xref: /openbmc/linux/include/net/tcp.h (revision 5a244f48)
1 /*
2  * INET		An implementation of the TCP/IP protocol suite for the LINUX
3  *		operating system.  INET is implemented using the  BSD Socket
4  *		interface as the means of communication with the user level.
5  *
6  *		Definitions for the TCP module.
7  *
8  * Version:	@(#)tcp.h	1.0.5	05/23/93
9  *
10  * Authors:	Ross Biro
11  *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
12  *
13  *		This program is free software; you can redistribute it and/or
14  *		modify it under the terms of the GNU General Public License
15  *		as published by the Free Software Foundation; either version
16  *		2 of the License, or (at your option) any later version.
17  */
18 #ifndef _TCP_H
19 #define _TCP_H
20 
21 #define FASTRETRANS_DEBUG 1
22 
23 #include <linux/list.h>
24 #include <linux/tcp.h>
25 #include <linux/bug.h>
26 #include <linux/slab.h>
27 #include <linux/cache.h>
28 #include <linux/percpu.h>
29 #include <linux/skbuff.h>
30 #include <linux/cryptohash.h>
31 #include <linux/kref.h>
32 #include <linux/ktime.h>
33 
34 #include <net/inet_connection_sock.h>
35 #include <net/inet_timewait_sock.h>
36 #include <net/inet_hashtables.h>
37 #include <net/checksum.h>
38 #include <net/request_sock.h>
39 #include <net/sock.h>
40 #include <net/snmp.h>
41 #include <net/ip.h>
42 #include <net/tcp_states.h>
43 #include <net/inet_ecn.h>
44 #include <net/dst.h>
45 
46 #include <linux/seq_file.h>
47 #include <linux/memcontrol.h>
48 
49 #include <linux/bpf.h>
50 #include <linux/filter.h>
51 #include <linux/bpf-cgroup.h>
52 
53 extern struct inet_hashinfo tcp_hashinfo;
54 
55 extern struct percpu_counter tcp_orphan_count;
56 void tcp_time_wait(struct sock *sk, int state, int timeo);
57 
58 #define MAX_TCP_HEADER	(128 + MAX_HEADER)
59 #define MAX_TCP_OPTION_SPACE 40
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 least 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 
132 #define TCP_DELACK_MAX	((unsigned)(HZ/5))	/* maximal time to delay before sending an ACK */
133 #if HZ >= 100
134 #define TCP_DELACK_MIN	((unsigned)(HZ/25))	/* minimal time to delay before sending an ACK */
135 #define TCP_ATO_MIN	((unsigned)(HZ/25))
136 #else
137 #define TCP_DELACK_MIN	4U
138 #define TCP_ATO_MIN	4U
139 #endif
140 #define TCP_RTO_MAX	((unsigned)(120*HZ))
141 #define TCP_RTO_MIN	((unsigned)(HZ/5))
142 #define TCP_TIMEOUT_MIN	(2U) /* Min timeout for TCP timers in jiffies */
143 #define TCP_TIMEOUT_INIT ((unsigned)(1*HZ))	/* RFC6298 2.1 initial RTO value	*/
144 #define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ))	/* RFC 1122 initial RTO value, now
145 						 * used as a fallback RTO for the
146 						 * initial data transmission if no
147 						 * valid RTT sample has been acquired,
148 						 * most likely due to retrans in 3WHS.
149 						 */
150 
151 #define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes
152 					                 * for local resources.
153 					                 */
154 #define TCP_KEEPALIVE_TIME	(120*60*HZ)	/* two hours */
155 #define TCP_KEEPALIVE_PROBES	9		/* Max of 9 keepalive probes	*/
156 #define TCP_KEEPALIVE_INTVL	(75*HZ)
157 
158 #define MAX_TCP_KEEPIDLE	32767
159 #define MAX_TCP_KEEPINTVL	32767
160 #define MAX_TCP_KEEPCNT		127
161 #define MAX_TCP_SYNCNT		127
162 
163 #define TCP_SYNQ_INTERVAL	(HZ/5)	/* Period of SYNACK timer */
164 
165 #define TCP_PAWS_24DAYS	(60 * 60 * 24 * 24)
166 #define TCP_PAWS_MSL	60		/* Per-host timestamps are invalidated
167 					 * after this time. It should be equal
168 					 * (or greater than) TCP_TIMEWAIT_LEN
169 					 * to provide reliability equal to one
170 					 * provided by timewait state.
171 					 */
172 #define TCP_PAWS_WINDOW	1		/* Replay window for per-host
173 					 * timestamps. It must be less than
174 					 * minimal timewait lifetime.
175 					 */
176 /*
177  *	TCP option
178  */
179 
180 #define TCPOPT_NOP		1	/* Padding */
181 #define TCPOPT_EOL		0	/* End of options */
182 #define TCPOPT_MSS		2	/* Segment size negotiating */
183 #define TCPOPT_WINDOW		3	/* Window scaling */
184 #define TCPOPT_SACK_PERM        4       /* SACK Permitted */
185 #define TCPOPT_SACK             5       /* SACK Block */
186 #define TCPOPT_TIMESTAMP	8	/* Better RTT estimations/PAWS */
187 #define TCPOPT_MD5SIG		19	/* MD5 Signature (RFC2385) */
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 
195 /*
196  *     TCP option lengths
197  */
198 
199 #define TCPOLEN_MSS            4
200 #define TCPOLEN_WINDOW         3
201 #define TCPOLEN_SACK_PERM      2
202 #define TCPOLEN_TIMESTAMP      10
203 #define TCPOLEN_MD5SIG         18
204 #define TCPOLEN_FASTOPEN_BASE  2
205 #define TCPOLEN_EXP_FASTOPEN_BASE  4
206 
207 /* But this is what stacks really send out. */
208 #define TCPOLEN_TSTAMP_ALIGNED		12
209 #define TCPOLEN_WSCALE_ALIGNED		4
210 #define TCPOLEN_SACKPERM_ALIGNED	4
211 #define TCPOLEN_SACK_BASE		2
212 #define TCPOLEN_SACK_BASE_ALIGNED	4
213 #define TCPOLEN_SACK_PERBLOCK		8
214 #define TCPOLEN_MD5SIG_ALIGNED		20
215 #define TCPOLEN_MSS_ALIGNED		4
216 
217 /* Flags in tp->nonagle */
218 #define TCP_NAGLE_OFF		1	/* Nagle's algo is disabled */
219 #define TCP_NAGLE_CORK		2	/* Socket is corked	    */
220 #define TCP_NAGLE_PUSH		4	/* Cork is overridden for already queued data */
221 
222 /* TCP thin-stream limits */
223 #define TCP_THIN_LINEAR_RETRIES 6       /* After 6 linear retries, do exp. backoff */
224 
225 /* TCP initial congestion window as per rfc6928 */
226 #define TCP_INIT_CWND		10
227 
228 /* Bit Flags for sysctl_tcp_fastopen */
229 #define	TFO_CLIENT_ENABLE	1
230 #define	TFO_SERVER_ENABLE	2
231 #define	TFO_CLIENT_NO_COOKIE	4	/* Data in SYN w/o cookie option */
232 
233 /* Accept SYN data w/o any cookie option */
234 #define	TFO_SERVER_COOKIE_NOT_REQD	0x200
235 
236 /* Force enable TFO on all listeners, i.e., not requiring the
237  * TCP_FASTOPEN socket option.
238  */
239 #define	TFO_SERVER_WO_SOCKOPT1	0x400
240 
241 
242 /* sysctl variables for tcp */
243 extern int sysctl_tcp_fastopen;
244 extern int sysctl_tcp_retrans_collapse;
245 extern int sysctl_tcp_stdurg;
246 extern int sysctl_tcp_rfc1337;
247 extern int sysctl_tcp_abort_on_overflow;
248 extern int sysctl_tcp_max_orphans;
249 extern int sysctl_tcp_fack;
250 extern int sysctl_tcp_reordering;
251 extern int sysctl_tcp_max_reordering;
252 extern int sysctl_tcp_dsack;
253 extern long sysctl_tcp_mem[3];
254 extern int sysctl_tcp_wmem[3];
255 extern int sysctl_tcp_rmem[3];
256 extern int sysctl_tcp_app_win;
257 extern int sysctl_tcp_adv_win_scale;
258 extern int sysctl_tcp_frto;
259 extern int sysctl_tcp_nometrics_save;
260 extern int sysctl_tcp_moderate_rcvbuf;
261 extern int sysctl_tcp_tso_win_divisor;
262 extern int sysctl_tcp_workaround_signed_windows;
263 extern int sysctl_tcp_slow_start_after_idle;
264 extern int sysctl_tcp_thin_linear_timeouts;
265 extern int sysctl_tcp_thin_dupack;
266 extern int sysctl_tcp_early_retrans;
267 extern int sysctl_tcp_recovery;
268 #define TCP_RACK_LOSS_DETECTION  0x1 /* Use RACK to detect losses */
269 
270 extern int sysctl_tcp_limit_output_bytes;
271 extern int sysctl_tcp_challenge_ack_limit;
272 extern int sysctl_tcp_min_tso_segs;
273 extern int sysctl_tcp_min_rtt_wlen;
274 extern int sysctl_tcp_autocorking;
275 extern int sysctl_tcp_invalid_ratelimit;
276 extern int sysctl_tcp_pacing_ss_ratio;
277 extern int sysctl_tcp_pacing_ca_ratio;
278 
279 extern atomic_long_t tcp_memory_allocated;
280 extern struct percpu_counter tcp_sockets_allocated;
281 extern unsigned long tcp_memory_pressure;
282 
283 /* optimized version of sk_under_memory_pressure() for TCP sockets */
284 static inline bool tcp_under_memory_pressure(const struct sock *sk)
285 {
286 	if (mem_cgroup_sockets_enabled && sk->sk_memcg &&
287 	    mem_cgroup_under_socket_pressure(sk->sk_memcg))
288 		return true;
289 
290 	return tcp_memory_pressure;
291 }
292 /*
293  * The next routines deal with comparing 32 bit unsigned ints
294  * and worry about wraparound (automatic with unsigned arithmetic).
