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)
  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
  51         // Filter ICMPv6 package types
  52         struct icmp6_filter filt;
  53         ICMP6_FILTER_SETBLOCKALL(&filt);
  54         ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &filt);
  55         setsockopt(sock, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
  56
  57         // Bind to all-nodes
  58         struct ipv6_mreq an = {ALL_IPV6_NODES, if_index};
  59         setsockopt(sock, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &an, sizeof(an));
  60
  61         // Let the kernel compute our checksums
  62         int val = 2;
  63         setsockopt(sock, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
  64
  65         // This is required by RFC 4861
  66         val = 255;
  67         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
  68
  69         // Bind to one device
  70         setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname));
  71
  72         // Add async-mode
  73         const pid_t ourpid = getpid();
  74         fcntl(sock, F_SETOWN, ourpid);
  75         fcntl(sock, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
  76
  77         // Get LL-addr
  78         FILE *fp = fopen("/proc/net/if_inet6", "r");
  79         if (fp) {
  80                 char addrbuf[33], ifbuf[16];
  81                 while (fscanf(fp, "%32s %*x %*x %*x %*x %15s", addrbuf, ifbuf) == 2) {
  82                         if (!strcmp(ifbuf, if_name)) {
  83                                 script_unhexlify((uint8_t*)&lladdr, sizeof(lladdr), addrbuf);
  84                                 break;
  85                         }
  86                 }
  87                 fclose(fp);
  88         }
  89
  90         // Open rtnetlink socket
  91         rtnl_sock = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE);
  92         struct sockaddr_nl rtnl_kernel = { .nl_family = AF_NETLINK };
  93         if (connect(rtnl_sock, (struct sockaddr*)&rtnl_kernel, sizeof(rtnl_kernel)))
  94                 return -1;
  95         uint32_t group = RTNLGRP_IPV6_IFADDR;
  96         setsockopt(rtnl_sock, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
  97
  98         // Add async-mode
  99         fcntl(rtnl_sock, F_SETOWN, ourpid);
 100         fcntl(rtnl_sock, F_SETFL, fcntl(rtnl_sock, F_GETFL) | O_ASYNC);
 101
 102         // Send RS
 103         signal(SIGALRM, ra_send_rs);
 104         ra_send_rs(SIGALRM);
 105
 106         return 0;
 107 }
 108
 109
 110 static void ra_send_rs(int signal __attribute__((unused)))
 111 {
 112         const struct icmp6_hdr rs = {ND_ROUTER_SOLICIT, 0, 0, {{0}}};
 113         const struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
 114         sendto(sock, &rs, sizeof(rs), MSG_DONTWAIT, (struct sockaddr*)&dest, sizeof(dest));
 115
 116         if (++rs_attempt <= 3)
 117                 alarm(4);
 118 }
 119
 120
 121 static int16_t pref_to_priority(uint8_t flags)
 122 {
 123         flags = (flags >> 3) & 0x03;
 124         return (flags == 0x0) ? 1024 : (flags == 0x1) ? 512 :
 125                         (flags == 0x3) ? 2048 : -1;
 126 }
 127
 128
 129 static void update_proc(const char *sect, const char *opt, uint32_t value)
 130 {
 131         char buf[64];
 132         snprintf(buf, sizeof(buf), "/proc/sys/net/ipv6/%s/%s/%s", sect, if_name, opt);
 133
 134         int fd = open(buf, O_WRONLY);
 135         write(fd, buf, snprintf(buf, sizeof(buf), "%u", value));
 136         close(fd);
 137 }
 138
 139
 140 static bool ra_deduplicate(const struct in6_addr *any, uint8_t length)
 141 {
 142         struct odhcp6c_entry entry = {IN6ADDR_ANY_INIT, length, 0, *any, 0, 0};
 143         struct odhcp6c_entry *x = odhcp6c_find_entry(STATE_RA_PREFIX, &entry);
 144         if (x && IN6_ARE_ADDR_EQUAL(&x->target, any)) {
 145                 odhcp6c_random(&x->target.s6_addr32[2], 2 * sizeof(uint32_t));
 146         } else if (odhcp6c_find_entry(STATE_IA_NA, &entry)) {
 147                 dhcpv6_request(DHCPV6_MSG_DECLINE);
 148                 raise(SIGUSR2);
 149         }
 150
 151         return !!x;
 152 }
 153
 154
 155 bool ra_rtnl_process(void)
 156 {
 157         bool found = false;
 158         uint8_t buf[8192];
 159         while (true) {
