usr.sbin/arp/arp.c

   1 /*
   2  * Copyright (c) 1984, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Sun Microsystems, Inc.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  * @(#) Copyright (c) 1984, 1993 The Regents of the University of California.  All rights reserved.
  37  * @(#)from: arp.c      8.2 (Berkeley) 1/2/94
  38  * $FreeBSD: src/usr.sbin/arp/arp.c,v 1.22.2.12 2003/04/16 10:02:37 ru Exp $
  39  * $DragonFly: src/usr.sbin/arp/arp.c,v 1.8 2006/01/19 23:19:31 dillon Exp $
  40  */
  41
  42 /*
  43  * arp - display, set, and delete arp table entries
  44  */
  45
  46
  47 #include <sys/param.h>
  48 #include <sys/file.h>
  49 #include <sys/socket.h>
  50 #include <sys/sockio.h>
  51 #include <sys/sysctl.h>
  52 #include <sys/ioctl.h>
  53 #include <sys/time.h>
  54
  55 #include <net/if.h>
  56 #include <net/if_dl.h>
  57 #include <net/if_types.h>
  58 #include <net/route.h>
  59 #include <net/iso88025.h>
  60
  61 #include <netinet/in.h>
  62 #include <netinet/if_ether.h>
  63
  64 #include <arpa/inet.h>
  65
  66 #include <ctype.h>
  67 #include <err.h>
  68 #include <errno.h>
  69 #include <netdb.h>
  70 #include <nlist.h>
  71 #include <paths.h>
  72 #include <stdio.h>
  73 #include <stdlib.h>
  74 #include <strings.h>
  75 #include <unistd.h>
  76
  77 void search(u_long addr, void (*action)(struct sockaddr_dl *sdl,
  78         struct sockaddr_inarp *sin, struct rt_msghdr *rtm));
  79 void print_entry(struct sockaddr_dl *sdl,
  80         struct sockaddr_inarp *addr, struct rt_msghdr *rtm);
  81 void nuke_entry(struct sockaddr_dl *sdl,
  82         struct sockaddr_inarp *addr, struct rt_msghdr *rtm);
  83 int delete(char *host, char *info);
  84 void usage(void);
  85 int set(int argc, char **argv);
  86 int get(char *host);
  87 int file(char *name);
  88 void getsocket(void);
  89 int my_ether_aton(char *a, struct ether_addr *n);
  90 int rtmsg(int cmd);
  91 int get_ether_addr(u_int32_t ipaddr, struct ether_addr *hwaddr);
  92
  93 static int pid;
  94 static int nflag;       /* no reverse dns lookups */
  95 static int aflag;       /* do it for all entries */
  96 static int cpuflag = -1;
  97 static int s = -1;
  98
  99 struct  sockaddr_in so_mask;
 100 struct  sockaddr_inarp blank_sin, sin_m;
 101 struct  sockaddr_dl blank_sdl, sdl_m;
 102 int     expire_time, flags, doing_proxy, proxy_only, found_entry;
 103 struct  {
 104         struct  rt_msghdr m_rtm;
 105         char    m_space[512];
 106 }       m_rtmsg;
 107
 108 /* which function we're supposed to do */
 109 #define F_GET           1
 110 #define F_SET           2
 111 #define F_FILESET       3
 112 #define F_REPLACE       4
 113 #define F_DELETE        5
 114
 115 #define ROUNDUP(a) \
 116         ((a) > 0 ? (1 + (((a) - 1) | (sizeof(long) - 1))) : sizeof(long))
 117 #define SETFUNC(f)      { if (func) usage(); func = (f); }
 118
 119 int
 120 main(int argc, char **argv)
 121 {
 122         int ch, func = 0;
 123         int rtn = 0;
 124
 125         pid = getpid();
 126         while ((ch = getopt(argc, argv, "ac:ndfsS")) != -1)
 127                 switch((char)ch) {
 128                 case 'a':
 129                         aflag = 1;
 130                         break;
 131                 case 'c':
 132                         cpuflag = strtol(optarg, NULL, 0);
 133                         break;
 134                 case 'd':
 135                         SETFUNC(F_DELETE);
 136                         break;
 137                 case 'n':
 138                         nflag = 1;
 139                         break;
 140                 case 'S':
 141                         SETFUNC(F_REPLACE);
 142                         break;
 143                 case 's':
 144                         SETFUNC(F_SET);
 145                         break;
 146                 case 'f' :
 147                         SETFUNC(F_FILESET);
 148                         break;
