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ifwatchd.c revision 1.2 
      1 /*	$NetBSD: ifwatchd.c,v 1.2 2001/11/19 10:20:34 martin Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 2001 Martin Husemann <martin (at) duskware.de>
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. The name of the author may not be used to endorse or promote products
     13  *    derived from this software withough specific prior written permission
     14  *
     15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     25  */
     26 
     27 #include <sys/types.h>
     28 #include <sys/param.h>
     29 #include <sys/socket.h>
     30 #include <sys/queue.h>
     31 #include <net/if.h>
     32 #include <net/if_dl.h>
     33 #include <net/route.h>
     34 #include <netinet/in.h>
     35 #include <arpa/inet.h>
     36 
     37 #include <stdio.h>
     38 #include <stdlib.h>
     39 #include <string.h>
     40 #include <unistd.h>
     41 #include <netdb.h>
     42 
     43 /* local functions */
     44 static void usage(void);
     45 static void dispatch(void*, size_t);
     46 static void check_addrs(char *cp, int addrs, int is_up);
     47 static void invoke_script(struct sockaddr *sa, int is_up, int ifindex);
     48 static void list_interfaces(const char *ifnames);
     49 static void rescan_interfaces(void);
     50 static void free_interfaces(void);
     51 static int find_interface(int index);
     52 
     53 /* stolen from /sbin/route */
     54 #define ROUNDUP(a) \
     55 	((a) > 0 ? (1 + (((a) - 1) | (sizeof(long) - 1))) : sizeof(long))
     56 #define ADVANCE(x, n) (x += ROUNDUP((n)->sa_len))
     57 
     58 /* global variables */
     59 static int verbose = 0;
     60 static const char *up_script = NULL;
     61 static const char *down_script = NULL;
     62 
     63 struct interface_data {
     64 	SLIST_ENTRY(interface_data) next;
     65 	int index;
     66 	char * ifname;
     67 };
     68 SLIST_HEAD(,interface_data) ifs = SLIST_HEAD_INITIALIZER(ifs);
     69 
     70 int
     71 main(int argc, char **argv)
     72 {
     73 	int c, s, n;
     74 	int errs = 0;
     75 	char msg[2048], *msgp;
     76 
     77 	while ((c = getopt(argc, argv, "vhu:d:")) != -1)
     78 		switch (c) {
     79 		case 'h':
     80 			usage();
     81 			return 0;
     82 		case 'v':
     83 			verbose++;
     84 			break;
     85 
     86 		case 'u':
     87 			up_script = optarg;
     88 			break;
     89 
     90 		case 'd':
     91 			down_script = optarg;
     92 			break;
     93 
     94 		default:
     95 			errs++;
     96 			break;
     97 		}
     98 
     99 	if (errs)
    100 		usage();
    101 
    102 	argv += optind;
    103 	argc -= optind;
    104 
    105 	if (argc <= 0)
    106 		usage();
    107 
    108 	if (verbose) {
    109 		printf("up_script: %s\ndown_script: %s\n",
    110 			up_script, down_script);
    111 		printf("verbosity = %d\n", verbose);
    112 	}
    113 
    114 	while (argc > 0) {
    115 	    list_interfaces(argv[0]);
    116 	    argv++; argc--;
    117 	}
    118 
    119 	if (!verbose)
    120 		daemon(0,0);
    121 
    122 	s = socket(PF_ROUTE, SOCK_RAW, 0);
    123 	if (s < 0) {
    124 		perror("open routing socket");
    125 		exit(1);
    126 	}
    127 
    128 	for (;;) {
    129 		n = read(s, msg, sizeof msg);
    130 		msgp = msg;
    131 		for (msgp = msg; n > 0; n -= ((struct rt_msghdr*)msgp)->rtm_msglen, msgp += ((struct rt_msghdr*)msgp)->rtm_msglen) {
    132 			dispatch(msgp, n);
    133 
    134 		}
    135 	}
    136 
    137 	close(s);
    138 	free_interfaces();
    139 
    140 	exit(0);
    141 }
    142 
    143 static void
    144 usage()
    145 {
    146 	fprintf(stderr,
    147 	    "usage:\n"
    148 	    "\tifwatchd [-h] [-v] [-u up-script] [-d down-script] ifname(s)\n"
    149 	    "\twhere:\n"
    150 	    "\t -h       show this help message\n"
    151 	    "\t -v       verbose/debug output, don't run in background\n"
    152 	    "\t -u <cmd> specify command to run on interface up event\n"
    153 	    "\t -d <cmd> specify command to run on interface down event\n");
    154 	exit(1);
