aboutsummaryrefslogtreecommitdiff
path: root/networking/ifplugd.c
blob: 18dcaff96ee6a2e144ec65e3a44de7eba702a0a3 (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
/* vi: set sw=4 ts=4: */
/*
 * ifplugd for busybox, based on ifplugd 0.28 (written by Lennart Poettering).
 *
 * Copyright (C) 2009 Maksym Kryzhanovskyy <xmaks@email.cz>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */
//config:config IFPLUGD
//config:	bool "ifplugd (10 kb)"
//config:	default y
//config:	help
//config:	Network interface plug detection daemon.

//applet:IF_IFPLUGD(APPLET(ifplugd, BB_DIR_USR_SBIN, BB_SUID_DROP))

//kbuild:lib-$(CONFIG_IFPLUGD) += ifplugd.o

//usage:#define ifplugd_trivial_usage
//usage:       "[OPTIONS]"
//usage:#define ifplugd_full_usage "\n\n"
//usage:       "Network interface plug detection daemon\n"
//usage:     "\n	-n		Don't daemonize"
//usage:     "\n	-s		Don't log to syslog"
//usage:     "\n	-i IFACE	Interface"
//usage:     "\n	-f/-F		Treat link detection error as link down/link up"
//usage:     "\n			(otherwise exit on error)"
//usage:     "\n	-a		Don't up interface at each link probe"
//usage:     "\n	-M		Monitor creation/destruction of interface"
//usage:     "\n			(otherwise it must exist)"
//usage:     "\n	-r PROG		Script to run"
//usage:     "\n	-x ARG		Extra argument for script"
//usage:     "\n	-I		Don't exit on nonzero exit code from script"
//usage:     "\n	-p		Don't run \"up\" script on startup"
//usage:     "\n	-q		Don't run \"down\" script on exit"
//usage:     "\n	-l		Always run script on startup"
//usage:     "\n	-t SECS		Poll time in seconds"
//usage:     "\n	-u SECS		Delay before running script after link up"
//usage:     "\n	-d SECS		Delay after link down"
//usage:     "\n	-m MODE		API mode (mii, priv, ethtool, wlan, iff, auto)"
//usage:     "\n	-k		Kill running daemon"

#include "libbb.h"

#include "fix_u32.h"
#include <linux/if.h>
#include <linux/mii.h>
#include <linux/ethtool.h>
#ifdef HAVE_NET_ETHERNET_H
/* musl breakage:
 * In file included from /usr/include/net/ethernet.h:10,
 *                  from networking/ifplugd.c:41:
 * /usr/include/netinet/if_ether.h:96: error: redefinition of 'struct ethhdr'
 *
 * Build succeeds without it on musl. Commented it out.
 * If on your system you need it, consider removing <linux/ethtool.h>
 * and copy-pasting its definitions here (<linux/ethtool.h> is what pulls in
 * conflicting definition of struct ethhdr on musl).
 */
/* # include <net/ethernet.h> */
#endif
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <linux/sockios.h>
#include <syslog.h>

#define __user
#include <linux/wireless.h>

#ifndef ETH_ALEN
# define ETH_ALEN  6
#endif

/*
From initial port to busybox, removed most of the redundancy by
converting implementation of a polymorphic interface to the strict
functional style. The main role is run a script when link state
changed, other activities like audio signal or detailed reports
are on the script itself.

One questionable point of the design is netlink usage:

We have 1 second timeout by default to poll the link status,
it is short enough so that there are no real benefits in
using netlink to get "instantaneous" interface creation/deletion
notifications. We can check for interface existence by just
doing some fast ioctl using its name.

