arp.c revision 186485
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 186485 2008-12-25 06:44:19Z trhodes $"); 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, sizeof(line), 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 } 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], "blackhole", 9) == 0) { 333 if (flags & RTF_REJECT) { 334 printf("Choose one of blackhole or reject, not both.\n"); 335 } 336 flags |= RTF_BLACKHOLE; 337 } else if (strncmp(argv[0], "reject", 6) == 0) { 338 if (flags & RTF_BLACKHOLE) { 339 printf("Choose one of blackhole or reject, not both.\n"); 340 } 341 flags |= RTF_REJECT; 342 } else if (strncmp(argv[0], "trail", 5) == 0) { 343 /* XXX deprecated and undocumented feature */ 344 printf("%s: Sending trailers is no longer supported\n", 345 host); 346 } 347 argv++; 348 } 349 ea = (struct ether_addr *)LLADDR(&sdl_m); 350 if (doing_proxy && !strcmp(eaddr, "auto")) { 351 if (!get_ether_addr(dst->sin_addr.s_addr, ea)) { 352 printf("no interface found for %s\n", 353 inet_ntoa(dst->sin_addr)); 354 return (1); 355 } 356 sdl_m.sdl_alen = ETHER_ADDR_LEN; 357 } else { 358 struct ether_addr *ea1 = ether_aton(eaddr); 359 360 if (ea1 == NULL) { 361 warnx("invalid Ethernet address '%s'", eaddr); 362 return (1); 363 } else { 364 *ea = *ea1; 365 sdl_m.sdl_alen = ETHER_ADDR_LEN; 366 } 367 } 368 for (;;) { /* try at most twice */ 369 rtm = rtmsg(RTM_GET, dst, &sdl_m); 370 if (rtm == NULL) { 371 warn("%s", host); 372 return (1); 373 } 374 addr = (struct sockaddr_inarp *)(rtm + 1); 375 sdl = (struct sockaddr_dl *)(SA_SIZE(addr) + (char *)addr); 376 if (addr->sin_addr.s_addr != dst->sin_addr.s_addr) 377 break; 378 if (sdl->sdl_family == AF_LINK && 379 !(rtm->rtm_flags & RTF_GATEWAY) && 380 valid_type(sdl->sdl_type) ) 381 break; 382 if (doing_proxy == 0) { 383 printf("set: can only proxy for %s\n", host); 384 return (1); 385 } 386 if (dst->sin_other & SIN_PROXY) { 387 printf("set: proxy entry exists for non 802 device\n"); 388 return (1); 389 } 390 dst->sin_other = SIN_PROXY; 391 proxy_only = 1; 392 } 393 394 if (sdl->sdl_family != AF_LINK) { 395 printf("cannot intuit interface index and type for %s\n", host); 396 return (1); 397 } 398 sdl_m.sdl_type = sdl->sdl_type; 399 sdl_m.sdl_index = sdl->sdl_index; 400 return (rtmsg(RTM_ADD, dst, &sdl_m) == NULL); 401} 402 403/* 404 * Display an individual arp entry 405 */ 406static int 407get(char *host) 408{ 409 struct sockaddr_inarp *addr; 410 411 addr = getaddr(host); 412 if (addr == NULL) 413 return (1); 414 if (0 == search(addr->sin_addr.s_addr, print_entry)) { 415 printf("%s (%s) -- no entry", 416 host, inet_ntoa(addr->sin_addr)); 417 if (rifname) 418 printf(" on %s", rifname); 419 printf("\n"); 420 return (1); 421 } 422 return (0); 423} 424 425/* 426 * Delete an arp entry 427 */ 428static int 429delete(char *host, int do_proxy) 430{ 431 struct sockaddr_inarp *addr, *dst; 432 struct rt_msghdr *rtm; 433 struct sockaddr_dl *sdl; 434 struct sockaddr_dl sdl_m; 435 436 dst = getaddr(host); 437 if (dst == NULL) 438 return (1); 439 dst->sin_other = do_proxy; 440 441 /* 442 * setup the data structure to notify the kernel 443 * it is the ARP entry the RTM_GET is interested 444 * in 445 */ 446 bzero(&sdl_m, sizeof(sdl_m)); 447 sdl_m.sdl_len = sizeof(sdl_m); 448 sdl_m.sdl_family = AF_LINK; 449 450 for (;;) { /* try twice */ 451 rtm = rtmsg(RTM_GET, dst, &sdl_m); 452 if (rtm == NULL) { 453 warn("%s", host); 454 return (1); 455 } 456 addr = (struct sockaddr_inarp *)(rtm + 1); 457 sdl = (struct sockaddr_dl *)(SA_SIZE(addr) + (char *)addr); 458 459 /* 460 * With the new L2/L3 restructure, the route 461 * returned is a prefix route. The important 462 * piece of information from the previous 463 * RTM_GET is the interface index. In the 464 * case of ECMP, the kernel will traverse 465 * the route group for the given entry. 