rarpd.tproj/rarpd.c

   1 /*
   2  * Copyright (c) 1999-2009 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * "Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
   7  * Reserved.  This file contains Original Code and/or Modifications of
   8  * Original Code as defined in and that are subject to the Apple Public
   9  * Source License Version 1.0 (the 'License').  You may not use this file
  10  * except in compliance with the License.  Please obtain a copy of the
  11  * License at http://www.apple.com/publicsource and read it before using
  12  * this file.
  13  *
  14  * The Original Code and all software distributed under the License are
  15  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  16  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  17  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  19  * License for the specific language governing rights and limitations
  20  * under the License."
  21  *
  22  * @APPLE_LICENSE_HEADER_END@
  23  */
  24 /*
  25  * Copyright (c) 1990 The Regents of the University of California.
  26  * All rights reserved.
  27  *
  28  * Redistribution and use in source and binary forms, with or without
  29  * modification, are permitted provided that: (1) source code distributions
  30  * retain the above copyright notice and this paragraph in its entirety, (2)
  31  * distributions including binary code include the above copyright notice and
  32  * this paragraph in its entirety in the documentation or other materials
  33  * provided with the distribution, and (3) all advertising materials mentioning
  34  * features or use of this software display the following acknowledgement:
  35  * ``This product includes software developed by the University of California,
  36  * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
  37  * the University nor the names of its contributors may be used to endorse
  38  * or promote products derived from this software without specific prior
  39  * written permission.
  40  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
  41  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
  42  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  43  */
  44 #include <sys/cdefs.h>
  45 #ifndef lint
  46 __unused char    copyright[] =
  47 "@(#) Copyright (c) 1990 The Regents of the University of California.\n\
  48  All rights reserved.\n";
  49 #endif                          /* not lint */
  50
  51 #ifndef lint
  52 __unused static char rcsid[] =
  53 "@(#) $Id: rarpd.c,v 1.3 2006/04/05 03:13:14 lindak Exp $";
  54 #endif
  55
  56
  57 /*
  58  * rarpd - Reverse ARP Daemon
  59  *
  60  * Usage:       rarpd -a [ -d -f ]
  61  *              rarpd [ -d -f ] interface
  62  */
  63
  64 #include <stdio.h>
  65 #include <stdlib.h>
  66 #include <syslog.h>
  67 #include <string.h>
  68 #include <strings.h>
  69 #include <sys/types.h>
  70 #include <unistd.h>
  71 #include <sys/time.h>
  72 #include <net/bpf.h>
  73 #include <sys/socket.h>
  74 #include <sys/ioctl.h>
  75 #include <net/if.h>
  76 #include <net/if_dl.h>
  77 #include <net/if_types.h>
  78 #include <netinet/in.h>
  79 #include <netinet/if_ether.h>
  80 #include <sys/errno.h>
  81 #include <sys/file.h>
  82 #include <netdb.h>
  83 #include <arpa/inet.h>
  84 #include <dirent.h>
  85
  86 #define FATAL           1       /* fatal error occurred */
  87 #define NONFATAL        0       /* non fatal error occurred */
  88
  89 /*
  90  * The structure for each interface.
  91  */
  92 struct if_info {
  93         int     ii_fd;          /* BPF file descriptor */
  94         u_char  ii_eaddr[6];    /* Ethernet address of this interface */
  95         in_addr_t ii_ipaddr;    /* IP address of this interface */
  96         in_addr_t ii_netmask;   /* subnet or net mask */
  97         struct if_info *ii_next;
  98 };
  99 /*
 100  * The list of all interfaces that are being listened to.  rarp_loop()
 101  * "selects" on the descriptors in this list.
