xref: /netbsd-src/usr.sbin/rarpd/rarpd.c (revision 76dfffe33547c37f8bdd446e3e4ab0f3c16cea4b)
1 /*	$NetBSD: rarpd.c,v 1.12 1996/03/21 18:28:23 jtc Exp $	*/
2 
3 /*
4  * Copyright (c) 1990 The Regents of the University of California.
5  * 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, and (3) all advertising materials mentioning
13  * features or use of this software display the following acknowledgement:
14  * ``This product includes software developed by the University of California,
15  * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
16  * the University nor the names of its contributors may be used to endorse
17  * or promote products derived from this software without specific prior
18  * written permission.
19  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
20  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
21  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
22  */
23 #ifndef lint
24 char    copyright[] =
25 "@(#) Copyright (c) 1990 The Regents of the University of California.\n\
26  All rights reserved.\n";
27 #endif				/* not lint */
28 
29 #ifndef lint
30 static char rcsid[] = "$NetBSD: rarpd.c,v 1.12 1996/03/21 18:28:23 jtc Exp $";
31 #endif
32 
33 
34 /*
35  * rarpd - Reverse ARP Daemon
36  *
37  * Usage:	rarpd -a [ -d -f ]
38  *		rarpd [ -d -f ] interface
39  */
40 
41 #include <stdio.h>
42 #include <stdlib.h>
43 #include <syslog.h>
44 #include <string.h>
45 #include <strings.h>
46 #include <sys/types.h>
47 #include <unistd.h>
48 #include <sys/time.h>
49 #include <net/bpf.h>
50 #include <sys/socket.h>
51 #include <sys/ioctl.h>
52 #include <net/if.h>
53 #include <net/if_dl.h>
54 #include <net/if_types.h>
55 #include <netinet/in.h>
56 #include <netinet/if_ether.h>
57 #include <sys/errno.h>
58 #include <sys/file.h>
59 #include <netdb.h>
60 #include <arpa/inet.h>
61 #include <dirent.h>
62 
63 #define FATAL		1	/* fatal error occurred */
64 #define NONFATAL	0	/* non fatal error occurred */
65 
66 /*
67  * The structure for each interface.
68  */
69 struct if_info {
70 	int     ii_fd;		/* BPF file descriptor */
71 	u_char  ii_eaddr[6];	/* Ethernet address of this interface */
72 	u_long  ii_ipaddr;	/* IP address of this interface */
73 	u_long  ii_netmask;	/* subnet or net mask */
74 	struct if_info *ii_next;
75 };
76 /*
77  * The list of all interfaces that are being listened to.  rarp_loop()
78  * "selects" on the descriptors in this list.
79  */
80 struct if_info *iflist;
81 
82 int    rarp_open     __P((char *));
83 void   init_one      __P((char *));
84 void   init_all      __P((void));
85 void   rarp_loop     __P((void));
86 void   lookup_eaddr  __P((char *, u_char *));
87 void   lookup_ipaddr __P((char *, u_long *, u_long *));
88 void   usage         __P((void));
89 void   rarp_process  __P((struct if_info *, u_char *));
90 void   rarp_reply    __P((struct if_info *, struct ether_header *, u_long));
91 void   update_arptab __P((u_char *, u_long));
