xref: /freebsd/sys/netinet/tcp_subr.c (revision 512bd18d)
1 /*-
2  * SPDX-License-Identifier: BSD-3-Clause
3  *
4  * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
5  *	The Regents of the University of California.  All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  * 3. Neither the name of the University nor the names of its contributors
16  *    may be used to endorse or promote products derived from this software
17  *    without specific prior written permission.
18  *
19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29  * SUCH DAMAGE.
30  *
31  *	@(#)tcp_subr.c	8.2 (Berkeley) 5/24/95
32  */
33 
34 #include <sys/cdefs.h>
35 __FBSDID("$FreeBSD$");
36 
37 #include "opt_compat.h"
38 #include "opt_inet.h"
39 #include "opt_inet6.h"
40 #include "opt_ipsec.h"
41 #include "opt_tcpdebug.h"
42 
43 #include <sys/param.h>
44 #include <sys/systm.h>
45 #include <sys/callout.h>
46 #include <sys/eventhandler.h>
47 #ifdef TCP_HHOOK
48 #include <sys/hhook.h>
49 #endif
50 #include <sys/kernel.h>
51 #ifdef TCP_HHOOK
52 #include <sys/khelp.h>
53 #endif
54 #include <sys/sysctl.h>
55 #include <sys/jail.h>
56 #include <sys/malloc.h>
57 #include <sys/refcount.h>
58 #include <sys/mbuf.h>
59 #ifdef INET6
60 #include <sys/domain.h>
61 #endif
62 #include <sys/priv.h>
63 #include <sys/proc.h>
64 #include <sys/sdt.h>
65 #include <sys/socket.h>
66 #include <sys/socketvar.h>
67 #include <sys/protosw.h>
68 #include <sys/random.h>
69 
70 #include <vm/uma.h>
71 
72 #include <net/route.h>
73 #include <net/if.h>
74 #include <net/if_var.h>
75 #include <net/vnet.h>
76 
77 #include <netinet/in.h>
78 #include <netinet/in_fib.h>
79 #include <netinet/in_kdtrace.h>
80 #include <netinet/in_pcb.h>
81 #include <netinet/in_systm.h>
82 #include <netinet/in_var.h>
83 #include <netinet/ip.h>
84 #include <netinet/ip_icmp.h>
85 #include <netinet/ip_var.h>
86 #ifdef INET6
87 #include <netinet/icmp6.h>
88 #include <netinet/ip6.h>
89 #include <netinet6/in6_fib.h>
90 #include <netinet6/in6_pcb.h>
91 #include <netinet6/ip6_var.h>
92 #include <netinet6/scope6_var.h>
93 #include <netinet6/nd6.h>
94 #endif
95 
96 #ifdef TCP_RFC7413
97 #include <netinet/tcp_fastopen.h>
98 #endif
99 #include <netinet/tcp.h>
100 #include <netinet/tcp_fsm.h>
101 #include <netinet/tcp_seq.h>
102 #include <netinet/tcp_timer.h>
103 #include <netinet/tcp_var.h>
104 #include <netinet/tcp_syncache.h>
105 #include <netinet/cc/cc.h>
106 #ifdef INET6
107 #include <netinet6/tcp6_var.h>
108 #endif
109 #include <netinet/tcpip.h>
110 #ifdef TCPPCAP
111 #include <netinet/tcp_pcap.h>
112 #endif
113 #ifdef TCPDEBUG
114 #include <netinet/tcp_debug.h>
115 #endif
116 #ifdef INET6
117 #include <netinet6/ip6protosw.h>
118 #endif
119 #ifdef TCP_OFFLOAD
120 #include <netinet/tcp_offload.h>
121 #endif
122 
123 #include <netipsec/ipsec_support.h>
124 
125 #include <machine/in_cksum.h>
126 #include <sys/md5.h>
127 
128 #include <security/mac/mac_framework.h>
129 
130 VNET_DEFINE(int, tcp_mssdflt) = TCP_MSS;
131 #ifdef INET6
132 VNET_DEFINE(int, tcp_v6mssdflt) = TCP6_MSS;
133 #endif
134 
135 struct rwlock tcp_function_lock;
136 
137 static int
138 sysctl_net_inet_tcp_mss_check(SYSCTL_HANDLER_ARGS)
139 {
140 	int error, new;
141 
142 	new = V_tcp_mssdflt;
143 	error = sysctl_handle_int(oidp, &new, 0, req);
144 	if (error == 0 && req->newptr) {
145 		if (new < TCP_MINMSS)
146 			error = EINVAL;
147 		else
148 			V_tcp_mssdflt = new;
149 	}
150 	return (error);
151 }
152 
153 SYSCTL_PROC(_net_inet_tcp, TCPCTL_MSSDFLT, mssdflt,
154     CTLFLAG_VNET | CTLTYPE_INT | CTLFLAG_RW, &VNET_NAME(tcp_mssdflt), 0,
155     &sysctl_net_inet_tcp_mss_check, "I",
156     "Default TCP Maximum Segment Size");
157 
158 #ifdef INET6
159 static int
160 sysctl_net_inet_tcp_mss_v6_check(SYSCTL_HANDLER_ARGS)
161 {
162 	int error, new;
163 
164 	new = V_tcp_v6mssdflt;
165 	error = sysctl_handle_int(oidp, &new, 0, req);
166 	if (error == 0 && req->newptr) {
167 		if (new < TCP_MINMSS)
168 			error = EINVAL;
169 		else
170 			V_tcp_v6mssdflt = new;
171 	}
172 	return (error);
173 }
174 
175 SYSCTL_PROC(_net_inet_tcp, TCPCTL_V6MSSDFLT, v6mssdflt,
176     CTLFLAG_VNET | CTLTYPE_INT | CTLFLAG_RW, &VNET_NAME(tcp_v6mssdflt), 0,
177     &sysctl_net_inet_tcp_mss_v6_check, "I",
178    "Default TCP Maximum Segment Size for IPv6");
179 #endif /* INET6 */
180 
181 /*
182  * Minimum MSS we accept and use. This prevents DoS attacks where
183  * we are forced to a ridiculous low MSS like 20 and send hundreds
184  * of packets instead of one. The effect scales with the available
185  * bandwidth and quickly saturates the CPU and network interface
186  * with packet generation and sending. Set to zero to disable MINMSS
187  * checking. This setting prevents us from sending too small packets.
188  */
189 VNET_DEFINE(int, tcp_minmss) = TCP_MINMSS;
190 SYSCTL_INT(_net_inet_tcp, OID_AUTO, minmss, CTLFLAG_VNET | CTLFLAG_RW,
191      &VNET_NAME(tcp_minmss), 0,
192     "Minimum TCP Maximum Segment Size");
193 
194 VNET_DEFINE(int, tcp_do_rfc1323) = 1;
195 SYSCTL_INT(_net_inet_tcp, TCPCTL_DO_RFC1323, rfc1323, CTLFLAG_VNET | CTLFLAG_RW,
196     &VNET_NAME(tcp_do_rfc1323), 0,
197     "Enable rfc1323 (high performance TCP) extensions");
198 
199 static int	tcp_log_debug = 0;
200 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_debug, CTLFLAG_RW,
201     &tcp_log_debug, 0, "Log errors caused by incoming TCP segments");
202 
203 static int	tcp_tcbhashsize;
204 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tcbhashsize, CTLFLAG_RDTUN | CTLFLAG_NOFETCH,
205     &tcp_tcbhashsize, 0, "Size of TCP control-block hashtable");
206 
207 static int	do_tcpdrain = 1;
208 SYSCTL_INT(_net_inet_tcp, OID_AUTO, do_tcpdrain, CTLFLAG_RW, &do_tcpdrain, 0,
209     "Enable tcp_drain routine for extra help when low on mbufs");
210 
211 SYSCTL_UINT(_net_inet_tcp, OID_AUTO, pcbcount, CTLFLAG_VNET | CTLFLAG_RD,
212     &VNET_NAME(tcbinfo.ipi_count), 0, "Number of active PCBs");
213 
214 static VNET_DEFINE(int, icmp_may_rst) = 1;
215 #define	V_icmp_may_rst			VNET(icmp_may_rst)
216 SYSCTL_INT(_net_inet_tcp, OID_AUTO, icmp_may_rst, CTLFLAG_VNET | CTLFLAG_RW,
217     &VNET_NAME(icmp_may_rst), 0,
218     "Certain ICMP unreachable messages may abort connections in SYN_SENT");
219 
220 static VNET_DEFINE(int, tcp_isn_reseed_interval) = 0;
221 #define	V_tcp_isn_reseed_interval	VNET(tcp_isn_reseed_interval)
222 SYSCTL_INT(_net_inet_tcp, OID_AUTO, isn_reseed_interval, CTLFLAG_VNET | CTLFLAG_RW,
223     &VNET_NAME(tcp_isn_reseed_interval), 0,
224     "Seconds between reseeding of ISN secret");
225 
226 static int	tcp_soreceive_stream;
227 SYSCTL_INT(_net_inet_tcp, OID_AUTO, soreceive_stream, CTLFLAG_RDTUN,
228     &tcp_soreceive_stream, 0, "Using soreceive_stream for TCP sockets");
229 
230 VNET_DEFINE(uma_zone_t, sack_hole_zone);
231 #define	V_sack_hole_zone		VNET(sack_hole_zone)
232 
233 #ifdef TCP_HHOOK
234 VNET_DEFINE(struct hhook_head *, tcp_hhh[HHOOK_TCP_LAST+1]);
235 #endif
236 
237 static struct inpcb *tcp_notify(struct inpcb *, int);
238 static struct inpcb *tcp_mtudisc_notify(struct inpcb *, int);
239 static void tcp_mtudisc(struct inpcb *, int);
240 static char *	tcp_log_addr(struct in_conninfo *inc, struct tcphdr *th,
241 		    void *ip4hdr, const void *ip6hdr);
242 
243 
244 static struct tcp_function_block tcp_def_funcblk = {
245 	"default",
246 	tcp_output,
247 	tcp_do_segment,
248 	tcp_default_ctloutput,
249 	NULL,
250 	NULL,
251 	NULL,
252 	NULL,
253 	NULL,
254 	NULL,
255 	0,
256 	0
257 };
258 
259 int t_functions_inited = 0;
260 struct tcp_funchead t_functions;
261 static struct tcp_function_block *tcp_func_set_ptr = &tcp_def_funcblk;
262 
263 static void
264 init_tcp_functions(void)
265 {
266 	if (t_functions_inited == 0) {
267 		TAILQ_INIT(&t_functions);
268 		rw_init_flags(&tcp_function_lock, "tcp_func_lock" , 0);
269 		t_functions_inited = 1;
270 	}
271 }
272 
273 static struct tcp_function_block *
274 find_tcp_functions_locked(struct tcp_function_set *fs)
275 {
276 	struct tcp_function *f;
277 	struct tcp_function_block *blk=NULL;
278 
279 	TAILQ_FOREACH(f, &t_functions, tf_next) {
280 		if (strcmp(f->tf_name, fs->function_set_name) == 0) {
281 			blk = f->tf_fb;
282 			break;
283 		}
284 	}
285 	return(blk);
286 }
287 
288 static struct tcp_function_block *
289 find_tcp_fb_locked(struct tcp_function_block *blk, struct tcp_function **s)
290 {
291 	struct tcp_function_block *rblk=NULL;
292 	struct tcp_function *f;
293 
294 	TAILQ_FOREACH(f, &t_functions, tf_next) {
295 		if (f->tf_fb == blk) {
296 			rblk = blk;
297 			if (s) {
298 				*s = f;
299 			}
300 			break;
301 		}
302 	}
303 	return (rblk);
304 }
305 
306 struct tcp_function_block *
307 find_and_ref_tcp_functions(struct tcp_function_set *fs)
308 {
309 	struct tcp_function_block *blk;
310 
311 	rw_rlock(&tcp_function_lock);
312 	blk = find_tcp_functions_locked(fs);
313 	if (blk)
314 		refcount_acquire(&blk->tfb_refcnt);
315 	rw_runlock(&tcp_function_lock);
316 	return(blk);
317 }
318 
319 struct tcp_function_block *
320 find_and_ref_tcp_fb(struct tcp_function_block *blk)
321 {
322 	struct tcp_function_block *rblk;
323 
324 	rw_rlock(&tcp_function_lock);
325 	rblk = find_tcp_fb_locked(blk, NULL);
326 	if (rblk)
327 		refcount_acquire(&rblk->tfb_refcnt);
328 	rw_runlock(&tcp_function_lock);
329 	return(rblk);
330 }
331 
332 
333 static int
334 sysctl_net_inet_default_tcp_functions(SYSCTL_HANDLER_ARGS)
335 {
336 	int error=ENOENT;
337 	struct tcp_function_set fs;
338 	struct tcp_function_block *blk;
339 
340 	memset(&fs, 0, sizeof(fs));
341 	rw_rlock(&tcp_function_lock);
342 	blk = find_tcp_fb_locked(tcp_func_set_ptr, NULL);
343 	if (blk) {
344 		/* Found him */
345 		strcpy(fs.function_set_name, blk->tfb_tcp_block_name);
346 		fs.pcbcnt = blk->tfb_refcnt;
347 	}
348 	rw_runlock(&tcp_function_lock);
349 	error = sysctl_handle_string(oidp, fs.function_set_name,
350 				     sizeof(fs.function_set_name), req);
351 
352 	/* Check for error or no change */
353 	if (error != 0 || req->newptr == NULL)
354 		return(error);
355 
356 	rw_wlock(&tcp_function_lock);
357 	blk = find_tcp_functions_locked(&fs);
358 	if ((blk == NULL) ||
359 	    (blk->tfb_flags & TCP_FUNC_BEING_REMOVED)) {
360 		error = ENOENT;
361 		goto done;
362 	}
363 	tcp_func_set_ptr = blk;
364 done:
365 	rw_wunlock(&tcp_function_lock);
366 	return (error);
367 }
368 
369 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, functions_default,
370 	    CTLTYPE_STRING | CTLFLAG_RW,
371 	    NULL, 0, sysctl_net_inet_default_tcp_functions, "A",
372 	    "Set/get the default TCP functions");
373 
374 static int
375 sysctl_net_inet_list_available(SYSCTL_HANDLER_ARGS)
376 {
377 	int error, cnt, linesz;
378 	struct tcp_function *f;
379 	char *buffer, *cp;
380 	size_t bufsz, outsz;
381 	bool alias;
382 
383 	cnt = 0;
384 	rw_rlock(&tcp_function_lock);
385 	TAILQ_FOREACH(f, &t_functions, tf_next) {
386 		cnt++;
387 	}
388 	rw_runlock(&tcp_function_lock);
389 
390 	bufsz = (cnt+2) * ((TCP_FUNCTION_NAME_LEN_MAX * 2) + 13) + 1;
391 	buffer = malloc(bufsz, M_TEMP, M_WAITOK);
392 
393 	error = 0;
394 	cp = buffer;
395 
396 	linesz = snprintf(cp, bufsz, "\n%-32s%c %-32s %s\n", "Stack", 'D',
397 	    "Alias", "PCB count");
398 	cp += linesz;
399 	bufsz -= linesz;
400 	outsz = linesz;
401 
402 	rw_rlock(&tcp_function_lock);
403 	TAILQ_FOREACH(f, &t_functions, tf_next) {
404 		alias = (f->tf_name != f->tf_fb->tfb_tcp_block_name);
405 		linesz = snprintf(cp, bufsz, "%-32s%c %-32s %u\n",
406 		    f->tf_fb->tfb_tcp_block_name,
407 		    (f->tf_fb == tcp_func_set_ptr) ? '*' : ' ',
408 		    alias ? f->tf_name : "-",
409 		    f->tf_fb->tfb_refcnt);
410 		if (linesz >= bufsz) {
411 			error = EOVERFLOW;
412 			break;
413 		}
414 		cp += linesz;
415 		bufsz -= linesz;
416 		outsz += linesz;
417 	}
418 	rw_runlock(&tcp_function_lock);
419 	if (error == 0)
420 		error = sysctl_handle_string(oidp, buffer, outsz + 1, req);
421 	free(buffer, M_TEMP);
422 	return (error);
423 }
424 
425 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, functions_available,
426 	    CTLTYPE_STRING|CTLFLAG_RD,
427 	    NULL, 0, sysctl_net_inet_list_available, "A",
428 	    "list available TCP Function sets");
429 
430 /*
431  * Target size of TCP PCB hash tables. Must be a power of two.
