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 * 4. 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: releng/10.1/sys/netinet/tcp_timewait.c 270057 2014-08-16 14:09:26Z bz $");
34
35 #include "opt_inet.h"
36 #include "opt_inet6.h"
37 #include "opt_tcpdebug.h"
38
39 #include <sys/param.h>
40 #include <sys/systm.h>
41 #include <sys/callout.h>
42 #include <sys/kernel.h>
43 #include <sys/sysctl.h>
44 #include <sys/malloc.h>
45 #include <sys/mbuf.h>
46 #include <sys/priv.h>
47 #include <sys/proc.h>
48 #include <sys/socket.h>
49 #include <sys/socketvar.h>
50 #include <sys/protosw.h>
51 #include <sys/random.h>
52
53 #include <vm/uma.h>
54
55 #include <net/route.h>
56 #include <net/if.h>
57 #include <net/vnet.h>
58
59 #include <netinet/in.h>
60 #include <netinet/in_pcb.h>
61 #include <netinet/in_systm.h>
62 #include <netinet/in_var.h>
63 #include <netinet/ip.h>
64 #include <netinet/ip_icmp.h>
65 #include <netinet/ip_var.h>
66 #ifdef INET6
67 #include <netinet/ip6.h>
68 #include <netinet6/in6_pcb.h>
69 #include <netinet6/ip6_var.h>
70 #include <netinet6/scope6_var.h>
71 #include <netinet6/nd6.h>
72 #endif
73 #include <netinet/tcp.h>
74 #include <netinet/tcp_fsm.h>
75 #include <netinet/tcp_seq.h>
76 #include <netinet/tcp_timer.h>
77 #include <netinet/tcp_var.h>
78 #ifdef INET6
79 #include <netinet6/tcp6_var.h>
80 #endif
81 #include <netinet/tcpip.h>
82 #ifdef TCPDEBUG
83 #include <netinet/tcp_debug.h>
84 #endif
85 #ifdef INET6
86 #include <netinet6/ip6protosw.h>
87 #endif
88
89 #include <machine/in_cksum.h>
90
91 #include <security/mac/mac_framework.h>
92
93 static VNET_DEFINE(uma_zone_t, tcptw_zone);
94 #define V_tcptw_zone VNET(tcptw_zone)
95 static int maxtcptw;
96
97 /*
98 * The timed wait queue contains references to each of the TCP sessions
99 * currently in the TIME_WAIT state. The queue pointers, including the
100 * queue pointers in each tcptw structure, are protected using the global
101 * tcbinfo lock, which must be held over queue iteration and modification.
102 */
103 static VNET_DEFINE(TAILQ_HEAD(, tcptw), twq_2msl);
104 #define V_twq_2msl VNET(twq_2msl)
105
106 static void tcp_tw_2msl_reset(struct tcptw *, int);
107 static void tcp_tw_2msl_stop(struct tcptw *);
108 static int tcp_twrespond(struct tcptw *, int);
109
110 static int
111 tcptw_auto_size(void)
112 {
113 int halfrange;
114
115 /*
116 * Max out at half the ephemeral port range so that TIME_WAIT
117 * sockets don't tie up too many ephemeral ports.
