xref: /freebsd/usr.sbin/rarpd/rarpd.c (revision a1a4f1a0d87b594d3f17a97dc0127eec1417e6f6)
1 /*
2  * Copyright (c) 1990, 1991, 1992, 1993, 1996
3  *	The Regents of the University of California.  All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that: (1) source code distributions
7  * retain the above copyright notice and this paragraph in its entirety, (2)
8  * distributions including binary code include the above copyright notice and
9  * this paragraph in its entirety in the documentation or other materials
10  * provided with the distribution, and (3) all advertising materials mentioning
11  * features or use of this software display the following acknowledgement:
12  * ``This product includes software developed by the University of California,
13  * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
14  * the University nor the names of its contributors may be used to endorse
15  * or promote products derived from this software without specific prior
16  * written permission.
17  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
18  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
19  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
20  */
21 
22 #ifndef lint
23 static const char copyright[] =
24 "@(#) Copyright (c) 1990, 1991, 1992, 1993, 1996\n\
25 The Regents of the University of California.  All rights reserved.\n";
26 #endif /* not lint */
27 
28 #ifndef lint
29 static const char rcsid[] =
30   "$FreeBSD$";
31 #endif /* not lint */
32 
33 /*
34  * rarpd - Reverse ARP Daemon
35  *
36  * Usage:	rarpd -a [ -fsv ] [ hostname ]
37  *		rarpd [ -fsv ] interface [ hostname ]
38  *
39  * 'hostname' is optional solely for backwards compatibility with Sun's rarpd.
40  * Currently, the argument is ignored.
41  */
42 #include <sys/param.h>
43 #include <sys/file.h>
44 #include <sys/ioctl.h>
45 #include <sys/socket.h>
46 #include <sys/time.h>
47 
48 #include <net/bpf.h>
49 #include <net/if.h>
50 #include <net/if_types.h>
51 #include <net/if_dl.h>
52 #include <net/route.h>
53 
54 #include <netinet/in.h>
55 #include <netinet/if_ether.h>
56 
57 #include <arpa/inet.h>
58 
59 #include <errno.h>
60 #include <netdb.h>
61 #include <stdio.h>
62 #include <string.h>
63 #include <syslog.h>
64 #include <stdlib.h>
65 #include <unistd.h>
66 
67 #if defined(SUNOS4) || defined(__FreeBSD__) /* XXX */
68 #define HAVE_DIRENT_H
69 #endif
70 
71 #ifdef HAVE_DIRENT_H
72 #include <dirent.h>
73 #else
74 #include <sys/dir.h>
75 #endif
76 
77 /* Cast a struct sockaddr to a structaddr_in */
78 #define SATOSIN(sa) ((struct sockaddr_in *)(sa))
79 
80 #ifndef TFTP_DIR
81 #define TFTP_DIR "/tftpboot"
82 #endif
83 
84 #if BSD >= 199200
85 #define ARPSECS (20 * 60)		/* as per code in netinet/if_ether.c */
86 #define REVARP_REQUEST ARPOP_REVREQUEST
87 #define REVARP_REPLY ARPOP_REVREPLY
88 #endif
89 
90 #ifndef ETHERTYPE_REVARP
91 #define ETHERTYPE_REVARP 0x8035
92 #define REVARP_REQUEST 3
93 #define REVARP_REPLY 4
94 #endif
95 
96 /*
97  * Map field names in ether_arp struct.  What a pain in the neck.
98  */
99 #ifdef SUNOS3
100 #undef arp_sha
101 #undef arp_spa
102 #undef arp_tha
103 #undef arp_tpa
104 #define arp_sha arp_xsha
105 #define arp_spa arp_xspa
106 #define arp_tha arp_xtha
107 #define arp_tpa arp_xtpa
108 #endif
109 
110 #ifndef __GNUC__
111 #define inline
112 #endif
113 
114 /*
115  * The structure for each interface.
116  */
117 struct if_info {
118 	struct	if_info *ii_next;
119 	int	ii_fd;		/* BPF file descriptor */
120 	u_long	ii_ipaddr;	/* IP address of this interface */
121 	u_long	ii_netmask;	/* subnet or net mask */
122 	u_char	ii_eaddr[6];	/* Ethernet address of this interface */
123 	char ii_ifname[sizeof(((struct ifreq *)0)->ifr_name) + 1];
124 };
125 
126 /*
127  * The list of all interfaces that are being listened to.  rarp_loop()
128  * "selects" on the descriptors in this list.