 102  */
 103 struct if_info *iflist;
 104
 105 int    rarp_open     __P((char *));
 106 int    rarp_bootable __P((in_addr_t));
 107 void   init_one      __P((char *));
 108 void   init_all      __P((void));
 109 void   rarp_loop     __P((void));
 110 void   lookup_eaddr  __P((char *, u_char *));
 111 void   lookup_ipaddr __P((char *, in_addr_t *, in_addr_t *));
 112 void   usage         __P((void));
 113 void   rarp_process  __P((struct if_info *, u_char *));
 114 void   rarp_reply    __P((struct if_info *, struct ether_header *, in_addr_t));
 115 void   update_arptab __P((u_char *, in_addr_t));
 116 void   err           __P((int, const char *,...));
 117 void   debug         __P((const char *,...));
 118 in_addr_t ipaddrtonetmask __P((in_addr_t));
 119
 120 int     aflag = 0;              /* listen on "all" interfaces  */
 121 int     dflag = 0;              /* print debugging messages */
 122 int     fflag = 0;              /* don't fork */
 123
 124 int
 125 main(argc, argv)
 126         int     argc;
 127         char  **argv;
 128 {
 129         int     op, pid, devnull, f;
 130         char   *ifname, *hostname, *name;
 131
 132         extern char *optarg;
 133         extern int optind, opterr;
 134
 135         if ((name = strrchr(argv[0], '/')) != NULL)
 136                 ++name;
 137         else
 138                 name = argv[0];
 139         if (*name == '-')
 140                 ++name;
 141
 142         /* All error reporting is done through syslogs. */
 143         openlog(name, LOG_PID | LOG_CONS, LOG_DAEMON);
 144
 145         opterr = 0;
 146         while ((op = getopt(argc, argv, "adf")) != EOF) {
 147                 switch (op) {
 148                 case 'a':
 149                         ++aflag;
 150                         break;
 151
 152                 case 'd':
 153                         ++dflag;
 154                         break;
 155
 156                 case 'f':
 157                         ++fflag;
 158                         break;
 159
 160                 default:
 161                         usage();
 162                         /* NOTREACHED */
 163                 }
 164         }
 165         ifname = argv[optind++];
 166         hostname = ifname ? argv[optind] : 0;
 167         if ((aflag && ifname) || (!aflag && ifname == 0))
 168                 usage();
 169
 170         if (aflag)
 171                 init_all();
 172         else
 173                 init_one(ifname);
 174
 175         if ((!fflag) && (!dflag)) {
 176                 pid = fork();
 177                 if (pid > 0)
 178                         /* Parent exits, leaving child in background. */
 179                         exit(0);
 180                 else
 181                         if (pid == -1) {
 182                                 err(FATAL, "cannot fork");
 183                                 /* NOTREACHED */
 184                         }
 185                 /* Fade into the background */
 186                 f = open("/dev/tty", O_RDWR);
 187                 if (f >= 0) {
 188                         if (ioctl(f, TIOCNOTTY, 0) < 0) {
 189                                 err(FATAL, "TIOCNOTTY: %s", strerror(errno));
 190                                 /* NOTREACHED */
 191                         }
 192                         (void) close(f);
 193                 }
 194                 (void) chdir("/");
 195                 (void) setpgid(0, getpid());
 196                 devnull = open("/dev/null", O_RDWR);
 197                 if (devnull >= 0) {
 198                         (void) dup2(devnull, 0);
 199                         (void) dup2(devnull, 1);
 200                         (void) dup2(devnull, 2);
 201                         if (devnull > 2)
 202                                 (void) close(devnull);
 203                 }
 204         }
 205         rarp_loop();
 206         /* NOTREACHED */
 207         return 0;
 208 }
 209 /*
 210  * Add 'ifname' to the interface list.  Lookup its IP address and network
 211  * mask and Ethernet address, and open a BPF file for it.
 212  */
 213 void
 214 init_one(ifname)
 215         char   *ifname;
 216 {
 217         struct if_info *p;
 218
 219         p = (struct if_info *)malloc(sizeof(*p));
 220         if (p == 0) {
 221                 err(FATAL, "malloc: %s", strerror(errno));
 222                 /* NOTREACHED */
 223         }
 224         p->ii_next = iflist;
 225         iflist = p;
 226
 227         p->ii_fd = rarp_open(ifname);
 228         lookup_eaddr(ifname, p->ii_eaddr);
 229         lookup_ipaddr(ifname, &p->ii_ipaddr, &p->ii_netmask);
 230 }
 231 /*
 232  * Initialize all "candidate" interfaces that are in the system
 233  * configuration list.  A "candidate" is up, not loopback and not
 234  * point to point.
