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 * @(#) Copyright (c) 1984, 1993 The Regents of the University of California. All rights reserved. 37 * @(#)from: arp.c 8.2 (Berkeley) 1/2/94 38 * $FreeBSD: src/usr.sbin/arp/arp.c,v 1.22.2.12 2003/04/16 10:02:37 ru Exp $ 39 * $DragonFly: src/usr.sbin/arp/arp.c,v 1.11 2008/02/03 00:41:44 swildner Exp $ 40 */ 41 42 /* 43 * arp - display, set, and delete arp table entries 44 */ 45 46 47 #include <sys/param.h> 48 #include <sys/file.h> 49 #include <sys/socket.h> 50 #include <sys/sockio.h> 51 #include <sys/sysctl.h> 52 #include <sys/ioctl.h> 53 #include <sys/time.h> 54 55 #include <net/if.h> 56 #include <net/if_dl.h> 57 #include <net/if_types.h> 58 #include <net/route.h> 59 60 #include <netinet/in.h> 61 #include <netinet/if_ether.h> 62 63 #include <arpa/inet.h> 64 65 #include <ctype.h> 66 #include <err.h> 67 #include <errno.h> 68 #include <netdb.h> 69 #include <nlist.h> 70 #include <paths.h> 71 #include <stdio.h> 72 #include <stdlib.h> 73 #include <string.h> 74 #include <unistd.h> 75 76 void search(u_long addr, void (*action)(struct sockaddr_dl *sdl, 77 struct sockaddr_inarp *sin, struct rt_msghdr *rtm)); 78 void print_entry(struct sockaddr_dl *sdl, 79 struct sockaddr_inarp *addr, struct rt_msghdr *rtm); 80 void nuke_entry(struct sockaddr_dl *sdl, 81 struct sockaddr_inarp *addr, struct rt_msghdr *rtm); 82 int delete(char *host, char *info); 83 void usage(void); 84 int set(int argc, char **argv); 85 int get(char *host); 86 int file(char *name); 87 void getsocket(void); 88 int my_ether_aton(char *a, struct ether_addr *n); 89 int rtmsg(int cmd); 90 int get_ether_addr(u_int32_t ipaddr, struct ether_addr *hwaddr); 91 92 static int pid; 93 static int nflag; /* no reverse dns lookups */ 94 static int aflag; /* do it for all entries */ 95 static int cpuflag = -1; 96 static int s = -1; 97 98 struct sockaddr_in so_mask; 99 struct sockaddr_inarp blank_sin, sin_m; 100 struct sockaddr_dl blank_sdl, sdl_m; 101 int expire_time, flags, doing_proxy, proxy_only, found_entry; 102 struct { 103 struct rt_msghdr m_rtm; 104 char m_space[512]; 105 } m_rtmsg; 106 107 /* which function we're supposed to do */ 108 #define F_GET 1 109 #define F_SET 2 110 #define F_FILESET 3 111 #define F_REPLACE 4 112 #define F_DELETE 5 113 114 #define ROUNDUP(a) \ 115 ((a) > 0 ? (1 + (((a) - 1) | (sizeof(long) - 1))) : sizeof(long)) 116 #define SETFUNC(f) { if (func) usage(); func = (f); } 117 118 int 119 main(int argc, char **argv) 120 { 121 int ch, func = 0; 122 int rtn = 0; 123 124 pid = getpid(); 125 while ((ch = getopt(argc, argv, "ac:ndfsS")) != -1) 126 switch((char)ch) { 127 case 'a': 128 aflag = 1; 129 break; 130 case 'c': 131 cpuflag = strtol(optarg, NULL, 0); 132 break; 133 