fix error

context.go

@@ -741,6 +741,7 @@ func (c *Context) ClientIP() string {
 	if remoteIP == nil {
 		return ""
 	}
+
 	if trusted && c.engine.ForwardedByClientIP && c.engine.RemoteIPHeaders != nil {
 		for _, headerName := range c.engine.RemoteIPHeaders {
 			ip, valid := validateHeader(c.requestHeader(headerName))
@@ -765,13 +766,19 @@ func (c *Context) RemoteIP() (net.IP, bool) {
 	if remoteIP == nil {
 		return nil, false
 	}
-	if c.engine.trustedCIDRs != nil {
+
-		for _, cidr := range c.engine.trustedCIDRs {
+	trustedCIDRs, err := c.engine.prepareTrustedCIDRs()
-			if cidr.Contains(remoteIP) {
+	if err == nil {
-				return remoteIP, true
+		c.engine.trustedCIDRs = trustedCIDRs
+		if c.engine.trustedCIDRs != nil {
+			for _, cidr := range c.engine.trustedCIDRs {
+				if cidr.Contains(remoteIP) {
+					return remoteIP, true
+				}
 			}
 		}
 	}
+
 	return remoteIP, false
 }
 

context_test.go

@@ -1430,7 +1430,7 @@ func TestContextClientIP(t *testing.T) {
 
 	// Only trust RemoteAddr
 	c.engine.TrustedProxies = []string{"40.40.40.40"}
-	assert.Equal(t, "30.30.30.30", c.ClientIP())
+	assert.Equal(t, "20.20.20.20", c.ClientIP())
 
 	// All steps are trusted
 	c.engine.TrustedProxies = []string{"40.40.40.40", "30.30.30.30", "20.20.20.20"}
@@ -1442,7 +1442,7 @@ func TestContextClientIP(t *testing.T) {
 
 	// Use hostname that resolves to all the proxies
 	c.engine.TrustedProxies = []string{"foo"}
-	assert.Equal(t, "20.20.20.20", c.ClientIP())
+	assert.Equal(t, "40.40.40.40", c.ClientIP())
 
 	// Use hostname that returns an error
 	c.engine.TrustedProxies = []string{"bar"}

gin.go

@@ -338,31 +338,32 @@ func (engine *Engine) Run(addr ...string) (err error) {
 }
 
 func (engine *Engine) prepareTrustedCIDRs() ([]*net.IPNet, error) {
-	if engine.TrustedProxies != nil {
+	if engine.TrustedProxies == nil {
-		cidr := make([]*net.IPNet, 0, len(engine.TrustedProxies))
+		return nil, nil
-		for _, trustedProxy := range engine.TrustedProxies {
-			if !strings.Contains(trustedProxy, "/") {
-				ip := parseIP(trustedProxy)
-				if ip == nil {
-					return cidr, &net.ParseError{Type: "IP address", Text: trustedProxy}
-				}
-
-				switch len(ip) {
-				case net.IPv4len:
-					trustedProxy += "/32"
-				case net.IPv6len:
-					trustedProxy += "/128"
-				}
-			}
-			_, cidrNet, err := net.ParseCIDR(trustedProxy)
-			if err != nil {
-				return cidr, err
-			}
-			cidr = append(cidr, cidrNet)
-		}
-		return cidr, nil
 	}
-	return nil, nil
+
+	cidr := make([]*net.IPNet, 0, len(engine.TrustedProxies))
+	for _, trustedProxy := range engine.TrustedProxies {
+		if !strings.Contains(trustedProxy, "/") {
+			ip := parseIP(trustedProxy)
+			if ip == nil {
+				return cidr, &net.ParseError{Type: "IP address", Text: trustedProxy}
+			}
+
+			switch len(ip) {
+			case net.IPv4len:
+				trustedProxy += "/32"
+			case net.IPv6len:
+				trustedProxy += "/128"
+			}
+		}
+		_, cidrNet, err := net.ParseCIDR(trustedProxy)
+		if err != nil {
+			return cidr, err
+		}
+		cidr = append(cidr, cidrNet)
+	}
+	return cidr, nil
 }
 
 // parseIP parse a string representation of an IP and returns a net.IP with the