xref: /freebsd/sys/netinet/tcp_subr.c (revision 642870485c089b57000fe538d3485e272b038d59)
1 /*-
2  * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
3  *	The Regents of the University of California.  All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. Neither the name of the University nor the names of its contributors
14  *    may be used to endorse or promote products derived from this software
15  *    without specific prior written permission.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27  * SUCH DAMAGE.
28  *
29  *	@(#)tcp_subr.c	8.2 (Berkeley) 5/24/95
30  */
31 
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD$");
34 
35 #include "opt_compat.h"
36 #include "opt_inet.h"
37 #include "opt_inet6.h"
38 #include "opt_ipsec.h"
39 #include "opt_tcpdebug.h"
40 
41 #include <sys/param.h>
42 #include <sys/systm.h>
43 #include <sys/callout.h>
44 #include <sys/eventhandler.h>
45 #ifdef TCP_HHOOK
46 #include <sys/hhook.h>
47 #endif
48 #include <sys/kernel.h>
49 #ifdef TCP_HHOOK
50 #include <sys/khelp.h>
51 #endif
52 #include <sys/sysctl.h>
53 #include <sys/jail.h>
54 #include <sys/malloc.h>
55 #include <sys/refcount.h>
56 #include <sys/mbuf.h>
57 #ifdef INET6
58 #include <sys/domain.h>
59 #endif
60 #include <sys/priv.h>
61 #include <sys/proc.h>
62 #include <sys/sdt.h>
63 #include <sys/socket.h>
64 #include <sys/socketvar.h>
65 #include <sys/protosw.h>
66 #include <sys/random.h>
67 
68 #include <vm/uma.h>
69 
70 #include <net/route.h>
71 #include <net/if.h>
72 #include <net/if_var.h>
73 #include <net/vnet.h>
74 
75 #include <netinet/in.h>
76 #include <netinet/in_fib.h>
77 #include <netinet/in_kdtrace.h>
78 #include <netinet/in_pcb.h>
79 #include <netinet/in_systm.h>
80 #include <netinet/in_var.h>
81 #include <netinet/ip.h>
82 #include <netinet/ip_icmp.h>
83 #include <netinet/ip_var.h>
84 #ifdef INET6
85 #include <netinet/icmp6.h>
86 #include <netinet/ip6.h>
87 #include <netinet6/in6_fib.h>
88 #include <netinet6/in6_pcb.h>
89 #include <netinet6/ip6_var.h>
90 #include <netinet6/scope6_var.h>
91 #include <netinet6/nd6.h>
92 #endif
93 
94 #ifdef TCP_RFC7413
95 #include <netinet/tcp_fastopen.h>
96 #endif
97 #include <netinet/tcp.h>
98 #include <netinet/tcp_fsm.h>
99 #include <netinet/tcp_seq.h>
100 #include <netinet/tcp_timer.h>
101 #include <netinet/tcp_var.h>
102 #include <netinet/tcp_syncache.h>
103 #include <netinet/cc/cc.h>
104 #ifdef INET6
105 #include <netinet6/tcp6_var.h>
106 #endif
107 #include <netinet/tcpip.h>
108 #ifdef TCPPCAP
109 #include <netinet/tcp_pcap.h>
110 #endif
111 #ifdef TCPDEBUG
112 #include <netinet/tcp_debug.h>
113 #endif
114 #ifdef INET6
115 #include <netinet6/ip6protosw.h>
116 #endif
117 #ifdef TCP_OFFLOAD
118 #include <netinet/tcp_offload.h>
119 #endif
120 
121 #include <netipsec/ipsec_support.h>
122 
123 #include <machine/in_cksum.h>
124 #include <sys/md5.h>
125 
126 #include <security/mac/mac_framework.h>
127 
128 VNET_DEFINE(int, tcp_mssdflt) = TCP_MSS;
129 #ifdef INET6
130 VNET_DEFINE(int, tcp_v6mssdflt) = TCP6_MSS;
131 #endif
132 
133 struct rwlock tcp_function_lock;
134 
135 static int
136 sysctl_net_inet_tcp_mss_check(SYSCTL_HANDLER_ARGS)
137 {
138 	int error, new;
139 
140 	new = V_tcp_mssdflt;
141 	error = sysctl_handle_int(oidp, &new, 0, req);
142 	if (error == 0 && req->newptr) {
143 		if (new < TCP_MINMSS)
144 			error = EINVAL;
145 		else
146 			V_tcp_mssdflt = new;
147 	}
148 	return (error);
149 }
150 
151 SYSCTL_PROC(_net_inet_tcp, TCPCTL_MSSDFLT, mssdflt,
152     CTLFLAG_VNET | CTLTYPE_INT | CTLFLAG_RW, &VNET_NAME(tcp_mssdflt), 0,
153     &sysctl_net_inet_tcp_mss_check, "I",
154     "Default TCP Maximum Segment Size");
155 
156 #ifdef INET6
157 static int
158 sysctl_net_inet_tcp_mss_v6_check(SYSCTL_HANDLER_ARGS)
159 {
160 	int error, new;
161 
162 	new = V_tcp_v6mssdflt;
163 	error = sysctl_handle_int(oidp, &new, 0, req);
164 	if (error == 0 && req->newptr) {
165 		if (new < TCP_MINMSS)
166 			error = EINVAL;
167 		else
168 			V_tcp_v6mssdflt = new;
169 	}
170 	return (error);
171 }
172 
173 SYSCTL_PROC(_net_inet_tcp, TCPCTL_V6MSSDFLT, v6mssdflt,
174     CTLFLAG_VNET | CTLTYPE_INT | CTLFLAG_RW, &VNET_NAME(tcp_v6mssdflt), 0,
175     &sysctl_net_inet_tcp_mss_v6_check, "I",
176    "Default TCP Maximum Segment Size for IPv6");
177 #endif /* INET6 */
178 
179 /*
180  * Minimum MSS we accept and use. This prevents DoS attacks where
181  * we are forced to a ridiculous low MSS like 20 and send hundreds
182  * of packets instead of one. The effect scales with the available
183  * bandwidth and quickly saturates the CPU and network interface
184  * with packet generation and sending. Set to zero to disable MINMSS
185  * checking. This setting prevents us from sending too small packets.
186  */
187 VNET_DEFINE(int, tcp_minmss) = TCP_MINMSS;
188 SYSCTL_INT(_net_inet_tcp, OID_AUTO, minmss, CTLFLAG_VNET | CTLFLAG_RW,
189      &VNET_NAME(tcp_minmss), 0,
190     "Minimum TCP Maximum Segment Size");
191 
192 VNET_DEFINE(int, tcp_do_rfc1323) = 1;
193 SYSCTL_INT(_net_inet_tcp, TCPCTL_DO_RFC1323, rfc1323, CTLFLAG_VNET | CTLFLAG_RW,
194     &VNET_NAME(tcp_do_rfc1323), 0,
195     "Enable rfc1323 (high performance TCP) extensions");
196 
197 static int	tcp_log_debug = 0;
198 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_debug, CTLFLAG_RW,
199     &tcp_log_debug, 0, "Log errors caused by incoming TCP segments");
200 
201 static int	tcp_tcbhashsize;
202 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tcbhashsize, CTLFLAG_RDTUN | CTLFLAG_NOFETCH,
203     &tcp_tcbhashsize, 0, "Size of TCP control-block hashtable");
204 
205 static int	do_tcpdrain = 1;
206 SYSCTL_INT(_net_inet_tcp, OID_AUTO, do_tcpdrain, CTLFLAG_RW, &do_tcpdrain, 0,
207     "Enable tcp_drain routine for extra help when low on mbufs");
208 
209 SYSCTL_UINT(_net_inet_tcp, OID_AUTO, pcbcount, CTLFLAG_VNET | CTLFLAG_RD,
210     &VNET_NAME(tcbinfo.ipi_count), 0, "Number of active PCBs");
211 
212 static VNET_DEFINE(int, icmp_may_rst) = 1;
213 #define	V_icmp_may_rst			VNET(icmp_may_rst)
214 SYSCTL_INT(_net_inet_tcp, OID_AUTO, icmp_may_rst, CTLFLAG_VNET | CTLFLAG_RW,
215     &VNET_NAME(icmp_may_rst), 0,
216     "Certain ICMP unreachable messages may abort connections in SYN_SENT");
217 
218 static VNET_DEFINE(int, tcp_isn_reseed_interval) = 0;
219 #define	V_tcp_isn_reseed_interval	VNET(tcp_isn_reseed_interval)
220 SYSCTL_INT(_net_inet_tcp, OID_AUTO, isn_reseed_interval, CTLFLAG_VNET | CTLFLAG_RW,
221     &VNET_NAME(tcp_isn_reseed_interval), 0,
222     "Seconds between reseeding of ISN secret");
223 
224 static int	tcp_soreceive_stream;
225 SYSCTL_INT(_net_inet_tcp, OID_AUTO, soreceive_stream, CTLFLAG_RDTUN,
226     &tcp_soreceive_stream, 0, "Using soreceive_stream for TCP sockets");
227 
228 VNET_DEFINE(uma_zone_t, sack_hole_zone);
229 #define	V_sack_hole_zone		VNET(sack_hole_zone)
230 
231 #ifdef TCP_HHOOK
232 VNET_DEFINE(struct hhook_head *, tcp_hhh[HHOOK_TCP_LAST+1]);
233 #endif
234 
235 static struct inpcb *tcp_notify(struct inpcb *, int);
236 static struct inpcb *tcp_mtudisc_notify(struct inpcb *, int);
237 static void tcp_mtudisc(struct inpcb *, int);
238 static char *	tcp_log_addr(struct in_conninfo *inc, struct tcphdr *th,
239 		    void *ip4hdr, const void *ip6hdr);
240 
241 
242 static struct tcp_function_block tcp_def_funcblk = {
243 	"default",
244 	tcp_output,
245 	tcp_do_segment,
246 	tcp_default_ctloutput,
247 	NULL,
248 	NULL,
249 	NULL,
250 	NULL,
251 	NULL,
252 	NULL,
253 	0,
254 	0
255 };
256 
257 int t_functions_inited = 0;
258 struct tcp_funchead t_functions;
259 static struct tcp_function_block *tcp_func_set_ptr = &tcp_def_funcblk;
260 
261 static void
262 init_tcp_functions(void)
263 {
264 	if (t_functions_inited == 0) {
265 		TAILQ_INIT(&t_functions);
266 		rw_init_flags(&tcp_function_lock, "tcp_func_lock" , 0);
267 		t_functions_inited = 1;
268 	}
269 }
270 
271 static struct tcp_function_block *
272 find_tcp_functions_locked(struct tcp_function_set *fs)
273 {
274 	struct tcp_function *f;
275 	struct tcp_function_block *blk=NULL;
276 
277 	TAILQ_FOREACH(f, &t_functions, tf_next) {
278 		if (strcmp(f->tf_fb->tfb_tcp_block_name, fs->function_set_name) == 0) {
279 			blk = f->tf_fb;
280 			break;
281 		}
282 	}
283 	return(blk);
284 }
285 
286 static struct tcp_function_block *
287 find_tcp_fb_locked(struct tcp_function_block *blk, struct tcp_function **s)
288 {
289 	struct tcp_function_block *rblk=NULL;
290 	struct tcp_function *f;
291 
292 	TAILQ_FOREACH(f, &t_functions, tf_next) {
293 		if (f->tf_fb == blk) {
294 			rblk = blk;
295 			if (s) {
296 				*s = f;
297 			}
298 			break;
299 		}
300 	}
301 	return (rblk);
302 }
303 
304 struct tcp_function_block *
305 find_and_ref_tcp_functions(struct tcp_function_set *fs)
306 {
307 	struct tcp_function_block *blk;
308 
309 	rw_rlock(&tcp_function_lock);
310 	blk = find_tcp_functions_locked(fs);
311 	if (blk)
312 		refcount_acquire(&blk->tfb_refcnt);
313 	rw_runlock(&tcp_function_lock);
314 	return(blk);
315 }
316 
317 struct tcp_function_block *
318 find_and_ref_tcp_fb(struct tcp_function_block *blk)
319 {
320 	struct tcp_function_block *rblk;
321 
322 	rw_rlock(&tcp_function_lock);
323 	rblk = find_tcp_fb_locked(blk, NULL);
324 	if (rblk)
325 		refcount_acquire(&rblk->tfb_refcnt);
326 	rw_runlock(&tcp_function_lock);
327 	return(rblk);
328 }
329 
330 
331 static int
332 sysctl_net_inet_default_tcp_functions(SYSCTL_HANDLER_ARGS)
333 {
334 	int error=ENOENT;
335 	struct tcp_function_set fs;
336 	struct tcp_function_block *blk;
337 
338 	memset(&fs, 0, sizeof(fs));
339 	rw_rlock(&tcp_function_lock);
340 	blk = find_tcp_fb_locked(tcp_func_set_ptr, NULL);
341 	if (blk) {
342 		/* Found him */
343 		strcpy(fs.function_set_name, blk->tfb_tcp_block_name);
344 		fs.pcbcnt = blk->tfb_refcnt;
345 	}
346 	rw_runlock(&tcp_function_lock);
347 	error = sysctl_handle_string(oidp, fs.function_set_name,
348 				     sizeof(fs.function_set_name), req);
349 
350 	/* Check for error or no change */
351 	if (error != 0 || req->newptr == NULL)
352 		return(error);
353 
354 	rw_wlock(&tcp_function_lock);
355 	blk = find_tcp_functions_locked(&fs);
356 	if ((blk == NULL) ||
357 	    (blk->tfb_flags & TCP_FUNC_BEING_REMOVED)) {
358 		error = ENOENT;
359 		goto done;
360 	}
361 	tcp_func_set_ptr = blk;
362 done:
363 	rw_wunlock(&tcp_function_lock);
364 	return (error);
365 }
366 
367 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, functions_default,
368 	    CTLTYPE_STRING | CTLFLAG_RW,
369 	    NULL, 0, sysctl_net_inet_default_tcp_functions, "A",
370 	    "Set/get the default TCP functions");
371 
372 static int
373 sysctl_net_inet_list_available(SYSCTL_HANDLER_ARGS)
374 {
375 	int error, cnt, linesz;
376 	struct tcp_function *f;
377 	char *buffer, *cp;
378 	size_t bufsz, outsz;
379 
380 	cnt = 0;
381 	rw_rlock(&tcp_function_lock);
382 	TAILQ_FOREACH(f, &t_functions, tf_next) {
383 		cnt++;
384 	}
385 	rw_runlock(&tcp_function_lock);
386 
387 	bufsz = (cnt+2) * (TCP_FUNCTION_NAME_LEN_MAX + 12) + 1;
388 	buffer = malloc(bufsz, M_TEMP, M_WAITOK);
389 
390 	error = 0;
391 	cp = buffer;
392 
393 	linesz = snprintf(cp, bufsz, "\n%-32s%c %s\n", "Stack", 'D', "PCB count");
394 	cp += linesz;
395 	bufsz -= linesz;
396 	outsz = linesz;
397 
398 	rw_rlock(&tcp_function_lock);
399 	TAILQ_FOREACH(f, &t_functions, tf_next) {
400 		linesz = snprintf(cp, bufsz, "%-32s%c %u\n",
401 		    f->tf_fb->tfb_tcp_block_name,
402 		    (f->tf_fb == tcp_func_set_ptr) ? '*' : ' ',
403 		    f->tf_fb->tfb_refcnt);
404 		if (linesz >= bufsz) {
405 			error = EOVERFLOW;
406 			break;
407 		}
408 		cp += linesz;
409 		bufsz -= linesz;
410 		outsz += linesz;
411 	}
412 	rw_runlock(&tcp_function_lock);
413 	if (error == 0)
414 		error = sysctl_handle_string(oidp, buffer, outsz + 1, req);
415 	free(buffer, M_TEMP);
416 	return (error);
417 }
418 
419 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, functions_available,
420 	    CTLTYPE_STRING|CTLFLAG_RD,
421 	    NULL, 0, sysctl_net_inet_list_available, "A",
422 	    "list available TCP Function sets");
423 
424 /*
425  * Target size of TCP PCB hash tables. Must be a power of two.
