Samuel Tan | d7ed851 | 2015-08-13 16:11:35 -0700 | [diff] [blame] | 1 | /* |
| 2 | * dhcpcd - DHCP client daemon |
| 3 | * Copyright (c) 2006-2015 Roy Marples <roy@marples.name> |
| 4 | * All rights reserved |
| 5 | |
| 6 | * Redistribution and use in source and binary forms, with or without |
| 7 | * modification, are permitted provided that the following conditions |
| 8 | * are met: |
| 9 | * 1. Redistributions of source code must retain the above copyright |
| 10 | * notice, this list of conditions and the following disclaimer. |
| 11 | * 2. Redistributions in binary form must reproduce the above copyright |
| 12 | * notice, this list of conditions and the following disclaimer in the |
| 13 | * documentation and/or other materials provided with the distribution. |
| 14 | * |
| 15 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND |
| 16 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| 17 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| 18 | * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE |
| 19 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| 20 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| 21 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| 22 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| 23 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| 24 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| 25 | * SUCH DAMAGE. |
| 26 | */ |
| 27 | |
| 28 | #include <errno.h> |
| 29 | #include <signal.h> |
| 30 | #include <stdlib.h> |
| 31 | #include <string.h> |
| 32 | #include <unistd.h> |
| 33 | |
| 34 | #define ELOOP_QUEUE 6 |
| 35 | #include "config.h" |
| 36 | #include "arp.h" |
| 37 | #include "common.h" |
| 38 | #include "dhcp.h" |
| 39 | #include "eloop.h" |
| 40 | #include "if.h" |
| 41 | #include "if-options.h" |
| 42 | #include "ipv4ll.h" |
| 43 | |
| 44 | static struct dhcp_message * |
| 45 | ipv4ll_make_lease(uint32_t addr) |
| 46 | { |
| 47 | uint32_t u32; |
| 48 | struct dhcp_message *dhcp; |
| 49 | uint8_t *p; |
| 50 | |
| 51 | dhcp = calloc(1, sizeof(*dhcp)); |
| 52 | if (dhcp == NULL) |
| 53 | return NULL; |
| 54 | /* Put some LL options in */ |
| 55 | dhcp->yiaddr = addr; |
| 56 | p = dhcp->options; |
| 57 | *p++ = DHO_SUBNETMASK; |
| 58 | *p++ = sizeof(u32); |
| 59 | u32 = htonl(LINKLOCAL_MASK); |
| 60 | memcpy(p, &u32, sizeof(u32)); |
| 61 | p += sizeof(u32); |
| 62 | *p++ = DHO_BROADCAST; |
| 63 | *p++ = sizeof(u32); |
| 64 | u32 = htonl(LINKLOCAL_BRDC); |
| 65 | memcpy(p, &u32, sizeof(u32)); |
| 66 | p += sizeof(u32); |
| 67 | *p++ = DHO_END; |
| 68 | |
| 69 | return dhcp; |
| 70 | } |
| 71 | |
| 72 | static in_addr_t |
| 73 | ipv4ll_pick_addr(const struct arp_state *astate) |
| 74 | { |
| 75 | in_addr_t addr; |
| 76 | struct interface *ifp; |
| 77 | const struct dhcp_state *state; |
| 78 | |
| 79 | for (;;) { |
| 80 | /* RFC 3927 Section 2.1 states that the first 256 and |
| 81 | * last 256 addresses are reserved for future use. |
| 82 | * See ipv4ll_start for why we don't use arc4_random. */ |
| 83 | addr = ntohl(LINKLOCAL_ADDR | |
| 84 | ((uint32_t)(random() % 0xFD00) + 0x0100)); |
| 85 | |
| 86 | /* No point using a failed address */ |
| 87 | if (addr == astate->failed.s_addr) |
