xref: /linux/include/net/tcp.h (revision 62a0e2fa40c5c06742b8b4997ba5095a3ec28503)
1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /*
3  * INET		An implementation of the TCP/IP protocol suite for the LINUX
4  *		operating system.  INET is implemented using the  BSD Socket
5  *		interface as the means of communication with the user level.
6  *
7  *		Definitions for the TCP module.
8  *
9  * Version:	@(#)tcp.h	1.0.5	05/23/93
10  *
11  * Authors:	Ross Biro
12  *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
13  */
14 #ifndef _TCP_H
15 #define _TCP_H
16 
17 #define FASTRETRANS_DEBUG 1
18 
19 #include <linux/list.h>
20 #include <linux/tcp.h>
21 #include <linux/bug.h>
22 #include <linux/slab.h>
23 #include <linux/cache.h>
24 #include <linux/percpu.h>
25 #include <linux/skbuff.h>
26 #include <linux/kref.h>
27 #include <linux/ktime.h>
28 #include <linux/indirect_call_wrapper.h>
29 
30 #include <net/inet_connection_sock.h>
31 #include <net/inet_timewait_sock.h>
32 #include <net/inet_hashtables.h>
33 #include <net/checksum.h>
34 #include <net/request_sock.h>
35 #include <net/sock_reuseport.h>
36 #include <net/sock.h>
37 #include <net/snmp.h>
38 #include <net/ip.h>
39 #include <net/tcp_states.h>
40 #include <net/tcp_ao.h>
41 #include <net/inet_ecn.h>
42 #include <net/dst.h>
43 #include <net/mptcp.h>
44 
45 #include <linux/seq_file.h>
46 #include <linux/memcontrol.h>
47 #include <linux/bpf-cgroup.h>
48 #include <linux/siphash.h>
49 
50 extern struct inet_hashinfo tcp_hashinfo;
51 
52 DECLARE_PER_CPU(unsigned int, tcp_orphan_count);
53 int tcp_orphan_count_sum(void);
54 
55 DECLARE_PER_CPU(u32, tcp_tw_isn);
56 
57 void tcp_time_wait(struct sock *sk, int state, int timeo);
58 
59 #define MAX_TCP_HEADER	L1_CACHE_ALIGN(128 + MAX_HEADER)
60 #define MAX_TCP_OPTION_SPACE 40
61 #define TCP_MIN_SND_MSS		48
62 #define TCP_MIN_GSO_SIZE	(TCP_MIN_SND_MSS - MAX_TCP_OPTION_SPACE)
63 
64 /*
65  * Never offer a window over 32767 without using window scaling. Some
66  * poor stacks do signed 16bit maths!
67  */
68 #define MAX_TCP_WINDOW		32767U
69 
70 /* Minimal accepted MSS. It is (60+60+8) - (20+20). */
71 #define TCP_MIN_MSS		88U
72 
73 /* The initial MTU to use for probing */
74 #define TCP_BASE_MSS		1024
75 
76 /* probing interval, default to 10 minutes as per RFC4821 */
77 #define TCP_PROBE_INTERVAL	600
78 
79 /* Specify interval when tcp mtu probing will stop */
80 #define TCP_PROBE_THRESHOLD	8
81 
82 /* After receiving this amount of duplicate ACKs fast retransmit starts. */
83 #define TCP_FASTRETRANS_THRESH 3
84 
85 /* Maximal number of ACKs sent quickly to accelerate slow-start. */
86 #define TCP_MAX_QUICKACKS	16U
87 
88 /* Maximal number of window scale according to RFC1323 */
89 #define TCP_MAX_WSCALE		14U
90 
91 /* urg_data states */
92 #define TCP_URG_VALID	0x0100
93 #define TCP_URG_NOTYET	0x0200
94 #define TCP_URG_READ	0x0400
95 
96 #define TCP_RETR1	3	/*
97 				 * This is how many retries it does before it
98 				 * tries to figure out if the gateway is
99 				 * down. Minimal RFC value is 3; it corresponds
100 				 * to ~3sec-8min depending on RTO.
101 				 */
102 
103 #define TCP_RETR2	15	/*
104 				 * This should take at least
105 				 * 90 minutes to time out.
106 				 * RFC1122 says that the limit is 100 sec.
107 				 * 15 is ~13-30min depending on RTO.
108 				 */
109 
110 #define TCP_SYN_RETRIES	 6	/* This is how many retries are done
111 				 * when active opening a connection.
112 				 * RFC1122 says the minimum retry MUST
113 				 * be at least 180secs.  Nevertheless
114 				 * this value is corresponding to
115 				 * 63secs of retransmission with the
116 				 * current initial RTO.
117 				 */
118 
119 #define TCP_SYNACK_RETRIES 5	/* This is how may retries are done
120 				 * when passive opening a connection.
121 				 * This is corresponding to 31secs of
122 				 * retransmission with the current
123 				 * initial RTO.
124 				 */
125 
126 #define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT
127 				  * state, about 60 seconds	*/
128 #define TCP_FIN_TIMEOUT	TCP_TIMEWAIT_LEN
129                                  /* BSD style FIN_WAIT2 deadlock breaker.
130 				  * It used to be 3min, new value is 60sec,
131 				  * to combine FIN-WAIT-2 timeout with
132 				  * TIME-WAIT timer.
133 				  */
134 #define TCP_FIN_TIMEOUT_MAX (120 * HZ) /* max TCP_LINGER2 value (two minutes) */
135 
136 #define TCP_DELACK_MAX	((unsigned)(HZ/5))	/* maximal time to delay before sending an ACK */
137 static_assert((1 << ATO_BITS) > TCP_DELACK_MAX);
138 
139 #if HZ >= 100
140 #define TCP_DELACK_MIN	((unsigned)(HZ/25))	/* minimal time to delay before sending an ACK */
141 #define TCP_ATO_MIN	((unsigned)(HZ/25))
142 #else
143 #define TCP_DELACK_MIN	4U
144 #define TCP_ATO_MIN	4U
145 #endif
146 #define TCP_RTO_MAX	((unsigned)(120*HZ))
147 #define TCP_RTO_MIN	((unsigned)(HZ/5))
148 #define TCP_TIMEOUT_MIN	(2U) /* Min timeout for TCP timers in jiffies */
149 
150 #define TCP_TIMEOUT_MIN_US (2*USEC_PER_MSEC) /* Min TCP timeout in microsecs */
151 
152 #define TCP_TIMEOUT_INIT ((unsigned)(1*HZ))	/* RFC6298 2.1 initial RTO value	*/
153 #define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ))	/* RFC 1122 initial RTO value, now
154 						 * used as a fallback RTO for the
155 						 * initial data transmission if no
156 						 * valid RTT sample has been acquired,
157 						 * most likely due to retrans in 3WHS.
158 						 */
159 
160 #define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes
161 					                 * for local resources.
162 					                 */
163 #define TCP_KEEPALIVE_TIME	(120*60*HZ)	/* two hours */
164 #define TCP_KEEPALIVE_PROBES	9		/* Max of 9 keepalive probes	*/
165 #define TCP_KEEPALIVE_INTVL	(75*HZ)
166 
167 #define MAX_TCP_KEEPIDLE	32767
168 #define MAX_TCP_KEEPINTVL	32767
169 #define MAX_TCP_KEEPCNT		127
170 #define MAX_TCP_SYNCNT		127
171 
172 /* Ensure that TCP PAWS checks are relaxed after ~2147 seconds
173  * to avoid overflows. This assumes a clock smaller than 1 Mhz.
174  * Default clock is 1 Khz, tcp_usec_ts uses 1 Mhz.
175  */
176 #define TCP_PAWS_WRAP (INT_MAX / USEC_PER_SEC)
177 
178 #define TCP_PAWS_MSL	60		/* Per-host timestamps are invalidated
179 					 * after this time. It should be equal
180 					 * (or greater than) TCP_TIMEWAIT_LEN
181 					 * to provide reliability equal to one
182 					 * provided by timewait state.
183 					 */
184 #define TCP_PAWS_WINDOW	1		/* Replay window for per-host
185 					 * timestamps. It must be less than
186 					 * minimal timewait lifetime.
187 					 */
188 /*
189  *	TCP option
190  */
191 
192 #define TCPOPT_NOP		1	/* Padding */
193 #define TCPOPT_EOL		0	/* End of options */
194 #define TCPOPT_MSS		2	/* Segment size negotiating */
195 #define TCPOPT_WINDOW		3	/* Window scaling */
196 #define TCPOPT_SACK_PERM        4       /* SACK Permitted */
197 #define TCPOPT_SACK             5       /* SACK Block */
198 #define TCPOPT_TIMESTAMP	8	/* Better RTT estimations/PAWS */
199 #define TCPOPT_MD5SIG		19	/* MD5 Signature (RFC2385) */
200 #define TCPOPT_AO		29	/* Authentication Option (RFC5925) */
201 #define TCPOPT_MPTCP		30	/* Multipath TCP (RFC6824) */
202 #define TCPOPT_FASTOPEN		34	/* Fast open (RFC7413) */
203 #define TCPOPT_EXP		254	/* Experimental */
204 /* Magic number to be after the option value for sharing TCP
205  * experimental options. See draft-ietf-tcpm-experimental-options-00.txt
206  */
207 #define TCPOPT_FASTOPEN_MAGIC	0xF989
208 #define TCPOPT_SMC_MAGIC	0xE2D4C3D9
209 
210 /*
211  *     TCP option lengths
212  */
213 
214 #define TCPOLEN_MSS            4
215 #define TCPOLEN_WINDOW         3
216 #define TCPOLEN_SACK_PERM      2
217 #define TCPOLEN_TIMESTAMP      10
218 #define TCPOLEN_MD5SIG         18
219 #define TCPOLEN_FASTOPEN_BASE  2
220 #define TCPOLEN_EXP_FASTOPEN_BASE  4
221 #define TCPOLEN_EXP_SMC_BASE   6
222 
223 /* But this is what stacks really send out. */
224 #define TCPOLEN_TSTAMP_ALIGNED		12
225 #define TCPOLEN_WSCALE_ALIGNED		4
226 #define TCPOLEN_SACKPERM_ALIGNED	4
227 #define TCPOLEN_SACK_BASE		2
228 #define TCPOLEN_SACK_BASE_ALIGNED	4
229 #define TCPOLEN_SACK_PERBLOCK		8
230 #define TCPOLEN_MD5SIG_ALIGNED		20
231 #define TCPOLEN_MSS_ALIGNED		4
232 #define TCPOLEN_EXP_SMC_BASE_ALIGNED	8
233 
234 /* Flags in tp->nonagle */
235 #define TCP_NAGLE_OFF		1	/* Nagle's algo is disabled */
236 #define TCP_NAGLE_CORK		2	/* Socket is corked	    */
237 #define TCP_NAGLE_PUSH		4	/* Cork is overridden for already queued data */
238 
239 /* TCP thin-stream limits */
240 #define TCP_THIN_LINEAR_RETRIES 6       /* After 6 linear retries, do exp. backoff */
241 
242 /* TCP initial congestion window as per rfc6928 */
243 #define TCP_INIT_CWND		10
244 
245 /* Bit Flags for sysctl_tcp_fastopen */
246 #define	TFO_CLIENT_ENABLE	1
247 #define	TFO_SERVER_ENABLE	2
248 #define	TFO_CLIENT_NO_COOKIE	4	/* Data in SYN w/o cookie option */
249 
250 /* Accept SYN data w/o any cookie option */
251 #define	TFO_SERVER_COOKIE_NOT_REQD	0x200
252 
253 /* Force enable TFO on all listeners, i.e., not requiring the
254  * TCP_FASTOPEN socket option.
255  */
256 #define	TFO_SERVER_WO_SOCKOPT1	0x400
257 
258 
259 /* sysctl variables for tcp */
260 extern int sysctl_tcp_max_orphans;
261 extern long sysctl_tcp_mem[3];
262 
263 #define TCP_RACK_LOSS_DETECTION  0x1 /* Use RACK to detect losses */
264 #define TCP_RACK_STATIC_REO_WND  0x2 /* Use static RACK reo wnd */
265 #define TCP_RACK_NO_DUPTHRESH    0x4 /* Do not use DUPACK threshold in RACK */
266 
267 extern atomic_long_t tcp_memory_allocated;
268 DECLARE_PER_CPU(int, tcp_memory_per_cpu_fw_alloc);
269 
270 extern struct percpu_counter tcp_sockets_allocated;
271 extern unsigned long tcp_memory_pressure;
272 
273 /* optimized version of sk_under_memory_pressure() for TCP sockets */
274 static inline bool tcp_under_memory_pressure(const struct sock *sk)
275 {
276 	if (mem_cgroup_sockets_enabled && sk->sk_memcg &&
277 	    mem_cgroup_under_socket_pressure(sk->sk_memcg))
278 		return true;
279 
280 	return READ_ONCE(tcp_memory_pressure);
281 }
282 /*
283  * The next routines deal with comparing 32 bit unsigned ints
284  * and worry about wraparound (automatic with unsigned arithmetic).
