xref: /linux/include/net/tcp.h (revision af1f459233d4edeef634f559539e7f4b64cb1d25)
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/inet_ecn.h>
41 #include <net/dst.h>
42 #include <net/mptcp.h>
43 
44 #include <linux/seq_file.h>
45 #include <linux/memcontrol.h>
46 #include <linux/bpf-cgroup.h>
47 #include <linux/siphash.h>
48 
49 extern struct inet_hashinfo tcp_hashinfo;
50 
51 DECLARE_PER_CPU(unsigned int, tcp_orphan_count);
52 int tcp_orphan_count_sum(void);
53 
54 void tcp_time_wait(struct sock *sk, int state, int timeo);
55 
56 #define MAX_TCP_HEADER	L1_CACHE_ALIGN(128 + MAX_HEADER)
57 #define MAX_TCP_OPTION_SPACE 40
58 #define TCP_MIN_SND_MSS		48
59 #define TCP_MIN_GSO_SIZE	(TCP_MIN_SND_MSS - MAX_TCP_OPTION_SPACE)
60 
61 /*
62  * Never offer a window over 32767 without using window scaling. Some
63  * poor stacks do signed 16bit maths!
64  */
65 #define MAX_TCP_WINDOW		32767U
66 
67 /* Minimal accepted MSS. It is (60+60+8) - (20+20). */
68 #define TCP_MIN_MSS		88U
69 
70 /* The initial MTU to use for probing */
71 #define TCP_BASE_MSS		1024
72 
73 /* probing interval, default to 10 minutes as per RFC4821 */
74 #define TCP_PROBE_INTERVAL	600
75 
76 /* Specify interval when tcp mtu probing will stop */
77 #define TCP_PROBE_THRESHOLD	8
78 
79 /* After receiving this amount of duplicate ACKs fast retransmit starts. */
80 #define TCP_FASTRETRANS_THRESH 3
81 
82 /* Maximal number of ACKs sent quickly to accelerate slow-start. */
83 #define TCP_MAX_QUICKACKS	16U
84 
85 /* Maximal number of window scale according to RFC1323 */
86 #define TCP_MAX_WSCALE		14U
87 
88 /* urg_data states */
89 #define TCP_URG_VALID	0x0100
90 #define TCP_URG_NOTYET	0x0200
91 #define TCP_URG_READ	0x0400
92 
93 #define TCP_RETR1	3	/*
94 				 * This is how many retries it does before it
95 				 * tries to figure out if the gateway is
96 				 * down. Minimal RFC value is 3; it corresponds
97 				 * to ~3sec-8min depending on RTO.
98 				 */
99 
100 #define TCP_RETR2	15	/*
101 				 * This should take at least
102 				 * 90 minutes to time out.
103 				 * RFC1122 says that the limit is 100 sec.
104 				 * 15 is ~13-30min depending on RTO.
105 				 */
106 
107 #define TCP_SYN_RETRIES	 6	/* This is how many retries are done
108 				 * when active opening a connection.
109 				 * RFC1122 says the minimum retry MUST
110 				 * be at least 180secs.  Nevertheless
111 				 * this value is corresponding to
112 				 * 63secs of retransmission with the
113 				 * current initial RTO.
114 				 */
115 
116 #define TCP_SYNACK_RETRIES 5	/* This is how may retries are done
117 				 * when passive opening a connection.
118 				 * This is corresponding to 31secs of
119 				 * retransmission with the current
120 				 * initial RTO.
121 				 */
122 
123 #define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT
124 				  * state, about 60 seconds	*/
125 #define TCP_FIN_TIMEOUT	TCP_TIMEWAIT_LEN
126                                  /* BSD style FIN_WAIT2 deadlock breaker.
127 				  * It used to be 3min, new value is 60sec,
128 				  * to combine FIN-WAIT-2 timeout with
129 				  * TIME-WAIT timer.
130 				  */
131 #define TCP_FIN_TIMEOUT_MAX (120 * HZ) /* max TCP_LINGER2 value (two minutes) */
132 
133 #define TCP_DELACK_MAX	((unsigned)(HZ/5))	/* maximal time to delay before sending an ACK */
134 #if HZ >= 100
135 #define TCP_DELACK_MIN	((unsigned)(HZ/25))	/* minimal time to delay before sending an ACK */
136 #define TCP_ATO_MIN	((unsigned)(HZ/25))
137 #else
138 #define TCP_DELACK_MIN	4U
139 #define TCP_ATO_MIN	4U
140 #endif
141 #define TCP_RTO_MAX	((unsigned)(120*HZ))
142 #define TCP_RTO_MIN	((unsigned)(HZ/5))
143 #define TCP_TIMEOUT_MIN	(2U) /* Min timeout for TCP timers in jiffies */
144 #define TCP_TIMEOUT_INIT ((unsigned)(1*HZ))	/* RFC6298 2.1 initial RTO value	*/
145 #define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ))	/* RFC 1122 initial RTO value, now
146 						 * used as a fallback RTO for the
147 						 * initial data transmission if no
148 						 * valid RTT sample has been acquired,
149 						 * most likely due to retrans in 3WHS.
150 						 */
151 
152 #define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes
153 					                 * for local resources.
154 					                 */
155 #define TCP_KEEPALIVE_TIME	(120*60*HZ)	/* two hours */
156 #define TCP_KEEPALIVE_PROBES	9		/* Max of 9 keepalive probes	*/
157 #define TCP_KEEPALIVE_INTVL	(75*HZ)
158 
159 #define MAX_TCP_KEEPIDLE	32767
160 #define MAX_TCP_KEEPINTVL	32767
161 #define MAX_TCP_KEEPCNT		127
162 #define MAX_TCP_SYNCNT		127
163 
164 #define TCP_PAWS_24DAYS	(60 * 60 * 24 * 24)
165 #define TCP_PAWS_MSL	60		/* Per-host timestamps are invalidated
166 					 * after this time. It should be equal
167 					 * (or greater than) TCP_TIMEWAIT_LEN
168 					 * to provide reliability equal to one
169 					 * provided by timewait state.
170 					 */
171 #define TCP_PAWS_WINDOW	1		/* Replay window for per-host
172 					 * timestamps. It must be less than
173 					 * minimal timewait lifetime.
174 					 */
175 /*
176  *	TCP option
177  */
178 
179 #define TCPOPT_NOP		1	/* Padding */
180 #define TCPOPT_EOL		0	/* End of options */
181 #define TCPOPT_MSS		2	/* Segment size negotiating */
182 #define TCPOPT_WINDOW		3	/* Window scaling */
183 #define TCPOPT_SACK_PERM        4       /* SACK Permitted */
184 #define TCPOPT_SACK             5       /* SACK Block */
185 #define TCPOPT_TIMESTAMP	8	/* Better RTT estimations/PAWS */
186 #define TCPOPT_MD5SIG		19	/* MD5 Signature (RFC2385) */
187 #define TCPOPT_MPTCP		30	/* Multipath TCP (RFC6824) */
188 #define TCPOPT_FASTOPEN		34	/* Fast open (RFC7413) */
189 #define TCPOPT_EXP		254	/* Experimental */
190 /* Magic number to be after the option value for sharing TCP
191  * experimental options. See draft-ietf-tcpm-experimental-options-00.txt
192  */
193 #define TCPOPT_FASTOPEN_MAGIC	0xF989
194 #define TCPOPT_SMC_MAGIC	0xE2D4C3D9
195 
196 /*
197  *     TCP option lengths
198  */
199 
200 #define TCPOLEN_MSS            4
201 #define TCPOLEN_WINDOW         3
202 #define TCPOLEN_SACK_PERM      2
203 #define TCPOLEN_TIMESTAMP      10
204 #define TCPOLEN_MD5SIG         18
205 #define TCPOLEN_FASTOPEN_BASE  2
206 #define TCPOLEN_EXP_FASTOPEN_BASE  4
207 #define TCPOLEN_EXP_SMC_BASE   6
208 
209 /* But this is what stacks really send out. */
210 #define TCPOLEN_TSTAMP_ALIGNED		12
211 #define TCPOLEN_WSCALE_ALIGNED		4
212 #define TCPOLEN_SACKPERM_ALIGNED	4
213 #define TCPOLEN_SACK_BASE		2
214 #define TCPOLEN_SACK_BASE_ALIGNED	4
215 #define TCPOLEN_SACK_PERBLOCK		8
216 #define TCPOLEN_MD5SIG_ALIGNED		20
217 #define TCPOLEN_MSS_ALIGNED		4
218 #define TCPOLEN_EXP_SMC_BASE_ALIGNED	8
219 
220 /* Flags in tp->nonagle */
221 #define TCP_NAGLE_OFF		1	/* Nagle's algo is disabled */
222 #define TCP_NAGLE_CORK		2	/* Socket is corked	    */
223 #define TCP_NAGLE_PUSH		4	/* Cork is overridden for already queued data */
224 
225 /* TCP thin-stream limits */
226 #define TCP_THIN_LINEAR_RETRIES 6       /* After 6 linear retries, do exp. backoff */
227 
228 /* TCP initial congestion window as per rfc6928 */
229 #define TCP_INIT_CWND		10
230 
231 /* Bit Flags for sysctl_tcp_fastopen */
232 #define	TFO_CLIENT_ENABLE	1
233 #define	TFO_SERVER_ENABLE	2
234 #define	TFO_CLIENT_NO_COOKIE	4	/* Data in SYN w/o cookie option */
235 
236 /* Accept SYN data w/o any cookie option */
237 #define	TFO_SERVER_COOKIE_NOT_REQD	0x200
238 
239 /* Force enable TFO on all listeners, i.e., not requiring the
240  * TCP_FASTOPEN socket option.
241  */
242 #define	TFO_SERVER_WO_SOCKOPT1	0x400
243 
244 
245 /* sysctl variables for tcp */
246 extern int sysctl_tcp_max_orphans;
247 extern long sysctl_tcp_mem[3];
248 
249 #define TCP_RACK_LOSS_DETECTION  0x1 /* Use RACK to detect losses */
250 #define TCP_RACK_STATIC_REO_WND  0x2 /* Use static RACK reo wnd */
251 #define TCP_RACK_NO_DUPTHRESH    0x4 /* Do not use DUPACK threshold in RACK */
252 
253 extern atomic_long_t tcp_memory_allocated;
254 DECLARE_PER_CPU(int, tcp_memory_per_cpu_fw_alloc);
255 
256 extern struct percpu_counter tcp_sockets_allocated;
257 extern unsigned long tcp_memory_pressure;
258 
259 /* optimized version of sk_under_memory_pressure() for TCP sockets */
260 static inline bool tcp_under_memory_pressure(const struct sock *sk)
261 {
262 	if (mem_cgroup_sockets_enabled && sk->sk_memcg &&
263 	    mem_cgroup_under_socket_pressure(sk->sk_memcg))
264 		return true;
265 
266 	return READ_ONCE(tcp_memory_pressure);
267 }
268 /*
269  * The next routines deal with comparing 32 bit unsigned ints
270  * and worry about wraparound (automatic with unsigned arithmetic).
