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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 #ifndef SOL_NETLINK
33 #define SOL_NETLINK 270
34 #endif
35
36 #ifndef NETLINK_ADD_MEMBERSHIP
37 #define NETLINK_ADD_MEMBERSHIP 1
38 #endif
39
40 #ifndef IFF_LOWER_UP
41 #define IFF_LOWER_UP 0x10000
42 #endif
43
44 #include "odhcp6c.h"
45 #include "ra.h"
46
47
48 static bool nocarrier = false;
49
50 static int sock = -1, rtnl = -1;
51 static int if_index = 0;
52 static char if_name[IF_NAMESIZE] = {0};
53 static volatile int rs_attempt = 0;
54 static struct in6_addr lladdr = IN6ADDR_ANY_INIT;
55
56 static void ra_send_rs(int signal __attribute__((unused)));
57
58 int ra_init(const char *ifname, const struct in6_addr *ifid)
59 {
60         const pid_t ourpid = getpid();
61         sock = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
62         if (sock < 0)
63                 return -1;
64
65         if_index = if_nametoindex(ifname);
66         if (!if_index)
67                 return -1;
68
69         strncpy(if_name, ifname, sizeof(if_name) - 1);
70         lladdr = *ifid;
71
72         rtnl = socket(AF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_ROUTE);
73         if (rtnl < 0)
74                 return -1;
75
76         struct sockaddr_nl rtnl_kernel = { .nl_family = AF_NETLINK };
77         if (connect(rtnl, (const struct sockaddr*)&rtnl_kernel, sizeof(rtnl_kernel)) < 0)
78                 return -1;
79
80         int val = RTNLGRP_LINK;
81         setsockopt(rtnl, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &val, sizeof(val));
82         fcntl(rtnl, F_SETOWN, ourpid);
83         fcntl(rtnl, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
84
85         struct {
86                 struct nlmsghdr hdr;
87                 struct ifinfomsg ifi;
88         } req = {
89                 .hdr = {sizeof(req), RTM_GETLINK, NLM_F_REQUEST, 1, 0},
90                 .ifi = {.ifi_index = if_index}
91         };
92         send(rtnl, &req, sizeof(req), 0);
93
94         // Filter ICMPv6 package types
95         struct icmp6_filter filt;
96         ICMP6_FILTER_SETBLOCKALL(&filt);
97         ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &filt);
98         setsockopt(sock, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
99
100         // Bind to all-nodes
101         struct ipv6_mreq an = {ALL_IPV6_NODES, if_index};
102         setsockopt(sock, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &an, sizeof(an));
103
104         // Let the kernel compute our checksums
105         val = 2;
106         setsockopt(sock, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
107
108         // This is required by RFC 4861
109         val = 255;
110         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
111
112         // Receive multicast hops
113         val = 1;
114         setsockopt(sock, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &val, sizeof(val));
115
116         // Bind to one device
117         setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname));
118
119         // Add async-mode
120         fcntl(sock, F_SETOWN, ourpid);
121         fcntl(sock, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
122
123         // Send RS
124         signal(SIGALRM, ra_send_rs);
125         ra_send_rs(SIGALRM);
126
127         return 0;
128 }
129
130
131 static void ra_send_rs(int signal __attribute__((unused)))
132 {
133         const struct icmp6_hdr rs = {ND_ROUTER_SOLICIT, 0, 0, {{0}}};
134         const struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
135         sendto(sock, &rs, sizeof(rs), MSG_DONTWAIT, (struct sockaddr*)&dest, sizeof(dest));
136
137         if (++rs_attempt <= 3)
138                 alarm(4);
139 }
140
141
142 static int16_t pref_to_priority(uint8_t flags)
143 {
144         flags = (flags >> 3) & 0x03;
145         return (flags == 0x0) ? 1024 : (flags == 0x1) ? 512 :
146                         (flags == 0x3) ? 2048 : -1;
147 }
148
149
150 static void update_proc(const char *sect, const char *opt, uint32_t value)
151 {
152         char buf[64];
153         snprintf(buf, sizeof(buf), "/proc/sys/net/ipv6/%s/%s/%s", sect, if_name, opt);
154
155         int fd = open(buf, O_WRONLY);
156         write(fd, buf, snprintf(buf, sizeof(buf), "%u", value));
157         close(fd);
158 }
159
160
161 bool ra_link_up(void)
162 {
163         static bool firstcall = true;
164         struct {
165                 struct nlmsghdr hdr;
166                 struct ifinfomsg msg;
167                 uint8_t pad[4000];
168         } resp;
169
170         bool ret = false;
171         ssize_t read;
172
173         do {
174                 read = recv(rtnl, &resp, sizeof(resp), MSG_DONTWAIT);
175                 if (read < 0 || !NLMSG_OK(&resp.hdr, (size_t)read) ||
176                                 resp.hdr.nlmsg_type != RTM_NEWLINK ||
177                                 resp.msg.ifi_index != if_index)