118 */
119 if (V_ipport_lastauto > V_ipport_firstauto)
120 halfrange = (V_ipport_lastauto - V_ipport_firstauto) / 2;
121 else
122 halfrange = (V_ipport_firstauto - V_ipport_lastauto) / 2;
123 /* Protect against goofy port ranges smaller than 32. */
124 return (imin(imax(halfrange, 32), maxsockets / 5));
125 }
126
127 static int
128 sysctl_maxtcptw(SYSCTL_HANDLER_ARGS)
129 {
130 int error, new;
131
132 if (maxtcptw == 0)
133 new = tcptw_auto_size();
134 else
135 new = maxtcptw;
136 error = sysctl_handle_int(oidp, &new, 0, req);
137 if (error == 0 && req->newptr)
138 if (new >= 32) {
139 maxtcptw = new;
140 uma_zone_set_max(V_tcptw_zone, maxtcptw);
141 }
142 return (error);
143 }
144
145 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, maxtcptw, CTLTYPE_INT|CTLFLAG_RW,
146 &maxtcptw, 0, sysctl_maxtcptw, "IU",
147 "Maximum number of compressed TCP TIME_WAIT entries");
148
149 VNET_DEFINE(int, nolocaltimewait) = 0;
150 #define V_nolocaltimewait VNET(nolocaltimewait)
151 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, nolocaltimewait, CTLFLAG_RW,
152 &VNET_NAME(nolocaltimewait), 0,
153 "Do not create compressed TCP TIME_WAIT entries for local connections");
154
155 void
156 tcp_tw_zone_change(void)
157 {
158
159 if (maxtcptw == 0)
160 uma_zone_set_max(V_tcptw_zone, tcptw_auto_size());
161 }
162
163 void
164 tcp_tw_init(void)
165 {
166
167 V_tcptw_zone = uma_zcreate("tcptw", sizeof(struct tcptw),
168 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
169 TUNABLE_INT_FETCH("net.inet.tcp.maxtcptw", &maxtcptw);
170 if (maxtcptw == 0)
171 uma_zone_set_max(V_tcptw_zone, tcptw_auto_size());
172 else
173 uma_zone_set_max(V_tcptw_zone, maxtcptw);
174 TAILQ_INIT(&V_twq_2msl);
175 }
176
177 #ifdef VIMAGE
178 void
179 tcp_tw_destroy(void)
180 {
181 struct tcptw *tw;
182
183 INP_INFO_WLOCK(&V_tcbinfo);
184 while((tw = TAILQ_FIRST(&V_twq_2msl)) != NULL)
185 tcp_twclose(tw, 0);
186 INP_INFO_WUNLOCK(&V_tcbinfo);
187
188 uma_zdestroy(V_tcptw_zone);
189 }
190 #endif
191
192 /*
193 * Move a TCP connection into TIME_WAIT state.
194 * tcbinfo is locked.
195 * inp is locked, and is unlocked before returning.
196 */
197 void
198 tcp_twstart(struct tcpcb *tp)
199 {
200 struct tcptw *tw;
201 struct inpcb *inp = tp->t_inpcb;
202 int acknow;
203 struct socket *so;
204 #ifdef INET6
205 int isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6;
206 #endif
207
208 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); /* tcp_tw_2msl_reset(). */
209 INP_WLOCK_ASSERT(inp);
210
211 if (V_nolocaltimewait) {
212 int error = 0;
213 #ifdef INET6
214 if (isipv6)
215 error = in6_localaddr(&inp->in6p_faddr);
216 #endif
217 #if defined(INET6) && defined(INET)
218 else
219 #endif
220 #ifdef INET
221 error = in_localip(inp->inp_faddr);
222 #endif
223 if (error) {
224 tp = tcp_close(tp);
225 if (tp != NULL)
226 INP_WUNLOCK(inp);
227 return;
228 }
229 }
230
231 tw = uma_zalloc(V_tcptw_zone, M_NOWAIT);
232 if (tw == NULL) {
233 tw = tcp_tw_2msl_scan(1);
234 if (tw == NULL) {
235 tp = tcp_close(tp);
236 if (tp != NULL)
237 INP_WUNLOCK(inp);
238 return;
239 }
240 }
241 tw->tw_inpcb = inp;
242
243 /*
244 * Recover last window size sent.
245 */
246 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt))
247 tw->last_win = (tp->rcv_adv - tp->rcv_nxt) >> tp->rcv_scale;
248 else
249 tw->last_win = 0;
250
251 /*
252 * Set t_recent if timestamps are used on the connection.
253 */
254 if ((tp->t_flags & (TF_REQ_TSTMP|TF_RCVD_TSTMP|TF_NOOPT)) ==
255 (TF_REQ_TSTMP|TF_RCVD_TSTMP)) {
256 tw->t_recent = tp->ts_recent;
257 tw->ts_offset = tp->ts_offset;
258 } else {
259 tw->t_recent = 0;
260 tw->ts_offset = 0;
261 }
262
263 tw->snd_nxt = tp->snd_nxt;
264 tw->rcv_nxt = tp->rcv_nxt;
265 tw->iss = tp->iss;
266 tw->irs = tp->irs;
267 tw->t_starttime = tp->t_starttime;
268 tw->tw_time = 0;
269
270 /* XXX
271 * If this code will
272 * be used for fin-wait-2 state also, then we may need
273 * a ts_recent from the last segment.
