xref: /openbmc/linux/include/net/tcp.h (revision e868d61272caa648214046a096e5a6bfc068dc8c)
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 
33 #include <net/inet_connection_sock.h>
34 #include <net/inet_timewait_sock.h>
35 #include <net/inet_hashtables.h>
36 #include <net/checksum.h>
37 #include <net/request_sock.h>
38 #include <net/sock.h>
39 #include <net/snmp.h>
40 #include <net/ip.h>
41 #include <net/tcp_states.h>
42 
43 #include <linux/seq_file.h>
44 
45 extern struct inet_hashinfo tcp_hashinfo;
46 
47 extern atomic_t tcp_orphan_count;
48 extern void tcp_time_wait(struct sock *sk, int state, int timeo);
49 
50 #define MAX_TCP_HEADER	(128 + MAX_HEADER)
51 
52 /*
53  * Never offer a window over 32767 without using window scaling. Some
54  * poor stacks do signed 16bit maths!
55  */
56 #define MAX_TCP_WINDOW		32767U
57 
58 /* Minimal accepted MSS. It is (60+60+8) - (20+20). */
59 #define TCP_MIN_MSS		88U
60 
61 /* Minimal RCV_MSS. */
62 #define TCP_MIN_RCVMSS		536U
63 
64 /* The least MTU to use for probing */
65 #define TCP_BASE_MSS		512
66 
67 /* After receiving this amount of duplicate ACKs fast retransmit starts. */
68 #define TCP_FASTRETRANS_THRESH 3
69 
70 /* Maximal reordering. */
71 #define TCP_MAX_REORDERING	127
72 
73 /* Maximal number of ACKs sent quickly to accelerate slow-start. */
74 #define TCP_MAX_QUICKACKS	16U
75 
76 /* urg_data states */
77 #define TCP_URG_VALID	0x0100
78 #define TCP_URG_NOTYET	0x0200
79 #define TCP_URG_READ	0x0400
80 
81 #define TCP_RETR1	3	/*
82 				 * This is how many retries it does before it
83 				 * tries to figure out if the gateway is
84 				 * down. Minimal RFC value is 3; it corresponds
85 				 * to ~3sec-8min depending on RTO.
86 				 */
87 
88 #define TCP_RETR2	15	/*
89 				 * This should take at least
90 				 * 90 minutes to time out.
91 				 * RFC1122 says that the limit is 100 sec.
92 				 * 15 is ~13-30min depending on RTO.
93 				 */
94 
95 #define TCP_SYN_RETRIES	 5	/* number of times to retry active opening a
96 				 * connection: ~180sec is RFC minimum	*/
97 
98 #define TCP_SYNACK_RETRIES 5	/* number of times to retry passive opening a
99 				 * connection: ~180sec is RFC minimum	*/
100 
101 
102 #define TCP_ORPHAN_RETRIES 7	/* number of times to retry on an orphaned
103 				 * socket. 7 is ~50sec-16min.
104 				 */
105 
106 
107 #define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT
108 				  * state, about 60 seconds	*/
109 #define TCP_FIN_TIMEOUT	TCP_TIMEWAIT_LEN
110                                  /* BSD style FIN_WAIT2 deadlock breaker.
111 				  * It used to be 3min, new value is 60sec,
112 				  * to combine FIN-WAIT-2 timeout with
113 				  * TIME-WAIT timer.
114 				  */
115 
116 #define TCP_DELACK_MAX	((unsigned)(HZ/5))	/* maximal time to delay before sending an ACK */
117 #if HZ >= 100
118 #define TCP_DELACK_MIN	((unsigned)(HZ/25))	/* minimal time to delay before sending an ACK */
119 #define TCP_ATO_MIN	((unsigned)(HZ/25))
120 #else
121 #define TCP_DELACK_MIN	4U
122 #define TCP_ATO_MIN	4U
123 #endif
124 #define TCP_RTO_MAX	((unsigned)(120*HZ))
125 #define TCP_RTO_MIN	((unsigned)(HZ/5))
126 #define TCP_TIMEOUT_INIT ((unsigned)(3*HZ))	/* RFC 1122 initial RTO value	*/
127 
128 #define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes
129 					                 * for local resources.
130 					                 */
131 
132 #define TCP_KEEPALIVE_TIME	(120*60*HZ)	/* two hours */
133 #define TCP_KEEPALIVE_PROBES	9		/* Max of 9 keepalive probes	*/
134 #define TCP_KEEPALIVE_INTVL	(75*HZ)
135 
136 #define MAX_TCP_KEEPIDLE	32767
137 #define MAX_TCP_KEEPINTVL	32767
138 #define MAX_TCP_KEEPCNT		127
139 #define MAX_TCP_SYNCNT		127
140 
141 #define TCP_SYNQ_INTERVAL	(HZ/5)	/* Period of SYNACK timer */
142 
143 #define TCP_PAWS_24DAYS	(60 * 60 * 24 * 24)
144 #define TCP_PAWS_MSL	60		/* Per-host timestamps are invalidated
145 					 * after this time. It should be equal
146 					 * (or greater than) TCP_TIMEWAIT_LEN
147 					 * to provide reliability equal to one
148 					 * provided by timewait state.
149 					 */
150 #define TCP_PAWS_WINDOW	1		/* Replay window for per-host
151 					 * timestamps. It must be less than
152 					 * minimal timewait lifetime.
