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