| 88 | continue; |
| 89 | |
| 90 | /* Ensure we don't have the address on another interface */ |
| 91 | TAILQ_FOREACH(ifp, astate->iface->ctx->ifaces, next) { |
| 92 | state = D_CSTATE(ifp); |
| 93 | if (state && state->addr.s_addr == addr) |
| 94 | break; |
| 95 | } |
| 96 | |
| 97 | /* Yay, this should be a unique and workable IPv4LL address */ |
| 98 | if (ifp == NULL) |
| 99 | break; |
| 100 | } |
| 101 | return addr; |
| 102 | } |
| 103 | |
| 104 | static void |
| 105 | ipv4ll_probed(struct arp_state *astate) |
| 106 | { |
| 107 | struct dhcp_state *state = D_STATE(astate->iface); |
| 108 | |
| 109 | if (state->state == DHS_IPV4LL_BOUND) { |
| 110 | ipv4_finaliseaddr(astate->iface); |
| 111 | return; |
| 112 | } |
| 113 | |
| 114 | if (state->state != DHS_BOUND) { |
| 115 | struct dhcp_message *offer; |
| 116 | |
| 117 | /* A DHCP lease could have already been offered. |
| 118 | * Backup and replace once the IPv4LL address is bound */ |
| 119 | offer = state->offer; |
| 120 | state->offer = ipv4ll_make_lease(astate->addr.s_addr); |
| 121 | if (state->offer == NULL) |
| 122 | logger(astate->iface->ctx, LOG_ERR, "%s: %m", __func__); |
| 123 | else |
| 124 | dhcp_bind(astate->iface, astate); |
| 125 | state->offer = offer; |
| 126 | } |
| 127 | } |
| 128 | |
| 129 | static void |
| 130 | ipv4ll_announced(struct arp_state *astate) |
| 131 | { |
| 132 | struct dhcp_state *state = D_STATE(astate->iface); |
| 133 | |
| 134 | state->conflicts = 0; |
| 135 | /* Need to keep the arp state so we can defend our IP. */ |
| 136 | } |
| 137 | |
| 138 | static void |
| 139 | ipv4ll_probe(void *arg) |
| 140 | { |
| 141 | |
| 142 | #ifdef IN_IFF_TENTATIVE |
| 143 | ipv4ll_probed(arg); |
| 144 | #else |
| 145 | arp_probe(arg); |
| 146 | #endif |
| 147 | } |
| 148 | |
| 149 | static void |
| 150 | ipv4ll_conflicted(struct arp_state *astate, const struct arp_msg *amsg) |
| 151 | { |
| 152 | struct dhcp_state *state = D_STATE(astate->iface); |
| 153 | in_addr_t fail; |
| 154 | |
| 155 | fail = 0; |
| 156 | /* RFC 3927 2.2.1, Probe Conflict Detection */ |
| 157 | if (amsg == NULL || |
| 158 | (amsg->sip.s_addr == astate->addr.s_addr || |
| 159 | (amsg->sip.s_addr == 0 && amsg->tip.s_addr == astate->addr.s_addr))) |
| 160 | fail = astate->addr.s_addr; |
| 161 | |
| 162 | /* RFC 3927 2.5, Conflict Defense */ |
| 163 | if (IN_LINKLOCAL(htonl(state->addr.s_addr)) && |
| 164 | amsg && amsg->sip.s_addr == state->addr.s_addr) |
| 165 | fail = state->addr.s_addr; |
| 166 | |
| 167 | if (fail == 0) |
| 168 | return; |
| 169 | |
| 170 | astate->failed.s_addr = fail; |
| 171 | arp_report_conflicted(astate, amsg); |
| 172 | |
| 173 | if (astate->failed.s_addr == state->addr.s_addr) { |
| 174 | time_t up; |
| 175 | |
| 176 | /* RFC 3927 Section 2.5 */ |
| 177 | up = uptime(); |
| 178 | if (state->defend + DEFEND_INTERVAL > up) { |
| 179 | logger(astate->iface->ctx, LOG_WARNING, |
| 180 | "%s: IPv4LL %d second defence failed for %s", |
| 181 | astate->iface->name, DEFEND_INTERVAL, |
| 182 | inet_ntoa(state->addr)); |
| 183 | dhcp_drop(astate->iface, "EXPIRE"); |
| 184 | } else { |
| 185 | logger(astate->iface->ctx, LOG_DEBUG, |
| 186 | "%s: defended IPv4LL address %s", |
