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         // 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         // Send RS
  94         signal(SIGALRM, ra_send_rs);
  95         ra_send_rs(SIGALRM);
  96
  97         return 0;
  98 }
  99
 100
 101 static void ra_send_rs(int signal __attribute__((unused)))
 102 {
 103         const struct icmp6_hdr rs = {ND_ROUTER_SOLICIT, 0, 0, {{0}}};
 104         const struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
 105         sendto(sock, &rs, sizeof(rs), MSG_DONTWAIT, (struct sockaddr*)&dest, sizeof(dest));
 106
 107         if (++rs_attempt <= 3)
 108                 alarm(4);
 109 }
 110
 111
 112 static int16_t pref_to_priority(uint8_t flags)
 113 {
 114         flags = (flags >> 3) & 0x03;
 115         return (flags == 0x0) ? 1024 : (flags == 0x1) ? 512 :
 116                         (flags == 0x3) ? 2048 : -1;
 117 }
 118
 119
 120 static void update_proc(const char *sect, const char *opt, uint32_t value)
 121 {
 122         char buf[64];
 123         snprintf(buf, sizeof(buf), "/proc/sys/net/ipv6/%s/%s/%s", sect, if_name, opt);
 124
 125         int fd = open(buf, O_WRONLY);
 126         write(fd, buf, snprintf(buf, sizeof(buf), "%u", value));
 127         close(fd);
 128 }
 129
 130
 131 bool ra_process(void)
 132 {
 133         bool found = false;
 134         uint8_t buf[1500];
 135         struct nd_router_advert *adv = (struct nd_router_advert*)buf;
 136         struct odhcp6c_entry entry = {IN6ADDR_ANY_INIT, 0, 0, IN6ADDR_ANY_INIT, 0, 0, 0};
 137         const struct in6_addr any = IN6ADDR_ANY_INIT;
 138
 139         while (true) {
 140                 struct sockaddr_in6 from;
 141                 socklen_t from_len = sizeof(from);
 142                 ssize_t len = recvfrom(sock, buf, sizeof(buf), MSG_DONTWAIT, &from, &from_len);
 143                 if (len < 0)
 144                         break;
 145                 else if (len < (ssize_t)sizeof(*adv))
 146                         continue;
 147
 148                 // Stop sending solicits
 149                 if (rs_attempt > 0) {
 150                         alarm(0);
 151                         rs_attempt = 0;
 152                 }
 153
 154                 if (!found) {
 155                         odhcp6c_expire();
 156                         found = true;
 157                 }
 158                 uint32_t router_valid = ntohs(adv->nd_ra_router_lifetime);
 159
 160                 // Parse default route
 161                 entry.target = any;
 162                 entry.length = 0;
 163                 entry.router = from.sin6_addr;
 164                 entry.priority = pref_to_priority(adv->nd_ra_flags_reserved);
 165                 if (entry.priority < 0)
 166                         entry.priority = pref_to_priority(0);
 167                 entry.valid = router_valid;
 168                 entry.preferred = entry.valid;
 169                 odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
 170
 171                 // Parse ND parameters
 172                 if (ntohl(adv->nd_ra_reachable) <= 3600000)
 173                         update_proc("neigh", "base_reachable_time_ms", ntohl(adv->nd_ra_reachable));
 174
 175                 if (ntohl(adv->nd_ra_retransmit) <= 60000)
 176                         update_proc("neigh", "retrans_time_ms", ntohl(adv->nd_ra_retransmit));
 177
 178
 179                 // Evaluate options
 180                 struct icmpv6_opt *opt;
 181                 icmpv6_for_each_option(opt, &adv[1], &buf[len]) {
 182                         if (opt->type == ND_OPT_MTU) {
 183                                 uint32_t *mtu = (uint32_t*)&opt->data[2];
 184                                 if (ntohl(*mtu) >= 1280 && ntohl(*mtu) <= 65535)
 185                                         update_proc("conf", "mtu", ntohl(*mtu));
 186                         } else if (opt->type == ND_OPT_ROUTE_INFORMATION && opt->len <= 3) {
 187                                 entry.router = from.sin6_addr;
 188                                 entry.target = any;
 189                                 entry.priority = pref_to_priority(opt->data[1]);
 190                                 entry.length = opt->data[0];
 191                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 192                                 entry.valid = ntohl(*valid);
 193                                 memcpy(&entry.target, &opt->data[6], (opt->len - 1) * 8);
 194
 195                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
 196                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
 197                                                 || IN6_IS_ADDR_MULTICAST(&entry.target))
 198                                         continue;
 199
 200                                 if (entry.priority > 0)
 201                                         odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
 202                         } else if (opt->type == ND_OPT_PREFIX_INFORMATION && opt->len == 4) {
 203                                 struct nd_opt_prefix_info *pinfo = (struct nd_opt_prefix_info*)opt;
 204                                 entry.router = any;
 205                                 entry.target = pinfo->nd_opt_pi_prefix;
 206                                 entry.priority = 256;
 207                                 entry.length = pinfo->nd_opt_pi_prefix_len;
 208                                 entry.valid = ntohl(pinfo->nd_opt_pi_valid_time);
 209                                 entry.preferred = ntohl(pinfo->nd_opt_pi_preferred_time);
 210
 211                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
 212                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
 213                                                 || IN6_IS_ADDR_MULTICAST(&entry.target)
 214                                                 || entry.valid < entry.preferred)
 215                                         continue;
 216
 217                                 if (pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_ONLINK)
 218                                         odhcp6c_update_entry_safe(STATE_RA_ROUTE, &entry, 7200);
 219
 220                                 if (!(pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_AUTO) ||
 221                                                 pinfo->nd_opt_pi_prefix_len != 64)
 222                                         continue;
 223
 224                                 entry.target.s6_addr32[2] = lladdr.s6_addr32[2];
 225                                 entry.target.s6_addr32[3] = lladdr.s6_addr32[3];
 226
 227                                 odhcp6c_update_entry_safe(STATE_RA_PREFIX, &entry, 7200);
 228                         } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 2) {
 229                                 entry.router = from.sin6_addr;
 230                                 entry.priority = 0;
 231                                 entry.length = 128;
 232                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 233                                 entry.valid = ntohl(*valid);
 234                                 entry.preferred = 0;
 235
 236                                 for (ssize_t i = 0; i < (opt->len - 1) / 2; ++i) {
 237                                         memcpy(&entry.target, &opt->data[6 + i * sizeof(entry.target)],
 238                                                         sizeof(entry.target));
 239                                         odhcp6c_update_entry(STATE_RA_DNS, &entry);
 240                                 }
 241                         }
 242                 }
 243
 244                 size_t ra_dns_len;
 245                 struct odhcp6c_entry *entry = odhcp6c_get_state(STATE_RA_DNS, &ra_dns_len);
 246                 for (size_t i = 0; i < ra_dns_len / sizeof(*entry); ++i)
 247                         if (IN6_ARE_ADDR_EQUAL(&entry[i].router, &from.sin6_addr) &&
 248                                         entry[i].valid > router_valid)
 249                                 entry[i].valid = router_valid;
 250         }
 251
 252         if (found)
 253                 odhcp6c_expire();
 254
 255         return found;
 256 }