2.11BSD#431 - /usr/src/sys/netinet/if_ether.c

   1: /*
   2:  * Copyright (c) 1982, 1986 Regents of the University of California.
   3:  * All rights reserved.
   4:  *
   5:  * Redistribution and use in source and binary forms are permitted
   6:  * provided that this notice is preserved and that due credit is given
   7:  * to the University of California at Berkeley. The name of the University
   8:  * may not be used to endorse or promote products derived from this
   9:  * software without specific prior written permission. This software
  10:  * is provided ``as is'' without express or implied warranty.
  11:  *
  12:  *	@(#)if_ether.c	7.6 (Berkeley) 12/7/87
  13:  */
  14: 
  15: /*
  16:  * Ethernet address resolution protocol.
  17:  * TODO:
  18:  *	run at splnet (add ARP protocol intr.)
  19:  *	link entries onto hash chains, keep free list
  20:  *	add "inuse/lock" bit (or ref. count) along with valid bit
  21:  */
  22: 
  23: #include "ether.h"
  24: #if NETHER > 0
  25: 
  26: #include "param.h"
  27: #include "systm.h"
  28: #include "mbuf.h"
  29: #include "socket.h"
  30: #include "time.h"
  31: #include "kernel.h"
  32: #include "errno.h"
  33: #include "ioctl.h"
  34: #include "syslog.h"
  35: 
  36: #include "domain.h"
  37: #include "protosw.h"
  38: #include "../net/if.h"
  39: #include "in.h"
  40: #include "in_systm.h"
  41: #include "ip.h"
  42: #include "if_ether.h"
  43: 
  44: #define ARPTAB_BSIZ 5       /* bucket size */
  45: #define ARPTAB_NB   13      /* number of buckets */
  46: #define ARPTAB_SIZE (ARPTAB_BSIZ * ARPTAB_NB)
  47: struct  arptab arptab[ARPTAB_SIZE];
  48: int arptab_size = ARPTAB_SIZE;  /* for arp command */
  49: 
  50: /*
  51:  * ARP trailer negotiation.  Trailer protocol is not IP specific,
  52:  * but ARP request/response use IP addresses.
  53:  */
  54: #define ETHERTYPE_IPTRAILERS ETHERTYPE_TRAIL
  55: 
  56: #define ARPTAB_HASH(a) \
  57:     ((short)((((a) >> 16) ^ (a)) & 0x7fff) % ARPTAB_NB)
  58: 
  59: #define ARPTAB_LOOK(at,addr) { \
  60:     register n; \
  61:     at = &arptab[ARPTAB_HASH(addr) * ARPTAB_BSIZ]; \
  62:     for (n = 0 ; n < ARPTAB_BSIZ ; n++,at++) \
  63:         if (at->at_iaddr.s_addr == addr) \
  64:             break; \
  65:     if (n >= ARPTAB_BSIZ) \
  66:         at = 0; \
  67: }
  68: 
  69: /* timer values */
  70: #define ARPT_AGE    (60*1)  /* aging timer, 1 min. */
  71: #define ARPT_KILLC  20  /* kill completed entry in 20 mins. */
  72: #define ARPT_KILLI  3   /* kill incomplete entry in 3 minutes */
  73: 
  74: u_char  etherbroadcastaddr[6] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
  75: extern struct ifnet loif;
  76: extern int hz;
  77: 
  78: /*
  79:  * Timeout routine.  Age arp_tab entries once a minute.
  80:  */
  81: arptimer()
  82: {
  83:     register struct arptab *at;
  84:     register i;
  85: 
  86:     TIMEOUT(arptimer, (caddr_t)0, ARPT_AGE * hz);
  87:     at = &arptab[0];
  88:     for (i = 0; i < ARPTAB_SIZE; i++, at++) {
  89:         if (at->at_flags == 0 || (at->at_flags & ATF_PERM))
  90:             continue;
  91:         if (++at->at_timer < ((at->at_flags&ATF_COM) ?
  92:             ARPT_KILLC : ARPT_KILLI))
  93:             continue;
  94:         /* timer has expired, clear entry */
  95:         arptfree(at);
  96:     }
  97: }
  98: 
  99: /*
 100:  * Broadcast an ARP packet, asking who has addr on interface ac.
