xref: /openbmc/linux/include/net/tcp.h (revision 31b90347)
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/dmaengine.h>
31 #include <linux/crypto.h>
32 #include <linux/cryptohash.h>
33 #include <linux/kref.h>
34 
35 #include <net/inet_connection_sock.h>
36 #include <net/inet_timewait_sock.h>
37 #include <net/inet_hashtables.h>
38 #include <net/checksum.h>
39 #include <net/request_sock.h>
40 #include <net/sock.h>
41 #include <net/snmp.h>
42 #include <net/ip.h>
43 #include <net/tcp_states.h>
44 #include <net/inet_ecn.h>
45 #include <net/dst.h>
46 
47 #include <linux/seq_file.h>
48 #include <linux/memcontrol.h>
49 
50 extern struct inet_hashinfo tcp_hashinfo;
51 
52 extern struct percpu_counter tcp_orphan_count;
53 void tcp_time_wait(struct sock *sk, int state, int timeo);
54 
55 #define MAX_TCP_HEADER	(128 + MAX_HEADER)
56 #define MAX_TCP_OPTION_SPACE 40
57 
58 /*
59  * Never offer a window over 32767 without using window scaling. Some
60  * poor stacks do signed 16bit maths!
61  */
62 #define MAX_TCP_WINDOW		32767U
63 
64 /* Minimal accepted MSS. It is (60+60+8) - (20+20). */
65 #define TCP_MIN_MSS		88U
66 
67 /* The least MTU to use for probing */
68 #define TCP_BASE_MSS		512
69 
70 /* After receiving this amount of duplicate ACKs fast retransmit starts. */
71 #define TCP_FASTRETRANS_THRESH 3
72 
73 /* Maximal reordering. */
74 #define TCP_MAX_REORDERING	127
75 
76 /* Maximal number of ACKs sent quickly to accelerate slow-start. */
77 #define TCP_MAX_QUICKACKS	16U
78 
79 /* urg_data states */
80 #define TCP_URG_VALID	0x0100
81 #define TCP_URG_NOTYET	0x0200
82 #define TCP_URG_READ	0x0400
83 
84 #define TCP_RETR1	3	/*
85 				 * This is how many retries it does before it
86 				 * tries to figure out if the gateway is
87 				 * down. Minimal RFC value is 3; it corresponds
88 				 * to ~3sec-8min depending on RTO.
89 				 */
90 
91 #define TCP_RETR2	15	/*
92 				 * This should take at least
93 				 * 90 minutes to time out.
94 				 * RFC1122 says that the limit is 100 sec.
95 				 * 15 is ~13-30min depending on RTO.
96 				 */
97 
98 #define TCP_SYN_RETRIES	 6	/* This is how many retries are done
99 				 * when active opening a connection.
100 				 * RFC1122 says the minimum retry MUST
101 				 * be at least 180secs.  Nevertheless
102 				 * this value is corresponding to
103 				 * 63secs of retransmission with the
104 				 * current initial RTO.
105 				 */
106 
107 #define TCP_SYNACK_RETRIES 5	/* This is how may retries are done
108 				 * when passive opening a connection.
109 				 * This is corresponding to 31secs of
110 				 * retransmission with the current
111 				 * initial RTO.
112 				 */
113 
114 #define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT
115 				  * state, about 60 seconds	*/
116 #define TCP_FIN_TIMEOUT	TCP_TIMEWAIT_LEN
117                                  /* BSD style FIN_WAIT2 deadlock breaker.
118 				  * It used to be 3min, new value is 60sec,
119 				  * to combine FIN-WAIT-2 timeout with
120 				  * TIME-WAIT timer.
121 				  */
122 
123 #define TCP_DELACK_MAX	((unsigned)(HZ/5))	/* maximal time to delay before sending an ACK */
124 #if HZ >= 100
125 #define TCP_DELACK_MIN	((unsigned)(HZ/25))	/* minimal time to delay before sending an ACK */
126 #define TCP_ATO_MIN	((unsigned)(HZ/25))
127 #else
128 #define TCP_DELACK_MIN	4U
129 #define TCP_ATO_MIN	4U
130 #endif
131 #define TCP_RTO_MAX	((unsigned)(120*HZ))
132 #define TCP_RTO_MIN	((unsigned)(HZ/5))
133 #define TCP_TIMEOUT_INIT ((unsigned)(1*HZ))	/* RFC6298 2.1 initial RTO value	*/
134 #define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ))	/* RFC 1122 initial RTO value, now
135 						 * used as a fallback RTO for the
136 						 * initial data transmission if no
137 						 * valid RTT sample has been acquired,
138 						 * most likely due to retrans in 3WHS.
139 						 */
140 
141 #define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes
142 					                 * for local resources.
143 					                 */
144 
145 #define TCP_KEEPALIVE_TIME	(120*60*HZ)	/* two hours */
146 #define TCP_KEEPALIVE_PROBES	9		/* Max of 9 keepalive probes	*/
147 #define TCP_KEEPALIVE_INTVL	(75*HZ)
148 
149 #define MAX_TCP_KEEPIDLE	32767
150 #define MAX_TCP_KEEPINTVL	32767
151 #define MAX_TCP_KEEPCNT		127
152 #define MAX_TCP_SYNCNT		127
153 
154 #define TCP_SYNQ_INTERVAL	(HZ/5)	/* Period of SYNACK timer */
155 
156 #define TCP_PAWS_24DAYS	(60 * 60 * 24 * 24)
157 #define TCP_PAWS_MSL	60		/* Per-host timestamps are invalidated
158 					 * after this time. It should be equal
159 					 * (or greater than) TCP_TIMEWAIT_LEN
160 					 * to provide reliability equal to one
161 					 * provided by timewait state.
162 					 */
163 #define TCP_PAWS_WINDOW	1		/* Replay window for per-host
164 					 * timestamps. It must be less than
165 					 * minimal timewait lifetime.
166 					 */
167 /*
168  *	TCP option
169  */
170 
171 #define TCPOPT_NOP		1	/* Padding */
172 #define TCPOPT_EOL		0	/* End of options */
173 #define TCPOPT_MSS		2	/* Segment size negotiating */
174 #define TCPOPT_WINDOW		3	/* Window scaling */
175 #define TCPOPT_SACK_PERM        4       /* SACK Permitted */
176 #define TCPOPT_SACK             5       /* SACK Block */
177 #define TCPOPT_TIMESTAMP	8	/* Better RTT estimations/PAWS */
178 #define TCPOPT_MD5SIG		19	/* MD5 Signature (RFC2385) */
179 #define TCPOPT_EXP		254	/* Experimental */
180 /* Magic number to be after the option value for sharing TCP
181  * experimental options. See draft-ietf-tcpm-experimental-options-00.txt
182  */
183 #define TCPOPT_FASTOPEN_MAGIC	0xF989
184 
185 /*
186  *     TCP option lengths
187  */
188 
189 #define TCPOLEN_MSS            4
190 #define TCPOLEN_WINDOW         3
191 #define TCPOLEN_SACK_PERM      2
192 #define TCPOLEN_TIMESTAMP      10
193 #define TCPOLEN_MD5SIG         18
194 #define TCPOLEN_EXP_FASTOPEN_BASE  4
195 
196 /* But this is what stacks really send out. */
197 #define TCPOLEN_TSTAMP_ALIGNED		12
198 #define TCPOLEN_WSCALE_ALIGNED		4
199 #define TCPOLEN_SACKPERM_ALIGNED	4
200 #define TCPOLEN_SACK_BASE		2
201 #define TCPOLEN_SACK_BASE_ALIGNED	4
202 #define TCPOLEN_SACK_PERBLOCK		8
203 #define TCPOLEN_MD5SIG_ALIGNED		20
204 #define TCPOLEN_MSS_ALIGNED		4
205 
206 /* Flags in tp->nonagle */
207 #define TCP_NAGLE_OFF		1	/* Nagle's algo is disabled */
208 #define TCP_NAGLE_CORK		2	/* Socket is corked	    */
209 #define TCP_NAGLE_PUSH		4	/* Cork is overridden for already queued data */
210 
211 /* TCP thin-stream limits */
212 #define TCP_THIN_LINEAR_RETRIES 6       /* After 6 linear retries, do exp. backoff */
213 
214 /* TCP initial congestion window as per draft-hkchu-tcpm-initcwnd-01 */
215 #define TCP_INIT_CWND		10
216 
217 /* Bit Flags for sysctl_tcp_fastopen */
218 #define	TFO_CLIENT_ENABLE	1
219 #define	TFO_SERVER_ENABLE	2
220 #define	TFO_CLIENT_NO_COOKIE	4	/* Data in SYN w/o cookie option */
221 
222 /* Process SYN data but skip cookie validation */
223 #define	TFO_SERVER_COOKIE_NOT_CHKED	0x100
224 /* Accept SYN data w/o any cookie option */
225 #define	TFO_SERVER_COOKIE_NOT_REQD	0x200
226 
227 /* Force enable TFO on all listeners, i.e., not requiring the
228  * TCP_FASTOPEN socket option. SOCKOPT1/2 determine how to set max_qlen.
