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 * @(#) Copyright (c) 1984, 1993 The Regents of the University of California. All rights reserved. 33 * @(#)from: arp.c 8.2 (Berkeley) 1/2/94 34 * $FreeBSD: src/usr.sbin/arp/arp.c,v 1.22.2.12 2003/04/16 10:02:37 ru Exp $ 35 */ 36 37 /* 38 * arp - display, set, and delete arp table entries 39 */ 40 41 42 #include <sys/param.h> 43 #include <sys/file.h> 44 #include <sys/socket.h> 45 #include <sys/sockio.h> 46 #include <sys/sysctl.h> 47 #include <sys/ioctl.h> 48 #include <sys/time.h> 49 50 #include <net/if.h> 51 #include <net/if_dl.h> 52 #include <net/if_types.h> 53 #include <net/route.h> 54 55 #include <netinet/in.h> 56 #include <netinet/if_ether.h> 57 58 #include <arpa/inet.h> 59 60 #include <ctype.h> 61 #include <err.h> 62 #include <errno.h> 63 #include <netdb.h> 64 #include <nlist.h> 65 #include <paths.h> 66 #include <stdio.h> 67 #include <stdlib.h> 68 #include <string.h> 69 #include <unistd.h> 70 71 void search(u_long addr, void (*action)(struct sockaddr_dl *sdl, 72 struct sockaddr_inarp *sin, struct rt_msghdr *rtm)); 73 void print_entry(struct sockaddr_dl *sdl, 74 struct sockaddr_inarp *addr, struct rt_msghdr *rtm); 75 void nuke_entry(struct sockaddr_dl *sdl, 76 struct sockaddr_inarp *addr, struct rt_msghdr *rtm); 77 int delete(char *host, char *info); 78 void usage(void); 79 int set(int argc, char **argv); 80 int get(char *host); 81 int file(char *name); 82 void getsocket(void); 83 int my_ether_aton(char *a, struct ether_addr *n); 84 int rtmsg(int cmd); 85 int get_ether_addr(u_int32_t ipaddr, struct ether_addr *hwaddr); 86 87 static int pid; 88 static int nflag; /* no reverse dns lookups */ 89 static int aflag; /* do it for all entries */ 90 static int cpuflag = -1; 91 static int s = -1; 92 93 struct sockaddr_in so_mask; 94 struct sockaddr_inarp blank_sin, sin_m; 95 struct sockaddr_dl blank_sdl, sdl_m; 96 int expire_time, flags, doing_proxy, proxy_only, found_entry; 97 struct { 98 struct rt_msghdr m_rtm; 99 char m_space[512]; 100 } m_rtmsg; 101 102 /* which function we're supposed to do */ 103 #define F_GET 1 104 #define F_SET 2 105 #define F_FILESET 3 106 #define F_REPLACE 4 107 #define F_DELETE 5 108 109 #define ROUNDUP(a) \ 110 ((a) > 0 ? (1 + (((a) - 1) | (sizeof(long) - 1))) : sizeof(long)) 111 #define SETFUNC(f) { if (func) usage(); func = (f); } 112 113 int 114 main(int argc, char **argv) 115 { 116 int ch, func = 0; 117 int rtn = 0; 118 119 pid = getpid(); 120 while ((ch = getopt(argc, argv, "ac:ndfsS")) != -1) 121 switch((char)ch) { 122 case 'a': 123 aflag = 1; 124 break; 125 case 'c': 126 cpuflag = strtol(optarg, NULL, 0); 127 break; 128 case 'd': 129 SETFUNC(F_DELETE); 130 break; 131 case 'n': 132 nflag = 1; 133 break; 134 case 'S': 135 SETFUNC(F_REPLACE); 136 break; 137 case 's': 138 SETFUNC(F_SET); 139 break; 140 case 'f' : 141 SETFUNC(F_FILESET); 142 break; 143 case '?': 144 default: 145 usage(); 146 } 147 argc -= optind; 148 argv += optind; 149 150 bzero(&so_mask, sizeof(so_mask)); 151 so_mask.sin_len = 