usr.sbin/rarpd/rarpd.c

   1 /*      $NetBSD: rarpd.c,v 1.57 2008/07/21 13:36:59 lukem 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.  Neither the name of
  13  * the University nor the names of its contributors may be used to endorse
  14  * or promote products derived from this software without specific prior
  15  * written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
  18  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
  19  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  20  */
  21 #include <sys/cdefs.h>
  22 #ifndef lint
  23 __COPYRIGHT("@(#) Copyright (c) 1990\
  24  The Regents of the University of California.  All rights reserved.");
  25 #endif /* not lint */
  26
  27 #ifndef lint
  28 __RCSID("$NetBSD: rarpd.c,v 1.57 2008/07/21 13:36:59 lukem Exp $");
  29 #endif
  30
  31
  32 /*
  33  * rarpd - Reverse ARP Daemon
  34  *
  35  * Usage:       rarpd -a [-d|-f] [-l]
  36  *              rarpd [-d|-f] [-l] interface [...]
  37  */
  38
  39 #include <sys/param.h>
  40 #include <sys/file.h>
  41 #include <sys/time.h>
  42 #include <sys/socket.h>
  43 #include <sys/ioctl.h>
  44
  45 #include <net/bpf.h>
  46 #include <net/if.h>
  47 #include <net/if_dl.h>
  48 #ifdef __NetBSD__
  49 #include <net/if_ether.h>
  50 #endif
  51 #include <net/if_types.h>
  52 #include <netinet/in.h>
  53 #ifdef __NetBSD__
  54 #include <netinet/if_inarp.h>
  55 #else
  56 #include <netinet/if_ether.h>
  57 #endif
  58
  59 #include <arpa/inet.h>
  60
  61 #include <errno.h>
  62 #include <dirent.h>
  63 #include <paths.h>
  64 #include <netdb.h>
  65 #include <stdio.h>
  66 #include <stdlib.h>
  67 #include <string.h>
  68 #include <syslog.h>
  69 #include <unistd.h>
  70 #include <util.h>
  71 #include <ifaddrs.h>
  72
  73 #define FATAL           1       /* fatal error occurred */
  74 #define NONFATAL        0       /* non fatal error occurred */
  75
  76 /*
  77  * The structure for each interface.
  78  */
  79 struct if_info {
  80         int     ii_fd;          /* BPF file descriptor */
  81         u_char  ii_eaddr[6];    /* Ethernet address of this interface */
  82         u_int32_t  ii_ipaddr;   /* IP address of this interface */
  83         u_int32_t  ii_netmask;  /* subnet or net mask */
  84         char    *ii_name;       /* interface name */
  85         struct if_info *ii_alias;
  86         struct if_info *ii_next;
  87 };
  88 /*
  89  * The list of all interfaces that are being listened to.  rarp_loop()
  90  * "selects" on the descriptors in this list.
  91  */
  92 struct if_info *iflist;
  93
  94 u_int32_t choose_ipaddr(u_int32_t **, u_int32_t, u_int32_t);
  95 void    debug(const char *,...)
  96         __attribute__((__format__(__printf__, 1, 2)));
  97 void    init_some(char *name);
  98 void    init_one(char *, u_int32_t);
  99 u_int32_t       ipaddrtonetmask(u_int32_t);
 100 void    lookup_eaddr(char *, u_char *);
 101 void    lookup_ipaddr(char *, u_int32_t *, u_int32_t *);
 102 int     main(int, char **);
 103 void    rarp_loop(void);
 104 int     rarp_open(char *);
 105 void    rarp_process(struct if_info *, u_char *);
 106 void    rarp_reply(struct if_info *, struct ether_header *, u_int32_t,
 107                    struct hostent *);
 108 void    rarperr(int, const char *,...)