case 'd': 134 SETFUNC(F_DELETE); 135 break; 136 case 'n': 137 nflag = 1; 138 break; 139 case 'S': 140 SETFUNC(F_REPLACE); 141 break; 142 case 's': 143 SETFUNC(F_SET); 144 break; 145 case 'f' : 146 SETFUNC(F_FILESET); 147 break; 148 case '?': 149 default: 150 usage(); 151 } 152 argc -= optind; 153 argv += optind; 154 155 bzero(&so_mask, sizeof(so_mask)); 156 so_mask.sin_len = 8; 157 so_mask.sin_addr.s_addr = 0xffffffff; 158 bzero(&blank_sin, sizeof(blank_sin)); 159 blank_sin.sin_len = sizeof(blank_sin); 160 blank_sin.sin_family = AF_INET; 161 bzero(&blank_sdl, sizeof(blank_sdl)); 162 blank_sdl.sdl_len = sizeof(blank_sdl); 163 blank_sdl.sdl_family = AF_LINK; 164 165 if (!func) 166 func = F_GET; 167 switch (func) { 168 case F_GET: 169 if (aflag) { 170 if (argc != 0) 171 usage(); 172 search(0, print_entry); 173 } else { 174 if (argc != 1) 175 usage(); 176 get(argv[0]); 177 } 178 break; 179 case F_SET: 180 case F_REPLACE: 181 if (argc < 2 || argc > 6) 182 usage(); 183 if (func == F_REPLACE) 184 delete(argv[0], NULL); 185 rtn = set(argc, argv) ? 1 : 0; 186 break; 187 case F_DELETE: 188 if (aflag) { 189 if (argc != 0) 190 usage(); 191 search(0, nuke_entry); 192 } else { 193 if (argc < 1 || argc > 2) 194 usage(); 195 rtn = delete(argv[0], argv[1]); 196 } 197 break; 198 case F_FILESET: 199 if (argc != 1) 200 usage(); 201 rtn = file(argv[0]); 202 break; 203 } 204 205 return(rtn); 206 } 207 208 /* 209 * Process a file to set standard arp entries 210 */ 211 int 212 file(char *name) 213 { 214 FILE *fp; 215 int i, retval; 216 char line[100], arg[5][50], *args[5], *p; 217 218 if ((fp = fopen(name, "r")) == NULL) 219 errx(1, "cannot open %s", name); 220 args[0] = &arg[0][0]; 221 args[1] = &arg[1][0]; 222 args[2] = &arg[2][0]; 223 args[3] = &arg[3][0]; 224 args[4] = &arg[4][0]; 225 retval = 0; 226 while(fgets(line, 100, fp) != NULL) { 227 if ((p = strchr(line, '#')) != NULL) 228 *p = '\0'; 229 for (p = line; isblank(*p); p++); 230 if (*p == '\n' || *p == '\0') 231 continue; 232 i = sscanf(p, "%49s %49s %49s %49s %49s", arg[0], arg[1], 233 arg[2], arg[3], arg[4]); 234 if (i < 2) { 235 warnx("bad line: %s", line); 236 retval = 1; 237 continue; 238 } 239 if (set(i, args)) 240 retval = 1; 241 } 242 fclose(fp); 243 return(retval); 244 } 245 246 void 247 getsocket(void) 248 { 249 if (s < 0) { 250 s = socket(PF_ROUTE, SOCK_RAW, 0); 251 if (s < 0) 252 err(1, "socket"); 253 } 254 } 255 256 /* 257 * Set an individual arp entry 258 */ 259 int 260 set(int argc, char **argv) 261 { 262 struct hostent *hp; 263 struct sockaddr_inarp *addr = &sin_m; 264 struct sockaddr_dl *sdl; 265 struct rt_msghdr *rtm = &(m_rtmsg.m_rtm); 266 struct ether_addr *ea; 267 char *host = argv[0], *eaddr = argv[1]; 268 269 getsocket(); 270 argc -= 2; 271 argv += 2; 272 sdl_m = blank_sdl; 273 sin_m = blank_sin; 274 addr->sin_addr.s_addr = inet_addr(host); 275 if (addr->sin_addr.s_addr == INADDR_NONE) { 276 if (!