 160                 ssize_t len = recv(rtnl_sock, buf, sizeof(buf), MSG_DONTWAIT);
 161                 if (len < 0)
 162                         break;
 163
 164                 for (struct nlmsghdr *nh = (struct nlmsghdr*)buf; NLMSG_OK(nh, (size_t)len);
 165                                         nh = NLMSG_NEXT(nh, len)) {
 166                         struct ifaddrmsg *ifa = NLMSG_DATA(nh);
 167                         struct in6_addr *addr = NULL;
 168                         if (NLMSG_PAYLOAD(nh, 0) < sizeof(*ifa) || ifa->ifa_index != if_index ||
 169                                         (nh->nlmsg_type == RTM_NEWADDR && !(ifa->ifa_flags & IFA_F_DADFAILED)) ||
 170                                         (nh->nlmsg_type == RTM_DELADDR && !(ifa->ifa_flags & IFA_F_TENTATIVE)) ||
 171                                         (nh->nlmsg_type != RTM_NEWADDR && nh->nlmsg_type != RTM_DELADDR))
 172                                 continue;
 173
 174                         ssize_t alen = NLMSG_PAYLOAD(nh, sizeof(*ifa));
 175                         for (struct rtattr *rta = (struct rtattr*)&ifa[1]; RTA_OK(rta, alen);
 176                                         rta = RTA_NEXT(rta, alen))
 177                                 if (rta->rta_type == IFA_ADDRESS && RTA_PAYLOAD(rta) >= sizeof(*addr))
 178                                         addr = RTA_DATA(rta);
 179
 180                         if (addr) {
 181                                 char ipbuf[INET6_ADDRSTRLEN];
 182                                 inet_ntop(AF_INET6, addr, ipbuf, sizeof(ipbuf));
 183                                 syslog(LOG_WARNING, "duplicate address detected: %s (code: %u:%x)",
 184                                                 ipbuf, (unsigned)nh->nlmsg_type, (unsigned)ifa->ifa_flags);
 185                                 found |= ra_deduplicate(addr, ifa->ifa_prefixlen);
 186                         }
 187                 }
 188         }
 189         return found;
 190 }
 191
 192
 193 bool ra_process(void)
 194 {
 195         bool found = false;
 196         uint8_t buf[1500];
 197         struct nd_router_advert *adv = (struct nd_router_advert*)buf;
 198         struct odhcp6c_entry entry = {IN6ADDR_ANY_INIT, 0, 0, IN6ADDR_ANY_INIT, 0, 0};
 199         const struct in6_addr any = IN6ADDR_ANY_INIT;
 200         odhcp6c_expire();
 201
 202         while (true) {
 203                 struct sockaddr_in6 from;
 204                 socklen_t from_len = sizeof(from);
 205                 ssize_t len = recvfrom(sock, buf, sizeof(buf), MSG_DONTWAIT, &from, &from_len);
 206                 if (len < 0)
 207                         break;
 208                 else if (len < (ssize_t)sizeof(*adv))
 209                         continue;
 210
 211                 // Stop sending solicits
 212                 if (rs_attempt > 0) {
 213                         alarm(0);
 214                         rs_attempt = 0;
 215                 }
 216
 217                 found = true;
 218                 uint32_t router_valid = ntohs(adv->nd_ra_router_lifetime);
 219
 220                 // Parse default route
 221                 entry.target = any;
 222                 entry.length = 0;
 223                 entry.router = from.sin6_addr;
 224                 entry.priority = pref_to_priority(adv->nd_ra_flags_reserved);
 225                 if (entry.priority < 0)
 226                         entry.priority = pref_to_priority(0);
 227                 entry.valid = router_valid;
 228                 entry.preferred = entry.valid;
 229                 odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
 230
 231                 // Parse ND parameters
 232                 if (adv->nd_ra_reachable)
 233                         update_proc("neigh", "base_reachable_time_ms", ntohl(adv->nd_ra_reachable));
 234
 235                 if (adv->nd_ra_retransmit)
 236                         update_proc("neigh", "retrans_time_ms", ntohl(adv->nd_ra_retransmit));
 237
 238
 239                 // Evaluate options
 240                 struct icmpv6_opt *opt;
 241                 icmpv6_for_each_option(opt, &adv[1], &buf[len]) {
 242                         if (opt->type == ND_OPT_MTU) {
 243                                 uint32_t *mtu = (uint32_t*)&opt->data[2];
 244                                 update_proc("conf", "mtu", ntohl(*mtu));