285  */
286 
287 static inline bool before(__u32 seq1, __u32 seq2)
288 {
289         return (__s32)(seq1-seq2) < 0;
290 }
291 #define after(seq2, seq1) 	before(seq1, seq2)
292 
293 /* is s2<=s1<=s3 ? */
294 static inline bool between(__u32 seq1, __u32 seq2, __u32 seq3)
295 {
296 	return seq3 - seq2 >= seq1 - seq2;
297 }
298 
299 static inline void tcp_wmem_free_skb(struct sock *sk, struct sk_buff *skb)
300 {
301 	sk_wmem_queued_add(sk, -skb->truesize);
302 	if (!skb_zcopy_pure(skb))
303 		sk_mem_uncharge(sk, skb->truesize);
304 	else
305 		sk_mem_uncharge(sk, SKB_TRUESIZE(skb_end_offset(skb)));
306 	__kfree_skb(skb);
307 }
308 
309 void sk_forced_mem_schedule(struct sock *sk, int size);
310 
311 bool tcp_check_oom(const struct sock *sk, int shift);
312 
313 
314 extern struct proto tcp_prot;
315 
316 #define TCP_INC_STATS(net, field)	SNMP_INC_STATS((net)->mib.tcp_statistics, field)
317 #define __TCP_INC_STATS(net, field)	__SNMP_INC_STATS((net)->mib.tcp_statistics, field)
318 #define TCP_DEC_STATS(net, field)	SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
319 #define TCP_ADD_STATS(net, field, val)	SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
320 
321 void tcp_tasklet_init(void);
322 
323 int tcp_v4_err(struct sk_buff *skb, u32);
324 
325 void tcp_shutdown(struct sock *sk, int how);
326 
327 int tcp_v4_early_demux(struct sk_buff *skb);
328 int tcp_v4_rcv(struct sk_buff *skb);
329 
330 void tcp_remove_empty_skb(struct sock *sk);
331 int tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size);
332 int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size);
333 int tcp_sendmsg_fastopen(struct sock *sk, struct msghdr *msg, int *copied,
334 			 size_t size, struct ubuf_info *uarg);
335 void tcp_splice_eof(struct socket *sock);
336 int tcp_send_mss(struct sock *sk, int *size_goal, int flags);
337 int tcp_wmem_schedule(struct sock *sk, int copy);
338 void tcp_push(struct sock *sk, int flags, int mss_now, int nonagle,
339 	      int size_goal);
340 void tcp_release_cb(struct sock *sk);
341 void tcp_wfree(struct sk_buff *skb);
342 void tcp_write_timer_handler(struct sock *sk);
343 void tcp_delack_timer_handler(struct sock *sk);
344 int tcp_ioctl(struct sock *sk, int cmd, int *karg);
345 enum skb_drop_reason tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb);
346 void tcp_rcv_established(struct sock *sk, struct sk_buff *skb);
347 void tcp_rcv_space_adjust(struct sock *sk);
348 int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
349 void tcp_twsk_destructor(struct sock *sk);
350 void tcp_twsk_purge(struct list_head *net_exit_list);
351 ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
352 			struct pipe_inode_info *pipe, size_t len,
353 			unsigned int flags);
354 struct sk_buff *tcp_stream_alloc_skb(struct sock *sk, gfp_t gfp,
355 				     bool force_schedule);
356 
357 static inline void tcp_dec_quickack_mode(struct sock *sk)
358 {
359 	struct inet_connection_sock *icsk = inet_csk(sk);
360 
361 	if (icsk->icsk_ack.quick) {
362 		/* How many ACKs S/ACKing new data have we sent? */
363 		const unsigned int pkts = inet_csk_ack_scheduled(sk) ? 1 : 0;
364 
365 		if (pkts >= icsk->icsk_ack.quick) {
366 			icsk->icsk_ack.quick = 0;
367 			/* Leaving quickack mode we deflate ATO. */
368 			icsk->icsk_ack.ato   = TCP_ATO_MIN;
369 		} else
370 			icsk->icsk_ack.quick -= pkts;
371 	}
372 }
373 
374 #define	TCP_ECN_OK		1
375 #define	TCP_ECN_QUEUE_CWR	2
376 #define	TCP_ECN_DEMAND_CWR	4
377 #define	TCP_ECN_SEEN		8
378 
379 enum tcp_tw_status {
380 	TCP_TW_SUCCESS = 0,
381 	TCP_TW_RST = 1,
382 	TCP_TW_ACK = 2,
383 	TCP_TW_SYN = 3
384 };
385 
386 
387 enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
388 					      struct sk_buff *skb,
389 					      const struct tcphdr *th,
390 					      u32 *tw_isn);
391 struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
392 			   struct request_sock *req, bool fastopen,
393 			   bool *lost_race);
394 enum skb_drop_reason tcp_child_process(struct sock *parent, struct sock *child,
395 				       struct sk_buff *skb);
396 void tcp_enter_loss(struct sock *sk);
397 void tcp_cwnd_reduction(struct sock *sk, int newly_acked_sacked, int newly_lost, int flag);
398 void tcp_clear_retrans(struct tcp_sock *tp);
399 void tcp_update_metrics(struct sock *sk);
400 void tcp_init_metrics(struct sock *sk);
401 void tcp_metrics_init(void);
402 bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst);
403 void __tcp_close(struct sock *sk, long timeout);
404 void tcp_close(struct sock *sk, long timeout);
405 void tcp_init_sock(struct sock *sk);
406 void tcp_init_transfer(struct sock *sk, int bpf_op, struct sk_buff *skb);
407 __poll_t tcp_poll(struct file *file, struct socket *sock,
408 		      struct poll_table_struct *wait);
409 int do_tcp_getsockopt(struct sock *sk, int level,
410 		      int optname, sockptr_t optval, sockptr_t optlen);
411 int tcp_getsockopt(struct sock *sk, int level, int optname,
412 		   char __user *optval, int __user *optlen);
413 bool tcp_bpf_bypass_getsockopt(int level, int optname);
414 int do_tcp_setsockopt(struct sock *sk, int level, int optname,
415 		      sockptr_t optval, unsigned int optlen);
416 int tcp_setsockopt(struct sock *sk, int level, int optname, sockptr_t optval,
417 		   unsigned int optlen);
418 void tcp_set_keepalive(struct sock *sk, int val);
419 void tcp_syn_ack_timeout(const struct request_sock *req);
420 int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
421 		int flags, int *addr_len);
422 int tcp_set_rcvlowat(struct sock *sk, int val);
423 int tcp_set_window_clamp(struct sock *sk, int val);
424 void tcp_update_recv_tstamps(struct sk_buff *skb,
425 			     struct scm_timestamping_internal *tss);
426 void tcp_recv_timestamp(struct msghdr *msg, const struct sock *sk,
427 			struct scm_timestamping_internal *tss);
428 void tcp_data_ready(struct sock *sk);
429 #ifdef CONFIG_MMU
430 int tcp_mmap(struct file *file, struct socket *sock,
431 	     struct vm_area_struct *vma);
432 #endif
433 void tcp_parse_options(const struct net *net, const struct sk_buff *skb,
434 		       struct tcp_options_received *opt_rx,
435 		       int estab, struct tcp_fastopen_cookie *foc);
436 
437 /*
438  *	BPF SKB-less helpers
439  */
440 u16 tcp_v4_get_syncookie(struct sock *sk, struct iphdr *iph,
441 			 struct tcphdr *th, u32 *cookie);
442 u16 tcp_v6_get_syncookie(struct sock *sk, struct ipv6hdr *iph,
443 			 struct tcphdr *th, u32 *cookie);
444 u16 tcp_parse_mss_option(const struct tcphdr *th, u16 user_mss);
445 u16 tcp_get_syncookie_mss(struct request_sock_ops *rsk_ops,
446 			  const struct tcp_request_sock_ops *af_ops,
447 			  struct sock *sk, struct tcphdr *th);
448 /*
449  *	TCP v4 functions exported for the inet6 API
450  */
451 
452 void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
453 void tcp_v4_mtu_reduced(struct sock *sk);
454 void tcp_req_err(struct sock *sk, u32 seq, bool abort);
455 void tcp_ld_RTO_revert(struct sock *sk, u32 seq);
456 int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
457 struct sock *tcp_create_openreq_child(const struct sock *sk,
458 				      struct request_sock *req,
459 				      struct sk_buff *skb);
460 void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst);
461 struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
462 				  struct request_sock *req,
463 				  struct dst_entry *dst,
464 				  struct request_sock *req_unhash,
465 				  bool *own_req);
466 int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
467 int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
468 int tcp_connect(struct sock *sk);
469 enum tcp_synack_type {
470 	TCP_SYNACK_NORMAL,
471 	TCP_SYNACK_FASTOPEN,
472 	TCP_SYNACK_COOKIE,
473 };
474 struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
475 				struct request_sock *req,
476 				struct tcp_fastopen_cookie *foc,
477 				enum tcp_synack_type synack_type,
478 				struct sk_buff *syn_skb);
479 int tcp_disconnect(struct sock *sk, int flags);
480 
481 void tcp_finish_connect(struct sock *sk, struct sk_buff *skb);
482 int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size);
483 void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
484 
485 /* From syncookies.c */
486 struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
487 				 struct request_sock *req,
488 				 struct dst_entry *dst);
489 int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th);
490 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
491 struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
492 					    struct sock *sk, struct sk_buff *skb,
493 					    struct tcp_options_received *tcp_opt,
494 					    int mss, u32 tsoff);
495 
496 #if IS_ENABLED(CONFIG_BPF)
497 struct bpf_tcp_req_attrs {
498 	u32 rcv_tsval;
499 	u32 rcv_tsecr;
500 	u16 mss;
501 	u8 rcv_wscale;
502 	u8 snd_wscale;
503 	u8 ecn_ok;
504 	u8 wscale_ok;
505 	u8 sack_ok;
506 	u8 tstamp_ok;
507 	u8 usec_ts_ok;
508 	u8 reserved[3];
509 };
510 #endif
511 
512 #ifdef CONFIG_SYN_COOKIES
513 
514 /* Syncookies use a monotonic timer which increments every 60 seconds.
515  * This counter is used both as a hash input and partially encoded into
516  * the cookie value.  A cookie is only validated further if the delta
517  * between the current counter value and the encoded one is less than this,
518  * i.e. a sent cookie is valid only at most for 2*60 seconds (or less if
519  * the counter advances immediately after a cookie is generated).
520  */
521 #define MAX_SYNCOOKIE_AGE	2
522 #define TCP_SYNCOOKIE_PERIOD	(60 * HZ)
523 #define TCP_SYNCOOKIE_VALID	(MAX_SYNCOOKIE_AGE * TCP_SYNCOOKIE_PERIOD)
524 
525 /* syncookies: remember time of last synqueue overflow
526  * But do not dirty this field too often (once per second is enough)
527  * It is racy as we do not hold a lock, but race is very minor.
528  */
529 static inline void tcp_synq_overflow(const struct sock *sk)
530 {
531 	unsigned int last_overflow;
532 	unsigned int now = jiffies;
533 
534 	if (sk->sk_reuseport) {
535 		struct sock_reuseport *reuse;
536 
537 		reuse = rcu_dereference(sk->sk_reuseport_cb);
538 		if (likely(reuse)) {
539 			last_overflow = READ_ONCE(reuse->synq_overflow_ts);
540 			if (!time_between32(now, last_overflow,
541 					    last_overflow + HZ))
542 				WRITE_ONCE(reuse->synq_overflow_ts, now);
543 			return;
544 		}
545 	}
546 
547 	last_overflow = READ_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp);
548 	if (!time_between32(now, last_overflow, last_overflow + HZ))
549 		WRITE_ONCE(tcp_sk_rw(sk)->rx_opt.ts_recent_stamp, now);
550 }
551 
552 /* syncookies: no recent synqueue overflow on this listening socket? */
553 static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
554 {
555 	unsigned int last_overflow;
556 	unsigned int now = jiffies;
557 
558 	if (sk->sk_reuseport) {
559 		struct sock_reuseport *reuse;
560 
561 		reuse = rcu_dereference(sk->sk_reuseport_cb);
562 		if (likely(reuse)) {
563 			last_overflow = READ_ONCE(reuse->synq_overflow_ts);
564 			return !time_between32(now, last_overflow - HZ,
565 					       last_overflow +
566 					       TCP_SYNCOOKIE_VALID);
567 		}
568 	}
569 
570 	last_overflow = READ_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp);
571 
572 	/* If last_overflow <= jiffies <= last_overflow + TCP_SYNCOOKIE_VALID,
573 	 * then we're under synflood. However, we have to use
574 	 * 'last_overflow - HZ' as lower bound. That's because a concurrent
575 	 * tcp_synq_overflow() could update .ts_recent_stamp after we read
576 	 * jiffies but before we store .ts_recent_stamp into last_overflow,
577 	 * which could lead to rejecting a valid syncookie.
578 	 */
579 	return !time_between32(now, last_overflow - HZ,
580 			       last_overflow + TCP_SYNCOOKIE_VALID);
581 }
582 
583 static inline u32 tcp_cookie_time(void)
584 {
585 	u64 val = get_jiffies_64();
586 
587 	do_div(val, TCP_SYNCOOKIE_PERIOD);
588 	return val;
589 }
590 
591 /* Convert one nsec 64bit timestamp to ts (ms or usec resolution) */
592 static inline u64 tcp_ns_to_ts(bool usec_ts, u64 val)
593 {
594 	if (usec_ts)
595 		return div_u64(val, NSEC_PER_USEC);
596 
597 	return div_u64(val, NSEC_PER_MSEC);
598 }
599 
600 u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
601 			      u16 *mssp);
602 __u32 cookie_v4_init_sequence(const struct sk_buff *skb, __u16 *mss);
603 u64 cookie_init_timestamp(struct request_sock *req, u64 now);
604 bool cookie_timestamp_decode(const struct net *net,
605 			     struct tcp_options_received *opt);
606 
607 static inline bool cookie_ecn_ok(const struct net *net, const struct dst_entry *dst)
608 {
609 	return READ_ONCE(net->ipv4.sysctl_tcp_ecn) ||
610 		dst_feature(dst, RTAX_FEATURE_ECN);
611 }
612 
613 #if IS_ENABLED(CONFIG_BPF)
614 static inline bool cookie_bpf_ok(struct sk_buff *skb)
615 {
616 	return skb->sk;
617 }
618 
619 struct request_sock *cookie_bpf_check(struct sock *sk, struct sk_buff *skb);
620 #else
621 static inline bool cookie_bpf_ok(struct sk_buff *skb)
622 {
623 	return false;
624 }
625 
626 static inline struct request_sock *cookie_bpf_check(struct net *net, struct sock *sk,
627 						    struct sk_buff *skb)
628 {
629 	return NULL;
630 }
631 #endif
632 
633 /* From net/ipv6/syncookies.c */
634 int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th);
635 struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
636 
637 u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
638 			      const struct tcphdr *th, u16 *mssp);
639 __u32 cookie_v6_init_sequence(const struct sk_buff *skb, __u16 *mss);
640 #endif
641 /* tcp_output.c */
642 
643 void tcp_skb_entail(struct sock *sk, struct sk_buff *skb);
644 void tcp_mark_push(struct tcp_sock *tp, struct sk_buff *skb);
645 void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
646 			       int nonagle);
647 int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs);
648 int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs);
649 void tcp_retransmit_timer(struct sock *sk);
650 void tcp_xmit_retransmit_queue(struct sock *);
651 void tcp_simple_retransmit(struct sock *);
652 void tcp_enter_recovery(struct sock *sk, bool ece_ack);
653 int tcp_trim_head(struct sock *, struct sk_buff *, u32);
654 enum tcp_queue {
655 	TCP_FRAG_IN_WRITE_QUEUE,
656 	TCP_FRAG_IN_RTX_QUEUE,
657 };
658 int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue,
659 		 struct sk_buff *skb, u32 len,
660 		 unsigned int mss_now, gfp_t gfp);
661 
662 void tcp_send_probe0(struct sock *);
663 int tcp_write_wakeup(struct sock *, int mib);
664 void tcp_send_fin(struct sock *sk);
665 void tcp_send_active_reset(struct sock *sk, gfp_t priority,
666 			   enum sk_rst_reason reason);
667 int tcp_send_synack(struct sock *);
668 void tcp_push_one(struct sock *, unsigned int mss_now);
669 void __tcp_send_ack(struct sock *sk, u32 rcv_nxt);
670 void tcp_send_ack(struct sock *sk);
671 void tcp_send_delayed_ack(struct sock *sk);
672 void tcp_send_loss_probe(struct sock *sk);
673 bool tcp_schedule_loss_probe(struct sock *sk, bool advancing_rto);
674 void tcp_skb_collapse_tstamp(struct sk_buff *skb,
675 			     const struct sk_buff *next_skb);
676 
677 /* tcp_input.c */
678 void tcp_rearm_rto(struct sock *sk);
679 void tcp_synack_rtt_meas(struct sock *sk, struct request_sock *req);
680 void tcp_done_with_error(struct sock *sk, int err);
681 void tcp_reset(struct sock *sk, struct sk_buff *skb);
682 void tcp_fin(struct sock *sk);
683 void tcp_check_space(struct sock *sk);
684 void tcp_sack_compress_send_ack(struct sock *sk);
685 
686 /* tcp_timer.c */
687 void tcp_init_xmit_timers(struct sock *);
688 static inline void tcp_clear_xmit_timers(struct sock *sk)
689 {
690 	if (hrtimer_try_to_cancel(&tcp_sk(sk)->pacing_timer) == 1)
691 		__sock_put(sk);
692 
693 	if (hrtimer_try_to_cancel(&tcp_sk(sk)->compressed_ack_timer) == 1)
694 		__sock_put(sk);
695 
696 	inet_csk_clear_xmit_timers(sk);
697 }
698 
699 unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
700 unsigned int tcp_current_mss(struct sock *sk);
701 u32 tcp_clamp_probe0_to_user_timeout(const struct sock *sk, u32 when);
702 
703 /* Bound MSS / TSO packet size with the half of the window */
704 static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
705 {
706 	int cutoff;
707 
708 	/* When peer uses tiny windows, there is no use in packetizing
709 	 * to sub-MSS pieces for the sake of SWS or making sure there
710 	 * are enough packets in the pipe for fast recovery.