432  *
433  * Note that this can be overridden by the kernel environment
434  * variable net.inet.tcp.tcbhashsize
435  */
436 #ifndef TCBHASHSIZE
437 #define TCBHASHSIZE	0
438 #endif
439 
440 /*
441  * XXX
442  * Callouts should be moved into struct tcp directly.  They are currently
443  * separate because the tcpcb structure is exported to userland for sysctl
444  * parsing purposes, which do not know about callouts.
445  */
446 struct tcpcb_mem {
447 	struct	tcpcb		tcb;
448 	struct	tcp_timer	tt;
449 	struct	cc_var		ccv;
450 #ifdef TCP_HHOOK
451 	struct	osd		osd;
452 #endif
453 };
454 
455 static VNET_DEFINE(uma_zone_t, tcpcb_zone);
456 #define	V_tcpcb_zone			VNET(tcpcb_zone)
457 
458 MALLOC_DEFINE(M_TCPLOG, "tcplog", "TCP address and flags print buffers");
459 MALLOC_DEFINE(M_TCPFUNCTIONS, "tcpfunc", "TCP function set memory");
460 
461 static struct mtx isn_mtx;
462 
463 #define	ISN_LOCK_INIT()	mtx_init(&isn_mtx, "isn_mtx", NULL, MTX_DEF)
464 #define	ISN_LOCK()	mtx_lock(&isn_mtx)
465 #define	ISN_UNLOCK()	mtx_unlock(&isn_mtx)
466 
467 /*
468  * TCP initialization.
469  */
470 static void
471 tcp_zone_change(void *tag)
472 {
473 
474 	uma_zone_set_max(V_tcbinfo.ipi_zone, maxsockets);
475 	uma_zone_set_max(V_tcpcb_zone, maxsockets);
476 	tcp_tw_zone_change();
477 }
478 
479 static int
480 tcp_inpcb_init(void *mem, int size, int flags)
481 {
482 	struct inpcb *inp = mem;
483 
484 	INP_LOCK_INIT(inp, "inp", "tcpinp");
485 	return (0);
486 }
487 
488 /*
489  * Take a value and get the next power of 2 that doesn't overflow.
490  * Used to size the tcp_inpcb hash buckets.
491  */
492 static int
493 maketcp_hashsize(int size)
494 {
495 	int hashsize;
496 
497 	/*
498 	 * auto tune.
499 	 * get the next power of 2 higher than maxsockets.
500 	 */
501 	hashsize = 1 << fls(size);
502 	/* catch overflow, and just go one power of 2 smaller */
503 	if (hashsize < size) {
504 		hashsize = 1 << (fls(size) - 1);
505 	}
506 	return (hashsize);
507 }
508 
509 /*
510  * Register a TCP function block with the name provided in the names
511  * array.  (Note that this function does NOT automatically register
512  * blk->tfb_tcp_block_name as a stack name.  Therefore, you should
513  * explicitly include blk->tfb_tcp_block_name in the list of names if
514  * you wish to register the stack with that name.)
515  *
516  * Either all name registrations will succeed or all will fail.  If
517  * a name registration fails, the function will update the num_names
518  * argument to point to the array index of the name that encountered
519  * the failure.
520  *
521  * Returns 0 on success, or an error code on failure.
522  */
523 int
524 register_tcp_functions_as_names(struct tcp_function_block *blk, int wait,
525     const char *names[], int *num_names)
526 {
527 	struct tcp_function *n;
528 	struct tcp_function_set fs;
529 	int error, i;
530 
531 	KASSERT(names != NULL && *num_names > 0,
532 	    ("%s: Called with 0-length name list", __func__));
533 	KASSERT(names != NULL, ("%s: Called with NULL name list", __func__));
534 
535 	if (t_functions_inited == 0) {
536 		init_tcp_functions();
537 	}
538 	if ((blk->tfb_tcp_output == NULL) ||
539 	    (blk->tfb_tcp_do_segment == NULL) ||
540 	    (blk->tfb_tcp_ctloutput == NULL) ||
541 	    (strlen(blk->tfb_tcp_block_name) == 0)) {
542 		/*
543 		 * These functions are required and you
544 		 * need a name.
545 		 */
546 		*num_names = 0;
547 		return (EINVAL);
548 	}
549 	if (blk->tfb_tcp_timer_stop_all ||
550 	    blk->tfb_tcp_timer_activate ||
551 	    blk->tfb_tcp_timer_active ||
552 	    blk->tfb_tcp_timer_stop) {
553 		/*
554 		 * If you define one timer function you
555 		 * must have them all.
556 		 */
557 		if ((blk->tfb_tcp_timer_stop_all == NULL) ||
558 		    (blk->tfb_tcp_timer_activate == NULL) ||
559 		    (blk->tfb_tcp_timer_active == NULL) ||
560 		    (blk->tfb_tcp_timer_stop == NULL)) {
561 			*num_names = 0;
562 			return (EINVAL);
563 		}
564 	}
565 
566 	refcount_init(&blk->tfb_refcnt, 0);
567 	blk->tfb_flags = 0;
568 	for (i = 0; i < *num_names; i++) {
569 		n = malloc(sizeof(struct tcp_function), M_TCPFUNCTIONS, wait);
570 		if (n == NULL) {
571 			error = ENOMEM;
572 			goto cleanup;
573 		}
574 		n->tf_fb = blk;
575 
576 		(void)strncpy(fs.function_set_name, names[i],
577 		    TCP_FUNCTION_NAME_LEN_MAX);
578 		fs.function_set_name[TCP_FUNCTION_NAME_LEN_MAX - 1] = '\0';
579 		rw_wlock(&tcp_function_lock);
580 		if (find_tcp_functions_locked(&fs) != NULL) {
581 			/* Duplicate name space not allowed */
582 			rw_wunlock(&tcp_function_lock);
583 			free(n, M_TCPFUNCTIONS);
584 			error = EALREADY;
585 			goto cleanup;
586 		}
587 		(void)strncpy(n->tf_name, names[i], TCP_FUNCTION_NAME_LEN_MAX);
588 		n->tf_name[TCP_FUNCTION_NAME_LEN_MAX - 1] = '\0';
589 		TAILQ_INSERT_TAIL(&t_functions, n, tf_next);
590 		rw_wunlock(&tcp_function_lock);
591 	}
592 	return(0);
593 
594 cleanup:
595 	/*
596 	 * Deregister the names we just added. Because registration failed
597 	 * for names[i], we don't need to deregister that name.
598 	 */
599 	*num_names = i;
600 	rw_wlock(&tcp_function_lock);
601 	while (--i >= 0) {
602 		TAILQ_FOREACH(n, &t_functions, tf_next) {
603 			if (!strncmp(n->tf_name, names[i],
604 			    TCP_FUNCTION_NAME_LEN_MAX)) {
605 				TAILQ_REMOVE(&t_functions, n, tf_next);
606 				n->tf_fb = NULL;
607 				free(n, M_TCPFUNCTIONS);
608 				break;
609 			}
610 		}
611 	}
612 	rw_wunlock(&tcp_function_lock);
613 	return (error);
614 }
615 
616 /*
617  * Register a TCP function block using the name provided in the name
618  * argument.
619  *
620  * Returns 0 on success, or an error code on failure.
621  */
622 int
623 register_tcp_functions_as_name(struct tcp_function_block *blk, const char *name,
624     int wait)
625 {
626 	const char *name_list[1];
627 	int num_names, rv;
628 
629 	num_names = 1;
630 	if (name != NULL)
631 		name_list[0] = name;
632 	else
633 		name_list[0] = blk->tfb_tcp_block_name;
634 	rv = register_tcp_functions_as_names(blk, wait, name_list, &num_names);
635 	return (rv);
636 }
637 
638 /*
639  * Register a TCP function block using the name defined in
640  * blk->tfb_tcp_block_name.
641  *
642  * Returns 0 on success, or an error code on failure.
643  */
644 int
645 register_tcp_functions(struct tcp_function_block *blk, int wait)
646 {
647 
648 	return (register_tcp_functions_as_name(blk, NULL, wait));
649 }
650 
651 int
652 deregister_tcp_functions(struct tcp_function_block *blk)
653 {
654 	struct tcp_function *f;
655 	int error=ENOENT;
656 
657 	if (strcmp(blk->tfb_tcp_block_name, "default") == 0) {
658 		/* You can't un-register the default */
659 		return (EPERM);
660 	}
661 	rw_wlock(&tcp_function_lock);
662 	if (blk == tcp_func_set_ptr) {
663 		/* You can't free the current default */
664 		rw_wunlock(&tcp_function_lock);
665 		return (EBUSY);
666 	}
667 	if (blk->tfb_refcnt) {
668 		/* Still tcb attached, mark it. */
669 		blk->tfb_flags |= TCP_FUNC_BEING_REMOVED;
670 		rw_wunlock(&tcp_function_lock);
671 		return (EBUSY);
672 	}
673 	while (find_tcp_fb_locked(blk, &f) != NULL) {
674 		/* Found */
675 		TAILQ_REMOVE(&t_functions, f, tf_next);
676 		f->tf_fb = NULL;
677 		free(f, M_TCPFUNCTIONS);
678 		error = 0;
679 	}
680 	rw_wunlock(&tcp_function_lock);
681 	return (error);
682 }
683 
684 void
685 tcp_init(void)
686 {
687 	const char *tcbhash_tuneable;
688 	int hashsize;
689 
690 	tcbhash_tuneable = "net.inet.tcp.tcbhashsize";
691 
692 #ifdef TCP_HHOOK
693 	if (hhook_head_register(HHOOK_TYPE_TCP, HHOOK_TCP_EST_IN,
694 	    &V_tcp_hhh[HHOOK_TCP_EST_IN], HHOOK_NOWAIT|HHOOK_HEADISINVNET) != 0)
695 		printf("%s: WARNING: unable to register helper hook\n", __func__);
696 	if (hhook_head_register(HHOOK_TYPE_TCP, HHOOK_TCP_EST_OUT,
697 	    &V_tcp_hhh[HHOOK_TCP_EST_OUT], HHOOK_NOWAIT|HHOOK_HEADISINVNET) != 0)
698 		printf("%s: WARNING: unable to register helper hook\n", __func__);
699 #endif
700 	hashsize = TCBHASHSIZE;
701 	TUNABLE_INT_FETCH(tcbhash_tuneable, &hashsize);
702 	if (hashsize == 0) {
703 		/*
704 		 * Auto tune the hash size based on maxsockets.
705 		 * A perfect hash would have a 1:1 mapping
706 		 * (hashsize = maxsockets) however it's been
707 		 * suggested that O(2) average is better.
708 		 */
709 		hashsize = maketcp_hashsize(maxsockets / 4);
710 		/*
711 		 * Our historical default is 512,
712 		 * do not autotune lower than this.
713 		 */
714 		if (hashsize < 512)
715 			hashsize = 512;
716 		if (bootverbose && IS_DEFAULT_VNET(curvnet))
717 			printf("%s: %s auto tuned to %d\n", __func__,
718 			    tcbhash_tuneable, hashsize);
719 	}
720 	/*
721 	 * We require a hashsize to be a power of two.
722 	 * Previously if it was not a power of two we would just reset it
723 	 * back to 512, which could be a nasty surprise if you did not notice
724 	 * the error message.
725 	 * Instead what we do is clip it to the closest power of two lower
726 	 * than the specified hash value.
727 	 */
728 	if (!powerof2(hashsize)) {
729 		int oldhashsize = hashsize;
730 
731 		hashsize = maketcp_hashsize(hashsize);
732 		/* prevent absurdly low value */
733 		if (hashsize < 16)
734 			hashsize = 16;
735 		printf("%s: WARNING: TCB hash size not a power of 2, "
736 		    "clipped from %d to %d.\n", __func__, oldhashsize,
737 		    hashsize);
738 	}
739 	in_pcbinfo_init(&V_tcbinfo, "tcp", &V_tcb, hashsize, hashsize,
740 	    "tcp_inpcb", tcp_inpcb_init, IPI_HASHFIELDS_4TUPLE);
741 
742 	/*
743 	 * These have to be type stable for the benefit of the timers.
744 	 */
745 	V_tcpcb_zone = uma_zcreate("tcpcb", sizeof(struct tcpcb_mem),
746 	    NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
747 	uma_zone_set_max(V_tcpcb_zone, maxsockets);
748 	uma_zone_set_warning(V_tcpcb_zone, "kern.ipc.maxsockets limit reached");
749 
750 	tcp_tw_init();
751 	syncache_init();
752 	tcp_hc_init();
753 
754 	TUNABLE_INT_FETCH("net.inet.tcp.sack.enable", &V_tcp_do_sack);
755 	V_sack_hole_zone = uma_zcreate("sackhole", sizeof(struct sackhole),
756 	    NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
757 
758 #ifdef TCP_RFC7413
759 	tcp_fastopen_init();
760 #endif
761 
762 	/* Skip initialization of globals for non-default instances. */
763 	if (!IS_DEFAULT_VNET(curvnet))
764 		return;
765 
766 	tcp_reass_global_init();
767 
768 	/* XXX virtualize those bellow? */
769 	tcp_delacktime = TCPTV_DELACK;
770 	tcp_keepinit = TCPTV_KEEP_INIT;
771 	tcp_keepidle = TCPTV_KEEP_IDLE;
772 	tcp_keepintvl = TCPTV_KEEPINTVL;
773 	tcp_maxpersistidle = TCPTV_KEEP_IDLE;
774 	tcp_msl = TCPTV_MSL;
775 	tcp_rexmit_min = TCPTV_MIN;
776 	if (tcp_rexmit_min < 1)
777 		tcp_rexmit_min = 1;
778 	tcp_persmin = TCPTV_PERSMIN;
779 	tcp_persmax = TCPTV_PERSMAX;
780 	tcp_rexmit_slop = TCPTV_CPU_VAR;
781 	tcp_finwait2_timeout = TCPTV_FINWAIT2_TIMEOUT;
782 	tcp_tcbhashsize = hashsize;
783 	/* Setup the tcp function block list */
784 	init_tcp_functions();
785 	register_tcp_functions(&tcp_def_funcblk, M_WAITOK);
786 
787 	if (tcp_soreceive_stream) {
788 #ifdef INET
789 		tcp_usrreqs.pru_soreceive = soreceive_stream;
790 #endif
791 #ifdef INET6
792 		tcp6_usrreqs.pru_soreceive = soreceive_stream;
793 #endif /* INET6 */
794 	}
795 
796 #ifdef INET6
797 #define TCP_MINPROTOHDR (sizeof(struct ip6_hdr) + sizeof(struct tcphdr))
798 #else /* INET6 */
799 #define TCP_MINPROTOHDR (sizeof(struct tcpiphdr))
800 #endif /* INET6 */
801 	if (max_protohdr < TCP_MINPROTOHDR)
802 		max_protohdr = TCP_MINPROTOHDR;
803 	if (max_linkhdr + TCP_MINPROTOHDR > MHLEN)
804 		panic("tcp_init");
805 #undef TCP_MINPROTOHDR
806 
807 	ISN_LOCK_INIT();
808 	EVENTHANDLER_REGISTER(shutdown_pre_sync, tcp_fini, NULL,
809 		SHUTDOWN_PRI_DEFAULT);
810 	EVENTHANDLER_REGISTER(maxsockets_change, tcp_zone_change, NULL,
811 		EVENTHANDLER_PRI_ANY);
812 #ifdef TCPPCAP
813 	tcp_pcap_init();
814 #endif
815 }
816 
817 #ifdef VIMAGE
818 static void
819 tcp_destroy(void *unused __unused)
820 {
821 	int n;
822 #ifdef TCP_HHOOK
823 	int error;
824 #endif
825 
826 	/*
827 	 * All our processes are gone, all our sockets should be cleaned
828 	 * up, which means, we should be past the tcp_discardcb() calls.