 109         __attribute__((__format__(__printf__, 2, 3)));
 110
 111 #if defined(__NetBSD__)
 112 #include "mkarp.h"
 113 #else
 114 void    update_arptab(u_char *, u_int32_t);
 115 #endif
 116
 117 void    usage(void);
 118
 119 static int      bpf_open(void);
 120 static int      rarp_check(u_char *, int);
 121
 122 #ifdef REQUIRE_TFTPBOOT
 123 int     rarp_bootable(u_int32_t);
 124 #endif
 125
 126 int     aflag = 0;              /* listen on "all" interfaces  */
 127 int     dflag = 0;              /* print debugging messages */
 128 int     fflag = 0;              /* don't fork */
 129 int     lflag = 0;              /* log all replies */
 130
 131 int
 132 main(int argc, char **argv)
 133 {
 134         int     op;
 135
 136         setprogname(*argv);
 137         /* All error reporting is done through syslogs. */
 138         openlog(getprogname(), LOG_PID, LOG_DAEMON);
 139
 140         opterr = 0;
 141         while ((op = getopt(argc, argv, "adfl")) != -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 'l':
 156                         ++lflag;
 157                         break;
 158
 159                 default:
 160                         usage();
 161                         /* NOTREACHED */
 162                 }
 163         }
 164         argc -= optind;
 165         argv += optind;
 166
 167         if ((aflag && argc != 0) || (!aflag && argc == 0))
 168                 usage();
 169
 170         if ((!fflag) && (!dflag)) {
 171                 if (daemon(0, 0))
 172                         rarperr(FATAL, "daemon");
 173                 pidfile(NULL);
 174         }
 175
 176         if (aflag)
 177                 init_some(NULL);
 178         else {
 179                 while (argc--)
 180                         init_some(*argv++);
 181         }
 182
 183         rarp_loop();
 184         /* NOTREACHED */
 185         return (0);
 186 }
 187
 188 /*
 189  * Add 'ifname' to the interface list.  Lookup its IP address and network
 190  * mask and Ethernet address, and open a BPF file for it.
 191  */
 192 void
 193 init_one(char *ifname, u_int32_t ipaddr)
 194 {
 195         struct if_info *h;
 196         struct if_info *p;
 197         int fd;
 198
 199         for (h = iflist; h != NULL; h = h->ii_next) {
 200                 if (!strcmp(h->ii_name, ifname))
 201                         break;
 202         }
 203         if (h == NULL) {
 204                 fd = rarp_open(ifname);
 205                 if (fd < 0)
 206                         return;
 207         } else {
 208                 fd = h->ii_fd;
 209         }
 210
 211         p = (struct if_info *)malloc(sizeof(*p));
 212         if (p == 0) {
 213                 rarperr(FATAL, "malloc: %s", strerror(errno));
 214                 /* NOTREACHED */
 215         }
 216         p->ii_name = strdup(ifname);
 217         if (p->ii_name == 0) {
 218                 rarperr(FATAL, "malloc: %s", strerror(errno));
 219                 /* NOTREACHED */
 220         }
 221         if (h != NULL) {
 222                 p->ii_alias = h->ii_alias;
 223                 h->ii_alias = p;
 224         } else {
 225                 p->ii_next = iflist;
 226                 iflist = p;
 227         }
 228
 229         p->ii_fd = fd;
 230         p->ii_ipaddr = ipaddr;
 231         lookup_eaddr(ifname, p->ii_eaddr);
 232         lookup_ipaddr(ifname, &p->ii_ipaddr, &p->ii_netmask);
 233 }
 234
 235 /*
 236  * Initialize all "candidate" interfaces that are in the system
 237  * configuration list.  A "candidate" is up, not loopback and not
 238  * point to point.
 239  */
 240 void
 241 init_some(char *name)
 242 {
 243         struct ifaddrs *ifap, *ifa, *p;
 244
 245         if (getifaddrs(&ifap) != 0) {
 246                 rarperr(FATAL, "getifaddrs: %s", strerror(errno));
 247                 /* NOTREACHED */
 248         }
 249
 250         p = NULL;
 251         for (ifa = ifap; ifa; ifa = ifa->ifa_next) {
 252 #define SIN(s)  ((struct sockaddr_in *) (s))
 253                 if (ifa->ifa_addr->sa_family != AF_INET)
 254                         continue;
 255                 if (name && strcmp(name, ifa->ifa_name))
 256                         continue;
 257                 if (p && !strcmp(p->ifa_name, ifa->ifa_name) &&
 258                     SIN(p->ifa_addr)->sin_addr.s_addr == SIN(ifa->ifa_addr)->sin_addr.s_addr)
 259                         continue;
 260                 p = ifa;
 261                 if ((ifa->ifa_flags &
 262                      (IFF_UP | IFF_LOOPBACK | IFF_POINTOPOINT)) != IFF_UP)
 263                         continue;
 264                 init_one(ifa->ifa_name, SIN(ifa->ifa_addr)->sin_addr.s_addr);
 265 #undef  SIN
 266         }
 267         freeifaddrs(ifap);
 268 }
 269
 270 void
 271 usage(void)
 272 {
 273         (void) fprintf(stderr, "Usage: %s -a [-d|-f] [-l]\n", getprogname());
 274         (void) fprintf(stderr, "\t%s [-d|-f] [-l] interface [...]\n",
 275             getprogname());
 276         exit(1);
 277 }
 278
 279 static int
 280 bpf_open(void)
 281 {
 282         int     fd;
 283         const char *device = _PATH_BPF;
 284         fd = open(device, O_RDWR);
 285
 286         if (fd < 0) {
 287                 rarperr(FATAL, "%s: %s", device, strerror(errno));
 288                 /* NOTREACHED */
 289         }
 290         return fd;
 291 }
 292 /*
 293  * Open a BPF file and attach it to the interface named 'device'.
