1 /*-
2 * SPDX-License-Identifier: BSD-1-Clause
3 *
4 * Copyright (c) 1990, 1991, 1992, 1993, 1996
5 * The Regents of the University of California. All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that: (1) source code distributions
9 * retain the above copyright notice and this paragraph in its entirety, (2)
10 * distributions including binary code include the above copyright notice and
11 * this paragraph in its entirety in the documentation or other materials
12 * provided with the distribution
13 *
14 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
15 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
16 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
17 */
18
19 #if 0
20 #ifndef lint
21 static const char copyright[] =
22 "@(#) Copyright (c) 1990, 1991, 1992, 1993, 1996\n\
23 The Regents of the University of California. All rights reserved.\n";
24 #endif /* not lint */
25 #endif
26 #include <sys/cdefs.h>
27 __FBSDID("$FreeBSD$");
28
29 /*
30 * rarpd - Reverse ARP Daemon
31 *
32 * Usage: rarpd -a [-dfsv] [-t directory] [-P pidfile] [hostname]
33 * rarpd [-dfsv] [-t directory] [-P pidfile] interface [hostname]
34 *
35 * 'hostname' is optional solely for backwards compatibility with Sun's rarpd.
36 * Currently, the argument is ignored.
37 */
38 #include <sys/param.h>
39 #include <sys/file.h>
40 #include <sys/ioctl.h>
41 #include <sys/socket.h>
42 #include <sys/time.h>
43
44 #include <net/bpf.h>
45 #include <net/ethernet.h>
46 #include <net/if.h>
47 #include <net/if_types.h>
48 #include <net/if_dl.h>
49 #include <net/route.h>
50
51 #include <netinet/in.h>
52 #include <netinet/if_ether.h>
53
54 #include <arpa/inet.h>
55
56 #include <dirent.h>
57 #include <errno.h>
58 #include <ifaddrs.h>
59 #include <netdb.h>
60 #include <stdarg.h>
61 #include <stdio.h>
62 #include <string.h>
63 #include <syslog.h>
64 #include <stdlib.h>
65 #include <unistd.h>
66 #include <libutil.h>
67
68 /* Cast a struct sockaddr to a struct sockaddr_in */
69 #define SATOSIN(sa) ((struct sockaddr_in *)(sa))
70
71 #ifndef TFTP_DIR
72 #define TFTP_DIR "/tftpboot"
73 #endif
74
75 #define ARPSECS (20 * 60) /* as per code in netinet/if_ether.c */
76 #define REVARP_REQUEST ARPOP_REVREQUEST
77 #define REVARP_REPLY ARPOP_REVREPLY
78
79 /*
80 * The structure for each interface.
81 */
82 struct if_info {
83 struct if_info *ii_next;
84 int ii_fd; /* BPF file descriptor */
85 in_addr_t ii_ipaddr; /* IP address */
86 in_addr_t ii_netmask; /* subnet or net mask */
87 u_char ii_eaddr[ETHER_ADDR_LEN]; /* ethernet address */
88 char ii_ifname[IF_NAMESIZE];
89 };
90
91 /*
92 * The list of all interfaces that are being listened to. rarp_loop()
93 * "selects" on the descriptors in this list.
94 */
95 static struct if_info *iflist;
96
97 static int verbose; /* verbose messages */
98 static const char *tftp_dir = TFTP_DIR; /* tftp directory */
99
100 static int dflag; /* messages to stdout/stderr, not syslog(3) */
101 static int sflag; /* ignore /tftpboot */
102
103 static u_char zero[6];
104
105 static char pidfile_buf[PATH_MAX];
106 static char *pidfile;
107 #define RARPD_PIDFILE "/var/run/rarpd.%s.pid"
108 static struct pidfh *pidfile_fh;
109
110 static int bpf_open(void);
111 static in_addr_t choose_ipaddr(in_addr_t **, in_addr_t, in_addr_t);
112 static char *eatoa(u_char *);
113 static int expand_syslog_m(const char *fmt, char **newfmt);
114 static void init(char *);
115 static void init_one(struct ifaddrs *, char *, int);
116 static char *intoa(in_addr_t);
117 static in_addr_t ipaddrtonetmask(in_addr_t);
118 static void logmsg(int, const char *, ...) __printflike(2, 3);
119 static int rarp_bootable(in_addr_t);
120 static int rarp_check(u_char *, u_int);
121 static void rarp_loop(void);
