aboutsummaryrefslogtreecommitdiff
path: root/networking/traceroute.c
blob: fa45db98a3d8f8d771856e321f8926dbc835be6b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
/* vi: set sw=4 ts=4: */
/*
 * Copyright (c) 1988, 1989, 1991, 1994, 1995, 1996, 1997, 1998, 1999, 2000
 *      The Regents of the University of California.  All rights reserved.
 *
 * Busybox port by Vladimir Oleynik (C) 2005 <dzo@simtreas.ru>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that: (1) source code distributions
 * retain the above copyright notice and this paragraph in its entirety, (2)
 * distributions including binary code include the above copyright notice and
 * this paragraph in its entirety in the documentation or other materials
 * provided with the distribution, and (3) all advertising materials mentioning
 * features or use of this software display the following acknowledgement:
 * ``This product includes software developed by the University of California,
 * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
 * the University nor the names of its contributors may be used to endorse
 * or promote products derived from this software without specific prior
 * written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

/*
 * traceroute host  - trace the route ip packets follow going to "host".
 *
 * Attempt to trace the route an ip packet would follow to some
 * internet host.  We find out intermediate hops by launching probe
 * packets with a small ttl (time to live) then listening for an
 * icmp "time exceeded" reply from a gateway.  We start our probes
 * with a ttl of one and increase by one until we get an icmp "port
 * unreachable" (which means we got to "host") or hit a max (which
 * defaults to 30 hops & can be changed with the -m flag).  Three
 * probes (change with -q flag) are sent at each ttl setting and a
 * line is printed showing the ttl, address of the gateway and
 * round trip time of each probe.  If the probe answers come from
 * different gateways, the address of each responding system will
 * be printed.  If there is no response within a 5 sec. timeout
 * interval (changed with the -w flag), a "*" is printed for that
 * probe.
 *
 * Probe packets are UDP format.  We don't want the destination
 * host to process them so the destination port is set to an
 * unlikely value (if some clod on the destination is using that
 * value, it can be changed with the -p flag).
 *
 * A sample use might be:
 *
 *     [yak 71]% traceroute nis.nsf.net.
 *     traceroute to nis.nsf.net (35.1.1.48), 30 hops max, 56 byte packet
 *      1  helios.ee.lbl.gov (128.3.112.1)  19 ms  19 ms  0 ms
 *      2  lilac-dmc.Berkeley.EDU (128.32.216.1)  39 ms  39 ms  19 ms
 *      3  lilac-dmc.Berkeley.EDU (128.32.216.1)  39 ms  39 ms  19 ms
 *      4  ccngw-ner-cc.Berkeley.EDU (128.32.136.23)  39 ms  40 ms  39 ms
 *      5  ccn-nerif22.Berkeley.EDU (128.32.168.22)  39 ms  39 ms  39 ms
 *      6  128.32.197.4 (128.32.197.4)  40 ms  59 ms  59 ms
 *      7  131.119.2.5 (131.119.2.5)  59 ms  59 ms  59 ms
 *      8  129.140.70.13 (129.140.70.13)  99 ms  99 ms  80 ms
 *      9  129.140.71.6 (129.140.71.6)  139 ms  239 ms  319 ms
 *     10  129.140.81.7 (129.140.81.7)  220 ms  199 ms  199 ms
 *     11  nic.merit.edu (35.1.1.48)  239 ms  239 ms  239 ms
 *
 * Note that lines 2 & 3 are the same.  This is due to a buggy
 * kernel on the 2nd hop system -- lbl-csam.arpa -- that forwards
 * packets with a zero ttl.
 *
 * A more interesting example is:
 *
 *     [yak 72]% traceroute allspice.lcs.mit.edu.
 *     traceroute to allspice.lcs.mit.edu (18.26.0.115), 30 hops max
 *      1  helios.ee.lbl.gov (128.3.112.1)  0 ms  0 ms  0 ms
 *      2  lilac-dmc.Berkeley.EDU (128.32.216.1)  19 ms  19 ms  19 ms
 *      3  lilac-dmc.Berkeley.EDU (128.32.216.1)  39 ms  19 ms  19 ms
 *      4  ccngw-ner-cc.Berkeley.EDU (128.32.136.23)  19 ms  39 ms  39 ms
 *      5  ccn-nerif22.Berkeley.EDU (128.32.168.22)  20 ms  39 ms  39 ms
 *      6  128.32.197.4 (128.32.197.4)  59 ms  119 ms  39 ms
 *      7  131.119.2.5 (131.119.2.5)  59 ms  59 ms  39 ms
 *      8  129.140.70.13 (129.140.70.13)  80 ms  79 ms  99 ms
 *      9  129.140.71.6 (129.140.71.6)  139 ms  139 ms  159 ms
 *     10  129.140.81.7 (129.140.81.7)  199 ms  180 ms  300 ms
 *     11  129.140.72.17 (129.140.72.17)  300 ms  239 ms  239 ms
 *     12  * * *
 *     13  128.121.54.72 (128.121.54.72)  259 ms  499 ms  279 ms
 *     14  * * *
 *     15  * * *
 *     16  * * *
 *     17  * * *
 *     18  ALLSPICE.LCS.MIT.EDU (18.26.0.115)  339 ms  279 ms  279 ms
 *
 * (I start to see why I'm having so much trouble with mail to
 * MIT.)  Note that the gateways 12, 14, 15, 16 & 17 hops away
 * either don't send ICMP "time exceeded" messages or send them
 * with a ttl too small to reach us.  14 - 17 are running the
 * MIT C Gateway code that doesn't send "time exceeded"s.  God
 * only knows what's going on with 12.
 *