 294  * Set immediate mode, and set a filter that accepts only RARP requests.
 295  */
 296 int
 297 rarp_open(char *device)
 298 {
 299         int     fd;
 300         struct ifreq ifr;
 301         u_int   dlt;
 302         int     immediate;
 303         u_int   bufsize;
 304
 305         static struct bpf_insn insns[] = {
 306                 BPF_STMT(BPF_LD | BPF_H | BPF_ABS, 12),
 307                 BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ETHERTYPE_REVARP, 0, 3),
 308                 BPF_STMT(BPF_LD | BPF_H | BPF_ABS, 20),
 309                 BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ARPOP_REVREQUEST, 0, 1),
 310                 BPF_STMT(BPF_RET | BPF_K,
 311                     sizeof(struct arphdr) +
 312                     2 * ETHER_ADDR_LEN + 2 * sizeof(struct in_addr) +
 313                     sizeof(struct ether_header)),
 314                 BPF_STMT(BPF_RET | BPF_K, 0),
 315         };
 316         static struct bpf_program filter = {
 317                 sizeof insns / sizeof(insns[0]),
 318                 insns
 319         };
 320
 321         fd = bpf_open();
 322
 323         /* Set immediate mode so packets are processed as they arrive. */
 324         immediate = 1;
 325         if (ioctl(fd, BIOCIMMEDIATE, &immediate) < 0) {
 326                 rarperr(FATAL, "BIOCIMMEDIATE: %s", strerror(errno));
 327                 /* NOTREACHED */
 328         }
 329         /* Set a 32k buffer size for kernel use */
 330         bufsize = 32768;
 331         if (ioctl(fd, BIOCSBLEN, &bufsize) < 0) {
 332                 rarperr(NONFATAL, "BIOCSBLEN:%d: %s", bufsize, strerror(errno));
 333         }
 334         (void)strlcpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
 335         if (ioctl(fd, BIOCSETIF, (caddr_t) & ifr) < 0) {
 336                 if (aflag) {    /* for -a skip non-ethernet interfaces */
 337                         close(fd);
 338                         return(-1);
 339                 }
 340                 rarperr(FATAL, "BIOCSETIF: %s", strerror(errno));
 341                 /* NOTREACHED */
 342         }
 343         /* Check that the data link layer is an Ethernet; this code won't work
 344          * with anything else. */
 345         if (ioctl(fd, BIOCGDLT, (caddr_t) & dlt) < 0) {
 346                 rarperr(FATAL, "BIOCGDLT: %s", strerror(errno));
 347                 /* NOTREACHED */
 348         }
 349         if (dlt != DLT_EN10MB) {
 350                 if (aflag) {    /* for -a skip non-ethernet interfaces */
 351                         close(fd);
 352                         return(-1);
 353                 }
 354                 rarperr(FATAL, "%s is not an ethernet", device);
 355                 /* NOTREACHED */
 356         }
 357         /* Set filter program. */
 358         if (ioctl(fd, BIOCSETF, (caddr_t) & filter) < 0) {
 359                 rarperr(FATAL, "BIOCSETF: %s", strerror(errno));
 360                 /* NOTREACHED */
 361         }
 362         return fd;
 363 }
 364 /*
 365  * Perform various sanity checks on the RARP request packet.  Return
 366  * false on failure and log the reason.
