arp.c revision 356780
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 33#if 0 34#ifndef lint 35static char const copyright[] = 36"@(#) Copyright (c) 1984, 1993\n\ 37 The Regents of the University of California. All rights reserved.\n"; 38#endif /* not lint */ 39 40#ifndef lint 41static char const sccsid[] = "@(#)from: arp.c 8.2 (Berkeley) 1/2/94"; 42#endif /* not lint */ 43#endif 44#include <sys/cdefs.h> 45__FBSDID("$FreeBSD: stable/10/usr.sbin/arp/arp.c 356780 2020-01-16 08:27:30Z eugen $"); 46 47/* 48 * arp - display, set, and delete arp table entries 49 */ 50 51#include <sys/param.h> 52#include <sys/file.h> 53#include <sys/socket.h> 54#include <sys/sockio.h> 55#include <sys/sysctl.h> 56#include <sys/ioctl.h> 57#include <sys/time.h> 58 59#include <net/if.h> 60#include <net/if_dl.h> 61#include <net/if_types.h> 62#include <net/route.h> 63#include <net/iso88025.h> 64 65#include <netinet/in.h> 66#include <netinet/if_ether.h> 67 68#include <arpa/inet.h> 69 70#include <ctype.h> 71#include <err.h> 72#include <errno.h> 73#include <netdb.h> 74#include <nlist.h> 75#include <paths.h> 76#include <stdio.h> 77#include <stdlib.h> 78#include <string.h> 79#include <strings.h> 80#include <unistd.h> 81 82typedef void (action_fn)(struct sockaddr_dl *sdl, struct sockaddr_in *s_in, 83 struct rt_msghdr *rtm); 84 85static int search(u_long addr, action_fn *action); 86static action_fn print_entry; 87static action_fn nuke_entry; 88 89static int delete(char *host); 90static void usage(void); 91static int set(int argc, char **argv); 92static int get(char *host); 93static int file(char *name); 94static struct rt_msghdr *rtmsg(int cmd, 95 struct sockaddr_in *dst, struct sockaddr_dl *sdl); 96static int get_ether_addr(in_addr_t ipaddr, struct ether_addr *hwaddr); 97static struct sockaddr_in *getaddr(char *host); 98static int valid_type(int type); 99 100static int nflag; /* no reverse dns lookups */ 101static char *rifname; 102 103static time_t expire_time; 104static int flags, doing_proxy; 105 106struct if_nameindex *ifnameindex; 107 108/* which function we're supposed to do */ 109#define F_GET 1 110#define F_SET 2 111#define F_FILESET 3 112#define F_REPLACE 4 113#define F_DELETE 5 114 115#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 int aflag = 0; /* do it for all entries */ 123 124 while ((ch = getopt(argc, argv, "andfsSi:")) != -1) 125 switch(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 'i': 145 rifname = optarg; 146 break; 147 case '?': 148 default: 149 usage(); 150 } 151 argc -= optind; 152 argv += optind; 153 154 if (!func) 155 func = F_GET; 156 if (rifname) { 157 if (func != F_GET && !