xref: /openbmc/linux/include/net/tcp.h (revision fa7f32422ea1ac276b45b96a540ed5981caaa61f)
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 extern struct inet_hashinfo tcp_hashinfo;
50 
51 extern struct percpu_counter tcp_orphan_count;
52 void tcp_time_wait(struct sock *sk, int state, int timeo);
53 
54 #define MAX_TCP_HEADER	(128 + MAX_HEADER)
55 #define MAX_TCP_OPTION_SPACE 40
56 
57 /*
58  * Never offer a window over 32767 without using window scaling. Some
59  * poor stacks do signed 16bit maths!
60  */
61 #define MAX_TCP_WINDOW		32767U
62 
63 /* Minimal accepted MSS. It is (60+60+8) - (20+20). */
64 #define TCP_MIN_MSS		88U
65 
66 /* The least MTU to use for probing */
67 #define TCP_BASE_MSS		1024
68 
69 /* probing interval, default to 10 minutes as per RFC4821 */
70 #define TCP_PROBE_INTERVAL	600
71 
72 /* Specify interval when tcp mtu probing will stop */
73 #define TCP_PROBE_THRESHOLD	8
74 
75 /* After receiving this amount of duplicate ACKs fast retransmit starts. */
76 #define TCP_FASTRETRANS_THRESH 3
77 
78 /* Maximal number of ACKs sent quickly to accelerate slow-start. */
79 #define TCP_MAX_QUICKACKS	16U
80 
81 /* urg_data states */
82 #define TCP_URG_VALID	0x0100
83 #define TCP_URG_NOTYET	0x0200
84 #define TCP_URG_READ	0x0400
85 
86 #define TCP_RETR1	3	/*
87 				 * This is how many retries it does before it
88 				 * tries to figure out if the gateway is
89 				 * down. Minimal RFC value is 3; it corresponds
90 				 * to ~3sec-8min depending on RTO.
91 				 */
92 
93 #define TCP_RETR2	15	/*
94 				 * This should take at least
95 				 * 90 minutes to time out.
96 				 * RFC1122 says that the limit is 100 sec.
97 				 * 15 is ~13-30min depending on RTO.
98 				 */
99 
100 #define TCP_SYN_RETRIES	 6	/* This is how many retries are done
101 				 * when active opening a connection.
102 				 * RFC1122 says the minimum retry MUST
103 				 * be at least 180secs.  Nevertheless
104 				 * this value is corresponding to
105 				 * 63secs of retransmission with the
106 				 * current initial RTO.
107 				 */
108 
109 #define TCP_SYNACK_RETRIES 5	/* This is how may retries are done
110 				 * when passive opening a connection.
111 				 * This is corresponding to 31secs of
112 				 * retransmission with the current
113 				 * initial RTO.
114 				 */
115 
116 #define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT
117 				  * state, about 60 seconds	*/
118 #define TCP_FIN_TIMEOUT	TCP_TIMEWAIT_LEN
119                                  /* BSD style FIN_WAIT2 deadlock breaker.
120 				  * It used to be 3min, new value is 60sec,
121 				  * to combine FIN-WAIT-2 timeout with
122 				  * TIME-WAIT timer.
123 				  */
124 
125 #define TCP_DELACK_MAX	((unsigned)(HZ/5))	/* maximal time to delay before sending an ACK */
126 #if HZ >= 100
127 #define TCP_DELACK_MIN	((unsigned)(HZ/25))	/* minimal time to delay before sending an ACK */
128 #define TCP_ATO_MIN	((unsigned)(HZ/25))
129 #else
130 #define TCP_DELACK_MIN	4U
131 #define TCP_ATO_MIN	4U
132 #endif
133 #define TCP_RTO_MAX	((unsigned)(120*HZ))
134 #define TCP_RTO_MIN	((unsigned)(HZ/5))
135 #define TCP_TIMEOUT_INIT ((unsigned)(1*HZ))	/* RFC6298 2.1 initial RTO value	*/
136 #define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ))	/* RFC 1122 initial RTO value, now
137 						 * used as a fallback RTO for the
138 						 * initial data transmission if no
139 						 * valid RTT sample has been acquired,
140 						 * most likely due to retrans in 3WHS.
141 						 */
142 
143 #define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes
144 					                 * for local resources.
145 					                 */
146 
147 #define TCP_KEEPALIVE_TIME	(120*60*HZ)	/* two hours */
148 #define TCP_KEEPALIVE_PROBES	9		/* Max of 9 keepalive probes	*/
149 #define TCP_KEEPALIVE_INTVL	(75*HZ)
150 
151 #define MAX_TCP_KEEPIDLE	32767
152 #define MAX_TCP_KEEPINTVL	32767
153 #define MAX_TCP_KEEPCNT		127
154 #define MAX_TCP_SYNCNT		127
155 
156 #define TCP_SYNQ_INTERVAL	(HZ/5)	/* Period of SYNACK timer */
157 
158 #define TCP_PAWS_24DAYS	(60 * 60 * 24 * 24)
159 #define TCP_PAWS_MSL	60		/* Per-host timestamps are invalidated
160 					 * after this time. It should be equal
161 					 * (or greater than) TCP_TIMEWAIT_LEN
162 					 * to provide reliability equal to one
163 					 * provided by timewait state.
164 					 */
165 #define TCP_PAWS_WINDOW	1		/* Replay window for per-host
166 					 * timestamps. It must be less than
167 					 * minimal timewait lifetime.
168 					 */
169 /*
170  *	TCP option
171  */
172 
173 #define TCPOPT_NOP		1	/* Padding */
174 #define TCPOPT_EOL		0	/* End of options */
175 #define TCPOPT_MSS		2	/* Segment size negotiating */
176 #define TCPOPT_WINDOW		3	/* Window scaling */
177 #define TCPOPT_SACK_PERM        4       /* SACK Permitted */
178 #define TCPOPT_SACK             5       /* SACK Block */
179 #define TCPOPT_TIMESTAMP	8	/* Better RTT estimations/PAWS */
180 #define TCPOPT_MD5SIG		19	/* MD5 Signature (RFC2385) */
181 #define TCPOPT_FASTOPEN		34	/* Fast open (RFC7413) */
182 #define TCPOPT_EXP		254	/* Experimental */
183 /* Magic number to be after the option value for sharing TCP
184  * experimental options. See draft-ietf-tcpm-experimental-options-00.txt
185  */
186 #define TCPOPT_FASTOPEN_MAGIC	0xF989
187 
188 /*
189  *     TCP option lengths
190  */
191 
192 #define TCPOLEN_MSS            4
193 #define TCPOLEN_WINDOW         3
194 #define TCPOLEN_SACK_PERM      2
195 #define TCPOLEN_TIMESTAMP      10
196 #define TCPOLEN_MD5SIG         18
197 #define TCPOLEN_FASTOPEN_BASE  2
198 #define TCPOLEN_EXP_FASTOPEN_BASE  4
199 
200 /* But this is what stacks really send out. */
201 #define TCPOLEN_TSTAMP_ALIGNED		12
202 #define TCPOLEN_WSCALE_ALIGNED		4
203 #define TCPOLEN_SACKPERM_ALIGNED	4
204 #define TCPOLEN_SACK_BASE		2
205 #define TCPOLEN_SACK_BASE_ALIGNED	4
206 #define TCPOLEN_SACK_PERBLOCK		8
207 #define TCPOLEN_MD5SIG_ALIGNED		20
208 #define TCPOLEN_MSS_ALIGNED		4
209 
210 /* Flags in tp->nonagle */
211 #define TCP_NAGLE_OFF		1	/* Nagle's algo is disabled */
212 #define TCP_NAGLE_CORK		2	/* Socket is corked	    */
213 #define TCP_NAGLE_PUSH		4	/* Cork is overridden for already queued data */
214 
215 /* TCP thin-stream limits */
216 #define TCP_THIN_LINEAR_RETRIES 6       /* After 6 linear retries, do exp. backoff */
217 
218 /* TCP initial congestion window as per rfc6928 */
219 #define TCP_INIT_CWND		10
220 
221 /* Bit Flags for sysctl_tcp_fastopen */
222 #define	TFO_CLIENT_ENABLE	1
223 #define	TFO_SERVER_ENABLE	2
224 #define	TFO_CLIENT_NO_COOKIE	4	/* Data in SYN w/o cookie option */
225 
226 /* Accept SYN data w/o any cookie option */
227 #define	TFO_SERVER_COOKIE_NOT_REQD	0x200
228 
229 /* Force enable TFO on all listeners, i.e., not requiring the
230  * TCP_FASTOPEN socket option.
