xref: /openbmc/linux/include/net/tcp.h (revision 81d67439)
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 TCP_DEBUG 1
22 #define FASTRETRANS_DEBUG 1
23 
24 #include <linux/list.h>
25 #include <linux/tcp.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 
49 extern struct inet_hashinfo tcp_hashinfo;
50 
51 extern struct percpu_counter tcp_orphan_count;
52 extern 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 /* Offer an initial receive window of 10 mss. */
64 #define TCP_DEFAULT_INIT_RCVWND	10
65 
66 /* Minimal accepted MSS. It is (60+60+8) - (20+20). */
67 #define TCP_MIN_MSS		88U
68 
69 /* The least MTU to use for probing */
70 #define TCP_BASE_MSS		512
71 
72 /* After receiving this amount of duplicate ACKs fast retransmit starts. */
73 #define TCP_FASTRETRANS_THRESH 3
74 
75 /* Maximal reordering. */
76 #define TCP_MAX_REORDERING	127
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	 5	/* number of times to retry active opening a
101 				 * connection: ~180sec is RFC minimum	*/
102 
103 #define TCP_SYNACK_RETRIES 5	/* number of times to retry passive opening a
104 				 * connection: ~180sec is RFC minimum	*/
105 
106 #define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT
107 				  * state, about 60 seconds	*/
108 #define TCP_FIN_TIMEOUT	TCP_TIMEWAIT_LEN
109                                  /* BSD style FIN_WAIT2 deadlock breaker.
110 				  * It used to be 3min, new value is 60sec,
111 				  * to combine FIN-WAIT-2 timeout with
112 				  * TIME-WAIT timer.
113 				  */
114 
115 #define TCP_DELACK_MAX	((unsigned)(HZ/5))	/* maximal time to delay before sending an ACK */
116 #if HZ >= 100
117 #define TCP_DELACK_MIN	((unsigned)(HZ/25))	/* minimal time to delay before sending an ACK */
118 #define TCP_ATO_MIN	((unsigned)(HZ/25))
119 #else
120 #define TCP_DELACK_MIN	4U
121 #define TCP_ATO_MIN	4U
122 #endif
123 #define TCP_RTO_MAX	((unsigned)(120*HZ))
124 #define TCP_RTO_MIN	((unsigned)(HZ/5))
125 #define TCP_TIMEOUT_INIT ((unsigned)(1*HZ))	/* RFC2988bis initial RTO value	*/
126 #define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ))	/* RFC 1122 initial RTO value, now
127 						 * used as a fallback RTO for the
128 						 * initial data transmission if no
129 						 * valid RTT sample has been acquired,
130 						 * most likely due to retrans in 3WHS.
131 						 */
132 
133 #define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes
134 					                 * for local resources.
135 					                 */
136 
137 #define TCP_KEEPALIVE_TIME	(120*60*HZ)	/* two hours */
138 #define TCP_KEEPALIVE_PROBES	9		/* Max of 9 keepalive probes	*/
139 #define TCP_KEEPALIVE_INTVL	(75*HZ)
140 
141 #define MAX_TCP_KEEPIDLE	32767
142 #define MAX_TCP_KEEPINTVL	32767
143 #define MAX_TCP_KEEPCNT		127
144 #define MAX_TCP_SYNCNT		127
145 
146 #define TCP_SYNQ_INTERVAL	(HZ/5)	/* Period of SYNACK timer */
147 
148 #define TCP_PAWS_24DAYS	(60 * 60 * 24 * 24)
149 #define TCP_PAWS_MSL	60		/* Per-host timestamps are invalidated
150 					 * after this time. It should be equal
151 					 * (or greater than) TCP_TIMEWAIT_LEN
152 					 * to provide reliability equal to one
153 					 * provided by timewait state.
154 					 */
155 #define TCP_PAWS_WINDOW	1		/* Replay window for per-host
156 					 * timestamps. It must be less than
157 					 * minimal timewait lifetime.
158 					 */
159 /*
160  *	TCP option
161  */
162 
163 #define TCPOPT_NOP		1	/* Padding */
164 #define TCPOPT_EOL		0	/* End of options */
165 #define TCPOPT_MSS		2	/* Segment size negotiating */
166 #define TCPOPT_WINDOW		3	/* Window scaling */
167 #define TCPOPT_SACK_PERM        4       /* SACK Permitted */
168 #define TCPOPT_SACK             5       /* SACK Block */
169 #define TCPOPT_TIMESTAMP	8	/* Better RTT estimations/PAWS */
170 #define TCPOPT_MD5SIG		19	/* MD5 Signature (RFC2385) */
171 #define TCPOPT_COOKIE		253	/* Cookie extension (experimental) */
172 
173 /*
174  *     TCP option lengths
175  */
176 
177 #define TCPOLEN_MSS            4
178 #define TCPOLEN_WINDOW         3
179 #define TCPOLEN_SACK_PERM      2
180 #define TCPOLEN_TIMESTAMP      10
181 #define TCPOLEN_MD5SIG         18
182 #define TCPOLEN_COOKIE_BASE    2	/* Cookie-less header extension */
183 #define TCPOLEN_COOKIE_PAIR    3	/* Cookie pair header extension */
184 #define TCPOLEN_COOKIE_MIN     (TCPOLEN_COOKIE_BASE+TCP_COOKIE_MIN)
185 #define TCPOLEN_COOKIE_MAX     (TCPOLEN_COOKIE_BASE+TCP_COOKIE_MAX)
186 
187 /* But this is what stacks really send out. */
188 #define TCPOLEN_TSTAMP_ALIGNED		12
189 #define TCPOLEN_WSCALE_ALIGNED		4
190 #define TCPOLEN_SACKPERM_ALIGNED	4
191 #define TCPOLEN_SACK_BASE		2
192 #define TCPOLEN_SACK_BASE_ALIGNED	4
193 #define TCPOLEN_SACK_PERBLOCK		8
194 #define TCPOLEN_MD5SIG_ALIGNED		20
195 #define TCPOLEN_MSS_ALIGNED		4
196 
197 /* Flags in tp->nonagle */
198 #define TCP_NAGLE_OFF		1	/* Nagle's algo is disabled */
199 #define TCP_NAGLE_CORK		2	/* Socket is corked	    */
200 #define TCP_NAGLE_PUSH		4	/* Cork is overridden for already queued data */
201 
202 /* TCP thin-stream limits */
203 #define TCP_THIN_LINEAR_RETRIES 6       /* After 6 linear retries, do exp. backoff */
204 
205 /* TCP initial congestion window as per draft-hkchu-tcpm-initcwnd-01 */
206 #define TCP_INIT_CWND		10
207 
208 extern struct inet_timewait_death_row tcp_death_row;
209 
210 /* sysctl variables for tcp */
211 extern int sysctl_tcp_timestamps;
212 extern int sysctl_tcp_window_scaling;
213 extern int sysctl_tcp_sack;
214 extern int sysctl_tcp_fin_timeout;
215 extern int sysctl_tcp_keepalive_time;
216 extern int sysctl_tcp_keepalive_probes;
217 extern int sysctl_tcp_keepalive_intvl;
218 extern int sysctl_tcp_syn_retries;
219 extern int sysctl_tcp_synack_retries;
220 extern int sysctl_tcp_retries1;
221 extern int sysctl_tcp_retries2;
222 extern int sysctl_tcp_orphan_retries;
223 extern int sysctl_tcp_syncookies;
224 extern int sysctl_tcp_retrans_collapse;
225 extern int sysctl_tcp_stdurg;
226 extern int sysctl_tcp_rfc1337;
227 extern int sysctl_tcp_abort_on_overflow;
228 extern int sysctl_tcp_max_orphans;
229 extern int sysctl_tcp_fack;
230 extern int sysctl_tcp_reordering;
231 extern int sysctl_tcp_ecn;
232 extern int sysctl_tcp_dsack;
233 extern long sysctl_tcp_mem[3];
234 extern int sysctl_tcp_wmem[3];
235 extern int sysctl_tcp_rmem[3];
236 extern int sysctl_tcp_app_win;
237 extern int sysctl_tcp_adv_win_scale;
238 extern int sysctl_tcp_tw_reuse;
239 extern int sysctl_tcp_frto;
240 extern int sysctl_tcp_frto_response;
241 extern int sysctl_tcp_low_latency;
242 extern int sysctl_tcp_dma_copybreak;
243 extern int sysctl_tcp_nometrics_save;
244 extern int sysctl_tcp_moderate_rcvbuf;
245 extern int sysctl_tcp_tso_win_divisor;
246 extern int sysctl_tcp_abc;
247 extern int sysctl_tcp_mtu_probing;
248 extern int sysctl_tcp_base_mss;
249 extern int sysctl_tcp_workaround_signed_windows;
250 extern int sysctl_tcp_slow_start_after_idle;
251 extern int sysctl_tcp_max_ssthresh;
252 extern int sysctl_tcp_cookie_size;
253 extern int sysctl_tcp_thin_linear_timeouts;
254 extern int sysctl_tcp_thin_dupack;
255 
256 extern atomic_long_t tcp_memory_allocated;
257 extern struct percpu_counter tcp_sockets_allocated;
258 extern int tcp_memory_pressure;
259 
260 /*
261  * The next routines deal with comparing 32 bit unsigned ints
262  * and worry about wraparound (automatic with unsigned arithmetic).
