sbin/routed/rdisc.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-3-Clause
   3  *
   4  * Copyright (c) 1995
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. Neither the name of the University nor the names of its contributors
  16  *    may be used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  *
  31  * $FreeBSD$
  32  */
  33
  34 #include "defs.h"
  35 #include <netinet/in_systm.h>
  36 #include <netinet/ip.h>
  37 #include <netinet/ip_icmp.h>
  38
  39 __RCSID("$FreeBSD$");
  40
  41 /* router advertisement ICMP packet */
  42 struct icmp_ad {
  43         u_int8_t    icmp_type;          /* type of message */
  44         u_int8_t    icmp_code;          /* type sub code */
  45         u_int16_t   icmp_cksum;         /* ones complement cksum of struct */
  46         u_int8_t    icmp_ad_num;        /* # of following router addresses */
  47         u_int8_t    icmp_ad_asize;      /* 2--words in each advertisement */
  48         u_int16_t   icmp_ad_life;       /* seconds of validity */
  49         struct icmp_ad_info {
  50             n_long  icmp_ad_addr;
  51             n_long  icmp_ad_pref;
  52         } icmp_ad_info[1];
  53 };
  54
  55 /* router solicitation ICMP packet */
  56 struct icmp_so {
  57         u_int8_t    icmp_type;          /* type of message */
  58         u_int8_t    icmp_code;          /* type sub code */
  59         u_int16_t   icmp_cksum;         /* ones complement cksum of struct */
  60         n_long      icmp_so_rsvd;
  61 };
  62
  63 union ad_u {
  64         struct icmp icmp;
  65         struct icmp_ad ad;
  66         struct icmp_so so;
  67 };
  68
  69
  70 int     rdisc_sock = -1;                /* router-discovery raw socket */
  71 static const struct interface *rdisc_sock_mcast; /* current multicast interface */
  72
  73 struct timeval rdisc_timer;
  74 int rdisc_ok;                           /* using solicited route */
  75
  76
  77 #define MAX_ADS 16                      /* at least one per interface */
  78 struct dr {                             /* accumulated advertisements */
  79     struct interface *dr_ifp;
  80     naddr   dr_gate;                    /* gateway */
  81     time_t  dr_ts;                      /* when received */
  82     time_t  dr_life;                    /* lifetime in host byte order */
  83     n_long  dr_recv_pref;               /* received but biased preference */
  84     n_long  dr_pref;                    /* preference adjusted by metric */
  85 };
  86 static const struct dr *cur_drp;
  87 static struct dr drs[MAX_ADS];
  88
  89 /* convert between signed, balanced around zero,
  90  * and unsigned zero-based preferences */
  91 #define SIGN_PREF(p) ((p) ^ MIN_PreferenceLevel)
  92 #define UNSIGN_PREF(p) SIGN_PREF(p)
  93 /* adjust unsigned preference by interface metric,
  94  * without driving it to infinity */
  95 #define PREF(p, ifp) ((int)(p) <= ((ifp)->int_metric+(ifp)->int_adj_outmetric)\
  96                       ? ((p) != 0 ? 1 : 0)                                  \
  97                       : (p) - ((ifp)->int_metric+(ifp)->int_adj_outmetric))
  98
  99 static void rdisc_sort(void);
 100
 101
 102 /* dump an ICMP Router Discovery Advertisement Message
 103  */
 104 static void
 105 trace_rdisc(const char  *act,
 106             naddr       from,
 107             naddr       to,
 108             struct interface *ifp,
 109             union ad_u  *p,
 110             u_int       len)
 111 {
 112         int i;
 113         n_long *wp, *lim;
 114
 115
 116         if (!TRACEPACKETS || ftrace == NULL)
 117                 return;
 118
 119         lastlog();
 120
 121         if (p->icmp.icmp_type == ICMP_ROUTERADVERT) {
 122                 (void)fprintf(ftrace, "%s Router Ad"
 123                               " from %s to %s via %s life=%d\n",
 124                               act, naddr_ntoa(from), naddr_ntoa(to),
 125                               ifp ? ifp->int_name : "?",
 126                               ntohs(p->ad.icmp_ad_life));
 127                 if (!TRACECONTENTS)
 128                         return;
 129
 130                 wp = &p->ad.icmp_ad_info[0].icmp_ad_addr;
 131                 lim = &wp[(len - sizeof(p->ad)) / sizeof(*wp)];
 132                 for (i = 0; i < p->ad.icmp_ad_num && wp <= lim; i++) {
 133                         (void)fprintf(ftrace, "\t%s preference=%d",
 134                                       naddr_ntoa(wp[0]), (int)ntohl(wp[1]));
 135                         wp += p->ad.icmp_ad_asize;
 136                 }
 137                 (void)fputc('\n',ftrace);
 138
 139         } else {
 140                 trace_act("%s Router Solic. from %s to %s via %s value=%#x",
 141                           act, naddr_ntoa(from), naddr_ntoa(to),
 142                           ifp ? ifp->int_name : "?",
 143                           (int)ntohl(p->so.icmp_so_rsvd));
 144         }
 145 }
 146
 147 /* prepare Router Discovery socket.
