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 <unistd.h>
  22
  23 #include <net/if.h>
  24 #include <sys/socket.h>
  25 #include <netinet/in.h>
  26 #include <netinet/icmp6.h>
  27
  28 #include <linux/rtnetlink.h>
  29
  30
  31 #include "odhcp6c.h"
  32 #include "ra.h"
  33
  34
  35 static int sock = -1, rtnl_sock = -1;
  36 static unsigned if_index = 0;
  37 static char if_name[IF_NAMESIZE] = {0};
  38 static volatile int rs_attempt = 0;
  39 static struct in6_addr lladdr = IN6ADDR_ANY_INIT;
  40
  41 static void ra_send_rs(int signal __attribute__((unused)));
  42
  43 int ra_init(const char *ifname)
  44 {
  45         sock = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
  46         if_index = if_nametoindex(ifname);
  47         strncpy(if_name, ifname, sizeof(if_name) - 1);
  48
  49         // Filter ICMPv6 package types
  50         struct icmp6_filter filt;
  51         ICMP6_FILTER_SETBLOCKALL(&filt);
  52         ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &filt);
  53         setsockopt(sock, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
  54
  55         // Bind to all-nodes
  56         struct ipv6_mreq an = {ALL_IPV6_NODES, if_index};
  57         setsockopt(sock, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &an, sizeof(an));
  58
  59         // Let the kernel compute our checksums
  60         int val = 2;
  61         setsockopt(sock, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
  62
  63         // This is required by RFC 4861
  64         val = 255;
  65         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
  66
  67         // Bind to one device
  68         setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname));
  69
  70         // Add async-mode
  71         const pid_t ourpid = getpid();
  72         fcntl(sock, F_SETOWN, ourpid);
  73         fcntl(sock, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
  74
  75         // Get LL-addr
  76         FILE *fp = fopen("/proc/net/if_inet6", "r");
  77         if (fp) {
  78                 char addrbuf[33], ifbuf[16];
  79                 while (fscanf(fp, "%32s %*x %*x %*x %*x %15s", addrbuf, ifbuf) == 2) {
  80                         if (!strcmp(ifbuf, if_name)) {
  81                                 script_unhexlify((uint8_t*)&lladdr, sizeof(lladdr), addrbuf);
  82                                 break;
  83                         }
  84                 }
  85                 fclose(fp);
  86         }
  87
  88         // Open rtnetlink socket
  89         rtnl_sock = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE);
  90         struct sockaddr_nl rtnl_kernel = { .nl_family = AF_NETLINK };
  91         if (connect(rtnl_sock, (struct sockaddr*)&rtnl_kernel, sizeof(rtnl_kernel)))
  92                 return -1;
  93         uint32_t group = RTNLGRP_IPV6_IFADDR;
  94         setsockopt(rtnl_sock, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
  95
  96         // Add async-mode
  97         fcntl(rtnl_sock, F_SETOWN, ourpid);
  98         fcntl(rtnl_sock, F_SETFL, fcntl(rtnl_sock, F_GETFL) | O_ASYNC);
  99
 100         // Send RS
 101         signal(SIGALRM, ra_send_rs);
 102         ra_send_rs(SIGALRM);
 103
 104         return 0;
 105 }
 106
 107
 108 static void ra_send_rs(int signal __attribute__((unused)))
 109 {
 110         const struct icmp6_hdr rs = {ND_ROUTER_SOLICIT, 0, 0, {{0}}};
 111         const struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
 112         sendto(sock, &rs, sizeof(rs), MSG_DONTWAIT, (struct sockaddr*)&dest, sizeof(dest));
 113
 114         if (++rs_attempt <= 3)
 115                 alarm(4);
 116 }
 117
 118
 119 static int16_t pref_to_priority(uint8_t flags)
 120 {
 121         flags = (flags >> 3) & 0x03;
 122         return (flags == 0x0) ? 1024 : (flags == 0x1) ? 512 :
 123                         (flags == 0x3) ? 2048 : -1;
 124 }
 125
 126
 127 static void update_proc(const char *sect, const char *opt, uint32_t value)
 128 {
 129         char buf[64];
 130         snprintf(buf, sizeof(buf), "/proc/sys/net/ipv6/%s/%s/%s", sect, if_name, opt);
 131
 132         int fd = open(buf, O_WRONLY);
 133         write(fd, buf, snprintf(buf, sizeof(buf), "%u", value));
 134         close(fd);
 135 }
 136
 137