(hp = gethostbyname(host))) { 277 warnx("%s: %s", host, hstrerror(h_errno)); 278 return(1); 279 } 280 bcopy((char *)hp->h_addr, (char *)&addr->sin_addr, 281 sizeof(addr->sin_addr)); 282 } 283 doing_proxy = flags = proxy_only = expire_time = 0; 284 while (argc-- > 0) { 285 if (strncmp(argv[0], "temp", 4) == 0) { 286 struct timeval tv; 287 gettimeofday(&tv, 0); 288 expire_time = tv.tv_sec + 20 * 60; 289 } 290 else if (strncmp(argv[0], "pub", 3) == 0) { 291 flags |= RTF_ANNOUNCE; 292 doing_proxy = 1; 293 if (argc && strncmp(argv[1], "only", 3) == 0) { 294 proxy_only = 1; 295 sin_m.sin_other = SIN_PROXY; 296 argc--; argv++; 297 } 298 } else if (strncmp(argv[0], "trail", 5) == 0) { 299 printf("%s: Sending trailers is no longer supported\n", 300 host); 301 } 302 argv++; 303 } 304 ea = (struct ether_addr *)LLADDR(&sdl_m); 305 if (doing_proxy && !strcmp(eaddr, "auto")) { 306 if (!get_ether_addr(addr->sin_addr.s_addr, ea)) { 307 printf("no interface found for %s\n", 308 inet_ntoa(addr->sin_addr)); 309 return(1); 310 } 311 sdl_m.sdl_alen = ETHER_ADDR_LEN; 312 } else { 313 if (my_ether_aton(eaddr, ea) == 0) 314 sdl_m.sdl_alen = ETHER_ADDR_LEN; 315 } 316 tryagain: 317 if (rtmsg(RTM_GET) < 0) { 318 warn("%s", host); 319 return(1); 320 } 321 addr = (struct sockaddr_inarp *)(rtm + 1); 322 sdl = (struct sockaddr_dl *)(ROUNDUP(addr->sin_len) + (char *)addr); 323 if (addr->sin_addr.s_addr == sin_m.sin_addr.s_addr) { 324 if (sdl->sdl_family == AF_LINK && 325 (rtm->rtm_flags & RTF_LLINFO) && 326 !(rtm->rtm_flags & RTF_GATEWAY)) switch (sdl->sdl_type) { 327 case IFT_ETHER: case IFT_FDDI: case IFT_ISO88023: 328 case IFT_ISO88024: case IFT_ISO88025: case IFT_L2VLAN: 329 goto overwrite; 330 } 331 if (doing_proxy == 0) { 332 printf("set: can only proxy for %s\n", host); 333 return(1); 334 } 335 if (sin_m.sin_other & SIN_PROXY) { 336 printf("set: proxy entry exists for non 802 device\n"); 337 return(1); 338 } 339 sin_m.sin_other = SIN_PROXY; 340 proxy_only = 1; 341 goto tryagain; 342 } 343 overwrite: 344 if (sdl->sdl_family != AF_LINK) { 345 printf("cannot intuit interface index and type for %s\n", host); 346 return(1); 347 } 348 sdl_m.sdl_type = sdl->sdl_type; 349 sdl_m.sdl_index = sdl->sdl_index; 350 return(rtmsg(RTM_ADD)); 351 } 352 353 /* 354 * Display an individual arp entry 355 */ 356 int 357 get(char *host) 358 { 359 struct hostent *hp; 360 struct sockaddr_inarp *addr = &sin_m; 361 362 sin_m = blank_sin; 363 addr->sin_addr.s_addr = inet_addr(host); 364 if (addr->sin_addr.s_addr == INADDR_NONE) { 365 if (!