arp.c revision 162795
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 162795 2006-09-29 16:07:44Z ru $"); 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 && !(func == F_DELETE && aflag)) 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 return (1); 354 } else { 355 *ea = *ea1; 356 sdl_m.sdl_alen = ETHER_ADDR_LEN; 357 } 358 } 359 for (;;) { /* try at most twice */ 360 rtm = rtmsg(RTM_GET, dst, &sdl_m); 361 if (rtm == NULL) { 362 warn("%s", host); 363 return (1); 364 } 365 addr = (struct sockaddr_inarp *)(rtm + 1); 366 sdl = (struct sockaddr_dl *)(SA_SIZE(addr) + (char *)addr); 367 if (addr->sin_addr.s_addr != dst->sin_addr.s_addr) 368 break; 369 if (sdl->sdl_family == AF_LINK && 370 (rtm->rtm_flags & RTF_LLINFO) && 371 !(rtm->rtm_flags & RTF_GATEWAY) && 372 valid_type(sdl->sdl_type) ) 373 break; 374 if (doing_proxy == 0) { 375 printf("set: can only proxy for %s\n", host); 376 return (1); 377 } 378 if (dst->sin_other & SIN_PROXY) { 379 printf("set: proxy entry exists for non 802 device\n"); 380 return (1); 381 } 382 dst->sin_other = SIN_PROXY; 383 proxy_only = 1; 384 } 385 386 if (sdl->sdl_family != AF_LINK) { 387 printf("cannot intuit interface index and type for %s\n", host); 388 return (1); 389 } 390 sdl_m.sdl_type = sdl->sdl_type; 391 sdl_m.sdl_index = sdl->sdl_index; 392 return (rtmsg(RTM_ADD, dst, &sdl_m) == NULL); 393} 394 395/* 396 * Display an individual arp entry 397 */ 398static int 399get(char *host) 400{ 401 struct sockaddr_inarp *addr; 402 403 addr = getaddr(host); 404 if (addr == NULL) 405 return (1); 406 if (0 == search(addr->sin_addr.s_addr, print_entry)) { 407 printf("%s (%s) -- no entry", 408 host, inet_ntoa(addr->sin_addr)); 409 if (rifname) 410 printf(" on %s", rifname); 411 printf("\n"); 412 return (1); 413 } 414 return (0); 415} 416 417/* 418 * Delete an arp entry 419 */ 420static int 421delete(char *host, int do_proxy) 422{ 423 struct sockaddr_inarp *addr, *dst; 424 struct rt_msghdr *rtm; 425 struct sockaddr_dl *sdl; 426 427 dst = getaddr(host); 428 if (dst == NULL) 429 return (1); 430 dst->sin_other = do_proxy; 431 for (;;) { /* try twice */ 432 rtm = rtmsg(RTM_GET, dst, NULL); 433 if (rtm == NULL) { 434 warn("%s", host); 435 return (1); 436 } 437 addr = (struct sockaddr_inarp *)(rtm + 1); 438 sdl = (struct sockaddr_dl *)(SA_SIZE(addr) + (char *)addr); 439 if (addr->sin_addr.s_addr == dst->sin_addr.s_addr && 440 sdl->sdl_family == AF_LINK && 441 (rtm->rtm_flags & RTF_LLINFO) && 442 !(rtm->rtm_flags & RTF_GATEWAY) && 443 valid_type(sdl->sdl_type) ) 444 break; /* found it */ 445 if (dst->sin_other & SIN_PROXY) { 446 fprintf(stderr, "delete: cannot locate %s\n",host); 447 return (1); 448 } 449 dst->sin_other = SIN_PROXY; 450 } 451 if (rtmsg(RTM_DELETE, dst, NULL) != NULL) { 452 printf("%s (%s) deleted\n", host, inet_ntoa(addr->sin_addr)); 453 return (0); 454 } 455 return (1); 456} 457 458/* 459 * Search the arp table and do some action on matching entries 460 */ 461static int 462search(u_long addr, action_fn *action) 463{ 464 int mib[6]; 465 