711 	 *
712 	 * On the other hand, for extremely large MSS devices, handling
713 	 * smaller than MSS windows in this way does make sense.
714 	 */
715 	if (tp->max_window > TCP_MSS_DEFAULT)
716 		cutoff = (tp->max_window >> 1);
717 	else
718 		cutoff = tp->max_window;
719 
720 	if (cutoff && pktsize > cutoff)
721 		return max_t(int, cutoff, 68U - tp->tcp_header_len);
722 	else
723 		return pktsize;
724 }
725 
726 /* tcp.c */
727 void tcp_get_info(struct sock *, struct tcp_info *);
728 
729 /* Read 'sendfile()'-style from a TCP socket */
730 int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
731 		  sk_read_actor_t recv_actor);
732 int tcp_read_skb(struct sock *sk, skb_read_actor_t recv_actor);
733 struct sk_buff *tcp_recv_skb(struct sock *sk, u32 seq, u32 *off);
734 void tcp_read_done(struct sock *sk, size_t len);
735 
736 void tcp_initialize_rcv_mss(struct sock *sk);
737 
738 int tcp_mtu_to_mss(struct sock *sk, int pmtu);
739 int tcp_mss_to_mtu(struct sock *sk, int mss);
740 void tcp_mtup_init(struct sock *sk);
741 
742 static inline void tcp_bound_rto(struct sock *sk)
743 {
744 	if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
745 		inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
746 }
747 
748 static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
749 {
750 	return usecs_to_jiffies((tp->srtt_us >> 3) + tp->rttvar_us);
751 }
752 
753 static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
754 {
755 	/* mptcp hooks are only on the slow path */
756 	if (sk_is_mptcp((struct sock *)tp))
757 		return;
758 
759 	tp->pred_flags = htonl((tp->tcp_header_len << 26) |
760 			       ntohl(TCP_FLAG_ACK) |
761 			       snd_wnd);
762 }
763 
764 static inline void tcp_fast_path_on(struct tcp_sock *tp)
765 {
766 	__tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
767 }
768 
769 static inline void tcp_fast_path_check(struct sock *sk)
770 {
771 	struct tcp_sock *tp = tcp_sk(sk);
772 
773 	if (RB_EMPTY_ROOT(&tp->out_of_order_queue) &&
774 	    tp->rcv_wnd &&
775 	    atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
776 	    !tp->urg_data)
777 		tcp_fast_path_on(tp);
778 }
779 
780 u32 tcp_delack_max(const struct sock *sk);
781 
782 /* Compute the actual rto_min value */
783 static inline u32 tcp_rto_min(const struct sock *sk)
784 {
785 	const struct dst_entry *dst = __sk_dst_get(sk);
786 	u32 rto_min = inet_csk(sk)->icsk_rto_min;
787 
788 	if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
789 		rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
790 	return rto_min;
791 }
792 
793 static inline u32 tcp_rto_min_us(const struct sock *sk)
794 {
795 	return jiffies_to_usecs(tcp_rto_min(sk));
796 }
797 
798 static inline bool tcp_ca_dst_locked(const struct dst_entry *dst)
799 {
800 	return dst_metric_locked(dst, RTAX_CC_ALGO);
801 }
802 
803 /* Minimum RTT in usec. ~0 means not available. */
804 static inline u32 tcp_min_rtt(const struct tcp_sock *tp)
805 {
806 	return minmax_get(&tp->rtt_min);
807 }
808 
809 /* Compute the actual receive window we are currently advertising.
810  * Rcv_nxt can be after the window if our peer push more data
811  * than the offered window.
812  */
813 static inline u32 tcp_receive_window(const struct tcp_sock *tp)
814 {
815 	s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;
816 
817 	if (win < 0)
818 		win = 0;
819 	return (u32) win;
820 }
821 
822 /* Choose a new window, without checks for shrinking, and without
823  * scaling applied to the result.  The caller does these things
824  * if necessary.  This is a "raw" window selection.
825  */
826 u32 __tcp_select_window(struct sock *sk);
827 
828 void tcp_send_window_probe(struct sock *sk);
829 
830 /* TCP uses 32bit jiffies to save some space.
831  * Note that this is different from tcp_time_stamp, which
832  * historically has been the same until linux-4.13.
833  */
834 #define tcp_jiffies32 ((u32)jiffies)
835 
836 /*
837  * Deliver a 32bit value for TCP timestamp option (RFC 7323)
838  * It is no longer tied to jiffies, but to 1 ms clock.
839  * Note: double check if you want to use tcp_jiffies32 instead of this.
840  */
841 #define TCP_TS_HZ	1000
842 
843 static inline u64 tcp_clock_ns(void)
844 {
845 	return ktime_get_ns();
846 }
847 
848 static inline u64 tcp_clock_us(void)
849 {
850 	return div_u64(tcp_clock_ns(), NSEC_PER_USEC);
851 }
852 
853 static inline u64 tcp_clock_ms(void)
854 {
855 	return div_u64(tcp_clock_ns(), NSEC_PER_MSEC);
856 }
857 
858 /* TCP Timestamp included in TS option (RFC 1323) can either use ms
859  * or usec resolution. Each socket carries a flag to select one or other
860  * resolution, as the route attribute could change anytime.
861  * Each flow must stick to initial resolution.
862  */
863 static inline u32 tcp_clock_ts(bool usec_ts)
864 {
865 	return usec_ts ? tcp_clock_us() : tcp_clock_ms();
866 }
867 
868 static inline u32 tcp_time_stamp_ms(const struct tcp_sock *tp)
869 {
870 	return div_u64(tp->tcp_mstamp, USEC_PER_MSEC);
871 }
872 
873 static inline u32 tcp_time_stamp_ts(const struct tcp_sock *tp)
874 {
875 	if (tp->tcp_usec_ts)
876 		return tp->tcp_mstamp;
877 	return tcp_time_stamp_ms(tp);
878 }
879 
880 void tcp_mstamp_refresh(struct tcp_sock *tp);
881 
882 static inline u32 tcp_stamp_us_delta(u64 t1, u64 t0)
883 {
884 	return max_t(s64, t1 - t0, 0);
885 }
886 
887 /* provide the departure time in us unit */
888 static inline u64 tcp_skb_timestamp_us(const struct sk_buff *skb)
889 {
890 	return div_u64(skb->skb_mstamp_ns, NSEC_PER_USEC);
891 }
892 
893 /* Provide skb TSval in usec or ms unit */
894 static inline u32 tcp_skb_timestamp_ts(bool usec_ts, const struct sk_buff *skb)
895 {
896 	if (usec_ts)
897 		return tcp_skb_timestamp_us(skb);
898 
899 	return div_u64(skb->skb_mstamp_ns, NSEC_PER_MSEC);
900 }
901 
902 static inline u32 tcp_tw_tsval(const struct tcp_timewait_sock *tcptw)
903 {
904 	return tcp_clock_ts(tcptw->tw_sk.tw_usec_ts) + tcptw->tw_ts_offset;
905 }
906 
907 static inline u32 tcp_rsk_tsval(const struct tcp_request_sock *treq)
908 {
909 	return tcp_clock_ts(treq->req_usec_ts) + treq->ts_off;
910 }
911 
912 #define tcp_flag_byte(th) (((u_int8_t *)th)[13])
913 
914 #define TCPHDR_FIN 0x01
915 #define TCPHDR_SYN 0x02
916 #define TCPHDR_RST 0x04
917 #define TCPHDR_PSH 0x08
918 #define TCPHDR_ACK 0x10
919 #define TCPHDR_URG 0x20
920 #define TCPHDR_ECE 0x40
921 #define TCPHDR_CWR 0x80
922 
923 #define TCPHDR_SYN_ECN	(TCPHDR_SYN | TCPHDR_ECE | TCPHDR_CWR)
924 
925 /* State flags for sacked in struct tcp_skb_cb */
926 enum tcp_skb_cb_sacked_flags {
927 	TCPCB_SACKED_ACKED	= (1 << 0),	/* SKB ACK'd by a SACK block	*/
928 	TCPCB_SACKED_RETRANS	= (1 << 1),	/* SKB retransmitted		*/
929 	TCPCB_LOST		= (1 << 2),	/* SKB is lost			*/
930 	TCPCB_TAGBITS		= (TCPCB_SACKED_ACKED | TCPCB_SACKED_RETRANS |
931 				   TCPCB_LOST),	/* All tag bits			*/
932 	TCPCB_REPAIRED		= (1 << 4),	/* SKB repaired (no skb_mstamp_ns)	*/
933 	TCPCB_EVER_RETRANS	= (1 << 7),	/* Ever retransmitted frame	*/
934 	TCPCB_RETRANS		= (TCPCB_SACKED_RETRANS | TCPCB_EVER_RETRANS |
935 				   TCPCB_REPAIRED),
936 };
937 
938 /* This is what the send packet queuing engine uses to pass
939  * TCP per-packet control information to the transmission code.
940  * We also store the host-order sequence numbers in here too.
941  * This is 44 bytes if IPV6 is enabled.
942  * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately.
943  */
944 struct tcp_skb_cb {
945 	__u32		seq;		/* Starting sequence number	*/
946 	__u32		end_seq;	/* SEQ + FIN + SYN + datalen	*/
947 	union {
948 		/* Note :
949 		 * 	  tcp_gso_segs/size are used in write queue only,
950 		 *	  cf tcp_skb_pcount()/tcp_skb_mss()
951 		 */
952 		struct {
953 			u16	tcp_gso_segs;
954 			u16	tcp_gso_size;
955 		};
956 	};
957 	__u8		tcp_flags;	/* TCP header flags. (tcp[13])	*/
958 
959 	__u8		sacked;		/* State flags for SACK.	*/
960 	__u8		ip_dsfield;	/* IPv4 tos or IPv6 dsfield	*/
961 	__u8		txstamp_ack:1,	/* Record TX timestamp for ack? */
962 			eor:1,		/* Is skb MSG_EOR marked? */
963 			has_rxtstamp:1,	/* SKB has a RX timestamp	*/
964 			unused:5;
965 	__u32		ack_seq;	/* Sequence number ACK'd	*/
966 	union {
967 		struct {
968 #define TCPCB_DELIVERED_CE_MASK ((1U<<20) - 1)
969 			/* There is space for up to 24 bytes */
970 			__u32 is_app_limited:1, /* cwnd not fully used? */
971 			      delivered_ce:20,
972 			      unused:11;
973 			/* pkts S/ACKed so far upon tx of skb, incl retrans: */
974 			__u32 delivered;
975 			/* start of send pipeline phase */
976 			u64 first_tx_mstamp;
977 			/* when we reached the "delivered" count */
978 			u64 delivered_mstamp;
979 		} tx;   /* only used for outgoing skbs */
980 		union {
981 			struct inet_skb_parm	h4;
982 #if IS_ENABLED(CONFIG_IPV6)
983 			struct inet6_skb_parm	h6;
984 #endif
985 		} header;	/* For incoming skbs */
986 	};
987 };
988 
989 #define TCP_SKB_CB(__skb)	((struct tcp_skb_cb *)&((__skb)->cb[0]))
990 
991 extern const struct inet_connection_sock_af_ops ipv4_specific;
992 
993 #if IS_ENABLED(CONFIG_IPV6)
994 /* This is the variant of inet6_iif() that must be used by TCP,
995  * as TCP moves IP6CB into a different location in skb->cb[]
996  */
997 static inline int tcp_v6_iif(const struct sk_buff *skb)
998 {
999 	return TCP_SKB_CB(skb)->header.h6.iif;
1000 }
1001 
1002 static inline int tcp_v6_iif_l3_slave(const struct sk_buff *skb)
1003 {
1004 	bool l3_slave = ipv6_l3mdev_skb(TCP_SKB_CB(skb)->header.h6.flags);
1005 
1006 	return l3_slave ? skb->skb_iif : TCP_SKB_CB(skb)->header.h6.iif;
1007 }
1008 
1009 /* TCP_SKB_CB reference means this can not be used from early demux */
1010 static inline int tcp_v6_sdif(const struct sk_buff *skb)
1011 {
1012 #if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
1013 	if (skb && ipv6_l3mdev_skb(TCP_SKB_CB(skb)->header.h6.flags))
1014 		return TCP_SKB_CB(skb)->header.h6.iif;
1015 #endif
1016 	return 0;
1017 }
1018 
1019 extern const struct inet_connection_sock_af_ops ipv6_specific;
1020 
1021 INDIRECT_CALLABLE_DECLARE(void tcp_v6_send_check(struct sock *sk, struct sk_buff *skb));
1022 INDIRECT_CALLABLE_DECLARE(int tcp_v6_rcv(struct sk_buff *skb));
1023 void tcp_v6_early_demux(struct sk_buff *skb);
1024 
1025 #endif
1026 
1027 /* TCP_SKB_CB reference means this can not be used from early demux */
1028 static inline int tcp_v4_sdif(struct sk_buff *skb)
1029 {
1030 #if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
1031 	if (skb && ipv4_l3mdev_skb(TCP_SKB_CB(skb)->header.h4.flags))
1032 		return TCP_SKB_CB(skb)->header.h4.iif;
1033 #endif
1034 	return 0;
1035 }
1036 
1037 /* Due to TSO, an SKB can be composed of multiple actual
1038  * packets.  To keep these tracked properly, we use this.