129  */
130 struct if_info *iflist;
131 
132 int verbose;			/* verbose messages */
133 int s;				/* inet datagram socket */
134 char *tftp_dir = TFTP_DIR;	/* tftp directory */
135 
136 #ifndef __P
137 #define __P(protos) ()
138 #endif
139 
140 #if BSD < 199200
141 extern	char *malloc();
142 extern	void exit();
143 #endif
144 extern	int ether_ntohost();
145 
146 void	init __P((char *));
147 void	init_one __P((struct ifreq *, char *));
148 char	*intoa __P((u_long));
149 u_long	ipaddrtonetmask __P((u_long));
150 char	*eatoa __P((u_char *));
151 int	rarp_bootable __P((u_long));
152 void	rarp_loop __P((void));
153 int	rarp_open __P((char *));
154 void	rarp_process __P((struct if_info *, u_char *, u_int));
155 void	rarp_reply __P((struct if_info *, struct ether_header *, u_long, u_int));
156 void	update_arptab __P((u_char *, u_long));
157 static void	usage __P((void));
158 
159 static	u_char zero[6];
160 
161 int sflag = 0;			/* ignore /tftpboot */
162 
163 void
164 main(argc, argv)
165 	int argc;
166 	char **argv;
167 {
168 	int op;
169 	char *ifname, *hostname, *name;
170 
171 	int aflag = 0;		/* listen on "all" interfaces  */
172 	int fflag = 0;		/* don't fork */
173 
174 	if ((name = strrchr(argv[0], '/')) != NULL)
175 		++name;
176 	else
177 		name = argv[0];
178 	if (*name == '-')
179 		++name;
180 
181 	/*
182 	 * All error reporting is done through syslogs.
183 	 */
184 	openlog(name, LOG_PID | LOG_CONS, LOG_DAEMON);
185 
186 	opterr = 0;
187 	while ((op = getopt(argc, argv, "afsv")) != -1) {
188 		switch (op) {
189 		case 'a':
190 			++aflag;
191 			break;
192 
193 		case 'f':
194 			++fflag;
195 			break;
196 
197 		case 's':
198 			++sflag;
199 			break;
200 
201 		case 'v':
202 			++verbose;
203 			break;
204 
205 		default:
206 			usage();
207 			/* NOTREACHED */
208 		}
209 	}
210 	ifname = argv[optind++];
211 	hostname =  ifname ? argv[optind] : NULL;
212 	if ((aflag && ifname) || (!aflag && ifname == NULL))
213 		usage();
214 
215 	if (aflag)
216 		init(NULL);
217 	else
218 		init(ifname);
219 
220 	if (!fflag) {
221 		if (daemon(0,0)) {
222 			syslog(LOG_ERR, "cannot fork");
223 			exit(1);
224 		}
225 	}
226 	rarp_loop();
227 }
228 
229 /*
230  * Add to the interface list.
231  */
232 void
233 init_one(ifrp, target)
234 	register struct ifreq *ifrp;
235 	register char *target;
236 {
237 	register struct if_info *ii;
238 	register struct sockaddr_dl *ll;
239 	int family;
240 	struct ifreq ifr;
241 
242 	family = ifrp->ifr_addr.sa_family;
243 	switch (family) {
244 
245 	case AF_INET:
246 #if BSD >= 199100
247 	case AF_LINK:
248 #endif
249 		(void)strncpy(ifr.ifr_name, ifrp->ifr_name,
250 		    sizeof(ifrp->ifr_name));
251 		if (ioctl(s, SIOCGIFFLAGS, (char *)&ifr) < 0) {
252 			syslog(LOG_ERR,
253 			    "SIOCGIFFLAGS: %.*s: %m",
254 				sizeof(ifrp->ifr_name), ifrp->ifr_name);
255 			exit(1);
256 		}
257 		if ((ifr.ifr_flags & IFF_UP) == 0 ||
258 		    (ifr.ifr_flags & (IFF_LOOPBACK | IFF_POINTOPOINT)) != 0)
259 			return;
260 		break;
261 
262 
263 	default:
264 		return;
265 	}
266 
267 	/* Don't bother going any further if not the target interface */
268 	if (target != NULL &&
269 	    strncmp(ifrp->ifr_name, target, sizeof(ifrp->ifr_name)) != 0)
270 		return;
271 
272 	/* Look for interface in list */
273 	for (ii = iflist; ii != NULL; ii = ii->ii_next)
274 		if (strncmp(ifrp->ifr_name, ii->ii_ifname,
275 		    sizeof(ifrp->ifr_name)) == 0)
276 			break;
277 
278 	/* Allocate a new one if not found */
279 	if (ii == NULL) {
280 		ii = (struct if_info *)malloc(sizeof(*ii));
281 		if (ii == NULL) {
