arp.c revision 96202
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 96202 2002-05-08 00:55:29Z kbyanc $"; 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/iso88025.h> 68#include <net/route.h> 69 70#include <netinet/in.h> 71#include <netinet/if_ether.h> 72 73#include <arpa/inet.h> 74 75#include <err.h> 76#include <errno.h> 77#include <netdb.h> 78#include <nlist.h> 79#include <paths.h> 80#include <stdio.h> 81#include <stdlib.h> 82#include <string.h> 83#include <strings.h> 84#include <unistd.h> 85 86void search(u_long addr, void (*action)(struct sockaddr_dl *sdl, 87 struct sockaddr_inarp *sin, struct rt_msghdr *rtm)); 88void print_entry(struct sockaddr_dl *sdl, 89 struct sockaddr_inarp *addr, struct rt_msghdr *rtm); 90void nuke_entry(struct sockaddr_dl *sdl, 91 struct sockaddr_inarp *addr, struct rt_msghdr *rtm); 92int delete(char *host, char *info); 93void usage(void); 94int set(int argc, char **argv); 95int get(char *host); 96int file(char *name); 97void getsocket(void); 98int my_ether_aton(char *a, struct ether_addr *n); 99int rtmsg(int cmd); 100int get_ether_addr(u_int32_t ipaddr, struct ether_addr *hwaddr); 101 102static int pid; 103static int nflag; /* no reverse dns lookups */ 104static int aflag; /* do it for all entries */ 105static int s = -1; 106 107struct sockaddr_in so_mask; 108struct sockaddr_inarp blank_sin, sin_m; 109struct sockaddr_dl blank_sdl, sdl_m; 110int expire_time, flags, doing_proxy, proxy_only, found_entry; 111struct { 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 127int 128main(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 */ 217int 218file(char *name) 219{ 220 FILE *fp; 221 int i, retval; 222 char line[100], arg[5][50], *args[5]; 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 i = sscanf(line, "%49s %49s %49s %49s %49s", arg[0], arg[1], 234 arg[2], arg[3], arg[4]); 235 if (i < 2) { 236 warnx("bad line: %s", line); 237 retval = 1; 238 continue; 239 } 240 if (set(i, args)) 241 retval = 1; 242 } 243 fclose(fp); 244 return (retval); 245} 246 247void 248getsocket(void) 249{ 250 if (s < 0) { 251 s = socket(PF_ROUTE, SOCK_RAW, 0); 252 if (s < 0) 253 err(1, "socket"); 254 } 255} 256 257/* 258 * Set an individual arp entry 259 */ 260int 261set(int argc, char **argv) 262{ 263 struct hostent *hp; 264 register struct sockaddr_inarp *addr = &sin_m; 265 register struct sockaddr_dl *sdl; 266 register struct rt_msghdr *rtm = &(m_rtmsg.m_rtm); 267 struct ether_addr *ea; 268 char *host = argv[0], *eaddr = argv[1]; 269 270 getsocket(); 271 argc -= 2; 272 argv += 2; 273 sdl_m = blank_sdl; 274 sin_m = blank_sin; 275 addr->sin_addr.s_addr = inet_addr(host); 276 if (addr->sin_addr.s_addr == INADDR_NONE) { 277 if (!