xref: /dragonfly/sys/netinet/tcp_usrreq.c (revision 0ac6bf9d)
1 /*
2  * Copyright (c) 2003, 2004 Jeffrey M. Hsu.  All rights reserved.
3  * Copyright (c) 2003, 2004 The DragonFly Project.  All rights reserved.
4  *
5  * This code is derived from software contributed to The DragonFly Project
6  * by Jeffrey M. Hsu.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  * 3. Neither the name of The DragonFly Project nor the names of its
17  *    contributors may be used to endorse or promote products derived
18  *    from this software without specific, prior written permission.
19  *
20  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
21  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
24  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
26  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
27  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
28  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
30  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  */
33 
34 /*
35  * Copyright (c) 2003, 2004 Jeffrey M. Hsu.  All rights reserved.
36  *
37  * License terms: all terms for the DragonFly license above plus the following:
38  *
39  * 4. All advertising materials mentioning features or use of this software
40  *    must display the following acknowledgement:
41  *
42  *	This product includes software developed by Jeffrey M. Hsu
43  *	for the DragonFly Project.
44  *
45  *    This requirement may be waived with permission from Jeffrey Hsu.
46  *    This requirement will sunset and may be removed on July 8 2005,
47  *    after which the standard DragonFly license (as shown above) will
48  *    apply.
49  */
50 
51 /*
52  * Copyright (c) 1982, 1986, 1988, 1993
53  *	The Regents of the University of California.  All rights reserved.
54  *
55  * Redistribution and use in source and binary forms, with or without
56  * modification, are permitted provided that the following conditions
57  * are met:
58  * 1. Redistributions of source code must retain the above copyright
59  *    notice, this list of conditions and the following disclaimer.
60  * 2. Redistributions in binary form must reproduce the above copyright
61  *    notice, this list of conditions and the following disclaimer in the
62  *    documentation and/or other materials provided with the distribution.
63  * 3. All advertising materials mentioning features or use of this software
64  *    must display the following acknowledgement:
65  *	This product includes software developed by the University of
66  *	California, Berkeley and its contributors.
67  * 4. Neither the name of the University nor the names of its contributors
68  *    may be used to endorse or promote products derived from this software
69  *    without specific prior written permission.
70  *
71  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
72  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
73  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
74  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
75  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
76  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
77  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
78  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
79  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
80  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
81  * SUCH DAMAGE.
82  *
83  *	From: @(#)tcp_usrreq.c	8.2 (Berkeley) 1/3/94
84  * $FreeBSD: src/sys/netinet/tcp_usrreq.c,v 1.51.2.17 2002/10/11 11:46:44 ume Exp $
85  * $DragonFly: src/sys/netinet/tcp_usrreq.c,v 1.38 2006/09/05 00:55:48 dillon Exp $
86  */
87 
88 #include "opt_ipsec.h"
89 #include "opt_inet6.h"
90 #include "opt_tcpdebug.h"
91 
92 #include <sys/param.h>
93 #include <sys/systm.h>
94 #include <sys/kernel.h>
95 #include <sys/malloc.h>
96 #include <sys/sysctl.h>
97 #include <sys/globaldata.h>
98 #include <sys/thread.h>
99 
100 #include <sys/mbuf.h>
101 #ifdef INET6
102 #include <sys/domain.h>
103 #endif /* INET6 */
104 #include <sys/socket.h>
105 #include <sys/socketvar.h>
106 #include <sys/protosw.h>
107 
108 #include <sys/thread2.h>
109 #include <sys/msgport2.h>
110 
111 #include <net/if.h>
112 #include <net/netisr.h>
113 #include <net/route.h>
114 
115 #include <netinet/in.h>
116 #include <netinet/in_systm.h>
117 #ifdef INET6
118 #include <netinet/ip6.h>
119 #endif
120 #include <netinet/in_pcb.h>
121 #ifdef INET6
122 #include <netinet6/in6_pcb.h>
123 #endif
124 #include <netinet/in_var.h>
125 #include <netinet/ip_var.h>
126 #ifdef INET6
127 #include <netinet6/ip6_var.h>
128 #endif
129 #include <netinet/tcp.h>
130 #include <netinet/tcp_fsm.h>
131 #include <netinet/tcp_seq.h>
132 #include <netinet/tcp_timer.h>
133 #include <netinet/tcp_var.h>
134 #include <netinet/tcpip.h>
135 #ifdef TCPDEBUG
136 #include <netinet/tcp_debug.h>
137 #endif
138 
139 #ifdef IPSEC
140 #include <netinet6/ipsec.h>
141 #endif /*IPSEC*/
142 
143 /*
144  * TCP protocol interface to socket abstraction.
145  */
146 extern	char *tcpstates[];	/* XXX ??? */
147 
148 static int	tcp_attach (struct socket *, struct pru_attach_info *);
149 static int	tcp_connect (struct tcpcb *, struct sockaddr *,
150 				 struct thread *);
151 #ifdef INET6
152 static int	tcp6_connect (struct tcpcb *, struct sockaddr *,
153 				 struct thread *);
154 #endif /* INET6 */
155 static struct tcpcb *
156 		tcp_disconnect (struct tcpcb *);
157 static struct tcpcb *
158 		tcp_usrclosed (struct tcpcb *);
159 
160 #ifdef TCPDEBUG
161 #define	TCPDEBUG0	int ostate = 0
162 #define	TCPDEBUG1()	ostate = tp ? tp->t_state : 0
163 #define	TCPDEBUG2(req)	if (tp && (so->so_options & SO_DEBUG)) \
164 				tcp_trace(TA_USER, ostate, tp, 0, 0, req)
165 #else
166 #define	TCPDEBUG0
167 #define	TCPDEBUG1()
168 #define	TCPDEBUG2(req)
169 #endif
170 
171 /*
172  * TCP attaches to socket via pru_attach(), reserving space,
173  * and an internet control block.