229  */
230 #define	TFO_SERVER_WO_SOCKOPT1	0x400
231 #define	TFO_SERVER_WO_SOCKOPT2	0x800
232 /* Always create TFO child sockets on a TFO listener even when
233  * cookie/data not present. (For testing purpose!)
234  */
235 #define	TFO_SERVER_ALWAYS	0x1000
236 
237 extern struct inet_timewait_death_row tcp_death_row;
238 
239 /* sysctl variables for tcp */
240 extern int sysctl_tcp_timestamps;
241 extern int sysctl_tcp_window_scaling;
242 extern int sysctl_tcp_sack;
243 extern int sysctl_tcp_fin_timeout;
244 extern int sysctl_tcp_keepalive_time;
245 extern int sysctl_tcp_keepalive_probes;
246 extern int sysctl_tcp_keepalive_intvl;
247 extern int sysctl_tcp_syn_retries;
248 extern int sysctl_tcp_synack_retries;
249 extern int sysctl_tcp_retries1;
250 extern int sysctl_tcp_retries2;
251 extern int sysctl_tcp_orphan_retries;
252 extern int sysctl_tcp_syncookies;
253 extern int sysctl_tcp_fastopen;
254 extern int sysctl_tcp_retrans_collapse;
255 extern int sysctl_tcp_stdurg;
256 extern int sysctl_tcp_rfc1337;
257 extern int sysctl_tcp_abort_on_overflow;
258 extern int sysctl_tcp_max_orphans;
259 extern int sysctl_tcp_fack;
260 extern int sysctl_tcp_reordering;
261 extern int sysctl_tcp_dsack;
262 extern long sysctl_tcp_mem[3];
263 extern int sysctl_tcp_wmem[3];
264 extern int sysctl_tcp_rmem[3];
265 extern int sysctl_tcp_app_win;
266 extern int sysctl_tcp_adv_win_scale;
267 extern int sysctl_tcp_tw_reuse;
268 extern int sysctl_tcp_frto;
269 extern int sysctl_tcp_low_latency;
270 extern int sysctl_tcp_dma_copybreak;
271 extern int sysctl_tcp_nometrics_save;
272 extern int sysctl_tcp_moderate_rcvbuf;
273 extern int sysctl_tcp_tso_win_divisor;
274 extern int sysctl_tcp_mtu_probing;
275 extern int sysctl_tcp_base_mss;
276 extern int sysctl_tcp_workaround_signed_windows;
277 extern int sysctl_tcp_slow_start_after_idle;
278 extern int sysctl_tcp_thin_linear_timeouts;
279 extern int sysctl_tcp_thin_dupack;
280 extern int sysctl_tcp_early_retrans;
281 extern int sysctl_tcp_limit_output_bytes;
282 extern int sysctl_tcp_challenge_ack_limit;
283 extern unsigned int sysctl_tcp_notsent_lowat;
284 extern int sysctl_tcp_min_tso_segs;
285 
286 extern atomic_long_t tcp_memory_allocated;
287 extern struct percpu_counter tcp_sockets_allocated;
288 extern int tcp_memory_pressure;
289 
290 /*
291  * The next routines deal with comparing 32 bit unsigned ints
292  * and worry about wraparound (automatic with unsigned arithmetic).
293  */
294 
295 static inline bool before(__u32 seq1, __u32 seq2)
296 {
297         return (__s32)(seq1-seq2) < 0;
298 }
299 #define after(seq2, seq1) 	before(seq1, seq2)
300 
301 /* is s2<=s1<=s3 ? */
302 static inline bool between(__u32 seq1, __u32 seq2, __u32 seq3)
303 {
304 	return seq3 - seq2 >= seq1 - seq2;
305 }
306 
307 static inline bool tcp_out_of_memory(struct sock *sk)
308 {
309 	if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
310 	    sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2))
311 		return true;
312 	return false;
313 }
314 
315 static inline bool tcp_too_many_orphans(struct sock *sk, int shift)
316 {
317 	struct percpu_counter *ocp = sk->sk_prot->orphan_count;
318 	int orphans = percpu_counter_read_positive(ocp);
319 
320 	if (orphans << shift > sysctl_tcp_max_orphans) {
321 		orphans = percpu_counter_sum_positive(ocp);
322 		if (orphans << shift > sysctl_tcp_max_orphans)
323 			return true;
324 	}
325 	return false;
326 }
327 
328 bool tcp_check_oom(struct sock *sk, int shift);
329 
330 /* syncookies: remember time of last synqueue overflow */
331 static inline void tcp_synq_overflow(struct sock *sk)
332 {
333 	tcp_sk(sk)->rx_opt.ts_recent_stamp = jiffies;
334 }
335 
336 /* syncookies: no recent synqueue overflow on this listening socket? */
337 static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
338 {
339 	unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
340 	return time_after(jiffies, last_overflow + TCP_TIMEOUT_FALLBACK);
341 }
342 
343 extern struct proto tcp_prot;
344 
345 #define TCP_INC_STATS(net, field)	SNMP_INC_STATS((net)->mib.tcp_statistics, field)
346 #define TCP_INC_STATS_BH(net, field)	SNMP_INC_STATS_BH((net)->mib.tcp_statistics, field)
347 #define TCP_DEC_STATS(net, field)	SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
348 #define TCP_ADD_STATS_USER(net, field, val) SNMP_ADD_STATS_USER((net)->mib.tcp_statistics, field, val)
349 #define TCP_ADD_STATS(net, field, val)	SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
350 
351 void tcp_tasklet_init(void);
352 
353 void tcp_v4_err(struct sk_buff *skb, u32);
354 
355 void tcp_shutdown(struct sock *sk, int how);
356 
357 void tcp_v4_early_demux(struct sk_buff *skb);
358 int tcp_v4_rcv(struct sk_buff *skb);
359 
360 int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
361 int tcp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
362 		size_t size);
363 int tcp_sendpage(struct sock *sk, struct page *page, int offset, size_t size,
364 		 int flags);
365 void tcp_release_cb(struct sock *sk);
366 void tcp_wfree(struct sk_buff *skb);
367 void tcp_write_timer_handler(struct sock *sk);
368 void tcp_delack_timer_handler(struct sock *sk);
369 int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
370 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
371 			  const struct tcphdr *th, unsigned int len);
372 void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
373 			 const struct tcphdr *th, unsigned int len);
374 void tcp_rcv_space_adjust(struct sock *sk);
375 void tcp_cleanup_rbuf(struct sock *sk, int copied);
376 int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
377 void tcp_twsk_destructor(struct sock *sk);
378 ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
379 			struct pipe_inode_info *pipe, size_t len,
380 			unsigned int flags);
381 
382 static inline void tcp_dec_quickack_mode(struct sock *sk,
383 					 const unsigned int pkts)
384 {
385 	struct inet_connection_sock *icsk = inet_csk(sk);
386 
387 	if (icsk->icsk_ack.quick) {
388 		if (pkts >= icsk->icsk_ack.quick) {
389 			icsk->icsk_ack.quick = 0;
390 			/* Leaving quickack mode we deflate ATO. */
391 			icsk->icsk_ack.ato   = TCP_ATO_MIN;
392 		} else
393 			icsk->icsk_ack.quick -= pkts;
394 	}
395 }
396 
397 #define	TCP_ECN_OK		1
398 #define	TCP_ECN_QUEUE_CWR	2
399 #define	TCP_ECN_DEMAND_CWR	4
400 #define	TCP_ECN_SEEN		8
401 
402 enum tcp_tw_status {
403 	TCP_TW_SUCCESS = 0,
404 	TCP_TW_RST = 1,
405 	TCP_TW_ACK = 2,
406 	TCP_TW_SYN = 3
407 };
408 
409 
410 enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
411 					      struct sk_buff *skb,
412 					      const struct tcphdr *th);
413 struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
414 			   struct request_sock *req, struct request_sock **prev,
415 			   bool fastopen);