178                         continue;
179
180                 bool hascarrier = resp.msg.ifi_flags & IFF_LOWER_UP;
181                 if (!firstcall && nocarrier != !hascarrier)
182                         ret = true;
183
184                 nocarrier = !hascarrier;
185                 firstcall = false;
186         } while (read > 0);
187
188         if (ret) {
189                 syslog(LOG_NOTICE, "carrier => %i event on %s", (int)!nocarrier, if_name);
190
191                 rs_attempt = 0;
192                 ra_send_rs(SIGALRM);
193         }
194
195         return ret;
196 }
197
198 static bool ra_icmpv6_valid(struct sockaddr_in6 *source, int hlim, uint8_t *data, size_t len)
199 {
200         struct icmp6_hdr *hdr = (struct icmp6_hdr*)data;
201         struct icmpv6_opt *opt, *end = (struct icmpv6_opt*)&data[len];
202
203         if (hlim != 255 || len < sizeof(*hdr) || hdr->icmp6_code)
204                 return false;
205
206         switch (hdr->icmp6_type) {
207         case ND_ROUTER_ADVERT:
208                 if (!IN6_IS_ADDR_LINKLOCAL(&source->sin6_addr))
209                         return false;
210
211                 opt = (struct icmpv6_opt*)((struct nd_router_advert*)data + 1);
212                 break;
213
214         default:
215                 return false;
216         }
217
218         icmpv6_for_each_option(opt, opt, end)
219                 ;
220
221         return opt == end;
222 }
223
224 bool ra_process(void)
225 {
226         bool found = false;
227         bool changed = false;
228         uint8_t buf[1500], cmsg_buf[128];
229         struct nd_router_advert *adv = (struct nd_router_advert*)buf;
230         struct odhcp6c_entry entry = {IN6ADDR_ANY_INIT, 0, 0, IN6ADDR_ANY_INIT, 0, 0, 0, 0, 0};
231         const struct in6_addr any = IN6ADDR_ANY_INIT;
232
233         if (IN6_IS_ADDR_UNSPECIFIED(&lladdr)) {
234                 // Autodetect interface-id if not specified
235                 FILE *fp = fopen("/proc/net/if_inet6", "r");
236                 if (fp) {
237                         char addrbuf[33], ifbuf[16];
238                         while (fscanf(fp, "%32s %*x %*x %*x %*x %15s", addrbuf, ifbuf) == 2) {
239                                 if (!strcmp(ifbuf, if_name)) {
240                                         script_unhexlify((uint8_t*)&lladdr, sizeof(lladdr), addrbuf);
241                                         break;
242                                 }
243                         }
244                         fclose(fp);
245                 }
246         }
247
248         while (true) {
249                 struct sockaddr_in6 from;
250                 struct iovec iov = {buf, sizeof(buf)};
251                 struct msghdr msg = {&from, sizeof(from), &iov, 1,
252                                 cmsg_buf, sizeof(cmsg_buf), 0};
253
254                 ssize_t len = recvmsg(sock, &msg, MSG_DONTWAIT);
255                 if (len <= 0)
256                         break;
257
258                 int hlim = 0;
259                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL;
260                                 ch = CMSG_NXTHDR(&msg, ch))
261                         if (ch->cmsg_level == IPPROTO_IPV6 &&
262                                         ch->cmsg_type == IPV6_HOPLIMIT)
263                                 memcpy(&hlim, CMSG_DATA(ch), sizeof(hlim));
264
265                 if (!ra_icmpv6_valid(&from, hlim, buf, len))
266                         continue;
267
268                 // Stop sending solicits
269                 if (rs_attempt > 0) {
270                         alarm(0);
271                         rs_attempt = 0;
272                 }
273
274                 if (!found) {
275                         odhcp6c_expire();
276                         found = true;
277                 }
278                 uint32_t router_valid = ntohs(adv->nd_ra_router_lifetime);
279
280                 // Parse default route
281                 entry.target = any;
282                 entry.length = 0;
283                 entry.router = from.sin6_addr;
284                 entry.priority = pref_to_priority(adv->nd_ra_flags_reserved);
285                 if (entry.priority < 0)
286                         entry.priority = pref_to_priority(0);
287                 entry.valid = router_valid;
288                 entry.preferred = entry.valid;
289                 changed |= odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
290
291                 // Parse hoplimit
292                 if (adv->nd_ra_curhoplimit)
293                         update_proc("conf", "hop_limit", adv->nd_ra_curhoplimit);
294
295                 // Parse ND parameters
296                 if (ntohl(adv->nd_ra_reachable) <= 3600000)
297                         update_proc("neigh", "base_reachable_time_ms", ntohl(adv->nd_ra_reachable));
298
299                 if (ntohl(adv->nd_ra_retransmit) <= 60000)