271  */
272 
273 static inline bool before(__u32 seq1, __u32 seq2)
274 {
275         return (__s32)(seq1-seq2) < 0;
276 }
277 #define after(seq2, seq1) 	before(seq1, seq2)
278 
279 /* is s2<=s1<=s3 ? */
280 static inline bool between(__u32 seq1, __u32 seq2, __u32 seq3)
281 {
282 	return seq3 - seq2 >= seq1 - seq2;
283 }
284 
285 static inline bool tcp_out_of_memory(struct sock *sk)
286 {
287 	if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
288 	    sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2))
289 		return true;
290 	return false;
291 }
292 
293 static inline void tcp_wmem_free_skb(struct sock *sk, struct sk_buff *skb)
294 {
295 	sk_wmem_queued_add(sk, -skb->truesize);
296 	if (!skb_zcopy_pure(skb))
297 		sk_mem_uncharge(sk, skb->truesize);
298 	else
299 		sk_mem_uncharge(sk, SKB_TRUESIZE(skb_end_offset(skb)));
300 	__kfree_skb(skb);
301 }
302 
303 void sk_forced_mem_schedule(struct sock *sk, int size);
304 
305 bool tcp_check_oom(struct sock *sk, int shift);
306 
307 
308 extern struct proto tcp_prot;
309 
310 #define TCP_INC_STATS(net, field)	SNMP_INC_STATS((net)->mib.tcp_statistics, field)
311 #define __TCP_INC_STATS(net, field)	__SNMP_INC_STATS((net)->mib.tcp_statistics, field)
312 #define TCP_DEC_STATS(net, field)	SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
313 #define TCP_ADD_STATS(net, field, val)	SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
314 
315 void tcp_tasklet_init(void);
316 
317 int tcp_v4_err(struct sk_buff *skb, u32);
318 
319 void tcp_shutdown(struct sock *sk, int how);
320 
321 int tcp_v4_early_demux(struct sk_buff *skb);
322 int tcp_v4_rcv(struct sk_buff *skb);
323 
324 void tcp_remove_empty_skb(struct sock *sk);
325 int tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size);
326 int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size);
327 int tcp_sendmsg_fastopen(struct sock *sk, struct msghdr *msg, int *copied,
328 			 size_t size, struct ubuf_info *uarg);
329 void tcp_splice_eof(struct socket *sock);
330 int tcp_send_mss(struct sock *sk, int *size_goal, int flags);
331 int tcp_wmem_schedule(struct sock *sk, int copy);
332 void tcp_push(struct sock *sk, int flags, int mss_now, int nonagle,
333 	      int size_goal);
334 void tcp_release_cb(struct sock *sk);
335 void tcp_wfree(struct sk_buff *skb);
336 void tcp_write_timer_handler(struct sock *sk);
337 void tcp_delack_timer_handler(struct sock *sk);
338 int tcp_ioctl(struct sock *sk, int cmd, int *karg);
339 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb);
340 void tcp_rcv_established(struct sock *sk, struct sk_buff *skb);
341 void tcp_rcv_space_adjust(struct sock *sk);
342 int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
343 void tcp_twsk_destructor(struct sock *sk);
344 void tcp_twsk_purge(struct list_head *net_exit_list, int family);
345 ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
346 			struct pipe_inode_info *pipe, size_t len,
347 			unsigned int flags);
348 struct sk_buff *tcp_stream_alloc_skb(struct sock *sk, gfp_t gfp,
349 				     bool force_schedule);
350 
351 static inline void tcp_dec_quickack_mode(struct sock *sk,
352 					 const unsigned int pkts)
353 {
354 	struct inet_connection_sock *icsk = inet_csk(sk);
355 
356 	if (icsk->icsk_ack.quick) {
357 		if (pkts >= icsk->icsk_ack.quick) {
358 			icsk->icsk_ack.quick = 0;
359 			/* Leaving quickack mode we deflate ATO. */
360 			icsk->icsk_ack.ato   = TCP_ATO_MIN;
361 		} else
362 			icsk->icsk_ack.quick -= pkts;
363 	}
364 }
365 
366 #define	TCP_ECN_OK		1
367 #define	TCP_ECN_QUEUE_CWR	2
368 #define	TCP_ECN_DEMAND_CWR	4
369 #define	TCP_ECN_SEEN		8
370 
371 enum tcp_tw_status {
372 	TCP_TW_SUCCESS = 0,
373 	TCP_TW_RST = 1,
374 	TCP_TW_ACK = 2,
375 	TCP_TW_SYN = 3
376 };
377 
378 
379 enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
380 					      struct sk_buff *skb,
381 					      const struct tcphdr *th);
382 struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
383 			   struct request_sock *req, bool fastopen,
384 			   bool *lost_race);
385 int tcp_child_process(struct sock *parent, struct sock *child,
386 		      struct sk_buff *skb);
387 void tcp_enter_loss(struct sock *sk);
388 void tcp_cwnd_reduction(struct sock *sk, int newly_acked_sacked, int newly_lost, int flag);
389 void tcp_clear_retrans(struct tcp_sock *tp);
390 void tcp_update_metrics(struct sock *sk);
391 void tcp_init_metrics(struct sock *sk);
392 void tcp_metrics_init(void);
393 bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst);
394 void __tcp_close(struct sock *sk, long timeout);
395 void tcp_close(struct sock *sk, long timeout);
396 void tcp_init_sock(struct sock *sk);
397 void tcp_init_transfer(struct sock *sk, int bpf_op, struct sk_buff *skb);
398 __poll_t tcp_poll(struct file *file, struct socket *sock,
399 		      struct poll_table_struct *wait);
400 int do_tcp_getsockopt(struct sock *sk, int level,
401 		      int optname, sockptr_t optval, sockptr_t optlen);
402 int tcp_getsockopt(struct sock *sk, int level, int optname,
403 		   char __user *optval, int __user *optlen);
404 bool tcp_bpf_bypass_getsockopt(int level, int optname);
405 int do_tcp_setsockopt(struct sock *sk, int level, int optname,
406 		      sockptr_t optval, unsigned int optlen);
407 int tcp_setsockopt(struct sock *sk, int level, int optname, sockptr_t optval,
408 		   unsigned int optlen);
409 void tcp_set_keepalive(struct sock *sk, int val);
410 void tcp_syn_ack_timeout(const struct request_sock *req);
411 int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
412 		int flags, int *addr_len);
413 int tcp_set_rcvlowat(struct sock *sk, int val);
414 int tcp_set_window_clamp(struct sock *sk, int val);
415 void tcp_update_recv_tstamps(struct sk_buff *skb,
416 			     struct scm_timestamping_internal *tss);
417 void tcp_recv_timestamp(struct msghdr *msg, const struct sock *sk,
418 			struct scm_timestamping_internal *tss);
419 void tcp_data_ready(struct sock *sk);
420 #ifdef CONFIG_MMU
421 int tcp_mmap(struct file *file, struct socket *sock,
422 	     struct vm_area_struct *vma);
423 #endif
424 void tcp_parse_options(const struct net *net, const struct sk_buff *skb,
425 		       struct tcp_options_received *opt_rx,
426 		       int estab, struct tcp_fastopen_cookie *foc);
427 const u8 *tcp_parse_md5sig_option(const struct tcphdr *th);
428 
429 /*
430  *	BPF SKB-less helpers
431  */
432 u16 tcp_v4_get_syncookie(struct sock *sk, struct iphdr *iph,
433 			 struct tcphdr *th, u32 *cookie);
434 u16 tcp_v6_get_syncookie(struct sock *sk, struct ipv6hdr *iph,
435 			 struct tcphdr *th, u32 *cookie);
436 u16 tcp_parse_mss_option(const struct tcphdr *th, u16 user_mss);
437 u16 tcp_get_syncookie_mss(struct request_sock_ops *rsk_ops,
438 			  const struct tcp_request_sock_ops *af_ops,
439 			  struct sock *sk, struct tcphdr *th);
440 /*
441  *	TCP v4 functions exported for the inet6 API
442  */
443 
444 void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
445 void tcp_v4_mtu_reduced(struct sock *sk);
446 void tcp_req_err(struct sock *sk, u32 seq, bool abort);
447 void tcp_ld_RTO_revert(struct sock *sk, u32 seq);
448 int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
449 struct sock *tcp_create_openreq_child(const struct sock *sk,
450 				      struct request_sock *req,
451 				      struct sk_buff *skb);
452 void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst);
453 struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
454 				  struct request_sock *req,
455 				  struct dst_entry *dst,
456 				  struct request_sock *req_unhash,
457 				  bool *own_req);
458 int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
459 int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
460 int tcp_connect(struct sock *sk);
461 enum tcp_synack_type {
462 	TCP_SYNACK_NORMAL,
463 	TCP_SYNACK_FASTOPEN,
464 	TCP_SYNACK_COOKIE,
465 };
466 struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
467 				struct request_sock *req,
468 				struct tcp_fastopen_cookie *foc,
469 				enum tcp_synack_type synack_type,
470 				struct sk_buff *syn_skb);
471 int tcp_disconnect(struct sock *sk, int flags);
472 
473 void tcp_finish_connect(struct sock *sk, struct sk_buff *skb);
474 int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size);
475 void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
476 
477 /* From syncookies.c */
478 struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
479 				 struct request_sock *req,
480 				 struct dst_entry *dst, u32 tsoff);
481 int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
482 		      u32 cookie);
483 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
484 struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
485 					    const struct tcp_request_sock_ops *af_ops,
486 					    struct sock *sk, struct sk_buff *skb);
487 #ifdef CONFIG_SYN_COOKIES
488 
489 /* Syncookies use a monotonic timer which increments every 60 seconds.
490  * This counter is used both as a hash input and partially encoded into
491  * the cookie value.  A cookie is only validated further if the delta
492  * between the current counter value and the encoded one is less than this,
493  * i.e. a sent cookie is valid only at most for 2*60 seconds (or less if
494  * the counter advances immediately after a cookie is generated).
495  */
496 #define MAX_SYNCOOKIE_AGE	2
497 #define TCP_SYNCOOKIE_PERIOD	(60 * HZ)
498 #define TCP_SYNCOOKIE_VALID	(MAX_SYNCOOKIE_AGE * TCP_SYNCOOKIE_PERIOD)
499 
500 /* syncookies: remember time of last synqueue overflow
501  * But do not dirty this field too often (once per second is enough)
502  * It is racy as we do not hold a lock, but race is very minor.
503  */
504 static inline void tcp_synq_overflow(const struct sock *sk)
505 {
506 	unsigned int last_overflow;
507 	unsigned int now = jiffies;
508 
509 	if (sk->sk_reuseport) {
510 		struct sock_reuseport *reuse;
511 
512 		reuse = rcu_dereference(sk->sk_reuseport_cb);
513 		if (likely(reuse)) {
514 			last_overflow = READ_ONCE(reuse->synq_overflow_ts);
515 			if (!time_between32(now, last_overflow,
516 					    last_overflow + HZ))
517 				WRITE_ONCE(reuse->synq_overflow_ts, now);
518 			return;
519 		}
520 	}
521 
522 	last_overflow = READ_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp);
523 	if (!time_between32(now, last_overflow, last_overflow + HZ))
524 		WRITE_ONCE(tcp_sk_rw(sk)->rx_opt.ts_recent_stamp, now);
525 }
526 
527 /* syncookies: no recent synqueue overflow on this listening socket? */
528 static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
529 {
530 	unsigned int last_overflow;
531 	unsigned int now = jiffies;
532 
533 	if (sk->sk_reuseport) {
534 		struct sock_reuseport *reuse;
535 
536 		reuse = rcu_dereference(sk->sk_reuseport_cb);
537 		if (likely(reuse)) {
538 			last_overflow = READ_ONCE(reuse->synq_overflow_ts);
539 			return !time_between32(now, last_overflow - HZ,
540 					       last_overflow +
541 					       TCP_SYNCOOKIE_VALID);
542 		}
543 	}
544 
545 	last_overflow = READ_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp);
546 
547 	/* If last_overflow <= jiffies <= last_overflow + TCP_SYNCOOKIE_VALID,
548 	 * then we're under synflood. However, we have to use
549 	 * 'last_overflow - HZ' as lower bound. That's because a concurrent
550 	 * tcp_synq_overflow() could update .ts_recent_stamp after we read
551 	 * jiffies but before we store .ts_recent_stamp into last_overflow,
552 	 * which could lead to rejecting a valid syncookie.
553 	 */
554 	return !time_between32(now, last_overflow - HZ,
555 			       last_overflow + TCP_SYNCOOKIE_VALID);
556 }
557 
558 static inline u32 tcp_cookie_time(void)
559 {
560 	u64 val = get_jiffies_64();
561 
562 	do_div(val, TCP_SYNCOOKIE_PERIOD);
563 	return val;
564 }
565 
566 u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
567 			      u16 *mssp);
568 __u32 cookie_v4_init_sequence(const struct sk_buff *skb, __u16 *mss);
569 u64 cookie_init_timestamp(struct request_sock *req, u64 now);
570 bool cookie_timestamp_decode(const struct net *net,
571 			     struct tcp_options_received *opt);
572 bool cookie_ecn_ok(const struct tcp_options_received *opt,
573 		   const struct net *net, const struct dst_entry *dst);
574 
575 /* From net/ipv6/syncookies.c */
576 int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th,
577 		      u32 cookie);
578 struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
579 
580 u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
581 			      const struct tcphdr *th, u16 *mssp);
582 __u32 cookie_v6_init_sequence(const struct sk_buff *skb, __u16 *mss);
583 #endif
584 /* tcp_output.c */
585 
586 void tcp_skb_entail(struct sock *sk, struct sk_buff *skb);
587 void tcp_mark_push(struct tcp_sock *tp, struct sk_buff *skb);
588 void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
589 			       int nonagle);
590 int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs);
591 int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs);
592 void tcp_retransmit_timer(struct sock *sk);
593 void tcp_xmit_retransmit_queue(struct sock *);
594 void tcp_simple_retransmit(struct sock *);
595 void tcp_enter_recovery(struct sock *sk, bool ece_ack);
596 int tcp_trim_head(struct sock *, struct sk_buff *, u32);
597 enum tcp_queue {
598 	TCP_FRAG_IN_WRITE_QUEUE,
599 	TCP_FRAG_IN_RTX_QUEUE,
600 };
601 int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue,
602 		 struct sk_buff *skb, u32 len,
603 		 unsigned int mss_now, gfp_t gfp);
604 
605 void tcp_send_probe0(struct sock *);
606 int tcp_write_wakeup(struct sock *, int mib);
607 void tcp_send_fin(struct sock *sk);
608 void tcp_send_active_reset(struct sock *sk, gfp_t priority);
609 int tcp_send_synack(struct sock *);
610 void tcp_push_one(struct sock *, unsigned int mss_now);
611 void __tcp_send_ack(struct sock *sk, u32 rcv_nxt);
612 void tcp_send_ack(struct sock *sk);
613 void tcp_send_delayed_ack(struct sock *sk);
614 void tcp_send_loss_probe(struct sock *sk);
615 bool tcp_schedule_loss_probe(struct sock *sk, bool advancing_rto);
616 void tcp_skb_collapse_tstamp(struct sk_buff *skb,
617 			     const struct sk_buff *next_skb);
618 
619 /* tcp_input.c */
620 void tcp_rearm_rto(struct sock *sk);
621 void tcp_synack_rtt_meas(struct sock *sk, struct request_sock *req);
622 void tcp_reset(struct sock *sk, struct sk_buff *skb);
623 void tcp_fin(struct sock *sk);
624 void tcp_check_space(struct sock *sk);
625 void tcp_sack_compress_send_ack(struct sock *sk);
626 
627 /* tcp_timer.c */
628 void tcp_init_xmit_timers(struct sock *);
629 static inline void tcp_clear_xmit_timers(struct sock *sk)
630 {
631 	if (hrtimer_try_to_cancel(&tcp_sk(sk)->pacing_timer) == 1)
632 		__sock_put(sk);
633 
634 	if (hrtimer_try_to_cancel(&tcp_sk(sk)->compressed_ack_timer) == 1)
635 		__sock_put(sk);
636 
637 	inet_csk_clear_xmit_timers(sk);
638 }
639 
640 unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
641 unsigned int tcp_current_mss(struct sock *sk);
642 u32 tcp_clamp_probe0_to_user_timeout(const struct sock *sk, u32 when);
643 
644 /* Bound MSS / TSO packet size with the half of the window */
645 static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
646 {
647 	int cutoff;
648 
649 	/* When peer uses tiny windows, there is no use in packetizing
650 	 * to sub-MSS pieces for the sake of SWS or making sure there
651 	 * are enough packets in the pipe for fast recovery.