426  *
427  * Note that this can be overridden by the kernel environment
428  * variable net.inet.tcp.tcbhashsize
429  */
430 #ifndef TCBHASHSIZE
431 #define TCBHASHSIZE	0
432 #endif
433 
434 /*
435  * XXX
436  * Callouts should be moved into struct tcp directly.  They are currently
437  * separate because the tcpcb structure is exported to userland for sysctl
438  * parsing purposes, which do not know about callouts.
439  */
440 struct tcpcb_mem {
441 	struct	tcpcb		tcb;
442 	struct	tcp_timer	tt;
443 	struct	cc_var		ccv;
444 #ifdef TCP_HHOOK
445 	struct	osd		osd;
446 #endif
447 };
448 
449 static VNET_DEFINE(uma_zone_t, tcpcb_zone);
450 #define	V_tcpcb_zone			VNET(tcpcb_zone)
451 
452 MALLOC_DEFINE(M_TCPLOG, "tcplog", "TCP address and flags print buffers");
453 MALLOC_DEFINE(M_TCPFUNCTIONS, "tcpfunc", "TCP function set memory");
454 
455 static struct mtx isn_mtx;
456 
457 #define	ISN_LOCK_INIT()	mtx_init(&isn_mtx, "isn_mtx", NULL, MTX_DEF)
458 #define	ISN_LOCK()	mtx_lock(&isn_mtx)
459 #define	ISN_UNLOCK()	mtx_unlock(&isn_mtx)
460 
461 /*
462  * TCP initialization.
463  */
464 static void
465 tcp_zone_change(void *tag)
466 {
467 
468 	uma_zone_set_max(V_tcbinfo.ipi_zone, maxsockets);
469 	uma_zone_set_max(V_tcpcb_zone, maxsockets);
470 	tcp_tw_zone_change();
471 }
472 
473 static int
474 tcp_inpcb_init(void *mem, int size, int flags)
475 {
476 	struct inpcb *inp = mem;
477 
478 	INP_LOCK_INIT(inp, "inp", "tcpinp");
479 	return (0);
480 }
481 
482 /*
483  * Take a value and get the next power of 2 that doesn't overflow.
484  * Used to size the tcp_inpcb hash buckets.
485  */
486 static int
487 maketcp_hashsize(int size)
488 {
489 	int hashsize;
490 
491 	/*
492 	 * auto tune.
493 	 * get the next power of 2 higher than maxsockets.
494 	 */
495 	hashsize = 1 << fls(size);
496 	/* catch overflow, and just go one power of 2 smaller */
497 	if (hashsize < size) {
498 		hashsize = 1 << (fls(size) - 1);
499 	}
500 	return (hashsize);
501 }
502 
503 int
504 register_tcp_functions(struct tcp_function_block *blk, int wait)
505 {
506 	struct tcp_function_block *lblk;
507 	struct tcp_function *n;
508 	struct tcp_function_set fs;
509 
510 	if (t_functions_inited == 0) {
511 		init_tcp_functions();
512 	}
513 	if ((blk->tfb_tcp_output == NULL) ||
514 	    (blk->tfb_tcp_do_segment == NULL) ||
515 	    (blk->tfb_tcp_ctloutput == NULL) ||
516 	    (strlen(blk->tfb_tcp_block_name) == 0)) {
517 		/*
518 		 * These functions are required and you
519 		 * need a name.
520 		 */
521 		return (EINVAL);
522 	}
523 	if (blk->tfb_tcp_timer_stop_all ||
524 	    blk->tfb_tcp_timer_activate ||
525 	    blk->tfb_tcp_timer_active ||
526 	    blk->tfb_tcp_timer_stop) {
527 		/*
528 		 * If you define one timer function you
529 		 * must have them all.
530 		 */
531 		if ((blk->tfb_tcp_timer_stop_all == NULL) ||
532 		    (blk->tfb_tcp_timer_activate == NULL) ||
533 		    (blk->tfb_tcp_timer_active == NULL) ||
534 		    (blk->tfb_tcp_timer_stop == NULL)) {
535 			return (EINVAL);
536 		}
537 	}
538 	n = malloc(sizeof(struct tcp_function), M_TCPFUNCTIONS, wait);
539 	if (n == NULL) {
540 		return (ENOMEM);
541 	}
542 	n->tf_fb = blk;
543 	strcpy(fs.function_set_name, blk->tfb_tcp_block_name);
544 	rw_wlock(&tcp_function_lock);
545 	lblk = find_tcp_functions_locked(&fs);
546 	if (lblk) {
547 		/* Duplicate name space not allowed */
548 		rw_wunlock(&tcp_function_lock);
549 		free(n, M_TCPFUNCTIONS);
550 		return (EALREADY);
551 	}
552 	refcount_init(&blk->tfb_refcnt, 0);
553 	blk->tfb_flags = 0;
554 	TAILQ_INSERT_TAIL(&t_functions, n, tf_next);
555 	rw_wunlock(&tcp_function_lock);
556 	return(0);
557 }
558 
559 int
560 deregister_tcp_functions(struct tcp_function_block *blk)
561 {
562 	struct tcp_function_block *lblk;
563 	struct tcp_function *f;
564 	int error=ENOENT;
565 
566 	if (strcmp(blk->tfb_tcp_block_name, "default") == 0) {
567 		/* You can't un-register the default */
568 		return (EPERM);
569 	}
570 	rw_wlock(&tcp_function_lock);
571 	if (blk == tcp_func_set_ptr) {
572 		/* You can't free the current default */
573 		rw_wunlock(&tcp_function_lock);
574 		return (EBUSY);
575 	}
576 	if (blk->tfb_refcnt) {
577 		/* Still tcb attached, mark it. */
578 		blk->tfb_flags |= TCP_FUNC_BEING_REMOVED;
579 		rw_wunlock(&tcp_function_lock);
580 		return (EBUSY);
581 	}
582 	lblk = find_tcp_fb_locked(blk, &f);
583 	if (lblk) {
584 		/* Found */
585 		TAILQ_REMOVE(&t_functions, f, tf_next);
586 		f->tf_fb = NULL;
587 		free(f, M_TCPFUNCTIONS);
588 		error = 0;
589 	}
590 	rw_wunlock(&tcp_function_lock);
591 	return (error);
592 }
593 
594 void
595 tcp_init(void)
596 {
597 	const char *tcbhash_tuneable;
598 	int hashsize;
599 
600 	tcbhash_tuneable = "net.inet.tcp.tcbhashsize";
601 
602 #ifdef TCP_HHOOK
603 	if (hhook_head_register(HHOOK_TYPE_TCP, HHOOK_TCP_EST_IN,
604 	    &V_tcp_hhh[HHOOK_TCP_EST_IN], HHOOK_NOWAIT|HHOOK_HEADISINVNET) != 0)
605 		printf("%s: WARNING: unable to register helper hook\n", __func__);
606 	if (hhook_head_register(HHOOK_TYPE_TCP, HHOOK_TCP_EST_OUT,
607 	    &V_tcp_hhh[HHOOK_TCP_EST_OUT], HHOOK_NOWAIT|HHOOK_HEADISINVNET) != 0)
608 		printf("%s: WARNING: unable to register helper hook\n", __func__);
609 #endif
610 	hashsize = TCBHASHSIZE;
611 	TUNABLE_INT_FETCH(tcbhash_tuneable, &hashsize);
612 	if (hashsize == 0) {
613 		/*
614 		 * Auto tune the hash size based on maxsockets.
615 		 * A perfect hash would have a 1:1 mapping
616 		 * (hashsize = maxsockets) however it's been
617 		 * suggested that O(2) average is better.
618 		 */
619 		hashsize = maketcp_hashsize(maxsockets / 4);
620 		/*
621 		 * Our historical default is 512,
622 		 * do not autotune lower than this.
623 		 */
624 		if (hashsize < 512)
625 			hashsize = 512;
626 		if (bootverbose && IS_DEFAULT_VNET(curvnet))
627 			printf("%s: %s auto tuned to %d\n", __func__,
628 			    tcbhash_tuneable, hashsize);
629 	}
630 	/*
631 	 * We require a hashsize to be a power of two.
632 	 * Previously if it was not a power of two we would just reset it
633 	 * back to 512, which could be a nasty surprise if you did not notice
634 	 * the error message.
635 	 * Instead what we do is clip it to the closest power of two lower
636 	 * than the specified hash value.
637 	 */
638 	if (!powerof2(hashsize)) {
639 		int oldhashsize = hashsize;
640 
641 		hashsize = maketcp_hashsize(hashsize);
642 		/* prevent absurdly low value */
643 		if (hashsize < 16)
644 			hashsize = 16;
645 		printf("%s: WARNING: TCB hash size not a power of 2, "
646 		    "clipped from %d to %d.\n", __func__, oldhashsize,
647 		    hashsize);
648 	}
649 	in_pcbinfo_init(&V_tcbinfo, "tcp", &V_tcb, hashsize, hashsize,
650 	    "tcp_inpcb", tcp_inpcb_init, NULL, 0, IPI_HASHFIELDS_4TUPLE);
651 
652 	/*
653 	 * These have to be type stable for the benefit of the timers.
654 	 */
655 	V_tcpcb_zone = uma_zcreate("tcpcb", sizeof(struct tcpcb_mem),
656 	    NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
657 	uma_zone_set_max(V_tcpcb_zone, maxsockets);
658 	uma_zone_set_warning(V_tcpcb_zone, "kern.ipc.maxsockets limit reached");
659 
660 	tcp_tw_init();
661 	syncache_init();
662 	tcp_hc_init();
663 
664 	TUNABLE_INT_FETCH("net.inet.tcp.sack.enable", &V_tcp_do_sack);
665 	V_sack_hole_zone = uma_zcreate("sackhole", sizeof(struct sackhole),
666 	    NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
667 
668 #ifdef TCP_RFC7413
669 	tcp_fastopen_init();
670 #endif
671 
672 	/* Skip initialization of globals for non-default instances. */
673 	if (!IS_DEFAULT_VNET(curvnet))
674 		return;
675 
676 	tcp_reass_global_init();
677 
678 	/* XXX virtualize those bellow? */
679 	tcp_delacktime = TCPTV_DELACK;
680 	tcp_keepinit = TCPTV_KEEP_INIT;
681 	tcp_keepidle = TCPTV_KEEP_IDLE;
682 	tcp_keepintvl = TCPTV_KEEPINTVL;
683 	tcp_maxpersistidle = TCPTV_KEEP_IDLE;
684 	tcp_msl = TCPTV_MSL;
685 	tcp_rexmit_min = TCPTV_MIN;
686 	if (tcp_rexmit_min < 1)
687 		tcp_rexmit_min = 1;
688 	tcp_persmin = TCPTV_PERSMIN;
689 	tcp_persmax = TCPTV_PERSMAX;
690 	tcp_rexmit_slop = TCPTV_CPU_VAR;
691 	tcp_finwait2_timeout = TCPTV_FINWAIT2_TIMEOUT;
692 	tcp_tcbhashsize = hashsize;
693 	/* Setup the tcp function block list */
694 	init_tcp_functions();
695 	register_tcp_functions(&tcp_def_funcblk, M_WAITOK);
696 
697 	if (tcp_soreceive_stream) {
698 #ifdef INET
699 		tcp_usrreqs.pru_soreceive = soreceive_stream;
700 #endif
701 #ifdef INET6
702 		tcp6_usrreqs.pru_soreceive = soreceive_stream;
703 #endif /* INET6 */
704 	}
705 
706 #ifdef INET6
707 #define TCP_MINPROTOHDR (sizeof(struct ip6_hdr) + sizeof(struct tcphdr))
708 #else /* INET6 */
709 #define TCP_MINPROTOHDR (sizeof(struct tcpiphdr))
710 #endif /* INET6 */
711 	if (max_protohdr < TCP_MINPROTOHDR)
712 		max_protohdr = TCP_MINPROTOHDR;
713 	if (max_linkhdr + TCP_MINPROTOHDR > MHLEN)
714 		panic("tcp_init");
715 #undef TCP_MINPROTOHDR
716 
717 	ISN_LOCK_INIT();
718 	EVENTHANDLER_REGISTER(shutdown_pre_sync, tcp_fini, NULL,
719 		SHUTDOWN_PRI_DEFAULT);
720 	EVENTHANDLER_REGISTER(maxsockets_change, tcp_zone_change, NULL,
721 		EVENTHANDLER_PRI_ANY);
722 #ifdef TCPPCAP
723 	tcp_pcap_init();
724 #endif
725 }
726 
727 #ifdef VIMAGE
728 static void
729 tcp_destroy(void *unused __unused)
730 {
731 	int n;
732 #ifdef TCP_HHOOK
733 	int error;
734 #endif
735 
736 	/*
737 	 * All our processes are gone, all our sockets should be cleaned
738 	 * up, which means, we should be past the tcp_discardcb() calls.
739 	 * Sleep to let all tcpcb timers really disappear and cleanup.
740 	 */
741 	for (;;) {
742 		INP_LIST_RLOCK(&V_tcbinfo);
743 		n = V_tcbinfo.ipi_count;
744 		INP_LIST_RUNLOCK(&V_tcbinfo);
745 		if (n == 0)
746 			break;
747 		pause("tcpdes", hz / 10);
748 	}
749 	tcp_hc_destroy();
750 	syncache_destroy();
751 	tcp_tw_destroy();
752 	in_pcbinfo_destroy(&V_tcbinfo);
753 	/* tcp_discardcb() clears the sack_holes up. */
754 	uma_zdestroy(V_sack_hole_zone);
755 	uma_zdestroy(V_tcpcb_zone);
756 
757 #ifdef TCP_RFC7413
758 	/*
759 	 * Cannot free the zone until all tcpcbs are released as we attach
760 	 * the allocations to them.