(hp = gethostbyname(host))) { 278 warnx("%s: %s", host, hstrerror(h_errno)); 279 return (1); 280 } 281 bcopy((char *)hp->h_addr, (char *)&addr->sin_addr, 282 sizeof addr->sin_addr); 283 } 284 doing_proxy = flags = proxy_only = expire_time = 0; 285 while (argc-- > 0) { 286 if (strncmp(argv[0], "temp", 4) == 0) { 287 struct timeval tv; 288 gettimeofday(&tv, 0); 289 expire_time = tv.tv_sec + 20 * 60; 290 } 291 else if (strncmp(argv[0], "pub", 3) == 0) { 292 flags |= RTF_ANNOUNCE; 293 doing_proxy = 1; 294 if (argc && strncmp(argv[1], "only", 3) == 0) { 295 proxy_only = 1; 296 sin_m.sin_other = SIN_PROXY; 297 argc--; argv++; 298 } 299 } else if (strncmp(argv[0], "trail", 5) == 0) { 300 printf("%s: Sending trailers is no longer supported\n", 301 host); 302 } 303 argv++; 304 } 305 ea = (struct ether_addr *)LLADDR(&sdl_m); 306 if (doing_proxy && !strcmp(eaddr, "auto")) { 307 if (!get_ether_addr(addr->sin_addr.s_addr, ea)) { 308 printf("no interface found for %s\n", 309 inet_ntoa(addr->sin_addr)); 310 return (1); 311 } 312 sdl_m.sdl_alen = ETHER_ADDR_LEN; 313 } else { 314 if (my_ether_aton(eaddr, ea) == 0) 315 sdl_m.sdl_alen = ETHER_ADDR_LEN; 316 } 317tryagain: 318 if (rtmsg(RTM_GET) < 0) { 319 warn("%s", host); 320 return (1); 321 } 322 addr = (struct sockaddr_inarp *)(rtm + 1); 323 sdl = (struct sockaddr_dl *)(ROUNDUP(addr->sin_len) + (char *)addr); 324 if (addr->sin_addr.s_addr == sin_m.sin_addr.s_addr) { 325 if (sdl->sdl_family == AF_LINK && 326 (rtm->rtm_flags & RTF_LLINFO) && 327 !(rtm->rtm_flags & RTF_GATEWAY)) switch (sdl->sdl_type) { 328 case IFT_ETHER: case IFT_FDDI: case IFT_ISO88023: 329 case IFT_ISO88024: case IFT_ISO88025: case IFT_L2VLAN: 330 goto overwrite; 331 } 332 if (doing_proxy == 0) { 333 printf("set: can only proxy for %s\n", host); 334 return (1); 335 } 336 if (sin_m.sin_other & SIN_PROXY) { 337 printf("set: proxy entry exists for non 802 device\n"); 338 return(1); 339 } 340 sin_m.sin_other = SIN_PROXY; 341 proxy_only = 1; 342 goto tryagain; 343 } 344overwrite: 345 if (sdl->sdl_family != AF_LINK) { 346 printf("cannot intuit interface index and type for %s\n", host); 347 return (1); 348 } 349 sdl_m.sdl_type = sdl->sdl_type; 350 sdl_m.sdl_index = sdl->sdl_index; 351 return (rtmsg(RTM_ADD)); 352} 353 354/* 355 * Display an individual arp entry 356 */ 357int 358get(char *host) 359{ 360 struct hostent *hp; 361 struct sockaddr_inarp *addr = &sin_m; 362 363 sin_m = blank_sin; 364 addr->sin_addr.s_addr = inet_addr(host); 365 if (addr->sin_addr.s_addr == INADDR_NONE) { 366 if (!(hp = gethostbyname(host))) 367 errx(1, "%s: %s", host, hstrerror(h_errno)); 368 bcopy((char *)hp->h_addr, (char *)&addr->sin_addr, 369 sizeof addr->sin_addr); 370 } 371 search(addr->sin_addr.s_addr, print_entry); 372 if (found_entry == 0) { 373 printf("%s (%s) -- no entry\n", 374 host, inet_ntoa(addr->sin_addr)); 375 return(1); 376 } 377 return(0); 378} 379 380/* 381 * Delete an arp entry 382 */ 383int 384delete(char *host, char *info) 385{ 386 struct hostent *hp; 387 register struct sockaddr_inarp *addr = &sin_m; 388 register struct rt_msghdr *rtm = &m_rtmsg.m_rtm; 389 struct sockaddr_dl *sdl; 390 391 getsocket(); 392 sin_m = blank_sin; 393 if (info) { 394 if (strncmp(info, "pub", 3) == 0) 395 sin_m.sin_other = SIN_PROXY; 396 else 397 usage(); 398 } 399 addr->sin_addr.s_addr = inet_addr(host); 400 if (addr->sin_addr.s_addr == INADDR_NONE) { 401 if (!