466 */ 467 if (sdl->sdl_family == AF_LINK && 468 !(rtm->rtm_flags & RTF_GATEWAY) && 469 valid_type(sdl->sdl_type) ) { 470 addr->sin_addr.s_addr = dst->sin_addr.s_addr; 471 break; 472 } 473 474 if (dst->sin_other & SIN_PROXY) { 475 fprintf(stderr, "delete: cannot locate %s\n",host); 476 return (1); 477 } 478 dst->sin_other = SIN_PROXY; 479 } 480 if (rtmsg(RTM_DELETE, dst, NULL) != NULL) { 481 printf("%s (%s) deleted\n", host, inet_ntoa(addr->sin_addr)); 482 return (0); 483 } 484 return (1); 485} 486 487/* 488 * Search the arp table and do some action on matching entries 489 */ 490static int 491search(u_long addr, action_fn *action) 492{ 493 int mib[6]; 494 size_t needed; 495 char *lim, *buf, *newbuf, *next; 496 struct rt_msghdr *rtm; 497 struct sockaddr_inarp *sin2; 498 struct sockaddr_dl *sdl; 499 char ifname[IF_NAMESIZE]; 500 int st, found_entry = 0; 501 502 mib[0] = CTL_NET; 503 mib[1] = PF_ROUTE; 504 mib[2] = 0; 505 mib[3] = AF_INET; 506 mib[4] = NET_RT_FLAGS; 507#ifdef RTF_LLINFO 508 mib[5] = RTF_LLINFO; 509#else 510 mib[5] = 0; 511#endif 512 if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0) 513 err(1, "route-sysctl-estimate"); 514 if (needed == 0) /* empty table */ 515 return 0; 516 buf = NULL; 517 for (;;) { 518 newbuf = realloc(buf, needed); 519 if (newbuf == NULL) { 520 if (buf != NULL) 521 free(buf); 522 errx(1, "could not reallocate memory"); 523 } 524 buf = newbuf; 525 st = sysctl(mib, 6, buf, &needed, NULL, 0); 526 if (st == 0 || errno != ENOMEM) 527 break; 528 needed += needed / 8; 529 } 530 if (st == -1) 531 err(1, "actual retrieval of routing table"); 532 lim = buf + needed; 533 for (next = buf; next < lim; next += rtm->rtm_msglen) { 534 rtm = (struct rt_msghdr *)next; 535 sin2 = (struct sockaddr_inarp *)(rtm + 1); 536 sdl = (struct sockaddr_dl *)((char *)sin2 + SA_SIZE(sin2)); 537 if (rifname && if_indextoname(sdl->sdl_index, ifname) && 538 strcmp(ifname, rifname)) 539 continue; 540 if (addr) { 541 if (addr != sin2->sin_addr.s_addr) 542 continue; 543 found_entry = 1; 544 } 545 (*action)(sdl, sin2, rtm); 546 } 547 free(buf); 548 return (found_entry); 549} 550 551/* 552 * Display an arp entry 553 */ 554static void 555print_entry(struct sockaddr_dl *sdl, 556 struct sockaddr_inarp *addr, struct rt_msghdr *rtm) 557{ 558 const char *host; 559 struct hostent *hp; 560 struct iso88025_sockaddr_dl_data *trld; 561 char ifname[IF_NAMESIZE]; 562 int seg; 563 564 if (nflag == 0) 565 hp = gethostbyaddr((caddr_t)&(addr->sin_addr), 566 sizeof addr->sin_addr, AF_INET); 567 else 568 hp = 0; 569 if (hp) 570 host = hp->h_name; 571 else { 572 host = "?"; 573 if (h_errno == TRY_AGAIN) 574 nflag = 1; 575 } 576 printf("%s (%s) at ", host, inet_ntoa(addr->sin_addr)); 577 if (sdl->sdl_alen) { 578 if ((sdl->sdl_type == IFT_ETHER || 579 sdl->sdl_type == IFT_L2VLAN || 580 sdl->sdl_type == IFT_BRIDGE) && 581 sdl->sdl_alen == ETHER_ADDR_LEN) 582 printf("%s", ether_ntoa((struct