92 void   err           __P((int, const char *,...));
93 void   debug         __P((const char *,...));
94 u_long ipaddrtonetmask __P((u_long));
95 
96 #ifdef REQUIRE_TFTPBOOT
97 int    rarp_bootable __P((u_long));
98 #endif
99 
100 int     aflag = 0;		/* listen on "all" interfaces  */
101 int     dflag = 0;		/* print debugging messages */
102 int     fflag = 0;		/* don't fork */
103 
104 int
105 main(argc, argv)
106 	int     argc;
107 	char  **argv;
108 {
109 	int     op, pid, devnull, f;
110 	char   *ifname, *hostname, *name;
111 
112 	extern char *optarg;
113 	extern int optind, opterr;
114 
115 	if (name = strrchr(argv[0], '/'))
116 		++name;
117 	else
118 		name = argv[0];
119 	if (*name == '-')
120 		++name;
121 
122 	/* All error reporting is done through syslogs. */
123 	openlog(name, LOG_PID | LOG_CONS, LOG_DAEMON);
124 
125 	opterr = 0;
126 	while ((op = getopt(argc, argv, "adf")) != EOF) {
127 		switch (op) {
128 		case 'a':
129 			++aflag;
130 			break;
131 
132 		case 'd':
133 			++dflag;
134 			break;
135 
136 		case 'f':
137 			++fflag;
138 			break;
139 
140 		default:
141 			usage();
142 			/* NOTREACHED */
143 		}
144 	}
145 	ifname = argv[optind++];
146 	hostname = ifname ? argv[optind] : 0;
147 	if ((aflag && ifname) || (!aflag && ifname == 0))
148 		usage();
149 
150 	if (aflag)
151 		init_all();
152 	else
153 		init_one(ifname);
154 
155 	if ((!fflag) && (!dflag)) {
156 		pid = fork();
157 		if (pid > 0)
158 			/* Parent exits, leaving child in background. */
159 			exit(0);
160 		else
161 			if (pid == -1) {
162 				err(FATAL, "cannot fork");
163 				/* NOTREACHED */
164 			}
165 		/* Fade into the background */
166 		f = open("/dev/tty", O_RDWR);
167 		if (f >= 0) {
168 			if (ioctl(f, TIOCNOTTY, 0) < 0) {
169 				err(FATAL, "TIOCNOTTY: %s", strerror(errno));
170 				/* NOTREACHED */
171 			}
172 			(void) close(f);
173 		}
174 		(void) chdir("/");
175 		(void) setpgrp(0, getpid());
176 		devnull = open("/dev/null", O_RDWR);
177 		if (devnull >= 0) {
178 			(void) dup2(devnull, 0);
179 			(void) dup2(devnull, 1);
180 			(void) dup2(devnull, 2);
181 			if (devnull > 2)
182 				(void) close(devnull);
183 		}
184 	}
185 	rarp_loop();
186 }
187 /*
188  * Add 'ifname' to the interface list.  Lookup its IP address and network
189  * mask and Ethernet address, and open a BPF file for it.
190  */
191 void
192 init_one(ifname)
193 	char   *ifname;
194 {
195 	struct if_info *p;
196 
197 	p = (struct if_info *)malloc(sizeof(*p));
198 	if (p == 0) {
199 		err(FATAL, "malloc: %s", strerror(errno));
200 		/* NOTREACHED */
201 	}
202 	p->ii_next = iflist;
203 	iflist = p;
204 
205 	p->ii_fd = rarp_open(ifname);
206 	lookup_eaddr(ifname, p->ii_eaddr);
207 	lookup_ipaddr(ifname, &p->ii_ipaddr, &p->ii_netmask);
208 }
209 /*
210  * Initialize all "candidate" interfaces that are in the system
211  * configuration list.  A "candidate" is up, not loopback and not
212  * point to point.