 235  */
 236 void
 237 init_all()
 238 {
 239         char inbuf[8192];
 240         struct ifconf ifc;
 241         struct ifreq *ifr;
 242         int fd;
 243         int i, len;
 244
 245         if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
 246                 err(FATAL, "socket: %s", strerror(errno));
 247                 /* NOTREACHED */
 248         }
 249
 250         ifc.ifc_len = sizeof(inbuf);
 251         ifc.ifc_buf = inbuf;
 252         if (ioctl(fd, SIOCGIFCONF, (caddr_t)&ifc) < 0 ||
 253             ifc.ifc_len < sizeof(struct ifreq)) {
 254                 err(FATAL, "init_all: SIOCGIFCONF: %s", strerror(errno));
 255                 /* NOTREACHED */
 256         }
 257         ifr = ifc.ifc_req;
 258         for (i = 0; i < ifc.ifc_len;
 259              i += len, ifr = (struct ifreq *)((caddr_t)ifr + len)) {
 260                 len = sizeof(ifr->ifr_name) + ifr->ifr_addr.sa_len;
 261                 if (ioctl(fd, SIOCGIFFLAGS, (caddr_t)ifr) < 0) {
 262                         err(FATAL, "init_all: SIOCGIFFLAGS: %s",
 263                             strerror(errno));
 264                         /* NOTREACHED */
 265                 }
 266                 if ((ifr->ifr_flags &
 267                     (IFF_UP | IFF_LOOPBACK | IFF_POINTOPOINT)) != IFF_UP)
 268                         continue;
 269                 init_one(ifr->ifr_name);
 270         }
 271         (void) close(fd);
 272 }
 273
 274 void
 275 usage()
 276 {
 277         (void) fprintf(stderr, "usage: rarpd -a [ -d -f ]\n");
 278         (void) fprintf(stderr, "       rarpd [ -d -f ] interface\n");
 279         exit(1);
 280 }
 281
 282 static int
 283 bpf_open()
 284 {
 285         int     fd;
 286         int     n = 0;
 287         char    device[sizeof "/dev/bpf000"];
 288
 289         /* Go through all the minors and find one that isn't in use. */
 290         do {
 291                 (void) snprintf(device, sizeof(device), "/dev/bpf%d", n++);
 292                 fd = open(device, O_RDWR);
 293         } while (fd < 0 && errno == EBUSY);
 294
 295         if (fd < 0) {
 296                 err(FATAL, "%s: %s", device, strerror(errno));
 297                 /* NOTREACHED */
 298         }
 299         return fd;
 300 }
 301 /*
 302  * Open a BPF file and attach it to the interface named 'device'.
 303  * Set immediate mode, and set a filter that accepts only RARP requests.
 304  */
 305 int
 306 rarp_open(device)
 307         char   *device;
 308 {
 309         int     fd;
 310         struct ifreq ifr;
 311         u_int   dlt;
 312         int     immediate;
 313
 314         static struct bpf_insn insns[] = {
 315                 BPF_STMT(BPF_LD | BPF_H | BPF_ABS, 12),
 316                 BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ETHERTYPE_REVARP, 0, 3),
 317                 BPF_STMT(BPF_LD | BPF_H | BPF_ABS, 20),
 318                 BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ARPOP_REVREQUEST, 0, 1),
 319                 BPF_STMT(BPF_RET | BPF_K, sizeof(struct ether_arp) +
 320                     sizeof(struct ether_header)),
 321                 BPF_STMT(BPF_RET | BPF_K, 0),
 322         };
 323         static struct bpf_program filter = {
 324                 sizeof insns / sizeof(insns[0]),
 325                 insns
 326         };
 327
 328         fd = bpf_open();
 329
 330         /* Set immediate mode so packets are processed as they arrive. */
 331         immediate = 1;
 332         if (ioctl(fd, BIOCIMMEDIATE, &immediate) < 0) {
 333                 err(FATAL, "BIOCIMMEDIATE: %s", strerror(errno));
 334                 /* NOTREACHED */
 335         }
 336         (void) strncpy(ifr.ifr_name, device, sizeof ifr.ifr_name);
 337         if (ioctl(fd, BIOCSETIF, (caddr_t) & ifr) < 0) {
 338                 err(FATAL, "BIOCSETIF: %s", strerror(errno));
 339                 /* NOTREACHED */
 340         }
 341         /* Check that the data link layer is an Ethernet; this code won't work
 342          * with anything else. */
 343         if (ioctl(fd, BIOCGDLT, (caddr_t) & dlt) < 0) {
 344                 err(FATAL, "BIOCGDLT: %s", strerror(errno));
 345                 /* NOTREACHED */
 346         }
 347         if (dlt != DLT_EN10MB) {
 348                 err(FATAL, "%s is not an ethernet", device);
 349                 /* NOTREACHED */
 350         }
 351         /* Set filter program. */
 352         if (ioctl(fd, BIOCSETF, (caddr_t) & filter) < 0) {
 353                 err(FATAL, "BIOCSETF: %s", strerror(errno));
 354                 /* NOTREACHED */
 355         }
 356         return fd;
 357 }
 358 /*
 359  * Perform various sanity checks on the RARP request packet.  Return
 360  * false on failure and log the reason.
