW_SYN_RECV state. 248 */ 249 static inline u32 tcp_synack_window(const struct request_sock *req) 250 { 251 return min(req->rsk_rcv_wnd, 65535U); 252 } 253 #endif /* _REQUEST_SOCK_H */ 254