 * The silent gateway 12 in the above may be the result of a bug in
 * the 4.[23]BSD network code (and its derivatives):  4.x (x <= 3)
 * sends an unreachable message using whatever ttl remains in the
 * original datagram.  Since, for gateways, the remaining ttl is
 * zero, the icmp "time exceeded" is guaranteed to not make it back
 * to us.  The behavior of this bug is slightly more interesting
 * when it appears on the destination system:
 *
 *      1  helios.ee.lbl.gov (128.3.112.1)  0 ms  0 ms  0 ms
 *      2  lilac-dmc.Berkeley.EDU (128.32.216.1)  39 ms  19 ms  39 ms
 *      3  lilac-dmc.Berkeley.EDU (128.32.216.1)  19 ms  39 ms  19 ms
 *      4  ccngw-ner-cc.Berkeley.EDU (128.32.136.23)  39 ms  40 ms  19 ms
 *      5  ccn-nerif35.Berkeley.EDU (128.32.168.35)  39 ms  39 ms  39 ms
 *      6  csgw.Berkeley.EDU (128.32.133.254)  39 ms  59 ms  39 ms
 *      7  * * *
 *      8  * * *
 *      9  * * *
 *     10  * * *
 *     11  * * *
 *     12  * * *
 *     13  rip.Berkeley.EDU (128.32.131.22)  59 ms !  39 ms !  39 ms !
 *
 * Notice that there are 12 "gateways" (13 is the final
 * destination) and exactly the last half of them are "missing".
 * What's really happening is that rip (a Sun-3 running Sun OS3.5)
 * is using the ttl from our arriving datagram as the ttl in its
 * icmp reply.  So, the reply will time out on the return path
 * (with no notice sent to anyone since icmp's aren't sent for
 * icmp's) until we probe with a ttl that's at least twice the path
 * length.  I.e., rip is really only 7 hops away.  A reply that
 * returns with a ttl of 1 is a clue this problem exists.
 * Traceroute prints a "!" after the time if the ttl is <= 1.
 * Since vendors ship a lot of obsolete (DEC's Ultrix, Sun 3.x) or
 * non-standard (HPUX) software, expect to see this problem
 * frequently and/or take care picking the target host of your
 * probes.
 *
 * Other possible annotations after the time are !H, !N, !P (got a host,
 * network or protocol unreachable, respectively), !S or !F (source
 * route failed or fragmentation needed -- neither of these should
 * ever occur and the associated gateway is busted if you see one).  If
 * almost all the probes result in some kind of unreachable, traceroute
 * will give up and exit.
 *
 * Notes
 * -----
 * This program must be run by root or be setuid.  (I suggest that
 * you *don't* make it setuid -- casual use could result in a lot
 * of unnecessary traffic on our poor, congested nets.)
 *
 * This program requires a kernel mod that does not appear in any
 * system available from Berkeley:  A raw ip socket using proto
 * IPPROTO_RAW must interpret the data sent as an ip datagram (as
 * opposed to data to be wrapped in a ip datagram).  See the README
 * file that came with the source to this program for a description
 * of the mods I made to /sys/netinet/raw_ip.c.  Your mileage may
 * vary.  But, again, ANY 4.x (x < 4) BSD KERNEL WILL HAVE TO BE
 * MODIFIED TO RUN THIS PROGRAM.
 *
 * The udp port usage may appear bizarre (well, ok, it is bizarre).
 * The problem is that an icmp message only contains 8 bytes of
 * data from the original datagram.  8 bytes is the size of a udp
 * header so, if we want to associate replies with the original
 * datagram, the necessary information must be encoded into the
 * udp header (the ip id could be used but there's no way to
 * interlock with the kernel's assignment of ip id's and, anyway,
 * it would have taken a lot more kernel hacking to allow this
 * code to set the ip id).  So, to allow two or more users to
 * use traceroute simultaneously, we use this task's pid as the
 * source port (the high bit is set to move the port number out
 * of the "likely" range).  To keep track of which probe is being
 * replied to (so times and/or hop counts don't get confused by a
 * reply that was delayed in transit), we increment the destination
 * port number before each probe.
 *
 * Don't use this as a coding example.  I was trying to find a
 * routing problem and this code sort-of popped out after 48 hours
 * without sleep.  I was amazed it ever compiled, much less ran.
 *
 * I stole the idea for this program from Steve Deering.  Since
 * the first release, I've learned that had I attended the right
 * IETF working group meetings, I also could have stolen it from Guy
 * Almes or Matt Mathis.  I don't know (or care) who came up with
 * the idea first.  I envy the originators' perspicacity and I'm
 * glad they didn't keep the idea a secret.
 *
 * Tim Seaver, Ken Adelman and C. Philip Wood provided bug fixes and/or
 * enhancements to the original distribution.
 *
 * I've hacked up a round-trip-route version of this that works by
 * sending a loose-source-routed udp datagram through the destination
 * back to yourself.  Unfortunately, SO many gateways botch source
 * routing, the thing is almost worthless.  Maybe one day...
 *
 *  -- Van Jacobson (van@ee.lbl.gov)
 *     Tue Dec 20 03:50:13 PST 1988
 */

