src/ra.c

   1 /**
   2  * Copyright (C) 2012-2013 Steven Barth <steven@midlink.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License v2 as published by
   6  * the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  */
  14
  15 #include <fcntl.h>
  16 #include <stdio.h>
  17 #include <signal.h>
  18 #include <string.h>
  19 #include <stddef.h>
  20 #include <stdbool.h>
  21 #include <syslog.h>
  22 #include <unistd.h>
  23
  24 #include <net/if.h>
  25 #include <arpa/inet.h>
  26 #include <sys/socket.h>
  27 #include <netinet/in.h>
  28 #include <netinet/icmp6.h>
  29
  30 #include <linux/rtnetlink.h>
  31
  32 #ifndef SOL_NETLINK
  33 #define SOL_NETLINK 270
  34 #endif
  35
  36 #ifndef NETLINK_ADD_MEMBERSHIP
  37 #define NETLINK_ADD_MEMBERSHIP 1
  38 #endif
  39
  40 #ifndef IFF_LOWER_UP
  41 #define IFF_LOWER_UP 0x10000
  42 #endif
  43
  44 #include "odhcp6c.h"
  45 #include "ra.h"
  46
  47
  48 static bool nocarrier = false;
  49
  50 static int sock = -1, rtnl = -1;
  51 static int if_index = 0;
  52 static char if_name[IF_NAMESIZE] = {0};
  53 static volatile int rs_attempt = 0;
  54 static struct in6_addr lladdr = IN6ADDR_ANY_INIT;
  55
  56 static void ra_send_rs(int signal __attribute__((unused)));
  57
  58 int ra_init(const char *ifname, const struct in6_addr *ifid)
  59 {
  60         const pid_t ourpid = getpid();
  61         sock = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
  62         if_index = if_nametoindex(ifname);
  63         strncpy(if_name, ifname, sizeof(if_name) - 1);
  64         lladdr = *ifid;
  65
  66         rtnl = socket(AF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_ROUTE);
  67         struct sockaddr_nl rtnl_kernel = { .nl_family = AF_NETLINK };
  68         connect(rtnl, (const struct sockaddr*)&rtnl_kernel, sizeof(rtnl_kernel));
  69
  70         int val = RTNLGRP_LINK;
  71         setsockopt(rtnl, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &val, sizeof(val));
  72         fcntl(rtnl, F_SETOWN, ourpid);
  73         fcntl(rtnl, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
  74
  75         struct {
  76                 struct nlmsghdr hdr;
  77                 struct ifinfomsg ifi;
  78         } req = {
  79                 .hdr = {sizeof(req), RTM_GETLINK, NLM_F_REQUEST, 1, 0},
  80                 .ifi = {.ifi_index = if_index}
  81         };
  82         send(rtnl, &req, sizeof(req), 0);
  83
  84         // Filter ICMPv6 package types
  85         struct icmp6_filter filt;
  86         ICMP6_FILTER_SETBLOCKALL(&filt);
  87         ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &filt);
  88         setsockopt(sock, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
  89
  90         // Bind to all-nodes
  91         struct ipv6_mreq an = {ALL_IPV6_NODES, if_index};
  92         setsockopt(sock, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &an, sizeof(an));
  93
  94         // Let the kernel compute our checksums
  95         val = 2;
  96         setsockopt(sock, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
  97
  98         // This is required by RFC 4861
  99         val = 255;
 100         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
 101
 102         // Receive multicast hops
 103         val = 1;
 104         setsockopt(sock, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &val, sizeof(val));
 105
 106         // Bind to one device
 107         setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname));
 108
 109         // Add async-mode
 110         fcntl(sock, F_SETOWN, ourpid);
 111         fcntl(sock, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
 112
 113         // Send RS
 114         signal(SIGALRM, ra_send_rs);
 115         ra_send_rs(SIGALRM);
 116
 117         return 0;
 118 }
 119
 120
 121 static void ra_send_rs(int signal __attribute__((unused)))
 122 {
 123         const struct icmp6_hdr rs = {ND_ROUTER_SOLICIT, 0, 0, {{0}}};
 124         const struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
 125         sendto(sock, &rs, sizeof(rs), MSG_DONTWAIT, (struct sockaddr*)&dest, sizeof(dest));
 126
 127         if (++rs_attempt <= 3)
 128                 alarm(4);
 129 }
 130
 131
 132 static int16_t pref_to_priority(uint8_t flags)
 133 {
 134         flags = (flags >> 3) & 0x03;
 135         return (flags == 0x0) ? 1024 : (flags == 0x1) ? 512 :
 136                         (flags == 0x3) ? 2048 : -1;
 137 }
 138
 139
 140 static void update_proc(const char *sect, const char *opt, uint32_t value)
 141 {
 142         char buf[64];
 143         snprintf(buf, sizeof(buf), "/proc/sys/net/ipv6/%s/%s/%s", sect, if_name, opt);
 144
 145         int fd = open(buf, O_WRONLY);
 146         write(fd, buf, snprintf(buf, sizeof(buf), "%u", value));
