Bitcoin Core 29.99.0
P2P Digital Currency
netif.cpp
Go to the documentation of this file.
1// Copyright (c) 2024 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
32namespace {
33
36std::optional<CNetAddr> FromSockAddr(const struct sockaddr* addr, std::optional<socklen_t> sa_len_opt)
37{
38 socklen_t sa_len = 0;
39 if (sa_len_opt.has_value()) {
40 sa_len = *sa_len_opt;
41 } else {
42 // If sockaddr length was not specified, determine it from the family.
43 switch (addr->sa_family) {
44 case AF_INET: sa_len = sizeof(struct sockaddr_in); break;
45 case AF_INET6: sa_len = sizeof(struct sockaddr_in6); break;
46 default:
47 return std::nullopt;
48 }
49 }
50 // Fill in a CService from the sockaddr, then drop the port part.
51 CService service;
52 if (service.SetSockAddr(addr, sa_len)) {
53 return (CNetAddr)service;
54 }
55 return std::nullopt;
56}
57
58// Linux and FreeBSD 14.0+. For FreeBSD 13.2 the code can be compiled but
59// running it requires loading a special kernel module, otherwise socket(AF_NETLINK,...)
60// will fail, so we skip that.
61#if defined(__linux__) || (defined(__FreeBSD__) && __FreeBSD_version >= 1400000)
62
63std::optional<CNetAddr> QueryDefaultGatewayImpl(sa_family_t family)
64{
65 // Create a netlink socket.
66 auto sock{CreateSock(AF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE)};
67 if (!sock) {
68 LogPrintLevel(BCLog::NET, BCLog::Level::Error, "socket(AF_NETLINK): %s\n", NetworkErrorString(errno));
69 return std::nullopt;
70 }
71
72 // Send request.
73 struct {
74 nlmsghdr hdr;
75 rtmsg data;
76 nlattr dst_hdr;
77 char dst_data[16];
78 } request{};
79
80 // Whether to use the first 4 or 16 bytes from request.dst_data.
81 const size_t dst_data_len = family == AF_INET ? 4 : 16;
82
83 request.hdr.nlmsg_type = RTM_GETROUTE;
84 request.hdr.nlmsg_flags = NLM_F_REQUEST;
85#ifdef __linux__
86 // Linux IPv4 / IPv6 - this must be present, otherwise no gateway is found
87 // FreeBSD IPv4 - does not matter, the gateway is found with or without this
88 // FreeBSD IPv6 - this must be absent, otherwise no gateway is found
89 request.hdr.nlmsg_flags |= NLM_F_DUMP;
90#endif
91 request.hdr.nlmsg_len = NLMSG_LENGTH(sizeof(rtmsg) + sizeof(nlattr) + dst_data_len);
92 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.
93 request.data.rtm_family = family;
94 request.data.rtm_dst_len = 0; // Prefix length.
95#ifdef __FreeBSD__
96 // Linux IPv4 / IPv6 this must be absent, 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 present, otherwise no gateway is found
99 request.data.rtm_flags = RTM_F_PREFIX;
100#endif
101 request.dst_hdr.nla_type = RTA_DST;
102 request.dst_hdr.nla_len = sizeof(nlattr) + dst_data_len;
103
104 if (sock->Send(&request, request.hdr.nlmsg_len, 0) != static_cast<ssize_t>(request.hdr.nlmsg_len)) {
105 LogPrintLevel(BCLog::NET, BCLog::Level::Error, "send() to netlink socket: %s\n", NetworkErrorString(errno));
106 return std::nullopt;
107 }
108
109 // Receive response.
110 char response[4096];
111 int64_t recv_result;
112 do {
113 recv_result = sock->Recv(response, sizeof(response), 0);
114 } while (recv_result < 0 && (errno == EINTR || errno == EAGAIN));
115 if (recv_result < 0) {
116 LogPrintLevel(BCLog::NET, BCLog::Level::Error, "recv() from netlink socket: %s\n", NetworkErrorString(errno));
117 return std::nullopt;
118 }
119
120 for (nlmsghdr* hdr = (nlmsghdr*)response; NLMSG_OK(hdr, recv_result); hdr = NLMSG_NEXT(hdr, recv_result)) {
121 rtmsg* r = (rtmsg*)NLMSG_DATA(hdr);
122 int remaining_len = RTM_PAYLOAD(hdr);
123
124 // Iterate over the attributes.