174  */
175 static int
176 tcp_usr_attach(struct socket *so, int proto, struct pru_attach_info *ai)
177 {
178 	int error;
179 	struct inpcb *inp;
180 	struct tcpcb *tp = 0;
181 	TCPDEBUG0;
182 
183 	crit_enter();
184 	inp = so->so_pcb;
185 	TCPDEBUG1();
186 	if (inp) {
187 		error = EISCONN;
188 		goto out;
189 	}
190 
191 	error = tcp_attach(so, ai);
192 	if (error)
193 		goto out;
194 
195 	if ((so->so_options & SO_LINGER) && so->so_linger == 0)
196 		so->so_linger = TCP_LINGERTIME;
197 	tp = sototcpcb(so);
198 out:
199 	TCPDEBUG2(PRU_ATTACH);
200 	crit_exit();
201 	return error;
202 }
203 
204 /*
205  * pru_detach() detaches the TCP protocol from the socket.
206  * If the protocol state is non-embryonic, then can't
207  * do this directly: have to initiate a pru_disconnect(),
208  * which may finish later; embryonic TCB's can just
209  * be discarded here.
210  */
211 static int
212 tcp_usr_detach(struct socket *so)
213 {
214 	int error = 0;
215 	struct inpcb *inp;
216 	struct tcpcb *tp;
217 	TCPDEBUG0;
218 
219 	crit_enter();
220 	inp = so->so_pcb;
221 	if (inp == NULL) {
222 		crit_exit();
223 		return EINVAL;	/* XXX */
224 	}
225 
226 	/*
227 	 * It's possible for the tcpcb (tp) to disconnect from the inp due
228 	 * to tcp_drop()->tcp_close() being called.  This may occur *after*
229 	 * the detach message has been queued so we may find a NULL tp here.
230 	 */
231 	if ((tp = intotcpcb(inp)) != NULL) {
232 		TCPDEBUG1();
233 		tp = tcp_disconnect(tp);
234 		TCPDEBUG2(PRU_DETACH);
235 	}
236 	crit_exit();
237 	return error;
238 }
239 
240 #define	COMMON_START(so, inp)		\
241 			TCPDEBUG0; 	\
242 					\
243 			crit_enter();	\
244 			inp = so->so_pcb; \
245 			do { \
246 				     if (inp == 0) { \
247 					     crit_exit(); \
248 					     return EINVAL; \
249 				     } \
250 				     tp = intotcpcb(inp); \
251 				     TCPDEBUG1(); \
252 		     } while(0)
253 
254 #define COMMON_END(req)	out: TCPDEBUG2(req); crit_exit(); return error; goto out
255 
256 
257 /*
258  * Give the socket an address.
259  */
260 static int
261 tcp_usr_bind(struct socket *so, struct sockaddr *nam, struct thread *td)
262 {
263 	int error = 0;
264 	struct inpcb *inp;
265 	struct tcpcb *tp;
266 	struct sockaddr_in *sinp;
267 
268 	COMMON_START(so, inp);
269 
270 	/*
271 	 * Must check for multicast addresses and disallow binding
272 	 * to them.
273 	 */
274 	sinp = (struct sockaddr_in *)nam;
275 	if (sinp->sin_family == AF_INET &&
276 	    IN_MULTICAST(ntohl(sinp->sin_addr.s_addr))) {
277 		error = EAFNOSUPPORT;
278 		goto out;
279 	}
280 	error = in_pcbbind(inp, nam, td);
281 	if (error)
282 		goto out;
283 	COMMON_END(PRU_BIND);
284 
285 }
286 
287 #ifdef INET6
288 static int
289 tcp6_usr_bind(struct socket *so, struct sockaddr *nam, struct thread *td)
290 {
291 	int error = 0;
292 	struct inpcb *inp;
293 	struct tcpcb *tp;
294 	struct sockaddr_in6 *sin6p;
295 
296 	COMMON_START(so, inp);
297 
298 	/*
299 	 * Must check for multicast addresses and disallow binding
300 	 * to them.
301 	 */
302 	sin6p = (struct sockaddr_in6 *)nam;
303 	if (sin6p->sin6_family == AF_INET6 &&
304 	    IN6_IS_ADDR_MULTICAST(&sin6p->sin6_addr)) {
305 		error = EAFNOSUPPORT;
306 		goto out;
307 	}
308 	inp->inp_vflag &= ~INP_IPV4;
309 	inp->inp_vflag |= INP_IPV6;
310 	if ((inp->inp_flags & IN6P_IPV6_V6ONLY) == 0) {
311 		if (IN6_IS_ADDR_UNSPECIFIED(&sin6p->sin6_addr))
312 			inp->inp_vflag |= INP_IPV4;
313 		else if (IN6_IS_ADDR_V4MAPPED(&sin6p->sin6_addr)) {
314 			struct sockaddr_in sin;
315 
316 			in6_sin6_2_sin(&sin, sin6p);
317 			inp->inp_vflag |= INP_IPV4;
318 			inp->inp_vflag &= ~INP_IPV6;
319 			error = in_pcbbind(inp, (struct sockaddr *)&sin, td);
320 			goto out;
321 		}
322 	}
323 	error = in6_pcbbind(inp, nam, td);
324 	if (error)
325 		goto out;
326 	COMMON_END(PRU_BIND);
327 }
328 #endif /* INET6 */
329 
330 #ifdef SMP
331 struct netmsg_inswildcard {
332 	struct lwkt_msg		nm_lmsg;
333 	struct inpcb		*nm_inp;
334 	struct inpcbinfo	*nm_pcbinfo;
335 };
336 
337 static int
338 in_pcbinswildcardhash_handler(struct lwkt_msg *msg0)
339 {
340 	struct netmsg_inswildcard *msg = (struct netmsg_inswildcard *)msg0;
341 
342 	in_pcbinswildcardhash_oncpu(msg->nm_inp, msg->nm_pcbinfo);
343 	lwkt_replymsg(&msg->nm_lmsg, 0);
344 	return (EASYNC);
345 }
346 #endif
347 
348 /*
349  * Prepare to accept connections.
350  */
351 static int
352 tcp_usr_listen(struct socket *so, struct thread *td)
353 {
354 	int error = 0;
355 	struct inpcb *inp;
356 	struct tcpcb *tp;
357 #ifdef SMP
358 	int cpu;
359 #endif
360 
361 	COMMON_START(so, inp);
362 	if (inp->inp_lport == 0) {
363 		error = in_pcbbind(inp, NULL, td);
364 		if (error != 0)
365 			goto out;
366 	}
367 
368 	tp->t_state = TCPS_LISTEN;
369 #ifdef SMP
370 	/*
371 	 * We have to set the flag because we can't have other cpus
372 	 * messing with our inp's flags.
