arp.c revision 87598
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 38static 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 45static char const sccsid[] = "@(#)from: arp.c 8.2 (Berkeley) 1/2/94"; 46#endif 47static const char rcsid[] = 48 "$FreeBSD: head/usr.sbin/arp/arp.c 87598 2001-12-10 06:42:56Z mikeh $"; 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 69#include <netinet/in.h> 70#include <netinet/if_ether.h> 71 72#include <arpa/inet.h> 73 74#include <err.h> 75#include <errno.h> 76#include <netdb.h> 77#include <nlist.h> 78#include <paths.h> 79#include <stdio.h> 80#include <stdlib.h> 81#include <strings.h> 82#include <unistd.h> 83 84void search(u_long addr, void (*action)(struct sockaddr_dl *sdl, 85 struct sockaddr_inarp *sin, struct rt_msghdr *rtm)); 86void print_entry(struct sockaddr_dl *sdl, 87 struct sockaddr_inarp *addr, struct rt_msghdr *rtm); 88void nuke_entry(struct sockaddr_dl *sdl, 89 struct sockaddr_inarp *addr, struct rt_msghdr *rtm); 90int delete(char *host, char *info); 91void ether_print(u_char *cp); 92void usage(void); 93int set(int argc, char **argv); 94int get(char *host); 95int file(char *name); 96void getsocket(void); 97int my_ether_aton(char *a, u_char *n); 98int rtmsg(int cmd); 99int get_ether_addr(u_int32_t ipaddr, u_char *hwaddr); 100 101static int pid; 102static int nflag; /* no reverse dns lookups */ 103static int aflag; /* do it for all entries */ 104static int s = -1; 105 106struct sockaddr_in so_mask; 107struct sockaddr_inarp blank_sin, sin_m; 108struct sockaddr_dl blank_sdl, sdl_m; 109int expire_time, flags, doing_proxy, proxy_only, found_entry; 110struct { 111 struct rt_msghdr m_rtm; 112 char m_space[512]; 113} m_rtmsg; 114 115/* which function we're supposed to do */ 116#define F_GET 1 117#define F_SET 2 118#define F_FILESET 3 119#define F_REPLACE 4 120#define F_DELETE 5 121 122#define ROUNDUP(a) \ 123 ((a) > 0 ? (1 + (((a) - 1) | (sizeof(long) - 1))) : sizeof(long)) 124#define SETFUNC(f) { if (func) usage(); func = (f); } 125 126int 127main(int argc, char *argv[]) 128{ 129 int ch, func = 0; 130 int rtn = 0; 131 132 pid = getpid(); 133 while ((ch = getopt(argc, argv, "andfsS")) != -1) 134 switch((char)ch) { 135 case 'a': 136 aflag = 1; 137 break; 138 case 'd': 139 SETFUNC(F_DELETE); 140 break; 141 case 'n': 142 nflag = 1; 143 break; 144 case 'S': 145 SETFUNC(F_REPLACE); 146 break; 147 case 's': 148 SETFUNC(F_SET); 149 break; 150 case 'f' : 151 SETFUNC(F_FILESET); 152 break; 153 case '?': 154 default: 155 usage(); 156 } 157 argc -= optind; 158 argv += optind; 159 160 bzero(&so_mask, sizeof(so_mask)); 161 so_mask.sin_family = 8; 162 so_mask.sin_addr.s_addr = 0xffffffff; 163 bzero(&blank_sin, sizeof(blank_sin)); 164 blank_sin.sin_len = sizeof(blank_sin); 165 blank_sin.sin_family = AF_INET; 166 bzero(&blank_sdl, sizeof(blank_sdl)); 167 blank_sdl.sdl_len = sizeof(blank_sdl); 168 blank_sdl.sdl_family = AF_LINK; 169 170 if (!func) 171 func = F_GET; 172 switch (func) { 173 case F_GET: 174 if (aflag) { 175 if (argc != 0) 176 usage(); 177 search(0, print_entry); 178 } else { 179 if (argc != 1) 180 usage(); 181 get(argv[0]); 182 } 183 break; 184 case F_SET: 185 case F_REPLACE: 186 if (argc < 2 || argc > 6) 187 usage(); 188 if (func == F_REPLACE) 189 (void) delete(argv[0], NULL); 190 rtn = set(argc, argv) ? 