1039  */
1040 static inline int tcp_skb_pcount(const struct sk_buff *skb)
1041 {
1042 	return TCP_SKB_CB(skb)->tcp_gso_segs;
1043 }
1044 
1045 static inline void tcp_skb_pcount_set(struct sk_buff *skb, int segs)
1046 {
1047 	TCP_SKB_CB(skb)->tcp_gso_segs = segs;
1048 }
1049 
1050 static inline void tcp_skb_pcount_add(struct sk_buff *skb, int segs)
1051 {
1052 	TCP_SKB_CB(skb)->tcp_gso_segs += segs;
1053 }
1054 
1055 /* This is valid iff skb is in write queue and tcp_skb_pcount() > 1. */
1056 static inline int tcp_skb_mss(const struct sk_buff *skb)
1057 {
1058 	return TCP_SKB_CB(skb)->tcp_gso_size;
1059 }
1060 
1061 static inline bool tcp_skb_can_collapse_to(const struct sk_buff *skb)
1062 {
1063 	return likely(!TCP_SKB_CB(skb)->eor);
1064 }
1065 
1066 static inline bool tcp_skb_can_collapse(const struct sk_buff *to,
1067 					const struct sk_buff *from)
1068 {
1069 	/* skb_cmp_decrypted() not needed, use tcp_write_collapse_fence() */
1070 	return likely(tcp_skb_can_collapse_to(to) &&
1071 		      mptcp_skb_can_collapse(to, from) &&
1072 		      skb_pure_zcopy_same(to, from) &&
1073 		      skb_frags_readable(to) == skb_frags_readable(from));
1074 }
1075 
1076 static inline bool tcp_skb_can_collapse_rx(const struct sk_buff *to,
1077 					   const struct sk_buff *from)
1078 {
1079 	return likely(mptcp_skb_can_collapse(to, from) &&
1080 		      !skb_cmp_decrypted(to, from));
1081 }
1082 
1083 /* Events passed to congestion control interface */
1084 enum tcp_ca_event {
1085 	CA_EVENT_TX_START,	/* first transmit when no packets in flight */
1086 	CA_EVENT_CWND_RESTART,	/* congestion window restart */
1087 	CA_EVENT_COMPLETE_CWR,	/* end of congestion recovery */
1088 	CA_EVENT_LOSS,		/* loss timeout */
1089 	CA_EVENT_ECN_NO_CE,	/* ECT set, but not CE marked */
1090 	CA_EVENT_ECN_IS_CE,	/* received CE marked IP packet */
1091 };
1092 
1093 /* Information about inbound ACK, passed to cong_ops->in_ack_event() */
1094 enum tcp_ca_ack_event_flags {
1095 	CA_ACK_SLOWPATH		= (1 << 0),	/* In slow path processing */
1096 	CA_ACK_WIN_UPDATE	= (1 << 1),	/* ACK updated window */
1097 	CA_ACK_ECE		= (1 << 2),	/* ECE bit is set on ack */
1098 };
1099 
1100 /*
1101  * Interface for adding new TCP congestion control handlers
1102  */
1103 #define TCP_CA_NAME_MAX	16
1104 #define TCP_CA_MAX	128
1105 #define TCP_CA_BUF_MAX	(TCP_CA_NAME_MAX*TCP_CA_MAX)
1106 
1107 #define TCP_CA_UNSPEC	0
1108 
1109 /* Algorithm can be set on socket without CAP_NET_ADMIN privileges */
1110 #define TCP_CONG_NON_RESTRICTED 0x1
1111 /* Requires ECN/ECT set on all packets */
1112 #define TCP_CONG_NEEDS_ECN	0x2
1113 #define TCP_CONG_MASK	(TCP_CONG_NON_RESTRICTED | TCP_CONG_NEEDS_ECN)
1114 
1115 union tcp_cc_info;
1116 
1117 struct ack_sample {
1118 	u32 pkts_acked;
1119 	s32 rtt_us;
1120 	u32 in_flight;
1121 };
1122 
1123 /* A rate sample measures the number of (original/retransmitted) data
1124  * packets delivered "delivered" over an interval of time "interval_us".
1125  * The tcp_rate.c code fills in the rate sample, and congestion
1126  * control modules that define a cong_control function to run at the end
1127  * of ACK processing can optionally chose to consult this sample when
1128  * setting cwnd and pacing rate.
1129  * A sample is invalid if "delivered" or "interval_us" is negative.
1130  */
1131 struct rate_sample {
1132 	u64  prior_mstamp; /* starting timestamp for interval */
1133 	u32  prior_delivered;	/* tp->delivered at "prior_mstamp" */
1134 	u32  prior_delivered_ce;/* tp->delivered_ce at "prior_mstamp" */
1135 	s32  delivered;		/* number of packets delivered over interval */
1136 	s32  delivered_ce;	/* number of packets delivered w/ CE marks*/
1137 	long interval_us;	/* time for tp->delivered to incr "delivered" */
1138 	u32 snd_interval_us;	/* snd interval for delivered packets */
1139 	u32 rcv_interval_us;	/* rcv interval for delivered packets */
1140 	long rtt_us;		/* RTT of last (S)ACKed packet (or -1) */
1141 	int  losses;		/* number of packets marked lost upon ACK */
1142 	u32  acked_sacked;	/* number of packets newly (S)ACKed upon ACK */
1143 	u32  prior_in_flight;	/* in flight before this ACK */
1144 	u32  last_end_seq;	/* end_seq of most recently ACKed packet */
1145 	bool is_app_limited;	/* is sample from packet with bubble in pipe? */
1146 	bool is_retrans;	/* is sample from retransmission? */
1147 	bool is_ack_delayed;	/* is this (likely) a delayed ACK? */
1148 };
1149 
1150 struct tcp_congestion_ops {
1151 /* fast path fields are put first to fill one cache line */
1152 
1153 	/* return slow start threshold (required) */
1154 	u32 (*ssthresh)(struct sock *sk);
1155 
1156 	/* do new cwnd calculation (required) */
1157 	void (*cong_avoid)(struct sock *sk, u32 ack, u32 acked);
1158 
1159 	/* call before changing ca_state (optional) */
1160 	void (*set_state)(struct sock *sk, u8 new_state);
1161 
1162 	/* call when cwnd event occurs (optional) */
1163 	void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
1164 
1165 	/* call when ack arrives (optional) */
1166 	void (*in_ack_event)(struct sock *sk, u32 flags);
1167 
1168 	/* hook for packet ack accounting (optional) */
1169 	void (*pkts_acked)(struct sock *sk, const struct ack_sample *sample);
1170 
1171 	/* override sysctl_tcp_min_tso_segs */
1172 	u32 (*min_tso_segs)(struct sock *sk);
1173 
1174 	/* call when packets are delivered to update cwnd and pacing rate,
1175 	 * after all the ca_state processing. (optional)
1176 	 */
1177 	void (*cong_control)(struct sock *sk, u32 ack, int flag, const struct rate_sample *rs);
1178 
1179 
1180 	/* new value of cwnd after loss (required) */
1181 	u32  (*undo_cwnd)(struct sock *sk);
1182 	/* returns the multiplier used in tcp_sndbuf_expand (optional) */
1183 	u32 (*sndbuf_expand)(struct sock *sk);
1184 
1185 /* control/slow paths put last */
1186 	/* get info for inet_diag (optional) */
1187 	size_t (*get_info)(struct sock *sk, u32 ext, int *attr,
1188 			   union tcp_cc_info *info);
1189 
1190 	char 			name[TCP_CA_NAME_MAX];
1191 	struct module		*owner;
1192 	struct list_head	list;
1193 	u32			key;
1194 	u32			flags;
1195 
1196 	/* initialize private data (optional) */
1197 	void (*init)(struct sock *sk);
1198 	/* cleanup private data  (optional) */
1199 	void (*release)(struct sock *sk);
1200 } ____cacheline_aligned_in_smp;
1201 
1202 int tcp_register_congestion_control(struct tcp_congestion_ops *type);
1203 void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
1204 int tcp_update_congestion_control(struct tcp_congestion_ops *type,
1205 				  struct tcp_congestion_ops *old_type);
1206 int tcp_validate_congestion_control(struct tcp_congestion_ops *ca);
1207 
1208 void tcp_assign_congestion_control(struct sock *sk);
1209 void tcp_init_congestion_control(struct sock *sk);
1210 void tcp_cleanup_congestion_control(struct sock *sk);
1211 int tcp_set_default_congestion_control(struct net *net, const char *name);
1212 void tcp_get_default_congestion_control(struct net *net, char *name);
1213 void tcp_get_available_congestion_control(char *buf, size_t len);
1214 void tcp_get_allowed_congestion_control(char *buf, size_t len);
1215 int tcp_set_allowed_congestion_control(char *allowed);
1216 int tcp_set_congestion_control(struct sock *sk, const char *name, bool load,
1217 			       bool cap_net_admin);
1218 u32 tcp_slow_start(struct tcp_sock *tp, u32 acked);
1219 void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked);
1220 
1221 u32 tcp_reno_ssthresh(struct sock *sk);
1222 u32 tcp_reno_undo_cwnd(struct sock *sk);
1223 void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked);
1224 extern struct tcp_congestion_ops tcp_reno;
1225 
1226 struct tcp_congestion_ops *tcp_ca_find(const char *name);
1227 struct tcp_congestion_ops *tcp_ca_find_key(u32 key);
1228 u32 tcp_ca_get_key_by_name(const char *name, bool *ecn_ca);
1229 #ifdef CONFIG_INET
1230 char *tcp_ca_get_name_by_key(u32 key, char *buffer);
1231 #else
1232 static inline char *tcp_ca_get_name_by_key(u32 key, char *buffer)
1233 {
1234 	return NULL;
1235 }
1236 #endif
1237 
1238 static inline bool tcp_ca_needs_ecn(const struct sock *sk)
1239 {
1240 	const struct inet_connection_sock *icsk = inet_csk(sk);
1241 
1242 	return icsk->icsk_ca_ops->flags & TCP_CONG_NEEDS_ECN;
1243 }
1244 
1245 static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
1246 {
1247 	const struct inet_connection_sock *icsk = inet_csk(sk);
1248 
1249 	if (icsk->icsk_ca_ops->cwnd_event)
1250 		icsk->icsk_ca_ops->cwnd_event(sk, event);
1251 }
1252 
1253 /* From tcp_cong.c */
1254 void tcp_set_ca_state(struct sock *sk, const u8 ca_state);
1255 
1256 /* From tcp_rate.c */
1257 void tcp_rate_skb_sent(struct sock *sk, struct sk_buff *skb);
1258 void tcp_rate_skb_delivered(struct sock *sk, struct sk_buff *skb,
1259 			    struct rate_sample *rs);
1260 void tcp_rate_gen(struct sock *sk, u32 delivered, u32 lost,
1261 		  bool is_sack_reneg, struct rate_sample *rs);
1262 void tcp_rate_check_app_limited(struct sock *sk);
1263 
1264 static inline bool tcp_skb_sent_after(u64 t1, u64 t2, u32 seq1, u32 seq2)
1265 {
1266 	return t1 > t2 || (t1 == t2 && after(seq1, seq2));
1267 }
1268 
1269 /* These functions determine how the current flow behaves in respect of SACK
1270  * handling. SACK is negotiated with the peer, and therefore it can vary
1271  * between different flows.
1272  *
1273  * tcp_is_sack - SACK enabled
1274  * tcp_is_reno - No SACK
1275  */
1276 static inline int tcp_is_sack(const struct tcp_sock *tp)
1277 {
1278 	return likely(tp->rx_opt.sack_ok);
1279 }
1280 
1281 static inline bool tcp_is_reno(const struct tcp_sock *tp)
1282 {
1283 	return !tcp_is_sack(tp);
1284 }
1285 
1286 static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
1287 {
1288 	return tp->sacked_out + tp->lost_out;
1289 }
1290 
1291 /* This determines how many packets are "in the network" to the best
1292  * of our knowledge.  In many cases it is conservative, but where
1293  * detailed information is available from the receiver (via SACK
1294  * blocks etc.) we can make more aggressive calculations.
1295  *
1296  * Use this for decisions involving congestion control, use just
1297  * tp->packets_out to determine if the send queue is empty or not.
1298  *
1299  * Read this equation as:
1300  *
1301  *	"Packets sent once on transmission queue" MINUS
1302  *	"Packets left network, but not honestly ACKed yet" PLUS
1303  *	"Packets fast retransmitted"
1304  */
1305 static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
1306 {
1307 	return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
1308 }
1309 
1310 #define TCP_INFINITE_SSTHRESH	0x7fffffff
1311 
1312 static inline u32 tcp_snd_cwnd(const struct tcp_sock *tp)
1313 {
1314 	return tp->snd_cwnd;
1315 }
1316 
1317 static inline void tcp_snd_cwnd_set(struct tcp_sock *tp, u32 val)
1318 {
1319 	WARN_ON_ONCE((int)val <= 0);
1320 	tp->snd_cwnd = val;
1321 }
1322 
1323 static inline bool tcp_in_slow_start(const struct tcp_sock *tp)
1324 {
1325 	return tcp_snd_cwnd(tp) < tp->snd_ssthresh;
1326 }
1327 
1328 static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
1329 {
1330 	return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
1331 }
1332 
1333 static inline bool tcp_in_cwnd_reduction(const struct sock *sk)
1334 {
1335 	return (TCPF_CA_CWR | TCPF_CA_Recovery) &
1336 	       (1 << inet_csk(sk)->icsk_ca_state);
1337 }
1338 
1339 /* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
1340  * The exception is cwnd reduction phase, when cwnd is decreasing towards
1341  * ssthresh.
1342  */
1343 static inline __u32 tcp_current_ssthresh(const struct sock *sk)
1344 {
1345 	const struct tcp_sock *tp = tcp_sk(sk);
1346 
1347 	if (tcp_in_cwnd_reduction(sk))
1348 		return tp->snd_ssthresh;
1349 	else
1350 		return max(tp->snd_ssthresh,
1351 			   ((tcp_snd_cwnd(tp) >> 1) +
1352 			    (tcp_snd_cwnd(tp) >> 2)));
1353 }
1354 
1355 /* Use define here intentionally to get WARN_ON location shown at the caller */
1356 #define tcp_verify_left_out(tp)	WARN_ON(tcp_left_out(tp) > tp->packets_out)
1357 
1358 void tcp_enter_cwr(struct sock *sk);
1359 __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst);
1360 
1361 /* The maximum number of MSS of available cwnd for which TSO defers
1362  * sending if not using sysctl_tcp_tso_win_divisor.
1363  */
1364 static inline __u32 tcp_max_tso_deferred_mss(const struct tcp_sock *tp)
1365 {
1366 	return 3;
1367 }
1368 
1369 /* Returns end sequence number of the receiver's advertised window */
1370 static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
1371 {
1372 	return tp->snd_una + tp->snd_wnd;
1373 }
1374 
1375 /* We follow the spirit of RFC2861 to validate cwnd but implement a more
1376  * flexible approach. The RFC suggests cwnd should not be raised unless
1377  * it was fully used previously. And that's exactly what we do in
1378  * congestion avoidance mode. But in slow start we allow cwnd to grow
1379  * as long as the application has used half the cwnd.
1380  * Example :
1381  *    cwnd is 10 (IW10), but application sends 9 frames.
1382  *    We allow cwnd to reach 18 when all frames are ACKed.
1383  * This check is safe because it's as aggressive as slow start which already
1384  * risks 100% overshoot. The advantage is that we discourage application to
1385  * either send more filler packets or data to artificially blow up the cwnd
1386  * usage, and allow application-limited process to probe bw more aggressively.