231  */
232 #define	TFO_SERVER_WO_SOCKOPT1	0x400
233 
234 extern struct inet_timewait_death_row tcp_death_row;
235 
236 /* sysctl variables for tcp */
237 extern int sysctl_tcp_timestamps;
238 extern int sysctl_tcp_window_scaling;
239 extern int sysctl_tcp_sack;
240 extern int sysctl_tcp_fastopen;
241 extern int sysctl_tcp_retrans_collapse;
242 extern int sysctl_tcp_stdurg;
243 extern int sysctl_tcp_rfc1337;
244 extern int sysctl_tcp_abort_on_overflow;
245 extern int sysctl_tcp_max_orphans;
246 extern int sysctl_tcp_fack;
247 extern int sysctl_tcp_reordering;
248 extern int sysctl_tcp_max_reordering;
249 extern int sysctl_tcp_dsack;
250 extern long sysctl_tcp_mem[3];
251 extern int sysctl_tcp_wmem[3];
252 extern int sysctl_tcp_rmem[3];
253 extern int sysctl_tcp_app_win;
254 extern int sysctl_tcp_adv_win_scale;
255 extern int sysctl_tcp_tw_reuse;
256 extern int sysctl_tcp_frto;
257 extern int sysctl_tcp_low_latency;
258 extern int sysctl_tcp_nometrics_save;
259 extern int sysctl_tcp_moderate_rcvbuf;
260 extern int sysctl_tcp_tso_win_divisor;
261 extern int sysctl_tcp_workaround_signed_windows;
262 extern int sysctl_tcp_slow_start_after_idle;
263 extern int sysctl_tcp_thin_linear_timeouts;
264 extern int sysctl_tcp_thin_dupack;
265 extern int sysctl_tcp_early_retrans;
266 extern int sysctl_tcp_limit_output_bytes;
267 extern int sysctl_tcp_challenge_ack_limit;
268 extern int sysctl_tcp_min_tso_segs;
269 extern int sysctl_tcp_min_rtt_wlen;
270 extern int sysctl_tcp_autocorking;
271 extern int sysctl_tcp_invalid_ratelimit;
272 extern int sysctl_tcp_pacing_ss_ratio;
273 extern int sysctl_tcp_pacing_ca_ratio;
274 
275 extern atomic_long_t tcp_memory_allocated;
276 extern struct percpu_counter tcp_sockets_allocated;
277 extern int tcp_memory_pressure;
278 
279 /* optimized version of sk_under_memory_pressure() for TCP sockets */
280 static inline bool tcp_under_memory_pressure(const struct sock *sk)
281 {
282 	if (mem_cgroup_sockets_enabled && sk->sk_memcg &&
283 	    mem_cgroup_under_socket_pressure(sk->sk_memcg))
284 		return true;
285 
286 	return tcp_memory_pressure;
287 }
288 /*
289  * The next routines deal with comparing 32 bit unsigned ints
290  * and worry about wraparound (automatic with unsigned arithmetic).
291  */
292 
293 static inline bool before(__u32 seq1, __u32 seq2)
294 {
295         return (__s32)(seq1-seq2) < 0;
296 }
297 #define after(seq2, seq1) 	before(seq1, seq2)
298 
299 /* is s2<=s1<=s3 ? */
300 static inline bool between(__u32 seq1, __u32 seq2, __u32 seq3)
301 {
302 	return seq3 - seq2 >= seq1 - seq2;
303 }
304 
305 static inline bool tcp_out_of_memory(struct sock *sk)
306 {
307 	if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
308 	    sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2))
309 		return true;
310 	return false;
311 }
312 
313 void sk_forced_mem_schedule(struct sock *sk, int size);
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 
331 extern struct proto tcp_prot;
332 
333 #define TCP_INC_STATS(net, field)	SNMP_INC_STATS((net)->mib.tcp_statistics, field)
334 #define __TCP_INC_STATS(net, field)	__SNMP_INC_STATS((net)->mib.tcp_statistics, field)
335 #define TCP_DEC_STATS(net, field)	SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
336 #define TCP_ADD_STATS(net, field, val)	SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
337 
338 void tcp_tasklet_init(void);
339 
340 void tcp_v4_err(struct sk_buff *skb, u32);
341 
342 void tcp_shutdown(struct sock *sk, int how);
343 
344 void tcp_v4_early_demux(struct sk_buff *skb);
345 int tcp_v4_rcv(struct sk_buff *skb);
346 
347 int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
348 int tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size);
349 int tcp_sendpage(struct sock *sk, struct page *page, int offset, size_t size,
350 		 int flags);
351 void tcp_release_cb(struct sock *sk);
352 void tcp_wfree(struct sk_buff *skb);
353 void tcp_write_timer_handler(struct sock *sk);
354 void tcp_delack_timer_handler(struct sock *sk);
355 int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
356 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb);
357 void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
358 			 const struct tcphdr *th, unsigned int len);
359 void tcp_rcv_space_adjust(struct sock *sk);
360 int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
361 void tcp_twsk_destructor(struct sock *sk);
362 ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
363 			struct pipe_inode_info *pipe, size_t len,
364 			unsigned int flags);
365 
366 static inline void tcp_dec_quickack_mode(struct sock *sk,
367 					 const unsigned int pkts)
368 {
369 	struct inet_connection_sock *icsk = inet_csk(sk);
370 
371 	if (icsk->icsk_ack.quick) {
372 		if (pkts >= icsk->icsk_ack.quick) {
373 			icsk->icsk_ack.quick = 0;
374 			/* Leaving quickack mode we deflate ATO. */
375 			icsk->icsk_ack.ato   = TCP_ATO_MIN;
376 		} else
377 			icsk->icsk_ack.quick -= pkts;
378 	}
379 }
380 
381 #define	TCP_ECN_OK		1
382 #define	TCP_ECN_QUEUE_CWR	2
383 #define	TCP_ECN_DEMAND_CWR	4
384 #define	TCP_ECN_SEEN		8
385 
386 enum tcp_tw_status {
387 	TCP_TW_SUCCESS = 0,
388 	TCP_TW_RST = 1,
389 	TCP_TW_ACK = 2,
390 	TCP_TW_SYN = 3
391 };
392 
393 
394 enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
395 					      struct sk_buff *skb,
396 					      const struct tcphdr *th);
397 struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
398 			   struct request_sock *req, bool fastopen);
399 int tcp_child_process(struct sock *parent, struct sock *child,
400 		      struct sk_buff *skb);
401 void tcp_enter_loss(struct sock *sk);
402 void tcp_clear_retrans(struct tcp_sock *tp);
403 void tcp_update_metrics(struct sock *sk);
404 void tcp_init_metrics(struct sock *sk);
405 void tcp_metrics_init(void);
406 bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst,
407 			bool paws_check, bool timestamps);
408 bool tcp_remember_stamp(struct sock *sk);
409 bool tcp_tw_remember_stamp(struct inet_timewait_sock *tw);
410 void tcp_fetch_timewait_stamp(struct sock *sk, struct dst_entry *dst);
411 void tcp_disable_fack(struct tcp_sock *tp);
412 void tcp_close(struct sock *sk, long timeout);
413 void tcp_init_sock(struct sock *sk);
414 unsigned int tcp_poll(struct file *file, struct socket *sock,
415 		      struct poll_table_struct *wait);
416 int tcp_getsockopt(struct sock *sk, int level, int optname,
417 		   char __user *optval, int __user *optlen);
418 int tcp_setsockopt(struct sock *sk, int level, int optname,
419 		   char __user *optval, unsigned int optlen);
420 int compat_tcp_getsockopt(struct sock *sk, int level, int optname,
421 			  char __user *optval, int __user *optlen);
422 int compat_tcp_setsockopt(struct sock *sk, int level, int optname,
423 			  char __user *optval, unsigned int optlen);
424 void tcp_set_keepalive(struct sock *sk, int val);
425 void tcp_syn_ack_timeout(const struct request_sock *req);
426 int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
427 		int flags, int *addr_len);
428 void tcp_parse_options(const struct sk_buff *skb,
429 		       struct tcp_options_received *opt_rx,
430 		       int estab, struct tcp_fastopen_cookie *foc);
431 const u8 *tcp_parse_md5sig_option(const struct tcphdr *th);
432 
433 /*
434  *	TCP v4 functions exported for the inet6 API
435  */
436 
437 void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
438 void tcp_v4_mtu_reduced(struct sock *sk);
439 void tcp_req_err(struct sock *sk, u32 seq, bool abort);
440 int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
441 struct sock *tcp_create_openreq_child(const struct sock *sk,
442 				      struct request_sock *req,
443 				      struct sk_buff *skb);
444 void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst);
445 struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
446 				  struct request_sock *req,
447 				  struct dst_entry *dst,
448 				  struct request_sock *req_unhash,
449 				  bool *own_req);
450 int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
451 int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
452 int tcp_connect(struct sock *sk);
453 enum tcp_synack_type {
454 	TCP_SYNACK_NORMAL,
455 	TCP_SYNACK_FASTOPEN,
456 	TCP_SYNACK_COOKIE,
457 };
458 struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
459 				struct request_sock *req,
460 				struct tcp_fastopen_cookie *foc,
461 				enum tcp_synack_type synack_type);
462 int tcp_disconnect(struct sock *sk, int flags);
463 
464 void tcp_finish_connect(struct sock *sk, struct sk_buff *skb);
465 int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size);
466 void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
467 
468 /* From syncookies.c */
469 struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
470 				 struct request_sock *req,
471 				 struct dst_entry *dst);
472 int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
473 		      u32 cookie);
474 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
475 #ifdef CONFIG_SYN_COOKIES
476 
477 /* Syncookies use a monotonic timer which increments every 60 seconds.
478  * This counter is used both as a hash input and partially encoded into
479  * the cookie value.  A cookie is only validated further if the delta
480  * between the current counter value and the encoded one is less than this,
481  * i.e. a sent cookie is valid only at most for 2*60 seconds (or less if
482  * the counter advances immediately after a cookie is generated).
483  */
484 #define MAX_SYNCOOKIE_AGE	2
485 #define TCP_SYNCOOKIE_PERIOD	(60 * HZ)
486 #define TCP_SYNCOOKIE_VALID	(MAX_SYNCOOKIE_AGE * TCP_SYNCOOKIE_PERIOD)
487 
488 /* syncookies: remember time of last synqueue overflow
489  * But do not dirty this field too often (once per second is enough)
490  * It is racy as we do not hold a lock, but race is very minor.