829 	 * Sleep to let all tcpcb timers really disappear and cleanup.
830 	 */
831 	for (;;) {
832 		INP_LIST_RLOCK(&V_tcbinfo);
833 		n = V_tcbinfo.ipi_count;
834 		INP_LIST_RUNLOCK(&V_tcbinfo);
835 		if (n == 0)
836 			break;
837 		pause("tcpdes", hz / 10);
838 	}
839 	tcp_hc_destroy();
840 	syncache_destroy();
841 	tcp_tw_destroy();
842 	in_pcbinfo_destroy(&V_tcbinfo);
843 	/* tcp_discardcb() clears the sack_holes up. */
844 	uma_zdestroy(V_sack_hole_zone);
845 	uma_zdestroy(V_tcpcb_zone);
846 
847 #ifdef TCP_RFC7413
848 	/*
849 	 * Cannot free the zone until all tcpcbs are released as we attach
850 	 * the allocations to them.
851 	 */
852 	tcp_fastopen_destroy();
853 #endif
854 
855 #ifdef TCP_HHOOK
856 	error = hhook_head_deregister(V_tcp_hhh[HHOOK_TCP_EST_IN]);
857 	if (error != 0) {
858 		printf("%s: WARNING: unable to deregister helper hook "
859 		    "type=%d, id=%d: error %d returned\n", __func__,
860 		    HHOOK_TYPE_TCP, HHOOK_TCP_EST_IN, error);
861 	}
862 	error = hhook_head_deregister(V_tcp_hhh[HHOOK_TCP_EST_OUT]);
863 	if (error != 0) {
864 		printf("%s: WARNING: unable to deregister helper hook "
865 		    "type=%d, id=%d: error %d returned\n", __func__,
866 		    HHOOK_TYPE_TCP, HHOOK_TCP_EST_OUT, error);
867 	}
868 #endif
869 }
870 VNET_SYSUNINIT(tcp, SI_SUB_PROTO_DOMAIN, SI_ORDER_FOURTH, tcp_destroy, NULL);
871 #endif
872 
873 void
874 tcp_fini(void *xtp)
875 {
876 
877 }
878 
879 /*
880  * Fill in the IP and TCP headers for an outgoing packet, given the tcpcb.
881  * tcp_template used to store this data in mbufs, but we now recopy it out
882  * of the tcpcb each time to conserve mbufs.
883  */
884 void
885 tcpip_fillheaders(struct inpcb *inp, void *ip_ptr, void *tcp_ptr)
886 {
887 	struct tcphdr *th = (struct tcphdr *)tcp_ptr;
888 
889 	INP_WLOCK_ASSERT(inp);
890 
891 #ifdef INET6
892 	if ((inp->inp_vflag & INP_IPV6) != 0) {
893 		struct ip6_hdr *ip6;
894 
895 		ip6 = (struct ip6_hdr *)ip_ptr;
896 		ip6->ip6_flow = (ip6->ip6_flow & ~IPV6_FLOWINFO_MASK) |
897 			(inp->inp_flow & IPV6_FLOWINFO_MASK);
898 		ip6->ip6_vfc = (ip6->ip6_vfc & ~IPV6_VERSION_MASK) |
899 			(IPV6_VERSION & IPV6_VERSION_MASK);
900 		ip6->ip6_nxt = IPPROTO_TCP;
901 		ip6->ip6_plen = htons(sizeof(struct tcphdr));
902 		ip6->ip6_src = inp->in6p_laddr;
903 		ip6->ip6_dst = inp->in6p_faddr;
904 	}
905 #endif /* INET6 */
906 #if defined(INET6) && defined(INET)
907 	else
908 #endif
909 #ifdef INET
910 	{
911 		struct ip *ip;
912 
913 		ip = (struct ip *)ip_ptr;
914 		ip->ip_v = IPVERSION;
915 		ip->ip_hl = 5;
916 		ip->ip_tos = inp->inp_ip_tos;
917 		ip->ip_len = 0;
918 		ip->ip_id = 0;
919 		ip->ip_off = 0;
920 		ip->ip_ttl = inp->inp_ip_ttl;
921 		ip->ip_sum = 0;
922 		ip->ip_p = IPPROTO_TCP;
923 		ip->ip_src = inp->inp_laddr;
924 		ip->ip_dst = inp->inp_faddr;
925 	}
926 #endif /* INET */
927 	th->th_sport = inp->inp_lport;
928 	th->th_dport = inp->inp_fport;
929 	th->th_seq = 0;
930 	th->th_ack = 0;
931 	th->th_x2 = 0;
932 	th->th_off = 5;
933 	th->th_flags = 0;
934 	th->th_win = 0;
935 	th->th_urp = 0;
936 	th->th_sum = 0;		/* in_pseudo() is called later for ipv4 */
937 }
938 
939 /*
940  * Create template to be used to send tcp packets on a connection.
941  * Allocates an mbuf and fills in a skeletal tcp/ip header.  The only
942  * use for this function is in keepalives, which use tcp_respond.
943  */
944 struct tcptemp *
945 tcpip_maketemplate(struct inpcb *inp)
946 {
947 	struct tcptemp *t;
948 
949 	t = malloc(sizeof(*t), M_TEMP, M_NOWAIT);
950 	if (t == NULL)
951 		return (NULL);
952 	tcpip_fillheaders(inp, (void *)&t->tt_ipgen, (void *)&t->tt_t);
953 	return (t);
954 }
955 
956 /*
957  * Send a single message to the TCP at address specified by
958  * the given TCP/IP header.  If m == NULL, then we make a copy
959  * of the tcpiphdr at th and send directly to the addressed host.
960  * This is used to force keep alive messages out using the TCP
961  * template for a connection.  If flags are given then we send
962  * a message back to the TCP which originated the segment th,
963  * and discard the mbuf containing it and any other attached mbufs.
964  *
965  * In any case the ack and sequence number of the transmitted
966  * segment are as specified by the parameters.
967  *
968  * NOTE: If m != NULL, then th must point to *inside* the mbuf.
969  */
970 void
971 tcp_respond(struct tcpcb *tp, void *ipgen, struct tcphdr *th, struct mbuf *m,
972     tcp_seq ack, tcp_seq seq, int flags)
973 {
974 	struct tcpopt to;
975 	struct inpcb *inp;
976 	struct ip *ip;
977 	struct mbuf *optm;
978 	struct tcphdr *nth;
979 	u_char *optp;
980 #ifdef INET6
981 	struct ip6_hdr *ip6;
982 	int isipv6;
983 #endif /* INET6 */
984 	int optlen, tlen, win;
985 	bool incl_opts;
986 
987 	KASSERT(tp != NULL || m != NULL, ("tcp_respond: tp and m both NULL"));
988 
989 #ifdef INET6
990 	isipv6 = ((struct ip *)ipgen)->ip_v == (IPV6_VERSION >> 4);
991 	ip6 = ipgen;
992 #endif /* INET6 */
993 	ip = ipgen;
994 
995 	if (tp != NULL) {
996 		inp = tp->t_inpcb;
997 		KASSERT(inp != NULL, ("tcp control block w/o inpcb"));
998 		INP_WLOCK_ASSERT(inp);
999 	} else
1000 		inp = NULL;
1001 
1002 	incl_opts = false;
1003 	win = 0;
1004 	if (tp != NULL) {
1005 		if (!(flags & TH_RST)) {
1006 			win = sbspace(&inp->inp_socket->so_rcv);
1007 			if (win > TCP_MAXWIN << tp->rcv_scale)
1008 				win = TCP_MAXWIN << tp->rcv_scale;
1009 		}
1010 		if ((tp->t_flags & TF_NOOPT) == 0)
1011 			incl_opts = true;
1012 	}
1013 	if (m == NULL) {
1014 		m = m_gethdr(M_NOWAIT, MT_DATA);
1015 		if (m == NULL)
1016 			return;
1017 		m->m_data += max_linkhdr;
1018 #ifdef INET6
1019 		if (isipv6) {
1020 			bcopy((caddr_t)ip6, mtod(m, caddr_t),
1021 			      sizeof(struct ip6_hdr));
1022 			ip6 = mtod(m, struct ip6_hdr *);
1023 			nth = (struct tcphdr *)(ip6 + 1);
1024 		} else
1025 #endif /* INET6 */
1026 		{
1027 			bcopy((caddr_t)ip, mtod(m, caddr_t), sizeof(struct ip));
1028 			ip = mtod(m, struct ip *);
1029 			nth = (struct tcphdr *)(ip + 1);
1030 		}
1031 		bcopy((caddr_t)th, (caddr_t)nth, sizeof(struct tcphdr));
1032 		flags = TH_ACK;
1033 	} else if (!M_WRITABLE(m)) {
1034 		struct mbuf *n;
1035 
1036 		/* Can't reuse 'm', allocate a new mbuf. */
1037 		n = m_gethdr(M_NOWAIT, MT_DATA);
1038 		if (n == NULL) {
1039 			m_freem(m);
1040 			return;
1041 		}
1042 
1043 		if (!m_dup_pkthdr(n, m, M_NOWAIT)) {
1044 			m_freem(m);
1045 			m_freem(n);
1046 			return;
1047 		}
1048 
1049 		n->m_data += max_linkhdr;
1050 		/* m_len is set later */
1051 #define xchg(a,b,type) { type t; t=a; a=b; b=t; }
1052 #ifdef INET6
1053 		if (isipv6) {
1054 			bcopy((caddr_t)ip6, mtod(n, caddr_t),
1055 			      sizeof(struct ip6_hdr));
1056 			ip6 = mtod(n, struct ip6_hdr *);
1057 			xchg(ip6->ip6_dst, ip6->ip6_src, struct in6_addr);
1058 			nth = (struct tcphdr *)(ip6 + 1);
1059 		} else
1060 #endif /* INET6 */
1061 		{
1062 			bcopy((caddr_t)ip, mtod(n, caddr_t), sizeof(struct ip));
1063 			ip = mtod(n, struct ip *);
1064 			xchg(ip->ip_dst.s_addr, ip->ip_src.s_addr, uint32_t);
1065 			nth = (struct tcphdr *)(ip + 1);
1066 		}
1067 		bcopy((caddr_t)th, (caddr_t)nth, sizeof(struct tcphdr));
1068 		xchg(nth->th_dport, nth->th_sport, uint16_t);
1069 		th = nth;
1070 		m_freem(m);
1071 		m = n;
1072 	} else {
1073 		/*
1074 		 *  reuse the mbuf.
1075 		 * XXX MRT We inherit the FIB, which is lucky.
1076 		 */
1077 		m_freem(m->m_next);
1078 		m->m_next = NULL;
1079 		m->m_data = (caddr_t)ipgen;
1080 		/* m_len is set later */
1081 #ifdef INET6
1082 		if (isipv6) {
1083 			xchg(ip6->ip6_dst, ip6->ip6_src, struct in6_addr);
1084 			nth = (struct tcphdr *)(ip6 + 1);
1085 		} else
1086 #endif /* INET6 */
1087 		{
1088 			xchg(ip->ip_dst.s_addr, ip->ip_src.s_addr, uint32_t);
1089 			nth = (struct tcphdr *)(ip + 1);
1090 		}
1091 		if (th != nth) {
1092 			/*
1093 			 * this is usually a case when an extension header
1094 			 * exists between the IPv6 header and the
1095 			 * TCP header.
1096 			 */
1097 			nth->th_sport = th->th_sport;
1098 			nth->th_dport = th->th_dport;
1099 		}
1100 		xchg(nth->th_dport, nth->th_sport, uint16_t);
1101 #undef xchg
1102 	}
1103 	tlen = 0;
1104 #ifdef INET6
1105 	if (isipv6)
1106 		tlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr);
1107 #endif
1108 #if defined(INET) && defined(INET6)
1109 	else
1110 #endif
1111 #ifdef INET
1112 		tlen = sizeof (struct tcpiphdr);
1113 #endif
1114 #ifdef INVARIANTS
1115 	m->m_len = 0;
1116 	KASSERT(M_TRAILINGSPACE(m) >= tlen,
1117 	    ("Not enough trailing space for message (m=%p, need=%d, have=%ld)",
1118 	    m, tlen, (long)M_TRAILINGSPACE(m)));
1119 #endif
1120 	m->m_len = tlen;
1121 	to.to_flags = 0;
1122 	if (incl_opts) {
1123 		/* Make sure we have room. */
1124 		if (M_TRAILINGSPACE(m) < TCP_MAXOLEN) {
1125 			m->m_next = m_get(M_NOWAIT, MT_DATA);
1126 			if (m->m_next) {
1127 				optp = mtod(m->m_next, u_char *);
1128 				optm = m->m_next;
1129 			} else
1130 				incl_opts = false;
1131 		} else {
1132 			optp = (u_char *) (nth + 1);
1133 			optm = m;
1134 		}
1135 	}
1136 	if (incl_opts) {
1137 		/* Timestamps. */
1138 		if (tp->t_flags & TF_RCVD_TSTMP) {
1139 			to.to_tsval = tcp_ts_getticks() + tp->ts_offset;
1140 			to.to_tsecr = tp->ts_recent;
1141 			to.to_flags |= TOF_TS;
1142 		}
1143 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1144 		/* TCP-MD5 (RFC2385). */
1145 		if (tp->t_flags & TF_SIGNATURE)
1146 			to.to_flags |= TOF_SIGNATURE;
1147 #endif
1148 		/* Add the options. */
1149 		tlen += optlen = tcp_addoptions(&to, optp);
1150 
1151 		/* Update m_len in the correct mbuf. */
1152 		optm->m_len += optlen;
1153 	} else
1154 		optlen = 0;
1155 #ifdef INET6
1156 	if (isipv6) {
1157 		ip6->ip6_flow = 0;
1158 		ip6->ip6_vfc = IPV6_VERSION;
1159 		ip6->ip6_nxt = IPPROTO_TCP;
1160 		ip6->ip6_plen = htons(tlen - sizeof(*ip6));
1161 	}
1162 #endif
1163 #if defined(INET) && defined(INET6)
1164 	else
1165 #endif
1166 #ifdef INET
1167 	{
1168 		ip->ip_len = htons(tlen);
1169 		ip->ip_ttl = V_ip_defttl;
1170 		if (V_path_mtu_discovery)
1171 			ip->ip_off |= htons(IP_DF);
1172 	}
1173 #endif
1174 	m->m_pkthdr.len = tlen;
1175 	m->m_pkthdr.rcvif = NULL;
1176 #ifdef MAC
1177 	if (inp != NULL) {
1178 		/*
1179 		 * Packet is associated with a socket, so allow the
1180 		 * label of the response to reflect the socket label.