652 	 *
653 	 * On the other hand, for extremely large MSS devices, handling
654 	 * smaller than MSS windows in this way does make sense.
655 	 */
656 	if (tp->max_window > TCP_MSS_DEFAULT)
657 		cutoff = (tp->max_window >> 1);
658 	else
659 		cutoff = tp->max_window;
660 
661 	if (cutoff && pktsize > cutoff)
662 		return max_t(int, cutoff, 68U - tp->tcp_header_len);
663 	else
664 		return pktsize;
665 }
666 
667 /* tcp.c */
668 void tcp_get_info(struct sock *, struct tcp_info *);
669 
670 /* Read 'sendfile()'-style from a TCP socket */
671 int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
672 		  sk_read_actor_t recv_actor);
673 int tcp_read_skb(struct sock *sk, skb_read_actor_t recv_actor);
674 struct sk_buff *tcp_recv_skb(struct sock *sk, u32 seq, u32 *off);
675 void tcp_read_done(struct sock *sk, size_t len);
676 
677 void tcp_initialize_rcv_mss(struct sock *sk);
678 
679 int tcp_mtu_to_mss(struct sock *sk, int pmtu);
680 int tcp_mss_to_mtu(struct sock *sk, int mss);
681 void tcp_mtup_init(struct sock *sk);
682 
683 static inline void tcp_bound_rto(const struct sock *sk)
684 {
685 	if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
686 		inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
687 }
688 
689 static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
690 {
691 	return usecs_to_jiffies((tp->srtt_us >> 3) + tp->rttvar_us);
692 }
693 
694 static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
695 {
696 	/* mptcp hooks are only on the slow path */
697 	if (sk_is_mptcp((struct sock *)tp))
698 		return;
699 
700 	tp->pred_flags = htonl((tp->tcp_header_len << 26) |
701 			       ntohl(TCP_FLAG_ACK) |
702 			       snd_wnd);
703 }
704 
705 static inline void tcp_fast_path_on(struct tcp_sock *tp)
706 {
707 	__tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
708 }
709 
710 static inline void tcp_fast_path_check(struct sock *sk)
711 {
712 	struct tcp_sock *tp = tcp_sk(sk);
713 
714 	if (RB_EMPTY_ROOT(&tp->out_of_order_queue) &&
715 	    tp->rcv_wnd &&
716 	    atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
717 	    !tp->urg_data)
718 		tcp_fast_path_on(tp);
719 }
720 
721 /* Compute the actual rto_min value */
722 static inline u32 tcp_rto_min(struct sock *sk)
723 {
724 	const struct dst_entry *dst = __sk_dst_get(sk);
725 	u32 rto_min = inet_csk(sk)->icsk_rto_min;
726 
727 	if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
728 		rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
729 	return rto_min;
730 }
731 
732 static inline u32 tcp_rto_min_us(struct sock *sk)
733 {
734 	return jiffies_to_usecs(tcp_rto_min(sk));
735 }
736 
737 static inline bool tcp_ca_dst_locked(const struct dst_entry *dst)
738 {
739 	return dst_metric_locked(dst, RTAX_CC_ALGO);
740 }
741 
742 /* Minimum RTT in usec. ~0 means not available. */
743 static inline u32 tcp_min_rtt(const struct tcp_sock *tp)
744 {
745 	return minmax_get(&tp->rtt_min);
746 }
747 
748 /* Compute the actual receive window we are currently advertising.
749  * Rcv_nxt can be after the window if our peer push more data
750  * than the offered window.
751  */
752 static inline u32 tcp_receive_window(const struct tcp_sock *tp)
753 {
754 	s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;
755 
756 	if (win < 0)
757 		win = 0;
758 	return (u32) win;
759 }
760 
761 /* Choose a new window, without checks for shrinking, and without
762  * scaling applied to the result.  The caller does these things
763  * if necessary.  This is a "raw" window selection.
764  */
765 u32 __tcp_select_window(struct sock *sk);
766 
767 void tcp_send_window_probe(struct sock *sk);
768 
769 /* TCP uses 32bit jiffies to save some space.
770  * Note that this is different from tcp_time_stamp, which
771  * historically has been the same until linux-4.13.
772  */
773 #define tcp_jiffies32 ((u32)jiffies)
774 
775 /*
776  * Deliver a 32bit value for TCP timestamp option (RFC 7323)
777  * It is no longer tied to jiffies, but to 1 ms clock.
778  * Note: double check if you want to use tcp_jiffies32 instead of this.
779  */
780 #define TCP_TS_HZ	1000
781 
782 static inline u64 tcp_clock_ns(void)
783 {
784 	return ktime_get_ns();
785 }
786 
787 static inline u64 tcp_clock_us(void)
788 {
789 	return div_u64(tcp_clock_ns(), NSEC_PER_USEC);
790 }
791 
792 /* This should only be used in contexts where tp->tcp_mstamp is up to date */
793 static inline u32 tcp_time_stamp(const struct tcp_sock *tp)
794 {
795 	return div_u64(tp->tcp_mstamp, USEC_PER_SEC / TCP_TS_HZ);
796 }
797 
798 /* Convert a nsec timestamp into TCP TSval timestamp (ms based currently) */
799 static inline u32 tcp_ns_to_ts(u64 ns)
800 {
801 	return div_u64(ns, NSEC_PER_SEC / TCP_TS_HZ);
802 }
803 
804 /* Could use tcp_clock_us() / 1000, but this version uses a single divide */
805 static inline u32 tcp_time_stamp_raw(void)
806 {
807 	return tcp_ns_to_ts(tcp_clock_ns());
808 }
809 
810 void tcp_mstamp_refresh(struct tcp_sock *tp);
811 
812 static inline u32 tcp_stamp_us_delta(u64 t1, u64 t0)
813 {
814 	return max_t(s64, t1 - t0, 0);
815 }
816 
817 static inline u32 tcp_skb_timestamp(const struct sk_buff *skb)
818 {
819 	return tcp_ns_to_ts(skb->skb_mstamp_ns);
820 }
821 
822 /* provide the departure time in us unit */
823 static inline u64 tcp_skb_timestamp_us(const struct sk_buff *skb)
824 {
825 	return div_u64(skb->skb_mstamp_ns, NSEC_PER_USEC);
826 }
827 
828 
829 #define tcp_flag_byte(th) (((u_int8_t *)th)[13])
830 
831 #define TCPHDR_FIN 0x01
832 #define TCPHDR_SYN 0x02
833 #define TCPHDR_RST 0x04
834 #define TCPHDR_PSH 0x08
835 #define TCPHDR_ACK 0x10
836 #define TCPHDR_URG 0x20
837 #define TCPHDR_ECE 0x40
838 #define TCPHDR_CWR 0x80
839 
840 #define TCPHDR_SYN_ECN	(TCPHDR_SYN | TCPHDR_ECE | TCPHDR_CWR)
841 
842 /* This is what the send packet queuing engine uses to pass
843  * TCP per-packet control information to the transmission code.
844  * We also store the host-order sequence numbers in here too.
845  * This is 44 bytes if IPV6 is enabled.
846  * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately.
847  */
848 struct tcp_skb_cb {
849 	__u32		seq;		/* Starting sequence number	*/
850 	__u32		end_seq;	/* SEQ + FIN + SYN + datalen	*/
851 	union {
852 		/* Note : tcp_tw_isn is used in input path only
853 		 *	  (isn chosen by tcp_timewait_state_process())
854 		 *
855 		 * 	  tcp_gso_segs/size are used in write queue only,
856 		 *	  cf tcp_skb_pcount()/tcp_skb_mss()
857 		 */
858 		__u32		tcp_tw_isn;
859 		struct {
860 			u16	tcp_gso_segs;
861 			u16	tcp_gso_size;
862 		};
863 	};
864 	__u8		tcp_flags;	/* TCP header flags. (tcp[13])	*/
865 
866 	__u8		sacked;		/* State flags for SACK.	*/
867 #define TCPCB_SACKED_ACKED	0x01	/* SKB ACK'd by a SACK block	*/
868 #define TCPCB_SACKED_RETRANS	0x02	/* SKB retransmitted		*/
869 #define TCPCB_LOST		0x04	/* SKB is lost			*/
870 #define TCPCB_TAGBITS		0x07	/* All tag bits			*/
871 #define TCPCB_REPAIRED		0x10	/* SKB repaired (no skb_mstamp_ns)	*/
872 #define TCPCB_EVER_RETRANS	0x80	/* Ever retransmitted frame	*/
873 #define TCPCB_RETRANS		(TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS| \
874 				TCPCB_REPAIRED)
875 
876 	__u8		ip_dsfield;	/* IPv4 tos or IPv6 dsfield	*/
877 	__u8		txstamp_ack:1,	/* Record TX timestamp for ack? */
878 			eor:1,		/* Is skb MSG_EOR marked? */
879 			has_rxtstamp:1,	/* SKB has a RX timestamp	*/
880 			unused:5;
881 	__u32		ack_seq;	/* Sequence number ACK'd	*/
882 	union {
883 		struct {
884 #define TCPCB_DELIVERED_CE_MASK ((1U<<20) - 1)
885 			/* There is space for up to 24 bytes */
886 			__u32 is_app_limited:1, /* cwnd not fully used? */
887 			      delivered_ce:20,
888 			      unused:11;
889 			/* pkts S/ACKed so far upon tx of skb, incl retrans: */
890 			__u32 delivered;
891 			/* start of send pipeline phase */
892 			u64 first_tx_mstamp;
893 			/* when we reached the "delivered" count */
894 			u64 delivered_mstamp;
895 		} tx;   /* only used for outgoing skbs */
896 		union {
897 			struct inet_skb_parm	h4;
898 #if IS_ENABLED(CONFIG_IPV6)
899 			struct inet6_skb_parm	h6;
900 #endif
901 		} header;	/* For incoming skbs */
902 	};
903 };
904 
905 #define TCP_SKB_CB(__skb)	((struct tcp_skb_cb *)&((__skb)->cb[0]))
906 
907 extern const struct inet_connection_sock_af_ops ipv4_specific;
908 
909 #if IS_ENABLED(CONFIG_IPV6)
910 /* This is the variant of inet6_iif() that must be used by TCP,
911  * as TCP moves IP6CB into a different location in skb->cb[]
912  */
913 static inline int tcp_v6_iif(const struct sk_buff *skb)
914 {
915 	return TCP_SKB_CB(skb)->header.h6.iif;
916 }
917 
918 static inline int tcp_v6_iif_l3_slave(const struct sk_buff *skb)
919 {
920 	bool l3_slave = ipv6_l3mdev_skb(TCP_SKB_CB(skb)->header.h6.flags);
921 
922 	return l3_slave ? skb->skb_iif : TCP_SKB_CB(skb)->header.h6.iif;
923 }
924 
925 /* TCP_SKB_CB reference means this can not be used from early demux */
926 static inline int tcp_v6_sdif(const struct sk_buff *skb)
927 {
928 #if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
929 	if (skb && ipv6_l3mdev_skb(TCP_SKB_CB(skb)->header.h6.flags))
930 		return TCP_SKB_CB(skb)->header.h6.iif;
931 #endif
932 	return 0;
933 }
934 
935 extern const struct inet_connection_sock_af_ops ipv6_specific;
936 
937 INDIRECT_CALLABLE_DECLARE(void tcp_v6_send_check(struct sock *sk, struct sk_buff *skb));
938 INDIRECT_CALLABLE_DECLARE(int tcp_v6_rcv(struct sk_buff *skb));
939 void tcp_v6_early_demux(struct sk_buff *skb);
940 
941 #endif
942 
943 /* TCP_SKB_CB reference means this can not be used from early demux */
944 static inline int tcp_v4_sdif(struct sk_buff *skb)
945 {
946 #if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
947 	if (skb && ipv4_l3mdev_skb(TCP_SKB_CB(skb)->header.h4.flags))
948 		return TCP_SKB_CB(skb)->header.h4.iif;
949 #endif
950 	return 0;
951 }
952 
953 /* Due to TSO, an SKB can be composed of multiple actual
954  * packets.  To keep these tracked properly, we use this.