Netlink code then can be just dropped (1k or more?)
*/


#define IFPLUGD_ENV_PREVIOUS "IFPLUGD_PREVIOUS"
#define IFPLUGD_ENV_CURRENT "IFPLUGD_CURRENT"

enum {
	FLAG_NO_AUTO			= 1 <<  0, // -a, Do not enable interface automatically
	FLAG_NO_DAEMON			= 1 <<  1, // -n, Do not daemonize
	FLAG_NO_SYSLOG			= 1 <<  2, // -s, Do not use syslog, use stderr instead
	FLAG_IGNORE_FAIL		= 1 <<  3, // -f, Ignore detection failure, retry instead (failure is treated as DOWN)
	FLAG_IGNORE_FAIL_POSITIVE	= 1 <<  4, // -F, Ignore detection failure, retry instead (failure is treated as UP)
	FLAG_IFACE			= 1 <<  5, // -i, Specify ethernet interface
	FLAG_RUN			= 1 <<  6, // -r, Specify program to execute
	FLAG_IGNORE_RETVAL		= 1 <<  7, // -I, Don't exit on nonzero return value of program executed
	FLAG_POLL_TIME			= 1 <<  8, // -t, Specify poll time in seconds
	FLAG_DELAY_UP			= 1 <<  9, // -u, Specify delay for configuring interface
	FLAG_DELAY_DOWN			= 1 << 10, // -d, Specify delay for deconfiguring interface
	FLAG_API_MODE			= 1 << 11, // -m, Force API mode (mii, priv, ethtool, wlan, auto)
	FLAG_NO_STARTUP			= 1 << 12, // -p, Don't run script on daemon startup
	FLAG_NO_SHUTDOWN		= 1 << 13, // -q, Don't run script on daemon quit
	FLAG_INITIAL_DOWN		= 1 << 14, // -l, Run "down" script on startup if no cable is detected
	FLAG_EXTRA_ARG			= 1 << 15, // -x, Specify an extra argument for action script
	FLAG_MONITOR			= 1 << 16, // -M, Use interface monitoring
#if ENABLE_FEATURE_PIDFILE
	FLAG_KILL			= 1 << 17, // -k, Kill a running daemon
#endif
};
#if ENABLE_FEATURE_PIDFILE
# define OPTION_STR "+ansfFi:r:It:+u:+d:+m:pqlx:Mk"
#else
# define OPTION_STR "+ansfFi:r:It:+u:+d:+m:pqlx:M"
#endif

enum { // interface status
	IFSTATUS_ERR = -1,
	IFSTATUS_DOWN = 0,
	IFSTATUS_UP = 1,
};

enum { // constant fds
	ioctl_fd = 3,
	netlink_fd = 4,
};

struct globals {
	smallint iface_last_status;
	smallint iface_prev_status;
	smallint iface_exists;
	smallint api_method_num;

	/* Used in getopt32, must have sizeof == sizeof(int) */
	unsigned poll_time;
	unsigned delay_up;
	unsigned delay_down;

	const char *iface;
	const char *api_mode;
	const char *script_name;
	const char *extra_arg;
};
#define G (*ptr_to_globals)
#define INIT_G() do { \
	SET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \
	G.iface_last_status = -1; \
	G.iface_exists   = 1; \
	G.poll_time      = 1; \
	G.delay_down     = 5; \
	G.iface          = "eth0"; \
	G.api_mode       = "a"; \
	G.script_name    = "/etc/ifplugd/ifplugd.action"; \
} while (0)


/* Utility routines */

static void set_ifreq_to_ifname(struct ifreq *ifreq)
{
	memset(ifreq, 0, sizeof(struct ifreq));
	strncpy_IFNAMSIZ(ifreq->ifr_name, G.iface);
}

static int network_ioctl(int request, void* data, const char *errmsg)
{
	int r = ioctl(ioctl_fd, request, data);
	if (r < 0 && errmsg)
		bb_perror_msg("%s failed", errmsg);
	return r;
}