761 	 */
762 	tcp_fastopen_destroy();
763 #endif
764 
765 #ifdef TCP_HHOOK
766 	error = hhook_head_deregister(V_tcp_hhh[HHOOK_TCP_EST_IN]);
767 	if (error != 0) {
768 		printf("%s: WARNING: unable to deregister helper hook "
769 		    "type=%d, id=%d: error %d returned\n", __func__,
770 		    HHOOK_TYPE_TCP, HHOOK_TCP_EST_IN, error);
771 	}
772 	error = hhook_head_deregister(V_tcp_hhh[HHOOK_TCP_EST_OUT]);
773 	if (error != 0) {
774 		printf("%s: WARNING: unable to deregister helper hook "
775 		    "type=%d, id=%d: error %d returned\n", __func__,
776 		    HHOOK_TYPE_TCP, HHOOK_TCP_EST_OUT, error);
777 	}
778 #endif
779 }
780 VNET_SYSUNINIT(tcp, SI_SUB_PROTO_DOMAIN, SI_ORDER_FOURTH, tcp_destroy, NULL);
781 #endif
782 
783 void
784 tcp_fini(void *xtp)
785 {
786 
787 }
788 
789 /*
790  * Fill in the IP and TCP headers for an outgoing packet, given the tcpcb.
791  * tcp_template used to store this data in mbufs, but we now recopy it out
792  * of the tcpcb each time to conserve mbufs.
793  */
794 void
795 tcpip_fillheaders(struct inpcb *inp, void *ip_ptr, void *tcp_ptr)
796 {
797 	struct tcphdr *th = (struct tcphdr *)tcp_ptr;
798 
799 	INP_WLOCK_ASSERT(inp);
800 
801 #ifdef INET6
802 	if ((inp->inp_vflag & INP_IPV6) != 0) {
803 		struct ip6_hdr *ip6;
804 
805 		ip6 = (struct ip6_hdr *)ip_ptr;
806 		ip6->ip6_flow = (ip6->ip6_flow & ~IPV6_FLOWINFO_MASK) |
807 			(inp->inp_flow & IPV6_FLOWINFO_MASK);
808 		ip6->ip6_vfc = (ip6->ip6_vfc & ~IPV6_VERSION_MASK) |
809 			(IPV6_VERSION & IPV6_VERSION_MASK);
810 		ip6->ip6_nxt = IPPROTO_TCP;
811 		ip6->ip6_plen = htons(sizeof(struct tcphdr));
812 		ip6->ip6_src = inp->in6p_laddr;
813 		ip6->ip6_dst = inp->in6p_faddr;
814 	}
815 #endif /* INET6 */
816 #if defined(INET6) && defined(INET)
817 	else
818 #endif
819 #ifdef INET
820 	{
821 		struct ip *ip;
822 
823 		ip = (struct ip *)ip_ptr;
824 		ip->ip_v = IPVERSION;
825 		ip->ip_hl = 5;
826 		ip->ip_tos = inp->inp_ip_tos;
827 		ip->ip_len = 0;
828 		ip->ip_id = 0;
829 		ip->ip_off = 0;
830 		ip->ip_ttl = inp->inp_ip_ttl;
831 		ip->ip_sum = 0;
832 		ip->ip_p = IPPROTO_TCP;
833 		ip->ip_src = inp->inp_laddr;
834 		ip->ip_dst = inp->inp_faddr;
835 	}
836 #endif /* INET */
837 	th->th_sport = inp->inp_lport;
838 	th->th_dport = inp->inp_fport;
839 	th->th_seq = 0;
840 	th->th_ack = 0;
841 	th->th_x2 = 0;
842 	th->th_off = 5;
843 	th->th_flags = 0;
844 	th->th_win = 0;
845 	th->th_urp = 0;
846 	th->th_sum = 0;		/* in_pseudo() is called later for ipv4 */
847 }
848 
849 /*
850  * Create template to be used to send tcp packets on a connection.
851  * Allocates an mbuf and fills in a skeletal tcp/ip header.  The only
852  * use for this function is in keepalives, which use tcp_respond.
853  */
854 struct tcptemp *
855 tcpip_maketemplate(struct inpcb *inp)
856 {
857 	struct tcptemp *t;
858 
859 	t = malloc(sizeof(*t), M_TEMP, M_NOWAIT);
860 	if (t == NULL)
861 		return (NULL);
862 	tcpip_fillheaders(inp, (void *)&t->tt_ipgen, (void *)&t->tt_t);
863 	return (t);
864 }
865 
866 /*
867  * Send a single message to the TCP at address specified by
868  * the given TCP/IP header.  If m == NULL, then we make a copy
869  * of the tcpiphdr at th and send directly to the addressed host.
870  * This is used to force keep alive messages out using the TCP
871  * template for a connection.  If flags are given then we send
872  * a message back to the TCP which originated the segment th,
873  * and discard the mbuf containing it and any other attached mbufs.
874  *
875  * In any case the ack and sequence number of the transmitted
876  * segment are as specified by the parameters.
877  *
878  * NOTE: If m != NULL, then th must point to *inside* the mbuf.
879  */
880 void
881 tcp_respond(struct tcpcb *tp, void *ipgen, struct tcphdr *th, struct mbuf *m,
882     tcp_seq ack, tcp_seq seq, int flags)
883 {
884 	struct tcpopt to;
885 	struct inpcb *inp;
886 	struct ip *ip;
887 	struct mbuf *optm;
888 	struct tcphdr *nth;
889 	u_char *optp;
890 #ifdef INET6
891 	struct ip6_hdr *ip6;
892 	int isipv6;
893 #endif /* INET6 */
894 	int optlen, tlen, win;
895 	bool incl_opts;
896 
897 	KASSERT(tp != NULL || m != NULL, ("tcp_respond: tp and m both NULL"));
898 
899 #ifdef INET6
900 	isipv6 = ((struct ip *)ipgen)->ip_v == (IPV6_VERSION >> 4);
901 	ip6 = ipgen;
902 #endif /* INET6 */
903 	ip = ipgen;
904 
905 	if (tp != NULL) {
906 		inp = tp->t_inpcb;
907 		KASSERT(inp != NULL, ("tcp control block w/o inpcb"));
908 		INP_WLOCK_ASSERT(inp);
909 	} else
910 		inp = NULL;
911 
912 	incl_opts = false;
913 	win = 0;
914 	if (tp != NULL) {
915 		if (!(flags & TH_RST)) {
916 			win = sbspace(&inp->inp_socket->so_rcv);
917 			if (win > TCP_MAXWIN << tp->rcv_scale)
918 				win = TCP_MAXWIN << tp->rcv_scale;
919 		}
920 		if ((tp->t_flags & TF_NOOPT) == 0)
921 			incl_opts = true;
922 	}
923 	if (m == NULL) {
924 		m = m_gethdr(M_NOWAIT, MT_DATA);
925 		if (m == NULL)
926 			return;
927 		m->m_data += max_linkhdr;
928 #ifdef INET6
929 		if (isipv6) {
930 			bcopy((caddr_t)ip6, mtod(m, caddr_t),
931 			      sizeof(struct ip6_hdr));
932 			ip6 = mtod(m, struct ip6_hdr *);
933 			nth = (struct tcphdr *)(ip6 + 1);
934 		} else
935 #endif /* INET6 */
936 		{
937 			bcopy((caddr_t)ip, mtod(m, caddr_t), sizeof(struct ip));
938 			ip = mtod(m, struct ip *);
939 			nth = (struct tcphdr *)(ip + 1);
940 		}
941 		bcopy((caddr_t)th, (caddr_t)nth, sizeof(struct tcphdr));
942 		flags = TH_ACK;
943 	} else if (!M_WRITABLE(m)) {
944 		struct mbuf *n;
945 
946 		/* Can't reuse 'm', allocate a new mbuf. */
947 		n = m_gethdr(M_NOWAIT, MT_DATA);
948 		if (n == NULL) {
949 			m_freem(m);
950 			return;
951 		}
952 
953 		if (!m_dup_pkthdr(n, m, M_NOWAIT)) {
954 			m_freem(m);
955 			m_freem(n);
956 			return;
957 		}
958 
959 		n->m_data += max_linkhdr;
960 		/* m_len is set later */
961 #define xchg(a,b,type) { type t; t=a; a=b; b=t; }
962 #ifdef INET6
963 		if (isipv6) {
964 			bcopy((caddr_t)ip6, mtod(n, caddr_t),
965 			      sizeof(struct ip6_hdr));
966 			ip6 = mtod(n, struct ip6_hdr *);
967 			xchg(ip6->ip6_dst, ip6->ip6_src, struct in6_addr);
968 			nth = (struct tcphdr *)(ip6 + 1);
969 		} else
970 #endif /* INET6 */
971 		{
972 			bcopy((caddr_t)ip, mtod(n, caddr_t), sizeof(struct ip));
973 			ip = mtod(n, struct ip *);
974 			xchg(ip->ip_dst.s_addr, ip->ip_src.s_addr, uint32_t);
975 			nth = (struct tcphdr *)(ip + 1);
976 		}
977 		bcopy((caddr_t)th, (caddr_t)nth, sizeof(struct tcphdr));
978 		xchg(nth->th_dport, nth->th_sport, uint16_t);
979 		th = nth;
980 		m_freem(m);
981 		m = n;
982 	} else {
983 		/*
984 		 *  reuse the mbuf.
985 		 * XXX MRT We inherit the FIB, which is lucky.
986 		 */
987 		m_freem(m->m_next);
988 		m->m_next = NULL;
989 		m->m_data = (caddr_t)ipgen;
990 		/* m_len is set later */
991 #ifdef INET6
992 		if (isipv6) {
993 			xchg(ip6->ip6_dst, ip6->ip6_src, struct in6_addr);
994 			nth = (struct tcphdr *)(ip6 + 1);
995 		} else
996 #endif /* INET6 */
997 		{
998 			xchg(ip->ip_dst.s_addr, ip->ip_src.s_addr, uint32_t);
999 			nth = (struct tcphdr *)(ip + 1);
1000 		}
1001 		if (th != nth) {
1002 			/*
1003 			 * this is usually a case when an extension header
1004 			 * exists between the IPv6 header and the
1005 			 * TCP header.
1006 			 */
1007 			nth->th_sport = th->th_sport;
1008 			nth->th_dport = th->th_dport;
1009 		}
1010 		xchg(nth->th_dport, nth->th_sport, uint16_t);
1011 #undef xchg
1012 	}
1013 	tlen = 0;
1014 #ifdef INET6
1015 	if (isipv6)
1016 		tlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr);
1017 #endif
1018 #if defined(INET) && defined(INET6)
1019 	else
1020 #endif
1021 #ifdef INET
1022 		tlen = sizeof (struct tcpiphdr);
1023 #endif
1024 #ifdef INVARIANTS
1025 	m->m_len = 0;
1026 	KASSERT(M_TRAILINGSPACE(m) >= tlen,
1027 	    ("Not enough trailing space for message (m=%p, need=%d, have=%ld)",
1028 	    m, tlen, (long)M_TRAILINGSPACE(m)));
1029 #endif
1030 	m->m_len = tlen;
1031 	to.to_flags = 0;
1032 	if (incl_opts) {
1033 		/* Make sure we have room. */
1034 		if (M_TRAILINGSPACE(m) < TCP_MAXOLEN) {
1035 			m->m_next = m_get(M_NOWAIT, MT_DATA);
1036 			if (m->m_next) {
1037 				optp = mtod(m->m_next, u_char *);
1038 				optm = m->m_next;
1039 			} else
1040 				incl_opts = false;
1041 		} else {
1042 			optp = (u_char *) (nth + 1);
1043 			optm = m;
1044 		}
1045 	}
1046 	if (incl_opts) {
1047 		/* Timestamps. */
1048 		if (tp->t_flags & TF_RCVD_TSTMP) {
1049 			to.to_tsval = tcp_ts_getticks() + tp->ts_offset;
1050 			to.to_tsecr = tp->ts_recent;
1051 			to.to_flags |= TOF_TS;
1052 		}
1053 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1054 		/* TCP-MD5 (RFC2385). */
1055 		if (tp->t_flags & TF_SIGNATURE)
1056 			to.to_flags |= TOF_SIGNATURE;
1057 #endif
1058 		/* Add the options. */
1059 		tlen += optlen = tcp_addoptions(&to, optp);
1060 
1061 		/* Update m_len in the correct mbuf. */
1062 		optm->m_len += optlen;
1063 	} else
1064 		optlen = 0;
1065 #ifdef INET6
1066 	if (isipv6) {
1067 		ip6->ip6_flow = 0;
1068 		ip6->ip6_vfc = IPV6_VERSION;
1069 		ip6->ip6_nxt = IPPROTO_TCP;
1070 		ip6->ip6_plen = htons(tlen - sizeof(*ip6));
1071 	}
1072 #endif
1073 #if defined(INET) && defined(INET6)
1074 	else
1075 #endif
1076 #ifdef INET
1077 	{
1078 		ip->ip_len = htons(tlen);
1079 		ip->ip_ttl = V_ip_defttl;
1080 		if (V_path_mtu_discovery)
1081 			ip->ip_off |= htons(IP_DF);
1082 	}
1083 #endif
1084 	m->m_pkthdr.len = tlen;
1085 	m->m_pkthdr.rcvif = NULL;
1086 #ifdef MAC
1087 	if (inp != NULL) {
1088 		/*
1089 		 * Packet is associated with a socket, so allow the
1090 		 * label of the response to reflect the socket label.
1091 		 */
1092 		INP_WLOCK_ASSERT(inp);
1093 		mac_inpcb_create_mbuf(inp, m);
1094 	} else {
1095 		/*
1096 		 * Packet is not associated with a socket, so possibly
1097 		 * update the label in place.
