arp.c revision 85123
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 85123 2001-10-19 00:33:26Z mdodd $"; 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 *sin, struct rt_msghdr *rtm); 88void nuke_entry(struct sockaddr_dl *sdl, 89 struct sockaddr_inarp *sin, 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; 105 106/* 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 ROUNDUP(a) \ 114 ((a) > 0 ? (1 + (((a) - 1) | (sizeof(long) - 1))) : sizeof(long)) 115#define SETFUNC(f) { if (func) usage(); func = (f); } 116 117int 118main(int argc, char *argv[]) 119{ 120 int ch, func = 0; 121 int rtn = 0; 122 123 pid = getpid(); 124 while ((ch = getopt(argc, argv, "andfsS")) != -1) 125 switch((char)ch) { 126 case 'a': 127 aflag = 1; 128 break; 129 case 'd': 130 SETFUNC(F_DELETE); 131 break; 132 case 'n': 133 nflag = 1; 134 break; 135 case 'S': 136 SETFUNC(F_REPLACE); 137 break; 138 case 's': 139 SETFUNC(F_SET); 140 break; 141 case 'f' : 142 SETFUNC(F_FILESET); 143 break; 144 case '?': 145 default: 146 usage(); 147 } 148 argc -= optind; 149 argv += optind; 150 151 if (!func) 152 func = F_GET; 153 switch (func) { 154 case F_GET: 155 if (aflag) { 156 if (argc != 0) 157 usage(); 158 search(0, print_entry); 159 } else { 160 if (argc != 1) 161 usage(); 162 get(argv[0]); 163 } 164 break; 165 case F_SET: 166 case F_REPLACE: 167 if (argc < 2 || argc > 6) 168 usage(); 169 if (func == F_REPLACE) 170 (void) delete(argv[0], NULL); 171 rtn = set(argc, argv) ? 1 : 0; 172 break; 173 case F_DELETE: 174 if (aflag) { 175 if (argc != 0) 176 usage(); 177 search(0, nuke_entry); 178 } else { 179 if (argc < 1 || argc > 2) 180 usage(); 181 rtn = delete(argv[0], argv[1]); 182 } 183 break; 184 case F_FILESET: 185 if (argc != 1) 186 usage(); 187 rtn = file(argv[0]); 188 break; 189 } 190 191 return(rtn); 192} 193 194/* 195 * Process a file to set standard arp entries 196 */ 197int 198file(char *name) 199{ 200 FILE *fp; 201 int i, retval; 202 char line[100], arg[5][50], *args[5]; 203 204 if ((fp = fopen(name, "r")) == NULL) 205 errx(1, "cannot open %s", name); 206 args[0] = &arg[0][0]; 207 args[1] = &arg[1][0]; 208 args[2] = &arg[2][0]; 209 args[3] = &arg[3][0]; 210 args[4] = &arg[4][0]; 211 retval = 0; 212 while(fgets(line, 100, fp) != NULL) { 213 i = sscanf(line, "%49s %49s %49s %49s %49s", arg[0], arg[1], 214 arg[2], arg[3], arg[4]); 215 if (i < 2) { 216 warnx("bad line: %s", line); 217 retval = 1; 218 continue; 219 } 220 if (set(i, args)) 221 retval = 1; 222 } 223 fclose(fp); 224 return (retval); 225} 226 227void 228getsocket(void) 229{ 230 if (s < 0) { 231 s = socket(PF_ROUTE, SOCK_RAW, 0); 232 if (s < 0) 233 err(1, "socket"); 234 } 235} 236 237struct