(hp = gethostbyname(host))) { 402 warnx("%s: %s", host, hstrerror(h_errno)); 403 return (1); 404 } 405 bcopy((char *)hp->h_addr, (char *)&addr->sin_addr, 406 sizeof addr->sin_addr); 407 } 408tryagain: 409 if (rtmsg(RTM_GET) < 0) { 410 warn("%s", host); 411 return (1); 412 } 413 addr = (struct sockaddr_inarp *)(rtm + 1); 414 sdl = (struct sockaddr_dl *)(ROUNDUP(addr->sin_len) + (char *)addr); 415 if (addr->sin_addr.s_addr == sin_m.sin_addr.s_addr) { 416 if (sdl->sdl_family == AF_LINK && 417 (rtm->rtm_flags & RTF_LLINFO) && 418 !(rtm->rtm_flags & RTF_GATEWAY)) switch (sdl->sdl_type) { 419 case IFT_ETHER: case IFT_FDDI: case IFT_ISO88023: 420 case IFT_ISO88024: case IFT_ISO88025: case IFT_L2VLAN: 421 goto delete; 422 } 423 } 424 if (sin_m.sin_other & SIN_PROXY) { 425 fprintf(stderr, "delete: can't locate %s\n",host); 426 return (1); 427 } else { 428 sin_m.sin_other = SIN_PROXY; 429 goto tryagain; 430 } 431delete: 432 if (sdl->sdl_family != AF_LINK) { 433 printf("cannot locate %s\n", host); 434 return (1); 435 } 436 if (rtmsg(RTM_DELETE) == 0) { 437 printf("%s (%s) deleted\n", host, inet_ntoa(addr->sin_addr)); 438 return (0); 439 } 440 return (1); 441} 442 443/* 444 * Search the arp table and do some action on matching entries 445 */ 446void 447search(u_long addr, void (*action)(struct sockaddr_dl *sdl, 448 struct sockaddr_inarp *sin, struct rt_msghdr *rtm)) 449{ 450 int mib[6]; 451 size_t needed; 452 char *lim, *buf, *next; 453 struct rt_msghdr *rtm; 454 struct sockaddr_inarp *sin2; 455 struct sockaddr_dl *sdl; 456 457 mib[0] = CTL_NET; 458 mib[1] = PF_ROUTE; 459 mib[2] = 0; 460 mib[3] = AF_INET; 461 mib[4] = NET_RT_FLAGS; 462 mib[5] = RTF_LLINFO; 463 if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0) 464 errx(1, "route-sysctl-estimate"); 465 if ((buf = malloc(needed)) == NULL) 466 errx(1, "malloc"); 467 if (sysctl(mib, 6, buf, &needed, NULL, 0) < 0) 468 errx(1, "actual retrieval of routing table"); 469 lim = buf + needed; 470 for (next = buf; next < lim; next += rtm->rtm_msglen) { 471 rtm = (struct rt_msghdr *)next; 472 sin2 = (struct sockaddr_inarp *)(rtm + 1); 473 (char *)sdl = (char *)sin2 + ROUNDUP(sin2->sin_len); 474 if (addr) { 475 if (addr != sin2->sin_addr.s_addr) 476 continue; 477 found_entry = 1; 478 } 479 (*action)(sdl, sin2, rtm); 480 } 481 free(buf); 482} 483 484/* 485 * Display an arp entry 486 */ 487void 488print_entry(struct sockaddr_dl *sdl, 489 struct sockaddr_inarp *addr, struct rt_msghdr *rtm) 490{ 491 const char *host; 492 struct hostent *hp; 493 struct iso88025_sockaddr_dl_data *trld; 494 char ifname[IF_NAMESIZE]; 495 int seg; 496 497 if (nflag == 0) 498 hp = gethostbyaddr((caddr_t)&(addr->sin_addr), 499 sizeof addr->sin_addr, AF_INET); 500 else 501 hp = 0; 502 if (hp) 503 host = hp->h_name; 504 else { 505 host = "?"; 506 if (h_errno == TRY_AGAIN) 507 nflag = 1; 508 } 509 printf("%s (%s) at ", host, inet_ntoa(addr->sin_addr)); 510 if (sdl->sdl_alen) 511 printf("%s", ether_ntoa((struct ether_addr *)LLADDR(sdl))); 512 else 513 printf("(incomplete)"); 514 if (if_indextoname(sdl->sdl_index, ifname) != NULL) 515 printf(" on %s", ifname); 516 if (rtm->rtm_rmx.rmx_expire == 0) 517 printf(" permanent"); 518 if (addr->sin_other & SIN_PROXY) 519 printf(" published (proxy only)"); 520 if (rtm->rtm_addrs & RTA_NETMASK) { 521 addr = (struct sockaddr_inarp *) 522 (ROUNDUP(sdl->sdl_len) + (char *)sdl); 523 if (addr->sin_addr.s_addr == 0xffffffff) 524 printf(" published"); 525 if (addr->sin_len != 8) 526 printf("(weird)"); 527 } 528 switch(sdl->sdl_type) { 529 case IFT_ETHER: 530 printf(" [ethernet]"); 531 break; 532 case IFT_ISO88025: 533 printf(" [token-ring]"); 534 trld = SDL_ISO88025(sdl); 535 if (trld->trld_rcf != 0) { 536 printf(" rt=%x", ntohs(trld->trld_rcf)); 537 for (seg = 0; 538 seg < ((TR_RCF_RIFLEN(trld->trld_rcf) - 2 ) / 2); 539 seg++) 540 printf(":%x", ntohs(trld->trld_route[seg])); 541 } 542 break; 543 case IFT_FDDI: 544 printf(" [fddi]"); 545 break; 546 case IFT_ATM: 547 printf(" [atm]"); 548 break; 549 case IFT_L2VLAN: 550 printf(" [vlan]"); 551 break; 552 default: 553 break; 554 } 555 556 printf("\n"); 557 558} 559 560/* 561 * Nuke an arp entry 562 */ 563void 564nuke_entry(struct sockaddr_dl *sdl __unused, 565 struct sockaddr_inarp *addr, struct rt_msghdr *rtm __unused) 566{ 567 char ip[20]; 568 569 snprintf(ip, sizeof(ip), "%s", inet_ntoa(addr->sin_addr)); 570 delete(ip, NULL); 571} 572 573int 574my_ether_aton(char *a, struct ether_addr *n) 575{ 576 struct ether_addr *ea; 577 578 if ((ea = ether_aton(a)) == NULL) { 579 warnx("invalid Ethernet address '%s'", a); 580 return (1); 581 } 582 *n = *ea; 583 return (0); 584} 585 586void 587usage(void) 588{ 589 fprintf(stderr, "%s\n%s\n%s\n%s\n%s\n%s\n%s\n", 590 "usage: arp [-n] hostname", 591 " arp [-n] -a", 592 " arp -d hostname [pub]", 593 " arp -d -a", 594 " arp -s hostname ether_addr [temp] [pub]", 595 " arp -S hostname ether_addr [temp] [pub]", 596 " arp -f filename"); 597 exit(1); 598} 599 600int 601rtmsg(int cmd) 602{ 603 static int seq; 604 int rlen; 605 register struct rt_msghdr *rtm = &m_rtmsg.m_rtm; 606 register char *cp = m_rtmsg.m_space; 607 register int l; 608 609 errno = 0; 610 if (cmd == RTM_DELETE) 611 goto doit; 612 bzero((char *)&m_rtmsg, sizeof(m_rtmsg)); 613 rtm->rtm_flags = flags; 614 rtm->rtm_version = RTM_VERSION; 615 616 switch (cmd) { 617 default: 618 errx(1, "internal wrong cmd"); 619 case RTM_ADD: 620 rtm->rtm_addrs |= RTA_GATEWAY; 621 rtm->rtm_rmx.rmx_expire = expire_time; 622 rtm->rtm_inits = RTV_EXPIRE; 623 rtm->rtm_flags |= (RTF_HOST | RTF_STATIC); 624 sin_m.sin_other = 0; 625 if (doing_proxy) { 626 if (proxy_only) 627 sin_m.sin_other = SIN_PROXY; 628 else { 629 rtm->rtm_addrs |= RTA_NETMASK; 630 rtm->rtm_flags &= ~RTF_HOST; 631 } 632 } 633 /* FALLTHROUGH */ 634 case RTM_GET: 635 rtm->rtm_addrs |= RTA_DST; 636 } 637#define NEXTADDR(w, s) \ 638 if (rtm->rtm_addrs & (w)) { \ 639 bcopy((char *)&s, cp, sizeof(s)); cp += ROUNDUP(sizeof(s));} 640 641 NEXTADDR(RTA_DST, sin_m); 642 NEXTADDR(RTA_GATEWAY, sdl_m); 643 NEXTADDR(RTA_NETMASK, so_mask); 644 645 rtm->rtm_msglen = cp - (char *)&m_rtmsg; 