 149                 case '?':
 150                 default:
 151                         usage();
 152                 }
 153         argc -= optind;
 154         argv += optind;
 155
 156         bzero(&so_mask, sizeof(so_mask));
 157         so_mask.sin_len = 8;
 158         so_mask.sin_addr.s_addr = 0xffffffff;
 159         bzero(&blank_sin, sizeof(blank_sin));
 160         blank_sin.sin_len = sizeof(blank_sin);
 161         blank_sin.sin_family = AF_INET;
 162         bzero(&blank_sdl, sizeof(blank_sdl));
 163         blank_sdl.sdl_len = sizeof(blank_sdl);
 164         blank_sdl.sdl_family = AF_LINK;
 165
 166         if (!func)
 167                 func = F_GET;
 168         switch (func) {
 169         case F_GET:
 170                 if (aflag) {
 171                         if (argc != 0)
 172                                 usage();
 173                         search(0, print_entry);
 174                 } else {
 175                         if (argc != 1)
 176                                 usage();
 177                         get(argv[0]);
 178                 }
 179                 break;
 180         case F_SET:
 181         case F_REPLACE:
 182                 if (argc < 2 || argc > 6)
 183                         usage();
 184                 if (func == F_REPLACE)
 185                         delete(argv[0], NULL);
 186                 rtn = set(argc, argv) ? 1 : 0;
 187                 break;
 188         case F_DELETE:
 189                 if (aflag) {
 190                         if (argc != 0)
 191                                 usage();
 192                         search(0, nuke_entry);
 193                 } else {
 194                         if (argc < 1 || argc > 2)
 195                                 usage();
 196                         rtn = delete(argv[0], argv[1]);
 197                 }
 198                 break;
 199         case F_FILESET:
 200                 if (argc != 1)
 201                         usage();
 202                 rtn = file(argv[0]);
 203                 break;
 204         }
 205
 206         return(rtn);
 207 }
 208
 209 /*
 210  * Process a file to set standard arp entries
 211  */
 212 int
 213 file(char *name)
 214 {
 215         FILE *fp;
 216         int i, retval;
 217         char line[100], arg[5][50], *args[5], *p;
 218
 219         if ((fp = fopen(name, "r")) == NULL)
 220                 errx(1, "cannot open %s", name);
 221         args[0] = &arg[0][0];
 222         args[1] = &arg[1][0];
 223         args[2] = &arg[2][0];
 224         args[3] = &arg[3][0];
 225         args[4] = &arg[4][0];
 226         retval = 0;
 227         while(fgets(line, 100, fp) != NULL) {
 228                 if ((p = strchr(line, '#')) != NULL)
 229                         *p = '\0';
 230                 for (p = line; isblank(*p); p++);
 231                 if (*p == '\n' || *p == '\0')
 232                         continue;
 233                 i = sscanf(p, "%49s %49s %49s %49s %49s", arg[0], arg[1],
 234                     arg[2], arg[3], arg[4]);
 235                 if (i < 2) {
 236                         warnx("bad line: %s", line);
 237                         retval = 1;
 238                         continue;
 239                 }
 240                 if (set(i, args))
 241                         retval = 1;
 242         }
 243         fclose(fp);
 244         return(retval);
 245 }
 246
 247 void
 248 getsocket(void)
 249 {
 250         if (s < 0) {
 251                 s = socket(PF_ROUTE, SOCK_RAW, 0);
 252                 if (s < 0)
 253                         err(1, "socket");
 254         }
 255 }
 256
 257 /*
 258  * Set an individual arp entry
 259  */
 260 int
 261 set(int argc, char **argv)
 262 {
 263         struct hostent *hp;
 264         struct sockaddr_inarp *addr = &sin_m;
 265         struct sockaddr_dl *sdl;
 266         struct rt_msghdr *rtm = &(m_rtmsg.m_rtm);
 267         struct ether_addr *ea;