263  */
264 
265 static inline int before(__u32 seq1, __u32 seq2)
266 {
267         return (__s32)(seq1-seq2) < 0;
268 }
269 #define after(seq2, seq1) 	before(seq1, seq2)
270 
271 /* is s2<=s1<=s3 ? */
272 static inline int between(__u32 seq1, __u32 seq2, __u32 seq3)
273 {
274 	return seq3 - seq2 >= seq1 - seq2;
275 }
276 
277 static inline bool tcp_too_many_orphans(struct sock *sk, int shift)
278 {
279 	struct percpu_counter *ocp = sk->sk_prot->orphan_count;
280 	int orphans = percpu_counter_read_positive(ocp);
281 
282 	if (orphans << shift > sysctl_tcp_max_orphans) {
283 		orphans = percpu_counter_sum_positive(ocp);
284 		if (orphans << shift > sysctl_tcp_max_orphans)
285 			return true;
286 	}
287 
288 	if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
289 	    atomic_long_read(&tcp_memory_allocated) > sysctl_tcp_mem[2])
290 		return true;
291 	return false;
292 }
293 
294 /* syncookies: remember time of last synqueue overflow */
295 static inline void tcp_synq_overflow(struct sock *sk)
296 {
297 	tcp_sk(sk)->rx_opt.ts_recent_stamp = jiffies;
298 }
299 
300 /* syncookies: no recent synqueue overflow on this listening socket? */
301 static inline int tcp_synq_no_recent_overflow(const struct sock *sk)
302 {
303 	unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
304 	return time_after(jiffies, last_overflow + TCP_TIMEOUT_FALLBACK);
305 }
306 
307 extern struct proto tcp_prot;
308 
309 #define TCP_INC_STATS(net, field)	SNMP_INC_STATS((net)->mib.tcp_statistics, field)
310 #define TCP_INC_STATS_BH(net, field)	SNMP_INC_STATS_BH((net)->mib.tcp_statistics, field)
311 #define TCP_DEC_STATS(net, field)	SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
312 #define TCP_ADD_STATS_USER(net, field, val) SNMP_ADD_STATS_USER((net)->mib.tcp_statistics, field, val)
313 #define TCP_ADD_STATS(net, field, val)	SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
314 
315 extern void tcp_v4_err(struct sk_buff *skb, u32);
316 
317 extern void tcp_shutdown (struct sock *sk, int how);
318 
319 extern int tcp_v4_rcv(struct sk_buff *skb);
320 
321 extern struct inet_peer *tcp_v4_get_peer(struct sock *sk, bool *release_it);
322 extern void *tcp_v4_tw_get_peer(struct sock *sk);
323 extern int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
324 extern int tcp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
325 		       size_t size);
326 extern int tcp_sendpage(struct sock *sk, struct page *page, int offset,
327 			size_t size, int flags);
328 extern int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
329 extern int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
330 				 struct tcphdr *th, unsigned len);
331 extern int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
332 			       struct tcphdr *th, unsigned len);
333 extern void tcp_rcv_space_adjust(struct sock *sk);
334 extern void tcp_cleanup_rbuf(struct sock *sk, int copied);
335 extern int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
336 extern void tcp_twsk_destructor(struct sock *sk);
337 extern ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
338 			       struct pipe_inode_info *pipe, size_t len,
339 			       unsigned int flags);
340 
341 static inline void tcp_dec_quickack_mode(struct sock *sk,
342 					 const unsigned int pkts)
343 {
344 	struct inet_connection_sock *icsk = inet_csk(sk);
345 
346 	if (icsk->icsk_ack.quick) {
347 		if (pkts >= icsk->icsk_ack.quick) {
348 			icsk->icsk_ack.quick = 0;
349 			/* Leaving quickack mode we deflate ATO. */
350 			icsk->icsk_ack.ato   = TCP_ATO_MIN;
351 		} else
352 			icsk->icsk_ack.quick -= pkts;
353 	}
354 }
355 
356 #define	TCP_ECN_OK		1
357 #define	TCP_ECN_QUEUE_CWR	2
358 #define	TCP_ECN_DEMAND_CWR	4
359 
360 static __inline__ void
361 TCP_ECN_create_request(struct request_sock *req, struct tcphdr *th)
362 {
363 	if (sysctl_tcp_ecn && th->ece && th->cwr)
364 		inet_rsk(req)->ecn_ok = 1;
365 }
366 
367 enum tcp_tw_status {
368 	TCP_TW_SUCCESS = 0,
369 	TCP_TW_RST = 1,
370 	TCP_TW_ACK = 2,
371 	TCP_TW_SYN = 3
372 };
373 
374 
375 extern enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
376 						     struct sk_buff *skb,
377 						     const struct tcphdr *th);
378 extern struct sock * tcp_check_req(struct sock *sk,struct sk_buff *skb,
379 				   struct request_sock *req,
380 				   struct request_sock **prev);
381 extern int tcp_child_process(struct sock *parent, struct sock *child,
382 			     struct sk_buff *skb);
383 extern int tcp_use_frto(struct sock *sk);
384 extern void tcp_enter_frto(struct sock *sk);
385 extern void tcp_enter_loss(struct sock *sk, int how);
386 extern void tcp_clear_retrans(struct tcp_sock *tp);
387 extern void tcp_update_metrics(struct sock *sk);
388 extern void tcp_close(struct sock *sk, long timeout);
389 extern unsigned int tcp_poll(struct file * file, struct socket *sock,
390 			     struct poll_table_struct *wait);
391 extern int tcp_getsockopt(struct sock *sk, int level, int optname,
392 			  char __user *optval, int __user *optlen);
393 extern int tcp_setsockopt(struct sock *sk, int level, int optname,
394 			  char __user *optval, unsigned int optlen);
395 extern int compat_tcp_getsockopt(struct sock *sk, int level, int optname,
396 				 char __user *optval, int __user *optlen);
397 extern int compat_tcp_setsockopt(struct sock *sk, int level, int optname,
398 				 char __user *optval, unsigned int optlen);
399 extern void tcp_set_keepalive(struct sock *sk, int val);
400 extern void tcp_syn_ack_timeout(struct sock *sk, struct request_sock *req);
401 extern int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
402 		       size_t len, int nonblock, int flags, int *addr_len);
403 extern void tcp_parse_options(struct sk_buff *skb,
404 			      struct tcp_options_received *opt_rx, u8 **hvpp,
405 			      int estab);
406 extern u8 *tcp_parse_md5sig_option(struct tcphdr *th);
407 
408 /*
409  *	TCP v4 functions exported for the inet6 API
410  */
411 
412 extern void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
413 extern int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
414 extern struct sock * tcp_create_openreq_child(struct sock *sk,
415 					      struct request_sock *req,
416 					      struct sk_buff *skb);
417 extern struct sock * tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