 147         close(fd);
 148 }
 149
 150
 151 bool ra_link_up(void)
 152 {
 153         struct {
 154                 struct nlmsghdr hdr;
 155                 struct ifinfomsg msg;
 156                 uint8_t pad[4000];
 157         } resp;
 158
 159         bool ret = false;
 160         ssize_t read;
 161
 162         do {
 163                 read = recv(rtnl, &resp, sizeof(resp), MSG_DONTWAIT);
 164                 if (!NLMSG_OK(&resp.hdr, read) || resp.hdr.nlmsg_type != RTM_NEWLINK ||
 165                                 resp.msg.ifi_index != if_index)
 166                         continue;
 167
 168                 bool hascarrier = resp.msg.ifi_flags & IFF_LOWER_UP;
 169                 if (nocarrier && hascarrier)
 170                         ret = true;
 171
 172                 nocarrier = !hascarrier;
 173         } while (read > 0);
 174
 175         if (ret) {
 176                 syslog(LOG_NOTICE, "carrier up event on %s", if_name);
 177                 rs_attempt = 0;
 178                 ra_send_rs(SIGALRM);
 179         }
 180
 181         return ret;
 182 }
 183
 184 bool ra_process(void)
 185 {
 186         bool found = false;
 187         bool changed = false;
 188         uint8_t buf[1500], cmsg_buf[128];
 189         struct nd_router_advert *adv = (struct nd_router_advert*)buf;
 190         struct odhcp6c_entry entry = {IN6ADDR_ANY_INIT, 0, 0, IN6ADDR_ANY_INIT, 0, 0, 0, 0, 0};
 191         const struct in6_addr any = IN6ADDR_ANY_INIT;
 192
 193         if (IN6_IS_ADDR_UNSPECIFIED(&lladdr)) {
 194                 // Autodetect interface-id if not specified
 195                 FILE *fp = fopen("/proc/net/if_inet6", "r");
 196                 if (fp) {
 197                         char addrbuf[33], ifbuf[16];
 198                         while (fscanf(fp, "%32s %*x %*x %*x %*x %15s", addrbuf, ifbuf) == 2) {
 199                                 if (!strcmp(ifbuf, if_name)) {
 200                                         script_unhexlify((uint8_t*)&lladdr, sizeof(lladdr), addrbuf);
 201                                         break;
 202                                 }
 203                         }
 204                         fclose(fp);
 205                 }
 206         }
 207
 208         while (true) {
 209                 struct sockaddr_in6 from;
 210                 struct iovec iov = {buf, sizeof(buf)};
 211                 struct msghdr msg = {&from, sizeof(from), &iov, 1,
 212                                 cmsg_buf, sizeof(cmsg_buf), 0};
 213
 214                 ssize_t len = recvmsg(sock, &msg, MSG_DONTWAIT);
 215                 if (len < 0)
 216                         break;
 217                 else if (len < (ssize_t)sizeof(*adv))
 218                         continue;
 219
 220                 int hlim = 0;
 221                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL;
 222                                 ch = CMSG_NXTHDR(&msg, ch))
 223                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 224                                         ch->cmsg_type == IPV6_HOPLIMIT)
 225                                 memcpy(&hlim, CMSG_DATA(ch), sizeof(hlim));
 226
 227                 if (hlim != 255)
 228                         continue;
 229
 230                 // Stop sending solicits
 231                 if (rs_attempt > 0) {
 232                         alarm(0);
 233                         rs_attempt = 0;
 234                 }
 235
 236                 if (!found) {
 237                         odhcp6c_expire();
 238                         found = true;
 239                 }
 240                 uint32_t router_valid = ntohs(adv->nd_ra_router_lifetime);
 241
 242                 // Parse default route
 243                 entry.target = any;
 244                 entry.length = 0;
 245                 entry.router = from.sin6_addr;
 246                 entry.priority = pref_to_priority(adv->nd_ra_flags_reserved);
 247                 if (entry.priority < 0)
 248                         entry.priority = pref_to_priority(0);
 249                 entry.valid = router_valid;
 250                 entry.preferred = entry.valid;
 251                 changed |= odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
 252
 253                 // Parse ND parameters
 254                 if (ntohl(adv->nd_ra_reachable) <= 3600000)
 255                         update_proc("neigh", "base_reachable_time_ms", ntohl(adv->nd_ra_reachable));
 256
 257                 if (ntohl(adv->nd_ra_retransmit) <= 60000)
 258                         update_proc("neigh", "retrans_time_ms", ntohl(adv->nd_ra_retransmit));
 259
 260
 261                 // Evaluate options
 262                 struct icmpv6_opt *opt;