955  */
956 static inline int tcp_skb_pcount(const struct sk_buff *skb)
957 {
958 	return TCP_SKB_CB(skb)->tcp_gso_segs;
959 }
960 
961 static inline void tcp_skb_pcount_set(struct sk_buff *skb, int segs)
962 {
963 	TCP_SKB_CB(skb)->tcp_gso_segs = segs;
964 }
965 
966 static inline void tcp_skb_pcount_add(struct sk_buff *skb, int segs)
967 {
968 	TCP_SKB_CB(skb)->tcp_gso_segs += segs;
969 }
970 
971 /* This is valid iff skb is in write queue and tcp_skb_pcount() > 1. */
972 static inline int tcp_skb_mss(const struct sk_buff *skb)
973 {
974 	return TCP_SKB_CB(skb)->tcp_gso_size;
975 }
976 
977 static inline bool tcp_skb_can_collapse_to(const struct sk_buff *skb)
978 {
979 	return likely(!TCP_SKB_CB(skb)->eor);
980 }
981 
982 static inline bool tcp_skb_can_collapse(const struct sk_buff *to,
983 					const struct sk_buff *from)
984 {
985 	return likely(tcp_skb_can_collapse_to(to) &&
986 		      mptcp_skb_can_collapse(to, from) &&
987 		      skb_pure_zcopy_same(to, from));
988 }
989 
990 /* Events passed to congestion control interface */
991 enum tcp_ca_event {
992 	CA_EVENT_TX_START,	/* first transmit when no packets in flight */
993 	CA_EVENT_CWND_RESTART,	/* congestion window restart */
994 	CA_EVENT_COMPLETE_CWR,	/* end of congestion recovery */
995 	CA_EVENT_LOSS,		/* loss timeout */
996 	CA_EVENT_ECN_NO_CE,	/* ECT set, but not CE marked */
997 	CA_EVENT_ECN_IS_CE,	/* received CE marked IP packet */
998 };
999 
1000 /* Information about inbound ACK, passed to cong_ops->in_ack_event() */
1001 enum tcp_ca_ack_event_flags {
1002 	CA_ACK_SLOWPATH		= (1 << 0),	/* In slow path processing */
1003 	CA_ACK_WIN_UPDATE	= (1 << 1),	/* ACK updated window */
1004 	CA_ACK_ECE		= (1 << 2),	/* ECE bit is set on ack */
1005 };
1006 
1007 /*
1008  * Interface for adding new TCP congestion control handlers
1009  */
1010 #define TCP_CA_NAME_MAX	16
1011 #define TCP_CA_MAX	128
1012 #define TCP_CA_BUF_MAX	(TCP_CA_NAME_MAX*TCP_CA_MAX)
1013 
1014 #define TCP_CA_UNSPEC	0
1015 
1016 /* Algorithm can be set on socket without CAP_NET_ADMIN privileges */
1017 #define TCP_CONG_NON_RESTRICTED 0x1
1018 /* Requires ECN/ECT set on all packets */
1019 #define TCP_CONG_NEEDS_ECN	0x2
1020 #define TCP_CONG_MASK	(TCP_CONG_NON_RESTRICTED | TCP_CONG_NEEDS_ECN)
1021 
1022 union tcp_cc_info;
1023 
1024 struct ack_sample {
1025 	u32 pkts_acked;
1026 	s32 rtt_us;
1027 	u32 in_flight;
1028 };
1029 
1030 /* A rate sample measures the number of (original/retransmitted) data
1031  * packets delivered "delivered" over an interval of time "interval_us".
1032  * The tcp_rate.c code fills in the rate sample, and congestion
1033  * control modules that define a cong_control function to run at the end
1034  * of ACK processing can optionally chose to consult this sample when
1035  * setting cwnd and pacing rate.
1036  * A sample is invalid if "delivered" or "interval_us" is negative.
1037  */
1038 struct rate_sample {
1039 	u64  prior_mstamp; /* starting timestamp for interval */
1040 	u32  prior_delivered;	/* tp->delivered at "prior_mstamp" */
1041 	u32  prior_delivered_ce;/* tp->delivered_ce at "prior_mstamp" */
1042 	s32  delivered;		/* number of packets delivered over interval */
1043 	s32  delivered_ce;	/* number of packets delivered w/ CE marks*/
1044 	long interval_us;	/* time for tp->delivered to incr "delivered" */
1045 	u32 snd_interval_us;	/* snd interval for delivered packets */
1046 	u32 rcv_interval_us;	/* rcv interval for delivered packets */
1047 	long rtt_us;		/* RTT of last (S)ACKed packet (or -1) */
1048 	int  losses;		/* number of packets marked lost upon ACK */
1049 	u32  acked_sacked;	/* number of packets newly (S)ACKed upon ACK */
1050 	u32  prior_in_flight;	/* in flight before this ACK */
1051 	u32  last_end_seq;	/* end_seq of most recently ACKed packet */
1052 	bool is_app_limited;	/* is sample from packet with bubble in pipe? */
1053 	bool is_retrans;	/* is sample from retransmission? */
1054 	bool is_ack_delayed;	/* is this (likely) a delayed ACK? */
1055 };
1056 
1057 struct tcp_congestion_ops {
1058 /* fast path fields are put first to fill one cache line */
1059 
1060 	/* return slow start threshold (required) */
1061 	u32 (*ssthresh)(struct sock *sk);
1062 
1063 	/* do new cwnd calculation (required) */
1064 	void (*cong_avoid)(struct sock *sk, u32 ack, u32 acked);
1065 
1066 	/* call before changing ca_state (optional) */
1067 	void (*set_state)(struct sock *sk, u8 new_state);
1068 
1069 	/* call when cwnd event occurs (optional) */
1070 	void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
1071 
1072 	/* call when ack arrives (optional) */
1073 	void (*in_ack_event)(struct sock *sk, u32 flags);
1074 
1075 	/* hook for packet ack accounting (optional) */
1076 	void (*pkts_acked)(struct sock *sk, const struct ack_sample *sample);
1077 
1078 	/* override sysctl_tcp_min_tso_segs */
1079 	u32 (*min_tso_segs)(struct sock *sk);
1080 
1081 	/* call when packets are delivered to update cwnd and pacing rate,
1082 	 * after all the ca_state processing. (optional)
1083 	 */
1084 	void (*cong_control)(struct sock *sk, const struct rate_sample *rs);
1085 
1086 
1087 	/* new value of cwnd after loss (required) */
1088 	u32  (*undo_cwnd)(struct sock *sk);
1089 	/* returns the multiplier used in tcp_sndbuf_expand (optional) */
1090 	u32 (*sndbuf_expand)(struct sock *sk);
1091 
1092 /* control/slow paths put last */
1093 	/* get info for inet_diag (optional) */
1094 	size_t (*get_info)(struct sock *sk, u32 ext, int *attr,
1095 			   union tcp_cc_info *info);
1096 
1097 	char 			name[TCP_CA_NAME_MAX];
1098 	struct module		*owner;
1099 	struct list_head	list;
1100 	u32			key;
1101 	u32			flags;
1102 
1103 	/* initialize private data (optional) */
1104 	void (*init)(struct sock *sk);
1105 	/* cleanup private data  (optional) */
1106 	void (*release)(struct sock *sk);
1107 } ____cacheline_aligned_in_smp;
1108 
1109 int tcp_register_congestion_control(struct tcp_congestion_ops *type);
1110 void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
1111 int tcp_update_congestion_control(struct tcp_congestion_ops *type,
1112 				  struct tcp_congestion_ops *old_type);
1113 int tcp_validate_congestion_control(struct tcp_congestion_ops *ca);
1114 
1115 void tcp_assign_congestion_control(struct sock *sk);
1116 void tcp_init_congestion_control(struct sock *sk);
1117 void tcp_cleanup_congestion_control(struct sock *sk);
1118 int tcp_set_default_congestion_control(struct net *net, const char *name);
1119 void tcp_get_default_congestion_control(struct net *net, char *name);
1120 void tcp_get_available_congestion_control(char *buf, size_t len);
1121 void tcp_get_allowed_congestion_control(char *buf, size_t len);
1122 int tcp_set_allowed_congestion_control(char *allowed);
1123 int tcp_set_congestion_control(struct sock *sk, const char *name, bool load,
1124 			       bool cap_net_admin);
1125 u32 tcp_slow_start(struct tcp_sock *tp, u32 acked);
1126 void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked);
1127 
1128 u32 tcp_reno_ssthresh(struct sock *sk);
1129 u32 tcp_reno_undo_cwnd(struct sock *sk);
1130 void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked);
1131 extern struct tcp_congestion_ops tcp_reno;
1132 
1133 struct tcp_congestion_ops *tcp_ca_find(const char *name);
1134 struct tcp_congestion_ops *tcp_ca_find_key(u32 key);
1135 u32 tcp_ca_get_key_by_name(struct net *net, const char *name, bool *ecn_ca);
1136 #ifdef CONFIG_INET
1137 char *tcp_ca_get_name_by_key(u32 key, char *buffer);
1138 #else
1139 static inline char *tcp_ca_get_name_by_key(u32 key, char *buffer)
1140 {
1141 	return NULL;
1142 }
1143 #endif
1144 
1145 static inline bool tcp_ca_needs_ecn(const struct sock *sk)
1146 {
1147 	const struct inet_connection_sock *icsk = inet_csk(sk);
1148 
1149 	return icsk->icsk_ca_ops->flags & TCP_CONG_NEEDS_ECN;
1150 }
1151 
1152 static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
1153 {
1154 	const struct inet_connection_sock *icsk = inet_csk(sk);
1155 
1156 	if (icsk->icsk_ca_ops->cwnd_event)
1157 		icsk->icsk_ca_ops->cwnd_event(sk, event);
1158 }
1159 
1160 /* From tcp_cong.c */
1161 void tcp_set_ca_state(struct sock *sk, const u8 ca_state);
1162 
1163 /* From tcp_rate.c */
1164 void tcp_rate_skb_sent(struct sock *sk, struct sk_buff *skb);
1165 void tcp_rate_skb_delivered(struct sock *sk, struct sk_buff *skb,
1166 			    struct rate_sample *rs);
1167 void tcp_rate_gen(struct sock *sk, u32 delivered, u32 lost,
1168 		  bool is_sack_reneg, struct rate_sample *rs);
1169 void tcp_rate_check_app_limited(struct sock *sk);
1170 
1171 static inline bool tcp_skb_sent_after(u64 t1, u64 t2, u32 seq1, u32 seq2)
1172 {
1173 	return t1 > t2 || (t1 == t2 && after(seq1, seq2));
1174 }
1175 
1176 /* These functions determine how the current flow behaves in respect of SACK
1177  * handling. SACK is negotiated with the peer, and therefore it can vary
1178  * between different flows.
1179  *
1180  * tcp_is_sack - SACK enabled
1181  * tcp_is_reno - No SACK
1182  */
1183 static inline int tcp_is_sack(const struct tcp_sock *tp)
1184 {
1185 	return likely(tp->rx_opt.sack_ok);
1186 }
1187 
1188 static inline bool tcp_is_reno(const struct tcp_sock *tp)
1189 {
1190 	return !tcp_is_sack(tp);
1191 }
1192 
1193 static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
1194 {
1195 	return tp->sacked_out + tp->lost_out;
1196 }
1197 
1198 /* This determines how many packets are "in the network" to the best
1199  * of our knowledge.  In many cases it is conservative, but where
1200  * detailed information is available from the receiver (via SACK
1201  * blocks etc.) we can make more aggressive calculations.
1202  *
1203  * Use this for decisions involving congestion control, use just
1204  * tp->packets_out to determine if the send queue is empty or not.
1205  *
1206  * Read this equation as:
1207  *
1208  *	"Packets sent once on transmission queue" MINUS
1209  *	"Packets left network, but not honestly ACKed yet" PLUS
1210  *	"Packets fast retransmitted"
1211  */
1212 static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
1213 {
1214 	return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
1215 }
1216 
1217 #define TCP_INFINITE_SSTHRESH	0x7fffffff
1218 
1219 static inline u32 tcp_snd_cwnd(const struct tcp_sock *tp)
1220 {
1221 	return tp->snd_cwnd;
1222 }
1223 
1224 static inline void tcp_snd_cwnd_set(struct tcp_sock *tp, u32 val)
1225 {
1226 	WARN_ON_ONCE((int)val <= 0);
1227 	tp->snd_cwnd = val;
1228 }
1229 
1230 static inline bool tcp_in_slow_start(const struct tcp_sock *tp)
1231 {
1232 	return tcp_snd_cwnd(tp) < tp->snd_ssthresh;
1233 }
1234 
1235 static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
1236 {
1237 	return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
1238 }
1239 
1240 static inline bool tcp_in_cwnd_reduction(const struct sock *sk)
1241 {
1242 	return (TCPF_CA_CWR | TCPF_CA_Recovery) &
1243 	       (1 << inet_csk(sk)->icsk_ca_state);
1244 }
1245 
1246 /* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
1247  * The exception is cwnd reduction phase, when cwnd is decreasing towards
1248  * ssthresh.