8; 152 so_mask.sin_addr.s_addr = 0xffffffff; 153 bzero(&blank_sin, sizeof(blank_sin)); 154 blank_sin.sin_len = sizeof(blank_sin); 155 blank_sin.sin_family = AF_INET; 156 bzero(&blank_sdl, sizeof(blank_sdl)); 157 blank_sdl.sdl_len = sizeof(blank_sdl); 158 blank_sdl.sdl_family = AF_LINK; 159 160 if (!func) 161 func = F_GET; 162 switch (func) { 163 case F_GET: 164 if (aflag) { 165 if (argc != 0) 166 usage(); 167 search(0, print_entry); 168 } else { 169 if (argc != 1) 170 usage(); 171 get(argv[0]); 172 } 173 break; 174 case F_SET: 175 case F_REPLACE: 176 if (argc < 2 || argc > 6) 177 usage(); 178 if (func == F_REPLACE) 179 delete(argv[0], NULL); 180 rtn = set(argc, argv) ? 1 : 0; 181 break; 182 case F_DELETE: 183 if (aflag) { 184 if (argc != 0) 185 usage(); 186 search(0, nuke_entry); 187 } else { 188 if (argc < 1 || argc > 2) 189 usage(); 190 rtn = delete(argv[0], argv[1]); 191 } 192 break; 193 case F_FILESET: 194 if (argc != 1) 195 usage(); 196 rtn = file(argv[0]); 197 break; 198 } 199 200 return(rtn); 201 } 202 203 /* 204 * Process a file to set standard arp entries 205 */ 206 int 207 file(char *name) 208 { 209 FILE *fp; 210 int i, retval; 211 char line[100], arg[5][50], *args[5], *p; 212 213 if ((fp = fopen(name, "r")) == NULL) 214 errx(1, "cannot open %s", name); 215 args[0] = &arg[0][0]; 216 args[1] = &arg[1][0]; 217 args[2] = &arg[2][0]; 218 args[3] = &arg[3][0]; 219 args[4] = &arg[4][0]; 220 retval = 0; 221 while(fgets(line, 100, fp) != NULL) { 222 if ((p = strchr(line, '#')) != NULL) 223 *p = '\0'; 224 for (p = line; isblank(*p); p++); 225 if (*p == '\n' || *p == '\0') 226 continue; 227 i = sscanf(p, "%49s %49s %49s %49s %49s", arg[0], arg[1], 228 arg[2], arg[3], arg[4]); 229 if (i < 2) { 230 warnx("bad line: %s", line); 231 retval = 1; 232 continue; 233 } 234 if (set(i, args)) 235 retval = 1; 236 } 237 fclose(fp); 238 return(retval); 239 } 240 241 void 242 getsocket(void) 243 { 244 if (s < 0) { 245 s = socket(PF_ROUTE, SOCK_RAW, 0); 246 if (s < 0) 247 err(1, "socket"); 248 } 249 } 250 251 /* 252 * Set an individual arp entry 253 */ 254 int 255 set(int argc, char **argv) 256 { 257 struct hostent *hp; 258 struct sockaddr_inarp *addr = &sin_m; 259 struct sockaddr_dl *sdl; 260 struct rt_msghdr *rtm = &(m_rtmsg.m_rtm); 261 struct ether_addr *ea; 262 char *host = argv[0], *eaddr = argv[1]; 263 264 getsocket(); 265 argc -= 2; 266 argv += 2; 267 sdl_m = blank_sdl; 268 sin_m = blank_sin; 269 addr->sin_addr.s_addr = inet_addr(host); 270 if (addr->sin_addr.s_addr == INADDR_NONE) { 271 if (!(hp = gethostbyname(host))) { 272 warnx("%s: %s", host, hstrerror(h_errno)); 273 return(1); 274 } 275 bcopy((char *)hp->h_addr, (char *)&addr->sin_addr, 276 sizeof(addr->sin_addr)); 277 } 278 doing_proxy = flags = proxy_only = expire_time = 0; 279 while (argc-- > 0) { 280 if (strncmp(argv[0], "temp", 4) == 0) { 281 struct timeval tv; 282 gettimeofday(&tv, 0); 283 expire_time = tv.tv_sec + 20 * 60; 284 } 285 else if (strncmp(argv[0], "pub", 3) == 0) { 286 flags |= RTF_ANNOUNCE; 287 doing_proxy = 1; 288 if (argc && strncmp(argv[1], "only", 3) == 0) { 289 proxy_only = 1; 290 sin_m.sin_other = SIN_PROXY; 291 argc--; argv++; 292 } 293 } else if (strncmp(argv[0], "trail", 5) == 0) { 294 printf("%s: Sending trailers is no longer supported\n", 295 host); 296 } 297 argv++; 298 } 299 ea = (struct ether_addr *)LLADDR(&sdl_m); 300 if (doing_proxy && !strcmp(eaddr, "auto")) { 301 if (!get_ether_addr(addr->sin_addr.s_addr, ea)) { 302 printf("no interface found for %s\n", 303 inet_ntoa(addr->sin_addr)); 304 return(1); 305 } 306 sdl_m.sdl_alen = ETHER_ADDR_LEN; 307 } else { 308 if (my_ether_aton(eaddr, ea) == 0) 309 sdl_m.sdl_alen = ETHER_ADDR_LEN; 310 } 311 tryagain: 312 if (rtmsg(RTM_GET) < 0) { 313 warn("%s", host); 314 return(1); 315 } 316 addr = (struct sockaddr_inarp *)(rtm + 1); 317 sdl = (struct sockaddr_dl *)(ROUNDUP(addr->sin_len) + (char *)addr); 318 if (addr->sin_addr.s_addr == sin_m.sin_addr.s_addr) { 319 if (sdl->sdl_family == AF_LINK && 320 (rtm->rtm_flags & RTF_LLINFO) && 321 !(rtm->rtm_flags & RTF_GATEWAY)) switch (sdl->sdl_type) { 322 case IFT_ETHER: case IFT_FDDI: case IFT_ISO88023: 323 case IFT_ISO88024: case IFT_ISO88025: case IFT_L2VLAN: 324 case IFT_CARP: 325 goto overwrite; 326 } 327 if (doing_proxy == 0) { 328 printf("set: can only proxy for %s\n", host); 329 return(1); 330 } 331 if (sin_m.sin_other & SIN_PROXY) { 332 printf("set: proxy entry exists for non 802 device\n"); 333 return(1); 334 } 335 sin_m.sin_other = SIN_PROXY; 336 proxy_only = 1; 337 goto tryagain; 338 } 339 overwrite: 340 if (sdl->sdl_family != AF_LINK) { 341 printf("cannot intuit interface index and type for %s\n", host); 342 return(1); 343 } 344 sdl_m.sdl_type = sdl->sdl_type; 345 sdl_m.sdl_index = sdl->sdl_index; 346 return(rtmsg(RTM_ADD)); 347 } 348 349 /* 350 * Display an individual arp entry 351 */ 352 int 353 get(char *host) 354 { 355 struct hostent *hp; 356 struct sockaddr_inarp *addr = &sin_m; 357 358 sin_m = blank_sin; 359 addr->sin_addr.s_addr = inet_addr(host); 360 if (addr->sin_addr.s_addr == INADDR_NONE) { 361 if (!(hp = gethostbyname(host))) 362 errx(1, "%s: %s", host, hstrerror(h_errno)); 363 bcopy((char *)hp->h_addr, (char *)&addr->sin_addr, 364 sizeof(addr->sin_addr)); 365 } 366 search(addr->sin_addr.s_addr, print_entry); 367 if (found_entry == 0) { 368 printf("%s (%s) -- no entry\n", 369 host, inet_ntoa(addr->sin_addr)); 370 return(1); 371 } 372 return(0); 373 } 374 375 /* 376 * Delete an arp entry 377 */ 378 int 379 delete(char *host, char *info) 380 { 381 struct hostent *hp; 382 struct sockaddr_inarp *addr = &sin_m; 383 struct rt_msghdr *rtm = &m_rtmsg.m_rtm; 384 struct sockaddr_dl *sdl; 385 386 getsocket(); 387 sin_m = blank_sin; 388 if (info) { 389 if (strncmp(info, "pub", 3) == 0) 390 sin_m.sin_other = SIN_PROXY; 391 else 392 usage(); 393 } 394 addr->sin_addr.s_addr = inet_addr(host); 395 if (addr->sin_addr.s_addr == INADDR_NONE) { 396 if (!