282 			syslog(LOG_ERR, "malloc: %m");
283 			exit(1);
284 		}
285 		bzero(ii, sizeof(*ii));
286 		ii->ii_fd = -1;
287 		(void)strncpy(ii->ii_ifname, ifrp->ifr_name,
288 		    sizeof(ifrp->ifr_name));
289 		ii->ii_ifname[sizeof(ii->ii_ifname) - 1] = '\0';
290 		ii->ii_next = iflist;
291 		iflist = ii;
292 	}
293 
294 	switch (family) {
295 
296 	case AF_INET:
297 		if (ioctl(s, SIOCGIFADDR, (char *)&ifr) < 0) {
298 			syslog(LOG_ERR, "ipaddr SIOCGIFADDR: %s: %m",
299 			    ii->ii_ifname);
300 			exit(1);
301 		}
302 		ii->ii_ipaddr = SATOSIN(&ifr.ifr_addr)->sin_addr.s_addr;
303 		if (ioctl(s, SIOCGIFNETMASK, (char *)&ifr) < 0) {
304 			syslog(LOG_ERR, "SIOCGIFNETMASK: %m");
305 			exit(1);
306 		}
307 		ii->ii_netmask = SATOSIN(&ifr.ifr_addr)->sin_addr.s_addr;
308 		if (ii->ii_netmask == 0)
309 			ii->ii_netmask = ipaddrtonetmask(ii->ii_ipaddr);
310 		if (ii->ii_fd < 0) {
311 			ii->ii_fd = rarp_open(ii->ii_ifname);
312 #if BSD < 199100
313 			/* Use BPF descriptor to get ethernet address. */
314 			if (ioctl(ii->ii_fd, SIOCGIFADDR, (char *)&ifr) < 0) {
315 				syslog(LOG_ERR, "eaddr SIOCGIFADDR: %s: %m",
316 				    ii->ii_ifname);
317 				exit(1);
318 			}
319 			bcopy(&ifr.ifr_addr.sa_data[0], ii->ii_eaddr, 6);
320 #endif
321 		}
322 		break;
323 
324 #if BSD >= 199100
325 		case AF_LINK:
326 			ll = (struct sockaddr_dl *)&ifrp->ifr_addr;
327 			if (ll->sdl_type == IFT_ETHER)
328 				bcopy(LLADDR(ll), ii->ii_eaddr, 6);
329 			break;
330 #endif
331 		}
332 }
333 /*
334  * Initialize all "candidate" interfaces that are in the system
335  * configuration list.  A "candidate" is up, not loopback and not
336  * point to point.
337  */
338 void
339 init(target)
340 	char *target;
341 {
342 	register int n;
343 	register struct ifreq *ifrp, *ifend;
344 	register struct if_info *ii, *nii, *lii;
345 	struct ifconf ifc;
346 	struct ifreq ibuf[16];
347 
348 	if ((s = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
349 		syslog(LOG_ERR, "socket: %m");
350 		exit(1);
351 	}
352 	ifc.ifc_len = sizeof ibuf;
353 	ifc.ifc_buf = (caddr_t)ibuf;
354 	if (ioctl(s, SIOCGIFCONF, (char *)&ifc) < 0 ||
355 	    (u_int)ifc.ifc_len < sizeof(struct ifreq)) {
356 		syslog(LOG_ERR, "SIOCGIFCONF: %m");
357 		exit(1);
358 	}
359 	ifrp = ibuf;
360 	ifend = (struct ifreq *)((char *)ibuf + ifc.ifc_len);
361 	while (ifrp < ifend) {
362 		init_one(ifrp, target);
363 
364 #if BSD >= 199100
365 		n = ifrp->ifr_addr.sa_len + sizeof(ifrp->ifr_name);
366 		if (n < sizeof(*ifrp))
367 			n = sizeof(*ifrp);
368 		ifrp = (struct ifreq *)((char *)ifrp + n);
369 #else
370 		++ifrp;
371 #endif
372 	}
373 
374 	/* Throw away incomplete interfaces */
375 	lii = NULL;
376 	for (ii = iflist; ii != NULL; ii = nii) {
377 		nii = ii->ii_next;
378 		if (ii->ii_ipaddr == 0 ||
379 		    bcmp(ii->ii_eaddr, zero, 6) == 0) {
380 			if (lii == NULL)
381 				iflist = nii;
382 			else
383 				lii->ii_next = nii;
384 			if (ii->ii_fd >= 0)
385 				close(ii->ii_fd);
386 			free(ii);
387 			continue;
388 		}
389 		lii = ii;
390 	}
391 
392 	/* Verbose stuff */
393 	if (verbose)
394 		for (ii = iflist; ii != NULL; ii = ii->ii_next)
395 			syslog(LOG_DEBUG, "%s %s 0x%08x %s",
396 			    ii->ii_ifname, intoa(ntohl(ii->ii_ipaddr)),
397 			    ntohl(ii->ii_netmask), eatoa(ii->ii_eaddr));
398 }
399 
400 static void
401 usage()
402 {
403 	(void)fprintf(stderr, "usage: rarpd [-afsv] [interface]\n");
404 	exit(1);
405 }
406 
407 static int
408 bpf_open()
409 {
410 	int fd;
411 	int n = 0;
412 	char device[sizeof "/dev/bpf000"];
413 
414 	/*
415 	 * Go through all the minors and find one that isn't in use.