1249  */
1250 static inline __u32 tcp_current_ssthresh(const struct sock *sk)
1251 {
1252 	const struct tcp_sock *tp = tcp_sk(sk);
1253 
1254 	if (tcp_in_cwnd_reduction(sk))
1255 		return tp->snd_ssthresh;
1256 	else
1257 		return max(tp->snd_ssthresh,
1258 			   ((tcp_snd_cwnd(tp) >> 1) +
1259 			    (tcp_snd_cwnd(tp) >> 2)));
1260 }
1261 
1262 /* Use define here intentionally to get WARN_ON location shown at the caller */
1263 #define tcp_verify_left_out(tp)	WARN_ON(tcp_left_out(tp) > tp->packets_out)
1264 
1265 void tcp_enter_cwr(struct sock *sk);
1266 __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst);
1267 
1268 /* The maximum number of MSS of available cwnd for which TSO defers
1269  * sending if not using sysctl_tcp_tso_win_divisor.
1270  */
1271 static inline __u32 tcp_max_tso_deferred_mss(const struct tcp_sock *tp)
1272 {
1273 	return 3;
1274 }
1275 
1276 /* Returns end sequence number of the receiver's advertised window */
1277 static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
1278 {
1279 	return tp->snd_una + tp->snd_wnd;
1280 }
1281 
1282 /* We follow the spirit of RFC2861 to validate cwnd but implement a more
1283  * flexible approach. The RFC suggests cwnd should not be raised unless
1284  * it was fully used previously. And that's exactly what we do in
1285  * congestion avoidance mode. But in slow start we allow cwnd to grow
1286  * as long as the application has used half the cwnd.
1287  * Example :
1288  *    cwnd is 10 (IW10), but application sends 9 frames.
1289  *    We allow cwnd to reach 18 when all frames are ACKed.
1290  * This check is safe because it's as aggressive as slow start which already
1291  * risks 100% overshoot. The advantage is that we discourage application to
1292  * either send more filler packets or data to artificially blow up the cwnd
1293  * usage, and allow application-limited process to probe bw more aggressively.
1294  */
1295 static inline bool tcp_is_cwnd_limited(const struct sock *sk)
1296 {
1297 	const struct tcp_sock *tp = tcp_sk(sk);
1298 
1299 	if (tp->is_cwnd_limited)
1300 		return true;
1301 
1302 	/* If in slow start, ensure cwnd grows to twice what was ACKed. */
1303 	if (tcp_in_slow_start(tp))
1304 		return tcp_snd_cwnd(tp) < 2 * tp->max_packets_out;
1305 
1306 	return false;
1307 }
1308 
1309 /* BBR congestion control needs pacing.
1310  * Same remark for SO_MAX_PACING_RATE.
1311  * sch_fq packet scheduler is efficiently handling pacing,
1312  * but is not always installed/used.
1313  * Return true if TCP stack should pace packets itself.
1314  */
1315 static inline bool tcp_needs_internal_pacing(const struct sock *sk)
1316 {
1317 	return smp_load_acquire(&sk->sk_pacing_status) == SK_PACING_NEEDED;
1318 }
1319 
1320 /* Estimates in how many jiffies next packet for this flow can be sent.
1321  * Scheduling a retransmit timer too early would be silly.
1322  */
1323 static inline unsigned long tcp_pacing_delay(const struct sock *sk)
1324 {
1325 	s64 delay = tcp_sk(sk)->tcp_wstamp_ns - tcp_sk(sk)->tcp_clock_cache;
1326 
1327 	return delay > 0 ? nsecs_to_jiffies(delay) : 0;
1328 }
1329 
1330 static inline void tcp_reset_xmit_timer(struct sock *sk,
1331 					const int what,
1332 					unsigned long when,
1333 					const unsigned long max_when)
1334 {
1335 	inet_csk_reset_xmit_timer(sk, what, when + tcp_pacing_delay(sk),
1336 				  max_when);
1337 }
1338 
1339 /* Something is really bad, we could not queue an additional packet,
1340  * because qdisc is full or receiver sent a 0 window, or we are paced.
1341  * We do not want to add fuel to the fire, or abort too early,
1342  * so make sure the timer we arm now is at least 200ms in the future,
1343  * regardless of current icsk_rto value (as it could be ~2ms)
1344  */
1345 static inline unsigned long tcp_probe0_base(const struct sock *sk)
1346 {
1347 	return max_t(unsigned long, inet_csk(sk)->icsk_rto, TCP_RTO_MIN);
1348 }
1349 
1350 /* Variant of inet_csk_rto_backoff() used for zero window probes */
1351 static inline unsigned long tcp_probe0_when(const struct sock *sk,
1352 					    unsigned long max_when)
1353 {
1354 	u8 backoff = min_t(u8, ilog2(TCP_RTO_MAX / TCP_RTO_MIN) + 1,
1355 			   inet_csk(sk)->icsk_backoff);
1356 	u64 when = (u64)tcp_probe0_base(sk) << backoff;
1357 
1358 	return (unsigned long)min_t(u64, when, max_when);
1359 }
1360 
1361 static inline void tcp_check_probe_timer(struct sock *sk)
1362 {
1363 	if (!tcp_sk(sk)->packets_out && !inet_csk(sk)->icsk_pending)
1364 		tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
1365 				     tcp_probe0_base(sk), TCP_RTO_MAX);
1366 }
1367 
1368 static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
1369 {
1370 	tp->snd_wl1 = seq;
1371 }
1372 
1373 static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq)
1374 {
1375 	tp->snd_wl1 = seq;
1376 }
1377 
1378 /*
1379  * Calculate(/check) TCP checksum
1380  */
1381 static inline __sum16 tcp_v4_check(int len, __be32 saddr,
1382 				   __be32 daddr, __wsum base)
1383 {
1384 	return csum_tcpudp_magic(saddr, daddr, len, IPPROTO_TCP, base);
1385 }
1386 
1387 static inline bool tcp_checksum_complete(struct sk_buff *skb)
1388 {
1389 	return !skb_csum_unnecessary(skb) &&
1390 		__skb_checksum_complete(skb);
1391 }
1392 
1393 bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb,
1394 		     enum skb_drop_reason *reason);
1395 
1396 
1397 int tcp_filter(struct sock *sk, struct sk_buff *skb);
1398 void tcp_set_state(struct sock *sk, int state);
1399 void tcp_done(struct sock *sk);
1400 int tcp_abort(struct sock *sk, int err);
1401 
1402 static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
1403 {
1404 	rx_opt->dsack = 0;
1405 	rx_opt->num_sacks = 0;
1406 }
1407 
1408 void tcp_cwnd_restart(struct sock *sk, s32 delta);
1409 
1410 static inline void tcp_slow_start_after_idle_check(struct sock *sk)
1411 {
1412 	const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1413 	struct tcp_sock *tp = tcp_sk(sk);
1414 	s32 delta;
1415 
1416 	if (!READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_slow_start_after_idle) ||
1417 	    tp->packets_out || ca_ops->cong_control)
1418 		return;
1419 	delta = tcp_jiffies32 - tp->lsndtime;
1420 	if (delta > inet_csk(sk)->icsk_rto)
1421 		tcp_cwnd_restart(sk, delta);
1422 }
1423 
1424 /* Determine a window scaling and initial window to offer. */
1425 void tcp_select_initial_window(const struct sock *sk, int __space,
1426 			       __u32 mss, __u32 *rcv_wnd,
1427 			       __u32 *window_clamp, int wscale_ok,
1428 			       __u8 *rcv_wscale, __u32 init_rcv_wnd);
1429 
1430 static inline int __tcp_win_from_space(u8 scaling_ratio, int space)
1431 {
1432 	s64 scaled_space = (s64)space * scaling_ratio;
1433 
1434 	return scaled_space >> TCP_RMEM_TO_WIN_SCALE;
1435 }
1436 
1437 static inline int tcp_win_from_space(const struct sock *sk, int space)
1438 {
1439 	return __tcp_win_from_space(tcp_sk(sk)->scaling_ratio, space);
1440 }
1441 
1442 /* inverse of __tcp_win_from_space() */
1443 static inline int __tcp_space_from_win(u8 scaling_ratio, int win)
1444 {
1445 	u64 val = (u64)win << TCP_RMEM_TO_WIN_SCALE;
1446 
1447 	do_div(val, scaling_ratio);
1448 	return val;
1449 }
1450 
1451 static inline int tcp_space_from_win(const struct sock *sk, int win)
1452 {
1453 	return __tcp_space_from_win(tcp_sk(sk)->scaling_ratio, win);
1454 }
1455 
1456 static inline void tcp_scaling_ratio_init(struct sock *sk)
1457 {
1458 	/* Assume a conservative default of 1200 bytes of payload per 4K page.
1459 	 * This may be adjusted later in tcp_measure_rcv_mss().
1460 	 */
1461 	tcp_sk(sk)->scaling_ratio = (1200 << TCP_RMEM_TO_WIN_SCALE) /
1462 				    SKB_TRUESIZE(4096);
1463 }
1464 
1465 /* Note: caller must be prepared to deal with negative returns */
1466 static inline int tcp_space(const struct sock *sk)
1467 {
1468 	return tcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf) -
1469 				  READ_ONCE(sk->sk_backlog.len) -
1470 				  atomic_read(&sk->sk_rmem_alloc));
1471 }
1472 
1473 static inline int tcp_full_space(const struct sock *sk)
1474 {
1475 	return tcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf));
1476 }
1477 
1478 static inline void tcp_adjust_rcv_ssthresh(struct sock *sk)
1479 {
1480 	int unused_mem = sk_unused_reserved_mem(sk);
1481 	struct tcp_sock *tp = tcp_sk(sk);
1482 
1483 	tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss);
1484 	if (unused_mem)
1485 		tp->rcv_ssthresh = max_t(u32, tp->rcv_ssthresh,
1486 					 tcp_win_from_space(sk, unused_mem));
1487 }
1488 
1489 void tcp_cleanup_rbuf(struct sock *sk, int copied);
1490 void __tcp_cleanup_rbuf(struct sock *sk, int copied);
1491 
1492 
1493 /* We provision sk_rcvbuf around 200% of sk_rcvlowat.
1494  * If 87.5 % (7/8) of the space has been consumed, we want to override
1495  * SO_RCVLOWAT constraint, since we are receiving skbs with too small
1496  * len/truesize ratio.
1497  */
1498 static inline bool tcp_rmem_pressure(const struct sock *sk)
1499 {
1500 	int rcvbuf, threshold;
1501 
1502 	if (tcp_under_memory_pressure(sk))
1503 		return true;
1504 
1505 	rcvbuf = READ_ONCE(sk->sk_rcvbuf);
1506 	threshold = rcvbuf - (rcvbuf >> 3);
1507 
1508 	return atomic_read(&sk->sk_rmem_alloc) > threshold;
1509 }
1510 
1511 static inline bool tcp_epollin_ready(const struct sock *sk, int target)
1512 {
1513 	const struct tcp_sock *tp = tcp_sk(sk);
1514 	int avail = READ_ONCE(tp->rcv_nxt) - READ_ONCE(tp->copied_seq);
1515 
1516 	if (avail <= 0)
1517 		return false;
1518 
1519 	return (avail >= target) || tcp_rmem_pressure(sk) ||
1520 	       (tcp_receive_window(tp) <= inet_csk(sk)->icsk_ack.rcv_mss);
1521 }
1522 
1523 extern void tcp_openreq_init_rwin(struct request_sock *req,
1524 				  const struct sock *sk_listener,
1525 				  const struct dst_entry *dst);
1526 
1527 void tcp_enter_memory_pressure(struct sock *sk);
1528 void tcp_leave_memory_pressure(struct sock *sk);
1529 
1530 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
1531 {
1532 	struct net *net = sock_net((struct sock *)tp);
1533 	int val;
1534 
1535 	/* Paired with WRITE_ONCE() in tcp_sock_set_keepintvl()
1536 	 * and do_tcp_setsockopt().
1537 	 */
1538 	val = READ_ONCE(tp->keepalive_intvl);
1539 
1540 	return val ? : READ_ONCE(net->ipv4.sysctl_tcp_keepalive_intvl);
1541 }
1542 
1543 static inline int keepalive_time_when(const struct tcp_sock *tp)
1544 {
1545 	struct net *net = sock_net((struct sock *)tp);
1546 	int val;
1547 
1548 	/* Paired with WRITE_ONCE() in tcp_sock_set_keepidle_locked() */
1549 	val = READ_ONCE(tp->keepalive_time);
1550 
1551 	return val ? : READ_ONCE(net->ipv4.sysctl_tcp_keepalive_time);
1552 }
1553 
1554 static inline int keepalive_probes(const struct tcp_sock *tp)
1555 {
1556 	struct net *net = sock_net((struct sock *)tp);
1557 	int val;
1558 
1559 	/* Paired with WRITE_ONCE() in tcp_sock_set_keepcnt()
1560 	 * and do_tcp_setsockopt().