416 int tcp_child_process(struct sock *parent, struct sock *child,
417 		      struct sk_buff *skb);
418 void tcp_enter_loss(struct sock *sk, int how);
419 void tcp_clear_retrans(struct tcp_sock *tp);
420 void tcp_update_metrics(struct sock *sk);
421 void tcp_init_metrics(struct sock *sk);
422 void tcp_metrics_init(void);
423 bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst,
424 			bool paws_check);
425 bool tcp_remember_stamp(struct sock *sk);
426 bool tcp_tw_remember_stamp(struct inet_timewait_sock *tw);
427 void tcp_fetch_timewait_stamp(struct sock *sk, struct dst_entry *dst);
428 void tcp_disable_fack(struct tcp_sock *tp);
429 void tcp_close(struct sock *sk, long timeout);
430 void tcp_init_sock(struct sock *sk);
431 unsigned int tcp_poll(struct file *file, struct socket *sock,
432 		      struct poll_table_struct *wait);
433 int tcp_getsockopt(struct sock *sk, int level, int optname,
434 		   char __user *optval, int __user *optlen);
435 int tcp_setsockopt(struct sock *sk, int level, int optname,
436 		   char __user *optval, unsigned int optlen);
437 int compat_tcp_getsockopt(struct sock *sk, int level, int optname,
438 			  char __user *optval, int __user *optlen);
439 int compat_tcp_setsockopt(struct sock *sk, int level, int optname,
440 			  char __user *optval, unsigned int optlen);
441 void tcp_set_keepalive(struct sock *sk, int val);
442 void tcp_syn_ack_timeout(struct sock *sk, struct request_sock *req);
443 int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
444 		size_t len, int nonblock, int flags, int *addr_len);
445 void tcp_parse_options(const struct sk_buff *skb,
446 		       struct tcp_options_received *opt_rx,
447 		       int estab, struct tcp_fastopen_cookie *foc);
448 const u8 *tcp_parse_md5sig_option(const struct tcphdr *th);
449 
450 /*
451  *	TCP v4 functions exported for the inet6 API
452  */
453 
454 void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
455 int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
456 struct sock *tcp_create_openreq_child(struct sock *sk,
457 				      struct request_sock *req,
458 				      struct sk_buff *skb);
459 struct sock *tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
460 				  struct request_sock *req,
461 				  struct dst_entry *dst);
462 int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
463 int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
464 int tcp_connect(struct sock *sk);
465 struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
466 				struct request_sock *req,
467 				struct tcp_fastopen_cookie *foc);
468 int tcp_disconnect(struct sock *sk, int flags);
469 
470 void tcp_connect_init(struct sock *sk);
471 void tcp_finish_connect(struct sock *sk, struct sk_buff *skb);
472 int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size);
473 void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
474 
475 /* From syncookies.c */
476 int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
477 		      u32 cookie);
478 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
479 			     struct ip_options *opt);
480 #ifdef CONFIG_SYN_COOKIES
481 #include <linux/ktime.h>
482 
483 /* Syncookies use a monotonic timer which increments every 64 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 128 seconds (or less if
488  * the counter advances immediately after a cookie is generated).
489  */
490 #define MAX_SYNCOOKIE_AGE 2
491 
492 static inline u32 tcp_cookie_time(void)
493 {
494 	struct timespec now;
495 	getnstimeofday(&now);
496 	return now.tv_sec >> 6; /* 64 seconds granularity */
497 }
498 
499 u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
500 			      u16 *mssp);
501 __u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb, __u16 *mss);
502 #else
503 static inline __u32 cookie_v4_init_sequence(struct sock *sk,
504 					    struct sk_buff *skb,
505 					    __u16 *mss)
506 {
507 	return 0;
508 }
509 #endif
510 
511 __u32 cookie_init_timestamp(struct request_sock *req);
512 bool cookie_check_timestamp(struct tcp_options_received *opt, struct net *net,
513 			    bool *ecn_ok);
514 
515 /* From net/ipv6/syncookies.c */
516 int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th,
517 		      u32 cookie);
518 struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
519 #ifdef CONFIG_SYN_COOKIES
520 u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
521 			      const struct tcphdr *th, u16 *mssp);
522 __u32 cookie_v6_init_sequence(struct sock *sk, const struct sk_buff *skb,
523 			      __u16 *mss);
524 #else
525 static inline __u32 cookie_v6_init_sequence(struct sock *sk,
526 					    struct sk_buff *skb,
527 					    __u16 *mss)
528 {
529 	return 0;
530 }
531 #endif
532 /* tcp_output.c */
533 
534 void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
535 			       int nonagle);
536 bool tcp_may_send_now(struct sock *sk);
537 int __tcp_retransmit_skb(struct sock *, struct sk_buff *);
538 int tcp_retransmit_skb(struct sock *, struct sk_buff *);
539 void tcp_retransmit_timer(struct sock *sk);
540 void tcp_xmit_retransmit_queue(struct sock *);
541 void tcp_simple_retransmit(struct sock *);
542 int tcp_trim_head(struct sock *, struct sk_buff *, u32);
543 int tcp_fragment(struct sock *, struct sk_buff *, u32, unsigned int);
544 
545 void tcp_send_probe0(struct sock *);
546 void tcp_send_partial(struct sock *);
547 int tcp_write_wakeup(struct sock *);
548 void tcp_send_fin(struct sock *sk);
549 void tcp_send_active_reset(struct sock *sk, gfp_t priority);
550 int tcp_send_synack(struct sock *);
551 bool tcp_syn_flood_action(struct sock *sk, const struct sk_buff *skb,
552 			  const char *proto);
553 void tcp_push_one(struct sock *, unsigned int mss_now);
554 void tcp_send_ack(struct sock *sk);
555 void tcp_send_delayed_ack(struct sock *sk);
556 void tcp_send_loss_probe(struct sock *sk);
557 bool tcp_schedule_loss_probe(struct sock *sk);
558 
559 /* tcp_input.c */
560 void tcp_cwnd_application_limited(struct sock *sk);
561 void tcp_resume_early_retransmit(struct sock *sk);
562 void tcp_rearm_rto(struct sock *sk);
563 void tcp_reset(struct sock *sk);
564 
565 /* tcp_timer.c */
566 void tcp_init_xmit_timers(struct sock *);
567 static inline void tcp_clear_xmit_timers(struct sock *sk)
568 {
569 	inet_csk_clear_xmit_timers(sk);
570 }
571 
572 unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
573 unsigned int tcp_current_mss(struct sock *sk);
574 
575 /* Bound MSS / TSO packet size with the half of the window */
576 static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
577 {
578 	int cutoff;
579 
580 	/* When peer uses tiny windows, there is no use in packetizing
581 	 * to sub-MSS pieces for the sake of SWS or making sure there
582 	 * are enough packets in the pipe for fast recovery.