125 rtattr *rta_gateway = nullptr;
126 int scope_id = 0;
127 for (rtattr* attr = RTM_RTA(r); RTA_OK(attr, remaining_len); attr = RTA_NEXT(attr, remaining_len)) {
128 if (attr->rta_type == RTA_GATEWAY) {
129 rta_gateway = attr;
130 } else if (attr->rta_type == RTA_OIF && sizeof(int) == RTA_PAYLOAD(attr)) {
131 std::memcpy(&scope_id, RTA_DATA(attr), sizeof(scope_id));
132 }
133 }
134
135 // Found gateway?
136 if (rta_gateway != nullptr) {
137 if (family == AF_INET && sizeof(in_addr) == RTA_PAYLOAD(rta_gateway)) {
138 in_addr gw;
139 std::memcpy(&gw, RTA_DATA(rta_gateway), sizeof(gw));
140 return CNetAddr(gw);
141 } else if (family == AF_INET6 && sizeof(in6_addr) == RTA_PAYLOAD(rta_gateway)) {
142 in6_addr gw;
143 std::memcpy(&gw, RTA_DATA(rta_gateway), sizeof(gw));
144 return CNetAddr(gw, scope_id);
145 }
146 }
147 }
148
149 return std::nullopt;
150}
151
152#elif defined(WIN32)
153
154std::optional<CNetAddr> QueryDefaultGatewayImpl(sa_family_t family)
155{
156 NET_LUID interface_luid = {};
157 SOCKADDR_INET destination_address = {};
158 MIB_IPFORWARD_ROW2 best_route = {};
159 SOCKADDR_INET best_source_address = {};
160 DWORD best_if_idx = 0;
161 DWORD status = 0;
162
163 // Pass empty destination address of the requested type (:: or 0.0.0.0) to get interface of default route.
164 destination_address.si_family = family;
165 status = GetBestInterfaceEx((sockaddr*)&destination_address, &best_if_idx);
166 if (status != NO_ERROR) {
167 LogPrintLevel(BCLog::NET, BCLog::Level::Error, "Could not get best interface for default route: %s\n", NetworkErrorString(status));
168 return std::nullopt;
169 }
170
171 // Get best route to default gateway.
172 // Leave interface_luid at all-zeros to use interface index instead.
173 status = GetBestRoute2(&interface_luid, best_if_idx, nullptr, &destination_address, 0, &best_route, &best_source_address);
174 if (status != NO_ERROR) {
175 LogPrintLevel(BCLog::NET, BCLog::Level::Error, "Could not get best route for default route for interface index %d: %s\n",
176 best_if_idx, NetworkErrorString(status));
177 return std::nullopt;
178 }
179
180 Assume(best_route.NextHop.si_family == family);
181 if (family == AF_INET) {
182 return CNetAddr(best_route.NextHop.Ipv4.sin_addr);
183 } else if(family == AF_INET6) {
184 return CNetAddr(best_route.NextHop.Ipv6.sin6_addr, best_route.InterfaceIndex);
185 }
186 return std::nullopt;
187}
188
189#elif defined(__APPLE__)
190
191#define ROUNDUP32(a) \
192 ((a) > 0 ? (1 + (((a) - 1) | (sizeof(uint32_t) - 1))) : sizeof(uint32_t))
193
195std::optional<CNetAddr> QueryDefaultGatewayImpl(sa_family_t family)
196{
197 // net.route.0.inet[6].flags.gateway
198 int mib[] = {CTL_NET, PF_ROUTE, 0, family, NET_RT_FLAGS, RTF_GATEWAY};
199 // The size of the available data is determined by calling sysctl() with oldp=nullptr. See sysctl(3).
200 size_t l = 0;
201 if (sysctl(/*name=*/mib, /*namelen=*/sizeof(mib) / sizeof(int), /*oldp=*/nullptr, /*oldlenp=*/&l, /*newp=*/nullptr, /*newlen=*/0) < 0) {
202 LogPrintLevel(BCLog::NET, BCLog::Level::Error, "Could not get sysctl length of routing table: %s\n", SysErrorString(errno));
203 return std::nullopt;
204 }
205 std::vector<std::byte> buf(l);
206 if (sysctl(/*name=*/mib, /*namelen=*/sizeof(mib) / sizeof(int), /*oldp=*/buf.data(), /*oldlenp=*/&l, /*newp=*/nullptr, /*newlen=*/0) < 0) {
207 LogPrintLevel(BCLog::NET, BCLog::Level::Error, "Could not get sysctl data of routing table: %s\n", SysErrorString(errno));
208 return std::nullopt;
209 }
210 // Iterate over messages (each message is a routing table entry).