1 : 0; 191 break; 192 case F_DELETE: 193 if (aflag) { 194 if (argc != 0) 195 usage(); 196 search(0, nuke_entry); 197 } else { 198 if (argc < 1 || argc > 2) 199 usage(); 200 rtn = delete(argv[0], argv[1]); 201 } 202 break; 203 case F_FILESET: 204 if (argc != 1) 205 usage(); 206 rtn = file(argv[0]); 207 break; 208 } 209 210 return(rtn); 211} 212 213/* 214 * Process a file to set standard arp entries 215 */ 216int 217file(char *name) 218{ 219 FILE *fp; 220 int i, retval; 221 char line[100], arg[5][50], *args[5]; 222 223 if ((fp = fopen(name, "r")) == NULL) 224 errx(1, "cannot open %s", name); 225 args[0] = &arg[0][0]; 226 args[1] = &arg[1][0]; 227 args[2] = &arg[2][0]; 228 args[3] = &arg[3][0]; 229 args[4] = &arg[4][0]; 230 retval = 0; 231 while(fgets(line, 100, fp) != NULL) { 232 i = sscanf(line, "%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 246void 247getsocket(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 */ 259int 260set(int argc, char **argv) 261{ 262 struct hostent *hp; 263 register struct sockaddr_inarp *addr = &sin_m; 264 register struct sockaddr_dl *sdl; 265 register struct rt_msghdr *rtm = &(m_rtmsg.m_rtm); 266 u_char *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 = (u_char *)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 = 6; 312 } else { 313 if (my_ether_aton(eaddr, ea) == 0) 314 sdl_m.sdl_alen = 6; 315 } 316tryagain: 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 } 343overwrite: 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 */ 356int 357get(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 */ 382int 383delete(char *host, char *info) 384{ 385 struct hostent *hp; 386 register struct sockaddr_inarp *addr = &sin_m; 387 register 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 } 407tryagain: 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 } 430delete: 431 if (sdl->sdl_family != AF_LINK) { 432 printf("cannot locate %s\n", host); 433 return (1); 434 } 435 if (rtmsg(RTM_DELETE) == 0) { 436 printf("%s (%s) deleted\n", host, inet_ntoa(addr->sin_addr)); 437 return (0); 438 } 439 return (1); 440} 441 442/* 443 * Search the arp table and do some action on matching entries 444 */ 445void 446search(u_long addr, void (*action)(struct sockaddr_dl *sdl, 447 struct sockaddr_inarp *sin, struct rt_msghdr *rtm)) 448{ 449 int mib[6]; 450 size_t needed; 451 char *lim, *buf, *next; 452 struct rt_msghdr *rtm; 453 struct sockaddr_inarp *sin2; 454 struct sockaddr_dl *sdl; 455 456 mib[0] = CTL_NET; 457 mib[1] = PF_ROUTE; 458 mib[2] = 0; 459 mib[3] = AF_INET; 460 mib[4] = NET_RT_FLAGS; 461 mib[5] = RTF_LLINFO; 462 if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0) 463 errx(1, "route-sysctl-estimate"); 464 if ((buf = malloc(needed)) == NULL) 465 errx(1, "malloc"); 466 if (sysctl(mib, 6, buf, &needed, NULL, 0) < 0) 467 errx(1, "actual retrieval of routing table"); 468 lim = buf + needed; 469 for (next = buf; next < lim; next += rtm->rtm_msglen) { 470 rtm = (struct rt_msghdr *)next; 471 sin2 = (struct sockaddr_inarp *)(rtm + 1); 472 (char *)sdl = (char *)sin2 + ROUNDUP(sin2->sin_len); 473 if (addr) { 474 if (addr != sin2->sin_addr.s_addr) 475 continue; 476 found_entry = 1; 477 } 478 (*action)(sdl, sin2, rtm); 479 } 480 free(buf); 481} 482 483/* 484 * Display an arp entry 485 */ 486void 487print_entry(struct sockaddr_dl *sdl, 488 struct sockaddr_inarp *addr, struct rt_msghdr *rtm) 489{ 490 const char *host; 491 