1561 	 */
1562 	val = READ_ONCE(tp->keepalive_probes);
1563 
1564 	return val ? : READ_ONCE(net->ipv4.sysctl_tcp_keepalive_probes);
1565 }
1566 
1567 static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
1568 {
1569 	const struct inet_connection_sock *icsk = &tp->inet_conn;
1570 
1571 	return min_t(u32, tcp_jiffies32 - icsk->icsk_ack.lrcvtime,
1572 			  tcp_jiffies32 - tp->rcv_tstamp);
1573 }
1574 
1575 static inline int tcp_fin_time(const struct sock *sk)
1576 {
1577 	int fin_timeout = tcp_sk(sk)->linger2 ? :
1578 		READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fin_timeout);
1579 	const int rto = inet_csk(sk)->icsk_rto;
1580 
1581 	if (fin_timeout < (rto << 2) - (rto >> 1))
1582 		fin_timeout = (rto << 2) - (rto >> 1);
1583 
1584 	return fin_timeout;
1585 }
1586 
1587 static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt,
1588 				  int paws_win)
1589 {
1590 	if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
1591 		return true;
1592 	if (unlikely(!time_before32(ktime_get_seconds(),
1593 				    rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS)))
1594 		return true;
1595 	/*
1596 	 * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
1597 	 * then following tcp messages have valid values. Ignore 0 value,
1598 	 * or else 'negative' tsval might forbid us to accept their packets.
1599 	 */
1600 	if (!rx_opt->ts_recent)
1601 		return true;
1602 	return false;
1603 }
1604 
1605 static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt,
1606 				   int rst)
1607 {
1608 	if (tcp_paws_check(rx_opt, 0))
1609 		return false;
1610 
1611 	/* RST segments are not recommended to carry timestamp,
1612 	   and, if they do, it is recommended to ignore PAWS because
1613 	   "their cleanup function should take precedence over timestamps."
1614 	   Certainly, it is mistake. It is necessary to understand the reasons
1615 	   of this constraint to relax it: if peer reboots, clock may go
1616 	   out-of-sync and half-open connections will not be reset.
1617 	   Actually, the problem would be not existing if all
1618 	   the implementations followed draft about maintaining clock
1619 	   via reboots. Linux-2.2 DOES NOT!
1620 
1621 	   However, we can relax time bounds for RST segments to MSL.
1622 	 */
1623 	if (rst && !time_before32(ktime_get_seconds(),
1624 				  rx_opt->ts_recent_stamp + TCP_PAWS_MSL))
1625 		return false;
1626 	return true;
1627 }
1628 
1629 bool tcp_oow_rate_limited(struct net *net, const struct sk_buff *skb,
1630 			  int mib_idx, u32 *last_oow_ack_time);
1631 
1632 static inline void tcp_mib_init(struct net *net)
1633 {
1634 	/* See RFC 2012 */
1635 	TCP_ADD_STATS(net, TCP_MIB_RTOALGORITHM, 1);
1636 	TCP_ADD_STATS(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
1637 	TCP_ADD_STATS(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
1638 	TCP_ADD_STATS(net, TCP_MIB_MAXCONN, -1);
1639 }
1640 
1641 /* from STCP */
1642 static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
1643 {
1644 	tp->lost_skb_hint = NULL;
1645 }
1646 
1647 static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
1648 {
1649 	tcp_clear_retrans_hints_partial(tp);
1650 	tp->retransmit_skb_hint = NULL;
1651 }
1652 
1653 union tcp_md5_addr {
1654 	struct in_addr  a4;
1655 #if IS_ENABLED(CONFIG_IPV6)
1656 	struct in6_addr	a6;
1657 #endif
1658 };
1659 
1660 /* - key database */
1661 struct tcp_md5sig_key {
1662 	struct hlist_node	node;
1663 	u8			keylen;
1664 	u8			family; /* AF_INET or AF_INET6 */
1665 	u8			prefixlen;
1666 	u8			flags;
1667 	union tcp_md5_addr	addr;
1668 	int			l3index; /* set if key added with L3 scope */
1669 	u8			key[TCP_MD5SIG_MAXKEYLEN];
1670 	struct rcu_head		rcu;
1671 };
1672 
1673 /* - sock block */
1674 struct tcp_md5sig_info {
1675 	struct hlist_head	head;
1676 	struct rcu_head		rcu;
1677 };
1678 
1679 /* - pseudo header */
1680 struct tcp4_pseudohdr {
1681 	__be32		saddr;
1682 	__be32		daddr;
1683 	__u8		pad;
1684 	__u8		protocol;
1685 	__be16		len;
1686 };
1687 
1688 struct tcp6_pseudohdr {
1689 	struct in6_addr	saddr;
1690 	struct in6_addr daddr;
1691 	__be32		len;
1692 	__be32		protocol;	/* including padding */
1693 };
1694 
1695 union tcp_md5sum_block {
1696 	struct tcp4_pseudohdr ip4;
1697 #if IS_ENABLED(CONFIG_IPV6)
1698 	struct tcp6_pseudohdr ip6;
1699 #endif
1700 };
1701 
1702 /* - pool: digest algorithm, hash description and scratch buffer */
1703 struct tcp_md5sig_pool {
1704 	struct ahash_request	*md5_req;
1705 	void			*scratch;
1706 };
1707 
1708 /* - functions */
1709 int tcp_v4_md5_hash_skb(char *md5_hash, const struct tcp_md5sig_key *key,
1710 			const struct sock *sk, const struct sk_buff *skb);
1711 int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
1712 		   int family, u8 prefixlen, int l3index, u8 flags,
1713 		   const u8 *newkey, u8 newkeylen);
1714 int tcp_md5_key_copy(struct sock *sk, const union tcp_md5_addr *addr,
1715 		     int family, u8 prefixlen, int l3index,
1716 		     struct tcp_md5sig_key *key);
1717 
1718 int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
1719 		   int family, u8 prefixlen, int l3index, u8 flags);
1720 struct tcp_md5sig_key *tcp_v4_md5_lookup(const struct sock *sk,
1721 					 const struct sock *addr_sk);
1722 
1723 #ifdef CONFIG_TCP_MD5SIG
1724 #include <linux/jump_label.h>
1725 extern struct static_key_false_deferred tcp_md5_needed;
1726 struct tcp_md5sig_key *__tcp_md5_do_lookup(const struct sock *sk, int l3index,
1727 					   const union tcp_md5_addr *addr,
1728 					   int family);
1729 static inline struct tcp_md5sig_key *
1730 tcp_md5_do_lookup(const struct sock *sk, int l3index,
1731 		  const union tcp_md5_addr *addr, int family)
1732 {
1733 	if (!static_branch_unlikely(&tcp_md5_needed.key))
1734 		return NULL;
1735 	return __tcp_md5_do_lookup(sk, l3index, addr, family);
1736 }
1737 
1738 enum skb_drop_reason
1739 tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
1740 		     const void *saddr, const void *daddr,
1741 		     int family, int dif, int sdif);
1742 
1743 
1744 #define tcp_twsk_md5_key(twsk)	((twsk)->tw_md5_key)
1745 #else
1746 static inline struct tcp_md5sig_key *
1747 tcp_md5_do_lookup(const struct sock *sk, int l3index,
1748 		  const union tcp_md5_addr *addr, int family)
1749 {
1750 	return NULL;
1751 }
1752 
1753 static inline enum skb_drop_reason
1754 tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
1755 		     const void *saddr, const void *daddr,
1756 		     int family, int dif, int sdif)
1757 {
1758 	return SKB_NOT_DROPPED_YET;
1759 }
1760 #define tcp_twsk_md5_key(twsk)	NULL
1761 #endif
1762 
1763 bool tcp_alloc_md5sig_pool(void);
1764 
1765 struct tcp_md5sig_pool *tcp_get_md5sig_pool(void);
1766 static inline void tcp_put_md5sig_pool(void)
1767 {
1768 	local_bh_enable();
1769 }
1770 
1771 int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
1772 			  unsigned int header_len);
1773 int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
1774 		     const struct tcp_md5sig_key *key);
1775 
1776 /* From tcp_fastopen.c */
1777 void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
1778 			    struct tcp_fastopen_cookie *cookie);
1779 void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
1780 			    struct tcp_fastopen_cookie *cookie, bool syn_lost,
1781 			    u16 try_exp);
1782 struct tcp_fastopen_request {
1783 	/* Fast Open cookie. Size 0 means a cookie request */
1784 	struct tcp_fastopen_cookie	cookie;
1785 	struct msghdr			*data;  /* data in MSG_FASTOPEN */
1786 	size_t				size;
1787 	int				copied;	/* queued in tcp_connect() */
1788 	struct ubuf_info		*uarg;
1789 };
1790 void tcp_free_fastopen_req(struct tcp_sock *tp);
1791 void tcp_fastopen_destroy_cipher(struct sock *sk);
1792 void tcp_fastopen_ctx_destroy(struct net *net);
1793 int tcp_fastopen_reset_cipher(struct net *net, struct sock *sk,
1794 			      void *primary_key, void *backup_key);
1795 int tcp_fastopen_get_cipher(struct net *net, struct inet_connection_sock *icsk,
1796 			    u64 *key);
1797 void tcp_fastopen_add_skb(struct sock *sk, struct sk_buff *skb);
1798 struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
1799 			      struct request_sock *req,
1800 			      struct tcp_fastopen_cookie *foc,
1801 			      const struct dst_entry *dst);
1802 void tcp_fastopen_init_key_once(struct net *net);
1803 bool tcp_fastopen_cookie_check(struct sock *sk, u16 *mss,
1804 			     struct tcp_fastopen_cookie *cookie);
1805 bool tcp_fastopen_defer_connect(struct sock *sk, int *err);
1806 #define TCP_FASTOPEN_KEY_LENGTH sizeof(siphash_key_t)
1807 #define TCP_FASTOPEN_KEY_MAX 2
1808 #define TCP_FASTOPEN_KEY_BUF_LENGTH \
1809 	(TCP_FASTOPEN_KEY_LENGTH * TCP_FASTOPEN_KEY_MAX)
1810 
1811 /* Fastopen key context */
1812 struct tcp_fastopen_context {
1813 	siphash_key_t	key[TCP_FASTOPEN_KEY_MAX];
1814 	int		num;
1815 	struct rcu_head	rcu;
1816 };
1817 
1818 void tcp_fastopen_active_disable(struct sock *sk);
1819 bool tcp_fastopen_active_should_disable(struct sock *sk);
1820 void tcp_fastopen_active_disable_ofo_check(struct sock *sk);
1821 void tcp_fastopen_active_detect_blackhole(struct sock *sk, bool expired);
1822 
1823 /* Caller needs to wrap with rcu_read_(un)lock() */
1824 static inline
1825 struct tcp_fastopen_context *tcp_fastopen_get_ctx(const struct sock *sk)
1826 {
1827 	struct tcp_fastopen_context *ctx;
1828 
1829 	ctx = rcu_dereference(inet_csk(sk)->icsk_accept_queue.fastopenq.ctx);
1830 	if (!ctx)
1831 		ctx = rcu_dereference(sock_net(sk)->ipv4.tcp_fastopen_ctx);
1832 	return ctx;
1833 }
1834 
1835 static inline
1836 bool tcp_fastopen_cookie_match(const struct tcp_fastopen_cookie *foc,
1837 			       const struct tcp_fastopen_cookie *orig)
1838 {
1839 	if (orig->len == TCP_FASTOPEN_COOKIE_SIZE &&
1840 	    orig->len == foc->len &&
1841 	    !memcmp(orig->val, foc->val, foc->len))
1842 		return true;
1843 	return false;
1844 }
1845 
1846 static inline
1847 int tcp_fastopen_context_len(const struct tcp_fastopen_context *ctx)
1848 {
1849 	return ctx->num;
1850 }
1851 
1852 /* Latencies incurred by various limits for a sender. They are
1853  * chronograph-like stats that are mutually exclusive.
