Feature: use Happy Eyeballs to make network connections (TCP-only) (#9199)

Hostnames like "content.openttd.org" resolve into multiple IPv4 and IPv6.
It is possible that either of the IPs is not working, either due to
a poorly configured OS (having IPv6 but no valid route), broken network
paths, or a service that is temporary unavailable.

Instead of trying the IPs one by one, waiting for a 3s timeout between
each, be a bit more like browsers, and stack attempts on top of each
other with slight delays. This is called Happy Eyebells.

Initially, try the first IPv6 address. If within 250ms there is no
connection yet, try the first IPv4 address. 250ms later, try the
second IPv6 address, etc, till all addresses are tried.

If any connection is created, abort all the other (pending) connections
and use the one that is created. If all fail 3s after the last connect(),
trigger a timeout for all.

1 files changed, 13 insertions, 78 deletions

diff --git a/src/network/core/address.cpp b/src/network/core/address.cpp
index d40a72420..205b5df22 100644
--- a/src/network/core/address.cpp
+++ b/src/network/core/address.cpp
@@ -14,8 +14,6 @@
 
 #include "../../safeguards.h"
 
-static const int DEFAULT_CONNECT_TIMEOUT_SECONDS = 3; ///< Allow connect() three seconds to connect.
-
 /**
  * Get the hostname; in case it wasn't given the
  * IPv4 dotted representation is given.
@@ -307,82 +305,6 @@ SOCKET NetworkAddress::Resolve(int family, int socktype, int flags, SocketList *
 }
 
 /**
- * Helper function to resolve a connected socket.
- * @param runp information about the socket to try not
- * @return the opened socket or INVALID_SOCKET
- */
-static SOCKET ConnectLoopProc(addrinfo *runp)
-{
-	const char *type = NetworkAddress::SocketTypeAsString(runp->ai_socktype);
-	const char *family = NetworkAddress::AddressFamilyAsString(runp->ai_family);
-	std::string address = NetworkAddress(runp->ai_addr, (int)runp->ai_addrlen).GetAddressAsString();
-
-	SOCKET sock = socket(runp->ai_family, runp->ai_socktype, runp->ai_protocol);
-	if (sock == INVALID_SOCKET) {
-		DEBUG(net, 1, "[%s] could not create %s socket: %s", type, family, NetworkError::GetLast().AsString());
-		return INVALID_SOCKET;
-	}
-
-	if (!SetNoDelay(sock)) DEBUG(net, 1, "[%s] setting TCP_NODELAY failed", type);
-
-	if (!SetNonBlocking(sock)) DEBUG(net, 0, "[%s] setting non-blocking mode failed", type);
-
-	int err = connect(sock, runp->ai_addr, (int)runp->ai_addrlen);
-	if (err != 0 && !NetworkError::GetLast().IsConnectInProgress()) {
-		DEBUG(net, 1, "[%s] could not connect to %s over %s: %s", type, address.c_str(), family, NetworkError::GetLast().AsString());
-		closesocket(sock);
-		return INVALID_SOCKET;
-	}
-
-	fd_set write_fd;
-	struct timeval tv;
-
-	FD_ZERO(&write_fd);
-	FD_SET(sock, &write_fd);
-
-	/* Wait for connect() to either connect, timeout or fail. */
-	tv.tv_usec = 0;
-	tv.tv_sec = DEFAULT_CONNECT_TIMEOUT_SECONDS;
-	int n = select(FD_SETSIZE, NULL, &write_fd, NULL, &tv);
-	if (n < 0) {
-		DEBUG(net, 1, "[%s] could not connect to %s: %s", type, address.c_str(), NetworkError::GetLast().AsString());
-		closesocket(sock);
-		return INVALID_SOCKET;
-	}
-
-	/* If no fd is selected, the timeout has been reached. */
-	if (n == 0) {
-		DEBUG(net, 1, "[%s] timed out while connecting to %s", type, address.c_str());
-		closesocket(sock);
-		return INVALID_SOCKET;
-	}
-
-	/* Retrieve last error, if any, on the socket. */
-	NetworkError socket_error = GetSocketError(sock);
-	if (socket_error.HasError()) {
-		DEBUG(net, 1, "[%s] could not connect to %s: %s", type, address.c_str(), socket_error.AsString());
-		closesocket(sock);
-		return INVALID_SOCKET;
-	}
-
-	/* Connection succeeded. */
-	DEBUG(net, 1, "[%s] connected to %s", type, address.c_str());
-
-	return sock;
-}
-
-/**
- * Connect to the given address.
- * @return the connected socket or INVALID_SOCKET.
- */
-SOCKET NetworkAddress::Connect()
-{
-	DEBUG(net, 1, "Connecting to %s", this->GetAddressAsString().c_str());
-
-	return this->Resolve(AF_UNSPEC, SOCK_STREAM, AI_ADDRCONFIG, nullptr, ConnectLoopProc);
-}
-
-/**
  * Helper function to resolve a listening.
  * @param runp information about the socket to try not
  * @return the opened socket or INVALID_SOCKET
@@ -486,3 +408,16 @@ void NetworkAddress::Listen(int socktype, SocketList *sockets)
 		default:        return "unsupported";
 	}
 }
+
+/**
+ * Get the peer name of a socket in string format.
+ * @param sock The socket to get the peer name of.
+ * @return The string representation of the peer name.
+ */
+/* static */ const std::string NetworkAddress::GetPeerName(SOCKET sock)
+{
+	sockaddr_storage addr;
+	socklen_t addr_len = sizeof(addr);
+	getpeername(sock, (sockaddr *)&addr, &addr_len);
+	return NetworkAddress(addr, addr_len).GetAddressAsString();
+}