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  std::optional<CNetAddr> FromSockAddr(const struct sockaddr* addr, std::optional<socklen_t> sa_len_opt)
 44  {
 45      socklen_t sa_len = 0;
 46      if (sa_len_opt.has_value()) {
 47          sa_len = *sa_len_opt;
 48      } else {
 49          // If sockaddr length was not specified, determine it from the family.
 50          switch (addr->sa_family) {
 51          case AF_INET: sa_len = sizeof(struct sockaddr_in); break;
 52          case AF_INET6: sa_len = sizeof(struct sockaddr_in6); break;
 53          default:
 54              return std::nullopt;
 55          }
 56      }
 57      // Fill in a CService from the sockaddr, then drop the port part.
 58      CService service;
 59      if (service.SetSockAddr(addr, sa_len)) {
 60          return (CNetAddr)service;
 61      }
 62      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  std::optional<CNetAddr> QueryDefaultGatewayImpl(sa_family_t family)
 74  {
 75      // Create a netlink socket.
 76      auto sock{CreateSock(AF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE)};
 77      if (!sock) {
 78          LogError("socket(AF_NETLINK): %s\n", NetworkErrorString(errno));
 79          return std::nullopt;
 80      }
 81  
 82      // Send request.
 83      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      } request{};
 89  
 90      // Whether to use the first 4 or 16 bytes from request.dst_data.
 91      const size_t dst_data_len = family == AF_INET ? 4 : 16;
 92  
 93      request.hdr.nlmsg_type = RTM_GETROUTE;
 94      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      request.hdr.nlmsg_flags |= NLM_F_DUMP;
100  #endif
101      request.hdr.nlmsg_len = NLMSG_LENGTH(sizeof(rtmsg) + sizeof(nlattr) + dst_data_len);
102      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      request.data.rtm_family = family;
104      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      request.dst_hdr.nla_type = RTA_DST;
112      request.dst_hdr.nla_len = sizeof(nlattr) + dst_data_len;
113  
114      if (sock->Send(&request, request.hdr.nlmsg_len, 0) != static_cast<ssize_t>(request.hdr.nlmsg_len)) {
115          LogError("send() to netlink socket: %s\n", NetworkErrorString(errno));
116          return std::nullopt;
117      }
118  
119      // Receive response.
120      char response[4096];
121      ssize_t total_bytes_read{0};
122      bool done{false};
123      while (!done) {
124          int64_t recv_result;
125          do {
126              recv_result = sock->Recv(response, sizeof(response), 0);
127          } while (recv_result < 0 && (errno == EINTR || errno == EAGAIN));
128          if (recv_result < 0) {
129              LogError("recv() from netlink socket: %s\n", NetworkErrorString(errno));
130              return std::nullopt;
131          }
132  
133          total_bytes_read += recv_result;
134          if (total_bytes_read > NETLINK_MAX_RESPONSE_SIZE) {
135              LogWarning("Netlink response exceeded size limit (%zu bytes, family=%d)\n", NETLINK_MAX_RESPONSE_SIZE, family);
136              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          for (nlmsghdr* hdr = (nlmsghdr*)response; NLMSG_OK(hdr, static_cast<recv_result_t>(recv_result)); hdr = NLMSG_NEXT(hdr, recv_result)) {
142              if (!(hdr->nlmsg_flags & NLM_F_MULTI)) {
143                  done = true;
144              }
145  
146              if (hdr->nlmsg_type == NLMSG_DONE) {
147                  done = true;
148                  break;
149              }
150  
151              rtmsg* r = (rtmsg*)NLMSG_DATA(hdr);
152              int remaining_len = RTM_PAYLOAD(hdr);
153  
154              if (hdr->nlmsg_type != RTM_NEWROUTE) {
155                  continue; // Skip non-route messages
156              }
157  
158              // Only consider default routes (destination prefix length of 0).
159              if (r->rtm_dst_len != 0) {
160                  continue;
161              }
162  
163              // Iterate over the attributes.
164              rtattr* rta_gateway = nullptr;
165              int scope_id = 0;
166              for (rtattr* attr = RTM_RTA(r); RTA_OK(attr, remaining_len); attr = RTA_NEXT(attr, remaining_len)) {
167                  if (attr->rta_type == RTA_GATEWAY) {
168                      rta_gateway = attr;
169                  } else if (attr->rta_type == RTA_OIF && sizeof(int) == RTA_PAYLOAD(attr)) {
170                      std::memcpy(&scope_id, RTA_DATA(attr), sizeof(scope_id));
171                  }
172              }
173  
174              // Found gateway?
175              if (rta_gateway != nullptr) {
176                  if (family == AF_INET && sizeof(in_addr) == RTA_PAYLOAD(rta_gateway)) {
177                      in_addr gw;
178                      std::memcpy(&gw, RTA_DATA(rta_gateway), sizeof(gw));
179                      return CNetAddr(gw);
180                  } else if (family == AF_INET6 && sizeof(in6_addr) == RTA_PAYLOAD(rta_gateway)) {
181                      in6_addr gw;
182                      std::memcpy(&gw, RTA_DATA(rta_gateway), sizeof(gw));
183                      return CNetAddr(gw, scope_id);
184                  }
185              }
186          }
187      }
188  
189      return std::nullopt;
190  }
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  std::optional<CNetAddr> QueryDefaultGateway(Network network)
299  {
300      Assume(network == NET_IPV4 || network == NET_IPV6);
301  
302      sa_family_t family;
303      if (network == NET_IPV4) {
304          family = AF_INET;
305      } else if(network == NET_IPV6) {
306          family = AF_INET6;
307      } else {
308          return std::nullopt;
309      }
310  
311      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      if (ret && !ret->IsBindAny()) {
316          return ret;
317      } else {
318          return std::nullopt;
319      }
320  }
321  
322  std::vector<CNetAddr> GetLocalAddresses()
323  {
324      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      struct ifaddrs* myaddrs;
370      if (getifaddrs(&myaddrs) == 0) {
371          for (struct ifaddrs* ifa = myaddrs; ifa != nullptr; ifa = ifa->ifa_next)
372          {
373              if (ifa->ifa_addr == nullptr) continue;
374              if ((ifa->ifa_flags & IFF_UP) == 0) continue;
375              if ((ifa->ifa_flags & IFF_LOOPBACK) != 0) continue;
376  
377              if (std::optional<CNetAddr> addr = FromSockAddr(ifa->ifa_addr, std::nullopt)) {
378                  addresses.push_back(*addr);
379              }
380          }
381          freeifaddrs(myaddrs);
382      }
383  #endif
384      return addresses;
385  }