1181 		 */
1182 		INP_WLOCK_ASSERT(inp);
1183 		mac_inpcb_create_mbuf(inp, m);
1184 	} else {
1185 		/*
1186 		 * Packet is not associated with a socket, so possibly
1187 		 * update the label in place.
1188 		 */
1189 		mac_netinet_tcp_reply(m);
1190 	}
1191 #endif
1192 	nth->th_seq = htonl(seq);
1193 	nth->th_ack = htonl(ack);
1194 	nth->th_x2 = 0;
1195 	nth->th_off = (sizeof (struct tcphdr) + optlen) >> 2;
1196 	nth->th_flags = flags;
1197 	if (tp != NULL)
1198 		nth->th_win = htons((u_short) (win >> tp->rcv_scale));
1199 	else
1200 		nth->th_win = htons((u_short)win);
1201 	nth->th_urp = 0;
1202 
1203 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1204 	if (to.to_flags & TOF_SIGNATURE) {
1205 		if (!TCPMD5_ENABLED() ||
1206 		    TCPMD5_OUTPUT(m, nth, to.to_signature) != 0) {
1207 			m_freem(m);
1208 			return;
1209 		}
1210 	}
1211 #endif
1212 
1213 	m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1214 #ifdef INET6
1215 	if (isipv6) {
1216 		m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
1217 		nth->th_sum = in6_cksum_pseudo(ip6,
1218 		    tlen - sizeof(struct ip6_hdr), IPPROTO_TCP, 0);
1219 		ip6->ip6_hlim = in6_selecthlim(tp != NULL ? tp->t_inpcb :
1220 		    NULL, NULL);
1221 	}
1222 #endif /* INET6 */
1223 #if defined(INET6) && defined(INET)
1224 	else
1225 #endif
1226 #ifdef INET
1227 	{
1228 		m->m_pkthdr.csum_flags = CSUM_TCP;
1229 		nth->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1230 		    htons((u_short)(tlen - sizeof(struct ip) + ip->ip_p)));
1231 	}
1232 #endif /* INET */
1233 #ifdef TCPDEBUG
1234 	if (tp == NULL || (inp->inp_socket->so_options & SO_DEBUG))
1235 		tcp_trace(TA_OUTPUT, 0, tp, mtod(m, void *), th, 0);
1236 #endif
1237 	TCP_PROBE3(debug__output, tp, th, m);
1238 	if (flags & TH_RST)
1239 		TCP_PROBE5(accept__refused, NULL, NULL, m, tp, nth);
1240 
1241 #ifdef INET6
1242 	if (isipv6) {
1243 		TCP_PROBE5(send, NULL, tp, ip6, tp, nth);
1244 		(void)ip6_output(m, NULL, NULL, 0, NULL, NULL, inp);
1245 	}
1246 #endif /* INET6 */
1247 #if defined(INET) && defined(INET6)
1248 	else
1249 #endif
1250 #ifdef INET
1251 	{
1252 		TCP_PROBE5(send, NULL, tp, ip, tp, nth);
1253 		(void)ip_output(m, NULL, NULL, 0, NULL, inp);
1254 	}
1255 #endif
1256 }
1257 
1258 /*
1259  * Create a new TCP control block, making an
1260  * empty reassembly queue and hooking it to the argument
1261  * protocol control block.  The `inp' parameter must have
1262  * come from the zone allocator set up in tcp_init().
1263  */
1264 struct tcpcb *
1265 tcp_newtcpcb(struct inpcb *inp)
1266 {
1267 	struct tcpcb_mem *tm;
1268 	struct tcpcb *tp;
1269 #ifdef INET6
1270 	int isipv6 = (inp->inp_vflag & INP_IPV6) != 0;
1271 #endif /* INET6 */
1272 
1273 	tm = uma_zalloc(V_tcpcb_zone, M_NOWAIT | M_ZERO);
1274 	if (tm == NULL)
1275 		return (NULL);
1276 	tp = &tm->tcb;
1277 
1278 	/* Initialise cc_var struct for this tcpcb. */
1279 	tp->ccv = &tm->ccv;
1280 	tp->ccv->type = IPPROTO_TCP;
1281 	tp->ccv->ccvc.tcp = tp;
1282 	rw_rlock(&tcp_function_lock);
1283 	tp->t_fb = tcp_func_set_ptr;
1284 	refcount_acquire(&tp->t_fb->tfb_refcnt);
1285 	rw_runlock(&tcp_function_lock);
1286 	/*
1287 	 * Use the current system default CC algorithm.
1288 	 */
1289 	CC_LIST_RLOCK();
1290 	KASSERT(!STAILQ_EMPTY(&cc_list), ("cc_list is empty!"));
1291 	CC_ALGO(tp) = CC_DEFAULT();
1292 	CC_LIST_RUNLOCK();
1293 
1294 	if (CC_ALGO(tp)->cb_init != NULL)
1295 		if (CC_ALGO(tp)->cb_init(tp->ccv) > 0) {
1296 			if (tp->t_fb->tfb_tcp_fb_fini)
1297 				(*tp->t_fb->tfb_tcp_fb_fini)(tp, 1);
1298 			refcount_release(&tp->t_fb->tfb_refcnt);
1299 			uma_zfree(V_tcpcb_zone, tm);
1300 			return (NULL);
1301 		}
1302 
1303 #ifdef TCP_HHOOK
1304 	tp->osd = &tm->osd;
1305 	if (khelp_init_osd(HELPER_CLASS_TCP, tp->osd)) {
1306 		if (tp->t_fb->tfb_tcp_fb_fini)
1307 			(*tp->t_fb->tfb_tcp_fb_fini)(tp, 1);
1308 		refcount_release(&tp->t_fb->tfb_refcnt);
1309 		uma_zfree(V_tcpcb_zone, tm);
1310 		return (NULL);
1311 	}
1312 #endif
1313 
1314 #ifdef VIMAGE
1315 	tp->t_vnet = inp->inp_vnet;
1316 #endif
1317 	tp->t_timers = &tm->tt;
1318 	/*	LIST_INIT(&tp->t_segq); */	/* XXX covered by M_ZERO */
1319 	tp->t_maxseg =
1320 #ifdef INET6
1321 		isipv6 ? V_tcp_v6mssdflt :
1322 #endif /* INET6 */
1323 		V_tcp_mssdflt;
1324 
1325 	/* Set up our timeouts. */
1326 	callout_init(&tp->t_timers->tt_rexmt, 1);
1327 	callout_init(&tp->t_timers->tt_persist, 1);
1328 	callout_init(&tp->t_timers->tt_keep, 1);
1329 	callout_init(&tp->t_timers->tt_2msl, 1);
1330 	callout_init(&tp->t_timers->tt_delack, 1);
1331 
1332 	if (V_tcp_do_rfc1323)
1333 		tp->t_flags = (TF_REQ_SCALE|TF_REQ_TSTMP);
1334 	if (V_tcp_do_sack)
1335 		tp->t_flags |= TF_SACK_PERMIT;
1336 	TAILQ_INIT(&tp->snd_holes);
1337 	/*
1338 	 * The tcpcb will hold a reference on its inpcb until tcp_discardcb()
1339 	 * is called.
1340 	 */
1341 	in_pcbref(inp);	/* Reference for tcpcb */
1342 	tp->t_inpcb = inp;
1343 
1344 	/*
1345 	 * Init srtt to TCPTV_SRTTBASE (0), so we can tell that we have no
1346 	 * rtt estimate.  Set rttvar so that srtt + 4 * rttvar gives
1347 	 * reasonable initial retransmit time.
1348 	 */
1349 	tp->t_srtt = TCPTV_SRTTBASE;
1350 	tp->t_rttvar = ((TCPTV_RTOBASE - TCPTV_SRTTBASE) << TCP_RTTVAR_SHIFT) / 4;
1351 	tp->t_rttmin = tcp_rexmit_min;
1352 	tp->t_rxtcur = TCPTV_RTOBASE;
1353 	tp->snd_cwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT;
1354 	tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT;
1355 	tp->t_rcvtime = ticks;
1356 	/*
1357 	 * IPv4 TTL initialization is necessary for an IPv6 socket as well,
1358 	 * because the socket may be bound to an IPv6 wildcard address,
1359 	 * which may match an IPv4-mapped IPv6 address.
1360 	 */
1361 	inp->inp_ip_ttl = V_ip_defttl;
1362 	inp->inp_ppcb = tp;
1363 #ifdef TCPPCAP
1364 	/*
1365 	 * Init the TCP PCAP queues.
1366 	 */
1367 	tcp_pcap_tcpcb_init(tp);
1368 #endif
1369 	if (tp->t_fb->tfb_tcp_fb_init) {
1370 		(*tp->t_fb->tfb_tcp_fb_init)(tp);
1371 	}
1372 	return (tp);		/* XXX */
1373 }
1374 
1375 /*
1376  * Switch the congestion control algorithm back to NewReno for any active
1377  * control blocks using an algorithm which is about to go away.
1378  * This ensures the CC framework can allow the unload to proceed without leaving
1379  * any dangling pointers which would trigger a panic.
1380  * Returning non-zero would inform the CC framework that something went wrong
1381  * and it would be unsafe to allow the unload to proceed. However, there is no
1382  * way for this to occur with this implementation so we always return zero.
1383  */
1384 int
1385 tcp_ccalgounload(struct cc_algo *unload_algo)
1386 {
1387 	struct cc_algo *tmpalgo;
1388 	struct inpcb *inp;
1389 	struct tcpcb *tp;
1390 	VNET_ITERATOR_DECL(vnet_iter);
1391 
1392 	/*
1393 	 * Check all active control blocks across all network stacks and change
1394 	 * any that are using "unload_algo" back to NewReno. If "unload_algo"
1395 	 * requires cleanup code to be run, call it.
1396 	 */
1397 	VNET_LIST_RLOCK();
1398 	VNET_FOREACH(vnet_iter) {
1399 		CURVNET_SET(vnet_iter);
1400 		INP_INFO_WLOCK(&V_tcbinfo);
1401 		/*
1402 		 * New connections already part way through being initialised
1403 		 * with the CC algo we're removing will not race with this code
1404 		 * because the INP_INFO_WLOCK is held during initialisation. We
1405 		 * therefore don't enter the loop below until the connection
1406 		 * list has stabilised.
1407 		 */
1408 		LIST_FOREACH(inp, &V_tcb, inp_list) {
1409 			INP_WLOCK(inp);
1410 			/* Important to skip tcptw structs. */
1411 			if (!(inp->inp_flags & INP_TIMEWAIT) &&
1412 			    (tp = intotcpcb(inp)) != NULL) {
1413 				/*
1414 				 * By holding INP_WLOCK here, we are assured
1415 				 * that the connection is not currently
1416 				 * executing inside the CC module's functions
1417 				 * i.e. it is safe to make the switch back to
1418 				 * NewReno.
1419 				 */
1420 				if (CC_ALGO(tp) == unload_algo) {
1421 					tmpalgo = CC_ALGO(tp);
1422 					/* NewReno does not require any init. */
1423 					CC_ALGO(tp) = &newreno_cc_algo;
1424 					if (tmpalgo->cb_destroy != NULL)
1425 						tmpalgo->cb_destroy(tp->ccv);
1426 				}
1427 			}
1428 			INP_WUNLOCK(inp);
1429 		}
1430 		INP_INFO_WUNLOCK(&V_tcbinfo);
1431 		CURVNET_RESTORE();
1432 	}
1433 	VNET_LIST_RUNLOCK();
1434 
1435 	return (0);
1436 }
1437 
1438 /*
1439  * Drop a TCP connection, reporting
1440  * the specified error.  If connection is synchronized,
1441  * then send a RST to peer.
1442  */
1443 struct tcpcb *
1444 tcp_drop(struct tcpcb *tp, int errno)
1445 {
1446 	struct socket *so = tp->t_inpcb->inp_socket;
1447 
1448 	INP_INFO_LOCK_ASSERT(&V_tcbinfo);
1449 	INP_WLOCK_ASSERT(tp->t_inpcb);
1450 
1451 	if (TCPS_HAVERCVDSYN(tp->t_state)) {
1452 		tcp_state_change(tp, TCPS_CLOSED);
1453 		(void) tp->t_fb->tfb_tcp_output(tp);
1454 		TCPSTAT_INC(tcps_drops);
1455 	} else
1456 		TCPSTAT_INC(tcps_conndrops);
1457 	if (errno == ETIMEDOUT && tp->t_softerror)
1458 		errno = tp->t_softerror;
1459 	so->so_error = errno;
1460 	return (tcp_close(tp));
1461 }
1462 
1463 void
1464 tcp_discardcb(struct tcpcb *tp)
1465 {
1466 	struct inpcb *inp = tp->t_inpcb;
1467 	struct socket *so = inp->inp_socket;
1468 #ifdef INET6
1469 	int isipv6 = (inp->inp_vflag & INP_IPV6) != 0;
1470 #endif /* INET6 */
1471 	int released;
1472 
1473 	INP_WLOCK_ASSERT(inp);
1474 
1475 	/*
1476 	 * Make sure that all of our timers are stopped before we delete the
1477 	 * PCB.
1478 	 *
1479 	 * If stopping a timer fails, we schedule a discard function in same
1480 	 * callout, and the last discard function called will take care of
1481 	 * deleting the tcpcb.
1482 	 */
1483 	tp->t_timers->tt_draincnt = 0;
1484 	tcp_timer_stop(tp, TT_REXMT);
1485 	tcp_timer_stop(tp, TT_PERSIST);
1486 	tcp_timer_stop(tp, TT_KEEP);
1487 	tcp_timer_stop(tp, TT_2MSL);
1488 	tcp_timer_stop(tp, TT_DELACK);
1489 	if (tp->t_fb->tfb_tcp_timer_stop_all) {
1490 		/*
1491 		 * Call the stop-all function of the methods,
1492 		 * this function should call the tcp_timer_stop()
1493 		 * method with each of the function specific timeouts.
1494 		 * That stop will be called via the tfb_tcp_timer_stop()
1495 		 * which should use the async drain function of the
1496 		 * callout system (see tcp_var.h).
1497 		 */
1498 		tp->t_fb->tfb_tcp_timer_stop_all(tp);
1499 	}
1500 
1501 	/*
1502 	 * If we got enough samples through the srtt filter,
1503 	 * save the rtt and rttvar in the routing entry.
1504 	 * 'Enough' is arbitrarily defined as 4 rtt samples.
1505 	 * 4 samples is enough for the srtt filter to converge
1506 	 * to within enough % of the correct value; fewer samples
1507 	 * and we could save a bogus rtt. The danger is not high
1508 	 * as tcp quickly recovers from everything.