583 	 *
584 	 * On the other hand, for extremely large MSS devices, handling
585 	 * smaller than MSS windows in this way does make sense.
586 	 */
587 	if (tp->max_window >= 512)
588 		cutoff = (tp->max_window >> 1);
589 	else
590 		cutoff = tp->max_window;
591 
592 	if (cutoff && pktsize > cutoff)
593 		return max_t(int, cutoff, 68U - tp->tcp_header_len);
594 	else
595 		return pktsize;
596 }
597 
598 /* tcp.c */
599 void tcp_get_info(const struct sock *, struct tcp_info *);
600 
601 /* Read 'sendfile()'-style from a TCP socket */
602 typedef int (*sk_read_actor_t)(read_descriptor_t *, struct sk_buff *,
603 				unsigned int, size_t);
604 int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
605 		  sk_read_actor_t recv_actor);
606 
607 void tcp_initialize_rcv_mss(struct sock *sk);
608 
609 int tcp_mtu_to_mss(struct sock *sk, int pmtu);
610 int tcp_mss_to_mtu(struct sock *sk, int mss);
611 void tcp_mtup_init(struct sock *sk);
612 void tcp_init_buffer_space(struct sock *sk);
613 
614 static inline void tcp_bound_rto(const struct sock *sk)
615 {
616 	if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
617 		inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
618 }
619 
620 static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
621 {
622 	return (tp->srtt >> 3) + tp->rttvar;
623 }
624 
625 void tcp_set_rto(struct sock *sk);
626 
627 static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
628 {
629 	tp->pred_flags = htonl((tp->tcp_header_len << 26) |
630 			       ntohl(TCP_FLAG_ACK) |
631 			       snd_wnd);
632 }
633 
634 static inline void tcp_fast_path_on(struct tcp_sock *tp)
635 {
636 	__tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
637 }
638 
639 static inline void tcp_fast_path_check(struct sock *sk)
640 {
641 	struct tcp_sock *tp = tcp_sk(sk);
642 
643 	if (skb_queue_empty(&tp->out_of_order_queue) &&
644 	    tp->rcv_wnd &&
645 	    atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
646 	    !tp->urg_data)
647 		tcp_fast_path_on(tp);
648 }
649 
650 /* Compute the actual rto_min value */
651 static inline u32 tcp_rto_min(struct sock *sk)
652 {
653 	const struct dst_entry *dst = __sk_dst_get(sk);
654 	u32 rto_min = TCP_RTO_MIN;
655 
656 	if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
657 		rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
658 	return rto_min;
659 }
660 
661 /* Compute the actual receive window we are currently advertising.
662  * Rcv_nxt can be after the window if our peer push more data
663  * than the offered window.
664  */
665 static inline u32 tcp_receive_window(const struct tcp_sock *tp)
666 {
667 	s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;
668 
669 	if (win < 0)
670 		win = 0;
671 	return (u32) win;
672 }
673 
674 /* Choose a new window, without checks for shrinking, and without
675  * scaling applied to the result.  The caller does these things
676  * if necessary.  This is a "raw" window selection.
677  */
678 u32 __tcp_select_window(struct sock *sk);
679 
680 void tcp_send_window_probe(struct sock *sk);
681 
682 /* TCP timestamps are only 32-bits, this causes a slight
683  * complication on 64-bit systems since we store a snapshot
684  * of jiffies in the buffer control blocks below.  We decided
685  * to use only the low 32-bits of jiffies and hide the ugly
686  * casts with the following macro.
687  */
688 #define tcp_time_stamp		((__u32)(jiffies))
689 
690 #define tcp_flag_byte(th) (((u_int8_t *)th)[13])
691 
692 #define TCPHDR_FIN 0x01
693 #define TCPHDR_SYN 0x02
694 #define TCPHDR_RST 0x04
695 #define TCPHDR_PSH 0x08
696 #define TCPHDR_ACK 0x10
697 #define TCPHDR_URG 0x20
698 #define TCPHDR_ECE 0x40
699 #define TCPHDR_CWR 0x80
700 
701 /* This is what the send packet queuing engine uses to pass
702  * TCP per-packet control information to the transmission code.
703  * We also store the host-order sequence numbers in here too.
704  * This is 44 bytes if IPV6 is enabled.
705  * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately.
706  */
707 struct tcp_skb_cb {
708 	union {
709 		struct inet_skb_parm	h4;
710 #if IS_ENABLED(CONFIG_IPV6)
711 		struct inet6_skb_parm	h6;
712 #endif
713 	} header;	/* For incoming frames		*/
714 	__u32		seq;		/* Starting sequence number	*/
715 	__u32		end_seq;	/* SEQ + FIN + SYN + datalen	*/
716 	__u32		when;		/* used to compute rtt's	*/
717 	__u8		tcp_flags;	/* TCP header flags. (tcp[13])	*/
718 
719 	__u8		sacked;		/* State flags for SACK/FACK.	*/
720 #define TCPCB_SACKED_ACKED	0x01	/* SKB ACK'd by a SACK block	*/
721 #define TCPCB_SACKED_RETRANS	0x02	/* SKB retransmitted		*/
722 #define TCPCB_LOST		0x04	/* SKB is lost			*/
723 #define TCPCB_TAGBITS		0x07	/* All tag bits			*/
724 #define TCPCB_EVER_RETRANS	0x80	/* Ever retransmitted frame	*/
725 #define TCPCB_RETRANS		(TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS)
726 
727 	__u8		ip_dsfield;	/* IPv4 tos or IPv6 dsfield	*/
728 	/* 1 byte hole */
729 	__u32		ack_seq;	/* Sequence number ACK'd	*/
730 };
731 
732 #define TCP_SKB_CB(__skb)	((struct tcp_skb_cb *)&((__skb)->cb[0]))
733 
734 /* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set
735  *
736  * If we receive a SYN packet with these bits set, it means a network is
737  * playing bad games with TOS bits. In order to avoid possible false congestion
738  * notifications, we disable TCP ECN negociation.
739  */
740 static inline void
741 TCP_ECN_create_request(struct request_sock *req, const struct sk_buff *skb,
742 		struct net *net)
743 {
744 	const struct tcphdr *th = tcp_hdr(skb);
745 
746 	if (net->ipv4.sysctl_tcp_ecn && th->ece && th->cwr &&
747 	    INET_ECN_is_not_ect(TCP_SKB_CB(skb)->ip_dsfield))
748 		inet_rsk(req)->ecn_ok = 1;
749 }
750 
751 /* Due to TSO, an SKB can be composed of multiple actual
752  * packets.  To keep these tracked properly, we use this.