#define TRACEROUTE_SO_DEBUG 0

/* TODO: undefs were uncommented - ??! we have config system for that! */
/* probably ok to remove altogether */
//#undef CONFIG_FEATURE_TRACEROUTE_VERBOSE
//#define CONFIG_FEATURE_TRACEROUTE_VERBOSE
//#undef CONFIG_FEATURE_TRACEROUTE_SOURCE_ROUTE
//#define CONFIG_FEATURE_TRACEROUTE_SOURCE_ROUTE
//#undef CONFIG_FEATURE_TRACEROUTE_USE_ICMP
//#define CONFIG_FEATURE_TRACEROUTE_USE_ICMP


#include <net/if.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <netinet/udp.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>

#include "libbb.h"
#include "inet_common.h"

#ifndef IPPROTO_ICMP
# define IPPROTO_ICMP 1
#endif
#ifndef IPPROTO_IP
# define IPPROTO_IP 0
#endif

/* Keep in sync with getopt32 call! */
enum {
	OPT_DONT_FRAGMNT = (1 << 0),    /* F */
	OPT_USE_ICMP     = (1 << 1) * ENABLE_FEATURE_TRACEROUTE_USE_ICMP, /* I */
	OPT_TTL_FLAG     = (1 << 2),    /* l */
	OPT_ADDR_NUM     = (1 << 3),    /* n */
	OPT_BYPASS_ROUTE = (1 << 4),    /* r */
	OPT_DEBUG        = (1 << 5),    /* d */
	OPT_VERBOSE      = (1 << 6) * ENABLE_FEATURE_TRACEROUTE_VERBOSE, /* v */
	OPT_IP_CHKSUM    = (1 << 7),    /* x */
	OPT_TOS          = (1 << 8),    /* t */
	OPT_DEVICE       = (1 << 9),    /* i */
	OPT_MAX_TTL      = (1 << 10),   /* m */
	OPT_PORT         = (1 << 11),   /* p */
	OPT_NPROBES      = (1 << 12),   /* q */
	OPT_SOURCE       = (1 << 13),   /* s */
	OPT_WAITTIME     = (1 << 14),   /* w */
	OPT_PAUSE_MS     = (1 << 15),   /* z */
	OPT_FIRST_TTL    = (1 << 16),   /* f */
};
#define verbose (option_mask32 & OPT_VERBOSE)

enum {
	SIZEOF_ICMP_HDR = 8,
	rcvsock = 3, /* receive (icmp) socket file descriptor */
	sndsock = 4, /* send (udp/icmp) socket file descriptor */
};

