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 * 4. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 */ 32 33 #if 0 34 #ifndef lint 35 static char const copyright[] = 36 "@(#) Copyright (c) 1984, 1993\n\ 37 The Regents of the University of California. All rights reserved.\n"; 38 #endif /* not lint */ 39 40 #ifndef lint 41 static char const sccsid[] = "@(#)from: arp.c 8.2 (Berkeley) 1/2/94"; 42 #endif /* not lint */ 43 #endif 44 #include <sys/cdefs.h> 45 __FBSDID("$FreeBSD$"); 46 47 /* 48 * arp - display, set, and delete arp table entries 49 */ 50 51 52 #include <sys/param.h> 53 #include <sys/file.h> 54 #include <sys/socket.h> 55 #include <sys/sockio.h> 56 #include <sys/sysctl.h> 57 #include <sys/ioctl.h> 58 #include <sys/time.h> 59 60 #include <net/if.h> 61 #include <net/if_dl.h> 62 #include <net/if_types.h> 63 #include <net/route.h> 64 #include <net/iso88025.h> 65 66 #include <netinet/in.h> 67 #include <netinet/if_ether.h> 68 69 #include <arpa/inet.h> 70 71 #include <ctype.h> 72 #include <err.h> 73 #include <errno.h> 74 #include <netdb.h> 75 #include <nlist.h> 76 #include <paths.h> 77 #include <stdio.h> 78 #include <stdlib.h> 79 #include <string.h> 80 #include <strings.h> 81 #include <unistd.h> 82 83 typedef void (action_fn)(struct sockaddr_dl *sdl, 84 struct sockaddr_inarp *s_in, struct rt_msghdr *rtm); 85 86 static int search(u_long addr, action_fn *action); 87 static action_fn print_entry; 88 static action_fn nuke_entry; 89 90 static int delete(char *host, int do_proxy); 91 static void usage(void); 92 static int set(int argc, char **argv); 93 static int get(char *host); 94 static int file(char *name); 95 static struct rt_msghdr *rtmsg(int cmd, 96 struct sockaddr_inarp *dst, struct sockaddr_dl *sdl); 97 static int get_ether_addr(in_addr_t ipaddr, struct ether_addr *hwaddr); 98 static struct sockaddr_inarp *getaddr(char *host); 99 static int valid_type(int type); 100 101 static int nflag; /* no reverse dns lookups */ 102 static char *rifname; 103 104 static int expire_time, flags, doing_proxy, proxy_only; 105 106 /* which function we're supposed to do */ 107 #define F_GET 1 108 #define F_SET 2 109 #define F_FILESET 3 110 #define F_REPLACE 4 111 #define F_DELETE 5 112 113 #define SETFUNC(f) { if (func) usage(); func = (f); } 114 115 int 116 main(int argc, char *argv[]) 117 { 118 int ch, func = 0; 119 int rtn = 0; 120 int aflag = 0; /* do it for all entries */ 121 122 while ((ch = getopt(argc, argv, "andfsSi:")) != -1) 123 switch((char)ch) { 124 case 'a': 125 aflag = 1; 126 break; 127 case 'd': 128 SETFUNC(F_DELETE); 129 break; 130 case 'n': 131 nflag = 1; 132 break; 133 case 'S': 134 SETFUNC(F_REPLACE); 135 break; 136 case 's': 137 SETFUNC(F_SET); 138 break; 139 case 'f' : 140 SETFUNC(F_FILESET); 141 break; 142 case 'i': 143 rifname = optarg; 144 break; 145 case '?': 146 default: 147 usage(); 148 } 149 argc -= optind; 150 argv += optind; 151 152 if (!func) 153 func = F_GET; 154 if (rifname) { 155 if (func != F_GET) 156 errx(1, "-i not applicable to this operation"); 157 if (if_nametoindex(rifname) == 0) { 158 if (errno == ENXIO) 159 errx(1, "interface %s does not exist", rifname); 160 else 161 err(1, "if_nametoindex(%s)", rifname); 162 } 163 } 164 switch (func) { 165 case F_GET: 166 if (aflag) { 167 if (argc != 0) 168 usage(); 169 search(0, print_entry); 170 } else { 171 if (argc != 1) 172 usage(); 173 rtn = get(argv[0]); 174 } 175 break; 176 case F_SET: 177 case F_REPLACE: 178 if (argc < 2 || argc > 6) 179 usage(); 180 if (func == F_REPLACE) 181 (void)delete(argv[0], 0); 182 rtn = set(argc, argv) ? 1 : 0; 183 break; 184 case F_DELETE: 185 if (aflag) { 186 if (argc != 0) 187 usage(); 188 search(0, nuke_entry); 189 } else { 190 if (argc == 2 && strncmp(argv[1], "pub", 3) == 0) 191 ch = SIN_PROXY; 192 else if (argc == 1) 193 ch = 0; 194 else 195 usage(); 196 rtn = delete(argv[0], ch); 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 static 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 err(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 /* 248 * Given a hostname, fills up a (static) struct sockaddr_inarp with 249 * the address of the host and returns a pointer to the 250 * structure. 251 */ 252 static struct sockaddr_inarp * 253 getaddr(char *host) 254 { 255 struct hostent *hp; 256 static struct sockaddr_inarp reply; 257 258 bzero(&reply, sizeof(reply)); 259 reply.sin_len = sizeof(reply); 260 reply.sin_family = AF_INET; 261 reply.sin_addr.s_addr = inet_addr(host); 262 if (reply.sin_addr.s_addr == INADDR_NONE) { 263 if (!(hp = gethostbyname(host))) { 264 warnx("%s: %s", host, hstrerror(h_errno)); 265 return (NULL); 266 } 267 bcopy((char *)hp->h_addr, (char *)&reply.sin_addr, 268 sizeof reply.sin_addr); 269 } 270 return (&reply); 271 } 272 273 /* 274 * Returns true if the type is a valid one for ARP. 275 */ 276 static int 277 valid_type(int type) 278 { 279 280 switch (type) { 281 case IFT_ETHER: 282 case IFT_FDDI: 283 case IFT_ISO88023: 284 case IFT_ISO88024: 285 case IFT_ISO88025: 286 case IFT_L2VLAN: 287 return (1); 288 default: 289 return (0); 290 } 291 } 292 293 /* 294 * Set an individual arp entry 295 */ 296 static int 297 set(int argc, char **argv) 298 { 299 struct sockaddr_inarp *addr; 300 struct sockaddr_inarp *dst; /* what are we looking for */ 301 struct sockaddr_dl *sdl; 302 struct rt_msghdr *rtm; 303 struct ether_addr *ea; 304 char *host = argv[0], *eaddr = argv[1]; 305 struct sockaddr_dl sdl_m; 306 307 argc -= 2; 308 argv += 2; 309 310 bzero(&sdl_m, sizeof(sdl_m)); 311 sdl_m.sdl_len = sizeof(sdl_m); 312 sdl_m.sdl_family = AF_LINK; 313 314 dst = getaddr(host); 315 if (dst == NULL) 316 return (1); 317 doing_proxy = flags = proxy_only = expire_time = 0; 318 while (argc-- > 0) { 319 if (strncmp(argv[0], "temp", 4) == 0) { 320 struct timeval tv; 321 gettimeofday(&tv, 0); 322 expire_time = tv.tv_sec + 20 * 60; 323 } 324 else if (strncmp(argv[0], "pub", 3) == 0) { 325 flags |= RTF_ANNOUNCE; 326 doing_proxy = 1; 327 if (argc && strncmp(argv[1], "only", 3) == 0) { 328 proxy_only = 1; 329 dst->sin_other = SIN_PROXY; 330 argc--; argv++; 331 } 332 } else if (strncmp(argv[0], "trail", 5) == 0) { 333 /* XXX deprecated