213  */
214 void
215 init_all()
216 {
217 	char inbuf[8192];
218 	struct ifconf ifc;
219 	struct ifreq ifreq, *ifr;
220 	int fd;
221 	int i, len;
222 
223 	if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
224 		err(FATAL, "socket: %s", strerror(errno));
225 		/* NOTREACHED */
226 	}
227 
228 	ifc.ifc_len = sizeof(inbuf);
229 	ifc.ifc_buf = inbuf;
230 	if (ioctl(fd, SIOCGIFCONF, (caddr_t)&ifc) < 0 ||
231 	    ifc.ifc_len < sizeof(struct ifreq)) {
232 		err(FATAL, "init_all: SIOCGIFCONF: %s", strerror(errno));
233 		/* NOTREACHED */
234 	}
235 	ifr = ifc.ifc_req;
236 	ifreq.ifr_name[0] = '\0';
237 	for (i = 0; i < ifc.ifc_len;
238 	     i += len, ifr = (struct ifreq *)((caddr_t)ifr + len)) {
239 		len = sizeof(ifr->ifr_name) + ifr->ifr_addr.sa_len;
240 		if (!strncmp(ifreq.ifr_name, ifr->ifr_name, sizeof(ifr->ifr_name)))
241 			continue;
242 		ifreq = *ifr;
243 		if (ioctl(fd, SIOCGIFFLAGS, (caddr_t)ifr) < 0) {
244 			err(FATAL, "init_all: SIOCGIFFLAGS: %s",
245 			    strerror(errno));
246 			/* NOTREACHED */
247 		}
248 		if ((ifr->ifr_flags &
249 		    (IFF_UP | IFF_LOOPBACK | IFF_POINTOPOINT)) != IFF_UP)
250 			continue;
251 		init_one(ifr->ifr_name);
252 	}
253 	(void) close(fd);
254 }
255 
256 void
257 usage()
258 {
259 	(void) fprintf(stderr, "usage: rarpd -a [ -d -f ]\n");
260 	(void) fprintf(stderr, "       rarpd [ -d -f ] interface\n");
261 	exit(1);
262 }
263 
264 static int
265 bpf_open()
266 {
267 	int     fd;
268 	int     n = 0;
269 	char    device[sizeof "/dev/bpf000"];
270 
271 	/* Go through all the minors and find one that isn't in use. */
272 	do {
273 		(void) sprintf(device, "/dev/bpf%d", n++);
274 		fd = open(device, O_RDWR);
275 	} while (fd < 0 && errno == EBUSY);
276 
277 	if (fd < 0) {
278 		err(FATAL, "%s: %s", device, strerror(errno));
279 		/* NOTREACHED */
280 	}
281 	return fd;
282 }
283 /*
284  * Open a BPF file and attach it to the interface named 'device'.
285  * Set immediate mode, and set a filter that accepts only RARP requests.
286  */
287 int
288 rarp_open(device)
289 	char   *device;
290 {
291 	int     fd;
292 	struct ifreq ifr;
293 	u_int   dlt;
294 	int     immediate;
295 
296 	static struct bpf_insn insns[] = {
297 		BPF_STMT(BPF_LD | BPF_H | BPF_ABS, 12),
298 		BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ETHERTYPE_REVARP, 0, 3),
299 		BPF_STMT(BPF_LD | BPF_H | BPF_ABS, 20),
300 		BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ARPOP_REVREQUEST, 0, 1),
301 		BPF_STMT(BPF_RET | BPF_K, sizeof(struct ether_arp) +
302 		    sizeof(struct ether_header)),
303 		BPF_STMT(BPF_RET | BPF_K, 0),
304 	};
305 	static struct bpf_program filter = {
306 		sizeof insns / sizeof(insns[0]),
307 		insns
308 	};
309 
310 	fd = bpf_open();
311 
312 	/* Set immediate mode so packets are processed as they arrive. */
313 	immediate = 1;
314 	if (ioctl(fd, BIOCIMMEDIATE, &immediate) < 0) {
315 		err(FATAL, "BIOCIMMEDIATE: %s", strerror(errno));
316 		/* NOTREACHED */
317 	}
318 	(void) strncpy(ifr.ifr_name, device, sizeof ifr.ifr_name);
319 	if (ioctl(fd, BIOCSETIF, (caddr_t) & ifr) < 0) {
320 		err(FATAL, "BIOCSETIF: %s", strerror(errno));
321 		/* NOTREACHED */
322 	}
323 	/* Check that the data link layer is an Ethernet; this code won't work
324 	 * with anything else. */
325 	if (ioctl(fd, BIOCGDLT, (caddr_t) & dlt) < 0) {
326 		err(FATAL, "BIOCGDLT: %s", strerror(errno));
327 		/* NOTREACHED */
328 	}
329 	if (dlt != DLT_EN10MB) {
330 		err(FATAL, "%s is not an ethernet", device);
331 		/* NOTREACHED */
332 	}
333 	/* Set filter program. */
334 	if (ioctl(fd, BIOCSETF, (caddr_t) & filter) < 0) {
335 		err(FATAL, "BIOCSETF: %s", strerror(errno));
336 		/* NOTREACHED */
337 	}
338 	return fd;
339 }
340 /*
341  * Perform various sanity checks on the RARP request packet.  Return
342  * false on failure and log the reason.
