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1 : : // Copyright (c) 2024-present The Bitcoin Core developers
2 : : // Distributed under the MIT software license, see the accompanying
3 : : // file COPYING or https://www.opensource.org/licenses/mit-license.php.
4 : :
5 : : #include <bitcoin-build-config.h> // IWYU pragma: keep
6 : :
7 : : #include <common/netif.h>
8 : :
9 : : #include <logging.h>
10 : : #include <netbase.h>
11 : : #include <util/check.h>
12 : : #include <util/sock.h>
13 : : #include <util/syserror.h>
14 : :
15 : : #if defined(__linux__)
16 : : #include <linux/rtnetlink.h>
17 : : #elif defined(__FreeBSD__)
18 : : #include <osreldate.h>
19 : : #if __FreeBSD_version >= 1400000
20 : : // Workaround https://github.com/freebsd/freebsd-src/pull/1070.
21 : : #define typeof __typeof
22 : : #include <netlink/netlink.h>
23 : : #include <netlink/netlink_route.h>
24 : : #endif
25 : : #elif defined(WIN32)
26 : : #include <iphlpapi.h>
27 : : #elif defined(__APPLE__)
28 : : #include <net/route.h>
29 : : #include <sys/sysctl.h>
30 : : #endif
31 : :
32 : : #ifdef HAVE_IFADDRS
33 : : #include <sys/types.h>
34 : : #include <ifaddrs.h>
35 : : #endif
36 : :
37 : : #include <type_traits>
38 : :
39 : : namespace {
40 : :
41 : : //! Return CNetAddr for the specified OS-level network address.
42 : : //! If a length is not given, it is taken to be sizeof(struct sockaddr_*) for the family.
43 : 0 : std::optional<CNetAddr> FromSockAddr(const struct sockaddr* addr, std::optional<socklen_t> sa_len_opt)
44 : : {
45 : 0 : socklen_t sa_len = 0;
46 [ # # ]: 0 : if (sa_len_opt.has_value()) {
47 : 0 : sa_len = *sa_len_opt;
48 : : } else {
49 : : // If sockaddr length was not specified, determine it from the family.
50 [ # # # ]: 0 : switch (addr->sa_family) {
51 : : case AF_INET: sa_len = sizeof(struct sockaddr_in); break;
52 : 0 : case AF_INET6: sa_len = sizeof(struct sockaddr_in6); break;
53 : 0 : default:
54 : 0 : return std::nullopt;
55 : : }
56 : : }
57 : : // Fill in a CService from the sockaddr, then drop the port part.
58 : 0 : CService service;
59 [ # # # # ]: 0 : if (service.SetSockAddr(addr, sa_len)) {
60 : 0 : return (CNetAddr)service;
61 : : }
62 : 0 : return std::nullopt;
63 : : }
64 : :
65 : : // Linux and FreeBSD 14.0+. For FreeBSD 13.2 the code can be compiled but
66 : : // running it requires loading a special kernel module, otherwise socket(AF_NETLINK,...)
67 : : // will fail, so we skip that.
68 : : #if defined(__linux__) || (defined(__FreeBSD__) && __FreeBSD_version >= 1400000)
69 : :
70 : : // Good for responses containing ~ 10,000-15,000 routes.
71 : : static constexpr ssize_t NETLINK_MAX_RESPONSE_SIZE{1'048'576};
72 : :
73 : 0 : std::optional<CNetAddr> QueryDefaultGatewayImpl(sa_family_t family)
74 : : {
75 : : // Create a netlink socket.
76 : 0 : auto sock{CreateSock(AF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE)};
77 [ # # ]: 0 : if (!sock) {
78 [ # # # # ]: 0 : LogError("socket(AF_NETLINK): %s\n", NetworkErrorString(errno));
79 : 0 : return std::nullopt;
80 : : }
81 : :
82 : : // Send request.
83 : 0 : struct {
84 : : nlmsghdr hdr; ///< Request header.
85 : : rtmsg data; ///< Request data, a "route message".
86 : : nlattr dst_hdr; ///< One attribute, conveying the route destination address.
87 : : char dst_data[16]; ///< Route destination address. To query the default route we use 0.0.0.0/0 or [::]/0. For IPv4 the first 4 bytes are used.
88 : 0 : } request{};
89 : :
90 : : // Whether to use the first 4 or 16 bytes from request.dst_data.