1387  */
1388 static inline bool tcp_is_cwnd_limited(const struct sock *sk)
1389 {
1390 	const struct tcp_sock *tp = tcp_sk(sk);
1391 
1392 	if (tp->is_cwnd_limited)
1393 		return true;
1394 
1395 	/* If in slow start, ensure cwnd grows to twice what was ACKed. */
1396 	if (tcp_in_slow_start(tp))
1397 		return tcp_snd_cwnd(tp) < 2 * tp->max_packets_out;
1398 
1399 	return false;
1400 }
1401 
1402 /* BBR congestion control needs pacing.
1403  * Same remark for SO_MAX_PACING_RATE.
1404  * sch_fq packet scheduler is efficiently handling pacing,
1405  * but is not always installed/used.
1406  * Return true if TCP stack should pace packets itself.
1407  */
1408 static inline bool tcp_needs_internal_pacing(const struct sock *sk)
1409 {
1410 	return smp_load_acquire(&sk->sk_pacing_status) == SK_PACING_NEEDED;
1411 }
1412 
1413 /* Estimates in how many jiffies next packet for this flow can be sent.
1414  * Scheduling a retransmit timer too early would be silly.
1415  */
1416 static inline unsigned long tcp_pacing_delay(const struct sock *sk)
1417 {
1418 	s64 delay = tcp_sk(sk)->tcp_wstamp_ns - tcp_sk(sk)->tcp_clock_cache;
1419 
1420 	return delay > 0 ? nsecs_to_jiffies(delay) : 0;
1421 }
1422 
1423 static inline void tcp_reset_xmit_timer(struct sock *sk,
1424 					const int what,
1425 					unsigned long when,
1426 					const unsigned long max_when)
1427 {
1428 	inet_csk_reset_xmit_timer(sk, what, when + tcp_pacing_delay(sk),
1429 				  max_when);
1430 }
1431 
1432 /* Something is really bad, we could not queue an additional packet,
1433  * because qdisc is full or receiver sent a 0 window, or we are paced.
1434  * We do not want to add fuel to the fire, or abort too early,
1435  * so make sure the timer we arm now is at least 200ms in the future,
1436  * regardless of current icsk_rto value (as it could be ~2ms)
1437  */
1438 static inline unsigned long tcp_probe0_base(const struct sock *sk)
1439 {
1440 	return max_t(unsigned long, inet_csk(sk)->icsk_rto, TCP_RTO_MIN);
1441 }
1442 
1443 /* Variant of inet_csk_rto_backoff() used for zero window probes */
1444 static inline unsigned long tcp_probe0_when(const struct sock *sk,
1445 					    unsigned long max_when)
1446 {
1447 	u8 backoff = min_t(u8, ilog2(TCP_RTO_MAX / TCP_RTO_MIN) + 1,
1448 			   inet_csk(sk)->icsk_backoff);
1449 	u64 when = (u64)tcp_probe0_base(sk) << backoff;
1450 
1451 	return (unsigned long)min_t(u64, when, max_when);
1452 }
1453 
1454 static inline void tcp_check_probe_timer(struct sock *sk)
1455 {
1456 	if (!tcp_sk(sk)->packets_out && !inet_csk(sk)->icsk_pending)
1457 		tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
1458 				     tcp_probe0_base(sk), TCP_RTO_MAX);
1459 }
1460 
1461 static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
1462 {
1463 	tp->snd_wl1 = seq;
1464 }
1465 
1466 static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq)
1467 {
1468 	tp->snd_wl1 = seq;
1469 }
1470 
1471 /*
1472  * Calculate(/check) TCP checksum
1473  */
1474 static inline __sum16 tcp_v4_check(int len, __be32 saddr,
1475 				   __be32 daddr, __wsum base)
1476 {
1477 	return csum_tcpudp_magic(saddr, daddr, len, IPPROTO_TCP, base);
1478 }
1479 
1480 static inline bool tcp_checksum_complete(struct sk_buff *skb)
1481 {
1482 	return !skb_csum_unnecessary(skb) &&
1483 		__skb_checksum_complete(skb);
1484 }
1485 
1486 bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb,
1487 		     enum skb_drop_reason *reason);
1488 
1489 
1490 int tcp_filter(struct sock *sk, struct sk_buff *skb);
1491 void tcp_set_state(struct sock *sk, int state);
1492 void tcp_done(struct sock *sk);
1493 int tcp_abort(struct sock *sk, int err);
1494 
1495 static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
1496 {
1497 	rx_opt->dsack = 0;
1498 	rx_opt->num_sacks = 0;
1499 }
1500 
1501 void tcp_cwnd_restart(struct sock *sk, s32 delta);
1502 
1503 static inline void tcp_slow_start_after_idle_check(struct sock *sk)
1504 {
1505 	const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1506 	struct tcp_sock *tp = tcp_sk(sk);
1507 	s32 delta;
1508 
1509 	if (!READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_slow_start_after_idle) ||
1510 	    tp->packets_out || ca_ops->cong_control)
1511 		return;
1512 	delta = tcp_jiffies32 - tp->lsndtime;
1513 	if (delta > inet_csk(sk)->icsk_rto)
1514 		tcp_cwnd_restart(sk, delta);
1515 }
1516 
1517 /* Determine a window scaling and initial window to offer. */
1518 void tcp_select_initial_window(const struct sock *sk, int __space,
1519 			       __u32 mss, __u32 *rcv_wnd,
1520 			       __u32 *window_clamp, int wscale_ok,
1521 			       __u8 *rcv_wscale, __u32 init_rcv_wnd);
1522 
1523 static inline int __tcp_win_from_space(u8 scaling_ratio, int space)
1524 {
1525 	s64 scaled_space = (s64)space * scaling_ratio;
1526 
1527 	return scaled_space >> TCP_RMEM_TO_WIN_SCALE;
1528 }
1529 
1530 static inline int tcp_win_from_space(const struct sock *sk, int space)
1531 {
1532 	return __tcp_win_from_space(tcp_sk(sk)->scaling_ratio, space);
1533 }
1534 
1535 /* inverse of __tcp_win_from_space() */
1536 static inline int __tcp_space_from_win(u8 scaling_ratio, int win)
1537 {
1538 	u64 val = (u64)win << TCP_RMEM_TO_WIN_SCALE;
1539 
1540 	do_div(val, scaling_ratio);
1541 	return val;
1542 }
1543 
1544 static inline int tcp_space_from_win(const struct sock *sk, int win)
1545 {
1546 	return __tcp_space_from_win(tcp_sk(sk)->scaling_ratio, win);
1547 }
1548 
1549 /* Assume a 50% default for skb->len/skb->truesize ratio.
1550  * This may be adjusted later in tcp_measure_rcv_mss().
1551  */
1552 #define TCP_DEFAULT_SCALING_RATIO (1 << (TCP_RMEM_TO_WIN_SCALE - 1))
1553 
1554 static inline void tcp_scaling_ratio_init(struct sock *sk)
1555 {
1556 	tcp_sk(sk)->scaling_ratio = TCP_DEFAULT_SCALING_RATIO;
1557 }
1558 
1559 /* Note: caller must be prepared to deal with negative returns */
1560 static inline int tcp_space(const struct sock *sk)
1561 {
1562 	return tcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf) -
1563 				  READ_ONCE(sk->sk_backlog.len) -
1564 				  atomic_read(&sk->sk_rmem_alloc));
1565 }
1566 
1567 static inline int tcp_full_space(const struct sock *sk)
1568 {
1569 	return tcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf));
1570 }
1571 
1572 static inline void __tcp_adjust_rcv_ssthresh(struct sock *sk, u32 new_ssthresh)
1573 {
1574 	int unused_mem = sk_unused_reserved_mem(sk);
1575 	struct tcp_sock *tp = tcp_sk(sk);
1576 
1577 	tp->rcv_ssthresh = min(tp->rcv_ssthresh, new_ssthresh);
1578 	if (unused_mem)
1579 		tp->rcv_ssthresh = max_t(u32, tp->rcv_ssthresh,
1580 					 tcp_win_from_space(sk, unused_mem));
1581 }
1582 
1583 static inline void tcp_adjust_rcv_ssthresh(struct sock *sk)
1584 {
1585 	__tcp_adjust_rcv_ssthresh(sk, 4U * tcp_sk(sk)->advmss);
1586 }
1587 
1588 void tcp_cleanup_rbuf(struct sock *sk, int copied);
1589 void __tcp_cleanup_rbuf(struct sock *sk, int copied);
1590 
1591 
1592 /* We provision sk_rcvbuf around 200% of sk_rcvlowat.
1593  * If 87.5 % (7/8) of the space has been consumed, we want to override
1594  * SO_RCVLOWAT constraint, since we are receiving skbs with too small
1595  * len/truesize ratio.
1596  */
1597 static inline bool tcp_rmem_pressure(const struct sock *sk)
1598 {
1599 	int rcvbuf, threshold;
1600 
1601 	if (tcp_under_memory_pressure(sk))
1602 		return true;
1603 
1604 	rcvbuf = READ_ONCE(sk->sk_rcvbuf);
1605 	threshold = rcvbuf - (rcvbuf >> 3);
1606 
1607 	return atomic_read(&sk->sk_rmem_alloc) > threshold;
1608 }
1609 
1610 static inline bool tcp_epollin_ready(const struct sock *sk, int target)
1611 {
1612 	const struct tcp_sock *tp = tcp_sk(sk);
1613 	int avail = READ_ONCE(tp->rcv_nxt) - READ_ONCE(tp->copied_seq);
1614 
1615 	if (avail <= 0)
1616 		return false;
1617 
1618 	return (avail >= target) || tcp_rmem_pressure(sk) ||
1619 	       (tcp_receive_window(tp) <= inet_csk(sk)->icsk_ack.rcv_mss);
1620 }
1621 
1622 extern void tcp_openreq_init_rwin(struct request_sock *req,
1623 				  const struct sock *sk_listener,
1624 				  const struct dst_entry *dst);
1625 
1626 void tcp_enter_memory_pressure(struct sock *sk);
1627 void tcp_leave_memory_pressure(struct sock *sk);
1628 
1629 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
1630 {
1631 	struct net *net = sock_net((struct sock *)tp);
1632 	int val;
1633 
1634 	/* Paired with WRITE_ONCE() in tcp_sock_set_keepintvl()
1635 	 * and do_tcp_setsockopt().
1636 	 */
1637 	val = READ_ONCE(tp->keepalive_intvl);
1638 
1639 	return val ? : READ_ONCE(net->ipv4.sysctl_tcp_keepalive_intvl);
1640 }
1641 
1642 static inline int keepalive_time_when(const struct tcp_sock *tp)
1643 {
1644 	struct net *net = sock_net((struct sock *)tp);
1645 	int val;
1646 
1647 	/* Paired with WRITE_ONCE() in tcp_sock_set_keepidle_locked() */
1648 	val = READ_ONCE(tp->keepalive_time);
1649 
1650 	return val ? : READ_ONCE(net->ipv4.sysctl_tcp_keepalive_time);
1651 }
1652 
1653 static inline int keepalive_probes(const struct tcp_sock *tp)
1654 {
1655 	struct net *net = sock_net((struct sock *)tp);
1656 	int val;
1657 
1658 	/* Paired with WRITE_ONCE() in tcp_sock_set_keepcnt()
1659 	 * and do_tcp_setsockopt().
1660 	 */
1661 	val = READ_ONCE(tp->keepalive_probes);
1662 
1663 	return val ? : READ_ONCE(net->ipv4.sysctl_tcp_keepalive_probes);
1664 }
1665 
1666 static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
1667 {
1668 	const struct inet_connection_sock *icsk = &tp->inet_conn;
1669 
1670 	return min_t(u32, tcp_jiffies32 - icsk->icsk_ack.lrcvtime,
1671 			  tcp_jiffies32 - tp->rcv_tstamp);
1672 }
1673 
1674 static inline int tcp_fin_time(const struct sock *sk)
1675 {
1676 	int fin_timeout = tcp_sk(sk)->linger2 ? :
1677 		READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fin_timeout);
1678 	const int rto = inet_csk(sk)->icsk_rto;
1679 
1680 	if (fin_timeout < (rto << 2) - (rto >> 1))
1681 		fin_timeout = (rto << 2) - (rto >> 1);
1682 
1683 	return fin_timeout;
1684 }
1685 
1686 static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt,
1687 				  int paws_win)
1688 {
1689 	if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
1690 		return true;
1691 	if (unlikely(!time_before32(ktime_get_seconds(),
1692 				    rx_opt->ts_recent_stamp + TCP_PAWS_WRAP)))
1693 		return true;
1694 	/*
1695 	 * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
1696 	 * then following tcp messages have valid values. Ignore 0 value,
1697 	 * or else 'negative' tsval might forbid us to accept their packets.
1698 	 */
1699 	if (!rx_opt->ts_recent)
1700 		return true;
1701 	return false;
1702 }
1703 
1704 static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt,
1705 				   int rst)
1706 {
1707 	if (tcp_paws_check(rx_opt, 0))
1708 		return false;
1709 
1710 	/* RST segments are not recommended to carry timestamp,
1711 	   and, if they do, it is recommended to ignore PAWS because
1712 	   "their cleanup function should take precedence over timestamps."
1713 	   Certainly, it is mistake. It is necessary to understand the reasons
1714 	   of this constraint to relax it: if peer reboots, clock may go
1715 	   out-of-sync and half-open connections will not be reset.
1716 	   Actually, the problem would be not existing if all
1717 	   the implementations followed draft about maintaining clock
1718 	   via reboots. Linux-2.2 DOES NOT!
