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 int (*rtx_syn_ack)(const struct sock *sk, 34 struct request_sock *req); 35 void (*send_ack)(const struct sock *sk, struct sk_buff *skb, 36 struct request_sock *req); 37 void (*send_reset)(const struct sock *sk, 38 struct sk_buff *skb, 39 enum sk_rst_reason reason); 40 void (*destructor)(struct request_sock *req); 41 void (*syn_ack_timeout)(const struct request_sock *req); 42 }; 43 44 int inet_rtx_syn_ack(const struct sock *parent, struct request_sock *req); 45 46 struct saved_syn { 47 u32 mac_hdrlen; 48 u32 network_hdrlen; 49 u32 tcp_hdrlen; 50 u8 data[]; 51 }; 52 53 /* struct request_sock - mini sock to represent a connection request 54 */ 55 struct request_sock { 56 struct sock_common __req_common; 57 #define rsk_refcnt __req_common.skc_refcnt 58 #define rsk_hash __req_common.skc_hash 59 #define rsk_listener __req_common.skc_listener 60 #define rsk_window_clamp __req_common.skc_window_clamp 61 #define rsk_rcv_wnd __req_common.skc_rcv_wnd 62 63 struct request_sock *dl_next; 64 u16 mss; 65 u8 num_retrans; /* number of retransmits */ 66 u8 syncookie:1; /* True if 67 * 1) tcpopts needs to be encoded in 68 * TS of SYN+ACK 69 * 2) ACK is validated by BPF kfunc. 70 */ 71 u8 num_timeout:7; /* number of timeouts */ 72 u32 ts_recent; 73 struct timer_list rsk_timer; 74 const struct request_sock_ops *rsk_ops; 75 struct sock *sk; 76 struct saved_syn *saved_syn; 77 u32 secid; 78 u32 peer_secid; 79 u32 timeout; 80 }; 81 82 static inline struct request_sock *inet_reqsk(const struct sock *sk) 83 { 84 return (struct request_sock *)sk; 85 } 86 87 static inline struct sock *req_to_sk(struct request_sock *req) 88 { 89 return (struct sock *)req; 90 } 91 92 /** 93 * skb_steal_sock - steal a socket from an sk_buff 94 * @skb: sk_buff to steal the socket from 95 * @refcounted: is set to true if the socket is reference-counted 96 * @prefetched: is set to true if the socket was assigned from bpf 97 */ 98 static inline struct sock *skb_steal_sock(struct sk_buff *skb, 99 bool *refcounted, bool *prefetched) 100 { 101 struct sock *sk = skb->sk; 102 103 if (!sk) { 104 *prefetched = false; 105 *refcounted = false; 106 return NULL; 107 } 108 109 *prefetched = skb_sk_is_prefetched(skb); 110 if (*prefetched) { 111 #if IS_ENABLED(CONFIG_SYN_COOKIES) 112 if (sk->sk_state == TCP_NEW_SYN_RECV && inet_reqsk(sk)->syncookie) { 113 struct request_sock *req = inet_reqsk(sk); 114 115 *refcounted = false; 116 sk = req->rsk_listener; 117 req->rsk_listener = NULL; 118 return sk; 119 } 120 #endif 121 *refcounted = sk_is_refcounted(sk); 122 } else { 123 *refcounted = true; 124 } 125 126 skb->destructor = NULL; 127 skb->sk = NULL; 128 return sk; 129 } 130 131 static inline void __reqsk_free(struct request_sock *req) 132 { 133 req->rsk_ops->destructor(req); 134 if (req->rsk_listener) 135 sock_put(req->rsk_listener); 136 kfree(req->saved_syn); 137 kmem_cache_free(req->rsk_ops->slab, req); 138 } 139 140 static inline void reqsk_free(struct request_sock *req) 141 { 142 DEBUG_NET_WARN_ON_ONCE(refcount_read(&req->rsk_refcnt) != 0); 143 __reqsk_free(req); 144 } 145 146 static inline void reqsk_put(struct request_sock *req) 147 { 148 if (refcount_dec_and_test(&req->rsk_refcnt)) 149 __reqsk_free(req); 150 } 151 152 /* 153 * For a TCP Fast Open listener - 154 * lock - protects the access to all the reqsk, which is co-owned by 155 * the listener and the child socket. 156 * qlen - pending TFO requests (still in TCP_SYN_RECV). 157 * max_qlen - max TFO reqs allowed before TFO is disabled. 