 361  */
 362 static int
 363 rarp_check(p, len)
 364         u_char *p;
 365         int     len;
 366 {
 367         struct ether_header *ep = (struct ether_header *) p;
 368         struct ether_arp *ap = (struct ether_arp *) (p + sizeof(*ep));
 369
 370         (void) debug("got a packet");
 371
 372         if (len < sizeof(*ep) + sizeof(*ap)) {
 373                 err(NONFATAL, "truncated request");
 374                 return 0;
 375         }
 376         /* XXX This test might be better off broken out... */
 377         if (ntohs (ep->ether_type) != ETHERTYPE_REVARP ||
 378             ntohs (ap->arp_hrd) != ARPHRD_ETHER ||
 379             ntohs (ap->arp_op) != ARPOP_REVREQUEST ||
 380             ntohs (ap->arp_pro) != ETHERTYPE_IP ||
 381             ap->arp_hln != 6 || ap->arp_pln != 4) {
 382                 err(NONFATAL, "request fails sanity check");
 383                 return 0;
 384         }
 385         if (bcmp((char *) &ep->ether_shost, (char *) &ap->arp_sha, 6) != 0) {
 386                 err(NONFATAL, "ether/arp sender address mismatch");
 387                 return 0;
 388         }
 389         if (bcmp((char *) &ap->arp_sha, (char *) &ap->arp_tha, 6) != 0) {
 390                 err(NONFATAL, "ether/arp target address mismatch");
 391                 return 0;
 392         }
 393         return 1;
 394 }
 395
 396 /*
 397  * Loop indefinitely listening for RARP requests on the
 398  * interfaces in 'iflist'.
 399  */
 400 void
 401 rarp_loop()
 402 {
 403         u_char *buf, *bp, *ep;
 404         int     cc, fd;
 405         fd_set  fds, listeners;
 406         int     bufsize, maxfd = 0;
 407         struct if_info *ii;
 408
 409         if (iflist == 0) {
 410                 err(FATAL, "no interfaces");
 411                 /* NOTREACHED */
 412         }
 413         if (ioctl(iflist->ii_fd, BIOCGBLEN, (caddr_t) & bufsize) < 0) {
 414                 err(FATAL, "BIOCGBLEN: %s", strerror(errno));
 415                 /* NOTREACHED */
 416         }
 417         buf = (u_char *) malloc((unsigned) bufsize);
 418         if (buf == 0) {
 419                 err(FATAL, "malloc: %s", strerror(errno));
 420                 /* NOTREACHED */
 421         }
 422         /*
 423          * Find the highest numbered file descriptor for select().
 424          * Initialize the set of descriptors to listen to.