416 	 */
417 	do {
418 		(void)sprintf(device, "/dev/bpf%d", n++);
419 		fd = open(device, O_RDWR);
420 	} while (fd < 0 && errno == EBUSY);
421 
422 	if (fd < 0) {
423 		syslog(LOG_ERR, "%s: %m", device);
424 		exit(1);
425 	}
426 	return fd;
427 }
428 
429 /*
430  * Open a BPF file and attach it to the interface named 'device'.
431  * Set immediate mode, and set a filter that accepts only RARP requests.
432  */
433 int
434 rarp_open(device)
435 	char *device;
436 {
437 	int fd;
438 	struct ifreq ifr;
439 	u_int dlt;
440 	int immediate;
441 
442 	static struct bpf_insn insns[] = {
443 		BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 12),
444 		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, ETHERTYPE_REVARP, 0, 3),
445 		BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 20),
446 		BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, REVARP_REQUEST, 0, 1),
447 		BPF_STMT(BPF_RET|BPF_K, sizeof(struct ether_arp) +
448 			 sizeof(struct ether_header)),
449 		BPF_STMT(BPF_RET|BPF_K, 0),
450 	};
451 	static struct bpf_program filter = {
452 		sizeof insns / sizeof(insns[0]),
453 		insns
454 	};
455 
456 	fd = bpf_open();
457 	/*
458 	 * Set immediate mode so packets are processed as they arrive.
459 	 */
460 	immediate = 1;
461 	if (ioctl(fd, BIOCIMMEDIATE, &immediate) < 0) {
462 		syslog(LOG_ERR, "BIOCIMMEDIATE: %m");
463 		exit(1);
464 	}
465 	(void)strncpy(ifr.ifr_name, device, sizeof ifr.ifr_name);
466 	if (ioctl(fd, BIOCSETIF, (caddr_t)&ifr) < 0) {
467 		syslog(LOG_ERR, "BIOCSETIF: %m");
468 		exit(1);
469 	}
470 	/*
471 	 * Check that the data link layer is an Ethernet; this code won't
472 	 * work with anything else.
473 	 */
474 	if (ioctl(fd, BIOCGDLT, (caddr_t)&dlt) < 0) {
475 		syslog(LOG_ERR, "BIOCGDLT: %m");
476 		exit(1);
477 	}
478 	if (dlt != DLT_EN10MB) {
479 		syslog(LOG_ERR, "%s is not an ethernet", device);
480 		exit(1);
481 	}
482 	/*
483 	 * Set filter program.
484 	 */
485 	if (ioctl(fd, BIOCSETF, (caddr_t)&filter) < 0) {
486 		syslog(LOG_ERR, "BIOCSETF: %m");
487 		exit(1);
488 	}
489 	return fd;
490 }
491 
492 /*
493  * Perform various sanity checks on the RARP request packet.  Return
494  * false on failure and log the reason.
495  */
496 static int
497 rarp_check(p, len)
498 	u_char *p;
499 	u_int len;
500 {
501 	struct ether_header *ep = (struct ether_header *)p;
502 	struct ether_arp *ap = (struct ether_arp *)(p + sizeof(*ep));
503 
504 	if (len < sizeof(*ep) + sizeof(*ap)) {
505 		syslog(LOG_ERR, "truncated request, got %d, expected %d",
506 				len, sizeof(*ep) + sizeof(*ap));
507 		return 0;
508 	}
509 	/*
510 	 * XXX This test might be better off broken out...
511 	 */
512 	if (ntohs(ep->ether_type) != ETHERTYPE_REVARP ||
513 	    ntohs(ap->arp_hrd) != ARPHRD_ETHER ||
514 	    ntohs(ap->arp_op) != REVARP_REQUEST ||
515 	    ntohs(ap->arp_pro) != ETHERTYPE_IP ||
516 	    ap->arp_hln != 6 || ap->arp_pln != 4) {
517 		syslog(LOG_DEBUG, "request fails sanity check");
518 		return 0;
519 	}
520 	if (bcmp((char *)&ep->ether_shost, (char *)&ap->arp_sha, 6) != 0) {
521 		syslog(LOG_DEBUG, "ether/arp sender address mismatch");
522 		return 0;
523 	}
524 	if (bcmp((char *)&ap->arp_sha, (char *)&ap->arp_tha, 6) != 0) {
525 		syslog(LOG_DEBUG, "ether/arp target address mismatch");
526 		return 0;
527 	}
528 	return 1;
529 }
530 
531 #ifndef FD_SETSIZE
532 #define FD_SET(n, fdp) ((fdp)->fds_bits[0] |= (1 << (n)))
533 #define FD_ISSET(n, fdp) ((fdp)->fds_bits[0] & (1 << (n)))
534 #define FD_ZERO(fdp) ((fdp)->fds_bits[0] = 0)
535 #endif
536 
537 /*
538  * Loop indefinitely listening for RARP requests on the
539  * interfaces in 'iflist'.