153 					 */
154 /*
155  *	TCP option
156  */
157 
158 #define TCPOPT_NOP		1	/* Padding */
159 #define TCPOPT_EOL		0	/* End of options */
160 #define TCPOPT_MSS		2	/* Segment size negotiating */
161 #define TCPOPT_WINDOW		3	/* Window scaling */
162 #define TCPOPT_SACK_PERM        4       /* SACK Permitted */
163 #define TCPOPT_SACK             5       /* SACK Block */
164 #define TCPOPT_TIMESTAMP	8	/* Better RTT estimations/PAWS */
165 #define TCPOPT_MD5SIG		19	/* MD5 Signature (RFC2385) */
166 
167 /*
168  *     TCP option lengths
169  */
170 
171 #define TCPOLEN_MSS            4
172 #define TCPOLEN_WINDOW         3
173 #define TCPOLEN_SACK_PERM      2
174 #define TCPOLEN_TIMESTAMP      10
175 #define TCPOLEN_MD5SIG         18
176 
177 /* But this is what stacks really send out. */
178 #define TCPOLEN_TSTAMP_ALIGNED		12
179 #define TCPOLEN_WSCALE_ALIGNED		4
180 #define TCPOLEN_SACKPERM_ALIGNED	4
181 #define TCPOLEN_SACK_BASE		2
182 #define TCPOLEN_SACK_BASE_ALIGNED	4
183 #define TCPOLEN_SACK_PERBLOCK		8
184 #define TCPOLEN_MD5SIG_ALIGNED		20
185 
186 /* Flags in tp->nonagle */
187 #define TCP_NAGLE_OFF		1	/* Nagle's algo is disabled */
188 #define TCP_NAGLE_CORK		2	/* Socket is corked	    */
189 #define TCP_NAGLE_PUSH		4	/* Cork is overridden for already queued data */
190 
191 extern struct inet_timewait_death_row tcp_death_row;
192 
193 /* sysctl variables for tcp */
194 extern int sysctl_tcp_timestamps;
195 extern int sysctl_tcp_window_scaling;
196 extern int sysctl_tcp_sack;
197 extern int sysctl_tcp_fin_timeout;
198 extern int sysctl_tcp_keepalive_time;
199 extern int sysctl_tcp_keepalive_probes;
200 extern int sysctl_tcp_keepalive_intvl;
201 extern int sysctl_tcp_syn_retries;
202 extern int sysctl_tcp_synack_retries;
203 extern int sysctl_tcp_retries1;
204 extern int sysctl_tcp_retries2;
205 extern int sysctl_tcp_orphan_retries;
206 extern int sysctl_tcp_syncookies;
207 extern int sysctl_tcp_retrans_collapse;
208 extern int sysctl_tcp_stdurg;
209 extern int sysctl_tcp_rfc1337;
210 extern int sysctl_tcp_abort_on_overflow;
211 extern int sysctl_tcp_max_orphans;
212 extern int sysctl_tcp_fack;
213 extern int sysctl_tcp_reordering;
214 extern int sysctl_tcp_ecn;
215 extern int sysctl_tcp_dsack;
216 extern int sysctl_tcp_mem[3];
217 extern int sysctl_tcp_wmem[3];
218 extern int sysctl_tcp_rmem[3];
219 extern int sysctl_tcp_app_win;
220 extern int sysctl_tcp_adv_win_scale;
221 extern int sysctl_tcp_tw_reuse;
222 extern int sysctl_tcp_frto;
223 extern int sysctl_tcp_frto_response;
224 extern int sysctl_tcp_low_latency;
225 extern int sysctl_tcp_dma_copybreak;
226 extern int sysctl_tcp_nometrics_save;
227 extern int sysctl_tcp_moderate_rcvbuf;
228 extern int sysctl_tcp_tso_win_divisor;
229 extern int sysctl_tcp_abc;
230 extern int sysctl_tcp_mtu_probing;
231 extern int sysctl_tcp_base_mss;
232 extern int sysctl_tcp_workaround_signed_windows;
233 extern int sysctl_tcp_slow_start_after_idle;
234 extern int sysctl_tcp_max_ssthresh;
235 
236 extern atomic_t tcp_memory_allocated;
237 extern atomic_t tcp_sockets_allocated;
238 extern int tcp_memory_pressure;
239 
240 /*
241  * The next routines deal with comparing 32 bit unsigned ints
242  * and worry about wraparound (automatic with unsigned arithmetic).
243  */
244 
245 static inline int before(__u32 seq1, __u32 seq2)
246 {
247         return (__s32)(seq1-seq2) < 0;
248 }
249 #define after(seq2, seq1) 	before(seq1, seq2)
250 
251 /* is s2<=s1<=s3 ? */
252 static inline int between(__u32 seq1, __u32 seq2, __u32 seq3)
253 {
254 	return seq3 - seq2 >= seq1 - seq2;
255 }
256 
257 
258 extern struct proto tcp_prot;
259 
260 DECLARE_SNMP_STAT(struct tcp_mib, tcp_statistics);
261 #define TCP_INC_STATS(field)		SNMP_INC_STATS(tcp_statistics, field)
262 #define TCP_INC_STATS_BH(field)		SNMP_INC_STATS_BH(tcp_statistics, field)
263 #define TCP_INC_STATS_USER(field) 	SNMP_INC_STATS_USER(tcp_statistics, field)
264 #define TCP_DEC_STATS(field)		SNMP_DEC_STATS(tcp_statistics, field)
265 #define TCP_ADD_STATS_BH(field, val)	SNMP_ADD_STATS_BH(tcp_statistics, field, val)
266 #define TCP_ADD_STATS_USER(field, val)	SNMP_ADD_STATS_USER(tcp_statistics, field, val)
267 
268 extern void			tcp_v4_err(struct sk_buff *skb, u32);
269 
270 extern void			tcp_shutdown (struct sock *sk, int how);
271 
272 extern int			tcp_v4_rcv(struct sk_buff *skb);
273 
274 extern int			tcp_v4_remember_stamp(struct sock *sk);
275 
276 extern int		    	tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
277 
278 extern int			tcp_sendmsg(struct kiocb *iocb, struct sock *sk,
279 					    struct msghdr *msg, size_t size);
280 extern ssize_t			tcp_sendpage(struct socket *sock, struct page *page, int offset, size_t size, int flags);
281 
282 extern int			tcp_ioctl(struct sock *sk,
283 					  int cmd,
284 					  unsigned long arg);
285 
286 extern int			tcp_rcv_state_process(struct sock *sk,
287 						      struct sk_buff *skb,
288 						      struct tcphdr *th,
289 						      unsigned len);
290 
291 extern int			tcp_rcv_established(struct sock *sk,
292 						    struct sk_buff *skb,
293 						    struct tcphdr *th,
294 						    unsigned len);
295 
296 extern void			tcp_rcv_space_adjust(struct sock *sk);
297 
298 extern void			tcp_cleanup_rbuf(struct sock *sk, int copied);
299 
300 extern int			tcp_twsk_unique(struct sock *sk,
301 						struct sock *sktw, void *twp);
302 
303 extern void			tcp_twsk_destructor(struct sock *sk);
304 
305 static inline void tcp_dec_quickack_mode(struct sock *sk,
306 					 const unsigned int pkts)
307 {
308 	struct inet_connection_sock *icsk = inet_csk(sk);
309 
310 	if (icsk->icsk_ack.quick) {
311 		if (pkts >= icsk->icsk_ack.quick) {
312 			icsk->icsk_ack.quick = 0;
313 			/* Leaving quickack mode we deflate ATO. */
314 			icsk->icsk_ack.ato   = TCP_ATO_MIN;
315 		} else
316 			icsk->icsk_ack.quick -= pkts;
317 	}
318 }
319 
320 extern void tcp_enter_quickack_mode(struct sock *sk);
321 
322 static inline void tcp_clear_options(struct tcp_options_received *rx_opt)
323 {
324  	rx_opt->tstamp_ok = rx_opt->sack_ok = rx_opt->wscale_ok = rx_opt->snd_wscale = 0;