 425          */
 426         FD_ZERO(&fds);
 427         for (ii = iflist; ii; ii = ii->ii_next) {
 428                 FD_SET(ii->ii_fd, &fds);
 429                 if (ii->ii_fd > maxfd)
 430                         maxfd = ii->ii_fd;
 431         }
 432         while (1) {
 433                 listeners = fds;
 434                 if (select(maxfd + 1, &listeners, (struct fd_set *) 0,
 435                         (struct fd_set *) 0, (struct timeval *) 0) < 0) {
 436                         err(FATAL, "select: %s", strerror(errno));
 437                         /* NOTREACHED */
 438                 }
 439                 for (ii = iflist; ii; ii = ii->ii_next) {
 440                         fd = ii->ii_fd;
 441                         if (!FD_ISSET(fd, &listeners))
 442                                 continue;
 443         again:
 444                         cc = read(fd, (char *) buf, bufsize);
 445                         /* Don't choke when we get ptraced */
 446                         if (cc < 0 && errno == EINTR)
 447                                 goto again;
 448                         /* Due to a SunOS bug, after 2^31 bytes, the file
 449                          * offset overflows and read fails with EINVAL.  The
 450                          * lseek() to 0 will fix things. */
 451                         if (cc < 0) {
 452                                 if (errno == EINVAL &&
 453                                     (lseek(fd, 0, SEEK_CUR) + bufsize) < 0) {
 454                                         (void) lseek(fd, 0, 0);
 455                                         goto again;
 456                                 }
 457                                 err(FATAL, "read: %s", strerror(errno));
 458                                 /* NOTREACHED */
 459                         }
 460                         /* Loop through the packet(s) */
 461 #define bhp ((struct bpf_hdr *)bp)
 462                         bp = buf;
 463                         ep = bp + cc;
 464                         while (bp < ep) {
 465                                 register int caplen, hdrlen;
 466
 467                                 caplen = bhp->bh_caplen;
 468                                 hdrlen = bhp->bh_hdrlen;
 469                                 if (rarp_check(bp + hdrlen, caplen))
 470                                         rarp_process(ii, bp + hdrlen);
 471                                 bp += BPF_WORDALIGN(hdrlen + caplen);
 472                         }
 473                 }
 474         }
 475 }
 476 #ifndef TFTP_DIR
 477 #define TFTP_DIR "/tftpboot"
 478 #endif
 479
 480 /*
 481  * True if this server can boot the host whose IP address is 'addr'.
 482  * This check is made by looking in the tftp directory for the
 483  * configuration file.
 484  */
 485 int
 486 rarp_bootable(addr)
 487         in_addr_t  addr;
 488 {
 489         register struct dirent *dent;
 490         register DIR *d;
 491         char    ipname[9];
 492         static DIR *dd = 0;
 493
 494         (void) snprintf(ipname, sizeof(ipname), "%08X", addr);
 495         /* If directory is already open, rewind it.  Otherwise, open it. */
 496         if ((d = dd) != NULL)
 497                 rewinddir(d);
 498         else {
 499                 if (chdir(TFTP_DIR) == -1) {
 500                         err(FATAL, "chdir: %s", strerror(errno));
 501                         /* NOTREACHED */
 502                 }
 503                 d = opendir(".");
 504                 if (d == 0) {
 505                         err(FATAL, "opendir: %s", strerror(errno));
 506                         /* NOTREACHED */
 507                 }
 508                 dd = d;
 509         }
 510         while ((dent = readdir(d)) != NULL)
 511                 if (strncmp(dent->d_name, ipname, 8) == 0)
 512                         return 1;
 513         return 0;
 514 }
 515 /*
 516  * Given a list of IP addresses, 'alist', return the first address that
 517  * is on network 'net'; 'netmask' is a mask indicating the network portion
 518  * of the address.
 519  */
 520 in_addr_t
 521 choose_ipaddr(alist, net, netmask)
 522         in_addr_t **alist;
 523         in_addr_t  net;
 524         in_addr_t  netmask;
 525 {
 526         for (; *alist; ++alist) {
 527                 if ((**alist & netmask) == net)
 528                         return **alist;
 529         }
 530         return 0;
 531 }
 532 /*
 533  * Answer the RARP request in 'pkt', on the interface 'ii'.  'pkt' has
 534  * already been checked for validity.  The reply is overlaid on the request.
