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