540  */
541 void
542 rarp_loop()
543 {
544 	u_char *buf, *bp, *ep;
545 	int cc, fd;
546 	fd_set fds, listeners;
547 	int bufsize, maxfd = 0;
548 	struct if_info *ii;
549 
550 	if (iflist == NULL) {
551 		syslog(LOG_ERR, "no interfaces");
552 		exit(1);
553 	}
554 	if (ioctl(iflist->ii_fd, BIOCGBLEN, (caddr_t)&bufsize) < 0) {
555 		syslog(LOG_ERR, "BIOCGBLEN: %m");
556 		exit(1);
557 	}
558 	buf = (u_char *)malloc((unsigned)bufsize);
559 	if (buf == NULL) {
560 		syslog(LOG_ERR, "malloc: %m");
561 		exit(1);
562 	}
563 
564 	while (1) {
565 		/*
566 		 * Find the highest numbered file descriptor for select().
567 		 * Initialize the set of descriptors to listen to.
568 		 */
569 		FD_ZERO(&fds);
570 		for (ii = iflist; ii != NULL; ii = ii->ii_next) {
571 			FD_SET(ii->ii_fd, &fds);
572 			if (ii->ii_fd > maxfd)
573 				maxfd = ii->ii_fd;
574 		}
575 		listeners = fds;
576 		if (select(maxfd + 1, &listeners, NULL, NULL, NULL) < 0) {
577 			/* Don't choke when we get ptraced */
578 			if (errno == EINTR)
579 				continue;
580 			syslog(LOG_ERR, "select: %m");
581 			exit(1);
582 		}
583 		for (ii = iflist; ii != NULL; ii = ii->ii_next) {
584 			fd = ii->ii_fd;
585 			if (!FD_ISSET(fd, &listeners))
586 				continue;
587 		again:
588 			cc = read(fd, (char *)buf, bufsize);
589 			/* Don't choke when we get ptraced */
590 			if (cc < 0 && errno == EINTR)
591 				goto again;
592 #if defined(SUNOS3) || defined(SUNOS4)
593 			/*
594 			 * Due to a SunOS bug, after 2^31 bytes, the
595 			 * file offset overflows and read fails with
596 			 * EINVAL.  The lseek() to 0 will fix things.
597 			 */
598 			if (cc < 0) {
599 				if (errno == EINVAL &&
600 				    (long)(tell(fd) + bufsize) < 0) {
601 					(void)lseek(fd, 0, 0);
602 					goto again;
603 				}
604 				syslog(LOG_ERR, "read: %m");
605 				exit(1);
606 			}
607 #endif
608 
609 			/* Loop through the packet(s) */
610 #define bhp ((struct bpf_hdr *)bp)
611 			bp = buf;
612 			ep = bp + cc;
613 			while (bp < ep) {
614 				register u_int caplen, hdrlen;
615 
616 				caplen = bhp->bh_caplen;
617 				hdrlen = bhp->bh_hdrlen;
618 				if (rarp_check(bp + hdrlen, caplen))
619 					rarp_process(ii, bp + hdrlen, caplen);
620 				bp += BPF_WORDALIGN(hdrlen + caplen);
621 			}
622 		}
623 	}
624 #undef bhp
625 }
626 
627 /*
628  * True if this server can boot the host whose IP address is 'addr'.
629  * This check is made by looking in the tftp directory for the
630  * configuration file.
631  */
632 int
633 rarp_bootable(addr)
634 	u_long addr;
635 {
636 #ifdef HAVE_DIRENT_H
637 	register struct dirent *dent;
638 #else
639 	register struct direct *dent;
640 #endif
641 	register DIR *d;
642 	char ipname[9];
643 	static DIR *dd = NULL;
644 
645 	(void)sprintf(ipname, "%08X", (unsigned int )ntohl(addr));
646 
647 	/*
648 	 * If directory is already open, rewind it.  Otherwise, open it.