 268         char *host = argv[0], *eaddr = argv[1];
 269
 270         getsocket();
 271         argc -= 2;
 272         argv += 2;
 273         sdl_m = blank_sdl;
 274         sin_m = blank_sin;
 275         addr->sin_addr.s_addr = inet_addr(host);
 276         if (addr->sin_addr.s_addr == INADDR_NONE) {
 277                 if (!(hp = gethostbyname(host))) {
 278                         warnx("%s: %s", host, hstrerror(h_errno));
 279                         return(1);
 280                 }
 281                 bcopy((char *)hp->h_addr, (char *)&addr->sin_addr,
 282                     sizeof(addr->sin_addr));
 283         }
 284         doing_proxy = flags = proxy_only = expire_time = 0;
 285         while (argc-- > 0) {
 286                 if (strncmp(argv[0], "temp", 4) == 0) {
 287                         struct timeval tv;
 288                         gettimeofday(&tv, 0);
 289                         expire_time = tv.tv_sec + 20 * 60;
 290                 }
 291                 else if (strncmp(argv[0], "pub", 3) == 0) {
 292                         flags |= RTF_ANNOUNCE;
 293                         doing_proxy = 1;
 294                         if (argc && strncmp(argv[1], "only", 3) == 0) {
 295                                 proxy_only = 1;
 296                                 sin_m.sin_other = SIN_PROXY;
 297                                 argc--; argv++;
 298                         }
 299                 } else if (strncmp(argv[0], "trail", 5) == 0) {
 300                         printf("%s: Sending trailers is no longer supported\n",
 301                                 host);
 302                 }
 303                 argv++;
 304         }
 305         ea = (struct ether_addr *)LLADDR(&sdl_m);
 306         if (doing_proxy && !strcmp(eaddr, "auto")) {
 307                 if (!get_ether_addr(addr->sin_addr.s_addr, ea)) {
 308                         printf("no interface found for %s\n",
 309                                inet_ntoa(addr->sin_addr));
 310                         return(1);
 311                 }
 312                 sdl_m.sdl_alen = ETHER_ADDR_LEN;
 313         } else {
 314                 if (my_ether_aton(eaddr, ea) == 0)
 315                         sdl_m.sdl_alen = ETHER_ADDR_LEN;
 316         }
 317 tryagain:
 318         if (rtmsg(RTM_GET) < 0) {
 319                 warn("%s", host);
 320                 return(1);
 321         }
 322         addr = (struct sockaddr_inarp *)(rtm + 1);
 323         sdl = (struct sockaddr_dl *)(ROUNDUP(addr->sin_len) + (char *)addr);
 324         if (addr->sin_addr.s_addr == sin_m.sin_addr.s_addr) {
 325                 if (sdl->sdl_family == AF_LINK &&
 326                     (rtm->rtm_flags & RTF_LLINFO) &&
 327                     !(rtm->rtm_flags & RTF_GATEWAY)) switch (sdl->sdl_type) {
 328                 case IFT_ETHER: case IFT_FDDI: case IFT_ISO88023:
 329                 case IFT_ISO88024: case IFT_ISO88025: case IFT_L2VLAN:
 330                         goto overwrite;
 331                 }
 332                 if (doing_proxy == 0) {
 333                         printf("set: can only proxy for %s\n", host);
 334                         return(1);
 335                 }
 336                 if (sin_m.sin_other & SIN_PROXY) {
 337                         printf("set: proxy entry exists for non 802 device\n");
 338                         return(1);
 339                 }
 340                 sin_m.sin_other = SIN_PROXY;
 341                 proxy_only = 1;
 342                 goto tryagain;
 343         }
 344 overwrite:
 345         if (sdl->sdl_family != AF_LINK) {
 346                 printf("cannot intuit interface index and type for %s\n", host);
 347                 return(1);
 348         }
 349         sdl_m.sdl_type = sdl->sdl_type;
 350         sdl_m.sdl_index = sdl->sdl_index;
 351         return(rtmsg(RTM_ADD));
 352 }
 353
 354 /*
 355  * Display an individual arp entry