1098 		 */
1099 		mac_netinet_tcp_reply(m);
1100 	}
1101 #endif
1102 	nth->th_seq = htonl(seq);
1103 	nth->th_ack = htonl(ack);
1104 	nth->th_x2 = 0;
1105 	nth->th_off = (sizeof (struct tcphdr) + optlen) >> 2;
1106 	nth->th_flags = flags;
1107 	if (tp != NULL)
1108 		nth->th_win = htons((u_short) (win >> tp->rcv_scale));
1109 	else
1110 		nth->th_win = htons((u_short)win);
1111 	nth->th_urp = 0;
1112 
1113 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1114 	if (to.to_flags & TOF_SIGNATURE) {
1115 		if (!TCPMD5_ENABLED() ||
1116 		    TCPMD5_OUTPUT(m, nth, to.to_signature) != 0) {
1117 			m_freem(m);
1118 			return;
1119 		}
1120 	}
1121 #endif
1122 
1123 	m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1124 #ifdef INET6
1125 	if (isipv6) {
1126 		m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
1127 		nth->th_sum = in6_cksum_pseudo(ip6,
1128 		    tlen - sizeof(struct ip6_hdr), IPPROTO_TCP, 0);
1129 		ip6->ip6_hlim = in6_selecthlim(tp != NULL ? tp->t_inpcb :
1130 		    NULL, NULL);
1131 	}
1132 #endif /* INET6 */
1133 #if defined(INET6) && defined(INET)
1134 	else
1135 #endif
1136 #ifdef INET
1137 	{
1138 		m->m_pkthdr.csum_flags = CSUM_TCP;
1139 		nth->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1140 		    htons((u_short)(tlen - sizeof(struct ip) + ip->ip_p)));
1141 	}
1142 #endif /* INET */
1143 #ifdef TCPDEBUG
1144 	if (tp == NULL || (inp->inp_socket->so_options & SO_DEBUG))
1145 		tcp_trace(TA_OUTPUT, 0, tp, mtod(m, void *), th, 0);
1146 #endif
1147 	TCP_PROBE3(debug__output, tp, th, m);
1148 	if (flags & TH_RST)
1149 		TCP_PROBE5(accept__refused, NULL, NULL, m, tp, nth);
1150 
1151 	TCP_PROBE5(send, NULL, tp, m, tp, nth);
1152 #ifdef INET6
1153 	if (isipv6)
1154 		(void) ip6_output(m, NULL, NULL, 0, NULL, NULL, inp);
1155 #endif /* INET6 */
1156 #if defined(INET) && defined(INET6)
1157 	else
1158 #endif
1159 #ifdef INET
1160 		(void) ip_output(m, NULL, NULL, 0, NULL, inp);
1161 #endif
1162 }
1163 
1164 /*
1165  * Create a new TCP control block, making an
1166  * empty reassembly queue and hooking it to the argument
1167  * protocol control block.  The `inp' parameter must have
1168  * come from the zone allocator set up in tcp_init().
1169  */
1170 struct tcpcb *
1171 tcp_newtcpcb(struct inpcb *inp)
1172 {
1173 	struct tcpcb_mem *tm;
1174 	struct tcpcb *tp;
1175 #ifdef INET6
1176 	int isipv6 = (inp->inp_vflag & INP_IPV6) != 0;
1177 #endif /* INET6 */
1178 
1179 	tm = uma_zalloc(V_tcpcb_zone, M_NOWAIT | M_ZERO);
1180 	if (tm == NULL)
1181 		return (NULL);
1182 	tp = &tm->tcb;
1183 
1184 	/* Initialise cc_var struct for this tcpcb. */
1185 	tp->ccv = &tm->ccv;
1186 	tp->ccv->type = IPPROTO_TCP;
1187 	tp->ccv->ccvc.tcp = tp;
1188 	rw_rlock(&tcp_function_lock);
1189 	tp->t_fb = tcp_func_set_ptr;
1190 	refcount_acquire(&tp->t_fb->tfb_refcnt);
1191 	rw_runlock(&tcp_function_lock);
1192 	/*
1193 	 * Use the current system default CC algorithm.
1194 	 */
1195 	CC_LIST_RLOCK();
1196 	KASSERT(!STAILQ_EMPTY(&cc_list), ("cc_list is empty!"));
1197 	CC_ALGO(tp) = CC_DEFAULT();
1198 	CC_LIST_RUNLOCK();
1199 
1200 	if (CC_ALGO(tp)->cb_init != NULL)
1201 		if (CC_ALGO(tp)->cb_init(tp->ccv) > 0) {
1202 			if (tp->t_fb->tfb_tcp_fb_fini)
1203 				(*tp->t_fb->tfb_tcp_fb_fini)(tp, 1);
1204 			refcount_release(&tp->t_fb->tfb_refcnt);
1205 			uma_zfree(V_tcpcb_zone, tm);
1206 			return (NULL);
1207 		}
1208 
1209 #ifdef TCP_HHOOK
1210 	tp->osd = &tm->osd;
1211 	if (khelp_init_osd(HELPER_CLASS_TCP, tp->osd)) {
1212 		if (tp->t_fb->tfb_tcp_fb_fini)
1213 			(*tp->t_fb->tfb_tcp_fb_fini)(tp, 1);
1214 		refcount_release(&tp->t_fb->tfb_refcnt);
1215 		uma_zfree(V_tcpcb_zone, tm);
1216 		return (NULL);
1217 	}
1218 #endif
1219 
1220 #ifdef VIMAGE
1221 	tp->t_vnet = inp->inp_vnet;
1222 #endif
1223 	tp->t_timers = &tm->tt;
1224 	/*	LIST_INIT(&tp->t_segq); */	/* XXX covered by M_ZERO */
1225 	tp->t_maxseg =
1226 #ifdef INET6
1227 		isipv6 ? V_tcp_v6mssdflt :
1228 #endif /* INET6 */
1229 		V_tcp_mssdflt;
1230 
1231 	/* Set up our timeouts. */
1232 	callout_init(&tp->t_timers->tt_rexmt, 1);
1233 	callout_init(&tp->t_timers->tt_persist, 1);
1234 	callout_init(&tp->t_timers->tt_keep, 1);
1235 	callout_init(&tp->t_timers->tt_2msl, 1);
1236 	callout_init(&tp->t_timers->tt_delack, 1);
1237 
1238 	if (V_tcp_do_rfc1323)
1239 		tp->t_flags = (TF_REQ_SCALE|TF_REQ_TSTMP);
1240 	if (V_tcp_do_sack)
1241 		tp->t_flags |= TF_SACK_PERMIT;
1242 	TAILQ_INIT(&tp->snd_holes);
1243 	/*
1244 	 * The tcpcb will hold a reference on its inpcb until tcp_discardcb()
1245 	 * is called.
1246 	 */
1247 	in_pcbref(inp);	/* Reference for tcpcb */
1248 	tp->t_inpcb = inp;
1249 
1250 	/*
1251 	 * Init srtt to TCPTV_SRTTBASE (0), so we can tell that we have no
1252 	 * rtt estimate.  Set rttvar so that srtt + 4 * rttvar gives
1253 	 * reasonable initial retransmit time.
1254 	 */
1255 	tp->t_srtt = TCPTV_SRTTBASE;
1256 	tp->t_rttvar = ((TCPTV_RTOBASE - TCPTV_SRTTBASE) << TCP_RTTVAR_SHIFT) / 4;
1257 	tp->t_rttmin = tcp_rexmit_min;
1258 	tp->t_rxtcur = TCPTV_RTOBASE;
1259 	tp->snd_cwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT;
1260 	tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT;
1261 	tp->t_rcvtime = ticks;
1262 	/*
1263 	 * IPv4 TTL initialization is necessary for an IPv6 socket as well,
1264 	 * because the socket may be bound to an IPv6 wildcard address,
1265 	 * which may match an IPv4-mapped IPv6 address.
1266 	 */
1267 	inp->inp_ip_ttl = V_ip_defttl;
1268 	inp->inp_ppcb = tp;
1269 #ifdef TCPPCAP
1270 	/*
1271 	 * Init the TCP PCAP queues.
1272 	 */
1273 	tcp_pcap_tcpcb_init(tp);
1274 #endif
1275 	if (tp->t_fb->tfb_tcp_fb_init) {
1276 		(*tp->t_fb->tfb_tcp_fb_init)(tp);
1277 	}
1278 	return (tp);		/* XXX */
1279 }
1280 
1281 /*
1282  * Switch the congestion control algorithm back to NewReno for any active
1283  * control blocks using an algorithm which is about to go away.
1284  * This ensures the CC framework can allow the unload to proceed without leaving
1285  * any dangling pointers which would trigger a panic.
1286  * Returning non-zero would inform the CC framework that something went wrong
1287  * and it would be unsafe to allow the unload to proceed. However, there is no
1288  * way for this to occur with this implementation so we always return zero.
1289  */
1290 int
1291 tcp_ccalgounload(struct cc_algo *unload_algo)
1292 {
1293 	struct cc_algo *tmpalgo;
1294 	struct inpcb *inp;
1295 	struct tcpcb *tp;
1296 	VNET_ITERATOR_DECL(vnet_iter);
1297 
1298 	/*
1299 	 * Check all active control blocks across all network stacks and change
1300 	 * any that are using "unload_algo" back to NewReno. If "unload_algo"
1301 	 * requires cleanup code to be run, call it.
1302 	 */
1303 	VNET_LIST_RLOCK();
1304 	VNET_FOREACH(vnet_iter) {
1305 		CURVNET_SET(vnet_iter);
1306 		INP_INFO_WLOCK(&V_tcbinfo);
1307 		/*
1308 		 * New connections already part way through being initialised
1309 		 * with the CC algo we're removing will not race with this code
1310 		 * because the INP_INFO_WLOCK is held during initialisation. We
1311 		 * therefore don't enter the loop below until the connection
1312 		 * list has stabilised.
1313 		 */
1314 		LIST_FOREACH(inp, &V_tcb, inp_list) {
1315 			INP_WLOCK(inp);
1316 			/* Important to skip tcptw structs. */
1317 			if (!(inp->inp_flags & INP_TIMEWAIT) &&
1318 			    (tp = intotcpcb(inp)) != NULL) {
1319 				/*
1320 				 * By holding INP_WLOCK here, we are assured
1321 				 * that the connection is not currently
1322 				 * executing inside the CC module's functions
1323 				 * i.e. it is safe to make the switch back to
1324 				 * NewReno.
1325 				 */
1326 				if (CC_ALGO(tp) == unload_algo) {
1327 					tmpalgo = CC_ALGO(tp);
1328 					/* NewReno does not require any init. */
1329 					CC_ALGO(tp) = &newreno_cc_algo;
1330 					if (tmpalgo->cb_destroy != NULL)
1331 						tmpalgo->cb_destroy(tp->ccv);
1332 				}
1333 			}
1334 			INP_WUNLOCK(inp);
1335 		}
1336 		INP_INFO_WUNLOCK(&V_tcbinfo);
1337 		CURVNET_RESTORE();
1338 	}
1339 	VNET_LIST_RUNLOCK();
1340 
1341 	return (0);
1342 }
1343 
1344 /*
1345  * Drop a TCP connection, reporting
1346  * the specified error.  If connection is synchronized,
1347  * then send a RST to peer.
1348  */
1349 struct tcpcb *
1350 tcp_drop(struct tcpcb *tp, int errno)
1351 {
1352 	struct socket *so = tp->t_inpcb->inp_socket;
1353 
1354 	INP_INFO_LOCK_ASSERT(&V_tcbinfo);
1355 	INP_WLOCK_ASSERT(tp->t_inpcb);
1356 
1357 	if (TCPS_HAVERCVDSYN(tp->t_state)) {
1358 		tcp_state_change(tp, TCPS_CLOSED);
1359 		(void) tp->t_fb->tfb_tcp_output(tp);
1360 		TCPSTAT_INC(tcps_drops);
1361 	} else
1362 		TCPSTAT_INC(tcps_conndrops);
1363 	if (errno == ETIMEDOUT && tp->t_softerror)
1364 		errno = tp->t_softerror;
1365 	so->so_error = errno;
1366 	return (tcp_close(tp));
1367 }
1368 
1369 void
1370 tcp_discardcb(struct tcpcb *tp)
1371 {
1372 	struct inpcb *inp = tp->t_inpcb;
1373 	struct socket *so = inp->inp_socket;
1374 #ifdef INET6
1375 	int isipv6 = (inp->inp_vflag & INP_IPV6) != 0;
1376 #endif /* INET6 */
1377 	int released;
1378 
1379 	INP_WLOCK_ASSERT(inp);
1380 
1381 	/*
1382 	 * Make sure that all of our timers are stopped before we delete the
1383 	 * PCB.
1384 	 *
1385 	 * If stopping a timer fails, we schedule a discard function in same
1386 	 * callout, and the last discard function called will take care of
1387 	 * deleting the tcpcb.
1388 	 */
1389 	tp->t_timers->tt_draincnt = 0;
1390 	tcp_timer_stop(tp, TT_REXMT);
1391 	tcp_timer_stop(tp, TT_PERSIST);
1392 	tcp_timer_stop(tp, TT_KEEP);
1393 	tcp_timer_stop(tp, TT_2MSL);
1394 	tcp_timer_stop(tp, TT_DELACK);
1395 	if (tp->t_fb->tfb_tcp_timer_stop_all) {
1396 		/*
1397 		 * Call the stop-all function of the methods,
1398 		 * this function should call the tcp_timer_stop()
1399 		 * method with each of the function specific timeouts.
1400 		 * That stop will be called via the tfb_tcp_timer_stop()
1401 		 * which should use the async drain function of the
1402 		 * callout system (see tcp_var.h).
1403 		 */
1404 		tp->t_fb->tfb_tcp_timer_stop_all(tp);
1405 	}
1406 
1407 	/*
1408 	 * If we got enough samples through the srtt filter,
1409 	 * save the rtt and rttvar in the routing entry.
1410 	 * 'Enough' is arbitrarily defined as 4 rtt samples.
1411 	 * 4 samples is enough for the srtt filter to converge
1412 	 * to within enough % of the correct value; fewer samples
1413 	 * and we could save a bogus rtt. The danger is not high
1414 	 * as tcp quickly recovers from everything.
1415 	 * XXX: Works very well but needs some more statistics!
1416 	 */
1417 	if (tp->t_rttupdated >= 4) {
1418 		struct hc_metrics_lite metrics;
1419 		uint32_t ssthresh;
1420 
1421 		bzero(&metrics, sizeof(metrics));
1422 		/*
1423 		 * Update the ssthresh always when the conditions below
1424 		 * are satisfied. This gives us better new start value
1425 		 * for the congestion avoidance for new connections.
1426 		 * ssthresh is only set if packet loss occurred on a session.
1427 		 *
1428 		 * XXXRW: 'so' may be NULL here, and/or socket buffer may be
1429 		 * being torn down.  Ideally this code would not use 'so'.
1430 		 */
1431 		ssthresh = tp->snd_ssthresh;
1432 		if (ssthresh != 0 && ssthresh < so->so_snd.sb_hiwat / 2) {
1433 			/*
1434 			 * convert the limit from user data bytes to
1435 			 * packets then to packet data bytes.
