feat: add func GetRequestPublicIp and IsInternalIP (#40)

* add: add func GetRequestPublicIp and IsInternalIP

* fix: fix test fileutil fail

Co-authored-by: zhanghu <305835360@qq.com>

netutil/net.go

@@ -5,6 +5,7 @@ import (
 	"io/ioutil"
 	"net"
 	"net/http"
+	"strings"
 )
 
 // GetInternalIp return internal ipv4
@@ -24,6 +25,26 @@ func GetInternalIp() string {
 	return ""
 }
 
+// GetRequestPublicIp return the requested public ip
+func GetRequestPublicIp(req *http.Request) string {
+	var ip string
+	for _, ip = range strings.Split(req.Header.Get("X-Forwarded-For"), ",") {
+		if ip = strings.TrimSpace(ip); ip != "" && !IsInternalIP(net.ParseIP(ip)) {
+			return ip
+		}
+	}
+
+	if ip = strings.TrimSpace(req.Header.Get("X-Real-Ip")); ip != "" && !IsInternalIP(net.ParseIP(ip)) {
+		return ip
+	}
+
+	if ip, _, _ = net.SplitHostPort(req.RemoteAddr); !IsInternalIP(net.ParseIP(ip)) {
+		return ip
+	}
+
+	return ip
+}
+
 // GetPublicIpInfo return public ip information
 // return the PublicIpInfo struct
 func GetPublicIpInfo() (*PublicIpInfo, error) {
@@ -122,3 +143,17 @@ func IsPublicIP(IP net.IP) bool {
 	}
 	return false
 }
+
+// IsInternalIP verify an ip is intranet or not
+func IsInternalIP(IP net.IP) bool {
+	if IP.IsLoopback() {
+		return true
+	}
+	if ip4 := IP.To4(); ip4 != nil {
+		return ip4[0] == 10 ||
+			(ip4[0] == 172 && ip4[1] >= 16 && ip4[1] <= 31) ||
+			(ip4[0] == 169 && ip4[1] == 254) ||
+			(ip4[0] == 192 && ip4[1] == 168)
+	}
+	return false
+}