300                         update_proc("neigh", "retrans_time_ms", ntohl(adv->nd_ra_retransmit));
301
302
303                 // Evaluate options
304                 struct icmpv6_opt *opt;
305                 icmpv6_for_each_option(opt, &adv[1], &buf[len]) {
306                         if (opt->type == ND_OPT_MTU) {
307                                 uint32_t *mtu = (uint32_t*)&opt->data[2];
308                                 if (ntohl(*mtu) >= 1280 && ntohl(*mtu) <= 65535)
309                                         update_proc("conf", "mtu", ntohl(*mtu));
310                         } else if (opt->type == ND_OPT_ROUTE_INFORMATION && opt->len <= 3) {
311                                 entry.router = from.sin6_addr;
312                                 entry.target = any;
313                                 entry.priority = pref_to_priority(opt->data[1]);
314                                 entry.length = opt->data[0];
315                                 uint32_t *valid = (uint32_t*)&opt->data[2];
316                                 entry.valid = ntohl(*valid);
317                                 memcpy(&entry.target, &opt->data[6], (opt->len - 1) * 8);
318
319                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
320                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
321                                                 || IN6_IS_ADDR_MULTICAST(&entry.target))
322                                         continue;
323
324                                 if (entry.priority > 0)
325                                         changed |= odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
326                         } else if (opt->type == ND_OPT_PREFIX_INFORMATION && opt->len == 4) {
327                                 struct nd_opt_prefix_info *pinfo = (struct nd_opt_prefix_info*)opt;
328                                 entry.router = any;
329                                 entry.target = pinfo->nd_opt_pi_prefix;
330                                 entry.priority = 256;
331                                 entry.length = pinfo->nd_opt_pi_prefix_len;
332                                 entry.valid = ntohl(pinfo->nd_opt_pi_valid_time);
333                                 entry.preferred = ntohl(pinfo->nd_opt_pi_preferred_time);
334
335                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
336                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
337                                                 || IN6_IS_ADDR_MULTICAST(&entry.target)
338                                                 || entry.valid < entry.preferred)
339                                         continue;
340
341                                 if (pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_ONLINK)
342                                         changed |= odhcp6c_update_entry_safe(STATE_RA_ROUTE, &entry, 7200);
343
344                                 if (!(pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_AUTO) ||
345                                                 pinfo->nd_opt_pi_prefix_len != 64)
346                                         continue;
347
348                                 entry.target.s6_addr32[2] = lladdr.s6_addr32[2];
349                                 entry.target.s6_addr32[3] = lladdr.s6_addr32[3];
350
351                                 changed |= odhcp6c_update_entry_safe(STATE_RA_PREFIX, &entry, 7200);
352                         } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 2) {
353                                 entry.router = from.sin6_addr;
354                                 entry.priority = 0;
355                                 entry.length = 128;
356                                 uint32_t *valid = (uint32_t*)&opt->data[2];
357                                 entry.valid = ntohl(*valid);
358                                 entry.preferred = 0;
359
360                                 for (ssize_t i = 0; i < (opt->len - 1) / 2; ++i) {
361                                         memcpy(&entry.target, &opt->data[6 + i * sizeof(entry.target)],
362                                                         sizeof(entry.target));
363                                         changed |= odhcp6c_update_entry(STATE_RA_DNS, &entry);
364                                 }
365                         }
366                 }
367
368                 size_t ra_dns_len;
369                 struct odhcp6c_entry *entry = odhcp6c_get_state(STATE_RA_DNS, &ra_dns_len);
370                 for (size_t i = 0; i < ra_dns_len / sizeof(*entry); ++i)
371                         if (IN6_ARE_ADDR_EQUAL(&entry[i].router, &from.sin6_addr) &&
372                                         entry[i].valid > router_valid)
373                                 entry[i].valid = router_valid;
374         }
375
376         if (found)
377                 odhcp6c_expire();
378
379         return found && changed;
380 }