122 static int rarp_open(char *);
123 static void rarp_process(struct if_info *, u_char *, u_int);
124 static void rarp_reply(struct if_info *, struct ether_header *,
125 in_addr_t, u_int);
126 static void update_arptab(u_char *, in_addr_t);
127 static void usage(void);
128
129 int
main(int argc,char * argv[])130 main(int argc, char *argv[])
131 {
132 int op;
133 char *ifname, *name;
134
135 int aflag = 0; /* listen on "all" interfaces */
136 int fflag = 0; /* don't fork */
137
138 if ((name = strrchr(argv[0], '/')) != NULL)
139 ++name;
140 else
141 name = argv[0];
142 if (*name == '-')
143 ++name;
144
145 /*
146 * All error reporting is done through syslog, unless -d is specified
147 */
148 openlog(name, LOG_PID | LOG_CONS, LOG_DAEMON);
149
150 opterr = 0;
151 while ((op = getopt(argc, argv, "adfsP:t:v")) != -1)
152 switch (op) {
153 case 'a':
154 ++aflag;
155 break;
156
157 case 'd':
158 ++dflag;
159 break;
160
161 case 'f':
162 ++fflag;
163 break;
164
165 case 's':
166 ++sflag;
167 break;
168
169 case 'P':
170 strncpy(pidfile_buf, optarg, sizeof(pidfile_buf) - 1);
171 pidfile_buf[sizeof(pidfile_buf) - 1] = '\0';
172 pidfile = pidfile_buf;
173 break;
174
175 case 't':
176 tftp_dir = optarg;
177 break;
178
179 case 'v':
180 ++verbose;
181 break;
182
183 default:
184 usage();
185 /* NOTREACHED */
186 }
187 argc -= optind;
188 argv += optind;
189
190 ifname = (aflag == 0) ? argv[0] : NULL;
191
192 if ((aflag && ifname) || (!aflag && ifname == NULL))
193 usage();
194
195 init(ifname);
196
197 if (!fflag) {
198 if (pidfile == NULL && ifname != NULL && aflag == 0) {
199 snprintf(pidfile_buf, sizeof(pidfile_buf) - 1,
200 RARPD_PIDFILE, ifname);
201 pidfile_buf[sizeof(pidfile_buf) - 1] = '\0';
202 pidfile = pidfile_buf;
203 }
204 /* If pidfile == NULL, /var/run/<progname>.pid will be used. */
205 pidfile_fh = pidfile_open(pidfile, 0600, NULL);
206 if (pidfile_fh == NULL)
207 logmsg(LOG_ERR, "Cannot open or create pidfile: %s",
208 (pidfile == NULL) ? "/var/run/rarpd.pid" : pidfile);
209 if (daemon(0,0)) {
210 logmsg(LOG_ERR, "cannot fork");
211 pidfile_remove(pidfile_fh);
212 exit(1);
213 }
214 pidfile_write(pidfile_fh);
215 }
216 rarp_loop();
217 return(0);
218 }
219
220 /*
221 * Add to the interface list.
222 */
223 static void
init_one(struct ifaddrs * ifa,char * target,int pass1)224 init_one(struct ifaddrs *ifa, char *target, int pass1)
225 {
226 struct if_info *ii, *ii2;
227 struct sockaddr_dl *ll;
228 int family;
229
230 family = ifa->ifa_addr->sa_family;
231 switch (family) {
232 case AF_INET:
233 if (pass1)
234 /* Consider only AF_LINK during pass1. */
235 return;
236 /* FALLTHROUGH */
237 case AF_LINK:
238 if (!(ifa->ifa_flags & IFF_UP) ||
239 (ifa->ifa_flags & (IFF_LOOPBACK | IFF_POINTOPOINT)))
240 return;
241 break;
242 default:
243 return;
244 }
245
246 /* Don't bother going any further if not the target interface */
247 if (target != NULL && strcmp(ifa->ifa_name, target) != 0)
248 return;
249
250 /* Look for interface in list */
251 for (ii = iflist; ii != NULL; ii = ii->ii_next)
252 if (strcmp(ifa->ifa_name, ii->ii_ifname) == 0)
253 break;
254
255 if (pass1 && ii != NULL)
256 /* We've already seen that interface once. */
257 return;
258
259 /* Allocate a new one if not found */
260 if (ii == NULL) {
261 ii = (struct if_info *)malloc(sizeof(*ii));
262 if (ii == NULL) {
263 logmsg(LOG_ERR, "malloc: %m");
264 pidfile_remove(pidfile_fh);
265 exit(1);
266 }
267 bzero(ii, sizeof(*ii));
268 ii->ii_fd = -1;
269 strlcpy(ii->ii_ifname, ifa->ifa_name, sizeof(ii->ii_ifname));
270 ii->ii_next = iflist;
271 iflist = ii;
272 } else if (!pass1 && ii->ii_ipaddr != 0) {
273 /*
274 * Second AF_INET definition for that interface: clone
275 * the existing one, and work on that cloned one.