/* Data section of the probe packet */
struct outdata_t {
	unsigned char seq;             /* sequence number of this packet */
	unsigned char ttl;             /* ttl packet left with */
// UNUSED. Retaining to have the same packet size.
	struct timeval tv_UNUSED PACKED; /* time packet left */
};

struct globals {
	struct ip *outip;
	struct outdata_t *outdata;
	len_and_sockaddr *dest_lsa;
	int packlen;                    /* total length of packet */
	int pmtu;                       /* Path MTU Discovery (RFC1191) */
	uint16_t ident;
	uint16_t port; // 32768 + 666;  /* start udp dest port # for probe packets */
	int waittime; // 5;             /* time to wait for response (in seconds) */
#if ENABLE_FEATURE_TRACEROUTE_SOURCE_ROUTE
	int optlen;                     /* length of ip options */
#else
#define optlen 0
#endif
	unsigned char recv_pkt[512];    /* last inbound (icmp) packet */
#if ENABLE_FEATURE_TRACEROUTE_SOURCE_ROUTE
	/* Maximum number of gateways (include room for one noop) */
#define NGATEWAYS ((int)((MAX_IPOPTLEN - IPOPT_MINOFF - 1) / sizeof(uint32_t)))
	/* loose source route gateway list (including room for final destination) */
	uint32_t gwlist[NGATEWAYS + 1];
#endif
};

#define G (*ptr_to_globals)
#define outip     (G.outip    )
#define outdata   (G.outdata  )
#define dest_lsa  (G.dest_lsa )
#define packlen   (G.packlen  )
#define pmtu      (G.pmtu     )
#define ident     (G.ident    )
#define port      (G.port     )
#define waittime  (G.waittime )
#if ENABLE_FEATURE_TRACEROUTE_SOURCE_ROUTE
# define optlen   (G.optlen   )
#endif
#define recv_pkt  (G.recv_pkt )
#define gwlist    (G.gwlist   )
#define INIT_G() do { \
	SET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \
	port = 32768 + 666; \
	waittime = 5; \
} while (0)

#define outicmp ((struct icmp *)(outip + 1))
#define outudp  ((struct udphdr *)(outip + 1))


static int
wait_for_reply(struct sockaddr_in *fromp)
{
	struct pollfd pfd[1];
	int cc = 0;
	socklen_t fromlen = sizeof(*fromp);

	pfd[0].fd = rcvsock;
	pfd[0].events = POLLIN;
	if (safe_poll(pfd, 1, waittime * 1000) > 0)
		cc = recvfrom(rcvsock, recv_pkt, sizeof(recv_pkt), 0,
			    (struct sockaddr *)fromp, &fromlen);
	return cc;
}

/*
 * Checksum routine for Internet Protocol family headers (C Version)
 */
static uint16_t
in_cksum(uint16_t *addr, int len)
{
	int nleft = len;
	uint16_t *w = addr;
	uint16_t answer;
	int sum = 0;

	/*
	 * Our algorithm is simple, using a 32 bit accumulator (sum),
	 * we add sequential 16 bit words to it, and at the end, fold
	 * back all the carry bits from the top 16 bits into the lower
	 * 16 bits.
	 */
	while (nleft > 1) {
		sum += *w++;
		nleft -= 2;
	}

	/* mop up an odd byte, if necessary */
	if (nleft == 1)
		sum += *(unsigned char *)w;

	/* add back carry outs from top 16 bits to low 16 bits */
	sum = (sum >> 16) + (sum & 0xffff);     /* add hi 16 to low 16 */
	sum += (sum >> 16);                     /* add carry */
	answer = ~sum;                          /* truncate to 16 bits */
	return answer;
}

static void
send_probe(int seq, int ttl)
{
	int len, res;
	void *out;

	/* Payload */
	outdata->seq = seq;
	outdata->ttl = ttl;
// UNUSED: was storing gettimeofday's result there, but never ever checked it
	/*memcpy(&outdata->tv, tp, sizeof(outdata->tv));*/

	if (option_mask32 & OPT_USE_ICMP) {
		outicmp->icmp_seq = htons(seq);

		/* Always calculate checksum for icmp packets */
		outicmp->icmp_cksum = 0;
		outicmp->icmp_cksum = in_cksum((uint16_t *)outicmp,
					packlen - (sizeof(*outip) + optlen));
		if (outicmp->icmp_cksum == 0)
			outicmp->icmp_cksum = 0xffff;
	}

//BUG! verbose is (x & OPT_VERBOSE), not a counter!
#if 0 //ENABLE_FEATURE_TRACEROUTE_VERBOSE
	/* XXX undocumented debugging hack */
	if (verbose > 1) {
		const uint16_t *sp;
		int nshorts, i;

		sp = (uint16_t *)outip;
		nshorts = (unsigned)packlen / sizeof(uint16_t);
		i = 0;
		printf("[ %d bytes", packlen);
		while (--nshorts >= 0) {
			if ((i++ % 8) == 0)
				printf("\n\t");
			printf(" %04x", ntohs(*sp));
			sp++;
		}
		if (packlen & 1) {
			if ((i % 8) == 0)
				printf("\n\t");
			printf(" %02x", *(unsigned char *)sp);
		}
		printf("]\n");
	}
#endif