 148  */
 149 static void
 150 get_rdisc_sock(void)
 151 {
 152         if (rdisc_sock < 0) {
 153                 rdisc_sock = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
 154                 if (rdisc_sock < 0)
 155                         BADERR(1,"rdisc_sock = socket()");
 156                 fix_sock(rdisc_sock,"rdisc_sock");
 157                 fix_select();
 158         }
 159 }
 160
 161
 162 /* Pick multicast group for router-discovery socket
 163  */
 164 void
 165 set_rdisc_mg(struct interface *ifp,
 166              int on)                    /* 0=turn it off */
 167 {
 168         struct group_req gr;
 169         struct sockaddr_in *sin;
 170
 171         assert(ifp != NULL);
 172
 173         if (rdisc_sock < 0) {
 174                 /* Create the raw socket so that we can hear at least
 175                  * broadcast router discovery packets.
 176                  */
 177                 if ((ifp->int_state & IS_NO_RDISC) == IS_NO_RDISC
 178                     || !on)
 179                         return;
 180                 get_rdisc_sock();
 181         }
 182
 183         if (!(ifp->int_if_flags & IFF_MULTICAST)) {
 184                 ifp->int_state &= ~(IS_ALL_HOSTS | IS_ALL_ROUTERS);
 185                 return;
 186         }
 187
 188         memset(&gr, 0, sizeof(gr));
 189         gr.gr_interface = ifp->int_index;
 190         sin = (struct sockaddr_in *)&gr.gr_group;
 191         sin->sin_family = AF_INET;
 192 #ifdef _HAVE_SIN_LEN
 193         sin->sin_len = sizeof(struct sockaddr_in);
 194 #endif
 195
 196         if (supplier
 197             || (ifp->int_state & IS_NO_ADV_IN)
 198             || !on) {
 199                 /* stop listening to advertisements
 200                  */
 201                 if (ifp->int_state & IS_ALL_HOSTS) {
 202                         sin->sin_addr.s_addr = htonl(INADDR_ALLHOSTS_GROUP);
 203                         if (setsockopt(rdisc_sock, IPPROTO_IP,
 204                                        MCAST_LEAVE_GROUP,
 205                                        &gr, sizeof(gr)) < 0)
 206                                 LOGERR("MCAST_LEAVE_GROUP ALLHOSTS");
 207                         ifp->int_state &= ~IS_ALL_HOSTS;
 208                 }
 209
 210         } else if (!(ifp->int_state & IS_ALL_HOSTS)) {
 211                 /* start listening to advertisements
 212                  */
 213                 sin->sin_addr.s_addr = htonl(INADDR_ALLHOSTS_GROUP);
 214                 if (setsockopt(rdisc_sock, IPPROTO_IP, MCAST_JOIN_GROUP,
 215                                &gr, sizeof(gr)) < 0) {
 216                         LOGERR("MCAST_JOIN_GROUP ALLHOSTS");
 217                 } else {
 218                         ifp->int_state |= IS_ALL_HOSTS;
 219                 }
 220         }
 221
 222         if (!supplier
 223             || (ifp->int_state & IS_NO_ADV_OUT)
 224             || !on) {
 225                 /* stop listening to solicitations
 226                  */
 227                 if (ifp->int_state & IS_ALL_ROUTERS) {
 228                         sin->sin_addr.s_addr = htonl(INADDR_ALLROUTERS_GROUP);
 229                         if (setsockopt(rdisc_sock, IPPROTO_IP,
 230                                        MCAST_LEAVE_GROUP,
 231                                        &gr, sizeof(gr)) < 0)
 232                                 LOGERR("MCAST_LEAVE_GROUP ALLROUTERS");
 233                         ifp->int_state &= ~IS_ALL_ROUTERS;
 234                 }
 235
 236         } else if (!(ifp->int_state & IS_ALL_ROUTERS)) {
 237                 /* start hearing solicitations
 238                  */
 239                 sin->sin_addr.s_addr = htonl(INADDR_ALLROUTERS_GROUP);
 240                 if (setsockopt(rdisc_sock, IPPROTO_IP, MCAST_JOIN_GROUP,
 241                                &gr, sizeof(gr)) < 0) {
 242                         LOGERR("MCAST_JOIN_GROUP ALLROUTERS");
 243                 } else {
 244                         ifp->int_state |= IS_ALL_ROUTERS;
 245                 }
 246         }
 247 }
 248
 249
 250 /* start supplying routes
 251  */
 252 void
 253 set_supplier(void)
 254 {
 255         struct interface *ifp;
 256         struct dr *drp;
 257
 258         if (supplier_set)
 259                 return;
 260
 261         trace_act("start supplying routes");
 262
 263         /* Forget discovered routes.