418 					  struct request_sock *req,
419 					  struct dst_entry *dst);
420 extern int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
421 extern int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr,
422 			  int addr_len);
423 extern int tcp_connect(struct sock *sk);
424 extern struct sk_buff * tcp_make_synack(struct sock *sk, struct dst_entry *dst,
425 					struct request_sock *req,
426 					struct request_values *rvp);
427 extern int tcp_disconnect(struct sock *sk, int flags);
428 
429 
430 /* From syncookies.c */
431 extern __u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS];
432 extern struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
433 				    struct ip_options *opt);
434 extern __u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb,
435 				     __u16 *mss);
436 
437 extern __u32 cookie_init_timestamp(struct request_sock *req);
438 extern bool cookie_check_timestamp(struct tcp_options_received *opt, bool *);
439 
440 /* From net/ipv6/syncookies.c */
441 extern struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
442 extern __u32 cookie_v6_init_sequence(struct sock *sk, struct sk_buff *skb,
443 				     __u16 *mss);
444 
445 /* tcp_output.c */
446 
447 extern void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
448 				      int nonagle);
449 extern int tcp_may_send_now(struct sock *sk);
450 extern int tcp_retransmit_skb(struct sock *, struct sk_buff *);
451 extern void tcp_retransmit_timer(struct sock *sk);
452 extern void tcp_xmit_retransmit_queue(struct sock *);
453 extern void tcp_simple_retransmit(struct sock *);
454 extern int tcp_trim_head(struct sock *, struct sk_buff *, u32);
455 extern int tcp_fragment(struct sock *, struct sk_buff *, u32, unsigned int);
456 
457 extern void tcp_send_probe0(struct sock *);
458 extern void tcp_send_partial(struct sock *);
459 extern int tcp_write_wakeup(struct sock *);
460 extern void tcp_send_fin(struct sock *sk);
461 extern void tcp_send_active_reset(struct sock *sk, gfp_t priority);
462 extern int tcp_send_synack(struct sock *);
463 extern void tcp_push_one(struct sock *, unsigned int mss_now);
464 extern void tcp_send_ack(struct sock *sk);
465 extern void tcp_send_delayed_ack(struct sock *sk);
466 
467 /* tcp_input.c */
468 extern void tcp_cwnd_application_limited(struct sock *sk);
469 
470 /* tcp_timer.c */
471 extern void tcp_init_xmit_timers(struct sock *);
472 static inline void tcp_clear_xmit_timers(struct sock *sk)
473 {
474 	inet_csk_clear_xmit_timers(sk);
475 }
476 
477 extern unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
478 extern unsigned int tcp_current_mss(struct sock *sk);
479 
480 /* Bound MSS / TSO packet size with the half of the window */
481 static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
482 {
483 	int cutoff;
484 
485 	/* When peer uses tiny windows, there is no use in packetizing
486 	 * to sub-MSS pieces for the sake of SWS or making sure there
487 	 * are enough packets in the pipe for fast recovery.
488 	 *
489 	 * On the other hand, for extremely large MSS devices, handling
490 	 * smaller than MSS windows in this way does make sense.
491 	 */
492 	if (tp->max_window >= 512)
493 		cutoff = (tp->max_window >> 1);
494 	else
495 		cutoff = tp->max_window;
496 
497 	if (cutoff && pktsize > cutoff)
498 		return max_t(int, cutoff, 68U - tp->tcp_header_len);
499 	else
500 		return pktsize;
501 }
502 
503 /* tcp.c */
504 extern void tcp_get_info(struct sock *, struct tcp_info *);
505 
506 /* Read 'sendfile()'-style from a TCP socket */
507 typedef int (*sk_read_actor_t)(read_descriptor_t *, struct sk_buff *,
508 				unsigned int, size_t);
509 extern int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
510 			 sk_read_actor_t recv_actor);
511 
512 extern void tcp_initialize_rcv_mss(struct sock *sk);
513 
514 extern int tcp_mtu_to_mss(struct sock *sk, int pmtu);
515 extern int tcp_mss_to_mtu(struct sock *sk, int mss);
516 extern void tcp_mtup_init(struct sock *sk);
517 extern void tcp_valid_rtt_meas(struct sock *sk, u32 seq_rtt);
518 
519 static inline void tcp_bound_rto(const struct sock *sk)
520 {
521 	if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
522 		inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
523 }
524 
525 static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
526 {
527 	return (tp->srtt >> 3) + tp->rttvar;
528 }
529 
530 static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
531 {
532 	tp->pred_flags = htonl((tp->tcp_header_len << 26) |
533 			       ntohl(TCP_FLAG_ACK) |
534 			       snd_wnd);
535 }
536 
537 static inline void tcp_fast_path_on(struct tcp_sock *tp)
538 {
539 	__tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
540 }
541 
542 static inline void tcp_fast_path_check(struct sock *sk)
543 {
544 	struct tcp_sock *tp = tcp_sk(sk);
545 
546 	if (skb_queue_empty(&tp->out_of_order_queue) &&
547 	    tp->rcv_wnd &&
548 	    atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
549 	    !tp->urg_data)
550 		tcp_fast_path_on(tp);
551 }
552 
553 /* Compute the actual rto_min value */
554 static inline u32 tcp_rto_min(struct sock *sk)
555 {
556 	struct dst_entry *dst = __sk_dst_get(sk);
557 	u32 rto_min = TCP_RTO_MIN;
558 
559 	if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
560 		rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
561 	return rto_min;
562 }
563 
564 /* Compute the actual receive window we are currently advertising.
565  * Rcv_nxt can be after the window if our peer push more data
566  * than the offered window.
567  */
568 static inline u32 tcp_receive_window(const struct tcp_sock *tp)
569 {
570 	s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;
571 
572 	if (win < 0)
573 		win = 0;
574 	return (u32) win;
575 }
576 
577 /* Choose a new window, without checks for shrinking, and without
578  * scaling applied to the result.  The caller does these things
579  * if necessary.  This is a "raw" window selection.
580  */
581 extern u32 __tcp_select_window(struct sock *sk);
582 
583 /* TCP timestamps are only 32-bits, this causes a slight
584  * complication on 64-bit systems since we store a snapshot
585  * of jiffies in the buffer control blocks below.  We decided
586  * to use only the low 32-bits of jiffies and hide the ugly
587  * casts with the following macro.