struct hostent *hp; 492 char ifname[IF_NAMESIZE]; 493 int seg; 494 495 if (nflag == 0) 496 hp = gethostbyaddr((caddr_t)&(addr->sin_addr), 497 sizeof addr->sin_addr, AF_INET); 498 else 499 hp = 0; 500 if (hp) 501 host = hp->h_name; 502 else { 503 host = "?"; 504 if (h_errno == TRY_AGAIN) 505 nflag = 1; 506 } 507 printf("%s (%s) at ", host, inet_ntoa(addr->sin_addr)); 508 if (sdl->sdl_alen) 509 ether_print(LLADDR(sdl)); 510 else 511 printf("(incomplete)"); 512 if (if_indextoname(sdl->sdl_index, ifname) != NULL) 513 printf(" on %s", ifname); 514 if (rtm->rtm_rmx.rmx_expire == 0) 515 printf(" permanent"); 516 if (addr->sin_other & SIN_PROXY) 517 printf(" published (proxy only)"); 518 if (rtm->rtm_addrs & RTA_NETMASK) { 519 addr = (struct sockaddr_inarp *) 520 (ROUNDUP(sdl->sdl_len) + (char *)sdl); 521 if (addr->sin_addr.s_addr == 0xffffffff) 522 printf(" published"); 523 if (addr->sin_len != 8) 524 printf("(weird)"); 525 } 526 switch(sdl->sdl_type) { 527 case IFT_ETHER: 528 printf(" [ethernet]"); 529 break; 530 case IFT_ISO88025: 531 printf(" [token-ring]"); 532 break; 533 case IFT_FDDI: 534 printf(" [fddi]"); 535 break; 536 case IFT_ATM: 537 printf(" [atm]"); 538 break; 539 case IFT_L2VLAN: 540 printf(" [vlan]"); 541 break; 542 default: 543 } 544 if (sdl->sdl_rcf != NULL) { 545 printf(" rt=%x", ntohs(sdl->sdl_rcf)); 546 for (seg = 0; seg < ((((ntohs(sdl->sdl_rcf) & 0x1f00) >> 8) - 2 ) / 2); seg++) 547 printf(":%x", ntohs(sdl->sdl_route[seg])); 548 } 549 550 printf("\n"); 551 552} 553 554/* 555 * Nuke an arp entry 556 */ 557void 558nuke_entry(struct sockaddr_dl *sdl __unused, 559 struct sockaddr_inarp *addr, struct rt_msghdr *rtm __unused) 560{ 561 char ip[20]; 562 563 snprintf(ip, sizeof(ip), "%s", inet_ntoa(addr->sin_addr)); 564 delete(ip, NULL); 565} 566 567void 568ether_print(u_char *cp) 569{ 570 printf("%02x:%02x:%02x:%02x:%02x:%02x", cp[0], cp[1], cp[2], cp[3], 571 cp[4], cp[5]); 572} 573 574int 575my_ether_aton(char *a, u_char *n) 576{ 577 int i, o[6]; 578 579 i = sscanf(a, "%x:%x:%x:%x:%x:%x", &o[0], &o[1], &o[2], 580 &o[3], &o[4], &o[5]); 581 if (i != 6) { 582 warnx("invalid Ethernet address '%s'", a); 583 return (1); 584 } 585 for (i=0; i<6; i++) 586 n[i] = o[i]; 587 return (0); 588} 589 590void 591usage(void) 592{ 593 fprintf(stderr, "%s\n%s\n%s\n%s\n%s\n%s\n%s\n", 594 "usage: arp [-n] hostname", 595 " arp [-n] -a", 596 " arp -d hostname [pub]", 597 " arp -d -a", 598 " arp -s hostname ether_addr [temp] [pub]", 599 " arp -S hostname ether_addr [temp] [pub]", 600 " arp -f filename"); 601 exit(1); 602} 603 604int 605rtmsg(int cmd) 606{ 607 static int seq; 608 int rlen; 609 register struct rt_msghdr *rtm = &m_rtmsg.m_rtm; 610 register char *cp = m_rtmsg.m_space; 611 register int l; 612 613 errno = 0; 614 if (cmd == RTM_DELETE) 615 goto doit; 616 bzero((char *)&m_rtmsg, sizeof(m_rtmsg)); 617 rtm->rtm_flags = flags; 618 rtm->rtm_version = RTM_VERSION; 619 620 switch (cmd) { 621 default: 622 errx(1, "internal wrong cmd"); 623 case RTM_ADD: 624 rtm->rtm_addrs |= RTA_GATEWAY; 625 rtm->rtm_rmx.rmx_expire = expire_time; 626 rtm->rtm_inits = RTV_EXPIRE; 627 rtm->rtm_flags |= (RTF_HOST | RTF_STATIC); 628 sin_m.sin_other = 0; 629 if (doing_proxy) { 630 if (proxy_only) 631 sin_m.sin_other = SIN_PROXY; 632 else { 633 rtm->rtm_addrs |= RTA_NETMASK; 634 rtm->rtm_flags &= ~RTF_HOST; 635 } 636 } 637 /* FALLTHROUGH */ 638 