325 }
326 
327 enum tcp_tw_status
328 {
329 	TCP_TW_SUCCESS = 0,
330 	TCP_TW_RST = 1,
331 	TCP_TW_ACK = 2,
332 	TCP_TW_SYN = 3
333 };
334 
335 
336 extern enum tcp_tw_status	tcp_timewait_state_process(struct inet_timewait_sock *tw,
337 							   struct sk_buff *skb,
338 							   const struct tcphdr *th);
339 
340 extern struct sock *		tcp_check_req(struct sock *sk,struct sk_buff *skb,
341 					      struct request_sock *req,
342 					      struct request_sock **prev);
343 extern int			tcp_child_process(struct sock *parent,
344 						  struct sock *child,
345 						  struct sk_buff *skb);
346 extern int			tcp_use_frto(struct sock *sk);
347 extern void			tcp_enter_frto(struct sock *sk);
348 extern void			tcp_enter_loss(struct sock *sk, int how);
349 extern void			tcp_clear_retrans(struct tcp_sock *tp);
350 extern void			tcp_update_metrics(struct sock *sk);
351 
352 extern void			tcp_close(struct sock *sk,
353 					  long timeout);
354 extern unsigned int		tcp_poll(struct file * file, struct socket *sock, struct poll_table_struct *wait);
355 
356 extern int			tcp_getsockopt(struct sock *sk, int level,
357 					       int optname,
358 					       char __user *optval,
359 					       int __user *optlen);
360 extern int			tcp_setsockopt(struct sock *sk, int level,
361 					       int optname, char __user *optval,
362 					       int optlen);
363 extern int			compat_tcp_getsockopt(struct sock *sk,
364 					int level, int optname,
365 					char __user *optval, int __user *optlen);
366 extern int			compat_tcp_setsockopt(struct sock *sk,
367 					int level, int optname,
368 					char __user *optval, int optlen);
369 extern void			tcp_set_keepalive(struct sock *sk, int val);
370 extern int			tcp_recvmsg(struct kiocb *iocb, struct sock *sk,
371 					    struct msghdr *msg,
372 					    size_t len, int nonblock,
373 					    int flags, int *addr_len);
374 
375 extern void			tcp_parse_options(struct sk_buff *skb,
376 						  struct tcp_options_received *opt_rx,
377 						  int estab);
378 
379 /*
380  *	TCP v4 functions exported for the inet6 API
381  */
382 
383 extern void		       	tcp_v4_send_check(struct sock *sk, int len,
384 						  struct sk_buff *skb);
385 
386 extern int			tcp_v4_conn_request(struct sock *sk,
387 						    struct sk_buff *skb);
388 
389 extern struct sock *		tcp_create_openreq_child(struct sock *sk,
390 							 struct request_sock *req,
391 							 struct sk_buff *skb);
392 
393 extern struct sock *		tcp_v4_syn_recv_sock(struct sock *sk,
394 						     struct sk_buff *skb,
395 						     struct request_sock *req,
396 							struct dst_entry *dst);
397 
398 extern int			tcp_v4_do_rcv(struct sock *sk,
399 					      struct sk_buff *skb);
400 
401 extern int			tcp_v4_connect(struct sock *sk,
402 					       struct sockaddr *uaddr,
403 					       int addr_len);
404 
405 extern int			tcp_connect(struct sock *sk);
406 
407 extern struct sk_buff *		tcp_make_synack(struct sock *sk,
408 						struct dst_entry *dst,
409 						struct request_sock *req);
410 
411 extern int			tcp_disconnect(struct sock *sk, int flags);
412 
413 extern void			tcp_unhash(struct sock *sk);
414 
415 /* From syncookies.c */
416 extern struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
417 				    struct ip_options *opt);
418 extern __u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb,
419 				     __u16 *mss);
420 
421 /* tcp_output.c */
422 
423 extern void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
424 				      int nonagle);
425 extern int tcp_may_send_now(struct sock *sk);
426 extern int tcp_retransmit_skb(struct sock *, struct sk_buff *);
427 extern void tcp_xmit_retransmit_queue(struct sock *);
428 extern void tcp_simple_retransmit(struct sock *);
429 extern int tcp_trim_head(struct sock *, struct sk_buff *, u32);
430 extern int tcp_fragment(struct sock *, struct sk_buff *, u32, unsigned int);
431 
432 extern void tcp_send_probe0(struct sock *);
433 extern void tcp_send_partial(struct sock *);
434 extern int  tcp_write_wakeup(struct sock *);
435 extern void tcp_send_fin(struct sock *sk);
436 extern void tcp_send_active_reset(struct sock *sk, gfp_t priority);
437 extern int  tcp_send_synack(struct sock *);
438 extern void tcp_push_one(struct sock *, unsigned int mss_now);
439 extern void tcp_send_ack(struct sock *sk);
440 extern void tcp_send_delayed_ack(struct sock *sk);
441 
442 /* tcp_input.c */
443 extern void tcp_cwnd_application_limited(struct sock *sk);
444 
445 /* tcp_timer.c */
446 extern void tcp_init_xmit_timers(struct sock *);
447 static inline void tcp_clear_xmit_timers(struct sock *sk)
448 {
449 	inet_csk_clear_xmit_timers(sk);
450 }
451 
452 extern unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
453 extern unsigned int tcp_current_mss(struct sock *sk, int large);
454 
455 /* tcp.c */
456 extern void tcp_get_info(struct sock *, struct tcp_info *);
457 
458 /* Read 'sendfile()'-style from a TCP socket */
459 typedef int (*sk_read_actor_t)(read_descriptor_t *, struct sk_buff *,
460 				unsigned int, size_t);
461 extern int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
462 			 sk_read_actor_t recv_actor);
463 
464 extern void tcp_initialize_rcv_mss(struct sock *sk);
465 
466 extern int tcp_mtu_to_mss(struct sock *sk, int pmtu);
467 extern int tcp_mss_to_mtu(struct sock *sk, int mss);
468 extern void tcp_mtup_init(struct sock *sk);
469 
470 static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
471 {
472 	tp->pred_flags = htonl((tp->tcp_header_len << 26) |
473 			       ntohl(TCP_FLAG_ACK) |
474 			       snd_wnd);
475 }
476 
477 static inline void tcp_fast_path_on(struct tcp_sock *tp)
478 {
479 	__tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
480 }
481 
482 static inline void tcp_fast_path_check(struct sock *sk)
483 {
484 	struct tcp_sock *tp = tcp_sk(sk);
485 
486 	if (skb_queue_empty(&tp->out_of_order_queue) &&
487 	    tp->rcv_wnd &&
488 	    atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
489 	    !tp->urg_data)
490 		tcp_fast_path_on(tp);
491 }
492 
493 /* Compute the actual receive window we are currently advertising.