276 * This must be another IP address for this interface,
277 * so avoid killing the previous configuration.
278 */
279 ii2 = (struct if_info *)malloc(sizeof(*ii2));
280 if (ii2 == NULL) {
281 logmsg(LOG_ERR, "malloc: %m");
282 pidfile_remove(pidfile_fh);
283 exit(1);
284 }
285 memcpy(ii2, ii, sizeof(*ii2));
286 ii2->ii_fd = -1;
287 ii2->ii_next = iflist;
288 iflist = ii2;
289
290 ii = ii2;
291 }
292
293 switch (family) {
294 case AF_INET:
295 ii->ii_ipaddr = SATOSIN(ifa->ifa_addr)->sin_addr.s_addr;
296 ii->ii_netmask = SATOSIN(ifa->ifa_netmask)->sin_addr.s_addr;
297 if (ii->ii_netmask == 0)
298 ii->ii_netmask = ipaddrtonetmask(ii->ii_ipaddr);
299 if (ii->ii_fd < 0)
300 ii->ii_fd = rarp_open(ii->ii_ifname);
301 break;
302
303 case AF_LINK:
304 ll = (struct sockaddr_dl *)ifa->ifa_addr;
305 switch (ll->sdl_type) {
306 case IFT_ETHER:
307 case IFT_L2VLAN:
308 bcopy(LLADDR(ll), ii->ii_eaddr, 6);
309 }
310 break;
311 }
312 }
313
314 /*
315 * Initialize all "candidate" interfaces that are in the system
316 * configuration list. A "candidate" is up, not loopback and not
317 * point to point.
318 */
319 static void
init(char * target)320 init(char *target)
321 {
322 struct if_info *ii, *nii, *lii;
323 struct ifaddrs *ifhead, *ifa;
324 int error;
325
326 error = getifaddrs(&ifhead);
327 if (error) {
328 logmsg(LOG_ERR, "getifaddrs: %m");
329 pidfile_remove(pidfile_fh);
330 exit(1);
331 }
332 /*
333 * We make two passes over the list we have got. In the first
334 * one, we only collect AF_LINK interfaces, and initialize our
335 * list of interfaces from them. In the second pass, we
336 * collect the actual IP addresses from the AF_INET
337 * interfaces, and allow for the same interface name to appear
338 * multiple times (in case of more than one IP address).
339 */
340 for (ifa = ifhead; ifa != NULL; ifa = ifa->ifa_next)
341 init_one(ifa, target, 1);
342 for (ifa = ifhead; ifa != NULL; ifa = ifa->ifa_next)
343 init_one(ifa, target, 0);
344 freeifaddrs(ifhead);
345
346 /* Throw away incomplete interfaces */
347 lii = NULL;
348 for (ii = iflist; ii != NULL; ii = nii) {
349 nii = ii->ii_next;
350 if (ii->ii_ipaddr == 0 ||
351 bcmp(ii->ii_eaddr, zero, 6) == 0) {
352 if (lii == NULL)
353 iflist = nii;
354 else
355 lii->ii_next = nii;
356 if (ii->ii_fd >= 0)
357 close(ii->ii_fd);
358 free(ii);
359 continue;
360 }
361 lii = ii;
362 }
363
364 /* Verbose stuff */
365 if (verbose)
366 for (ii = iflist; ii != NULL; ii = ii->ii_next)
367 logmsg(LOG_DEBUG, "%s %s 0x%08x %s",
368 ii->ii_ifname, intoa(ntohl(ii->ii_ipaddr)),
369 (in_addr_t)ntohl(ii->ii_netmask), eatoa(ii->ii_eaddr));
370 }
371
372 static void
usage(void)373 usage(void)
374 {
375
376 (void)fprintf(stderr, "%s\n%s\n",
377 "usage: rarpd -a [-dfsv] [-t directory] [-P pidfile]",
378 " rarpd [-dfsv] [-t directory] [-P pidfile] interface");
379 exit(1);
380 }
381
382 static int
bpf_open(void)383 bpf_open(void)
384 {
385 int fd;
386 int n = 0;
387 char device[sizeof "/dev/bpf000"];
388
389 /*
390 * Go through all the minors and find one that isn't in use.