295  */
296 
297 static inline bool before(__u32 seq1, __u32 seq2)
298 {
299         return (__s32)(seq1-seq2) < 0;
300 }
301 #define after(seq2, seq1) 	before(seq1, seq2)
302 
303 /* is s2<=s1<=s3 ? */
304 static inline bool between(__u32 seq1, __u32 seq2, __u32 seq3)
305 {
306 	return seq3 - seq2 >= seq1 - seq2;
307 }
308 
309 static inline bool tcp_out_of_memory(struct sock *sk)
310 {
311 	if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
312 	    sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2))
313 		return true;
314 	return false;
315 }
316 
317 void sk_forced_mem_schedule(struct sock *sk, int size);
318 
319 static inline bool tcp_too_many_orphans(struct sock *sk, int shift)
320 {
321 	struct percpu_counter *ocp = sk->sk_prot->orphan_count;
322 	int orphans = percpu_counter_read_positive(ocp);
323 
324 	if (orphans << shift > sysctl_tcp_max_orphans) {
325 		orphans = percpu_counter_sum_positive(ocp);
326 		if (orphans << shift > sysctl_tcp_max_orphans)
327 			return true;
328 	}
329 	return false;
330 }
331 
332 bool tcp_check_oom(struct sock *sk, int shift);
333 
334 
335 extern struct proto tcp_prot;
336 
337 #define TCP_INC_STATS(net, field)	SNMP_INC_STATS((net)->mib.tcp_statistics, field)
338 #define __TCP_INC_STATS(net, field)	__SNMP_INC_STATS((net)->mib.tcp_statistics, field)
339 #define TCP_DEC_STATS(net, field)	SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
340 #define TCP_ADD_STATS(net, field, val)	SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
341 
342 void tcp_tasklet_init(void);
343 
344 void tcp_v4_err(struct sk_buff *skb, u32);
345 
346 void tcp_shutdown(struct sock *sk, int how);
347 
348 int tcp_v4_early_demux(struct sk_buff *skb);
349 int tcp_v4_rcv(struct sk_buff *skb);
350 
351 int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
352 int tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size);
353 int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size);
354 int tcp_sendpage(struct sock *sk, struct page *page, int offset, size_t size,
355 		 int flags);
356 int tcp_sendpage_locked(struct sock *sk, struct page *page, int offset,
357 			size_t size, int flags);
358 ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
359 		 size_t size, int flags);
360 void tcp_release_cb(struct sock *sk);
361 void tcp_wfree(struct sk_buff *skb);
362 void tcp_write_timer_handler(struct sock *sk);
363 void tcp_delack_timer_handler(struct sock *sk);
364 int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
365 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb);
366 void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
367 			 const struct tcphdr *th);
368 void tcp_rcv_space_adjust(struct sock *sk);
369 int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
370 void tcp_twsk_destructor(struct sock *sk);
371 ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
372 			struct pipe_inode_info *pipe, size_t len,
373 			unsigned int flags);
374 
375 static inline void tcp_dec_quickack_mode(struct sock *sk,
376 					 const unsigned int pkts)
377 {
378 	struct inet_connection_sock *icsk = inet_csk(sk);
379 
380 	if (icsk->icsk_ack.quick) {
381 		if (pkts >= icsk->icsk_ack.quick) {
382 			icsk->icsk_ack.quick = 0;
383 			/* Leaving quickack mode we deflate ATO. */
384 			icsk->icsk_ack.ato   = TCP_ATO_MIN;
385 		} else
386 			icsk->icsk_ack.quick -= pkts;
387 	}
388 }
389 
390 #define	TCP_ECN_OK		1
391 #define	TCP_ECN_QUEUE_CWR	2
392 #define	TCP_ECN_DEMAND_CWR	4
393 #define	TCP_ECN_SEEN		8
394 
395 enum tcp_tw_status {
396 	TCP_TW_SUCCESS = 0,
397 	TCP_TW_RST = 1,
398 	TCP_TW_ACK = 2,
399 	TCP_TW_SYN = 3
400 };
401 
402 
403 enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
404 					      struct sk_buff *skb,
405 					      const struct tcphdr *th);
406 struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
407 			   struct request_sock *req, bool fastopen);
408 int tcp_child_process(struct sock *parent, struct sock *child,
409 		      struct sk_buff *skb);
410 void tcp_enter_loss(struct sock *sk);
411 void tcp_cwnd_reduction(struct sock *sk, int newly_acked_sacked, int flag);
412 void tcp_clear_retrans(struct tcp_sock *tp);
413 void tcp_update_metrics(struct sock *sk);
414 void tcp_init_metrics(struct sock *sk);
415 void tcp_metrics_init(void);
416 bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst);
417 void tcp_disable_fack(struct tcp_sock *tp);
418 void tcp_close(struct sock *sk, long timeout);
419 void tcp_init_sock(struct sock *sk);
420 unsigned int tcp_poll(struct file *file, struct socket *sock,
421 		      struct poll_table_struct *wait);
422 int tcp_getsockopt(struct sock *sk, int level, int optname,
423 		   char __user *optval, int __user *optlen);
424 int tcp_setsockopt(struct sock *sk, int level, int optname,
425 		   char __user *optval, unsigned int optlen);
426 int compat_tcp_getsockopt(struct sock *sk, int level, int optname,
427 			  char __user *optval, int __user *optlen);
428 int compat_tcp_setsockopt(struct sock *sk, int level, int optname,
429 			  char __user *optval, unsigned int optlen);
430 void tcp_set_keepalive(struct sock *sk, int val);
431 void tcp_syn_ack_timeout(const struct request_sock *req);
432 int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
433 		int flags, int *addr_len);
434 void tcp_parse_options(const struct net *net, const struct sk_buff *skb,
435 		       struct tcp_options_received *opt_rx,
436 		       int estab, struct tcp_fastopen_cookie *foc);
437 const u8 *tcp_parse_md5sig_option(const struct tcphdr *th);
438 
439 /*
440  *	TCP v4 functions exported for the inet6 API
441  */
442 
443 void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
444 void tcp_v4_mtu_reduced(struct sock *sk);
445 void tcp_req_err(struct sock *sk, u32 seq, bool abort);
446 int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
447 struct sock *tcp_create_openreq_child(const struct sock *sk,
448 				      struct request_sock *req,
449 				      struct sk_buff *skb);
450 void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst);
451 struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
452 				  struct request_sock *req,
453 				  struct dst_entry *dst,
454 				  struct request_sock *req_unhash,
455 				  bool *own_req);
456 int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
457 int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
458 int tcp_connect(struct sock *sk);
459 enum tcp_synack_type {
460 	TCP_SYNACK_NORMAL,
461 	TCP_SYNACK_FASTOPEN,
462 	TCP_SYNACK_COOKIE,
463 };
464 struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
465 				struct request_sock *req,
466 				struct tcp_fastopen_cookie *foc,
467 				enum tcp_synack_type synack_type);
468 int tcp_disconnect(struct sock *sk, int flags);
469 
470 void tcp_finish_connect(struct sock *sk, struct sk_buff *skb);
471 int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size);
472 void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
473 
474 /* From syncookies.c */
475 struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
476 				 struct request_sock *req,
477 				 struct dst_entry *dst, u32 tsoff);
478 int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
479 		      u32 cookie);
480 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
481 #ifdef CONFIG_SYN_COOKIES
482 
483 /* Syncookies use a monotonic timer which increments every 60 seconds.
484  * This counter is used both as a hash input and partially encoded into
485  * the cookie value.  A cookie is only validated further if the delta
486  * between the current counter value and the encoded one is less than this,
487  * i.e. a sent cookie is valid only at most for 2*60 seconds (or less if
488  * the counter advances immediately after a cookie is generated).
489  */
490 #define MAX_SYNCOOKIE_AGE	2
491 #define TCP_SYNCOOKIE_PERIOD	(60 * HZ)
492 #define TCP_SYNCOOKIE_VALID	(MAX_SYNCOOKIE_AGE * TCP_SYNCOOKIE_PERIOD)
493 
494 /* syncookies: remember time of last synqueue overflow
495  * But do not dirty this field too often (once per second is enough)
496  * It is racy as we do not hold a lock, but race is very minor.
497  */
498 static inline void tcp_synq_overflow(const struct sock *sk)
499 {
500 	unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
501 	unsigned long now = jiffies;
502 
503 	if (time_after(now, last_overflow + HZ))
504 		tcp_sk(sk)->rx_opt.ts_recent_stamp = now;
505 }
506 
507 /* syncookies: no recent synqueue overflow on this listening socket? */
508 static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
509 {
510 	unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
511 
512 	return time_after(jiffies, last_overflow + TCP_SYNCOOKIE_VALID);
513 }
514 
515 static inline u32 tcp_cookie_time(void)
516 {
517 	u64 val = get_jiffies_64();
518 
519 	do_div(val, TCP_SYNCOOKIE_PERIOD);
520 	return val;
521 }
522 
523 u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
524 			      u16 *mssp);
525 __u32 cookie_v4_init_sequence(const struct sk_buff *skb, __u16 *mss);
526 u64 cookie_init_timestamp(struct request_sock *req);
527 bool cookie_timestamp_decode(const struct net *net,
528 			     struct tcp_options_received *opt);
529 bool cookie_ecn_ok(const struct tcp_options_received *opt,
530 		   const struct net *net, const struct dst_entry *dst);
531 
532 /* From net/ipv6/syncookies.c */
533 int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th,
534 		      u32 cookie);
535 struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
536 
537 u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
538 			      const struct tcphdr *th, u16 *mssp);
539 __u32 cookie_v6_init_sequence(const struct sk_buff *skb, __u16 *mss);
540 #endif
541 /* tcp_output.c */
542 
543 u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
544 		     int min_tso_segs);
545 void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
546 			       int nonagle);
547 int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs);
548 int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs);
549 void tcp_retransmit_timer(struct sock *sk);
550 void tcp_xmit_retransmit_queue(struct sock *);
551 void tcp_simple_retransmit(struct sock *);
552 void tcp_enter_recovery(struct sock *sk, bool ece_ack);
553 int tcp_trim_head(struct sock *, struct sk_buff *, u32);
554 int tcp_fragment(struct sock *, struct sk_buff *, u32, unsigned int, gfp_t);
555 
556 void tcp_send_probe0(struct sock *);
557 void tcp_send_partial(struct sock *);
558 int tcp_write_wakeup(struct sock *, int mib);
559 void tcp_send_fin(struct sock *sk);
560 void tcp_send_active_reset(struct sock *sk, gfp_t priority);
561 int tcp_send_synack(struct sock *);
562 void tcp_push_one(struct sock *, unsigned int mss_now);
563 void tcp_send_ack(struct sock *sk);
564 void tcp_send_delayed_ack(struct sock *sk);
565 void tcp_send_loss_probe(struct sock *sk);
566 bool tcp_schedule_loss_probe(struct sock *sk);
567 void tcp_skb_collapse_tstamp(struct sk_buff *skb,
568 			     const struct sk_buff *next_skb);
569 
570 /* tcp_input.c */
571 void tcp_rearm_rto(struct sock *sk);
572 void tcp_synack_rtt_meas(struct sock *sk, struct request_sock *req);
573 void tcp_reset(struct sock *sk);
574 void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, struct sk_buff *skb);
575 void tcp_fin(struct sock *sk);
576 
577 /* tcp_timer.c */
578 void tcp_init_xmit_timers(struct sock *);
579 static inline void tcp_clear_xmit_timers(struct sock *sk)
580 {
581 	hrtimer_cancel(&tcp_sk(sk)->pacing_timer);
582 	inet_csk_clear_xmit_timers(sk);
583 }
584 
585 unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
586 unsigned int tcp_current_mss(struct sock *sk);
587 
588 /* Bound MSS / TSO packet size with the half of the window */
589 static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
590 {
591 	int cutoff;
592 
593 	/* When peer uses tiny windows, there is no use in packetizing
594 	 * to sub-MSS pieces for the sake of SWS or making sure there
595 	 * are enough packets in the pipe for fast recovery.
