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