391 */
392 do {
393 (void)sprintf(device, "/dev/bpf%d", n++);
394 fd = open(device, O_RDWR);
395 } while ((fd == -1) && (errno == EBUSY));
396
397 if (fd == -1) {
398 logmsg(LOG_ERR, "%s: %m", device);
399 pidfile_remove(pidfile_fh);
400 exit(1);
401 }
402 return fd;
403 }
404
405 /*
406 * Open a BPF file and attach it to the interface named 'device'.
407 * Set immediate mode, and set a filter that accepts only RARP requests.
408 */
409 static int
rarp_open(char * device)410 rarp_open(char *device)
411 {
412 int fd;
413 struct ifreq ifr;
414 u_int dlt;
415 int immediate;
416
417 static struct bpf_insn insns[] = {
418 BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 12),
419 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, ETHERTYPE_REVARP, 0, 3),
420 BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 20),
421 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, REVARP_REQUEST, 0, 1),
422 BPF_STMT(BPF_RET|BPF_K, sizeof(struct ether_arp) +
423 sizeof(struct ether_header)),
424 BPF_STMT(BPF_RET|BPF_K, 0),
425 };
426 static struct bpf_program filter = {
427 sizeof insns / sizeof(insns[0]),
428 insns
429 };
430
431 fd = bpf_open();
432 /*
433 * Set immediate mode so packets are processed as they arrive.
434 */
435 immediate = 1;
436 if (ioctl(fd, BIOCIMMEDIATE, &immediate) == -1) {
437 logmsg(LOG_ERR, "BIOCIMMEDIATE: %m");
438 goto rarp_open_err;
439 }
440 strlcpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
441 if (ioctl(fd, BIOCSETIF, (caddr_t)&ifr) == -1) {
442 logmsg(LOG_ERR, "BIOCSETIF: %m");
443 goto rarp_open_err;
444 }
445 /*
446 * Check that the data link layer is an Ethernet; this code won't
447 * work with anything else.
448 */
449 if (ioctl(fd, BIOCGDLT, (caddr_t)&dlt) == -1) {
450 logmsg(LOG_ERR, "BIOCGDLT: %m");
451 goto rarp_open_err;
452 }
453 if (dlt != DLT_EN10MB) {
454 logmsg(LOG_ERR, "%s is not an ethernet", device);
455 goto rarp_open_err;
456 }
457 /*
458 * Set filter program.
459 */
460 if (ioctl(fd, BIOCSETF, (caddr_t)&filter) == -1) {
461 logmsg(LOG_ERR, "BIOCSETF: %m");
462 goto rarp_open_err;
463 }
464 return fd;
465
466 rarp_open_err:
467 pidfile_remove(pidfile_fh);
468 exit(1);
469 }
470
471 /*
472 * Perform various sanity checks on the RARP request packet. Return
473 * false on failure and log the reason.
474 */
475 static int
rarp_check(u_char * p,u_int len)476 rarp_check(u_char *p, u_int len)
477 {
478 struct ether_header *ep = (struct ether_header *)p;
479 struct ether_arp *ap = (struct ether_arp *)(p + sizeof(*ep));
480
481 if (len < sizeof(*ep) + sizeof(*ap)) {
482 logmsg(LOG_ERR, "truncated request, got %u, expected %lu",
483 len, (u_long)(sizeof(*ep) + sizeof(*ap)));
484 return 0;
485 }
486 /*
487 * XXX This test might be better off broken out...
488 */
489 if (ntohs(ep->ether_type) != ETHERTYPE_REVARP ||
490 ntohs(ap->arp_hrd) != ARPHRD_ETHER ||
491 ntohs(ap->arp_op) != REVARP_REQUEST ||
492 ntohs(ap->arp_pro) != ETHERTYPE_IP ||
493 ap->arp_hln != 6 || ap->arp_pln != 4) {
494 logmsg(LOG_DEBUG, "request fails sanity check");
495 return 0;
496 }
497 if (bcmp((char *)&ep->ether_shost, (char *)&ap->arp_sha, 6) != 0) {
498 logmsg(LOG_DEBUG, "ether/arp sender address mismatch");
499 return 0;
500 }
501 if (bcmp((char *)&ap->arp_sha, (char *)&ap->arp_tha, 6) != 0) {
502 logmsg(LOG_DEBUG, "ether/arp target address mismatch");
503 return 0;
504 }
505 return 1;
506 }
507
508 /*
509 * Loop indefinitely listening for RARP requests on the
510 * interfaces in 'iflist'.