(func == F_DELETE && aflag)) 158 errx(1, "-i not applicable to this operation"); 159 if (if_nametoindex(rifname) == 0) { 160 if (errno == ENXIO) 161 errx(1, "interface %s does not exist", rifname); 162 else 163 err(1, "if_nametoindex(%s)", rifname); 164 } 165 } 166 switch (func) { 167 case F_GET: 168 if (aflag) { 169 if (argc != 0) 170 usage(); 171 search(0, print_entry); 172 } else { 173 if (argc != 1) 174 usage(); 175 rtn = get(argv[0]); 176 } 177 break; 178 case F_SET: 179 case F_REPLACE: 180 if (argc < 2 || argc > 6) 181 usage(); 182 if (func == F_REPLACE) 183 (void)delete(argv[0]); 184 rtn = set(argc, argv) ? 1 : 0; 185 break; 186 case F_DELETE: 187 if (aflag) { 188 if (argc != 0) 189 usage(); 190 search(0, nuke_entry); 191 } else { 192 if (argc != 1) 193 usage(); 194 rtn = delete(argv[0]); 195 } 196 break; 197 case F_FILESET: 198 if (argc != 1) 199 usage(); 200 rtn = file(argv[0]); 201 break; 202 } 203 204 if (ifnameindex != NULL) 205 if_freenameindex(ifnameindex); 206 207 return (rtn); 208} 209 210/* 211 * Process a file to set standard arp entries 212 */ 213static int 214file(char *name) 215{ 216 FILE *fp; 217 int i, retval; 218 char line[100], arg[5][50], *args[5], *p; 219 220 if ((fp = fopen(name, "r")) == NULL) 221 err(1, "cannot open %s", name); 222 args[0] = &arg[0][0]; 223 args[1] = &arg[1][0]; 224 args[2] = &arg[2][0]; 225 args[3] = &arg[3][0]; 226 args[4] = &arg[4][0]; 227 retval = 0; 228 while(fgets(line, sizeof(line), fp) != NULL) { 229 if ((p = strchr(line, '#')) != NULL) 230 *p = '\0'; 231 for (p = line; isblank(*p); p++); 232 if (*p == '\n' || *p == '\0') 233 continue; 234 i = sscanf(p, "%49s %49s %49s %49s %49s", arg[0], arg[1], 235 arg[2], arg[3], arg[4]); 236 if (i < 2) { 237 warnx("bad line: %s", line); 238 retval = 1; 239 continue; 240 } 241 if (set(i, args)) 242 retval = 1; 243 } 244 fclose(fp); 245 return (retval); 246} 247 248/* 249 * Given a hostname, fills up a (static) struct sockaddr_in with 250 * the address of the host and returns a pointer to the 251 * structure. 252 */ 253static struct sockaddr_in * 254getaddr(char *host) 255{ 256 struct hostent *hp; 257 static struct sockaddr_in reply; 258 259 bzero(&reply, sizeof(reply)); 260 reply.sin_len = sizeof(reply); 261 reply.sin_family = AF_INET; 262 reply.sin_addr.s_addr = inet_addr(host); 263 if (reply.sin_addr.s_addr == INADDR_NONE) { 264 if (!(hp = gethostbyname(host))) { 265 warnx("%s: %s", host, hstrerror(h_errno)); 266 return (NULL); 267 } 268 bcopy((char *)hp->h_addr, (char *)&reply.sin_addr, 269 sizeof reply.sin_addr); 270 } 271 return (&reply); 272} 273 274/* 275 * Returns true if the type is a valid one for ARP. 276 */ 277static int 278valid_type(int type) 279{ 280 281 switch (type) { 282 case IFT_ETHER: 283 case IFT_FDDI: 284 case IFT_INFINIBAND: 285 case IFT_ISO88023: 286 case IFT_ISO88024: 287 case IFT_ISO88025: 288 case IFT_L2VLAN: 289 case IFT_BRIDGE: 290 return (1); 291 default: 292 return (0); 293 } 294} 295 296/* 297 * Set an individual arp entry 298 */ 299static int 300set(int argc, char **argv) 301{ 302 struct sockaddr_in *addr; 303 struct sockaddr_in *dst; /* what are we looking for */ 304 struct sockaddr_dl *sdl; 305 struct rt_msghdr *rtm; 306 struct