 245                         } else if (opt->type == ND_OPT_ROUTE_INFORMATION && opt->len <= 3) {
 246                                 entry.router = from.sin6_addr;
 247                                 entry.target = any;
 248                                 entry.priority = pref_to_priority(opt->data[1]);
 249                                 entry.length = opt->data[0];
 250                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 251                                 entry.valid = ntohl(*valid);
 252                                 memcpy(&entry.target, &opt->data[6], (opt->len - 1) * 8);
 253
 254                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
 255                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
 256                                                 || IN6_IS_ADDR_MULTICAST(&entry.target))
 257                                         continue;
 258
 259                                 if (entry.priority > 0)
 260                                         odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
 261                         } else if (opt->type == ND_OPT_PREFIX_INFORMATION && opt->len == 4) {
 262                                 struct nd_opt_prefix_info *pinfo = (struct nd_opt_prefix_info*)opt;
 263                                 entry.router = any;
 264                                 entry.target = pinfo->nd_opt_pi_prefix;
 265                                 entry.priority = 256;
 266                                 entry.length = pinfo->nd_opt_pi_prefix_len;
 267                                 entry.valid = ntohl(pinfo->nd_opt_pi_valid_time);
 268                                 entry.preferred = ntohl(pinfo->nd_opt_pi_preferred_time);
 269
 270                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
 271                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
 272                                                 || IN6_IS_ADDR_MULTICAST(&entry.target)
 273                                                 || entry.valid < entry.preferred)
 274                                         continue;
 275
 276                                 if (pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_ONLINK)
 277                                         odhcp6c_update_entry_safe(STATE_RA_ROUTE, &entry, 7200);
 278
 279                                 if (!(pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_AUTO) ||
 280                                                 pinfo->nd_opt_pi_prefix_len != 64)
 281                                         continue;
 282
 283                                 entry.target.s6_addr32[2] = lladdr.s6_addr32[2];
 284                                 entry.target.s6_addr32[3] = lladdr.s6_addr32[3];
 285
 286                                 odhcp6c_update_entry_safe(STATE_RA_PREFIX, &entry, 7200);
 287                         } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 2) {
 288                                 entry.router = from.sin6_addr;
 289                                 entry.priority = 0;
 290                                 entry.length = 128;
 291                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 292                                 entry.valid = ntohl(*valid);
 293                                 entry.preferred = 0;
 294
 295                                 for (ssize_t i = 0; i < (opt->len - 1) / 2; ++i) {
 296                                         memcpy(&entry.target, &opt->data[6 + i * sizeof(entry.target)],
 297                                                         sizeof(entry.target));
 298                                         odhcp6c_update_entry(STATE_RA_DNS, &entry);
 299                                 }
 300                         }
 301                 }
 302
 303                 size_t ra_dns_len;
 304                 struct odhcp6c_entry *entry = odhcp6c_get_state(STATE_RA_DNS, &ra_dns_len);
 305                 for (size_t i = 0; i < ra_dns_len / sizeof(*entry); ++i)
 306                         if (IN6_ARE_ADDR_EQUAL(&entry[i].router, &from.sin6_addr) &&
 307                                         entry[i].valid > router_valid)
 308                                 entry[i].valid = router_valid;
 309         }
 310
 311         odhcp6c_expire();
 312         return found;
 313 }