491  */
492 static inline void tcp_synq_overflow(const struct sock *sk)
493 {
494 	unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
495 	unsigned long now = jiffies;
496 
497 	if (time_after(now, last_overflow + HZ))
498 		tcp_sk(sk)->rx_opt.ts_recent_stamp = now;
499 }
500 
501 /* syncookies: no recent synqueue overflow on this listening socket? */
502 static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
503 {
504 	unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
505 
506 	return time_after(jiffies, last_overflow + TCP_SYNCOOKIE_VALID);
507 }
508 
509 static inline u32 tcp_cookie_time(void)
510 {
511 	u64 val = get_jiffies_64();
512 
513 	do_div(val, TCP_SYNCOOKIE_PERIOD);
514 	return val;
515 }
516 
517 u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
518 			      u16 *mssp);
519 __u32 cookie_v4_init_sequence(const struct sk_buff *skb, __u16 *mss);
520 __u32 cookie_init_timestamp(struct request_sock *req);
521 bool cookie_timestamp_decode(struct tcp_options_received *opt);
522 bool cookie_ecn_ok(const struct tcp_options_received *opt,
523 		   const struct net *net, const struct dst_entry *dst);
524 
525 /* From net/ipv6/syncookies.c */
526 int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th,
527 		      u32 cookie);
528 struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
529 
530 u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
531 			      const struct tcphdr *th, u16 *mssp);
532 __u32 cookie_v6_init_sequence(const struct sk_buff *skb, __u16 *mss);
533 #endif
534 /* tcp_output.c */
535 
536 u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
537 		     int min_tso_segs);
538 void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
539 			       int nonagle);
540 bool tcp_may_send_now(struct sock *sk);
541 int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs);
542 int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs);
543 void tcp_retransmit_timer(struct sock *sk);
544 void tcp_xmit_retransmit_queue(struct sock *);
545 void tcp_simple_retransmit(struct sock *);
546 int tcp_trim_head(struct sock *, struct sk_buff *, u32);
547 int tcp_fragment(struct sock *, struct sk_buff *, u32, unsigned int, gfp_t);
548 
549 void tcp_send_probe0(struct sock *);
550 void tcp_send_partial(struct sock *);
551 int tcp_write_wakeup(struct sock *, int mib);
552 void tcp_send_fin(struct sock *sk);
553 void tcp_send_active_reset(struct sock *sk, gfp_t priority);
554 int tcp_send_synack(struct sock *);
555 void tcp_push_one(struct sock *, unsigned int mss_now);
556 void tcp_send_ack(struct sock *sk);
557 void tcp_send_delayed_ack(struct sock *sk);
558 void tcp_send_loss_probe(struct sock *sk);
559 bool tcp_schedule_loss_probe(struct sock *sk);
560 void tcp_skb_collapse_tstamp(struct sk_buff *skb,
561 			     const struct sk_buff *next_skb);
562 
563 /* tcp_input.c */
564 void tcp_resume_early_retransmit(struct sock *sk);
565 void tcp_rearm_rto(struct sock *sk);
566 void tcp_synack_rtt_meas(struct sock *sk, struct request_sock *req);
567 void tcp_reset(struct sock *sk);
568 void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, struct sk_buff *skb);
569 void tcp_fin(struct sock *sk);
570 
571 /* tcp_timer.c */
572 void tcp_init_xmit_timers(struct sock *);
573 static inline void tcp_clear_xmit_timers(struct sock *sk)
574 {
575 	inet_csk_clear_xmit_timers(sk);
576 }
577 
578 unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
579 unsigned int tcp_current_mss(struct sock *sk);
580 
581 /* Bound MSS / TSO packet size with the half of the window */
582 static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
583 {
584 	int cutoff;
585 
586 	/* When peer uses tiny windows, there is no use in packetizing
587 	 * to sub-MSS pieces for the sake of SWS or making sure there
588 	 * are enough packets in the pipe for fast recovery.
589 	 *
590 	 * On the other hand, for extremely large MSS devices, handling
591 	 * smaller than MSS windows in this way does make sense.
592 	 */
593 	if (tp->max_window > TCP_MSS_DEFAULT)
594 		cutoff = (tp->max_window >> 1);
595 	else
596 		cutoff = tp->max_window;
597 
598 	if (cutoff && pktsize > cutoff)
599 		return max_t(int, cutoff, 68U - tp->tcp_header_len);
600 	else
601 		return pktsize;
602 }
603 
604 /* tcp.c */
605 void tcp_get_info(struct sock *, struct tcp_info *);
606 
607 /* Read 'sendfile()'-style from a TCP socket */
608 int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
609 		  sk_read_actor_t recv_actor);
610 
611 void tcp_initialize_rcv_mss(struct sock *sk);
612 
613 int tcp_mtu_to_mss(struct sock *sk, int pmtu);
614 int tcp_mss_to_mtu(struct sock *sk, int mss);
615 void tcp_mtup_init(struct sock *sk);
616 void tcp_init_buffer_space(struct sock *sk);
617 
618 static inline void tcp_bound_rto(const struct sock *sk)
619 {
620 	if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
621 		inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
622 }
623 
624 static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
625 {
626 	return usecs_to_jiffies((tp->srtt_us >> 3) + tp->rttvar_us);
627 }
628 
629 static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
630 {
631 	tp->pred_flags = htonl((tp->tcp_header_len << 26) |
632 			       ntohl(TCP_FLAG_ACK) |
633 			       snd_wnd);
634 }
635 
636 static inline void tcp_fast_path_on(struct tcp_sock *tp)
637 {
638 	__tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
639 }
640 
641 static inline void tcp_fast_path_check(struct sock *sk)
642 {
643 	struct tcp_sock *tp = tcp_sk(sk);
644 
645 	if (RB_EMPTY_ROOT(&tp->out_of_order_queue) &&
646 	    tp->rcv_wnd &&
647 	    atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
648 	    !tp->urg_data)
649 		tcp_fast_path_on(tp);
650 }
651 
652 /* Compute the actual rto_min value */
653 static inline u32 tcp_rto_min(struct sock *sk)
654 {
655 	const struct dst_entry *dst = __sk_dst_get(sk);
656 	u32 rto_min = TCP_RTO_MIN;
657 
658 	if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
659 		rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
660 	return rto_min;
661 }
662 
663 static inline u32 tcp_rto_min_us(struct sock *sk)
664 {
665 	return jiffies_to_usecs(tcp_rto_min(sk));
666 }
667 
668 static inline bool tcp_ca_dst_locked(const struct dst_entry *dst)
669 {
670 	return dst_metric_locked(dst, RTAX_CC_ALGO);
671 }
672 
673 /* Minimum RTT in usec. ~0 means not available. */
674 static inline u32 tcp_min_rtt(const struct tcp_sock *tp)
675 {
676 	return minmax_get(&tp->rtt_min);
677 }
678 
679 /* Compute the actual receive window we are currently advertising.
680  * Rcv_nxt can be after the window if our peer push more data
681  * than the offered window.
682  */
683 static inline u32 tcp_receive_window(const struct tcp_sock *tp)
684 {
685 	s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;
686 
687 	if (win < 0)
688 		win = 0;
689 	return (u32) win;
690 }
691 
692 /* Choose a new window, without checks for shrinking, and without
693  * scaling applied to the result.  The caller does these things
694  * if necessary.  This is a "raw" window selection.
695  */
696 u32 __tcp_select_window(struct sock *sk);
697 
698 void tcp_send_window_probe(struct sock *sk);
699 
700 /* TCP timestamps are only 32-bits, this causes a slight
701  * complication on 64-bit systems since we store a snapshot
702  * of jiffies in the buffer control blocks below.  We decided
703  * to use only the low 32-bits of jiffies and hide the ugly
704  * casts with the following macro.
705  */
706 #define tcp_time_stamp		((__u32)(jiffies))
707 
708 static inline u32 tcp_skb_timestamp(const struct sk_buff *skb)
709 {
710 	return skb->skb_mstamp.stamp_jiffies;
711 }
712 
713 
714 #define tcp_flag_byte(th) (((u_int8_t *)th)[13])
715 
716 #define TCPHDR_FIN 0x01
717 #define TCPHDR_SYN 0x02
718 #define TCPHDR_RST 0x04
719 #define TCPHDR_PSH 0x08
720 #define TCPHDR_ACK 0x10
721 #define TCPHDR_URG 0x20
722 #define TCPHDR_ECE 0x40
723 #define TCPHDR_CWR 0x80
724 
725 #define TCPHDR_SYN_ECN	(TCPHDR_SYN | TCPHDR_ECE | TCPHDR_CWR)
726 
727 /* This is what the send packet queuing engine uses to pass
728  * TCP per-packet control information to the transmission code.
729  * We also store the host-order sequence numbers in here too.
730  * This is 44 bytes if IPV6 is enabled.
731  * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately.