 264          */
 265         for (drp = drs; drp < &drs[MAX_ADS]; drp++) {
 266                 drp->dr_recv_pref = 0;
 267                 drp->dr_life = 0;
 268         }
 269         rdisc_age(0);
 270
 271         supplier_set = 1;
 272         supplier = 1;
 273
 274         /* Do not start advertising until we have heard some RIP routes */
 275         LIM_SEC(rdisc_timer, now.tv_sec+MIN_WAITTIME);
 276
 277         /* Switch router discovery multicast groups from soliciting
 278          * to advertising.
 279          */
 280         LIST_FOREACH(ifp, &ifnet, int_list) {
 281                 if (ifp->int_state & IS_BROKE)
 282                         continue;
 283                 ifp->int_rdisc_cnt = 0;
 284                 ifp->int_rdisc_timer.tv_usec = rdisc_timer.tv_usec;
 285                 ifp->int_rdisc_timer.tv_sec = now.tv_sec+MIN_WAITTIME;
 286                 set_rdisc_mg(ifp, 1);
 287         }
 288
 289         /* get rid of any redirects */
 290         del_redirects(0,0);
 291 }
 292
 293
 294 /* age discovered routes and find the best one
 295  */
 296 void
 297 rdisc_age(naddr bad_gate)
 298 {
 299         time_t sec;
 300         struct dr *drp;
 301
 302
 303         /* If only advertising, then do only that. */
 304         if (supplier) {
 305                 /* If switching from client to server, get rid of old
 306                  * default routes.
 307                  */
 308                 if (cur_drp != NULL)
 309                         rdisc_sort();
 310                 rdisc_adv();
 311                 return;
 312         }
 313
 314         /* If we are being told about a bad router,
 315          * then age the discovered default route, and if there is
 316          * no alternative, solicit a replacement.
 317          */
 318         if (bad_gate != 0) {
 319                 /* Look for the bad discovered default route.
 320                  * Age it and note its interface.
 321                  */
 322                 for (drp = drs; drp < &drs[MAX_ADS]; drp++) {
 323                         if (drp->dr_ts == 0)
 324                                 continue;
 325
 326                         /* When we find the bad router, then age the route
 327                          * to at most SUPPLY_INTERVAL.
 328                          * This is contrary to RFC 1256, but defends against
 329                          * black holes.
 330                          */
 331                         if (drp->dr_gate == bad_gate) {
 332                                 sec = (now.tv_sec - drp->dr_life
 333                                        + SUPPLY_INTERVAL);
 334                                 if (drp->dr_ts > sec) {
 335                                         trace_act("age 0.0.0.0 --> %s via %s",
 336                                                   naddr_ntoa(drp->dr_gate),
 337                                                   drp->dr_ifp->int_name);
 338                                         drp->dr_ts = sec;
 339                                 }
 340                                 break;
 341                         }
 342                 }
 343         }
 344
 345         rdisc_sol();
 346         rdisc_sort();
 347
 348         /* Delete old redirected routes to keep the kernel table small,
 349          * and to prevent black holes.  Check that the kernel table
 350          * matches the daemon table (i.e. has the default route).
 351          * But only if RIP is not running and we are not dealing with
 352          * a bad gateway, since otherwise age() will be called.
 353          */
 354         if (rip_sock < 0 && bad_gate == 0)
 355                 age(0);
 356 }
 357
 358
 359 /* Zap all routes discovered via an interface that has gone bad
 360  *      This should only be called when !(ifp->int_state & IS_ALIAS)
 361  */
 362 void
 363 if_bad_rdisc(struct interface *ifp)
 364 {
 365         struct dr *drp;
 366
 367         for (drp = drs; drp < &drs[MAX_ADS]; drp++) {
 368                 if (drp->dr_ifp != ifp)
 369                         continue;
 370                 drp->dr_recv_pref = 0;
 371                 drp->dr_ts = 0;
 372                 drp->dr_life = 0;
 373         }
 374
 375         /* make a note to re-solicit, turn RIP on or off, etc. */
 376         rdisc_timer.tv_sec = 0;
 377 }
 378
 379
 380 /* mark an interface ok for router discovering.
 381  */
 382 void
 383 if_ok_rdisc(struct interface *ifp)
 384 {
 385         set_rdisc_mg(ifp, 1);
 386
 387         ifp->int_rdisc_cnt = 0;
 388         ifp->int_rdisc_timer.tv_sec = now.tv_sec + (supplier
 389                                                     ? MIN_WAITTIME
 390                                                     : MAX_SOLICITATION_DELAY);
 391         if (timercmp(&rdisc_timer, &ifp->int_rdisc_timer, >))
 392                 rdisc_timer = ifp->int_rdisc_timer;
 393 }
 394
 395
 396 /* get rid of a dead discovered router
 397  */
 398 static void
 399 del_rdisc(struct dr *drp)
 400 {
 401         struct interface *ifp;
 402         naddr gate;
 403         int i;
 404
 405
 406         del_redirects(gate = drp->dr_gate, 0);
 407         drp->dr_ts = 0;
 408         drp->dr_life = 0;
 409
 410
 411         /* Count the other discovered routes on the interface.