case RTM_GET: 639 rtm->rtm_addrs |= RTA_DST; 640 } 641#define NEXTADDR(w, s) \ 642 if (rtm->rtm_addrs & (w)) { \ 643 bcopy((char *)&s, cp, sizeof(s)); cp += ROUNDUP(sizeof(s));} 644 645 NEXTADDR(RTA_DST, sin_m); 646 NEXTADDR(RTA_GATEWAY, sdl_m); 647 NEXTADDR(RTA_NETMASK, so_mask); 648 649 rtm->rtm_msglen = cp - (char *)&m_rtmsg; 650doit: 651 l = rtm->rtm_msglen; 652 rtm->rtm_seq = ++seq; 653 rtm->rtm_type = cmd; 654 if ((rlen = write(s, (char *)&m_rtmsg, l)) < 0) { 655 if (errno != ESRCH || cmd != RTM_DELETE) { 656 warn("writing to routing socket"); 657 return (-1); 658 } 659 } 660 do { 661 l = read(s, (char *)&m_rtmsg, sizeof(m_rtmsg)); 662 } while (l > 0 && (rtm->rtm_seq != seq || rtm->rtm_pid != pid)); 663 if (l < 0) 664 warn("read from routing socket"); 665 return (0); 666} 667 668/* 669 * get_ether_addr - get the hardware address of an interface on the 670 * the same subnet as ipaddr. 671 */ 672#define MAX_IFS 32 673 674int 675get_ether_addr(u_int32_t ipaddr, u_char *hwaddr) 676{ 677 struct ifreq *ifr, *ifend, *ifp; 678 u_int32_t ina, mask; 679 struct sockaddr_dl *dla; 680 struct ifreq ifreq; 681 struct ifconf ifc; 682 struct ifreq ifs[MAX_IFS]; 683 int sock; 684 685 sock = socket(AF_INET, SOCK_DGRAM, 0); 686 if (sock < 0) 687 err(1, "socket"); 688 689 ifc.ifc_len = sizeof(ifs); 690 ifc.ifc_req = ifs; 691 if (ioctl(s, SIOCGIFCONF, &ifc) < 0) { 692 warnx("ioctl(SIOCGIFCONF)"); 693 close(sock); 694 return 0; 695 } 696 697 /* 698 * Scan through looking for an interface with an Internet 699 * address on the same subnet as `ipaddr'. 700 */ 701 ifend = (struct ifreq *) (ifc.ifc_buf + ifc.ifc_len); 702 for (ifr = ifc.ifc_req; ifr < ifend; ) { 703 if (ifr->ifr_addr.sa_family == AF_INET) { 704 ina = ((struct sockaddr_in *) 705 &ifr->ifr_addr)->sin_addr.s_addr; 706 strncpy(ifreq.ifr_name, ifr->ifr_name, 707 sizeof(ifreq.ifr_name)); 708 /* 709 * Check that the interface is up, 710 * and not point-to-point or loopback. 711 */ 712 if (ioctl(s, SIOCGIFFLAGS, &ifreq) < 0) 713 continue; 714 if ((ifreq.ifr_flags & 715 (IFF_UP|IFF_BROADCAST|IFF_POINTOPOINT| 716 IFF_LOOPBACK|IFF_NOARP)) 717 != (IFF_UP|IFF_BROADCAST)) 718 goto nextif; 719 /* 720 * Get its netmask and check that it's on 721 * the right subnet. 722 */ 723 if (ioctl(s, SIOCGIFNETMASK, &ifreq) < 0) 724 continue; 725 mask = ((struct sockaddr_in *) 726 &ifreq.ifr_addr)->sin_addr.s_addr; 727 if ((ipaddr & mask) != (ina & mask)) 728 goto nextif; 729 break; 730 } 731nextif: 732 ifr = (struct ifreq *) ((char *)&ifr->ifr_addr 733 + MAX(ifr->ifr_addr.sa_len, sizeof(ifr->ifr_addr))); 734 } 735 736 if (ifr >= ifend) { 737 close(sock); 738 return 0; 739 } 740 741 /* 742 * Now scan through again looking for a link-level address 743 * for this interface. 744 */ 745 ifp = ifr; 746 for (ifr = ifc.ifc_req; ifr < ifend; ) { 747 if (strcmp(ifp->ifr_name, ifr->ifr_name) == 0 748 && ifr->ifr_addr.sa_family == AF_LINK) { 749 /* 750 * Found the link-level address - copy it out 751 */ 752 dla = (struct sockaddr_dl *) &ifr->ifr_addr; 753 memcpy(hwaddr, LLADDR(dla), dla->sdl_alen); 754 close (s); 755 printf("using interface %s for proxy with address ", 756 ifp->ifr_name); 757 ether_print(hwaddr); 758 printf("\n"); 759 return dla->sdl_alen; 760 } 761 ifr = (struct ifreq *) ((char *)&ifr->ifr_addr 762 + MAX(ifr->ifr_addr.sa_len, sizeof(ifr->ifr_addr))); 763 } 764 return 0; 765} 766