 101:  */
 102: arpwhohas(ac, addr)
 103:     register struct arpcom *ac;
 104:     struct in_addr *addr;
 105: {
 106:     register struct mbuf *m;
 107:     register struct ether_header *eh;
 108:     register struct ether_arp *ea;
 109:     struct sockaddr sa;
 110: 
 111:     if ((m = m_get(M_DONTWAIT, MT_DATA)) == NULL)
 112:         return;
 113:     m->m_len = sizeof *ea;
 114:     m->m_off = MMAXOFF - m->m_len;
 115:     ea = mtod(m, struct ether_arp *);
 116:     eh = (struct ether_header *)sa.sa_data;
 117:     bzero((caddr_t)ea, sizeof (*ea));
 118:     bcopy((caddr_t)etherbroadcastaddr, (caddr_t)eh->ether_dhost,
 119:         sizeof(eh->ether_dhost));
 120:     eh->ether_type = ETHERTYPE_ARP;     /* if_output will swap */
 121:     ea->arp_hrd = htons(ARPHRD_ETHER);
 122:     ea->arp_pro = htons(ETHERTYPE_IP);
 123:     ea->arp_hln = sizeof(ea->arp_sha);  /* hardware address length */
 124:     ea->arp_pln = sizeof(ea->arp_spa);  /* protocol address length */
 125:     ea->arp_op = htons(ARPOP_REQUEST);
 126:     bcopy((caddr_t)ac->ac_enaddr, (caddr_t)ea->arp_sha,
 127:        sizeof(ea->arp_sha));
 128:     bcopy((caddr_t)&ac->ac_ipaddr, (caddr_t)ea->arp_spa,
 129:        sizeof(ea->arp_spa));
 130:     bcopy((caddr_t)addr, (caddr_t)ea->arp_tpa, sizeof(ea->arp_tpa));
 131:     sa.sa_family = AF_UNSPEC;
 132:     (*ac->ac_if.if_output)(&ac->ac_if, m, &sa);
 133: }
 134: 
 135: int useloopback = 1;    /* use loopback interface for local traffic */
 136: 
 137: /*
 138:  * Resolve an IP address into an ethernet address.  If success,
 139:  * desten is filled in.  If there is no entry in arptab,
 140:  * set one up and broadcast a request for the IP address.
 141:  * Hold onto this mbuf and resend it once the address
 142:  * is finally resolved.  A return value of 1 indicates
 143:  * that desten has been filled in and the packet should be sent
 144:  * normally; a 0 return indicates that the packet has been
 145:  * taken over here, either now or for later transmission.
 146:  *
 147:  * We do some (conservative) locking here at splimp, since
 148:  * arptab is also altered from input interrupt service (ecintr/ilintr
 149:  * calls arpinput when ETHERTYPE_ARP packets come in).
 150:  */
 151: arpresolve(ac, m, destip, desten, usetrailers)
 152:     register struct arpcom *ac;
 153:     struct mbuf *m;
 154:     register struct in_addr *destip;
 155:     register u_char *desten;
 156:     int *usetrailers;
 157: {
 158:     register struct arptab *at;
 159:     struct sockaddr_in sin;
 160:     u_long lna;
 161:     int s;
 162: 
 163:     *usetrailers = 0;
 164:     if (in_broadcast(*destip)) {    /* broadcast address */
 165:         bcopy((caddr_t)etherbroadcastaddr, (caddr_t)desten,
 166:             sizeof(etherbroadcastaddr));
 167:         return (1);
 168:     }
 169:     lna = in_lnaof(*destip);
 170:     /* if for us, use software loopback driver if up */
 171:     if (destip->s_addr == ac->ac_ipaddr.s_addr) {
 172:         /*
 173: 		 * This test used to be
 174: 		 *	if (loif.if_flags & IFF_UP)
 175: 		 * It allowed local traffic to be forced
 176: 		 * through the hardware by configuring the loopback down.
 177: 		 * However, it causes problems during network configuration
 178: 		 * for boards that can't receive packets they send.
 179: 		 * It is now necessary to clear "useloopback"
 180: 		 * to force traffic out to the hardware.