(hp = gethostbyname(host))) { 397 warnx("%s: %s", host, hstrerror(h_errno)); 398 return(1); 399 } 400 bcopy((char *)hp->h_addr, (char *)&addr->sin_addr, 401 sizeof(addr->sin_addr)); 402 } 403 tryagain: 404 if (rtmsg(RTM_GET) < 0) { 405 warn("%s", host); 406 return(1); 407 } 408 addr = (struct sockaddr_inarp *)(rtm + 1); 409 sdl = (struct sockaddr_dl *)(ROUNDUP(addr->sin_len) + (char *)addr); 410 if (addr->sin_addr.s_addr == sin_m.sin_addr.s_addr) { 411 if (sdl->sdl_family == AF_LINK && 412 (rtm->rtm_flags & RTF_LLINFO) && 413 !(rtm->rtm_flags & RTF_GATEWAY)) switch (sdl->sdl_type) { 414 case IFT_ETHER: case IFT_FDDI: case IFT_ISO88023: 415 case IFT_ISO88024: case IFT_ISO88025: case IFT_L2VLAN: 416 case IFT_CARP: 417 goto delete; 418 } 419 } 420 if (sin_m.sin_other & SIN_PROXY) { 421 fprintf(stderr, "delete: can't locate %s\n",host); 422 return(1); 423 } else { 424 sin_m.sin_other = SIN_PROXY; 425 goto tryagain; 426 } 427 delete: 428 if (sdl->sdl_family != AF_LINK) { 429 printf("cannot locate %s\n", host); 430 return(1); 431 } 432 if (aflag && (rtm->rtm_flags & RTF_STATIC)) { 433 sdl->sdl_alen = 0; 434 sdl->sdl_slen = 0; 435 if (rtmsg(RTM_CHANGE) == 0) { 436 printf("%s (%s) cleared\n", 437 host, inet_ntoa(addr->sin_addr)); 438 return(0); 439 } 440 } else { 441 if (rtmsg(RTM_DELETE) == 0) { 442 printf("%s (%s) deleted\n", 443 host, inet_ntoa(addr->sin_addr)); 444 return(0); 445 } 446 } 447 return(1); 448 } 449 450 /* 451 * Search the arp table and do some action on matching entries 452 */ 453 void 454 search(u_long addr, void (*action)(struct sockaddr_dl *sdl, 455 struct sockaddr_inarp *sin, struct rt_msghdr *rtm)) 456 { 457 int mib[7]; 458 int miblen; 459 size_t needed; 460 char *lim, *buf, *next; 461 struct rt_msghdr *rtm; 462 struct sockaddr_inarp *sin2; 463 struct sockaddr_dl *sdl; 464 465 mib[0] = CTL_NET; 466 mib[1] = PF_ROUTE; 467 mib[2] = 0; 468 mib[3] = AF_INET; 469 mib[4] = NET_RT_FLAGS; 470 mib[5] = RTF_LLINFO; 471 if (cpuflag >= 0) { 472 mib[6] = cpuflag; 473 miblen = 7; 474 } else { 475 miblen = 6; 476 } 477 if (sysctl(mib, miblen, NULL, &needed, NULL, 0) < 0) 478 errx(1, "route-sysctl-estimate"); 479 if ((buf = malloc(needed)) == NULL) 480 errx(1, "malloc"); 481 if (sysctl(mib, miblen, buf, &needed, NULL, 0) < 0) 482 errx(1, "actual retrieval of routing table"); 483 lim = buf + needed; 484 for (next = buf; next < lim; next += rtm->rtm_msglen) { 485 rtm = (struct rt_msghdr *)next; 486 sin2 = (struct sockaddr_inarp *)(rtm + 1); 487 sdl = (struct sockaddr_dl *)((char *)sin2 + ROUNDUP(sin2->sin_len)); 488 if (addr) { 489 if (addr != sin2->sin_addr.s_addr) 490 continue; 491 found_entry = 1; 492 } 493 (*action)(sdl, sin2, rtm); 494 } 495 free(buf); 496 } 497 498 /* 499 * Display an arp entry 500 */ 501 void 502 print_entry(struct sockaddr_dl *sdl, 503 struct sockaddr_inarp *addr, struct rt_msghdr *rtm) 504 { 505 const char *host; 506 struct hostent *hp; 507 char ifname[IF_NAMESIZE]; 508 509 if (nflag == 0) 510 hp = gethostbyaddr(&(addr->sin_addr), sizeof(addr->sin_addr), 511 AF_INET); 512 else 513 hp = NULL; 514 if (hp) 515 host = hp->h_name; 516 else { 517 host = "?"; 518 if (h_errno == TRY_AGAIN) 519 nflag = 1; 520 } 521 printf("%s (%s) at ", host, inet_ntoa(addr->sin_addr)); 522 if (sdl->sdl_alen) 523 printf("%s", ether_ntoa((struct ether_addr *)LLADDR(sdl))); 524 else 525 printf("(incomplete)"); 526 if (if_indextoname(sdl->sdl_index, ifname) != NULL) 527 printf(" on %s", ifname); 528 if (rtm->rtm_rmx.rmx_expire == 0) 529 printf(" permanent"); 530 if (addr->sin_other & SIN_PROXY) 531 printf(" published (proxy only)"); 532 if (rtm->rtm_addrs & RTA_NETMASK) { 533 addr = (struct sockaddr_inarp *) 534 (ROUNDUP(sdl->sdl_len) + (char *)sdl); 535 if (addr->sin_addr.s_addr == 0xffffffff) 536 printf(" published"); 537 if (addr->sin_len != 8) 538 printf("(weird)"); 539 } 540 switch(sdl->sdl_type) { 541 case IFT_ETHER: 542 printf(" [ethernet]"); 543 break; 544 case IFT_L2VLAN: 545 printf(" [vlan]"); 546 break; 547 case IFT_CARP: 548 printf(" [carp]"); 549 default: 550 break; 551 } 552 553 printf("\n"); 554 555 } 556 557 /* 558 * Nuke an arp entry 559 */ 560 void 561 nuke_entry(struct sockaddr_dl *sdl __unused, 562 struct sockaddr_inarp *addr, struct rt_msghdr *rtm __unused) 563 { 564 char ip[20]; 565 566 snprintf(ip, sizeof(ip), "%s", inet_ntoa(addr->sin_addr)); 567 delete(ip, NULL); 568 } 569 570 int 571 my_ether_aton(char *a, struct ether_addr *n) 572 { 573 struct ether_addr *ea; 574 575 if ((ea = ether_aton(a)) == NULL) { 576 warnx("invalid Ethernet address '%s'", a); 577 return(1); 578 } 579 *n = *ea; 580 return(0); 581 } 582 583 void 584 usage(void) 585 { 586 fprintf(stderr, "%s\n%s\n%s\n%s\n%s\n%s\n%s\n", 587 "usage: arp [-n] [-c cpu] hostname", 588 " arp [-n] [-c cpu] -a", 589 " arp -d hostname [pub]", 590 " arp -d -a", 591 " arp -s hostname ether_addr [temp] [pub [only]]", 592 " arp -S hostname ether_addr [temp] [pub [only]]", 593 " arp -f filename"); 594 exit(1); 595 } 596 597 int 598 rtmsg(int cmd) 599 { 600 static int seq; 601 int rlen; 602 struct rt_msghdr *rtm = &m_rtmsg.m_rtm; 603 char *cp = m_rtmsg.m_space; 604 int l; 605 606 errno = 0; 607 if (cmd == RTM_DELETE || cmd == RTM_CHANGE) 608 goto doit; 609 bzero((char *)&m_rtmsg, sizeof(m_rtmsg)); 610 rtm->rtm_flags = flags; 611 rtm->rtm_version = RTM_VERSION; 612 613 switch (cmd) { 614 default: 615 errx(1, "internal wrong cmd"); 616 case RTM_ADD: 617 rtm->rtm_addrs |= RTA_GATEWAY; 618 rtm->rtm_rmx.rmx_expire = expire_time; 619 rtm->rtm_inits = RTV_EXPIRE; 620 rtm->rtm_flags |= (RTF_HOST | RTF_STATIC); 621 sin_m.sin_other = 0; 622 if (doing_proxy) { 623 if (proxy_only) 624 sin_m.sin_other = SIN_PROXY; 625 else { 626 rtm->rtm_addrs |= RTA_NETMASK; 627 rtm->rtm_flags &= ~RTF_HOST; 628 } 629 } 630 /* FALLTHROUGH */ 631 case RTM_GET: 632 rtm->rtm_addrs |= RTA_DST; 633 } 634 #define NEXTADDR(w, s) \ 635 if (rtm->rtm_addrs & (w)) { \ 636 bcopy((char *)&s, cp, sizeof(s)); cp += ROUNDUP(sizeof(s));} 637 638 NEXTADDR(RTA_DST, sin_m); 639 NEXTADDR(RTA_GATEWAY, sdl_m); 640 NEXTADDR(RTA_NETMASK, so_mask); 641 642 rtm->rtm_msglen = cp - (char *)&m_rtmsg; 643 doit: 644 l = rtm->rtm_msglen; 645 rtm->rtm_seq = ++seq; 