649 	 */
650 	if ((d = dd) != NULL)
651 		rewinddir(d);
652 	else {
653 		if (chdir(tftp_dir) == -1) {
654 			syslog(LOG_ERR, "chdir: %s: %m", tftp_dir);
655 			exit(1);
656 		}
657 		d = opendir(".");
658 		if (d == NULL) {
659 			syslog(LOG_ERR, "opendir: %m");
660 			exit(1);
661 		}
662 		dd = d;
663 	}
664 	while ((dent = readdir(d)) != NULL)
665 		if (strncmp(dent->d_name, ipname, 8) == 0)
666 			return 1;
667 	return 0;
668 }
669 
670 /*
671  * Given a list of IP addresses, 'alist', return the first address that
672  * is on network 'net'; 'netmask' is a mask indicating the network portion
673  * of the address.
674  */
675 u_long
676 choose_ipaddr(alist, net, netmask)
677 	u_long **alist;
678 	u_long net;
679 	u_long netmask;
680 {
681 	for (; *alist; ++alist)
682 		if ((**alist & netmask) == net)
683 			return **alist;
684 	return 0;
685 }
686 
687 /*
688  * Answer the RARP request in 'pkt', on the interface 'ii'.  'pkt' has
689  * already been checked for validity.  The reply is overlaid on the request.
690  */
691 void
692 rarp_process(ii, pkt, len)
693 	struct if_info *ii;
694 	u_char *pkt;
695 	u_int len;
696 {
697 	struct ether_header *ep;
698 	struct hostent *hp;
699 	u_long target_ipaddr;
700 	char ename[256];
701 
702 	ep = (struct ether_header *)pkt;
703 	/* should this be arp_tha? */
704 	if (ether_ntohost(ename, &ep->ether_shost) != 0) {
705 		syslog(LOG_ERR, "cannot map %s to name",
706 			eatoa(ep->ether_shost));
707 		return;
708 	}
709 
710 	if ((hp = gethostbyname(ename)) == NULL) {
711 		syslog(LOG_ERR, "cannot map %s to IP address", ename);
712 		return;
713 	}
714 
715 	/*
716 	 * Choose correct address from list.
717 	 */
718 	if (hp->h_addrtype != AF_INET) {
719 		syslog(LOG_ERR, "cannot handle non IP addresses for %s",
720 								ename);
721 		return;
722 	}
723 	target_ipaddr = choose_ipaddr((u_long **)hp->h_addr_list,
724 				      ii->ii_ipaddr & ii->ii_netmask,
725 				      ii->ii_netmask);
726 	if (target_ipaddr == 0) {
727 		syslog(LOG_ERR, "cannot find %s on net %s",
728 		       ename, intoa(ntohl(ii->ii_ipaddr & ii->ii_netmask)));
729 		return;
730 	}
731 	if (sflag || rarp_bootable(target_ipaddr))
732 		rarp_reply(ii, ep, target_ipaddr, len);
733 	else if (verbose > 1)
734 		syslog(LOG_INFO, "%s %s at %s DENIED (not bootable)",
735 		    ii->ii_ifname,
736 		    eatoa(ep->ether_shost),
737 		    intoa(ntohl(target_ipaddr)));
738 }
739 
740 /*
741  * Poke the kernel arp tables with the ethernet/ip address combinataion
742  * given.  When processing a reply, we must do this so that the booting
743  * host (i.e. the guy running rarpd), won't try to ARP for the hardware
744  * address of the guy being booted (he cannot answer the ARP).