343  */
344 static int
345 rarp_check(p, len)
346 	u_char *p;
347 	int     len;
348 {
349 	struct ether_header *ep = (struct ether_header *) p;
350 	struct ether_arp *ap = (struct ether_arp *) (p + sizeof(*ep));
351 
352 	(void) debug("got a packet");
353 
354 	if (len < sizeof(*ep) + sizeof(*ap)) {
355 		err(NONFATAL, "truncated request");
356 		return 0;
357 	}
358 	/* XXX This test might be better off broken out... */
359 #ifdef __FreeBSD__
360 	/* BPF (incorrectly) returns this in host order. */
361 	if (ep->ether_type != ETHERTYPE_REVARP ||
362 #else
363 	if (ntohs (ep->ether_type) != ETHERTYPE_REVARP ||
364 #endif
365 	    ntohs (ap->arp_hrd) != ARPHRD_ETHER ||
366 	    ntohs (ap->arp_op) != ARPOP_REVREQUEST ||
367 	    ntohs (ap->arp_pro) != ETHERTYPE_IP ||
368 	    ap->arp_hln != 6 || ap->arp_pln != 4) {
369 		err(NONFATAL, "request fails sanity check");
370 		return 0;
371 	}
372 	if (bcmp((char *) &ep->ether_shost, (char *) &ap->arp_sha, 6) != 0) {
373 		err(NONFATAL, "ether/arp sender address mismatch");
374 		return 0;
375 	}
376 	if (bcmp((char *) &ap->arp_sha, (char *) &ap->arp_tha, 6) != 0) {
377 		err(NONFATAL, "ether/arp target address mismatch");
378 		return 0;
379 	}
380 	return 1;
381 }
382 
383 /*
384  * Loop indefinitely listening for RARP requests on the
385  * interfaces in 'iflist'.
386  */
387 void
388 rarp_loop()
389 {
390 	u_char *buf, *bp, *ep;
391 	int     cc, fd;
392 	fd_set  fds, listeners;
393 	int     bufsize, maxfd = 0;
394 	struct if_info *ii;
395 
396 	if (iflist == 0) {
397 		err(FATAL, "no interfaces");
398 		/* NOTREACHED */
399 	}
400 	if (ioctl(iflist->ii_fd, BIOCGBLEN, (caddr_t) & bufsize) < 0) {
401 		err(FATAL, "BIOCGBLEN: %s", strerror(errno));
402 		/* NOTREACHED */
403 	}
404 	buf = (u_char *) malloc((unsigned) bufsize);
405 	if (buf == 0) {
406 		err(FATAL, "malloc: %s", strerror(errno));
407 		/* NOTREACHED */
408 	}
409 	/*
410          * Find the highest numbered file descriptor for select().
411          * Initialize the set of descriptors to listen to.