sockaddr_in so_mask = {8, 0, 0, { 0xffffffff}}; 238struct sockaddr_inarp blank_sin = {sizeof(blank_sin), AF_INET }, sin_m; 239struct sockaddr_dl blank_sdl = {sizeof(blank_sdl), AF_LINK }, sdl_m; 240int expire_time, flags, doing_proxy, proxy_only, found_entry; 241struct { 242 struct rt_msghdr m_rtm; 243 char m_space[512]; 244} m_rtmsg; 245 246/* 247 * Set an individual arp entry 248 */ 249int 250set(int argc, char **argv) 251{ 252 struct hostent *hp; 253 register struct sockaddr_inarp *sin = &sin_m; 254 register struct sockaddr_dl *sdl; 255 register struct rt_msghdr *rtm = &(m_rtmsg.m_rtm); 256 u_char *ea; 257 char *host = argv[0], *eaddr = argv[1]; 258 259 getsocket(); 260 argc -= 2; 261 argv += 2; 262 sdl_m = blank_sdl; 263 sin_m = blank_sin; 264 sin->sin_addr.s_addr = inet_addr(host); 265 if (sin->sin_addr.s_addr == INADDR_NONE) { 266 if (!(hp = gethostbyname(host))) { 267 warnx("%s: %s", host, hstrerror(h_errno)); 268 return (1); 269 } 270 bcopy((char *)hp->h_addr, (char *)&sin->sin_addr, 271 sizeof sin->sin_addr); 272 } 273 doing_proxy = flags = proxy_only = expire_time = 0; 274 while (argc-- > 0) { 275 if (strncmp(argv[0], "temp", 4) == 0) { 276 struct timeval tv; 277 gettimeofday(&tv, 0); 278 expire_time = tv.tv_sec + 20 * 60; 279 } 280 else if (strncmp(argv[0], "pub", 3) == 0) { 281 flags |= RTF_ANNOUNCE; 282 doing_proxy = 1; 283 if (argc && strncmp(argv[1], "only", 3) == 0) { 284 proxy_only = 1; 285 sin_m.sin_other = SIN_PROXY; 286 argc--; argv++; 287 } 288 } else if (strncmp(argv[0], "trail", 5) == 0) { 289 printf("%s: Sending trailers is no longer supported\n", 290 host); 291 } 292 argv++; 293 } 294 ea = (u_char *)LLADDR(&sdl_m); 295 if (doing_proxy && !strcmp(eaddr, "auto")) { 296 if (!get_ether_addr(sin->sin_addr.s_addr, ea)) { 297 printf("no interface found for %s\n", 298 inet_ntoa(sin->sin_addr)); 299 return (1); 300 } 301 sdl_m.sdl_alen = 6; 302 } else { 303 if (my_ether_aton(eaddr, ea) == 0) 304 sdl_m.sdl_alen = 6; 305 } 306tryagain: 307 if (rtmsg(RTM_GET) < 0) { 308 warn("%s", host); 309 return (1); 310 } 311 sin = (struct sockaddr_inarp *)(rtm + 1); 312 sdl = (struct sockaddr_dl *)(ROUNDUP(sin->sin_len) + (char *)sin); 313 if (sin->sin_addr.s_addr == sin_m.sin_addr.s_addr) { 314 if (sdl->sdl_family == AF_LINK && 315 (rtm->rtm_flags & RTF_LLINFO) && 316 !