745  */
746 #if BSD >= 199200
747 static struct sockaddr_inarp sin_inarp = {
748 	sizeof(struct sockaddr_inarp), AF_INET
749 };
750 static struct sockaddr_dl sin_dl = {
751 	sizeof(struct sockaddr_dl), AF_LINK, 0, IFT_ETHER, 0, 6
752 };
753 static struct {
754 	struct rt_msghdr rthdr;
755 	char rtspace[512];
756 } rtmsg;
757 
758 void
759 update_arptab(ep, ipaddr)
760 	u_char *ep;
761 	u_long ipaddr;
762 {
763 	register int cc;
764 	register struct sockaddr_inarp *ar, *ar2;
765 	register struct sockaddr_dl *ll, *ll2;
766 	register struct rt_msghdr *rt;
767 	register int xtype, xindex;
768 	static pid_t pid;
769 	int r;
770 	static seq;
771 
772 	r = socket(PF_ROUTE, SOCK_RAW, 0);
773 	if (r < 0) {
774 		syslog(LOG_ERR, "raw route socket: %m");
775 		exit(1);
776 	}
777 	pid = getpid();
778 
779 	ar = &sin_inarp;
780 	ar->sin_addr.s_addr = ipaddr;
781 	ll = &sin_dl;
782 	bcopy(ep, LLADDR(ll), 6);
783 
784 	/* Get the type and interface index */
785 	rt = &rtmsg.rthdr;
786 	bzero(rt, sizeof(rtmsg));
787 	rt->rtm_version = RTM_VERSION;
788 	rt->rtm_addrs = RTA_DST;
789 	rt->rtm_type = RTM_GET;
790 	rt->rtm_seq = ++seq;
791 	ar2 = (struct sockaddr_inarp *)rtmsg.rtspace;
792 	bcopy(ar, ar2, sizeof(*ar));
793 	rt->rtm_msglen = sizeof(*rt) + sizeof(*ar);
794 	errno = 0;
795 	if (write(r, rt, rt->rtm_msglen) < 0 && errno != ESRCH) {
796 		syslog(LOG_ERR, "rtmsg get write: %m");
797 		close(r);
798 		return;
799 	}
800 	do {
801 		cc = read(r, rt, sizeof(rtmsg));
802 	} while (cc > 0 && (rt->rtm_seq != seq || rt->rtm_pid != pid));
803 	if (cc < 0) {
804 		syslog(LOG_ERR, "rtmsg get read: %m");
805 		close(r);
806 		return;
807 	}
808 	ll2 = (struct sockaddr_dl *)((u_char *)ar2 + ar2->sin_len);
809 	if (ll2->sdl_family != AF_LINK) {
810 		/*
811 		 * XXX I think this means the ip address is not on a
812 		 * directly connected network (the family is AF_INET in
813 		 * this case).
814 		 */
815 		syslog(LOG_ERR, "bogus link family (%d) wrong net for %08X?\n",
816 		    ll2->sdl_family, ipaddr);
817 		close(r);
818 		return;
819 	}
820 	xtype = ll2->sdl_type;
821 	xindex = ll2->sdl_index;
822 
823 	/* Set the new arp entry */
824 	bzero(rt, sizeof(rtmsg));
825 	rt->rtm_version = RTM_VERSION;
826 	rt->rtm_addrs = RTA_DST | RTA_GATEWAY;
827 	rt->rtm_inits = RTV_EXPIRE;
828 	rt->rtm_rmx.rmx_expire = time(0) + ARPSECS;
829 	rt->rtm_flags = RTF_HOST | RTF_STATIC;
830 	rt->rtm_type = RTM_ADD;
831 	rt->rtm_seq = ++seq;
832 
833 	bcopy(ar, ar2, sizeof(*ar));
834 
835 	ll2 = (struct sockaddr_dl *)((u_char *)ar2 + sizeof(*ar2));
836 	bcopy(ll, ll2, sizeof(*ll));
837 	ll2->sdl_type = xtype;
838 	ll2->sdl_index = xindex;
839 
840 	rt->rtm_msglen = sizeof(*rt) + sizeof(*ar2) + sizeof(*ll2);
841 	errno = 0;
842 	if (write(r, rt, rt->rtm_msglen) < 0 && errno != EEXIST) {
843 		syslog(LOG_ERR, "rtmsg add write: %m");
844 		close(r);
845 		return;
846 	}
847 	do {
848 		cc = read(r, rt, sizeof(rtmsg));
849 	} while (cc > 0 && (rt->rtm_seq != seq || rt->rtm_pid != pid));
850 	close(r);
851 	if (cc < 0) {
852 		syslog(LOG_ERR, "rtmsg add read: %m");
853 		return;
854 	}
855 }
856 #else
857 void
858 update_arptab(ep, ipaddr)
859 	u_char *ep;
860 	u_long ipaddr;
861 {
862 	struct arpreq request;
863 	struct sockaddr_in *sin;
864 
865 	request.arp_flags = 0;
866 	sin = (struct sockaddr_in *)&request.arp_pa;
867 	sin->sin_family = AF_INET;
868 	sin->sin_addr.s_addr = ipaddr;
869 	request.arp_ha.sa_family = AF_UNSPEC;
870 	bcopy((char *)ep, (char *)request.arp_ha.sa_data, 6);
871 
872 	if (ioctl(s, SIOCSARP, (caddr_t)&request) < 0)
873 		syslog(LOG_ERR, "SIOCSARP: %m");
874 }
875 #endif
876 
877 /*
878  * Build a reverse ARP packet and sent it out on the interface.
879  * 'ep' points to a valid REVARP_REQUEST.  The REVARP_REPLY is built
880  * on top of the request, then written to the network.
881  *
882  * RFC 903 defines the ether_arp fields as follows.  The following comments
883  * are taken (more or less) straight from this document.
884  *
885  * REVARP_REQUEST
886  *
887  * arp_sha is the hardware address of the sender of the packet.
888  * arp_spa is undefined.
889  * arp_tha is the 'target' hardware address.