373 	 */
374 	inp->inp_flags |= INP_WILDCARD_MP;
375 	for (cpu = 0; cpu < ncpus2; cpu++) {
376 		struct netmsg_inswildcard *msg;
377 
378 		if (cpu == mycpu->gd_cpuid) {
379 			in_pcbinswildcardhash(inp);
380 			continue;
381 		}
382 
383 		msg = kmalloc(sizeof(struct netmsg_inswildcard), M_LWKTMSG,
384 		    M_INTWAIT);
385 		lwkt_initmsg(&msg->nm_lmsg, &netisr_afree_rport, 0,
386 		    lwkt_cmd_func(in_pcbinswildcardhash_handler),
387 		    lwkt_cmd_op_none);
388 		msg->nm_inp = inp;
389 		msg->nm_pcbinfo = &tcbinfo[cpu];
390 		lwkt_sendmsg(tcp_cport(cpu), &msg->nm_lmsg);
391 	}
392 #else
393 	in_pcbinswildcardhash(inp);
394 #endif
395 	COMMON_END(PRU_LISTEN);
396 }
397 
398 #ifdef INET6
399 static int
400 tcp6_usr_listen(struct socket *so, struct thread *td)
401 {
402 	int error = 0;
403 	struct inpcb *inp;
404 	struct tcpcb *tp;
405 #ifdef SMP
406 	int cpu;
407 #endif
408 
409 	COMMON_START(so, inp);
410 	if (inp->inp_lport == 0) {
411 		if (!(inp->inp_flags & IN6P_IPV6_V6ONLY))
412 			inp->inp_vflag |= INP_IPV4;
413 		else
414 			inp->inp_vflag &= ~INP_IPV4;
415 		error = in6_pcbbind(inp, (struct sockaddr *)0, td);
416 	}
417 	if (error == 0)
418 		tp->t_state = TCPS_LISTEN;
419 #ifdef SMP
420 	/*
421 	 * We have to set the flag because we can't have other cpus
422 	 * messing with our inp's flags.
423 	 */
424 	inp->inp_flags |= INP_WILDCARD_MP;
425 	for (cpu = 0; cpu < ncpus2; cpu++) {
426 		struct netmsg_inswildcard *msg;
427 
428 		if (cpu == mycpu->gd_cpuid) {
429 			in_pcbinswildcardhash(inp);
430 			continue;
431 		}
432 
433 		msg = kmalloc(sizeof(struct netmsg_inswildcard), M_LWKTMSG,
434 		    M_INTWAIT);
435 		lwkt_initmsg(&msg->nm_lmsg, &netisr_afree_rport, 0,
436 		    lwkt_cmd_func(in_pcbinswildcardhash_handler),
437 		    lwkt_cmd_op_none);
438 		msg->nm_inp = inp;
439 		msg->nm_pcbinfo = &tcbinfo[cpu];
440 		lwkt_sendmsg(tcp_cport(cpu), &msg->nm_lmsg);
441 	}
442 #else
443 	in_pcbinswildcardhash(inp);
444 #endif
445 	COMMON_END(PRU_LISTEN);
446 }
447 #endif /* INET6 */
448 
449 /*
450  * Initiate connection to peer.
451  * Create a template for use in transmissions on this connection.
452  * Enter SYN_SENT state, and mark socket as connecting.
453  * Start keep-alive timer, and seed output sequence space.
454  * Send initial segment on connection.
455  */
456 static int
457 tcp_usr_connect(struct socket *so, struct sockaddr *nam, struct thread *td)
458 {
459 	int error = 0;
460 	struct inpcb *inp;
461 	struct tcpcb *tp;
462 	struct sockaddr_in *sinp;
463 
464 	COMMON_START(so, inp);
465 
466 	/*
467 	 * Must disallow TCP ``connections'' to multicast addresses.
468 	 */
469 	sinp = (struct sockaddr_in *)nam;
470 	if (sinp->sin_family == AF_INET
471 	    && IN_MULTICAST(ntohl(sinp->sin_addr.s_addr))) {
472 		error = EAFNOSUPPORT;
473 		goto out;
474 	}
475 
476 	prison_remote_ip(td, 0, &sinp->sin_addr.s_addr);
477 
478 	if ((error = tcp_connect(tp, nam, td)) != 0)
479 		goto out;
480 	error = tcp_output(tp);
481 	COMMON_END(PRU_CONNECT);
482 }
483 
484 #ifdef INET6
485 static int
486 tcp6_usr_connect(struct socket *so, struct sockaddr *nam, struct thread *td)
487 {
488 	int error = 0;
489 	struct inpcb *inp;
490 	struct tcpcb *tp;
491 	struct sockaddr_in6 *sin6p;
492 
493 	COMMON_START(so, inp);
494 
495 	/*
496 	 * Must disallow TCP ``connections'' to multicast addresses.
497 	 */
498 	sin6p = (struct sockaddr_in6 *)nam;
499 	if (sin6p->sin6_family == AF_INET6
500 	    && IN6_IS_ADDR_MULTICAST(&sin6p->sin6_addr)) {
501 		error = EAFNOSUPPORT;
502 		goto out;
503 	}
504 
505 	if (IN6_IS_ADDR_V4MAPPED(&sin6p->sin6_addr)) {
506 		struct sockaddr_in sin;
507 
508 		if ((inp->inp_flags & IN6P_IPV6_V6ONLY) != 0) {
509 			error = EINVAL;
510 			goto out;
511 		}
512 
513 		in6_sin6_2_sin(&sin, sin6p);
514 		inp->inp_vflag |= INP_IPV4;
515 		inp->inp_vflag &= ~INP_IPV6;
516 		if ((error = tcp_connect(tp, (struct sockaddr *)&sin, td)) != 0)
517 			goto out;
518 		error = tcp_output(tp);
519 		goto out;
520 	}
521 	inp->inp_vflag &= ~INP_IPV4;
522 	inp->inp_vflag |= INP_IPV6;
523 	inp->inp_inc.inc_isipv6 = 1;
524 	if ((error = tcp6_connect(tp, nam, td)) != 0)
525 		goto out;
526 	error = tcp_output(tp);
527 	COMMON_END(PRU_CONNECT);
528 }
529 #endif /* INET6 */
530 
531 /*
532  * Initiate disconnect from peer.