511 */
512 static void
rarp_loop(void)513 rarp_loop(void)
514 {
515 u_char *buf, *bp, *ep;
516 int cc, fd;
517 fd_set fds, listeners;
518 int bufsize, maxfd = 0;
519 struct if_info *ii;
520
521 if (iflist == NULL) {
522 logmsg(LOG_ERR, "no interfaces");
523 goto rarpd_loop_err;
524 }
525 if (ioctl(iflist->ii_fd, BIOCGBLEN, (caddr_t)&bufsize) == -1) {
526 logmsg(LOG_ERR, "BIOCGBLEN: %m");
527 goto rarpd_loop_err;
528 }
529 buf = malloc(bufsize);
530 if (buf == NULL) {
531 logmsg(LOG_ERR, "malloc: %m");
532 goto rarpd_loop_err;
533 }
534
535 while (1) {
536 /*
537 * Find the highest numbered file descriptor for select().
538 * Initialize the set of descriptors to listen to.
539 */
540 FD_ZERO(&fds);
541 for (ii = iflist; ii != NULL; ii = ii->ii_next) {
542 FD_SET(ii->ii_fd, &fds);
543 if (ii->ii_fd > maxfd)
544 maxfd = ii->ii_fd;
545 }
546 listeners = fds;
547 if (select(maxfd + 1, &listeners, NULL, NULL, NULL) == -1) {
548 /* Don't choke when we get ptraced */
549 if (errno == EINTR)
550 continue;
551 logmsg(LOG_ERR, "select: %m");
552 goto rarpd_loop_err;
553 }
554 for (ii = iflist; ii != NULL; ii = ii->ii_next) {
555 fd = ii->ii_fd;
556 if (!FD_ISSET(fd, &listeners))
557 continue;
558 again:
559 cc = read(fd, (char *)buf, bufsize);
560 /* Don't choke when we get ptraced */
561 if ((cc == -1) && (errno == EINTR))
562 goto again;
563
564 /* Loop through the packet(s) */
565 #define bhp ((struct bpf_hdr *)bp)
566 bp = buf;
567 ep = bp + cc;
568 while (bp < ep) {
569 u_int caplen, hdrlen;
570
571 caplen = bhp->bh_caplen;
572 hdrlen = bhp->bh_hdrlen;
573 if (rarp_check(bp + hdrlen, caplen))
574 rarp_process(ii, bp + hdrlen, caplen);
575 bp += BPF_WORDALIGN(hdrlen + caplen);
576 }
577 }
578 }
579 #undef bhp
580 return;
581
582 rarpd_loop_err:
583 pidfile_remove(pidfile_fh);
584 exit(1);
585 }
586
587 /*
588 * True if this server can boot the host whose IP address is 'addr'.
589 * This check is made by looking in the tftp directory for the
590 * configuration file.
591 */
592 static int
rarp_bootable(in_addr_t addr)593 rarp_bootable(in_addr_t addr)
594 {
595 struct dirent *dent;
596 DIR *d;
597 char ipname[9];
598 static DIR *dd = NULL;
599
600 (void)sprintf(ipname, "%08X", (in_addr_t)ntohl(addr));
601
602 /*
603 * If directory is already open, rewind it. Otherwise, open it.
604 */
605 if ((d = dd) != NULL)
606 rewinddir(d);
607 else {
608 if (chdir(tftp_dir) == -1) {
609 logmsg(LOG_ERR, "chdir: %s: %m", tftp_dir);
610 goto rarp_bootable_err;
611 }
612 d = opendir(".");
613 if (d == NULL) {
614 logmsg(LOG_ERR, "opendir: %m");
615 goto rarp_bootable_err;
616 }
617 dd = d;
618 }
619 while ((dent = readdir(d)) != NULL)
620 if (strncmp(dent->d_name, ipname, 8) == 0)
621 return 1;
622 return 0;
623
624 rarp_bootable_err:
625 pidfile_remove(pidfile_fh);
626 exit(1);
627 }
628
629 /*
630 * Given a list of IP addresses, 'alist', return the first address that
631 * is on network 'net'; 'netmask' is a mask indicating the network portion
632 * of the address.
633 */
634 static in_addr_t
choose_ipaddr(in_addr_t ** alist,in_addr_t net,in_addr_t netmask)635 choose_ipaddr(in_addr_t **alist, in_addr_t net, in_addr_t netmask)
636 {
637
638 for (; *alist; ++alist)
639 if ((**alist & netmask) == net)
640 return **alist;
641 return 0;
642 }
643
644 /*
645 * Answer the RARP request in 'pkt', on the interface 'ii'. 'pkt' has
646 * already been checked for validity. The reply is overlaid on the request.