274 */
275 acknow = tp->t_flags & TF_ACKNOW;
276
277 /*
278 * First, discard tcpcb state, which includes stopping its timers and
279 * freeing it. tcp_discardcb() used to also release the inpcb, but
280 * that work is now done in the caller.
281 *
282 * Note: soisdisconnected() call used to be made in tcp_discardcb(),
283 * and might not be needed here any longer.
284 */
285 tcp_discardcb(tp);
286 so = inp->inp_socket;
287 soisdisconnected(so);
288 tw->tw_cred = crhold(so->so_cred);
289 SOCK_LOCK(so);
290 tw->tw_so_options = so->so_options;
291 SOCK_UNLOCK(so);
292 if (acknow)
293 tcp_twrespond(tw, TH_ACK);
294 inp->inp_ppcb = tw;
295 inp->inp_flags |= INP_TIMEWAIT;
296 tcp_tw_2msl_reset(tw, 0);
297
298 /*
299 * If the inpcb owns the sole reference to the socket, then we can
300 * detach and free the socket as it is not needed in time wait.
301 */
302 if (inp->inp_flags & INP_SOCKREF) {
303 KASSERT(so->so_state & SS_PROTOREF,
304 ("tcp_twstart: !SS_PROTOREF"));
305 inp->inp_flags &= ~INP_SOCKREF;
306 INP_WUNLOCK(inp);
307 ACCEPT_LOCK();
308 SOCK_LOCK(so);
309 so->so_state &= ~SS_PROTOREF;
310 sofree(so);
311 } else
312 INP_WUNLOCK(inp);
313 }
314
315 #if 0
316 /*
317 * The appromixate rate of ISN increase of Microsoft TCP stacks;
318 * the actual rate is slightly higher due to the addition of
319 * random positive increments.
320 *
321 * Most other new OSes use semi-randomized ISN values, so we
322 * do not need to worry about them.
323 */
324 #define MS_ISN_BYTES_PER_SECOND 250000
325
326 /*
327 * Determine if the ISN we will generate has advanced beyond the last
328 * sequence number used by the previous connection. If so, indicate
329 * that it is safe to recycle this tw socket by returning 1.
330 */
331 int
332 tcp_twrecycleable(struct tcptw *tw)
333 {
334 tcp_seq new_iss = tw->iss;
335 tcp_seq new_irs = tw->irs;
336
337 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
338 new_iss += (ticks - tw->t_starttime) * (ISN_BYTES_PER_SECOND / hz);
339 new_irs += (ticks - tw->t_starttime) * (MS_ISN_BYTES_PER_SECOND / hz);
340
341 if (SEQ_GT(new_iss, tw->snd_nxt) && SEQ_GT(new_irs, tw->rcv_nxt))
342 return (1);
343 else
344 return (0);
345 }
346 #endif
347
348 /*
349 * Returns 1 if the TIME_WAIT state was killed and we should start over,
350 * looking for a pcb in the listen state. Returns 0 otherwise.
351 */
352 int
353 tcp_twcheck(struct inpcb *inp, struct tcpopt *to __unused, struct tcphdr *th,
354 struct mbuf *m, int tlen)
355 {
356 struct tcptw *tw;
357 int thflags;
358 tcp_seq seq;
359
360 /* tcbinfo lock required for tcp_twclose(), tcp_tw_2msl_reset(). */
361 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
362 INP_WLOCK_ASSERT(inp);
363
364 /*
365 * XXXRW: Time wait state for inpcb has been recycled, but inpcb is
366 * still present. This is undesirable, but temporarily necessary
367 * until we work out how to handle inpcb's who's timewait state has
368 * been removed.
369 */
370 tw = intotw(inp);
371 if (tw == NULL)
372 goto drop;
373
374 thflags = th->th_flags;
375
376 /*
377 * NOTE: for FIN_WAIT_2 (to be added later),
378 * must validate sequence number before accepting RST
379 */
380
381 /*
382 * If the segment contains RST:
383 * Drop the segment - see Stevens, vol. 2, p. 964 and
384 * RFC 1337.
385 */
386 if (thflags & TH_RST)
387 goto drop;
388
389 #if 0
390 /* PAWS not needed at the moment */
391 /*
392 * RFC 1323 PAWS: If we have a timestamp reply on this segment
393 * and it's less than ts_recent, drop it.