753  */
754 static inline int tcp_skb_pcount(const struct sk_buff *skb)
755 {
756 	return skb_shinfo(skb)->gso_segs;
757 }
758 
759 /* This is valid iff tcp_skb_pcount() > 1. */
760 static inline int tcp_skb_mss(const struct sk_buff *skb)
761 {
762 	return skb_shinfo(skb)->gso_size;
763 }
764 
765 /* Events passed to congestion control interface */
766 enum tcp_ca_event {
767 	CA_EVENT_TX_START,	/* first transmit when no packets in flight */
768 	CA_EVENT_CWND_RESTART,	/* congestion window restart */
769 	CA_EVENT_COMPLETE_CWR,	/* end of congestion recovery */
770 	CA_EVENT_LOSS,		/* loss timeout */
771 	CA_EVENT_FAST_ACK,	/* in sequence ack */
772 	CA_EVENT_SLOW_ACK,	/* other ack */
773 };
774 
775 /*
776  * Interface for adding new TCP congestion control handlers
777  */
778 #define TCP_CA_NAME_MAX	16
779 #define TCP_CA_MAX	128
780 #define TCP_CA_BUF_MAX	(TCP_CA_NAME_MAX*TCP_CA_MAX)
781 
782 #define TCP_CONG_NON_RESTRICTED 0x1
783 #define TCP_CONG_RTT_STAMP	0x2
784 
785 struct tcp_congestion_ops {
786 	struct list_head	list;
787 	unsigned long flags;
788 
789 	/* initialize private data (optional) */
790 	void (*init)(struct sock *sk);
791 	/* cleanup private data  (optional) */
792 	void (*release)(struct sock *sk);
793 
794 	/* return slow start threshold (required) */
795 	u32 (*ssthresh)(struct sock *sk);
796 	/* lower bound for congestion window (optional) */
797 	u32 (*min_cwnd)(const struct sock *sk);
798 	/* do new cwnd calculation (required) */
799 	void (*cong_avoid)(struct sock *sk, u32 ack, u32 acked, u32 in_flight);
800 	/* call before changing ca_state (optional) */
801 	void (*set_state)(struct sock *sk, u8 new_state);
802 	/* call when cwnd event occurs (optional) */
803 	void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
804 	/* new value of cwnd after loss (optional) */
805 	u32  (*undo_cwnd)(struct sock *sk);
806 	/* hook for packet ack accounting (optional) */
807 	void (*pkts_acked)(struct sock *sk, u32 num_acked, s32 rtt_us);
808 	/* get info for inet_diag (optional) */
809 	void (*get_info)(struct sock *sk, u32 ext, struct sk_buff *skb);
810 
811 	char 		name[TCP_CA_NAME_MAX];
812 	struct module 	*owner;
813 };
814 
815 int tcp_register_congestion_control(struct tcp_congestion_ops *type);
816 void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
817 
818 void tcp_init_congestion_control(struct sock *sk);
819 void tcp_cleanup_congestion_control(struct sock *sk);
820 int tcp_set_default_congestion_control(const char *name);
821 void tcp_get_default_congestion_control(char *name);
822 void tcp_get_available_congestion_control(char *buf, size_t len);
823 void tcp_get_allowed_congestion_control(char *buf, size_t len);
824 int tcp_set_allowed_congestion_control(char *allowed);
825 int tcp_set_congestion_control(struct sock *sk, const char *name);
826 int tcp_slow_start(struct tcp_sock *tp, u32 acked);
827 void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w);
828 
829 extern struct tcp_congestion_ops tcp_init_congestion_ops;
830 u32 tcp_reno_ssthresh(struct sock *sk);
831 void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked, u32 in_flight);
832 u32 tcp_reno_min_cwnd(const struct sock *sk);
833 extern struct tcp_congestion_ops tcp_reno;
834 
835 static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
836 {
837 	struct inet_connection_sock *icsk = inet_csk(sk);
838 
839 	if (icsk->icsk_ca_ops->set_state)
840 		icsk->icsk_ca_ops->set_state(sk, ca_state);
841 	icsk->icsk_ca_state = ca_state;
842 }
843 
844 static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
845 {
846 	const struct inet_connection_sock *icsk = inet_csk(sk);
847 
848 	if (icsk->icsk_ca_ops->cwnd_event)
849 		icsk->icsk_ca_ops->cwnd_event(sk, event);
850 }
851 
852 /* These functions determine how the current flow behaves in respect of SACK
853  * handling. SACK is negotiated with the peer, and therefore it can vary
854  * between different flows.
855  *
856  * tcp_is_sack - SACK enabled
857  * tcp_is_reno - No SACK
858  * tcp_is_fack - FACK enabled, implies SACK enabled
859  */
860 static inline int tcp_is_sack(const struct tcp_sock *tp)
861 {
862 	return tp->rx_opt.sack_ok;
863 }
864 
865 static inline bool tcp_is_reno(const struct tcp_sock *tp)
866 {
867 	return !tcp_is_sack(tp);
868 }
869 
870 static inline bool tcp_is_fack(const struct tcp_sock *tp)
871 {
872 	return tp->rx_opt.sack_ok & TCP_FACK_ENABLED;
873 }
874 
875 static inline void tcp_enable_fack(struct tcp_sock *tp)
876 {
877 	tp->rx_opt.sack_ok |= TCP_FACK_ENABLED;
878 }
879 
880 /* TCP early-retransmit (ER) is similar to but more conservative than
881  * the thin-dupack feature.  Enable ER only if thin-dupack is disabled.
882  */
883 static inline void tcp_enable_early_retrans(struct tcp_sock *tp)
884 {
885 	tp->do_early_retrans = sysctl_tcp_early_retrans &&
886 		sysctl_tcp_early_retrans < 4 && !sysctl_tcp_thin_dupack &&
887 		sysctl_tcp_reordering == 3;
888 }
889 
890 static inline void tcp_disable_early_retrans(struct tcp_sock *tp)
891 {
892 	tp->do_early_retrans = 0;
893 }
894 
895 static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
896 {
897 	return tp->sacked_out + tp->lost_out;
898 }
899 
900 /* This determines how many packets are "in the network" to the best
901  * of our knowledge.  In many cases it is conservative, but where
902  * detailed information is available from the receiver (via SACK
903  * blocks etc.) we can make more aggressive calculations.
904  *
905  * Use this for decisions involving congestion control, use just
906  * tp->packets_out to determine if the send queue is empty or not.
907  *
908  * Read this equation as:
909  *
910  *	"Packets sent once on transmission queue" MINUS
911  *	"Packets left network, but not honestly ACKed yet" PLUS
912  *	"Packets fast retransmitted"
913  */
914 static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
915 {
916 	return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
917 }
918 
919 #define TCP_INFINITE_SSTHRESH	0x7fffffff
920 
921 static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
922 {
923 	return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
924 }
925 
926 static inline bool tcp_in_cwnd_reduction(const struct sock *sk)
927 {
928 	return (TCPF_CA_CWR | TCPF_CA_Recovery) &
929 	       (1 << inet_csk(sk)->icsk_ca_state);
930 }
931 
932 /* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
933  * The exception is cwnd reduction phase, when cwnd is decreasing towards
934  * ssthresh.
935  */
936 static inline __u32 tcp_current_ssthresh(const struct sock *sk)
937 {
938 	const struct tcp_sock *tp = tcp_sk(sk);
939 
940 	if (tcp_in_cwnd_reduction(sk))
941 		return tp->snd_ssthresh;
942 	else
943 		return max(tp->snd_ssthresh,
944 			   ((tp->snd_cwnd >> 1) +
945 			    (tp->snd_cwnd >> 2)));
946 }
947 
948 /* Use define here intentionally to get WARN_ON location shown at the caller */
949 #define tcp_verify_left_out(tp)	WARN_ON(tcp_left_out(tp) > tp->packets_out)
950 
951 void tcp_enter_cwr(struct sock *sk, const int set_ssthresh);
952 __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst);
953 
954 /* The maximum number of MSS of available cwnd for which TSO defers
955  * sending if not using sysctl_tcp_tso_win_divisor.
956  */
957 static inline __u32 tcp_max_tso_deferred_mss(const struct tcp_sock *tp)
958 {
959 	return 3;
960 }
961 
962 /* Slow start with delack produces 3 packets of burst, so that
963  * it is safe "de facto".  This will be the default - same as
964  * the default reordering threshold - but if reordering increases,
965  * we must be able to allow cwnd to burst at least this much in order
966  * to not pull it back when holes are filled.