and undocumented feature */ 334 printf("%s: Sending trailers is no longer supported\n", 335 host); 336 } 337 argv++; 338 } 339 ea = (struct ether_addr *)LLADDR(&sdl_m); 340 if (doing_proxy && !strcmp(eaddr, "auto")) { 341 if (!get_ether_addr(dst->sin_addr.s_addr, ea)) { 342 printf("no interface found for %s\n", 343 inet_ntoa(dst->sin_addr)); 344 return (1); 345 } 346 sdl_m.sdl_alen = ETHER_ADDR_LEN; 347 } else { 348 struct ether_addr *ea1 = ether_aton(eaddr); 349 350 if (ea1 == NULL) 351 warnx("invalid Ethernet address '%s'", eaddr); 352 else { 353 *ea = *ea1; 354 sdl_m.sdl_alen = ETHER_ADDR_LEN; 355 } 356 } 357 for (;;) { /* try at most twice */ 358 rtm = rtmsg(RTM_GET, dst, &sdl_m); 359 if (rtm == NULL) { 360 warn("%s", host); 361 return (1); 362 } 363 addr = (struct sockaddr_inarp *)(rtm + 1); 364 sdl = (struct sockaddr_dl *)(SA_SIZE(addr) + (char *)addr); 365 if (addr->sin_addr.s_addr != dst->sin_addr.s_addr) 366 break; 367 if (sdl->sdl_family == AF_LINK && 368 (rtm->rtm_flags & RTF_LLINFO) && 369 !(rtm->rtm_flags & RTF_GATEWAY) && 370 valid_type(sdl->sdl_type) ) 371 break; 372 if (doing_proxy == 0) { 373 printf("set: can only proxy for %s\n", host); 374 return (1); 375 } 376 if (dst->sin_other & SIN_PROXY) { 377 printf("set: proxy entry exists for non 802 device\n"); 378 return (1); 379 } 380 dst->sin_other = SIN_PROXY; 381 proxy_only = 1; 382 } 383 384 if (sdl->sdl_family != AF_LINK) { 385 printf("cannot intuit interface index and type for %s\n", host); 386 return (1); 387 } 388 sdl_m.sdl_type = sdl->sdl_type; 389 sdl_m.sdl_index = sdl->sdl_index; 390 return (rtmsg(RTM_ADD, dst, &sdl_m) == NULL); 391 } 392 393 /* 394 * Display an individual arp entry 395 */ 396 static int 397 get(char *host) 398 { 399 struct sockaddr_inarp *addr; 400 401 addr = getaddr(host); 402 if (addr == NULL) 403 return (1); 404 if (0 == search(addr->sin_addr.s_addr, print_entry)) { 405 printf("%s (%s) -- no entry", 406 host, inet_ntoa(addr->sin_addr)); 407 if (rifname) 408 printf(" on %s", rifname); 409 printf("\n"); 410 return (1); 411 } 412 return (0); 413 } 414 415 /* 416 * Delete an arp entry 417 */ 418 static int 419 delete(char *host, int do_proxy) 420 { 421 struct sockaddr_inarp *addr, *dst; 422 struct rt_msghdr *rtm; 423 struct sockaddr_dl *sdl; 424 425 dst = getaddr(host); 426 if (dst == NULL) 427 return (1); 428 dst->sin_other = do_proxy; 429 for (;;) { /* try twice */ 430 rtm = rtmsg(RTM_GET, dst, NULL); 431 if (rtm == NULL) { 432 warn("%s", host); 433 return (1); 434 } 435 addr = (struct sockaddr_inarp *)(rtm + 1); 436 sdl = (struct sockaddr_dl *)(SA_SIZE(addr) + (char *)addr); 437 if (addr->sin_addr.s_addr == dst->sin_addr.s_addr && 438 sdl->sdl_family == AF_LINK && 439 (rtm->rtm_flags & RTF_LLINFO) && 440 !