import project

host.go

@@ -0,0 +1,78 @@
+/*
+ *    Copyright (c) 2018 Unrud<unrud@outlook.com>
+ *
+ *    This file is part of Remote-Touchpad.
+ *
+ *    Foobar is free software: you can redistribute it and/or modify
+ *    it under the terms of the GNU General Public License as published by
+ *    the Free Software Foundation, either version 3 of the License, or
+ *    (at your option) any later version.
+ *
+ *    Remote-Touchpad is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with Foobar.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package main
+
+import (
+	"fmt"
+	"net"
+	"strings"
+)
+
+func FindDefaultHost() string {
+	fallbackAddr := ""
+	for _, publicIP := range []string{"2001:4860:4860::8888", "8.8.8.8"} {
+		addr := fmt.Sprintf("[%s]:80", publicIP)
+		conn, err := net.Dial("udp", addr)
+		if err != nil {
+			continue
+		}
+		conn.Close()
+		host, _, err := net.SplitHostPort(conn.LocalAddr().String())
+		if err != nil {
+			continue
+		}
+		return host
+	}
+	interfaces, err := net.Interfaces()
+	if err != nil {
+		goto fallback
+	}
+	for _, inter := range interfaces {
+		if inter.Flags&net.FlagUp == 0 || inter.Flags&net.FlagLoopback != 0 {
+			continue
+		}
+		addrs, err := inter.Addrs()
+		if err != nil {
+			continue
+		}
+	addrs:
+		for _, addr := range addrs {
+			ip, _, err := net.ParseCIDR(addr.String())
+			if err != nil {
+				continue
+			}
+			if fallbackAddr == "" {
+				fallbackAddr = ip.String()
+			}
+			for _, linkLocalPrefix := range []string{"169.254.", "fe8", "fe9", "fea", "feb"} {
+				if strings.HasPrefix(ip.String(), linkLocalPrefix) {
+					continue addrs
+				}
+			}
+			return ip.String()
+		}
+
+	}
+fallback:
+	if fallbackAddr != "" {
+		return fallbackAddr
+	}
+	return "localhost"
+}