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