1436 			 */
1437 			ssthresh = (ssthresh + tp->t_maxseg / 2) / tp->t_maxseg;
1438 			if (ssthresh < 2)
1439 				ssthresh = 2;
1440 			ssthresh *= (tp->t_maxseg +
1441 #ifdef INET6
1442 			    (isipv6 ? sizeof (struct ip6_hdr) +
1443 				sizeof (struct tcphdr) :
1444 #endif
1445 				sizeof (struct tcpiphdr)
1446 #ifdef INET6
1447 			    )
1448 #endif
1449 			    );
1450 		} else
1451 			ssthresh = 0;
1452 		metrics.rmx_ssthresh = ssthresh;
1453 
1454 		metrics.rmx_rtt = tp->t_srtt;
1455 		metrics.rmx_rttvar = tp->t_rttvar;
1456 		metrics.rmx_cwnd = tp->snd_cwnd;
1457 		metrics.rmx_sendpipe = 0;
1458 		metrics.rmx_recvpipe = 0;
1459 
1460 		tcp_hc_update(&inp->inp_inc, &metrics);
1461 	}
1462 
1463 	/* free the reassembly queue, if any */
1464 	tcp_reass_flush(tp);
1465 
1466 #ifdef TCP_OFFLOAD
1467 	/* Disconnect offload device, if any. */
1468 	if (tp->t_flags & TF_TOE)
1469 		tcp_offload_detach(tp);
1470 #endif
1471 
1472 	tcp_free_sackholes(tp);
1473 
1474 #ifdef TCPPCAP
1475 	/* Free the TCP PCAP queues. */
1476 	tcp_pcap_drain(&(tp->t_inpkts));
1477 	tcp_pcap_drain(&(tp->t_outpkts));
1478 #endif
1479 
1480 	/* Allow the CC algorithm to clean up after itself. */
1481 	if (CC_ALGO(tp)->cb_destroy != NULL)
1482 		CC_ALGO(tp)->cb_destroy(tp->ccv);
1483 
1484 #ifdef TCP_HHOOK
1485 	khelp_destroy_osd(tp->osd);
1486 #endif
1487 
1488 	CC_ALGO(tp) = NULL;
1489 	inp->inp_ppcb = NULL;
1490 	if (tp->t_timers->tt_draincnt == 0) {
1491 		/* We own the last reference on tcpcb, let's free it. */
1492 		TCPSTATES_DEC(tp->t_state);
1493 		if (tp->t_fb->tfb_tcp_fb_fini)
1494 			(*tp->t_fb->tfb_tcp_fb_fini)(tp, 1);
1495 		refcount_release(&tp->t_fb->tfb_refcnt);
1496 		tp->t_inpcb = NULL;
1497 		uma_zfree(V_tcpcb_zone, tp);
1498 		released = in_pcbrele_wlocked(inp);
1499 		KASSERT(!released, ("%s: inp %p should not have been released "
1500 			"here", __func__, inp));
1501 	}
1502 }
1503 
1504 void
1505 tcp_timer_discard(void *ptp)
1506 {
1507 	struct inpcb *inp;
1508 	struct tcpcb *tp;
1509 
1510 	tp = (struct tcpcb *)ptp;
1511 	CURVNET_SET(tp->t_vnet);
1512 	INP_INFO_RLOCK(&V_tcbinfo);
1513 	inp = tp->t_inpcb;
1514 	KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL",
1515 		__func__, tp));
1516 	INP_WLOCK(inp);
1517 	KASSERT((tp->t_timers->tt_flags & TT_STOPPED) != 0,
1518 		("%s: tcpcb has to be stopped here", __func__));
1519 	tp->t_timers->tt_draincnt--;
1520 	if (tp->t_timers->tt_draincnt == 0) {
1521 		/* We own the last reference on this tcpcb, let's free it. */
1522 		TCPSTATES_DEC(tp->t_state);
1523 		if (tp->t_fb->tfb_tcp_fb_fini)
1524 			(*tp->t_fb->tfb_tcp_fb_fini)(tp, 1);
1525 		refcount_release(&tp->t_fb->tfb_refcnt);
1526 		tp->t_inpcb = NULL;
1527 		uma_zfree(V_tcpcb_zone, tp);
1528 		if (in_pcbrele_wlocked(inp)) {
1529 			INP_INFO_RUNLOCK(&V_tcbinfo);
1530 			CURVNET_RESTORE();
1531 			return;
1532 		}
1533 	}
1534 	INP_WUNLOCK(inp);
1535 	INP_INFO_RUNLOCK(&V_tcbinfo);
1536 	CURVNET_RESTORE();
1537 }
1538 
1539 /*
1540  * Attempt to close a TCP control block, marking it as dropped, and freeing
1541  * the socket if we hold the only reference.
1542  */
1543 struct tcpcb *
1544 tcp_close(struct tcpcb *tp)
1545 {
1546 	struct inpcb *inp = tp->t_inpcb;
1547 	struct socket *so;
1548 
1549 	INP_INFO_LOCK_ASSERT(&V_tcbinfo);
1550 	INP_WLOCK_ASSERT(inp);
1551 
1552 #ifdef TCP_OFFLOAD
1553 	if (tp->t_state == TCPS_LISTEN)
1554 		tcp_offload_listen_stop(tp);
1555 #endif
1556 #ifdef TCP_RFC7413
1557 	/*
1558 	 * This releases the TFO pending counter resource for TFO listen
1559 	 * sockets as well as passively-created TFO sockets that transition
1560 	 * from SYN_RECEIVED to CLOSED.
1561 	 */
1562 	if (tp->t_tfo_pending) {
1563 		tcp_fastopen_decrement_counter(tp->t_tfo_pending);
1564 		tp->t_tfo_pending = NULL;
1565 	}
1566 #endif
1567 	in_pcbdrop(inp);
1568 	TCPSTAT_INC(tcps_closed);
1569 	if (tp->t_state != TCPS_CLOSED)
1570 		tcp_state_change(tp, TCPS_CLOSED);
1571 	KASSERT(inp->inp_socket != NULL, ("tcp_close: inp_socket NULL"));
1572 	so = inp->inp_socket;
1573 	soisdisconnected(so);
1574 	if (inp->inp_flags & INP_SOCKREF) {
1575 		KASSERT(so->so_state & SS_PROTOREF,
1576 		    ("tcp_close: !SS_PROTOREF"));
1577 		inp->inp_flags &= ~INP_SOCKREF;
1578 		INP_WUNLOCK(inp);
1579 		ACCEPT_LOCK();
1580 		SOCK_LOCK(so);
1581 		so->so_state &= ~SS_PROTOREF;
1582 		sofree(so);
1583 		return (NULL);
1584 	}
1585 	return (tp);
1586 }
1587 
1588 void
1589 tcp_drain(void)
1590 {
1591 	VNET_ITERATOR_DECL(vnet_iter);
1592 
1593 	if (!do_tcpdrain)
1594 		return;
1595 
1596 	VNET_LIST_RLOCK_NOSLEEP();
1597 	VNET_FOREACH(vnet_iter) {
1598 		CURVNET_SET(vnet_iter);
1599 		struct inpcb *inpb;
1600 		struct tcpcb *tcpb;
1601 
1602 	/*
1603 	 * Walk the tcpbs, if existing, and flush the reassembly queue,
1604 	 * if there is one...
1605 	 * XXX: The "Net/3" implementation doesn't imply that the TCP
1606 	 *      reassembly queue should be flushed, but in a situation
1607 	 *	where we're really low on mbufs, this is potentially
1608 	 *	useful.
1609 	 */
1610 		INP_INFO_WLOCK(&V_tcbinfo);
1611 		LIST_FOREACH(inpb, V_tcbinfo.ipi_listhead, inp_list) {
1612 			if (inpb->inp_flags & INP_TIMEWAIT)
1613 				continue;
1614 			INP_WLOCK(inpb);
1615 			if ((tcpb = intotcpcb(inpb)) != NULL) {
1616 				tcp_reass_flush(tcpb);
1617 				tcp_clean_sackreport(tcpb);
1618 #ifdef TCPPCAP
1619 				if (tcp_pcap_aggressive_free) {
1620 					/* Free the TCP PCAP queues. */
1621 					tcp_pcap_drain(&(tcpb->t_inpkts));
1622 					tcp_pcap_drain(&(tcpb->t_outpkts));
1623 				}
1624 #endif
1625 			}
1626 			INP_WUNLOCK(inpb);
1627 		}
1628 		INP_INFO_WUNLOCK(&V_tcbinfo);
1629 		CURVNET_RESTORE();
1630 	}
1631 	VNET_LIST_RUNLOCK_NOSLEEP();
1632 }
1633 
1634 /*
1635  * Notify a tcp user of an asynchronous error;
1636  * store error as soft error, but wake up user
1637  * (for now, won't do anything until can select for soft error).
1638  *
1639  * Do not wake up user since there currently is no mechanism for
1640  * reporting soft errors (yet - a kqueue filter may be added).
1641  */
1642 static struct inpcb *
1643 tcp_notify(struct inpcb *inp, int error)
1644 {
1645 	struct tcpcb *tp;
1646 
1647 	INP_INFO_LOCK_ASSERT(&V_tcbinfo);
1648 	INP_WLOCK_ASSERT(inp);
1649 
1650 	if ((inp->inp_flags & INP_TIMEWAIT) ||
1651 	    (inp->inp_flags & INP_DROPPED))
1652 		return (inp);
1653 
1654 	tp = intotcpcb(inp);
1655 	KASSERT(tp != NULL, ("tcp_notify: tp == NULL"));
1656 
1657 	/*
1658 	 * Ignore some errors if we are hooked up.
1659 	 * If connection hasn't completed, has retransmitted several times,
1660 	 * and receives a second error, give up now.  This is better
1661 	 * than waiting a long time to establish a connection that
1662 	 * can never complete.
1663 	 */
1664 	if (tp->t_state == TCPS_ESTABLISHED &&
1665 	    (error == EHOSTUNREACH || error == ENETUNREACH ||
1666 	     error == EHOSTDOWN)) {
1667 		if (inp->inp_route.ro_rt) {
1668 			RTFREE(inp->inp_route.ro_rt);
1669 			inp->inp_route.ro_rt = (struct rtentry *)NULL;
1670 		}
1671 		return (inp);
1672 	} else if (tp->t_state < TCPS_ESTABLISHED && tp->t_rxtshift > 3 &&
1673 	    tp->t_softerror) {
1674 		tp = tcp_drop(tp, error);
1675 		if (tp != NULL)
1676 			return (inp);
1677 		else
1678 			return (NULL);
1679 	} else {
1680 		tp->t_softerror = error;
1681 		return (inp);
1682 	}
1683 #if 0
1684 	wakeup( &so->so_timeo);
1685 	sorwakeup(so);
1686 	sowwakeup(so);
1687 #endif
1688 }
1689 
1690 static int
1691 tcp_pcblist(SYSCTL_HANDLER_ARGS)
1692 {
1693 	int error, i, m, n, pcb_count;
1694 	struct inpcb *inp, **inp_list;
1695 	inp_gen_t gencnt;
1696 	struct xinpgen xig;
1697 
1698 	/*
1699 	 * The process of preparing the TCB list is too time-consuming and
1700 	 * resource-intensive to repeat twice on every request.
1701 	 */
1702 	if (req->oldptr == NULL) {
1703 		n = V_tcbinfo.ipi_count +
1704 		    counter_u64_fetch(V_tcps_states[TCPS_SYN_RECEIVED]);
1705 		n += imax(n / 8, 10);
1706 		req->oldidx = 2 * (sizeof xig) + n * sizeof(struct xtcpcb);
1707 		return (0);
1708 	}
1709 
1710 	if (req->newptr != NULL)
1711 		return (EPERM);
1712 
1713 	/*
1714 	 * OK, now we're committed to doing something.
1715 	 */
1716 	INP_LIST_RLOCK(&V_tcbinfo);
1717 	gencnt = V_tcbinfo.ipi_gencnt;
1718 	n = V_tcbinfo.ipi_count;
1719 	INP_LIST_RUNLOCK(&V_tcbinfo);
1720 
1721 	m = counter_u64_fetch(V_tcps_states[TCPS_SYN_RECEIVED]);
1722 
1723 	error = sysctl_wire_old_buffer(req, 2 * (sizeof xig)
1724 		+ (n + m) * sizeof(struct xtcpcb));
1725 	if (error != 0)
1726 		return (error);
1727 
1728 	xig.xig_len = sizeof xig;
1729 	xig.xig_count = n + m;
1730 	xig.xig_gen = gencnt;
1731 	xig.xig_sogen = so_gencnt;
1732 	error = SYSCTL_OUT(req, &xig, sizeof xig);
1733 	if (error)
1734 		return (error);
1735 
1736 	error = syncache_pcblist(req, m, &pcb_count);
1737 	if (error)
1738 		return (error);
1739 
1740 	inp_list = malloc(n * sizeof *inp_list, M_TEMP, M_WAITOK);
1741 
1742 	INP_INFO_WLOCK(&V_tcbinfo);
1743 	for (inp = LIST_FIRST(V_tcbinfo.ipi_listhead), i = 0;
1744 	    inp != NULL && i < n; inp = LIST_NEXT(inp, inp_list)) {
1745 		INP_WLOCK(inp);
1746 		if (inp->inp_gencnt <= gencnt) {
1747 			/*
1748 			 * XXX: This use of cr_cansee(), introduced with
1749 			 * TCP state changes, is not quite right, but for
1750 			 * now, better than nothing.