647 */
648 static void
rarp_process(struct if_info * ii,u_char * pkt,u_int len)649 rarp_process(struct if_info *ii, u_char *pkt, u_int len)
650 {
651 struct ether_header *ep;
652 struct hostent *hp;
653 in_addr_t target_ipaddr;
654 char ename[256];
655
656 ep = (struct ether_header *)pkt;
657 /* should this be arp_tha? */
658 if (ether_ntohost(ename, (struct ether_addr *)&ep->ether_shost) != 0) {
659 logmsg(LOG_ERR, "cannot map %s to name",
660 eatoa(ep->ether_shost));
661 return;
662 }
663
664 if ((hp = gethostbyname(ename)) == NULL) {
665 logmsg(LOG_ERR, "cannot map %s to IP address", ename);
666 return;
667 }
668
669 /*
670 * Choose correct address from list.
671 */
672 if (hp->h_addrtype != AF_INET) {
673 logmsg(LOG_ERR, "cannot handle non IP addresses for %s",
674 ename);
675 return;
676 }
677 target_ipaddr = choose_ipaddr((in_addr_t **)hp->h_addr_list,
678 ii->ii_ipaddr & ii->ii_netmask,
679 ii->ii_netmask);
680 if (target_ipaddr == 0) {
681 logmsg(LOG_ERR, "cannot find %s on net %s",
682 ename, intoa(ntohl(ii->ii_ipaddr & ii->ii_netmask)));
683 return;
684 }
685 if (sflag || rarp_bootable(target_ipaddr))
686 rarp_reply(ii, ep, target_ipaddr, len);
687 else if (verbose > 1)
688 logmsg(LOG_INFO, "%s %s at %s DENIED (not bootable)",
689 ii->ii_ifname,
690 eatoa(ep->ether_shost),
691 intoa(ntohl(target_ipaddr)));
692 }
693
694 /*
695 * Poke the kernel arp tables with the ethernet/ip address combinataion
696 * given. When processing a reply, we must do this so that the booting
697 * host (i.e. the guy running rarpd), won't try to ARP for the hardware
698 * address of the guy being booted (he cannot answer the ARP).
699 */
700 static struct sockaddr_in sin_inarp = {
701 sizeof(struct sockaddr_in), AF_INET, 0,
702 {0},
703 {0},
704 };
705
706 static struct sockaddr_dl sin_dl = {
707 sizeof(struct sockaddr_dl), AF_LINK, 0, IFT_ETHER, 0, 6,
708 0, ""
709 };
710
711 static struct {
712 struct rt_msghdr rthdr;
713 char rtspace[512];
714 } rtmsg;
715
716 static void
update_arptab(u_char * ep,in_addr_t ipaddr)717 update_arptab(u_char *ep, in_addr_t ipaddr)
718 {
719 struct timespec tp;
720 int cc;
721 struct sockaddr_in *ar, *ar2;
722 struct sockaddr_dl *ll, *ll2;
723 struct rt_msghdr *rt;
724 int xtype, xindex;
725 static pid_t pid;
726 int r;
727 static int seq;
728
729 r = socket(PF_ROUTE, SOCK_RAW, 0);
730 if (r == -1) {
731 logmsg(LOG_ERR, "raw route socket: %m");
732 pidfile_remove(pidfile_fh);
733 exit(1);
734 }
735 pid = getpid();
736
737 ar = &sin_inarp;
738 ar->sin_addr.s_addr = ipaddr;
739 ll = &sin_dl;
740 bcopy(ep, LLADDR(ll), 6);
741
742 /* Get the type and interface index */
743 rt = &rtmsg.rthdr;
744 bzero(&rtmsg, sizeof(rtmsg));
745 rt->rtm_version = RTM_VERSION;
746 rt->rtm_addrs = RTA_DST;
747 rt->rtm_type = RTM_GET;
748 rt->rtm_seq = ++seq;
749 ar2 = (struct sockaddr_in *)rtmsg.rtspace;
750 bcopy(ar, ar2, sizeof(*ar));
751 rt->rtm_msglen = sizeof(*rt) + sizeof(*ar);
752 errno = 0;
753 if ((write(r, rt, rt->rtm_msglen) == -1) && (errno != ESRCH)) {
754 logmsg(LOG_ERR, "rtmsg get write: %m");
755 close(r);
756 return;
757 }
758 do {
759 cc = read(r, rt, sizeof(rtmsg));
760 } while (cc > 0 && (rt->rtm_type != RTM_GET || rt->rtm_seq != seq ||
761 rt->rtm_pid != pid));
762 if (cc == -1) {
763 logmsg(LOG_ERR, "rtmsg get read: %m");
764 close(r);
765 return;
766 }
767 ll2 = (struct sockaddr_dl *)((u_char *)ar2 + ar2->sin_len);
768 if (ll2->sdl_family != AF_LINK) {
769 /*
770 * XXX I think this means the ip address is not on a
771 * directly connected network (the family is AF_INET in
772 * this case).