394 */
395 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
396 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
397 if ((thflags & TH_ACK) == 0)
398 goto drop;
399 goto ack;
400 }
401 /*
402 * ts_recent is never updated because we never accept new segments.
403 */
404 #endif
405
406 /*
407 * If a new connection request is received
408 * while in TIME_WAIT, drop the old connection
409 * and start over if the sequence numbers
410 * are above the previous ones.
411 */
412 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) {
413 tcp_twclose(tw, 0);
414 return (1);
415 }
416
417 /*
418 * Drop the segment if it does not contain an ACK.
419 */
420 if ((thflags & TH_ACK) == 0)
421 goto drop;
422
423 /*
424 * Reset the 2MSL timer if this is a duplicate FIN.
425 */
426 if (thflags & TH_FIN) {
427 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0);
428 if (seq + 1 == tw->rcv_nxt)
429 tcp_tw_2msl_reset(tw, 1);
430 }
431
432 /*
433 * Acknowledge the segment if it has data or is not a duplicate ACK.
434 */
435 if (thflags != TH_ACK || tlen != 0 ||
436 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt)
437 tcp_twrespond(tw, TH_ACK);
438 drop:
439 INP_WUNLOCK(inp);
440 m_freem(m);
441 return (0);
442 }
443
444 void
445 tcp_twclose(struct tcptw *tw, int reuse)
446 {
447 struct socket *so;
448 struct inpcb *inp;
449
450 /*
451 * At this point, we are in one of two situations:
452 *
453 * (1) We have no socket, just an inpcb<->twtcp pair. We can free
454 * all state.
455 *
456 * (2) We have a socket -- if we own a reference, release it and
457 * notify the socket layer.
458 */
459 inp = tw->tw_inpcb;
460 KASSERT((inp->inp_flags & INP_TIMEWAIT), ("tcp_twclose: !timewait"));
461 KASSERT(intotw(inp) == tw, ("tcp_twclose: inp_ppcb != tw"));
462 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); /* tcp_tw_2msl_stop(). */
463 INP_WLOCK_ASSERT(inp);
464
465 tw->tw_inpcb = NULL;
466 tcp_tw_2msl_stop(tw);
467 inp->inp_ppcb = NULL;
468 in_pcbdrop(inp);
469
470 so = inp->inp_socket;
471 if (so != NULL) {
472 /*
473 * If there's a socket, handle two cases: first, we own a
474 * strong reference, which we will now release, or we don't
475 * in which case another reference exists (XXXRW: think
476 * about this more), and we don't need to take action.
477 */
478 if (inp->inp_flags & INP_SOCKREF) {
479 inp->inp_flags &= ~INP_SOCKREF;
480 INP_WUNLOCK(inp);
481 ACCEPT_LOCK();
482 SOCK_LOCK(so);
483 KASSERT(so->so_state & SS_PROTOREF,
484 ("tcp_twclose: INP_SOCKREF && !SS_PROTOREF"));
485 so->so_state &= ~SS_PROTOREF;
486 sofree(so);
487 } else {
488 /*
489 * If we don't own the only reference, the socket and
490 * inpcb need to be left around to be handled by
491 * tcp_usr_detach() later.
492 */
493 INP_WUNLOCK(inp);
494 }
495 } else
496 in_pcbfree(inp);
497 TCPSTAT_INC(tcps_closed);
498 crfree(tw->tw_cred);
499 tw->tw_cred = NULL;
500 if (reuse)
501 return;
502 uma_zfree(V_tcptw_zone, tw);
503 }
504
505 static int
506 tcp_twrespond(struct tcptw *tw, int flags)
507 {
508 struct inpcb *inp = tw->tw_inpcb;
509 #if defined(INET6) || defined(INET)
510 struct tcphdr *th = NULL;
511 #endif
512 struct mbuf *m;
513 #ifdef INET
514 struct ip *ip = NULL;
515 #endif
516 u_int hdrlen, optlen;
517 int error = 0; /* Keep compiler happy */
518 struct tcpopt to;
519 #ifdef INET6
520 struct ip6_hdr *ip6 = NULL;
521 int isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6;
522 #endif
523 hdrlen = 0; /* Keep compiler happy */
524
525 INP_WLOCK_ASSERT(inp);
526
527 m = m_gethdr(M_NOWAIT, MT_DATA);
528 if (m == NULL)
529 return (ENOBUFS);
530 m->m_data += max_linkhdr;
531
532 #ifdef MAC
533 mac_inpcb_create_mbuf(inp, m);
534 #endif
535
536 #ifdef INET6
537 if (isipv6) {
538 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
539 ip6 = mtod(m, struct ip6_hdr *);
540 th = (struct tcphdr *)(ip6 + 1);
541 tcpip_fillheaders(inp, ip6, th);
542 }
543 #endif
544 #if defined(INET6) && defined(INET)
545 else
546 #endif
547 #ifdef INET
548 {
549 hdrlen = sizeof(struct tcpiphdr);
550 ip = mtod(m, struct ip *);
551 th = (struct tcphdr *)(ip + 1);
552 tcpip_fillheaders(inp, ip, th);
553 }
554 #endif
555 to.to_flags = 0;
556
557 /*
558 * Send a timestamp and echo-reply if both our side and our peer
559 * have sent timestamps in our SYN's and this is not a RST.