/* Link detection routines and table */

static smallint detect_link_mii(void)
{
	/* char buffer instead of bona-fide struct avoids aliasing warning */
	char buf[sizeof(struct ifreq)];
	struct ifreq *const ifreq = (void *)buf;

	struct mii_ioctl_data *mii = (void *)&ifreq->ifr_data;

	set_ifreq_to_ifname(ifreq);

	if (network_ioctl(SIOCGMIIPHY, ifreq, "SIOCGMIIPHY") < 0) {
		return IFSTATUS_ERR;
	}

	mii->reg_num = 1;

	if (network_ioctl(SIOCGMIIREG, ifreq, "SIOCGMIIREG") < 0) {
		return IFSTATUS_ERR;
	}

	return (mii->val_out & 0x0004) ? IFSTATUS_UP : IFSTATUS_DOWN;
}

static smallint detect_link_priv(void)
{
	/* char buffer instead of bona-fide struct avoids aliasing warning */
	char buf[sizeof(struct ifreq)];
	struct ifreq *const ifreq = (void *)buf;

	struct mii_ioctl_data *mii = (void *)&ifreq->ifr_data;

	set_ifreq_to_ifname(ifreq);

	if (network_ioctl(SIOCDEVPRIVATE, ifreq, "SIOCDEVPRIVATE") < 0) {
		return IFSTATUS_ERR;
	}

	mii->reg_num = 1;

	if (network_ioctl(SIOCDEVPRIVATE+1, ifreq, "SIOCDEVPRIVATE+1") < 0) {
		return IFSTATUS_ERR;
	}

	return (mii->val_out & 0x0004) ? IFSTATUS_UP : IFSTATUS_DOWN;
}

static smallint detect_link_ethtool(void)
{
	struct ifreq ifreq;
	struct ethtool_value edata;

	set_ifreq_to_ifname(&ifreq);

	edata.cmd = ETHTOOL_GLINK;
	ifreq.ifr_data = (void*) &edata;

	if (network_ioctl(SIOCETHTOOL, &ifreq, "ETHTOOL_GLINK") < 0) {
		return IFSTATUS_ERR;
	}

	return edata.data ? IFSTATUS_UP : IFSTATUS_DOWN;
}

static smallint detect_link_iff(void)
{
	struct ifreq ifreq;

	set_ifreq_to_ifname(&ifreq);

	if (network_ioctl(SIOCGIFFLAGS, &ifreq, "SIOCGIFFLAGS") < 0) {
		return IFSTATUS_ERR;
	}

	/* If IFF_UP is not set (interface is down), IFF_RUNNING is never set
	 * regardless of link status. Simply continue to report last status -
	 * no point in reporting spurious link downs if interface is disabled
	 * by admin. When/if it will be brought up,
	 * we'll report real link status.
	 */
	if (!(ifreq.ifr_flags & IFF_UP) && G.iface_last_status != IFSTATUS_ERR)
		return G.iface_last_status;

	return (ifreq.ifr_flags & IFF_RUNNING) ? IFSTATUS_UP : IFSTATUS_DOWN;
}

static smallint detect_link_wlan(void)
{
	int i;
	struct iwreq iwrequest;
	uint8_t mac[ETH_ALEN];

	memset(&iwrequest, 0, sizeof(iwrequest));
	strncpy_IFNAMSIZ(iwrequest.ifr_ifrn.ifrn_name, G.iface);

	if (network_ioctl(SIOCGIWAP, &iwrequest, "SIOCGIWAP") < 0) {
		return IFSTATUS_ERR;
	}

	memcpy(mac, &iwrequest.u.ap_addr.sa_data, ETH_ALEN);

	if (mac[0] == 0xFF || mac[0] == 0x44 || mac[0] == 0x00) {
		for (i = 1; i < ETH_ALEN; ++i) {
			if (mac[i] != mac[0])
				return IFSTATUS_UP;
		}
		return IFSTATUS_DOWN;
	}

	return IFSTATUS_UP;
}

enum { // api mode
	API_ETHTOOL, // 'e'
	API_MII,     // 'm'
	API_PRIVATE, // 'p'
	API_WLAN,    // 'w'
	API_IFF,     // 'i'
	API_AUTO,    // 'a'
};

static const char api_modes[] ALIGN1 = "empwia";