 412          */
 413         i = 0;
 414         ifp = drp->dr_ifp;
 415         for (drp = drs; drp < &drs[MAX_ADS]; drp++) {
 416                 if (drp->dr_ts != 0
 417                     && drp->dr_ifp == ifp)
 418                         i++;
 419         }
 420
 421         /* If that was the last good discovered router on the interface,
 422          * then solicit a new one.
 423          * This is contrary to RFC 1256, but defends against black holes.
 424          */
 425         if (i != 0) {
 426                 trace_act("discovered router %s via %s"
 427                           " is bad--have %d remaining",
 428                           naddr_ntoa(gate), ifp->int_name, i);
 429         } else if (ifp->int_rdisc_cnt >= MAX_SOLICITATIONS) {
 430                 trace_act("last discovered router %s via %s"
 431                           " is bad--re-solicit",
 432                           naddr_ntoa(gate), ifp->int_name);
 433                 ifp->int_rdisc_cnt = 0;
 434                 ifp->int_rdisc_timer.tv_sec = 0;
 435                 rdisc_sol();
 436         } else {
 437                 trace_act("last discovered router %s via %s"
 438                           " is bad--wait to solicit",
 439                           naddr_ntoa(gate), ifp->int_name);
 440         }
 441 }
 442
 443
 444 /* Find the best discovered route,
 445  * and discard stale routers.
 446  */
 447 static void
 448 rdisc_sort(void)
 449 {
 450         struct dr *drp, *new_drp;
 451         struct rt_entry *rt;
 452         struct rt_spare new;
 453         struct interface *ifp;
 454         u_int new_st = 0;
 455         n_long new_pref = 0;
 456
 457
 458         /* Find the best discovered route.
 459          */
 460         new_drp = NULL;
 461         for (drp = drs; drp < &drs[MAX_ADS]; drp++) {
 462                 if (drp->dr_ts == 0)
 463                         continue;
 464                 ifp = drp->dr_ifp;
 465
 466                 /* Get rid of expired discovered routers.
 467                  */
 468                 if (drp->dr_ts + drp->dr_life <= now.tv_sec) {
 469                         del_rdisc(drp);
 470                         continue;
 471                 }
 472
 473                 LIM_SEC(rdisc_timer, drp->dr_ts+drp->dr_life+1);
 474
 475                 /* Update preference with possibly changed interface
 476                  * metric.
 477                  */
 478                 drp->dr_pref = PREF(drp->dr_recv_pref, ifp);
 479
 480                 /* Prefer the current route to prevent thrashing.
 481                  * Prefer shorter lifetimes to speed the detection of
 482                  * bad routers.
 483                  * Avoid sick interfaces.
 484                  */
 485                 if (new_drp == NULL
 486                     || (!((new_st ^ drp->dr_ifp->int_state) & IS_SICK)
 487                         && (new_pref < drp->dr_pref
 488                             || (new_pref == drp->dr_pref
 489                                 && (drp == cur_drp
 490                                     || (new_drp != cur_drp
 491                                         && new_drp->dr_life > drp->dr_life)))))
 492                     || ((new_st & IS_SICK)
 493                         && !(drp->dr_ifp->int_state & IS_SICK))) {
 494                             new_drp = drp;
 495                             new_st = drp->dr_ifp->int_state;
 496                             new_pref = drp->dr_pref;
 497                 }
 498         }
 499
 500         /* switch to a better default route
 501          */
 502         if (new_drp != cur_drp) {
 503                 rt = rtget(RIP_DEFAULT, 0);
 504
 505                 /* Stop using discovered routes if they are all bad
 506                  */
 507                 if (new_drp == NULL) {
 508                         trace_act("turn off Router Discovery client");
 509                         rdisc_ok = 0;
 510
 511                         if (rt != NULL
 512                             && (rt->rt_state & RS_RDISC)) {
 513                                 new = rt->rt_spares[0];
 514                                 new.rts_metric = HOPCNT_INFINITY;
 515                                 new.rts_time = now.tv_sec - GARBAGE_TIME;
 516                                 rtchange(rt, rt->rt_state & ~RS_RDISC,
 517                                          &new, 0);
 518                                 rtswitch(rt, 0);
 519                         }
 520
 521                 } else {
 522                         if (cur_drp == NULL) {
 523                                 trace_act("turn on Router Discovery client"
 524                                           " using %s via %s",
 525                                           naddr_ntoa(new_drp->dr_gate),
 526                                           new_drp->dr_ifp->int_name);
 527                                 rdisc_ok = 1;
 528
 529                         } else {
 530                                 trace_act("switch Router Discovery from"
 531                                           " %s via %s to %s via %s",
 532                                           naddr_ntoa(cur_drp->dr_gate),
 533                                           cur_drp->dr_ifp->int_name,
 534                                           naddr_ntoa(new_drp->dr_gate),
 535                                           new_drp->dr_ifp->int_name);
 536                         }
 537
 538                         memset(&new, 0, sizeof(new));