533  * If connection never passed embryonic stage, just drop;
534  * else if don't need to let data drain, then can just drop anyways,
535  * else have to begin TCP shutdown process: mark socket disconnecting,
536  * drain unread data, state switch to reflect user close, and
537  * send segment (e.g. FIN) to peer.  Socket will be really disconnected
538  * when peer sends FIN and acks ours.
539  *
540  * SHOULD IMPLEMENT LATER PRU_CONNECT VIA REALLOC TCPCB.
541  */
542 static int
543 tcp_usr_disconnect(struct socket *so)
544 {
545 	int error = 0;
546 	struct inpcb *inp;
547 	struct tcpcb *tp;
548 
549 	COMMON_START(so, inp);
550 	tp = tcp_disconnect(tp);
551 	COMMON_END(PRU_DISCONNECT);
552 }
553 
554 /*
555  * Accept a connection.  Essentially all the work is
556  * done at higher levels; just return the address
557  * of the peer, storing through addr.
558  */
559 static int
560 tcp_usr_accept(struct socket *so, struct sockaddr **nam)
561 {
562 	int error = 0;
563 	struct inpcb *inp;
564 	struct tcpcb *tp = NULL;
565 	TCPDEBUG0;
566 
567 	crit_enter();
568 	inp = so->so_pcb;
569 	if (so->so_state & SS_ISDISCONNECTED) {
570 		error = ECONNABORTED;
571 		goto out;
572 	}
573 	if (inp == 0) {
574 		crit_exit();
575 		return (EINVAL);
576 	}
577 	tp = intotcpcb(inp);
578 	TCPDEBUG1();
579 	in_setpeeraddr(so, nam);
580 	COMMON_END(PRU_ACCEPT);
581 }
582 
583 #ifdef INET6
584 static int
585 tcp6_usr_accept(struct socket *so, struct sockaddr **nam)
586 {
587 	int error = 0;
588 	struct inpcb *inp;
589 	struct tcpcb *tp = NULL;
590 	TCPDEBUG0;
591 
592 	crit_enter();
593 	inp = so->so_pcb;
594 
595 	if (so->so_state & SS_ISDISCONNECTED) {
596 		error = ECONNABORTED;
597 		goto out;
598 	}
599 	if (inp == 0) {
600 		crit_exit();
601 		return (EINVAL);
602 	}
603 	tp = intotcpcb(inp);
604 	TCPDEBUG1();
605 	in6_mapped_peeraddr(so, nam);
606 	COMMON_END(PRU_ACCEPT);
607 }
608 #endif /* INET6 */
609 /*
610  * Mark the connection as being incapable of further output.
611  */
612 static int
613 tcp_usr_shutdown(struct socket *so)
614 {
615 	int error = 0;
616 	struct inpcb *inp;
617 	struct tcpcb *tp;
618 
619 	COMMON_START(so, inp);
620 	socantsendmore(so);
621 	tp = tcp_usrclosed(tp);
622 	if (tp)
623 		error = tcp_output(tp);
624 	COMMON_END(PRU_SHUTDOWN);
625 }
626 
627 /*
628  * After a receive, possibly send window update to peer.
629  */
630 static int
631 tcp_usr_rcvd(struct socket *so, int flags)
632 {
633 	int error = 0;
634 	struct inpcb *inp;
635 	struct tcpcb *tp;
636 
637 	COMMON_START(so, inp);
638 	tcp_output(tp);
639 	COMMON_END(PRU_RCVD);
640 }
641 
642 /*
643  * Do a send by putting data in output queue and updating urgent
644  * marker if URG set.  Possibly send more data.  Unlike the other
645  * pru_*() routines, the mbuf chains are our responsibility.  We
646  * must either enqueue them or free them.  The other pru_* routines
647  * generally are caller-frees.
648  */
649 static int
650 tcp_usr_send(struct socket *so, int flags, struct mbuf *m,
651 	     struct sockaddr *nam, struct mbuf *control, struct thread *td)
652 {
653 	int error = 0;
654 	struct inpcb *inp;
655 	struct tcpcb *tp;
656 #ifdef INET6
657 	int isipv6;
658 #endif
659 	TCPDEBUG0;
660 
661 	crit_enter();
662 	inp = so->so_pcb;
663 
664 	if (inp == NULL) {
665 		/*
666 		 * OOPS! we lost a race, the TCP session got reset after
667 		 * we checked SS_CANTSENDMORE, eg: while doing uiomove or a
668 		 * network interrupt in the non-critical section of sosend().
669 		 */
670 		if (m)
671 			m_freem(m);
672 		if (control)
673 			m_freem(control);
674 		error = ECONNRESET;	/* XXX EPIPE? */
675 		tp = NULL;
676 		TCPDEBUG1();
677 		goto out;
678 	}
679 #ifdef INET6
680 	isipv6 = nam && nam->sa_family == AF_INET6;
681 #endif /* INET6 */
682 	tp = intotcpcb(inp);
683 	TCPDEBUG1();
684 	if (control) {
685 		/* TCP doesn't do control messages (rights, creds, etc) */
686 		if (control->m_len) {
687 			m_freem(control);
688 			if (m)
689 				m_freem(m);
690 			error = EINVAL;
691 			goto out;
692 		}
693 		m_freem(control);	/* empty control, just free it */
694 	}
695 	if(!(flags & PRUS_OOB)) {
696 		sbappendstream(&so->so_snd, m);
697 		if (nam && tp->t_state < TCPS_SYN_SENT) {
698 			/*
699 			 * Do implied connect if not yet connected,
700 			 * initialize window to default value, and
701 			 * initialize maxseg/maxopd using peer's cached
702 			 * MSS.