 181: 		 */
 182:         if (useloopback) {
 183:             sin.sin_family = AF_INET;
 184:             sin.sin_addr = *destip;
 185:             (void) looutput(&loif, m, (struct sockaddr *)&sin);
 186:             /*
 187: 			 * The packet has already been sent and freed.
 188: 			 */
 189:             return (0);
 190:         } else {
 191:             bcopy((caddr_t)ac->ac_enaddr, (caddr_t)desten,
 192:                 sizeof(ac->ac_enaddr));
 193:             return (1);
 194:         }
 195:     }
 196:     s = splimp();
 197:     ARPTAB_LOOK(at, destip->s_addr);
 198:     if (at == 0) {          /* not found */
 199:         if (ac->ac_if.if_flags & IFF_NOARP) {
 200:             bcopy((caddr_t)ac->ac_enaddr, (caddr_t)desten, 3);
 201:             desten[3] = (lna >> 16) & 0x7f;
 202:             desten[4] = (lna >> 8) & 0xff;
 203:             desten[5] = lna & 0xff;
 204:             splx(s);
 205:             return (1);
 206:         } else {
 207:             at = arptnew(destip);
 208:             if (at == 0)
 209:                 panic("arpresolve: no free entry");
 210:             at->at_hold = m;
 211:             arpwhohas(ac, destip);
 212:             splx(s);
 213:             return (0);
 214:         }
 215:     }
 216:     at->at_timer = 0;       /* restart the timer */
 217:     if (at->at_flags & ATF_COM) {   /* entry IS complete */
 218:         bcopy((caddr_t)at->at_enaddr, (caddr_t)desten,
 219:             sizeof(at->at_enaddr));
 220: #ifdef I_WANT_MY_MACHINE_TO_CRASH
 221:         if (at->at_flags & ATF_USETRAILERS)
 222:             *usetrailers = 1;
 223: #endif
 224:         splx(s);
 225:         return (1);
 226:     }
 227:     /*
 228: 	 * There is an arptab entry, but no ethernet address
 229: 	 * response yet.  Replace the held mbuf with this
 230: 	 * latest one.
 231: 	 */
 232:     if (at->at_hold)
 233:         m_freem(at->at_hold);
 234:     at->at_hold = m;
 235:     arpwhohas(ac, destip);      /* ask again */
 236:     splx(s);
 237:     return (0);
 238: }
 239: 
 240: /*
 241:  * Called from 10 Mb/s Ethernet interrupt handlers
 242:  * when ether packet type ETHERTYPE_ARP
 243:  * is received.  Common length and type checks are done here,
 244:  * then the protocol-specific routine is called.
 245:  */
 246: arpinput(ac, m)
 247:     struct arpcom *ac;
 248:     struct mbuf *m;
 249: {
 250:     register struct arphdr *ar;
 251: 
 252:     if (ac->ac_if.if_flags & IFF_NOARP)
 253:         goto out;
 254:     IF_ADJ(m);
 255:     if (m->m_len < sizeof(struct arphdr))
 256:         goto out;
 257:     ar = mtod(m, struct arphdr *);
 258:     if (ntohs(ar->ar_hrd) != ARPHRD_ETHER)
 259:         goto out;
 260:     if (m->m_len < sizeof(struct arphdr) + 2 * ar->ar_hln + 2 * ar->ar_pln)
 261:         goto out;
 262: 
 263:     switch (ntohs(ar->ar_pro)) {
 264: 
 265:     case ETHERTYPE_IP:
 266:     case ETHERTYPE_IPTRAILERS:
 267:         in_arpinput(ac, m);
 268:         return;
 269: 
 270:     default:
 271:         break;
 272:     }
 273: out:
 274:     m_freem(m);
 275: }
 276: 
 277: /*
 278:  * ARP for Internet protocols on 10 Mb/s Ethernet.
 279:  * Algorithm is that given in RFC 826.
 280:  * In addition, a sanity check is performed on the sender
 281:  * protocol address, to catch impersonators.
 282:  * We also handle negotiations for use of trailer protocol:
 283:  * ARP replies for protocol type ETHERTYPE_TRAIL are sent
 284:  * along with IP replies if we want trailers sent to us,
 285:  * and also send them in response to IP replies.