 138 static bool ra_deduplicate(const struct in6_addr *any, uint8_t length)
 139 {
 140         struct odhcp6c_entry entry = {IN6ADDR_ANY_INIT, length, 0, *any, 0, 0};
 141         struct odhcp6c_entry *x = odhcp6c_find_entry(STATE_RA_PREFIX, &entry);
 142         if (x && IN6_ARE_ADDR_EQUAL(&x->target, any)) {
 143                 odhcp6c_random(&x->target.s6_addr32[2], 2 * sizeof(uint32_t));
 144         } else if (odhcp6c_find_entry(STATE_IA_NA, &entry)) {
 145                 dhcpv6_request(DHCPV6_MSG_DECLINE);
 146                 raise(SIGUSR2);
 147         }
 148
 149         return !!x;
 150 }
 151
 152
 153 bool ra_rtnl_process(void)
 154 {
 155         bool found = false;
 156         uint8_t buf[8192];
 157         while (true) {
 158                 ssize_t len = recv(rtnl_sock, buf, sizeof(buf), MSG_DONTWAIT);
 159                 if (len < 0)
 160                         break;
 161
 162                 for (struct nlmsghdr *nh = (struct nlmsghdr*)buf; NLMSG_OK(nh, (size_t)len);
 163                                         nh = NLMSG_NEXT(nh, len)) {
 164                         struct ifaddrmsg *ifa = NLMSG_DATA(nh);
 165                         struct in6_addr *addr = NULL;
 166                         if (NLMSG_PAYLOAD(nh, 0) < sizeof(*ifa) || ifa->ifa_index != if_index ||
 167                                         (nh->nlmsg_type == RTM_NEWADDR && !(ifa->ifa_flags & IFA_F_DADFAILED)) ||
 168                                         (nh->nlmsg_type == RTM_DELADDR && !(ifa->ifa_flags & IFA_F_TENTATIVE)))
 169                                 continue;
 170
 171                         ssize_t alen = NLMSG_PAYLOAD(nh, sizeof(*ifa));
 172                         for (struct rtattr *rta = (struct rtattr*)&ifa[1]; RTA_OK(rta, alen);
 173                                         rta = RTA_NEXT(rta, alen))
 174                                 if (rta->rta_type == IFA_ADDRESS && RTA_PAYLOAD(rta) >= sizeof(*addr))
 175                                         addr = RTA_DATA(rta);
 176
 177                         if (addr)
 178                                 found |= ra_deduplicate(addr, ifa->ifa_prefixlen);
 179                 }
 180         }
 181         return found;
 182 }
 183
 184
 185 bool ra_process(void)
 186 {
 187         bool found = false;
 188         uint8_t buf[1500];
 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};
 191         const struct in6_addr any = IN6ADDR_ANY_INIT;
 192         odhcp6c_expire();
 193
 194         while (true) {
 195                 struct sockaddr_in6 from;
 196                 socklen_t from_len = sizeof(from);
 197                 ssize_t len = recvfrom(sock, buf, sizeof(buf), MSG_DONTWAIT, &from, &from_len);
 198                 if (len < 0)
 199                         break;
 200                 else if (len < (ssize_t)sizeof(*adv))
 201                         continue;
 202
 203                 // Stop sending solicits
 204                 if (rs_attempt > 0) {
 205                         alarm(0);
 206                         rs_attempt = 0;
 207                 }
 208
 209                 found = true;
 210                 uint32_t router_valid = ntohs(adv->nd_ra_router_lifetime);
 211
 212                 // Parse default route
 213                 entry.router = from.sin6_addr;
 214                 entry.priority = pref_to_priority(adv->nd_ra_flags_reserved);
 215                 if (entry.priority < 0)
 216                         entry.priority = pref_to_priority(0);
 217                 entry.valid = router_valid;
 218                 entry.preferred = entry.valid;
 219                 odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
 220
 221                 // Parse ND parameters
 222                 if (adv->nd_ra_reachable)
 223                         update_proc("neigh", "base_reachable_time_ms", ntohl(adv->nd_ra_reachable));
 224
 225                 if (adv->nd_ra_retransmit)
 226                         update_proc("neigh", "retrans_time_ms", ntohl(adv->nd_ra_retransmit));
 227
 228
 229                 // Evaluate options
 230                 struct icmpv6_opt *opt;
 231                 icmpv6_for_each_option(opt, &adv[1], &buf[len]) {
 232                         if (opt->type == ND_OPT_MTU) {