(rtm->rtm_flags & RTF_GATEWAY)) switch (sdl->sdl_type) { 317 case IFT_ETHER: case IFT_FDDI: case IFT_ISO88023: 318 case IFT_ISO88024: case IFT_ISO88025: case IFT_L2VLAN: 319 goto overwrite; 320 } 321 if (doing_proxy == 0) { 322 printf("set: can only proxy for %s\n", host); 323 return (1); 324 } 325 if (sin_m.sin_other & SIN_PROXY) { 326 printf("set: proxy entry exists for non 802 device\n"); 327 return(1); 328 } 329 sin_m.sin_other = SIN_PROXY; 330 proxy_only = 1; 331 goto tryagain; 332 } 333overwrite: 334 if (sdl->sdl_family != AF_LINK) { 335 printf("cannot intuit interface index and type for %s\n", host); 336 return (1); 337 } 338 sdl_m.sdl_type = sdl->sdl_type; 339 sdl_m.sdl_index = sdl->sdl_index; 340 return (rtmsg(RTM_ADD)); 341} 342 343/* 344 * Display an individual arp entry 345 */ 346int 347get(char *host) 348{ 349 struct hostent *hp; 350 struct sockaddr_inarp *sin = &sin_m; 351 352 sin_m = blank_sin; 353 sin->sin_addr.s_addr = inet_addr(host); 354 if (sin->sin_addr.s_addr == INADDR_NONE) { 355 if (!(hp = gethostbyname(host))) 356 errx(1, "%s: %s", host, hstrerror(h_errno)); 357 bcopy((char *)hp->h_addr, (char *)&sin->sin_addr, 358 sizeof sin->sin_addr); 359 } 360 search(sin->sin_addr.s_addr, print_entry); 361 if (found_entry == 0) { 362 printf("%s (%s) -- no entry\n", 363 host, inet_ntoa(sin->sin_addr)); 364 return(1); 365 } 366 return(0); 367} 368 369/* 370 * Delete an arp entry 371 */ 372int 373delete(char *host, char *info) 374{ 375 struct hostent *hp; 376 register struct sockaddr_inarp *sin = &sin_m; 377 register struct rt_msghdr *rtm = &m_rtmsg.m_rtm; 378 struct sockaddr_dl *sdl; 379 380 getsocket(); 381 sin_m = blank_sin; 382 if (info) { 383 if (strncmp(info, "pub", 3) == 0) 384 sin_m.sin_other = SIN_PROXY; 385 else 386 usage(); 387 } 388 sin->sin_addr.s_addr = inet_addr(host); 389 if (sin->sin_addr.s_addr == INADDR_NONE) { 390 if (!(hp = gethostbyname(host))) { 391 warnx("%s: %s", host, hstrerror(h_errno)); 392 return (1); 393 } 394 bcopy((char *)hp->h_addr, (char *)&sin->sin_addr, 395 sizeof sin->sin_addr); 396 } 397tryagain: 398 if (rtmsg(RTM_GET) < 0) { 399 warn("%s", host); 400 return (1); 401 } 402 sin = (struct sockaddr_inarp *)(rtm + 1); 403 sdl = (struct sockaddr_dl *)(ROUNDUP(sin->sin_len) + (char *)sin); 404 if (sin->sin_addr.s_addr == sin_m.sin_addr.s_addr) { 405 if (sdl->sdl_family == AF_LINK && 406 (rtm->rtm_flags & RTF_LLINFO) && 407 !(rtm->rtm_flags & RTF_GATEWAY)) switch (sdl->sdl_type) { 408 case IFT_ETHER: case IFT_FDDI: case IFT_ISO88023: 409 case IFT_ISO88024: case IFT_ISO88025: case IFT_L2VLAN: 410 goto delete; 411 } 412 } 413 if (sin_m.sin_other & SIN_PROXY) { 414 fprintf(stderr, "delete: can't locate %s\n",host); 415 return (1); 416 } else { 417 sin_m.sin_other = SIN_PROXY; 418 goto tryagain; 419 } 420delete: 421 if (sdl->sdl_family != AF_LINK) { 422 printf("cannot locate %s\n", host); 423 return (1); 424 } 425 if (rtmsg(RTM_DELETE) == 0) { 426 printf("%s (%s) deleted\n", host, inet_ntoa(sin->sin_addr)); 427 return (0); 428 } 429 return (1); 430} 431 432/* 433 * Search the arp table and do some action on matching entries 434 */ 435void 436search(u_long addr, void (*action)(struct sockaddr_dl *sdl, 437 struct sockaddr_inarp *sin, struct rt_msghdr *rtm)) 438{ 439 int mib[6]; 440 size_t needed; 441 char *lim, *buf, *next; 442 struct rt_msghdr *rtm; 443 struct sockaddr_inarp *sin; 444 struct sockaddr_dl *sdl; 445 446 mib[0] = CTL_NET; 447 mib[1] = PF_ROUTE; 448 mib[2] = 0; 449 mib[3] = AF_INET; 450 mib[4] = NET_RT_FLAGS; 451 mib[5] = RTF_LLINFO; 452 if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0) 453 errx(1, "route-sysctl-estimate"); 454 if ((buf = malloc(needed)) == NULL) 455 errx(1, "malloc"); 456 if (sysctl(mib, 6, buf, &needed, NULL, 0) < 0) 457 errx(1, "actual retrieval of routing table"); 458 lim = buf + needed; 459 for (next = buf; next < lim; next += rtm->rtm_msglen) { 460 rtm = (struct rt_msghdr *)next; 461 sin = (struct sockaddr_inarp *)(rtm + 1); 462 (char *)sdl = (char *)sin + ROUNDUP(sin->sin_len); 463 if (addr) { 464 if (addr != sin->sin_addr.s_addr) 465 continue; 466 found_entry = 1; 467 } 468 (*action)(sdl, sin, rtm); 469 } 470 free(buf); 471} 472 473/* 474 * Display an arp entry 475 */ 476void 477print_entry(struct sockaddr_dl *sdl, 478 struct sockaddr_inarp *sin, struct rt_msghdr *rtm) 479{ 480 const char *host; 481 struct hostent *hp; 482 char ifname[IF_NAMESIZE]; 483 int seg; 484 485 if (nflag == 0) 486 hp = gethostbyaddr((caddr_t)&(sin->sin_addr), 487 sizeof sin->sin_addr, AF_INET); 488 else 489 hp = 0; 490 if (hp) 491 host = hp->h_name; 492 else { 493 host = "?"; 494 if (h_errno == TRY_AGAIN) 495 nflag = 1; 496 } 497 printf("%s (%s) at ", host, inet_ntoa(sin->sin_addr)); 498 if (sdl->sdl_alen) 499 ether_print(LLADDR(sdl)); 500 else 501 printf("(incomplete)"); 502 if (if_indextoname(sdl->sdl_index, ifname) != NULL) 503 printf(" on %s", ifname); 504 if (rtm->rtm_rmx.rmx_expire == 0) 505 printf(" permanent"); 506 if (sin->sin_other & SIN_PROXY) 507 printf(" published (proxy only)"); 508 if (rtm->rtm_addrs & RTA_NETMASK) { 509 sin = (struct sockaddr_inarp *) 510 (ROUNDUP(sdl->sdl_len) + (char *)sdl); 511 if (sin->sin_addr.s_addr == 0xffffffff) 512 printf(" published"); 513 if (sin->sin_len != 8) 514 printf("(weird)"); 515 } 516 switch(sdl->sdl_type) { 517 case IFT_ETHER: 518 printf(" [ethernet]"); 519 break; 520 case IFT_ISO88025: 521 printf(" [token-ring]"); 522 break; 523 case IFT_FDDI: 524 printf(" [fddi]"); 525 break; 526 case IFT_ATM: 527 printf(" [atm]"); 528 break; 529 case IFT_L2VLAN: 530 printf(" [vlan]"); 531 break; 532 default: 533 } 534 if (sdl->sdl_rcf != NULL) { 535 printf(" rt=%x", ntohs(sdl->sdl_rcf)); 536 for (seg = 