1719 
1720 	   However, we can relax time bounds for RST segments to MSL.
1721 	 */
1722 	if (rst && !time_before32(ktime_get_seconds(),
1723 				  rx_opt->ts_recent_stamp + TCP_PAWS_MSL))
1724 		return false;
1725 	return true;
1726 }
1727 
1728 bool tcp_oow_rate_limited(struct net *net, const struct sk_buff *skb,
1729 			  int mib_idx, u32 *last_oow_ack_time);
1730 
1731 static inline void tcp_mib_init(struct net *net)
1732 {
1733 	/* See RFC 2012 */
1734 	TCP_ADD_STATS(net, TCP_MIB_RTOALGORITHM, 1);
1735 	TCP_ADD_STATS(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
1736 	TCP_ADD_STATS(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
1737 	TCP_ADD_STATS(net, TCP_MIB_MAXCONN, -1);
1738 }
1739 
1740 /* from STCP */
1741 static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
1742 {
1743 	tp->lost_skb_hint = NULL;
1744 }
1745 
1746 static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
1747 {
1748 	tcp_clear_retrans_hints_partial(tp);
1749 	tp->retransmit_skb_hint = NULL;
1750 }
1751 
1752 #define tcp_md5_addr tcp_ao_addr
1753 
1754 /* - key database */
1755 struct tcp_md5sig_key {
1756 	struct hlist_node	node;
1757 	u8			keylen;
1758 	u8			family; /* AF_INET or AF_INET6 */
1759 	u8			prefixlen;
1760 	u8			flags;
1761 	union tcp_md5_addr	addr;
1762 	int			l3index; /* set if key added with L3 scope */
1763 	u8			key[TCP_MD5SIG_MAXKEYLEN];
1764 	struct rcu_head		rcu;
1765 };
1766 
1767 /* - sock block */
1768 struct tcp_md5sig_info {
1769 	struct hlist_head	head;
1770 	struct rcu_head		rcu;
1771 };
1772 
1773 /* - pseudo header */
1774 struct tcp4_pseudohdr {
1775 	__be32		saddr;
1776 	__be32		daddr;
1777 	__u8		pad;
1778 	__u8		protocol;
1779 	__be16		len;
1780 };
1781 
1782 struct tcp6_pseudohdr {
1783 	struct in6_addr	saddr;
1784 	struct in6_addr daddr;
1785 	__be32		len;
1786 	__be32		protocol;	/* including padding */
1787 };
1788 
1789 union tcp_md5sum_block {
1790 	struct tcp4_pseudohdr ip4;
1791 #if IS_ENABLED(CONFIG_IPV6)
1792 	struct tcp6_pseudohdr ip6;
1793 #endif
1794 };
1795 
1796 /*
1797  * struct tcp_sigpool - per-CPU pool of ahash_requests
1798  * @scratch: per-CPU temporary area, that can be used between
1799  *	     tcp_sigpool_start() and tcp_sigpool_end() to perform
1800  *	     crypto request
1801  * @req: pre-allocated ahash request
1802  */
1803 struct tcp_sigpool {
1804 	void *scratch;
1805 	struct ahash_request *req;
1806 };
1807 
1808 int tcp_sigpool_alloc_ahash(const char *alg, size_t scratch_size);
1809 void tcp_sigpool_get(unsigned int id);
1810 void tcp_sigpool_release(unsigned int id);
1811 int tcp_sigpool_hash_skb_data(struct tcp_sigpool *hp,
1812 			      const struct sk_buff *skb,
1813 			      unsigned int header_len);
1814 
1815 /**
1816  * tcp_sigpool_start - disable bh and start using tcp_sigpool_ahash
1817  * @id: tcp_sigpool that was previously allocated by tcp_sigpool_alloc_ahash()
1818  * @c: returned tcp_sigpool for usage (uninitialized on failure)
1819  *
1820  * Returns 0 on success, error otherwise.
1821  */
1822 int tcp_sigpool_start(unsigned int id, struct tcp_sigpool *c);
1823 /**
1824  * tcp_sigpool_end - enable bh and stop using tcp_sigpool
1825  * @c: tcp_sigpool context that was returned by tcp_sigpool_start()
1826  */
1827 void tcp_sigpool_end(struct tcp_sigpool *c);
1828 size_t tcp_sigpool_algo(unsigned int id, char *buf, size_t buf_len);
1829 /* - functions */
1830 int tcp_v4_md5_hash_skb(char *md5_hash, const struct tcp_md5sig_key *key,
1831 			const struct sock *sk, const struct sk_buff *skb);
1832 int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
1833 		   int family, u8 prefixlen, int l3index, u8 flags,
1834 		   const u8 *newkey, u8 newkeylen);
1835 int tcp_md5_key_copy(struct sock *sk, const union tcp_md5_addr *addr,
1836 		     int family, u8 prefixlen, int l3index,
1837 		     struct tcp_md5sig_key *key);
1838 
1839 int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
1840 		   int family, u8 prefixlen, int l3index, u8 flags);
1841 void tcp_clear_md5_list(struct sock *sk);
1842 struct tcp_md5sig_key *tcp_v4_md5_lookup(const struct sock *sk,
1843 					 const struct sock *addr_sk);
1844 
1845 #ifdef CONFIG_TCP_MD5SIG
1846 struct tcp_md5sig_key *__tcp_md5_do_lookup(const struct sock *sk, int l3index,
1847 					   const union tcp_md5_addr *addr,
1848 					   int family, bool any_l3index);
1849 static inline struct tcp_md5sig_key *
1850 tcp_md5_do_lookup(const struct sock *sk, int l3index,
1851 		  const union tcp_md5_addr *addr, int family)
1852 {
1853 	if (!static_branch_unlikely(&tcp_md5_needed.key))
1854 		return NULL;
1855 	return __tcp_md5_do_lookup(sk, l3index, addr, family, false);
1856 }
1857 
1858 static inline struct tcp_md5sig_key *
1859 tcp_md5_do_lookup_any_l3index(const struct sock *sk,
1860 			      const union tcp_md5_addr *addr, int family)
1861 {
1862 	if (!static_branch_unlikely(&tcp_md5_needed.key))
1863 		return NULL;
1864 	return __tcp_md5_do_lookup(sk, 0, addr, family, true);
1865 }
1866 
1867 #define tcp_twsk_md5_key(twsk)	((twsk)->tw_md5_key)
1868 #else
1869 static inline struct tcp_md5sig_key *
1870 tcp_md5_do_lookup(const struct sock *sk, int l3index,
1871 		  const union tcp_md5_addr *addr, int family)
1872 {
1873 	return NULL;
1874 }
1875 
1876 static inline struct tcp_md5sig_key *
1877 tcp_md5_do_lookup_any_l3index(const struct sock *sk,
1878 			      const union tcp_md5_addr *addr, int family)
1879 {
1880 	return NULL;
1881 }
1882 
1883 #define tcp_twsk_md5_key(twsk)	NULL
1884 #endif
1885 
1886 int tcp_md5_alloc_sigpool(void);
1887 void tcp_md5_release_sigpool(void);
1888 void tcp_md5_add_sigpool(void);
1889 extern int tcp_md5_sigpool_id;
1890 
1891 int tcp_md5_hash_key(struct tcp_sigpool *hp,
1892 		     const struct tcp_md5sig_key *key);
1893 
1894 /* From tcp_fastopen.c */
1895 void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
1896 			    struct tcp_fastopen_cookie *cookie);
1897 void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
1898 			    struct tcp_fastopen_cookie *cookie, bool syn_lost,
1899 			    u16 try_exp);
1900 struct tcp_fastopen_request {
1901 	/* Fast Open cookie. Size 0 means a cookie request */
1902 	struct tcp_fastopen_cookie	cookie;
1903 	struct msghdr			*data;  /* data in MSG_FASTOPEN */
1904 	size_t				size;
1905 	int				copied;	/* queued in tcp_connect() */
1906 	struct ubuf_info		*uarg;
1907 };
1908 void tcp_free_fastopen_req(struct tcp_sock *tp);
1909 void tcp_fastopen_destroy_cipher(struct sock *sk);
1910 void tcp_fastopen_ctx_destroy(struct net *net);
1911 int tcp_fastopen_reset_cipher(struct net *net, struct sock *sk,
1912 			      void *primary_key, void *backup_key);
1913 int tcp_fastopen_get_cipher(struct net *net, struct inet_connection_sock *icsk,
1914 			    u64 *key);
1915 void tcp_fastopen_add_skb(struct sock *sk, struct sk_buff *skb);
1916 struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
1917 			      struct request_sock *req,
1918 			      struct tcp_fastopen_cookie *foc,
1919 			      const struct dst_entry *dst);
1920 void tcp_fastopen_init_key_once(struct net *net);
1921 bool tcp_fastopen_cookie_check(struct sock *sk, u16 *mss,
1922 			     struct tcp_fastopen_cookie *cookie);
1923 bool tcp_fastopen_defer_connect(struct sock *sk, int *err);
1924 #define TCP_FASTOPEN_KEY_LENGTH sizeof(siphash_key_t)
1925 #define TCP_FASTOPEN_KEY_MAX 2
1926 #define TCP_FASTOPEN_KEY_BUF_LENGTH \
1927 	(TCP_FASTOPEN_KEY_LENGTH * TCP_FASTOPEN_KEY_MAX)
1928 
1929 /* Fastopen key context */
1930 struct tcp_fastopen_context {
1931 	siphash_key_t	key[TCP_FASTOPEN_KEY_MAX];
1932 	int		num;
1933 	struct rcu_head	rcu;
1934 };
1935 
1936 void tcp_fastopen_active_disable(struct sock *sk);
1937 bool tcp_fastopen_active_should_disable(struct sock *sk);
1938 void tcp_fastopen_active_disable_ofo_check(struct sock *sk);
1939 void tcp_fastopen_active_detect_blackhole(struct sock *sk, bool expired);
1940 
1941 /* Caller needs to wrap with rcu_read_(un)lock() */
1942 static inline
1943 struct tcp_fastopen_context *tcp_fastopen_get_ctx(const struct sock *sk)
1944 {
1945 	struct tcp_fastopen_context *ctx;
1946 
1947 	ctx = rcu_dereference(inet_csk(sk)->icsk_accept_queue.fastopenq.ctx);
1948 	if (!ctx)
1949 		ctx = rcu_dereference(sock_net(sk)->ipv4.tcp_fastopen_ctx);
1950 	return ctx;
1951 }
1952 
1953 static inline
1954 bool tcp_fastopen_cookie_match(const struct tcp_fastopen_cookie *foc,
1955 			       const struct tcp_fastopen_cookie *orig)
1956 {
1957 	if (orig->len == TCP_FASTOPEN_COOKIE_SIZE &&
1958 	    orig->len == foc->len &&
1959 	    !memcmp(orig->val, foc->val, foc->len))
1960 		return true;
1961 	return false;
1962 }
1963 
1964 static inline
1965 int tcp_fastopen_context_len(const struct tcp_fastopen_context *ctx)
1966 {
1967 	return ctx->num;
1968 }
1969 
1970 /* Latencies incurred by various limits for a sender. They are
1971  * chronograph-like stats that are mutually exclusive.
1972  */
1973 enum tcp_chrono {
1974 	TCP_CHRONO_UNSPEC,
1975 	TCP_CHRONO_BUSY, /* Actively sending data (non-empty write queue) */
1976 	TCP_CHRONO_RWND_LIMITED, /* Stalled by insufficient receive window */
1977 	TCP_CHRONO_SNDBUF_LIMITED, /* Stalled by insufficient send buffer */
1978 	__TCP_CHRONO_MAX,
1979 };
1980 
1981 void tcp_chrono_start(struct sock *sk, const enum tcp_chrono type);
1982 void tcp_chrono_stop(struct sock *sk, const enum tcp_chrono type);
1983 
1984 /* This helper is needed, because skb->tcp_tsorted_anchor uses
1985  * the same memory storage than skb->destructor/_skb_refdst
1986  */
1987 static inline void tcp_skb_tsorted_anchor_cleanup(struct sk_buff *skb)
1988 {
1989 	skb->destructor = NULL;
1990 	skb->_skb_refdst = 0UL;
1991 }
1992 
1993 #define tcp_skb_tsorted_save(skb) {		\
1994 	unsigned long _save = skb->_skb_refdst;	\
1995 	skb->_skb_refdst = 0UL;
1996 
1997 #define tcp_skb_tsorted_restore(skb)		\
1998 	skb->_skb_refdst = _save;		\
1999 }
2000 
2001 void tcp_write_queue_purge(struct sock *sk);
2002 
2003 static inline struct sk_buff *tcp_rtx_queue_head(const struct sock *sk)
2004 {
2005 	return skb_rb_first(&sk->tcp_rtx_queue);
2006 }
2007 
2008 static inline struct sk_buff *tcp_rtx_queue_tail(const struct sock *sk)
2009 {
2010 	return skb_rb_last(&sk->tcp_rtx_queue);
2011 }
2012 
2013 static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk)
2014 {
2015 	return skb_peek_tail(&sk->sk_write_queue);
2016 }
2017 
2018 #define tcp_for_write_queue_from_safe(skb, tmp, sk)			\
2019 	skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
2020 
2021 static inline struct sk_buff *tcp_send_head(const struct sock *sk)
2022 {
2023 	return skb_peek(&sk->sk_write_queue);
2024 }
2025 
2026 static inline bool tcp_skb_is_last(const struct sock *sk,
2027 				   const struct sk_buff *skb)
2028 {
2029 	return skb_queue_is_last(&sk->sk_write_queue, skb);
2030 }
2031 
2032 /**
2033  * tcp_write_queue_empty - test if any payload (or FIN) is available in write queue
2034  * @sk: socket
2035  *
2036  * Since the write queue can have a temporary empty skb in it,
2037  * we must not use "return skb_queue_empty(&sk->sk_write_queue)"
2038  */
2039 static inline bool tcp_write_queue_empty(const struct sock *sk)
2040 {
2041 	const struct tcp_sock *tp = tcp_sk(sk);
2042 
2043 	return tp->write_seq == tp->snd_nxt;
2044 }
2045 
2046 static inline bool tcp_rtx_queue_empty(const struct sock *sk)
2047 {
2048 	return RB_EMPTY_ROOT(&sk->tcp_rtx_queue);
2049 }
2050 
2051 static inline bool tcp_rtx_and_write_queues_empty(const struct sock *sk)
2052 {
2053 	return tcp_rtx_queue_empty(sk) && tcp_write_queue_empty(sk);
2054 }
2055 
2056 static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
2057 {
2058 	__skb_queue_tail(&sk->sk_write_queue, skb);
2059 
2060 	/* Queue it, remembering where we must start sending. */
2061 	if (sk->sk_write_queue.next == skb)
2062 		tcp_chrono_start(sk, TCP_CHRONO_BUSY);
2063 }
2064 
2065 /* Insert new before skb on the write queue of sk.  */
2066 static inline void tcp_insert_write_queue_before(struct sk_buff *new,
2067 						  struct sk_buff *skb,
2068 						  struct sock *sk)
2069 {
2070 	__skb_queue_before(&sk->sk_write_queue, skb, new);
2071 }
2072 
2073 static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
2074 {
2075 	tcp_skb_tsorted_anchor_cleanup(skb);
2076 	__skb_unlink(skb, &sk->sk_write_queue);
2077 }
2078 
2079 void tcp_rbtree_insert(struct rb_root *root, struct sk_buff *skb);
2080 
2081 static inline void tcp_rtx_queue_unlink(struct sk_buff *skb, struct sock *sk)
2082 {
2083 	tcp_skb_tsorted_anchor_cleanup(skb);
2084 	rb_erase(&skb->rbnode, &sk->tcp_rtx_queue);
2085 }
2086 
2087 static inline void tcp_rtx_queue_unlink_and_free(struct sk_buff *skb, struct sock *sk)
2088 {
2089 	list_del(&skb->tcp_tsorted_anchor);
2090 	tcp_rtx_queue_unlink(skb, sk);
2091 	tcp_wmem_free_skb(sk, skb);
2092 }
2093 
2094 static inline void tcp_write_collapse_fence(struct sock *sk)
2095 {
2096 	struct sk_buff *skb = tcp_write_queue_tail(sk);
2097 
2098 	if (skb)
2099 		TCP_SKB_CB(skb)->eor = 1;
2100 }
2101 
2102 static inline void tcp_push_pending_frames(struct sock *sk)
2103 {
2104 	if (tcp_send_head(sk)) {
2105 		struct tcp_sock *tp = tcp_sk(sk);
2106 
2107 		__tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
2108 	}
2109 }
2110 
2111 /* Start sequence of the skb just after the highest skb with SACKed
2112  * bit, valid only if sacked_out > 0 or when the caller has ensured
2113  * validity by itself.