412          */
413 	FD_ZERO(&fds);
414 	for (ii = iflist; ii; ii = ii->ii_next) {
415 		FD_SET(ii->ii_fd, &fds);
416 		if (ii->ii_fd > maxfd)
417 			maxfd = ii->ii_fd;
418 	}
419 	while (1) {
420 		listeners = fds;
421 		if (select(maxfd + 1, &listeners, (struct fd_set *) 0,
422 			(struct fd_set *) 0, (struct timeval *) 0) < 0) {
423 			err(FATAL, "select: %s", strerror(errno));
424 			/* NOTREACHED */
425 		}
426 		for (ii = iflist; ii; ii = ii->ii_next) {
427 			fd = ii->ii_fd;
428 			if (!FD_ISSET(fd, &listeners))
429 				continue;
430 	again:
431 			cc = read(fd, (char *) buf, bufsize);
432 			/* Don't choke when we get ptraced */
433 			if (cc < 0 && errno == EINTR)
434 				goto again;
435 			/* Due to a SunOS bug, after 2^31 bytes, the file
436 			 * offset overflows and read fails with EINVAL.  The
437 			 * lseek() to 0 will fix things. */
438 			if (cc < 0) {
439 				if (errno == EINVAL &&
440 				    (lseek(fd, 0, SEEK_CUR) + bufsize) < 0) {
441 					(void) lseek(fd, 0, 0);
442 					goto again;
443 				}
444 				err(FATAL, "read: %s", strerror(errno));
445 				/* NOTREACHED */
446 			}
447 			/* Loop through the packet(s) */
448 #define bhp ((struct bpf_hdr *)bp)
449 			bp = buf;
450 			ep = bp + cc;
451 			while (bp < ep) {
452 				register int caplen, hdrlen;
453 
454 				caplen = bhp->bh_caplen;
455 				hdrlen = bhp->bh_hdrlen;
456 				if (rarp_check(bp + hdrlen, caplen))
457 					rarp_process(ii, bp + hdrlen);
458 				bp += BPF_WORDALIGN(hdrlen + caplen);
459 			}
460 		}
461 	}
462 }
463 
464 #ifdef REQUIRE_TFTPBOOT
465 
466 #ifndef TFTP_DIR
467 #define TFTP_DIR "/tftpboot"
468 #endif
469 
470 /*
471  * True if this server can boot the host whose IP address is 'addr'.
472  * This check is made by looking in the tftp directory for the
473  * configuration file.
474  */
475 int
476 rarp_bootable(addr)
477 	u_long  addr;
478 {
479 	register struct dirent *dent;
480 	register DIR *d;
481 	char    ipname[9];
482 	static DIR *dd = 0;
483 
484 	(void) sprintf(ipname, "%08X", addr);
485 	/* If directory is already open, rewind it.  Otherwise, open it. */
486 	if (d = dd)
487 		rewinddir(d);
488 	else {
489 		if (chdir(TFTP_DIR) == -1) {
490 			err(FATAL, "chdir: %s", strerror(errno));
491 			/* NOTREACHED */
492 		}
493 		d = opendir(".");
494 		if (d == 0) {
495 			err(FATAL, "opendir: %s", strerror(errno));
496 			/* NOTREACHED */
497 		}
498 		dd = d;
499 	}
500 	while (dent = readdir(d))
501 		if (strncmp(dent->d_name, ipname, 8) == 0)
502 			return 1;
503 	return 0;
504 }
505 #endif /* REQUIRE_TFTPBOOT */
506 
507 /*
508  * Given a list of IP addresses, 'alist', return the first address that
509  * is on network 'net'; 'netmask' is a mask indicating the network portion
510  * of the address.
511  */
512 u_long
513 choose_ipaddr(alist, net, netmask)
514 	u_long **alist;
515 	u_long  net;
516 	u_long  netmask;
517 {
518 	for (; *alist; ++alist) {
519 		if ((**alist & netmask) == net)
520 			return **alist;
521 	}
522 	return 0;
523 }
524 /*
525  * Answer the RARP request in 'pkt', on the interface 'ii'.  'pkt' has
526  * already been checked for validity.  The reply is overlaid on the request.