static const struct {
	const char *name;
	smallint (*func)(void);
} method_table[] ALIGN_PTR = {
	{ "SIOCETHTOOL"       , &detect_link_ethtool },
	{ "SIOCGMIIPHY"       , &detect_link_mii     },
	{ "SIOCDEVPRIVATE"    , &detect_link_priv    },
	{ "wireless extension", &detect_link_wlan    },
	{ "IFF_RUNNING"       , &detect_link_iff     },
};

static const char *strstatus(int status)
{
	if (status == IFSTATUS_ERR)
		return "error";
	return "down\0up" + (status * 5);
}

static int run_script(const char *action)
{
	char *env_PREVIOUS, *env_CURRENT;
	char *argv[5];
	int r;

	bb_info_msg("executing '%s %s %s'", G.script_name, G.iface, action);

	argv[0] = (char*) G.script_name;
	argv[1] = (char*) G.iface;
	argv[2] = (char*) action;
	argv[3] = (char*) G.extra_arg;
	argv[4] = NULL;

	env_PREVIOUS = xasprintf("%s=%s", IFPLUGD_ENV_PREVIOUS, strstatus(G.iface_prev_status));
	putenv(env_PREVIOUS);
	env_CURRENT = xasprintf("%s=%s", IFPLUGD_ENV_CURRENT, strstatus(G.iface_last_status));
	putenv(env_CURRENT);

	/* r < 0 - can't exec, 0 <= r < 0x180 - exited, >=0x180 - killed by sig (r-0x180) */
	r = spawn_and_wait(argv);

	bb_unsetenv_and_free(env_PREVIOUS);
	bb_unsetenv_and_free(env_CURRENT);

	bb_info_msg("exit code: %d", r & 0xff);
	return (option_mask32 & FLAG_IGNORE_RETVAL) ? 0 : r;
}

static void up_iface(void)
{
	struct ifreq ifrequest;

	if (!G.iface_exists)
		return;

	set_ifreq_to_ifname(&ifrequest);
	if (network_ioctl(SIOCGIFFLAGS, &ifrequest, "getting interface flags") < 0) {
		G.iface_exists = 0;
		return;
	}

	if (!(ifrequest.ifr_flags & IFF_UP)) {
		ifrequest.ifr_flags |= IFF_UP;
		/* Let user know we mess up with interface */
		bb_simple_info_msg("upping interface");
		if (network_ioctl(SIOCSIFFLAGS, &ifrequest, "setting interface flags") < 0) {
			if (errno != ENODEV && errno != EADDRNOTAVAIL)
				xfunc_die();
			G.iface_exists = 0;
			return;
		}
	}

#if 0 /* why do we mess with IP addr? It's not our business */
	if (network_ioctl(SIOCGIFADDR, &ifrequest, "can't get interface address") < 0) {
	} else if (ifrequest.ifr_addr.sa_family != AF_INET) {
		bb_perror_msg("the interface is not IP-based");
	} else {
		((struct sockaddr_in*)(&ifrequest.ifr_addr))->sin_addr.s_addr = INADDR_ANY;
		network_ioctl(SIOCSIFADDR, &ifrequest, "can't set interface address");
	}
	network_ioctl(SIOCGIFFLAGS, &ifrequest, "can't get interface flags");
#endif
}

static void maybe_up_new_iface(void)
{
	if (!(option_mask32 & FLAG_NO_AUTO))
		up_iface();

#if 0 /* bloat */
	struct ifreq ifrequest;
	struct ethtool_drvinfo driver_info;

	set_ifreq_to_ifname(&ifrequest);
	driver_info.cmd = ETHTOOL_GDRVINFO;
	ifrequest.ifr_data = &driver_info;
	if (network_ioctl(SIOCETHTOOL, &ifrequest, NULL) == 0) {
		char buf[sizeof("/xx:xx:xx:xx:xx:xx")];