494  * Rcv_nxt can be after the window if our peer push more data
495  * than the offered window.
496  */
497 static inline u32 tcp_receive_window(const struct tcp_sock *tp)
498 {
499 	s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;
500 
501 	if (win < 0)
502 		win = 0;
503 	return (u32) win;
504 }
505 
506 /* Choose a new window, without checks for shrinking, and without
507  * scaling applied to the result.  The caller does these things
508  * if necessary.  This is a "raw" window selection.
509  */
510 extern u32	__tcp_select_window(struct sock *sk);
511 
512 /* TCP timestamps are only 32-bits, this causes a slight
513  * complication on 64-bit systems since we store a snapshot
514  * of jiffies in the buffer control blocks below.  We decided
515  * to use only the low 32-bits of jiffies and hide the ugly
516  * casts with the following macro.
517  */
518 #define tcp_time_stamp		((__u32)(jiffies))
519 
520 /* This is what the send packet queuing engine uses to pass
521  * TCP per-packet control information to the transmission
522  * code.  We also store the host-order sequence numbers in
523  * here too.  This is 36 bytes on 32-bit architectures,
524  * 40 bytes on 64-bit machines, if this grows please adjust
525  * skbuff.h:skbuff->cb[xxx] size appropriately.
526  */
527 struct tcp_skb_cb {
528 	union {
529 		struct inet_skb_parm	h4;
530 #if defined(CONFIG_IPV6) || defined (CONFIG_IPV6_MODULE)
531 		struct inet6_skb_parm	h6;
532 #endif
533 	} header;	/* For incoming frames		*/
534 	__u32		seq;		/* Starting sequence number	*/
535 	__u32		end_seq;	/* SEQ + FIN + SYN + datalen	*/
536 	__u32		when;		/* used to compute rtt's	*/
537 	__u8		flags;		/* TCP header flags.		*/
538 
539 	/* NOTE: These must match up to the flags byte in a
540 	 *       real TCP header.
541 	 */
542 #define TCPCB_FLAG_FIN		0x01
543 #define TCPCB_FLAG_SYN		0x02
544 #define TCPCB_FLAG_RST		0x04
545 #define TCPCB_FLAG_PSH		0x08
546 #define TCPCB_FLAG_ACK		0x10
547 #define TCPCB_FLAG_URG		0x20
548 #define TCPCB_FLAG_ECE		0x40
549 #define TCPCB_FLAG_CWR		0x80
550 
551 	__u8		sacked;		/* State flags for SACK/FACK.	*/
552 #define TCPCB_SACKED_ACKED	0x01	/* SKB ACK'd by a SACK block	*/
553 #define TCPCB_SACKED_RETRANS	0x02	/* SKB retransmitted		*/
554 #define TCPCB_LOST		0x04	/* SKB is lost			*/
555 #define TCPCB_TAGBITS		0x07	/* All tag bits			*/
556 
557 #define TCPCB_EVER_RETRANS	0x80	/* Ever retransmitted frame	*/
558 #define TCPCB_RETRANS		(TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS)
559 
560 #define TCPCB_URG		0x20	/* Urgent pointer advanced here	*/
561 
562 #define TCPCB_AT_TAIL		(TCPCB_URG)
563 
564 	__u16		urg_ptr;	/* Valid w/URG flags is set.	*/
565 	__u32		ack_seq;	/* Sequence number ACK'd	*/
566 };
567 
568 #define TCP_SKB_CB(__skb)	((struct tcp_skb_cb *)&((__skb)->cb[0]))
569 
570 #include <net/tcp_ecn.h>
571 
572 /* Due to TSO, an SKB can be composed of multiple actual
573  * packets.  To keep these tracked properly, we use this.
574  */
575 static inline int tcp_skb_pcount(const struct sk_buff *skb)
576 {
577 	return skb_shinfo(skb)->gso_segs;
578 }
579 
580 /* This is valid iff tcp_skb_pcount() > 1. */
581 static inline int tcp_skb_mss(const struct sk_buff *skb)
582 {
583 	return skb_shinfo(skb)->gso_size;
584 }
585 
586 static inline void tcp_dec_pcount_approx(__u32 *count,
587 					 const struct sk_buff *skb)
588 {
589 	if (*count) {
590 		*count -= tcp_skb_pcount(skb);
591 		if ((int)*count < 0)
592 			*count = 0;
593 	}
594 }
595 
596 static inline void tcp_packets_out_inc(struct sock *sk,
597 				       const struct sk_buff *skb)
598 {
599 	struct tcp_sock *tp = tcp_sk(sk);
600 	int orig = tp->packets_out;
601 
602 	tp->packets_out += tcp_skb_pcount(skb);
603 	if (!orig)
604 		inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
605 					  inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
606 }
607 
608 static inline void tcp_packets_out_dec(struct tcp_sock *tp,
609 				       const struct sk_buff *skb)
610 {
611 	tp->packets_out -= tcp_skb_pcount(skb);
612 }
613 
614 /* Events passed to congestion control interface */
615 enum tcp_ca_event {
616 	CA_EVENT_TX_START,	/* first transmit when no packets in flight */
617 	CA_EVENT_CWND_RESTART,	/* congestion window restart */
618 	CA_EVENT_COMPLETE_CWR,	/* end of congestion recovery */
619 	CA_EVENT_FRTO,		/* fast recovery timeout */
620 	CA_EVENT_LOSS,		/* loss timeout */
621 	CA_EVENT_FAST_ACK,	/* in sequence ack */
622 	CA_EVENT_SLOW_ACK,	/* other ack */
623 };
624 
625 /*
626  * Interface for adding new TCP congestion control handlers
627  */
628 #define TCP_CA_NAME_MAX	16
629 #define TCP_CA_MAX	128
630 #define TCP_CA_BUF_MAX	(TCP_CA_NAME_MAX*TCP_CA_MAX)
631 
632 #define TCP_CONG_NON_RESTRICTED 0x1
633 #define TCP_CONG_RTT_STAMP	0x2
634 
635 struct tcp_congestion_ops {
636 	struct list_head	list;
637 	unsigned long flags;
638 
639 	/* initialize private data (optional) */
640 	void (*init)(struct sock *sk);
641 	/* cleanup private data  (optional) */
642 	void (*release)(struct sock *sk);
643 
644 	/* return slow start threshold (required) */
645 	u32 (*ssthresh)(struct sock *sk);
646 	/* lower bound for congestion window (optional) */
647 	u32 (*min_cwnd)(const struct sock *sk);
648 	/* do new cwnd calculation (required) */
649 	void (*cong_avoid)(struct sock *sk, u32 ack,
650 			   u32 rtt, u32 in_flight, int good_ack);
651 	/* call before changing ca_state (optional) */
652 	void (*set_state)(struct sock *sk, u8 new_state);
653 	/* call when cwnd event occurs (optional) */
654 	void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
655 	/* new value of cwnd after loss (optional) */
656 	u32  (*undo_cwnd)(struct sock *sk);
657 	/* hook for packet ack accounting (optional) */
658 	void (*pkts_acked)(struct sock *sk, u32 num_acked, ktime_t last);
659 	/* get info for inet_diag (optional) */
660 	void (*get_info)(struct sock *sk, u32 ext, struct sk_buff *skb);
661 
662 	char 		name[TCP_CA_NAME_MAX];
663 	struct module 	*owner;
664 };
665 
666 extern int tcp_register_congestion_control(struct tcp_congestion_ops *type);
667 extern void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
668 
669 extern void tcp_init_congestion_control(struct sock *sk);