527  */
528 void
529 rarp_process(ii, pkt)
530 	struct if_info *ii;
531 	u_char *pkt;
532 {
533 	struct ether_header *ep;
534 	struct hostent *hp;
535 	u_long  target_ipaddr;
536 	char    ename[256];
537 	struct	in_addr in;
538 
539 	ep = (struct ether_header *) pkt;
540 
541 	if (ether_ntohost(ename, &ep->ether_shost) != 0 ||
542 	    (hp = gethostbyname(ename)) == 0)
543 		return;
544 
545 	/* Choose correct address from list. */
546 	if (hp->h_addrtype != AF_INET) {
547 		err(FATAL, "cannot handle non IP addresses");
548 		/* NOTREACHED */
549 	}
550 	target_ipaddr = choose_ipaddr((u_long **) hp->h_addr_list,
551 	    ii->ii_ipaddr & ii->ii_netmask, ii->ii_netmask);
552 
553 	if (target_ipaddr == 0) {
554 		in.s_addr = ii->ii_ipaddr & ii->ii_netmask;
555 		err(NONFATAL, "cannot find %s on net %s\n",
556 		    ename, inet_ntoa(in));
557 		return;
558 	}
559 #ifdef REQUIRE_TFTPBOOT
560 	if (rarp_bootable(htonl(target_ipaddr)))
561 #endif
562 		rarp_reply(ii, ep, target_ipaddr);
563 }
564 /*
565  * Lookup the ethernet address of the interface attached to the BPF
566  * file descriptor 'fd'; return it in 'eaddr'.
567  */
568 void
569 lookup_eaddr(ifname, eaddr)
570 	char *ifname;
571 	u_char *eaddr;
572 {
573 	char inbuf[8192];
574 	struct ifconf ifc;
575 	struct ifreq *ifr;
576 	struct sockaddr_dl *sdl;
577 	int fd;
578 	int i, len;
579 
580 	/* We cannot use SIOCGIFADDR on the BPF descriptor.
581 	   We must instead get all the interfaces with SIOCGIFCONF
582 	   and find the right one.  */
583 
584 	/* Use datagram socket to get Ethernet address. */
585 	if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
586 		err(FATAL, "socket: %s", strerror(errno));
587 		/* NOTREACHED */
588 	}
589 
590 	ifc.ifc_len = sizeof(inbuf);
591 	ifc.ifc_buf = inbuf;
592 	if (ioctl(fd, SIOCGIFCONF, (caddr_t)&ifc) < 0 ||
593 	    ifc.ifc_len < sizeof(struct ifreq)) {
594 		err(FATAL, "lookup_eaddr: SIOGIFCONF: %s", strerror(errno));
595 		/* NOTREACHED */
596 	}
597 	ifr = ifc.ifc_req;
598 	for (i = 0; i < ifc.ifc_len;
599 	     i += len, ifr = (struct ifreq *)((caddr_t)ifr + len)) {
600 		len = sizeof(ifr->ifr_name) + ifr->ifr_addr.sa_len;
601 		sdl = (struct sockaddr_dl *)&ifr->ifr_addr;
602 		if (sdl->sdl_family != AF_LINK || sdl->sdl_type != IFT_ETHER ||
603 		    sdl->sdl_alen != 6)
604 			continue;
605 		if (!strncmp(ifr->ifr_name, ifname, sizeof(ifr->ifr_name))) {
606 			bcopy((caddr_t)LLADDR(sdl), (caddr_t)eaddr, 6);
607 			if (dflag)
608 				fprintf(stderr, "%s: %x:%x:%x:%x:%x:%x\n",
609 				    ifr->ifr_name, eaddr[0], eaddr[1],
610 				    eaddr[2], eaddr[3], eaddr[4], eaddr[5]);
611 			return;
612 		}
613 	}
614 
615 	err(FATAL, "lookup_eaddr: Never saw interface `%s'!", ifname);
616 }
617 /*
618  * Lookup the IP address and network mask of the interface named 'ifname'.