91 [ # # ]: 0 : const size_t dst_data_len = family == AF_INET ? 4 : 16;
92 : :
93 : 0 : request.hdr.nlmsg_type = RTM_GETROUTE;
94 : 0 : request.hdr.nlmsg_flags = NLM_F_REQUEST;
95 : : #ifdef __linux__
96 : : // Linux IPv4 / IPv6 - this must be present, otherwise no gateway is found
97 : : // FreeBSD IPv4 - does not matter, the gateway is found with or without this
98 : : // FreeBSD IPv6 - this must be absent, otherwise no gateway is found
99 : 0 : request.hdr.nlmsg_flags |= NLM_F_DUMP;
100 : : #endif
101 : 0 : request.hdr.nlmsg_len = NLMSG_LENGTH(sizeof(rtmsg) + sizeof(nlattr) + dst_data_len);
102 : 0 : request.hdr.nlmsg_seq = 0; // Sequence number, used to match which reply is to which request. Irrelevant for us because we send just one request.
103 : 0 : request.data.rtm_family = family;
104 : 0 : request.data.rtm_dst_len = 0; // Prefix length.
105 : : #ifdef __FreeBSD__
106 : : // Linux IPv4 / IPv6 this must be absent, otherwise no gateway is found
107 : : // FreeBSD IPv4 - does not matter, the gateway is found with or without this
108 : : // FreeBSD IPv6 - this must be present, otherwise no gateway is found
109 : : request.data.rtm_flags = RTM_F_PREFIX;
110 : : #endif
111 : 0 : request.dst_hdr.nla_type = RTA_DST;
112 : 0 : request.dst_hdr.nla_len = sizeof(nlattr) + dst_data_len;
113 : :
114 [ # # # # ]: 0 : if (sock->Send(&request, request.hdr.nlmsg_len, 0) != static_cast<ssize_t>(request.hdr.nlmsg_len)) {
115 [ # # # # ]: 0 : LogError("send() to netlink socket: %s\n", NetworkErrorString(errno));
116 : 0 : return std::nullopt;
117 : : }
118 : :
119 : : // Receive response.
120 : : char response[4096];
121 : : ssize_t total_bytes_read{0};
122 : : bool done{false};
123 [ # # ]: 0 : while (!done) {
124 : 0 : int64_t recv_result;
125 : 0 : do {
126 [ # # ]: 0 : recv_result = sock->Recv(response, sizeof(response), 0);
127 [ # # # # ]: 0 : } while (recv_result < 0 && (errno == EINTR || errno == EAGAIN));
128 [ # # ]: 0 : if (recv_result < 0) {
129 [ # # # # ]: 0 : LogError("recv() from netlink socket: %s\n", NetworkErrorString(errno));
130 : 0 : return std::nullopt;
131 : : }
132 : :
133 : 0 : total_bytes_read += recv_result;
134 [ # # ]: 0 : if (total_bytes_read > NETLINK_MAX_RESPONSE_SIZE) {
135 [ # # ]: 0 : LogWarning("Netlink response exceeded size limit (%zu bytes, family=%d)\n", NETLINK_MAX_RESPONSE_SIZE, family);
136 : 0 : return std::nullopt;
137 : : }
138 : :
139 : : using recv_result_t = std::conditional_t<std::is_signed_v<decltype(NLMSG_HDRLEN)>, int64_t, decltype(NLMSG_HDRLEN)>;
140 : :
141 [ # # # # : 0 : for (nlmsghdr* hdr = (nlmsghdr*)response; NLMSG_OK(hdr, static_cast<recv_result_t>(recv_result)); hdr = NLMSG_NEXT(hdr, recv_result)) {
# # ]
142 [ # # ]: 0 : if (!(hdr->nlmsg_flags & NLM_F_MULTI)) {
143 : 0 : done = true;
144 : : }
145 : :
146 [ # # ]: 0 : if (hdr->nlmsg_type == NLMSG_DONE) {
147 : : done = true;
148 : : break;
149 : : }
150 : :
151 : 0 : rtmsg* r = (rtmsg*)NLMSG_DATA(hdr);
152 : 0 : int remaining_len = RTM_PAYLOAD(hdr);
153 : :
154 [ # # ]: 0 : if (hdr->nlmsg_type != RTM_NEWROUTE) {
155 : 0 : continue; // Skip non-route messages
156 : : }
157 : :
158 : : // Only consider default routes (destination prefix length of 0).
159 [ # # ]: 0 : if (r->rtm_dst_len != 0) {
160 : 0 : continue;
161 : : }
162 : :
163 : : // Iterate over the attributes.