 535  */
 536 void
 537 rarp_process(ii, pkt)
 538         struct if_info *ii;
 539         u_char *pkt;
 540 {
 541         struct ether_header *ep;
 542         struct hostent *hp;
 543         in_addr_t  target_ipaddr;
 544         char    ename[256];
 545         struct  in_addr in;
 546
 547         ep = (struct ether_header *) pkt;
 548
 549         if (ether_ntohost(ename, (struct ether_addr *)&ep->ether_shost) != 0 ||
 550             (hp = gethostbyname(ename)) == 0)
 551                 return;
 552
 553         /* Choose correct address from list. */
 554         if (hp->h_addrtype != AF_INET) {
 555                 err(FATAL, "cannot handle non IP addresses");
 556                 /* NOTREACHED */
 557         }
 558         target_ipaddr = choose_ipaddr((in_addr_t **) hp->h_addr_list,
 559             ii->ii_ipaddr & ii->ii_netmask, ii->ii_netmask);
 560
 561         if (target_ipaddr == 0) {
 562                 in.s_addr = ii->ii_ipaddr & ii->ii_netmask;
 563                 err(NONFATAL, "cannot find %s on net %s\n",
 564                     ename, inet_ntoa(in));
 565                 return;
 566         }
 567         if (rarp_bootable(htonl(target_ipaddr)))
 568                 rarp_reply(ii, ep, target_ipaddr);
 569 }
 570 /*
 571  * Lookup the ethernet address of the interface attached to the BPF
 572  * file descriptor 'fd'; return it in 'eaddr'.
 573  */
 574 void
 575 lookup_eaddr(ifname, eaddr)
 576         char *ifname;
 577         u_char *eaddr;
 578 {
 579         char inbuf[8192];
 580         struct ifconf ifc;
 581         struct ifreq *ifr;
 582         struct sockaddr_dl *sdl;
 583         int fd;
 584         int i, len;
 585
 586         /* We cannot use SIOCGIFADDR on the BPF descriptor.
 587            We must instead get all the interfaces with SIOCGIFCONF
 588            and find the right one.  */
 589
 590         /* Use datagram socket to get Ethernet address. */
 591         if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
 592                 err(FATAL, "socket: %s", strerror(errno));
 593                 /* NOTREACHED */
 594         }
 595
 596         ifc.ifc_len = sizeof(inbuf);
 597         ifc.ifc_buf = inbuf;
 598         if (ioctl(fd, SIOCGIFCONF, (caddr_t)&ifc) < 0 ||
 599             ifc.ifc_len < sizeof(struct ifreq)) {
 600                 err(FATAL, "lookup_eaddr: SIOGIFCONF: %s", strerror(errno));
 601                 /* NOTREACHED */
 602         }
 603         ifr = ifc.ifc_req;
 604         for (i = 0; i < ifc.ifc_len;
 605              i += len, ifr = (struct ifreq *)((caddr_t)ifr + len)) {
 606                 len = sizeof(ifr->ifr_name) + ifr->ifr_addr.sa_len;
 607                 sdl = (struct sockaddr_dl *)&ifr->ifr_addr;
 608                 if (sdl->sdl_family != AF_LINK || sdl->sdl_type != IFT_ETHER ||
 609                     sdl->sdl_alen != 6)
 610                         continue;
 611                 if (!strncmp(ifr->ifr_name, ifname, sizeof(ifr->ifr_name))) {
 612                         bcopy((caddr_t)LLADDR(sdl), (caddr_t)eaddr, 6);
 613                         if (dflag)
 614                                 fprintf(stderr, "%s: %x:%x:%x:%x:%x:%x\n",
 615                                     ifr->ifr_name, eaddr[0], eaddr[1],
 616                                     eaddr[2], eaddr[3], eaddr[4], eaddr[5]);
 617                         return;
 618                 }
 619         }
 620
 621         err(FATAL, "lookup_eaddr: Never saw interface `%s'!", ifname);
 622 }
 623 /*
 624  * Lookup the IP address and network mask of the interface named 'ifname'.