703 			 */
704 #ifdef INET6
705 			if (isipv6)
706 				error = tcp6_connect(tp, nam, td);
707 			else
708 #endif /* INET6 */
709 			error = tcp_connect(tp, nam, td);
710 			if (error)
711 				goto out;
712 			tp->snd_wnd = TTCP_CLIENT_SND_WND;
713 			tcp_mss(tp, -1);
714 		}
715 
716 		if (flags & PRUS_EOF) {
717 			/*
718 			 * Close the send side of the connection after
719 			 * the data is sent.
720 			 */
721 			socantsendmore(so);
722 			tp = tcp_usrclosed(tp);
723 		}
724 		if (tp != NULL) {
725 			if (flags & PRUS_MORETOCOME)
726 				tp->t_flags |= TF_MORETOCOME;
727 			error = tcp_output(tp);
728 			if (flags & PRUS_MORETOCOME)
729 				tp->t_flags &= ~TF_MORETOCOME;
730 		}
731 	} else {
732 		if (sbspace(&so->so_snd) < -512) {
733 			m_freem(m);
734 			error = ENOBUFS;
735 			goto out;
736 		}
737 		/*
738 		 * According to RFC961 (Assigned Protocols),
739 		 * the urgent pointer points to the last octet
740 		 * of urgent data.  We continue, however,
741 		 * to consider it to indicate the first octet
742 		 * of data past the urgent section.
743 		 * Otherwise, snd_up should be one lower.
744 		 */
745 		sbappendstream(&so->so_snd, m);
746 		if (nam && tp->t_state < TCPS_SYN_SENT) {
747 			/*
748 			 * Do implied connect if not yet connected,
749 			 * initialize window to default value, and
750 			 * initialize maxseg/maxopd using peer's cached
751 			 * MSS.
752 			 */
753 #ifdef INET6
754 			if (isipv6)
755 				error = tcp6_connect(tp, nam, td);
756 			else
757 #endif /* INET6 */
758 			error = tcp_connect(tp, nam, td);
759 			if (error)
760 				goto out;
761 			tp->snd_wnd = TTCP_CLIENT_SND_WND;
762 			tcp_mss(tp, -1);
763 		}
764 		tp->snd_up = tp->snd_una + so->so_snd.sb_cc;
765 		tp->t_flags |= TF_FORCE;
766 		error = tcp_output(tp);
767 		tp->t_flags &= ~TF_FORCE;
768 	}
769 	COMMON_END((flags & PRUS_OOB) ? PRU_SENDOOB :
770 		   ((flags & PRUS_EOF) ? PRU_SEND_EOF : PRU_SEND));
771 }
772 
773 /*
774  * Abort the TCP.
775  */
776 static int
777 tcp_usr_abort(struct socket *so)
778 {
779 	int error = 0;
780 	struct inpcb *inp;
781 	struct tcpcb *tp;
782 
783 	COMMON_START(so, inp);
784 	tp = tcp_drop(tp, ECONNABORTED);
785 	COMMON_END(PRU_ABORT);
786 }
787 
788 /*
789  * Receive out-of-band data.
790  */
791 static int
792 tcp_usr_rcvoob(struct socket *so, struct mbuf *m, int flags)
793 {
794 	int error = 0;
795 	struct inpcb *inp;
796 	struct tcpcb *tp;
797 
798 	COMMON_START(so, inp);
799 	if ((so->so_oobmark == 0 &&
800 	     (so->so_state & SS_RCVATMARK) == 0) ||
801 	    so->so_options & SO_OOBINLINE ||
802 	    tp->t_oobflags & TCPOOB_HADDATA) {
803 		error = EINVAL;
804 		goto out;
805 	}
806 	if ((tp->t_oobflags & TCPOOB_HAVEDATA) == 0) {
807 		error = EWOULDBLOCK;
808 		goto out;
809 	}
810 	m->m_len = 1;
811 	*mtod(m, caddr_t) = tp->t_iobc;
812 	if ((flags & MSG_PEEK) == 0)
813 		tp->t_oobflags ^= (TCPOOB_HAVEDATA | TCPOOB_HADDATA);
814 	COMMON_END(PRU_RCVOOB);
815 }
816 
817 /* xxx - should be const */
818 struct pr_usrreqs tcp_usrreqs = {
819 	tcp_usr_abort, tcp_usr_accept, tcp_usr_attach, tcp_usr_bind,
820 	tcp_usr_connect, pru_connect2_notsupp, in_control, tcp_usr_detach,
821 	tcp_usr_disconnect, tcp_usr_listen, in_setpeeraddr, tcp_usr_rcvd,
822 	tcp_usr_rcvoob, tcp_usr_send, pru_sense_null, tcp_usr_shutdown,
823 	in_setsockaddr, sosend, soreceive, sopoll
824 };
825 
826 #ifdef INET6
827 struct pr_usrreqs tcp6_usrreqs = {
828 	tcp_usr_abort, tcp6_usr_accept, tcp_usr_attach, tcp6_usr_bind,
829 	tcp6_usr_connect, pru_connect2_notsupp, in6_control, tcp_usr_detach,
830 	tcp_usr_disconnect, tcp6_usr_listen, in6_mapped_peeraddr, tcp_usr_rcvd,
831 	tcp_usr_rcvoob, tcp_usr_send, pru_sense_null, tcp_usr_shutdown,
832 	in6_mapped_sockaddr, sosend, soreceive, sopoll
833 };
834 #endif /* INET6 */
835 
836 static int
837 tcp_connect_oncpu(struct tcpcb *tp, struct sockaddr_in *sin,
838 		  struct sockaddr_in *if_sin)
839 {
840 	struct inpcb *inp = tp->t_inpcb, *oinp;
841 	struct socket *so = inp->inp_socket;
842 	struct tcpcb *otp;
843 	struct rmxp_tao *taop;
844 	struct rmxp_tao tao_noncached;
845 
846 	oinp = in_pcblookup_hash(&tcbinfo[mycpu->gd_cpuid],
847 	    sin->sin_addr, sin->sin_port,
848 	    inp->inp_laddr.s_addr != INADDR_ANY ?