732  */
733 struct tcp_skb_cb {
734 	__u32		seq;		/* Starting sequence number	*/
735 	__u32		end_seq;	/* SEQ + FIN + SYN + datalen	*/
736 	union {
737 		/* Note : tcp_tw_isn is used in input path only
738 		 *	  (isn chosen by tcp_timewait_state_process())
739 		 *
740 		 * 	  tcp_gso_segs/size are used in write queue only,
741 		 *	  cf tcp_skb_pcount()/tcp_skb_mss()
742 		 */
743 		__u32		tcp_tw_isn;
744 		struct {
745 			u16	tcp_gso_segs;
746 			u16	tcp_gso_size;
747 		};
748 	};
749 	__u8		tcp_flags;	/* TCP header flags. (tcp[13])	*/
750 
751 	__u8		sacked;		/* State flags for SACK/FACK.	*/
752 #define TCPCB_SACKED_ACKED	0x01	/* SKB ACK'd by a SACK block	*/
753 #define TCPCB_SACKED_RETRANS	0x02	/* SKB retransmitted		*/
754 #define TCPCB_LOST		0x04	/* SKB is lost			*/
755 #define TCPCB_TAGBITS		0x07	/* All tag bits			*/
756 #define TCPCB_REPAIRED		0x10	/* SKB repaired (no skb_mstamp)	*/
757 #define TCPCB_EVER_RETRANS	0x80	/* Ever retransmitted frame	*/
758 #define TCPCB_RETRANS		(TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS| \
759 				TCPCB_REPAIRED)
760 
761 	__u8		ip_dsfield;	/* IPv4 tos or IPv6 dsfield	*/
762 	__u8		txstamp_ack:1,	/* Record TX timestamp for ack? */
763 			eor:1,		/* Is skb MSG_EOR marked? */
764 			unused:6;
765 	__u32		ack_seq;	/* Sequence number ACK'd	*/
766 	union {
767 		struct {
768 			/* There is space for up to 24 bytes */
769 			__u32 in_flight:30,/* Bytes in flight at transmit */
770 			      is_app_limited:1, /* cwnd not fully used? */
771 			      unused:1;
772 			/* pkts S/ACKed so far upon tx of skb, incl retrans: */
773 			__u32 delivered;
774 			/* start of send pipeline phase */
775 			struct skb_mstamp first_tx_mstamp;
776 			/* when we reached the "delivered" count */
777 			struct skb_mstamp delivered_mstamp;
778 		} tx;   /* only used for outgoing skbs */
779 		union {
780 			struct inet_skb_parm	h4;
781 #if IS_ENABLED(CONFIG_IPV6)
782 			struct inet6_skb_parm	h6;
783 #endif
784 		} header;	/* For incoming skbs */
785 	};
786 };
787 
788 #define TCP_SKB_CB(__skb)	((struct tcp_skb_cb *)&((__skb)->cb[0]))
789 
790 
791 #if IS_ENABLED(CONFIG_IPV6)
792 /* This is the variant of inet6_iif() that must be used by TCP,
793  * as TCP moves IP6CB into a different location in skb->cb[]
794  */
795 static inline int tcp_v6_iif(const struct sk_buff *skb)
796 {
797 	bool l3_slave = skb_l3mdev_slave(TCP_SKB_CB(skb)->header.h6.flags);
798 
799 	return l3_slave ? skb->skb_iif : TCP_SKB_CB(skb)->header.h6.iif;
800 }
801 #endif
802 
803 /* Due to TSO, an SKB can be composed of multiple actual
804  * packets.  To keep these tracked properly, we use this.
805  */
806 static inline int tcp_skb_pcount(const struct sk_buff *skb)
807 {
808 	return TCP_SKB_CB(skb)->tcp_gso_segs;
809 }
810 
811 static inline void tcp_skb_pcount_set(struct sk_buff *skb, int segs)
812 {
813 	TCP_SKB_CB(skb)->tcp_gso_segs = segs;
814 }
815 
816 static inline void tcp_skb_pcount_add(struct sk_buff *skb, int segs)
817 {
818 	TCP_SKB_CB(skb)->tcp_gso_segs += segs;
819 }
820 
821 /* This is valid iff skb is in write queue and tcp_skb_pcount() > 1. */
822 static inline int tcp_skb_mss(const struct sk_buff *skb)
823 {
824 	return TCP_SKB_CB(skb)->tcp_gso_size;
825 }
826 
827 static inline bool tcp_skb_can_collapse_to(const struct sk_buff *skb)
828 {
829 	return likely(!TCP_SKB_CB(skb)->eor);
830 }
831 
832 /* Events passed to congestion control interface */
833 enum tcp_ca_event {
834 	CA_EVENT_TX_START,	/* first transmit when no packets in flight */
835 	CA_EVENT_CWND_RESTART,	/* congestion window restart */
836 	CA_EVENT_COMPLETE_CWR,	/* end of congestion recovery */
837 	CA_EVENT_LOSS,		/* loss timeout */
838 	CA_EVENT_ECN_NO_CE,	/* ECT set, but not CE marked */
839 	CA_EVENT_ECN_IS_CE,	/* received CE marked IP packet */
840 	CA_EVENT_DELAYED_ACK,	/* Delayed ack is sent */
841 	CA_EVENT_NON_DELAYED_ACK,
842 };
843 
844 /* Information about inbound ACK, passed to cong_ops->in_ack_event() */
845 enum tcp_ca_ack_event_flags {
846 	CA_ACK_SLOWPATH		= (1 << 0),	/* In slow path processing */
847 	CA_ACK_WIN_UPDATE	= (1 << 1),	/* ACK updated window */
848 	CA_ACK_ECE		= (1 << 2),	/* ECE bit is set on ack */
849 };
850 
851 /*
852  * Interface for adding new TCP congestion control handlers
853  */
854 #define TCP_CA_NAME_MAX	16
855 #define TCP_CA_MAX	128
856 #define TCP_CA_BUF_MAX	(TCP_CA_NAME_MAX*TCP_CA_MAX)
857 
858 #define TCP_CA_UNSPEC	0
859 
860 /* Algorithm can be set on socket without CAP_NET_ADMIN privileges */
861 #define TCP_CONG_NON_RESTRICTED 0x1
862 /* Requires ECN/ECT set on all packets */
863 #define TCP_CONG_NEEDS_ECN	0x2
864 
865 union tcp_cc_info;
866 
867 struct ack_sample {
868 	u32 pkts_acked;
869 	s32 rtt_us;
870 	u32 in_flight;
871 };
872 
873 /* A rate sample measures the number of (original/retransmitted) data
874  * packets delivered "delivered" over an interval of time "interval_us".
875  * The tcp_rate.c code fills in the rate sample, and congestion
876  * control modules that define a cong_control function to run at the end
877  * of ACK processing can optionally chose to consult this sample when
878  * setting cwnd and pacing rate.
879  * A sample is invalid if "delivered" or "interval_us" is negative.
880  */
881 struct rate_sample {
882 	struct	skb_mstamp prior_mstamp; /* starting timestamp for interval */
883 	u32  prior_delivered;	/* tp->delivered at "prior_mstamp" */
884 	s32  delivered;		/* number of packets delivered over interval */
885 	long interval_us;	/* time for tp->delivered to incr "delivered" */
886 	long rtt_us;		/* RTT of last (S)ACKed packet (or -1) */
887 	int  losses;		/* number of packets marked lost upon ACK */
888 	u32  acked_sacked;	/* number of packets newly (S)ACKed upon ACK */
889 	u32  prior_in_flight;	/* in flight before this ACK */
890 	bool is_app_limited;	/* is sample from packet with bubble in pipe? */
891 	bool is_retrans;	/* is sample from retransmission? */
892 };
893 
894 struct tcp_congestion_ops {
895 	struct list_head	list;
896 	u32 key;
897 	u32 flags;
898 
899 	/* initialize private data (optional) */
900 	void (*init)(struct sock *sk);
901 	/* cleanup private data  (optional) */
902 	void (*release)(struct sock *sk);
903 
904 	/* return slow start threshold (required) */
905 	u32 (*ssthresh)(struct sock *sk);
906 	/* do new cwnd calculation (required) */
907 	void (*cong_avoid)(struct sock *sk, u32 ack, u32 acked);
908 	/* call before changing ca_state (optional) */
909 	void (*set_state)(struct sock *sk, u8 new_state);
910 	/* call when cwnd event occurs (optional) */
911 	void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
912 	/* call when ack arrives (optional) */
913 	void (*in_ack_event)(struct sock *sk, u32 flags);
914 	/* new value of cwnd after loss (optional) */
915 	u32  (*undo_cwnd)(struct sock *sk);
916 	/* hook for packet ack accounting (optional) */
917 	void (*pkts_acked)(struct sock *sk, const struct ack_sample *sample);
918 	/* suggest number of segments for each skb to transmit (optional) */
919 	u32 (*tso_segs_goal)(struct sock *sk);
920 	/* returns the multiplier used in tcp_sndbuf_expand (optional) */
921 	u32 (*sndbuf_expand)(struct sock *sk);
922 	/* call when packets are delivered to update cwnd and pacing rate,
923 	 * after all the ca_state processing. (optional)
924 	 */
925 	void (*cong_control)(struct sock *sk, const struct rate_sample *rs);
926 	/* get info for inet_diag (optional) */
927 	size_t (*get_info)(struct sock *sk, u32 ext, int *attr,
928 			   union tcp_cc_info *info);
929 
930 	char 		name[TCP_CA_NAME_MAX];
931 	struct module 	*owner;
932 };
933 
934 int tcp_register_congestion_control(struct tcp_congestion_ops *type);
935 void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
936 
937 void tcp_assign_congestion_control(struct sock *sk);
938 void tcp_init_congestion_control(struct sock *sk);
939 void tcp_cleanup_congestion_control(struct sock *sk);
940 int tcp_set_default_congestion_control(const char *name);
941 void tcp_get_default_congestion_control(char *name);
942 void tcp_get_available_congestion_control(char *buf, size_t len);
943 void tcp_get_allowed_congestion_control(char *buf, size_t len);
944 int tcp_set_allowed_congestion_control(char *allowed);
945 int tcp_set_congestion_control(struct sock *sk, const char *name);
946 u32 tcp_slow_start(struct tcp_sock *tp, u32 acked);
947 void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked);
948 
949 u32 tcp_reno_ssthresh(struct sock *sk);
950 void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked);
951 extern struct tcp_congestion_ops tcp_reno;
952 
953 struct tcp_congestion_ops *tcp_ca_find_key(u32 key);
954 u32 tcp_ca_get_key_by_name(const char *name, bool *ecn_ca);
955 #ifdef CONFIG_INET
956 char *tcp_ca_get_name_by_key(u32 key, char *buffer);
957 #else
958 static inline char *tcp_ca_get_name_by_key(u32 key, char *buffer)
959 {
960 	return NULL;
961 }
962 #endif
963 
964 static inline bool tcp_ca_needs_ecn(const struct sock *sk)
965 {
966 	const struct inet_connection_sock *icsk = inet_csk(sk);
967 
968 	return icsk->icsk_ca_ops->flags & TCP_CONG_NEEDS_ECN;
969 }
970 
971 static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
972 {
973 	struct inet_connection_sock *icsk = inet_csk(sk);
974 
975 	if (icsk->icsk_ca_ops->set_state)
976 		icsk->icsk_ca_ops->set_state(sk, ca_state);
977 	icsk->icsk_ca_state = ca_state;
978 }
979 
980 static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
981 {
982 	const struct inet_connection_sock *icsk = inet_csk(sk);
983 
984 	if (icsk->icsk_ca_ops->cwnd_event)
985 		icsk->icsk_ca_ops->cwnd_event(sk, event);
986 }
987 
988 /* From tcp_rate.c */
989 void tcp_rate_skb_sent(struct sock *sk, struct sk_buff *skb);
990 void tcp_rate_skb_delivered(struct sock *sk, struct sk_buff *skb,
991 			    struct rate_sample *rs);
992 void tcp_rate_gen(struct sock *sk, u32 delivered, u32 lost,
993 		  struct skb_mstamp *now, struct rate_sample *rs);
994 void tcp_rate_check_app_limited(struct sock *sk);
995 
996 /* These functions determine how the current flow behaves in respect of SACK
997  * handling. SACK is negotiated with the peer, and therefore it can vary
998  * between different flows.