 356  */
 357 int
 358 get(char *host)
 359 {
 360         struct hostent *hp;
 361         struct sockaddr_inarp *addr = &sin_m;
 362
 363         sin_m = blank_sin;
 364         addr->sin_addr.s_addr = inet_addr(host);
 365         if (addr->sin_addr.s_addr == INADDR_NONE) {
 366                 if (!(hp = gethostbyname(host)))
 367                         errx(1, "%s: %s", host, hstrerror(h_errno));
 368                 bcopy((char *)hp->h_addr, (char *)&addr->sin_addr,
 369                     sizeof(addr->sin_addr));
 370         }
 371         search(addr->sin_addr.s_addr, print_entry);
 372         if (found_entry == 0) {
 373                 printf("%s (%s) -- no entry\n",
 374                     host, inet_ntoa(addr->sin_addr));
 375                 return(1);
 376         }
 377         return(0);
 378 }
 379
 380 /*
 381  * Delete an arp entry
 382  */
 383 int
 384 delete(char *host, char *info)
 385 {
 386         struct hostent *hp;
 387         struct sockaddr_inarp *addr = &sin_m;
 388         struct rt_msghdr *rtm = &m_rtmsg.m_rtm;
 389         struct sockaddr_dl *sdl;
 390
 391         getsocket();
 392         sin_m = blank_sin;
 393         if (info) {
 394                 if (strncmp(info, "pub", 3) == 0)
 395                         sin_m.sin_other = SIN_PROXY;
 396                 else
 397                         usage();
 398         }
 399         addr->sin_addr.s_addr = inet_addr(host);
 400         if (addr->sin_addr.s_addr == INADDR_NONE) {
 401                 if (!(hp = gethostbyname(host))) {
 402                         warnx("%s: %s", host, hstrerror(h_errno));
 403                         return(1);
 404                 }
 405                 bcopy((char *)hp->h_addr, (char *)&addr->sin_addr,
 406                     sizeof(addr->sin_addr));
 407         }
 408 tryagain:
 409         if (rtmsg(RTM_GET) < 0) {
 410                 warn("%s", host);
 411                 return(1);
 412         }
 413         addr = (struct sockaddr_inarp *)(rtm + 1);
 414         sdl = (struct sockaddr_dl *)(ROUNDUP(addr->sin_len) + (char *)addr);
 415         if (addr->sin_addr.s_addr == sin_m.sin_addr.s_addr) {
 416                 if (sdl->sdl_family == AF_LINK &&
 417                     (rtm->rtm_flags & RTF_LLINFO) &&
 418                     !(rtm->rtm_flags & RTF_GATEWAY)) switch (sdl->sdl_type) {
 419                 case IFT_ETHER: case IFT_FDDI: case IFT_ISO88023:
 420                 case IFT_ISO88024: case IFT_ISO88025: case IFT_L2VLAN:
 421                         goto delete;
 422                 }
 423         }
 424         if (sin_m.sin_other & SIN_PROXY) {
 425                 fprintf(stderr, "delete: can't locate %s\n",host);
 426                 return(1);
 427         } else {
 428                 sin_m.sin_other = SIN_PROXY;
 429                 goto tryagain;
 430         }
 431 delete:
 432         if (sdl->sdl_family != AF_LINK) {
 433                 printf("cannot locate %s\n", host);
 434                 return(1);
 435         }
 436         if (aflag && (rtm->rtm_flags & RTF_STATIC)) {
 437                 sdl->sdl_alen = 0;
 438                 sdl->sdl_slen = 0;
 439                 if (rtmsg(RTM_CHANGE) == 0) {
 440                         printf("%s (%s) cleared\n",
 441                                 host, inet_ntoa(addr->sin_addr));
 442                         return(0);
 443                 }
 444         } else {
 445                 if (rtmsg(RTM_DELETE) == 0) {
 446                         printf("%s (%s) deleted\n",
 447                                 host, inet_ntoa(addr->sin_addr));
 448                         return(0);
 449                 }
 450         }
 451         return(1);
 452 }
 453
 454 /*
 455  * Search the arp table and do some action on matching entries
 456  */
 457 void
 458 search(u_long addr, void (*action)(struct sockaddr_dl *sdl,
 459         struct sockaddr_inarp *sin, struct rt_msghdr *rtm))