0; seg < ((((ntohs(sdl->sdl_rcf) & 0x1f00) >> 8) - 2 ) / 2); seg++) 537 printf(":%x", ntohs(sdl->sdl_route[seg])); 538 } 539 540 printf("\n"); 541 542} 543 544/* 545 * Nuke an arp entry 546 */ 547void 548nuke_entry(struct sockaddr_dl *sdl, 549 struct sockaddr_inarp *sin, struct rt_msghdr *rtm) 550{ 551 char ip[20]; 552 553 snprintf(ip, sizeof(ip), "%s", inet_ntoa(sin->sin_addr)); 554 delete(ip, NULL); 555} 556 557void 558ether_print(u_char *cp) 559{ 560 printf("%02x:%02x:%02x:%02x:%02x:%02x", cp[0], cp[1], cp[2], cp[3], 561 cp[4], cp[5]); 562} 563 564int 565my_ether_aton(char *a, u_char *n) 566{ 567 int i, o[6]; 568 569 i = sscanf(a, "%x:%x:%x:%x:%x:%x", &o[0], &o[1], &o[2], 570 &o[3], &o[4], &o[5]); 571 if (i != 6) { 572 warnx("invalid Ethernet address '%s'", a); 573 return (1); 574 } 575 for (i=0; i<6; i++) 576 n[i] = o[i]; 577 return (0); 578} 579 580void 581usage(void) 582{ 583 fprintf(stderr, "%s\n%s\n%s\n%s\n%s\n%s\n%s\n", 584 "usage: arp [-n] hostname", 585 " arp [-n] -a", 586 " arp -d hostname [pub]", 587 " arp -d -a", 588 " arp -s hostname ether_addr [temp] [pub]", 589 " arp -S hostname ether_addr [temp] [pub]", 590 " arp -f filename"); 591 exit(1); 592} 593 594int 595rtmsg(int cmd) 596{ 597 static int seq; 598 int rlen; 599 register struct rt_msghdr *rtm = &m_rtmsg.m_rtm; 600 register char *cp = m_rtmsg.m_space; 601 register int l; 602 603 errno = 0; 604 if (cmd == RTM_DELETE) 605 goto doit; 606 bzero((char *)&m_rtmsg, sizeof(m_rtmsg)); 607 rtm->rtm_flags = flags; 608 rtm->rtm_version = RTM_VERSION; 609 610 switch (cmd) { 611 default: 612 errx(1, "internal wrong cmd"); 613 case RTM_ADD: 614 rtm->rtm_addrs |= RTA_GATEWAY; 615 rtm->rtm_rmx.rmx_expire = expire_time; 616 rtm->rtm_inits = RTV_EXPIRE; 617 rtm->rtm_flags |= (RTF_HOST | RTF_STATIC); 618 sin_m.sin_other = 0; 619 if (doing_proxy) { 620 if (proxy_only) 621 sin_m.sin_other = SIN_PROXY; 622 else { 623 rtm->rtm_addrs |= RTA_NETMASK; 624 rtm->rtm_flags &= ~RTF_HOST; 625 } 626 } 627 /* FALLTHROUGH */ 628 case RTM_GET: 629 rtm->rtm_addrs |= RTA_DST; 630 } 631#define NEXTADDR(w, s) \ 632 if (rtm->rtm_addrs & (w)) { \ 633 bcopy((char *)&s, cp, sizeof(s)); cp += ROUNDUP(sizeof(s));} 634 635 NEXTADDR(RTA_DST, sin_m); 636 NEXTADDR(RTA_GATEWAY, sdl_m); 637 NEXTADDR(RTA_NETMASK, so_mask); 638 639 rtm->rtm_msglen = cp - (char *)&m_rtmsg; 640doit: 641 l = rtm->rtm_msglen; 642 rtm->rtm_seq = ++seq; 643 rtm->rtm_type = cmd; 644 if ((rlen = write(s, (char *)&m_rtmsg, l)) < 0) { 645 if (errno != ESRCH || cmd != RTM_DELETE) { 646 warn("writing to routing socket"); 647 return (-1); 648 } 649 } 650 do { 651 l = read(s, (char *)&m_rtmsg, sizeof(m_rtmsg)); 652 } while (l > 0 && (rtm->rtm_seq != seq || rtm->rtm_pid != pid)); 653 if (l < 0) 654 warn("read from routing socket"); 655 return (0); 656} 657 658/* 659 * get_ether_addr - get the hardware address of an interface on the 660 * the same subnet as ipaddr. 