619  */
620 void
621 lookup_ipaddr(ifname, addrp, netmaskp)
622 	char   *ifname;
623 	u_long *addrp;
624 	u_long *netmaskp;
625 {
626 	int     fd;
627 	struct ifreq ifr;
628 
629 	/* Use datagram socket to get IP address. */
630 	if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
631 		err(FATAL, "socket: %s", strerror(errno));
632 		/* NOTREACHED */
633 	}
634 	(void) strncpy(ifr.ifr_name, ifname, sizeof ifr.ifr_name);
635 	if (ioctl(fd, SIOCGIFADDR, (char *) &ifr) < 0) {
636 		err(FATAL, "SIOCGIFADDR: %s", strerror(errno));
637 		/* NOTREACHED */
638 	}
639 	*addrp = ((struct sockaddr_in *) & ifr.ifr_addr)->sin_addr.s_addr;
640 	if (ioctl(fd, SIOCGIFNETMASK, (char *) &ifr) < 0) {
641 		perror("SIOCGIFNETMASK");
642 		exit(1);
643 	}
644 	*netmaskp = ((struct sockaddr_in *) & ifr.ifr_addr)->sin_addr.s_addr;
645 	/* If SIOCGIFNETMASK didn't work, figure out a mask from the IP
646 	 * address class. */
647 	if (*netmaskp == 0)
648 		*netmaskp = ipaddrtonetmask(*addrp);
649 
650 	(void) close(fd);
651 }
652 /*
653  * Poke the kernel arp tables with the ethernet/ip address combinataion
654  * given.  When processing a reply, we must do this so that the booting
655  * host (i.e. the guy running rarpd), won't try to ARP for the hardware
656  * address of the guy being booted (he cannot answer the ARP).
657  */
658 void
659 update_arptab(ep, ipaddr)
660 	u_char *ep;
661 	u_long  ipaddr;
662 {
663 	int     s;
664 	struct arpreq request;
665 	struct sockaddr_in *sin;
666 
667 	request.arp_flags = 0;
668 	sin = (struct sockaddr_in *) & request.arp_pa;
669 	sin->sin_family = AF_INET;
670 	sin->sin_addr.s_addr = ipaddr;
671 	request.arp_ha.sa_family = AF_UNSPEC;
672 	/* This is needed #if defined(COMPAT_43) && BYTE_ORDER != BIG_ENDIAN,
673 	   because AF_UNSPEC is zero and the kernel assumes that a zero
674 	   sa_family means that the real sa_family value is in sa_len.  */
675 	request.arp_ha.sa_len = 16; /* XXX */
676 	bcopy((char *) ep, (char *) request.arp_ha.sa_data, 6);
677 
678 #if 0
679 	s = socket(AF_INET, SOCK_DGRAM, 0);
680 	if (ioctl(s, SIOCSARP, (caddr_t) & request) < 0) {
681 		err(NONFATAL, "SIOCSARP: %s", strerror(errno));
682 	}
683 	(void) close(s);
684 #endif
685 }
686 /*
687  * Build a reverse ARP packet and sent it out on the interface.
688  * 'ep' points to a valid ARPOP_REVREQUEST.  The ARPOP_REVREPLY is built
689  * on top of the request, then written to the network.
690  *
691  * RFC 903 defines the ether_arp fields as follows.  The following comments
692  * are taken (more or less) straight from this document.
693  *
694  * ARPOP_REVREQUEST
695  *
696  * arp_sha is the hardware address of the sender of the packet.
697  * arp_spa is undefined.
698  * arp_tha is the 'target' hardware address.
699  *   In the case where the sender wishes to determine his own
700  *   protocol address, this, like arp_sha, will be the hardware
701  *   address of the sender.
702  * arp_tpa is undefined.
703  *
704  * ARPOP_REVREPLY
705  *
706  * arp_sha is the hardware address of the responder (the sender of the
707  *   reply packet).
708  * arp_spa is the protocol address of the responder (see the note below).
709  * arp_tha is the hardware address of the target, and should be the same as
710  *   that which was given in the request.
711  * arp_tpa is the protocol address of the target, that is, the desired address.
712  *
713  * Note that the requirement that arp_spa be filled in with the responder's
714  * protocol is purely for convenience.  For instance, if a system were to use
715  * both ARP and RARP, then the inclusion of the valid protocol-hardware
716  * address pair (arp_spa, arp_sha) may eliminate the need for a subsequent
717  * ARP request.