1509 	 * XXX: Works very well but needs some more statistics!
1510 	 */
1511 	if (tp->t_rttupdated >= 4) {
1512 		struct hc_metrics_lite metrics;
1513 		uint32_t ssthresh;
1514 
1515 		bzero(&metrics, sizeof(metrics));
1516 		/*
1517 		 * Update the ssthresh always when the conditions below
1518 		 * are satisfied. This gives us better new start value
1519 		 * for the congestion avoidance for new connections.
1520 		 * ssthresh is only set if packet loss occurred on a session.
1521 		 *
1522 		 * XXXRW: 'so' may be NULL here, and/or socket buffer may be
1523 		 * being torn down.  Ideally this code would not use 'so'.
1524 		 */
1525 		ssthresh = tp->snd_ssthresh;
1526 		if (ssthresh != 0 && ssthresh < so->so_snd.sb_hiwat / 2) {
1527 			/*
1528 			 * convert the limit from user data bytes to
1529 			 * packets then to packet data bytes.
1530 			 */
1531 			ssthresh = (ssthresh + tp->t_maxseg / 2) / tp->t_maxseg;
1532 			if (ssthresh < 2)
1533 				ssthresh = 2;
1534 			ssthresh *= (tp->t_maxseg +
1535 #ifdef INET6
1536 			    (isipv6 ? sizeof (struct ip6_hdr) +
1537 				sizeof (struct tcphdr) :
1538 #endif
1539 				sizeof (struct tcpiphdr)
1540 #ifdef INET6
1541 			    )
1542 #endif
1543 			    );
1544 		} else
1545 			ssthresh = 0;
1546 		metrics.rmx_ssthresh = ssthresh;
1547 
1548 		metrics.rmx_rtt = tp->t_srtt;
1549 		metrics.rmx_rttvar = tp->t_rttvar;
1550 		metrics.rmx_cwnd = tp->snd_cwnd;
1551 		metrics.rmx_sendpipe = 0;
1552 		metrics.rmx_recvpipe = 0;
1553 
1554 		tcp_hc_update(&inp->inp_inc, &metrics);
1555 	}
1556 
1557 	/* free the reassembly queue, if any */
1558 	tcp_reass_flush(tp);
1559 
1560 #ifdef TCP_OFFLOAD
1561 	/* Disconnect offload device, if any. */
1562 	if (tp->t_flags & TF_TOE)
1563 		tcp_offload_detach(tp);
1564 #endif
1565 
1566 	tcp_free_sackholes(tp);
1567 
1568 #ifdef TCPPCAP
1569 	/* Free the TCP PCAP queues. */
1570 	tcp_pcap_drain(&(tp->t_inpkts));
1571 	tcp_pcap_drain(&(tp->t_outpkts));
1572 #endif
1573 
1574 	/* Allow the CC algorithm to clean up after itself. */
1575 	if (CC_ALGO(tp)->cb_destroy != NULL)
1576 		CC_ALGO(tp)->cb_destroy(tp->ccv);
1577 
1578 #ifdef TCP_HHOOK
1579 	khelp_destroy_osd(tp->osd);
1580 #endif
1581 
1582 	CC_ALGO(tp) = NULL;
1583 	inp->inp_ppcb = NULL;
1584 	if (tp->t_timers->tt_draincnt == 0) {
1585 		/* We own the last reference on tcpcb, let's free it. */
1586 		TCPSTATES_DEC(tp->t_state);
1587 		if (tp->t_fb->tfb_tcp_fb_fini)
1588 			(*tp->t_fb->tfb_tcp_fb_fini)(tp, 1);
1589 		refcount_release(&tp->t_fb->tfb_refcnt);
1590 		tp->t_inpcb = NULL;
1591 		uma_zfree(V_tcpcb_zone, tp);
1592 		released = in_pcbrele_wlocked(inp);
1593 		KASSERT(!released, ("%s: inp %p should not have been released "
1594 			"here", __func__, inp));
1595 	}
1596 }
1597 
1598 void
1599 tcp_timer_discard(void *ptp)
1600 {
1601 	struct inpcb *inp;
1602 	struct tcpcb *tp;
1603 
1604 	tp = (struct tcpcb *)ptp;
1605 	CURVNET_SET(tp->t_vnet);
1606 	INP_INFO_RLOCK(&V_tcbinfo);
1607 	inp = tp->t_inpcb;
1608 	KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL",
1609 		__func__, tp));
1610 	INP_WLOCK(inp);
1611 	KASSERT((tp->t_timers->tt_flags & TT_STOPPED) != 0,
1612 		("%s: tcpcb has to be stopped here", __func__));
1613 	tp->t_timers->tt_draincnt--;
1614 	if (tp->t_timers->tt_draincnt == 0) {
1615 		/* We own the last reference on this tcpcb, let's free it. */
1616 		TCPSTATES_DEC(tp->t_state);
1617 		if (tp->t_fb->tfb_tcp_fb_fini)
1618 			(*tp->t_fb->tfb_tcp_fb_fini)(tp, 1);
1619 		refcount_release(&tp->t_fb->tfb_refcnt);
1620 		tp->t_inpcb = NULL;
1621 		uma_zfree(V_tcpcb_zone, tp);
1622 		if (in_pcbrele_wlocked(inp)) {
1623 			INP_INFO_RUNLOCK(&V_tcbinfo);
1624 			CURVNET_RESTORE();
1625 			return;
1626 		}
1627 	}
1628 	INP_WUNLOCK(inp);
1629 	INP_INFO_RUNLOCK(&V_tcbinfo);
1630 	CURVNET_RESTORE();
1631 }
1632 
1633 /*
1634  * Attempt to close a TCP control block, marking it as dropped, and freeing
1635  * the socket if we hold the only reference.
1636  */
1637 struct tcpcb *
1638 tcp_close(struct tcpcb *tp)
1639 {
1640 	struct inpcb *inp = tp->t_inpcb;
1641 	struct socket *so;
1642 
1643 	INP_INFO_LOCK_ASSERT(&V_tcbinfo);
1644 	INP_WLOCK_ASSERT(inp);
1645 
1646 #ifdef TCP_OFFLOAD
1647 	if (tp->t_state == TCPS_LISTEN)
1648 		tcp_offload_listen_stop(tp);
1649 #endif
1650 #ifdef TCP_RFC7413
1651 	/*
1652 	 * This releases the TFO pending counter resource for TFO listen
1653 	 * sockets as well as passively-created TFO sockets that transition
1654 	 * from SYN_RECEIVED to CLOSED.
1655 	 */
1656 	if (tp->t_tfo_pending) {
1657 		tcp_fastopen_decrement_counter(tp->t_tfo_pending);
1658 		tp->t_tfo_pending = NULL;
1659 	}
1660 #endif
1661 	in_pcbdrop(inp);
1662 	TCPSTAT_INC(tcps_closed);
1663 	if (tp->t_state != TCPS_CLOSED)
1664 		tcp_state_change(tp, TCPS_CLOSED);
1665 	KASSERT(inp->inp_socket != NULL, ("tcp_close: inp_socket NULL"));
1666 	so = inp->inp_socket;
1667 	soisdisconnected(so);
1668 	if (inp->inp_flags & INP_SOCKREF) {
1669 		KASSERT(so->so_state & SS_PROTOREF,
1670 		    ("tcp_close: !SS_PROTOREF"));
1671 		inp->inp_flags &= ~INP_SOCKREF;
1672 		INP_WUNLOCK(inp);
1673 		SOCK_LOCK(so);
1674 		so->so_state &= ~SS_PROTOREF;
1675 		sofree(so);
1676 		return (NULL);
1677 	}
1678 	return (tp);
1679 }
1680 
1681 void
1682 tcp_drain(void)
1683 {
1684 	VNET_ITERATOR_DECL(vnet_iter);
1685 
1686 	if (!do_tcpdrain)
1687 		return;
1688 
1689 	VNET_LIST_RLOCK_NOSLEEP();
1690 	VNET_FOREACH(vnet_iter) {
1691 		CURVNET_SET(vnet_iter);
1692 		struct inpcb *inpb;
1693 		struct tcpcb *tcpb;
1694 
1695 	/*
1696 	 * Walk the tcpbs, if existing, and flush the reassembly queue,
1697 	 * if there is one...
1698 	 * XXX: The "Net/3" implementation doesn't imply that the TCP
1699 	 *      reassembly queue should be flushed, but in a situation
1700 	 *	where we're really low on mbufs, this is potentially
1701 	 *	useful.
1702 	 */
1703 		INP_INFO_WLOCK(&V_tcbinfo);
1704 		LIST_FOREACH(inpb, V_tcbinfo.ipi_listhead, inp_list) {
1705 			if (inpb->inp_flags & INP_TIMEWAIT)
1706 				continue;
1707 			INP_WLOCK(inpb);
1708 			if ((tcpb = intotcpcb(inpb)) != NULL) {
1709 				tcp_reass_flush(tcpb);
1710 				tcp_clean_sackreport(tcpb);
1711 #ifdef TCPPCAP
1712 				if (tcp_pcap_aggressive_free) {
1713 					/* Free the TCP PCAP queues. */
1714 					tcp_pcap_drain(&(tcpb->t_inpkts));
1715 					tcp_pcap_drain(&(tcpb->t_outpkts));
1716 				}
1717 #endif
1718 			}
1719 			INP_WUNLOCK(inpb);
1720 		}
1721 		INP_INFO_WUNLOCK(&V_tcbinfo);
1722 		CURVNET_RESTORE();
1723 	}
1724 	VNET_LIST_RUNLOCK_NOSLEEP();
1725 }
1726 
1727 /*
1728  * Notify a tcp user of an asynchronous error;
1729  * store error as soft error, but wake up user
1730  * (for now, won't do anything until can select for soft error).
1731  *
1732  * Do not wake up user since there currently is no mechanism for
1733  * reporting soft errors (yet - a kqueue filter may be added).
1734  */
1735 static struct inpcb *
1736 tcp_notify(struct inpcb *inp, int error)
1737 {
1738 	struct tcpcb *tp;
1739 
1740 	INP_INFO_LOCK_ASSERT(&V_tcbinfo);
1741 	INP_WLOCK_ASSERT(inp);
1742 
1743 	if ((inp->inp_flags & INP_TIMEWAIT) ||
1744 	    (inp->inp_flags & INP_DROPPED))
1745 		return (inp);
1746 
1747 	tp = intotcpcb(inp);
1748 	KASSERT(tp != NULL, ("tcp_notify: tp == NULL"));
1749 
1750 	/*
1751 	 * Ignore some errors if we are hooked up.
1752 	 * If connection hasn't completed, has retransmitted several times,
1753 	 * and receives a second error, give up now.  This is better
1754 	 * than waiting a long time to establish a connection that
1755 	 * can never complete.
1756 	 */
1757 	if (tp->t_state == TCPS_ESTABLISHED &&
1758 	    (error == EHOSTUNREACH || error == ENETUNREACH ||
1759 	     error == EHOSTDOWN)) {
1760 		if (inp->inp_route.ro_rt) {
1761 			RTFREE(inp->inp_route.ro_rt);
1762 			inp->inp_route.ro_rt = (struct rtentry *)NULL;
1763 		}
1764 		return (inp);
1765 	} else if (tp->t_state < TCPS_ESTABLISHED && tp->t_rxtshift > 3 &&
1766 	    tp->t_softerror) {
1767 		tp = tcp_drop(tp, error);
1768 		if (tp != NULL)
1769 			return (inp);
1770 		else
1771 			return (NULL);
1772 	} else {
1773 		tp->t_softerror = error;
1774 		return (inp);
1775 	}
1776 #if 0
1777 	wakeup( &so->so_timeo);
1778 	sorwakeup(so);
1779 	sowwakeup(so);
1780 #endif
1781 }
1782 
1783 static int
1784 tcp_pcblist(SYSCTL_HANDLER_ARGS)
1785 {
1786 	int error, i, m, n, pcb_count;
1787 	struct inpcb *inp, **inp_list;
1788 	inp_gen_t gencnt;
1789 	struct xinpgen xig;
1790 
1791 	/*
1792 	 * The process of preparing the TCB list is too time-consuming and
1793 	 * resource-intensive to repeat twice on every request.
1794 	 */
1795 	if (req->oldptr == NULL) {
1796 		n = V_tcbinfo.ipi_count +
1797 		    counter_u64_fetch(V_tcps_states[TCPS_SYN_RECEIVED]);
1798 		n += imax(n / 8, 10);
1799 		req->oldidx = 2 * (sizeof xig) + n * sizeof(struct xtcpcb);
1800 		return (0);
1801 	}
1802 
1803 	if (req->newptr != NULL)
1804 		return (EPERM);
1805 
1806 	/*
1807 	 * OK, now we're committed to doing something.
1808 	 */
1809 	INP_LIST_RLOCK(&V_tcbinfo);
1810 	gencnt = V_tcbinfo.ipi_gencnt;
1811 	n = V_tcbinfo.ipi_count;
1812 	INP_LIST_RUNLOCK(&V_tcbinfo);
1813 
1814 	m = counter_u64_fetch(V_tcps_states[TCPS_SYN_RECEIVED]);
1815 
1816 	error = sysctl_wire_old_buffer(req, 2 * (sizeof xig)
1817 		+ (n + m) * sizeof(struct xtcpcb));
1818 	if (error != 0)
1819 		return (error);
1820 
1821 	xig.xig_len = sizeof xig;
1822 	xig.xig_count = n + m;
1823 	xig.xig_gen = gencnt;
1824 	xig.xig_sogen = so_gencnt;
1825 	error = SYSCTL_OUT(req, &xig, sizeof xig);
1826 	if (error)
1827 		return (error);
1828 
1829 	error = syncache_pcblist(req, m, &pcb_count);
1830 	if (error)
1831 		return (error);
1832 
1833 	inp_list = malloc(n * sizeof *inp_list, M_TEMP, M_WAITOK);
1834 
1835 	INP_INFO_WLOCK(&V_tcbinfo);
1836 	for (inp = LIST_FIRST(V_tcbinfo.ipi_listhead), i = 0;
1837 	    inp != NULL && i < n; inp = LIST_NEXT(inp, inp_list)) {
1838 		INP_WLOCK(inp);
1839 		if (inp->inp_gencnt <= gencnt) {
1840 			/*
1841 			 * XXX: This use of cr_cansee(), introduced with
1842 			 * TCP state changes, is not quite right, but for
1843 			 * now, better than nothing.
1844 			 */
1845 			if (inp->inp_flags & INP_TIMEWAIT) {
1846 				if (intotw(inp) != NULL)
1847 					error = cr_cansee(req->td->td_ucred,
1848 					    intotw(inp)->tw_cred);
1849 				else
1850 					error = EINVAL;	/* Skip this inp. */
1851 			} else
1852 				error = cr_canseeinpcb(req->td->td_ucred, inp);
1853 			if (error == 0) {
1854 				in_pcbref(inp);
1855 				inp_list[i++] = inp;
1856 			}
1857 		}
1858 		INP_WUNLOCK(inp);
1859 	}
1860 	INP_INFO_WUNLOCK(&V_tcbinfo);
1861 	n = i;
1862 
1863 	error = 0;
1864 	for (i = 0; i < n; i++) {
1865 		inp = inp_list[i];
1866 		INP_RLOCK(inp);
1867 		if (inp->inp_gencnt <= gencnt) {
1868 			struct xtcpcb xt;
1869 
1870 			tcp_inptoxtp(inp, &xt);
1871 			INP_RUNLOCK(inp);
1872 			error = SYSCTL_OUT(req, &xt, sizeof xt);
1873 		} else
1874 			INP_RUNLOCK(inp);
1875 	}
1876 	INP_INFO_RLOCK(&V_tcbinfo);
1877 	for (i = 0; i < n; i++) {
1878 		inp = inp_list[i];
1879 		INP_RLOCK(inp);
1880 		if (!in_pcbrele_rlocked(inp))
1881 			INP_RUNLOCK(inp);
1882 	}
1883 	INP_INFO_RUNLOCK(&V_tcbinfo);
1884 
1885 	if (!error) {
1886 		/*
1887 		 * Give the user an updated idea of our state.