 367  */
 368 static int
 369 rarp_check(u_char *p, int len)
 370 {
 371         struct ether_header *ep = (struct ether_header *) p;
 372 #ifdef __NetBSD__
 373         struct arphdr *ap = (struct arphdr *) (p + sizeof(*ep));
 374 #else
 375         struct ether_arp *ap = (struct ether_arp *) (p + sizeof(*ep));
 376 #endif
 377
 378         if (len < (int)(sizeof(*ep) + sizeof(*ap))) {
 379                 rarperr(NONFATAL, "truncated request");
 380                 return 0;
 381         }
 382 #ifdef __NetBSD__
 383         /* now that we know the fixed part of the ARP hdr is there: */
 384         if (len < (int)(sizeof(*ap) + 2 * ap->ar_hln + 2 * ap->ar_pln)) {
 385                 rarperr(NONFATAL, "truncated request");
 386                 return 0;
 387         }
 388 #endif
 389         /* XXX This test might be better off broken out... */
 390 #ifdef __FreeBSD__
 391         /* BPF (incorrectly) returns this in host order. */
 392         if (ep->ether_type != ETHERTYPE_REVARP ||
 393 #else
 394         if (ntohs (ep->ether_type) != ETHERTYPE_REVARP ||
 395 #endif
 396 #ifdef __NetBSD__
 397             ntohs (ap->ar_hrd) != ARPHRD_ETHER ||
 398             ntohs (ap->ar_op) != ARPOP_REVREQUEST ||
 399             ntohs (ap->ar_pro) != ETHERTYPE_IP ||
 400             ap->ar_hln != 6 || ap->ar_pln != 4) {
 401 #else
 402             ntohs (ap->arp_hrd) != ARPHRD_ETHER ||
 403             ntohs (ap->arp_op) != ARPOP_REVREQUEST ||
 404             ntohs (ap->arp_pro) != ETHERTYPE_IP ||
 405             ap->arp_hln != 6 || ap->arp_pln != 4) {
 406 #endif
 407                 rarperr(NONFATAL, "request fails sanity check");
 408                 return 0;
 409         }
 410 #ifdef __NetBSD__
 411         if (memcmp((char *) &ep->ether_shost, ar_sha(ap), 6) != 0) {
 412 #else
 413         if (memcmp((char *) &ep->ether_shost, ap->arp_sha, 6) != 0) {
 414 #endif
 415                 rarperr(NONFATAL, "ether/arp sender address mismatch");
 416                 return 0;
 417         }
 418         {
 419 #ifdef __NetBSD__
 420                 caddr_t tha = ar_tha(ap);
 421
 422                 if (!tha || memcmp(ar_sha(ap), tha, 6) != 0) {
 423 #else
 424                 if (memcmp((char *) &ap->arp_sha, (char *) &ap->arp_tha, 6) != 0) {
 425 #endif
 426                         rarperr(NONFATAL, "ether/arp target address mismatch");
 427                         return 0;
 428                 }
 429         }
 430         return 1;
 431 }
 432
 433 /*
 434  * Loop indefinitely listening for RARP requests on the
 435  * interfaces in 'iflist'.
 436  */
 437 void
 438 rarp_loop(void)
 439 {
 440         u_char *buf, *bp, *ep;
 441         int     cc, fd;
 442         fd_set  fds, listeners;
 443         int     bufsize, maxfd = 0;
 444         struct if_info *ii;
 445
 446         if (iflist == 0) {
 447                 rarperr(FATAL, "no interfaces");
 448                 /* NOTREACHED */
 449         }
 450         if (ioctl(iflist->ii_fd, BIOCGBLEN, (caddr_t) & bufsize) < 0) {
 451                 rarperr(FATAL, "BIOCGBLEN: %s", strerror(errno));
 452                 /* NOTREACHED */
 453         }
 454         buf = (u_char *) malloc((unsigned) bufsize);
 455         if (buf == 0) {
 456                 rarperr(FATAL, "malloc: %s", strerror(errno));
 457                 /* NOTREACHED */
 458         }
 459         /*
 460          * Find the highest numbered file descriptor for select().
 461          * Initialize the set of descriptors to listen to.