 286:  * This allows either end to announce the desire to receive
 287:  * trailer packets.
 288:  * We reply to requests for ETHERTYPE_TRAIL protocol as well,
 289:  * but don't normally send requests.
 290:  */
 291: in_arpinput(ac, m)
 292:     register struct arpcom *ac;
 293:     struct mbuf *m;
 294: {
 295:     register struct ether_arp *ea;
 296:     struct ether_header *eh;
 297:     register struct arptab *at;  /* same as "merge" flag */
 298:     struct mbuf *mcopy = 0;
 299:     struct sockaddr_in sin;
 300:     struct sockaddr sa;
 301:     struct in_addr isaddr, itaddr, myaddr;
 302:     int proto, op, s, completed = 0;
 303: 
 304:     myaddr = ac->ac_ipaddr;
 305:     ea = mtod(m, struct ether_arp *);
 306:     proto = ntohs(ea->arp_pro);
 307:     op = ntohs(ea->arp_op);
 308:     bcopy((caddr_t)ea->arp_spa, (caddr_t)&isaddr, sizeof (isaddr));
 309:     bcopy((caddr_t)ea->arp_tpa, (caddr_t)&itaddr, sizeof (itaddr));
 310:     if (!bcmp((caddr_t)ea->arp_sha, (caddr_t)ac->ac_enaddr,
 311:       sizeof (ea->arp_sha)))
 312:         goto out;   /* it's from me, ignore it. */
 313:     if (!bcmp((caddr_t)ea->arp_sha, (caddr_t)etherbroadcastaddr,
 314:         sizeof (ea->arp_sha))) {
 315:         printf("arp: ether address is broadcast for IP address %x!\n",
 316:             ntohl(isaddr.s_addr));
 317:         goto out;
 318:     }
 319:     if (isaddr.s_addr == myaddr.s_addr) {
 320:         printf("%s: %s\n",
 321:             "duplicate IP address!! sent from ethernet address",
 322:             ether_sprintf(ea->arp_sha));
 323:         itaddr = myaddr;
 324:         if (op == ARPOP_REQUEST)
 325:             goto reply;
 326:         goto out;
 327:     }
 328:     s = splimp();
 329:     ARPTAB_LOOK(at, isaddr.s_addr);
 330:     if (at) {
 331:         bcopy((caddr_t)ea->arp_sha, (caddr_t)at->at_enaddr,
 332:             sizeof(ea->arp_sha));
 333:         if ((at->at_flags & ATF_COM) == 0)
 334:             completed = 1;
 335:         at->at_flags |= ATF_COM;
 336:         if (at->at_hold) {
 337:             sin.sin_family = AF_INET;
 338:             sin.sin_addr = isaddr;
 339:             (*ac->ac_if.if_output)(&ac->ac_if,
 340:                 at->at_hold, (struct sockaddr *)&sin);
 341:             at->at_hold = 0;
 342:         }
 343:     }
 344:     if (at == 0 && itaddr.s_addr == myaddr.s_addr) {
 345:         /* ensure we have a table entry */
 346:         if (at = arptnew(&isaddr)) {
 347:             bcopy((caddr_t)ea->arp_sha, (caddr_t)at->at_enaddr,
 348:                 sizeof(ea->arp_sha));
 349:             completed = 1;
 350:             at->at_flags |= ATF_COM;
 351:         }
 352:     }
 353:     splx(s);
 354: reply:
 355:     switch (proto) {
 356: 
 357:     case ETHERTYPE_IPTRAILERS:
 358:         /* partner says trailers are OK */
 359:         if (at)
 360:             at->at_flags |= ATF_USETRAILERS;
 361:         /*
 362: 		 * Reply to request iff we want trailers.
 363: 		 */
 364:         if (op != ARPOP_REQUEST || ac->ac_if.if_flags & IFF_NOTRAILERS)
 365:             goto out;
 366:         break;
 367: 
 368:     case ETHERTYPE_IP:
 369:         /*
 370: 		 * Reply if this is an IP request,
 371: 		 * or if we want to send a trailer response.
 372: 		 * Send the latter only to the IP response
 373: 		 * that completes the current ARP entry.