| 187 | astate->iface->name, inet_ntoa(state->addr)); |
| 188 | state->defend = up; |
| 189 | return; |
| 190 | } |
| 191 | } |
| 192 | |
| 193 | arp_cancel(astate); |
| 194 | if (++state->conflicts == MAX_CONFLICTS) |
| 195 | logger(astate->iface->ctx, LOG_ERR, |
| 196 | "%s: failed to acquire an IPv4LL address", |
| 197 | astate->iface->name); |
| 198 | astate->addr.s_addr = ipv4ll_pick_addr(astate); |
| 199 | eloop_timeout_add_sec(astate->iface->ctx->eloop, |
| 200 | state->conflicts >= MAX_CONFLICTS ? |
| 201 | RATE_LIMIT_INTERVAL : PROBE_WAIT, |
| 202 | ipv4ll_probe, astate); |
| 203 | } |
| 204 | |
| 205 | void |
| 206 | ipv4ll_start(void *arg) |
| 207 | { |
| 208 | struct interface *ifp = arg; |
| 209 | struct dhcp_state *state = D_STATE(ifp); |
| 210 | struct arp_state *astate; |
| 211 | struct ipv4_addr *ap; |
| 212 | |
| 213 | if (state->arp_ipv4ll) |
| 214 | return; |
| 215 | |
| 216 | /* RFC 3927 Section 2.1 states that the random number generator |
| 217 | * SHOULD be seeded with a value derived from persistent information |
| 218 | * such as the IEEE 802 MAC address so that it usually picks |
| 219 | * the same address without persistent storage. */ |
| 220 | if (state->conflicts == 0) { |
| 221 | unsigned int seed; |
| 222 | |
| 223 | if (sizeof(seed) > ifp->hwlen) { |
| 224 | seed = 0; |
| 225 | memcpy(&seed, ifp->hwaddr, ifp->hwlen); |
| 226 | } else |
| 227 | memcpy(&seed, ifp->hwaddr + ifp->hwlen - sizeof(seed), |
| 228 | sizeof(seed)); |
| 229 | initstate(seed, state->randomstate, sizeof(state->randomstate)); |
| 230 | } |
| 231 | |
| 232 | if ((astate = arp_new(ifp, NULL)) == NULL) |
| 233 | return; |
| 234 | |
| 235 | state->arp_ipv4ll = astate; |
| 236 | astate->probed_cb = ipv4ll_probed; |
| 237 | astate->announced_cb = ipv4ll_announced; |
| 238 | astate->conflicted_cb = ipv4ll_conflicted; |
| 239 | |
| 240 | if (IN_LINKLOCAL(htonl(state->addr.s_addr))) { |
| 241 | astate->addr = state->addr; |
| 242 | arp_announce(astate); |
| 243 | return; |
| 244 | } |
| 245 | |
| 246 | if (state->offer && IN_LINKLOCAL(ntohl(state->offer->yiaddr))) { |
| 247 | astate->addr.s_addr = state->offer->yiaddr; |
| 248 | free(state->offer); |
| 249 | state->offer = NULL; |
| 250 | ap = ipv4_iffindaddr(ifp, &astate->addr, NULL); |
| 251 | } else |
| 252 | ap = ipv4_iffindlladdr(ifp); |
| 253 | if (ap) { |
| 254 | astate->addr = ap->addr; |
| 255 | ipv4ll_probed(astate); |
| 256 | return; |
| 257 | } |
| 258 | |
| 259 | setstate(state->randomstate); |
| 260 | /* We maybe rebooting an IPv4LL address. */ |
| 261 | if (!IN_LINKLOCAL(htonl(astate->addr.s_addr))) { |
| 262 | logger(ifp->ctx, LOG_INFO, "%s: probing for an IPv4LL address", |
| 263 | ifp->name); |
| 264 | astate->addr.s_addr = INADDR_ANY; |
| 265 | } |
| 266 | if (astate->addr.s_addr == INADDR_ANY) |
| 267 | astate->addr.s_addr = ipv4ll_pick_addr(astate); |
| 268 | #ifdef IN_IFF_TENTATIVE |
| 269 | ipv4ll_probed(astate); |
| 270 | #else |
| 271 | arp_probe(astate); |
| 272 | #endif |
| 273 | } |
| 274 | |
| 275 | void |
| 276 | ipv4ll_stop(struct interface *ifp) |
| 277 | { |
| 278 | struct dhcp_state *state = D_STATE(ifp); |
| 279 | |
| 280 | eloop_timeout_delete(ifp->ctx->eloop, NULL, state->arp_ipv4ll); |
| 281 | } |