718  */
719 void
720 rarp_reply(ii, ep, ipaddr)
721 	struct if_info *ii;
722 	struct ether_header *ep;
723 	u_long  ipaddr;
724 {
725 	int     n;
726 	struct ether_arp *ap = (struct ether_arp *) (ep + 1);
727 	int     len;
728 
729 	update_arptab((u_char *) & ap->arp_sha, ipaddr);
730 
731 	/* Build the rarp reply by modifying the rarp request in place. */
732 #ifdef __FreeBSD__
733 	/* BPF (incorrectly) wants this in host order. */
734 	ep->ether_type = ETHERTYPE_REVARP;
735 #else
736 	ep->ether_type = htons(ETHERTYPE_REVARP);
737 #endif
738 	ap->ea_hdr.ar_hrd = htons(ARPHRD_ETHER);
739 	ap->ea_hdr.ar_pro = htons(ETHERTYPE_IP);
740 	ap->arp_op = htons(ARPOP_REVREPLY);
741 
742 	bcopy((char *) &ap->arp_sha, (char *) &ep->ether_dhost, 6);
743 	bcopy((char *) ii->ii_eaddr, (char *) &ep->ether_shost, 6);
744 	bcopy((char *) ii->ii_eaddr, (char *) &ap->arp_sha, 6);
745 
746 	bcopy((char *) &ipaddr, (char *) ap->arp_tpa, 4);
747 	/* Target hardware is unchanged. */
748 	bcopy((char *) &ii->ii_ipaddr, (char *) ap->arp_spa, 4);
749 
750 	len = sizeof(*ep) + sizeof(*ap);
751 	n = write(ii->ii_fd, (char *) ep, len);
752 	if (n != len) {
753 		err(NONFATAL, "write: only %d of %d bytes written", n, len);
754 	}
755 }
756 /*
757  * Get the netmask of an IP address.  This routine is used if
758  * SIOCGIFNETMASK doesn't work.
759  */
760 u_long
761 ipaddrtonetmask(addr)
762 	u_long  addr;
763 {
764 	if (IN_CLASSA(addr))
765 		return IN_CLASSA_NET;
766 	if (IN_CLASSB(addr))
767 		return IN_CLASSB_NET;
768 	if (IN_CLASSC(addr))
769 		return IN_CLASSC_NET;
770 	err(FATAL, "unknown IP address class: %08X", addr);
771 	/* NOTREACHED */
772 }
773 
774 #if __STDC__
775 #include <stdarg.h>
776 #else
777 #include <varargs.h>
778 #endif
779 
780 void
781 #if __STDC__
782 err(int fatal, const char *fmt,...)
783 #else
784 err(fmt, va_alist)
785 	int     fatal;
786 	char   *fmt;
787 va_dcl
788 #endif
789 {
790 	va_list ap;
791 #if __STDC__
792 	va_start(ap, fmt);
793 #else
794 	va_start(ap);
795 #endif
796 	if (dflag) {
797 		if (fatal)
798 			(void) fprintf(stderr, "rarpd: error: ");
799 		else
800 			(void) fprintf(stderr, "rarpd: warning: ");
801 		(void) vfprintf(stderr, fmt, ap);
802 		(void) fprintf(stderr, "\n");
803 	}
804 	vsyslog(LOG_ERR, fmt, ap);
805 	va_end(ap);
806 	if (fatal)
807 		exit(1);
808 	/* NOTREACHED */
809 }
810 
811 void
812 #if __STDC__
813 debug(const char *fmt,...)
814 #else
815 debug(fmt, va_alist)
816 	char   *fmt;
817 va_dcl
818 #endif
819 {
820 	va_list ap;
821 
822 	if (dflag) {
823 #if __STDC__
824 		va_start(ap, fmt);
825 #else
826 		va_start(ap);
827 #endif
828 		(void) fprintf(stderr, "rarpd: ");
829 		(void) vfprintf(stderr, fmt, ap);
830 		va_end(ap);
831 		(void) fprintf(stderr, "\n");
832 	}
833 }
834