967  */
968 static __inline__ __u32 tcp_max_burst(const struct tcp_sock *tp)
969 {
970 	return tp->reordering;
971 }
972 
973 /* Returns end sequence number of the receiver's advertised window */
974 static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
975 {
976 	return tp->snd_una + tp->snd_wnd;
977 }
978 bool tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight);
979 
980 static inline void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss,
981 				       const struct sk_buff *skb)
982 {
983 	if (skb->len < mss)
984 		tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
985 }
986 
987 static inline void tcp_check_probe_timer(struct sock *sk)
988 {
989 	const struct tcp_sock *tp = tcp_sk(sk);
990 	const struct inet_connection_sock *icsk = inet_csk(sk);
991 
992 	if (!tp->packets_out && !icsk->icsk_pending)
993 		inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
994 					  icsk->icsk_rto, TCP_RTO_MAX);
995 }
996 
997 static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
998 {
999 	tp->snd_wl1 = seq;
1000 }
1001 
1002 static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq)
1003 {
1004 	tp->snd_wl1 = seq;
1005 }
1006 
1007 /*
1008  * Calculate(/check) TCP checksum
1009  */
1010 static inline __sum16 tcp_v4_check(int len, __be32 saddr,
1011 				   __be32 daddr, __wsum base)
1012 {
1013 	return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base);
1014 }
1015 
1016 static inline __sum16 __tcp_checksum_complete(struct sk_buff *skb)
1017 {
1018 	return __skb_checksum_complete(skb);
1019 }
1020 
1021 static inline bool tcp_checksum_complete(struct sk_buff *skb)
1022 {
1023 	return !skb_csum_unnecessary(skb) &&
1024 		__tcp_checksum_complete(skb);
1025 }
1026 
1027 /* Prequeue for VJ style copy to user, combined with checksumming. */
1028 
1029 static inline void tcp_prequeue_init(struct tcp_sock *tp)
1030 {
1031 	tp->ucopy.task = NULL;
1032 	tp->ucopy.len = 0;
1033 	tp->ucopy.memory = 0;
1034 	skb_queue_head_init(&tp->ucopy.prequeue);
1035 #ifdef CONFIG_NET_DMA
1036 	tp->ucopy.dma_chan = NULL;
1037 	tp->ucopy.wakeup = 0;
1038 	tp->ucopy.pinned_list = NULL;
1039 	tp->ucopy.dma_cookie = 0;
1040 #endif
1041 }
1042 
1043 bool tcp_prequeue(struct sock *sk, struct sk_buff *skb);
1044 
1045 #undef STATE_TRACE
1046 
1047 #ifdef STATE_TRACE
1048 static const char *statename[]={
1049 	"Unused","Established","Syn Sent","Syn Recv",
1050 	"Fin Wait 1","Fin Wait 2","Time Wait", "Close",
1051 	"Close Wait","Last ACK","Listen","Closing"
1052 };
1053 #endif
1054 void tcp_set_state(struct sock *sk, int state);
1055 
1056 void tcp_done(struct sock *sk);
1057 
1058 static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
1059 {
1060 	rx_opt->dsack = 0;
1061 	rx_opt->num_sacks = 0;
1062 }
1063 
1064 u32 tcp_default_init_rwnd(u32 mss);
1065 
1066 /* Determine a window scaling and initial window to offer. */
1067 void tcp_select_initial_window(int __space, __u32 mss, __u32 *rcv_wnd,
1068 			       __u32 *window_clamp, int wscale_ok,
1069 			       __u8 *rcv_wscale, __u32 init_rcv_wnd);
1070 
1071 static inline int tcp_win_from_space(int space)
1072 {
1073 	return sysctl_tcp_adv_win_scale<=0 ?
1074 		(space>>(-sysctl_tcp_adv_win_scale)) :
1075 		space - (space>>sysctl_tcp_adv_win_scale);
1076 }
1077 
1078 /* Note: caller must be prepared to deal with negative returns */
1079 static inline int tcp_space(const struct sock *sk)
1080 {
1081 	return tcp_win_from_space(sk->sk_rcvbuf -
1082 				  atomic_read(&sk->sk_rmem_alloc));
1083 }
1084 
1085 static inline int tcp_full_space(const struct sock *sk)
1086 {
1087 	return tcp_win_from_space(sk->sk_rcvbuf);
1088 }
1089 
1090 static inline void tcp_openreq_init(struct request_sock *req,
1091 				    struct tcp_options_received *rx_opt,
1092 				    struct sk_buff *skb)
1093 {
1094 	struct inet_request_sock *ireq = inet_rsk(req);
1095 
1096 	req->rcv_wnd = 0;		/* So that tcp_send_synack() knows! */
1097 	req->cookie_ts = 0;
1098 	tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq;
1099 	tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
1100 	tcp_rsk(req)->snt_synack = 0;
1101 	req->mss = rx_opt->mss_clamp;
1102 	req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0;
1103 	ireq->tstamp_ok = rx_opt->tstamp_ok;
1104 	ireq->sack_ok = rx_opt->sack_ok;
1105 	ireq->snd_wscale = rx_opt->snd_wscale;
1106 	ireq->wscale_ok = rx_opt->wscale_ok;
1107 	ireq->acked = 0;
1108 	ireq->ecn_ok = 0;
1109 	ireq->ir_rmt_port = tcp_hdr(skb)->source;
1110 	ireq->ir_num = ntohs(tcp_hdr(skb)->dest);
1111 }
1112 
1113 void tcp_enter_memory_pressure(struct sock *sk);
1114 
1115 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
1116 {
1117 	return tp->keepalive_intvl ? : sysctl_tcp_keepalive_intvl;
1118 }
1119 
1120 static inline int keepalive_time_when(const struct tcp_sock *tp)
1121 {
1122 	return tp->keepalive_time ? : sysctl_tcp_keepalive_time;
1123 }
1124 
1125 static inline int keepalive_probes(const struct tcp_sock *tp)
1126 {
1127 	return tp->keepalive_probes ? : sysctl_tcp_keepalive_probes;
1128 }
1129 
1130 static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
1131 {
1132 	const struct inet_connection_sock *icsk = &tp->inet_conn;
1133 
1134 	return min_t(u32, tcp_time_stamp - icsk->icsk_ack.lrcvtime,
1135 			  tcp_time_stamp - tp->rcv_tstamp);
1136 }
1137 
1138 static inline int tcp_fin_time(const struct sock *sk)
1139 {
1140 	int fin_timeout = tcp_sk(sk)->linger2 ? : sysctl_tcp_fin_timeout;
1141 	const int rto = inet_csk(sk)->icsk_rto;
1142 
1143 	if (fin_timeout < (rto << 2) - (rto >> 1))
1144 		fin_timeout = (rto << 2) - (rto >> 1);
1145 
1146 	return fin_timeout;
1147 }
1148 
1149 static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt,
1150 				  int paws_win)
1151 {
1152 	if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
1153 		return true;
1154 	if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
1155 		return true;
1156 	/*
1157 	 * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
1158 	 * then following tcp messages have valid values. Ignore 0 value,
1159 	 * or else 'negative' tsval might forbid us to accept their packets.
1160 	 */
1161 	if (!rx_opt->ts_recent)
1162 		return true;
1163 	return false;
1164 }
1165 
1166 static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt,
1167 				   int rst)
1168 {
1169 	if (tcp_paws_check(rx_opt, 0))
1170 		return false;
1171 
1172 	/* RST segments are not recommended to carry timestamp,
1173 	   and, if they do, it is recommended to ignore PAWS because
1174 	   "their cleanup function should take precedence over timestamps."
1175 	   Certainly, it is mistake. It is necessary to understand the reasons
1176 	   of this constraint to relax it: if peer reboots, clock may go
1177 	   out-of-sync and half-open connections will not be reset.