 539                         new.rts_ifp = new_drp->dr_ifp;
 540                         new.rts_gate = new_drp->dr_gate;
 541                         new.rts_router = new_drp->dr_gate;
 542                         new.rts_metric = HOPCNT_INFINITY-1;
 543                         new.rts_time = now.tv_sec;
 544                         if (rt != NULL) {
 545                                 rtchange(rt, rt->rt_state | RS_RDISC, &new, 0);
 546                         } else {
 547                                 rtadd(RIP_DEFAULT, 0, RS_RDISC, &new);
 548                         }
 549                 }
 550
 551                 cur_drp = new_drp;
 552         }
 553
 554         /* turn RIP on or off */
 555         if (!rdisc_ok || rip_interfaces > 1) {
 556                 rip_on(0);
 557         } else {
 558                 rip_off();
 559         }
 560 }
 561
 562
 563 /* handle a single address in an advertisement
 564  */
 565 static void
 566 parse_ad(naddr from,
 567          naddr gate,
 568          n_long pref,                   /* signed and in network order */
 569          u_short life,                  /* in host byte order */
 570          struct interface *ifp)
 571 {
 572         static struct msg_limit bad_gate;
 573         struct dr *drp, *new_drp;
 574
 575
 576         if (gate == RIP_DEFAULT
 577             || !check_dst(gate)) {
 578                 msglim(&bad_gate, from,"router %s advertising bad gateway %s",
 579                        naddr_ntoa(from),
 580                        naddr_ntoa(gate));
 581                 return;
 582         }
 583
 584         /* ignore pointers to ourself and routes via unreachable networks
 585          */
 586         if (ifwithaddr(gate, 1, 0) != NULL) {
 587                 trace_pkt("    discard Router Discovery Ad pointing at us");
 588                 return;
 589         }
 590         if (!on_net(gate, ifp->int_net, ifp->int_mask)) {
 591                 trace_pkt("    discard Router Discovery Ad"
 592                           " toward unreachable net");
 593                 return;
 594         }
 595
 596         /* Convert preference to an unsigned value
 597          * and later bias it by the metric of the interface.
 598          */
 599         pref = UNSIGN_PREF(ntohl(pref));
 600
 601         if (pref == 0 || life < MinMaxAdvertiseInterval) {
 602                 pref = 0;
 603                 life = 0;
 604         }
 605
 606         for (new_drp = NULL, drp = drs; drp < &drs[MAX_ADS]; drp++) {
 607                 /* accept new info for a familiar entry
 608                  */
 609                 if (drp->dr_gate == gate) {
 610                         new_drp = drp;
 611                         break;
 612                 }
 613
 614                 if (life == 0)
 615                         continue;       /* do not worry about dead ads */
 616
 617                 if (drp->dr_ts == 0) {
 618                         new_drp = drp;  /* use unused entry */
 619
 620                 } else if (new_drp == NULL) {
 621                         /* look for an entry worse than the new one to
 622                          * reuse.
 623                          */
 624                         if ((!(ifp->int_state & IS_SICK)
 625                              && (drp->dr_ifp->int_state & IS_SICK))
 626                             || (pref > drp->dr_pref
 627                                 && !((ifp->int_state ^ drp->dr_ifp->int_state)
 628                                      & IS_SICK)))
 629                                 new_drp = drp;
 630
 631                 } else if (new_drp->dr_ts != 0) {
 632                         /* look for the least valuable entry to reuse
 633                          */
 634                         if ((!(new_drp->dr_ifp->int_state & IS_SICK)
 635                              && (drp->dr_ifp->int_state & IS_SICK))
 636                             || (new_drp->dr_pref > drp->dr_pref
 637                                 && !((new_drp->dr_ifp->int_state
 638                                       ^ drp->dr_ifp->int_state)
 639                                      & IS_SICK)))
 640                                 new_drp = drp;
 641                 }
 642         }
 643
 644         /* forget it if all of the current entries are better */
 645         if (new_drp == NULL)
 646                 return;
 647
 648         new_drp->dr_ifp = ifp;
 649         new_drp->dr_gate = gate;
 650         new_drp->dr_ts = now.tv_sec;
 651         new_drp->dr_life = life;
 652         new_drp->dr_recv_pref = pref;
 653         /* bias functional preference by metric of the interface */
 654         new_drp->dr_pref = PREF(pref,ifp);
 655
 656         /* after hearing a good advertisement, stop asking
 657          */
 658         if (!(ifp->int_state & IS_SICK))
 659                 ifp->int_rdisc_cnt = MAX_SOLICITATIONS;
 660 }
 661
 662
 663 /* Compute the IP checksum
 664  *      This assumes the packet is less than 32K long.
 665  */
 666 static u_short
 667 in_cksum(u_short *p,
 668          u_int len)
 669 {
 670         u_int sum = 0;
 671         int nwords = len >> 1;
 672
 673         while (nwords-- != 0)
 674                 sum += *p++;
 675
 676         if (len & 1)
 677                 sum += *(u_char *)p;
 678
 679         /* end-around-carry */
 680         sum = (sum >> 16) + (sum & 0xffff);
 681         sum += (sum >> 16);
 682         return (~sum);
 683 }
 684
 685
 686 /* Send a router discovery advertisement or solicitation ICMP packet.