 625  */
 626 void
 627 lookup_ipaddr(ifname, addrp, netmaskp)
 628         char   *ifname;
 629         in_addr_t *addrp;
 630         in_addr_t *netmaskp;
 631 {
 632         int     fd;
 633         struct ifreq ifr;
 634
 635         /* Use datagram socket to get IP address. */
 636         if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
 637                 err(FATAL, "socket: %s", strerror(errno));
 638                 /* NOTREACHED */
 639         }
 640         (void) strncpy(ifr.ifr_name, ifname, sizeof ifr.ifr_name);
 641         if (ioctl(fd, SIOCGIFADDR, (char *) &ifr) < 0) {
 642                 err(FATAL, "SIOCGIFADDR: %s", strerror(errno));
 643                 /* NOTREACHED */
 644         }
 645         *addrp = ((struct sockaddr_in *) & ifr.ifr_addr)->sin_addr.s_addr;
 646         if (ioctl(fd, SIOCGIFNETMASK, (char *) &ifr) < 0) {
 647                 perror("SIOCGIFNETMASK");
 648                 exit(1);
 649         }
 650         *netmaskp = ((struct sockaddr_in *) & ifr.ifr_addr)->sin_addr.s_addr;
 651         /* If SIOCGIFNETMASK didn't work, figure out a mask from the IP
 652          * address class. */
 653         if (*netmaskp == 0)
 654                 *netmaskp = ipaddrtonetmask(*addrp);
 655
 656         (void) close(fd);
 657 }
 658 /*
 659  * Poke the kernel arp tables with the ethernet/ip address combinataion
 660  * given.  When processing a reply, we must do this so that the booting
 661  * host (i.e. the guy running rarpd), won't try to ARP for the hardware
 662  * address of the guy being booted (he cannot answer the ARP).
 663  */
 664 void
 665 update_arptab(ep, ipaddr)
 666         u_char *ep;
 667         in_addr_t  ipaddr;
 668 {
 669         //int     s;
 670         struct arpreq request;
 671         struct sockaddr_in *sin;
 672
 673         request.arp_flags = 0;
 674         sin = (struct sockaddr_in *) & request.arp_pa;
 675         sin->sin_family = AF_INET;
 676         sin->sin_addr.s_addr = ipaddr;
 677         request.arp_ha.sa_family = AF_UNSPEC;
 678         /* This is needed #if defined(COMPAT_43) && BYTE_ORDER != BIG_ENDIAN,
 679            because AF_UNSPEC is zero and the kernel assumes that a zero
 680            sa_family means that the real sa_family value is in sa_len.  */
 681         request.arp_ha.sa_len = 16; /* XXX */
 682         bcopy((char *) ep, (char *) request.arp_ha.sa_data, 6);
 683
 684 #if 0
 685         s = socket(AF_INET, SOCK_DGRAM, 0);
 686         if (ioctl(s, SIOCSARP, (caddr_t) & request) < 0) {
 687                 err(NONFATAL, "SIOCSARP: %s", strerror(errno));
 688         }
 689         (void) close(s);
 690 #endif
 691 }
 692 /*
 693  * Build a reverse ARP packet and sent it out on the interface.
 694  * 'ep' points to a valid ARPOP_REVREQUEST.  The ARPOP_REVREPLY is built
 695  * on top of the request, then written to the network.
 696  *
 697  * RFC 903 defines the ether_arp fields as follows.  The following comments
 698  * are taken (more or less) straight from this document.
 699  *
 700  * ARPOP_REVREQUEST
 701  *
 702  * arp_sha is the hardware address of the sender of the packet.
 703  * arp_spa is undefined.
 704  * arp_tha is the 'target' hardware address.
 705  *   In the case where the sender wishes to determine his own
 706  *   protocol address, this, like arp_sha, will be the hardware
 707  *   address of the sender.
 708  * arp_tpa is undefined.
 709  *
 710  * ARPOP_REVREPLY
 711  *
 712  * arp_sha is the hardware address of the responder (the sender of the
 713  *   reply packet).
 714  * arp_spa is the protocol address of the responder (see the note below).
 715  * arp_tha is the hardware address of the target, and should be the same as
 716  *   that which was given in the request.
 717  * arp_tpa is the protocol address of the target, that is, the desired address.
 718  *
 719  * Note that the requirement that arp_spa be filled in with the responder's
 720  * protocol is purely for convenience.  For instance, if a system were to use
 721  * both ARP and RARP, then the inclusion of the valid protocol-hardware
 722  * address pair (arp_spa, arp_sha) may eliminate the need for a subsequent
 723  * ARP request.