size_t needed; 466 char *lim, *buf, *newbuf, *next; 467 struct rt_msghdr *rtm; 468 struct sockaddr_inarp *sin2; 469 struct sockaddr_dl *sdl; 470 char ifname[IF_NAMESIZE]; 471 int st, found_entry = 0; 472 473 mib[0] = CTL_NET; 474 mib[1] = PF_ROUTE; 475 mib[2] = 0; 476 mib[3] = AF_INET; 477 mib[4] = NET_RT_FLAGS; 478 mib[5] = RTF_LLINFO; 479 if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0) 480 err(1, "route-sysctl-estimate"); 481 if (needed == 0) /* empty table */ 482 return 0; 483 buf = NULL; 484 for (;;) { 485 newbuf = realloc(buf, needed); 486 if (newbuf == NULL) { 487 if (buf != NULL) 488 free(buf); 489 errx(1, "could not reallocate memory"); 490 } 491 buf = newbuf; 492 st = sysctl(mib, 6, buf, &needed, NULL, 0); 493 if (st == 0 || errno != ENOMEM) 494 break; 495 needed += needed / 8; 496 } 497 if (st == -1) 498 err(1, "actual retrieval of routing table"); 499 lim = buf + needed; 500 for (next = buf; next < lim; next += rtm->rtm_msglen) { 501 rtm = (struct rt_msghdr *)next; 502 sin2 = (struct sockaddr_inarp *)(rtm + 1); 503 sdl = (struct sockaddr_dl *)((char *)sin2 + SA_SIZE(sin2)); 504 if (rifname && if_indextoname(sdl->sdl_index, ifname) && 505 strcmp(ifname, rifname)) 506 continue; 507 if (addr) { 508 if (addr != sin2->sin_addr.s_addr) 509 continue; 510 found_entry = 1; 511 } 512 (*action)(sdl, sin2, rtm); 513 } 514 free(buf); 515 return (found_entry); 516} 517 518/* 519 * Display an arp entry 520 */ 521static void 522print_entry(struct sockaddr_dl *sdl, 523 struct sockaddr_inarp *addr, struct rt_msghdr *rtm) 524{ 525 const char *host; 526 struct hostent *hp; 527 struct iso88025_sockaddr_dl_data *trld; 528 char ifname[IF_NAMESIZE]; 529 int seg; 530 531 if (nflag == 0) 532 hp = gethostbyaddr((caddr_t)&(addr->sin_addr), 533 sizeof addr->sin_addr, AF_INET); 534 else 535 hp = 0; 536 if (hp) 537 host = hp->h_name; 538 else { 539 host = "?"; 540 if (h_errno == TRY_AGAIN) 541 nflag = 1; 542 } 543 printf("%s (%s) at ", host, inet_ntoa(addr->sin_addr)); 544 if (sdl->sdl_alen) { 545 if ((sdl->sdl_type == IFT_ETHER || 546 sdl->sdl_type == IFT_L2VLAN || 547 sdl->sdl_type == IFT_BRIDGE) && 548 sdl->sdl_alen == ETHER_ADDR_LEN) 549 printf("%s", ether_ntoa((struct ether_addr *)LLADDR(sdl))); 550 else { 551 int n = sdl->sdl_nlen > 0 ? sdl->sdl_nlen + 1 : 0; 552 553 printf("%s", link_ntoa(sdl) + n); 554 } 555 } else 556 printf("(incomplete)"); 557 if (if_indextoname(sdl->sdl_index, ifname) != NULL) 558 printf(" on %s", ifname); 559 if (rtm->rtm_rmx.rmx_expire == 0) 560 printf(" permanent"); 561 if (addr->sin_other & SIN_PROXY) 562 printf(" published (proxy only)"); 563 if (rtm->rtm_addrs & RTA_NETMASK) { 564 addr = (struct sockaddr_inarp *) 565 (SA_SIZE(sdl) + (char *)sdl); 566 if (addr->sin_addr.s_addr == 0xffffffff) 567 printf(" published"); 568 if (addr->sin_len != 8) 569 printf("(weird)"); 570 } 571 switch(sdl->sdl_type) { 572 case IFT_ETHER: 573 printf(" [ethernet]"); 574 break; 575 case IFT_ISO88025: 576 printf(" [token-ring]"); 577 trld = SDL_ISO88025(sdl); 578 if (trld->trld_rcf != 0) { 579 printf(" rt=%x", ntohs(trld->trld_rcf)); 580 for (seg = 0; 581 seg < ((TR_RCF_RIFLEN(trld->trld_rcf) - 2 ) / 2); 582 seg++) 583 printf(":%x", ntohs(*(trld->trld_route[seg]))); 584 } 585 break; 586 case IFT_FDDI: 587 printf(" [fddi]"); 588 break; 589 case IFT_ATM: 590 printf(" [atm]"); 591 break; 592 case IFT_L2VLAN: 593 printf(" [vlan]"); 594 break; 595 case IFT_IEEE1394: 596 printf(" [firewire]"); 597 break; 598 case IFT_BRIDGE: 599 printf(" [bridge]"); 600 break; 601 default: 602 break; 603 } 604 605 printf("\n"); 606 607} 608 609/* 610 * Nuke an arp entry 611 */ 612static void 613nuke_entry(struct sockaddr_dl *sdl __unused, 614 struct sockaddr_inarp *addr, struct rt_msghdr *rtm __unused) 615{ 616 char ip[20]; 617 618 snprintf(ip, sizeof(ip), "%s", inet_ntoa(addr->sin_addr)); 619 (void)delete(ip, 0); 620} 621 622static void 623usage(void) 624{ 625 fprintf(stderr, "%s\n%s\n%s\n%s\n%s\n%s\n%s\n", 626 "usage: arp [-n] [-i interface] hostname", 627 " arp [-n] [-i interface] -a", 628 " arp -d hostname [pub]", 629 " arp -d [-i interface] -a", 630 " arp -s hostname ether_addr [temp] [pub [only]]", 631 " arp -S hostname ether_addr [temp] [pub [only]]", 632 " arp -f filename"); 633 exit(1); 634} 635 636static struct rt_msghdr * 637rtmsg(int cmd, struct sockaddr_inarp *dst, struct sockaddr_dl *sdl) 638{ 639 static int seq; 640 int rlen; 641 int l; 642 struct sockaddr_in so_mask; 643 static int s = -1; 644 static pid_t pid; 645 646 static struct { 647 struct rt_msghdr m_rtm; 648 char m_space[512]; 649 } m_rtmsg; 650 651 struct rt_msghdr *rtm = &m_rtmsg.m_rtm; 652 char *cp = m_rtmsg.m_space; 653 654 if (s < 0) { /* first time: open socket, get pid */ 655 s = socket(PF_ROUTE, SOCK_RAW, 0); 656 if (s < 0) 657 err(1, "socket"); 658 pid = getpid(); 659 } 660 bzero(&so_mask, sizeof(so_mask)); 661 so_mask.sin_len = 8; 662 so_mask.sin_addr.s_addr = 0xffffffff; 663 664 errno = 0; 665 /* 666 * XXX RTM_DELETE relies on a previous RTM_GET to fill the buffer 667 * appropriately. 668 */ 669 if (cmd == RTM_DELETE) 670 goto doit; 671 bzero((char *)&m_rtmsg, sizeof(m_rtmsg)); 672 rtm->rtm_flags = flags; 673 rtm->rtm_version = RTM_VERSION; 674 675 switch (cmd) { 676 default: 677 errx(1, "internal wrong cmd"); 678 case RTM_ADD: 679 rtm->rtm_addrs |= RTA_GATEWAY; 680 rtm->rtm_rmx.rmx_expire = expire_time; 681 rtm->rtm_inits = RTV_EXPIRE; 682 rtm->rtm_flags |= (RTF_HOST | RTF_STATIC); 683 dst->sin_other = 0; 684 if (doing_proxy) { 685 if (proxy_only) 686 dst->sin_other = SIN_PROXY; 687 else { 688 rtm->rtm_addrs |= RTA_NETMASK; 689 rtm->rtm_flags &= ~RTF_HOST; 690 } 691 } 692 /* FALLTHROUGH */ 693 case RTM_GET: 694 rtm->rtm_addrs |= RTA_DST; 695 } 696#define NEXTADDR(w, s) \ 697 if ((s) != NULL && rtm->rtm_addrs & (w)) { \ 698 bcopy((s), cp, sizeof(*(s))); cp += SA_SIZE(s);} 699 700 NEXTADDR(RTA_DST, dst); 701 NEXTADDR(RTA_GATEWAY, sdl); 702 NEXTADDR(RTA_NETMASK, &so_mask); 703 704 rtm->rtm_msglen = cp - (char *)&m_rtmsg; 705doit: 706 l = rtm->rtm_msglen; 707 rtm->rtm_seq = ++seq; 708 