#if defined(IP_TTL)
	if (setsockopt(sndsock, IPPROTO_IP, IP_TTL,
				(char *)&ttl, sizeof(ttl)) < 0) {
		bb_perror_msg_and_die("setsockopt ttl %d", ttl);
	}
#endif

	len = packlen - sizeof(*outip);
	if (option_mask32 & OPT_USE_ICMP)
		out = outicmp;
	else {
		out = outdata;
		len -= sizeof(*outudp);
		set_nport(dest_lsa, htons(port + seq));
	}
	res = xsendto(sndsock, out, len,
			(struct sockaddr *)&dest_lsa->u.sa, dest_lsa->len);
	if (res != len) {
		bb_info_msg("sent %d octets, ret=%d", len, res);
	}
}

#if ENABLE_FEATURE_TRACEROUTE_VERBOSE
/*
 * Convert an ICMP "type" field to a printable string.
 */
static inline const char *
pr_type(unsigned char t)
{
	static const char *const ttab[] = {
	"Echo Reply",   "ICMP 1",       "ICMP 2",       "Dest Unreachable",
	"Source Quench", "Redirect",    "ICMP 6",       "ICMP 7",
	"Echo",         "Router Advert", "Router Solicit", "Time Exceeded",
	"Param Problem", "Timestamp",   "Timestamp Reply", "Info Request",
	"Info Reply",   "Mask Request", "Mask Reply"
	};

	if (t >= ARRAY_SIZE(ttab))
		return "OUT-OF-RANGE";

	return ttab[t];
}
#endif

#if !ENABLE_FEATURE_TRACEROUTE_VERBOSE
#define packet_ok(cc, from, seq) \
	packet_ok(cc, seq)
#endif
static int
packet_ok(int cc, const struct sockaddr_in *from, int seq)
{
	const struct icmp *icp;
	unsigned char type, code;
	int hlen;
	const struct ip *ip;

	ip = (struct ip *) recv_pkt;
	hlen = ip->ip_hl << 2;
	if (cc < hlen + ICMP_MINLEN) {
#if ENABLE_FEATURE_TRACEROUTE_VERBOSE
		if (verbose)
			printf("packet too short (%d bytes) from %s\n", cc,
				inet_ntoa(from->sin_addr));
#endif
		return 0;
	}
	cc -= hlen;
	icp = (struct icmp *)(recv_pkt + hlen);
	type = icp->icmp_type;
	code = icp->icmp_code;
	/* Path MTU Discovery (RFC1191) */
	pmtu = 0;
	if (code == ICMP_UNREACH_NEEDFRAG)
		pmtu = ntohs(icp->icmp_nextmtu);

	if ((type == ICMP_TIMXCEED && code == ICMP_TIMXCEED_INTRANS)
	 || type == ICMP_UNREACH
	 || type == ICMP_ECHOREPLY
	) {
		const struct ip *hip;
		const struct udphdr *up;

		hip = &icp->icmp_ip;
		hlen = hip->ip_hl << 2;
		if (option_mask32 & OPT_USE_ICMP) {
			struct icmp *hicmp;

			/* XXX */
			if (type == ICMP_ECHOREPLY
			 && icp->icmp_id == htons(ident)
			 && icp->icmp_seq == htons(seq)
			) {
				return -2;
			}

			hicmp = (struct icmp *)((unsigned char *)hip + hlen);
			if (hlen + SIZEOF_ICMP_HDR <= cc
			 && hip->ip_p == IPPROTO_ICMP
			 && hicmp->icmp_id == htons(ident)
			 && hicmp->icmp_seq == htons(seq)
			) {
				return (type == ICMP_TIMXCEED ? -1 : code + 1);
			}
		} else {
			up = (struct udphdr *)((char *)hip + hlen);
			if (hlen + 12 <= cc
			 && hip->ip_p == IPPROTO_UDP
// Off: since we do not form the entire IP packet,
// but defer it to kernel, we can't set source port,
// and thus can't check it here in the reply
			/* && up->source == htons(ident) */
			 && up->dest == htons(port + seq)
			) {
				return (type == ICMP_TIMXCEED ? -1 : code + 1);
			}
		}
	}
#if ENABLE_FEATURE_TRACEROUTE_VERBOSE
	if (verbose) {
		int i;
		uint32_t *lp = (uint32_t *)&icp->icmp_ip;

		printf("\n%d bytes from %s to "
		       "%s: icmp type %d (%s) code %d\n",
			cc, inet_ntoa(from->sin_addr),
			inet_ntoa(ip->ip_dst),
			type, pr_type(type), icp->icmp_code);
		for (i = 4; i < cc; i += sizeof(*lp))
			printf("%2d: x%8.8x\n", i, *lp++);
	}
#endif
	return 0;
}