 460 {
 461         int mib[7];
 462         int miblen;
 463         size_t needed;
 464         char *lim, *buf, *next;
 465         struct rt_msghdr *rtm;
 466         struct sockaddr_inarp *sin2;
 467         struct sockaddr_dl *sdl;
 468
 469         mib[0] = CTL_NET;
 470         mib[1] = PF_ROUTE;
 471         mib[2] = 0;
 472         mib[3] = AF_INET;
 473         mib[4] = NET_RT_FLAGS;
 474         mib[5] = RTF_LLINFO;
 475         if (cpuflag >= 0) {
 476             mib[6] = cpuflag;
 477             miblen = 7;
 478         } else {
 479             miblen = 6;
 480         }
 481         if (sysctl(mib, miblen, NULL, &needed, NULL, 0) < 0)
 482                 errx(1, "route-sysctl-estimate");
 483         if ((buf = malloc(needed)) == NULL)
 484                 errx(1, "malloc");
 485         if (sysctl(mib, miblen, buf, &needed, NULL, 0) < 0)
 486                 errx(1, "actual retrieval of routing table");
 487         lim = buf + needed;
 488         for (next = buf; next < lim; next += rtm->rtm_msglen) {
 489                 rtm = (struct rt_msghdr *)next;
 490                 sin2 = (struct sockaddr_inarp *)(rtm + 1);
 491                 sdl = (struct sockaddr_dl *)((char *)sin2 + ROUNDUP(sin2->sin_len));
 492                 if (addr) {
 493                         if (addr != sin2->sin_addr.s_addr)
 494                                 continue;
 495                         found_entry = 1;
 496                 }
 497                 (*action)(sdl, sin2, rtm);
 498         }
 499         free(buf);
 500 }
 501
 502 /*
 503  * Display an arp entry
 504  */
 505 void
 506 print_entry(struct sockaddr_dl *sdl,
 507         struct sockaddr_inarp *addr, struct rt_msghdr *rtm)
 508 {
 509         const char *host;
 510         struct hostent *hp;
 511         struct iso88025_sockaddr_dl_data *trld;
 512         char ifname[IF_NAMESIZE];
 513         int seg;
 514
 515         if (nflag == 0)
 516                 hp = gethostbyaddr((caddr_t)&(addr->sin_addr),
 517                     sizeof(addr->sin_addr), AF_INET);
 518         else
 519                 hp = 0;
 520         if (hp)
 521                 host = hp->h_name;
 522         else {
 523                 host = "?";
 524                 if (h_errno == TRY_AGAIN)
 525                         nflag = 1;
 526         }
 527         printf("%s (%s) at ", host, inet_ntoa(addr->sin_addr));
 528         if (sdl->sdl_alen)
 529                 printf("%s", ether_ntoa((struct ether_addr *)LLADDR(sdl)));
 530         else
 531                 printf("(incomplete)");
 532         if (if_indextoname(sdl->sdl_index, ifname) != NULL)
 533                 printf(" on %s", ifname);
 534         if (rtm->rtm_rmx.rmx_expire == 0)
 535                 printf(" permanent");
 536         if (addr->sin_other & SIN_PROXY)
 537                 printf(" published (proxy only)");
 538         if (rtm->rtm_addrs & RTA_NETMASK) {
 539                 addr = (struct sockaddr_inarp *)
 540                         (ROUNDUP(sdl->sdl_len) + (char *)sdl);
 541                 if (addr->sin_addr.s_addr == 0xffffffff)
 542                         printf(" published");
 543                 if (addr->sin_len != 8)
 544                         printf("(weird)");
 545         }
 546         switch(sdl->sdl_type) {
 547             case IFT_ETHER:
 548                 printf(" [ethernet]");
 549                 break;
 550             case IFT_ISO88025:
 551                 printf(" [token-ring]");
 552                 trld = SDL_ISO88025(sdl);
 553                 if (trld->trld_rcf != 0) {
 554                         printf(" rt=%x", ntohs(trld->trld_rcf));
 555                         for (seg = 0;
 556                              seg < ((TR_RCF_RIFLEN(trld->trld_rcf) - 2 ) / 2);
 557                              seg++)
 558                                 printf(":%x", ntohs(*(trld->trld_route[seg])));