ether_addr *ea; 307 char *host = argv[0], *eaddr = argv[1]; 308 struct sockaddr_dl sdl_m; 309 310 argc -= 2; 311 argv += 2; 312 313 bzero(&sdl_m, sizeof(sdl_m)); 314 sdl_m.sdl_len = sizeof(sdl_m); 315 sdl_m.sdl_family = AF_LINK; 316 317 dst = getaddr(host); 318 if (dst == NULL) 319 return (1); 320 doing_proxy = flags = expire_time = 0; 321 while (argc-- > 0) { 322 if (strcmp(argv[0], "temp") == 0) { 323 struct timespec tp; 324 int max_age; 325 size_t len = sizeof(max_age); 326 327 clock_gettime(CLOCK_MONOTONIC, &tp); 328 if (sysctlbyname("net.link.ether.inet.max_age", 329 &max_age, &len, NULL, 0) != 0) 330 err(1, "sysctlbyname"); 331 expire_time = tp.tv_sec + max_age; 332 } else if (strcmp(argv[0], "pub") == 0) { 333 flags |= RTF_ANNOUNCE; 334 doing_proxy = 1; 335 if (argc && strcmp(argv[1], "only") == 0) { 336 /* 337 * Compatibility: in pre FreeBSD 8 times 338 * the "only" keyword used to mean that 339 * an ARP entry should be announced, but 340 * not installed into routing table. 341 */ 342 argc--; argv++; 343 } 344 } else if (strcmp(argv[0], "blackhole") == 0) { 345 if (flags & RTF_REJECT) { 346 errx(1, "Choose one of blackhole or reject, " 347 "not both."); 348 } 349 flags |= RTF_BLACKHOLE; 350 } else if (strcmp(argv[0], "reject") == 0) { 351 if (flags & RTF_BLACKHOLE) { 352 errx(1, "Choose one of blackhole or reject, " 353 "not both."); 354 } 355 flags |= RTF_REJECT; 356 } else { 357 warnx("Invalid parameter '%s'", argv[0]); 358 usage(); 359 } 360 argv++; 361 } 362 ea = (struct ether_addr *)LLADDR(&sdl_m); 363 if (doing_proxy && !strcmp(eaddr, "auto")) { 364 if (!get_ether_addr(dst->sin_addr.s_addr, ea)) { 365 warnx("no interface found for %s", 366 inet_ntoa(dst->sin_addr)); 367 return (1); 368 } 369 sdl_m.sdl_alen = ETHER_ADDR_LEN; 370 } else { 371 struct ether_addr *ea1 = ether_aton(eaddr); 372 373 if (ea1 == NULL) { 374 warnx("invalid Ethernet address '%s'", eaddr); 375 return (1); 376 } else { 377 *ea = *ea1; 378 sdl_m.sdl_alen = ETHER_ADDR_LEN; 379 } 380 } 381 382 /* 383 * In the case a proxy-arp entry is being added for 384 * a remote end point, the RTF_ANNOUNCE flag in the 385 * RTM_GET command is an indication to the kernel 386 * routing code that the interface associated with 387 * the prefix route covering the local end of the 388 * PPP link should be returned, on which ARP applies. 389 */ 390 rtm = rtmsg(RTM_GET, dst, &sdl_m); 391 if (rtm == NULL) { 392 warn("%s", host); 393 return (1); 394 } 395 addr = (struct sockaddr_in *)(rtm + 1); 396 sdl = (struct sockaddr_dl *)(SA_SIZE(addr) + (char *)addr); 397 398 if ((sdl->sdl_family != AF_LINK) || 399 (rtm->rtm_flags & RTF_GATEWAY) || 400 !valid_type(sdl->sdl_type)) { 401 warnx("cannot intuit interface index and type for %s", host); 402 return (1); 403 } 404 sdl_m.sdl_type = sdl->sdl_type; 405 sdl_m.sdl_index = sdl->sdl_index; 406 return (rtmsg(RTM_ADD, dst, &sdl_m) == NULL); 407} 408 409/* 410 * Display