arp.c revision 151989
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 35static 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 41static 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: head/usr.sbin/arp/arp.c 151989 2005-11-03 00:56:43Z thompsa $"); 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 83typedef void (action_fn)(struct sockaddr_dl *sdl, 84 struct sockaddr_inarp *s_in, struct rt_msghdr *rtm); 85 86static int search(u_long addr, action_fn *action); 87static action_fn print_entry; 88static action_fn nuke_entry; 89 90static int delete(char *host, int do_proxy); 91static void usage(void); 92static int set(int argc, char **argv); 93static int get(char *host); 94static int file(char *name); 95static struct rt_msghdr *rtmsg(int cmd, 96 struct sockaddr_inarp *dst, struct sockaddr_dl *sdl); 97static int get_ether_addr(in_addr_t ipaddr, struct ether_addr *hwaddr); 98static struct sockaddr_inarp *getaddr(char *host); 99static int valid_type(int type); 100 101static int nflag; /* no reverse dns lookups */ 102static char *rifname; 103 104static 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 115int 116main(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 */ 212static int 213file(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 */ 252static struct sockaddr_inarp * 253getaddr(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 */ 276static int 277valid_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 case IFT_BRIDGE: 288 return (1); 289 default: 290 return (0); 291 } 292} 293 294/* 295 * Set an individual arp entry 296 */ 297static int 298set(int argc, char **argv) 299{ 300 struct sockaddr_inarp *addr; 301 struct sockaddr_inarp *dst; /* what are we looking for */ 302 struct sockaddr_dl *sdl; 303 struct rt_msghdr *rtm; 304 struct ether_addr *ea; 305 char *host = argv[0], *eaddr = argv[1]; 306 struct sockaddr_dl sdl_m; 307 308 argc -= 2; 309 argv += 2; 310 311 bzero(&sdl_m, sizeof(sdl_m)); 312 sdl_m.sdl_len = sizeof(sdl_m); 313 sdl_m.sdl_family = AF_LINK; 314 315 dst = getaddr(host); 316 if (dst == NULL) 317 return (1); 318 doing_proxy = flags = proxy_only = expire_time = 0; 319 while (argc-- > 0) { 320 if (strncmp(argv[0], "temp", 4) == 0) { 321 struct timeval tv; 322 gettimeofday(&tv, 0); 323 expire_time = tv.tv_sec + 20 * 60; 324 } 325 else if (strncmp(argv[0], "pub", 3) == 0) { 326 flags |= RTF_ANNOUNCE; 327 doing_proxy = 1; 328 if (argc && strncmp(argv[1], "only", 3) == 0) { 329 proxy_only = 1; 330 dst->sin_other = SIN_PROXY; 331 argc--; argv++; 332 } 333 } else if (strncmp(argv[0], "trail", 5) == 0) { 334 /* XXX deprecated and undocumented feature */ 335 printf("%s: Sending trailers is no longer supported\n", 336 host); 337 } 338 argv++; 339 } 340 ea = (struct ether_addr *)LLADDR(&sdl_m); 341 if (doing_proxy && !strcmp(eaddr, "auto")) { 342 if (!get_ether_addr(dst->sin_addr.s_addr, ea)) { 343 printf("no interface found for %s\n", 344 inet_ntoa(dst->sin_addr)); 345 return (1); 346 } 347 sdl_m.sdl_alen = ETHER_ADDR_LEN; 348 } else { 349 struct ether_addr *ea1 = ether_aton(eaddr); 350 351 if (ea1 == NULL) 352 warnx("invalid Ethernet address '%s'", eaddr); 353 else { 354 *ea = *ea1; 355 sdl_m.sdl_alen = ETHER_ADDR_LEN; 356 } 357 } 358 for (;;) { /* try at most twice */ 359 rtm = rtmsg(RTM_GET, dst, &sdl_m); 360 if (rtm == NULL) { 361 warn("%s", host); 362 return (1); 363 } 364 addr = (struct sockaddr_inarp *)(rtm + 1); 365 sdl = (struct sockaddr_dl *)(SA_SIZE(addr) + (char *)addr); 366 if (addr->sin_addr.s_addr != dst->sin_addr.s_addr) 367 break; 368 if (sdl->sdl_family == AF_LINK && 369 (rtm->rtm_flags & RTF_LLINFO) && 370 !(rtm->rtm_flags & RTF_GATEWAY) && 371 valid_type(sdl->sdl_type) ) 372 break; 373 if (doing_proxy == 0) { 374 printf("set: can only proxy for %s\n", host); 375 return (1); 376 } 377 if (dst->sin_other & SIN_PROXY) { 378 printf("set: proxy entry exists for non 802 device\n"); 379 return (1); 380 } 381 dst->sin_other = SIN_PROXY; 382 proxy_only = 1; 383 } 384 385 if (sdl->sdl_family != AF_LINK) { 386 printf("cannot intuit interface index and type for %s\n", host); 387 return (1); 388 } 389 sdl_m.sdl_type = sdl->sdl_type; 390 sdl_m.sdl_index = sdl->sdl_index; 391 return (rtmsg(RTM_ADD, dst, &sdl_m) == NULL); 392} 393 394/* 395 * Display an individual arp entry 396 */ 397static int 398get(char *host) 399{ 400 struct sockaddr_inarp *addr; 401 402 addr = getaddr(host); 403 if (addr == NULL) 404 return (1); 405 if (0 == search(addr->sin_addr.s_addr, print_entry)) { 406 printf("%s (%s) -- no entry", 407 host, inet_ntoa(addr->sin_addr)); 408 if (rifname) 409 printf(" on %s", rifname); 410 printf("\n"); 411 return (1); 412 } 413 return (0); 414} 415 416/* 417 * Delete an arp entry 418 */ 419static int 420delete(char *host, int do_proxy) 421{ 422 struct sockaddr_inarp *addr, *dst; 423 struct rt_msghdr *rtm; 424 struct sockaddr_dl *sdl; 425 426 dst = getaddr(host); 427 if (dst == NULL) 428 return (1); 429 dst->sin_other = do_proxy; 430 for (;;) { /* try twice */ 431 rtm = rtmsg(RTM_GET, dst, NULL); 432 if (rtm == NULL) { 433 warn("%s", host); 434 return (1); 435 } 436 addr = (struct sockaddr_inarp *)(rtm + 1); 437 sdl = (struct sockaddr_dl *)(SA_SIZE(addr) + (char *)addr); 438 if (addr->sin_addr.s_addr == dst->sin_addr.s_addr && 439 sdl->sdl_family == AF_LINK && 440 (rtm->rtm_flags & RTF_LLINFO) && 441 !(rtm->rtm_flags & RTF_GATEWAY) && 442 valid_type(sdl->sdl_type) ) 443 break; /* found it */ 444 if (dst->sin_other & SIN_PROXY) { 445 fprintf(stderr, "delete: cannot locate %s\n",host); 446 return (1); 447 } 448 dst->sin_other = SIN_PROXY; 449 } 450 if (rtmsg(RTM_DELETE, dst, NULL) != NULL) { 451 printf("%s (%s) deleted\n", host, inet_ntoa(addr->sin_addr)); 452 return (0); 453 } 454 return (1); 455} 456 457/* 458 * Search the arp table and do some action on matching entries 459 */ 460static int 461search(u_long addr, action_fn *action) 462{ 463 int mib[6]; 464 size_t needed; 465 char *lim, *buf, *newbuf, *next; 466 struct rt_msghdr *rtm; 467 struct sockaddr_inarp *sin2; 468 struct sockaddr_dl *sdl; 469 char ifname[IF_NAMESIZE]; 470 int st, found_entry = 0; 471 472 mib[0] = CTL_NET; 473 mib[1] = PF_ROUTE; 474 mib[2] = 0; 475 mib[3] = AF_INET; 476 mib[4] = NET_RT_FLAGS; 477 mib[5] = RTF_LLINFO; 478 if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0) 479 err(1, "route-sysctl-estimate"); 480 if (needed == 0) /* empty table */ 481 return 0; 482 buf = NULL; 483 for (;;) { 484 newbuf = realloc(buf, needed); 485 if (newbuf == NULL) { 486 if (buf != NULL) 487 free(buf); 488 errx(1, "could not reallocate memory"); 489 } 490 buf = newbuf; 491 st = sysctl(mib, 6, buf, &needed, NULL, 0); 492 if (st == 0 || errno != ENOMEM) 493 break; 494 needed += needed / 8; 495 } 496 if (st == -1) 497 err(1, "actual retrieval of routing table"); 498 lim = buf + needed; 499 for (next = buf; next < lim; next += rtm->rtm_msglen) { 500 rtm = (struct rt_msghdr *)next; 501 sin2 = (struct sockaddr_inarp *)(rtm + 1); 502 sdl = (struct sockaddr_dl *)((char *)sin2 + SA_SIZE(sin2)); 503 if (rifname && if_indextoname(sdl->sdl_index, ifname) && 504 strcmp(ifname, rifname)) 505 continue; 506 if (addr) { 507 if (addr != sin2->sin_addr.s_addr) 508 continue; 509 found_entry = 1; 510 } 511 (*action)(sdl, sin2, rtm); 512 } 513 free(buf); 514 return (found_entry); 515} 516 517/* 518 * Display an arp entry 519 */ 520static void 521print_entry(struct sockaddr_dl *sdl, 522 struct sockaddr_inarp *addr, struct rt_msghdr *rtm) 523{ 524 const char *host; 525 struct hostent *hp; 526 struct iso88025_sockaddr_dl_data *trld; 527 char ifname[IF_NAMESIZE]; 528 int seg; 529 530 if (nflag == 0) 531 hp = gethostbyaddr((caddr_t)&(addr->sin_addr), 532 sizeof addr->sin_addr, AF_INET); 533 else 534 hp = 0; 535 if (hp) 536 host = hp->h_name; 537 else { 538 host = "?"; 539 if (h_errno == TRY_AGAIN) 540 nflag = 1; 541 } 542 printf("%s (%s) at ", host, inet_ntoa(addr->sin_addr)); 543 if (sdl->sdl_alen) { 544 if ((sdl->sdl_type == IFT_ETHER || 545 sdl->sdl_type == IFT_L2VLAN || 546 sdl->sdl_type == IFT_BRIDGE) && 547 sdl->sdl_alen == ETHER_ADDR_LEN) 548 printf("%s", ether_ntoa((struct ether_addr *)LLADDR(sdl))); 549 else { 550 int n = sdl->sdl_nlen > 0 ? sdl->sdl_nlen + 1 : 0; 551 552 printf("%s", link_ntoa(sdl) + n); 553 } 554 } else 555 printf("(incomplete)"); 556 if (if_indextoname(sdl->sdl_index, ifname) != NULL) 557 printf(" on %s", ifname); 558 if (rtm->rtm_rmx.rmx_expire == 0) 559 printf(" permanent"); 560 if (addr->sin_other & SIN_PROXY) 561 printf(" published (proxy only)"); 562 if (rtm->rtm_addrs & RTA_NETMASK) { 563 addr = (struct sockaddr_inarp *) 564 (SA_SIZE(sdl) + (char *)sdl); 565 if (addr->sin_addr.s_addr == 0xffffffff) 566 printf(" published"); 567 if (addr->sin_len != 8) 568 printf("(weird)"); 569 } 570 switch(sdl->sdl_type) { 571 case IFT_ETHER: 572 printf(" [ethernet]"); 573 break; 574 case IFT_ISO88025: 575 printf(" [token-ring]"); 576 trld = SDL_ISO88025(sdl); 577 if (trld->trld_rcf != 0) { 578 