849 		inp->inp_laddr : if_sin->sin_addr,
850 	    inp->inp_lport, 0, NULL);
851 	if (oinp != NULL) {
852 		if (oinp != inp && (otp = intotcpcb(oinp)) != NULL &&
853 		    otp->t_state == TCPS_TIME_WAIT &&
854 		    (ticks - otp->t_starttime) < tcp_msl &&
855 		    (otp->t_flags & TF_RCVD_CC))
856 			tcp_close(otp);
857 		else
858 			return (EADDRINUSE);
859 	}
860 	if (inp->inp_laddr.s_addr == INADDR_ANY)
861 		inp->inp_laddr = if_sin->sin_addr;
862 	inp->inp_faddr = sin->sin_addr;
863 	inp->inp_fport = sin->sin_port;
864 	inp->inp_cpcbinfo = &tcbinfo[mycpu->gd_cpuid];
865 	in_pcbinsconnhash(inp);
866 
867 	/* Compute window scaling to request.  */
868 	while (tp->request_r_scale < TCP_MAX_WINSHIFT &&
869 	    (TCP_MAXWIN << tp->request_r_scale) < so->so_rcv.sb_hiwat)
870 		tp->request_r_scale++;
871 
872 	soisconnecting(so);
873 	tcpstat.tcps_connattempt++;
874 	tp->t_state = TCPS_SYN_SENT;
875 	callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp);
876 	tp->iss = tcp_new_isn(tp);
877 	tcp_sendseqinit(tp);
878 
879 	/*
880 	 * Generate a CC value for this connection and
881 	 * check whether CC or CCnew should be used.
882 	 */
883 	if ((taop = tcp_gettaocache(&tp->t_inpcb->inp_inc)) == NULL) {
884 		taop = &tao_noncached;
885 		bzero(taop, sizeof *taop);
886 	}
887 
888 	tp->cc_send = CC_INC(tcp_ccgen);
889 	if (taop->tao_ccsent != 0 &&
890 	    CC_GEQ(tp->cc_send, taop->tao_ccsent)) {
891 		taop->tao_ccsent = tp->cc_send;
892 	} else {
893 		taop->tao_ccsent = 0;
894 		tp->t_flags |= TF_SENDCCNEW;
895 	}
896 
897 	return (0);
898 }
899 
900 #ifdef SMP
901 
902 struct netmsg_tcp_connect {
903 	struct lwkt_msg		nm_lmsg;
904 	struct tcpcb		*nm_tp;
905 	struct sockaddr_in	*nm_sin;
906 	struct sockaddr_in	*nm_ifsin;
907 };
908 
909 static int
910 tcp_connect_handler(lwkt_msg_t lmsg)
911 {
912 	struct netmsg_tcp_connect *msg = (void *)lmsg;
913 	int error;
914 
915 	error = tcp_connect_oncpu(msg->nm_tp, msg->nm_sin, msg->nm_ifsin);
916 	lwkt_replymsg(lmsg, error);
917 	return(EASYNC);
918 }
919 
920 #endif
921 
922 /*
923  * Common subroutine to open a TCP connection to remote host specified
924  * by struct sockaddr_in in mbuf *nam.  Call in_pcbbind to assign a local
925  * port number if needed.  Call in_pcbladdr to do the routing and to choose
926  * a local host address (interface).  If there is an existing incarnation
927  * of the same connection in TIME-WAIT state and if the remote host was
928  * sending CC options and if the connection duration was < MSL, then
929  * truncate the previous TIME-WAIT state and proceed.
930  * Initialize connection parameters and enter SYN-SENT state.
931  */
932 static int
933 tcp_connect(struct tcpcb *tp, struct sockaddr *nam, struct thread *td)
934 {
935 	struct inpcb *inp = tp->t_inpcb;
936 	struct sockaddr_in *sin = (struct sockaddr_in *)nam;
937 	struct sockaddr_in *if_sin;
938 	int error;
939 #ifdef SMP
940 	lwkt_port_t port;
941 #endif
942 
943 	if (inp->inp_lport == 0) {
944 		error = in_pcbbind(inp, (struct sockaddr *)NULL, td);
945 		if (error)
946 			return (error);
947 	}
948 
949 	/*
950 	 * Cannot simply call in_pcbconnect, because there might be an
951 	 * earlier incarnation of this same connection still in
952 	 * TIME_WAIT state, creating an ADDRINUSE error.
953 	 */
954 	error = in_pcbladdr(inp, nam, &if_sin);
955 	if (error)
956 		return (error);
957 
958 #ifdef SMP
959 	port = tcp_addrport(sin->sin_addr.s_addr, sin->sin_port,
960 	    inp->inp_laddr.s_addr ?
961 		inp->inp_laddr.s_addr : if_sin->sin_addr.s_addr,
962 	    inp->inp_lport);
963 
964 	if (port->mp_td != curthread) {
965 		struct netmsg_tcp_connect msg;
966 
967 		lwkt_initmsg(&msg.nm_lmsg, &curthread->td_msgport, 0,
968 		    lwkt_cmd_func(tcp_connect_handler), lwkt_cmd_op_none);
969 		msg.nm_tp = tp;
970 		msg.nm_sin = sin;
971 		msg.nm_ifsin = if_sin;
972 		error = lwkt_domsg(port, &msg.nm_lmsg);
973 	} else
974 #endif
975 		error = tcp_connect_oncpu(tp, sin, if_sin);
976 
977 	return (error);
978 }
979 
980 #ifdef INET6
981 static int
982 tcp6_connect(struct tcpcb *tp, struct sockaddr *nam, struct thread *td)
983 {
984 	struct inpcb *inp = tp->t_inpcb, *oinp;
985 	struct socket *so = inp->inp_socket;
986 	struct tcpcb *otp;
987 	struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)nam;
988 	struct in6_addr *addr6;
989 	struct rmxp_tao *taop;
990 	struct rmxp_tao tao_noncached;
991 	int error;
992 
993 	if (inp->inp_lport == 0) {
994 		error = in6_pcbbind(inp, (struct sockaddr *)0, td);
995 		if (error)
996 			return error;
997 	}
998 
999 	/*
1000 	 * Cannot simply call in_pcbconnect, because there might be an
1001 	 * earlier incarnation of this same connection still in
1002 	 * TIME_WAIT state, creating an ADDRINUSE error.
