contrib/dhcpcd/src/ipv4ll.c

   1 /* SPDX-License-Identifier: BSD-2-Clause */
   2 /*
   3  * dhcpcd - DHCP client daemon
   4  * Copyright (c) 2006-2020 Roy Marples <roy@marples.name>
   5  * 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  *
  16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  26  * SUCH DAMAGE.
  27  */
  28
  29 #include <arpa/inet.h>
  30
  31 #include <assert.h>
  32 #include <errno.h>
  33 #include <stdbool.h>
  34 #include <stdio.h>
  35 #include <stdlib.h>
  36 #include <string.h>
  37 #include <unistd.h>
  38
  39 #define ELOOP_QUEUE     IPV4LL
  40 #include "config.h"
  41 #include "arp.h"
  42 #include "common.h"
  43 #include "dhcp.h"
  44 #include "eloop.h"
  45 #include "if.h"
  46 #include "if-options.h"
  47 #include "ipv4.h"
  48 #include "ipv4ll.h"
  49 #include "logerr.h"
  50 #include "sa.h"
  51 #include "script.h"
  52
  53 static const struct in_addr inaddr_llmask = {
  54         .s_addr = HTONL(LINKLOCAL_MASK)
  55 };
  56 static const struct in_addr inaddr_llbcast = {
  57         .s_addr = HTONL(LINKLOCAL_BCAST)
  58 };
  59
  60 static void
  61 ipv4ll_pickaddr(struct interface *ifp)
  62 {
  63         struct in_addr addr = { .s_addr = 0 };
  64         struct ipv4ll_state *state;
  65
  66         state = IPV4LL_STATE(ifp);
  67         setstate(state->randomstate);
  68
  69         do {
  70                 long r;
  71
  72 again:
  73                 /* RFC 3927 Section 2.1 states that the first 256 and
  74                  * last 256 addresses are reserved for future use.
  75                  * See ipv4ll_start for why we don't use arc4random. */
  76                 /* coverity[dont_call] */
  77                 r = random();
  78                 addr.s_addr = ntohl(LINKLOCAL_ADDR |
  79                     ((uint32_t)(r % 0xFD00) + 0x0100));
  80
  81                 /* No point using a failed address */
  82                 if (IN_ARE_ADDR_EQUAL(&addr, &state->pickedaddr))
  83                         goto again;
  84                 /* Ensure we don't have the address on another interface */
  85         } while (ipv4_findaddr(ifp->ctx, &addr) != NULL);
  86
  87         /* Restore the original random state */
  88         setstate(ifp->ctx->randomstate);
  89         state->pickedaddr = addr;
  90 }
  91
  92 int
  93 ipv4ll_subnetroute(rb_tree_t *routes, struct interface *ifp)
  94 {
  95         struct ipv4ll_state *state;
  96         struct rt *rt;
  97         struct in_addr in;
  98
  99         assert(ifp != NULL);
 100         if ((state = IPV4LL_STATE(ifp)) == NULL ||
 101             state->addr == NULL)
 102                 return 0;
 103
 104         if ((rt = rt_new(ifp)) == NULL)
 105                 return -1;
 106
 107         in.s_addr = state->addr->addr.s_addr & state->addr->mask.s_addr;
 108         sa_in_init(&rt->rt_dest, &in);
 109         in.s_addr = state->addr->mask.s_addr;
 110         sa_in_init(&rt->rt_netmask, &in);
 111         in.s_addr = INADDR_ANY;
 112         sa_in_init(&rt->rt_gateway, &in);
 113         sa_in_init(&rt->rt_ifa, &state->addr->addr);
 114         return rt_proto_add(routes, rt) ? 1 : 0;
 115 }
 116
 117 int
 118 ipv4ll_defaultroute(rb_tree_t *routes, struct interface *ifp)
 119 {
 120         struct ipv4ll_state *state;
 121         struct rt *rt;
 122         struct in_addr in;
 123
 124         assert(ifp != NULL);
 125         if ((state = IPV4LL_STATE(ifp)) == NULL ||
 126             state->addr == NULL)
 127                 return 0;
 128