999  *
1000  * tcp_is_sack - SACK enabled
1001  * tcp_is_reno - No SACK
1002  * tcp_is_fack - FACK enabled, implies SACK enabled
1003  */
1004 static inline int tcp_is_sack(const struct tcp_sock *tp)
1005 {
1006 	return tp->rx_opt.sack_ok;
1007 }
1008 
1009 static inline bool tcp_is_reno(const struct tcp_sock *tp)
1010 {
1011 	return !tcp_is_sack(tp);
1012 }
1013 
1014 static inline bool tcp_is_fack(const struct tcp_sock *tp)
1015 {
1016 	return tp->rx_opt.sack_ok & TCP_FACK_ENABLED;
1017 }
1018 
1019 static inline void tcp_enable_fack(struct tcp_sock *tp)
1020 {
1021 	tp->rx_opt.sack_ok |= TCP_FACK_ENABLED;
1022 }
1023 
1024 /* TCP early-retransmit (ER) is similar to but more conservative than
1025  * the thin-dupack feature.  Enable ER only if thin-dupack is disabled.
1026  */
1027 static inline void tcp_enable_early_retrans(struct tcp_sock *tp)
1028 {
1029 	struct net *net = sock_net((struct sock *)tp);
1030 
1031 	tp->do_early_retrans = sysctl_tcp_early_retrans &&
1032 		sysctl_tcp_early_retrans < 4 && !sysctl_tcp_thin_dupack &&
1033 		net->ipv4.sysctl_tcp_reordering == 3;
1034 }
1035 
1036 static inline void tcp_disable_early_retrans(struct tcp_sock *tp)
1037 {
1038 	tp->do_early_retrans = 0;
1039 }
1040 
1041 static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
1042 {
1043 	return tp->sacked_out + tp->lost_out;
1044 }
1045 
1046 /* This determines how many packets are "in the network" to the best
1047  * of our knowledge.  In many cases it is conservative, but where
1048  * detailed information is available from the receiver (via SACK
1049  * blocks etc.) we can make more aggressive calculations.
1050  *
1051  * Use this for decisions involving congestion control, use just
1052  * tp->packets_out to determine if the send queue is empty or not.
1053  *
1054  * Read this equation as:
1055  *
1056  *	"Packets sent once on transmission queue" MINUS
1057  *	"Packets left network, but not honestly ACKed yet" PLUS
1058  *	"Packets fast retransmitted"
1059  */
1060 static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
1061 {
1062 	return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
1063 }
1064 
1065 #define TCP_INFINITE_SSTHRESH	0x7fffffff
1066 
1067 static inline bool tcp_in_slow_start(const struct tcp_sock *tp)
1068 {
1069 	return tp->snd_cwnd < tp->snd_ssthresh;
1070 }
1071 
1072 static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
1073 {
1074 	return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
1075 }
1076 
1077 static inline bool tcp_in_cwnd_reduction(const struct sock *sk)
1078 {
1079 	return (TCPF_CA_CWR | TCPF_CA_Recovery) &
1080 	       (1 << inet_csk(sk)->icsk_ca_state);
1081 }
1082 
1083 /* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
1084  * The exception is cwnd reduction phase, when cwnd is decreasing towards
1085  * ssthresh.
1086  */
1087 static inline __u32 tcp_current_ssthresh(const struct sock *sk)
1088 {
1089 	const struct tcp_sock *tp = tcp_sk(sk);
1090 
1091 	if (tcp_in_cwnd_reduction(sk))
1092 		return tp->snd_ssthresh;
1093 	else
1094 		return max(tp->snd_ssthresh,
1095 			   ((tp->snd_cwnd >> 1) +
1096 			    (tp->snd_cwnd >> 2)));
1097 }
1098 
1099 /* Use define here intentionally to get WARN_ON location shown at the caller */
1100 #define tcp_verify_left_out(tp)	WARN_ON(tcp_left_out(tp) > tp->packets_out)
1101 
1102 void tcp_enter_cwr(struct sock *sk);
1103 __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst);
1104 
1105 /* The maximum number of MSS of available cwnd for which TSO defers
1106  * sending if not using sysctl_tcp_tso_win_divisor.
1107  */
1108 static inline __u32 tcp_max_tso_deferred_mss(const struct tcp_sock *tp)
1109 {
1110 	return 3;
1111 }
1112 
1113 /* Returns end sequence number of the receiver's advertised window */
1114 static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
1115 {
1116 	return tp->snd_una + tp->snd_wnd;
1117 }
1118 
1119 /* We follow the spirit of RFC2861 to validate cwnd but implement a more
1120  * flexible approach. The RFC suggests cwnd should not be raised unless
1121  * it was fully used previously. And that's exactly what we do in
1122  * congestion avoidance mode. But in slow start we allow cwnd to grow
1123  * as long as the application has used half the cwnd.
1124  * Example :
1125  *    cwnd is 10 (IW10), but application sends 9 frames.
1126  *    We allow cwnd to reach 18 when all frames are ACKed.
1127  * This check is safe because it's as aggressive as slow start which already
1128  * risks 100% overshoot. The advantage is that we discourage application to
1129  * either send more filler packets or data to artificially blow up the cwnd
1130  * usage, and allow application-limited process to probe bw more aggressively.
1131  */
1132 static inline bool tcp_is_cwnd_limited(const struct sock *sk)
1133 {
1134 	const struct tcp_sock *tp = tcp_sk(sk);
1135 
1136 	/* If in slow start, ensure cwnd grows to twice what was ACKed. */
1137 	if (tcp_in_slow_start(tp))
1138 		return tp->snd_cwnd < 2 * tp->max_packets_out;
1139 
1140 	return tp->is_cwnd_limited;
1141 }
1142 
1143 /* Something is really bad, we could not queue an additional packet,
1144  * because qdisc is full or receiver sent a 0 window.