596 	 *
597 	 * On the other hand, for extremely large MSS devices, handling
598 	 * smaller than MSS windows in this way does make sense.
599 	 */
600 	if (tp->max_window > TCP_MSS_DEFAULT)
601 		cutoff = (tp->max_window >> 1);
602 	else
603 		cutoff = tp->max_window;
604 
605 	if (cutoff && pktsize > cutoff)
606 		return max_t(int, cutoff, 68U - tp->tcp_header_len);
607 	else
608 		return pktsize;
609 }
610 
611 /* tcp.c */
612 void tcp_get_info(struct sock *, struct tcp_info *);
613 
614 /* Read 'sendfile()'-style from a TCP socket */
615 int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
616 		  sk_read_actor_t recv_actor);
617 
618 void tcp_initialize_rcv_mss(struct sock *sk);
619 
620 int tcp_mtu_to_mss(struct sock *sk, int pmtu);
621 int tcp_mss_to_mtu(struct sock *sk, int mss);
622 void tcp_mtup_init(struct sock *sk);
623 void tcp_init_buffer_space(struct sock *sk);
624 
625 static inline void tcp_bound_rto(const struct sock *sk)
626 {
627 	if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
628 		inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
629 }
630 
631 static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
632 {
633 	return usecs_to_jiffies((tp->srtt_us >> 3) + tp->rttvar_us);
634 }
635 
636 static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
637 {
638 	tp->pred_flags = htonl((tp->tcp_header_len << 26) |
639 			       ntohl(TCP_FLAG_ACK) |
640 			       snd_wnd);
641 }
642 
643 static inline void tcp_fast_path_on(struct tcp_sock *tp)
644 {
645 	__tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
646 }
647 
648 static inline void tcp_fast_path_check(struct sock *sk)
649 {
650 	struct tcp_sock *tp = tcp_sk(sk);
651 
652 	if (RB_EMPTY_ROOT(&tp->out_of_order_queue) &&
653 	    tp->rcv_wnd &&
654 	    atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
655 	    !tp->urg_data)
656 		tcp_fast_path_on(tp);
657 }
658 
659 /* Compute the actual rto_min value */
660 static inline u32 tcp_rto_min(struct sock *sk)
661 {
662 	const struct dst_entry *dst = __sk_dst_get(sk);
663 	u32 rto_min = TCP_RTO_MIN;
664 
665 	if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
666 		rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
667 	return rto_min;
668 }
669 
670 static inline u32 tcp_rto_min_us(struct sock *sk)
671 {
672 	return jiffies_to_usecs(tcp_rto_min(sk));
673 }
674 
675 static inline bool tcp_ca_dst_locked(const struct dst_entry *dst)
676 {
677 	return dst_metric_locked(dst, RTAX_CC_ALGO);
678 }
679 
680 /* Minimum RTT in usec. ~0 means not available. */
681 static inline u32 tcp_min_rtt(const struct tcp_sock *tp)
682 {
683 	return minmax_get(&tp->rtt_min);
684 }
685 
686 /* Compute the actual receive window we are currently advertising.
687  * Rcv_nxt can be after the window if our peer push more data
688  * than the offered window.
689  */
690 static inline u32 tcp_receive_window(const struct tcp_sock *tp)
691 {
692 	s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;
693 
694 	if (win < 0)
695 		win = 0;
696 	return (u32) win;
697 }
698 
699 /* Choose a new window, without checks for shrinking, and without
700  * scaling applied to the result.  The caller does these things
701  * if necessary.  This is a "raw" window selection.
702  */
703 u32 __tcp_select_window(struct sock *sk);
704 
705 void tcp_send_window_probe(struct sock *sk);
706 
707 /* TCP uses 32bit jiffies to save some space.
708  * Note that this is different from tcp_time_stamp, which
709  * historically has been the same until linux-4.13.
710  */
711 #define tcp_jiffies32 ((u32)jiffies)
712 
713 /*
714  * Deliver a 32bit value for TCP timestamp option (RFC 7323)
715  * It is no longer tied to jiffies, but to 1 ms clock.
716  * Note: double check if you want to use tcp_jiffies32 instead of this.
717  */
718 #define TCP_TS_HZ	1000
719 
720 static inline u64 tcp_clock_ns(void)
721 {
722 	return local_clock();
723 }
724 
725 static inline u64 tcp_clock_us(void)
726 {
727 	return div_u64(tcp_clock_ns(), NSEC_PER_USEC);
728 }
729 
730 /* This should only be used in contexts where tp->tcp_mstamp is up to date */
731 static inline u32 tcp_time_stamp(const struct tcp_sock *tp)
732 {
733 	return div_u64(tp->tcp_mstamp, USEC_PER_SEC / TCP_TS_HZ);
734 }
735 
736 /* Could use tcp_clock_us() / 1000, but this version uses a single divide */
737 static inline u32 tcp_time_stamp_raw(void)
738 {
739 	return div_u64(tcp_clock_ns(), NSEC_PER_SEC / TCP_TS_HZ);
740 }
741 
742 
743 /* Refresh 1us clock of a TCP socket,
744  * ensuring monotically increasing values.
745  */
746 static inline void tcp_mstamp_refresh(struct tcp_sock *tp)
747 {
748 	u64 val = tcp_clock_us();
749 
750 	if (val > tp->tcp_mstamp)
751 		tp->tcp_mstamp = val;
752 }
753 
754 static inline u32 tcp_stamp_us_delta(u64 t1, u64 t0)
755 {
756 	return max_t(s64, t1 - t0, 0);
757 }
758 
759 static inline u32 tcp_skb_timestamp(const struct sk_buff *skb)
760 {
761 	return div_u64(skb->skb_mstamp, USEC_PER_SEC / TCP_TS_HZ);
762 }
763 
764 
765 #define tcp_flag_byte(th) (((u_int8_t *)th)[13])
766 
767 #define TCPHDR_FIN 0x01
768 #define TCPHDR_SYN 0x02
769 #define TCPHDR_RST 0x04
770 #define TCPHDR_PSH 0x08
771 #define TCPHDR_ACK 0x10
772 #define TCPHDR_URG 0x20
773 #define TCPHDR_ECE 0x40
774 #define TCPHDR_CWR 0x80
775 
776 #define TCPHDR_SYN_ECN	(TCPHDR_SYN | TCPHDR_ECE | TCPHDR_CWR)
777 
778 /* This is what the send packet queuing engine uses to pass
779  * TCP per-packet control information to the transmission code.
780  * We also store the host-order sequence numbers in here too.
781  * This is 44 bytes if IPV6 is enabled.
782  * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately.
783  */
784 struct tcp_skb_cb {
785 	__u32		seq;		/* Starting sequence number	*/
786 	__u32		end_seq;	/* SEQ + FIN + SYN + datalen	*/
787 	union {
788 		/* Note : tcp_tw_isn is used in input path only
789 		 *	  (isn chosen by tcp_timewait_state_process())
790 		 *
791 		 * 	  tcp_gso_segs/size are used in write queue only,
792 		 *	  cf tcp_skb_pcount()/tcp_skb_mss()
793 		 */
794 		__u32		tcp_tw_isn;
795 		struct {
796 			u16	tcp_gso_segs;
797 			u16	tcp_gso_size;
798 		};
799 
800 		/* Used to stash the receive timestamp while this skb is in the
801 		 * out of order queue, as skb->tstamp is overwritten by the
802 		 * rbnode.