670 extern void tcp_cleanup_congestion_control(struct sock *sk);
671 extern int tcp_set_default_congestion_control(const char *name);
672 extern void tcp_get_default_congestion_control(char *name);
673 extern void tcp_get_available_congestion_control(char *buf, size_t len);
674 extern void tcp_get_allowed_congestion_control(char *buf, size_t len);
675 extern int tcp_set_allowed_congestion_control(char *allowed);
676 extern int tcp_set_congestion_control(struct sock *sk, const char *name);
677 extern void tcp_slow_start(struct tcp_sock *tp);
678 
679 extern struct tcp_congestion_ops tcp_init_congestion_ops;
680 extern u32 tcp_reno_ssthresh(struct sock *sk);
681 extern void tcp_reno_cong_avoid(struct sock *sk, u32 ack,
682 				u32 rtt, u32 in_flight, int flag);
683 extern u32 tcp_reno_min_cwnd(const struct sock *sk);
684 extern struct tcp_congestion_ops tcp_reno;
685 
686 static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
687 {
688 	struct inet_connection_sock *icsk = inet_csk(sk);
689 
690 	if (icsk->icsk_ca_ops->set_state)
691 		icsk->icsk_ca_ops->set_state(sk, ca_state);
692 	icsk->icsk_ca_state = ca_state;
693 }
694 
695 static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
696 {
697 	const struct inet_connection_sock *icsk = inet_csk(sk);
698 
699 	if (icsk->icsk_ca_ops->cwnd_event)
700 		icsk->icsk_ca_ops->cwnd_event(sk, event);
701 }
702 
703 /* This determines how many packets are "in the network" to the best
704  * of our knowledge.  In many cases it is conservative, but where
705  * detailed information is available from the receiver (via SACK
706  * blocks etc.) we can make more aggressive calculations.
707  *
708  * Use this for decisions involving congestion control, use just
709  * tp->packets_out to determine if the send queue is empty or not.
710  *
711  * Read this equation as:
712  *
713  *	"Packets sent once on transmission queue" MINUS
714  *	"Packets left network, but not honestly ACKed yet" PLUS
715  *	"Packets fast retransmitted"
716  */
717 static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
718 {
719 	return (tp->packets_out - tp->left_out + tp->retrans_out);
720 }
721 
722 /* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
723  * The exception is rate halving phase, when cwnd is decreasing towards
724  * ssthresh.
725  */
726 static inline __u32 tcp_current_ssthresh(const struct sock *sk)
727 {
728 	const struct tcp_sock *tp = tcp_sk(sk);
729 	if ((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_CWR | TCPF_CA_Recovery))
730 		return tp->snd_ssthresh;
731 	else
732 		return max(tp->snd_ssthresh,
733 			   ((tp->snd_cwnd >> 1) +
734 			    (tp->snd_cwnd >> 2)));
735 }
736 
737 static inline void tcp_sync_left_out(struct tcp_sock *tp)
738 {
739 	BUG_ON(tp->rx_opt.sack_ok &&
740 	       (tp->sacked_out + tp->lost_out > tp->packets_out));
741 	tp->left_out = tp->sacked_out + tp->lost_out;
742 }
743 
744 extern void tcp_enter_cwr(struct sock *sk, const int set_ssthresh);
745 extern __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst);
746 
747 /* Slow start with delack produces 3 packets of burst, so that
748  * it is safe "de facto".
749  */
750 static __inline__ __u32 tcp_max_burst(const struct tcp_sock *tp)
751 {
752 	return 3;
753 }
754 
755 /* RFC2861 Check whether we are limited by application or congestion window
756  * This is the inverse of cwnd check in tcp_tso_should_defer
757  */
758 static inline int tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight)
759 {
760 	const struct tcp_sock *tp = tcp_sk(sk);
761 	u32 left;
762 
763 	if (in_flight >= tp->snd_cwnd)
764 		return 1;
765 
766 	if (!sk_can_gso(sk))
767 		return 0;
768 
769 	left = tp->snd_cwnd - in_flight;
770 	if (sysctl_tcp_tso_win_divisor)
771 		return left * sysctl_tcp_tso_win_divisor < tp->snd_cwnd;
772 	else
773 		return left <= tcp_max_burst(tp);
774 }
775 
776 static inline void tcp_minshall_update(struct tcp_sock *tp, int mss,
777 				       const struct sk_buff *skb)
778 {
779 	if (skb->len < mss)
780 		tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
781 }
782 
783 static inline void tcp_check_probe_timer(struct sock *sk)
784 {
785 	struct tcp_sock *tp = tcp_sk(sk);
786 	const struct inet_connection_sock *icsk = inet_csk(sk);
787 
788 	if (!tp->packets_out && !icsk->icsk_pending)
789 		inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
790 					  icsk->icsk_rto, TCP_RTO_MAX);
791 }
792 
793 static inline void tcp_push_pending_frames(struct sock *sk)
794 {
795 	struct tcp_sock *tp = tcp_sk(sk);
796 
797 	__tcp_push_pending_frames(sk, tcp_current_mss(sk, 1), tp->nonagle);
798 }
799 
800 static inline void tcp_init_wl(struct tcp_sock *tp, u32 ack, u32 seq)
801 {
802 	tp->snd_wl1 = seq;
803 }
804 
805 static inline void tcp_update_wl(struct tcp_sock *tp, u32 ack, u32 seq)
806 {
807 	tp->snd_wl1 = seq;
808 }
809 
810 /*
811  * Calculate(/check) TCP checksum
812  */
813 static inline __sum16 tcp_v4_check(int len, __be32 saddr,
814 				   __be32 daddr, __wsum base)
815 {
816 	return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base);
817 }
818 
819 static inline __sum16 __tcp_checksum_complete(struct sk_buff *skb)
820 {
821 	return __skb_checksum_complete(skb);
822 }
823 
824 static inline int tcp_checksum_complete(struct sk_buff *skb)
825 {
826 	return !skb_csum_unnecessary(skb) &&
827 		__tcp_checksum_complete(skb);
828 }
829 
830 /* Prequeue for VJ style copy to user, combined with checksumming. */
831 
832 static inline void tcp_prequeue_init(struct tcp_sock *tp)
833 {
834 	tp->ucopy.task = NULL;
835 	tp->ucopy.len = 0;
836 	tp->ucopy.memory = 0;
837 	skb_queue_head_init(&tp->ucopy.prequeue);
838 #ifdef CONFIG_NET_DMA
839 	tp->ucopy.dma_chan = NULL;
840 	tp->ucopy.wakeup = 0;
841 	tp->ucopy.pinned_list = NULL;
842 	tp->ucopy.dma_cookie = 0;
843 #endif
844 }
845 
846 /* Packet is added to VJ-style prequeue for processing in process
847  * context, if a reader task is waiting. Apparently, this exciting
848  * idea (VJ's mail "Re: query about TCP header on tcp-ip" of 07 Sep 93)
849  * failed somewhere. Latency? Burstiness? Well, at least now we will
850  * see, why it failed. 8)8)				  --ANK
851  *
852  * NOTE: is this not too big to inline?
