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
  33 #include "odhcp6c.h"
  34 #include "ra.h"
  35
  36
  37 static int sock = -1;
  38 static unsigned if_index = 0;
  39 static char if_name[IF_NAMESIZE] = {0};
  40 static volatile int rs_attempt = 0;
  41 static struct in6_addr lladdr = IN6ADDR_ANY_INIT;
  42
  43 static void ra_send_rs(int signal __attribute__((unused)));
  44
  45 int ra_init(const char *ifname, const struct in6_addr *ifid)
  46 {
  47         sock = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
  48         if_index = if_nametoindex(ifname);
  49         strncpy(if_name, ifname, sizeof(if_name) - 1);
  50         lladdr = *ifid;
  51
  52         // Filter ICMPv6 package types
  53         struct icmp6_filter filt;
  54         ICMP6_FILTER_SETBLOCKALL(&filt);
  55         ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &filt);
  56         setsockopt(sock, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
  57
  58         // Bind to all-nodes
  59         struct ipv6_mreq an = {ALL_IPV6_NODES, if_index};
  60         setsockopt(sock, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &an, sizeof(an));
  61
  62         // Let the kernel compute our checksums
  63         int val = 2;
  64         setsockopt(sock, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
  65
  66         // This is required by RFC 4861
  67         val = 255;
  68         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
  69
  70         // Receive multicast hops
  71         val = 1;
  72         setsockopt(sock, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &val, sizeof(val));
  73
  74         // Bind to one device
  75         setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname));
  76
  77         // Add async-mode
  78         const pid_t ourpid = getpid();
  79         fcntl(sock, F_SETOWN, ourpid);
  80         fcntl(sock, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
  81
  82         // Send RS
  83         signal(SIGALRM, ra_send_rs);
  84         ra_send_rs(SIGALRM);
  85
  86         return 0;
  87 }
  88
  89
  90 static void ra_send_rs(int signal __attribute__((unused)))
  91 {
  92         const struct icmp6_hdr rs = {ND_ROUTER_SOLICIT, 0, 0, {{0}}};
  93         const struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
  94         sendto(sock, &rs, sizeof(rs), MSG_DONTWAIT, (struct sockaddr*)&dest, sizeof(dest));
  95
  96         if (++rs_attempt <= 3)
  97                 alarm(4);
  98 }
  99
 100
 101 static int16_t pref_to_priority(uint8_t flags)
 102 {
 103         flags = (flags >> 3) & 0x03;
 104         return (flags == 0x0) ? 1024 : (flags == 0x1) ? 512 :
 105                         (flags == 0x3) ? 2048 : -1;
 106 }
 107
 108
 109 static void update_proc(const char *sect, const char *opt, uint32_t value)
 110 {
 111         char buf[64];
 112         snprintf(buf, sizeof(buf), "/proc/sys/net/ipv6/%s/%s/%s", sect, if_name, opt);
 113
 114         int fd = open(buf, O_WRONLY);
 115         write(fd, buf, snprintf(buf, sizeof(buf), "%u", value));
 116         close(fd);
 117 }
 118
 119
 120 bool ra_process(void)
 121 {
 122         bool found = false;
 123         bool changed = false;
 124         uint8_t buf[1500], cmsg_buf[128];
 125         struct nd_router_advert *adv = (struct nd_router_advert*)buf;
 126         struct odhcp6c_entry entry = {IN6ADDR_ANY_INIT, 0, 0, IN6ADDR_ANY_INIT, 0, 0, 0};
 127         const struct in6_addr any = IN6ADDR_ANY_INIT;
 128
 129         if (IN6_IS_ADDR_UNSPECIFIED(&lladdr)) {
 130                 // Autodetect interface-id if not specified
 131                 FILE *fp = fopen("/proc/net/if_inet6", "r");
 132                 if (fp) {
 133                         char addrbuf[33], ifbuf[16];
 134                         while (fscanf(fp, "%32s %*x %*x %*x %*x %15s", addrbuf, ifbuf) == 2) {
 135                                 if (!strcmp(ifbuf, if_name)) {
 136                                         script_unhexlify((uint8_t*)&lladdr, sizeof(lladdr), addrbuf);
 137                                         break;
 138                                 }
 139                         }
 140                         fclose(fp);
 141                 }
 142         }
 143
 144         while (true) {
 145                 struct sockaddr_in6 from;
 146                 struct iovec iov = {buf, sizeof(buf)};
 147                 struct msghdr msg = {&from, sizeof(from), &iov, 1,
 148                                 cmsg_buf, sizeof(cmsg_buf), 0};
 149
 150                 ssize_t len = recvmsg(sock, &msg, MSG_DONTWAIT);
 151                 if (len < 0)
 152                         break;
 153                 else if (len < (ssize_t)sizeof(*adv))
 154                         continue;
 155
 156                 int hlim = 0;
 157                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL;
 158                                 ch = CMSG_NXTHDR(&msg, ch))
 159                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 160                                         ch->cmsg_type == IPV6_HOPLIMIT)
 161                                 memcpy(&hlim, CMSG_DATA(ch), sizeof(hlim));
 162
 163                 if (hlim != 255)
 164                         continue;
 165
 166                 // Stop sending solicits
 167                 if (rs_attempt > 0) {
 168                         alarm(0);
 169                         rs_attempt = 0;
 170                 }
 171
 172                 if (!found) {
 173                         odhcp6c_expire();
 174                         found = true;
 175                 }
 176                 uint32_t router_valid = ntohs(adv->nd_ra_router_lifetime);
 177
 178                 // Parse default route
 179                 entry.target = any;