 462          */
 463         FD_ZERO(&fds);
 464         for (ii = iflist; ii; ii = ii->ii_next) {
 465                 FD_SET(ii->ii_fd, &fds);
 466                 if (ii->ii_fd > maxfd)
 467                         maxfd = ii->ii_fd;
 468         }
 469         while (1) {
 470                 listeners = fds;
 471                 if (select(maxfd + 1, &listeners, (struct fd_set *) 0,
 472                         (struct fd_set *) 0, (struct timeval *) 0) < 0) {
 473                         rarperr(FATAL, "select: %s", strerror(errno));
 474                         /* NOTREACHED */
 475                 }
 476                 for (ii = iflist; ii; ii = ii->ii_next) {
 477                         fd = ii->ii_fd;
 478                         if (!FD_ISSET(fd, &listeners))
 479                                 continue;
 480                 again:
 481                         cc = read(fd, (char *) buf, bufsize);
 482                         /* Don't choke when we get ptraced */
 483                         if (cc < 0 && errno == EINTR)
 484                                 goto again;
 485                         /* Due to a SunOS bug, after 2^31 bytes, the file
 486                          * offset overflows and read fails with EINVAL.  The
 487                          * lseek() to 0 will fix things. */
 488                         if (cc < 0) {
 489                                 if (errno == EINVAL &&
 490                                     (lseek(fd, 0, SEEK_CUR) + bufsize) < 0) {
 491                                         (void)lseek(fd, 0, 0);
 492                                         goto again;
 493                                 }
 494                                 rarperr(FATAL, "read: %s", strerror(errno));
 495                                 /* NOTREACHED */
 496                         }
 497                         /* Loop through the packet(s) */
 498 #define bhp ((struct bpf_hdr *)bp)
 499                         bp = buf;
 500                         ep = bp + cc;
 501                         while (bp < ep) {
 502                                 int caplen, hdrlen;
 503
 504                                 caplen = bhp->bh_caplen;
 505                                 hdrlen = bhp->bh_hdrlen;
 506                                 debug("received packet on %s", ii->ii_name);
 507
 508                                 if (rarp_check(bp + hdrlen, caplen))
 509                                         rarp_process(ii, bp + hdrlen);
 510                                 bp += BPF_WORDALIGN(hdrlen + caplen);
 511                         }
 512                 }
 513         }
 514 }
 515
 516 #ifdef REQUIRE_TFTPBOOT
 517
 518 #ifndef TFTP_DIR
 519 #define TFTP_DIR "/tftpboot"
 520 #endif
 521
 522 /*
 523  * True if this server can boot the host whose IP address is 'addr'.
 524  * This check is made by looking in the tftp directory for the
 525  * configuration file.
 526  */
 527 int
 528 rarp_bootable(u_int32_t addr)
 529 {
 530         struct dirent *dent;
 531         DIR *d;
 532         char    ipname[9];
 533         static DIR *dd = 0;
 534
 535         (void)snprintf(ipname, sizeof(ipname), "%08X", addr);
 536         /* If directory is already open, rewind it.  Otherwise, open it. */
 537         if (d = dd)
 538                 rewinddir(d);
 539         else {
 540                 if (chdir(TFTP_DIR) == -1) {
 541                         rarperr(FATAL, "chdir: %s", strerror(errno));
 542                         /* NOTREACHED */
 543                 }
 544                 d = opendir(".");
 545                 if (d == 0) {
 546                         rarperr(FATAL, "opendir: %s", strerror(errno));
 547                         /* NOTREACHED */
 548                 }
 549                 dd = d;
 550         }
 551         while (dent = readdir(d))
 552                 if (strncmp(dent->d_name, ipname, 8) == 0)
 553                         return 1;
 554         return 0;
 555 }
 556 #endif /* REQUIRE_TFTPBOOT */
 557
 558 /*
 559  * Given a list of IP addresses, 'alist', return the first address that
 560  * is on network 'net'; 'netmask' is a mask indicating the network portion
 561  * of the address.
 562  */
 563 u_int32_t
 564 choose_ipaddr(u_int32_t **alist, u_int32_t net, u_int32_t netmask)
 565 {
 566
 567         for (; *alist; ++alist) {
 568                 if ((**alist & netmask) == net)
 569                         return **alist;
 570         }
 571         return 0;
 572 }
 573 /*
 574  * Answer the RARP request in 'pkt', on the interface 'ii'.  'pkt' has
 575  * already been checked for validity.  The reply is overlaid on the request.
 576  */
 577 void
 578 rarp_process(struct if_info *ii, u_char *pkt)
 579 {
 580         struct ether_header *ep;
 581         struct hostent *hp;
 582         u_int32_t  target_ipaddr = 0;
 583         char    ename[MAXHOSTNAMELEN + 1];
 584         struct  in_addr in;
 585
 586         ep = (struct ether_header *) pkt;
 587
 588         if (ether_ntohost(ename, (struct ether_addr *)&ep->ether_shost) != 0) {
 589                 debug("no IP address for %s",
 590                     ether_ntoa((struct ether_addr *)&ep->ether_shost));
 591                 return;
 592         }
 593         ename[sizeof(ename)-1] = '\0';
 594
 595         if ((hp = gethostbyname(ename)) == 0) {
 596                 debug("gethostbyname(%s) failed: %s", ename,
 597                     hstrerror(h_errno));
 598                 return;
 599         }
 600
 601         /* Choose correct address from list. */
 602         if (hp->h_addrtype != AF_INET) {
 603                 rarperr(FATAL, "cannot handle non IP addresses");
 604                 /* NOTREACHED */
 605         }
 606         for (;; ii = ii->ii_alias) {
 607                 target_ipaddr = choose_ipaddr((u_int32_t **) hp->h_addr_list,
 608                     ii->ii_ipaddr & ii->ii_netmask, ii->ii_netmask);
 609                 if (target_ipaddr != 0)
 610                         break;
 611                 if (ii->ii_alias == NULL)
 612                         break;
 613         }
 614
 615         if (target_ipaddr == 0) {
 616                 in.s_addr = ii->ii_ipaddr & ii->ii_netmask;
 617                 rarperr(NONFATAL, "cannot find %s on net %s",
 618                     ename, inet_ntoa(in));
 619                 return;
 620         }
 621 #ifdef REQUIRE_TFTPBOOT
 622         if (rarp_bootable(htonl(target_ipaddr)))
 623 #endif
 624                 rarp_reply(ii, ep, target_ipaddr, hp);
 625 #ifdef REQUIRE_TFTPBOOT
 626         else
 627                 debug("%08X not bootable", htonl(target_ipaddr));
 628 #endif
 629 }
 630 /*
 631  * Lookup the ethernet address of the interface attached to the BPF
 632  * file descriptor 'fd'; return it in 'eaddr'.