 374: 		 */
 375:         if (op != ARPOP_REQUEST &&
 376:             (completed == 0 || ac->ac_if.if_flags & IFF_NOTRAILERS))
 377:             goto out;
 378:     }
 379:     if (itaddr.s_addr == myaddr.s_addr) {
 380:         /* I am the target */
 381:         bcopy((caddr_t)ea->arp_sha, (caddr_t)ea->arp_tha,
 382:             sizeof(ea->arp_sha));
 383:         bcopy((caddr_t)ac->ac_enaddr, (caddr_t)ea->arp_sha,
 384:             sizeof(ea->arp_sha));
 385:     } else {
 386:         ARPTAB_LOOK(at, itaddr.s_addr);
 387:         if (at == NULL || (at->at_flags & ATF_PUBL) == 0)
 388:             goto out;
 389:         bcopy((caddr_t)ea->arp_sha, (caddr_t)ea->arp_tha,
 390:             sizeof(ea->arp_sha));
 391:         bcopy((caddr_t)at->at_enaddr, (caddr_t)ea->arp_sha,
 392:             sizeof(ea->arp_sha));
 393:     }
 394: 
 395:     bcopy((caddr_t)ea->arp_spa, (caddr_t)ea->arp_tpa,
 396:         sizeof(ea->arp_spa));
 397:     bcopy((caddr_t)&itaddr, (caddr_t)ea->arp_spa,
 398:         sizeof(ea->arp_spa));
 399:     ea->arp_op = htons(ARPOP_REPLY);
 400:     /*
 401: 	 * If incoming packet was an IP reply,
 402: 	 * we are sending a reply for type IPTRAILERS.
 403: 	 * If we are sending a reply for type IP
 404: 	 * and we want to receive trailers,
 405: 	 * send a trailer reply as well.
 406: 	 */
 407:     if (op == ARPOP_REPLY)
 408:         ea->arp_pro = htons(ETHERTYPE_IPTRAILERS);
 409:     else if (proto == ETHERTYPE_IP &&
 410:         (ac->ac_if.if_flags & IFF_NOTRAILERS) == 0)
 411:         mcopy = m_copy(m, 0, (int)M_COPYALL);
 412:     eh = (struct ether_header *)sa.sa_data;
 413:     bcopy((caddr_t)ea->arp_tha, (caddr_t)eh->ether_dhost,
 414:         sizeof(eh->ether_dhost));
 415:     eh->ether_type = ETHERTYPE_ARP;
 416:     sa.sa_family = AF_UNSPEC;
 417:     (*ac->ac_if.if_output)(&ac->ac_if, m, &sa);
 418:     if (mcopy) {
 419:         ea = mtod(mcopy, struct ether_arp *);
 420:         ea->arp_pro = htons(ETHERTYPE_IPTRAILERS);
 421:         (*ac->ac_if.if_output)(&ac->ac_if, mcopy, &sa);
 422:     }
 423:     return;
 424: out:
 425:     m_freem(m);
 426:     return;
 427: }
 428: 
 429: /*
 430:  * Free an arptab entry.
 431:  */
 432: arptfree(at)
 433:     register struct arptab *at;
 434: {
 435:     int s = splimp();
 436: 
 437:     if (at->at_hold)
 438:         m_freem(at->at_hold);
 439:     at->at_hold = 0;
 440:     at->at_timer = at->at_flags = 0;
 441:     at->at_iaddr.s_addr = 0;
 442:     splx(s);
 443: }
 444: 
 445: /*
 446:  * Enter a new address in arptab, pushing out the oldest entry
 447:  * from the bucket if there is no room.
 448:  * This always succeeds since no bucket can be completely filled
 449:  * with permanent entries (except from arpioctl when testing whether
 450:  * another permanent entry will fit).
 451:  * MUST BE CALLED AT SPLIMP.