803 		 */
804 		ktime_t		swtstamp;
805 	};
806 	__u8		tcp_flags;	/* TCP header flags. (tcp[13])	*/
807 
808 	__u8		sacked;		/* State flags for SACK/FACK.	*/
809 #define TCPCB_SACKED_ACKED	0x01	/* SKB ACK'd by a SACK block	*/
810 #define TCPCB_SACKED_RETRANS	0x02	/* SKB retransmitted		*/
811 #define TCPCB_LOST		0x04	/* SKB is lost			*/
812 #define TCPCB_TAGBITS		0x07	/* All tag bits			*/
813 #define TCPCB_REPAIRED		0x10	/* SKB repaired (no skb_mstamp)	*/
814 #define TCPCB_EVER_RETRANS	0x80	/* Ever retransmitted frame	*/
815 #define TCPCB_RETRANS		(TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS| \
816 				TCPCB_REPAIRED)
817 
818 	__u8		ip_dsfield;	/* IPv4 tos or IPv6 dsfield	*/
819 	__u8		txstamp_ack:1,	/* Record TX timestamp for ack? */
820 			eor:1,		/* Is skb MSG_EOR marked? */
821 			has_rxtstamp:1,	/* SKB has a RX timestamp	*/
822 			unused:5;
823 	__u32		ack_seq;	/* Sequence number ACK'd	*/
824 	union {
825 		struct {
826 			/* There is space for up to 24 bytes */
827 			__u32 in_flight:30,/* Bytes in flight at transmit */
828 			      is_app_limited:1, /* cwnd not fully used? */
829 			      unused:1;
830 			/* pkts S/ACKed so far upon tx of skb, incl retrans: */
831 			__u32 delivered;
832 			/* start of send pipeline phase */
833 			u64 first_tx_mstamp;
834 			/* when we reached the "delivered" count */
835 			u64 delivered_mstamp;
836 		} tx;   /* only used for outgoing skbs */
837 		union {
838 			struct inet_skb_parm	h4;
839 #if IS_ENABLED(CONFIG_IPV6)
840 			struct inet6_skb_parm	h6;
841 #endif
842 		} header;	/* For incoming skbs */
843 	};
844 };
845 
846 #define TCP_SKB_CB(__skb)	((struct tcp_skb_cb *)&((__skb)->cb[0]))
847 
848 
849 #if IS_ENABLED(CONFIG_IPV6)
850 /* This is the variant of inet6_iif() that must be used by TCP,
851  * as TCP moves IP6CB into a different location in skb->cb[]
852  */
853 static inline int tcp_v6_iif(const struct sk_buff *skb)
854 {
855 	bool l3_slave = ipv6_l3mdev_skb(TCP_SKB_CB(skb)->header.h6.flags);
856 
857 	return l3_slave ? skb->skb_iif : TCP_SKB_CB(skb)->header.h6.iif;
858 }
859 
860 /* TCP_SKB_CB reference means this can not be used from early demux */
861 static inline int tcp_v6_sdif(const struct sk_buff *skb)
862 {
863 #if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
864 	if (skb && ipv6_l3mdev_skb(TCP_SKB_CB(skb)->header.h6.flags))
865 		return TCP_SKB_CB(skb)->header.h6.iif;
866 #endif
867 	return 0;
868 }
869 #endif
870 
871 /* TCP_SKB_CB reference means this can not be used from early demux */
872 static inline bool inet_exact_dif_match(struct net *net, struct sk_buff *skb)
873 {
874 #if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
875 	if (!net->ipv4.sysctl_tcp_l3mdev_accept &&
876 	    skb && ipv4_l3mdev_skb(TCP_SKB_CB(skb)->header.h4.flags))
877 		return true;
878 #endif
879 	return false;
880 }
881 
882 /* TCP_SKB_CB reference means this can not be used from early demux */
883 static inline int tcp_v4_sdif(struct sk_buff *skb)
884 {
885 #if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
886 	if (skb && ipv4_l3mdev_skb(TCP_SKB_CB(skb)->header.h4.flags))
887 		return TCP_SKB_CB(skb)->header.h4.iif;
888 #endif
889 	return 0;
890 }
891 
892 /* Due to TSO, an SKB can be composed of multiple actual
893  * packets.  To keep these tracked properly, we use this.
894  */
895 static inline int tcp_skb_pcount(const struct sk_buff *skb)
896 {
897 	return TCP_SKB_CB(skb)->tcp_gso_segs;
898 }
899 
900 static inline void tcp_skb_pcount_set(struct sk_buff *skb, int segs)
901 {
902 	TCP_SKB_CB(skb)->tcp_gso_segs = segs;
903 }
904 
905 static inline void tcp_skb_pcount_add(struct sk_buff *skb, int segs)
906 {
907 	TCP_SKB_CB(skb)->tcp_gso_segs += segs;
908 }
909 
910 /* This is valid iff skb is in write queue and tcp_skb_pcount() > 1. */
911 static inline int tcp_skb_mss(const struct sk_buff *skb)
912 {
913 	return TCP_SKB_CB(skb)->tcp_gso_size;
914 }
915 
916 static inline bool tcp_skb_can_collapse_to(const struct sk_buff *skb)
917 {
918 	return likely(!TCP_SKB_CB(skb)->eor);
919 }
920 
921 /* Events passed to congestion control interface */
922 enum tcp_ca_event {
923 	CA_EVENT_TX_START,	/* first transmit when no packets in flight */
924 	CA_EVENT_CWND_RESTART,	/* congestion window restart */
925 	CA_EVENT_COMPLETE_CWR,	/* end of congestion recovery */
926 	CA_EVENT_LOSS,		/* loss timeout */
927 	CA_EVENT_ECN_NO_CE,	/* ECT set, but not CE marked */
928 	CA_EVENT_ECN_IS_CE,	/* received CE marked IP packet */
929 	CA_EVENT_DELAYED_ACK,	/* Delayed ack is sent */
930 	CA_EVENT_NON_DELAYED_ACK,
931 };
932 
933 /* Information about inbound ACK, passed to cong_ops->in_ack_event() */
934 enum tcp_ca_ack_event_flags {
935 	CA_ACK_SLOWPATH		= (1 << 0),	/* In slow path processing */
936 	CA_ACK_WIN_UPDATE	= (1 << 1),	/* ACK updated window */
937 	CA_ACK_ECE		= (1 << 2),	/* ECE bit is set on ack */
938 };
939 
940 /*
941  * Interface for adding new TCP congestion control handlers
942  */
943 #define TCP_CA_NAME_MAX	16
944 #define TCP_CA_MAX	128
945 #define TCP_CA_BUF_MAX	(TCP_CA_NAME_MAX*TCP_CA_MAX)
946 
947 #define TCP_CA_UNSPEC	0
948 
949 /* Algorithm can be set on socket without CAP_NET_ADMIN privileges */
950 #define TCP_CONG_NON_RESTRICTED 0x1
951 /* Requires ECN/ECT set on all packets */
952 #define TCP_CONG_NEEDS_ECN	0x2
953 
954 union tcp_cc_info;
955 
956 struct ack_sample {
957 	u32 pkts_acked;
958 	s32 rtt_us;
959 	u32 in_flight;
960 };
961 
962 /* A rate sample measures the number of (original/retransmitted) data
963  * packets delivered "delivered" over an interval of time "interval_us".
964  * The tcp_rate.c code fills in the rate sample, and congestion
965  * control modules that define a cong_control function to run at the end
966  * of ACK processing can optionally chose to consult this sample when
967  * setting cwnd and pacing rate.
968  * A sample is invalid if "delivered" or "interval_us" is negative.
969  */
970 struct rate_sample {
971 	u64  prior_mstamp; /* starting timestamp for interval */
972 	u32  prior_delivered;	/* tp->delivered at "prior_mstamp" */
973 	s32  delivered;		/* number of packets delivered over interval */
974 	long interval_us;	/* time for tp->delivered to incr "delivered" */
975 	long rtt_us;		/* RTT of last (S)ACKed packet (or -1) */
976 	int  losses;		/* number of packets marked lost upon ACK */
977 	u32  acked_sacked;	/* number of packets newly (S)ACKed upon ACK */
978 	u32  prior_in_flight;	/* in flight before this ACK */
979 	bool is_app_limited;	/* is sample from packet with bubble in pipe? */
980 	bool is_retrans;	/* is sample from retransmission? */
981 };
982 
983 struct tcp_congestion_ops {
984 	struct list_head	list;
985 	u32 key;
986 	u32 flags;
987 
988 	/* initialize private data (optional) */
989 	void (*init)(struct sock *sk);
990 	/* cleanup private data  (optional) */
991 	void (*release)(struct sock *sk);
992 
993 	/* return slow start threshold (required) */
994 	u32 (*ssthresh)(struct sock *sk);
995 	/* do new cwnd calculation (required) */
996 	void (*cong_avoid)(struct sock *sk, u32 ack, u32 acked);
997 	/* call before changing ca_state (optional) */
998 	void (*set_state)(struct sock *sk, u8 new_state);
999 	/* call when cwnd event occurs (optional) */
1000 	void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
1001 	/* call when ack arrives (optional) */
1002 	void (*in_ack_event)(struct sock *sk, u32 flags);
1003 	/* new value of cwnd after loss (required) */
1004 	u32  (*undo_cwnd)(struct sock *sk);
1005 	/* hook for packet ack accounting (optional) */
1006 	void (*pkts_acked)(struct sock *sk, const struct ack_sample *sample);
1007 	/* suggest number of segments for each skb to transmit (optional) */
1008 	u32 (*tso_segs_goal)(struct sock *sk);
1009 	/* returns the multiplier used in tcp_sndbuf_expand (optional) */
1010 	u32 (*sndbuf_expand)(struct sock *sk);
1011 	/* call when packets are delivered to update cwnd and pacing rate,
1012 	 * after all the ca_state processing. (optional)
1013 	 */
1014 	void (*cong_control)(struct sock *sk, const struct rate_sample *rs);
1015 	/* get info for inet_diag (optional) */
1016 	size_t (*get_info)(struct sock *sk, u32 ext, int *attr,
1017 			   union tcp_cc_info *info);
1018 
1019 	char 		name[TCP_CA_NAME_MAX];
1020 	struct module 	*owner;
1021 };
1022 
1023 int tcp_register_congestion_control(struct tcp_congestion_ops *type);
1024 void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
1025 
1026 void tcp_assign_congestion_control(struct sock *sk);
1027 void tcp_init_congestion_control(struct sock *sk);
1028 void tcp_cleanup_congestion_control(struct sock *sk);
1029 int tcp_set_default_congestion_control(const char *name);
1030 void tcp_get_default_congestion_control(char *name);
1031 void tcp_get_available_congestion_control(char *buf, size_t len);
1032 void tcp_get_allowed_congestion_control(char *buf, size_t len);
1033 int tcp_set_allowed_congestion_control(char *allowed);
1034 int tcp_set_congestion_control(struct sock *sk, const char *name, bool load, bool reinit);
1035 u32 tcp_slow_start(struct tcp_sock *tp, u32 acked);
1036 void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked);
1037 
1038 u32 tcp_reno_ssthresh(struct sock *sk);
1039 u32 tcp_reno_undo_cwnd(struct sock *sk);
1040 void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked);
1041 extern struct tcp_congestion_ops tcp_reno;
1042 
1043 struct tcp_congestion_ops *tcp_ca_find_key(u32 key);
1044 u32 tcp_ca_get_key_by_name(const char *name, bool *ecn_ca);
1045 #ifdef CONFIG_INET
1046 char *tcp_ca_get_name_by_key(u32 key, char *buffer);
1047 #else
1048 static inline char *tcp_ca_get_name_by_key(u32 key, char *buffer)
1049 {
1050 	return NULL;
1051 }
1052 #endif
1053 
1054 static inline bool tcp_ca_needs_ecn(const struct sock *sk)
1055 {
1056 	const struct inet_connection_sock *icsk = inet_csk(sk);
1057 
1058 	return icsk->icsk_ca_ops->flags & TCP_CONG_NEEDS_ECN;
1059 }
1060 
1061 static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
1062 {
1063 	struct inet_connection_sock *icsk = inet_csk(sk);
1064 
1065 	if (icsk->icsk_ca_ops->set_state)
1066 		icsk->icsk_ca_ops->set_state(sk, ca_state);
1067 	icsk->icsk_ca_state = ca_state;
1068 }
1069 
1070 static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
1071 {
1072 	const struct inet_connection_sock *icsk = inet_csk(sk);
1073 
1074 	if (icsk->icsk_ca_ops->cwnd_event)
1075 		icsk->icsk_ca_ops->cwnd_event(sk, event);
1076 }
1077 
1078 /* From tcp_rate.c */
1079 void tcp_rate_skb_sent(struct sock *sk, struct sk_buff *skb);
1080 void tcp_rate_skb_delivered(struct sock *sk, struct sk_buff *skb,
1081 			    struct rate_sample *rs);
1082 void tcp_rate_gen(struct sock *sk, u32 delivered, u32 lost,
1083 		  struct rate_sample *rs);
1084 void tcp_rate_check_app_limited(struct sock *sk);
1085 
1086 /* These functions determine how the current flow behaves in respect of SACK
1087  * handling. SACK is negotiated with the peer, and therefore it can vary
1088  * between different flows.