 233                                 update_proc("conf", "mtu", ntohl(*((uint32_t*)&opt->data[2])));
 234                         } else if (opt->type == ND_OPT_ROUTE_INFORMATION && opt->len <= 3) {
 235                                 entry.router = from.sin6_addr;
 236                                 entry.target = any;
 237                                 entry.priority = pref_to_priority(opt->data[1]);
 238                                 entry.length = opt->data[0];
 239                                 entry.valid = ntohl(*((uint32_t*)&opt->data[2]));
 240                                 memcpy(&entry.target, &opt->data[6], (opt->len - 1) * 8);
 241
 242                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
 243                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
 244                                                 || IN6_IS_ADDR_MULTICAST(&entry.target))
 245                                         continue;
 246
 247                                 if (entry.priority > 0)
 248                                         odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
 249                         } else if (opt->type == ND_OPT_PREFIX_INFORMATION && opt->len == 4) {
 250                                 struct nd_opt_prefix_info *pinfo = (struct nd_opt_prefix_info*)opt;
 251                                 entry.router = any;
 252                                 entry.target = pinfo->nd_opt_pi_prefix;
 253                                 entry.priority = 256;
 254                                 entry.length = pinfo->nd_opt_pi_prefix_len;
 255                                 entry.valid = ntohl(pinfo->nd_opt_pi_valid_time);
 256                                 entry.preferred = ntohl(pinfo->nd_opt_pi_preferred_time);
 257
 258                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
 259                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
 260                                                 || IN6_IS_ADDR_MULTICAST(&entry.target)
 261                                                 || entry.valid < entry.preferred)
 262                                         continue;
 263
 264                                 if (pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_ONLINK)
 265                                         odhcp6c_update_entry_safe(STATE_RA_ROUTE, &entry, 7200);
 266
 267                                 if (!(pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_AUTO) ||
 268                                                 pinfo->nd_opt_pi_prefix_len != 64)
 269                                         continue;
 270
 271                                 entry.target.s6_addr32[2] = lladdr.s6_addr32[2];
 272                                 entry.target.s6_addr32[3] = lladdr.s6_addr32[3];
 273
 274                                 odhcp6c_update_entry_safe(STATE_RA_PREFIX, &entry, 7200);
 275                         } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 2) {
 276                                 entry.router = from.sin6_addr;
 277                                 entry.priority = 0;
 278                                 entry.length = 128;
 279                                 entry.valid = ntohl(*((uint32_t*)&opt->data[2]));
 280                                 entry.preferred = 0;
 281
 282                                 for (ssize_t i = 0; i < (opt->len - 1) / 2; ++i) {
 283                                         memcpy(&entry.target, &opt->data[6 + i * sizeof(entry.target)],
 284                                                         sizeof(entry.target));
 285                                         odhcp6c_update_entry(STATE_RA_DNS, &entry);
 286                                 }
 287                         }
 288                 }
 289
 290                 size_t ra_dns_len;
 291                 struct odhcp6c_entry *entry = odhcp6c_get_state(STATE_RA_DNS, &ra_dns_len);
 292                 for (size_t i = 0; i < ra_dns_len / sizeof(*entry); ++i)
 293                         if (IN6_ARE_ADDR_EQUAL(&entry[i].router, &from.sin6_addr) &&
 294                                         entry[i].valid > router_valid)
 295                                 entry[i].valid = router_valid;
 296         }
 297
 298         odhcp6c_expire();
 299         return found;
 300 }