ether_addr *)LLADDR(sdl))); 583 else { 584 int n = sdl->sdl_nlen > 0 ? sdl->sdl_nlen + 1 : 0; 585 586 printf("%s", link_ntoa(sdl) + n); 587 } 588 } else 589 printf("(incomplete)"); 590 if (if_indextoname(sdl->sdl_index, ifname) != NULL) 591 printf(" on %s", ifname); 592 if (rtm->rtm_rmx.rmx_expire == 0) 593 printf(" permanent"); 594 if (addr->sin_other & SIN_PROXY) 595 printf(" published (proxy only)"); 596 if (rtm->rtm_flags & RTF_ANNOUNCE) 597 printf(" published"); 598 switch(sdl->sdl_type) { 599 case IFT_ETHER: 600 printf(" [ethernet]"); 601 break; 602 case IFT_ISO88025: 603 printf(" [token-ring]"); 604 trld = SDL_ISO88025(sdl); 605 if (trld->trld_rcf != 0) { 606 printf(" rt=%x", ntohs(trld->trld_rcf)); 607 for (seg = 0; 608 seg < ((TR_RCF_RIFLEN(trld->trld_rcf) - 2 ) / 2); 609 seg++) 610 printf(":%x", ntohs(*(trld->trld_route[seg]))); 611 } 612 break; 613 case IFT_FDDI: 614 printf(" [fddi]"); 615 break; 616 case IFT_ATM: 617 printf(" [atm]"); 618 break; 619 case IFT_L2VLAN: 620 printf(" [vlan]"); 621 break; 622 case IFT_IEEE1394: 623 printf(" [firewire]"); 624 break; 625 case IFT_BRIDGE: 626 printf(" [bridge]"); 627 break; 628 default: 629 break; 630 } 631 632 printf("\n"); 633 634} 635 636/* 637 * Nuke an arp entry 638 */ 639static void 640nuke_entry(struct sockaddr_dl *sdl __unused, 641 struct sockaddr_inarp *addr, struct rt_msghdr *rtm __unused) 642{ 643 char ip[20]; 644 645 snprintf(ip, sizeof(ip), "%s", inet_ntoa(addr->sin_addr)); 646 (void)delete(ip, 0); 647} 648 649static void 650usage(void) 651{ 652 fprintf(stderr, "%s\n%s\n%s\n%s\n%s\n%s\n%s\n", 653 "usage: arp [-n] [-i interface] hostname", 654 " arp [-n] [-i interface] -a", 655 " arp -d hostname [pub]", 656 " arp -d [-i interface] -a", 657 " arp -s hostname ether_addr [temp] [reject | blackhole] [pub [only]]", 658 " arp -S hostname ether_addr [temp] [reject | blackhole] [pub [only]]", 659 " arp -f filename"); 660 exit(1); 661} 662 663static struct rt_msghdr * 664rtmsg(int cmd, struct sockaddr_inarp *dst, struct sockaddr_dl *sdl) 665{ 666 static int seq; 667 int rlen; 668 int l; 669 struct sockaddr_in so_mask, *som = &so_mask; 670 static int s = -1; 671 static pid_t pid; 672 673 static struct { 674 struct rt_msghdr m_rtm; 675 char m_space[512]; 676 } m_rtmsg; 677 678 struct rt_msghdr *rtm = &m_rtmsg.m_rtm; 679 char *cp = m_rtmsg.m_space; 680 681 if (s < 0) { /* first time: open socket, get pid */ 682 s = socket(PF_ROUTE, SOCK_RAW, 0); 683 if (s < 0) 684 err(1, "socket"); 685 pid = getpid(); 686 } 687 bzero(&so_mask, sizeof(so_mask)); 688 so_mask.sin_len = 8; 689 so_mask.sin_addr.s_addr = 0xffffffff; 690 691 errno = 0; 692 /* 693 * XXX RTM_DELETE relies on a previous RTM_GET to fill the buffer 694 * appropriately. 695 */ 696 if (cmd == RTM_DELETE) 697 goto doit; 698 bzero((char *)&m_rtmsg, sizeof(m_rtmsg)); 699 rtm->rtm_flags = flags; 700 rtm->rtm_version = RTM_VERSION; 701 702 switch (cmd) { 703 default: 704 errx(1, "internal wrong cmd"); 705 case RTM_ADD: 706 rtm->rtm_addrs |= RTA_GATEWAY; 707 rtm->rtm_rmx.rmx_expire = expire_time; 708 rtm->rtm_inits = RTV_EXPIRE; 709 rtm->rtm_flags |= (RTF_HOST | RTF_STATIC); 710 dst->sin_other = 0; 711 if (doing_proxy) { 712 if (proxy_only) 713 dst->sin_other = SIN_PROXY; 714 else { 715 rtm->rtm_addrs |= RTA_NETMASK; 716 rtm->rtm_flags &= ~RTF_HOST; 717 } 718 } 719 /* FALLTHROUGH */ 720 case RTM_GET: 721 