164 : 0 : rtattr* rta_gateway = nullptr;
165 : 0 : int scope_id = 0;
166 [ # # # # : 0 : for (rtattr* attr = RTM_RTA(r); RTA_OK(attr, remaining_len); attr = RTA_NEXT(attr, remaining_len)) {
# # ]
167 [ # # ]: 0 : if (attr->rta_type == RTA_GATEWAY) {
168 : : rta_gateway = attr;
169 [ # # # # ]: 0 : } else if (attr->rta_type == RTA_OIF && sizeof(int) == RTA_PAYLOAD(attr)) {
170 : 0 : std::memcpy(&scope_id, RTA_DATA(attr), sizeof(scope_id));
171 : : }
172 : : }
173 : :
174 : : // Found gateway?
175 [ # # ]: 0 : if (rta_gateway != nullptr) {
176 [ # # # # ]: 0 : if (family == AF_INET && sizeof(in_addr) == RTA_PAYLOAD(rta_gateway)) {
177 : 0 : in_addr gw;
178 [ # # ]: 0 : std::memcpy(&gw, RTA_DATA(rta_gateway), sizeof(gw));
179 [ # # ]: 0 : return CNetAddr(gw);
180 [ # # # # ]: 0 : } else if (family == AF_INET6 && sizeof(in6_addr) == RTA_PAYLOAD(rta_gateway)) {
181 : 0 : in6_addr gw;
182 [ # # ]: 0 : std::memcpy(&gw, RTA_DATA(rta_gateway), sizeof(gw));
183 [ # # ]: 0 : return CNetAddr(gw, scope_id);
184 : : }
185 : : }
186 : : }
187 : : }
188 : :
189 : 0 : return std::nullopt;
190 : 0 : }
191 : :
192 : : #elif defined(WIN32)
193 : :
194 : : std::optional<CNetAddr> QueryDefaultGatewayImpl(sa_family_t family)
195 : : {
196 : : NET_LUID interface_luid = {};
197 : : SOCKADDR_INET destination_address = {};
198 : : MIB_IPFORWARD_ROW2 best_route = {};
199 : : SOCKADDR_INET best_source_address = {};
200 : : DWORD best_if_idx = 0;
201 : : DWORD status = 0;
202 : :
203 : : // Pass empty destination address of the requested type (:: or 0.0.0.0) to get interface of default route.
204 : : destination_address.si_family = family;
205 : : status = GetBestInterfaceEx((sockaddr*)&destination_address, &best_if_idx);
206 : : if (status != NO_ERROR) {
207 : : LogError("Could not get best interface for default route: %s\n", NetworkErrorString(status));
208 : : return std::nullopt;
209 : : }
210 : :
211 : : // Get best route to default gateway.
212 : : // Leave interface_luid at all-zeros to use interface index instead.
213 : : status = GetBestRoute2(&interface_luid, best_if_idx, nullptr, &destination_address, 0, &best_route, &best_source_address);
214 : : if (status != NO_ERROR) {
215 : : LogError("Could not get best route for default route for interface index %d: %s\n",
216 : : best_if_idx, NetworkErrorString(status));
217 : : return std::nullopt;
218 : : }
219 : :
220 : : Assume(best_route.NextHop.si_family == family);
221 : : if (family == AF_INET) {
222 : : return CNetAddr(best_route.NextHop.Ipv4.sin_addr);
223 : : } else if(family == AF_INET6) {
224 : : return CNetAddr(best_route.NextHop.Ipv6.sin6_addr, best_route.InterfaceIndex);
225 : : }
226 : : return std::nullopt;
227 : : }
228 : :
229 : : #elif defined(__APPLE__)
230 : :
231 : : #define ROUNDUP32(a) \
232 : : ((a) > 0 ? (1 + (((a) - 1) | (sizeof(uint32_t) - 1))) : sizeof(uint32_t))
233 : :
234 : : //! MacOS: Get default gateway from route table. See route(4) for the format.
235 : : std::optional<CNetAddr> QueryDefaultGatewayImpl(sa_family_t family)
236 : : {
237 : : // net.route.0.inet[6].flags.gateway
238 : : int mib[] = {CTL_NET, PF_ROUTE, 0, family, NET_RT_FLAGS, RTF_GATEWAY};
239 : : // The size of the available data is determined by calling sysctl() with oldp=nullptr. See sysctl(3).