1003 	 */
1004 	error = in6_pcbladdr(inp, nam, &addr6);
1005 	if (error)
1006 		return error;
1007 	oinp = in6_pcblookup_hash(inp->inp_cpcbinfo,
1008 				  &sin6->sin6_addr, sin6->sin6_port,
1009 				  IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr) ?
1010 				      addr6 : &inp->in6p_laddr,
1011 				  inp->inp_lport,  0, NULL);
1012 	if (oinp) {
1013 		if (oinp != inp && (otp = intotcpcb(oinp)) != NULL &&
1014 		    otp->t_state == TCPS_TIME_WAIT &&
1015 		    (ticks - otp->t_starttime) < tcp_msl &&
1016 		    (otp->t_flags & TF_RCVD_CC))
1017 			otp = tcp_close(otp);
1018 		else
1019 			return (EADDRINUSE);
1020 	}
1021 	if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
1022 		inp->in6p_laddr = *addr6;
1023 	inp->in6p_faddr = sin6->sin6_addr;
1024 	inp->inp_fport = sin6->sin6_port;
1025 	if ((sin6->sin6_flowinfo & IPV6_FLOWINFO_MASK) != NULL)
1026 		inp->in6p_flowinfo = sin6->sin6_flowinfo;
1027 	in_pcbinsconnhash(inp);
1028 
1029 	/* Compute window scaling to request.  */
1030 	while (tp->request_r_scale < TCP_MAX_WINSHIFT &&
1031 	    (TCP_MAXWIN << tp->request_r_scale) < so->so_rcv.sb_hiwat)
1032 		tp->request_r_scale++;
1033 
1034 	soisconnecting(so);
1035 	tcpstat.tcps_connattempt++;
1036 	tp->t_state = TCPS_SYN_SENT;
1037 	callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp);
1038 	tp->iss = tcp_new_isn(tp);
1039 	tcp_sendseqinit(tp);
1040 
1041 	/*
1042 	 * Generate a CC value for this connection and
1043 	 * check whether CC or CCnew should be used.
1044 	 */
1045 	if ((taop = tcp_gettaocache(&tp->t_inpcb->inp_inc)) == NULL) {
1046 		taop = &tao_noncached;
1047 		bzero(taop, sizeof *taop);
1048 	}
1049 
1050 	tp->cc_send = CC_INC(tcp_ccgen);
1051 	if (taop->tao_ccsent != 0 &&
1052 	    CC_GEQ(tp->cc_send, taop->tao_ccsent)) {
1053 		taop->tao_ccsent = tp->cc_send;
1054 	} else {
1055 		taop->tao_ccsent = 0;
1056 		tp->t_flags |= TF_SENDCCNEW;
1057 	}
1058 
1059 	return (0);
1060 }
1061 #endif /* INET6 */
1062 
1063 /*
1064  * The new sockopt interface makes it possible for us to block in the
1065  * copyin/out step (if we take a page fault).  Taking a page fault while
1066  * in a critical section is probably a Bad Thing.  (Since sockets and pcbs
1067  * both now use TSM, there probably isn't any need for this function to
1068  * run in a critical section any more.  This needs more examination.)
1069  */
1070 int
1071 tcp_ctloutput(struct socket *so, struct sockopt *sopt)
1072 {
1073 	int	error, opt, optval;
1074 	struct	inpcb *inp;
1075 	struct	tcpcb *tp;
1076 
1077 	error = 0;
1078 	crit_enter();		/* XXX */
1079 	inp = so->so_pcb;
1080 	if (inp == NULL) {
1081 		crit_exit();
1082 		return (ECONNRESET);
1083 	}
1084 	if (sopt->sopt_level != IPPROTO_TCP) {
1085 #ifdef INET6
1086 		if (INP_CHECK_SOCKAF(so, AF_INET6))
1087 			error = ip6_ctloutput(so, sopt);
1088 		else
1089 #endif /* INET6 */
1090 		error = ip_ctloutput(so, sopt);
1091 		crit_exit();
1092 		return (error);
1093 	}
1094 	tp = intotcpcb(inp);
1095 
1096 	switch (sopt->sopt_dir) {
1097 	case SOPT_SET:
1098 		switch (sopt->sopt_name) {
1099 		case TCP_NODELAY:
1100 		case TCP_NOOPT:
1101 			error = sooptcopyin(sopt, &optval, sizeof optval,
1102 					    sizeof optval);
1103 			if (error)
1104 				break;
1105 
1106 			switch (sopt->sopt_name) {
1107 			case TCP_NODELAY:
1108 				opt = TF_NODELAY;
1109 				break;
1110 			case TCP_NOOPT:
1111 				opt = TF_NOOPT;
1112 				break;
1113 			default:
1114 				opt = 0; /* dead code to fool gcc */
1115 				break;
1116 			}
1117 
1118 			if (optval)
1119 				tp->t_flags |= opt;
1120 			else
1121 				tp->t_flags &= ~opt;
1122 			break;
1123 
1124 		case TCP_NOPUSH:
1125 			error = sooptcopyin(sopt, &optval, sizeof optval,
1126 					    sizeof optval);
1127 			if (error)
1128 				break;
1129 
1130 			if (optval)
1131 				tp->t_flags |= TF_NOPUSH;
1132 			else {
1133 				tp->t_flags &= ~TF_NOPUSH;
1134 				error = tcp_output(tp);
1135 			}
1136 			break;
1137 
1138 		case TCP_MAXSEG:
1139 			error = sooptcopyin(sopt, &optval, sizeof optval,
1140 					    sizeof optval);
1141 			if (error)
1142 				break;
1143 
1144 			if (optval > 0 && optval <= tp->t_maxseg)
1145 				tp->t_maxseg = optval;
1146 			else
1147 				error = EINVAL;
1148 			break;
1149 
1150 		default:
1151 			error = ENOPROTOOPT;
1152 			break;
1153 		}
1154 		break;
1155 
1156 	case SOPT_GET:
1157 		switch (sopt->sopt_name) {
1158 		case TCP_NODELAY:
1159 			optval = tp->t_flags & TF_NODELAY;
1160 			break;
1161 		case TCP_MAXSEG:
1162 			optval = tp->t_maxseg;
1163 			break;
1164 		case TCP_NOOPT:
1165 			optval = tp->t_flags & TF_NOOPT;
1166 			break;
1167 		case TCP_NOPUSH:
1168 			optval = tp->t_flags & TF_NOPUSH;
1169 			break;
1170 		default:
1171 			error = ENOPROTOOPT;
1172 			break;
1173 		}
1174 		if (error == 0)
1175 			error = sooptcopyout(sopt, &optval, sizeof optval);
1176 		break;
1177 	}
1178 	crit_exit();
1179 	return (error);
1180 }
1181 
1182 /*
1183  * tcp_sendspace and tcp_recvspace are the default send and receive window
1184  * sizes, respectively.  These are obsolescent (this information should
1185  * be set by the route).