158 * 159 * XXX (TFO) - ideally these fields can be made as part of "listen_sock" 160 * structure above. But there is some implementation difficulty due to 161 * listen_sock being part of request_sock_queue hence will be freed when 162 * a listener is stopped. But TFO related fields may continue to be 163 * accessed even after a listener is closed, until its sk_refcnt drops 164 * to 0 implying no more outstanding TFO reqs. One solution is to keep 165 * listen_opt around until sk_refcnt drops to 0. But there is some other 166 * complexity that needs to be resolved. E.g., a listener can be disabled 167 * temporarily through shutdown()->tcp_disconnect(), and re-enabled later. 168 */ 169 struct fastopen_queue { 170 struct request_sock *rskq_rst_head; /* Keep track of past TFO */ 171 struct request_sock *rskq_rst_tail; /* requests that caused RST. 172 * This is part of the defense 173 * against spoofing attack. 174 */ 175 spinlock_t lock; 176 int qlen; /* # of pending (TCP_SYN_RECV) reqs */ 177 int max_qlen; /* != 0 iff TFO is currently enabled */ 178 179 struct tcp_fastopen_context __rcu *ctx; /* cipher context for cookie */ 180 }; 181 182 /** struct request_sock_queue - queue of request_socks 183 * 184 * @rskq_accept_head - FIFO head of established children 185 * @rskq_accept_tail - FIFO tail of established children 186 * @rskq_defer_accept - User waits for some data after accept() 187 * 188 */ 189 struct request_sock_queue { 190 spinlock_t rskq_lock; 191 u8 rskq_defer_accept; 192 193 u32 synflood_warned; 194 atomic_t qlen; 195 atomic_t young; 196 197 struct request_sock *rskq_accept_head; 198 struct request_sock *rskq_accept_tail; 199 struct fastopen_queue fastopenq; /* Check max_qlen != 0 to determine 200 * if TFO is enabled. 201 */ 202 }; 203 204 void reqsk_queue_alloc(struct request_sock_queue *queue); 205 206 void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req, 207 bool reset); 208 209 static inline bool reqsk_queue_empty(const struct request_sock_queue *queue) 210 { 211 return READ_ONCE(queue->rskq_accept_head) == NULL; 212 } 213 214 static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue, 215 struct sock *parent) 216 { 217 struct request_sock *req; 218 219 spin_lock_bh(&queue->rskq_lock); 220 req = queue->rskq_accept_head; 221 if (req) { 222 sk_acceptq_removed(parent); 223 WRITE_ONCE(queue->rskq_accept_head, req->dl_next); 224 if (queue->rskq_accept_head == NULL) 225 queue->rskq_accept_tail = NULL; 226 } 227 spin_unlock_bh(&queue->rskq_lock); 228 return req; 229 } 230 231 static inline void reqsk_queue_removed(struct request_sock_queue *queue, 232 const struct request_sock *req) 233 { 234 if (req->num_timeout == 0) 235 atomic_dec(&queue->young); 236 atomic_dec(&queue->qlen); 237 } 238 239 static inline void reqsk_queue_added(struct request_sock_queue *queue) 240 { 241 atomic_inc(&queue->young); 242 atomic_inc(&queue->qlen); 243 } 244 245 static inline int reqsk_queue_len(const struct request_sock_queue *queue) 246 { 247 return atomic_read(&queue->qlen); 248 } 249 250 static inline int reqsk_queue_len_young(const struct request_sock_queue *queue) 251 { 252 return atomic_read(&queue->young); 253 } 254 255 /* RFC 7323 2.3 Using the Window Scale Option 256 * The window field (SEG.WND) of every outgoing segment, with the 257 * exception of <SYN> segments, MUST be right-shifted by 258 * Rcv.Wind.Shift bits. 259 * 260 * This means the SEG.WND carried in SYNACK can not exceed 65535. 261 * We use this property to harden TCP stack while in NEW_SYN_RECV state. 262 */ 263 static inline u32 tcp_synack_window(const struct request_sock *req) 264 { 265 return min(req->rsk_rcv_wnd, 65535U); 266 } 267 #endif /* _REQUEST_SOCK_H */ 268