1145  * We do not want to add fuel to the fire, or abort too early,
1146  * so make sure the timer we arm now is at least 200ms in the future,
1147  * regardless of current icsk_rto value (as it could be ~2ms)
1148  */
1149 static inline unsigned long tcp_probe0_base(const struct sock *sk)
1150 {
1151 	return max_t(unsigned long, inet_csk(sk)->icsk_rto, TCP_RTO_MIN);
1152 }
1153 
1154 /* Variant of inet_csk_rto_backoff() used for zero window probes */
1155 static inline unsigned long tcp_probe0_when(const struct sock *sk,
1156 					    unsigned long max_when)
1157 {
1158 	u64 when = (u64)tcp_probe0_base(sk) << inet_csk(sk)->icsk_backoff;
1159 
1160 	return (unsigned long)min_t(u64, when, max_when);
1161 }
1162 
1163 static inline void tcp_check_probe_timer(struct sock *sk)
1164 {
1165 	if (!tcp_sk(sk)->packets_out && !inet_csk(sk)->icsk_pending)
1166 		inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
1167 					  tcp_probe0_base(sk), TCP_RTO_MAX);
1168 }
1169 
1170 static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
1171 {
1172 	tp->snd_wl1 = seq;
1173 }
1174 
1175 static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq)
1176 {
1177 	tp->snd_wl1 = seq;
1178 }
1179 
1180 /*
1181  * Calculate(/check) TCP checksum
1182  */
1183 static inline __sum16 tcp_v4_check(int len, __be32 saddr,
1184 				   __be32 daddr, __wsum base)
1185 {
1186 	return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base);
1187 }
1188 
1189 static inline __sum16 __tcp_checksum_complete(struct sk_buff *skb)
1190 {
1191 	return __skb_checksum_complete(skb);
1192 }
1193 
1194 static inline bool tcp_checksum_complete(struct sk_buff *skb)
1195 {
1196 	return !skb_csum_unnecessary(skb) &&
1197 		__tcp_checksum_complete(skb);
1198 }
1199 
1200 /* Prequeue for VJ style copy to user, combined with checksumming. */
1201 
1202 static inline void tcp_prequeue_init(struct tcp_sock *tp)
1203 {
1204 	tp->ucopy.task = NULL;
1205 	tp->ucopy.len = 0;
1206 	tp->ucopy.memory = 0;
1207 	skb_queue_head_init(&tp->ucopy.prequeue);
1208 }
1209 
1210 bool tcp_prequeue(struct sock *sk, struct sk_buff *skb);
1211 bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb);
1212 
1213 #undef STATE_TRACE
1214 
1215 #ifdef STATE_TRACE
1216 static const char *statename[]={
1217 	"Unused","Established","Syn Sent","Syn Recv",
1218 	"Fin Wait 1","Fin Wait 2","Time Wait", "Close",
1219 	"Close Wait","Last ACK","Listen","Closing"
1220 };
1221 #endif
1222 void tcp_set_state(struct sock *sk, int state);
1223 
1224 void tcp_done(struct sock *sk);
1225 
1226 int tcp_abort(struct sock *sk, int err);
1227 
1228 static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
1229 {
1230 	rx_opt->dsack = 0;
1231 	rx_opt->num_sacks = 0;
1232 }
1233 
1234 u32 tcp_default_init_rwnd(u32 mss);
1235 void tcp_cwnd_restart(struct sock *sk, s32 delta);
1236 
1237 static inline void tcp_slow_start_after_idle_check(struct sock *sk)
1238 {
1239 	struct tcp_sock *tp = tcp_sk(sk);
1240 	s32 delta;
1241 
1242 	if (!sysctl_tcp_slow_start_after_idle || tp->packets_out)
1243 		return;
1244 	delta = tcp_time_stamp - tp->lsndtime;
1245 	if (delta > inet_csk(sk)->icsk_rto)
1246 		tcp_cwnd_restart(sk, delta);
1247 }
1248 
1249 /* Determine a window scaling and initial window to offer. */
1250 void tcp_select_initial_window(int __space, __u32 mss, __u32 *rcv_wnd,
1251 			       __u32 *window_clamp, int wscale_ok,
1252 			       __u8 *rcv_wscale, __u32 init_rcv_wnd);
1253 
1254 static inline int tcp_win_from_space(int space)
1255 {
1256 	return sysctl_tcp_adv_win_scale<=0 ?
1257 		(space>>(-sysctl_tcp_adv_win_scale)) :
1258 		space - (space>>sysctl_tcp_adv_win_scale);
1259 }
1260 
1261 /* Note: caller must be prepared to deal with negative returns */
1262 static inline int tcp_space(const struct sock *sk)
1263 {
1264 	return tcp_win_from_space(sk->sk_rcvbuf -
1265 				  atomic_read(&sk->sk_rmem_alloc));
1266 }
1267 
1268 static inline int tcp_full_space(const struct sock *sk)
1269 {
1270 	return tcp_win_from_space(sk->sk_rcvbuf);
1271 }
1272 
1273 extern void tcp_openreq_init_rwin(struct request_sock *req,
1274 				  const struct sock *sk_listener,
1275 				  const struct dst_entry *dst);
1276 
1277 void tcp_enter_memory_pressure(struct sock *sk);
1278 
1279 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
1280 {
1281 	struct net *net = sock_net((struct sock *)tp);
1282 
1283 	return tp->keepalive_intvl ? : net->ipv4.sysctl_tcp_keepalive_intvl;
1284 }
1285 
1286 static inline int keepalive_time_when(const struct tcp_sock *tp)
1287 {
1288 	struct net *net = sock_net((struct sock *)tp);
1289 
1290 	return tp->keepalive_time ? : net->ipv4.sysctl_tcp_keepalive_time;
1291 }
1292 
1293 static inline int keepalive_probes(const struct tcp_sock *tp)
1294 {
1295 	struct net *net = sock_net((struct sock *)tp);
1296 
1297 	return tp->keepalive_probes ? : net->ipv4.sysctl_tcp_keepalive_probes;
1298 }
1299 
1300 static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
1301 {
1302 	const struct inet_connection_sock *icsk = &tp->inet_conn;
1303 
1304 	return min_t(u32, tcp_time_stamp - icsk->icsk_ack.lrcvtime,
1305 			  tcp_time_stamp - tp->rcv_tstamp);
1306 }
1307 
1308 static inline int tcp_fin_time(const struct sock *sk)
1309 {
1310 	int fin_timeout = tcp_sk(sk)->linger2 ? : sock_net(sk)->ipv4.sysctl_tcp_fin_timeout;
1311 	const int rto = inet_csk(sk)->icsk_rto;
1312 
1313 	if (fin_timeout < (rto << 2) - (rto >> 1))
1314 		fin_timeout = (rto << 2) - (rto >> 1);
1315 
1316 	return fin_timeout;
1317 }
1318 
1319 static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt,
1320 				  int paws_win)
1321 {
1322 	if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
1323 		return true;
1324 	if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
1325 		return true;
1326 	/*
1327 	 * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
1328 	 * then following tcp messages have valid values. Ignore 0 value,
1329 	 * or else 'negative' tsval might forbid us to accept their packets.
1330 	 */
1331 	if (!rx_opt->ts_recent)
1332 		return true;
1333 	return false;
1334 }
1335 
1336 static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt,
1337 				   int rst)
1338 {
1339 	if (tcp_paws_check(rx_opt, 0))
1340 		return false;
1341 
1342 	/* RST segments are not recommended to carry timestamp,
1343 	   and, if they do, it is recommended to ignore PAWS because
1344 	   "their cleanup function should take precedence over timestamps."
1345 	   Certainly, it is mistake. It is necessary to understand the reasons
1346 	   of this constraint to relax it: if peer reboots, clock may go
1347 	   out-of-sync and half-open connections will not be reset.
1348 	   Actually, the problem would be not existing if all
1349 	   the implementations followed draft about maintaining clock
1350 	   via reboots. Linux-2.2 DOES NOT!