 559                 }
 560                 break;
 561             case IFT_L2VLAN:
 562                 printf(" [vlan]");
 563                 break;
 564             default:
 565                 break;
 566         }
 567
 568         printf("\n");
 569
 570 }
 571
 572 /*
 573  * Nuke an arp entry
 574  */
 575 void
 576 nuke_entry(struct sockaddr_dl *sdl __unused,
 577         struct sockaddr_inarp *addr, struct rt_msghdr *rtm __unused)
 578 {
 579         char ip[20];
 580
 581         snprintf(ip, sizeof(ip), "%s", inet_ntoa(addr->sin_addr));
 582         delete(ip, NULL);
 583 }
 584
 585 int
 586 my_ether_aton(char *a, struct ether_addr *n)
 587 {
 588         struct ether_addr *ea;
 589
 590         if ((ea = ether_aton(a)) == NULL) {
 591                 warnx("invalid Ethernet address '%s'", a);
 592                 return(1);
 593         }
 594         *n = *ea;
 595         return(0);
 596 }
 597
 598 void
 599 usage(void)
 600 {
 601         fprintf(stderr, "%s\n%s\n%s\n%s\n%s\n%s\n%s\n",
 602                 "usage: arp [-n] hostname",
 603                 "       arp [-n] -a",
 604                 "       arp -d hostname [pub]",
 605                 "       arp -d -a",
 606                 "       arp -s hostname ether_addr [temp] [pub]",
 607                 "       arp -S hostname ether_addr [temp] [pub]",
 608                 "       arp -f filename");
 609         exit(1);
 610 }
 611
 612 int
 613 rtmsg(int cmd)
 614 {
 615         static int seq;
 616         int rlen;
 617         struct rt_msghdr *rtm = &m_rtmsg.m_rtm;
 618         char *cp = m_rtmsg.m_space;
 619         int l;
 620
 621         errno = 0;
 622         if (cmd == RTM_DELETE || cmd == RTM_CHANGE)
 623                 goto doit;
 624         bzero((char *)&m_rtmsg, sizeof(m_rtmsg));
 625         rtm->rtm_flags = flags;
 626         rtm->rtm_version = RTM_VERSION;
 627
 628         switch (cmd) {
 629         default:
 630                 errx(1, "internal wrong cmd");
 631         case RTM_ADD:
 632                 rtm->rtm_addrs |= RTA_GATEWAY;
 633                 rtm->rtm_rmx.rmx_expire = expire_time;
 634                 rtm->rtm_inits = RTV_EXPIRE;
 635                 rtm->rtm_flags |= (RTF_HOST | RTF_STATIC);
 636                 sin_m.sin_other = 0;
 637                 if (doing_proxy) {
 638                         if (proxy_only)
 639                                 sin_m.sin_other = SIN_PROXY;
 640                         else {
 641                                 rtm->rtm_addrs |= RTA_NETMASK;
 642                                 rtm->rtm_flags &= ~RTF_HOST;
 643                         }
 644                 }
 645                 /* FALLTHROUGH */
 646         case RTM_GET:
 647                 rtm->rtm_addrs |= RTA_DST;
 648         }
 649 #define NEXTADDR(w, s) \
 650         if (rtm->rtm_addrs & (w)) { \
 651                 bcopy((char *)&s, cp, sizeof(s)); cp += ROUNDUP(sizeof(s));}
 652
 653         NEXTADDR(RTA_DST, sin_m);
 654         NEXTADDR(RTA_GATEWAY, sdl_m);
 655         NEXTADDR(RTA_NETMASK, so_mask);
 656
 657         rtm->rtm_msglen = cp - (char *)&m_rtmsg;
 658 doit:
 659         l = rtm->rtm_msglen;
 660         rtm->rtm_seq = ++seq;
 661         rtm->rtm_type = cmd;
 662         if ((rlen = write(s, (char *)&m_rtmsg, l)) < 0) {
 663                 if (errno != ESRCH || (cmd != RTM_DELETE && cmd != RTM_CHANGE)) {
 664                         warn("writing to routing socket");
 665                         return(-1);
 666                 }
 667         }
 668         do {
 669                 l = read(s, (char *)&m_rtmsg, sizeof(m_rtmsg));
 670         } while (l > 0 && (rtm->rtm_seq != seq || rtm->rtm_pid != pid));
 671         if (l < 0)
 672                 warn("read from routing socket");
 673         return(0);
 674 }
 675
 676 /*
 677  * get_ether_addr - get the hardware address of an interface on the
 678  * the same subnet as ipaddr.
