I have several IPv4 / IPv6 addresses on a host and I wish to use a specific one. So I set up the bind so it would use that. It seems to be using that for the bind() in the listen socket but not for the outgoing connections.
I’ve tried settings externalip. That only seems to change the “localaddresses” returned by getnetworkinfo. I’m guessing that’s mostly useful for NAT.
What is required is to bind the socket to the -bind address prior to connecting to the remote site, not the usual way this would be done. I’ve looked at the code in net.cpp and netbase.cpp and boost appears to be in use and the location of the -bind ip constant is not obvious to me. I’m not skilled with c++. Here’s a rough outline of what needs to be done but I don’t have the skill to do it in the cpp environment. Perhaps someone else will pick up this thread.
Found this doing research on the issue. No error checking.
int sockfd = socket(AF_INET, SOCK_STREAM, 0); // Bind to a specific network interface (and optionally a specific local port) struct sockaddr_in localaddr; localaddr.sin_family = AF_INET; localaddr.sin_addr.s_addr = inet_addr(“192.168.1.100”); localaddr.sin_port = 0; // Any local port will do bind(sockfd, (struct sockaddr *)&localaddr, sizeof(localaddr));
This seems like an unusual request. Do you need bitcoin to use different outgoing IP address than other applications on the system?
I feel that this is needed for avoiding mess up with IPv6 privacy randomized addresses.
This request looks reasonable. Is there still interest in it?
Something like this should do it (and pass the proper argument to ConnectSocketDirectly() untested):
0-bool ConnectSocketDirectly(const CService &addrConnect, const Sock& sock, int nTimeout, bool manual_connection)
1+bool ConnectSocketDirectly(const std::optional<CNetAddr>& addr_from, const CService &addrConnect, const Sock& sock, int nTimeout, bool manual_connection)
2 {
3 // Create a sockaddr from the specified service.
4 struct sockaddr_storage sockaddr;
5 socklen_t len = sizeof(sockaddr);
6 if (sock.Get() == INVALID_SOCKET) {
7 LogPrintf("Cannot connect to %s: invalid socket\n", addrConnect.ToStringAddrPort());
8 return false;
9 }
10 if (!addrConnect.GetSockAddr((struct sockaddr*)&sockaddr, &len)) {
11 LogPrintf("Cannot connect to %s: unsupported network\n", addrConnect.ToStringAddrPort());
12 return false;
13 }
14
15+ if (addr_from.has_value()) {
16+ struct sockaddr_storage storage;
17+ struct sockaddr* saddr_from = reinterpret_cast<struct sockaddr*>(&storage);
18+ socklen_t saddr_from_len = sizeof(storage);
19+ if (!CService{addr_from.value(), /*port=*/0}.GetSockAddr(saddr_from, &saddr_from_len)) {
20+ LogPrintLevel(
21+ BCLog::NET,
22+ BCLog::Level::Error,
23+ "Cannot connect to %s: unsupported network of the specified outbound address %s\n",
24+ addrConnect.ToStringAddrPort(),
25+ addr_from->ToStringAddr());
26+ return false;
27+ }
28+ if (sock.Bind(saddr_from, saddr_from_len) == SOCKET_ERROR) {
29+ LogPrintLevel(
30+ BCLog::NET,
31+ BCLog::Level::Error,
32+ "Cannot connect to %s: unable to bind to the specified outbound address %s: %s\n",
33+ addrConnect.ToStringAddrPort(),
34+ addr_from->ToStringAddr(),
35+ NetworkErrorString(WSAGetLastError()));
36+ return false;
37+ }
38+ }
39+
40 // Connect to the addrConnect service on the hSocket socket.
41 if (sock.Connect(reinterpret_cast<struct sockaddr*>(&sockaddr), len) == SOCKET_ERROR) {
I’m running 3 node implementations: Core, Knots, and Libre on one VPS with symlinked blocks, so I would benefit from this feature directly. I’m going to do some reviews then take a crack at this unless someone else is still interested, or if anyone wants to share ideas for this.
edit: #35027