661 */ 662#define MAX_IFS 32 663 664int 665get_ether_addr(u_int32_t ipaddr, u_char *hwaddr) 666{ 667 struct ifreq *ifr, *ifend, *ifp; 668 u_int32_t ina, mask; 669 struct sockaddr_dl *dla; 670 struct ifreq ifreq; 671 struct ifconf ifc; 672 struct ifreq ifs[MAX_IFS]; 673 int s; 674 675 s = socket(AF_INET, SOCK_DGRAM, 0); 676 if (s < 0) 677 err(1, "socket"); 678 679 ifc.ifc_len = sizeof(ifs); 680 ifc.ifc_req = ifs; 681 if (ioctl(s, SIOCGIFCONF, &ifc) < 0) { 682 warnx("ioctl(SIOCGIFCONF)"); 683 close(s); 684 return 0; 685 } 686 687 /* 688 * Scan through looking for an interface with an Internet 689 * address on the same subnet as `ipaddr'. 690 */ 691 ifend = (struct ifreq *) (ifc.ifc_buf + ifc.ifc_len); 692 for (ifr = ifc.ifc_req; ifr < ifend; ) { 693 if (ifr->ifr_addr.sa_family == AF_INET) { 694 ina = ((struct sockaddr_in *) 695 &ifr->ifr_addr)->sin_addr.s_addr; 696 strncpy(ifreq.ifr_name, ifr->ifr_name, 697 sizeof(ifreq.ifr_name)); 698 /* 699 * Check that the interface is up, 700 * and not point-to-point or loopback. 701 */ 702 if (ioctl(s, SIOCGIFFLAGS, &ifreq) < 0) 703 continue; 704 if ((ifreq.ifr_flags & 705 (IFF_UP|IFF_BROADCAST|IFF_POINTOPOINT| 706 IFF_LOOPBACK|IFF_NOARP)) 707 != (IFF_UP|IFF_BROADCAST)) 708 goto nextif; 709 /* 710 * Get its netmask and check that it's on 711 * the right subnet. 712 */ 713 if (ioctl(s, SIOCGIFNETMASK, &ifreq) < 0) 714 continue; 715 mask = ((struct sockaddr_in *) 716 &ifreq.ifr_addr)->sin_addr.s_addr; 717 if ((ipaddr & mask) != (ina & mask)) 718 goto nextif; 719 break; 720 } 721nextif: 722 ifr = (struct ifreq *) ((char *)&ifr->ifr_addr 723 + MAX(ifr->ifr_addr.sa_len, sizeof(ifr->ifr_addr))); 724 } 725 726 if (ifr >= ifend) { 727 close(s); 728 return 0; 729 } 730 731 /* 732 * Now scan through again looking for a link-level address 733 * for this interface. 734 */ 735 ifp = ifr; 736 for (ifr = ifc.ifc_req; ifr < ifend; ) { 737 if (strcmp(ifp->ifr_name, ifr->ifr_name) == 0 738 && ifr->ifr_addr.sa_family == AF_LINK) { 739 /* 740 * Found the link-level address - copy it out 741 */ 742 dla = (struct sockaddr_dl *) &ifr->ifr_addr; 743 memcpy(hwaddr, LLADDR(dla), dla->sdl_alen); 744 close (s); 745 printf("using interface %s for proxy with address ", 746 ifp->ifr_name); 747 ether_print(hwaddr); 748 printf("\n"); 749 return dla->sdl_alen; 750 } 751 ifr = (struct ifreq *) ((char *)&ifr->ifr_addr 752 + MAX(ifr->ifr_addr.sa_len, sizeof(ifr->ifr_addr))); 753 } 754 return 0; 755} 756