773 */
774 logmsg(LOG_ERR, "bogus link family (%d) wrong net for %08X?\n",
775 ll2->sdl_family, ipaddr);
776 close(r);
777 return;
778 }
779 xtype = ll2->sdl_type;
780 xindex = ll2->sdl_index;
781
782 /* Set the new arp entry */
783 bzero(rt, sizeof(rtmsg));
784 rt->rtm_version = RTM_VERSION;
785 rt->rtm_addrs = RTA_DST | RTA_GATEWAY;
786 rt->rtm_inits = RTV_EXPIRE;
787 clock_gettime(CLOCK_MONOTONIC, &tp);
788 rt->rtm_rmx.rmx_expire = tp.tv_sec + ARPSECS;
789 rt->rtm_flags = RTF_HOST | RTF_STATIC;
790 rt->rtm_type = RTM_ADD;
791 rt->rtm_seq = ++seq;
792
793 bcopy(ar, ar2, sizeof(*ar));
794
795 ll2 = (struct sockaddr_dl *)((u_char *)ar2 + sizeof(*ar2));
796 bcopy(ll, ll2, sizeof(*ll));
797 ll2->sdl_type = xtype;
798 ll2->sdl_index = xindex;
799
800 rt->rtm_msglen = sizeof(*rt) + sizeof(*ar2) + sizeof(*ll2);
801 errno = 0;
802 if ((write(r, rt, rt->rtm_msglen) == -1) && (errno != EEXIST)) {
803 logmsg(LOG_ERR, "rtmsg add write: %m");
804 close(r);
805 return;
806 }
807 do {
808 cc = read(r, rt, sizeof(rtmsg));
809 } while (cc > 0 && (rt->rtm_type != RTM_ADD || rt->rtm_seq != seq ||
810 rt->rtm_pid != pid));
811 close(r);
812 if (cc == -1) {
813 logmsg(LOG_ERR, "rtmsg add read: %m");
814 return;
815 }
816 }
817
818 /*
819 * Build a reverse ARP packet and sent it out on the interface.
820 * 'ep' points to a valid REVARP_REQUEST. The REVARP_REPLY is built
821 * on top of the request, then written to the network.
822 *
823 * RFC 903 defines the ether_arp fields as follows. The following comments
824 * are taken (more or less) straight from this document.
825 *
826 * REVARP_REQUEST
827 *
828 * arp_sha is the hardware address of the sender of the packet.
829 * arp_spa is undefined.
830 * arp_tha is the 'target' hardware address.
831 * In the case where the sender wishes to determine his own
832 * protocol address, this, like arp_sha, will be the hardware
833 * address of the sender.
834 * arp_tpa is undefined.
835 *
836 * REVARP_REPLY
837 *
838 * arp_sha is the hardware address of the responder (the sender of the
839 * reply packet).
840 * arp_spa is the protocol address of the responder (see the note below).
841 * arp_tha is the hardware address of the target, and should be the same as
842 * that which was given in the request.
843 * arp_tpa is the protocol address of the target, that is, the desired address.
844 *
845 * Note that the requirement that arp_spa be filled in with the responder's
846 * protocol is purely for convenience. For instance, if a system were to use
847 * both ARP and RARP, then the inclusion of the valid protocol-hardware
848 * address pair (arp_spa, arp_sha) may eliminate the need for a subsequent
849 * ARP request.
850 */
851 static void
rarp_reply(struct if_info * ii,struct ether_header * ep,in_addr_t ipaddr,u_int len)852 rarp_reply(struct if_info *ii, struct ether_header *ep, in_addr_t ipaddr,
853 u_int len)
854 {
855 u_int n;
856 struct ether_arp *ap = (struct ether_arp *)(ep + 1);
857
858 update_arptab((u_char *)&ap->arp_sha, ipaddr);
859
860 /*
861 * Build the rarp reply by modifying the rarp request in place.