(hp = gethostbyname(host))) 366 errx(1, "%s: %s", host, hstrerror(h_errno)); 367 bcopy((char *)hp->h_addr, (char *)&addr->sin_addr, 368 sizeof(addr->sin_addr)); 369 } 370 search(addr->sin_addr.s_addr, print_entry); 371 if (found_entry == 0) { 372 printf("%s (%s) -- no entry\n", 373 host, inet_ntoa(addr->sin_addr)); 374 return(1); 375 } 376 return(0); 377 } 378 379 /* 380 * Delete an arp entry 381 */ 382 int 383 delete(char *host, char *info) 384 { 385 struct hostent *hp; 386 struct sockaddr_inarp *addr = &sin_m; 387 struct rt_msghdr *rtm = &m_rtmsg.m_rtm; 388 struct sockaddr_dl *sdl; 389 390 getsocket(); 391 sin_m = blank_sin; 392 if (info) { 393 if (strncmp(info, "pub", 3) == 0) 394 sin_m.sin_other = SIN_PROXY; 395 else 396 usage(); 397 } 398 addr->sin_addr.s_addr = inet_addr(host); 399 if (addr->sin_addr.s_addr == INADDR_NONE) { 400 if (!(hp = gethostbyname(host))) { 401 warnx("%s: %s", host, hstrerror(h_errno)); 402 return(1); 403 } 404 bcopy((char *)hp->h_addr, (char *)&addr->sin_addr, 405 sizeof(addr->sin_addr)); 406 } 407 tryagain: 408 if (rtmsg(RTM_GET) < 0) { 409 warn("%s", host); 410 return(1); 411 } 412 addr = (struct sockaddr_inarp *)(rtm + 1); 413 sdl = (struct sockaddr_dl *)(ROUNDUP(addr->sin_len) + (char *)addr); 414 if (addr->sin_addr.s_addr == sin_m.sin_addr.s_addr) { 415 if (sdl->sdl_family == AF_LINK && 416 (rtm->rtm_flags & RTF_LLINFO) && 417 !(rtm->rtm_flags & RTF_GATEWAY)) switch (sdl->sdl_type) { 418 case IFT_ETHER: case IFT_FDDI: case IFT_ISO88023: 419 case IFT_ISO88024: case IFT_ISO88025: case IFT_L2VLAN: 420 goto delete; 421 } 422 } 423 if (sin_m.sin_other & SIN_PROXY) { 424 fprintf(stderr, "delete: can't locate %s\n",host); 425 return(1); 426 } else { 427 sin_m.sin_other = SIN_PROXY; 428 goto tryagain; 429 } 430 delete: 431 if (sdl->sdl_family != AF_LINK) { 432 printf("cannot locate %s\n", host); 433 return(1); 434 } 435 if (aflag && (rtm->rtm_flags & RTF_STATIC)) { 436 sdl->sdl_alen = 0; 437 sdl->sdl_slen = 0; 438 if (rtmsg(RTM_CHANGE) == 0) { 439 printf("%s (%s) cleared\n", 440 host, inet_ntoa(addr->sin_addr)); 441 return(0); 442 } 443 } else { 444 if (rtmsg(RTM_DELETE) == 0) { 445 printf("%s (%s) deleted\n", 446 host, inet_ntoa(addr->sin_addr)); 447 return(0); 448 } 449 } 450 return(1); 451 } 452 453 /* 454 * Search the arp table and do some action on matching entries 455 */ 456 void 457 search(u_long addr, void (*action)(struct sockaddr_dl *sdl, 458 struct sockaddr_inarp *sin, struct rt_msghdr *rtm)) 459 { 460 int mib[7]; 461 int miblen; 462 size_t needed; 463 char *lim, *buf, *next; 464 struct rt_msghdr *rtm; 465 struct sockaddr_inarp *sin2; 466 struct sockaddr_dl *sdl; 467 468 mib[0] = CTL_NET; 469 mib[1] = PF_ROUTE; 470 mib[2] = 0; 471 mib[3] = AF_INET; 472 mib[4] = NET_RT_FLAGS; 473 