    155 }
    156 
    157 static void
    158 dispatch(void *msg, size_t len)
    159 {
    160 	struct rt_msghdr *hd = msg;
    161 	struct ifa_msghdr *ifam;
    162 	int is_up;
    163 
    164 	is_up = 0;
    165 	switch (hd->rtm_type) {
    166 	case RTM_NEWADDR:
    167 		is_up = 1;
    168 		goto work;
    169 	case RTM_DELADDR:
    170 		is_up = 0;
    171 		goto work;
    172 	case RTM_IFANNOUNCE:
    173 		rescan_interfaces();
    174 		break;
    175 	}
    176 	if (verbose)
    177 		printf("unknown message ignored\n");
    178 	return;
    179 
    180 work:
    181 	ifam = (struct ifa_msghdr *)msg;
    182 	check_addrs((char *)(ifam + 1), ifam->ifam_addrs, is_up);
    183 }
    184 
    185 static void
    186 check_addrs(cp, addrs, is_up)
    187 	char    *cp;
    188 	int     addrs, is_up;
    189 {
    190 	struct sockaddr *sa;
    191 	int ifndx = 0, i;
    192 
    193 	if (addrs == 0)
    194 	    return;
    195 	for (i = 1; i; i <<= 1) {
    196 	    if (i & addrs) {
    197 		sa = (struct sockaddr *)cp;
    198 		if (i == RTA_IFP) {
    199 		    struct sockaddr_dl * li = (struct sockaddr_dl*)sa;
    200 		    ifndx = li->sdl_index;
    201 		    if (!find_interface(ifndx)) {
    202 			if (verbose)
    203 			    printf("ignoring change on interface #%d\n", ifndx);
    204 			return;
    205 		    }
    206 		} else if (i == RTA_IFA) {
    207 		    invoke_script(sa, is_up, ifndx);
    208 		}
    209 		ADVANCE(cp, sa);
    210 	    }
    211 	}
    212 }
    213 
    214 static void
    215 invoke_script(sa, is_up, ifindex)
    216 	struct sockaddr *sa;
    217 	int is_up, ifindex;
    218 {
    219 	char addr[NI_MAXHOST], ifname_buf[IFNAMSIZ], *ifname, *cmd;
    220 	const char *script;
    221 
    222 	ifname = if_indextoname(ifindex, ifname_buf);
    223 	if (sa->sa_len == 0) {
    224 	    fprintf(stderr, "illegal socket address (sa_len == 0)\n");
    225 	    return;
    226 	}
    227 
    228 	if (getnameinfo(sa, sa->sa_len, addr, sizeof addr, NULL, 0, NI_NUMERICHOST)) {
    229 	    if (verbose)
    230 		printf("getnameinfo failed\n");
    231 	    return;	/* this address can not be handled */
    232 	}
    233 
    234 	script = is_up? up_script : down_script;
    235 	if (script == NULL) return;
    236 
    237 	asprintf(&cmd, "%s \"%s\" %s \"%s\"", script, ifname,
    238 			is_up?"up":"down", addr);
    239 	if (cmd == NULL) {
    240 	    fprintf(stderr, "out of memory\n");
    241 	    return;
    242 	}
    243 	if (verbose)
    244 	    printf("calling: %s\n", cmd);
    245 	system(cmd);
    246 	free(cmd);
    247 }
    248 
    249 static void list_interfaces(const char *ifnames)
    250 {
    251 	char * names = strdup(ifnames);
    252 	char * name, *lasts;
    253 	static const char sep[] = " \t";
    254 	struct interface_data * p;
    255 
    256 	for (name = strtok_r(names, sep, &lasts); name != NULL; name = strtok_r(NULL, sep, &lasts)) {
    257 	    p = malloc(sizeof(*p));
    258 	    SLIST_INSERT_HEAD(&ifs, p, next);
    259 	    p->ifname = strdup(name);
    260 	    p->index = if_nametoindex(p->ifname);
    261 	    if (verbose)
    262 		printf("interface \"%s\" has index %d\n", p->ifname, p->index);
    263 	}
    264 	free(names);
    265 }
    266 
    267 static void rescan_interfaces()
    268 {
    269 	struct interface_data * p;
    270 
    271 	SLIST_FOREACH(p, &ifs, next) {
    272 	    p->index = if_nametoindex(p->ifname);
    273 	    if (verbose)
    274 		printf("interface \"%s\" has index %d\n", p->ifname, p->index);
    275 	}
    276 }
    277 
    278 static void free_interfaces()
    279 {
    280 	struct interface_data * p;
    281 
    282 	while (!SLIST_EMPTY(&ifs)) {
    283 	    p = SLIST_FIRST(&ifs);
    284 	    SLIST_REMOVE_HEAD(&ifs, next);
    285 	    free(p->ifname);
    286 	    free(p);
    287 	}
    288 }
    289 
    290 static int find_interface(index)
    291 	int index;
    292 {
    293 	struct interface_data * p;
    294 
    295 	SLIST_FOREACH(p, &ifs, next)
    296 	    if (p->index == index)
    297 		return 1;
    298 	return 0;
    299 }
    300