 129         if ((rt = rt_new(ifp)) == NULL)
 130                 return -1;
 131
 132         in.s_addr = INADDR_ANY;
 133         sa_in_init(&rt->rt_dest, &in);
 134         sa_in_init(&rt->rt_netmask, &in);
 135         sa_in_init(&rt->rt_gateway, &in);
 136         sa_in_init(&rt->rt_ifa, &state->addr->addr);
 137         return rt_proto_add(routes, rt) ? 1 : 0;
 138 }
 139
 140 ssize_t
 141 ipv4ll_env(FILE *fp, const char *prefix, const struct interface *ifp)
 142 {
 143         const struct ipv4ll_state *state;
 144         const char *pf = prefix == NULL ? "" : "_";
 145         struct in_addr netnum;
 146
 147         assert(ifp != NULL);
 148         if ((state = IPV4LL_CSTATE(ifp)) == NULL || state->addr == NULL)
 149                 return 0;
 150
 151         /* Emulate a DHCP environment */
 152         if (efprintf(fp, "%s%sip_address=%s",
 153             prefix, pf, inet_ntoa(state->addr->addr)) == -1)
 154                 return -1;
 155         if (efprintf(fp, "%s%ssubnet_mask=%s",
 156             prefix, pf, inet_ntoa(state->addr->mask)) == -1)
 157                 return -1;
 158         if (efprintf(fp, "%s%ssubnet_cidr=%d",
 159             prefix, pf, inet_ntocidr(state->addr->mask)) == -1)
 160                 return -1;
 161         if (efprintf(fp, "%s%sbroadcast_address=%s",
 162             prefix, pf, inet_ntoa(state->addr->brd)) == -1)
 163                 return -1;
 164         netnum.s_addr = state->addr->addr.s_addr & state->addr->mask.s_addr;
 165         if (efprintf(fp, "%s%snetwork_number=%s",
 166             prefix, pf, inet_ntoa(netnum)) == -1)
 167                 return -1;
 168         return 5;
 169 }
 170
 171 static void
 172 ipv4ll_announced_arp(struct arp_state *astate)
 173 {
 174         struct ipv4ll_state *state = IPV4LL_STATE(astate->iface);
 175
 176         state->conflicts = 0;
 177 }
 178
 179 #ifndef KERNEL_RFC5227
 180 /* This is the callback by ARP freeing */
 181 static void
 182 ipv4ll_free_arp(struct arp_state *astate)
 183 {
 184         struct ipv4ll_state *state;
 185
 186         state = IPV4LL_STATE(astate->iface);
 187         if (state != NULL && state->arp == astate)
 188                 state->arp = NULL;
 189 }
 190
 191 /* This is us freeing any ARP state */
 192 static void
 193 ipv4ll_freearp(struct interface *ifp)
 194 {
 195         struct ipv4ll_state *state;
 196
 197         state = IPV4LL_STATE(ifp);
 198         if (state == NULL || state->arp == NULL)
 199                 return;
 200
 201         eloop_timeout_delete(ifp->ctx->eloop, NULL, state->arp);
 202         arp_free(state->arp);
 203         state->arp = NULL;
 204 }
 205 #else
 206 #define ipv4ll_freearp(ifp)
 207 #endif
 208
 209 static void
 210 ipv4ll_not_found(struct interface *ifp)
 211 {
 212         struct ipv4ll_state *state;
 213         struct ipv4_addr *ia;
 214         struct arp_state *astate;
 215
 216         state = IPV4LL_STATE(ifp);
 217         ia = ipv4_iffindaddr(ifp, &state->pickedaddr, &inaddr_llmask);
 218 #ifdef IN_IFF_NOTREADY
 219         if (ia == NULL || ia->addr_flags & IN_IFF_NOTREADY)
 220 #endif
 221                 loginfox("%s: using IPv4LL address %s",
 222                   ifp->name, inet_ntoa(state->pickedaddr));
 223         if (ia == NULL) {
 224                 if (ifp->ctx->options & DHCPCD_TEST)
 225                         goto test;
 226                 ia = ipv4_addaddr(ifp, &state->pickedaddr,
 227                     &inaddr_llmask, &inaddr_llbcast,