mib[5] = RTF_LLINFO; 474 if (cpuflag >= 0) { 475 mib[6] = cpuflag; 476 miblen = 7; 477 } else { 478 miblen = 6; 479 } 480 if (sysctl(mib, miblen, NULL, &needed, NULL, 0) < 0) 481 errx(1, "route-sysctl-estimate"); 482 if ((buf = malloc(needed)) == NULL) 483 errx(1, "malloc"); 484 if (sysctl(mib, miblen, buf, &needed, NULL, 0) < 0) 485 errx(1, "actual retrieval of routing table"); 486 lim = buf + needed; 487 for (next = buf; next < lim; next += rtm->rtm_msglen) { 488 rtm = (struct rt_msghdr *)next; 489 sin2 = (struct sockaddr_inarp *)(rtm + 1); 490 sdl = (struct sockaddr_dl *)((char *)sin2 + ROUNDUP(sin2->sin_len)); 491 if (addr) { 492 if (addr != sin2->sin_addr.s_addr) 493 continue; 494 found_entry = 1; 495 } 496 (*action)(sdl, sin2, rtm); 497 } 498 free(buf); 499 } 500 501 /* 502 * Display an arp entry 503 */ 504 void 505 print_entry(struct sockaddr_dl *sdl, 506 struct sockaddr_inarp *addr, struct rt_msghdr *rtm) 507 { 508 const char *host; 509 struct hostent *hp; 510 char ifname[IF_NAMESIZE]; 511 512 if (nflag == 0) 513 hp = gethostbyaddr(&(addr->sin_addr), sizeof(addr->sin_addr), 514 AF_INET); 515 else 516 hp = 0; 517 if (hp) 518 host = hp->h_name; 519 else { 520 host = "?"; 521 if (h_errno == TRY_AGAIN) 522 nflag = 1; 523 } 524 printf("%s (%s) at ", host, inet_ntoa(addr->sin_addr)); 525 if (sdl->sdl_alen) 526 printf("%s", ether_ntoa((struct ether_addr *)LLADDR(sdl))); 527 else 528 printf("(incomplete)"); 529 if (if_indextoname(sdl->sdl_index, ifname) != NULL) 530 printf(" on %s", ifname); 531 if (rtm->rtm_rmx.rmx_expire == 0) 532 printf(" permanent"); 533 if (addr->sin_other & SIN_PROXY) 534 printf(" published (proxy only)"); 535 if (rtm->rtm_addrs & RTA_NETMASK) { 536 addr = (struct sockaddr_inarp *) 537 (ROUNDUP(sdl->sdl_len) + (char *)sdl); 538 if (addr->sin_addr.s_addr == 0xffffffff) 539 printf(" published"); 540 if (addr->sin_len != 8) 541 printf("(weird)"); 542 } 543 switch(sdl->sdl_type) { 544 case IFT_ETHER: 545 printf(" [ethernet]"); 546 break; 547 case IFT_L2VLAN: 548 printf(" [vlan]"); 549 break; 550 default: 551 break; 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] [-c cpu] hostname", 589 " arp [-n] [-c cpu] -a", 590 " arp -d hostname [pub]", 591 " arp -d -a", 592 " arp -s hostname ether_addr [temp] [pub [only]]", 593 " arp -S hostname ether_addr [temp] [pub [only]]", 594 " arp -f filename"); 595 exit(1); 596 } 597 598 int 599 rtmsg(int cmd) 600 { 601 static int seq; 602 int rlen; 603 struct rt_msghdr *rtm = &m_rtmsg.m_rtm; 604 char *cp = m_rtmsg.m_space; 605 int l; 606 607 errno = 0; 608 if (cmd == RTM_DELETE || cmd == RTM_CHANGE) 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 && cmd != RTM_CHANGE)) { 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