890  *   In the case where the sender wishes to determine his own
891  *   protocol address, this, like arp_sha, will be the hardware
892  *   address of the sender.
893  * arp_tpa is undefined.
894  *
895  * REVARP_REPLY
896  *
897  * arp_sha is the hardware address of the responder (the sender of the
898  *   reply packet).
899  * arp_spa is the protocol address of the responder (see the note below).
900  * arp_tha is the hardware address of the target, and should be the same as
901  *   that which was given in the request.
902  * arp_tpa is the protocol address of the target, that is, the desired address.
903  *
904  * Note that the requirement that arp_spa be filled in with the responder's
905  * protocol is purely for convenience.  For instance, if a system were to use
906  * both ARP and RARP, then the inclusion of the valid protocol-hardware
907  * address pair (arp_spa, arp_sha) may eliminate the need for a subsequent
908  * ARP request.
909  */
910 void
911 rarp_reply(ii, ep, ipaddr, len)
912 	struct if_info *ii;
913 	struct ether_header *ep;
914 	u_long ipaddr;
915 	u_int len;
916 {
917 	int n;
918 	struct ether_arp *ap = (struct ether_arp *)(ep + 1);
919 
920 	update_arptab((u_char *)&ap->arp_sha, ipaddr);
921 
922 	/*
923 	 * Build the rarp reply by modifying the rarp request in place.
924 	 */
925 	ap->arp_op = htons(REVARP_REPLY);
926 
927 #ifdef BROKEN_BPF
928 	ep->ether_type = ETHERTYPE_REVARP;
929 #endif
930 	bcopy((char *)&ap->arp_sha, (char *)&ep->ether_dhost, 6);
931 	bcopy((char *)ii->ii_eaddr, (char *)&ep->ether_shost, 6);
932 	bcopy((char *)ii->ii_eaddr, (char *)&ap->arp_sha, 6);
933 
934 	bcopy((char *)&ipaddr, (char *)ap->arp_tpa, 4);
935 	/* Target hardware is unchanged. */
936 	bcopy((char *)&ii->ii_ipaddr, (char *)ap->arp_spa, 4);
937 
938 	/* Zero possible garbage after packet. */
939 	bzero((char *)ep + (sizeof(*ep) + sizeof(*ap)),
940 			len - (sizeof(*ep) + sizeof(*ap)));
941 	n = write(ii->ii_fd, (char *)ep, len);
942 	if (n != len)
943 		syslog(LOG_ERR, "write: only %d of %d bytes written", n, len);
944 	if (verbose)
945 		syslog(LOG_INFO, "%s %s at %s REPLIED", ii->ii_ifname,
946 		    eatoa(ap->arp_tha),
947 		    intoa(ntohl(ipaddr)));
948 }
949 
950 /*
951  * Get the netmask of an IP address.  This routine is used if
952  * SIOCGIFNETMASK doesn't work.
953  */
954 u_long
955 ipaddrtonetmask(addr)
956 	u_long addr;
957 {
958 	addr = ntohl(addr);
959 	if (IN_CLASSA(addr))
960 		return htonl(IN_CLASSA_NET);
961 	if (IN_CLASSB(addr))
962 		return htonl(IN_CLASSB_NET);
963 	if (IN_CLASSC(addr))
964 		return htonl(IN_CLASSC_NET);
965 	syslog(LOG_DEBUG, "unknown IP address class: %08X", addr);
966 	return htonl(0xffffffff);
967 }
968 
969 /*
970  * A faster replacement for inet_ntoa().
971  */
972 char *
973 intoa(addr)
974 	u_long addr;
975 {
976 	register char *cp;
977 	register u_int byte;
978 	register int n;
979 	static char buf[sizeof(".xxx.xxx.xxx.xxx")];
980 
981 	cp = &buf[sizeof buf];
982 	*--cp = '\0';
983 
984 	n = 4;
985 	do {
986 		byte = addr & 0xff;
987 		*--cp = byte % 10 + '0';
988 		byte /= 10;
989 		if (byte > 0) {
990 			*--cp = byte % 10 + '0';
991 			byte /= 10;
992 			if (byte > 0)
993 				*--cp = byte + '0';
994 		}
995 		*--cp = '.';
996 		addr >>= 8;
997 	} while (--n > 0);
998 
999 	return cp + 1;
1000 }
1001 
1002 char *
1003 eatoa(ea)
1004 	register u_char *ea;
1005 {
1006 	static char buf[sizeof("xx:xx:xx:xx:xx:xx")];
1007 
1008 	(void)sprintf(buf, "%x:%x:%x:%x:%x:%x",
1009 	    ea[0], ea[1], ea[2], ea[3], ea[4], ea[5]);
1010 	return (buf);
1011 }
1012