 633  */
 634 void
 635 lookup_eaddr(char *ifname, u_char *eaddr)
 636 {
 637         struct ifaddrs *ifap, *ifa;
 638         struct sockaddr_dl *sdl;
 639
 640         if (getifaddrs(&ifap) != 0) {
 641                 rarperr(FATAL, "getifaddrs: %s", strerror(errno));
 642                 /* NOTREACHED */
 643         }
 644
 645         for (ifa = ifap; ifa; ifa = ifa->ifa_next) {
 646                 sdl = (struct sockaddr_dl *)ifa->ifa_addr;
 647                 if (sdl->sdl_family != AF_LINK || sdl->sdl_type != IFT_ETHER ||
 648                     sdl->sdl_alen != 6)
 649                         continue;
 650                 if (!strcmp(ifa->ifa_name, ifname)) {
 651                         memmove((caddr_t)eaddr, (caddr_t)LLADDR(sdl), 6);
 652                         debug("%s: %x:%x:%x:%x:%x:%x",
 653                             ifa->ifa_name, eaddr[0], eaddr[1],
 654                             eaddr[2], eaddr[3], eaddr[4], eaddr[5]);
 655                         freeifaddrs(ifap);
 656                         return;
 657                 }
 658         }
 659         rarperr(FATAL, "lookup_eaddr: Never saw interface `%s'!", ifname);
 660         freeifaddrs(ifap);
 661 }
 662 /*
 663  * Lookup the IP address and network mask of the interface named 'ifname'.
 664  */
 665 void
 666 lookup_ipaddr(char *ifname, u_int32_t *addrp, u_int32_t *netmaskp)
 667 {
 668         int     fd;
 669
 670         /* Use datagram socket to get IP address. */
 671         if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
 672                 rarperr(FATAL, "socket: %s", strerror(errno));
 673                 /* NOTREACHED */
 674         }
 675         if (*addrp == INADDR_ANY) {
 676                 struct ifreq ifr;
 677                 memset(&ifr, 0, sizeof(ifr));
 678                 (void)strncpy(ifr.ifr_name, ifname, sizeof ifr.ifr_name);
 679                 if (ioctl(fd, SIOCGIFADDR, (char *) &ifr) < 0) {
 680                         rarperr(FATAL, "SIOCGIFADDR: %s", strerror(errno));
 681                         /* NOTREACHED */
 682                 }
 683                 *addrp = ((struct sockaddr_in *) & ifr.ifr_addr)->sin_addr.s_addr;
 684                 if (ioctl(fd, SIOCGIFNETMASK, (char *) &ifr) < 0) {
 685                         perror("SIOCGIFNETMASK");
 686                         exit(1);
 687                 }
 688                 *netmaskp = ((struct sockaddr_in *) & ifr.ifr_addr)->sin_addr.s_addr;
 689         } else {
 690                 struct ifaliasreq ifra;
 691                 memset(&ifra, 0, sizeof(ifra));
 692                 (void)strncpy(ifra.ifra_name, ifname, sizeof ifra.ifra_name);
 693                 ((struct sockaddr_in *) & ifra.ifra_addr)->sin_family = AF_INET;
 694                 ((struct sockaddr_in *) & ifra.ifra_addr)->sin_addr.s_addr = *addrp;
 695                 if (ioctl(fd, SIOCGIFALIAS, (char *) &ifra) < 0) {
 696                         rarperr(FATAL, "SIOCGIFALIAS: %s", strerror(errno));
 697                         /* NOTREACHED */
 698                 }
 699                 *addrp = ((struct sockaddr_in *) & ifra.ifra_addr)->sin_addr.s_addr;
 700                 *netmaskp = ((struct sockaddr_in *) & ifra.ifra_mask)->sin_addr.s_addr;
 701         }
 702         /* If SIOCGIFNETMASK didn't work, figure out a mask from the IP
 703          * address class. */
 704         if (*netmaskp == 0)
 705                 *netmaskp = ipaddrtonetmask(*addrp);
 706
 707         (void)close(fd);
 708 }
 709 /*
 710  * Poke the kernel arp tables with the ethernet/ip address combinataion
 711  * given.  When processing a reply, we must do this so that the booting
 712  * host (i.e. the guy running rarpd), won't try to ARP for the hardware
 713  * address of the guy being booted (he cannot answer the ARP).