1751 			 */
1752 			if (inp->inp_flags & INP_TIMEWAIT) {
1753 				if (intotw(inp) != NULL)
1754 					error = cr_cansee(req->td->td_ucred,
1755 					    intotw(inp)->tw_cred);
1756 				else
1757 					error = EINVAL;	/* Skip this inp. */
1758 			} else
1759 				error = cr_canseeinpcb(req->td->td_ucred, inp);
1760 			if (error == 0) {
1761 				in_pcbref(inp);
1762 				inp_list[i++] = inp;
1763 			}
1764 		}
1765 		INP_WUNLOCK(inp);
1766 	}
1767 	INP_INFO_WUNLOCK(&V_tcbinfo);
1768 	n = i;
1769 
1770 	error = 0;
1771 	for (i = 0; i < n; i++) {
1772 		inp = inp_list[i];
1773 		INP_RLOCK(inp);
1774 		if (inp->inp_gencnt <= gencnt) {
1775 			struct xtcpcb xt;
1776 			void *inp_ppcb;
1777 
1778 			bzero(&xt, sizeof(xt));
1779 			xt.xt_len = sizeof xt;
1780 			/* XXX should avoid extra copy */
1781 			bcopy(inp, &xt.xt_inp, sizeof *inp);
1782 			inp_ppcb = inp->inp_ppcb;
1783 			if (inp_ppcb == NULL)
1784 				bzero((char *) &xt.xt_tp, sizeof xt.xt_tp);
1785 			else if (inp->inp_flags & INP_TIMEWAIT) {
1786 				bzero((char *) &xt.xt_tp, sizeof xt.xt_tp);
1787 				xt.xt_tp.t_state = TCPS_TIME_WAIT;
1788 			} else {
1789 				bcopy(inp_ppcb, &xt.xt_tp, sizeof xt.xt_tp);
1790 				if (xt.xt_tp.t_timers)
1791 					tcp_timer_to_xtimer(&xt.xt_tp, xt.xt_tp.t_timers, &xt.xt_timer);
1792 			}
1793 			if (inp->inp_socket != NULL)
1794 				sotoxsocket(inp->inp_socket, &xt.xt_socket);
1795 			else {
1796 				bzero(&xt.xt_socket, sizeof xt.xt_socket);
1797 				xt.xt_socket.xso_protocol = IPPROTO_TCP;
1798 			}
1799 			xt.xt_inp.inp_gencnt = inp->inp_gencnt;
1800 			INP_RUNLOCK(inp);
1801 			error = SYSCTL_OUT(req, &xt, sizeof xt);
1802 		} else
1803 			INP_RUNLOCK(inp);
1804 	}
1805 	INP_INFO_RLOCK(&V_tcbinfo);
1806 	for (i = 0; i < n; i++) {
1807 		inp = inp_list[i];
1808 		INP_RLOCK(inp);
1809 		if (!in_pcbrele_rlocked(inp))
1810 			INP_RUNLOCK(inp);
1811 	}
1812 	INP_INFO_RUNLOCK(&V_tcbinfo);
1813 
1814 	if (!error) {
1815 		/*
1816 		 * Give the user an updated idea of our state.
1817 		 * If the generation differs from what we told
1818 		 * her before, she knows that something happened
1819 		 * while we were processing this request, and it
1820 		 * might be necessary to retry.
1821 		 */
1822 		INP_LIST_RLOCK(&V_tcbinfo);
1823 		xig.xig_gen = V_tcbinfo.ipi_gencnt;
1824 		xig.xig_sogen = so_gencnt;
1825 		xig.xig_count = V_tcbinfo.ipi_count + pcb_count;
1826 		INP_LIST_RUNLOCK(&V_tcbinfo);
1827 		error = SYSCTL_OUT(req, &xig, sizeof xig);
1828 	}
1829 	free(inp_list, M_TEMP);
1830 	return (error);
1831 }
1832 
1833 SYSCTL_PROC(_net_inet_tcp, TCPCTL_PCBLIST, pcblist,
1834     CTLTYPE_OPAQUE | CTLFLAG_RD, NULL, 0,
1835     tcp_pcblist, "S,xtcpcb", "List of active TCP connections");
1836 
1837 #ifdef INET
1838 static int
1839 tcp_getcred(SYSCTL_HANDLER_ARGS)
1840 {
1841 	struct xucred xuc;
1842 	struct sockaddr_in addrs[2];
1843 	struct inpcb *inp;
1844 	int error;
1845 
1846 	error = priv_check(req->td, PRIV_NETINET_GETCRED);
1847 	if (error)
1848 		return (error);
1849 	error = SYSCTL_IN(req, addrs, sizeof(addrs));
1850 	if (error)
1851 		return (error);
1852 	inp = in_pcblookup(&V_tcbinfo, addrs[1].sin_addr, addrs[1].sin_port,
1853 	    addrs[0].sin_addr, addrs[0].sin_port, INPLOOKUP_RLOCKPCB, NULL);
1854 	if (inp != NULL) {
1855 		if (inp->inp_socket == NULL)
1856 			error = ENOENT;
1857 		if (error == 0)
1858 			error = cr_canseeinpcb(req->td->td_ucred, inp);
1859 		if (error == 0)
1860 			cru2x(inp->inp_cred, &xuc);
1861 		INP_RUNLOCK(inp);
1862 	} else
1863 		error = ENOENT;
1864 	if (error == 0)
1865 		error = SYSCTL_OUT(req, &xuc, sizeof(struct xucred));
1866 	return (error);
1867 }
1868 
1869 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, getcred,
1870     CTLTYPE_OPAQUE|CTLFLAG_RW|CTLFLAG_PRISON, 0, 0,
1871     tcp_getcred, "S,xucred", "Get the xucred of a TCP connection");
1872 #endif /* INET */
1873 
1874 #ifdef INET6
1875 static int
1876 tcp6_getcred(SYSCTL_HANDLER_ARGS)
1877 {
1878 	struct xucred xuc;
1879 	struct sockaddr_in6 addrs[2];
1880 	struct inpcb *inp;
1881 	int error;
1882 #ifdef INET
1883 	int mapped = 0;
1884 #endif
1885 
1886 	error = priv_check(req->td, PRIV_NETINET_GETCRED);
1887 	if (error)
1888 		return (error);
1889 	error = SYSCTL_IN(req, addrs, sizeof(addrs));
1890 	if (error)
1891 		return (error);
1892 	if ((error = sa6_embedscope(&addrs[0], V_ip6_use_defzone)) != 0 ||
1893 	    (error = sa6_embedscope(&addrs[1], V_ip6_use_defzone)) != 0) {
1894 		return (error);
1895 	}
1896 	if (IN6_IS_ADDR_V4MAPPED(&addrs[0].sin6_addr)) {
1897 #ifdef INET
1898 		if (IN6_IS_ADDR_V4MAPPED(&addrs[1].sin6_addr))
1899 			mapped = 1;
1900 		else
1901 #endif
1902 			return (EINVAL);
1903 	}
1904 
1905 #ifdef INET
1906 	if (mapped == 1)
1907 		inp = in_pcblookup(&V_tcbinfo,
1908 			*(struct in_addr *)&addrs[1].sin6_addr.s6_addr[12],
1909 			addrs[1].sin6_port,
1910 			*(struct in_addr *)&addrs[0].sin6_addr.s6_addr[12],
1911 			addrs[0].sin6_port, INPLOOKUP_RLOCKPCB, NULL);
1912 	else
1913 #endif
1914 		inp = in6_pcblookup(&V_tcbinfo,
1915 			&addrs[1].sin6_addr, addrs[1].sin6_port,
1916 			&addrs[0].sin6_addr, addrs[0].sin6_port,
1917 			INPLOOKUP_RLOCKPCB, NULL);
1918 	if (inp != NULL) {
1919 		if (inp->inp_socket == NULL)
1920 			error = ENOENT;
1921 		if (error == 0)
1922 			error = cr_canseeinpcb(req->td->td_ucred, inp);
1923 		if (error == 0)
1924 			cru2x(inp->inp_cred, &xuc);
1925 		INP_RUNLOCK(inp);
1926 	} else
1927 		error = ENOENT;
1928 	if (error == 0)
1929 		error = SYSCTL_OUT(req, &xuc, sizeof(struct xucred));
1930 	return (error);
1931 }
1932 
1933 SYSCTL_PROC(_net_inet6_tcp6, OID_AUTO, getcred,
1934     CTLTYPE_OPAQUE|CTLFLAG_RW|CTLFLAG_PRISON, 0, 0,
1935     tcp6_getcred, "S,xucred", "Get the xucred of a TCP6 connection");
1936 #endif /* INET6 */
1937 
1938 
1939 #ifdef INET
1940 void
1941 tcp_ctlinput(int cmd, struct sockaddr *sa, void *vip)
1942 {
1943 	struct ip *ip = vip;
1944 	struct tcphdr *th;
1945 	struct in_addr faddr;
1946 	struct inpcb *inp;
1947 	struct tcpcb *tp;
1948 	struct inpcb *(*notify)(struct inpcb *, int) = tcp_notify;
1949 	struct icmp *icp;
1950 	struct in_conninfo inc;
1951 	tcp_seq icmp_tcp_seq;
1952 	int mtu;
1953 
1954 	faddr = ((struct sockaddr_in *)sa)->sin_addr;
1955 	if (sa->sa_family != AF_INET || faddr.s_addr == INADDR_ANY)
1956 		return;
1957 
1958 	if (cmd == PRC_MSGSIZE)
1959 		notify = tcp_mtudisc_notify;
1960 	else if (V_icmp_may_rst && (cmd == PRC_UNREACH_ADMIN_PROHIB ||
1961 		cmd == PRC_UNREACH_PORT || cmd == PRC_UNREACH_PROTOCOL ||
1962 		cmd == PRC_TIMXCEED_INTRANS) && ip)
1963 		notify = tcp_drop_syn_sent;
1964 
1965 	/*
1966 	 * Hostdead is ugly because it goes linearly through all PCBs.
1967 	 * XXX: We never get this from ICMP, otherwise it makes an
1968 	 * excellent DoS attack on machines with many connections.
1969 	 */
1970 	else if (cmd == PRC_HOSTDEAD)
1971 		ip = NULL;
1972 	else if ((unsigned)cmd >= PRC_NCMDS || inetctlerrmap[cmd] == 0)
1973 		return;
1974 
1975 	if (ip == NULL) {
1976 		in_pcbnotifyall(&V_tcbinfo, faddr, inetctlerrmap[cmd], notify);
1977 		return;
1978 	}
1979 
1980 	icp = (struct icmp *)((caddr_t)ip - offsetof(struct icmp, icmp_ip));
1981 	th = (struct tcphdr *)((caddr_t)ip + (ip->ip_hl << 2));
1982 	INP_INFO_RLOCK(&V_tcbinfo);
1983 	inp = in_pcblookup(&V_tcbinfo, faddr, th->th_dport, ip->ip_src,
1984 	    th->th_sport, INPLOOKUP_WLOCKPCB, NULL);
1985 	if (inp != NULL && PRC_IS_REDIRECT(cmd)) {
1986 		/* signal EHOSTDOWN, as it flushes the cached route */
1987 		inp = (*notify)(inp, EHOSTDOWN);
1988 		if (inp != NULL)
1989 			INP_WUNLOCK(inp);
1990 	} else if (inp != NULL)  {
1991 		if (!(inp->inp_flags & INP_TIMEWAIT) &&
1992 		    !(inp->inp_flags & INP_DROPPED) &&
1993 		    !(inp->inp_socket == NULL)) {
1994 			icmp_tcp_seq = ntohl(th->th_seq);
1995 			tp = intotcpcb(inp);
1996 			if (SEQ_GEQ(icmp_tcp_seq, tp->snd_una) &&
1997 			    SEQ_LT(icmp_tcp_seq, tp->snd_max)) {
1998 				if (cmd == PRC_MSGSIZE) {
1999 					/*
2000 					 * MTU discovery:
2001 					 * If we got a needfrag set the MTU
2002 					 * in the route to the suggested new
2003 					 * value (if given) and then notify.
2004 					 */
2005 				    	mtu = ntohs(icp->icmp_nextmtu);
2006 					/*
2007 					 * If no alternative MTU was
2008 					 * proposed, try the next smaller
2009 					 * one.
2010 					 */
2011 					if (!mtu)
2012 						mtu = ip_next_mtu(
2013 						    ntohs(ip->ip_len), 1);
2014 					if (mtu < V_tcp_minmss +
2015 					    sizeof(struct tcpiphdr))
2016 						mtu = V_tcp_minmss +
2017 						    sizeof(struct tcpiphdr);
2018 					/*
2019 					 * Only process the offered MTU if it
2020 					 * is smaller than the current one.
2021 					 */
2022 					if (mtu < tp->t_maxseg +
2023 					    sizeof(struct tcpiphdr)) {
2024 						bzero(&inc, sizeof(inc));
2025 						inc.inc_faddr = faddr;
2026 						inc.inc_fibnum =
2027 						    inp->inp_inc.inc_fibnum;
2028 						tcp_hc_updatemtu(&inc, mtu);
2029 						tcp_mtudisc(inp, mtu);
2030 					}
2031 				} else
2032 					inp = (*notify)(inp,
2033 					    inetctlerrmap[cmd]);
2034 			}
2035 		}
2036 		if (inp != NULL)
2037 			INP_WUNLOCK(inp);
2038 	} else {
2039 		bzero(&inc, sizeof(inc));
2040 		inc.inc_fport = th->th_dport;
2041 		inc.inc_lport = th->th_sport;
2042 		inc.inc_faddr = faddr;
2043 		inc.inc_laddr = ip->ip_src;
2044 		syncache_unreach(&inc, th);
2045 	}
2046 	INP_INFO_RUNLOCK(&V_tcbinfo);
2047 }
2048 #endif /* INET */
2049 
2050 #ifdef INET6
2051 void
2052 tcp6_ctlinput(int cmd, struct sockaddr *sa, void *d)
2053 {
2054 	struct in6_addr *dst;
2055 	struct tcphdr *th;
2056 	struct inpcb *(*notify)(struct inpcb *, int) = tcp_notify;
2057 	struct ip6_hdr *ip6;
2058 	struct mbuf *m;
2059 	struct inpcb *inp;
2060 	struct tcpcb *tp;
2061 	struct icmp6_hdr *icmp6;
2062 	struct ip6ctlparam *ip6cp = NULL;
2063 	const struct sockaddr_in6 *sa6_src = NULL;
2064 	struct in_conninfo inc;
2065 	tcp_seq icmp_tcp_seq;
2066 	unsigned int mtu;
2067 	unsigned int off;
2068 
2069 
2070 	if (sa->sa_family != AF_INET6 ||
2071 	    sa->sa_len != sizeof(struct sockaddr_in6))
2072 		return;
2073 
2074 	/* if the parameter is from icmp6, decode it. */
2075 	if (d != NULL) {
2076 		ip6cp = (struct ip6ctlparam *)d;
2077 		icmp6 = ip6cp->ip6c_icmp6;
2078 		m = ip6cp->ip6c_m;
2079 		ip6 = ip6cp->ip6c_ip6;
2080 		off = ip6cp->ip6c_off;
2081 		sa6_src = ip6cp->ip6c_src;
2082 		dst = ip6cp->ip6c_finaldst;
2083 	} else {
2084 		m = NULL;
2085 		ip6 = NULL;
2086 		off = 0;	/* fool gcc */
2087 		sa6_src = &sa6_any;
2088 		dst = NULL;
2089 	}
2090 
2091 	if (cmd == PRC_MSGSIZE)
2092 		notify = tcp_mtudisc_notify;
2093 	else if (V_icmp_may_rst && (cmd == PRC_UNREACH_ADMIN_PROHIB ||
2094 		cmd == PRC_UNREACH_PORT || cmd == PRC_UNREACH_PROTOCOL ||
2095 		cmd == PRC_TIMXCEED_INTRANS) && ip6 != NULL)
2096 		notify = tcp_drop_syn_sent;
2097 
2098 	/*
2099 	 * Hostdead is ugly because it goes linearly through all PCBs.