588  */
589 #define tcp_time_stamp		((__u32)(jiffies))
590 
591 #define tcp_flag_byte(th) (((u_int8_t *)th)[13])
592 
593 #define TCPHDR_FIN 0x01
594 #define TCPHDR_SYN 0x02
595 #define TCPHDR_RST 0x04
596 #define TCPHDR_PSH 0x08
597 #define TCPHDR_ACK 0x10
598 #define TCPHDR_URG 0x20
599 #define TCPHDR_ECE 0x40
600 #define TCPHDR_CWR 0x80
601 
602 /* This is what the send packet queuing engine uses to pass
603  * TCP per-packet control information to the transmission code.
604  * We also store the host-order sequence numbers in here too.
605  * This is 44 bytes if IPV6 is enabled.
606  * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately.
607  */
608 struct tcp_skb_cb {
609 	union {
610 		struct inet_skb_parm	h4;
611 #if defined(CONFIG_IPV6) || defined (CONFIG_IPV6_MODULE)
612 		struct inet6_skb_parm	h6;
613 #endif
614 	} header;	/* For incoming frames		*/
615 	__u32		seq;		/* Starting sequence number	*/
616 	__u32		end_seq;	/* SEQ + FIN + SYN + datalen	*/
617 	__u32		when;		/* used to compute rtt's	*/
618 	__u8		flags;		/* TCP header flags.		*/
619 	__u8		sacked;		/* State flags for SACK/FACK.	*/
620 #define TCPCB_SACKED_ACKED	0x01	/* SKB ACK'd by a SACK block	*/
621 #define TCPCB_SACKED_RETRANS	0x02	/* SKB retransmitted		*/
622 #define TCPCB_LOST		0x04	/* SKB is lost			*/
623 #define TCPCB_TAGBITS		0x07	/* All tag bits			*/
624 
625 #define TCPCB_EVER_RETRANS	0x80	/* Ever retransmitted frame	*/
626 #define TCPCB_RETRANS		(TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS)
627 
628 	__u32		ack_seq;	/* Sequence number ACK'd	*/
629 };
630 
631 #define TCP_SKB_CB(__skb)	((struct tcp_skb_cb *)&((__skb)->cb[0]))
632 
633 /* Due to TSO, an SKB can be composed of multiple actual
634  * packets.  To keep these tracked properly, we use this.
635  */
636 static inline int tcp_skb_pcount(const struct sk_buff *skb)
637 {
638 	return skb_shinfo(skb)->gso_segs;
639 }
640 
641 /* This is valid iff tcp_skb_pcount() > 1. */
642 static inline int tcp_skb_mss(const struct sk_buff *skb)
643 {
644 	return skb_shinfo(skb)->gso_size;
645 }
646 
647 /* Events passed to congestion control interface */
648 enum tcp_ca_event {
649 	CA_EVENT_TX_START,	/* first transmit when no packets in flight */
650 	CA_EVENT_CWND_RESTART,	/* congestion window restart */
651 	CA_EVENT_COMPLETE_CWR,	/* end of congestion recovery */
652 	CA_EVENT_FRTO,		/* fast recovery timeout */
653 	CA_EVENT_LOSS,		/* loss timeout */
654 	CA_EVENT_FAST_ACK,	/* in sequence ack */
655 	CA_EVENT_SLOW_ACK,	/* other ack */
656 };
657 
658 /*
659  * Interface for adding new TCP congestion control handlers
660  */
661 #define TCP_CA_NAME_MAX	16
662 #define TCP_CA_MAX	128
663 #define TCP_CA_BUF_MAX	(TCP_CA_NAME_MAX*TCP_CA_MAX)
664 
665 #define TCP_CONG_NON_RESTRICTED 0x1
666 #define TCP_CONG_RTT_STAMP	0x2
667 
668 struct tcp_congestion_ops {
669 	struct list_head	list;
670 	unsigned long flags;
671 
672 	/* initialize private data (optional) */
673 	void (*init)(struct sock *sk);
674 	/* cleanup private data  (optional) */
675 	void (*release)(struct sock *sk);
676 
677 	/* return slow start threshold (required) */
678 	u32 (*ssthresh)(struct sock *sk);
679 	/* lower bound for congestion window (optional) */
680 	u32 (*min_cwnd)(const struct sock *sk);
681 	/* do new cwnd calculation (required) */
682 	void (*cong_avoid)(struct sock *sk, u32 ack, u32 in_flight);
683 	/* call before changing ca_state (optional) */
684 	void (*set_state)(struct sock *sk, u8 new_state);
685 	/* call when cwnd event occurs (optional) */
686 	void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
687 	/* new value of cwnd after loss (optional) */
688 	u32  (*undo_cwnd)(struct sock *sk);
689 	/* hook for packet ack accounting (optional) */
690 	void (*pkts_acked)(struct sock *sk, u32 num_acked, s32 rtt_us);
691 	/* get info for inet_diag (optional) */
692 	void (*get_info)(struct sock *sk, u32 ext, struct sk_buff *skb);
693 
694 	char 		name[TCP_CA_NAME_MAX];
695 	struct module 	*owner;
696 };
697 
698 extern int tcp_register_congestion_control(struct tcp_congestion_ops *type);
699 extern void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
700 
701 extern void tcp_init_congestion_control(struct sock *sk);
702 extern void tcp_cleanup_congestion_control(struct sock *sk);
703 extern int tcp_set_default_congestion_control(const char *name);
704 extern void tcp_get_default_congestion_control(char *name);
705 extern void tcp_get_available_congestion_control(char *buf, size_t len);
706 extern void tcp_get_allowed_congestion_control(char *buf, size_t len);
707 extern int tcp_set_allowed_congestion_control(char *allowed);
708 extern int tcp_set_congestion_control(struct sock *sk, const char *name);
709 extern void tcp_slow_start(struct tcp_sock *tp);
710 extern void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w);
711 
712 extern struct tcp_congestion_ops tcp_init_congestion_ops;
713 extern u32 tcp_reno_ssthresh(struct sock *sk);
714 extern void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 in_flight);
715 extern u32 tcp_reno_min_cwnd(const struct sock *sk);
716 extern struct tcp_congestion_ops tcp_reno;
717 
718 static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
719 {
720 	struct inet_connection_sock *icsk = inet_csk(sk);
721 
722 	if (icsk->icsk_ca_ops->set_state)
723 		icsk->icsk_ca_ops->set_state(sk, ca_state);
724 	icsk->icsk_ca_state = ca_state;
725 }
726 
727 static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
728 {
729 	const struct inet_connection_sock *icsk = inet_csk(sk);
730 
731 	if (icsk->icsk_ca_ops->cwnd_event)
732 		icsk->icsk_ca_ops->cwnd_event(sk, event);
733 }
734 
735 /* These functions determine how the current flow behaves in respect of SACK
736  * handling. SACK is negotiated with the peer, and therefore it can vary
737  * between different flows.