1186  */
1187 u_long	tcp_sendspace = 1024*32;
1188 SYSCTL_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_RW,
1189     &tcp_sendspace , 0, "Maximum outgoing TCP datagram size");
1190 u_long	tcp_recvspace = 57344;	/* largest multiple of PAGE_SIZE < 64k */
1191 SYSCTL_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_RW,
1192     &tcp_recvspace , 0, "Maximum incoming TCP datagram size");
1193 
1194 /*
1195  * Attach TCP protocol to socket, allocating
1196  * internet protocol control block, tcp control block,
1197  * bufer space, and entering LISTEN state if to accept connections.
1198  */
1199 static int
1200 tcp_attach(struct socket *so, struct pru_attach_info *ai)
1201 {
1202 	struct tcpcb *tp;
1203 	struct inpcb *inp;
1204 	int error;
1205 	int cpu;
1206 #ifdef INET6
1207 	int isipv6 = INP_CHECK_SOCKAF(so, AF_INET6) != NULL;
1208 #endif
1209 
1210 	if (so->so_snd.sb_hiwat == 0 || so->so_rcv.sb_hiwat == 0) {
1211 		error = soreserve(so, tcp_sendspace, tcp_recvspace,
1212 				  ai->sb_rlimit);
1213 		if (error)
1214 			return (error);
1215 	}
1216 	cpu = mycpu->gd_cpuid;
1217 	error = in_pcballoc(so, &tcbinfo[cpu]);
1218 	if (error)
1219 		return (error);
1220 	inp = so->so_pcb;
1221 #ifdef INET6
1222 	if (isipv6) {
1223 		inp->inp_vflag |= INP_IPV6;
1224 		inp->in6p_hops = -1;	/* use kernel default */
1225 	}
1226 	else
1227 #endif
1228 	inp->inp_vflag |= INP_IPV4;
1229 	tp = tcp_newtcpcb(inp);
1230 	if (tp == 0) {
1231 		int nofd = so->so_state & SS_NOFDREF;	/* XXX */
1232 
1233 		so->so_state &= ~SS_NOFDREF;	/* don't free the socket yet */
1234 #ifdef INET6
1235 		if (isipv6)
1236 			in6_pcbdetach(inp);
1237 		else
1238 #endif
1239 		in_pcbdetach(inp);
1240 		so->so_state |= nofd;
1241 		return (ENOBUFS);
1242 	}
1243 	tp->t_state = TCPS_CLOSED;
1244 	return (0);
1245 }
1246 
1247 /*
1248  * Initiate (or continue) disconnect.
1249  * If embryonic state, just send reset (once).
1250  * If in ``let data drain'' option and linger null, just drop.
1251  * Otherwise (hard), mark socket disconnecting and drop
1252  * current input data; switch states based on user close, and
1253  * send segment to peer (with FIN).
1254  */
1255 static struct tcpcb *
1256 tcp_disconnect(struct tcpcb *tp)
1257 {
1258 	struct socket *so = tp->t_inpcb->inp_socket;
1259 
1260 	if (tp->t_state < TCPS_ESTABLISHED)
1261 		tp = tcp_close(tp);
1262 	else if ((so->so_options & SO_LINGER) && so->so_linger == 0)
1263 		tp = tcp_drop(tp, 0);
1264 	else {
1265 		soisdisconnecting(so);
1266 		sbflush(&so->so_rcv);
1267 		tp = tcp_usrclosed(tp);
1268 		if (tp)
1269 			tcp_output(tp);
1270 	}
1271 	return (tp);
1272 }
1273 
1274 /*
1275  * User issued close, and wish to trail through shutdown states:
1276  * if never received SYN, just forget it.  If got a SYN from peer,
1277  * but haven't sent FIN, then go to FIN_WAIT_1 state to send peer a FIN.
1278  * If already got a FIN from peer, then almost done; go to LAST_ACK
1279  * state.  In all other cases, have already sent FIN to peer (e.g.
1280  * after PRU_SHUTDOWN), and just have to play tedious game waiting
1281  * for peer to send FIN or not respond to keep-alives, etc.
1282  * We can let the user exit from the close as soon as the FIN is acked.
1283  */
1284 static struct tcpcb *
1285 tcp_usrclosed(struct tcpcb *tp)
1286 {
1287 
1288 	switch (tp->t_state) {
1289 
1290 	case TCPS_CLOSED:
1291 	case TCPS_LISTEN:
1292 		tp->t_state = TCPS_CLOSED;
1293 		tp = tcp_close(tp);
1294 		break;
1295 
1296 	case TCPS_SYN_SENT:
1297 	case TCPS_SYN_RECEIVED:
1298 		tp->t_flags |= TF_NEEDFIN;
1299 		break;
1300 
1301 	case TCPS_ESTABLISHED:
1302 		tp->t_state = TCPS_FIN_WAIT_1;
1303 		break;
1304 
1305 	case TCPS_CLOSE_WAIT:
1306 		tp->t_state = TCPS_LAST_ACK;
1307 		break;
1308 	}
1309 	if (tp && tp->t_state >= TCPS_FIN_WAIT_2) {
1310 		soisdisconnected(tp->t_inpcb->inp_socket);
1311 		/* To prevent the connection hanging in FIN_WAIT_2 forever. */
1312 		if (tp->t_state == TCPS_FIN_WAIT_2)
1313 			callout_reset(tp->tt_2msl, tcp_maxidle,
1314 				      tcp_timer_2msl, tp);
1315 	}
1316 	return (tp);
1317 }
1318