 687  */
 688 static void
 689 send_rdisc(union ad_u *p,
 690            int p_size,
 691            struct interface *ifp,
 692            naddr dst,                   /* 0 or unicast destination */
 693            int  type)                   /* 0=unicast, 1=bcast, 2=mcast */
 694 {
 695         struct sockaddr_in rsin;
 696         int flags;
 697         const char *msg;
 698
 699
 700         memset(&rsin, 0, sizeof(rsin));
 701         rsin.sin_addr.s_addr = dst;
 702         rsin.sin_family = AF_INET;
 703 #ifdef _HAVE_SIN_LEN
 704         rsin.sin_len = sizeof(rsin);
 705 #endif
 706         flags = MSG_DONTROUTE;
 707
 708         switch (type) {
 709         case 0:                         /* unicast */
 710         default:
 711                 msg = "Send";
 712                 break;
 713
 714         case 1:                         /* broadcast */
 715                 if (ifp->int_if_flags & IFF_POINTOPOINT) {
 716                         msg = "Send pt-to-pt";
 717                         rsin.sin_addr.s_addr = ifp->int_dstaddr;
 718                 } else {
 719                         msg = "Send broadcast";
 720                         rsin.sin_addr.s_addr = ifp->int_brdaddr;
 721                 }
 722                 break;
 723
 724         case 2:                         /* multicast */
 725                 msg = "Send multicast";
 726                 if (ifp->int_state & IS_DUP) {
 727                         trace_act("abort multicast output via %s"
 728                                   " with duplicate address",
 729                                   ifp->int_name);
 730                         return;
 731                 }
 732                 if (rdisc_sock_mcast != ifp) {
 733                         /* select the right interface. */
 734                         struct ip_mreqn mreqn;
 735
 736                         memset(&mreqn, 0, sizeof(struct ip_mreqn));
 737                         mreqn.imr_ifindex = ifp->int_index;
 738                         if (0 > setsockopt(rdisc_sock,
 739                                            IPPROTO_IP, IP_MULTICAST_IF,
 740                                            &mreqn,
 741                                            sizeof(mreqn))) {
 742                                 LOGERR("setsockopt(rdisc_sock,"
 743                                        "IP_MULTICAST_IF)");
 744                                 rdisc_sock_mcast = NULL;
 745                                 return;
 746                         }
 747                         rdisc_sock_mcast = ifp;
 748                 }
 749                 flags = 0;
 750                 break;
 751         }
 752
 753         if (rdisc_sock < 0)
 754                 get_rdisc_sock();
 755
 756         trace_rdisc(msg, (ifp ? ifp->int_addr : 0), rsin.sin_addr.s_addr, ifp,
 757                     p, p_size);
 758
 759         if (0 > sendto(rdisc_sock, p, p_size, flags,
 760                        (struct sockaddr *)&rsin, sizeof(rsin))) {
 761                 if (ifp == NULL || !(ifp->int_state & IS_BROKE))
 762                         msglog("sendto(%s%s%s): %s",
 763                                ifp != NULL ? ifp->int_name : "",
 764                                ifp != NULL ? ", " : "",
 765                                inet_ntoa(rsin.sin_addr),
 766                                strerror(errno));
 767                 if (ifp != NULL)
 768                         if_sick(ifp);
 769         }
 770 }
 771
 772
 773 /* Send an advertisement
 774  */
 775 static void
 776 send_adv(struct interface *ifp,
 777          naddr  dst,                    /* 0 or unicast destination */
 778          int    type)                   /* 0=unicast, 1=bcast, 2=mcast */
 779 {
 780         union ad_u u;
 781         n_long pref;
 782
 783
 784         memset(&u, 0, sizeof(u.ad));
 785
 786         u.ad.icmp_type = ICMP_ROUTERADVERT;
 787         u.ad.icmp_ad_num = 1;
 788         u.ad.icmp_ad_asize = sizeof(u.ad.icmp_ad_info[0])/4;
 789
 790         u.ad.icmp_ad_life = stopint ? 0 : htons(ifp->int_rdisc_int*3);
 791
 792         /* Convert the configured preference to an unsigned value,
 793          * bias it by the interface metric, and then send it as a
 794          * signed, network byte order value.