1089  *
1090  * tcp_is_sack - SACK enabled
1091  * tcp_is_reno - No SACK
1092  * tcp_is_fack - FACK enabled, implies SACK enabled
1093  */
1094 static inline int tcp_is_sack(const struct tcp_sock *tp)
1095 {
1096 	return tp->rx_opt.sack_ok;
1097 }
1098 
1099 static inline bool tcp_is_reno(const struct tcp_sock *tp)
1100 {
1101 	return !tcp_is_sack(tp);
1102 }
1103 
1104 static inline bool tcp_is_fack(const struct tcp_sock *tp)
1105 {
1106 	return tp->rx_opt.sack_ok & TCP_FACK_ENABLED;
1107 }
1108 
1109 static inline void tcp_enable_fack(struct tcp_sock *tp)
1110 {
1111 	tp->rx_opt.sack_ok |= TCP_FACK_ENABLED;
1112 }
1113 
1114 static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
1115 {
1116 	return tp->sacked_out + tp->lost_out;
1117 }
1118 
1119 /* This determines how many packets are "in the network" to the best
1120  * of our knowledge.  In many cases it is conservative, but where
1121  * detailed information is available from the receiver (via SACK
1122  * blocks etc.) we can make more aggressive calculations.
1123  *
1124  * Use this for decisions involving congestion control, use just
1125  * tp->packets_out to determine if the send queue is empty or not.
1126  *
1127  * Read this equation as:
1128  *
1129  *	"Packets sent once on transmission queue" MINUS
1130  *	"Packets left network, but not honestly ACKed yet" PLUS
1131  *	"Packets fast retransmitted"
1132  */
1133 static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
1134 {
1135 	return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
1136 }
1137 
1138 #define TCP_INFINITE_SSTHRESH	0x7fffffff
1139 
1140 static inline bool tcp_in_slow_start(const struct tcp_sock *tp)
1141 {
1142 	return tp->snd_cwnd < tp->snd_ssthresh;
1143 }
1144 
1145 static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
1146 {
1147 	return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
1148 }
1149 
1150 static inline bool tcp_in_cwnd_reduction(const struct sock *sk)
1151 {
1152 	return (TCPF_CA_CWR | TCPF_CA_Recovery) &
1153 	       (1 << inet_csk(sk)->icsk_ca_state);
1154 }
1155 
1156 /* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
1157  * The exception is cwnd reduction phase, when cwnd is decreasing towards
1158  * ssthresh.
1159  */
1160 static inline __u32 tcp_current_ssthresh(const struct sock *sk)
1161 {
1162 	const struct tcp_sock *tp = tcp_sk(sk);
1163 
1164 	if (tcp_in_cwnd_reduction(sk))
1165 		return tp->snd_ssthresh;
1166 	else
1167 		return max(tp->snd_ssthresh,
1168 			   ((tp->snd_cwnd >> 1) +
1169 			    (tp->snd_cwnd >> 2)));
1170 }
1171 
1172 /* Use define here intentionally to get WARN_ON location shown at the caller */
1173 #define tcp_verify_left_out(tp)	WARN_ON(tcp_left_out(tp) > tp->packets_out)
1174 
1175 void tcp_enter_cwr(struct sock *sk);
1176 __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst);
1177 
1178 /* The maximum number of MSS of available cwnd for which TSO defers
1179  * sending if not using sysctl_tcp_tso_win_divisor.
1180  */
1181 static inline __u32 tcp_max_tso_deferred_mss(const struct tcp_sock *tp)
1182 {
1183 	return 3;
1184 }
1185 
1186 /* Returns end sequence number of the receiver's advertised window */
1187 static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
1188 {
1189 	return tp->snd_una + tp->snd_wnd;
1190 }
1191 
1192 /* We follow the spirit of RFC2861 to validate cwnd but implement a more
1193  * flexible approach. The RFC suggests cwnd should not be raised unless
1194  * it was fully used previously. And that's exactly what we do in
1195  * congestion avoidance mode. But in slow start we allow cwnd to grow
1196  * as long as the application has used half the cwnd.
1197  * Example :
1198  *    cwnd is 10 (IW10), but application sends 9 frames.
1199  *    We allow cwnd to reach 18 when all frames are ACKed.
1200  * This check is safe because it's as aggressive as slow start which already
1201  * risks 100% overshoot. The advantage is that we discourage application to
1202  * either send more filler packets or data to artificially blow up the cwnd
1203  * usage, and allow application-limited process to probe bw more aggressively.
1204  */
1205 static inline bool tcp_is_cwnd_limited(const struct sock *sk)
1206 {
1207 	const struct tcp_sock *tp = tcp_sk(sk);
1208 
1209 	/* If in slow start, ensure cwnd grows to twice what was ACKed. */
1210 	if (tcp_in_slow_start(tp))
1211 		return tp->snd_cwnd < 2 * tp->max_packets_out;
1212 
1213 	return tp->is_cwnd_limited;
1214 }
1215 
1216 /* Something is really bad, we could not queue an additional packet,
1217  * because qdisc is full or receiver sent a 0 window.
1218  * We do not want to add fuel to the fire, or abort too early,
1219  * so make sure the timer we arm now is at least 200ms in the future,
1220  * regardless of current icsk_rto value (as it could be ~2ms)
1221  */
1222 static inline unsigned long tcp_probe0_base(const struct sock *sk)
1223 {
1224 	return max_t(unsigned long, inet_csk(sk)->icsk_rto, TCP_RTO_MIN);
1225 }
1226 
1227 /* Variant of inet_csk_rto_backoff() used for zero window probes */
1228 static inline unsigned long tcp_probe0_when(const struct sock *sk,
1229 					    unsigned long max_when)
1230 {
1231 	u64 when = (u64)tcp_probe0_base(sk) << inet_csk(sk)->icsk_backoff;
1232 
1233 	return (unsigned long)min_t(u64, when, max_when);
1234 }
1235 
1236 static inline void tcp_check_probe_timer(struct sock *sk)
1237 {
1238 	if (!tcp_sk(sk)->packets_out && !inet_csk(sk)->icsk_pending)
1239 		inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
1240 					  tcp_probe0_base(sk), TCP_RTO_MAX);
1241 }
1242 
1243 static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
1244 {
1245 	tp->snd_wl1 = seq;
1246 }
1247 
1248 static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq)
1249 {
1250 	tp->snd_wl1 = seq;
1251 }
1252 
1253 /*
1254  * Calculate(/check) TCP checksum
1255  */
1256 static inline __sum16 tcp_v4_check(int len, __be32 saddr,
1257 				   __be32 daddr, __wsum base)
1258 {
1259 	return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base);
1260 }
1261 
1262 static inline __sum16 __tcp_checksum_complete(struct sk_buff *skb)
1263 {
1264 	return __skb_checksum_complete(skb);
1265 }
1266 
1267 static inline bool tcp_checksum_complete(struct sk_buff *skb)
1268 {
1269 	return !skb_csum_unnecessary(skb) &&
1270 		__tcp_checksum_complete(skb);
1271 }
1272 
1273 bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb);
1274 int tcp_filter(struct sock *sk, struct sk_buff *skb);
1275 
1276 #undef STATE_TRACE
1277 
1278 #ifdef STATE_TRACE
1279 static const char *statename[]={
1280 	"Unused","Established","Syn Sent","Syn Recv",
1281 	"Fin Wait 1","Fin Wait 2","Time Wait", "Close",
1282 	"Close Wait","Last ACK","Listen","Closing"
1283 };
1284 #endif
1285 void tcp_set_state(struct sock *sk, int state);
1286 
1287 void tcp_done(struct sock *sk);
1288 
1289 int tcp_abort(struct sock *sk, int err);
1290 
1291 static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
1292 {
1293 	rx_opt->dsack = 0;
1294 	rx_opt->num_sacks = 0;
1295 }
1296 
1297 u32 tcp_default_init_rwnd(u32 mss);
1298 void tcp_cwnd_restart(struct sock *sk, s32 delta);
1299 
1300 static inline void tcp_slow_start_after_idle_check(struct sock *sk)
1301 {
1302 	const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1303 	struct tcp_sock *tp = tcp_sk(sk);
1304 	s32 delta;
1305 
1306 	if (!sysctl_tcp_slow_start_after_idle || tp->packets_out ||
1307 	    ca_ops->cong_control)
1308 		return;
1309 	delta = tcp_jiffies32 - tp->lsndtime;
1310 	if (delta > inet_csk(sk)->icsk_rto)
1311 		tcp_cwnd_restart(sk, delta);
1312 }
1313 
1314 /* Determine a window scaling and initial window to offer. */
1315 void tcp_select_initial_window(int __space, __u32 mss, __u32 *rcv_wnd,
1316 			       __u32 *window_clamp, int wscale_ok,
1317 			       __u8 *rcv_wscale, __u32 init_rcv_wnd);
1318 
1319 static inline int tcp_win_from_space(int space)
1320 {
1321 	int tcp_adv_win_scale = sysctl_tcp_adv_win_scale;
1322 
1323 	return tcp_adv_win_scale <= 0 ?