2114  */
2115 static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
2116 {
2117 	if (!tp->sacked_out)
2118 		return tp->snd_una;
2119 
2120 	if (tp->highest_sack == NULL)
2121 		return tp->snd_nxt;
2122 
2123 	return TCP_SKB_CB(tp->highest_sack)->seq;
2124 }
2125 
2126 static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
2127 {
2128 	tcp_sk(sk)->highest_sack = skb_rb_next(skb);
2129 }
2130 
2131 static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
2132 {
2133 	return tcp_sk(sk)->highest_sack;
2134 }
2135 
2136 static inline void tcp_highest_sack_reset(struct sock *sk)
2137 {
2138 	tcp_sk(sk)->highest_sack = tcp_rtx_queue_head(sk);
2139 }
2140 
2141 /* Called when old skb is about to be deleted and replaced by new skb */
2142 static inline void tcp_highest_sack_replace(struct sock *sk,
2143 					    struct sk_buff *old,
2144 					    struct sk_buff *new)
2145 {
2146 	if (old == tcp_highest_sack(sk))
2147 		tcp_sk(sk)->highest_sack = new;
2148 }
2149 
2150 /* This helper checks if socket has IP_TRANSPARENT set */
2151 static inline bool inet_sk_transparent(const struct sock *sk)
2152 {
2153 	switch (sk->sk_state) {
2154 	case TCP_TIME_WAIT:
2155 		return inet_twsk(sk)->tw_transparent;
2156 	case TCP_NEW_SYN_RECV:
2157 		return inet_rsk(inet_reqsk(sk))->no_srccheck;
2158 	}
2159 	return inet_test_bit(TRANSPARENT, sk);
2160 }
2161 
2162 /* Determines whether this is a thin stream (which may suffer from
2163  * increased latency). Used to trigger latency-reducing mechanisms.
2164  */
2165 static inline bool tcp_stream_is_thin(struct tcp_sock *tp)
2166 {
2167 	return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
2168 }
2169 
2170 /* /proc */
2171 enum tcp_seq_states {
2172 	TCP_SEQ_STATE_LISTENING,
2173 	TCP_SEQ_STATE_ESTABLISHED,
2174 };
2175 
2176 void *tcp_seq_start(struct seq_file *seq, loff_t *pos);
2177 void *tcp_seq_next(struct seq_file *seq, void *v, loff_t *pos);
2178 void tcp_seq_stop(struct seq_file *seq, void *v);
2179 
2180 struct tcp_seq_afinfo {
2181 	sa_family_t			family;
2182 };
2183 
2184 struct tcp_iter_state {
2185 	struct seq_net_private	p;
2186 	enum tcp_seq_states	state;
2187 	struct sock		*syn_wait_sk;
2188 	int			bucket, offset, sbucket, num;
2189 	loff_t			last_pos;
2190 };
2191 
2192 extern struct request_sock_ops tcp_request_sock_ops;
2193 extern struct request_sock_ops tcp6_request_sock_ops;
2194 
2195 void tcp_v4_destroy_sock(struct sock *sk);
2196 
2197 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
2198 				netdev_features_t features);
2199 struct tcphdr *tcp_gro_pull_header(struct sk_buff *skb);
2200 struct sk_buff *tcp_gro_lookup(struct list_head *head, struct tcphdr *th);
2201 struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb,
2202 				struct tcphdr *th);
2203 INDIRECT_CALLABLE_DECLARE(int tcp4_gro_complete(struct sk_buff *skb, int thoff));
2204 INDIRECT_CALLABLE_DECLARE(struct sk_buff *tcp4_gro_receive(struct list_head *head, struct sk_buff *skb));
2205 INDIRECT_CALLABLE_DECLARE(int tcp6_gro_complete(struct sk_buff *skb, int thoff));
2206 INDIRECT_CALLABLE_DECLARE(struct sk_buff *tcp6_gro_receive(struct list_head *head, struct sk_buff *skb));
2207 #ifdef CONFIG_INET
2208 void tcp_gro_complete(struct sk_buff *skb);
2209 #else
2210 static inline void tcp_gro_complete(struct sk_buff *skb) { }
2211 #endif
2212 
2213 void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
2214 
2215 static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
2216 {
2217 	struct net *net = sock_net((struct sock *)tp);
2218 	u32 val;
2219 
2220 	val = READ_ONCE(tp->notsent_lowat);
2221 
2222 	return val ?: READ_ONCE(net->ipv4.sysctl_tcp_notsent_lowat);
2223 }
2224 
2225 bool tcp_stream_memory_free(const struct sock *sk, int wake);
2226 
2227 #ifdef CONFIG_PROC_FS
2228 int tcp4_proc_init(void);
2229 void tcp4_proc_exit(void);
2230 #endif
2231 
2232 int tcp_rtx_synack(const struct sock *sk, struct request_sock *req);
2233 int tcp_conn_request(struct request_sock_ops *rsk_ops,
2234 		     const struct tcp_request_sock_ops *af_ops,
2235 		     struct sock *sk, struct sk_buff *skb);
2236 
2237 /* TCP af-specific functions */
2238 struct tcp_sock_af_ops {
2239 #ifdef CONFIG_TCP_MD5SIG
2240 	struct tcp_md5sig_key	*(*md5_lookup) (const struct sock *sk,
2241 						const struct sock *addr_sk);
2242 	int		(*calc_md5_hash)(char *location,
2243 					 const struct tcp_md5sig_key *md5,
2244 					 const struct sock *sk,
2245 					 const struct sk_buff *skb);
2246 	int		(*md5_parse)(struct sock *sk,
2247 				     int optname,
2248 				     sockptr_t optval,
2249 				     int optlen);
2250 #endif
2251 #ifdef CONFIG_TCP_AO
2252 	int (*ao_parse)(struct sock *sk, int optname, sockptr_t optval, int optlen);
2253 	struct tcp_ao_key *(*ao_lookup)(const struct sock *sk,
2254 					struct sock *addr_sk,
2255 					int sndid, int rcvid);
2256 	int (*ao_calc_key_sk)(struct tcp_ao_key *mkt, u8 *key,
2257 			      const struct sock *sk,
2258 			      __be32 sisn, __be32 disn, bool send);
2259 	int (*calc_ao_hash)(char *location, struct tcp_ao_key *ao,
2260 			    const struct sock *sk, const struct sk_buff *skb,
2261 			    const u8 *tkey, int hash_offset, u32 sne);
2262 #endif
2263 };
2264 
2265 struct tcp_request_sock_ops {
2266 	u16 mss_clamp;
2267 #ifdef CONFIG_TCP_MD5SIG
2268 	struct tcp_md5sig_key *(*req_md5_lookup)(const struct sock *sk,
2269 						 const struct sock *addr_sk);
2270 	int		(*calc_md5_hash) (char *location,
2271 					  const struct tcp_md5sig_key *md5,
2272 					  const struct sock *sk,
2273 					  const struct sk_buff *skb);
2274 #endif
2275 #ifdef CONFIG_TCP_AO
2276 	struct tcp_ao_key *(*ao_lookup)(const struct sock *sk,
2277 					struct request_sock *req,
2278 					int sndid, int rcvid);
2279 	int (*ao_calc_key)(struct tcp_ao_key *mkt, u8 *key, struct request_sock *sk);
2280 	int (*ao_synack_hash)(char *ao_hash, struct tcp_ao_key *mkt,
2281 			      struct request_sock *req, const struct sk_buff *skb,
2282 			      int hash_offset, u32 sne);
2283 #endif
2284 #ifdef CONFIG_SYN_COOKIES
2285 	__u32 (*cookie_init_seq)(const struct sk_buff *skb,
2286 				 __u16 *mss);
2287 #endif
2288 	struct dst_entry *(*route_req)(const struct sock *sk,
2289 				       struct sk_buff *skb,
2290 				       struct flowi *fl,
2291 				       struct request_sock *req,
2292 				       u32 tw_isn);
2293 	u32 (*init_seq)(const struct sk_buff *skb);
2294 	u32 (*init_ts_off)(const struct net *net, const struct sk_buff *skb);
2295 	int (*send_synack)(const struct sock *sk, struct dst_entry *dst,
2296 			   struct flowi *fl, struct request_sock *req,
2297 			   struct tcp_fastopen_cookie *foc,
2298 			   enum tcp_synack_type synack_type,
2299 			   struct sk_buff *syn_skb);
2300 };
2301 
2302 extern const struct tcp_request_sock_ops tcp_request_sock_ipv4_ops;
2303 #if IS_ENABLED(CONFIG_IPV6)
2304 extern const struct tcp_request_sock_ops tcp_request_sock_ipv6_ops;
2305 #endif
2306 
2307 #ifdef CONFIG_SYN_COOKIES
2308 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
2309 					 const struct sock *sk, struct sk_buff *skb,
2310 					 __u16 *mss)
2311 {
2312 	tcp_synq_overflow(sk);
2313 	__NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESSENT);
2314 	return ops->cookie_init_seq(skb, mss);
2315 }
2316 #else
2317 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
2318 					 const struct sock *sk, struct sk_buff *skb,
2319 					 __u16 *mss)
2320 {
2321 	return 0;
2322 }
2323 #endif
2324 
2325 struct tcp_key {
2326 	union {
2327 		struct {
2328 			struct tcp_ao_key *ao_key;
2329 			char *traffic_key;
2330 			u32 sne;
2331 			u8 rcv_next;
2332 		};
2333 		struct tcp_md5sig_key *md5_key;
2334 	};
2335 	enum {
2336 		TCP_KEY_NONE = 0,
2337 		TCP_KEY_MD5,
2338 		TCP_KEY_AO,
2339 	} type;
2340 };
2341 
2342 static inline void tcp_get_current_key(const struct sock *sk,
2343 				       struct tcp_key *out)
2344 {
2345 #if defined(CONFIG_TCP_AO) || defined(CONFIG_TCP_MD5SIG)
2346 	const struct tcp_sock *tp = tcp_sk(sk);
2347 #endif
2348 
2349 #ifdef CONFIG_TCP_AO
2350 	if (static_branch_unlikely(&tcp_ao_needed.key)) {
2351 		struct tcp_ao_info *ao;
2352 
2353 		ao = rcu_dereference_protected(tp->ao_info,
2354 					       lockdep_sock_is_held(sk));
2355 		if (ao) {
2356 			out->ao_key = READ_ONCE(ao->current_key);
2357 			out->type = TCP_KEY_AO;
2358 			return;
2359 		}
2360 	}
2361 #endif
2362 #ifdef CONFIG_TCP_MD5SIG
2363 	if (static_branch_unlikely(&tcp_md5_needed.key) &&
2364 	    rcu_access_pointer(tp->md5sig_info)) {
2365 		out->md5_key = tp->af_specific->md5_lookup(sk, sk);
2366 		if (out->md5_key) {
2367 			out->type = TCP_KEY_MD5;
2368 			return;
2369 		}
2370 	}
2371 #endif
2372 	out->type = TCP_KEY_NONE;
2373 }
2374 
2375 static inline bool tcp_key_is_md5(const struct tcp_key *key)
2376 {
2377 	if (static_branch_tcp_md5())
2378 		return key->type == TCP_KEY_MD5;
2379 	return false;
2380 }
2381 
2382 static inline bool tcp_key_is_ao(const struct tcp_key *key)
2383 {
2384 	if (static_branch_tcp_ao())
2385 		return key->type == TCP_KEY_AO;
2386 	return false;
2387 }
2388 
2389 int tcpv4_offload_init(void);
2390 
2391 void tcp_v4_init(void);
2392 void tcp_init(void);
2393 
2394 /* tcp_recovery.c */
2395 void tcp_mark_skb_lost(struct sock *sk, struct sk_buff *skb);
2396 void tcp_newreno_mark_lost(struct sock *sk, bool snd_una_advanced);
2397 extern s32 tcp_rack_skb_timeout(struct tcp_sock *tp, struct sk_buff *skb,
2398 				u32 reo_wnd);
2399 extern bool tcp_rack_mark_lost(struct sock *sk);
2400 extern void tcp_rack_advance(struct tcp_sock *tp, u8 sacked, u32 end_seq,
2401 			     u64 xmit_time);
2402 extern void tcp_rack_reo_timeout(struct sock *sk);
2403 extern void tcp_rack_update_reo_wnd(struct sock *sk, struct rate_sample *rs);
2404 
2405 /* tcp_plb.c */
2406 
2407 /*
2408  * Scaling factor for fractions in PLB. For example, tcp_plb_update_state
2409  * expects cong_ratio which represents fraction of traffic that experienced
2410  * congestion over a single RTT. In order to avoid floating point operations,
2411  * this fraction should be mapped to (1 << TCP_PLB_SCALE) and passed in.
2412  */
2413 #define TCP_PLB_SCALE 8
2414 
2415 /* State for PLB (Protective Load Balancing) for a single TCP connection. */
2416 struct tcp_plb_state {
2417 	u8	consec_cong_rounds:5, /* consecutive congested rounds */
2418 		unused:3;
2419 	u32	pause_until; /* jiffies32 when PLB can resume rerouting */
2420 };
2421 
2422 static inline void tcp_plb_init(const struct sock *sk,
2423 				struct tcp_plb_state *plb)
2424 {
2425 	plb->consec_cong_rounds = 0;
2426 	plb->pause_until = 0;
2427 }
2428 void tcp_plb_update_state(const struct sock *sk, struct tcp_plb_state *plb,
2429 			  const int cong_ratio);
2430 void tcp_plb_check_rehash(struct sock *sk, struct tcp_plb_state *plb);
2431 void tcp_plb_update_state_upon_rto(struct sock *sk, struct tcp_plb_state *plb);
2432 
2433 /* At how many usecs into the future should the RTO fire? */
2434 static inline s64 tcp_rto_delta_us(const struct sock *sk)
2435 {
2436 	const struct sk_buff *skb = tcp_rtx_queue_head(sk);
2437 	u32 rto = inet_csk(sk)->icsk_rto;
2438 
2439 	if (likely(skb)) {
2440 		u64 rto_time_stamp_us = tcp_skb_timestamp_us(skb) + jiffies_to_usecs(rto);
2441 
2442 		return rto_time_stamp_us - tcp_sk(sk)->tcp_mstamp;
2443 	} else {
2444 		WARN_ONCE(1,
2445 			"rtx queue emtpy: "
2446 			"out:%u sacked:%u lost:%u retrans:%u "
2447 			"tlp_high_seq:%u sk_state:%u ca_state:%u "
2448 			"advmss:%u mss_cache:%u pmtu:%u\n",
2449 			tcp_sk(sk)->packets_out, tcp_sk(sk)->sacked_out,
2450 			tcp_sk(sk)->lost_out, tcp_sk(sk)->retrans_out,
2451 			tcp_sk(sk)->tlp_high_seq, sk->sk_state,
2452 			inet_csk(sk)->icsk_ca_state,
2453 			tcp_sk(sk)->advmss, tcp_sk(sk)->mss_cache,
2454 			inet_csk(sk)->icsk_pmtu_cookie);
2455 		return jiffies_to_usecs(rto);
2456 	}
2457 
2458 }
2459 
2460 /*
2461  * Save and compile IPv4 options, return a pointer to it
2462  */
2463 static inline struct ip_options_rcu *tcp_v4_save_options(struct net *net,
2464 							 struct sk_buff *skb)
2465 {
2466 	const struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt;
2467 	struct ip_options_rcu *dopt = NULL;
2468 
2469 	if (opt->optlen) {
2470 		int opt_size = sizeof(*dopt) + opt->optlen;
2471 
2472 		dopt = kmalloc(opt_size, GFP_ATOMIC);
2473 		if (dopt && __ip_options_echo(net, &dopt->opt, skb, opt)) {
2474 			kfree(dopt);
2475 			dopt = NULL;
2476 		}
2477 	}
2478 	return dopt;
2479 }
2480 
2481 /* locally generated TCP pure ACKs have skb->truesize == 2
2482  * (check tcp_send_ack() in net/ipv4/tcp_output.c )
2483  * This is much faster than dissecting the packet to find out.