1178 	   Actually, the problem would be not existing if all
1179 	   the implementations followed draft about maintaining clock
1180 	   via reboots. Linux-2.2 DOES NOT!
1181 
1182 	   However, we can relax time bounds for RST segments to MSL.
1183 	 */
1184 	if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
1185 		return false;
1186 	return true;
1187 }
1188 
1189 static inline void tcp_mib_init(struct net *net)
1190 {
1191 	/* See RFC 2012 */
1192 	TCP_ADD_STATS_USER(net, TCP_MIB_RTOALGORITHM, 1);
1193 	TCP_ADD_STATS_USER(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
1194 	TCP_ADD_STATS_USER(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
1195 	TCP_ADD_STATS_USER(net, TCP_MIB_MAXCONN, -1);
1196 }
1197 
1198 /* from STCP */
1199 static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
1200 {
1201 	tp->lost_skb_hint = NULL;
1202 }
1203 
1204 static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
1205 {
1206 	tcp_clear_retrans_hints_partial(tp);
1207 	tp->retransmit_skb_hint = NULL;
1208 }
1209 
1210 /* MD5 Signature */
1211 struct crypto_hash;
1212 
1213 union tcp_md5_addr {
1214 	struct in_addr  a4;
1215 #if IS_ENABLED(CONFIG_IPV6)
1216 	struct in6_addr	a6;
1217 #endif
1218 };
1219 
1220 /* - key database */
1221 struct tcp_md5sig_key {
1222 	struct hlist_node	node;
1223 	u8			keylen;
1224 	u8			family; /* AF_INET or AF_INET6 */
1225 	union tcp_md5_addr	addr;
1226 	u8			key[TCP_MD5SIG_MAXKEYLEN];
1227 	struct rcu_head		rcu;
1228 };
1229 
1230 /* - sock block */
1231 struct tcp_md5sig_info {
1232 	struct hlist_head	head;
1233 	struct rcu_head		rcu;
1234 };
1235 
1236 /* - pseudo header */
1237 struct tcp4_pseudohdr {
1238 	__be32		saddr;
1239 	__be32		daddr;
1240 	__u8		pad;
1241 	__u8		protocol;
1242 	__be16		len;
1243 };
1244 
1245 struct tcp6_pseudohdr {
1246 	struct in6_addr	saddr;
1247 	struct in6_addr daddr;
1248 	__be32		len;
1249 	__be32		protocol;	/* including padding */
1250 };
1251 
1252 union tcp_md5sum_block {
1253 	struct tcp4_pseudohdr ip4;
1254 #if IS_ENABLED(CONFIG_IPV6)
1255 	struct tcp6_pseudohdr ip6;
1256 #endif
1257 };
1258 
1259 /* - pool: digest algorithm, hash description and scratch buffer */
1260 struct tcp_md5sig_pool {
1261 	struct hash_desc	md5_desc;
1262 	union tcp_md5sum_block	md5_blk;
1263 };
1264 
1265 /* - functions */
1266 int tcp_v4_md5_hash_skb(char *md5_hash, struct tcp_md5sig_key *key,
1267 			const struct sock *sk, const struct request_sock *req,
1268 			const struct sk_buff *skb);
1269 int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
1270 		   int family, const u8 *newkey, u8 newkeylen, gfp_t gfp);
1271 int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
1272 		   int family);
1273 struct tcp_md5sig_key *tcp_v4_md5_lookup(struct sock *sk,
1274 					 struct sock *addr_sk);
1275 
1276 #ifdef CONFIG_TCP_MD5SIG
1277 struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
1278 					 const union tcp_md5_addr *addr,
1279 					 int family);
1280 #define tcp_twsk_md5_key(twsk)	((twsk)->tw_md5_key)
1281 #else
1282 static inline struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
1283 					 const union tcp_md5_addr *addr,
1284 					 int family)
1285 {
1286 	return NULL;
1287 }
1288 #define tcp_twsk_md5_key(twsk)	NULL
1289 #endif
1290 
1291 bool tcp_alloc_md5sig_pool(void);
1292 
1293 struct tcp_md5sig_pool *tcp_get_md5sig_pool(void);
1294 static inline void tcp_put_md5sig_pool(void)
1295 {
1296 	local_bh_enable();
1297 }
1298 
1299 int tcp_md5_hash_header(struct tcp_md5sig_pool *, const struct tcphdr *);
1300 int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
1301 			  unsigned int header_len);
1302 int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
1303 		     const struct tcp_md5sig_key *key);
1304 
1305 /* From tcp_fastopen.c */
1306 void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
1307 			    struct tcp_fastopen_cookie *cookie, int *syn_loss,
1308 			    unsigned long *last_syn_loss);
1309 void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
1310 			    struct tcp_fastopen_cookie *cookie, bool syn_lost);
1311 struct tcp_fastopen_request {
1312 	/* Fast Open cookie. Size 0 means a cookie request */
1313 	struct tcp_fastopen_cookie	cookie;
1314 	struct msghdr			*data;  /* data in MSG_FASTOPEN */
1315 	u16				copied;	/* queued in tcp_connect() */
1316 };
1317 void tcp_free_fastopen_req(struct tcp_sock *tp);
1318 
1319 extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
1320 int tcp_fastopen_reset_cipher(void *key, unsigned int len);
1321 void tcp_fastopen_cookie_gen(__be32 src, __be32 dst,
1322 			     struct tcp_fastopen_cookie *foc);
1323 void tcp_fastopen_init_key_once(bool publish);
1324 #define TCP_FASTOPEN_KEY_LENGTH 16
1325 
1326 /* Fastopen key context */
1327 struct tcp_fastopen_context {
1328 	struct crypto_cipher	*tfm;
1329 	__u8			key[TCP_FASTOPEN_KEY_LENGTH];
1330 	struct rcu_head		rcu;
1331 };
1332 
1333 /* write queue abstraction */
1334 static inline void tcp_write_queue_purge(struct sock *sk)
1335 {
1336 	struct sk_buff *skb;
1337 
1338 	while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL)
1339 		sk_wmem_free_skb(sk, skb);
1340 	sk_mem_reclaim(sk);
1341 	tcp_clear_all_retrans_hints(tcp_sk(sk));
1342 }
1343 
1344 static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)
1345 {
1346 	return skb_peek(&sk->sk_write_queue);
1347 }
1348 
1349 static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk)
1350 {
1351 	return skb_peek_tail(&sk->sk_write_queue);
1352 }
1353 
1354 static inline struct sk_buff *tcp_write_queue_next(const struct sock *sk,
1355 						   const struct sk_buff *skb)
1356 {
1357 	return skb_queue_next(&sk->sk_write_queue, skb);
1358 }
1359 
1360 static inline struct sk_buff *tcp_write_queue_prev(const struct sock *sk,
1361 						   const struct sk_buff *skb)
1362 {
1363 	return skb_queue_prev(&sk->sk_write_queue, skb);
1364 }
1365 
1366 #define tcp_for_write_queue(skb, sk)					\
1367 	skb_queue_walk(&(sk)->sk_write_queue, skb)
1368 
1369 #define tcp_for_write_queue_from(skb, sk)				\
1370 	skb_queue_walk_from(&(sk)->sk_write_queue, skb)
1371 
1372 #define tcp_for_write_queue_from_safe(skb, tmp, sk)			\
1373 	skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
1374 
1375 static inline struct sk_buff *tcp_send_head(const struct sock *sk)
1376 {
1377 	return sk->sk_send_head;
1378 }
1379 
1380 static inline bool tcp_skb_is_last(const struct sock *sk,
1381 				   const struct sk_buff *skb)
1382 {
1383 	return skb_queue_is_last(&sk->sk_write_queue, skb);
1384 }
1385 
1386 static inline void tcp_advance_send_head(struct sock *sk, const struct sk_buff *skb)