1888 		 * If the generation differs from what we told
1889 		 * her before, she knows that something happened
1890 		 * while we were processing this request, and it
1891 		 * might be necessary to retry.
1892 		 */
1893 		INP_LIST_RLOCK(&V_tcbinfo);
1894 		xig.xig_gen = V_tcbinfo.ipi_gencnt;
1895 		xig.xig_sogen = so_gencnt;
1896 		xig.xig_count = V_tcbinfo.ipi_count + pcb_count;
1897 		INP_LIST_RUNLOCK(&V_tcbinfo);
1898 		error = SYSCTL_OUT(req, &xig, sizeof xig);
1899 	}
1900 	free(inp_list, M_TEMP);
1901 	return (error);
1902 }
1903 
1904 SYSCTL_PROC(_net_inet_tcp, TCPCTL_PCBLIST, pcblist,
1905     CTLTYPE_OPAQUE | CTLFLAG_RD, NULL, 0,
1906     tcp_pcblist, "S,xtcpcb", "List of active TCP connections");
1907 
1908 #ifdef INET
1909 static int
1910 tcp_getcred(SYSCTL_HANDLER_ARGS)
1911 {
1912 	struct xucred xuc;
1913 	struct sockaddr_in addrs[2];
1914 	struct inpcb *inp;
1915 	int error;
1916 
1917 	error = priv_check(req->td, PRIV_NETINET_GETCRED);
1918 	if (error)
1919 		return (error);
1920 	error = SYSCTL_IN(req, addrs, sizeof(addrs));
1921 	if (error)
1922 		return (error);
1923 	inp = in_pcblookup(&V_tcbinfo, addrs[1].sin_addr, addrs[1].sin_port,
1924 	    addrs[0].sin_addr, addrs[0].sin_port, INPLOOKUP_RLOCKPCB, NULL);
1925 	if (inp != NULL) {
1926 		if (inp->inp_socket == NULL)
1927 			error = ENOENT;
1928 		if (error == 0)
1929 			error = cr_canseeinpcb(req->td->td_ucred, inp);
1930 		if (error == 0)
1931 			cru2x(inp->inp_cred, &xuc);
1932 		INP_RUNLOCK(inp);
1933 	} else
1934 		error = ENOENT;
1935 	if (error == 0)
1936 		error = SYSCTL_OUT(req, &xuc, sizeof(struct xucred));
1937 	return (error);
1938 }
1939 
1940 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, getcred,
1941     CTLTYPE_OPAQUE|CTLFLAG_RW|CTLFLAG_PRISON, 0, 0,
1942     tcp_getcred, "S,xucred", "Get the xucred of a TCP connection");
1943 #endif /* INET */
1944 
1945 #ifdef INET6
1946 static int
1947 tcp6_getcred(SYSCTL_HANDLER_ARGS)
1948 {
1949 	struct xucred xuc;
1950 	struct sockaddr_in6 addrs[2];
1951 	struct inpcb *inp;
1952 	int error;
1953 #ifdef INET
1954 	int mapped = 0;
1955 #endif
1956 
1957 	error = priv_check(req->td, PRIV_NETINET_GETCRED);
1958 	if (error)
1959 		return (error);
1960 	error = SYSCTL_IN(req, addrs, sizeof(addrs));
1961 	if (error)
1962 		return (error);
1963 	if ((error = sa6_embedscope(&addrs[0], V_ip6_use_defzone)) != 0 ||
1964 	    (error = sa6_embedscope(&addrs[1], V_ip6_use_defzone)) != 0) {
1965 		return (error);
1966 	}
1967 	if (IN6_IS_ADDR_V4MAPPED(&addrs[0].sin6_addr)) {
1968 #ifdef INET
1969 		if (IN6_IS_ADDR_V4MAPPED(&addrs[1].sin6_addr))
1970 			mapped = 1;
1971 		else
1972 #endif
1973 			return (EINVAL);
1974 	}
1975 
1976 #ifdef INET
1977 	if (mapped == 1)
1978 		inp = in_pcblookup(&V_tcbinfo,
1979 			*(struct in_addr *)&addrs[1].sin6_addr.s6_addr[12],
1980 			addrs[1].sin6_port,
1981 			*(struct in_addr *)&addrs[0].sin6_addr.s6_addr[12],
1982 			addrs[0].sin6_port, INPLOOKUP_RLOCKPCB, NULL);
1983 	else
1984 #endif
1985 		inp = in6_pcblookup(&V_tcbinfo,
1986 			&addrs[1].sin6_addr, addrs[1].sin6_port,
1987 			&addrs[0].sin6_addr, addrs[0].sin6_port,
1988 			INPLOOKUP_RLOCKPCB, NULL);
1989 	if (inp != NULL) {
1990 		if (inp->inp_socket == NULL)
1991 			error = ENOENT;
1992 		if (error == 0)
1993 			error = cr_canseeinpcb(req->td->td_ucred, inp);
1994 		if (error == 0)
1995 			cru2x(inp->inp_cred, &xuc);
1996 		INP_RUNLOCK(inp);
1997 	} else
1998 		error = ENOENT;
1999 	if (error == 0)
2000 		error = SYSCTL_OUT(req, &xuc, sizeof(struct xucred));
2001 	return (error);
2002 }
2003 
2004 SYSCTL_PROC(_net_inet6_tcp6, OID_AUTO, getcred,
2005     CTLTYPE_OPAQUE|CTLFLAG_RW|CTLFLAG_PRISON, 0, 0,
2006     tcp6_getcred, "S,xucred", "Get the xucred of a TCP6 connection");
2007 #endif /* INET6 */
2008 
2009 
2010 #ifdef INET
2011 void
2012 tcp_ctlinput(int cmd, struct sockaddr *sa, void *vip)
2013 {
2014 	struct ip *ip = vip;
2015 	struct tcphdr *th;
2016 	struct in_addr faddr;
2017 	struct inpcb *inp;
2018 	struct tcpcb *tp;
2019 	struct inpcb *(*notify)(struct inpcb *, int) = tcp_notify;
2020 	struct icmp *icp;
2021 	struct in_conninfo inc;
2022 	tcp_seq icmp_tcp_seq;
2023 	int mtu;
2024 
2025 	faddr = ((struct sockaddr_in *)sa)->sin_addr;
2026 	if (sa->sa_family != AF_INET || faddr.s_addr == INADDR_ANY)
2027 		return;
2028 
2029 	if (cmd == PRC_MSGSIZE)
2030 		notify = tcp_mtudisc_notify;
2031 	else if (V_icmp_may_rst && (cmd == PRC_UNREACH_ADMIN_PROHIB ||
2032 		cmd == PRC_UNREACH_PORT || cmd == PRC_UNREACH_PROTOCOL ||
2033 		cmd == PRC_TIMXCEED_INTRANS) && ip)
2034 		notify = tcp_drop_syn_sent;
2035 
2036 	/*
2037 	 * Hostdead is ugly because it goes linearly through all PCBs.
2038 	 * XXX: We never get this from ICMP, otherwise it makes an
2039 	 * excellent DoS attack on machines with many connections.
2040 	 */
2041 	else if (cmd == PRC_HOSTDEAD)
2042 		ip = NULL;
2043 	else if ((unsigned)cmd >= PRC_NCMDS || inetctlerrmap[cmd] == 0)
2044 		return;
2045 
2046 	if (ip == NULL) {
2047 		in_pcbnotifyall(&V_tcbinfo, faddr, inetctlerrmap[cmd], notify);
2048 		return;
2049 	}
2050 
2051 	icp = (struct icmp *)((caddr_t)ip - offsetof(struct icmp, icmp_ip));
2052 	th = (struct tcphdr *)((caddr_t)ip + (ip->ip_hl << 2));
2053 	INP_INFO_RLOCK(&V_tcbinfo);
2054 	inp = in_pcblookup(&V_tcbinfo, faddr, th->th_dport, ip->ip_src,
2055 	    th->th_sport, INPLOOKUP_WLOCKPCB, NULL);
2056 	if (inp != NULL && PRC_IS_REDIRECT(cmd)) {
2057 		/* signal EHOSTDOWN, as it flushes the cached route */
2058 		inp = (*notify)(inp, EHOSTDOWN);
2059 		goto out;
2060 	}
2061 	icmp_tcp_seq = th->th_seq;
2062 	if (inp != NULL)  {
2063 		if (!(inp->inp_flags & INP_TIMEWAIT) &&
2064 		    !(inp->inp_flags & INP_DROPPED) &&
2065 		    !(inp->inp_socket == NULL)) {
2066 			tp = intotcpcb(inp);
2067 			if (SEQ_GEQ(ntohl(icmp_tcp_seq), tp->snd_una) &&
2068 			    SEQ_LT(ntohl(icmp_tcp_seq), tp->snd_max)) {
2069 				if (cmd == PRC_MSGSIZE) {
2070 					/*
2071 					 * MTU discovery:
2072 					 * If we got a needfrag set the MTU
2073 					 * in the route to the suggested new
2074 					 * value (if given) and then notify.
2075 					 */
2076 					mtu = ntohs(icp->icmp_nextmtu);
2077 					/*
2078 					 * If no alternative MTU was
2079 					 * proposed, try the next smaller
2080 					 * one.
2081 					 */
2082 					if (!mtu)
2083 						mtu = ip_next_mtu(
2084 						    ntohs(ip->ip_len), 1);
2085 					if (mtu < V_tcp_minmss +
2086 					    sizeof(struct tcpiphdr))
2087 						mtu = V_tcp_minmss +
2088 						    sizeof(struct tcpiphdr);
2089 					/*
2090 					 * Only process the offered MTU if it
2091 					 * is smaller than the current one.
2092 					 */
2093 					if (mtu < tp->t_maxseg +
2094 					    sizeof(struct tcpiphdr)) {
2095 						bzero(&inc, sizeof(inc));
2096 						inc.inc_faddr = faddr;
2097 						inc.inc_fibnum =
2098 						    inp->inp_inc.inc_fibnum;
2099 						tcp_hc_updatemtu(&inc, mtu);
2100 						tcp_mtudisc(inp, mtu);
2101 					}
2102 				} else
2103 					inp = (*notify)(inp,
2104 					    inetctlerrmap[cmd]);
2105 			}
2106 		}
2107 	} else {
2108 		bzero(&inc, sizeof(inc));
2109 		inc.inc_fport = th->th_dport;
2110 		inc.inc_lport = th->th_sport;
2111 		inc.inc_faddr = faddr;
2112 		inc.inc_laddr = ip->ip_src;
2113 		syncache_unreach(&inc, icmp_tcp_seq);
2114 	}
2115 out:
2116 	if (inp != NULL)
2117 		INP_WUNLOCK(inp);
2118 	INP_INFO_RUNLOCK(&V_tcbinfo);
2119 }
2120 #endif /* INET */
2121 
2122 #ifdef INET6
2123 void
2124 tcp6_ctlinput(int cmd, struct sockaddr *sa, void *d)
2125 {
2126 	struct in6_addr *dst;
2127 	struct inpcb *(*notify)(struct inpcb *, int) = tcp_notify;
2128 	struct ip6_hdr *ip6;
2129 	struct mbuf *m;
2130 	struct inpcb *inp;
2131 	struct tcpcb *tp;
2132 	struct icmp6_hdr *icmp6;
2133 	struct ip6ctlparam *ip6cp = NULL;
2134 	const struct sockaddr_in6 *sa6_src = NULL;
2135 	struct in_conninfo inc;
2136 	struct tcp_ports {
2137 		uint16_t th_sport;
2138 		uint16_t th_dport;
2139 	} t_ports;
2140 	tcp_seq icmp_tcp_seq;
2141 	unsigned int mtu;
2142 	unsigned int off;
2143 
2144 	if (sa->sa_family != AF_INET6 ||
2145 	    sa->sa_len != sizeof(struct sockaddr_in6))
2146 		return;
2147 
2148 	/* if the parameter is from icmp6, decode it. */
2149 	if (d != NULL) {
2150 		ip6cp = (struct ip6ctlparam *)d;
2151 		icmp6 = ip6cp->ip6c_icmp6;
2152 		m = ip6cp->ip6c_m;
2153 		ip6 = ip6cp->ip6c_ip6;
2154 		off = ip6cp->ip6c_off;
2155 		sa6_src = ip6cp->ip6c_src;
2156 		dst = ip6cp->ip6c_finaldst;
2157 	} else {
2158 		m = NULL;
2159 		ip6 = NULL;
2160 		off = 0;	/* fool gcc */
2161 		sa6_src = &sa6_any;
2162 		dst = NULL;
2163 	}
2164 
2165 	if (cmd == PRC_MSGSIZE)
2166 		notify = tcp_mtudisc_notify;
2167 	else if (V_icmp_may_rst && (cmd == PRC_UNREACH_ADMIN_PROHIB ||
2168 		cmd == PRC_UNREACH_PORT || cmd == PRC_UNREACH_PROTOCOL ||
2169 		cmd == PRC_TIMXCEED_INTRANS) && ip6 != NULL)
2170 		notify = tcp_drop_syn_sent;
2171 
2172 	/*
2173 	 * Hostdead is ugly because it goes linearly through all PCBs.
2174 	 * XXX: We never get this from ICMP, otherwise it makes an
2175 	 * excellent DoS attack on machines with many connections.
2176 	 */
2177 	else if (cmd == PRC_HOSTDEAD)
2178 		ip6 = NULL;
2179 	else if ((unsigned)cmd >= PRC_NCMDS || inet6ctlerrmap[cmd] == 0)
2180 		return;
2181 
2182 	if (ip6 == NULL) {
2183 		in6_pcbnotify(&V_tcbinfo, sa, 0,
2184 			      (const struct sockaddr *)sa6_src,
2185 			      0, cmd, NULL, notify);
2186 		return;
2187 	}
2188 
2189 	/* Check if we can safely get the ports from the tcp hdr */
2190 	if (m == NULL ||
2191 	    (m->m_pkthdr.len <
2192 		(int32_t) (off + sizeof(struct tcp_ports)))) {
2193 		return;
2194 	}
2195 	bzero(&t_ports, sizeof(struct tcp_ports));
2196 	m_copydata(m, off, sizeof(struct tcp_ports), (caddr_t)&t_ports);
2197 	INP_INFO_RLOCK(&V_tcbinfo);
2198 	inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_dst, t_ports.th_dport,
2199 	    &ip6->ip6_src, t_ports.th_sport, INPLOOKUP_WLOCKPCB, NULL);
2200 	if (inp != NULL && PRC_IS_REDIRECT(cmd)) {
2201 		/* signal EHOSTDOWN, as it flushes the cached route */
2202 		inp = (*notify)(inp, EHOSTDOWN);
2203 		goto out;
2204 	}
2205 	off += sizeof(struct tcp_ports);
2206 	if (m->m_pkthdr.len < (int32_t) (off + sizeof(tcp_seq))) {
2207 		goto out;
2208 	}
2209 	m_copydata(m, off, sizeof(tcp_seq), (caddr_t)&icmp_tcp_seq);
2210 	if (inp != NULL)  {
2211 		if (!(inp->inp_flags & INP_TIMEWAIT) &&
2212 		    !(inp->inp_flags & INP_DROPPED) &&
2213 		    !(inp->inp_socket == NULL)) {
2214 			tp = intotcpcb(inp);
2215 			if (SEQ_GEQ(ntohl(icmp_tcp_seq), tp->snd_una) &&
2216 			    SEQ_LT(ntohl(icmp_tcp_seq), tp->snd_max)) {
2217 				if (cmd == PRC_MSGSIZE) {
2218 					/*
2219 					 * MTU discovery:
2220 					 * If we got a needfrag set the MTU
2221 					 * in the route to the suggested new
2222 					 * value (if given) and then notify.