(rtm->rtm_flags & RTF_GATEWAY) && 441 valid_type(sdl->sdl_type) ) 442 break; /* found it */ 443 if (dst->sin_other & SIN_PROXY) { 444 fprintf(stderr, "delete: cannot locate %s\n",host); 445 return (1); 446 } 447 dst->sin_other = SIN_PROXY; 448 } 449 if (rtmsg(RTM_DELETE, dst, NULL) != NULL) { 450 printf("%s (%s) deleted\n", host, inet_ntoa(addr->sin_addr)); 451 return (0); 452 } 453 return (1); 454 } 455 456 /* 457 * Search the arp table and do some action on matching entries 458 */ 459 static int 460 search(u_long addr, action_fn *action) 461 { 462 int mib[6]; 463 size_t needed; 464 char *lim, *buf, *newbuf, *next; 465 struct rt_msghdr *rtm; 466 struct sockaddr_inarp *sin2; 467 struct sockaddr_dl *sdl; 468 char ifname[IF_NAMESIZE]; 469 int st, found_entry = 0; 470 471 mib[0] = CTL_NET; 472 mib[1] = PF_ROUTE; 473 mib[2] = 0; 474 mib[3] = AF_INET; 475 mib[4] = NET_RT_FLAGS; 476 mib[5] = RTF_LLINFO; 477 if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0) 478 err(1, "route-sysctl-estimate"); 479 if (needed == 0) /* empty table */ 480 return 0; 481 buf = NULL; 482 for (;;) { 483 newbuf = realloc(buf, needed); 484 if (newbuf == NULL) { 485 if (buf != NULL) 486 free(buf); 487 errx(1, "could not reallocate memory"); 488 } 489 buf = newbuf; 490 st = sysctl(mib, 6, buf, &needed, NULL, 0); 491 if (st == 0 || errno != ENOMEM) 492 break; 493 needed += needed / 8; 494 } 495 if (st == -1) 496 err(1, "actual retrieval of routing table"); 497 lim = buf + needed; 498 for (next = buf; next < lim; next += rtm->rtm_msglen) { 499 rtm = (struct rt_msghdr *)next; 500 sin2 = (struct sockaddr_inarp *)(rtm + 1); 501 sdl = (struct sockaddr_dl *)((char *)sin2 + SA_SIZE(sin2)); 502 if (rifname && if_indextoname(sdl->sdl_index, ifname) && 503 strcmp(ifname, rifname)) 504 continue; 505 if (addr) { 506 if (addr != sin2->sin_addr.s_addr) 507 continue; 508 found_entry = 1; 509 } 510 (*action)(sdl, sin2, rtm); 511 } 512 free(buf); 513 return (found_entry); 514 } 515 516 /* 517 * Display an arp entry 518 */ 519 static void 520 print_entry(struct sockaddr_dl *sdl, 521 struct sockaddr_inarp *addr, struct rt_msghdr *rtm) 522 { 523 const char *host; 524 struct hostent *hp; 525 struct iso88025_sockaddr_dl_data *trld; 526 char ifname[IF_NAMESIZE]; 527 int seg; 528 529 if (nflag == 0) 530 hp = gethostbyaddr((caddr_t)&(addr->sin_addr), 531 sizeof addr->sin_addr, AF_INET); 532 else 533 hp = 0; 534 if (hp) 535 host = hp->h_name; 536 else { 537 host = "?"; 538 if (h_errno == TRY_AGAIN) 539 nflag = 1; 540 } 541 printf("%s (%s) at ", host, inet_ntoa(addr->sin_addr)); 542 if (sdl->sdl_alen) { 543 if ((sdl->sdl_type == IFT_ETHER || 544 sdl->sdl_type == IFT_L2VLAN) && 545 sdl->sdl_alen == ETHER_ADDR_LEN) 546 printf("%s", ether_ntoa((struct ether_addr *)LLADDR(sdl))); 547 else { 548 int n = sdl->sdl_nlen > 0 ? sdl->sdl_nlen + 1 : 0; 549 550 printf("%s", link_ntoa(sdl) + n); 551 } 552 } else 553 printf("(incomplete)"); 554 if (if_indextoname(sdl->sdl_index, ifname) != NULL) 555 printf(" on %s", ifname); 556 if (rtm->rtm_rmx.rmx_expire == 0) 557 printf(" permanent"); 558 if (addr->sin_other & SIN_PROXY) 559 printf(" published (proxy only)"); 560 if (rtm->rtm_addrs & RTA_NETMASK) { 561 addr = (struct sockaddr_inarp *) 562 (SA_SIZE(sdl) + (char *)sdl); 563 if (addr->sin_addr.s_addr == 0xffffffff) 564 printf(" published"); 565 if (addr->sin_len != 8) 566 printf("(weird)"); 567 } 568 switch(sdl->sdl_type) { 