211 for (size_t msg_pos = 0; msg_pos < buf.size(); ) {
212 if ((msg_pos + sizeof(rt_msghdr)) > buf.size()) return std::nullopt;
213 const struct rt_msghdr* rt = (const struct rt_msghdr*)(buf.data() + msg_pos);
214 const size_t next_msg_pos = msg_pos + rt->rtm_msglen;
215 if (rt->rtm_msglen < sizeof(rt_msghdr) || next_msg_pos > buf.size()) return std::nullopt;
216 // Iterate over addresses within message, get destination and gateway (if present).
217 // Address data starts after header.
218 size_t sa_pos = msg_pos + sizeof(struct rt_msghdr);
219 std::optional<CNetAddr> dst, gateway;
220 for (int i = 0; i < RTAX_MAX; i++) {
221 if (rt->rtm_addrs & (1 << i)) {
222 // 2 is just sa_len + sa_family, the theoretical minimum size of a socket address.
223 if ((sa_pos + 2) > next_msg_pos) return std::nullopt;
224 const struct sockaddr* sa = (const struct sockaddr*)(buf.data() + sa_pos);
225 if ((sa_pos + sa->sa_len) > next_msg_pos) return std::nullopt;
226 if (i == RTAX_DST) {
227 dst = FromSockAddr(sa, sa->sa_len);
228 } else if (i == RTAX_GATEWAY) {
229 gateway = FromSockAddr(sa, sa->sa_len);
230 }
231 // Skip sockaddr entries for bit flags we're not interested in,
232 // move cursor.
233 sa_pos += ROUNDUP32(sa->sa_len);
234 }
235 }
236 // Found default gateway?
237 if (dst && gateway && dst->IsBindAny()) { // Route to 0.0.0.0 or :: ?
238 return *gateway;
239 }
240 // Skip to next message.
241 msg_pos = next_msg_pos;
242 }
243 return std::nullopt;
244}
245
246#else
247
248// Dummy implementation.
249std::optional<CNetAddr> QueryDefaultGatewayImpl(sa_family_t)
250{
251 return std::nullopt;
252}
253
254#endif
255
256}
257
258std::optional<CNetAddr> QueryDefaultGateway(Network network)
259{
260 Assume(network == NET_IPV4 || network == NET_IPV6);
261
262 sa_family_t family;
263 if (network == NET_IPV4) {
264 family = AF_INET;
265 } else if(network == NET_IPV6) {
266 family = AF_INET6;
267 } else {
268 return std::nullopt;
269 }
270
271 std::optional<CNetAddr> ret = QueryDefaultGatewayImpl(family);
272
273 // It's possible for the default gateway to be 0.0.0.0 or ::0 on at least Windows
274 // for some routing strategies. If so, return as if no default gateway was found.
275 if (ret && !ret->IsBindAny()) {
276 return ret;
277 } else {
278 return std::nullopt;
279 }
280}
281
282std::vector<CNetAddr> GetLocalAddresses()
283{
284 std::vector<CNetAddr> addresses;
285#ifdef WIN32
286 DWORD status = 0;
287 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.
288 std::vector<std::byte> out_buf(15000, {}); // Start with 15KB allocation as recommended in GetAdaptersAddresses documentation.
289 while (true) {
290 ULONG out_buf_len = out_buf.size();
291 status = GetAdaptersAddresses(AF_UNSPEC, GAA_FLAG_SKIP_ANYCAST | GAA_FLAG_SKIP_MULTICAST | GAA_FLAG_SKIP_DNS_SERVER | GAA_FLAG_SKIP_FRIENDLY_NAME,
292 nullptr, reinterpret_cast<PIP_ADAPTER_ADDRESSES>(out_buf.data()), &out_buf_len);
293 if (status == ERROR_BUFFER_OVERFLOW && out_buf.size() < MAX_ADAPTER_ADDR_SIZE) {
294 // If status == ERROR_BUFFER_OVERFLOW, out_buf_len will contain the needed size.