 724  */
 725 void
 726 rarp_reply(ii, ep, ipaddr)
 727         struct if_info *ii;
 728         struct ether_header *ep;
 729         in_addr_t  ipaddr;
 730 {
 731         int     n;
 732         struct ether_arp *ap = (struct ether_arp *) (ep + 1);
 733         int     len;
 734
 735         update_arptab((u_char *) & ap->arp_sha, ipaddr);
 736
 737         /* Build the rarp reply by modifying the rarp request in place. */
 738         ep->ether_type = htons(ETHERTYPE_REVARP);
 739         ap->ea_hdr.ar_hrd = htons(ARPHRD_ETHER);
 740         ap->ea_hdr.ar_pro = htons(ETHERTYPE_IP);
 741         ap->arp_op = htons(ARPOP_REVREPLY);
 742
 743         bcopy((char *) &ap->arp_sha, (char *) &ep->ether_dhost, 6);
 744         bcopy((char *) ii->ii_eaddr, (char *) &ep->ether_shost, 6);
 745         bcopy((char *) ii->ii_eaddr, (char *) &ap->arp_sha, 6);
 746
 747         bcopy((char *) &ipaddr, (char *) ap->arp_tpa, 4);
 748         /* Target hardware is unchanged. */
 749         bcopy((char *) &ii->ii_ipaddr, (char *) ap->arp_spa, 4);
 750
 751         len = sizeof(*ep) + sizeof(*ap);
 752         n = write(ii->ii_fd, (char *) ep, len);
 753         if (n != len) {
 754                 err(NONFATAL, "write: only %d of %d bytes written", n, len);
 755         }
 756 }
 757 /*
 758  * Get the netmask of an IP address.  This routine is used if
 759  * SIOCGIFNETMASK doesn't work.
 760  */
 761 in_addr_t
 762 ipaddrtonetmask(addr)
 763         in_addr_t  addr;
 764 {
 765         if (IN_CLASSA(addr))
 766                 return IN_CLASSA_NET;
 767         if (IN_CLASSB(addr))
 768                 return IN_CLASSB_NET;
 769         if (IN_CLASSC(addr))
 770                 return IN_CLASSC_NET;
 771         err(FATAL, "unknown IP address class: %08X", addr);
 772         /* NOTREACHED */
 773         return 0;
 774 }
 775
 776 #if __STDC__
 777 #include <stdarg.h>
 778 #else
 779 #include <varargs.h>
 780 #endif
 781
 782 void
 783 #if __STDC__
 784 err(int fatal, const char *fmt,...)
 785 #else
 786 err(fmt, va_alist)
 787         int     fatal;
 788         char   *fmt;
 789 va_dcl
 790 #endif
 791 {
 792         va_list ap;
 793 #if __STDC__
 794         va_start(ap, fmt);
 795 #else
 796         va_start(ap);
 797 #endif
 798         if (dflag) {
 799                 if (fatal)
 800                         (void) fprintf(stderr, "rarpd: error: ");
 801                 else
 802                         (void) fprintf(stderr, "rarpd: warning: ");
 803                 (void) vfprintf(stderr, fmt, ap);
 804                 (void) fprintf(stderr, "\n");
 805         }
 806         vsyslog(LOG_ERR, fmt, ap);
 807         va_end(ap);
 808         if (fatal)
 809                 exit(1);
 810         /* NOTREACHED */
 811 }
 812
 813 void
 814 #if __STDC__
 815 debug(const char *fmt,...)
 816 #else
 817 debug(fmt, va_alist)
 818         char   *fmt;
 819 va_dcl
 820 #endif
 821 {
 822         va_list ap;
 823
 824         if (dflag) {
 825 #if __STDC__
 826                 va_start(ap, fmt);
 827 #else
 828                 va_start(ap);
 829 #endif
 830                 (void) fprintf(stderr, "rarpd: ");
 831                 (void) vfprintf(stderr, fmt, ap);
 832                 va_end(ap);
 833                 (void) fprintf(stderr, "\n");
 834         }
 835 }