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, rtnl_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         // Bind to one device
  71         setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname));
  72
  73         // Add async-mode
  74         const pid_t ourpid = getpid();
  75         fcntl(sock, F_SETOWN, ourpid);
  76         fcntl(sock, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
  77
  78         if (IN6_IS_ADDR_UNSPECIFIED(&lladdr)) {
  79                 // Autodetect interface-id if not specified
  80                 FILE *fp = fopen("/proc/net/if_inet6", "r");
  81                 if (fp) {
  82                         char addrbuf[33], ifbuf[16];
  83                         while (fscanf(fp, "%32s %*x %*x %*x %*x %15s", addrbuf, ifbuf) == 2) {
  84                                 if (!strcmp(ifbuf, if_name)) {
  85                                         script_unhexlify((uint8_t*)&lladdr, sizeof(lladdr), addrbuf);
  86                                         break;
  87                                 }
  88                         }
  89                         fclose(fp);
  90                 }
  91         }
  92
  93         // Open rtnetlink socket
  94         rtnl_sock = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE);
  95         struct sockaddr_nl rtnl_kernel = { .nl_family = AF_NETLINK };
  96         if (connect(rtnl_sock, (struct sockaddr*)&rtnl_kernel, sizeof(rtnl_kernel)))
  97                 return -1;
  98         uint32_t group = RTNLGRP_IPV6_IFADDR;
  99         setsockopt(rtnl_sock, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
 100
 101         // Add async-mode
 102         fcntl(rtnl_sock, F_SETOWN, ourpid);
 103         fcntl(rtnl_sock, F_SETFL, fcntl(rtnl_sock, F_GETFL) | O_ASYNC);
 104
 105         // Send RS
 106         signal(SIGALRM, ra_send_rs);
 107         ra_send_rs(SIGALRM);
 108
 109         return 0;
 110 }
 111
 112
 113 static void ra_send_rs(int signal __attribute__((unused)))
 114 {
 115         const struct icmp6_hdr rs = {ND_ROUTER_SOLICIT, 0, 0, {{0}}};
 116         const struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
 117         sendto(sock, &rs, sizeof(rs), MSG_DONTWAIT, (struct sockaddr*)&dest, sizeof(dest));
 118
 119         if (++rs_attempt <= 3)
 120                 alarm(4);
 121 }
 122
 123
 124 static int16_t pref_to_priority(uint8_t flags)
 125 {
 126         flags = (flags >> 3) & 0x03;
 127         return (flags == 0x0) ? 1024 : (flags == 0x1) ? 512 :
 128                         (flags == 0x3) ? 2048 : -1;
 129 }
 130
 131
 132 static void update_proc(const char *sect, const char *opt, uint32_t value)
 133 {
 134         char buf[64];
 135         snprintf(buf, sizeof(buf), "/proc/sys/net/ipv6/%s/%s/%s", sect, if_name, opt);
 136
 137         int fd = open(buf, O_WRONLY);
 138         write(fd, buf, snprintf(buf, sizeof(buf), "%u", value));
 139         close(fd);
 140 }
 141
 142
 143 static bool ra_deduplicate(const struct in6_addr *any, uint8_t length)
 144 {
 145   struct odhcp6c_entry entry = {IN6ADDR_ANY_INIT, length, 0, *any, 0, 0, 0};
 146         struct odhcp6c_entry *x = odhcp6c_find_entry(STATE_RA_PREFIX, &entry);
 147         if (x && IN6_ARE_ADDR_EQUAL(&x->target, any)) {
 148                 odhcp6c_random(&x->target.s6_addr32[2], 2 * sizeof(uint32_t));
 149         } else if (odhcp6c_find_entry(STATE_IA_NA, &entry)) {
 150                 dhcpv6_request(DHCPV6_MSG_DECLINE);
 151                 raise(SIGUSR2);
 152         }
 153
 154         return !!x;
 155 }
 156
 157
 158 bool ra_rtnl_process(void)
 159 {
 160         bool found = false;
 161         uint32_t elapsed = odhcp6c_elapsed();
 162         uint8_t buf[8192];
 163         while (true) {
 164                 ssize_t len = recv(rtnl_sock, buf, sizeof(buf), MSG_DONTWAIT);
 165                 if (len < 0)
 166                         break;
 167
 168                 if (elapsed > 10)
 169                         continue;
 170
 171                 for (struct nlmsghdr *nh = (struct nlmsghdr*)buf; NLMSG_OK(nh, (size_t)len);
 172                                         nh = NLMSG_NEXT(nh, len)) {
 173                         struct ifaddrmsg *ifa = NLMSG_DATA(nh);