/*
 * Construct an Internet address representation.
 * If the -n flag has been supplied, give
 * numeric value, otherwise try for symbolic name.
 */
static void
print_inetname(const struct sockaddr_in *from)
{
	const char *ina;

	ina = inet_ntoa(from->sin_addr);
	if (option_mask32 & OPT_ADDR_NUM)
		printf("  %s", ina);
	else {
		char *n = NULL;
		if (from->sin_addr.s_addr != INADDR_ANY)
			n = xmalloc_sockaddr2host_noport((struct sockaddr*)from);
		printf("  %s (%s)", (n ? n : ina), ina);
		free(n);
	}
}

static void
print(int cc, const struct sockaddr_in *from)
{
	print_inetname(from);
	if (verbose) {
		const struct ip *ip;
		int hlen;

		ip = (struct ip *) recv_pkt;
		hlen = ip->ip_hl << 2;
		cc -= hlen;
		printf(" %d bytes to %s", cc, inet_ntoa(ip->ip_dst));
	}
}

static void
print_delta_ms(unsigned t1p, unsigned t2p)
{
	unsigned tt = t2p - t1p;
	printf("  %u.%03u ms", tt / 1000, tt % 1000);
}

/*
Usage: [-dFIlnrvx] [-g gateway] [-i iface] [-f first_ttl]
[-m max_ttl] [ -p port] [-q nqueries] [-s src_addr] [-t tos]
[-w waittime] [-z pausemsecs] host [packetlen]"
*/

int traceroute_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int traceroute_main(int argc, char **argv)
{
	int minpacket;
	int ttl, i;
	int seq = 0;
	int tos = 0;
	int max_ttl = 30;
	int nprobes = 3;
	int first_ttl = 1;
	unsigned pausemsecs = 0;
	unsigned op;
	char *source;
	char *device;
	char *tos_str;
	char *max_ttl_str;
	char *port_str;
	char *nprobes_str;
	char *waittime_str;
	char *pausemsecs_str;
	char *first_ttl_str;
#if ENABLE_FEATURE_TRACEROUTE_SOURCE_ROUTE
	llist_t *source_route_list = NULL;
	int lsrr = 0;
#endif

	INIT_G();

#if ENABLE_FEATURE_TRACEROUTE_SOURCE_ROUTE
	opt_complementary = "x-x:g::";
#else
	opt_complementary = "x-x";
#endif

	op = getopt32(argv, "FIlnrdvxt:i:m:p:q:s:w:z:f:"
#if ENABLE_FEATURE_TRACEROUTE_SOURCE_ROUTE
					"g:"
#endif
		, &tos_str, &device, &max_ttl_str, &port_str, &nprobes_str
		, &source, &waittime_str, &pausemsecs_str, &first_ttl_str
#if ENABLE_FEATURE_TRACEROUTE_SOURCE_ROUTE
		, &source_route_list
#endif
	);

#if 0 /* IGNORED */
	if (op & OPT_IP_CHKSUM)
		bb_error_msg("warning: ip checksums disabled");
#endif
	if (op & OPT_TOS)
		tos = xatou_range(tos_str, 0, 255);
	if (op & OPT_MAX_TTL)
		max_ttl = xatou_range(max_ttl_str, 1, 255);
	if (op & OPT_PORT)
		port = xatou16(port_str);
	if (op & OPT_NPROBES)
		nprobes = xatou_range(nprobes_str, 1, INT_MAX);
	if (op & OPT_SOURCE) {
		/*
		 * set the ip source address of the outbound
		 * probe (e.g., on a multi-homed host).
		 */
		if (getuid() != 0)
			bb_error_msg_and_die("you must be root to use -s");
	}
	if (op & OPT_WAITTIME)
		waittime = xatou_range(waittime_str, 1, 24 * 60 * 60);
	if (op & OPT_PAUSE_MS)
		pausemsecs = xatou_range(pausemsecs_str, 0, 60 * 60 * 1000);
	if (op & OPT_FIRST_TTL)
		first_ttl = xatou_range(first_ttl_str, 1, max_ttl);