2100 	 * XXX: We never get this from ICMP, otherwise it makes an
2101 	 * excellent DoS attack on machines with many connections.
2102 	 */
2103 	else if (cmd == PRC_HOSTDEAD)
2104 		ip6 = NULL;
2105 	else if ((unsigned)cmd >= PRC_NCMDS || inet6ctlerrmap[cmd] == 0)
2106 		return;
2107 
2108 	if (ip6 == NULL) {
2109 		in6_pcbnotify(&V_tcbinfo, sa, 0,
2110 			      (const struct sockaddr *)sa6_src,
2111 			      0, cmd, NULL, notify);
2112 		return;
2113 	}
2114 
2115 	/* Check if we can safely get the ports from the tcp hdr */
2116 	if (m == NULL ||
2117 	    (m->m_pkthdr.len <
2118 		(int32_t) (off + offsetof(struct tcphdr, th_seq)))) {
2119 		return;
2120 	}
2121 
2122 	th = (struct tcphdr *) mtodo(ip6cp->ip6c_m, ip6cp->ip6c_off);
2123 	INP_INFO_RLOCK(&V_tcbinfo);
2124 	inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_dst, th->th_dport,
2125 	    &ip6->ip6_src, th->th_sport, INPLOOKUP_WLOCKPCB, NULL);
2126 	if (inp != NULL && PRC_IS_REDIRECT(cmd)) {
2127 		/* signal EHOSTDOWN, as it flushes the cached route */
2128 		inp = (*notify)(inp, EHOSTDOWN);
2129 		if (inp != NULL)
2130 			INP_WUNLOCK(inp);
2131 	} else if (inp != NULL)  {
2132 		if (!(inp->inp_flags & INP_TIMEWAIT) &&
2133 		    !(inp->inp_flags & INP_DROPPED) &&
2134 		    !(inp->inp_socket == NULL)) {
2135 			icmp_tcp_seq = ntohl(th->th_seq);
2136 			tp = intotcpcb(inp);
2137 			if (SEQ_GEQ(icmp_tcp_seq, tp->snd_una) &&
2138 			    SEQ_LT(icmp_tcp_seq, tp->snd_max)) {
2139 				if (cmd == PRC_MSGSIZE) {
2140 					/*
2141 					 * MTU discovery:
2142 					 * If we got a needfrag set the MTU
2143 					 * in the route to the suggested new
2144 					 * value (if given) and then notify.
2145 					 */
2146 					mtu = ntohl(icmp6->icmp6_mtu);
2147 					/*
2148 					 * If no alternative MTU was
2149 					 * proposed, or the proposed
2150 					 * MTU was too small, set to
2151 					 * the min.
2152 					 */
2153 					if (mtu < IPV6_MMTU)
2154 						mtu = IPV6_MMTU - 8;
2155 
2156 
2157 					bzero(&inc, sizeof(inc));
2158 					inc.inc_fibnum = M_GETFIB(m);
2159 					inc.inc_flags |= INC_ISIPV6;
2160 					inc.inc6_faddr = *dst;
2161 					if (in6_setscope(&inc.inc6_faddr,
2162 						m->m_pkthdr.rcvif, NULL))
2163 						goto unlock_inp;
2164 
2165 					/*
2166 					 * Only process the offered MTU if it
2167 					 * is smaller than the current one.
2168 					 */
2169 					if (mtu < tp->t_maxseg +
2170 					    (sizeof (*th) + sizeof (*ip6))) {
2171 						tcp_hc_updatemtu(&inc, mtu);
2172 						tcp_mtudisc(inp, mtu);
2173 						ICMP6STAT_INC(icp6s_pmtuchg);
2174 					}
2175 				} else
2176 					inp = (*notify)(inp,
2177 					    inet6ctlerrmap[cmd]);
2178 			}
2179 		}
2180 unlock_inp:
2181 		if (inp != NULL)
2182 			INP_WUNLOCK(inp);
2183 	} else {
2184 		bzero(&inc, sizeof(inc));
2185 		inc.inc_fibnum = M_GETFIB(m);
2186 		inc.inc_flags |= INC_ISIPV6;
2187 		inc.inc_fport = th->th_dport;
2188 		inc.inc_lport = th->th_sport;
2189 		inc.inc6_faddr = *dst;
2190 		inc.inc6_laddr = ip6->ip6_src;
2191 		syncache_unreach(&inc, th);
2192 	}
2193 	INP_INFO_RUNLOCK(&V_tcbinfo);
2194 }
2195 #endif /* INET6 */
2196 
2197 
2198 /*
2199  * Following is where TCP initial sequence number generation occurs.
2200  *
2201  * There are two places where we must use initial sequence numbers:
2202  * 1.  In SYN-ACK packets.
2203  * 2.  In SYN packets.
2204  *
2205  * All ISNs for SYN-ACK packets are generated by the syncache.  See
2206  * tcp_syncache.c for details.
2207  *
2208  * The ISNs in SYN packets must be monotonic; TIME_WAIT recycling
2209  * depends on this property.  In addition, these ISNs should be
2210  * unguessable so as to prevent connection hijacking.  To satisfy
2211  * the requirements of this situation, the algorithm outlined in
2212  * RFC 1948 is used, with only small modifications.
2213  *
2214  * Implementation details:
2215  *
2216  * Time is based off the system timer, and is corrected so that it
2217  * increases by one megabyte per second.  This allows for proper
2218  * recycling on high speed LANs while still leaving over an hour
2219  * before rollover.
2220  *
2221  * As reading the *exact* system time is too expensive to be done
2222  * whenever setting up a TCP connection, we increment the time
2223  * offset in two ways.  First, a small random positive increment
2224  * is added to isn_offset for each connection that is set up.
2225  * Second, the function tcp_isn_tick fires once per clock tick
2226  * and increments isn_offset as necessary so that sequence numbers
2227  * are incremented at approximately ISN_BYTES_PER_SECOND.  The
2228  * random positive increments serve only to ensure that the same
2229  * exact sequence number is never sent out twice (as could otherwise
2230  * happen when a port is recycled in less than the system tick
2231  * interval.)
2232  *
2233  * net.inet.tcp.isn_reseed_interval controls the number of seconds
2234  * between seeding of isn_secret.  This is normally set to zero,
2235  * as reseeding should not be necessary.
2236  *
2237  * Locking of the global variables isn_secret, isn_last_reseed, isn_offset,
2238  * isn_offset_old, and isn_ctx is performed using the TCP pcbinfo lock.  In
2239  * general, this means holding an exclusive (write) lock.
2240  */
2241 
2242 #define ISN_BYTES_PER_SECOND 1048576
2243 #define ISN_STATIC_INCREMENT 4096
2244 #define ISN_RANDOM_INCREMENT (4096 - 1)
2245 
2246 static VNET_DEFINE(u_char, isn_secret[32]);
2247 static VNET_DEFINE(int, isn_last);
2248 static VNET_DEFINE(int, isn_last_reseed);
2249 static VNET_DEFINE(u_int32_t, isn_offset);
2250 static VNET_DEFINE(u_int32_t, isn_offset_old);
2251 
2252 #define	V_isn_secret			VNET(isn_secret)
2253 #define	V_isn_last			VNET(isn_last)
2254 #define	V_isn_last_reseed		VNET(isn_last_reseed)
2255 #define	V_isn_offset			VNET(isn_offset)
2256 #define	V_isn_offset_old		VNET(isn_offset_old)
2257 
2258 tcp_seq
2259 tcp_new_isn(struct tcpcb *tp)
2260 {
2261 	MD5_CTX isn_ctx;
2262 	u_int32_t md5_buffer[4];
2263 	tcp_seq new_isn;
2264 	u_int32_t projected_offset;
2265 
2266 	INP_WLOCK_ASSERT(tp->t_inpcb);
2267 
2268 	ISN_LOCK();
2269 	/* Seed if this is the first use, reseed if requested. */
2270 	if ((V_isn_last_reseed == 0) || ((V_tcp_isn_reseed_interval > 0) &&
2271 	     (((u_int)V_isn_last_reseed + (u_int)V_tcp_isn_reseed_interval*hz)
2272 		< (u_int)ticks))) {
2273 		read_random(&V_isn_secret, sizeof(V_isn_secret));
2274 		V_isn_last_reseed = ticks;
2275 	}
2276 
2277 	/* Compute the md5 hash and return the ISN. */
2278 	MD5Init(&isn_ctx);
2279 	MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_fport, sizeof(u_short));
2280 	MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_lport, sizeof(u_short));
2281 #ifdef INET6
2282 	if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) {
2283 		MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->in6p_faddr,
2284 			  sizeof(struct in6_addr));
2285 		MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->in6p_laddr,
2286 			  sizeof(struct in6_addr));
2287 	} else
2288 #endif
2289 	{
2290 		MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_faddr,
2291 			  sizeof(struct in_addr));
2292 		MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_laddr,
2293 			  sizeof(struct in_addr));
2294 	}
2295 	MD5Update(&isn_ctx, (u_char *) &V_isn_secret, sizeof(V_isn_secret));
2296 	MD5Final((u_char *) &md5_buffer, &isn_ctx);
2297 	new_isn = (tcp_seq) md5_buffer[0];
2298 	V_isn_offset += ISN_STATIC_INCREMENT +
2299 		(arc4random() & ISN_RANDOM_INCREMENT);
2300 	if (ticks != V_isn_last) {
2301 		projected_offset = V_isn_offset_old +
2302 		    ISN_BYTES_PER_SECOND / hz * (ticks - V_isn_last);
2303 		if (SEQ_GT(projected_offset, V_isn_offset))
2304 			V_isn_offset = projected_offset;
2305 		V_isn_offset_old = V_isn_offset;
2306 		V_isn_last = ticks;
2307 	}
2308 	new_isn += V_isn_offset;
2309 	ISN_UNLOCK();
2310 	return (new_isn);
2311 }
2312 
2313 /*
2314  * When a specific ICMP unreachable message is received and the
2315  * connection state is SYN-SENT, drop the connection.  This behavior
2316  * is controlled by the icmp_may_rst sysctl.
2317  */
2318 struct inpcb *
2319 tcp_drop_syn_sent(struct inpcb *inp, int errno)
2320 {
2321 	struct tcpcb *tp;
2322 
2323 	INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
2324 	INP_WLOCK_ASSERT(inp);
2325 
2326 	if ((inp->inp_flags & INP_TIMEWAIT) ||
2327 	    (inp->inp_flags & INP_DROPPED))
2328 		return (inp);
2329 
2330 	tp = intotcpcb(inp);
2331 	if (tp->t_state != TCPS_SYN_SENT)
2332 		return (inp);
2333 
2334 	tp = tcp_drop(tp, errno);
2335 	if (tp != NULL)
2336 		return (inp);
2337 	else
2338 		return (NULL);
2339 }
2340 
2341 /*
2342  * When `need fragmentation' ICMP is received, update our idea of the MSS
2343  * based on the new value. Also nudge TCP to send something, since we
2344  * know the packet we just sent was dropped.
2345  * This duplicates some code in the tcp_mss() function in tcp_input.c.
2346  */
2347 static struct inpcb *
2348 tcp_mtudisc_notify(struct inpcb *inp, int error)
2349 {
2350 
2351 	tcp_mtudisc(inp, -1);
2352 	return (inp);
2353 }
2354 
2355 static void
2356 tcp_mtudisc(struct inpcb *inp, int mtuoffer)
2357 {
2358 	struct tcpcb *tp;
2359 	struct socket *so;
2360 
2361 	INP_WLOCK_ASSERT(inp);
2362 	if ((inp->inp_flags & INP_TIMEWAIT) ||
2363 	    (inp->inp_flags & INP_DROPPED))
2364 		return;
2365 
2366 	tp = intotcpcb(inp);
2367 	KASSERT(tp != NULL, ("tcp_mtudisc: tp == NULL"));
2368 
2369 	tcp_mss_update(tp, -1, mtuoffer, NULL, NULL);
2370 
2371 	so = inp->inp_socket;
2372 	SOCKBUF_LOCK(&so->so_snd);
2373 	/* If the mss is larger than the socket buffer, decrease the mss. */
2374 	if (so->so_snd.sb_hiwat < tp->t_maxseg)
2375 		tp->t_maxseg = so->so_snd.sb_hiwat;
2376 	SOCKBUF_UNLOCK(&so->so_snd);
2377 
2378 	TCPSTAT_INC(tcps_mturesent);
2379 	tp->t_rtttime = 0;
2380 	tp->snd_nxt = tp->snd_una;
2381 	tcp_free_sackholes(tp);
2382 	tp->snd_recover = tp->snd_max;
2383 	if (tp->t_flags & TF_SACK_PERMIT)
2384 		EXIT_FASTRECOVERY(tp->t_flags);
2385 	tp->t_fb->tfb_tcp_output(tp);
2386 }
2387 
2388 #ifdef INET
2389 /*
2390  * Look-up the routing entry to the peer of this inpcb.  If no route
2391  * is found and it cannot be allocated, then return 0.  This routine
2392  * is called by TCP routines that access the rmx structure and by
2393  * tcp_mss_update to get the peer/interface MTU.
2394  */
2395 uint32_t
2396 tcp_maxmtu(struct in_conninfo *inc, struct tcp_ifcap *cap)
2397 {
2398 	struct nhop4_extended nh4;
2399 	struct ifnet *ifp;
2400 	uint32_t maxmtu = 0;
2401 
2402 	KASSERT(inc != NULL, ("tcp_maxmtu with NULL in_conninfo pointer"));
2403 
2404 	if (inc->inc_faddr.s_addr != INADDR_ANY) {
2405 
2406 		if (fib4_lookup_nh_ext(inc->inc_fibnum, inc->inc_faddr,
2407 		    NHR_REF, 0, &nh4) != 0)
2408 			return (0);
2409 
2410 		ifp = nh4.nh_ifp;
2411 		maxmtu = nh4.nh_mtu;
2412 
2413 		/* Report additional interface capabilities. */
2414 		if (cap != NULL) {
2415 			if (ifp->if_capenable & IFCAP_TSO4 &&
2416 			    ifp->if_hwassist & CSUM_TSO) {
2417 				cap->ifcap |= CSUM_TSO;
2418 				cap->tsomax = ifp->if_hw_tsomax;
2419 				cap->tsomaxsegcount = ifp->if_hw_tsomaxsegcount;
2420 				cap->tsomaxsegsize = ifp->if_hw_tsomaxsegsize;
2421 			}
2422 		}
2423 		fib4_free_nh_ext(inc->inc_fibnum, &nh4);
2424 	}
2425 	return (maxmtu);
2426 }
2427 #endif /* INET */
2428 
2429 #ifdef INET6
2430 uint32_t
2431 tcp_maxmtu6(struct in_conninfo *inc, struct tcp_ifcap *cap)
2432 {
2433 	struct nhop6_extended nh6;
2434 	struct in6_addr dst6;
2435 	uint32_t scopeid;
2436 	struct ifnet *ifp;
2437 	uint32_t maxmtu = 0;
2438 
2439 	KASSERT(inc != NULL, ("tcp_maxmtu6 with NULL in_conninfo pointer"));
2440 
2441 	if (!IN6_IS_ADDR_UNSPECIFIED(&inc->inc6_faddr)) {
2442 		in6_splitscope(&inc->inc6_faddr, &dst6, &scopeid);
2443 		if (fib6_lookup_nh_ext(inc->inc_fibnum, &dst6, scopeid, 0,
2444 		    0, &nh6) != 0)
2445 			return (0);
2446 
2447 		ifp = nh6.nh_ifp;
2448 		maxmtu = nh6.nh_mtu;
2449 
2450 		/* Report additional interface capabilities. */
2451 		if (cap != NULL) {
2452 			if (ifp->if_capenable & IFCAP_TSO6 &&
2453 			    ifp->if_hwassist & CSUM_TSO) {
2454 				cap->ifcap |= CSUM_TSO;
2455 				cap->tsomax = ifp->if_hw_tsomax;
2456 				cap->tsomaxsegcount = ifp->if_hw_tsomaxsegcount;
2457 				cap->tsomaxsegsize = ifp->if_hw_tsomaxsegsize;
2458 			}
2459 		}
2460 		fib6_free_nh_ext(inc->inc_fibnum, &nh6);
2461 	}
2462 
2463 	return (maxmtu);
2464 }
2465 #endif /* INET6 */
2466 
2467 /*
2468  * Calculate effective SMSS per RFC5681 definition for a given TCP
2469  * connection at its current state, taking into account SACK and etc.