1324 		(space>>(-tcp_adv_win_scale)) :
1325 		space - (space>>tcp_adv_win_scale);
1326 }
1327 
1328 /* Note: caller must be prepared to deal with negative returns */
1329 static inline int tcp_space(const struct sock *sk)
1330 {
1331 	return tcp_win_from_space(sk->sk_rcvbuf -
1332 				  atomic_read(&sk->sk_rmem_alloc));
1333 }
1334 
1335 static inline int tcp_full_space(const struct sock *sk)
1336 {
1337 	return tcp_win_from_space(sk->sk_rcvbuf);
1338 }
1339 
1340 extern void tcp_openreq_init_rwin(struct request_sock *req,
1341 				  const struct sock *sk_listener,
1342 				  const struct dst_entry *dst);
1343 
1344 void tcp_enter_memory_pressure(struct sock *sk);
1345 void tcp_leave_memory_pressure(struct sock *sk);
1346 
1347 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
1348 {
1349 	struct net *net = sock_net((struct sock *)tp);
1350 
1351 	return tp->keepalive_intvl ? : net->ipv4.sysctl_tcp_keepalive_intvl;
1352 }
1353 
1354 static inline int keepalive_time_when(const struct tcp_sock *tp)
1355 {
1356 	struct net *net = sock_net((struct sock *)tp);
1357 
1358 	return tp->keepalive_time ? : net->ipv4.sysctl_tcp_keepalive_time;
1359 }
1360 
1361 static inline int keepalive_probes(const struct tcp_sock *tp)
1362 {
1363 	struct net *net = sock_net((struct sock *)tp);
1364 
1365 	return tp->keepalive_probes ? : net->ipv4.sysctl_tcp_keepalive_probes;
1366 }
1367 
1368 static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
1369 {
1370 	const struct inet_connection_sock *icsk = &tp->inet_conn;
1371 
1372 	return min_t(u32, tcp_jiffies32 - icsk->icsk_ack.lrcvtime,
1373 			  tcp_jiffies32 - tp->rcv_tstamp);
1374 }
1375 
1376 static inline int tcp_fin_time(const struct sock *sk)
1377 {
1378 	int fin_timeout = tcp_sk(sk)->linger2 ? : sock_net(sk)->ipv4.sysctl_tcp_fin_timeout;
1379 	const int rto = inet_csk(sk)->icsk_rto;
1380 
1381 	if (fin_timeout < (rto << 2) - (rto >> 1))
1382 		fin_timeout = (rto << 2) - (rto >> 1);
1383 
1384 	return fin_timeout;
1385 }
1386 
1387 static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt,
1388 				  int paws_win)
1389 {
1390 	if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
1391 		return true;
1392 	if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
1393 		return true;
1394 	/*
1395 	 * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
1396 	 * then following tcp messages have valid values. Ignore 0 value,
1397 	 * or else 'negative' tsval might forbid us to accept their packets.
1398 	 */
1399 	if (!rx_opt->ts_recent)
1400 		return true;
1401 	return false;
1402 }
1403 
1404 static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt,
1405 				   int rst)
1406 {
1407 	if (tcp_paws_check(rx_opt, 0))
1408 		return false;
1409 
1410 	/* RST segments are not recommended to carry timestamp,
1411 	   and, if they do, it is recommended to ignore PAWS because
1412 	   "their cleanup function should take precedence over timestamps."
1413 	   Certainly, it is mistake. It is necessary to understand the reasons
1414 	   of this constraint to relax it: if peer reboots, clock may go
1415 	   out-of-sync and half-open connections will not be reset.
1416 	   Actually, the problem would be not existing if all
1417 	   the implementations followed draft about maintaining clock
1418 	   via reboots. Linux-2.2 DOES NOT!
1419 
1420 	   However, we can relax time bounds for RST segments to MSL.
1421 	 */
1422 	if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
1423 		return false;
1424 	return true;
1425 }
1426 
1427 bool tcp_oow_rate_limited(struct net *net, const struct sk_buff *skb,
1428 			  int mib_idx, u32 *last_oow_ack_time);
1429 
1430 static inline void tcp_mib_init(struct net *net)
1431 {
1432 	/* See RFC 2012 */
1433 	TCP_ADD_STATS(net, TCP_MIB_RTOALGORITHM, 1);
1434 	TCP_ADD_STATS(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
1435 	TCP_ADD_STATS(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
1436 	TCP_ADD_STATS(net, TCP_MIB_MAXCONN, -1);
1437 }
1438 
1439 /* from STCP */
1440 static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
1441 {
1442 	tp->lost_skb_hint = NULL;
1443 }
1444 
1445 static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
1446 {
1447 	tcp_clear_retrans_hints_partial(tp);
1448 	tp->retransmit_skb_hint = NULL;
1449 }
1450 
1451 union tcp_md5_addr {
1452 	struct in_addr  a4;
1453 #if IS_ENABLED(CONFIG_IPV6)
1454 	struct in6_addr	a6;
1455 #endif
1456 };
1457 
1458 /* - key database */
1459 struct tcp_md5sig_key {
1460 	struct hlist_node	node;
1461 	u8			keylen;
1462 	u8			family; /* AF_INET or AF_INET6 */
1463 	union tcp_md5_addr	addr;
1464 	u8			prefixlen;
1465 	u8			key[TCP_MD5SIG_MAXKEYLEN];
1466 	struct rcu_head		rcu;
1467 };
1468 
1469 /* - sock block */
1470 struct tcp_md5sig_info {
1471 	struct hlist_head	head;
1472 	struct rcu_head		rcu;
1473 };
1474 
1475 /* - pseudo header */
1476 struct tcp4_pseudohdr {
1477 	__be32		saddr;
1478 	__be32		daddr;
1479 	__u8		pad;
1480 	__u8		protocol;
1481 	__be16		len;
1482 };
1483 
1484 struct tcp6_pseudohdr {
1485 	struct in6_addr	saddr;
1486 	struct in6_addr daddr;
1487 	__be32		len;
1488 	__be32		protocol;	/* including padding */
1489 };
1490 
1491 union tcp_md5sum_block {
1492 	struct tcp4_pseudohdr ip4;
1493 #if IS_ENABLED(CONFIG_IPV6)
1494 	struct tcp6_pseudohdr ip6;
1495 #endif
1496 };
1497 
1498 /* - pool: digest algorithm, hash description and scratch buffer */
1499 struct tcp_md5sig_pool {
1500 	struct ahash_request	*md5_req;
1501 	void			*scratch;
1502 };
1503 
1504 /* - functions */
1505 int tcp_v4_md5_hash_skb(char *md5_hash, const struct tcp_md5sig_key *key,
1506 			const struct sock *sk, const struct sk_buff *skb);
1507 int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
1508 		   int family, u8 prefixlen, const u8 *newkey, u8 newkeylen,
1509 		   gfp_t gfp);
1510 int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
1511 		   int family, u8 prefixlen);
1512 struct tcp_md5sig_key *tcp_v4_md5_lookup(const struct sock *sk,
1513 					 const struct sock *addr_sk);
1514 
1515 #ifdef CONFIG_TCP_MD5SIG
1516 struct tcp_md5sig_key *tcp_md5_do_lookup(const struct sock *sk,
1517 					 const union tcp_md5_addr *addr,
1518 					 int family);
1519 #define tcp_twsk_md5_key(twsk)	((twsk)->tw_md5_key)
1520 #else
1521 static inline struct tcp_md5sig_key *tcp_md5_do_lookup(const struct sock *sk,
1522 					 const union tcp_md5_addr *addr,
1523 					 int family)
1524 {
1525 	return NULL;
1526 }
1527 #define tcp_twsk_md5_key(twsk)	NULL
1528 #endif
1529 
1530 bool tcp_alloc_md5sig_pool(void);
1531 
1532 struct tcp_md5sig_pool *tcp_get_md5sig_pool(void);
1533 static inline void tcp_put_md5sig_pool(void)
1534 {
1535 	local_bh_enable();
1536 }
1537 
1538 int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
1539 			  unsigned int header_len);
1540 int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
1541 		     const struct tcp_md5sig_key *key);
1542 
1543 /* From tcp_fastopen.c */
1544 void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
1545 			    struct tcp_fastopen_cookie *cookie, int *syn_loss,
1546 			    unsigned long *last_syn_loss);
1547 void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
1548 			    struct tcp_fastopen_cookie *cookie, bool syn_lost,
1549 			    u16 try_exp);
1550 struct tcp_fastopen_request {
1551 	/* Fast Open cookie. Size 0 means a cookie request */
1552 	struct tcp_fastopen_cookie	cookie;
1553 	struct msghdr			*data;  /* data in MSG_FASTOPEN */
1554 	size_t				size;
1555 	int				copied;	/* queued in tcp_connect() */
1556 };
1557 void tcp_free_fastopen_req(struct tcp_sock *tp);
1558 
1559 extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
1560 int tcp_fastopen_reset_cipher(void *key, unsigned int len);
1561 void tcp_fastopen_add_skb(struct sock *sk, struct sk_buff *skb);
1562 struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
1563 			      struct request_sock *req,
1564 			      struct tcp_fastopen_cookie *foc);
1565 void tcp_fastopen_init_key_once(bool publish);
1566 bool tcp_fastopen_cookie_check(struct sock *sk, u16 *mss,
1567 			     struct tcp_fastopen_cookie *cookie);
1568 bool tcp_fastopen_defer_connect(struct sock *sk, int *err);
1569 #define TCP_FASTOPEN_KEY_LENGTH 16
1570 
1571 /* Fastopen key context */
1572 struct tcp_fastopen_context {
1573 	struct crypto_cipher	*tfm;
1574 	__u8			key[TCP_FASTOPEN_KEY_LENGTH];
1575 	struct rcu_head		rcu;
1576 };
1577 
1578 extern unsigned int sysctl_tcp_fastopen_blackhole_timeout;
1579 void tcp_fastopen_active_disable(struct sock *sk);
1580 bool tcp_fastopen_active_should_disable(struct sock *sk);
1581 void tcp_fastopen_active_disable_ofo_check(struct sock *sk);
1582 void tcp_fastopen_active_timeout_reset(void);
1583 
1584 /* Latencies incurred by various limits for a sender. They are
1585  * chronograph-like stats that are mutually exclusive.