569 case IFT_ETHER: 570 printf(" [ethernet]"); 571 break; 572 case IFT_ISO88025: 573 printf(" [token-ring]"); 574 trld = SDL_ISO88025(sdl); 575 if (trld->trld_rcf != 0) { 576 printf(" rt=%x", ntohs(trld->trld_rcf)); 577 for (seg = 0; 578 seg < ((TR_RCF_RIFLEN(trld->trld_rcf) - 2 ) / 2); 579 seg++) 580 printf(":%x", ntohs(*(trld->trld_route[seg]))); 581 } 582 break; 583 case IFT_FDDI: 584 printf(" [fddi]"); 585 break; 586 case IFT_ATM: 587 printf(" [atm]"); 588 break; 589 case IFT_L2VLAN: 590 printf(" [vlan]"); 591 break; 592 case IFT_IEEE1394: 593 printf(" [firewire]"); 594 break; 595 default: 596 break; 597 } 598 599 printf("\n"); 600 601 } 602 603 /* 604 * Nuke an arp entry 605 */ 606 static void 607 nuke_entry(struct sockaddr_dl *sdl __unused, 608 struct sockaddr_inarp *addr, struct rt_msghdr *rtm __unused) 609 { 610 char ip[20]; 611 612 snprintf(ip, sizeof(ip), "%s", inet_ntoa(addr->sin_addr)); 613 (void)delete(ip, 0); 614 } 615 616 static void 617 usage(void) 618 { 619 fprintf(stderr, "%s\n%s\n%s\n%s\n%s\n%s\n%s\n", 620 "usage: arp [-n] [-i interface] hostname", 621 " arp [-n] [-i interface] -a", 622 " arp -d hostname [pub]", 623 " arp -d -a", 624 " arp -s hostname ether_addr [temp] [pub]", 625 " arp -S hostname ether_addr [temp] [pub]", 626 " arp -f filename"); 627 exit(1); 628 } 629 630 static struct rt_msghdr * 631 rtmsg(int cmd, struct sockaddr_inarp *dst, struct sockaddr_dl *sdl) 632 { 633 static int seq; 634 int rlen; 635 int l; 636 struct sockaddr_in so_mask; 637 static int s = -1; 638 static pid_t pid; 639 640 static struct { 641 struct rt_msghdr m_rtm; 642 char m_space[512]; 643 } m_rtmsg; 644 645 struct rt_msghdr *rtm = &m_rtmsg.m_rtm; 646 char *cp = m_rtmsg.m_space; 647 648 if (s < 0) { /* first time: open socket, get pid */ 649 s = socket(PF_ROUTE, SOCK_RAW, 0); 650 if (s < 0) 651 err(1, "socket"); 652 pid = getpid(); 653 } 654 bzero(&so_mask, sizeof(so_mask)); 655 so_mask.sin_len = 8; 656 so_mask.sin_addr.s_addr = 0xffffffff; 657 658 errno = 0; 659 /* 660 * XXX RTM_DELETE relies on a previous RTM_GET to fill the buffer 661 * appropriately. 662 */ 663 if (cmd == RTM_DELETE) 664 goto doit; 665 bzero((char *)&m_rtmsg, sizeof(m_rtmsg)); 666 rtm->rtm_flags = flags; 667 rtm->rtm_version = RTM_VERSION; 668 669 switch (cmd) { 670 default: 671 errx(1, "internal wrong cmd"); 672 case RTM_ADD: 673 rtm->rtm_addrs |= RTA_GATEWAY; 674 rtm->rtm_rmx.rmx_expire = expire_time; 675 rtm->rtm_inits = RTV_EXPIRE; 676 rtm->rtm_flags |= (RTF_HOST | RTF_STATIC); 677 dst->sin_other = 0; 678 if (doing_proxy) { 679 if (proxy_only) 680 dst->sin_other = SIN_PROXY; 681 else { 682 rtm->rtm_addrs |= RTA_NETMASK; 683 rtm->rtm_flags &= ~RTF_HOST; 684 } 685 } 686 /* FALLTHROUGH */ 687 case RTM_GET: 688 rtm->rtm_addrs |= RTA_DST; 689 } 690 #define NEXTADDR(w, s) \ 691 if ((s) != NULL && rtm->rtm_addrs & (w)) { \ 692 bcopy((s), cp, sizeof(*(s))); cp += SA_SIZE(s);} 693 694 NEXTADDR(RTA_DST, dst); 695 NEXTADDR(RTA_GATEWAY, sdl); 696 NEXTADDR(RTA_NETMASK, &so_mask); 697 698 rtm->rtm_msglen = cp - (char *)&m_rtmsg; 699 doit: 700 l = rtm->rtm_msglen; 701 rtm->rtm_seq = ++seq; 702 rtm->rtm_type = cmd; 703 if ((rlen = write(s, (char *)&m_rtmsg, l)) < 0) { 704 if (errno != ESRCH || cmd != RTM_DELETE) { 705 warn("writing to routing socket"); 706 return (NULL); 707 } 708 } 709 do { 710 l = read(s, (char *)&m_rtmsg, sizeof(m_rtmsg)); 711 } while (l > 0 && (rtm->rtm_seq != seq || rtm->rtm_pid != pid)); 712 if (l < 0) 713 warn("read from routing socket"); 714 return (rtm); 715 } 716 717 /* 718 * get_ether_addr - get the hardware address of an interface on the 719 * the same subnet as ipaddr. 720 */ 721 #define MAX_IFS 32 722 723 static int 724 get_ether_addr(in_addr_t ipaddr, struct ether_addr *hwaddr) 725 { 726 struct ifreq *ifr, *ifend, *ifp; 727 in_addr_t ina, mask; 728 struct sockaddr_dl *dla; 729 struct ifreq ifreq; 730 struct ifconf ifc; 731 struct ifreq ifs[MAX_IFS]; 732 int sock; 733 int retval = 0; 734 735 sock = socket(AF_INET, SOCK_DGRAM, 0); 736 if (sock < 0) 737 err(1, "socket"); 738 739 ifc.ifc_len = sizeof(ifs); 740 ifc.ifc_req = ifs; 741 if (ioctl(sock, SIOCGIFCONF, &ifc) < 0) { 742 warnx("ioctl(SIOCGIFCONF)"); 743 goto done; 744 } 745 746 #define NEXTIFR(i) \ 747 ((struct ifreq *)((char *)&(i)->ifr_addr \ 748 + MAX((i)->ifr_addr.sa_len, sizeof((i)->ifr_addr))) ) 749 750 /* 751 * Scan through looking for an interface with an Internet 752 * address on the same subnet as `ipaddr'. 753 */ 754 ifend = (struct ifreq *)(ifc.ifc_buf + ifc.ifc_len); 755 for (ifr = ifc.ifc_req; ifr < ifend; ifr = NEXTIFR(ifr) ) { 756 if (ifr->ifr_addr.sa_family != AF_INET) 757 continue; 758 /* XXX can't we use *ifr instead of ifreq ? */ 759 strncpy(ifreq.ifr_name, ifr->ifr_name, 760 sizeof(ifreq.ifr_name)); 761 /* 762 * Check that the interface is up, 763 * and not point-to-point or loopback. 764 */ 765 if (ioctl(sock, SIOCGIFFLAGS, &ifreq) < 0) 766 continue; 767 if ((ifreq.ifr_flags & 768 (IFF_UP|IFF_BROADCAST|IFF_POINTOPOINT| 769 IFF_LOOPBACK|IFF_NOARP)) 770 != (IFF_UP|IFF_BROADCAST)) 771 continue; 772 /* 773 * Get its netmask and check that it's on 774 * the right subnet. 775 */ 776 if (ioctl(sock, SIOCGIFNETMASK, &ifreq) < 0) 777 continue; 778 mask = ((struct sockaddr_in *) 779 &ifreq.ifr_addr)->sin_addr.s_addr; 780 ina = ((struct sockaddr_in *) 781 &ifr->ifr_addr)->sin_addr.s_addr; 782 if ((ipaddr & mask) == (ina & mask)) 783 break; /* ok, we got it! */ 784 } 785 786 if (ifr >= ifend) 787 goto done; 788 789 /* 790 * Now scan through again looking for a link-level address 791 * for this interface. 792 */ 793 ifp = ifr; 794 for (ifr = ifc.ifc_req; ifr < ifend; ifr = NEXTIFR(ifr)) 795 if (strcmp(ifp->ifr_name, ifr->ifr_name) == 0 && 796 ifr->ifr_addr.sa_family == AF_LINK) 797 break; 798 if (ifr >= ifend) 799 goto done; 800 /* 801 * Found the link-level address - copy it out 802 */ 803 dla = (struct sockaddr_dl *) &ifr->ifr_addr; 804 memcpy(hwaddr, LLADDR(dla), dla->sdl_alen); 805 printf("using interface %s for proxy with address ", 806 ifp->ifr_name); 807 printf("%s\n", ether_ntoa(hwaddr)); 808 retval = dla->sdl_alen; 809 done: 810 close(sock); 811 return (retval); 812 } 813