an individual arp entry 411 */ 412static int 413get(char *host) 414{ 415 struct sockaddr_in *addr; 416 417 addr = getaddr(host); 418 if (addr == NULL) 419 return (1); 420 if (0 == search(addr->sin_addr.s_addr, print_entry)) { 421 printf("%s (%s) -- no entry", 422 host, inet_ntoa(addr->sin_addr)); 423 if (rifname) 424 printf(" on %s", rifname); 425 printf("\n"); 426 return (1); 427 } 428 return (0); 429} 430 431/* 432 * Delete an arp entry 433 */ 434static int 435delete(char *host) 436{ 437 struct sockaddr_in *addr, *dst; 438 struct rt_msghdr *rtm; 439 struct sockaddr_dl *sdl; 440 struct sockaddr_dl sdl_m; 441 442 dst = getaddr(host); 443 if (dst == NULL) 444 return (1); 445 446 /* 447 * Perform a regular entry delete first. 448 */ 449 flags &= ~RTF_ANNOUNCE; 450 451 /* 452 * setup the data structure to notify the kernel 453 * it is the ARP entry the RTM_GET is interested 454 * in 455 */ 456 bzero(&sdl_m, sizeof(sdl_m)); 457 sdl_m.sdl_len = sizeof(sdl_m); 458 sdl_m.sdl_family = AF_LINK; 459 460 for (;;) { /* try twice */ 461 rtm = rtmsg(RTM_GET, dst, &sdl_m); 462 if (rtm == NULL) { 463 warn("%s", host); 464 return (1); 465 } 466 addr = (struct sockaddr_in *)(rtm + 1); 467 sdl = (struct sockaddr_dl *)(SA_SIZE(addr) + (char *)addr); 468 469 /* 470 * With the new L2/L3 restructure, the route 471 * returned is a prefix route. The important 472 * piece of information from the previous 473 * RTM_GET is the interface index. In the 474 * case of ECMP, the kernel will traverse 475 * the route group for the given entry. 476 */ 477 if (sdl->sdl_family == AF_LINK && 478 !(rtm->rtm_flags & RTF_GATEWAY) && 479 valid_type(sdl->sdl_type) ) { 480 addr->sin_addr.s_addr = dst->sin_addr.s_addr; 481 break; 482 } 483 484 /* 485 * Regualar entry delete failed, now check if there 486 * is a proxy-arp entry to remove. 487 */ 488 if (flags & RTF_ANNOUNCE) { 489 warnx("delete: cannot locate %s", host); 490 return (1); 491 } 492 493 flags |= RTF_ANNOUNCE; 494 } 495 rtm->rtm_flags |= RTF_LLDATA; 496 if (rtmsg(RTM_DELETE, dst, NULL) != NULL) { 497 printf("%s (%s) deleted\n", host, inet_ntoa(addr->sin_addr)); 498 return (0); 499 } 500 return (1); 501} 502 503 504/* 505 * Search the arp table and do some action on matching entries 506 */ 507static int 508search(u_long addr, action_fn *action) 509{ 510 int mib[6]; 511 size_t needed; 512 char *lim, *buf, *next; 513 struct rt_msghdr *rtm; 514 struct sockaddr_in *sin2; 515 struct sockaddr_dl *sdl; 516 char ifname[IF_NAMESIZE]; 517 int st, found_entry = 0; 518 519 mib[0] = CTL_NET; 520 mib[1] = PF_ROUTE; 521 mib[2] = 0; 522 mib[3] = AF_INET; 523 mib[4] = NET_RT_FLAGS; 524#ifdef RTF_LLINFO 525 mib[5] = RTF_LLINFO; 526#else 527 mib[5] = 0; 528#endif 529 if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0) 530 err(1, "route-sysctl-estimate"); 531 if (needed == 0) /* empty table */ 532 return 0; 533 buf = NULL; 534 for (;;) { 535 buf = reallocf(buf, needed); 