853  */
854 static inline int tcp_prequeue(struct sock *sk, struct sk_buff *skb)
855 {
856 	struct tcp_sock *tp = tcp_sk(sk);
857 
858 	if (!sysctl_tcp_low_latency && tp->ucopy.task) {
859 		__skb_queue_tail(&tp->ucopy.prequeue, skb);
860 		tp->ucopy.memory += skb->truesize;
861 		if (tp->ucopy.memory > sk->sk_rcvbuf) {
862 			struct sk_buff *skb1;
863 
864 			BUG_ON(sock_owned_by_user(sk));
865 
866 			while ((skb1 = __skb_dequeue(&tp->ucopy.prequeue)) != NULL) {
867 				sk->sk_backlog_rcv(sk, skb1);
868 				NET_INC_STATS_BH(LINUX_MIB_TCPPREQUEUEDROPPED);
869 			}
870 
871 			tp->ucopy.memory = 0;
872 		} else if (skb_queue_len(&tp->ucopy.prequeue) == 1) {
873 			wake_up_interruptible(sk->sk_sleep);
874 			if (!inet_csk_ack_scheduled(sk))
875 				inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
876 						          (3 * TCP_RTO_MIN) / 4,
877 							  TCP_RTO_MAX);
878 		}
879 		return 1;
880 	}
881 	return 0;
882 }
883 
884 
885 #undef STATE_TRACE
886 
887 #ifdef STATE_TRACE
888 static const char *statename[]={
889 	"Unused","Established","Syn Sent","Syn Recv",
890 	"Fin Wait 1","Fin Wait 2","Time Wait", "Close",
891 	"Close Wait","Last ACK","Listen","Closing"
892 };
893 #endif
894 
895 static inline void tcp_set_state(struct sock *sk, int state)
896 {
897 	int oldstate = sk->sk_state;
898 
899 	switch (state) {
900 	case TCP_ESTABLISHED:
901 		if (oldstate != TCP_ESTABLISHED)
902 			TCP_INC_STATS(TCP_MIB_CURRESTAB);
903 		break;
904 
905 	case TCP_CLOSE:
906 		if (oldstate == TCP_CLOSE_WAIT || oldstate == TCP_ESTABLISHED)
907 			TCP_INC_STATS(TCP_MIB_ESTABRESETS);
908 
909 		sk->sk_prot->unhash(sk);
910 		if (inet_csk(sk)->icsk_bind_hash &&
911 		    !(sk->sk_userlocks & SOCK_BINDPORT_LOCK))
912 			inet_put_port(&tcp_hashinfo, sk);
913 		/* fall through */
914 	default:
915 		if (oldstate==TCP_ESTABLISHED)
916 			TCP_DEC_STATS(TCP_MIB_CURRESTAB);
917 	}
918 
919 	/* Change state AFTER socket is unhashed to avoid closed
920 	 * socket sitting in hash tables.
921 	 */
922 	sk->sk_state = state;
923 
924 #ifdef STATE_TRACE
925 	SOCK_DEBUG(sk, "TCP sk=%p, State %s -> %s\n",sk, statename[oldstate],statename[state]);
926 #endif
927 }
928 
929 extern void tcp_done(struct sock *sk);
930 
931 static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
932 {
933 	rx_opt->dsack = 0;
934 	rx_opt->eff_sacks = 0;
935 	rx_opt->num_sacks = 0;
936 }
937 
938 /* Determine a window scaling and initial window to offer. */
939 extern void tcp_select_initial_window(int __space, __u32 mss,
940 				      __u32 *rcv_wnd, __u32 *window_clamp,
941 				      int wscale_ok, __u8 *rcv_wscale);
942 
943 static inline int tcp_win_from_space(int space)
944 {
945 	return sysctl_tcp_adv_win_scale<=0 ?
946 		(space>>(-sysctl_tcp_adv_win_scale)) :
947 		space - (space>>sysctl_tcp_adv_win_scale);
948 }
949 
950 /* Note: caller must be prepared to deal with negative returns */
951 static inline int tcp_space(const struct sock *sk)
952 {
953 	return tcp_win_from_space(sk->sk_rcvbuf -
954 				  atomic_read(&sk->sk_rmem_alloc));
955 }
956 
957 static inline int tcp_full_space(const struct sock *sk)
958 {
959 	return tcp_win_from_space(sk->sk_rcvbuf);
960 }
961 
962 static inline void tcp_openreq_init(struct request_sock *req,
963 				    struct tcp_options_received *rx_opt,
964 				    struct sk_buff *skb)
965 {
966 	struct inet_request_sock *ireq = inet_rsk(req);
967 
968 	req->rcv_wnd = 0;		/* So that tcp_send_synack() knows! */
969 	tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq;
970 	req->mss = rx_opt->mss_clamp;
971 	req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0;
972 	ireq->tstamp_ok = rx_opt->tstamp_ok;
973 	ireq->sack_ok = rx_opt->sack_ok;
974 	ireq->snd_wscale = rx_opt->snd_wscale;
975 	ireq->wscale_ok = rx_opt->wscale_ok;
976 	ireq->acked = 0;
977 	ireq->ecn_ok = 0;
978 	ireq->rmt_port = tcp_hdr(skb)->source;
979 }
980 
981 extern void tcp_enter_memory_pressure(void);
982 
983 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
984 {
985 	return tp->keepalive_intvl ? : sysctl_tcp_keepalive_intvl;
986 }
987 
988 static inline int keepalive_time_when(const struct tcp_sock *tp)
989 {
990 	return tp->keepalive_time ? : sysctl_tcp_keepalive_time;
991 }
992 
993 static inline int tcp_fin_time(const struct sock *sk)
994 {
995 	int fin_timeout = tcp_sk(sk)->linger2 ? : sysctl_tcp_fin_timeout;
996 	const int rto = inet_csk(sk)->icsk_rto;
997 
998 	if (fin_timeout < (rto << 2) - (rto >> 1))
999 		fin_timeout = (rto << 2) - (rto >> 1);
1000 
1001 	return fin_timeout;
1002 }
1003 
1004 static inline int tcp_paws_check(const struct tcp_options_received *rx_opt, int rst)
1005 {
1006 	if ((s32)(rx_opt->rcv_tsval - rx_opt->ts_recent) >= 0)
1007 		return 0;
1008 	if (get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS)
1009 		return 0;
1010 
1011 	/* RST segments are not recommended to carry timestamp,
1012 	   and, if they do, it is recommended to ignore PAWS because
1013 	   "their cleanup function should take precedence over timestamps."
