fix loopback addr

internal/host/host.go

@@ -5,18 +5,10 @@ import (
 	"strconv"
 )
 
-func isPrivateIP(addr string) bool {
+func isValidIP(addr string) bool {
 	ip := net.ParseIP(addr)
 	if ip4 := ip.To4(); ip4 != nil {
-		// Following RFC 4193, Section 3. Local IPv6 Unicast Addresses which says:
-		//   The Internet Assigned Numbers Authority (IANA) has reserved the
-		//   following three blocks of the IPv4 address space for private internets:
-		//     10.0.0.0        -   10.255.255.255  (10/8 prefix)
-		//     172.16.0.0      -   172.31.255.255  (172.16/12 prefix)
-		//     192.168.0.0     -   192.168.255.255 (192.168/16 prefix)
-		return ip4[0] == 10 ||
-			(ip4[0] == 172 && ip4[1]&0xf0 == 16) ||
-			(ip4[0] == 192 && ip4[1] == 168)
+		return !ip4.IsLoopback()
 	}
 	// Following RFC 4193, Section 3. Private Address Space which says:
 	//   The Internet Assigned Numbers Authority (IANA) has reserved the
@@ -66,7 +58,7 @@ func Extract(hostPort string, lis net.Listener) (string, error) {
 			default:
 				continue
 			}
-			if isPrivateIP(ip.String()) {
+			if isValidIP(ip.String()) {
 				return net.JoinHostPort(ip.String(), port), nil
 			}
 		}

internal/host/host_test.go

@@ -38,7 +38,7 @@ func TestPrivateIP(t *testing.T) {
 	}
 	for _, test := range tests {
 		t.Run(test.addr, func(t *testing.T) {
-			res := isPrivateIP(test.addr)
+			res := isValidIP(test.addr)
 			if res != test.expect {
 				t.Fatalf("expected %t got %t", test.expect, res)
 			}