 174                         struct in6_addr *addr = NULL;
 175                         if (NLMSG_PAYLOAD(nh, 0) < sizeof(*ifa) || ifa->ifa_index != if_index ||
 176                                         (nh->nlmsg_type == RTM_NEWADDR && !(ifa->ifa_flags & IFA_F_DADFAILED)) ||
 177                                         (nh->nlmsg_type == RTM_DELADDR && !(ifa->ifa_flags & IFA_F_TENTATIVE)) ||
 178                                         (nh->nlmsg_type != RTM_NEWADDR && nh->nlmsg_type != RTM_DELADDR))
 179                                 continue;
 180
 181                         ssize_t alen = NLMSG_PAYLOAD(nh, sizeof(*ifa));
 182                         for (struct rtattr *rta = (struct rtattr*)&ifa[1]; RTA_OK(rta, alen);
 183                                         rta = RTA_NEXT(rta, alen))
 184                                 if (rta->rta_type == IFA_ADDRESS && RTA_PAYLOAD(rta) >= sizeof(*addr))
 185                                         addr = RTA_DATA(rta);
 186
 187                         if (addr) {
 188                                 char ipbuf[INET6_ADDRSTRLEN];
 189                                 inet_ntop(AF_INET6, addr, ipbuf, sizeof(ipbuf));
 190                                 syslog(LOG_WARNING, "duplicate address detected: %s (code: %u:%x)",
 191                                                 ipbuf, (unsigned)nh->nlmsg_type, (unsigned)ifa->ifa_flags);
 192                                 found |= ra_deduplicate(addr, ifa->ifa_prefixlen);
 193                         }
 194                 }
 195         }
 196         return found;
 197 }
 198
 199
 200 bool ra_process(void)
 201 {
 202         bool found = false;
 203         uint8_t buf[1500];
 204         struct nd_router_advert *adv = (struct nd_router_advert*)buf;
 205         struct odhcp6c_entry entry = {IN6ADDR_ANY_INIT, 0, 0, IN6ADDR_ANY_INIT, 0, 0, 0};
 206         const struct in6_addr any = IN6ADDR_ANY_INIT;
 207
 208         while (true) {
 209                 struct sockaddr_in6 from;
 210                 socklen_t from_len = sizeof(from);
 211                 ssize_t len = recvfrom(sock, buf, sizeof(buf), MSG_DONTWAIT, &from, &from_len);
 212                 if (len < 0)
 213                         break;
 214                 else if (len < (ssize_t)sizeof(*adv))
 215                         continue;
 216
 217                 // Stop sending solicits
 218                 if (rs_attempt > 0) {
 219                         alarm(0);
 220                         rs_attempt = 0;
 221                 }
 222
 223                 if (!found) {
 224                         odhcp6c_expire();
 225                         found = true;
 226                 }
 227                 uint32_t router_valid = ntohs(adv->nd_ra_router_lifetime);
 228
 229                 // Parse default route
 230                 entry.target = any;
 231                 entry.length = 0;
 232                 entry.router = from.sin6_addr;
 233                 entry.priority = pref_to_priority(adv->nd_ra_flags_reserved);
 234                 if (entry.priority < 0)
 235                         entry.priority = pref_to_priority(0);
 236                 entry.valid = router_valid;
 237                 entry.preferred = entry.valid;
 238                 odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
 239
 240                 // Parse ND parameters
 241                 if (ntohl(adv->nd_ra_reachable) <= 3600000)
 242                         update_proc("neigh", "base_reachable_time_ms", ntohl(adv->nd_ra_reachable));
 243
 244                 if (ntohl(adv->nd_ra_retransmit) <= 60000)
 245                         update_proc("neigh", "retrans_time_ms", ntohl(adv->nd_ra_retransmit));
 246
 247
 248                 // Evaluate options
 249                 struct icmpv6_opt *opt;
 250                 icmpv6_for_each_option(opt, &adv[1], &buf[len]) {
 251                         if (opt->type == ND_OPT_MTU) {
 252                                 uint32_t *mtu = (uint32_t*)&opt->data[2];
 253                                 if (ntohl(*mtu) >= 1280 && ntohl(*mtu) <= 65535)
 254                                         update_proc("conf", "mtu", ntohl(*mtu));
 255                         } else if (opt->type == ND_OPT_ROUTE_INFORMATION && opt->len <= 3) {