1014 	   Certainly, it is mistake. It is necessary to understand the reasons
1015 	   of this constraint to relax it: if peer reboots, clock may go
1016 	   out-of-sync and half-open connections will not be reset.
1017 	   Actually, the problem would be not existing if all
1018 	   the implementations followed draft about maintaining clock
1019 	   via reboots. Linux-2.2 DOES NOT!
1020 
1021 	   However, we can relax time bounds for RST segments to MSL.
1022 	 */
1023 	if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
1024 		return 0;
1025 	return 1;
1026 }
1027 
1028 #define TCP_CHECK_TIMER(sk) do { } while (0)
1029 
1030 static inline void tcp_mib_init(void)
1031 {
1032 	/* See RFC 2012 */
1033 	TCP_ADD_STATS_USER(TCP_MIB_RTOALGORITHM, 1);
1034 	TCP_ADD_STATS_USER(TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
1035 	TCP_ADD_STATS_USER(TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
1036 	TCP_ADD_STATS_USER(TCP_MIB_MAXCONN, -1);
1037 }
1038 
1039 /*from STCP */
1040 static inline void clear_all_retrans_hints(struct tcp_sock *tp){
1041 	tp->lost_skb_hint = NULL;
1042 	tp->scoreboard_skb_hint = NULL;
1043 	tp->retransmit_skb_hint = NULL;
1044 	tp->forward_skb_hint = NULL;
1045 	tp->fastpath_skb_hint = NULL;
1046 }
1047 
1048 /* MD5 Signature */
1049 struct crypto_hash;
1050 
1051 /* - key database */
1052 struct tcp_md5sig_key {
1053 	u8			*key;
1054 	u8			keylen;
1055 };
1056 
1057 struct tcp4_md5sig_key {
1058 	u8			*key;
1059 	u16			keylen;
1060 	__be32			addr;
1061 };
1062 
1063 struct tcp6_md5sig_key {
1064 	u8			*key;
1065 	u16			keylen;
1066 #if 0
1067 	u32			scope_id;	/* XXX */
1068 #endif
1069 	struct in6_addr		addr;
1070 };
1071 
1072 /* - sock block */
1073 struct tcp_md5sig_info {
1074 	struct tcp4_md5sig_key	*keys4;
1075 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
1076 	struct tcp6_md5sig_key	*keys6;
1077 	u32			entries6;
1078 	u32			alloced6;
1079 #endif
1080 	u32			entries4;
1081 	u32			alloced4;
1082 };
1083 
1084 /* - pseudo header */
1085 struct tcp4_pseudohdr {
1086 	__be32		saddr;
1087 	__be32		daddr;
1088 	__u8		pad;
1089 	__u8		protocol;
1090 	__be16		len;
1091 };
1092 
1093 struct tcp6_pseudohdr {
1094 	struct in6_addr	saddr;
1095 	struct in6_addr daddr;
1096 	__be32		len;
1097 	__be32		protocol;	/* including padding */
1098 };
1099 
1100 union tcp_md5sum_block {
1101 	struct tcp4_pseudohdr ip4;
1102 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
1103 	struct tcp6_pseudohdr ip6;
1104 #endif
1105 };
1106 
1107 /* - pool: digest algorithm, hash description and scratch buffer */
1108 struct tcp_md5sig_pool {
1109 	struct hash_desc	md5_desc;
1110 	union tcp_md5sum_block	md5_blk;
1111 };
1112 
1113 #define TCP_MD5SIG_MAXKEYS	(~(u32)0)	/* really?! */
1114 
1115 /* - functions */
1116 extern int			tcp_v4_calc_md5_hash(char *md5_hash,
1117 						     struct tcp_md5sig_key *key,
1118 						     struct sock *sk,
1119 						     struct dst_entry *dst,
1120 						     struct request_sock *req,
1121 						     struct tcphdr *th,
1122 						     int protocol, int tcplen);
1123 extern struct tcp_md5sig_key	*tcp_v4_md5_lookup(struct sock *sk,
1124 						   struct sock *addr_sk);
1125 
1126 extern int			tcp_v4_md5_do_add(struct sock *sk,
1127 						  __be32 addr,
1128 						  u8 *newkey,
1129 						  u8 newkeylen);
1130 
1131 extern int			tcp_v4_md5_do_del(struct sock *sk,
1132 						  __be32 addr);
1133 
1134 extern struct tcp_md5sig_pool	**tcp_alloc_md5sig_pool(void);
1135 extern void			tcp_free_md5sig_pool(void);
1136 
1137 extern struct tcp_md5sig_pool	*__tcp_get_md5sig_pool(int cpu);
1138 extern void			__tcp_put_md5sig_pool(void);
1139 
1140 static inline
1141 struct tcp_md5sig_pool		*tcp_get_md5sig_pool(void)
1142 {
1143 	int cpu = get_cpu();
1144 	struct tcp_md5sig_pool *ret = __tcp_get_md5sig_pool(cpu);
1145 	if (!ret)
1146 		put_cpu();
1147 	return ret;
1148 }
1149 
1150 static inline void		tcp_put_md5sig_pool(void)
1151 {
1152 	__tcp_put_md5sig_pool();
1153 	put_cpu();
1154 }
1155 
1156 /* write queue abstraction */
1157 static inline void tcp_write_queue_purge(struct sock *sk)
1158 {
1159 	struct sk_buff *skb;
1160 
1161 	while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL)
1162 		sk_stream_free_skb(sk, skb);
1163 	sk_stream_mem_reclaim(sk);
1164 }
1165 
1166 static inline struct sk_buff *tcp_write_queue_head(struct sock *sk)
1167 {
1168 	struct sk_buff *skb = sk->sk_write_queue.next;
1169 	if (skb == (struct sk_buff *) &sk->sk_write_queue)
1170 		return NULL;
1171 	return skb;
1172 }
1173 
1174 static inline struct sk_buff *tcp_write_queue_tail(struct sock *sk)
1175 {
1176 	struct sk_buff *skb = sk->sk_write_queue.prev;
1177 	if (skb == (struct sk_buff *) &sk->sk_write_queue)
1178 		return NULL;
1179 	return skb;
1180 }
1181 
1182 static inline struct sk_buff *tcp_write_queue_next(struct sock *sk, struct sk_buff *skb)
1183 {
1184 	return skb->next;