1351 
1352 	   However, we can relax time bounds for RST segments to MSL.
1353 	 */
1354 	if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
1355 		return false;
1356 	return true;
1357 }
1358 
1359 bool tcp_oow_rate_limited(struct net *net, const struct sk_buff *skb,
1360 			  int mib_idx, u32 *last_oow_ack_time);
1361 
1362 static inline void tcp_mib_init(struct net *net)
1363 {
1364 	/* See RFC 2012 */
1365 	TCP_ADD_STATS(net, TCP_MIB_RTOALGORITHM, 1);
1366 	TCP_ADD_STATS(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
1367 	TCP_ADD_STATS(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
1368 	TCP_ADD_STATS(net, TCP_MIB_MAXCONN, -1);
1369 }
1370 
1371 /* from STCP */
1372 static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
1373 {
1374 	tp->lost_skb_hint = NULL;
1375 }
1376 
1377 static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
1378 {
1379 	tcp_clear_retrans_hints_partial(tp);
1380 	tp->retransmit_skb_hint = NULL;
1381 }
1382 
1383 union tcp_md5_addr {
1384 	struct in_addr  a4;
1385 #if IS_ENABLED(CONFIG_IPV6)
1386 	struct in6_addr	a6;
1387 #endif
1388 };
1389 
1390 /* - key database */
1391 struct tcp_md5sig_key {
1392 	struct hlist_node	node;
1393 	u8			keylen;
1394 	u8			family; /* AF_INET or AF_INET6 */
1395 	union tcp_md5_addr	addr;
1396 	u8			key[TCP_MD5SIG_MAXKEYLEN];
1397 	struct rcu_head		rcu;
1398 };
1399 
1400 /* - sock block */
1401 struct tcp_md5sig_info {
1402 	struct hlist_head	head;
1403 	struct rcu_head		rcu;
1404 };
1405 
1406 /* - pseudo header */
1407 struct tcp4_pseudohdr {
1408 	__be32		saddr;
1409 	__be32		daddr;
1410 	__u8		pad;
1411 	__u8		protocol;
1412 	__be16		len;
1413 };
1414 
1415 struct tcp6_pseudohdr {
1416 	struct in6_addr	saddr;
1417 	struct in6_addr daddr;
1418 	__be32		len;
1419 	__be32		protocol;	/* including padding */
1420 };
1421 
1422 union tcp_md5sum_block {
1423 	struct tcp4_pseudohdr ip4;
1424 #if IS_ENABLED(CONFIG_IPV6)
1425 	struct tcp6_pseudohdr ip6;
1426 #endif
1427 };
1428 
1429 /* - pool: digest algorithm, hash description and scratch buffer */
1430 struct tcp_md5sig_pool {
1431 	struct ahash_request	*md5_req;
1432 	void			*scratch;
1433 };
1434 
1435 /* - functions */
1436 int tcp_v4_md5_hash_skb(char *md5_hash, const struct tcp_md5sig_key *key,
1437 			const struct sock *sk, const struct sk_buff *skb);
1438 int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
1439 		   int family, const u8 *newkey, u8 newkeylen, gfp_t gfp);
1440 int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
1441 		   int family);
1442 struct tcp_md5sig_key *tcp_v4_md5_lookup(const struct sock *sk,
1443 					 const struct sock *addr_sk);
1444 
1445 #ifdef CONFIG_TCP_MD5SIG
1446 struct tcp_md5sig_key *tcp_md5_do_lookup(const struct sock *sk,
1447 					 const union tcp_md5_addr *addr,
1448 					 int family);
1449 #define tcp_twsk_md5_key(twsk)	((twsk)->tw_md5_key)
1450 #else
1451 static inline struct tcp_md5sig_key *tcp_md5_do_lookup(const struct sock *sk,
1452 					 const union tcp_md5_addr *addr,
1453 					 int family)
1454 {
1455 	return NULL;
1456 }
1457 #define tcp_twsk_md5_key(twsk)	NULL
1458 #endif
1459 
1460 bool tcp_alloc_md5sig_pool(void);
1461 
1462 struct tcp_md5sig_pool *tcp_get_md5sig_pool(void);
1463 static inline void tcp_put_md5sig_pool(void)
1464 {
1465 	local_bh_enable();
1466 }
1467 
1468 int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
1469 			  unsigned int header_len);
1470 int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
1471 		     const struct tcp_md5sig_key *key);
1472 
1473 /* From tcp_fastopen.c */
1474 void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
1475 			    struct tcp_fastopen_cookie *cookie, int *syn_loss,
1476 			    unsigned long *last_syn_loss);
1477 void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
1478 			    struct tcp_fastopen_cookie *cookie, bool syn_lost,
1479 			    u16 try_exp);
1480 struct tcp_fastopen_request {
1481 	/* Fast Open cookie. Size 0 means a cookie request */
1482 	struct tcp_fastopen_cookie	cookie;
1483 	struct msghdr			*data;  /* data in MSG_FASTOPEN */
1484 	size_t				size;
1485 	int				copied;	/* queued in tcp_connect() */
1486 };
1487 void tcp_free_fastopen_req(struct tcp_sock *tp);
1488 
1489 extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
1490 int tcp_fastopen_reset_cipher(void *key, unsigned int len);
1491 void tcp_fastopen_add_skb(struct sock *sk, struct sk_buff *skb);
1492 struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
1493 			      struct request_sock *req,
1494 			      struct tcp_fastopen_cookie *foc,
1495 			      struct dst_entry *dst);
1496 void tcp_fastopen_init_key_once(bool publish);
1497 #define TCP_FASTOPEN_KEY_LENGTH 16
1498 
1499 /* Fastopen key context */
1500 struct tcp_fastopen_context {
1501 	struct crypto_cipher	*tfm;
1502 	__u8			key[TCP_FASTOPEN_KEY_LENGTH];
1503 	struct rcu_head		rcu;
1504 };
1505 
1506 /* write queue abstraction */
1507 static inline void tcp_write_queue_purge(struct sock *sk)
1508 {
1509 	struct sk_buff *skb;
1510 
1511 	while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL)
1512 		sk_wmem_free_skb(sk, skb);
1513 	sk_mem_reclaim(sk);
1514 	tcp_clear_all_retrans_hints(tcp_sk(sk));
1515 }
1516 
1517 static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)
1518 {
1519 	return skb_peek(&sk->sk_write_queue);
1520 }
1521 
1522 static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk)
1523 {
1524 	return skb_peek_tail(&sk->sk_write_queue);
1525 }
1526 
1527 static inline struct sk_buff *tcp_write_queue_next(const struct sock *sk,
1528 						   const struct sk_buff *skb)
1529 {
1530 	return skb_queue_next(&sk->sk_write_queue, skb);
1531 }
1532 
1533 static inline struct sk_buff *tcp_write_queue_prev(const struct sock *sk,
1534 						   const struct sk_buff *skb)
1535 {
1536 	return skb_queue_prev(&sk->sk_write_queue, skb);
1537 }
1538 
1539 #define tcp_for_write_queue(skb, sk)					\
1540 	skb_queue_walk(&(sk)->sk_write_queue, skb)
1541 
1542 #define tcp_for_write_queue_from(skb, sk)				\
1543 	skb_queue_walk_from(&(sk)->sk_write_queue, skb)
1544 
1545 #define tcp_for_write_queue_from_safe(skb, tmp, sk)			\
1546 	skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
1547 
1548 static inline struct sk_buff *tcp_send_head(const struct sock *sk)
1549 {
1550 	return sk->sk_send_head;
1551 }
1552 
1553 static inline bool tcp_skb_is_last(const struct sock *sk,
1554 				   const struct sk_buff *skb)
1555 {
1556 	return skb_queue_is_last(&sk->sk_write_queue, skb);
1557 }
1558 
1559 static inline void tcp_advance_send_head(struct sock *sk, const struct sk_buff *skb)
1560 {
1561 	if (tcp_skb_is_last(sk, skb))
1562 		sk->sk_send_head = NULL;
1563 	else
1564 		sk->sk_send_head = tcp_write_queue_next(sk, skb);
1565 }
1566 
1567 static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
1568 {
1569 	if (sk->sk_send_head == skb_unlinked)
1570 		sk->sk_send_head = NULL;
1571 	if (tcp_sk(sk)->highest_sack == skb_unlinked)
1572 		tcp_sk(sk)->highest_sack = NULL;
1573 }
1574 
1575 static inline void tcp_init_send_head(struct sock *sk)
1576 {
1577 	sk->sk_send_head = NULL;
1578 }
1579 
1580 static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1581 {
1582 	__skb_queue_tail(&sk->sk_write_queue, skb);
1583 }
1584 
1585 static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1586 {
1587 	__tcp_add_write_queue_tail(sk, skb);
1588 
1589 	/* Queue it, remembering where we must start sending. */
1590 	if (sk->sk_send_head == NULL) {
1591 		sk->sk_send_head = skb;
1592 
1593 		if (tcp_sk(sk)->highest_sack == NULL)
1594 			tcp_sk(sk)->highest_sack = skb;
1595 	}
1596 }
1597 
1598 static inline void __tcp_add_write_queue_head(struct sock *sk, struct sk_buff *skb)
1599 {
1600 	__skb_queue_head(&sk->sk_write_queue, skb);
1601 }
1602 
1603 /* Insert buff after skb on the write queue of sk.  */
1604 static inline void tcp_insert_write_queue_after(struct sk_buff *skb,
1605 						struct sk_buff *buff,
1606 						struct sock *sk)
1607 {
1608 	__skb_queue_after(&sk->sk_write_queue, skb, buff);
1609 }
1610 
1611 /* Insert new before skb on the write queue of sk.  */
1612 static inline void tcp_insert_write_queue_before(struct sk_buff *new,
1613 						  struct sk_buff *skb,
1614 						  struct sock *sk)
1615 {
1616 	__skb_queue_before(&sk->sk_write_queue, skb, new);
1617 
1618 	if (sk->sk_send_head == skb)
1619 		sk->sk_send_head = new;
1620 }
1621 
1622 static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
1623 {
1624 	__skb_unlink(skb, &sk->sk_write_queue);
1625 }
1626 
1627 static inline bool tcp_write_queue_empty(struct sock *sk)
1628 {
1629 	return skb_queue_empty(&sk->sk_write_queue);
1630 }
1631 
1632 static inline void tcp_push_pending_frames(struct sock *sk)
1633 {
1634 	if (tcp_send_head(sk)) {
1635 		struct tcp_sock *tp = tcp_sk(sk);
1636 
1637 		__tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
1638 	}
1639 }
1640 
1641 /* Start sequence of the skb just after the highest skb with SACKed
1642  * bit, valid only if sacked_out > 0 or when the caller has ensured
1643  * validity by itself.
1644  */
1645 static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
1646 {
1647 	if (!tp->sacked_out)
1648 		return tp->snd_una;
1649 
1650 	if (tp->highest_sack == NULL)
1651 		return tp->snd_nxt;
1652 
1653 	return TCP_SKB_CB(tp->highest_sack)->seq;
1654 }
1655 
1656 static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
1657 {
1658 	tcp_sk(sk)->highest_sack = tcp_skb_is_last(sk, skb) ? NULL :
1659 						tcp_write_queue_next(sk, skb);
1660 }
1661 
1662 static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
1663 {
1664 	return tcp_sk(sk)->highest_sack;
1665 }
1666 
1667 static inline void tcp_highest_sack_reset(struct sock *sk)
1668 {
1669 	tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk);
1670 }
1671 
1672 /* Called when old skb is about to be deleted (to be combined with new skb) */
1673 static inline void tcp_highest_sack_combine(struct sock *sk,
1674 					    struct sk_buff *old,
1675 					    struct sk_buff *new)
1676 {
1677 	if (tcp_sk(sk)->sacked_out && (old == tcp_sk(sk)->highest_sack))
1678 		tcp_sk(sk)->highest_sack = new;
1679 }
1680 
1681 /* This helper checks if socket has IP_TRANSPARENT set */
1682 static inline bool inet_sk_transparent(const struct sock *sk)
1683 {
1684 	switch (sk->sk_state) {
1685 	case TCP_TIME_WAIT:
1686 		return inet_twsk(sk)->tw_transparent;
1687 	case TCP_NEW_SYN_RECV:
1688 		return inet_rsk(inet_reqsk(sk))->no_srccheck;
1689 	}
1690 	return inet_sk(sk)->transparent;
1691 }
1692 
1693 /* Determines whether this is a thin stream (which may suffer from
1694  * increased latency). Used to trigger latency-reducing mechanisms.