1854  */
1855 enum tcp_chrono {
1856 	TCP_CHRONO_UNSPEC,
1857 	TCP_CHRONO_BUSY, /* Actively sending data (non-empty write queue) */
1858 	TCP_CHRONO_RWND_LIMITED, /* Stalled by insufficient receive window */
1859 	TCP_CHRONO_SNDBUF_LIMITED, /* Stalled by insufficient send buffer */
1860 	__TCP_CHRONO_MAX,
1861 };
1862 
1863 void tcp_chrono_start(struct sock *sk, const enum tcp_chrono type);
1864 void tcp_chrono_stop(struct sock *sk, const enum tcp_chrono type);
1865 
1866 /* This helper is needed, because skb->tcp_tsorted_anchor uses
1867  * the same memory storage than skb->destructor/_skb_refdst
1868  */
1869 static inline void tcp_skb_tsorted_anchor_cleanup(struct sk_buff *skb)
1870 {
1871 	skb->destructor = NULL;
1872 	skb->_skb_refdst = 0UL;
1873 }
1874 
1875 #define tcp_skb_tsorted_save(skb) {		\
1876 	unsigned long _save = skb->_skb_refdst;	\
1877 	skb->_skb_refdst = 0UL;
1878 
1879 #define tcp_skb_tsorted_restore(skb)		\
1880 	skb->_skb_refdst = _save;		\
1881 }
1882 
1883 void tcp_write_queue_purge(struct sock *sk);
1884 
1885 static inline struct sk_buff *tcp_rtx_queue_head(const struct sock *sk)
1886 {
1887 	return skb_rb_first(&sk->tcp_rtx_queue);
1888 }
1889 
1890 static inline struct sk_buff *tcp_rtx_queue_tail(const struct sock *sk)
1891 {
1892 	return skb_rb_last(&sk->tcp_rtx_queue);
1893 }
1894 
1895 static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk)
1896 {
1897 	return skb_peek_tail(&sk->sk_write_queue);
1898 }
1899 
1900 #define tcp_for_write_queue_from_safe(skb, tmp, sk)			\
1901 	skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
1902 
1903 static inline struct sk_buff *tcp_send_head(const struct sock *sk)
1904 {
1905 	return skb_peek(&sk->sk_write_queue);
1906 }
1907 
1908 static inline bool tcp_skb_is_last(const struct sock *sk,
1909 				   const struct sk_buff *skb)
1910 {
1911 	return skb_queue_is_last(&sk->sk_write_queue, skb);
1912 }
1913 
1914 /**
1915  * tcp_write_queue_empty - test if any payload (or FIN) is available in write queue
1916  * @sk: socket
1917  *
1918  * Since the write queue can have a temporary empty skb in it,
1919  * we must not use "return skb_queue_empty(&sk->sk_write_queue)"
1920  */
1921 static inline bool tcp_write_queue_empty(const struct sock *sk)
1922 {
1923 	const struct tcp_sock *tp = tcp_sk(sk);
1924 
1925 	return tp->write_seq == tp->snd_nxt;
1926 }
1927 
1928 static inline bool tcp_rtx_queue_empty(const struct sock *sk)
1929 {
1930 	return RB_EMPTY_ROOT(&sk->tcp_rtx_queue);
1931 }
1932 
1933 static inline bool tcp_rtx_and_write_queues_empty(const struct sock *sk)
1934 {
1935 	return tcp_rtx_queue_empty(sk) && tcp_write_queue_empty(sk);
1936 }
1937 
1938 static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1939 {
1940 	__skb_queue_tail(&sk->sk_write_queue, skb);
1941 
1942 	/* Queue it, remembering where we must start sending. */
1943 	if (sk->sk_write_queue.next == skb)
1944 		tcp_chrono_start(sk, TCP_CHRONO_BUSY);
1945 }
1946 
1947 /* Insert new before skb on the write queue of sk.  */
1948 static inline void tcp_insert_write_queue_before(struct sk_buff *new,
1949 						  struct sk_buff *skb,
1950 						  struct sock *sk)
1951 {
1952 	__skb_queue_before(&sk->sk_write_queue, skb, new);
1953 }
1954 
1955 static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
1956 {
1957 	tcp_skb_tsorted_anchor_cleanup(skb);
1958 	__skb_unlink(skb, &sk->sk_write_queue);
1959 }
1960 
1961 void tcp_rbtree_insert(struct rb_root *root, struct sk_buff *skb);
1962 
1963 static inline void tcp_rtx_queue_unlink(struct sk_buff *skb, struct sock *sk)
1964 {
1965 	tcp_skb_tsorted_anchor_cleanup(skb);
1966 	rb_erase(&skb->rbnode, &sk->tcp_rtx_queue);
1967 }
1968 
1969 static inline void tcp_rtx_queue_unlink_and_free(struct sk_buff *skb, struct sock *sk)
1970 {
1971 	list_del(&skb->tcp_tsorted_anchor);
1972 	tcp_rtx_queue_unlink(skb, sk);
1973 	tcp_wmem_free_skb(sk, skb);
1974 }
1975 
1976 static inline void tcp_push_pending_frames(struct sock *sk)
1977 {
1978 	if (tcp_send_head(sk)) {
1979 		struct tcp_sock *tp = tcp_sk(sk);
1980 
1981 		__tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
1982 	}
1983 }
1984 
1985 /* Start sequence of the skb just after the highest skb with SACKed
1986  * bit, valid only if sacked_out > 0 or when the caller has ensured
1987  * validity by itself.
1988  */
1989 static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
1990 {
1991 	if (!tp->sacked_out)
1992 		return tp->snd_una;
1993 
1994 	if (tp->highest_sack == NULL)
1995 		return tp->snd_nxt;
1996 
1997 	return TCP_SKB_CB(tp->highest_sack)->seq;
1998 }
1999 
2000 static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
2001 {
2002 	tcp_sk(sk)->highest_sack = skb_rb_next(skb);
2003 }
2004 
2005 static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
2006 {
2007 	return tcp_sk(sk)->highest_sack;
2008 }
2009 
2010 static inline void tcp_highest_sack_reset(struct sock *sk)
2011 {
2012 	tcp_sk(sk)->highest_sack = tcp_rtx_queue_head(sk);
2013 }
2014 
2015 /* Called when old skb is about to be deleted and replaced by new skb */
2016 static inline void tcp_highest_sack_replace(struct sock *sk,
2017 					    struct sk_buff *old,
2018 					    struct sk_buff *new)
2019 {
2020 	if (old == tcp_highest_sack(sk))
2021 		tcp_sk(sk)->highest_sack = new;
2022 }
2023 
2024 /* This helper checks if socket has IP_TRANSPARENT set */
2025 static inline bool inet_sk_transparent(const struct sock *sk)
2026 {
2027 	switch (sk->sk_state) {
2028 	case TCP_TIME_WAIT:
2029 		return inet_twsk(sk)->tw_transparent;
2030 	case TCP_NEW_SYN_RECV:
2031 		return inet_rsk(inet_reqsk(sk))->no_srccheck;
2032 	}
2033 	return inet_test_bit(TRANSPARENT, sk);
2034 }
2035 
2036 /* Determines whether this is a thin stream (which may suffer from
2037  * increased latency). Used to trigger latency-reducing mechanisms.
2038  */
2039 static inline bool tcp_stream_is_thin(struct tcp_sock *tp)
2040 {
2041 	return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
2042 }
2043 
2044 /* /proc */
2045 enum tcp_seq_states {
2046 	TCP_SEQ_STATE_LISTENING,
2047 	TCP_SEQ_STATE_ESTABLISHED,
2048 };
2049 
2050 void *tcp_seq_start(struct seq_file *seq, loff_t *pos);
2051 void *tcp_seq_next(struct seq_file *seq, void *v, loff_t *pos);
2052 void tcp_seq_stop(struct seq_file *seq, void *v);
2053 
2054 struct tcp_seq_afinfo {
2055 	sa_family_t			family;
2056 };
2057 
2058 struct tcp_iter_state {
2059 	struct seq_net_private	p;
2060 	enum tcp_seq_states	state;
2061 	struct sock		*syn_wait_sk;
2062 	int			bucket, offset, sbucket, num;
2063 	loff_t			last_pos;
2064 };
2065 
2066 extern struct request_sock_ops tcp_request_sock_ops;
2067 extern struct request_sock_ops tcp6_request_sock_ops;
2068 
2069 void tcp_v4_destroy_sock(struct sock *sk);
2070 
2071 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
2072 				netdev_features_t features);
2073 struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb);
2074 INDIRECT_CALLABLE_DECLARE(int tcp4_gro_complete(struct sk_buff *skb, int thoff));
2075 INDIRECT_CALLABLE_DECLARE(struct sk_buff *tcp4_gro_receive(struct list_head *head, struct sk_buff *skb));
2076 INDIRECT_CALLABLE_DECLARE(int tcp6_gro_complete(struct sk_buff *skb, int thoff));
2077 INDIRECT_CALLABLE_DECLARE(struct sk_buff *tcp6_gro_receive(struct list_head *head, struct sk_buff *skb));
2078 void tcp_gro_complete(struct sk_buff *skb);
2079 
2080 void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
2081 
2082 static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
2083 {
2084 	struct net *net = sock_net((struct sock *)tp);
2085 	u32 val;
2086 
2087 	val = READ_ONCE(tp->notsent_lowat);
2088 
2089 	return val ?: READ_ONCE(net->ipv4.sysctl_tcp_notsent_lowat);
2090 }
2091 
2092 bool tcp_stream_memory_free(const struct sock *sk, int wake);
2093 
2094 #ifdef CONFIG_PROC_FS
2095 int tcp4_proc_init(void);
2096 void tcp4_proc_exit(void);
2097 #endif
2098 
2099 int tcp_rtx_synack(const struct sock *sk, struct request_sock *req);
2100 int tcp_conn_request(struct request_sock_ops *rsk_ops,
2101 		     const struct tcp_request_sock_ops *af_ops,
2102 		     struct sock *sk, struct sk_buff *skb);
2103 
2104 /* TCP af-specific functions */
2105 struct tcp_sock_af_ops {
2106 #ifdef CONFIG_TCP_MD5SIG
2107 	struct tcp_md5sig_key	*(*md5_lookup) (const struct sock *sk,
2108 						const struct sock *addr_sk);
2109 	int		(*calc_md5_hash)(char *location,
2110 					 const struct tcp_md5sig_key *md5,
2111 					 const struct sock *sk,
2112 					 const struct sk_buff *skb);
2113 	int		(*md5_parse)(struct sock *sk,
2114 				     int optname,
2115 				     sockptr_t optval,
2116 				     int optlen);
2117 #endif
2118 };
2119 
2120 struct tcp_request_sock_ops {
2121 	u16 mss_clamp;
2122 #ifdef CONFIG_TCP_MD5SIG
2123 	struct tcp_md5sig_key *(*req_md5_lookup)(const struct sock *sk,
2124 						 const struct sock *addr_sk);
2125 	int		(*calc_md5_hash) (char *location,
2126 					  const struct tcp_md5sig_key *md5,
2127 					  const struct sock *sk,
2128 					  const struct sk_buff *skb);
2129 #endif
2130 #ifdef CONFIG_SYN_COOKIES
2131 	__u32 (*cookie_init_seq)(const struct sk_buff *skb,
2132 				 __u16 *mss);
2133 #endif
2134 	struct dst_entry *(*route_req)(const struct sock *sk,
2135 				       struct sk_buff *skb,
2136 				       struct flowi *fl,
2137 				       struct request_sock *req);
2138 	u32 (*init_seq)(const struct sk_buff *skb);
2139 	u32 (*init_ts_off)(const struct net *net, const struct sk_buff *skb);
2140 	int (*send_synack)(const struct sock *sk, struct dst_entry *dst,
2141 			   struct flowi *fl, struct request_sock *req,
2142 			   struct tcp_fastopen_cookie *foc,
2143 			   enum tcp_synack_type synack_type,
2144 			   struct sk_buff *syn_skb);
2145 };
2146 
2147 extern const struct tcp_request_sock_ops tcp_request_sock_ipv4_ops;
2148 #if IS_ENABLED(CONFIG_IPV6)
2149 extern const struct tcp_request_sock_ops tcp_request_sock_ipv6_ops;
2150 #endif
2151 
2152 #ifdef CONFIG_SYN_COOKIES
2153 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
2154 					 const struct sock *sk, struct sk_buff *skb,
2155 					 __u16 *mss)
2156 {
2157 	tcp_synq_overflow(sk);
2158 	__NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESSENT);
2159 	return ops->cookie_init_seq(skb, mss);
2160 }
2161 #else
2162 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
2163 					 const struct sock *sk, struct sk_buff *skb,
2164 					 __u16 *mss)
2165 {
2166 	return 0;
2167 }
2168 #endif
2169 
2170 int tcpv4_offload_init(void);
2171 
2172 void tcp_v4_init(void);
2173 void tcp_init(void);
2174 
2175 /* tcp_recovery.c */
2176 void tcp_mark_skb_lost(struct sock *sk, struct sk_buff *skb);
2177 void tcp_newreno_mark_lost(struct sock *sk, bool snd_una_advanced);
2178 extern s32 tcp_rack_skb_timeout(struct tcp_sock *tp, struct sk_buff *skb,
2179 				u32 reo_wnd);
2180 extern bool tcp_rack_mark_lost(struct sock *sk);
2181 extern void tcp_rack_advance(struct tcp_sock *tp, u8 sacked, u32 end_seq,
2182 			     u64 xmit_time);
2183 extern void tcp_rack_reo_timeout(struct sock *sk);
2184 extern void tcp_rack_update_reo_wnd(struct sock *sk, struct rate_sample *rs);
2185 
2186 /* tcp_plb.c */
2187 
2188 /*
2189  * Scaling factor for fractions in PLB. For example, tcp_plb_update_state
2190  * expects cong_ratio which represents fraction of traffic that experienced
2191  * congestion over a single RTT. In order to avoid floating point operations,
2192  * this fraction should be mapped to (1 << TCP_PLB_SCALE) and passed in.