1586  */
1587 enum tcp_chrono {
1588 	TCP_CHRONO_UNSPEC,
1589 	TCP_CHRONO_BUSY, /* Actively sending data (non-empty write queue) */
1590 	TCP_CHRONO_RWND_LIMITED, /* Stalled by insufficient receive window */
1591 	TCP_CHRONO_SNDBUF_LIMITED, /* Stalled by insufficient send buffer */
1592 	__TCP_CHRONO_MAX,
1593 };
1594 
1595 void tcp_chrono_start(struct sock *sk, const enum tcp_chrono type);
1596 void tcp_chrono_stop(struct sock *sk, const enum tcp_chrono type);
1597 
1598 /* write queue abstraction */
1599 static inline void tcp_write_queue_purge(struct sock *sk)
1600 {
1601 	struct sk_buff *skb;
1602 
1603 	tcp_chrono_stop(sk, TCP_CHRONO_BUSY);
1604 	while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL)
1605 		sk_wmem_free_skb(sk, skb);
1606 	sk_mem_reclaim(sk);
1607 	tcp_clear_all_retrans_hints(tcp_sk(sk));
1608 }
1609 
1610 static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)
1611 {
1612 	return skb_peek(&sk->sk_write_queue);
1613 }
1614 
1615 static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk)
1616 {
1617 	return skb_peek_tail(&sk->sk_write_queue);
1618 }
1619 
1620 static inline struct sk_buff *tcp_write_queue_next(const struct sock *sk,
1621 						   const struct sk_buff *skb)
1622 {
1623 	return skb_queue_next(&sk->sk_write_queue, skb);
1624 }
1625 
1626 static inline struct sk_buff *tcp_write_queue_prev(const struct sock *sk,
1627 						   const struct sk_buff *skb)
1628 {
1629 	return skb_queue_prev(&sk->sk_write_queue, skb);
1630 }
1631 
1632 #define tcp_for_write_queue(skb, sk)					\
1633 	skb_queue_walk(&(sk)->sk_write_queue, skb)
1634 
1635 #define tcp_for_write_queue_from(skb, sk)				\
1636 	skb_queue_walk_from(&(sk)->sk_write_queue, skb)
1637 
1638 #define tcp_for_write_queue_from_safe(skb, tmp, sk)			\
1639 	skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
1640 
1641 static inline struct sk_buff *tcp_send_head(const struct sock *sk)
1642 {
1643 	return sk->sk_send_head;
1644 }
1645 
1646 static inline bool tcp_skb_is_last(const struct sock *sk,
1647 				   const struct sk_buff *skb)
1648 {
1649 	return skb_queue_is_last(&sk->sk_write_queue, skb);
1650 }
1651 
1652 static inline void tcp_advance_send_head(struct sock *sk, const struct sk_buff *skb)
1653 {
1654 	if (tcp_skb_is_last(sk, skb))
1655 		sk->sk_send_head = NULL;
1656 	else
1657 		sk->sk_send_head = tcp_write_queue_next(sk, skb);
1658 }
1659 
1660 static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
1661 {
1662 	if (sk->sk_send_head == skb_unlinked) {
1663 		sk->sk_send_head = NULL;
1664 		tcp_chrono_stop(sk, TCP_CHRONO_BUSY);
1665 	}
1666 	if (tcp_sk(sk)->highest_sack == skb_unlinked)
1667 		tcp_sk(sk)->highest_sack = NULL;
1668 }
1669 
1670 static inline void tcp_init_send_head(struct sock *sk)
1671 {
1672 	sk->sk_send_head = NULL;
1673 }
1674 
1675 static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1676 {
1677 	__skb_queue_tail(&sk->sk_write_queue, skb);
1678 }
1679 
1680 static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1681 {
1682 	__tcp_add_write_queue_tail(sk, skb);
1683 
1684 	/* Queue it, remembering where we must start sending. */
1685 	if (sk->sk_send_head == NULL) {
1686 		sk->sk_send_head = skb;
1687 		tcp_chrono_start(sk, TCP_CHRONO_BUSY);
1688 
1689 		if (tcp_sk(sk)->highest_sack == NULL)
1690 			tcp_sk(sk)->highest_sack = skb;
1691 	}
1692 }
1693 
1694 static inline void __tcp_add_write_queue_head(struct sock *sk, struct sk_buff *skb)
1695 {
1696 	__skb_queue_head(&sk->sk_write_queue, skb);
1697 }
1698 
1699 /* Insert buff after skb on the write queue of sk.  */
1700 static inline void tcp_insert_write_queue_after(struct sk_buff *skb,
1701 						struct sk_buff *buff,
1702 						struct sock *sk)
1703 {
1704 	__skb_queue_after(&sk->sk_write_queue, skb, buff);
1705 }
1706 
1707 /* Insert new before skb on the write queue of sk.  */
1708 static inline void tcp_insert_write_queue_before(struct sk_buff *new,
1709 						  struct sk_buff *skb,
1710 						  struct sock *sk)
1711 {
1712 	__skb_queue_before(&sk->sk_write_queue, skb, new);
1713 
1714 	if (sk->sk_send_head == skb)
1715 		sk->sk_send_head = new;
1716 }
1717 
1718 static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
1719 {
1720 	__skb_unlink(skb, &sk->sk_write_queue);
1721 }
1722 
1723 static inline bool tcp_write_queue_empty(struct sock *sk)
1724 {
1725 	return skb_queue_empty(&sk->sk_write_queue);
1726 }
1727 
1728 static inline void tcp_push_pending_frames(struct sock *sk)
1729 {
1730 	if (tcp_send_head(sk)) {
1731 		struct tcp_sock *tp = tcp_sk(sk);
1732 
1733 		__tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
1734 	}
1735 }
1736 
1737 /* Start sequence of the skb just after the highest skb with SACKed
1738  * bit, valid only if sacked_out > 0 or when the caller has ensured
1739  * validity by itself.
1740  */
1741 static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
1742 {
1743 	if (!tp->sacked_out)
1744 		return tp->snd_una;
1745 
1746 	if (tp->highest_sack == NULL)
1747 		return tp->snd_nxt;
1748 
1749 	return TCP_SKB_CB(tp->highest_sack)->seq;
1750 }
1751 
1752 static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
1753 {
1754 	tcp_sk(sk)->highest_sack = tcp_skb_is_last(sk, skb) ? NULL :
1755 						tcp_write_queue_next(sk, skb);
1756 }
1757 
1758 static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
1759 {
1760 	return tcp_sk(sk)->highest_sack;
1761 }
1762 
1763 static inline void tcp_highest_sack_reset(struct sock *sk)
1764 {
1765 	tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk);
1766 }
1767 
1768 /* Called when old skb is about to be deleted (to be combined with new skb) */
1769 static inline void tcp_highest_sack_combine(struct sock *sk,
1770 					    struct sk_buff *old,
1771 					    struct sk_buff *new)
1772 {
1773 	if (tcp_sk(sk)->sacked_out && (old == tcp_sk(sk)->highest_sack))
1774 		tcp_sk(sk)->highest_sack = new;
1775 }
1776 
1777 /* This helper checks if socket has IP_TRANSPARENT set */
1778 static inline bool inet_sk_transparent(const struct sock *sk)
1779 {
1780 	switch (sk->sk_state) {
1781 	case TCP_TIME_WAIT:
1782 		return inet_twsk(sk)->tw_transparent;
1783 	case TCP_NEW_SYN_RECV:
1784 		return inet_rsk(inet_reqsk(sk))->no_srccheck;
1785 	}
1786 	return inet_sk(sk)->transparent;
1787 }
1788 
1789 /* Determines whether this is a thin stream (which may suffer from
1790  * increased latency). Used to trigger latency-reducing mechanisms.