2470  */
2471 u_int
2472 tcp_maxseg(const struct tcpcb *tp)
2473 {
2474 	u_int optlen;
2475 
2476 	if (tp->t_flags & TF_NOOPT)
2477 		return (tp->t_maxseg);
2478 
2479 	/*
2480 	 * Here we have a simplified code from tcp_addoptions(),
2481 	 * without a proper loop, and having most of paddings hardcoded.
2482 	 * We might make mistakes with padding here in some edge cases,
2483 	 * but this is harmless, since result of tcp_maxseg() is used
2484 	 * only in cwnd and ssthresh estimations.
2485 	 */
2486 #define	PAD(len)	((((len) / 4) + !!((len) % 4)) * 4)
2487 	if (TCPS_HAVEESTABLISHED(tp->t_state)) {
2488 		if (tp->t_flags & TF_RCVD_TSTMP)
2489 			optlen = TCPOLEN_TSTAMP_APPA;
2490 		else
2491 			optlen = 0;
2492 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
2493 		if (tp->t_flags & TF_SIGNATURE)
2494 			optlen += PAD(TCPOLEN_SIGNATURE);
2495 #endif
2496 		if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks > 0) {
2497 			optlen += TCPOLEN_SACKHDR;
2498 			optlen += tp->rcv_numsacks * TCPOLEN_SACK;
2499 			optlen = PAD(optlen);
2500 		}
2501 	} else {
2502 		if (tp->t_flags & TF_REQ_TSTMP)
2503 			optlen = TCPOLEN_TSTAMP_APPA;
2504 		else
2505 			optlen = PAD(TCPOLEN_MAXSEG);
2506 		if (tp->t_flags & TF_REQ_SCALE)
2507 			optlen += PAD(TCPOLEN_WINDOW);
2508 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
2509 		if (tp->t_flags & TF_SIGNATURE)
2510 			optlen += PAD(TCPOLEN_SIGNATURE);
2511 #endif
2512 		if (tp->t_flags & TF_SACK_PERMIT)
2513 			optlen += PAD(TCPOLEN_SACK_PERMITTED);
2514 	}
2515 #undef PAD
2516 	optlen = min(optlen, TCP_MAXOLEN);
2517 	return (tp->t_maxseg - optlen);
2518 }
2519 
2520 static int
2521 sysctl_drop(SYSCTL_HANDLER_ARGS)
2522 {
2523 	/* addrs[0] is a foreign socket, addrs[1] is a local one. */
2524 	struct sockaddr_storage addrs[2];
2525 	struct inpcb *inp;
2526 	struct tcpcb *tp;
2527 	struct tcptw *tw;
2528 	struct sockaddr_in *fin, *lin;
2529 #ifdef INET6
2530 	struct sockaddr_in6 *fin6, *lin6;
2531 #endif
2532 	int error;
2533 
2534 	inp = NULL;
2535 	fin = lin = NULL;
2536 #ifdef INET6
2537 	fin6 = lin6 = NULL;
2538 #endif
2539 	error = 0;
2540 
2541 	if (req->oldptr != NULL || req->oldlen != 0)
2542 		return (EINVAL);
2543 	if (req->newptr == NULL)
2544 		return (EPERM);
2545 	if (req->newlen < sizeof(addrs))
2546 		return (ENOMEM);
2547 	error = SYSCTL_IN(req, &addrs, sizeof(addrs));
2548 	if (error)
2549 		return (error);
2550 
2551 	switch (addrs[0].ss_family) {
2552 #ifdef INET6
2553 	case AF_INET6:
2554 		fin6 = (struct sockaddr_in6 *)&addrs[0];
2555 		lin6 = (struct sockaddr_in6 *)&addrs[1];
2556 		if (fin6->sin6_len != sizeof(struct sockaddr_in6) ||
2557 		    lin6->sin6_len != sizeof(struct sockaddr_in6))
2558 			return (EINVAL);
2559 		if (IN6_IS_ADDR_V4MAPPED(&fin6->sin6_addr)) {
2560 			if (!IN6_IS_ADDR_V4MAPPED(&lin6->sin6_addr))
2561 				return (EINVAL);
2562 			in6_sin6_2_sin_in_sock((struct sockaddr *)&addrs[0]);
2563 			in6_sin6_2_sin_in_sock((struct sockaddr *)&addrs[1]);
2564 			fin = (struct sockaddr_in *)&addrs[0];
2565 			lin = (struct sockaddr_in *)&addrs[1];
2566 			break;
2567 		}
2568 		error = sa6_embedscope(fin6, V_ip6_use_defzone);
2569 		if (error)
2570 			return (error);
2571 		error = sa6_embedscope(lin6, V_ip6_use_defzone);
2572 		if (error)
2573 			return (error);
2574 		break;
2575 #endif
2576 #ifdef INET
2577 	case AF_INET:
2578 		fin = (struct sockaddr_in *)&addrs[0];
2579 		lin = (struct sockaddr_in *)&addrs[1];
2580 		if (fin->sin_len != sizeof(struct sockaddr_in) ||
2581 		    lin->sin_len != sizeof(struct sockaddr_in))
2582 			return (EINVAL);
2583 		break;
2584 #endif
2585 	default:
2586 		return (EINVAL);
2587 	}
2588 	INP_INFO_RLOCK(&V_tcbinfo);
2589 	switch (addrs[0].ss_family) {
2590 #ifdef INET6
2591 	case AF_INET6:
2592 		inp = in6_pcblookup(&V_tcbinfo, &fin6->sin6_addr,
2593 		    fin6->sin6_port, &lin6->sin6_addr, lin6->sin6_port,
2594 		    INPLOOKUP_WLOCKPCB, NULL);
2595 		break;
2596 #endif
2597 #ifdef INET
2598 	case AF_INET:
2599 		inp = in_pcblookup(&V_tcbinfo, fin->sin_addr, fin->sin_port,
2600 		    lin->sin_addr, lin->sin_port, INPLOOKUP_WLOCKPCB, NULL);
2601 		break;
2602 #endif
2603 	}
2604 	if (inp != NULL) {
2605 		if (inp->inp_flags & INP_TIMEWAIT) {
2606 			/*
2607 			 * XXXRW: There currently exists a state where an
2608 			 * inpcb is present, but its timewait state has been
2609 			 * discarded.  For now, don't allow dropping of this
2610 			 * type of inpcb.
2611 			 */
2612 			tw = intotw(inp);
2613 			if (tw != NULL)
2614 				tcp_twclose(tw, 0);
2615 			else
2616 				INP_WUNLOCK(inp);
2617 		} else if (!(inp->inp_flags & INP_DROPPED) &&
2618 			   !(inp->inp_socket->so_options & SO_ACCEPTCONN)) {
2619 			tp = intotcpcb(inp);
2620 			tp = tcp_drop(tp, ECONNABORTED);
2621 			if (tp != NULL)
2622 				INP_WUNLOCK(inp);
2623 		} else
2624 			INP_WUNLOCK(inp);
2625 	} else
2626 		error = ESRCH;
2627 	INP_INFO_RUNLOCK(&V_tcbinfo);
2628 	return (error);
2629 }
2630 
2631 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DROP, drop,
2632     CTLFLAG_VNET | CTLTYPE_STRUCT | CTLFLAG_WR | CTLFLAG_SKIP, NULL,
2633     0, sysctl_drop, "", "Drop TCP connection");
2634 
2635 /*
2636  * Generate a standardized TCP log line for use throughout the
2637  * tcp subsystem.  Memory allocation is done with M_NOWAIT to
2638  * allow use in the interrupt context.
2639  *
2640  * NB: The caller MUST free(s, M_TCPLOG) the returned string.
2641  * NB: The function may return NULL if memory allocation failed.
2642  *
2643  * Due to header inclusion and ordering limitations the struct ip
2644  * and ip6_hdr pointers have to be passed as void pointers.
2645  */
2646 char *
2647 tcp_log_vain(struct in_conninfo *inc, struct tcphdr *th, void *ip4hdr,
2648     const void *ip6hdr)
2649 {
2650 
2651 	/* Is logging enabled? */
2652 	if (tcp_log_in_vain == 0)
2653 		return (NULL);
2654 
2655 	return (tcp_log_addr(inc, th, ip4hdr, ip6hdr));
2656 }
2657 
2658 char *
2659 tcp_log_addrs(struct in_conninfo *inc, struct tcphdr *th, void *ip4hdr,
2660     const void *ip6hdr)
2661 {
2662 
2663 	/* Is logging enabled? */
2664 	if (tcp_log_debug == 0)
2665 		return (NULL);
2666 
2667 	return (tcp_log_addr(inc, th, ip4hdr, ip6hdr));
2668 }
2669 
2670 static char *
2671 tcp_log_addr(struct in_conninfo *inc, struct tcphdr *th, void *ip4hdr,
2672     const void *ip6hdr)
2673 {
2674 	char *s, *sp;
2675 	size_t size;
2676 	struct ip *ip;
2677 #ifdef INET6
2678 	const struct ip6_hdr *ip6;
2679 
2680 	ip6 = (const struct ip6_hdr *)ip6hdr;
2681 #endif /* INET6 */
2682 	ip = (struct ip *)ip4hdr;
2683 
2684 	/*
2685 	 * The log line looks like this:
2686 	 * "TCP: [1.2.3.4]:50332 to [1.2.3.4]:80 tcpflags 0x2<SYN>"
2687 	 */
2688 	size = sizeof("TCP: []:12345 to []:12345 tcpflags 0x2<>") +
2689 	    sizeof(PRINT_TH_FLAGS) + 1 +
2690 #ifdef INET6
2691 	    2 * INET6_ADDRSTRLEN;
2692 #else
2693 	    2 * INET_ADDRSTRLEN;
2694 #endif /* INET6 */
2695 
2696 	s = malloc(size, M_TCPLOG, M_ZERO|M_NOWAIT);
2697 	if (s == NULL)
2698 		return (NULL);
2699 
2700 	strcat(s, "TCP: [");
2701 	sp = s + strlen(s);
2702 
2703 	if (inc && ((inc->inc_flags & INC_ISIPV6) == 0)) {
2704 		inet_ntoa_r(inc->inc_faddr, sp);
2705 		sp = s + strlen(s);
2706 		sprintf(sp, "]:%i to [", ntohs(inc->inc_fport));
2707 		sp = s + strlen(s);
2708 		inet_ntoa_r(inc->inc_laddr, sp);
2709 		sp = s + strlen(s);
2710 		sprintf(sp, "]:%i", ntohs(inc->inc_lport));
2711 #ifdef INET6
2712 	} else if (inc) {
2713 		ip6_sprintf(sp, &inc->inc6_faddr);
2714 		sp = s + strlen(s);
2715 		sprintf(sp, "]:%i to [", ntohs(inc->inc_fport));
2716 		sp = s + strlen(s);
2717 		ip6_sprintf(sp, &inc->inc6_laddr);
2718 		sp = s + strlen(s);
2719 		sprintf(sp, "]:%i", ntohs(inc->inc_lport));
2720 	} else if (ip6 && th) {
2721 		ip6_sprintf(sp, &ip6->ip6_src);
2722 		sp = s + strlen(s);
2723 		sprintf(sp, "]:%i to [", ntohs(th->th_sport));
2724 		sp = s + strlen(s);
2725 		ip6_sprintf(sp, &ip6->ip6_dst);
2726 		sp = s + strlen(s);
2727 		sprintf(sp, "]:%i", ntohs(th->th_dport));
2728 #endif /* INET6 */
2729 #ifdef INET
2730 	} else if (ip && th) {
2731 		inet_ntoa_r(ip->ip_src, sp);
2732 		sp = s + strlen(s);
2733 		sprintf(sp, "]:%i to [", ntohs(th->th_sport));
2734 		sp = s + strlen(s);
2735 		inet_ntoa_r(ip->ip_dst, sp);
2736 		sp = s + strlen(s);
2737 		sprintf(sp, "]:%i", ntohs(th->th_dport));
2738 #endif /* INET */
2739 	} else {
2740 		free(s, M_TCPLOG);
2741 		return (NULL);
2742 	}
2743 	sp = s + strlen(s);
2744 	if (th)
2745 		sprintf(sp, " tcpflags 0x%b", th->th_flags, PRINT_TH_FLAGS);
2746 	if (*(s + size - 1) != '\0')
2747 		panic("%s: string too long", __func__);
2748 	return (s);
2749 }
2750 
2751 /*
2752  * A subroutine which makes it easy to track TCP state changes with DTrace.
2753  * This function shouldn't be called for t_state initializations that don't
2754  * correspond to actual TCP state transitions.
2755  */
2756 void
2757 tcp_state_change(struct tcpcb *tp, int newstate)
2758 {
2759 #if defined(KDTRACE_HOOKS)
2760 	int pstate = tp->t_state;
2761 #endif
2762 
2763 	TCPSTATES_DEC(tp->t_state);
2764 	TCPSTATES_INC(newstate);
2765 	tp->t_state = newstate;
2766 	TCP_PROBE6(state__change, NULL, tp, NULL, tp, NULL, pstate);
2767 }
2768