 228                     DHCP_INFINITE_LIFETIME, DHCP_INFINITE_LIFETIME);
 229         }
 230         if (ia == NULL)
 231                 return;
 232 #ifdef IN_IFF_NOTREADY
 233         if (ia->addr_flags & IN_IFF_NOTREADY)
 234                 return;
 235         logdebugx("%s: DAD completed for %s", ifp->name, ia->saddr);
 236 #endif
 237
 238 test:
 239         state->addr = ia;
 240         state->down = false;
 241         if (ifp->ctx->options & DHCPCD_TEST) {
 242                 script_runreason(ifp, "TEST");
 243                 eloop_exit(ifp->ctx->eloop, EXIT_SUCCESS);
 244                 return;
 245         }
 246         rt_build(ifp->ctx, AF_INET);
 247         astate = arp_announceaddr(ifp->ctx, &ia->addr);
 248         if (astate != NULL)
 249                 astate->announced_cb = ipv4ll_announced_arp;
 250         script_runreason(ifp, "IPV4LL");
 251         dhcpcd_daemonise(ifp->ctx);
 252 }
 253
 254 static void
 255 ipv4ll_found(struct interface *ifp)
 256 {
 257         struct ipv4ll_state *state = IPV4LL_STATE(ifp);
 258
 259         ipv4ll_freearp(ifp);
 260         if (++state->conflicts == MAX_CONFLICTS)
 261                 logerrx("%s: failed to acquire an IPv4LL address",
 262                     ifp->name);
 263         ipv4ll_pickaddr(ifp);
 264         eloop_timeout_add_sec(ifp->ctx->eloop,
 265             state->conflicts >= MAX_CONFLICTS ?
 266             RATE_LIMIT_INTERVAL : PROBE_WAIT,
 267             ipv4ll_start, ifp);
 268 }
 269
 270 static void
 271 ipv4ll_defend_failed(struct interface *ifp)
 272 {
 273         struct ipv4ll_state *state = IPV4LL_STATE(ifp);
 274
 275         ipv4ll_freearp(ifp);
 276         ipv4_deladdr(state->addr, 1);
 277         state->addr = NULL;
 278         rt_build(ifp->ctx, AF_INET);
 279         script_runreason(ifp, "IPV4LL");
 280         ipv4ll_pickaddr(ifp);
 281         ipv4ll_start(ifp);
 282 }
 283
 284 #ifndef KERNEL_RFC5227
 285 static void
 286 ipv4ll_not_found_arp(struct arp_state *astate)
 287 {
 288
 289         ipv4ll_not_found(astate->iface);
 290 }
 291
 292 static void
 293 ipv4ll_found_arp(struct arp_state *astate, __unused const struct arp_msg *amsg)
 294 {
 295
 296         ipv4ll_found(astate->iface);
 297 }
 298
 299 static void
 300 ipv4ll_defend_failed_arp(struct arp_state *astate)
 301 {
 302
 303         ipv4ll_defend_failed(astate->iface);
 304 }
 305 #endif
 306
 307 void
 308 ipv4ll_start(void *arg)
 309 {
 310         struct interface *ifp = arg;
 311         struct ipv4ll_state *state;
 312         struct ipv4_addr *ia;
 313         bool repick;
 314 #ifndef KERNEL_RFC5227
 315         struct arp_state *astate;
 316 #endif
 317
 318         if ((state = IPV4LL_STATE(ifp)) == NULL) {
 319                 ifp->if_data[IF_DATA_IPV4LL] = calloc(1, sizeof(*state));
 320                 if ((state = IPV4LL_STATE(ifp)) == NULL) {
 321                         logerr(__func__);
 322                         return;
 323                 }
 324         }
 325
 326         /* RFC 3927 Section 2.1 states that the random number generator
 327          * SHOULD be seeded with a value derived from persistent information
 328          * such as the IEEE 802 MAC address so that it usually picks
 329          * the same address without persistent storage. */
 330         if (!state->seeded) {
 331                 unsigned int seed;
 332                 char *orig;
 333
 334                 if (sizeof(seed) > ifp->hwlen) {
 335                         seed = 0;
 336                         memcpy(&seed, ifp->hwaddr, ifp->hwlen);