1791  */
1792 static inline bool tcp_stream_is_thin(struct tcp_sock *tp)
1793 {
1794 	return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
1795 }
1796 
1797 /* /proc */
1798 enum tcp_seq_states {
1799 	TCP_SEQ_STATE_LISTENING,
1800 	TCP_SEQ_STATE_ESTABLISHED,
1801 };
1802 
1803 int tcp_seq_open(struct inode *inode, struct file *file);
1804 
1805 struct tcp_seq_afinfo {
1806 	char				*name;
1807 	sa_family_t			family;
1808 	const struct file_operations	*seq_fops;
1809 	struct seq_operations		seq_ops;
1810 };
1811 
1812 struct tcp_iter_state {
1813 	struct seq_net_private	p;
1814 	sa_family_t		family;
1815 	enum tcp_seq_states	state;
1816 	struct sock		*syn_wait_sk;
1817 	int			bucket, offset, sbucket, num;
1818 	loff_t			last_pos;
1819 };
1820 
1821 int tcp_proc_register(struct net *net, struct tcp_seq_afinfo *afinfo);
1822 void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo);
1823 
1824 extern struct request_sock_ops tcp_request_sock_ops;
1825 extern struct request_sock_ops tcp6_request_sock_ops;
1826 
1827 void tcp_v4_destroy_sock(struct sock *sk);
1828 
1829 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
1830 				netdev_features_t features);
1831 struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb);
1832 int tcp_gro_complete(struct sk_buff *skb);
1833 
1834 void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
1835 
1836 static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
1837 {
1838 	struct net *net = sock_net((struct sock *)tp);
1839 	return tp->notsent_lowat ?: net->ipv4.sysctl_tcp_notsent_lowat;
1840 }
1841 
1842 static inline bool tcp_stream_memory_free(const struct sock *sk)
1843 {
1844 	const struct tcp_sock *tp = tcp_sk(sk);
1845 	u32 notsent_bytes = tp->write_seq - tp->snd_nxt;
1846 
1847 	return notsent_bytes < tcp_notsent_lowat(tp);
1848 }
1849 
1850 #ifdef CONFIG_PROC_FS
1851 int tcp4_proc_init(void);
1852 void tcp4_proc_exit(void);
1853 #endif
1854 
1855 int tcp_rtx_synack(const struct sock *sk, struct request_sock *req);
1856 int tcp_conn_request(struct request_sock_ops *rsk_ops,
1857 		     const struct tcp_request_sock_ops *af_ops,
1858 		     struct sock *sk, struct sk_buff *skb);
1859 
1860 /* TCP af-specific functions */
1861 struct tcp_sock_af_ops {
1862 #ifdef CONFIG_TCP_MD5SIG
1863 	struct tcp_md5sig_key	*(*md5_lookup) (const struct sock *sk,
1864 						const struct sock *addr_sk);
1865 	int		(*calc_md5_hash)(char *location,
1866 					 const struct tcp_md5sig_key *md5,
1867 					 const struct sock *sk,
1868 					 const struct sk_buff *skb);
1869 	int		(*md5_parse)(struct sock *sk,
1870 				     int optname,
1871 				     char __user *optval,
1872 				     int optlen);
1873 #endif
1874 };
1875 
1876 struct tcp_request_sock_ops {
1877 	u16 mss_clamp;
1878 #ifdef CONFIG_TCP_MD5SIG
1879 	struct tcp_md5sig_key *(*req_md5_lookup)(const struct sock *sk,
1880 						 const struct sock *addr_sk);
1881 	int		(*calc_md5_hash) (char *location,
1882 					  const struct tcp_md5sig_key *md5,
1883 					  const struct sock *sk,
1884 					  const struct sk_buff *skb);
1885 #endif
1886 	void (*init_req)(struct request_sock *req,
1887 			 const struct sock *sk_listener,
1888 			 struct sk_buff *skb);
1889 #ifdef CONFIG_SYN_COOKIES
1890 	__u32 (*cookie_init_seq)(const struct sk_buff *skb,
1891 				 __u16 *mss);
1892 #endif
1893 	struct dst_entry *(*route_req)(const struct sock *sk, struct flowi *fl,
1894 				       const struct request_sock *req);
1895 	u32 (*init_seq)(const struct sk_buff *skb);
1896 	u32 (*init_ts_off)(const struct net *net, const struct sk_buff *skb);
1897 	int (*send_synack)(const struct sock *sk, struct dst_entry *dst,
1898 			   struct flowi *fl, struct request_sock *req,
1899 			   struct tcp_fastopen_cookie *foc,
1900 			   enum tcp_synack_type synack_type);
1901 };
1902 
1903 #ifdef CONFIG_SYN_COOKIES
1904 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1905 					 const struct sock *sk, struct sk_buff *skb,
1906 					 __u16 *mss)
1907 {
1908 	tcp_synq_overflow(sk);
1909 	__NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESSENT);
1910 	return ops->cookie_init_seq(skb, mss);
1911 }
1912 #else
1913 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1914 					 const struct sock *sk, struct sk_buff *skb,
1915 					 __u16 *mss)
1916 {
1917 	return 0;
1918 }
1919 #endif
1920 
1921 int tcpv4_offload_init(void);
1922 
1923 void tcp_v4_init(void);
1924 void tcp_init(void);
1925 
1926 /* tcp_recovery.c */
1927 extern void tcp_rack_mark_lost(struct sock *sk);
1928 extern void tcp_rack_advance(struct tcp_sock *tp, u8 sacked, u32 end_seq,
1929 			     u64 xmit_time);
1930 extern void tcp_rack_reo_timeout(struct sock *sk);
1931 
1932 /* At how many usecs into the future should the RTO fire? */
1933 static inline s64 tcp_rto_delta_us(const struct sock *sk)
1934 {
1935 	const struct sk_buff *skb = tcp_write_queue_head(sk);
1936 	u32 rto = inet_csk(sk)->icsk_rto;
1937 	u64 rto_time_stamp_us = skb->skb_mstamp + jiffies_to_usecs(rto);
1938 
1939 	return rto_time_stamp_us - tcp_sk(sk)->tcp_mstamp;
1940 }
1941 
1942 /*
1943  * Save and compile IPv4 options, return a pointer to it
1944  */
1945 static inline struct ip_options_rcu *tcp_v4_save_options(struct net *net,
1946 							 struct sk_buff *skb)
1947 {
1948 	const struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt;
1949 	struct ip_options_rcu *dopt = NULL;
1950 
1951 	if (opt->optlen) {
1952 		int opt_size = sizeof(*dopt) + opt->optlen;
1953 
1954 		dopt = kmalloc(opt_size, GFP_ATOMIC);
1955 		if (dopt && __ip_options_echo(net, &dopt->opt, skb, opt)) {
1956 			kfree(dopt);
1957 			dopt = NULL;
1958 		}
1959 	}
1960 	return dopt;
1961 }
1962 
1963 /* locally generated TCP pure ACKs have skb->truesize == 2
1964  * (check tcp_send_ack() in net/ipv4/tcp_output.c )
1965  * This is much faster than dissecting the packet to find out.
1966  * (Think of GRE encapsulations, IPv4, IPv6, ...)
1967  */
1968 static inline bool skb_is_tcp_pure_ack(const struct sk_buff *skb)
1969 {
1970 	return skb->truesize == 2;
1971 }
1972 
1973 static inline void skb_set_tcp_pure_ack(struct sk_buff *skb)
1974 {
1975 	skb->truesize = 2;
1976 }
1977 
1978 static inline int tcp_inq(struct sock *sk)
1979 {
1980 	struct tcp_sock *tp = tcp_sk(sk);
1981 	int answ;
1982 
1983 	if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
1984 		answ = 0;
1985 	} else if (sock_flag(sk, SOCK_URGINLINE) ||
1986 		   !tp->urg_data ||
1987 		   before(tp->urg_seq, tp->copied_seq) ||
1988 		   !before(tp->urg_seq, tp->rcv_nxt)) {
1989 
1990 		answ = tp->rcv_nxt - tp->copied_seq;
1991 
1992 		/* Subtract 1, if FIN was received */
1993 		if (answ && sock_flag(sk, SOCK_DONE))
1994 			answ--;
1995 	} else {
1996 		answ = tp->urg_seq - tp->copied_seq;
1997 	}
1998 
1999 	return answ;
2000 }
2001 
2002 int tcp_peek_len(struct socket *sock);
2003 
2004 static inline void tcp_segs_in(struct tcp_sock *tp, const struct sk_buff *skb)
2005 {
2006 	u16 segs_in;
2007 
2008 	segs_in = max_t(u16, 1, skb_shinfo(skb)->gso_segs);
2009 	tp->segs_in += segs_in;
2010 	if (skb->len > tcp_hdrlen(skb))
2011 		tp->data_segs_in += segs_in;
2012 }
2013 
2014 /*
2015  * TCP listen path runs lockless.
2016  * We forced "struct sock" to be const qualified to make sure
2017  * we don't modify one of its field by mistake.
2018  * Here, we increment sk_drops which is an atomic_t, so we can safely
2019  * make sock writable again.
2020  */
2021 static inline void tcp_listendrop(const struct sock *sk)
2022 {
2023 	atomic_inc(&((struct sock *)sk)->sk_drops);
2024 	__NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENDROPS);
2025 }
2026 
2027 enum hrtimer_restart tcp_pace_kick(struct hrtimer *timer);
2028 
2029 /*
2030  * Interface for adding Upper Level Protocols over TCP
2031  */
2032 
2033 #define TCP_ULP_NAME_MAX	16
2034 #define TCP_ULP_MAX		128
2035 #define TCP_ULP_BUF_MAX		(TCP_ULP_NAME_MAX*TCP_ULP_MAX)
2036 
2037 struct tcp_ulp_ops {
2038 	struct list_head	list;
2039 
2040 	/* initialize ulp */
2041 	int (*init)(struct sock *sk);
2042 	/* cleanup ulp */
2043 	void (*release)(struct sock *sk);
2044 
2045 	char		name[TCP_ULP_NAME_MAX];
2046 	struct module	*owner;
2047 };
2048 int tcp_register_ulp(struct tcp_ulp_ops *type);
2049 void tcp_unregister_ulp(struct tcp_ulp_ops *type);
2050 int tcp_set_ulp(struct sock *sk, const char *name);
2051 void tcp_get_available_ulp(char *buf, size_t len);
2052 void tcp_cleanup_ulp(struct sock *sk);
2053 
2054 /* Call BPF_SOCK_OPS program that returns an int. If the return value
2055  * is < 0, then the BPF op failed (for example if the loaded BPF
2056  * program does not support the chosen operation or there is no BPF
2057  * program loaded).
2058  */
2059 #ifdef CONFIG_BPF
2060 static inline int tcp_call_bpf(struct sock *sk, int op)
2061 {
2062 	struct bpf_sock_ops_kern sock_ops;
2063 	int ret;
2064 
2065 	if (sk_fullsock(sk))
2066 		sock_owned_by_me(sk);
2067 
2068 	memset(&sock_ops, 0, sizeof(sock_ops));
2069 	sock_ops.sk = sk;
2070 	sock_ops.op = op;
2071 
2072 	ret = BPF_CGROUP_RUN_PROG_SOCK_OPS(&sock_ops);
2073 	if (ret == 0)
2074 		ret = sock_ops.reply;
2075 	else
2076 		ret = -1;
2077 	return ret;
2078 }
2079 #else
2080 static inline int tcp_call_bpf(struct sock *sk, int op)
2081 {
2082 	return -EPERM;
2083 }
2084 #endif
2085 
2086 static inline u32 tcp_timeout_init(struct sock *sk)
2087 {
2088 	int timeout;
2089 
2090 	timeout = tcp_call_bpf(sk, BPF_SOCK_OPS_TIMEOUT_INIT);
2091 
2092 	if (timeout <= 0)
2093 		timeout = TCP_TIMEOUT_INIT;
2094 	return timeout;
2095 }
2096 
2097 static inline u32 tcp_rwnd_init_bpf(struct sock *sk)
2098 {
2099 	int rwnd;
2100 
2101 	rwnd = tcp_call_bpf(sk, BPF_SOCK_OPS_RWND_INIT);
2102 
2103 	if (rwnd < 0)
2104 		rwnd = 0;
2105 	return rwnd;
2106 }
2107 
2108 static inline bool tcp_bpf_ca_needs_ecn(struct sock *sk)
2109 {
2110 	return (tcp_call_bpf(sk, BPF_SOCK_OPS_NEEDS_ECN) == 1);
2111 }
2112 #endif	/* _TCP_H */
2113