 795          */
 796         pref = UNSIGN_PREF(ifp->int_rdisc_pref);
 797         u.ad.icmp_ad_info[0].icmp_ad_pref = htonl(SIGN_PREF(PREF(pref, ifp)));
 798
 799         u.ad.icmp_ad_info[0].icmp_ad_addr = ifp->int_addr;
 800
 801         u.ad.icmp_cksum = in_cksum((u_short*)&u.ad, sizeof(u.ad));
 802
 803         send_rdisc(&u, sizeof(u.ad), ifp, dst, type);
 804 }
 805
 806
 807 /* Advertise for Router Discovery
 808  */
 809 void
 810 rdisc_adv(void)
 811 {
 812         struct interface *ifp;
 813
 814         if (!supplier)
 815                 return;
 816
 817         rdisc_timer.tv_sec = now.tv_sec + NEVER;
 818
 819         LIST_FOREACH(ifp, &ifnet, int_list) {
 820                 if (0 != (ifp->int_state & (IS_NO_ADV_OUT | IS_BROKE)))
 821                         continue;
 822
 823                 if (!timercmp(&ifp->int_rdisc_timer, &now, >)
 824                     || stopint) {
 825                         send_adv(ifp, htonl(INADDR_ALLHOSTS_GROUP),
 826                                  (ifp->int_state&IS_BCAST_RDISC) ? 1 : 2);
 827                         ifp->int_rdisc_cnt++;
 828
 829                         intvl_random(&ifp->int_rdisc_timer,
 830                                      (ifp->int_rdisc_int*3)/4,
 831                                      ifp->int_rdisc_int);
 832                         if (ifp->int_rdisc_cnt < MAX_INITIAL_ADVERTS
 833                             && (ifp->int_rdisc_timer.tv_sec
 834                                 > MAX_INITIAL_ADVERT_INTERVAL)) {
 835                                 ifp->int_rdisc_timer.tv_sec
 836                                 = MAX_INITIAL_ADVERT_INTERVAL;
 837                         }
 838                         timevaladd(&ifp->int_rdisc_timer, &now);
 839                 }
 840
 841                 if (timercmp(&rdisc_timer, &ifp->int_rdisc_timer, >))
 842                         rdisc_timer = ifp->int_rdisc_timer;
 843         }
 844 }
 845
 846
 847 /* Solicit for Router Discovery
 848  */
 849 void
 850 rdisc_sol(void)
 851 {
 852         struct interface *ifp;
 853         union ad_u u;
 854
 855
 856         if (supplier)
 857                 return;
 858
 859         rdisc_timer.tv_sec = now.tv_sec + NEVER;
 860
 861         LIST_FOREACH(ifp, &ifnet, int_list) {
 862                 if (0 != (ifp->int_state & (IS_NO_SOL_OUT | IS_BROKE))
 863                     || ifp->int_rdisc_cnt >= MAX_SOLICITATIONS)
 864                         continue;
 865
 866                 if (!timercmp(&ifp->int_rdisc_timer, &now, >)) {
 867                         memset(&u, 0, sizeof(u.so));
 868                         u.so.icmp_type = ICMP_ROUTERSOLICIT;
 869                         u.so.icmp_cksum = in_cksum((u_short*)&u.so,
 870                                                    sizeof(u.so));
 871                         send_rdisc(&u, sizeof(u.so), ifp,
 872                                    htonl(INADDR_ALLROUTERS_GROUP),
 873                                    ((ifp->int_state&IS_BCAST_RDISC) ? 1 : 2));
 874
 875                         if (++ifp->int_rdisc_cnt >= MAX_SOLICITATIONS)
 876                                 continue;
 877
 878                         ifp->int_rdisc_timer.tv_sec = SOLICITATION_INTERVAL;
 879                         ifp->int_rdisc_timer.tv_usec = 0;
 880                         timevaladd(&ifp->int_rdisc_timer, &now);
 881                 }
 882
 883                 if (timercmp(&rdisc_timer, &ifp->int_rdisc_timer, >))
 884                         rdisc_timer = ifp->int_rdisc_timer;
 885         }
 886 }
 887
 888
 889 /* check the IP header of a possible Router Discovery ICMP packet */
 890 static struct interface *               /* 0 if bad */
 891 ck_icmp(const char *act,
 892         naddr   from,
 893         struct interface *ifp,
 894         naddr   to,
 895         union ad_u *p,
 896         u_int   len)
 897 {
 898         const char *type;
 899
 900
 901         if (p->icmp.icmp_type == ICMP_ROUTERADVERT) {
 902                 type = "advertisement";
 903         } else if (p->icmp.icmp_type == ICMP_ROUTERSOLICIT) {
 904                 type = "solicitation";
 905         } else {
 906                 return 0;
 907         }
 908
 909         if (p->icmp.icmp_code != 0) {
 910                 trace_pkt("unrecognized ICMP Router %s code=%d from %s to %s",
 911                           type, p->icmp.icmp_code,
 912                           naddr_ntoa(from), naddr_ntoa(to));
 913                 return 0;
 914         }
 915
 916         trace_rdisc(act, from, to, ifp, p, len);
 917
 918         if (ifp == NULL)
 919                 trace_pkt("unknown interface for router-discovery %s"
 920                           " from %s to %s",
 921                           type, naddr_ntoa(from), naddr_ntoa(to));
 922
 923         return ifp;
 924 }
 925
 926
 927 /* read packets from the router discovery socket
 928  */
 929 void
 930 read_d(void)
 931 {
 932         static struct msg_limit bad_asize, bad_len;
 933 #ifdef USE_PASSIFNAME
 934         static struct msg_limit  bad_name;
 935 #endif
 936         struct sockaddr_in from;
 937         int n, fromlen, cc, hlen;
 938         struct {
 939 #ifdef USE_PASSIFNAME
 940                 char    ifname[IFNAMSIZ];
 941 #endif
 942                 union {