		/* Get MAC */
		buf[0] = '\0';
		set_ifreq_to_ifname(&ifrequest);
		if (network_ioctl(SIOCGIFHWADDR, &ifrequest, NULL) == 0) {
			sprintf(buf, "/%02X:%02X:%02X:%02X:%02X:%02X",
				(uint8_t)(ifrequest.ifr_hwaddr.sa_data[0]),
				(uint8_t)(ifrequest.ifr_hwaddr.sa_data[1]),
				(uint8_t)(ifrequest.ifr_hwaddr.sa_data[2]),
				(uint8_t)(ifrequest.ifr_hwaddr.sa_data[3]),
				(uint8_t)(ifrequest.ifr_hwaddr.sa_data[4]),
				(uint8_t)(ifrequest.ifr_hwaddr.sa_data[5]));
		}

		bb_info_msg("using interface %s%s with driver<%s> (version: %s)",
			G.iface, buf, driver_info.driver, driver_info.version);
	}
#endif
	if (G.api_mode[0] == 'a')
		G.api_method_num = API_AUTO;
}

static smallint detect_link(void)
{
	smallint status;

	if (!G.iface_exists)
		return (option_mask32 & FLAG_MONITOR) ? IFSTATUS_DOWN : IFSTATUS_ERR;

	/* Some drivers can't detect link status when the interface is down.
	 * I imagine detect_link_iff() is the most vulnerable.
	 * That's why -a "noauto" in an option, not a hardwired behavior.
	 */
	if (!(option_mask32 & FLAG_NO_AUTO))
		up_iface();

	if (G.api_method_num == API_AUTO) {
		int i;
		smallint sv_logmode;

		sv_logmode = logmode;
		for (i = 0; i < ARRAY_SIZE(method_table); i++) {
			logmode = LOGMODE_NONE;
			status = method_table[i].func();
			logmode = sv_logmode;
			if (status != IFSTATUS_ERR) {
				G.api_method_num = i;
				bb_info_msg("using %s detection mode", method_table[i].name);
				break;
			}
		}
	} else {
		status = method_table[G.api_method_num].func();
	}

	if (status == IFSTATUS_ERR) {
		if (option_mask32 & FLAG_IGNORE_FAIL)
			status = IFSTATUS_DOWN;
		else if (option_mask32 & FLAG_IGNORE_FAIL_POSITIVE)
			status = IFSTATUS_UP;
		else if (G.api_mode[0] == 'a')
			bb_simple_error_msg("can't detect link status");
	}

	if (status != G.iface_last_status) {
		G.iface_prev_status = G.iface_last_status;
		G.iface_last_status = status;
	}

	return status;
}

static NOINLINE int check_existence_through_netlink(void)
{
	int iface_len;
	/* Buffer was 1K, but on linux-3.9.9 it was reported to be too small.
	 * netlink.h: "limit to 8K to avoid MSG_TRUNC when PAGE_SIZE is very large".
	 * Note: on error returns (-1) we exit, no need to free replybuf.
	 */
	enum { BUF_SIZE = 8 * 1024 };
	char *replybuf = xmalloc(BUF_SIZE);

	iface_len = strlen(G.iface);
	while (1) {
		struct nlmsghdr *mhdr;
		ssize_t bytes;

		bytes = recv(netlink_fd, replybuf, BUF_SIZE, MSG_DONTWAIT);
		if (bytes < 0) {
			if (errno == EAGAIN)
				goto ret;
			if (errno == EINTR)
				continue;
			bb_simple_perror_msg("netlink: recv");
			return -1;
		}

		mhdr = (struct nlmsghdr*)replybuf;
		while (bytes > 0) {
			if (!NLMSG_OK(mhdr, bytes)) {
				bb_simple_error_msg("netlink packet too small or truncated");
				return -1;
			}

			if (mhdr->nlmsg_type == RTM_NEWLINK || mhdr->nlmsg_type == RTM_DELLINK) {
				struct rtattr *attr;
				int attr_len;

				if (mhdr->nlmsg_len < NLMSG_LENGTH(sizeof(struct ifinfomsg))) {
					bb_simple_error_msg("netlink packet too small or truncated");
					return -1;
				}

				attr = IFLA_RTA(NLMSG_DATA(mhdr));
				attr_len = IFLA_PAYLOAD(mhdr);