1185 }
1186 
1187 #define tcp_for_write_queue(skb, sk)					\
1188 		for (skb = (sk)->sk_write_queue.next;			\
1189 		     (skb != (struct sk_buff *)&(sk)->sk_write_queue);	\
1190 		     skb = skb->next)
1191 
1192 #define tcp_for_write_queue_from(skb, sk)				\
1193 		for (; (skb != (struct sk_buff *)&(sk)->sk_write_queue);\
1194 		     skb = skb->next)
1195 
1196 static inline struct sk_buff *tcp_send_head(struct sock *sk)
1197 {
1198 	return sk->sk_send_head;
1199 }
1200 
1201 static inline void tcp_advance_send_head(struct sock *sk, struct sk_buff *skb)
1202 {
1203 	struct tcp_sock *tp = tcp_sk(sk);
1204 
1205 	sk->sk_send_head = skb->next;
1206 	if (sk->sk_send_head == (struct sk_buff *)&sk->sk_write_queue)
1207 		sk->sk_send_head = NULL;
1208 	/* Don't override Nagle indefinately with F-RTO */
1209 	if (tp->frto_counter == 2)
1210 		tp->frto_counter = 3;
1211 }
1212 
1213 static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
1214 {
1215 	if (sk->sk_send_head == skb_unlinked)
1216 		sk->sk_send_head = NULL;
1217 }
1218 
1219 static inline void tcp_init_send_head(struct sock *sk)
1220 {
1221 	sk->sk_send_head = NULL;
1222 }
1223 
1224 static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1225 {
1226 	__skb_queue_tail(&sk->sk_write_queue, skb);
1227 }
1228 
1229 static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1230 {
1231 	__tcp_add_write_queue_tail(sk, skb);
1232 
1233 	/* Queue it, remembering where we must start sending. */
1234 	if (sk->sk_send_head == NULL)
1235 		sk->sk_send_head = skb;
1236 }
1237 
1238 static inline void __tcp_add_write_queue_head(struct sock *sk, struct sk_buff *skb)
1239 {
1240 	__skb_queue_head(&sk->sk_write_queue, skb);
1241 }
1242 
1243 /* Insert buff after skb on the write queue of sk.  */
1244 static inline void tcp_insert_write_queue_after(struct sk_buff *skb,
1245 						struct sk_buff *buff,
1246 						struct sock *sk)
1247 {
1248 	__skb_append(skb, buff, &sk->sk_write_queue);
1249 }
1250 
1251 /* Insert skb between prev and next on the write queue of sk.  */
1252 static inline void tcp_insert_write_queue_before(struct sk_buff *new,
1253 						  struct sk_buff *skb,
1254 						  struct sock *sk)
1255 {
1256 	__skb_insert(new, skb->prev, skb, &sk->sk_write_queue);
1257 }
1258 
1259 static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
1260 {
1261 	__skb_unlink(skb, &sk->sk_write_queue);
1262 }
1263 
1264 static inline int tcp_skb_is_last(const struct sock *sk,
1265 				  const struct sk_buff *skb)
1266 {
1267 	return skb->next == (struct sk_buff *)&sk->sk_write_queue;
1268 }
1269 
1270 static inline int tcp_write_queue_empty(struct sock *sk)
1271 {
1272 	return skb_queue_empty(&sk->sk_write_queue);
1273 }
1274 
1275 /* /proc */
1276 enum tcp_seq_states {
1277 	TCP_SEQ_STATE_LISTENING,
1278 	TCP_SEQ_STATE_OPENREQ,
1279 	TCP_SEQ_STATE_ESTABLISHED,
1280 	TCP_SEQ_STATE_TIME_WAIT,
1281 };
1282 
1283 struct tcp_seq_afinfo {
1284 	struct module		*owner;
1285 	char			*name;
1286 	sa_family_t		family;
1287 	int			(*seq_show) (struct seq_file *m, void *v);
1288 	struct file_operations	*seq_fops;
1289 };
1290 
1291 struct tcp_iter_state {
1292 	sa_family_t		family;
1293 	enum tcp_seq_states	state;
1294 	struct sock		*syn_wait_sk;
1295 	int			bucket, sbucket, num, uid;
1296 	struct seq_operations	seq_ops;
1297 };
1298 
1299 extern int tcp_proc_register(struct tcp_seq_afinfo *afinfo);
1300 extern void tcp_proc_unregister(struct tcp_seq_afinfo *afinfo);
1301 
1302 extern struct request_sock_ops tcp_request_sock_ops;
1303 
1304 extern int tcp_v4_destroy_sock(struct sock *sk);
1305 
1306 extern int tcp_v4_gso_send_check(struct sk_buff *skb);
1307 extern struct sk_buff *tcp_tso_segment(struct sk_buff *skb, int features);
1308 
1309 #ifdef CONFIG_PROC_FS
1310 extern int  tcp4_proc_init(void);
1311 extern void tcp4_proc_exit(void);
1312 #endif
1313 
1314 /* TCP af-specific functions */
1315 struct tcp_sock_af_ops {
1316 #ifdef CONFIG_TCP_MD5SIG
1317 	struct tcp_md5sig_key	*(*md5_lookup) (struct sock *sk,
1318 						struct sock *addr_sk);
1319 	int			(*calc_md5_hash) (char *location,
1320 						  struct tcp_md5sig_key *md5,
1321 						  struct sock *sk,
1322 						  struct dst_entry *dst,
1323 						  struct request_sock *req,
1324 						  struct tcphdr *th,
1325 						  int protocol, int len);
1326 	int			(*md5_add) (struct sock *sk,
1327 					    struct sock *addr_sk,
1328 					    u8 *newkey,
1329 					    u8 len);
1330 	int			(*md5_parse) (struct sock *sk,
1331 					      char __user *optval,
1332 					      int optlen);
1333 #endif
1334 };
1335 
1336 struct tcp_request_sock_ops {
1337 #ifdef CONFIG_TCP_MD5SIG
1338 	struct tcp_md5sig_key	*(*md5_lookup) (struct sock *sk,
1339 						struct request_sock *req);
1340 #endif
1341 };
1342 
1343 extern void tcp_v4_init(struct net_proto_family *ops);
1344 extern void tcp_init(void);
1345 
1346 #endif	/* _TCP_H */
1347