295 // Unfortunately, this cannot be fully relied on, because another process may have added interfaces.
296 // So to avoid getting stuck due to a race condition, double the buffer size at least
297 // once before retrying (but only up to the maximum allowed size).
298 out_buf.resize(std::min(std::max<size_t>(out_buf_len, out_buf.size()) * 2, MAX_ADAPTER_ADDR_SIZE));
299 } else {
300 break;
301 }
302 }
303
304 if (status != NO_ERROR) {
305 // This includes ERROR_NO_DATA if there are no addresses and thus there's not even one PIP_ADAPTER_ADDRESSES
306 // record in the returned structure.
307 LogPrintLevel(BCLog::NET, BCLog::Level::Error, "Could not get local adapter addreses: %s\n", NetworkErrorString(status));
308 return addresses;
309 }
310
311 // Iterate over network adapters.
312 for (PIP_ADAPTER_ADDRESSES cur_adapter = reinterpret_cast<PIP_ADAPTER_ADDRESSES>(out_buf.data());
313 cur_adapter != nullptr; cur_adapter = cur_adapter->Next) {
314 if (cur_adapter->OperStatus != IfOperStatusUp) continue;
315 if (cur_adapter->IfType == IF_TYPE_SOFTWARE_LOOPBACK) continue;
316
317 // Iterate over unicast addresses for adapter, the only address type we're interested in.
318 for (PIP_ADAPTER_UNICAST_ADDRESS cur_address = cur_adapter->FirstUnicastAddress;
319 cur_address != nullptr; cur_address = cur_address->Next) {
320 // "The IP address is a cluster address and should not be used by most applications."
321 if ((cur_address->Flags & IP_ADAPTER_ADDRESS_TRANSIENT) != 0) continue;
322
323 if (std::optional<CNetAddr> addr = FromSockAddr(cur_address->Address.lpSockaddr, static_cast<socklen_t>(cur_address->Address.iSockaddrLength))) {
324 addresses.push_back(*addr);
325 }
326 }
327 }
328#elif (HAVE_DECL_GETIFADDRS && HAVE_DECL_FREEIFADDRS)
329 struct ifaddrs* myaddrs;
330 if (getifaddrs(&myaddrs) == 0) {
331 for (struct ifaddrs* ifa = myaddrs; ifa != nullptr; ifa = ifa->ifa_next)
332 {
333 if (ifa->ifa_addr == nullptr) continue;
334 if ((ifa->ifa_flags & IFF_UP) == 0) continue;
335 if ((ifa->ifa_flags & IFF_LOOPBACK) != 0) continue;
336
337 if (std::optional<CNetAddr> addr = FromSockAddr(ifa->ifa_addr, std::nullopt)) {
338 addresses.push_back(*addr);
339 }
340 }
341 freeifaddrs(myaddrs);
342 }
343#endif
344 return addresses;
345}
int ret
#define Assume(val)
Assume is the identity function.
Definition: check.h:118
Network address.
Definition: netaddress.h:112
A combination of a network address (CNetAddr) and a (TCP) port.
Definition: netaddress.h:531
bool SetSockAddr(const struct sockaddr *paddr, socklen_t addrlen)
Set CService from a network sockaddr.
Definition: netaddress.cpp:810
#define LogPrintLevel(category, level,...)
Definition: logging.h:272
@ NET
Definition: logging.h:43
Network
A network type.
Definition: netaddress.h:32
@ NET_IPV6
IPv6.
Definition: netaddress.h:40
@ NET_IPV4
IPv4.
Definition: netaddress.h:37
std::function< std::unique_ptr< Sock >(int, int, int)> CreateSock
Socket factory.
Definition: netbase.cpp:581
std::vector< CNetAddr > GetLocalAddresses()
Return all local non-loopback IPv4 and IPv6 network addresses.
Definition: netif.cpp:282
std::optional< CNetAddr > QueryDefaultGateway(Network network)
Query the OS for the default gateway for network.
Definition: netif.cpp:258
std::string NetworkErrorString(int err)
Return readable error string for a network error code.
Definition: sock.cpp:422
std::string SysErrorString(int err)
Return system error string from errno value.
Definition: syserror.cpp:19