rtm->rtm_addrs |= RTA_DST; 722 } 723#define NEXTADDR(w, s) \ 724 if ((s) != NULL && rtm->rtm_addrs & (w)) { \ 725 bcopy((s), cp, sizeof(*(s))); cp += SA_SIZE(s);} 726 727 NEXTADDR(RTA_DST, dst); 728 NEXTADDR(RTA_GATEWAY, sdl); 729 NEXTADDR(RTA_NETMASK, som); 730 731 rtm->rtm_msglen = cp - (char *)&m_rtmsg; 732doit: 733 l = rtm->rtm_msglen; 734 rtm->rtm_seq = ++seq; 735 rtm->rtm_type = cmd; 736 if ((rlen = write(s, (char *)&m_rtmsg, l)) < 0) { 737 if (errno != ESRCH || cmd != RTM_DELETE) { 738 warn("writing to routing socket"); 739 return (NULL); 740 } 741 } 742 do { 743 l = read(s, (char *)&m_rtmsg, sizeof(m_rtmsg)); 744 } while (l > 0 && (rtm->rtm_seq != seq || rtm->rtm_pid != pid)); 745 if (l < 0) 746 warn("read from routing socket"); 747 return (rtm); 748} 749 750/* 751 * get_ether_addr - get the hardware address of an interface on the 752 * the same subnet as ipaddr. 753 */ 754#define MAX_IFS 32 755 756static int 757get_ether_addr(in_addr_t ipaddr, struct ether_addr *hwaddr) 758{ 759 struct ifreq *ifr, *ifend, *ifp; 760 in_addr_t ina, mask; 761 struct sockaddr_dl *dla; 762 struct ifreq ifreq; 763 struct ifconf ifc; 764 struct ifreq ifs[MAX_IFS]; 765 int sock; 766 int retval = 0; 767 768 sock = socket(AF_INET, SOCK_DGRAM, 0); 769 if (sock < 0) 770 err(1, "socket"); 771 772 ifc.ifc_len = sizeof(ifs); 773 ifc.ifc_req = ifs; 774 if (ioctl(sock, SIOCGIFCONF, &ifc) < 0) { 775 warnx("ioctl(SIOCGIFCONF)"); 776 goto done; 777 } 778 779#define NEXTIFR(i) \ 780 ((struct ifreq *)((char *)&(i)->ifr_addr \ 781 + MAX((i)->ifr_addr.sa_len, sizeof((i)->ifr_addr))) ) 782 783 /* 784 * Scan through looking for an interface with an Internet 785 * address on the same subnet as `ipaddr'. 786 */ 787 ifend = (struct ifreq *)(ifc.ifc_buf + ifc.ifc_len); 788 for (ifr = ifc.ifc_req; ifr < ifend; ifr = NEXTIFR(ifr) ) { 789 if (ifr->ifr_addr.sa_family != AF_INET) 790 continue; 791 strncpy(ifreq.ifr_name, ifr->ifr_name, 792 sizeof(ifreq.ifr_name)); 793 ifreq.ifr_addr = ifr->ifr_addr; 794 /* 795 * Check that the interface is up, 796 * and not point-to-point or loopback. 797 */ 798 if (ioctl(sock, SIOCGIFFLAGS, &ifreq) < 0) 799 continue; 800 if ((ifreq.ifr_flags & 801 (IFF_UP|IFF_BROADCAST|IFF_POINTOPOINT| 802 IFF_LOOPBACK|IFF_NOARP)) 803 != (IFF_UP|IFF_BROADCAST)) 804 continue; 805 /* 806 * Get its netmask and check that it's on 807 * the right subnet. 808 */ 809 if (ioctl(sock, SIOCGIFNETMASK, &ifreq) < 0) 810 continue; 811 mask = ((struct sockaddr_in *) 812 &ifreq.ifr_addr)->sin_addr.s_addr; 813 ina = ((struct sockaddr_in *) 814 &ifr->ifr_addr)->sin_addr.s_addr; 815 if ((ipaddr & mask) == (ina & mask)) 816 break; /* ok, we got it! */ 817 } 818 819 if (ifr >= ifend) 820 goto done; 821 822 /* 823 * Now scan through again looking for a link-level address 824 * for this interface. 825 */ 826 ifp = ifr; 827 for (ifr = ifc.ifc_req; ifr < ifend; ifr = NEXTIFR(ifr)) 828 if (strcmp(ifp->ifr_name, ifr->ifr_name) == 0 && 829 ifr->ifr_addr.sa_family == AF_LINK) 830 break; 831 if (ifr >= ifend) 832 goto done; 833 /* 834 * Found the link-level address - copy it out 835 */ 836 dla = (struct sockaddr_dl *) &ifr->ifr_addr; 837 memcpy(hwaddr, LLADDR(dla), dla->sdl_alen); 838 printf("using interface %s for proxy with address ", 839 ifp->ifr_name); 840 printf("%s\n", ether_ntoa(hwaddr)); 841 retval = dla->sdl_alen; 842done: 843 close(sock); 844 return (retval); 845} 846