printf(" rt=%x", ntohs(trld->trld_rcf)); 579 for (seg = 0; 580 seg < ((TR_RCF_RIFLEN(trld->trld_rcf) - 2 ) / 2); 581 seg++) 582 printf(":%x", ntohs(*(trld->trld_route[seg]))); 583 } 584 break; 585 case IFT_FDDI: 586 printf(" [fddi]"); 587 break; 588 case IFT_ATM: 589 printf(" [atm]"); 590 break; 591 case IFT_L2VLAN: 592 printf(" [vlan]"); 593 break; 594 case IFT_IEEE1394: 595 printf(" [firewire]"); 596 break; 597 case IFT_BRIDGE: 598 printf(" [bridge]"); 599 break; 600 default: 601 break; 602 } 603 604 printf("\n"); 605 606} 607 608/* 609 * Nuke an arp entry 610 */ 611static void 612nuke_entry(struct sockaddr_dl *sdl __unused, 613 struct sockaddr_inarp *addr, struct rt_msghdr *rtm __unused) 614{ 615 char ip[20]; 616 617 snprintf(ip, sizeof(ip), "%s", inet_ntoa(addr->sin_addr)); 618 (void)delete(ip, 0); 619} 620 621static void 622usage(void) 623{ 624 fprintf(stderr, "%s\n%s\n%s\n%s\n%s\n%s\n%s\n", 625 "usage: arp [-n] [-i interface] hostname", 626 " arp [-n] [-i interface] -a", 627 " arp -d hostname [pub]", 628 " arp -d -a", 629 " arp -s hostname ether_addr [temp] [pub]", 630 " arp -S hostname ether_addr [temp] [pub]", 631 " arp -f filename"); 632 exit(1); 633} 634 635static struct rt_msghdr * 636rtmsg(int cmd, struct sockaddr_inarp *dst, struct sockaddr_dl *sdl) 637{ 638 static int seq; 639 int rlen; 640 int l; 641 struct sockaddr_in so_mask; 642 static int s = -1; 643 static pid_t pid; 644 645 static struct { 646 struct rt_msghdr m_rtm; 647 char m_space[512]; 648 } m_rtmsg; 649 650 struct rt_msghdr *rtm = &m_rtmsg.m_rtm; 651 char *cp = m_rtmsg.m_space; 652 653 if (s < 0) { /* first time: open socket, get pid */ 654 s = socket(PF_ROUTE, SOCK_RAW, 0); 655 if (s < 0) 656 err(1, "socket"); 657 pid = getpid(); 658 } 659 bzero(&so_mask, sizeof(so_mask)); 660 so_mask.sin_len = 8; 661 so_mask.sin_addr.s_addr = 0xffffffff; 662 663 errno = 0; 664 /* 665 * XXX RTM_DELETE relies on a previous RTM_GET to fill the buffer 666 * appropriately. 667 */ 668 if (cmd == RTM_DELETE) 669 goto doit; 670 bzero((char *)&m_rtmsg, sizeof(m_rtmsg)); 671 rtm->rtm_flags = flags; 672 rtm->rtm_version = RTM_VERSION; 673 674 switch (cmd) { 675 default: 676 errx(1, "internal wrong cmd"); 677 case RTM_ADD: 678 rtm->rtm_addrs |= RTA_GATEWAY; 679 rtm->rtm_rmx.rmx_expire = expire_time; 680 rtm->rtm_inits = RTV_EXPIRE; 681 rtm->rtm_flags |= (RTF_HOST | RTF_STATIC); 682 dst->sin_other = 0; 683 if (doing_proxy) { 684 if (proxy_only) 685 dst->sin_other = SIN_PROXY; 686 else { 687 rtm->rtm_addrs |= RTA_NETMASK; 688 rtm->rtm_flags &= ~RTF_HOST; 689 } 690 } 691 /* FALLTHROUGH */ 692 case RTM_GET: 693 rtm->rtm_addrs |= RTA_DST; 694 } 695#define NEXTADDR(w, s) \ 696 if ((s) != NULL && rtm->rtm_addrs & (w)) { \ 697 bcopy((s), cp, sizeof(*(s))); cp += SA_SIZE(s);} 698 699 NEXTADDR(RTA_DST, dst); 700 NEXTADDR(RTA_GATEWAY, sdl); 701 NEXTADDR(RTA_NETMASK, &so_mask); 702 703 rtm->rtm_msglen = cp - (char *)&m_rtmsg; 704doit: 705 l = rtm->rtm_msglen; 706 rtm->rtm_seq = ++seq; 707 rtm->rtm_type = cmd; 708 if ((rlen = write(s, (char *)&m_rtmsg, l)) < 0) { 709 if (errno != ESRCH || cmd != RTM_DELETE) { 710 warn("writing to routing socket"); 711 return (NULL); 712 } 713 } 714 do { 715 l = read(s, (char *)&m_rtmsg, sizeof(m_rtmsg)); 716 } while (l > 0 && (rtm->rtm_seq != seq || rtm->rtm_pid != pid)); 717 if (l < 0) 718 warn("read from routing socket"); 719 return (rtm); 720} 721 722/* 723 * get_ether_addr - get the hardware address of an interface on the 724 * the same subnet as ipaddr. 725 */ 726#define MAX_IFS 32 727 728static int 729get_ether_addr(in_addr_t ipaddr, struct ether_addr *hwaddr) 730{ 731 struct ifreq *ifr, *ifend, *ifp; 732 in_addr_t ina, mask; 733 struct sockaddr_dl *dla; 734 struct ifreq ifreq; 735 struct ifconf ifc; 736 struct ifreq ifs[MAX_IFS]; 737 int sock; 738 int retval = 0; 739 740 sock = socket(AF_INET, SOCK_DGRAM, 0); 741 if (sock < 0) 742 err(1, "socket"); 743 744 ifc.ifc_len = sizeof(ifs); 745 ifc.ifc_req = ifs; 746 if (ioctl(sock, SIOCGIFCONF, &ifc) < 0) { 747 warnx("ioctl(SIOCGIFCONF)"); 748 goto done; 749 } 750 751#define NEXTIFR(i) \ 752 ((struct ifreq *)((char *)&(i)->ifr_addr \ 753 + MAX((i)->ifr_addr.sa_len, sizeof((i)->ifr_addr))) ) 754 755 /* 756 * Scan through looking for an interface with an Internet 757 * address on the same subnet as `ipaddr'. 758 */ 759 ifend = (struct ifreq *)(ifc.ifc_buf + ifc.ifc_len); 760 for (ifr = ifc.ifc_req; ifr < ifend; ifr = NEXTIFR(ifr) ) { 761 if (ifr->ifr_addr.sa_family != AF_INET) 762 continue; 763 /* XXX can't we use *ifr instead of ifreq ? */ 764 strncpy(ifreq.ifr_name, ifr->ifr_name, 765 sizeof(ifreq.ifr_name)); 766 /* 767 * Check that the interface is up, 768 * and not point-to-point or loopback. 769 */ 770 if (ioctl(sock, SIOCGIFFLAGS, &ifreq) < 0) 771 continue; 772 if ((ifreq.ifr_flags & 773 (IFF_UP|IFF_BROADCAST|IFF_POINTOPOINT| 774 IFF_LOOPBACK|IFF_NOARP)) 775 != (IFF_UP|IFF_BROADCAST)) 776 continue; 777 /* 778 * Get its netmask and check that it's on 779 * the right subnet. 780 */ 781 if (ioctl(sock, SIOCGIFNETMASK, &ifreq) < 0) 782 continue; 783 mask = ((struct sockaddr_in *) 784 &ifreq.ifr_addr)->sin_addr.s_addr; 785 ina = ((struct sockaddr_in *) 786 &ifr->ifr_addr)->sin_addr.s_addr; 787 if ((ipaddr & mask) == (ina & mask)) 788 break; /* ok, we got it! */ 789 } 790 791 if (ifr >= ifend) 792 goto done; 793 794 /* 795 * Now scan through again looking for a link-level address 796 * for this interface. 797 */ 798 ifp = ifr; 799 for (ifr = ifc.ifc_req; ifr < ifend; ifr = NEXTIFR(ifr)) 800 if (strcmp(ifp->ifr_name, ifr->ifr_name) == 0 && 801 ifr->ifr_addr.sa_family == AF_LINK) 802 break; 803 if (ifr >= ifend) 804 goto done; 805 /* 806 * Found the link-level address - copy it out 807 */ 808 dla = (struct sockaddr_dl *) &ifr->ifr_addr; 809 memcpy(hwaddr, LLADDR(dla), dla->sdl_alen); 810 printf("using interface %s for proxy with address ", 811 ifp->ifr_name); 812 printf("%s\n", ether_ntoa(hwaddr)); 813 retval = dla->sdl_alen; 814done: 815 close(sock); 816 return (retval); 817} 818