2223 					 */
2224 					mtu = ntohl(icmp6->icmp6_mtu);
2225 					/*
2226 					 * If no alternative MTU was
2227 					 * proposed, or the proposed
2228 					 * MTU was too small, set to
2229 					 * the min.
2230 					 */
2231 					if (mtu < IPV6_MMTU)
2232 						mtu = IPV6_MMTU - 8;
2233 					bzero(&inc, sizeof(inc));
2234 					inc.inc_fibnum = M_GETFIB(m);
2235 					inc.inc_flags |= INC_ISIPV6;
2236 					inc.inc6_faddr = *dst;
2237 					if (in6_setscope(&inc.inc6_faddr,
2238 						m->m_pkthdr.rcvif, NULL))
2239 						goto out;
2240 					/*
2241 					 * Only process the offered MTU if it
2242 					 * is smaller than the current one.
2243 					 */
2244 					if (mtu < tp->t_maxseg +
2245 					    sizeof (struct tcphdr) +
2246 					    sizeof (struct ip6_hdr)) {
2247 						tcp_hc_updatemtu(&inc, mtu);
2248 						tcp_mtudisc(inp, mtu);
2249 						ICMP6STAT_INC(icp6s_pmtuchg);
2250 					}
2251 				} else
2252 					inp = (*notify)(inp,
2253 					    inet6ctlerrmap[cmd]);
2254 			}
2255 		}
2256 	} else {
2257 		bzero(&inc, sizeof(inc));
2258 		inc.inc_fibnum = M_GETFIB(m);
2259 		inc.inc_flags |= INC_ISIPV6;
2260 		inc.inc_fport = t_ports.th_dport;
2261 		inc.inc_lport = t_ports.th_sport;
2262 		inc.inc6_faddr = *dst;
2263 		inc.inc6_laddr = ip6->ip6_src;
2264 		syncache_unreach(&inc, icmp_tcp_seq);
2265 	}
2266 out:
2267 	if (inp != NULL)
2268 		INP_WUNLOCK(inp);
2269 	INP_INFO_RUNLOCK(&V_tcbinfo);
2270 }
2271 #endif /* INET6 */
2272 
2273 
2274 /*
2275  * Following is where TCP initial sequence number generation occurs.
2276  *
2277  * There are two places where we must use initial sequence numbers:
2278  * 1.  In SYN-ACK packets.
2279  * 2.  In SYN packets.
2280  *
2281  * All ISNs for SYN-ACK packets are generated by the syncache.  See
2282  * tcp_syncache.c for details.
2283  *
2284  * The ISNs in SYN packets must be monotonic; TIME_WAIT recycling
2285  * depends on this property.  In addition, these ISNs should be
2286  * unguessable so as to prevent connection hijacking.  To satisfy
2287  * the requirements of this situation, the algorithm outlined in
2288  * RFC 1948 is used, with only small modifications.
2289  *
2290  * Implementation details:
2291  *
2292  * Time is based off the system timer, and is corrected so that it
2293  * increases by one megabyte per second.  This allows for proper
2294  * recycling on high speed LANs while still leaving over an hour
2295  * before rollover.
2296  *
2297  * As reading the *exact* system time is too expensive to be done
2298  * whenever setting up a TCP connection, we increment the time
2299  * offset in two ways.  First, a small random positive increment
2300  * is added to isn_offset for each connection that is set up.
2301  * Second, the function tcp_isn_tick fires once per clock tick
2302  * and increments isn_offset as necessary so that sequence numbers
2303  * are incremented at approximately ISN_BYTES_PER_SECOND.  The
2304  * random positive increments serve only to ensure that the same
2305  * exact sequence number is never sent out twice (as could otherwise
2306  * happen when a port is recycled in less than the system tick
2307  * interval.)
2308  *
2309  * net.inet.tcp.isn_reseed_interval controls the number of seconds
2310  * between seeding of isn_secret.  This is normally set to zero,
2311  * as reseeding should not be necessary.
2312  *
2313  * Locking of the global variables isn_secret, isn_last_reseed, isn_offset,
2314  * isn_offset_old, and isn_ctx is performed using the TCP pcbinfo lock.  In
2315  * general, this means holding an exclusive (write) lock.
2316  */
2317 
2318 #define ISN_BYTES_PER_SECOND 1048576
2319 #define ISN_STATIC_INCREMENT 4096
2320 #define ISN_RANDOM_INCREMENT (4096 - 1)
2321 
2322 static VNET_DEFINE(u_char, isn_secret[32]);
2323 static VNET_DEFINE(int, isn_last);
2324 static VNET_DEFINE(int, isn_last_reseed);
2325 static VNET_DEFINE(u_int32_t, isn_offset);
2326 static VNET_DEFINE(u_int32_t, isn_offset_old);
2327 
2328 #define	V_isn_secret			VNET(isn_secret)
2329 #define	V_isn_last			VNET(isn_last)
2330 #define	V_isn_last_reseed		VNET(isn_last_reseed)
2331 #define	V_isn_offset			VNET(isn_offset)
2332 #define	V_isn_offset_old		VNET(isn_offset_old)
2333 
2334 tcp_seq
2335 tcp_new_isn(struct tcpcb *tp)
2336 {
2337 	MD5_CTX isn_ctx;
2338 	u_int32_t md5_buffer[4];
2339 	tcp_seq new_isn;
2340 	u_int32_t projected_offset;
2341 
2342 	INP_WLOCK_ASSERT(tp->t_inpcb);
2343 
2344 	ISN_LOCK();
2345 	/* Seed if this is the first use, reseed if requested. */
2346 	if ((V_isn_last_reseed == 0) || ((V_tcp_isn_reseed_interval > 0) &&
2347 	     (((u_int)V_isn_last_reseed + (u_int)V_tcp_isn_reseed_interval*hz)
2348 		< (u_int)ticks))) {
2349 		read_random(&V_isn_secret, sizeof(V_isn_secret));
2350 		V_isn_last_reseed = ticks;
2351 	}
2352 
2353 	/* Compute the md5 hash and return the ISN. */
2354 	MD5Init(&isn_ctx);
2355 	MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_fport, sizeof(u_short));
2356 	MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_lport, sizeof(u_short));
2357 #ifdef INET6
2358 	if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) {
2359 		MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->in6p_faddr,
2360 			  sizeof(struct in6_addr));
2361 		MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->in6p_laddr,
2362 			  sizeof(struct in6_addr));
2363 	} else
2364 #endif
2365 	{
2366 		MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_faddr,
2367 			  sizeof(struct in_addr));
2368 		MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_laddr,
2369 			  sizeof(struct in_addr));
2370 	}
2371 	MD5Update(&isn_ctx, (u_char *) &V_isn_secret, sizeof(V_isn_secret));
2372 	MD5Final((u_char *) &md5_buffer, &isn_ctx);
2373 	new_isn = (tcp_seq) md5_buffer[0];
2374 	V_isn_offset += ISN_STATIC_INCREMENT +
2375 		(arc4random() & ISN_RANDOM_INCREMENT);
2376 	if (ticks != V_isn_last) {
2377 		projected_offset = V_isn_offset_old +
2378 		    ISN_BYTES_PER_SECOND / hz * (ticks - V_isn_last);
2379 		if (SEQ_GT(projected_offset, V_isn_offset))
2380 			V_isn_offset = projected_offset;
2381 		V_isn_offset_old = V_isn_offset;
2382 		V_isn_last = ticks;
2383 	}
2384 	new_isn += V_isn_offset;
2385 	ISN_UNLOCK();
2386 	return (new_isn);
2387 }
2388 
2389 /*
2390  * When a specific ICMP unreachable message is received and the
2391  * connection state is SYN-SENT, drop the connection.  This behavior
2392  * is controlled by the icmp_may_rst sysctl.
2393  */
2394 struct inpcb *
2395 tcp_drop_syn_sent(struct inpcb *inp, int errno)
2396 {
2397 	struct tcpcb *tp;
2398 
2399 	INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
2400 	INP_WLOCK_ASSERT(inp);
2401 
2402 	if ((inp->inp_flags & INP_TIMEWAIT) ||
2403 	    (inp->inp_flags & INP_DROPPED))
2404 		return (inp);
2405 
2406 	tp = intotcpcb(inp);
2407 	if (tp->t_state != TCPS_SYN_SENT)
2408 		return (inp);
2409 
2410 	tp = tcp_drop(tp, errno);
2411 	if (tp != NULL)
2412 		return (inp);
2413 	else
2414 		return (NULL);
2415 }
2416 
2417 /*
2418  * When `need fragmentation' ICMP is received, update our idea of the MSS
2419  * based on the new value. Also nudge TCP to send something, since we
2420  * know the packet we just sent was dropped.
2421  * This duplicates some code in the tcp_mss() function in tcp_input.c.
2422  */
2423 static struct inpcb *
2424 tcp_mtudisc_notify(struct inpcb *inp, int error)
2425 {
2426 
2427 	tcp_mtudisc(inp, -1);
2428 	return (inp);
2429 }
2430 
2431 static void
2432 tcp_mtudisc(struct inpcb *inp, int mtuoffer)
2433 {
2434 	struct tcpcb *tp;
2435 	struct socket *so;
2436 
2437 	INP_WLOCK_ASSERT(inp);
2438 	if ((inp->inp_flags & INP_TIMEWAIT) ||
2439 	    (inp->inp_flags & INP_DROPPED))
2440 		return;
2441 
2442 	tp = intotcpcb(inp);
2443 	KASSERT(tp != NULL, ("tcp_mtudisc: tp == NULL"));
2444 
2445 	tcp_mss_update(tp, -1, mtuoffer, NULL, NULL);
2446 
2447 	so = inp->inp_socket;
2448 	SOCKBUF_LOCK(&so->so_snd);
2449 	/* If the mss is larger than the socket buffer, decrease the mss. */
2450 	if (so->so_snd.sb_hiwat < tp->t_maxseg)
2451 		tp->t_maxseg = so->so_snd.sb_hiwat;
2452 	SOCKBUF_UNLOCK(&so->so_snd);
2453 
2454 	TCPSTAT_INC(tcps_mturesent);
2455 	tp->t_rtttime = 0;
2456 	tp->snd_nxt = tp->snd_una;
2457 	tcp_free_sackholes(tp);
2458 	tp->snd_recover = tp->snd_max;
2459 	if (tp->t_flags & TF_SACK_PERMIT)
2460 		EXIT_FASTRECOVERY(tp->t_flags);
2461 	tp->t_fb->tfb_tcp_output(tp);
2462 }
2463 
2464 #ifdef INET
2465 /*
2466  * Look-up the routing entry to the peer of this inpcb.  If no route
2467  * is found and it cannot be allocated, then return 0.  This routine
2468  * is called by TCP routines that access the rmx structure and by
2469  * tcp_mss_update to get the peer/interface MTU.
2470  */
2471 uint32_t
2472 tcp_maxmtu(struct in_conninfo *inc, struct tcp_ifcap *cap)
2473 {
2474 	struct nhop4_extended nh4;
2475 	struct ifnet *ifp;
2476 	uint32_t maxmtu = 0;
2477 
2478 	KASSERT(inc != NULL, ("tcp_maxmtu with NULL in_conninfo pointer"));
2479 
2480 	if (inc->inc_faddr.s_addr != INADDR_ANY) {
2481 
2482 		if (fib4_lookup_nh_ext(inc->inc_fibnum, inc->inc_faddr,
2483 		    NHR_REF, 0, &nh4) != 0)
2484 			return (0);
2485 
2486 		ifp = nh4.nh_ifp;
2487 		maxmtu = nh4.nh_mtu;
2488 
2489 		/* Report additional interface capabilities. */
2490 		if (cap != NULL) {
2491 			if (ifp->if_capenable & IFCAP_TSO4 &&
2492 			    ifp->if_hwassist & CSUM_TSO) {
2493 				cap->ifcap |= CSUM_TSO;
2494 				cap->tsomax = ifp->if_hw_tsomax;
2495 				cap->tsomaxsegcount = ifp->if_hw_tsomaxsegcount;
2496 				cap->tsomaxsegsize = ifp->if_hw_tsomaxsegsize;
2497 			}
2498 		}
2499 		fib4_free_nh_ext(inc->inc_fibnum, &nh4);
2500 	}
2501 	return (maxmtu);
2502 }
2503 #endif /* INET */
2504 
2505 #ifdef INET6
2506 uint32_t
2507 tcp_maxmtu6(struct in_conninfo *inc, struct tcp_ifcap *cap)
2508 {
2509 	struct nhop6_extended nh6;
2510 	struct in6_addr dst6;
2511 	uint32_t scopeid;
2512 	struct ifnet *ifp;
2513 	uint32_t maxmtu = 0;
2514 
2515 	KASSERT(inc != NULL, ("tcp_maxmtu6 with NULL in_conninfo pointer"));
2516 
2517 	if (!IN6_IS_ADDR_UNSPECIFIED(&inc->inc6_faddr)) {
2518 		in6_splitscope(&inc->inc6_faddr, &dst6, &scopeid);
2519 		if (fib6_lookup_nh_ext(inc->inc_fibnum, &dst6, scopeid, 0,
2520 		    0, &nh6) != 0)
2521 			return (0);
2522 
2523 		ifp = nh6.nh_ifp;
2524 		maxmtu = nh6.nh_mtu;
2525 
2526 		/* Report additional interface capabilities. */
2527 		if (cap != NULL) {
2528 			if (ifp->if_capenable & IFCAP_TSO6 &&
2529 			    ifp->if_hwassist & CSUM_TSO) {
2530 				cap->ifcap |= CSUM_TSO;
2531 				cap->tsomax = ifp->if_hw_tsomax;
2532 				cap->tsomaxsegcount = ifp->if_hw_tsomaxsegcount;
2533 				cap->tsomaxsegsize = ifp->if_hw_tsomaxsegsize;
2534 			}
2535 		}
2536 		fib6_free_nh_ext(inc->inc_fibnum, &nh6);
2537 	}
2538 
2539 	return (maxmtu);
2540 }
2541 #endif /* INET6 */
2542 
2543 /*
2544  * Calculate effective SMSS per RFC5681 definition for a given TCP
2545  * connection at its current state, taking into account SACK and etc.