738  *
739  * tcp_is_sack - SACK enabled
740  * tcp_is_reno - No SACK
741  * tcp_is_fack - FACK enabled, implies SACK enabled
742  */
743 static inline int tcp_is_sack(const struct tcp_sock *tp)
744 {
745 	return tp->rx_opt.sack_ok;
746 }
747 
748 static inline int tcp_is_reno(const struct tcp_sock *tp)
749 {
750 	return !tcp_is_sack(tp);
751 }
752 
753 static inline int tcp_is_fack(const struct tcp_sock *tp)
754 {
755 	return tp->rx_opt.sack_ok & 2;
756 }
757 
758 static inline void tcp_enable_fack(struct tcp_sock *tp)
759 {
760 	tp->rx_opt.sack_ok |= 2;
761 }
762 
763 static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
764 {
765 	return tp->sacked_out + tp->lost_out;
766 }
767 
768 /* This determines how many packets are "in the network" to the best
769  * of our knowledge.  In many cases it is conservative, but where
770  * detailed information is available from the receiver (via SACK
771  * blocks etc.) we can make more aggressive calculations.
772  *
773  * Use this for decisions involving congestion control, use just
774  * tp->packets_out to determine if the send queue is empty or not.
775  *
776  * Read this equation as:
777  *
778  *	"Packets sent once on transmission queue" MINUS
779  *	"Packets left network, but not honestly ACKed yet" PLUS
780  *	"Packets fast retransmitted"
781  */
782 static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
783 {
784 	return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
785 }
786 
787 #define TCP_INFINITE_SSTHRESH	0x7fffffff
788 
789 static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
790 {
791 	return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
792 }
793 
794 /* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
795  * The exception is rate halving phase, when cwnd is decreasing towards
796  * ssthresh.
797  */
798 static inline __u32 tcp_current_ssthresh(const struct sock *sk)
799 {
800 	const struct tcp_sock *tp = tcp_sk(sk);
801 	if ((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_CWR | TCPF_CA_Recovery))
802 		return tp->snd_ssthresh;
803 	else
804 		return max(tp->snd_ssthresh,
805 			   ((tp->snd_cwnd >> 1) +
806 			    (tp->snd_cwnd >> 2)));
807 }
808 
809 /* Use define here intentionally to get WARN_ON location shown at the caller */
810 #define tcp_verify_left_out(tp)	WARN_ON(tcp_left_out(tp) > tp->packets_out)
811 
812 extern void tcp_enter_cwr(struct sock *sk, const int set_ssthresh);
813 extern __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst);
814 
815 /* Slow start with delack produces 3 packets of burst, so that
816  * it is safe "de facto".  This will be the default - same as
817  * the default reordering threshold - but if reordering increases,
818  * we must be able to allow cwnd to burst at least this much in order
819  * to not pull it back when holes are filled.
820  */
821 static __inline__ __u32 tcp_max_burst(const struct tcp_sock *tp)
822 {
823 	return tp->reordering;
824 }
825 
826 /* Returns end sequence number of the receiver's advertised window */
827 static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
828 {
829 	return tp->snd_una + tp->snd_wnd;
830 }
831 extern int tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight);
832 
833 static inline void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss,
834 				       const struct sk_buff *skb)
835 {
836 	if (skb->len < mss)
837 		tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
838 }
839 
840 static inline void tcp_check_probe_timer(struct sock *sk)
841 {
842 	struct tcp_sock *tp = tcp_sk(sk);
843 	const struct inet_connection_sock *icsk = inet_csk(sk);
844 
845 	if (!tp->packets_out && !icsk->icsk_pending)
846 		inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
847 					  icsk->icsk_rto, TCP_RTO_MAX);
848 }
849 
850 static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
851 {
852 	tp->snd_wl1 = seq;
853 }
854 
855 static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq)
856 {
857 	tp->snd_wl1 = seq;
858 }
859 
860 /*
861  * Calculate(/check) TCP checksum
862  */
863 static inline __sum16 tcp_v4_check(int len, __be32 saddr,
864 				   __be32 daddr, __wsum base)
865 {
866 	return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base);
867 }
868 
869 static inline __sum16 __tcp_checksum_complete(struct sk_buff *skb)
870 {
871 	return __skb_checksum_complete(skb);
872 }
873 
874 static inline int tcp_checksum_complete(struct sk_buff *skb)
875 {
876 	return !skb_csum_unnecessary(skb) &&
877 		__tcp_checksum_complete(skb);
878 }
879 
880 /* Prequeue for VJ style copy to user, combined with checksumming. */
881 
882 static inline void tcp_prequeue_init(struct tcp_sock *tp)
883 {
884 	tp->ucopy.task = NULL;
885 	tp->ucopy.len = 0;
886 	tp->ucopy.memory = 0;
887 	skb_queue_head_init(&tp->ucopy.prequeue);
888 #ifdef CONFIG_NET_DMA
889 	tp->ucopy.dma_chan = NULL;
890 	tp->ucopy.wakeup = 0;
891 	tp->ucopy.pinned_list = NULL;
892 	tp->ucopy.dma_cookie = 0;
893 #endif
894 }
895 
896 /* Packet is added to VJ-style prequeue for processing in process
897  * context, if a reader task is waiting. Apparently, this exciting
898  * idea (VJ's mail "Re: query about TCP header on tcp-ip" of 07 Sep 93)
899  * failed somewhere. Latency? Burstiness? Well, at least now we will
900  * see, why it failed. 8)8)				  --ANK
901  *
902  * NOTE: is this not too big to inline?
903  */
904 static inline int tcp_prequeue(struct sock *sk, struct sk_buff *skb)
905 {
906 	struct tcp_sock *tp = tcp_sk(sk);
907 
908 	if (sysctl_tcp_low_latency || !tp->ucopy.task)
909 		return 0;
910 
911 	__skb_queue_tail(&tp->ucopy.prequeue, skb);
912 	tp->ucopy.memory += skb->truesize;
913 	if (tp->ucopy.memory > sk->sk_rcvbuf) {
914 		struct sk_buff *skb1;
915 
916 		BUG_ON(sock_owned_by_user(sk));
917 
918 		while ((skb1 = __skb_dequeue(&tp->ucopy.prequeue)) != NULL) {
919 			sk_backlog_rcv(sk, skb1);
920 			NET_INC_STATS_BH(sock_net(sk),
921 					 LINUX_MIB_TCPPREQUEUEDROPPED);
922 		}
923 
924 		tp->ucopy.memory = 0;
925 	} else if (skb_queue_len(&tp->ucopy.prequeue) == 1) {
926 		wake_up_interruptible_sync_poll(sk_sleep(sk),
927 					   POLLIN | POLLRDNORM | POLLRDBAND);
928 		if (!inet_csk_ack_scheduled(sk))
929 			inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
930 						  (3 * tcp_rto_min(sk)) / 4,
931 						  TCP_RTO_MAX);
932 	}
933 	return 1;
934 }
935 
936 
937 #undef STATE_TRACE
938 
939 #ifdef STATE_TRACE
940 static const char *statename[]={
941 	"Unused","Established","Syn Sent","Syn Recv",
942 	"Fin Wait 1","Fin Wait 2","Time Wait", "Close",
943 	"Close Wait","Last ACK","Listen","Closing"
944 };
945 #endif
946 extern void tcp_set_state(struct sock *sk, int state);
947 
948 extern void tcp_done(struct sock *sk);
949 
950 static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
951 {
952 	rx_opt->dsack = 0;
953 	rx_opt->num_sacks = 0;
954 }
955 
956 /* Determine a window scaling and initial window to offer. */
957 extern void tcp_select_initial_window(int __space, __u32 mss,
958 				      __u32 *rcv_wnd, __u32 *window_clamp,
959 				      int wscale_ok, __u8 *rcv_wscale,
960 				      __u32 init_rcv_wnd);
961 
962 static inline int tcp_win_from_space(int space)
963 {
964 	return sysctl_tcp_adv_win_scale<=0 ?