2193  */
2194 #define TCP_PLB_SCALE 8
2195 
2196 /* State for PLB (Protective Load Balancing) for a single TCP connection. */
2197 struct tcp_plb_state {
2198 	u8	consec_cong_rounds:5, /* consecutive congested rounds */
2199 		unused:3;
2200 	u32	pause_until; /* jiffies32 when PLB can resume rerouting */
2201 };
2202 
2203 static inline void tcp_plb_init(const struct sock *sk,
2204 				struct tcp_plb_state *plb)
2205 {
2206 	plb->consec_cong_rounds = 0;
2207 	plb->pause_until = 0;
2208 }
2209 void tcp_plb_update_state(const struct sock *sk, struct tcp_plb_state *plb,
2210 			  const int cong_ratio);
2211 void tcp_plb_check_rehash(struct sock *sk, struct tcp_plb_state *plb);
2212 void tcp_plb_update_state_upon_rto(struct sock *sk, struct tcp_plb_state *plb);
2213 
2214 /* At how many usecs into the future should the RTO fire? */
2215 static inline s64 tcp_rto_delta_us(const struct sock *sk)
2216 {
2217 	const struct sk_buff *skb = tcp_rtx_queue_head(sk);
2218 	u32 rto = inet_csk(sk)->icsk_rto;
2219 	u64 rto_time_stamp_us = tcp_skb_timestamp_us(skb) + jiffies_to_usecs(rto);
2220 
2221 	return rto_time_stamp_us - tcp_sk(sk)->tcp_mstamp;
2222 }
2223 
2224 /*
2225  * Save and compile IPv4 options, return a pointer to it
2226  */
2227 static inline struct ip_options_rcu *tcp_v4_save_options(struct net *net,
2228 							 struct sk_buff *skb)
2229 {
2230 	const struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt;
2231 	struct ip_options_rcu *dopt = NULL;
2232 
2233 	if (opt->optlen) {
2234 		int opt_size = sizeof(*dopt) + opt->optlen;
2235 
2236 		dopt = kmalloc(opt_size, GFP_ATOMIC);
2237 		if (dopt && __ip_options_echo(net, &dopt->opt, skb, opt)) {
2238 			kfree(dopt);
2239 			dopt = NULL;
2240 		}
2241 	}
2242 	return dopt;
2243 }
2244 
2245 /* locally generated TCP pure ACKs have skb->truesize == 2
2246  * (check tcp_send_ack() in net/ipv4/tcp_output.c )
2247  * This is much faster than dissecting the packet to find out.
2248  * (Think of GRE encapsulations, IPv4, IPv6, ...)
2249  */
2250 static inline bool skb_is_tcp_pure_ack(const struct sk_buff *skb)
2251 {
2252 	return skb->truesize == 2;
2253 }
2254 
2255 static inline void skb_set_tcp_pure_ack(struct sk_buff *skb)
2256 {
2257 	skb->truesize = 2;
2258 }
2259 
2260 static inline int tcp_inq(struct sock *sk)
2261 {
2262 	struct tcp_sock *tp = tcp_sk(sk);
2263 	int answ;
2264 
2265 	if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
2266 		answ = 0;
2267 	} else if (sock_flag(sk, SOCK_URGINLINE) ||
2268 		   !tp->urg_data ||
2269 		   before(tp->urg_seq, tp->copied_seq) ||
2270 		   !before(tp->urg_seq, tp->rcv_nxt)) {
2271 
2272 		answ = tp->rcv_nxt - tp->copied_seq;
2273 
2274 		/* Subtract 1, if FIN was received */
2275 		if (answ && sock_flag(sk, SOCK_DONE))
2276 			answ--;
2277 	} else {
2278 		answ = tp->urg_seq - tp->copied_seq;
2279 	}
2280 
2281 	return answ;
2282 }
2283 
2284 int tcp_peek_len(struct socket *sock);
2285 
2286 static inline void tcp_segs_in(struct tcp_sock *tp, const struct sk_buff *skb)
2287 {
2288 	u16 segs_in;
2289 
2290 	segs_in = max_t(u16, 1, skb_shinfo(skb)->gso_segs);
2291 
2292 	/* We update these fields while other threads might
2293 	 * read them from tcp_get_info()
2294 	 */
2295 	WRITE_ONCE(tp->segs_in, tp->segs_in + segs_in);
2296 	if (skb->len > tcp_hdrlen(skb))
2297 		WRITE_ONCE(tp->data_segs_in, tp->data_segs_in + segs_in);
2298 }
2299 
2300 /*
2301  * TCP listen path runs lockless.
2302  * We forced "struct sock" to be const qualified to make sure
2303  * we don't modify one of its field by mistake.
2304  * Here, we increment sk_drops which is an atomic_t, so we can safely
2305  * make sock writable again.
2306  */
2307 static inline void tcp_listendrop(const struct sock *sk)
2308 {
2309 	atomic_inc(&((struct sock *)sk)->sk_drops);
2310 	__NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENDROPS);
2311 }
2312 
2313 enum hrtimer_restart tcp_pace_kick(struct hrtimer *timer);
2314 
2315 /*
2316  * Interface for adding Upper Level Protocols over TCP
2317  */
2318 
2319 #define TCP_ULP_NAME_MAX	16
2320 #define TCP_ULP_MAX		128
2321 #define TCP_ULP_BUF_MAX		(TCP_ULP_NAME_MAX*TCP_ULP_MAX)
2322 
2323 struct tcp_ulp_ops {
2324 	struct list_head	list;
2325 
2326 	/* initialize ulp */
2327 	int (*init)(struct sock *sk);
2328 	/* update ulp */
2329 	void (*update)(struct sock *sk, struct proto *p,
2330 		       void (*write_space)(struct sock *sk));
2331 	/* cleanup ulp */
2332 	void (*release)(struct sock *sk);
2333 	/* diagnostic */
2334 	int (*get_info)(const struct sock *sk, struct sk_buff *skb);
2335 	size_t (*get_info_size)(const struct sock *sk);
2336 	/* clone ulp */
2337 	void (*clone)(const struct request_sock *req, struct sock *newsk,
2338 		      const gfp_t priority);
2339 
2340 	char		name[TCP_ULP_NAME_MAX];
2341 	struct module	*owner;
2342 };
2343 int tcp_register_ulp(struct tcp_ulp_ops *type);
2344 void tcp_unregister_ulp(struct tcp_ulp_ops *type);
2345 int tcp_set_ulp(struct sock *sk, const char *name);
2346 void tcp_get_available_ulp(char *buf, size_t len);
2347 void tcp_cleanup_ulp(struct sock *sk);
2348 void tcp_update_ulp(struct sock *sk, struct proto *p,
2349 		    void (*write_space)(struct sock *sk));
2350 
2351 #define MODULE_ALIAS_TCP_ULP(name)				\
2352 	__MODULE_INFO(alias, alias_userspace, name);		\
2353 	__MODULE_INFO(alias, alias_tcp_ulp, "tcp-ulp-" name)
2354 
2355 #ifdef CONFIG_NET_SOCK_MSG
2356 struct sk_msg;
2357 struct sk_psock;
2358 
2359 #ifdef CONFIG_BPF_SYSCALL
2360 int tcp_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore);
2361 void tcp_bpf_clone(const struct sock *sk, struct sock *newsk);
2362 #endif /* CONFIG_BPF_SYSCALL */
2363 
2364 #ifdef CONFIG_INET
2365 void tcp_eat_skb(struct sock *sk, struct sk_buff *skb);
2366 #else
2367 static inline void tcp_eat_skb(struct sock *sk, struct sk_buff *skb)
2368 {
2369 }
2370 #endif
2371 
2372 int tcp_bpf_sendmsg_redir(struct sock *sk, bool ingress,
2373 			  struct sk_msg *msg, u32 bytes, int flags);
2374 #endif /* CONFIG_NET_SOCK_MSG */
2375 
2376 #if !defined(CONFIG_BPF_SYSCALL) || !defined(CONFIG_NET_SOCK_MSG)
2377 static inline void tcp_bpf_clone(const struct sock *sk, struct sock *newsk)
2378 {
2379 }
2380 #endif
2381 
2382 #ifdef CONFIG_CGROUP_BPF
2383 static inline void bpf_skops_init_skb(struct bpf_sock_ops_kern *skops,
2384 				      struct sk_buff *skb,
2385 				      unsigned int end_offset)
2386 {
2387 	skops->skb = skb;
2388 	skops->skb_data_end = skb->data + end_offset;
2389 }
2390 #else
2391 static inline void bpf_skops_init_skb(struct bpf_sock_ops_kern *skops,
2392 				      struct sk_buff *skb,
2393 				      unsigned int end_offset)
2394 {
2395 }
2396 #endif
2397 
2398 /* Call BPF_SOCK_OPS program that returns an int. If the return value
2399  * is < 0, then the BPF op failed (for example if the loaded BPF
2400  * program does not support the chosen operation or there is no BPF
2401  * program loaded).
2402  */
2403 #ifdef CONFIG_BPF
2404 static inline int tcp_call_bpf(struct sock *sk, int op, u32 nargs, u32 *args)
2405 {
2406 	struct bpf_sock_ops_kern sock_ops;
2407 	int ret;
2408 
2409 	memset(&sock_ops, 0, offsetof(struct bpf_sock_ops_kern, temp));
2410 	if (sk_fullsock(sk)) {
2411 		sock_ops.is_fullsock = 1;
2412 		sock_owned_by_me(sk);
2413 	}
2414 
2415 	sock_ops.sk = sk;
2416 	sock_ops.op = op;
2417 	if (nargs > 0)
2418 		memcpy(sock_ops.args, args, nargs * sizeof(*args));
2419 
2420 	ret = BPF_CGROUP_RUN_PROG_SOCK_OPS(&sock_ops);
2421 	if (ret == 0)
2422 		ret = sock_ops.reply;
2423 	else
2424 		ret = -1;
2425 	return ret;
2426 }
2427 
2428 static inline int tcp_call_bpf_2arg(struct sock *sk, int op, u32 arg1, u32 arg2)
2429 {
2430 	u32 args[2] = {arg1, arg2};
2431 
2432 	return tcp_call_bpf(sk, op, 2, args);
2433 }
2434 
2435 static inline int tcp_call_bpf_3arg(struct sock *sk, int op, u32 arg1, u32 arg2,
2436 				    u32 arg3)
2437 {
2438 	u32 args[3] = {arg1, arg2, arg3};
2439 
2440 	return tcp_call_bpf(sk, op, 3, args);
2441 }
2442 
2443 #else
2444 static inline int tcp_call_bpf(struct sock *sk, int op, u32 nargs, u32 *args)
2445 {
2446 	return -EPERM;
2447 }
2448 
2449 static inline int tcp_call_bpf_2arg(struct sock *sk, int op, u32 arg1, u32 arg2)
2450 {
2451 	return -EPERM;
2452 }
2453 
2454 static inline int tcp_call_bpf_3arg(struct sock *sk, int op, u32 arg1, u32 arg2,
2455 				    u32 arg3)
2456 {
2457 	return -EPERM;
2458 }
2459 
2460 #endif
2461 
2462 static inline u32 tcp_timeout_init(struct sock *sk)
2463 {
2464 	int timeout;
2465 
2466 	timeout = tcp_call_bpf(sk, BPF_SOCK_OPS_TIMEOUT_INIT, 0, NULL);
2467 
2468 	if (timeout <= 0)
2469 		timeout = TCP_TIMEOUT_INIT;
2470 	return min_t(int, timeout, TCP_RTO_MAX);
2471 }
2472 
2473 static inline u32 tcp_rwnd_init_bpf(struct sock *sk)
2474 {
2475 	int rwnd;
2476 
2477 	rwnd = tcp_call_bpf(sk, BPF_SOCK_OPS_RWND_INIT, 0, NULL);
2478 
2479 	if (rwnd < 0)
2480 		rwnd = 0;
2481 	return rwnd;
2482 }
2483 
2484 static inline bool tcp_bpf_ca_needs_ecn(struct sock *sk)
2485 {
2486 	return (tcp_call_bpf(sk, BPF_SOCK_OPS_NEEDS_ECN, 0, NULL) == 1);
2487 }
2488 
2489 static inline void tcp_bpf_rtt(struct sock *sk)
2490 {
2491 	if (BPF_SOCK_OPS_TEST_FLAG(tcp_sk(sk), BPF_SOCK_OPS_RTT_CB_FLAG))
2492 		tcp_call_bpf(sk, BPF_SOCK_OPS_RTT_CB, 0, NULL);
2493 }
2494 
2495 #if IS_ENABLED(CONFIG_SMC)
2496 extern struct static_key_false tcp_have_smc;
2497 #endif
2498 
2499 #if IS_ENABLED(CONFIG_TLS_DEVICE)
2500 void clean_acked_data_enable(struct inet_connection_sock *icsk,
2501 			     void (*cad)(struct sock *sk, u32 ack_seq));
2502 void clean_acked_data_disable(struct inet_connection_sock *icsk);
2503 void clean_acked_data_flush(void);
2504 #endif
2505 
2506 DECLARE_STATIC_KEY_FALSE(tcp_tx_delay_enabled);
2507 static inline void tcp_add_tx_delay(struct sk_buff *skb,
2508 				    const struct tcp_sock *tp)
2509 {
2510 	if (static_branch_unlikely(&tcp_tx_delay_enabled))
2511 		skb->skb_mstamp_ns += (u64)tp->tcp_tx_delay * NSEC_PER_USEC;
2512 }
2513 
2514 /* Compute Earliest Departure Time for some control packets
2515  * like ACK or RST for TIME_WAIT or non ESTABLISHED sockets.
2516  */
2517 static inline u64 tcp_transmit_time(const struct sock *sk)
2518 {
2519 	if (static_branch_unlikely(&tcp_tx_delay_enabled)) {
2520 		u32 delay = (sk->sk_state == TCP_TIME_WAIT) ?
2521 			tcp_twsk(sk)->tw_tx_delay : tcp_sk(sk)->tcp_tx_delay;
2522 
2523 		return tcp_clock_ns() + (u64)delay * NSEC_PER_USEC;
2524 	}
2525 	return 0;
2526 }
2527 
2528 #endif	/* _TCP_H */
2529