536 if (buf == NULL) 537 errx(1, "could not reallocate memory"); 538 st = sysctl(mib, 6, buf, &needed, NULL, 0); 539 if (st == 0 || errno != ENOMEM) 540 break; 541 needed += needed / 8; 542 } 543 if (st == -1) 544 err(1, "actual retrieval of routing table"); 545 lim = buf + needed; 546 for (next = buf; next < lim; next += rtm->rtm_msglen) { 547 rtm = (struct rt_msghdr *)next; 548 sin2 = (struct sockaddr_in *)(rtm + 1); 549 sdl = (struct sockaddr_dl *)((char *)sin2 + SA_SIZE(sin2)); 550 if (rifname && if_indextoname(sdl->sdl_index, ifname) && 551 strcmp(ifname, rifname)) 552 continue; 553 if (addr) { 554 if (addr != sin2->sin_addr.s_addr) 555 continue; 556 found_entry = 1; 557 } 558 (*action)(sdl, sin2, rtm); 559 } 560 free(buf); 561 return (found_entry); 562} 563 564/* 565 * Display an arp entry 566 */ 567 568static void 569print_entry(struct sockaddr_dl *sdl, 570 struct sockaddr_in *addr, struct rt_msghdr *rtm) 571{ 572 const char *host; 573 struct hostent *hp; 574 struct iso88025_sockaddr_dl_data *trld; 575 struct if_nameindex *p; 576 int seg; 577 578 if (ifnameindex == NULL) 579 if ((ifnameindex = if_nameindex()) == NULL) 580 err(1, "cannot retrieve interface names"); 581 582 if (nflag == 0) 583 hp = gethostbyaddr((caddr_t)&(addr->sin_addr), 584 sizeof addr->sin_addr, AF_INET); 585 else 586 hp = 0; 587 if (hp) 588 host = hp->h_name; 589 else { 590 host = "?"; 591 if (h_errno == TRY_AGAIN) 592 nflag = 1; 593 } 594 printf("%s (%s) at ", host, inet_ntoa(addr->sin_addr)); 595 if (sdl->sdl_alen) { 596 if ((sdl->sdl_type == IFT_ETHER || 597 sdl->sdl_type == IFT_L2VLAN || 598 sdl->sdl_type == IFT_BRIDGE) && 599 sdl->sdl_alen == ETHER_ADDR_LEN) 600 printf("%s", 601 ether_ntoa((struct ether_addr *)LLADDR(sdl))); 602 else { 603 int n = sdl->sdl_nlen > 0 ? sdl->sdl_nlen + 1 : 0; 604 605 printf("%s", link_ntoa(sdl) + n); 606 } 607 } else 608 printf("(incomplete)"); 609 610 for (p = ifnameindex; p && p->if_index && p->if_name; p++) { 611 if (p->if_index == sdl->sdl_index) { 612 printf(" on %s", p->if_name); 613 break; 614 } 615 } 616 617 if (rtm->rtm_rmx.rmx_expire == 0) 618 printf(" permanent"); 619 else { 620 static struct timespec tp; 621 if (tp.tv_sec == 0) 622 clock_gettime(CLOCK_MONOTONIC, &tp); 623 if ((expire_time = rtm->rtm_rmx.rmx_expire - tp.tv_sec) > 0) 624 printf(" expires in %d seconds", (int)expire_time); 625 else 626 printf(" expired"); 627 } 628 if (rtm->rtm_flags & RTF_ANNOUNCE) 629 printf(" published"); 630 switch(sdl->sdl_type) { 631 case IFT_ETHER: 632 printf(" [ethernet]"); 633 break; 634 case IFT_ISO88025: 635 printf(" [token-ring]"); 636 trld = SDL_ISO88025(sdl); 637 if (trld->trld_rcf != 0) { 638 printf(" rt=%x", ntohs(trld->trld_rcf)); 639 for (seg = 0; 640 seg < ((TR_RCF_RIFLEN(trld->trld_rcf) - 2 ) / 2); 641 seg++) 642 printf(":%x", ntohs(*(trld->trld_route[seg]))); 643 } 644 break; 645 case IFT_FDDI: 646 printf(" [fddi]"); 647 break; 648 case