2546  */
2547 u_int
2548 tcp_maxseg(const struct tcpcb *tp)
2549 {
2550 	u_int optlen;
2551 
2552 	if (tp->t_flags & TF_NOOPT)
2553 		return (tp->t_maxseg);
2554 
2555 	/*
2556 	 * Here we have a simplified code from tcp_addoptions(),
2557 	 * without a proper loop, and having most of paddings hardcoded.
2558 	 * We might make mistakes with padding here in some edge cases,
2559 	 * but this is harmless, since result of tcp_maxseg() is used
2560 	 * only in cwnd and ssthresh estimations.
2561 	 */
2562 #define	PAD(len)	((((len) / 4) + !!((len) % 4)) * 4)
2563 	if (TCPS_HAVEESTABLISHED(tp->t_state)) {
2564 		if (tp->t_flags & TF_RCVD_TSTMP)
2565 			optlen = TCPOLEN_TSTAMP_APPA;
2566 		else
2567 			optlen = 0;
2568 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
2569 		if (tp->t_flags & TF_SIGNATURE)
2570 			optlen += PAD(TCPOLEN_SIGNATURE);
2571 #endif
2572 		if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks > 0) {
2573 			optlen += TCPOLEN_SACKHDR;
2574 			optlen += tp->rcv_numsacks * TCPOLEN_SACK;
2575 			optlen = PAD(optlen);
2576 		}
2577 	} else {
2578 		if (tp->t_flags & TF_REQ_TSTMP)
2579 			optlen = TCPOLEN_TSTAMP_APPA;
2580 		else
2581 			optlen = PAD(TCPOLEN_MAXSEG);
2582 		if (tp->t_flags & TF_REQ_SCALE)
2583 			optlen += PAD(TCPOLEN_WINDOW);
2584 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
2585 		if (tp->t_flags & TF_SIGNATURE)
2586 			optlen += PAD(TCPOLEN_SIGNATURE);
2587 #endif
2588 		if (tp->t_flags & TF_SACK_PERMIT)
2589 			optlen += PAD(TCPOLEN_SACK_PERMITTED);
2590 	}
2591 #undef PAD
2592 	optlen = min(optlen, TCP_MAXOLEN);
2593 	return (tp->t_maxseg - optlen);
2594 }
2595 
2596 static int
2597 sysctl_drop(SYSCTL_HANDLER_ARGS)
2598 {
2599 	/* addrs[0] is a foreign socket, addrs[1] is a local one. */
2600 	struct sockaddr_storage addrs[2];
2601 	struct inpcb *inp;
2602 	struct tcpcb *tp;
2603 	struct tcptw *tw;
2604 	struct sockaddr_in *fin, *lin;
2605 #ifdef INET6
2606 	struct sockaddr_in6 *fin6, *lin6;
2607 #endif
2608 	int error;
2609 
2610 	inp = NULL;
2611 	fin = lin = NULL;
2612 #ifdef INET6
2613 	fin6 = lin6 = NULL;
2614 #endif
2615 	error = 0;
2616 
2617 	if (req->oldptr != NULL || req->oldlen != 0)
2618 		return (EINVAL);
2619 	if (req->newptr == NULL)
2620 		return (EPERM);
2621 	if (req->newlen < sizeof(addrs))
2622 		return (ENOMEM);
2623 	error = SYSCTL_IN(req, &addrs, sizeof(addrs));
2624 	if (error)
2625 		return (error);
2626 
2627 	switch (addrs[0].ss_family) {
2628 #ifdef INET6
2629 	case AF_INET6:
2630 		fin6 = (struct sockaddr_in6 *)&addrs[0];
2631 		lin6 = (struct sockaddr_in6 *)&addrs[1];
2632 		if (fin6->sin6_len != sizeof(struct sockaddr_in6) ||
2633 		    lin6->sin6_len != sizeof(struct sockaddr_in6))
2634 			return (EINVAL);
2635 		if (IN6_IS_ADDR_V4MAPPED(&fin6->sin6_addr)) {
2636 			if (!IN6_IS_ADDR_V4MAPPED(&lin6->sin6_addr))
2637 				return (EINVAL);
2638 			in6_sin6_2_sin_in_sock((struct sockaddr *)&addrs[0]);
2639 			in6_sin6_2_sin_in_sock((struct sockaddr *)&addrs[1]);
2640 			fin = (struct sockaddr_in *)&addrs[0];
2641 			lin = (struct sockaddr_in *)&addrs[1];
2642 			break;
2643 		}
2644 		error = sa6_embedscope(fin6, V_ip6_use_defzone);
2645 		if (error)
2646 			return (error);
2647 		error = sa6_embedscope(lin6, V_ip6_use_defzone);
2648 		if (error)
2649 			return (error);
2650 		break;
2651 #endif
2652 #ifdef INET
2653 	case AF_INET:
2654 		fin = (struct sockaddr_in *)&addrs[0];
2655 		lin = (struct sockaddr_in *)&addrs[1];
2656 		if (fin->sin_len != sizeof(struct sockaddr_in) ||
2657 		    lin->sin_len != sizeof(struct sockaddr_in))
2658 			return (EINVAL);
2659 		break;
2660 #endif
2661 	default:
2662 		return (EINVAL);
2663 	}
2664 	INP_INFO_RLOCK(&V_tcbinfo);
2665 	switch (addrs[0].ss_family) {
2666 #ifdef INET6
2667 	case AF_INET6:
2668 		inp = in6_pcblookup(&V_tcbinfo, &fin6->sin6_addr,
2669 		    fin6->sin6_port, &lin6->sin6_addr, lin6->sin6_port,
2670 		    INPLOOKUP_WLOCKPCB, NULL);
2671 		break;
2672 #endif
2673 #ifdef INET
2674 	case AF_INET:
2675 		inp = in_pcblookup(&V_tcbinfo, fin->sin_addr, fin->sin_port,
2676 		    lin->sin_addr, lin->sin_port, INPLOOKUP_WLOCKPCB, NULL);
2677 		break;
2678 #endif
2679 	}
2680 	if (inp != NULL) {
2681 		if (inp->inp_flags & INP_TIMEWAIT) {
2682 			/*
2683 			 * XXXRW: There currently exists a state where an
2684 			 * inpcb is present, but its timewait state has been
2685 			 * discarded.  For now, don't allow dropping of this
2686 			 * type of inpcb.
2687 			 */
2688 			tw = intotw(inp);
2689 			if (tw != NULL)
2690 				tcp_twclose(tw, 0);
2691 			else
2692 				INP_WUNLOCK(inp);
2693 		} else if (!(inp->inp_flags & INP_DROPPED) &&
2694 			   !(inp->inp_socket->so_options & SO_ACCEPTCONN)) {
2695 			tp = intotcpcb(inp);
2696 			tp = tcp_drop(tp, ECONNABORTED);
2697 			if (tp != NULL)
2698 				INP_WUNLOCK(inp);
2699 		} else
2700 			INP_WUNLOCK(inp);
2701 	} else
2702 		error = ESRCH;
2703 	INP_INFO_RUNLOCK(&V_tcbinfo);
2704 	return (error);
2705 }
2706 
2707 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DROP, drop,
2708     CTLFLAG_VNET | CTLTYPE_STRUCT | CTLFLAG_WR | CTLFLAG_SKIP, NULL,
2709     0, sysctl_drop, "", "Drop TCP connection");
2710 
2711 /*
2712  * Generate a standardized TCP log line for use throughout the
2713  * tcp subsystem.  Memory allocation is done with M_NOWAIT to
2714  * allow use in the interrupt context.
2715  *
2716  * NB: The caller MUST free(s, M_TCPLOG) the returned string.
2717  * NB: The function may return NULL if memory allocation failed.
2718  *
2719  * Due to header inclusion and ordering limitations the struct ip
2720  * and ip6_hdr pointers have to be passed as void pointers.
2721  */
2722 char *
2723 tcp_log_vain(struct in_conninfo *inc, struct tcphdr *th, void *ip4hdr,
2724     const void *ip6hdr)
2725 {
2726 
2727 	/* Is logging enabled? */
2728 	if (tcp_log_in_vain == 0)
2729 		return (NULL);
2730 
2731 	return (tcp_log_addr(inc, th, ip4hdr, ip6hdr));
2732 }
2733 
2734 char *
2735 tcp_log_addrs(struct in_conninfo *inc, struct tcphdr *th, void *ip4hdr,
2736     const void *ip6hdr)
2737 {
2738 
2739 	/* Is logging enabled? */
2740 	if (tcp_log_debug == 0)
2741 		return (NULL);
2742 
2743 	return (tcp_log_addr(inc, th, ip4hdr, ip6hdr));
2744 }
2745 
2746 static char *
2747 tcp_log_addr(struct in_conninfo *inc, struct tcphdr *th, void *ip4hdr,
2748     const void *ip6hdr)
2749 {
2750 	char *s, *sp;
2751 	size_t size;
2752 	struct ip *ip;
2753 #ifdef INET6
2754 	const struct ip6_hdr *ip6;
2755 
2756 	ip6 = (const struct ip6_hdr *)ip6hdr;
2757 #endif /* INET6 */
2758 	ip = (struct ip *)ip4hdr;
2759 
2760 	/*
2761 	 * The log line looks like this:
2762 	 * "TCP: [1.2.3.4]:50332 to [1.2.3.4]:80 tcpflags 0x2<SYN>"
2763 	 */
2764 	size = sizeof("TCP: []:12345 to []:12345 tcpflags 0x2<>") +
2765 	    sizeof(PRINT_TH_FLAGS) + 1 +
2766 #ifdef INET6
2767 	    2 * INET6_ADDRSTRLEN;
2768 #else
2769 	    2 * INET_ADDRSTRLEN;
2770 #endif /* INET6 */
2771 
2772 	s = malloc(size, M_TCPLOG, M_ZERO|M_NOWAIT);
2773 	if (s == NULL)
2774 		return (NULL);
2775 
2776 	strcat(s, "TCP: [");
2777 	sp = s + strlen(s);
2778 
2779 	if (inc && ((inc->inc_flags & INC_ISIPV6) == 0)) {
2780 		inet_ntoa_r(inc->inc_faddr, sp);
2781 		sp = s + strlen(s);
2782 		sprintf(sp, "]:%i to [", ntohs(inc->inc_fport));
2783 		sp = s + strlen(s);
2784 		inet_ntoa_r(inc->inc_laddr, sp);
2785 		sp = s + strlen(s);
2786 		sprintf(sp, "]:%i", ntohs(inc->inc_lport));
2787 #ifdef INET6
2788 	} else if (inc) {
2789 		ip6_sprintf(sp, &inc->inc6_faddr);
2790 		sp = s + strlen(s);
2791 		sprintf(sp, "]:%i to [", ntohs(inc->inc_fport));
2792 		sp = s + strlen(s);
2793 		ip6_sprintf(sp, &inc->inc6_laddr);
2794 		sp = s + strlen(s);
2795 		sprintf(sp, "]:%i", ntohs(inc->inc_lport));
2796 	} else if (ip6 && th) {
2797 		ip6_sprintf(sp, &ip6->ip6_src);
2798 		sp = s + strlen(s);
2799 		sprintf(sp, "]:%i to [", ntohs(th->th_sport));
2800 		sp = s + strlen(s);
2801 		ip6_sprintf(sp, &ip6->ip6_dst);
2802 		sp = s + strlen(s);
2803 		sprintf(sp, "]:%i", ntohs(th->th_dport));
2804 #endif /* INET6 */
2805 #ifdef INET
2806 	} else if (ip && th) {
2807 		inet_ntoa_r(ip->ip_src, sp);
2808 		sp = s + strlen(s);
2809 		sprintf(sp, "]:%i to [", ntohs(th->th_sport));
2810 		sp = s + strlen(s);
2811 		inet_ntoa_r(ip->ip_dst, sp);
2812 		sp = s + strlen(s);
2813 		sprintf(sp, "]:%i", ntohs(th->th_dport));
2814 #endif /* INET */
2815 	} else {
2816 		free(s, M_TCPLOG);
2817 		return (NULL);
2818 	}
2819 	sp = s + strlen(s);
2820 	if (th)
2821 		sprintf(sp, " tcpflags 0x%b", th->th_flags, PRINT_TH_FLAGS);
2822 	if (*(s + size - 1) != '\0')
2823 		panic("%s: string too long", __func__);
2824 	return (s);
2825 }
2826 
2827 /*
2828  * A subroutine which makes it easy to track TCP state changes with DTrace.
2829  * This function shouldn't be called for t_state initializations that don't
2830  * correspond to actual TCP state transitions.
2831  */
2832 void
2833 tcp_state_change(struct tcpcb *tp, int newstate)
2834 {
2835 #if defined(KDTRACE_HOOKS)
2836 	int pstate = tp->t_state;
2837 #endif
2838 
2839 	TCPSTATES_DEC(tp->t_state);
2840 	TCPSTATES_INC(newstate);
2841 	tp->t_state = newstate;
2842 	TCP_PROBE6(state__change, NULL, tp, NULL, tp, NULL, pstate);
2843 }
2844 
2845 /*
2846  * Create an external-format (``xtcpcb'') structure using the information in
2847  * the kernel-format tcpcb structure pointed to by tp.  This is done to
2848  * reduce the spew of irrelevant information over this interface, to isolate
2849  * user code from changes in the kernel structure, and potentially to provide
2850  * information-hiding if we decide that some of this information should be
2851  * hidden from users.
2852  */
2853 void
2854 tcp_inptoxtp(const struct inpcb *inp, struct xtcpcb *xt)
2855 {
2856 	struct tcpcb *tp = intotcpcb(inp);
2857 	sbintime_t now;
2858 
2859 	if (inp->inp_flags & INP_TIMEWAIT) {
2860 		bzero(xt, sizeof(struct xtcpcb));
2861 		xt->t_state = TCPS_TIME_WAIT;
2862 	} else {
2863 		xt->t_state = tp->t_state;
2864 		xt->t_flags = tp->t_flags;
2865 		xt->t_sndzerowin = tp->t_sndzerowin;
2866 		xt->t_sndrexmitpack = tp->t_sndrexmitpack;
2867 		xt->t_rcvoopack = tp->t_rcvoopack;
2868 
2869 		now = getsbinuptime();
2870 #define	COPYTIMER(ttt)	do {						\
2871 		if (callout_active(&tp->t_timers->ttt))			\
2872 			xt->ttt = (tp->t_timers->ttt.c_time - now) /	\
2873 			    SBT_1MS;					\
2874 		else							\
2875 			xt->ttt = 0;					\
2876 } while (0)
2877 		COPYTIMER(tt_delack);
2878 		COPYTIMER(tt_rexmt);
2879 		COPYTIMER(tt_persist);
2880 		COPYTIMER(tt_keep);
2881 		COPYTIMER(tt_2msl);
2882 #undef COPYTIMER
2883 		xt->t_rcvtime = 1000 * (ticks - tp->t_rcvtime) / hz;
2884 
2885 		bcopy(tp->t_fb->tfb_tcp_block_name, xt->xt_stack,
2886 		    TCP_FUNCTION_NAME_LEN_MAX);
2887 	}
2888 
2889 	xt->xt_len = sizeof(struct xtcpcb);
2890 	in_pcbtoxinpcb(inp, &xt->xt_inp);
2891 	if (inp->inp_socket == NULL)
2892 		xt->xt_inp.xi_socket.xso_protocol = IPPROTO_TCP;
2893 }
2894