240 : : size_t l = 0;
241 : : if (sysctl(/*name=*/mib, /*namelen=*/sizeof(mib) / sizeof(int), /*oldp=*/nullptr, /*oldlenp=*/&l, /*newp=*/nullptr, /*newlen=*/0) < 0) {
242 : : LogError("Could not get sysctl length of routing table: %s\n", SysErrorString(errno));
243 : : return std::nullopt;
244 : : }
245 : : std::vector<std::byte> buf(l);
246 : : if (sysctl(/*name=*/mib, /*namelen=*/sizeof(mib) / sizeof(int), /*oldp=*/buf.data(), /*oldlenp=*/&l, /*newp=*/nullptr, /*newlen=*/0) < 0) {
247 : : LogError("Could not get sysctl data of routing table: %s\n", SysErrorString(errno));
248 : : return std::nullopt;
249 : : }
250 : : // Iterate over messages (each message is a routing table entry).
251 : : for (size_t msg_pos = 0; msg_pos < buf.size(); ) {
252 : : if ((msg_pos + sizeof(rt_msghdr)) > buf.size()) return std::nullopt;
253 : : const struct rt_msghdr* rt = (const struct rt_msghdr*)(buf.data() + msg_pos);
254 : : const size_t next_msg_pos = msg_pos + rt->rtm_msglen;
255 : : if (rt->rtm_msglen < sizeof(rt_msghdr) || next_msg_pos > buf.size()) return std::nullopt;
256 : : // Iterate over addresses within message, get destination and gateway (if present).
257 : : // Address data starts after header.
258 : : size_t sa_pos = msg_pos + sizeof(struct rt_msghdr);
259 : : std::optional<CNetAddr> dst, gateway;
260 : : for (int i = 0; i < RTAX_MAX; i++) {
261 : : if (rt->rtm_addrs & (1 << i)) {
262 : : // 2 is just sa_len + sa_family, the theoretical minimum size of a socket address.
263 : : if ((sa_pos + 2) > next_msg_pos) return std::nullopt;
264 : : const struct sockaddr* sa = (const struct sockaddr*)(buf.data() + sa_pos);
265 : : if ((sa_pos + sa->sa_len) > next_msg_pos) return std::nullopt;
266 : : if (i == RTAX_DST) {
267 : : dst = FromSockAddr(sa, sa->sa_len);
268 : : } else if (i == RTAX_GATEWAY) {
269 : : gateway = FromSockAddr(sa, sa->sa_len);
270 : : }
271 : : // Skip sockaddr entries for bit flags we're not interested in,
272 : : // move cursor.
273 : : sa_pos += ROUNDUP32(sa->sa_len);
274 : : }
275 : : }
276 : : // Found default gateway?
277 : : if (dst && gateway && dst->IsBindAny()) { // Route to 0.0.0.0 or :: ?
278 : : return *gateway;
279 : : }
280 : : // Skip to next message.
281 : : msg_pos = next_msg_pos;
282 : : }
283 : : return std::nullopt;
284 : : }
285 : :
286 : : #else
287 : :
288 : : // Dummy implementation.
289 : : std::optional<CNetAddr> QueryDefaultGatewayImpl(sa_family_t)
290 : : {
291 : : return std::nullopt;
292 : : }
293 : :
294 : : #endif
295 : :
296 : : }
297 : :
298 : 0 : std::optional<CNetAddr> QueryDefaultGateway(Network network)
299 : : {
300 [ # # ]: 0 : Assume(network == NET_IPV4 || network == NET_IPV6);
301 : :
302 : 0 : sa_family_t family;
303 [ # # ]: 0 : if (network == NET_IPV4) {
304 : : family = AF_INET;
305 [ # # ]: 0 : } else if(network == NET_IPV6) {
306 : : family = AF_INET6;
307 : : } else {
308 : 0 : return std::nullopt;
309 : : }
310 : :
311 : 0 : std::optional<CNetAddr> ret = QueryDefaultGatewayImpl(family);
312 : :
313 : : // It's possible for the default gateway to be 0.0.0.0 or ::0 on at least Windows
314 : : // for some routing strategies. If so, return as if no default gateway was found.
315 [ # # # # : 0 : if (ret && !ret->IsBindAny()) {
# # ]
316 [ # # ]: 0 : return ret;
317 : : } else {
318 : 0 : return std::nullopt;
319 : : }
320 : 0 : }
321 : :
322 : 0 : std::vector<CNetAddr> GetLocalAddresses()
323 : : {
324 : 0 : std::vector<CNetAddr> addresses;
325 : : #ifdef WIN32
326 : : DWORD status = 0;
327 : : constexpr size_t MAX_ADAPTER_ADDR_SIZE = 4 * 1000 * 1000; // Absolute maximum size of adapter addresses structure we're willing to handle, as a precaution.