 714  */
 715 #ifndef __NetBSD__
 716 void
 717 update_arptab(u_char *ep, u_int32_t ipaddr)
 718 {
 719         struct arpreq request;
 720         struct sockaddr_in *sin;
 721
 722         request.arp_flags = 0;
 723         sin = (struct sockaddr_in *) & request.arp_pa;
 724         sin->sin_family = AF_INET;
 725         sin->sin_addr.s_addr = ipaddr;
 726         request.arp_ha.sa_family = AF_UNSPEC;
 727         /* This is needed #if defined(COMPAT_43) && BYTE_ORDER != BIG_ENDIAN,
 728            because AF_UNSPEC is zero and the kernel assumes that a zero
 729            sa_family means that the real sa_family value is in sa_len.  */
 730         request.arp_ha.sa_len = 16; /* XXX */
 731         memmove((char *) request.arp_ha.sa_data, (char *)ep, 6);
 732
 733 #if 0
 734         s = socket(AF_INET, SOCK_DGRAM, 0);
 735         if (ioctl(s, SIOCSARP, (caddr_t) & request) < 0) {
 736                 rarperr(NONFATAL, "SIOCSARP: %s", strerror(errno));
 737         }
 738         (void)close(s);
 739 #endif
 740 }
 741 #endif
 742
 743 /*
 744  * Build a reverse ARP packet and sent it out on the interface.
 745  * 'ep' points to a valid ARPOP_REVREQUEST.  The ARPOP_REVREPLY is built
 746  * on top of the request, then written to the network.
 747  *
 748  * RFC 903 defines the ether_arp fields as follows.  The following comments
 749  * are taken (more or less) straight from this document.
 750  *
 751  * ARPOP_REVREQUEST
 752  *
 753  * arp_sha is the hardware address of the sender of the packet.
 754  * arp_spa is undefined.
 755  * arp_tha is the 'target' hardware address.
 756  *   In the case where the sender wishes to determine his own
 757  *   protocol address, this, like arp_sha, will be the hardware
 758  *   address of the sender.
 759  * arp_tpa is undefined.
 760  *
 761  * ARPOP_REVREPLY
 762  *
 763  * arp_sha is the hardware address of the responder (the sender of the
 764  *   reply packet).
 765  * arp_spa is the protocol address of the responder (see the note below).
 766  * arp_tha is the hardware address of the target, and should be the same as
 767  *   that which was given in the request.
 768  * arp_tpa is the protocol address of the target, that is, the desired address.
 769  *
 770  * Note that the requirement that arp_spa be filled in with the responder's
 771  * protocol is purely for convenience.  For instance, if a system were to use
 772  * both ARP and RARP, then the inclusion of the valid protocol-hardware
 773  * address pair (arp_spa, arp_sha) may eliminate the need for a subsequent
 774  * ARP request.