862 */
863 ap->arp_op = htons(REVARP_REPLY);
864
865 #ifdef BROKEN_BPF
866 ep->ether_type = ETHERTYPE_REVARP;
867 #endif
868 bcopy((char *)&ap->arp_sha, (char *)&ep->ether_dhost, 6);
869 bcopy((char *)ii->ii_eaddr, (char *)&ep->ether_shost, 6);
870 bcopy((char *)ii->ii_eaddr, (char *)&ap->arp_sha, 6);
871
872 bcopy((char *)&ipaddr, (char *)ap->arp_tpa, 4);
873 /* Target hardware is unchanged. */
874 bcopy((char *)&ii->ii_ipaddr, (char *)ap->arp_spa, 4);
875
876 /* Zero possible garbage after packet. */
877 bzero((char *)ep + (sizeof(*ep) + sizeof(*ap)),
878 len - (sizeof(*ep) + sizeof(*ap)));
879 n = write(ii->ii_fd, (char *)ep, len);
880 if (n != len)
881 logmsg(LOG_ERR, "write: only %d of %d bytes written", n, len);
882 if (verbose)
883 logmsg(LOG_INFO, "%s %s at %s REPLIED", ii->ii_ifname,
884 eatoa(ap->arp_tha),
885 intoa(ntohl(ipaddr)));
886 }
887
888 /*
889 * Get the netmask of an IP address. This routine is used if
890 * SIOCGIFNETMASK doesn't work.
891 */
892 static in_addr_t
ipaddrtonetmask(in_addr_t addr)893 ipaddrtonetmask(in_addr_t addr)
894 {
895
896 addr = ntohl(addr);
897 if (IN_CLASSA(addr))
898 return htonl(IN_CLASSA_NET);
899 if (IN_CLASSB(addr))
900 return htonl(IN_CLASSB_NET);
901 if (IN_CLASSC(addr))
902 return htonl(IN_CLASSC_NET);
903 logmsg(LOG_DEBUG, "unknown IP address class: %08X", addr);
904 return htonl(0xffffffff);
905 }
906
907 /*
908 * A faster replacement for inet_ntoa().
909 */
910 static char *
intoa(in_addr_t addr)911 intoa(in_addr_t addr)
912 {
913 char *cp;
914 u_int byte;
915 int n;
916 static char buf[sizeof(".xxx.xxx.xxx.xxx")];
917
918 cp = &buf[sizeof buf];
919 *--cp = '\0';
920
921 n = 4;
922 do {
923 byte = addr & 0xff;
924 *--cp = byte % 10 + '0';
925 byte /= 10;
926 if (byte > 0) {
927 *--cp = byte % 10 + '0';
928 byte /= 10;
929 if (byte > 0)
930 *--cp = byte + '0';
931 }
932 *--cp = '.';
933 addr >>= 8;
934 } while (--n > 0);
935
936 return cp + 1;
937 }
938
939 static char *
eatoa(u_char * ea)940 eatoa(u_char *ea)
941 {
942 static char buf[sizeof("xx:xx:xx:xx:xx:xx")];
943
944 (void)sprintf(buf, "%x:%x:%x:%x:%x:%x",
945 ea[0], ea[1], ea[2], ea[3], ea[4], ea[5]);
946 return (buf);
947 }
948
949 static void
logmsg(int pri,const char * fmt,...)950 logmsg(int pri, const char *fmt, ...)
951 {
952 va_list v;
953 FILE *fp;
954 char *newfmt;
955
956 va_start(v, fmt);
957 if (dflag) {
958 if (pri == LOG_ERR)
959 fp = stderr;
960 else
961 fp = stdout;
962 if (expand_syslog_m(fmt, &newfmt) == -1) {
963 vfprintf(fp, fmt, v);
964 } else {
965 vfprintf(fp, newfmt, v);
966 free(newfmt);
967 }
968 fputs("\n", fp);
969 fflush(fp);
970 } else {
971 vsyslog(pri, fmt, v);
972 }
973 va_end(v);
974 }
975
976 static int
expand_syslog_m(const char * fmt,char ** newfmt)977 expand_syslog_m(const char *fmt, char **newfmt) {
978 const char *str, *m;
979 char *p, *np;
980
981 p = strdup("");
982 str = fmt;
983 while ((m = strstr(str, "%m")) != NULL) {
984 asprintf(&np, "%s%.*s%s", p, (int)(m - str),
985 str, strerror(errno));
986 free(p);
987 if (np == NULL) {
988 errno = ENOMEM;
989 return (-1);
990 }
991 p = np;
992 str = m + 2;
993 }
994
995 if (*str != '\0') {
996 asprintf(&np, "%s%s", p, str);
997 free(p);
998 if (np == NULL) {
999 errno = ENOMEM;
1000 return (-1);
1001 }
1002 p = np;
1003 }
1004
1005 *newfmt = p;
1006 return (0);
1007 }
1008