646 rtm->rtm_type = cmd; 647 if ((rlen = write(s, (char *)&m_rtmsg, l)) < 0) { 648 if (errno != ESRCH || (cmd != RTM_DELETE && cmd != RTM_CHANGE)) { 649 warn("writing to routing socket"); 650 return(-1); 651 } 652 } 653 do { 654 l = read(s, (char *)&m_rtmsg, sizeof(m_rtmsg)); 655 } while (l > 0 && (rtm->rtm_seq != seq || rtm->rtm_pid != pid)); 656 if (l < 0) 657 warn("read from routing socket"); 658 return(0); 659 } 660 661 /* 662 * get_ether_addr - get the hardware address of an interface on the 663 * the same subnet as ipaddr. 664 */ 665 #define MAX_IFS 32 666 667 int 668 get_ether_addr(u_int32_t ipaddr, struct ether_addr *hwaddr) 669 { 670 struct ifreq *ifr, *ifend, *ifp; 671 u_int32_t ina, mask; 672 struct sockaddr_dl *dla; 673 struct ifreq ifreq; 674 struct ifconf ifc; 675 struct ifreq ifs[MAX_IFS]; 676 int sock; 677 678 sock = socket(AF_INET, SOCK_DGRAM, 0); 679 if (sock < 0) 680 err(1, "socket"); 681 682 ifc.ifc_len = sizeof(ifs); 683 ifc.ifc_req = ifs; 684 if (ioctl(sock, SIOCGIFCONF, &ifc) < 0) { 685 warnx("ioctl(SIOCGIFCONF)"); 686 close(sock); 687 return(0); 688 } 689 690 /* 691 * Scan through looking for an interface with an Internet 692 * address on the same subnet as `ipaddr'. 693 */ 694 ifend = (struct ifreq *) (ifc.ifc_buf + ifc.ifc_len); 695 for (ifr = ifc.ifc_req; ifr < ifend; ) { 696 if (ifr->ifr_addr.sa_family == AF_INET) { 697 ina = ((struct sockaddr_in *) 698 &ifr->ifr_addr)->sin_addr.s_addr; 699 strncpy(ifreq.ifr_name, ifr->ifr_name, 700 sizeof(ifreq.ifr_name)); 701 /* 702 * Check that the interface is up, 703 * and not point-to-point or loopback. 704 */ 705 if (ioctl(sock, SIOCGIFFLAGS, &ifreq) < 0) 706 continue; 707 if ((ifreq.ifr_flags & 708 (IFF_UP|IFF_BROADCAST|IFF_POINTOPOINT| 709 IFF_LOOPBACK|IFF_NOARP)) 710 != (IFF_UP|IFF_BROADCAST)) 711 goto nextif; 712 /* 713 * Get its netmask and check that it's on 714 * the right subnet. 715 */ 716 if (ioctl(sock, SIOCGIFNETMASK, &ifreq) < 0) 717 continue; 718 mask = ((struct sockaddr_in *) 719 &ifreq.ifr_addr)->sin_addr.s_addr; 720 if ((ipaddr & mask) != (ina & mask)) 721 goto nextif; 722 break; 723 } 724 nextif: 725 ifr = (struct ifreq *) ((char *)&ifr->ifr_addr 726 + MAX(ifr->ifr_addr.sa_len, sizeof(ifr->ifr_addr))); 727 } 728 729 if (ifr >= ifend) { 730 close(sock); 731 return(0); 732 } 733 734 /* 735 * Now scan through again looking for a link-level address 736 * for this interface. 737 */ 738 ifp = ifr; 739 for (ifr = ifc.ifc_req; ifr < ifend; ) { 740 if (strcmp(ifp->ifr_name, ifr->ifr_name) == 0 741 && ifr->ifr_addr.sa_family == AF_LINK) { 742 /* 743 * Found the link-level address - copy it out 744 */ 745 dla = (struct sockaddr_dl *) &ifr->ifr_addr; 746 memcpy(hwaddr, LLADDR(dla), dla->sdl_alen); 747 close (sock); 748 printf("using interface %s for proxy with address ", 749 ifp->ifr_name); 750 printf("%s\n", ether_ntoa(hwaddr)); 751 return(dla->sdl_alen); 752 } 753 ifr = (struct ifreq *) ((char *)&ifr->ifr_addr 754 + MAX(ifr->ifr_addr.sa_len, sizeof(ifr->ifr_addr))); 755 } 756 return(0); 757 } 758