 943                         struct ip ip;
 944                         u_char  b[512];
 945                 } pkt;
 946         } buf;
 947         union ad_u *p;
 948         n_long *wp;
 949         struct interface *ifp;
 950
 951
 952         for (;;) {
 953                 fromlen = sizeof(from);
 954                 cc = recvfrom(rdisc_sock, &buf, sizeof(buf), 0,
 955                               (struct sockaddr*)&from,
 956                               &fromlen);
 957                 if (cc <= 0) {
 958                         if (cc < 0 && errno != EWOULDBLOCK)
 959                                 LOGERR("recvfrom(rdisc_sock)");
 960                         break;
 961                 }
 962                 if (fromlen != sizeof(struct sockaddr_in))
 963                         logbad(1,"impossible recvfrom(rdisc_sock) fromlen=%d",
 964                                fromlen);
 965 #ifdef USE_PASSIFNAME
 966                 if ((cc -= sizeof(buf.ifname)) < 0)
 967                         logbad(0,"missing USE_PASSIFNAME; only %d bytes",
 968                                cc+sizeof(buf.ifname));
 969 #endif
 970
 971                 hlen = buf.pkt.ip.ip_hl << 2;
 972                 if (cc < hlen + ICMP_MINLEN)
 973                         continue;
 974                 p = (union ad_u *)&buf.pkt.b[hlen];
 975                 cc -= hlen;
 976
 977 #ifdef USE_PASSIFNAME
 978                 ifp = ifwithname(buf.ifname, 0);
 979                 if (ifp == NULL)
 980                         msglim(&bad_name, from.sin_addr.s_addr,
 981                                "impossible rdisc if_ name %.*s",
 982                                IFNAMSIZ, buf.ifname);
 983 #else
 984                 /* If we could tell the interface on which a packet from
 985                  * address 0 arrived, we could deal with such solicitations.
 986                  */
 987                 ifp = ((from.sin_addr.s_addr == 0)
 988                        ? 0 : iflookup(from.sin_addr.s_addr));
 989 #endif
 990                 ifp = ck_icmp("Recv", from.sin_addr.s_addr, ifp,
 991                               buf.pkt.ip.ip_dst.s_addr, p, cc);
 992                 if (ifp == NULL)
 993                         continue;
 994                 if (ifwithaddr(from.sin_addr.s_addr, 0, 0)) {
 995                         trace_pkt("    "
 996                                   "discard our own Router Discovery message");
 997                         continue;
 998                 }
 999
1000                 switch (p->icmp.icmp_type) {
1001                 case ICMP_ROUTERADVERT:
1002                         if (p->ad.icmp_ad_asize*4
1003                             < (int)sizeof(p->ad.icmp_ad_info[0])) {
1004                                 msglim(&bad_asize, from.sin_addr.s_addr,
1005                                        "intolerable rdisc address size=%d",
1006                                        p->ad.icmp_ad_asize);
1007                                 continue;
1008                         }
1009                         if (p->ad.icmp_ad_num == 0) {
1010                                 trace_pkt("    empty?");
1011                                 continue;
1012                         }
1013                         if (cc != (int)(sizeof(p->ad)
1014                                         - sizeof(p->ad.icmp_ad_info)
1015                                         + (p->ad.icmp_ad_num
1016                                            * sizeof(p->ad.icmp_ad_info[0])))) {
1017                                 msglim(&bad_len, from.sin_addr.s_addr,
1018                                        "rdisc length %d does not match ad_num"
1019                                        " %d", cc, p->ad.icmp_ad_num);
1020                                 continue;
1021                         }
1022                         if (supplier)
1023                                 continue;
1024                         if (ifp->int_state & IS_NO_ADV_IN)
1025                                 continue;
1026
1027                         wp = &p->ad.icmp_ad_info[0].icmp_ad_addr;
1028                         for (n = 0; n < p->ad.icmp_ad_num; n++) {
1029                                 parse_ad(from.sin_addr.s_addr,
1030                                          wp[0], wp[1],
1031                                          ntohs(p->ad.icmp_ad_life),
1032                                          ifp);
1033                                 wp += p->ad.icmp_ad_asize;
1034                         }
1035                         break;
1036
1037
1038                 case ICMP_ROUTERSOLICIT:
1039                         if (!supplier)
1040                                 continue;
1041                         if (ifp->int_state & IS_NO_ADV_OUT)
1042                                 continue;
1043                         if (stopint)
1044                                 continue;
1045
1046                         /* XXX
1047                          * We should handle messages from address 0.
1048                          */
1049
1050                         /* Respond with a point-to-point advertisement */
1051                         send_adv(ifp, from.sin_addr.s_addr, 0);
1052                         break;
1053                 }
1054         }
1055
1056         rdisc_sort();
1057 }