 256                                 entry.router = from.sin6_addr;
 257                                 entry.target = any;
 258                                 entry.priority = pref_to_priority(opt->data[1]);
 259                                 entry.length = opt->data[0];
 260                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 261                                 entry.valid = ntohl(*valid);
 262                                 memcpy(&entry.target, &opt->data[6], (opt->len - 1) * 8);
 263
 264                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
 265                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
 266                                                 || IN6_IS_ADDR_MULTICAST(&entry.target))
 267                                         continue;
 268
 269                                 if (entry.priority > 0)
 270                                         odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
 271                         } else if (opt->type == ND_OPT_PREFIX_INFORMATION && opt->len == 4) {
 272                                 struct nd_opt_prefix_info *pinfo = (struct nd_opt_prefix_info*)opt;
 273                                 entry.router = any;
 274                                 entry.target = pinfo->nd_opt_pi_prefix;
 275                                 entry.priority = 256;
 276                                 entry.length = pinfo->nd_opt_pi_prefix_len;
 277                                 entry.valid = ntohl(pinfo->nd_opt_pi_valid_time);
 278                                 entry.preferred = ntohl(pinfo->nd_opt_pi_preferred_time);
 279
 280                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
 281                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
 282                                                 || IN6_IS_ADDR_MULTICAST(&entry.target)
 283                                                 || entry.valid < entry.preferred)
 284                                         continue;
 285
 286                                 if (pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_ONLINK)
 287                                         odhcp6c_update_entry_safe(STATE_RA_ROUTE, &entry, 7200);
 288
 289                                 if (!(pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_AUTO) ||
 290                                                 pinfo->nd_opt_pi_prefix_len != 64)
 291                                         continue;
 292
 293                                 entry.target.s6_addr32[2] = lladdr.s6_addr32[2];
 294                                 entry.target.s6_addr32[3] = lladdr.s6_addr32[3];
 295
 296                                 odhcp6c_update_entry_safe(STATE_RA_PREFIX, &entry, 7200);
 297                         } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 2) {
 298                                 entry.router = from.sin6_addr;
 299                                 entry.priority = 0;
 300                                 entry.length = 128;
 301                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 302                                 entry.valid = ntohl(*valid);
 303                                 entry.preferred = 0;
 304
 305                                 for (ssize_t i = 0; i < (opt->len - 1) / 2; ++i) {
 306                                         memcpy(&entry.target, &opt->data[6 + i * sizeof(entry.target)],
 307                                                         sizeof(entry.target));
 308                                         odhcp6c_update_entry(STATE_RA_DNS, &entry);
 309                                 }
 310                         }
 311                 }
 312
 313                 size_t ra_dns_len;
 314                 struct odhcp6c_entry *entry = odhcp6c_get_state(STATE_RA_DNS, &ra_dns_len);
 315                 for (size_t i = 0; i < ra_dns_len / sizeof(*entry); ++i)
 316                         if (IN6_ARE_ADDR_EQUAL(&entry[i].router, &from.sin6_addr) &&
 317                                         entry[i].valid > router_valid)
 318                                 entry[i].valid = router_valid;
 319         }
 320
 321         if (found)
 322                 odhcp6c_expire();
 323
 324         return found;
 325 }