2484  * (Think of GRE encapsulations, IPv4, IPv6, ...)
2485  */
2486 static inline bool skb_is_tcp_pure_ack(const struct sk_buff *skb)
2487 {
2488 	return skb->truesize == 2;
2489 }
2490 
2491 static inline void skb_set_tcp_pure_ack(struct sk_buff *skb)
2492 {
2493 	skb->truesize = 2;
2494 }
2495 
2496 static inline int tcp_inq(struct sock *sk)
2497 {
2498 	struct tcp_sock *tp = tcp_sk(sk);
2499 	int answ;
2500 
2501 	if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
2502 		answ = 0;
2503 	} else if (sock_flag(sk, SOCK_URGINLINE) ||
2504 		   !tp->urg_data ||
2505 		   before(tp->urg_seq, tp->copied_seq) ||
2506 		   !before(tp->urg_seq, tp->rcv_nxt)) {
2507 
2508 		answ = tp->rcv_nxt - tp->copied_seq;
2509 
2510 		/* Subtract 1, if FIN was received */
2511 		if (answ && sock_flag(sk, SOCK_DONE))
2512 			answ--;
2513 	} else {
2514 		answ = tp->urg_seq - tp->copied_seq;
2515 	}
2516 
2517 	return answ;
2518 }
2519 
2520 int tcp_peek_len(struct socket *sock);
2521 
2522 static inline void tcp_segs_in(struct tcp_sock *tp, const struct sk_buff *skb)
2523 {
2524 	u16 segs_in;
2525 
2526 	segs_in = max_t(u16, 1, skb_shinfo(skb)->gso_segs);
2527 
2528 	/* We update these fields while other threads might
2529 	 * read them from tcp_get_info()
2530 	 */
2531 	WRITE_ONCE(tp->segs_in, tp->segs_in + segs_in);
2532 	if (skb->len > tcp_hdrlen(skb))
2533 		WRITE_ONCE(tp->data_segs_in, tp->data_segs_in + segs_in);
2534 }
2535 
2536 /*
2537  * TCP listen path runs lockless.
2538  * We forced "struct sock" to be const qualified to make sure
2539  * we don't modify one of its field by mistake.
2540  * Here, we increment sk_drops which is an atomic_t, so we can safely
2541  * make sock writable again.
2542  */
2543 static inline void tcp_listendrop(const struct sock *sk)
2544 {
2545 	atomic_inc(&((struct sock *)sk)->sk_drops);
2546 	__NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENDROPS);
2547 }
2548 
2549 enum hrtimer_restart tcp_pace_kick(struct hrtimer *timer);
2550 
2551 /*
2552  * Interface for adding Upper Level Protocols over TCP
2553  */
2554 
2555 #define TCP_ULP_NAME_MAX	16
2556 #define TCP_ULP_MAX		128
2557 #define TCP_ULP_BUF_MAX		(TCP_ULP_NAME_MAX*TCP_ULP_MAX)
2558 
2559 struct tcp_ulp_ops {
2560 	struct list_head	list;
2561 
2562 	/* initialize ulp */
2563 	int (*init)(struct sock *sk);
2564 	/* update ulp */
2565 	void (*update)(struct sock *sk, struct proto *p,
2566 		       void (*write_space)(struct sock *sk));
2567 	/* cleanup ulp */
2568 	void (*release)(struct sock *sk);
2569 	/* diagnostic */
2570 	int (*get_info)(struct sock *sk, struct sk_buff *skb);
2571 	size_t (*get_info_size)(const struct sock *sk);
2572 	/* clone ulp */
2573 	void (*clone)(const struct request_sock *req, struct sock *newsk,
2574 		      const gfp_t priority);
2575 
2576 	char		name[TCP_ULP_NAME_MAX];
2577 	struct module	*owner;
2578 };
2579 int tcp_register_ulp(struct tcp_ulp_ops *type);
2580 void tcp_unregister_ulp(struct tcp_ulp_ops *type);
2581 int tcp_set_ulp(struct sock *sk, const char *name);
2582 void tcp_get_available_ulp(char *buf, size_t len);
2583 void tcp_cleanup_ulp(struct sock *sk);
2584 void tcp_update_ulp(struct sock *sk, struct proto *p,
2585 		    void (*write_space)(struct sock *sk));
2586 
2587 #define MODULE_ALIAS_TCP_ULP(name)				\
2588 	__MODULE_INFO(alias, alias_userspace, name);		\
2589 	__MODULE_INFO(alias, alias_tcp_ulp, "tcp-ulp-" name)
2590 
2591 #ifdef CONFIG_NET_SOCK_MSG
2592 struct sk_msg;
2593 struct sk_psock;
2594 
2595 #ifdef CONFIG_BPF_SYSCALL
2596 int tcp_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore);
2597 void tcp_bpf_clone(const struct sock *sk, struct sock *newsk);
2598 #endif /* CONFIG_BPF_SYSCALL */
2599 
2600 #ifdef CONFIG_INET
2601 void tcp_eat_skb(struct sock *sk, struct sk_buff *skb);
2602 #else
2603 static inline void tcp_eat_skb(struct sock *sk, struct sk_buff *skb)
2604 {
2605 }
2606 #endif
2607 
2608 int tcp_bpf_sendmsg_redir(struct sock *sk, bool ingress,
2609 			  struct sk_msg *msg, u32 bytes, int flags);
2610 #endif /* CONFIG_NET_SOCK_MSG */
2611 
2612 #if !defined(CONFIG_BPF_SYSCALL) || !defined(CONFIG_NET_SOCK_MSG)
2613 static inline void tcp_bpf_clone(const struct sock *sk, struct sock *newsk)
2614 {
2615 }
2616 #endif
2617 
2618 #ifdef CONFIG_CGROUP_BPF
2619 static inline void bpf_skops_init_skb(struct bpf_sock_ops_kern *skops,
2620 				      struct sk_buff *skb,
2621 				      unsigned int end_offset)
2622 {
2623 	skops->skb = skb;
2624 	skops->skb_data_end = skb->data + end_offset;
2625 }
2626 #else
2627 static inline void bpf_skops_init_skb(struct bpf_sock_ops_kern *skops,
2628 				      struct sk_buff *skb,
2629 				      unsigned int end_offset)
2630 {
2631 }
2632 #endif
2633 
2634 /* Call BPF_SOCK_OPS program that returns an int. If the return value
2635  * is < 0, then the BPF op failed (for example if the loaded BPF
2636  * program does not support the chosen operation or there is no BPF
2637  * program loaded).
2638  */
2639 #ifdef CONFIG_BPF
2640 static inline int tcp_call_bpf(struct sock *sk, int op, u32 nargs, u32 *args)
2641 {
2642 	struct bpf_sock_ops_kern sock_ops;
2643 	int ret;
2644 
2645 	memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp));
2646 	if (sk_fullsock(sk)) {
2647 		sock_ops.is_fullsock = 1;
2648 		sock_owned_by_me(sk);
2649 	}
2650 
2651 	sock_ops.sk = sk;
2652 	sock_ops.op = op;
2653 	if (nargs > 0)
2654 		memcpy(sock_ops.args, args, nargs * sizeof(*args));
2655 
2656 	ret = BPF_CGROUP_RUN_PROG_SOCK_OPS(&sock_ops);
2657 	if (ret == 0)
2658 		ret = sock_ops.reply;
2659 	else
2660 		ret = -1;
2661 	return ret;
2662 }
2663 
2664 static inline int tcp_call_bpf_2arg(struct sock *sk, int op, u32 arg1, u32 arg2)
2665 {
2666 	u32 args[2] = {arg1, arg2};
2667 
2668 	return tcp_call_bpf(sk, op, 2, args);
2669 }
2670 
2671 static inline int tcp_call_bpf_3arg(struct sock *sk, int op, u32 arg1, u32 arg2,
2672 				    u32 arg3)
2673 {
2674 	u32 args[3] = {arg1, arg2, arg3};
2675 
2676 	return tcp_call_bpf(sk, op, 3, args);
2677 }
2678 
2679 #else
2680 static inline int tcp_call_bpf(struct sock *sk, int op, u32 nargs, u32 *args)
2681 {
2682 	return -EPERM;
2683 }
2684 
2685 static inline int tcp_call_bpf_2arg(struct sock *sk, int op, u32 arg1, u32 arg2)
2686 {
2687 	return -EPERM;
2688 }
2689 
2690 static inline int tcp_call_bpf_3arg(struct sock *sk, int op, u32 arg1, u32 arg2,
2691 				    u32 arg3)
2692 {
2693 	return -EPERM;
2694 }
2695 
2696 #endif
2697 
2698 static inline u32 tcp_timeout_init(struct sock *sk)
2699 {
2700 	int timeout;
2701 
2702 	timeout = tcp_call_bpf(sk, BPF_SOCK_OPS_TIMEOUT_INIT, 0, NULL);
2703 
2704 	if (timeout <= 0)
2705 		timeout = TCP_TIMEOUT_INIT;
2706 	return min_t(int, timeout, TCP_RTO_MAX);
2707 }
2708 
2709 static inline u32 tcp_rwnd_init_bpf(struct sock *sk)
2710 {
2711 	int rwnd;
2712 
2713 	rwnd = tcp_call_bpf(sk, BPF_SOCK_OPS_RWND_INIT, 0, NULL);
2714 
2715 	if (rwnd < 0)
2716 		rwnd = 0;
2717 	return rwnd;
2718 }
2719 
2720 static inline bool tcp_bpf_ca_needs_ecn(struct sock *sk)
2721 {
2722 	return (tcp_call_bpf(sk, BPF_SOCK_OPS_NEEDS_ECN, 0, NULL) == 1);
2723 }
2724 
2725 static inline void tcp_bpf_rtt(struct sock *sk, long mrtt, u32 srtt)
2726 {
2727 	if (BPF_SOCK_OPS_TEST_FLAG(tcp_sk(sk), BPF_SOCK_OPS_RTT_CB_FLAG))
2728 		tcp_call_bpf_2arg(sk, BPF_SOCK_OPS_RTT_CB, mrtt, srtt);
2729 }
2730 
2731 #if IS_ENABLED(CONFIG_SMC)
2732 extern struct static_key_false tcp_have_smc;
2733 #endif
2734 
2735 #if IS_ENABLED(CONFIG_TLS_DEVICE)
2736 void clean_acked_data_enable(struct inet_connection_sock *icsk,
2737 			     void (*cad)(struct sock *sk, u32 ack_seq));
2738 void clean_acked_data_disable(struct inet_connection_sock *icsk);
2739 void clean_acked_data_flush(void);
2740 #endif
2741 
2742 DECLARE_STATIC_KEY_FALSE(tcp_tx_delay_enabled);
2743 static inline void tcp_add_tx_delay(struct sk_buff *skb,
2744 				    const struct tcp_sock *tp)
2745 {
2746 	if (static_branch_unlikely(&tcp_tx_delay_enabled))
2747 		skb->skb_mstamp_ns += (u64)tp->tcp_tx_delay * NSEC_PER_USEC;
2748 }
2749 
2750 /* Compute Earliest Departure Time for some control packets
2751  * like ACK or RST for TIME_WAIT or non ESTABLISHED sockets.
2752  */
2753 static inline u64 tcp_transmit_time(const struct sock *sk)
2754 {
2755 	if (static_branch_unlikely(&tcp_tx_delay_enabled)) {
2756 		u32 delay = (sk->sk_state == TCP_TIME_WAIT) ?
2757 			tcp_twsk(sk)->tw_tx_delay : tcp_sk(sk)->tcp_tx_delay;
2758 
2759 		return tcp_clock_ns() + (u64)delay * NSEC_PER_USEC;
2760 	}
2761 	return 0;
2762 }
2763 
2764 static inline int tcp_parse_auth_options(const struct tcphdr *th,
2765 		const u8 **md5_hash, const struct tcp_ao_hdr **aoh)
2766 {
2767 	const u8 *md5_tmp, *ao_tmp;
2768 	int ret;
2769 
2770 	ret = tcp_do_parse_auth_options(th, &md5_tmp, &ao_tmp);
2771 	if (ret)
2772 		return ret;
2773 
2774 	if (md5_hash)
2775 		*md5_hash = md5_tmp;
2776 
2777 	if (aoh) {
2778 		if (!ao_tmp)
2779 			*aoh = NULL;
2780 		else
2781 			*aoh = (struct tcp_ao_hdr *)(ao_tmp - 2);
2782 	}
2783 
2784 	return 0;
2785 }
2786 
2787 static inline bool tcp_ao_required(struct sock *sk, const void *saddr,
2788 				   int family, int l3index, bool stat_inc)
2789 {
2790 #ifdef CONFIG_TCP_AO
2791 	struct tcp_ao_info *ao_info;
2792 	struct tcp_ao_key *ao_key;
2793 
2794 	if (!static_branch_unlikely(&tcp_ao_needed.key))
2795 		return false;
2796 
2797 	ao_info = rcu_dereference_check(tcp_sk(sk)->ao_info,
2798 					lockdep_sock_is_held(sk));
2799 	if (!ao_info)
2800 		return false;
2801 
2802 	ao_key = tcp_ao_do_lookup(sk, l3index, saddr, family, -1, -1);
2803 	if (ao_info->ao_required || ao_key) {
2804 		if (stat_inc) {
2805 			NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPAOREQUIRED);
2806 			atomic64_inc(&ao_info->counters.ao_required);
2807 		}
2808 		return true;
2809 	}
2810 #endif
2811 	return false;
2812 }
2813 
2814 enum skb_drop_reason tcp_inbound_hash(struct sock *sk,
2815 		const struct request_sock *req, const struct sk_buff *skb,
2816 		const void *saddr, const void *daddr,
2817 		int family, int dif, int sdif);
2818 
2819 #endif	/* _TCP_H */
2820