 337                 } else
 338                         memcpy(&seed, ifp->hwaddr + ifp->hwlen - sizeof(seed),
 339                             sizeof(seed));
 340                 /* coverity[dont_call] */
 341                 orig = initstate(seed,
 342                     state->randomstate, sizeof(state->randomstate));
 343
 344                 /* Save the original state. */
 345                 if (ifp->ctx->randomstate == NULL)
 346                         ifp->ctx->randomstate = orig;
 347
 348                 /* Set back the original state until we need the seeded one. */
 349                 setstate(ifp->ctx->randomstate);
 350                 state->seeded = true;
 351         }
 352
 353         /* Find the previosuly used address. */
 354         if (state->pickedaddr.s_addr != INADDR_ANY)
 355                 ia = ipv4_iffindaddr(ifp, &state->pickedaddr, NULL);
 356         else
 357                 ia = NULL;
 358
 359         /* Find an existing IPv4LL address and ensure we can work with it. */
 360         if (ia == NULL)
 361                 ia = ipv4_iffindlladdr(ifp);
 362
 363         repick = false;
 364 #ifdef IN_IFF_DUPLICATED
 365         if (ia != NULL && ia->addr_flags & IN_IFF_DUPLICATED) {
 366                 state->pickedaddr = ia->addr; /* So it's not picked again. */
 367                 repick = true;
 368                 ipv4_deladdr(ia, 0);
 369                 ia = NULL;
 370         }
 371 #endif
 372
 373         state->addr = ia;
 374         state->down = true;
 375         if (ia != NULL) {
 376                 state->pickedaddr = ia->addr;
 377 #ifdef IN_IFF_TENTATIVE
 378                 if (ia->addr_flags & (IN_IFF_TENTATIVE | IN_IFF_DETACHED)) {
 379                         loginfox("%s: waiting for DAD to complete on %s",
 380                             ifp->name, inet_ntoa(ia->addr));
 381                         return;
 382                 }
 383 #endif
 384 #ifdef IN_IFF_DUPLICATED
 385                 loginfox("%s: using IPv4LL address %s", ifp->name, ia->saddr);
 386 #endif
 387         } else {
 388                 loginfox("%s: probing for an IPv4LL address", ifp->name);
 389                 if (repick || state->pickedaddr.s_addr == INADDR_ANY)
 390                         ipv4ll_pickaddr(ifp);
 391         }
 392
 393 #ifdef KERNEL_RFC5227
 394         ipv4ll_not_found(ifp);
 395 #else
 396         ipv4ll_freearp(ifp);
 397         state->arp = astate = arp_new(ifp, &state->pickedaddr);
 398         if (state->arp == NULL)
 399                 return;
 400
 401         astate->found_cb = ipv4ll_found_arp;
 402         astate->not_found_cb = ipv4ll_not_found_arp;
 403         astate->announced_cb = ipv4ll_announced_arp;
 404         astate->defend_failed_cb = ipv4ll_defend_failed_arp;
 405         astate->free_cb = ipv4ll_free_arp;
 406         arp_probe(astate);
 407 #endif
 408 }
 409
 410 void
 411 ipv4ll_drop(struct interface *ifp)
 412 {
 413         struct ipv4ll_state *state;
 414         bool dropped = false;
 415         struct ipv4_state *istate;
 416
 417         assert(ifp != NULL);
 418
 419         ipv4ll_freearp(ifp);
 420
 421         if ((ifp->options->options & DHCPCD_NODROP) == DHCPCD_NODROP)
 422                 return;
 423
 424         state = IPV4LL_STATE(ifp);
 425         if (state && state->addr != NULL) {
 426                 ipv4_deladdr(state->addr, 1);
 427                 state->addr = NULL;
 428                 dropped = true;
 429         }
 430