965 		(space>>(-sysctl_tcp_adv_win_scale)) :
966 		space - (space>>sysctl_tcp_adv_win_scale);
967 }
968 
969 /* Note: caller must be prepared to deal with negative returns */
970 static inline int tcp_space(const struct sock *sk)
971 {
972 	return tcp_win_from_space(sk->sk_rcvbuf -
973 				  atomic_read(&sk->sk_rmem_alloc));
974 }
975 
976 static inline int tcp_full_space(const struct sock *sk)
977 {
978 	return tcp_win_from_space(sk->sk_rcvbuf);
979 }
980 
981 static inline void tcp_openreq_init(struct request_sock *req,
982 				    struct tcp_options_received *rx_opt,
983 				    struct sk_buff *skb)
984 {
985 	struct inet_request_sock *ireq = inet_rsk(req);
986 
987 	req->rcv_wnd = 0;		/* So that tcp_send_synack() knows! */
988 	req->cookie_ts = 0;
989 	tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq;
990 	req->mss = rx_opt->mss_clamp;
991 	req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0;
992 	ireq->tstamp_ok = rx_opt->tstamp_ok;
993 	ireq->sack_ok = rx_opt->sack_ok;
994 	ireq->snd_wscale = rx_opt->snd_wscale;
995 	ireq->wscale_ok = rx_opt->wscale_ok;
996 	ireq->acked = 0;
997 	ireq->ecn_ok = 0;
998 	ireq->rmt_port = tcp_hdr(skb)->source;
999 	ireq->loc_port = tcp_hdr(skb)->dest;
1000 }
1001 
1002 extern void tcp_enter_memory_pressure(struct sock *sk);
1003 
1004 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
1005 {
1006 	return tp->keepalive_intvl ? : sysctl_tcp_keepalive_intvl;
1007 }
1008 
1009 static inline int keepalive_time_when(const struct tcp_sock *tp)
1010 {
1011 	return tp->keepalive_time ? : sysctl_tcp_keepalive_time;
1012 }
1013 
1014 static inline int keepalive_probes(const struct tcp_sock *tp)
1015 {
1016 	return tp->keepalive_probes ? : sysctl_tcp_keepalive_probes;
1017 }
1018 
1019 static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
1020 {
1021 	const struct inet_connection_sock *icsk = &tp->inet_conn;
1022 
1023 	return min_t(u32, tcp_time_stamp - icsk->icsk_ack.lrcvtime,
1024 			  tcp_time_stamp - tp->rcv_tstamp);
1025 }
1026 
1027 static inline int tcp_fin_time(const struct sock *sk)
1028 {
1029 	int fin_timeout = tcp_sk(sk)->linger2 ? : sysctl_tcp_fin_timeout;
1030 	const int rto = inet_csk(sk)->icsk_rto;
1031 
1032 	if (fin_timeout < (rto << 2) - (rto >> 1))
1033 		fin_timeout = (rto << 2) - (rto >> 1);
1034 
1035 	return fin_timeout;
1036 }
1037 
1038 static inline int tcp_paws_check(const struct tcp_options_received *rx_opt,
1039 				 int paws_win)
1040 {
1041 	if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
1042 		return 1;
1043 	if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
1044 		return 1;
1045 	/*
1046 	 * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
1047 	 * then following tcp messages have valid values. Ignore 0 value,
1048 	 * or else 'negative' tsval might forbid us to accept their packets.
1049 	 */
1050 	if (!rx_opt->ts_recent)
1051 		return 1;
1052 	return 0;
1053 }
1054 
1055 static inline int tcp_paws_reject(const struct tcp_options_received *rx_opt,
1056 				  int rst)
1057 {
1058 	if (tcp_paws_check(rx_opt, 0))
1059 		return 0;
1060 
1061 	/* RST segments are not recommended to carry timestamp,
1062 	   and, if they do, it is recommended to ignore PAWS because
1063 	   "their cleanup function should take precedence over timestamps."
1064 	   Certainly, it is mistake. It is necessary to understand the reasons
1065 	   of this constraint to relax it: if peer reboots, clock may go
1066 	   out-of-sync and half-open connections will not be reset.
1067 	   Actually, the problem would be not existing if all
1068 	   the implementations followed draft about maintaining clock
1069 	   via reboots. Linux-2.2 DOES NOT!
1070 
1071 	   However, we can relax time bounds for RST segments to MSL.
1072 	 */
1073 	if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
1074 		return 0;
1075 	return 1;
1076 }
1077 
1078 static inline void tcp_mib_init(struct net *net)
1079 {
1080 	/* See RFC 2012 */
1081 	TCP_ADD_STATS_USER(net, TCP_MIB_RTOALGORITHM, 1);
1082 	TCP_ADD_STATS_USER(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
1083 	TCP_ADD_STATS_USER(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
1084 	TCP_ADD_STATS_USER(net, TCP_MIB_MAXCONN, -1);
1085 }
1086 
1087 /* from STCP */
1088 static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
1089 {
1090 	tp->lost_skb_hint = NULL;
1091 	tp->scoreboard_skb_hint = NULL;
1092 }
1093 
1094 static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
1095 {
1096 	tcp_clear_retrans_hints_partial(tp);
1097 	tp->retransmit_skb_hint = NULL;
1098 }
1099 
1100 /* MD5 Signature */
1101 struct crypto_hash;
1102 
1103 /* - key database */
1104 struct tcp_md5sig_key {
1105 	u8			*key;
1106 	u8			keylen;
1107 };
1108 
1109 struct tcp4_md5sig_key {
1110 	struct tcp_md5sig_key	base;
1111 	__be32			addr;
1112 };
1113 
1114 struct tcp6_md5sig_key {
1115 	struct tcp_md5sig_key	base;
1116 #if 0
1117 	u32			scope_id;	/* XXX */
1118 #endif
1119 	struct in6_addr		addr;
1120 };
1121 
1122 /* - sock block */
1123 struct tcp_md5sig_info {
1124 	struct tcp4_md5sig_key	*keys4;
1125 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
1126 	struct tcp6_md5sig_key	*keys6;
1127 	u32			entries6;
1128 	u32			alloced6;
1129 #endif
1130 	u32			entries4;
1131 	u32			alloced4;
1132 };
1133 
1134 /* - pseudo header */
1135 struct tcp4_pseudohdr {
1136 	__be32		saddr;
1137 	__be32		daddr;
1138 	__u8		pad;
1139 	__u8		protocol;
1140 	__be16		len;
1141 };
1142 
1143 struct tcp6_pseudohdr {
1144 	struct in6_addr	saddr;
1145 	struct in6_addr daddr;
1146 	__be32		len;
1147 	__be32		protocol;	/* including padding */
1148 };
1149 
1150 union tcp_md5sum_block {
1151 	struct tcp4_pseudohdr ip4;
1152 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
1153 	struct tcp6_pseudohdr ip6;
1154 #endif
1155 };
1156 
1157 /* - pool: digest algorithm, hash description and scratch buffer */
1158 struct tcp_md5sig_pool {
1159 	struct hash_desc	md5_desc;
1160 	union tcp_md5sum_block	md5_blk;
1161 };
1162 
1163 /* - functions */
1164 extern int tcp_v4_md5_hash_skb(char *md5_hash, struct tcp_md5sig_key *key,
1165 			       struct sock *sk, struct request_sock *req,
1166 			       struct sk_buff *skb);
1167 extern struct tcp_md5sig_key * tcp_v4_md5_lookup(struct sock *sk,
1168 						 struct sock *addr_sk);