				while (RTA_OK(attr, attr_len)) {
					if (attr->rta_type == IFLA_IFNAME) {
						int len = RTA_PAYLOAD(attr);
						if (len > IFNAMSIZ)
							len = IFNAMSIZ;
						if (iface_len <= len
						 && strncmp(G.iface, RTA_DATA(attr), len) == 0
						) {
							G.iface_exists = (mhdr->nlmsg_type == RTM_NEWLINK);
						}
					}
					attr = RTA_NEXT(attr, attr_len);
				}
			}

			mhdr = NLMSG_NEXT(mhdr, bytes);
		}
	}

 ret:
	free(replybuf);
	return G.iface_exists;
}

#if ENABLE_FEATURE_PIDFILE
static NOINLINE pid_t read_pid(const char *filename)
{
	int len;
	char buf[128];

	len = open_read_close(filename, buf, 127);
	if (len > 0) {
		buf[len] = '\0';
		/* returns ULONG_MAX on error => -1 */
		return bb_strtoul(buf, NULL, 10);
	}
	return 0;
}
#endif

int ifplugd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int ifplugd_main(int argc UNUSED_PARAM, char **argv)
{
	int iface_status;
	int delay_time;
	const char *iface_status_str;
	struct pollfd netlink_pollfd[1];
	unsigned opts;
	const char *api_mode_found;
#if ENABLE_FEATURE_PIDFILE
	char *pidfile_name;
	pid_t pid_from_pidfile;
#endif

	INIT_G();

	opts = getopt32(argv, OPTION_STR,
		&G.iface, &G.script_name, &G.poll_time, &G.delay_up,
		&G.delay_down, &G.api_mode, &G.extra_arg);
	G.poll_time *= 1000;

	applet_name = xasprintf("ifplugd(%s)", G.iface);

#if ENABLE_FEATURE_PIDFILE
	pidfile_name = xasprintf(CONFIG_PID_FILE_PATH "/ifplugd.%s.pid", G.iface);
	pid_from_pidfile = read_pid(pidfile_name);

	if (opts & FLAG_KILL) {
		if (pid_from_pidfile > 0)
			/* Upstream tool use SIGINT for -k */
			kill(pid_from_pidfile, SIGINT);
		return EXIT_SUCCESS;
	}

	if (pid_from_pidfile > 0 && kill(pid_from_pidfile, 0) == 0)
		bb_simple_error_msg_and_die("daemon already running");
#endif

	api_mode_found = strchr(api_modes, G.api_mode[0]);
	if (!api_mode_found)
		bb_error_msg_and_die("unknown API mode '%s'", G.api_mode);
	G.api_method_num = api_mode_found - api_modes;

	if (!(opts & FLAG_NO_DAEMON))
		bb_daemonize_or_rexec(DAEMON_CHDIR_ROOT, argv);

	xmove_fd(xsocket(AF_INET, SOCK_DGRAM, 0), ioctl_fd);
	if (opts & FLAG_MONITOR) {
		int fd = create_and_bind_to_netlink(NETLINK_ROUTE, RTMGRP_LINK, 0);
		xmove_fd(fd, netlink_fd);
	}

	write_pidfile(pidfile_name);

	/* this can't be moved before socket creation */
	if (!(opts & FLAG_NO_SYSLOG)) {
		openlog(applet_name, 0, LOG_DAEMON);
		logmode |= LOGMODE_SYSLOG;
	}

	bb_signals(0
		| (1 << SIGINT )
		| (1 << SIGTERM)
		| (1 << SIGQUIT)
		| (1 << SIGHUP ) /* why we ignore it? */
		/* | (1 << SIGCHLD) - run_script does not use it anymore */
		, record_signo);

	bb_info_msg("started: %s", bb_banner);

	if (opts & FLAG_MONITOR) {
		struct ifreq ifrequest;
		set_ifreq_to_ifname(&ifrequest);
		G.iface_exists = (network_ioctl(SIOCGIFINDEX, &ifrequest, NULL) == 0);
	}

