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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 * 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 * 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 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 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