rtm->rtm_type = cmd; 709 if ((rlen = write(s, (char *)&m_rtmsg, l)) < 0) { 710 if (errno != ESRCH || cmd != RTM_DELETE) { 711 warn("writing to routing socket"); 712 return (NULL); 713 } 714 } 715 do { 716 l = read(s, (char *)&m_rtmsg, sizeof(m_rtmsg)); 717 } while (l > 0 && (rtm->rtm_seq != seq || rtm->rtm_pid != pid)); 718 if (l < 0) 719 warn("read from routing socket"); 720 return (rtm); 721} 722 723/* 724 * get_ether_addr - get the hardware address of an interface on the 725 * the same subnet as ipaddr. 726 */ 727#define MAX_IFS 32 728 729static int 730get_ether_addr(in_addr_t ipaddr, struct ether_addr *hwaddr) 731{ 732 struct ifreq *ifr, *ifend, *ifp; 733 in_addr_t ina, mask; 734 struct sockaddr_dl *dla; 735 struct ifreq ifreq; 736 struct ifconf ifc; 737 struct ifreq ifs[MAX_IFS]; 738 int sock; 739 int retval = 0; 740 741 sock = socket(AF_INET, SOCK_DGRAM, 0); 742 if (sock < 0) 743 err(1, "socket"); 744 745 ifc.ifc_len = sizeof(ifs); 746 ifc.ifc_req = ifs; 747 if (ioctl(sock, SIOCGIFCONF, &ifc) < 0) { 748 warnx("ioctl(SIOCGIFCONF)"); 749 goto done; 750 } 751 752#define NEXTIFR(i) \ 753 ((struct ifreq *)((char *)&(i)->ifr_addr \ 754 + MAX((i)->ifr_addr.sa_len, sizeof((i)->ifr_addr))) ) 755 756 /* 757 * Scan through looking for an interface with an Internet 758 * address on the same subnet as `ipaddr'. 759 */ 760 ifend = (struct ifreq *)(ifc.ifc_buf + ifc.ifc_len); 761 for (ifr = ifc.ifc_req; ifr < ifend; ifr = NEXTIFR(ifr) ) { 762 if (ifr->ifr_addr.sa_family != AF_INET) 763 continue; 764 /* XXX can't we use *ifr instead of ifreq ? */ 765 strncpy(ifreq.ifr_name, ifr->ifr_name, 766 sizeof(ifreq.ifr_name)); 767 /* 768 * Check that the interface is up, 769 * and not point-to-point or loopback. 770 */ 771 if (ioctl(sock, SIOCGIFFLAGS, &ifreq) < 0) 772 continue; 773 if ((ifreq.ifr_flags & 774 (IFF_UP|IFF_BROADCAST|IFF_POINTOPOINT| 775 IFF_LOOPBACK|IFF_NOARP)) 776 != (IFF_UP|IFF_BROADCAST)) 777 continue; 778 /* 779 * Get its netmask and check that it's on 780 * the right subnet. 781 */ 782 if (ioctl(sock, SIOCGIFNETMASK, &ifreq) < 0) 783 continue; 784 mask = ((struct sockaddr_in *) 785 &ifreq.ifr_addr)->sin_addr.s_addr; 786 ina = ((struct sockaddr_in *) 787 &ifr->ifr_addr)->sin_addr.s_addr; 788 if ((ipaddr & mask) == (ina & mask)) 789 break; /* ok, we got it! */ 790 } 791 792 if (ifr >= ifend) 793 goto done; 794 795 /* 796 * Now scan through again looking for a link-level address 797 * for this interface. 798 */ 799 ifp = ifr; 800 for (ifr = ifc.ifc_req; ifr < ifend; ifr = NEXTIFR(ifr)) 801 if (strcmp(ifp->ifr_name, ifr->ifr_name) == 0 && 802 ifr->ifr_addr.sa_family == AF_LINK) 803 break; 804 if (ifr >= ifend) 805 goto done; 806 /* 807 * Found the link-level address - copy it out 808 */ 809 dla = (struct sockaddr_dl *) &ifr->ifr_addr; 810 memcpy(hwaddr, LLADDR(dla), dla->sdl_alen); 811 printf("using interface %s for proxy with address ", 812 ifp->ifr_name); 813 printf("%s\n", ether_ntoa(hwaddr)); 814 retval = dla->sdl_alen; 815done: 816 close(sock); 817 return (retval); 818} 819