 180                 entry.length = 0;
 181                 entry.router = from.sin6_addr;
 182                 entry.priority = pref_to_priority(adv->nd_ra_flags_reserved);
 183                 if (entry.priority < 0)
 184                         entry.priority = pref_to_priority(0);
 185                 entry.valid = router_valid;
 186                 entry.preferred = entry.valid;
 187                 changed |= odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
 188
 189                 // Parse ND parameters
 190                 if (ntohl(adv->nd_ra_reachable) <= 3600000)
 191                         update_proc("neigh", "base_reachable_time_ms", ntohl(adv->nd_ra_reachable));
 192
 193                 if (ntohl(adv->nd_ra_retransmit) <= 60000)
 194                         update_proc("neigh", "retrans_time_ms", ntohl(adv->nd_ra_retransmit));
 195
 196
 197                 // Evaluate options
 198                 struct icmpv6_opt *opt;
 199                 icmpv6_for_each_option(opt, &adv[1], &buf[len]) {
 200                         if (opt->type == ND_OPT_MTU) {
 201                                 uint32_t *mtu = (uint32_t*)&opt->data[2];
 202                                 if (ntohl(*mtu) >= 1280 && ntohl(*mtu) <= 65535)
 203                                         update_proc("conf", "mtu", ntohl(*mtu));
 204                         } else if (opt->type == ND_OPT_ROUTE_INFORMATION && opt->len <= 3) {
 205                                 entry.router = from.sin6_addr;
 206                                 entry.target = any;
 207                                 entry.priority = pref_to_priority(opt->data[1]);
 208                                 entry.length = opt->data[0];
 209                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 210                                 entry.valid = ntohl(*valid);
 211                                 memcpy(&entry.target, &opt->data[6], (opt->len - 1) * 8);
 212
 213                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
 214                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
 215                                                 || IN6_IS_ADDR_MULTICAST(&entry.target))
 216                                         continue;
 217
 218                                 if (entry.priority > 0)
 219                                         changed |= odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
 220                         } else if (opt->type == ND_OPT_PREFIX_INFORMATION && opt->len == 4) {
 221                                 struct nd_opt_prefix_info *pinfo = (struct nd_opt_prefix_info*)opt;
 222                                 entry.router = any;
 223                                 entry.target = pinfo->nd_opt_pi_prefix;
 224                                 entry.priority = 256;
 225                                 entry.length = pinfo->nd_opt_pi_prefix_len;
 226                                 entry.valid = ntohl(pinfo->nd_opt_pi_valid_time);
 227                                 entry.preferred = ntohl(pinfo->nd_opt_pi_preferred_time);
 228
 229                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
 230                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
 231                                                 || IN6_IS_ADDR_MULTICAST(&entry.target)
 232                                                 || entry.valid < entry.preferred)
 233                                         continue;
 234
 235                                 if (pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_ONLINK)
 236                                         changed |= odhcp6c_update_entry_safe(STATE_RA_ROUTE, &entry, 7200);
 237
 238                                 if (!(pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_AUTO) ||
 239                                                 pinfo->nd_opt_pi_prefix_len != 64)
 240                                         continue;
 241
 242                                 entry.target.s6_addr32[2] = lladdr.s6_addr32[2];
 243                                 entry.target.s6_addr32[3] = lladdr.s6_addr32[3];
 244
 245                                 changed |= odhcp6c_update_entry_safe(STATE_RA_PREFIX, &entry, 7200);
 246                         } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 2) {
 247                                 entry.router = from.sin6_addr;
 248                                 entry.priority = 0;
 249                                 entry.length = 128;
 250                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 251                                 entry.valid = ntohl(*valid);
 252                                 entry.preferred = 0;
 253
 254                                 for (ssize_t i = 0; i < (opt->len - 1) / 2; ++i) {
 255                                         memcpy(&entry.target, &opt->data[6 + i * sizeof(entry.target)],
 256                                                         sizeof(entry.target));
 257                                         changed |= odhcp6c_update_entry(STATE_RA_DNS, &entry);
 258                                 }
 259                         }
 260                 }
 261
 262                 size_t ra_dns_len;
 263                 struct odhcp6c_entry *entry = odhcp6c_get_state(STATE_RA_DNS, &ra_dns_len);
 264                 for (size_t i = 0; i < ra_dns_len / sizeof(*entry); ++i)
 265                         if (IN6_ARE_ADDR_EQUAL(&entry[i].router, &from.sin6_addr) &&
 266                                         entry[i].valid > router_valid)
 267                                 entry[i].valid = router_valid;
 268         }
 269
 270         if (found)
 271                 odhcp6c_expire();
 272
 273         return found && changed;
 274 }