1169 extern int tcp_v4_md5_do_add(struct sock *sk, __be32 addr, u8 *newkey,
1170 			     u8 newkeylen);
1171 extern int tcp_v4_md5_do_del(struct sock *sk, __be32 addr);
1172 
1173 #ifdef CONFIG_TCP_MD5SIG
1174 #define tcp_twsk_md5_key(twsk)	((twsk)->tw_md5_keylen ? 		 \
1175 				 &(struct tcp_md5sig_key) {		 \
1176 					.key = (twsk)->tw_md5_key,	 \
1177 					.keylen = (twsk)->tw_md5_keylen, \
1178 				} : NULL)
1179 #else
1180 #define tcp_twsk_md5_key(twsk)	NULL
1181 #endif
1182 
1183 extern struct tcp_md5sig_pool * __percpu *tcp_alloc_md5sig_pool(struct sock *);
1184 extern void tcp_free_md5sig_pool(void);
1185 
1186 extern struct tcp_md5sig_pool	*tcp_get_md5sig_pool(void);
1187 extern void tcp_put_md5sig_pool(void);
1188 
1189 extern int tcp_md5_hash_header(struct tcp_md5sig_pool *, struct tcphdr *);
1190 extern int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, struct sk_buff *,
1191 				 unsigned header_len);
1192 extern int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
1193 			    struct tcp_md5sig_key *key);
1194 
1195 /* write queue abstraction */
1196 static inline void tcp_write_queue_purge(struct sock *sk)
1197 {
1198 	struct sk_buff *skb;
1199 
1200 	while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL)
1201 		sk_wmem_free_skb(sk, skb);
1202 	sk_mem_reclaim(sk);
1203 	tcp_clear_all_retrans_hints(tcp_sk(sk));
1204 }
1205 
1206 static inline struct sk_buff *tcp_write_queue_head(struct sock *sk)
1207 {
1208 	return skb_peek(&sk->sk_write_queue);
1209 }
1210 
1211 static inline struct sk_buff *tcp_write_queue_tail(struct sock *sk)
1212 {
1213 	return skb_peek_tail(&sk->sk_write_queue);
1214 }
1215 
1216 static inline struct sk_buff *tcp_write_queue_next(struct sock *sk, struct sk_buff *skb)
1217 {
1218 	return skb_queue_next(&sk->sk_write_queue, skb);
1219 }
1220 
1221 static inline struct sk_buff *tcp_write_queue_prev(struct sock *sk, struct sk_buff *skb)
1222 {
1223 	return skb_queue_prev(&sk->sk_write_queue, skb);
1224 }
1225 
1226 #define tcp_for_write_queue(skb, sk)					\
1227 	skb_queue_walk(&(sk)->sk_write_queue, skb)
1228 
1229 #define tcp_for_write_queue_from(skb, sk)				\
1230 	skb_queue_walk_from(&(sk)->sk_write_queue, skb)
1231 
1232 #define tcp_for_write_queue_from_safe(skb, tmp, sk)			\
1233 	skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
1234 
1235 static inline struct sk_buff *tcp_send_head(struct sock *sk)
1236 {
1237 	return sk->sk_send_head;
1238 }
1239 
1240 static inline bool tcp_skb_is_last(const struct sock *sk,
1241 				   const struct sk_buff *skb)
1242 {
1243 	return skb_queue_is_last(&sk->sk_write_queue, skb);
1244 }
1245 
1246 static inline void tcp_advance_send_head(struct sock *sk, struct sk_buff *skb)
1247 {
1248 	if (tcp_skb_is_last(sk, skb))
1249 		sk->sk_send_head = NULL;
1250 	else
1251 		sk->sk_send_head = tcp_write_queue_next(sk, skb);
1252 }
1253 
1254 static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
1255 {
1256 	if (sk->sk_send_head == skb_unlinked)
1257 		sk->sk_send_head = NULL;
1258 }
1259 
1260 static inline void tcp_init_send_head(struct sock *sk)
1261 {
1262 	sk->sk_send_head = NULL;
1263 }
1264 
1265 static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1266 {
1267 	__skb_queue_tail(&sk->sk_write_queue, skb);
1268 }
1269 
1270 static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1271 {
1272 	__tcp_add_write_queue_tail(sk, skb);
1273 
1274 	/* Queue it, remembering where we must start sending. */
1275 	if (sk->sk_send_head == NULL) {
1276 		sk->sk_send_head = skb;
1277 
1278 		if (tcp_sk(sk)->highest_sack == NULL)
1279 			tcp_sk(sk)->highest_sack = skb;
1280 	}
1281 }
1282 
1283 static inline void __tcp_add_write_queue_head(struct sock *sk, struct sk_buff *skb)
1284 {
1285 	__skb_queue_head(&sk->sk_write_queue, skb);
1286 }
1287 
1288 /* Insert buff after skb on the write queue of sk.  */
1289 static inline void tcp_insert_write_queue_after(struct sk_buff *skb,
1290 						struct sk_buff *buff,
1291 						struct sock *sk)
1292 {
1293 	__skb_queue_after(&sk->sk_write_queue, skb, buff);
1294 }
1295 
1296 /* Insert new before skb on the write queue of sk.  */
1297 static inline void tcp_insert_write_queue_before(struct sk_buff *new,
1298 						  struct sk_buff *skb,
1299 						  struct sock *sk)
1300 {
1301 	__skb_queue_before(&sk->sk_write_queue, skb, new);
1302 
1303 	if (sk->sk_send_head == skb)
1304 		sk->sk_send_head = new;
1305 }
1306 
1307 static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
1308 {
1309 	__skb_unlink(skb, &sk->sk_write_queue);
1310 }
1311 
1312 static inline int tcp_write_queue_empty(struct sock *sk)
1313 {
1314 	return skb_queue_empty(&sk->sk_write_queue);
1315 }
1316 
1317 static inline void tcp_push_pending_frames(struct sock *sk)
1318 {
1319 	if (tcp_send_head(sk)) {
1320 		struct tcp_sock *tp = tcp_sk(sk);
1321 
1322 		__tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
1323 	}
1324 }
1325 
1326 /* Start sequence of the highest skb with SACKed bit, valid only if
1327  * sacked > 0 or when the caller has ensured validity by itself.
1328  */
1329 static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
1330 {
1331 	if (!tp->sacked_out)
1332 		return tp->snd_una;
1333 
1334 	if (tp->highest_sack == NULL)
1335 		return tp->snd_nxt;
1336 
1337 	return TCP_SKB_CB(tp->highest_sack)->seq;
1338 }
1339 
1340 static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
1341 {
1342 	tcp_sk(sk)->highest_sack = tcp_skb_is_last(sk, skb) ? NULL :
1343 						tcp_write_queue_next(sk, skb);
1344 }
1345 
1346 static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
1347 {
1348 	return tcp_sk(sk)->highest_sack;
1349 }
1350 
1351 static inline void tcp_highest_sack_reset(struct sock *sk)
1352 {
1353 	tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk);
1354 }
1355 
1356 /* Called when old skb is about to be deleted (to be combined with new skb) */
1357 static inline void tcp_highest_sack_combine(struct sock *sk,
1358 					    struct sk_buff *old,
1359 					    struct sk_buff *new)
1360 {
1361 	if (tcp_sk(sk)->sacked_out && (old == tcp_sk(sk)->highest_sack))
1362 		tcp_sk(sk)->highest_sack = new;
1363 }
1364 
1365 /* Determines whether this is a thin stream (which may suffer from
1366  * increased latency). Used to trigger latency-reducing mechanisms.