#if ENABLE_FEATURE_TRACEROUTE_SOURCE_ROUTE
	if (source_route_list) {
		while (source_route_list) {
			len_and_sockaddr *lsa;

			if (lsrr >= NGATEWAYS)
				bb_error_msg_and_die("no more than %d gateways", NGATEWAYS);
			lsa = xhost_and_af2sockaddr(llist_pop(&source_route_list), 0, AF_INET);
			gwlist[lsrr] = lsa->u.sin.sin_addr.s_addr;
			free(lsa);
			++lsrr;
		}
		optlen = (lsrr + 1) * sizeof(gwlist[0]);
	}
#endif

	minpacket = sizeof(*outip) + SIZEOF_ICMP_HDR + sizeof(*outdata) + optlen;
	if (!(op & OPT_USE_ICMP))
		minpacket += sizeof(*outudp) - SIZEOF_ICMP_HDR;
	packlen = minpacket;

	/* Process destination and optional packet size */
	argv += optind;
	argc -= optind;
	switch (argc) {
	case 2:
		packlen = xatoul_range(argv[1], minpacket, 32 * 1024);
		/* Fall through */
	case 1:
		dest_lsa = xhost2sockaddr(argv[0], port);
		break;
	default:
		bb_show_usage();
	}

	/* Ensure the socket fds won't be 0, 1 or 2 */
	bb_sanitize_stdio();

	xmove_fd(xsocket(AF_INET, SOCK_RAW, IPPROTO_ICMP), rcvsock);
#if TRACEROUTE_SO_DEBUG
	if (op & OPT_DEBUG)
		setsockopt(rcvsock, SOL_SOCKET, SO_DEBUG,
				&const_int_1, sizeof(const_int_1));
#endif
	if (op & OPT_BYPASS_ROUTE)
		setsockopt(rcvsock, SOL_SOCKET, SO_DONTROUTE,
				&const_int_1, sizeof(const_int_1));

	if (op & OPT_USE_ICMP)
		xmove_fd(xsocket(AF_INET, SOCK_RAW, IPPROTO_ICMP), sndsock);
	else
		xmove_fd(xsocket(AF_INET, SOCK_DGRAM, 0), sndsock);
#if ENABLE_FEATURE_TRACEROUTE_SOURCE_ROUTE
#if defined(IP_OPTIONS)
	if (lsrr > 0) {
		unsigned char optlist[MAX_IPOPTLEN];

		/* final hop */
		gwlist[lsrr] = dest_lsa->u.sin.sin_addr.s_addr;
		++lsrr;

		/* force 4 byte alignment */
		optlist[0] = IPOPT_NOP;
		/* loose source route option */
		optlist[1] = IPOPT_LSRR;
		i = lsrr * sizeof(gwlist[0]);
		optlist[2] = i + 3;
		/* pointer to LSRR addresses */
		optlist[3] = IPOPT_MINOFF;
		memcpy(optlist + 4, gwlist, i);

		if (setsockopt(sndsock, IPPROTO_IP, IP_OPTIONS,
				(char *)optlist, i + sizeof(gwlist[0])) < 0) {
			bb_perror_msg_and_die("IP_OPTIONS");
		}
	}
#endif /* IP_OPTIONS */
#endif /* CONFIG_FEATURE_TRACEROUTE_SOURCE_ROUTE */
#ifdef SO_SNDBUF
	if (setsockopt(sndsock, SOL_SOCKET, SO_SNDBUF, &packlen, sizeof(packlen)) < 0) {
		bb_perror_msg_and_die("SO_SNDBUF");
	}
#endif
#ifdef IP_TOS
	if ((op & OPT_TOS) && setsockopt(sndsock, IPPROTO_IP, IP_TOS, &tos, sizeof(tos)) < 0) {
		bb_perror_msg_and_die("setsockopt tos %d", tos);
	}
#endif
#ifdef IP_DONTFRAG
	if (op & OPT_DONT_FRAGMNT)
		setsockopt(sndsock, IPPROTO_IP, IP_DONTFRAG,
				&const_int_1, sizeof(const_int_1));
#endif
#if TRACEROUTE_SO_DEBUG
	if (op & OPT_DEBUG)
		setsockopt(sndsock, SOL_SOCKET, SO_DEBUG,
				&const_int_1, sizeof(const_int_1));
#endif
	if (op & OPT_BYPASS_ROUTE)
		setsockopt(sndsock, SOL_SOCKET, SO_DONTROUTE,
				&const_int_1, sizeof(const_int_1));

	outip = xzalloc(packlen);

	if (op & OPT_USE_ICMP) {
		ident = getpid() | 0x8000;
		outicmp->icmp_type = ICMP_ECHO;
		outicmp->icmp_id = htons(ident);
		outdata = (struct outdata_t *)((char *)outicmp + SIZEOF_ICMP_HDR);
	} else {
		outdata = (struct outdata_t *)(outudp + 1);
	}

	if (op & OPT_DEVICE) /* hmm, do we need error check? */
		setsockopt_bindtodevice(sndsock, device);

	if (op & OPT_SOURCE) {
		len_and_sockaddr *source_lsa = xdotted2sockaddr(source, 0);
		/* Ping does this (why?) */
		if (setsockopt(sndsock, IPPROTO_IP, IP_MULTICAST_IF,
				&source_lsa->u.sa, source_lsa->len))
			bb_error_msg_and_die("can't set multicast source interface");
//TODO: we can query source port we bound to,
// and check it in replies... if we care enough
		xbind(sndsock, &source_lsa->u.sa, source_lsa->len);
		free(source_lsa);
	}