1387 {
1388 	if (tcp_skb_is_last(sk, skb))
1389 		sk->sk_send_head = NULL;
1390 	else
1391 		sk->sk_send_head = tcp_write_queue_next(sk, skb);
1392 }
1393 
1394 static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
1395 {
1396 	if (sk->sk_send_head == skb_unlinked)
1397 		sk->sk_send_head = NULL;
1398 }
1399 
1400 static inline void tcp_init_send_head(struct sock *sk)
1401 {
1402 	sk->sk_send_head = NULL;
1403 }
1404 
1405 static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1406 {
1407 	__skb_queue_tail(&sk->sk_write_queue, skb);
1408 }
1409 
1410 static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1411 {
1412 	__tcp_add_write_queue_tail(sk, skb);
1413 
1414 	/* Queue it, remembering where we must start sending. */
1415 	if (sk->sk_send_head == NULL) {
1416 		sk->sk_send_head = skb;
1417 
1418 		if (tcp_sk(sk)->highest_sack == NULL)
1419 			tcp_sk(sk)->highest_sack = skb;
1420 	}
1421 }
1422 
1423 static inline void __tcp_add_write_queue_head(struct sock *sk, struct sk_buff *skb)
1424 {
1425 	__skb_queue_head(&sk->sk_write_queue, skb);
1426 }
1427 
1428 /* Insert buff after skb on the write queue of sk.  */
1429 static inline void tcp_insert_write_queue_after(struct sk_buff *skb,
1430 						struct sk_buff *buff,
1431 						struct sock *sk)
1432 {
1433 	__skb_queue_after(&sk->sk_write_queue, skb, buff);
1434 }
1435 
1436 /* Insert new before skb on the write queue of sk.  */
1437 static inline void tcp_insert_write_queue_before(struct sk_buff *new,
1438 						  struct sk_buff *skb,
1439 						  struct sock *sk)
1440 {
1441 	__skb_queue_before(&sk->sk_write_queue, skb, new);
1442 
1443 	if (sk->sk_send_head == skb)
1444 		sk->sk_send_head = new;
1445 }
1446 
1447 static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
1448 {
1449 	__skb_unlink(skb, &sk->sk_write_queue);
1450 }
1451 
1452 static inline bool tcp_write_queue_empty(struct sock *sk)
1453 {
1454 	return skb_queue_empty(&sk->sk_write_queue);
1455 }
1456 
1457 static inline void tcp_push_pending_frames(struct sock *sk)
1458 {
1459 	if (tcp_send_head(sk)) {
1460 		struct tcp_sock *tp = tcp_sk(sk);
1461 
1462 		__tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
1463 	}
1464 }
1465 
1466 /* Start sequence of the skb just after the highest skb with SACKed
1467  * bit, valid only if sacked_out > 0 or when the caller has ensured
1468  * validity by itself.
1469  */
1470 static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
1471 {
1472 	if (!tp->sacked_out)
1473 		return tp->snd_una;
1474 
1475 	if (tp->highest_sack == NULL)
1476 		return tp->snd_nxt;
1477 
1478 	return TCP_SKB_CB(tp->highest_sack)->seq;
1479 }
1480 
1481 static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
1482 {
1483 	tcp_sk(sk)->highest_sack = tcp_skb_is_last(sk, skb) ? NULL :
1484 						tcp_write_queue_next(sk, skb);
1485 }
1486 
1487 static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
1488 {
1489 	return tcp_sk(sk)->highest_sack;
1490 }
1491 
1492 static inline void tcp_highest_sack_reset(struct sock *sk)
1493 {
1494 	tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk);
1495 }
1496 
1497 /* Called when old skb is about to be deleted (to be combined with new skb) */
1498 static inline void tcp_highest_sack_combine(struct sock *sk,
1499 					    struct sk_buff *old,
1500 					    struct sk_buff *new)
1501 {
1502 	if (tcp_sk(sk)->sacked_out && (old == tcp_sk(sk)->highest_sack))
1503 		tcp_sk(sk)->highest_sack = new;
1504 }
1505 
1506 /* Determines whether this is a thin stream (which may suffer from
1507  * increased latency). Used to trigger latency-reducing mechanisms.
1508  */
1509 static inline bool tcp_stream_is_thin(struct tcp_sock *tp)
1510 {
1511 	return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
1512 }
1513 
1514 /* /proc */
1515 enum tcp_seq_states {
1516 	TCP_SEQ_STATE_LISTENING,
1517 	TCP_SEQ_STATE_OPENREQ,
1518 	TCP_SEQ_STATE_ESTABLISHED,
1519 };
1520 
1521 int tcp_seq_open(struct inode *inode, struct file *file);
1522 
1523 struct tcp_seq_afinfo {
1524 	char				*name;
1525 	sa_family_t			family;
1526 	const struct file_operations	*seq_fops;
1527 	struct seq_operations		seq_ops;
1528 };
1529 
1530 struct tcp_iter_state {
1531 	struct seq_net_private	p;
1532 	sa_family_t		family;
1533 	enum tcp_seq_states	state;
1534 	struct sock		*syn_wait_sk;
1535 	int			bucket, offset, sbucket, num;
1536 	kuid_t			uid;
1537 	loff_t			last_pos;
1538 };
1539 
1540 int tcp_proc_register(struct net *net, struct tcp_seq_afinfo *afinfo);
1541 void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo);
1542 
1543 extern struct request_sock_ops tcp_request_sock_ops;
1544 extern struct request_sock_ops tcp6_request_sock_ops;
1545 
1546 void tcp_v4_destroy_sock(struct sock *sk);
1547 
1548 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
1549 				netdev_features_t features);
1550 struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb);
1551 int tcp_gro_complete(struct sk_buff *skb);
1552 
1553 void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
1554 
1555 static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
1556 {
1557 	return tp->notsent_lowat ?: sysctl_tcp_notsent_lowat;
1558 }
1559 
1560 static inline bool tcp_stream_memory_free(const struct sock *sk)
1561 {
1562 	const struct tcp_sock *tp = tcp_sk(sk);
1563 	u32 notsent_bytes = tp->write_seq - tp->snd_nxt;
1564 
1565 	return notsent_bytes < tcp_notsent_lowat(tp);
1566 }
1567 
1568 #ifdef CONFIG_PROC_FS
1569 int tcp4_proc_init(void);
1570 void tcp4_proc_exit(void);
1571 #endif
1572 
1573 /* TCP af-specific functions */
1574 struct tcp_sock_af_ops {
1575 #ifdef CONFIG_TCP_MD5SIG
1576 	struct tcp_md5sig_key	*(*md5_lookup) (struct sock *sk,
1577 						struct sock *addr_sk);
1578 	int			(*calc_md5_hash) (char *location,
1579 						  struct tcp_md5sig_key *md5,
1580 						  const struct sock *sk,
1581 						  const struct request_sock *req,
1582 						  const struct sk_buff *skb);
1583 	int			(*md5_parse) (struct sock *sk,
1584 					      char __user *optval,
1585 					      int optlen);
1586 #endif
1587 };
1588 
1589 struct tcp_request_sock_ops {
1590 #ifdef CONFIG_TCP_MD5SIG
1591 	struct tcp_md5sig_key	*(*md5_lookup) (struct sock *sk,
1592 						struct request_sock *req);
1593 	int			(*calc_md5_hash) (char *location,
1594 						  struct tcp_md5sig_key *md5,
1595 						  const struct sock *sk,
1596 						  const struct request_sock *req,
1597 						  const struct sk_buff *skb);
1598 #endif
1599 };
1600 
1601 int tcpv4_offload_init(void);
1602 
1603 void tcp_v4_init(void);
1604 void tcp_init(void);
1605 
1606 #endif	/* _TCP_H */
1607