 452:  */
 453: struct arptab *
 454: arptnew(addr)
 455:     struct in_addr *addr;
 456: {
 457:     register n;
 458:     int oldest = -1;
 459:     register struct arptab *at, *ato = NULL;
 460:     static int first = 1;
 461: 
 462:     if (first) {
 463:         first = 0;
 464:         TIMEOUT(arptimer, (caddr_t)0, hz);
 465:     }
 466:     at = &arptab[ARPTAB_HASH(addr->s_addr) * ARPTAB_BSIZ];
 467:     for (n = 0; n < ARPTAB_BSIZ; n++,at++) {
 468:         if (at->at_flags == 0)
 469:             goto out;    /* found an empty entry */
 470:         if (at->at_flags & ATF_PERM)
 471:             continue;
 472:         if ((int) at->at_timer > oldest) {
 473:             oldest = at->at_timer;
 474:             ato = at;
 475:         }
 476:     }
 477:     if (ato == NULL)
 478:         return (NULL);
 479:     at = ato;
 480:     arptfree(at);
 481: out:
 482:     at->at_iaddr = *addr;
 483:     at->at_flags = ATF_INUSE;
 484:     return (at);
 485: }
 486: 
 487: arpioctl(cmd, data)
 488:     int cmd;
 489:     caddr_t data;
 490: {
 491:     register struct arpreq *ar = (struct arpreq *)data;
 492:     register struct arptab *at;
 493:     register struct sockaddr_in *sin;
 494:     int s;
 495: 
 496:     if (ar->arp_pa.sa_family != AF_INET ||
 497:         ar->arp_ha.sa_family != AF_UNSPEC)
 498:         return (EAFNOSUPPORT);
 499:     sin = (struct sockaddr_in *)&ar->arp_pa;
 500:     s = splimp();
 501:     ARPTAB_LOOK(at, sin->sin_addr.s_addr);
 502:     if (at == NULL) {       /* not found */
 503:         if (cmd != SIOCSARP) {
 504:             splx(s);
 505:             return (ENXIO);
 506:         }
 507:         if (ifa_ifwithnet(&ar->arp_pa) == NULL) {
 508:             splx(s);
 509:             return (ENETUNREACH);
 510:         }
 511:     }
 512:     switch (cmd) {
 513: 
 514:     case SIOCSARP:      /* set entry */
 515:         if (at == NULL) {
 516:             at = arptnew(&sin->sin_addr);
 517:             if (at == NULL) {
 518:                 splx(s);
 519:                 return (EADDRNOTAVAIL);
 520:             }
 521:             if (ar->arp_flags & ATF_PERM) {
 522:             /* never make all entries in a bucket permanent */
 523:                 register struct arptab *tat;
 524: 
 525:                 /* try to re-allocate */
 526:                 tat = arptnew(&sin->sin_addr);
 527:                 if (tat == NULL) {
 528:                     arptfree(at);
 529:                     splx(s);
 530:                     return (EADDRNOTAVAIL);
 531:                 }
 532:                 arptfree(tat);
 533:             }
 534:         }
 535:         bcopy((caddr_t)ar->arp_ha.sa_data, (caddr_t)at->at_enaddr,
 536:             sizeof(at->at_enaddr));
 537:         at->at_flags = ATF_COM | ATF_INUSE |
 538:             (ar->arp_flags & (ATF_PERM|ATF_PUBL|ATF_USETRAILERS));
 539:         at->at_timer = 0;
 540:         break;
 541: 
 542:     case SIOCDARP:      /* delete entry */
 543:         arptfree(at);
 544:         break;
 545: 
 546:     case SIOCGARP:      /* get entry */
 547:         bcopy((caddr_t)at->at_enaddr, (caddr_t)ar->arp_ha.sa_data,
 548:             sizeof(at->at_enaddr));
 549:         ar->arp_flags = at->at_flags;
 550:         break;
 551:     }
 552:     splx(s);
 553:     return (0);
 554: }
 555: 
 556: /*
 557:  * Convert Ethernet address to printable (loggable) representation.
 558:  */
 559: char *
 560: ether_sprintf(ap)
 561:     register u_char *ap;
 562: {
 563:     register i;
 564:     static char etherbuf[18];
 565:     register char *cp = etherbuf;
 566:     static char digits[] = "0123456789abcdef";
 567: 
 568:     for (i = 0; i < 6; i++) {
 569:         *cp++ = digits[*ap >> 4];
 570:         *cp++ = digits[*ap++ & 0xf];
 571:         *cp++ = ':';
 572:     }
 573:     *--cp = 0;
 574:     return (etherbuf);
 575: }
 576: #endif

Defined functions

Defined variables

Defined macros