 263                 icmpv6_for_each_option(opt, &adv[1], &buf[len]) {
 264                         if (opt->type == ND_OPT_MTU) {
 265                                 uint32_t *mtu = (uint32_t*)&opt->data[2];
 266                                 if (ntohl(*mtu) >= 1280 && ntohl(*mtu) <= 65535)
 267                                         update_proc("conf", "mtu", ntohl(*mtu));
 268                         } else if (opt->type == ND_OPT_ROUTE_INFORMATION && opt->len <= 3) {
 269                                 entry.router = from.sin6_addr;
 270                                 entry.target = any;
 271                                 entry.priority = pref_to_priority(opt->data[1]);
 272                                 entry.length = opt->data[0];
 273                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 274                                 entry.valid = ntohl(*valid);
 275                                 memcpy(&entry.target, &opt->data[6], (opt->len - 1) * 8);
 276
 277                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
 278                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
 279                                                 || IN6_IS_ADDR_MULTICAST(&entry.target))
 280                                         continue;
 281
 282                                 if (entry.priority > 0)
 283                                         changed |= odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
 284                         } else if (opt->type == ND_OPT_PREFIX_INFORMATION && opt->len == 4) {
 285                                 struct nd_opt_prefix_info *pinfo = (struct nd_opt_prefix_info*)opt;
 286                                 entry.router = any;
 287                                 entry.target = pinfo->nd_opt_pi_prefix;
 288                                 entry.priority = 256;
 289                                 entry.length = pinfo->nd_opt_pi_prefix_len;
 290                                 entry.valid = ntohl(pinfo->nd_opt_pi_valid_time);
 291                                 entry.preferred = ntohl(pinfo->nd_opt_pi_preferred_time);
 292
 293                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
 294                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
 295                                                 || IN6_IS_ADDR_MULTICAST(&entry.target)
 296                                                 || entry.valid < entry.preferred)
 297                                         continue;
 298
 299                                 if (pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_ONLINK)
 300                                         changed |= odhcp6c_update_entry_safe(STATE_RA_ROUTE, &entry, 7200);
 301
 302                                 if (!(pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_AUTO) ||
 303                                                 pinfo->nd_opt_pi_prefix_len != 64)
 304                                         continue;
 305
 306                                 entry.target.s6_addr32[2] = lladdr.s6_addr32[2];
 307                                 entry.target.s6_addr32[3] = lladdr.s6_addr32[3];
 308
 309                                 changed |= odhcp6c_update_entry_safe(STATE_RA_PREFIX, &entry, 7200);
 310                         } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 2) {
 311                                 entry.router = from.sin6_addr;
 312                                 entry.priority = 0;
 313                                 entry.length = 128;
 314                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 315                                 entry.valid = ntohl(*valid);
 316                                 entry.preferred = 0;
 317
 318                                 for (ssize_t i = 0; i < (opt->len - 1) / 2; ++i) {
 319                                         memcpy(&entry.target, &opt->data[6 + i * sizeof(entry.target)],
 320                                                         sizeof(entry.target));
 321                                         changed |= odhcp6c_update_entry(STATE_RA_DNS, &entry);
 322                                 }
 323                         }
 324                 }
 325
 326                 size_t ra_dns_len;
 327                 struct odhcp6c_entry *entry = odhcp6c_get_state(STATE_RA_DNS, &ra_dns_len);
 328                 for (size_t i = 0; i < ra_dns_len / sizeof(*entry); ++i)
 329                         if (IN6_ARE_ADDR_EQUAL(&entry[i].router, &from.sin6_addr) &&
 330                                         entry[i].valid > router_valid)
 331                                 entry[i].valid = router_valid;
 332         }
 333
 334         if (found)
 335                 odhcp6c_expire();
 336
 337         return found && changed;
 338 }