1695  */
1696 static inline bool tcp_stream_is_thin(struct tcp_sock *tp)
1697 {
1698 	return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
1699 }
1700 
1701 /* /proc */
1702 enum tcp_seq_states {
1703 	TCP_SEQ_STATE_LISTENING,
1704 	TCP_SEQ_STATE_ESTABLISHED,
1705 };
1706 
1707 int tcp_seq_open(struct inode *inode, struct file *file);
1708 
1709 struct tcp_seq_afinfo {
1710 	char				*name;
1711 	sa_family_t			family;
1712 	const struct file_operations	*seq_fops;
1713 	struct seq_operations		seq_ops;
1714 };
1715 
1716 struct tcp_iter_state {
1717 	struct seq_net_private	p;
1718 	sa_family_t		family;
1719 	enum tcp_seq_states	state;
1720 	struct sock		*syn_wait_sk;
1721 	int			bucket, offset, sbucket, num;
1722 	loff_t			last_pos;
1723 };
1724 
1725 int tcp_proc_register(struct net *net, struct tcp_seq_afinfo *afinfo);
1726 void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo);
1727 
1728 extern struct request_sock_ops tcp_request_sock_ops;
1729 extern struct request_sock_ops tcp6_request_sock_ops;
1730 
1731 void tcp_v4_destroy_sock(struct sock *sk);
1732 
1733 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
1734 				netdev_features_t features);
1735 struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb);
1736 int tcp_gro_complete(struct sk_buff *skb);
1737 
1738 void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
1739 
1740 static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
1741 {
1742 	struct net *net = sock_net((struct sock *)tp);
1743 	return tp->notsent_lowat ?: net->ipv4.sysctl_tcp_notsent_lowat;
1744 }
1745 
1746 static inline bool tcp_stream_memory_free(const struct sock *sk)
1747 {
1748 	const struct tcp_sock *tp = tcp_sk(sk);
1749 	u32 notsent_bytes = tp->write_seq - tp->snd_nxt;
1750 
1751 	return notsent_bytes < tcp_notsent_lowat(tp);
1752 }
1753 
1754 #ifdef CONFIG_PROC_FS
1755 int tcp4_proc_init(void);
1756 void tcp4_proc_exit(void);
1757 #endif
1758 
1759 int tcp_rtx_synack(const struct sock *sk, struct request_sock *req);
1760 int tcp_conn_request(struct request_sock_ops *rsk_ops,
1761 		     const struct tcp_request_sock_ops *af_ops,
1762 		     struct sock *sk, struct sk_buff *skb);
1763 
1764 /* TCP af-specific functions */
1765 struct tcp_sock_af_ops {
1766 #ifdef CONFIG_TCP_MD5SIG
1767 	struct tcp_md5sig_key	*(*md5_lookup) (const struct sock *sk,
1768 						const struct sock *addr_sk);
1769 	int		(*calc_md5_hash)(char *location,
1770 					 const struct tcp_md5sig_key *md5,
1771 					 const struct sock *sk,
1772 					 const struct sk_buff *skb);
1773 	int		(*md5_parse)(struct sock *sk,
1774 				     char __user *optval,
1775 				     int optlen);
1776 #endif
1777 };
1778 
1779 struct tcp_request_sock_ops {
1780 	u16 mss_clamp;
1781 #ifdef CONFIG_TCP_MD5SIG
1782 	struct tcp_md5sig_key *(*req_md5_lookup)(const struct sock *sk,
1783 						 const struct sock *addr_sk);
1784 	int		(*calc_md5_hash) (char *location,
1785 					  const struct tcp_md5sig_key *md5,
1786 					  const struct sock *sk,
1787 					  const struct sk_buff *skb);
1788 #endif
1789 	void (*init_req)(struct request_sock *req,
1790 			 const struct sock *sk_listener,
1791 			 struct sk_buff *skb);
1792 #ifdef CONFIG_SYN_COOKIES
1793 	__u32 (*cookie_init_seq)(const struct sk_buff *skb,
1794 				 __u16 *mss);
1795 #endif
1796 	struct dst_entry *(*route_req)(const struct sock *sk, struct flowi *fl,
1797 				       const struct request_sock *req,
1798 				       bool *strict);
1799 	__u32 (*init_seq)(const struct sk_buff *skb);
1800 	int (*send_synack)(const struct sock *sk, struct dst_entry *dst,
1801 			   struct flowi *fl, struct request_sock *req,
1802 			   struct tcp_fastopen_cookie *foc,
1803 			   enum tcp_synack_type synack_type);
1804 };
1805 
1806 #ifdef CONFIG_SYN_COOKIES
1807 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1808 					 const struct sock *sk, struct sk_buff *skb,
1809 					 __u16 *mss)
1810 {
1811 	tcp_synq_overflow(sk);
1812 	__NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESSENT);
1813 	return ops->cookie_init_seq(skb, mss);
1814 }
1815 #else
1816 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1817 					 const struct sock *sk, struct sk_buff *skb,
1818 					 __u16 *mss)
1819 {
1820 	return 0;
1821 }
1822 #endif
1823 
1824 int tcpv4_offload_init(void);
1825 
1826 void tcp_v4_init(void);
1827 void tcp_init(void);
1828 
1829 /* tcp_recovery.c */
1830 
1831 /* Flags to enable various loss recovery features. See below */
1832 extern int sysctl_tcp_recovery;
1833 
1834 /* Use TCP RACK to detect (some) tail and retransmit losses */
1835 #define TCP_RACK_LOST_RETRANS  0x1
1836 
1837 extern int tcp_rack_mark_lost(struct sock *sk);
1838 
1839 extern void tcp_rack_advance(struct tcp_sock *tp,
1840 			     const struct skb_mstamp *xmit_time, u8 sacked);
1841 
1842 /*
1843  * Save and compile IPv4 options, return a pointer to it
1844  */
1845 static inline struct ip_options_rcu *tcp_v4_save_options(struct sk_buff *skb)
1846 {
1847 	const struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt;
1848 	struct ip_options_rcu *dopt = NULL;
1849 
1850 	if (opt->optlen) {
1851 		int opt_size = sizeof(*dopt) + opt->optlen;
1852 
1853 		dopt = kmalloc(opt_size, GFP_ATOMIC);
1854 		if (dopt && __ip_options_echo(&dopt->opt, skb, opt)) {
1855 			kfree(dopt);
1856 			dopt = NULL;
1857 		}
1858 	}
1859 	return dopt;
1860 }
1861 
1862 /* locally generated TCP pure ACKs have skb->truesize == 2
1863  * (check tcp_send_ack() in net/ipv4/tcp_output.c )
1864  * This is much faster than dissecting the packet to find out.
1865  * (Think of GRE encapsulations, IPv4, IPv6, ...)
1866  */
1867 static inline bool skb_is_tcp_pure_ack(const struct sk_buff *skb)
1868 {
1869 	return skb->truesize == 2;
1870 }
1871 
1872 static inline void skb_set_tcp_pure_ack(struct sk_buff *skb)
1873 {
1874 	skb->truesize = 2;
1875 }
1876 
1877 static inline int tcp_inq(struct sock *sk)
1878 {
1879 	struct tcp_sock *tp = tcp_sk(sk);
1880 	int answ;
1881 
1882 	if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
1883 		answ = 0;
1884 	} else if (sock_flag(sk, SOCK_URGINLINE) ||
1885 		   !tp->urg_data ||
1886 		   before(tp->urg_seq, tp->copied_seq) ||
1887 		   !before(tp->urg_seq, tp->rcv_nxt)) {
1888 
1889 		answ = tp->rcv_nxt - tp->copied_seq;
1890 
1891 		/* Subtract 1, if FIN was received */
1892 		if (answ && sock_flag(sk, SOCK_DONE))
1893 			answ--;
1894 	} else {
1895 		answ = tp->urg_seq - tp->copied_seq;
1896 	}
1897 
1898 	return answ;
1899 }
1900 
1901 int tcp_peek_len(struct socket *sock);
1902 
1903 static inline void tcp_segs_in(struct tcp_sock *tp, const struct sk_buff *skb)
1904 {
1905 	u16 segs_in;
1906 
1907 	segs_in = max_t(u16, 1, skb_shinfo(skb)->gso_segs);
1908 	tp->segs_in += segs_in;
1909 	if (skb->len > tcp_hdrlen(skb))
1910 		tp->data_segs_in += segs_in;
1911 }
1912 
1913 /*
1914  * TCP listen path runs lockless.
1915  * We forced "struct sock" to be const qualified to make sure
1916  * we don't modify one of its field by mistake.
1917  * Here, we increment sk_drops which is an atomic_t, so we can safely
1918  * make sock writable again.
1919  */
1920 static inline void tcp_listendrop(const struct sock *sk)
1921 {
1922 	atomic_inc(&((struct sock *)sk)->sk_drops);
1923 	__NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENDROPS);
1924 }
1925 
1926 #endif	/* _TCP_H */
1927