 679  */
 680 #define MAX_IFS         32
 681
 682 int
 683 get_ether_addr(u_int32_t ipaddr, struct ether_addr *hwaddr)
 684 {
 685         struct ifreq *ifr, *ifend, *ifp;
 686         u_int32_t ina, mask;
 687         struct sockaddr_dl *dla;
 688         struct ifreq ifreq;
 689         struct ifconf ifc;
 690         struct ifreq ifs[MAX_IFS];
 691         int sock;
 692
 693         sock = socket(AF_INET, SOCK_DGRAM, 0);
 694         if (sock < 0)
 695                 err(1, "socket");
 696
 697         ifc.ifc_len = sizeof(ifs);
 698         ifc.ifc_req = ifs;
 699         if (ioctl(sock, SIOCGIFCONF, &ifc) < 0) {
 700                 warnx("ioctl(SIOCGIFCONF)");
 701                 close(sock);
 702                 return(0);
 703         }
 704
 705         /*
 706         * Scan through looking for an interface with an Internet
 707         * address on the same subnet as `ipaddr'.
 708         */
 709         ifend = (struct ifreq *) (ifc.ifc_buf + ifc.ifc_len);
 710         for (ifr = ifc.ifc_req; ifr < ifend; ) {
 711                 if (ifr->ifr_addr.sa_family == AF_INET) {
 712                         ina = ((struct sockaddr_in *)
 713                                 &ifr->ifr_addr)->sin_addr.s_addr;
 714                         strncpy(ifreq.ifr_name, ifr->ifr_name,
 715                                 sizeof(ifreq.ifr_name));
 716                         /*
 717                          * Check that the interface is up,
 718                          * and not point-to-point or loopback.
 719                          */
 720                         if (ioctl(sock, SIOCGIFFLAGS, &ifreq) < 0)
 721                                 continue;
 722                         if ((ifreq.ifr_flags &
 723                              (IFF_UP|IFF_BROADCAST|IFF_POINTOPOINT|
 724                                         IFF_LOOPBACK|IFF_NOARP))
 725                              != (IFF_UP|IFF_BROADCAST))
 726                                 goto nextif;
 727                         /*
 728                          * Get its netmask and check that it's on
 729                          * the right subnet.
 730                          */
 731                         if (ioctl(sock, SIOCGIFNETMASK, &ifreq) < 0)
 732                                 continue;
 733                         mask = ((struct sockaddr_in *)
 734                                 &ifreq.ifr_addr)->sin_addr.s_addr;
 735                         if ((ipaddr & mask) != (ina & mask))
 736                                 goto nextif;
 737                         break;
 738                 }
 739 nextif:
 740                 ifr = (struct ifreq *) ((char *)&ifr->ifr_addr
 741                     + MAX(ifr->ifr_addr.sa_len, sizeof(ifr->ifr_addr)));
 742         }
 743
 744         if (ifr >= ifend) {
 745                 close(sock);
 746                 return(0);
 747         }
 748
 749         /*
 750         * Now scan through again looking for a link-level address
 751         * for this interface.
 752         */
 753         ifp = ifr;
 754         for (ifr = ifc.ifc_req; ifr < ifend; ) {
 755                 if (strcmp(ifp->ifr_name, ifr->ifr_name) == 0
 756                     && ifr->ifr_addr.sa_family == AF_LINK) {
 757                         /*
 758                          * Found the link-level address - copy it out
 759                          */
 760                         dla = (struct sockaddr_dl *) &ifr->ifr_addr;
 761                         memcpy(hwaddr,  LLADDR(dla), dla->sdl_alen);
 762                         close (sock);
 763                         printf("using interface %s for proxy with address ",
 764                                 ifp->ifr_name);
 765                         printf("%s\n", ether_ntoa(hwaddr));
 766                         return(dla->sdl_alen);
 767                 }
 768                 ifr = (struct ifreq *) ((char *)&ifr->ifr_addr
 769                     + MAX(ifr->ifr_addr.sa_len, sizeof(ifr->ifr_addr)));
 770         }
 771         return(0);
 772 }