646doit: 647 l = rtm->rtm_msglen; 648 rtm->rtm_seq = ++seq; 649 rtm->rtm_type = cmd; 650 if ((rlen = write(s, (char *)&m_rtmsg, l)) < 0) { 651 if (errno != ESRCH || cmd != RTM_DELETE) { 652 warn("writing to routing socket"); 653 return (-1); 654 } 655 } 656 do { 657 l = read(s, (char *)&m_rtmsg, sizeof(m_rtmsg)); 658 } while (l > 0 && (rtm->rtm_seq != seq || rtm->rtm_pid != pid)); 659 if (l < 0) 660 warn("read from routing socket"); 661 return (0); 662} 663 664/* 665 * get_ether_addr - get the hardware address of an interface on the 666 * the same subnet as ipaddr. 667 */ 668#define MAX_IFS 32 669 670int 671get_ether_addr(u_int32_t ipaddr, struct ether_addr *hwaddr) 672{ 673 struct ifreq *ifr, *ifend, *ifp; 674 u_int32_t ina, mask; 675 struct sockaddr_dl *dla; 676 struct ifreq ifreq; 677 struct ifconf ifc; 678 struct ifreq ifs[MAX_IFS]; 679 int sock; 680 681 sock = socket(AF_INET, SOCK_DGRAM, 0); 682 if (sock < 0) 683 err(1, "socket"); 684 685 ifc.ifc_len = sizeof(ifs); 686 ifc.ifc_req = ifs; 687 if (ioctl(sock, SIOCGIFCONF, &ifc) < 0) { 688 warnx("ioctl(SIOCGIFCONF)"); 689 close(sock); 690 return 0; 691 } 692 693 /* 694 * Scan through looking for an interface with an Internet 695 * address on the same subnet as `ipaddr'. 696 */ 697 ifend = (struct ifreq *) (ifc.ifc_buf + ifc.ifc_len); 698 for (ifr = ifc.ifc_req; ifr < ifend; ) { 699 if (ifr->ifr_addr.sa_family == AF_INET) { 700 ina = ((struct sockaddr_in *) 701 &ifr->ifr_addr)->sin_addr.s_addr; 702 strncpy(ifreq.ifr_name, ifr->ifr_name, 703 sizeof(ifreq.ifr_name)); 704 /* 705 * Check that the interface is up, 706 * and not point-to-point or loopback. 707 */ 708 if (ioctl(sock, SIOCGIFFLAGS, &ifreq) < 0) 709 continue; 710 if ((ifreq.ifr_flags & 711 (IFF_UP|IFF_BROADCAST|IFF_POINTOPOINT| 712 IFF_LOOPBACK|IFF_NOARP)) 713 != (IFF_UP|IFF_BROADCAST)) 714 goto nextif; 715 /* 716 * Get its netmask and check that it's on 717 * the right subnet. 718 */ 719 if (ioctl(sock, SIOCGIFNETMASK, &ifreq) < 0) 720 continue; 721 mask = ((struct sockaddr_in *) 722 &ifreq.ifr_addr)->sin_addr.s_addr; 723 if ((ipaddr & mask) != (ina & mask)) 724 goto nextif; 725 break; 726 } 727nextif: 728 ifr = (struct ifreq *) ((char *)&ifr->ifr_addr 729 + MAX(ifr->ifr_addr.sa_len, sizeof(ifr->ifr_addr))); 730 } 731 732 if (ifr >= ifend) { 733 close(sock); 734 return 0; 735 } 736 737 /* 738 * Now scan through again looking for a link-level address 739 * for this interface. 740 */ 741 ifp = ifr; 742 for (ifr = ifc.ifc_req; ifr < ifend; ) { 743 if (strcmp(ifp->ifr_name, ifr->ifr_name) == 0 744 && ifr->ifr_addr.sa_family == AF_LINK) { 745 /* 746 * Found the link-level address - copy it out 747 */ 748 dla = (struct sockaddr_dl *) &ifr->ifr_addr; 749 memcpy(hwaddr, LLADDR(dla), dla->sdl_alen); 750 close (sock); 751 printf("using interface %s for proxy with address ", 752 ifp->ifr_name); 753 printf("%s\n", ether_ntoa(hwaddr)); 754 return dla->sdl_alen; 755 } 756 ifr = (struct ifreq *) ((char *)&ifr->ifr_addr 757 + MAX(ifr->ifr_addr.sa_len, sizeof(ifr->ifr_addr))); 758 } 759 return 0; 760} 761