IFT_ATM: 649 printf(" [atm]"); 650 break; 651 case IFT_L2VLAN: 652 printf(" [vlan]"); 653 break; 654 case IFT_IEEE1394: 655 printf(" [firewire]"); 656 break; 657 case IFT_BRIDGE: 658 printf(" [bridge]"); 659 break; 660 case IFT_INFINIBAND: 661 printf(" [infiniband]"); 662 break; 663 default: 664 break; 665 } 666 667 printf("\n"); 668 669} 670 671/* 672 * Nuke an arp entry 673 */ 674static void 675nuke_entry(struct sockaddr_dl *sdl __unused, 676 struct sockaddr_in *addr, struct rt_msghdr *rtm) 677{ 678 char ip[20]; 679 680 if (rtm->rtm_flags & RTF_PINNED) 681 return; 682 683 snprintf(ip, sizeof(ip), "%s", inet_ntoa(addr->sin_addr)); 684 delete(ip); 685} 686 687static void 688usage(void) 689{ 690 fprintf(stderr, "%s\n%s\n%s\n%s\n%s\n%s\n%s\n", 691 "usage: arp [-n] [-i interface] hostname", 692 " arp [-n] [-i interface] -a", 693 " arp -d hostname [pub]", 694 " arp -d [-i interface] -a", 695 " arp -s hostname ether_addr [temp] [reject | blackhole] [pub [only]]", 696 " arp -S hostname ether_addr [temp] [reject | blackhole] [pub [only]]", 697 " arp -f filename"); 698 exit(1); 699} 700 701static struct rt_msghdr * 702rtmsg(int cmd, struct sockaddr_in *dst, struct sockaddr_dl *sdl) 703{ 704 static int seq; 705 int rlen; 706 int l; 707 struct sockaddr_in so_mask, *som = &so_mask; 708 static int s = -1; 709 static pid_t pid; 710 711 static struct { 712 struct rt_msghdr m_rtm; 713 char m_space[512]; 714 } m_rtmsg; 715 716 struct rt_msghdr *rtm = &m_rtmsg.m_rtm; 717 char *cp = m_rtmsg.m_space; 718 719 if (s < 0) { /* first time: open socket, get pid */ 720 s = socket(PF_ROUTE, SOCK_RAW, 0); 721 if (s < 0) 722 err(1, "socket"); 723 pid = getpid(); 724 } 725 bzero(&so_mask, sizeof(so_mask)); 726 so_mask.sin_len = 8; 727 so_mask.sin_addr.s_addr = 0xffffffff; 728 729 errno = 0; 730 /* 731 * XXX RTM_DELETE relies on a previous RTM_GET to fill the buffer 732 * appropriately. 733 */ 734 if (cmd == RTM_DELETE) 735 goto doit; 736 bzero((char *)&m_rtmsg, sizeof(m_rtmsg)); 737 rtm->rtm_flags = flags; 738 rtm->rtm_version = RTM_VERSION; 739 740 switch (cmd) { 741 default: 742 errx(1, "internal wrong cmd"); 743 case RTM_ADD: 744 rtm->rtm_addrs |= RTA_GATEWAY; 745 rtm->rtm_rmx.rmx_expire = expire_time; 746 rtm->rtm_inits = RTV_EXPIRE; 747 rtm->rtm_flags |= (RTF_HOST | RTF_STATIC | RTF_LLDATA); 748 if (doing_proxy) { 749 rtm->rtm_addrs |= RTA_NETMASK; 750 rtm->rtm_flags &= ~RTF_HOST; 751 } 752 /* FALLTHROUGH */ 753 case RTM_GET: 754 rtm->rtm_addrs |= RTA_DST; 755 } 756#define NEXTADDR(w, s) \ 757 do { \ 758 if ((s) != NULL && rtm->rtm_addrs & (w)) { \ 759 bcopy((s), cp, sizeof(*(s))); \ 760 cp += SA_SIZE(s); \ 761 } \ 762 } while (0) 763 764 NEXTADDR(RTA_DST, dst); 765 NEXTADDR(RTA_GATEWAY, sdl); 766 NEXTADDR(RTA_NETMASK, som); 767 768 rtm->rtm_msglen = cp - (char *)&m_rtmsg; 769doit: 770 l = rtm->rtm_msglen; 771 rtm->rtm_seq = ++seq; 772 rtm->rtm_type = cmd; 773 if ((rlen = write(s, (char *)&m_rtmsg, l)) < 0) { 774 if (errno != ESRCH || cmd != RTM_DELETE) { 775 warn("writing to routing socket"); 776 return (NULL); 777 } 778 } 779 do { 780 l = read(s, (char *)&m_rtmsg, sizeof(m_rtmsg)); 781 } while (l > 0 && (rtm->rtm_seq != seq || rtm->rtm_pid != pid)); 782 if (l < 0) 783 warn("read from routing socket"); 784 return (rtm); 785} 786 787/* 788 * get_ether_addr - get the hardware address of an interface on the 789 * the same subnet as ipaddr. 790 */ 791#define MAX_IFS 32 792 793static int 794get_ether_addr(in_addr_t ipaddr, struct ether_addr *hwaddr) 795{ 796 struct ifreq *ifr, *ifend, *ifp; 797 in_addr_t ina, mask; 798 struct sockaddr_dl *dla; 799 struct ifreq ifreq; 800 struct ifconf ifc; 801 struct ifreq ifs[MAX_IFS]; 802 int sock; 803 int retval = 0; 804 805 sock = socket(AF_INET, SOCK_DGRAM, 0); 806 if (sock < 0) 807 err(1, "socket"); 808 809 ifc.ifc_len = sizeof(ifs); 810 ifc.ifc_req = ifs; 811 if (ioctl(sock, SIOCGIFCONF, &ifc) < 0) { 812 warnx("ioctl(SIOCGIFCONF)"); 813 goto done; 814 } 815 816#define NEXTIFR(i) \ 817 ((struct ifreq *)((char *)&(i)->ifr_addr \ 818 + MAX((i)->ifr_addr.sa_len, sizeof((i)->ifr_addr))) ) 819 820 /* 821 * Scan through looking for an interface with an Internet 822 * address on the same subnet as `ipaddr'. 823 */ 824 ifend = (struct ifreq *)(ifc.ifc_buf + ifc.ifc_len); 825 for (ifr = ifc.ifc_req; ifr < ifend; ifr = NEXTIFR(ifr) ) { 826 if (ifr->ifr_addr.sa_family != AF_INET) 827 continue; 828 strncpy(ifreq.ifr_name, ifr->ifr_name, 829 sizeof(ifreq.ifr_name)); 830 ifreq.ifr_addr = ifr->ifr_addr; 831 /* 832 * Check that the interface is up, 833 * and not point-to-point or loopback. 834 */ 835 if (ioctl(sock, SIOCGIFFLAGS, &ifreq) < 0) 836 continue; 837 if ((ifreq.ifr_flags & 838 (IFF_UP|IFF_BROADCAST|IFF_POINTOPOINT| 839 IFF_LOOPBACK|IFF_NOARP)) != (IFF_UP|IFF_BROADCAST)) 840 continue; 841 /* Get its netmask and check that it's on the right subnet. */ 842 if (ioctl(sock, SIOCGIFNETMASK, &ifreq) < 0) 843 continue; 844 mask = ((struct sockaddr_in *) 845 &ifreq.ifr_addr)->sin_addr.s_addr; 846 ina = ((struct sockaddr_in *) 847 &ifr->ifr_addr)->sin_addr.s_addr; 848 if ((ipaddr & mask) == (ina & mask)) 849 break; /* ok, we got it! */ 850 } 851 852 if (ifr >= ifend) 853 goto done; 854 855 /* 856 * Now scan through again looking for a link-level address 857 * for this interface. 858 */ 859 ifp = ifr; 860 for (ifr = ifc.ifc_req; ifr < ifend; ifr = NEXTIFR(ifr)) 861 if (strcmp(ifp->ifr_name, ifr->ifr_name) == 0 && 862 ifr->ifr_addr.sa_family == AF_LINK) 863 break; 864 if (ifr >= ifend) 865 goto done; 866 /* 867 * Found the link-level address - copy it out 868 */ 869 dla = (struct sockaddr_dl *) &ifr->ifr_addr; 870 memcpy(hwaddr, LLADDR(dla), dla->sdl_alen); 871 printf("using interface %s for proxy with address %s\n", ifp->ifr_name, 872 ether_ntoa(hwaddr)); 873 retval = dla->sdl_alen; 874done: 875 close(sock); 876 return (retval); 877} 878