328 : : std::vector<std::byte> out_buf(15000, {}); // Start with 15KB allocation as recommended in GetAdaptersAddresses documentation.
329 : : while (true) {
330 : : ULONG out_buf_len = out_buf.size();
331 : : status = GetAdaptersAddresses(AF_UNSPEC, GAA_FLAG_SKIP_ANYCAST | GAA_FLAG_SKIP_MULTICAST | GAA_FLAG_SKIP_DNS_SERVER | GAA_FLAG_SKIP_FRIENDLY_NAME,
332 : : nullptr, reinterpret_cast<PIP_ADAPTER_ADDRESSES>(out_buf.data()), &out_buf_len);
333 : : if (status == ERROR_BUFFER_OVERFLOW && out_buf.size() < MAX_ADAPTER_ADDR_SIZE) {
334 : : // If status == ERROR_BUFFER_OVERFLOW, out_buf_len will contain the needed size.
335 : : // Unfortunately, this cannot be fully relied on, because another process may have added interfaces.
336 : : // So to avoid getting stuck due to a race condition, double the buffer size at least
337 : : // once before retrying (but only up to the maximum allowed size).
338 : : out_buf.resize(std::min(std::max<size_t>(out_buf_len, out_buf.size()) * 2, MAX_ADAPTER_ADDR_SIZE));
339 : : } else {
340 : : break;
341 : : }
342 : : }
343 : :
344 : : if (status != NO_ERROR) {
345 : : // This includes ERROR_NO_DATA if there are no addresses and thus there's not even one PIP_ADAPTER_ADDRESSES
346 : : // record in the returned structure.
347 : : LogError("Could not get local adapter addresses: %s\n", NetworkErrorString(status));
348 : : return addresses;
349 : : }
350 : :
351 : : // Iterate over network adapters.
352 : : for (PIP_ADAPTER_ADDRESSES cur_adapter = reinterpret_cast<PIP_ADAPTER_ADDRESSES>(out_buf.data());
353 : : cur_adapter != nullptr; cur_adapter = cur_adapter->Next) {
354 : : if (cur_adapter->OperStatus != IfOperStatusUp) continue;
355 : : if (cur_adapter->IfType == IF_TYPE_SOFTWARE_LOOPBACK) continue;
356 : :
357 : : // Iterate over unicast addresses for adapter, the only address type we're interested in.
358 : : for (PIP_ADAPTER_UNICAST_ADDRESS cur_address = cur_adapter->FirstUnicastAddress;
359 : : cur_address != nullptr; cur_address = cur_address->Next) {
360 : : // "The IP address is a cluster address and should not be used by most applications."
361 : : if ((cur_address->Flags & IP_ADAPTER_ADDRESS_TRANSIENT) != 0) continue;
362 : :
363 : : if (std::optional<CNetAddr> addr = FromSockAddr(cur_address->Address.lpSockaddr, static_cast<socklen_t>(cur_address->Address.iSockaddrLength))) {
364 : : addresses.push_back(*addr);
365 : : }
366 : : }
367 : : }
368 : : #elif defined(HAVE_IFADDRS)
369 : 0 : struct ifaddrs* myaddrs;
370 [ # # ]: 0 : if (getifaddrs(&myaddrs) == 0) {
371 [ # # ]: 0 : for (struct ifaddrs* ifa = myaddrs; ifa != nullptr; ifa = ifa->ifa_next)
372 : : {
373 [ # # ]: 0 : if (ifa->ifa_addr == nullptr) continue;
374 [ # # ]: 0 : if ((ifa->ifa_flags & IFF_UP) == 0) continue;
375 [ # # ]: 0 : if ((ifa->ifa_flags & IFF_LOOPBACK) != 0) continue;
376 : :
377 [ # # # # ]: 0 : if (std::optional<CNetAddr> addr = FromSockAddr(ifa->ifa_addr, std::nullopt)) {
378 [ # # ]: 0 : addresses.push_back(*addr);
379 : 0 : }
380 : : }
381 : 0 : freeifaddrs(myaddrs);
382 : : }
383 : : #endif
384 : 0 : return addresses;
385 : 0 : }
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