	if (G.iface_exists)
		maybe_up_new_iface();

	iface_status = detect_link();
	if (iface_status == IFSTATUS_ERR)
		goto exiting;
	iface_status_str = strstatus(iface_status);

	if (opts & FLAG_MONITOR) {
		bb_info_msg("interface %s",
			G.iface_exists ? "exists"
			: "doesn't exist, waiting");
	}
	/* else we assume it always exists, but don't mislead user
	 * by potentially lying that it really exists */

	if (G.iface_exists) {
		bb_info_msg("link is %s", iface_status_str);
	}

	if ((!(opts & FLAG_NO_STARTUP)
	     && iface_status == IFSTATUS_UP
	    )
	 || (opts & FLAG_INITIAL_DOWN)
	) {
		if (run_script(iface_status_str) != 0)
			goto exiting;
	}

	/* Main loop */
	netlink_pollfd[0].fd = netlink_fd;
	netlink_pollfd[0].events = POLLIN;
	delay_time = 0;
	while (1) {
		int iface_status_old;

		switch (bb_got_signal) {
		case SIGINT:
		case SIGTERM:
			bb_got_signal = 0;
			goto cleanup;
		case SIGQUIT:
			bb_got_signal = 0;
			goto exiting;
		default:
			bb_got_signal = 0;
		/* do not clear bb_got_signal if already 0, this can lose signals */
		case 0:
			break;
		}

		if (poll(netlink_pollfd,
				(opts & FLAG_MONITOR) ? 1 : 0,
				G.poll_time
			) < 0
		) {
			if (errno == EINTR)
				continue;
			bb_simple_perror_msg("poll");
			goto exiting;
		}

		if ((opts & FLAG_MONITOR)
		 && (netlink_pollfd[0].revents & POLLIN)
		) {
			int iface_exists_old;

			iface_exists_old = G.iface_exists;
			G.iface_exists = check_existence_through_netlink();
			if (G.iface_exists < 0) /* error */
				goto exiting;
			if (iface_exists_old != G.iface_exists) {
				bb_info_msg("interface %sappeared",
						G.iface_exists ? "" : "dis");
				if (G.iface_exists)
					maybe_up_new_iface();
			}
		}

		/* note: if !G.iface_exists, returns DOWN */
		iface_status_old = iface_status;
		iface_status = detect_link();
		if (iface_status == IFSTATUS_ERR) {
			if (!(opts & FLAG_MONITOR))
				goto exiting;
			iface_status = IFSTATUS_DOWN;
		}
		iface_status_str = strstatus(iface_status);

		if (iface_status_old != iface_status) {
			bb_info_msg("link is %s", iface_status_str);

			if (delay_time) {
				/* link restored its old status before
				 * we ran script. don't run the script: */
				delay_time = 0;
			} else {
				delay_time = monotonic_sec();
				if (iface_status == IFSTATUS_UP)
					delay_time += G.delay_up;
				if (iface_status == IFSTATUS_DOWN)
					delay_time += G.delay_down;
#if 0  /* if you are back in 1970... */
				if (delay_time == 0) {
					sleep1();
					delay_time = 1;
				}
#endif
			}
		}

		if (delay_time && (int)(monotonic_sec() - delay_time) >= 0) {
			if (run_script(iface_status_str) != 0)
				goto exiting;
			delay_time = 0;
		}
	} /* while (1) */

 cleanup:
	if (!(opts & FLAG_NO_SHUTDOWN)
	 && (iface_status == IFSTATUS_UP
	     || (iface_status == IFSTATUS_DOWN && delay_time)
	    )
	) {
		setenv(IFPLUGD_ENV_PREVIOUS, strstatus(iface_status), 1);
		setenv(IFPLUGD_ENV_CURRENT, strstatus(-1), 1);
		run_script("down\0up"); /* reusing string */
	}

 exiting:
	remove_pidfile(pidfile_name);
	bb_simple_error_msg_and_die("exiting");
}