560 */
561 if (tw->t_recent && flags == TH_ACK) {
562 to.to_flags |= TOF_TS;
563 to.to_tsval = tcp_ts_getticks() + tw->ts_offset;
564 to.to_tsecr = tw->t_recent;
565 }
566 optlen = tcp_addoptions(&to, (u_char *)(th + 1));
567
568 m->m_len = hdrlen + optlen;
569 m->m_pkthdr.len = m->m_len;
570
571 KASSERT(max_linkhdr + m->m_len <= MHLEN, ("tcptw: mbuf too small"));
572
573 th->th_seq = htonl(tw->snd_nxt);
574 th->th_ack = htonl(tw->rcv_nxt);
575 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
576 th->th_flags = flags;
577 th->th_win = htons(tw->last_win);
578
579 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
580 #ifdef INET6
581 if (isipv6) {
582 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
583 th->th_sum = in6_cksum_pseudo(ip6,
584 sizeof(struct tcphdr) + optlen, IPPROTO_TCP, 0);
585 ip6->ip6_hlim = in6_selecthlim(inp, NULL);
586 error = ip6_output(m, inp->in6p_outputopts, NULL,
587 (tw->tw_so_options & SO_DONTROUTE), NULL, NULL, inp);
588 }
589 #endif
590 #if defined(INET6) && defined(INET)
591 else
592 #endif
593 #ifdef INET
594 {
595 m->m_pkthdr.csum_flags = CSUM_TCP;
596 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
597 htons(sizeof(struct tcphdr) + optlen + IPPROTO_TCP));
598 ip->ip_len = htons(m->m_pkthdr.len);
599 if (V_path_mtu_discovery)
600 ip->ip_off |= htons(IP_DF);
601 error = ip_output(m, inp->inp_options, NULL,
602 ((tw->tw_so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0),
603 NULL, inp);
604 }
605 #endif
606 if (flags & TH_ACK)
607 TCPSTAT_INC(tcps_sndacks);
608 else
609 TCPSTAT_INC(tcps_sndctrl);
610 TCPSTAT_INC(tcps_sndtotal);
611 return (error);
612 }
613
614 static void
615 tcp_tw_2msl_reset(struct tcptw *tw, int rearm)
616 {
617
618 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
619 INP_WLOCK_ASSERT(tw->tw_inpcb);
620 if (rearm)
621 TAILQ_REMOVE(&V_twq_2msl, tw, tw_2msl);
622 tw->tw_time = ticks + 2 * tcp_msl;
623 TAILQ_INSERT_TAIL(&V_twq_2msl, tw, tw_2msl);
624 }
625
626 static void
627 tcp_tw_2msl_stop(struct tcptw *tw)
628 {
629
630 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
631 TAILQ_REMOVE(&V_twq_2msl, tw, tw_2msl);
632 }
633
634 struct tcptw *
635 tcp_tw_2msl_scan(int reuse)
636 {
637 struct tcptw *tw;
638
639 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
640 for (;;) {
641 tw = TAILQ_FIRST(&V_twq_2msl);
642 if (tw == NULL || (!reuse && (tw->tw_time - ticks) > 0))
643 break;
644 INP_WLOCK(tw->tw_inpcb);
645 tcp_twclose(tw, reuse);
646 if (reuse)
647 return (tw);
648 }
649 return (NULL);
650 }
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