1367  */
1368 static inline unsigned int tcp_stream_is_thin(struct tcp_sock *tp)
1369 {
1370 	return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
1371 }
1372 
1373 /* /proc */
1374 enum tcp_seq_states {
1375 	TCP_SEQ_STATE_LISTENING,
1376 	TCP_SEQ_STATE_OPENREQ,
1377 	TCP_SEQ_STATE_ESTABLISHED,
1378 	TCP_SEQ_STATE_TIME_WAIT,
1379 };
1380 
1381 struct tcp_seq_afinfo {
1382 	char			*name;
1383 	sa_family_t		family;
1384 	struct file_operations	seq_fops;
1385 	struct seq_operations	seq_ops;
1386 };
1387 
1388 struct tcp_iter_state {
1389 	struct seq_net_private	p;
1390 	sa_family_t		family;
1391 	enum tcp_seq_states	state;
1392 	struct sock		*syn_wait_sk;
1393 	int			bucket, offset, sbucket, num, uid;
1394 	loff_t			last_pos;
1395 };
1396 
1397 extern int tcp_proc_register(struct net *net, struct tcp_seq_afinfo *afinfo);
1398 extern void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo);
1399 
1400 extern struct request_sock_ops tcp_request_sock_ops;
1401 extern struct request_sock_ops tcp6_request_sock_ops;
1402 
1403 extern void tcp_v4_destroy_sock(struct sock *sk);
1404 
1405 extern int tcp_v4_gso_send_check(struct sk_buff *skb);
1406 extern struct sk_buff *tcp_tso_segment(struct sk_buff *skb, u32 features);
1407 extern struct sk_buff **tcp_gro_receive(struct sk_buff **head,
1408 					struct sk_buff *skb);
1409 extern struct sk_buff **tcp4_gro_receive(struct sk_buff **head,
1410 					 struct sk_buff *skb);
1411 extern int tcp_gro_complete(struct sk_buff *skb);
1412 extern int tcp4_gro_complete(struct sk_buff *skb);
1413 
1414 #ifdef CONFIG_PROC_FS
1415 extern int tcp4_proc_init(void);
1416 extern void tcp4_proc_exit(void);
1417 #endif
1418 
1419 /* TCP af-specific functions */
1420 struct tcp_sock_af_ops {
1421 #ifdef CONFIG_TCP_MD5SIG
1422 	struct tcp_md5sig_key	*(*md5_lookup) (struct sock *sk,
1423 						struct sock *addr_sk);
1424 	int			(*calc_md5_hash) (char *location,
1425 						  struct tcp_md5sig_key *md5,
1426 						  struct sock *sk,
1427 						  struct request_sock *req,
1428 						  struct sk_buff *skb);
1429 	int			(*md5_add) (struct sock *sk,
1430 					    struct sock *addr_sk,
1431 					    u8 *newkey,
1432 					    u8 len);
1433 	int			(*md5_parse) (struct sock *sk,
1434 					      char __user *optval,
1435 					      int optlen);
1436 #endif
1437 };
1438 
1439 struct tcp_request_sock_ops {
1440 #ifdef CONFIG_TCP_MD5SIG
1441 	struct tcp_md5sig_key	*(*md5_lookup) (struct sock *sk,
1442 						struct request_sock *req);
1443 	int			(*calc_md5_hash) (char *location,
1444 						  struct tcp_md5sig_key *md5,
1445 						  struct sock *sk,
1446 						  struct request_sock *req,
1447 						  struct sk_buff *skb);
1448 #endif
1449 };
1450 
1451 /* Using SHA1 for now, define some constants.
1452  */
1453 #define COOKIE_DIGEST_WORDS (SHA_DIGEST_WORDS)
1454 #define COOKIE_MESSAGE_WORDS (SHA_MESSAGE_BYTES / 4)
1455 #define COOKIE_WORKSPACE_WORDS (COOKIE_DIGEST_WORDS + COOKIE_MESSAGE_WORDS)
1456 
1457 extern int tcp_cookie_generator(u32 *bakery);
1458 
1459 /**
1460  *	struct tcp_cookie_values - each socket needs extra space for the
1461  *	cookies, together with (optional) space for any SYN data.
1462  *
1463  *	A tcp_sock contains a pointer to the current value, and this is
1464  *	cloned to the tcp_timewait_sock.
1465  *
1466  * @cookie_pair:	variable data from the option exchange.
1467  *
1468  * @cookie_desired:	user specified tcpct_cookie_desired.  Zero
1469  *			indicates default (sysctl_tcp_cookie_size).
1470  *			After cookie sent, remembers size of cookie.
1471  *			Range 0, TCP_COOKIE_MIN to TCP_COOKIE_MAX.
1472  *
1473  * @s_data_desired:	user specified tcpct_s_data_desired.  When the
1474  *			constant payload is specified (@s_data_constant),
1475  *			holds its length instead.
1476  *			Range 0 to TCP_MSS_DESIRED.
1477  *
1478  * @s_data_payload:	constant data that is to be included in the
1479  *			payload of SYN or SYNACK segments when the
1480  *			cookie option is present.
1481  */
1482 struct tcp_cookie_values {
1483 	struct kref	kref;
1484 	u8		cookie_pair[TCP_COOKIE_PAIR_SIZE];
1485 	u8		cookie_pair_size;
1486 	u8		cookie_desired;
1487 	u16		s_data_desired:11,
1488 			s_data_constant:1,
1489 			s_data_in:1,
1490 			s_data_out:1,
1491 			s_data_unused:2;
1492 	u8		s_data_payload[0];
1493 };
1494 
1495 static inline void tcp_cookie_values_release(struct kref *kref)
1496 {
1497 	kfree(container_of(kref, struct tcp_cookie_values, kref));
1498 }
1499 
1500 /* The length of constant payload data.  Note that s_data_desired is
1501  * overloaded, depending on s_data_constant: either the length of constant
1502  * data (returned here) or the limit on variable data.
1503  */
1504 static inline int tcp_s_data_size(const struct tcp_sock *tp)
1505 {
1506 	return (tp->cookie_values != NULL && tp->cookie_values->s_data_constant)
1507 		? tp->cookie_values->s_data_desired
1508 		: 0;
1509 }
1510 
1511 /**
1512  *	struct tcp_extend_values - tcp_ipv?.c to tcp_output.c workspace.
1513  *
1514  *	As tcp_request_sock has already been extended in other places, the
1515  *	only remaining method is to pass stack values along as function
1516  *	parameters.  These parameters are not needed after sending SYNACK.
1517  *
1518  * @cookie_bakery:	cryptographic secret and message workspace.
1519  *
1520  * @cookie_plus:	bytes in authenticator/cookie option, copied from
1521  *			struct tcp_options_received (above).
1522  */
1523 struct tcp_extend_values {
1524 	struct request_values		rv;
1525 	u32				cookie_bakery[COOKIE_WORKSPACE_WORDS];
1526 	u8				cookie_plus:6,
1527 					cookie_out_never:1,
1528 					cookie_in_always:1;
1529 };
1530 
1531 static inline struct tcp_extend_values *tcp_xv(struct request_values *rvp)
1532 {
1533 	return (struct tcp_extend_values *)rvp;
1534 }
1535 
1536 extern void tcp_v4_init(void);
1537 extern void tcp_init(void);
1538 
1539 #endif	/* _TCP_H */
1540