 775  */
 776 void
 777 rarp_reply(struct if_info *ii, struct ether_header *ep, u_int32_t ipaddr,
 778            struct hostent *hp)
 779 {
 780         int     n;
 781 #ifdef __NetBSD__
 782         struct arphdr *ap = (struct arphdr *) (ep + 1);
 783 #else
 784         struct ether_arp *ap = (struct ether_arp *) (ep + 1);
 785 #endif
 786
 787         int     len;
 788
 789 #ifdef __NetBSD__
 790         (void)mkarp((u_int8_t *)ar_sha(ap), ipaddr);
 791 #else
 792         update_arptab((u_char *) & ap->arp_sha, ipaddr);
 793 #endif
 794
 795         /* Build the rarp reply by modifying the rarp request in place. */
 796 #ifdef __FreeBSD__
 797         /* BPF (incorrectly) wants this in host order. */
 798         ep->ether_type = ETHERTYPE_REVARP;
 799 #else
 800         ep->ether_type = htons(ETHERTYPE_REVARP);
 801 #endif
 802 #ifdef __NetBSD__
 803         ap->ar_hrd = htons(ARPHRD_ETHER);
 804         ap->ar_pro = htons(ETHERTYPE_IP);
 805         ap->ar_op = htons(ARPOP_REVREPLY);
 806
 807         memmove((char *) &ep->ether_dhost, ar_sha(ap), 6);
 808         memmove((char *) &ep->ether_shost, (char *) ii->ii_eaddr, 6);
 809         memmove(ar_sha(ap), (char *) ii->ii_eaddr, 6);
 810
 811         memmove(ar_tpa(ap), (char *) &ipaddr, 4);
 812         /* Target hardware is unchanged. */
 813         memmove(ar_spa(ap), (char *) &ii->ii_ipaddr, 4);
 814
 815         len = sizeof(*ep) + sizeof(*ap) +
 816             2 * ap->ar_pln + 2 * ap->ar_hln;
 817 #else
 818         ap->ea_hdr.ar_hrd = htons(ARPHRD_ETHER);
 819         ap->ea_hdr.ar_pro = htons(ETHERTYPE_IP);
 820         ap->arp_op = htons(ARPOP_REVREPLY);
 821
 822         memmove((char *) &ep->ether_dhost, (char *) &ap->arp_sha, 6);
 823         memmove((char *) &ep->ether_shost, (char *) ii->ii_eaddr, 6);
 824         memmove((char *) &ap->arp_sha, (char *) ii->ii_eaddr, 6);
 825
 826         memmove((char *) ap->arp_tpa, (char *) &ipaddr, 4);
 827         /* Target hardware is unchanged. */
 828         memmove((char *) ap->arp_spa, (char *) &ii->ii_ipaddr, 4);
 829
 830         len = sizeof(*ep) + sizeof(*ap);
 831 #endif
 832
 833         debug("%s asked; %s replied",
 834             ether_ntoa((struct ether_addr *)ar_tha(ap)), hp->h_name);
 835         if (lflag)
 836                 syslog(LOG_INFO, "%s asked; %s replied",
 837                     ether_ntoa((struct ether_addr *)ar_tha(ap)), hp->h_name);
 838         n = write(ii->ii_fd, (char *) ep, len);
 839         if (n != len) {
 840                 rarperr(NONFATAL, "write: only %d of %d bytes written", n, len);
 841         }
 842 }
 843 /*
 844  * Get the netmask of an IP address.  This routine is used if
 845  * SIOCGIFNETMASK doesn't work.
 846  */
 847 u_int32_t
 848 ipaddrtonetmask(u_int32_t addr)
 849 {
 850
 851         if (IN_CLASSA(addr))
 852                 return IN_CLASSA_NET;
 853         if (IN_CLASSB(addr))
 854                 return IN_CLASSB_NET;
 855         if (IN_CLASSC(addr))
 856                 return IN_CLASSC_NET;
 857         rarperr(FATAL, "unknown IP address class: %08X", addr);
 858         /* NOTREACHED */
 859         return(-1);
 860 }
 861
 862 #include <stdarg.h>
 863
 864 void
 865 rarperr(int fatal, const char *fmt,...)
 866 {
 867         va_list ap;
 868
 869         va_start(ap, fmt);
 870         if (dflag) {
 871                 if (fatal)
 872                         (void)fprintf(stderr, "%s: error: ", getprogname());
 873                 else
 874                         (void)fprintf(stderr, "%s: warning: ", getprogname());
 875                 (void)vfprintf(stderr, fmt, ap);
 876                 va_end(ap);
 877                 va_start(ap, fmt);
 878                 (void)fprintf(stderr, "\n");
 879         }
 880         vsyslog(LOG_ERR, fmt, ap);
 881         va_end(ap);
 882         if (fatal)
 883                 exit(1);
 884         /* NOTREACHED */
 885 }
 886
 887 void
 888 debug(const char *fmt,...)
 889 {
 890         va_list ap;
 891
 892         va_start(ap, fmt);
 893         if (dflag) {
 894                 (void)fprintf(stderr, "%s: ", getprogname());
 895                 (void)vfprintf(stderr, fmt, ap);
 896                 va_end(ap);
 897                 va_start(ap, fmt);
 898                 (void)fprintf(stderr, "\n");
 899         }
 900         vsyslog(LOG_WARNING, fmt, ap);
 901         va_end(ap);
 902 }