	/* Revert to non-privileged user after opening sockets */
	xsetgid(getgid());
	xsetuid(getuid());

	printf("traceroute to %s (%s)", argv[0],
			xmalloc_sockaddr2dotted_noport(&dest_lsa->u.sa));
	if (op & OPT_SOURCE)
		printf(" from %s", source);
	printf(", %d hops max, %d byte packets\n", max_ttl, packlen);

	for (ttl = first_ttl; ttl <= max_ttl; ++ttl) {
//TODO: make it protocol agnostic (get rid of sockaddr_in)
		struct sockaddr_in from;
		uint32_t lastaddr = 0;
		int probe;
		int unreachable = 0; /* counter */
		int gotlastaddr = 0; /* flags */
		int got_there = 0;
		int first = 1;

		printf("%2d", ttl);
		for (probe = 0; probe < nprobes; ++probe) {
			int cc;
			unsigned t1;
			unsigned t2;
			struct ip *ip;

			if (!first && pausemsecs > 0)
				usleep(pausemsecs * 1000);
			fflush_all();

			t1 = monotonic_us();
			send_probe(++seq, ttl);
			first = 0;

			while ((cc = wait_for_reply(&from)) != 0) {
				t2 = monotonic_us();
				i = packet_ok(cc, &from, seq);
				/* Skip short packet */
				if (i == 0)
					continue;
				if (!gotlastaddr
				 || from.sin_addr.s_addr != lastaddr
				) {
					print(cc, &from);
					lastaddr = from.sin_addr.s_addr;
					gotlastaddr = 1;
				}
				print_delta_ms(t1, t2);
				ip = (struct ip *)recv_pkt;
				if (op & OPT_TTL_FLAG)
					printf(" (%d)", ip->ip_ttl);
				if (i == -2) {
					if (ip->ip_ttl <= 1)
						printf(" !");
					got_there = 1;
					break;
				}
				/* time exceeded in transit */
				if (i == -1)
					break;
				i--;
				switch (i) {
				case ICMP_UNREACH_PORT:
					if (ip->ip_ttl <= 1)
						printf(" !");
					got_there = 1;
					break;
				case ICMP_UNREACH_NET:
					printf(" !N");
					++unreachable;
					break;
				case ICMP_UNREACH_HOST:
					printf(" !H");
					++unreachable;
					break;
				case ICMP_UNREACH_PROTOCOL:
					printf(" !P");
					got_there = 1;
					break;
				case ICMP_UNREACH_NEEDFRAG:
					printf(" !F-%d", pmtu);
					++unreachable;
					break;
				case ICMP_UNREACH_SRCFAIL:
					printf(" !S");
					++unreachable;
					break;
				case ICMP_UNREACH_FILTER_PROHIB:
				case ICMP_UNREACH_NET_PROHIB:   /* misuse */
					printf(" !A");
					++unreachable;
					break;
				case ICMP_UNREACH_HOST_PROHIB:
					printf(" !C");
					++unreachable;
					break;
				case ICMP_UNREACH_HOST_PRECEDENCE:
					printf(" !V");
					++unreachable;
					break;
				case ICMP_UNREACH_PRECEDENCE_CUTOFF:
					printf(" !C");
					++unreachable;
					break;
				case ICMP_UNREACH_NET_UNKNOWN:
				case ICMP_UNREACH_HOST_UNKNOWN:
					printf(" !U");
					++unreachable;
					break;
				case ICMP_UNREACH_ISOLATED:
					printf(" !I");
					++unreachable;
					break;
				case ICMP_UNREACH_TOSNET:
				case ICMP_UNREACH_TOSHOST:
					printf(" !T");
					++unreachable;
					break;
				default:
					printf(" !<%d>", i);
					++unreachable;
					break;
				}
				break;
			}
			if (cc == 0)
				printf("  *");
		}
		bb_putchar('\n');
		if (got_there
		 || (unreachable > 0 && unreachable >= nprobes - 1)
		) {
			break;
		}
	}
	return 0;
}