 431         /* Free any other link local addresses that might exist. */
 432         if ((istate = IPV4_STATE(ifp)) != NULL) {
 433                 struct ipv4_addr *ia, *ian;
 434
 435                 TAILQ_FOREACH_SAFE(ia, &istate->addrs, next, ian) {
 436                         if (IN_LINKLOCAL(ntohl(ia->addr.s_addr))) {
 437                                 ipv4_deladdr(ia, 0);
 438                                 dropped = true;
 439                         }
 440                 }
 441         }
 442
 443         if (dropped) {
 444                 rt_build(ifp->ctx, AF_INET);
 445                 script_runreason(ifp, "IPV4LL");
 446         }
 447 }
 448
 449 void
 450 ipv4ll_reset(struct interface *ifp)
 451 {
 452         struct ipv4ll_state *state = IPV4LL_STATE(ifp);
 453
 454         if (state == NULL)
 455                 return;
 456         ipv4ll_freearp(ifp);
 457         state->pickedaddr.s_addr = INADDR_ANY;
 458         state->seeded = false;
 459 }
 460
 461 void
 462 ipv4ll_free(struct interface *ifp)
 463 {
 464
 465         assert(ifp != NULL);
 466
 467         ipv4ll_freearp(ifp);
 468         free(IPV4LL_STATE(ifp));
 469         ifp->if_data[IF_DATA_IPV4LL] = NULL;
 470 }
 471
 472 /* This may cause issues in BSD systems, where running as a single dhcpcd
 473  * daemon would solve this issue easily. */
 474 #ifdef HAVE_ROUTE_METRIC
 475 int
 476 ipv4ll_recvrt(__unused int cmd, const struct rt *rt)
 477 {
 478         struct dhcpcd_ctx *ctx;
 479         struct interface *ifp;
 480
 481         /* Only interested in default route changes. */
 482         if (sa_is_unspecified(&rt->rt_dest))
 483                 return 0;
 484
 485         /* If any interface is running IPv4LL, rebuild our routing table. */
 486         ctx = rt->rt_ifp->ctx;
 487         TAILQ_FOREACH(ifp, ctx->ifaces, next) {
 488                 if (IPV4LL_STATE_RUNNING(ifp)) {
 489                         rt_build(ctx, AF_INET);
 490                         break;
 491                 }
 492         }
 493
 494         return 0;
 495 }
 496 #endif
 497
 498 struct ipv4_addr *
 499 ipv4ll_handleifa(int cmd, struct ipv4_addr *ia, pid_t pid)
 500 {
 501         struct interface *ifp;
 502         struct ipv4ll_state *state;
 503
 504         ifp = ia->iface;
 505         state = IPV4LL_STATE(ifp);
 506         if (state == NULL)
 507                 return ia;
 508
 509         if (cmd == RTM_DELADDR &&
 510             state->addr != NULL &&
 511             IN_ARE_ADDR_EQUAL(&state->addr->addr, &ia->addr))
 512         {
 513                 loginfox("%s: pid %d deleted IP address %s",
 514                     ifp->name, pid, ia->saddr);
 515                 ipv4ll_defend_failed(ifp);
 516                 return ia;
 517         }
 518
 519 #ifdef IN_IFF_DUPLICATED
 520         if (cmd != RTM_NEWADDR)
 521                 return ia;
 522         if (!IN_ARE_ADDR_EQUAL(&state->pickedaddr, &ia->addr))
 523                 return ia;
 524         if (!(ia->addr_flags & IN_IFF_NOTUSEABLE))
 525                 ipv4ll_not_found(ifp);
 526         else if (ia->addr_flags & IN_IFF_DUPLICATED) {
 527                 logerrx("%s: DAD detected %s", ifp->name, ia->saddr);
 528                 ipv4ll_freearp(ifp);
 529                 ipv4_deladdr(ia, 1);
 530                 state->addr = NULL;
 531                 rt_build(ifp->ctx, AF_INET);
 532                 ipv4ll_found(ifp);
 533                 return NULL;
 534         }
 535 #endif
 536
 537         return ia;
 538 }